[Fusion of Erwinia chrysanthemi spheroplasts in an electric fields].

A new approach has been elaborated for electrofusion of Erwinia chrysanthemi spheroplasts. The new approach consists of superimposition of high voltage impulses on the pellet of tightly contacting cells in the course of centrifugation. The mixture of spheroplasts of two genetically marked strains was placed into the special centrifuge chambers and spinned for 15 min at 2500 g to get a compressed pellet between chamber electrodes.

[Principles of cytogenetic examination for detecting occupational hazards].

The main principles are stated of carrying out a cytogenetic examination of human populations on the basis of critical analysis of data from literature and the authors' own experience in this field. The method for estimation of sister chromatid exchanges is shown expedient to be used together with the chromosome aberration analysis in carrying out cytogenetic examinations. Statistically ascertained approaches are adduced to select the necessary amount of persons examined in groups and the number of cells for analysis when using methods for estimation of sister chromatid exchanges and chromosome aberrations.

[Statistical analysis of the elimination of chromosome-type aberrations and the fate of the aberrant cells].

The regularities of elimination of gamma-ray induced chromosome aberrations in human nonstimulated lymphocytes and the fate of aberrant cells have been studied. The cells at the first, second and third post-irradiation divisions were identified by the technique of differential staining of sister chromatids. A mathematical model has been suggested to describe the processes of formation, multiplication and death of the cells with dicentrics.

[Effect of thiophosphamide on the frequency of chromosome aberrations in cells heterozygous for ataxia-telangiectasia].

Chromosome aberration rate in ataxia-teleangiectasia (AT) heterozygotes exposed to thiophosphamide in lymphocyte culture was compared to that in control donors. AT heterozygotes demonstrated an increased number of chromosome aberrations. The patterns of concentraion relationships in AT heterozygotes are depictable by the same equation as in control donors.

[Spontaneous level of sister chromosome exchanges and their distribution in human cells].

Blood of practically healthy donors of both sexes (27 females and 23 males) was cultured under the standard conditions during 96 hours. Bromodeoxyuridine (BUdR) was added at the final concentration of 10 mkg/ml 28 hours before harvesting. The slides were stained with acridine orange and Giemsa for differential staining of chromatids.

[Individual variation in the frequency of chromosome aberrations under the influence of chemical mutagens. I. Inter-cultural and inter-individual variations in the effect of mutagens on human lymphocytes].

The study of the distribution law of human peripheral blood cultures for the sensitivity to thiophosphamide was performed. In the first experiment the blood from one person was used, in the second one the blood was used from different persons. "The percent of aberrant cells" and "the number of chromosome breaks per 100 cells" were scored.

[Individual variations in the frequency of chromosome aberrations following exposure to chemical mutagens. III. Interindividual differences at different stages of the cell cycle].

The object of this investigation was the sensitivity to chemical mutagens of chromosomes of human lymphocytes obtained from different individuals. The distribution of individuals with respect to their sensitivity to fotrin and cytosine-arabinoside was studied. Tests for two characteristics were used, viz.

[Individual variations in the frequency of chromosome aberrations following exposure to chemical mutagens. II. Interindividual variation in the frequency of chromosome aberrations in the presence of different mutagen concentrations].

The object of this investigation was the distribution of human periferal blood cultured obtained from different donors with respect to their sensitivity to different concentrations of thiophosphamide (10, 20 and 30 mcg/ml for 1 hour). Two test characteristics were studied, "the proportion of aberrant metaphases" and "the number of chromosome breaks per 100 cells". It is shown that the distribution of individuals does not depend on the mutagen concentration, being normal in all the series of experiments.

[Mathematical modeling of the relationship between the cytogenetic effect and the concentration of the mutagen].

The effect of different concentrations of thiophosphamide on the culture of human leucocytes was investigated. Three mathematical models were studied, one of which, being satisfactory for describing the experimental data, was chosen. According to this model a quantity of aberrant cells changes with the concentration of thiophosphamide non-linearly and can be described according to the equation A=exp[-(KC+alpha)2], where A is a portion of normal cells, C - a concentration of a mutagen, K and alpha - the coefficients, while exp[-alpha2] is the control level of normal metaphases.