Tyrosine hydroxylase activity and expression of its gene in mice with contrasting capacity to dominate in social stress]

Changes of tyrosine hydroxylase (TH) activity and level of mRNA of TH gene in PT and CBA/Lac mouse strains, which are contrast by ability to dominate in heterogenous populations, were investigated. It was established, that the activity of TH both in dominate PT and subordinate CBA/Lac mice in hypothalamus, hippocampus and brain stem elevated in one hour after forming of micropopulations. But the appearance of this increase was different: activation of TH in hypothalamus and brain stem of PT mice was stronger then one in CBA/Lac mice. Moreover, the beginning of the reaction in brain stem of PT mice was earlier then that of CBA/Lac mice. MRNA level of TH gene in hypothalamus and brain stem in one hour was elevated only in PT mice for 50% and 200%, respectively. No changing in expression TH gene was found in hippocampus. In conclusion, it was suggested that the activation of catecholamine biosynthesis under social stress in hypothalamus and brain stem of male mice was due to the TH activation and increase of its gene expression.     

Role of Genotype, Social Stress, and Season in the Regulation of Hormonal Function of Testes Incubated in Vitro in Mice

Micropopulations consisting of six male mice of different genotypes were studied (each of lines A/He, CBA/Lac, C57BL/6J, DD, YT, and PT was represented by one male). Interlinear differences in the level of social dominance and the effects of genotype, social hierarchy, and season on in vitro testosterone production by testes were examined under different incubation conditions. The testosterone production was estimated under control conditions and under stimulation with human chorionic gonadotropin (CG). Significant genetic differences in the initial and CG-stimulated testosterone production by testes incubated in vitro were found. By the control production, the genotypes fell into two groups: lines C57BL/6J, A/He, and CBA/Lac had low production of the hormone; lines YT, PT, and DD, high production. By responsiveness of gonads to CG, the genotypes fell into three groups: line CBA/Lac had low testosterone production by testes; lines C57BL/6J, A/He, YT, and DD, line PT, intermediate production; and line PT, high production. The obtained data indicate stability of genetic polymorphism for the responsiveness of testes to gonadotropins, because neither season nor the formation of social hierarchy could significantly change the interlinear differences. In line PT characterized by high hormonal activity of gonads in the control and under stimulation with gonadotropins, males became dominant in a significantly greater number of cases studied during the formation of hierarchy in micropopulations. The dynamics of both control production of a male sex hormone and responsiveness of testes to CG was established in vitro during the formation of social hierarchy; the effects of season on this dynamics were revealed. Specific characteristics of secretory activity of testes were detected in the control and under stimulation with gonadotropins, depending on incubation conditions. Seasonal and genotypic characteristics of the responsiveness of testes to CG were revealed under different incubation conditions. Genotypic characteristics indicate interlinear differences in the degree of inertia of testosterone biosynthesis on exposure to gonadotropins.     

The role of genotype, social stress, and season of the year in regulation of hormonal function of murine testis in vitro

Micropopulations consisting of six male mice of different genotypes were studied (each of lines A/He, CBA/Lac, C57BL/6J, DD, YT, and PT was represented by one male). Interlinear differences in the level of social dominance and the effects of genotype, social hierarchy, and season on in vitro testosterone production by testes were examined under different incubation conditions. The testosterone production was estimated under control conditions and under stimulation with human chorionic gonadotropin (CG). Significant genetic differences in the initial and CG-stimulated testosterone production by testes incubated in vitro were found. By the control production, the genotypes fell into two groups: lines C57BL/6J, A/He, and CBA/Lac had low production of the hormone; lines YT, PT, and DD, high production. By responsiveness of gonads to CG, the genotypes fell into three groups: line CBA/Lac had low testosterone production by testes; lines C57BL/6J, A/He, YT, and DD, line PT, intermediate production; and line PT, high production. The obtained data indicate stability of genetic polymorphism for the responsiveness of testes to gonadotropins, because neither season nor the formation of social hierarchy could significantly change the interlinear differences. In line PT characterized by high hormonal activity of gonads in the control and under stimulation with gonadotropins, males became dominant in a significantly greater number of cases studied during the formation of hierarchy in micropopulations. The dynamics of both control production of a male sex hormone and responsiveness of testes to CG was established in vitro during the formation of social hierarchy; the effects of season on this dynamics were revealed. Specific characteristics of secretory activity of testes were detected in the control and under stimulation with gonadotropins, depending on incubation conditions. Seasonal and genotypic characteristics of the responsiveness of testes to CG were revealed under different incubation conditions. Genotypic characteristics indicate interlinear differences in the degree of inertia of testosterone biosynthesis on exposure to gonadotropins.     

Genetic-neurochemical analysis of the role of brain catecholamines in the manifestation of dominance in male mice in micropopulations

The ability of male mice to dominate in micropopulations, in connection with brain catecholamines was studied. It was shown that the F1 obtained from breeding PT and CBA/Lac which have respectively large and small numbers of high rank males were of high level of dominance in micropopulations. Moreover, they had high levels of noradrenaline and dopamine in hippocampus, striatum and brain stem, and low--in hypothalamus.     

Growth and development peculiarities of testicles in postpubertal period in inbred mice lines PT and CBA/Lac

The goal of this study is to perform a comparative genetic investigation of testicle development during the postpubescence period (from days 70 to 90 of life) in the inbred mice lines PT and CBA/Lac. Interlinear differences in the body and testicular weight, serum testosterone concentration, number of epididymal spermatozoa, area of testicular epithelium, semeniferous tubule lumen, and insulae of Leydig cells were analyzed. It was found that the morphological and histomorphometric parameters of testicles in males from the PT line compared to the males of the CBA/Lac line did not reach a definitive stage with the end of the post-pubescence period and kept on developing until day 90 of life. Therefore, genetic differences remain in the postpubertal testicular development of laboratory mice.     

Spermatogenesis parameters and testosterone production at puberty as predictors of testicular functional activity in mice (<Emphasis Type="Italic">Mus musculus</Emphasis>)

The aim of this study was to investigate fertility-associated parameters of spermatogenesis and androgenic status in male laboratory mice at puberty and to assess their prognostic significance in the realization of the definitive testicular function. In three inbred murine strains, BALB/cLac, CBA/Lac and PT, the serum testosterone level, its testicular concentration, epididymal sperm count (sperm reserve) and portion of sperm with abnormal head morphology were evaluated on days 45 (puberty) and 90 (adulthood) of postnatal development. CBA/Lac males were characterized by a lower epididymal sperm count vs. other strains at both ages indicative of poorer spermatogenesis. At the same time, CBA/Lac males had a lower portion of sperm with abnormal head morphology, and this could be considered as a compensatory reaction aimed at improving sperm fertility. Distinct inter-strain differences in the portion of sperm with morphologically abnormal heads were established at both ages, while the inter-strain ratio remained invariable (BALB/cLac > PT > CBA/Lac). Thus, the level of abnormal spermatogenesis in the pubertal period may have a predictive significance for the definitive testicular activity in adult mice. No inter-strain and age-dependent changes were found in serum and testicular testosterone levels except for the PT strain, in which both testosterone levels rose from puberty to adulthood, suggesting a shift of the pubertal testosterone peak towards later times. Our data show that in male laboratory mice the genetic peculiarities of the testicular function manifest themselves during puberty and persist until adulthood.     

Interstrain differences in testicular responses to hCG: effects of a female exposition

It is known that among many animal species, including laboratory mice, a short-time exposition to a female causes activation of the pituitary-testicular axis in males, which then rapidly decreases. Effects of a prolonged female exposition on the testicular testosterone output in response to hCG injections were investigated in adult males of two inbred mice strains CBA/Lac and PT. The males of both genotypes kept with females for 5 days were injected subcutaneously with 10 IU of hCG 120 minutes before decapitation. Males of the same genotype and similar age keeping alone were served as control. The serum testosterone concentration and its testicular content were measured with immune-enzyme assay. It has been shown that the hCG increased the testosterone concentration and its testicular content in control males of both strains, but the testosterone output was expressed more significantly in PT males in comparison with CBA/Lac. The prolonged exposition of a female itself did not influence the testosterone output in males of both strains. However, it increased significantly the testicular response to hCG in PT strain. The data obtained suggest that a long-term exposition of a female could reinforce the testicular reactivity to hCG in genotype-dependent manner.     

Interlinear differences in generative function formation in pubescence of male mice

The formation of generative function in pubescence is studied in males of three inbred mice lines BALB/cLac, CBA/Lac, and PT. From days 35 through 60 of life every 5 days the amount of sperm cells and the quantity of abnormal heads of spermatozoa in males are calculated in both epididymises and the morphometry of the testicles, epididymises, and seminal vesicles is carried out. Interlinear deviations in the pubertal dynamics of the parameters of spermatogenesis and the morphometric indexes are determined, indicating a weak spermatogenesis process in males of CBA/Lac in comparison with males from the other lines. Males from the line CBA/Lac are characterized by a low amount of epididymal spermatozoa combined with low frequency of abnormal spermatozoon heads; these traits can be considered as a compensatory process that increases fertility. By the end of the period, i.e., on days 55–60 of life, the males of all three inbred mice lines have not reached the definitive level in the number of epididymal spermatozoa; the weight of the testicles, epididymise, and seminal vesicles; and body weight. Thus, in laboratory mice, the beginning of reproductive activity is not connected with these reproductive indexes reaching the definitive level. The results of the study show that in adult mature males of laboratory mice the interlinear deviations in generative function emerge in the pubertal period and persist thereafter.     

The Role of Genotype in the Formation of Leydig Cell Hormone Function during Postnatal Ontogeny in Diallele Crosses of Laboratory Mice

Production of testosterone by Leydig cells in the postnatal ontogeny during sexual maturation under in vitro stimulation by chorionic gonadotropin, dibutiryl-cAMP, and pregnenolon was studied in males of four inbred mouse lines (BALB/c, PT, CBA/Lac, and A/He) and their F1 reciprocal hybrids. Highly statistically significant association between the animal genotype and age was revealed for all parameters studied, which indicates the genotype-dependent formation of the Leydig cell hormone function during the postnatal ontogeny. The effect of genotype was characterized by two specific features. First, in each postnatal ontogeny stage examined correlative genetic variability of the cAMP- and substrate-dependent Leydig cell responsiveness was observed. Second, during postnatal ontogeny coordinated genetic variability underwent substantial ontogenetic changes. Definite pattern of genetic differences in the Leydig cell hormone activity was formed only at the late pubertal–early post-pubertal stage (60th day after birth). This process coincided with the completion of the Leydig cell morphological differentiation and the appearance of mature cells in the population. Thus, formation of the Leydig cell hormone function during postnatal ontogeny is under coordinated genetic control, which itself undergoes significant changes during sexual maturation.     

Effect of a single severe stress on behaviour of males and females in the mouse inbred strains CBA/Lac and C57BL/6J

The effect of single severe stress in the form of forced swimming on the behavior of males and females in the mouse inbred strains CBA/Lac and C57BL/6J were examined in the open field test. Measurements were carried out within two hours after the stress exposure (Trial 1) and repeated 2 hours thereafter (Trial 2). Intact males and females of the both mouse strains which tested in the open field twice too were used as control. An increased latency was found until first escape from the center both in males and females of the CBA/Lac strain within two hours after the end of forced swimming. This parameter was still high in females in the Trial2. Four out of seven behavior parameters were changed in females of the C57BL/6J strain two hours after the stress exposure, but their behavior was similar to control in the Trial 2. The males of the C57BL/6J strain demonstrated the least changed behavior in the open field test after the stress exposure with the exception of increased number of grooming in the Trial 1. Further on, a detailed analysis of repeated testing in the open field within intact and stressed mice of both strains was performed. This comparison allowed revealing hereditary and gender peculiarities in the mouse behavior after single severe stress exposure. The results are discussed in respect to the possible genetically inherent increased traitanxiety in females of C57BL/6J strain and the state of anxiety in females of CBA/Lac strain.     

Effect of intranasal administration of dopamine on anxiety and locomotor activity of two lines of mice

Intranasal administration of dopamine (0.3; 3 and 30 microg/kg) on anxious behaviour of mice was studied using elevated plus-maze and open fields tests and the pinch-induced catalepsy on parallel bars test. Dopamine was introduced as nose drops or inhalation of nanoparticles of the compound solution in C57B1/6J and CBA/Lac mice with differences of dopaminergic function features. In our experiment, dopamine had anxiolytic and elevated motor activity effects in C57B1/6J, but not in the CBA/Lac mice. Nose drops were more effective than inhalation; perhaps, it was a more stressful manipulation. Apparently dopamine increased the number of CBA/Lac mice who demonstrated catalepsy and the reflex duration. Indeed, the neurotransmitter is active in different psycho-emotional phenomena.     

Experience of defeat increases the susceptibility to catatonic - like state in mice

The ability to develop the catatonic-like state (reflex immobility reaction - RIR) due to stimulation of the skin at the scruff was investigated in mice of two strains — C57BL/6J and CBA/Lac. The total time of immobility and number of paroxysms during test were measured. It has been shown that the number of paroxysms was significantly fewer and the total time of immobility was significantly longer in CBA/Lac strain than in C57BL/6J. In each strain group housed animals as well as submissive ones with successive experience of defeats demonstrated a more expressed immobility than individually housed or aggressive males with successive experience of victories, respectively. Changing the social status in aggressive animals as a consequence of confrontation with aggressive males resulted in the increased immobility in CBA/Lac but not in C57BL/6J mice. The results suggest that the experience of defeat in submissive males is connected with increased ability to develop RIR.     

Comparative characteristics of the parameters of an aggressive reaction in 2 mouse genotypes

The parameters have been studied of the aggressive reaction of male mice of CBA/Lac and C57BL/6J lines differing by olfactory sensitivity to zoosocial pheromone stimuli. It has been shown that CBA males, characterized by a high olfactory sensitivity, have lower latency of the first attack than C57BL males with low olfactory sensitivity. A prolonged distant exposition to an unknown litter and male appearance lowers the latency of the first attack in mice of the studied lines proportionally to their meanings demonstrated after short time exposition. The number of attacks and total time of attacking is considerably higher in C57BL mice during the whole test period (15 min) than in CBA mice in which aggressivity is already sharply lowered after 5 min of agonistic interactions. The factors are discussed, influencing the parameters of mice aggressive reaction.     

Generation of low-dose paralysis in the absence of the ability to secrete antibody.

(CBA/N female x BALB/c male)F1 male mice carry an X-linked defect, originating from CBA/N mice, which renders them unable to generate an antibody response to SSS-III. Histocompatible (BALB/c female x CBA/N male) reciprocal F1 male hybrids do not carry the X-linked defect and therefore generate a readily detectable PFC response to SSS-III, which can be adoptively transferred into nonresponding reciprocal F1 male mice. In the present work, we show that this adoptive response could be inhibited in recipient (CBA/N female x BALB/c male)F1 male nonresponding mice in which low dose paralysis had been induced. Evidence is presented which indicates that such suppression is of host rather than donor cell origin. The capacity to develop low-dose paralysis, a phenomenon that is antigen specific and has been attributed to the action of suppressor T cells, indicates that nonresponding (CBA/N female x BALB/c male) F1 males (and presumably the CBA/N progenitor strain) have the ability to recognize this antigen. Furthermore, since these animals fail to make a serum antibody response to SSS-III, the signal that activates suppressor T cells cannot be circulating antibody or antigen-antibody complexes. These findings are most consistent with the view that low-dose paralysis of the response to SSS-III is not dependent on antibody-mediated feedback inhibition; rather, it is an active process mediated by suppressor T cells.     

Frequency of X-Y chromosome dissociation in mouse spermatocytes from interstrain crosses,recombinant inbred strains,and chimeras: Possible involvement of paternal genome imprinting

The frequency of dissociation of the X-Y chromosome bivalent in diakinesis-metaphase I spermatocytes differs significantly between two inbred mouse strains, CBA (29%) and KE (7%), that were used to obtain reciprocal F1 hybrids, and to develop recombinant inbred (R1) strains. The level of X-Y dissociation was significantly higher in (KExCBA)F1 hybrids sired by the CBA males (24%) than in reciprocal F1 hybrids (12%), revealing the inheritance after the father. Among 14 RI strains, nine were concordant with KE, one with CBA, and four had intermediate phenotype, significantly different from both progenitor strains. This shows that at least two genes are involved, and their possible linkage with agouti and Trf loci is suggested. The linkage with agouti was confirmed by testing additional 10 CBXE incipient RI strains. There was no significant difference in the level of X-Y dissociation between EXCB RI strains derived from the original cross sired by the CBA males and CBXE RI strains derived from the reciprocal cross. The involvement of the Y chromosome-linked factors was unlikely because it was found earlier (Krzanowska, 1989: Gamete Res 23:357–365) that two congenic strains, KE and KE.CBA, differing with respect to the source of the Y chromosome, had the same level of X-Y dissociation. Thus, the difference obtained between reciprocal F1 hybrids is interpreted in terms of paternal genome imprinting imposed by CBA males and propagated only in the presence of some alleles derived from this strain. Analysis of six KE ? CBA-T6 chimeras, among them three germ line chimeras, points to the conclusion that the tendency to low or high level of X-Y chromosome dissociation is expressed rather autonomously by KE or CBA-T6 spermatocytes (as recognized by a marker chromosome pair), respectively, and was not modified by the presence of somatic cells of the opposite strain. © 1994 Wiley-Liss, Inc.     

Sex and H-2 haplotype control the resistance of CBA-BALB hybrids to the induction of T cell lymphoma by Moloney leukemia virus

CBA/N and CBA/CaHN have a significantly longer latent period than other inbred mouse strains between infection with Moloney murine leukemia virus and the appearance of T cell lymphoma. The genetic characteristics of this resistance have been analyzed in the F1 hybrids of CBA/N and CBA/CaHN with BALB H-2 congenic strains. Sexual phenotype and H-2 haplotype significantly influenced survival in the F1 hybrids of CBA/CaHN with BALB. In the F1 with BALB/cJ and BALB/cAnN (both H-2d), the males survived significantly longer than the females; but in the F1 with BALB.K (H-2k) and BALB.B (H-2b), the survival of males and females was the same. Survival was not prolonged by the recessive X-linked immunodeficiency gene xid or other genes on the CBA/N X-chromosome, because the (CBA/N X BALB/c)F1 male and the reciprocal (BALB/c X CBA/N)F1 male, which does not carry the CBA X-chromosome, were equally resistant. H-2 haplotype did not influence survival among the BALB H-2 congenics, and sex had little effect on the resistance of the CBA and BALB parents. These results demonstrate that a sex-dependent gene linked to H-2 significantly influences the expression of CBA genes for lymphoma resistance in the F1 hybrid with BALB.     

Genetic aspects of the reaction of humoral immunity to collagen in humans and animals. Report I. Analysis of polymorphism of autoantibody levels to collagen type I in mice NZB X NZW (F1)

The study of polymorphism of humoral immunoreactions to the type I (AC) collagen in CBA/Lac, C57B1/6-J inbred mice and NZB X NZW (F1) hybrids showed the presence of genetically determined variability of the above mentioned trait. The analysis of intralinear dispersions of AC levels in NZB X NZW (F1) mice revealed sex dimorphism and age variability of the trait. A suggestion was made that sex hormones are important factors in ontogenic formation and modulation of autoimmunity to the type I collagen in NZB X NZW (F1) mice.     

Social domination and reproductive success in male laboratory mice (Mus musculus)

The task of the present study was to evaluate effect of social status and of genotype on success of reproduction of male laboratory mice with use of ethological model of social hierarchy of “minimal socium”. The model represents the paired maintenance of two male mice of different genotypes (PT and CBA/Lac). The mice resided for 30 days in one experimental cage and established between them the dominant-subordinant relations. After this, each pair of males was supplemented by two DD/He females. Regardless of their genotype, the dominants became fathers more often than the subordinants and left more offspring. It has been established that the complete suppression of fertility did not occur. It is suggested that this allows them to make genetic contribution to the next generation and to remain in the genetic pool of population.     

The role of genotype in the formation of Leydig cell hormone function during postnatal ontogeny in diallele crosses of laboratory mice

Production of testosterone by Leydig cells during the postnatal ontogeny in pubescence under in vitro stimulation by chorionic gonadotropin, dibutiryl-cAMP, and pregnenolon was studied in males of four inbred mouse lines (BALB/c, RT, CBA/Lac, and A/He) and their F1 reciprocal hybrids. Highly statistically significant association between the animal genotype and age was revealed for all parameters studied, which indicates the genotype-dependent formation of the Leydig cell hormone function during the postnatal ontogeny. The effect of genotype was characterized by two specific features. First, in each postnatal ontogeny stages examined correlative genetic variability in respect of the cAMP- and substrate-dependent indices of Leydig cell reactivity was observed. Second, during postnatal ontogeny coordinated genetic variability was subjected to substantial ontogenetic rearrangements. Definite pattern of genetic differences in the Leydig cell hormone activity was formed only at the late pubertal--early post- pubertal stage (60th day after birth). This process coincided with the completion of the Leydig cell morphological differentiation and the appearance of mature cells in the population. Thus, formation of the Leydig cell hormone activity during postnatal ontogeny is under coordinated genetic control, which is also subjected to substantial changes during pubertal differentiation.     

Effect of genotype on the development of aggressive and submissive behavior in the mouse

Aggressive and submissive behaviour was studied in CBA/Lac and C57BL/6J strains of mice during long-term intermale interaction with syngenic partners. It was shown that the aggressiveness of aggressive C57BL/6J animals was more expressive than that of CBA/Lac' ones. The structure of submissive behaviour of this strains' encounters was also significantly different. Prolonged-defeat experience changed the character of submissive behaviour of C57BL/6J, but not of CBA/Lac' ones. Aggression of dominant animals considerably decreased in both strains. It is suggested that CBA/Lac and C57BL/6J mice had different mechanisms of suppression of intermale aggression.