High androgen production by ovarian thecal interstitial cells: a mechanism for delayed ovulation in a tropical vespertilionid bat, Scotophilus heathi

Quantification of Urinary Sex Steroids in the Big Brown Bat (Eptesicus fuscus)

AbstractBats (order Chiroptera) are the second largest group of mammals, diverging ~52.5 million years ago. Many species exhibit an unusual reproductive cycle and extreme longevity without reproductive senescence, yet steroid profiles exist for few bats. Big brown bats (Eptesicus fuscus) are temperate insectivores found throughout North America. They mate promiscuously in fall, store sperm during winter hibernation, and have delayed ovulation and fertilization in spring. Here, we report the first urinary steroid profile in bats by quantifying 17β-estradiol (E₂) in captive male and female E. fuscus across their reproductive cycle. Male bats had higher urinary E₂ levels than females, and adults had higher levels than yearlings following creatinine adjustment for hydration. In nonpregnant females, several seasonal differences in creatinine-adjusted and unadjusted urinary E₂ levels were observed. Urinary E₂ was higher in males than females in winter for both conditions and in autumn for creatinine-adjusted levels. We quantified progesterone (P₄) in a subset of females. In nonpregnant females, urinary P₄ was constant across seasons except for unadjusted levels, which were highest in the summer. In pregnant females, urinary E₂ and P₄ levels peaked beginning ~20 d before parturition, with both steroids returning to baseline in the following weeks. Knowing how urinary steroid levels fluctuate with age and sex and across the annual season is key to understanding reproductive cycling in bats. Our research furthers the potential for bats as a model for medical reproductive research. Moreover, it complements previous studies on the potential role of steroids in primer pheromonal effects in bats.

Transcriptomic and metabolomic insights into the variety of sperm storage in oviduct of egg layers

In birds, the sperm storage tubules (SST) are dispersed in uterovaginal junction (UVJ) and highly correlated with differential capacity of sperm storage (SS) in and among species with unspecified mechanisms. Here, the SS duration of 252 egg layer breeders was evaluated in 5 rounds with 3 phenotypic traits to screen high- and low-SS individuals, respectively, followed with transcriptome of UVJ tissues and metabolome of serum (high-SS vs. low-SS) to decipher the candidate genes and biochemical markers correlated with differential SS capacity. Histological characterization suggested slightly higher density of SST in UVJ (high-SS vs. low-SS). Transcriptome analyses identified 596 differentially expressed genes (336 upregulated vs. 260 downregulated), which were mainly enriched in gene ontology terms of homeostasis, steroid and lipid metabolism and hormone activity, and 12 significant pathways (P < 0.05) represented by calcium, steroid, and lipid metabolism. Immunohistochemical staining of GNAQ, ST6GAL1, ADFP, and PCNA showed similar distribution in UVJ tissues between 2 groups. Several candidates (HSD11B2, DIO2, AQP3, GNAQ, NANS, ST6GAL1) combined with 4 (11β-prostaglandin F2α, prostaglandin B1, 7α-hydroxytestosterone, and N-acetylneuraminic acid) of 40 differential metabolites enriched in serum metabolome were considered as regulators and biomarkers of SS duration in egg layer breeders. The integrated transcriptome and metabolome analyses of chicken breeder hens will provide novel insights for exploration and improvement of differential SS capacity in birds.

Systemic adiponectin treatment reverses polycystic ovary syndrome-like features in an animal model

The present study examined the efficacy of adiponectin for regulating the reproductive, metabolic and fertility status of mice with polycystic ovary syndrome (PCOS). PCOS was induced in prepubertal (21- to 22-day-old) mice using dehydroepiandrosterone (6mg 100g-1day-1 for 25days), after which mice were administered either a low or high dose of adiponectin (5 or 15µgmL-1, s.c., respectively). PCOS mice exhibited typical features, including the presence of numerous cystic follicles, increased circulating androgens, increased body mass, altered steroidogenesis, decreased insulin receptor expression and increased serum triglycerides, serum glucose, Toll-like receptor (TLR)-4 (a marker of inflammation) and vascular endothelial growth factor (VEGF; a marker of angiogenesis). These parameters were significantly correlated with a reduction in adiponectin in PCOS mice compared with vehicle-treated control mice. Exogenous adiponectin treatment of PCOS mice restored body mass and circulating androgen, triglyceride and glucose levels. Adiponectin also restored ovarian expression of steroidogenic markers (LH receptors, steroidogenic acute regulatory protein and 3β-hydroxysteroid dehydrogenase), insulin receptor, TLR-4 and VEGF levels in control mice. Adiponectin restored ovulation in PCOS mice, as indicated by the presence of a corpus luteum and attainment of pregnancy. These findings suggest that adiponectin effectively facilitates fertility in anovulatory PCOS. We hypothesise that systemic adiponectin treatment may be a promising therapeutic strategy for the management of PCOS.

Prolactin modulates luteal activity in the short-nosed fruit bat, Cynopterus sphinx during delayed embryonic development

The aim of this study was to evaluate the role of prolactin as a modulator of luteal steroidogenesis during the period of delayed embryonic development in Cynopterus sphinx. A marked decline in circulating prolactin levels was noted during the months of November through December coinciding with the period of decreased serum progesterone and delayed embryonic development. The seasonal changes in serum prolactin levels correlated positively with circulating progesterone (P) level, but inversely with circulating melatonin level during first pregnancy showing delayed development in Cynopterus sphinx. The results also showed decreased expression of prolactin receptor-short form (PRL-RS) both in the corpus luteum and in the utero-embryonic unit during the period of delayed embryonic development. Bats treated in vivo with prolactin during the period of delayed development showed significant increase in serum progesterone and estradiol levels together with significant increase in the expression of PRL-RS, luteinizing hormone receptor (LH-R), steroidogenic acute receptor protein (STAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) in the ovary. Prolactin stimulated ovarian angiogenesis (vascular endothelial growth factor) and cell survival (B-cell lymphoma 2) in vivo. Significant increases in ovarian progesterone production and the expression of prolactin-receptor, LH-R, STAR and 3β-HSD proteins were noted following the exposure of LH or prolactin in vitro during the delayed period. In conclusion, short-day associated increased melatonin level may be responsible for decreased prolactin release during November-December. The decline in prolactin level might play a role in suppressing P and estradiol-17β (E2) estradiol levels thereby causing delayed embryonic development in C. sphinx.

Sperm Storage in the Female Reproductive Tract

The capacity for sperm storage within the female reproductive tract occurs widely across all groups of vertebrate species and is exceptionally well developed in some reptiles (maximum duration seven years) and fishes (maximum duration >1 year). Although there are many reports on both the occurrence of female sperm storage in diverse species and its adaptive benefits, few studies have been directed toward explaining the mechanisms involved. In this article we review recent findings in birds and mammals in an effort to develop hypotheses that could be translated into research applications in animal breeding technologies. There are pockets of evidence to suggest that the local epithelial cells, sometimes arranged as sperm storage tubules, can respond to spermatozoa by producing heat shock proteins as well as providing an environment rich in antioxidants. Moreover, the local immune system seems to tolerate the arrival of spermatozoa, while retaining the ability to combat the arrival of infectious microorganisms.

Localization of resistin and its possible roles in the ovary of a vespertilionid bat, Scotophilus heathi

The aim of the present study was to evaluate the expression and effect of resistin on ovarian activities of Scotophilus heathi. Immunohistochemical study showed marked variation in resistin immunostaining during different reproductive phases. Most intense immunostaining of resistin was noticed in thecal-interstitial cells in ovary during the period of delayed ovulation, the period of increased androgen synthesis and suppressed ovulation. The changes in ovarian resistin level also correlated positively with circulating leptin level and body white adipose tissue accumulation. The in vitro study showed that resistin alone preferentially stimulated progesterone synthesis, but with luteinizing hormone (LH) stimulated androgen secretion. Resistin alone dose-dependently increased expression of LH-receptor, steroidogenic acute regulatory protein and insulin receptor proteins in the ovary, whereas together with LH showed dose-dependent stimulatory effect on expression of androgen receptor and insulin receptor proteins in the ovary. In conclusion, during the period of fat accumulation increased ovarian resistin level may be responsible for increased androgen synthesis through insulin receptor mediated pathways in the ovary of S. heathi.

Effects of seasonal adiposity on ovarian activity of Vespertilionid bat, Scotophilus heathi: proteomics analysis

In present study comparative proteomics was utilized to identify ovarian protein profiles and correlate the expression of these proteins with adiposity induced changes in ovarian activity leading to suppression of ovulation (delayed ovulation) in the bat, S. heathi. To achieve this, two-dimension gel electrophoresis combined with protein identification by tandem mass spectrometry (LC-MS/MS) was applied. Protein profiles were obtained from intact ovaries of bats collected during recrudescence (basal body weight) and delayed ovulation (increased body weight) phases of reproductive cycle. Out of 42 differentially expressed protein spots, 15 protein spots were identified by LC-MS/MS. A majority of the 15 protein spots identified belonged to a group of enzymes within the glycolytic and citrate cycles. Greater concentrations of these enzymes were found during the period of delayed ovulation, which may be responsible for an increase in the production of ATP within the ovary. The increased metabolic activity and energy production observed within the ovary during winter dormancy may be required for increased steroidogenic activity during this period. The protein 14-3-3 identified by LC-MS/MS was verified by immunoblotting, which confirmed its increased expression during the period of delayed ovulation and may be associated with development of insulin resistance. Treatment with adipokines (adiponectin, resistin) is responsible for increased expression of 14-3-3 protein in the ovary of S. heathi. Adiposity-associated rise in adipokines are thus responsible for increased expression of 14-3-3 protein in the ovary of S. heathi, which may be responsible for prolonged survival of antral follicles and suppression of ovulation. The 14-3-3 protein may represent a new marker for adiposity associated ovarian anovulation (disorders).

Effects of resistin on ovarian folliculogenesis and steroidogenesis in the vespertilionid bat, Scotophilus heathi

The bat Scotophilus heathi exhibit prolonged anovulatory condition known as delayed ovulation coinciding with the period of extensive fat accumulation. The present study was undertaken to find out whether extensive accumulation of fat in S. heathi is responsible for suppression of ovarian activity by increasing production of adipokine resistin in the bat. This was achieved by (a) investigating variation in serum resistin level in relation to the changes in the body fat mass and (b) evaluating the effect of resistin treatment on ovarian activity with reference to steroid synthesis. An attempt was also made to determine whether resistin mediate its effects on ovary through signal transducer and activator of transcription 3 (STAT3) signaling mechanism. The results showed significant seasonal variation in serum resistin level with the peak level coinciding with the period of maximum fat accumulation, high circulating androgen level and period of anovulation. The treatment with resistin to the bat caused increase in androstenedione due to stimulatory effects on 3β-hydroxysteroid dehydrogenase, but decrease in estradiol level due to inhibitory effect on aromatase. Resistin treatment increased androgen receptor protein together with increased insulin receptor but not through conventional luteinizing hormone receptor and steroidogenic acute regulatory protein mediated pathways. This study further showed that resistin treatment increases androstenedione synthesis and up-regulates insulin receptor in the ovary through STAT3 mediated pathways. These findings suggest that obese women through increased resistin synthesis may causes development of non-ovulatory antral follicles through insulin receptor signaling cascade.

Effects of adiponectin on ovarian folliculogenesis and steroidogenesis in the vespertilionid bat, Scotophilus heathi

The bat Scotophilus heathi undergo anovulation, known as delayed ovulation, coinciding with the period of seasonal adiposity due to fat accumulation. Because adiponectin is a well known fat cell product, it might be responsible for adiposity related anovulation in S. heathi. The aim of this study was thus to evaluate the effects of adiponectin treatment on ovarian activity in S. heathi. The bat during the period of delayed ovulation was treated with adiponectin (25 μg/day) for 12 days. Changes taken place in the ovarian activity of the treated bat was compared with the control bat and results obtained are presented here. Adiponectin treatment significantly decreased body mass by depleting adipose tissue. It acts directly upon the ovary and promotes antral follicular development by stimulating cell proliferation and modulating ovarian steroidogenesis. The bat treated with adiponectin showed significant decrease in circulating androstenedione (A4) and estradiol (E2) levels, but increase in circulating progesterone (P4) level. The inhibitory effect of adiponectin on androgen synthesis may be due to decreased thecal-interstitial cells differentiation in stroma by suppressing adiponectin receptor type 1 (AdipoR1), luteinizing hormone (LH) and insulin receptors in the ovary of S. heathi. The study provides evidences suggesting that the adiponectin treatment suppresses adiposity and restores normal ovarian activity.

Localization of adiponectin and its receptor and its possible roles in the ovary of a vespertilionid bat, Scotophilus heathi

The aim of this study was to evaluate the seasonal variation in serum adiponectin levels and ovarian expression of adiponectin and its receptor in the Scotophilus heathi bat and their relationship to the changes in the body fat mass, serum insulin and luteinizing hormone (LH) levels, and ovarian activity. A very high level of circulating adiponectin was found during recrudescence, whereas a very low level of circulating adiponectin was observed during pre-ovulatory period. The increased circulating adiponectin level coincided with fat deposition, insulin resistance and hyperinsulinemia (HI) in S. heathi. Immunocytochemical study in the ovary of bat showed localization of adiponectin mainly in thecal-interstitial cells (TICs), and adiponectin receptor 1 (AdipoR1) in the granulosa cells of growing follicles, but showed no staining in atretic follicle. Seasonal changes in ovarian adiponectin and AdipoR1 levels showed two peaks (during recrudescence and ovulatory phases) coinciding with two periods of follicular development. Adiponectin in the absence of LH, as occur during recrudescence, stimulates androstenedione (A4) synthesis in vitro by up-regulating the insulin receptor (IR). Adiponectin in presence of LH, as occur during pre-ovulatory phase, inhibits A4 synthesis in vitro by down-regulating androgen receptor (AR). Further, the in vitro study showed that adiponectin, in presence of LH, also promotes luteinizing hormone receptor (LH-R) and steroidogenic acute regulatory protein (StAR) level in the ovary, which might help in development of ovulatory follicles. In brief, adiponectin in the absence of LH induces increased A4 synthesis and consequently the condition of delayed ovulation, whereas in the presence LH suppresses both synthesis and action of A4 and thus induces preovulatory condition in the ovary of S. heathi.

Mechanisms of sperm storage in the female reproductive tract: an interspecies comparison

Once semen has been collected for artificial insemination, it is diluted into extenders designed to prevent its deterioration over the period prior to insemination. If the semen is not frozen, the extenders provide protection for a period of a few hours to a few days, depending on species. Despite the efforts of biotechnologists to increase the duration of storage without compromising fertility, there has been relatively little progress for many years. However, comparative studies in diverse species have revealed that long-term sperm storage (up to months and years) within the female reproductive tract is relatively commonplace in reptiles, fishes, birds and amphibians. Even among mammals, some species of bat have evolved mechanisms for storing spermatozoa for several months in the uterus or oviduct so that they can mate in the autumn but postpone fertilization until the spring. We currently know little about the mechanisms that support such long-term sperm storage, mainly because evidence from such species is either absent or fragmentary. Nevertheless, parallels between mammalian and other systems, where spermatozoa are sequestered in sperm storage tubules, suggest that the enclosure of spermatozoa within pockets of epithelial cells may be sufficient to achieve long-term sperm storage. In addition, recent evidence from sperm-storing bats has suggested an alternative, or additional, hypothesis that the modulation of apoptosis within epithelial cells is important in controlling sperm survival. Despite a lack of direct experimental evidence from a wide variety of species, I propose that there is now enough evidence to warrant investigation of these hypotheses.

Sperm storage in the female reproductive tract of Scotophilus heathii: role of androgen

The aim of the present study was to investigate the mechanism of androgen-mediated, prolonged sperm-storage in the female reproductive tract of the bat, Scotophilus heathii. The bat treated in vivo with flutamide, an androgen antagonist, showed loss of spermatozoa at the storage site, utero-tubal junction. Immunocytochemistry and Western blot analysis revealed the presence of increased expression of Bcl2 in the epithelial cell lining of the utero-tubal junction during the period of sperm-storage. Treatment with testosterone in vitro caused a significant dose-dependent increase in expression of the survival factor Bcl2, whereas treatment with flutamide together with testosterone caused a significant decline in Bcl2 in the utero-tubal junction of S. heathii. Together with the expression of Bcl2, the utero-tubal junction also expresses the death signal, caspase3. Expression of caspase3 decreased during January, but increased in February during the late stage of sperm storage. Androgen stimulated Bcl2 synthesis in the utero-tubal junction via the non-genomic MAP kinase signaling pathway. In conclusion, this study suggests that androgen promotes sperm storage in S. heathii by stimulating the survival factor Bcl2 in the utero-tubal junction. It is further hypothesized that a balance between the survival factor, Bcl2, and the death signal, caspase3, determines the duration of sperm storage in S. heathii.

Increased circulating leptin level inhibits folliculogenesis in vespertilionid bat, Scotophilus heathii

The present study investigates the mechanism by which obesity associated rise in leptin and insulin levels cause anovulation in vespertilionid bat, Scotophilus heathii. In the ovary of S. heathii, leptin and insulin receptors were mainly localized in interstitial and thecal cells and in the granulosa cells of primary follicles suggesting its possible role in androgen synthesis and follicular development. Adiposity associated increase in circulating leptin level down regulate ovarian LH-receptor expression and produce characteristic morphological changes in the antral follicles, such as hypertrophy of granulosa cells and a sharp decline in the rate of proliferation as well as apoptosis in the antral follicles. These follicles are referred as unique antral follicle. The in vitro study confirmed the in vivo findings that the high dose of leptin suppresses apoptosis and LH receptors. The present study thus showed that the adiposity associated increase in leptin during the first phase of follicular development inhibits folliculogenesis and simultaneously suppresses both follicular proliferation and apoptosis by reducing sensitivity to gonadotropin stimulation and decreasing circulating LH levels.

Evidence of androgen-dependent sperm storage in female reproductive tract of Scotophilus heathi

The aim of present study was to investigate the role of androgen in sperm storage in the female genital tract of Scotophilus heathi. Spermatozoa were observed in the distal part of oviduct and utero-tubal junction of all the female bats collected between January and early March. Increase in circulating testosterone level coincided with the arrangement of sperm with their head oriented towards the epithelial lining of reproductive tract. Immunocytochemical and Western blot analysis revealed the presence of androgen receptor (AR) only in the distal part of the oviduct and utero-tubal junction, the site of sperm storage. Localization of AR in the cytoplasm of luminal epithelial cells in utero-tubal junction of S. heathi suggests non-genomic action of androgen at the site of sperm storage. Further study showed the presence of intense immunoreactivity of androgen binding protein (ABP) in the glandular epithelial cells of utero-tubal junction. It is hypothesized that androgen creates a unique microenvironment e.g. secretion of ABP within lumen of utero-tubal junction which helps to store spermatozoa for prolonged period in the female genital tract of S. heathi.

Melatonin affects steroidogenesis and delayed ovulation during winter in vespertilionid bat, Scotophilus heathi

The aim of this study was to evaluate the role of melatonin in ovarian activity of Scotophilus heathi particularly in reference to changes in steroidogenesis and steroid receptor expression during the anovulatory period of delayed ovulation. Female S. heathi showed an increased circulating melatonin level during the period of delayed ovulation in winter coinciding with the increased androstenedione (A(4)) levels, body fat and ovarian androgen receptor expression. The circulating melatonin level decreased to a low level after winter during the period of ovulation in March which also coincided with the decreased circulating A(4) levels and body fat. The circulating estrogen (E(2)) showed two peaks corresponding with the two waves of follicular development in November and February. Both the isoforms of progesterone receptor (PR), PR-A and PR-B, remained high throughout the follicular development, but expression of PR-A declined significantly during the ovulation. The treatment with melatonin, both in vitro and in vivo, significantly increased progesterone and A(4), but not the estradiol synthesis by the ovaries of S. heathi. The study further suggested that the increased androgens during winter may be primarily due to the stimulatory effect of melatonin on steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity. Therefore the increased circulating melatonin level in S. heathi during winter delay (inhibits) ovulation through increased androgen synthesis, but suppression of estradiol synthesis.

Melatonin regulates delayed embryonic development in the short-nosed fruit bat, Cynopterus sphinx

The aim of the present study was to evaluate the seasonal variation in serum melatonin levels and their relationship to the changes in the serum progesterone level, ovarian steroidogenesis, and embryonic development during two successive pregnancies of Cynopterus sphinx. Circulating melatonin concentrations showed two peaks; one coincided with the period of low progesterone synthesis and delayed embryonic development, whereas the second peak coincided with regressing corpus luteum. This finding suggests that increased serum melatonin level during November–December may be responsible for delayed embryonic development by suppressing progesterone synthesis. The study showed increased melatonin receptors (MTNR1A and MTNR1B) in the corpus luteum and in the utero–embryonic unit during the period of delayed embryonic development. The in vitro study showed that a high dose of melatonin suppressed progesterone synthesis, whereas a lower dose of melatonin increased progesterone synthesis by the ovary. The effects of melatonin on ovarian steroidogenesis are mediated through changes in the expression of peripheral-type benzodiazepine receptor, P450 side chain cleavage enzyme, and LH receptor proteins. This study further showed a suppressive impact of melatonin on the progesterone receptor (PGR) in the utero–embryonic unit; this effect might contribute to delayed embryonic development in C. sphinx. The results of the present study thus suggest that a high circulating melatonin level has a dual contribution in retarding embryonic development in C. sphinx by impairing progesterone synthesis as well as by inhibiting progesterone action by reducing expression of PGR in the utero–embryonic unit.

Pattern of ovarian protein synthesis and secretion during the reproductive cycle ofScotophilus heathi: synthesis of an albumin-like protein

Ovarian proteins synthesized de novo and secreted in vitro were investigated during different stages of the reproductive cycle of Scotophilus heathi. We found increased ovarian protein synthesis and secretion during the recrudescence and the preovulatory periods, coinciding with two peaks of follicular development and steroidogenesis. The ovaries synthesized protein at a low rate during quiescence and the late phase of delayed ovulation. In vitro analysis using 35 S-methionine incorporation showed increased synthesis of 66 kDa protein during delayed ovulation, but secretion of this protein declined markedly during the preovulatory period. N-terminal sequencing of the 66 kDa protein showed that it shares 70% homology with human serum albumin. Immunocytochemistry indicated that this protein is found primarily in the granulosa cells of the follicles. Whether the increase in albumin production by the ovaries during delayed ovulation is associated with a hyperinsulinemic and hyperandrogenic condition requires further investigation.

Luteal cell steroidogenesis in relation to delayed embryonic development in the Indian short-nosed fruit bat, Cynopterus sphinx

The primary aim of this study was to determine the possible cause of slow or delayed embryonic development in Cynopterus sphinx by investigating morphological and steroidogenic changes in the corpus luteum (CL) and circulating hormone concentrations during two pregnancies of a year. This species showed delayed post-implantational embryonic development during gastrulation of the first pregnancy. Morphological features of the CL showed normal luteinization during both pregnancies. The CL did not change significantly in luteal cell size during the delay period of the first pregnancy as compared with the second pregnancy. The circulating progesterone and 17beta-estradiol concentrations were significantly lower during the period of delayed embryonic development as compared with the same stage of embryonic development during the second pregnancy. We also showed a marked decline in the activity of 3beta-hydroxysteroid dehydrogenase, P450 side chain cleavage enzyme, and steroidogenic acute regulatory peptide in the CL during the delay period. This may cause low circulating progesterone and estradiol synthesis and consequently delay embryonic development. What causes the decrease in steroidogenic factors in the CL during the period of delayed development in C. sphinx is under investigation.

Relationship between delayed embryonic development and metabolic factors and fat deposition in fruit bat Cynopterus sphinx

The present study was undertaken in the fruit bat Cynopterus sphinx, which breeds twice in quick succession at Varanasi, India. Its gestation period varies significantly in the two successive pregnancies of the year owing to delayed embryonic development during the first (winter) pregnancy. The primary aim of the present study was to determine the role of metabolic factors in delayed embryonic development in the fruit bat C. sphinx. Variation in bodyweight, fat deposition, oxygen (O2) consumption rate, basal metabolic rate (BMR), body temperature (Tb) and hepatic succinate dehydrogenase (SDH) activity, along with circulating levels of thyroid hormones (tri-iodothyronine and thyroxine), were examined as metabolic factors during the two successive pregnancies in C. sphinx. The increase in bodyweight observed in November was due to accumulation of white adipose tissue in the posterior abdominal region. A significant decline in O2 consumption rate, BMR, Tb and SDH activity was found in early winter in November–December, which coincides closely with the period of fat accumulation and with the period of delayed embryonic development in C. sphinx. A significantly higher O2 consumption rate, BMR, Tb and SDH activity was noted during the second pregnancy in, when embryonic development was relatively faster. Thyroid hormone levels were high during the period of embryonic delay compared with levels during the remaining months. The results of the present study suggest that the delayed embryonic development in C. sphinx during early winter may be due to a low O2 consumption rate, BMR, Tb and SDH activity in November–December. The energy saved by suppressing embryonic development in this species may be advantageous for fat accumulation. Increased thyroid hormone levels during the early winter period might facilitate fat accumulation in C. sphinx.

Adiposity associated rise in leptin impairs ovarian activity during winter dormancy in Vespertilionid bat, Scotophilus heathi

The aim of the study was to evaluate the seasonal variation in serum leptin levels in a natural population of the female bat,Scotophilus heathiand their relationship to the changes in the body mass, serum insulin level, and ovarian activity. Circulating leptin level varied significantly over the season and correlated positively with the changes in body mass, and circulating insulin and androstenedione (A4) levels. Circulating leptin concentrations showed two peaks; one coincides with the maximum fat accumulation prior to winter dormancy, whereas the second shorter peak coincides with late pregnancy. Thein vivostudy inS. heathishowed that the increased circulating leptin level during winter dormancy coincides with the decreased expression of ovarian steroidogenic acute regulatory (StAR) protein, and low circulating estradiol (E2) level. At the same time, increased circulating leptin level coincides with increased expression of ovarian insulin receptor and high circulating A4 level. The low circulating leptin level during preovulatory period coincides with the increase in StAR protein but decrease in insulin receptor protein. Thein vitrostudy confirmed thein vivoobservations of inhibitory effect of leptin on LH induced StAR expression and E2production, whereas the stimulatory effect of leptin (high dose) on LH induced expression of insulin receptor protein and A4 production. However, pharmacological dose of leptin produced inhibitory effect on the expression of insulin receptor protein. The results of the present study thus suggest that high circulating leptin level during winter dormancy promotes adiposity and impairs ovarian activity by suppressing StAR-mediated E2production as well as by enhancing insulin receptor-mediated A4 synthesis thereby contributing anovulatory condition of delayed ovulation inS. heathi.

Evidence of increased endometrial vascular permeability at the time of implantation in the short-nosed fruit bat, Cyanopterus sphinx

Early embryonic development and implantation were studied in tropical short-nosed fruit bat Cyanopterus sphinx. We report preimplantation development and embryo implantation. Different stages of cleavage were observed in embryo by direct microscopic examination of fresh embryos after retrieving them either from the oviduct or the uterus at different days, up to the day of implantation. Generally, the embryos enter the uterus at the 8-cell stage. Embryonic development continued without any delay and blastocyst were formed showing attachment to the uterine epithelium at the mesometrial side of the uterus. A distinct blue band was formed in the uterus. The site of blastocyst attachment was visualized as a blue band following intravenous injection of pontamine blue. Implantation occurred 9+/-0.7 days after mating. This study reports that bat embryonic development can be studied like other laboratory animals and that this bat shows blue dye reaction, indicating the site and exact time of implantation. This blue dye reaction can be used to accurately find post-implantational delay. We prove conclusively that this species of tropical bat does not have any type of embryonic diapause.

Ovulation induction by antiestrogens in an Indian tropical vespertillionid bat, Scotophilus heathi

The ovulation induction property of ICI 182,780 a pure antiestrogen and enclomiphene citrate (ENC) was carried out in Scotophilus heathi, an Indian tropical vespertillionid bat, during December to February i.e., preovulatory period. This bat ovulates two ova naturally and shows ovulatory asynchrony. The study showed that 100 ìg of ENC followed by 10 IU hCG resulted in significantly lower number of ovulation. Whereas, the pure antiestrogen ICI 182,780 at a dose of 100 ìg followed by 10 IU hCG resulted in ovulation induction (4.2 +/- 0.4), which is significantly different in comparison to other groups. This is possibly the first report of ovulation induction using this pure antiestrogen i.e., ICI 182,780 in any bat as well as in any animal model that exhibits temporary anovulation similar to polycystic ovary disease (PCOD). This antiestrogen may be useful to induce ovulation in PCOD patients.

Hormonal induction of ovulation stimulates atresia of antral follicles in a vespertilionid bat, Scotophilus heathi

Scotophilus heathi is a seasonally monoestrous subtropical vespertilionid bat found at Varanasi, India. Although the antral follicles remain present in the ovaries of S. heathi from November till March, ovulation is delayed in this species until early March. In order to understand the mechanism of ovulation suppression during this period of delayed ovulation, the effects of human chorionic gonadotropin (hCG), pregnant mare's serum gonadotropin (PMSG), follicle stimulating hormone (FSH) and gonadotropin releasing hormone agonist (GnRH agonist) on ovarian morphology and steroid concentration were investigated. Hormonal treatments were given as a single i.p. dose 24 h after capture. The bats were sacrificed 48 h after the injection. Treatment with hCG, PMSG, FSH and GnRH agonist failed to induce ovulation in S. heathi, although these hormones produced a high degree of ovarian stimulation. The administration of hCG and PMSG induced ovarian enlargement, intense hyperemia, marked changes in the interstitial cells (ICs), development of several antral follicles and a varying degree of abnormalities in the oocytes of most of the antral follicles. In the bats treated with hCG, PMSG and GnRH agonist, androstenedione concentration increased significantly to extraordinarily high levels, whereas estradiol concentration decreased. Administration of FSH caused regression of ICs and pyknosis of granulosa cells in the majority of antral follicles. FSH did not enhance androstenedione concentration. The results of the present study suggest that the failure of hormonal treatments to induce ovulation during the period of delayed ovulation might be due to a seasonal desensitization of ovarian follicles in S. heathi. The hormonal treatment instead stimulated the ICs to produce a high level of androstenedione resulting in atretic changes of the antral follicles.

Histochemical localization of enzymes and lipids in the ovary of a vespertilionid bat, Scotophilus heathi, during the reproductive cycle

The present study describes seasonal changes in delta5 3beta hydroxysteroid dehydrogenase (3beta-HSD), glusose-6 phosphates dehydrogenase (G-6-PD), and lipids in the ovary of a vespertilionid bat, Scotophilus heathi. Total lipids and 3beta-HSD activity are restricted to thecal and interstitial cells of the ovary. The total lipids, 3beta-HSD, and G-6-PD significantly increase during recrudescence, and remain high during winter dormancy and breeding as compared to the other reproductive phases. High incidence of lipids and enzyme activity in interstitial cells during the breeding period and at the time of ovulation clearly suggests that these cells are actively involved in steroidogenesis. A decline in enzymes and lipid activity during winter dormancy, which correlates with the declining levels of steroidogenesis, might be the factors responsible for prolonged survival of the Graafian follicle in the ovary of S. heathi.

Relationship between corticosterone and body weight, androstenedione and insulin during the period of delayed ovulation in a vespertilionid bat, Scotophilus heathi

The aim of the present study was to evaluate the relationship between corticosterone, body weight, insulin and androstenedione in order to understand the role of adrenal in contributing hyperandrogenism during delayed ovulation in S. heathi. The circulating corticosterone concentration in female S. heathi showed significant seasonal variation. The peak corticosterone concentration observed during August-September coincides with increased feeding activities in S. heathi. The present study noted a seasonal variation in relationship of corticosterone with insulin and androstenedione in S. heathi. An inverse relationship of corticosterone with insulin and androstenedione was found during August to December, but not during January to May. A seasonal variation in the effect of adrenocorticotropic hormone (ACTH) on adrenal corticosterone production in vitro was observed during reproductive cycle. Corticosterone production in vitro by adrenal declined significantly as compared to the control during quiescence in September. The finding suggests that adrenal attained the peak responsiveness to ACTH during September. ACTH significantly enhanced the androstenedione production by the adrenal in vitro during December, when the circulating androstenedione was also high in S. heathi. This suggests that the adrenal may also contribute to hyperandrogenism during the period of delayed ovulation in S. heathi. Further studies are required to reveal the unique pattern of seasonal relationship between corticosterone, insulin and androstenedione in S. heathi.

Seasonal adiposity and delayed ovulation in a vespertilionid bat, Scotophilus heathi: role of tumor necrosis factor-alpha

The aim of this article was to evaluate the physiological significance of tumor necrosis factor-alpha (TNF-alpha) in seasonal accumulation of adipose tissue, hyperinsulinemia, and anovulation in Scotophilus heathi. The result showed seasonal variations in the circulating TNF-alpha level. A higher level of circulating TNF-alpha was observed during quiescence and recrudescence, whereas a lower level of TNF-alpha was observed during winter dormancy and the preovulatory period. An increased circulating TNF-alpha level coincided closely with accumulation of adipose tissue and hyperinsulinemia. Immunocytochemical localization of TNF-alpha in the ovary showed immunoreactivity mainly in the oocytes and theca-interstitial cells. The oocytes of small and medium-sized follicles showed strong TNF-alpha immunostaining, whereas weak immunoreactivity was observed in the large antral follicles. The atretic follicles showed mild TNF-alpha immunostaining. TNF-alpha immunoreactivity in the ovary was slightly higher during the quiescence and preovulatory periods compared with the periods of recrudescence and winter dormancy. TNF-alpha alone significantly increased androstenedione and estradiol production by the ovary in vitro but did not augment the luteinizing hormone (LH)-induced androstenedione production. However, TNF-alpha did augment LH-induced estradiol production. The results of this study suggest the involvement of TNF-alpha in the interaction among adipose tissue accumulation, insulin resistance, and ovarian activity in S. heathi.

The corpus luteum and interstitial tissue in a marsupial, the brushtail possum (Trichosurus vulpecula)

The Australian brushtail possum (Trichosurus vulpecula) is a nocturnal, arboreal marsupial. It has become a pest of significant ecological and economic importance in New Zealand, and thus a renewed interest in understanding the reproductive biology of this species has been generated. The corpus luteum (CL) in possums is a largely autonomous gland in that it does not rely on pituitary hormones to function and is not responsive to luteolytic agents for its demise. Its importance in regulating the oestrous cycle and pregnancy has been established; however, little is known regarding the mechanisms involved in its function. Interstitial tissue (IT) is a prominent feature found throughout the ovarian stroma, yet little is known regarding the origin or function of these cells. Based on histological examinations, our data support the hypothesis that interstitial tissue arises from a unique cell type called medullary cords during early ovarian development. Using possum-specific probes for proteins involved in steroidogenesis, receptors for pituitary hormones and members of the TGF-beta superfamily we have initiated studies investigating the expression of genes that may be important in the function and regulation of the CL and interstitial tissue. Results show that both tissues are steroidogenic and that both express receptors for prolactin and luteinising hormone (LH). Collectively these findings suggest that prolactin and LH may be important in the regulation of steroidogenesis in the CL and interstitial tissue in possums.

Changes of ovarian interstitial cell hormone receptors and behavior of resident mesenchymal cells in developing and adult rats with steroid-induced sterility

In the present paper, we report that injection of testosterone propionate (500 microg) during the critical window of rat development (postnatal day 5) induces temporary appearance of aged interstitial cells in developing ovaries (days 7 and 10). Aged interstitial cells showed large size (> or = 12 microm), enhanced androgen receptor (AR) and low estrogen (ER) and luteinizing hormone receptor (LHR) expression. Although normal mature interstitial cells (large size and strong ER and LHR expression) appeared later (day 14), and ovaries of androgenized rats were similar to normal ovaries between days 14 and 35, ovaries of adult androgenized females showed only aged and no mature interstitial cells. Androgenization on day 10 caused the development of aged interstitial cells on day 14, but adult ovaries were normal. Long lasting postnatal estrogenization (estradiol dipropionate for four postnatal weeks) caused in developing and adult ovaries a lack of interstitial cell development beyond the immature state. Immature interstitial cells were characterized by a small size (< or = 7 microm) and a lack of AR, ER and LHR expression. Because the critical window for steroid-induced sterility coincides with the termination of immune adaptation, we also investigated distribution of mesenchymal cells (Thy-1 mast cells and pericytes, ED1 monocyte-derived cells, CD8 T cells, and cells expressing OX-62 of dendritic cells) in developing and adult ovaries. Developing ovaries of normal, androgenized and estrogenized females were populated by similar mesenchymal cells, regardless of differences in the state of differentiation of interstitial cells. However, mesenchymal cells in adult ovaries showed distinct behavior. In normal adult ovaries, differentiation of mature interstitial cells was accompanied by differentiation of mesenchymal cells. Aged interstitial cells in ovaries of androgenized rats showed precipitous degeneration of resident mesenchymal cells. Immature interstitial cells in ovaries of estrogenized rats showed a lack of differentiation of resident mesenchymal cells. These observations indicate that an alteration of interstitial cell differentiation during immune adaptation toward the aged phenotype results in precipitous degeneration of resident mesenchymal cells and premature aging of ovaries in adult rats, and alteration toward immature phenotype results in a lack of differentiation of mesenchymal cells and permanent immaturity of ovaries in adult females.

Seasonal changes in circulating steroid concentration and their correlation with the ovarian activity in the female Indian sheath-tailed bat, Taphozous longimanus

The relationship between ovarian activity and circulating steroid concentration was studied in the female sheath-tailed bat, Taphozous longimanus. T. longimanus breeds twice in rapid succession during the year at Varanasi, India. Ovarian recrudescence was observed during September, and antral follicles were first observed during the month of October. Circulating androstenedione concentration showed an increase beginning in October, reaching a peak in December. This increase in androstenedione concentration correlated with the period of heavy accumulation of adipose tissue and increase in body mass. Antral follicles grow slowly during the period of high circulating androstenedione concentration from October to December. There was a sharp decline in androstenedione concentration during January. Simultaneously with the decline in androstenedione concentration, a sharp increase in size of the antral follicle and circulating estradiol concentration was noticed. Soon thereafter, one of the follicles ruptures, followed by fertilization and the commencement of the first pregnancy. During the second pregnancy, antral follicles first appeared during late pregnancy in March in the contralateral ovary that lacked the corpus luteum. One follicle developed rapidly and quickly attained a preovulatory stage in April. This is reflected in a sharp increase in estradiol concentration during this period. Ovulation was observed immediately following the first pregnancy in May. During this period, androstenedione concentration remained low. The results of the present study suggest that high androstenedione concentration during October to December (winter dormancy) may be responsible for slow follicular development and delays ovulation in T. longimanus. It is further hypothesized that the geographical variation in reproductive pattern of T. longimanus could be due to variation in the duration of fat storage and associated changes in the androstenedione concentration.

Proliferative activity of follicles and serum steroid concentration in Scotophilus heathi (vespertilionid bat) during periods of delayed ovulation

Follicular kinetics were studied using immunocytochemical localization of proliferating cell nuclear antigen (PCNA) and changes in circulating steroid concentrations to investigate the cause of prolonged survival of Graafian follicles and delayed ovulation in the vespertilionid bat Scotophilus heathi. PCNA immunoreactivity was limited to the granulosa cells and varied with stage of follicular development and reproductive phase. Two waves of follicular growth appear to be initiated in October and February. The first wave resulted in the appearance of some late antral follicles in November. These antral follicles grew slowly and differed from typical mammalian Graafian follicles, as the cells of their cumulus oophoricus were large and hypertrophied. The second wave of follicular development resulted in fresh recruitment and selection of dominant follicles in February. The steroid-hormone profile showed an unusually high concentration of circulating androstenedione from October to December. The estradiol concentration showed two peaks coinciding with two peaks of PCNA immunoreactivity. The results show that the unusually high androstenedione concentration might be responsible for the development of non-ovulatory Graafian follicles with hypertrophied granulosa cells, which survive for a prolonged period. The decline in androstenedione concentration allows the development of ovulatory follicles in S. heathi.

Mechanism of delayed ovulation in a vespertilionid bat, scotophilus heathi: role of gonadotropin, insulin, and insulin-like growth factor-1

The aim of this study was to evaluate the effects of luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin, and insulin-like growth factor-1 (IGF-1) on ovarian androstenedione synthesis to understand the mechanism responsible for delayed ovulation in Scotophilus heathi. We found that LH stimulated a dose-dependent increase in androstenedione synthesis by the ovary in vitro. This study also showed a clear seasonal variation in the ability of the ovary to produce androstenedione in vitro in response to LH and FSH stimulation. In response to LH and FSH, maximum quantities of androstenedione were produced during recrudescence in November. The same doses of gonadotropins during the preovulatory period in February stimulated comparatively low androstenedione secretion by the ovary. On the basis of these data, we suggest that in S. heathi, ovarian responsiveness to LH and FSH peaks during recrudescence. This study also showed a seasonal variation in the effects of insulin and IGF-1 on ovarian androstenedione production in vitro. Peak ovarian responsiveness to insulin and IGF-1 was observed during quiescence in September. It is hypothesized that increased insulin/IGF-1 sensitivity during September may be responsible for increased responsiveness to LH. Increased LH release, if coincident with the period of enhanced ovarian responsiveness to LH, may result in the excessive androstenedione production responsible for delayed ovulation in S. heathi.

Induction of ovulation by clomiphene citrate in the Indian vespertilionid bat, Scotophilus heathi

The ovulation induction property of clomiphene citrate (CC) and human chorionic gonadotropin (hCG) was studied in Scotophilius heathi, an Indian tropical vespertilionid bat, during the period of delayed ovulation between December to early January. The results of the study showed that 10 microg of CC alone was ineffective to induce ovulation, whereas 100 microg CC and 10 IU hCG alone induced ovulation. A significant (P < 0.01) increase in the ovulation rate was observed when 10 microg CC followed by 10 IU hCG, compared to 10 IU hCG and 100 microg CC alone groups. Finally, CC at a 100 microg dose, followed by 10 IU hCG, produced superovulation (14.00 +/- 0. 70), which is significantly different in comparison to all other groups. This is the first report of ovulation induced by CC in the Indian tropical bat as well as in any animal model that exhibits temporary anovulation similar to polycystic ovary syndrome (PCOD) during the normal physiology of reproduction.

Studies on the origin of ovarian interstitial tissue and the incidence of endometrial hyperplasia in domestic and feral cats

Ovarian interstitial cells (OICs) are a common feature of mammalian gonads but little is understood concerning their origin or functional significance. This study investigated the development and steroidogenic potential of OIC in feral and colony-reared feline queens. Reproductive tracts, collected from a total of 50 female colony and feral cats, were fixed and analyzed by morphometry. Ovarian sections were also immuno-stained for the expression of the steroidogenic enzymes 17alpha-hydroxylase/17,20 lyase cytochrome P450 (P450c17), 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD), and aromatase. These findings were related to serum estradiol and testosterone concentrations and to the degree of existing cystic endometrial hyperplasia (CEH). Feral cats had three times as many OICs as colony-reared queens (2713 +/- 855 vs 744 +/- 494 cells/mm(2), P < 0.01). These cells were lipid laden and expressed both P450c17 and 3beta-HSD at levels that were higher than those seen in the theca interna of adjacent follicles. Aromatase expression was undetectable. The pattern of enzyme expression was consistent with development of interstitial tissue from atretic follicles and the potential for continued steroid secretion during the anestrum. The incidence of CEH was higher in older (>5 years old; 88.2%) than in younger (2-4 years; 30%) colony queens (P < 0. 01), whereas no such disease was evident in any of the feral cats. Estradiol levels were higher in colony-reared than in feral cats, but testosterone levels were not different. These data are consistent with the transformation of the theca interna of atretic follicles in cats into OICs that retain a similar, or even enhanced, steroidogenic phenotype. Colony-reared cats exhibit a predisposition to CEH compared with feral queens that is associated with elevated serum estradiol concentrations. Whether or not OICs somehow prevent the development of uterine disease or otherwise reflect a gonadal response to reduced negative feedback on the hypothalamic-pituitary axis remains to be determined.

Possibility of inhibin as a regulator of androstenedione production by the ovary during the period of delayed ovulation in a vespertilionid bat, Scotophilus heathi

The aim of the present study was to evaluate the role of inhibin in regulating androstenedione production by the ovary of Scotophilus heathi during the period of delayed ovulation. Inhibin alone increased the androstenedione synthesis in vitro by the ovary during all reproductive phases, but augmented the hCG induced androstenedione production only during November. The follicles produced significantly higher androstenedione as compared to the stromal or granulosa cell in response to both hCG and inhibin. However, inhibin augmented hCG stimulated androstenedione in the stromal cell only. Immunoreactivity of inhibin subtype alpha, betaA and betaB were mainly localized in the thecal and interstitial cell from September to November and then declined during the preovulatory period. However, in granulosa cells weak to moderate immunoreactivity of all inhibin subtype was observed during these phases. These results indicate the possible role of inhibin in regulating androstenedione synthesis by the ovary and thus. may be indirectly responsible for causing delayed ovulation in S. heathi.

The relationship between testicular activity, accessory sex glands, and circulating steroid concentration during the reproductive cycle in a male Indian vespertilionid bat,Scotophilus heathi

The relationship between spermatogenesis, accessory sex glands, Leydig cell activity, and circulating concentrations of testosterone and androstenedione in male Scotophilus heathi, the greater yellow bat, was studied. Scotophilus heathi accumulated fat prior to winter dormancy at Varanasi, India. Spermatogenesis was seasonal and extended over the period November to March, with the testes becoming quiescent during winter. Monthly changes in testis and accessory sex gland masses showed two peaks, in November and January. Accessory gland secretory activity and fructose concentration showed only one peak, during January and February, which coincided with the mating period. The mass in the epididymides and their histological changes reflect the influence of testicular spermatogenesis. However, sperm were found in the cauda epididymidis during the spermatogenically quiescent period of winter dormancy. The Leydig cells showed intense side chain cleavage (SCC) enzyme activity from August to December. In late January and February, males had smaller Leydig cells and low SCC activity. Monthly changes in serum testosterone concentration included two peaks in November and January, coinciding with peak spermatogenic activity, whereas androstenedione showed only one peak, an unusually high concentration in November. The circulating serum androstenedione concentration may be responsible for the unique reproductive activity noted in this bat.

Adiposity and androstenedione production in relation to delayed ovulation in the Indian bat, Scotophilus heathi

Observations on body weight, circulating androstenedione concentrations and morphology of ovarian stroma were made in Scotophilus heathi during the period of delayed ovulation to make a comparison with polycystic ovarian syndrome in women. Body weight of bats increased from a level of 31.00 +/- 0.30 g in August and reached a peak of 45.00 +/- 0.46 g in November. This increase in body weight was due to accumulation of adipose tissue. The body weight declined gradually from December onwards and finally reached a basal level in March. The circulating androstenedione concentration showed a gradual increase from 36.80 +/- 15.54 ng/ml in August and reached a peak level of 220.50 +/- 50.10 ng/ml in November. Androstenedione concentration reached the lowest level in the March, just before ovulation. Morphological study showed extensive distribution of luteinized stromal cells or interstitial cells (ICs). Morphometric study showed that during the period of ovulatory delay, more than 75% area of the ovary was occupied by the ICs. Hyperandrogenism, anovulation, obesity (fat deposition) and stromal hyperthecosis present during delayed ovulation in S. heathi may serve as an experimental model for some aspects of the polycystic ovarian condition in women.

Glycogen accumulation in the ovarian follicle of Indian vespertilionid bat, Scotophilus heathi during the period of delayed ovulation

Massive accumulation of glycogen in the follicles of Scotophilus heathi during the period of delayed ovulation was noticed. The follicles which survive for prolonged periods are morphologically specialized. The accumulation of glycogen was noticed in the granulosa cells. The egg cytoplasm, thecal cells and interstitial cells were almost devoid of glycogen. The first sign of a glycogen deposit in the ovary was noticed during the recrudescence phase (October) in late pre-antral follicles. Most of the morphologically healthy late pre-antral and antral follicles showed a positive reaction with PAS and Best carmine from October to early February. Morphologically atretic follicles showed only a mild glycogen accumulation. Little or no glycogen accumulation was noticed in some of the healthy late-antral follicles before ovulation during late February and early March. HCG-induced antral follicles during quiescence also did not show any accumulation of glycogen. The study suggests that glycogen laden follicles are not suitable for ovulation and may be the reason for the occurrence of delayed ovulation in S. heathi.