Neural crest-derived neurons invade the ovary but not the testis during mouse gonad development.

Testes and ovaries undergo sex-specific morphogenetic changes and adopt strikingly different morphologies, despite the fact that both arise from a common precursor, the bipotential gonad. Previous studies showed that recruitment of vasculature is critical for testis patterning. However, vasculature is not recruited into the early ovary. Peripheral innervation is involved in patterning development of many organs but has been given little attention in gonad development. In this study, we show that while innervation in the male reproductive complex is restricted to the epididymis and vas deferens and never invades the interior of the testis, neural crest-derived innervation invades the interior of the ovary around E16.5. Individual neural crest cells colonize the ovary, differentiate into neurons and glia, and form a dense neural network within the ovarian medulla. Using a sex-reversing mutant mouse line, we show that innervation is specific to ovary development, is not dependent on the genetic sex of gonadal or neural crest cells, and may be blocked by repressive guidance signals elevated in the male pathway. This study reveals another aspect of sexually dimorphic gonad development, establishes a precise timeline and structure of ovarian innervation, and raises many questions for future research.

Developmental Origins of Hypothalamic Cells Controlling Reproduction.

The hypothalamus-pituitary-gonadal (HPG) axis is the most critical modulator of reproductive function. Genetic or environmental insults to the HPG axis during developmental windows can persist into adulthood, and processes such as gonadal hormone synthesis, timing of puberty, and fertility can be affected. At the level of the hypothalamus, multiple regions develop at different times and are under the control of a concert of signaling pathways and transcription factors required for their patterning and maturation. In this review, we highlight factors and pathways involved in specification and ultimate differentiation of neuronal and other cellular subtypes of the hypothalamus contributing to the HPG axis. Specifically, we discuss development of the arcuate and anteroventral periventricular nuclei, as well as forebrain development as it relates to reproductive function. Precise control of kisspeptin and gonadotropin-releasing hormone neuron, as well as tanycyte, development is necessary for understanding and ultimately treating developmental disruptions resulting in infertility.

Sex-Specific Effects of Chronic Administration of Relaxin-3 on Food Intake, Body Weight and the Hypothalamic-Pituitary-Gonadal Axis in Rats.

The present study examined the effects of chronic central administration of relaxin-3 (RLN3) on food intake, body weight and fat mass in intact and sterilised male and female rats, as well as on hypothalamic-pituitary-gonadal (HPG) axis activity in intact male and female rats that received i.c.v. infusions of RLN3 (400 pmol/day) or vehicle during a 14-day period. The intact RLN3-injected rats displayed a higher body weight than the vehicle-treated groups, and this increase was statistically significantly stronger in female rats compared to male rats. In addition, feed efficiency and gonadal white adipose tissue weight were higher in female RLN3-injected rats. Chronic i.c.v. administration of RLN3 activated the HPG axis in intact male rats, whereas inhibition of the HPG axis was observed in intact female rats. RLN3 significantly increased the plasma levels of luteinising hormone and follicular-stimulating hormone in male rats but not in female rats. Conversely, hypothalamic expression of gonadotrophin-releasing hormone mRNA was decreased by RLN3 in female rats but not in male rats. In addition, the plasma levels of oestradiol were significantly decreased by RLN3 administration in female rats. Consequently, intact RLN3-injected female rats failed to display phasic inhibition of eating during oestrus. Sex-specific effects of RLN3 on food intake and body weight were also observed in ovariectomised female and orchidectomised male rats, suggesting that the sex-specific effects of RLN3 on energy metabolism are independent on the differential effects of RLN3 on HPG axis activity in male and female rats.

What's in a Name? Roles of RFamide-Related Peptides Beyond Gonadotrophin Inhibition.

RFamide-related peptides (RFRPs) have been heavily implicated in the control of reproductive function subsequent to their discovery more than 16 years ago. However, recent studies using genetic and pharmacological tools have challenged their importance in regulating the hypothalamic-pituitary-gonadal axis. It is generally accepted that RFRPs act as part of a wider RFamide system, which involves two receptors, called the neuropeptide FF receptors (NPFFR1 and R2), and includes the closely-related neuropeptide NPFF. NPFF has been studied ever since the 1980s and many of the functions of NPFF are also shared by RFRPs. The current review questions whether these functions of NPFF are indeed specific to just NPFF alone and presents evidence from both neuroendocrine and pharmacological perspectives. Furthermore, recently emerging new functions of RFRPs are discussed with the overall goal of clarifying the functions of RFRPs beyond the hypothalamic-pituitary-gonadal axis.

Epithelial and neural cadherin expression in the mammalian reproductive tract and gametes and their participation in fertilization-related events.

Mammalian fertilization involves a series of well-orchestrated cell-cell interaction steps between gametes, as well as among spermatozoa and somatic cells of both the male and female reproductive tracts. Cadherins are Ca(2+)-dependent glycoproteins that have been involved in cellular adhesion and signaling in somatic cells. Taking into account that Ca(2+) ions are required during fertilization, the involvement of these proteins in adhesion events during this process can be anticipated. This report presents an overview on two members of classical cadherins, Epithelial (E-) and Neural (N-) cadherin in reproductive biology. Its provides evidence of studies done by several research groups about the expression of E- and N-cadherin during spermatogenesis, oogenesis and folliculogenesis, and their involvement in gamete transport in the reproductive tracts. Moreover, it describes current knowledge of E- and N-cadherin presence in cells of the cumulus-oocyte complex and spermatozoa from several mammalian species, and shows gathered evidence on their participation in different steps of the fertilization process. A brief summary on general information of both proteins is also presented.

Ureteral complications in the era of laparoscopic living donor nephrectomy: do we need to preserve the gonadal vein with the specimen?

BACKGROUND AND PURPOSE: The aim of this study was to analyze the ureteral complication rate in recipients transplanted with laparoscopically retrieved kidneys in our institution's 8-year experience when the gonal vein was not preserved with the specimen during the donor procedure. PATIENTS AND METHODS: We reviewed the records of 800 consecutive laparoscopic donor nephrectomy patients. Donor sex, age, body mass index, warm ischemia time, hospital length of stay, donor and recipient serum creatinine levels, and incidence and type of complications including the incidence of ureteral complications were recorded. RESULTS: Mean patient age was 39 +/- 10 years. Mean body mass index was 27 +/- 5. A total of 482 cases were treated purely laparoscopically. Of them, 318 were performed hand assisted. Seven hundred and ninety-three procedures were done on the left side and seven were done on the right side. The overall rate of intraoperative complications was 2.9%. The overall open conversion rate was 1.4%. The overall rate of postoperative complications was 3.9%. The postoperative day-7 serum creatinine values of the donors were 1.4 +/- 0.3 mg/dL. Mean creatinine in all patients at 1 week after transplantation was 1.5 +/- 0.2 mg/dL. We had one case of ureteral stricture in the recipients of laparoscopically procured kidneys without gonadal vein preservation technique among 800 patients. CONCLUSION: Gonadal vein preservation with the entire specimen during laparoscopic donor nephrectomy procedure is not a necessary step to protect periureteral blood supply to prevent ureteral strictures.

Immunohistochemical localization of serotonin (5-hydroxytryptamine) in the gonad and digestive gland of Mya arenaria (Mollusca: Bivalvia).

Serotonin (5-hydroxytryptamine or 5-HT) C(10)H(12)N(2)O plays a central role in several physiological processes in marine molluscs, especially in reproduction. 5-HT acts as a neurohormone to modulate spawning, parturition and meiosis by reinitiating prophase in arrested oocytes. Preliminary experiments using 10(-5)M 5-HT dissolved in aquarium water showed that 5-HT induced spawning movements in ripe clams and in both sexes of Mya arenaria while only a few males released sperm. The occurrence of serotoninergic fibers was demonstrated by PAP immunohistochemical reaction in the gonad of both sexes during gametogenesis. In an organism infected by the trematode parasite Prosorhynchus squamatus, we showed that serotoninergic innervation completely disappeared around the gonad's follicles. Although the gonad and digestive gland are intertwined, no serotoninergic innervations were found in the digestive gland. These findings suggest, for the first time to our knowledge in the soft shell clam, that serotonin might be involved in the regulation of gametogenesis.

Sensory innervation of the ovotestis in the snail Helix aspersa.

Because oviposition in the land snail Helix aspersa is a metabolically expensive process coupled to a high fixed cost, one expects oviposition to occur only when the clutch size surpasses a minimum value at which the reproductive benefit exceeds the cost. We propose that neural innervation of the gonad allows H. aspersa to monitor oocyte production and ensure an adequate supply of gametes prior to ovulation. The ovotestis is innervated by a branch of the intestinal nerve in which the majority of axon fibres measure <0.2 microm in diameter. We found a strong positive correlation between the number of mature oocytes in the ovotestis and the frequency of spontaneous afferent spikes in the nerve branch. Tactile stimulation of the ovotestis resulted in a 20-fold increase in afferent spikes and an efferent reflex directed towards the ovotestis and the pericardium. Afferent activity also increased 10-fold after an experimentally induced increase in the volume of the ovotestis. These results suggest that the growing oocytes expand the walls of the acini and trigger action potentials in the mechanosensitive nerve terminals that lie within the acinar walls. We hypothesize that the resulting tonic signal is permissive for ovulation. In addition, a phasic sensory signal may occur during ovulation to trigger CNS motor output related to oviposition.

Target-dependent differentiation and development of molluscan neurons and neuroendocrine cells: use of parasitisation as a tool.

Specimens of the freshwater snail Lymnaea stagnalis infected with the schistosome parasite Trichobilharzia ocellata show a strongly inhibited development of their reproductive tract. We hypothesised that the effects of the underdevelopment of targets are reflected at the level of the neuronal development of (i) the motor neurons innervating the male copulation organ and (ii) neuroendocrine cells regulating the gonad. We determined the state of neuronal development by measuring cell number, cell size and neuropeptide gene expression. Our results show that the neuronal development of both copulation controlling anterior lobe motor neurons of the right cerebral ganglion and neuroendocrine caudodorsal cells, which produce neuropeptides regulating ovulation, egg laying and accompanying behaviour, are affected in parasitised animals in which their respective target organs were not developed. The cell bodies were smaller and fewer cells were found to express neuropeptide genes compared to those in non-parasitised animals. These effects were not observed in the appropriate controls. Backfills and lesions of the penis nerve have shown that the inhibited development of central motor neurons in parasitised snails is target dependent; neighbouring neurons that have no connection with the male copulation organ are not affected. Our data suggest that this effect is established by target-derived neurotrophic factors that need this connection for being transported to the innervating motor neurons. We propose that the effect on the neuroendocrine caudodorsal cells is mediated by a humoral factor, since they have no known connection with their target. We have shown that the size and gene expression of motor neurons controlling copulation behaviour in the pond snail Lymnaea stagnalis are related to the size of their target, the copulation organ, and depend on the connection with this target.

Acetylcholinesterase-positive innervation is present at undifferentiated stages of the sea turtle Lepidochelis olivacea embryo gonads: implications for temperature-dependent sex determination.

In embryos of different reptile species, incubation temperature triggers a cascade of endocrine events that lead to gonad sex differentiation. The cellular and molecular mechanisms by which temperature sets in motion this process are still controversial. Here, we begin evaluating the possible participation of the nervous system in temperature-dependent sex determination by showing the existence and origin of acetylcholinesterase (AchE)-positive nerve fibers in undifferentiated gonads of the Lepidochelys olivacea (L. olivacea) sea turtle putative male and female embryos, along the thermosensitive period for sex determination (TPSD; stages 20-27). AChE-positive nerve bundles and fibers were readily visualized until developmental stage 24 and thereafter. DiI injections and confocal imaging showed that some of these gonadal nerves arise from the lower thoracic and upper lumbar spinal cord levels, and might thus be sensory in nature. Because the vertebrate spinal cord is capable of integrating by itself thermoregulatory responses with no intervention of uppermost levels of the central nervous system, we also evaluated spinal cord maturation during the TPSD. The maturation of the spinal cord was more advanced in putative female than in male embryos, when sex determination is taking place for each sex; this process starts and ends earlier in male than in female embryos. Together these observations open the possibility that the spinal cord and the innervation derived from it could play a direct role in driving or modulating the process of temperature-dependent gonad sex determination and/or differentiation, particularly in female L. olivacea embryos.

Estrogen receptor function as revealed by knockout studies: neuroendocrine and behavioral aspects.

Estrogens are an important class of steroid hormones, involved in the development of brain, skeletal, and soft tissues. These hormones influence adult behaviors, endocrine state, and a host of other physiological functions. Given the recent cloning of a second estrogen receptor (ER) cDNA (the ER beta), work on alternate spliced forms of ER alpha, and the potential for membrane estrogen receptors, an animal with a null background for ER alpha function is invaluable for distinguishing biological responses of estrogens working via the ER alpha protein and those working via another ER protein. Data generated to date, and reviewed here, indicate that there are profound ramifications of the ER alpha disruption on behavior and neuroendocrine function. First, data on plasma levels of estradiol (E2), testosterone (T), and luteinizing hormone (LH) in wild-type (WT) versus ER alpha- mice confirm that ER alpha is essential in females for normal regulation of the hypothalamic-pituitary gonadal axis. Second, ovariectomized female ER alpha- mice do not display sexual receptivity when treated with a hormonal regime of estrogen and progesterone that induces receptivity in WT littermates. Finally, male sexual behaviors are disrupted in ER alpha- animals. Given decades of data on these topics our findings may seem self-evident. However, these data represent the most direct test currently possible of the specific role of the ER alpha protein on behavior and neuroendocrinology. The ER alpha- mouse can be used to ascertain the specific functions of ER alpha, to suggest functions for the other estrogen receptors, and to study indirect effects of ER alpha on behavior via actions on other receptors, neurotransmitters, and neuropeptides.

Progesterone receptor function from a behavioral perspective.

Hormonal induction of sexual receptivity in ovariectomized female mice can be effectively reinstated by sequential administration of estradiol and progesterone. In this regard, mice appear to be similar to other rodents. While it is generally accepted that hypothalamic progesterone receptors function as estradiol-induced transcription factors in the induction of sexual receptivity in rats, hamsters, and guinea pigs, relatively little is known about their role in the mouse, a species which exhibits genotypic and strain differences in the responsiveness to steroid hormones. Using a transgenic mouse carrying a null mutation for the progesterone receptor by gene targeting, we examined the role of the progesterone receptor as a coordinator of key regulatory events in the induction of sexual receptivity. A concordance between hypothalamic progesterone receptor levels and behavioral responsiveness was established by comparing the homozygous mutant, heterozygous mutant, and wild-type littermates. The behavioral and biochemical findings reveal the importance of estradiol-induced progesterone receptors for the expression of sexual behavior in female mice. The behavioral response of the two parental mouse strains from which the recombinant genotype was generated was also examined. As an extension of our earlier studies on the ligand-independent activation of progesterone receptors by neurotransmitters, the behavioral effect of dopamine in the facilitation of sexual receptivity in mice was also examined. The studies provide further evidence that steroid hormone receptors function as general transcription factors to achieve the integration of neural information in the central nervous system, and they assign a more important role for progesterone receptors than hitherto envisioned.

Detection and transduction of daylength in birds.

Daylength is an important environmental cue used by temperate zone avian species to time the onset of seasonal reproductive activity. Photic cues are detected by extra-retinal, extra-pineal central nervous system elements, and are rapidly transduced to an efferent signal. In this paper, we describe the brain locus of putative encephalic photoreceptors in birds, and explore the pathway of information transfer from photic input to the reproductive axis. To this end, we examine how photoreceptors might communicate with the hypothalamic-pituitary axis, and how brain peptides vary seasonally. Recent studies indicate that brain photoreceptors lie in the lateral septum and in the tuberal hypothalamus, and co-express proteins characteristic of retinal photoreceptors, as well as vasoactive-intestinal polypeptide (VIP). At the light microscopic level, photoreceptor cells appear to communicate with gonadotropin-releasing hormone (GnRH) neurons, and vice versa. Expression of VIP-like immunoreactivity is highest in photorefractory animals while GnRH-like immunoreactivity is highest in photosensitive birds. Expression of these CNS peptides is correlated with changes in plasma prolactin and luteinizing hormone (LH), suggesting a mechanism mediating seasonal cyclicity.

Epitope mapping with ELISA of an antibody against oxytocin used for the characterization of an oxytocin-like epitope in the sex segmental ganglia of the leech Erpobdella octoculata.

1. Using direct, inhibiting and competitive enzyme-linked immunosorbent assay (ELISA), two steps were involved in the mapping of the recognition site of a polyclonal antibody against oxytocin (OT). 2. The percentage of cross-reactivity between OT and the N-terminal or the C-terminal fragment of OT demonstrated that the C-terminal fragment is the antigenic part of OT. 3. The percentage of cross-reactivity between OT and other molecules of the OT family indicated that the amino acid in the 8-position and the C-terminal amide of the OT molecule contribute to the recognition. 4. In the two sex segmental ganglia of the leech Erpobdella octoculata, where cells immunoreactive to the anti-OT are detected, the antibody has allowed to characterize an epitope close to the mammalian OT by its C-terminal part.

Monoaminergic and cholinergic mechanisms of reproduction control in marine bivalve molluscs and echinoderms: a review.

The autoreproduction ability is one of the most important properties of living systems. Evolution of metazoans ensured their reproduction by means of such determinants as sexual cells developing in specialized organs, in gonads. In most marine invertebrates, the gonad produces tens of millions of gametes per reproductive cycle. This reproduction level guarantees the species resistance in the external environment and is provided by the whole organism, though in unfavourable ecological conditions the gonad may become a source of trophic and energy material and it can maintain the viability of organism by means or the mass, often total, lysis of sexual cells. This metabolic interaction of a part (gonad) and the whole (organism) presumes the existence of the strictly determined relations between them, on the one hand, and more or less pronounced autonomy, on the other hand. The isolated organs, including gonads, are capable of fulfilling specific functions for a short period of time by means of local regulation. However, there is no full autonomy between the gonad and the organism: the hierarchical relations set in between them.

Organogenesis in C. elegans: positioning of neurons and muscles in the egg-laying system.

One of the final stages in the development of egg-laying behavior in the nematode C. elegans is the organization of 8 motor neurons (2 HSN and 6 VC cells) and 8 muscles into a motor system to control the opening of the vulva. Using mutations that disrupt the development of specific components of the egg-laying system and laser microsurgery to ablate selected precursor cells, we have determined that the guidance of the egg-laying neurons and muscles, and in particular the VC neurons and vulval muscles, into the vulval region is dependent on interactions with surrounding epithelial and gonadal tissue and appears to be independent of neuron-neuron and neuron-muscle interactions. The development of the egg-laying system can be described as a series of cell interactions in which certain cells arise through induction and subsequently provide inductive cues themselves.

[Peptidergic and monoaminergic innervation of the gonads in the holothurian Cucumaria japonica]. / Peptidergicheskaia i monoaminergicheskaia innervatsiia goloturii Cucumaria japonica.

In the holothurian gonad structure of the peptidergic and monoaminergic systems has been described. Axons of their cells form tissue and hemal terminals. Epithelial cells and smooth myocytes of the gonadal wall get direct innervation, having contacts with the axonal terminals that are separated by the cleft 50-75 nm in the diameter. It is possible that neuropeptides and biogenic monoamines are transported to the germ and follicular cells of the germinative gonadal zone via hemolymph of the hemal sinus.

Development of the innervation of the urogenital complex in the fetal mouse.

The developing urogenital complex of the fetal mouse was studied by means of silver impregnation and electron microscopy. These studies showed that: 1) the mesonephric field is innervated during prenatal stages (Wolffian nerve); 2) nerve penetration precedes the differentiation of the gonads and related ducts; and 3) the Wolffian nerve arises during the earliest stages from the first pair of abdominal rami communicantes. The identity between the fetal Wolffian nerve and the nerve of the suspensory ligament (higher pathway) of the adult is discussed.

[Gonad innervation in bivalve mollusks]. / Innervatsiia polovoi zhelezy dvustvorchatykh molliuskov.

In marine Lamellibranchia--Patinopecten yessoensis (Jay) and Crenomytilus grayanus (Dunker)--neural cells, small ganglia and neural fibres have been revealed in the gonad wall. The sensitive and effector parts are presented by rather variable morphological formations. By means of histochemical and ultrastructural investigations, functional affiliation of axons is revealed and their relations to tissue elements of the gonad are demonstrated. The effector neural apparatus is formed by peptidergic, cholinergic and monoaminergic axons. Most of the axons, forming a thick network, are monoaminergic. There are some essential differences in the structure of the monoaminergic plexuses in juvenile and mature individuals. No specialized membrane differentiations, specific for sinapses, have been found.