[Contents of extracellular DNA in blood of irradiated rats]. / Soderzhanie vnekletochnoi DNK v krovi obluchennykh krys.

Intact rat plasma contains high-molecular DNA which moves as a single fraction in 0.5% agarose electrophoresis. As early as 2-5 hours after gamma-irradiation in a dose of 1-100 Gy there appears low-molecular DNA (about 180 nucleotide pairs), the amount of which directly correlates with the irradiation dose 5 hours after the exposure. Blot-hybridization showed that low-molecular DNA has no common nucleotide sequences with high-molecular DNA, though has sites similar to genome repeat sequences.

[Detection of the determinants of tetracycline A, B and C resistance in Shigella and Salmonella using DNA probes]. / Opredelenie determinant resistentnosti k tetratsiklinu klassov A, B i C u shigell i sal'monell s pomoshch'iu DNK-zondov.

Genetic determinants of tetracycline resistance of classes A, B and C were detected with DNA probes labeled with radioactive phosphorus (32P) in Shigella (44 strains) and Salmonella (50 strains). It was shown that in the Shigella strains the frequency of the Tet A gene amounted to 66 per cent, the frequency of the Tet B gene was equal to 84 per cent, the frequency of their combination was equal to 50 per cent and the frequency of the Tet C gene was nil. In the Salmonella strains the frequency of the Tet A, Tet B and Tet C genes was equal to 0.100 and 20 per cent, respectively, and that of their combination amounted to 20%. Possible use of the DNA probes in epidemiological analysis of outbreaks of Shigella and Salmonella infections is suggested.

[Information value of the indices of the nonspecific resistance of the body]. / Ob informativnosti nekotorykh pokazatelei nespetsificheskoi rezistentnosti organizma.

A number of nonspecific resistance characteristics in mice, such as the total number of peritoneal exudate cells, the percentage and absolute number of macrophages, their cytochemical activity in the spontaneous tetrazolium test and cytochemical capacity, have been studied by comparison with the resistance of the animals to tularemia infection induced by Francisella tularensis, Gaiskii's vaccinal strain 15. Of these characteristics, the cytochemical capacity of peritoneal exudate macrophages, i.e. the total cytochemical activity of macrophages contained in a unit of volume, has been the most informative as regards the level of nonspecific resistance to this infection. Other characteristics under study cannot serve as criteria for the evaluation of the nonspecific resistance of the body to F. tularensis.

[Evaluation of the functional activity of peritoneal macrophages using the tetrazolium test]. / Otsenka funktsional'noi aktivnosti peritoneal'nykh makrofagov s pomoshch'iu tetrazolievogo testa.

The redox activity of peritoneal macrophages has been evaluated in the modified NBT test using tetranitro blue tetrazolium. This method permits the calculation of the total amount of peritoneal macrophages and the determination of their glass adherence per cent and their cytochemical activity value. The advantages of this method over the study of the phagocytic activity by means of phage T2 is shown.

[Migration of the ampicillin transposon in enteropathogenic Escherichia]. / Migratsiia ampitsillinovogo transpozona u énteropatogennykh ésherikhii.

Migration of Tn 1 from plasmid RP4 into the chromosome of enteropathogenic Escherichia (EPE) of serogroups O124 and O111 was studied. E. coli K 12 LC 411 (RP4) was used as the donor. It was shown that the transposition rate markedly differed depending on the period of ;the cell isolation from Tn 1 in the chromosome, i. e. during conjugation or after several subcultures of the transconjugants from the autonomic plasmid onto the selective media. During the conjugation process the migration rate of Tn 1 was equal to 0.5 and 0.8 per cell acquiring the plasmid. The transposition rate in the EPE carrying the R factor for a long period of time was 2.4 . 10(-2) and 1.4 . 10(-2) respectively for each serogroup. The above differences in the migration rate of Tn 1 were not concerned with changes in the environment.

[Phagocytosis of enteropathogenic escherichiae of serogroup 0124:K72(B17)]. / Fagotsitoz énteropatogennykh ésherikhii serogruppy 0124:K72(B17)

Experiments with phagocytosis of E. coli O124 in the macrophage tissue culture demonstrated a different phagocytability of the S- and R-forms of these bacteria determined by their concentration in the medium. The ingestive and digestive capacity depended on the bacterial virulence. Since R-forms of E. coli O124 lost their virulent properties and macrophage resistance it can be considered that the structure of their lipopolysaccharides served as the chemical substrate responsible for their different phagocytability.