title: Ultraviolet light induction of diphtheria toxin-resistant mutants of normal and xeroderma pigmentosum human fibroblasts.
abstract: The UV induction of diphtheria toxin-resistant (DTr) mutants in normal and xeroderma pigmentosum human fibroblasts has been quantitatively characterized. A concentration of diphtheria toxin at which DTr cells are cross-resistant to Pseudomonas aeruginosa exotoxin A was determined and used in the selection of resistant mutants. Recovery of mutants was not influenced by the presence of wild-type cell densities of 1-8 x 10(5) per 9-cm plate, indicating no metabolic cooperation exists, in contrast to what is seen in the selection of some other variant phenotypes. Expression periods for UV-induced mutations differed with the severity of mutagen treatment and cell strain used. A relatively long (10-15 days after UV treatment) expression period was required for the maximum recovery of DTr mutants. Maximum recovery was followed by a decrease in mutation frequency on subsequent days evaluated. An apparent linear dose response within the dose range used was observed for UV-induced mutations in both normal and xeroderma pigmentosum fibroblasts. Our results indicate that xeroderma pigmentosum fibroblasts have higher UV-induced mutation frequencies per unit UV dose but similar frequencies per unit survival compared to normal cells within the range of UV doses tested.
mesh_terms: D002478:Cells, Cultured; D004167:Diphtheria Toxin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004351:Drug Resistance; D005347:Fibroblasts; D006801:Humans; D009154:Mutation / Q000528:radiation effects*; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
chemical_list: D004167:Diphtheria Toxin