Pregnancy-related changes in the mouse oviduct and uterus revealed by differential binding of fluoresceinated lectins

Functional glycosylation in the human and mammalian uterus

Background

Glycosylation is the most common and structurally diverse of all the post-translational modifications of proteins. Lipids and extracellular matrices are also often glycosylated. The mammalian uterus is highly enriched in glycoconjugates that are associated with the apical surfaces of epithelial cells and the secretions released by both epithelial and stromal cells. These glycoconjugates interact primarily with sperm, the implanting embryo, the fetus, and any pathogen that happens to gain entry into the uterus. Secretions of the endometrial glands increase substantially during the luteal phase of the menstrual cycle. These secretions are highly enriched in glycoproteins and mucins that promote specific uterine functions.

Findings

Lectins and antibodies have been employed in the majority of the studies focused on uterine glycosylation have employed to define the expression of carbohydrate sequences. However, while these studies provide insight about potential glycosylation, precise information about glycan structure is lacking. Direct sequencing studies that employ biochemical or mass spectrometric methods are far more definitive, but have rarely been employed with uterine glycoproteins. Both lectin/antibody binding and direct carbohydrate sequencing studies that have been focused on the mammalian uterus are reviewed. The primary functional role of the eutherian uterus is to facilitate fertilization and nurture the developing embryo/fetus. Trophoblasts are the primary cells that mediate the binding of the embryo and placenta to the uterine lining. In mammals that utilize hemochorial placentation, they invade the decidua, the specialized endometrial lining that forms during pregnancy. Trophoblasts have also been analyzed for their lectin/antibody binding as a complement to the analysis of the uterine cells and tissues. They will also be reviewed here.

Conclusions

The functional roles of the glycans linked to uterine and trophoblast glycoconjugates remain enigmatic. Another major question in the human is whether defects in placental or uterine glycosylation play a role in the development the Great Obstetrical Syndromes. More recent findings indicate that changes in glycosylation occur in trophoblasts obtained from patients that develop preeclampsia and preterm birth. The functional significance of these changes remain to be defined. Whether such shifts happen during the development of other types of obstetrical syndromes remains to be determined.

High-resolution three-dimensional in vivo imaging of mouse oviduct using optical coherence tomography

The understanding of the reproductive events and the molecular mechanisms regulating fertility and infertility in humans relies heavily on the analysis of the corresponding phenotypes in mouse models. While molecular genetic approaches provide significant insight into the molecular regulation of these processes, the lack of live imaging methods that allow for detailed visualization of the mouse reproductive organs limits our investigations of dynamic events taking place during the ovulation, the fertilization and the pre-implantation stages of embryonic development. Here we introduce an in vivo three-dimensional imaging approach for visualizing the mouse oviduct and reproductive events with micro-scale spatial resolution using optical coherence tomography (OCT). This method relies on the natural tissue optical contrast and does not require the application of any contrast agents. For the first time, we present live high-resolution images of the internal structural features of the oviduct, as well as other reproductive organs and the oocytes surrounded by cumulus cells. These results provide the basis for a wide range of live dynamic studies focused on understanding fertility and infertility.

Modifications of carbohydrate residues in the sheep oviductal ampulla after superovulation

Epithelium of oviductal ampulla was studied in normal and in superovulated sheep using morphologic analysis and lectin glycohistochemistry. The lining epithelium consisted of two types of cells, ciliated and nonciliated cells. Unlike superovulated samples, the nonciliated cells from control ewes showed apical protrusions indicating an apocrine secretory activity. The ciliated cells showed lectin-binding sites mainly at the level of the cilia which bound all the used lectins except Peanut agglutinin, suggesting the lack of glycans terminating with Galβ1,3GalNAc. In superovulated specimens, the ciliated cells with high mannosylated glycans Concanavalin A (Con A) and GlcNAc and GalNac termini Griffonia simplicifolia agglutinin II (GSA II) and Dolicurus biflorus agglutinin (DBA) decreased. The luminal surface of nonciliated cells showed all investigated sugar residues in controls, whereas it was lacking in high mannosylated (Con A) and terminal GalNAcα1,3(LFucα1,2)Galβ1,3/4GlcNAcβ1 sequence (DBA) in superovulated ewes. Apical protrusions from control ampullae nonciliated cells showed glycans containing mannose, GlcNac, GalNAc, galactose, and α2,3-linked sialic acid (Con A, KOH-sialidase- Wheat germ agglutnin [WGA], GSA II, SBA, Griffonia simplicifolia agglutinin-isolectin B4 [GSA I-B4], Maackia amurensis agglutinin II [MAL II]). The supranuclear cytoplasm of nonciliated cells expressed terminal GlcNAc (GSA II) in all specimens, also O-linked glycans (mucin-type glycans) with GalNAc and sialic acid termini (Helix pomatia agglutinin [HPA] and MAL II) in control animals, and also N-linked glycans with fucose, galactose, lactosamine, and α2,3-linked sialic acid termini (Ulex europaeus agglutinin I [UEA I], GSA I-B4, Ricinus communis agglutinin120 [RCA120], and Sambucus nigra agglutinin [SNA] ) in superovulated ewes. These results report for the first time that the superovulation treatment affects the secretory activity and the glycan pattern of the epithelium lining the sheep oviductal ampulla.

Detection of glycosylated proteins in rabbit oviductal isthmus and uterine endometrium during early embryo development

In this study, lectin histochemistry was performed on paraffin sections to compare carbohydrate expression of oviductal isthmus and uterine endometrium in rabbits during early embryo development. Rabbit embryos are surrounded not only by the zona pellucida but also by tubal secretion-derived mucinous coat material, the mucin coat. Twenty sexually mature females were euthanized at 0 (pre-ovulatory group) and 24, 72 and 96 h after insemination (pseudopregnancy group). The following lectin-binding agents were used: Arachis hypogaea, Peanut (PNA) to label galactosyl (β-1,3)N- acetyl-galactosamine, Dolichos biflorus Agglutinin (DBA) to label galactosyl (β-1,4)N- acetyl-galactosamine, Lens curinaris (LCA) to label α--mannose, α-d-glucose and Pisum sativum agglutinin (PSA) to label α-d-mannose, α-d-glucose. Blood was collected by cardiac puncture, and direct enzyme immunoassay technique was used to measure progesterone concentration. A significant increase in total plasma progesterone concentrations was detected at 96 h post-ovulation when compared with 0, 24 and 72 h post-ovulation (2.9 ± 0.5 vs 0.5 ± 0.15, 1.6 ± 0.5 and 1.5 ± 0.4 ng/ml, at 96 h vs 0, 24 and 72 h post-ovulation, respectively). No differences between pre-ovulatory and pseudopregnant females were observed for glycoprotein localization in isthmus. In contrast, in the endometrium, differences in the glycoprotein detection between pre-ovulatory and pseudopregnant stages were detected. PNA to label galactosyl (β-1,3)N- acetyl-galactosamine was not detected at the pre-ovulatory stage, but its presence was detected at 24 h after ovulation. Both PSA and LCA to label α-d-mannose, α-d-glucose were only detected at 72 h after ovulation. DBA detection was similar for all stages of the reproductive cycle. Therefore, N-acetyl-galactosamine secreted from isthmus could be involved in the formation of the embryonic mucin coat. d-galactose (PNA), d-glucose and d-mannose (PSA and LCA) might be crucial for the implantation period.

Glycan-modifying enzymes in luminal fluid of the mammalian epididymis: an overview of their potential role in sperm maturation

Testicular spermatozoa and those present within the proximal regions of the epididymis are unable to bind to the zona pellucida, the extracellular coat that surrounds the oocyte, and fertilize the egg. They acquire progressive motility and fertilizing ability during passage through the epididymis. Mammalian spermatozoa undergo biochemical and physiological changes during epididymal transit that are collectively termed epididymal maturation. The process involves several intracellular and extracellular changes in the spermatozoon, including remodeling of the sperm plasma membrane and modifications of glycan moieties of the sperm surface glycoconjugates. Two sets of glycan-modifying enzymes, namely glycohydrolases that cleave sugar residues and glycosyltransferases that add sugar residues to the existing glycoconjugates, are present in the epididymal luminal fluid that surrounds spermatozoa. Thus, it is reasonable to expect that glycan chains present on the sperm surface will interact with these glycan-modifying enzymes in the epididymal fluid. In this article, I have attempted to summarize and present an overview on the potential role of these glycan-modifying enzymes in sperm maturation.

Carbohydrates and glycoproteins involved in bovine fertilization in vitro

In the present study, efforts were made towards identifying carbohydrates and glycoproteins involved in bovine in vitro fertilization (IVF). In vitro matured cumulus-oocyte complexes (COCs) were inseminated in the presence of a variety of carbohydrates and glycoproteins to determine which glycoconjugates act as competitive inhibitors of oocyte penetration. Among the carbohydrates and glycoproteins tested, D-mannose, fucoidan, dextran sulfate, and fibronectin were the most potent inhibitors of oocyte penetration (90% or more inhibition), while L-fucose and vitronectin inhibited the penetration rate to a lesser extent (around 50% inhibition). Other carbohydrates caused less than 40% inhibition (i.e., D-galactose, N-acetyl-D-galactosamine, D-fucose, and sialic acid) or were not effective as inhibitors of oocyte penetration (i.e., mannan, N-acetyl-D-glucosamine, dextran, and heparan sulfate). Heparin was the only carbohydrate that significantly increased the penetration rate. To exclude a possible toxic effect on spermatozoa, sperm motility was evaluated over time by means of computer-assisted sperm analysis in the presence of carbohydrates and/or glycoproteins that inhibited the penetration rate with 40% or more. L-fucose, dextran sulfate, and vitronectin did not significantly influence total and progressive sperm motility, whereas D-mannose, fucoidan, and fibronectin caused a significant, but slight reduction in both motility parameters. These results are indicative for the involvement of D-mannose, L-fucose, fucoidan, dextran sulfate, fibronectin, and vitronectin in bovine IVF.

Capacitated acrosome-intact mouse spermatozoa bind to Sepharose beads coated with functional neoglycoproteins

Capacitated acrosome-intact mouse spermatozoa bind to the egg's extracellular coat, the zona pellucida (ZP), in a carbohydrate-mediated receptor-ligand manner. The tight irreversible binding of the opposite gametes triggers a signal transduction pathway resulting in the exocytosis of acrosomal contents (i.e., induction of the acrosome reaction [AR]). Previously, we demonstrated that a hexose (mannose) and two amino sugars (N-acetylglucosamine and N-acetylgalactosamine), when covalently conjugated to bovine serum albumin (BSA) (functional neoglycoproteins, ngps), mimicked mZP3 and induced the AR [Biol. Reprod. 60 (1999) 94-101]. To further elucidate the specificity of sperm-ngp interaction and the mZP3 mimicking role of the functional ngps, we have examined binding of the mouse spermatozoa to Sepharose 4B beads coated with the functional and non-functional ngps as well as BSA, ovalbumin (OVA), or asialofetuin (ASF). A significantly greater number of capacitated acrosome-intact spermatozoa bound to the beads coated with functional ngps than the beads coated with non-functional ngps, BSA, OVA, or ASF. The binding was temperature-sensitive and was highest when the sperm-bead assay was carried out at 37 degrees C. Blocking of in vitro capacitation, by including calmodulin antagonists in the incubation medium, prevented sperm from binding to the beads. Furthermore, inclusion of free sugars (mannose, N-acetylglucosamine, or N-acetylgalactosamine) in the binding assay, either individually or as a mixture, inhibited sperm-bead binding in a concentration-dependent manner. Taken together, our data provide evidence strongly suggesting that binding of capacitated spermatozoa to the ngp-coated Sepharose beads is specific. The beads that mimic zona-intact eggs provide an excellent tool for examining pharmacological effects of reagents that alter the sperm function. In addition, the immobilized ngp(s) will be useful as an affinity medium to isolate the sperm surface receptor(s) that recognize and bind to the sugar residues.

Pyriform cell differentiation in Podarcis sicula is accompanied by the appearance of surface glycoproteins bearing alpha-galNAc terminated chains

The present histochemical and cytochemical study using a lectin panel (WGA, GSI-A4, GSI-B4, PSA UEA-I, PNA, LCA, Con-A, DBA, MPA, BPA) has demonstrated that, in Podarcis sicula, the differentiation of small follicle cells into pyriform cells by means of intermediate cells is accompanied by the appearance of glycoproteins bearing alpha-GalNAc terminated O-linked side chains on the cell surface. The distribution of DBA- and MPA-binding sites over the follicular epithelium changed during the different stages of oocyte growth. DBA- and MPA-binding sites first appeared at the beginning of folliculogenesis within the zona pellucida (ZP) and on the surface of small cells, i.e., the stem cells of pyriform cells. Afterward, labeling was evident on the cell surfaces of intermediate cells and, later on, also of pyriform cells. On the other hand, no labeling was detected on the small cells located under the basal lamina, which, reportedly, do not differentiate into pyriform cells (Filosa et al. J. Embryol. Exp. Morphol., 1979; 15:297-316). Once pyriform cells were differentiated, the distribution of DBA- and MPA-binding sites over the follicular epithelium remained unchanged until intermediate and pyriform cells underwent apoptosis (Motta et al. J. Exp. Zool., 1996; 276:233-241) and the follicular epithelium transformed into a monolayer composed of small follicle cells only (Filosa Mon. Zool. Ital., 1973; 7:151-165). During this stage of oocyte growth, DBA and MPA labeling gradually decreased to completely disappear in the follicular epithelium of vitellogenic follicles. It is noteworthy that the observed changes in the distribution of DBA- and MPA-binding sites represent the first evidence recognized by lectins of a gradual modification of surface glycoprotein distribution over the follicular epithelium in the ovarian follicles of nonmammalian vertebrates so far studied. Finally, the zona pellucida (ZP), characterized by the presence of GalNAc, GluNAc, Man, and Gal, was demonstrated to be first synthetized by the oocyte and later on by the follicle cells.

Expression of glucosamine trisaccharides on the rat uterine surface is altered by clomiphene citrate

We have studied histochemically the effects of clomiphene citrate on the expression of oligosacchrides on the apical plasma membrane of uterine epithelial cells using the lectin Phytolacca americana. Ovariectomized sexually mature rats were given a single injection of either clomiphene in two concentrations or estradiol 17 beta or progesterone and were killed 24 hr later. Uterine tissue was labeled with Phytolacca americana conjugated with avidin and subsequently labeled with biotinalyted ferritin and prepared for transmission electron microscopy. Our results indicate that clomiphene and to a lesser degree progesterone significantly increased lectin binding. However, the increase was not as large as that observed with a single dose of estrodiol 17 beta. When the proportion of lectin positivity in relation to total membrane length was analyzed, treatment with clomiphene and progesterone did not have significantly different effects. Low dose clomiphene did not have a significant effect as compared with controls. Our data show that clomiphene has a dose-dependent adverse effect on lectin binding as compared with ovarian hormones. We suggest that these effects contribute to low pregnancy rates with clomiphene use.

Ultrastructural studies of glycan changes in the apical surface of the uterine epithelium during pre-ovulatory and and pre-implantation stages in the marmoset monkey

It has been postulated that carbohydrates are involved in a variety of cell-cell interactions including blastocyst implantation. In primates, there are only limited investigations on the ultrastructural localisation of the cyclic changes in uterine epithelial surface carbohydrates. Our aim was to investigate such changes during the pre-ovulatory and pre-implantation stages of the reproductive cycle in the marmoset monkey. After fixation of endometrial tissues, avidin-ferritin lectin cytochemistry was employed for apical surface glycan detection at the ultrastructural level. Five lectins were used including Canavalia ensiformis (Con A), Lotus tetragonolobus (LTA), Glycine max (SBA), Phytolacca americana (PWM) and Triticum vulgaris (WGA). Morphometry was used to quantitate changes in the intensity of lectin staining by determining the total number of ferritin particles per unit length of membrane. Surface and intra-cytoplasmic vesicles, stained by the lectins, were also examined. Quantitative ferritin assessment showed that 1 day before presumed implantation (days 11 to 12 after ovulation in the marmoset monkey) there was a significant increase in Con A, LTA and SBA staining on the apical uterine epithelial plasma membrane compared to the pre-ovulatory phase and earlier stages of pregnancy (days 4-8 after ovulation). A significant increase in PWM was also detected from early pregnancy to pre-implantation stages. All lectins except WGA produced reproducible staining within reproductive cycle groups. The greatest variation and intensity of epithelial surface staining was observed with WGA and the weakest with LTA. The patchy staining with LTA compared with thick coverage by WGA indicated the complexity of the carbohydrate arrangement in the glycocalyx of the uterine surface plasma membrane. Reduction of WGA reactivity after neuraminidase treatment suggested that the lectin binding might be related to the presence of heavily sialylated apical uterine membrane glycoconjugates. This is the first high-resolution study in primates to report quantitative cyclic changes in fucosyl, galactosyl, glucosyl, and mannosyl sugar residues of the apical uterine epithelial glycocalyx. The findings support the concept that uterine epithelial glycocalyx surface carbohydrates play a role in preparing a receptive uterine surface.

The role of carbohydrates in the induction of the acrosome reaction in mouse spermatozoa

Capacitated acrosome-intact mouse spermatozoa bind to the egg's zona pellucida in a receptor-ligand-mediated manner. Mouse zona pellucida 3 (mZP3) is a glycoprotein that functions as a primary ligand and inducer of the acrosome reaction (AR). Multiple sugar residues on mZP3 are thought to be recognized by complementary sugar binding enzymes (glycosidases or glycosyltransferases) or sugar binding lectin-like proteins on the sperm surface. To elucidate the nature of the sugar residues involved in sperm-egg recognition, several neoglycoproteins (ngps) were tested for their ability to induce the AR. Ngps are synthetic glycoproteins with a known monosaccharide conjugated to BSA. Capacitated mouse spermatozoa were treated in the absence or presence of several concentrations of ngps. A significantly greater number of spermatozoa underwent the AR in the presence of mannose-BSA, N-acetylglucosamine-BSA, and N-acetylgalactosamine-BSA than in their absence. Glucose-BSA or galactose-BSA had no effect on the AR. Inclusion of millimolar concentrations of unconjugated sugars (mannose, N-acetylglucosamine, or N-acetylgalactosamine) neither induced the AR nor blocked induction of the AR by ngps. These results demonstrate that some sugar residues can induce the AR, but only when conjugated to a protein backbone. Glucosaminyl-BSA (but not mannosyl-BSA or galactosaminyl-BSA) was a substrate for sperm-surface galactosyltransferase (GT), an enzyme thought to function as a receptor by binding to complementary glucosaminyl residues on mZP3. These data suggest a possible interaction between protein-conjugated glucosaminyl residues and sperm GT in the induction of the AR.

Isolation and characterization of a protein with homology to angiotensin converting enzyme from the periacrosomal plasma membrane of equine spermatozoa

The periacrosomal plasma membrane of spermatozoa is involved in sperm binding to oviductal epithelial cells and to the zona pellucida. A protein of 68-70 kD molecular mass was purified biochemically from the isolated periacrosomal plasma membrane of equine spermatozoa as a possible receptor for adhesion of spermatozoa to oviductal epithelial cells. A polyclonal antibody raised in rabbits against the purified equine sperm membrane protein recognized the 70 kD and an antigenically related to 32 kD protein in preparations of isolated periacrosomal sperm plasma membrane and in detergent extracted ejaculated and epididymal spermatozoa. A larger protein (approximately 110 kD) was detected in equine testis. Two antigenically related proteins (64 and 45 kD) were recognized on the plasma membrane of cynomolgus macaque spermatozoa. In vitro sperm-binding assays were performed in the presence of antigen-binding fragments or IgG purified from the polyclonal antiserum to investigate a possible function to the isolated protein in binding of equine spermatozoa to homologous oviductal epithelial cells or zona pellucida. Incubation with antigen-binding fragments or IgG purified from the antiserum did not inhibit binding of equine spermatozoa either to oviductal epithelial cells or the zona pellucida. On ultrastructural examination, the antibody bound exclusively to the cytoplasmic side of the periacrosomal plasma membrane of equine and macaque spermatozoa. Microsequence analysis of 13 residues of sequence showed strong homology with a number of angiotensin converting enzymes: An 84% identity was identified with testis specific and somatic forms of human and mouse angiotensin-converting enzyme. Immunocytochemistry and immunoblot analysis established that the protein is specific for the periacrosomal membrane of ejaculated, epididymal, and testicular stallion spermatozoa.

Localisation of glycans in the placenta: a comparative study of epitheliochorial, endotheliochorial, and haemomonochorial placentation

Specimens of mid-term (horse), near-term (pig, cow, sheep, mink) and term (human) placentae and associated tissues have been examined with a panel of 15 biotinylated lectins combined with an avidin-peroxidase revealing system. The aim of this study has been to analyse the expression of glycans at the materno-fetal interface in order to establish whether the morphological diversity exhibited by these six species is reflected by accompanying biochemical diversity, or whether similar types of glycan are expressed in tissues performing similar functions. Lectin staining intensity was scored in the following elements of the interhaemal placental barrier: maternal capillaries, maternal uterine epithelium, the materno-fetal interdigitating microvillous membrane (brush border in the human), trophoblast, and fetal capillaries. A high degree of biochemical diversity was found in the glycan expression of the various placental components within and among placental types. Each layer showed widely differing patterns of lectin binding between species, with only a few findings in common: 1) the relative lack of simple fucosyl termini, 2) the presence of non-bisected bi/tri-antennary N-glycan in most layers, 3) an abundance of terminal N-acetyl galactosamine, and 4) the restriction of high mannose glycans to intracellular granules. This diversity may be a mechanism to avoid hybridisation, although glycan patterns may change between conception and placental development, or it may have evolved as a consequence of morphological changes. It is possible that it may also be part of the cause, rather than the result, of the structural diversity that is so characteristic of mammalian placentation.

Functions of proteins secreted by oviduct epithelial cells

Studies on embryonic development in vitro as well as observations in vivo, suggested that two aspects of oviduct physiology are important for early development. On one side has to be considered the oviduct "environment": temperature, pH, osmotic pressure, nutrients, oxygen tension, free radical scavengers, etc. On the other, the oviduct "active components": stimulatory and/or regulatory molecules, supposed to finely regulate the fertilisation process and the first differentiative steps. While the physical environment of the oviduct has been under investigation for some decades, studies on oviduct-specific molecules and their functions have only been developed much more recently. The amount of information on this topic, however, has rapidly reached the size that demands a summary. In this review the descriptive literature on oviduct specific proteins will be examined as a basis for illustrating the possible functions of these molecules. In particular their role in fertilisation and early embryonic cleavages will be analysed in some details. Finally a section is devoted to the presence and physiological significance of growth factors in oviduct fluid.

Lectin binding and identification of sialic acid acceptor sugars in rabbit oviduct under hormone administration

Localization of individual glycosidic residues and sialic acid acceptor sugars was investigated by conjugated lectins in the rabbit oviduct under physiological hormonal conditions and human chorionic gonadotropin (HCG) administration. Ampulla and isthmus were found to exhibit lectin binding profiles typical of each hormonal stage. Two different sialylated glycomolecules were identified within the epithelial lining; in particular, sialoglycoconjugates characterized by the terminal sequence sialic acid-galactose were visualized in the secretory cells and the sialic acid-N-acetylgalactosamine terminal disaccharides were localized on both ciliated and secretory cells of the entire oviduct. Surface and cytoplasmic sialoglycoconjugates were also found to exhibit a differential behaviour inside the two oviduct tracts examined. Present findings further supported the idea that in ampulla and isthmus, the greatest modifications consequent to hormone treatment take place at different times.

Estrous cycle-related alterations in the expression of glycoconjugates and lectins in the mouse endometrium shown histochemically

Alterations of the hormonal status may influence diverse cell features relevant to intra- and intercellular communication. We studied histochemically the expression of glycans and endogenous sugar-binding proteins (endolectins) in the mouse endometrium during the estrous cycle. The avidin-biotin-peroxidase complex (ABC) technique was used on paraffin sections with a panel of biotinylated lectins and neoglycoproteins. Stage-specific changes were observed with Galanthus nivalis agglutinin (GNA), Ulex europaeus-I agglutinin (UEA-1), Sambucus nigra agglutinin (SNA), Ricinus communis agglutinin (RCA-I) and Glycine max agglutinin (SBA) in both the luminal and the glandular epithelium, but to a lesser extent in the latter. The stromal constituents also exhibited modifications in lectin-binding profiles in cyclic mice. In addition to the analysis of cell glycans endogenous carbohydrate-binding sites were studied using synthetic probes, biotinylated neoglycoproteins. These tools made it possible to conclude that hormonal status can affect the expression of endolectins. We have attempted to correlate the glycohistochemical findings with recently published data obtained biochemically. The results indicate that phase-specific alterations in lectin-binding glycoproteins and endolectins occur in the endometrium of mice associated with their short reproductive cycle.

Regional variations in the ultrastructural features of secretory cells in the rat oviductal epithelium

BACKGROUND

In mammals, the oviductal secretory cells and their secretions play important roles in reproductive and developmental events. Therefore, many electron microscopic studies of mammalian oviductal epithelial cells have been performed.

METHODS

The secretory cells in various regions of the rat oviduct during the estrous cycle were examined by transmission electron microscopy.

RESULTS

In the fimbriae, the secretory cells contained small secretory granules with moderately electron-dense matrices and many large bodies that resembled lipid droplets. In the ampullar cells, small secretory granules with moderately electron-dense matrices were observed in the apical cytoplasm. In the isthmus, the secretory cells contained numerous secretory granules with moderately electron-dense matrices. Electron-dense areas were frequently observed in many of the granules of the isthmic cells. Vesicles, partially filled with a dense substance, frequently were observed in the isthmic cells and occasionally in the ampullar cells. Very long stereocilia projected from the surfaces of the isthmic secretory cells into the lumen. Exocytosis of the secretory granules was observed. In addition, there was evidence to suggest the release of the bodies that resembled lipid droplet occurred. Cysts and ciliated vacuoles that appeared to be intraepithelial were frequently observed in the fimbrial and ampullar epithelia. No dramatic changes in the relative numbers of ciliated and secretory cells in any oviductal segment were observed during the estrous cycle.

CONCLUSIONS

Our ultrastructural observations of the rat oviduct revealed marked regional variations in the morphological features of secretory cells. These results may provide insight into regional and cellular differences in the function of the rat oviduct.

Receptivity is a polarity dependent special function of hormonally regulated uterine epithelial cells

Useful knowledge of the mechanisms which regulate ovoreceptivity and implantation remains elusive in spite of increasing efforts to apply the technology of biochemistry and to a lesser extent, cellular and molecular biology to the analysis of the problem. Existing models used to analyze interactions of the blastocyst and endometrial cells of the uterus have been unable to account for nongenotypic embryonic losses, particularly those following in vitro fertilization and embryo transfer. Separation of endometrial uterine epithelial (UE) and uterine stromal (US) cells was used to demonstrate that each cell type responds independently and interdependently to the same regulatory signals. Cultured by classical techniques UE cells proved unable to respond to steroid hormone signals. For this reason UE cell cultures could not be used to develop an experimental cell system that mimicked growth and development of UE cells in utero. The failure of classical UE cell cultures derived from their inability to maintain epithelial cell polarity. Polarity, the spatial asymmetry of plasma membrane domains, is intrinsic to the structure and function of an epithelial cell. Apical and basolateral surfaces have different lipid and protein compositions which are correlates of the special functions of that epithelial cell. As epithelial cells differentiate they must, in response to regulatory cues, direct the flux of membrane components moving into and out of each surface in order to establish the polarity characteristic of each stage specific expression. The acquisition of receptivity by the apical surface of the UE cell may be considered to be such a special function. To prove this hypothesis polarized cultures of primary UE cells had to be developed that were hormonally responsive. Such an experimental cell system could serve as a model for in vitro implantation. This essay describes such a culture system in which blastocysts cocultured with UE cells in the presence of estrogen, will as predicted, fail to attach. This polarized UE cell system provides a functional in vitro model to study ovoreceptivity. It is now feasible to initiate studies of hormonal regulation of the composition and function of UE cell plasma membranes as they reflect the nonreceptive, receptive, and refractory nature of its apical surface.

Distribution of lectin binding sites in the oviducts of cycling and hormone-treated pigs

Gamete transport, fertilization, and early embryonic development take place in different regions of the oviduct and under different hormonal conditions. The objective of this study was to use lectins to detect variation in the distribution of glycosylated molecules on the surface of the epithelia that influence these events. Oviducts were collected from gilts on day 1 (estrus) and day 16 (diestrus) of the estrous cycle, and from gilts that were bilaterally ovariectomized on day 4 of the estrous cycle, and were subsequently treated with estradiol valerate (100 micrograms/day), progesterone (200 mg/day), or corn oil vehicle for 11 days. Six biotinylated lectins, Triticum vulgaris (WGA), Arachis hypogaea (PNA), Ulex europeus (UEA-I), Dolichos biflorus (DBA), Ricinus communis (RCA-I), and Canavalia ensiformis (Con A), were used to probe tissue from the isthmus and ampulla using peroxidase-conjugated avidin as the marker. In cyclic gilts, WGA and DBA stained more strongly in the isthmus than the ampulla on both cycle days. Staining with PNA was patchy, but greater on the apical surface of isthmic epithelium on day 16 than day 1. With UEA-I, staining was more intense in the ampulla on day 16 than day 1. Staining by PNA and UEA-I was suppressed in both the ampulla and isthmus with estradiol treatment. DBA staining was suppressed in the isthmus with both estradiol and progesterone treatments. Cilia were labelled by all lectins except WGA and PNA. Thus glycosylation patterns vary in the porcine oviduct with region and hormonal state, reflecting the variety of events that may be influenced.

Observations by scanning electron microscopy of oviductal epithelial cells from cows at follicular and luteal phases

The luminal surfaces of epithelial cells in various regions of the bovine oviduct from cows, at the follicular and luteal phases of the estrous cycle, were examined by scanning electron microscopy. Marked cyclic changes were observed on the surface of the epithelium in the fimbriae and ampulla, but few changes were found in the isthmus and uterotubal junction. The epithelium of the fimbriae and ampulla of oviducts in the follicular phase were densely ciliated, and the cilia concealed the apical processes of the nonciliated cells. In the luteal phase, the nonciliated cells predominated in the epithelium and most of the ciliated cells were hidden by the bulbous processes of the nonciliated cells. The epithelium of the ampullar-isthmic junction showed similar changes, but to a lesser extent. In the isthmus and at the utero-tubal junction, the apical surfaces of the nonciliated cells were flat or gently rounded during the estrous cycle. Quantitative examinations by light microscopy showed that the mean percentage of ciliated cells significantly decreased in the fimbriae and ampulla at the luteal phase, but not in the other regions. The height of ciliated cells decreased dramatically in the fimbriae, ampulla, and ampullar-isthmic junction at the luteal phase. By contrast, the height of nonciliated cells decreased significantly in the ampullar-isthmic junction, isthmus, and utero-tubal junction at the luteal phase, but not in the fimbriae and ampullae. The results demonstrate that there are regional variations and cellular differences in the cyclic changes associated with the oviductal epithelial cells in the cow.

Galactose-binding lectins as markers of pregnancy-related glycoproteins

Protein extracts from pregnant mouse endometria were compared with those obtained from non-pregnant and pseudopregnant mice to detect early pregnancy-specific galactose-rich glycoproteins. Gradient gel electrophoresis combined with lectin overlay and lectin histochemistry were used to identify Ricinus communis I (RCA-I), R. communis II (RCA-II) and Cytisus scoparius (CSA) lectin binding glycoproteins. Using this approach, galactose-rich glycoproteins were identified that were maximally expressed in the estrus phase of non-pregnant endometria and also those that had peak expression in pregnancy. Lectin histochemistry revealed pregnancy related changes in three portions of mouse endometrium: endometrial glands, luminal epithelium and its basement membrane. Two major glycoproteins (RCA-I reactive 64 kDa and RCA-II reactive 35 kDa) were specifically expressed in peri-implantation endometrium on days 3 and 4 of pregnancy. The appearance of these glycoproteins during the period of the implantation window in mouse suggests that they could serve as markers of uterine receptivity to the implanting blastocyst.

Examination by scanning electron microscopy of oviductal epithelium of the prolific Chinese Meishan pig at follicular and luteal phases

The luminal surfaces of epithelial cells in the fimbriae, ampulla, isthmus, and utero-tubal junction of the oviducts of the prolific Chinese Meishan pig at follicular and luteal phases of the estrous cycle were examined by scanning electron microscopy. Marked cyclic changes were observed on the surfaces of cells in the fimbriae and ampulla, but little change was found in the isthmus and at the utero-tubal junction. The cells of the fimbrial epithelium in the follicular phase were densely ciliated, and the cilia partially concealed the bulbous processes of the secretory cells. In the luteal phase, the secretory cells predominated in the epithelium, and most of the ciliated cells were hidden by the processes of the secretory cells. The ampullar epithelium showed similar changes, but to a lesser extent. In the isthmus and at the utero-tubal junction, the secretory cells had many microvilli on their bulbous processes at the follicular phase, but they were flat and the microvilli were fewer in number and shorter in length during the luteal phase. Conspicuous solitary cilia protruded from the surfaces of secretory cells in the fimbriae and ampulla during the luteal phase. These results demonstrate that there are regional variations in the cyclic changes associated with the oviductal epithelial cells of the Chinese Meishan pig.

Implanting mouse embryo stain with a LNF-I bearing fluorescent probe at their mural trophectodermal side

Mouse embryos at implantation stage were stained successfully with lacto-N-fucopentaose I (LNF-I) bearing neoglycoprotein labeled with rhodamine synthesized by us for the first time. The fluorescent neoglycoproteins carrying LNF-II, -III, LND-I, or LNT failed to stain the embryos. The embryo was stained only at the cell surface of trophectoderm at the mural side. Since the attachment of the mouse embryo to the uteric epithelium occurs at its mural side trophectoderm and LNF-I is the key substance in mouse implantation (Lindenberg, S. et al, (1988) J. Reprod. Fert. 83, 149-158), the material stained with the probe carrying LNF-I appears to be the molecule responsive to attachment to the endometrium surface and leading to implantation.

Immunocytochemical localization of an oviductal zona pellucida glycoprotein in the oviductal epithelium of the golden hamster

The immunocytochemical localization of an oviductal glycoprotein associated with ovulated eggs was investigated. Using a monoclonal antibody, we studied three regions of epithelium in the golden hamster oviduct. The monoclonal antibody reacted with the oviductal epithelium throughout the fimbriae and isthmus. Intense binding was observed in the ampulla and isthmus, especially in the caudal isthmus. In addition, reactive materials were present in the ovarian bursal sac and lumen of the ampulla. At the ultrastructural level, the monoclonal antibody reacted specifically with putative secretory granules and Golgi apparatus of nonciliated cells in the oviductal epithelium. Other cellular organelles did not react. Quantitative data indicated that the immunolabelings were intense in the ampullar and isthmic cells but weak in the fimbrial cells. Lipid droplet-like granules of the fimbriae and lysosome-like vesicles of the isthmus did not react with the monoclonal antibody. In all cases, ciliated cells did not react with the monoclonal antibody. These results suggest that the glycoprotein is primarily produced and secreted by ampullar and isthmic secretory cells and is then accumulated in the ovarian bursal sac. These findings may provide insight into regional and cellular differences in secretion of the golden hamster oviduct.

Expression of villin in the mouse oviduct and the seminiferous ducts

Villin, a 95-kD cytoskeletal protein selectively expressed in the microvilli of some absorptive cells was localized immunohistochemically in the oviduct and the seminiferous excretory ducts of the mouse. Villin was found in the proximal part of the oviduct, comprising the preampulla, ampulla, and part of the isthmus. Distal to the isthmus the oviductal cells lining the junctura and the intrauterine colliculus tubaris were devoid of villin. No villin could be detected in the uterine cells. Ductuli efferentes, connecting the rete testis with the epididymis were the only portion of the male seminiferous ductal system expressing villin. The cells lining the epididymis and the vas deferens were devoid of villin. These data show that villin is selectively expressed in male and female reproductive systems and that it is limited to anatomically defined proximal portions of the reproductive ducts.

Estrogen induces N-linked glycoprotein expression by immature mouse uterine epithelial cells

Characterization of complex glycoconjugates and the effects of estrogen on their expression in immature mouse uterine epithelial cells are reported. The secreted fraction contained nonanionic, O-linked lactosaminoglycan (LAG)-bearing proteins of Mr 30,000-40,000 as well as anionic, O-linked, LAG-bearing glycoproteins with very high apparent molecular weight (greater than 670K). Heparan sulfate (HS) proteoglycans and HS linked to little or no protein were found in the secreted fraction as well. A very similar array of glycoconjugates was found in the nonhydrophobic fraction of cell-associated macromolecules. In addition, the hydrophobic cell-associated fraction contained nonanionic, LAG-bearing glycoproteins of approximately 250K, anionic LAG-bearing glycoproteins distributing over a wide range of molecular weights, and HS proteoglycans with median molecular weights of approximately 250K. In contrast to the glycoproteins produced by their mature counterparts, virtually all glycoproteins produced by immature cells were O-linked. Estrogen treatment of immature mice caused uterine epithelial cells to secrete anionic, high molecular weight (greater than 670K) N-linked glycoproteins as a major product. These estrogen-responsive glycoproteins did not appear to contain LAGs. Estrogen treatment also markedly decreased the proportion of all hydrophobic glycoconjugates in the cell-associated fraction. Collectively, these observations indicate that one aspect of the estrogen-induced maturation of uterine epithelial cells is the stimulation of N-linked glycoprotein synthesis and secretion. Furthermore, stimulation of N-linked glycoprotein synthesis by itself is insufficient to support N-linked LAG glycoprotein production.

Differences in lectin binding patterns of normal human endometrium between proliferative and secretory phases

Lectin binding patterns in normal human endometrium were examined by light and electron microscopy using seven different lectins (ConA, WGA, RCA, PNA, UEA-1, DBA, and SBA). For light microscopic observations, criteria based on the incidence and intensity of cells positive for the lectin staining were adopted to evaluate the different staining patterns of the proliferative and secretory endometria obtained by the avidin-biotin-peroxidase complex (ABC) technique. At the light microscopic level, ConA, WGA, and RCA stained endometrial glandular cells in both phases. The number of PNA-positive cells with the binding sites entirely limited to the apical surface tended to be reduced slightly in the secretory phase. UEA-1 weakly stained the apical surface of glandular cells in the proliferative phase but not in the secretory phase. Among the lectins used in this study, DBA and SBA displayed remarkable changes between the phases. That is, in the proliferative phase they produced only a faint or slight positive stain at the apical surface, but the incidence and intensity of DBA- and the SBA-positive glandular cells increased in the secretory phase. By electron microscopy, the reaction product of ConA was observed in the plasma membrane, endoplasmic reticulum, nuclear envelope, and the Golgi apparatus, and the binding sites of RCA and DBA were observed in the plasma and Golgi membranes. Between both phases, the reactivity of ConA and RCA showed almost no change. However, the secretory endometrial cells containing the DBA-positive Golgi apparatus were markedly increased in number compared with the proliferative ones bearing the lectin-positive organelles.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical and radioautographic study of glycoprotein secretion in the epithelium lining the uterine tubes of mice

Two-month-old female Swiss mice that had come into estrus were injected intravenously with L-3H-fucose and killed at 5, 15, 40 min, and 4 h after injection. Pieces of the isthmus and of the ampulla of the uterine tubes were processed for light- and electron-microscopic radioautography. Incorporation of 3H-fucose was more intense in the isthmian secretory cells than in the ciliated cells of the ampulla. Electron-microscopic radioautography of the isthmian secretory cells demonstrated that 3H-fucose was incorporated into newly synthesized glycoproteins in the Golgi apparatus from where labelled glycoproteins migrated mainly to secretory granules and apical microvilli. The histochemical technique using ruthenium red confirmed the presence of glycoproteins in the contents of the secretory granules released to the lumen of the uterine tubes as demonstrated by radioautography. Other glycoproteins are transported inside small vesicles and most likely are related to the renewal of the plasma membrane. The role of the secretory glycoproteins in various events of mammalian reproduction is discussed.

Ultrastructural evidence that specialized regions of the murine oviduct contribute a glycoprotein to the extracellular matrix of mouse oocytes

Previous studies have identified a glycoprotein (GP215) that is secreted by the murine oviductal epithelium and subsequently becomes sequestered within the perivitelline space of oocytes and developing embryos (Kapur and Johnson, Dev. Biol. 112:89-93, 1985; J. Exp. Zool. 238:249-260, 1986). The ultrastructural localizations of GP215 in the perivitelline space of ovulated oocytes and in the oviductal epithelium are described here. The glycoprotein is shown to be associated with a morphologically discrete extracellular matrix that provides a unique microenvironment for fertilization and early developmental events. In addition, putative secretory granules that contain this glycoprotein are observed in specific segments of the murine oviductal epthelium, suggesting regional differences in the composition of oviductal secretions.

Distribution of some Gal beta 1-3(4)GlcNAc related carbohydrate antigens on the mouse uterine epithelium in relation to the peri-implantational period

Using monoclonal antibodies of defined carbohydrate specificity we have looked at the distribution of various Gal beta 1-3(4)GlcNAc related oligosaccharide determinants in the mouse uterus during the first 6 days of pregnancy. Frozen sections of uterus from B6D2F1, B6CBF1 or B6D2F1/BOM female mice were incubated with the monoclonal antibodies and then with a fluorescein isothiocyanate conjugate of goat anti-mouse IgM and viewed by epifluorescence illumination. None of the antibodies bound specifically to stroma cells but antibodies recognising difucosylated Gal beta 1-3(4)GlcNAc structures, the monofucosylated type II determinant (SSEA-1) and an H type I oligosaccharide bound to cells of the uterine luminal epithelium and glands and to the uterine secretions. Antibodies recognising the three different types of saccharide showed independent changes in staining intensity during early pregnancy. The antibody which recognises H type I structures (667/9E9) showed a change in distribution from binding to most cells of the uterine epithelium in the non-pregnant mouse and on day 3 of pregnancy to binding restricted to areas of epithelial cells interspersed with non-staining clumps of cells between days 4 and 5 of pregnancy.

Lectin-binding characteristics of mouse oviduct and uterus associated with pregnancy block by autologous antiprogesterone monoclonal antibody

Oviducts and uteri were removed from BALB/cJ and F1 (CBA/Ca X BALB/cJ) mice at known stages post coitum and following treatment with an antiprogesterone monoclonal antibody (DB3) or a non-specific immunoglobulin (DNP). Thin sections of tissue were prepared and reacted with fluorescent conjugates of a wide range of lectins to determine if saccharide alterations were associated with the pregnancy-inhibiting effect of the DB3 antibody in BALB/c, but not F1, individuals. The ampullary region of the DB3-treated BALB/c mice showed the most marked changes, with an almost total inhibition of lectin binding, particularly for N-acetylglucosamine residues. There was also a reduced affinity for a lectin reactive with N-acetylgalactosamine in the uteri of DB3-treated BALB/c mice, associated with an extended expression during gestation of this saccharide in the proximal region of the oviduct in such mice. These are the first biochemical alterations in reproductive tract epithelia to be associated with the efficacy of the DB3 antibody in preventing pregnancy.

Lectin binding sites on human endocervix: a comparison with secretory and proliferative endometrium

Endocervix and corresponding endometrium of women of reproductive age were studied histochemically with 13 fluorescein isothiocyanate-labeled lectins to delineate the differences between the epithelial cells in two anatomical sites. Lectin from Maclura pomifera (MPA), Ulex europaeus (UEA-I), Glycine max (SBA), and Vicia villosa (VVA) bound only to endocervical epithelium and were the only four lectins that distinguished endocervical from endometrial epithelium. These differences were independent of menstrual cyclic changes and blood group antigen secretion. These data show that lectins can be used to histochemically distinguish endocervical from endometrial glands.

Oncodevelopmental carbohydrate antigens: distribution of ECMA 2 and 3 antigens in embryonic and adult tissues of the mouse and in teratocarcinomas

Immunohistochemical studies revealed the oncodevelopmental nature of two carbohydrate antigens, ECMA 2 and ECMA 3. In the mouse, the antigens were first detected in late 1-cell embryos, markedly expressed until the early post-implantation stage and progressively disappeared thereafter. They were hardly detectable at day 9-10 of embryogenesis but were present in primordial germ cells until day 12. In adult mice the antigens were present in the oviduct and cauda epididymis. Pregnancy induced expression of the antigens was observed in the uterus. The nasal chamber of the embryo and some cells in the small intestine of the adult were the only two additional sites where one or two of the antigens were significantly detected. Thus, ECMA 2 and 3 antigens were closely related to early embryogenesis and reproduction. Although expression of ECMA 2 paralleled that of ECMA 3 in normal mice, their distributions were significantly different in teratocarcinoma cells.

Differential distribution of receptors for two fucose-binding lectins in embryos and adult tissues of the mouse

Ulex europaeus agglutinin-I (UEA-I) recognizes the Fuc alpha 1----2 Gal linkage. Receptors for UEA-I were not detected in mouse embryos until the 13th day of embryo-genesis, except for their temporary expression in early trophectoderm cells. In adult mice, UEA-I receptors were detected at various sites, including cells of the digestive tracts, the bronchial epithelium, Hassall's corpuscle of the thymus, and the skin. The fucose-binding protein of Lotus tetragonolobus (FBP) is another lectin that recognizes fucosyl residues. The distribution of FBP receptors was significantly different from that of UEA-I receptors. FBP receptors were first detected in late 8-cell embryos and were expressed in the embryonic ectoderm, visceral endoderm, and trophoblastic giant cells in egg-cylinders. At later stages, the distribution of FBP receptors became restricted to certain parts of the embryo. In the adult, the distribution of FBP receptors was more restricted than that of UEA-I receptors. Particularly in embryos before the 11th day of gestation, the distribution of FBP receptors resembled that of SSEA-1, which is defined by the Gal beta 1----4(Fuc alpha 1----3) GlcNAc linkage. From the specificity of FBP, we inferred that the disappearance of SSEA-1 and FBP receptors during embryogenesis is not the result of alpha 1----2 fucosylation of the terminal galactosyl residue in the determinant. The fact that the expression of two fucose-related cell-surface markers, i.e., UEA-I receptors and SSEA-1 (or FBP receptors), is developmentally regulated in an entirely different fashion is an excellent example illustrating the precise control of differentiation-dependent alterations in cell-surface carbohydrates.

Glycoproteins in rabbit uterus during implantation. Differential localization visualized using 3H-N-acetyl-glucosamine labelling and FITC-conjugated lectins

The synthesis of glycoproteins in rabbit uterine epithelium during the late preimplantation period was studied using tritiated N-acetylglucosamine. In vivo labelling was achieved by the intra-uterine implantation of agar gel columns containing the precursor. Autoradiography showed the radioactivity to be predominantly localized in the apical cell surfaces, with single cells exhibiting an accumulation of silver grains in their supranuclear cytoplasm. After gel electrophoresis of uterine flushings, activity was mainly found in the beta-glycoprotein fraction. Fluorescein isothiocyanate (FITC)-conjugated wheat-germ agglutinin reacted with the apical cytoplasm and surfaces of the endometrial cells. However, FITC-conjugated concanavalin A exhibited a different binding pattern, reacting first with the basal cytoplasm, and later with the apical cytoplasm. After concanavalin-A staining, single cells exhibited positive vesicles in their lateral and apical parts. These cells may be released into the uterine lumen until 210 h post column. Neither of the lectins reacted with ciliated cells. Concanavalin A showed an affinity for the beta-glycoprotein fraction of the uterine secretion. The results indicate that, although all endometrial cells contain glycoproteins, only a few of these seem to be involved in the synthesis of secretory products.

Distribution of lectin binding sites in rabbit oviduct

The carbohydrate histochemistry of the rabbit oviduct has been examined by the use of four lectins conjugated with horseradish peroxidase as histochemical reagents. Each lectin gave a very distinct typical pattern of binding, but for each lectin there was no difference between the distribution of binding sites in ampulla and isthmus. Wheat germ lectin bound exclusively with the connective tissue of the oviduct folds; winged pea lectin was detected only in the ciliated cells; peanut lectin binding sites were visualized in the secretory cells; the binding reactivity of soybean lectin was limited to the basal part of the cilia. Although it is very difficult at present to correlate the distribution of lectin binding sites with the function of the positive cells, some hypotheses have been advanced.

Pregnancy-related changes in the human endometrium revealed by lectin histochemistry

The binding of 22 fluorescein isothiocyanate (FITC) conjugated lectins to human proliferative phase and pregnant endometrium was studied histochemically. Only the lectin from Bauhinia purpurea (BPA) reacted exclusively with the epithelial cells. All the others reacted to a certain extent with glandular and/or stromal cells. Lectins from soybean (SBA), and Vicia villosa seeds (VVA) reacted with endometrial glands of pregnancy but not with the glands of the proliferative endometrium. In the proliferative endometrium SBA reacted only with cells of the surface endometrium. Lectin from peanuts (PNA) reacted only with some glands in the proliferative endometrium but was unreactive with others. In pregnant endometrium PNA reacted with all glands. Lectins from lentils (LCA) and red kidney beans (PHA-E and PHA-L) reacted with endometrial glands of the proliferative phase but not with the glands from pregnant endometrium. We thus show that FITC labeled lectins define specific carbohydrate moieties selectively expressed on either proliferative phase or pregnant endometrial glands.

Lectin histochemistry of human placenta

The human placenta was studied histochemically using 23 fluorescein-isothiocyanate-labeled lectins. Distinct patterns of staining, as well as some differences between first-trimester and term placenta, were discerned. Eleven lectins (HPA, VVA, BPA, HAA, SBA, PNA, GSA-I, MPA, RCA-I, RCA-II, and UEA-I) did not react with the trophoblast. Two lectins (LCA and PEA) reacted with the trophoblast of first-trimester placenta but not with the trophoblast of third-trimester placenta. The remaining ten lectins (ConA, Suc.ConA, WGA, GSA-II, LAA, STA, DBA, LBA, PHA-E, and PHA-L) reacted with the trophoblast of both first- and third-trimester placenta, and two of these lectins (ConA and Suc.ConA) reacted preferentially with the syncytiotrophoblast. Five lectins (LAA, STA, DBA, GSA-II, and LBA) reacted with nuclei of the cytotrophoblast. The nuclei of some stromal and syncytiotrophoblastic cells were also reactive. Eighteen lectins reacted with the trophoblastic basement membrane, and all reacted with Hofbauer cells and the stroma of the villi. Lectin binding was influenced by the mode of fixation and tissue processing. These data show that some lectins can be used to identify components of the placental villi (e.g., basement, membrane) to characterize differences between the first- and third-trimester trophoblast, and to distinguish the cytotrophoblast from the syncytiotrophoblast.

Lectin binding sites of the mouse ovary, intraovarian and ovulated ova

Fluorescein isothiocyanate (FITC) labeled lectins were used to study the distribution of specific binding sites in histologic sections of mouse ovaries as well as ovulated ova. Four distinct patterns of reactivity of the components of the follicle (exclusive of the ovum) and the surrounding ovarian stroma were recognized: uniform staining of granulosa cells, theca cells and surrounding stroma; weak to moderate staining of the granulosa cells and strong staining of the theca cells and stromal cells; no reactivity of the granulosa cells coupled with strong reactivity of the theca and stromal cells; no reactivity with any component of the cumulus oophorus. Three lectins (from Triticum vulgare, Arachis hypogaea and Maclura pomifera) distinctly accentuated the basal lamina of the cumulus oophorus. The reaction of lectins with oocytes and zona pellucida revealed six distinct patterns: no reactivity with either structure; weak reactivity with the cytoplasm of the oocyte and no reactivity with the zona pellucida; very strong reactivity with the cytoplasm of the oocyte and no reactivity with the zona pellucida; moderate reactivity with both the oocyte and the zona pellucida; moderate reactivity with the oocyte and very strong reactivity with the zona pellucida; no reactivity with the oocyte and moderate reactivity with the zona pellucida. The same pattern of reactivity was seen in the ovulated ova in the oviduct except for the lectin from Arachis hypogaea, the reactivity of which changed upon ovulation and/or fertilization of the ovum. These data provide a list of lectin markers for distinct components of the mouse ovary.