CHROMOSOME PAINTING IN HIGHLY IRRADIATED CHERNOBYL VICTIMS - A FOLLOW-UP-STUDY TO EVALUATE THE STABILITY OF SYMMETRICAL TRANSLOCATIONS AND THE INFLUENCE OF CLONAL ABERRATIONS FOR RETROSPECTIVE DOSE ESTIMATION

Follow-up fluorescence in situ hybridization (FISH) measurements of sy mmetrical translocations were performed in peripheral blood lymphocyte s from 12 highly irradiated victims of the Chernobyl nuclear power pla nt accident biannually, between September 1991 and July 1994, to inves tigate the persistence of these aberration type with time post-exposur e. Translocations were determined using biotin-labelled painting DNA p robes for human chromosomes 1, 4 and 12 and a digoxigenin-labelled alp ha-satellite pancentromeric DNA probe. In 11 of 12 cases the transloca tion frequencies remained fairly constant during the observation perio d, which allows to generate comparable dose estimates on the various s ampling times. In one case (no. 9) the existence of a cell clone conta ining the consistent chromosome rearrangement t(1;13) (q25;q14) was id entified using FISH in rehybridized slides with a digoxigenin-labelled painting DNA probe for chromosome 13 and a separate G-banding analysi s. To obtain reliable dose estimates, total translocation frequency ha s to be corrected for the high contribution (16.5-23.5%) of this clona l translocation.