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T Nohmi

Publications and source records attributed to T Nohmi.

113 records · Page 7Linked to original sources
PubMed1979

Differential mutagenicities of triamino benzenes against Salmonella typhimurium TA98 in the presence of S9 fractions from polychlorinated biphenyls-, phenobarbital- or 3-methylcholanthrene-pretreated rats, hamsters and mice.

Mutagenicity of 6 aminobenzene derivatives against Salmonella typhimurium TA98 was studied in the presence of various S9 fractions. S9, which has been prepared form the livers of rats, hamsters and mice after pretreatment with different types of inducers; polychlorinated biphenyls, phenobarbital and 3-methylcholanthrene, was used as the methabolic activating enzyme in this mutation assay. The S9 fractions from 3-methylcholanthrene-treated rats and mice are most useful for mutation induction by the all aminobenzenes used. The mutagenic activity of the compounds was clearly correlated to 3-methylcholanthrene-induced cytochrome P-450. However, any significant correlation between aniline hydroxylase activity and the mutagenesis was not observed.

Aniline Hydroxylase↗
PubMedDate not supplied

New mutations in cloned Escherichia coli umuDC genes: novel phenotypes of strains carrying a umuC125 plasmid.

The umuDC locus of Escherichia coli is required for most mutagenesis by UV and many chemicals. Mutations in E. coli umuDC genes cloned on pBR322-derived plasmids were isolated by two methods. First, spontaneously-arising mutant umuDC plasmids that failed to confer cold-sensitive growth on a lexA51(Def) strain were isolated by selection. Second, mutant umuDC plasmids that affected apparent mutant yield after UV-irradiation in a strain carrying umuD+C+ in the chromosome were isolated by screening hydroxylamine-mutagenized umuD+C+ plasmids. pBR322-derived umuD+C+ plasmids inhibited the induction of the SOS response of lexA+ strains as measured by expression of din::Mu dl(lac Ap) fusions but most mutant plasmids did not. Mutant plasmids defective in complementation of chromosomal umuD44, umuC36, or both were found among those selected for failure to confer cold-sensitivity, whereas those identified by the screening procedure yielded mostly mutant plasmids with more complex phenotypes. We studied in greater detail a plasmid, pLM109, carrying the umuC125 mutation. This plasmid increased the sensitivity of lexA+ strains to killing by UV-irradiation but was able to complement the deficiencies of umuC mutants in UV mutagenesis. pLM109 failed to confer cold-sensitive growth on lexA(Def) strains but inhibited SOS induction in lexA+ strains. The effect of pLM109 on the UV sensitivity of lexA(Def) strains was similar to that of the parental umuD+C+ plasmid. The mutation responsible for the phenotypes of pLM109 was localized to a 615-bp fragment. DNA sequencing revealed that the umuC125 mutation was a G:C----A:T transition that changed codon 39 of umuC from GCC----GTC thus changing Ala39 to Val39. The implications of the umuC125 mutation for umuDC-dependent effects on UV-mutagenesis and cell survival after UV damage are discussed.

Alleles↗
PubMedDate not supplied

Characterization of mixed-function oxidases and purified cytochrome P-450 of livers of house musk shrew, Suncus murinus.

Characteristics of mixed-function oxidases in the liver of house musk shrew, Suncus murinus, were studied. The basal level of cytochrome P-450 and the activity of drug-metabolizing enzyme in hepatic microsomes of Suncus murinus is relatively lower than that of rats, while the level of cytochrome b5 and NADPH-cytochrome c reductase is approximately the same as that of rats. The treatment of Suncus murinus with phenobarbital and 3-methylcholanthrene elevated the level of cytochrome P-450 and the activity of drug-metabolizing enzymes, but not the level of cytochrome b5. Two distinct forms of cytochrome P-450 have been purified from hepatic microsomes of 3-methylcholanthrene-treated Suncus murinus. These forms have their absorption maximum at 448.0 nm and 448.5 nm in CO-bound reduced form, and one is in the high-spin state and the other is in the low-spin state. They are different in their molecular weights (53,500 and 55,000) and in their spectral and catalytic properties. Characteristics of these forms were compared with those of the major forms of cytochrome P-450 purified from livers of rats treated with 3-methylcholanthrene.

Animals↗