title: [Possible mechanisms of the occurrence of chromosome aberrations. I. Patterns in the occurrence of aberrations induced by ultraviolet irradiation].
abstract: The frequency of chromosome aberrations induced by UV light at wavelengths 254, 265, 280 and 302 using doses 2-10 J/m2 in the primary culture of mouse embryonic fibroblasts during the G1, S and G2 phases was studied at metaphase of the first mitosis. Two classes of chromosome aberrations were distinguished. These classes differ in the time intervals of the final establishment of the cell cycle. The aberrations of the class 1 emerge before the beginning of prometaphase (possibly, at interphase). Formation of the second class aberrations is completed during the metaphase. It is shown that the class 1 aberrations occur with almost the same rate in approx. 7% of cells, irrespective of the cell cycle, irradiation dose and wavelength. It is suggested that these aberrations arise as a result of indirect UV action on the chromosome structures; the mechanism of their emergence does not depend on DNA replication. The class 2 aberrations do not appear after UV irradiation during the post-DNA-synthetic G2 phase of the cell cycle. However, after UV treatment at the G1 or S periods, they represent the majority of aberrations and their rate increases almost monotonously with the radiation dose. The UV action spectrum for these aberrations coincides with the adsorption spectrum of thymidine and the action spectrum for DNA cross-links. Thus, it may be inferred that formation of DNA cross-links following thymine dimerization is the first step in formation of UV-induced aberrations of the class 2. The passage of cells through DNA replication is a very important step in the process of their emergence.
mesh_terms: D000167:Acriflavine / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000187:drug effects / Q000528:radiation effects; D007399:Interphase / Q000187:drug effects / Q000528:radiation effects; D051379:Mice; D008807:Mice, Inbred BALB C; D012854:Sister Chromatid Exchange / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D000167:Acriflavine; D002110:Caffeine
vernacular_title: Vozmozhnye mekhanizmy vozniknoveniia perestroek khromosom. Soobshchenie I. Zakonomernosti vozniknoveniiia perestroek pri ul'trafioletovom obluchenii.