Zona pellucida as physiological trigger for the induction of acrosome reaction

Summary.  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 μl^-1. After 20, 40 and 60 min of incubation at 37 °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 μl^-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 μl^-1 and K = 0.2 ZP μl^-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.     

An in vitro promoting role for hydrogen peroxide in human sperm capacitation

A complex process of maturation called capacitation is an essential step for spermatozoa to fertilize oocytes. Recent studies have shown that reactive oxygen species (ROS) can enhance the capacitation of human spermatozoa and sperm-zona interaction. We have investigated whether hydrogen peroxide (H₂O₂) could trigger capacitation of human spermatozoa and the acrosome reaction. The addition of catalase, a specific H₂0₂ scavenger, at the beginning of the capacitation process decreased the levels of both hyperactivation and induced-acrosome reaction whereas catalase added 15 min before the induction of the acrosome reaction by the calcium ionophore had no effect. Supplementation of the medium with H₂O₂ resulted in increased levels of hyperactivation and the acrosome reaction, whereas H₂O₂ added 15 min before induction of the acrosome reaction did not have any stimulatory effect. These results suggest that H₂O₂ may be involved in the capacitation process of human spermatozoa but not in the acrosome reaction.     

Pentoxifylline acts synergistically with A23187 to increase the penetration of zona-free hamster oocytes by cryopreserved human spermatozoa

The number of cryopreserved human spermatozoa which penetrated zona-free hamster oocytes afier stimulation with 2μmol A23187 per litre was increased by the hrther addition of 0.6 or 3.6 mmol pentoxifjrlline per litre. With spermatozoa prepared by washing by repeated centrifugation, the median numbers of sperm headd/egg were 1.9, 7.9 and 10.8 in the presence of 0, 0.6 or 3.6 mmol pentoxifylline per litre, respectively. A similar effect was observed with spermatozoa prepared on a Percoll gradient. As A23187 inhibited sperm motility, and this was exacerbated by pentoxifylline, the increased penetration rate of hamster oocytes cannot be explained by improved sperm motility. The number of spermatozoa stimulated to acrosome react by 2 μmol A23187 per litre was increased 3-fold by 3.6 mmol pentoxifylline per litre and 4-fold by 5 mmol caffeine per litre. These data suggest that CAMP may act synergistically with Ca²⁺ to stimulate the acrosome reaction. Pentoxifjrlline may improve the fertility of poor-quality human spermatozoa by enhancing their ability to respond to the Ca²⁺ signal produced by binding to the zona pellucida.     

Effect of natural antioxidants, superoxide dismutase and hydrogen peroxide on capacitation of frozen-thawed bull spermatozoa

Summary.  Bovine spermatozoa from frozenthawed semen are sensitive to lipid peroxidation. Vitamin E protects sperm membrane against oxidative damage. Sperm capacitation produces structural changes on the plasma membrane. Reactive oxygen species could be involved in the capacitation process. The aim of this work was to study the influence of natural antioxidants on the plasma membrane and the influence of reactive oxygen species during bovine sperm capacitation. Sperm samples were frozen in a standard diluent, with and without vitamin E (1 mg ml^-1). Heparin (60 μg ml^-1) was used as a sperm capacitation inductor. Sperm capacitation was evaluated by chlorotetracycline assay. Lipid peroxidation was determined by the 2-thiobarbituric acid assay. A diminution of thiobarbituric acid reactive substances was observed in sperm samples frozen with vitamin E ( P < 0.05). The addition of vitamin E to the freezing diluent had no effect on the capacitated pattern ( P > 0.05).
When vitamin E and vitamin E + vitamin C were added to the capacitation medium, a significant decrease in the percentage of capacitated spermatozoa ( P < 0.05) was observed in both cases. The addition of superoxide dismutase (0.1 mg ml^-1) or H₂O₂ (50 μM) in the incubation medium, decreased the percentage of capacitated spermatozoa ( P < 0.05). Vitamin E protects the plasma membrane against lipid peroxidation during sperm capacitation, and the presence of superoxide anion would be necessary for frozen-thawed bull sperm capacitation.     

Effect of angiotensin converting enzyme (ACE) and angiotensins on human sperm functions

Summary.  The presence of components of the renin angiotensin system (RAS) and specific receptors of angiotensin II in the female and male reproductive tract supports the hypothesis that reproductive functions may be controlled by RAS. Therefore, the present study investigated the influence of ACE and angiotensins on sperm functions and the sperm–egg interaction.
The experiments did not indicate direct effects of ACE on the capacitation process or acrosome reaction. Release of ACE from human spermatozoa during capacitation was not related to their ability to undergo acrosome reaction after stimulation with ionophore. Therefore, ACE release does not seem to be a useful clinical marker for human sperm capacitation. However, decreased binding of human spermatozoa to the oolemma of zona-free hamster oocytes after inhibition of ACE by captopril indicates that kininase II is involved in sperm–egg interactions. In contrast to other studies, incubation with captopril had no influence on sperm binding to the zona pellucida. Because effects of ACE on sperm–egg interactions but not on capacitation or acrosome reaction were observed, several experiments were performed to study the influence of substrates and products on the acrosome reaction. Angiotensin II induced the acrosome reaction dose-dependently, whereas angiotensin I had no effect on the acrosome reaction. The effect of angiotensin II on acrosome reaction seems to be calcium-dependent and mediated by protein kinases. Since a specific type 2 angiotensin II receptor inhibits the acrosome reaction induced by angiotensin II, this subtype of receptors may be present at the surface of sperm heads. Another clue for the presence of type 2 receptors on human spermatozoa is the finding that pertussis toxin did not inhibit the angiotensin II induced acrosome reaction. In contrast to type 1 angiotensin II receptors, type 2 receptors are known to be G-protein independent.     

Effect of genistein on acrosome reaction and zona pellucida binding independent of protein tyrosine kinase inhibition in bull

Aim： To investigate if the phytoestrogen, genistein, affects essential functions of cryopreserved bovine spermatozoa. Methods： The effect of genistein upon motility was assessed by computer-assisted motion analysis. Hemizona assay was performed to detect the ability of spermatozoa binding to the zona pellucida. The inducibility of the acrosome reaction using progesterone and ZP3-6 peptide was analysed by fluorescein-conjugated Pisum sativum agglutinin （FITC-PSA）/Hoechst 33258 double staining. Capacitation after incubation with genistein was assessed by the chlortetracycline （CTC） assay. Immunoblots showed the pattern of protein tyrosine phosphorylation of cryopreserved bovine spermatozoa. Results： Immunodetection of tyrosine-phosphorylated proteins showed that genistein did not affect tyrosine phosphorylation in cryopreserved bovine spermatozoa. However, genistein significantly reduced the progesterone- and ZP3-6 peptide-mediated induction of the acrosome reaction and led to a dose-dependent inhibition of sperm-zona pellucida binding; while sperm motility and capacitation were not affected by this phytoestrogen, as indicated by computer-assisted sperm motion analysis and the CTC assay, respectively. Conclusion： Our results suggest that in cryopreserved bovine spermatozoa, genistein affects a protein tyrosine phosphorylation-independent signal transduction pathway that is involved in sperm capacitation, the acrosome reaction and sperm-zona pellucida binding.     

The influence of sperm/zona pellucida collision rates on zona binding

Summary. The satisfying success rates reported with intra-cytoplasmic sperm injection (ICSI) urged clinicians and scientists to re-address the emphasis in the management of the male factor patient towards gamete manipulation in order to circumvent the underlying problem causing fertilization failure. We have designed a study to (i) calculate the collision rate of a sperm population with the human zona pellucida, using a mathematical hypothesis and (ii) use the calculated collision rate to evaluate subsequent zona binding results obtained under hemizona assay conditions. Microdroplets were used to co-incubate sperm and human oocytes in order to evaluate zona binding. Using microvolumes, the track followed by sperm, as well as the maximum distance travelled were employed to calculate the collision rate of sperm and zona pellucida. The sperm concentrations of swim up samples were adjusted to 4 × 10⁶ and 0.8 × 10⁶ sperm ml⁻¹. Five separate droplets each of 20 μl containing 4 × 10⁶ sperm ml⁻¹ (80000 motile sperm) and 200 μl containing 0.8 × 10⁶ sperm ml⁻¹ (160000 motile sperm), respectively, were prepared. Both volumes were incubated for 18 h at 37°C. The mean (±SD) number of spermatozoa tightly bound to hemizona, incubated in 20 μl and 200 μl sperm droplets, was 2444±612 and 548±315, respectively ( P = 0.0001). The results can be used as a guideline to calculate the optimum insemination concentration needed for a specific sperm population to ensure the maximum collision rates with the oocyte.     

Physiological action of oestradiol on the acrosome reaction in human spermatozoa

The acrosome is a secretory vesicle located in the sperm head. The acrosome reaction consists in the fusion of the sperm plasma membrane with the external acrosomal membrane. It has been observed that this reaction does not take place in spermatozoa incubated in cervical mucus, hydrogel that contains high concentrations of oestradiol in the peri-ovulatory period. The objective of the present study was to analyse the influence of oestradiol on the acrosome reaction in human spermatozoa to evaluate the possible inhibitory effect of this hormone. Spermatozoa were incubated in progesterone (10.1 nmol l⁻¹); oestradiol plus progesterone (oestradiol at 840 pmol l⁻¹ and progesterone at 10.1 nmol l⁻¹), oestradiol (840 pmol l⁻¹) and control (without steroidal hormones) for 30 min, 60 min, 240 min and 24 h. The acrosome reaction was evaluated by stain with Hoechst 33258 and fluorescein isothiocyanate-conjugated Pisum sativum agglutinin lectin. Progesterone-incubated spermatozoa showed the highest percentage of acrosome reaction ( P  <   0.05). Spermatozoa incubated with oestradiol and oestradiol plus progesterone showed the lowest percentage of acrosome reaction. The present study demonstrates the inhibitory role of oestradiol on the acrosome reaction, stimulated by progesterone in human spermatozoa under physiological conditions.     

Effect of bafilomycin A1, a specific inhibitor of vacuolar (V-type) proton ATPases, on the capacitation of rabbit spermatozoa

Mammalian spermatozoa maintain precisely regulated ionic gradients that must be modified during capacitation and the acrosome reaction. In other cell types, ionic gradients are mainly regulated by the presence in plasma membranes of three metabolically different types of ATPases. The modifications induced during in vitro capacitation of rabbit spermatozoa by the specific inhibition of V-type H+-ATPases with bafilomycin A were studied. We used chlortetracycline binding to rabbit spermatozoa to monitor capacitation, and the coomassie brilliant blue method to identify acrosome-reacted sperm cells. There was a significant difference between the percentage of epididymal (66 +/- 7%) and ejaculated (43 +/- 11%) spermatozoa capacitated in vitro, after a 6-h incubation period in the presence of Ca2+ without ATPase inhibitor. The presence of bafilomycin significantly reduced these numbers (25 +/- 11 and 16+/- 8%, epididymal and ejaculated spermatozoa, respectively) and eliminated the difference. Ejaculated spermatozoa capacitated in the absence of bafilomycin showed a linear increase in the percentage of acrosome reactions induced by the addition of A23187 (12 +/- 5, 23+/- 6 and 31 +/- 5 after 15, 30 and 45 min). The presence of 0.2 micromol l-1 bafilomycin during the capacitation incubation induced a significant decrease in the acrosome reaction percentages (4 +/- 2, 8 +/- 3 and 14 +/- 4 after 15, 30 and 45 min). The addition of bafilomycin after the capacitating period had no effect upon the induction of the acrosome reaction by A23187. These results indicate that vacuolar ATPases play an important role during rabbit sperm capacitation. However, once the spermatozoa have been capacitated, V-type ATPases do not have a significant participation during the acrosome reaction.     

Modulation of human sperm function by follicular fluid

Human follicular fluid (hFF), present in the ampullary environment, can reduce the number of sperm bound to the zona pellucida. The aim of the present study was to investigate the effects of follicular fluid on sperm function. The presence of 50% v/v follicular fluid resulted in a significant reduction in the number of bound spermatozoa with respect to control medium (12.7 +/- 5.5 sp HZ(-1) versus 24.6 +/- 5.7 sp HZ(-1), P = 0.03) as measured by the hemizona binding assay. This reduction in zona binding capacity was not associated with a loss of sperm viability, motility or a premature acrosomal reaction. When capacitated spermatozoa were previously exposed 1 h to follicular fluid, a significant reduction in the number of alpha-d-mannose binding sites on sperm head was detected (23.7 +/- 3.1% versus 15.5 +/- 2.4%, P < 0.05). In addition, sperm fertilizing capacity (assessed as the acrosome reaction to ionophore challenge score) in the presence of follicular fluid was also diminished (38.0 +/- 4.8% versus 22.6 +/- 4.9%, P < 0.01). No modification in the pattern of protein tyrosine phosphorylation which occurs during capacitation was observed in the presence of the fluid. Taken together, the results indicate that the decrease in sperm zona-binding capacity observed in the presence of hFF was related to a lower number of sperm containing alpha-d-mannose receptors.     

Secretion of macromolecules by the rat epididymis

Sperm maturation in the rat epididymis is dependent on the secretion of specific proteins by the epididymal epithelium and subsequent interaction of these proteins with spermatozoa. Evidence has shown that fertility and motility development of epididymal spermatozoa may be impaired by interfering the interaction of these proteins with spermatozoa. When the spermatozoa reach the cauda epididymidis, they are fully mature but their longevity is maintained by being stored in a quiescent state in the cauda. The unique ionic medium therein (low Na⁺, low Ca²⁺, high K⁺ and low pH) suppresses sperm motility and hence reserving energy for the vital processes of capacitation and fertilization. During ejaculation, when the spermatozoa are mixed with the copious secretion from the accessory glands they burst into vigorous motility. This results from an influx of sodium coupled to efflux of K⁺ and H⁺ across the mature sperm membrane. In the presence of a peptide secreted by the cauda epididymidis, these ionic events activate the already mature but otherwise inactive spermatozoa to full motility.     

Separation of human spermatozoa with hyaluronic acid induces, and Percoll® inhibits, the acrosome reaction

The effect on the acrosome reaction of human spermatozoa of two widely used sperm separation media, hyaluronic acid (Sperm Select®) and Percoll®, was studied. Viable and highly motile fractions of human spermatozoa were separated from seminal plasma using self-migration on a Percoll® gradient. After translocation of separated spermatozoa from the Percoll® solution to a culture medium, serum, Percoll® or hyaluronic acid (Sperm Select®) was added to aliquots of the spermatozoa containing culture medium. At increasing time intervals, the influx of ⁴⁵Ca²⁺ into spermatozoa was measured and the concentration of viable spermatozoa that had undergone the acrosome reaction was analysed using the triple stain technique. Serum was found to be necessary to support sperm motility and viability. Compared to culture medium with serum only, addition of hyaluronic acid induced influx of ⁴⁵Ca²⁺ and the acrosome reaction, whilst Percoll® inhibited both of these actions. Hyaluronic acid (Sperm Select®) added to spermatozoa separated by a 'swim-up' method induced, and the addition of Percoll® inhibited, influx of ⁴⁵Ca²⁺ when compared to the addition of culture medium with serum only. This study demonstrates that both hyaluronic acid (Sperm Select®) and Percoll® affect the acrosome reaction and the prerequisite for Ca²⁺ influx in human spermatozoa. These effects should be taken into consideration when using these media for preparation of spermatozoa for insemination or for fertilization in vitro.     

Electron microscopic evidence on the acrosomal status of bound sperm and their penetration into human hemizonae pellucida after storage in a buffered salt solution.

The hemizona assay (HZA) was developed to evaluate sperm binding potential using microbisected human zona pellucida. In this study, eight human oocytes stored in a buffered salt solution for 60 days were bisected into two identical hemispheres (hemizonae) and coincubated with the spermatozoa from a fertile man. All evaluated spermatozoa were tightly bound to the outer surface or had begun penetration into the zona pellucida. The hemizonae with bound spermatozoa were prepared and fixed for transmission electron microscopy (TEM) using standard techniques. Among the 108 sperm bound to the zone we were able to evaluate 25 by TEM. Twenty (80%) of the zona bound spermatozoa were partially or completely acrosome reacted, while six (20%) of the zona bound sperm had intact acrosomes. Acrosome intact, partially acrosome reacted and completely reacted spermatozoa were observed within the zona. Penetration pathways or tunnels were seen within the zona matrix. The results illustrate, that typically spermatozoa tightly bound the human zona pellucida show induction of the acrosome reaction. Importantly, following storage of human eggs in salt solution (buffered to 7.4), the zona pellucida retain their biological and functional characteristics for at least 90 days.     

Scavenging effect of N-acetyl-L-cysteine against reactive oxygen species in human semen: a possible therapeutic modality for male factor infertility?

Summary. A new approach to reduce the level of reactive oxygen species (ROS) in human semen by using N-acetyl-L-cysteine (NAG) was evaluated. Semen samples were incubated with or without NAC (1.0 nig ml⁻¹) at room temperature. The chemiluminescent signal of the oxidation of luminol was detected by means of an MTP reader after 0, 20, 40, 60 and 120 min, respectively, using 200 μM luminol. In addition, the dose-dependent action of NAC (0.1, 1.0 and 5.0 mg ml⁻¹) and the influence of NAC on functional sperm parameters (motility and acrosome reaction) were studied.
ROS levels decreased significantly after 20 min incubation with NAG. This reduction was greater in the high ROS group (>30 000 counts/10⁷ viable sperm at t = 0) than in the low ROS group (<30 000). In addition, a marked dose-dependence of NAC was observed. Concerning sperm function, total sperm motility improved after incubation with NAC, but no significant change was observed with respect to the acrosome reaction.
NAC (at concentrations of 1.0 mg ml⁻¹) significantly reduced ROS in human semen and showed the possibility of improving impaired sperm function. After further testing NAC might be useful for the treatment of male infertility patients.     

Synchronous assay for human sperm capacitation and the acrosome reaction

A synchronous acrosome reaction system was established for human spermatozoa. Seminal plasma is removed from the spermatozoa by centrifugation and the washed spermatozoa are capacitated in a modified BWW medium (without exogenous substrates) containing 35 mg/ml human serum albumin for 3 h at 37 C. Subsequently, 10 microM ionophore A23187 (final concentration) is added, the mixture incubated for 15 min at 37 C and the percent acrosome reaction determined by a modified triple stain technique (trypan blue stain omitted). Since no significant decrease in sperm motility occurs during incubation or after ionophore treatment, a vital stain does not need to be employed, allowing the use of any acrosome detection technique. The average percentage of acrosome-rejected spermatozoa after ionophore treatment (40 +/- 10%) was about 2- to 3-fold higher than that seen without ionophore treatment. Ionophore treatment for 15 min failed to stimulate the acrosome reaction in spermatozoa incubated for less than 3 h. Additionally, the presence of substrates in the BWW medium, higher sperm numbers, increased ionophore concentrations or longer incubation periods did not enhance the induction of the acrosome reaction. Ionomycin, a more specific calcium ionophore than A23187, produced essentially the same results as A23187 but tended to decrease sperm motility. This synchronous acrosome reaction system for human spermatozoa is relatively simple and can be used to study the effect of modulators on capacitation and/or the acrosome reaction.     

The influence of homogenous zona pellucida on human spermatozoa hyperactivation, acrosome reaction and zona binding

The study aimed to evaluate the changes in sperm motion characteristics and the occurrence of hyperactivation among sperm populations after exposure to human zona pellucida. Motile spermatozoa samples were used to evaluate the sperm-zona binding capacity, zona-induced acrosome reaction and changes in sperm motion characteristics. Sperm motion characteristic changes studied included straight line velocity, curvilinear velocity, amplitude of lateral head displacement, straightness and beat cross frequency. Recordings were performed on semen immediately after liquefaction, 3 h capacitation and after exposure to solubilised human zona pellucida. The semen samples were divided into morphology categories, namely six (16 +/- 1.4% normal forms, normal patterns), 31 (8 +/- 1.7% normal forms, G-pattern) and 27 (3 +/- 1.3% normal forms, P-pattern). The Hemizona Indices for the three morphology groups namely normal, G-patterns and P-patterns, were 77 +/- 6%, 61 +/- 5% and 41 +/- 5% respectively (P 相似文献   

Paramagnetic beads coated with Pisum sativum agglutinin bind to human spermatozoa undergoing the acrosome reaction

Summary. For the evaluation of sperm functions it is important to assess the acrosome reaction after induction with various stimuli. Acrosome reaction tests normally include the capacitation of spermatozoa, treatment with an inducer, and detection of acrosomal loss by dyes, lectins or antibodies. Since most of these methods are time-consuming or require expensive equipment, paramagnetic beads coated with Pisum sativum agglutinin (PSA) were investigated for their usefulness in facilitating the detection of human sperm acrosome reaction.
Binding of PSA beads to the acrosomal region increased significantly after incubation of capacitated spermatozoa with 10 μM A23187 (20.3±6.7% [mean±SD, absolute binding], n = 21), 1 mM dibutyryladenosine cyclic monophosphate (17.1±8.5%, n = 25) and 10 mM phorbol myristate acetate (21.1±12.5%, n = 10). Bead binding was significantly reduced by preincubation with a protein kinase inhibitor. Beads bound to Concanavalin A (ConA) were also attached to the acrosomal region after induction of the acrosome reaction by A23187 or dbcAMP, but a lower number of spermatozoa were bound to ConA-beads than to PSA beads. Pre-treatment of spermatozoa with α-methyl-D-mannoside before addition of the PSA beads markedly decreased bead binding, which indicates its mannose-specificity. Electron microscopic examinations demonstrated that PSA beads mainly bound to membrane structures of spermatozoa that were undergoing, but had not completed the acrosome reaction.     

Role of ions and ion channels in capacitation and acrosome reaction of spermatozoa

Capacitation and acrosome reaction are important prerequisites of the fertilization process. Capacitation is a highlycomplex phenomenon occurring in the female genital tract, rendering the spermatozoa capable of binding and fusionwith the oocyte. During capacitation various biochemical and biophysical changes occur in the spermatozoa and thespermatozoal membranes. Ions and ion channels also play important roles in governing the process of capacitation bychanging the fluxes of different ions which in turn controls various characteristics of capacitated spermatozoa. Alongwith the mobilization of ions the generation of free radicals and efflux of cholesterol also plays an impo~.nt role in thecapacitation state of the spermatozoa. The generation of free radical and efflux of cholesterol change the mechano-dynamic properties of the membrane by oxidation of the polyunsaturated lipids and by generating the cholesterol freepatches. The process of capacitation renders the spermatozoa responsive to the inducers of the acrosome reaction. Theglycoprotein zona pellucida 3 (ZP3) of the egg coat zona pellucida is the potent physiological stimulator of the acro-some reaction; progesterone, a major component of the follicular fluid, is also an inducer of the acrosome reaction.The inducers of the acrosome reaction cause the activation of the various ion-channels leading to high influxes of calci-um, sodium and bicarbonate. The efflux of cholesterol during the process of capacitation alters the permeability of themembrane to the ions and generate areas which are prone to fusion and ve.siculation process during the acrosome reactioa. this review focuses mainly on effects of the ion and ion-channels, free radicals, and membrane fluidity changesduring the process of capacitation and acrosome reaction.     

Capacitation and induction of the acrosome reaction in bull spermatozoa with norepinephrine

Identification of norepinephrine (NE) within the microenvironment of the bovine oviduct suggests a potential role for catecholamines in the events surrounding fertilization. Previous studies have shown that the catecholamines capacitate and induce the acrosome reaction in spermatozoa from several species. The current project was undertaken to investigate the role of catecholamines in bovine sperm capacitation and the acrosome reaction. Freshly ejaculated bovine spermatozoa were incubated in NE (0-1000 ng/mL) and induced to acrosome-react with lysophosphatidylcholine (LPC). Additionally, spermatozoa capacitated with heparin were incubated with NE (0-1000 ng/mL) to assess its ability to induce the acrosome-reaction in capacitated spermatozoa. Concentrations of NE were chosen on the basis of physiological concentrations previously determined for bovine oviductal fluid. NE at concentrations of 10 and 20 ng/mL capacitated bovine spermatozoa after 2 hours of incubation. Additionally, spermatozoa incubated for 2 hours with heparin were induced to acrosome-react with 10 and 20 ng/mL NE. Interestingly, higher concentrations of NE inhibited both capacitation and the acrosome reaction. Incubating spermatozoa with dopamine or epinephrine did not result in capacitation or the acrosome reaction, suggesting that the action of NE was specific to that catecholamine. The ability of NE to capacitate or induce the acrosome reaction appears to be dependent on the presence of another membrane-destabilizing factor. Although adrenergic receptors have not been identified on spermatozoa from any species, the action of NE on spermatozoa may be a receptor-mediated event. This study suggests a possible function for oviductal catecholamines in sperm preparation prior to fertilization.     

Can a cumulus cell complex be used to select spermatozoa for assisted reproduction?

Since the onset of intracytoplasmic sperm injection, researchers have intensified the search for the ideal spermatozoa to be used for injection. The aim of this study was to record the functional role of cumulus cell interaction with human spermatozoa as far as capacitation, acrosome reaction, morphology, zona binding and chromatin packaging quality are concerned. Using a previously described cumulus oophorus model, we recorded specific sperm functional aspects of sperm populations that transverse a cumulus cells mass. Control spermatozoa were kept under similar experimental conditions in the culture media only. Results indicated cumulus cells to be beneficial to spermatozoa as far as functional and capacitational events are concerned. The mean percentage of morphologically normal spermatozoa in the control sample was 6.9%, while the spermatozoa that traversed the cumulus oophorus (test) had a significantly higher percentage of normal forms (mean 9.5%; P  ≤   0.01). We observed a decline in the percentage of CMA3-positive spermatozoa when we compared the control population (49.1%) to the test, i.e. 38.4%, ( P  = <0.05), thus implying that the spermatozoa with good chromatin condensation increased during cumulus penetration. Significantly more ( P  ≤   0.01) acrosome-reacted spermatozoa were found in the penetrated spermatozoa (mean 23%) than in the control spermatozoa (mean 11%). The test spermatozoa had a higher zona binding capacity with significantly more ( P  ≤   0.01) tightly bound spermatozoa on the hemizona (61 ± 15) than the control spermatozoa (47 ± 18). In the absence of sophisticated and expensive sperm selection products, the use of a cumulus model to select spermatozoa for intracellular sperm injection seems to be an alternative method.