IRRADIATION-INDUCED CHROMOSOME ABERRATIONS IN NORMAL HUMAN LEUKOCYTES IN CULTURE

Abstract

An investigation of irradiation-induced chromosome aberrations in human leukocytes in short-term culture is described. In the production of one-hit aberrations there appeared to be a linear response to dose, but no dose-rate effect. The data were compatible with either a linear or a possible power- function relationship between dose and aberration frequency in the production of two-hit aberrations. The small sample size was considered to be the most probable explanation for this lack of discrimination. A defintte dose-rate response was observed in the production of twohit aberrations, the larger number being produced at the higher dose-rate. It is difficult to compare induction rates as derived from different laboratories, owing possibly to differert methods of scoring, and also to attempt to derive break-rates'' by combining one-hit and two-hit aberration data. Because of a definite dose-rate effect on the production of two-hit aberrations, and also because these are expected to occur as a power-function of the dose, induction rates might more properly be calculated for each type of aberration separately. These studies indicate that irradiation-induced polyploidy follows from the initial induction of endoreduplication. The chromosome pairs of the endoreduplicated cells appear to fall apart at the first mitotic division following diplochromosome induction,more » to result in tetraploid daughter cells. Short-term cultures of human leukocytes provide a satisfactory system in which to examine irradiation effects. (auth)« less