The lymphocytes of small mammals. A model for research in cytogenetics?

The influence of nuclear characteristics such as chromosome number, chromosome arm number or amount of R-band material on the yield of radiation-induced chromosome aberrations has been re-evaluated on the basis of some recent experiments with the harlequin-staining method to distinguish the first from subsequent divisions. The results obtained up to now show that differences in cell kinetics of stimulated peripheral blood lymphocytes, causing a different distribution of first and following mitoses at the time of observation, can result in an underestimate of the incidence of unstable chromosome aberrations such as dicentric chromosomes when the observations are performed at a standardized fixation time without taking into account the cell generation. If, however, only first-division mitoses are considered, the radiosensitivity of the cells appears to be independent on nuclear characteristics. Furthermore, observations on whole-body irradiated animals show that, owing to the very short survival time of lymphocytes carrying chromosome aberrations, mammals generally available for such experiments represent inappropriate models when cytogenetic effects in somatic cells are to be followed for long periods of time after an acute exposure to ionizing radiation or after a chronic exposure.