Assessment of herb field mouse (Sylvaemus uralensis) migration in the area of the East Urals Radioactive Trace using measurements of bone-seeking 90Sr.

The dynamics of rodent population in the area of East Urals Radioactive Trace (EURT) is one of the controversial issues, which are of key importance for the radiobiological and radioecological interpretation of the observed radiation effects. The objective of the paper is to evaluate the probability of migration in population of the herb field mouse (Sylvaemus uralensis Pall., 1811) based on 90Sr activity concentrations in the mouse bones. Radiometric data for bones of 768 mice captured at 9 sites in the EURT territory (with different environmental contamination levels) in 2001-2012 were used. The distribution of bone-seeking 90Sr in the juvenile age group of mice is used as a model of the width of radionuclide distribution in the bones of permanent inhabitants. Comparison of the model predictions and observations in different age and functional groups within the population structure allows simulating the probability of migration and evaluating the fraction of migrants. It is shown that the accumulation of 90Sr in bones correlates with soil contamination at the capture sites. Individual variability in the specific activity of 90Sr in the skeleton tends to increase with the age of animals. The rate of herb field mouse migration is estimated as 7 and 15% per year (for underyearlings and wintered individuals, respectively). The animals captured in the EURT area (all animals, including juvenile individuals) are "diluted" with animals from non-contaminated territories by 5-12%. The average half-time of substitution of the exposed population by migrants from non-contaminated territories is 8 years. Today, the fraction of descendants of the animals, that for generations have permanently inhabited the EURT territory since 1957, is negligible (on average-1.2% and not exceeding 17%). The proposed method of probabilistic analysis of 90Sr in the bones could be used to study migration activity of other species of rodents.

Otoliths as object of EPR dosimetric research.

Otoliths are the organs which fish use for hearing and keeping balance. Otoliths are the most calcified tissues in the fish body. In contrast to bones, otoliths are not affected by remodeling and, therefore, they are expected to accumulate any dose from ionizing radiation during lifetime. Therefore, EPR dosimetry with fish otoliths could be an important tool for dose reconstruction in radiobiology and radioecology. It could also provide useful information remediation actions to de-contaminate waterbodies. Consequently, in the present study, otoliths of three contaminated fish species (roach (Rutilus rutilus), pike (Esox lucius) and perch (Perca Fluviatilis)) were examined with Electron Paramagnetic Resonance (EPR) spectroscopy. The fish were caught at storage reservoirs of liquid radioactive waste from Mayak PA and from the upper reach of the Techa River, which have been contaminated with different levels of radionuclide activity concentrations. It is shown that the radiation-induced EPR signal of otolith is stable and characterized by a linear dose response. However, the slope of the calibration curve (corresponding to the radiation sensitivity of the material) is not the same for different species; this may be caused by differences in mineralization. The reconstructed doses were found to be in the range from undetectable (in fish from the upper stream of the Techa River) up to 265 Gy (in roach from the most contaminated waterbody). In parallel, otoliths were measured with ß-counter to detect 90Sr/90Y. Samples were also tested on the presence of alpha-emitters, but no alpha activity above background could be detected. However, a significant activity concentration of 90Sr was detected (from 1 × 101 to 2 × 104 Bq/g). The EPR doses measured correlated with the 90Sr activity concentration measured in the otolith samples.

Hereditary component of variation in 90Sr deposition in inbred mice under exogenous conditions that affect bone formation.

Bone-seeking radionuclides (specifically 90Sr) accumulate in the bone tissue and act as a long-term source of internal irradiation. Their behaviour in the body has been studied in detail, while the impact of inheritance has not been established. On one hand, the genetic determination of both skeletal morphology and calcium metabolism is indirect evidence that the kinetics of deposition of alkaline-earth radioisotopes in the skeleton also have a hereditary component. On the other hand, analysis of 90Sr kinetics in different inbred mouse strains did not reveal any differences between the mice. This study used a classical approach to evaluating the hereditary component of variation in quantitative traits, namely, a variant of familial analysis (the method of twin families). The growth of the skeleton is known to be accompanied by distinct changes in 90Sr accumulation. That is why the hereditary (familial) component of variation in 90Sr kinetics in the bone tissue of CBA mice was analyzed under the influences that modify growth processes Individual parameters of 90Sr accumulation differed between experimental groups by a factor of 2-4.5. At the same time, features of 90Sr accumulation proved to be characteristic of entire families. The results show that the intrafamilial correlation in 90Sr deposition in the skeleton is highly significant (R = 0.542, P ≤ 0.0001) and comparable to that of morphological parameters (R = 0.532-0.546, P ≤ 0.0001). The results confirm the existence of statistically significant intrafamilial correlations of weight and metabolic parameters, which is similarly expressed in different families, thereby providing evidence for hereditary determination of 90Sr metabolism. At the same time, the stability of 90Sr metabolism inheritance to changes in morphophysiology and environmental influences (including those close to pathogenic ones) is shown. This is evidence of its authenticity and significance. The results obtained can be extrapolated to humans instead of directly analyzing the role of hereditary factors in the metabolism of toxic compounds, which are difficult and unethical to perform in human subjects.

Contemporary radiation doses to murine rodents inhabiting the most contaminated part of the EURT.

The contemporary radiation doses to the organs and tissues of murine rodents inhabiting the most contaminated part of the EURT were estimated. The bones of animals trapped in 2005 at territories with a surface (90)Sr contamination of 24-40 MBq/m(2) were used for dose reconstruction. The concentration of (90)Sr in the animals' skulls was measured using the nondestructive method of bone radiometry. The dose estimation procedure included application of the published values of absorbed fractions of beta-radiation energy for different combinations of source and target organs, accounting for the distribution of radionuclide by organs and tissues. Twelve conversion coefficients were obtained to link the skeleton (90)Sr concentration and doses to eleven organs and the whole body. The whole-body dose rate on the 45th day after the beginning of exposure normalised to whole-body activity is 0.015 (mGy day(-1))/(Bq g(-1)). The estimation yields the following values of doses for Microtus agrestis, Sylvaemus uralensis and Clethrionomys rutilus, respectively: maximum absorbed doses in the skeleton: 267, 121 and 160 mGy; mean whole body internal doses: 37, 14 and 23 mGy; mean internal dose rates on the last day before trapping: 1.2; 0.44 and 0.75 mGy/day. Approaches to the assessment of doses to foetuses and to offspring before weaning were also developed.

[The adaptive strategy of rodent populations living in conditions of radioactive and chemical environmental pollution].

The comparative analysis of demographic, morphological and physiological processes in mouselike rodents in pollution zones (90Sr + 90Y, 137Cs) on East-Ural radioactive track (EURT) and (Cu + Cd + Pb + Zn + SO2) on a site near copper-smelting factory is carried out. The direct (not mediated) defeat of animals by an irradiation leads to inherited adaptation (density preservation, tolerance increase to pollution, migration decrease and so forth). The mediated defeat of animals at pollution by metals influences animals as a result of degradation of a vegetative cover, reducing a forage reserve, shelters and reproduction places. Population is decreasing, migration is increasing. Hence, population reacts onto direct defeat of animals or on inhabitancy locuses degradation, id est unspecifically, without dependence from the physical and chemical nature of pollution.

[The kinetics of 90Sr: genotypic determining].

The genotypic component of the variability (intrafamily correlation) of body mass, mass of thigh-bones and concentration of 90Sr in bone tissue were evaluated in the progeny of the laboratory mice of CBA line which were in the conditions of normal or slow development of skeleton since their birthday and which got a single injection of 90Sr in the late ontogenesis. The evaluation was made with the control of the effects of sex and age membership of animals and also taking into account the conditions of their development. Significant intrafamily correlation of the concentration of 90Sr was revealed. It can be compared with the morphological signs, which are the evidence of existence of genotypic determinacy of the kinetics of 90Sr.

[Accumulation of 90Sr in the bone tissue of the northern mole vole, living in the head part of the East Ural Radioactive Trace]. / Nakoplenie 90Sr v kostnoi tkani obyknovennoi slepushonki, obitaiushchei v golovnoi chasti Vostochno-Ural'skogo radioaktivnogo sleda.

Deposition of 90Sr in a bone tissue of the northern mole-vole (Ellobius talpinus Pallas, 1770) living in the head part of the East Ural Radioactive Trace (EURT) (density of pollution by 90Sr 37 MBq/m2 - 1000 Ci/km2) was investigated. Features of the rodent are digging (underground) way of life, family organization of settlements and weak migratory activity. Authentic (p < 0.01) interfamily distinctions in concentration 90Sr are revealed on the background of absence of sexual and are features of accumulation the radionuclides inside separate families, thus individual parameters differ in 7 times. It is established, that the level of accumilation of 90Sr is comparable with that in other species of small mammals in this territory. Age inversion of accumulation of 90Sr earlier found out in other species of mammals on the EURT is confirmed.

[Individual variation of 90Sr deposition and its variability depending on the genotypic homogeneity of the sample]. / Individual'naia izmenchivost' deponirovaniia 90Sr i ee variabel'nost' v zavisimosti ot genotipicheskoi odnorodnosti vyborki.

Individual peculiarities of 90Sr skeleton deposition in CBA mice were investigated. Differences in the radionuclide accumulation were not more than two times. Sex features in 90Sr deposition were not revealed. The range of individual variability of 90Sr deposition was analyzed in inbred mice in comparison with outbred stock and voles from natural population; it was found that variability in the radionuclide accumulation increased with sample genotypic heterogeneity.

[Chromosomal instability in offspring of voles in unfavorable radiation zones]. / Khromosomnaia nestabil'nost' u potomkov polevok iz zony radiatsionnogo neblagopoluchiia.

A high frequency of cells having chromosomal aberrations was shown to be preserved in the first generation of laboratory offspring of common voles, whose ancestors were captured near the East Ural radioactive track (EURT). In F2 and F3, a decrease in frequency was observed. Most likely, the cytogenetic effects observed were caused by environmental contamination with plutonium in the locality of capture. An increased chromosomal instability observed in the first laboratory generation of nonirradiated common voles was caused by reversible modifications in the expression of mutator genes inherited from parents exposed to alpha-irradiation rather than by classic mutations occurred in specific loci.

[The individual characteristics of 90Sr accumulation in the body of 2 species of the common vole inhabiting the territory of the eastern Urals radioactive trace]. / Individual'nye osobennosti akkumuliatsii 90Sr v organizme dvukh vidov serykh polevok, obitaiushchikh na territorii Vostochno-Ural'skogo radioaktivnogo sleda.

Individual peculiarities of 90Sr skeleton deposition in voles M. gregalis and M. arvalis inhabiting at the territory of East Ural Radioactive Trace were investigated. More high accumulation of radionuclide in the organism of M. gregalis was registered. Considerable variations (3-6 times more, than in linear mice ones) of individual indices of radionuclide accumulation exceeding interspecies level are found. Possible reasons of both interspecies differences and an individual deposition' variability were discussed.

[Hereditary chromosome instability in the common vole (Microtus arvalis) from the region of the Kyshtym nuclear accident--fact or hypothesis?]. / Nasleduemaia khromosomnaia nestabil'nost' u obyknovennoi polevki (Microtus arvalis) iz raiona Kyshtymskoi iadrenoi avarii--fakt ili gipoteza?

In bone marrow cells of common voles living within the Eastern Urals radioactive track (EURT) and adjacent area, the frequency of chromosomal aberrations was higher than in cells of control animals. In several animals, the proportion of aberrant cells was significantly higher; cells with multiple chromosomal lesions prevailed among the aberrant cells. Frequency of chromosomal aberrations did not depend on the absorbed dose of beta-radiation. Taking into account the radiation background in trapping sites, the level of cytogenetic damage in the animals studies should be considered unexpectedly high. Outside the EURT, two voles with mutant karyotypes were caught. It was hypothesized that carriers of hereditary chromosome instability appeared in the population studies as a result of exposure to ionizing radiation.

[Comparison of the stability of morphometric and nonmetric skeletal characteristics of inbred mice with regard to environmental exposure in prenatal development]. / Sravnenie ustoichivosti morfometricheskikh i nemetricheskikh kharakteristik skeleta lineinykh myshei k sredovym vozdeistviiam v prenatal'nom razvitii.

The influence of some environmental factors on size and shape of mandible in BALB/cJLacSto inbred mice was studied during prenatal development by multivariate morphometric methods. The factors under study were: introduction of methylthiouracil into the diet of pregnant females; injections of pregnant females with adrenocorticotropic or parathyroid hormones; keeping the females at low temperatures (two regimes). It was established that the changes of mandible shape caused by the changes of conditions of prenatal development did not achieve the level of differences between strains, and mouse strain identification was possible under various conditions of animal's keeping. It has been shown by comparison of these results with preceding data that the nonmetric skeletal traits were more stable to the influence of the same factors than morphometric ones. This gives us the foundations to consider the method of evaluation of phenetic distances between natural groups of animals for the set of non-metric threshold skeletal traits more suitable for detection of genetical differentiation of wild populations.

[Experimental study of the stability of expression of non-metrical threshold skeletal traits in inbred mice]. / Eksperimental'noe izuchenie ustoichivosti proiavleniia nemetricheskikh porogovykh priznakov skeleta u lineinykh myshei.

The influence of some environmental factors during prenatal development on manifestation of non-metrical threshold skeletal traits in BALB/c inbred mice was studied. The factors under study were: introduction of metilthiouracil into the diet of pregnant females; injections of pregnant females with adrenocorticotropic or parathyreoid hormones; keeping the females at low temperatures (two regimens). Offsprings of the females treated were examined for twenty five skeletal characters using Berry-Sjøvold's method. Despite the fact that their body weights decreased in all experimental groups, phenetical distances between the treated and control groups were much smaller than those between different inbred strains. Reliability of genetical interpretation of interpopulational differences in non-metrical skeletal traits is higher for the characters which are not correlated with total body sizes.