[The effect of polymorphism of genes of xenobiotics detoxication on the frequencies of spontaneous and induced chromosome aberrations in human lymphocytes].

Here presented the data on the frequencies of chromosome aberrations in lymphocytes of peripheral blood of 97 volunteers depending on genotypes by genes of xenobiotics detoxication before and after gamma-irradiation with dose of 1 Gy in vitro. The frequencies of aberrations were estimated by analyzing not less than 500-1000 metaphases per person. The data of cytogenetic analysis were compared with the results of PCR-genotyping of loci GSTM1, GSTT1, GSTP1, CYP1A1, CYP2D6, NAT2, and MTHFR. The significant differences by the frequencies of aberrations between "single-locus" genotypes were not found except for GSTM1 locus, for which the enhanced frequency of spontaneous aberrations of chromosome type in "positive" genotypes compared to "zero" ones, i.e., homozygotes by deletion (p = 0.04) was observed. The minimum frequency of spontaneous aberrations of chromosome type was recorded for carriers of double homozygotes by deletion of GSTM1-GSTT1: 0.0006 +/- 0.0003 against 0.0027 +/- 0.0003 for the rest of genotypes (p = 0.016 by the Mann-Witney test). The frequency of gamma-induced chromosome aberrations was correlated with the total amount of minor alleles in loci GSTP1, NAT2, and MTHFR (r = 0.25 at p = 0.0065).

[Stable and unstable chromosome aberrations in humans and other mammals in relation to the problems of biological dosimetry].

Literature data of long-term cytogenetic follow-up of people exposed to radiation as a results of different radiation accidents are considered for the purpose of discussing of some problems of biological dosimetry. The results obtained for mammals are also presented. Of particular interest is a decrease in the level of dicentrics and symmetrical translocations in peripheral blood lymphocytes with the time after acute exposure depending on the dose of irradiation. The frequency of dicentrics decreases in accordance to the exponential law passing the fast and slow phases of elimination. In different radiation situations the values of the parameter which defines the half-life period of lymphocytes characterizing 50% reduction of cells with dicentrics markedly vary. However a general regularity is a decrease in the parameter value as the exposure dose increases. The level of stable translocations estimates by the EISH method remains relatively constant at doses below 1-2 Gy. At higher doses their level in peripheral blood lymphocytes declines with time due to which the retrospective dose appears to be underestimated. The reasons of such regularity, the role of various factors affecting the scoring of translocations, criteria of analysis of the given chromosome aberrations are discussed in the context of common agreements between leading European laboratories on the use of FISH for improving biological dosimetric estimates.

[Genotype dependence of cytogenetic and epidemiological characteristics in the liquidators of the accident at the ChNPP].

The dependence of the level of unstable chromosome aberrations and nononcological diseases on the genotype in 57 liquidators of the ChNPP accident was studied. Candidate genes presumably affecting radiosensitivity were highly polymorphic loci of xenobiotic detoxication genes (glutathione-S-transferases GSTM1, GSTT1, GSTP1) and the 5,10-methylenetetrahydrofolate reductase gene (MTHFR) involved in DNA methylation and synthesis. An increased frequency (0.014 +/- 0.001 per cell) of unstable chromosome aberrations, including radiation-specific dicentrics and centric rings (0.0015 +/- 0.0002 per cell), has been found to be preserved in the group of liquidators examined in 2006-2007. No associations of polymorphism for each of the studied genes with cytogenetic parameters were revealed. Increased frequencies of chromosome aberrations were recorded in homozygous carriers of a deletion at the GSTM1 locus in combination with homozygosity for minor alleles at the MTHFR and GSTP1 loci (p = 0.00002 and p = 0.0233, respectively). The number of homozygous carriers of the minor allele GSTP1 was increased among patients with chronic obstructive pulmonary disease and in liquidators with acute circulation disturbances (p = 0.014 and p = 0.04, respectively). Double homozygotes for GSTM1 and GSTT1 deletions were significantly more frequent among subjects with benign tumors (cysts, polyps, p = 0.015) and with benign thyroid tumors (p = 0.017). This genotype has proved to be protective for patients with severe cardiovascular diseases (acute circulation disturbances, p = 0.027).

[The theory and practice of constructing calibration curves in biodozimetry].

The methodical peculiarities of experimental construction of regression "dose-effect" relationships used for the dose reconstruction are discussed. The method of computer simulations is applied to study the efficiency of different statistical procedures for plotting regression curves as well as the dependence of errors in dose prediction on the volume of examined material and on the choice of doses for a calibration curve. The causes of essential variability of calibrations obtained by different teams of researchers are discussed. A number of methodical recommendations is given for statistical processing of cytogenetic data. The procedure of constructing calibration dose dependence of the frequency of dicentrics on the basis experiments with in vitro gamma-irradiation of lymphocytes from blood samples of 5 donors is considered in detail. The expressions for statistical errors occurring in the dose reconstruction made on the base of the frequency of aberrations were derived and checked by the computer experiment.

[The problem of the transgeneration phenomenon of genome instability in sick children of different age groups after the accident at the Chernobyl Nuclear Power Plant].

A complex genetic examination of children which belong to two cohorts and their parents were carried out. The first cohort included children and constantly living on territories contaminated with radionuclides (Novozybkov district, Bryansk region). They were subdivided in groups according to the ontogenetic age periods of development of their parents at the time of the Chernobyl accident. In the children born in 1986-1995 the level of aberrant genomes is significantly higher as compared to the control (p < 0.001). In children born in 1998-2002 the differences are insignificant (p > 0.05). The frequency of aberrant genomes had a tendency to decrease with the period of time between the birth date of a child and the moment of the accident. Analysis of the results of cytogenetic investigation for the same living on territories with different densities of radioactive contamination (zone I-- 627-688 kBq/m2, 137Cs and zone II-- 135-402 kBq/m2, 137Cs) revealed insignificant differences in the spectrum and average frequencies of chromosome aberrations. The second cohort included children born in 1987-1991 and 1993-2002 from irradiated fathers (Chernobyl clean-up workers) and unirradiated mothers living on territories without radionuclide contamination. These children also displayed increased frequencies of aberrant genomes as compared to the control (p < 0.001). The analysis of the dynamics years of birth of cytogenetic disturbances in the same cohorts of children showed the average frequencies of aberrant genomes remain higher than the control level. In most of the children of both cohorts the repair synthesis of genome DNA by gamma- and UV-radiation is reduced as compared to one in the children from the control group.

[The cytogenetic effects in persons who suffered as a result of the accident at the Chernobyl Atomic Electric Power Station]. / Tsitogeneticheskie éffekty u lits, postradavshikh v rezul'tate avarii na Chernobyl'skoi AES.

Frequency of chromosome aberration was evaluated in 537 persons taken part in amelioration after the accident. The highest rate of aberration was found in covering builders and dosimetric: 3.24 +/- 0.25 and 3.11 +/- 0.43 per 100 cells, respectively. The mean rate of aberrations among the Chernobyl NPP staff was 2.37 +/- 0.20 per 100 cells, in the other examined groups the mean yield of aberration varied from 1.31 to 1.47 per 100 cells. The found aberration rates correspond to the equivalent whole body doses in the range from 131 to 515 mGy as evaluated by the established dose-response curve. In the group of covering builders the individual aberration rates varied more markedly, and corresponded to the equivalent whole body dose up to about 1 Gy. Slides of 27 individuals were checked by an automated dicentric scoring system. The results showed a satisfactory correlation between the frequencies of dicentrics per chromosome detected by routine and computer methods.

[The effect of prolonged gamma irradiation at a decreasing dose rate on survivability and gene mutation induction in cultured Chinese hamster cells]. / Vliianie protiazhennogo gamma-oblucheniia so spadaiushchei moshchnost'iu dozy na vyzhivaemost' i induktsiiu gennykh mutatsii v kul'tiviruemykh kletkakh kitaiskogo khomiachka.

Continuous gamma irradiation at decreasing dose rate was shown to be less effective than acute exposure with regard to the lethal effect and frequency of mutations of resistance to 6-thioguanine in cultured Chinese hamster cells. The cell population subjected to continuous irradiation was more radioresistant than the intact one. Lethal and genetic effects of continuous irradiation at decreasing dose rate were mainly determined by the contribution of the radiation dose received during the first 24 h of exposure.

[Mutations of resistance to 6-thioguanine following roentgen irradiation and subsequent treatment with cytosine arabinoside combined with hydroxyurea in Chinese hamster cells in the G1 phase]. / Mutatsii rezistentnosti k 6-tioguaninu posle rentgenovskogo oblucheniia i posleduiushchei obrabotki tsitozinarabinozidom v sochetanii s oksimochevinoi kletok kitaiskogo khomiachka v G1 faze.

A study was made of the effect of two-hour treatment of Chinese hamster cells with cytosine arabinoside (AraC) combined with hydroxyurea (HU) at the G1 phase of the cell cycle on lethal and mutagenic effects of X-radiation (50 to 400 cGy). The inhibitors were shown to increase a spontaneous mutation level of the resistance to 6-thioguanine: this increase augmented by 3 times as the time the treatment increased from 1-2 to 6 h. However, while sharply enhancing the inactivating effect of X-radiation (the enhancement coefficient was 2.6) Arac+HU caused an additive, or a somewhat lesser, effect as estimated by the yield of mutations. It is suggested that AraC combined with hydroxyurea fail to modify the radiation-induced premutation damages.

[Cytogenetic effect of irradiation and subsequent cytosine arabinoside and hydroxyurea treatment on Chinese hamster cells in the G1 phase of the cell cycle]. / Tsitogeneticheskii éffekt oblucheniia i posleduiushchei obarbotki tsitozinarabinozidom i oksimochevinoi kletok kitaiskogo khomiachka v G1-faze kletochnogo tsikla.

A two-hour treatment of Chinese hamster cells at the G1 stage of the cell cycle with arabinoside cytosine combined with hydroxyurea after X-irradiation (50-300 cGy) produced a 2- to 4-fold increase in the frequency of chromosome aberrations. The mitotic selection method was used to synchronize the cells. The potentiating effect of the inhibitors, that was estimated by the yield of centric exchanges, decreased with increasing radiation dose. It is suggested that DNA repair processes determining a linear component of the dose-response curve are modified within the dose-range under study.

[Induction of mutations resistant to 6-thioguanine by fast neutrons in cultured Chinese hamster cells]. / Induktsiia mutatsii rezistentnosti k 6-tioguaninu bystrymi neitronami v kul'ture kletok kitaiskogo khomiachika.

A study was made of induction of mutations, resistant to 6-thioguanine (TGr), and reproductive death of Chinese hamster cells after irradiation by fission-spectrum fast neutrons (mean energy of 0.75 MeV) with doses of 10-130 cGy. A high relative biological effectiveness (RBE) of fast neutrons was shown. The maximum RBE values (13-16) were within the dose range inducing minimum mutagenic and lethal effects. RBE decreased with the dose increase. Inspite of high mutagenic effectiveness of neutrons, estimated according to TGr mutation frequency per cell per dose unit, their relative mutagenic effectiveness, estimated per cell per one lethal event, did not substantially differ from that of X-radiation.

[Gene mutations, chromosome aberrations and survival after the x-ray irradiation of a Chinese hamster cell culture protected by cysteamine]. / Gennye mutatsii, aberratsii khromosom i vyzhivaemost' posle rentgenovskogo oblucheniia kul'tury kletok kitaiskogo khomiachka v usloviiakh zashchity tsisteaminom.

The protective effect of cysteamine against 6-thioguanine-resistance (TCr) mutations, chromosome aberrations and inactivation caused by X-ray in cultured cells of Chinese hamster (clone 431) has been studied. The dose-effect curves have been obtained under irradiation condition without protector and with it. Dose-modifying factor of 2 was calculated for chromosome aberrations and cells inactivation and 2,8 for TCr mutations. It is supposed that the cysteamine acts on the general mechanisms involved in damages realization which results in gene mutations, chromosome aberrations and cell inactivation.

[Patterns in the x-ray induction of mutations in resistance to 5-thioguanine in Chinese hamster cell cultures studied using cysteamine]. / Izuchenie zakonomernostei induktsii rentgenovymi luchami mutatsii rezistentnosti k 6-tioguaninu v kul'turakh kletok kitaiskogo khomiachka v usloviiakh primeneniia tsisteamina.

X-ray induction of 5-thioguanine resistance mutations and the protective effect of cysteamine were studied in cultured cells of chinese hamster clone 431. Expression of mutations was studied for 8--10 days of post-irradiated growth, when cells surviving radiation at doses 200, 400, 600, 800 R were passing from 3 to 12 generations. The maximum frequency of induced mutations was found after 3-5 generations. After reaching the maximum, the number of registered mutations decreased with the number of cell generations. Pre-irradiated treatment with 5mM cysteamine decreased induction of mutations 2--4 times when using doses 200--800 R. The frequency of mutations induced by mere radiation increased non-linearly with increasing doses, while in the presence of cysteamine the linear dose dependence was observed.

[Processes of chromosome damage repair in unstimulated human peripheral blood lyphocytes by the method of fractional irradiation and temperature variation]. / Izuchenie protsessov vosstanovleniia povrezhdenii khromosom v nestimulirovannykh limfotsitakh perifericheskoi krovi cheloveka metodom fraktsionnirovannogo oblucheniia i var'irovaniia temperatury

The fractionation experiments were carried out on resting lymphocytes. Non-stimulated lymphocytes were X-irradiated at the total dose of 200 r separated into two equal parts by either 5-hour or 20-hour intervals. The whole blood samples were kept during the intervals between the exposure at the temperature of 20 degrees centigrade or 37 degrees centigrade. All the cultures were made after the last radiation exposure at 37 degrees centigrade. Dicentrics and centric rings were scored. It is shown that a fractionation effect takes place in resting lymphocytes when the whole blood was kept for intervals between the half-dose at 37 degrees centigrade and is absent at the temperature of 20 degrees centigrade. It is suggested that there is the repair in lymphocytes at the stage G0, AT least, from the dose of 100 r.

[Reparative processes of damaged chromosomes in non-stimulated human peripheral blood lymphocytes by the fractionated irradiation method and temperature variation]. / Izuchenie protsessov vosstanovleniia povrezhdenii khromosom v nestimulirovannykh limfotsitakh perifericheskoi krovi cheloveka metodom fraktsionirovannogo oblucheniia i var'irovaniia temperatury

The fractionation experiments were carried out on resting lymphocytes. Non-stimulated lymphocytes were X-irradiated at the total dose of 200 r separated into two equal parts by either 5-hour or 20-hour intervals. The whole blood samples were kept during the intervals between the exposure at the temperature of 20degrees C or 37degrees C. All the cultures were made after the last radiation exposure at 37degrees C. Dicentrics and centric rings were scored. It is shown that a fractionation effect takes place in resting lymlf-dose at 37degrees C and is absent at the temperature of 20degrees C. It is suggested that there is the repair in lymphocytes at the stage Go, at least, from the dose of 100 r.