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91.
- 1 One of the major developments in ecology has been the recognition of the importance of spatial and temporal scale in describing patterns of distribution and abundance. This article develops a quantitative framework that includes both spatial and temporal scale, then uses it to review what has been learned about a well studied group of mobile organisms — marine birds in the Bering Sea.
- 2 Review showed that lateral gradients in density are by far the most frequently measured property of birds away from colonies in the Bering Sea. Gradients are related to a variety of environmental factors, depending on spatial scale.
- 3 Review within a quantitative framework showed that the assumptions for interpreting the spatial dynamics responsible for observed patterns are rarely stated, that interpretations of pattern at sea have focused on individual movements in relation to food concentration, and that little is known about wind and water-driven movements, or rates of death and recruitment away from colonies.
- 4 Several lines of evidence support the hypothesis that distribution and feeding are linked to the rate of resupply of nekton to birds near the sea surface.
- 5 The framework provided here permits the relative importance of competing processes to be stated and evaluated as a function of spatial scale. The framework should be useful in summarizing the spatial dynamics of other groups of mobile organisms.
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Amelioration of aluminium toxicity in wheat by fluoride 总被引:4,自引:1,他引:3
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SCHNEIDER HA 《Bacteriological reviews》1960,24(1):186-191
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Reduced glutathione, in concentrations approximating those occurring in intact rat liver, causes swelling of rat liver mitochondria in vitro which is different in kinetics and extent from that yielded by L-thyroxine. The effect is also given by cysteine, which is more active, and reduced coenzyme A, but not by L-ascorbate, cystine, or oxidized glutathione. The optimum pH is 6.5, whereas thyroxine-induced swelling is optimal at pH 7.5. The GSH-induced swelling is not inhibited by DNP or dicumarol, nor by high concentrations of sucrose, serum albumin, or polyvinylpyrrolidone, in contrast to thyroxine-induced swelling. ATP inhibits the GSH swelling, but ADP and AMP are ineffective. Mn(-+) is a very potent inhibitor, but Mg(++) is ineffective. Ethylenediaminetetraacetate is also an effective inhibitor of GSH-induced swelling. The respiratory inhibitors amytal and antimycin A do not inhibit the swelling action of GSH, but cyanide does; these findings are consistent with the view that the oxidation-reduction state of the respiratory chain between cytochrome c and oxygen is a determinant of GSH-induced swelling. Reversal of GSH-induced swelling by osmotic means or by ATP in KCl media could not be observed. Large losses of nucleotides and protein occur during the swelling by GSH, suggesting that the action is irreversible. The characteristically drastic swelling action of GSH could be prevented if L-thyroxine was also present in the medium. 相似文献
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