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The relationship of unscheduled DNA synthesis to mutagenesis and chromosomal aberrations
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nium, and micronuclei in polychromatic erythrocytes. Mitomycin C, however, failed to induce mutations in Chinese hamster lung cells in vitro or in the hostmediated assay.
142 Mitchell, A.D., D.E. Robinson, D.T. Tajiri, T.-J.A. Kan, G.P. Sterling, P.A. McAfee and C.F. Kirchner, Biochemical Cytogenetics Program, Stanford Research Institute, Menlo Park, Calif. 94025 (U.S.A.) The relationship of unscheduled DNA synthesis to mutagenesis and chromosomal aberrations An in vitro unscheduled DNA synthesis (UDS) prescreening approach has been developed b y which the incorporation of tritiated thymidine in the repair of mutagen- or carcinogen-induced DNA damage is measured in DNA extracted from human diploid fibroblasts, WI-38 cells. The results from this test system correlate well with the classification of chemicals as mutagens or carcinogens based on the results of in vivo bioassays. However, to utilize fully the results from this testing, we are currently examining the interrelationships between in vitro and in vivo UDS as well as between mutagenesis, the formation of cytogenetic aberrations, and UDS. The results of comparing the effects of reference mutagens in various systems including in vitro and in vivo UDS, in vitro and in vivo cytogenetics tests as measured b y sister-chromatid exchanges, and in vitro mutagenesis in the L5178Y mouse l y m p h o m a forward mutation system will be presented. T h e s t u d y was s u p p o r t e d in p a r t b y N I E H S R e s e a r c h G r a n t No. 1 - R 0 1 - E S - 0 1 2 S l - 0 1 a n d NCI C o n t r a c t No. N O 1 / C P - 6 5 8 5 4 . A b b r e v i a t i o n : U D S , u n s c h e d u l e d D N A synthesis.
143 Monti-Bragadin a, C., N. Babudri a, M. Tamaro a, M. Cinco a and A.M. Molina b, a Institute of Microbiology, University of Trieste (Italy), and h Institute of Microbiology, University of Siena (Italy) The effect of bacterial plasmids on mutagenesis Some R plasmids are known to increase the number of spontaneous or induced mutants in bacterial strains carrying them. Taking advantage of this fact, Ames introduced the pKM101 plasmid into his strains of Salmonella typhimurium, thus making them more sensitive to mutagens. In a survey on the effect of plasmids on mutagenesis, we examined more than 70 plasmids of many different incompatibility groups. The results showed that 9 o u t of 10 N group plasmids, all the 7 members of the Is group, R62 (a naturally occurring hybrid between an I and N group plasmid), J R 6 6 a
nium, and micronuclei in polychromatic erythrocytes. Mitomycin C, however, failed to induce mutations in Chinese hamster lung cells in vitro or in the hostmediated assay.
142 Mitchell, A.D., D.E. Robinson, D.T. Tajiri, T.-J.A. Kan, G.P. Sterling, P.A. McAfee and C.F. Kirchner, Biochemical Cytogenetics Program, Stanford Research Institute, Menlo Park, Calif. 94025 (U.S.A.) The relationship of unscheduled DNA synthesis to mutagenesis and chromosomal aberrations An in vitro unscheduled DNA synthesis (UDS) prescreening approach has been developed b y which the incorporation of tritiated thymidine in the repair of mutagen- or carcinogen-induced DNA damage is measured in DNA extracted from human diploid fibroblasts, WI-38 cells. The results from this test system correlate well with the classification of chemicals as mutagens or carcinogens based on the results of in vivo bioassays. However, to utilize fully the results from this testing, we are currently examining the interrelationships between in vitro and in vivo UDS as well as between mutagenesis, the formation of cytogenetic aberrations, and UDS. The results of comparing the effects of reference mutagens in various systems including in vitro and in vivo UDS, in vitro and in vivo cytogenetics tests as measured b y sister-chromatid exchanges, and in vitro mutagenesis in the L5178Y mouse l y m p h o m a forward mutation system will be presented. T h e s t u d y was s u p p o r t e d in p a r t b y N I E H S R e s e a r c h G r a n t No. 1 - R 0 1 - E S - 0 1 2 S l - 0 1 a n d NCI C o n t r a c t No. N O 1 / C P - 6 5 8 5 4 . A b b r e v i a t i o n : U D S , u n s c h e d u l e d D N A synthesis.
143 Monti-Bragadin a, C., N. Babudri a, M. Tamaro a, M. Cinco a and A.M. Molina b, a Institute of Microbiology, University of Trieste (Italy), and h Institute of Microbiology, University of Siena (Italy) The effect of bacterial plasmids on mutagenesis Some R plasmids are known to increase the number of spontaneous or induced mutants in bacterial strains carrying them. Taking advantage of this fact, Ames introduced the pKM101 plasmid into his strains of Salmonella typhimurium, thus making them more sensitive to mutagens. In a survey on the effect of plasmids on mutagenesis, we examined more than 70 plasmids of many different incompatibility groups. The results showed that 9 o u t of 10 N group plasmids, all the 7 members of the Is group, R62 (a naturally occurring hybrid between an I and N group plasmid), J R 6 6 a