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  • 1
    Digitale Medien
    Digitale Medien
    Difficulties in location and acceptance of phloem sap combined with reduced concentration of phloem amino acids explain lowered performance of the aphid Rhopalosiphum padi on nitrogen deficient barley (Hordeum vulgare) seedlings (2000)
    Springer
    Entomologia experimentalis et applicata 97 (2000), S. 203-210 
    Details
    ISSN: 1570-7458
    Schlagwort(e): EPG ; stylectomy ; phloem amino acids ; nitrogen ; aphid-plant interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Effects of nitrogen deficiency in hydroponically grown barley seedlings (Hordeum vulgare L.) on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated. Plant growth was significantly reduced in seedlings grown without nitrogen. Aphid intrinsic rate of increase (r m) was also significantly lower on these plants compared with that on plants grown with 8 mol m−3 nitrogen. Phloem sap was collected from seedling stems by aphid stylectomy and amino acids quantified by HPLC. There was a significant reduction in the concentration of non-essential amino acids as a group, but not of essential amino acids. Electrical penetration graphs (EPG) indicated that aphids reached the phloem more quickly and fed for longer on plants grown with nitrogen. This is the first reported study in which this combination of techniques has been used to understand the interactions of an aphid and plant under different environmental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004022608401
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  • 2
    Digitale Medien
    Digitale Medien
    Behavioural induction in Drosophila: timing and specificity (2000)
    Springer
    Entomologia experimentalis et applicata 94 (2000), S. 159-171 
    Details
    ISSN: 1570-7458
    Schlagwort(e): Drosophila ; induction ; habituation ; associative learning ; T-maze olfactometer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Experiments reported in this paper investigate the properties of a change in the responsiveness of adult Drosophila melanogaster induced by exposure to different rearing media. This effect has previously been described as habituation or associative learning. Exposure to food medium containing 0.08% menthol induced a positive response to menthol odour in a T-maze olfactometer. A brief (one hour) exposure to mentholic food just before testing was sufficient to induce a change in responsiveness. The effect did not persist through periods of more than an hour of separation from mentholic medium. Effects induced by exposure to a single compound were not specific to that compound alone. Menthol-reared flies (MRFs) differed from plain reared flies (PRFs) in their responsiveness to the odours of benzaldehyde and ethyl acetate, as well as menthol, and exposure to ethyl acetate induced a change in response to menthol odour. That there was an induced positive response to menthol in MRFs suggests that conventional habituation is insufficient to explain the induced change in responsiveness, but the generalised nature of this behavioural induction in MRFs is hard to explain in terms of associative learning. The mechanism underlying the induction remains elusive.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003998715018
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  • 3
    Digitale Medien
    Digitale Medien
    An Ab Initio Study of the Complexes Formed by the Positive Acetylene Ion with the Hydrogen and Nitrogen Molecules and the Argon Atom (2000)
    Springer
    Journal of cluster science 11 (2000), S. 381-389 
    Details
    ISSN: 1572-8862
    Schlagwort(e): acetylene ion ; complex ; hydrogen ; nitrogen ; argon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The complexes formed by the positive acetylene ion with the hydrogen molecule, the nitrogen molecule, and the argon atom are investigated with ab initio calculations using the 6-311G** and the 6-31+G(2df,2pd) basis sets. MP2/6-311G** energies and optimum geometries are obtained, as well as single-point MP3, MP4, and QCISD(T) energies with the MP2/6-311G** optimized geometries. Single-point calculations are performed with the 6-31+G(2df,2pd) basis set at MP2/6-311G** optimized geometries.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009053924254
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  • 4
    Digitale Medien
    Digitale Medien
    Lack of Evolutionary Divergence in Courtship Songs of Drosophila pseudoobscura Subspecies (2000)
    Springer
    Journal of insect behavior 13 (2000), S. 255-262 
    Details
    ISSN: 1572-8889
    Schlagwort(e): courtship song ; wingbeat ; sexual isolation ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007744416116
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  • 5
    Digitale Medien
    Digitale Medien
    Copulatory Courtship in Drosophila birchii and D. serrata, Species Recognition and Sexual Selection (2000)
    Springer
    Journal of insect behavior 13 (2000), S. 361-373 
    Details
    ISSN: 1572-8889
    Schlagwort(e): Drosophila ; copulatory courtship ; mate choice ; cryptic female choice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two endemic Australian Drosophila species, D. birchii and D. serrata, have a copulatory courtship, i.e., the males court the female mainly during copulation. In the present study we found the males of both species to mount their prospective mating partners selectively, exhibiting both sex and species recognition. The males began to sing after mounting the female, and they often exhibited also postcopulatory displays typical to copulatory courtship. D. birchii and D. serrata females discriminated against males which did not sing during mounting/copulation, which suggests that the females utilize cryptic female choice. Our findings raise the question of how widespread a phenomenon cryptic female choice is in Drosophila species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007710218609
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  • 6
    Digitale Medien
    Digitale Medien
    Nitrogen leaching and crop availability in manured catch crop systems in Sweden (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 139-152 
    Details
    ISSN: 1573-0867
    Schlagwort(e): nitrogen ; N leaching ; liquid manure ; catch crops ; N mineralization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Results are presented from five years (1990–1995) of a field leaching experiment on a sandy soil in south-west Sweden. The aim was to study N leaching, change in soil organic N and N mineralization in cropping systems with continuous use of liquid manure (two application rates) and catch crops. N leaching from drains, N uptake in crops and mineral N in the soil were measured. Simulation models were used to calculate the N budget and N mineralization in the soil and to make predictions of improved fertilization strategies in relation to manure applications and changing the time for incorporation of catch crops. In treatments without catch crops, a normal and a double application of manure increased average N leaching by 15 and 34%, respectively, compared to treatment with commercial fertilizer. Catch crops reduced N leaching by, on average, 60% in treatments with a normal application of manure and commercial fertilizer, but only by 35% in the treatment with double the normal application rate of manure. Incorporation of catch crops in spring increased simulated net N mineralization during the crop vegetation period, and also during early autumn. In conclusion, manured systems resulted in larger N leaching than those receiving commercial fertilizer, mainly due to larger applications of mineral N in spring. More careful adaptation of commercial N fertilization with respect to the amounts of NH4-N applied with manure could, according to the simulations, reduce N leaching. Under-sown ryegrass catch crops effectively reduced N leaching in manured systems. Incorporating catch crop residues in late autumn instead of spring might be preferable with respect to N availability in the soil for the next crop, and would not increase N leaching.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009821519042
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  • 7
    Digitale Medien
    Digitale Medien
    Role of Calcium in the Evolution of Superconductivity in a (La2−xRx)Ba2(CayCu4+y)Oz (R = Y, Er, Gd) System (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 37-40 
    Details
    ISSN: 1572-9605
    Schlagwort(e): LaBaCuO ; calcium ; superconductivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract It has been reported that, by adding equal amounts of CaO and CuO to non superconducting La3Ba3Cu6O z (La-336), a series of superconductors with nominal compositions La3Ca y Ba3Cu6+y O z were prepared with maximum Ton c ∼ 80K. Similar studies on addition of CaO and CuO in nonsuperconducting LaBaCu2O z (La-112) resulted into superconducting LaCaBaCu3O z (La-1113). To date no attempt has been made to synthesize La2CaBa2Cu5O z (La-2125) superconducting phase by addition of CaO and CuO to non superconducting La2Ba2Cu4O z (La-224) system. Also no reports are published to study the effect of replacing larger La3+-ions (1.01Å) by smaller rare earth ions viz Y3+(0.89Å), Er3+(0.91Å), Gd3+(0.91Å) on the structural and superconducting properties of (La2−x R x )Ba2(Ca y Cu4+y )O z (LRBCaC); 0.0 ≤ x ≤ 0.5; y=2x system. In this paper, we report the method of synthesis, structural and superconducting property characterization using X-ray diffraction, oxygen content measurements using iodometry, resistivity measurements using d.c. four probe technique and a.c. susceptibility measurements in the temperature range RT to 15K. Also a comparative study, on the evolution of superconducting phase with Ca-concentration for different rare earth substitutions for LRBCaC system in the context of hole doping mechanism, is carried out.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007765907530
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  • 8
    Digitale Medien
    Digitale Medien
    Nutrient flows and land use change in a rural catchment: a modelling approach (2000)
    Springer
    Landscape ecology 15 (2000), S. 187-199 
    Details
    ISSN: 1572-9761
    Schlagwort(e): BOD5 ; catchment ; empirical model ; land use change ; land use scenarios ; nitrogen ; phosphorus ; runoff ; SO4
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to 5.1, 0.32 to 0.13, 78 to 48, and 7.4 to 3.5 kg ha−1 yr−1, respectively. The most significant decreases occurred in agricultural subcatchments while the changes were insignificant in the forested upper course catchment. A simple empirical model which incorporates land-use pattern, fertilization intensity, soil parameters and water discharge accurately described the variations of total-N and total-P runoff in both the whole catchment and its agricultural subcatchments (R 2 varies from 0.95–0.99 for N to 0.49–0.93 for P). In small agricultural subcatchments the rate of fertilization is found the most important factor for nitrogen runoff, whereas in larger mosaic watersheds land use pattern plays the main role. Seven alternative scenarios compiled on the base of the empirical model allow to forecast potential nitrogen and phosphorus losses from the catchment. This information can be used in further landscape and regional planning of the whole region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008181811552
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  • 9
    Digitale Medien
    Digitale Medien
    Patterning defects in the primary axonal scaffolds caused by the mutations of the extradenticle and homothorax genes in the embryonic Drosophila brain (2000)
    Springer
    Development genes and evolution 210 (2000), S. 289-299 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Brain development ; Axonal scaffold ; Extradenticle ; Homothorax ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  During early brain development in Drosophila a highly stereotyped pattern of axonal scaffolds evolves by precise pioneering and selective fasciculation of neural fibers in the newly formed brain neuromeres. Using an axonal marker, Fasciclin II, we show that the activities of the extradenticle (exd) and homothorax (hth) genes are essential to this axonal patterning in the embryonic brain. Both genes are expressed in the developing brain neurons, including many of the tract founder cluster cells. Consistent with their expression profiles, mutations of exd and hth strongly perturb the primary axonal scaffolds. Furthermore, we show that mutations of exd and hth result in profound patterning defects of the developing brain at the molecular level including stimulation of the orthodenticle gene and suppression of the empty spiracles and cervical homeotic genes. In addition, expression of a Drosophila Pax6 gene, eyeless, is significantly suppressed in the mutants except for the most anterior region. These results reveal that, in addition to their homeotic regulatory functions in trunk development, exd and hth have important roles in patterning the developing brain through coordinately regulating various nuclear regulatory genes, and imply molecular commonalities between the developmental mechanisms of the brain and trunk segments, which were conventionally considered to be largely independent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050316
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  • 10
    Digitale Medien
    Digitale Medien
    Analysis of a swallow homologue from Drosophila pseudoobscura (2000)
    Springer
    Development genes and evolution 210 (2000), S. 157-161 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Swallow ; bicoid ; Drosophila ; mRNA localization ; Oogenesis ; Embryogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  We analyzed a functional homologue of the swallow gene from Drosophila pseudoobscura. The swallow gene of D. melanogaster plays an essential role in localizing bicoid mRNA in oocytes, and swallow mutant embryos show anterior pattern defects that result from the lack of localization of the bicoid morphogen. The pseudoobscura homologue rescues the function of swallow mutants when introduced into the genome of D. melanogaster, and its expression is similar to that of the melanogaster gene. The predicted pseudoobscura and melanogaster proteins are 49% identical and 69% conserved. The coiled-coil domain previously identified in the melanogaster swallow protein is strongly conserved in the pseudoobscura homologue, but the weak similarity of the melanogaster swallow protein to the RNP class of RNA-binding proteins is not conserved in the pseudoobscura homologue. These and other observations suggest a structural role for swallow in localizing bicoid mRNA, perhaps as part of the egg cytoskeleton.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050023
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  • 11
    Digitale Medien
    Digitale Medien
    Changes in cell shape in the ventral neuroectoderm of Drosophila melanogaster depend on the activity of the achaete-scute complex genes (2000)
    Springer
    Development genes and evolution 210 (2000), S. 190-199 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Ventral neuroectoderm ; Cell shape ; Achaete-scute complex ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  In the embryonic ventral neuroectoderm of Drosophila melanogaster the proneural genes achaete, scute, and lethal of scute are expressed in clusters of cells from which the neuroblasts delaminate in a stereotyped orthogonal array. Analyses of the ventral neuroectoderm before and during delamination of the first two populations of neuroblasts show that cells in all regions of proneural gene activity change their form prior to delamination. Furthermore, the form changes in the neuroectodermal cells of embryos lacking the achaete-scute complex, of embryos mutant for the neurogenic gene Delta, and of embryos overexpressing l’sc suggest that these genes are responsible for most of the morphological alterations observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050303
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  • 12
    Digitale Medien
    Digitale Medien
    Effect of exogenous calcium on Agrobacterium tumefaciens-mediated gene transfer in Hevea brasiliensis (rubber tree) friable calli (2000)
    Springer
    Plant cell reports 19 (2000), S. 851-855 
    Details
    ISSN: 1432-203X
    Schlagwort(e): Key words Rubber tree ; Agrobacterium tumefaciens ; calcium ; gene transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The influence of CaCl2 was investigated on Agrobacterium tumefaciens-mediated gene transfer in Hevea brasiliensis friable calli which are usually proliferated on maintenance medium (MM) containing 9 mM CaCl2.Five A. tumefaciens strains (C58pMP90, C58pGV2260, AGL1, LBA4404 and EHA 105) and two binary vectors (pGIN and pCAMBIA2301) were tested and the strain EHA105pC2301 was selected to conduct further experiments. The calli were precultured on MM containing a range of CaCl2 concentrations, then inoculated with Agrobacterium suspension. Transfer of friable calli from MM containing 9 mM CaCl2 to calcium-free medium significantly enhanced the transient β-glucuronidase activity. Interestingly, the use of calcium-free Agrobacterium resuspension medium to inoculate friable calli again dramatically increased the transformation efficiency. Induction of Agrobacterium's virulence with acetosyringone remained an important factor to stimulate transformation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002990000208
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  • 13
    Digitale Medien
    Digitale Medien
    Coexistence of drosophilid flies: Aggregation, patch size diversity and parasitism (2000)
    Springer
    Ecological research 15 (2000), S. 93-100 
    Details
    ISSN: 1440-1703
    Schlagwort(e): aggregation ; coexistence ; Drosophila ; parasitism ; patch size
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: We carried out field experiments to investigate the coexistence of Drosophila species in domestic and forest areas on the basis of the aggregation model. Three cosmopolitan species Drosophila simulans Sturtevant, Drosophila melanogaster Meigen and Drosophila immigrans Sturtevant, and a native species, Drosophila auraria Peng, emerged abundantly from banana placed at the domestic station, while Drosophila immigrans and five native species, Drosophila lutescens Okada, Drosophila rufa Kikkawa and Peng, Drosophila bizonata Kikkawa and Peng, Drosophila sternopleuralis Okada and Kurokawa and Scaptodrosophila coracina (Kikkawa and Peng), were abundant at the forest station. The present analysis suggests that their coexistence was facilitated by the aggregation mechanism. In the cosmopolitan species, the density of individuals that emerged from patches increased with the increase of patch size, but the relationship between fly density and patch size was not clear in the native species. This difference in distribution patterns between the cosmopolitan and native species is likely to be due to the difference in the female visiting behavior. In the present analysis, however, it was not clear whether patch size diversity facilitated their coexistence or not. The effect of patch size diversity may have been masked, because the effect of aggregation was more prominent. The rate of parasitism by wasps was high in October at the domestic station, and in May and June at the forest station. The present result suggests that the rate of parasitism was density-dependent, at least at the domestic station, and therefore parasitism facilitates the coexistence of drosophilid species in domestic areas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1440-1703.2000.00328.x
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  • 14
    Digitale Medien
    Digitale Medien
    Oxygen Metastable Defects in Calcium Titanate Thin Films (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 675-681 
    Details
    ISSN: 1572-8943
    Schlagwort(e): calcium ; diffusion ; metastable defect ; oxide ion ; perovskite ; sputtering ; thin film ; titanate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Metastable defects of oxygen in calcium titanate thin films with perovskite structure were studied. Thin films of calcium titanate were deposited by a magnetron sputtering method. The oxygen defects were evaluated, using the results of oxygen diffusion experiments. The thin film process had tendencies of creation of a large amount of oxygen point defects and the wide range of non equilibrium solid solution at room temperature. Thecrystal distortion was increasing with deviation from the stoichiometric composition. Although the metastable defects were decreasing due to the annealing, annealed samples had more oxygen defects in a few magnitude orders than single crystals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010125322433
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  • 15
    Digitale Medien
    Digitale Medien
    Kinetics of the Electrons in Striations of Spherical Glow Discharges (2000)
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 87-110 
    Details
    ISSN: 1572-8986
    Schlagwort(e): striations ; nitrogen ; spherical discharge ; spatially inhomogeneous Boltzmann equation ; electron velocity distribution function ; dc glow discharge
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Recent observations of spherical striations in large-volume nitrogen dcdischarges with a central anode have stimulated investigations of thenonlocal electron kinetics in these striations by solving the spatiallyinhomogeneous Boltzmann equation adapted to spherical geometry. Becausethe radial course of the electric potential is largely unknown in thisdischarge, different models concerning its radial course have been developedand used. These models are based on the measured radii of the striationsand the assumption that the potential drop between successive striationsdoes not change. As a consequence, with decreasing distance between thestriations the electric field strongly increases toward the centralanode. It has been found that spherical striations are only obtained ifthe electric field is strongly modulated. In this case, a highly nonlocalbehavior of the velocity distribution function and strongly modulatedradial courses of the macroscopic quantities have been obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006973911319
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  • 16
    Digitale Medien
    Digitale Medien
    Effects of norepinephrine on the metabolism of fatty acids with different chain lengths in the perfused rat liver (2000)
    Springer
    Molecular and cellular biochemistry 205 (2000), S. 13-23 
    Details
    ISSN: 1573-4919
    Schlagwort(e): perfused rat liver ; norepinephrine ; fatty acids ; metabolism ; ketogenesis ; calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The effects of norepinephrine on ketogenesis in isolated hepatocytes have been reported as ranging from stimulation to inhibition. The present work was planned with the aim of clarifying these discrepancies. The experimental system was the once-through perfused liver from fasted and fed rats. Fatty acids with chain lengths varying from 8-18 were infused. The effects of norepinephrine depended on the metabolic state of the rat and on the nature of the fatty acid. Norepinephrine clearly inhibited ketogenesis from long-chain fatty acids (stearate 〉 palmitate 〉 oleate), but had little effect on ketogenesis from medium-chain fatty acids (octanoate and laureate). With palmitate the decrease in oxygen uptake was restricted to the substrate stimulated portion; with stearate, the decrease exceeded the substrate stimulated portion; with oleate, oxygen uptake was transiently inhibited. Withdrawal of Ca2+ attenuated the inhibitory effects. 14CO2 production from [1-14C]oleate was inhibited. Net uptake of the fatty acids was not affected by norepinephrine. In livers from fed rats, oxygen uptake and ketogenesis from stearate were only transiently inhibited. The conclusions are: (a) in the fasted state norepinephrine reduces ketogenesis and respiration by means of a Ca2+-dependent mechanism; (b) the degree of inhibition varies with the chain length and the degree of saturation of the fatty acids; (c) norepinephrine favours esterification of the activated long-chain fatty acids in detriment to oxidation; (d) in the fed state the stimulatory action of norepinephrine on glycogen catabolism induces conditions which are able to reverse inhibition of ketogenesis and oxygen uptake.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007094310429
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  • 17
    Digitale Medien
    Digitale Medien
    Regulation of Na/K-ATPase β1-subunit gene expression by ouabain and other hypertrophic stimuli in neonatal rat cardiac myocytes (2000)
    Springer
    Molecular and cellular biochemistry 215 (2000), S. 65-72 
    Details
    ISSN: 1573-4919
    Schlagwort(e): Na/K-ATPase ; calcium ; signal transduction ; ouabain ; Ras ; mitogen-activated protein kinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Partial inhibition of Na/K-ATPase by ouabain causes hypertrophic growth and regulates several early and late response genes, including that of Na/K-ATPase α3 subunit, in cultured neonatal rat cardiac myocytes. The aim of this work was to determine whether ouabain and other hypertrophic stimuli affect Na/K-ATPase β1 subunit gene expression. When myocytes were exposed to non-toxic concentrations of ouabain, ouabain increased β1 subunit mRNA in a dose- and time-dependent manner. Like the α3 gene, β1 mRNA was also regulated by several other well-known hypertrophic stimuli including phenylephrine, a phorbol ester, endothelin-1, and insulin-like growth factor, suggesting involvement of growth signals in regulation of β1 expression. Ouabain failed to increase β1 subunit mRNA in the presence of actinomycin D. Using a luciferase reporter gene that is directed by the 5′-flanking region of the β1 subunit gene, transient transfection assay showed that ouabain augmented the expression of luciferase. These data support the proposition that ouabain regulates the β1 subunit through a transcriptional mechanism. The effect of ouabain on β1 subunit induction, like that on α3 repression, was dependent on extracellular Ca2+ and on calmodulin. Inhibitions of PKC, Ras, and MEK, however, had different quantitive effects on ouabain-induced regulations of β1 and α3 subunits. The findings show that partial inhibition of Na/K-ATPase activates multiple signaling pathways that regulate growth-related genes, including those of two subunit isoforms of Na/K-ATPase, in a gene-specific manner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026503319387
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  • 18
    Digitale Medien
    Digitale Medien
    Protein kinase C-γ phorbol-binding domain involved in protein-protein interaction (2000)
    Springer
    Molecular and cellular biochemistry 209 (2000), S. 69-77 
    Details
    ISSN: 1573-4919
    Schlagwort(e): protein kinase C ; phorbol-binding domain ; protein interaction ; calcium ; phospholipids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Protein kinase C-γ (PKC-γ) contains two cysteine-rich regions (Cys1, Cys2) responsible for interaction with phospholipids. However, previous experiments suggested that, only Cys1 represents the high affinity site involved in diacylglycerol-dependent activation of PKC-γ. This raises the question whether Cys2 might participate in other functions of the PKC-γ regulatory domain. The purpose of our studies was to examine the ability of Cys2 domain to bind cellular proteins. The Cys2 domain (residues 92-173) was expressed as a fusion protein with glutathione-S-transferase (GST) in Escherichia coli and purified. In order to investigate protein-protein interaction of Cys2 domain we used affinity column and an overlay assay. Our results demonstrate that the Cys2 domain of PKC-γ binds several proteins from rat brain extracts. In the absence of phospholipids the Cys2 domain binds some proteins in the cytosolic fraction of rat brain, but no binding was detected with the proteins extracted from particulate fraction. Ca2+ at 1 μM concentration potentiated binding of cellular proteins to Cys2 domain. In the absence of Ca2+ the Cys2 domain binds proteins in the cytosolic fraction of rat brain in the presence of phosphatidylserine and to the lesser extend in the presence of phosphatidylinositol but neither phosphatidylcholine nor phosphatidylethanolamine. These results suggest that the Cys2 domain of PKC-γ has the ability to interact with two classes of proteins. One class binds the Cys2 domain in the phosphatidylserine dependent fashion, and the other proteins bind Cys-2 domain in the Ca2+ dependent and phospholipid independent manner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007063331593
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  • 19
    Digitale Medien
    Digitale Medien
    Cytosolic Ca2+ concentration during Ca2+ depletion of isolated rat hearts (2000)
    Springer
    Molecular and cellular biochemistry 203 (2000), S. 169-175 
    Details
    ISSN: 1573-4919
    Schlagwort(e): calcium ; heart ; rats ; fluorescence spectroscopy ; Indo-1
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Reperfusion of isolated mammalian hearts with a Ca2+-containing solution after a short Ca2+-free period at 37°:C results in massive influx of Ca2+ into the cells and irreversible cell damage: the Ca2+paradox. Information about the free intracellular, cytosolic [Ca2+] ([Ca2+]i) during Ca2+ depletion is essential to assess the possibility of Ca2+ influx through reversed Na+/Ca2+ exchange upon Ca2+ repletion. Furthermore, the increase in end-diastolic pressure often seen during Ca2+-free perfusion of intact hearts may be similar to that seen during ischemia and caused by liberation of Ca2+ from intracellular stores. Therefore, in this study, we measured [Ca2+]i during Ca2+- free perfusion of isolated rat hearts. To this end, the fluorescent indicator Indo-1 was loaded into isolated Langendorff-perfused hearts and Ca2+-transients were recorded. Ca2+-transients disappeared within 1 min of Ca2+ depletion. Systolic [Ca2+]i during control perfusion was 268±54 nM. Diastolic [Ca2+]i during control perfusion was 114±34 nM and decreased to 53±19 nM after 10 min of Ca2+ depletion. Left ventricular end-diastolic pressure (LVEDP) significantly increased from 13±4 mmHg during control perfusion after Indo-1 AM loading to 31±5 mmHg after 10 min Ca2+ depletion. Left ventricular developed pressure did not recover during Ca2+ repletion, indicating a full Ca2+ paradox. These results show that LVEDP increased during Ca2+ depletion despite a decrease in [Ca2+]i, and is therefore not comparable to the contracture seen during ischemia. Furthermore, calculation of the driving force for the Na+/Ca2+ exchanger showed that reversed Na+/Ca2+ exchange during Ca2+ repletion is not able to increase [Ca2+]i to cytotoxic levels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007066422997
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  • 20
    Digitale Medien
    Digitale Medien
    Signal transduction mechanism in human neutrophil: comparative study between the ζ and β-protein kinase c isotypes (2000)
    Springer
    Molecular and cellular biochemistry 203 (2000), S. 143-151 
    Details
    ISSN: 1573-4919
    Schlagwort(e): protein kinase C ; ζ-PKC ; pseudosubstrate ; calcium ; neutrophil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Role of protein kinase C (PKC) isotypes in the regulation of neutrophil function are not clearly known. In the present study we purified the β-PKC and ζ-PKC isotypes from human neutrophil. Both the isotypes are immunoreactive only to their respective antibodies. ζ-PKC was further confirmed by RT-PCR using specific primer. Co-factor requirements for both the kinases were found to be different when DG and ceramide were used as second messenger. Selective substrate specificities were determined for both β and ζ-PKC using isotype specific pseudosubstrates viz., [Ser25]PKC [19-31] and [Ser119]PKC[113-130] respectively. Endogenous protein phosphorylation by purified β-PKC and ζ-PKC showed their functional differences in neutrophil. β-PKC phosphorylated 13, 15, 19, 33, 36, 47, 80 and 92 kDa proteins and ζ-PKC phosphorylated 19, 22, 42, 47, 75 and 87 kDa proteins, only exception was the phosphorylation of 47 kDa protein which had been phosphorylated by both the kinases. Differences in phosphorylation between β-PKC and ζ-PKC clearly indicate the selective role for these PKC isotypes in the activation sequences of neutrophil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007097220890
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  • 21
    Digitale Medien
    Digitale Medien
    Thermal analysis of the plasma membrane Ca2+-ATPase (2000)
    Springer
    Molecular and cellular biochemistry 209 (2000), S. 105-112 
    Details
    ISSN: 1573-4919
    Schlagwort(e): Ca2+-ATPase ; thermal analysis ; cholesterol ; calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The plasma membrane Ca2+-ATPase is a well known enzyme in eucaryotes able to extrude calcium to the extracellular space in order to restore intracellular calcium to very low levels. This ATPase needs plasma membrane lipids such as acidic phospholipids in order to maintain its activity. In this study, we investigated the role that calcium and cholesterol play on the thermal stability of the Ca2+-ATPase isolated from cardiac sarcolemma and erythrocyte membranes. Calcium showed a stabilizing and protective effect when the enzyme was exposed to high temperatures. This stabilizing effect showed by calcium was potentiated in the presence of cholesterol. These protection effects were reflected on several thermodynamic parameters such as T50, ▵Hvh and apparent ▵G, indicating that calcium might induce a conformational change stabilized in the presence of cholesterol that confers enzyme thermostability. The effect shown by cholesterol on ▵Hvh and apparent ▵H
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007182907274
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  • 22
    Digitale Medien
    Digitale Medien
    Unmodified calcium concentrations in tumour necrosis factor receptor subtype-mediated apoptotic cell death (2000)
    Springer
    Molecular and cellular biochemistry 211 (2000), S. 19-26 
    Details
    ISSN: 1573-4919
    Schlagwort(e): tumour necrosis factor ; receptors ; subtypes ; calcium ; apoptosis ; cancer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Tumour necrosis factor-α (TNF) receptors mediate a variety of effects dependent on cell type. A role for Ca2+ in TNF-induced death remains uncertain. Here we investigated restricting intracellular/extracellular Ca2+ in HeLa epithelial carcinoma cells expressing low and high levels of p75TNFR receptor subtype and KYM-1 rhabdomyosarcoma cells, models of rapid TNF-induced apoptosis. Ca2+-chelators EGTA and BAPTA-AM as well as microsomal Ca2+-ATPase inhibitor thapsigargin, did not alter TNF-induced death. TNF was also unable to alter resting [Ca2+]i levels which remained 〈 200 nM even during times when these cells were undergoing apoptotic cell death. These findings indicate no role for modulated Ca2+ concentrations in TNF-induced apoptotic cell death.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007189911897
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  • 23
    Digitale Medien
    Digitale Medien
    Chemical Composition of Fruits and Leaves Eaten by Short-Nosed Fruit Bat, Cynopterus sphinx (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2825-2841 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Bats ; calcium ; folivory ; frugivory ; nutrition ; protein ; Pteropodidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We evaluated organic and macromineral composition of selected fruits and leaves consumed by the short-nosed fruit bat, Cynopterus sphinx in South India. Results of principal components analysis (PCA) comparing soluble carbohydrates, crude protein, and crude fats indicate a higher percentage of protein in leaves and a higher percentage of carbohydrates and lipids in fruits. However, results of a paired t test comparing these organic components indicated no differences between fruits and leaves. Among the fruits analyzed, Musa x paradisiaca had the highest percentage of carbohydrates, and Psidium guajava had the highest percentage of lipids. Leaves of Cassia fistula, Moringa oleifera, coccinia cordifolia, and F. religiosa had the highest percentage of protein. PCA of selected macrominerals (Ca, Na, K, and P) indicate higher levels of Ca in leaves than in fruits. Results of t tests comparing these macrominerals revealed a difference between fruits and leaves for Ca, but not for the other macrominerals. Among the leaves analyzed, Ca was highest in mature leaves of C. fistula and lowest in leaves of F. religiosa. Leaves of M. oleifera and fruits of Achras sapota were highest in sodium. Among fruits analyzed for macrominerals, Ca was highest in F. bengalensis and lowest in Prosopis juliflora, A. sapota, and M. x paradisiaca. Potassium levels were highest in leaves of C. cordifolia and fruit pods of Prosopis juliflora. Phosphorus content was highest in leaves of M. oleifera and fruits of M. x paradisiaca. The relatively high concentrations of protein and calcium in leaves eaten by C. sphinx supports the hypothesis that leaves are important dietary sources for this plant-visiting bat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026446011693
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  • 24
    Digitale Medien
    Digitale Medien
    Conversion of Nitrogen to Protein and Amino Acids in Wild Fruits (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 1749-1763 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Conversion factor ; free amino acids ; fruits ; Kjeldahl ; nitrogen ; nutrition ; protein ; pulp ; secondary metabolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Protein content of plant tissues is usually estimated by multiplying total nitrogen by a conversion factor of 6.25. This technique assumes that all nitrogen originates from protein. When applied to fruit pulp, it overestimates protein content because pulp typically contains free amino acids and many nitrogenous secondary metabolites. At issue is the extent of error and, consequently, what the conversion factor between nitrogen and protein should be. We calculated a conversion factor based on pulp samples from 18 species collected in the southeastern United States. We also report a new and simple method of estimating protein and free amino acids in fruit pulp. Because previous studies have found high variation in protein and secondary metabolite content among fruit species, use of a single conversion factor for all species will generate error. In an attempt to reduce such error, we calculated protein contents and conversion factors separately for two common fruit types: lipid-rich/carbohydrate-poor and lipid-poor/carbohydrate-rich. We found no difference between these types of fruit and hence combined results in calculating an average conversion factor of 5.64. Use of an accurate conversion factor is important in estimating protein consumption by wild animals and in formulating diets of captive animals. It can also reveal whether loss of body mass in captive animals on fruit diets is due to insufficient protein consumption, secondary metabolite toxicity, or an imbalance of amino acids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005503316406
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  • 25
    Digitale Medien
    Digitale Medien
    Effect of dephostatin on intracellular free calcium concentration and amylase secretion in isolated rat pancreatic acinar cells (2000)
    Springer
    Molecular and cellular biochemistry 205 (2000), S. 163-169 
    Details
    ISSN: 1573-4919
    Schlagwort(e): calcium ; pancreatic acinar cell ; dephostatin ; cholecystokinin ; amylase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract This study investigates the effects of dephostatin, a new tyrosine phosphatase inhibitor, on intracellular free calcium concentration ([Ca2+]i) and amylase secretion in collagenase dispersed rat pancreatic acinar cells. Dephostatin evoked a sustained elevation in [Ca2+]i by mobilizing calcium from intracellular calcium stores in either the absence of extracellular calcium or the presence of lanthanium chloride (LaCl3). Pretreatment of acinar cells with dephostatin prevented cholecystokinin-octapeptide (CCK-8)-induced signal of [Ca2+]i and inhibited the oscillatory pattern initiated by aluminium fluoride (AlF- 4), whereas co-incubation with CCK-8 enhances the plateau phase of calcium response to CCK-8 without modifying the transient calcium spike. The effects of dephostatin on calcium mobilization were reversed by the presence of the sulfhydryl reducing agent, dithiothreitol. Stimulation of acinar cells with thapsigargin in the absence of extracellular Ca2+ resulted in a transient rise in [Ca2+]i . Application of dephostatin in the continuous presence of thapsigargin caused a small but sustained elevation in [Ca2+]i . These results suggest that dephostatin can mobilize Ca2+ from both a thapsigargin-sensitive and thapsigargin-insensitive intracellular stores in pancreatic acinar cells. In addition, dephostatin can stimulate the release of amylase from pancreatic acinar cells and moreover, reduce the secretory response to CCK-8. The results indicate that dephostatin can release calcium from intracellular calcium pools and consequently induces amylase secretion in pancreatic acinar cells. These effects are likely due to the oxidizing effects of this compound.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007086401390
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  • 26
    Digitale Medien
    Digitale Medien
    Stimulatory effect of regucalcin on proteolytic activity is impaired in the kidney cortex cytosol of rats with saline ingestion (2000)
    Springer
    Molecular and cellular biochemistry 206 (2000), S. 1-6 
    Details
    ISSN: 1573-4919
    Schlagwort(e): regucalcin ; calcium ; protease ; rat kidney cytosol ; saline ingestion ; hypertensive state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The effect of regucalcin (RC) on neutral proteolytic activity in the cytosol of rat kidney cortex was investigated. Proteolytic activity was significantly increased by the presence of RC (0.01 + 0.10 μM) in the enzyme reaction mixture. This increase was completely abolished by the addition of anti-RC monoclonal antibody (150 ng/ml). When the renal cortex cytosol was incubated without RC addition, the degradation of globin of substrate was demonstrated by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. This degradation was clearly inhibited by the addition of anti-RC antibody (150 ng/ml), indicating that protein degradation results partly from the cytosolic endogenous RC. Meanwhile, proteolytic activity was significantly decreased in the renal cortex cytosol of rats with saline ingestion for 2, 7, and 14 days. The effect of RC (0.1 μM) in increasing proteolytic activity was weakened in the kidney cortex cytosol of saline-ingested rats. The present study suggests that endogenous RC plays a role in the activation of proteases in the renal cortex cytosol, and that the RC effect is impaired in saline-ingested rats.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007007626813
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  • 27
    Digitale Medien
    Digitale Medien
    Influence of sustained mechanical stress on Egr-1 mRNA expression in cultured human endothelial cells (2000)
    Springer
    Molecular and cellular biochemistry 210 (2000), S. 101-108 
    Details
    ISSN: 1573-4919
    Schlagwort(e): human endothelial cells ; mechanical stress ; immediate early genes ; protein kinase C ; calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Restenosis after initially successful balloon angioplasty of coronary artery stenosis remains a major problem in clinical cardiology. Previous studies have identified pathogenetic factors which trigger cell proliferation and vascular remodeling ultimately leading to restenosis. Since there is evidence that endothelial cells adjacent to the angioplasty wound area synthesize factors which may initiate this process, we investigated the effects of mechanical stimulation on endothelial gene expression in vitro and focussed on the influence of sustained mechanical stress on expression of immediate early genes which have previously been shown to be induced in the vascular wall in vivo. Primary cultured human umbilical vein endothelial cells (HUVEC) and the human endothelial cell line EA.hy 926 were plated on collagen-coated silicone membranes and subjected to constant longitudinal stress of approximately 20% for 10 min to 6 h. Total RNA was isolated and the expression of the immediate early genes c-Fos and Egr-1 was studied by Northern blot analysis. We found a rapid upregulation c-Fos and Egr-1 mRNA which started at 10 min and reached its maxima at 30 min. HUVEC lost most of their stretch response after the third passage whereas immediate early gene expression was constantly in EA.hy 926 cells. Using specific inhibitors we investigated the contribution of several signal transduction pathways to stretch-activated Egr-1 mRNA expression. We found significant suppression of stretch-induced Egr-1 mRNA expression by protein kinase C (PKC) inhibition (p 〈 0.05) and by calcium depletion (EA.hy926, p 〈 0. 05; HUVEC, p = 0.063). No effect on stretch-activated Egr-1 mRNA expression was detected by inhibition of protein kinase A, blockade of stretch-activated cation channels or inhibition of microtubule synthesis. We conclude that sustained mechanical strain induces Egr-1 mRNA expression by PKC- and calcium-dependent mechanisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007126218740
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  • 28
    Digitale Medien
    Digitale Medien
    Control of cardiomyocyte gene expression as drug target (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 135-142 
    Details
    ISSN: 1573-4919
    Schlagwort(e): gene expression ; catecholamines ; angiotensin II ; heart failure ; myosin ; hypertension ; eprosartan
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Pressure overload of the heart is associated with a perturbed gene expression of the cardiomyocyte leading to an impaired pump function. The ensuing neuro-endocrine activation results in disordered influences of angiotensin II and catecholamines on gene expression. To assess whether angiotensin II type 1 receptor inhibition can also counteract a raised sympathetic nervous system activity, spontaneously hypertensive rats fed a hypercaloric diet were treated with eprosartan (daily 90 mg/kg body wt) and cardiovascular parameters were monitored with implanted radiotelemetry pressure transducers. Both, blood pressure and heart rate were increased (p 〈 0.05) by the hypercaloric diet. Although eprosartan reduced (p 〈 0.05) the raised systolic and diastolic blood pressure, the diet-induced rise in heart rate was blunted only partially. In addition to drugs interfering with the enhanced catecholamine influence, compounds should be considered that selectively affect cardiomyocyte gene expression via 'metabolic' signals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007181626766
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  • 29
    Digitale Medien
    Digitale Medien
    Angiotensin II-induced changes in G-protein expression and resistance of renal microvessels in young genetically hypertensive rats (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 121-129 
    Details
    ISSN: 1573-4919
    Schlagwort(e): angiotensin II ; SHR ; preglomerular arterioles ; G-proteins ; cAMP ; hypertension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Altered regulation of cAMP may contribute to enhanced renal reactivity to angiotensin II (Ang II) in spontaneously hypertensive rats (SHR). Such a phenomenon may occur in renal preglomerular arterioles and may involve changes in expression of GTP-binding regulatory proteins. We have examined the effects of Ang II on steady state levels of Gαi-1,2, Gαi-3 Gαs and Gαq in preglomerular arterioles from young marginally hypertensive SHR and on mean arterial pressure (MAP), renal vascular resistance (RVR) and renal cAMP excretion (UcAMP.V). Young (5-6 week old) SHR and Wistar Kyoto (WKY) rats received Ang II (35 ng/kg/min, s.c.) or vehicle for 7 days via osmotic minipumps. Urine was collected over the last 24 h. On day seven, MAP and renal blood flow were measured in anesthetized rats and RVR was determined. Preglomerular arterioles were isolated by perfusing the kidneys with iron oxide and using a series of mechanical steps coupled with the use of a magnet to retain iron-laden vessels. Membranes were prepared and the expressions of Gαi-1,2, Gαi-3, Gαs and Gαq were evaluated by Western immunoblotting. Baseline MAP (124 ± 6 mmHg) was only marginally (p 〉 0.05) higher in SHR when compared with WKY rats (110 ± 4 mmHg). RBF (3.04 ± 0.16 mL/min) was significantly lower and RVR (41.10 ± 1.37 mmHg.min/mL) was significantly higher in SHR when compared to age-matched WKY rats (4.36 ± 0.30 mL/min and 25.79 ± 1.58 mmHg.min/mL, respectively). Ang II significantly increased MAP in SHR (17 mmHg) but not in WKY rats. These increases in MAP were accompanied by significant increases in RVR in SHR (48% over control) but not in WKY rats. Compared to WKY rats, preglomerular arterioles from SHR exhibited significantly higher basal expression of Gαi-1,2 (11- fold), Gαi-3 (13-fold) and Gαs (3-fold). Chronic infusion of Ang II, however, downregulated the expression of Gαs (by 53%; p 〈 0.05), Gαi-1,2 ( by 72%; p 〈 0.05) and Gαi-3 (by 35%; p 〉 0.05) in SHR preglomerular arterioles but significantly upregulated the expression of these proteins in WKY by 3-, 8- and 15-fold, respectively. Basal levels of Gαq were not different in preglomerular arterioles from the two strains but were downregulated by Ang II in both WKY (74% of basal) and SHR (52% of control). Baseline UcAMP.V was significantly lower in SHR (31.22 ± 6.51 nmol/24 h) compared with WKY rats (65.33 ± 3.60 nmol/24 h). Chronic Ang II infusion significantly increased UcAMP.V in SHR as well as WKY rats. These data clearly demonstrate that expressions of Gi isoforms as well as Gs in renal microvessels are elevated during early stages of hypertension and suggest that the elevated levels of Gi proteins may be directly associated with a blunted adenylyl cyclase-cAMP cascade in the renal microvasculature. Furthermore, Ang II appears to directly downregulate the expression of Gs in young SHR but not in young WKY renal microvessels. Such diversity in its effect on G-protein expression may be important for enhanced renal sensitivity to Ang II in SHR.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007125525858
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  • 30
    Digitale Medien
    Digitale Medien
    Designing antisense to inhibit the renin-angiotensin system (2000)
    Springer
    Molecular and cellular biochemistry 212 (2000), S. 145-153 
    Details
    ISSN: 1573-4919
    Schlagwort(e): angiotensin ; antisense ; oligodeoxynucleotide ; plasmid ; adeno-associated virus ; hypertension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Overactive renin-angiotensin system has been indicated in numerous pathological situations. Current treatment is based on pharmaceutical compounds, which work on the proteins level. Undisputedly helpful, it is not, however, flawless. Some of the drawbacks include adverse effects and non-compliance problem, since in many cases medicine has to be taken at least once a day for a long time. Therefore it seems logical to try a different approach, for instance to correct the disease at the gene expression level, possibly having a choice of shorter or longer-lasting effects. This current review combines results, relevant to the angiotensin system, with the antisense approach, which decreases amount of target protein by interfering at the mRNA level. Dependent on the tool used - oligodeoxynucleotide, plasmid or viral vector, the antisense effect lasts from few days to months.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007192624989
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  • 31
    Digitale Medien
    Digitale Medien
    The Ca2+-Transporting Activity of Rat Liver Microsomes in Response to Protein Undernutrition: Implications for Liver Tumor Promotion (2000)
    Springer
    Bioscience reports 20 (2000), S. 93-98 
    Details
    ISSN: 1573-4935
    Schlagwort(e): ATPase ; calcium ; liver ; protein malnutrition ; transport ; tumor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The effect of protein undernutrition on the activity of the smoothendoplasmic reticulum (microsomal) Ca2+-ATPase (SERCA) wasinvestigated. After 12 weeks of ad libitum ingestion of low proteindiet (5% protein), a significant depression (p〈0.05) of liver ERCa2+-ATPase activity (68.6% depression) was observed. However,no significant effects on cytochrome P450 activity and relative liverweight were found. It is proposed that low protein diet by inhibitingthe rat liver SERCA activity, might increase the cytosolic free calciumion concentration ([Ca2+]) and promote the development of livertumor. The possible mechanisms of low protein diet induced inhibition ofSERCA activity are highlighted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005563216215
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  • 32
    Digitale Medien
    Digitale Medien
    Letter to the Editor: Sequence-specific resonance assignments and partial unfolding of extracellular domains II and III of E-cadherin (2000)
    Springer
    Journal of biomolecular NMR 16 (2000), S. 181-182 
    Details
    ISSN: 1573-5001
    Schlagwort(e): calcium ; cell adhesion ; NMR assignments
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008306727354
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  • 33
    Digitale Medien
    Digitale Medien
    High rate algal pond operating strategies for urban wastewater nitrogen removal (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 331-339 
    Details
    ISSN: 1573-5176
    Schlagwort(e): algal biomass ; algal uptake ; ammonia stripping ; biological nutrient removal ; high rate algal ponds ; nitrogen ; nutrients ; nitrification ; urban wastewater treatment ; waste stabilisation ponds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two experimental high rate algal ponds (HRAPs) (1.5m2, 570 L per unit), each with a secondaryclarifier for algal biomass separation (0.025 m2,without recirculation), were fed with urban wastewaterfor a one-year period (June 1993 to July 1994). TheHRAPs were installed on the roof of the Department ofHydraulic, Coastal and Environmental Engineering ofthe Technical University of Catalonia, Barcelona,Spain (lat. 41° 24′ 42″ N; long. 2° 7′42″ E). Nitrogen removal efficiency and changes intotal nitrogen, total organic nitrogen,NH4 +-N, and oxidized nitrogen underdifferent hydraulic retention times (HRTs) werecompared. HRAP A was always operated at a higherHRT than HRAP B. Both HRAPs were subjected to thesame environmental conditions of solar radiation, airtemperature and influent water quality. Grab samplesof influent, effluent of the HRAP (mixed liquor) andfinal effluent from the clarifiers were taken once aweek. The annual average nitrogen removal was 73% forHRAP A, and 57% for HRAP B. Higher removal in HRAP Awas due to a lower inorganic nitrogen concentration inits effluent. Significant differences (p〉 0.05) inthe relative proportions of nitrogen forms between thetwo HRAPs were observed only in autumn and winter.This was mainly because HRAP B did not achieve a highlevel of NH4 +-N removal by stripping andalgal uptake, as observed in HRAP A. NH4 +-Nstripping was the most important mechanism fornitrogen removal (mean efficiency of 47% and 32% inHRAP A and B, respectively) followed by algal uptake,and subsequent algal separation in the clarifiers(mean efficiency of 26% and 25% in HRAP A and Brespectively). The conclusion of this study is thatHRT determines both the nitrogen removal efficiencyand the distribution of nitrogen forms in the effluentof a HRAP. The nitrogen removal level can becontrolled through suitable HRT operating strategies.By operating at a HRT of 4 days in spring and summer,and 10 days in autumn and winter, nitrogenconcentration in the effluent of a HRAP system can bereduced to less than 15 mg L-1 N.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008146421368
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  • 34
    Digitale Medien
    Digitale Medien
    Involvement of intracellular regulatory systems in the adaptive effects of transient anoxia in vitro (2000)
    Springer
    Neuroscience and behavioral physiology 30 (2000), S. 357-363 
    Details
    ISSN: 1573-899X
    Schlagwort(e): Anoxia ; brain slices ; calcium ; phosphoinositides ; adaptation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The involvement of the calcium and phosphoinositide intracellular regulatory systems in the molecular-cellular mechanisms of adaptation of the brain to hypoxia induced by transient anoxia were studied in slices of rat olfactory cortex. Anoxia lasting 2 min initiated the development of moderate but stable activation of intracellular regulatory systems during the reoxygenation period, with increases in binding of Ca2+ to intracellular hydrophobic domains and increases in the level of polyphosphoiositide metabolism. During this period, cells in the slices released neuromediator factors into the perfusion fluid; transfer of these to recipient slices induced similar changes in the activities of intracellular regulatory system components in the recipient slices. After anoxia lasting 10 min, NMDA-mediated pathogenic hyperactivity of the calcium and phosphoinositide systems developed. Preliminary moderate activation of these systems by transient anoxia or neuromodulator factors released by cells in response to transient anoxia prevented disruption of intracellular regulatory system activity induced by subsequent longer-lasting anoxia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02471790
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  • 35
    Digitale Medien
    Digitale Medien
    Identification ofDrosophila mutant with memory defects after acquisition of conditioned reflex suppression of courtship (2000)
    Springer
    Neuroscience and behavioral physiology 30 (2000), S. 307-313 
    Details
    ISSN: 1573-899X
    Schlagwort(e): Memory ; suppression of courting ; Drosophila ; mutants ; P insertion mutagenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Four lines were selected from a collection of 33 lines prepared by P insertion mutagenesis using a single-copy P-element system; the males of these four lines showed memory defects after acquisition of conditioned reflex suppression of courting. In two lines (P171 and P95), the dynamics of retention of the conditioned reflex in the repeated impregnated-female courting test were similar to those of known short-term memory mutantsdnc andrut. In line P153, the dynamics were more reminiscent of the memory dynamics in a known medium-term memory mutant,amn. In line P124, the learning index was insignificant immediately after training was completed, which may indicate that this line was unable to acquire conditioned reflex suppression of courting. Determination of the positions of the P elements (P171: 48A-B; P153: 49B-C; P124; 67B–68A; P95: 77C-D) showed no correspondence with previously known mutations producing memory lesions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02471783
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  • 36
    Digitale Medien
    Digitale Medien
    Incidence of bacteria involved in nitrogen and sulphur cycles in tropical shrimp culture ponds (2000)
    Springer
    Aquaculture international 8 (2000), S. 463-472 
    Details
    ISSN: 1573-143X
    Schlagwort(e): nitrogen ; organic matter ; shrimp culture ; sulphur cycle bacteria ; water quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009250004999
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  • 37
    Digitale Medien
    Digitale Medien
    Sources, sinks, and fluxes of nutrients (N + P) in a small highly modified urban estuary in southern California (2000)
    Springer
    Urban ecosystems 4 (2000), S. 125-144 
    Details
    ISSN: 1573-1642
    Schlagwort(e): nitrogen ; phosphorus ; macroalgae ; estuary ; anthropogenic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik
    Notizen: Abstract Our objective was to begin to investigate sources, sinks, and flux rates of nitrogen (N) and phosphorus (P) in Famosa Slough, a small (12 ha) highly modified urban estuary in San Diego, California, U.S.A. The hydrology of Famosa Slough has been modified by culverts that dampen tidal influence and seasonal runoff from two urban watersheds, each of which has been implicated as a nutrient source that generates nuisance algal blooms. In 1995 and 1996, the ranges of nutrients measured in the water column were extremely wide; upper values exceeded those in other estuaries identified as eutrophic. Average dissolved inorganic nitrogen ranged from 2 to 250 μM, while dissolved inorganic phosphorus ranged from 〈1 to 15 μM. Nutrient content of the water changed rapidly both spatially and temporally depending on the tides and rainfall. While tidal water dominated this system, especially in the dry season, our results indicate that Famosa Slough's small watershed, not the larger watershed of the San Diego River, was the major source of nutrients during rainfall. Sediment nutrients were also high (∼3 mg N g dry wt−1 and 0.600 mg P g dry wt−1). Short-term flux studies suggest that the large accumulations of opportunistic green macroalgae commonly found in this estuary, and possibly the sediments, may act as a large and rapid sink for nutrients during times of high nutrient supply. We suggest that small, shallow estuaries in urban settings may have more complex and rapid nutrient dynamics than those found in larger systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011359311384
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  • 38
    Digitale Medien
    Digitale Medien
    Parental Imprinting in Drosophila (2000)
    Springer
    Genetica 109 (2000), S. 35-44 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; heterochromatin ; imprinting ; parental effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Genetic imprinting is a form of epigenetic silencing. But with a twist. The twist is that while imprinting results in the silencing of genes, chromosome regions or entire chromosome sets, this silencing occurs only after transmission of the imprinted region by one sex of parent. Thus genetic imprinting reflects intertwined levels of epigenetic and developmental modulation of gene expression. Imprinting has been well documented and studied in Drosophila, however, these studies have remained largely unknown due to nothing more significant than differences in terminology. Imprinting in Drosophilais invariably associated with heterochromatin or regions with unusual chromatin structure. The imprint appears to spread from imprinted centers that reside within heterochromatin and these are, seemingly, the only regions that are normally imprinted in Drosophila. This is significant as it implies that while imprinting occurs in Drosophila, it is generally without phenotypic consequence. Hence the evolution of imprinting, at least in Drosophila, is unlikely to be driven by the function of specific imprinted genes. Thus, the study of imprinting in Drosophilahas the potential to illuminate the mechanism and biological function of imprinting, and challenge models based solely on imprinting of mammalian genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026592318341
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  • 39
    Digitale Medien
    Digitale Medien
    Searching for a Common Centromeric Structural Motif: Drosophila Centromeric Satellite DNAs Show Propensity to form Telomeric-Like Unusual DNA Structures (2000)
    Springer
    Genetica 109 (2000), S. 71-75 
    Details
    ISSN: 1573-6857
    Schlagwort(e): centromere ; heterochromatin ; non B-DNA structures ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The molecular basis of centromere formation in a particular chromosomal region is not yet understood. In higher eukaryotes, no specific DNA sequence is required for the assembly of the kinetochore, but similar centromeric chromatins are formed on different centromere DNA sequences. Although epigenesis has been proposed as the main mechanism for centromere specification, DNA recognition must also play a role. Through the analysis of Drosophilacentromeric DNA sequences, we found that dodeca satellite and 18HT satellite are able to form unusual DNA structures similar to those formed by telomeric sequences. These findings suggest the existence of a common centromeric structural DNA motif which we feel merits further investigation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026546510127
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  • 40
    Digitale Medien
    Digitale Medien
    Genetic and biochemical analysis of brown eye mutation in Drosophila nasuta nasuta and Drosophila nasuta albomicans (2000)
    Springer
    Genetica 109 (2000), S. 235-243 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; brown eye ; eye pigments ; fitness ; gene localization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract By analyzing the progeny of crosses involving brown eye mutants and the wild types in two members of Drosophila nasuta subgroup namely D. n. nasuta and D. n. albomicans we could show that the mutant gene is recessive, located in the chromosome 2 and the alleles of this gene are present at different loci. A study of fitness in the eye color mutants in comparison with the wild types revealed that D. n. nasuta mutant has higher viability at both 25 ± 1°C and ambient temperatures; while D. n. albomicans mutant has faster rate of development only at 25 ± 1°C. Quantitative analysis of eye pigments in the mutants revealed that there is biosynthesis of both pteridines and xanthommatins unlike in bw/bw of D. melanogaster, where only xanthommatins are synthesized. In both the species, the pteridine quantities in mutants are similar; whereas xanthommatin quantity in $$\user1{bw}_n \user1{/bw}_n$$ is 10 times higher than that of $$\user1{bw}_a \user1{/bw}_a$$ . Further, the F1 progeny of intraspecific crosses (wild type X mutant) are found to have high amounts of pteridine, even when compared with parental wild type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017505400086
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  • 41
    Digitale Medien
    Digitale Medien
    Dnop56, a Drosophila gene homologous to the yeast nucleolar NOP56 gene (2000)
    Springer
    Genetica 109 (2000), S. 275-282 
    Details
    ISSN: 1573-6857
    Schlagwort(e): DmNop56 ; DsNop56 ; Drosophila ; molecular evolution ; snoRNPs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Small nucleolar RNAs (snoRNAs) are trans‐acting factors involved in maturation of rRNA and have been classified into Box C/D and Box H/ACA families. Most of the snoRNAs occur as ribonucleoprotein complexes with snoRNA‐associated proteins (snoRNPs). All Box C/D snoRNAs in yeast form complexes with Nop1p, Nop56p and Nop58p. Similarly, it has been reported that Box H/ACA‐containing snoRNAs form complexes with yeast Gar1p. Nop56p and Nop58p homologs have been described in several species. Here we report the isolation and molecular characterization of the Dnop56 genes from D. melanogaster and D. subobscura which show a very similar structure. Drosophila Nop56p proteins contain lysine‐rich regions at their carboxy‐terminus, and show a high degree of similarity to other Nop56p proteins from different organisms. Phylogenetic relationships among these proteins and other snoRNPs have been established.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017596312331
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  • 42
    Digitale Medien
    Digitale Medien
    Calmodulin-dependent and -independent apoptosis in cells of a Drosophila neuronal cell line (2000)
    Springer
    Apoptosis 5 (2000), S. 133-140 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; calmodulin ; caspases ; cell line ; Drosophila ; neuron
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract This study was undertaken to reveal apoptotic pathways in neurons using a Drosophila neuronal cell line derived from larval central nervous system. We could induce apoptotic cell death in the cells by a Ca2+ ionophore (A23187), a protein kinase inhibitor (H-7), an RNA synthesis inhibitor (actinomycin D) and a protein synthesis inhibitor (cycloheximide). All the apoptosis induced by each chemical required Ca2+ ions, although the origin of Ca2+ ions were different: apoptosis induced by A23187 was dependent on extracellular Ca2+ ions whereas those by the other three chemicals utilized intracellular Ca2+ ions. Furthermore, different reactions to W-7, a calmodulin inhibitor, were found: W-7 prevented the cell death by each of the three chemicals but not by A23187. Based on the results, we proposed that the apoptotic pathways are classified into two types in individual cells. One pathway induced by H-7, actinomycin D or cycloheximide is calmodulin-dependent (pathway H), and another induced by A23187 is calmodulin-independent (pathway A).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009676528805
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  • 43
    Digitale Medien
    Digitale Medien
    An episode of accelerated amino acid change in Drosophila esterase-6 associated with a change in physiological function (2000)
    Springer
    Genetica 110 (2000), S. 231-244 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; , esterase-6 ; function ; sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In most lineages of the subgenus Sophophora esterase-6 is a homodimeric haemolymph protein. In the melanogaster subgroup of species it has become a monomer which is mainly expressed in the male sperm ejaculatory duct. Our analyses of esterase-6 sequences from three melanogaster subgroup species and two close relatives reveal a brief period of accelerated amino acid sequence change during the transition between the ancestral and derived states. In this period of 2–6Myr the ratio of replacement to silent site substitutions (0.51) is about three times higher than the values in other lineages of the phylogeny. There are about 50 more replacements in this period than would be predicted from the ratios of replacement to silent site substitutions found elsewhere in the phylogeny. Modelling on the known structure of a related acetylcholinesterase suggests that an unusually high proportion of the replacements in the transitional branch are non-conservative changes on the protein surface. Up to half the accelerated replacement rate can be accounted for by clusters of changes to the face of the molecule containing the opening of the active site gorge. This includes changes in and around regions homologous to peripheral substrate binding sites in acetylcholinesterase. There are also three changes in glycosylation status. One region predicted to lie on the protein surface which becomes markedly more hydrophilic is proposed to be the ancestral dimerisation site that is lost in the transitional branch.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1012727814167
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  • 44
    Digitale Medien
    Digitale Medien
    Impact of Multiple Insertions of two Retroelements, ZAM and Idefix at an Euchromatic Locus (2000)
    Springer
    Genetica 109 (2000), S. 53-59 
    Details
    ISSN: 1573-6857
    Schlagwort(e): chromatin structure ; Drosophila ; mutagenic effect ; retroelements ; white
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Transposable elements represent a large fraction of eukaryotic genomes and they are thought to play an important role in chromatin structure. ZAMand Idefixare two LTR-retrotransposons from Drosophila melanogastervery similar in structure to vertebrate retroviruses. In all the strains where their distribution has been studied, ZAMappears to be present exclusively in the intercalary heterochromatin while Idefixcopies are mainly found in the centromeric heterochromatin with very few copies in euchromatin. Their distribution varies in a specific strain called RevI in which the mobilization of ZAMand Idefixis highly induced. In this strain, 15 copies of ZAMand 30 copies of Idefixare found on the chromosomal arms in addition to their usual distribution. Amongst the loci where new copies are detected, a hotspot for their insertion has been detected at the whitelocus where up to four elements occurred within a 3-kb fragment at the 5′ end of this gene. This property of ZAMand Idefixto accumulate at a defined site provides an interesting paradigm to bring insight into the effect exerted by multiple insertions of transposable elements at an euchromatic locus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026534207401
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  • 45
    Digitale Medien
    Digitale Medien
    Variations of male cuticular hydrocarbons with geoclimatic variables: an adaptative mechanism in Drosophila melanogaster? (2000)
    Springer
    Genetica 110 (2000), S. 117-130 
    Details
    ISSN: 1573-6857
    Schlagwort(e): adaptation ; Drosophila ; hydrocarbons ; latitude ; longitude ; natural populations ; polymorphism ; temperaturey ; vapour pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 7-tricosene (7T) and 7-pentacosene (7P) are the major components of cuticular hydrocarbons in Drosophila simulans and D. melanogaster males. A chemical study of 16 isofemale lines of D. melanogaster sampled at the first and eighth generations in laboratory conditions showed the stability of chromatographical profiles. Then a large scale study of male 7T/7P polymorphism was performed with 85 populations of D. melanogaster and 29 of D. simulans collected all over the world. There were significant correlations of the values of the balanced ratio (7T − 7P)/(7T + 7P) with geo-climatic parameters, such as latitude, longitude, mean temperature, temperature range and vapour pressure. Parallel variations were also reported for the homologous linear alkanes (23 and 25 Carbon atoms) but not for the longer branched alkanes (27 and 29 Carbon atoms). No correlation was significant for the D. simulans populations studied. In this species a similar polymorphism of 7T/7P was found but restricted to a few populations from West Equatorial Africa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017987220814
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  • 46
    Digitale Medien
    Digitale Medien
    Genetic variance in temperature dependent adult size deriving from physiological genetic variation at temperature boundaries (2000)
    Springer
    Genetica 110 (2000), S. 195-207 
    Details
    ISSN: 1573-6857
    Schlagwort(e): biophysics ; body size ; Drosophila ; ectotherm ; genetic variance ; stress ; temperature extreme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An increase in genetic variation in body size has often been observed under stress; an increase in dominance variance and interaction variance as well as in additive genetic variance has been reported. The increase in genetic variation must be caused by physiological mechanisms that are specific to adverse environments. A model is proposed to explain the occurrence of an increase in genetic variation in body size in Drosophila at extreme temperatures. The model has parameters specific to the low- and high-temperature regions of the viable range. Additive genetic variation in the boundary temperatures leads to a marked increase in additive genetic variation in development rate and body size at extreme temperatures. Additive genetic variation in the temperature sensitivity in the low- and high-temperature regions adds non-additive genetic variation. Development rate shows patterns in additive genetic variation that differ from the patterns of genetic variation in body size; therefore, the genetic correlation between development rate and body size changes sign repeatedly as a function of temperature. The existence of dominance in the genetic variation in the boundary temperatures or in the low- and high-temperature sensitivities leads to a higher total genetic variance due to higher dominance and interaction variance, for both development rate and body size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017974618477
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  • 47
    Digitale Medien
    Digitale Medien
    Composition and Proposed Nutritional Importance of Exudates Eaten by Saddleback (Saguinus fuscicollis) and Mustached (Saguinus mystax) Tamarins (2000)
    Springer
    International journal of primatology 21 (2000), S. 69-83 
    Details
    ISSN: 1573-8604
    Schlagwort(e): tamarin ; saguinus ; exudate ; mineral ; calcium ; feeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract I provide the first comprehensive data on the composition and mineral content of exudates eaten by saddleback (Saguinus fuscicollis) and mustached tamarins (S. mystax) and assess Garber's (1984; 1993) hypotheses on the potential nutritional importance of exudates in the diet of tamarins. In accordance with his initial findings, nutritional analyses show that the gums consumed are relatively high in calcium and may serve to balance a diet otherwise low in this mineral and high in phosphorus. However, the data on the seasonal variation in the amount consumed do not support the hypothesis that exudates are of particular nutritional importance during the later stages of gestation or lactation for saddleback or mustached tamarins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005423629627
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  • 48
    Digitale Medien
    Digitale Medien
    Short-term Cover Crop Decomposition in Organic and Conventional Soils: Characterization of Soil C, N, Microbial and Plant Pathogen Dynamics (2000)
    Springer
    European journal of plant pathology 106 (2000), S. 37-50 
    Details
    ISSN: 1573-8469
    Schlagwort(e): carbon ; cellulose ; cover crop ; damping-off ; discriminant analysis ; lignin ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Stages of oat–vetch cover crop decomposition were characterized over time in terms of carbon and nitrogen cycling, microbial activity and damping-off pathogen dynamics in organically and conventionally managed soils in a field and a controlled incubation experiment. A measurement of relative growth consisting of radial growth of a fungal colony over non-sterilized soil divided by that over sterilized soil was used as an assay of suppressiveness. No differences in relative growth of Pythium aphanidermatum and Rhizoctonia solani were detected between organic and conventionally managed soils amended with cover crop residue. Significant effects of cover crop decomposition stage on the relative growth of both pathogens were obtained. Relative growth of P. aphanidermatum was highest just after incorporation and decreased 3 weeks after incorporation. Relative growth of R. solani was highest about 20 days after incorporation, and decreased 2 weeks later in the organic system, but continued to increase in the conventional system. In both experiments, the N or C content, C:N ratio or dry weight of retrieved debris were significantly correlated with relative growth of P. aphanidermatum. Relative growth of R. solani was significantly correlated with the C:N ratio of soil or the C or N content of debris. Microbial activity was not consistently associated with relative growth of either pathogen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008720731062
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  • 49
    Digitale Medien
    Digitale Medien
    Co-development of wetland soils and benthic invertebrate communities following salt marsh creation (2000)
    Springer
    Wetlands ecology and management 8 (2000), S. 197-207 
    Details
    ISSN: 1572-9834
    Schlagwort(e): benthic invertebrates ; mitigation ; nitrogen ; organic matter ; pedogenesis ; phosphorus ; plant productivity ; restoration and rehabilitation ; salt marsh ; wetland creation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The development of wetland soil characteristics andbenthic invertebrate communities were evaluated increated Spartina alterniflorasalt marshes inNorth Carolina ranging in age from 1 to 25 years-old.A combination of measurements from different-agecreated marshes as well as periodic measurements overtime on two marshes were used to (1) document rates ofwetland pedogenesis, especially soil organic matter,and, (2) explore relationships between soil andbenthic invertebrate community development. Soilmacro-organic matter (MOM, the living and dead rootand rhizome mat), organic C and N increased and bulkdensity decreased during the 25 years following marshestablishment. The most dramatic changes in bulkdensity, MOM, C and N occurred within the upper 10 cmof the soil with lesser changes below this depth.Created marshes were sinks for organic C (90–140g·m-2·yr-1) and N (7–11g·m-2·yr-1) but not for P (0–1g·m-2·yr-1). The density of benthicinvertebrates (〉250 μm) and subsurface-depositfeeding oligochaetes also increased over time oncreated salt marshes. Invertebrate and oligochaetedensity were strongly related to MOM content(r2= 0.83–0.87) and soil organic C(r2= 0.52–0.82) and N (r2= 0.62–0.84). Thesefindings suggest that, in created salt marshes,development of the benthic invertebrate community istied to marsh soil formation, especially accumulationof organic matter as MOM and soil. Field studies thatmanipulate the quantity and quality of soil organicmatter are needed to elucidate the relationshipbetween salt marsh pedogenesis and benthicinvertebrate community development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008448620605
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  • 50
    Digitale Medien
    Digitale Medien
    Histone H1-Mediated Transfection: Serum Inhibition Can Be Overcome by Ca2+ Ions (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 229-235 
    Details
    ISSN: 1573-904X
    Schlagwort(e): transfection ; serum inhibition ; H1 histone ; DOSPER ; calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. One of the drawbacks of polycationic and cationic liposomalgene transfer is its sensitivity to serum. Gene therapy requires thetransfectant-DNA complex to be resistant to serum as well as blood.Since Ca2+ has proved to be an efficient cofactor of polycationic genetransfer, we decided to investigate its effects on transfection in thepresence of serum. Methods. We studied transgene expression of luciferase gene (pCMVLuc) on ECV 304 human endothelial cells using H1 histone andDOSPER as transfectants in the presence of 0-100% fetal calf serum. Results. H1-and DOSPER-mediated transfection was found to beinhibited by serum above the concentration of 10%. If 2 mM Ca2+ or2 mM Ca2+/0.1 mM chloroquine was included in the culture mediumwhich replace the transfection mixture and was left on the cells for24 hours postincubation, the inhibiting effect of even 100% serumwas overcome. Conclusions. A high serum level does not interfere with binding anduptake of H1- and DOSPER-DNA complexes, but inhibits subsequentsteps such as endosomal escape. Ca2+ in the form of nascent calciumphosphate microprecipitates and other lysosomolytical agents facilitateendosomal/lysosomal release by their fusigenic and membranolyticactivity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007581700996
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  • 51
    Digitale Medien
    Digitale Medien
    Distinct requirements for the AP-3 adaptor complex in pigment granule and synaptic vesicle biogenesis in Drosophila melanogaster (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 1003-1014 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Key words AP-3 ; Biogenesis ; Pigment granule ; Synaptic vesicle ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The AP-3 adaptor protein complex has been implicated in the biogenesis of lysosome-related organelles, such as pigment granules/melanosomes, and synaptic vesicles. Here we compare the relative importance of AP-3 in the biogenesis of these organelles in Drosophila melanogaster. We report that the Drosophila pigmentation mutants orange and ruby carry genetic lesions in the σ3 and β3-adaptin subunits of the AP-3 complex, respectively. Electron microscopy reveals dramatic reductions in the numbers of electron-dense pigment granules in the eyes of these AP-3 mutants. Mutant flies also display greatly reduced levels of pigments housed in these granules. In contrast, electron microscopy of retinula cells reveals numerous synaptic vesicles in both AP-3 mutant and wild-type flies, while behavioral assays show apparently normal locomotor ability of AP-3 mutant larvae. Together, these results demonstrate that Drosophila AP-3 is critical for the biogenesis of pigment granules, but is apparently not essential for formation of a major population of synaptic vesicles in vivo.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00008688
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  • 52
    Digitale Medien
    Digitale Medien
    Physiological regulation of plant-atmosphere ammonia exchange (2000)
    Springer
    Plant and soil 221 (2000), S. 95-102 
    Details
    ISSN: 1573-5036
    Schlagwort(e): ammonia exchange ; apoplast ; atmosphere ; glutamine synthetase ; nitrogen ; photorespiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Plants have a compensation point for NH3 which ranges from 0.1 to 20 nmol mol-1, and may be several-fold higher or lower than naturally occurring atmospheric NH3 concentrations. This implies that NH3 fluxes over vegetated surfaces are bi-directional and that ammonia exchange with the atmosphere in many cases contributes significantly to the nitrogen economy of vegetation. Physiological regulation of plant–atmosphere NH3 fluxes is mediated via processes involved in nitrogen uptake, transport and metabolism. A rapid turnover of NH3 + in plant leaves leads to the establishment of a finite NH3 + concentration in the leaf apoplastic solution. This concentration determines, together with that of H+, the size of the NH3 compensation point. Barley and oilseed rape plants with access to NH3 + in the root medium have higher apoplastic NH3 + concentrations than plants absorbing NO3 -. Furthermore, the apoplastic NH3 + concentration increases with the external NH3 + concentration. Inhibition of GS leads to a rapid and substantial increase in apoplastic NH3 + and barley mutants with reduced GS activity have higher apoplastic NH3 + than wild-type plants. Increasing rates of photorespiration do not affect the steady-state NH3 + or H+ concentration in tissue or apoplast of oilseed rape, indicating that the NH3 + produced is assimilated efficiently. Nevertheless, NH3 emission increases due to a temperature-mediated displacement of the chemical equilibrium between gaseous and aqueous NH3 in the apoplast. Sugarbeet plants grown with NO3 - seem to be temporarily C-limited in the light due to a repression of respiration. As a consequence, the activity of chloroplastic GS declines during the day causing a major part of NH3 + liberated in photorespiration to be assimilated during darkness when 2-oxoglutarate is supplied in high rates by respiration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004761931558
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  • 53
    Digitale Medien
    Digitale Medien
    Changes in root morphology of white lupin (Lupinus albus L.) and its adaptation to soils with heterogeneous alkaline/acid profiles (2000)
    Springer
    Plant and soil 218 (2000), S. 197-205 
    Details
    ISSN: 1573-5036
    Schlagwort(e): acid soil ; calcium ; cluster roots ; heterogeneous soil profile ; limed soil ; lupins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The ability of Lupinus albus L. to adapt to a heterogeneous soil profile containing acid subsoil below limed topsoil of the same type, and to utilize nutrients by significantly altering its root system structure, was investigated using specially constructed soil profile tubes. Plants grown in homogeneous acid profiles had the fastest growth while those grown in homogeneous limed-soil profiles showed the slowest growth and exhibited some chlorosis after 19 days. Limed topsoil combined with an acid subsoil profile initially retarded plant growth similar to that in a homogeneous limed soil. However, after 68 days significantly greater growth had occurred in the limed/acid soil treatment relative to the homogeneous limed soil, indicating plants had benefited from the acid subsoil stratum. Plants in the homogeneous limed soil profile had lower concentrations of P, Fe and Mn in shoots compared with those in heterogeneous soils. In contrast, the concentration of Ca increased by 74%, due mainly to an increase in the water-soluble Ca fraction. When grown in a heterogeneous limed/acid soil profile, concentrations of P, Ca, K, Mg, Fe, Mn and Zn in shoots were comparable to those grown in a soil with a homogeneous acid profile. Although total root production was lower in the homogeneous limed-soil profile compared to the acid-soil containing profiles, cluster root mass was maintained at a level comparable with that in acid soil. The roots in heterogeneous soil profiles exhibited extensive plasticity, demonstrating a root-type specific, morphological response to the soil conditions. Within the acid subsoil of a heterogeneous profile, there was a large increase in cluster root mass compared with non-cluster roots. The proliferation of cluster roots in acid soil below limed topsoil may enhance the plant's ability to exploit this soil and facilitate the cultivation of L. albus on limed soil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1014967720952
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  • 54
    Digitale Medien
    Digitale Medien
    A comparison between Ca and Sr cycling in forest ecosystems (2000)
    Springer
    Plant and soil 225 (2000), S. 299-310 
    Details
    ISSN: 1573-5036
    Schlagwort(e): Acer pseudoplatanus L. ; calcium ; Fagus sylvatica L. ; Karst ; Picea abies L. ; strontium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In favourable conditions, the 87Sr/86Sr isotope ratios of the Sr delivered by rain and soil mineral weathering differ. Assuming that Ca and Sr behave similarly in forest ecosystems, several authors have used the 87Sr/86Sr variation in forest compartments to calculate the contribution of rain and mineral weathering to Ca fluxes and pools. However, there are a number of experimental reports showing that Ca and Sr may behave differently in the soil and in the plant. We have tested this Ca–Sr analogy in the field by measuring the variation of Sr and Ca concentrations, fluxes and pools in spruce, beech and maple stands on granite, sandstone and limestone. Results show that (1) variations of Ca and Sr concentrations are generally correlated at each level of the ecosystems. (2) In spruce on acid soils, a preferential uptake of Ca over Sr occurs (Aubure spruce Sr/Ca = 0.8×10−3; soil exchangeable Sr/Ca between 2 and 6×10−3). On calcareous soils, a preferential uptake of Sr over Ca by spruce may occur. (3) In spruce and beech on acid and calcareous soils, a preferential translocation of Ca over Sr from roots to leaves occurs ((Sr/Ca) in leaves was between 10 and 90% of that in roots). (4) The biological cycling of Ca and Sr leads to an enrichment of the upper soil layers in Ca and Sr. Compared to Sr, Ca accumulates in the upper layer of acid soils because Ca cycling through litterfall is favoured over Sr cycling, and possibly because of the selectivity of acid organic exchangers for Ca.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026570812307
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  • 55
    Digitale Medien
    Digitale Medien
    Nitrogen and base cation uptake in seedlings of Acer pseudoplatanus and Calamagrostis villosa exposed to an acidified environment (2000)
    Springer
    Plant and soil 226 (2000), S. 71-77 
    Details
    ISSN: 1573-5036
    Schlagwort(e): acid soil ; ammonium ; calcium ; magnesium ; nitrate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effects of solution acidity and form of nitrogen on net nutrient uptake rates in Acer pseudoplatanus and Calamagrostis villosa seedlings were examined as part of a complex ecological study. Uptake rates were measured by the depletion method under controlled conditions (temperature 20 °C, irradiance 400 μmol m−2 s−1 PAR) from a nutrient solution containing 1.5 mM nitrogen in the form of nitrate or ammonium or an equimolar mixture of both. The solution acidity was kept constant at pH 5.5 (control treatment), 4.5 or 3.5 (low pH treatments). Strongly acid pH decreased or stopped the uptake rates of NO3 −, Mg2+ and Ca2+, but the uptake of NH4 + was not changed in both species. Ammonium ions reduced the uptake rate of NO3 − in Acer but increased the uptake rate in Calamagrostis. Ammonium as the sole source of nitrogen had a strong negative impact on the uptake rates of calcium and magnesium and this effect was independent of the media acidification usually connected with NH4 + uptake and assimilation. However, the negative effect of ammonium ions on the base cation uptake was more pronounced at low pH values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026545415275
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  • 56
    Digitale Medien
    Digitale Medien
    The effect of three or five years of set-aside on the husbandry and grain yield of subsequent cereal crops in the UK (2000)
    Springer
    Plant and soil 225 (2000), S. 279-297 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cereal ; cereal quality ; cereal yields ; natural regeneration ; nitrogen ; nitrogen uptake ; rye-grass ; set-aside ; white clover
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract During the period 1993–1997, at six contrasting sites located throughout England, two successive cereal test crops were grown both with and without nitrogen fertiliser after three or five years of set-aside or after continuous arable cropping. Vegetation during set-aside included natural regeneration and perennial rye-grass (Lolium perenne) with or without white clover (Trifolium repens), managed by mowing on one or more occasions per year. Establishment of the successive cereal test crops after destruction of the set-aside was generally not a problem. Fertile tiller numbers were increased by inclusion of clover in the set-aside cover or application of inorganic nitrogen. The presence of couch grass (Elytrigia repens) or volunteer cereals in the set-aside covers provided alternative hosts for take-all (Gaeumanomyces graminis) and eyespot (Pseudocercosporella herpotrichoides) and take-all caused some yield reductions in following cereal crops. Management during the set-aside period significantly affected grain yields of the subsequent cereal crops in the majority of the site-year combinations. However, these effects were not as large as would be expected after traditional break crops and were frequently masked by the application of nitrogen fertiliser. Mean yields increased by 80% due to the application nitrogen at the optimum rate compared to nil nitrogen. Most of the effects of set-aside treatment on grain yield were shown to be attributable to soil mineral nitrogen content, but at some sites, infections by take-all or eyespot also accounted for some of the variation. There were no effects of pests that could be related to treatment. The presence of sown clover during the set-aside period had the most consistent effect across sites, affecting tiller populations, grain yield and grain quality of cereal crops. At some sites, establishing a sown cover during the set-aside period, or cutting the cover more than once a year, improved grain yield and quality, and reduced the incidence of some specific weeds and disease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026531528082
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  • 57
    Digitale Medien
    Digitale Medien
    Root-shoot interactions in mineral nutrition (2000)
    Springer
    Plant and soil 226 (2000), S. 57-69 
    Details
    ISSN: 1573-5036
    Schlagwort(e): ABA ; K/Na selectivity ; nitrate reduction ; nitrogen ; phloem ; phosphate ; root-shoot interactions ; salinity ; xylem
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In this paper four classes of co-operative root-shoot interations are addressed. (I) Nitrogen concentrations in the xylem sap originating from the root and in the phloem sap as exported from source leaves are much lower than those required for growth by apices and developing organs. Enrichment of xylem sap N is achieved by xylem to xylem (X-X) transfer, by which reduced N, but not nitrate, is abstracted from the xylem of leaf traces and loaded into xylem vessels serving the shoot apex. Nitrogen enrichment of phloem sap from source leaves is enacted by transfer of reduced N from xylem to phloem (X-P transfer). Quantitative data for the extent of the contribution of X-X and X-P transfer to the nutrition of young organs of Ricinus communis L. and for their change with time are presented. (II) Shoot and root cooperate in nitrate reduction and assimilation. The partitioning of this process between shoot and root is shifted towards the root under conditions of nitrate- and K-deficiency and under salt stress, while P deficiency shifts nitrate reduction almost totally to the shoot. All four changes in partitioning can be attributed to the need for cation-anion balance during xylem transport and the change in electrical charge occurring with nitrate reduction. (III) Even maintenance of the specificity of ion uptake by the root may – in addition to its need for energy – require a shoot-root interaction. This is shown to be needed in the case of the maintenance of K/Na selectivity under the highly adverse condition of salt stress and absence of K supply from the soil. (IV) Hormonal root to shoot interactions are required in the whole plant for sensing mineral imbalances in the soil. This is shown and addressed for conditions of salt stress and of P deficiency, both of which lead to a strong ABA signalling from root to shoot but result in different patterns of response in the shoot.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026431408238
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  • 58
    Digitale Medien
    Digitale Medien
    Dynamics of biomass and N accumulation of alfalfa under three N fertilization rates (2000)
    Springer
    Plant and soil 219 (2000), S. 177-185 
    Details
    ISSN: 1573-5036
    Schlagwort(e): alfalfa ; growth ; Medicago sativa L. ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The dynamics of biomass and N accumulation following defoliation of alfalfa and the application of N fertilization has rarely been studied under field conditions, particularly in the seeding year. Our objectives were to determine the effect of N fertilization on the dynamics of biomass and N accumulation during the first regrowth of alfalfa in the seeding year, and to determine if a model describing critical N concentration developed for established stands could be used in the seeding year. In two separate experiments conducted in 1992 and 1993, the biomass and N accumulation of alfalfa grown with three N rates (0, 40 and 80 kg N ha-1) were determined weekly. Maximum shoot growth was reached with 40 kg N ha-1 in 1992, and maximum shoot growth was not reached with the highest N fertilization rate in 1993. Nitrogen fixation, root N reserves and soil inorganic N uptake when no N was applied were, therefore, not sufficient to ensure non-limiting N conditions, particularly when growth rates were the highest between 14 to 21 d after defoliation. Nitrogen fertilization increased shoot biomass accumulation in the first 21 d of regrowth, biomass partitioning to the shoots and shoot and taproot N concentrations. The model parameters of critical N concentration developed by Lemaire et al. (1985) for established stands of alfalfa were not adequate in the seeding year. The N requirements per unit of shoot biomass produced are greater in the seeding year than on established stands, and this was attributed to a greater proportion of leaves in the seeding year.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004749828745
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  • 59
    Digitale Medien
    Digitale Medien
    13C NMR study of pine needle decomposition (2000)
    Springer
    Plant and soil 219 (2000), S. 273-278 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cellulose ; lignin ; litter ; nitrogen ; Pinus radiata ; tannins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The quality of substrates in plantation forest litter, and their chemistry, can influence decomposition and N cycling. We studied the decomposition of Pinus radiata D. Don needles suspended on branches in windrows, for 3 yr after clear-cutting, using improved solid-state 13C NMR and chemical analysis. The NMR spectra suggested that the concentration of condensed tannins was 12–22%, and showed they were chemically altered during the period 4–12 months after clear-cutting. The spectra showed no evidence for further chemical modification of the tannins during the second or third years. Data for P. radiata needle decomposition in New Zealand indicated rapid loss of mass in the first 3 months, and condensed tannins did not appear to prevent mineralization of C or N. The tannin and lignin concentrations increased with decomposition of the needles, which was consistent with the early mineralization of readily available C compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004783502067
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  • 60
    Digitale Medien
    Digitale Medien
    The effects of slash burning on ecosystem nutrients during the land preparation phase of shifting cultivation (2000)
    Springer
    Plant and soil 220 (2000), S. 247-260 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cations ; fire ; nitrogen ; nutrients ; phosphorus ; slash-and-burn ; soil ; tropical forests
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The most commonly observed change in soil following slash-and-burn clearing of tropical forest is a short-term increase in nutrient availability. Studies of shifting cultivation commonly cite the incorporation of nutrient-rich ash from consumed aboveground biomass into soil as the reason for this change. The effects of soil heating on nutrient availability have been examined only rarely in field studies of slash-and-burn, and soil heating as a mechanism of nutrient release is most often assumed to be of minor importance in the field. Few budgets for above and belowground nutrient flux have been developed in the tropics, and a survey of results from field and laboratory studies indicates that soils are sufficiently heated during most slash-and-burn events, particularly in dry and monsoonal climates, to cause significant, even substantial release of nutrients from non-plant-available into plant-available forms in soil. Conversely, large aboveground losses of nutrients during and after burning often result in low quantities of nutrients that are released to soil. Assessing the biophysical sustainability of an agricultural practice requires detailed information about nutrient flux and loss incurred during management. To this end, current conceptual models of shifting cultivation should be revised to more accurately describe these fluxes and losses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004741125636
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  • 61
    Digitale Medien
    Digitale Medien
    Soil patchiness in juniper-sagebrush-grass communities of central Oregon (2000)
    Springer
    Plant and soil 223 (2000), S. 47-61 
    Details
    ISSN: 1573-5036
    Schlagwort(e): correlograms ; nitrogen ; soil arthropods ; soil resource islands ; variograms ; vesicular-arbuscular mycorrhizae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This study compared the sizes, spacings and properties (soil moisture, pH, nitrogen, soil arthropods and VAM) of soil resource islands and bare patches in sagebrush-grass communities invaded by western juniper versus those without juniper. We analyzed 1000 surface soil samples taken from nine 50-m radius circular plots sampled in December of 1991 and May of 1992 on ‘The Island’, one of the few undisturbed areas of sagebrush-grass shrubland in Oregon. Spatial structure was interpreted from correlograms (Moran's I) and standardized semivariograms. The presence of juniper was associated with increased bare area and smaller, more widely spaced grass and sagebrush plants. Soil arthropod numbers and biomass in plots with juniper were only roughly one-fifth of those in sagebrush-grass plots in December. The dominant soil pattern in both sagebrush-grass and juniper-sagebrush-grass plots was regularly-distributed patches spanning a range of sizes and spacings. Plots with juniper had greater patchiness at shorter lags (〈3 m), and patchiness was more developed for soil moisture, net nitrification, and net N mineralization, whereas sagebrush-grass plots had greater patchiness at longer lags (3 – 9 m) and patchiness was more developed for NO3–N, arthropod numbers and biomass. These differences in soil patterns with and without juniper indicate that juniper responds to, or causes, changes in the size of resource islands under sage and grass when it invades sage-grass communities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004745329332
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  • 62
    Digitale Medien
    Digitale Medien
    Estimating crop N uptake from organic residues using a new approach to the 15N isotope dilution technique (2000)
    Springer
    Plant and soil 223 (2000), S. 33-46 
    Details
    ISSN: 1573-5036
    Schlagwort(e): crop residues ; nitrogen ; organic residues
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Experiments were conducted to test a new approach to the 15N isotope dilution technique for estimating crop N uptake from organic inputs. Soils were pre-labelled with 15N fertiliser and a carbon source. These were then incubated until there was stabilisation of the 15N abundance of the inorganic N pool and resumption of inorganic N concentrations. Residues were then applied to the soils and planted with ryegrass (Lolium perenneL.) to determine the nitrogen derived from the residue (Ndfr) using the isotope dilution equations. This method was compared with the direct method, i.e. where 15N-labelled residues were added to the soil and Ndfr in the ryegrass calculated directly. Estimates of percentage nitrogen derived from the residue (%Ndfr) alfalfa (Medicago sativaL.) in the ryegrass, were similar, 22 and 23% for the direct and soil pre-labelling methods, respectively, in the Wechsel sandy loam. Also, estimates of the %Ndfr from soybean (Glycine max (L.) Merr) residues in the Krumbach sandy loam were similar 34% (direct) and 36% (soil pre-labelling approach). However, in the Seibersdorf clay loam, the %Ndfr from soybean was 49% using the direct method and 61% using the soil pre-labelling method; yet Ndfr from common bean residue was 46% using the direct approach and 40% using the pre-labelling, not significantly different (P 〉 0.05). The soil pre-labelling approach appears to give realistic values for Ndfr. It was not possible to obtain an estimate of Ndfr using the soil pre-labelling method from the maize residues (Zea mays L.) in two of the soils, as there was no increase in the total N of the ryegrass over the growing period. This was probably due to microbial immobilisation of inorganic N, as a result of the wide C:N ratio of the residue added. The results suggest that the new soil pre-labelling method is feasible and that it is a potentially useful technique for measuring N release from a wide range or organic residues, but it requires further field-testing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004789103949
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  • 63
    Digitale Medien
    Digitale Medien
    Chemistry and toughness predict leaf litter decomposition rates over a wide spectrum of functional types and taxa in central Argentina (2000)
    Springer
    Plant and soil 218 (2000), S. 21-30 
    Details
    ISSN: 1573-5036
    Schlagwort(e): carbon ; functional types ; leaf tensile strength ; litter quality ; mass loss ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Litter decomposition, a major determinant of ecosystem functioning, is strongly influenced by the litter quality of different species. We aimed at (1) relating interspecific variation in leaf litter decomposition rate to the functional types different species belong to; and (2) understanding the chemical and/or physical basis for such variation and its robustness to environmental factors. We selected 52 Angiosperms from a climatic gradient in central-western Argentina, representing the widest range of functional types and habitats published so far. Ten litter samples of each species were simultaneously buried for 9 weeks during the 1996 summer in an experimental decomposition bed. Decomposition rate was defined as the percentage of dry mass loss after incubation. Chemical litter quality was measured as carbon (C) content, nitrogen (N) content, and C-to-N ratio. Since tensile strength of litter and living leaves were strongly correlated, the latter was chosen as an indicator of physical litter quality. A subset of 15 species representing different functional types was also incubated in England for 15 weeks, following a similar experimental procedure. Litter C-to-N and leaf tensile strength of the leaves showed the strongest negative associations with decomposition rate, both at the species and at the functional-type level. Decomposition rates of the same species in Argentina and in England were strongly correlated. This reinforces previous evidence that species rankings in terms of litter decomposition rates are robust to methodological and environmental factors. This paper has shown new evidence of plant control over the turnover of organic matter through litter quality, and confirms, over a broad spectrum of functional types, general models of resource allocation. The strong correlations between leaf tensile strength – a trait that is easy and quick to measure in a large number of species – decomposition rate, and C-to-N ratio indicate that leaf tensile strength can be useful in linking plant quality to decomposition patterns at the ecosystem level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1014981715532
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  • 64
    Digitale Medien
    Digitale Medien
    On variation in forest floor thickness across four red pine plantations in Pennsylvania, USA (2000)
    Springer
    Plant and soil 219 (2000), S. 57-69 
    Details
    ISSN: 1573-5036
    Schlagwort(e): decomposition ; litter quality ; mycorrhiza ; nitrogen ; phosphorus ; saprotrophic microorganisms ; tannins ; forest soils ; acidification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We studied variation in forest floor thickness in four plantations of red pine (Pinus resinosa Ait.) which were similar in age, soil type and associated vegetation. The plantations were located (west to east) in the Clear Creek, Moshannon, Sproul and Tiadaghton State Forests of Pennsylvania, USA. A gradient in forest floor thickness exists across these plantations; the forest floor is thickest in the west and it becomes progressively thinner toward the east. Decomposition of imported litter increased from west to east, suggesting that the variation in forest floor thickness is related to variation in the rate of decomposition. Decomposition rates were related to saprotroph abundance. Variation in forest floor N and phenolic concentrations, in overall mycorrhiza density and in the relative proportions of three common mycorrhiza morphotypes could not explain the variation in decomposition rate. The P concentrations and pH of the forest floor were significantly lower at Clear Creek and Moshannon, where decomposition rates were lowest, compared to Sproul and Tiadaghton, where decomposition rates were most rapid. This suggests that P concentration and pH may have exerted some control on decomposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004748220856
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  • 65
    Digitale Medien
    Digitale Medien
    The relationship between ions, vigour and salinity tolerance of Acacia seeds (2000)
    Springer
    Plant and soil 220 (2000), S. 229-233 
    Details
    ISSN: 1573-5036
    Schlagwort(e): Acacia ; calcium ; potassium ; salinity tolerance ; seed germination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Seeds of A. bivenosa DC. Prod., A. coriacea DC., A. elata A. Cunn. Ex Benth., A. farnesiana (L.) Willd., A. nilotica Willd. ex Del., A. salicina Lindl., A. saligna (Labill.) H. Wendle., A. senegal (L.) Willd., A. tortilis (Forsk.) Hayne and A. tumida F. Muell. ex Benth. were tested for their final germination percentage (FG) in distilled water (DW) and in 25–400 mol m-3 NaCl, germination rate (1/t50, where t50 is the time to 50% of final germination in DW), Ca and K concentration (Caunt, Kunt), the leakage of these ions when soaked for 24 h in DW (CaDW, KDW) and the leakage (additional to that in DW) when soaked in 250 mol m-3 NaCl (CaNaCl, KNaCl). Linear regression revealed significant positive relationships between salinity tolerance (I50, the concentration of NaCl required to reduce final germination to 50% of the control value in DW) and FG, Rate, Caunt/Kunt and CaNaCl/KNaCl. There was also a significant negative relationship between I50 and Kunt. Multiple regression equations were developed to predict I50 from the above parameters. Equations based on (1) FG and Rate, (2) Caunt and Kunt, and (3) any of these four factors, accounted for 61, 60 and 79%, respectively, of the variation in I50. Further equations, introducing the leakage of ions into DW and NaCl and the ratios of ion concentrations monitored, improved the predictive value of the equation. The best equation, accounting for 93% of the variation was: I50 = 108 + 422 Rate − 1.32 Kunt + 16.3 CaDW − 5.4 KDW + 71.6 K/CaDW. These equations provide a screening test for salt tolerance of Acaciaseed germination based on simple and rapid laboratory chemical analyses and germination tests.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004701231183
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  • 66
    Digitale Medien
    Digitale Medien
    Dynamics of mineral N availability in grassland ecosystems under increased [CO2]: hypotheses evaluated using the Hurley Pasture Model (2000)
    Springer
    Plant and soil 224 (2000), S. 153-170 
    Details
    ISSN: 1573-5036
    Schlagwort(e): climate change ; immobilisation ; mineralisation ; N-turnover ; nitrogen ; soil organic matter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The following arguments are outlined and then illustrated by the response of the Hurley Pasture Model to [CO2] doubling in the climate of southern Britain. 1. The growth of N-limited vegetation is determined by the concentration of N in the soil mineral N pools and high turnover rates of these pools (i.e., large input and output fluxes) contribute positively to growth. 2. The size and turnover rates of the soil mineral N pools are determined overwhelmingly by N cycling into all forms of organic matter (plants, animals, soil biomass and soil organic matter — `immobilisation' in a broad sense) and back again by mineralisation. Annual system N gains (by N2 fixation and atmospheric deposition) and losses (by leaching, volatilisation, nitrification and denitrification) are small by comparison. 3. Elevated [CO2] enriches the organic matter in plants and soils with C, which leads directly to increased removal of N from the soil mineral N pools into plant biomass, soil biomass and soil organic matter (SOM). ‘Immobilisation’ in the broad sense then exceeds mineralisation. This is a transient state and as long as it exists the soil mineral N pools are depleted, N gaseous and leaching losses are reduced and the ecosystem gains N. Thus, net immobilisation gradually increases the N status of the ecosystem. 4. At the same time, elevated [CO2] increases symbiotic and non-symbiotic N2 fixation. Thus, more N is gained each year as well as less lost. Effectively, the extra C fixed in elevated [CO2] is used to capture and retain more N and so the N cycle tracks the C cycle. 5. However, the amount of extra N fixed and retained by the ecosystem each year will always be small (ca. 5–10 kg N ha-1 yr-1) compared with amount of N in the immobilisation-mineralisation cycle (ca. 1000 kg N ha-1 yr-1). Consequently, the ecosystem can take decades to centuries to gear up to a new equilibrium higher-N state. 6. The extent and timescale of the depletion of the mineral N pools in elevated [CO2] depends on the N status of the system and the magnitude of the overall system N gains and losses. Small changes in the large immobilisation—mineralisation cycle have large effects on the small mineral N pools. Consequently, it is possible to obtain a variety of growth responses within 1–10 year experiments. Ironically, ecosystem models — artificial constructs — may be the best or only way of determining what is happening in the real world.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004640327512
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  • 67
    Digitale Medien
    Digitale Medien
    Autumn leaf colours as indicators of decomposition rate in sycamore (Acer pseudoplatanus L.) (2000)
    Springer
    Plant and soil 225 (2000), S. 33-38 
    Details
    ISSN: 1573-5036
    Schlagwort(e): deciduous tree ; foliar pigmentation ; fungus ; litter mass loss ; nitrogen ; phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We tested the hypothesis that there is a causal connection between autumn colour, nutrient concentration and decomposibility of fresh leaf litter. Samples from patches of different autumn colours within the leaves of the deciduous tree sycamore (Acer pseudoplatanus) were sealed into litter bags and incubated for one winter in an outdoor leaf mould bed. Green leaf patches were decomposed faster than yellow or brown patches and this corresponded with the higher N and P concentrations in the former. Black patches, indicating colonisation by the tar spot fungus Rhytisma acerinum, were particularly high in P, but were decomposed very slowly, owing probably to resource immobilisation by the fungus. The results supported the hypothesis and were consistent with a previous study reporting an interspecific link between autumn coloration and decomposition rate. Autumn leaf colour of deciduous woody plants may serve as a useful predictor of litter decomposibility in ecosystem or biome scale studies where extensive direct measurements of litter chemistry and decomposition are not feasible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026530214258
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  • 68
    Digitale Medien
    Digitale Medien
    Salinity induced nuclear and DNA degradation in meristematic cells of soybean (Glycine max (L.)) roots (2000)
    Springer
    Plant growth regulation 30 (2000), S. 49-54 
    Details
    ISSN: 1573-5087
    Schlagwort(e): calcium ; DNA degradation ; meristematic root cells ; salt stress ; soybean
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Changes in the nuclei of meristematic root cells of soybean (Glycine max (L.) Merr. cv. Acme) in response to severe salinity were studied. Root growth was inhibited by 200 mM NaCl, when 1 mM CaCl_2 was present in the culture media. Increasing CaCl_2 up to 5 mM partially prevented this inhibition. However, inhibition also occurred with 100~mM NaCl without CaCl_2. We examined the meristematic cells under a series of NaCl treatments. Nuclear deformation of the cells occurred with 24 h of 150 mM or higher NaCl, and was followed by degradation of nuclei in the apical region of the root. TEM observation and agarose gel electrophoretic analysis confirmed that root tip nuclear DNA deformed or degraded with 150 mM or higher NaCl concentrations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006311619937
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  • 69
    Digitale Medien
    Digitale Medien
    Tracing mangrove carbon in suspended matter and aquatic fauna of the Gautami–Godavari Delta, Bay of Bengal (India) (2000)
    Springer
    Hydrobiologia 431 (2000), S. 225-241 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Stable isotope tracers ; carbon ; nitrogen ; mangroves ; litterfall ; suspended matter ; zooplankton ; macrobenthos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Stable carbon isotopic composition and C/N ratio were used to trace the input of carbon associated with mangrove litter into the estuary of the Godavari–Gautami delta system and Kakinada bay (Andhra Pradesh, India). Suspended organic matter in the mangrove channels was more depleted in 13C (average δ13C = −24.5‰) than in Kakinada bay which showed δ13C values for suspended matter (average δ13C = −22.7‰) closer to those expected for marine phytoplankton. Suspended organic matter from mangrove channels was enriched in nitrogen (average C/N atom ratio ≤ 12.7) and 13C (average δ13C = −24.5‰) relative to mangrove leaf litter, which had a C/N ratio of 75 and a δ13C value of −28‰. Lowest C/N ratios for suspended matter were observed during southwest monsoon when rainfall was highest. Although in general, mangrove litter fall was also lower during this period, no clear correlation was observed between litter fall and C/N ratio of suspended matter. In general, the composition of suspended matter pointed towards phytoplankton as a major component. Isotopic composition of zooplankton suggested selective feeding on 13C-enriched, marine phytoplankton in open Kakinada bay and on 13C-depleted organic matter, such as estuarine phytoplankton and mangrove litter, in the mangrove channels. From the δ13C signature, it appeared that mangrove carbon was present to some extent in zooplankton and macrofauna from the mangrove mudflats and channels, but the signal rapidly decreased in Kakinada bay. Nitrogen isotopic composition of zooplankton and macrofauna indicated a progressive enrichment of 15N away from the mangrove forest towards the northern part of Kakinada bay, in approach of Kakinada city. This is thought to reflect input of anthropogenic nitrogen enriched in 15N and subsequent uptake of this enriched nitrogen into the aquatic food chain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004072310525
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  • 70
    Digitale Medien
    Digitale Medien
    Nutrient losses in runoff from grasslandand shrubland habitats in southern New Mexico: II. Field plots (2000)
    Springer
    Biogeochemistry 49 (2000), S. 69-86 
    Details
    ISSN: 1573-515X
    Schlagwort(e): Bouteloua eriopoda ; Chihuahuan Desert ; desertification ; hydrology ; Larrea tridentata ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Losses of dissolved nutrients (N, P, K, Ca, Mg, Na,Cl, and SO4) in runoff were measured on grasslandand shrubland plots in the Chihuahuan desert ofsouthern New Mexico. Runoff began at a lowerthreshold of rainfall in shrublands than ingrasslands, and the runoff coefficient averaged 18.6%in shrubland plots over a 7-year period. In contrast,grassland plots lost 5.0 to 6.3% of incidentprecipitation in runoff during a 5.5-year period. Nutrient losses from shrubland plots were greater thanfrom grassland plots, with nitrogen losses averaging0.33 kg ha−1 yr−1 vs0.15 kg ha−1 yr−1, respectively, during a 3-year period. Thegreater nutrient losses in shrublands were due tohigher runoff, rather than higher nutrientconcentrations in runoff. In spite of these nutrientlosses in runoff, all plots showed net accumulationsof most elements due to inputs from atmosphericdeposition. Therefore, loss of soil nutrients byhillslope runoff cannot, by itself, account for thedepletion of soil fertility associated withdesertification in the Chihuahuan desert.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006246126915
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  • 71
    Digitale Medien
    Digitale Medien
    Changes in Sr/Ca, Ba/Ca and 87Sr/86Sr ratios between trophic levels in two forest ecosystems in the northeastern U.S.A. (2000)
    Springer
    Biogeochemistry 49 (2000), S. 87-101 
    Details
    ISSN: 1573-515X
    Schlagwort(e): barium ; calcium ; food chain ; forest ; songbird ; strontium isotope
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract The variability and biologicalfractionation of Sr/Ca, Ba/Ca and 87Sr/86Srratios were studied in a soil–plant–invertebrate–bird food chain in two forested ecosystems withcontrasting calcium availability in the northeasternU.S.A. Chemical measurements were made of the soilexchange pool, leaves, caterpillars, snails, and boththe femurs and eggshells of breeding insectivorousmigratory songbirds. 87Sr/86Sr values weretransferred up the food chain from the soil exchangepool to leaves, caterpillars, snails and eggshellswithout modification. Adult birds were the oneexception; their 87Sr/86Sr values generallyreflected those of lower trophic levels at each site,but were lower and more variable, probably becausetheir strontium was derived in part from foods intropical winter habitats where lower87Sr/86Sr ratios are likely to predominate. Sr/Ca and Ba/Ca ratios decreased at each successive trophiclevel, supporting previous suggestions that Sr/Ca andBa/Ca ratios can be used to identify the trophic levelat which an organism is primarily feeding. The changesin Sr/Ca and Ba/Ca ratios we measured for vegetationand insects were comparable to similar measurementsmade previously (but based on single samples of eachorganism) in an alpine ecosystem. Changes in Sr/Ca andBa/Ca ratios between birds and their food have notpreviously been measured, but the values we obtainedwere similar to those for herbivorous and carnivorousmammals at similar trophic levels. Our results provideevidence that supports the use of Sr/Ca ratios in thedetermination of human paleodiets and suggests thatSr/Ca ratios may also provide a useful tool in studiesof modern food webs. Furthermore, our findings suggestthat 90Sr from nuclear fallout will notbioaccumulate in forests and that changes in Sr/Caratios between trophic levels will need to beconsidered in some cases when using87Sr/86Sr as a tracer of calciumbiogeochemistry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006390707989
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  • 72
    Digitale Medien
    Digitale Medien
    Nutrient fluxes in intertidal communities of a South European lagoon (Ria Formosa) – similarities and differences with a northern Wadden Sea bay (Sylt-Rømø Bay) (2000)
    Springer
    Hydrobiologia 436 (2000), S. 217-235 
    Details
    ISSN: 1573-5117
    Schlagwort(e): nutrient flux ; nitrogen ; phosphate ; tidal flats ; temperature ; geographical comparison
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract During an annual cycle, flux rates of oxygen, nitrate, nitrite, ammonium, phosphate and silicate were measured in light and dark bell jars at three sites in Ria Formosa (Algarve, Portugal) enclosing either a natural macrophytic community (macroalgae on sand or mud, a seagrass bed of Zostera noltii) or bare sediments. The results are compared with a preceeding study in which the same bell jar technique has been applied in the Sylt-Rømø Bay of the northern Wadden Sea. Nitrate flux was mainly directed from the water column to the benthic communities in Ria Formosa, as well as in the Sylt-Rømø Bay. However, nitrate uptake was higher in the northern, more eutrophic study area. In Ria Formosa, nutrient concentrations were lower than in the Sylt-Rømø Bay possibly due to strong water exchange with Atlantic waters. High temperatures and strong insolation had a greater impact on nitrate fluxes in Ria Formosa than in the Sylt-Rømø Bay. Bioturbating macrofauna increased ammonium efflux in the Sylt- Rømø Bay while this effect was not as pronounced in the Ria Formosa study sites. Benthic phosphate uptake dominated in the Ria Formosa and was correlated to initial phosphate concentrations in incoming waters. At both study sites, oxygen and nutrient fluxes were correlated with temperature. Additionally, flux rates were strongly influenced by biotic components and levels of eutrophication. A literature survey showed that mainly in temperate regions, material fluxes increase with temperature, whereas in warmer areas, ammonium and phosphate fluxes between sediment and water were generally lower.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026542621512
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  • 73
    Digitale Medien
    Digitale Medien
    Control of Telomere Elongation and Telomeric Silencing in Drosophila Melanogaster (2000)
    Springer
    Genetica 109 (2000), S. 61-70 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; heterochromatin ; telomere ; transcription ; transposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chromosome length in Drosophilais maintained by the targeted transposition of two families of non-LTR retrotransposons, HeT-Aand TART. Although the rate of transposition to telomeres is sufficient to counterbalance loss from the chromosome ends due to incomplete DNA replication, transposition as a mechanism for elongating chromosome ends raises the possibility of damaged or deleted telomeres, because of its stochastic nature. Recent evidence suggests that HeT-Atransposition is controlled at the levels of transcription and reverse transcription. HeT-Atranscription is found primarily in mitotically active cells, and transcription of a w +reporter gene inserted into the 2L telomere increases when the homologous telomere is partially or completely deleted. The terminal HeT-Aarray may be important as a positive regulator of this activity in cis, and the subterminal satellite appears to be an important negative regulator in cis. A third chromosome modifier has been identified that increases the level of reverse transcriptase activity on a HeT-A RNA template and greatly increases the transposition of HeT-A. Thus, the host appears to play a role in transposition of these elements. Taken together, these results suggest that control of HeT-Atransposition is more complex than previously thought.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026548503320
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  • 74
    Digitale Medien
    Digitale Medien
    Models of Calmodulin Trapping and CaM Kinase II Activation in a Dendritic Spine (2000)
    Springer
    Journal of computational neuroscience 8 (2000), S. 65-86 
    Details
    ISSN: 1573-6873
    Schlagwort(e): LTP ; CaM kinase II ; calmodulin ; calcium ; dendritic spine ; dentate ; computational model ; hippocampus ; phosphorylation ; autophosphorylation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin , Physik
    Notizen: Abstract Activation of calcium/calmodulin-dependent protein kinase II (CaMKII) by calmodulin following calcium entry into the cell is important for long-term potentiation (LTP). Here a model of calmodulin binding and trapping by CaMKII in a dendritic spine was used to estimate levels and durations of CaMKII activation following LTP-inducing tetani. The calcium signal was calcium influx through NMDA receptor channels computed in a highly detailed dentate granule cell model. Calcium could bind to calmodulin and calmodulin to CaMKII. CaMKII subunits were either free, bound with calmodulin, trapped, autonomous, or capped. Strong low-frequency tetanic input produced little calmodulin trapping or CaMKII activation. Strong high-frequency tetanic input caused large numbers of CaMKII subunits to become trapped, and CaMKII was strongly activated. Calmodulin trapping and CaMKII activation were highly dependent on tetanus frequency (particularly between 10 and 100 Hz) and were highly sensitive to relatively small changes in the calcium signal. Repetition of a short high-frequency tetanus was necessary to achieve high levels of CaMKII activation. Three stages of CaMKII activation were found in the model: a short, highly activated stage; an intermediate, moderately active stage; and a long-lasting third stage, whose duration depended on dephosphorylation rates but whose decay rate was faster at low CaMKII activation levels than at high levels. It is not clear which of these three stages is most important for LTP.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008969032563
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  • 75
    Digitale Medien
    Digitale Medien
    Molecular organization of the Drosophila melanogaster Adh chromosomal region in D. replete and D. buzzatii, two distantly related species of the Drosophila subgenus (2000)
    Springer
    Chromosome research 8 (2000), S. 375-385 
    Details
    ISSN: 1573-6849
    Schlagwort(e): Adh ; Drosophila ; FISH ; genome evolution ; repleta group
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The molecular organization of a 1.944-Mb chromosomal region of Drosophila melanogaster around the Adh locus has been analyzed in two repleta group species: D. repleta and D. buzzatii. The extensive genetic and molecular information about this region in D. melanogaster makes it a prime choice for comparative studies of genomic organization among distantly related species. A set of 26 P1 phages from D. melanogaster were successfully hybridized using fluorescence in-situ hybridization (FISH) to the salivary gland chromosomes of both repleta group species. The results show that the Adh region is distributed in D. repleta and D. buzzatii over six distant sites of chromosome 3, homologous to chromosomal arm 2L of D. melanogaster (Muller's element B). This observation implies a density of 2.57 fixed breakpoints per Mb in the Adh region and suggests a considerable reorganization of this chromosomal element via the fixation of paracentric inversions. Nevertheless, breakpoint density in the Adh region is three times lower than that estimated for D. repleta chromosome 2, homologous to D. melanogaster 3R (Muller's element E). Differences in the rate of evolution among chromosomal elements are seemingly persistent in the Drosophila genus over long phylogenetic distances.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009206702214
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  • 76
    Digitale Medien
    Digitale Medien
    Distribution of the Transposable Element Minos in the Genus Drosophila (2000)
    Springer
    Genetica 108 (2000), S. 263-267 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; horizontal transfer ; Minos ; Tc1-like ; Tc1-marinerfamily ; transposable elements ; transposon distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We analyzed 28 species of the genus Drosophilafor the presence of the Tc1-like transposable element Minosusing Southern blot hybridization under high stringency conditions. The Minostransposon was found in members of both the Drosophilaand the Sophophorasubgenus showing a distribution that is wider if compared to other well-studied Drosophilatransposons such as the Pelement, hoboand mariner. The presence of Minos-hybridizing sequences was discontinuous in the Sophophorasubgenus, especially in the melanogasterspecies group. Using the Polymerase Chain Reaction we amplified a portion corresponding to the putative Minostransposase from different Drosophilaspecies. Cloning and sequence analysis of randomly selected Minoscopies from D. mojavensisis, D. saltansand D. willistonisupports the idea that event(s) of horizontal transfer may have contributed to the spreading of this transposon in the Drosophilagenus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004185024017
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  • 77
    Digitale Medien
    Digitale Medien
    Spatial differences in patterns of modification: selection on hairy in Drosophila melanogaster wings (2000)
    Springer
    Genetica 109 (2000), S. 169-181 
    Details
    ISSN: 1573-6857
    Schlagwort(e): artificial selection ; atavistic structures ; Drosophila ; pattern formation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Artificial selection was carried out for over 45 generations to enhance and suppress expression of the mutation hairy on the Drosophila melanogaster wing. Whole chromosome mapping of X‐linked and autosomal modifiers of sense organ number displayed regional differences in magnitude and direction of their effects. Regional specificity of modifier effects was also seen in some interchromosomal interactions. Scanning electron microscopy allowed precise measurement of sense organ size and position along the L3 longitudinal wing vein. Sense organ size varied in a predictable fashion along the proximal–distal axis, and the dorsal pattern differed from the ventral pattern. The high and low selection lines differed most in the proximal portion of the L3 vein. Extra sense organs in the High line were often associated with vein fragments at locations predicted from ancestral vein patterns. Thus, regional specificity of polygenic or quantitative trait locus modifier effects was identified in several different parts of the wing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017531404454
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  • 78
    Digitale Medien
    Digitale Medien
    Genetic analysis of extended lifespan in Drosophila melanogaster III. On the relationship between artificially selected and wild stocks (2000)
    Springer
    Genetica 109 (2000), S. 245-253 
    Details
    ISSN: 1573-6857
    Schlagwort(e): artificial selection ; Drosophila ; lifespan ; mortality ; paraquat ; DDT ; recovery hypothesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Adult lifespans, age‐specific survival, age‐specific mortality, survival times on paraquat, and survival times on DDT were assayed in seven lines of Drosophila melanogaster, including two genetically heterogeneous wild lines recently collected from nature, and three inbred and recombinant inbred lines derived from an artificial selection experiment for increased lifespan. Survival on paraquat is positively correlated with adult lifespan. DDT resistance is uncorrelated with either paraquat resistance or lifespan. The wild lines are unexceptional with respect to average lifespan, paraquat resistance, age‐specific survivorship, and leveling off of mortality rates at advanced ages, but have high levels of DDT resistance. Cluster analysis groups the wild lines with three unselected laboratory stocks in one cluster, while two long‐lived elite recombinant inbred lines form a second cluster. Long‐lived laboratory‐adapted lines are quantitatively differentiated from the wild stocks, both with respect to average adult lifespans and resistance to an oxidizing agent. We reject the ‘recovery’ hypothesis, which proposes that Drosophila artificially selected for long life have phenotypes that merely recover the wild state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017569318401
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  • 79
    Digitale Medien
    Digitale Medien
    Role of AWD/Nucleoside Diphosphate Kinase in Drosophila Development (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 293-300 
    Details
    ISSN: 1573-6881
    Schlagwort(e): abnormal wing discs ; lethal mutant ; Drosophila ; Killer-of-prune ; prune
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract The abnormal wing discs gene of Drosophila encodes a soluble protein with nucleosidediphosphate kinase activity. This enzymic activity is necessary for the biological function ofthe abnormal wing discs gene product. Complete loss of function, i.e., null, mutations causelethality after the larval stage. Most larval organs in such null mutant larvae appear to benormal, but the imaginal discs are small and incapable of normal differentiation.Killer-of-prune is a neomorphic mutation in the abnormal wing discs gene. It causes dominant lethalityin larvae that lack prune gene activity. The Killer-of-prune mutant protein may have alteredsubstrate specificity. Null mutant larvae have a low level of nucleoside diphosphate kinaseactivity. This suggests that there may be additional Drosophila genes that encode proteinswith nucleoside dipthosphate kinase activity. Candidate genes have been found in theDrosophila genome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005545214937
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  • 80
    Digitale Medien
    Digitale Medien
    Common Mechanisms of Y Chromosome Evolution (2000)
    Springer
    Genetica 109 (2000), S. 105-111 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; evolution ; heterochromatin ; Y chromosome
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Y chromosome evolution is characterized by the expansion of genetic inertness along the Y chromosome and changes in the chromosome structure, especially the tendency of becoming heterochromatic. It is generally assumed that the sex chromosome pair has developed from a pair of homologues. In an evolutionary process the proto-Y-chromosome, with a very short differential segment, develops in its final stage into a completely heterochromatic and to a great extends genetically eroded Y chromosome. The constraints evolving the Y chromosome have been the objects of speculation since the discovery of sex chromosomes. Several models have been suggested. We use the exceptional situation of the in Drosophila mirandato analyze the molecular process in progress involved in Y chromosome evolution. We suggest that the first steps in the switch from a euchromatic proto-Y-chromosome into a completely heterochromatic Y chromosome are driven by the accumulation of transposable elements, especially retrotransposons inserted along the evolving nonrecombining part of the Y chromosome. In this evolutionary process trapping and accumulation of retrotransposons on the proto-Y-chromosome should lead to conformational changes that are responsible for successive silencing of euchromatic genes, both intact or already mutated ones and eventually transform functionally euchromatic domains into genetically inert heterochromatin. Accumulation of further mutations, deletions, and duplications followed by the evolution and expansion of tandem repetitive sequence motifs of high copy number (satellite sequences) together with a few vital genes for male fertility will then represent the final state of the degenerated Y chromosome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026584016524
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  • 81
    Digitale Medien
    Digitale Medien
    Transport of Ca2+ from Sarcoplasmic Reticulum to Mitochondria in Rat Ventricular Myocytes (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 97-104 
    Details
    ISSN: 1573-6881
    Schlagwort(e): Mitochondria ; sarcoplasmic reticulum ; calcium ; caffeine ; myocytes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Studies with electron microscopy have shown that sarcoplasmic reticulum (SR) andmitochondria locate close to each other in cardiac muscle cells. We investigated the hypothesis thatthis proximity results in a transient exposure of mitochondrial Ca2+ uniporter (CaUP) to highconcentrations of Ca2+ following Ca2+ release from the SR and thus an influx of Ca2+into mitochondria. Single ventricular myocytes of rat were skinned by exposing them to aphysiological solution containing saponin (0.2 mg/ml). Cytosolic Ca2+ concentration ([Ca2+]c)and mitochondrial Ca2+ concentration ([Ca2+]m) were measured with fura-2 and rhod2,respectively. Application of caffeine (10 mM) induced a concomitant increase in[Ca2+]c and [Ca2+]m.Ruthenium red, at concentrations that block CaUP but not SR release, diminished thecaffeine-induced increase in [Ca2+]m but not[Ca2+]c. In the presence of 1 mM BAPTA, a Ca2+ chelator,the caffeine-induced increase in [Ca2+]m was reduced substantially less than [Ca2+]c. Moreover,inhibition of SR Ca2+ pump with two different concentrations of thapsigargin caused anincrease in [Ca2+]m, which was related to the rate of [Ca2+]c increase. Finally, electronmicroscopy showed that sites of junctions between SR and T tubules from which Ca2+ is released,or Ca2+ release units, CRUs, are preferentially located in close proximity to mitochondria.The distance between individual SR Ca2+ release channels (feet or ryanodine receptors) isvery short, ranging between approximately 37 and 270 nm. These results are consistent withthe idea that there is a preferential coupling of Ca2+ transport from SR to mitochondria incardiac muscle cells, because of their structural proximity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005520714221
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  • 82
    Digitale Medien
    Digitale Medien
    Effects of extracts from sporoderm-broken spores of Ganoderma lucidum on HeLa cells (2000)
    Springer
    Cell biology and toxicology 16 (2000), S. 201-206 
    Details
    ISSN: 1573-6822
    Schlagwort(e): calcium ; cell cycle ; cell growth ; Ganoderma lucidum ; spores
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The effects of extracts from Ganoderma lucidum spores on the growth of human cervix uteri tumor HeLa cells as well as on the cell cycle and intracellular calcium level were investigated. Alcohol extracts were prepared from sporoderm-broken and sporoderm-nonbroken spores (termed extract I and extract II) of G. lucidum. Extract I was then subjected to silica gel chromatography to obtain extract III. Cytotoxicity was examined by means of trypan blue exclusion and MTT tests. It was found that extract I and extract III, but not extract II strongly inhibited the growth of HeLa cells, and that extract III was more effective than extract I. Moreover, extract III was shown to be capable of blocking the cell cycle at the transition from G1 to S phase and inducing a marked decrease of intracellular calcium level, determined by flow cytometry and the specific fluorescent calcium probe Fura-2, respectively. These results imply that (1) the breaking of G. lucidum spores improves the release of cytotoxic activity and (2) the effective extract might influence the cell cycle and cellular signal transduction by altering the calcium transport system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007663006548
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  • 83
    Digitale Medien
    Digitale Medien
    Inflammatory Mediators and Modulation of Blood–Brain Barrier Permeability (2000)
    Springer
    Cellular and molecular neurobiology 20 (2000), S. 131-147 
    Details
    ISSN: 1573-6830
    Schlagwort(e): blood–brain barrier ; inflammation ; permeability ; electrical resistance ; calcium ; tight junction ; signal transduction ; receptor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 1. Unlike some interfaces between the blood and the nervous system (e.g., nerve perineurium), the brain endothelium forming the blood–brain barrier can be modulated by a range of inflammatory mediators. The mechanisms underlying this modulation are reviewed, and the implications for therapy of the brain discussed. 2. Methods for measuring blood–brain barrier permeability in situ include the use of radiolabeled tracers in parenchymal vessels and measurements of transendothelial resistance and rate of loss of fluorescent dye in single pial microvessels. In vitro studies on culture models provide details of the signal transduction mechanisms involved. 3. Routes for penetration of polar solutes across the brain endothelium include the paracellular tight junctional pathway (usually very tight) and vesicular mechanisms. Inflammatory mediators have been reported to influence both pathways, but the clearest evidence is for modulation of tight junctions. 4. In addition to the brain endothelium, cell types involved in inflammatory reactions include several closely associated cells including pericytes, astrocytes, smooth muscle, microglia, mast cells, and neurons. In situ it is often difficult to identify the site of action of a vasoactive agent. In vitro models of brain endothelium are experimentally simpler but may also lack important features generated in situ by cell:cell interaction (e.g. induction, signaling). 5. Many inflammatory agents increase both endothelial permeability and vessel diameter, together contributing to significant leak across the blood–brain barrier and cerebral edema. This review concentrates on changes in endothelial permeability by focusing on studies in which changes in vessel diameter are minimized. 6. Bradykinin (Bk)2 increases blood–brain barrier permeability by acting on B2 receptors. The downstream events reported include elevation of [Ca2+]i, activation of phospholipase A2, release of arachidonic acid, and production of free radicals, with evidence that IL-1β potentiates the actions of Bk in ischemia. 7. Serotonin (5HT) has been reported to increase blood–brain barrier permeability in some but not all studies. Where barrier opening was seen, there was evidence for activation of 5-HT2 receptors and a calcium-dependent permeability increase. 8. Histamine is one of the few central nervous system neurotransmitters found to cause consistent blood–brain barrier opening. The earlier literature was unclear, but studies of pial vessels and cultured endothelium reveal increased permeability mediated by H2 receptors and elevation of [Ca2+]i and an H1 receptor-mediated reduction in permeability coupled to an elevation of cAMP. 9. Brain endothelial cells express nucleotide receptors for ATP, UTP, and ADP, with activation causing increased blood–brain barrier permeability. The effects are mediated predominantly via a P2U (P2Y2) G-protein-coupled receptor causing an elevation of [Ca2+]i; a P2Y1 receptor acting via inhibition of adenyl cyclase has been reported in some in vitro preparations. 10. Arachidonic acid is elevated in some neural pathologies and causes gross opening of the blood–brain barrier to large molecules including proteins. There is evidence that arachidonic acid acts via generation of free radicals in the course of its metabolism by cyclooxygenase and lipoxygenase pathways. 11. The mechanisms described reveal a range of interrelated pathways by which influences from the brain side or the blood side can modulate blood–brain barrier permeability. Knowledge of the mechanisms is already being exploited for deliberate opening of the blood–brain barrier for drug delivery to the brain, and the pathways capable of reducing permeability hold promise for therapeutic treatment of inflammation and cerebral edema.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007074420772
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  • 84
    Digitale Medien
    Digitale Medien
    Molecular Cloning and Chromosomal Localization of Human Salt-Tolerant Protein (2000)
    Springer
    Genetica 108 (2000), S. 259-262 
    Details
    ISSN: 1573-6857
    Schlagwort(e): hypertension ; salt sensitivity ; SH3 domain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have isolated a novel human cDNA coding for human salt-tolerant protein (HSTP), that is a homologue of the rat salt-tolerant protein (STP) and may contribute to salt-induced hypertension by modulating renal cation transport. The nucleotide sequence (1988 bp) of the HSTP cDNA contains an open reading frame encoding a polypeptide comprising 545 amino acids, two residues fewer than the rat STP cDNA. The predicted amino acid sequence exhibits 92% identity to that of the rat protein. HSTP contains predicted coiled-coil domains and Src Homology 3 domain, and shows a high degree of identity to CIP4 (Cdc42 target protein) and human Trip 10 (thyroid-hormone receptor interacting protein). We have mapped the HSTPgene to human chromosome 19 by fluorescence in situhybridization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004132919896
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  • 85
    Digitale Medien
    Digitale Medien
    Versatility of Conviction: Heterochromatin as Both a Repressor and an Activator of Transcription (2000)
    Springer
    Genetica 109 (2000), S. 19-24 
    Details
    ISSN: 1573-6857
    Schlagwort(e): chromosomal proteins ; Drosophila ; heterochromatin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026544717126
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  • 86
    Digitale Medien
    Digitale Medien
    Mitochondrial Calcium in Heart Cells: Beat-to-Beat Oscillations or Slow Integration of Cytosolic Transients? (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 27-33 
    Details
    ISSN: 1573-6881
    Schlagwort(e): Heart ; excitation-contraction coupling ; calcium ; mitochondrial permeability transition pore
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Mitochondria have been implicated in intracellular Ca2+ signaling in many cell types. Theinner mitochondrial membrane contains Ca2+-transporting proteins, which catalyze Ca2+ uptakeand extrusion. Intramitochondrial (matrix) Ca2+, in turn, regulates the activity of Krebs cycledehydrogenases and, ultimately, the rate of ATP synthesis. In the myocardium, controversyremains whether the fast cytosolic Ca2+ transients underlying excitation-contraction couplingin beating cells are rapidly transmitted into the matrix compartment or slowly integratedby the mitochondrial Ca2+ transporters. This mini-review critically summarizes the recentexperimental work in this field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005556227425
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  • 87
    Digitale Medien
    Digitale Medien
    Inactivation of Mitochondrial Permeability Transition Pore by Octylguanidine and Octylamine (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 193-198 
    Details
    ISSN: 1573-6881
    Schlagwort(e): Mitochondria ; octylguanidine ; octylamine ; carboxyatractyloside ; permeability transition ; kidney mitochondria ; nonspecific pore ; calcium ; mitochondrial calcium ; mitochondrial membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Mitochondrial permeability transition occurs through a Ca2+-dependent opening of atransmembrane pore, whose identity has been attributed to that of the adenine nucleotide translocase(ANT). In this work, we induced permeability transition by adding 0.5 μM carboxyatractyloside.The process was evaluated analyzing Ca2+ efflux, a drop in transmembrane electric gradient,and swelling. We found that the amphiphyllic cations octylguanidine and octylamine, at theconcentration of 100 μM, inhibited, almost completely, nonspecific membrane permeability.Hexylguanidine, hexylamine, as well as guanidine chloride and hydroxylamine failed to doso. The inhibition was reversed after the addition of 40 mM Li+, Na+ K+,Rb+, or Cs+; K+ wasthe most effective. We propose that the positive charge of the amines interact with negativecharges of membrane proteins, more likely the ADP/ATP carrier, while the alkyl chain penetratesinto the hydrophobic milieu of the inner membrane, fixing the reagent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005516115189
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  • 88
    Digitale Medien
    Digitale Medien
    Jasmonate-Induced Responses of Nicotiana sylvestris Results in Fitness Costs Due to Impaired Competitive Ability for Nitrogen (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 915-952 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Nicotiana sylvestris ; nitrogen ; nicotine ; allocation ; growth ; reproduction ; induced defenses ; costs of defense
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We present the first evidence for a fitness cost of an inducible response that is detectable in a nitrogen (N) currency. Nicotine is an induced defense in Nicotiana sylvestris that can utilize 5–8% of the plant's total N, an investment that apparently cannot be recouped by metabolism. Induced nicotine production is endogenously regulated by jasmonic acid (JA), and we treated leaves with the methyl ester of this wound hormone (MeJA) in quantities (0, 25, 250 μg) known to elicit changes in endogenous JA and subsequent nicotine responses comparable to those elicited by mechanical wounding and herbivory in this species. We grew plants in competition chambers (CCs) in which three same-sized plants could compete for a communal but fixed pool of 15NO3 to quantify the outcome of competition for this fitness-limiting resource that is used both in defense and seed production. Competition profoundly increased all measures of growth and reproductive performance measured per milligram of N acquired. While plants acquired all the N supplied to them in the hydroponic solution, plants grown in CCs (as compared those grown in individual chambers—ICs) retained more of this N and produced more biomass, had larger nicotine contents, allocated less of their N to nicotine, produced larger floral stalks with more flowers, aborted fewer flowers, matured more capsules, and produced a greater mass of seed. Plants grown in ICs produced heavier seed, but this difference did not translate into a difference in seed viability. MeJA treatment increased nicotine concentrations in proportion to the amount applied and significantly reduced growth (13–23%) and reproductive (31–44%) performance for plants grown with uninduced competitors, reflecting a large opportunity cost of induction. The effects of MeJA treatment on growth and reproduction were significantly less pronounced for plants grown in ICs. MeJA treatment significantly reduced the ability of plants to compete for [15N]KNO3 (reducing uptake by 9.5% and 23.7% for 25- and 250-μg MeJA-treated plants, respectively); no reductions in N acquisition were found in IC grown plants treated with MeJA. This impairment of competitive ability could account for 41–47% of the jasmonate-induced reductions in biomass by the day 15 harvest and 12–20% of the reductions in seed set and, in addition, created by "opportunity benefit" for neighboring uninduced plants, which grew larger, aborted fewer flowers, and matured more seed (a 28% increase) than did uninduced plants competing with similarly uninduced plants. Competition dramatically increased plant growth and reproductive performance, and MeJA treatment of these high-performing plants significantly reduced their competitive ability, which translated into opportunity costs for induced plants and opportunity benefits for neighboring uninduced plants. Induced plants minimized these fitness costs by reducing their use of recently acquired N for nicotine biosynthesis when growing with competitors. MeJA treatments also altered stalk length, flower production, flower abortion, and allocation to seed mass. In spite of all this plasticity, induced responses incur large fitness costs, costs that could be in part attributed to reductions in competitive ability for N. We conclude that inducibility functions to minimize these costs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005408208826
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  • 89
    Digitale Medien
    Digitale Medien
    Effects of excreta return on properties of a grazed pasture soil (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 79-85 
    Details
    ISSN: 1573-0867
    Schlagwort(e): exchangeable cations ; nitrogen ; soil carbon ; soil quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The long term impact of excreta return on some chemical and biological properties of a pasture soil fertilised with sulphur and phosphate was studied in a system that had been with or without excreta for 23 years. Excreta free areas that had developed under electric fencelines, and parallel transects in the paddocks, were sampled to provide this comparison. Sampling was to 300 mm depth in 0–75, 75–150 and 150–300 mm sections. Total carbon and nitrogen were 20% higher in the 0–150 mm soil layer of areas receiving excreta but did not differ in the 150–300 mm layer. Carbon:nitrogen ratios were similar in both systems as was mineralisable nitrogen, both absolutely and as a percentage of total in the 0–75 mm layer. Significantly more N was mineralised in the 75–150 mm layers of the areas receiving excreta but this was reversed in the 150–300 mm layer. Nitrification rate was higher in all layers of the excreta areas. Inorganic and organic P fractions did not differ significantly. Total P was significantly higher in the 0–75 mm layer and significantly lower in the 150–300 mm layer of the excreta areas. Exchangeable potassium was much higher throughout the excreta areas while this was offset by calcium. The sum of the cations was similar in both areas. Excreta affected most of the diagnostic soil tests used for fertiliser recommendations. The soil properties measured did not reflect clearly the differences in productivity that were obvious in the two areas. It is concluded that excreta return has a impact resulting in increased organic matter storage. Short-term effects of urine have a greater impact on productivity. The major effect is on the disposition of cations and available P.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009842727493
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  • 90
    Digitale Medien
    Digitale Medien
    Nitrogen in percolation water in paddy fields with a rice/wheat rotation (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 75-82 
    Details
    ISSN: 1573-0867
    Schlagwort(e): nitrogen ; leaching ; paddy soil ; wheat ; rice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Nitrogen in percolation water was observed in paddy field soil under rice/wheat rotation. Different N-application rates were designed. Porous pipes were installed in triplicate at depths of 30, 60 and 90 cm to collect the water in the period of wheat growth. Suction cups were installed in triplicate at the same depths to collect the water during the period of rice growth. NH4 +, NO3 - and total N in the water were analysed with a continuous-flow nitrogen analyzer. Results showed that nitrate was the predominant form of nitrogen in percolation water during the period of wheat growth. Nitrate leaching was high in early spring after the `tillering fertilisation'. More than 50 mg l-1 of nitrate concentration in percolation water was observed for 30 and 60 cm in depth and more than 15 mg l-1 were observed for 90 cm. The concentration decreased quickly and was very low, less than 2 mg l-1 usually, in the earring stage of wheat. Nitrate in water was low, less than 1.5 mg l-1 usually, when the field was flooded during the period of rice growth. Some soluble organic N existed in the water. Nitrate in percolation water increased when the field was drained. The leaching loss of nitrogen during winter wheat growth period was estimated to be about 3.4% of the N-fertiliser applied at the normal application rate of farmers; for the rice growth period it was around 1.8%. Although a reduced N-application decreased N leaching, it caused a marked decrease in crop yield.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009712404335
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  • 91
    Digitale Medien
    Digitale Medien
    Nitrogen (N) management in the ‘De Marke’ dairy farming system (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 231-240 
    Details
    ISSN: 1573-0867
    Schlagwort(e): nitrogen ; N ; nitrate ; ammonia ; dairy farming ; systems research ; environment ; sandy soils ; groundwater ; leaching
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In the sandy regions of The Netherlands, high losses of N from intensified dairy farms are threatening the environment. Therefore, government defined decreasing maximum levy-free N surplusses for the period 1998–2008. On most dairy farms, the current N surplus has to be reduced by half at least. Farmers fear that realizing these surplusses will be expensive, because it limits application of animal manure, which then has to be exported or additional land has to be bought. Moreover, farmers are worried about the impact on soil fertility. To explore the possibilities for reducing surplusses of average intensive farms by improved nutrient management, farming systems research is carried out at prototype farm ‘De Marke’. Results are compared with results of a commercial farm in the mid-1980s, the moment that systems research started and introduction of the milk quota system put a halt to further intensification. Results indicate that average intensive farms can realise a reduction in N surplus to a level below the defined final maximum, without the need to buy land or to export slurry. Inputs of N in purchased feeds and fertilisers decreased by 56 and 78%, respectively. Important factors are reduced feed intake per unit milk, as a result of a higher milk yield per cow, less young stock and judicious feeding, an improved utilization of ‘home-made’ manure and a considered balance between the grassland and maize area. Changed soil fertility status did not constrain crop production. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg l-1, within a few years.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009885419512
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  • 92
    Digitale Medien
    Digitale Medien
    Transport of dissolved inorganic nitrogen from the major rivers to estuaries in China (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 13-22 
    Details
    ISSN: 1573-0867
    Schlagwort(e): biogeochemistry ; estuary ; nitrogen ; river ; transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Long-term results of the monthly measurement of dissolved inorganic nitrogen (DIN) concentrations in three major rivers in China are presented. These data are combined with river discharge data to calculate the DIN loads discharged into the ocean. About 774.90 × 103, 55.38 × 103and 144.55 × 103tons of DIN were transported to their respective estuaries each year by the Changjiang, the Huanghe and the Zhujiang in 1980–1989, mainly in the form of nitrate (〉 80 percent). The annual transport of DIN and mean concentration of nitrate in the Changjiang had increased drastically (four-fold) in the last 29 years, especially during the 1980s. Although nitrate concentrations of the Zhujiang and the Huanghe had also increased in the 1980s, their total annual loads of DIN varied mainly with annual runoff volumes, showing no obvious uptrends. Our results also demonstrate that the majority of the DIN load of each river was transported in the high-flow period (70–80 percent). A positive relationship is observed between the annual DIN transport of the Changjiang and the annual application of chemical fertilizers in its catchment. The annual DIN loads of the Huanghe and the Zhujiang were influenced mainly by runoff volume, and also by application of chemical fertilizers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009896032188
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  • 93
    Digitale Medien
    Digitale Medien
    Nitrogen mobilization in Asia (2000)
    Springer
    Nutrient cycling in agroecosystems 57 (2000), S. 1-12 
    Details
    ISSN: 1573-0867
    Schlagwort(e): Asia ; fertilizer ; ammonia ; food ; greenhouse effect ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The addition of anthropogenic N by food and energy production to the global environment contributes to the greenhouse effect, acid deposition, photochemical smog, stratospheric ozone depletion and eutrophication of fresh and marine waters. On a global basis, anthropogenic N mobilization is greater then natural sources of bio-reactive N. Currently, Asia is a hotspot of N mobilization and distribution to downwind and downstream environments, primarily due to food production. Asia's contribution will continue to increase, not only due to population growth, but also to increases in the per capita consumption of food and energy. This paper provides an overview of the global N cycle, presents an analysis of N dynamics within agroecosystems, examines N mobilization in Asia and discusses possible rates of N mobilization in the future.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009832221034
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  • 94
    Digitale Medien
    Digitale Medien
    Pruning effects on root distribution and nutrient dynamics in an acacia hedgerow planting in northern Kenya (2000)
    Springer
    Agroforestry systems 50 (2000), S. 59-75 
    Details
    ISSN: 1572-9680
    Schlagwort(e): below-ground competition ; carbohydrates ; nitrogen ; nutrient leaching ; resin cores
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Tree pruning is a common management practice in agroforestry for mulching and reducing competition between the annual and perennial crop. The below-ground effects of pruning, however, are poorly understood. Therefore, nutrient dynamics and root distribution were assessed in hedgerow plantings of Acacia saligna (Labill.) H.L. Wendl. after tree pruning. Pruning to a height of 1.5 m was carried out in March and September 1996. In July and October 1996, the fine root distribution (〈 2 mm) and their carbohydrate contents were determined at three distances to the tree row by soil coring. At the same time, foliar nutrient contents were assessed, whereas nutrient leaching was measured continuously. The highest root length density (RLD) was always found in the topsoil (0–0.15 m) directly under the hedgerow (0–0.25 m distance to trees). Pruning diminished the RLD in the acacia plots at all depths and positions. The relative vertical distribution of total roots did not differ between trees with or without pruning, but live root abundance in the subsoil was comparatively lower when trees were pruned than without pruning. In the dry season, the proportion of dead roots of pruned acacias was higher than of unpruned ones, while the fine roots of unpruned trees contained more glucose than those of pruned trees. Pruning effectively reduced root development and may decrease potential below-ground competition with intercropped plants, but the reduction in subsoil roots also increased the danger of nutrient losses by leaching. Leaching losses of such mobile nutrients as NO3− were likely to occur especially in the alley between pruned hedgerows and tended to be higher after pruning. The reduced size of the root system of pruned acacias negatively affected their P and Mn nutrition. Pruning also reduced the function of the trees as a safety net against the leaching of nutrients for both NO3− and Mn, though not for other studied elements. If nutrient capture is an important aim of an agroforestry system, the concept of alley cropping with pruning should be revised for a more efficient nutrient recycling in the system described here.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006498709454
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  • 95
    Digitale Medien
    Digitale Medien
    Acoustic and Volumetric Virial Coefficients of Nitrogen (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 1033-1044 
    Details
    ISSN: 1572-9567
    Schlagwort(e): intermolecular potential ; nitrogen ; speed of sound ; virial coefficients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Speeds of sound in nitrogen were measured at temperatures between 170 and 400 K at amount-of-substance densities between 40 and 400 mol·m−3. From these measurements, second and third acoustic virial coefficients were obtained. The parameters of two- and three-body isotropic intermolecular potential-energy models were optimized in a simultaneous fit to the second and third acoustic virial coefficients and the ordinary second and third virial coefficients of nitrogen reported by Nowak et al. The results, which shows that the acoustic and ordinary virial coefficients are mutually consistent, may be used to predict second and third virial coefficients, and their acoustic counterparts, over a wide range of temperatures. The parameters of an anisotropic site-site potential-energy model were also obtained from a fit to the acoustic and ordinary second virial coefficients alone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026489719404
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  • 96
    Digitale Medien
    Digitale Medien
    An Improved Greenspan Acoustic Viscometer (2000)
    Springer
    International journal of thermophysics 21 (2000), S. 983-997 
    Details
    ISSN: 1572-9567
    Schlagwort(e): acoustic resonator ; argon ; Greenspan viscometer ; helium ; helium-xenon mixture ; methane ; nitrogen ; speed of sound ; viscosity of gases ; xenon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An improved Greenspan acoustic viscometer (double Helmholtz resonator) was used to measure the viscosity of gases at temperatures from 250 to 400 K and at pressures up to 3.4 MPa. The improvements include a vibration damping suspension and the relocation of the fill duct. The fill duct, which is needed to supply gas to the resonator, was connected to the center of the resonator to eliminate acoustic coupling between the resonator and the manifold. In anticipation of handling corrosive gases, all surfaces of the apparatus that are exposed to the test gas are made of metal. The viscometer was tested with argon, helium, xenon, nitrogen, and methane. Isothermal measurements were carried out at 298.15 and 348.15 K and at pressures up to 3.2 MPa. Without calibration, the results differed from published viscosity data by −0.8% to +0.3% (0.47% r.m.s.). These results are significantly better than previous results from Greenspan viscometers. The measurements also yielded the speed of sound, which differed from literature data by +0.16% to +0.20% (0.18% r.m.s.). Adding empirical effective-area and effective-volume corrections to the data analysis decreased the r.m.s. deviations to 0.12% for the viscosity and to 0.006% for the speed of sound. No unusual phenomena were encountered when the viscometer was tested with a helium-xenon mixture between 250 and 375 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026471901657
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  • 97
    Digitale Medien
    Digitale Medien
    Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: A review (2000)
    Springer
    Agroforestry systems 49 (2000), S. 201-221 
    Details
    ISSN: 1572-9680
    Schlagwort(e): biomass transfer ; integrated nutrient management ; nitrogen ; nutrient cycling ; phosphorus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed along farm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia has been recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia and more recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paper reviews the potential of tithonia green biomass for soil fertility improvement based on recent research in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about 3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produce about 1 kg biomass (tender stems + leaves) m−1 yr−1 on a dry weight basis. Tithonia biomass decomposes rapidly after application to soil, and incorporated biomass can be an effective source of N, P and K for crops. In some cases, maize yields were even higher with incorporation of tithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. In addition to providing nutrients, tithonia incorporated at 5 t dry matter ha−1 can reduce P sorption and increase soil microbial biomass. Because of high labor requirements for cutting and carrying the biomass to fields, the use of tithonia biomass as a nutrient source is more profitable with high-value crops such as vegetables than with relatively low-valued maize. The transfer of tithonia biomass to fields constitutes the redistribution of nutrients within the landscape rather than a net input of nutrients. External inputs of nutrients would eventually be required to sustain production of tithonia when biomass is continually cut and transferred to agricultural land.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006339025728
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  • 98
    Digitale Medien
    Digitale Medien
    Carbon dioxide enrichment and nitrogen fertilization effects on cotton (Gossypium hirsutum L.) plant residue chemistry and decomposition (2000)
    Springer
    Plant and soil 220 (2000), S. 89-98 
    Details
    ISSN: 1573-5036
    Schlagwort(e): Carbohydrates ; CO2 ; lignin ; nitrogen ; proanthocyanidins ; soil respiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Increased atmospheric carbon dioxide (CO2) concentration will likely cause changes in plant productivity and composition that might affect soil decomposition processes. The objective of this study was to test to what extent elevated CO2 and N fertility-induced changes in residue quality controlled decomposition rates. Cotton (Gossypium hirsutum L.) was grown in 8-l pots and exposed to two concentrations of CO2 (390 or 722 μmol mol-1) and two levels of N fertilization (1.0 or 0.25 g l-1 soil) within greenhouse chambers for 8 wks. Plants were then chemically defoliated and air-dried. Leaf, stem and root residues were assayed for total non-structural carbohydrates (TNC), lignin (LTGA), proanthocyanidins (PA), C and N. Respiration rates of an unsterilized sandy soil (Lakeland Sand) mixed with residues from the various treatments were determined using a soda lime trap to measure CO2 release. At harvest, TNC and PA concentrations were 17 to 45% higher in residues previously treated with elevated CO2 compared with controls. Leaf and stem residue LTGA concentrations were not significantly affected by either the elevated CO2 or N fertilization treatments, although root residue LTGA concentration was 30% greater in plants treated with elevated CO2. The concentration of TNC in leaf residues from the low N fertilization treatment was 2.3 times greater than that in the high N fertilization treatment, although TNC concentration in root and stem residues was suppressed 13 to 23% by the low soil N treatment. PA and LTGA concentrations in leaf, root and stem residues were affected by less than 10% by the low N fertilization treatment. N concentration was 14 to 44% lower in residues obtained from the elevated CO2 and low N fertilization treatments. In the soil microbial respiration assay, cumulative CO2 release was 10 to 14% lower in soils amended with residues from the elevated CO2 and low N fertility treatments, although treatment differences diminished as the experiment progressed. Treatment effects on residue N concentration and C:N ratios appeared to be the most important factors affecting soil microbial respiration. The results of our study strongly suggest that, although elevated CO2 and N fertility may have significant impact on post-harvest plant residue quality of cotton, neither factor is likely to substantially affect decomposition. Thus, C cycling might not be affected in this way, but via simple increases in plant biomass production.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004773404948
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  • 99
    Digitale Medien
    Digitale Medien
    Nutrient limitations in wet, drained and rewetted fen meadows: evaluation of methods and results (2000)
    Springer
    Plant and soil 220 (2000), S. 35-47 
    Details
    ISSN: 1573-5036
    Schlagwort(e): drainage ; fertilisation ; nature management ; nitrogen ; nutrient contents ; nutrients ; peat ; phosphate ; potassium ; restoration ; rewetting ; shoot biomass ; species richness ; wetlands
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Restoration of wet grassland communities on peat soils involves management of nutrient supply and hydrology. The concept of nutrient limitation was discussed as well as its interaction with drainage and rewetting of severely drained peat soils. Different methods of assessing nutrient limitation were compared and the type and extent of nutrient limitation were determined for several wet grassland communities. It was concluded that a full-factorial field fertilisation experiment is the most preferable method. Plant tissue analyses and soil chemical analyses were considered less suitable, although they may provide helpful additional information. Fertilisation experiments in the laboratory using sods or using test plants appear to be the proper means to study mechanisms or processes, but have a restricted predictive value for field situations. Generalising the results, it seems that many relativily undisturbed grassland plant communities on peaty soils are characterised by N limitation. Phosphate limitation for vegetation on peat soils is mainly observed in specific circumstances such as extreme calcium richness, high concentrations of Fe or as a result of drainage or long-term hay cropping. The latter two may also cause K limitation. Rewetting is regarded as a prerequisite in restoring wet grassland communities. Further restoration measures to influence nutrient availability depend on aims of the management and the individual site conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004735618905
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  • 100
    Digitale Medien
    Digitale Medien
    Temporal changes in C, P and N concentrations in soil solution following application of synthetic sheep urine to a soil under grass (2000)
    Springer
    Plant and soil 222 (2000), S. 1-13 
    Details
    ISSN: 1573-5036
    Schlagwort(e): carbon ; defoliation ; nitrogen ; phosphorus ; sheep urine ; soil solution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We have determined the temporal changes in the concentration of dissolved organic carbon (DOC) and P and N components in soil solution following application of synthetic sheep urine (500 kg N ha-1) to a brown forest soil in boxes sown with Agrostis capillaris. Three contrasting defoliation treatments (no cutting, single cut before urine application and regular cutting twice per week) plus a fallow soil were studied. The synthetic urine contained 15N labelled urea and was P-free. Intact soil cores were taken after 2, 7, 14, 21 and 56 d and centrifuged to obtain soil solution. The urea in the synthetic urine was rapidly hydrolysed in the soil, increasing soil solution pH, DOC and total dissolved phosphorus (TDP) concentrations. For the regularly defoliated sward, DOC and P reached maximum concentrations (4000 mg DOC L-1 and 59 mg TDP L-1) on day 7. From their peak values, pH and DOC and P concentrations generally decreased with time and at day 56 were near those of the control. Concentrations of NH4 + and NO3 - in the no-urine treatments fluctuated and the greatest treatment differences were between the fallow soil and the soil sown with grass. Adding synthetic urine increased NH4 + concentrations during the first week, but NO3 - concentrations decreased. This was consistent with the 15N labelling of the NO3 - pool which required 3 weeks to reach that of 15NH4 +. Dissolved organic nitrogen (DON) reached a maximum value at day 7 with a concentration of 409 mg N L-1. The DON in soil solution contained no detectable amounts of 15N label indicating that it was derived from sources in the soil. Differences in soil solution composition related to the effect of the other cutting treatments and the fallow treatment were small compared to the effect of synthetic urine addition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004799323646
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