Chromosomal damage and repair in G1-phase Chinese hamster ovary cells exposed to charged-particle beams.
Chromosomal fragmentation was examined in G1-phase Chinese hamster ovary cells using the premature chromosome condensation (PCC) technique. The yield and distribution of chromatin breaks, the lesions revealed by PCC, were measured in cells exposed to X rays or each of nine particle beams covering a range of LET from 0.56 to 2700 keV/microns. The average number of breaks per cell was found to be linearly proportional to the fluence of high-LET neon ions (183 keV/microns). Assuming a linear response for the other beams, the level of breakage per unit dose rose from a plateau at the lowest LET values to a peak in the 100-200 keV/microns range and then declined continuously thereafter, eventually falling well below the low-LET plateau. The maximum breakage RBE was 1.5. The average number of breaks per particle traversal rose steadily from 0.006 to 11 breaks/cell as the LET increased from 0.56 to 2700 keV/microns. The breaks were distributed randomly within the cell population after low-LET irradiation, but became progressively over-dispersed with increasing LET. Rejoining of prematurely condensed chromosomes plus fragments was followed for up to 5 h for four particle beams having LET values between 0.56 and 183 keV/microns. An LET-dependent trend toward higher levels of residual fragments was observed.
Goodwin
E H
EH
Cell and Molecular Biology Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Blakely
E A
EA
Tobias
C A
CA
D000818:Animals; D016466:CHO Cells; D002843:Chromatin / Q000528:radiation effects; D002875:Chromosomes / Q000528:radiation effects*; D006224:Cricetinae; D004249:DNA Damage; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D004735:Energy Transfer; D008938:Mitosis; D014965:X-Rays
D002843:Chromatin