Reproductive Hormone Secretion Research Articles

Serum Levels of Tryptophan, 5-Hydroxytryptophan and Serotonin in Patients Affected with Different Forms of Amenorrhea

Tryptophan (Trp) is present in the serum, partly bound to albumine and in the free form. The unbound portion of circulating tryptophan has the property of crossing the hematoencephalic barrier and being converted within the brain into serotonin (5-HT) through the enzymatic processes of hydroxylation and decarboxylation. The serotoninergic system plays an important role in neuroendocrine control of reproductive hormone secretion, and in particular, it may influence GnRH pulsatility, a function essential for reproductive processes. In this study, we analysed serum levels of tryptophan, serotonin and 5-hydroxytryptophan (5-HTP) in women with three different forms of amenorrhea: 16 patients were diagnosed with anorexia nervosa, 60 patients with functional hypothalamic amenorrhea, and 14 patients with hyperprolactinemia. Data were compared with those of a group of 25 healthy women. Serum Trp levels were significantly (P ≤ 0.05) lower in the anorexic (11.64 ± 0.53 μg/ml, mean ± S.E.) than in the control (12.98 ± 0.37 μg/ml) groups. In addition, in the anorexic group a statistical dispersion of Trp values was shown indicating a bimodal data distribution suggesting the existence of two different subgroups of patients. Regarding 5-HTP, an increase of its serum level was observed in all the groups with amenorrhea with the highest value in hyperprolactinemic patients. On the contrary, no statistical differences in serum 5-HT levels among the four analyzed groups were observed.This study shows that women affected by various forms of amenorrhea present an altered metabolism of tryptophan via serotonin and, in particular, markedly high differences are observed between the two subgroups of anorexic patients.

Effect of feeding allowance level on embryonic survival, IGF‐1, insulin, GH, leptin and progesterone secretion in early pregnancy gilts

The present experiment was conducted to evaluate the effects of feeding allowance level on embryonic survival, uterine development and reproductive hormone secretion in early gestation gilts. A total of 54 F1 crosses of Landrace x Large white gilts were randomly allocated to three treatment groups of high (H, 2 x maintenance), medium (M, 1.2 x maintenance) and low (L, 0.6 x maintenance) feeding level after mating. Blood samples and uterine flushings were collected on day 12, 25 and 35 of pregnancy, and embryonic survival rate was estimated. Concentrations of insulin-like growth factor I (IGF)-1, insulin, growth harmone (GH), leptin and progesterone in serum and uterine flushings were determined by enzyme-linked immunosorbent assay. Embryonic survival was affected by dietary treatment; total number of viable embryos and embryo survival of group M were higher than other groups in the early pregnancy (p < 0.05). Greater foetal weight in M gilts was achieved when gestation advanced to day 35 (p < 0.05), though there was no difference on day 25 of pregnancy among treatments. No appreciable differences were observed in the crown-rump length on day 25 and 35 of pregnancy among groups. Greater weight of uterus and products of conception were identified in M gilts compared with group H and L (p = 0.024 and p = 0.005, respectively) on day 25 of pregnancy. The hormone level was greatly affected by feeding allowance level. In serum, concentrations of IGF-1, leptin and insulin tended to be greater in H than in M and L during the early gestation, while concentrations of GH were greater in M and progesterone were the lowest in H. At the same time, feed allowance level affected the concentration of IGF-1, insulin, GH, leptin and progesterone in uterine flushings. These data demonstrated that feed allowance level after mating has important consequence on embryo survival, embryo development and uterine development, possibly mediated by nutrition level inducing changes in concentrations of reproductive hormones and/or intermediary metabolites in early pregnancy.

Inhibition of gonadotropin secretion by gonadotropin‐inhibitory hormone: it's all in your head

The seminal work of Geoffery Harris cemented neural substances of hypothalamic origin as key in the control of gonadal function (Harris, 1950). Subsequently, Amoss et al. (1971) and Schally et al. (1971) independently isolated the neuropeptide that directly simulates pituitary gonadotropin secretion and thus, it was termed gonadotropin releasing-hormone (GnRH). Since that time, the search has been underway to identify the location (Wintermantel et al. 2006) and phenotype of neurotransmitters and neuropeptides which allow the GnRH-containing neurons to respond to the multiple internal and external cues (Herbison, 2006) regulating GnRH secretion and by extension controlling sexual reproduction. Tsutsui et al. (2000) provided a new perspective on the control of gonadotropin secretion when they reported a hypothalamic peptide whose inhibitory action on gonadotropin release from quail anterior pituitaries as indicated in figure 1, was consistent with it being a gonadotropin inhibitory hormone. The neuropeptide was termed GnIH for its direct but converse effect (from GnRH) on pituitary gonadotropin secretion (fig. 1). Figure 1 GnIH directly inhibits the activity of GnRH neurons rendering it a putative GnRH-IH in rodents Until most recently, GnIH remained a pituitary GnIH as evidence for hypothalamic site of action was lacking. Now, the groups of Allan Herbison (Ducret et al. 2009) and in this issue of The Journal of Physiology Meenakshi Alreja (Wu et al. 2009) have independently shown that GnIH has direct inhibitory actions on GnRH neurons. The GnIH reduces rates of firing and induces hyperpolarization in substantial portions of the total population of GnRH neurons. Moreover, since GnIH neurons in rats are not neurosecretory (Rizwan et al. 2009), it appears at least in rodents that the GnIH in other vertebrates, may have largely a hypothalamic site of action on gonadotropin secretion (fig. 1). Therefore, the long repudiated GnRH-IH neuropeptide seems to be GnIH. The question remains as to which of the multiple internal and external cues that inhibit activity of GnRH neurons are mediated by activation of GnIH-containing neurons. For example, pulsatile GnRH release is regulated by a negative feedback system. Since the GnRH neurons themselves do not contain classical steroid receptors, gonadal steroids must act through alternative mechanisms such as direct membrane effects or steroid-sensitive presynaptic inputs to GnRH neurons (see Kelly & Ronnekleiv 2008 for review). If GnIH neurons are steroid sensitive, then they could play a pivotal role in inhibition of GnRH secretion via gonadal steroids. Likewise, stress inhibits reproduction. Preliminary evidence suggests that GnIH expression increases in rats during exposure to acute stressors (Kirby et al. 2007). Perhaps the most intriguing aspect of the GnIH peptide is its impact on reproductive behaviour. In male rats, GnIH-related peptides reduce the full sequela of male sexual behaviours (Johnson et al. 2007). Accordingly, input to GnRH neurons from GnIH-containing neurons may provide the link between reproductive hormone secretion and reproductive behaviour (Coquelin & Bronson, 1980). The above speculation notwithstanding, the neurons containing GnIH are poised to exert control of gonadotropin secretion from within the hypothalamus. Thus, the GnIH peptide is likely to emerge as a key regulator of GnRH secretion through its direct actions on GnRH neurons.

Fasting-induced suppression of LH secretion does not require activation of ATP-sensitive potassium channels

Reproductive hormone secretions are inhibited by fasting and restored by feeding. Metabolic signals mediating these effects include fluctuations in serum glucose, insulin, and leptin. Because ATP-sensitive potassium (K(ATP)) channels mediate glucose sensing and many actions of insulin and leptin in neurons, we assessed their role in suppressing LH secretion during food restriction. Vehicle or a K(ATP) channel blocker, tolbutamide, was infused into the lateral cerebroventricle in ovariectomized mice that were either fed or fasted for 48 h. Tolbutamide infusion resulted in a twofold increase in LH concentrations in both fed and fasted mice compared with both fed and fasted vehicle-treated mice. However, tolbutamide did not reverse the suppression of LH in the majority of fasted animals. In sulfonylurea (SUR)1-null mutant (SUR1(-/-)) mice, which are deficient in K(ATP) channels, and their wild-type (WT) littermates, a 48-h fast was found to reduce serum LH concentrations in both WT and SUR(-/-) mice. The present study demonstrates that 1) blockade of K(ATP) channels elevates LH secretion regardless of energy balance and 2) acute fasting suppresses LH secretion in both SUR1(-/-) and WT mice. These findings support the hypothesis that K(ATP) channels are linked to the regulation of gonadotropin-releasing hormone (GnRH) release but are not obligatory for mediating the effects of fasting on GnRH/LH secretion. Thus it is unlikely that the modulation of K(ATP) channels either as part of the classical glucose-sensing mechanism or as a component of insulin or leptin signaling plays a major role in the suppression of GnRH and LH secretion during food restriction.

Ancestral TSH Mechanism Signals Summer in a Photoperiodic Mammal

In mammals, day-length-sensitive (photoperiodic) seasonal breeding cycles depend on the pineal hormone melatonin, which modulates secretion of reproductive hormones by the anterior pituitary gland [1]. It is thought that melatonin acts in the hypothalamus to control reproduction through the release of neurosecretory signals into the pituitary portal blood supply, where they act on pituitary endocrine cells [2]. Contrastingly, we show here that during the reproductive response of Soay sheep exposed to summer day lengths, the reverse applies: Melatonin acts directly on anterior-pituitary cells, and these then relay the photoperiodic message back into the hypothalamus to control neuroendocrine output. The switch to long days causes melatonin-responsive cells in the pars tuberalis (PT) of the anterior pituitary to increase production of thyrotrophin (TSH). This acts locally on TSH-receptor-expressing cells in the adjacent mediobasal hypothalamus, leading to increased expression of type II thyroid hormone deiodinase (DIO2). DIO2 initiates the summer response by increasing hypothalamic tri-iodothyronine (T3) levels. These data and recent findings in quail [3] indicate that the TSH-expressing cells of the PT play an ancestral role in seasonal reproductive control in vertebrates. In mammals this provides the missing link between the pineal melatonin signal and thyroid-dependent seasonal biology.

Luteal phase estrogen is decreased in regularly menstruating older women compared with a reference population of younger women

To compare daily reproductive hormone secretion in regularly menstruating older versus younger women. This was a prospective cohort study. Daily morning urine samples were obtained from 106 women, 28 of whom were aged between 20 and 34 years (mean: 27.8+/-3.7 y) and 78 of whom were aged between 35 and 50 years (mean: 40.3+/-3.7 y). Lower luteal estrone-3-glucuronide levels were seen in the older versus the younger group (82.7 vs 93.5 ng/ml, P=0.035). The pregnanediol-3-glucuronide levels in the older group were lower than those in the younger group throughout the entire cycle. The median length of the follicular phase was shorter in the older versus younger women (13 vs 14.5 d, P=0.005). There was no significant difference in the median luteal phase lengths between groups. We report the new finding that regularly menstruating older women not only have lower pregnanediol-3-glucuronide levels but also have a significant reduction in luteal phase estrone-3-glucuronide compared with a contemporaneous cohort of younger women. This combined deficit may play a key role during the luteal-follicular transition, potentially affecting follicle recruitment and decreasing fecundity in the subsequent cycle.

Emerging methodologies for the study of hypothalamic gonadotropin-releasing-hormone (GnRH) neurons

Gonadotropin-releasing-hormone (GnRH) neurons form part of a central neural oscillator that controls sexual reproduction through intermittent release of the GnRH peptide. Activity of GnRH neurons, and by extension release of GnRH, has been proposed to reflect intrinsic properties and synaptic input of GnRH neurons. To study GnRH neurons, we used traditional electrophysiology and computational methods. These emerging methodologies enhance the elucidation of processing in GnRH neurons. We used dynamic current-clamping to understand how living GnRH somata process input from glutamate and GABA, two key neurotransmitters in the neuroendocrine hypothalamus. In order to study the impact of synaptic integration in dendrites and neuronal morphology, we have developed full-morphology models of GnRH neurons. Using dynamic clamping, we have demonstrated that small-amplitude glutamatergic currents can drive repetitive firing in GnRH neurons. Furthermore, application of simulated GABAergic synapses with a depolarized reversal potential have revealed two functional subpopulations of GnRH neurons: one population in which GABA chronically depolarizes membrane potential (without inducing action potentials) and a second population in which GABAergic excitation results in slow spiking. Finally, when AMPA-type and GABA-type simulated inputs are applied together, action potentials occur when the AMPA-type conductance occurs during the descending phase of GABAergic excitation and at the nadir of GABAergic inhibition. Compartmental computer models have shown that excitatory synapses at >300 microns from somtata are unable to drive spiking with purely passive dendrites. In models with active dendrites, distal synapses are more efficient at driving spiking than somatic inputs. We then used our models to extend the results from dynamic current clamping at GnRH somata to distribute synaptic inputs along the dendrite. We show that propagation delays for dendritic synapses alter synaptic integration in GnRH neurons by widening the temporal window of interaction for the generation of action potentials. Finally, we have shown that changes in dendrite morphology can modulate the output of GnRH neurons by altering the efficacy of action potential generation in response to after-depolarization potentials (ADPs). Taken together, the methodologies of dynamic current clamping and multi-compartmental modeling can make major contributions to the study of synaptic integration and structure-function relationships in hypothalamic GnRH neurons. Use of these methodological approaches will continue to provide keen insights leading to conceptual advances in our understanding of reproductive hormone secretion in normal and pathological physiology and open the door to understanding whether the mechanisms of pulsatile GnRH release are conserved across species.

The Cannabinoid System and Male Reproductive Functions

Cannabinoids, the main active components of marijuana, have been shown to exert different adverse effects on male reproduction both in vertebrates and invertebrates. In vivo, cannabinoids exert negative effects on hypothalamic-hypophyseal reproductive hormone secretion and testicular endocrine and exocrine functions. Furthermore, a large amount of experimental data obtained in vitro have clearly shown that cannabinoids negatively influence important sperm functions, including motility and acrosome reaction, two fundamental processes necessary for oocyte fertilisation. These inhibitory effects are mediated by the direct action of cannabinoids on sperm through the activation of the cannabinoid receptor subtype CNR1 that has been shown to be expressed in mature sperm. In the present paper, we briefly review the effects of cannabinoids and endocannabinoids, a particular group of endogenously produced cannabinoids, on male reproductive function.

Effects of chronic food restriction and treatments with leptin or ghrelin on different reproductive parameters of male rats

The existence of a close relationship between energy status and reproductive function is well-documented, especially in females, but its underlying mechanisms remain to be fully unfolded. This study aimed to examine the effects of restriction of daily calorie intake, as well as chronic treatments with the metabolic hormones leptin and ghrelin, on the secretion of different reproductive hormones, namely pituitary gonadotropins and prolactin, as well as testosterone, in male rats. Restriction (50%) in daily food intake for 20 days significantly reduced body weight as well as plasma PRL and T levels, without affecting basal LH and FSH concentrations and testicular weight. Chronic administration of leptin to rats fed ad libitum increased plasma PRL levels and decreased circulating T, while it did not alter other hormonal parameters under analysis. In contrast, in rats subjected to 50% calorie restriction, leptin administration increased plasma T levels and reduced testis weight. Conversely, ghrelin failed to induce major hormonal changes but tended to increase testicular weight in fed animals, while repeated ghrelin injections in food-restricted males dramatically decreased plasma LH and T concentrations and reduced testis weight. In sum, we document herein the isolated and combined effects of metabolic stress (50% food restriction) and leptin or ghrelin treatments on several reproductive hormones in adult male rats. Overall, our results further stress the impact and complex way of action of different metabolic cues, such as energy status and key hormones, in reproductive function also in the male.

Some endocrine traits of transgenic rabbits. I. Changes in plasma and milk hormones

The aim of these studies was to compare some endocrine and non-endocrine characteristics of transgenic (carrying mammary gland-specific mWAP-hFVIII gene construct) and non-transgenic rabbits. The concentrations of corticosterone, progesterone, testosterone, estradiol, insulin-like growth factor I (IGF-I) and human factor VIII (hFVIII) in the blood plasma of adult females (9 months of age, third generation transgenic animals), adult males, and young females (1-2 months of age, fourth generation of transgenic animals), as well as in the milk of lactating adult females, were analyzed by using RIA. In addition, litter size and body mass of pups born by transgenic and non-transgenic females from the third generation were compared. Transgenic animals were compared with their non-transgenic siblings (the same genetic and epigenetic background). Transgenesis did not influence plasma hFVIII, but significantly increased corticosterone (in all animals), reduced IGF-I (in adult males and females), testosterone and estradiol, (in young females) and altered progesterone (increase in adult males and decrease in adult females) concentrations in blood plasma. In addition, transgenic females had higher milk concentrations of testosterone, but not progesterone or IGF-I than their non-transgenic sisters. These endocrine changes were not associated with changes in litter size. Transgenic male (but not female) pups have smaller body mass than control animals. These observations demonstrate the influence of transgenesis per se on the animal growth and endocrine system (secretion of reproductive and stress steroid hormones as well as growth factors) over four generations.

Hypocretin/Orexin: A Molecular Link Between Sleep, Energy Regulation, and Pleasure

Hypocretin (Hcrt) is a neurotransmitter of the dorsal and lateral hypothalamus that regulates sleep, appetite, and energy consumption. Recent evidence indicates that it is also involved in pleasure/reward-seeking. Mutation of the Hcrt-receptor gene causes narcolepsy in canines, and Hcrt knockout mice exhibit narcolepsy-like symptoms. Human narcoleptics do not commonly have mutations in the ligand or receptor but do have degeneration of Hcrt-containing neurons, possibly through an autoimmune mechanism. When Hcrt neurons degenerate in mice, hypophagia and obesity are observed, symptoms that are also present in some human narcoleptics. This article reviews the recent literature with regard to the many functions of this single molecule. The authors suggest that eating habits and impulsivity may be topics worth exploring in the evaluation of narcoleptic patients.

Intrahypothalamic neuroendocrine actions of corticotropin-releasing factor.

Most studies of the neuroendocrine effects of corticotropin-releasing factor (CRF) have focused on its role in the regulation of the pituitary-adrenal axis; activation of this axis follows release of the peptide from CRF-containing terminals in the median eminence. However, a sizeable proportion of CRF fibres terminate within the hypothalamus itself, where synaptic contacts with other hypothalamic neuropeptidergic neurons (e.g. gonadotropin-releasing hormone-containing and opioidergic neurons) have been identified. Here, we summarize physiological and pharmacological data which provide insights into the nature and significance of these intrahypothalamic connections. It is now clear that CRF is a potent secretagogue of the three major endogenous opioid peptides (beta-endorphin, Met-enkephalin and dynorphin) and that it stimulates opioidergic neurons tonically. In the case of beta-endorphin, another hypothalamic peptide, arginine vasopressin, appears to be an essential mediator of CRF's effect, suggesting the occurrence of CRF synapses on, or in the vicinity of, vasopressin neurons; morphological support for this assumption is still wanting. Evidence for direct and indirect inhibitory effects of CRF on sexual behaviour and secretion of reproductive hormones is also presented; the indirect pathways include opioidergic neurons. An important conclusion from all these studies is that, in addition to its better known functions in producing adaptive responses during stressful situations, CRF might also contribute to the coordinated functioning of various components of the neuroendocrine system under basal conditions. Although feedback regulation of hypothalamic neuronal activity by peripheral steroids is a well-established tenet of endocrinology, data on modulation of the intrahypothalamic actions of CRF by adrenal and sex steroids are just emerging. Some of these newer findings may be useful in framing questions related to the mechanisms underlying disease states (such as depressive illness) in which CRF has been strongly implicated.

Auditory stimulation of reproductive function in male Rufous-winged Sparrows, Aimophila carpalis

Prolonged exposure to conspecific song stimulates gonadal function and reproductive hormone secretion in female birds but few studies have investigated the physiological effects of conspecific song exposure on males outside of short-term, aggressive interactions. We exposed male Rufous-winged Sparrows, Aimophila carpalis, either to conspecific song (CS Song), to heterospecific song (Black-throated Sparrow, Amphispiza bilineata; HS Song), or to no recorded song (No Song) for 59 consecutive days (two h per day). Birds were exposed to short days (8L:16D) for the first 21 days of treatment and were then transferred to long days (13L:11D) for the remaining 38 days. During long day exposure, CS Song birds experienced faster growth of testes than HS Song and No Song birds. HS Song birds also grew their testes faster than No Song birds. Plasma luteinizing hormone (LH) and testosterone did not differ between CS Song and No Song birds. However, plasma LH was higher in HS Song birds compared to other groups. There were no differences in hypothalamic immunocytochemical labeling for gonadotropin-releasing hormone, its precursor proGnRH, or gonadotropin-inhibitory hormone, nor were there differences in two song control nuclei volumes (HVC and RA) between CS Song and No Song treatment groups. Furthermore, we found no effect of heterospecific song on free-living Rufous-winged Sparrow aggressive behaviors. These data indicate that long-term exposure to auditory stimuli, such as song, can influence the reproductive system of male songbirds and different types of auditory stimuli can have differential effects on reproductive function.

PRODUCTION AND FUNCTION OF SECRETONEURIN IN THE GOLDFISH (Carassius auratus) PITUITARY GLAND

Secretoneurin (SN) is a 33–34 amino acid neuropeptide derived from secretogranin-II (SgII), a member of the chromogranin family. GnRH increases anterior pituitary SgII messenger RNA levels concomitant with luteinizing hormone (LH) release in goldfish (gf). Synthetic gfSN stimulates LH release in vivo. Our previous study demonstrated for the first time that gfSN had a direct effect to increase LH release and production in vitro, using static incubation of goldfish pituitary tissues. Recent experiments of primary dispersed gf pituitary cell culture also showed that 1 nM and 10 nM of gfSN respectively induced 2.5-fold (p<0.001) and 1.9-fold (p<0.01) increments of LH secretion after 12 hours. Using a western blot analysis with an anti-gfSN antiserum, two SgIIderived proteins (~57 kDa and ~30 kDa) were detected in the gf pituitary, as well as one ~20-kDa protein in the gf brain. In order to detect SgII processing to generate free gfSN (3.66 kDa), we utilized a reversed-phase high-performance liquid chromatography to separate and isolate low molecular weight proteins contained in gf brain and pituitary. Mass spectrum and dot blot analyses were established for characterizing SNrelated peptides. We have potentially identified free gfSN in the brain and pituitary. Salmon GnRH (sGnRH) decreased the levels of the major SgIIderived protein (~57 kDa), by 76% (p<0.05) after 12-hour static treatment of dispersed gf pituitary cells, suggesting GnRH stimulates the generation free gfSN peptide from SgII. Immunohistochemistry revealed that SNreactive peptides are produced only in prolactin cells of the anterior pituitary. SN is found in the pituitary and hypothalamus, and is a potential new hormone or paracrine factor regulating reproductive hormone secretion. Supported by NSERC-Canada and the University of Ottawa. (platform)

Hypothalamic Gonadotrophin‐Releasing Hormone Expression in Female Monkeys with Different Sensitivity to Stress

Psychosocial stress, combined with mild dieting and moderate exercise, are observed in women seeking treatment for hypothalamic amenorrhea. Using female cynomolgus macaques, we previously reported that the same combination of mild stresses suppressed reproductive hormone secretion and menstrual cycles in some individuals (stress-sensitive, SS), but not in others (highly stress-resilient, HSR). Compared to HSR monkeys, SS monkeys exhibited lower oestradiol and progesterone levels at the midcycle peak and decreased gene expression in the central serotonergic system during nonstressed cycles. Because steroids and serotonin impinge upon the hypothalamic-pituitary-gonadal (HPG) axis, we hypothesised that the differences between SS and HSR monkeys in the sensitivity of the HPG axis to stress may ultimately manifest in differences in the gonadotrophin-releasing hormone (GnRH) system. GnRH in situ hybridisation and immunohistochemistry were performed with hypothalamic sections from SS and HSR animals, euthanised in the early follicular phase of a nonstressed menstrual cycle. Compared to HSR monkeys, SS monkeys exhibited a significantly higher number and density of GnRH cell bodies, as well as a higher number of soma with extremely robust expression of GnRH mRNA, but SS monkeys exhibited a lower density of immunostained GnRH fibres in the median eminence. We suggest that neuronal mechanisms involved in the control of GnRH synthesis, transport and release differ in SS compared to HSR animals.

Stimulatory Effect of Morning Bright Light on Reproductive Hormones and Ovulation: Results of a Controlled Crossover Trial

Objectives:Studies have shown a shortening of the menstrual cycle following light exposure in women with abnormally long menstrual cycles or with winter depression, suggesting that artificial light can influence reproductive hormones and ovulation. The study was designed to investigate this possibility.Design:Placebo-controlled, crossover, counterbalanced order.Setting:Medical centres and participants' homes in Novosibirsk (55°N), Russia.Participants:Twenty-two women, aged 19–37 years, with baseline menstrual cycle length 28.1–37.8 d and no clinically evident endocrine abnormalities completed the study. The study lasted for two menstrual cycles separated by at least one off-protocol cycle.Interventions:During one experimental cycle, bright light was administered at home for 1 wk with a light box emitting white light at 4,300 lux at 41 cm for 45 min shortly after awakening. During the other experimental cycle, dim light was <100 lux at 41 cm with a one-tube fluorescent source.Outcome Measures:Blood samples and ultrasound scans were obtained in the afternoon before and after the week of light exposure, on day ∼7 and 14 after menstruation onset. Further ultrasound scans after day 14 documented ovulation. Serum was assayed for thyroid-stimulating hormone (TSH), prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2).Results:Concentrations of PRL, LH, and FSH were significantly increased with bright versus dim light exposure, as was follicle size (ANOVA, intervention × day, p = 0.0043, 0.014, 0.049, and 0.042, respectively). The number of ovulatory cycles increased after exposure to bright compared to dim light (12 versus 6 cycles, Wilcoxon tied p = 0.034).Conclusions:Morning exposure to bright light in the follicular phase of the menstrual cycle stimulates the secretion of hypophyseal reproductive hormones, promotes ovary follicle growth, and increases ovulation rates in women with slightly lengthened menstrual cycles. This might be a promising method to overcome infertility.

Manganese acts centrally to activate reproductive hormone secretion and pubertal development in male rats

Manganese (Mn) is an important element for normal growth and reproduction. Because Mn accumulates in the hypothalamus and is capable of stimulating puberty-related hormones in female rats, we assessed whether this metal could cause similar effects in male rats. We have demonstrated that MnCl 2, when administered acutely into the third ventricle of the brain, acts dose dependently to stimulate luteinizing hormone (LH) release. Furthermore, there was a dose dependent stimulation in the secretion of LH-releasing hormone (LHRH) from the medial basal hypothalamus in vitro, and administration of an LHRH receptor antagonist in vivo blocks Mn-induced LH release. To assess potential chronic effects of the metal, male pups were supplemented with 10 or 25 mg MnCl 2 per kg by gastric gavage from day 15 until days 48 or 55, at which times developmental signs of spermatogenesis were assessed. Results demonstrate that while significant effects were not observed with the 10 mg/kg dose, the animals receiving the 25 mg/kg dose showed increased LH ( p < 0.05), FSH ( p < 0.01) and testosterone ( p < 0.01) levels at 55 days of age. Furthermore, there was a concomitant increase in both daily sperm production ( p < 0.05) and efficiency of spermatogenesis ( p < 0.05), demonstrating a Mn-induced acceleration in spermatogenesis. Our results suggest Mn is a stimulator of prepubertal LHRH/LH secretion and may facilitate the normal onset of male puberty. These data also suggest that the metal may contribute to male precocious pubertal development should an individual be exposed to low but elevated levels of Mn too early in life.

Impact of social environment on female chimpanzee reproductive cycles

The socio-sexual environment of a female is known to affect ovarian function. Increased male contact can enhance menstrual cycle regularity. Conversely, social deprivation constitutes a form of stress that often alters cyclicity and the secretion of reproductive hormones. The present study was carried out on captive female chimpanzees to examine possible interactions among housing conditions, menstrual cycle length, morphological changes in secondary sexual character expression and endocrine release patterns related to follicular and luteal function. Animals were housed over a period of 2 years either with a male conspecific or singly. Blood samples were collected over three cycles, and anogenital swelling changes registered to define menstrual cycle phases. Fecal sampling techniques were used to monitor cortisol as a measure of stress-load. Male presence seemed to affect female cyclicity. Females housed with a male had shorter and more regular cycles than singly housed females. Prolactin, gonadotropins and estradiol levels were generally higher in paired females during specific cycle phases. Group variation was not always significant. No differences were found in progesterone. Sexually cohabited females tended to have lower fecal cortisol metabolites immediately before and after maximum tumescence. We suggest that the close behavioral, physical and olfactory contact with a male conspecific can act as a sort of zeitgeber to modulate ovarian function by stabilizing the female cycle and, perhaps, enhancing folliculogenesis and ovulation.

345 EFFECT OF FOLLICLE STIMULATING HORMONE AND HUMAN CHORIONIC GONADOTROPHIN ON THE IN VITRO MATURATION OF CANINE OOCYTES

Growth, maturation, and ovulation of the Graafian follicle depend on appropriate patterns of secretion, sufficient concentrations, and adequate ratios of various reproductive hormones, especially follicle stimulating hormone (FSH) and luteinizing hormone (LH) (Van Tol et al. 1996 Mol. Reprod. Dev. 45, 218–224). The present study investigated the effects of FSH and human chorionic gonadotrophin (hCG) on the nuclear maturation of canine oocytes. In addition, in order to investigate the effect of stage of the estrous cycle on the meiotic competence of canine oocytes matured in vitro, oocytes were collected from various reproductive states and matured in vitro in the presence of the gonadotrophins. Estrous cycle stage was evaluated for each bitch by ovarian morphology, and bitches were categorized according to the stage of the estrous cycle (anestrus, follicular, or diestrus) prior to oocyte collection. Recovered oocytes were cultured in serum-free tissue culture medium (TCM)-199 supplemented with various concentrations of FSH (Exp. 1: 0, 0.1, 1.0, or 10 IU) or hCG (Exp. 2: 0, 0.5, 1.0, or 10 IU) or both (Exp. 3: 1 IU FSH + 1 IU hCG) for 72 h to determine the effective concentration of these hormones, and to examine their combined effect. After maturation culture, oocytes were denuded in PBS containing 0.1% (w/v) hyaluronidase by gentle pipetting. The denuded oocytes were stained with Hoechst 33342 in glycerol and the nuclear state of oocytes was evaluated under UV light. The rates of maturation to the MII stage were significantly higher (P &amp;lt; 0.05) when follicular-stage oocytes were supplemented with 1 IU FSH (6.2%) compared with the other FSH-supplemented groups (0.0 to 3.3%) or to the control (1.8%), or 0.1 or 10.0 IU FSH (0 to 1.2%). Significantly higher (P &amp;lt; 0.05) maturation rate to MII stage was observed in follicular-stage oocytes supplemented with 1.0 IU hCG (7.2%) compared with the control or other hCG-supplemented groups (0 to 1.5%). However, FSH and hCG together did not improve the nuclear maturation rate of canine oocytes (2.4%) compared with FSH (6.2%) and hCG alone (7.2%). In conclusion, FSH or hCG alone significantly increased the maturation of canine oocytes to the MII stage. This work was supported by grant No. M1062503005-06N250300510 from KOSEF, Republic of Korea.

Underlying physiological control of reproduction in urban and forest‐dwelling European blackbirds Turdus merula

The development and the continual expansion of urban areas have not only destroyed natural habitats, but also have drastically changed the environmental and ecological conditions of these areas. Consequently, species that have settled in these new man‐made ecosystems are exposed to considerable alternations in environmental conditions compared to their ‘wild’ conspecifics. To understand the impact of human‐induced environmental changes on life history events such as reproduction, we compared the timing of the reproductive season and its underlying endocrine control in free‐living European blackbirds Turdus merula inhabiting urban and nearby forest areas. Body mass, fat score, gonadal size, luteinizing hormone (LH), testosterone (T), and estradiol (E2) were measured. Urban blackbirds developed their gonads approximately three weeks earlier than forest birds, whereas the timing of gonadal regression did not differ. There are several factors (e.g. artificial light, temperature, food availability, and social cues) which may have caused the differences in the temporal organization of gonadal growth between the urban and forest‐living populations. The advanced gonadal development of urban blackbirds did not coincide with an earlier secretion of reproductive hormones. In contrast, urban males had lower plasma LH and T levels during testicular growth than forest males. Differences in social interactions and environmental conditions may explain the contrast of gonadal development and the timing of hormone secretion between urban and forest blackbirds.