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991.
Climate change and temperature-dependent biogeography: oxygen limitation of thermal tolerance in animals 总被引:2,自引:0,他引:2
Pörtner HO 《Die Naturwissenschaften》2001,88(4):137-146
Recent years have shown a rise in mean global temperatures and a shift in the geographical distribution of ectothermic animals. For a cause and effect analysis the present paper discusses those physiological processes limiting thermal tolerance. The lower heat tolerance in metazoa compared with unicellular eukaryotes and bacteria suggests that a complex systemic rather than molecular process is limiting in metazoa. Whole-animal aerobic scope appears as the first process limited at low and high temperatures, linked to the progressively insufficient capacity of circulation and ventilation. Oxygen levels in body fluids may decrease, reflecting excessive oxygen demand at high temperatures or insufficient aerobic capacity of mitochondria at low temperatures. Aerobic scope falls at temperatures beyond the thermal optimum and vanishes at low or high critical temperatures when transition to an anaerobic mitochondrial metabolism occurs. The adjustment of mitochondrial densities on top of parallel molecular or membrane adjustments appears crucial for maintaining aerobic scope and for shifting thermal tolerance. In conclusion, the capacity of oxygen delivery matches full aerobic scope only within the thermal optimum. At temperatures outside this range, only time-limited survival is supported by residual aerobic scope, then anaerobic metabolism and finally molecular protection by heat shock proteins and antioxidative defence. In a cause and effect hierarchy, the progressive increase in oxygen limitation at extreme temperatures may even enhance oxidative and denaturation stress. As a corollary, capacity limitations at a complex level of organisation, the oxygen delivery system, define thermal tolerance limits before molecular functions become disturbed. 相似文献
992.
IntroductionFertilizationisessentialforagriculturalproduction ,butunreasonablyapplyingfertilizerscouldresultinseriesofproblemssuchascropqualitydecline,fertilizeruseefficiencydecrease,residualfertilizerspollution groundwaterandriversandnitrogencontented … 相似文献
993.
IntroductionThealuminosilicatesheetsofbentonitepossessanetnegativeelectricalchargecompensatedforbyinorganicexchangeablecations(e.g.,Na+andCa2+),whichstronglyhydratedinthepresenceofwater.Surfacepropertiesofnaturalbentonitecanbemodifiedbysimpleionexchangewi… 相似文献
994.
IntroductionAtmosphericnitrousoxide (N2 O)isaveryradioactivelyactivegreenhousegas,alsocontributingtothedepletionofozonelayerofstratosphere .AtmosphericN2 Omainlyoriginatedfromnitrificationanddenitrificationinterrestrialecosystems.Grasslandecosystem ,accoun… 相似文献
995.
This paper investigates the current treatment of environmental issues by two companies within the large made-to-order sector. Fifty questionnaires were issued to the design team of each company to assess current practice in the integration of environmental issues with design activities, awareness of environmental issues, awareness of existing environmental design tools and the preferred format for a potential clean design tool. 相似文献
996.
Ants have a well developed olfactory sense, which they need both for the perception of environmental chemicals, and for a
highly sophisticated intraspecific communication system based on pheromones. The question arises therefore as to how different
odors are coded in the antennal lobe, the first central neuropil to process olfactory information. We measured odor-evoked
activity patterns using in vivo neuropil calcium recording in the antennal lobe of the ant Camponotus rufipes. We found that (a) odors elicit focal activity spots (diameter ca. 20 μm) which most probably represent the olfactory glomeruli;
(b) different odors are coded in odor specific patterns of such activated spots, and a particular spot can participate in
the pattern for different odors; (c) calcium increased in the activated spots within the 2-s stimulation period and slowly
declined thereafter.
Received: 10 March 1999 / Accepted in revised form: 5 July 1999 相似文献
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