MORPHOLOGICALLY ABNORMAL TAILED LYMPHOCYT E NUCLEI AND THEIR ASSOCIATION WITH DICENTRIC CHROMOSOMES IN PATIENTS EXPOSED TO IONIZING-RADIATION

Lymphocyte nuclei with a narrow outgrowth into the cytoplasm (''tail'' ) were detected on peripheral blood smears of patients exposed to ioni zing radiation during the clean up after the Chernobyl meltdown (liqui dators). On average, lymphocytes with tailed nuclei occurred at a freq uency of 0.43% and 0.15% in exposed patients (n = 101) and healthy don ors (n = 50), respectively; the difference between the samples was sig nificant, P < 0.001. The coefficient of correlation between frequencie s of lymphocytes with tailed nuclei and those with dicentric chromosom es was 0.74 (n = 27, P < 0.001). The frequency of lymphocytes with dic entric chromosomes was increased in 9 out of 10 patients, in which lym phocytes with tailed nuclei occurred at a frequency larger than 0.8%. A double-color FISH was used to localize centromeric (not more than tw o signals) and telomeric (not more than one signal) regions in nuclear tails. Abnormal tailed lymphocyte nuclei were assumed to result from breaking the chromosome bridges formed by the dicentric chromosomes.