title: Kinetics of chromatid break repair in G2-human fibroblasts exposed to low- and high-LET radiations.
abstract: The purpose of this study is to determine the kinetics of chromatid break rejoining following exposure to radiations of different quality. Exponentially growing human fibroblast cells AG1522 were irradiated with gamma-rays, energetic carbon (290 MeV/u), silicon (490 MeV/u) and iron (200 MeV/u, 600 MeV/u). Chromosomes were prematurely condensed using calyculin A. Prematurely condensed chromosomes were collected after several post-irradiation incubation times, ranging from 5 to 600 minutes, and the number of chromatid breaks and exchanges in G2 cells were scored. The relative biological effectiveness (RBE) for initial chromatid breaks per unit dose showed LET dependency having a peak at 55 keV/micrometers silicon (2.4) or 80 keV/micrometers carbon particles (2.4) and then decreased with increasing LET. The kinetics of chromatid break rejoining following low- or high-LET irradiation consisted of two exponential components. Chromatid breaks decreased rapidly after exposure, and then continued to decrease at a slower rate. The rejoining kinetics was similar for exposure to each type of radiation, although the rate of unrejoined breaks was higher for high-LET radiation. Chromatid exchanges were also formed quickly.
authors.affiliation: NASA Lyndon B. Johnson Space Center, Radiation Biophysics Laboratory, USA.
authors.forename: T
authors.initials: T
authors.lastname: Kawata
authors.forename: M
authors.initials: M
authors.lastname: Durante
authors.forename: K
authors.initials: K
authors.lastname: George
authors.forename: Y
authors.initials: Y
authors.lastname: Furusawa
authors.forename: E
authors.initials: E
authors.lastname: Gotoh
authors.forename: N
authors.initials: N
authors.lastname: Takai
authors.forename: H
authors.initials: H
authors.lastname: Wu
authors.forename: F A
authors.initials: FA
authors.lastname: Cucinotta
mesh_terms: D002460:Cell Line; D002842:Chromatids / Q000502:physiology / Q000528:radiation effects*; D002869:Chromosome Aberrations; D019457:Chromosome Breakage; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000502:physiology / Q000528:radiation effects; D016195:G2 Phase / Q000502:physiology / Q000528:radiation effects*; D005720:Gamma Rays; D020450:Heavy Ions; D006801:Humans; D007700:Kinetics; D018499:Linear Energy Transfer; D008387:Marine Toxins; D010080:Oxazoles; D012062:Relative Biological Effectiveness
chemical_list: D008387:Marine Toxins; D010080:Oxazoles; C059041:calyculin A