A new approach in the study of the differential radiosensitivity of mammalian chromosomes

Using the harlequin-staining technique to distinguish the first from later mitotic divisions, the influence of the cell-cycle duration on the frequencies of aberrations induced in lymphocytes has been studied for two species, man and rabbit, displaying apparently great differences in radiosensitivity. These results demonstrate that, at 48 hr, the standardized time of cultivation used in the studies reported in the literature, only 27% of rabbit lymphocytes are in first division whereas 45% are in second and 28% in third. Providing only cells in first division are examined, there exists, in fact, no significant difference between man and rabbit with respect to the yield of radiation-induced dicentric chromosomes.