[Molecular-biological properties of blood lymphocytes of Hodgkin's lymphoma patients. Plausible possibility of treatment effect prognosis].

Hodgkin's lymphoma (HL) patients were investigated before and during chemical and radiation therapy. The properties of peripheral blood lymphocytes of the HL patients before treatment have been compared with healthy donors and the patients during the treatment. The genetic damage--frequency of cells with micronuclei (MN), the level of DNA single- and double-strand breaks (SSB and DSB), DNA-protein cross-links (DPC) have been studied. Biochemical and physiological parameters have been compared as well: the concentration of reactive oxygen species (ROS), the ability to the adaptive response induction. The radiosensitivity of lymphocytes in vitro exposed to the 1 Gy irradiation has also been determined (by MN test). It was shown that in Hodgkin's lymphoma patients' lymphocytes (in comparison with healthy donors) the frequency of cells with MN does not change, the level of SSBs and DSBs increases, the amount of DPC does not change, and ROS concentration (on average) significantly increases because of the part of the population that have high ROS content. The ROS concentration decreases to control level, the frequency of cells with MN increases, the level of DSBs does not change but the level of DPCs (which prevents the determination of DSB) increases in the patients during treatment. It was also discovered that lymphocyte radiosensitivity correlates with the MN cells frequency before treatment and the ROS concentration. These results make it possible to suppose that the high MN frequency and high ROS concentration in Hodgkin's lymphoma patient lymphocytes (before treatment) can serve as prognostic factors for the effectiveness of radio and chemical therapy.

[Particularities of blood lymphocyte response to irradiation in vitro in breast cancer patients].

DNA breaks and their repair efficiency were analyzed in irradiated in vitro lymphocytes (at doses 1 Gy, gamma-radiation of 60Co, dose rate 1 Gy/min) isolated from peripheral blood of 41 untreated patients with breast cancer and 25 healthy donors using the DNA comet assay under non-denaturing conditions (mainly double-strand DNA breaks (DSB), as well as apoptotic cell death using the DNA halo assay. To estimate the expression of bystander effect, the cells were incubated in a culture medium obtained from lymphocytes irradiated in vitro at doses 1 Gy. The average DSB level in blood lymphocytes of breast cancer patients was shown to be significantly higher (p < 0.05) compared with that in control donors. In general, the following effects were observed in irradiated in vitro lymphocytes of cancer patients: (1) increased sensitivity to y-radiation-induced DNA DSBs compared with lymphocytes from healthy donors, (2) reduced repair efficiency of these damages. Incubation of irradiated blood lymphocytes in a medium from irradiated cells led to an increased relative number of DNA DSBs and an elevated fraction of cells dying through apoptotic pathway both in blood lymphocytes from cancer patients and control donors. However, these non-targeted effects were more expressed for the blood lymphocytes of breast cancer patients.

[Genome damage and reactive oxygen species production in the progenies of irradiated CHO-K1 cells].

A series of experiments to study the delayed effects of gamma-radiation exposure in different generations of the progenies of the Chinese hamster ovary CHO-K1 irradiated cells has been conducted. It has been shown that in the progenies of the cells irradiated with a dose of 1 Gy, the following effects are observed: in the 9-27 cell generations - increase in the genome damage, intracellular production of reactive oxygen species, apoptotic cells percentage and cell sensitivity to additional exposure (irradiation at a dose of 10 Gy); in the 30-42 cell generations - decrease of the studied parameters up to control values and increased resistance to additional exposure. It is assumed that the decrease of the studied parameters up to the control values in the 30-42 postirradiation generations of cells is caused by elimination of damaged cells or transition of genomic instability into a hidden (latent) condition.

[Double-strand DNA breaks induction and repair in human blood lymphocytes irradiated with adapting dose].

Using a DNA-comet assay was shown that irradiation of human blood lymphocytes at G1 cell cycle with a low conditioning dose (5 cGy) induces an adaptive response (AR) manifested in reduction of the double-strand DNA (DSB) amount induced by challenging dose at 10 Gy. 24 h after conditioning irradiation (48 h after PHA addition) in cells irradiated at both conditioning and challenging doses a relative DBS amount was approximately 24% less in comparison to versus a control irradiated at challenging dose only. 48 h after adapting irradiation this index increased to approximately 35%, while 72 h after was decreased to approximately 29%. AR observed by us during 72 h after its induction did not accompanied by statistically significant changes in DBS repair enhancing. It is possible to assume that basic role in AR forming in lymphocytes under experimental conditions used by us playing the processes preventing radiation-induced DBS formation (antioxidant defense system activation, chromatin conformation changes ets).

[New approaches to diagnostics and identification of possible damages in normal humans under the conditions of microgravity and exposure to low doses of radiation].

The issues of radiation risk evaluation were addressed in the investigation of cytogenetic and molecular-biological changes in lymphocytes of cosmonauts and pilots of high-altitude airplanes. The goal was to determine individual sensitivity to the flight conditions and an additional factor (lymphocyte exposure to 1 Gy in situ), and adaptability as an index of induction of cell and organism resistance to extreme conditions.

[Influence of chronic exposure to low doses of gamma-radiation and 90Sr on the level of DNA breaks and cell sensitivity to hydrogen peroxide in the mouse spleen].

Using comet assay, a statistically significant increase (p < 0.05) in the level of DNA breaks in spleen cells was revealed in male CBA/lac mice exposed to gamma-radiation (1.7 cGy/day) or 90Sr (150-250 Bq/day) for 210 days. The level of DNA breaks also increased under combined exposure to both gamma-radiation and 90Sr (p < 0.05), but to a lesser degree than under exposure to each of these factors alone. Upon additional in vitro treatment of spleen cells with hydrogen peroxide, the relative increase in the level of DNA breaks was smaller in cells of irradiated mice than in the control. The ratio of the level of DNA breaks after hydrogen peroxide treatment to that before this treatment in control mice was 4.2 +/- 0.9, compared to 1.4 +/- 0.6 in gamma-irradiated mice, 1.9 +/- 0.8 in 90Sr-irradiated mice, and 2.3 +/- 0.8 in mice exposed to both gamma- and 90Sr-irradiation.

[Radiation-induced DNA double-stranded breaks and the dynamics of apoptotic death of human peripheral lymphocytes].

DNA double-stranded breaks and their association with the development of radiation-induced peripheral lymphocyte apoptosis were studied in healthy donors exposed to in vitro gamma-irradiation in a dose of 1 Gy. It was shown that irradiation in 1-Gy dose caused a significant (p < 0.05) increase in the frequency of cells in late apoptosis 4 hours after irradiation and a rise in their frequency in early apoptosis 24 hours following this procedure. A significant correlation (r = 0.52, p < 0.05) was recorded between the primary level of radiation-induced DNA double-stranded breaks and the frequency of cells in late apoptosis following 4 hours, which suggests that DNA double-stranded breaks as a signal to trigger cell apoptotic death are of great importance.

[Individual cytogenetic and molecular-biological characteristics of lymphocytes in blood of pilots and cosmonauts].

The purpose of this paper was the investigation of the pilots and of cosmonauts individual sensitivity to the fly conditions, to the additional irradiation (in the dose of 1 Gy), the adaptive response manifestation (in the doses 0.05 and 0.5 Gy). The DNA comet assay (the double strand DNA breaks was determined) and the method of unstable chromosome aberrations in metaphase was used. The human blood lymphocytes was the object of investigation. The significant individual differences were discovered in pilots and in cosmonauts in the initial DNA damage; in the sensitivity to the additional irradiation. The frequency of the adaptive response induction was decreased in the pilots in the comparison with the control group. The adaptive response was registered in cosmonauts (3 men). It is supposed that DNA damage, chromosome aberrations, sensitivity to the additional irradiation, the adaptive response manifestations can be used as biological markers of individual risk disease.