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Biomedical subjects

V S Levashev

Publications and source records attributed to V S Levashev.

At least 19 recordsLinked to original sources
PubMed1987

[Role of cyclic 3',5'-adenosine monophosphate in the development of Salmonella infection in an experiment].

The changes in cAMP levels in spleen macrophages of mice infected with low-virulent and virulent Salmonella strains and the effect of propranolol on Salmonella reproduction in the spleen, and the outcome of Salmonella-induced infection have been studied. A persistent increase in cAMP levels in spleen macrophages during Salmonella infection caused by virulent Salmonella strains has been demonstrated. Low-virulent Salmonella strains failed to cause the elevation of cAMP levels in spleen macrophages. Propranolol injection to mice prevented intensive Salmonella reproduction in the spleen and diminished the animal mortality rate.

Animals↗
PubMed1986

[Sensitivity of the intestinal microflora of patients to antimicrobial preparations studied in order to conduct rational antibiotic treatment].

The oral administration of amikacin, ampiox, nystatin to CBA mice and the external treatment of the animals with 1% chlorhexidine solution makes it possible to create the germ-free state in the animals which must be then kept in a sterile box. If such animals receive the decantate of the patient's feces, introduced in a single administration, the microflora, which is subsequently formed in the intestine of the recipient animals, is identical to the donor's microflora. This permits the rapid and accurate determination of the sensitivity of the patient's intestinal microflora to different antimicrobial preparations and their combinations. The antibacterial preparations, effectively suppressing the patient's intestinal anaerobic opportunistic microflora in the intestine of the recipient mice, produce, if subsequently prescribed for treatment, a pronounced corrective effect on such microflora in the patient's intestine.

Adolescent↗
PubMed1985

[Role of peritoneal macrophages in the development of an experimental Salmonella infection].

The effect produced on the course of Salmonella infection in mice by the removal of peritoneal macrophages with agarose has been studied. Peritoneal macrophages have been shown to control the multiplication of faintly virulent and virulent S. typhimurium strains in the spleen of mice. In immune mice the elimination of the virulent strain of the causative agent of superinfection may occur without the control of peritoneal macrophages.

Animals↗
PubMed1984

[Transfer of kanamycin resistance among familial strains of Enterobacteriaceae isolated from a chronic bacterial carrier of Salmonella schottmuelleri].

Escherichia coli, Enterobacter aerogenes and S. schottmuelleri were isolated from the large intestine of a bacteriocarrier. E. coli and E. aerogenes strains proved to be resistant to a number of antibiotics. Plasmids were detected in DNA preparations obtained from E. coli strains. After the hybridization of these E. coli strains with E. coli C600 5K and S. schottmuelleri at 28 degrees C the transfer of resistance to kanamycin was found to occur. From some of the transconjugates thus obtained resistance to kanamycin was transferred to E. aerogenes. This resistance was found to be controlled by the plasmid with a molecular weight exceeding 2 Md. The fact that S. schottmuelleri in the carrier's body retained their sensitivity to antibiotics can be explained by the absence of the transfer of plasmid Kmr at a temperature exceeding 28 degrees C and by the existence of the infective agent in an ecological niche other than that of E. coli.

Carrier State↗
PubMed1983

[Bacteriostatic action of penicillin on Escherichia coli K12].

Penicillin has been found to have a bacteriostatic effect on logarithmically growing E. coli K-12 cells. The capacity for mitosis is restored due to the aggregation of cells. The bacteriostatic effect of this antibiotic is not linked with morphological changes in the cells.

Cell Division↗
PubMed1983

[Bacteriophage P22 H5 transfection and infection of plasmid Salmonella strains].

The results of the Ca2+-dependent transfection of the DNA of bacteriophage P22 H5 to constructed Salmonella typhimurium F'- and R+-strains LT2 WT-R and SA118 demonstrated that in these salmonellae the effectiveness of transfection depended on the specificity of the interrelation of plasmids with host strains. Plasmids RA1, R538-1 and RP1 stimulated the transfection of S. typhimurium strain LT2 WT-R, but suppressed the transfection ability of S. typhimurium strain SA118. At the same time the expression of the function of plasmids R446b and R64-11 did not depend on the host strain, as the former did not affect and the latter suppressed the release of transfectants in both Salmonella strains. The presence of plasmids R124, RA1, R64-11 and R724 in strain SA118, heat-sensitive in respect to the synthesis of cell-wall lipopolysaccharide, not only led to a decrease in the effectiveness of transfection; the effectiveness of the inoculation of bacteriophage P22 H5 was also suppressed 10(4) times in the presence of plasmid R124 and at least 10(10) times in the presence of 3 other plasmids. The development of resistance to S-specific bacteriophage P22 H5 was not linked with disturbances in the adsorption of this bacteriophage. Besides, the addition of CaCl2 into the medium completely removed the limitation of infection with bacteriophage P22 H5, determined by plasmid R124.

Calcium↗
PubMed1979

[Transforming activity of R- and Lac-plasmids of clinical strains of Gram-negative bacteria].

The isolated plasmid DNA of clinical strains of Gram-negative bacteria were shown to have transforming activity when E. coli strain 0600 and S. typhimurium strain LT-2 were used as recipients. The frequency of transformation depended on the recipient strain and the character of the plasmids. The presence of deletion mutants was revealed among the transformants. Such mutants occurred with varying frequency, most often in S. typhimurium strain LT-20; the reason for this phenomenon is at present under discussion. The transformation of plasmids controlling lactose splitting and their conjugation transfer into recipient S. typhimurium strain LT-2 is possible only under condition of using recipient (R+). The possibility of the formation of the cointegrate (R and lac plasmids) in recipient S. typhimurium strain LT-2 is discussed.

DNA, Bacterial↗
PubMed1978

[Transforming activity of plasmid R6K DNA on Serratia marcescens strain 20-10. The behavior of the plasmid in the transformants].

The authors described transformation of S. marcescens, strain 20-10, of the isolated R6K plasmide DNA. As demonstrated by centrifugation in cesium chloride gradient and electrophoresis in agarose, the plasmide was present in the transformants in the form identical to R6K in E. coli K12. Analysis of the transforming activity of R6K plasmide from Serratia and E. coli K12 strains with a complete and defective restriction system showed S. marsescens, strain 20-10, to possess specific system of restriction and modification. In studying beta-lactamase activity and Serratia and E. coli strains ampicillin and streptomycin resistance revealed differences in the phenotypical expression of the plasmide signs in the heterologous and homologous host.

DNA, Bacterial↗
PubMed1977

[Entobacterial transformation by R6K plasmid DNA].

Preparations of DNA of R6K plasmide obtained by various methods on the basis of the "clarified" lysate: by gel filtration on sepharose 4B, centrifugation in cesium chloride with ethidium bromide gradient, were analysed in the E. coli C600. S. typhimurium AG37, Pr. vulgaris 4636, S. marcescens 20-10 transformation. The frequency of transformation proved to depend on the extent of DNA purification. Factors influencing the E. coli C600 competence and the transformation efficacy (the phase of the culture growth, the concentration of cells in the mixture with DNA, theCaCl2 concentration, the time of the cell incubation at 42 degrees C) were studied. Kinetics of the phenotypical expression of the plasmide signs of ampicillin and streptomycin resistance in transformation was also studied in this work.

Calcium Chloride↗
PubMed1977

[Mapping the fucidin resistance marker in S. typhimurium and a study of the properties of its transductants].

The fusidic resistance marker in S. typhimurium is contransduced in 95% of cases by means of P 22 phage with the streptomycin resistance marker. The transfer of the fusidic acid resistance gene doesn't lead to any significant alterations in the tranductants' properties (morphology, antigenic structure, growth rate, biochemical activity, sensitivity to other antibiotics). The fusidic acid resistant mutants and transductants studied displayed a significantly decreased virulence to albino mice. The rate of this decrease, however, doesn't correspond to the degree of transductants' resistance. Virulent variants are also possible.

Animals↗
PubMed1977

[Morphologic mutant of Escherichia coli K12 having disorders in morphology, division and cell wall biosynthesis].

A study was made of the properties of a spherical mutant obtained from the E. coli K12 HfrC strain under the effect of N-nitroso-N-methyl-urea. The growth of the mutant of full value media was characterized by a marked reduction of the cell division at the rest phase, but exponential growth phase failed to differ from the growth of the parental strain. Electron microscopic study of surface structures of the mutant cells which grew under physiological conditions permitted to distinguish two types: the first type had a typical structure of the cell wall characteristic of Gram negative microbes; the second type was framed by a bicontour membrane without any distinct structure. The presence of these two types of cells was also confirmed by their different sensitivity to the ionic detergents. On the basis of chemical analysis of peptidoglycan of the cell wall (which was markedly decreased in amount in the mutant cells), and also of the unsually high accumlation of the UDP-precursors of peptidoglycan under conditions of penicillin action it is supposed that normal regulation of metabolism of the cell walls was deranged. Mutation designated by 11rA symbol was plotted by phase PI transduction alongside of strA gene.

Cell Division↗
PubMed1977

[Characteristics of the deletion mutant of plasmid R6K].

Deletion plasmide R6Kdelta with the mol wt of 17.2.10(6) dalton isolated from the E. coli chi 925 (R6K) is described. This plasmide expresses no resistance to streptomycin, is replicated in the E. coli K12 under relaxed control and is resistant to the treatment with the eliminating agents. Analysis of plasmide DNA with the aid of electrophoresis in agarose gel demonstrated that R6K delta has one site attacked by restriction endonucleases Eco. RI and Bam HI. These data were confirmed by the determination of the transforming activity of the corresponding DNA restrictors. It is supposed that the isolated plasmide was identical with plasmide RSF1040. A possibility of using R6K delta as a genetic vector for obtaining recombination DNA molecules in vitro is discussed.

DNA Restriction Enzymes↗