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Induction of heritable translocations with methyl methanesulfonate in male mice
393 agent and then mated for 8 consecutive weeks to assess the mutagenic potential at every stage of spermatogenesis. In Segment I studies, males are dosed for 60 days (which covers all stages of spermatogenesis) and then mated for 1 or 2 weeks. Therefore, the mating results from a Segment I study show immediately if drug exposure causes DL effects. Survey of literature with published results on both test systems shows that c o m p o u n d s that were positive in DL test were also positive in Segment I Study while those that were negative also showed a similar correspondence. This observed perfect agreement between the two test systems was expected and demonstrates that the DL effect can be ascertained directly from Segment I studies.
37 R. Lang and I.-D. Adler, Schering AG, Researeh Laboratories, Berlin/Bergkamen, and Gesellschaft ffir Strahlen- und Umweltforschung, Mfinchen (Germany) Induction of heritable translocations with methyl methanesulfonate in male mice For the evaluation of induced heritable translocations by methyl methanesulfonate (MMS) late spermatids and early spermatozoa were tested. A comparison of fertility data and cytogenetic analyses of the F1 males was performed to assess the accuracy of identification of semisterile translocation heterozygotes by the reduction of litter size. NMRI males of proven fertility were injected intraperitoneally with 40 mg/kg of MMS. 250 F~ male progeny sired 4 to 10 days after treatment and 245 F~ control males were tested for their reproductive performance. F~ males that in three matings produced at least once 10 live implants with none or only one dead and in another two matings at least once a litter of 10 or more live offspring were considered fully fertile. F~ males that did not meet these criteria were mated again for further fertility testing and to collect F2 sons from the semisterile males. The testes of all sterile, semisterile and non-classifiable F~ males as well as those of the semisterile F2 sons from semisterile F~ males were prepared for cytogenetic analysis. A total of 14 semisterile and 14 sterile males (28; 11.2%) were observed in the MMS group. Of these 20 (8.0%) could be identified cytogenetically as heterozygous translocation carriers, i.e. 6 sterile and 14 semisterile males. Heritability of the reciprocal translocation was confirmed for the semisterile F~ males by cytogenetic identification of translocation carriers among the F2 progeny. There were no sterile or semisterile males among the 245 F1 controls. In assessing the accuracy of classification the frequency of false positives was c o m p u t e d directly from the observed fertility data. Based on 5 matings and applying the rules outlined above it was 16%. Further matings reduced the frequency of false positives to approximately 1%. Since the animals declared normal were n o t analysed cytogenetically, strictly speaking the probability of false negatives cannot be calculated, however, making certain assumptions a statistical approach is possible.
37 R. Lang and I.-D. Adler, Schering AG, Researeh Laboratories, Berlin/Bergkamen, and Gesellschaft ffir Strahlen- und Umweltforschung, Mfinchen (Germany) Induction of heritable translocations with methyl methanesulfonate in male mice For the evaluation of induced heritable translocations by methyl methanesulfonate (MMS) late spermatids and early spermatozoa were tested. A comparison of fertility data and cytogenetic analyses of the F1 males was performed to assess the accuracy of identification of semisterile translocation heterozygotes by the reduction of litter size. NMRI males of proven fertility were injected intraperitoneally with 40 mg/kg of MMS. 250 F~ male progeny sired 4 to 10 days after treatment and 245 F~ control males were tested for their reproductive performance. F~ males that in three matings produced at least once 10 live implants with none or only one dead and in another two matings at least once a litter of 10 or more live offspring were considered fully fertile. F~ males that did not meet these criteria were mated again for further fertility testing and to collect F2 sons from the semisterile males. The testes of all sterile, semisterile and non-classifiable F~ males as well as those of the semisterile F2 sons from semisterile F~ males were prepared for cytogenetic analysis. A total of 14 semisterile and 14 sterile males (28; 11.2%) were observed in the MMS group. Of these 20 (8.0%) could be identified cytogenetically as heterozygous translocation carriers, i.e. 6 sterile and 14 semisterile males. Heritability of the reciprocal translocation was confirmed for the semisterile F~ males by cytogenetic identification of translocation carriers among the F2 progeny. There were no sterile or semisterile males among the 245 F1 controls. In assessing the accuracy of classification the frequency of false positives was c o m p u t e d directly from the observed fertility data. Based on 5 matings and applying the rules outlined above it was 16%. Further matings reduced the frequency of false positives to approximately 1%. Since the animals declared normal were n o t analysed cytogenetically, strictly speaking the probability of false negatives cannot be calculated, however, making certain assumptions a statistical approach is possible.