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671.
Abstract Cross tolerance, whereby tolerance to one environmental stress is correlated with tolerance to other stressors, is thought to be widespread in insects. We used lines of Drosophila melanogaster Meigen (Diptera: Drosophilidae) selected for survival at a 1-h exposure to −5°C to examine the extent to which this selection results in increased tolerance to other stresses, including high and low temperatures, desiccation and starvation. While selection improved tolerance to acute cold exposure and survival at −5°C, there was little effect of selection regime on tolerance to other stressors. There was no correlation between tolerances to any of the stressors, suggesting different mechanisms of tolerance. This supports arguments that correlations between stress tolerances during selection experiments with D. melanogaster may be coincidental. The magnitude of heat-hardening was apparently constrained by basal tolerance among lines, but the magnitude of the rapid cold-hardening response was not correlated with basal cold tolerance, implying that the relationship between inducible and basal tolerances differs at high and low temperatures. 相似文献
672.
The possibility that, in the rabbit, sulfate is actively transported across the choroid plexuses was investigated by ventriculo-cisternal perfusion in the absence and presence of carrier. No evidence for this could be found. Penetration of sulfate from blood to brain and CSF was measured in the intact animal equilibration was very slow, indicating the presence of high barriers for this solute, but the low steady-state level in the brain, approached in these experiments, was quite consistent with slow passive permeability aacross the barriers, with free exchange between extracellular fluid and CSF. The clearance of another slowly penetrating solute, creatinine, from the perfusion fluid during ventriculo-cisternal perfusion was comparabl with that of sulfate. 相似文献
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674.
Stella Charleson Jillian F. Evans Robert J. Zamboni Yves Leblanc Brian J. Fitzsimmons Claire Leveill Philippe Dupuis Anthony W. Ford-Hutchinson 《Prostaglandins & other lipid mediators》1986,32(4)
Specific high-affinity binding sites for [3H]-leukotriene B4 have been identified on membrane preparations from rat and human leukocytes. The rat and human leukocyte membrane preparations show linearity of binding with increasing protein concentration, saturable binding and rapid dissociation of binding by excess unlabelled leukotriene B4. Dissociation constants of 0.5 to 2.5 nM and maximum binding of 5000 fmoles/mg protein were obtained for [3H] leukotriene B4 binding to these preparations. Displacement of [3H]-leukotriene B4 by leukotriene B4 was compared with displacement by leukotriene B3 and leukotriene B5 which differ from leukotriene B4 only by the absence of a double bond at carbon 14 or the presence of an additional double bond at carbon 17, respectively. Leukotriene B3 was shown to be equipotent to leukotriene B4 in ability to displace [3H]-leukotriene B4 from both rat and human leukocyte membranes while leukotriene B5 was 20–50 fold less potent. The relative potencies for the displacement of [3]-leukotriene B4 by leukotrienes B3, B4 and B5 on rat and human leukocyte membranes were shown to correlate well with their potencies for the induction of the aggregation of rat leukocytes and the chemokinesis of human leukocytes. 相似文献
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Sharon LR Simon Lise Lamoureux Margot Plews Michael Stobart Jillian LeMaistre Ute Ziegler Catherine Graham Stefanie Czub Martin Groschup J David Knox 《Proteome science》2008,6(1):23