Gonadal Stimulation Research Articles

Transcriptome profiling of gonad-stimulating factors in thoracic ganglia and a potential role of Indian hedgehog gene in vitellogenesis of banana shrimp Fenneropenaeus merguiensis

Shrimp reproduction is controlled by several factors. Central nervous tissues, especially thoracic ganglia and brain, are known sources of gonad stimulating factors (GSFs) in crustaceans, but the GSFs in shrimp have not yet been clarified. Hence, we aimed to characterize and study putative GSFs from thoracic ganglia of adult female Fenneropenaeus merguiensis. An analysis of thoracic ganglia transcriptome revealed 3224 putative GSFs of a total 77,681 unigenes. Only 376 putative GSFs were differentially expressed during ovarian developmental stages. Eight candidate GSFs were validated for their expression patterns in thoracic ganglia, including the Indian hedgehog gene. F. merguiensis Indian hedgehog (FmIHH) was then investigated for its role in vitellogenesis. The obtained full-length cDNA of FmIHH was similar to other crustacean IHHs rather than Sonic and Desert HHs. The FmIHH was dominantly expressed in thoracic ganglia, and its expression was significantly increased in the vitellogenic stages before being downregulated at the mature stage of ovarian development. Injection of the recombinant FmIHH (His-TF-IHH) protein stimulated vitellogenin expression in ovaries on day 3 and 7, and also increased the gonadosomatic index. In addition, crustacean hyperglycemic hormone expression and total sugar were significantly decreased in eyestalks and hemolymph, respectively, after injection of His-TF-IHH, while lactic acid was increased. Both total sugar and lactic acid were unchanged in ovaries of His-TF-IHH injected shrimp. These results suggested that FmIHH plays a crucial role in vitellogenesis and regulate sugar uptake during ovarian development.

Ambulacrarian insulin-related peptides and their putative receptors suggest how insulin and similar peptides may have evolved from insulin-like growth factor.

BackgroundSome insulin/IGF-related peptides (irps) stimulate a receptor tyrosine kinase (RTK) that transfers the extracellular hormonal signal into an intracellular response. Other irps, such as relaxin, do not use an RTK, but a G-protein coupled receptor (GPCR). This is unusual since evolutionarily related hormones typically either use the same or paralogous receptors. In arthropods three different irps, i.e. arthropod IGF, gonadulin and Drosophila insulin-like peptide 7 (dilp7), likely evolved from a gene triplication, as in several species genes encoding these three peptides are located next to one another on the same chromosomal fragment. These arthropod irps have homologs in vertebrates, suggesting that the initial gene triplication was perhaps already present in the last common ancestor of deuterostomes and protostomes. It would be interesting to know whether this is indeed so and how insulin might be related to this trio of irps.MethodologyGenes encoding irps as well as their putative receptors were identified in genomes and transcriptomes from echinoderms and hemichordates.ResultsA similar triplet of genes coding for irps also occurs in some ambulacrarians. Two of these are orthologs of arthropod IGF and dilp7 and the third is likely a gonadulin ortholog. In echinoderms, two novel irps emerged, gonad stimulating substance (GSS) and multinsulin, likely from gene duplications of the IGF and dilp7-like genes respectively. The structures of GSS diverged considerably from IGF, which would suggest they use different receptors from IGF, but no novel irp receptors evolved. If IGF and GSS use different receptors, and the evolution of GSS from a gene duplication of IGF is not associated with the appearance of a novel receptor, while irps are known to use two different types of receptors, the ancestor of GSS and IGF might have acted on both types of receptors while one or both of its descendants act on only one. There are three ambulacrarian GPCRs that have amino acid sequences suggestive of being irp GPCRs, two of these are orthologs of the gonadulin and dilp7 receptors. This suggests that the third might be an IGF receptor, and that by deduction, GSS only acts on the RTK. The evolution of GSS from IGF may represent a pattern, where IGF gene duplications lead to novel genes coding for shorter peptides that activate an RTK. It is likely this is how insulin and the insect neuroendocrine irps evolved independently from IGF.ConclusionThe local gene triplication described from arthropods that yielded three genes encoding irps was already present in the last common ancestor of protostomes and deuterostomes. It seems plausible that irps, such as those produced by neuroendocrine cells in the brain of insects and echinoderm GSS evolved independently from IGF and, thus, are not true orthologs, but the result of convergent evolution.

Retinal and extra-retinal photoreceptor responses and reproductive performance of Japanese quail (Coturnix coturnix japonica) following exposure to different photoperiodic regime

Japanese quail is a truly photoperiodic avian species. In general long days are gonado-stimulatory and short days are gonado-inhibitory for this poultry bird. To investigate the correlation of retinal and extra-retinal photoreceptors with different photoperiodic conditions quail were divided into 2 groups and kept under long day (16L: 8D) and short day (8L: 16D) condition separately to develop photosensitivity and scotosensitivity respectively. Transfer of long day quail to intermediate day-length (13.5L: 10.5D) developed photorefractoriness (relative) and prolonged exposure to short photoperiodic conditions led the birds to develop scotorefractoriness. Increased expression of mRNA and immunosignaling of photoreceptors rhodopsin, transducin in eye and hypothalamus while decreased mRNA expression of melatonin receptors (Mel1b, Mel1c) were noted in the eyes of photosensitive (PS) and scotorefractory (SR) quail compared to photorefractory (PR) and scotosensitive (SS) birds respectively. Decreased expression of hypothalamic GnIH and melatonin receptors mRNA was observed in PS and SR birds compared to PR and SS birds respectively. Modulation of retinal and extra retinal photoreceptors leads to increased spermatogenesis as well as mRNA expression of steroidogenic genes and androgen receptor in the testis of sexually active PS and SR quail. These results led us to conclude that gonadal stimulation in PS as well as SR quail is outcome of activated retinal and extra retinal photoreceptors which lowered melatonin receptors and GnIH expression. Contrarily testicular inhibition in PR and SS is the outcome of decreased photoperception. It is suggested that decreased photoperception in SS quail increases after prolong exposure of the short day (in SR) leading to increased activity of HPG axis.

Insights on Molecular Mechanisms of Ovarian Development in Decapod Crustacea: Focus on Vitellogenesis-Stimulating Factors and Pathways.

Vitellogenesis in crustaceans is an energy-consuming process. Though the underlying mechanisms of ovarian maturation in decapod Crustacea are still unclear, evidence indicates the process to be regulated by antagonistically-acting inhibitory and stimulating factors specifically originating from X-organ/sinus gland (XO/SG) complex. Among the reported neuromediators, neuropeptides belonging to the crustacean hyperglycemic hormone (CHH)-family have been studied extensively. The structure and dynamics of inhibitory action of vitellogenesis-inhibiting hormone (VIH) on vitellogenesis have been demonstrated in several species. Similarly, the stimulatory effects of other neuropeptides of the CHH-family on crustacean vitellogenesis have also been validated. Advancement in transcriptomic sequencing and comparative genome analysis has led to the discovery of a large number of neuromediators, peptides, and putative peptide receptors having pleiotropic and novel functions in decapod reproduction. Furthermore, differing research strategies have indicated that neurotransmitters and steroid hormones play an integrative role by stimulating neuropeptide secretion, thus demonstrating the complex intertwining of regulatory factors in reproduction. However, the molecular mechanisms by which the combinatorial effect of eyestalk hormones, neuromediators and other factors coordinate to regulate ovarian maturation remain elusive. These multifunctional substances are speculated to control ovarian maturation possibly via the autocrine/paracrine pathway by acting directly on the gonads or by indirectly exerting their stimulatory effects by triggering the release of a putative gonad stimulating factor from the thoracic ganglion. Acting through receptors, they possibly affect levels of cyclic nucleotides (cAMP and cGMP) and Ca2+ in target tissues leading to the regulation of vitellogenesis. The “stimulatory paradox” effect of eyestalk ablation on ovarian maturation continues to be exploited in commercial aquaculture operations, and is outweighed by the detrimental physiological effects of this procedure. In this regard, the development of efficient alternatives to eyestalk ablation based on scientific knowledge is a necessity. In this article, we focus principally on the signaling pathways of positive neuromediators and other factors regulating crustacean reproduction, providing an overview of their proposed receptor-mediated stimulatory mechanisms, intracellular signaling, and probable interaction with other hormonal signals. Finally, we provide insight into future research directions on crustacean reproduction as well as potential applications of such research to aquaculture technology development.

Migratory strategy explains differences in timing of female reproductive development in seasonally sympatric songbirds

Abstract Divergent migratory strategies among populations can result in population‐level differences in timing of reproduction (allochrony) and local adaptation. However, the mechanisms underlying among‐population variation in timing are insufficiently understood, particularly in females. We studied differences in reproductive development and its related mechanisms along the hypothalamic–pituitary–gonadal axis (HPG) in closely related migratory and sedentary (i.e. resident) female dark‐eyed juncos (Junco hyemalis) living together in sympatry during early spring. Despite exposure to the same environmental cues in early spring, residents initiate breeding prior to the departure of migrants for their breeding grounds. We investigated whether residents would be more reproductively developed than migrants based on their behavioural differences. Alternatively, females could exhibit similar reproductive development in response to the same environmental cues despite differences in migratory behaviour. To compare their degree of reproductive development during seasonal sympatry and the underlying mechanisms of these differences, we collected ovarian and liver tissue in early spring prior to migration and compared transcript abundance of genes associated with reproduction using quantitative PCR. We also used stable hydrogen isotopes to infer relative breeding and wintering latitude of migrants. We found higher transcript abundance of luteinizing hormone receptor and aromatase in the ovary in addition to significantly heavier ovaries in residents than in migrants. Together, these results suggest greater sensitivity and response to upstream endocrine stimulation in resident females. Transcript abundance for other receptors in the ovary and liver associated with reproduction, however, did not differ between populations. When comparing ovarian development within migrants, females with lower hydrogen isotopes (indicating higher breeding latitudes) had smaller ovaries, suggesting that longer‐distance migrations may further delay reproductive development. Based on differences in ovary mass and transcript abundance, we conclude that females that differ in migratory strategy also differ in timing of reproductive development. These results support that divergent migratory behaviour drives allochrony and could enable reproductive isolation between populations; mechanistic differences at the level of gonadal stimulation can explain these differences in timing of reproductive development. A free Plain Language Summary can be found within the Supporting Information of this article.

Effect of leucine enkephalin administration on ovarian maturation in the freshwater crab Travancoriana schirnerae

The current study focused on the effect of administration of the neurotransmitter leucine enkephalin on ovarian maturation in the freshwater crab Travancoriana schirnerae . The crabs were administered with leucine enkephalin in multiple doses (10 µl/injection) and their dissected ovaries were processed for histomorphological analyses. Ovarian maturation was assessed by both macroscopic and microscopic observations such as ovarian index, mean oocyte diameter, oocyte proportion values and histological examinations of the ovaries of control and treated crabs. Our observations revealed significantly higher ovarian index, oocyte diameter and oocyte proportion values in treatments over controls. Leucine enkephalin treatment induced previtellogenic ovary to grow into primary vitellogenic, primary vitellogenic to secondary vitellogenic 1 secondary vitellogenic 1 and 2 to secondary vitellogenic 3 stage as evinced by the presence of a large number of primary previtellogenic ovaries in previtellogenic oocytes, larger proportion of secondary vitellogenic oocytes in primary vitellogenic ovaries and secondary vitellogenic stage 3 oocytes in secondary vitellogenic stage 1 ovaries of treated crabs over the controls. The conversion of previtellogenic ovary to early vitellogenic, early to middle and middle to late vitellogenic ovaries in treated crabs probably indicate the stimulatory effect of leucine enkephalin on ovaries either by triggering the release of the gonad stimulating hormone synthesized and released from the brain or thoracic ganglion or by blocking the release of the gonad inhibiting hormone synthesized and secreted by the X organ-sinus gland complex of the eyestalks or both. The results of the present study clearly indicate that leucine enkephalin has a stimulatory effect on ovarian maturation in T. schirnerae , thus shortening the period of maturation of ovary, which can be utilized in large-scale production of the species concerned. Further studies are needed to check the efficacy of this neurotransmitter as a supplement in diet to induce ovarian maturation of this species.

Development and Validation of an Enzyme Immunoassay for Fecal Dehydroepiandrosterone Sulfate in Japanese Macaques (Macaca fuscata)

Measuring hormonal profiles is important in monitoring stress, physical fitness, and reproductive status in primates. Noninvasive methods have been used to measure several steroid hormones in primates without causing them stress. However, few studies have used feces or urine to measure dehydroepiandrosterone sulfate (DHEAS), an important precursor of sex steroids that has been studied as a biomarker of aging, pregnancy, and stress in humans and nonhuman primates. We developed an enzyme immunoassay to detect DHEAS in the feces of Japanese macaques (Macaca fuscata). Our subjects included eight singly housed Japanese macaques. To validate the assay, we administrated oral DHEA to one male and one female macaque, collected their feces, and measured DHEAS levels over time. Given that DHEAS is related to gonadal steroids and the stress response, we also measured DHEAS concentrations in response to adrenal (adrenocorticotropic hormone [ACTH]) and gonadal (human chorionic gonadotropin [hCG]) stimulation. Our assay successfully detected DHEAS in Japanese macaque feces, and levels of DHEAS were associated with the amount of DHEA ingested. Parallelism and accuracy tests revealed that fecal extracts were reliable measures of DHEAS. Neither ACTH nor hCG challenge appeared to affect DHEAS levels. The method we describe is less expensive than that using the commercially available kits and is applicable to investigations involving aging, stress, and reproduction in Japanese macaques.

Environmental and biological cues for spawning in the crown-of-thorns starfish.

Sporadic outbreaks of the coral-eating crown-of-thorns starfish are likely to be due, at least in part, to spatial and temporal variation in reproductive and settlement success. For gonochoric and broadcast spawning species such as crown-of-thorns starfish, spawning synchrony is fundamental for achieving high rates of fertilization. Highly synchronized gamete release within and among distinct populations is typically the result of the entrainment of neurohormonal endogenous rhythms by cues from the environment. In this study, we conducted multiple spawning assays to test the effects of temperature change, reduced salinity and nutrient enrichment of seawater, phytoplankton, gametes (sperm and eggs), and the combined effect of sperm and phytoplankton on the likelihood of spawning in male and female crown-of-thorns starfish. We also investigated sex-specific responses to each of these potential spawning cues. We found that (1) abrupt temperature change (an increase of 4°C) induced spawning in males, but less so in females; (2) males often spawned in response to the presence of phytoplankton, but none of the females spawned in response to these cues; (3) the presence of sperm in the water column induced males and females to spawn, although additive and synergistic effects of sperm and phytoplankton were not significant; and (4) males are more sensitive to the spawning cues tested and most likely spawn prior to females. We propose that environmental cues act as spawning ‘inducers’ by causing the release of hormones (gonad stimulating substance) in sensitive males, while biological cues (pheromones) from released sperm, in turn, act as spawning ‘synchronizers’ by triggering a hormonal cascade resulting in gamete shedding by conspecifics. Given the immediate temporal linkage between the timing of spawning and fertilization events, variability in the extent and synchronicity of gamete release will significantly influence reproductive success and may account for fluctuations in the abundance of crown-of-thorns starfish.

Noise Induces Hypothyroidism and Gonadal Dysfunction Via Stimulation of Pineal–Adrenal Axis in Chicks

Noise is a world-wide problem that causes nervous, endocrine and cardiovascular disorders, and eventually health hazards in humans and animals. Objective of the current work is to investigate endocrine interaction in noise stress, which subsequently affects other endocrine functions including gonads in a poultry bird like chicks. Gravimetric, ultrastructural and hormonal status of the endocrine organs were examined to ascertain the effects of noise stress. Acute noise at 60 dB had no effect, but at 80 and 100 dB each for 3 h, increased pineal and serum serotonin, and adrenal and serum corticosterone, epinephrine and norepinephrine concentrations, without any change in thyroid or gonadal hormones. Chronic noise exposure at 60, 80 and 100 dB each for 6 h, daily for 7 days, drastically disturbed normal behavior, and quantum of food consumption and water intake. Chronic exposure also significantly decreased body weight including thyroid, ovary and testis weight, and increased adrenal weight. Noise stress caused ultrastructural changes leading to stimulations of pinealocytes (with abundance of rough endoplasmic reticulum and mitochondria), adrenocortical cells (enlarged nuclei and abundance of smooth endoplasmic reticulum) and adrenomedullary cells (enlarged nuclei with presence of chromaffin granules) were observed in noise stress. Additionally, pineal and serum serotonin, N-acetyl serotonin and melatonin, and adrenal and serum corticosterone, epinephrine and norepinephrine levels were significantly elevated following chronic noise exposure. Contrarily, thyroid activity was suppressed with atrophied thyroid follicles followed by declined levels of serum T3 and T4 with elevation of TSH level. Simultaneously, serum 17β-estradiol (E2) and testosterone (T) concentrations were also significantly declined in all the doses of chronic noise. These changes were dose dependent of noise exposure. The findings suggest that (a) adrenal and pineal glands respond primarily to noise and secondarily act on other endocrine organs including gonads in chicks, (b) adrenal directly and/or indirectly causes thyroid and gonadal dysfunctions via pineal following noise exposure in chicks.

Apoptosis-mediated testicular alteration in Japanese quail (Coturnix coturnix japonica) in response to temporal phase relation of serotonergic and dopaminergic oscillations.

Reproductive performance of many avian species, including Japanese quail, is reported to be modulated by specific temporal phase relation of serotonergic and dopaminergic oscillations. Accordingly, it has been shown that the serotonin precursor 5-HTP and the dopamine precursor l-DOPA given 8 h apart induce gonadal suppression and given 12h apart lead to gonadal stimulation, while other temporal relationships were found to be ineffective. In the present study, we investigated the effects of 8- and 12-h phase relation of neural oscillations on testicular responses including expression of GnRH-I, GnIH, pro-apoptotic proteins (p53 and Bax), inactive and active executioner caspase-3, and the uncleaved DNA repair enzyme PARP-1. Testicular volume and mass decreased significantly in 8-h quail and increased in 12-h quail compared with controls. Expression of ir-GnIH, p53, Bax and active-caspase-3 increased and that of GnRH-I, pro-caspase-3 and uncleaved PARP-1 decreased in 8-h quail compared with controls. A TUNEL assay also confirmed testicular regression in these quail. Testes of 12-h quail exhibited significantly increased expression of GnRH-I, pro-caspase-3 and uncleaved PARP-1 compared with the control group. Our findings suggest that differential response of avian testes to 8- and 12-h phase relation of serotonergic and dopaminergic neural oscillations may be attributed to autocrine/paracrine action of GnIH expression, which is upregulated in regressed testes, leading to apoptotic changes, and downregulated in developed testes, causing apoptotic inhibition. It is concluded that specific phase relation of neural oscillations may modulate the local testicular GnRH-GnIH system and alter the apoptotic mechanism in quail testes. Moreover, these findings highlight the physiological effects of time-dependent drug delivery, including the specific time intervals between two drugs.

Nesfatin-1: Localization and expression in avian gonads and its modulation by temporal phase relation of neural oscillations in female Japanese quail, Coturnix coturnix japonica

In a search for new appetite-controlling signals, the peptide nesfatin-1, expressed in the brain and peripheral tissues of rodents and humans has been reported to regulate feeding by reducing food intake. Recently it has also been reported that nesfatin-1 might be involved in regulating the reproductive axis in fishes and mammals, but its expression and physiological role if any, is not yet known in birds. In the present study, localization and expression of nesfatin-1 was observed in the testis, ovary and shell gland of poultry species Japanese quail, Coturnix coturnix japonica.Our earlier studies have reported that serotonin precursor 5-HTP and dopamine precursor l-DOPA given 8h apart induces gonadal suppression, when given 12h apart leads to gonadal stimulation while other relationships were found ineffective. In the present study intense ir-nesfatin-1 was observed in the regressed ovary (stromal cells) and shell gland (endometrium) of 8-h Japanese quail while in 12-h quail, weak and scarce immunostaining for nesfatin-1 was detected in the hyperactive ovary and shell gland compared to control.These findings led us to conclude that, an inverse relationship exists between ovarian activity (both in the control and simulated conditions) and nesfatin-1 expression. Present avian study, first of its kind, also suggests the role of nesfatin-1 in reproductive regulation possibly via appetite control and energy balance in female Japanese quail and needs to be investigated further in relation to food intake.

Photoperiodic regulation of seasonal responses in Indian weaver bird (Ploceus philippinus)

Photoperiod (=day length) is the vital factor for the regulation of behavioral and physiological activities in many avian species. This study investigated the seasonal cycles of testicular growth and secondary sexual characteristics of Indian weaver bird under natural day length (NDL) and the effects of duration and intensity of light on photoperiodic induction. In the first experiment, groups of birds (n = 7 each) were exposed to under NDL in April 2008 and May 2009 for 8 and 12 months, respectively. In second and third experiment, birds (n = 6 each group) were exposed to different photoperiods (11.5L:12.5D, 12L:12D, 13L:11D, and 15L:9D) at the same (500 lux) light intensity, and to 13L:11D at different light intensities (10-, 50-, 500-, and 800-lux). Observations on testis size, molt, and plumage score were recorded 2-week (molt and plumage) or at 4-week intervals (testes). Both the NDL groups showed similar seasonal cycles of testicular growth-regression and secondary sexual characteristics. Second and third experiments suggest that the photoperiodic induction was depending upon duration and intensity of the light. Birds showed testicular growth-regression cycle followed by molt and plumage color change only under 13L:11D and 15L:9D and only 500- and 800-lux under 13L:11D photoperiod but not under 11.5L:12.5D and 12L:12D and 10- and 50-lux light intensities. Pre- and post-nuptial molting on body feathers were progressed with gonadal stimulation–maturation and regression cycle under 13L:11D and 15L:9D. Results under different light–dark cycles suggest that day length of about 12 h or more and above the threshold level of light intensity are essential for the induction of photoperiodic responses.

Effects of naloxone, serotonin, and dopamine on reproduction of the freshwater crabBarytelphusa guerini

Several investigators suggest a relationship between neurotransmitters, serotonin (also called 5-hydroxytryptamine, 5-HT), and dopamine (DA) in the regulation of growth and reproductive development of vertebrate species, rather than the invertebrate species. In this study, we evaluated the role of 5-HT and DA in reproductive development of an invertebrate species, the freshwater crab Barytelphusa guerini. We tested the effects of 5-HT both alone and combined, and also the effects of an opioid antagonist naloxone, on reproductive development of B. guerini in terms of testicular and ovarian developmental parameters. Injection of either 5-HT or naloxone alone significantly increased the ovarian index and the oocyte diameter in female crabs, and the testicular index and testicular follicular diameter in male crabs. In contrast, injection of DA inhibited all the reproductive measures in both sexes. Co-injection of 5-HT with DA exhibited no significant effects on the reproductive development in both sexes compared to the control treatments. These results suggest that 5-HT, DA, and exogenous naloxone may be involved in the regulation of gonad stimulating hormone (GSH) and/or gonad inhibiting hormone (GIH). These results also provide evidence that naloxone may regulate endogenous neurotransmitters and its downstream hormones, GSH and GIH.

Photoperiodic regulation of seasonal reproduction, molt and body weight in the migratory male yellow-breasted bunting (Emberiza aureola)

Photoperiod has been shown to be a major source of temporal information regulating reproduction and associated functions in a number of avian species. We studied seasonal cycles of testicular volume, molt and body weight in natural and temperature-controlled conditions and under different artificial photoperiods in the yellow-breasted buntings. Buntings posses seasonal cycles of testicular volume, molt, body weight and fattening with no major difference between natural and temperature-controlled conditions. These cycles follow an annual solar cycle suggesting the possibility of their photoperiodic control. To confirm this, photosensitive birds were studied under 9L/15D (close to shortest day length), 12L/12D (equinox day length) and 14L/10D (close to longest day length) for 18 months. Buntings showed testicular growth followed by regression and development of photorefractoriness; molt and body weight change only under 12L/12D and 14L/10D but not under 9L/15D. Reinitiation of above responses did not occur following initial cycles under stimulatory photoperiods precluding the possibility of circannual rhythm involvement. Birds exhibited an incomplete prenuptial molt of body feathers during gonadal stimulation under long days followed by complete postnuptial molt of body and primary feathers that progressed with gonadal regression. Exposure of photosensitive birds to light–dark cycles constituting 9–16h of light/day suggested that daily photoperiod of about 12h or more is essential in inducing testicular growth and function. These results clearly indicate that buntings are capable of fine discrimination of photoperiodic information and use annual changes in day length as an environmental factor to time their seasonal responses.

Effect of cadmium on the ovarian development in the freshwater prawn Macrobrachium rosenbergii (De Man)

In this investigation, effect of cadmium chloride (25 μg/l) on oogenesis of freshwater prawn, Macrobrachium rosenbergii was studied. In vivo experiments were performed with both intact and eyestalk ablated prawns. The intact, cadmium-exposed prawns exhibited decrease in Gonado Somatic Index (GSI) and ovarian development compared to controls. Whereas, ablated treated ovary showed reduction of yolk material and oocyte membrane thickness at the end of 15 days exposure. Interestingly, the control prawn showed normal cellular architecture of gills, hepatopancreas and ovary with mature oocytes. But, the gills of treated prawns showed lamellar hypertrophy, cuticular dystrophy and irregular arrangement of epithelial cells. Hepatopancreas showed reduction in both tubular diameter and basement membrane thickness. Conspicuously, ovary showed hypertrophied primary oocytes with more vacuoles in intact-treated group. Cadmium had increased gonad inhibiting hormone (GIH) secretion and decreased gonad stimulating hormone (GSH) release as evident with the retardation of gonadal maturation in the intact prawns.

Temporal Phase Relation of Circadian Neural Oscillations Alters RFamide-Related Peptide-3 and Testicular Function in the Mouse

In order to study the effect of the temporal synergism of neural oscillations on reproductive regulation and the response of RFamide-related peptide-3 (RFRP-3; a mammalian ortholog of avian gonadotropin-inhibitory hormone), expression of immunoreactive RFRP-3 in the neurons of the dorsomedial nucleus of the hypothalamus was monitored in sexually immature and mature laboratory mice (study I). In study II, the effects of serotonin and dopamine precursors (5-hydroxytryptophan and L-dihydroxyphenylalanine; injected daily, 8 or 12 h apart, for 13 days in 3-week-old mice) on testicular activity and immunoreactive RFRP-3 neurons were studied until 24 days after treatment. Results indicate high levels of expression of immunoreactive RFRP-3 in the sexually immature and 8-hour mice (simulating gonadal suppression), while a low level was noted in mature and 12-hour mice (simulating gonadal stimulation). These findings not only suggest the modulation of gonadal development in mice (during the course of puberty attainment) by changing the temporal phase relation of serotonergic and dopaminergic oscillations (as in some seasonally breeding species), but also demonstrate an inverse correlation of RFRP-3 neurons and gonadal activity in both control and experimental conditions.

Indução do crescimento ovariano em Aegla uruguayana (Crustacea, Anomura, Aeglidae) mediante a incorporação de neuroreguladores ao alimento

O efeito estimulante da spiperona e da naloxana sob a maturação ovariana foram avaliados em fêmeas de Aegla uruguayana Schmitt, 1942 e, para isto, tais neuroreguladores foram incorporados ao alimento e administrados a uma dose de 10-8 mol/animal a cada sessão de alimentação. Fêmeas adultas foram coletadas com puçá em um arroio próximo à cidade de Salto, Província de Buenos Aires, Argentina. Dez fêmeas foram sacrificadas, medidas, pesadas e os seus ovários foram retirados e pesados para a determinação do índice gonadossomático (IG). As demais fêmeas (30) foram divididas em três grupos experimentais - (a) controle: alimentadas com pellets controle composto por ração para peixe - 34% de proteína e 43% de proteína; (b) spiperona: alimentadas com pellets controle enriquecidos com spiperona; (c) naloxana: alimentadas com pellets controle enriquecidos com naloxana. Após 7 semanas as fêmeas foram sacrificadas e avaliado o IG. Os ovários e o hepatopâncreas foram quantificados quanto aos níveis de lipídeos totais e colesterol. A naloxana produziu um aumento significativo nos níveis de lipídeos tanto nas gônadas como no hepatopâncreas em relação ao grupo controle. A spiperona produziu aumento significativo nos níveis de lipídeos nas gônadas e no hepatopâncreas e de colesterol no hepatopâncreas quando comparados ao controle. Os níveis de lipídeos foram significativamente menores na hemolinfa das fêmeas que foram alimentadas com pellets com spiperona e maiores nas fêmeas tratadas com naloxana quando comparadas as fêmeas que foram alimentadas apenas com ração. A spiperona e a naloxana, ao inibir os efeitos da dopamina e dos opióides endógenos, provavelmente causaram a secreção do hormônio estimulante das gônadas e a inibição do hormônio inibidor das gônadas, causando, portanto indução do desenvolvimento ovariano. Tal hipótese é reforçada pelos aumentos do índice gonadossomático verificado nestes grupos experimentais.

Inhibin A Production after Gonadotropin Stimulus: A New Method to Detect Ovarian Tissue in Ovotesticular Disorder of Sex Development

Background/Aims: While laboratory methods for the detection of testicular tissue are well standardized, currently there is no available test to demonstrate the presence of ovarian tissue. We evaluated the effectiveness of gonadal stimulation with luteinizing hormone (LH)/follicle-stimulating hormone (FSH) for the detection of ovarian tissue in patients with disorders of sex development (DSD). Methods: Ten patients with congenital adrenal hyperplasia (CAH) as ovarian-positive controls, 10 with cryptorchidism (ovarian-negative controls), 13 patients with DSD of no defined etiology and 7 patients with ovotesticular DSD (true hermaphroditism, TH) were included in the study. They underwent a daily injection of both LH and FSH on 3 consecutive days. LH, FSH, estradiol, testosterone and inhibin A were measured before treatment, 24 h after the 1st dose and 24 h after the 3rd dose. Results: Estradiol increased in all CAH and TH patients, with a median value of 155.1 and 92.6 pg/ml, respectively, after the 3rd injection. Inhibin A also increased in all CAH and TH patients, with a median value of 70.4 and 32.2 pg/ml, respectively, after the 3rd injection. There was no change in these hormones in the other groups. Conclusion: The LH/FSH stimulation test might be a useful method to detect the presence of ovarian tissue.

Induction of ovarian growth in the red claw crayfish, Cherax quadricarinatus, by the enkephalinergic antagonist naloxone: in vivo and in vitro studies

Summary The effects of spiperone and domperidone (dopaminergic antagonists), as well as naloxone (enkephalinergic antagonist) on ovarian growth of the crayfish Cherax quadricarinatus, were evaluated during the non-reproductive period. In vivo assays were carried out by administering these compounds by adding them to the crayfish food, and subsequently measuring the oocyte diameter (oocytes in secondary vitellogenesis). Only naloxone produced a significantly (p <0.05) higher oocyte diameter than that of the controls, suggesting that this antagonist was blocking the effects of endogenous enkcephalins on the secretion of one or more neurohormones involved in crustacean reproduction. To test this hypothesis, an in vitro incubation of ovarian pieces with thoracic ganglion (TG), a source of the gonad stimulating hormone (GSH), or eyestalk tissue (ET), the source of the gonad inhibiting hormone (GIH), with or without naloxone added to the incubation medium, was done. A significant increase of ovarian growth was observed when TG was present. Moreover, the addition of naloxone to this preparation was able to further increase the ovarian growth, presumably by preventing enkephalinergic inhibition of GSH secretion.

Exogenous T3mimics long day lengths in Siberian hamsters

Siberian hamsters (Phodopus sungorus) exhibit seasonal cycles of reproduction driven by changes in day length. Day length is encoded endogenously by the duration of nocturnal melatonin (Mel) secretion from the pineal gland. Short-duration Mel signals stimulate reproduction and long-duration signals inhibit reproduction. The mechanism by which Mel signals are decoded at the level of neural target tissues remains uncharacterized. In Siberian hamsters, exposure to short day lengths or injections of Mel in long days results in a decrease in hypothalamic expression of type 2 iodothyronine deiodinase (Dio2) mRNA. Dio2 catalyzes the conversion of the thyroid hormone thyroxine to triiodothyronine (T3). Thus exposure to short and long day lengths should decrease and increase hypothalamic T3 concentrations, respectively. We tested the hypothesis that exogenous T3 administered to short-day hamsters would mimic exposure to long day lengths with respect to gonadal stimulation. Hamsters gestated and raised in short day lengths that exhibited photoinhibition of the testes were given daily subutaneous injections of T3 or saline vehicle for 4 wk beginning at week 12 of life. The results indicate that exogenous T3 induced gonadal growth in short-day hamsters and delayed spontaneous gonadal development by an interval equal to the number of weeks during which T3 was administered. T3 injections delayed gonadal regression if given coincident with the transfer of hamsters from long to short day lengths. These results suggest that T3 mimics long day exposure in Siberian hamsters and may serve as an intermediate step between the Mel rhythm and the reproductive response.