Immunohistochemical localization of prostaglandin H synthase in the sheep placenta from early pregnancy to term.

Prostaglandin H synthase (PGHS) activity within intrauterine tissues is considered to catalyze a critical step in prostaglandin (PG) biosynthesis at parturition. In sheep, the placenta is a major site of PG production throughout pregnancy, but little information is available concerning the cells that are responsible. Therefore we determined the distribution of immunoreactive (IR-) PGHS in ovine placental tissue obtained at different times of pregnancy using immunohistochemical techniques. In placentomes from early pregnancy (Days 30-54), IR-PGHS was present in maternal epithelial syncytium, but was not detectable in trophoblast cells. Between Day 54 and Day 100, the number of cells that stained positive for PGHS declined in the maternal epithelial layer in the body of the placenta, but IR-PGHS was present in maternal epithelial cells overlying the vascular cones of the placental hemophagous zone. It was also present in the chorionic fibroblasts, but remained undetectable from all classes of trophoblast cells. IR-PGHS was first detectable in the trophoblastic epithelium by Day 114. Between Day 119 and term the trophoblast mononuclear epithelial cells were intensely immunopositive for PGHS, although immunonegative binucleate cells were present. The maternal epithelium was immunonegative except during the last 7-10 days of pregnancy when PGHS immunostaining appeared in both basal and apical regions of the placenta. Thus, the cellular localization of IR-PGHS changes during ovine pregnancy, from predominantly maternal during the first half of gestation to undetectable and then to predominantly trophoblastic between Day 114 and term, suggesting a gestation-dependent change in sites of PG production during ovine pregnancy. Appearance of IR-PGHS in the trophoblast precedes activation of the fetal hypothalamic-pituitary-adrenal axis, generally considered to provide the trigger to the onset of parturition in sheep, and would therefore appear to be regulated through alternative pathways or mechanisms.     

Increase in 15-hydroxyprostaglandin dehydrogenase activity in the ovine placentome at parturition and effect of oestrogen

Type 1 NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (PGDH) is the key enzyme for metabolism of active primary prostaglandins to inactive forms in gestational tissues. The present study examined the activity and immunolocalization of PGDH in the ovine placenta, fetal membranes and uterus over the latter half of pregnancy, and its potential regulation by oestradiol. Placenta, fetal membranes and myometrium were collected from sheep with known single insemination dates on days 70, 100 and 135 of gestation and in active labour demonstrated by electromyographic activity. In addition, chronically catheterized fetuses were infused with oestradiol (100 microgram kg(-1) per 24 h) (n = 5) or saline vehicle into the fetus from day 120 to day 125. PGDH activity measured in placental extracts remained constant from day 70 to day 135 of gestation, and then significantly (P < 0.05) increased by 300% in active labour. Immunoreactive PGDH was localized in the placentome at all stages and was present predominantly in the fetal component of the placentome in uninucleate, but not in binucleate, trophoblast cells. Similarly, in the fetal membranes PGDH immuno-reactivity was present in the uninucleate trophoblast but not in the binucleate cells of the chorion. PGDH immunostaining was also present in the endometrial luminal epithelium, in the smooth muscle of the myometrium, and the glandular epithelium of the cervix. Infusion of oestradiol into the fetal circulation from day 120 to day 125 of gestation had no effect on placental PGDH activity. Immunohistochemistry was used to localize oestrogen receptor alpha in intrauterine tissues to investigate further the failure of oestradiol to increase PGDH activity. Immunoreactive oestrogen receptor alpha was not present in the fetal component of the placenta, although it was expressed in adjacent maternal-derived cells. It is concluded that (1) PGDH activity increases in late gestation; (2) PGDH is expressed in uninucleate trophoblast cells in the ovine placenta and fetal membranes, and also in the maternal endometrial epithelium and stroma, myometrium and cervix; (3) oestrogen receptor alpha is not expressed in fetal cells in the placenta or fetal membranes; and (4) the increase in PGDH activity is not regulated by oestradiol administered to the fetus.     

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 gestation and from three failing extraspecific donkey-in-horse pregnancies. Proliferation in the superficial strata of the endometrium was increased by day 18 of gestation and this effect could be mimicked by supplementing with oestradiol benzoate during the last 6 days of a prolonged period (18-36 days) of progesterone administration. Fetal chorionic girdle cells were proliferating vigorously at days 30-32 of gestation, but stopped dividing after they invaded the endometrium, while the trophoblast cells of the allantochorion showed an increase in mitotic activity after day 38. The luminal epithelium of the endometrium started to proliferate only after the primary villi of the true epitheliochorial placenta had been formed, and during days 58-70 this effect was seen only in the pregnant horn in which placentation was further advanced. During the second half of gestation, most of the mitotic activity was confined to the periphery of the microcotyledons which were still growing. In the donkey-in-horse pregnancies, proliferation rates of the maternal and fetal epithelial at day 70 of gestation were markedly reduced in areas of heavy endometrial lymphocyte infiltration and poor placentation. These results provide a basis for further studies on factors that influence invasive and non-invasive placentation.     

Ultrastructure of the full-term shark yolk sac placenta. III. The maternal attachment site

During mid- and late gestation, the uterus of sandbar sharks possesses specialized sites for exchange of metabolites between the mother and fetus. Attachment sites are highly vascular, rugose elevations of the maternal uterine lining that interdigitate with the fetal placenta. The maternal epithelium remains intact and there is no erosion. The attachment site consists of a simple, low columnar juxtaluminal epithelium underlain by an extensive vascular network. Juxtaluminal epithelial cells possess branched microvilli, saccular invaginations of the apical surface, and coated pits. They contain numerous coated vesicles, lipid-like inclusions, a prominent rough endoplasmic reticulum, and many free ribosomes. Tight junctions join the luminal aspect of adjacent cells. Lateral cell boundaries are highly folded and interdigitated. Capillaries are closely apposed to the basal cell surfaces. The endothelium is pinocytotically active. Comparison with the uterine epithelium of non-placental sharks, mammalian epitheliochorial placentae, and selected transporting epithelia reveals that the structure of the maternal shark placenta is consistent with its putative multiple functions, viz: (1) nutrient transfer; (2) transport of macromolecules, e.g., immunoglobulins; (3) respiration; and (4) osmotic and ionic regulation.     

Developmental pattern of glucose-6-phosphatase activity in the small intestine of the mouse fetus.

The distribution of glucose-6-phosphatase (G6Pase) activity in the epithelium of the small intestine in mouse embryos (the last 4 days of gestation) was studied by electron microscope cytochemistry and by enzymatic assays. At 16 days, the lead phosphate deposited by the cytochemical reaction is localized on the rough endoplasmic reticulum (RER) and nuclear envelope of very few cells in the duodenum and jejunum. Positive cells are more frequently seen in the upper part of the developing villi. At 17 days of gestation, a tremendous burst in RER differentiation is noticed in all parts of the small intestine and concomitantly glycogen disappears. At 18 days of gestation all the principal cells of the intestinal mucosa show a well differentiated positive RER and the enzyme is also present in the smooth endoplasmic reticulum. Biochemically, G6Pase activity is detected in the proximal 2 thirds of the small intestine at 17 days of gestation and appears at 18 days in the last third. Afterwards the activity increases up until birth. These results suggest (1) that the endoplasmic reticulum differentiates very late in the intestinal mucosa of mouse embryos (2) that the differentiation with respect to G6Pase is asynchronous between the enterocytes, (3) that for a given cell all the cisternae of RER are involved in G6Pase synthesis at the same moment and (4) that the enterocytes of the duodenum differentiate sooner and faster that those of the jejunum and ileum.     

Ultrastructural studies on the placentae of streptozotocin induced maternal diabetes in the rat

Following induction of diabetes by a single injection of (IP) streptozotocin (STZ) to pregnant Wistar rats on days 2, 4 and 6 to 12 of gestation, fetuses and placentae were collected on day 20. The controls were either untreated or vehicle treated; alternatively following STZ injection, 2-6 IU of insulin was administered (sc) daily until term. The placentae were fixed in a glutaraldehyde and paraformaldehyde mixture and ultrathin sections were examined under the electron microscope. The structure of the vehicle treated control resembled that of the untreated control. The insulin control group had pathological changes similar to those of the diabetic group but with considerably less frequency. The giant cells in the basal zone of STZ group were numerous; they had abundant dilated cisternae of rough endoplasmic reticulum, intracytoplasmic fibrinoid and nuclear inclusions. The trophospongial cells presented numerous clear vacuoles, lysosomes and myelin bodies. Enlarged vacuoles often impinged deeply on the nucleus. The glycogen cells disintegrated resulting in cyst formation. In the labyrinthine zone, layer I trophoblast revealed increased number of large pores through which layer II trophoblast projected into the maternal sinusoid. Layer II had abundant glycogen, lipid droplets and lysosomes. Layer III had imbibed much fluid and appeared foamy with swollen organelles. Fibrinoid substance was produced by the giant cells, basophils and the trophoblast bordering the maternal sinusoids. Cyst development was preceded by degeneration of glycogen cells in the basal zone and of the trophoblast in the labyrinthine zone. Pronounced development of gonadotropin/somatotropin granule-like 'secretory granules' and smooth endoplasmic reticulum associated lipid droplets also characterised the labyrinthine trophoblast. The observed placental pathology appears to correlate well with the intrauterine growth retardation and fetal malformations recorded in this animal model.     

Placentation in the degu (Octodon degus): analogies with extrasubplacental trophoblast and human extravillous trophoblast

This study examined the placentation in the degu, the origin of the extrasubplacental trophoblast (EST) (extravillous trophoblast in human), and the activity of Na+/K+ ATPase in the placental barrier during different gestational ages, as part of a wider effort to understand the reproductive biology of this species. Fifteen degus at the first stage of gestation, midgestation and at term of pregnancy were studied. At day 27 of gestation, the subplacenta is formed under the wall of the central excavation. Simultaneously, the outermost trophoblast of the ectoplacental cone differentiated into secondary trophoblast giant cells that lie on the outside of the placenta, forming an interface with the maternal cells in the decidua. These giant cells immunostained positive for cytokeratin (CK) and placental lactogen (hPL) until term. During this period, the EST merged from the subplacenta to the decidua and immunostained negative for CK, but at term, immunostained for CK and hPL in the maternal vessels. The vascular mesenchyme of the central excavation invaded the chorioallantoic placenta during this period, forming two fetal lobules of labyrinthine-fine syncytium, the zone of the placental barrier. The activity of Na+/K+ ATPase in the placental barrier was constant during the gestational period. The residual syncytium at the periphery of the placental disc and between the lobules was not invaded by fetal mesenchyme and formed the marginal and interlobular labyrinthine syncytium that immunostained first for CK, and later for hPL, as in the labyrinthine fine syncytium. The presence of intracytoplasmic electron-dense material in the interlobular labyrinthine syncytium suggested a secretory process in these cells that are bathed in maternal blood. Placentas obtained from vaginal births presented a large, single lobe, absence of the subplacenta, and a reduced interlobular labyrinthine syncytium. At day 27, the inverted visceral yolk sac is observed and its columnar epithelium immunostained for CK and hPL. This suggests that the yolk sac is an early secretory organ. The epithelium of the parietal yolk sac covers the placenta. The origin of the EST in the degu placenta and its migration to maternal vessels allows us to present this animal model for the study of pregnancy pathologies related to alterations in the migration of the extravillous trophoblast.     

Placentation in the degu (Octodon degus): Analogies with extrasubplacental trophoblast and human extravillous trophoblast

This study examined the placentation in the degu, the origin of the extrasubplacental trophoblast (EST) (extravillous trophoblast in human), and the activity of Na⁺/K⁺ ATPase in the placental barrier during different gestational ages, as part of a wider effort to understand the reproductive biology of this species. Fifteen degus at the first stage of gestation, midgestation and at term of pregnancy were studied. At day 27 of gestation, the subplacenta is formed under the wall of the central excavation. Simultaneously, the outermost trophoblast of the ectoplacental cone differentiated into secondary trophoblast giant cells that lie on the outside of the placenta, forming an interface with the maternal cells in the decidua. These giant cells immunostained positive for cytokeratin (CK) and placental lactogen (hPL) until term. During this period, the EST merged from the subplacenta to the decidua and immunostained negative for CK, but at term, immunostained for CK and hPL in the maternal vessels. The vascular mesenchyme of the central excavation invaded the chorioallantoic placenta during this period, forming two fetal lobules of labyrinthine-fine syncytium, the zone of the placental barrier. The activity of Na⁺/K⁺ ATPase in the placental barrier was constant during the gestational period. The residual syncytium at the periphery of the placental disc and between the lobules was not invaded by fetal mesenchyme and formed the marginal and interlobular labyrinthine syncytium that immunostained first for CK, and later for hPL, as in the labyrinthine fine syncytium. The presence of intracytoplasmic electron-dense material in the interlobular labyrinthine syncytium suggested a secretory process in these cells that are bathed in maternal blood. Placentas obtained from vaginal births presented a large, single lobe, absence of the subplacenta, and a reduced interlobular labyrinthine syncytium. At day 27, the inverted visceral yolk sac is observed and its columnar epithelium immunostained for CK and hPL. This suggests that the yolk sac is an early secretory organ. The epithelium of the parietal yolk sac covers the placenta. The origin of the EST in the degu placenta and its migration to maternal vessels allows us to present this animal model for the study of pregnancy pathologies related to alterations in the migration of the extravillous trophoblast.     

Development of the implantation chamber in the pregnant bitch.

Uteri taken from 25 bitches at various times during the early stages of pregnancy were studies cytologically to determine how the implantation chamber developed and how fetal-maternal relations were established. On day 13 after the end of estrus, knobs of trophoblastic syncytium formed and became wedged between cells of the uterine luminal epithelium. The syncytium quickly spread along the uterine lumen and into the mouths of the glands, dislodging and surrounding maternal cells. As invasion continued trophoblastic villi, consisting of cores of cytotrophoblast covered by a continuous layer of syncytium, penetrated deeper into the endometrium. The syncytium spread to surround maternal vessels and decidual cells. By day 26 the trophoblast had extended down to the large lacunae. Here syncytial trophoblast covering tips of the villi degenerated, leaving cytotrophoblast exposed to the necrotic zone. These cells possessed characteristics of absorbing cells. Hematomas were formed by focal necrosis of fetal and endometrial tissue at the poles of the implantation sites. Large pools of extravasated blood accumulated and red blood cells were phagocytized by surrounding trophoblastic cells. Therefore, the endotheliochorial relationship in the canine placenta appeared to be established by syncytial trophoblast invading a cellular endometrium. In the necrotic zone and hematomas, cellular trophoblast may have lost its syncytial covering, but elsewhere maternal vessels and decidual cells in the placenta were in direct contact only with syncytial trophoblast.     

Ultrastructure of trophoblast giant cell transformation during the invasive stage of implantation of the mouse embryo

The fine structure of abembryonic and mural trophoblast cells of mouse embryos was analyzed during the initial stages of invasion of the endometrial stroma by the embryo (days 6-8 of pregnancy). On day 6 of pregnancy, most trophoblastic cells are flat and have spindle-shaped nuclei. A few large, round trophoblastic cells (giant cells) are present at the abembryonic pole. As pregnancy proceeds through days 7 and 8, the area occupied by the trophoblast becomes larger because of an increase in the trophoblastic cell population, growth of giant cells, and rearrangement of the latter cells into a network containing maternal blood. As flat cells transform into giant cells, their content of ribosomes, granular endoplasmic reticulum, Golgi complexes, lysosomelike bodies, and heterophagosomes increases. Reichert's membrane is always lined by cell bodies or by laminar processes of trophoblastic cells that are provided with small pores. Transformation of flat cells into giant cells is associated with an activation of the giant cells and their acquisition of invasive behavior.     

Alterations in the expression of homing-associated molecules at the maternal/fetal interface during the course of pregnancy.

One of the most fascinating immunologic questions is how the genetically distinct fetus is able to survive and develop within the mother without provoking an immune rejection response. The pregnant uterus undergoes rapid morphological and functional changes, and these changes may influence the nature of local immune responses at the maternal/fetal interface at different stages of gestation. We hypothesized that specialized mechanisms exist to control access of maternal leukocyte subsets to the decidua and that these mechanisms are modulated during the course of pregnancy. At the critical period of initial placenta development, the maternal/fetal interface displays an unparalleled compartmentalization of microenvironmental domains associated with highly differentiated vessels expressing vascular addressins in nonoverlapping patterns and with recruitment of specialized leukocyte subsets (monocytes, granulated metrial gland cells, and granulocytes) thought to support, modulate, and regulate trophoblast invasion. One of the most striking observations at this time of gestation is the almost complete exclusion of lymphocytes from the maternal/fetal interface. The second half of pregnancy is characterized by a partial loss of microenvironmental specialization and different switches in vascular specificity within the decidua basalis, paralleling dramatic changes in the populations of recruited leukocytes (e.g., a striking influx of lymphocytes, especially T cells). In the term pregnant uterus, the expression of all vascular addressins decreased dramatically; only weakly staining maternal vascular segments remained. These segments may define sites of extremely low residual traffic in the term decidua, which contains remarkably few maternal leukocytes overall. Our results suggest that the maternal/fetal interface represents a situation in which leukocyte trafficking is exquisitely regulated to allow entry of specialized leukocyte subsets that may play a fundamental role in immune regulation during pregnancy.     

Microfluorometric study of glucose-6-phosphate and malate dehydrogenases in histologically defined areas of the uterus in cyclic and pregnant ewes

Activities of glucose-6-phosphate dehydrogenase (E.C. 1.1.1.49; G6PDH) and malate dehydrogenase (E.C. 1.1.1.37; MDH) were determined fluorometrically in freeze-dried sections of the sheep uterus during the estrous cycle and pregnancy. Samples (0.2–0.3 μg) from the luminal epithelium, uterine glands, maternal caruncles, fetal cotyledons and intercotyledonary trophoblast were assayed in a small aliquot (5 μl) of the reaction medium under oil.Activity of G6PDH in the luminal epithelium, uterine glands and maternal caruncles did not change during the estrous cycle. Activity of MDH in the uterine glands did not change during the cycle, but in the luminal epithelium and maternal caruncles highest activities were found on day 9 and day 2 post-estrus, respectively.The enzyme activities in the fetal tissues were lower than in the maternal tissues. In all maternal tissues, MDH and G6PDH activities decreased during early pregnancy, but after implantation, the activities increased significantly. In fetal tissues G6PDH activity increased, whereas MDH activity decreased during the second half of gestation. These results suggest an increased rate of pentose shunt activity in both maternal and fetal tissues, and an increased rate of Krebs' cycle activity in the maternal but not in the fetal tissues.     

Ultrastructural features of the nucleus and cytoplasm of rat trophoblast cells of the connective zone of the placenta and labyrinth

Ultrastructural organization of the rat trophoblast cells in the connective zone of placenta and labyrinth was investigated on the 12-14th days of gestation. A clear distinction was revealed in the cytoplasm ultrastructure of two cell subpopulations within the connective zone of placenta, i.e. glycogen and trophospongium cells. The former display a well defined network of long thin channels of granular endoplasmic reticulum situated mainly around the glycogen clusters. On the contrary, the latter are rich in the smooth endoplasmic reticulum but lacking glycogen accumulation. Differences in the nucleolar ultrastructure in these two cell subpopulations are not very considerable. A characteristic feature of glycogen cells is the presence of numerous round or oval small-fibrillar nucleolus-like bodies with the diameter of granules 20 nm. The trophoblast cells of the labyrinth are heavily laden with polysomes, which sometimes attach to short channels of the granular endoplasmic reticulum. Not often there occur short profiles of the agranular endoplasmic reticulum. Nucleolus-like bodies are found in all the cell types examined. This means that the nucleolus-like bodies may arise not only on the lampbrush chromosomes in the oocytes or polytene chromosomes, but also in the somatic cells which are capable of dividing mitotically.     

Monoclonal antibody (SBU-1 and SBU-3) identification of cells dissociated from the sheep placentomal trophoblast.

We studied the localization of alpha-keratin in the sheep placenta using an alpha-keratin-specific monoclonal antibody (MAb) SBU-1, and examined the feasibility of using this MAb as a marker for determining the purity of isolated uninucleate cells from the placentomal trophoblast. At about 30-50 days of gestation the placentomal and interplacentomal uninucleate cells and some binucleate cells were stained by SBU-1, whereas only the apical region of the syncytial cytoplasm was stained with this MAb. Other cells stained included the uterine and endometrial glandular epithelial cells and fibroblast-like cells in the endometrium and chorionic villi. At about 100-130 days of gestation only the trophoblast uninucleate cells were stained by SBU-1. Approximately 60% of cells isolated from placentomes at 100-130 days of gestation were stained by SBU-1, and they had similar morphological features to the trophoblast uninucleate cells. The number of binucleate cells present was confirmed by their affinity for MAb SBU-3. These results show that MAb SBU-1 is an excellent marker for trophoblast uninucleate cells from placenta of sheep at the later stages of pregnancy.     

Ultrastructural morphometric analysis of the uterine epithelium during early pregnancy in the sheep

Stereological techniques were used to quantify ultrastructural changes in the caruncular epithelium during the pre- (Day 13), peri- (Day 16) and post- (Days 19 and 22) attachment periods of placentation. Tissues from Day-13 non-pregnant ewes were used as controls. Uteri for stereological evaluation were perfused via the uterine artery with 3% glutaraldehyde and separated into proximal, middle and distal regions. Tissues from caruncular areas were processed for electron microscopy. Volume fractions (Vv) of nuclei, mitochondria, lipid and cytoplasmic granules were estimated by point-counting volumetry. Surface areas per unit tissue volume (Sv) of mitochondrial membranes and cristae, Golgi, plasmalemma, endoplasmic reticulum and nuclear membranes were estimated by line-intersection counting. The only significant difference between pregnant and non-pregnant uterine epithelium at Day 13, a time before attachment, was a lower Sv of smooth endoplasmic reticulum (SER) in tissue from pregnant ewes. This value returned to control (non-pregnant Day 13) levels at Day 16, and was again significantly reduced at Days 19 and 22. The Vv of lipid decreased significantly at Day 16 and remained at reduced levels thereafter. These changes may reflect the effects of conceptus products on lipid storage and mobilization. The Sv of rough endoplasmic reticulum (RER) significantly increased on Day 16 of gestation, and remained elevated on Day 19. These results may reflect increased synthesis of protein for export at these times. In general, several of the values measured which may be indicative of cellular metabolism were reduced at Day 22 of pregnancy, perhaps suggesting diminished metabolism by the uterine epithelium after attachment of the trophoblast.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural observations on the maturation of the placental labyrinth of the golden hamster (days 10 to 16 of gestation).

Morphogenesis of the labyrinthine part of the chorioallantoic placenta of the golden hamster between day 10 of gestation and term (day 16) was studied by light and electron microscopy. During this period the labyrinth increases greatly in both size and complexity. Trabeculae of the labyrinth, thin partitions composed of trophoblastic tissue and fetal capillaries which delimit the maternal blood spaces, apparently proliferate both by appositional and interstitial growth. From the time of its formation (day 9 of gestation) until term the labyrinth is hemotrichorial in organization (i.e. three layers of trophoblast separate maternal blood from fetal capillaries). Both the inner and intermediate layers of trophoblast (layers III and II, respectively) are syncytial. The outer trophoblastic layer (III), which is in direct contact with maternal blood, remains cellular, although many of its component cells grow to giant cell dimensions ("labyrinthine giant cells"). Between the tenth and fourteenth days of gestation the anatomical barrier to diffusion between maternal and fetal blood is progressively reduced. This is accomplished both by gradual attenuation of the trophoblastic layers and fetal capillary endothelium and by the formation of discontinuities (gaps) in layer I, and diaphragmed fenestrae in fetal capillary endothelium. The labyrinthine placental barrier is fully developed and probably attains maximal functional efficiency by the fourteenth day of gestation. Late in the fifteenth day of gestation, a few hours before parturition, distinct degenerative changes are apparent in the trophoblastic layers and fetal capillaries of the trabeculae. The factors responsible for initiation these degenerative changes and the onset of parturition are still controversial.     

The expression of Fas/FasL and apoptosis in yak placentomes

To clarify the status and distribution of Fas and Fas-Ligand (FasL) in yak's placentomes, immunohistochemistry (IHC) was carried out to analyze the expression and location of Fas and FasL in paraffin embedded sections. The area of positive stained sites was selected and measured using image analyses software (Image Pro-Plus 6.0). So the positive index (PI) was calculated to estimate the intensity of protein expression according to the percentage of positive area in corresponding compartment of the placentomes. In cotyledonary villi, Fas mainly presented on the villous trophoblast cells in early pregnancy. The positive index reached a maximum of 20.7±8.8 at the third month of pregnancy. Then Fas was declined rapidly along with the progress of gestation and the value was 2.8±1.3 after the 7th month of pregnancy. However, in caruncular crypts, Fas was mainly localized to isolated cells or clustered cells of the uterine stroma underlying the caruncular epithelium. The intensity was lower and the positive index was changed between 4.7±0.9 and 8.5±1.6 throughout gestation. For FasL, it gave a distinct immunostained distribution. In cotyledonary villi, FasL was localized dominantly and strongly in the cytoplasm of binuclear, mononuclear and trinuclear trophoblast giant cells (TGC). The positive index of FasL maintained a moderate level all through the gestation. In caruncular crypts, the expression of FasL was weak and the positive index was declined. Only in the first two months, maternal uterine epithelial cells intensely expressed FasL and the index reached to the maximum of 19.8±5.2. The result of subcellular localization of Fas ligand using immunoelectron microscopy technology indicated that FasL was subcellular located in some intracellular vesicles of TGC. This means the vesicles of trophoblast giant cells itself can express FasL. By the TUNEL method, apoptosis was detected in yak placentomes. The amount of apoptotic cells was rare. The fetal chorionic trophoblast cells and caruncular crypt epithelium cells demonstrated higher percentage of apoptosis in middle pregnancy, which suggested that apoptosis plays an important role in placental cellular regeneration. In addition, the apoptosis of maternal caruncular stromal cells provides a local mechanism for maternal immunotolerance to the fetus and this mechanism was mediated by Fas-FasL pathway.     

Determinants of trophoblast lineage and cell subtype specification in the mouse placenta

Cells of the trophoblast lineage make up the epithelial compartment of the placenta, and their rapid development is essential for the establishment and maintenance of pregnancy. A diverse array of specialized trophoblast subtypes form throughout gestation and are responsible for mediating implantation, as well as promotion of blood to the implantation site, changes in maternal physiology, and nutrient and gas exchange between the fetal and maternal blood supplies. Within the last decade, targeted mutations in mice and the study of trophoblast stem cells in vitro have contributed greatly to our understanding of trophoblast lineage development. Here, we review recent insights into the molecular pathways regulating trophoblast lineage segregation, stem cell maintenance, and subtype differentiation.     

Fetal cells in the maternal circulation during first trimester in pregnancies

To investigate the presence of fetal cells in the maternal circulation during early pregnancy, the polymerase chain reaction was used to test the presence of human Y chromosome-specific ZFY and SRY gene DNA sequences in maternal peripheral blood specimens from 19 women carrying male fetuses and 12 women carrying female fetuses. The presence of fetal cells was suggested as early as 6 weeks gestation in 1 of the 19 women bearing male fetuses. Fetal cells were present in the maternal circulation of 15 of the 19 women by 9 weeks gestation, and in only 1 of the 19 were fetal cells not detected until the 12th week after conception. These results suggest that identification of fetal cells in the maternal circulation is possible with a properly designed and executed polymerase chain reaction. However, there was considerable variation with respect to when these fetal cells first became detectable during pregnancy. These fetal cells are potentially a valuable source of material for biochemical and genetic studies of the fetuses.     

Changes in glycan distribution within the porcine interhaemal barrier during gestation

Changing patterns of glycan distribution are described in porcine placentae at 15, 19, 26, 43, 58, 69 and 109 days gestation, using a carefully selected panel of lectins that allowed partial analysis of saccharide classes and sequences. The lectins used were from Galanthus nivalis, Pisum sativum, Phaseolus vulgaris (leukohaemagglutinin), Triticum vulgaris, Tetragonolobus purpureus, Ulex europaeus-1, Arachis hypogaea, Erythrina cristagalli, Glycine max, Maclura pomifera, Wisteria floribunda, Dolichos biflorus, Maackia amurensis, Sambucus nigra and Limax flavus. During the course of gestation the trophoblast developed from a smooth to a deeply folded membrane, while enlarging fetal and maternal capillaries grew closer to each other. The fetomaternal interface expressed many classes of saccharide, both O-and N-linked, but failed to bind DBA, MAA and SNA. Many granules were present in the maternal epithelium, and a striking feature was the appearance of staining with DBA and UEA-1 by day 43. This stage of pregnancy was also associated with changes in trophoblast glycan expression, with a diminution in staining intensity of AHA, MPA and LTA, but an increased intensity with ECA, SBA and WFA. Changes in lectin binding throughout gestation are correlated with previous ultrastructural findings and their relevance to the immunological and functional aspects of pregnancy is discussed.