[Mutation processes in the natural populations of Drosophila and Hirundo rustica from Ukrainian radiation contaminated territories].

Natural populations of Drosophila melanogaster and Hirundo rustica that reside at the territories with different levels of radioactive pollution were investigated. The levels of visible mutations, sex-linked mutations and gonad reduction of Drosophila and the rate of interphase markers of chromosomal instability in erythrocytes of birds were selected as parameters for population monitoring. The results point out to possible reverse dependence among the level of chromosomal instability of birds, the rate of lethal mutations in sex chromosome of Drosophila and the density of radioactive pollution.

[Study on genetic radioresistance of natural Drosophila Melanogaster population from radionuclide contaminated regions of Byelarus]. / Issledovanie geneticheskoi radiochuvstvitel'nosti prirodnykh populiatsii Drosophila melanogaster iz zagriaznennykh radionuklidami raionov Belarusi.j

Over the period from 1998 to 2000 adaptation to unfavorable ecological factors was revealed to be formed in natural Drosophila melanogaster populations from various regions of Belarus with increased radiation background due to the Chernobyl accident. This adaptation was shown to be of non-specific character, since the populations from radiation regions were more resistant to the effect of not only factors of physical nature (irradiation), but also to that of chemical mutagen ethylmethanesulphonate. Assessment of population resistance was carried out by means of tests of dominant lethal mutations and recessive sex-linked lethal mutations.

[Chromosomal and ontogenetic instability in sibling species of common vole (Microtus arvalis group): comparative aspects]. / Khromosomnaia i ontogeneticheskaia nestabil'nost' u vidov-dvoinikov obyknovennoi polevki (gruppa Microtus arvalis): sravnitel'nye aspekty.

Populations of chromosomal sibling species Microtus arvalis and Microtus rossiaemeridionalis were studied in Ural region in habitats affected by high radiation and the control ones. Frequency of chromosome disturbances in the marrow cells and fluctuating asymmetry (FA) of 8 craniometric characters were investigated. In impact populations the frequency of chromosome aberration was very high. Such frequency was also maintained in the offspring of the first laboratory generation of M. arvalis. In natural and control populations of both species frequently occurred individuals with anomalies in sex chromosome. Individuals of M. rossiaemeridionalis from Totsky radioactive region (forest-steppe zone) were characterized by very high integrative FA in comparison with control populations (southern taiga). At the same time neighboring impact and control populations of M. arvalis from southern taiga did not differ in this character. Despite the high level of caryotype divergence M. arvalis and M. rossiaemeridionalis showed similarity in mutation process that causes chromosome disturbances in somatic and germinative cells. Probably the level of FA of measured characters in both species is connected rather with geographical location than with man influence.

[Analysis of recessive sex-linked lethal mutations in genotypically different strains of Drosophila melanogaster MS and w, exposed in the 5-kilometer zone of the accident at the Chernobyl nuclear reactor]. / Analiz retsessivnykh stseplennykh s polom letal'nykh mutatsii v genotipicheski razlichaiushchikhsia liniiakh Drosophila melanogaster MS i w, éksponirovannykh v 5-kilometrovoi zone avarii na Chernobyl'skoi AES.

The frequency of induced and spontaneous recessive sex-linked lethal mutations (RSLLM) in Drosophila melanogaster strains w and ms was estimated after their chronic irradiation in the five-kilometer zone of the Chernobyl' meltdown. The mutagenic effect of relatively low radiation doses was analyzed. In an experiment conducted in 1990, a significant increase in the RSLLM frequency was recorded, while, in 1991, no significant difference between the experiment and control was found.

[Analysis of dominant and recessive sex-linked lethal mutations induced by low radiation doses in genetically different strains of Drosophila melanogaster w and MS]. / Analiz dominantnykh i retsessivnykh stseplennykh s polom letal'nykh mutatsii, indutsirovannykh malymi dozami radiatsii, v genotipicheski razlichaiushchikhsia.

Frequencies of induced recessive sex-linked lethal mutations (RSLLM) and dominant lethal mutations (DLM) were analyzed in genetically different Drosophila melanogaster strains w and ms after their exposure to radiation on radioactive soil in laboratory conditions. The RSLLM test applied to males after their 14-day radiation exposure yielded controversial results. An analysis of induced and spontaneous DLM demonstrated an increase in the frequency of early embryonic lethal mutations in the experiment (radiation exposure) in comparison with the control (spontaneous mutation rate) in both strains examined.

Effect of low temperature on radiation-induced genetic damage in Drosophila melanogaster: response of motile sperm and late spermatids.

The response of fully mature motile sperm and late spermatids when challenged with X-radiation at 0 degrees C has been studied in sex-linked recessive lethals, II-III translocations and dominant lethality experiments. At 0 degrees C a significant increase in both mutagenic and clastogenic damage was detected compared to that obtained at 24 degrees C. Furthermore, the results of experiments performed with different postirradiation temperatures demonstrate that the low temperature during irradiation was the sole factor responsible for the observed increase. In the recessive lethal and translocation tests the response of late spermatids was higher than that shown by motile spermatozoa. As a whole, the results, which are rather similar to data reported on the effect of irradiation in oxygen of the same cell stages, suggest that the low temperature acted as a dose-modifying factor.

The children of parents exposed to atomic bombs: estimates of the genetic doubling dose of radiation for humans.

The data collected in Hiroshima and Nagasaki during the past 40 years on the children of survivors of the atomic bombings and on the children of a suitable control population are analyzed on the basis of the newly revised estimates of radiation doses. No statistically significant effects emerge with respect to eight different indicators. Since, however, it may confidently be assumed some mutations were induced, we have taken the data at face value and calculated the minimal gametic doubling doses of acute radiation for the individual indicators at various probability levels. An effort has also been made to calculate the most probable doubling dose for the indicators combined. The latter value is between 1.7 and 2.2 Sv. It is suggested the appropriate figure for chronic radiation would be between 3.4 and 4.5 Sv. These estimates suggest humans are less sensitive to the genetic effects of radiation than has been assumed on the basis of past extrapolations from experiments with mice.

[Segregation of the somatic and germ-cell pathways of development in Drosophila]. / Segregatsiia somaticheskogo i polovogo putei razvitiia u drozofily.

Two groups of lethal mutations that are expressed only in somatic cells were isolated using the gonosomic selective method. The mutations tend to be organized in clusters along the sex chromosome. Analysis of mutation expression allowed to characterize the degree of changes in genetic diversity of somatic and germ lines in development; it is minimal in the III instar larvae and prepupae and maximal in the I and II instar larvae and pupae.

The TX;Y test for the detection of nondisjunction and chromosome breakage in Drosophila melanogaster. II. Results of female exposures.

The TX; Y test is a short-term assay for the detection of sex-chromosome nondisjunction and chromosome breakage in Drosophila melanogaster. It has been used in previous work following the exposure of males. In this work, females are exposed. When females are the exposed parent, only chromosome gain can be detected. Positive results for the induction of aneuploidy were obtained following exposures of females to X-rays, 10 degrees C cold shock, and colchicine. No increase in aneuploidy was obtained following exposures of females to DMSO and trifluralin. Comparison with similar work in males reveals no consistent pattern concerning the more appropriate sex to use for aneuploidy testing in Drosophila, as colchicine was found to be positive in females only and DMSO and trifluralin were effective in males only. Further work is necessary to validate the TX; Y test and to understand the relative efficacy of female and male exposures to aneuploidy inducing agents in Drosophila.

[Mutability of the germ cells of the progeny of irradiated male Drosophila]. / Mutabil'nost' polovykh kletok potomstva obluchennykh samtsov drozofil.

The increased frequency of random and radiation-induced mutation was registered in germ cells of drosophila irradiated male descendants of the first generation. The effect observed depended on of radiation dose delivered to parent males, test dose to progeny, type of mutation registered, and sex of the descendants under study.

Cytogenetic effects of microwave irradiation on male germ cells of the mouse.

Hybrid male mice were exposed to 2.45 GHz microwaves for 30 min/day, 6 days a week for two consecutive weeks at power densities of 1.0, 100 or 400 W m-2, with sham-exposed controls. Rectal temperatures before and after exposure were measured on days 1, 6 and 12. Measurements made on day 1 were treated with caution because of heterogeneity in rectal temperatures taken before exposure between the groups of mice given different treatments. On days 6 and 12, rectal temperatures rose by approximately 1 degree C in mice sham exposed, or exposed to 1 W m-2 or 100 W m-2. Only in the group of mice exposed to 400 W m-2 was the mean rise in rectal temperature during exposure (about 3 degrees C) significantly increased above the sham value. In groups killed 2-3 days after treatment (mainly meiotic exposure) frequencies of chromosome aberrations in spermatocytes showed no significant heterogeneity although the highest frequency of 1.5 per cent was at the highest (400 W m-2) power density. Another group killed 30 days after 100 W m-2 exposures (spermatogonial sampling) showed no significant increase over controls in chromosome aberration frequency. There was a small but significant increase in sperm count with increasing power density in mice killed 12-13 days after exposure, but a non-significant one in those exposed as spermatogonia (killed 41 days later). Thus effects were markedly less severe than those reported previously by Manikowska-Czerska et al. (1985) with a very similar radiation regime and were probably caused by the temperature enhancement.

The effect of repeated microwave irradiation on the frequency of sex-linked recessive lethal mutations in Drosophila melanogaster.

The effect of repeated microwave irradiation (2375 MHz, CW) on mutagenic changes in Drosophila melanogaster was investigated. Oregon-R males were exposed to sublethal doses of microwaves (15 W/cm2 for 60 min, 20 W/cm2 for 10 min, and 25 W/cm2 for 5 min) for 5 days. The Muller-5 cross was used to detect sex-linked recessive lethal mutations. 4 lethals were found in treated groups but their frequency was not significantly different from that of the control group. No cumulative effect of repeated exposures on the mortality of the treated males was observed; on the contrary, their mortality decreased with the number of exposures. Irradiation did not affect the sex ratio of the F1. A significant decrease in the number of F1 offspring was noted in the group exposed to the power density of 15 W/cm2. A negative thermal effect of microwaves on male germ cells was probably manifested by this long exposure.

[Cytogenetic effects of 1,4-dihydropyridine in various test systems]. / Tsitogeneticheskii éffekt 1,4-digidropiridina v razlichnykh test-sistemakh.

Cytogenetic effect of 1,4-dihydropyridine was studied in different test-systems. The preparation is shown to decrease the level of complete sex-chromosome losses in Drosophila and chromosome aberration frequency in Allium fistulosum seedlings. The preparation does not affect spontaneous mutability of bone marrow cells in mice, high doses of the preparation have no mutagenic potential. Thus, 1,4-dihydropyridine shows antimutagenic activity reducing the chromosome mutation level in sex and somatic cells of eucaryotic organisms. Absence of the effect on mice chromosomes may testify to the specificity of 1,4-dihydropyridine action.

Interpretation of cytogenetic damage induced in the germ line of male mice exposed for over 1 year to 239Pu alpha particles, fission neutrons, or 60Co gamma rays.

The relative biological effectiveness (RBE) of 239Pu alpha particles, fission neutrons (0.85 MeV), and 60Co gamma rays has been evaluated for the induction of reciprocal chromosome translocations in spermatogonia and of chromosome/chromatid fragments and chromatid rearrangements in the primary spermatocyte of adult male B6CF1 mice. Age concurrency was maintained for both internal and external radiations which were delivered at about 1 rad/week for 239Pu (single intravenous dose of 10 microCi/kg), 0.67, 1.67, and 2.67 rad/week for neutrons, and 6.95, 17.4, and 32 rad/week for gamma rays for at least 60 weeks. In terms of frequency of translocations, the response to the alpha emitter was nonlinear (concave downward) with little dose-response predictability; to cumulative neutron exposures the response was linear, without evidence of a dose-rate effect; and to gamma radiation the responses were linear, and a significant dose-rate effect was seen. RBE estimates are variable. For translocations, the n/gamma ratio is between 10 and 24, depending upon weekly dose level, and the ratio is 1 or less for the alpha particle relative to the neutron. For fragments, the n/gamma ratio is 18 to 22, depending upon age factors, and alpha/n is 1.5. For chromatid rearrangements, n/gamma is 7 and alpha/n is essentially indeterminate, but much below one. The overall response to the alpha emitter is interpreted to be a complex function of (a) microdosimetric heterogeneity, (b) a nearly invariant deposition pattern in the gonad, (c) the high sensitivity of differentiating spermatogonia to cell killing, and (d) the capacity of stem cells in relatively radiation-free areas to progressively assume the major spermatogenic role.

[X-ray-induced breaks in the X chromosomes in Drosophila lines of various radiosensitivities]. / Izuchenie indutsirovannykh rentgenovymi luchami razryvov X-khromosom v liniiakh drozofily s razlichnoi radiochuvstvitel'nost'iu.

The frequency of X-ray induced X-chromosome breaks has been studied in females of the line rad (2) 201G1 hypersensitive to radiation and in females of the control line selected from the same population. The frequency of X-chromosome breaks was judged based on the frequency of X0 males occurrence. Synergism of the effects of X-rays (at doses 0.1, 0.5 and 1.0 kr) and of hyperthermia (+37 degrees C, 5.5 hours) applied after irradiation served as an indirect evidence for the functioning of DNA repair systems. It is demonstrated that radiosensitivity of mature oocytes of the lines compared was equal and that hyperthermia applied after irradiation increased the latter effect in both lines. Young oocytes of the control line were radioresistant, and hyperthermia applied after irradiation enhanced its effect. Opposite to them, young oocytes of the rad line females were radiosensitive. They did not differ from mature oocytes in the frequency of X-chromosome losses. Synergism of the two factors (irradiation and hyperthermia) was not registered in young oocytes. On the basis of the results obtained, it may be concluded that radiosensitivity of young oocytes in the hypersensitive line is conditioned by the failure of DNA repair systems and that the rad (2) 201G1 gene may be considered, in relation to the genes controlling DNA repair, as a suppressor functioning selectively at a certain stage of oogenesis.

Effect of hyperthermia on radiation-induced chromosome loss in female Drosophila melanogaster.

Three-day-old adult females of mutagen sensitive mutants: mus (1)101D1, mus(1)102D2, mus(1)103D1, mus(1)104D1, mus(1)105D1, mus(3)302D2; meiotic mutants: mei-9D2, mei-9D3, mei-218, and controls st, and w, were subjected to 38 degrees C for 1 hour and 1200R of gamma rays, brooded daily, and nondisjunction and the loss of X chromosomes determined. This was done in an attempt to gain more information on the hyperthermia sensitization of radiation-induced damage. In several strains the hyperthermia treatment sensitized immature class-1 oocytes--the most radiation-resistant stage--to radiation-induced chromosome loss. This class of oocytes is believed to have the greatest number of repair enzymes, and supports the hypothesis that hyperthermia increases radiation-induced genetic damage by interference with repair enzymes. The mature oocytes, which are believed to lack repair enzymes (stage 14), were the most sensitive to heat treatment and radiation. Hyperthermia failed to increase radiation-induced chromosome loss in the meiotic mutants. Hyperthermia may affect excision repair. There was no clear-cut correlation between other defective DNA pathways and influence of hyperthermia on radiation-induced chromosome loss in Drosophila females. The failure of hyperthermia to increase radiation-induced chromosome loss in meiotic mutants may indicate that radiation sensitization by hyperthermia also may be due to interference with chromosome segregation.

Developmental patterns of three X chromosomal enzyme activities in the brains of female and male mice. Lack of sex-dependent reaction to a fractionated prenatal x-ray dose.

The developmental profiles of the activities of the X chromosome-linked enzymes alpha-galactosidase, hypoxanthine guanine phosphoribosyltransferase, and glucose-6-phosphate dehydrogenase were studied in the brains of mice. X chromosome inactivation, which takes place at an early stage of development, led to identical enzyme activities in females and males between the 15th day of gestation and the 64th day after birth. The enzyme activities were also studied after an X-ray dose of 3 times 1.05 Gy, delivered on gestational days 11, 12 and 13. Treatment with this dose, but not with 3 times 0.95 Gy or 1.15 Gy, respectively, was followed by the death of predominantly female offspring within 2 days after birth. The assumption that the reason for this might be a reactivation of inactive female X chromosomal genes in brain cells was tested in the present experiment. There were marked radiation-induced alterations of the activities of the above-mentioned enzymes. However, sex differences of these enzyme activities were not found after the irradiation treatment. A participation of X chromosome reactivation in the elevated mortality of female offspring is therefore unlikely.