IRRADIATION-INDUCED CHROMOSOME ABERRATIONS IN NORMAL HUMAN LEUKOCYTES IN CULTURE

Abstract

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 definite dose-rate response was observed in the production of two-hit 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 different 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, to result in tetraploid daughter cells.