The cytogenetic effects of 22-MeV neutrons

22-MeV neutrons affecting the culture of human peripheral blood lymphocytes have been studied for their cytogenetic peculiarities. Linear character of the dependence of chromosome aberrations yield within the dose range of 0.2-4.0 Gy is noted. Relative biological efficiency of 22-MeV neutrons reaches the highest values at low doses (18.8-2.4). Pair fragments and dicentrics prevail in spectrum of aberrations.     

Decrease of incidence of chromosome aberrations after a course of hyperbaric oxygenation

The influence of the course of hyperbaric oxygenation (HBO) on the peripheral blood lymphocytes chromosomes of 7 patients with different pathology and of 3 healthy volunteers was studied. It is proved that after HBO course the frequency of chromosome, aberrations of chromatid type hasn't been practically changed whereas the frequency of aberrations of chromosome type significantly decreases by three times on the whole.     

Quantitative analysis of sister chromatid exchanges in the cell]

Assuming a random nature of distribution of sister chromatid exchanges (SCE) in a karyotype, the formulae have been obtained allowing the calculation of the number of SCE that are overlooked because of a limited resolving power of the SCE detection method. The results obtained mean that the actual number of SCE is more than the observed one, the part of overlooked exchanges being increased with the heightening of the SCE level. Taking into account overlook exchanges, the formula has been obtained that makes possible the calculation of the expected number of SCE observed in any group of chromosomes. These results were applied in the analysis of the SCE distribution among chromosomes. A better conformity has been obtained between the expected results and the observed ones, than under the assumption that the observed SCE are distributed in proportion to the lengths of chromosomes. The obtained formulae are of use in interpreting the lack of the observed SCE in small chromosomes and the excess of them in large ones.     

Modified method of differential staining of sister chromatids]

A modified method of obtaining differential staining of sister chromatids is described. It is simple, rapid, and effective, and at the same time inexpensive and accessible, since it allows one to use available reagents. When 5-bromdeoxyuridine was administered 24 hours before fixation into the Chinese hamster cell culture the percentage of metaphases with a differential chromatid staining constituted 95--98, and when this substance was administered 28 hours before fixation into the human lymphocyte culture this percentage varied from 75 to 92, depending on the individual. The mean number of sister chromatid exchanges in human lymphocytes failed to depend on the time of fixation.