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排序方式: 共有397条查询结果,搜索用时 312 毫秒
1.
N D Klimchuk M S Kitsara O M Frolova N M Balaeva 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(2):41-45
Experiments on the laboratory cultures of lice infected by Weigl's method revealed that the spontaneous, erythromycin-resistant mutant of R. prowazekii strain E, adapted to the vector's organism, retained its resistance to erythromycin during 50 successive passages without the maintenance concentrations of this antibiotic. The above strain remained sensitive to tetracycline and levomycetin. Its level of sensitivity to the latter antibiotics was similar to that of R. prowazekii strains cultivated in the vector's organism for a long time. 相似文献
2.
Biophysics - Abstract—The goal of the present study was to investigate the molecular mechanisms that underlie heart and skeletal muscle damage in male Wistar rats weighing 200–250 g in... 相似文献
3.
The possibility of obtaining the mutants of R. prowazekii, strain E, by exposing these organisms to the action of N-methyl-N-nitro-N-nitrosoguanidine was studied; this substance, used in doses of 5-10 micrograms, showed a mutagenic effect on rickettsiae suspended in physiological saline, after their exposure for 10-20 minutes at 37 degrees C. The mutants thus obtained proved to be resistant to erythromycin and rifampicin and were characterized by heterogeneity in the degree and stability of their antibiotic resistance. The effectiveness of selection was increased if mutagen-treated rickettsiae were selected after the first passage in chick embryos. The induced mutants differed from the original rickettsial strain by their lower infectiosity for chick embryos. 相似文献
4.
血管内皮舒张因子在氧自由基所致慢性缺氧大鼠肺内动脉收缩中的作用 总被引:1,自引:0,他引:1
以黄嘌岭(X)-黄嘌呤氧化酶(XO)系统产生氧自由基,应用微量生物测定法观察慢性缺氧(5000m,10d)对大鼠氧自由基所致肺内动脉收缩的影响及内皮舒张因子(EDRF)在其中的作用。慢性缺氧大鼠有内皮的肺内动脉环对氧自由基的收缩反应较正常环境中的对照动物明显增强,加入EDRF灭活剂还原型血红蛋白(RHb)后更加显著;而加入超氧化物歧化酶(铜锌SOD)后则减弱,甚至消除。反之,不论加入RHb或SOD对氧自由基所致去内皮肺内动脉环的收缩反应均无明显影响。上述结果表明慢性缺氧引起肺内动脉收缩增强与EDRF有密切关系:慢性缺氧可能使EDRF的作用减弱,肺内动脉对氧自由基的反应性增强。表示EDRF及其与氧自由基的关系在慢性缺氧性肺动脉高压的形成中可能具有十分重要的意义。 相似文献
5.
A P Savchenko M I Frolova A A Smirnov Z Zh Mamytova S B Bekzhigitov 《Vestnik rentgenologii i radiologii》1991,(6):19-25
A study of the correlation between electrophysiologic effects of intracoronary injections of radiopaque agents and anatomical features of blood supply of cardiac conduction was carried out in 60 patients with intact coronary arteries. Coronary angiography was performed in all the patients. Disorders in cardiac conduction and repolarization in the myocardium were observed in intracoronary injection of radiopaque agents, which was accompanied by the development of S-A bradycardia. A bradyarrhythmic reaction type depends on prevalence of the left or right coronary artery in the atrial blood supply and cardiac conduction. The bradyarrhythmic effect was more pronounced in injection of a radiopaque agent in the right artery than in the left one. 相似文献
6.
Currents entering through single channels with conductivity 10 pS were produced on the membrane of an isolated neuron of the fresh-water molluskPlanorbarius corneus in the presence of suberyldicholine (5 µM) by the patch-clamp technique (cell-attached configuration). The times of stay of the channels in the open and closed states, as well as the durations of pulse bursts and clusters, were measured. The distributions of the time intervals obtained experimentally were approximated for open states by one exponential function: to=27±3 msec (n=21), and for closed states by a sum of three exponentials: tc1=9.5±1.0 msec (n=21); tc2=171±33 msec (n=19); tc3=5.2±1.0 sec (n=21). The burst durations are characterized by the presence of two exponential functions in the distribution: tb2=20±14 msec (n=10), tb2=203±23 msec (n=10), and the clusters by three exponential functions: tk1=33±11 msec (n=8), tk2=274±84 msec (n=8), and tk3=1.5±0.5 sec (n=9). Thus, for work of a chemoactivated channel associated with nicotinic-type cholinoreceptors in a mollusk neuron we can suggest a kinetic scheme with one open and three nonconducting states: C O D1A2 D2A2. The two "long-lived" closed states of the channel may be associated with desensitization of the integral response of the neurons to the application of suberyldicholine. Values were obtained for the rate constants of these proposed reactions. It is suggested that this model may be useful in analyzing the action of cholinomimetics and blockers on the molluskan neuronal membrane.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 588–595, September–October, 1991. 相似文献
7.
8.
The results of the morphometric study of Plantago lanceolata L. grown, in nursery, from seeds of the first and second post-accident reproductions within the thirty-kilometer zone around the crippled Chernobyl reactor show no relationship between the alterations in some quantitative indices and the variability of gamma-radiation background in places where maternal plants grow. 相似文献
9.
Eukaryotic polypeptide chain release factor eRF3 is an eRF1- and ribosome-dependent guanosine triphosphatase. 总被引:11,自引:1,他引:10
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L Frolova X Le Goff G Zhouravleva E Davydova M Philippe L Kisselev 《RNA (New York, N.Y.)》1996,2(4):334-341
Termination of translation in eukaryotes is governed by two polypeptide chain release factors, eRF1 and eRF3 on the ribosome. eRF1 promotes stop-codon-dependent hydrolysis of peptidyl-tRNA, and eRF3 interacts with eRF1 and stimulates eRF1 activity in the presence of GTP. Here, we have demonstrated that eRF3 is a GTP-binding protein endowed with a negligible, if any, intrinsic GTPase activity that is profoundly stimulated by the joint action of eRF1 and the ribosome. Separately, neither eRF1 nor the ribosome display this effect. Thus, eRF3 functions as a GTPase in the quaternary complex with ribosome, eRF1, and GTP. From the in vitro uncoupling of the peptidyl-tRNA and GTP hydrolyses achieved in this work, we conclude that in ribosomes both hydrolytic reactions are mediated by the formation of the ternary eRF1-eRF3-GTP complex. eRF1 and the ribosome form a composite GTPase-activating protein (GAP) as described for other G proteins. A dual role for the revealed GTPase complex is proposed: in " GTP state," it controls the positioning of eRF1 toward stop codon and peptidyl-tRNA, whereas in "GDP state," it promotes release of eRFs from the ribosome. The initiation, elongation, and termination steps of protein synthesis seem to be similar with respect to GTPase cycles. 相似文献
10.