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排序方式: 共有938条查询结果,搜索用时 0 毫秒
931.
The protein subunit of calf brain neurofilament 总被引:24,自引:0,他引:24
932.
Constancy and control of heart rate during an increase in temperature in the Antarctic fish Pagothenia borchgrevinki 总被引:2,自引:0,他引:2
The effect of an acute temperature increase on the control of the heart of the Antarctic teleost Pagothenia borchgrevinki was examined. Heart rate was thermally independent over the range −1.2°C to 3°C, although increasing the temperature from −1.2°C to 3°C elicited a decrease in ventral aortic pressure. Administration of the muscarinic receptor antagonist atropine and the β-adrenoreceptor antagonist sotalol abolished the thermal independence of heart rate, with heart rate increasing at Q10=2. As temperature was increased from −1.2°C to 3°C, cholinergic tone on the heart also increased, from 44.6±4.2% to 70.0±8.4%. At the same time the adrenergic tone increased from 35.5±3.3% to 43.0±3.1%, but the effect on the heart was masked by the increase of cholinergic tone, leading to the thermal independence of heart rate. 相似文献
933.
N Vettakkorumakankav M J Danson D W Hough K J Stevenson M Davison J Young 《Biochimie et biologie cellulaire》1992,70(1):70-75
Dihydrolipoamide dehydrogenase, a flavin disulfide reductase, has been purified and characterized from Haloferax volcanii. The enzyme is a dimer of relative mass 128,000, with an optimal activity at pH 9.0 in 1 M NaCl. Following reduction with its substrate, dihydrolipoamide, the enzyme is inactivated through covalent bond formation with the trivalent arsenical p-aminophenyl arsenoxide. The amino acid composition and the amino acid sequence of the first 49 residues of the N-terminus have been determined. 相似文献
934.
Biased sex ratios of young of birds and mammals clearly occur and may have an adaptive significance, but we rarely know the stage at which a bias is generated, or the mechanism. If a bias is generated prior to birth, studies of marsupials may be insightful because gestation is short and neonates are relatively undifferentiated. This study investigated whether biased sex ratios in Antechinus agilis are generated in the brief period between birth and the attachment of young to the mother''s teats. When all young born, or just pouch young, or supernumerary young were considered, litters were strongly biased towards females (0.32 males), and there was no significant difference across the groups, so a bias is generated before birth in this species. Evidence from counts of corpora lutea suggests that embryo loss during gestation cannot account fully for the level of bias observed. Therefore, prefertilization mechanisms must contribute to the generation of sex-biased litters in this marsupial. 相似文献
935.
P F Davison 《Biopolymers》1967,5(8):715-721
The time required for the completion of the process of strand separation in λ bacteriophage DNA preparations exposed to strongly alkaline conditions in aqueous glycerol solutions was directly proportional to the viscosity of the solvent. This finding supports the idea that the rate-limiting step in the denaturation of high molecular weight DNA is the uncoiling of the strands and in the course of this uncoiling the forces arising from electrostatic and entropic factors must overcome the hydrodynamic viscous drag of the solvent resisting the translation of the polynucleotide strands. 相似文献
936.
937.
ATM-dependent telomere loss in aging human diploid fibroblasts and DNA damage lead to the post-translational activation of p53 protein involving poly(ADP-ribose) polymerase. 总被引:25,自引:1,他引:24 下载免费PDF全文
H Vaziri M D West R C Allsopp T S Davison Y S Wu C H Arrowsmith G G Poirier S Benchimol 《The EMBO journal》1997,16(19):6018-6033
938.