Gonadal hormone effects on entrained and free-running circadian activity rhythms in the developing diurnal rodent Octodon degus

The slowly maturing, long-lived rodent Octodon degus (degu) provides a unique opportunity to examine the development of the circadian system during adolescence. These studies characterize entrained and free-running activity rhythms in gonadally intact and prepubertally gonadectomized male and female degus across the first year of life to clarify the impact of sex and gonadal hormones on the circadian system during adolescence. Gonadally intact degus exhibited a delay in the phase angle of activity onset (Psi(on)) during puberty, which reversed as animals became reproductively competent. Gonadectomy before puberty prevented this phase delay. However, the effect of gonadal hormones during puberty on Psi(on) does not result from changes in the period of the underlying circadian pacemaker. A sex difference in Psi(on) and free-running period (tau) emerged several months after puberty; these developmental changes are not likely to be related, since the sex difference in Psi(on) emerged before the sex difference in tau. Changes in the levels of circulating hormones cannot explain the emergence of these sex differences, since there is a rather lengthy delay between the age at which degus reach sexual maturity and the age at which Psi(on) and tau become sexually dimorphic. However, postnatal exposure to gonadal hormones is required for sexual differentiation of Psi(on) and tau, since these sex differences were absent in prepubertally gonadectomized degus. These data suggest that gonadal hormones modulate the circadian system during adolescent development and provide a new model for postpubertal sexual differentiation of a central nervous system structure.     

Evidence for extended action of gonadal hormones on the organization of sexually dimorphic behavior and morphology in gray short-tailed opossums (Monodelphis domestica)

Male and female gray short-tailed opossums were gonadectomized (GDX), or treated with the estrogen receptor antagonist tamoxifen citrate (TX), or corn oil (OIL) (control) during the 5th postnatal week, a time period equivalent to the 3rd postnatal week in rats and associated with high levels of circulating gonadal hormones and neural aromatase activity in this marsupial species. In adulthood following gonadectomy (for animals not previously gonadectomized) and replacement therapy with estradiol or testosterone, GDX males showed less male-typical scent marking and had shorter phalluses than OIL and TX males. Following replacement therapy with estradiol, GDX females were more likely to fight with and less likely to mate with stimulus males than TX females; OIL females were intermediate in these measures. Along with previous findings, these results suggest that gonadal hormones act over an extended postnatal period to organize sexually dimorphic behavior and morphology in male gray opossums and may have some effect on the organization of aggressive behavior in females of this species.     

Sex-specific changes in platelet aggregation and secretion with sexual maturity in pigs.

Cardiovascular disease may begin early in adolescence. Platelets release factors contributing to vascular disease. Experiments were designed to test the hypothesis that hormonal transitions associated with sexual maturity differentially affect platelet aggregation and secretion in males and females. Platelets were collected from juvenile (2-3 mo) and sexually mature (adult; 5-6 mo) male and female pigs (n=8/group). Maturation was evidenced by increased weight of reproductive tissue and changes in circulating levels of gonadal hormones. Aggregation to ADP (10 microM) and collagen (6 microg/ml) and ATP secretion to 50 nM thrombin were determined by turbidimetric analysis and bioluminescence, respectively. Total platelet counts, platelet turnover, and mean platelet volume did not change with maturity. Platelet aggregation and ATP secretion decreased in females but increased in males with maturity, whereas total ATP content remained unchanged in platelets from females but increased in platelets from males. Platelet fibrinogen receptor, P-selectin expression, and receptors for sex steroids did not change with sexual maturation. Plasma C-reactive protein and brain-type natriuretic peptide also did not change. Results indicate that changes in platelet aggregation and secretion change with sexual maturity differently in females and males. These observations provide evidence on which clinical studies could be designed to examine platelet characteristics in human children and young adults.     

Maturation costs affect maturation timing: sexual reproduction in a heterogonic hydra

If maturation is more costly for females, they may need more distinct environmental cues to induce sexual reproduction than males. We verified this hypothesis by comparing the indirect costs of maturation to males and females of the heterogonic Hydra oligactis, reproducing both asexually and sexually. The laboratory experiments revealed that males mature 2 weeks earlier than the first females at falling temperatures simulating the natural conditions that precede sexual reproduction. The difference between the energy costs of maturation for males versus females has been considered a likely factor responsible for the observed difference in maturation time. Available food supply positively affected the percentage of sexually mature females, indicating that females are more sensitive to food limitation than males. The number of gonads was correlated positively with the size of mature hydra for both males and females. However, males produced twice as many testes as ovaries produced by females. We postulate that females are induced later than males in order to prevent gonadal development after an unseasonable drop in temperature. As sexual reproduction in H. oligactis interferes with asexual budding, under favorable conditions for asexual proliferation unnecessary gonadal development decreases an individual’s fitness through reduction of the number of produced offspring.     

Role of the serotoninergic system in the acceleration of sexual maturation in wild Norway rats selected for reduced aggressiveness toward humans

The role of the serotoninergic system in acceleration of the sexual development of domesticated rats (Rattus norvegicus) was assessed. The onset of age-related changes in hypothalamic serotonin during prepubertal period occurred earlier in domesticated than in aggressive male rats. Blockade of the serotoninergic system after p-chlorophenylalanine (PCPA) administration on days 40 and 44 delayed the development of the reproductive system in both aggressive and domesticated males. In 60-day-old rats treated with PCPA, levels of testosterone in plasma and the number of mature spermatozoa in epididymis were decreased compared to controls. At the same time, the administration of PCPA on days 30 and 34 did not modify basal testosterone secretion and other parameters in 60-day-old aggressive rats and produced a decrease similar to PCPA injections on days 40 and 44, although less pronounced, in the weights of testes in domesticated animals. Administration of 5-hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, on days 30, 32, 34, 36 and 38 increased plasma testosterone levels and weights of the sex organs in 60-day-old domesticated males, but did not significantly affect the development of reproductive system in aggressive animals. These data indicate that serotonin stimulates sexual development of males during prepubertal period and this activating effect of serotonin occurs earlier in domesticated than in aggressive males. They also suggest that the acceleration in sexual maturation of domesticated rats could result from changes in the ontogenetic dynamic of hypothalamic serotonin induced by a selection for low aggressiveness towards man.     

Behavioral characterization of non-copulating male mice

Non-copulating (NC) males are those animals that do not mate in spite of repeated testing with sexually receptive females. They have been observed in several species including rats and mice. The present experiment was designed to perform a detailed behavioral characterization of NC male mice. Thus, we evaluated their sexual incentive motivation for a sexually receptive female or a sexually active male, olfactory preference for volatile and non-volatile odors from females or males, and olfactory discrimination between female and male volatile odors and food related odors (milk versus vinegar). We compared the activity of the accessory olfactory system (AOS) in copulating (C) and NC males in response to estrous bedding using the induction of Fos-immunoreactivity (Fos-IR) as a measure of neuronal activation. We also determined if estradiol or dopamine treatment could induce sexual behavior in NC males. Finally, we compared the testis weight and the number of penile spines in C, NC, and gonadectomized males. In the sexual incentive motivation test C males spend significantly more time in the female incentive zone than in the male incentive zone. On the other hand, NC males spend the same amount of time in both incentive zones. In tests of olfactory preference, NC males spent less time investigating estrous odors than C males. As well, NC males discriminate urine from conspecifics but they spend less time smelling these odors than C males. In addition, no increase in Fos expression is observed in NC males when they are exposed to odors from estrous females. Our data also suggest that the deficits observed in NC males are not due to lower circulating levels of gonadal hormones, because estradiol supplementation does not induce sexual behavior in these animals, and their testis weight and the number of penile spines are normal. The results suggest that NC males are not sexually motivated by the receptive females and their odors.     

Protein binding glucocorticoid hormones (transcortin) during peri-and postnatal ontogenesis and pregnancy in rats]

The constants of association and the energy of interaction between transcortin and cortisol, the binding ability and other characteristics of transcortin have been studied in the embryos, sexually immature and mature young and old females, females on the 14th and 21st days of pregnancy, immature and mature males. The constant of association in all the groups amounted to ca. 10(8) and the energy of interaction ca. 10 Cal/mole. The embryos and immature rats of both sexes are characterized by relatively low levels of the binding ability of transcortin. During the sexual maturation, the level of transcortin increased--insignificantly in males and markedly in females. The level of transcortin in the latter remained almost invariable during pregnancy and senescence. By the electrophoretic and sedimentation properties transcortin was the same in different groups. The high level of transcortin during pregnancy corresponded to the high level of hormones bound by transcortin, the level of these hormones in the embryos being much lower than in the mother.     

betaFSH,betaLH and growth hormone gene expression in blue gourami (Trichogaster trichopterus,Pallas 1770) during spermatogenesis and male sexual behavior

The relationship between gonadal development (histological evidence for spermiogenesis and/or spermatogenesis), sexual behavior (nest-building) and mRNA levels of gonadotropins (betaFSH and betaLH) and growth hormone (GH) in the male pituitary was investigated. Amplification of betaFSH cDNA showed a significantly higher mRNA level in mature males (whether sexually active or not) than in juveniles. However, following PCR amplification of betaLH cDNA, a significantly higher mRNA level was found in the sexually active group compared to the sexually inactive group. These results suggest that FSH may participate in spermatogenesis, whereas LH is more involved in spermiogenesis. The GH mRNA level increased slightly during the maturation process but no significant differences were found between the groups studied.     

Early manipulation of juvenile hormone has sexually dimorphic effects on mature adult behavior in Drosophila melanogaster

Hormones are critical for the development, maturation, and maintenance of physiological systems; therefore, understanding their involvement during maturation of the brain is important for the elucidation of mechanisms by which adults become behaviorally competent. Changes in exogenous and endogenous factors encountered during sexual maturation can have long lasting effects in mature adults. In this study, we investigated the role of the gonadotropic hormone, juvenile hormone (JH), in the modulation of adult behaviors in Drosophila. Here we utilized methoprene (a synthetic JH analog) and precocene (a JH synthesis inhibitor) to manipulate levels of JH in sexually immature male and female Drosophila with or without decreased synthesis of neuronal dopamine (DA). Locomotion and courtship behavior were assayed once the animals had grown to sexual maturity. The results demonstrate a sexually dimorphic role for JH in the modulation of these centrally controlled behaviors in mature animals that is dependent on the age of the animals assayed, and present DA as a candidate neuronal factor that differentially interacts with JH depending on the sex of the animal. The data also suggest that JH modulates these behaviors through an indirect mechanism. Since gonadotropic hormones and DA interact in mammals to affect brain development and later function, our results suggest that this mechanism for the development of adult behavioral competence may be evolutionarily conserved.     

Age of ovary determines remaining life expectancy in old ovariectomized mice

We investigated the capacity of young ovaries, transplanted into old ovariectomized CBA mice, to improve remaining life expectancy of the hosts. Donor females were sexually mature 2-month-olds; recipients were prepubertally ovariectomized at 3 weeks and received transplants at 5, 8 or 11 months of age. Relative to ovariectomized control females, life expectancy at 11 months was increased by 60% in 11-month recipient females and by 40% relative to intact control females. Only 20% of the 11-month transplant females died in the 300-day period following ovarian transplantation, whereas nearly 65% of the ovariectomized control females died during this same period. The 11-month-old recipient females resumed oestrus and continued to cycle up to several months beyond the age of control female reproductive senescence. Across the three recipient age groups, transplantation of young ovaries increased life expectancy in proportion to the relative youth of the ovary. Our results relate to recent findings on the gonadal input upon aging in Caenorhabditis elegans and may suggest how the mammalian gonad, including that of humans, could regulate aging and determine longevity.     

Biochemical composition of the Atlantic bonito Sarda sarda from the Aegean Sea (eastern Mediterranean Sea) in different stages of sexual maturity

The content (% wet mass) in water, ash, lipid, crude protein, DNA and RNA of different tissues was determined during sexual maturation of bonitos Sarda sarda from the Aegean Sea. A total of 220 specimens were collected in the following stages of sexual maturity: immature, resting, developing, mature, spawning and spent. Highest lipid levels in the white muscle, red muscle and liver were measured in immature specimens, while lowest levels were found in spawning bonitos. The gradual percentage of lipid reduction from immature to spawning bonitos was relatively higher in the liver (females 71·2% and males 64·4%) than in the white (females 59·2% and males 53·5%) and red (females 62·1% and males 51·7%) muscle. Lipid levels in the gonads increased gradually from the immature to spawning stage. The decrease of lipid in the somatic tissues was more intense in females than in males, and gonadal lipid content was higher in females than in males. There was a strong reverse correlation between water and lipid percentage in all tissues. Protein content decreased significantly only in spawning bonitos. The percentage of protein reduction from immature to spawning stage was relatively higher in males than in females in both white (females 3·4% and males 4·6%) and red (females 4·6% and males 5·1%) muscles. Protein content in the liver was significantly lower than in the other tissues, being highest in mature females. Gonadal protein content in females increased with maturation and decreased after spawning. The content in ash exhibited considerable stability. The RNA:DNA ratio exhibited a similar pattern of variation in both muscles. The RNA:DNA ratio increased during gonadal development gradually from the developing to spent stage. It was concluded that in S. sarda during gonadal development, there was an increase in gonadal lipid accompanied by a decrease in somatic tissue lipid reserves. Thus, reproductive inactive bonitos have more lipid in their edible part and a higher nutritional value than active ones.     

Physiological characteristics of platelet serotonin in rats

Physiological characteristics of platelet serotonin (5-HT) levels in rats of Wistar origin were investigated by use of a recently developed method. By comparison of populations of male and female rats (N = 281) similar unimodal frequency distributions, with a tendency to higher values in females (1.61 vs. 1.70 micrograms 5HT/mg platelet protein; p less than 0.01), were found. For a group of 55 animals, monitored twice for this parameter within a week interval, a remarkable intraindividual constancy in time, the mean difference between two determinations being 5.5%, was shown. No age-dependence could be demonstrated for platelet serotonin concentrations in 5- to 30-week-old rats, nor were there significant circadian or seasonal oscillations.     

Endocrine influences on the actions of morphine: IV. Effects of sex and strain

The antinociceptive and temperature responses to morphine were compared in male and female rats from two different strains. Males of both the Sprague-Dawley and Wistar-Furth strains were slightly more responsive to the acute actions of morphine than were females of the same strain. However, Wistar-Furth animals required approximately twice the dose of morphine to display equivalent antinociceptive responses and four times the dose of display equivalent hypothermic responses when compared with Sprague-Dawley animals. During chronic morphine treatment, the development of tolerance was slightly more rapid in males than in females and in Sprague-Dawley animals than in Wistar-Furth animals. Gonadal hormones also influenced morphine responses. Ovariectomized rats were significantly more responsive acutely to morphine and developed tolerance less rapidly than estradiol-treated females. However, alterations of gonadal hormones in males did not affect morphine responses. These results indicate that morphine responses vary considerably between strains of animals and are influenced by gonadal hormones of females, but not of males.     

Comparison of the gonadal response of wild and laboratory field voles (Microtus agrestis) to different photoperiods

Weanling male and female field voles from laboratory stock and from the F1 generation of wild-caught animals were placed in a long (16L:8D) or short (6L:18D) photoperiod for 28 or 56 days. Both types of field vole showed the well-established effect of photoperiod upon sexual maturation, with animals in the long photoperiod having larger and more active gonads than animals in the short photoperiod. After 28 and 56 days laboratory stock females were more mature, sexually, and had a higher growth rate than did Wild F1 females. There was no difference between the two types of males at 28 days, but by 56 days laboratory stock males were more sexually mature and had a higher growth rate than did Wild F1 males. These differences between the two types occurred in the long and short photoperiods. There was no interaction between photoperiod and type of vole. The use of laboratory stock animals in experiments could lead to an incorrect assessment of the effect of photoperiod in the control of seasonal breeding in wild populations.     

Sex hormone-dependent brain maturation and sexual behaviour in rats.

In male and female rats the endogenous steroid and gonadotrophin secretion was inhibited by injecting high doses of chlormadinone acetate (CmAc) from day 14 to 24 of life, i. e. during the period of brain maturation. In adulthood the males treated prepubertally with CmAc exhibited reduced sexual activity and fertility, whereas the females did not differ from the controls. More complete sex hormone deficiency during brain maturation was achieved by castration on day 14 of life. Controls were castrated at normal puberty time (40--60 days). Both groups were then substituted with androgens or oestrogens. In the females castrated on day 14 no impairment of sexual behaviour was observed as compared to the later castrated controls. In contrast, the early castrated males showed delayed onset of mounting behaviour. At autopsy, the weights of their sex organs were found to be lower than in the controls despite equal testosterone replacement for several months. These findings speak in favour of a permanently diminished responsiveness to androgens in males having been exposed to more or less severe androgen deficiency during sex specific brain maturation. Hence, the maturation of a male hypothalamus as well as the differentiation appears to depend at least in part on the presence of androgens, whereas in females it runs without hormonal influence.     

Sex differences in juvenile mouse social behavior are influenced by sex chromosomes and social context

Play behavior in juvenile primates, rats and other species is sexually dimorphic, with males showing more play than females. In mice, sex differences in juvenile play have only been examined in out-bred CD-1 mice. In this strain, contrary to other animals, male mice display less play soliciting than females. Using an established same-sex dyadic interaction test, we examined play in in-bred C57BL/6J (B6) 21-day-old mice. When paired with non-siblings, males tended to be more social than females, spending more time exploring the test cage. Females displayed significantly more anogenital sniffing and solicited play more frequently than did males. To determine if the origin of the sex difference was sex chromosome genes or gonadal sex, next we used the four core genotype mouse. We found significant interactions between gonadal sex and genotype for several behaviors. Finally, we asked if sibling pairs (as compared to non-siblings) would display qualitatively or quantitatively different behavior. In fact, XX females paired with a sibling were more social and less exploratory or investigative, whereas XY males exhibited less investigative and play soliciting behaviors in tests with siblings. Many neurobehavioral disorders, like autism spectrum disorder (ASD), are sexually dimorphic in incidence and patients interact less than normal with other children. Our results suggest that sex chromosome genes interact with gonadal hormones to shape the development of juvenile social behavior, and that social context can drastically alter sex differences. These data may have relevance for understanding the etiology of sexually dimorphic disorders such as ASD.     

Effects of male sex hormones on specific uptake and release of 3H-serotonin in the rat hypothalamus in vitro]

With the use of "isotopic method" a study was made of the main parameters of functional activity of serotoninergic elements of hypothalamus--the specific uptake and release of 5-OT. The animals used were sexually mature rats castrated on the first postnatal day. In sexually mature intact males the specific uptake of 3H-5-OT by serotoninergic structures of the anterior hypothalamus was significantly lower than in females. Castration of animals on the first day of life resulted in the increase of specific 5-OT uptake in sexually mature males up to that observed in females. There were no differences between the sexes in the rate of spontaneous release of 5-OT. However, response to K(+)-depolarization in the anterior hypothalamus of intact males was significantly lower than that in females. In the hypothalamus of males castrated neonatally the amplitude of the response to the effect of the depolarizing agent was increase up to the level observed in females. By the results obtained it is indicated that elimination of the effect of male hormones on the first postnatal day results in the increase of 5-OT uptake and release in the hypothalamus of sexually mature rat males.     

虎纹蛙促性腺激素含量随年龄及季节的变化(英文)

促性腺激素（ＧｔＨ;或ＬＨ和ＦＳＨ）在脊椎动物生殖调节中起中Ｃ作用;脑垂体和血浆ＧｔＨ水平在一定程度上反映着动物体的生殖生理状态。在蛙类,对脑垂体和血浆的ＬＨ及ＦＳＨ含量进行过较全面研究的,仅在牛蛙和日本蟾蜍有过报道,结果显示它们的ＬＨ和ＦＳＨ的含量存在有种类差异性。虎纹蛙属中国二级保护动物,也是唯一受保护的蛙类,对其生殖生物学的基础内容进行研究具有重要的意义。 为此,本文利用放射免疫测定法,测定了虎纹蛙幼蛙和不同性腺发育阶段（季节）成蛙脑垂体与血浆的ＬＨ及ＦＳＨ含量,以弄清这些激素的含量变化与年龄、季节（性腺发育阶段）变化的关系,以期为虎纹蛙的基础生殖生物学及蛙类的生殖内分泌学充实新的内容,为虎纹蛙的人工繁殖和保护提供理论依据。结果是：幼蛙血浆ＬＨ水平显著高于各期成蛙（Ｆｉｇ．Ａ）,血浆ＦＳＨ水平显著低于成熟前期成蛙,而和其它各性腺发育阶段成蛙相当（Ｆｉｇ．Ｂ）。而脑垂体ＬＨ或ＦＳＨ的含量显著低于各期成蛙（Ｆｉｇ．Ｃ＆Ｄ）。这说明,幼蛙脑垂体已具有一定的合成和释放ＬＨ及ＦＳＨ的能力。 成蛙脑垂体和血浆ＬＨ及ＦＳＨ水平随性腺发育阶段（季节）的不同而有一定的变化：雌蛙血浆ＬＨ水平在成熟期最高,性腺再发育期最低;     

Sexual experience interacts with steroid exposure to shape the partner preferences of rats

A three-phase experiment manipulated sexual experience and hormone exposure (perinatally and in adulthood) in female rats housed individually from weaning so as to limit peripubertal social and sexual experience. Noncontact partner preference for a male or estrous female rat was measured both before and after sexual experience, first while rats were under the influence of circulating testosterone propionate (TP) and later after priming them with ovarian hormones (estradiol benzoate and progesterone; EB & P). When implanted with TP capsules and tested while sexually naive, all groups of female rats preferred females to males without differing statistically. However, following three sexual experience sessions with estrous females, differences emerged between the masculinized and control groups in the magnitude of their female-directed preference, with masculinized females demonstrating a significantly greater preference for estrous females. Sexual experience with male rats under EB & P did not result in a significant shift in preference in any group. Histological assessment indicated that the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) was increased by exposure to TP postnatally, and SDN-POA volume correlated positively with partner preference scores but only when rats were both sexually experienced and exposed to circulating TP in adulthood. These results suggest that sexual experience interacts with steroid exposure to shape partner preference.     

Testosterone Control of Male-Type Sexual Behavior in the Tammar Wallaby (Macropus eugenii)

In the tammar wallaby,Macropus eugenii,the expression of male-type sexual behavior is apparently determined by the activating effects of testicular hormones in adulthood. The incidence of male-type copulatory behavior and sexual checking behavior was compared in intact (control) males, control females, testosterone-treated females, and three groups of males castrated either postnatally (24–26 days of age), prepubertally (14.5 months of age), or in adulthood. All three groups of castrated male wallabies showed a very low incidence of male sexual behavior in adult life, comparable to that shown by the untreated females. Adult female wallabies with 100-mg testosterone implants showed a high incidence of male sexual behavior which was indistinguishable from that shown by intact males. The results suggest that sex differences in male-type behavior in the tammar wallaby are due to short-term inductive effects of testosterone acting on a sexually indifferent brain. There is no evidence of any long-term organizational effects of testosterone acting in fetal or neonatal life on the neural pathways controlling male-type sex behavior in this marsupial mammal.