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the essential enzymes. The general validity of both mechanisms has been confirmed by screening of typical ring-substituted 3,3-dimethyl-I-phenyltriazenes in a direct and host-mediated yeast test and in Drosophila. Moreover, the importance of additional structural factors for the observed mutagenic activity of triazenes has been established. The diversity in genetic effectiveness will be discussed in terms of current reaction mechanisms.
33 LOPRIENO, N., R. BARALE,S. BARONCELLI,C. BAUER, G. BRONZETTI,A. CAMMELLINI, G. CERCIGNANI, A. CINCI, C. LEPORINI, R. NIERI, M. NOZZOLINI, A. M. RossI, C. SERRA AND C. CORSI, Laboratorio di Mutagenesi e Differenziamento del C.N.R. and Istituto di Genetica dell'UniversitY, Pisa (Italy).
The use of yeast genetic systems in environmental mutagenesis Two alkylating monofunctional agents (ethylmethanesulphonate, EMS, and methylmethanesulphonate, MMS) were used to induce genetic effects, such as gene conversions and gene recombinations in diploid strains of S. cerevisiae and S. pombe, and gene mutation in a haploid strain of S. pombe. The test systems used for studying these genetic effects were represented by gene conversions in the trp 5 and ade 2 loci of S. cerevisiae, by gene recombinations for ade 7 locus of S. pombe and by gene mutations in five adenine loci of S. pombe, for evaluating forward mutations which are scored on a non-selective medium. In environmental mutagenesis the mutagenic activity of a chemical compound depends on the possible influence of the mammalian metabolism on the compound in the liver or another organ. Therefore an assay was developed for analyizng the mutagenic activity of EMS and MMS in the presence of mouse liver microsomal enzymes in vitro. All three genetic systems have been tested with such an assay. Finally EMS and MMS were tested in the host-mediated assays. Yeast cells were injected intraperitoneally into the mouse, which was treated orally with different doses of the compounds under analysis. After different times the yeast cells were recovered from the mouse's peritoneum and plated on appropriate medium to score the induced genetic effects. Comparative data with different assays have been collected so far, to define quantitatively the different sensitivities of the three systems. Statistical treatments of all the data b y regression analysis has allowed the comparison between the three genetic systems and in all cases the frequency of the induced genetic effect per mmole of the mutagenic agent per hour was evaluated. The quantitative analysis done in these experiments allows a better extrapolation of the present data to other genetic systems in other organisms. Abbreviations: EMS, ethyl methanesulphonate; MMS, methyl methanesulphonate.
34 MALAVEILLE, C., M. CAMUS, R. MONTESANOAND H. BARTSCH, International Agency for Research on Cancer, Lyon (France).
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the essential enzymes. The general validity of both mechanisms has been confirmed by screening of typical ring-substituted 3,3-dimethyl-I-phenyltriazenes in a direct and host-mediated yeast test and in Drosophila. Moreover, the importance of additional structural factors for the observed mutagenic activity of triazenes has been established. The diversity in genetic effectiveness will be discussed in terms of current reaction mechanisms.
33 LOPRIENO, N., R. BARALE,S. BARONCELLI,C. BAUER, G. BRONZETTI,A. CAMMELLINI, G. CERCIGNANI, A. CINCI, C. LEPORINI, R. NIERI, M. NOZZOLINI, A. M. RossI, C. SERRA AND C. CORSI, Laboratorio di Mutagenesi e Differenziamento del C.N.R. and Istituto di Genetica dell'UniversitY, Pisa (Italy).
The use of yeast genetic systems in environmental mutagenesis Two alkylating monofunctional agents (ethylmethanesulphonate, EMS, and methylmethanesulphonate, MMS) were used to induce genetic effects, such as gene conversions and gene recombinations in diploid strains of S. cerevisiae and S. pombe, and gene mutation in a haploid strain of S. pombe. The test systems used for studying these genetic effects were represented by gene conversions in the trp 5 and ade 2 loci of S. cerevisiae, by gene recombinations for ade 7 locus of S. pombe and by gene mutations in five adenine loci of S. pombe, for evaluating forward mutations which are scored on a non-selective medium. In environmental mutagenesis the mutagenic activity of a chemical compound depends on the possible influence of the mammalian metabolism on the compound in the liver or another organ. Therefore an assay was developed for analyizng the mutagenic activity of EMS and MMS in the presence of mouse liver microsomal enzymes in vitro. All three genetic systems have been tested with such an assay. Finally EMS and MMS were tested in the host-mediated assays. Yeast cells were injected intraperitoneally into the mouse, which was treated orally with different doses of the compounds under analysis. After different times the yeast cells were recovered from the mouse's peritoneum and plated on appropriate medium to score the induced genetic effects. Comparative data with different assays have been collected so far, to define quantitatively the different sensitivities of the three systems. Statistical treatments of all the data b y regression analysis has allowed the comparison between the three genetic systems and in all cases the frequency of the induced genetic effect per mmole of the mutagenic agent per hour was evaluated. The quantitative analysis done in these experiments allows a better extrapolation of the present data to other genetic systems in other organisms. Abbreviations: EMS, ethyl methanesulphonate; MMS, methyl methanesulphonate.
34 MALAVEILLE, C., M. CAMUS, R. MONTESANOAND H. BARTSCH, International Agency for Research on Cancer, Lyon (France).
