The Cycle of Stress: A Systematic Review of the Impact of Chronic Psychological Stress Models on the Rodent Estrous Cycle

Stress is known to impair reproduction through interactions between the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. However, while it is well accepted that stress can alter estrous cycle regularity, a key indicator of female's HPG axis function, effects of different types of psychological stress have been inconsistent. This systematic review evaluated the impact of rodent models of psychological stress on estrous cyclicity, while reporting biological parameters pertaining to HPA or HPG axis function assessed within these studies. We performed a systematic database search and included articles that implemented a psychological stress model in rodents and reported estrous cyclicity for at least two cycles after initiation of stress. Of the 32 studies included, 62.5% reported post-stress alterations to estrous cyclicity, with Chronic Mild Stress (CMS) models showing the most conclusive effects. Twenty-five studies measured HPG or HPA axis markers, with cycle disruptions being commonly observed in parallel with altered estradiol and increased corticosterone levels. Our review highlights gaps in reporting estrous cyclicity assessments and makes recommendations to improve comparability between studies.

Effect of circadian rhythm and menstrual cycle on physical performance in women: a systematic review

The literature has extensively investigated potential factors influencing women's performance, including the menstrual cycle and the circadian rhythm. However, review articles exploring the combined influence of both factors remain lacking in the literature. The study aimed to systematically review the literature on the relationship between the circadian rhythm and menstrual cycle on physical performance in women. The review followed the PRISMA guidelines. The search was performed on the Web of Science, PubMed, Scopus, SPORTDiscus, and Google Scholar databases. Of the 1205 records identified, four articles met the inclusion criteria. From four articles, two studies found a significant interaction between the time of day and phase of the menstrual cycle with physical performance. The isometric strength increased in the afternoon in the mid-luteal phase (versus the morning in the mid-luteal phase, p < 0.05), and the maximum cycling power was higher in the afternoon in the mid-follicular phase (versus the morning in the mid-follicular phase, p < 0.01). Our findings suggest that the time of day and the menstrual cycle phase affect physical performance, with the daytime potentially having a more significant influence. However, the results should be interpreted cautiously due to the limited studies and diverse methodologies used to monitor the menstrual cycle phase. This review reinforces the need for further investigation to understand better the combined effects of the circadian rhythm and menstrual cycle on women's physical performance.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=380965, identifier CRD42022380965.

Dynamic Expression of Follicle-Stimulating Hormone and Estrogen mRNA Receptors Associated with microRNAs 34a and -let-7c in Canine Follicles during the Estrous Cycle

The genes encoding for estrogen receptor (ESR2) and follicle-stimulating hormone receptor (FSHR) play crucial roles in ovarian follicular development. This study aimed to determine the expression levels of miRNAs predicted against FSHR and ESR2 mRNAs in follicular cells related to their target genes during the estrous cycle in canines. Antral follicles were dissected from 72 ovaries following ovariohysterectomies. MiRNAs regulating FSHR and ESR2 genes were selected from miRNA databases, and mature miRNA and mRNA expression profiling was performed using real-time polymerase chain reaction (PCR). The best miRNA for each target gene was selected considering the quantitative PCR (qPCR) performance and target prediction probability, selecting only miRNAs with a binding p-value of 1.0, and choosing cfa-miR-34a and cfa-let-7c for FSHR and ESR2, respectively. The expression levels comparing the different phases of the estrous cycle were evaluated using ANOVA. Pearson correlations between the expression pattern of each miRNA and their target genes were performed. Each miRNA and its target genes were expressed in the granulosa cells in all estrous phases. FSHR remained low in anestrus and proestrus, increased (p < 0.05) to the highest level in estrus, and decreased (p < 0.05) in diestrus. ESR2 showed the same trend as FSHR, with the highest (p < 0.05) expression in estrus and the lowest (p < 0.05) in anestrus and proestrus. A tendency for an inverse relationship was observed between the expression of miR-34a and FSHR only in the anestrus phase, while an inverse correlation (r = -0.8) was found between miRNA-7c and ESR2 (p < 0.01). The expression profile of miR-34a and miR-let-7c and their predicted target genes of dog ovarian follicles throughout the estrous cycle observed in this study suggest a role in the transcriptional regulation of FSHR and ESR2, which is the first evidence of the involvement of these miRNAs in the canine follicular function.

Reproductive endocrinology of wild female woolly monkeys (Lagothrix lagotricha poeppigii) during puberty, ovarian cyclicity, and pregnancy

Behavioral observations can provide clues about female reproductive status. However, the study of the endocrine dynamics that underlie processes such as puberty, ovulation, conception, and gestation, may help increase our understanding of female reproductive biology. We used noninvasive methods to study female reproductive endocrinology in wild woolly monkeys (genus Lagothrix). We extracted ovarian steroid hormones from fecal samples collected non-invasively to examine changes in the concentrations of progesterone and estrogen metabolites (pregnanediol-3-glucuronide and estrone-3-glucuronide, respectively) during periods of female puberty, ovarian cyclicity, and pregnancy. The two subadult females in our study showed significant increases in ovarian hormone concentrations before disappearing and presumably dispersing, suggesting that they might reach the onset of puberty before emigrating from their natal groups. Ovarian cycle length in adult females was, on average, ~22 days (N = 21). Of the 10 cycling females, five conceived and four gave birth to offspring, with an average gestation period of ~214 days, but the infant born to the female with the shortest estimated gestation period (182 days) disappeared within a month after parturition. The fact that less than half of all cycling females conceived, and that only three out of five of those females gave birth to offspring that survived past the first month, suggests that reproduction is energetically costly for female woolly monkeys. Ovarian cycle length and gestation period among woolly monkeys are similar to those in their closest relatives, spider monkeys and muriquis suggesting that reproductive physiology may be highly conserved among females within the Tribe Atelini.

Relationship among Serum Progestagens, Cortisol, and Prolactin in Pregnant and Cycling Asian Elephants in Thailand

The aim of this study was to examine relationships among serum progestagens, cortisol, and prolactin in pregnant and normal cycling Asian elephants living in tourist camps in northern Thailand. Samples were collected twice a month for 22 months from nine elephants. Of those, four were pregnant (24.3 ± 2.9 years of age; range 21−28 years) and five (20.2 ± 9.6 years; range 8−34 years) exhibited normal ovarian cycles based on serum progestagen analyses. Gestation was divided into three periods: 1st (week 1−31), 2nd (week 32−62), and 3rd (week 63 to parturition), while the estrous cycle was divided into the follicular and luteal phases. Serum progestagens were higher during the luteal phase of the cycle (p < 0.003), whereas cortisol and prolactin were similar. In pregnant elephants, there were no differences in serum progestagens or cortisol concentrations across the three gestational periods, whereas prolactin concentrations increased significantly during the 2nd and 3rd periods (p < 0.0001). By contrast, prolactin concentrations in nonpregnant elephants were consistently low throughout the ovarian cycle. In one cycling female, prolactin concentrations were similar to pregnant elephants, perhaps because she was an allomother to two calves. Another cycling female exhibited consistently elevated cortisol concentrations, 5 to 10 times higher than the other elephants. There were no correlations between serum progestagens, cortisol, and prolactin throughout gestation; however, serum progestagens and cortisol were positively related in cycling elephants (r = 0.386, p < 0.001). From our results, there were a number of individual differences in reproductive hormonal patterns, so it is important to develop personalized monitoring programs for each elephant to enhance breeding success and create sustaining captive populations of elephants in Asia.

Preliminary results of blood growth differentiation factor-9 (GDF-9) measurement in cats: future aspects of GDF-9 on stage of the cycle and spaying history

Growth differentiation factor-9 (GDF-9), an oocyte-derived member of the TGF-β superfamily, plays an essential role in regulation of follicular development. This study aimed to determine the cyclic changes in serum GDF-9 concentration, compare its levels before and after ovariohysterectomy (OHE), and investigate its potential as a tool in ovarian remnant syndrome (ORS) diagnosis in cats. GDF-9 measurements were performed on 50 cats referred for routine OHE. The stage of the estrous cycle was determined by vaginal cytology and measurement of serum estradiol and progesterone levels was carried out to detect the cyclic changes in circulating GDF-9. One week after OHE, serum samples were collected again from 30 cats to reveal differences in GDF-9 levels. GDF-9 levels in the follicular phase were significantly higher than those in the interestrus (p⟨0.05). The postoperative analysis could be performed. GDF-9 levels slightly decreased one week after OHE (p=0.053). In conclusion, blood GDF-9 levels change during the estrous cycle, and may decrease with age in cats. However, further studies are needed to reveal the efficiency of GDF-9 in ORS diagnosis.

Comparative neuroanatomical distribution and expression levels of neuropeptide F in the central nervous system of the female freshwater prawn, Macrobrachium rosenbergii, during the ovarian cycle

Neuropeptide F (NPF) plays critical roles in controlling the feeding and reproduction of prawns. In the present study, we investigated changes in the expression levels of Macrobrachium rosenbergii neuropeptide F (MrNPF), and its neuroanatomical distribution in eyestalk (ES), brain (BR), subesophageal ganglion (SEG), thoracic ganglia (TG), and abdominal ganglia (AG), during the ovarian cycle of female prawn. By qRT-PCR, the amount of MrNPF transcripts exhibited a gradual increase in the ES, BR, and combined SEG and TG from stages I and II, to reach a maximum level at stage III, and slightly declined at stage IV, respectively. The highest to lowest expression levels were detected in combined SEG and TG, BR, ES, and AG, respectively. MrNPF immunolabeling was observed in several neuronal clusters, associated fibers, and neuropils of these central nervous system (CNS) tissues. MrNPF-ir was more intense in neurons and neuropils of SEG and TG than those found in other parts of the CNS. The number of MrNPF-ir neurons and intensity of MrNPF-ir were higher in the ES, BR, SEG, and TG at the late stages than those at the early stages of the ovarian cycle, while those in AG exhibited insignificant change. Taken together, there is a correlation between changes in the neuroanatomical distribution of MrNPF and stages of the ovarian cycle, implying that MrNPF may be an important neuropeptide that integrates sensory stimuli, including photo-, chemo-, and gustatory receptions, to control feeding and reproduction, particularly ovarian development, of this female prawn, M. rosenbergii.

Effects of the Menstrual Cycle on Jumping, Sprinting and Force-Velocity Profiling in Resistance-Trained Women: A Preliminary Study

The aim of this study was to examine the effects of the menstrual cycle on vertical jumping, sprint performance and force-velocity profiling in resistance-trained women. A group of resistance-trained eumenorrheic women (n = 9) were tested in three phases over the menstrual cycle: bleeding phase, follicular phase, and luteal phase (i.e., days 1-3, 7-10, and 19-21 of the cycle, respectively). Each testing phase consisted of a battery of jumping tests (i.e., squat jump [SJ], countermovement jump [CMJ], drop jump from a 30 cm box [DJ30], and the reactive strength index) and 30 m sprint running test. Two different applications for smartphone (My Jump 2 and My Sprint) were used to record the jumping and sprinting trials, respectively, at high speed (240 fps). The repeated measures ANOVA reported no significant differences (p ≥ 0.05, ES < 0.25) in CMJ, DJ30, reactive strength index and sprint times between the different phases of the menstrual cycle. A greater SJ height performance was observed during the follicular phase compared to the bleeding phase (p = 0.033, ES = -0.22). No differences (p ≥ 0.05, ES < 0.45) were found in the CMJ and sprint force-velocity profile over the different phases of the menstrual cycle. Vertical jump, sprint performance and the force-velocity profiling remain constant in trained women, regardless of the phase of the menstrual cycle.

Re-evaluation of reproductive cycle and fecundity of finetooth sharks Carcharhinus isodon (Valenciennes 1839) from the Northwest Atlantic Ocean, with new observations on ovarian cycle and reproductive endocrinology of biennially reproducing sharks

To provide updated information on life history for improved fishery management, the reproductive cycle of the finetooth shark Carcharhinus isodon from Northwest Atlantic (NWA) populations was investigated by examining temporal changes in morphology and histology of reproductive organs. Changes in plasma concentrations of gonadal sex hormones in relation to reproductive stage were also examined. Increases in testis width, epididymis head width, plasma testosterone concentrations and occurrence of mature spermatozoa were observed in male sharks between December and April, suggesting a seasonal pattern in reproduction that culminates with copulatory activity in May. Increases in maximum follicular diameter, oviducal gland width, plasma 17β-estradiol concentrations and occurrence of vitellogenic follicles were observed in non-pregnant female sharks during the same time period along with the occurrence of newly pregnant females in May, demonstrating strong synchronicity between male and female reproductive cycles. Pregnant females bearing full-term embryos were also observed in May, indicating that parturition occurs between mid-May and early June and gestation requires 12 months. Only transient temporal changes in follicle size and oviducal gland width were observed in pregnant females, indicating that reproductive periodicity is biennial; nonetheless, a single female exhibiting signs of concurrent vitellogenesis and pregnancy was observed. Mean brood size ± S.D. was 3.9 ± 0.9 offspring/female. Fecundity was not significantly correlated with female size, in part due to an unexpectedly high rate of early embryo mortality, which occurred in 11% of pregnant females, and was more common in larger individuals. Changes in ovarian activity during mid-pregnancy were observed, suggesting possible roles for the ovary in regulating some aspects of early to mid-gestation. This study confirms that earlier characterizations of the reproductive cycle and fecundity in NWA finetooth sharks remain valid for use in fishery management. This study also highlights unusual features of finetooth shark pregnancy (e.g., early embryo death, mid-pregnancy changes in ovarian function) that may have broader relevance to understanding elasmobranch reproduction.

Ovine uterine artery hydrogen sulfide biosynthesis in vivo: effects of ovarian cycle and pregnancy†

Uterine vasodilation dramatically increases during the follicular phase of the estrous cycle and pregnancy, which are estrogen-dominant physiological states. Uterine vasodilation is believed to be mainly controlled by local uterine artery (UA) production of vasodilators and angiogenic factors. The extremely potent vasodilator and proangiogenic hydrogen sulfide (H2S) is synthesized via metabolizing L-cysteine by cystathionine β-synthase (CBS) and cystathionine γ-lyase (CTH). This study was designed to determine if UA H2S production increases with augmented expression and/or activity of CBS and/or CTH during the ovarian cycle and pregnancy in sheep. Uterine arteries from intact nonpregnant (NP) luteal and follicular phase and late (130-135 days, term ≈ 145 days) pregnant (P) ewes were collected; endothelium-enriched proteins (UAendo) and endothelium-denuded smooth muscle (UAvsm) were mechanically prepared for accessing CBS and CTH proteins by immunoblotting; their cellular localization was determined by semi-quantitative immunofluorescence microscopy. H2S production was measured by the methylene blue assay. Immunoblotting revealed that CBS but not CTH protein was greater in P > > > NP follicular > luteal UAendo and UAvsm (P < 0.001). H2S production was greater in P > > > NP UAendo and UAvsm (P < 0.01). Pregnancy-augmented UAendo and UAvsm H2S production was inhibited by the specific CBS but not CTH inhibitor. CBS and CTH proteins were localized to both endothelium and smooth muscle; however, only CBS protein was significantly greater in P vs NP UA endothelium and smooth muscle. Thus, ovine UA H2S production is significantly augmented via selectively upregulating endothelium and smooth muscle CBS during the follicular phase and pregnancy in vivo.

Plasma volume variation across the menstrual cycle among healthy women of reproductive age: A prospective cohort study

Increases in reproductive hormones like estrogen, play an important role in the remarkable increases in plasma volume observed in pregnancy. Accurate estimates of plasma volume expansion during pregnancy depend on correctly timing and measuring plasma volume in nonpregnant women. However, to date, there is no consensus on the pattern of plasma volume across the menstrual cycle. We prospectively measured plasma volume in 45 women across a single menstrual cycle. A urine-based fertility monitor was used to time three clinic visits to distinct points in the menstrual cycle: the early follicular phase (~day 2), periovulation (~day 12), and the mid-point of the luteal phase (~day 21)-based on a 28-day cycle length. Healthy women aged 18-41 years with regular menstrual cycles and a healthy body weight were enrolled in the study. At each visit, blood samples were collected before and after injection of 0.25 mg/kg body weight of indocyanine green dye (ICG). Pre- and post-ICG injection plasma samples were used to measure plasma volume. Preinjection samples were used to measure ovarian hormones and plasma osmolality. Mean plasma volume was highest during the early follicular phase (2,276 ± 478 ml); it declined to 2,232 ± 509 ml by the late follicular phase and to 2,228 ± 502 ml by the midluteal phase. This study found that overall variations in plasma volume are small across the menstrual cycle. Therefore, in clinical practice and research, the menstrual cycle phase may not be an important consideration when evaluating plasma volume among women of reproductive age.

GABAA receptor currents in the dorsal motor nucleus of the vagus in females: influence of ovarian cycle and 5α-reductase inhibition

The dorsal motor nucleus of the vagus (DMV) contains the preganglionic motor neurons important in the regulation of glucose homeostasis and gastrointestinal function. Despite the role of sex in the regulation of these processes, few studies examine the role of sex and/or ovarian cycle in the regulation of synaptic neurotransmission to the DMV. Since GABAergic neurotransmission is critical to normal DMV function, the present study used in vitro whole cell patch-clamping to investigate whether sex differences exist in GABAergic neurotransmission to DMV neurons. It additionally investigated whether the ovarian cycle plays a role in those sex differences. The frequency of phasic GABAA receptor-mediated inhibitory postsynaptic currents in DMV neurons from females was lower compared with males, and this effect was TTX sensitive and abolished by ovariectomy (OVX). Amplitudes of GABAergic currents (both phasic and tonic) were not different. However, females demonstrated significantly more variability in the amplitude of both phasic and tonic GABAA receptor currents. This difference was eliminated by OVX in females, suggesting that these differences were related to reproductive hormone levels. This was confirmed for GABAergic tonic currents by comparing females in two ovarian stages, estrus versus diestrus. Female mice in diestrus had larger tonic current amplitudes compared with those in estrus, and this increase was abolished after administration of a 5α-reductase inhibitor but not modulation of estrogen. Taken together, these findings demonstrate that DMV neurons undergo GABAA receptor activity plasticity as a function of sex and/or sex steroids.NEW & NOTEWORTHY Results show that GABAergic signaling in dorsal vagal motor neurons (DMV) demonstrates sex differences and fluctuates across the ovarian cycle in females. These findings are the first to demonstrate that female GABAA receptor activity in this brain region is modulated by 5α-reductase-dependent hormones. Since DMV activity is critical to both glucose and gastrointestinal homeostasis, these results suggest that sex hormones, including those synthesized by 5α-reductase, contribute to visceral, autonomic function related to these physiological processes.

Assessing female reproductive status of spectral tarsier (Tarsius tarsier) using fecal steroid hormone metabolite analysis

The wild population of spectral tarsier is declining and attempts to breed the species in captivity have been of limited success. One possible reason for this is that information on the reproductive biology of Tarsius tarsier is extremely limited and data on the species reproductive physiology are completely lacking. We validated fecal estrogen (E-total) and progesterone metabolite (5-P-3OH) measurements for monitoring female ovarian activity and pregnancy. We used this approach to provide the first data on cycle and pregnancy length based on endocrine information in this species. We collected regular fecal samples in combination with observations on socio-sexual behaviors for a maximum of 15 months from three females maintained at Primate Research Center of Bogor Agricultural University, Indonesia. Hormonal profiles indicated that behavioral estrus was associated with marked elevations in fecal E-total concentrations followed by increases in 5-P-3OH levels indicating luteal function. Pregnancy was characterized by low levels of E-total and 5-P-3OH during the first month and markedly rising concentrations thereafter. An ovarian cycle length of 21.7 ± 5.7 days was found. Gestation length was 128d (live infant), 131d (stillbirth), and 164d (death of mother and infant due to dystocia). Despite the small sample size, the study demonstrates the overall validity of fecal sex hormone metabolite measurements for reproductive monitoring in female T. tarsier, as such, the methods described here may ultimately help to improve the breeding management of the species in captivity. They may also offer new opportunities for investigating basic questions of tarsier reproductive biology in the wild by using fecal hormone metabolite analysis to diagnose pregnant animals and determine reproductive rates in relation to ecological and other factors influencing tarsier reproduction. Thus, non-invasive assessment of female reproductive condition as described here may ultimately contribute to facilitate in and ex situ conservation efforts of this endangered primate species.

Species Comparison of Postnatal Development of the Female Reproductive System

The postnatal development of the female reproductive system in laboratory animals and humans is reviewed. To enable a meaningful species comparison of the developing female reproductive system, common definitions of developmental processes were established with a focus made on aspects that are similar across species. A species comparison of the key endocrine, morphologic, and functional (onset of ovarian cycles and ability to reproduce) features of postnatal development of the female reproductive system is provided for human, nonhuman primate, dog, rat, and also mouse, minipig, and rabbit where possible. Species differences in the timing and control of female sexual maturation are highlighted. Additionally, a species comparison of the type and timing of female reproductive ovarian cycles was compiled. Human development provided the frame of reference, and then other common laboratory species were compared. The comparison has inherent challenges because the processes involved and sequence of events can differ greatly across species. Broad strokes were taken to assign a particular average age to an event and are to be used with caution. Methods of evaluation of postnatal female reproductive development in laboratory animals are discussed. Lastly, control rodent data from one of the author's laboratory on vaginal opening, first estrus, estrous cyclicity, and the histopathology involved with the developing female rat and mouse are presented. The information provided in this review is intended to be a resource for the design and interpretation of juvenile animal toxicity testing and ultimately, the relevance of the data to characterize potential risks for women and girls. Birth Defects Research 110:163-189, 2018. © 2017 Wiley Periodicals, Inc.

Kisspeptin: a new marker for human pre-ovulation

Kisspeptin is a polypeptide that plays an important role in reproductive endocrine regulation. The aim of present study was to investigate the dynamic trend of kisspeptin levels during the menstrual cycle and to elucidate the relationship between kisspeptin ovulation. First, 15 female volunteers with regular menstrual cycles were recruited to detect the change in serum and urine kisspeptin levels over one menstrual cycle within each individual. Subsequently, 114 serum samples and 79 urine samples from 114 individuals were randomly collected at the outpatient department to better ascertain the results. Kisspeptin levels showed a distinctive stage-specific pattern during the normal menstrual cycle in both serum and urine. It was low during the first 5 days, while the first surge appeared on the 11th day (the diameter of the dominant follicle was approximately 1.2 cm). Later, a second smaller surge appeared around the 14th day and the same changes were identified in serum and urine. Furthermore, serum kisspeptin levels were positively related to 17-β estradiol (E₂) level increase. Thus, kisspeptin surge in serum and urine may be used as a marker for dominant follicle development and pre-ovulation. Moreover, kisspeptin may also play a vital role in female reproduction through regulating hormonal state.

Estrogenic suppression of binge-like eating elicited by cyclic food restriction and frustrative-nonreward stress in female rats

Because binge eating and emotional eating vary through the menstrual cycle in human females, we investigated cyclic changes in binge-like eating in female rats and their control by estrogens. Binge-like eating was elicited by three cycles of 4 days of food restriction and 4 days of free feeding followed by a single frustrative nonreward-stress episode (15 min visual and olfactory exposure to a familiar palatable food) immediately before presentation of the palatable food. Intact rats showed binge-like eating during the diestrous and proestrous phases of the ovarian cycle, but not during the estrous (periovulatory) phase. Ovariectomized (OVX) rats not treated with estradiol (E2) displayed binge-like eating, whereas E2-treated OVX rats did not. The procedure did not increase signs of anxiety in an open-field test. OVX rats not treated with E2 that were subjected to food restriction and sacrificed immediately after frustrative nonreward had increased numbers of cells expressing phosphorylated extracellular signal-regulated kinases (ERK) in the central nucleus of the amygdala (CeA), paraventricular nucleus of hypothalamus (PVN), and dorsal and ventral bed nuclei of the stria terminalis (BNST) compared with nonrestricted or E2-treated rats. These data suggest that this female rat model is appropriate for mechanistic studies of some aspects of menstrual-cycle effects on emotional and binge eating in human females, that anxiety is not a sufficient cause of binge-like eating, and that the PVN, CeA, and BNST may contribute to information processing underlying binge-like eating.

Variation in circulating antimüllerian hormone precursor during the periovulatory and acute postovulatory phases of the human ovarian cycle

OBJECTIVE

To determine whether the relative quantity of circulating AMH precursor (proAMH) declines relative to levels of the active form (AMH_N,C) in the periovulatory phase of the ovarian cycle.

DESIGN

Longitudinal study.

SETTING

Local community.

PATIENT(S)

Sixteen women aged between 18 to 30 years with regular menstrual cycles between 25 to 35 days long.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Serum concentrations of proAMH and total AMH (proAMH and AMH_N,C combined) measured by immunoassay, with relative levels of proAMH expressed as the AMH prohormone index (API = [ProAMH]/[Total AMH] × 100).

RESULT(S)

The mean API in the 11 eligible women fell from 20.7 during the luteinizing hormone (LH) surge period to 18.7 during the acute postsurge period. No statistically significant differences in the API were observed among samples taken at single time points in the early follicular, midfollicular, midluteal, and late luteal phases.

CONCLUSION(S)

This study suggests that activation of AMH by proteolytic enzymes is largely stable throughout the ovarian cycle. However, there is a subtle but robust decrease in the level of proAMH relative to AMH_N,C in the acute postovulatory period. This may indicate that periovulatory increases in prohormone convertases cause increases in proAMH cleavage rates. Alternatively, rapid changes in the hierarchy of follicle developmental stages during ovulation may result in changes in the relative ratios of proAMH and AMH_N,C.

Evidence for the involvement of dopamine in stress-induced suppression of reproduction in the cichlid fish Oreochromis mossambicus

In the present study, we examined whether stress-induced suppression of reproduction is mediated through the catecholaminergic neurotransmitter dopamine (DA) in the female cichlid fish Oreochromis mossambicus. In the first experiment, application of antibody against tyrosine hydroxylase (TH; a marker for DA) in brain sections revealed the presence of intensely stained TH immunoreactive cells in the preoptic area (POA) and nucleus preopticus (NPO) during the previtellogenic phase. These cells showed weak immunoreactivity during the vitellogenic and prespawning phases concomitant with darkly stained luteinising hormone (LH) immunoreactive content in the proximal pars distalis (PPD) of the pituitary gland and fully ripened follicles (stage V) in the ovary of control fish. However, in fish exposed to aquacultural stressors, TH secreting cells remained intensely stained in POA and NPO regions during the prespawning phase, indicating increased synthetic and secretory activity, which was reflected by a significantly higher DA content compared to controls. Increased DA activity as a result of stress was associated with a decrease in the LH immunoreactive content in the PPD and an absence of stage V follicles in the ovary. In the second experiment, administration of DA caused effects similar to those in stressed fish, whereas DA receptor antagonist domperidone (DOM) treatment significantly increased the LH content in the PPD and the number of stage V follicles in unstressed fish. On the other hand, treatment of stressed fish with DOM resulted in dark accumulations of LH immunoreactive content in the PPD accompanied by the presence of stage V follicles in the ovary. Taken together, these results suggest an additional pathway for the inhibitory effects of stress through dopaminergic neurones along the reproductive axis.

Engineering the ovarian cycle using in vitro follicle culture

STUDY QUESTION

Can cultured follicles model the ovarian cycle, including follicular- and luteal-phase hormone synthesis patterns and ovulation?

SUMMARY ANSWER

Under gonadotrophin stimulation, murine follicles grown in an encapsulated three-dimensional system ovulate in vitro and murine and human follicle hormone synthesis mimics follicular and luteal phases expected in vivo.

WHAT IS KNOWN ALREADY

Studies of the human ovary and follicle function are limited by the availability of human tissue and lack of in vitro models. We developed an encapsulated in vitro follicle growth (eIVFG) culture system, which preserves 3D follicular structure. Thus far, the alginate system has supported the culture of follicles from mice, dog, rhesus macaque, baboon and human. These studies have shown that cultured follicles synthesize steroid hormones similar to those observed during the follicular phase in vivo.

STUDY DESIGN, SIZE, DURATION

Cultured murine follicles were treated with human chorionic gonadotrophin (hCG) and epidermal growth factor (EGF) and either assayed for luteinization or removed from alginate beads and assayed for ovulation. Human follicles were also cultured, treated with follicle-stimulating hormone (FSH), hCG and EGF to mimic gonadotrophin changes throughout the ovarian cycle, and culture medium was assayed for hormone production.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Murine and human follicles were cultured in alginate hydrogel and hormone production [17β-estradiol, progesterone, inhibin A, inhibin B, activin A and anti-Müllerian hormone (AMH)] was quantified in medium by enzyme-linked immuno assay (ELISA). Human ovarian tissue was acquired from females between 6 and 34 years of age with a cancer diagnosis. These participants were undergoing ovarian tissue cryopreservation at National Physicians Cooperative sites as part of the Oncofertility Consortium.

MAIN RESULTS AND THE ROLE OF CHANCE

When grown in this system, 96% of mouse follicles ovulated in response to hCG and released meiotically competent eggs. Ovulated follicles recapitulated transcriptional, morphologic and hormone synthesis patterns post-luteinizing hormone (LH/hCG). In addition to rodent follicles, individual human follicles secreted steroid and peptide hormones that mimicked the patterns of serum hormones observed during the menstrual cycle.

LIMITATIONS, REASONS FOR CAUTION

This was a descriptive study of an in vitro model of ovulation and the ovarian hormone cycle. The ovulation studies were limited to murine tissue and further studies are needed to optimize conditions using other species.

WIDER IMPLICATIONS OF THE FINDINGS

The eIVFG system reliably phenocopies the in vivo ovarian cycle and provides a new tool to study human follicle biology and the influence of cycling female hormones on other tissue systems in vitro.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by NIH U54 HD041857, NIH U54 HD076188, NIH UH2 E5022920, NIH UH3 TR001207 and F30 AG040916 (R.M.S.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Reproductive biology of the greeneye spurdog Squalus chloroculus (Squaliformes, Squalidae)

The reproduction of the greeneye spurdog Squalus chloroculus was studied based on animals caught in the multispecies and multi-gear southern and eastern scalefish and shark fishery on the upper continental slope off southern Australia. One hundred and ninety-nine females (502-990 mm, total length, L_T ) and 189 males (515-810 mm L_T ) were examined. The female reproductive cycle, based on 41 breeding animals, is continuous and triennial, with the pregnancy period estimated to be 31-34 months, seasonal and synchronous with the ovarian cycle; a third of the breeding female population is estimated to give birth between September and December each year. The estimated L_T at which 50% of females are mature is 799 mm (95% c.i.: 794, 804), whereas the L_T at which 50% are maternal is 825 mm (95% c.i.: 817-833), but these estimates are probably biased by the phenomenon of apparent change of L_T at maternity and L_T at maturity following severe length-selective fishing mortality. Litters ranged from four to 15 embryos with a 1:1 sex ratio, and litter size increased with maternal length. The breeding cycle of males is neither seasonal nor synchronous with the female cycle. The estimated L_T of males where 50% are mature was 629 mm (95% c.i.: 603, 645).

Ovarian cycle-linked plasticity of δ-GABAA receptor subunits in hippocampal interneurons affects γ oscillations in vivo

GABA_A receptors containing δ subunits (δ-GABA_ARs) are GABA-gated ion channels with extra- and perisynaptic localization, strong sensitivity to neurosteroids (NS), and a high degree of plasticity. In selective brain regions they are expressed on specific principal cells and interneurons (INs), and generate a tonic conductance that controls neuronal excitability and oscillations. Plasticity of δ-GABA_ARs in principal cells has been described during states of altered NS synthesis including acute stress, puberty, ovarian cycle, pregnancy and the postpartum period, with direct consequences on neuronal excitability and network dynamics. The defining network events implicated in cognitive function, memory formation and encoding are γ oscillations (30–120 Hz), a well-timed loop of excitation and inhibition between principal cells and PV-expressing INs (PV + INs). The δ-GABA_ARs of INs can modify γ oscillations, and a lower expression of δ-GABA_ARs on INs during pregnancy alters γ frequency recorded in vitro. The ovarian cycle is another physiological event with large fluctuations in NS levels and δ-GABA_ARs. Stages of the cycle are paralleled by swings in memory performance, cognitive function, and mood in both humans and rodents. Here we show δ-GABA_ARs changes during the mouse ovarian cycle in hippocampal cell types, with enhanced expression during diestrus in principal cells and specific INs. The plasticity of δ-GABA_ARs on PV-INs decreases the magnitude of γ oscillations continuously recorded in area CA1 throughout several days in vivo during diestrus and increases it during estrus. Such recurring changes in γ magnitude were not observed in non-cycling wild-type (WT) females, cycling females lacking δ-GABA_ARs only on PV-INs (PV-Gabrd^-/-), and in male mice during a time course equivalent to the ovarian cycle. Our findings may explain the impaired memory and cognitive performance experienced by women with premenstrual syndrome (PMS) or premenstrual dysphoric disorder (PMDD).

Central expression and anorectic effect of brain-derived neurotrophic factor are regulated by circulating estradiol levels

Estrogens potently suppress food intake. Compelling evidence suggests that estradiol, the primary form of estrogens, reduces food intake by facilitating other anorectic signals. Brain-derived neurotrophic factor (BDNF), like estradiol, appears to suppress food intake by affecting meal size. We hypothesized that estradiol modulates Bdnf expression and the anorectic effect of BDNF. The first goal was to determine whether Bdnf expression was regulated by endogenous estradiol of cycling rats and by cyclic estradiol treatment using ovariectomized rats. Bdnf expression within the ventromedial nucleus of hypothalamus (VMH) was temporally elevated at estrus following the estradiol peak, which coincided with the decline in feeding at this phase of the ovarian cycle. Additionally, food intake and body weight were increased following ovariectomy with a parallel decrease in Bdnf expression in the VMH. All of these alterations were reversed by cyclic estradiol treatment, suggesting that Bdnf expression within the VMH was regulated in an estradiol-dependent manner. The second goal was to determine whether estradiol modulates the anorectic effect of BDNF. Sham-operated estrous rats and ovariectomized rats cyclically treated with estradiol responded to a lower dose of central administration of BDNF to decrease food intake than male rats and oil-treated ovariectomized rats, implying that endogenous estradiol or cyclic estradiol replacement increased the sensitivity to anorectic effect of BDNF. These data indicate that Bdnf expression within the VMH and the anorectic effect of BDNF varied depending on plasma estradiol levels, suggesting that estradiol may regulate BDNF signaling to regulate feeding.

Reproductive Biology of the Coyote (Canis latrans): Integration of Mating Behavior, Reproductive Hormones, and Vaginal Cytology

The reproductive biology of wild Canis species is often described as unique among mammals because an unusual combination of behavioral and physiological characteristics including a seasonally monestrous cycle, copulatory lock or tie, obligatory pseudopregnancy, social monogamy, and biparental care of the young. We investigated social behavior, endocrine profiles, and vaginal cytology of female coyotes (Canis latrans) during 4 breeding seasons, 2000-2003. Blood levels of estradiol, progesterone, prolactin, and relaxin were measured, and mating behavior and changes in vaginal epithelium were documented. After aligning the data from each individual to her estimated day of ovulation, we compared pregnant coyotes with nonpregnant females and evaluated temporal relationships among hormone levels, behavior, and vaginal cytology. We found that patterns of proceptive and receptive behaviors correlated with the secretion of steroid hormones, as did vaginal epithelial cytomorphosis. In addition, although progesterone levels of pregnant and pseudopregnant coyotes were indistinguishable, prolactin demonstrated a discernible intergroup difference and relaxin was only detectable in pregnant females. Although this study included characteristics not previously published for this species, it also showed how key aspects of reproduction were correlated temporally, and emphasized the importance of an integrated perspective when addressing the reproductive biology of coyotes, or other wild species of canids.

Neurosteroid synthesis-mediated regulation of GABA(A) receptors: relevance to the ovarian cycle and stress

Recently, we demonstrated cyclic alterations in GABA(A) receptor (GABA(A)R) subunit composition over the ovarian cycle correlated with fluctuations in progesterone levels. However, it remains unclear whether this physiological regulation of GABA(A)Rs is directly mediated by hormones. Here, we show that both ovarian and stress hormones are capable of reorganizing GABA(A)Rs by actions through neurosteroid metabolites. The cyclic alterations in GABA(A)Rs demonstrated in female mice can be mimicked with exogenous progesterone treatment in males or in ovariectomized females. Progesterone (5 mg/kg, twice daily) upregulates the expression of GABA(A)R delta subunits and enhances the tonic inhibition mediated by these receptors in dentate gyrus granule cells (DGGCs). These changes in males as well as ovarian cycle-induced changes in females can be blocked by finasteride, an antagonist of neurosteroid synthesis from progesterone. The altered GABA(A)R expression is unaffected by the progesterone receptor antagonist RU486 [mifepristone (11beta-[p-(dimethylamino)phenyl]-17beta-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one)], suggesting that neurosteroid synthesis and not progesterone receptor activation underlies the hormone-mediated effects on GABA(A)R expression. Neurosteroids can alter GABA(A)R expression on a rapid timescale, because GABA(A)R upregulation can be induced in brain slices maintained in vitro after a short (30 min) treatment with the neurosteroid 3alpha,5alpha-tetrahydrodeoxycorticosterone (THDOC) (100 nM). Consistent with these rapid alterations, acute stress, a condition known to quickly raise THDOC levels, within 30 min induces upregulation of GABA(A)R delta subunit expression and increase tonic inhibition in DGGCs. These results reveal that several physiological conditions characterized by elevations in neurosteroid levels induce a reorganization of GABA(A)Rs through the action of neurosteroids.

Assessment of female reproductive status in captive-housed Hanuman langurs (Presbytis entellus) by measurement of urinary and fecal steroid excretion patterns

The study reports on the use of urinary and fecal hormone measurements for monitoring female reproductive status in captive-housed Hanuman langurs (Presbytis entellus). Matched urine and fecal samples collected throughout 7 complete menstrual cycles of two females, and during part of one pregnancy in a third female were analyzed. Estrone conjugates (E1C) and immunoreactive pregnanediol glucuronide (PdG) in urine and immunoreactive estradiol (E2), progesterone (P4), pregnanediol (Pd) and 20α-hydroxyprogesterone (20αOHP) in feces were measured by enzymeimmunoassay. E1C and PdG in urine were excreted in a cyclic pattern with E1C levels increasing 3- to 4-fold during the follicular phase to reach preovulatory peak values 2 days before a defined rise in PdG concentrations. Cycle lengths ranged between 20 and 34 days comprising a variable follicular phase of 7-21 days and a more consistent luteal phase of 12-14 days. High pressure liquid chromatography (HPLC) analysis of fecal extracts confirmed the presence of all fecal hormones measured, but indicated large amounts of additional immunoreactivity in the three progestin assays. The patterns of excretion of fecal E2 and all three fecal progestins corresponded well with those of steroid metabolites in urine in showing a clear and well defined follicular phase E2 rise followed by a luteal phase progestin increase. Measurement of 20αOHP immunoreactivity revealed the most stable baseline and the highest follicular/luteal phase differential. Levels of all hormones were clearly elevated during pregnancy although urinary E1C and PdG showed a more pronounced increase compared to fecal metabolites. The results indicate that urinary and fecal hormone analysis can be applied to noninvasive monitoring of reproductive status in the Hanuman langur. © 1995 Wiley-Liss, Inc.