title: Formation of DNA single-strand breaks by near-ultraviolet and gamma-rays in normal and Bloom's syndrome skin fibroblasts.
abstract: The formation of single-strand breaks by near-ultraviolet light at 313 nm and by aerobic gamma-rays was compared for skin fibroblast monolayer cultures from 4 normal donors (NF) and 8 patients with Bloom's syndrome (BS) by the alkaline elution method. In 6 of 8 BS strains, the number of breaks induced by near-ultraviolet light, 2.25 kJ/sq m, at 0 degrees was comparable to NF, while elevated breakage was observed in BS strains HG 369 and HG 916. Breakage frequencies were increased substantially in 6 of 8 BS strains relative to NF when the near-ultraviolet light exposure was at 37 degrees. BS strain GM 2520 represents an exception since normal breakage frequencies were induced both at 0 degrees and 37 degrees. Aerobic gamma-rays (75 R) induced comparable numbers of single-strand breaks in BS and NF strains at 0 degrees. The breakage frequencies were reduced an average of 17% in NF when the same dose was given at 30 degrees followed by 6 min incubation. Under the same conditions, the breakage frequencies were on the average reduced by 42% relative to 0 degrees in the BS strains, indicating that they possess normal or possibly slightly increased capacities for the rejoining of gamma-ray-induced breaks.
mesh_terms: D000332:Aerobiosis; D002478:Cells, Cultured; D004247:DNA / Q000528:radiation effects*; D004260:DNA Repair; D004392:Dwarfism; D005720:Gamma Rays; D006801:Humans; D013684:Telangiectasis / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D004247:DNA