Asynchronous DNA replication detected by fluorescence in situ hybridisation as a possible indicator of genetic damage in human lymphocytes.

The present study aimed to correlate the DNA replication timing of different genes with genetic damage and frequency of cancer. Using a fluorescence in situ hybridisation (FISH) approach, the replication timing of three loci, two human genes possessing transcriptional capability and involved in both the cellular response to genetic damage and cancer development (TP53 and RB1) and the non-coding locus D22S163, was evaluated. The data obtained show that normal human lymphocytes exposed in vitro to known DNA-damaging agents, e.

[Mathematical analysis of genetic effects of low doses of ionizing radiation].

The comparative study of effects of low doses of radiation on peripheral blood lymphocytes of persons occupationally exposed to radiation and non-exposed ones was carried out. The main attention was paid to radio-adaptive response forming under consistent exposure to low (0.05 Gy) and damaging (2 Gy) doses of gamma-irradiation.

[Genetic analysis of recessive lethal mutations induced by the influenza virus in the X chromosome of Drosophila melanogaster].

Mutagenic potential of the influenza virus was evaluated. Based on its capacity of inducing recessive lethal mutations in the X chromosome of Drosophila melanogaster, the influenza virus can be classified as a moderate-activity mutagen. Its mutagenicity does not depend on ability to reproduce in the cell system.

[Frequency of chromosome aberrations in residents of the Semipalatinsk Oblast].

Cytogenetic analysis of the population of the Beskaragai district of the Semipalatinsk oblast adjacent to the territory of the nuclear test site was conducted by means of an ecological genetic questionnaire and cytogenetic examination of metaphase chromosomes. An increase in the total mutation level in the region was observed. The frequency of chromosome aberrations among the population of the Beskaragai district (3.

No evidence for radiation-induced clastogenic factors after in vitro or in vivo exposure of human blood.

Experiments were performed with human plasma irradiated in vitro or in vivo in order to evaluate the extent to which clastogenic factors might disturb the adaptive response to DNA-damaging factors currently studied in our laboratory. The studies were carried out with plasma isolated from whole blood given 4 Gy of X-rays in vitro and with plasma from people receiving local radiotherapy at a total dose of about 60 Gy gamma rays. Addition of irradiated plasma to culture medium did not result in a statistically significant increase in structural aberrations in chromosomes of non-irradiated normal blood.

[Interferon activates DNA repair genes in UV-irradiated human cells].

Unscheduled DNA synthesis in human fibroblasts pretreated with natural and recombinant interferons was studied by scintillated radiometry. UDS was increased in fibroblasts pretreated 7 days before UV-irradiation. Newly synthesized proteins induced in cells after interferon treatment were compared with heat shock proteins.

[Mechanism of the antimutagenic effect of interferon in human fibroblasts based on induced protein analysis].

Proteins induced in human fibroblasts after treatment of some antimutagens (interferon, p-aminobenzoic acid, heating and vaccinia virus infection) were identified by means of polyacrylamide gel electrophoresis (10-15%) followed by fluorography of the gel. Influenza virus proteins (A/WSN/33) were used as markers to determine the molecular weights of the new proteins. The results obtained suggest that interferon, p-aminobenzoic acid, heating and vaccinia virus infection induced proteins with mol.

[Infection of repair-deficient human cells by the vaccinia virus decreases the formation of gamma-induced DNA breaks].

The alkaline elution method was used to study DNA breaks induced by the different mutagens in human cells. Normal fibroblasts and fibroblasts from patients with homocystinuria, deficient in gamma-type repair were shown to be resistant to gamma-radiation after the vaccinia virus infection. In both cell lines there was a decrease in the number of the mutagen-induced DNA breaks.

[Optimization of protective properties of interferons in human cells exposed to mutagens estimated by the DNA repair activity].

Protective properties of human interferons against physical and chemical mutagens have been described earlier. This work was aimed at detecting an optimum of protective action of interferons in human fibroblasts using two criteria: the number of single-strand DNA breaks formed and the index of DNA repair synthesis. The protective ability of interferon was shown to be expressed starting after 4 h of cells' pretreatment and proceeding through 40 h in experiments with N-methyl-N-nitro-N-nitrosoquanidin.

[Effect of nitrosourea in small doses on the frequency of mutation in Salmonella typhimurium].

The effect of N-nitroso-N-methylurea (NMU), N-nitroso-N,N'-dimethylurea (NDMU) and N-nitroso-N-ethylurea (NEU) at doses less than 100 mkg/ml on mutability of Salmonella typhimurium strains of Ames' system (G-46, TA-1950, TA-1535, TA-100, TA-1538) has been studied. NMU and NEU at doses of 5-10 mkg/ml have been found to increase the survival and decrease the number of reversions from auxotrophity in histidine to prototrophity. The effect of given doses of NMU and NEU on bacteria repair activity has been shown.

[Effect of nonmutagenic doses of 1,4-bis-diazoacetylbutane on Streptomyces griseus].

Streptomyces griseus 15 was subjected to the action of 1,4-bis-diazoacetyl butane (DAB) taken at concentrations of 10 to 50,000 micrograms/ml. Small doses (10-100 micrograms/ml) of DAB had no mutagenic action and activated the cultural growth (the viability and the survival rate of spores increased on solid media, while the biomass yield rised in liquid media). Experiments were conducted using the method of orthogonal planning of a bifactorial experiment, and the role of the exposure time rised with a decrease in the mutagen concentration.

[Biologically active ribonucleoproteins of cells infected with fowl plague virus].

The results of studies of physico-chemical and biological properties of virus-specific ribonucleoproteins (RNP) in influenza infection are presented. Particular attention is given to the infectious properties of RNP. The earliest infectivity was found to be associated with RNP structures sedimenting from nuclear extract in a zone of 30-40S.