title: Spontaneous expulsion of micronuclei by enucleation in the micronucleus assay.
abstract: The effect of enucleation on the frequency of micronuclei induced by mitomycin C (MMC) and vincristine (VCR) was examined in mouse L-929 cells enucleated with cytochalasin B (Cyt-B). Approximately 30% of the L-929 cells became enucleated cells during the 8-h incubation in medium containing 8 micrograms/ml of Cyt-B. Using this enucleation technique, we estimated the reduction rate of 2 mutagen-induced micronuclei by enucleation. Treatment with MMC caused a dose-dependent induction of micronuclei in L-929 cells, with the reduction rate being 38.6% at the lowest dosage (0.0125 microgram/ml), which induced mostly mono-micronuclei in L-929 cells, and 6.8% at the highest dosage (0.1 microgram/ml), which induced many multi-micronuclei. Furthermore, VCR also induced micronuclei in a dose-dependent way in L-929 cells, and the same tendency for micronucleus reduction as with MMC was observed. The reduction rate of micronucleated cells by enucleation was estimated to be about 31-39% when the micronucleated cells contain mono-micronuclei. Therefore, the rate of reduction is affected by the number of micronuclei per cell, and the reduction depends on the increase in the number of micronuclei per cell.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects*; D003571:Cytochalasin B / Q000494:pharmacology*; D007739:L Cells / Q000187:drug effects* / Q000648:ultrastructure; D051379:Mice; D016685:Mitomycin; D008937:Mitomycins / Q000494:pharmacology*; D009152:Mutagenicity Tests / Q000379:methods*; D014750:Vincristine / Q000494:pharmacology*
chemical_list: D008937:Mitomycins; D003571:Cytochalasin B; D016685:Mitomycin; D014750:Vincristine