Percentage Of Acrosome-reacted Spermatozoa Research Articles

Involvement of CATSPER 2 mutation in a familial context of unexplained infertility and fertilization failure associated with hearing loss: a case report

To explore the functional implications of a homozygous CATSPER 2 (cation channel for sperm) deletion within the acrosome reaction pathway during fertilization in 2 brothers, who have unexplained infertility and hearing loss. Case report. Two twin brothers aged 30 years with hearing loss and unexplained infertility. Molecular genetic diagnosis of deafness. Evaluation of the acrosome reaction and calcium mobilization assays after induction by progesterone and ionomycin on spermatozoa of the CATSPER 2-mutated patient and on fertile controls. Fertilization rate during conventional in vitro fertilization. Molecular genetic test. Percentage of acrosome-reacted spermatozoa with peanut agglutinin lectin staining. Recording of progesterone and ionomycin-induced intracellular calcium signals with a fluorescent probe. Mr. S and his brother have normal, conventional sperm parameters. Both brothers have had repeated intrauterine insemination failures and one fertilization failure after conventional in vitro fertilization. Mr. S obtained 2 healthy babies after intracytoplasmic sperm injection. Genetic analysis found a homozygote deletion of the STRC (stereocilin) gene (NM 153700: c.1-? 5328+?del) that removes the CATSPER 2 gene. Mutation of the STRC gene is known to be associated with hearing loss. Sperm functional tests revealed an inability of progesterone to activate intracellular calcium signaling and to induce acrosome reaction. We demonstrate the absence of a calcium signal and acrosome reaction after progesterone in our patient with a CATSPER 2 mutation. We emphasize the importance of the male medical interview and of the genetic investigation of hearing loss. We show that in vitro fertilization-intracytoplasmic sperm injection is necessary, even where normal sperm parameters are present.

Membrane remodulation and hyperactivation are impaired in frozen-thawed sperm of low-fertility bulls

Bulls used in artificial insemination programmes worldwide undergo quality control checks, which are typically based on the evaluation of sperm motility and morphology. Despite this, some bulls can have lower than expected field fertility and the reasons for this remain to be elucidated. Here we hypothesised that sperm from bulls of varying fertility will differ in their ability to undergo capacitation-related events including an increase in membrane fluidity, protein tyrosine phosphorylation, hyperactivation and the acrosome reaction. Firstly, we used frozen-thawed semen from 10 high-fertility (HF) and 10 low-fertility (LF) bulls, and subjected them to in vitro capacitating conditions, following which sperm viability, membrane fluidity, acrosome integrity and protein tyrosine phosphorylation were assessed using flow cytometry. We then assessed the ability of sperm to undergo hyperactivation (induced using caffeine) utilising computer-assisted sperm analysis, and the acrosome reaction (induced using calcium ionophore) using flow cytometry. When sperm were incubated in capacitating conditions, a higher percentage of viable sperm from HF bulls exhibited high membrane fluidity when compared to LF bulls (8.8 ± 0.8% and 5.8 ± 1.2%, respectively; mean ± standard error; P < 0.05). There was no difference between fertility groups in the percentage of acrosome-reacted sperm following the incubation in in vitro capacitating conditions or following the induction of the acrosome reaction using calcium ionophore. However, more sperm from HF bulls became hyperactive in response to caffeine stimulation than sperm from LF bulls (21.6 ± 2.5% versus 14.1 ± 2.4%, respectively; mean ± standard error; P < 0.05). Taken together, sperm from LF bulls had an impaired ability to undergo membrane remodulation and to hyperactivate when induced in vitro. These are key events in the journey of sperm along the female reproductive tract and in the interaction with the oocyte and thus could explain the lower field fertility exhibited by some bulls.

Prolonged exposure of human spermatozoa in polyvinylpyrrolidone has detrimental effects on sperm biological characteristics.

Polyvinylpyrrolidone (PVP) has been utilized in intracytoplasmic sperm injection (ICSI) for immobilization and manipulation of spermatozoa. This study aims to determine the suitable time that sperm cells could be safely exposed to PVP during ICSI procedure. Twenty-five normal semen samples were prepared using the swim-up method and then were exposed to 10% PVP at different time intervals (15, 30 and 60min). The effect of PVP on sperm parameters (viability and morphology), DNA fragmentation index (sperm chromatin dispersion test), chromatin quality (aniline blue, toluidine blue and chromomycin A3 staining), acrosome reaction, mitochondrial membrane potential and sperm ultrastructure was assessed at different time intervals. Our results showed that prolonged sperm exposure in PVP for 15, 30 and 60min significantly affects viability and morphology with a concomitant increase in DNA fragmentation and abnormal chromatin structure, while the percentage of acrosome-reacted spermatozoa was additionally increased. In addition, the spermatozoa with high mitochondrial membrane potential were significantly decreased compared to unexposed spermatozoa to PVP. In conclusion, the detrimental effects of PVP were increased significantly following sperm exposure in PVP after 15min. Therefore, the sperm exposure to PVP should be limited to less than 15min during ICSI procedure.

Seminal antigenicity affects mitochondrial membrane potential and acrosome reaction ability of the spermatozoa during cryopreservation

The objective of this study was to assess the influence of spermatozoa surface antigenic proteins on the functional competence of bovine neat and frozen-thawed semen. The breeding bulls (n = 38) were screened for seminal antigenic levels in neat semen based on the agglutination titrations with anti-sperm antibody (ASA). Bulls having high (n = 8) and low (n = 7) antigenic levels were selected and spermatozoa functional parameters were analyzed in neat and frozen-thawed semen samples. In neat semen, kinematics such as straightness (73.6 ± 1.0 and 66.9 ± 1.5%), linearity (48.6 ± 1.2 and 40.1 ± 3.9%), curvilinear velocity (103.3 ± 2.6 and 93.4 ± 3.8 μm/s), straight-line velocity (65.7 ± 2.6 and 53.7 ± 2.2 μm/s) and average path velocity (53.8 ± 2.5 and 39.8 ± 2.3 μm/s) were significantly high (p < 0.05) in samples with lower antigenicity. The percentage of spermatozoa that can penetrate mucus (49.9 ± 2.3 and 37.1 ± 3.2) was significantly higher in semen samples with low ASAs. The total motile (84.0 ± 2.5 and 86.0 ± 1.5) and progressive motile (68.4 ± 3.7 and 69.2 ± 1.6) spermatozoa were higher in neat semen samples with higher antigenicity. A significantly (p < 0.05) higher mitochondrial membrane potential was observed in neat (82.5 ± 2.8 and 69.0 ± 2.0%) and post-thaw (28 ± 5. 6 and 16 ± 3.7%) samples of the lower antigenic group. The percentage of acrosome-reacted spermatozoa was significantly (p < 0.05) higher in neat (58.7 ± 2.9 and 52.6 ± 1.8), but reduced significantly (p < 0.05) in post-thaw (32.0 ± 2.0 and 48.0 ± 2.6) semen of higher antigenic groups. The study reveals that higher seminal antigenicity reduces mitochondrial membrane potential and acrosome reaction ability in post-thaw spermatozoa.

Sperm cryostorage in a dry tank: An accurate alternative

This prospective study aimed to determine the effects of dry nitrogen cryostorage on human sperm characteristics in comparison with liquid nitrogen cryostorage. For this purpose, 42 men undergoing routine semen analysis (21 normozoospermia and 21 with altered semen parameters) were analyzed. After slow freezing, half of the straws of each sample were randomly stored in liquid and dry tanks, at the top and bottom levels of the latter. After 6 months storage, thawed samples were treated by density gradient centrifugation and sperm characteristics were compared. There was no difference in sperm progressive motility (15.1% ± 14.2% vs. 15.1% ± 12.7%; p = 0.76), sperm vitality (25.5% ± 17.7% vs. 26.2% ± 19%; p = 0.71), percentages of acrosome-reacted spermatozoa (38% ± 8.5% vs. 38.5% ± 7.4%; p = 0.53) and DNA fragmentation spermatozoa (27.3% ± 12.4% vs. 28.5% ± 12.9%, p = 0.47) after cryostorage in the dry or the liquid nitrogen tank. Moreover, we did not observe differences between either cryostorage system for normal and altered sperm samples. This lack of difference was also observed whatever the floor level of cryostorage in the dry tank. The temperature measurement of the dry tank showed a stable temperature at −194 °C throughout storage whatever the storage floor level, guaranteeing the stability of the low temperatures suitable for human sperm storage. Because of its greater safety, dry storage without contact with the liquid phase should be preferred and can be a useful alternative for the cryostorage of human sperm samples.

Fluorescent analysis of boar sperm capacitation process in vitro

BackgroundCapacitation involves physiological changes that spermatozoa must undergo in the female reproductive tract or in vitro to obtain the ability to bind, penetrate and fertilize the egg. Up to date, several methods have been developed to characterize this complex biological process. The goal of the presented study is to mutually compare several fluorescent techniques, check their ability to detect changes in molecular processes during the capacitation progress and determine their ability to predict the percentage of acrosome reacted (AR) sperm after the exposure to solubilized zona pellucida (ZP). The capacitation process was analyzed using four fluorescent techniques: 1. chlortetracycline (CTC) staining, 2. anti-acrosin antibody (ACR.2) assay, 3. anti-phosphotyrosine (pY) antibody assay, 4. fluorescein isothiocyanate-conjugated phalloidin (FITC-phall) assay. All these methods were tested using fluorescent microscopy and flow cytometry.ResultsAll selected methods are capable to detect the capacitation progress of boar sperm in vitro, but there are significant differences in their outcome when using fluorescent microscopy or flow cytometry experimental arrangements and subsequent statistical analysis (KW-ANOVA). Also, the ability to predict the absolute numbers of sperm which will undergo ZP-induced AR differ significantly (CTC and ACR.2 gave the best predictions).ConclusionsOur study compared four largely used methods used to characterize capacitation process, highlighted their differences and showed that all are able to detect capacitation progress, CTC and ACR.2 are furthermore able to accurately predict the percentage of AR sperm after ZP-induced AR.

Regulation of boar sperm functionality by the nitric oxide synthase/nitric oxide system

PurposeNitric oxide (NO) is a free radical synthesized mainly by nitric oxide synthases (NOSs). NO regulates many aspects in sperm physiology in different species. However, in vitro studies investigating NOS distribution, and how NO influences sperm capacitation and fertilization (IVF) in porcine, have been lacking. Therefore, our study aimed to clarify these aspects.MethodsTwo main experiments were conducted: (i) boar spermatozoa were capacitated in the presence/absence of S-nitrosoglutathione (GSNO), a NO donor, and two NOS inhibitors, NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) and aminoguanidine hemisulfate salt (AG), and (ii) IVF was performed in the presence or not of these supplements, but neither the oocytes nor the sperm were previously incubated in the supplemented media.ResultsOur results suggest that NOS distribution could be connected to pathways which lead to capacitation. Treatments showed significant differences after 30 min of incubation, compared to time zero in almost all motility parameters (P < 0.05). When NOSs were inhibited, three protein kinase A (PKA) substrates (~ 75, ~ 55, and ~50 kDa) showed lower phosphorylation levels between treatments (P < 0.05). No differences were observed in total tyrosine phosphorylation levels evaluated by Western blotting nor in situ. The percentage of acrosome-reacted sperm and phosphatidylserine translocation was significantly lower with L-NAME. Both inhibitors reduced sperm intracellular calcium concentration and IVF parameters, but L-NAME impaired sperm ability to penetrate denuded oocytes.ConclusionsThese findings point out to the importance of both sperm and cumulus-oocyte-derived NO in the IVF outcome in porcine.

The Effect of Density Gradient Centrifugation and Magnetic-Activated Cell Sorting with the Combination of Both on Bovine Spermatozoa Kinematics, Viability and Acrosome Status

Conventional and novel spermatozoa separation techniques have their own strength and weaknesses. Both are widely used in assisted reproductive technologies (ARTs). In this study, combinations of two separation methods against single separation methods were evaluated. Freshly ejaculated semen was collected and divided into five groups; control, density gradient centrifugation (DGC), magnetic activated cell sorting (MACS), DGC-MACS and MACS-DGC; based on the sequence of separation. Evaluation of spermatozoa kinematics, viability and acrosome status for each group were done by computer assisted semen analysis (CASA), hypo-osmotic swelling test (HOST) and chlorotetracycline (CTC) staining respectively. Results show that DGC yield the fastest spermatozoa velocity and highest percentage of viable spermatozoa fraction compared to other groups. However, they also produced a high percentage of acrosome-reacted spermatozoa. Spermatozoa isolated through DGC-MACS shows the highest percentage of non-capacitated spermatozoa. However, spermatozoa isolated through DGC-MACS yields slower spermatozoa velocity population and lower percentage of viable sperm compared to spermatozoa isolated through DGC. Isolation of spermatozoa through MACS-DGC yields slower population of spermatozoa velocity with a lower percentage of non-capacitated spermatozoa compared to spermatozoa isolated through DGC-MACS. DGC separation and its combination with MACS had yield different spermatozoa quality. This distinct characteristic is likely suitable for in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) procedure respectively.

Sperm-bound antisperm antibodies prevent capacitation of bovine spermatozoa

It was hypothesized here that sperm-bound antisperm antibodies (ASAs) impair the ability of bovine spermatozoa to undergo capacitation, bind to the zona pellucida, and complete the acrosome reaction. The effect of ASA binding on these functions was evaluated in frozen/thawed spermatozoa from four bulls before and after induction of ASAs. Ejaculates were divided into ASA negative (<10% immunoglobulin [Ig]G- and IgA-bound spermatozoa) or ASA positive (≥20% IgG and/or IgA-bound spermatozoa). The percentage of capacitated (Merocyanine 540 positive) live spermatozoa in response to heparin was lower in ASA-positive than ASA-negative ejaculates (P < 0.0001). Treatment with heparin resulted in a higher percentage of capacitated spermatozoa compared with control treatments in ASA-negative but not ASA-positive ejaculates. The percentage of capacitated spermatozoa after heparin treatment was negatively correlated with IgA (P = 0.02, R2 = −0.48) but not IgG binding. Sperm binding to the zona pellucida was lower in IgA-positive (six spermatozoa/oocyte; 3–10 spermatozoa/oocyte) than IgA-negative ejaculates (seven spermatozoa/oocyte; 4–13 spermatozoa/oocyte) (P = 0.019). Zona binding was negatively correlated with the percentage of IgA-bound spermatozoa (P = 0.04; R2 = −0.24) but not IgG-bound spermatozoa. The percentage of acrosome-reacted spermatozoa was higher in calcium ionophore A23187-treated than control aliquots in both ASA-negative and ASA-positive ejaculates (P < 0.0001). However, the percentage of acrosome-reacted spermatozoa did not differ between ASA-positive and ASA-negative samples, and no correlation was identified with IgG or IgA binding. It was concluded that sperm-bound IgA affected the ability of bovine spermatozoa to undergo capacitation. ASAs inhibited the changes in plasma membrane fluidity associated with capacitation and binding of spermatozoa to the zona pellucida.

145 EFFECT OF RELAXIN ON FERTILIZING ABILITY OF BUFFALO SPERM

The aim of this work was to evaluate the effect of relaxin, known to improve fertility parameters of frozen-thawed sperm in other species (Miah et al. 2006 J. Reprod. Dev. 52, 773–779; Miah et al. 2007 Anim. Sci. J. 78, 495–502), on buffalo sperm motility, capacitation, and fertilizing capability. Frozen-thawed sperm from 2 bulls (4 replicates each) were separated by Percoll, diluted to a 20 × 106 mL–1 concentration and incubated in TALP medium in the absence of capacitating agents (negative control), in the presence of 10 μg mL–1 of heparin (positive control) and 100 ng mL–1 of relaxin for 2 h. Following incubation, sperm were exposed for 15 min to 60 mg mL–1 of lysophosphatidylcholine, a fusogenic agent known to induce the acrosome reaction only on capacitated sperm. To evaluate acrosome-reacted (AR) live sperm, cells were fixed and stained with Trypan blue-Giemsa (Kovacs and Foote 1992 Biotech. Histochem. 67, 119–124) and evaluated (800 sperm counted/group). Sperm motility was examined by a phase contrast microscope, whereas the fertilizing capability was evaluated by heterologous IVF. Abattoir-derived bovine oocytes (n = 258, 86 per group) were in vitro matured and fertilized according to standard procedures (Rubessa et al. 2011 Theriogenology 76, 1347–1355) with buffalo sperm in the absence of capacitating agents and in the presence of 10 μg mL–1 of heparin and 100 ng mL–1 of relaxin. Twenty hours after IVF, presumptive zygotes were denuded and cultured in SOF for 24 h, when cleavage rate was evaluated and confirmed by fixation with absolute ethanol overnight and staining with 2.5 μg mL–1 of Hoechst 33342 after zona removal by pronase (2 mg mL–1) digestion. The differences in the percentages of AR sperm and cleavage among groups were analysed by a chi square test and those in sperm motility by Student's t-test. Acrosomal loss was observed in 10.8% of the sperm after thawing, which may indicate freezing-induced capacitation, and, hence, this value was detracted from the percentages of AR recorded following incubation. After 2 h of incubation, 100 ng mL–1 of relaxin significantly (P &lt; 0.05) increased the percentages of live AR sperm (P &lt; 0.05) compared with the negative control (31.3 ± 2.2 and 25.8 ± 2.8, respectively), with intermediate results in the positive control (27.0 ± 2.2). Motility was significantly improved (P &lt; 0.05) when sperm were exposed to 100 ng mL–1 of relaxin compared with both the negative and positive control (73.7 ± 2.4, 60.0 ± 4.1, and 60.0 ± 7.1, respectively). A significant (P &lt; 0.05) improvement of cleavage rate was recorded both in the positive control (71.5 ± 4.8) and in the group treated with 100 ng mL–1 of relaxin (70.7 ± 0.5) compared with negative control (52.1 ± 1.5). In conclusion, these preliminary results indicate that relaxin at the concentration of 100 ng mL–1 improves sperm motility, capacitation, and the IVF capability of buffalo sperm.

Estudio de los daños estructurales tras la inmovilización espermática previa a la microinyección intracitoplasmática de espermatozoides en sujetos teratozoospérmicos

ObjectiveTo describe and compare the ultrastructural alterations, DNA fragmentation and acrosome status that could cause sperm immobilisation prior to intracytoplasmic sperm injection, in samples from normozoospermic and teratozoospermic males. Material and methodsFor this study we used 15 sperm samples from consenting normozoospermic donors and 20 samples from teratozoospermic males, submitted for assisted reproduction at Instituto Bernabeu of Alicante. To assess the ultrastructural alterations induced by immobilisation, human oocytes were used as containers for spermatozoa and then observed by transmission electron microscopy. DNA fragmentation was assessed using TUNEL and acrosome status using fluorescein isothiocyanate-conjugated Pisum sativum agglutinin. The control group consisted of sperm without manipulation. Statistical analysis between groups was performed by ANOVA. ResultsThe results showed that immobilised spermatozoa presented the same damage in plasma and acrosomal membranes in the samples from both normozoospermic and teratozoospermic subjects. After assessing DNA fragmentation in the cells from normozoospermic and teratozoospermic patients by the TUNEL technique, we observed that the percentage of spermatozoa with DNA fragmentation did not increase in the immobilised group compared with the control group. However, the percentage of acrosome-reacted sperm was significantly greater in immobilised spermatozoa than in the control group in both normozoospermic and teratozoospermic males. ConclusionThe results of this study show that the structural damage caused by immobilisation in spermatozoa from teratozoospermic and normozoospermic males is independent of sperm morphology. In addition, the immobilisation does not cause DNA fragmentation. However, the percentage of acrosome-reacted sperm was greater in the immobilised group than in the control group, in both normozoospermic and teratozoospermic subjects.

In vitro induction of the acrosome reaction in spermatozoa from endangered Spanish bulls: Effect of breed, culture media and incubation time

Current conservation programs for endangered species have been widely benefited from the use of modern assisted reproductive techniques. However, at the present time, there is little information available regarding the use of locally adapted cattle breeds on IVF programs, and even less about their sperm behavior. The aims of this study were to (1) evaluate standard acrosome reaction (AR) protocols in cryopreserved semen doses of Andalusian endangered cattle breeds, and (2) investigate the effect of breed, culture medium supplementation and incubation time on AR test results. To this end, 80 frozen semen doses from 16 bulls (5 semen samples per bull) of five different cattle breeds (3 Berrendo en Colorado, 6 Berrendo en Negro, 2 Cardena Andaluza, 1 Pajuna and 4 Retinta) were in vitro incubated in three test media (Heparin, BSA or their combination), using Sp-TALP as a control, to induce in vitro AR. The percentage of acrosome-reacted spermatozoa was evaluated using fluorescence techniques (FITC-PNA and Propidium Iodide) at four time-points (0, 30, 60 or 120min.). Throughout the whole experiment, spermatozoa incubated with a combination of both supplements (Heparin and BSA) showed significantly (P<0.05) higher results than those processed with Heparin or BSA alone. In contrast, the control media (without supplementation) showed the lowest results. We also found a significant (P<0.05) influence of cattle breed on the dynamics of the in vitro induced AR using different protocols. Based on our results, we can conclude that the response pattern of in vitro induced AR depends not only on culture media and incubation time but also on the cattle breed. Therefore, all these factors must be taken in consideration to assess the rate of AR sperm in bulls.

Effect of Eurycoma longifolia Jack (Tongkat ali) extract on human spermatozoa in vitro

Eurycoma longifolia (Tongkat ali; TA) is a Malaysian shrub used to treat various illnesses including male infertility. Considering that TA is used to improve male fertility and no report regarding its safety has been published, this study investigated the effects of TA extract on various sperm functions. Semen samples of 27 patients and 13 donors were divided into two groups, washed and swim-up spermatozoa, and incubated with different concentrations of TA (1, 10, 20, 100, 2000μgml(-1) ) for 1h at 37°C. A sample without addition of TA served as control. For washed spermatozoa, significant dose-dependent trends were found for vitality, total motility, acrosome reaction and reactive oxygen species-positive spermatozoa. However, these trends were only significant if the highest concentrations were included in the calculation. Contrary, the increase in the percentage of acrosome-reacted spermatozoa with increasing TA concentrations is very significant (P<0.0001), and a significant difference (P=0.0069) to the control could even be recorded at 20μg TA per ml. For swim-up spermatozoa, no trend could be observed. Results indicate that the TA extract has no deleterious effects on sperm functions at therapeutically used concentrations (<2.5μgml(-1) ). However, at very high concentrations, TA may have harmful effects in vitro.

Effects of anti-lipid peroxidases on frozen-thawed boar spermatozoa

This study evaluated the effects of anti-lipid peroxidases when supplemented to the thawing and incubation media of frozen-thawed boar spermatozoa. Semen pellets were thawed and incubated in media with 1.0 mM α-tocopherol or diethylenetriamine. After 1 h, the acrosome reaction was induced using calcium ionophore A23187, and acrosomes were evaluated using Wells--Awa staining. The number of spermatozoa with fragmented DNA was evaluated using silver staining after single-cell gel electrophoresis. Membrane lipid peroxidation was measured by the end point generation of malondialdehyde. The diethylenetriamine-supplemented media had a higher (P < 0.05) percentage of acrosome-reacted spermatozoa (84.4 ± 4.1%) compared to the control (78.3 ± 4.2%) and α-tocopherol-supplemented (78.0 ± 3.9%). The control had a higher (P < 0.05) percentage of spermatozoa with fragmented DNA (59.3 ± 4.3%) compared to the DETA (28.7 ± 4.1%) and α-tocopherol supplementation (28.0 ± 3.8%). Spermatozoa supplemented with diethylenetriamine had higher amounts (P < 0.05) of malondialdehyde generated (3.60 ± 0.05 μM/10(7) cells) compared to the α-tocopherol supplementation (0.14 ± 0.05 μM/10(7) cells) and the control (0.12 ± 0.05 μM/10(7) cells). These results indicate that supplementing with either 1.0 mM diethylenetriamine or α-tocopherol during semen thawing and incubation protects against DNA fragmentation, and diethylenetriamine increases the percent of spermatozoa capable of completing the acrosome reaction that could induce membrane lipid peroxidation.

311 MELATONIN PROMOTES IN VITRO SPERM CAPACITATION IN BUFFALO (BUBALUS BUBALIS)

Melatonin, the main hormone secreted by the pineal gland, plays many roles in reproduction. In ram spermatozoa, melatonin administration increases plasminogen activator activity (Tsantarliotou MP et al. 2007 Theriogenology 69, 458-465), known to be involved in sperm capacitation and acrosome reaction (Taitzoglou IA et al. 1996 Mol. Androl. 8, 187-197). The aim of this study was to evaluate the efficiency of melatonin to induce buffalo in vitro sperm capacitation, indirectly assessed by estimating the capability of spermatozoa to acrosome-react. Frozen-thawed semen from 4 different bulls was pooled and treated by swim-up in order to select only the motile population. Spermatozoa (n = 829) were assessed immediately after swim- up separation, to evaluate the incidence of acrosomal loss in non-treated cells (time 0). The remaining spermatozoa were incubated in the absence of capacitating agents (negative control; n = 513), in the presence of 0.01 mM heparin (positive control; n = 775), 10 μM melatonin (n = 684), 100 μM melatonin (n = 751), and 1 mM melatonin (n = 650), for 2 h. Sperm were then exposed for 15 min to 60 μg mL-1 of lysophosphatidylcholine, an agent known to induce acrosome reaction (AR) only on capacitated spermatozoa. Trypan blue was used first to differentiate live from dead spermatozoa and the dried smears were then fixed in 37% formaldehyde and stained with Giemsa for acrosome evaluation by microscopic examination. The percentage of acrosome-reacted spermatozoa in each group was used to assess the efficiency of capacitation under different incubation conditions. The experiment was repeated 4 times. Differences among groups were analyzed by chi-square test. Acrosomal loss was observed only in 2.1% of the sperm population at time 0. Interestingly, sperm treatment with both heparin and the different concentrations of melatonin resulted in a significantly higher incidence of AR compared to the negative control (24.4, 20.5, 20.0, 23.6 v. 8.0% for the positive control, 10 μM melatonin, 100 μM melatonin, 1 mM melatonin, and the negative control, respectively; P &lt; 0.01). These results demonstrated that melatonin determines capacitation of buffalo spermatozoa in vitro. Furthermore, the effect of melatonin was comparable to that of heparin, that is, the capacitating agent currently used in the IVF system. The capacitating effect was observed at all the tested concentrations, and viability was not affected. This suggests to extend the range of concentrations to test in future studies, in order to identify the optimal dose. Moreover, considering the seasonality of the species and the great differences in fertility attitude of buffalo bulls, it would be interesting to investigate the capacitation effect of melatonin in relation to both the season and the bull.

322 EFFECT OF PLASMIN ON ACROSOME REACTION OF BUFFALO (BUBALUS BUBALIS) SPERMATOZOA IN VITRO

Fertilization is a critical step of the in vitro embryo production (IVEP) technology in buffalo. It is known that proteolytic enzymes are involved in different steps of the fertilization process; among these, a critical role may be played by the plasminogen activator-plasmin system. It has been demonstrated that plasmin, the active enzyme of this system, induces acrosome reaction (AR) in bull spermatozoa (Taitzoglou IA et al. 2003 Andrologia 35, 112-116). The aim of this study was to investigate the effect of plasmin on the ability of buffalo sperm to undergo the AR. Frozen- thawed sperm from 4 buffalo bulls were treated by swim-up and incubated with 0.01 mM heparin for 4 h. At 0, 2, and 4 h, aliquots of spermatozoa were exposed for 10 min to 60 μg mL-1 of lysophosphatidylcholine (LPC), as positive control, and to 0.01 μg mL-1 of plasmin. This concentration was chosen after a preliminary dose-response trial. Another sample from each treatment was incubated with IVF medium (negative control). After 10 min, sperm motility was evaluated and sperm were fixed in 37% formaldehyde and stained with trypan blue-Giemsa for subsequent microscopic examination. The total number of sperm counted, over 3 replicates, was 1269 for the negative control, 1293 for LPC, and 1238 for plasmin, equally distributed among incubation times. Differences among groups were analyzed by chi-square test. After swim-up, acrosomal loss was observed only in 4% of the sperm. The addition of 0.01 μg mL-1 of plasmin for 10 min to buffalo spermatozoa at time 0 significantly (P &lt; 0.01) enhanced (23%) AR compared with the control (7.8%), with the same efficiency of LPC (17.1%). After 2 h of incubation with heparin, both plasmin and LPC increased the AR compared to the control (24.4, 20.1, and 14.0%, respectively; P &lt; 0.01). After 4 h, plasmin gave higher percentages of AR (27.2%) compared to both the control (21.0%; P &lt; 0.05) and LPC (19.2%; P &lt; 0.01). Another interesting result is the improved motility recorded with plasmin compared to both the control and LPC groups at 2 h of incubation (90, 75, and 75%, respectively; P &lt; 0.05) and at 4 h of incubation (75, 60, and 60%, respectively; P &lt; 0.05). Finally, no differences in sperm viability were observed between plasmin and the control, whereas a decreased viability was found when LPC was used at 0 h (96.2, 95.0, and 89.0%, respectively, for plasmin, control, and LPC; P &lt; 0.05), at 2 h (85.0, 87.5, and 77.0%, respectively, for plasmin, control, and LPC; P &lt; 0.01), and at 4 h (85.0, 93.3, and 81.1%, respectively, for plasmin, control, and LPC; P &lt; 0.01). In conclusion, we found that addition of plasmin to capacitated sperm increases the percentage of acrosome-reacted spermatozoa and improves motility. Our results suggest that plasmin may play a role in events surrounding fertilization and suggest to evaluate in further studies whether the addition of plasmin during IVF improves the IVEP efficiency in buffalo.

Pentoxifylline increases sperm penetration into zona-free hamster oocytes without increasing the acrosome reaction.

Several drugs have been used to stimulate human sperm motility, including 3-deoxy-adenosine, caffeine, and pentoxifylline. Pentoxifylline is an inhibitor of the phosphodiesterase and may stimulate sperm motility by increasing the intracellular levels of cAMP. In this study we have evaluated the effect of pentoxifylline in the outcome of the sperm penetration assay into zona-free hamster oocytes. Twenty-seven semen samples, obtained for diagnostic purposes, were used. After the motile sperm were selected by the swim-up technique, the samples were divided into two aliquots. One aliquot was incubated with 1 mg ml-1 of pentoxifylline at 37 degrees C, 5% CO2 for 30 min. The control aliquot was incubated with culture medium. The samples were then washed and resuspended in fresh, pentoxifylline-free medium, at a sperm concentration of 10 x 10(6) cells ml-1. One hundred microlitres of each sperm suspension was then deposited under oil and 30-40 zona-free hamster oocytes were added. After 6 h of gamete coincubation, the percentage of penetrated oocytes and the number of decondensed sperm heads were evaluated. The percentage of acrosome-reacted sperm was evaluated using the Pisum sativum lectin. The percentage of zona-free hamster oocytes penetrated was increased after pentoxifylline-treatment. The percentage of acrosome reacted sperm and the number of decondensed sperm heads per egg were not different between the control and the pentoxifylline-treated groups. The results suggest that the beneficial effect of pentoxifylline upon the sperm cells is not mediated by stimulation of the acrosome reaction.

Sperm ecto‐protein kinase and its protein substrate: Novel regulators of membrane fusion during acrosome reaction

Previously we have purified and characterized a unique plasma membrane-specific cyclic AMP-independent ecto-protein kinase (ecto-CIK) as well as its ecto-phosphoprotein substrate (MPS) using caprine sperm model. This study reports for the first time the role of the sperm external surface protein phosphorylation system on sperm acrosome reaction, which is essential for fertilization. Calcium ionophore A23187 has been used to trigger the sperm acrosome reaction in vitro. Treatment of sperm cells with CIK antibody (dil: 1:500) causes a significant decrease (approx. 50%) in percentage of acrosome reacted sperm. Onset of the acrosome reaction causes a remarkable increase in the rate of acrosin release from the cells in the medium. However, CIK antibody inhibits significantly (approx. 50%) the acrosin release. The level of membrane-bound MPS as estimated by ELISA and the degree of its phosphorylation catalyzed by the endogenous ecto-CIK, increase significantly with the progress of the acrosome reaction. Both the parameters increase by approximately 100% during the 20 min of the reaction. MPS antibody (1:100 dilution) markedly decreases (approx. 75%) percentage of acrosome-reacted sperm. MPS antibody as well shows high efficacy to inhibit acrosin release from spermatozoa. The results demonstrate that the cell-surface protein kinase and its protein substrate are essential for membrane fusion component of acrosome reaction. The data are consistent with the view that MPS regulates acrosomal membrane fusion with the overlying plasma membrane by the mechanism of its phosphorylation and dephosphorylation.

Effect of bull on in vitro sperm capacitation induced by different agents in buffalo species (Bubalus bubalis)

The aim of this work was to evaluate the effect of bull on the efficacy of different capacitating agents in buffalo. Spermatozoa derived from 4 different bulls were incubated in absence of a capacitating agent, in presence of 0.01 mM heparin and in 20% buffalo estrous serum (BES) for 2 hours Sperm were then exposed to lysophosphatidylcholine, an agent that induces acrosome reaction only on capacitated spermatozoa A double staining technique with Trypan-blue/Giemsa was used to evaluate viability and acrosome status of spermatozoa fixed in 37% formaldehyde. The efficiency of capacitation was evaluated by assessing the percentage of acrosome-reacted (AR) spermatozoa in the treated groups. A bull effect on sperm capacitation in vitro was demonstrated, as indicated by differences in the percentage of AR sperm among bulls regardless of the treatment. In particular when heparin was used as capacitating agent bull C gave higher percentages of AR sperm than bull A (22.7 vs. 14.0%, respectively) with intermediate values for bulls B and D (16.7 and 19.1%, respectively), whereas when BES was used bull D was the most efficient one (22.1, 21.9, 25.0, and 35.0% for bulls A, B, C and D, respectively).

Reduction of Oxidative Stress in Bovine Spermatozoa During Flow Cytometric Sorting

The goal of the study was to investigate the effect of antioxidant supplementation on the quality of frozen-thawed flow cytometrically sorted bull spermatozoa. Twelve ejaculates from two Holstein Friesian bulls were sorted according to the Beltsville Sperm Sexing Technology. Each ejaculate was divided into three parts and processed as (i) unsorted controls, (ii) according to a standard sorting protocol and (iii) in the presence of different antioxidants (S-AO). Cooling and freezing of the samples were performed in the same way for all three groups, except that antioxidants were added to the TRIS-egg-yolk freezing extender for those semen samples that were already sorted in the presence of antioxidants. The semen quality in frozen-thawed samples was determined by morphology analysis immediately after thawing, motility estimation in a thermo-resistance test after 0, 6, 12 and 24 h incubation at 37 degrees C and Fluorescein isothiocyanate conjugated PNA/propidium iodide (FITC-PNA/PI) staining after 0, 12 and 24 h of incubation at 37 degrees C. There was a significantly higher (p < 0.05) percentage of motile spermatozoa in S-AO samples in comparison to unsorted frozen-thawed control at 0, 6 and 24 h after thawing and compared with normally sorted samples at all times after thawing. The percentage of damaged acrosomes was significantly lower (p < 0.05) in S-AO samples than in the unsorted controls (20.8 +/- 6.9% vs 30.3 +/- 12.0%). The percentage of morphologically abnormal spermatozoa in this group was significantly lower (p < 0.05) than in the unsorted controls and normally sorted samples (25.8 +/- 5.2%, 36.0 +/- 12.5% and 35.1 +/- 7.4%, respectively). Analysis of frozen-thawed spermatozoa with FITC/PI revealed no significant difference in membrane integrity at 0 and 12 h after sorting, but after 24 h of incubation the S-AO samples had a significantly higher (p < 0.001) percentage of spermatozoa with intact membranes in comparison to unsorted controls and normally sorted semen (40.7 +/- 6.3%, 7.8 +/- 4.7% and 7.4 +/- 4.6%, respectively). The percentage of acrosome-reacted spermatozoa was significantly lower (p < 0.05) in the S-AO samples than in the unsorted controls (14.1 +/- 7.5%, 23.4 +/- 5.4% and 28.8 +/- 6.3% vs 25.9 +/- 14.4%, 38.5 +/- 16.7% and 79.8 +/- 4.1%, for 0, 12 and 24 h after thawing, respectively) and in comparison to normally sorted semen 24 h after thawing (67.3 +/- 10.0%). This study demonstrates the highly protective effects of antioxidants on the quality of flow cytometrically sorted frozen-thawed bull spermatozoa.