title: Concentration-dependent mutation of diploid human lymphoblasts by methylnitronitrosoguanidine: the importance of phenotypic lag.
abstract: The mutation of diploid human lymphoblasts by methylnitronitrosoguanidine (MNNG) was measured over the range of 0--45 ng of MNNG/ml of of medium. We found a 12-day lag in the phenotypic expression of 6-thioguanine resistance; the occurrence of this lag was independent of MNNG concentration. We hypothesize that the unexpectedly long lag period reflects a requirement for the loss of previously existing molecules of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) after mutation at the HGPRT locus.
mesh_terms: D002470:Cell Survival; D002874:Chromosome Mapping; D003470:Culture Media; D004351:Drug Resistance; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000378:metabolism; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000187:drug effects* / Q000648:ultrastructure; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology*; D009154:Mutation; D010641:Phenotype; D013866:Thioguanine / Q000494:pharmacology; D013997:Time Factors
chemical_list: D003470:Culture Media; D008769:Methylnitronitrosoguanidine; D007041:Hypoxanthine Phosphoribosyltransferase; D013866:Thioguanine