2021 Volume 86 Issue 1 Pages 67-77
Radiation-induced chromosomal aberrations in cultured human peripheral blood lymphocytes have been investigated as a validated measure for biodosimetry. The analysis of the kinetics of cells carrying chromosomal aberrations in the early stage of cell proliferation is expected to provide a better understanding of the mechanisms underlying the transmission and persistence of chromosomal aberrations. However, studies on the fate of unstable aberrations in consecutive divisions are limited. In this work, morphology-based analyses of the chromosomal aberrations in the second metaphase (M2) cells by comparing with those in the first metaphase (M1) cells were conducted by using peripheral blood lymphocytes cultured in the presence of 5-bromo-2′-deoxyuridine (BrdU) for 48 and 72 h after in vitro 2.0 Gy gamma irradiation. Unstable chromosomal aberrations were analyzed by 4′,6-diaminido-2-phenylindole (DAPI) staining, in combination with fluorescence in situ hybridization (FISH) using painting probes of three different colors (three-color FISH). As a result, a high frequency of duplicated fragments was detected in unstable M2 cells, implying the persistence of cells with excess fragments generated in the first mitotic division by unequal segregation. A close microscopic observation of M2 cells showed irregularly shaped chromatin structure generated probably through the asynchronous replication of fragments generated in the first mitotic division. When compared with the results of M1 cells, the frequency of M2 cells carrying unstable chromosomal aberrations decreased by 43% and that of dicentric chromosomes per cell decreased by 46%. By revisiting morphology-oriented microscopic examinations, the cytogenetic features of cells carrying unstable chromosomal aberrations were precisely described.
