[Mutagenesis in Muridae from regions with increased radiation level]. / Mutatsionnyi protsess u myshevidnykh gryzunov, obitaiushchikh v raionakh s povyshennym fonom radiatsii.

Genetic monitoring of wild populations of mouse-like rodents has been carried out since 1992 in areas with the increased radioactivity in the south of the Bryansk region. The radioactive background ranged from 0.20 to 2.20 mkGy/h. Over 400 rodents of different species have been examined. Bank vole constituted more than a half of the examined animals. The genetic effect of radiation was estimated by the frequency of micronuclei in normochromatic erythrocytes of peripheral blood and by the frequency of abnormal sperm heads. In house mice the frequency of reciprocal translocations and the level of embryo mortality were studied in the progeny of the caught male mice mated with intact laboratory females. The data obtained demonstrate that the yield of induced genetic disorders by all tests was relatively low and only in a few cases the frequency of disturbances tended to increase with an increase in the level of radionuclide contamination in the examined areas.

Genetic disorders in house mouse germ cells after the Chernobyl catastrophe.

Genetic effects were studied in house mice caught from 1986 to 1994 in regions polluted by radionuclides as a result of the Chernobyl disaster. The dose rates of gamma-radiation on the soil surface ranged from 0.0002 to 2 mGy/h. The frequency of reciprocal translocations in mouse spermatocytes was relatively low, but increased with the dose rate. Embryo mortality was increased only in the progeny of male mice in males caught in 1987 in the area with maximal contamination. The frequency of mice heterozygous for recessive lethal mutations decreased with time after the accident.

[Genetic disorders in house mice after the accident at Chernobyl power plant]. / Geneticheskie narusheniia u domovykh myshei posle avarii na Chernobyl'skoi AES.

Genetic effects were studied in house mice caught from 1986 to 1994 in regions polluted by radionuclides as a result of the Chernobyl disaster. The dose rates of gamma-radiation on the soil surface ranged from 0.02 to 200 mR/h. The frequency of reciprocal translocations in mouse spermatocytes was relatively low, but increased with the dose rate. Embryo mortality was increased only in the progeny of male mice caught in 1987 in the area with maximum contamination. The frequency of mice heterozygous for recessive lethal mutations decreased with the time after the accident.

[The genetic monitoring of the house mouse population from areas contaminated by radionuclides as a result of the accident at the Chernobyl Atomic Electric Power Station]. / Geneticheskii monitoring populiatsii domovykh myshei iz raionov, zagriaznennykh radionuklidami v rezul'tate avarii na Chernobyl'skoi AES.

In 1986-1994, genetic effects of radiation on males of wild mice caught in areas of radioactive contamination after the Chernobyl reactor accident were studied. The gamma-radiation dose rates on the soil surface in the areas varied from 0,02 to 200 mR/h. The frequency of reciprocal translocations in mouse spermatocytes was relatively low and increased linearly with increasing of the dose rate. The levels of recessive lethal mutations in mouse populations did not depend on the radiation dose rate in the areas and decreased with a time.

[Genetic sequelae of the accident at the Chernobyl nuclear power plant in house mice (Mus musculus)]. / Geneticheskie posledstviia avarii na Chernobyl'skoi AES u domovykh myshei (Mus musculus).

Genetic disorders were studied in house mice caught from 1986 to 1993 in areas contaminated by radionuclides after the Chernobyl disaster. Dose rates on soil surface ranged from 0.02 to 200 mR/h. Frequency of reciprocal translocations in spermatocytes of the mice studied was relatively low, but increased with dose rate. In populations, frequency of mice heterozygous for recessive lethal mutations decreased with time after the accident. The data obtained allow us to assume that induced mutations may lead to elimination of germ cells and decreased viability in mice heterozygous for the mutations. These processes result in removing excess mutations from the population.

[Modification of the genetic effect of radiation in mice exposed in the region of the Chernobyl Atomic Electric Power Station]. / Modifikatsiia geneticheskogo éffekta radiatsii u myshei, éksponirovannykh v raione Chernobyl'skoi AES.

A study was made of the protective effect of beta-carotine and ephasol against genetic damages in germ cells of male mice, exposed within the zone of Chernobyl NPP or ingested by 137Cs. The analysis of reproductive function, frequencies of dominant lethal mutations, abnormal sperm heads, reciprocal translocations and testis mass decrease show that both agents are more effective in protection against reproductive function damages than against genetic effects.

[The radioprotective action of efazol under different conditions of irradiation of the germ cells of male mice]. / Radiozashchitnoe deistvie éfazola pri raznykh usloviiakh oblucheniia polovykh samtsov myshei.

A study was made of the protective effect of ephasol against genetic damages induced in mice germ cells by single, fractionated and chronic gamma radiation. Study of male reproductive ability, frequency of induced dominant lethal mutations, abnormal sperm heads and reciprocal translocation show that the efficacy of ephasol was higher in condition of chronic exposure.

[The micronucleus frequency in the somatic cells of murine rodents residing in a 30-kilometer area of the Chernobyl Atomic Electric Power Station]. / Chastota mikroiader v somaticheskikh kletkakh myshevidnykh gryzunov, prebyvavshikh v 30-kilometrovoi zone Chernobyl'skoi AES.

The chromosome aberration frequency in murine somatic cells was studied. Animals from natural populations as well as laboratory mice exposed within the ten-kilometers zone of the Chernobyl accident were examined. Increase in micronuclei rate in bone marrow cells, erythrocytes of peripheral blood and hepatocytes was found in animals exposed to more high background radiation. Under chronic exposure the pattern of effect dependence on dose rate was similar both in somatic and sex cells.

Genetic effects of testicular incorporation of 137Cs in mice.

A comparative estimation of the frequencies of genetic disorders induced in germ cells of male mice by a single or long-term exposure to incorporated 137Cs or to external gamma-radiation has been carried out. The frequencies of dominant lethal mutations induced by a single exposure were similar with both types of radiation. In stem cell spermatogonia the frequency of reciprocal translocations was significantly lower in the case of single 137Cs administration than upon external gamma-radiation. Upon long-term administration the genetic efficiencies of both types of radiation were similar.

[Genetic effect of incorporated 137 Cs in male mice after single injection of the isotope]. / Geneticheskii éffect inkorporirovannogo 137 Cs u samtsov myshei pri odnokratnom vvedenii izotopa.

A comparative study of the incidence of genetic damages induced in mouse male germ cells by a single injection of 137Cs and external gamma-irradiation shows that the incidence of dominant lethal mutations in the postmeiotic cells is similar with both radiation types. The frequency of reciprocal translocations in stem cell spermatogonia was considerably lower with 137Cs than with external gamma-irradiation which might be attributed to the prolonged effect of the radionuclide.

[Genetic effect of incorporated 137 Cs on male mice after long-term administration of the isotope]. / Geneticheskii éffect inkorporirovannogo 137 Cs u samtsov myshei pri dlitelnom vvedenii izotopa.

A comparative study has been made of the incidence of genetic damages to male mouse germ cells induced by chronic action of incorporated 137Cs and external gamma-radiation. It has been shown that the genetic efficiency was nearly the same with both radiation types under conditions of equal, with respect to time and value, absorbed dose formation in gonads.

[Genetic disorders in laboratory mice, exposed in the region of the Chernobyl Atomic Power Plant four years after the accident]. / Geneticheskie narusheniia u laboratornykh myshei, éksponirovannykh v raione Chernobyl'skoi AES spustia 4 goda posle avarii.

Mice (CBA x C57BL)F1, of both sex and males C57BL were exposed within the 10 km zone of the Chernobyl Nuclear Power Station during 14, 22 and 34 days. Genetic damages of chronic radiation in the exposed adult mice, and in the course of embryogenesis, was studied. The gonadal absorbed radiation doses of the exposed mice varied from 0.5 to 1.5 Gy. The frequencies of dominant lethal mutations, abnormal sperm heads and reciprocal translocations linearly increase with increasing absorbed radiation doses. Among 49 males exposed at the embryonal stage one male heterozygote for reciprocal translocation was revealed. In other males of this group, reciprocal translocation yield was low. No uniform dependence of genetic effects from mice genotype was revealed.

[Electron microscopic analysis of synaptonemal complexes of male laboratory mice exposed during the period of embryogenesis in the vicinity of the Chernobyl Nuclear Power Station]. / Elektronno-mikroskopicheskii analiz sinaptonemnykh kompleksov samtsov laboratornykh myshei, éksponirovannykh v period émbriogeneza v raione Chernobylskoi AES.

Four male mice were shown to have decreased fertility among 74 laboratory male mice exposed in the Chernobyl APP area during embryogenesis. Electron microscopic analysis of synaptonemal complexes (SC) of at zygotene-diplotene and light-optic analysis of chromosome aberrations at diakinesis-metaphase 1 demonstrated the presence of interchromosome translocations in autosomal chromosomes, and also intrachromosome translocations in two of four animals. The frequency of chromosome translocations in SC preparations was on the average 1.8 times higher than their frequency at the diakinesis-metaphase 1 stage. High percentage of cells in which associations of sex bivalent axes (XY) with the axes of autosomal bivalents were observed in the SC preparations and reduced fertility in the animals studied confirmed the Forejt's hypothesis that such associations caused the arrest of cells at pachytene and, as a consequence, disturbed the process of embryogenesis.

Genetic disorders in mice exposed to radiation in the vicinity of the Chernobyl nuclear power station.

Induced reciprocal translocations in spermatocytes of mice, either caught or exposed at the site, were observed at all levels of radioactive contamination around the Chernobyl nuclear power station. The frequency of reciprocal translocations was relatively low and increased linearly with increasing dose rate. Among 74 male mice exposed as early embryos, four reciprocal translocation heterozygotes were found. Furthermore, an increase in embryonic mortality and frequency of abnormal sperm heads was observed after termination of exposure, but these decreased rapidly with post-exposure time.

[Genetic effects in mice exposed to the 10-km area around the Chernobyl Atomic Energy Station]. / Geneticheskie éffekty u myshei, éksponirovannykh v 10-kilometrovoi zone chernobyl'skoi AES.

Mice (CBAxC57BL) F of both sexes were exposed within the 10 km zone of Chernobyl nuclear power station. Genetic damage of phone chronic effect of increased radiation in exposed adult mice and in the course of embryogenesis was studied. The total absorbed radiation doses in testes varied from 1.85 to 0.42 Gy in embryos and from 3.4 to 2.7 Gy in adult males. Increase of dominant lethal mutations (DLM) and abnormal sperm heads (ASH) was only observed right after the end of exposure of adult males. The yield of reciprocal translocations (RT) in these males was relatively low. Among the males exposed at the stage of early embryogenesis, 4 heterozygotes for RT were revealed. In other males of this group the RT yield was low.

[Genetic disorders in laboratory mice exposed in the area of the Chernobyl Atomic Electric Power Station]. / Geneticheskie narusheniia u laboratornykh myshei, éksponirovannykh v raione Chernobyl'skoi AES.

Laboratory male mice (CBA X C57Bl)F1 were exposed in three sectors with different contamination degree of radionuclides within 30 km-zone of the Chernobyl Atomic Power Plant. The total absorbed radiation doses in testes were 0.1; 3 and 25 Gy, respectively. Great depression of spermatogenesis was observed in exposed mice up to complete sterility in males from the most contaminated sector. The mutagenic effect of radiation was relatively low and did not increase with growth of the contamination degree.

[Reciprocal translocations in mice found in the vicinity of the Chernobyl nuclear power station]. / Retsiproknye translokatsii u myshei, nadkhodivshikhsia v raione Chernobyl'skoi AES.

A study was made of the incidence of genetic damage to germ cells of male mice taken from or exposed within the thirty-kilometer zone of Chernobyl, the contaminated no-man's-land around the reactor that failed. At all contamination levels mouse spermatocytes exhibited reciprocal translocations, a relatively low frequency of which increased with increasing dose rate. Heterozygotes, with respect to reciprocal translocations (5%), were found among males exposed to enhanced radiation background as early embryos.

[The noncorrespondence of the geographic ranges of the host and the causative agent]. / O nesootvetstvii arealov khoziaina i vozbuditela.

For the first time the experimental and field studies of Leptospira infections, carried out over the period of 6 years, have revealed that the habitat of striped field mice (Apodemus agrarius Pallas 1778) serving as a host for Leptospira pomona, serovar mozdok, is much wider than the habitat of the infective agent proper. The presence of an animal species highly sensitive to a definite leptospiral serovar and serving as its reservoir at a given locality cannot be regarded as a proof of the presence of the epizootic process without bacteriological confirmation. But, in the absence of homologous Leptospira carriage, intensive leptospiral seroconversion can be attributed to a population other than that of the host.

[The functioning of a drained natural focus of leptospirosis in a nonchernozem area]. / Funktsionirovanie osushennogo prirodnogo ochaga leptospirozov v Nechernozem'e.

The drainage of a natural focus of leptospirosis of the flood plain-swamp type, carried out over the period of 15 years, has led to changes in the species structure of small mammals and to an increase in the number of Leptospira-carrying species. Nevertheless, like before drainage, the prevalent species and the main carrier of leptospires is still the root vole (Microtus oeconomus Pallas). The intensity of the epizootic process among small mammals at the final stage of drainage has proved to be similar to that at the initial stage. At the same time the cultivated fields created on the drained territory of the natural focus abound, by the time of harvesting, with small mammals among whom the intensive epizootic process takes place.

[Differences in the susceptibility of field mice from the Altai Territory and Moscow Province to Leptospira of serovar mozdok and serogroup Pomona]. / Razlichiia v vospriimchivosti polevykh myshei Altaiskogo kraia i Moskovskoi oblasti k leptospiram serovara mozdok serogruppy Pomona.

Adult striped field mice (Apodemus agrarius) caught in the Altai region proved to be insusceptible to experimental infection when inoculated with Leptospira of serovar mozdok, serogroup Pomona. In pregnant females, though infected with this organism, no leptospiruria was observed. At the same time nonpubescent animals became Leptospira carriers, females becoming carriers 4.5 times more frequently than males. The formation of antibodies to Leptospira in the test rodents was poorly pronounced and did not depend on their sex, age, physiological state and the presence of renal leptospirosis. But all adult striped field mice belonging to the population of the Moscow region became Leptospira carriers in such experiments.