Sperm surface fibronectin. Expression following capacitation

The Arg-Gly-Asp (RGD) amino acid sequence plays a role in many cell-to-cell and cell-to-matrix adhesion systems, as a recognition sequence for cell membrane receptors termed integrins. Receptors of the VLA subfamily of integrins recognize fibronectin, laminin, and collagen. Given the authors' findings that fibronectin-derived, RDG-containing peptides competitively inhibit sperm-oolemmal adhesion and penetration in both heterologous (human-hamster) and homologous (hamster-hamster) gamete interactions, the expression of fibronectin on the surface of fresh, capacitated, and acrosome-reacted human spermatozoa was studied. The majority of fresh spermatozoa did not display fibronectin on their plasma membrane (0 to 16% positive), as demonstrated by the lack of binding of both monoclonal and polyclonal anti-fibronectin antibodies. In contrast, a significantly greater proportion of spermatozoa (varying between 18% to 100% for different donors) incubated overnight under capacitating conditions reacted with anti-fibronectin antibodies. The induction of an acrosome reaction with progesterone did not alter the proportion of sperm displaying fibronectin or its distribution on the sperm surface. A physiologic role of fibronectin in sperm-oolemmal interaction was suggested by the effects of anti-fibronectin antibodies on sperm oolemmal adhesion and penetration of hamster eggs by human spermatozoa, which were both significantly reduced (P less than 0.001).

Sperm penetration into a hyaluronic acid polymer as a means of monitoring functional competence

The diagnostic significance of sperm penetration assays based on a commercially available hyaluronate preparation (Sperm Select) has been investigated in the male partners of 77 couples characterized by a normal female partner. Sperm penetration into hyaluronate was highly correlated with the ability of the same sperm populations to penetrate bovine cervical mucus and, moreover, depended on the same attributes of semen quality, including the morphology of the spermatozoa, their number, and their motility as reflected by their mean path velocity. Stepwise multiple regression analyses employing these independent variables generated r values of 0.821 to 0.931, depending on the criterion of hyaluronate penetration used; path velocity was consistently the most informative variable according to the standardized regression coefficients. The relationship between hyaluronate penetration and sperm movement was so close that multiple regression equations could be generated that were capable of accounting for up to 76% of the variance in sperm velocity measurements obtained with a computerized image analysis system. Regression equations could also be generated using the hyaluronate penetration data that could account for 65% of the variance observed in an A23187-enhanced zona-free hamster oocyte penetration test, including the successful identification of the subpopulation of patients in whom 0% oocyte penetration had been recorded. Within the same data set, independent variables based on bovine cervical mucus penetration could only account for 43.5% of the variance in sperm-oocyte fusion. Hyaluronate penetration therefore appears to offer a simple, objective means of generating information on the functional competence of human spermatozoa that should find a role in routine diagnostic services where the more specialized tests are not available.

Fucoidin inhibits the zona pellucida-induced acrosome reaction in human spermatozoa

We recently reported that fucoidin (a polymer of predominantly sulfated L-fucose) significantly inhibits tight binding of human sperm to the human zona pellucida in vitro and that several oligosaccharides obtained after acid hydrolysis possess sperm-zona pellucida binding inhibitory activity equal to the original fucoidin. This inhibition may be specific to sperm-zona interactions or may be the consequence of the interruption of capacitation, a series of biochemical and physiological events leading to final sperm maturation, that must occur for successful fertilization. Completion of capacitation is most often determined by assessing two end-points of the process: acquisition of hyperactivated motility and ability to complete the acrosome reaction. Here, we examined the effects of fucoidin on these two end-points of capacitation in vitro. Fucoidin did not affect the proportion of sperm with hyperstimulated motility. Neither did fucoidin cause an increase in sperm that had spontaneously acrosome-reacted at 4.5 hours compared to controls as evaluated by indirect immunofluorescence using the acrosomal marker, monoclonal antibody, T-6. Comparable percentages of sperm had completed the acrosome reaction when exogenously stimulated by calcium ionophore A23187 with and without the addition of fucoidin. However, in the presence of fucoidin, stimulation of the acrosome reaction by acid solubilized human zonae pellucidae was significantly inhibited. These data indicate that fucoidin does not impede the normal progression of capacitation. These results provide strong evidence to support the hypothesis is that the inhibitory effect of fucoidin is at the level of the sperm membrane since inhibition can be bypassed by increasing intracellular calcium directly with a calcium ionophore.

Detection of a soluble acrosome reaction-inducing factor, different from serum albumin, associated with the ovulated egg-cumulus complex

Soluble extracts of the ovulated hamster egg-cumulus complex (ECC) were tested on capacitated sperm for activity in inducing the physiological acrosome reaction (AR). Evidence for occurrence of the physiological AR included enhanced sperm penetration of intact homologous zonae pellucidae as well as induction of AR in nonattached and in zona-bound sperm following a brief coincubation with test compound. Since hamster serum albumin, a major protein of hamster body fluids, also induces spontaneous ARs under certain conditions, it was used as one of the comparators for the acrosome reaction inducing factor (ARIF; Westrick et al., Biol Reprod 32 [Suppl 1]. 213, 1985) activity in the ECC. Sperm exposure to concentrations of the soluble ECC extract ranging from 0.04 to 0.2 mg protein/ml significantly increased penetration of salt-stored zonae by 36%, mean numbers of penetrating sperm by 90%, ARs in nonattached sperm by 65%, and ARs in zona-bound sperm by 102%. Hamster serum albumin added after completion of capacitation had no significant effect on these parameters. We conclude that 1) the ovulated ECC contains a soluble ARIF that augments zona-induced ARs and sperm penetration and 2) the ARIF is not serum albumin.

Sperm proteins that serve as receptors for the zona pellucida and their post-testicular modification

The search for molecules on the surface of mammalian sperm that are responsible for the binding of sperm to the zona pellucida has led to the identification of a number of different surface proteins. Different experimental approaches have been used to identify these proteins and the strength of the evidence for their putative role in zona binding is therefore quite variable. In this paper we have discussed some of the approaches that are used to identify cell adhesion molecules and criteria that might be applied in future research. Further research will be required to answer questions as to whether multiple surface antigens are involved in zona binding and if the sperm receptors for the zona are conserved among species. Both of these results would be expected based on what is known about cell adhesion in other systems. We have also discussed the modifications that occur to surface proteins after the sperm leave the testis and how these modifications can potentially activate or increase the efficiency of the function of a protein in zona binding.

Time course and pattern of cortical granule breakdown in hamster eggs after sperm fusion

We have determined the temporal relationship between sperm fusion and cortical granule breakdown in the hamster egg. Sperm fusion was determined by the Hoechst-transfer method (Stewart-Savage and Bavister: Dev Biol 128:150-157, 1988), and cortical granules were visualized with fluorescein isothiocynate-conjugated Lens culinaris agglutinin (Cherr et al. J Exp Zool 246:81-93, 1988). By 55 min after insemination, there was an 85% reduction in the density of cortical granules (fewer than four granules/100 microns2). Taking this value as the completion of the cortical reaction, analysis of the data indicate that the cortical reaction was completed 9 min after sperm fusion and 3 min after the formation of the zona and cell surface blocks to polyspermy. There was no obvious spatial pattern of granule loss in eggs that had a Hoechst-positive sperm but had not completed the cortical reaction.

Modifications of the mouse zona pellucida during oocyte maturation and egg activation: effects of newborn calf serum and fetuin

A precocious but limited loss of cortical granules (CG) occurs during mouse oocyte maturation both in vivo and in vitro. Although CG loss during maturation in vivo is not associated with changes in the zona pellucida (ZP), a maturation-associated conversion of ZP2 to ZP2f occurs during oocyte maturation in vitro in serum-free medium. We now demonstrate that a maturation-associated change of ZP3 to ZP3f, as assessed by a reduction in sperm binding, also occurs during maturation in vitro in serum-free medium, and that both newborn calf serum (NCS) and fetuin, each of which inhibits the ZP2 conversion, also inhibit the ZP3 conversion. The concentration-dependence of the NCS- and fetuin-mediated inhibition of the ZP2 conversion, coupled with the concentration of fetuin present in NCS, is consistent with fetuin being the component present in NCS that is primarily responsible for this inhibition. Although NCS can inhibit the ZP modifications that occur during oocyte maturation in vitro, ionophore treatment of eggs, which results in an extensive release of CGs over a short period of time, overcomes the inhibitory effect of NCS on the ZP2 conversion. Results of these studies suggest a potential regulatory function of serum-derived components in the formation of a fertilizable egg.

Collagenase as an agent for dissolving the zona pellucida of hamster and mouse oocytes

Crude preparations of collagenase, which have been used commonly for tissue dissociation, contain proteases that dissolve zonae pellucidae of hamster and mouse oocytes without reducing the ability of the oolemma to fuse with spermatozoa. This gentle proteolytic removal of zona is particularly useful for the study of sperm-oocyte fusion in mice, as trypsin, chymotrypsin and pronase damage the mouse oolemma.

Fertilization failure and dysfunctions as possible causes for human idiopathic infertility

Consideration of the most common currently practiced laboratory assays for human spermatozoal fertility are discussed, with reference to the relevance of such assays to success or failure in human in vitro fertilization (IVF). Such IVF therapy should be the definitive challenge for human spermatozoal fertilization ability. However, when fertilization fails, is polyspermic, or is suboptimal, then questions concerning the step or steps in the process of fertilization which are dysfunctional remain unanswered. Quite possibly new assays need to be devised to address these problems, while in the meantime our present laboratory assay systems need to be improved to discern those defects in fertilization which operate in many cases of human idiopathic infertility.

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.

Applications of flow cytometry to artificial insemination: a review

Flow cytometry is a technique in which sub-populations of cells can be analysed and separated according to the staining pattern seen with various fluorescent markers. This review describes some of the ways in which flow cytometry can be applied to the investigation of sperm populations, either as a means of quality control of semen or to examine the characteristics of different sub-populations of sperm within an ejaculate. These methods can replace or augment existing subjective assessments of semen characteristics. Using this technique it is possible to produce aliquots of sexed sperm for insemination or for in vitro fertilisation. An objective assessment can be made of the effects of environmental stress on male physiology by monitoring changes in semen quality.

In vitro fertilization in ctenophores: sperm entry, mitosis, and the establishment of bilateral symmetry in Beroe ovata

We have found ways to control in vitro fertilization in a ctenophore (Beroe ovata) for the first time. This is based on the existence of a partial block to self-fertilization at the time of gamete release which can be overcome by removal of the egg envelope. It has allowed us to exploit the excellent optical properties of Beroe eggs to make detailed observations on all events from sperm penetration or penetrations in these physiologically polyspermic eggs to first cleavage, and to extend our initial observations (Carré and Sardet, 1984). Sperm entry is characterized by local modifications of the egg cortex in a 70-microns zone around the penetration site or sites. Upon sperm entry, the egg surface contracts and relaxes locally, then a fertilization cone forms and disappears. These events are accompanied by localized exocytosis, growth of a ring of microvilli, thickening of the egg cortex, and gathering of mitochondria around the sperm pronuclei. The female pronucleus then migrates beneath the egg surface toward one or successive sperm pronuclei. The fusion of pronuclei, sperm and egg chromatin intermixing, and mitosis were also observed with exceptional clarity. Furthermore, we have noticed that the direction of the last trajectory of the female pronucleus tends to define the orientation of the mitotic spindle, and as a consequence the position of first unipolar cleavage furrow. This in turn determines the future sagittal plane of the embryo and of the adult B. ovata.

Aggregation of beta-1,4-galactosyltransferase on mouse sperm induces the acrosome reaction

beta-1,4-Galactosyltransferase (GalTase) is present on the surface of mouse sperm, where it functions during fertilization by binding to oligosaccharide residues in the egg zona pellucida. The specific oligosaccharide substrates for sperm GalTase reside on the glycoprotein ZP3, which possesses both sperm-binding and acrosome reaction-inducing activity. A variety of reagents that perturb sperm GalTase activity inhibit sperm binding to the zona pellucida, including UDP-galactose, N-acetylglucosamine, alpha-lactalbumin, and anti-GalTase Fab fragments. However, none of these reagents are able to cross-link GalTase within the membrane nor are they able to induce the acrosome reaction. On the other hand, intact anti-GalTase IgG blocks sperm-zona binding as well as induces the acrosome reaction. Anti-GalTase IgG induces the acrosome reaction by aggregating GalTase on the sperm plasma membrane, as shown by the inability of anti-Gal-Tase Fab fragments to induce the acrosome reaction unless cross-linked with goat anti-rabbit IgG. These data suggest that zona pellucida oligosaccharides induce the acrosome reaction by clustering GalTase on the sperm surface.

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)

Comparison of sperm binding potential of uninseminated, inseminated-unfertilized, and fertilized-noncleaved human oocytes under hemizona assay conditions

In this study, human oocytes obtained after ovarian hyperstimulation for in vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT) were utilized to evaluate sperm/zona pellucida binding potential. Three groups of oocytes were evaluated: 1) uninseminated; 2) inseminated-unfertilized; and 3) fertilized-uncleaved. All oocytes had undergone germinal vesicle breakdown at the time of retrieval and were salt-stored (pH 7.2) for not more than 30 days. Sperm binding was recorded under hemizona assay (HZA) conditions using spermatozoa from eight fertile men (HZA control) and from 1) four teratozoospermic (HZA test) and 2) four normozoospermic (HZA test) infertile men. First, the mean numbers (+/- SD) of sperm tightly bound for fertile controls and teratospermic men to hemizonae from uninseminated oocytes were 69.7 +/- 16 and 14.5 +/- 7, respectively (P = 0.02). Likewise, hemizonae from uninseminated oocytes bound 102.0 +/- 19 and 114.0 +/- 28, respectively, for fertile controls and normospermic men (P = 0.5). Second, hemizonae obtained from inseminated-unfertilized IVF oocytes bound 44.2 +/- 12 and 19.7 +/- 6 for fertile controls and teratospermic men, respectively (P = 0.02). This category of oocytes bound 100.5 +/- 7 and 108.5 +/- 11 sperm, respectively, for fertile controls and normospermic semen (P = 0.3). Third, HZA results of fertilized but uncleaved oocytes showed a mean number of tightly bound sperm of 6.0 +/- 4 compared with 65.0 +/- 1 in control, uninseminated oocytes using fertile sperm. These results demonstrate that uninseminated and inseminated-unfertilized human oocytes, salt-stored under controlled pH conditions, give reliable information regarding sperm binding potential under HZA conditions.

Influence of polymorphonuclear granulocytes on the zona-free hamster oocyte assay

To gain more insight into a possible detrimental influence of polymorphonuclear granulocytes (PMN) on fertility, PMN were added to spermatozoa and oocytes in the hamster oocyte assay. Addition of 2.5 x 10(6)/ml PMN to the sperm suspension at the start of the first incubation period (capacitation period) resulted in a significant decrease (P less than 0.03) in the number of decondensed sperm-heads per hamster oocyte (the decondensation index). When a concentration of 0.5 x 10(6)/ml PMN was used, no decrease was found. Stimulation of PMN by phorbol myristate acetate (PMA) did not enhance the inhibitory action of PMN. After incubation of oocytes with PMN for 1 h, an almost total inhibition of decondensation was observed. A significant inhibition could also be obtained when unstimulated PMN (2.5 x 10(6] were added at the start often 3 h coincubation period of spermatozoa and oocytes (P less than 0.004). The inhibition by PMN decreased to a nonsignificant level when the hydroxyl radical scavenger thiourea was present. The possible mechanisms by which PMN affect the results of the hamster oocyte assay and the possible implications of the presence of PMN in the genital tract are discussed.

Human spermatozoa do not undergo the acrosome reaction during storage in the cervix

Incubation of human spermatozoa in capacitation media for 24 hours resulted in a significant increase in acrosome-reacted spermatozoa compared with preincubation (baseline) levels. By contrast, sperm samples recovered from the cervix for as long as 72 hours after coitus showed only baseline percentages of acrosome-reacted spermatozoa. These results indicate that human spermatozoa do not undergo the acrosome reaction during cervical storage even if they undergo capacitation.

The effect of porcine follicular fluid on the interaction of boar spermatozoa with zona-free hamster ova

Boar spermatozoa were cocultured with zona-free hamster ova (eggs) to assess the effects of preovulatory porcine follicular fluid (pFF) in the capacitation medium or gamete coculture (fertilization) medium (pFF; 0, 10 or 40% v/v) on subsequent sperm-egg interaction. Increasing pFF concentrations in the capacitation medium resulted in a progressive decrease in the average numbers of sperm attaching to or penetrating each ovum. When pFF was included in the fertilization medium, but not in the capacitation medium, the average numbers of sperm attaching to or penetrating each ovum and the percentage of ova with sperm attached decreased markedly with increasing pFF concentrations. The percentage of ova with greater than five sperm attached decreased from 84% to 13% and 0% with 0%, 10% and 40% pFF, respectively. Sperm attachment was completely inhibited in approximately 50% of the ova cocultured in 40% pFF. The percentage of ova penetrated by greater than five sperm decreased from 82% to 21% and 7% with 0%, 10% and 40% pFF, respectively. Preincubation of ova in 40% pFF prior to coculture with sperm also resulted in a reduction in sperm attachment and penetration. These results suggest that pFF contains substance(s) that alter the ability of boar spermatozoa to interact with the hamster ovum plasma membrane in vitro.

Effect of smoking on concentration, motility and zona-free hamster test on human sperm

The effect of smoking on sperm concentration, motility, and zona-free hamster egg sperm penetration assay (SPA) was evaluated in 293 smokers of more than 10 cigarettes/day and 382 nonsmokers. Prerequisites for inclusion in the study were sperm concentration of greater than 10 x 10(6)/ml, sperm motility of greater than 30%, and normal morphology of greater than 60%. Although a lower sperm concentration was found in smokers, no significant difference was observed in sperm motility and SPA.

Localization of rabbit sperm acrosin during the acrosome reaction induced by immobilized zona matrix

To better understand the loss of the acrosomal cap on the surface of the zona pellucida and the function of the equatorial-postacrosomal region after the acrosome reaction, we have constructed an in vitro system using heat-solubilized zonae pellucidae dried onto a coverslip and incubated with capacitated spermatozoa. This system allows good optical resolution of spermatozoonzona interaction. Induction of the acrosome reaction by zonae on coverslips (30%) is comparable to the induction of the reaction reported previously for rabbit spermatozoa using solubilized zonae in solution. Antiserum to rabbit proacrosin, antiserum to a porcine 49-kDa proacrosin fragment, and antiserum to a porcine 14-kDa C-terminal acrosin fragment were utilized to monitor the acrosome reaction. Rabbit proacrosin/acrosin is not present on the surface of live, acrosome-intact, swimming spermatozoa. After contact with zona, the acrosome reaction begins and proacrosin/acrosin becomes available to bind antibody, first as a crescent in the apical region and then more posteriorly until the entire anterior acrosome is labeled. Proacrosin/acrosin remains on the equatorial and postacrosomal regions of acrosome-reacted spermatozoa and also remains associated with the acrosomal cap even after the spermatozoon is no longer associated with it. Further studies using zona-coated coverslips should lead to a more detailed understanding of the mechanism of zona penetration.

Influence of incubation time/temperature on acrosome reaction/sperm penetration assay

The acrosomal status of human spermatozoa was studied in relation to the score of the sperm penetration assay (SPA) at low-temperature (4 degrees C) incubation for induction and synchronization of the acrosome reaction (AR) and the incubation time of spermatozoa in conventional SPA. Spermatozoa were collected from 18 patients, selected by the "swim-up" method and treated in three different ways: (1) short-term incubation group (SIG): 3 h incubation at 37 degrees C, and (2) long-term incubation group (LIG): 20 h incubation at 37 degrees C, and (3) low temperature group (LTG): 24 h incubation at 4 degrees C followed by additional incubation at 37 degrees C for 3 h. The conventional methods of incubation, i.e. SIG (3 h) and LIG (20 h) did not show any significant differences as evaluated by the sperm penetration rate and the number of decondensing sperm heads per oocyte. In contrast, in the LTG all parameters were significantly increased, especially those of penetration rate (p less than 0.0005) and decondensing sperm heads per oocyte (p less than 0.0005). The percentage of AR significantly increased (p less than 0.0005) in the LTG (14.7%) compared with SIG (6.1%) and LIG (10.6%). A significant correlation was demonstrated between AR and the parameters used for evaluation of the SPA. The penetration rate (Spearman test, r = 0.462, n = 54, p less than 0.003) was the most significant parameter correlated with AR. It would appear that only human spermatozoa having completed AR are capable of fusing with the zona-free hamster ova.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of the capacity of ram epididymal and ejaculated sperm to undergo the acrosome reaction and penetrate ova

An understanding of epididymal maturation of sperm requires descriptions of changes in membrane properties and their relation to changes in cell function. While sperm membranes have been studied in some detail in rams, few reports address associated functional changes. This report provides such data by evaluating (a) the time course of sperm acrosome reaction (AR) induction for cells from each epididymal region; (b) the capacity of epididymal sperm to penetrate ova; (c) differences in physiological AR and general sperm degeneration; and (d) acrosin release of epididymal sperm. Ram epididymal (caput, corpus, and proximal and distal cauda) and ejaculated (EJ) sperm were incubated in vitro to assess their capacity to undergo an AR. Light microscopy revealed that in sperm populations which had traversed the proximal cauda epididymidis, greater than or equal to 50% exhibited an endogenous AR in less time (less than 17 h) than did sperm isolated from more proximal regions of the epididymis (22-greater than 50 h). Heparin added to sperm did not stimulate the AR in epididymal or EJ sperm, whereas addition of a calcium ionophore (A23187) increased AR rates for cauda and EJ sperm, but not caput or corpus sperm. A second experiment evaluating percent AR, percent motile cells, and percent hamster ova penetrated revealed that sperm isolated from regions proximal to the cauda epididymidis failed to penetrate ova. When cauda or EJ sperm exhibited motility greater than 5% and AR greater than 24%, penetration of hamster eggs occurred. Comparisons of acrosomal integrity by electron or light microscopy were not different for sperm at any stage of epididymal maturation, suggesting that minimal nonspecific membrane changes occur and that light microscopy is valid for evaluating the acrosomal status of ram spermatozoa. Acrosin activity (sperm bound and dissociated) also was measured. Both total activity and release of acrosin from sperm to the medium during an 8-h incubation was greater for mature than for immature sperm. Results from these experiments are discussed in relation to the changes that must occur in sperm as they acquire the capacity to undergo an AR and penetrate hamster ova.

Zona pellucida-mediated acrosomal exocytosis in mouse spermatozoa: characterization of an intermediate stage prior to the completion of the acrosome reaction

The zona pellucida (ZP)-induced acrosome reaction in mouse sperm proceeds in two steps, identified by three sperm fluorescence patterns observed sequentially with the fluorescent probe chlortetracycline. Capacitated, acrosome-intact sperm displaying a B pattern proceed to an intermediate S pattern, and then progress from the S pattern to the fully acrosome-reacted AR pattern. Previously, it was not feasible to characterize the nature of the transient intermediate S pattern. Recently, it was demonstrated that sperm bind to the ZP of eggs treated with 12-O-tetradecanoyl phorbol-13-acetate (TPA) and undergo a B to S transition, but do not complete the acrosome reaction. These cells accumulate in the S pattern and fail to undergo the S to AR transition (Endo, Y., Schultz, R. M., and Kopf, G. S. 1987a. Dev. Biol. 119, 119-209). The present study utilized ZP from TPA-treated eggs to assess the state of S pattern sperm. The kinetics of the B to S transition of sperm incubated with either structurally intact or solubilized ZP from untreated or TPA-treated eggs are identical. Addition of either solubilized ZP from untreated eggs or A-23187 to S pattern sperm bound to intact or solubilized ZP from TPA-treated eggs induces the S to AR transition, while ZP from TPA-treated or fertilized eggs does not. Loss of the transmembrane pH gradient in the anterior portion of the sperm head, monitored by the fluorescent pH probe 9-N-dodecyl aminoacridine, follows the B to S transition in sperm incubated with ZP from unfertilized eggs, but no loss is observed when the B to S transition is induced using ZP from TPA-treated eggs. Subsequent addition of solubilized ZP from untreated eggs or A-23187 results in the loss of the transmembrane pH gradient of these S pattern sperm. Addition of nigericin to S pattern sperm bound to ZP from TPA-treated eggs discharges the transmembrane pH gradient and causes the S to AR transition. In contrast, nigericin added to B pattern sperm discharges the pH gradient but does not induce a B to S transition. Electron microscopic evaluation of S pattern-arrested sperm using ZP from TPA-treated eggs reveals intact plasma and outer acrosomal membranes. These results suggest that ZP from TPA-treated and fertilized eggs are modified such that the ZP ligands inducing the S to AR transition are lost or are inactivated.(ABSTRACT TRUNCATED AT 400 WORDS)

Hemizona assay: use of fresh versus salt-stored human oocytes to evaluate sperm binding potential to the zona pellucida

The hemizona assay (HZA) has a high predictive value for in vitro fertilization (IVF) results. Oocyte quality plays a significant role in the validation of this test. The question was asked whether human salt-stored oocytes (up to 30 days) are damaged and subsequently lose their sperm binding capacity when compared to fresh human oocytes. Equivalent binding in both the salt-stored and the fresh group of oocytes was observed in the hemizonae incubated with normal semen as well as in their matching halves incubated with semen from an infertile man. Based on the results, we conclude that salt-stored oocytes (pH 7.0) give reliable information regarding sperm binding potential under HZA conditions.