title: Induction of 8-azaguanine resistance and sister chromatid exchange in human lymphocytes exposed to mitomycin C and X rays in vitro.
abstract: Indirect evidence implies that 8-azaguanine-resistant (AGr) lymphocytes in human peripheral blood are mutants associated with the loss of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus on the active X chromosome, the mutation frequency increasing linearly with age. AGr variants are readily induced in lymphocytes exposed to mitomycin C in vitro, their incidence correlating with induced sister chromatid exchanges (SCEs). Although SCE events and the development of an AGr phenotype may reflect a common type of DNA damage, mitomycin C-induced Agr variants are not mutants but are suggested to be cells having a transcriptional block at the HPRT locus. AGr variants are also readily induced by X rays in vitro, their incidence correlates closely with the incidence of aberrations induced in the X chromosome and they are considered to have a mutational origin.
mesh_terms: D000367:Age Factors; D001375:Azaguanine / Q000494:pharmacology; D002478:Cells, Cultured; D003434:Crossing Over, Genetic / Q000187:drug effects*; D004351:Drug Resistance; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000528:radiation effects; D008937:Mitomycins / Q000494:pharmacology*; D009154:Mutation / Q000187:drug effects*; D012737:Sex Factors; D012854:Sister Chromatid Exchange / Q000187:drug effects*; D014965:X-Rays
chemical_list: D008937:Mitomycins; D001375:Azaguanine