[Modification of the mutagenic effects of gamma radiation by heavy metal salts]. / Modifikatsiia mutagennykh éffektov gamma-izluchenii soliami tiazhelykh metallov.

The effect of K2Cr2O7 and (CH3COO)2Pb on the mutagenic activity of gamma rays was studied by a micronucleus test in mouse bone marrow polychromatocytes. Acute and chronic combined actions of the two factors were investigated. Chromium ions (VI) enhanced mutagenic effects of gamma rays in both acute and chronic experiments. In the acute experiments lead ions (II) below 15 mg/kg body weight decreased the number of gamma-ray-induced micronuclei, while higher doses increased it. Chronic combined action of lead ions (III) and gamma rays inhibited mutagenic activity of radiation.

[The micronucleus frequency in the somatic cells of murine rodents residing in a 30-kilometer area of the Chernobyl Atomic Electric Power Station]. / Chastota mikroiader v somaticheskikh kletkakh myshevidnykh gryzunov, prebyvavshikh v 30-kilometrovoi zone Chernobyl'skoi AES.

The chromosome aberration frequency in murine somatic cells was studied. Animals from natural populations as well as laboratory mice exposed within the ten-kilometers zone of the Chernobyl accident were examined. Increase in micronuclei rate in bone marrow cells, erythrocytes of peripheral blood and hepatocytes was found in animals exposed to more high background radiation. Under chronic exposure the pattern of effect dependence on dose rate was similar both in somatic and sex cells.

[The effect of phenol derivatives on the antimutagenic activity of dextran]. / Vliianie proizvodnykh fenola na antimutagennuiu aktivnost' dekstrana.

The effects of dextran + hydrazine or amino derivative of dibunol and of dextran + cystafos derivatives with different degree of modification of their molecules on the mutagenic activity of gamma irradiation were studied using the micronucleus test in polychromatophilic erythrocytes of the mouse bone marrow. The effects of these compounds on differentiation of the erythroid series has also been studied. The mutagenic activity of gamma irradiation was most markedly inhibited by the copolymer dextran and the amino derivative dibunol. The optimal structure of copolymers was 1 heterocyclic link per 3 non-oxidized links of dextran, while the increasing number of active links in the dextran molecule insignificantly enhanced its antimutagenic effect. The studied compounds effectively protected erythropoiesis.

[Antimutagenic activity of dextran gammaphos derivatives]. / Antimutagennaia aktivnost' dekstranovykh proizvodnykh gammafosa.

In experiments with V-79 Chinese hamster cell culture the influence of dextran gammaphos derivatives on the mutagenic effects of gamma-radiation was studied by the number of cells with micronuclei and fragmented nuclei. Products of interaction between gammaphos and dialdehyde dextran were shown to have a higher antimutagenic activity than gammaphos.

Role of the carbamoylation reaction in the biological activity of methyl nitrosourea.

Study of the mutagenic action of methyl nitrosourea (MNU) on the CHO-AT3-2 Chinese hamster cell at 2 regimes of cell treatment (a short-term regime and prolonged 1-h treatment) revealed that increase in the duration of treatment enhanced both cell lethality and clastogenic and mutagenic effects at the TK locus and did not influence the mutation frequency at the OUAr locus. On the basis of kinetic considerations it can be concluded that the base-pair substitution-type mutants (e.g., OUAr) appear as a result of DNA alkylation and the mutants at loci with a wide spectrum of registered mutants (the TK locus) are related to a greater extent to the carbamoylating activity of MNU. This conclusion is confirmed by measurements of the effects of sequential treatment with MNU (7 min) and KNCO (1 h). A synergistic increase in lethality, clastogenicity and mutagenicity at the TK locus was found in experiments with the combined treatment of cells with ethyl methanesulfonate (EMS) and KNCO. Besides, pretreatment of cells with potassium cyanate and subsequent exposure to MNU, EMS and benzopyrene (BP) produced synergistic effects in all the tests: lethality, clastogenicity and mutation frequency at the OUAr and TK loci. Posttreatment of cells with KNCO also led to a synergistic increase in the effects of MNU, EMS and BP treatment in several tests, but not in the OUAr locus. The possible mechanism and levels of interactions between alkylation and carbamoylation and the possibility that potassium cyanate causes supramolecular lesions are discussed.

[The antimutagenic activity of compounds of modified polyglucin]. / Antimutagennaia aktivnost' soedinenii modifitsirovannogo poligliukina.

The effect of modified polygluquin compounds on gamma-irradiated nuclei of V-79 Chinese hamster cells has been studied. Antimutagenic properties of the compounds are determined by aldehyde groups and oxidized chains.

[Potassium cyanate modification of the toxic and mutagenic effects of gamma radiation and benzo(a)pyrene]. / Modifikatsiia tsianatom kaliia toksicheskikh i mutagennykh éffektov gamma-izlucheniia i benzo(a)pirena.

In experiments with CHO-AT3-2 cell culture, a study was made of the effect of potassium cyanate (KNCO) on the effect of gamma radiation and benzo(a)pyrene (BP) by the following tests: cell viability, induction of cells with micronuclei and fragmented nuclei and mutations by thymidine kinase (TK) and Na+/K+-ATPase loci. Some tests have revealed the increase in the effect of gamma radiation and BP produced by potassium cyanate. It is suggested that the sensitizing effects are related to repair system inhibition and/or changes in the cell chromatin structure produced by KNCO.

[Specificity of mutagenic effect of N-nitroso-N-methylurea and relation between its mutagenic activity and carbamoylating properties]. / Spetsifichnost' mutagennogo deistviia N-nitrozo-N-metilmocheviny i sviaz' ee mutagennoi aktivnosti s karbamoiliruiushchimi svoistvami.

Significance of carbamoylation for mutagenic effects of N-nitroso-N-methyl-urea (NMU) on the CHO-AT3-2 cell line of Chinese hamster was studied. True point mutations occurred, due to alkylation. Carbamoylation combined with alkylation, or carbamoylation after alkylation induced the increase in other types of gene mutations as well as micro- and macroaberrations. These effects may be explained by the synergistic effect of alkylation and carbamoylation. Possible mechanisms and levels of interaction between alkylation and carbamoylation are discussed.

[Cypermethrin induction of micronuclei in mammalian somatic cells]. / Induktsiia tsipermetrinom mikroiader v somaticheskikh kletkakh mlekopitaiushchikh.

The genotoxic effects of the preparative cypermethrin form on the induction of micronuclei in cultured Chinese hamster V-79 cells and polychromatic erythrocytes of mouse bone marrow have been studied. The cypermethrin has induced micronuclei in cultured cells without metabolic activation in toxic concentrations, similar effects being observed in polychromatic erythrocytes after treatment with subtoxic concentrations.

[Mechanism of the antimutagenic action of dibunol]. / K voprosu o mekhanizme antimutagennogo deistviia dibunola.

In experiments with cultured V-79 Chinese hamster cells a study was made of the influence of dibunol on the level of gamma-radiation-induced micronuclei and sedimentation properties of cell nucleoids during ultracentrifugation in a neutral sucrose gradient. Protection of DNA molecule against the effects of both primary and secondary damages was found to be involved in the mechanism of the protective action of dibunol.

[Effect of alkylation and carbamoylation on the characteristics of genetic damage to mammalian somatic cells cultured in vitro]. / Vliianie alkilirovaniia i karbamoilirovaniia na kharakter geneticheskikh povrezhdenii v somaticheskikh kletkakh mlekopitaiushchikh, kul'tiviruemykh in vitro.

Genetic effects of alkylation alone and combined with carbamoylation were studied following treatment of CHO-AT3-2 Chinese hamster cell line with N-nitroso-N-methylurea for 7 and 60 min. Gene mutations at HGPRT and Na+/K+-ATPase loci, micronuclei, cells with fragmented nuclei and lethality caused by NMU were recorded. Prolonged exposure to the mutagen made these effects more pronounced, particularly the fragmented nuclei and cell death. The combined action of the two mechanisms, therefore, enhanced the mutagenic effects of alkylation and expanded the range of DNA lesions towards greater incidence of gross damage to chromosomes and chromatids.

[Phenthiuram induction of micronuclei in mammalian somatic cells]. / Induktsiia fentiuramom mikroiader v somaticheskikh kletkakh mlekopitaiushchikh.

Genotoxic effects of the preparative-form phenthiuram on the induction of micronuclei in cultured Chinese hamster V-79 cells and polychromatic erythrocytes of mouse bone marrow have been studied. The phenthiuram induced cytogenetic effects in cultured somatic cells without metabolic activation being only in toxic concentrations. Similar effects were observed in polychromatic erythrocytes after treatment with subtoxic concentrations.

[Inhibition by diphenols of the induction of micronuclei by gamma-radiation]. / Ingibirovanie difenolami induktsii mikroiader gamma-izlucheniem.

A study was made of the influence of diphenols (for instance, resorcinol, hydroquinone, and pyrocatechin) on gamma-radiation induction of micronuclei (1.5 Gy). The position of the diphenol molecule hydroxyl group (the isomeric effect) was shown to influence their antimutagenic activity. This antimutagenic effect of the diphenols is associated with their ability to produce semiquinone and quinone forms which are peculiar for the process of oxidation of pyrocatechin (ortho-) and hydroquinone (para-) as opposed to resorcinol (meta-position of the hydroxyl group).

[Relation of the antimutagenic activity of simple phenols to the number of hydroxyl groups]. / Zavisimost' antimutagennoi aktivnosti prostykh fenolov ot chisla gidroksil'nykh grupp.

The influence of mono-phenol, di-resorcinol and tri-pyrogallol hydroxyl groups of simple unsubstituted phenols on the mutagenic potentials of benzo(a)pyrene was studied in vivo (micronuclear test on bone marrow polychromatic erythrocytes) and in vitro (test of direct point mutations at V79/HGPRT system induced by metabolic activation by mouse liver microsomal enzymes). The phenols decreased the mutagenic activity of benzo(a)pyrene in in vivo tests, with pyrogallol being the most active, it followed by resorcinol and phenol. The mixtures of benzo(a) pyrene + pyrogallol and benzo(a)pyrene + resorcinol were significantly less mutagenic in in vitro tests than benzo(a)pyrene and benzo(a)pyrene + phenol.

Increased antimutagenic activity of simple substituted phenols mixed with the hindered phenolic antioxidant dibunol.

The micronucleus test using mouse bone-marrow polychromatic erythrocytes was used to study the extent to which benzo[a]pyrene (BP) mutagenicity was inhibited by mixtures of simple phenols (resorcinol and pyrogallol) with and without the complex hindered-phenol antioxidant dibunol (2,6-di-tert-butyl-4-methylphenol). Mixtures of these phenolic compounds inhibited BP mutagenicity more effectively than did the individual constituents. One can assume that the simple phenols regenerated in the presence of dibunol from the tissue-oxidized forms increase the formation of detoxified or less mutagenic metabolites of BP.

[Comparative study of the antimutagenic activity of diphenols]. / Sravnitel'noe izuchenie antimutagennoi aktivnosti difenolov.

Comparative study of the ability of three diphenols (pyrocathechol, resorcinol and hydroquinone) to inhibit the mutagenic activity of benzo(a)pyrene was carried out using the test for micronuclei account in mice polychromatic erythrocytes. It was suggested that the antimutagenic activity of diphenols used is mostly due to isomeric effect, i.e. the position of hydroxy-groups in molecules of diphenols.

[Experimental study of the antimutagenic properties of 5-methylresorcinol]. / Eksperimental'noe izuchenie antimutagennykh svoistv 5-metilrezotsina.

A study was made of the effect of 5-methylresorcinol (5-MR) on mutagenic activity of benzo(a)pyrene (BP) and of the action of gamma-radiation in in-vitro and in-vivo systems. The induction of direct gene mutations in Chinese hamster cells V-79 and micronuclei in mouse bone marrow reticulocytes was efficiently suppressed by 5-MR treatment. The antimutagenic activity of 5-MR can be explained by inhibition of free-radical processes.