Ultraviolet-induced chromosome aberrations and mitotic delay in human fibroblast cells.

Some of the immediate and long-term effects of UV irradiation (2537 A) on human fibroblasts have been studied by measuring the DNA content of individual nuclei and examining metaphase chromosomes in the irradiated population for up to 18 days. Time-lapse cinematography was used to demonstrate that irradiation of diploid human fibroblasts during a wave of DNA synthesis causes rapid radiation death in a proportion of cells and severe reduction in mitotic activity. Measurement of the DNA content by a spectrophotometric method of individual nuclei remaining attached to the substrate 28 and 52 h after irradiation showed that cells with high DNA values accumulate in the irradiated population. However, significant numbers of giant cells were not maintained in the surviving population. Metaphases sampled up to 31 h after UV irradiation contained predominantly chromatid deletions. Exchange aberrations were less frequent and were not found in cells sampled up to 10 h after irradiation. UV had no immediately apparent effect on mitotic chromosomes, even at high doses. None of the surviving cultures contained a significant number of cells with stable translocations or polyploidy.