Studies on isolated cloned populations from irradiated human embryonic cell cultures

The recovery of substrains with stable chromosome aberrations from irradiated fibroblast cultures is reported. Four human fetal cell strains were exposed to 600 rad of gamma rays at 200 rad/min. The efficiency of recovering viable cloned subpopulations was approximately 87%, and the frequency of clones with abnormal chromosomes was 40/100 colonies. G-band chromosome analyses for 34 abnormal substrains was described. Karyotypes of some of the clones with complex rearrangements are also presented. Analyses of a total of 47 aberrant events in the 34 abnormal substrains revealed a 7:1 and a 9:1 translocation-inversion and translocation-depletion ratios, respectively. Five of the abnormal substrains were continuously cultured; all except one showed signs of senescence toward the end of 44±10 doublings. Unusual prolonged proliferation capacity was observed in substrain FFS-1-9. The significance of this finding is discussed.