title: The occurrence of DNA strand breaks after hyperthermic treatments of mammalian cells with and without radiation.
abstract: Strand breaks were detected in the DNA of Ehrlich ascites cells as well as in HeLa S3 cells directly after 1-5 hr at 43-45 degrees C by the use of the unwinding in high salt/hydroxylapatite method. The strand breaks found could not be attributed to the decay of incorporated tritiated thymidine. When the cells were incubated at 37 degrees C after the hyperthermic treatments, the amount of strand breaks formed remained at a constant level. Hyperthermia inhibited the repair of "radiation-induced" strand breaks. The repair curves obtained this way show a heat-dose-dependent decrease of the relative weight of the fast component of repair. Similar repair curves of "radiation-induced" strand breaks could be obtained by mixing heat inactivated and vital control cells prior to irradiation. In the latter case, however, the DNA repair was inhibited to a greater extent for identical levels of cell survival. The possible underlying molecular mechanisms are discussed.
mesh_terms: D000818:Animals; D002286:Carcinoma, Ehrlich Tumor; D002460:Cell Line; D004260:DNA Repair; D004273:DNA, Neoplasm / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006367:HeLa Cells / Q000528:radiation effects; D006358:Hot Temperature; D006801:Humans; D013997:Time Factors
chemical_list: D004273:DNA, Neoplasm