Inbreeding effects in Drosophila congenic strains: the influence of genetic background of different origin

Aim. To compare reproductive indices and stress resistance of Drosophila at outbreeding and inbreeding. Methods. Drosophila melanogaster congenic strains with incomplete development of the radial wing vein – radius incompletus – were used: the laboratory one and the strain, in which the mutation was placed into the genetic background of wild type strain, which originates from the natural population from radiation contaminated territory. Before the experiment strains have passed 65 generations of inbreeding. Viability (number of individuals, pupa stage mortality), dominant lethal mutations frequency and life span of imago at starvation were analysed. Results. After inbreeding, there was a decrease in the frequency of dominant lethal mutations and an increase in viability of the strain, which originates from the natural population, and a decrease of mortality at the pupal stage in both strains. Decreased life span of imago at starvation has been shown only for the inbred strain, which originates from the natural population. Conclusions. Inbreeding for 65 generations has no significant negative effect on reproductive indices; reduction of stress resistance during inbreeding has been shown only for the strain, which originates from the radiation contaminated territory. Keywords: Drosophila, viability, dominant lethal mutations, life span of imago at starvation, inbreeding.

Antimutagenic activity of probiotic drugs on the example of Drosophila

Probiotic preparations were obtained on the basis of cryopreserved forms of pure cultures of L. plantarum and B. subtilis using freeze drying. The antimutagenic activity of the obtained probiotic preparations was investigated in relation to 1%, 0.1% and 0.01% concentrations of cobalt sulfate using the example of dominant lethal mutations of Drosophila. A positive antimutagenic effect of probiotic preparations was shown in relation to 0.1% and 0.01% concentrations of CoSO4 with an exposure duration of at least 3 days.

Significant increase in the dominant lethal mutations: benzo(a)pyrene

Background: Use of biomarkers particularly under in vivo condition is of importance in risk assessment. This study is proposed to identify the in vivo antigenotoxic potential using dominant lethal mutation test in B(a)P exposed, turmeric fed animals and evaluate the role of turmeric in counteracting the germ cell mutations. Methods: Twenty four male mice were taken and divided into 4 groups each group containing 6 mice/group. The first and second group received stock diet (control) while the third and fourth groups received 5% turmeric diet for a period of one month. At the end of feeding period, second and fourth group received a single dose of benzo(a)pyrene 1mg/mouse intraperitoneally. After 1 week each male mouse was mated to 3 female mice at 1,4, 8 and 12 week intervals. On 13th day from mid point of mating, the females were sacrificed and live and dead embryos were counted to study the pre and post implantation loss of embryos. The differences in the frequencies of pre and post implant deaths were done by comparing treated with control group at 4-time periods by analysis of variance (ANOVA) and chi-square test which is used to compare treatment group and positive control with negative control. Results: Feeding of 5% turmeric and treatment with a single dose of B(a)P did not show any significant effect on the mutagenic index or the frequency of pregnancy in treated groups compared with control. There was no apparent induction of dominant lethal mutations in B(a)P or B(a)P+Turmeric treated groups. No post implantation dominant lethal effects produced by B(a)P could be detected in this study. The induction of B(a)P and treatment with turmeric did not influence the dominant lethal test. Conclusion: B(a)P did not produce a significant increase in the dominant lethal mutations. Turmeric also did not give any positive response and may be considered as non-mutagenic. The negative result suggests that under the conditions of the test the test substance may not be genotoxic in the germ cell of the treated sex of the test species.

Impact of chromium and boron compounds on the reproductive function in rats

The purpose of this research is to study the process of mutagenesis and the reproductive function in male rats under separate and combined exposure to chromium and boron compounds. The experiment was conducted on two groups of animals. The first group was used to assess the ability of potassium dichromate and boric acid to induce mutation in germ and somatic cells under isolated and combined administration with the use of the dominant lethal mutations test and the micronuclei test in the polychromatophilic erythrocytes of the bone marrow. The second group was used to test the combined and separate effect of the compounds under consideration on the reproductive function of male rats during the spermatogenesis cycle. When used in specific doses, boron compounds are a promising means of preventing and correcting chromium-induced effects in chromium production facility workers and people who live in ecologically adverse regions.

Analysis of embryonic mortality frequency in Drosophila melanogaster stocks with radius incompletus mutation under inbreeding conditions

It is known that inbreeding leads to homozygotization of alleles of the most genes. The rate of this process is determined by the degree of kinship between crossed individuals. In addition, inbred breeding is accompanied by a change in the structure and functioning of the genome of cells of females’ generative system: mutational level increases and oogenetic segregation may be violated. This leads to a decrease in the number of laid eggs and an increase in the level of embryonic mortality. This process, described as "the effect of resistance to selection," is aimed at adapting to external conditions and associated with the selection of viable offspring. The character of manifestations of mutational variability is determined to a large extent by the direction of selection. However, up to now our knowledge of the role of the genotype in controlling the level of embryonic mortality in Drosophila melanogaster stocks in conditions of inbred breeding is not deep enough. The purpose of our work was to analyze the frequency of dominant lethal mutations in Drosophila stocks from radiation-contaminated regions of Ukraine (Polesskoe and Ozero), carrying radius incompletus mutation, depending on the degree of inbreeding. It is shown that under conditions of severe inbreeding (without selection) changes in the total frequency of dominant lethal mutations have a cyclic character, which depends on the genotype of the stocks. So, in radius incompletus stock, the indicator studied increases after 10 generations of selection and remains at enough high level for 20 generations. For the stocks from radiation-contaminated territories of Ukraine with radius incompletus mutation, which are contrasting in the level of embryonic mortality, two decrease peaks are shown (for the stock ri(Oz) – after 5 and 65 generations of inbreeding) and an increase (for the line ri(Pol) – after 5 and 32 generations of inbreeding) of the total frequency of dominant lethal mutations. The main factor influencing the change in the mortality level at the stage of early embryogenesis in Drosophila carrying radius incompletus mutation is the genotype of the stocks that are used in the work. It’s contribution increases after 10 (h2gen=44.78), 15 (h2gen=45.86) and 100 (h2gen=46.36) generations of inbreeding. The effect of inbred breeding was observed after 32 (h2inbr=22.61) and 65 (h2inbr=11.89) generations. The combined effect of both factors on the total frequency of dominant lethal mutations is shown for each of the generations studied. The highest values were shown after the 5th (h2comb=53.86) and the 65th (h2comb =40.63) generations of inbred breeding.

Impact of Acrylamide on Calcium Signaling and Cytoskeletal Filaments in Testes From F344 Rat

Acrylamide (AA) at high exposure levels is neurotoxic, induces testicular toxicity, and increases dominant lethal mutations in rats. RNA-sequencing in testes was used to identify differentially expressed genes (DEG), explore AA-induced pathway perturbations that could contribute to AA-induced testicular toxicity and then used to derive a benchmark dose (BMD). Male F344/DuCrl rats were administered 0.0, 0.5, 1.5, 3.0, 6.0, or 12.0 mg AA/kg bw/d in drinking water for 5, 15, or 31 days. The experimental design used exposure levels that spanned and exceeded the exposure levels used in the rat dominant lethal, 2-generation reproductive toxicology, and cancer bioassays. The time of sample collection was based on previous studies that developed gene expression–based BMD. At 12.0 mg/kg, there were 38, 33, and 65 DEG ( P value <.005; fold change >1.5) in the testes after 5, 15, or 31 days of exposure, respectively. At 31 days, there was a dose-dependent increase in the number of DEG, and at 12.0 mg/kg/d the top three functional clusters affected by AA exposure were actin filament organization, response to calcium ion, and regulation of cell proliferation. The BMD lower 95% confidence limit using DEG ranged from 1.8 to 6.8 mg/kg compared to a no-observed-adverse-effect-level of 2.0 mg/kg/d for male reproductive toxicity. These results are consistent with the known effects of AA on calcium signaling and cytoskeletal actin filaments leading to neurotoxicity and suggest that AA can cause rat dominant lethal mutations by these same mechanisms leading to impaired chromosome segregation during cell division.