Corpus Luteum Of Pregnancy Research Articles

Collaborative work on evaluation of ovarian toxicity 8) Two- or four-week repeated-dose studies and fertility study of Anastrozole in female rats

The main focus of this study was to determine the optimal administration period in terms of toxic effects on ovarian morphological changes. To assess the morphological and functional changes induced by anastrozole in ovaries, the compound was administered to female rats at dose levels or 0, 0.01, 0.1 and 50 mg/kg for 2 or 4 weeks in the repeated dose toxicity study and at levels of 0, 0.01, 0.1 and 5 mg/kg from 2 weeks prior to mating to Day 7 or pregnancy in the female fertility study. In the repeated dose toxicity study, large abnormal atretic follicles, follicular cysts, a decrease in corpus luteum and depletion of developing corpus luteum were observed in the 1 and/or 50 mg/kg groups of both the 2-week and 4-week studies in a histopathological examination of the ovaries. In the female fertility study, the pregnancy rate was decreased in the 5 mg/kg group. Irregular estrous cycles, such as an extended cycle or no cycle, were observed in the 0.1 and 5 mg/kg groups. At necropsy, decreased numbers of implantations, corpora lutea and live fetuses were noted in the 1 and/or 5 mg/kg groups. Based on these findings, histopathological changes in the ovary are important endpoints for the evaluation of drugs inducing ovarian damage. We conclude that a 2-week administration period is sufficient to detect ovarian toxicity of anastrozole in a repeated dose toxicity study.

Collaborative work on evaluation of ovarian toxicity 7) Effects of 2- or 4- week repeated dose studies and fertility study of cyclophosphamide in female rats

The main focus of this study was to determine the optimal administration period concerning the toxic effects on ovarian morphological changes in the repeated dose toxicity study. In order to assess the morphological and functional changes induced in the ovary by cyclophosphamide (CP), the compound was administrated to female rats at dose levels of 0, 5, 10 and 20 mg/kg for the repeated dose toxicity study for 2 or 4 weeks, and at 0, 5, 10, and 20 mg/kg for the female fertility study from 2 weeks prior to mating to Day 7 of pregnancy. In the repeated dose toxicity study, increases in large sized atretic follicles, atrophy of corpora lutea were observed in the 20 mg/kg group in the 4-week study by the histopathological examination of the ovaries. There were no drug-related changes in the ovary in the 2-week study. In the female fertility study, the numbers of implantation were slightly decreased and the corpora lutea of pregnancy was not observed in the 20 mg/kg group. The dose-dependent increase in the incidence of post-implantation loss was observed, and no abnormalities were observed in the estrus cycle and mating in all treated groups. From these findings, the histopathological changes in the ovary are important endpoints for the evaluation of drug-induced ovarian damage as well as caesarean section. In conclusion, a 4-week administration period is sufficient to detect the ovarian toxicity of CP in the repeated dose toxicity study.

Human Chorionic Gonadotropin: "The Magic Molecule"

hCG is a glycoprotein molecule composed of two dissimilar subunits, alpha(�±) and beta(�) subunits, linked together with hydrogen and disulphide bonds. All cells produce hCG. However hCG molecule secreted by the placenta has a longer half life, owing to the glycosylation of its �-subunit. The only definitely known function of hCG, is to support the corpus luteum of pregnancy. Uses of hCG include diagnosis of normal as well as nonviable, ectopic and molar pregnancy, as a tumor marker and for aneuploidy screening, while for therapy it is used in various steps of assisted conception, recurrent or threatened abortion, preterm labor and as antifertility vaccine. Many more areas are yet to be explored, where this enigmatic molecule has the capacity to do wonders.

Asp330 and Tyr331 in the C-terminal Cysteine-rich Region of the Luteinizing Hormone Receptor Are Key Residues in Hormone-induced Receptor Activation

The luteinizing hormone (LH) receptor plays an essential role in male and female gonadal function. Together with the follicle-stimulating hormone (FSH) and thyroid stimulating hormone (TSH) receptors, the LH receptor forms the family of glycoprotein hormone receptors. All glycoprotein hormone receptors share a common modular topography, with an N-terminal extracellular ligand binding domain and a C-terminal seven-transmembrane transduction domain. The ligand binding domain consists of 9 leucine-rich repeats, flanked by N- and C-terminal cysteine-rich regions. Recently, crystal structures have been published of the extracellular domains of the FSH and TSH receptors. However, the C-terminal cysteine-rich region (CCR), also referred to as the "hinge region," was not included in these structures. Both structure and function of the CCR therefore remain unknown. In this study we set out to characterize important domains within the CCR of the LH receptor. First, we mutated all cysteines and combinations of cysteines in the CCR to identify the most probable disulfide bridges. Second, we exchanged large parts of the LH receptor CCR by its FSH receptor counterparts, and characterized the mutant receptors in transiently transfected HEK 293 cells. We zoomed in on important regions by focused exchange and deletion mutagenesis followed by alanine scanning. Mutations in the CCR specifically decreased the potencies of LH and hCG, because the potency of the low molecular weight agonist Org 41841 was unaffected. Using this unbiased approach, we identified Asp(330) and Tyr(331) as key amino acids in LH/hCG mediated signaling.

Maintenance of Pregnancy in Dairy Cattle After Treatment with Human Chorionic Gonadotropin or Gonadotropin-Releasing Hormone

The objectives were to determine whether a single injection of either human chorionic gonadotropin (hCG) or GnRH would: 1) increase ancillary formation of new luteal structures, 2) increase serum concentrations of progesterone, and 3) increase pregnancy survival in dairy females treated once between 26 and 71 d of pregnancy. A total of 421 cows were enrolled between January and November 2001, with 92, 106, and 223 females (included 68 nulliparous heifers at 1 location) treated at the 3 locations. Upon diagnosis of pregnancy, females were allocated randomly to receive 100μg of GnRH, 1,000 IU of hCG, or 2mL of saline. Blood samples were collected at 0, 1, 2, and 4 wk after treatment, and pregnancy status was reassessed at 1, 2, and 4 wk. New luteal structures were formed in 23.8% of cattle, with hCG (50%) and GnRH (26%) being more effective than saline (7%). Treatment had no effect on the proportion of females forming 2 new luteal structures (7.6%), and 36.2% of all induced structures regressed during the 4-wk study period. Pregnancy losses were unaffected by treatment, stage of pregnancy, or number of induced luteal structures but were nearly 9-fold greater in females in which induced luteal structures regressed. No loss occurred in females having 2 new luteal structures. Pregnancy losses decreased quadratically from 30 to 42 d. Serum progesterone did not differ among treatments, but among females forming new luteal structures, progesterone was greater at 1 (7.2±0.3 vs. 6.3±0.2 ng/ mL) and 2 wk (7.0±0.3 vs. 6.1±0.2 ng/mL) after treatment. Progesterone at the first pregnancy diagnosis was predictive of imminent pregnancy loss; the lower the initial progesterone, the sooner subsequent loss was observed. The right ovary was dominant in the location of new luteal structures. Regression of new luteal structures occurred more often on the left ovary and contra-lateral to the corpus luteum of pregnancy (53.2 vs. 22%). In conclusion, treatment of dairy cattle with either GnRH or hCG failed to prevent pregnancy loss, but concentrations of progesterone were predictive of subsequent pregnancy loss.

Monoamine oxidase A is highly expressed by the human corpus luteum of pregnancy

To investigate the physiological characteristics of the corpus luteum (CL) of pregnancy, we raised a mAb, human corpus luteum (HCL)-4, against human luteal cells obtained from CL of pregnancy. The affinity-purified antigen from human CL of pregnancy or placenta using HCL-4 was a 61 kDa protein. The partial amino acid sequence of the antigenic protein was identical to that of human monoamine oxidase A (MAOA, EC1.4.3.4). MAOA has been shown to catabolize catecholamines that were reported to regulate luteal function in CL and vasoconstriction in various organs. Immunohistochemistry using HCL-4 mAb showed that MAOA was intensely expressed on large luteal cells and moderately expressed on small luteal cells in the CL of pregnancy. In the CL of menstrual cycle, MAOA was weakly detected on large luteal cells but not detected at all on small luteal cells. Western blotting analysis confirmed the high expression of MAOA in CL of pregnancy. Northern blot analysis also showed the expression of MAOA mRNA in human CL, and showed that its expression was higher in CL of pregnancy than in CL of menstrual cycle. The increased expression of MAOA in the CL of pregnancy suggests the contribution of MAOA to the function of the CL of pregnancy.

Angiogenesis in the human corpus luteum.

Angiogenesis is important for the formation and development of the corpus luteum and for maintenance of luteal function. Blood vessel regression is an important physiological phenomenon in the corpus luteum, which is associated with tissue involution during structural luteolysis. Angiogenesis actively occurs during the early luteal phase and is completed by the mid-luteal phase. Perivascular cells (pericytes) increase in number from the early luteal phase to the mid-luteal phase, suggesting that blood vessels are gradually stabilized until the mid-luteal phase. In the corpus luteum undergoing luteolysis, blood vessels and pericytes decrease in number, which is related to structural involution. In the corpus luteum of early pregnancy, the number of blood vessels with pericytes increases, suggesting that angiogenesis occurs again, accompanied by blood vessel stabilization. These changes in vasculature of the corpus luteum are regulated by the collaboration with vascular endothelial growth factor, which is involved in proliferation of vascular endothelial cells, and angiopoietins, which are involved in stabilization of blood vessels. This review focuses on angiogenesis, blood vessel stabilization and blood vessel regression during the divergent phases of luteal formation, luteal regression and luteal rescue by pregnancy. (Reprod Med Biol 2008; 7: 91-103).

Le paradoxe cardiovasculaire de la grossesse

Despite widespread accessibility to prenatal care, little is known on the mechanisms initiating early maternal adaptation to pregnancy. Moreover, preeclampsia and intrauterine growth retardation remain the most frequent and serious complications of pregnancy. Recent studies, both in humans and in laboratory animals, have shown that very early events in gestation may be important determinants for the continuation of healthy pregnancy. Certain of these early adaptations appear to be linked to the corpus luteum of pregnancy, as ovarian steroid hormones (especially progesterone) would set the basic hemodynamic conditions, more specifically, generalized vasodilation. This new hemodynamic setup initiates a vicious cycle in which the renin - angiotensin - aldosterone system is activated, together with the resetting of the control of antidiuretic hormone secretion relative to plasma osmolality. This leads to a gradual and substantial increase in plasma volume and a parallel increase in cardiac function (both heart rate and stroke volume) with the goal of maintaining blood pressure in the face of the generalised vasodilation. This includes the creation of a functional arterio-venous shunt represented by the utero-placental circulation. By the end of the first trimester, the decrease in peripheral vascular resistance is marked relative to the increase in cardiac output, resulting in a significant decrease in blood pressure that will be maintained until the third trimester. It is proposed that in preeclampsia, these very early events (vasodilation - increased plasma volume) fail to occur, resulting in an absence of the usual decrease in blood pressure, which is normally seen in the second trimester of pregnancy, and hypertension in the third trimester. Experimental animals, especially the rat, are suitable models to study this early maternal adaptation to pregnancy, since both endocrine and hemodynamic changes appear to be similar to humans.

The effect of relaxin on the oxytocin receptor in human uterine smooth muscle cells

Experimental objectives: Activation of the oxytocin receptor (OTR) induces phospholipase C induced PIP 2 turnover in the human uterus. Relaxin (RLX), a polypeptide hormone produced in the corpus luteum of pregnancy as well as in the placenta and decidua inhibits PIP 2 turnover and subsequent signaling in human myometrium. The purpose of this study was to evaluate a possible effect of RLX on OTR regulation in human uterine smooth muscle cells. Primary cultures of myometrium from term pregnant women undergoing elective caesarean section were incubated for different time periods (0–96 h) and with different concentrations of RLX [10 pg/ml–20 μg/ml]. The effects on OTR binding, mRNA and protein expression were evaluated by means of 125I‐OVT binding assay, RT‐PCR and flow cytometry. Results: Prolonged RLX incubation was able to inhibit 30–40% of OTR binding while binding affinity remained unchanged. Oxytocin receptor mRNA and protein expression were down regulated by RLX about 50% and 35% respectively. Conclusion: We report for the first time an effect of RLX on OTR regulation in human uterine myometrial cells. The above results indicate that high local uterine RLX concentrations may be involved in uterine quiescence during human pregnancy by down regulating the OTR.

OC98: How mifepristone affects corpus luteum in early pregnancy; a prospective, controlled study

OC98: How mifepristone affects corpus luteum in early pregnancy; a prospective, controlled study

161 EFFECT OF MELOXICAM TREATMENT ON PREGNANCY RATES IN HOLSTEIN HEIFERS

We previously reported that administration of flunixin meglumine two times at a critical stage approaching pregnancy recognition associated with corpus luteum maintenance increased early embryo survival and pregnancy rate via an additive antiluteolytic effect with the conceptus (Guzeloglu et al. 2006 Reprod. Fertil. Dev. 18, 183). In this study, the objective was to determine if a single administration of meloxicam, a non-steroid anti-inflammatory drug (NSAID) with a longer half-life, could be used instead of flunixin meglumine to avoid repeated injections in heifers at a critical stage following insemination to increase pregnancy rate due to its inhibitory effect on PGF2� synthesis. Eighty-five 15-18-month-old Holstein heifers were synchronized; following insemination (Day 0), the heifers were randomly assigned to receive a subcutaneous meloxicam injection (0.5 mg kg-1; n = 37) in the afternoon of Day 15 or left untreated as controls (n = 48). Pregnancy rates were defined as the percentage of heifers diagnosed pregnant by ultrasound between Days 31 and 38 after AI. The effect of treatment on pregnancy rates was analyzed by chi-square test. Meloxicam treatment on Day 15 after insemination dramatically decreased the pregnancy rates in the heifers (25 of 48 (52%) in the control group vs. 9 of 37 (24.3%) in the meloxicam-treated group; P < 0.01). This result indicates that administration of meloxicam around a time associated with pregnancy recognition and corpus luteum maintenance was harmful to the pregnancy even though the drug is considered to be safe during pregnancy in cattle. It is concluded that direct or indirect effects of meloxicam on the uterine environment and/or embryo are not favorable at least during early pregnancy in cattle. How meloxicam exerted its detrimental effect on pregnancy warrants further investigation.

Understanding Relaxin in the Female Reproductive System

Recent advances in our understanding of the hormone relaxin, and the discovery of its specific receptor LGR7, have provided a series of new tools and paradigms, with which to re-examine many aspects of female reproductive physiology classically associated with this hormone. It is important to distinguish those effects resulting from the endocrine actions of relaxin, due to secretion of the hormone, and possibly its precursor, from the corpus luteum of pregnancy, notably in rodents and other non-primate mammals, from the many local effects possibly involving paracrine interactions between receptors and locally synthesized hormone. Because in many tissues relaxin serves to upregulate the common second messenger cAMP, its effects are hard to unravel from other cAMP stimulants, with which there is inevitably some degree of redundancy. In this review, particularly the important role of relaxin in implantation is addressed, and also briefly the more established functions relating to uterine growth, cervical softening, placental development and rupture of the amniotic membranes. Keywords: relaxin, lgr, implantation, placenta, cervix

Mechanisms for Establishment of Pregnancy in Mammalian Species

Cross-talk between the embryo and mother is necessary for the establishment of successful pregnancy. In the mouse, cervical stimuli during mating induce prolactin secretion from the pituitary and formation of the corpus luteum (CL) of pregnancy. Placental lactogen supports the maintenance of pregnancy after implantation. In the human, the embryo secretes chorionic gonadotropin (hCG), which has lenbinizing hormone (LH) activity and maintains pregnancy before the luteal-placental shift occurs. In cattle and sheep, the mechanism underlying the establishment of pregnancy is unique. Their embryos secrete interferon (IFN)-τ, which is related to type I IFNs. IFN-τ prevents the secretion of prostaglandin F2α(PGF2α) from the uterine endometrium by suppressing the expression of estrogen and oxytocin receptor. In the pig, estrogen secreted from the conceptus is a factor for maternal recognition of pregnancy. Estrogen leads to a shift in the direction of PGF2α secretion from endocrine to exocrine and inhibits the regression of CL. Thus, each species has specific mechanisms for the establishment of pregnancy.

Angiogenesis in the Human Corpus Luteum: Changes in Expression of Angiopoietins in the Corpus Luteum throughout the Menstrual Cycle and in Early Pregnancy

Blood vessel stabilization is regulated by angiopoietins and important for angiogenesis in the corpus luteum. To study angiogenesis and blood vessel stabilization in the human corpus luteum, changes in expression of angiopoietin (Ang)-1, Ang-2, and their specific receptor, Tie-2, together with the number of blood vessels and pericytes were examined in the corpus luteum throughout the menstrual cycle and in early pregnancy. The number of blood vessels and pericytes was determined by immunohistochemistry for CD34 and alpha-smooth muscle actin, respectively. Ang and Tie-2 expression were examined by immunohistochemistry or RT-PCR. The number of blood vessels increased during the early luteal phase, whereas the number of pericytes was small in the early luteal phase and increased in the midluteal phase, suggesting that angiogenesis is undergoing during the early luteal phase and blood vessels are stabilized in the midluteal phase. Blood vessels and pericytes decreased in number during the late luteal phase. The increased number of both blood vessels and pericytes seen in the corpus luteum of early pregnancy suggests that angiogenesis is undergoing accompanied by blood vessel stabilization. Ang-2 expression with low Ang-1 expression was found during the early luteal phase. Thereafter, increasing Ang-1 expression during the midluteal phase, declining Ang-1 expression with continued Ang-2 expression during the late luteal phase, and relatively high Ang-1 expression in early pregnancy were observed. The change in Ang expression is closely associated with angiogenesis, blood vessel stabilization, and blood vessel regression during the divergent phases of luteal formation, luteal regression, and luteal rescue by pregnancy.

Mechanisms of Relaxin‐Mediated Premature Birth

In women, circulating relaxin is produced by the corpus luteum of pregnancy. The levels of relaxin are predominantly determined by the luteal mass, the number of corpora lutea present. Relaxin levels are highest after ovulation induction, which stimulates formation of many corpora lutea. Elevated relaxin levels in the first trimester of pregnancy are maintained throughout pregnancy and are linearly related to preterm birth. In an in vitro model of late human pregnancy cervix, relaxin increases MMP-1 and MMP-3 and decreases TIMP-1 levels, thus acting as a positive regulator of matrix metalloproteinases. In an in vivo rhesus monkey model of early pregnancy, relaxin decreases cervical collagen content, decreases cervical lumican levels, and stimulates MMP-7 levels. Early effects of relaxin in the uterus include increasing endometrial arteriole number and increasing the number of leukocytes, uterine natural killer cells, macrophages, and neutrophils. These cells release many cytokines which contribute to changes that stimulate and facilitate uterine contractility. If these changes persist in late pregnancy, relaxin may be a mediator of labor. Excess relaxin may produce these changes at an accelerated rate, causing preterm birth.

Promoter-2-derived Cyp19 expression in bovine granulosa cells coincides with gene-specific DNA hypo-methylation

Cyp19, the key gene of oestrogen biosynthesis, is expressed at very different concentrations and from different promoters in bovine granulosa cells (GCs) and in pregnant corpora lutea (CL), respectively. The present study was aimed to investigate if DNA methylation and thus epigenetic mechanisms might play a potential role in the regulation of Cyp19 expression and promoter-specific activity in GCs of cycling versus CL of pregnant cows. It was demonstrated that GCs express high concentrations of promoter-2-derived Cyp19 transcripts whereas CL samples isolated before and after implantation, and at the end of the first trimester, showed very low Cyp19 transcript concentrations, all of them derived from promoter 1.1. Two genomic regions including promoter 1.1 and promoter 2 were largely unmethylated in GCs but methylated in all CL samples. The data suggest that promoter-2-derived high-level expression but not promoter-1.1-derived low-level expression of Cyp19 might be controlled by cell-type-specific DNA methylation.

Role of apoptosis in functional luteolysis in the pregnant rabbit corpus luteum: Evidence of a role for placental-derived factors in promoting luteal cell survival

Corpora lutea (CL) were isolated from one rabbit ovary on days 4, 8, 16 (peak luteal function), 28 (functional regression) and 30 of pregnancy and processed for biochemical analysis of DNA integrity. Analysis of DNA integrity revealed the presence of oligonucleosomal fragments in day 28 and day 30 CL but not in day 16 CL. The extent of low molecular weight (<15 kb) DNA labeling was 6.6 +/- 0.84 fold higher in day 30 as compared to day 16 CL (mean +/- SEM; n = 4, P < 0.01). In a second series of experiments, healthy CL collected from day 16 pregnant rabbits were incubated for 2 h in the absence or presence of 250 microg/ml of placental extract (PE) obtained from day 16 and/or day 30 placentas. Analysis of DNA integrity revealed that extensive apoptosis occurred in CL incubated in medium alone and in medium containing day 30 PE. In contrast, day 16 PE significantly suppressed apoptosis vs control (70 +/- 4%). In a third series of experiments, expression of mRNA for bcl-x and bax was measured by Northern analysis of CL treated without and with day 16 PE using cRNA probes for bcl-x and bax developed in our laboratory by RT-PCR. Treatment with PE significantly reduced bax mRNA levels but did not change bcl-x mRNA levels. These studies provide evidence that functional luteolysis in the pregnant rabbit CL is correlated with the occurrence of apoptosis. The data suggest that a factor(s) derived from the placenta may be responsible for the prolongation of CL life span during pregnancy by its ability to alter the bax:bcl -x rheostat and suppress apoptosis.

The expression of cytosolic and mitochondrial type II acyl-CoA thioesterases is upregulated in the porcine corpus luteum during pregnancy

Acyl-CoA thioesterases hydrolyze acyl-CoAs to free fatty acids and CoASH, thereby regulating fatty acid metabolism. This activity is catalyzed by numerous structurally related and unrelated enzymes, of which several acyl-CoA thioesterases have been shown to be regulated via the peroxisome proliferator-activated receptor alpha, strongly linking them to fatty acid metabolism. Two protein families have recently been characterized, the type I acyl-CoA thioesterase gene family and the type II protein family, which are expressed in cytosol, mitochondria and peroxisomes. Still, only little is known about regulation of their expression and precise functions in vivo. In the present study, we have investigated the activity and expression of acyl-CoA thioesterase in the porcine ovary during different phases of the estrus cycle. The activity was low in homogenates obtained during the immature and follicular phases, increasing nearly 4-fold during the luteal phase, with the highest activity being found in the pregnant corpus luteum (about 7-fold higher than in immature follicles). The increase in homogenate activity in corpus luteum from pregnant pigs was due to a moderate increase in the cytosolic activity, and an approximately 20–25-fold increase in the mitochondrial fraction. Western blot analysis showed no detectable expression of the type I acyl-CoA thioesterases (CTE-I and MTE-I) and revealed that the increased activity in cytosol and mitochondria is due to increased expression of the type II acyl-CoA thioesterases (CTE-II and MTE-II). This apparent hormonal regulation of expression of the type II acyl-CoA thioesterase may provide new insights into the functions of these enzymes in the mammalian ovary.

Chorionic gonadotrophin beta subunit mRNA but not luteinising hormone beta subunit mRNA is expressed in the pituitary of the common marmoset (Callithrix jacchus).

The pituitary gonadotrophins LH and FSH are responsible for regulation of gametogenesis in the testis and ovary. Chorionic gonadotrophin (CG), a third closely related glycoprotein hormone derived by gene duplication of the LHbeta gene and secreted by the placenta in primates, is essential for the rescue of the corpus luteum and maintenance of pregnancy. We have recently shown that marmoset (m) CGbeta mRNA is highly expressed in the pituitary of the common marmoset (Callithrix jacchus) and that LH is less active than human CG in activating the human LH receptor lacking exon 10. To investigate further which gonadotrophin is the actual ligand of the LH receptor (LHR) of the marmoset monkey that naturally lacks exon 10, we identified and characterised the genomic organisation of the mLHbeta gene and its expression. Intergenic PCR amplification of the region encompassing the mLHbeta and the mCGbeta genes revealed that, surprisingly, mCGbeta is located 20 kbp upstream of the LHbeta gene, whereas in other species the intergenic distance is approximately 2-3 kbp. Sequence analysis of the mLHbeta coding region showed 70% identity to mCGbeta and 90% identity to human LHbeta at the amino acid level. Both gonadotrophin beta subunits are present at the genomic level, but RT-PCR of pituitary and placental total RNA using specific oligonucleotides for mCGbeta and mLHbeta showed high expression of mCGbeta mRNA in both tissues, whereas LHbeta was expressed neither in the pituitary nor in the placenta. Thus mLHbeta mRNA is lacking in the marmoset pituitary. Immunohistochemistry of marmoset pituitaries showed that mCG was confined to the gonadotrophes, and partly co-localised in cells stained positively for FSH. Western blot analysis confirmed the presence of mCG in the pituitary. Northern blot analysis using mCGbeta as a probe displayed one transcript of 0.7 kb in the pituitary and detected two transcripts of 1.1 kb and 2 kb in the marmoset placenta. Our results suggest that, in the common marmoset, CG is the only gonadotrophin with luteinising function that is present in the pituitary. We postulate that, owing to an unknown mutational event in evolution, expression of mLH was completely abolished, and CG - which, unlike LH, acts normally even when exon 10 is missing from the LHR - took over its function.

Apoptosis does not affect the vasculature of the corpus luteum of pregnancy in the rat.

There has been much research into the mechanics of angiogenesis and many studies have demonstrated that newly formed vessels regress during angiogenesis. This vascular involution has been shown to involve basement membrane dissolution and endothelial cell apoptosis. The corpus luteum provides an ideal in vivo model to study physiologic angiogenesis and studies have shown that involution of newly formed vessels occurs during corpus luteum regression. However, few studies to date have investigated the role of apoptosis on the vasculature which develops during pregnancy. By the use of the TUNEL technique to detect apoptotic cells and immunohistochemistry to distinguish between endothelial cells and pericytes, this present study demonstrated that the vasculature of the corpus luteum of pregnancy in the rat does not undergo apoptosis.