[Elimination of radiation-induced chromosome damage in a culture of human peripheral blood lymphocytes. II. The frequency of aberrations in the 1st to 5th postradiation mitoses].

The number of chromosome aberrations was estimated in the first-fifth mitoses in human peripheral blood lymphocytes cultured with PHA after gamma-irradiation in vitro with 1.5, 3 and 6 Gy doses. The lymphocytes of irradiated blood were incubated at 37 degrees with BrdU (20 micrograms/ml) for 62-122 hours. The first-fifth postirratiation mitoses were identified by the sister chromatid differential staining technique. At all the doses used with cells passing through the first and next postirradiation divisions, the decrease in the number of aberrant metaphases and all the aberration of chromosome type were observed, and with the increase in dose speed of their elimination was growing. No essential differences were found in frequency of paired fragments in the first-fourth mitoses after irradiation with 1.5 Gy dose, in the first-third mitoses after irradiation with 3 Gy dose or in the first-second mitoses after irradiation with 6 Gy dose. In lymphocyte cultures, exposed in 3 and 6 Gy doses, the number of dicentrics in the second mitosis was approximately 2 times smaller than in the first one, and in the third mitosis it was 2 times smaller than in the second one. In the first mitosis, almost all the dicentries were accompanied with paired fragments, in the second and third mitoses the shape of dicentrics without fragments was nearly 30-70%, and in the fourth-fifth mitoses it was almost 95-100%. The decrease in the number of atypical chromosomes, with cells passing through the first and next postirradiation mitoses, was noted only when lymphocytes irradiated with 6 Gy dose were analysed; with 1.5 and 3 Gy doses, the frequency of aberrations in the first-fifth and in the first-fourth mitoses was approximately equal.