[Induction of transpositions of hobo-elements in chronically irradiated cells of dysgenetic and non-dysgenetic individuals of Drosophila melanogaster]

This paper studies the effect of chronic γ-radiation of different intensities on the induction of hobo-elements in cells ofdysgenetic and non-dysgenetic drosophila species. The level of gonadal atrophy, DNA damage, and mutability of the mini-white locus is estimated. It is shown that the frequency of displacements of the hobo-elements increases with the increase in the chronic irradiation dose, where an essential role belongs to the maternal effect. The level of DNA damage in the cells of embryos and larvae varies and depends on the conditions of induction of hobo-transposons. Analysis of the PCR products showed that chronic irradiation in a certain range of accumulated doses is able to induce formation of new copies of the hobo-elements. At the same time, the structure of deleted hobo-sequences may vary in response to higher doses of irradiation.

[Peculiar features of forming radiation effects in inbred populations of Drosophila melanogaster differing in cytotype]

A comparative evaluation of the sensitivity of inbred wild-type flies differing in the cytotype to the action of low-intensity radiation of different duration was conducted taking into account the integral parameters of survival. The strong dependence of the frequency of radiation-induced DNA damage (in the neutralpH version) to the cells of individuals on the dose of low-intensity radiation and stages of spermatogenesis was established. The hyper-radiosensitivity was found in the individuals of Charolles (R-cytotype), Harwich (P-cytotype), and Oregon-R (H-cytotype) strains irradiated during the early stages of spermatogenesis (spermatogonia-spermatocytes) and containing in their genotype transposons Bari 1, P and hobo, respectively. While drosophila line Canton-S exhibited dysgenetic properties against the background of several cytotypes (E, I and M), the effect of hormesis was identified under the same experimental conditions. With the increase in the dose of low-intensity irradiation, the frequency of the DNA damage either increased (for Canton-S) or reduced (for Harwich and Charolles). At that, the profile of fertility and. survival of wild-type stocks studied was maintained at a significantly high level. The important role of the cytotype and mobile genetic elements responsible for its formation in the modification of the effects of low-intensity γ-radiation is shown.

[Evaluation of effects of gamma-irradiation at low doses on repair and meiotic recombination mutants of Drosophila melanogaster]

A comparative study of the effects of gene mutations mus209, mus309, mei-41 and rad54 of Drosophila melanogaster on the sensitivity to low-level exposure of different duration was carried out. Taken into account was the survival rate at different stages of ontogeny, female fecundity, the frequency of dominant lethal mutations (DLM) and the DNA damage. mei-41 and rad-54 mutants were most sensitive to the action of low dose radiation (80 mGy) in terms of survival and DLM. However, at the level of DNA damage, an increased radiosensitivity is observed only at larger doses of low intensity irradiation. Based on these observations, we can conclude about the importance of repair and its genes in the formation of the effect of low level doses of ionizing radiation in Drosophila.

[The radiationally induced change of level of double-stranded breaks DNA in neuroblasts of larvae and frequency of lethal mutations in sex cells of males Drosophila melanogaster]

The level of damage DNA in neyroblastes of larvae and frequency of recessive sex-linked lethal mutations of males from chronically irradiated populations Drosophila melanogaster, differing on mobile P-elements patterns, was estimated. Received results testify, that exposition in conditions a chronic gamma-radiation (absorbed radiation dose at one generation is compounds 10 mGy) result to increase of significance of parameters and change of sensitivity of cells to following of an acute irradiation in a dose of 3 Gy.

[Ecological and genetic monitoring of muridae from populations undergone to the chronic irradiation]

In work the data of long-term researches of consequences of chronic irradiation and radioactive pollution on a population of muridaea living in a zone of failure on the Chernobyl atomic power station and in territory of Northern radioecological station are resulted. It is shown, that chronic influence by investigated factors leads to authentically significant change of size of the genetic load determined on a level cytogenetic damages, intensity of reproduction, fertility.

[The dynamics of variability of the genotype of experimental populations of Drosophila melanogaster by chronic radiation exposure]

The reaction on the irradiation in a dose 3 Gy of experimental populations of Drosophila melanogaster, differing on mobile genetic element patterns, chronically irradiated in low doses ionising radiation was investigated. Received results testify that the effect of radioadaptation is found out only in populations with an initial genotype and is not revealed at populations containing P-mobile elements. It is shown, that in chronically irradiated populations D. melanogaster with an initial genotype, decrease in frequency recessive lethal mutations after a sharp irradiation in a dose 3 Gy is observed. The analysis of frequency of dominant lethal mutations and gonads atrophy such tendency has not revealed. It is supposed, that the mechanisms participating in formation of the adaptive answer, induced with an irradiation and transpositions activity of mobile elements differ.

[The dynamics of survival rate of experimental polulations of Drosophila melanogaster undergone to a chronic irradiation]

In genetically non-uniform populations Drosophila melanogaster in conditions of a chronic irradiation in a doze 10-11 sGy/generation dynamics parameters of populations was investigated. It is established, that number of individuals in irradiated populations is lower, than in control. It is revealed, that viability of populations undergone to a chronic irradiation depends on their genotype. The gradual increase in fruitfulness, viability of individuals and the decrease in a level of lethal mutations in a number of generations after an irradiation in small dozes is caused by adaptable opportunities of the populations.

[The hormonal and genetic effects induced by an irradiation in small dozes at Tradescantia (a clone 02)]

The purpose of the present work was studying the possible interrelation of the hormonal status of plants and size of the genetic effects induced by an irradiation in small dozes. The frequency of somatic mutations in strings Tradescantia (a clone 02) at an irradiation in dozes up to 28 cGy was estimated. Influence radiations in a range from background up to 28 cGy on the maintenance in inflorescences Tradescantia (a clone 02) the basic groups of plant hormones is investigated: abscisic acid, cytokinin, auxin and gibberellin A3. It is shown, that small dozes of an irradiation cause extremely radical changes of hormonal balance in fabrics of inflorescences Tradescantia. Received results are discussed with attraction of the data on influence phytohormones on kinetics a cellular cycle.

[The influence of low doze gamma-irradiation on life span of Drosophila mutants with defects of DNA damage sensation and repair]

It was shown that life span of wild type strain Canton-S increased after low doze gamma-irradiation. It was revealed the decrease of life span after irradiation in Drosophila mutants with defects of DNA damage sensation and repair genes mei-9 and mei-41, both in homozygous and heterozygous lines. In mei-41 line males' lives longer than females in contrast to other lines.

[Genetic aspects of the irradiation in small doses of laboratory lines and experimental populations Drosophila melanogaster]

One of explanations of revealed effects of small doses of an irradiation is induced genetic instability on which background there is a realization of the various radiobiological reactions resulting as to stimulation, and significant oppression of the vital functions of a cell or an organism. In work the given estimations of consequences of an irradiation in small doses of mutant lines of the drosophila are submitted. Paramount value in definition of their size and an orientation of reaction of a genotype is supposed, that, have processes leaders to change of activity of mobile genetic elements and programmed destruction of a cell.

[Life-span in generations of chronic irradiated Drosophila wild type isogenic and geterogenic strains]

With the goal to study radioadaptation on life-span and observe the role in this phenomenon of genotype, we investigated the dynamics of life-span in 14 consistent generations after chronic gamma-irradiation in heterogenic (Canton-S) and isogenic (Oregon-R spa) Drosophila wild type strains. The gamma-source was 226Ra in dose 60 cGy per generation. The animals kept in standard conditions (25 degrees C and 12 h lighting). Was shown, that the dynamics of median life-span in wild type strains Canton-S and Oregon-R spa was different and the character of alterations depends on genetic heterogeneity. After chronic irradiation in generations in heterogenic line Canton-S since 5 generation cyclic life-span oscillations disappeared, values of median life-span leave on a plateau. Since the 8th generation the life-span values of irradiated populations exceeded all the control values. As a result of the irradiation practically in all generations in isogenic line Oregon-R spa occurs increasing of life-span with the comparing to non-irradiated control. This is possible due to the positive influence of radio-induced heterogeneity on the life-span of isogenic strain. Thus, chronic irradiation led to violation of natural cyclic dynamics of Drosophila life-span in heterogenic strain, discovered in the end 80-s' years by F. Lints and D. Ismaylov. Irradiation of isogenic strain led to increasing of life-span in all generations.

[The influence of gamma-irradiation in low doses on the rate of dominant lethal mutations in drosophila melanogaster]

The dose-rate effect of acute and chronic irradiation in the dose of 0.2 Gy in Drosophila melanogaster repair (mei-41, mus209 [Russian character: see text] mus309) and free radicals detoxication (sod) mutant strains was investigated. Was shown the lack of dose rate effect on the rate of dominant lethal mutations in mei-41, mus209 and sod. However in mus309, that has defect in the main Drosophila pathway of the DNA double strand breack repair, the increase of the mutation rate after chronic irradiation was observed (inverse dose-rate effect). The obtained results suggest the main role of DNA double strand breack repair in dose-rate effect formation in Drosophila.

[Effect of low-dose irradiation on the lifespan in various strains of Drosophila melanogaster]

Drosophila melanogaster strains defective in repair, antioxidant defense, and apoptosis displayed a higher aging rate than the wild-type strains when unexposed to ionizing radiation. Irradiation changed the lifespan depending on the genotype. The lifespan and the functional (neuromuscular) activity, which reflects the "life quality", changed in the same direction. A mechanism was suggested for the remote effect of low-dose irradiation on the lifespan. Since cells with a weakened defense system accumulate lesions and age at a higher rate, their elimination in early ontogeny decelerates age-related changes and decreases the aging rate. In subsequent generations, this somatic stress response (hormesis) is replaced by negative genetic effects at the population level and, consequently, the lifespan decreases.

[The genetic effects induced by an irradiation in low doses at Drosophila melanogaster]

This article generalizes the results received by authors in researches of genetic effects of an irradiation for Drosophila. It is supposed, that the main effect of low intensity irradiation is connected with the induced genetic instability on which background the realization of effects of a different direction is possible.

[The influence of ecdysone-containing phytopreparations on life span of Drosophila melanogaster strains depending on the genotype]

The longevity of Drosophila strains has been investigated after treatment by a hormone 20-hydroxyecdysone (80% solution) and a phytoecdysteroid-containing metaverone preparation (contains 5-7% of 20-hydroxyecdysone) in preimaginal stages of development. It is shown, that life expectancy of ecdysone-deficient woc strain exceeds life expectancy of wild type Canton-S strain by 46%, whereas ecdysone or metaverone treatment removes these distinctions. At the same time, treatment by ecdysteroid-containing preparations of Canton-S has not induced any essential alteration of life span. Thus, the new ageing gene woc has been discovered, the woc mutation essentially increases the life span of Drosophila, and its effect is mediated by a hormone 20-hydroxyecdysone and has the threshold corresponding natural physiological concentration of this hormone in an insect organism. The data have confirmed the conception of "antagonistic pleiotropy" according to which only mutations having advantages during the prereproductive and reproductive period are fixed in evolution, and their negative effect is delayed up to a postreproductive stage of life cycle. As a result we can see accumulation with age of structural and functional damages which increase probability of death. Indeed, genes of ecdysone synthesis play fundamentally important role in early development and sexual reproduction of insects, however essentially reduce their life span.

[Genetics aspects of different light regime influence on drosophila life span]

It was analyzed the difference of Drosophila life span in strains with low activity of Sod or excision repair enzyme Mus210 (homolog of yeast RAD4 and mammal XPC) in comparison with wild type strain Canton-S in conditions of 24 h and 0 h light. Mutants having low capacity to detoxify free radicals and repair DNA are characterized by stronger difference between life span at 24 h and 0 h light in comparison with wild type strain. Thus the life span increasing in the dark is due to decline of free radical and DNA lesions production. In wild type strain the effect of 12 h dusky light had not more effect on life span than intensive 24 h light. In most cases the difference between life span at 0 h and 24 h light was too much in males than in females, especially in Sod strain.

[The ecology-genetic consequences of chronic irradiation for the populations of the plants and animals]

The modem presentations are considered in the review about the consequences for the genotype of animals and of plants of the chronic action of factors of low intensity. Inoffer is spoken about possible dug the chronic irradiation in small doses in microevolution events.

[Aging rate after continual low dose irradiation of drosophila strains with apoptosis deregulation]

In this article the results of investigations of interrelation between radio-induced apoptosis in larvae nervous system and aging in imago are presented. It was shown that the apoptosis level of larvae nervous ganglion 2.5 folds increased after exposure to ionizing radiation (54 cGy). Irradiation of stocks with higher apoptosis induction sensitivity, bearing mutations of inhibitor apoptosis protein th (allele th1 and th4) and wild type strain Berlin leaded to elevation of activity at all ages and accordingly to decreasing of aging speed. Whereas in stocks with lower apoptosis induction sensitivity (with mutations of genes rpr, grim, hid, dArk and Dcp-1) this effect was not observed. The obtained results suggested that radiation-induced apoptosis could be one of the mechanisms preventing aging.

[Age dynamics of the activity of the imago after chronic irradiation of larvae from the Drosophila line with disruption of apoptosis regulation]

The relationship was studied between radiation-induced apoptosis in the nervous system of Drosophila larvae and the age dynamics in adult fly neuromuscular activity. The level of apoptosis in the neural ganglia of third-instar larvae from the wild-type strain increased 2.5 times after larval exposure to ionizing radiation (54 cGy). Irradiation of the strain with enhanced sensitivity to apoptosis induction, which carries a mutation in gene-inhibitor of apoptosis th (allele th4), and the wild-type strain Berlin led to an increase in neuromuscular activity of adult flies throughout the experiment and, consequently, to reduced aging rate. Conversely, this effect was not observed in strains with reduced sensitivity to induction of apoptosis (with mutations in genes dArk and Dcp-1).

[Induction of mutations in unirradiated X-chromosome of Drosophila melanogaster hybrids of repair deficient females mei-41 [D5] and mus209 [B1] and irradiated males M5]

It has been analyzed the frequency of the recessive lethal mutations in the unirradiated X-chromosome of Drosophila. Females of wild type (CS) as well as of error-prone (mei-41) and error-free (mus209) mutant strains were used. In CS hybrids the increasing of the mutation rate (p < 0.05) was found. In muc209 hybrids the mutation rate was not affected. In mei-41 hybrids the tendency to decreasing of the mutation rate was found. The obtained results demonstrate the possible role of error-prone repair in the inducing of mutations in the unirradiated X-chromosome in the presence of irradiated homologue.

[Longevity of Drosophila after exposure to low doses of radiation and etoposide]

The review of perennial researches of the authors on a problem of radiation-induced aging is presented. From the point of view of radiogenetics it is represented perspective to investigate influence of an exogenous irradiating in small doses on fruit fly with defined mutation by phenotypes, that allows to repute a role of separate genes and mechanisms, controlled by them, in a determination of lifetime. At lines described by differences in pattern of mobile genetical elements, the different reaction to an irradiating explained from the point of view of features of the given mobile elements is found. The processing etoposide in concentration 5 microM on preimaginal stages of line with defects of a reparation (mei-41D5) and hypersensibility to an induction apoptosis (wg1-7, wg7L74, th1 [symbol: see text] th4) results in down-stroke of lifetime. The dominant effect of a gene mei-41D5 in a regulation of etoposide-induced change of lifetime is found. Is exhibited, that at lines with defects proapoptosis of genes reaper and Dcp1, the lifetime after influence, both ionizing irradiating, and inducer apoptosis etoposide is enlarged in comparison with the control.

[The role of reaper-dependent apoptosis in radiation-induced life-span alterations in Drosophila melanogaster]

This is the result of studying on a problem of radio-induced ageing. From the point of view of radiation genetics it is perspective to investigate influence of low doze irradiation on individuals with the mutant phenotypes that allows to assume a role of separate genes and mechanisms controllable by them in determination of life span and ageing. The role of a reaper-dependent way of apoptosis regulation in the induced change of life span is shown. The assumption is put forward that apoptosis has the important role during ageing an animal organism.

[Role of apoptotic cell death in radioinduced aging in Drosophila melanogaster]

The attempt in made to estimate a role of programmed cell death (apoptosis) in radio-induced life span alteration and aging. It was shown with the use of mutant Drosophila melanogaster laboratory strains, that the disfunction of a reaper-dependent apoptosis pathway, together with the action of ionizing radiation and/or apoptosis inductor etoposide, could lead to change of life span and a pace of aging. In Drosophila strain with defect of proapoptosis gene reaper, the increase of life span after irradiation and etoposide treatment was observed. At the same time the strain with overexpression of a protease dcp-1 gene and the strain with the defect of antiapoptosis diap-1/th gene decreased the life span after irradiation and etoposide treatment. The obtained facts are discussed from a position of participation of apoptosis deregulation in radio-induced and natural aging of whole organisms.

[Radioinduced change in life span of laboratory strains of Drosophila melanogaster]

Chronic irradiation (accumulated dose 0.6-0.8 Gy) was shown to change the life span in male Drosophila melanogaster. Death was retarded in wild-type strains and accelerated in mutant strains defective in DNA repair and displaying a higher sensitivity to induction of apoptosis.

[Genetic effects in Drosophila melanogaster induced by chronic low-dose irradiation]

It was investigated the influence of the chronic gamma-irradiation in the dose rate of 0.17 sGy/h on the rate of genetic variability in the laboratory strains of Drosophila melanogaster with genotypic distinguishes in mobile genetic elements and defects in the DNA repair processes. It was shown that the rates of induction of recessive lethal mutations depended on genotype of investigated strains. In the different strains we have observed an increase as well as a decrease of the mutation rate. Also in was established that irradiation leads to the frequencies of the GD-sterility and mutability of the snw and h(w+) in the P-M and H-E dysgenic crosses. The obtained results suggest that mobile genetic elements play an important role in the forming of genetic effects in response to low dose irradiation.

[The role of genetic instability in cell aging]

The current research literature on the mechanisms responsible for maintenance of the genomic stability and their role in cell senescence both in vivo and in vitro is reviewed. Various types of age-dependent genomic destabilization in senescent cells are considered. Genetic instability of senescent cells is assumed to be associated with the life span and aging of an entire organism.

[Variability in the longevity of Drosophila imagoes under chronic irradiation at low doses]

The investigation of life span variability induced by a chronic influence of low doses gamma irradiation on the laboratory stocks of D. melanogaster, distinguishing by mobile genetic units, were carried out. Shown was the link of life span alterations in D. melanogaster with features of cytotype and genotype in tested stocks and with induced apoptotic cell death. The life span variation can be determined by a genomic destabilisation with an induction of mobile genetic elements in conditions of chronic gamma irradiation.

[Effect of chronic low-dose irradiation and etoposide on the life spain of Drosophila melanogaster strain mei-41]

Longevity is a temporal characteristic dependent on the level of equilibrium between the damaging and restorative processes in an organism. This is a complex parameter determined by both genotypic and external factors. In experiments with the mutant strain of Drosophila melanogaster mei-41D5, it was demonstrated that chronic exposure to low-dose radiation can change the longevity of flies. A decrease in the longevity of both males and homo- and heterozygous females of this strain was also caused by specific inducers of apoptosis. We suggest that apoptosis plays a certain role in the aging of an organism and that the dominant gene mei-41D5 takes part in determining longevity in Drosophila.

[The level of dysgenic sterility and recessive mutations induced in laboratory strains of Drosophila melanogaster exposed to chronic low-dose gamma irradiation]

Recent investigations showed that genetic instability accounts for many radiobiological effects. However, mechanisms underlying this phenomenon are still poorly understood. Assuming that mobile genetic elements may be involved in the induction of genetic instability, we studied parameters that characterize the activity of these elements in Drosophila melanogaster: hybrid dysgenesis and the level of recessive lethal mutations. In our experiments, we used D. melanogaster strains that differed in the type of hybrid dysgenesis (P-M and H-E). It was demonstrated that chronic exposure to radiation leads to substantial changes in the genetic structure of a population and an enhanced level of dysgenic sterility. Our results indicate that genetic instability and adaptation to the effect of chronic gamma-radiation are associated with the radiation-induced mobilization of mobile genetic elements.

[Results of the studies on radiation ecology and radiation biology at the Institute of Biology of Komi Science Center of Ural division of Russian Academy of Science (on 40th anniversary of the Department of Radiation Ecology)]

Information about the foundation and history of the Radiation Ecology Department and results of the researches on the effect of increased background radiation level on plant and animal populations, migration of radionuclides in natural biocoenosies with increased radiation level are presented.

[Current aspects of radiobiology of Drosophila melanogaster. Apoptosis and aging]

The mechanisms of post radiation life span alteration are reviewed and discussed. The mechanisms underlying radiation induced organism aging and death are not well understood and under great interest. What is the cause of radiation-induced "aging"? What are the mechanisms leading to senescence and death? Recent achievements in molecular biology and genetics suggest that cell senescence is determined by telomeres reduction (Biokhimiya, 1997). This mechanism seems to play an important role in aging. However the aging in postmitotic organisms (for example Drosophila melanogaster) can not be explained by telomeres reduction mechanism. It is suggested that radiation induced life span alteration can be explained by deregulation of apoptosis in multicellular organisms.

[Genetic effects of chronic irradiation of low intensity]

The report reveals the results of genetic studies of biological consequences of Chernobyl NPP accident and experiment with low radiation carried out in 1986-1996 years. The report deals with the results of cytogenetics observation of "liqudators" and data of genetic analysis of some laboratory strains of Drosophila melanogaster. It supposed, that the alteration level of mutability may be explained in destabilization of genotype. The essential part in induction of genotype destabilization replies the genome instability mechanisms.

[The mutability of natural populations and laboratory strains of Drosophila under conditions of chronic irradiation at small doses of low intensity]

The frequency of irradiation-induced recessive lethals has been studied in chromosomes 1 and 2 of Drosophila melanogaster. It supposed, that the higher level of mutability may be explained in destabilization of genotype. The essential part in induction of genotype destabilization replies the genome instability mechanisms.

[The monitoring of natural populations of Dactylis glomerata L. in the area of the accident at the Chernobyl Atomic Electric Power Station]

Results of five years monitoring (1986-1991) of seed quality (SQ) and chlorophyll mutation frequency (MF) of Dactylis glomerata L., growing within 30-km zone of Chernobyl NPP are presented. It was shown that during initial postaccident period (1986, 1987) the criteria depend of the gamma-phone on the sampling plots. It was not found the correlation between SQ, MF and duration of plant growing under condition chronic irradiation.

[The dynamics of the frequency of cytogenetic disorders in micropopulations of murine rodents inhabiting the region of the accident at the Chernobyl Atomic Electric Power Station]

Cytogenetic examination of some species of Muridae from Chernobyl region was carried out in 1986-1993. It was revealed that the dynamic of cytogenetic aberrations in cells of animals from territories with distinct level of radioactive contamination differed.

[Results of the cytogenetic examination of the people taking part in the clean-up of the accident at the Chernobyl AES]

Chromosome preparations from peripheral blood cells of 117 subjects who took part in liquidation of Chernobyl NPP accident consequences in 1986 have been investigated. The number of chromosome aberrations has been shown to increase considerably. A short-term exposure has been found to be 5-7 times more effective than long-term one.

[Embryonic mortality of the root vole as an index of the effect of small doses of natural radioactivity on genetic processes in populations]

A study was made of the pre- and post-implantation death of (F2--F4) Microtus oeconomus progeny whose parents lived in territories where natural radiation background was increased (an exposition dose-rate of 3.6-144.0 pC/kg X s). The spontaneous rate of pre- and post-implantation death of progeny of irradiated (experimental) animals was higher than that of intact ones (control). The animals kept in conditions of chronic irradiation (46.2 pC/kg X s) exhibited a more pronounced discrepancy in embryonal death rate. It is suggested that genetic differences in the populations were responsible for different rate of embryonal death of the control and experimental animals.

[Dynamic analysis of the induction of chromosome aberrations in the bone marrow cells of laboratory mice]

A study was made of the incidence of such damages as breaks, gaps, and exchanges occurring in bone marrow cells of CBA mice after irradiation with a dose of 12.9 mC/kg. Males and females exhibited a similar spontaneous chromosome aberration level. Nevertheless, the experimental results obtained indicate that males are more radiosensitive than females.