Chemosignals from isolated females have antimutagenic effect in dividing the cells of bone marrow from male mice of the CBA strain

A level of X-ray induced mitotic disturbances in the cells of the bone marrow of male mice was studied under the modifying influence of chemosignals from isolated adult female mice of the CBA strain. It has been shown that the frequency of chromosomal aberrations in irradiated (4 Gr) males after exposing them for 24 hours on bedding soiled with female chemosignals is lower than in irradiated males in cages with clean bedding. The mechanisms and importance of the antimutagenic effect of female house mouse chemosignals are discussed.     

Balance hypothesis of action of socially significant volatile chemosignals on reactivity of chromosome machinery of the bone marrow dividing cells in the house mouse Mus domesticus L

Volatile chemosignals released by female CBA laboratory mice have been shown to produce action of different direction, depending on conditions of performance of experiment, on chromosome machinery of bone marrow cells in syngenic adult males. Thus, chemosignals secreted into environment by isolated adult females decrease frequency of mitotic disturbances in bone marrow dividing cells in male recipients as compared with spontaneous level in control animals. At the same time, 2,5-dimethylpyrazine - pheronome released only by high density caged females - increases frequency of mitotic disturbances. Preliminary 24-h-long action of chemosignals of isolated females decreases effect of the subsequent action of 2,5-dimethylpyrazine, although the level of disturbances exceeds that in control animals. The simultaneous action of used chemosignals neutralizes completely the 2,5-dimethylpyrazine action, the frequency of mitotic disturbances being not different from that after chemosignals of isolated females. The hypothesis is put forward about dependence of the revealed cytogenetic effects in male recipients on zoosocial conditions of maintenance of female donors of chemocommunication signals.     

The balance hypothesis of the effect of socially important volatile chemosignals on reactivity of chromosome machinery of bone marrow dividing cells in the house mouse <Emphasis Type="Italic">Mus musculus</Emphasis>

Volatile chemosignals released by female CBA mice are shown to affect the chromosome machinery of bone marrow cells in mature syngenic males in different ways depending on the experimental conditions. Chemosignals excreted by solitary adult females decrease the frequency of mitotic disturbances in bone marrow dividing cells of male recipients as compared with the spontaneous level in control animals. At the same time, 2,5-dimethylpyrazine, a pheromone released only by females caged at high densities, increases the frequency of mitotic disturbances. A preliminary 24-h treatment of males with chemosignals excreted by solitary females reduces the effect of a subsequent exposure to 2,5-dimethylpyrazine, however, the frequency of disturbances is still higher than that in the control. The simultaneous exposure to both chemosignals results in complete neutralization of the 2,5-dimethylpyrazine effect, and the frequency of mitotic disturbances does not differ from that observed after the exposure to solitary female chemosignals. It is hypothesized that the cytogenetic effects found in male recipients depend on the social housing conditions under which female chemosignal donors were kept.     

The alteration of attractiveness of intact males mice to females chemosignals, subjected of ionizing radiation in sublethal dose

After irradiation in a dose 4 Gy female mice of CBA and C57Bl/6 (female CBA during 18-23 days, female C57Bl/6 - 4-10 days) secretes with urine volatile components (chemosignals) which possess higher, than secretes intact females, attractiveness for intact males the same strains irrespective of a genotype. When estimation relative attractiveness postradiation secretes female mice CBA and C57Bl/6 intact males prefer chemosignals singenic (genetically identical) females during 1-23 day after irradiation. Observed olfactorial reaction male mice more differ from norm. In which males prefer chemosignals of allogenic (with a strange genotype) females. This disturbances identifed as postradiation reversion attractiving males of chemosignals, dependent on the genotype of females. Typical for norm chemosignalisation at females restored for 43 days after the irradiation. The mechanism and biological advisability of this phenomenon are discussed.     

Sex-dependent frequency and type of autosomal univalency at the first meiotic metaphase in mouse germ cells

Univalents at the first meiotic metaphase in mouse spermatocytes occur mainly in the XY pair, making it difficult to compare the amounts of univalency in males and females. In this study, the amounts of autosomal univalency in male and female meiosis were compared using the model strain CBA-T6, in which univalency of the small marker autosome pair T6 has been shown to occur very frequently in spermatocytes. Mice from inbred CBA and DBA strains were also analysed. The total frequencies of univalency (sex chromosomes plus autosomes) in metaphase I spermatocytes were 45.6% in CBA, 36.9% in CBA-T6, and 37.3% in DBA males. The aneuploidy in metaphase II spermatocytes ranged from 1.4 to 3% in these strains, which was in agreement with previous findings that most primary spermatocytes with abnormal chromosome configurations are arrested in their development before metaphase II. In the CBA-T6 strain, autosomal univalency at metaphase I mostly involved chromosome pair T6; however, its frequency differed significantly between the sexes, amounting to 18.9% in spermatocytes and 4.3% in oocytes. In the CBA strain, autosomal univalents at metaphase I were seen in 7.7% of the spermatocytes and 1.4% of the oocytes and, in DBA mice, in 4.9% of the spermatocytes and 3.8% of the oocytes. However, in DBA oocytes, when univalency occurred it usually concerned a greater number of bivalents in one cell (range: 2-19 disjoined bivalents), a phenomenon very rare in males of this strain. This study shows that univalent formation differs between the male and female types of meiosis.     

Intermittent stimulation and delay of puberty by urinary chemosignals and social contact in wild stock female house mice (Mus Domesticus)

A sequence of six experiments using wild stock house mouse (Mus domesticus) tested the effects of intermittent stimulation with either the urinary chemosignal released by grouped female mice or social contact from grouped females on the age of first vaginal oestrus in young females. Weanling female mice were exposed to bedding soiled by grouped females or cages containing grouped females for 15 min periods, then removed for a prescribed period, and placed again in a cage with soiled bedding or grouped females. The nature of the exposure to the puberty delaying effect, the number of total exposures each day, the total length of exposure to the stimulus, and the total time period over which the exposures occurred were varied. None of the treatment regimes employed here with soiled bedding from grouped females resulted in delays in the onset of first oestrus in test females. Young females exposed to grouped females for 6 or 8 exposures in a 4 h period, 6 or 8 exposures in an 8 h period, or 8 exposures in a 12 h period were significantly delayed in attaining puberty relative to control females that were exposed to cages containing clean bedding. These results are in contrast to earlier findings involving chemosignals that accelerate first oestrus wherein young females exhibited the capacity to accumulate the exposures to the urinary chemosignals from males, females in oestrus and pregnant or lactating females. Direct exposure to the grouped females on an intermittent basis can provide stimulation that is cummulative and results in delays in the onset of first oestrus.     

Puberty in pine voles, Microtus pinetorum, and the influence of chemosignals on female reproduction

We investigated the reproductive biology of an induced ovulator, the pine vole (Microtus pinetorum). Male puberty, measured as age at first impregnation, was found to occur as early as 44 days of age. Female puberty measured as age at first conception, was found to occur as early as 32 days of age, considerably earlier than previously reported. Females paired with stud males exhibited a doubling of uterine weight within 12 h, and vaginal sperm were present after 48 h. This indicates that although behavioral responses to males--including mating--require prolonged contact, physiological responses to males occur rapidly. Chemosignals from males slightly increased uterine and ovarian weights of females, but chemosignals from other females did not. Young females paired with stud males for 48 h in the presence of soiled bedding from the female's family had significantly smaller increases in ovarian and uterine weights than similar females paired on clean bedding. Suppression of reproduction in female offspring while they remain with the extended family unit is discussed as a life-history tactic and as a possible mechanism for inbreeding avoidance.     

Effect of volatile excretions induced with thymus-dependent antigen in female mice on the behavioural responses of males

It was found that thymus-dependent antigen sheep red blood cells in the optimal immunogenic dose (1 x 10(8) cells/mouse) induced in female mice of CBA and B6 strain secretion of attractive urinary volatile components (VCs), and in the supraoptimal dose (1 x 10(9) cells/mouse)--aversive VCs for intact males CBA strain. In a direct comparison of the properties ofVCs-immunized mice of CBA and B6, a modification of the effect of constitutive chemosignalling: disturbance of ability of females VCs to attract allogeneic males, was observed. The role of thymus-dependent antigen dose and sex of animals in the mechanism of generation of antigen-induced chemosignals is discussed.     

家鸡联会复合体的亚显微结构分析

本文以表面铺展——硝酸银染色技术,对家鸡的联会复合体(Syneptonemal Complex,SC)作亚显微结构分析。根据对10个精母细胞和10个卵母细胞SC的测量结果,绘制组型图。发现雌雄家鸡的常染色体的SC组型相同。在精母细胞中,性染色体(ZZ)的行为与常染色体相似。在卵母细胞中,性染色体ZW的长度不同,长轴为Z,短轴为W,两者之间只有部分配对,形成SC。从早粗线期到晚粗线期,由同源配对调整为非同源配对。另外,在一只雌鸡中,第一次观察到,有些细胞的常染色体能正常配对,而性染色体完全不配对的现象。     

Peripubertal exposure to male odors influences female puberty and adult expression of male-directed odor preference in mice

Testosterone-dependent olfactory signals emitted by male are well known to accelerate female puberty in mice (Vandenbergh effect). However, it remains unclear whether these chemosignals also influence adult expression of male-directed odor preference. Therefore, we exposed female mice to intact or castrated male bedding (vs clean bedding as control) during the peripubertal period (postnatal day (PD) 21–38) and measured male-directed odor preference in adulthood. At PD45 or PD60, females exposed to intact male odors, and thus showing puberty acceleration, preferred to investigate odors from intact males over females or castrated males. Females exposed to castrated male odors did not show puberty acceleration but preferred male (intact or castrated) over female odors. Finally, control females did not show any odor preference when tested at PD45, although a preference for male odors emerged later (PD60). In a second experiment, females that were exposed to intact male odors after pubertal transition (PD36–53) also preferred intact male over castrated male odors. In conclusion, our results indicate that peripubertal exposure to male odors induced early expression of male-directed odor preference regardless of puberty-accelerating effect and that induction of male-directed odor preference is not specific to the peripubertal period.     

Analysis for Pheromone-Induced Cytogenetic Disturbances Depending on Major Urinary Proteins of Laboratory Mouse Males

Young male CBA/LacStoRap mice for 2 h were exposed to pheromones that are transferred by major urinary proteins of sexually mature males of the same strain. The treatment was conducted using either a complete set of the major urinary proteins typical of the CBA mice or incomplete set of protein fractions detected in some animals. The effect of pheromones was estimated 24 h after treatment by cytogenetic analysis for disturbances in dividing bone marrow cells at anaphase–telophase and in germ cells at metaphase I. The frequency of both mitotic and meiotic disturbances was significantly increased after exposure to pheromones associated with the complete spectrum of the major urinary proteins. Conversely, no cytogenetic effect was observed in the absence of particular protein fractions. Possible consequences of the pheromonal effect on the genomes of somatic and germ cells are discussed as well as the relationships between pheromones and the major urinary proteins.     

Completion of meiosis in male zebrafish (<Emphasis Type="Italic">Danio rerio</Emphasis>) despite lack of DNA mismatch repair gene <Emphasis Type="Italic">mlh1</Emphasis>

Mlh1 is a member of DNA mismatch repair (MMR) machinery and is also essential for the stabilization of crossovers during the first meiotic division. Recently, we have shown that zebrafish mlh1 mutant males are completely infertile because of a block in metaphase I, whereas females are fertile but have aneuploid progeny. When studying fertility in males in a two-fold more inbred background, we have however observed low numbers of fertilized eggs (approximately 0.4%). Histological examination of the testis has revealed that all spermatogenic stages prior to spermatids (spermatogonia, primary spermatocytes, and secondary spermatocytes) are significantly increased in the mutant, whereas the total weight of spermatids and spermatozoa is highly decreased (1.8 mg in wild-type vs. 0.1 mg in mutants), a result clearly different from our previous study in which outbred males lack secondary spermatocytes or postmeiotic cells. Thus, a delay of both meiotic divisions occurs rather than complete arrest during meiosis I in these males. Eggs fertilized with mutant sperm develop as malformed embryos and are aneuploid making this male phenotype much more similar to that previously described in the mutant females. Therefore, crossovers are still essential for proper meiosis, but meiotic cell divisions can progress without it, suggesting that this mutant is a suitable model for studying the cellular mechanisms of completing meiosis without crossover stabilization. Marcelo C. Leal and Harma Feitsma contributed equally to this work. This work was supported by the Brazilian Foundation CAPES, the Cancer Genomics Center (Nationaal Regie Orgaan Genomics), the European Union-funded FP6 Integrated Project ZF-MODELS, and Utrecht University.     

Chromosomal abnormalities and spleenocyte production in laboratory mouse males after exposure to stress chemosignals

Activity of antibody producing spleenocytes and chromosome stability in bone marrow cells from laboratory mouse males of CBA strain after exposure to different chemosignals excreted by stressed or irradiated syngeneic donors was studied. It has been shown that the exposure of the recipient males to volatiles from donor males (stressed by swimming) decreases quantity of antibody-producing cells in 1, 3 and 10 days after the treatment. The same exposure increased the chromosome aberrations level in dividing bone marrow cells from CBA recipients in 1 day after the treatment. Similar changes were observed in 24 h after exposure to volatiles of irradiated donors or to synthetic mouse pheromone, 2,5-dimethylpyrazine. Possible mechanisms of chemosignals effect on the immune system are discussed.     

Cross-Fostering of Male Mice Subtly Affects Female Olfactory Preferences

The maternal environment has been shown to influence female olfactory preferences through early chemosensory experience. However, little is known about the influence of the maternal environment on chemosignals. In this study, we used two inbred mouse strains, C57BL/6 (C57) and BALB/c (BALB), and explored whether adoption could alter male chemosignals and thus influence female olfactory preferences. In Experiment 1, C57 pups were placed with BALB dams. Adult BALB females then served as the subjects in binary choice tests between paired male urine odours (BALB vs. C57, BALB vs. adopted C57 and C57 vs. adopted C57). In Experiment 2, BALB pups were placed with C57 dams, and C57 females served as the subjects in binary choice tests between paired male urine odours (C57 vs. BALB, C57 vs. adopted BALB, and BALB vs. adopted BALB). In both experiments, we found that females preferred the urine of males from different genetic backgrounds, suggesting that female olfactory preferences may be driven by genetic compatibility. Cross-fostering had subtle effects on female olfactory preferences. Although the females showed no preference between the urine odours of adopted and non-adopted males of the other strain, the BALB females preferred the urine odour of BALB males to that of adopted C57 males, whereas the C57 females showed no preference between the urine odour of C57 and adopted BALB males. Using gas chromatography-mass spectrometry (GC-MS) and stepwise discriminant analysis, we found that the ratios of volatile chemicals from urine and preputial gland secretions were altered in the fostered male mice; these changes may have resulted in the behavioural changes observed in the females. Overall, the results suggest that female mice prefer urine odours from males with different genetic backgrounds; this preference may be driven by genetic compatibility. The early maternal environment influences the chemosignals of males and thus may influence the olfactory preferences of females. Our study provides additional evidence in support of genotype-dependent maternal influences on phenotypic variability in adulthood.     

Differential expression of vasa homologue gene in the germ cells during oogenesis and spermatogenesis in a teleost fish, tilapia, Oreochromis niloticus

Vas (a Drosophila vasa homologue) gene expression pattern in germ cells during oogenesis and spermatogenesis was examined using all genetic females and males of a teleost fish, tilapia. Primordial germ cells (PGC) reach the gonadal anlagen 3 days after hatching (7 days after fertilization), the time when the gonadal anlagen was first formed. Prior to meiosis, no differences in vas RNA are observed in male and female germ cells. In the ovary, vas is expressed strongly in oogonia to diplotene oocytes and becomes localized as patches in auxocytes and then strong signals are uniformly distributed in the cytoplasm of previtellogenic oocytes, followed by a decrease from vitellogenic to postvitellogenic oocytes. In the testis, vas signals are strong in spermatogonia and decrease in early primary spermatocytes. No vas RNA expression is evident in either diplotene primary spermatocytes, secondary spermatocytes, spermatids or spermatozoa. The observed differences in vas RNA expression suggest a differential function of vas in the regulation of meiotic progression of female and male germ cells.     

Positional cloning and characterization of mouse mei8, a disrupted allelle of the meiotic cohesin Rec8

A novel mutation, mei8, was isolated in a forward genetic screen for infertility mutations induced by chemical mutagenesis of ES cells. Homozygous mutant mice are sterile. Mutant females exhibit ovarian dysgenesis and lack ovarian follicles at reproductive maturity. Affected males have small testes due to arrest of spermatogenesis during meiotic prophase I. Genetic mapping and positional cloning of mei8 led to the identification of a mutation in Rec8, a homolog of the yeast meiosis-specific cohesin gene REC8. Analysis of meiosis in Rec8(mei8)/Rec8(mei8) spermatocytes showed that, while initiation of recombination and synapsis occurs, REC8 is required for the completion and/or maintenance of synapsis, cohesion of sister chromatids, and the formation of chiasmata, as it is in other organisms. However, unlike yeast and Caenorhabditis elegans, localization of REC8 on meiotic chromosomes is not required for the assembly of axial elements.     

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.