Biomedical subjects

R A Bronson

Publications and source records attributed to R A Bronson.

At least 37 records · Page 2Linked to original sources

PubMed1992

Evidence for the presence of an integrin cell adhesion receptor on the oolemma of unfertilized human oocytes.

The Arg-Gly-Asp peptide (RGD), contained in several extracellular matrix proteins such as fibronectin, laminin, vitronectin, and collagen, is a tripeptide that plays a role as a recognition sequence in many cell-to-cell and cell-to-matrix adhesion mechanisms, through its interaction with several receptors of the integrin family. We previously described the ability of the oolemma of hamster oocytes to bind GRGDTP coupled to the surface of activated immunobeads and demonstrated that RGD-containing oligopeptides inhibit the adhesion of human and hamster spermatozoa to zona-free hamster oocytes and their subsequent penetration. In the present experiments, we show, utilizing immunobeads coated with an RGD-containing peptide (PepTiteTM 2000), that the oolemma of unfertilized human eggs is also able to recognize this adhesion sequence. The binding of PepTiteTM 2000-coated immunobeads to the oolemma was inhibited by the oligopeptide GRGDTP as well as by fibronectin and laminin. When immunobeads were prepared with a PepTiteTM concentration of 10 micrograms/ml, GRGDTP 150 micrograms/ml, laminin 80 micrograms/ml, and fibronectin 60 micrograms/ml inhibited bead rosetting on the egg surface. These data suggest that a specific binding moiety for RGD is present on the human egg surface. The binding of fibronectin to the oolemma was also demonstrated by the rosetting of immunobeads coupled with antifibronectin antibody to human oocytes after their exposure to 1 mg/ml free fibronectin. Such binding of fibronectin to the oolemma could be inhibited by coincubation with a monoclonal antibody directed against the cell adhesion fragment of fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Monoclonal antibodies identify Fc gamma receptors on unfertilized human oocytes but not spermatozoa.

Oolemmal Fc receptors have previously been shown to play a role in the promotion of adhesion by antibody labeled human spermatozoa to zona-free hamster eggs. In this work, we demonstrated the presence of Fc gamma RI, Fc gamma RII and Fc gamma RIII on the oolemma of unfertilized human oocytes by means of monoclonal antibodies directed against these receptors, detected both by immunobead rosetting and indirect immunofluorescence. These receptors were also functionally active in that they were able to bind human aggregated IgG, human IgG-Fc, mouse IgG1 and IgG2a. While the presence of oolemmal IgG-Fc receptors might play a role in reproductive failure, by their promotion of polyspermic fertilization, in cases where antisperm antibodies bound to the spermatozoan surface, their role in the normal physiology of fertilization or in other events unrelated to sperm incorporation remains to be determined. In contrast, Fc gamma receptors were not present on human spermatozoa, irrespective of their functional state (fresh ejaculated, capacitated or acrosome reacted).

Adult↗

PubMed1992

A microwell sperm penetration assay.

Egg penetration rates in a modified SPA using microwells in tissue typing plates were comparable with those in a standard assay. This technique allows sperm penetrating ability to be determined using single zona-free hamster eggs and as few as 10,000 spermatozoa.

Animals↗

PubMed1992

Correlation between puberty and the development of autoimmunity to spermatozoa in men with cystic fibrosis.

OBJECTIVE: To test the hypothesis that puberty is a necessary factor in the pathogenesis of autoimmunity to sperm in men with cystic fibrosis (CF), we studied prepubertal and postpubertal males with CF versus an age-matched group of males with type 1 diabetes as controls. DESIGN: Sera from CF and diabetic males treated at University Hospital, State University of New York, Stony Brook, were tested by indirect immunobead binding for antisperm antibodies and by radioimmunoassay for testosterone (T), luteinizing hormone, and follicle-stimulating hormone. The finding of autoantibodies to spermatozoa was correlated with chronological age, as well as with clinical and hormonal pubertal status. RESULTS: Autoimmunity to sperm, as detected by humoral antisperm antibodies, was documented solely in postpubertal males, as judged by hormonal and clinical criteria. Eighty-three percent of sexually mature CF males and 6.3% (1 of 16) diabetic males exhibited autoantibodies to sperm. These antibodies were only detected when serum T levels were > 8.7 nmol/L (250 ng/dL). CONCLUSIONS: These results suggest that puberty, and presumably, active spermatogenesis is a requirement for the development of autoimmunity to sperm in men with CF.

Adolescent↗

PubMed1991

Complement component C1q and its receptor are involved in the interaction of human sperm with zona-free hamster eggs.

C1q is a component of the classical complement pathway that can react with the Fc-fragment of immunoglobulins and with other proteins, such as fibronectin, laminin, and a specific C1q receptor present on several cell types. Given its role in many adhesion systems, mainly related to phagocytosis, we tested the effects of C1q on the interaction between human spermatozoa and zona-free hamster eggs. The presence of C1q in the medium used for gamete coincubation resulted in promotion of sperm-oolemma adhesion and an inhibition of penetration. The number of adherent sperm per egg at 5 micrograms/ml concentration was 90 +/- 35 vs. 29 +/- 7 for the control (P less than 0.001). At 1 microgram/ml, the lower concentration at which C1q had an effect, the number of penetrating sperm/egg was 0.6 vs. 1.7 for the control without C1q (P less than 0.01), and the percent of penetrated eggs was 28% vs. 85%. At 50 micrograms/ml, the percent of penetrated eggs was 7%, with a penetration index of 0.07. The addition of C1q to the medium resulted in sperm agglutination, which varied between sperm donors. The presence of C1q receptors, as detected by anti-C1qR monoclonal antibodies (Mabs), was demonstrated both on zona-free hamster eggs by immunobead rosetting and on human spermatozoa by immunobead binding and indirect immunofluorescence. Mabs directed against different epitopes of C1qR had different effects on gamete interaction, with a partial inhibition of penetration mediated by some of them. The binding of C1q to antibody-free human spermatozoa was also demonstrated both by means of indirect immunofluorescence and utilizing 125I-C1q.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Inhibition of human sperm-zona pellucida tight binding in the presence of antisperm antibody positive polyclonal patient sera.

Patient sera previously characterized as containing high levels of IgG and IgA antisperm antibodies that bound to the sperm surface, most specifically the head region, were evaluated for their effect on sperm-zona pellucida tight binding as assessed by the hemizona assay (HZA). Of the ten patient sera tested, 7 reduced zona binding by approximately half. Two of the most strongly inhibitory (greater than 70% inhibition) were examined for their effect on the prefertilization maturation of sperm. The patient sera did not affect sperm motion characteristics, or development of hyperactivated motility. However, in the presence of these sera some impedance was noted in calcium uptake after stimulation with human follicular fluid and in the acrosome reaction after calcium ionophore induction. Whether these two sera specifically affect sperm-zona pellucida binding or non-specifically affect the normal progression of capacitation remains to be eludicated.

Calcium↗

PubMed1991

Failure to detect integrins of the beta-2 subclass on the human sperm surface.

Several cell-to-cell recognition systems utilize the tripeptide Asp-Gly-Arg (RGD) as a cell surface signaling sequence. Mac-1, a member of the integrin subfamily defined by the beta-2 subunit, recognizes C3bi by means of an RGD sequence. Because C3 complement components have been detected on the gamete surfaces and RGD has been demonstrated to be involved in sperm-egg interaction, we explored the possibility that a member of the b2 integrin subfamily was present on the sperm surface and involved in egg recognition. Two methods were utilized to detect integrins on the sperm surface. Sperm were exposed to Mabs directed against different epitopes of each member of this integrin subfamily; and spermatozoa were tested for their ability to bind zymosan or yeast, since Mac-1 bearing cells possess this property. Both methods failed to demonstrate such integrins on the sperm surface, suggesting that another RGD receptor is involved in gamete recognition.

Acrosome↗

PubMed1990

Characterization of humoral antibodies reactive with spermatozoa, N-acetyl galactosamine, and a putative blood group antigen in seminal plasma.

Antisperm antibodies in sera of infertile women may react differently with spermatozoa of different men. We studied the reactivity of these antibodies with spermatozoa from men of varying blood group status. Increased immunoglobulin binding to sperm of group A or AB men was noted when compared with group O men. A diminution in binding of immunoglobulins to spermatozoa after absorption of these sera with human group A or AB red blood cells was noted as well as after coincubation of sera and sperm with N-acetyl galactosamine, the terminal sugar of blood group antigen A. These observations suggest that antibodies directed against blood group antigens adsorbed to sperm of secretor males may account in part for variations in immunobead binding levels between sperm of different men.

Acetylgalactosamine↗

PubMed1990

Sperm-oolemmal interaction: role of the Arg-Gly-Asp (RGD) adhesion peptide.

The Arg-Gly-Asp tripeptide (RGD) plays a widespread role in cell-to-cell and cell-to-matrix recognition. We demonstrated that an RGD-containing peptide (Arg-Gly-Asp-Val, RGDV) inhibits both oolemmal binding and penetration of zona-free hamster eggs by human spermatozoa in vitro when added to the incubation medium. These results suggest that RGD-containing proteins may play a role in sperm-oolemmal interactions required for fertilization.

Animals↗

PubMed1990

Effects of incubation time in serum and capacitation on spermatozoal reactivity with antisperm antibodies.

Sperm reside within the female reproductive tract before the occurrence of fertilization. During this time they undergo surface modifications associated with changes in their functional state. To study their antigenic expression, capacitated and acrosome-reacted sperm were incubated with sera that had previously been tested for antisperm antibodies against fresh washed sperm, as detected by indirect immunobead binding. Forty-eight percent of previously positive and 20% of previously negative sera reacted differently with sperm after an extended time (18 hours) of incubation in serum or after sperm capacitation. These results suggest that current techniques of antisperm antibodies detection be modified to include testing sera after prolonged incubation times with both capacitated as well as fresh sperm.

Acrosome↗

PubMed1990

Antisperm antibodies induce polyspermy by promoting adherence of human sperm to zona-free hamster eggs.

Certain antisperm antibodies (ASAs) in the sera of infertile men or women promote the penetration of zona-free hamster eggs by spermatozoa. We have shown previously that this enhancement of penetration occurs through mechanisms other than an alteration in the acrosomal structure of antibody-labelled spermatozoa. In the present study, small limited populations of antibody-labelled and antibody-free spermatozoa from fertile donors were observed serially by phase contrast, epifluorescence and scanning electron microscopy following their adherence to the oolemma of zona-free hamster eggs. The adherence of ASA-labelled spermatozoa to the zona-free hamster egg was markedly increased and occurred earlier when compared with antibody-free spermatozoa from the same ejaculate. The likelihood of entry of an antibody-labelled spermatozoon into the ooplasm, however, once adherent to the oolemma was not different to that of an antibody-free spermatozoa, and the ultrastructural steps of incorporation of antibody-labelled human spermatozoa were also similar to those observed during fertilization of hamster eggs by spermatozoa of several other species. These observations indicate that ASAs promote polyspermic fertilization of zona-free hamster eggs primarily through their enhancement of sperm--oolemmal binding.

Acrosome↗

PubMed1990

Evidence that an Arg-Gly-Asp adhesion sequence plays a role in mammalian fertilization.

The Arg-Gly-Asp (RGD) sequence is known to play a role in many recognition systems involved in cell-to-cell and cell-to-matrix adhesion. In our experiments we demonstrated that an RGD-dependent recognition is involved in sperm-oolemmal adhesion and egg penetration. Following coincubation of RGD-containing oligopeptides in a heterologous system (human sperm and zona-free hamster eggs), a significant decrease in the number of oolemma-adherent sperm was noted at 15 microM RGDV (Arg-Gly-Asp-Val) and at 5 microM GRGDTP (Gly-Arg-Gly-Asp-Thr-Pro), and fertilization was completely inhibited at 250 microM RGDV and 30 microM GRGDTP. In a homologous system (hamster sperm and zona-free hamster eggs), a concentration-dependent decrease in oolemmal adhesion and egg penetration was also noted, with complete inhibition of fertilization at 200 microM GRGDTP. The specificity of the receptor was confirmed by the fact that small changes in aminoacid composition impaired the peptide's effectiveness and that peptide-dependent inhibition of fertilization was partially reversible in competition studies. The presence of a molecule on the oolemma capable of binding the RGD sequence was demonstrated by using immunobeads coupled with an RGD-containing hexapeptide (GRGDTP), which rosetted over the egg surface in a manner reversible by the addition of free GRGDTP in the medium.

Amino Acid Sequence↗

PubMed1990

Identification of an oolemmal IgG Fc receptor: its role in promoting binding of antibody-labelled human sperm to zona-free hamster eggs.

Antisperm antibodies (ASAs) present in sera of infertile men and women have been shown either to promote or inhibit penetration of zona-free hamster eggs by antibody-labelled human spermatozoa. Increased numbers of oolemmal-bound sperm have been noted in association with increased sperm penetration frequencies, following antibody labelling, when compared with antibody-free sperm. The promotion of adherence of ASA-labelled sperm to the oolemma could be mediated through the binding of antibodies to common epitopes present on the sperm and egg surfaces or through Fc-mediated binding to an oolemmal Fc receptor. In support of the latter hypothesis, we report that zona-free hamster eggs bind aggregated human IgG and IgG Fc fragments. The presence of an oolemmal IgG Fc receptor has been confirmed using a rat monoclonal antibody (2.4G2) directed against a murine IgG Fc receptor (Fc gamma RII) as judged both by indirect immunofluorescence and by immunobead binding. In addition, the pre-incubation of zona-free hamster eggs with IgG Fc diminished both adhesion to and penetration of the oolemma by human spermatozoa.

Animals↗

PubMed1989

The detection in human sera of antisperm antibodies reactive with FA-1, an evolutionarily conserved antigen, and with murine spermatozoa.

Evolutionarily conserved antigens are present on spermatozoa of several mammalian species. We tested sera from infertile men and women containing antisperm antibodies (ASAs) for their reactivity with FA-1, an antigen known to be present on murine and human spermatozoa. Fifty percent of male sera and 63% of female sera contained anti-FA-1 antibodies, as judged by enzyme linked immunosorbent assay (ELISA). Fourteen percent of male sera and 50% of female sera were also shown to possess ASAs reactive with living mouse spermatozoa, and murine in vitro fertilization was inhibited by human antibodies. These results suggest that the transfer of immunoglobulins from human sera to spermatozoa of other species may provide a model to study how ASAs effect sperm function.

Absorption↗

PubMed1989

The long-term predictive value of the zona-free hamster ova sperm penetration assay.

Three hundred sixty-nine infertile couples were followed for 2 to 5 years in a study designed to determine the clinical long-term predictive value of the zona-free hamster ova sperm penetration assay (SPA). Semen analysis (SA), SPA, and a full infertility workup were done in all cases, and only couples in whom the female had no evident cause of infertility were included in the study. During the follow-up period, 106 couples (29%) achieved a pregnancy. Sixteen percent of 131 men who had an SPA of 0%, 23% of 120 men with 1% to 19%, and 48% of 118 men who had a penetration of greater than 19% impregnated their wives 2 to 5 years after the assays. Significant difference in fertility prognosis was found between those who had an SPA greater than 19% and those with an SPA less than 20% (48% versus 20%). Sperm penetration assay greater than 19% was predictive of higher pregnancy rates in both oligospermic (41% versus 17%) and unexplained infertile couples (52% versus 24%). The specificity and positive predictive values of the SPA were higher than those of the SA (77% versus 57% and 48% versus 37%). These findings emphasize the value and importance of the SPA in determining the long-term fertility potential of men.

Animals↗

PubMed1989

Effects of anti-sperm antibodies on human sperm ultrastructure and function.

The ultrastructural appearance of a highly motile population of spermatozoa from a fertile donor was evaluated following antibody labeling with each of several sperm head-directed anti-sperm antibodies (ASAs) and subsequent incubation in a capacitating medium in vitro. Acrosomes were classified into categories which are believed to represent stages in the acrosome reaction. Quantitative analysis revealed no difference in acrosomal morphology of antibody-labeled sperm between treatment groups despite a varying degree of enhancement or inhibition of sperm egg-penetrating ability. We conclude that ASAs affect gamete interaction through mechanisms other than an alteration in the acrosome reaction.

Antibodies↗

PubMed1988

Detection in human sera of antibodies directed against the hamster egg oolemma.

Heteroantibodies were demonstrated by indirect immunofluorescence in human sera, which reacted with unfertilized and fertilized hamster eggs. Oolemmal antigens to which these antibodies were directed were distinct from antigen present on the surface of living human spermatozoa. Both species-specific and tissue-specific heteroantibodies were demonstrated by absorption with hamster liver and ovary. An increased degree of heteroantibody binding was noted following penetration of zona-free hamster eggs by human spermatozoa, indicating that an alteration in oolemmal antigen distribution had occurred. No evidence was found, however, that antisperm antibodies in these sera reacted with zona-free hamster eggs following their fertilization.

Animals↗

PubMed1988

Luteal phase sera and progesterone enhance sperm penetration in the hamster egg assay.

The hormonal factors responsible for variation in sperm penetration rates of zona-free hamster ova caused by the use of human sera were investigated. Sera obtained at different times in the menstrual cycle, 17-beta estradiol (E2), or progesterone (P) was added to Biggers Whitten and Whittingham (BWW) medium used for the sperm penetration assay. Luteal phase sera enhanced egg penetration significantly when compared with either follicular or preovulatory sera (48.8% versus 23% and 25%; P less than 0.01). E2 at concentrations of 2 pg/ml to 2 X 10(6) pg/ml had no effect on sperm motility or egg penetration. Addition of P to control media at final concentrations of 0.5 to 50 ng/ml caused a significant elevation of egg penetration (68% to 91% to 96%; P less than 0.01) without affecting sperm motility. Since P has been shown to have a direct effect on plasma membranes and to bind to spermatozoan plasma membrane, the authors propose that P could have a physiologic role during capacitation or sperm egg interaction in vivo.

Animals↗