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191.
Glenn D. Prestwich Gae E. Kovalick John K. Koeppe 《Biochemical and biophysical research communications》1982,107(3):966-973
The synthesis and testing of several diazocarbonyl JH analogs (diazo JHA) which act as photoaffinity labels for insect juvenile hormone binding proteins are described. The best competitor, 10,11-epoxyfarnesyl diazoacetate, has been shown to irreversibly reduce [3H]-JH III binding to both ovarian and hemolymph JHBP from Leucophaeamaderae after irradiation at 254 nm for 20 seconds. No loss of activity was observed after incubation of JHBP and diazo JHA without irradiation. Protection from photoinactivation by diazo JHA II was achieved by the presence of an equimolar amount of JH III during the photolysis. Photoaffinity labeled proteins show loss of binding capacity without alteration of the binding affinity. This is the first example of the use of a photoaffinity label in the study of JH action on a molecular level, and may become a valuable tool in the elucidation of JH-receptor-chromatin interactions. 相似文献
192.
Fine structure of the recB and recC gene region of Escherichia coli 总被引:14,自引:0,他引:14
M Sasaki T Fujiyoshi K Shimada Y Takagi 《Biochemical and biophysical research communications》1982,109(2):414-422
193.
Hugo J. Niggli Peter A. Cerutti 《Biochemical and biophysical research communications》1982,105(3):1215-1223
The nucleosomal distribution of cis-syn cyclobutyl-type thymine photodimers was determined in normal human skin fibroblasts following irradiation with low doses of far-ultraviolet light at 254 nm and nearultraviolet light at 313 nm. The thymine photodimer concentrations were determined by high pressure liquid chromatography in acid hydrolysates of total cellular DNA and of nucleosomal core- and chromatosomal-DNA. The lesion concentrations in linker-DNA were calculated from these data. While thymine photodimers were distributed uniformely following 254 nm irradiation they were enriched by a factor of 2.4 – 4.2 in nucleosomal linker DNA after exposure to 313 nm light. 相似文献
194.
Why the evolution of resistance to anthropogenic toxins normally involves major gene changes: the limits to natural selection 总被引:1,自引:1,他引:0
M. R. Macnair 《Genetica》1991,84(3):213-219
Standard population genetic theory suggests that adaptation should normally be achieved by the spread of many genes each of small effect (polygenes), and that adaptation by major genes should be unusual. Such models depend on consideration of the rates of acquisition of adaptation. In practice, adaptation to pollutants and anthropogenic toxins has most frequently been achieved by the spread of major genes. A simple model is developed to explain this discrepancy, in which the determining factor is not the rate of spread, but the maximum response achievable under the two contrasting models of polygenic or major gene inheritance. In the short term, for a given mean and genetic variance, characters in which the additive genetic variance is produced by the segregation of many genes of small effect at intermediate gene frequencies are unable to produce as large a response to directional selection as characters in which the variance is caused by genes of large effect at low frequency. If the target for selection is a long way from the mean prior to selection (as it may well be for adaptation to novel anthropogenic stresses) then adaptation can only be achieved by species possessing major genes. The model is discussed with reference to the example of heavy metal tolerance in plants. 相似文献
195.
Most green gemmules of Spongilla lacustris survived enclosure in ice at –20 °C for up to 30 days; however, their rate of germination at 20 °C was less rapid than that of control gemmules. The length of time spent at low temperature had little effect on gemmule survival. In contrast, repeated cooling to –20 °C and warming to 4 °C led to a progressive decline in gemmule viability. These results indicate that cold injury occurs primarily during transitions between high and low temperatures. 相似文献
196.
Salinity tolerance and morphology of the osmoregulation organs in Cladocera with special reference to Cladocera from the Aral sea 总被引:6,自引:2,他引:4
Nick V. Aladin 《Hydrobiologia》1991,225(1):291-299
The hyperosmotic regulation of adult Cladocera is determined mainly by the amount of salts consumed with the food and by reabsorption of salts in cells of the nuchal (neck) organ. The hypoosmotic regulation both in adults and embryos is determined mainly by excretion of salts in special epipodite cells or in cells of the nuchal (neck) organ. The salinity of the Aral sea for the last 30 years increased from 8–10 to 26–28, which led to changes in the Cladocera fauna. At present only 4 species of Cladocera inhabit the Aral sea instead of 14 species that were previously found. These changes are in agreement with osmoregulation capacities of Cladocera.
Note added in proof. Since this paper was accepted for publication, all Cladocera have disappeared from the Aral Sea. This happened when salinity reached 30–32. This disappearance was predicted by and agrees with earlier laboratory experiments with Aral Sea Cladocera (Aladin, 1982b). 相似文献
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L. E. Francois 《Plant and Soil》1992,147(2):163-170
The boron tolerance of two summer squash cultivars (Cucurbita pepo L. Aristocrat Zucchini and Peter Pan Scallop) and one winter squash cultivar (Cucurbita moschata Poir. Butter boy) was determined in large, outdoor sand cultures. Boron treatments were imposed by irrigation with culture solutions that contained 1.0, 3.0, 6.0, 9.0, 12.0, or 15.0 mg B L-1. Relative fruit yields of Zucchini, Scallop, and Butter boy were reduced 5.2%, 9.8%, and 4.3% with each unit (mg L-1) increase in soil solution B (Bsw)>2.7, 4.9, and 1.0 mg B L-1, respectively. Reduced yields of all cultivars were attributed to a reduction in fruit number and not fruit size. Boron concentrations in leaves and fruit were directly correlated to Bsw. 相似文献