Isolation and partial characterization of a pregnancy-associated glycoprotein family from the goat placenta

Antigen(s) immunologically related to pregnancy-associated glycoproteins (PAGs) have previously been detected in the serum of pregnant goats. In this work, we describe a partial characterization of a family of PAGs isolated from the placenta of the goat. The procedure, monitored by RIA, included extraction of proteins at neutral pH, acidic, and ammonium sulfate precipitations; and gel filtration and ion exchange chromatographies. Immunoreactivity, initially located in the acidic supernatant and in the 40-80% ammonium sulfate fractions, was equally apportioned between the 0.04 and 0.08 M NaCl DEAE fractions. After further purification of both DEAE fractions, the preparations were subjected to one- and two-dimensional electrophoresis, and individual polypeptides were analyzed by amino acid sequencing. Three PAGs, which differed in amino acid sequence and apparent molecular masses (62, 59, and 55 kDa), were detected, each containing several isoforms with different pls: caprine (c) PAG62 (pl: 5.1, 4.8), cPAG59 (pl: 6.2, 5.9, 5.6), and cPAG55 (pl: 5.3, 5.1, 4.9). These proteins had high sequence identities to each other and to PAGs purified from other species. Each had two putative N-glycosylation sites within the 27 amino terminal residues sequenced. This work demonstrates that PAGs are present in goat placenta and that multiple forms are expressed.

Rapid purification and properties of human glycodelin (endometrial alpha2-globulin)

The method presented can easily produce milligram amounts of glycodelin from pregnancy endometrium, with a 19% yield. It involves anion-exchange chromatography, gel permeation and chromatofocusing; it results in one stainable band at Mr 28,000 after sodium dodecyl sulphate-polyacrylamide electrophoresis, as well as after immunoblot analysis, performed using an affinity-purified IgG fraction from an antiserum against glycodelin. In spite of this, the corresponding gel isoelectric focusing pattern gives four stainable bands with pI values between 4.55 and 5.2. Western immunoblot analysis of tissue extracts indicates the presence of glycodelin epitopes associated with materials heavier than the native protein. Circular dichroism spectra of the highly purified protein in water solutions indicate a large amount of beta-sheet conformation, whereas those obtained with different proportions of 2-propanol in water, show an increased proportion of alpha-helix conformation.

Identification of actin as an estradiol 17-beta-stimulated protein in the human placenta

Addition of estradiol 17-beta to first trimester human placental minces resulted in an increased synthesis of a protein of apparent molecular weight 45 kDa. The specific involvement of estrogen in the stimulation of this protein was established by demonstrating a reduction in the level of this protein by the addition of CGS 16949 A, an inhibitor of aromatase, a key enzyme in the biosynthesis of estradiol 17-beta and ICI 182,780, an estrogen receptor antagonist. The protein was purified to homogeneity and N-terminal sequencing of two of the internal peptides obtained by enzymatic digestion of the protein, as well as the absence of a free N-terminal indicated that it could be actin. This was confirmed by Western blotting using commercially available actin antiserum. The role of estradiol 17-beta in the stimulation of actin synthesis in human placenta was also established by monitoring the quantitative inhibition of DNase I by actin.

A novel gene isolated from human placenta located in Down syndrome critical region on chromosome 21

Down syndrome is the most common birth defect, which is caused by trisomy 21. We identified a novel gene in the so-called Down syndrome critical region by EST mapping to genomic DNA and following cDNA cloning. The gene, designated DCRB (Down syndrome Critical Region gene B), consisted of three exons of 1095 bp in total and encoded a large open reading frame of 118 amino acid residues. The amino acids sequence of DCRB showed no significant homology to any known protein. Northern blot analysis showed that DCRB is mainly expressed in the placenta, in which a major 1.1-kb band and a minor 2.0-kb band were detected. Minor bands of 1.4 kb and 2.2 kb were also detected in adult heart and skeletal muscle.

Purification of pregnancy zone protein and its receptor binding domain from human plasma

A new significantly improved method for purification of pregnancy zone protein (PZP), alpha 2-macroglobulin (alpha 2M), and the C-terminal PZP receptor binding domain is presented. Several steps in an earlier procedure have been deleted, and modifications in the gradients in the DEAE step leave most of the contaminants bound to a DEAE-Sephacel gel. This procedure makes possible the rapid, simultaneous purification of both of these closely related unstable proteins in native form from human plasma, with no thiolester cleavage or formation of tetrameric PZP. The final preparations of both alpha 2M and PZP are pure as determined by nonreducing and reducing polyacrylamide gel electrophoresis following silver staining and no cross-contamination can be observed. The yield has been significantly improved and typically more than 500 mg PZP can be obtained from 1 liter pregnancy plasma. Furthermore, the stability of PZP at different temperatures on storage was studied. In liquid nitrogen PZP can be maintained in native dimeric form with intact thiolester for many years. The storage of native PZP with intact functional properties during and after purification is an obligatory prerequisite to elucidate the biological role of PZP. The receptor binding domain of PZP can be cleaved from the PZP-methylamine complex by papain and isolated from the other peptides by S-200 gel filtration. The cleavage site was determined and the C-terminal fragment was identified with several site-specific monoclonal antibodies against PZP.

Development of a purification procedure for the placental protein 14 involving metal-chelate affinity chromatography and hydrophobic interaction chromatography

Placental protein 14 was isolated from the biological material of patients undergoing legal abortions. The major part of ballast protein was removed by ion-exchange chromatography on DEAE-Sepharose and CM-Sepharose. Albumin was separated by chromatography on Blue-Sepharose. Complete purification was obtained by metal-chelate affinity chromatography on Nickel-Chelate Sepharose and hydrophobic interaction chromatography on Phenyl-Sepharose and Octyl-Sepharose. The protein was not exposed to denaturing agents or extreme pH.

A procedure for human pregnancy zone protein (and human alpha 2-macroglobulin) purification using hydrophobic interaction chromatography on phenyl-sepharose CL-4B column

In the present work we describe a procedure for the purification of human pregnancy zone protein (PZP) from pooled late pregnancy plasma by using hydrophobic interaction chromatography (HIC) on a phenyl-Sepharose column. The HIC step allowed the complete isolation of haptoglobins and the partial separation of human alpha 2-macroglobulin (alpha 2-M) from a protein fraction containing PZP previously obtained by a DEAE-Sephacel chromatography. Pure and native PZP, with a recovery of nearly 25% and biological activity of protease-binding, was obtained by two definitive final steps consisting of zinc-chelate and size-filtration chromatographies. Moreover, we further present an alternative procedure for the purification of alpha 2-M from the same pregnancy plasma, based on the differential elution of PZP and alpha 2-M from the HIC. This purification step gave rise to a highly purified product with a recovery of 10%. This differential elution could be explained by differences in surface hydrophobicity observed between both proteins. In addition, considering the different hydrophobic properties exhibited by native PZP and PZP-protease complexes, HIC on phenyl-Sepharose column could also be used for separating both conformational states of PZP.

Placenta growth factor-1 is chemotactic, mitogenic, and angiogenic

The placental-derived growth factor (PIGF) is a dimeric glycoprotein showing a high degree of sequence similarity to the vascular endothelial growth factor. Alternative splicing of the PIGF primary transcript gives rise to two forms, named PIGF-1 and PIGF-2, which differ only in the insertion of a highly basic 21-amino acid stretch at the carboxyl end. The presence of the PIGF mRNA in thyroid, placenta, lung, and goiter has indicated the tissues where this factor functions. However, the role of PIGF in vascular development has not yet been clearly established. In the present study, we described the purification of PIGF-1 from overexpressing eukaryotic cells and then measured the angiogenic activity of the purified PIGF-1 in vivo in the rabbit cornea and the chick chorioallantoic membrane assays. In both in vivo assays, PIGF-1 induced a strong neovascularization process that was blocked by affinity-purified anti-PIGF-1 antibody. In the avascular cornea, PIGF-1 induced angiogenesis in a dose-dependent manner and seemed to be at least as effective (if not more effective) than vascular endothelial growth factor and basic fibroblast growth factor under the same conditions and at the same concentration. PIGF-1 was shown to induce cell growth and migration of endothelial cells from bovine coronary postcapillary venules and from human umbilical veins. In these two in vitro assays, PIGF-1 seemed to have a comparable effect to that of vascular endothelial growth factor and basic fibroblast growth factor on the cultured microvascular endothelium (eg, capillary venule endothelial cells). In summary, this is the first study to demonstrate that PIGF-1 can induce angiogenesis in vivo and stimulate the migration and proliferation of endothelial cells in vitro.

Determination of proteins secreted by growing rat decidual cells in vitro

Proteins secreted by rat decidual cells while growing in culture medium were monitored on gel electrophoresis. It was done by assuming that outgrowing cells in vitro mimic differentiated endometrial stromal tissue in vivo following attachment of embryo. The decidual cells were obtained from implantation swellings of day 10 pregnant rats, maintained in serum free medium and the cell dependent protein profile was analysed after 48 hr on single dimensional polyacrylamide gel electrophoresis (SDS-PAGE). The proteins identified were in molecular weight range of 29, 43 and 66 kDa respectively. The result indicated involvement of the differentiated stromal cells in secreting these low molecular weight proteins.

Extracellular matrix-associated serine protease inhibitors (Mr 33,000, 31,000, and 27,000) are single-gene products with differential glycosylation: cDNA cloning of the 33-kDa inhibitor reveals its identity to tissue factor pathway inhibitor-2

Recently, we reported the identification and partial characterization of three serine protease inhibitors (M(r) 33,000, 31,000, and 27,000) from the extracellular matrix (ECM) of human umbilical vein endothelial cells and skin cells. Here, we report that a full-length cDNA clone for the 33-kDa inhibitor from SV-40 transformed human skin fibroblasts (t12FB) is identical to a recombinant trypsin/tissue factor pathway inhibitor called TFPI-2 from placenta. By immunoblotting, the three inhibitors from ECM and cell lysates demonstrated cross-reactivity with an antiTFPI-2 IgG. To further elucidate how these inhibitors are related, pulse-chase labeling of t12FB with [35S]methionine followed by immunoprecipitation with antiTFPI-2 IgG was performed on ECM and cytosolic proteins. A precursor-product relationship did not exist between the three inhibitors from ECM. In contrast, the various species of inhibitors from cytosolic fractions demonstrated a precursor-product relationship. Within the cytosolic fraction, 26-, 29-, and 30-kDa inhibitors were detected in the early chases (0 and 15 min) but they form precursors to the synthesis of the 33-kDa inhibitor which accumulated in the later chases (30 min to 1 h). When pulse-chase experiments were performed in the presence of tunicamycin, synthesis as well as sequestration of the three inhibitors into ECM was completely inhibited. In the presence of tunicamycin, the cells synthesized and sequestered a single 25.5-kDa inhibitor into ECM. Peak quantities of the 25.5-kDa inhibitor appeared in the ECM after 6 h chase while they were 1 h for the 27- and 31-kDa inhibitors and 3 h for the 33-kDa inhibitor. To further support that the three inhibitors are related but only differ in the extent of glycosylation, the 33-kDa inhibitor from the t12FB ECM was deglycosylated with N-glycosidase F and the products were identified by immunoblotting with antiTFPI-2 IgG. The enzyme released the 31-, 27-, and 25.5-kDa inhibitors from the 33-kDa inhibitor. Collectively, these results demonstrate that the ECM-associated 33-, 31-, and 27-kDa inhibitors are biosynthetic products of a single gene with differential glycosylation. The 25.5-kDa inhibitor is unglycosylated, whereas 27- and 30- to 31-kDa inhibitors are partially glycosylated and the 33-kDa inhibitor is fully glycosylated. Inhibition of glycosylation significantly retarded the rate of secretion of the inhibitor but did not prevent its association with ECM. Quantitation of the inhibitors with cell-conditioned medium and ECM fractions reveals that 70-75% were ECM-associated and 25-30% cell-associated. None or very little of the inhibitors (0-2%) remained in a conditioned medium. Because they are primarily associated with ECM, the inhibitors may play a major role in ECM remodeling and turnover.

Glycodelin from seminal plasma is a differentially glycosylated form of contraceptive glycodelin-A

Glycodelin-A is a human amniotic fluid-derived glycoprotein with contraceptive and immunosuppressive activities. An immunoreactive form of glycodelin was detected in seminal plasma over a decade ago, but definitive characterization of this glycoprotein was not pursued. We considered it unlikely that the seminal plasma of fertile men would contain an appreciable amount of contraceptive glycodelin-A. To address this issue we purified seminal plasma glycodelin (glycodelin-S) and performed comparative studies with glycodelin-A. Glycodelin-S behaved differently when compared with glycodelin-A during sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing but identically after enzymatic deglycosylation. N-terminal sequencing of glycodelin-A and glycodelin-S gave identical results, and digestion with trypsin gave identical peptide fragments. The glycoproteins were also found to be indistinguishable from each other based upon immunological analyses. These results indicate that glycodelin-S and glycodelin-A have similar overall protein structure, suggesting the likelihood that these glycoproteins are differentially glycosylated forms of very similar proteins. This latter possibility is supported by lectin binding studies indicating that, unlike glycodelin-A, glycodelin-S does not manifest any affinity for lectins from Wisteria floribunda or Sambucus nigra. The results of sugar analysis and neuraminidase digestion also lead us to conclude that glycodelin-S and glycodelin-A are differentially glycosylated forms of similar proteins. Our evidence indicates that glycodelin-A mediated its biological activities via its unusual oligosaccharide sequences that are not associated with glycodelin-S. In lectin-immunoassay no appreciable amount of contraceptive glycodelin-A was found in the 22 seminal plasma samples studied.

Synthesis and physiological activity of heterodimers comprising different splice forms of vascular endothelial growth factor and placenta growth factor

Vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) are members of a dimeric-growth-factor family with angiogenic properties. VEGF is a highly potent and specific mitogen for endothelial cells, playing a vital role in angiogenesis in vivo. The role of PIGF is less clear. We expressed the monomeric splice forms VEGF-165, VEGF-121, PIGF-1 and PIGF-2 as unfused genes in Escherichia coli using the pCYTEXP expression system. In vitro dimerization experiments revealed that both homo- and hetero-dimers can be formed from these monomeric proteins. The dimers were tested for their ability to promote capillary growth in vivo and stimulate DNA synthesis in cultured human vascular endothelial cells. Heterodimers comprising different VEGF splice forms, or combinations of VEGF/PIGF splice forms, showed mitogenic activity. The results demonstrate that four different heterodimeric growth factors are likely to have as yet uncharacterized functions in vivo.

High yield expression and secretion of the ovine pregnancy recognition hormone interferon-tau by Pichia pastoris

The early conceptus (embryo and associated membranes) of domestic ruminats signals its presence to the maternal uterus through production of interferon-tau (IFN-tau). Production of IFN-tau ensures continued production of progesterone, the hormone of pregnancy, by the ovarian corpus luteum. This paper reports the high-level expression and efficient secretion of biologically active recombinant ovine IFN-tau (rOvIFN-tau) by Pichia pastoris. The developed method produces more than 80% pure recombinant ovine IFN-tau, obviating the need for further purification for many purposes. Initial fermentation studies produced IFN-tau at 280 mg/liter and demonstrate the potential of this system for large-scale production of IFN-tau.

Purification of lysosomal membrane proteins from human placenta

A major portion of the intracellular hydrolytic reactions are confined to lysosomes, whose membrane proteins take care of the proper lumenal milieu and the release of the degradation products. To obtain material for structural characterization of the transport proteins, we elaborated a procedure for isolation of lysosomal membranes and separation of their proteins in a two-dimensional electrophoresis. In a first step dense lysosomes were isolated from human placenta using a Percoll gradient. Subsequently, lysosomal membranes were purified by immunoadsorption. The procedure yielded mg-amounts of lysosomal membranes. Proteins associated with lysosomal membranes, acid beta-glucosidase, acetyl-coenzyme A:alpha-glucosaminide N-acetyltransferase, CD63/LIMP I, and h-lamp-2 were enriched approximately 300-fold as compared to the initial homogenate. Separation of the membrane proteins was achieved in a two-dimensional electrophoresis. The procedure is expected to yield material for structural studies on lysosomal membrane proteins with suspected defects in lysosomal storage diseases.

Purification and characterization of a naturally occurring vascular endothelial growth factor.placenta growth factor heterodimer

Vascular endothelial growth factor (VEGF) is a potent and selective mitogen for endothelial cells that is angiogenic in vivo and induced by hypoxia. A homologous protein, placenta growth factor (PlGF), is also reported to be mitogenic for endothelial cells in culture. The rat GS-9L glioma cell line produces not only VEGF homodimers but also PlGF homodimers and a novel heterodimer composed of VEGF and PlGF subunits. All three dimeric forms were purified to apparent homogeneity, and their structures and mitogenic activities were compared. VEGF.PlGF heterodimers are vascular endothelial cell mitogens nearly as potent as VEGF homodimers. Therefore, some of the biological activities attributed to VEGF homodimers might be mediated by VEGF.PlGF heterodimers. In contrast, pure PlGF homodimers are mitogenic for endothelial cells only at high, possibly non-physiologic concentrations; thus the biological relevance of their mitogenic activity for these cells is not obvious. However, the existence of not only homodimers but also heterodimers clearly extends the similarity between the VEGF/PlGF and the homologous platelet-derived growth factor systems.

Factors affecting fertilization: endometrial placental protein 14 reduces the capacity of human spermatozoa to bind to the human zona pellucida

OBJECTIVE

To examine whether placental protein 14 (PP14) may affect directly those sperm functions crucial to fertilization and early embryo development.

DESIGN

In these prospective studies, we evaluated semen samples of fertile men incubated under capacitating conditions with and without PP14.

SETTING

Academic tertiary institution.

INTERVENTIONS

Biologically active PP14 was purified from human midtrimester amniotic fluid by anion exchange and immunoaffinity chromatography. After separation of the motile fraction, spermatozoa were incubated for 30 minutes with or without PP14 (concentration range of 0.01 to 100 micrograms/mL), washed, and then aliquots were prepared for use in the different assays. Human sperm-zona pellucida (ZP) binding was assessed using the hemizona assay (HZA) in a 4-hour gametes coincubation period. Sperm motility parameters were evaluated using a computerized semen analyzer. The acrosome reaction (AR) was determined by fluorescein isothiocyanate-conjugated Pisum sativum agglutinin and indirect immunofluorescence.

MAIN OUTCOME MEASURES

Sperm-ZP binding, sperm motility patterns, and AR.

RESULTS

Preincubation of sperm (and not the hemizonae) with PP14 produced a significant and dose-dependent inhibition of binding in the HZA. Monoclonal antibodies generated against PP14 showed no direct effect in the HZA and partially neutralized the inhibitory activity of PP14 in the HZA. Insulin-like growth factor binding protein-1 (IGFBP-1), an endometrial stromal cell product, showed no effect in the HZA. Neither PP14 nor IGFBP-1 interfered with sperm motility parameters or the AR.

CONCLUSIONS

Placental protein 14 produced a potent, fast, and dose-dependent inhibition of binding of human spermatozoa to the human ZP without affecting other prefertilization events (i.e., hyperactivated motility or AR). The detrimental effect on sperm-zona interaction seems to be specific for this endometrial epithelial protein (not observed with an endometrial stromal product) and may have fundamental bearance to the fertilization process thus providing a mechanism for endometriosis-related infertility.

Dynorphin A(1-8) in human placenta: amino acid sequence determined by tandem mass spectrometry

Presence of the kappa receptor-preferring neuropeptide dynorphin A(1-8) in human placenta has been demonstrated by mass spectrometry to establish rigorously the appropriate molecular weight and amino acid sequence. Liquid secondary ionization mass spectrometry produced the protonated molecule ion, (M + H)+, at m/z 981 of the endogenous peptide, and tandem mass spectrometry collected the product ion spectrum that contained the appropriate amino acid sequence-determining fragment ions produced from the precursor ion (M + H)+. The amino acid sequence of the peptide is YGGFLRRI.

Purification and characterization of a pregnancy-associated protein: TJ6s

PROBLEM

Characterization of the soluble form of a novel protein, TJ6 (TJ6s) with immune suppressive activity from murine fetoplacental units.

METHOD

Preferential ammonium sulfate precipitation, gel filtration and ion-exchange chromatography were employed to purify the protein TJ6s from murine fetoplacental units using an anti-peptide antibody as a detection tool. Biological activity of the purified protein was studied in lymphocyte proliferation assays.

RESULTS

Purified TJ6s has a M(r) of approximately 18 kDa as evidenced by SDS-PAGE in both reducing and non reducing conditions. It exerted a strong anti-proliferative activity in both anti-CD3 and Con A proliferation lymphocyte proliferation assays but not in a PHA assay, suggesting that the anti-proliferative effects on T cells are exerted only on cells specifically activated directly through T cell receptor complex.

CONCLUSION

The results indicate that TJ6s is a novel anti-proliferative protein that has many of the characteristics that are considered necessary for survival of the fetal allograft.

Placenta growth factor. Potentiation of vascular endothelial growth factor bioactivity, in vitro and in vivo, and high affinity binding to Flt-1 but not to Flk-1/KDR

The recently identified placenta growth factor (PIGF) is a member of the vascular endothelial growth factor (VEGF) family of growth factors. PIGF displays a 53% identity with the platelet-derived growth factor-like region of VEGF. By alternative splicing of RNA, two PIGF isoforms are generated: PIGF131 (PIGF-1) and PIGF152 (PIGF-2). Relative to PIGF131, PIGF152 has a 21-amino acid insertion enriched in basic amino acids. Little is known at the present time about the significance and function of these proteins. To assess their potential role, we cloned the cDNAs coding for both isoforms, expressed them in mammalian cells, and purified to apparent homogeneity the recombinant proteins. Like VEGF, the PIGF isoforms are homodimeric glycoproteins. PIGF131 is a non-heparin binding protein, whereas PIGF152 strongly binds to heparin. We examined the ability of PIGF to bind to soluble VEGF receptors, Flt-1 and Flk-1/KDR, and characterized the binding of PIGF to endothelial cells. While the PIGF proteins bound with high affinity to Flt-1, they failed to bind to Flk-1/KDR. Binding of 125I-PIGF to human endothelial cells revealed two classes of sites, having high and low affinity. The high affinity site is consistent with Flt-1; the identity of the low affinity site remains to be determined. Purified PIGF isoforms had little or no direct mitogenic or permeability-enhancing activity. However, they were able to significantly potentiate the action of low concentrations of VEGF in vitro and, more strikingly, in vivo.

Carbohydrate-binding profile of a pregnancy-associated rat uterine glycoprotein

Sugar-binding proteins obtained from the peri-implantation uterine tissue have been thought in recent years to have significant roles in embryo implantation, where carbohydrate moieties of the protein are actively involved. Based on this rationale a mannose-containing glycoprotein/lectin (named uterine agglutinin or UA) was purified by Concanavalin A (Con A) affinity chromatography in a previous study. A modification of the original purification procedure to include a 33% ammonium sulfate fractionation improves the yield of the protein significantly. An alternative purification procedure by Mannan affinity matrix, indicates that apart from containing mannose, UA possesses mannose-binding properties as well. In this paper, we report some of the biochemical and more specifically, the carbohydrate-binding characteristics of UA. The protein is seen to contain mannose-6-phosphate (M-6-P)-binding sites, which is of importance since M-6-P receptors have a large number of biologically significant roles, including that of binding to growth factors. SDS-PAGE, gel filtration chromatography and alkaline PAGE indicate the homogenous nature of the protein with subunit molecular weights of 36 kDa and 19 kDa, and a native size of 64 kDa. Amino acid analysis shows glycine, glutamic acid and aspartic acid to be the major constituents. UA is a glycoprotein and shows presence of N-acetyl glucosamine and galactose, apart from mannose. De nove synthesis studies in the presence of tunicamycin show that the carbohydrate moiety of the glycoprotein is attached by N-linkage to the protein. Binding characteristics of the protein is studied quantitatively in which (125I)-labelled lectin is bound to Mannan-Sepharose affinity matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Solubilization and purification of the retinol-binding protein receptor from human placental membranes

The membrane receptor for retinol-binding protein (RBP) has been solubilized from human placental brush-border membranes with octyl-beta-glucoside, Nonidet P-40 and CHAPS. A method, based on the preferential precipitation of 125I-RBP-receptor complex with poly(ethylene glycol) 8000, was developed in order to measure the RBP-binding activity in the detergent extracts. The receptor was fairly stable (4 degrees C, 7 days) in octyl-beta-glucoside and Nonidet P-40, but quickly lost activity in CHAPS. The detergent-solubilized form retained all the properties characteristic of the membrane-bound protein, except for a small decrease in affinity for RBP (3- and 7-fold in Nonidet P-40 and octyl-beta-glucoside respectively). The receptor was isolated using recombinant RBP coupled to Reacti-Gel 6X affinity matrix. The purified material contained major and minor protein species of 63 and 55 kDa respectively on SDS/PAGE.

Modulation of spermatozoa and zona pellucida properties by the soluble acrosome reaction-inducing factor of the ovulated egg-cumulus complex

Three sources of hamster periovulatory fluids (+/- heat inactivation at 56 degrees C), with bovine serum albumin (BSA) as control, were tested for effects on penetration of three classes of eggs by hamster sperm precapacitated in BSA. These fluids were a soluble extract of cumulus oophorus fluid (COF) from the ovulated hamster egg-cumulus complex, serum, and follicular fluid. Egg types were ovulated, salt-stored (ovulated), and follicular. In both COF and serum, there were significant differences among egg types in mean penetration, and significant effects of fluid addition. In contrast, there was no effect of follicular fluid and no differences between follicular and stored eggs. For the follicular eggs (combined data, normalized, ranked), patterns of response to the three factors (+/- heating) were different: only unheated COF and heated serum increased penetration significantly above BSA control levels (average rank 20.2, 41.4, 38, for BSA, COF (unheated), serum (heated), respectively). This indicated that the active component in COF was heat labile, not present in either serum or follicular fluid, and, therefore, of oviductal origin. Oviduct and/or COF exposure of eggs and sperm was tested for effects as an acrosome reaction inducing factor (ARIF) for acrosome reactions (AR; zona-bound and free-swimming sperm) and on sperm:zona binding and penetration. The COF ARIF for free-swimming sperm AR was heat stable. Penetration of follicular eggs increased after incubation in COF prior to sperm addition, but a greater response occurred when COF was added to eggs with sperm. In kinetic experiments, 25 min following sperm attachment, follicular eggs had lost 41% of initially bound sperm, vs. 23% for ovulated eggs, and had only 16 AR sperm/egg, vs. 26 for ovulated. Follicular eggs incubated in COF (then washed three times) had the same number of bound AR sperm as ovulated eggs. Acid solubilized zona pellucida (ASZP) from ovulated eggs was more effective as an ARIF per zona than ASZP from follicular eggs. Zonae of follicular eggs, as evidenced by dissolution times in beta-mercaptoethanol (beta-MEOH), were not "harder" than those of ovulated eggs. There were differences in lectin binding antigens on zonae of both fresh and stored, follicular and ovulated, eggs. We conclude that multiple biological factors orchestrate sperm:egg interactions in the ampulla. Our data are consistent with the presence of at least three effective components: 1) the oviductal lectin-binding antigen (ZPO or oviductin), 2) an additional heat-labile component, and 3) the heat-stable ARIF for free-swimming sperm.

An endogenous inhibitor of prostaglandin synthesis in human decidua

Human first trimester decidual tissue has been reported to contain an inhibitor of cyclo-oxygenase enzyme, but a careful reading of the literature indicates that the inhibitor may be human albumin. Our own studies also showed that high levels of albumin were present in samples from homogenised decidual tissues. We therefore digested the tissue to obtain isolated cells and washed them extensively to minimise contamination with blood. Homogenates of such cells did not bind arachidonic acid, and inhibited cyclo-oxygenase enzyme-1 (COX-1) activity. The cellular factor inhibited COX-1 at concentrations of 60-100 micrograms protein/ml, and was therefore more potent than human albumin (0.5-2.0 mg/ml). The inhibitory activity was lost after heat treatment (100 degrees C for 10 mins) and after digestion with trypsin or papain, but was resistant to mercaptoethanol and urea. Preliminary data indicated that the protein had a molecular weight > 30 kD.

Purification and characterization of a low molecular weight zinc binding protein from human placenta

A low molecular weight, native zinc binding, cytosolic protein (LMZP) has been isolated, purified and characterized from human normal term placenta. Gel filtration of heat treated placental cytosol after sequential acetone precipitation (80% ppt) revealed a major zinc binding protein in the range of low molecular weight. This partially purified zinc binding fraction was further fractionated on DEAE-Sephadex A-25. The zinc was eluted in one of the three peak fractions. Further, the purity of zinc binding protein was confirmed on fast protein liquid chromatography (FPLC). The purified placental LMZP was homogenous on SDS-polyacrylamide gel electrophoresis with a single band. Ultraviolet (UV) spectrum of LMZP showed an absorption maximum at 257 nm which disappeared at pH 2. Molecular weight of LMZP as determined by gel chromatography, SDS-polyacrylamide gel electrophoresis and amino acid analysis was 6 kDa. It was calculated that 1 g atom of zinc was bound to 1 mole of the LMZP. Unlike in classical metallothionein, the amino acid composition of placental LMZP revealed the presence of aromatic amino acids, lower content of cysteine and higher content of histidine, glutamic acid and aspartic acid (10, 9 and 5 residues/mole, respectively).