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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 13 (1997), S. 0 
    ISSN: 1748-7692
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The Pacific walrus (Odobenus rosmarus divergens) population is an important ecological and economic resource of the Bering Sea region. We describe population change, beginning with a low in 1950, through a high in about 1980, and ending in 1989. Estimates of abundance for the years after 1989 were not attempted due to the lack of harvest data and other population parameters. Selective hunting practices resulted in biased data regarding population composition and reproductive performance. Rates of reproduction had to be estimated from ovarian data, which indicated a dramatic drop in the 1980s. High harvests in the 1980s likely contributed to a decline in the population, but uncertainties as to accuracy of population estimates and other data raise reasonable doubts, especially with respect to the number of males, for which the most recent (1985) population estimate suggests a sharp decline. Past population estimates were revised upwards to compensate for walruses underwater and not seen in aerial surveys. The weaknesses in the available data make it clear that effective management of the population will require many improvements in collection of data regarding harvests, population structure, reproduction, and population trend.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 0370-2693
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 15 (1971), S. 346-355 
    ISSN: 1432-1254
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 280 (1979), S. 506-508 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] All experiments were performed on single smooth muscle cells isolated from the stomach muscle of the toad, Bufo marinus, by an enzymatic digestion technique that involved the use of trypsin and collagenase. Isolated cells obtained by this technique exhibit physiological, pharmacological, metabolic ...
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 277 (1979), S. 32-36 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The mechanism of β-adrenergic relaxation was investigated in isolated smooth muscle cells. β-adrenergic agents stimulate cyclic AMP-dependent phosphorylation, enhance Na+/K+ transport and induce relaxation. The stimulation of ...
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 431 (1996), S. 473-482 
    ISSN: 1432-2013
    Schlagwort(e): Key wordsMitochondria ; Smooth muscle ; Calcium FCCP ; Cyanide ; TMRE ; Ruthenium red
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Recent evidence, from a variety of cell types, suggests that mitochondria play an important role in shaping the change in intracellular calcium concentration ([Ca2+]i) that occurs during physiological stimu-lation. In the present study, using a range of inhibitors of mitochondrial Ca2+ uptake, we have examined the contribution of mitochondria to Ca2+ removal from the cytosol of smooth muscle cells following stimulation. In voltage-clamped single smooth muscle cells, we found that following a 8-s train of depolarizing pulses, the rate of Ca2+ extrusion from the cytosol was reduced by more than 50% by inhibitors of cytochrome oxidase or exposure of cells to the protonophore carbonyl cyanide P-trifluoromethoxy-phenylhydrazone. Using the potential-sensitive indicator tetramethyl rhodamine ethyl ester, we confirmed that the effect of these agents was associated with depolarization of the mitochond-rial membrane. Since, the primary function of the mitochondria is to provide the cell’s ATP, it could be argued that it is the ATP supply to the ion pumps which is limiting the rate of Ca2+ removal. However, experiments carried out with the mitochondrial Ca2+ uniporter inhibitor ruthenium red produced similar results, while the ATP synthetase inhibitor oligomycin had no effect, suggesting that the effect was not due to ATP insufficiency. These results establish that mitochondria in smooth muscle cells play a significant role in removing Ca2+ from the cytosol following stimulation. The uptake of Ca2+ into mitochondria is proposed to stimu-late mitochondrial ATP production, thereby providing a means for matching increased energy demand, following the cell’s rise in [Ca2+]i, with increased cellular ATP production.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Polar biology 3 (1984), S. 11-18 
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Walruses (Odobenus rosmarus) feed primarily on benthic invertebrates, but they are known to eat seals (Phocidae) occasionally, ostensibly when the benthic foods are unavailable. We investigated reports of a marked increase in occurrence of seal-eating walruses in the Bering Strait region in the late 1970's by examining stomach contents of animals taken in the spring harvests by Eskimos. We also obtained relevant information during visual surveys of marine mammals in the region. Our findings from the stomachs indicated that seal eating was 10 to 100 times more common during the 1970's and early 1980's (0.6–3.0%, N=645) than it had been in the previous three decades (0.07–0.20%, N=4015). In addition, we observed walruses in possession of seal remains in 1978 and 1979, where we had not seen such a phenomenon before in the previous 25 years. We attribute the increased predatory interaction between seals and walruses partly to a larger walrus population and, especially in 1979, to unusually restrictive spring ice conditions, which tended to cause greater than usual overlap of their distributions. Stomach contents of walruses taken in the Chukchi Sea in summer, where the ranges of walruses and seals overlap broadly in all years, have indicated a similarly high rate of occurrence of seal eaters (8.6% in the 1960's, N=35; 11.4% in 1983, N=44). As a whole, our findings indicate that most of the seal eating is predation, rather than scavenging of carrion. They also indicate that it is not rare or aberrant but common behavior, and that it could exert a significant impact on seal populations in some areas.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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