[Before and after Chernobyl Accident (Memoirs, Researches Hypotheses)].

In the first part of the article the results of studies performed in the 1970-1980s on the progeny of irradiated animals (drosophila, mouse, rat) are presented. It was found that except severe disorders in this progeny named non target genetic radiation effects were observed (genome instability, increased cancer risk, impaired fitness) which were similar to the late somatic radiation effects. The hypothesis on the likeness of pathogenic nature of somatic and genetic effects of ionizing radiation was proposed. Comparison of effects of parental irradiation in humans and animals gave reason to propose that the frequency of severe disorders observed in the progeny (stillbirth, birth defects etc.) depends on the reproductive potential of a species. In the second part of the article the reminiscences on the author's work in Chernobyl in 1987 are presented. The last part is devoted to description of the main results, obtained in the post Chernobyl period in the frames of various national and international projects.

Frequency of chromosomal aberrations in lymphocytes of peripheral blood in patients with solid tumors.

There was carried out a study to compare the frequency of spontaneous chromosomal aberrations (CA) in lymphocytes of peripheral blood between the group of cancer patients with different types of solid tumors and the group of healthy people of the same age. There was established a significant increase in the average frequency of CA in cancer patients. Analysis of the group of patients has revealed its heterogeneity: in the majority of patients the individual frequency of CA significantly exceeded the average frequency of CA in the control group, in some - did not differ from that. The first patients were described as the group with "generalized" genomic instability. Also this group differed by increased radiosensitivity of lymphocyte chromosomes during their irradiation in vivo.

Dose-Response of Micronuclei in Binucleated and Mononucleated Lymphocytes from Cytochalasin Culture (Irradiation in vivo and in vitro).

The dose-responses of micronuclei (MN) in binucleated (BN) and mononucleated (MONO) lymphocytes cultivated with cytochalasin B (CBMN-assay) were studied. Irradiation of lymphocytes was performed in vitro (donor A) at the single dose of 1 and 2 Gy of (60)Co y-rays, or in vivo, during whole-body exposure of a cancer patient (donor B) to (60)Co γ-rays each day at a single dose of 0.115 Gy up to a total dose of 1.15 Gy. The linear dose-response for MN was determined in both BN and MONO lymphocytes of donor B. It means that when CBMN assay is applied, the MN in MONO cells represent those preexisted in vivo before each exposure. On the contrary, in lymphocytes of donor A irradiated in vitro an essential elevated MN yield with an - increased dose was observed only in BN lymphocytes. A slight dose dependent elevation of MN in MONO cells seems to be due to either their division before cytochalasin was introduced in the culture medium or their insensitivity to the CB block of cytokinesis.

[Comparative evaluation of the predictive value of UroVysion and AURKA FISH tests of urine sediment cells for the diagnosis of bladder cancer].

Informative value of two tests based on FISH of exfoliated urothelial cells in urine sediment (AURKA and UroVysion) was compared in the group of patients (31 persons) with the history of bladder cancer. Coincidence in results of both FISH assays was found in 93.5%. These preliminary data offer the possibility of replacing the expensive UroVysion kit by the less expensive AURKA FISH probe and it could be used for monitoring of recurrence in bladder cancer patients.

[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.

[The polymorphism of DNA repair genes XRCC1, XRCC3 and the level of chromosomal aberrations in the Uranium workers].

Association between the polymorphism of DNA repair genes XRCC1 Arg399ln and XRCC3 Thr241Met and the frequency of chromosomal aberrations in the uranium workers was studied. The Gln/Gln genotype of gene XRCC1 was associated with a significant increase in the number of chromosomal aberrations as compared to the corresponding homozygous wild type Arg/Arg (p < 0.05). The frequency of chromosomal aberrations in heterozygous carriers of the XRCC3gene Thr/Met was lower than in the homozygous carriers of the wild type Thr/Thr (p < 0.001).

[Radiation-induced "bystander effect" revealed by means of adaptive response in cocultured lymphocytes from humans of different genders].

The "bystander effect" was investigated in mixed cultures of lymphocytes from humans of opposite genders. Development of the adaptive response (AR) in non-irradiated female/male cells was estimated after adaptive pretreatment of opposite gender lymphocytes, chromosome aberrations being evaluated. Experiments were performed using two schedules of adaptive (0.05 Gy) and challenging (1 Gy) irradiations: G0-G1 and G1-G1. The results obtained indicate the development of a mediated adaptive response ("bystander effect") in the lymphocytes neighboring pre-irradiated cells, as well as the influence of a time scheme of adapting and challenging irradiations on the amount of induced chromosome aberrations in mixed cultures and a possible dependence of the adaptive response intensity on the donor gender.

[The age dynamics of spontaneous and induced in vitro chromosome aberrations in human lymphocytes under natural and radiation induced senescence].

The frequency of translocations, detected by FISH in lymphocytes of control donors increased with increasing age as quadratic function. This process is elevated in persons exposed to radiation at low-doses. It means that the level of translocations could be used as an indicator of biological age. Moreover the frequency of translocations should be taken into account when biological reconstruction of absorbed dose is carried out. The frequency of dicentrics, detected by FISH and FPG methods increased with age in both groups compared and in equal rate, the linear model being fit the data best. The rate of age-increase for translocations is much higher than for dicentrics. Chromosomal radiosensitivity of lymphocytes in vitro tends to increase with age in control group and significantly decrease--in exposed one, that is low-dose radiation exposure changes the character of age dependence of cytogenetic radiosensitivity.

[The dose-response of unstable chromosome exchanges in lymphocytes of cancer patients undergone whole-body fractionated gamma-rays exposure at the total dose 1.15 Gy].

The dose-response of unstable chromosome exchanges (UCE) in lymphocytes of 4 cancer patients undergone whole-body fractionated gamma-rays exposure (at the daily dose of 0.115 Gy up to the total dose 1.15 Gy) was compared with corresponding dose-response for lymphocytes of the same patients, irradiated in vitro at the same dose range. In vivo irradiation yielded lower frequency of UCE on the dose unit than in vitro irradiation. It was shown that the in vivo dose-response curve gives more adequate dose estimation than in vitro one. This curve could be used for reconstruction of absorbed dose in the cases of analogous character of in-controlled irradiation of people.

[Association of genetic polymorphism in GSTM1 and GSTT1 with the frequency of chromosomal aberrations in the uranium workers].

Association between genetic polymorphism in GSTM1 and GSTT1 and frequency of chromosomal aberrations in the workers occupationally exposed to uranium during 1-25 years in Tselinniy mining/milling complex in the North Kazakhstan was investigated. It was found that the frequency of chromosomal aberrations in uranium workers was significantly higher than in matched control, being correlated with the duration of exposure. No association between frequency of chromosomal aberrations and polymorphism for each gene (GSTM1 and GSTT1) was observed, whereas frequency of chromosomal aberrations in the homozygous carriers of null alleles of both GSTM1 and GSTT1 genes was higher than in the homozygous carriers of normal alleles.

[Transgenerational transmission of radiation-induced genomic instability and predisposition to carcinogenesis].

The paper deals with a history of radiobiological investigations carried out at the Center since 1925 which have contributed to the present-day conception on the influence of damaged DNA on stochastic (carcinogenesis) and non-stochastic (accelerated aging) late radiation pathology in exposed biological objects. A phenomenological and pathogenetic similarity of somatic (in irradiated organisms) and genetic (in progeny of irradiated parents) consequences of exposure to ionizing radiation is suggested and our data are presented pointing to a possibility of germ cells of irradiated parents to transmit genomic instability to the progeny thus increasing risk of carcinogenesis.

[The effect of low-dose irradiation and of age on the in vitro radiosensitivity of human lymphocytes].

The effect of low-dose irradiation and of age on the radiosensitivity of human lymphocytes was studies in two groups: control (67 people) and exposed to uncontrolled low-dose irradiation in past (165 people). Radiosensitivity of lymphocytes was estimated by the level of chromosome aberrations induced in vitro by gamma-radiation Cs137 at the dose 1.5 Gy. In exposed children the frequency of induced chromosome aberrations was higher and in the exposed adults--lower in comparison to the coresponding controls. To investigate an age response of the number of chromosome aberrations three statistical approaches were used: the correlation analysis of individual data, the correlation analysis of means for 10-years intervals, the comparison of 3 age groups. In control group no significant alteration in the level of induced chromosome aberrations with age was found. However the significant negative correlation between these two parameters was revealed in exposed group, which likely is due to the opposite direction of differences in radiosensitivity of exposed children and adults from the corresponding controls.

[The effect of age and low-dose irradiation on the chromosomal aberration frequency in human lymphocytes].

The effect of age and of low-dose irradiation on the base level of chromosomal aberrations in lymphocytes was studied in two human groups: control one (128 people) and exposed in past to uncontrolled low-dose irradiation (283 people). In exposed group the frequencies of all types of chromosome aberrations were higher comparing to control group. For the investigation of the age response of the number of chromosomal aberrations three statistical approaches were used: correlation analysis of individual data, correlation analysis of mean frequencies of chromosomal aberrations for 10 years intervals, comparison of 3 age groups (young, middle age and old). In control group the significant increase of the level of chromosomal aberrations with age was found only when six 10-year intervals were analysed. In exposed group significant age increase of chromosomal aberration frequency (particularly due to double fragments) was observed with all 3 approaches. Low-dose irradiation of people is supposed to cause the functional defects of repair systems, controlling the level of genetic damages and they accumulate more intensive through age.

[Investigation of radiation-induced "bystaner effect" using model of adaptive response in mixed lymphocyte culture from humans of different gender].

The novel method for the investigation of radiation-induced "bystander effect" has been tested on the model of mixed lymphocyte culture from humans of different gender. The "bystander effect" was estimated by the ability of nonirradiated female/male cells to develop an adaptive response in mixed culture with irradiated at the dose 0.05 Gy of X-rays G0 lymphocytes of opposite gender. The preliminary results indicate that both irradiated lymphocytes and non-irradiated but neighbouring with pre-exposed cells are less susceptible to the genetic damages manifested as chromosome aberrations induced in G1 lymphocytes by a subsequent high dose of X-ray (1.0 Gy). Direct adaptive response as well as indirect one were expressed more obvious in female lymphocytes.

[Transgenerational transmission of radiation induced genomic instability].

Stability of genome is one of the evolutionary important trait of cells. Various mutations (gene, chromosomal, genomic) as well as artificial manipulations with genomes (inbreeding, DNA transfection, introduction of Br-DU in DNA) cause the genetic instability. Ionizing radiation is known as the factor which induced instability of genome in late mitotic descendants of cells after in vitro and in vivo exposure. Radiation induced genetic instability can be transmitted through germline cells. On the cell level both types of radiation induced genomic instability are manifested in elevated frequency of mutations, chromosome aberrations, micronuclei, increased radiosensitivity, disappearance of adaptive response, changes in gene expression. In studies of 1970-1980 years clear evidences on the different morphological and functional injuries in tissues of irradiated organisms as well as in tissues of the progeny of exposed parents were obtained. On the organism level the instability of mitotic and of meiotic progeny of irradiated cells is resulted in increased risk of cancer and of other somatic diseases. It seems to be useful to review the earlier radiobiology literature where delayed and transgenerational effects of ionizing radiation on tissues and on organisms level were clearly shown in animals. For the estimation of pathogenic role of radiation induced genomic instability in humans, particularly in children of exposed parents the parallel study of the same human cohorts using clinical parameters and various characteristic of genomic instability seems to be very important.

[Complex cytogenetic characteristic of people suffered from Chernobyl accident].

A cytogenetic study was performed on Chernobyl cleanup workers, on their children, on persons evacuated from contaminated aeria (adult and children), on so named "veterans of particular risk" irradiated due to the accidents on the nuclear plant, testing of nuclear weapons etc. and on control donors. The yield of stable (FISH analysis) and of unstable chromosome aberrations, micronuclei in both lymphocytes and erythrocytes, HPRT mutations was found to be increased in exposed groups as compared to control ones. In children of liquidators and in evacuated children we observed genomic instability and increased in vitro chromosomal radiosensitivity. Acceleration of age accumulation of translocations characterized the exposed population in comparison with control group. People with the highest level of routine chromosome aberrations had cardiovascular and digestive diseases more often likely than those with the lowest level. In frame of International Project ECP-6--"Biological dosimetry" the dose-responses for dicentrics and translocations were constructed in dose range 0-100 cGy of gamma-irradiation on the base of data of 8 laboratories. On cancer patients undergone whole-body gamma-irradiation (every day at the dose 11.5 cGy to a total of dose 57.5 cGy) we constructed the dose-responses for the dicentrics and translocations and compared them with the dose-responses for these aberrations after the in vitro irradiation of lymphocytes of the same patients. For the dicentrics the effectiveness of the in vivo irradiation was less than of the in vitro one. No differences were found for translocations.

Comparative study of postradiation genotoxic changes in mammalian cells by biochemical and cytogenetic methods.

The results of studying the genotoxic effect of radiation on endometrial cells of irradiated rats using comet assay correlated with the index of spontaneous DNA degradation. Studying the genotoxic effect of in vitro irradiation (2 Gy) on human lymphocytes by means of chromosome analysis and fluorometric assay of nucleoids DNA in irradiated leukocytes also yielded similar results. Measuring of the biochemical marker holds much promise as an express method of evaluation of the genotoxic effect of radiation on mammalian somatic cells.

[Age dymamics of stable chromosome aberration frequency in humans with natural and pathological senescence]. / Vozrastnaia dinamika chastoty stabil'nykh khromosomnykh aberratsii u cheloveka pri estestvennom i patologicheskom starenii.

The age dynamics of stable chromosome aberration (SCA) frequency was analysed by fluorescent in situ hybridization (FISH) in human blood lymphocytes derived from donors, irradiated by low doses of ionizing radiation (Chernobyl clean-up workers, nuclear weapon testers, etc.) and patients with hereditary premature aging--Werner's syndrome and Hutchinson-Gilford's syndrome. It was found that the level of SCA was age-dependent and increased in irradiated persons. So, the SCA level may be really an index of a so-called "radiation senescence", and may show a real biological age of irradiated persons. The patients with Werner's syndrome demonstrate increased SCA level in blood lymphocytes, corresponding to the premature aging of the organisms. But in the case of another form of premature aging--Hutchinson--Gilford's syndrome-- no rise of SCA level was found. Some possible reasons of such results are discussed.

[Cytological and molecular changes in the atypical case of accelerated human aging]. / Tsitologicheskie i molekuliarnye izmeneniia pri netipichnom sluchae uskorennogo stareniia cheloveka.

A complex research of cells of a patient with unusual form of premature ageing was made. The clinical picture is not typical for any of known forms of hereditary premature aging--progerias. Skin fibroblasts of the patient AG has limited proliferation capacity in vitro. It was shown by fluorescent-immunochemical hybridization (FISH-method), that the level of stable chromosome aberrations in AG blood lymphocytes was characteristic of aged 55-65 years, though as he was only 26 years old. Some characteristic peculiarities, typical for progerias, were found in the reaction of skin fibroblasts of AG to growth factors addition. Some clinical and biochemical peculiarities are results rather, than reasons of the disease. The conclusion is that the premature ageing in this case is a manifestation of Werner's syndrome--one of hereditary forms of accelerated senescence.

[Comparison of cytogenetic response of human lymphocytes to in vivo and in vitro exposure to low-dose gamma rays. Translocations and dicentrics detected by the FISH technique]. / Sravnenie tsitogeneticheskoi reaktsii limfotsitov cheloveka na obluchenie v malykh dozakh gamma-izlucheniia in vivo i in vitro. Translokatsii i ditsentriki, opredeliaemye FISH-metodom.

On peripheral lymphocytes of 5 cancer patients undergone wholebody therapeutic irradiation (at daily dose of 10 cGy up to total dose 50 cGy of 60Co gamma-rays) the dose response of unstable and stable chromosomal exchanges detected by FISH was compared with the dose response of the some aberrations in lymphocytes irradiated in vitro. The dose response fitted well to linear function. For dicentrics the lower slope of dose-response curve was found for in vivo irradiated lymphocytes as compared to the dose-response curve obtained for in vitro irradiated lymphocytes of the same patients. No difference between in vivo and in vitro irradiation of lymphocytes was found for translocations. The frequency of translocations increased faster with the dose than the frequency of dicentrics only in lymphocytes irradiated in vivo.