Effects of Exposure of Animals to Oxygen Atmosphere at Low Pressure on Lipid Peroxidation and Antioxidant Defense.

Relatively short-term (2.5 or 5 h) exposure of Wistar rats to oxygen atmosphere at moderate pressure (1.10-1.15 atm) resulted in an increase in LPO level and reduction of antioxidant activity in the blood serum. An increase in malondialdehyde concentration 1 day after termination of the exposure was followed by a decrease in the inhibiting activity of free radical oxidation of liposomal phospholipids induced by Fe(II) ions (100 µm). Malondialdehyde concentration increased by 1.29 times already after 2.5-h exposure and did not changed when the duration of the exposure to oxygen atmosphere was prolonged to 5 h. These data confirm the necessity of using substances potentiating antioxidant defense of the body during exposure to normobaric oxygenation.

Geno- and cytotoxic effects in bone marrow cells and peripheral blood induced by the prolonged administration of 131I to the laboratory rats. / GENO- TA TsYTOTOKSYChNI EFEKTY V KLITYNAKh KISTKOVOGO MOZKU TA PERYFERYChNOI KROVI, INDUKOVANI TRYVALYM NADKhODZhENNIaM RADIOIZOTOPU 131I DO ORGANIZMU LABORATORNYKh ShchURIV.

OBJECTIVE: to evaluate the state of to assess the state of hematopoietic system of experimental rats according to the geno and cytotoxic effects in bone marrow and changes in morphology composition of peripheral blood caused by prolonged 131I intake. MATERIALS AND METHODS: Within 15 days sodium iodide with activity of 29,3 kBq/animal was daily orally administered to Wistar rats. At 1, 2, 3, 7 and 15 days specific radioisotope activity, level of micronuclei in bone marrow cells, cyto toxicity index, number of erythrocytes and leucocytes in peripheral blood were determined. RESULTS: It is established that the maximum genotoxic effect induced by 131I prolonged intake was formed at the early terms of observations followed by the reduction of cytogenetic damage in bone marrow cells of rats, while the cytotoxic effect of 131I was formed at the remote terms of administration. Changes in peripheral blood morphology were caused by left shift leukocytosis due to immature forms of neutrophils. In leucograms throughout the experi ment increased levels of lymphocyte atypical forms were observed. CONCLUSION: Prolonged administration of 131I to the laboratory rats does not cause dose dependent changes of cyto and genotoxic markers in the bone marrow and peripheral blood cells.

Radiation-induced instability of human genome. / Radiacionno-inducirovannaja nestabil''nost'' genoma cheloveka.

A brief review is dedicated to the phenomenon of radiation-induced genomic instability where the increased level of genomic changes in the offspring of irradiated cells is characteristic. Particular attention is paid to the problems of genomic instability induced by the low-dose radiation, role of the bystander effect in formation of radiation-induced instability, and its relationship with individual radiosensitivity. We believe that in accordance with the paradigm of modern radiobiology the increased human individual radiosensitivity can be formed due to the genome instability onset and is a significant risk factor for radiation-induced cancer.

Radiation-induced chromosomal instability of human lymphocytes as a marker of breast cancer risk. / Radiacijno-indukovana hromosomna nestabil''nist'' limfocytiv ljudyny jak pokaznyk ryzyku raku grudnoi' zalozy.

OBJECTIVE: to assess the variability of the levels of chromosome aberrations induced by the in vitro irradiation of lymphocytes of breast cancer (BC) patients in comparison with healthy individuals. Materials and methods. Samples of peripheral blood for lymphocyte cultures were obtained from 44 healthy women and 37 primary patients with BC (T1-2N1M0). Lymphocyte X-ray irradiation was carried out at G0 and G2 phase of lymphocyte cell cycle (G0 and G2 assay) with the dose of 1,5 Gy before PHA stimulation in G0 assay and 0,5 Gy - at 47 h of cultivation in G2 assay. Preparations of metaphase chromosomes were made according standard protocols. Results and conclusions. Inter-individual variation of G2 chromosome aberration yields was significantly higher in comparison with G0 chromosomal radiosensitivity in both examined groups. According to G2 assay the fraction of individuals with elevated chromosomal radiosensitivity among healthy women and BC patients was 11.4 and 38 %, respectively. The results obtained support the concept of association between predisposition to BC, radiationinduced G2 chromosomal instability and efficiency of DNA repair activated by cell irradiation in G2 phase. It is assumed that individuals with elevated G2 aberration scores from the control group need further examinations on the BC risk and primary prevention of radiation induced cancer.

Fractionated low-dose radiation exposure potentiates proliferation of implanted tumor cells.

AIM: The purpose of this study is to test whether whole-body fractionated exposure of tumor-free animals to low doses of low-LET radiation (at the total delivered dose of 1.0 Gy of X-rays) is capable of potentiating growth of subsequently implanted tumor cells. MATERIALS AND METHODS: Adult male rats were fractionally exposed to low doses of X-rays (10 acute exposures with 0.1 Gy each and with a frequency of 1 exposure per 3 days). The next day after the last irradiation rats were implanted with Guerin carcinoma (GC) cells. On the 12th and 18th days after implantation of GC cells, animals were sacrificed, and the mass of tumors was measured by weighing them, although the kinetics of tumor growth was also examined by daily measurements of the dimensions of tumors. Cytotoxic effects in the bone marrow were assessed flow cytometrically in acridine orange-stained unfractionated bone marrow cells using the ratio of polychromatic erythrocytes (PCE) to normochromatic erythrocytes (NCE). RESULTS: In irradiated rats, tumors grew apparently faster than in unirradiated rats for up to 18 days after implantation of GC cells. On the 18th day after implantation of GC cells the average value of the mass of tumors in irradiated rats was 2.8-fold higher compared with the average value of the mass of tumors in unirradiated rats (p < 0.05). On this day post-implantation, the bone marrow in irradiated animals was 1.8-fold more suppressed (as evidenced by decreased PCE/NCE ratios) than that in animals that were irradiated, but were not implanted with GC cells (p > 0.05), and was 1.4-fold more suppressed than that in animals that were not irradiated, but were implanted with GC cells (p > 0.05). CONCLUSION: Fractionated irradiation of tumor-free animals with low doses of X-rays potentiates proliferation of subsequently implanted GC cells. This potentiation seems to be associated with radiation-induced impaired hematopoiesis.

Chromosomal radiosensitivity in Ukrainian breast cancer patients and healthy individuals.

AIM: Recent studies showed that increased chromosomal damage induced by ionizing radiation is observed among patients with different tumor types. The aim of the study was evaluation of chromosomal radiosensitivity in breast cancer (BC) patients (n = 37) and healthy women (n = 44). METHODS: Chromosomal radiosensitivity was assessed with G0 and G2 assay. For G0 assay lymphocytes were exposed in vitro to 1,5 Gy of X-rays before culture setting. For G2 assay lymphocytes were irradiated with 0,5 Gy of X-rays after 47 h of incubation. RESULTS: Significant differences in mean scores both of G0 and G2 assay between breast cancer patients and controls were observed indicating the increased chromosomal radiosensitivity of lymphocytes of cancer patients. 11% of healthy women and 38% of BC patients were determined to be radiosensitive with G2 assay. CONCLUSION: Obtained results support the concept of association between elevated individual G2 chromosomal radiosensitivity and predisposition to BC.

The long-range cytotoxic effect in tumor-bearing animals.

AIM: The relationship between cancer and patient health is still of great interest for experimental and clinical oncology. The tumor can adversely affect surrounding and distant tissues as well. However, effects of the tumor on distant tissues are much less studied than its effects on surrounding tissues. This study was aimed to test whether the tumor could trigger cytotoxic and/or genotoxic signals with respect to the distant proliferative tissue such as bone marrow. MATERIALS AND METHODS: Rats were subcutaneously implanted with Guerin carcinoma cells, and on the 12(th) and 18(th) days after implantation both cytotoxic and genotoxic effects were assessed by flow cytometry in acridine orange stained unfractionated bone marrow cells isolated from femur. The cytotoxic effect was assessed using ratios of the following cell populations: total nucleated cells (TNC)/total enucleated erythrocytes (TE); polychromatic erythrocytes (PCE)/normochromatic erythrocytes (NCE). The genotoxic effect was assessed by quantification of micronucleated PCE (MNPCE) within the population of PCE. RESULTS: A significant cytotoxic effect was observed in tumor-bearing animals on the 12(th) and 18(th) days after implantation (≈ 2-fold decrease in both TNC/TE and PCE/NCE ratios compared with corresponding parameters in control animals). There was also a genotoxic effect in these animals (a slight increase in the number of MNPCE), however, this effect was insignificant. The PCE/NCE ratio reversely correlated with the tumor weight which is suggestive of the link between erythropoietic cytotoxicity and tumor progression. CONCLUSION: Cytotoxic insult to the bone marrow is likely to be associated with the mechanism(s) triggered by distantly located tumors whose growth may correlate with the cytotoxic effect.

Cancer prevention today: from healthy lifestyle and early detection to integrative multidisciplinary prevention and treatment.

Cancer prevention is recognized to be one the most efficient strategy in reducing cancer incidence and mortality. The world leading experts in the field of basic, clinical, epidemiologic and behavioral science presented their most innovative and promising findings and achievements during the Eighth Annual AACR International Conference on Frontiers in Cancer Prevention Research held from December 6-9, 2009, in Houston, TX, USA. In total around 800 participants from all over the world took an active part in the rich variety of the Conference session formats covering wide area of the most vital cancer research problems with strong emphasis on the early detection research, the latest developments in the tumor microenvironment, international prevention mechanisms, integrative prevention, targeted prevention and treatment, and efficient implementation of basic sciences into clinical practice.

Increased individual chromosomal radiosensitivity of human lymphocytes as a parameter of cancer risk.

AIM: Evaluation of chromosomal radiosensitivity of healthy individuals and determination those with the increased susceptibility to radiogenic cancer. METHODS: Cytogenetic examination of radiation induced injuries in lymphocytes of healthy individuals (n=103) was carried out on the basis of G(2)-assay. Test system of peripheral blood lymphocytes with metaphase analysis was used. RESULTS: On the basis of the obtained "stage-effect" and "dose-effect" calibrating curves the scheme of cytogenetic examinations of healthy individuals was developed. Analysis of cytogenetic parameters induced by G(2) irradiation at 1.5 Gy dose revealed their high interindividual variability. The highest differences were registered for chromatid type aberrations (CV=42.1%) with the chromatid break predominance in the spectrum (CV=37.5%). Statistical analysis of the distributions of the obtained individual cytogenetic parameters indicated 12% individuals with increased chromosomal radiosensitivity. CONCLUSIONS: Cytogenetic evaluation of individual chromosomal radiosensitivity based on G(2)-assay has its perspectives in the formation of groups with increased risk of radiogenic cancer developing and its primary prophylactics among healthy population.

Persistence of chromosome aberrations in peripheral lymphocytes from Hodgkin's lymphoma remission patients.

PURPOSE: To analyse spontaneous and in vitro bleomycin-induced chromosome aberrations in peripheral lymphocytes taken from Hodgkin's disease patients after prolonged (up to 31 years) remission periods, and to consider these data from the point of view of the carcinogenic potential of anticancer therapy. MATERIALS AND METHODS: Conventional analysis of chromosome preparations stained with azure-eosin. RESULTS: The mean frequency and patterns of both spontaneous and induced aberrations in remission patients were significantly different from comparison groups (healthy donors and primary Hodgkin's disease patients). Individual values were characterized with high variation and did not show correlation with post-therapy time. New cancer cases diagnosed in remission patients were more frequent in subjects with high chromosome sensitivity to in vitro bleomycin challenge than in patients whose sensitivity to bleomycin was at a control level. CONCLUSIONS: The results are interpreted as suggesting that the tumorigenic potential of radiochemotherapy is mediated via induction of genetic instability in exposed cells. Long after the therapy, the instability may become an initiating event in the development of new malignancies in affected tissues, whereas the instability induced in haemopoietic stem cells may reveal itself in peripheral lymphocytes derived from formerly exposed precursors.

Cytogenetic adaptive response in cultured human lymphocytes: dependence on the time of exposure to adapting and challenging doses of gamma-rays.

Human lymphocytes from 16 healthy donors were exposed in vitro to an adapting dose of gamma-rays (0.05 Gy) at G0, or G1, or G1/S stage of the cell cycle and subsequently to a challenging dose of gamma-rays at G1, or G1/S, or S (1 Gy), or G2 (0.5 Gy) stage. Frequencies and distributions of the induced chromosome aberrations were analyzed in first-division metaphases. The data averaged over the donors revealed the protective action of the adapting exposure under the irradiation schemes with the challenging dose delivered at S or G2 stage. The majority of aberrations induced at these stages belonged to the chromatid type, and their yield was significantly higher in G2-exposed cells than in S-exposed cells. However, the relative reduction of the challenging dose effect (about 34%) in the adapted cells did not depend on the magnitude of this effect, and its value remained the same (within the experimental error) if aberrations were subdivided into chromosome and chromatid types or grouped as total deletions and total fragments. The adaptive response was not revealed under the schemes with the challenging dose delivered at G1 or G1/S stage. Analysis of the individual results showed that, in one and the same donor, the adaptive response could be observed under one irradiation scheme and not observed under other schemes, the most effective schemes being those with the challenging dose delivered at G2 stage. Four donors, however, did not show the adaptive response even under such schemes. Data on aberration distributions suggested that different repair processes, rather than a unique one, may underlie the adaptive response.

The effects of radiation and alkylating agents on chromatin degradation in normal and tumour lymphoid cells.

The dynamic of chromatin degradation was studied in thymocytes and LS/BL tumour cells. In permeabilised LS/BL cells, the rate of DNA degradation induced by endogenous calcium and magnesium-dependent endonuclease was approx. 25 times slower than in thymocytes. In LS/BL cells irradiation does not induce chromatin degradation. The alkylating agent TS 160 induced chromatin degradation in both LS/BL lymphosarcoma cells and thymocytes.

A comparison of chromatin degradation in irradiated normal and tumorous lymphoid cells.

Irradiation of mice with doses of 2 and 4 Gy induced extensive chromatin degradation in the thymocytes within 6 hours accompanied by an increase in polydeoxynucleotide (PDN) content (36 and 42 times, respectively). Fifteen hours after irradiation the PDN level was considerably lower, however, still being 4.7 and 14 times the control values after doses of 2 and 4 Gy. The PDN content in control LS/BL lymphosarcoma cells was similar as that in the thymocytes of non-irradiated mice. Unlike in the thymocytes, irradiation of lymphosarcoma cells did induce no statistically significant increase in the PDN level 6 and 15 hours after the irradiation, respectively. It has been reported previously (Matyásová et al. 1973) that chromatin of LS/BL cells degraded similarly as that in the irradiated thymocytes. The results of the present experiments thus provide additional evidence for changes of LS/BL cell properties due to long term cultivation. These cells, however, are still able to react by chromatin fragmentation to nitrogen mustard treatment.

The radiosensitivity of lymphosarcoma cells as determined by the liver colony method.

The liver colony method is based on the observation that intravenous injection of an appropriate number of LS/BL cells into isologous non-irradiated hosts leads to the formation of colonies of proliferating cells in the livers of these animals. The relationship between the number of cells injected and the number of colonies appearing in the livers was determined. This technique was used to measure the radiation sensitivity of LS/BL cells and it yielded a Do of 1.05 Gy. The results show that LS/BL cells have a similar radiation sensitivity as other mammalian cells. The liver colony assay used to determine the radiation sensitivity of the lymphosarcoma LS/BL cells can also be used whenever the number of viable tumour cells in a suspension is to be estimated.

Viscosimetric analysis of the occurrence and repair of DNA single-strand breaks in irradiated animal tissues.

The yields of immediate DNA single-strand breaks in normal tumour tissues of irradiated animals were measured by a viscosimetric method of determination of high-polymer single-strand DNA molecular weight in alkaline nuclear lysates. It has been shown that in irradiated thymus, bone marrow leukocytes, Ehrlich ascitic carcinoma and Zaidel hepatoma cells (first group by tissues) in vivo the yields of DNA single-strand breaks were characterized by 80 to 130 eV per break. In in vivo irradiated liver, lymph node, spleen, and sarcoma 180 cells (second group of tissues) the yields of DNA single-strand breaks have been characterized by 30 to 40 eV per break. DNA single-strand breaks of the first group of tissues have rejoined 1 hour after the irradiation in vivo; DNA single-strand breaks of the second group have not done so.

Transformation of Bacillus thuringiensis subsp. galleria protoplasts by plasmid pBC16.

Protoplasts of the entomopathogenic bacterium Bacillus thuringiensis subsp. galleria were transformed by plasmid pBC16. The frequency of transformation was much lower than that of Bacillus subtilis. All isolated B. thuringiensis transformants were characterized by increased sensitivity to lysozyme as compared with the original strain.