title: On the time course of the interactions between DNA breaks in the production of a radiation-induced chromosome exchange aberration.
abstract: Quiescent human lymphocytes were X-irradiated and allowed to repair for various times at 37 degrees C before the cells were challenged with the DNA-repair inhibitor ara-C. The observed yield of chromosome exchange aberrations (dicentrics) was about twice the yield induced by X-rays alone, if ara-C was added immediately after irradiation. The yield as a function of the repair time between X-irradiation and ara-C treatment decreased with a half-life of 15-30 min and was almost down to the baseline yield for X-rays alone after 1 h. This shows that an exchange aberration can be formed from a short-lived DNA break. In contrast, previously published results from dose-split experiments demonstrate that the half-life of the interacting DNA breaks is of the order of several hours. A model is proposed which can account for the different estimates of the time course of the interactions involved in the process which leads to an exchange aberration.
authors.affiliation: National Institute of Radiation Protection, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Holmberg
mesh_terms: D002869:Chromosome Aberrations; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair / Q000187:drug effects; D006207:Half-Life; D006801:Humans; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000187:drug effects / Q000528:radiation effects*; D008938:Mitosis; D013997:Time Factors; D014965:X-Rays
chemical_list: D003561:Cytarabine; D004247:DNA