Effects of bleomycin on Down's syndrome lymphocytes in culture.

Blood lymphocytes from 3 Down's syndrome (DS) and 3 age- and sex-matched normal probands were studied for the induction of chromosomal aberrations and sister-chromatid exchange (SCEs). Treatment with bleomycin (30 and 60 ng) at the initiation of culture showed a dose-dependent increase in the incidence of dicentric and ring chromosome aberrations. In contrast, the cells which were treated for the last 24 h in culture with bleomycin did not show an increase in chromosome-type aberrations. The proportion of metaphases in M1, M2, and M3 in cultures was not different between DS and normal cells. Sister-chromatid exchange frequency did not show significant changes between DS and normal individuals.