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Topic:Placenta
The equine placenta is a vital organ that facilitates nutrient and gas exchange between the mare and the developing fetus during pregnancy. It plays a role in hormone production and immune modulation to support fetal development. The placenta in horses is classified as a diffuse, epitheliochorial type, characterized by the widespread attachment of the chorionic villi to the endometrium. Research on the equine placenta encompasses studies on its structure, function, and the physiological processes involved in its development and maintenance. This page compiles peer-reviewed research studies and scholarly articles that explore the morphology, function, and clinical implications of the placenta in equine reproduction and health.
[Demonstration of Chlamydia from an equine abortion]. The isolation and identification of a chlamydial agent from an equine fetus is reported. The fetus was aborted by a mare with respiratory disease and fever in the 9th month of pregnancy. The serum of the mare was investigated by the compliment fixation test. Specific antibodies were detected for chlamydial antigen in a titer of > 1:40 and for equine herpes virus 1 antigen in a titer of 1:32. Pathological lesions were not found in the organs of the fetus. Chlamydiae were detected in the placenta by ELISA and subsequently isolated by cell culture. Using PCR technique the agent was identified ...
Equine retained placenta: technique for and tolerance to umbilical artery injections of collagenase. Under laboratory conditions and in clinical experiments, bacterial collagenase has proven to be effective in hydrolyzing placenta and detaching cotyledon from caruncle in the bovine species. Laboratory studies in which placental samples were incubated with collagenase have also demonstrated that collagenase is 3.7 times more effective in hydrolyzing equine placenta than bovine placenta. This led to the hypothesis that collagenase may be a potential treatment for mares with retained placenta. However, that collagenase may hydrolyze the uterine wall and perforate the uterus was a concern. It was...
Cell proliferation patterns during development of the equine placenta. Placentation involves considerable growth and reorganization of both maternal and fetal tissues. In this investigation, immunohistochemical localization of the proliferation marker Ki-67 antigen was used to monitor cell division during placentation in mares. Endometrial biopsies were obtained from eight mares between day 14 and day 26 of pregnancy and from eight anoestrous mares that had been treated with various combinations of progesterone and oestrogen. Samples of endometrium and fetal membranes were obtained from 19 mares carrying normal horse conceptuses between day 30 and day 250 of gest...
Cannulation in situ of equine umbilicus. Identification by gas chromatography-mass spectrometry (GC-MS) of differences in steroid content between arterial and venous supplies to and from the placental surface. Equine umbilicus was cannulated in utero and a series of cord plasma samples removed for analysis. After steroid extraction and derivatisation, gas chromatographic-mass spectrometric (GC-MS) analysis demonstrated large differences in steroid content between the plasma samples obtained from the umbilical artery and vein, the blood supplies leading to and from the placental surface, respectively. 3Beta-hydroxy-5,7-androstadien-17-one, dehydroepiandrosterone, pregnenolone, 3beta-hydroxy-5alpha-pregnan-20-one, 5-pregnene-3beta,20beta-diol and 5beta-pregnane-3beta,20beta-diol were identified as maj...
Factors controlling epidermal growth factor (EGF) gene expression in the endometrium of the mare. Previous studies showed a dramatic increase in EGF gene expression in the endometrial glands of pregnant mares around day 40 after ovulation. To investigate how the steroid hormones of pregnancy might regulate this expression, in situ hybridization was used to monitor the levels of EGF mRNA in endometrial biopsies obtained from seasonally anoestrous or ovariectomised mares given exogenous progesterone and oestrogen, alone or in combination, for up to 46 days. Biopsies were also taken from mares during the non-pregnant cycle, during normal pregnancies and pregnancies compromised by endometrial ...
Equine placental cup cells show glycan expression distinct from that of both chorionic girdle progenitor cells and early allantochorionic trophoblast of the placenta. Using lectin histochemistry on plastic-embedded material, the glycosylation patterns of equine girdle and cup cells, and associated endometrial glands, have been investigated from 37 to 67 days gestation. Results were compared with the glycosylation of the 50-day allantochorionic trophoblast of the established equine placenta that will later form the microcotyledons. The differentiated cup cells, which secrete equine chorionic gonadotropin (eCG), showed a pattern of glycosylation that was distinct both from the progenitor girdle cells and the allantochorionic trophoblast, with granules that bo...
Identification of a new aspartic proteinase expressed by the outer chorionic cell layer of the equine placenta. The pregnancy-associated glycoproteins (PAGs) are placental antigens that were initially characterized as pregnancy markers in the maternal circulation of domestic ruminant species. They are members of the aspartic proteinase gene family, having greatest sequence identity with pepsinogens. However, some are not capable of functioning as enzymes. The PAGs are associated with a large gene family within the Artiodactyla order (cattle, camels, pigs). So far, no members of this family have been characterized in species outside this order. This report describes the cloning and initial characterizati...
A lectin binding analysis of glycosylation patterns during development of the equine placenta. The glycosylation of the equine interhaemal barrier and areola was studied throughout the period of gestation. Placentae of 35, 37, 50, 119, 152, 200, 280 and 300 days gestation were investigated, using semithin plastic embedded sections and a panel of 15 biotinylated lectins with an avidin-peroxidase revealing system. Glycosylation of the trophoblast and maternal epithelium showed the most change during the first 50 days of gestation, being associated with the initial stages of adhesion and attachment. In the trophoblast, non-bisected tri/tetraantennary complex N-glycan was only evident after...
Endocrinology of pregnancy: chorionic somatomammotropins and pregnancy-associated glycoproteins: review. The two main groups of placental proteins of ruminants are discussed in this paper: chorionic somatomammotropins (placental lactogens) and pregnancy-specific (-associated) proteins. Placental lactogens belong to the prolactin and growth hormone family. They stimulate mammogenesis, fetal growth and maternal metabolism. Pregnancy-specific proteins and pregnancy-associated glycoproteins belong to the aspartic proteinase family like pepsin, cathepsin D and E. These two groups of proteins are secreted in the maternal circulation by the binucleate cells after their migration to and fusion with the u...
The potential of collagenase as a new therapy for separation of human retained placenta: hydrolytic potency on human, equine and bovine placentae. The purpose of this study was to determine to what degree bacterial collagenase may digest human placentae compared to equine and bovine placentae. Placenta samples from human, equine and bovine were incubated with bacterial collagenase solution at various concentrations. The degree of hydrolysis and collagen breakdown was measured by the release of total proteins and hydroxyproline into the incubation media. Also, whole placentae were injected via umbilical cord arteries with collagenase solution (200 U/ml, 200 ml total volume in human and 1000 ml in equine) and hydrolysis determined chemical...
An aspartic proteinase expressed in the equine placenta. This manuscript describes the cloning of a novel aspartic proteinase expressed in the placenta of the horse (order Perrisodactyla). Evidence for similar genes in the cat (Carnivora) and ruminants (Artiodactyla), indicates that these molecules have been conserved within widely divergent species with distinct types of placentation. Since ePAG is produced by the outer cell layer (trophoblast) of the placenta, it can tentatively be grouped with the pregnancy-associated glycoproteins (PAG) of cattle, sheep, and pig. The high sequence identity that ePAG shares with pepsinogens as well as the PAG, in...
Expression of epidermal growth factor and its receptor in equine placental tissues. Northern blot and in situ hybridization techniques have demonstrated a marked increase in mRNA encoding epidermal growth factor (EGF) in the endometrium of mares, coincident with the start of interdigitation between the allantochorion and endometrium during placentation. In the present study, the unusually high EGF expression in the epithelium of the endometrial glands was shown to be maintained until at least day 250 of gestation (term = 320-340 days) in mares carrying normal horse conceptuses. However, in mares carrying failing donkey-in-horse pregnancies created by embryo transfer, EGF expr...
Characterization of the equine glycoprotein hormone alpha-subunit gene reveals divergence in the mechanism of pituitary and placental expression. The equine glycoprotein hormone alpha-subunit gene is expressed in both pituitary and placenta, unlike that of all other nonprimate mammals studied, in which expression is limited to pituitary. Previous studies of the 5'-flanking region of the equine alpha-subunit promoter have revealed unique characteristics as well as similarities with the human alpha-subunit promoter, which demonstrates a similar pattern of tissue-specific expression. We have cloned and sequenced the equine alpha-subunit gene and have used tissue culture systems and transgenic mice to characterize its expression. Unlike the...
The equine immune response to endometrial cups. Out of all the areas of comparative immunological study in the horse, the field of reproductive immunology has proven to be one of the most fertile and exciting. Maternal immunological interactions with the fetus involve a set of events which prevent maternal rejection of trophoblastic tissue invading the uterus, and at the same time control this invasion to regulate growth and prevent damage to maternal tissues. Unique features of equine placentation make it exceptionally well-suited to studying these immunological interactions.
Interspecific and extraspecific pregnancies in equids: anything goes. Equids possess the unusual ability to interbreed freely among the phenotypically and karyotypically diverse member species of the genus to produce viable, but usually infertile, offspring. The mule (female horse x male donkey) was humanity's first successful attempt at genetic engineering and its clear expression of both parental phenotypes has contributed much to our understanding of genetic inheritance over the centuries. Even more surprising, mares and donkeys have been shown to be capable of carrying to term a range of true, xenogeneic extraspecies pregnancies created by embryo transfer, i...
Use of transabdominal ultrasound-guided amniocentesis for detection of equid herpesvirus 1-induced fetal infection in utero. To evaluate transabdominal ultrasound-guided amniocentesis for detection of equid herpes-virus 1 (EHV-1)-induced fetal infection in utero. Methods: 4 Welsh Mountain mares. Methods: Pregnant mares were inoculated intranasally with EHV-1 during the ninth month of gestation. Amniocentesis was initiated on postinoculation day (PID) 12, and was performed at 2- to 3-day intervals in standing mares under deep sedation. Amniotic fluid samples were tested by virus isolation (VI), polymerase chain reaction (PCR), and immunoperoxidase cytologic examination (IC) for detection of EHV-1. Results: Exposure t...
Carbonic anhydrase activity in different placenta types: a comparative study of pig, horse, cow, mink, rat, and human. The placenta has multiple functions, being the organ which provides oxygen and nutrients to the developing conceptus. In the placenta, the enzyme carbonic anhydrase (CA) may provide ions for exchange with Na+, K+, and Cl- in transepithelial movement of ions and fluid, as well as facilitating carbon dioxide diffusion. It can also be active in intermediary metabolism, such as gluconeogenesis, urea, and fatty acid synthesis. Placental material from pig, horse, cow, mink, rat, and human was therefore investigated, representing placenta types with variations in shape, internal architecture, and nat...
Biosynthesis and possible biological roles of progestagens during equine pregnancy and in the newborn foal. Major progress on the endocrinology of the pregnant mare has been possible thanks to the catheterised equine fetal preparation developed by Marian Silver. In particular, these preparations led to the identification of the source of progestagens within the feto-placental unit and provided the impetus for further work on their biosynthesis and biological activities. The biosynthesis of the progestagens involves close interaction between the fetus, the endometrium and the placenta, and gives rise to some fundamental biochemical questions. The biological role of the progestagens is also discussed:...
Fetal calcium homeostasis. The mammalian fetus is maintained hypercalcaemic relative to its mother primarily by the action of a placental calcium pump located in the basal plasma membrane of the trophoblast. It is suggested that the activity of this pump is stimulated by a mid-molecular fragment of parathyroid hormone-related protein [PTHrP(38-94NH2)], produced in the placenta (and also in the parathyroid glands of fetal lambs and calves) as a result of post translational processing. In the sheep, calcitriol is an important determinant of fetal calcium homeostasis and it, too, stimulates the transport of calcium across ...
Placental localization of relaxin in the pregnant mare. In situ hybridization employing a cRNA probe derived from a 428-bp fragment of equine relaxin was used to localize relaxin mRNA, and immunocytochemistry was used to localize relaxin itself, in tissues of the placenta-endometrium interface recovered between 33 and 153 days of gestation from mares carrying intraspecific horse, interspecific mule and extraspecific donkey conceptuses. Immunocytochemical staining was also used to localize trophoblast-specific and class I major histocompatibility complex (MHC) antigens on some specimens. Relaxin mRNA and relaxin were both present in the single-cell ...
A developmental switch in expression from blastocyst to endometrial/placental-type cytochrome P450 aromatase genes in the pig and horse. Pig blastocysts exhibit a transient period of estrogen production at periimplantation, with a second, more sustained period of estrogen synthesis occurring in endometrium and placenta at later pregnancy. Previously we reported the isolation of cDNA clones encoding a novel isoform of cytochrome P450 aromatase (the terminal enzyme in the estrogen biosynthetic pathway) from porcine periimplantation blastocysts. The present study investigated pregnancy-associated expression, in blastocysts and maternal reproductive tract tissues of this and an additional mRNA transcript encoding a distinct P450 ar...
Ultrasonographic evaluation of the equine placenta by transrectal and transabdominal approach in the normal pregnant mare. The objective of this study was to determine normal variations in the utero placental thickness during mid- and late gestation in the mare. Normal, healthy pregnant mares (n = 9) were examined monthly from 4 mo of gestation until parturition by transrectal and transabdominal ultrasonography. At each examination, the combined thickness of the uterus and the placenta (CTUP) was measured at the placento-cervical junction (transrectally) and at the uterine body or the uterine horns (transabdominally). In addition, the echogenicity of the amniotic and allantoic fluids was evaluated by transrectal u...
Studies into aromatase activity associated with fetal allantochorionic and maternal endometrial tissues of equine placenta. Identification of metabolites by gas chromatography mass spectrometry. Maternal endometrial and fetal allantochorionic tissues were separated manually from the placentae of seven healthy thoroughbred and three pony mares, ranging in gestational age from 100 to 318 days. The homogeneity of subcellular fractions prepared from these tissues was assessed initially using the marker enzymes, succinate dehydrogenase, NADPH cytochrome C reductase and lactate dehydrogenase for the mitochondrial, microsomal and cytosolic fractions, respectively. Light microscopy and histochemical analysis demonstrated that the separated fetal allantochorionic membrane, which is made up of ...
Differential effect of trilostane on the progestin milieu in the pregnant mare. Trilostane, a competitive inhibitor of 3 beta-hydroxysteroid dehydrogenase, was administered intravenously to pregnant mares (n = 3) between day 277 and day 282 of gestation to determine its effect on the progestin milieu. In addition, placental tissue from mares at mid-gestation (150-300 days) (n = 4) were exposed to either deuterium-labelled pregnenolone alone or deuterium-labelled pregnenolone and trilostane to examine the effect of trilostane on placental metabolism of pregnenolone. Blood samples were collected from indwelling jugular catheters at frequent intervals for 48 h after infusion...
Analysis of MHC class I expression in equine trophoblast cells using in situ hybridization. Down-regulation of major histocompatibility complex (MHC) genes by trophoblast cells is considered to be a primary mechanism preventing maternal immune rejection of the fetal-placental unit in mammalian pregnancy by rendering these cells, which form the primary barrier between mother and fetus, relatively non-antigenic. In situ hybridization with probes encoding human and horse MHC class I genes was used to characterize the pattern of MHC class I mRNA expression in the various forms of horse trophoblast. Strong hybridization signals were observed in the invasive trophoblast cells of chorionic ...
Histopathological and immunofluorescent studies on transplacental infection in experimentally induced abortion by equine arteritis virus. Five pregnant mares, at between 6 and 8 months gestation, were experimentally infected with the Bucyrus strain of equine arteritis virus (EAV). Of the five mares, four aborted and one died. The pathogenesis of the abortions was studied, using histopathologic techniques, tissue immunofluorescence and virus isolation. Common microscopic lesions in the maternal reproductive organs indicated myometritis with a degeneration of the myocytes and an infiltration of the mononuclear cells. Epithelial cells of the endometrial gland showed sporadic degeneration. Lesions in the fetal tissue included an atr...
