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排序方式: 共有1324条查询结果,搜索用时 15 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.
Nina I. Smirnova Galina V. Chekhovskaya Natalia I. Davidova Ludmila F. Livanova Galina A. Yeroshenko 《FEMS microbiology letters》1996,136(2):175-180
Abstract The presence of a temperate phage was demonstrated in a strain of Vibrio cholerae O139 isolated from a patient. Spontaneous variants with translucent colonies had lost this phage. The loss of the phage was associated with increased hydrophobicity, indicating the loss of the capsule. These clones were sensitive to serum bactericidal activity, showed decreased expression of such presumed virulence factors as proteases, motility and mannose-sensitive pili. Furthermore, excision of the phage made the strain dependent on purines for growth. 相似文献
4.
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
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.
Total and polysome-bound ribosomes and the uptake and incorporation of3H-uridine and14C-leucine were examined in dividing microspores and in pollen grains isolated from anthers of 6 different developmental stages. Direct evidence was obtained that the formation of cytoplasm of the vegetative cell following microspore division is related to a rapid activation of RNA and protein synthesis and of ribosomes in differentiating pollen. Total ribosomes associated with gametophytic programme rose about 10times and the process of differentiation was accompanied by a rapid increase in uptake capacity of pollen grains for both uridine and leucine. Pollen development after cytoplasm synthesis and starch deposition continued by pollen maturation, which was characterized by a decline in RNA synthesis, dissociation of polysomes and by a further rise of transport activity of pollen grain wall for exogenous substrates, indicating probable pollen adaptation for utilization of metabolites from the degenerating tapetal cytoplasm. 相似文献
8.
9.
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
10.
Anthers of diploid genotypes of Solanum tuberosum capable of androgenesis were cultured on different media to examine the effect on induction of pollen embryogenesis of 2,4-d and lactose. Anthers cultured in callogenic medium with 2,4-d and sucrose produced pollen derived embryoids only exceptionally. When sucrose was replaced by lactose the frequency of embryogenesis was as high or higher than in embryogenic auxin-free medium. Substitution of lactose for sucrose in the embryogenic medium had no effect. Supplementing the embryogenic medium with 2,4-d strongly reduced the frequency of pollen embryoids in the presence of sucrose but not with lactose.Abbreviations 2,4-d
2,4-dichlorophenoxyacetic acid 相似文献