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  • phosphorus  (73)
  • apoptosis  (52)
  • Springer  (125)
  • American Chemical Society
  • American Meteorological Society
  • 1995-1999  (125)
  • 1990-1994
  • 1955-1959
  • 1999  (125)
Collection
Keywords
Publisher
  • Springer  (125)
  • American Chemical Society
  • American Meteorological Society
Years
  • 1995-1999  (125)
  • 1990-1994
  • 1955-1959
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  • 1
    Electronic Resource
    Electronic Resource
    Ni–Zn–P alloy deposition from sulfate bath: inhibitory effect of zinc (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 1171-1176 
    Details
    ISSN: 1572-8838
    Keywords: alloys ; cyclic voltammetry ; electrodeposition ; electroless deposition ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy deposition from a sulphate bath, containing sodium hypophosphite as reducer, was investigated. To increase the plating rate, the deposition parameters were optimized. The effect of process parameters (T, pH and [Zn2+]) on the plating rate and deposit composition was examined and it was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition. As a consequence, the percentage of zinc in the electroless Ni–Zn–P alloys never reaches high values. Using cyclic voltammetry the electrodeposition mechanism of Ni–Zn–P alloys was investigated. It was observed that the zinc deposition inhibits the nickel discharge and, as a consequence, its catalytic activity on hypophosphite oxidation. It was also found that increase in temperature or pH leads to the deposition of nickel rich alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003426904395
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  • 2
    Electronic Resource
    Electronic Resource
    Microstructural characterization and corrosion resistance of Ni–Zn–P alloys electrolessly deposited from a sulphate bath (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 637-645 
    Details
    ISSN: 1572-8838
    Keywords: alloys ; electroless ; microstructure ; morphology ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy coatings were obtained on an iron substrate from a sulfate bath at various pH values. The effects of changes in bath pH on alloy composition, morphology, microstructure and corrosion resistance were studied. Scanning electron microscopy was performed to observe the morphological change of the deposits with bath pH. Coating crystallinity was investigated by grazing incidence asymmetric Bragg X-ray diffraction and transmission electron microscopy. A transition from an amorphous to polycrystalline structure was observed on increasing the bath alkalinity, and thus decreasing the phosphorus content of the alloys. A single crystalline phase corresponding to face-centred-cubic nickel was identified in the alloys obtained from a strong alkaline solution. An increase in zinc percentage up to 23% in the deposits does not change the f.c.c. nickel crystalline structure. Corrosion potential and polarization resistance measurements indicated that the corrosion resistance of electroless Ni–Zn–P alloys depends strongly on the microstructure and chemical composition. The deposits obtained at pH 9.0–9.5 and with 11.4–12.5% zinc and 11.8–11.2% phosphorous exhibited the best corrosion resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026441403282
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  • 3
    Electronic Resource
    Electronic Resource
    Apoptosis and p53 gene expression in male reproductive tissues of cadmium exposed rats (1999)
    Springer
    BioMetals 12 (1999), S. 131-139 
    Details
    ISSN: 1572-8773
    Keywords: cadmium ; apoptosis ; RT-PCR ; p53 gene expression ; testes ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Reverse transcription (RT) PCR technique was used to investigate the mechanism of apoptosis induced by Cd and the change of its related genes in testes and prostate of rats. Adult male rats were given a single (s.c.) injection of CdC l2 0, 2.5, 5.0, 10 μmol/kg. 48 h and 72 h after administration of Cd, animals were sacrificed. The results indicated that Cd can induce apoptosis in testes via p53-independent pathway. No apoptosis occurred in prostate in any of the Cd-exposed groups. There was a clearly negative relationship in testes between p53 gene expression and Cd exposure and this dose-response relationship was observed both at 48 h and 72 h. There was a very small increase of this gene expression in the dorsolateral lobe of the prostate in Cd exposed groups. The other apoptosis related gene, bcl-x, was not detectable in either control or Cd-exposed group in testes and dorsal prostate. Although the MT-I gene was expressed in testes or dorsal prostate both in control and exposed groups, no overexpression of MT-I gene was found after administration of Cd . The expression of MT-I in the ventral prostate was not detected in the control group, but a weak expression was found after Cd exposure. Since p53 is a tumo r suppressor gene which can inhibit tumorigenesis, the consequence of a Cd-induced decrease of p53 in testes may have a relation to the known risk of Cd tumorigenesis in this tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009273711068
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of repeated manure and fertilizer phosphorus additions on soil phosphorus dynamics under a soybean-wheat rotation (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 150-155 
    Details
    ISSN: 1432-0789
    Keywords: Key words Phosphorus dynamics ; Olsen ; phosphorus ; Soil phosphorus fractions ; Manure ; Soybean-wheat rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (Pi) and organic P (P0) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha–1 applied to both soybean and wheat) in the absence and presence of 16 t ha–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg–1 was 17.9 kg ha–1 of fertilizer P in unmanured plots and 5.6 kg ha–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO3-extractable Pi (NaHCO3-Pi) and NaHCO3-extractable P0 (NaHCO3-P0)], moderately labile [NaOH-extractable Pi (NaOH-Pi) and NaOH-extractable P0 (NaOH-P0)] and stable [HCl-extractable P (HCl-P) and H2SO4/H2O2-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO3-Pi and -P0 and NaOH-Pi, and -P0 fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO3-Pi, NaOH-Pi and NaOH-P0 fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050477
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  • 5
    Electronic Resource
    Electronic Resource
    Stable isotope (δ13C and δ15N) signatures of sedimented organic matter as indicators of historic lake trophic state (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 205-221 
    Details
    ISSN: 1573-0417
    Keywords: carbon isotopes ; diatoms ; lake management ; nitrogen isotopes ; phosphorus ; radium-226 ; sediments ; trophic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008078222806
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  • 6
    Electronic Resource
    Electronic Resource
    Calibration of diatoms along a nutrient gradient in Florida Everglades Water Conservation Area-2A, USA (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 413-437 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; Everglades ; phosphorus ; wetland ; calibration ; multivariate ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781 μg g-1, and was not found to be correlated with the other geochemical variables. Canonical correspondence analysis (CCA) was used to examine which environmental variables correlated most closely with the distributions in diatom taxa. Canonical correspondence analysis with forward selection, constrained and partial CCA, and Monte Carlo permutation tests of significance show the most significant changes in diatom assemblages along the P gradient (p 〈 0.01), with additional species differences correlated with soil C, N, Ca, and BSi. Weighted-averaging (WA) regression and calibration models of diatom assemblages to P and BSi were developed. The diatom-based inference model for soil [P] had a high apparent r2 (0.86) with RMSEboot = 218 μg g-1. Indicator diatom species identified by assessing species WA optima and WA tolerance to [P], such as Nitzschia amphibia and N. palea for high [P] (~1300-1400 μ g-1) and Achnanthes minutissima var. scotica and Mastogloia smithii for low [P] (~400-600 μg g-1), may be useful as monitoring tools for eutrophication in WCA-2A as well as other areas of the Everglades. Diatom assemblages analyzed by cluster analysis were related to location within WCA-2A, and dominant taxa within clusters are discussed in relation to the geochemical variables measured as well as hydrology and pH. Diversity of diatom assemblages and a ‘Disturbance Index’ based on diatom data are discussed in relation to the historically P-limited Everglades ecosystem. Diatom assemblages should be very useful for reconstructions of [P] through time in the Florida Everglades, provided diatoms are well preserved in soil cores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008049224045
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  • 7
    Electronic Resource
    Electronic Resource
    Controlling soil water content in fertiliser dissolution experiments (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 7-14 
    Details
    ISSN: 1573-0867
    Keywords: fertiliser formulation ; nutrients ; phosphorus ; relative humidity ; soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 °C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 °C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009816716466
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  • 8
    Electronic Resource
    Electronic Resource
    Transfers of phosphorus within three dairy farming systems receiving varying inputs in feeds and fertilizers (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 63-75 
    Details
    ISSN: 1573-0867
    Keywords: dairy systems ; feeds ; fertilizers ; phosphorus ; P surplus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inputs of phosphorus (P) above requirements for production on dairy farms lead to surplus P with increased risk of P transfer in land run-off to surface waters causing eutrophication. The impact of reducing surplus P inputs in purchased feeds and fertilizers on milk and forage production was investigated in a comparison of three dairy farm systems on chalkland soils in southern England over a 3-year period. In accordance with current commercial practice, no attempt was made to regulate P inputs in system 1, which accumulated an average annual surplus of 23 kg P ha-1. Progressive reductions in purchased feed and/or fertilizer inputs into systems 2 and 3 decreased surplus P to 17 and 3 kg ha-1, respectively, without apparently limiting either milk or herbage dry matter production. The estimated reduction in faecal P output from system 3 cows fed a low P diet compared to system 1 cows fed a high P diet was 26%. Milk P concentrations significantly (P 〈0.001) increased in systems 2 and 3 which included maize in the diet. Output of P in milk and meat products, as a proportion of the total dietary P inputs, increased from 28% in system 1 to 36% in system 3. Surplus P was greatest in continuous maize fields receiving both dairy manure and starter P fertilizer. Withholding P fertilizer in system 3 did not reduce P offtake in cut herbage on soils of moderate P fertility. Total annual losses of P in storm run-off and leaching were no greater than annual inputs of P from the atmosphere (0.5 kg ha-1). The results indicate there is scope to reduce surplus P on commercial dairy farms without sacrificing production targets at least in the short term. Purchased feeds are the largest of the P inputs on intensive dairy farms, yet these are rarely quantified on commercial holdings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009860915462
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  • 9
    Electronic Resource
    Electronic Resource
    Applications of poultry litter and triple superphosphate fertilizer to a sandy soil: effects on soil phosphorus status and profile distribution (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 233-242 
    Details
    ISSN: 1573-0867
    Keywords: leaching ; phosphorus ; poultry litter ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine P loadings, added through poultry litter, sufficient to cause downward movement of P from the cultivated layer of a sandy soil, six rates of poultry litter were applied annually for four years to a site in central England. (total loading 0 – 1119 kg P ha-1). A single extra plot also received an extra 1000 kg ha-1 as triple superphosphate (TSP; total loading 2119 kg P ha-1) and three other treatments received 200 – 800 kg ha-1 P as TSP only. Annual soil sampling in 30-cm increments to 1.5-m depth provided information on P build-up in the topsoil and P movement to depth. There were strong linear trends between P balance (P applied – P removed in crops) and total P, Olsen bicarbonate extractable P and water-soluble P in the topsoil. Phosphorus from TSP and poultry litter fell on the same regression lines, suggesting that both would be equally effective as fertilizer sources. We calculated that 100 kg ha-1 surplus total P would increase the Olsen extractable P content by c. 6 mg kg-1 and the water-soluble P by c. 5 mg kg-1. Thus, relatively large amounts of P would need to be applied to raise soil P status. We found some evidence of P movement into the soil layers immediately below cultivation depth. However, neither soil sampling nor soil solution extracted through Teflon water samplers showed evidence of movement into the deep subsoil (1 m) despite large P loadings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009744706679
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  • 10
    Electronic Resource
    Electronic Resource
    Inorganic phosphorus and manure effects on bahiagrass production on a Spodosol (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 259-266 
    Details
    ISSN: 1573-0867
    Keywords: bahiagrass ; manure ; pasture fertilization ; phosphorus ; phosphorus cycling ; Spodosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations have traditionally been based upon clipping studies. Inclusion of P from manure, not originally considered when P recommendations were developed for pastures, may minimize the need for P fertilization without reducing bahiagrass production or P uptake. The objective of this research was to determine if manure contributes greatly to the P crop nutrient requirement. A 2-year field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried manure ha-1 with 0, 17, 34, 51, and 68 kg inorganic P ha-1 from triple superphosphate to evaluate bahiagrass yield, root distribution, and P uptake response on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). Because air-dried manure was used in the field study, a greenhouse study was employed to confirm that there were no differences in bahiagrass yield or P uptake from either air-dried or fresh cattle (Bos spp.) manure sources. There were no manure or manure by P interaction effects on yield or P uptake of bahiagrass indicating that manure source did not effect grass production in the greenhouse. In the field study, bahiagrass roots were distributed into the Bh horizon, and the Bh horizon had at least four times more Mehlich-1 extractable P than that of the Ap horizon. This horizon was most likely acting as a main source for P-uptake by the grass. This observation was further confirmed by no yield response to levels of inorganic P application in 1989. A linear-response-and-plateau (R2=0.196) relationship with a critical point of 15.4 kg P ha-1 was found in 1990. Bahiagrass yield and P uptake were not dependent on P fertilization, either from manure or inorganic P, due to the availability of P from the Bh horizon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009831011649
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  • 11
    Electronic Resource
    Electronic Resource
    Regulation of cardiomyocyte apoptosis in ischemic reperfused mouse heart by glutathione peroxidase (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 13-21 
    Details
    ISSN: 1573-4919
    Keywords: apoptosis ; DNA fragmentation ; GSHPx-1 knockout mice ; GSHPx-1 transgenic mice ; ischemia/repurfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Apoptosis, a genetically controlled programmed cell death, has been found to play a role in ischemic reperfusion injury in several animal species including rats and rabbits. To examine whether this is also true for other animals, an isolated perfused mouse heart was subjected to 30 min of ischemia followed by 2 h of reperfusion. Experiments were terminated before ischemia (baseline), after ischemia, and at 30, 60, 90 and 120 min of reperfusion. At the end of each experiment, hearts were processed for the evaluation of apoptosis and DNA laddering. The in situ end labeling (ISEL) technique was used to detect apoptotic cardiomyocyte nuclei while DNA laddering was evaluated by subjecting the DNA obtained from the cardiomyocytes to 1.8% agarose gel electrophoresis followed by photographing under UV illumination. The results of our study revealed that apoptotic cells appear only after 60 min of reperfusion as demonstrated by the intense fluorescence of the immunostained genomic DNA when observed under fluorescence microscopy. None of the ischemic hearts showed any evidence of apoptosis. These results were corroborated with the findings of DNA fragmentation showing increased ladders of DNA bands in the same reperfused hearts representing integer multiples of the internucleosomal DNA length (about 180 bp). Since our previous studies showed a role of glutathione peroxidase (GSHPx) in apoptotic cell death, we performed identical experiments using isolated hearts from GSHPx-l knockout mice and transgenic mice overexpressing GSHPx-l. GSHPx-l knockout mice showed evidence of apoptotic cell death even after 30 min of reperfusion. Significant number of apoptotic cells were found in the cardiomyocytes as compared to non-transgenic control animals. To the contrary, very few apoptotic cells were found in the hearts of the transgenic mice overexpressing GSHPx-l. Hearts of GSHPx-l knockout mice were more susceptible to ischemia/reperfusion injury while transgenic mice overexpressing GSHPx- 1 were less susceptible to ischemia reperfusion injury compared to non-transgenic control animals. The results of this study clearly demonstrate a role of GSHPx in ischemia/reperfusion-induced apoptosis in mouse heart.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006905910140
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  • 12
    Electronic Resource
    Electronic Resource
    Human DU145 prostate cancer cells overexpressing mitogen-activated protein kinase phosphatase-1 are resistant to Fas ligand-induced mitochondrial perturbations and cellular apoptosis (1999)
    Springer
    Molecular and cellular biochemistry 199 (1999), S. 169-178 
    Details
    ISSN: 1573-4919
    Keywords: MKP-1 ; Fas ligand ; Fas ; apoptosis ; prostate cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Recent studies have suggested that MAP kinase phosphatase 1 (MKP-1) is overexpressed in prostate cancer. To evaluate the role of MKP-1 in regulating cell death and tumor growth in prostate cancer, MKP-1 was conditionally overexpressed in the human prostate cancer cell line DU145. Overexpression of MKP-1 in DU145 cells blocked activation of stress-activated protein kinase (SAPK/JNK). MKP-1 overexpression in DU-145 cells was also found to inhibit Fas ligand (FasL)-induced apoptosis, as well as block the activation of caspases by Fas engagement. In addition, MKP-1 blocked the activation of apoptosis by transfected MEKK-1 and ASK-1, presumably through its inhibition of the SAPK/JNK family of enzymes. MKP-1 blocked the ability of FasL to induce loss of mitochondrial transmembrane potential (Δγm), suggesting that MKP-1 acts upstream of mitochondrial pro-apoptotic events induced by FasL and that the SAPK/JNK pathway may form the signaling link between Fas receptor and mitochondrial dysfunction. Thus, MKP-1 overexpression in prostate cancer may play a role in promoting prostate carcinogenesis by inhibiting FasL-induced cell death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006980326855
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  • 13
    Electronic Resource
    Electronic Resource
    Poly(ADP-ribosylation) and apoptosis (1999)
    Springer
    Molecular and cellular biochemistry 199 (1999), S. 125-137 
    Details
    ISSN: 1573-4919
    Keywords: apoptosis ; ADP-ribosylation ; caspases ; PARP ; PARG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Poly(ADP-ribosylation) is a post-translational modification playing a relevant role in DNA damage recovery, DNA replication and viral integration. Several reports also suggest a modulation of this process during cell death by apoptosis. The aim of this review is to discuss the possible involvement of poly(ADP-ribosylation) during apoptosis, by dealing with general considerations on apoptosis, and further examining the correlation between NAD consumption and cell death, the regulation of poly(ADP-ribose) metabolism in apoptotic cells, the effect of poly(ADP-ribose) polymerase inhibition on cell death occurrence and the use of enzyme cleavage as a marker of apoptosis. Finally, the future prospects of the research in this area will be addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006962716377
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  • 14
    Electronic Resource
    Electronic Resource
    A dual approach in the study of poly (ADP-ribose) polymerase: In vitro random mutagenesis and generation of deficient mice (1999)
    Springer
    Molecular and cellular biochemistry 193 (1999), S. 53-60 
    Details
    ISSN: 1573-4919
    Keywords: DNA binding protein ; NAD metabolism ; cellular response to DNA damage ; γ-rays ; alkylating agents ; genomic instability ; apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A dual approach to the study of poly (ADP-ribose)polymerase (PARP) in terms of its structure and function has been developed in our laboratory. Random mutagenesis of the DNA binding domain and catalytic domain of the human PARP, has allowed us to identify residues that are crucial for its enzymatic activity. In parallel PARP knock-out mice were generated by inactivation of both alleles by gene targeting. We showed that: (i) they are exquisitely sensitive to γ-irradiation, (ii) they died rapidly from acute radiation toxicity to the small intestine, (iii) they displayed a high genomic instability to γ-irradiation and MNU injection and, (iv) bone marrow cells rapidly underwent apoptosis following MNU treatment, demonstrating that PARP is a survival factor playing an essential and positive role during DNA damage recovery and survival.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006947707713
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  • 15
    Electronic Resource
    Electronic Resource
    Involvement of PARP and poly(ADP-ribosyl)ation in the early stages of apoptosis and DNA replication (1999)
    Springer
    Molecular and cellular biochemistry 193 (1999), S. 137-148 
    Details
    ISSN: 1573-4919
    Keywords: PARP ; poly(ADP-ribosyl)ation ; apoptosis ; DNA replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We have focused on the roles of PARP and poly(ADP-ribosyl)ation early in apoptosis, as well as during the early stages of differentiation-linked DNA replication. In both nuclear processes, a transient burst of PAR synthesis and PARP expression occurs early, prior to internucleosomal DNA cleavage before commitment to apoptosis as well as at the round of DNA replication prior to the onset of terminal differentiation. In intact human osteosarcoma cells undergoing spontaneous apoptosis, both PARP and PAR decreased after this early peak, concomitant with the inactivation and cleavage of PARP by caspase-3 and the onset of substantial DNA and nuclear fragmentation. Whereas 3T3-L1, osteosarcoma cells, and immortalized PARP +/+ fibroblasts exhibited this early burst of PAR synthesis during Fas-mediated apoptosis, neither PARP-depleted 3T3-L1 PARP-antisense cells nor PARP -/- fibroblasts showed this response. Consequently, whereas control cells progressed into apoptosis, as indicated by induction of caspase-3-like PARP-cleavage activity, PARP-antisense cells and PARP -/- fibroblasts did not, indicating a requirement for PARP and poly(ADP-ribosyl)ation of nuclear proteins at an early reversible stage of apoptosis. In parallel experiments, a transient increase in PARP expression and activity were also noted in 3T3-L1 preadipocytes 24 h after induction of differentiation, a stage at which ~95% of the cells were in S-phase, but not in PARP-depleted antisense cells, which were consequently unable to complete the round of DNA replication required for differentiation. PARP, a component of the multiprotein DNA replication complex (MRC) that catalyzes viral DNA replication in vitro, poly(ADP-ribosyl)ates 15 of ~40 MRC proteins, including DNA pol α, DNA topo I, and PCNA. Depletion of endogenous PARP by antisense RNA expression in 3T3-L1 cells results in MRCs devoid of any DNA pol α and DNA pol δ activities. Surprisingly, there was no new expression of PCNA and DNA pol α, as well as the transcription factor E2F-1 in PARP-antisense cells during entry into S-phase, suggesting that PARP may play a role in the expression of these proteins, perhaps by interacting with a site in the promoters for these genes.
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    URL: http://dx.doi.org/10.1023/A:1006988832729
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    Bcl-2, survivin and variant CD44 v7-v10 are downregulated and p53 is upregulated in breast cancer cells by progesterone: Inhibition of cell growth and induction of apoptosis (1999)
    Springer
    Molecular and cellular biochemistry 202 (1999), S. 53-61 
    Details
    ISSN: 1573-4919
    Keywords: breast cancer cells ; anti-apoptotic genes ; apoptosis ; progesterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Progesterone inhibits the proliferation of normal breast epithelial cells in vivo, as well as breast cancer cells in vitro. But the biologic mechanism of this inhibition remains to be determined. We explored the possibility that an antiproliferative activity of progesterone in breast cancer cell lines is due to its ability to induce apoptosis. Since p53, bcl-2 and survivin genetically control the apoptotic process, we investigated whether or not these genes could be involved in the progesterone-induced apoptosis. We found a maximal 90% inhibition of cell proliferation with T47-D breast cancer cells after exposure to 10 μM progesterone for 72 h. Control progesterone receptor negative MDA-231 cancer cells were unresponsive to 10 μM progesterone. The earliest sign of apoptosis is translocation of phosphatidylserine from the inner to the outer leaflet of the plasma membrane and can be monitored by the calcium-dependent binding of annexin V in conjunction with flow cytometry. After 24 h of exposure to 10 μM progesterone, cytofluorometric analysis of T47-D breast cancer cells indicated 43% were annexin V-positive and had undergone apoptosis and no cells showed signs of cellular necrosis (propidium iodide negative). After 72 h of exposure to 10 μM progesterone, 48% of the cells had undergone apoptosis and 40% were annexin V positive/propidium iodide positive indicating signs of necrosis. Control untreated cancer cells did not undergo apoptosis. Evidence proving apoptosis was also demonstrated by fragmentation of nuclear DNA into multiples of oligonucleosomal fragments. After 24 h of exposure of T47-D cells to either 1 or 10 μM progesterone, we observed a marked down-regulation of protooncogene bcl-2 protein and mRNA levels. mRNA levels of survivin and the metastatic variant CD44 v7-v10 were also downregulated. Progesterone increased p53 mRNA levels. These results demonstrate that progesterone at relative high physiological concentrations, but comparable to those seen in plasma during the third trimester of human pregnancy, exhibited a strong antiproliferative effect on breast cancer cells and induced apoptosis.
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    URL: http://dx.doi.org/10.1023/A:1007081021483
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  • 17
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    Role of nitric oxide in the induction of apoptosis by smokeless tobacco extract (1999)
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 51-57 
    Details
    ISSN: 1573-4919
    Keywords: smokeless tobacco ; apoptosis ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Smokeless tobacco usage is, a growing public health concern in the United States. Lesions of the oral cavity have been clearly linked to smokeless tobacco use. The objective of this study was to determine the biochemical effects of smokeless tobacco extract (STE) exposure upon hamster cheek pouch cell (HCPC-1) cultures. HCPC-1 cells were exposed to a 5 -fold dose-range of STE (0.5, 1.0 and 2.5%) over a time-course of 24-96 h. Following each exposure we measured various biochemical parameters of cell proliferation and cell death. Cell viability, cell cycle progression and S-phase DNA synthesis were measured as markers of cell proliferation. We measured lactate dehydrogenase leakage as a marker of cell membrane damage and cell death due to necrosis. No significant alterations were observed in cell cycle progression and cell proliferation as a result of exposure to STE. LDH measured colorimetrically indicated no significant effect with the lower doses (0.5, 1.0 and 2.5% STE). Apoptosis measured as the A0 peak and by the TUNEL procedure revealed that STE caused significant rates of apoptosis. Maximal apoptosis was noted between 48-96 h. In order to probe the mechanism further we measured the levels of nitrites as an indicator of nitric oxide (NO) in the media. NO levels were significantly elevated at the doses that caused an induction of apoptosis. The results from this study indicate that STE causes a dose-dependent induction of apoptosis and that this is mediated by nitric oxide.
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    URL: http://dx.doi.org/10.1023/A:1006985700851
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  • 18
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    Clostridial toxins: Molecular probes of Rho-dependent signaling and apoptosis (1999)
    Springer
    Molecular and cellular biochemistry 193 (1999), S. 37-42 
    Details
    ISSN: 1573-4919
    Keywords: Rho ; GTPase ; toxins ; Clostridium ; signal transduction ; apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The Rho family small GTPases are members of the Ras superfamily of small GTPases. Rho proteins were first determined to act as key regulators of many types of actin cytoskeletal-dependent cellular functions. Recent work by several investigators indicates that Rho GTPases are also critical modulators of several important intracellular and nuclear signal transduction pathways. Certain clostridial toxins and exoenzymes covalently modify, and thereby inactivate, specific types of Rho family GTPases. As such, these microbial enzymes have proven invaluable in helping to identify structural and functional attributes of Rho GTPases.
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    URL: http://dx.doi.org/10.1023/A:1006939505896
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  • 19
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    Functional analysis of poly(ADP-ribose) polymerase in Drosophila melanogaster (1999)
    Springer
    Molecular and cellular biochemistry 193 (1999), S. 103-108 
    Details
    ISSN: 1573-4919
    Keywords: Poly(ADP-ribose) polymerase ; Drosophila melanogaster ; alternative splicing ; apoptosis ; DNA repair ; development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Poly(ADP-ribose) polymerase (PARP) is conserved in eukaryotes. To analyze the function of PARP, we isolated and characterized the gene for PARP in Drosophila melanogaster. The PARP gene consisted of six translatable exons and spanned more than 50 kb. The DNA binding domain is encoded by exons 1-4. Although the consensus cleavage site of CED-3 like protease during apoptosis is conserved from human to Xenopus laevis PARPs, it is neither conserved in the corresponding region of Drosophila nor Sarcophaga peregrina. There are two cDNAs species in Drosophila. One cDNA could encode the full length PARP protein (PARP I), while the other is a truncated cDNA which could encode a partial-length PARP protein (PARP II), which lacks the automodification domain and is possibly produced by alternative splicing. The expression of these two forms of PARP in E. coli demonstrated that while PARP II has the catalytic NAD-binding domain and DNA-binding domain it is enzymatically inactive. On the other hand PARP I is active. A deletion mutant of PARP gene could grow to the end of embryogenesis but did not grow to the adult fly. These results suggest that the PARP gene plays an important function during the development of Drosophila.
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    URL: http://dx.doi.org/10.1023/A:1006920429095
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  • 20
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    Newly discovered anti-inflammatory properties of the benzamides and nicotinamides (1999)
    Springer
    Molecular and cellular biochemistry 193 (1999), S. 119-125 
    Details
    ISSN: 1573-4919
    Keywords: benzamides ; nicotinamides ; apoptosis ; inflammation ; NF-kB ; DNA repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Our laboratory has concentrated on the possible regulation the benzamides and nicotinamides may have on the processes of DNA repair and apoptosis. Recent reports [14-16] have suggested that both apoptosis and inflammation are regulated by the transcription factor NF-kB. We have initiated studies regarding the hypothesis that the benzamides and nicotinamides could inhibit the production of tumor necrosis factor alpha (TNFalpha) and the inflammatory response as well as induce apoptosis via inhibition of NF-kB. Our data have shown that nicotinamide and two N-substituted benzamides, metoclopramide (MCA) and 3-chloroprocainamide (3-CPA), gave dose dependent inhibition of lipopolysacharide induced TNFalpha in the mouse within the dose range of 10-500 mg/kg. Moreover, lung edema was prevented in the rat by 3 ï 50 mg/kg doses of 3-CPA or MCA, and 100-200 μM doses of MCA could also inhibit NF-kB in Hela cells. Taken together these data strongly support the notion that benzamides and nicotinamides have potent anti-inflammatory and antitumor properties, because their primary mechanism of action is regulated by inhibition at the gene transcription level of NF-kB, which in turn inhibits TNFalpha and induces apoptosis.
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    URL: http://dx.doi.org/10.1023/A:1006932714982
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  • 21
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    Growth arrest and induction of apoptosis in breast cancer cells by antisense depletion of protein kinase A-RIα subunit: p53-independent mechanism of action (1999)
    Springer
    Molecular and cellular biochemistry 195 (1999), S. 25-36 
    Details
    ISSN: 1573-4919
    Keywords: antisense oligonucleotide ; apoptosis ; cAMP-dependent protein kinase ; cancer cells ; growth inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The enhanced expression of the RIα subunit of cyclic AMP-dependent protein kinase type 1 (PKA-I) has been correlated with cancer cell growth. We have investigated the effects of sequence-specific inhibition of RIα gene expression on the growth of MCF-7 human breast cancer cells. We report that RIα antisense treatment results in a reduction in RIα expression at both mRNA and protein levels and inhibition of cell growth. The growth inhibition was accompanied by changes in cell morphology, cleavage of poly(ADP-ribose) polymerase (PARP) and appearance of apoptotic nuclei. In addition, bcl-2 protein level was reduced and p53 expression increased in growth arrested cells. Interestingly, RIα antisense inhibited cell viability and induced apoptosis in the absence of p53, suggesting that these actions of RIα antisense are exerted independent of p53. In contrast, two- and four-base mismatched control oligonucleotides had no effect on either cell growth or morphology. These results demonstrate that the RIα antisense, which efficiently depletes the growth stimulatory molecule RIα, induces cell differentiation and apoptosis, providing a new approach to combat breast cancer cell growth.
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    URL: http://dx.doi.org/10.1023/A:1006990231186
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    TNF-α induced altered signaling mechanism in human neutrophil (1999)
    Springer
    Molecular and cellular biochemistry 197 (1999), S. 97-108 
    Details
    ISSN: 1573-4919
    Keywords: neutrophil ; PKC ; TNF-α ; apoptosis ; DNA fragmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the present study we investigated the TNF-α induced signal transduction mechanism in human neutrophil. Exogenously added TNF-α affects both PKC activity and its translocation from cytosol to the membrane. Endogenous protein phosphorylation pattern is inhibited in TNF-α induced neutrophil in Ca-dependent and Ca-independent manner, including a major 47 and 66 kDa cytosolic proteins, which may be implicated in superoxide anion generation. However TNF-α dose dependently enhances the expression of ζ-PKC isotype but not the β-PKC. Morphology and cell cytotoxicity are studied in TNF-α treated neutrophil to understand the TNF-α induced cell death or apoptosis and these experiment is further confirmed by DNA fragmentation analysis. These results clearly demonstrate that TNF-α induces cellular death of human neutrophil at least in part by enhanced expression of Ca-independent ζ-PKC. These observations provide an insight towards understanding the function of ζ-PKC in apoptotic pathway.
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    URL: http://dx.doi.org/10.1023/A:1006935114624
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    Diminished energy metabolism and enhanced apoptosis in livers of B6C3F1 mice treated with the antihepatocarcinogen rotenone (1999)
    Springer
    Molecular and cellular biochemistry 201 (1999), S. 25-32 
    Details
    ISSN: 1573-4919
    Keywords: rotenone ; apoptosis ; oncogenes ; liver cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Rotenone decreases the incidence of hepatocellular carcinoma and lowers rates of hepatocellular proliferation. In an effort to delineate mechanisms involved, the in vivo effect of rotenone on liver mitochondrial metabolism, apoptotic machinery as well as elements of the hepatic signal transduction pathways were investigated. Mitochondria from livers of male B6C3F1 mice fed a standard diet containing 600 ppm rotenone for 7 days were uncoupled or inhibited when succinate or glutamate plus malate were used as the substrate, respectively. These livers also showed a significant increase in apoptosis compared with control livers. Furthermore, rotenone increased the expression of c-myc mRNA to 5-fold of control values within 3 days, an effect which was still observed (3-fold) after 7 days. Levels of p53 mRNA were also increased 3-fold after 1 day, but declined to control levels by 7 days. Rotenone also caused a transient, yet marked increase in liver particulate glyceraldehyde phosphate dehydrogenase (GAPDH) protein expression, while it did not alter the expression of the cytosolic form of the enzyme. Conversely, mRNA of the proto-oncogene H-ras showed a decline of 35% after 3 days of rotenone treatment, and remained diminished for the duration of the experiment. These data suggest that rotenone may act as an anticancer agent by diminishing mitochondrial bioenergetics which prevents basal hepatocyte proliferation and lowers the threshold for liver cells with DNA damage to undergo apoptosis.
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    URL: http://dx.doi.org/10.1023/A:1007024905046
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    Preparative High-Resolution Two-Dimensional Electrophoresis Enables the Identification of RNA Polymerase B Transcription Factor 3 as an Apoptosis-Associated Protein in the Human BL60–2 Burkitt Lymphoma Cell Line (1999)
    Springer
    The protein journal 18 (1999), S. 225-231 
    Details
    ISSN: 1573-4943
    Keywords: Two-dimensional electrophoresis ; MALDI-MS ; apoptosis ; RNA polymerase B transcription factor 3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Apoptosis or programmed cell death is essential in the process of controlling lymphocyte growth and selection. We identified RNA polymerase B transcription factor 3 (BTF3), which is associated with anti-IgM antibody-mediated apoptosis, using a subclone of the human Burkitt lymphoma cell line BL60. To identify the transcription factor BTF3, which is expressed only in minor amounts, we used preparative high-resolution two-dimensional gel electrophoresis (2DE) employing carrier ampholytes for isoelectric focusing. Comparison of the 2DE protein patterns from apoptotic and nonapoptotic cells showed BTF3 as a predominantly altered protein spot. The characterization of the differentially expressed transcription factor and 13 marker proteins described in this study were performed by internal Edman microsequencing and/or by peptide mass fingerprinting using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The proteome analysis was significantly improved by performing the newly developed preparative high-resolution two-dimensional gels employing high protein concentrations.
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    URL: http://dx.doi.org/10.1023/A:1020636308270
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    Retention of nutrients in river basins (1999)
    Springer
    Aquatic ecology 33 (1999), S. 29-40 
    Details
    ISSN: 1573-5125
    Keywords: denitrification ; nature restoration ; nitrogen ; phosphorus ; riparian areas ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Denmark, as in many other European countries, the diffuse losses of nitrogen (N) and phosphorus (P) from the rural landscape are the major causes of surface water eutrophication and groundwater pollution. The export of total N and total P from the Gjern river basin amounted to 18.2 kg ha−1 and 0.63 kg P ha−1 during June 1994 to May 1995. Diffuse losses of N and P from agricultural areas were the main nutrient source in the river basin contributing 76% and 51%, respectively, of the total export. Investigations of nutrient cycling in the Gjern river basin have revealed the importance of permanent nutrient sinks (denitrification and overbank sedimentation) and temporary nutrient storage in watercourses. Temporary retention of N and P in the watercourses thus amounted to 7.2–16.1 g N m−2 yr−1 and 3.7–8.3 g P m−2 yr−1 during low-flow periods. Deposition of P on temporarily flooded riparian areas amounted from 0.16 to 6.50 g P m−2 during single irrigation and overbank flood events, whereas denitrification of nitrate amounted on average to 7.96 kg N yr−1 per running metre watercourse in a minerotrophic fen and 1.53 kg N yr−1 per linear metre watercourse in a wet meadow. On average, annual retention of N and P in 18 Danish shallow lakes amounted to 32.5 g N m−2 yr−1 and 0.30 g P m−2 yr−1, respectively, during the period 1989–1995. The results indicate that permanent nutrient sinks and temporary nutrient storage in river systems represent an important component of river basin nutrient budgets. Model estimates of the natural retention potential of the Gjern river basin revealed an increase from 38.8 to 81.4 tonnes yr−1 and that P-retention increased from −0.80 to 0.90 tonnes yr−1 following restoration of the water courses, riparian areas and a shallow lake. Catchment management measures such as nature restoration at the river basin scale can thus help to combat diffuse nutrient pollution.
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    URL: http://dx.doi.org/10.1023/A:1009947907811
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    Variation in nutrient availability and plant species diversity across forb and graminoid zones of a Northern New England high salt marsh (1999)
    Springer
    Plant ecology 143 (1999), S. 219-228 
    Details
    ISSN: 1573-5052
    Keywords: mineralization ; nitrogen ; phosphorus ; salinity ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant zonation patterns across New England salt marshes have been investigated for years, but how nutrient availability differs between zones has received little attention. We investigated how N availability, P availability, and plant N status varied across Juncus gerardii, Spartina patens, and mixed forb zones of a Northern New England high salt marsh. We also investigated relationships between several edaphic factors and community production and diversity across the high marsh. P availability, soil salinity, and soil moisture were higher in the mixed forb zone than in the two graminoid zones. NH+ 4-N availability was highest in the J. gerardii zone, but NO− 3-N availability and mid season net N mineralization rates did not vary among zones. Plant tissue N concentrations were highest in the mixed forb zone and lowest in the S. patens zone, reflecting plant physiologies more so than soil N availability. Community production was highest in the J. gerardii zone and was positively correlated with N availability and negatively correlated with soil moisture. Plant species diversity was highest in the mixed forb zone and was positively correlated with P availability and soil salinity. Thus, nutrient availability, plant N status, and plant species diversity varied across zones of this high marsh. Further investigation is needed to ascertain if soil nutrient availability influences or is a result of the production and diversity differences that exist between vegetation zones of New England high salt marshes.
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    URL: http://dx.doi.org/10.1023/A:1009887727465
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    Protein Kinase C Targeting in Antineoplastic Treatment Strategies (1999)
    Springer
    Investigational new drugs 17 (1999), S. 227-240 
    Details
    ISSN: 1573-0646
    Keywords: apoptosis ; protein kinase C ; sphingoid bases ; safingol ; diglyceride ; bryostatin 1 ; staurosporine ; 7-hydroxy staurosporine (UCN-01) ; 4′-N-benzoyl staurosporine (CGP-41251) ; calphostin C (UCN-1028c)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Neoplastic cell survival is governed by a balance between pro-apoptotic and anti-apoptotic signals. Noteworthy among several anti-apoptotic signaling elements is the protein kinase C (PKC) isoenzyme family, which mediates a central cytoprotective effect in the regulation of cell survival. Activation of PKC, and subsequent recruitment of numerous downstream elements such as the mitogen-activated protein kinase (MAPK) cascade, opposes initiation of the apoptotic cell death program by diverse cytotoxic stimuli. The understanding that the lethal actions of numerous antineoplastic agents are, in many instances, antagonized by cytoprotective signaling systems has been an important stimulus for the development of novel antineoplastic strategies. In this regard, inhibition of PKC, which has been shown to initiate apoptosis in a variety of malignant cell types, has recently been the focus of intense interest. Furthermore, there is accumulating evidence that selective targeting of PKC may prove useful in improving the therapeutic efficacy of established antineoplastic agents. Such chemosensitizing strategies can involve either (a) direct inhibition of PKC (e.g., following acute treatment with relatively specific inhibitors such as the synthetic sphingoid base analog safingol, or the novel staurosporine derivatives UCN-01 and CGP-41251) or (b) down-regulation (e.g., following chronic treatment with the non-tumor-promoting PKC activator bryostatin 1). In preclinical model systems, suppression of the cytoprotective function(s) of PKC potentiates the activity of cytotoxic agents (e.g., cytarabine) as well as ionizing radiation, and efforts to translate these findings into the clinical arena in humans are currently underway. Although the PKC-driven cytoprotective signaling systems affected by these treatments have not been definitively characterized, interference with PKC activity has been associated with loss of the mitogen-activated protein kinase (MAPK) response. Accordingly, recent pre-clinical studies have demonstrated that pharmacological disruption of the primary MEK-ERK module can mimic the chemopotentiating and radiopotentiating actions of PKC inhibition and/or down-regulation.
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    URL: http://dx.doi.org/10.1023/A:1006328303451
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    Activation-Induced Apoptosis of Peripheral Lymphocytes Treated with 7-Hydroxystaurosporine, UCN-01 (1999)
    Springer
    Investigational new drugs 17 (1999), S. 335-341 
    Details
    ISSN: 1573-0646
    Keywords: UCN-01 ; IL-2 receptor ; Fas ; Fas-ligand ; apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract 7-hydroxystaurosporine (UCN-01) is a new anticancer agentwhich exerts an inhibitory effect on cell cycle check points andis currently under phase I clinical trials in US and Japan.Preliminary clinical data indicated that UCN-01 remained inplasma at high concentrations for long periods of time. Thisunavoidable high plasma drug exposure is likely to lead tohematological toxicities in patients. In the present study,cultured human peripheral blood lymphocytes (PBLs) were used toevaluate the possible hematological toxicities of UCN-01treatment. UCN-01 induces apoptosis, and the induction ofapoptosis-related surface markers were also examined toinvestigate the involvement of these molecules in UCN-01-inducedapoptosis in PBLs. in vitroviability of PBLs wasdecreased by high dose of UCN-01 (25 μM, 3-day exposure). Thiseffect of UCN-01 was significantly suppressed by the presence ofhuman serum, suggesting that some specific inhibitory factor(s)in human serum may antagonize the lympholytic effect of UCN-01.The percentage of annexin V-positive PI-negative cells increasedwith exposure to UCN-01 in a time- and dose-dependent manner; byup to 30.3% after exposure to 25 μM UCN-01 for 3 days.At the same time, the expression of both interleukin-2 receptor(IL-2R, CD25) and Fas (CD95), analyzed by flow cytometry, wasinduced. Con A-stimulated PBLs were more sensitive toUCN-01-induced apoptosis than non-stimulated lymphocytes andUCN-01 increased the sFas-L released into culture medium from conA-stimulated PBLs. Therefore, lymphocyte depletion mediated byactivation-induced apoptosis is likely to occur in patientstreated with UCN-01 at high doses.
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    URL: http://dx.doi.org/10.1023/A:1006374118879
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    Influence of bcl-2 on antibody productivity in high cell density perfusion cultures of hybridoma (1999)
    Springer
    Cytotechnology 30 (1999), S. 95-106 
    Details
    ISSN: 1573-0778
    Keywords: apoptosis ; Bcl-2 ; fixed-bed ; hollow fibre ; hybridoma ; perfusion ; protein-free medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Apoptosis is an active, genetically determined death mechanism which can be induced by a wide range of physiological factors and by mild stress. It is the predominant form of cell death during the production of antibodies from murine hybridoma cell lines. A number of studies have now demonstrated that the suppression of this death pathway, by means of over-expression of survival genes such as bcl-2, results in improved cellular robustness and antibody productivity during batch culture. In the present study, the influence of bcl-2 expression on hybridoma productivity in two high density perfusion bioreactor systems was investigated. In the first system, a fixed-bed reactor, the DNA content in the spent medium was 25% higher in the control (TB/C3-pEF) culture than that found in the bcl-2 transfected (TB/C3-bcl2) cultures at all perfusion rates. This is indicative of a higher level of cell death in the control cell line. The average antibody concentration for the TB/C3-pEF cell line was 14.9 mg L-1 at perfusion rates of 2.6 and 5.2 d-1. However, for the TB/C3-bcl2 cell line it was 33 mg L-1 at dilution rates of 2 and 4 d-1. A substantial increase in antibody concentration was also found in the Integra Tecnomouse hollow fibre reactor. The antibody titre in the TB/C3-bcl2 cassette was nearly 100% higher than that in the TB/C3-pEF cassette during the cultivation period which lasted 6 weeks. Clearly, these results demonstrate the positive impact of bcl-2 over-expression on production of antibody in hybridoma perfusion cultures.
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    URL: http://dx.doi.org/10.1023/A:1008055702079
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    Effect of meteorology and nutrient load on oxygen depletion in a Danish micro-tidal estuary (1999)
    Springer
    Aquatic ecology 33 (1999), S. 55-64 
    Details
    ISSN: 1573-5125
    Keywords: estuaries ; nitrogen ; oxygen depletion ; phosphorus ; regression model ; vertical mixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e. 〈15% of saturation) by more than 50%.
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    URL: http://dx.doi.org/10.1023/A:1009956210537
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    Co-expression of bcl-2 and bag-1, apoptosis suppressing genes, prolonged viable culture period of hybridoma and enhanced antibody production (1999)
    Springer
    Cytotechnology 31 (1999), S. 143-151 
    Details
    ISSN: 1573-0778
    Keywords: antibody productivity ; apoptosis ; BAG-1 ; Bcl-2 ; cell survival ; hybridoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Human bcl-2 and bag-1 DNA were introduced into mouse hybridoma 2E3- O cells and expressed. The expression of bcl-2 in BCMGneo-bcl2 transfectants was confirmed by ELISA and that of bag-1 in pZeo-bag1 was confirmed by western blotting. In batch cultures, the over-expression of bcl-2 prolonged the culture period by 2 days and co-expression of bcl-2 and bag-1 prolonged the culture period by 3 days. The delayed increase in the dead cell number in culture of the bcl-2 and bag-1 cotransfectant indicated the additional antiapoptosis effect of bcl-2 and bag-1 cotransfection in comparison with the bcl-2 only transfection. The bcl-2 transfectants (2E3O-Bcl2) produced antibody twofold per batch culture in comparison with 2E3-O cells transfected with BCMGSneo (2E3O-Mock). Enhancement of this MoAb production was due to the improved survival of the cells and was not due to stimulation of antibody production rate per cell by Bcl-2 expression. And the bcl-2 and bag-1 co-transfectant (2E3O-Bcl2-BAG1) produced antibody approximately fourfold of 2E3O-Mock per batch culture. Enhancement of this MoAb production was due to the improved survival of the cells and was partly due to stimulation of MoAb production rate per cell in the non-growing phase by the cotransfection. The method to engineer hybridoma cells genetically with bcl-2 and bag-1 for increasing viability and productivity would be widely applied for improving antibody productivity of hybridoma cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008080407581
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    A novel 96-well scintillation proximity assay for the measurement of apoptosis (1999)
    Springer
    Cytotechnology 31 (1999), S. 271-282 
    Details
    ISSN: 1573-0778
    Keywords: annexin V ; Apo-2 ligand ; apoptosis ; Cytostar-T® scintillating microplates ; flow cytometry ; lymphotoxin (LT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The translocation of phospholipids across the plasma membrane has been widely documented as one of the earliest measurable biochemical events of apoptosis. Using fluorescently labelled annexin V, which preferentially binds phosphatidylserine (PS) in the presence of Ca2+, the externalization of PS can be measured and apoptosis quantified using flow cytometry. Conventional detection methods utilizing annexin V, while faster than in situ DNA end-labelling or DNA laddering, require extensive sample preparation which may compromise samples and makes rapid, high volume screening prohibitive. This paper describes a novel assay for the measurement of apoptosis based upon binding of radiolabelled annexin V to apoptotic cells attached to the growth surface of a 96-well scintillating microplate (Cytostar-T®). We compared measurements of apoptosis made by flow cytometry to those obtained with the scintillating microplate in three model systems, treatment of: mouse connective tissue (L-M) cells with lymphotoxin (LT), human lung carcinoma (H460) cells with Apo-2 ligand and human umbilical vein endothelial (HUVE) cells with staurosporine. In this assay, we compare both direct and indirect labelling methods by utilizing either iodinated annexin V or biotinylated annexin V/[35S] streptavidin to radiolabel apoptotic cells. The signal detected is a direct consequence of the binding of annexin V to externalized PS on apoptotic cells and the proximity of the label to the base of the plate. Using this method, separation of bound and unbound radiolabel signal occurs directly within the well resulting in a sensitive assay that requires minimal manipulation and can accomodate a large number of samples.
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    URL: http://dx.doi.org/10.1023/A:1008053320396
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    Effects of Potato-cyst Nematodes (Globodera pallida) and Soil pH on Root Growth, Nutrient Uptake and Crop Growth of Potato (1999)
    Springer
    European journal of plant pathology 105 (1999), S. 61-76 
    Details
    ISSN: 1573-8469
    Keywords: core sampling ; foliar nutrient concentrations ; minirhizotrons ; nitrogen ; phosphorus ; potassium ; Rhizolab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potato-cyst nematodes (Globodera pallida) cause severe yield losses in potato. Plants infected with potato-cyst nematodes generally have reduced concentrations of nitrogen, phosphorus and potassium in the foliage. This study investigated whether reduced growth of nematode-infected potato is caused by nutrient limitation. Experiments in the field and in containers showed that phosphorus concentration correlated best with total crop biomass at early stages of growth. The role of phosphorus in nematode damage was further investigated in the field and in the Wageningen Rhizolab. The experimental field was infested with potato-cyst nematodes and two levels of nematode density were established by fumigation with a nematicide. Prior applications of calcium carbonate resulted in pHKCl levels of 4.8 and 6.1. Two levels of phosphorus fertiliser were applied: either 0 or 225 kg P ha−1. In the Wageningen Rhizolab, soil of both pH levels from the field was used after treatment with 1 MRad gamma irradiation to kill the nematodes. Subsequently, half of the soil was inoculated with cysts to give a nematode density of 30 viable juveniles per gram of soil. In the field, nine weeks after planting, the total crop biomass ranged from 107 g m−2 for the treatment with nematodes at pHKCl 6.1 without phosphorus fertiliser to 289 g m−2 for the fumigated treatment at pHKCl 4.8 with phosphorus fertiliser. The differences in total biomass for the various treatments were explained by differences in foliar phosphorus concentration. Nematodes induced or aggravated P deficiency and reduced total biomass. This was not the only damage mechanism as at high, non-limiting levels of foliar phosphorus concentration, nematodes still reduced total biomass. In the Wageningen Rhizolab, directly after planting, the number of roots visible against minirhizotrons was reduced by nematodes. However, the increase of root number in the nematode treatment continued longer than in the control, until root number was higher than that of the control. The compensary root growth of the nematode treatment was restricted to the top 30 cm and nematodes reduced rooting depth. High soil pH reduced growth, mainly by reducing the availability of phosphate. Both nematodes and high soil pH reduced nutrient uptake per unit root length. Our results lead us to suggest an interaction between nematodes and soil pH, with nematode damage being higher at pHKCl 6.1 than at pHKCl 4.8.
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    URL: http://dx.doi.org/10.1023/A:1008641511688
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    Verotoxin/Globotriaosyl Ceramide Recognition: Angiopathy, Angiogenesis and Antineoplasia (1999)
    Springer
    Bioscience reports 19 (1999), S. 345-354 
    Details
    ISSN: 1573-4935
    Keywords: Glycolipid ; apoptosis ; intracellular traffic ; multidrug resistance ; ovarian carcinoma ; astrocytoma ; post transplant lymphoproliferative disease ; bone marrow purging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Verotoxin (VT) is involved in the etiology of both hemorrhagic colitis and the hemolytic uremic syndrome which are microvasculopathies of the colon and pediatric renal glomerulus respectively. Thus, VT can be considered a vasotoxin. Cell sensitivity in vitro varies according to the receptor glycolipid (globotriaosyl ceramide-Gb3) expression and also to intracellular trafficking of the receptor/toxin complex, such that in highly sensitive cells, the toxin is targeted to the endoplasmic reticulum and nuclear envelope. Such cells include tumor cells which have become drug resistant. Thus Gb3 is upregulated in certain tumors and when such tumor cells become drug resistant, their sensitivity to verotoxin increases. This may be due to a direct role of the MDR1 drug efflux pump in glycolipid biosynthesis. In addition to the tumor tissue, the toxin receptor may also be expressed in the tumor neovasculature suggesting that activated endothelial cells may be verotoxin sensitive. Thus VT may have both a direct and indirect antineoplastic potential. VT has proved highly effective in a xenograft cancer model and the possible therapeutic use of VT is discussed.
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    URL: http://dx.doi.org/10.1023/A:1020299819637
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    Ceramide Glycanase Activities in Human Cancer Cells (1999)
    Springer
    Bioscience reports 19 (1999), S. 449-460 
    Details
    ISSN: 1573-4935
    Keywords: ceramide glycanase ; cancer cells ; glycosphingolipid ; sphingosine ; ceramide ; apoptosis ; PPMP ; PDMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Ceramide glycanase (CGase) activities have been detected in different human tumor cells (colon, carcinoma Colo-205; neuroblastoma, IMR-32; breast cancer lines, SKBr3 and MCF7). However, the level of enzymatic activity is lower in these cells compared to that present in other mammalian tissues reported before (Basu, M., Kelly, P., Girzadas, M. A., Li, Z., and Basu, S. Methods Enzymol. (in press)). The majority of CGase activity was found in the 100,000g soluble supernatant fraction isolated from all these cell lines and tissues. Using the soluble enzyme, the requirement for optimum CGase activity was found to be consistent with previous observations found for rat and rabbit tissues (Basu, M., Dastgheib, S., Girzadas, M. A., O'Donnell, P. H., Westervelt, C. W., Li, Z., Inokuchi, J. I., and Basu, S. (1998) Acta Pol. Biochim. 42:327). The CGase activities from both Colo-205 and IMR-32 cells are optimum at a protein to detergent ratio of one. All the mammalian CGases, including human cancer cells, show an optimum pH between 5.5 and 5.8 in sodium acetate buffer. The CGase activities from cancer cells are found to be cation-independent; however, mercury, zinc, and copper ions seem to inhibit the enzyme activity substantially in both tumor cells lines. The mercury ion inhibition of CGase activities from all different sources indicates a possible structural homology in the CGase proteins. Radiolabeled substrates, labeled at the sphingosine double bond or at the 3-position of sphingosine without modifying double bond of sphingosine were used in this investigation. Both were active substrates with all enzyme preparations isolated from different cancer cells (apparent Km, 500 μM for nLcOse5[3H-DT]Cer and 350 μM for GgOse4[sph-3-3H]Cer with Colo-205 enzyme). Structural analogues of ceramide and sphingosine (L-PPMP, L-PDMP, alkylamines, and Tamoxifen) inhibited cancer cell CGase activities in vitro.
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    URL: http://dx.doi.org/10.1023/A:1020220524180
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    Adenosine-induced cell death: evidence for receptor-mediated signalling (1999)
    Springer
    Apoptosis 4 (1999), S. 197-211 
    Details
    ISSN: 1573-675X
    Keywords: Adenosine ; apoptosis ; necrosis ; physiopathological implications.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Adenosine modulates the proliferation, survival and apoptosis of many different cell types, ranging from epithelial, endothelial and smooth muscle cells, to cells of the immune and neural lineages. In this review, we critically discuss the available in vitro and in vivo data which support a role for adenosine in both development-associated apoptosis, and in diseases characterized by either pathologically increased cell death (e.g., ischemia, trauma and aging-associated neurodegeneration) or abnormally reduced spontaneous apoptosis (e.g., cancer). Particular emphasis is given to the possible role of extracellular adenosine receptors, since these may represent novel and attractive molecular targets for the pharmacological modulation of apoptosis. In some instances, adenosine-induced cell death has been demonstrated to require entry of the nucleoside inside cells; however, in many other cases, activation of specific adenosine extracellular receptors has been demonstrated. Of the four G protein-coupled adenosine receptors so far identified, the A2A and the A3 receptors have been specifically implicated in modulation of cell death. For the A3 receptor, results obtained by exposing both cardiomyocytes and brain astrocytes to graded concentrations of selective agonists suggest induction of both cell protection and cell death. Such opposite effects, which likely depend on the degree of receptor activation, may have important therapeutic implications in the pharmacological modulation of cardiac and brain ischemia. For the A2A receptor, recent intriguing data suggest a specific role in immune cell death and immunosuppression, which may be relevant to both adenosine-deaminase-immunodeficiency syndrome (a pathology characterized by accumulation of adenosine to toxic levels) and in tumors where induction of apoptosis via activation of specific extracellular receptors may be desirable. Finally, preliminary data suggest that, in a similar way to the adenosine-deaminase-immunodeficiency syndrome, the abnormal accumulation of adenosine in degenerative muscular diseases may contribute to muscle cell death. Although the role of adenosine receptors in this effect still remains to be determined, these data suggest that adenosine-induced apoptosis may also represent a novel pathogenic pathway in muscular dystrophies.
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    URL: http://dx.doi.org/10.1023/A:1009666707307
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    Apoptin®-induced apoptosis: a review (1999)
    Springer
    Apoptosis 4 (1999), S. 317-319 
    Details
    ISSN: 1573-675X
    Keywords: Anti-tumor therapy ; Apoptin® ; apoptosis ; Bcl-2 ; p53.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Apoptin, a protein encoded by an avian virus, induces apoptosis in various cultured human tumorigenic and/ or transformed cell lines, e.g. derived from breast and lung tumor, leukemia, lymphoma, osteosarcoma melanoma, cholangiocarcinoma, and hepatoma. In such cells, Apoptin induces p53-independent apoptosis, and the proto-oncogene Bcl-2 can accelerate this effect. The latter is surprising for, in general, Bcl-2 is known to inhibit e.g., p53-induced apoptosis. On the other hand, in normal non-transformed human cells, Apoptin is unable to induce apoptosis, even when Bcl-2 is over-expressed. In animal models Apoptin-induced apoptosis appears to be a safe and efficient anti-tumor agent. These data, in continuation with the observations that Apoptin is specifically stimulated by Bcl-2 in tumor cells, does not need p53, and is not inhibited by Bcr-Abl in these cells, imply that Apoptin is a potential anti-tumor therapy.
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    URL: http://dx.doi.org/10.1023/A:1009687019221
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    Apoptosis in ventricular myocytes: the role of tumor suppressor proteins (1999)
    Springer
    Apoptosis 4 (1999), S. 229-234 
    Details
    ISSN: 1573-675X
    Keywords: Adenovirus ; apoptosis ; Bcl-2 ; p53 ; Rb ; ventricular myocytes.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Apoptosis or programmed cell death is an important physiologic event crucial for the selective removal of damaged or unwanted cells from body tissues. In the cardiovascular system, apoptosis has been observed in the vasculature and myocardium. Untimely or inappropriate myocardial cell loss through an apoptotic process may contribute to ventricular remodeling and the ultimate demise of ventricular function following injury. Therapeutic interventions designed to modulate or prevent myocardial apoptotic cell loss may therefore prove beneficial in maintaining cardiac function. Incite into the molecular mechanisms that govern apoptosis in mammalian cells has led to the identification of several key factors that promote or prevent the apoptotic process. In this report, we discuss putative regulators of cardiac cell apoptosis with specific reference to the tumor suppressor proteins, p53 and Rb. The interplay between these factors, as well as the anti-apoptotic molecules related to the Bcl-2 the family are discussed in the context of the heart under normal and disease conditions.
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    URL: http://dx.doi.org/10.1023/A:1009640124029
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    Tau protein is involved in the apoptotic process induced by anti-microtubule agents on neuroblastoma cells (1999)
    Springer
    Apoptosis 4 (1999), S. 47-58 
    Details
    ISSN: 1573-675X
    Keywords: Anti-microtubule agents ; apoptosis ; doxorubicin ; neuroblastoma ; tau ; taxoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Paclitaxel and docetaxel are potent anti-microtubule and antimitotic agents that induce apoptosis in bone marrow-derived cells and epithelial cells. This study examined apoptosis induced by anti-microtubule agents in the neuroblastoma SK-N-SH cell line with a special focus on tau protein which is one of the main Microtubule-Associated- Proteins (MAPs) in neuronal cells. In time, treatment with 1 μM paclitaxel successively induced formation of bundles, then pseudo-asters concomitantly with mitotic block and phosphorylation of bcl-2 (48 h), then phosphorylation of tau and externalization of phosphatidylserine at the early phase of apoptosis (72 h) and finally DNA fragmentation (96 h). Similar results were obtained with 0.5 μM vinorelbine. Paclitaxel induced a lower increase in tau phosphorylation in differentiated SK-N-SH/RA+ cells which are less sensitive to apoptosis. Moreover, doxorubicin whose mechanism of action is independent of microtubules also induced immunostaining of tau at 72 h treatment. In conclusion, our results on neuroblastoma cells show that overexpression of hyperphosphorylated tau is involved in the apoptotic process induced by anti-microtubule agents and may be extended to others cytostatic drugs. Thus, tau protein may play a role in the cellular events observed in neuroblastoma cells undergoing apoptosis.
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    URL: http://dx.doi.org/10.1023/A:1009682116158
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    IL-3 induces apoptosis in a ras-transformed myeloid cell line (1999)
    Springer
    Apoptosis 4 (1999), S. 71-80 
    Details
    ISSN: 1573-675X
    Keywords: abl ; apoptosis ; interleukin-3 ; oncogenes ; ras.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Growth factors promote cell survival and proliferation. Homeostasis is maintained by programmed cell death which occurs when the growth stimulus is withdrawn, in response to negative growth regulators such as interferons, TNF-α and CD95 ligand, or following differentiation. Although acutely-transforming oncogenes often overcome the need for growth factors, growth regulatory cytokines can influence proliferative responses of transformed cells. In this study we investigated the effects of IL-3 on the proliferative responses of parental bone marrow-derived 32D cells and cells transformed with ras and abl oncogenes. We show that treatment of ras-transformed 32D cells with IL-3 reduced proliferative responses and decreased colony-forming ability. These effects were exacerbated in the absence of serum and associated with inhibition of tyrosine kinase activity, down-regulation of RAS and MYC expression, and induction of apoptosis as indicated by DNA fragmentation. In contrast, treatment of parental 32D cells with IL-3, which is obligatory for cell survival and proliferation, increased tyrosine kinase activity, upregulated MYC and RAS expression and maintained DNA integrity. With abl-transformed cells, proliferation and colony-forming ability were also inhibited by IL-3. Tyrosine kinase activity and MYC expression were reduced, but early apoptosis was not evident. Calcium uptake however, was stimulated by IL-3 in both parental and oncogene-transformed cells. These results suggest that threshold levels of tyrosine kinase activity are necessary for cell survival and proliferation and that with ras-transformed cells, IL-3 treatment may result in this threshold being breached. We conclude that in some situations, growth-promoting cytokines can inhibit proliferation of transformed cells and induce cell death by apoptosis.
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    URL: http://dx.doi.org/10.1023/A:1009686220607
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    Ameloblast apoptosis and IGF-1 receptor expression in the continuously erupting rat incisor model (1999)
    Springer
    Apoptosis 4 (1999), S. 441-447 
    Details
    ISSN: 1573-675X
    Keywords: ameloblasts ; amelogenesis ; apoptosis ; insulin-like growth factor.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Enamel-producing cells (ameloblasts) pass through several phenotypic and functional stages during enamel formation. In the transition between secretory and maturation stages, about one quarter of the ameloblasts suddenly undergo apoptosis. We have studied this phenomenon using the continuously erupting rat incisor model. A special feature of this model is that all stages of ameloblast differentiation are presented within a single longitudinal section of the developing tooth. This permits investigation of the temporal sequence of gene and growth factor receptor expression during ameloblast differentiation and apoptosis. We describe the light and electron microscopic morphology of ameloblast apoptosis and the pattern of insulin-like growth factor-1 receptor expression by ameloblasts in the continuously erupting rat incisor model. In the developing rat incisor, ameloblast apoptosis is associated with downregulated expression of the insulin-like growth factor-1 receptor. These data are consistent with the hypothesis that ameloblasts are “hard wired” for apoptosis and that insulin-like growth factor-1 receptor expression is required to block the default apoptotic pathway. Possible mechanisms of insulin-like growth factor-1 inhibition of ameloblast apoptosis are presented. The rat incisor model may be useful in studies of physiological apoptosis as it presents apoptosis in a predictable pattern in adult tissues.
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    URL: http://dx.doi.org/10.1023/A:1009600409421
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    Apoptotic cell death and related gene expression in metastatic tumors of AKR lymphomas of varying malignancy (1999)
    Springer
    Apoptosis 4 (1999), S. 429-440 
    Details
    ISSN: 1573-675X
    Keywords: AKR lymphoma malignancy variants ; apoptosis ; apoptosis-related gene expression ; tumor progression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Resistance to apoptosis may be related to tumor progression, due to the implications it might have on both tumor mass and genetic instability. We compared the tendency to spontaneous apoptosis and the proliferative capacity of metastatic growths of several AKR lymphoma variants (TAU-45, TAU-47, TAU-44, TAU-33, TAU-42 and TAU-46, in the order of increasing metastatic potential). We further compared the expression of several apoptosis-related genes. Cell proliferative capacity did not appear to determine malignant behavior since, on the whole, a decrease in S + G2M fraction was observed with increasing malignancy. Sensitivity to apoptotic cell death decreased with increasing malignancy when comparing the TAU-45, TAU-47, TAU-44 and TAU-33 variants, suggesting a role of reduced apoptosis in this T-cell lymphoma. An increase in Bcl-2 content with increasing aggressiveness among these variants, implicates this protein in this tumor progression-related resistance to apoptosis. However, the two variants of highest malignancy, TAU-42 and TAU-46, did not follow the same trend, since they displayed a relatively high content in apoptotic cells and a low Bcl-2 content. Fas receptor expression did not correlate with tendency to apoptosis, indicating that malignant behavior in the AKR lymphoma does not depend on CD95/Fas/APO1 downregulation. Overexpression of p53 was observed only in one of the variants of lowest malignancy.
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    URL: http://dx.doi.org/10.1023/A:1009648325350
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    Signalling steps in apoptosis by ether lipids (1999)
    Springer
    Apoptosis 4 (1999), S. 419-427 
    Details
    ISSN: 1573-675X
    Keywords: Anti-oxidant defence ; apoptosis ; ether lipids ; glutathione ; ionising radiation ; stress.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have investigated the mechanisms of induction of apoptosis by the antineoplastic ether lipid ET-18-OCH3 (ALP) in sensitive S49wt mouse lymphoma cells and ALP-resistant S49ar variants, both with wild-type p53, and in related L1210 cells with mutated p53. Ether lipid-resistant S49ar cells were cross-resistant to extracellular stress factors (cold shock, heat shock, H2O2, dimethylsulfoxide) and to radiation-induced apoptosis but not to physiological apoptotic signals (dexamethasone, growth factor deprivation, thapsigargin, C2-ceramide) and expressed similar levels of the apoptosis-regulating proteins Bcl-2, Bcl-X, Bax, Bad and Bak as did the parent S49wt cells. The uptake of [3H]-ALP was strongly reduced in the stress-resistant cells but this was not associated with significant differences in membrane cholesterol:phospholipid content nor in membrane microviscosity. In S49ar cells the activity of the antioxidant enzyme glutathione peroxidase (GSH-Px) was increased 4-fold and depletion of glutathione with the drug L-buthionine-S-R-sulfoximine (L-BSO) lowered the resistance of S49ar cells to ALP, stress factors and ionising radiation. The results indicate that ether lipids induce apoptosis by imposing a special form of physico-chemical stress, mediated by reactive oxygen species but independent of p53 status. The capacity of glutathione-dependent anti-oxidant defence appeared an important and shared determinant of the sensitivity to ether lipids, several types of extracellular stress and ionising radiation.
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    URL: http://dx.doi.org/10.1023/A:1009644208512
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    Sequential occurrence of mitochondrial and plasma membrane alterations, fluctuations in cellular Ca2+ and pH during initial and later phases of cell death (1999)
    Springer
    Apoptosis 4 (1999), S. 455-460 
    Details
    ISSN: 1573-675X
    Keywords: Annexin V ; apoptosis ; flow cytometry ; intracellular Ca2+ ; intracellular pH ; mitochondrial membrane potential.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The sequential occurrence of plasma and mitochondrial membrane alterations, intra-cellular pH shifts and changes in intracellular Ca2+ concentration after induction of cell death was monitored by flow cytometry in Jurkat and HSB2-cells. Cell death was induced by treatment with anti-Fas antibodies or by irradiation. Phosphatidylserine (PS) exposure and plasma membrane integrity were measured with FITC-Annexin V adhesion and by Propidium Iodide exclusion. Transition of the mitochondrial membrane potential was monitored by the occurrence of decay of DiOC6 fluorescence. Intracellular pH shifts were monitored by changes in the ratio of fluorescence at 575 nm and at 635 nm of SNARF-1-AM. Fluctuations in intracellular Ca2+ concentration were established by changes in Fura red quenching. The Jurkat cells were sensitive to anti-Fas treatment, while HSB-2 cells were not. HSB-2 cells appeared more sensitive to radiation damage than Jurkat cells. In all experiments the transition of mitochondrial membrane potential occurred first, almost immediately followed by PS exposure. Fluctuations in intracellular Ca2+ concentration occurred later and were less outspoken. A decrease in intracellular pH occurred not earlier than 24 hours after anti-Fas treatment. Chelation of intracellular Ca2+ concentration with BAPTA-AM had no effect on the time sequence of cell death related events.
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    URL: http://dx.doi.org/10.1023/A:1009604510329
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soilwater and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1007/BF01007574
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    Ecosystem constraints to symbiotic nitrogen fixers: A simple model and its implications (1999)
    Springer
    Biogeochemistry 46 (1999), S. 179-202 
    Details
    ISSN: 1573-515X
    Keywords: carbon dioxide ; grazing ; nitrogen fixation ; nitrogen limitation ; phosphorus ; shade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The widespread occurrence ofN limitation to net primary production (NPP) and other ecosystem processes, despite the ubiquitous occurrence ofN-fixing symbioses, remains a significant puzzle in terrestrial ecology. We describe a simple simulation model for an ecosystem containing a generic nonfixer and a symbioticN fixer, based on: (1) a higher cost forN acquisition byN fixers than nonfixers; (2) growth of fixers and fixation ofN only when lowN availability limits the growth of nonfixers, and other resources are available; and (3) losses of fixedN from the system only when the quantity of availableN exceeds plant and microbial demands. Despite the disadvantages faced by theN fixer under these conditions,N fixation and loss adjustN availability close to the availability of other resources, and biomass and NPP in this simple model can be substantially but only transientlyN limited. We then modify the model by adding: (1) losses ofN in forms other than excess availableN (e.g., dissolved organicN, trace gases produced by nitrification); and (2) constraints to the growth and activity ofN fixers imposed by differential effects of shading,P limitation, and grazing. The combination of these processes is sufficient to describe an open system, with input from both precipitation andN fixation, that is nevertheless stronglyN-limited at equilibrium. This model is useful for exploring causes and consequences of constraints toN fixation, and hence ofN limitation, and we believe it will also be useful for evaluating howN fixation and limitation interact with elevatedCO 2 and other components of global enviromental change.
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    URL: http://dx.doi.org/10.1007/BF01007579
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  • 47
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006156213761
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    Pharmacodynamics and Toxicodynamics of Drug Action: Signaling in Cell Survival and Cell Death (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 790-798 
    Details
    ISSN: 1573-904X
    Keywords: MAPK ; caspases ; chemopreventive agents ; phase II drug metabolizing enzymes ; apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In therapeutic response to drugs, the plasma concentration range leads to the establishment of a safe and effective dosage regimen. Our hypothesis is that by studying drug concentration-dependent effect on signal transduction mechanisms, a better understanding of the beneficial pharmacodynamic and adverse toxicodynamic responses elicited by the drug may be achieved. Using two classes of chemopreventive compounds (phenolic antioxidants and isothiocyanates), we illustrate the potential utility of two signal transduction pathways elicited by these agents to predict the pharmacodynamic effect (induction of Phase II drug metabolizing enzymes) and the potential toxicodynamic response (stimulation of caspase activity and cytotoxic cell death). At lower concentration, phenolic antioxidants and isothiocyanates activate mitogen-activated protein kinase (MAPK; extracellular signal-regulated protein kinase 2, ERK2; and c-Jun N-terminal kinase 1, JNK1) in a concentration-and time-dependent manner. The activation of MAPK by these compounds may lead to the induction of cell survival/protection genes such as c-jun, c-fos, or Phase II drug metabolizing enzymes. However, at higher concentrations, these agents activate another signaling molecule, ICE/Ced3 cysteine protease enzymes (caspases) leading to apoptotic cell death. The activation of these pathways may dictate the fate of the cells/tissues upon exposure to drugs or chemicals. At lower concentrations, these compounds activate MAPK leading to the induction of Phase II genes, which may protect the cells/tissues against toxic insults and therefore may enhance cell survival. On the other hand, at higher concentrations, these agents may activate the caspases, which may lead to apoptotic cell death, and have toxicity. Understanding the activation of these and other signal transduction events elicited by various drugs and chemicals may yield insights into the regulation of gene expression of drug metabolizing enzymes and cytotoxicity. Thus, the study of signaling events in cell survival (hemeostasis) and cell death (cytotoxicity) may have practical application during pharmaceutical drug development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011953431486
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  • 49
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    The limits of phosphorus removal in wetlands (1999)
    Springer
    Wetlands ecology and management 7 (1999), S. 165-175 
    Details
    ISSN: 1572-9834
    Keywords: flow ; loading ; models ; phosphorus ; removal limits ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphorus concentrations exported from wetlands are explored via data and a first order model. The graph of outlet concentration versus areal phosphorus loading is used to display these data and the model. For a given wetland, data and models show that P concentrations show an ‘S’ curve response to increasing P loadings. The lower plateau is the background concentration and the upper plateau is the inlet concentration. The position of the ascending limb between the two plateaus is positioned differently for different wetlands. Phosphorus (P) removal in wetlands is often typified by a stable decreasing gradient of P concentrations from inlet to outlet, and an accompanying stable decreasing gradient in P assimilation. Limits to removal are inherent in the physical, chemical and biological processes. A lower outlet concentration limit exists because of the P cycle in the un-impacted wetland. The loading at which the outlet concentration departs from background, the lower knee in the loading curve, varies from wetland to wetland. An upper outlet concentration limit is imposed by the source concentration for extremely high inflows. The first order mass balance equation interpolates between these limits. The model gives further insights about performance within an overall envelope. The water carrying capacity of the wetland precludes flows in excess of the hydraulic conveyance capacity, thus limiting the possible P loadings to the system. Conversely, extremely low hydraulic loadings cause the wetland to be dominated by atmospheric additions and losses. The central tendency of inter-system data in the North American Database is shown to be inadequate to draw generalized conclusions about ecosystem processes in an individual wetland. The proposed ‘one gram rule’ of Richardson, et al. (1997) is shown to be an over-simplification.
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    URL: http://dx.doi.org/10.1023/A:1008415401082
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  • 50
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    Effects of phosphorus nutrition on tiller emergence in wheat (1999)
    Springer
    Plant and soil 209 (1999), S. 283-295 
    Details
    ISSN: 1573-5036
    Keywords: leaf emergence ; phosphorus ; photosynthesis ; tillering ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus (P) deficiency limits the yield of wheat, particularly by reducing the number of ears per unit of area because of a poor tiller emergence. The objectives of this work were to (i) determine whether tiller emergence under low phosphorus availability is a function of the availability of assimilates for growth or a direct result of low P availability, (ii) attempt to establish a quantitative relation between an index of the availability of P in the plant and the effects of P deficiency on tiller emergence, and (iii) to provide a better understanding of the mechanisms involved in tiller emergence in field-grown wheat. Wheat (Triticum aestivum L., cv. INTA Oasis), was grown in the field under drip irrigation on a typic Argiudol, low in P (5.5 μg P g-1 soil Bray & Kurtz I) in Balcarce, Argentina. Treatments consisted of the combination of three levels of P fertilization 0, 60 and 200 kg P2O5 ha-1, and two levels of assimilate availability, a control (non-shaded) and 65% of reduction in incident irradiance from seedling emergence until the end of tillering (shaded). Phosphorus treatments significantly modified the pattern of growth and development of the plants. Shading reduced the growth and concentration of water-soluble carbohydrates in leaves and stems. Leaf photosynthetic rate at saturating irradiance was reduced by P deficiency, but was not affected by shading. At shoot P concentrations less than 4.2 g P kg-1 the heterogeneity in the plant population increased with respect to the number of plants bearing a certain tiller. At a shoot P concentration of 1.7 g P kg-1 tillering ceased completely. Phosphorus deficiency directly altered the normal pattern of tiller emergence by slowing the emergence of leaves on the main stem (i.e. increasing the phyllochron), and by reducing the maximum rate of tiller emergence for each tiller.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004690404870
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    The effect of regeneration burns on the growth, nutrient acquisition and mycorrhizae of Eucalyptus regnans F. Muell. (mountain ash) seedlings (1999)
    Springer
    Plant and soil 210 (1999), S. 273-283 
    Details
    ISSN: 1573-5036
    Keywords: ectomycorrhizae ; Eucalyptus regnans ; forest burns ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to compare the effects on the growth of Eucalyptus regnans seedlings of unheated soil and soil heated to different extents (as indicated by soil colour–bright red or black) in burnt logging coupes, and to separate the effects of heating of the soil on direct nutrient availability and on morphotypes and effectiveness of ectomycorrhizae. Burnt soils were collected from three logging coupes burnt 2, 14 and 25 months previously and unbumt soil from adjacent regrowth forests. Compared to unburnt soil, the early seedling growth was stimulated in black burnt soil from all coupes (burnt 2, 14 and 25 months previously). Seedling growth was generally poor in red burnt soil, especially in soil collected 2 months after burning. However, the concentration of extractable P was extremely high in red burnt soil, especially in soil collected 2 months after burning. In black burnt soil, extractable P was increased in soil 2 months after burning, but not in the soils collected 14 or 25 months after burning. However, both total P content and concentration in seedlings were increased in all collections of black burnt soil. Frequency of ectomycorrhizae was high in seedlings grown in all black burnt soils, but the mycorrhizal mantles were poorly developed in seedlings in black burnt soil collected 2 months after burning. Seedlings were also ectomycorrhizal in red burnt soil, except in soil collected 2 months after burning. Fine root inocula from seedlings grown in black burnt soils collected 14 and 25 months after burning significantly stimulated both seedling growth and P uptake compared with the uninoculated control, whereas the fine root inocula from the seedlings grown in all the other soils did not. These results suggest that, in black burnt soil, both direct nutritional changes and changes in the ectomycorrhizae may contribute to seedling growth promotion after regeneration burns. The generally poor seedling growth in red burnt soils is likely to have been due to N deficiency as the seedlings in these soils were yellow-green and the tissue concentrations of N were significantly lower than in other treatments.
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    URL: http://dx.doi.org/10.1023/A:1004609912315
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    Persistence of tree related patterns in soil nutrients following slash-and-burn disturbance in the tropics (1999)
    Springer
    Plant and soil 209 (1999), S. 137-157 
    Details
    ISSN: 1573-5036
    Keywords: fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
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    URL: http://dx.doi.org/10.1023/A:1004503023973
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    Nitrogen and phosphorus requirement of the microbiota in soils of the Bornhöved Lake district (1999)
    Springer
    Plant and soil 212 (1999), S. 173-181 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphatase activity ; phosphorus ; protease activity ; soil microbial biomass ; substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Estimating in situ N and P status of the soil microbiota is complicated because microbiological features reflect potentials rather than field conditions. Complementary microbiological assays were, therefore, combined to evaluate the N and P requirement of the microbiota in seven agricultural, grassland and forest topsoils of the Bornhöved Lake district as follows: (i) the sensitivity of the substrate-induced respiration (SIR) to supplemental addition of N and P was monitored during microbial growth and (ii) soil protease and phosphatase activities were analysed and related to soil mass and microbial biomass content. Nitrogen addition increased the maximal SIR rate in all except one soil indicating that the growth of organisms is restricted by this element when easily degradable C source is present. Supplemental N (and in some cases also P) retarded the respiratory response within the first 24 h which suggests microbial sensitivity and/or greater anabolic efficiency. With additional N the maximal SIR rate was most strongly enhanced in topsoils of the beech forest and the dystric alder forest. Thus, the microbial growth in these soils that were below litter horizons seems to be mostly restricted by N. Supplemental P positively affected respiratory response of soils under monoculture, wet grassland and dystric alder forest. In the dystric alder forest soil, high rates of alkaline and unbuffered phosphatase activity were observed when activity was related to either soil mass or microbial biomass content. The data of proteolytic and phospholytic enzymes are discussed with reference to nutrient deficiency and microbial strategy for N and P adsorption.
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    URL: http://dx.doi.org/10.1023/A:1004677427165
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    Root-induced modifications of the exchange of phosphate ion between soil solution and soil solid phase (1999)
    Springer
    Plant and soil 211 (1999), S. 103-110 
    Details
    ISSN: 1573-5036
    Keywords: bioavailability ; isotopic evaluation ; phosphate ion exchange ; phosphorus ; rhizosphere ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The uptake of phosphorus (P) by roots results in a depletion of phosphate ions (PO4) in the rhizosphere. The corresponding decrease in PO4 concentration in the soil solution (CP) gives rise to a replenishment of P from the solid phase which is time- and CP-dependent. This PO4 exchange which reflects the buffer power of the soil for PO4 also varies with the composition and the physico-chemical conditions of the soil. As root activity can modify these physico-chemical conditions in the rhizosphere, the question arises whether these modifications affect the ability of PO4 bound to the soil solid phase to exchange with PO4 in soil solution. The aim of the present work was to measure and compare the parameters which describe the amount of PO4 bound to soil solid phase that is capable to replenish solution P for both rhizosphere and bulk soils. The soil sample was a P-enriched, calcareous topsoil collected from a long-term fertiliser trial. Rhizosphere soil samples were obtained by growing dense mats of roots at the surface of 3 mm thick soil layer for one week. Three plant species were compared: oilseed rape (Brassica napus L., cv Goeland) pea (Pisum sativum L., cv. Solara) and maize ( Zea mays L., cv. Volga). The time- and CP-dependence of the PO4 exchange from soil to solution were described using an isotopic dilution method. The measured CP values were 0.165 mg P L−1 for bulk soil and 0.111, 0.101 and 0.081 mg P L−1 for rhizosphere soils of maize, pea and rape, respectively. The kinetics of the PO4 exchange between liquid and solid phases of soil were significantly different between rhizosphere and bulk soils. However, when changes in CP were accounted for, the parameters describing the PO4 exchange with time and CP between soil solution and soil solid phase were found to be very close for bulk and rhizosphere soils. For this calcareous and P-enriched soil, plant species differed in their ability to deplete PO4 in solution. The resulting changes in the ability of the soil solid phase to replenish solution PO4 were almost fully explained by the depletion of soil solution P.
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    URL: http://dx.doi.org/10.1023/A:1004485432261
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    Effect of ethrel on apoptosis in carrot protoplasts (1999)
    Springer
    Plant growth regulation 27 (1999), S. 119-123 
    Details
    ISSN: 1573-5087
    Keywords: apoptosis ; carrot protoplast ; DNA ladder ; ethrel ; ethylene ; nucleus condensation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In recent years, apoptosis has been reported to exist in plants during normal development and in response to stress. However, little is known about the relation of hormones to this form of programmed cell death. Here, we report examination of characteristics of apoptosis in carrot protoplasts induced by ethylene evolved from ethrel (2-chloroethylphosphonic acid). Nucleus condensation and DNA ladders were observed, and neutral comet assay, which detects DNA cleavage, also provided evidence that ethrel treatment resulted in nuclear DNA fragmentation. Strikingly, a close correlation between the incidence of DNA comets and the percentage of apoptotic protoplasts was shown in ethrel-treated carrot protoplasts. In conclusion, this study demonstrated that ethylene is an active inducer of apoptosis in carrot protoplasts, and that ethylene-induced plant cell death showed characteristics similar to those of apoptosis in animals.
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    URL: http://dx.doi.org/10.1023/A:1006105101813
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    Qualitative and quantitative investigations of phytoplankton in Lake Ringsjön, Scania, Sweden (1999)
    Springer
    Hydrobiologia 404 (1999), S. 27-40 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; fish reduction ; phosphorus ; biomanipulation ; blue-green algae ; cyanobacteria ; Microcystis ; Anabaena ; Aphanizomenon ; Aulacoseira ; cryptomonads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The algal record from Lake Ringsjön covers a period of more than 100 years. Towards the end of the 19th century, the lake had a well-functioning commercial fishery, when a brownish mess began to appear in the water, clogging-up the fishing nets and making fishing difficult. This was the first record of algal problems in the lake. Following complaints from the fishermen, the algal flora was investigated and the mess was stated to be a mass development of diatoms belonging to the genus Melosira ( Aulacoseira). Diatom maxima then appeared regularly in spring and autumn, whereas blue-green algae only occurred occasionally and in low abundances. Between 1900 and 1950, nutrient concentrations slowly increased in the lake. Algal blooms of Anabaena lemmermannii and Gloeotrichia echinulata began to appear in summer. Between 1960 and 1980, the lake developed into a hypertrophic status with extensive blooms of blue-green algae from May to October, including high biomasses of mainly Microcystis spp. This severe pollution started with increased usage of the lake, increased tourism and recreation, intensified farming with the introduction of artificial fertilization, and also the diversion of sewage water from a sewage treatment plant. In 1968, cattle death was reported and in 1981, algal toxicity was verified by mouse bioassay. After a period of extremely poor water quality, the lake began to show signs of improvement as a result of the nutrient and fish reduction programmes. The very heavy blooms of blue-green algae decreased and the duration of blooms became shorter. The Microcystis species were to a certain extent replaced by Anabaena and Aphanizomenon species, and biodiversity of algae increased. With respect to the algal community, the lake has improved considerably, but is still eutrophic and suffers summer blooms of toxic blue-green algae.
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    URL: http://dx.doi.org/10.1023/A:1003757504155
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    Synthesis of theoretical and empirical experiences from nutrient and cyprinid reductions in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 145-156 
    Details
    ISSN: 1573-5117
    Keywords: biomanipulation ; nutrient reduction ; zooplankton ; phytoplankton ; bottom-up ; top-down ; phosphorus ; submerged vegetation ; benthic macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
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    URL: http://dx.doi.org/10.1023/A:1003788900521
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    Relationships between eutrophication variables: from nutrient loading to transparency (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 375-387 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; multi-lake studies ; phosphorus ; nitrogen ; chlorophyll-a ; transparency ; zooplankton ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring data obtained from 231 freshwater lakes and ponds in the Netherlands, covering the period 1980–1996, were used to analyse the relationships between (a) transparency and chlorophyll-a, and the effect of system characteristics on this relationship, (b) chlorophyll-aand nutrient concentrations, and the effect of biological variables and (c) nutrient concentrations and nutrient loading. (a) Chlorophyll-aimposes a maximum on water transparency, but deviations from this maximum can be large. Reducing chlorophyll-a, therefore, does not guarantee a sufficient improvement of transparency. Soil type and the average depth of a lake were shown to influence the relationship between chlorophyll-aand transparency. (b) The maximum ratios of both chlorophyll-a: total-P and chlorophyll-a: total-N were higher in systems dominated by filamentous cyanobacteria than in systems dominated by other algae, indicating the efficiency of the former group with respect to nutrients. In systems with an areal coverage with submersed macrophytes above 5%, concentrations of chlorophyll-aand nutrients were lower than in systems with lower coverages. The ratios between chlorophyll-aand nutrients were lower at coverages larger than 10%. This indicates both bottom-up and top-down control of algae by macrophytes. Grazing pressure by zooplankton was also found to lower the chlorophyll-a: nutrient ratios. (c) System specific linear relationships were found between the average concentrations of total-P and total-N in the incoming water and the summer mean concentration in the lake. This allows the assessment of admissible loads for individual lakes, with narrower confidence limits compared to traditional relationships based on combined data from many lakes. From the analysis, it is concluded that the chain of relationships from nutrient loading to transparency is complex, and depends on biological variables as well as system characteristics.
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    URL: http://dx.doi.org/10.1023/A:1017090931476
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    Relationships of some ecological factors with the associations of vegetation in British rivers (1999)
    Springer
    Hydrobiologia 415 (1999), S. 117-122 
    Details
    ISSN: 1573-5117
    Keywords: vegetation ; floristic associations ; habitat ; enrichment ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During River Habitat Surveys on the physical structure of watercourses in Britain between 1995 and 98, detailed assessments of the floristic associations, physical habitat and water chemistry were made at 165 sites over a wide range of vegetation types. Botanical data from a total of 340 relevés from within these RHS were recorded. The vegetation was classified phyto-sociologically on the basis of the abundance of characteristic species, resulting in 45 aquatic, swamp and mire associations being identified together with nine other communities which could not be completely classified phyto-sociologically. The associations were assigned to 22 alliances, 13 orders and 11 classes excluding communities dominated by filamentous algae. Water enrichment (as soluble and total phosphorus) was the most significant factor for the differentiation of the communities but pH, conductivity and alkalinity were also important.
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    URL: http://dx.doi.org/10.1023/A:1003820308436
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    Biomass characterization of Azolla filiculoides grown in natural ecosystems and wastewater (1999)
    Springer
    Hydrobiologia 415 (1999), S. 323-327 
    Details
    ISSN: 1573-5117
    Keywords: biofilter ; productivity ; phosphorus ; water quality ; Azolla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aquatic pteridophyte Azolla, a small-leaf floating plant, which lives in symbiosis with a nitrogen fixing cyanobacteria, Anabaena azollae, was widespread throughout water channels and hydrographic basins of Portugal. Azolla is also the aim of a study for its utilization as a biofilter for wastewater purification, namely for phosphorus removal (± 36%). The goal of this work is to compare the growth characteristics and biomass composition of this water fern in natural ecosystems with those obtained in some wastewaters. Plant growth rate (0.107± 0.037 d-1) and productivity (5.8 g dw m-2 d-1) suggest that Azolla can grow well in partially treated domestic wastewater, but not in diluted pig wastes. This fact, associated to its biomass composition, namely in phosphorus content (1.38 ±0.20%), increase the possibility of this plant being used to improve wastewater discharge quality. It may also be possible to use the biomass as a biofertiliser or as a feed supplement for aquatic and terrestrial animals due to its protein, crude fiber and mineral content.
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    URL: http://dx.doi.org/10.1023/A:1003824426183
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    URL: http://dx.doi.org/10.1007/BF00993000
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1× 104 kg nitrogen and 3.91×104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7×104 kg (676 kg/ha) nitrogen and 3.88×104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55×104 kg nitrogen and 0.40×104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    URL: http://dx.doi.org/10.1007/BF00992870
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    Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 21-34 
    Details
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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    Pore water N and P concentration in a floodplain marsh of the Lower Paraná River* (1999)
    Springer
    Hydrobiologia 392 (1999), S. 65-71 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; pore water ; macrophyte ; floodplain ; Paraná River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4 + concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4 + depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4 + and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4 + did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3 - contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.
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    Poor water quality in Loch Leven (Scotland) in 1995 in spite of reduced phosphorus loadings since 1985: the influences of catchment management and inter-annual weather variation (1999)
    Springer
    Hydrobiologia 403 (1999), S. 135-151 
    Details
    ISSN: 1573-5117
    Keywords: lake ; phosphorus ; loading ; restoration ; Loch Leven ; Scotland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eight tonnes of phosphorus in all forms (total phosphorus, TP) entered Loch Leven from its catchment in 1995, compared to 20 t in 1985. Diffuse run-off from the land, and waste from over-wintering geese contributed 59% of the total loading in 1995 cf. 42% in 1985. Point-sources of sewage, and waste-water from fish-rearing ponds, produced the rest. Inputs of phosphorus in soluble reactive form (SRP) totalled 5 t, i.e. 63% of the TP loading in 1995, as compared with 1985 values of 11.8 t and 59%. Point-sources of SRP contributed 54% of the total SRP input in 1995 cf. 69% in 1985. Loadings from three sewage treatment works (STW) totalled 3.1 t TP in 1995 as compared with 5.3 t in 1985; this included 2.6 t SRP (cf. 3.6 t). Daily per capita outputs of the upgraded Kinross North and Milnathort STWs were 0.68 g and 0.81 g TP, respectively, compared with pre-upgrade values of 1.77 g and 2.03 g. Nett reductions in TP and SRP loadings between 1985 and 1995, are 55% and 59% respectively. These values are attributable as much to the lower rainfall of 890 mm over the period of study in 1995, compared to 1250 mm in 1985, as to ‘managed’ elimination of P usage at a major industrial source, and upgrades of STWs. In spite of these cutbacks, a combination of the lower rainfall and an extraordinarily hot summer in 1995 negated the expected reduction in lake phosphorus and chlorophyll levels. The lowered specific areal loading of ca. 0.7 g P m−2 estimated for 1995 still considerably exceeds the ideal maximum for the loch. These statistics nevertheless ignore the significance of a reduction of ca. 7 t in P entering the system in bio-available form, a recently completed upgrade of a major STW and channelling of effluent from a small works out of the catchment.
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    Simulating the effects of biomanipulation on the food web of Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 131-144 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; model ; excretion ; grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjön, in particular the long-term effects of biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment and lake water. The model simulates densities of fish and phytoplankton adequately, both before and after biomanipulation, although the actual lake phytoplankton density varied more year-to-year compared to the model predictions. According to the model, a biomanipulation will cause an increase in zooplankton biomass. This prediction contradicts available field data from the lake which do not indicate any significant change in zooplankton biomass resulting from the performed biomanipulation. This discrepancy may partly be attributed to structural uncertainties in the model, related to the size structure of predators on zooplankton, i.e. the omnivorous fish community. The simulations suggest that phosphorus was routed along the pelagic food chain to a larger extent after omnivorous fish were removed, whereas the amount of phosphorus routed via the sediment and benthivorous fish decreased following fish removal. Accordingly, translocation of phosphorus from sediment to water by benthivorous fish is predicted to be substantially reduced by biomanipulation, resulting in an overall reduction in the release of new phosphorus to phytoplankton. Irrespective of simulated fishing effort (reduction of ≤0.5% d−1 for two years), the model predicts that P-release from the sediment and the external load will remain sufficiently high to force the system back to its previous state within a decade. Thus, recurrent biomanipulations and/or combined abatement strategies may be necessary to maintain low phytoplankton density. Known structural model uncertainties may however affect the robustness of such detailed predictions about the system resilience.
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    Internal phosphorus loading in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 19-26 
    Details
    ISSN: 1573-5117
    Keywords: sediment ; phosphorus ; eutrophication ; biomanipulation ; fish ; Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ringsjön did not respond with decreased algal production following a substantial reduction in external phosphorus loading. This is typical of many shallow lakes which for decades have received excessive amounts of nutrients. The inertia is due to large amounts of phosphorus (P) stored in sediments and biota, causing internal phosphorus loading. Much of this phosphorus is thought to be released from the organic-rich profundal sediments. In Lake Ringsjön, only one third of the total bottom area is covered by such sediments, the rest being dominated by sand and silt. In the profundal sediments bulk P content was not exceptionally high (approximately 2 mg P·g DW−1), while the pore water phosphate concentrations, especially in Sätofta Basin, were very high, indicating large potential for phosphorus release to the water. This is also indicated by the large proportion of Fe- and Al-bound P in the sediments of Sätofta Basin. Although there are no direct quantifications of phosphorus release from the sediments in Lake Ringsjön, measurements of phosphorus concentrations in the water mass as well as budget calculations for the three basins clearly show a high capacity for internal loading. Phosphorus concentrations generally increase during summer, when external additions are minimal. Until 1980, the annual external phosphorus addition to Lake Ringsjön greatly exceeded the output, showing that the lake was an efficient phosphorus trap. Since then, input and output have been balanced, but in recent years signs that the lake is once again retaining phosphorus on an annual basis are evident. There are marked differences between the three basins, with Western Basin generally retaining phosphorus, while the upstream Eastern Basin and Sätofta Basin during the 1980s often exported phosphorus. It is not possible to evaluate the effects of the fish biomanipulation on the internal loading of phosphorus from the sediment.
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    Simulating the effects of biomanipulation on the food web of Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 131-144 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; model ; excretion ; grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dynamic, process-oriented, deterministic and phosphorus-based model was developed to simulate the food web dynamics of Lake Ringsjön, in particular the long-term effects of biomanipulation in terms of reduction of omnivorous fish. The model contains 14 state variables, each with a differential equation describing sources and sinks of phosphorus. The state variables encompass piscivorous and omnivorous fish, zooplankton, phytoplankton, sediment and lake water. The model simulates densities of fish and phytoplankton adequately, both before and after biomanipulation, although the actual lake phytoplankton density varied more year-to-year compared to the model predictions. According to the model, a biomanipulation will cause an increase in zooplankton biomass. This prediction contradicts available field data from the lake which do not indicate any significant change in zooplankton biomass resulting from the performed biomanipulation. This discrepancy may partly be attributed to structural uncertainties in the model, related to the size structure of predators on zooplankton, i.e. the omnivorous fish community. The simulations suggest that phosphorus was routed along the pelagic food chain to a larger extent after omnivorous fish were removed, whereas the amount of phosphorus routed via the sediment and benthivorous fish decreased following fish removal. Accordingly, translocation of phosphorus from sediment to water by benthivorous fish is predicted to be substantially reduced by biomanipulation, resulting in an overall reduction in the release of new phosphorus to phytoplankton. Irrespective of simulated fishing effort (reduction of ≤0.5% d−1 for two years), the model predicts that P-release from the sediment and the external load will remain sufficiently high to force the system back to its previous state within a decade. Thus, recurrent biomanipulations and/or combined abatement strategies may be necessary to maintain low phytoplankton density. Known structural model uncertainties may however affect the robustness of such detailed predictions about the system resilience.
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    Internal phosphorus loading in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 19-26 
    Details
    ISSN: 1573-5117
    Keywords: sediment ; phosphorus ; eutrophication ; biomanipulation ; fish ; Sweden
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ringsjön did not respond with decreased algal production following a substantial reduction in external phosphorus loading. This is typical of many shallow lakes which for decades have received excessive amounts of nutrients. The inertia is due to large amounts of phosphorus (P) stored in sediments and biota, causing internal phosphorus loading. Much of this phosphorus is thought to be released from the organic-rich profundal sediments. In Lake Ringsjön, only one third of the total bottom area is covered by such sediments, the rest being dominated by sand and silt. In the profundal sediments bulk P content was not exceptionally high (approximately 2 mg P·g DW−1), while the pore water phosphate concentrations, especially in Sätofta Basin, were very high, indicating large potential for phosphorus release to the water. This is also indicated by the large proportion of Fe- and Al-bound P in the sediments of Sätofta Basin. Although there are no direct quantifications of phosphorus release from the sediments in Lake Ringsjön, measurements of phosphorus concentrations in the water mass as well as budget calculations for the three basins clearly show a high capacity for internal loading. Phosphorus concentrations generally increase during summer, when external additions are minimal. Until 1980, the annual external phosphorus addition to Lake Ringsjön greatly exceeded the output, showing that the lake was an efficient phosphorus trap. Since then, input and output have been balanced, but in recent years signs that the lake is once again retaining phosphorus on an annual basis are evident. There are marked differences between the three basins, with Western Basin generally retaining phosphorus, while the upstream Eastern Basin and Sätofta Basin during the 1980s often exported phosphorus. It is not possible to evaluate the effects of the fish biomanipulation on the internal loading of phosphorus from the sediment.
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    Qualitative and quantitative investigations of phytoplankton in Lake Ringsjön, Scania, Sweden (1999)
    Springer
    Hydrobiologia 404 (1999), S. 27-40 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; fish reduction ; phosphorus ; biomanipulation ; blue-green algae ; cyanobacteria ; Microcystis ; Anabaena ; Aphanizomenon ; Aulacoseira ; cryptomonads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The algal record from Lake Ringsjön covers a period of more than 100 years. Towards the end of the 19th century, the lake had a well-functioning commercial fishery, when a brownish mess began to appear in the water, clogging-up the fishing nets and making fishing difficult. This was the first record of algal problems in the lake. Following complaints from the fishermen, the algal flora was investigated and the mess was stated to be a mass development of diatoms belonging to the genus Melosira ( Aulacoseira). Diatom maxima then appeared regularly in spring and autumn, whereas blue-green algae only occurred occasionally and in low abundances. Between 1900 and 1950, nutrient concentrations slowly increased in the lake. Algal blooms of Anabaena lemmermannii and Gloeotrichia echinulata began to appear in summer. Between 1960 and 1980, the lake developed into a hypertrophic status with extensive blooms of blue-green algae from May to October, including high biomasses of mainly Microcystis spp. This severe pollution started with increased usage of the lake, increased tourism and recreation, intensified farming with the introduction of artificial fertilization, and also the diversion of sewage water from a sewage treatment plant. In 1968, cattle death was reported and in 1981, algal toxicity was verified by mouse bioassay. After a period of extremely poor water quality, the lake began to show signs of improvement as a result of the nutrient and fish reduction programmes. The very heavy blooms of blue-green algae decreased and the duration of blooms became shorter. The Microcystis species were to a certain extent replaced by Anabaena and Aphanizomenon species, and biodiversity of algae increased. With respect to the algal community, the lake has improved considerably, but is still eutrophic and suffers summer blooms of toxic blue-green algae.
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    The N and P budget of the shallow, flushed lake Müggelsee: retention, external and internal load (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 159-166 
    Details
    ISSN: 1573-5117
    Keywords: shallow lake ; nutrient loading ; retention ; nitrogen ; phosphorus ; release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shallow (mean depth 4.9 m), polymictic and eutrophic lake Müggelsee was highly loaded with phosphorus (6 gP m-2a-1) and nitrogen (170 gN m-2a-1) by the river Spree up to the end of the 1980s. Annual load declined by 40–50% during the last years (1991–97). Phosphorus retention fluctuated strongly during the seasonal cycle between −200 and +100 kgP d-1and from year to year between −44% and + 26% of the P import. At the end of the eighties, the P retention capacity of the sediment was exceeded and Müggelsee became a source of phosphorus. The lake regained its ability to retain P in the sediments after external load reduction in the 1990s. However, the internal load of P reached the level of the external one. The release of P during summer was strongly related to the import of nitrate. On long-term average (1979–1997), less than 1% of the P input was retained in Müggelsee. About 24% of the nitrogen load were removed in the lake on annual mean. This rate decreased during the last years.
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    URL: http://dx.doi.org/10.1023/A:1017023717324
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    Surficial sediment composition as a record of environmental changes in the catchment of shallow Lake Petersdorf, Brandenburg, Germany (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 185-192 
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    ISSN: 1573-5117
    Keywords: shallow lake ; sediment ; dy ; phosphorus ; calcium ; metals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A chemical characterization of the surficial sediment (0–20 cm) of type `dy' (org-Cpart/TNpart〉10) of the anthropogenically polluted shallow Lake Petersdorf is presented. Eighty samples were analyzed for a set of parameters, i.e. dry weight, loss on ignition (LOI), total inorganic carbon (TIC), N, S, P, Ca, Si, As, Fe, Al, Mn, Zn, Cd, and Pb. LOI, TIC, N, S, Ca, P, and Zn tend to accumulate at a water depth 〉2 m (70.6% of the lake surface) in contrast to Mn and Fe which are more widely distributed, and Cd and Pb which are accumulated in the lake part close to a road. The enrichment factors of certain elements, e.g. Al (23.9%), Si (31.5%), P (12.2%), and Ca (68.7%) from 20 cm sediment depth up to the surface, are attributed to incisive changes in the immediate catchment. Erosion, fertilization, amelioration, and separation of the peatland north of the lake by a dam within the last 60 yrs resulted in the change of Lake Petersdorf from a dystrophic to a eutrophic stage. This enhanced the mineralization of its meso-humic (LOI/TNpart=20.6) sediment.
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    URL: http://dx.doi.org/10.1023/A:1017059330528
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    Long-term phytoplankton changes in acid and limed lakes in SW Sweden (1999)
    Springer
    Hydrobiologia 394 (1999), S. 93-102 
    Details
    ISSN: 1573-5117
    Keywords: acidification ; phosphorus ; oligotrophication ; cyanophyceans ; desmids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton development in the acidified Lakes Östra Nedsjön and Ömmern, situated in SW Sweden, was followed during 1973–92. The former lake was first limed in 1971–73 which increased the pH value from ca 5.3 to 6, without affecting the plankton markedly. In Lake Ömmern, acidification lowered the pH value from ca 6 to 5.3 during 1976–1981, which caused oligotrophication and reduced number of species. In 1981/82 both lakes were limed, and during the following period treatments were regularly made, resulting in average pH levels of 7.2 and 6.9, respectively. The concentrations of humic compounds and phosphorus increased and the distribution of the major plankton groups was markedly changed. In both lakes the cyanophycean volume decreased, whereas diatoms became quantitatively important. Especially in relation to the acidic period 1979–81, there was increased species richness in both lakes. However, in contrast to the development in Lake Ömmern, the desmids were eliminated in Lake Ö.Nedsjön, where the pre-acidification phytoplankton was not restored.
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    A reservoir in management-induced transition between ecological states (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 325-333 
    Details
    ISSN: 1573-5117
    Keywords: reservoir ; phosphorus ; algal blooms ; water treatment ; ferric dosing ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of phosphorus control on the nutrient dynamics and biological activity of Foxcote Reservoir, a small impounded reservoir operated by Anglian Water are discussed. Phosphorus precipitation using iron salts was commenced in 1981 to improve the treatability of previously algal-laden water and continued until 1994 when the reservoir was closed as a water supply source. A marked decrease in algal biomass was observed after an initial delay, which coincided with an increase in the abundance of aquatic macrophytes. There were also marked shifts in the macrophyte community during the following 10 years, with an increase in Elodea and an initial increase then decline in Chara. The zooplankton community also changed with an increase in the larger bodied Daphma pulex. No overall change in the rate of denitrification was observed, although patterns of silica depletion showed changes in frequency. Trends in wildfowl counts over this period reflect changes in the ecology of the reservoir.
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    Legislative challenges for lake eutrophication control in Europe (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 389-401 
    Details
    ISSN: 1573-5117
    Keywords: legislation ; eutrophication ; phosphorus ; nitrogen ; wildlife conservation ; SSSI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is no single piece of legislation which comprehensively addresses the problem of eutrophication of freshwater lakes. An examination is made of the extent to which national and EU laws applicable in England and Wales may be used to reduce phosphorus inputs to eutrophicated lakes. This case study is then used to outline the shortcomings of existing legislation and the future challenges for lake eutrophication control. Applicable legislation may be divided into that relating to nature conservation, to water quality and to agricultural extensification. Nature conservation laws are applicable, in that lakes designated as Sites of Special Scientific Interest (SSSIs), are theoretically safeguarded from degradation. The main limitation of the SSSI system lies in the boundary definition process under which, as a rule, no other category of legally protected land may be designated. Thus, the use of surrounding buffer land to protect water quality at the catchment level is generally precluded. The introduction of consultation areas around SSSIs of international importance under the EU Directive on Habitats is unlikely to alleviate the problem, since the area involved remains minimal compared to the extent of the majority of catchments. Intensive agricultural practices are responsible for significant nutrient enrichment of rivers and lakes, so that legislation aimed at extensification is also relevant. Examples of agricultural extensification include the Environrnentally Sensitive Areas programme and various options available for Set-Aside land. However, the prime purpose of such initiatives is the alleviation of surplus and budgetary problems and, as such, they fall short of a fully integrated approach to the ecological management of farmland. Nutrient enrichment is, essentially, a water quality issue, but policy and legislation in this area are not yet sufficiently developed to address the problem comprehensively. The current regulatory process for water quality carries the potential to work comparatively well for point sources under the system of consents to discharge. This potential is limited, however, by the paucity of information available on ecologically acceptable concentrations of phosphorus in discharges. In addition, the consents system is not constructed to deal effectively with diffuse agricultural losses of phosphorus, since, unlike point sources, these tend to arise from the cumulative effect of many activities. The main legislative challenge for lake eutrophication control lies in the area of diffuse agricultural losses of phosphorus. In this respect, experience in the U.S.A. reveals that the use of comprehensive and catchment-wide ‘Best Management Practices’ is capable of producing significant water quality improvements, providing that some degree of mandatory compliance is incorporated.
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    Lake and catchment management in Denmark (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 419-432 
    Details
    ISSN: 1573-5117
    Keywords: Integrated lake management ; biomanipulation ; lake recovery ; phosphorus ; nitrogen ; eutrophication ; restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The majority of Danish lakes are highly eutrophic due to high nutrient input from domestic sources and agricultural activities. Reduced nutrient retention, and more rapid removal, in catchments as a result of agricultural drainage of wetlands and lakes and channelisation or culverting of streams also play a role. Attempts have recently been made to reduce nutrient loading on lakes by intervening at the source level and by improving the retention capacity of catchment areas. The former measures include phosphorus stripping and nitrogen removal at sewage works, increased use of phosphate-free detergents, and regulations concerning animal fertiliser storage capacity, fertiliser application practices, fertilisation plans and green cover in winter. In order to improve nutrient retention capacity of catchments, wetlands and lakes have been re-established and channelised streams have been remeandered. In addition, cultivation-free buffer strips have been established alongside natural streams and there has been a switch to manual weed control. These measures have resulted in a 73% reduction of the mean total phosphorus concentration of point-source polluted streams since 1978; in contrast, there has been no significant change in the total nitrogen concentration. Despite the major reduction in stream phosphorus concentrations, lake water quality has often not improved. This may reflect a too high external or internal phosphorus loading or biological resistance. Various physico-chemical restoration measures have been used, including dredging and oxidation of the hypolimnion with nitrate and oxygen. Biological restoration measures have been employed in 17 Danish lakes. The methods include reducing the abundance of cyprinids, stocking with 0+ pike ( Esox lucius) to control 0+ cyprinids, and promoting macrophyte recolonization by protecting germinal submerged macrophyte beds against grazing waterfowl and transplanting out macrophyte shoots. In several lakes, marked and long-lasting improvements have been obtained. The findings to date indicate that fish manipulation has a long-term effect in shallow lakes, providing nutrient loading is reduced to a level so low as to ensure an equilibrium lake water phosphorus concentration of less than 0.05–0.1 mg phosphorus l−1. If nitrogen loading is very low, however, positive results may be obtained at higher phosphorus concentrations. Macrophyte refuges and transplantation seem to be the most successful as restoration measures in the same nutrient-phosphorus regime as fish manipulation.
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    URL: http://dx.doi.org/10.1023/A:1017071602549
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    URL: http://dx.doi.org/10.1023/A:1006076405557
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 × 104 kg nitrogen and 3.91 × 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 × 104 kg (676 kg/ha) nitrogen and 3.88 × 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 × 104 kg nitrogen and 0.40 × 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    URL: http://dx.doi.org/10.1023/A:1006073408623
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    The fate of NH4NO3 added toSphagnum magettanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m−2 yr−1 were made toSphagnum magellanicurn cores at two-week intervalsin situ at four sites across Europe, i.e. Lakkasuo (Finland). Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N∶P ratio 68) and greatest in Moidach More (N∶P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4 + in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3 − were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition bySphagnum mosses.
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    URL: http://dx.doi.org/10.1007/BF00992874
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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    URL: http://dx.doi.org/10.1007/BF01007576
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soil-water and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1023/A:1006152112852
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    Ecosystem constraints to symbiotic nitrogen fixers: a simple model and its implications (1999)
    Springer
    Biogeochemistry 46 (1999), S. 179-202 
    Details
    ISSN: 1573-515X
    Keywords: carbon dioxide ; grazing ; nitrogen fixation ; nitrogen limitation ; phosphorus ; shade
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The widespread occurrence of N limitation to net primary production (NPP) and other ecosystem processes, despite the ubiquitous occurrence of N-fixing symbioses, remains a significant puzzle in terrestrial ecology. We describe a simple simulation model for an ecosystem containing a generic nonfixer and a symbiotic N fixer, based on: (1) a higher cost for N acquisition by N fixers than nonfixers; (2) growth of fixers and fixation of N only when low N availability limits the growth of nonfixers, and other resources are available; and (3) losses of fixed N from the system only when the quantity of available N exceeds plant and microbial demands. Despite the disadvantages faced by the N fixer under these conditions, N fixation and loss adjust N availability close to the availability of other resources, and biomass and NPP in this simple model can be substantially but only transiently N limited. We then modify the model by adding: (1) losses of N in forms other than excess available N (e.g., dissolved organic N, trace gases produced by nitrification); and (2) constraints to the growth and activity of N fixers imposed by differential effects of shading, P limitation, and grazing. The combination of these processes is sufficient to describe an open system, with input from both precipitation and N fixation, that is nevertheless strongly N-limited at equilibrium. This model is useful for exploring causes and consequences of constraints to N fixation, and hence of N limitation, and we believe it will also be useful for evaluating how N fixation and limitation interact with elevated CO2 and other components of global enviromental change.
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    URL: http://dx.doi.org/10.1023/A:1006185020121
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    A comparison of fractionation methods for forms of phosphorus in soils (1999)
    Springer
    Biogeochemistry 47 (1999), S. 25-38 
    Details
    ISSN: 1573-515X
    Keywords: Hedley fractionation ; phosphorus ; Ruttenberg fractionation ; soil phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We used l6 soils to compare the Hedley method for soil phosphorus fractionation to an alternative method recently developed by Ruttenberg to differentiate among P fractions in marine sediments. For forms of labile and Fe-bound P in soils, these methods were poorly correlated, with the Hedley fractionation showing a greater ability to discriminate among variations in plant-available P. For Ca-bound P, total organic P, and total P, the methods were well correlated (r2 = 0.93, 0.48, 0.74, respectively), although the sum of P measured in the Ruttenberg extractions is only 45% of the total P recovered by the Hedley fractionation. The Hedley fractionation seems superior when an index of plant-available phosphorus and a separation of organic and inorganic forms is needed, whereas the Ruttenberg method allows a separation of CaCO3-bound P from apatite-P, which is potentially useful in calcareous soils.
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    URL: http://dx.doi.org/10.1023/A:1006105420235
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    A comparison of fractionation methods for forms of phosphorus in soils (1999)
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    Biogeochemistry 47 (1999), S. 25-38 
    Details
    ISSN: 1573-515X
    Keywords: Hedley fractionation ; phosphorus ; Ruttenberg fractionation ; soil phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We used 16 soils to compare the Hedley method for soil phosphorus fractionation to an alternative method recently developed by Ruttenberg to differentiate among P fractions in marine sediments. For forms of labile and Fe-bound P in soils, these methods were poorly correlated, with the Hedley fractionation showing a greater ability to discriminate among variations in plant-available P. For Ca-bound P, total organic P, and total P, the methods were well correlated (r2=0.93, 0.48, 0.74, respectively), although the sum of P measured in the Ruttenberg extractions is only 45% of the total P recovered by the Hedley fractionation. The Hedley fractionation seems superior when an index of plant-available phosphorus and a separation of organic and inorganic forms is needed, whereas the Ruttenberg method allows a separation of CaCO3-bound P from apatite-P, which is potentially useful in calcareous soils.
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    URL: http://dx.doi.org/10.1007/BF00993095
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    Mitochondrial Events in the Life and Death of Animal Cells: A Brief Overview (1999)
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    Journal of bioenergetics and biomembranes 31 (1999), S. 291-304 
    Details
    ISSN: 1573-6881
    Keywords: Cell death ; aging ; necrosis ; apoptosis ; mitochondria ; oxidative phosphorylation ; electron transport chain ; ATP synthase ; cytochrome c ; mitochondrial DNA ; reactive oxygen species (ROS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Traditionally, mitochondria have been viewed as the “powerhouse” of the cell, i.e., the site of theoxidative phosphorylation machinery involved in ATP production. Consequently, much of theresearch conducted on mitochondria over the past 4 decades has focused on elucidating both thosemolecular events involved in ATP synthesis by oxidative phosphorylation and those involved inthe biogenesis of the oxidative phosphorylation machinery. While monumental achievements havebeen made, and continue to be made, in the study of these remarkable but extremely complexprocesses essential for the life of most animal cells, it has been only in recent years that a largebody of biological and biomedical scientists have come to recognize that mitochondria participatein other important processes. Two of these are cell death and aging which, not surprisingly, are relatedprocesses both involving, in part, the oxidative phosphorylation machinery. This new awareness hassparked a new and growing area of mitochondrial research, that has become of great interest to awide variety of scientists ranging from those involved in elucidating the role of mitochondria incell death and aging to those interested in either suppressing or facilitating these processes as itrelates to identifying new therapies or drugs for human disease. It is the purpose of this briefintroductory review to provide an overview of those mitochondrial events involved in the life anddeath of animal cells and to indicate how these events might relate to the human aging process.Much more is known, much remains controversial, and even more remains to be learned as indicatedin the excellent set of minireviews that follow.
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    URL: http://dx.doi.org/10.1023/A:1005453700533
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    Mitochondria at the Crossroad of Apoptotic Cell Death (1999)
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    Journal of bioenergetics and biomembranes 31 (1999), S. 321-326 
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    ISSN: 1573-6881
    Keywords: Mitochondria ; apoptosis ; caspases ; cytochrome c ; Fas ; bcl-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract In the past few years, it has become widely appreciated that apoptotic cell death generallyinvolves activation of a family of proteases, the caspases, which undermine the integrity ofthe cell by cleavage of critical intracellular substrates. Caspases, which are synthesized asinactive zymogens, are themselves caspase substrates and this cleavage leads to their activation.Hence, the potential exists for cascades of caspases leading to cell death. However, it has beenrecently recognized that another, perhaps more prominent route to caspase activation, involvesthe mitochondria. Upon receipt of apoptotic stimuli, either externally or internally generated,cells initiate signaling pathways which converge upon the mitochondria to promote release ofcytochrome C to the cytoplasm; cytochrome c, thus released, acts as a potent cofactor incaspase activation. Even cell surface “death receptors” such as Fas, which can trigger directcaspase activation (and potentially a caspase cascade), appear to utilize mitochondria as partof an amplification mechanism; it has been recently demonstrated that activated caspases cancleave key substrates to trigger mitochondrial release of cytochrome c, thereby inducing furthercaspase activation and amplifying the apoptotic signal. Therefore, mitochondria play a centralrole in apoptotic cell death, serving as a repository for cytochrome c.
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    URL: http://dx.doi.org/10.1023/A:1005471701441
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    Mitochondrial Uncoupling: Role of Uncoupling Protein Anion Carriers and Relationship to Thermogenesis and Weight Control “The Benefits of Losing Control” (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 493-506 
    Details
    ISSN: 1573-6881
    Keywords: Energy expenditure ; reactive oxygen species ; cellular viability ; apoptosis ; necrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Uncoupling proteins, a subgroup of the mitochondrial anion transporter superfamily, have beenidentified in prokaryotes, plants, and mammalian cells. Evolutionary conservation of thesemolecules reflects their importance as regulators of two critical mitochondrial functions, i.e.,ATP synthesis and the production of reactive oxygen species (ROS). Although the amino acidsequences of the three mammalian uncoupling proteins, UCP1, UCP2 and UCP3, are verysimilar, each homolog is the product of a unique gene and important differences have beendemonstrated in their tissue-specific expression and regulation. UCP1 and UCP3 appear to bekey regulators of energy expenditure, and hence, nonshivering thermogenesis, either in brownadipose tissue (UCP1) or skeletal muscle (UCP3). UCP2 is expressed more ubiquitously,although generally at low levels, in many tissues. There is conflicting evidence about itsimportance as a regulator of resting metabolic rate. However, evidence suggests that thishomolog might modulate the mitochondrial generation of ROS in some cell types, includingmacrophages and hepatocytes. While the induction of various uncoupling protein homologsprovides adaptive advantages, both to the organism (e.g., thermogenesis) and to individual cells(e.g., reduced ROS), increased uncoupling protein activity also increases cellular vulnerability tonecrosis by compromising the mitochondrial membrane potential. This narrow “risk—benefit”margin necessitates tight control of uncoupling protein activity in order to preserve cellularviability and much remains to be learned about the regulatory mechanisms involved.
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    URL: http://dx.doi.org/10.1023/A:1005452624640
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    Hepatotoxicity due to mitochondrial dysfunction (1999)
    Springer
    Cell biology and toxicology 15 (1999), S. 367-373 
    Details
    ISSN: 1573-6822
    Keywords: apoptosis ; drugs ; hepatitis ; mitochondria ; steatosis ; steatohepatitis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mitochondria are involved in fatty acid β-oxidation, the tricarboxylic acid cycle, and oxidative phosphorylation, which provide most of the cell energy. Mitochondria are also the main source of reactive oxygen species in the cell and are involved in cell demise through opening of the mitochondrial permeability transition pore. It was therefore to be expected that mitochondrial dysfunction could be a major mechanism of drug-induced liver disease. Microvesicular steatosis (which may cause liver failure, coma, and death) is the consequence of severe impairment of mitochondrial β-oxidation. Endogenous compounds (such as cytokines or female sex hormones) or xenobiotics (including toxins such as ethanol and drugs such as aspirin, valproic acid, ibuprofen, or zidovudine) can inhibit β-oxidation directly or through a primary effect on the mitochondrial genome or the respiratory chain itself. In some patients, infections and cytokines, or inborn errors of β-oxidation enzymes or the mitochondrial genome, may favor the appearance of drug-induced microvesicular steatosis. Nonalcoholic steatohepatitis may develop under conditions causing prolonged, microvesicular, and/or macrovacuolar steatosis. In this condition, chronic impairment of mitochondrial β-oxidation (causing steatosis) and the respiratory chain (increasing the production of ROS) lead to lipid peroxidation, which, in turn, may cause the diverse lesions of steatohepatitis, namely, necrosis, inflammation, Mallory's bodies, and fibrosis. Finally, mitochondria are involved in several forms of drug-induced cytolytic hepatitis, through inhibition or uncoupling of respiration or through a drug-induced or reactive metabolite-induced mitochondrial permeability transition. The latter effect commits hepatocytes to either apoptosis or necrosis, depending on the number of organelles that have undergone the permeability transition.
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    URL: http://dx.doi.org/10.1023/A:1007649815992
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    The Involvement of p53 in Dopamine-Induced Apoptosis of Cerebellar Granule Neurons and Leukemic Cells Overexpressing p53 (1999)
    Springer
    Cellular and molecular neurobiology 19 (1999), S. 261-276 
    Details
    ISSN: 1573-6830
    Keywords: Parkinson's disease ; catecholamines ; oxidative metabolites ; phosphorylation ; DNA damage ; apoptosis ; p53
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The pathogenesis of the selective degeneration of the dopaminergic neurons in Parkinson's disease is still enigmatic. Recently we have shown that dopamine can induce apoptosis in postmitotic neuronal cells, as well as in other cellular systems, thus suggesting a role for this endogenous neurotransmitter and associated oxidative stress in the neuronal death process. 2. Dopamine has been shown to be capable of inducing DNA damage through its oxidative metabolites. p53 is a transcription factor that has a major role in determining cell fate in response to DNA damage. We therefore examined the possible correlation between dopamine-triggered apoptosis, DNA damage and levels of total phosphorylated p53 protein in cultured mouse cerebellar granule neurons. 3. Marked DNA damage and apoptotic nuclear condensation and fragmentation were detected within several hours of exposure to dopamine. An associated marked threefold increase in p53 phosphorylation was observed within this time window. Using a temperature-sensitive p53 activation system in leukemia LTR6 cells, were found that p53 inactivation dramatically attenuated dopamine toxicity. 4. We therefore conclude that DNA damage and p53 activation may have a role in mediating dopamine-induced apoptosis. Modulation of the p53 system may therefore have a protective role against the toxicity of this endogenous neurotransmitter and associated oxidative stress.
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    URL: http://dx.doi.org/10.1023/A:1006933312401
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    Culture filtrates of Aspergillus fumigatus induce different modes of cell death in human cancer cell lines (1999)
    Springer
    Mycopathologia 146 (1999), S. 67-74 
    Details
    ISSN: 1573-0832
    Keywords: apoptosis ; Aspergillus fumigatus ; cell death ; culture filtrate(s) ; necrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Aspergillus fumigatus culture filtrate (CF) has a potent cytotoxic effect on three human cancer cell lines (DLKP, A549 and HEp-2) and initiates cell death by apoptosis but the execution of the apoptotic process is incomplete. DLKP cells treated with A. fumigatus CF demonstrate features associated with apoptosis but cytoplasmic and nuclear fragmentation were not observed and cells ultimately underwent necrosis. The apoptotic process commenced in A549 and HEp-2 cells upon exposure to CF, cell shrinkage was observed but membrane blebbing and apoptotic body formation were not detected and detached cells died by necrosis. In contrast, extensive nuclear fragmentation and apoptotic body formation were evident in DLKP and A549 cells treated with anti-neoplastic agents. This work indicates that A. fumigatus CF is cytotoxic to cancer cells and can initiate apoptosis but that the complete apoptotic pathway is not followed.
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    URL: http://dx.doi.org/10.1023/A:1007092112873
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    Nutrient cycling and growth in forest ecosystems of south western Australia: Relevance to agricultural landscapes (1999)
    Springer
    Agroforestry systems 45 (1999), S. 215-244 
    Details
    ISSN: 1572-9680
    Keywords: biodiversity ; disturbance ; nitrogen ; phosphorus ; resilience ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient and hydrologic cycles in harvested native forests in southern Australia are largely balanced. For example, we have little or no evidence of any decline in nutrient capital or availability in harvested forests. Short-term and small-scale reductions in evapotranspiration due to loss of leaf area after harvesting are adequately balanced at the landscape scale by large areas of regenerating or older-age forest. In contrast, agricultural systems on similar soils are a) dependent on large inputs of fertilisers to maintain growth and b) frequently subject to increasing salinity and waterlogging or other forms of degradation. The large-scale replacement of long-lived communities of perennial and often deep- rooting native species with annual crops or other communities of shallow-rooting species might be better managed within the framework of knowledge developed from studies of native plant communities. However, application of such a mimic concept to systems of low natural productivity is limited when agricultural systems require continued high productivity. Nonetheless, the mimic concept may help in developing sustainable management of agriculture on marginal lands, and contribute to the nutritional resilience of agroecosystems. Relevant characteristics for mimic agroecosystems in south western Australia include: high species diversity, diversity of rooting attributes, utilisation of different forms of nutrients (especially of N and P) in space and time, and the promotion of practices which increase soil organic matter content.
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    Effect of nitrogen and phosphorus addition on phenanthrene biodegradation in four soils (1999)
    Springer
    Biodegradation 10 (1999), S. 43-50 
    Details
    ISSN: 1572-9729
    Keywords: biodegradation ; nitrogen ; nutrients ; phenanthrene ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation. To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus. Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus. Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added. The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils. To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008359606545
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  • 93
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    Does water and phosphorus uptake limit leaf growth of Rhizoctonia-infected wheat seedlings? (1999)
    Springer
    Plant and soil 209 (1999), S. 157-166 
    Details
    ISSN: 1573-5036
    Keywords: hydraulic conductivity ; leaf growth ; phosphorus ; Rhizoctonia ; water status ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Wheat seedlings infected with a pure inoculum of the root-rotting fungus Rhizoctonia solani were grown in pots designed to fit in pressure chambers, to allow the effects of the Rhizoctonia infection on leaf growth to be studied while maintaining the leaves at elevated water status. Wheat was grown to the third leaf stage in soil inoculated with three different levels of Rhizoctonia, and the pots were then pressurised for seven days to maintain the leaf xylem at the point of bleeding (ie. the leaves were at full turgor). The reduction in leaf expansion caused by Rhizoctonia was not overcome by pressurisation, indicating that a reduced supply of water to the leaves was not responsible for reduced leaf growth. The addition of phosphorus to pots marginally deficient in P did not increase the leaf growth of Rhizoctonia-infected plants, despite increased P uptake to the leaves. These results indicate that a reduced supply of water to the leaves and a supply of phosphorus that was bordering on deficient was not the cause of the growth reduction in seedlings with Rhizoctonia infection. The nature of this reduced growth remains uncertain but may involve growth regulators produced by the fungus, or by the plant as a result of the infection process. The mechanism of these growth reductions is of interest as it may provide a key to the development of plant resistance mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004374516088
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  • 94
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    Synthesis of theoretical and empirical experiences from nutrient and cyprinid reductions in Lake Ringsjön (1999)
    Springer
    Hydrobiologia 404 (1999), S. 145-156 
    Details
    ISSN: 1573-5117
    Keywords: biomanipulation ; nutrient reduction ; zooplankton ; phytoplankton ; bottom-up ; top-down ; phosphorus ; submerged vegetation ; benthic macrofauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003788900521
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  • 95
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    Retention of nutrients in river systems: dependence on specific runoff and hydraulic load (1999)
    Springer
    Hydrobiologia 410 (1999), S. 111-122 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; nitrogen ; retention ; river systems ; specific runoff ; hydraulic load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The total nutrient inputs (emissions) from point and diffuse sources into 100 different river basins in Europe are compared with the measured load (transport). The catchment areas range between 121 and 194 000 km2. Other characteristic parameters of the basins, including specific runoff, surface water area and the nutrient concentration show large differences. Independent of the different methods applied for estimating nutrient emissions, these are in general higher than the actual transport. The ratio of the transport to the emission was used to exclude the effects of basin size and to facilitate comparisons between river basins. A statistical model of the retention, including net sedimentation and denitrification, is derived for the description of the discrepancy between the measured transport and the estimated total emission of nutrients, which is assumed to reflect retention of nutrients in a river system. It was found that the load-weighted retention of phosphorus is controlled practically only by the specific runoff of the basin. The load- weighted retention of nitrogen is further dependent on the proportion of the basin area occupied by surface water, the basin size itself and the mean annual nitrogen concentration at a specific monitoring station. Application of the statistical model reduces the mean deviation between the calculated emissions and the values given by different authors from about 40% to 20%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003735225869
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  • 96
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    The fate of NH4NO3 added to Sphagnum magellanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m-2 yr-1 were made to Sphagnum magellanicum cores at two-week intervals in situ at four sites across Europe, i.e. Lakkasuo (Finland), Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N:P ratio 68) and greatest in Moidach More (N:P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4+ in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3- were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition by Sphagnum mosses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006133828518
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  • 97
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    Distribution and speciation of phosphorus along a salinity gradient in intertidal marsh sediments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 197-221 
    Details
    ISSN: 1573-515X
    Keywords: intertidal marshes ; phosphorus ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We examined forms of solid phosphorus fractions in intertidal marsh sediments along a salinity (0–22‰) gradient in a river-dominated estuary and in a marine-dominated salt marsh with insignificant freshwater input. Freshwater marsh sediments had the highest ratio of organic N:P of between 28:1 and 47:1 mol:mol, compared to 21:1 to 31:1 mol:mol in the saltmarshes, which is consistent with a trend toward P-limitation of primary production in freshwater and N-limitation in salt marshes. However, total P concentration, 24.7 ± 11.1 µmol P g dw-1 (±1 SD) averaged over the upper meter of sediment, was greatest in the freshwater marsh where bioavailablity of P is apparently limited. In the freshwater marsh the greatest fraction of total P (24–51%) was associated with humic acids, while the importance of humic-P decreased with increasing salinity to 1–23% in the salt marshes. Inorganic P contributed considerably less to total sediment P in the freshwater marsh (15–40%) than in the salt marshes (33–85%). In reduced sediments at all sites, phosphate bound to aluminum oxides and clays was an important inorganic P pool irrespective of salinity. Inorganic P associated with ferric iron [Fe(III)] phases was most abundant in surface sediments of freshwater and brackish marshes, while Ca-bound P dominated inorganic P pools in the salt marshes. Thus, our results showed that particle-bound P in marsh sediments exhibited changes in chemical association along the salinity gradient of an estuarine system, which is a likely consequence of changes in ionic strength and the availability of iron and calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006136621465
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  • 98
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    Distribution and speciation of phosphorus along a salinity gradient in intertidal marsh sediments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 197-221 
    Details
    ISSN: 1573-515X
    Keywords: intertidal marshes ; phosphorus ; sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We examined forms of solid phosphorus fractions in intertidal marsh sediments along a salinity (0–22%.) gradient in a river-dominated estuary and in a marine-dominated salt marsh with insignificant freshwater input. Freshwater marsh sediments had the highest ratio of organic N:P of between 28:1 and 47:1 mol:mol, compared to 21∶1 to 31∶1 mol∶mol in the saltmarshes, which is consistent with a trend toward P-limitation of primary production in freshwater and N-limitation in salt marshes. However, total P concentration, 24.7±11.1μmol P g dw−1 (±1 SD) averaged over the upper meter of sediment, was greatest in the freshwater marsh where bioavailablity of P is apparently limited. In the freshwater marsh the greatest fraction of total P (24–51%.) was associated with humic acids, while the importance of humic-P decreased with increasing salinity to 1–23%. in the salt marshes. Inorganic P contributed considerably less to total sediment P in the freshwater marsh (15–40%.) than in the salt marshes (33–85%.). In reduced sediments at all sites, phosphate bound to aluminum oxides and clays was an important inorganic P pool irrespective of salinity. Inorganic P associated with ferric iron [Fe(III)] phases was most abundant in surface sediments of freshwater and brackish marshes, while Ca-bound P dominated inorganic P pools in the salt marshes. Thus, our results showed that particle-bound P in marsh sediments exhibited changes in chemical association along the salinity gradient of an estuarine system, which is a likely consequence of changes in ionic strength and the availability of iron and calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01106781
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  • 99
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    Fas-mediated apoptosis is attenuated in preneoplastic GST-P-positive hepatocytes isolated from diethylnitrosamine-treated rats (1999)
    Springer
    Cell biology and toxicology 15 (1999), S. 239-247 
    Details
    ISSN: 1573-6822
    Keywords: apoptosis ; bile acid ; diethylnitrosamine ; enzyme-altered foci ; Fas ; hepatocytes ; p53 ; preneoplastic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Previous reports have indicated that apoptosis is selectively decreased in enzyme-altered foci (EAF) in the livers of rats treated with a carcinogen. Here we have investigated the effects of an anti-Fas antibody (anti-Fas Ab) on EAF cells in vitro. Hepatocytes were isolated from rats treated repeatedly with diethylnitrosamine (DEN), whose livers contained glutathione S-transferase P (GST-P)-positive EAF. Subsequently, primary cultures of GST-P-positive and GST-P-negative hepatocytes were established and exposed to anti-Fas Ab. Anti-Fas Ab (4 μg/ml) preferentially induced apoptosis in GST-P-negative cells. Furthermore, GST-P-positive cells were shown to be resistant to p53-mediated apoptosis. We conclude that EAF hepatocytes are resistant to Fas-mediated apoptosis in vitro. This lack of response may explain the selective decrease in apoptosis in EAF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007663729113
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  • 100
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    Modelling regional and large-scale response of Baltic Sea ecosystems to nutrient load reductions (1999)
    Springer
    Hydrobiologia 393 (1999), S. 35-43 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; modelling ; biogeochemical cycles ; nitrogen ; phosphorus ; load reduction ; Baltic Sea ; Gulf of Finland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The entire Baltic Sea, as well as many of its different sub-regions, are subject to eutrophication due to high nutrient inputs. To plan expensive water management measures one needs a tool to quantify effects of different water management policy decisions. The tools implemented here are simulation models based on similar descriptions of biochemical interactions in the water and sediments but coupled to different hydrodynamical models. For the Baltic Proper a 1D physical model with high vertical resolution but horizontally integrated was used. Simulations for 20 years made with 50% load reduction each 5 year show that for this domain and at these scales the recovery would take decades. The most effective is reduction of phosphorus, while reduction of only nitrogen leads to a dramatic increase in cyanobacteria blooms. For the Gulf of Finland a high-resolution 3D hydrodynamic model was coupled to a more crude 3D-box biogeochemical model describing concrete conditions during August and November 1991. In the Eastern Gulf of Finland the effects of a 50% load reduction from the St. Petersburg region are pronounced even after two weeks. Here, nitrogen reduction would be more beneficial than that of phosphorus, both locally and at a larger scale. The conclusion from these simulations is that the difference in effects of nitrogen versus phosphorus reduction is dependent on scales and locations of management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003529531198
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