[THE INFLUENCE OF THE PREPARATION PRETREATMENT ON IN SITU DETECTION OF 5-METHYLCYTOSINE IN METAPHASE CHROMOSOMES AND IN INTERPHASE NUCLEI].

Qualitative and quantitate analysis of DNA methylation in situ at the level of cells, chromosomes and chromosomal domains is extremely important for the diagnosis and treatment of various diseases, the study of ageing and the consequences of environmental impacts. An important question arises, whether the revealed in situ methylation pattern reflects DNA methylation per se and (or) availability of the DNA for antibodies, which in turn depends on the peculiarities of chromatin structure and chromosome condensation. These events can lead to an incorrect evaluation of the actual pattern of DNA methylation. To avoid this shortcoming as far as possible, we have modified the most widely used method of revealing 5-methylcytosine in situ with monoclonal antibodies. Here we have shown that the detection of DNA methylation staining of chromosomes including C-heterochromatin, chromosomal arms and sister chromatids is drastically dependent on pretreatment of chromosomal preparations for immunocytochemical study using fluorescent antibodies. Using undifferentiated stem cells of mouse embryonal carcinoma line F9, it has been found that change in preparations storage results in a sharp fluorescence decrease up to complete disappearance of the signal in centromeric heterochromatin. With the help of the method described in the work, we have first revealed the asymmetry of sister chromatids methylation in metaphase chromosomes of F9 cell and lymphocytes of human periphery blood. This may lead to asymmetry of transcriptional signature of daughter cells after division. The proposed here modification of 5-methylcytosine detection in situ provides a more complete characterization of methylation of chromosomes and chromosomal domains, compared to previously published methods.

[Comparative analysis of cytogenetic examination of control groups of subjects carried out in different Russian laboratories].

The incidence of unstable chromosome aberrations in peripheral blood lymphocytes from unirradiated control subjects was analyzed using cytogenetic data obtained from 9 cytogenetic laboratories located in Moscow, St.-Petersburg, Obninsk, and Dubna (Russia). The objective of this study was to estimate the level and spectrum of spontaneous chromosome aberrations in human lymphocytes. 1140 blood samples were taken from 1112 subjects (594 men and 546 women) aged 1 to 72. The total metaphase number was 466795. The uniform Giemsa method for peripheral blood lymphocyte cultures was used. After counting 466795 metaphases, 4288 chromosomal aberrations of various types were classified. The most frequent types of aberrations were acentrics and chromatid deletions. They made up 90% of the total number of aberrations. The remaining 10% were exchange aberrations. The number of chromosome exchanges (dicentrics and centric rings) was twice the number of chromatid exchanges. Overall, the portion ofcells with chromosomal or (and) chromatid aberrations was 0.89 +/- 0.01%; the frequency of acentrics was 0.29 +/- 0.01; the frequency of dicentrics was 0.046 +/- 0.003; the frequency of unstable chromosome aberrations was 0.35 +/- 0.01; and the frequency of chromatid aberrations was 0.57 +/- 0.01 per 100 cells.

Cytogenetic study of professional rescue rangers of Russian Ministry of Emergencies.

Cytogenetic studies in rescue rangers of the Russian Ministry of Emergencies has shown that this category of specialists are exposed to genotoxic factors during their professional activity. The level of induction of cytogenetic injuries of rescue team members depended on labor conditions, genotype (glutathione-S-transferase M1 and T1 xenobiotic detoxication genes), and tobacco smoking.

[Chromosomal aberrations and parameters of oxidative stress in Chernobyl clean-up workers in a remote period after ionizing radiation]. / Khromosomnye aberratsii i pokazateli okislitel'nogo stressa u likvidatorov posledstvii avarii na Chernobyl'skoi AES v otdalennom periode posle deistviia ioniziruiushchei radiatsii.

This investigation was performed to test a supposition about the influence of disturbances in antioxidative system on cytogenetical parameters in Chernobyl' clean-up workers. It was shown that some cytogenetical parameters straightly correlated with the parameters of oxidative stress, while other cytogenetical parameters show just reverse correlations. Apparently, these relationships are not of cause-and-effect type, but they reflect a complex processes occurring in humans for a long period after radiation exposure.

[Some complexities in evaluating radiation-induced mutagenic effects in man]. / O nekotorykh slozhnostiakh v otsenke radiatsionno-indutsirovannykh mutagennykh éffektov u cheloveka.

Chromosomal aberrations in somatic cells (circulating lymphocytes) have been investigated in a remote period in different groups of people who suffered from radiation accidents. The chromosomal radiation markers were found even decades after irradiation. The question about the necessity of registration of non-classical mutagenic effects after human irradiation is raised.

[Chromosomal anomalies of human gametes and intrauterine selection. Research on female gametes]. / Khromosomnye anomalii gamet cheloveka i vnutriutrobnyi otbor. Issledovanie zhenskikh gamet.

The results of cytogenetical analysis of human oocytes are summarized. The chromosomal disorders in human gametes and in spontaneous abortions are comparatively analyzed.

[Chromosome abnormalities of human gametes and intrauterine selection. Male gametes]. / Khromosomnye anomalii gamet cheloveka i vnutriutrobnyi otbor. Issledovanie muzhskikh gamet.

Man appears to be unique among mammals with respect to very high level of reproductive wastage. It seems reasonable to suppose that many early losses attribute to cytogenetical abnormalities. However, this stage of pregnancy is difficult to be studied. The investigation of gametes is one of the most reliable ways to estimate the cytogenetical disorders in early life. The results from cytogenetical analysis of human male gametes are summarized.

[Chromosomal disorders in the oocytes of rats after stress exposure in the preovulatory period]. / Khromosomnye narusheniia v ootsitakh krys posle stressovogo vozdeistviia v preovuliatornom periode.

Female rats at the stage of proestrus have been subjected to a stress effect--immobilization for an hour. Oocytes were cytogenetically analyzed and embryonal mortality was determined. It is shown that this stress effect at the end of the fist meiotic division of the oocytes increased the rate of aneuploid gametes and the level of embryonal mortality.

[Variants of chromosome compactization and the estimation of the capacity of mammalian oocytes for further development]. / Varianty kompaktizatsii khromosom i otsenka sposobnosti ootsitov mlekopitaiushchikh k dal'neishemu razvitiiu.

The morphology of chromatin in spontaneously ovulated rat's oocytes was investigated. The degree of chromatin condensation was shown to vary widely: along with the typical cytological picture of metaphase II, both highly condensed (clamped) and decondensed ("not typical") forms of chromosomes were observed. A direct relation was discovered between the prevalence of the not typical morphological forms of oocyte chromosomes and the level of embryonal death. The shape of clamped and decondensed forms increased in the oocytes from old rats and in post-ovulatory aged oocytes.