title: Effects of X-irradiation on cell-cycle progression, induction of chromosomal aberrations and cell killing in ataxia telangiectasia (AT) fibroblasts.
abstract: Survival, cumulative labeling indices, chromosomal aberrations and cell-cycle distribution by flow microfluorometry (FMF) were studied in fibroblasts from normal and three ataxia telangiectasia (AT) families after X-irradiation during density-inhibition of growth and immediate release by subculture to low density. Homozygotic AT (proband) fibroblasts were very hypersensitive to cell killing by X-irradiation (D0 = 40-45 rad). Fibroblasts from AT heterozygotes (parents) were minimally hypersensitive, with D0's (100-110 rad) slightly lower than those for normal fibroblasts (D0 = 120-140 rad). There were three different response groups for a G1 phase block induced by 400 rad of X-rays: (1) minimal or no G1 block was observed in AT homozygote cell strains; (2) 10-20% of the cells were blocked in G1 in normal cell strains; and (3) 50% or more of the cells were blocked in AT heterozygote strains. FMF profiles and cumulative labeling indices showed that homozygotic AT cells irradiated in plateau phase moved into the S-phase following subculture with no additional delay over non-irradiated controls. Homozygotic AT cells showed not only a 4-5 times higher frequency of X-ray-induced chromosomal aberrations than normal strains, but approximately 30% of these were of the chromatid-type. There were no differences in the frequency or type of X-ray-induced chromosomal aberrations between normal and heterozygotic AT cells.
mesh_terms: D000293:Adolescent; D000328:Adult; D001260:Ataxia Telangiectasia / Q000235:genetics*; D002453:Cell Cycle / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D002648:Child; D002869:Chromosome Aberrations; D004260:DNA Repair; D005260:Female; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D014965:X-Rays