[Effect of temperature on the development of chromosome aberrations in human blood lymphocytes irradiated in pulse and continuous modes at BARS-6 reactor].

Summarized results of 5 repeated experiments of comparative study of radiation effects of the pulse reactor BARS-6 either in a single pulse or a continuos irradiation mode on human lymphocytes are presented. Higher efficiency (30-40%) of continuous irradiation (exposure duration 1 h) rather than pulse irradiation with ultra-high dose rates (1-2.5) x 10(6) Gy/min (pulse duration 65 micros) was confirmed. The efficiency ratio did not depend on the temperature, 20 degrees C or 0 degrees C, during the exposure. Cell repair system and chromatin conformation influence on the results obtained is discussed.

[The comparative analysis of gene and structural somatic mutations in inhabitants of Orel district areas contaminated with radionuclides as a result of Chernobyl accident].

The results of comparative analysis of gene and structural mutations found in peripheral blood lymphocytes of inhabitants of Orel district areas contaminated with radionuclides as a result of Chernobyl accident are presented. The average level of 137Cs contamination in those areas ranged about 22-113 kBq/m2. In the study group was found the enhanced frequency of somatic cells with gene and structural mutations compared with laboratory control level by synchronous applying a T-cell receptor (TCR) loci mutation assay and cytogenetic analysis of unstable aberrations. The case-control comparison was carried out using the measured mutation frequencies and cases of various thyroid gland sickness recognized by ultrasonic examination. The cytogenetic assay did not show the statistical difference between healthy group and subjects with thyroid gland sickness. The average frequency of TCR loci mutation cells in the subjects with thyroid gland sickness was found to be statistically higher comparing with healthy persons. This finding was true for each study region and for Orel district in total. The subgroup of subject exposed in utero in 1986, soon after accident was analyzed. Both cytogenetic and TCR loci mutation assays shown enhancement of average mutation frequency in somatic cells in the subjects of this subgroup with thyroid gland sickness comparing with healthy persons.

[Results of dynamic cytogenetic study of children and teenagers living in areas, radioactive by contaminated after the Chernobyl accident].

Results of multiyear cytogenetic study of children and teenagers living in areas, radioactive by contaminated after Chernobyl accident, were adduced. Mean density of 137Cs contamination in two compared living areas were 111 and 200 kBq/m2 and mean external doses accumulated for 1986-2001 were 6.7 and 11.4 mGy correspondingly. Averaged thyroid doses receives by subjects of all age groups in the second area were approximately 1.5 times higher than in the first area; in the youngest group (0-1 year) the doses were 114.3 and 174.3 mGy. During 17 years cytogenetic investigation approximately from 30% to 60% of examined persons were observed the increased level of chromosome aberrations in lymphocytes of peripheral blood. Average frequency of unstable aberrations (acentrics, dicentrics and centric rings) constituted about 0.4 per 100 cells (0.22 per 100 cells in controls) during all period of observation. Level of marker aberrations (dicentrics and centric rings) was increased almost all times of study and varied within 0.04-0.19 per 100 cell (0.03 in control group). The parallel investigation of frequency of stable aberrations by FISH method showed up their level about 3 times exceeding observed dicentrics level. Comparably higher indexes of cytogenetic disturbances were revealed in group exposed in utero during period of accident.

[The combined action of gamma irradiation and hyperthermia on the structure of the cell population in the Chinese hamster]. / Kombinirovannoe deistvie gamma-oblucheniia i gipertermii na strukturu populiatsii kletok kitaiskogo khomiachka.

A change in the structure of FAF-28 Chinese hamster cell population occurred during 24 h following gamma-irradiation or hyperthermia heating, or the effect of both factors was studied by flow cytofluorometry. With radiation delivered immediately after heating the distribution of cells among cycle phases was nearly the same as with hyperthermia alone: the share of cells at the S-phase was invariable during the first 4-6 h, then it slowly diminished; at G1 it slowly decreased and at G2 increased. When irradiation preceded heating the pattern of cell redistribution during the first hours was the same as that with radiation alone: the "wave" of transition from G1 to S phase was the same, but shorter in amplitude and longer in time; then cells were accumulated at G2+M and remained there for 24 h. Thus, of the two factors applied, the first was the major one in changing the cell population structure during the first hours after treatment. In 24 h the result was the same, that is, the considerable accumulation of cells at G2+M.

[DNA replication in mammalian cells exposed to the action of physical, chemical or biological factors. IV. 5-fluorodeoxyuridine modifies the effect of hyperthermia on DNA synthesis and the survival of HeLa cells]. / Replikatsiia DNK v kletkakh mlekopitaiushchikh pri deistvii faktorov fizicheskoi, khimicheskoi ili biologicheskoi prirody. IV. 5-ftordezoksiuridin modifitsiruet vliianie gipertermii na sintez DNK i vyzhivaemost' kletok HeLa.

Preliminary incubation of logarithmically growing HeLa cells with FUdR decreases an inhibitory effect of hyperthermia (43 degrees C, 1 hour) on DNA synthesis. The hyperthermia alone inhibits DNA synthesis considerably: the label in acid-precipitable material accounts for 30% of control level. Preliminary incubation of the cells with FUdR (10(-6)) for 24 or 6 hours (plus 18 hours in fresh medium) decreases the effect: the label yields account for 50 or 90% of the respective control levels. A molecular weight of nascent DNA synthetized in the cells after hyperthermia or incubation with FUdR is lower than the control one but it increases rapidly during postincubation. Nucleoid of cells treated with FUdR has a sedimentation velocity which exceeds that of the control cells by more than 25%. Preliminary incubation with FUdR sensitizes the cells to hyperthermia. The effect is not believed to be associated with cells synchronization since the treatment of the cells with FUdR for 2 or 6 hours, when FUdR itself does not exert its toxic effect, brings about sensibilization of cells to hyperthermia. It is suggested that modification of the cell viability and DNA replication are related to some changes of chromatine structure induced by FUdR.