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  • Articles  (75)
  • Springer  (74)
  • Geological Society of America (GSA)
  • Institute of Physics
  • 2015-2019  (12)
  • 2010-2014  (8)
  • 1995-1999  (54)
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  • Biology  (75)
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  • Articles  (75)
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  • 1
    Electronic Resource
    Electronic Resource
    Effects of ammonium ions on the depolarization-induced and direct activation of the contractile apparatus in mechanically skinned fast-twitch skeletal muscle fibres of the rat (1996)
    Springer
    Journal of muscle research and cell motility 17 (1996), S. 611-616 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned fibre preparations from the extensor digitorum longus muscle of the rat were used to test whether a rise in myoplasmic [NH4 +] in the range 2–10 mm interferes with the mechanism of excitation-contraction coupling in fast-twitch mammalian muscle. Under our conditions (pH 7.10, Mg2+ 1 mm, temperature 23° C), [NH4 +] up to 10 mm had little effect on the Ca+-activated force and on the peak of the t-system depolarization-induced force response. However, the duration of the depolarization-induced force response was decreased significantly at [NH4 +] ≥2 mm. From these data we conclude that the intracellular accumulation of NH4 + is not likely to play a major role in fatigue. Nevertheless, the build up of NH4 + during fatigue, may have a significant inhibitory effect on the force output by decreasing the duration of the t-system depolarization-induced activation of the contractile apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154055
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  • 2
    Electronic Resource
    Electronic Resource
    Microfluorometric analyses of glycogen in freshly dissected, single skeletal muscle fibres of the cane toad using a mechanically skinned fibre preparation (1998)
    Springer
    Journal of muscle research and cell motility 19 (1998), S. 631-638 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The main objective of this study was to analyse glycogen in single muscle fibres, using a recently developed microfluorometric method which detects subpicomol amounts of NADPH, glucose and glycogen (as glucosyl units) (detection limit 0.16–0.17pmol in a 25nl sample) without fluorochrome amplification. The fibres were freshly dissected from the twitch region of the iliofibularis muscle of the cane toad (Bufo marinus), and were mechanically skinned under paraffin oil to gain access to the intracellular compartments. The results show that: (1) glycogen concentrations in toad skeletal muscle fibres range between 25.8 and 369mmol glucosyl units/litre fibre volume; (2) there is a large variation in glycogen content between individual fibres from the iliofibularis muscle of one animal; (3) there are seasonal differences in the glycogen content of toad single muscle fibres; (4) the total amount of glycogen in single muscle fibres of the toad does not decrease significantly when storing the tissue, under paraffin oil, at 20–25°C for up to 6h or at 4°C for up to 24h; and (5) 15–26% of fibre glycogen can be washed in an aqueous solution at pH 5–7, within 5min, while 74–85% of fibre glycogen remains associated with the washed skinned fibre, even after 40min exposure of the skinned fibre preparation to the aqueous environment. The retention of most glycogen in the fibre preparation after mechanical removal of the plasma membrane and extensive washing indicates that in toad skeletal muscle fibres the largest proportion of glycogen is tightly bound to intracellular structures. The results also show that the skinned muscle fibre preparation is well suited for microfluorometric glycogen determination, since low molecular weight non-glycogen contributors to the fluorescence signal can be removed from the myoplasmic space prior to the glycogen hydrolysis step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005377030193
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of the vacuum drying of frozen tissues (1953)
    Springer
    Bulletin of mathematical biology 15 (1953), S. 411-429 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A general theory of the drying of frozen tissue is developed and applied to the measurement of the drying rate of frozen guinea pig liver. It is shown that for a given temperature of the subliming ice crystals the mininum drying time of a piece of guinea pig liver is greater than the minimum sublimation time of a piece of ice of the same size and shape by a factor of the order of one thousand. This fact has many implications in the design of freeze-dry apparatus which will be developed in a following paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02476434
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  • 4
    Electronic Resource
    Electronic Resource
    Mycorrhizae from Denali National Park and Preserve, Alaska (1995)
    Springer
    Mycorrhiza 6 (1995), S. 21-29 
    Details
    ISSN: 1432-1890
    Keywords: Key words Mycorrhizae ; Arctic-alpine ; Dark septate fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Roots of 40 taxa of higher plants (Pteridophyta, Spermatophyta) from two alpine study sites in Denali National Park and Preserve in central Alaska were examined for their mycorrhizal colonization. We observed ectomycorrhizae on six species: Betula nana, Salix reticulata, Salix polaris, Salix arctica, Polygonum viviparum, and Dryas octopetala. Seven taxa, Cassiope tetragona, Empetrum nigrum, Ledum palustre subsp. decumbens, Ledum palustre subsp. groenlandicum, Loiseleuria procumbens, Vaccinium uliginosum and Vaccinium vitis–idaea (all Ericales), had ericoid mycorrhizae. One species, Arctostaphylos alpina, formed a typical arbutoid mycorrhiza. Two species (Sibbaldia procumbens and Aconitum delphinifolium) showed well-developed VA mycorrhizae, whereas three species of plants (Lycopodium clavatum, Silene acaulis and Oxytropis scammaniana) had vesicles, but no arbuscules. The roots of 11 other plants (Lycopodium clavatum, Lycopodium selago, Silene acaulis, Gentiana algida, Lupinus arcticus, Oxytropis scammaniana, Pedicularis langsdorffii, Pedicularis capitata, Pedicularis verticillata, Artemisia sp. and Carex bigelowii) had a variety of intracellular colonizations which are referred to as dark septate fungi. No mycorrhizae were found on 12 other plants: Equisetum arvense, Equisetum variegatum, Lycopodium alpinum, Polygonum bistorta, Saxifraga hieracifolia, Saxifraga hirculus, Astragalus alpinus, Pedicularis kanei, Petasites frigidus, Carex podocarpa, Carex microchaeta and Poa arctica. A possible ecological role of dark septate fungi is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050101
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  • 5
    Electronic Resource
    Electronic Resource
    Coring artifacts and contaminant inventories in lake sediment (1996)
    Springer
    Journal of paleolimnology 15 (1996), S. 99-106 
    Details
    ISSN: 1573-0417
    Keywords: lake sediments ; gravity core ; freeze core ; coring artifacts ; contaminant concentration ; contaminant inventory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sediments of Lake 382, Experimental Lakes Area, Canada, were sampled at six sites using a 5-cm Wildco KB core sampler (KB), a similar device incorporating a ball check valve (BC), and a 0.2 m by 1.2 m flat-faced aluminum freeze core sampler (FC). Cores were sectioned at 1-cm intervals to a depth of 15 cm. Contaminant (210Pb and 137Cs) concentrations (Bq g-1) were measured by gamma spectroscopy, and inventories (Bq cm-2) were calculated following standard methods. Sediments collected using FC, BC and KB had similar contaminant concentrations, however, cores collected by FC and BC had lower estimated inventories than KB cores. Differences between estimates appear to be caused by differences in the water content (WC) of core material. Laboratory studies confirm that FC sediments have higher WC than tube-cored sediment. We hypothesize that ice crystal formation increases the WC of freeze cores, resulting in lower contaminant inventories. Loss of surficial sediment caused by a ‘bow wave’ may have a similar effect on BC samples. We conclude that KB core gear is appropriate for sampling sediments to measure contaminant concentrations and inventories in recently deposited sediments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00176992
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of pollination intensity on the vigor of the sporophytic and gametophytic generation of Cucurbita texana (1997)
    Springer
    Sexual plant reproduction 10 (1997), S. 236-240 
    Details
    ISSN: 1432-2145
    Keywords: Key words Cucurbita texana ; Pollen ; Pollen performance ; Pollen competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We examined the effects of pollen competition (pollen load size) on sporophytic vigor and gametophytic performance in Cucurbita texana, a wild gourd, while controlling for alternative interpretations of the data. Under field conditions we compared the vigor of progeny produced from large and small pollen loads and examined the in vitro performance of the pollen produced by the progeny. We found that the progeny from large pollen loads germinated faster and had a greater reproductive output (male flowers and fruits) than progeny produced from small pollen loads. In addition, we found that the pollen produced on plants derived from large pollen loads grew faster in vitro than the pollen produced on plants derived from small pollen loads. These findings indicate that pollen competition affects the performance of the resulting sporophytic generation and the microgametophytes they produce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050092
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  • 7
    Electronic Resource
    Electronic Resource
    Variation in sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo and their F1 and F2 generations (1998)
    Springer
    Sexual plant reproduction 11 (1998), S. 265-271 
    Details
    ISSN: 1432-2145
    Keywords: Key words Cucurbita ; Pollen tube growth ; Pollen performance ; Hybridization ; Variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This study examines sporophytic and gametophytic vigor in wild and cultivated varieties of Cucurbita pepo L. and their hybrids in order to determine whether hybrid vigor extends to the microgametophyte generation. It also examines the variation in sporophytic and gametophytic vigor to discern the non-genetic influences of pollen provisioning by the sporophyte on pollen performance from the genetic influences of the microgametophyte’s own genotype on pollen performance. A cultivated and a wild C. pepo and their F1 and the F2 generations were grown under field conditions and flower and fruit production were monitored over one summer. We found that the four types of plants differed significantly in the number of male and female flowers and the number of fruits they produced. The F1 plants produced significantly more male flowers and marginally more female flowers and fruits than the parental lines. To estimate gametophytic vigor pollen was germinated in vitro and pollen tube length measured after 30 min. We found that pollen tubes from the F1 plants had significantly greater growth than tubes from the parental lines or the F2 generation, indicating that hybrid vigor extends to the microgametophytic generation. By partitioning the variance of pollen tube growth into ’within’ and ’among’ plant components of variation, we were able to show that the genotype of the microgametophyte influences pollen performance in vitro, but that expression of hybrid vigor in the microgametophyte is likely to be due to an environmental effect related to provisioning of the pollen grains during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050152
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  • 8
    Electronic Resource
    Electronic Resource
    Cloning and characterisation of glutamine synthetase from Colletotrichum gloeosporioides and demonstration of elevated expression during pathogenesis on Stylosanthes guianensis (1997)
    Springer
    Current genetics 31 (1997), S. 447-454 
    Details
    ISSN: 1432-0983
    Keywords: Key words Expression quantification ; Glutamine synthetase ; Pathogenesis ; Nitrogen metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments were designed to clone and identify genes of the fungal phytopathogen Colletotrichum gloeosporioides expressed at high levels during growth on the compatible host Stylosanthes guianensis when compared with expression in axenic culture. A cDNA clone (pCgGS) that hybridised preferentially to a cDNA probe prepared from infected leaves was isolated by the differential screening of a cDNA library from a nitrogen-starved axenic culture of C. gloeosporioides. The DNA sequence of pCgGS is highly homologous to genes for glutamine synthetase (GS) in other organisms. pCgGS contained all of the conserved regions assigned as catalytic domains in GS enzymes. Comparison with genomic sequences indicated that in C. gloeosporioides the GS gene is present as a single copy with three introns. To our knowledge this is the first report of the cloning of a GS from a filamentous fungus. A second clone (pCgRL1) was also isolated and represented a partial cDNA of the 25s rRNA of C. gloeosporioides. Because pCgRL1 did not hybridise to plant rRNA under high-stringency hybridisation conditions, it was used as a reference to quantify the expression of fungal GS mRNA during pathogenesis in S. guianensis compared to fungal growth in axenic culture. The results indicated that elevated expression of GS occurred during pathogenesis of C. gloeosporioides on S. guianensis, particularly at early stages of infection where expression was about six-times higher than during growth in rich culture media. This work also demonstrates that fungal-specific 25s rRNA fragments, such as pCgRL1, have considerable utility as a reference for quantifying pathogen gene expression in infected plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050228
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of Barbiturates on Facilitative Glucose Transporters are Pharmacologically Specific and Isoform Selective (1999)
    Springer
    The journal of membrane biology 169 (1999), S. 45-53 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Barbiturates — Glucose transport — Anesthetics — Pharmacologic specificity — Isoform selectivity — Binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Barbiturates inhibit GLUT-1-mediated glucose transport across the blood-brain barrier, in cultured mammalian cells, and in human erythrocytes. Barbiturates also interact directly with GLUT-1. The hypotheses that this inhibition of glucose transport is (i) selective, preferring barbiturates over halogenated hydrocarbon inhalation anesthetics, and (ii) specific, favoring some GLUT-# isoforms over others were tested. Several oxy- and thio-barbiturates inhibited [3H]-2-deoxyglucose uptake by GLUT-1 expressing murine fibroblasts with IC50s of 0.2–2.9 mm. Inhibition of GLUT-1 by barbiturates correlates with their overall lipid solubility and pharmacology, and requires hydrophobic side chains on the core barbiturate structure. In contrast, several halogenated hydrocarbons and ethanol (all ≤10 mm) do not significantly inhibit glucose transport. The interaction of these three classes of anesthetics with purified GLUT-1 was evaluated by quenching of intrinsic protein fluorescence and displayed similar specificities and characteristics. The ability of barbiturates to inhibit other facilitative glucose transporters was determined in cell types expressing predominantly one isoform. Pentobarbital inhibits [3H]-2-deoxyglucose and [14C]-3-O-methyl-glucose uptake in cells expressing GLUT-1, GLUT-2, and GLUT-3 with IC50s of ∼1 mm. In contrast, GLUT-4 expressed in insulin-stimulated rat adipocytes was much less sensitive than the other isoforms to inhibition by pentobarbital (IC50 of 〉10 mm). Thus, barbiturates selectively inhibit glucose transport by some, but not all, facilitative glucose transporter isoforms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005900
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  • 10
    Electronic Resource
    Electronic Resource
    Weakly nonlinear stability analyses of one-dimensional Turing pattern formation in activator-inhibitor/immobilizer model systems (1995)
    Springer
    Journal of mathematical biology 33 (1995), S. 771-815 
    Details
    ISSN: 1432-1416
    Keywords: Turing patterns ; CIMA/starch ; Brussellator/immobilizer ; Schnackenberg/immobilizer model systems ; One-dimensional nonlinear stability analyses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract The development of one-dimensional Turing patterns characteristic of the chlorite-iodide-malonic acid/starch reaction as well as analogous Brussellator/immobilizer and Schnackenberg/immobilizer model systems is investigated by means of a weakly nonlinear stability analysis applied to the appropriately scaled governing equations. Then the theoretical predictions deduced from these pattern formation studies are compared with experimental evidence relevant to the Turing diffusive instabilities under examination in order to explain more fully the transition to such stationary symmetry-breaking spatial structures when the temperature or pool species concentrations vary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187282
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