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Effect of repair systems on the mutagenicity of N-nitrosodialkylamines in Salmonella typhimurium
JEMS Abstracts/Mutation Research 334 (1995) 385-427
405
When rotenone was added to HeLa $3, BHK21, and C3H10T1/2 cells, the chromosomes of their metaphases aggregated within 0.5 h after exposure, began to decondense forming interphase nuclei after 3 h, and then their endoreduplicated metaphases appeared. This suggests that rotenone induces metaphases of various cells to endoreduplicate.
these results, it is suggested that superoxide as well as hydrogen peroxide may be implicated in the mutagenicity of CSS.
46 Miyasaka, R., S. Hayashi, T. Kimura, S. Ueda and H. Nishioka, Bio-system Research Laboratory, Doshisha University, Karasuma-Imadegawa, Kamigyo-ku, Kyoto 602, Japan
Effect of repair systems on the mutagenicity of N-nitrosodialkylamines in Salmonella typhimurium
Implication of reactive oxygen species in bacterial mutagenesis of cigarette smoke Many kinds of mutagens/carcinogens have been identified in cigarette smoke. Further, generation of hydrogen peroxide has been found when cigarette smoke was introduced into phosphate buffer. In order to examine the generation of reactive oxygen species (ROS) from cigarette smoke, we carried out a bio-assay for detection of ROS using E. coli mutants lacking activity of either catalase, superoxide dismutase (SOD) or both, namely DSH19 (katEG), DSH56 (sodAB) or DSH67 (katEG sodAB) which have been constructed by us. The assay, called kat-sod assay, consists of (1) the sensitivity test and (2) the gene expression test. (1) was carried out by culturestreaking on agar plate and (2) by measurement of/3-galactosidase activity. Their sensitivities and gene expression levels were compared to those of their wild strain, DSH7. Smoke of 13 Japanese cigarettes (brand Peace) was trapped in distilled water (10 ml) by an aspirator as the standard smoking condition and the cigarette smoke solution (CSS) obtained was used as the sample. From the result of the assay, it was found that both hydrogen peroxide and superoxide were produced in the sample. Also we examined the effect of SOD and catalase on the mutagenicity of CSS using S. typhimurium TA98 (+ $9 mix) and found that both suppressed the mutagenicity effectively. From
47 Mochizuki, M., K. Itoh and H. Murakami, Kyoritsu College of Pharmacy, Shibakoen 1-5-30, Minato-ku, Tokyo 105, Japan
N-Nitrosodialkylamines induce mutation after metabolic activation through a-hydroxylation. Mutagenicity levels of N-nitrosodialkylamines (alkyl = methyl, NDM; propyl, NDP and butyl, NDB) correlate with those of the corresponding N-nitroso-N-(hydroxymethyl)alkylamines, except for N-nitrosodiethylamine (NDE) which shows very weak mutagenicity. In the present study, we developed experimental conditions to result effectively in positive mutagenicity with NDE by using 3 ml $9 in 10 ml $9 mix, pre-incubation at 37°C for 60 min, and shaking at 160 strokes/min. The Salmonella typhimurium O6-alkylguanine alkyltransferase (AGT) deficient strains YG7100, YG7104 and YG7108 were used in addition to TA1535 to determine the effects of DNA alkylation and repair system on the mutagenicity. The mutagenicity was NDM > NDB > NDP >> NDE in TA1535 and YG7100, while in YG7104 and YG7108 mutagenicity was NDM > NDP ~ NDB > NDE. YG7104, a deficient strain of the ogt gene, was more sensitive to NDM than TA1535, while YG7108, a deficient strain of both the ada and ogt genes, was most sensitive. With NDE, NDP and NDB, there were very few differences in mutagenicity between YG7104 and YG7108. These results suggest that DNA damage with NDM was repaired with AGT produced both from the ada and ogt genes, and DNA damage of NDE, NDP and NDB was repaired mainly by the ogt gene product. 48 Mori, M. a, H. Kobayashi a, C. Sugiyama a and C. Furihata b, a Safety and Analytical Research
405
When rotenone was added to HeLa $3, BHK21, and C3H10T1/2 cells, the chromosomes of their metaphases aggregated within 0.5 h after exposure, began to decondense forming interphase nuclei after 3 h, and then their endoreduplicated metaphases appeared. This suggests that rotenone induces metaphases of various cells to endoreduplicate.
these results, it is suggested that superoxide as well as hydrogen peroxide may be implicated in the mutagenicity of CSS.
46 Miyasaka, R., S. Hayashi, T. Kimura, S. Ueda and H. Nishioka, Bio-system Research Laboratory, Doshisha University, Karasuma-Imadegawa, Kamigyo-ku, Kyoto 602, Japan
Effect of repair systems on the mutagenicity of N-nitrosodialkylamines in Salmonella typhimurium
Implication of reactive oxygen species in bacterial mutagenesis of cigarette smoke Many kinds of mutagens/carcinogens have been identified in cigarette smoke. Further, generation of hydrogen peroxide has been found when cigarette smoke was introduced into phosphate buffer. In order to examine the generation of reactive oxygen species (ROS) from cigarette smoke, we carried out a bio-assay for detection of ROS using E. coli mutants lacking activity of either catalase, superoxide dismutase (SOD) or both, namely DSH19 (katEG), DSH56 (sodAB) or DSH67 (katEG sodAB) which have been constructed by us. The assay, called kat-sod assay, consists of (1) the sensitivity test and (2) the gene expression test. (1) was carried out by culturestreaking on agar plate and (2) by measurement of/3-galactosidase activity. Their sensitivities and gene expression levels were compared to those of their wild strain, DSH7. Smoke of 13 Japanese cigarettes (brand Peace) was trapped in distilled water (10 ml) by an aspirator as the standard smoking condition and the cigarette smoke solution (CSS) obtained was used as the sample. From the result of the assay, it was found that both hydrogen peroxide and superoxide were produced in the sample. Also we examined the effect of SOD and catalase on the mutagenicity of CSS using S. typhimurium TA98 (+ $9 mix) and found that both suppressed the mutagenicity effectively. From
47 Mochizuki, M., K. Itoh and H. Murakami, Kyoritsu College of Pharmacy, Shibakoen 1-5-30, Minato-ku, Tokyo 105, Japan
N-Nitrosodialkylamines induce mutation after metabolic activation through a-hydroxylation. Mutagenicity levels of N-nitrosodialkylamines (alkyl = methyl, NDM; propyl, NDP and butyl, NDB) correlate with those of the corresponding N-nitroso-N-(hydroxymethyl)alkylamines, except for N-nitrosodiethylamine (NDE) which shows very weak mutagenicity. In the present study, we developed experimental conditions to result effectively in positive mutagenicity with NDE by using 3 ml $9 in 10 ml $9 mix, pre-incubation at 37°C for 60 min, and shaking at 160 strokes/min. The Salmonella typhimurium O6-alkylguanine alkyltransferase (AGT) deficient strains YG7100, YG7104 and YG7108 were used in addition to TA1535 to determine the effects of DNA alkylation and repair system on the mutagenicity. The mutagenicity was NDM > NDB > NDP >> NDE in TA1535 and YG7100, while in YG7104 and YG7108 mutagenicity was NDM > NDP ~ NDB > NDE. YG7104, a deficient strain of the ogt gene, was more sensitive to NDM than TA1535, while YG7108, a deficient strain of both the ada and ogt genes, was most sensitive. With NDE, NDP and NDB, there were very few differences in mutagenicity between YG7104 and YG7108. These results suggest that DNA damage with NDM was repaired with AGT produced both from the ada and ogt genes, and DNA damage of NDE, NDP and NDB was repaired mainly by the ogt gene product. 48 Mori, M. a, H. Kobayashi a, C. Sugiyama a and C. Furihata b, a Safety and Analytical Research