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PubMedDate not supplied

Changes in the pituitary metabolism of monoamines (dopamine, norepinephrine, and serotonin) in female and male rainbow trout (Oncorhynchus mykiss) during gonadal recrudescence.

The dynamics of the levels and metabolism of dopamine, norepinephrine, and serotonin were studied in pituitaries of male and female rainbow trout at different stages of gonadal development. In female rainbow trout, the turnover of dopamine (calculated using the inhibitor of tyrosine hydroxylase alpha-methyl-p-tyrosine methyl-ester HCl), serotonin metabolism, and norepinephrine levels decreased in the advanced stage of exogenous vitellogenesis with respect to the initial stage. However, data obtained in males did not show changes in either serotonergic or noradrenergic metabolism during the last stages of gonadal development. However, an increase of dopaminergic turnover was noticed in the male fish at the end of spermiation. Finally, pituitary dopaminergic activity was significantly higher in immature (prepubescent stage) than in adult fish.

Animals↗
PubMed1996

[Harmfulness of obesity in children to their health].

With the increase of obese children, harmfulness of obesity to their health was studied to lay a basis for formulating corresponding intervention measures. Blood sugar, intelligent quotient (IQ), thyroid function, cardiac and pulmonary function, and index of gonad development were determined in 150 obese children and 150 normal healthy children. Results showed baseline secretion of insulin and C-polypeptide in obese children were significantly higher than that in controls, and thyroid function, total IQ, speech IQ and operation IQ all were relatively lower, cardiac and pulmonary function was significantly lower, and gonad development and maturity took place earlier in the former than in those in the latter. It indicated that there were a lot of risk factors harmful to their health in obese children.

Adolescent↗
PubMed2000

Differences in mGnRH and cGnRH-II contents in pituitaries and discrete brain areas of Rana rugulosa W. according to age and stage of maturity.

(1) In tadpoles, chicken-II gonadotropin-releasing hormone (cGnRH-II) could be measured in the brains before metamorphosis, but mammalian gonadotropin-releasing hormone (mGnRH) did not appear until the stage of metamorphosis, i.e. cGnRH-II appeared earlier than mGnRH during ontogenesis. (2) During the metamorphic climax, mGnRH content increased more rapidly than cGnRH-II; the content of mGnRH was about two times of that of cGnRH-II. (3) In juveniles and adults, the content of mGnRH and cGnRH-II, and the distribution pattern of mGnRH (but not cGnRH-II) in the brains and pituitaries changed with age and stages of gonadal development. mGnRH mainly distributed in the rostral brain areas, whereas cGnRH-II had a widespread distribution in the brain. (4) Both mGnRH and cGnRH-II were present in the pituitaries at each stage of maturity. The gonadotropin-releasing hormone (GnRH) content at sexually maturity was significantly higher than that at other stages of gonadal development, and the content of mGnRH was about 15-18 times of that of cGnRH-II. (5) These results suggest that both mGnRH and cGnRH-II are potentially involved in the direct regulation of pituitary gonadotropes, and mGnRH may be the major active form, cGnRH-II may also serve as a neurotransmitter or neuromodulator in the brain.

Age Factors↗
PubMed2001

Gonadotropins in insects: an overview.

Control of gonad development in insects requires juvenile hormone, ecdysteroids, and a peptidic brain gonadotropin(s). Compared to vertebrates, the situation in insects with respect to the molecular structure of gonadotropins is far less uniform. Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) of vertebrates are glycoproteins that are synthezised in the hypothalamus and released from the anterior pituitary. They stimulate gonad development, the production of progesterone or of sex steroids (estrogens, androgens). None of the known insect gonadotropins is a glycoprotein, neither can they be grouped into a single peptide family. In Drosophila, two G-protein coupled receptors, structurally related to the mammalian glycoprotein hormone receptors, have been identified. Nothing is known about their natural ligands. The sex-steroids of insects are likely to be ecdysteroids (20E in females, E in males of some species). Some of the identified gonadotropins speed up vitellogenesis (locust OMP and some -PF/-RFamide peptides) or stimulate ecdysteroid production by the ovaries (locust-OMP and Aedes- OEH) or testis (testis ecdysiotropin of Lymantria). In flies, the only as yet identified gonadotropin is the cAMP-generating peptide of Neobellieria. The seeming absence of uniformity in gonadotropins in insects might be due to a multitude of factors that can stimulate ecdysteroid production and/or to the use of different bioassays. Arch.

Amino Acid Sequence↗
PubMed2002

The role of SF1 in adrenal and reproductive function: insight from naturally occurring mutations in humans.

Steroidogenic factor 1 is a monomeric orphan nuclear receptor and one of several hundreds of transcription factors encoded in the human genome. It regulates the transcription of many genes involved in gonadal development, sexual differentiation, steroidogenesis and reproduction. Recently, mutations in the gene encoding SF1 have been identified in several patients with primary adrenal failure and 46,XY sex-reversal. Interpreting the consequences of these mutations provides further understanding of transcription factor haploinsufficiency in human genetic disease as well as the exquisite sensitivity of humans to gene-dosage effects during adrenal and gonadal development.

Adrenal Gland Diseases↗
PubMed1992

Brain grafts of migratory GnRH cells induce gonadal recovery in hypogonadal (hpg) mice.

Gonadotropin-releasing hormone (GnRH) neurons are derived from the olfactory placode and migrate into the CNS during embryogenesis. During this migration the GnRH neuronal population follows a very specific pathway through the nasal septum and forebrain with individual neurons 'stopping' at various points along the way. Following migration GnRH neurons elaborate axonal projections, the major one to the median eminence. The function of this neurosecretory connection can then be assessed by activation of the pituitary-gonadal axis. In previous experiments we had demonstrated that grafted post-migratory GnRH neurons could send axons to the median eminence and initiate gonadal development in hypogonadal (hpg) mice that lack GnRH. In the present experiment, grafts derived from the embryonic nasal septum, which contains the migratory population of GnRH neurons, were used to determine if the transplanted GnRH neurons could (1) continue their migration in the adult host brain, (2) elaborate axons to their normal target in the host and (3) stimulate the host pituitary-gonadal axis to induce gonadal development. Nasal tissue from normal mouse embryos was implanted into the preoptic area (n = 8), anterior hypothalamus (n = 3) or third ventricle (n = 1) of adult hpg males. Following survival of 10 days to 10 weeks, the distribution of GnRH immunoreactive elements was assessed and testicular weight recorded. Surviving GnRH neurons were few in number and were found within the graft (n = 3), the host brain (n = 2) or both (n = 1). Four grafts resulted in specific outgrowth of GnRH axons through the host parenchyma to the median eminence.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Sexually dimorphic effects of NMDA receptor antagonism on brain-pituitary-gonad axis development in the platyfish.

The N-methyl-D-aspartate glutamate receptor (NMDAR) is found in hypothalamic nuclei involved in the regulation of reproduction in several species of mammals and fishes. NMDAR is believed to affect reproductive development and function by regulating gonadotropin releasing hormone (GnRH)-producing cells. These pathways are likely to be sexually dimorphic, as are several other neurotransmitter systems involved in reproductive function. In this report, male and female platyfish received intraperitoneal injections of 0, 5, 10, 20, 40 or 60 microg/g body wt. of the non-competitive NMDAR antagonist MK-801. Injections began at 6 weeks of age and continued thrice weekly until control animals reached puberty, as evidenced by anal fin maturation. The percent of pubescent animals was significantly affected by sex and treatment, with fewer MK-801-injected females in puberty than control females at each dose (P<0.001), and fewer pubescent females than males at 10, 20 and 40 microg/g (P<0.05). There were no MK-801-related effects in males. Histological analyses revealed typical immature gonads and pituitary glands in treated females, and typical mature morphology in control females and all males. Immunocytochemical distribution of the R1 subunit of the NMDAR within the brain-pituitary-gonad (BPG) axis was limited to GnRH-containing brain cells in all animals; however, NMDAR1 distribution was in an immature pattern in treated females and a mature pattern in all others. Neural concentrations of GnRH were unaffected by MK-801 treatment in both sexes. These data suggest that in the platyfish, NMDAR influence on reproductive development is sexually dimorphic and occurs at, or above, the level of GnRH-containing cells of the BPG axis.

Animals↗
PubMed1992

Inhibitory effects of a luteinizing-hormone-releasing hormone agonist implant on ovine fetal gonadotrophin secretion and pituitary sensitivity to luteinizing-hormone-releasing hormone.

Sheep fetuses at day 70 of gestation (term = 145 days) were implanted subcutaneously with a biodegradable implant containing a luteinizing-hormone-releasing hormone (LHRH) agonist (buserelin) to investigate whether treatment with LHRH agonist would induce a state of desensitization of the fetal gonadotrophs and thus influence fetal gonadal development. Treatment with the LHRH agonist for 35-40 days caused a significant reduction in mean fetal plasma concentrations of LH and follicle-stimulating hormone (FSH) compared with control fetuses. LH pulses were evident in control fetuses but were completely abolished by buserelin treatment. Furthermore, the pituitary content of LH and FSH was significantly depleted in fetuses implanted with LHRH agonist. A bolus intravenous injection of 500 ng LHRH given to control fetuses caused a rapid and significant increase in plasma LH and FSH concentrations which was sustained for at least 60 min after injection. Pretreatment with buserelin completely abolished the LH and FSH responses to a bolus injection of LHRH. There were no differences between the sexes in fetal gonadotrophin concentrations or pituitary sensitivity to LHRH in control or agonist-treated fetuses. Furthermore, buserelin treatment for 35-40 days had no effect on the morphological appearance of the fetal gonads when compared with control fetuses, at least to day 110 of pregnancy. These results provide evidence for the induction of a state of desensitization of the LHRH receptors of the fetal pituitary gonadotrophs following long-term treatment with an LHRH agonist, but provide no evidence for a role for gonadotrophin secretion in gonadal development at this stage in fetal life.

Analysis of Variance↗
PubMed1994

Developmental expression of mouse steroidogenic factor-1, an essential regulator of the steroid hydroxylases.

As an initial step toward understanding its role in steroidogenesis, we studied the developmental profile of steroidogenic factor-1 (SF-1), a nuclear receptor that regulates the steroid hydroxylases. SF-1 transcripts first appear on embryonic day 9 (E9) in the urogenital ridge, the probable source of steroidogenic cells of both adrenals and gonads. By E11, after the adrenals and gonads are clearly separate, SF-1 transcripts are detected throughout the adrenal primordium. Thereafter, adrenal expression of SF-1 localizes to the cortex. Consistent with its proposed role in regulating cholesterol side-chain cleavage enzyme (SCC), SF-1 is expressed before SCC. During the sexually undifferentiated stage of gonadal development (E9-E12), all embryos express SF-1 in the genital ridge. As testicular cords form in males, SF-1 transcripts are diffusely expressed throughout the testis, whereas SCC mRNA is limited to the interstitium. These differences between SF-1 and SCC reflect SF-1 expression by Sertoli cells, as shown by Northern blotting and in situ hybridization. In contrast to its persistent expression in the embryonic testis, SF-1 transcripts disappear from the ovary between E13.5-E16.5, reappearing only during late gestation (E18.5). Thus, expression of SF-1 in the embryonic gonad is sexually dimorphic. Coupled with the demonstration of SF-1 mRNA in Sertoli cells, these data suggest that SF-1 plays a role in gonadal development distinct from regulating the steroidogenic enzymes. Additionally, SF-1 is expressed in the embryonic forebrain, implying a role in neural development.

Adrenal Glands↗
PubMed2000

Reproductive function in male rats after brief in utero exposure to diethylstilboestrol.

Long-term effects of brief in utero exposure to diethylstilboestrol (DES) during a foetal period known to be critical for gonadal development were evaluated. Rats were exposed to DES (100 microg/kg body-weight) from day 17 to 19 of pregnancy. All of the DES-treated pregnant rats (11/11) ate parts or whole of their offspring during the first day after birth (p=0.03). Surviving male offspring were examined on day 63 post-partum. DES induced a reduction in weight of the testis (p=0.06) and ventral prostate (p=0.07), even after this short exposure. DES tended to reduce the number of Sertoli cells (p=0.13). Our findings indicate that even a short in utero exposure of rats to DES during a critical period for gonadal development results in cannibalism and reduced testis and ventral prostate weight.

Animals↗
PubMed2006

Attraction rules: germ cell migration in zebrafish.

The migration of zebrafish primordial germ cell towards the region where the gonad develops is guided by the chemokine SDF-1a. Recent studies show that soon after their specification, the cells undergo a series of morphological alterations before they become motile and are able to respond to attractive cues. As migratory cells, primordial germ cells move towards their target while correcting their path upon exiting a cyclic phase in which morphological cell polarity is lost. In the following stages, the cells gather at specific locations and move as cell clusters towards their final target. In all of these stages, zebrafish germ cells respond as individual cells to alterations in the shape of the sdf-1a expression domain, by directed migration towards their target - the position where the gonad develops.

Animals↗
PubMed2001

Developmental regulation of connexin 43 expression in fetal mouse testicular cells.

Multiple connexins have been identified in testicular cells. Several lines of evidences indicate that, among them, connexin 43 (Cx43) may be unique for control of gonad development and spermatogenesis. To date, however, it is not known whether Cx43 is expressed in the fetal testis and what possible types of cellular interactions mediated by this connexin are critical to male fertility. In the present work, expression of Cx43 was investigated at various developmental ages in cryosections from mouse testis by using specific antibodies against Cx43. In serial or double-labeled sections, Cx43 localization was compared with immunocytochemical distribution of steroidogenic enzyme, 3beta-hydroxysteroid dehydrogenase (3betaHSD), Mullerian inhibitory hormone (MIH), and germinal nuclear cell antigen (GCNA1), which are specific markers, respectively, of interstitial Leydig, Sertoli, and germinal cells. Sections were analyzed by fluorescence microscopy. We found that Cx43 immunofluorescence (IF) was uniformly distributed in the undifferentiated gonad at 11.5 days post coitus (dpc) and in cells of the mesonephric tubules. In the undifferentiated gonad, Cx43 was localized between primordial germ cells and somatic cells. At 12.5 dpc, when the gonad has undergone sexual differentiation, in the interstitium Cx43 was localized in Leydig cells and in the seminiferous cord it was localized between adjacent Sertoli cells. In Leydig and Sertoli cells, Cx43 labeling increased at 14.5, 16.5, and 18.5 dpc. From day 12.5 up to 18.5 dpc, Cx43 was also localized in cell borders between germinal and Sertoli cells. In conclusion, this study demonstrates that from the earliest stages of gonadal development, Cx43 is expressed in the principal cell types that participate in the control of male fertility. It also shows that Cx43 expression in Leydig and Sertoli cells increase during fetal life. Finally, it provides evidence that, throughout embryonic life, Cx43 forms gap junctions between Sertoli and germinal cells.

Animals↗
PubMed2006

Herbimycin A suppresses mitotic activity and egg production of female Schistosoma mansoni.

The eggs of the endoparasite Schistosoma are the causative agent of schistosomiasis, an important disease of humans, which is endemic in (sub-) tropical regions. The absence of a vaccine with sufficient protective qualities and increasing resistance to approved and established drugs like praziquantel, justify the exploration of novel ways to fight schistosomes. Our strategy is based on interference with the sexual maturation of the female. Prerequisites for gonad development in adult females are a continuous pairing contact with the male and significantly increased mitotic activity. In this study we show that the male governs sexual maturation of the female, as the separation of couples causes a clear reduction of female mitotic activity and, consequently, egg production. We demonstrate that treatment of schistosomes with Herbimycin A, an inhibitor of protein tyrosine kinases (PTKs), mimics the separation of couples as the drug blocks mitotic activity and egg production of paired females. However, the synthesis of the eggshell precursor protein p14 is elevated. Furthermore, we show for the first time in invertebrates that Herbimycin A decreases tyrosine phosphorylation and PTK stability in schistosomes. Summarised, our data provide evidence that PTKs have key functions in regulating gonad development, eggshell gene expression and, consequently, egg production. Therefore, we suggest envisaging schistosome PTKs as novel targets for strategies to combat schistosomiasis.

Animals↗
PubMed2005

Attenuation of gonadal response to photostimulation following ablation of neurons in the lateral septal organ of chicks.

Many avian species in temperate zones respond to long photoperiods by showing recrudescence of gonads. Compelling evidence show that non-retinal, non-pineal photoreceptors exist in the avian brain. Within the ventral forebrain are specialized neurons that respond to light found in the medial portion of a circumventricular organ called the lateral septal organ (LSO). The objective of this study was to examine whether the integrity of the LSO was critical for rapid gonadal development in young male chicks placed under long day photostimulation. Birds were initially kept on a short photoperiod (LD 8:16) until 2 weeks of age, at which time bilateral electrolytic lesions were administered to the LSO. After surgery, birds were transferred to a long photoperiod (LD 16:8) and fed a chick starter diet containing 0.2% sulfamethazine (SMZ). The combination of a long day plus SMZ is known to stimulate sexual maturation in male chicks. In four separate experiments conducted to date, bilateral lesions directed to the LSO and lesions that missed and were placed caudal and ventral to the target resulted in a significant decrease in testes weight, compared to sham-operated controls (P<0.05). Results suggest that neurons in the LSO may be directly involved in responding to long photoperiods and stimulating gonadal development in broiler chicks.

Analysis of Variance↗
PubMed1993

Sustained hormonal responses of Siberian hamsters (Phodopus sungorus) to a single longer day at weaning.

Siberian hamsters undergo gonadal development for several weeks after exposure to a single longer day at weaning. To characterize changes in gonadotropin secretion after a single acute light stimulus, hamsters housed in a long photoperiod (16L:8D) were given a single longer day (20L:4D) or maintained in the 16L:8D photoperiod at 19 days of age and transferred to a short photoperiod (8L:16D) on Day 20. Elevated plasma FSH concentrations were detected in male hamsters at 5, 7, and 12 but not at 17 days after the single longer day. Melatonin treatment during light exposure and on two succeeding nights blocked the stimulatory effect of light on the reproductive axis; melatonin injections limited to one night were marginally effective. Pinealectomy during the dark phase of the photocycle and the resultant truncation of the melatonin signal for one night did not stimulate a greater degree of gonadal development than pinealectomy during the light phase. We conclude that the single extra 4-h light pulse at weaning alters hypothalamic-pituitary function for approximately 2 wk. Trophic effects of the light pulse appear to be mediated by suppression of melatonin secretion for several days; one truncate melatonin signal is not sufficient to simulate the effects of a single long day on the reproductive axis.

Animals↗
PubMed2005

Delayed Sry and Sox9 expression in developing mouse gonads underlies B6-Y(DOM) sex reversal.

The phenomenon of B6-Y(DOM) sex reversal arises when certain variants of the Mus domesticus Y chromosome are crossed onto the genetic background of the C57BL/6J (B6) inbred mouse strain, which normally carries a Mus musculus-derived Y chromosome. While the sex reversal has been assumed to involve strain-specific variations in structure or expression of Sry, the actual cause has not been identified. Here we used in situ hybridization to study expression of Sry, and the critical downstream gene Sox9, in strains containing different chromosome combinations to investigate the cause of B6-Y(DOM) sex reversal. Our findings establish that a delay of expression of Sry(DOM) relative to Sry(B6) underlies B6-Y(DOM) sex reversal and provide the first molecular confirmation that Sry must act during a critical time window to appropriately activate Sox9 and effect male testis determination before the onset of the ovarian-determining pathway.

Animals↗
PubMed2004

Perception and possible utilization of moonlight intensity for reproductive activities in a lunar-synchronized spawner, the golden rabbitfish.

Rabbitfishes are known to spawn synchronously around the species-specific lunar phase. It is considered that they perceive and utilize cues from the moon in order to be synchronized gonadal development and spawning with the lunar cycle. Using the golden rabbitfish, Siganus guttatus, which spawns synchronously around the first quarter moon during the reproductive season, we measured the fluctuation of melatonin levels and examined the response of the fish to moonlight intensity. Daily fluctuation of melatonin concentration in the blood of golden rabbitfish showed low levels during daytime and high levels during night-time, suggesting that melatonin functions in the perception and utilization of photoperiod. Plasma melatonin concentration at the new moon was higher than that at the full moon. When the fish were exposed to moonlight at midnight of the both moon phases, the melatonin concentrations decreased to the control levels. These results show that the fish possibly perceive moonlight intensity and plasma melatonin fluctuates according to 'lightness' at a point of night. At the first spawning period (experiment was started one month before the spawning), the fish reared under natural conditions spawned at the expected spawning dates, whereas the fish reared under the constant darkness and lightness of night did not spawn. At the second spawning period (experiment was started 2 weeks before the spawning), the fish reared under the conditions of natural and constant darkness of night spawned but not that of constant lightness of night. It is possible that night conditions are related to synchronous gonadal development and spawning in the golden rabbitfish.

Analysis of Variance↗
PubMedDate not supplied

Androgen-induced prevention of the outgrowth of cranial gonadal suspensory ligaments in fetal rats.

Normal and disturbed testicular descent is frequently approached exclusively through a consideration of the caudal testicular suspensory apparatus. This is surprising, because embryonal gonads develop with both cranial and caudal suspensory ligaments, and the sexes differ with respect to the persistence and development of both the cranial and the caudal ligaments. The current study examined the possible role of fetal testicular androgens in male-specific failure of the development of the cranial gonadal suspensory apparatus in rats. Normal male fetuses were studied, as well as fetuses exposed to the anti-androgen flutamide from day 10 after conception. Females were given daily injections of methyl-testosterone alone or in combination with the anti-androgen cyproterone acetate from day 15 after conception, and were studied on day 22. The cranial ligaments remained of minor extension in normal males but developed considerably in females. They developed in female fashion in males exposed to flutamide, and persisted throughout postnatal life. Cranial ligaments did not develop in females that had been exposed to methyl-testosterone. Simultaneous treatment with a large dose of cyproterone acetate effectively counteracted this effect. Fetal testicular testosterone thus appears to play a key role in the prevention of the outgrowth of the cranial gonadal/genital ligament in rats. The supposed function of this suspensory apparatus makes it likely that its persistence in males, as the consequence of inappropriate androgen action during fetal life, facilitates disturbance of testicular descent. This finding may contribute to understanding developmental disorders underlying disturbed testis descent in humans.

Androgens↗