Differences in the macromolecular composition of the zona pellucida isolated from pig oocytes, eggs, and zygotes

Fourier Transform Infrared Spectroscopic Analysis of the Intact Zona Pellucida of the Mammalian Egg: Changes in the Secondary Structure of Bovine Zona Pellucida Proteins During Fertilization

The zona pellucida is the acellular transparent envelope surrounding the mammalian oocyte. An analysis of the changes in the structures of zona pellucida proteins is essential for understanding the molecular mechanisms underlying the important physiological roles of the zona during fertilization and prelmplantatlon. The hardening of the zona caused by the structural changes during fertilization is generally accepted to be responsible for blocking polyspermy. In this study, we analyzed changes in the secondary structure of the zona during fertilization by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy. The predominance of β-sheet structure in porcine ovarian egg zona proteins in water was ascertained using FTIR spectra. α-Helix structure was also present. The attenuated total reflection (ATR)-FTIR spectrum of intact, unsolubilized porcine zonae pellucidae from ovarian eggs Indicated that the zona proteins in the native zona pellucida also have β-structure as the main constituent. Attenuated total reflectlon-FTIR spectroscopy of intact bovine zona pellucida obtained from ovarian and fertilized eggs at the blastocyst stage revealed that the β-structure content Increased during fertilization. Furthermore, a reduction of the thickness of the zona during fertilization was observed using transmission electron microscopy. Therefore, the change in the zona architecture that causes hardening of the zona during fertilization is accompanied by changes in the secondary structure of the zona proteins.

Polyspermic penetration in porcine IVM-IVF systems

Although techniques for in vitro production of porcine embryos have proceeded very rapidly during the past decade, polyspermic penetration still remains a persistent obstacle to porcine in vitro fertilization (IVF) systems. Considerable research on in vitro polyspermic penetration in porcine in vitro-matured (IVM) oocytes has been undertaken to try to solve this problem. In the current paper, recent advancements in overcoming the problems of polyspermy in porcine IVF systems are reviewed. Partial induction of the acrosome reaction of boar spermatozoa in IVF media that contain caffeine is likely to be one of the major causes of polyspermy. A reduction in the number of incompletely acrosome-reacted spermatozoa, which can bind tightly to the zona pellucida and mask free sperm receptors of the zona pellucida, could reduce the incidence of polyspermic penetration; however, morphological differences in the reaction of the zona pellucida have been observed between IVM and ovulated oocytes, which suggests that altered zona morphology may be another cause of polyspermic penetration. It has been shown that the developmental ability of polyspermic porcine embryos to the blastocyst stage is similar to that of normal embryos but that developmental competence to term is much lower. To overcome the current problems of polyspermy, it is suggested that future efforts should be focused on controlling boar sperm function and/or sperm-zona binding to achieve the final maturation associated with normal zona modifications of porcine oocytes at fertilization.

Differences in proteinase digestibility of the zona pellucida of in vivo and in vitro derived porcine oocytes and embryos

Embryo transfer practitioners know very well that, in a variety of species, there are differences between in vitro- and in vivo-derived embryos. It is assumed that these differences are results of suboptimal in vitro conditions leading to cytoplasmic and nuclear imperfections that will result in decreased embryo viability. In the present investigation the resistance of the zona pellucida of in vivo- and ex vivo-derived porcine embryos to a proteolytic enzyme is addressed. Ovulated but unfertilized oocytes, in vitro and in vivo-derived embryos of various developmental stages were exposed to a 0.5% pronase solution. The zonae of ovulated oocytes and in vivo-derived embryos at various stages of development took much longer to be digested than zonae of comparable in vitro-stages. Residence of in vitro derived embryos in an oviduct, no matter whether excised or in situ, significantly increased the zona resistance to pronase digestion. Embryonal stages normally residing in the uterus exhibited a distinctly decreased zona resistance to pronase. The culture of IVF embryos in an excised oviduct brought about a 6- to 14-fold increase in time required for zona digestion. A 24 h residence of IVF-derived embryos in the oviduct of a live recipient resulted in a digestion time for the zona of, on average, 48 h versus 1.4 h in the controls. Individual differences were substantial. The observations suggest that there must be structural changes in the zona pellucida or some sort of protective coating deposited while ova or embryos reside in the oviduct supplying protection against the action of proteolytic enzymes.

Cyclic Related and Pathological Changes in the Lectin-binding Sites on the Swine Oviduct

This study was carried out to compare the lectin-binding pattern in the normal and pathological oviduct of sows during the ovarian cycle. Lectin-binding patterns showed differences between segments, phases of ovarian cycle and presence of morphologic lesions. In the infundibulum, it was observed that the cysts, in the follicular phase, reduced Ricinus communis-I (RCA-I) and Ulex europaeus-I (UEA-I) binding. Furthermore, in the pathological oviducts of the luteal-phase group, there is a reduction of Concanavalia ensiformis (Con-A) reactivity in this segment of the tube having wall cysts, adenomyosis and diverticulus. The Arachis hypogaea (PNA) binding in the infundibulum, during the luteal phase, decreased in the tube having adenomyosis. In animals with wall cysts, the Con-A, Triticum vulgaris (WGA) and RCA-I reactivity was minor in the glycocalyx of the isthmus epithelium during follicular phase. Con-A and Dolichos biflorus (DBA) binding pattern was minor in the luteal-phase isthmus of the tube having wall cysts, adenomyosis and diverticulus. In the ampulla, the wall cysts impaired the Con-A reaction only in the basal region of the epithelium, in the follicular phase. Binding with Con-A was decreased in the ampulla of animals in the luteal phase in the tube lesions with cysts and diverticulus. In addition, the diverticulus observed in the ampulla, during the luteal phase, reduced the PNA tubaric binding. The results of this study showed that the morphologic alterations modify the sugar pattern in the oviduct of sows. These modifications in glycoconjugates may be one of the reasons for the failure of fertility in sows.

Effect of oviductal and cumulus cells on zona pellucida and cortical granules of porcine oocytes fertilized in vitro with epididymal spermatozoa

The objective of this study was to evaluate the effects of porcine oviductal epithelial cell (POEC) monolayers and cumulus cells on the zona pellucida (ZP) and cortical granules (CG) of in vitro matured porcine oocytes. Denuded and cumulus-enclosed oocytes were exposed to POEC before or during in vitro fertilization (IVF). The functional effects of the co-culture system were the tested on the ZP resistance, measured by the time necessary to dissolve the ZP with 0.1% pronase, and the distribution and density of the cortical granules. CG density in the equator and cortex of each oocyte was evaluated by confocal microscopy after staining with fluorescein isothiocyanate-labelled peanut agglutinin (FITC-PNA). Both variables were assessed immediately after an in vitro maturation period (IVM group), 3 and 6h after culture with or without (Control) oviductal cells (Experiment 1) and 3h after insemination with frozen-thawed epididymal spermatozoa in the presence or absence (Control) of oviductal cells (Experiment 2). The time to dissolve the ZP of oocytes from IVM group was 440.4 +/- 61.7 s and no difference was observed among groups in Experiment 1. In contrast, the density of CG was affected; oocytes pre-incubated for 6h had a higher density than those pre-incubated for 3 h (P <0.001). Oocytes fertilized in vitro in the presence of POEC (Experiment 2) had a similar ZP digestion time as control oocytes 3 h after insemination. The presence of POEC during IVF as well as the presence of cumulus cells had no effect on the density and distribution of CG. However, a significant decrease in the density of CG was observed in the fertilized oocytes compared to in vitro matured oocytes (P <0.001). It is concluded that under the conditions employed the oviductal and cumulus cells in the perifertilization period had no effect on ZP hardening and CG density. However, an increase in CG density was observed when oocytes were maintained in culture. In addition, no hardening of ZP was observed after IVF, and denuded and cumulus-enclosed oocytes showed similar cortical reactions after insemination with epididymal spermatozoa regardless of the presence of POEC.

Subzonal Older Adult Fibroblast Insertion in Both In Vivo–Fertilized and Nuclear Transfer Rabbit Zygotes and Embryos: Effects on Further In Vitro Embryo Development

In the present work, we evaluated the effect on further in vitro embryo development of inserting rabbit adult fibroblasts into in vivo-fertilized rabbit embryos. To this end, we inserted either 4 or 15-20 rabbit adult fibroblasts in two different early embryo stages of development, 1-cell stage and 4-8-cell stage embryos. We observed that fibroblast insertion not only did not negatively affect further embryo development, but also may have exerted a positive effect on development on it. Therefore, in forthcoming works were where we intend to study a possible cell helper role on early embryo development. The early embryo microenvironment may reprogram somatic cell gene expression of fibroblasts inserted within the embryo, making them suitable as nuclear donors.

Zona reaction in porcine oocytes fertilized in vivo and in vitro as seen with scanning electron microscopy

Morphological changes in zona pellucidae (ZP) isolated from in vitro-matured (IVM) and ovulated porcine oocytes were compared before or after fertilization in vitro and in vivo, respectively, by using scanning electron microscopy (SEM). The ZP of some ovulated or IVM oocytes and in vivo- or in vitro-fertilized (IVF) zygotes were equally split into two halves while immersed in an enzyme-inhibitor solution, using a surgical blade. After washing, intact and ZP halves were fixed in 1% glutaraldehyde solution in 0.1 M cacodylate buffer, processed, and examined using SEM. The outer surface of ZP in ovulated oocytes had a mesh-like structure. The outer morphology in IVM oocytes was more smooth although the mesh-like structure was still visible at high magnification. In in vivo zygotes and IVM-IVF zygotes, this lysed, mesh-like structure was more obvious. The inner surface of ZP had some small depressions (orifices). The mean number of orifices per 100 micrometer(2) of ZP surface was larger in IVM oocytes as compared to ovulated ones. The number of orifices per 100 micrometer(2) decreased in IVM-IVF zygotes as compared to IVM oocytes; whereas, in vivo zygotes did not differ from ovulated oocytes. The mean diameter of intact ZP as well as their mean thickness was greater in ovulated oocytes than IVM oocytes. The mean thickness of the ZP was larger in ovulated oocytes than IVM ones. The ZP thickness was larger in zygotes than in in vivo oocytes, whereas that of IVM-IVF zygotes did not differ from that of IVM oocytes. These results indicate that the morphology of ZP and the ZP reaction at sperm penetration appears to be much different between IVM oocytes and ovulated ones.

Identification and localization of plasminogen activator inhibitor-1 within the porcine oviduct

The porcine oviduct synthesizes de novo and secretes a number of proteins into culture medium, many of which are unidentified. The objectives of the present study were to 1) semipurify and identify a M(r) 45 000 secreted protein of the oviduct, 2) examine its synthesis within the three functional segments (infundibulum, ampulla, and isthmus), and 3) evaluate its distribution throughout the oviduct. Oviductal tissue was collected during early pregnancy, divided into functional segments, and subsequently cultured. Medium was collected, and the M(r) 45 000 protein was concentrated by gel-filtration chromatography. The semipurified protein was transferred onto a polyvinylidene fluoride membrane and subjected to N-terminal amino acid analysis. The 26-amino acid sequence was 96% identical to that of pig plasminogen activator inhibitor (PAI)-1. Analysis by 1-dimensional SDS-PAGE and fluorography of rabbit anti-human PAI-1-immunoprecipitated product confirmed PAI-1. Subsequent 2-dimensional SDS-PAGE and fluorographic analyses of media revealed greater PAI-1 synthesis by the isthmus than by the ampulla or infundibulum. PAI-1 was immunolocalized throughout the oviduct and was heavily concentrated in the apical region of epithelial cells. Immunogold electron microscopy localized PAI-1 within putative secretory granules in the epithelial apical region and also associated with cilia in the isthmus. Isthmic PAI expression suggests a crucial role in protecting the preimplantation embryo from proteolytic degradation as well as in regulation of extracellular matrix turnover and remodeling.

Proteases with plasminogen activator activity in hamster oviduct

At present the physiological role of most oviductal proteins remains unknown. In this work, we present evidence that the oviductal secretion as well as the crude oviductal tissue-extract show proteolytic-like esterase and amidase activity. The proteolytic activity of the oviductal enzymes was higher in the oviducts of superovulated hamster females than in those of normal ones, indicating that gonadotrophic hormones would stimulate the synthesis and secretion of these enzymes. Some of their properties were analyzed in the 15,600-g supernatant of both oviductal tissue extracts (OE) and oviductal fluid (OF). The enzymatic activity toward the synthetic substrates p-tosyl-l-arginine methyl ester-HCl (TAME) and alpha-N-benzoyl-dl-arginine-p-nitroanilide HCl (BAPNA) was activated by calcium ions, reached a maximum at pH 7.5, and was inhibited by soybean trypsin inhibitor (SBTI), N-alpha-p-tosyl-l-lysine chloromethyl ketone HCl (TLCK), phenyl methyl sulfonyl fluoride (PMSF), and benzamidine. The OE glycoprotein fraction recognized by WGA-Sepharose affinity columns (37% total proteins) showed proteolytic activity with properties similar to the OE and OF enzymes. The protease activity could be ascribed to a plasminogen activator (PA) detected in the Triton X-100 treated tissue crude membrane fraction (Triton-CMF) and in the oviductal secretion of the superovulated females. In the Triton-CMF fraction, 100% of the proteolytic activity was plasminogen-dependent. The use of amiloride, a selective urokinase-type plasminogen activator (uPA) inhibitor, shows that 90% of this activity was due to a tissue-type plasminogen activator (tPA) and 10% to uPA whereas in the uterus 100% of the activity was tPA. Only a small percentage of the OF proteolytic activity was plasminogen-dependent, probably due to the presence of PA inhibitors in this medium.

Analysis of zona pellucida modifications due to cortical granule exocytosis in single porcine oocytes, using enhanced chemiluminescence

The present study was carried out to determine whether modification of zona pellucida (ZP) of a single oocyte following the cortical granule (CG) exocytosis induced by electrical stimulation could be analyzed using enhanced chemiluminescent (ECL) detection of the biotinylated ZP in a porcine oocyte. When a biotinylated ZP derived from a single oocyte matured in vitro was subjected to SDS-PAGE, 3 major bands (ZP1, ZP2 and ZP3) were observed following ECL detection. In these oocytes, CGs staining with fluorescein isothiocyanate (FITC)-labeled peanut agglutinin (FITC-PNA) had formed a monolayer underlying the plasma membrane. Electrical stimulation to induce artificial activation caused a decline in the fluorescent intensity of the CGs with a concomitant decrease in the amounts of ZP1 and ZP2 bands. However, the mobility changes of ZP1 and ZP2 on SDS-PAGE were not found under the inhibitory condition of the CG exocytosis in which oocytes were treated with ethylene glycol-bis(beta-aminoethyl ether) N, N, N',N'-tetraacetic acid (EGTA) or 1, 2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid tetrakis(acetoxymethyl) ester (BAPTA/AM). In addition, when a time-dependent decrease in amounts of ZP1 and ZP2 bands on SDS-PAGE was observed in a single oocyte during activation, a maximum decrease in these bands was detected in oocytes incubated for at least 3.5 h after electrical stimulation. These results show that the method employed, ECL detection of the biotinylated ZP of a single oocyte, is a valuable tool for the analysis of ZP modification resulting from a decrease in amounts of ZP1 and ZP2 glycoproteins in combination with exocytosis of CGs, and that the prolonged period after activation is required for complete ZP modification in porcine oocytes.

Changes in the bovine zona pellucida induced by plasmin or embryonic plasminogen activator

Effects of bovine plasmin and plasminogen activator recovered from bovine embryo-conditioned medium (bePA) on the polypeptide profile and solubility of bovine zonae pellucidae (ZP) were evaluated. ZP were isolated from bovine ovarian oocytes and incubated at 39 degrees C with 0, 100, or 200 microg/ml plasmin for 0, 24, or 48 hr or bePA with 0 or 100 microg/ml human plasminogen for 0 or 48 hr. ZP were evaluated either by SDS-PAGE or for changes in solubility using a zona pellucida dissolution time (ZPDT) assay. Two prominent polypeptides, molecular weight (MW) 76,000 and 65,000, and two minor polypeptides, MW 23,000 and 22,000, were resolved by SDS-PAGE. No changes occurred in the polypeptide profile for ZP incubated with 0 microg/ml plasmin for 0, 24, or 48 hr, and ZPDT did not differ (P > 0.10). Treatment with 100 or 200 microg/ml plasmin induced reductions in the MW 76,000, 23,000, and 22,000 polypeptides and the appearance of MW 45,000 and <10,000 polypeptides. ZPDT were less (P < 0.05) in 100 and 200 microg/ml compared with 0 microg/ml plasmin. Polypeptide profiles and ZPDT for ZP incubated with bePA were similar (P > 0.10) to ZP incubated with unconditioned medium. Addition of human plasminogen to ZP incubated with bePA reduced the MW 76,000, 23,000, and 22,000 polypeptides, caused the appearance of MW 45,000 and 20,000 polypeptides, and decreased ZPDT (P < 0.05). These results demonstrate that bovine plasmin is capable of proteolytically degrading the bovine ZP and that bePA can indirectly affect the ZP by converting plasminogen to plasmin.

Molecules involved in mammalian sperm-egg interaction

To achieve fertilization, sperm and egg are equipped with specific molecules which mediate the steps of gamete interaction. In mammals, the first interaction between sperm and egg occurs at an egg-specific extracellular matrix, the zona pellucida (zp). The three glycoproteins, ZP1, ZP2, and ZP3, that comprise the zp have been characterized from many species and assigned different roles in gamete interaction. A large number of candidate-binding partners for the zp proteins have been described; a subset of these have been characterized structurally and functionally. Galactosyltransferase, sp56, zona receptor kinase, and spermadhesins are thought to participate in the primary binding between sperm and zp and may initiate the exocytotic release of hydrolytic enzymes in the sperm head, the acrosome reaction. Digestion of the zp by these enzymes enables sperm to traverse the zp, at which time the proteins PH20, proacrosin, sp38, and Sp17 are thought to participate in secondary binding between the acrosome-reacted sperm and zp. Once through the zp, sperm and egg plasma membranes meet and fuse in a process reported to involve the egg integrin alpha 6 beta 1 and the sperm proteins DE and fertilin. These molecules and the processes involved in gamete interaction are reviewed in this chapter within a physiological context.

Binding of boar spermatozoa to porcine oocytes: effect of low molecular weight 17-kDa protein

The effect of seminal plasma and low molecular weight ACR.3 (17 kDa) protein on boar spermatozoa-porcine oocyte binding was examined. Boar seminal plasma that contains the sperm-adhesive ACR.3 protein was added to spermatozoa prior to their coincubation with oocytes, and the binding capacity of the spermatozoa so treated was compared to that of untreated cells. Similarly, purified ACR.3 protein, that binds to the egg zona pellucida, was added to noncapacitated spermatozoa, and the binding capacity of treated and untreated cells was again evaluated. In the two cases, the treatment of spermatozoa reduced their capacity to bind to the zona pellucida. We propose that the reduction in binding is due to competition for the ACR.3 binding sites on the zona pellucida between the soluble ACR.3 protein and the ACR.3 protein attached to the sperm surface. Furthermore, sperm-ZP binding was examined in the presence of ACR.3 monoclonal antibody, which specifically reacts with ACR.3 protein. Preliminary results show that addition of ACR.3 monoclonal antibody to a suspension of boar spermatozoa prior to their coincubation with oocytes did not markedly change sperm-zona binding in comparison with the control untreated spermatozoa. Our results suggest that ACR.3 protein may mediate the primary sperm-egg zona pellucida binding, and that it is one of the likely candidates for the primary sperm-ZP binding protein.

Lectin binding patterns of porcine oviduct mucosa and endometrium during the oestrous cycle

Important functions of the oviduct during reproduction include the provision of an optimal environment for gametes and zygotes and nutrition of the early embryo. These functions are ensured by the secretion of an oviductal fluid which is known to contain organ-specific glycoproteins. Glycoconjugates of the apical glycocalyx are considered to play a major role in cell recognition and interaction processes. In the present investigation, binding patterns of Con A, HPA, LTA, RCA I, UEA I, and WGA were studied in defined segments of the oviduct (infundibulum, ampulla, isthmus) and in the uterus during the oestrous cycle. The carbohydrate distribution showed regional as well as time dependent differences. LTA, HPA and WGA reacted strongly with Golgi regions and secretory granules in the oviduct epithelium during the follicular phase, indicating high secretory activity. LTA, HPA, and UEA I also revealed a varying carbohydrate composition of the glycocalyx during the oestrous cycle. Prominent regional differences in glycoconjugate expression were shown in oviductal segments by LTA and HPA binding: during the follicular phase, LTA binding sites were only present on epithelial cells of the isthmic segment, the ampulla and infundibulum being unreactive. D-N-acetyl-galactosamine residues were demonstrated on ciliated epithelial cells of the ampulla and infundibulum exclusively during oestrus. The glycocalyx of uterine epithelial cells was clearly defined by HPA, WGA, LTA, RCA I and UEA I; LTA binding was restricted to the secretory phase. The observation of regional and time dependent variability in glycoconjugate distribution strongly indicates their specific physiological functions in reproductive processes.

Effect of estrogen-treated porcine ampulla oviductal epithelial cells on early embryonic development in vitro and characterization of their protein synthetic activity

Recent studies by Buhi et al. have demonstrated that estrogen (E2) is responsible for the induction of de novo synthesis and secretion of certain oviductal secretory proteins (OSP) and inhibition of other OSP in porcine oviductal explant cultures. The present work was undertaken to evaluate the effect of E2-treated oviductal epithelial cell coculture on the development of early porcine embryos derived from in vitro matured and fertilized oocytes. In vitro synthesis of secretory proteins by E2-treated oviductal cells used for coculture was also investigated by one-dimensional (1D) and two-dimensional (2D) sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE). The results showed that the cleavage rate was significantly enhanced by coculturing fertilized eggs with E2-treated oviductal epithelial cells. The in vitro protein synthetic pattern of oviductal secretory proteins was influenced by E2 treatment. These variations included the disappearance of one protein (82,000 M(r)) and the appearance of another (33,000 M(r)) in the E2-treated group as assessed by 1D-SDS-PAGE. Additional proteins of M(r) 97,000 and an M(r) 36,000-45,000 complex were increased in abundance by the E2 treatment. Analyses by 2D-SDS-PAGE revealed three major E2-dependent proteins, of M(r) 45,000 (pI 5.5), 43,000 (pI 5.5) and a 36,000-45,000 M(r) (pI 4.8) protein complex, whereas polypeptides of M(r) 97,000 (pI 5.1), 36,000 (pI 8.0) and 25,000 (pI 6.8) were inhibited by E2 treatment. The results demonstrated that porcine epithelial cell protein synthetic patterns are influenced by E2 treatment and that estradiol treatment of oviductal cells may increase the rate of zygote cleavage during early development in vitro in pigs.

Post-fertilization changes in the zona pellucida glycoproteins of rat eggs

The zona pellucida (ZP) is the extracellular coat surrounding the mammalian egg. Numerous evidence supports the role of ZP carbohydrate residues as the specific sperm receptors. In this study we used lectins to study different distribution patterns of carbohydrate residues in the rat ZP, and to follow changes at fertilization. ZP were collected from follicular, ovulated, and fertilized eggs, incubated with one of 11 different biotin-labeled lectins, followed by avidin-fluorescein isothiocyanate (FITC) complex, and visualized by epifluorescent microscopy. For electron microscope (EM) histochemistry, eggs were embedded in LR white and ultrathin sections were stained with the complex Ricinus communis lectin (RCA-1)-colloidal gold. Some lectins (RCA-I, Glycine max) bound to the entire ZP while others were restricted to the inner or outer zones [Griffonia simplicifolia, Concanovalia ensiformis, Triticum vulgaris (WGA), succinyl-WGA]. Other lectins (Lens culinaris, Ulex europhaeus) were totally excluded. The RCA-1 binding pattern changed following sperm penetration, from homogeneous in ZP of ovulated eggs (57%) to uneven in ZP of fertilized (71%) or activated (68%) eggs. Our results demonstrate an uneven distribution of different sugar residues in the rat ZP, and a post-fertilization change in the distribution of beta-galactose, which is specifically recognized by RCA-I, presumably correlated with other changes in the ZP that lead to the block to polyspermy.

Localization of the mRNA encoding the zona protein ZP3 alpha in the porcine ovary, oocyte and embryo by non-radioactive in situ hybridization

The mRNA of the zona pellucida glycoprotein ZP3 alpha was localized in frozen sections of pig ovaries, isolated oocytes and early embryos by in situ hybridization using biotinylated oligonucleotide probes. In follicles, the distribution of mRNA for ZP3 alpha was correlated with the developmental stage: in primordial and primary follicles, the mRNA was shown to be predominantly localized in the oocyte. In secondary follicles, mRNA was found in both the oocyte and follicle cells. In tertiary and preovulatory follicles, the follicle cells showed distinct staining, whereas the oocyte was labelled weakly. In the early embryo, i.e. 2 days after fertilization, mRNA for ZP3 alpha could not be demonstrated. Our results suggest that, in the pig, the zona pellucida protein ZP3 alpha is synthesized by the oocyte and the follicle cells in sequence. After fertilization, synthesis of ZP3 alpha is terminated.

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.

Hormonal control of the biosynthesis of hamster oviductin

In several mammalian species, the epithelial secretory cells of the oviduct synthesize and secrete specific glycoproteins that become associated with the zona pellucida of the ovulated oocyte. These glycoproteins are collectively designated as oviductins. A monoclonal antibody directed against hamster oviductin was used to study the ontogeny of this glycoprotein. Indirect immunofluorescence experiments performed on sections of hamster oviduct revealed that the glycoprotein begins to be secreted in 10-day-old females and that all of the oviductal secretory cells showed fluorescent staining by day 14. The intensity of the immunofluorescence reaction reached a maximum in the 28-day-old females. The oviducts of the 7-day-old hamster incorporated [35S]methionine in vitro into several proteins; however, the production and secretion of detectable amounts of radiolabeled oviductin only began at 14 days of age and reached a maximum at day 28 of age. It appears that the ontogeny of oviductin parallels the hormone dependent changes leading to sexual maturation and that its maximum secretion is already established at the time of the first ovulatory cycle. These results are substantiated by the fact that the production of oviductin is induced in estradiol-treated, but not progesterone or non-treated prepubertal animals, as determined by indirect immunofluorescence experiments.

Oviductins possess chitinase- and mucin-like domains: a lead in the search for the biological function of these oviduct-specific ZP-associating glycoproteins

Over the last 10 years considerable progress has been made in the immunological and biochemical characterization of oviduct-specific glycoproteins. It is now well established that a subclass of these secretory products, designated as oviductins, associate with the zona pellucida of the ovulated oocyte and with the early embryo. Recent reports on the cloning of cDNAs of oviductins from various species, including that of golden hamster (Mesocricetus auratus) oviductin by our laboratory, allowed us to compare their deduced amino acid sequences with those of other proteins. Optimal alignment analysis showed that oviductins contain regions of significant similarity with catalytically inactive mammalian members of the bacterial and microfilarial chitinase protein family. Most importantly, a close examination of the hamster and human deduced amino acid sequences revealed that both glycoproteins possess contiguous Ser/Thr rich repeated units, clustered in their carboxy-terminal portions. These mucin-type motifs are similar in the hamster and human glycoprotein, although hamster oviductin contains more of these complete units. This striking feature might indicate that these molecules play a similar role to mucin-type glycoproteins, e.g., in protecting the oocyte and early embryo against attacks from their environment. We propose a model whereby oviductins are targeted to the oocyte via the interaction of their chitinase-like domains with specific oligosaccharide moieties of the zona pellucida. Once localized to this structure, oviductin molecules would act as a protective shield around the oocyte and early embryo by virtue of their densely glycosylated mucin-type domains.

Biochemical characterization of a bovine oviduct-specific sialo-glycoprotein that sustains sperm viability in vitro

A bovine oviduct-specific glycoprotein (BOGP) that sustained the viability of bovine spermatozoa in vitro was purified from an extract of bovine oviducts. The amino-terminal amino acid sequence of BOGP was found to be a homologous with that of oviductin, a protein from hamster that was recently characterized by Mallete and Bleau (1993: Biochem. J. 295, 437-445). Purified BOGP was characterized as a sialo-glycoprotein containing N-linked and O-linked sialo-oligosaccharides side chains with galactose, mannose, N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, fucose and sialic acids in its core protein (57 kDa). Intact BOGP has a wide range of isoelectric points (pIs) from 6.5 to 3.0 but a narrow range of molecular masses around 95 kDa. On isoelectric focusing of neuraminidase-treated BOGP (AS-BOGP), a narrow band with a pI of 9.3 was observed, and the ability of AS-BOGP to maintain sperm viability was negligible. We propose that BOGP is a mucin-type sialo-glycoprotein with a molecular mass of 72 kDa that contains one N-linked and approx. 15 O-linked sialo-oligosaccharide chains. These side chains appear to be important for the maintenance of sperm viability.

Affinity binding of hamster oviductin to spermatozoa and its influence on in vitro fertilization

The aim of this study was to determine the influence of hamster oviductal glycoprotein (oviductin) on in vitro gamete interaction. Oviductin was purified from the oviducts using lithium 3,5-diiodosalicylate, followed by phenol extraction. Immunocytochemistry using indirect fluorescence staining revealed that oviductin binds to the sperm anterior acrosomal region. The specific binding of oviductin resulted in inhibition of in vitro fertilization in studies using cumulus-free oocytes. The inhibitory effect was dependent on the concentration of oviductin and occurred in both ovarian and oviductal oocytes but not zona-free oocytes, indicating that sperm-zona interaction was interferred by oviduction. However, the inhibitory effect of oviductin in sperm-zona interaction was reduced when cumulus-enclosed oocytes from ovaries and oviducts were used, indicating that the egg investment including cumulus oophorus has some effect on oviductin-sperm complex and maintaining the fertilizing ability.

Biochemical characterization of hamster oviductin as a sulphated zona pellucida-binding glycoprotein

Oviductins are a family of glycoproteins, synthesized and released by oviductal secretory cells, which bind to the zona pellucida of the oocyte after ovulation. Hamster oviductin migrates as diffuse species of 160-350 kDa during SDS/PAGE under reducing as well as non-reducing conditions. In this report, we describe the one-step purification of hamster oviductin using either immuno- or lectin-affinity chromatography. Probing with specific lectins showed that the glycoprotein contains terminal alpha-D-GalNAc, and either terminal alpha-D-NeuAc or non-terminal beta-D-(GlcNAc)2 residues, but fails to react with concanavalin A and Ulex Europeus A-1 lectins which are specific for branched alpha-D-mannose and alpha-L-fucose moieties respectively. Intraovarian oocytes do not contain this glycoprotein and we demonstrate here that the immunoaffinity-purified oviductin readily binds to their zonae pellucidae in vitro, thus mimicking the in vivo phenomenon. Two major immunologically related forms of hamster oviductin (named alpha and beta) were characterized using one- and two-dimensional gel electrophoresis. The alpha-form (160-210 kDa) has an acidic pI of 3.5-4.5 and the beta-form (approx. 210-350 kDa) is localized at the cathodic site in the isoelectric focusing dimension; in between these two major forms lies a smear of minor-charge isomers. Peptide mapping of both major forms with papain and Staphylococcus aureus V8 protease yielded fragments of identical size. Moreover, the two forms share the same N-terminal sequence which display no significant homology with other reported proteins. Treatment with trifluoromethanesulphonic acid showed that a protein with the size and pI of the alpha-form can be generated from the beta-form. Both the alpha- and beta-forms are sulphated on O-linked oligosaccharide side chains but are not phosphorylated. Collectively, these results suggest that the hamster oviductin polymorphism observed in two-dimensional PAGE is a consequence of different glycosylation patterns and not the polypeptide chain itself. Hamster oviductin is mostly O-glycosylated and contains a few N-linked oligosaccharide side chains (approx. 10 kDa). We propose that hamster oviductin is a mucin-type glycoprotein which might act as a protective secretion influencing the first steps of the reproductive process necessary for the normal triggering of fertilization and early embryonic development.

Immunocytochemical localization of oviduct-specific glycoproteins in the oviductal epithelium from cows at follicular and luteal phases

The immunocytochemical localization of bovine oviduct-specific glycoproteins was investigated by light and electron microscopy. Using monoclonal antibodies (MAbs) specific for bovine oviductal glycoproteins, 3 regions (fimbriae, ampulla, and isthmus) of the epithelium in the bovine oviduct we studied during the follicular and luteal phases. The MAbs reacted specifically with the oviductal epithelial cells. Intense labeling was observed in the ampullar and fimbrial epithelia of cows at the follicular phase, but the reactions were weaker at the luteal phase. In the isthmus, the immunohistochemical reaction was faint during both follicular and luteal phases. At the ultrastructural level, the MAbs bound selectively to putative secretory granules of nonciliated cells in the ampulla and fimbriae, but not in the isthmus. These results suggest that there are cyclic changes and regional differences in the production of glycoproteins in the bovine oviduct.

Immunological detection of an oviductal glycoprotein in the rat

In the golden hamster, high-molecular-weight glycoproteins are secreted by the epithelial cells of the oviduct. The present study was designed to investigate the possibility that the rat oviduct produces specific glycoproteins similar to the oviductal glycoproteins (GHOGPs) of the golden hamster. Oviductal extracts and oviductal fluids obtained from ovulatory rats were analysed by immunoblotting for the presence of glycoproteins that cross-react with a monoclonal antibody (MAb) against GHOGPs. The MAb immunoreacted with a broad band of proteins with a range of molecular weights (MWs) of above 330 kD in oviductal extracts or oviductal fluid after fractionation by electrophoresis under reducing conditions, but these proteins were not present in serum and uterine flushings. An immunohistochemical study demonstrated that the MAb bound strongly to the epithelial cells of the oviduct and, to a lesser extent, to those of the large intestine. Weak reactions were also observed with some other tissues. However, similar material of high MW was not detected in extracts of tissues from the other organs, suggesting that the glycoprotein of high MW that reacted with the MAb is specific for the oviduct. Ultrastructural immunocytochemistry revealed that the MAb reacted specifically with putative secretory granules of nonciliated cells in the oviductal epithelium. These results indicate that the oviductal epithelial cells of the rat produce a specific glycoprotein that is immunologically similar to GHOGPs.

Production and characterization of monoclonal antibodies specific for bovine oviductal glycoproteins

Four monoclonal antibodies (MAbs) were produced in rat cells against materials obtained from the bovine oviduct. The MAbs (1H10, 2A4, 2C5, and 1B12) reacted strongly with the oviductal epithelium of cows in the follicular phase. An immunohistochemical study demonstrated that each of the MAbs bound strongly to the supranuclear cytoplasm of epithelial cells of the oviduct, but not of the stromal cells. Antigens that reacted with the MAbs were characterized by immunoblotting analysis of proteins after fractionation by SDS-PAGE under reducing conditions of oviductal flushings obtained from cows at estrus. All MAbs strongly stained a band of protein with a molecular weight (MW) of 85-97 kD. MAb 1H10 also reacted with the minor band of a 55-kD protein. Similar antigens were not detected in uterine flushings, follicular fluid, and serum. No specific immunohistochemical reactivity with the MAbs was observed with other tissues from the reproductive tract and with nonreproductive tissues. The immunohistochemical reactions were completely eliminated by pretreatment of tissues with trypsin, but not with periodic acid, results that suggest that the antigenic determinants that react with the MAbs were proteinaceous rather than carbohydrate. We have thus established clones that produce 4 MAbs that are specific for oviduct-specific glycoproteins of the cow.

In vitro synthesis of oviductal secretory proteins by estrogen-treated ovariectomized gilts

The objective of this study was to identify, characterize, and examine oviductal secretory proteins (OSP) synthesized de novo by whole oviduct (WO), ampulla (A), and isthmic (I) tissue from ovariectomized (OVX), corn oil (CO)-, estrogen (E)-, progesterone (P)-, and E + P-treated gilts. Oviducts were collected from OVX gilts after CO, E, P, or E + P treatment for 11 consecutive days and tissue was incubated with 3H-leucine (3H-leu). Rates of 3H-leu incorporation into nondialyzable macromolecules by WO explants were greater (P less than 0.01) with E- compared to CO-, P-, or E + P-treated gilts and greater (P less than 0.05) by A explants with E- compared to CO-, P-, or E + P-treated gilts. An effect of location was noted, with A having a greater (P less than 0.01) rate of incorporation than WO or I. Conditioned culture medium was analyzed by one (1D)- and two-dimensional (2D) sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography. Analyses by 1D-SDS-PAGE revealed three major E-dependent bands (335,000, 100,000, and 80,000 M(r)) in WO and A, and one (335,000 M(r)) in the I. A 20,000 M(r) band found in A was inhibited by E, while a 60,000 M(r) band found in the A was induced by P. Analyses by 2D-SDS-PAGE resolved major E-dependent bands 2 (100,000 M(r)) and 3 (80,000 M(r)) into basic and acidic 100,000 M(r) proteins and a 75,000-85,000 M(r) protein (pI less than 4), respectively, found in WO and A, but not in I. A basic 20,000 M(r) protein and an acidic 45,000 M(r) complex, both found in A, were inhibited by E. Gel filtration of culture medium revealed a high M(r) fraction (greater than 2 x 10(6)) that was induced by E and was 6.8-fold greater in medium from A than from I. This study clearly demonstrates that 1) WO and A tissue from E-treated gilts de novo synthesize and secrete three major proteins (basic 100,000, acidic 100,000, and 75,000-85,000 M(r)); 2) these E-dependent proteins are not found in I or with other treatment; 3) several protein complexes synthesized by A are inhibited by E treatment; and 4) a high M(r) fraction, produced primarily in the A, is induced or amplified by E.

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.

Immunological characterization of oviductal glycoproteins associated with the zona pellucida of the golden hamster egg

Three monoclonal antibodies (MAbs) were produced against materials obtained from the golden hamster oviduct. The MAbs (C11E8, C8B11, and A3D5) selectively reacted with the zona pellucida (ZP) of oviductal eggs. An immunohistochemical study demonstrated that all MAbs bound strongly to the epithelial cells of the oviduct and, to a lesser extent, of the uterus, the cervix, and the vagina. Weak reactions were also observed with some other tissues. All immunohistochemical reactions were completely eliminated by treatment of tissues with periodic acid, suggesting that the antigenic determinants that react with the MAbs are carbohydrate in nature. Antigens that reacted with the MAbs were characterized by immunoblotting analyses of 1- or 2-dimensional polyacrylamide gels after electrophoresis to fractionate tissue extracts under reducing conditions. With the oviductal extract, C11E8 and A3D5 specifically bound to broad bands that corresponded to macromolecules of more than 200 and 160 kD, respectively, whereas C8B11 reacted with a broad range of macromolecules, with the strongest reactivity being detected at molecular weights (MWs) higher than 160 kD. The macromolecules that reacted with the MAbs had carbamilation trains, suggestive of extensive microheterogeneity with respect to charge and size. Similar substances of high MW were not detected in extracts of tissues from the other reproductive organs. In addition, one MAb-positive oviductal antigen bound to the ZP of ovarian eggs, but the others did not bind to the ZP of ovarian eggs. This result indicates that the binding activity is specific for the oviductal glycoproteins. We have thus established clones that produce 3 different MAbs with strong affinity for oviduct-specific glycoproteins, one of which is associated with the ZP of the golden hamster.

The zona pellucida binds the mature form of an oviductal glycoprotein (oviductin)

The use of a monoclonal antibody (MAb) specific for the oviductal zona pellucida (ZP) of the hamster has demonstrated that a new antigen (oviductin) is acquired by the ZP during transit of the oocyte in the oviduct. The epitope that is recognized by the MAb bears a terminal N-acetyl-D-galactosamine residue. We conducted a study in order to determine whether this immunoreactivity of the oviductal ZP results from the addition of the terminal sugar residue to a preformed ZP protein or from the transfer of the mature glycoprotein produced by oviductal secretory cells. We measured the incorporation of [35S]methionine into proteins using four different incubation systems: cumulus oophorus (CO) alone, CO in the presence of oviductal fluid, CO co-incubated with empty oviducts, and CO within intact oviducts. At the end of the incubation period, the ZP, vitelli, dispersed cumulus without oocyte, oviducts, and culture medium were isolated and analyzed for their protein content by sodiumdodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), autoradiography, and immunodetection. The cumulus cells synthesized several proteins, independently of the oviductal environment; however, none of these proteins corresponded to oviductin. The ZP and the vitelli of cumulus oophorus that were incubated either alone or in the presence of oviductal fluid did not contain radioactive oviductin. When the oviduct (empty or intact) was present in the incubation system, radiolabeled oviductin was synthesized and secreted into the incubation medium. The ZP picked up a detectable amount of radioactive antigen only in the system in which intact oviducts were incubated.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of lectin receptors sites in the zona pellucida of follicular and ovulated rat oocytes

Carbohydrates of the zona pellucida (ZP) in mammals are believed to have a role in sperm-egg interaction. We have characterized the biochemical nature and distribution of the carbohydrate residues of rat ZP at the light (LM) and electron microscope (EM) levels, using lectins as probes. Immature female rats were induced to superovulate and cumulus-oocyte complexes were isolated from the oviduct, fixed with glutaraldehyde, and embedded in araldite for LM and LR-Gold for EM histochemistry. For examination of follicular oocytes, rat ovaries were fixed with glutaraldehyde and embedded in paraffin. The araldite or paraffin sections were deresined or deparaffinized, respectively, labeled with biotin-tagged lectins as probes, and avidin-biotin-peroxidase complex as visualant. For EM examination, thin LR-Gold sections were labeled with RCA-I colloidal gold complex (RCA/G) and stained with uranyl acetate. LM analyses indicate that in ovulated oocytes the ZP intensely binds peanut agglutinin (PNA); succinylated wheat germ agglutinin, (S-WGA), Griffonia simplisifolia agglutinin-I (GS-I) and soybean agglutinin (SBA), and to a lesser extent, lectins from Ricinus communis (RCA-I), Concanavaia ensiformis (Con A), Ulex europoeus (UEA-I), and wheat germ agglutinin (WGA). The neighboring cumulus cells are considerably less reactive and exhibit membrane staining only with Con A, WGA, and PNA. EM analysis of RCA/G binding revealed intensive binding to the inner layer region of the ZP and moderate binding to cytoplasmic vesicles of the cumulus cells. The ZP of follicular oocytes exhibits a different lectin binding pattern, expressed in staining strongly with PNA and S-WGA, and in a tendency of the lectin receptors to occur in the outer portion of the ZP.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro and in vivo association of an oviduct estrus-associated protein with bovine zona pellucida

The interaction between the bovine egg zona pellucida and a 97 kDa estrus-associated protein produced by the oviduct was examined in vitro and in vivo. In vitro matured bovine eggs were incubated with oviduct fluid recovered throughout the estrous cycle from separate indwelling cannulae placed in the ampulla and isthmus of the same oviduct. Immunofluorescence techniques and a polyclonal antiserum against the 97 kDa protein were used to localize this protein on washed eggs previously incubated with oviduct fluid. Intensity and distribution of immunofluorescence varied with stage of cycle and to a lesser degree with region of oviduct from which the oviduct fluid was obtained. The most intense fluorescence was observed on the zonae pellucidae of eggs incubated with oviduct fluid pooled from days near estrus and ovulation compared to fluid pooled from luteal stage days. The immunofluorescence of isthmus-derived oviduct fluid was more intense than was ampulla-derived oviduct fluid collected near estrus. The zonae pellucidae of 7-day-old embryos flushed from the uterus displayed immunofluorescence comparable to that observed on the zonae pellucidae of eggs incubated in vitro with peri-estrus oviduct fluid. No immunofluorescence was observed associated with the perivitelline space, egg cytoplasm, or blastomeres. The apparent uptake of a 97 kDa estrus-associated protein by the zonae pellucidae of eggs in vitro and embryos in vivo may indicate that this protein functions in fertilization and/or early embryo development.

Ultrastructural evidence for an association between an oviductal glycoprotein and the zona pellucida of the golden hamster egg

The ultrastructural localization of an oviductal glycoprotein, designated ZP-0 in golden hamster oviductal eggs, was investigated by immunolabeling methods using a monoclonal antibody (C11E8). Immunofluorescence staining showed that C11E8 specifically reacted with the zona pellucida of the oviductal egg but not the ovarian egg. In an immunoelectron microscopic study applying the protein-A gold technique, gold particles were distributed throughout the zona pellucida of the oviductal eggs and were also associated with the perivitelline matrix. Structures within the eggs and cumulus cells did not react with C11E8. Quantitative evaluations of the degree of labeling demonstrated that a large number of gold particles was bound to the zone pellucida, especially in the middle layer. Moreover, in bovine testicular hyaluronidase-treated eggs the density of labeling decreased only in the outer third of the zona pellucida. These results show that ZP-0 to the was associated with the zona pellucida and perivitelline matrix of the golden hamster egg after ovulation and suggest that there are topographical differences in the binding activity of ZP-0 to the zona pellucida. In addition, the decrease in labeling density of ZP-O induced by hyaluronidase appears to be related to changes in the properties of the outer layer of the zona pellucida.

Characterization and localization of a mouse egg cortical granule antigen prior to and following fertilization or egg activation

Immunological approaches were used to characterize an antigen that is present within the cortical granules of mouse oocytes and eggs. Immunoelectron microscopy shows a specific localization of the antigen to the cortical granules in the cortex of mouse oocytes and eggs. Following in vitro fertilization, the antigen is present in the perivitelline space and is associated with the zona pellucida. No cortical granules and very little antigen are detected in the two-cell embryo. This antiserum detects a protein of Mr = 75,000 (p75) following immunostaining of egg proteins on Western blots, or immunoprecipitation of metabolically labeled oocyte proteins or radio-iodinated egg proteins. p75 is also present in exudates obtained from A23187-treated eggs, as detected by either radio-iodination of the released egg proteins, or maturation and ionophore activation of metabolically labeled oocytes. Two-dimensional gel electrophoresis of radio-iodinated egg proteins reveals four species of p75 with pIs between 4.9 and 5.3, whereas only the most basic form of p75 is detected in metabolically labeled oocytes. Multiple forms of the radio-iodinated p75 are present in the exudate of ionophore-treated eggs. p75 displays a greater electrophoretic mobility under nonreducing conditions, indicating the presence of intramolecular disulfide bonds, a common characteristic of secreted proteins. We conclude that p75 is synthesized in oocytes, modified and packaged into cortical granules, and released from eggs following fertilization or activation.

Structural and functional relationships between mouse and hamster zona pellucida glycoproteins

The hamster egg's extracellular coat, or zona pellucida, consists of three glycoproteins, designated hZP1, hZP2, and hZP3, that exhibit extensive heterogeneity on SDS-PAGE. hZP1 is a relatively minor component of hamster zonae pellucidae, as compared with hZP2 and hZP3. In the presence of reducing agents, hZP1, 200,000 apparent Mr, migrates on SDS-PAGE with an apparent Mr of 103,000. This suggests that hZP1, like mouse ZP1, is composed of two polypeptides held together by intermolecular disulfides. When purified hamster ZP glycoproteins were tested at relatively low concentrations in an in vitro competition assay, employing either hamster or mouse gametes, only hZP3 (56,000 apparent Mr) exhibited sperm receptor activity (i.e., inhibited binding of sperm to eggs). Thus, apparently hZP3 is the hamster counterpart of mouse ZP3, the mouse egg receptor for sperm. Furthermore, at relatively high concentrations, solubilized hamster egg ZP preparations induced both hamster and mouse sperm to undergo the acrosome reaction in vitro. hZP3 is encoded by a relatively abundant ovarian mRNA that is detected by a mouse ZP3 cDNA probe and is the same size, about 1.5 kb, as mRNA encoding the mouse sperm receptor, ZP3 (83,000 apparent Mr). Like mouse ZP2, hZP2 undergoes limited proteolysis following artificial activation of hamster eggs in vitro. Results of in vitro assays employing intact eggs and isolated zonae pellucidae demonstrate that hamster eggs possess a ZP2-proteinase which has a substrate specificity similar to that of the mouse enzyme. These observations are discussed in terms of structural and functional relationships that may exist between hamster and mouse zona pellucida glycoproteins.

De novo synthesis and release of polypeptides from cyclic and early pregnant porcine oviductal tissue in explant culture

The objective of the present study was to identify and characterize in a limited manner the major de novo oviductal secretory proteins (OSP) synthesized and released by the porcine oviduct. Oviductal tissue was collected on various days of the estrous cycle (EC) and early pregnancy (EP) and cultured in a modified minimal essential medium supplemented with 100 muCi L-[3H]-leucine. Oviductal secretory activity, as measured by the rate of incorporation of 3H-leucine (dpm/mg wet tissue weight) into nondialyzable macromolecules, was greatest (P less than .01) between days 0 and 2 and reached its lowest levels on days 10 to 15. There was no difference between left and right side or pregnancy status. This increased rate of incorporation at proestrus and estrus is temporally associated with elevated levels of estrogen. Incorporation rate for ampulla was greater than for the isthmus. Analysis of oviductal culture medium by one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis and fluorography revealed three protein bands of relative molecular weight (Mr) 335,000, 115,000, and 85,000, which were associated with proestrus, estrus, and metestrus and were not detectable on other days. All three proteins also incorporated 3H-glucosamine. The 115,000 Mr band was the major 3H-glucosamine-labeled protein. Two protein bands (Mr 60,000 and 20,000) were expressed with increasing progesterone during diestrus. Other de novo synthesized protein bands appear to be present throughout the EC and EP with little modulation by estrogen or progesterone. Thus, this study demonstrates that for the porcine oviduct, the increase in the incorporation rate of 3H-leucine into OSP by both whole oviduct and ampulla and de novo synthesis and secretion of three glycoproteins, Mr 335,000, 115,000, and 85,000, were associated with proestrus and estrus when events such as fertilization and early cleavage stages of embryo development occurred.

Characterization of a proteinase that cleaves zona pellucida glycoprotein ZP2 following activation of mouse eggs

Here, we describe an in vitro assay that has permitted further characterization of a proteinase (called "ZP2-proteinase") that is released upon activation of ovulated mouse eggs and cleaves ZP2, one of three glycoproteins present in mouse zonae pellucidae. Results presented suggest that ZP2-proteinase readily diffuses through the zona pellucida within 5 min of activation of eggs by ionophore A23187 and carries out limited proteolysis of ZP2. Appearance of ZP2-proteinase is completely dependent upon activation of eggs, consistent with it being present in cortical granule exudate. The proteinase is insensitive to a wide variety of proteinase inhibitors, but is inhibited when either an anti-ZP2 monoclonal antibody or an Fab fragment of the antibody is bound to ZP2. Proteolysis occurs near the amino- or carboxy-terminus of ZP2, producing a 23,000 Mr glycopeptide(s) that remains attached to ZP2 by intramolecular disulfide bonds. HPLC fractionation of activated egg exudate suggests that ZP2-proteinase has an apparent Mr between 21,000 and 34,000. Proteolysis of ZP2 correlates with "hardening" of the zona pellucida following egg activation and, thus, may be responsible for one aspect of the zona reaction.

Egg envelope conversion following fertilization in Bufo japonicus

The envelope of the Bufo japonicus egg becomes impenetrable to sperm following fertilization. Electrophoretic analysis of envelopes showed that two glycoprotein components with apparent molecular weights of 65,000 and 61,000 were hydrolyzed during fertilization to 62,000 and 58,000, respectively. These two envelope components were structurally related as shown by peptide mapping and deglycosylation studies. Hardening of the envelope following egg activation was also observed, as detected by an increase in the envelope melting temperature. The involvement of proteolytic activities in the envelope hydrolysis and hardening reactions was demonstrated using protease inhibitors, and was verified for the hydrolysis reaction by observing a loss of mass in deglycosylated envelope components obtained before and after fertilization. A low ionic strength medium (less than 50 mM) was required for both the hardening and hydrolysis reactions. Envelopes from eggs activated in a high ionic strength medium were resistant to lysin from sperm, indicating that neither hydrolysis nor hardening was necessary to block lysin activity on the envelope. Both envelope hydrolysis and hardening could be effected in the absence of sperm (i.e., when eggs were activated by electric shock) and after egg jelly had been removed, indicating that neither sperm nor jelly factors were required for the envelope modifications. In addition, when eggs were activated in the presence of NH4Cl to suppress cortical granule exocytosis, envelope hardening and hydrolysis were still observed, indicating that a cortical granule-derived factor may not be involved.

Zona-induced acrosome reaction of hamster spermatozoa

It is well established that the zonae pellucidae of mature unfertilized eggs have the ability to induce the acrosome reaction of capacitated spermatozoa. To determine if this capacity of the zona is species-specific, hamster spermatozoa were allowed to attach to the zonae of homologous and heterologous eggs and examined for the acrosome reaction. The zonae of eggs from six different species were tested and the zona of hamster egg was found to have the strongest capacity to induce the acrosome reaction of hamster spermatozoa, followed by human and rat zonae. The zonae and mouse, guinea pig, and domestic fowl eggs were incapable of inducing the acrosome reaction of hamster spermatozoa. The acrosome reaction-inducing ability of the hamster zona was found to increase during maturation in the ovary. The zona of mature unfertilized hamster eggs maintained their acrosome reaction-inducing ability even after aldehyde fixation or storage in a highly concentrated solution of ammonium sulfate.

Molecular changes in the human zona pellucida associated with fertilization and human sperm-zona interactions

The zona pellucida (ZP) is a specialized extracellular matrix surrounding the mature oocyte. Specific functions ascribed to the ZP include sperm-binding, induction of the acrosome reaction, and involvement in the "slow block" to polyspermy. We have examined the ZP from a variety of human eggs recovered from follicular aspirates. Mechanically isolated ZP were heat-solubilized, iodinated, and characterized by SDS-PAGE. Under nonreducing conditions, the human ZP is characterized by two species of 92-120K (ZP1,2) and 57-73K (ZP3). After reduction, ZP1,2 separates into two components of 97K (ZP1) and 82K (ZP2), with ZP3 at 70K. Under reducing conditions, ZP specifically isolated from fertilized eggs reveals approximately equal proportions of all three iodinated ZP molecules. However, ZP specifically isolated from fertilized eggs reveals a substantial disappearance of ZP1. The ZP from unfertilized eggs does not display this modification of ZP1, even when solubilized zonae are co-incubated with sperm or sperm lysates. We suggest that this molecular change in ZP1 is a direct result of the egg cortical reaction. This demonstrates, for the first time, structural changes in the human ZP directly associated with fertilization. In additional studies, we have demonstrated that capacitated human sperm can be saturated with heat-solubilized ZP, demonstrating the presence of human ZP-binding proteins, and that the binding characteristics of zonae isolated from nonfertilized and fertilized eggs differ. Human sperm proteins having an affinity for solubilized zonae have also been identified at 16K, 18K, 19K, 35K, and 60K.

A glycoprotein of oviductal origin alters biochemical properties of the zona pellucida of hamster egg

Eggs were isolated from ovaries and oviducts of the golden hamster and the components of zonae pellucidae were examined using density gradient SDS-polyacrylamide electrophoresis. Zonae of ovarian eggs (ZP-OVA) had three major components corresponding to the so-called ZP-1, ZP-2, and ZP-3. Zonae of recently ovulated eggs collected from oviducts (ZP-OVI) had a 200-240 K component (ZP-O) in addition to the three components present in ZP-OVA. When ovarian and oviductal eggs were stained with FITC-conjugated B. simplicifolia-1 lectin (BS-1), which specifically binds to alpha-D-galactose- or alpha-N-acetyl-D-galactosamine-like terminal saccharide residues, ZP-OVI was intensely stained, while ZP-OVA was not. ZP-OVA gained the ability to bind to BS-1 after a brief treatment with oviduct extracts. These results suggest that biochemical properties of hamster zonae change after transport of eggs from ovary to the oviduct. The addition of the 200-240 K component of oviductal origin to preexisting zona components seems to be responsible for this change.

On the macromolecular composition of the zona pellucida from porcine oocytes

The chemical and immunological relation between the glycoprotein components of the pig oocyte zona pellucida resolved by two-dimensional polyacrylamide gel electrophoresis was investigated. After disulfide bond reduction, four microheterogeneous glycoprotein components with apparent molecular weights of 25K, 55K, 65K, and 90K were resolved. When disulfide bonds were left unreduced, two microheterogeneous glycoprotein components were resolved with apparent molecular weights of 55K and 90K. Actin was present, but as a contaminant of the zona pellucida rather than as a true component. The structural relation of these components was investigated using deglycosylation with trifluoromethane-sulfonic acid, limited proteolysis with Staphylococcus aureus V8 protease, amino acid and carbohydrate composition analyses, sequence analysis, and monoclonal antibodies. The 25K and 65K components comigrated with the 90K component when disulfide bonds were not reduced. When the intermolecular disulfide bonds crosslinking the two components were reduced, the 25K and 65K components behaved independently. The 25K and 65K components were derived from the 90K glycoprotein family by proteolysis. The 25K component originated from the C-terminal end, and the 65K component from the N-terminal end of the 90K glycoprotein. The 55K component was composed of two chemically and antigenically distinct glycoproteins, termed 55K alpha and 55K beta, that electrophoretically comigrated. The N-terminal amino acid of the 55K alpha family was blocked. The 55K beta family had an N-terminal amino acid sequence of Asp-Val-Pro-Thr-Ile-Gly-Leu-Ser-X-Ala-Pro-Thr. Thus, the two to four electrophoretic components of the zona pellucida observed on gel electrophoresis are derived from three glycoprotein families.