Genetic effects of radiocarbon in reproductive cells of male mice

The genetic effect of incorporated radiocarbon was studied after single, long-term (33 days) and chronic (6 and 12 months) treatment of male mice (CBA X C57B1) F1 with [14C]glucose. The genetic effect in male germ cells was estimated by 3 tests: DLM frequency in post- and pre-meiotic cells, RT frequency in stem spermatogonia and frequency of abnormal sperm heads. Absorbed doses in the gonads were: 0.22, 0.50 and 1.01 Gy, after a single exposure; 0.74 and 1.47 Gy, after long-term exposures; and 0.006 and 0.031 Gy, after chronic exposure for 6 months; and 0.013 and 0.066 Gy, for 12 months. The results suggest that DLM frequency in post-meiotic cells increased linearly with increasing the dose of 14C single and long-term exposures at a dose of 1.47 Gy only. A chronic treatment with [14C]glucose induced no increase in DLM frequency. RT frequency in stem spermatogonia was statistically significantly higher than the control level after the single and long-term exposure to 14C. A comparison of the results with the results of external single and chronic gamma-irradiation allows the conclusion that the relative genetic efficiency of radiocarbon as compared with that of gamma-rays is about 1.     

Genetic action of 131I and 125I on the germ cells of male mice

A study was made of the genetic effects of iodine radioactive isotopes in male germ cells of (CBA X C57Bl)F1 hybrid mice. After a single intraperitoneal administration of Na131I (1.48 to 740 kBq/g) or Na125I (148 to 7400 kBq/g) to males the occurrence of dominant lethal mutations (DLM), reciprocal translocations (RT), and abnormal sperm heads (ASH) was studied. The radioactive iodine isotopes induced DLM at the postmeiotic spermatogenesis stages only. After the effect of the isotopes, the frequency of RT increased insignificantly with dose. The frequency of ASH was only increased with the highest 131I dose. Relative biological effectiveness of 131I and 125I was less than 1 with a reference to the indices under study.     

Antimutagenic effects on male germ cells of mice

The alkylating agent cyclophosphamide (CPA) and the antioxidant ethoxyquin (EQ) were administered perorally to NMRI mice. The strong clastogenic action of CPA on spermatogonia was diminished by simultaneous doses of EQ. Higher doses of the antioxidant produced greater anticlastogenic action. Furthermore, the action of the mutagen and the antioxidant on the late spermatids and the spermatozoa was observed using the dominant lethal test. The antioxidant had only a weak influence on these postmeiotic stages.     

Decreased reproductive performance in xCT-knockout male mice

Sulphoxidation occurs in protamines that are enriched in cysteine and supplies chromatin for packaging. The extracellular fluid contains higher levels of oxidised cysteine (cystine), and some cells utilise system x_c^?, a cystine transporter in which xCT is the main protein component, to fulfil the need for cysteine. We hypothesised that system x_c^? might ensure the supply of cysteine needed for spermatogenesis. The reproductive ability of xCT^?/? male mice at 6- to 18-weeks of age appeared to be lower than xCT^+/+ male mice. The courtship behaviour of the xCT^?/? male mice was undynamic, which appeared to be associated with the low reproductive ability of xCT^?/? male mice. xCT was found to be expressed in mouse testes, notably in Sertoli cells, as well as in the epididymis and the levels were increased at the time of sexual maturation. Despite the normal histological appearance of testicular tissues, the cauda epididymis of xCT^?/? mice contained round, greater numbers of immature spermatogenic cells than that of xCT^+/+ mice. However, there were no significant differences in the numbers of sperm stored in the cauda epididymis or in the concentrations of cysteine or glutathione in the testes. The resulting sperm had normal fertilising ability. Thus, system x_c^? appears to function as a backup system for supplying cysteine to testes and play a pivotal role in supplying cysteine for normal sexual behaviour by a mechanism that is different from that for the supply of cysteine in spermatogenesis.     

Genetic and nutritional effects on male traits and reproductive performance in Tribolium flour beetles

In Tribolium flour beetles and other organisms, individuals migrate between heterogeneous environments where they often encounter markedly different nutritional conditions. Under these circumstances, theory suggests that genotype-by-environment interactions (GEI) may be important in facilitating adaptation to new environments and maintaining genetic variation for male traits subject to directional selection. Here, we used a nested half-sib breeding design with Tribolium castaneum to partition the separate and joint effects of male genotype and nutritional environment on phenotypic variation in a comprehensive suite of life-history traits, reproductive performance measures across three sequential sexual selection episodes, and fitness. When male genotypes were tested across three nutritional environments, considerable phenotypic plasticity was found for male mating and insemination success, longevity and traits related to larval development. Our results also revealed significant additive genetic variation for male mating rate, sperm offence ability (P(2)), longevity and total fitness and for several traits reflecting both larval and adult resource use. In addition, we found evidence supporting GEI for sperm defence ability (P(1)), adult longevity and larval development; thus, no single male genotype outperforms others in every nutritional environment. These results provide insight into the potential roles of phenotypic plasticity and GEI in facilitating Tribolium adaptation to new environments in ecological and evolutionary time.     

Genetic effects of combined chemical-X-ray treatments in male mouse germ cells

Several studies have shown that the yield of genetic damage induced by radiation in male mouse germ cells can be modified by chemical treatments. Pre-treatments with radio-protecting agents have given contradictory results but this appears to be largely attributable to the different germ cell stages tested and dependent upon the level of radiation damage induced. Pre-treatments which enhance the yield of genetic damage have been reported although, as yet, no tests have been conducted with radio-sensitizers. Another form of interaction between chemicals and radiation is specifically found with spermatogonial stem cells. Chemicals that kill cells can, by population depletion, substantially and predictably modify the genetic response to subsequent radiation exposure over a period of several days, or even weeks. Enhancement and reduction in the genetic yield can be attained, dependent upon the interval between treatments, with the modification also varying with the type of genetic damage scored. Post-treatment with one chemical has been shown to reduce the genetic response to radiation exposure.     

Genetic variation in fertility of heat-stressed male mice

The damaging effects of heat stress on male fertility are evident in developing spermatozoa expressed in ejaculates 18-28 days post-stress in mice. Our objectives were to: (1) assess genetic variation in fertility of heat-stressed male mice and (2) determine response to selection for fertility after heat stress in male mice. Mature male mice were exposed to heat stress (35+/-1 degrees C; n=50) or control (21+/-1 degrees C; n=10) conditions for 24h (day 0) and then hemicastrated for tissue collection. Two periods of mating tests followed, period 1 (from days 3 to 11) when no reductions in fertility were anticipated, and period 2 (days 18-26) when variation in fertility was expected. Period 2 pregnant females were sacrificed in late gestation. Males were indexed by multiplying overall mean ovulation rate by pre-implantation survival and number of pregnant period 2 mates. The five highest and five lowest ranking males were identified as heat stress resistant and susceptible, respectively. Resistant males were 61.2units superior in the index, 57.5% greater in pregnancy rate, and 57.6 total fetuses greater than susceptible males. Progeny of resistant sires were superior to progeny of susceptible sires in estimated breeding value by 4.5units for the index, 4.1% for pregnancy rate, and 5.2 fetuses (P<0.0001). Heritability estimates for the index, pregnancy rate, and number of fetuses ranged from 0.09 to 0.13, suggesting male fertility following heat stress is heritable and responds to selection.     

Intrauterine position effects on steroid metabolism and steroid receptors of reproductive organs in male mice.

Mice differ in their adult reproductive characteristics as a function of whether they developed in utero between two male fetuses (2M males), which have higher testosterone levels, or between two female fetuses (0M males), which have higher estradiol levels. The present study was designed to further characterize biochemical parameters of 2M and 0M adult male mice. Activities of testicular steroidogenic enzymes, namely delta 5-3 beta-hydroxysteroid dehydrogenase/isomerase, 17 alpha-hydroxylase, and C17,20-lyase (C21SCC P450), were measured by means of radiometric assays and HPLC fractionation of substrate and products. Activity of 5 alpha-reductase in both seminal vesicle and prostate was measured by similar techniques. Estrogen and androgen receptor concentrations, which indicate capacity to respond to steroid hormones, were also examined in the accessory sex organs. For both seminal vesicle and prostate, 5 alpha-reductase activities were approximately 60% greater in 2M males than in 0M males, indicating greater capacity to form dihydrotestosterone from testosterone in organs from 2M mice. No significant differences were found in testicular steroidogenic enzymes between 2M and 0M animals, whereas the trend for all three activities was higher for 2M males than for 0M males. While no differences were found in estrogen receptor concentrations, 0M prostates had three times the concentration of androgen receptors (occupied receptors) compared to 2M prostates. Our findings suggest that intrauterine fetal position exerts a significant influence on subsequent adult androgen metabolism and androgen responsiveness in reproductive organs of adult male mice.     

The reproductive correlates of social hierarchy in laboratory male mice

In laboratory male mice the effects of social hierarchy on hormonal and spermatogenic testicular function, accessory organs and testicular weights, sexual behaviour have been investigated using an experimental model of social hierarchy, which is characterised by a minimal size (two male mice) and 5 days period of social interactions. The social rank of the partners was detected by asymmetry in aggressive behaviour. Using the experimental condition, when the both partners have no preferences for exclusive use of area we demonstrated that there were no rank differences in the number of mounts and testicular testosterone content. Nevertheless a rank asymmetry in the male sniffing behaviour towards a receptive female, weights of the testes, seminal vesicles, epididymes and the number of epididymal sperm was kept up in a stable social group. Social dominance was found to affect negatively on testicular testosterone increase in response to introduction of a receptive female and sexual attractiveness of male to a receptive female in both dominant and subordinate males. The results obtained demonstrate the impact of social hierarchy on reproduction in laboratory male mice, particular in respect of spermatogenesis and the testicular testosterone in response to a receptive female.     

Cytotoxic and genotoxic effects of methotrexate in germ cells of male Swiss mice

Methotrexate (MTX) is an anti-metabolite drug widely used in the treatment of neoplastic disorders, rheumatoid arthritis and psoriasis. Developed as an analogue of folic acid, it inhibits purine and pyrimidine synthesis that accounts for its therapeutic efficacy as well as for its toxicities. MTX has narrow therapeutic index and its toxicity has been reported in various organ systems including gastrointestinal, haematologic and central nervous system. The objective of the present study is to investigate the germ cell toxicity induced by MTX in male Swiss mice. MTX was administered intraperitoneally (ip) at the doses of 5, 10, 20 and 40mg/kg to mice (20-25g) weekly once (wk) for 5 and 10 weeks. The animals were sacrificed 1 week after receiving the last treatment of MTX. The germ cell toxicity was evaluated using testes weight (wt), sperm count, sperm head morphology, sperm comet assay, histology, TUNEL and halo assay in testis. MTX treatment significantly reduced the sperm count and increased the occurrence of sperm head abnormalities in a dose dependent manner. It induced the testicular toxicity as evident from the histology of testis. Sperm comet, TUNEL and halo assay in testis also revealed significant DNA damage after MTX treatment. On the basis of the present study, it can be concluded that MTX induced germ cell toxicity in mice.     

Genetic loss of Faah compromises male fertility in mice

Marijuana is the most commonly used illicit drug. Although there is some indication that reproductive functions in males are impaired in chronic marijuana users, the genetic evidence and underlying causes remain largely unknown. Herein we show that genetic loss of Faah, which encodes fatty acid amide hydrolase (FAAH), results in elevated levels of anandamide, an endocannabinoid, in the male reproductive system, leading to compromised fertilizing capacity of sperm. This defect is rescued by superimposing deletion of cannabinoid receptor 1 (Cnr1). Retention of Faah(-/-) sperm on the egg zona pellucida provides evidence that the capacity of sperm to penetrate the zona barrier is hampered by elevated anandamide levels. Collectively, the results show that aberrant endocannabinoid signaling via CNR1 impairs normal sperm function. Besides unveiling a new regulatory mechanism of sperm function, this study has clinical significance in male fertility.     

The effects of methyltestosteone on reproductive function in male greyhounds

Oral administration of methyltestosterone (MT) at 50 mg/dog/day to intact adult male greyhounds for 90 d resulted in decreased (P < 0.05) mean daily sperm output and mean testicular length. Additionally, the mean diameter of seminiferous tubules in MT-treated dogs tended to decrease (P = 0.08). Mean concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) and concentrations of testosterone in serum were also decreased or tended to decrease (P = 0.0003 to 0.059) at various sampling periods during MT treatment, suggesting alterations in spermatogenesis resulted from decreased serum concentrations of gonadotropins and steroids. Mean daily sperm output, mean testicular length, mean seminiferous tubule diameter and mean concentrations of FSH in serum were not decreased (P > 0.05) at the end of a 90-d recovery period. However, mean concentrations of serum LH and concentrations of testosterone were still lower (P < 0.05) during five of six and one of six sampling times, respectively, during the recovery period than the pretreatment levels, suggesting a prolonged effect of MT treatment on the pituitary/gonadal axis.     

The reproductive performance of XX/XY male chimeric mice

The reproductive performance of male aggregation chimeric mice was examined. C57BL/6 in equilibrium BALB/c male chimeras and control animals, C57BL/6, BALB/c, and their reciprocal F1 crosses, were mated with ICR females. Of 45 overt chimeras, 13 produced mixed-genotype progenies and were revealed to be XY/XY chimeras. By karyotype analysis 16 of 32 single-genotype progeny chimeras were determined to be XX/XY chimeras, but the remaining single-genotype progeny chimeras showed only XY metaphase plates, so that their chromosomal sex could not be determined. The mean litter size of C57BL/6 was significantly higher than that of BALB/c. In contrast, the birth rate of C57BL/6 was lower than that of BALB/c. XY/XY chimeras showed almost the same performance as C57BL/6 for litter size and as BALB/c for birth rate. There were no significant differences for both traits between the reciprocal F1 crosses and XY/XY chimeras. The mean litter size of XX/XY chimeras was lower than that of XY/XY chimeras and the differences was statistically significant. Some XX/XY chimeras had very small testes, while XY/XY chimeras had normal testes. Such results indicate that the reproductive performance of XX/XY male chimeras is inferior to that of XY/XY males.     

Beta-cypermethrin impairs reproductive function in male mice by inducing oxidative stress

Cypermethrin (CYP), an insecticide, has deleterious effects on male reproductive function. The objective was to identify whether the effects of beta-CYP on male reproductive organs were associated with oxidative stress. Three doses of beta-CYP (1, 10, and 20 mg/kg) were administered to male mice for 35 d, with or without vitamin E (20 mg/kg). The moderate (10 mg/kg) and high (20 mg/kg) doses of beta-CYP not only decreased body weight and the weight of the testes, epididymides, seminal vesicles, and prostate (P < 0.05) but also reduced serum testosterone concentration and the expression of steroidogenic acute regulatory protein (P < 0.05), in addition to damaging the seminiferous tubules and sperm development. Furthermore, moderate and high doses of beta-CYP administration decreased sperm number, sperm motility, and intact acrosome rate (P < 0.05). Based on ultrastructural analyses, high doses of beta-CYP produced swelling and degeneration of mitochondria and the smooth endoplasmic reticulum of Leydig cells and caused the formation of concentric circles. These toxic effects of beta-CYP may be mediated by increasing oxidative stress, as the moderate and high doses of this compound increased malondialdehyde and nitric oxide in testes (P < 0.05); reduced the activity of catalase, glutathione peroxidase (GSH-Px), and superoxide dismutase (P < 0.05); and activated ERK1/2 (P < 0.05). Vitamin E reversed the effects of beta-CYP on testosterone production and testis damage (P < 0.05 vs. the high-dose group). Therefore, we inferred that beta-CYP damaged the structure of testes and decreased sperm output by inducing oxidative stress.     

Induction of meiotic disturbances in spermatocytes I by pheromones as an inhibiting mechanism of male reproductive function in house mice

The influence of pheromons on reproduction and other important physiological characteristics has been reported for many mammalian species. However, mechanisms of this action at the level of target cells still remain unclear. A study was made of the influence of non-identified pheromones from adult males and a female pheromone 2,5-dimethylpyrazine on germ cells of CBA inbred strain mice. Cytogenetic analysis shows a significant increase in such meiotic disturbances as multivalent associations and autsomal univalents 24 h after exposure to pheromonal cues. Results of in situ hybridization show that the level of c-fos and c-jun expression is significantly higher 3.5 h after exposure to pheromones of adult males. It is likely that destabilization of chromosomal apparatus in dividing meiotic cells forms the basis of some reproductive effects of murine pheromones. Possible mechanisms of pheromone influence on reproduction are discussed.