Cryopreservation of human semen. Comparison of cryopreservatives, sources of variability, and prediction of post-thaw survival

Human semen was cryopreserved using Human Sperm Preservation Medium, TEST-Yolk buffer, or glycerol alone. Sperm characteristics for each specimen were measured before and after freezing to determine which cryopreservative resulted in better cryosurvival and recovery of motile sperm. Sperm frozen in Human Sperm Preservation Medium had a significantly better recovery of all semen parameters (motility, velocity, and recovery) than either TEST-Yolk or glycerol alone. Statistical analyses also were done to examine the variability between and within donor semen specimens. Differences between donors, between specimens, and measurements within donors all contributed to variability of sperm characteristics. Specimen-to-specimen variability for a given donor represented 12% to 47% of the total variability, whereas processing and measurement variability represented 12% to 41%. Donors also varied in the ability of their sperm to tolerate freezing. There was a relationship between motile count after dilution with cryopreservative and post-thaw motile count. This relationship allows the prediction of poor-thaw survival before freezing a specimen.

A transient rise in intracellular Ca2+ is a precursor reaction to the zona pellucida-induced acrosome reaction in mouse sperm and is blocked by the induced acrosome reaction inhibitor 3-quinuclidinyl benzilate

The acrosome reaction induced by the zona pellucida in mouse sperm has been shown to proceed in two stages experimentally distinguishable by the fluorescent probe chlortetracycline. Entry into the first stage of sperm bound to isolated, structurally intact zonae pellucidae is blocked by the compound 3-quinuclidinyl benzilate. In this study, we show, utilizing the fluorescent Ca2+ indicator fluo-3, that the first stage of the zona-induced acrosome reaction is characterized by an increase in intracellular Ca2+, followed by a decrease as the acrosome reaction proceeds. This calcium transient is completely suppressed by 3-quinuclidinyl benzilate. We conclude that the Ca2+ transient is induced by the zona pellucida and is required for the zona-induced acrosome reaction. Blockage of this sperm intracellular Ca2+ transient provides a mechanism for the inhibitory action of 3-quinuclidinyl benzilate on the zona-induced acrosome reaction in mouse sperm.

Recombinant mouse ZP3 inhibits sperm binding and induces the acrosome reaction

Mammalian fertilization involves interactions of sperm surface receptors with ligands of the zona pellucida, an extracellular matrix surrounding the ovulated egg. In mouse, the zona is composed of three glycoproteins. One of them, ZP3, participates in primary sperm binding and in the subsequent triggering of the sperm's acrosome reaction. Considerable evidence suggests that carbohydrate determinants of ZP3 are responsible for binding to sperm and may be important for acrosomal exocytosis. A full-length cDNA encoding mouse ZP3 was assembled and cloned into expression vectors that contained either a cytomegalovirus (CMV) or a vaccinia (P11) promoter. Mouse L-929 cells were stably transformed with the pZP3-CMV constructs, and green monkey CV-1 cells were infected with a recombinant vaccinia virus containing ZP3. rZP3 was affinity purified from culture media and detected on Western blots as a single 60- to 70-kDa band, which differed in molecular weight from native ZP3 (mean, 83 kDa). Nevertheless, rZP3 is biologically active. rZP3 decreases sperm-zona binding with a potency equivalent to that of native zona pellucida and, like native ZP3, rZP3 triggers acrosomal exocytosis in capacitated mouse sperm. Thus, rZP3 isolated from both rodent and primate cells appears to contain those carbohydrate and protein structures necessary for ZP3's dual role in fertilization.

Role of G proteins in mouse egg activation: stimulatory effects of acetylcholine on the ZP2 to ZP2f conversion and pronuclear formation in eggs expressing a functional m1 muscarinic receptor

Sperm-mediated egg activation may be analogous to ligand-mediated signal transduction through G protein-coupled receptors. We investigated this possibility in the mouse egg by microinjecting mouse oocytes with an m1 muscarinic receptor mRNA. Following oocyte maturation in vitro, the metaphase II-arrested eggs were treated with acetylcholine and its effect was examined on zona pellucida modifications and pronuclear formation, which are end points of early and late egg activation, respectively. Treatment of these eggs with acetylcholine reveals that both the ZP2 to ZP2f conversion and pronuclear formation occur. Atropine and microinjected GDP beta S block the acetylcholine-induced ZP2 conversion, suggesting that the acetylcholine effects are mediated via a functional G protein-coupled m1 receptor. The acetylcholine-induced ZP2 conversion, however, is not inhibited by pertussis toxin under conditions in which greater than 90% of the endogenous Gi is inactivated by ADP ribosylation. The presence of a pertussis toxin-insensitive G protein, Gq, is detected by immunoblotting; this G protein could be a candidate to mediate the pertussis toxin-insensitive effects of acetylcholine. Results of these experiments are consistent with the hypothesis that receptor-mediated G protein activation may play a role in egg activation.

A large domain common to sperm receptors (Zp2 and Zp3) and TGF-beta type III receptor

A new family of mosaic proteins is defined by sequence analysis. The family is characterized by a 260 residue domain common to proteins of apparently diverse function and tissue specificity: sperm receptors Zp2 and Zp3, betaglycan (also called TGF-beta type III receptor), uromodulin, as well as the major zymogen granule membrane protein (GP-2). The location of the common domain is similar with respect to putative transmembrane regions. The results lead to the hypothesis that this type of domain has a common tertiary structure and that there is a functional similarity in the recognition mechanism of the sperm receptor system and the TGF-beta receptor complex.

Enhancing in vitro fertilization of mouse oocytes by partial zona pellucida digestion

This work was undertaken in order to evaluate the effect of partial zona digestion on fertilization in vitro of mouse oocytes and assess zona surface changes induced by the procedure. Three hundred forty-six oocytes allocated for treatment were exposed to Ham's F-10 medium supplemented with 0.5% Pronase for either 3 min (188 oocytes) or 5 min (158 oocytes); 324 oocytes served as controls. Oocyte losses incurred as a result of the procedure were small (15 oocytes; 4.3%). Control and Pronase-treated oocytes were each divided into four subgroups and inseminated with 5 x 10(5), 5 x 10(4), 5 x 10(3), or 5 x 10(2) sperm cells/ml. Fertilization was assessed 8 hr following insemination by the appearance of two pronuclei and development to the two- to four-cell stage the following day. The morphology of the zona pellucida following Pronase treatment was assessed by phase-contrast and scanning electron (SEM) microscopies performed immediately after treatment. Fertilization rate of control oocytes was 80% at a sperm concentration of 500,000/ml and gradually declined to approximately 30% at 500 cells/ml. In contrast, treated oocytes inseminated with 500 sperm cells/ml demonstrated a normal rate of fertilization. At this low sperm concentration the longer Pronase treatment was significantly (P less than 0.05) more efficient in enhancing fertilization (69 and 88% for 3 and 5 min of Pronase treatment, respectively). Polyspermic fertilization was not observed in any of the subgroups. Phase-contrast microscopic examination of oocytes at the time of Pronase treatment showed an initial swelling of the zona pellucida for 30-60 sec with a time-dependent increase in its transparency.

Biology of mammalian fertilization: role of the zona pellucida

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Inhibition of fertilization by a monoclonal antibody recognizing the oligosaccharide sequence GalNAc beta 1----4Gal beta 1----4 on the mouse zona pellucida

Mouse eggs and pre-implantation stage embryos express on their surfaces a carbohydrate epitope, TEC-2, defined by an IgM monoclonal antibody, TEC-02. The TEC-2 epitope involves the oligosaccharide sequence GalNAc beta 1----4Gal beta 1----4 that is expressed on the plasma membrane and zona pellucida of mouse eggs and on a very limited number of other cell types. In this study we addressed the question whether or not the binding of TEC-02 antibody to the mouse eggs would interfere with their fertilization. Our data showed that the TEC-2 epitope is carried by two zona pellucida glycoproteins, ZP2 and ZP3. Binding of TEC-02 antibody to mouse eggs inhibited specifically and in a dose-dependent manner their fertilization in vitro. The inhibitory effect of TEC-02 antibody was dependent on the presence of an intact zona pellucida. Direct radioantibody binding assays indicated that the TEC-02 antibody completely inhibited fertilization at a concentration at which one quarter of all available TEC-2 binding sites was occupied. Binding of TEC-02 antibody to an egg did not interfere with initial attachment of the sperm to the egg but inhibited maintenance of sperm binding to the zona pellucida, the secondary binding. The combined data indicate that TEC-2, which is a well-defined zona pellucida specific carbohydrate epitope, might be a part of the secondary sperm receptor.

Analysis of the contraceptive potential of antibodies against native and deglycosylated porcine ZP3 in vivo and in vitro

We have undertaken a comparative analysis of the contraceptive activity of antibodies directed against the porcine sperm receptor zona pellucida antigen (ZP3) and its Mr = 32,000 polypeptide core (DGZP-32). The strategies employed for this analysis included the induction of active immunity in a primate, the common marmoset, and an in vitro fertilization protocol involving the use of viable human ova. In both experimental situations, antibodies against ZP3 were shown to exhibit contraceptive activity, leading respectively to the induction of long-term infertility in the primate model and to the complete inhibition of human fertilization in vitro. The in vivo studies also revealed that the induction of high titer antibodies against ZP3 was inevitably associated with the appearance of an ovarian pathology characterized by the progressive depletion of the primordial follicle pool within one to two years. This side effect could not be alleviated by the use of DGZP-32 as antigen since the induction of immunity against this polypeptide was also associated with the eventual appearance of an ovarian pathology identical to that observed with ZP3. Furthermore, the DGZP-32 peptide was less effective than ZP3 in inducing the formation of antibodies capable of inhibiting the fertilization of human ova in vitro. We conclude that significant problems remain with the use of deglycosylated zona peptides for the development of contraceptive vaccines and that their potential will not be realized until the epitopes responsible for the induction of infertility and the primordial follicle depletion have been identified and segregated.

Structural analysis of the N-linked carbohydrate chains of the 55-kDa glycoprotein family (PZP3) from porcine zona pellucida

The N-linked oligosaccharides, released by hydrazinolysis from the major 55-kDa family, PZP3, of porcine zona pellucida glycoproteins, were separated into neutral (28%) and acidic (72%) carbohydrate chains by anion-exchange HPLC. By competition assay, it was shown that the mixture of neutral chains has the sperm-receptor activity, while that of the acidic chains has no activity. Their carbohydrate structures were analyzed after the reducing ends were modified with 2-aminopyridine. The neutral chains were fractionated into several components by reverse-phase and normal-phase HPLC. By sequential glycosidase digestion and 500-MHz 1H-NMR spectroscopy, the structures of three major components were determined. The structures of some of the minor components were analyzed only by sequential glycosidase digestion. By these analyses, it was found that a diantennary complex-type structure with a fucose residue was predominant in the neutral chains. Furthermore, the analyses of the endo-beta-galactosidase digests of the acidic chains revealed that the partially sulfated and sialylated N-acetyllactosamines are linked to the non-reducing ends of diantennary, triantennary, and tetra-antennary complex-type neutral chains, forming heterogeneous acidic chains.

Long-term effects of porcine zonae pellucidae immunocontraception on ovarian function in feral horses (Equus caballus)

Ten feral mares free-roaming in Maryland, USA, were inoculated with porcine zonae pellucidae (PZP) protein before the breeding season for three consecutive years (1988-90). Ovarian function was monitored for 51 days during the peak of the breeding season after the third annual PZP inoculation, in seven of these mares and in four untreated control mares, by means of urinary oestrone conjugates and nonspecific progesterone metabolites. None of the ten inoculated mares became pregnant in 1990, compared with 55% of 20 control mares, which included two of the four monitored for ovarian function. Three of the untreated mares demonstrated apparent normal ovarian activity, characterized by preovulatory oestrogen peaks, concurrent progesterone nadirs at ovulation, breeding activity, and luteal-phase progesterone increases after ovulation. Two of the seven monitored PZP-treated mares demonstrated ovulatory cycles that did not result in conception. One was pregnant as a result of conception in 1989 and demonstrated a normal, late-gestation, endocrine profile. The remaining four PZP-treated mares revealed no evidence of ovulation, and urinary oestrogen concentrations were significantly depressed. The experiments indicated that (i) a third consecutive annual PZP booster inoculation is greater than 90% effective in preventing pregnancies in mares and (ii) three consecutive years of PZP treatment may interfere with normal ovarian function as shown by markedly depressed oestrogen secretion.

Autoimmune disease of the ovary induced by a ZP3 peptide from the mouse zona pellucida

We describe a novel experimental system in mice for the study of ovarian autoimmune disease, a condition encountered in women with premature ovarian failure. The ovarian autoimmune disease is induced in B6AF1 mice by a 15-amino acid peptide (Cys-Ser-Asn-Ser-Ser-Ser-Ser-Gln-Phe-Gln-Ile-His-Gly-Pro-Arg) from mouse ZP3, the sperm-binding component of the zona pellucida that surrounds growing and mature oocytes. Whereas the peptide induces both T cell and antibody responses, adoptive transfer of CD4+ T cell lines derived from affected animals causes oophoritis without observable antibodies to the zona pellucida peptide. The primacy of the T cell response in the pathogenesis of disease is further substantiated by defining oophoritogenic peptides as small as eight amino acids (Asn-Ser-Ser-Ser-Ser-Gln-Phe-Gln) that do not elicit an antibody response to the full-length ZP3 peptide. The identification of a well characterized peptide as a causative agent of autoimmune oophoritis should facilitate understanding of the pathogenesis of this T cell-mediated autoimmune disease. Because the proteins of the zona pellucida are conserved among mammals (the mouse and human ZP3 proteins are 67% identical), this murine model may lead to better understanding of the pathogenesis of human autoimmune oophoritis.

Mouse gamete adhesion molecules

Complementary adhesion molecules are located on the surface of mouse eggs and sperm. These molecules support species-specific interactions between sperm and eggs that lead to gamete fusion (fertilization). Modification of these molecules shortly after gamete fusion assists in prevention of polyspermic fertilization. mZP3, an 83,000-Mr glycoprotein located in the egg extracellular coat, or zona pellucida, serves as primary sperm receptor. Gamete adhesion in mice is carbohydrate-mediated, since sperm recognize and bind to certain mZP3 serine/threonine- (O-) linked oligosaccharides. As a consequence of binding to mZP3, sperm undergo the acrosome reaction, which enables them to penetrate the zona pellucida and fertilize the egg. A 56,000-Mr protein called sp56, which is located in plasma membrane surrounding acrosome-intact mouse sperm heads, is a putative primary egg-binding protein. It is suggested that sp56 recognizes and binds to certain mZP3 O-linked oligosaccharides. Acrosome-reacted sperm remain bound to eggs by interacting with mZP2, a 120,000-Mr zona pellicida glycoprotein. Thus, mZP2 serves as secondary sperm receptor. Perhaps a sperm protease associated with inner acrosomal membrane, possibly (pro)acrosin, serves as secondary egg-binding protein. These and, perhaps, other egg and sperm surface molecules regulate fertilization in mice. Homologous molecules apparently regulate fertilization in other mammals.

Role of the lysine and arginine residues of vitellogenin in high affinity binding to vitellogenin receptors in locust oocyte membranes

A specific cell surface receptor mediates the endocytosis of the yolk protein vitellogenin (VTG), a lipoglycoprotein, into growing oocytes of the insect Locusta migratoria. The ability of the VTG receptor to recognize VTG was analyzed in binding tests after modification by five lysine-specific and two other reagents. Progressive chemical modification of the lysyl and arginyl residues resulted in reduction or loss of the derivatized VTG to compete for binding to the VTG receptor with unmodified VTG. Although the precise role of the lysine residues in receptor binding remains to be defined we conclude that they are involved in expression of a recognition site interacting with the binding domain of the VTG receptor. Sulfhydryl groups are not involved in the conformation of the recognition site or binding ability of VTG.

Evidence for the presence of high-mannose/hybrid oligosaccharide chain(s) on the mouse ZP2 and ZP3

Previous studies from this laboratory have identified a novel alpha-D-mannosidase on plasma membranes of rat, mouse, hamster, and human spermatozoa [Tulsiani et al. J Cell Biol 1989; 109:1257; Biol Reprod 1990; 42:843]. Inhibition of the mouse sperm surface alpha-D-mannosidase inhibits sperm-egg binding in vitro, suggesting that the sperm enzyme may have a receptor-like role in binding to the complementary molecules (presumably mannose-containing oligosaccharide [OS] chains) on the mouse zona pellucida (ZP) glycoconjugates [Cornwall et al. Biol Reprod 1991; 44:913]. In the studies reported here, we demonstrate the presence of high-mannose/hybrid-type OS on mouse zona components. Zona-intact eggs, prepared from superovulated mice, were radioiodinated, and the individual zona components (ZP1, ZP2, and ZP3) were isolated by electrophoresis followed by electroelution. The purified ZP components, when resolved by immobilized concanavalin A column chromatography, showed the following results: 1) Nearly all of the ZP1 applied to the immobilized lectin eluted in the column flow-through (effluent) fractions, and no radioactivity eluted with alpha-methyl mannoside, suggesting that ZP1 may not contain high-mannose/hybrid OS. 2) A significant amount of both ZP2 and ZP3 bound to the immobilized lectin, and nearly 16% and 8% of the two components, respectively, were repeatedly eluted with alpha-methyl mannoside.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo and in vitro study of the lesions produced with a computerized radiofrequency system

For many years, radiofrequency-generated lesions have been used for the treatment of pain and abnormal movements. However, the reliability of this method has been questioned because of the variation in the size of lesions produced by the electrode at different times and temperatures. A 500-kHz radiofrequency generator with different electrodes was used to determine the size of lesions, using different time and temperature exposures. A computerized feedback mechanism kept the tip temperature constant during the production of the lesion, regardless of varying tissue impedance. Eight electrodes of different size and tip characteristics were evaluated at different temperatures and time settings, both in vitro and in vivo. Graphic display of the curves in time were obtained at 65, 70, 75, 80, 85 and 90 degrees C. The effects of thermo-coagulation were studied in vitro in fresh egg whites, using time intervals of 20, 40, 60, 80 and 100 s, and in vivo, in the subcortical white matter of 20 adult New Zealand white rabbits. Animals were sacrificed after 7 days. Lesions were photographed and measured under magnification. In all cases, the coagulated masses were ellipsoid, with regular, well-demarcated borders. A two-way statistical analysis of variance was done. The coagulum size increased with higher temperatures and with larger probes. The increase was significant in both diameter and length (p = 0.001). In contrast, the use of different times at the same level of temperature showed no significant increase in most of the electrodes. There were two statistical significant time effects, for both diameter and length, with the monopolar 2-mm electrode. The use of real-time monitoring with graphic display and the feedback information provided for the computerized control of power and current allows high precision of the temperature at the electrode tip during the production of the lesion.

Immunogenicity of deglycosylated zona pellucida antigens and their inhibitory effects on fertility in rabbits

Influence of carbohydrates on the immunogenicity and immunocontraceptive potential of zona pellucida glycoproteins has been investigated in rabbits. Porcine zonae pellucidae, following deglycosylation with trifluoromethane-sulfonic acid, retained significant immunogenic potential, as shown by the ability to generate antibodies which cross-reacted with the heterologous antigen. Antibody response, however, was much stronger against the native zona glycoproteins, thereby suggesting that both carbohydrate and protein moieties contribute to the overall immunogenicity of the zona pellucida antigens. Contraceptive efficacy of active immunization with the deglycosylated zona antigens, when evaluated by mating experiments, demonstrated inhibition of fertility in all immunized rabbits. Normal ovarian functions were disrupted in these animals, as revealed by the reduction in ovarian weights and gross impairment of folliculogenesis. Flushing of the oviducts of the immunized animals yielded a markedly reduced number of ova ovulated in response to hCG administration, none of which were fertilizable. Results collectively suggest that active heteroimmunization with deglycosylated zona pellucida antigens is effective in reducing fertility in rabbits.

The cellular immune response to immunization with zona pellucida antigens

The cellular immune response of mice to porcine and rat zona pellucida and cynomolgus macaques to porcine zona pellucida antigens was evaluated. Mice mounted a vigorous cellular response to both antigens, as determined by the T cell proliferation response in vitro. There was poor cross-reactivity to murine zonae by T cells or serum antibodies from mice immunized with rat zona pellucida. Nevertheless, ovaries from the mice immunized with rat zona had significantly fewer antral follicles than adjuvant-treated controls, suggesting that the immune response to the zona antigen disrupted follicular development. T cells from two macaques that had been immunized with porcine zona pelludica proteins proliferated in vitro in response to this antigen. Both macaques also had strong antibody responses. The patterns of urinary steroid metabolites in these animals provided clear evidence of ovarian malfunction following immunization. The data indicate that a significant cellular immune response is generated upon immunization of animals with zona pellucida antigens regardless of whether the antigens are cross reactive with the host zona antigens. Whether impaired ovarian function and follicular development are related to the cellular response must be determined in future studies.

A mouse oocyte-specific protein that binds to a region of mZP3 promoter responsible for oocyte-specific mZP3 gene expression

The gene encoding mZP3, the mouse sperm receptor, is expressed exclusively in growing oocytes during oogenesis. To investigate the molecular basis of oocyte-specific mZP3 gene expression, we generated several lines of mice harboring a transgene that contains 470 bp of mZP3 gene 5'-flanking sequence (nucleotides -470 to +10) fused to the firefly luciferase gene coding region. Three of four expressing transgenic lines exhibited luciferase activity only in growing oocytes, suggesting that the 470-bp fragment is sufficient to direct Iocyte-specific expression of the luciferase gene. Results of DNase I footprinting and gel mobility shift assays suggested the presence of an ovary-specific protein that binds to a small region (nucleotides-99 to -86) within the 470-bp fragment of the mZP3 promoter, with 5'-G(G/A)T(G/A)A-3' representing the minimal sequence required for binding. Southwestern (DNA-protein) gel blots revealed the presence of an oocyte-specific, approximately 60,000-Mr protein, called OSP-1, that binds to the minimal sequence. Changes in levels of OSP-1 during oogenesis and early cleavage are consistent with the pattern of mZP3 gene expression during these developmental stages in mice. Therefore, OSP-1 may be a mammalian oocyte-specific transcription factor involved in regulating oocyte-specific mZP3 gene expression.

Masking of anionic sites by deposits in lamina rara externa in immune complex nephritis in rats

Alterations in glomerular basement membrane (GBM) anionic sites associated with immune deposits (ID) were observed using polyethyleneimine (PEI) as a cationic probe in serum sickness nephritis induced by egg albumin (EA). The anionic sites were fewer in number than in other GBM segments and were irregular in distribution in most, but not all, of the segments of the GBM with ID on the epithelial side of the lamina densa (LD). The disappearance of anionic sites was obvious in areas where the internal aspects of the lamina rara externa (LRE) of the GBM were occupied by ID, even if the ID were very small. In contrast, the disappearance of anionic sites was not evident, even though no change in anionic sites was found in some areas, where the ID had departed from the internal aspects of the LRE and a pale band was seen between the ID and the LD. Further, PEI aggregates, showing localization of anionic sites, were seen within the low density ID, but no PEI aggregates were seen within the high density ID. The results suggest that: 1) whether or not ID induce the disappearance of anionic sites is independent of the size of the ID, but is dependent on the density of and the place occupied by the ID, and 2) the ID seem to induce the disappearance of anionic sites by masking rather than destroying them.

The cloning and characterization of a maternally expressed novel zinc finger nuclear phosphoprotein (xnf7) in Xenopus laevis

We report the cloning of a cDNA (xnf7) coding for a maternally expressed Xenopus protein that becomes highly enriched in nuclei of the central nervous system during later development and in nuclei of adult brain. The protein also shows stage-specific nuclear/cytoplasmic partitioning and phosphorylation that may be related to its function. In addition, it binds to double-stranded DNA in vitro. The conceptual protein produced by the xnf7 clone contains several acidic domains, a novel zinc finger domain, three putative p34cdc2 protein kinase phosphorylation sites, and a bipartite basic nuclear localization signal. The xnf7 mRNA was detected as a maternal transcript that decreased in abundance during development through the gastrula stage. It was reexpressed at the neural stage in mesoderm and neural tissues, and its reexpression was not dependent upon the normal juxtaposition of the mesoderm and ectoderm that occurs during neural induction as demonstrated by high titer in exogastrulae. In situ hybridization showed enrichment of the mRNA in the neural tube and a small amount in the mesoderm at the late neurula stage. Xnf7 is normally phosphorylated during oocyte maturation. The bacterially expressed xnf7 protein was phosphorylated in vitro by purified maturation-promoting factor at a threonine in a small N-terminal domain containing one of the p34cdc2 protein kinase phosphorylation sites, but not by several other protein kinases. The structural domains present in the protein and its localization in nuclei suggest that the xnf7 gene product performs an important nuclear function during early development, perhaps as a transcription factor or a structural component of chromatin.

Blocking of human sperm-zona interaction by monoclonal antibodies to a glycoprotein family (ZP4) of porcine zona pellucida

To study zona pellucida antigens involved in human fertilization, five monoclonal antibodies (MAbs)--2A1, 2G3, 4A2, 4E12, and 5H4--were produced to a glycoprotein family (ZP4) isolated from heat-solubilized porcine zonae pellucidae. Each MAb reacted not only with solubilized porcine zona glycoproteins but also with the glycoproteins deglycosylated by trifluoromethanesulfonic acid treatment. They also reacted with intact zonae pellucidae of porcine and human oocytes. Three (4A2, 4E12, and 5H4) of the five MAbs showed a significant blocking effect on human sperm binding and penetration of human zonae pellucidae. The 5H4 MAb showed a strong reaction with ZP4 and ZP1 glycoprotein families of porcine zonae pellucidae, and four other MAbs reacted more strongly with ZP3 than with ZP4. The reactivity of 5H4 with porcine zona glycoproteins was destroyed by chymotrypsin digestion, but the antigen epitope was resistant to proteolysis by trypsin and endoproteinase Lys-C. A peptide fragment reactive to 5H4 was isolated by reverse-phase HPLC from endoproteinase Lys-C-treated ZP4 glycoproteins, and its molecular mass was determined to be 7 kDa by SDS-PAGE. These results suggested that the antigen epitope corresponding to 5H4 is a good candidate for development of a contraceptive vaccine.

Vitellogenesis in Anolis pulchellus: induction of VTG-like protein in liver explants from male and immature lizards

Vitellogenin (VTG) synthesis has been described as an ideal system to study the hormonal regulation of gene expression. In Xenopus the molecular aspects of this control have been analyzed; however, in other non-mammalian species such as reptiles, very few studies approaching this level have been undertaken. We report on the induction by estradiol-17 beta of VTG-like proteins in liver explants from adult males and immature male and female lizards (A. pulchellus). A concentration of 10(-7) M was optimum for adult males while a higher concentration (10(-6) M) is required for the immature animals. No differences were observed in the hormonal induction in male and female immature animals, suggesting that there are no sexual distinctions in the liver at this stage. The effect of the hormone in male liver appears to be primarily on mRNA synthesis, since increases in 3H-uridine incorporation in total RNA were prevented by addition of 1 microgram/ml of the RNA polymerase II inhibitor alpha-Amanitin; however, rRNA synthesis was also increased as observed by agarose gel analysis. A 48 hr lag period was required for the detection of the intracellular as well as the secreted VTG-like protein. Electrophoretical analysis of the secretory products revealed the induction of a group of phosphoproteins immunologically related to yolk lipovitellin whose molecular weights range from 116,000 to 200,000.

Isolation, composition, and biological activity of sugar chains of porcine oocyte zona pellucida 55K glycoproteins

ZP3, a preparation of the 55K families of porcine oocyte zona pellucida, possesses carbohydrate-dependent ligand activity for boar sperm. The aim of the present study was to analyze ZP3 N- and O-linked oligosaccharides with respect to size distribution, composition, and role in sperm-zona recognition events. Digestion of denatured ZP3 with peptide N-glycosidase F (PNGaseF) released the majority of N-glycans which fractionated on Sephadex G-75 resin as a polydisperse population with apparent molecular masses ranging from 1,900-8,200 Da. The higher molecular weight N-glycans were characterized by the presence of strongly anionic sulfated/sialylated polylactosamine structures. Alkaline-borohydride treatment of the PNGaseF-digested core proteins liberated O-glycans as a heterogeneous population of oligosaccharide alcohols, which were fractionated on a Sephadex G-50 column. Compositional analyses indicated sulfated polylactosamine units associated with the higher molecular weight O-glycans. Preincubation of boar sperm with ZP3 or purified O-glycans, but not N-glycans, inhibited subsequent attachment to zona-encased oocytes. Purified O-glycans were, however, 2 to 3 orders of magnitude less effective than ZP3 as competitive ligands. The results document the extreme heterogeneity of the ZP3 carbohydrate moiety, in large part attributable to a broad spectrum of variably sized N- and O-linked sulfated polylactosamines. Ligand competition bioassays suggest that O-glycans mediate, at least in part, the sperm adhesive properties of ZP3 and strongly imply that high-affinity interaction of ZP3 sugar chains with complementary sperm receptors is dependent upon their covalent association with core proteins.

The nuclear-cytoplasmic distribution of the Xenopus nuclear factor, xnf7, coincides with its state of phosphorylation during early development

We describe the characterization in Xenopus laevis of a nuclear protein, xnf7, which is first detected in the oocyte GV and is eventually enriched in nuclei of cells of the adult brain. Previous studies have shown that this protein contains zinc-finger-like structures and acidic domains typical of transcriptional activators, and is phosphorylated in vitro by p34cdc2 protein kinase. The protein also binds to double-stranded DNA. These data suggest that xnf7 may function as a transcription factor. During oocyte maturation, xnf7 is released into the cytoplasm and is not detectable in nuclei until the mid-blastula-gastrula stage of development. Western blot analysis of xnf7 isolated from oocytes and eggs showed the existence of multiple bands or isoforms of the protein. Unique isoforms that are generated during oocyte maturation are the result of phosphorylation. The phosphorylated isoforms remain in the cytoplasm until the mid-blastula stage. The re-accumulation of protein in the embryonic nuclei at this time correlates with the increase in abundance of the less phosphorylated isoforms. The xnf7 protein possesses a nuclear localization signal (NLS) similar to the bipartite signal found in nucleoplasmin. Newly synthesized xnf7 accumulated in the oocyte GV to detectable levels within a few hours following synthesis suggesting that retention of the protein in the cytoplasm during early cleavage may be due to a process that interferes with the function of the NLS. These data suggest that compartmentalization and/or post-translational modification of the nuclear protein xnf7 may be involved in regulating its function during early development.

Activation and subsequent degradation of proacrosin is mediated by zona pellucida glycoproteins, negatively charged polysaccharides, and DNA

Boar proacrosin (E.C. 3.4.21.10, Mw 53 kD) was isolated by a modified method and subjected to autoactivation. Previously described molecular intermediates of 49 and 43 kD and a stable form (beta-acrosin, 35 kD) were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoactivation was expedited in the presence of either zona pellucida glycoproteins, fucoidan, or DNA. The end point of this accelerated conversion was the complete degradation of otherwise stable beta-acrosin via the formation of a characteristic active intermediate protein of 30 kD. All intermediate molecular forms observed during proacrosin activation/conversion exhibited the N-terminal sequence of the boar acrosin heavy chain, indicating a C-terminal processing mechanism. Hence zona pellucida glycoproteins stimulate proacrosin activation as well as acrosin degradation. Such a mechanism of proenzyme activation and degradation is to our knowledge described here for the first time and points to a previously unrecognized role of zona pellucida during gamete interaction.

Differential binding of gold-labeled zona pellucida glycoproteins mZP2 and mZP3 to mouse sperm membrane compartments

Egg zona pellucida glycoproteins mZP3 and mZP2 serve as primary and secondary sperm receptors, respectively, during initial stages of fertilization in mice [Wassarman (1988) A. Rev. Biochem. 57, 415–442]. These receptors interact with complementary egg-binding proteins (EBPs) located on the sperm surface to support species-specific gamete adhesion. Results of whole-mount autoradiographic experiments suggest that purified egg mZP3 and mZP2 bind preferentially to acrosome-intact (AI) and acrosome-reacted (AR) sperm heads, respectively [Bleil and Wassarman (1986) J. Cell Biol. 102, 1363–1371]. Here, we used purified egg mZP2, egg mZP3 and fetuin, which were coupled directly to colloidal gold (‘gold-probes’), to examine binding of these glycoproteins to membrane compartments of AI and AR sperm by transmission electron microscopy. mZP3 gold-probes were found associated primarily with plasma membrane overlying the acrosomal and post-acrosomal regions of AI sperm heads. They were also found associated with plasma membrane overlying the post-acrosomal region of AR sperm heads. mZP2 gold-probes were found associated primarily with inner acrosomal membrane of AR sperm heads, although some gold was associated with outer acrosomal membrane of AI sperm that had holes in plasma membrane overlying the acrosome. Fetuin gold-probes, used to assess background levels of binding, were bound at relatively low levels to plasma membrane and inner acrosomal membrane of AI and AR sperm, respectively. None of the gold-probes exhibited significant binding to sperm tails, or to red blood cells and residual bodies present in sperm preparations. These results provide further evidence that mZP2 and mZP3 bind preferentially to heads of AR and AI sperm, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The hemizona assay (HZA) as an experimental model to evaluate the inhibition of sperm binding to the murine zona pellucida by isolated zona pellucida protein

Compelling evidence has demonstrated that zona binding represents gamete recognition by sperm binding with high affinity and specificity to complex glycoproteins of the zona pellucida. In the present study we evaluated the hemizona assay (HZA) in the investigation of the interaction of mouse spermatozoa with unfertilized murine oocytes and hemizonae after exposure to solubilized murine zonae pellucidae proteins. The zonae pellucidae were isolated from ovarian tissue following described mincing techniques. The sperm binding characteristics of murine spermatozoa were studied by using SDS-PAGE isolated ZP2 (+/- 120 Kd) and ZP3 (+/- 83 Kd) components of the zona pellucida. Sperm receptor activity was examined in a competitive gamete binding fashion using the HZA as an indicator of sperm/zona interaction. The results illustrated that isolated, solubilized ZP2 and ZP3 glycoprotein moieties of the zona pellucida inhibited sperm binding to hemizonae and oocytes when compared to controls, and that the HZA can be utilized as an internally controlled homologous bioassay to evaluate the effects of zona pellucida proteins on tight binding of spermatozoa to the zona pellucida.

[Determining riboflavin level in urine (comparative analysis of the methods)]

Four methods of riboflavin content estimation in urine were studied: they are based on specific titration of vitamin B by riboflavin-binding protein (1), riboflavin decomposition by boiling in alkali (2), riboflavin fluorescence suppression by dithionate (3), and high-performance liquid chromatography. A conclusion has been made on the necessity of a home standard for riboflavin estimation by methods 1-3. The results obtained with the above methods correlated well, regression equations were derived describing correlation of these results. Methods 1 and 3 are most simple and highly specific and sensitive, therefore they could be recommended for wide use in large-scale clinical investigations.

Isolation and characterization of a full-length cDNA encoding the 55-kDa rabbit zona pellucida protein

A full-length cDNA (rc55) encoding the major rabbit zona pellucida (ZP) glycoprotein (55 kDa) has been cloned and sequenced. A lambda gt11 expression library was constructed using poly(A)+ mRNA isolated from sexually immature rabbit ovaries which contain large numbers of developing follicles. The rc55 cDNA was identified using affinity purified polyclonal antibodies specific to ZP antigens which are shared among mammalian species. The deduced amino acid sequence of the full-length rc55 clone was matched to the NH2-terminal 25-amino acid sequence obtained for this protein. The predicted amino acid sequence consists of 540 amino acids including a putative signal peptide of 18-24 residues and six potential N-glycosylation sites. The cDNA hybridizes to a 2000-base species of mRNA from rabbit ovary which is not detected in other rabbit tissues. The message is present early in ovarian follicular development and is approximately 600-fold greater in sexually immature as compared with sexually mature rabbit ovaries. This cDNA was expressed as a cro-beta-galactosidase fusion protein using the pEX expression vector. Antibodies against native rabbit ZP, affinity-purified on the recombinant 55-kDa ZP protein, were found to recognize the native rabbit ZP glycoprotein, indicating partial conservation of native epitopes in the expressed recombinant protein.

Zona pellucida modifications in the mouse in the absence of oocyte activation

Mouse oocytes arrested in metaphase II exhibit zona hardening and a reduced fertilization rate after exposure to the cryoprotectant dimethylsulfoxide (Johnson J, In Vitro Fertil Embryo Transfer 6:168-175, 1989) but do not undergo parthenogenetic activation (Johnson and Pickering, Development 100:313-324, 1987). This paper shows that dimethylsulfoxide causes proteolytic modification of the zona pellucida glycoprotein ZP2 and inhibition of sperm binding. These effects of dimethylsulfoxide are caused by premature exocytosis of the cortical granules, a process that is initiated usually on fertilization. A model for the mechanism of action of dimethylsulfoxide is proposed based on the combined effects of cytoskeletal modification and osmotic shock. The presence of serum before and during the exposure to dimethylsulfoxide was found to reduce significantly these deleterious effects on the mouse zona pellucida without inhibiting the cortical granule release. These results highlight the suitability of dimethylsulfoxide as a tool to study the mechanisms leading to cortical granule release. Use of dimethylsulfoxide allows the separation of oocyte parthenogenetic activation from cortical granule release, and addition of serum allows separation of cortical granule release from the action of the cortical granule contents. Their use allows a dissection of the mechanisms underlying each of these three related events.

Generation of a mouse sperm membrane fraction with zona receptor activity

To identify mouse sperm components involved in primary sperm binding to zonae pellucidae, a mouse sperm plasma membrane-enriched fraction was generated using a vortex method. The crude membrane fraction recovered after vortexing was resolved into three bands and a pellet by centrifugation on a discontinuous sucrose gradient. Ultrastructural analysis indicated that Bands 2 and 3 were composed predominantly of membranes, although Band 3 was contaminated with mitochondria; Band 1 and the gradient pellet contained insufficient material and were unsuitable for ultrastructural analysis. To determine where plasma membranes migrate in the gradient, sperm were labeled vectorially with 125I; subsequently, membrane fractions were analyzed by SDS-PAGE and autoradiography. Band 2 was enriched threefold in radiolabel when compared with Band 3. Examination of intact and vortexed sperm stained with regionally distributed anti-mouse sperm monoclonal antibodies revealed that vortexing removed anterior head plasma membrane preferentially. Bioactivity, defined as the ability to inhibit primary sperm binding to the zona pellucida in a concentration-dependent manner, was contained in the crude membrane fraction and Band 2 exclusively, with inhibition of 53% and 44%, respectively, at the maximum concentration tested. Band 3 exhibited no significant bioactivity. We conclude from these results that a plasma membrane-enriched fraction, Band 2, isolated from mouse cauda epididymal sperm, exhibits zona pellucida receptor activity.

Interaction of zona pellucida glycoproteins, sulphated carbohydrates and synthetic polymers with proacrosin, the putative egg-binding protein from mammalian spermatozoa

Fertilization in mammals is a unique cell-cell recognition event that involves specific receptors on the surface of each gamete. Previous work has shown that proacrosin, a protein found within the acrosome of mammalian spermatozoa, binds non-enzymatically to zona pellucida glycoproteins (ZPGPs) that surround the egg and that this binding can be inhibited by sulphated polysaccharides such as fucoidan. The mechanism of this interaction has been investigated using 125I-ZPGPs and 125I-fucoidan as probes. Results show that it involves poly(sulphate) groups on zona glycoproteins that bind with high affinity (Kd = 1.2 to 5.0 × 10(−8)M) to complementary ‘docking’ sites on proacrosin. The spatial orientation of these sulphates, together with the tertiary structure of the target protein, determines the selectivity of polymer binding. Thus, dextran sulphate and poly(vinyl sulphate) are strong inhibitors of the above probes whereas dextran, chondroitin sulphates A and C and poly(vinyl phosphate) are ineffective. Proacrosin, therefore, has properties analogous to those described for ‘bindin’, the egg adhesion protein found within the acrosomal vesicle of sea urchin spermatozoa.

Two-dimensional polyacrylamide gel electrophoresis characterization of APz, a sperm protein involved in zona binding in the pig and evidence for its binding to specific zona glycoproteins

A boar sperm integral plasma membrane protein (APz) involved in the adhesion of uncapacitated and capacitated sperm to the porcine zona pellucida (ZP) has been characterized by two-dimensional polyacrylamide gel electrophoresis (PAGE) and tested for its ability to bind to various zona glycopeptides. APz shows microheterogeneity and focuses over a wide pH range, with predominant forms focusing above pH 7. The protein, when excised from nonreducing polyacrylamide gels, inhibited sperm-egg binding and bound heat-solubilized zonae preventing these zonae from blocking sperm binding to eggs. In an indirect assay, a polyclonal monovalent antibody, which blocks sperm-egg binding and which is absorbed by APz, was used to determine the ability of zona glycopeptides to prevent the sperm-egg blocking activity of the antibody from being absorbed by intact sperm. When whole heat-solubilized ZP was added to sperm at doses that block sperm-egg binding and the excess ZP was removed, the sperm-egg blocking activity of the antibody was not absorbed by these sperm, and antibody-containing supernatants blocked the binding of untreated sperm to eggs as effectively as antibody that was not mixed with fresh sperm. When alpha ZP3 was used in the same manner, sperm-egg blocking activity again was not absorbed by antibody-treated cells. Beta ZP3, however, failed to block sperm-egg binding and failed to absorb the sperm-egg blocking activity of the antibody. These findings support the argument that the action of APz is physiologically significant and involves specific binding sites on the ZP3 component of the ZP.

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.

How the egg regulates sperm function during gamete interaction: facts and fantasies

Although details of the molecular mechanism are not yet clear, considerable evidence suggests that the egg-specific extracellular matrix component ZP3 regulates an essential event of sperm function, the acrosome reaction. Spatial control of this exocytotic event appears to be exerted by immobilization of the triggering ligand, ZP3, in the zona pellucida matrix surrounding the egg. Our data suggest that the signal transduction pathway in sperm activated by this ligand involves highly conserved components that are involved in many other eukaryotic signalling events. Recent experiments indicate that the murine zona pellucida glycoprotein ZP3 regulates acrosomal exocytosis by aggregating its corresponding receptors (ZP3-Rs) located in the mouse sperm plasma membrane. In other experiments, we have identified a putative ZP3-R of mouse sperm with Mr 95,000. Indirect immunofluorescence localizes this ZP3-R, termed p95, to the acrosomal region of the mouse sperm head, which is the anticipated location for ZP3-Rs. Membrane fractionation studies indicate that p95 cofractionates with a plasma membrane-enriched preparation from sperm that contains zona pellucida-receptor activity. In addition to its role as a ZP3-R, p95 also serves as a substrate for a tyrosine kinase in response to zona pellucida binding. On the basis of the data presented here, and borrowing heavily from findings for other signalling systems, we have formulated two testable hypotheses that are compatible with the available data: either p95 is itself a protein tyrosine kinase receptor, or p95 serves as a ZP3 receptor and is separate from a protein tyrosine kinase that is activated during gamete interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Further characterization of the porcine zona pellucida antigen corresponding to monoclonal antibody 3A4-2G1 exclusively cross-reactive with porcine and human zonae pellucidae

Biochemical and molecular analyses were performed for the porcine zona pellucida (ZP) antigen corresponding to the monoclonal antibody (Mab) 3A4-2G1 exclusively cross-reactive with porcine and human zonae pellucidae (ZPe). By SDS-PAGE and Western blot analysis, Mab 3A4-2G1 reacted with a 92-kDa component of solubilized porcine ZP (s-PZP) under non-reducing conditions, while reacting with a 23-kDa component under reducing conditions. Diagonal SDS-PAGE revealed that the 92-kDa component was composed of 69 kDa and 23 kDa molecules. In two-dimensional O'Farrell's electrophoresis, the antigen molecules reactive to Mab 3A4-2G1 were distributed over a wide range of PI as a family of proteins around 92 kDa and 23 kDa regions under non-reducing and reducing conditions, respectively. A murine antiserum raised to the isolated 23-kDa component reacted not only with the 23-kDa but also with the 92-kDa glycoprotein family. The anti-23 kDa serum showed a strong inhibitory effect on human sperm-egg interaction by in vitro fertilization. The reactivity of s-PZP to Mab 3A4-2G1 was markedly reduced by treatments with proteolytic enzymes but not significantly with glycosidic enzymes. However, chemical deglycosylation of the antigen markedly reduced the antigen's activity. These results suggested that Mab 3A4-2G1 recognized a conformational antigen epitope structure of ZP.

Endocrine response in rabbits immunized with native versus deglycosylated porcine zona pellucida antigens

Previous studies evaluating porcine zona pellucida antigens for immunocontraceptive purposes have in some cases revealed altered ovarian function in association with antibody response. This study was undertaken in an attempt to identify zona immunogens that do not cause adverse endocrine effects. To this end, we investigated the effects of highly purified preparations of native and deglycosylated pig zona pellucida antigens on ovarian function and immune response in the rabbit. Thirty female rabbits were immunized, 5 per group, with 100 micrograms each of either 1) SIZP, solubilized isolated zonae pellucidae; 2) ZP3, a purified porcine zona preparation containing the two principle glycoproteins, ZP3 alpha and ZP3 beta, endo-beta-galactosidase-digested ZP3 glycoproteins (approximately 30% deglycosylated) termed 3) ZP3 alpha/EBGD and 4) ZP3 beta/EBGD; and chemically deglycosylated ZP3 alpha and ZP3 beta (greater than or equal to 92% deglycosylated), termed 5) ZP3 alpha/DG and 6) ZP3 beta/DG. Rabbits injected with saline (n = 2) or Freund's adjuvant alone (n = 3) served as controls. Serum LH, FSH, estradiol, and progesterone were measured at 5-day intervals during seven 20-day cycles of hCG-induced pseudopregnancy over 42 wk. Anti-ZP3 titers, determined by RIA, developed in all treatment groups and correlated directly with carbohydrate content. Animals immunized with SIZP, ZP3, and ZP3 beta/EBGD showed a significant elevation of LH and FSH and a significant decline of peak progesterone levels by the fourth pseudopregnancy cycle. In contrast, animals immunized with ZP3 alpha/EBGD, ZP3 alpha/DG, and ZP3 beta/DG showed no significant elevations of gonadotropins and continued to display cyclic progesterone secretion in response to hCG.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of extracellular matrix on the expression of specific ovarian proteins

A unique ovarian follicle cell culture system has been established to analyze the effects of extracellular matrix (ECM) on early granulosa cell differentiation. Primary and early secondary follicles isolated from ovaries of sexually immature rabbits were grown on poly-D-lysine or Englebreth-Holm-Swarm basement membrane biomatrix substrata (EHS) in serum-free, hormonally defined medium. Granulosa cells from these follicles were examined for growth pattern characteristics and for secretory protein synthesis by two-dimensional (2D) PAGE. Whereas some proteins were synthesized by cells on either matrix, the expression of other secreted proteins was markedly affected by the ECM used. Secretion of zona pellucida (ZP) proteins was demonstrated by ELISA assays and immunoblots of one-dimensional (1D) and 2D-PAGE separations of secreted proteins probed with monoclonal and epitope-selected antibodies. Expression of two ZP proteins was altered by ECM: 55-kDa endo-beta-galactosidase (EBGD)-treated ZP glycoprotein (55-kDaEBGD) was secreted by cells grown on either ECM, but a greater amount of 75-kDaEBGD was secreted by cells grown on poly-D-lysine. These studies are the first to show that granulosa cells from early-stage follicles express ZP proteins in vitro in the absence of oocytes, although proper post-translational modification may not occur. They also demonstrate the dramatic effect of ECM on the expression of these and other secretory proteins.

Genomic organization and polypeptide primary structure of zona pellucida glycoprotein hZP3, the hamster sperm receptor

During the course of fertilization in mammals, free-swimming sperm bind tightly to receptors located in the egg extracellular coat, or zona pellucida. Recently, the hamster sperm receptor, a 56,000 Mr zona pellucida glycoprotein called hZP3, was identified and partially characterized (C. C. Moller et al., (1990). Dev. Biol. 137, 276-286). Here, we describe genomic cloning of hZP3, certain organizational features of the hZP3 gene, and primary structures of hZP3 mRNA and polypeptide. The findings are compared with reported results of comparable analyses of the mouse sperm receptor, an 83,000 Mr zona pellucida glycoprotein called mZP3. Such comparisons reveal a high degree of conservation of genomic organization and polypeptide structure for the two mammalian sperm receptors, despite the considerable difference in their Mrs. These findings are of interest in view of the extremely restricted expression of the ZP3 gene during development and the important role of ZP3 oligosaccharides in gamete adhesion.

Fetuin inhibits zona pellucida hardening and conversion of ZP2 to ZP2f during spontaneous mouse oocyte maturation in vitro in the absence of serum

The zona pellucida of mouse oocytes becomes resistant to chymotrypsin digestion, or "hardened", when spontaneous maturation occurs in serum-free medium (De Felici and Siracusa, Gam Res 1982; 6:107). The hardened zona pellucida is refractory to sperm penetration, thus preventing fertilization. Conversion of the zona pellucida glycoprotein ZP2 to ZP2f by a protease from precociously released oocyte cortical granules appears to be a major contributory factor of zona pellucida hardening (Ducibella et al., Dev Biol 1990; 137:46). Fetal bovine serum (FBS) prevents zona hardening and the ZP2 to ZP2f conversion during oocyte maturation in vitro (Downs et al., Gam Res 1986; 15:115; Ducibella et al., Dev Biol 1990; 137:46). This study was conducted to determine whether fetuin, a major glycoprotein constituent of FBS and a protease inhibitor, could prevent zona pellucida hardening during murine oocyte maturation in serum-free medium. Commercially available preparations of fetuin purified by three different methods were all active in inhibiting zona pellucida hardening in a concentration-dependent manner. Further chromatographic purification of one of these preparations indicated that the activity preventing zona pellucida hardening was associated specifically with fetuin. Fetuin also inhibited the conversion of ZP2 to ZP2f in a concentration-dependent manner during oocyte maturation in serum-free medium. Moreover, oocytes that matured in serum-free medium containing fetuin could be fertilized and could undergo preimplantation development to the blastocyst stage. These results indicate that fetuin, a component of FBS, inhibits zona pellucida hardening during oocyte maturation, and suggest that fetuin acts by preventing the proteolytic conversion of ZP2 to ZP2f by precociously released cortical granules.

Changes in the composition of the hamster zona pellucida after fertilization in vivo but not in vitro

Hamster zonae pellucidae were obtained from follicular oocytes, superovulated eggs, and eggs fertilized in vivo or in vitro. Zonae were labelled with N-succinimidyl-3(4-hydroxy,5-[125I]iodophenyl)propionate, and compared on single- and two-dimensional SDS-PAGE. Single-dimensional electrophoresis showed considerable differences between zona categories in the amount of label that they incorporated; follicular zonae incorporated the least label and zonae from eggs fertilized in vivo the most. On two-dimensional electrophoresis, polypeptides from 3 of the 4 zona categories migrated into 4 major groups: two of these groups each with Mr 150,000-250,000 were within the Mr range of ZP1, and two others, at Mr 90,000 and 55,000, appeared to be analogous to ZP2 and ZP3, respectively. The fourth zona category (zonae from eggs fertilized in vivo) showed a changed polypeptide profile as well as incorporating the most label; one of the polypeptides, Mr 150,000-250,000, was undetectable, but a train of Mr 70,000-90,000 polypeptides and a discrete polypeptide at Mr 20,000 were new. Since this changed profile did not occur in zonae from superovulated eggs, or in zonae from eggs fertilized in vitro, a synergism between oviductal factors and factors from the spermatozoon or egg, or both, towards the zona in vivo is indicated.

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.

Use of a radiometric technique for rapid sensitivity testing of mycobacteria in Scotland: the first year's experience

We report the first year's experience of the use of a radiometric technique for sensitivity testing of mycobacterial isolates in Scotland. The techniques (using the Bactec 460 instrument) was much quicker than conventional methods (for example the mean time to obtain results for 60 strains of M.tuberculosis was 14.4 days, compared with 44.9 days for conventional methods). There was good agreement between results obtained by the two methods. Preliminary results also indicated the value of the radiometric technique for rapid isolation of mycobacteria from clinical samples (mean of 10.6 days with the radiometric technique compared with 26.7 days using egg media) although for optimal recovery, both techniques should be used in parallel.

Regulation of oogenesis: the piscine receptor for vitellogenin

The receptor-mediated uptake of vitellogenin (VTG), a plasmatic lipophosphoglycoprotein, is crucial for oocyte growth in egg-laying animals. The plasma membrane receptor for VTG was characterized from oocytes of coho salmon, Oncorhynchus kisutch. In direct binding studies, the receptor exhibited high affinity (Kd, 180 nM) for salmonid VTG, and by ligand blotting with radiolabelled VTG it was visualized as a protein with an apparent Mr of 100,000, under non-reducing conditions. The fish VTG receptor was shown to share key structural elements with VTG receptors from chicken and Xenopus laevis. Namely, cross-reactivity at the level of ligand recognition was observed among VTG receptors from these species and immunological relatedness was demonstrated by immunoblotting with anti-chicken VTG receptor antibodies. In addition, as in chicken and Xenopus, binding of VTG to fish oocyte receptors was shown to be mediated by the lipovitellin domain of VTG. These results clearly indicate that regulation of oocyte growth at the level of yolk formation has been accomplished by the conservation of structural features of receptors required for internalization of VTG.