Browsing by Author "A. Krishna"

Now showing 1 - 20 of 40

A possible direct action of oxytocin on spermatogenesis and steroidogenesis in pre-pubertal mouse
(Blackwell Publishing Ltd, 2018) S. Anjum; A. Anuradha; A. Krishna
The aim of this study was to evaluate the effects of in vivo and in vitro treatments of oxytocin (OT) on the testis of pre-pubertal mice. The OT treatment produced significant changes in the spermatogenic and steroidogenic activity by increasing expression of OT-receptor in the testis of pre-pubertal mice. Treatment with OT showed increased proliferation of germ cells as indicated by increased number of spermatocytes and round spermatids. Dose-dependent increase in expression of PCNA, Bcl-2 and AR proteins was observed in the testis of OT-treated mice as compared with the control and further supports the role of OT in germ cell proliferation and survival. The pre-pubertal mice treated with increasing dose of OT showed significant increase in testosterone synthesis due to dose-dependent stimulatory effects on 3β-HSD activity and increased expression of STAR, LH-receptor (LH-R) and gonadotrophin-releasing hormone receptor (GnRH-R) proteins in the testis. The in vitro study has confirmed in vivo finding showing direct action of OT on testicular steroidogenesis. Thus, OT stimulates testicular spermatogenesis and steroidogenesis by directly acting on testis in mice. © 2018 Blackwell Verlag GmbH
Adiposity and androstenedione production in relation to delayed ovulation in the Indian bat, Scotophilus heathi
(1997) Abhilasha; A. Krishna
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.
Antagonistic effect of progesterone towards estradiol dipropionate-induced changes in glycogen content in uterus and vagina of P-mice
(Birkhäuser-Verlag, 1985) G. Tripathi; A. Krishna
Estradiol dipropionate induces an increase (3-fold) in the uterine glycogen content and a decrease (4-fold) in the vaginal glycogen content of Parkes (P) mice. Progesterone antagonizes this estradiol dipropionate-induced response in both the uterine and vaginal tissue. The degree of this antagonism is more pronounced in the uterus than in the vagina. © 1985 Birkhäuser Verlag.
Changes in circulating insulin and corticosterone concentrations during different reproductive phases and their relationships to body weight and androstenedione concentration of male Scotophilus heathi
(John Wiley and Sons Inc., 1998) A. Krishna; Kavita Singh; Jayashree Doval; D. Chanda
The aim of the present study was to determine the serum levels of insulin and corticosterone during different reproductive stages in a natural population of the male bat, Scotophilus heathi and their relationship to body weight and androstenedione level. Changes in body weight were marked by weight gain before winter dormancy and weight loss during winter dormancy. Circulating insulin level varied significantly over the season and correlated positively with changes in body weight and androstenedione level. Circulating corticosterone level also varied significantly over the season but correlated negatively with changes in body weight and androstenedione level. High corticosterone level during August coincided with a period of increased feeding activity in this species. The results suggest that insulin may act as an anabolic agent to promote fat deposition and corticosterone exerts a predominantly fat-mobilizing influence. A high insulin level prior to winter dormancy may be an important factor responsible for inducing high androstenedione concentration shown in Scotophilus heathi.
Changes in nitric oxide (NO) synthase isoforms and NO in the ovary of Heteropneustes fossilis (Bloch.) during the reproductive cycle
(2008) Vrajesh Tripathi; A. Krishna
The purpose of the study was to demonstrate the presence of nitric oxide (NO) synthase (NOS) isoforms (neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS)) and the role of NO in the ovary of Heteropneustes fossilis. In one half of the ovary collected during different reproductive stages, NOS isoforms were localized immunohistochemically in paraffin sections whereas the other half was processed for NOS and NO quantification using western blot followed by densitometry and nitrate/nitrite assay respectively. The role of NO on oocyte maturation was studied by examining the effect of NO donor (sodium nitroprusside; SNP) and NOS inhibitor (Nω-nitro-L-arginine methyl ester) on 17α,200-dihydroxy-4-pregnen-3-one (17α,20β-P)-induced germinal vesicle breakdown (GVBD) in the cultured oocyte collected during prespawning phase. NOS immunostaining was predominantly localized in previtellogenic follicles, with nNOS detected in the nucleus and cytoplasm of oocytes whereas iNOS and eNOS localized in granulosa, theca cells, and cytoplasm of oocytes. The NOS expression was higher in previtellogenic phase when compared with vitellogenic phase, The nitrate/nitrite concentrations in ovary showed gradual increase from recrudescence (4.9± 0.19 nM/mg protein) to late previtellogenic phase (7.02 ± 0.53 nM/mg protein), but showed a sharp decline during the vitellogenic phase (0.41 ± 0.053 nM/mg protein). Serum and ovarian nitrate/nitrite level showed a close association during the reproductive cycle. The results showed an increase in NOS activity and nitrate/nitrite concentrations as the follicle grow suggesting involvement of NO in follicular development. SNP significantly inhibited 17α,200-P-induced GVBD in fish oocytes. Thus, it is concluded that the fish ovary possesses NOS/NO system and a possibility that NO has a role in follicular development and regulation of oocyte maturation in fish, H. fossilis. © 2008 Society for Endocrinology.
Changes in serum leptin, insulin, androstenedione and luteinizing hormone during ovarian cycle in the bat, Taphozous longimanus
(2008) U.P. Singh; A. Krishna; Kunwar P. Bhatnagar
Detailed reproductive pattern and associated endocrine characteristics have been documented in only a few species of order Chiroptera. The aim of the present study was to examine the changes in body weight, serum insulin, leptin, androstenedione and luteinizing hormone (LH) concentrations during annual ovarian cycle in the sheath-tailed bat, Taphozous longimanus. Bats were sampled over three years. Leptin, a satiety hormone produced primarily by adipose tissue, provides information to feeding center of the brain about nutritional status, fat mass, appetite and energy expenditure. The circulating concentration of leptin begins to increase from October and attains a peak in December. The peak serum leptin concentration coincides with body weight in November before winter dormancy in December. The serum leptin levels dissociate from body weight during December. The other peaks of serum leptin levels coincide with late stages of the two successive pregnancies. The serum insulin concentration begins to increase from September and attains a peak during December. The insulin concentration remains low from January to August. The circulating androstenedione concentration begins to increase in October, reaching a peak in December. This increase in androstenedione concentration correlated with the period of heavy accumulation of abdominal fat and increase in body weight. There was a sharp decline in androstenedione concentration and body weight in January. The serum LH shows peaks, in November, coinciding with the peaked body weight, the other peaks in January and May, coinciding with ovulation for the two successive pregnancies. The high leptin and insulin levels might be responsible for the maintenance of reproductive response and gonadal function during adverse environmental condition in the winter, while high androstenedione, and associated body weight along with LH might be responsible for maintaining basal gonadal function. We conclude that high leptin, androstenedione and insulin serve, as signal for the reproductive functions in that sufficient body fat are available to meet the caloric demands and maintain normal function during adverse winter conditions. © 2008 Akadémiai Kiadó.
Changes in the mast cell number and degranulation pattern during periovulatory period and after blocking gonadotrophin surge in mice ovarian compartments.
(1994) A. Krishna; K. Jaiswal
Mast cell in the ovary of cyclic mice were observed in the ovarian medulla, hilum and bursa, but not in the cortex. A significant increase in the degranulation of mast cells was observed in the hilum and bursa but not in the medulla following the gonadotrophin (Gn) surge as compared with before the surge at proestrus. The results of pentobarbital treatment at proestrus imply the significant role played by estradiol 17-beta (E2) in inducing mast cells migration and degranulation, specially in the medullary, cortical and bursal region of the ovary. The results indicate differential regulation of mast cells number and degranulation in different ovarian compartments of mice.
Compartmentalized mast cell degranulations in the ovarian hilum, fat pad, bursa and blood vessel regions of the cyclic hamster: Relationships to ovarian histamine and blood flow
(1991) A. Krishna; P.F. Terranova
Ovaries from hamsters on each day of the oestrous cycle at 09.00 h were observed for the number of mast cells, the pattern of mast cell degranulation. histamine concentration and blood flow. On day 4 (pro-oestrus), ovaries were also observed at 9.00, 15.00and21.00 h. Mast cell degranulation was evaluated by 3 criteria: (1) no degranulation = less than 5 granules dispersed from the cell; (2) moderate degranulation = 5 or more granules dispersed but less than 15, and (3) extensive degranulation = 15 or more granules released. Blood flow was determined using radio-active microspheres in anaesthetized animals. Mast cells were observed in fat pad (beyond 2 mm of the bursal mesothelium). bursal (within 2 mm of the bursal mesothelium). hilum and near ovarian blood vessels (these 4 regions are collectively called the ovarian complex). The distribution of ovarian mast cells was not uniform. Most mast cells were near ovarian blood vessels (42.2%) and in the fat pad (37.2%). A moderate number of eel Is were in the bursal wall (20%) and only a few cells were observed in the hilum (0.64%). Mast cell number remained unchanged on days 1-4 of the cycle in each ovarian compartment. However, summation of the number of mast cells m the entire ovarian complex revealed a significant decline in number at 15.00 hon pro-oes-trus. Alterations in mast cell degranulation were primarily restricted to 2 periods of the cycle (pro-oestrus and di-oes-trus). An increase in moderate hut not extensive degranulation was observed in only the fat pad and bursa on day 2 when compared with day I values. In most ovarian compartments on pro-oestrus, degranulation was higher than on any other day of the cycle. At 15.00 h on pro-oestrus, extensive degranulation in bursa. fat pad and blood vessel regions (but not hilum) coincided with an increase in ovarian histamine and decline in number of mast cells; ovarian blood flow also increased at that time but remained unchanged the remainder of the cycle. The results indicate that significant mast cell degranulation could occur on days other than pro-oestrus, although on pro-oestrus mast cell degranulation was increased, that not all ovarian compartments exhibit the same pattern of mast cell degranulation and that changes in ovarian blood may correlate with increased histamine and mast cell degranulation on pro-oestrus but not necessarily on other days of the cycle. © 1991 S. Karger AG, Basel.
Die Regio olfactoria der Fledermaus Scotophilus heathi. Licht- und elektronenmikroskopische Studien
(1992) A.S. Mendoza; A. Krishna; J. Endler; W. Kühnel
The present investigation reports light and electron microscopical aspects of the main olfactory epithelium (MOE) of the insectivorous bat Scotophilus heathi. Serial frontal sections of the nose and associated structures reveal: 1) that the MOE is located on most of the ethmoturbinals and on the proximal upper portion of the nasal septum; and 2) that the vomeronasal organ is absent in this species. The ultrastructure of the MOE of Scotophilus heathi is similar to that observed in other vertebrates. Moreover, we did not observe significant morphological differences between the MOE of male and female animals. Nevertheless, the supranuclear region of the supporting cells of males and females shows a different amount and distribution of “lysosome-like” cell organelles at the two times of the year investigated. © 1992, Gustav Fischer Verlag Jena GmbH. All rights reserved.
Differential rates of fetal growth in two successive pregnancies in the emballonurid bat, Taphozous longimanus hardwicke
(1982) A. Krishna; C.J. Dominic
[No abstract available]
Effects of cimetidine, H2 receptor antagonist, on follicular and luteal development in the mice.
(1994) K. Jaiswal; A. Krishna
The effects of various doses, duration and frequency of cimetidine treatment on vaginal cycle, ovulation, ovarian histology and follicular kinetics were investigated. In addition, studies were performed to assess the reversibility in ovarian functions following withdrawal of cimetidine treatment. A statistically significant (P < 0.05) decline in ovarian and uterine weights, but not in body and adrenal weights, were observed in females treated with cimetidine four times daily for long-term as compared with the controls. Ovarian and uterine weights recovered to pretreatment levels following withdrawal of the treatment. Cimetidine treatment caused irregularities in the reproductive cyclicity of mice. Cimetidine treatment causes adverse effect on ovarian function depending on the time, duration and frequency of treatment. Treatment for only one day at proestrus induced significant (P < 0.05) decline in ovulatory efficiency. However, administration of cimetidine, four times daily, for either 6 or 14 days caused ovarian dysfunction. The treatment depressed the number of healthy preantral and antral follicles as well as number of healthy corpus luteum (CL) in the ovary. Absence of healthy CL, presence of several atretic late antral follicles and reproductive acyclicity provide evidence for the failure of ovulation in mice treated with cimetidine four times per day for 14 days. Moreover, when cimetidine was administered twice daily, the ovaries also showed newly formed CL. The results, thus, suggest that the effects of cimetidine on ovulation are dependent on dose, duration and frequency of treatment. Blockage of ovulation in long-term cimetidine treated mice could be due to its influence on follicular atresia. Ovulation had occurred in these females after withdrawal of cimetidine treatment.
Effects of hCG and PMSG on responsiveness of ovary during period of delayed ovulation in an Indian vespertilionid bat, Scotophilus heathi
(1992) U.P. Singh; A. Krishna
[No abstract available]
Effects of metformin treatment on luteal phase progesterone concentration in polycystic ovary syndrome
(Associacao Brasileira de Divulgacao Cientifica, 2004) K.J. Meenakumari; S. Agarwal; A. Krishna; L.K. Pandey
The causes of luteal phase progesterone deficiency in polycystic ovary syndrome (PCOS) are not known. To determine the possible involvement of hyperinsulinemia in luteal phase progesterone deficiency in women with PCOS, we examined the relationship between progesterone, luteinizing hormone (LH) and insulin during the luteal phase and studied the effect of metformin on luteal progesterone levels in PCOS. Patients with PCOS (19 women aged 18-35 years) were treated with metformin (500 mg three times daily) for 4 weeks prior to the test cycle and throughout the study period, and submitted to ovulation induction with clomiphene citrate. Blood samples were collected from control (N = 5, same age range as PCOS women) and PCOS women during the late follicular (one sample) and luteal (3 samples) phases and LH, insulin and progesterone concentrations were determined. Results were analyzed by one-way analysis of variance (ANOVA), Duncan's test and Karl Pearson's coefficient of correlation (r). The endocrine study showed low progesterone level (4.9 ng/ml) during luteal phase in the PCOS women as compared with control (21.6 ng/ml). A significant negative correlation was observed between insulin and progesterone (r = -0.60; P < 0.01) and between progesterone and LH (r = -0.56; P < 0.05) concentrations, and a positive correlation (r = 0.83; P < 0.001) was observed between LH and insulin. The study further demonstrated a significant enhancement in luteal progesterone concentration (16.97 ng/ml) in PCOS women treated with metformin. The results suggest that hyperinsulinemia/insulin resistance may be responsible for low progesterone levels during the luteal phase in PCOS. The luteal progesterone level may be enhanced in PCOS by decreasing insulin secretion with metformin.
High androgen production by ovarian thecal interstitial cells: A mechanism for delayed ovulation in a tropical vespertilionid bat, Scotophilus heathi
(Journals of Reproduction and Fertility Ltd, 1996) Abhilasha; A. Krishna
The steroid hormone profile of Scotophilus heathi, an Indian tropical vespertilionid bat, was studied, with special reference to the period of delayed ovulation. The results show unusually high concentrations of circulating androstenedione and testosterone during the first half of the period of delayed ovulation, whereas the concentrations of progesterone and oestradiol were relatively low during this period. Androstenedione, testosterone and oestradiol concentrations were high during the period of ovarian recrudescence (October-November). The oestradiol concentration increased, whereas androstenedione and testos-terone declined significantly, before ovulation. Studies in vitro showed that the ovary secretes more androstenedione and testosterone than does the adrenal. A histological study showed that a major part of the ovary of S. heathi was occupied by hypertrophied interstitial cells. An immunocytochemical study showed ovarian thecal interstitial cells as the major site of high androgen synthesis in the ovary. During the period of delayed ovulation the bat ovaries thus resemble the ovaries from women with polycystic ovaries in which abnormally high androgen secretion from hypertrophied interstitial cells prevent ovulation. © 1996 Journals of Reproduction and Fertility Ltd.
Histamine, mast cells and ovarian function
(1989) A. Krishna; K. Beesley; P.F. Terranova
Mast cells, endothelial cells, basophils and platelets are potential sources of histamine in the ovary. Little is known about the role of the latter three cell types in ovarian function. Several studies have revealed changes in the number and degranulation (release of histamine) of mast cells in the ovary during the cycle. Mast cells degranulate on pro-oestrus in the rodent ovary, and mast cells numbers increase in the theca externa of the dominant follicle in the bovine ovary. In rodents, mast cells are limited to the ovarian hilum and are not observed in follicles, corpora lutea and interstitium; this contrasts with larger species such as man, cows and monkeys where mast cells are observed throughout the ovary. Evidence is accumulating that mast cell degranulation in the ovary may be regulated by neuronal input. Neurones have been shown to have close morphological relationships with mast cells in the ovary. Histamine participates in regulating capillary permeability and blood flow in the ovary. These actions are induced by injections of LH, yet the mechanism by which LH induces mast cell degranulation is unknown. Histamine stimulates ovarian contractility, ovulation and follicular progesterone secretion in vitro. Whether these actions of histamine occur in vivo are currently unknown. This review gives a chronological description of the discoveries of the effects of histamine on ovarian function and makes suggestions for future research in this area.
Histochemical localization of enzymes and lipids in the ovary of a vespertilionid bat, Scotophilus heathi, during the reproductive cycle.
(2005) U.P. Singh; A. Krishna; T.D. Smith; K.P. Bhatnagar
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.
Immunocytochemical studies on the pituitary pars distalis of the tropical vespertilionid bat, scotophilus heath with reference to the ovarian cycle
(1996) U.P. Singh; A. Krishna
Changes in the anterior pituitary in relation to the ovarian cycle and ovulation in female Scotophilus heathi are described. TSH, LH, FSH and PRL cells have been identified in the pars distalis (PD) by immunocytochemistry using the per-oxidase-antiperoxidase technique. LH, FSH and PRL cells exhibited significant variation during the reproductive cycle of female S. heathi. The areal fractions of the PD occupied by LH and FSH cells were significantly (p < 0.05) higher during winter dormancy and the breeding phase as compared to the quiescence phase. The mean areal fraction of LH and FSH cells declined in March, following ovulation. The areal fraction of PD occupied by PRL cells varied from a minimum during winter dormancy to a maximum during pregnancy. Several of the PRL cells exhibited a degranulated appearance during winter dormancy suggesting PRL release. The areal fraction of TSH immunoreactive cells did not show a significant (p > 0.05) variation during the reproductive cycle. No evidence of involution was observed in the PD cells during the period of delayed ovulation.RH release. © 1996 S. Karger AG, Basel.
Inhibitory effects of melatonin on testosterone but not on androstenedione production during winter in the vespertilionid bat, Scotophilus heathi
(1995) Kavita Singh; A. Krishna
Abstract: The possible effects of melatonin on testosterone and androstenedione production in vitro by testes of wild‐caught bats, Scotophilus heathi, during different reproductive phases were investigated. Bats were captured during reproductive quiescent (April‐August), recrudescent (September‐October), breeding (November‐February), and winter dormancy (late December‐January) phases. Testes were incubated in media‐199 for 2 h at 37°C with luteinizing hormone (LH) and with or without melatonin. Melatonin had no effect on LH‐induced testosterone (T) or androstenedione (A) production during the quiescent, recrudescent, and breeding phases. However, it significantly (P<0.05) suppressed LH‐induced T production but had no effect on A during winter dormancy. Testicular 17β‐hydroxy steroid dehydrogenase (17β‐HSD) activity was then measured in the testes from bats trapped during quiescence, breeding, and winter dormancy. Interestingly, melatonin along with LH caused suppression of 17β‐HSD activities (3.56 ± 0.03 unit/min/mg protein) when compared with levels of LH treated testes (7.10 ± 1.15 unit/min/mg protein) during winter dormancy, while it had no significant effect on 17β‐HSD activity during quiescence and breeding phases. These results suggest that in S. heathi, melatonin during winter dormancy suppresses LH‐induced T production by the testes via the suppression of 17β‐HSD activity. This may be the reason for the decline in testicular activity during winter dormancy. Copyright © 1995, Wiley Blackwell. All rights reserved
Mechanism of delayed ovulation in a vespertilionid bat, Scotophilus heathi: Role of gonadotropin, insulin, and insulin-like growth factor-1
(2000) A. Krishna; Abhilasha
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.
Melatonin regulates delayed embryonic development in the short-nosed fruit bat, Cynopterus sphinx
(2009) Arnab Banerjee; K.J. Meenakumari; S. Udin; A. Krishna
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. © 2009 Society for Reproduction and Fertility.