[An assessment of relative contribution of DNA reparation and glutathione-dependent pathway of detoxification in response of Chlorella algae to uranium].

Toxicity of 238U (as uranyl nitrate) in the range of 0.04-84 micromol/L for Chlorella (Chlorella vulgaris Beijerink) was investigated. The best approximation for relationship between the toxic effect in Chlorella and 238U Concentrations is observed using the hormetic Brain-Cousens model. A significant increase in Chlorella biomass, estimated as the optical density of suspension, as well as the level of fluorescence of chlorophyll was observed in the range of 17-29 micromol/L with the maximum at a 23 micromol/L. It was found that 38 micromol/L of 238U induced a significant toxic effect; while at 53 micromol/L inhibition of Chlorella biomass by 50% was observed. According to our observations, the toxic effect of low concentrations of 238U was increased in the presence of 0.02 micromol/L caffeine (used as inhibitor of DNA repair processes) or DL-buthionine-(S, R)-sulfoximine (used as a selective inhibitor of the key glutathione biosynthetic pathway).

[Radiation risk assessment for plant reference species (Pinus sylvestris and Vicia cracca) from the area of radium production waste storage].

The risk of an enhanced level of radionuclides of the uranium and thorium decay series in the environment for reference plant species (Pinus sylvestris and Vicia cracca) was assessed. 238U, 230Th, 226Ra, 210Po, 232Th and 228Th concentration factors for plants were found to be lower than one. The aboveground parts of Vicia cracca sampled from the area of the radium production waste storage mainly accumulated 22Ra, Pinus sylvestris branches--210Pb, 226Ra and 210Po. LOEDR calculated for the chromosome aberration frequency in both plant studies was 17-71 microGy/h. LOERD values for the reproductive capacity decrease in P. sylvestris and V. cracca were 17-71 microGy/h and 116-258 microGy/h, correspondingly. EDR10 for the chromosome aberration frequency in P. sylvestris and V. cracca were 148 and 347 microGy/h, that is, correspondingly, 255 and 708 times higher that background values. EDR10 for the plant reproductive capacity was 11-34 microGy/h, which 19-69 times increases the background values.

[Regularities of lateral distribution of uranium and thorium decay series radionuclides in the anthropogenically changed soils from the area of radium production waste storage].

Cartographical investigations of the territory of radium production waste storage has shown some changes in lateral differentiation of radionuclides of uranium and thorium decay series to occur during 27 years (1981-2008). Those changes are caused mostly by flat denudation typical for fluvial terrace. At present radionuclides of uranium and thorium decay series are concentrated mostly in flood lands and relief depressions. At the same time, decrease in the radionuclide activity concentration in 0-20 cm soil layer is observed with changes in lateral distribution. Total stocks of 226Ra, 210Pb and 210Po within catena soils studied in the northern and southern parts of the waste storage decreased 3-6 times, 238U - 2 times, and did not significantly change in case of 232Th during 27 years. Nonetheless, most of the samples studied are referred to radioactive waste both according to Russian standards (SPORO-2002) and IAEA safety norms (IAEA, 2004).

[Assessment of soil degradation in regions of nuclear power explosions at Semipalatinsk Nuclear Test Site].

Degree of the soil cover degradation at the "Balapan" and "Experimental field" test sites was assessed based on Allium-test of soil toxicity results and international guidelines on radioactive restriction of solid materials (IAEA, 2004) and environment (Smith, 2005). Soil cover degradation maps of large-scale (1 : 25000) were made. The main part of the area mapped belongs to high-contaminated toxic degraded soil. A relationship between the soil toxicity and the total radionuclide activity concentrations was found to be described by power functions. When the calculated value (equal to 413-415 Bq/kg of air dry soil) increases, the soil becomes toxic for plants. This value is 7.8 times higher than the maximal value for background territories (53 Bq/kg) surrounding SNTS. Russian sanitary and hygienic guidelines (Radiation safety norms, 2009; Sanitary regulations of radioactive waste management, 2003) underestimate the degree of soil radioactive contamination for plants.

[The assessment of no adverse effect doses for plant populations chronically exposed to radionuclides of uranium and thorium decay series].

Dose rates cause no adverse effects on natural populations of Pinus sylvestris L. and Vicia cracca L. inhabiting territories contaminated by uranium mill tailings and radium production wastes (Vodny settlement, Komi Republic) were determined. A significant increase in embryonic lethal mutation frequency in V. cracca legumes and decrease in seedlings survival rate as compared with control values were registered at dose rate equal to 1.67 mGy/day, that is 280 times higher than the one calculated for the reference site. The adverse effects in P. sylvestris expressed in increased frequency of chromosome aberrations in meristematic root tips and decreased reproductive capacity of seeds were determined at absorbed dose rate equal to 0.083 mGy/day. Data obtained show that the decrease in plant reproductive capacity in case of chronic exposure of radionuclides of uranium and thorium decay series can observe at lower weighted absorbed dose rates than in case of environmental contamination by artificial radionuclides.

[The assessment of radionuclide contamination and toxicity of soils sampled from "experimental field" site of Semipalatinsk nuclear test site].

Large-scale maps (1:25000) of soil contamination with radionuclides, lateral distribution of 137Cs, 90Sr, Fe and Mn water-soluble compounds and soil toxicity in "Experimental field" site of Semipalatinsk nuclear test site were charted. At present soils from studied site (4 km2) according to basic sanitary standards of radiation safety adopted in Russian Federation (OSPORB) do not attributed to radioactive wastes with respect to data on artificial radionuclide concentration, but they do in compliance with IAEA safety guide. The soils studied can not be released from regulatory control due to radioactive decay of 137Cs and 90Sr and accumulation-decay of 241Am up to 2106 year according to IAEA concept of exclusion, exemption and clearance. Data on bioassay "increase of Chlorella vulgaris Beijer biomass production in aqueous extract from soils" show that the largest part of soils from the studied site (74%) belongs to stimulating or insignificantly influencing on the algae reproduction due to water-soluble compounds effect. Toxic soils occupy 26% of the territory. The main factors effecting the algae reproduction in the aqueous extracts from soil are Fe concentration and 90Sr specific activity: 90Sr inhibits but Fe stimulates algae biomass production.

[Assessment of modern radioecological situation at nuclear explosion "Chagan" (Balapan Site, Semipalatinsk Nuclear Test Site, Kazakhstan)].

Results on estimation of modern radioecological situation at nuclear explosion "Chagan" based on large-scale cartographic studies (1:25000) of a test area (4 km2) are presented. Maximum gamma-irradiation doses were observed at bulk of ground surrounded a crater and at radioactive fall-outs extended to the North-East and to the SouthWest from the crater. Based on data on artificial radionuclide specific activity most part of soil samples were attributed to radioactive wastes according to IAEA (1996) and OSPORB (1999). Natural decrease of soil radioactivity up to safety level due to 60Co, 137Cs, 90Sr, 152Eu, 154Eu radioactive decay and 241Am accumulation-decay will not take place within the next 60 years at the studied area.

[The estimation of ionizing irradiation impact on Vicia cracca cenopopulations growing on the territory contaminated with the wastes of radium production].

The radiation exposure on cenopopulations Vicea cracca L. growing on the territory contaminated with the wastes of radium production was estimated. The relationship between the chromosome aberration in seedlings root tip cells and irradiation dose was found to be linear. The significant cytogenetic effects in chronically irradiated Vicia cracca cenopopulation are observed at doses (equal to 0.006-0.7 Gy) 10 times upward the natural radiation background level. The reduced reproductive success (significantly increased embryonic lethal mutation level) is observed at weighted absorbed doses (equal to 0.2-0.7 Gy) up to 200-700 times higher than the natural radiation background level. It is showh, that the radiation hygienic standards of permissible exposure are noticeably stricter that the radioecological limits.

[The mechanisms of 232Th and of Ce (III) toxic action on Chlorella vulgaris Beijer. Estimation of 232Th radiation impact contribution into toxic effect induced].

232Th and Ce (III) toxic effects and its modifications with caffeine and D,L-buthionine-(S,R)-sulphoximine on Chlorella vulgaris Beijer were studied using an optical density measure after 24 hours growth. Concentrations of 232Th or of Ce--toxic effect relationship were shown to be nonlinear. In the first (nontoxic) concentration range (for Ce 0.036-1.642 micromol/L and for 232Th 0.001-1.551 micromol/L) algae biomass production registered by optical density do not significantly differ from the control one. In the second (toxic) concentration range dose-effect relationship for 232Th is characterized with quadratic dependence and in the case of Ce--with exponential dependence. 232Th radiation component contribution into effect observed is appeared as induction of DNA damages additional to spontaneous at the radionuclide concentration (equal to 0.345 micromol/L) that is three times lower than in case of the non-radioactive chemical analog Ce (1.071 micromol/L).

[Quantitative estimation combined chemical and radioactive exposure on biological objects].

We summarized the researches to estimate the methods of combined (chemical and/or radioactive nature) factor action on biological objects. The data examined indicate that methods commonly used need a revision and adaptation in case of analyzing data on biological effects in natural plant and animal populations. Basic principles of evaluation of man-caused factor contribution into variation level observed in natural population are discussed.

[Genetic variance in Vicia cracca cenopopulation inhabiting site with enhanced level of natural radioactivity].

The contribution of low dose rate ionizing radiation into genetic variance in Vicia cracca L. cenopopulation inhabiting high natural background territories more then 40 years quantity estimation was made. Incorporated in the aboveground parts of Vicia cracca 230Th determine both the level of intrapopulation genetic variance and the adaptive possibility. Significantly increased frequency of double fragments was revealed in root tips of plants inhabiting all experimental plots. This type of damages depends on 226Ra concentrations accumulated in the aboveground parts of Vicia cracca. External irradiation influences the embryonic lethals. It was found that the relative contribution on mutagenesis induced by ionizing radiation was significant and was about 3-5% of the total variance.

[The effects on non-human species inhabiting areas with enhanced level of natural radioactivity in the north of Russia].

The results of long-term radioecological investigations in areas with enhanced level of natural radioactivity in the north of Russia were summarized. Negative changes in animals and in plants inhabiting areas with increased level of natural radioactivity in Komi Republic were revealed. These changes were reveased in increased levels of chromosomal and genomic mutations, destructive processes in internal tissues of animals, disturbances of reproductive functions and reduction of posterity's viability. Compensatory processes that allow animals and plants to survive in extremely adverse conditions both radium and uranium-radium contamination were observed as well. However, obvious signs of adaptation didn't observed. In contrast, in different plant species inhabiting area with increased level of natural radioactivity in taiga zone of Republic Sakha (Yakutia), the stimulation of growth processes, of photosynthesis, endogenous low molecular weight antioxidants synthesis and adaptive response were revealed. Presented findings in review reflect the complex picture of the microevolutionary changes occurring in populations of plants and of animals inhabiting the areas with increased level of natural radioactivity.

[The influence of cadmium and potassium on the level of cytogenetic effects induced by thorium-232 in Allium cepa root meristem].

The influence of different concentrations of cadmium and potassium on the levels of mutagenic and cytotoxic effects induced by thallium-232 in Allium cepa root meristem has been studied. The combined action of 232Th (0.8 microM) with cadmium in non-toxic (0.009 microM) and toxic (5 microM) concentrations resulted in sinergetic increase of the frequency of aberrant cells in Allium cepa root meristem. Decrease of the mutagenic effect to the additive level and antagonism with respect to the cytotoxic one was observed only at the certain concentrations of 232Th (0.8 microM) and Cd (0.09 microM) and the time of impact 30 h. In contrast to the heavy metal cadmium the essential for plants potassium at all studied concentrations (0.008, 6, 13 mM) decreased the number of cytogenetic aberrations in control experiments and under the effect of 232Th. The maximum protective effect of potassium was detected at the concentration 13 mM.

[Mechanisms of 232Th effects on Chlorella vulgaris Beljer and modifications of it's toxic effect with caffeine and buthionine sulfoximine].

232Th effects and its modifications with caffeine and D, L-buthionine-(S, R)-sulphoximine in Chlorella vulgaris Beijer cells was studied with use an optical density measure after 24 hours growth. Was shown relationship between concentration and toxic effect that is nonlinear and characterized with three parts different in induced damages level. In the first concentration range (0.001-1.551 micromol/l) chlorella growth parameters don't significantly differ from control ones. In the second one (1.724-3.017 micromol/1) statistically significant increase of optical density is but the effect does not dependent on 232Th concentration. The 232Th concentration (>3.448 micromol/l) increase the monotonous decrease in optical density was observed. The main role in 232Th toxic effect decrease make processes of DNA reparation, but not free radical scavenging with glutathione.

[Toxic and cytogenetic effects induced in Allium cepa with low concenrations of Cd and 232th].

232Th (7.76 x 10(-7) M) and Cd (0.89 x 10(-8) M) in concentrations which do not exceed officially prescribed standards when entering with water do not increase the frequency of chromosome aberrations in comparison with the control. Such concentrations do not cause toxic effects in plants on the levels of tissues and of the whole organism but they do display their activity on the cell level damaging division spindle. Dependence "cadmium concentration-effect" is not linear for any type of cytogenetical damages. At the concentration of cadmium 0.89 x 10(-7) M its influence on formation of division spindle is weakened and the frequency of chromosome aberrations is reducing in comparison with the control and with the effects induced at lower concentrations of cadmium in solution (0.89 x 10(-8) M). Cadmium in high concentration (5.34 x 10(-5) M) causes significant toxic and mutagenic effects.