G-BANDING ANALYSIS OF RADIATION-INDUCED CHROMOSOME-DAMAGE IN LYMPHOCYTES OF HIROSHIMA A-BOMB SURVIVORS

The present report describes the G-band analysis; of somatic chromosomes in lymphocytes from 63 A-bomb survivors in Hiroshima to determine the type and frequency of radiation-induced chromosome aberrations. (1) The cells with stable-type chromosome aberrations (Cs cells) predominated among the aberrant cells, and showed a dose-dependent increase. All stable chromosome aberrations were classified into nine categories: reciprocal translocations, translocations of complex type, insertions, complex exchanges, peri- and paracentric inversions, terminal and interstitial deletions, and unidentified rearrangements. The frequencies of aberrations were found to increase with increasing dose for all aberration categories. Reciprocal translocations predominate in all dose ranges and among the chromosome aberrations classified. (2) The linear model was fitted to test the dose-response relationship for Cs cell frequencies. Employing a constant neutron RBEs of 10, an estimated linear slope of 15.2%/Sv was obtained for DS86 bone marrow dose with an intercept of 2.9 % at dose 0. (3) Statistical analysis of data on 3,370 break sites showed good correlations between relative DNA content and the distribution of chromosome breaks involved in translocations, although the involvement of chromosome 1 is significantly higher.