title: An ionizing radiation-sensitive mutant of CHO cells: irs-20. III. Chromosome aberrations, DNA breaks and mitotic delay.
abstract: The ionizing radiation-sensitive mutant of CHO cells, irs-20, showed a defect in the rate and extent of rejoining of gamma-ray-induced DNA double-strand breaks (dsbs) compared with the parental CHO cells as measured using pulsed-field gel electrophoresis. Virtually all rejoined in wild-type cells but some 20-30% failed to rejoin in the mutant cells during a 5-h period after irradiation. An increased level of chromosome-type aberrations per unit dose was seen in irs-20 cells compared with wild-type cells irradiated during the G1 phase. For the irs-20 cells, about half the dose was required to produce the same chromosome-type aberration frequency. Chromatid-type aberrations were induced in G1-irradiated irs-20 cells at frequencies nearly the same as for chromosome types. For the parental wild-type CHO 10B2 cells, only chromosome types were seen. The distribution of aberrations among cells was not significantly different from Poisson for wild-type cells, but this was not the case for irs-20 cells where the overdispersion was highly significant. The mutant irs-20 cells displayed a much greater cell cycle delay per unit dose (about five-fold) in reaching mitosis after irradiation in G1 than the more radioresistant wild-type parental cells.
authors.affiliation: Department of Radiological Health Sciences, Colorado State University, Fort Collins 80523.
authors.forename: M A
authors.initials: MA
authors.lastname: Stackhouse
authors.forename: J S
authors.initials: JS
authors.lastname: Bedford
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects; D002453:Cell Cycle / Q000528:radiation effects; D002869:Chromosome Aberrations; D006224:Cricetinae; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D005720:Gamma Rays; D008938:Mitosis / Q000528:radiation effects*; D009154:Mutation; D010641:Phenotype; D011836:Radiation Tolerance
chemical_list: D004247:DNA