[Increase of general toxic effects and decrease of hepatocarcinogenic effects of diethylnitrosamine administered to mice in conjunction with isopropanol].

It is considered that diethylnitrosamine (DENA) is metabolized mostly in the liver with producing highly reactive compounds alkylating cellular macromolecules and causing toxic and carcinogenic effects. However, competitive inhibition of cytochrome P450 2E1, which metabolizes DENA, by its other substrate, isopropanol, does not weaken, but enhances the toxicity of DENA effect on mice and reduces the number of preneoplastic nodules and liver tumors induced by it. In short-term tests for mutagenicity (in the Ames test and the SOS-hromotest) DENA causes moderate damage of DNA that reduces liver microsomal enzymes, that metabolize nitrosamines. The obtained data indicate the predominant role of the initial compound as compared to its metabolites in toxic, and probably hepatocarcinogenic, effects on DNA in mice.

[Evaluation of cytotocicity and efficiency of antioxidant protection of hydrophilic derivatives of 2,4,6-trialkylphenols in Escherichia coli cells].

The effects of five new derivatives of 2,6-dialkyl-4-propylphenole containing in para-radical different ionogenic groups (-SO3Na, -S-SO3Na, -S-(NH2)2Cl) in the presence and in the absence of hydrogen peroxide on the survival of E. coli AB1157 cells and its isogenic strain defective in repair enzyme genes were studied. Cell survival treated with hydrogen peroxide was remarkably increased in the presence of (3-(3,5-dimethyl-4-hydroxyphenyl)propyl)-1-sulphonate of sodium (Cl). Replacement of methyl ortho-radicals in the structure of Cl for tret-buthyl or cyclohexyl groups led to a decrease of the compounds ability to protect the cells from exogenic hydrogen peroxide. Between derivatives of 2,6-di-tret-buthylphenol the compound with thiosulphonate group demonstrated properties comparable with those for its sulphonate analog, then a chloride of isotiurone at concentration 3 mM completely suppressed the growth of cells in presence and in the absence of H2O2. Compound Cl may be considered as most perspective for detail analysis as antioxidant.

[The dependence of cytotoxicity and antioxidant activity of ammonii derivatives of alkylphenols upon percularities of their structure].

Effect of seven structurally similar N, N-dimethyl-(4-hydroxyaryl)alkylammonium chlorides in the presence and in the absence of hydrogen peroxide on the survival of E. coli cells AB1157 and its isogenic strain BH910 defective in genes of repair enzymes has been analyzed. Among the studied compounds only chloride of N,N-dimethyl-(3,5-dimethyl-4-hydroxybenzyl)ammonium (C1) has no cytotoxic properties and increases the survive of the cells of both strains in the presence of H2O2 better than trolox (water soluble analog of alpha-tocopherol). C1 analogs: 3-methyl-(5-di(tert-butyl)-4-hydroxybenzyl) and 3-(3,5-di(tert-butyl)-4-hydroxyphenyl)propyl)amines derivatives effectively protected from H2O2 only mutant cells BH910. Among the structural analogs of C1 cytotoxicity increases at substitution of methyl groups in aromatic cycle by tert-butyl and cyclohexyl groups. Only C1 among the seven new compounds is the most promising antioxidant for the subsequent more detailed analysis.

[Antioxidative activity of thiophane [bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl)sulfide].

The antioxidant activity, mutagenicity, and genotoxicity of bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl)sulfide (thiophane) were studied using bacterial tests. The results of both an Ames test and SOS chromotest, as well as those studying the survival of E. coli cells deficient in enzymes responsible for the repair of DNA oxidative damage, testify to the fact that thiophane is not mutagenic and genotoxic, and it protects Salmonella typhimurium cells better than the well-known antioxidant trolox.

[New promising antioxidants based on 2,6-dimethylphenol].

Three new sulfur-containing derivatives of 2,6-dimethylphenol were synthesized. Their antioxidative activity, mutagenicity, and genotoxicity were examined by bacterial tests and by calculating the dominant lethal mutations in murine embryonic cells. It was shown that all the compounds synthesized have a marked antioxidative effect and no genotoxic or mutagenic properties. One of the antioxidants, 4-(3-dodecylthiopropyl)-2,6-dimethylphenol, increases the survival of cells of both the wild-type Escherichia coli strain and bacterial strains defective in the genes of repair enzymes and has a more distinct antioxidative effect than the classic antioxidants alpha-tocopherol and trolox, increasing the survival of cells devoid of repair enzymes.

[Extracellular chitinase production by wild-type B-10 and mutant M-1 strains of Serratia marcescens]. / Obrazovanie vnekletochnykh khitinaz prirodnym (B-10) i mutantnym (M-1) shtammami Serratia marcescens.

Molecular weights of extracellular chitinases from wild-type B-10 (62, 54, 43, 38, and 21 kDa) and mutant M-1 strains of Serratia marcescens (62, 52, 43, 38, and 21 kDa) were estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the absence of chitin inductors, chitinolytic enzymes were not found in the culture liquid of B-10, while M-10 cells produced the chitinase complex (to 470 pU/cell). Crystalline chitin insignificantly stimulated the synthesis of chitinases with molecular weights of 62, 54, and 21 kDa by B-10 (up to 20 pU/cell), but caused overproduction of all chitinases by the mutant strain (up to 2600 pU/cell). Colloidal chitin induced the production of chitinases by cells of both strains. Two peaks of chitinolytic activity were observed during cultivation of strains B-10 (350 and 450 pU/cell) and M-1 (2200 and 2400 pU/cell). The first peak of cell productivity was associated with biosynthesis of the chitinase complex. The second peak was related to the production of enzymes with molecular weights of 54, 43, 38, and 21 kDa (B-10) or 43, 38, and 21 kDa (M-1).

[Study of the DNA primary structure effect on induction of mutations by alkylating agents]. / Issledovanie vliianiia osobennostei pervichnoi struktury DNK na vozniknovenie mutatsii, indutsirovannykh alkiliruuiushchimi agentami.

Analysis and comparison of mutation spectra is one of the major tasks of molecular biology, since mutation spectra often reveal important properties of various mutagens and proteins involved in the repair/replication systems. Mutability is known to vary significantly along the nucleotide sequence. Mutations are abundant at certain positions (mutation hotspots). In this work, we applied regression analysis based on the basic logic patterns to understand the role of the nucleotide sequence context in mutation induction. The spectra of mutations induced by various alkylating agents were studied. The nucleotide bases at positions -2, -1, +1 and +2 were shown to have the most significant effect in G:C-->A:T replacements.

[Isolation and properties of extracellular lipase of native (B-10) and mutant (M-1) Serratia marcescens strains]. / Vydelenie i svoistva preparatov vnekletochnykh lipaz prirodnogo (B-10) i mutantnogo (M-1) shtammov Serratia marcescens.

The cultivation conditions of wild-type strain V-10 and mutant strain M-1 (overproducer of endonuclease and chitinase) of Serratia marcescens optimal for extracellular lipase biosynthesis were determined. The strain V-10 displayed the maximal lipase yield (840 AU/ml) after 10-12 h of cultivation; the strain M-1 (33 AU/ml), after 25-30 h. The data showed that extracellular lipases from V-10 and M-1 can be precipitated in a weakly acid medium (pH 5.0 and 4.5, respectively). This property was used to obtain partially purified lipase preparations. The effect of the ionic composition of the reaction mixture on the activities of these enzymatic preparations was studied. Both preparations displayed highest activities in weakly alkaline media (pH 8.0); however, the wild-type strain lipase displayed a higher thermal stability and stability at alkaline pH compared with M-1 lipase. Both lipases were activated by various anionic and nonionic surfactants and inactive in the presence of cetyltrimethylammonium bromide.

[Determination of the genotoxicity of fullerene C60 and fullerol using the method of somatic mosaics on cells of Drosophila melanogaster wing and SOS-chromotest]. / Opredelenie genotoksichnosti fullerena C60 i fullerola metodom somaticheskikh mozaikov na kletkakh kryla Drosophila melanogaster i v SOS-khromotest.

Genotoxicity of fullerene C60 was been determined in a prokaryotic in vitro test and in an eukaryotic in vivo system. The SOS chromotest of fullerene C60 in the Escherichia coli strain PQ37 revealed no genotoxicity either with or without activation of the rat liver homogenate. To perform the somatic mutation and recombination genotoxicity test (SMART) on somatic wing cells, Drosophila melanogaster larvae were grown on a standard medium with or without fullerene dope. No statistically significant differences were observed at the same fullerene concentrations in the SOS chromotest (0.45 micrograms/ml). Only at the highest possible fullerene concentration of 2.24 micrograms per 1 ml medium, a slight genotoxic effect was observed in wing cells. Fullerol demonstrates no mutagenic effect at a concentration of 2.46 mg/ml.

[Molecular mechanisms of the initiation of complete and mosaic mutations]. / Molekuliarnye mekhanizmy vozniknoveniia polnykh i mozaichnykh mutatsii.

To study the molecular basis of the origin of complete and mosaic mutants, pBR322 plasmid with one- or two-stranded DNA damage was constructed by limited chemical modification of the plasmid DNA. Damage of one strand of DNA resulted in induction of mosaic mutants. Data were obtained indicating that complete mutations arise as a result of damage of two strands in the region of the mutagenized gene.

[Effect of adenine, adenosine and adenylic nucleotides on the mutagenic action of hydroxylamine]. / Vliianie adenina, adenozina i adenilovykh nukleotidov na mutagennoe deistvie gidroksilamina

The effect of some adenyl precursors of DNA synthesis on the mutagenic activity of hydroxylamine (HA) is studied. It is shown that the addition of adenine to a suspension of Escherichia coli B cells increases the yield of mutants by more than two times as compared with HA alone. The effects of adenosine, AMP and dAMP are somewhat different. It is suggested that the increase of the HA mutagenic effect produced by the addition of adenine may be due to: 1) the excess of the amount of adenylic precursors of DNA synthesis over guanilic ones, which promotes the erroneous base-pairing during the replication of the HA modified template; 2) the modification of adenylic precursors by HA into N6-oxy-dATP, and their incorporation into DNA. The mutagenic effect of N6-hydroxyadenosine, the product of the adenine modification by HA, in E. coli B pur- was studied. The experiments showed that N6-hyrdoxyadenosine induced about 1% of mutations, a relatively low lethal effect (the cell survival was 80%), and provided a high mutagenic action of this compound.

[Effect of adenine, adenosine and adenylic nucleotides on the mutagenic effect of hydroxylamine]. / Vliianie adenina, adenozina i adenilovykh nukleotidov na mutagennoe deistvie gidroksilamina

The effect of some adenyl precursors of DNA synthesis on the mutagenic activity of hydroxylamine (HA) is studied. It is shown that the addition of adenine to a suspension of Escherichia coli B cells increases the yield of mutants by more than two times as compared with HA alone. The effects of adenosine, AMP and dAMP are somewhat different. It is suggested that the increase of the HA mutagenic effect produced by the addition of adenine may be due to: 1) the excess of the amount of adenylic precursors of DNA synthesis over guanilic ones, which promotes the erroneous base-pairing during the replication of the HA modified template; 2) the modification of adenylic precursors by HA into N6-oxy-dATP, and their incorporation into DNA. The mutagenic effect of N6-hydroxyadenosine, the product of the adenine modification by HA, in E. coli B pur- was studied. The experiments showed that N6-hydroxyadenosine induced about 1% of mutations, a relatively low lethal effect (the cell survival was 80%), and provided a high mutagenic action of this compound.

[The influence of adenine, adenosine and adenylic nucleotides on the mutagenic action of hydroxylamine]. / Vliianie adenia, adenozina i adenilovkh nukleotidov na mutagennoe deistvie gidroksilamina

The effect of some adenyl precurosors of DNA synthesis on the mutagenic activity oh hydroxylamine (HA) is studied. It is shown that the addition of adenine to a suspension of Escherichia coli Bcells increases the yield of mutants by more than two times as compared with HA alone. The effects of adenosine, AMP and dAMP are somewhat different. It is suggested that the increase of the HAmutagenic effect produced by the addition of adenine may be due to:1) the excess of the amount of adenylic precursors of DNA synthesis over guanilic ones, which promotes the erroneous base-pairing during the replication of the HA modified template; 2) the modification of adenylic precursors by HA into N6-oxy-dATP, and their incorporation into DNA. The mutagenic effect of N6-hydroxyadenosine, the product of the adenine modification by HA, in E. coli Bpur- was studied. The experiments showed that N6-hydroxyadenosine induced about 1% of mutations, a relatively low lethal effect (the cell survival was 80%), and provided a high mutagenic action of this compound.