[Effects of long-term low dose radiation--relationship between chromosomal translocation and the cellular oncogenes]

To clarify the late effects of long-term exposure to low doses of radiation, chromosomal aberrations in the lymphocytes of radiological technologists (RT) were analyzed by the trypsin G-banding method. Structural aberrations were identified in 384 (2.5%) of 15,442 cells analyzed from 53 RT as compared to 177 (1.6%) of 11,136 cells from 36 healthy controls. Most of structural aberrations in both groups was translocations, and this frequency was significantly higher in the RT than in the controls. Translocations of chromosomes, such as Nos. 1, 2, 7 and 14 in RT and Nos. 1, 3, 7 and 14 in controls, was observed in over 7% of the cells. 7/14 translocations were the most frequent reciprocal translocations in RT. However, the frequency of 7/14 translocations was not significantly different between the RT and controls. In these cases, most of the break points were localized in band 14q11-12 and 7q32-36. At the chromosomal sites which were related to the sites of ski, abl, myb, mos, myc, N-myc oncogenes, very low incidences of translocation were detected in RT. However, none of the RT demonstrated abnormal clones of cells with identical chromosomal aberrations.