Co-expression of mannose-ligand and non-nuclear progesterone receptors on motile human sperm identifies an acrosome-reaction inducible subpopulation

Effects of lactoferrin, a protein present in the female reproductive tract, on parameters of human sperm capacitation and gamete interaction

In a recent study, lactoferrin (LF) was detected in human oviductal secretion. The protein was able to bind to oocytes and sperm, and modulated gamete interaction. The aim of the present study was to investigate the effect of LF on parameters related to human sperm capacitation and sperm-zona pellucida interaction. Semen samples were obtained from healthy normozoospermic donors (n = 7). Human follicular fluids and oocytes were collected from patients undergoing in vitro fertilization. Motile sperm obtained by swim-up were incubated for 6 or 22 h under capacitating conditions with LF (0-100 μg/mL). After incubations, viability, motility, presence of α-d-mannose receptors (using a fluorescent probe on mannose coupled to bovine serum albumin), spontaneous and induced acrosome reaction (assessed with Pisum sativum agglutinin conjugated to fluorescein isothiocyanate), and tyrosine phosphorylation of sperm proteins were evaluated. Sperm-zona pellucida interaction in the presence of LF was investigated using the hemizone assay. The presence of LF did not affect sperm viability or motility, but caused a dose-dependent significant decrease in sperm α-d-mannose-binding sites, and the effect was already significant with the lowest concentration of the protein used after 22 h incubation. Dose-dependent significant increases in both induced acrosome reaction and tyrosine phosphorylation of sperm proteins were observed in the presence of LF. The present data indicate that LF modulates parameters of sperm function. The inhibition of gamete interaction by LF could be partially explained by the decrease in sperm d-mannose-binding sites. The presence of the LF promoted sperm capacitation in vitro.

Proteins from human oviductal tissue-conditioned medium modulate sperm capacitation

BACKGROUND

Spermatozoa acquire the ability to fertilize an oocyte when they become capacitated. Capacitation takes place when sperm pass through the female reproductive tract, interacting with female fluids. Both tyrosine phosphorylation of sperm proteins and the ability to respond to acrosome reaction (AR) inducers have been associated with sperm capacitation. Recent data indicate that conditioned media (CM) from human oviductal tissue culture decrease sperm affinity for the zona pellucida in vitro. Since capacitation enables the sperm-oocyte interaction, the aim of the present study was to investigate the effect of CM on events related to sperm capacitation and to assess whether these effects were permanent.

METHODS

Oviductal tissue was obtained from premenopausal patients (scheduled for hysterectomies because of uterine fibromyoma). The tissues were cultured as explants and CM were collected. Explant viability was assessed as tissue DNA integrity. Normozoospermic semen samples were obtained from healthy donors. Motile spermatozoa were incubated under capacitating conditions with or without increasing protein concentrations of CM for 6 or 22 h. Human follicular fluid-induced AR was detected by the Pisum sativum technique. Tyrosine phosphorylated proteins were detected with a monoclonal anti-phosphotyrosine antibody.

RESULTS

The incubation of spermatozoa in the presence of increasing concentrations of conditioned medium (CM) proteins caused a dose-dependent decrease in both tyrosine phosphorylation of sperm proteins and in the level of AR induction. When CM was removed from the sperm incubation media, the effects were reversed. Heat-inactivated CM did not affect either tyrosine phosphorylation or the induction of AR.

CONCLUSIONS

The present data suggest that proteins secreted from human oviductal tissue are able to inhibit events associated with sperm capacitation in vitro.

Cadmium concentrations in blood and seminal plasma: correlations with sperm number and motility in three male populations (infertility patients, artificial insemination donors, and unselected volunteers)

To investigate a possible common environmental exposure that may partially explain the observed decrease in human semen quality, we correlated seminal plasma and blood cadmium levels with sperm concentration and sperm motility. We studied three separate human populations: group 1, infertility patients (Long Island, NY, USA); group 2, artificial insemination donors (AID) (Rochester, NY, USA); and group 3, general population volunteers (Rochester, NY, USA). Information about confounding factors was collected by questionnaire. Seminal plasma cadmium did not correlate with blood cadmium (Spearman correlation, n = 91, r = -0.092, P = 0.386, NS). Both blood and seminal plasma cadmium were significantly higher among infertility patients than the other subjects studied (for example, median seminal plasma cadmium was 0.282 microg/L in infertility patients versus 0.091 microg/L in AID and 0.092 microg/L in general population volunteers; Kruskal-Wallis test, P < 0.001). The percentage of motile sperm and sperm concentration correlated inversely with seminal plasma cadmium among the infertility patients (r = -0.201, P < 0.036 and r = -0.189, P < 0.05, respectively), but not in the other two groups. Age (among infertility patients) was the only positive confounder correlating with seminal plasma cadmium. To validate our human findings in an animal model, we chronically exposed adolescent male Wistar rats to low-moderate cadmium in drinking water. Though otherwise healthy, the rats exhibited decreases in epididymal sperm count and sperm motility associated with cadmium dose and time of exposure. Our human and rat study results are consistent with the hypothesis that environmental cadmium exposures may contribute significantly to reduced human male sperm concentration and sperm motility.

Binding of recombinant human proacrosin/acrosin to zona pellucida glycoproteins. II. Participation of mannose residues in the interaction

OBJECTIVE

To assess the interaction of human proacrosin/acrosin with mannose residues coupled to a protein backbone.

DESIGN

Prospective study.

SETTING

Basic research laboratory.

PATIENT(S)

Recombinant proteins derived from human proacrosin (Rec-40, Rec-30, Rec-20, Rec-10, and Rec-6) and bovine serum albumin (BSA)-mannose as ligand.

INTERVENTION(S)

In vitro binding assay developed to assess proacrosin/acrosin-BSA-mannose interaction.

MAIN OUTCOME MEASURE(S)

Proacrosin/acrosin binding to BSA-mannose; estimation of binding affinity.

RESULT(S)

All recombinant proteins of acrosin but Rec-6 (residues 1-59 of proacrosin) specifically bound to BSA-mannose. Rec-40 (proacrosin) showed the highest binding affinity (dissociation constant K(d), 162 nM), followed by N-terminal fragments Rec-30 (248 nM), Rec-20 (359 nM), and Rec-10 (402 nM). A significant decrease in binding activity was observed when acrosin proteins were treated with denaturing agents such as urea or heat. The beta-mercaptoethanol treatment produced a 39% decrease on Rec-30 binding to BSA-mannose; in contrast, no effect was observed with Rec-40, suggesting the presence of at least two types of mannose-binding sites.

CONCLUSION(S)

[1] Proacrosin interacts with mannose residues through binding sites located at both the N- and C-terminal portion of the protein, [2] the full-length protein is required for maximal BSA-mannose binding, and [3] binding sites are stabilized by noncovalent bonds and by disulfide linkages.

Doses of levonorgestrel comparable to that delivered by the levonorgestrel-releasing intrauterine system can modify the in vitro expression of zona binding sites of human spermatozoa

BACKGROUND

The levonorgestrel-releasing intrauterine system (LNG-IUS) exerts its contraceptive effect by interfering with sperm transport through the female genital tract and with ovulation. However, the possibility cannot be discarded that the device exerts a direct effect on sperm function, thus, helping prevent fertilization.

OBJECTIVES

The purpose of this study is to evaluate whether LNG at doses comparable to that measured in the uterus during the use of the LNG-IUS affects the detection of D-mannose binding sites or zona pellucida (ZP) receptors on human spermatozoa. The association with acrosomal status was also investigated.

METHODS

Seventeen semen samples from fertile men were used, and spermatozoa were separated using a Percoll gradient and incubated for 22 h at 37 degrees C under 5% CO(2) in air. Capacitated spermatozoa were exposed for 30 min to 1,000 or 10,000 ng/mL of LNG or control medium. D-Mannose binding sites were detected using commercial D-mannosylated bovine serum albumin conjugated with fluorescein isothiocyanate, and the percentage of specific patterns (II and III) was recorded. The acrosome reaction was evaluated using the Pisum sativum technique.

RESULTS

Levonorgestrel releasing significantly increased (p < .001) the percentage of spermatozoa with D-mannose receptors localized in pattern III, and this increase was dose dependent and a significant increase (p < .001) in the percentage of acrosome-reacted spermatozoa. Double staining confirmed an association between the location of the zona receptor and acrosomal status.

RESULTS

The in vitro exposure of capacitated spermatozoa to the assayed doses of LNG increased the proportion of spermatozoa with fewer chances of interacting with the ZP. Further studies should be carried out to confirm whether this mechanism is part of the contraceptive action of the LNG-IUS.

In vitro effect of levonorgestrel on sperm fertilizing capacity and mouse embryo development

The objectives of this study were to assess the expression of alpha-d-mannose binding sites in human spermatozoa, human sperm-oocyte interaction and the development of early stages of mouse embryo in the presence of levonorgestrel (LNG). Semen samples were obtained from 16 normozoospermic men. Spermatozoa were separated by Percoll gradient and incubated overnight for capacitation. The kinetic analysis of the expression of alpha-D-mannose binding sites was determined at 0, 4 and 22 h and in 22 h-capacitated spermatozoa that had been exposed to 1, 10 or 100 ng/mL of LNG or to a control medium for 30 min. Sperm binding sites for alpha-D-mannose were detected using commercial alpha-D-mannosylated bovine serum albumin conjugated with fluorescein isothiocyanate. To evaluate sperm-oocyte interaction, each oocyte was placed in a 100-microL droplet containing one of the three doses of LNG or control medium and inseminated with 1.0 x 10(5) motile spermatozoa/mL, after which the number of bound spermatozoa was evaluated. A total of 157 two-cell embryos recovered from eight mice was pooled and assigned randomly to treatment (1, 10 or 100 ng/mL of LNG) or control groups. There was a significant increase in the expression of specific alpha-d-mannose binding sites (Patterns II and III) during the incubation of spermatozoa under capacitating conditions. In the presence of LNG, results showed that there was no significant difference in the expression of specific alpha-d-mannose binding sites (Patterns II and III) at any LNG concentration tested compared with those spermatozoa in control medium. None of the LNG concentrations were capable of modifying the number of spermatozoa tightly bound to the human zona pellucida. There was no association between the presence or absence of LNG or the different doses of LNG evaluated and mouse embryo development. In conclusion, the hypothesis that in vitro exposure to LNG could interfere with sperm function and could contribute to the mechanism of action of this form of contraception was not confirmed but cannot be ruled out by the results of this study.

The sperm, a neuron with a tail: 'neuronal' receptors in mammalian sperm

A number of plasma membrane receptor types originally thought to be specific to neurons have been found in other somatic cells. More surprisingly, the mammalian sperm and neuron appear to share many of these 'neuronal' receptors. The morphology, chromosome number, genomic activity, and functions of those two cell types are as unlike as any two cells in the body, but they both achieve their highly disparate goals with the aid of a number of the same receptors. Exocytosis in neurons and sperm is essential to the functions of these cells and is strongly influenced by similar receptors. 'Neuronal' receptor types in sperm may also play a role in the control of sperm motility (a function of course not shared by neurons). This review will consider the evidence for the presence of sperm plasma membrane 'neuronal' receptors and for their significance to mammalian sperm function. The persuasiveness of the evidence varies depending on the receptor being considered, but there is strong experimental support for the presence and importance of a number of 'neuronal' receptors in sperm.

Seminal lead concentrations negatively affect outcomes of artificial insemination

OBJECTIVE

To determine the relationships among seminal lead levels, acrosome status, and artificial insemination cycle fecundity (AI f) in semen donors.

DESIGN

Longitudinal analysis of seminal lead levels, sperm function testing, and fecundity.

SETTING

University medical center andrology and research laboratories.

PATIENT(S)

Semen donors (n = 15) participating in a therapeutic donor insemination program.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Seminal plasma lead levels, acrosome sensitivity to progesterone (P) and voltage-gated potassium channel inhibitors (e.g., charybdotoxin [CBTx]), and AI f.

RESULT(S)

Seminal plasma lead levels and AI f were strongly negatively correlated. Semen donors were divided into three groups by acrosome response to P: normal (CBTx sensitive [Rs] or CBTx resistant [Rr]: responders) and reduced (nonresponders [NR]) (Rs > Rr >> NR). Seminal lead differed among the three groups (NR > Rr > Rs). Comparison of 330 artificial insemination cycles from four Rs, four Rr, and two NR demonstrated that cycle AI f also differed significantly between groups (Rs >Rr >>NR).

CONCLUSION(S)

Measurements of seminal plasma lead, P-stimulated acrosome loss, and sensitivity to CBTx may provide prognostic information on the fertility status of potential donors as well as male infertility patients. Such evaluations may assist in donor acceptance, or in the case of patients, in selection of the appropriate treatment regimen.

Receptors and channels regulating acrosome reactions

Prospective clinical studies informed by cloning and sequencing of sperm surface receptors and metal ion channels have elucidated critical early steps in the acrosome reaction that explain aspects of metal ion-related male infertility. Induction of the acrosome reaction is proposed to include non-nuclear progesterone receptor activation of Shaker-related sperm head voltage-gated potassium ion channels (VGKC). Men express VGKC isoforms with differing sensitivities to lead (Pb(2+)) inhibition, thus explaining interindividual variabilities in Pb(2+)-related male infertility. VGKC opening induces calcium (Ca(2+)) transients, and a signalling cascade induced by zona receptor aggregation requires an actin cytoskeleton created by the VGKC-induced Ca(2+) transients. Actin polymerization and stabilization, favoured by zinc (Zn(2+)) and depolymerized by cadmium (Cd(2+)), may mediate low Zn(2+) and high Cd(2+) infertile states. Zona receptor aggregation induces phosphotyrosine signals at sites, including sperm voltage-dependent Ca(2+) channels (VDCC), intermediate in electrophysiology between T- and L-type channels. Sperm surface VDCC localize at the sperm equatorial segment, the terminus of zona receptor translocation. Opening of VDCC admits a second Ca(2+) wave that activates phospholipase C phosphorylated in the zona receptor cascade. Phospholipase C induces fusogenic lipids and activates actin-severing proteins, depolymerizing the actin cytoskeleton and permitting apposition and fusion of acrosomal and plasma membranes.

Recognition of a human sperm surface protein involved in the progesterone-initiated acrosome reaction by antisera against an endomembrane progesterone binding protein from porcine liver

Antisera against a porcine liver endomembrane progesterone (P4)-binding protein inhibited the P4-initiated acrosome reaction (AR) but not the ionomycin-initiated AR of human sperm. Indirect immunofluorescence studies detected antigen in the sperm head that moved during capacitation from a posterior head region to a midhead region. Moreover, the antisera detected a 44.6 kDa protein in western blots of sperm digitonin extracts. These results suggest that a sperm protein with at least partial homology to the liver endomembrane P4-binding protein, is a putative P4-receptor on the sperm plasma membrane involved in the P4-initiated AR.

Progesterone-mediated calcium influx and acrosome reaction of human spermatozoa: pharmacological investigation of T-type calcium channels

The mechanisms of the progesterone (P4)-activated Ca2+ influx and the relationship between the intracellular free Ca2+ concentration ([Ca2+]i) and the acrosome reaction (AR) were investigated in this study. We compared the [Ca2+]i of uncapacitated and capacitated human sperm populations in response to P4 stimulation; characterized the effects of the pharmacological agents pimozide and mibefradil, inhibitors of T-type voltage-operated calcium channels (VOCCT), on the P4-activated Ca2+ influx; and determined the effects of these drugs on the P4-initiated AR. Since pimozide can also inhibit calmodulin-dependent enzymes, we examined the effects of the calmodulin antagonist, calmidazolium, on the above-mentioned events. The basal [Ca2+]i and the amplitude of the P4-activated Ca2+ influx were significantly (p < 0.05) higher in capacitated sperm populations. Also, in capacitated sperm populations, all three pharmacological agents significantly (p < 0.05) inhibited the P4-activated Ca2+ influx (IC50): calmidazolium (0.7 microM) > pimozide (8 microM) > mibefradil (11 microM). By contrast, the effects of these drugs on the P4-initiated AR were varied: pimozide (10 and 20 microM) significantly (p < 0.05) increased the percentage of AR spermatozoa, calmidazolium was without effect, and mibefradil (20 microM) significantly (p < 0.05) inhibited the AR. These disparate results do not allow us to reach any definitive conclusion concerning the role of a sperm VOCCT in the mechanism of the P4-initiated AR. However, the differences between the [Ca2+]i and AR effects, in particular the inverse relationship in the case of pimozide, suggest a dissociation between the amplitude of the P4-stimulated Ca2+ signal and the downstream biological effect of that signal, the AR.

Zona pellucida as physiological trigger for the induction of acrosome reaction

To evaluate the kinetics of acrosome reaction, sperm samples from four fertile donors were prepared by swim-up and incubated with solutions of human zonae containing 0.1, 0.15, 0.3, 0.5 and 1.0 zonae microliter-1. After 20, 40 and 60 min of incubation at 37 degrees C, aliquots were taken for evaluation of the acrosomal status. The results showed a distinct time- and dose dependence of the acrosome reaction induced by solubilized zona proteins. After 60 min of incubation in 1.0 zonae microliter-1, about 80% of the spermatozoa showed signs of acrosomal loss; about 40% were completely acrosome-reacted. In addition, zona-bound sperm showed the same ratios of acrosome-reacted spermatozoa in control experiments. The velocity of acrosome reaction was calculated by means of a double-reciprocal plot being 2.0-2.5% min-1 for completely reacted spermatozoa and those showing signs of acrosome reaction. However, both subgroups differed considerably in their constants of equilibrium (K = 2.0 ZP microliter-1 and K = 0.2 ZP microliter-1, respectively). In nonreacted and partly reacted spermatozoa results might indicate a disturbed course of acrosome reaction or possibly the existence of different subpopulations in respect of sperm competition.

Identification of insulin-like growth factor I in bovine seminal plasma and its receptor on spermatozoa: influence on sperm motility

Insulin-like growth factor I (IGF-I) has been identified in human seminal plasma. This study was conducted to determine whether IGF-I is present in bovine seminal plasma, whether sperm cells express the IGF-I receptor (IGF-IR), and whether IGF-I affects sperm motility. Semen samples were collected from bulls by electroejaculation and maintained at 37 degrees C, and motility of sperm was assessed. After centrifugation to separate sperm cells from seminal plasma, the seminal plasma was submitted to a validated heterologous RIA for IGF-I. Significant concentrations of IGF-I (116.29 +/- 40.83 ng/ml expressed as mean +/- SD) were measured in bovine seminal plasma. Sperm cells were washed with buffer and subjected to either radioreceptor assay (RRA) or immunocytochemistry (IC). RRA revealed a single high affinity for the IGF-IR with a Kd of 0.83 nM as determined by the computer program LIGAND. IC, using three monoclonal antibodies, localized the IGF-IR to the acrosomal region of the sperm. Computer-assisted sperm-motion analysis was used to determine the effects of IGF-I and IGF-II on bovine sperm motility parameters. Both IGF-I and IGF-II increased sperm motility and straight-line velocity (p < 0.05) relative to the control. The presence of IGF-IR on sperm, the presence of IGF-I in semen, and the ability of IGF-I to stimulate sperm motility provide evidence that the IGF system may be involved in the fertilization process in the bovine species.

Recent advances in clinical/molecular andrology

During the last decade there were extensive investigations in clinical and molecular andrology with emphasis on assisted reproduction, micromanipulation techniques of gametes, sperm/egg interaction, male contraception, diabetes mellitus, varicocele, andropause versus menopause, sexual dysfunction, associated hypertension/stress, prostatic carcinoma and molecular parameters of male reproduction. Sperm hyperactivation is a required step in capacitation sequence. Sperm motility is measured by videotape to evaluate the Straight Line Velocity (microm/s) (VSLI). Fertilization/embryonic development results from single sperm transfer (S-MIST) and multiple sperm transfer. Fertilization/embryo development is achieved by injection of immotile sperm into the perivitelline space. To assess sperm viability, a supravital stain suitable for use in combination with immunofluorescent assay, Hoeschst 33258, is used. The dye fluoresces with an intense blue when bound to DNA. To assess sperm plasma membrane integrity, a hypo-osmotic swelling test (HOST) is performed, using fluoresceinated D-mannose enriched albumin (FITC-DMA). The ability of sperm to swell under hypo-osmotic conditions indicates an intact membrane. A human protein, C-peptide, thought to be a useless byproduct of insulin may protect against devastating heart and nerve damage that diabetes causes. Human diabetics may benefit from the substance. Over 15 million Americans have diabetes, in which blood sugar levels rise out of control. There are two types of diabetics: Type I diabetics produce no insulin, the hormone that regulates blood sugar. Type II diabetics are unable to use their insulin properly. Diabetics are at great risk of heart disease and nerve damage, as arteries throughout the body leak and nerve-cell impulses fail. C-peptide is a byproduct of insulin production; it can be produced by the body or synthetically. Production of this protein is not induced by insulin, so diabetics who take insulin do not get C-peptide with it. Varicocele occurs unilaterally on the left side in 78% to 93% of men. Typically the presence of a varicocele is associated with an abnormal semen analysis (sperm density and morphology) and a decreased testicular volume on the affected side. Impaired sperm motility occurs in 89.5% of all varicocele patients. Varicocele ligation improves semen parameters in two thirds of patients. A few studies on andropause included sexual dysfunction, hormonal changes, medical/psychological correlates of impotence, ostenopenia/osteoporosis and bone loss; indices of bone remodeling, testosterone supplementation, androgen, negative feedback and hypothalamo-pituitary-testicular axis. Prostatic cancer is the second leading cause of cancer death for men between the ages of 60 and 80. Early detection involves a simple blood test for prostate specific antigen (PSA). Regular screening and early detection are essential. This is an important test because a high antigen count can be the only symptom. Since no screening is 100% accurate, physicians recommend both a PSA blood test and a physical examination. Although heredity plays a major role in whether a man will develop prostate cancer, men who lead healthy lives can dramatically reduce their chances of cancer: low-fat diet, eating plenty of fruits and vegetables and not smoking. Recent advances in molecular andrology include peptide hormone binding proteins; gonadotropin-releasing hormone (GnRH) agonists/antagonists analog; gonadotropins/their receptors; growth factors/reproduction; peptides as intratesticular regulators; molecular cloning of reproductive proteins/peptides. Gene cloning is applied for characterization/expression of genes coding. The interaction of gp120 with CD4 receptor plays a role in syncytium formation, apoptosis and CD4 cell deletion in human immunodeficiency virus (HIV) infection. The recombinant V3 peptide of fragment 307-330 of HIV-1 can induce sperm head agglutination. The generation process of react

Identification and characterization of functional nongenomic progesterone receptors on human sperm membrane

The presence of functional nongenomic progesterone (P) receptors in human spermatozoa has been investigated by equilibrium binding studies in intact spermatozoa, ligand blot and Western blot analysis of sperm lysates, as well as determination of the effects of the steroid on sperm intracellular Ca2+ concentrations. Binding experiments were performed using progesterone-11alpha-glucuronide-[125I]iodotyramine as tracer. Computer analysis of competition curves using different steroids as competitors indicated the presence of two distinct binding sites for P. The high affinity site (Kd in the nanomolar range) appears to be specific for P, whereas the low affinity one (Kd in the micromolar range) binds with equal affinity 11beta-hydroxyprogesterone (11betaOHP) and 17alpha-hydroxyprogesterone (17alphaOHP). A significant correlation exists among affinity constants (as determined by binding studies) and EC50 values for the effects of P, 11betaOHP, and 17alphaOHP on intracellular Ca2+ in fura-2-loaded spermatozoa, strongly indicating the involvement of P-binding sites in the biological effect of the steroid. In particular, dose-response curves for P were biphasic, with an EC50 in the nanomolar range and another in the micromolar range. Conversely, curves for 11betaOHP and 17alphaOHP were monophasic, with an EC50 just in the micromolar range. Ligand blot analysis of sperm total lysates performed with peroxidase-conjugated P revealed the presence of two binding proteins of 54 and 57 kDa that were specific for P. Indeed, peroxidase-conjugated P binding was blocked by the simultaneous presence of the unconjugated steroid. Using alpha c262 antibody, which is directed against the P-binding domain of genomic receptor, we detected two proteins of similar molecular mass (54 and 57 kDa), whereas using antibodies directed against the DNA-binding and N-terminal domains of the genomic P receptors, the two proteins were not detected. In addition, p54 and p57 appear to be mostly localized in sperm membranes and virtually absent in the cytoplasm. The involvement of these proteins in the biological effects of P is indicated by the strong inhibitory effect of alpha c262 on P-induced acrosome reaction of capacitated human spermatozoa.

Acrobeads test as a predictor of fertilization in vitro

PROBLEM

To determine whether the results of the Acrobeads test, which measures the expression of the complement regulator molecule CD46 on the inner acrosomal membrane following the acrosome reaction, accurately identifies semen specimens that will exhibit reduced or failed fertilization following conventional IVF insemination.

METHOD

The Acrobeads test was performed on semen specimens from 97 consecutive patients preparing to undergo an IVF cycle utilizing a standardized insemination protocol. Motile sperm populations were examined at 6 h and 24 h post-isolation for sperm-bead agglutination. Results of the Acrobeads test were compared to that of TRITC-PSA staining in matched specimens to directly measure the spontaneous loss of acrosome content. The percentages of TRITC-PSA-negative sperm were determined in freshly isolated motile populations and in duplicate aliquots incubated 18 to 20 h under sperm capacitating conditions. The relationship between the results of both analyses estimating spontaneous acrosome reactions and the rate of fertilization of metaphase II oocytes was examined.

RESULTS

The Acrobeads score did not correlate significantly with the rate of fertilization by insemination at 6 h or at 24 h. The negative predictive value of this test was 21.4%. There was no correlation between the Acrobeads score and the percentage of sperm undergoing a spontaneous acrosome reaction as detected by TRITC-PSA labeling. In contrast, the increment increase in the percentage of spontaneous acrosome reactions as quantified by TRITC-PSA staining was correlated with the fertilization rate.

CONCLUSIONS

Contrary to previous reports, our prospective, double-blinded study failed to demonstrate that the Acrobeads test can accurately predict fertilization outcome in IVF. Therefore, the routine use of this test to screen patients prior to an IVF cycle in order to select appropriate treatment (i.e., ICSI) cannot be recommended.

Progesterone binding to plasma membrane and cytosol receptors in the amphibian oocyte

We have found a single class of progesterone binding sites at the amphibian oocyte plasma membrane, whereas two progesterone receptor forms, similar to those in chick and human, are present in the cytosol. In this study both plasma membranes and 105,000 x g cytosol from Rana pipiens oocytes were photoaffinity labeled with the synthetic progestin [3H]R5020. SDS-polyacrylamide gel electrophoresis of the photolabeled proteins in the oocyte cytosol indicate that the two forms have molecular weights essentially identical to that found for human breast tissue and chick oviduct, i.e., 80 and 110 kDa, and that the forms were present in approximately equimolar ratios. In contrast, the plasma membrane form is present as a single 110 kDa species and accounts for at least 50% of the total 110 kDa species. The presence of large amounts of the 110 kDa protein in both membrane and cytosol suggests that the plasma membrane receptor may not be unique, and that the 110 kDa form may function both in membrane and cytosol and/or that part of the cytosolic 110 kDa form represents progesterone receptor in the process of being transported to or from the plasma membrane.