Ejaculated compared with epididymal stallion sperm vitrification

The aim of this study was to evaluate the effect of trehalose and lactose extenders on ejaculated and epididymal stallion sperm vitrification. Ejaculated semen samples were collected from seven fertile stallions, and cauda epididymis samples were collected from ten stallion carcasses after slaughter. Both the ejaculated and the epididymis samples were diluted and vitrified using INRA 96® and bovine serum albumin as well as trehalose or lactose. As a control, ejaculated and epididymal samples were collected and frozen using the conventional method. Vitrification was performed by immersing sperm suspensions directly in LN2. After thawing or devitrification, there was assessment of samples for sperm motility using computer-assisted analysis. Viability was assessed using SYBR-14 and propidium iodide (PI) and acrosome integrity by fluorescein using isothiocyanate combined with peanut agglutinin (FITC-PNA) and PI. Epididymal sperm vitrification with trehalose (EPT) or lactose (EPL) resulted in greater progressive sperm motility than sperm of the control sample (EPC). After post-thaw/devitrification of sperm in the EPT group, sperm motility was greater (P<0.001) compared to that using EPL (50.72 ± 5.09% compared with 34.21 ± 3.02%). The results from assessment of ejaculated sperm samples after undergoing the vitrification process indicated cells were less viable (P<0.001) than the control (EJC) sample. In conclusion, vitrification of epididymal stallion sperm using trehalose might be a beneficial alternative for the long-term storage of sperm samples with great economic value. Spermatozoa from vitrified ejaculates of stallions, however, had lesser motility and viability rates than samples subjected to conventional freezing.

Antioxidant effect of lemon balm (Melissa officinalis) and mate tea (Ilex paraguensys) on quality, lipid peroxidation and DNA oxidation of cryopreserved boar epididymal spermatozoa

In this study, we investigated the protective ability of the addition of two antioxidant herb extracts, mate tea and lemon balm, on boar epididymal frozen-thawed spermatozoa quality. Testes from mature boars were collected at local slaughterhouse, and sperm samples from epididymis were recovered by flushing. Spermatozoa were cryopreserved in lactose-egg yolk buffer supplemented with various concentrations of lemon balm and mate tea (0, 2.5, 5 and 10 g l(-1) ) using the straw-freezing procedure. Motion parameters, acrosome and plasma membrane integrity, lipoperoxidation levels and DNA oxidative damage (8-hydroxy-2'-deoxyguanosine base lesion) were evaluated. There were no differences among experimental groups with regard to motility characteristics, viability, acrosome and plasma membrane integrity; however, the highest concentration of lemon balm produced significant (P < 0.05) improvement in curvilinear trajectory, straightness and amplitude of lateral head displacement after thawing. The supplementation of freezing extender with mate tea and lemon balm reduced sperm lipid membrane peroxidation, and only mate tea protected DNA against oxidative damage during cryopreservation at 120 min post-thawing (P < 0.05). Mate tea experimental extender at concentration of 10 g l(-1) showed the lowest percentage of sperm oxidised DNA and malondialdehyde generation; thus, mate tea is a potential candidate such as antioxidant compound on boar sperm cryopreservation medium.

Cryopreservation of epididymal stallion sperm

Any event that makes semen collection or mating impossible, such as death, castration, or injury, may terminate a stallion's breeding career. Fortunately, stallion sperm which are capable of fertilization can be harvested from the epididymis, and frozen for future use. However, the fertility of frozen-thawed epididymal sperm has been found to be lower than that of ejaculated sperm. Therefore, this study aimed to optimize the fertility of frozen epididymal stallion sperm by investigating the effects of different cryoprotectants and freezing protocols on sperm quality. Dimethylformamide was tested alone or combination with pasteurized egg yolk as substitute of fresh egg yolk. In addition, the effect of the pre-freeze stabilization on sperm quality was analyzed. Heterospermic samples obtained from stallion epididymis were collected and cryopreserved in lactose-egg-yolk extender or in the same extender with varying content of cryoprotectant and content of egg yolk, stabilized and no-stabilized. Sperm motility, viability, hypoosmotic swelling test (HOST) and acrosome integrity were evaluated post-thawing. No improvement was observed on the replacement of fresh yolk by pasteurized egg yolk, whereas the results suggest that dimethylformamide is a cryoprotectant suitable for cryopreservation of equine epididymal semen, even better than glycerol. In addition, we found that the stabilization before freezing on epididymal stallion sperm, can improve sperm quality parameters.

244 PROTEIN TYROSINE PHOSPHORYLATION PATTERN OF SPERM BOUND TO THE PORCINE OVIDUCT DURING THE PERIOVULATION STAGE

The interaction of spermatozoa and oviductal epithelial cells (OEC) is a controlled process that regulates sperm capacitation and the acquisition of fertilizing ability until the time of ovulation. A crucial signalling event involved in capacitation is protein tyrosine phosphorylation. In previous studies, we have demonstrated changes in the pattern of protein tyrosine phosphorylation in boar sperm after the co-culture with OEC. The aim of this study was to characterise the pattern of protein tyrosine phosphorylation in boar sperm bound or unbound to the oviduct of the sow during the periovulation stage. Eight crossbred multiparous sows were inseminated with 3 × 109 sperm. The animals were anesthetized and laparotomies were performed at 36 h after insemination. Ovaries and oviducts were exposed through a midventral incision for collection. Each oviduct was divided into four parts: the ampulla, ampullary-isthmic junction, isthmus, and utero-tubal junction. All segments of the oviduct were flushed to recover spermatozoa, which were subsequently fixed. Tissue obtained from each of the oviduct segments were fixed and embedded in a paraffin block. Sections were mounted on poly-l-lysine-coated slides and deparaffinized. Flushed sperm and oviductal sections were analysed by indirect immunofluorescence using monoclonal antiphosphotyrosine antibodies. Three different sperm subpopulations were determined according to the distribution of protein tyrosine phosphorylation observed: nonphosphorylated spermatozoa (pattern 1), subequatorial segment or subequatorial segment and flagellum phosphorylation (pattern 2), and subequatorial segment and head or flagellum phosphorylation, or both (pattern 3). Data were analysed with SPSS (IBM, Armonk, NY, USA) using one-way ANOVA. After flushing, most sperm were recovered from the utero-tubal junction segment of the oviduct, and sperm exhibited a higher proportion of pattern 2 (81.62%). Unbound sperm showed a high level of protein tyrosine phosphorylation in the subequatorial segment, head and flagellum in the isthmus (32.34%), ampullary-isthmic junction (37.70%), or ampulla region (35.11%; P < 0.05). Very few sperm were attached to OEC, and sperm oviduct binding was mainly found in the isthmus region. The most common tyrosine phosphorylation distribution observed in sperm attached to OEC was pattern 1 (84.21%), although labelling to the subequatorial segment was also observed. Our results showed that only sperm that did not display tyrosine phosphorylation on the sperm acrosome region (head) were found bound to OEC. In conclusion, distinct protein tyrosine phosphorylation patterns were found on sperm bound to OEC. This interaction could be used as a tool for selecting a population of sperm containing low levels of tyrosine phosphorylation.

Crystallisation pattern of vestibular mucus and its relation to vestibular electrical resistance in cycling sow

Changes in the genital mucus around the oestrus are used by different diagnostic methods to determine optimal fertilisation time. In the current study, the authors evaluated the different arborisation patterns found in vestibular mucus, and also established its relationship with vestibular resistance changes during oestrus. Thirty multiparous sows were checked by transrectal ultrasonography to determine ovulation time every 12 hours. Vestibular resistance was measured with a commercial resistance probe, and vestibular mucus ferning was also evaluated every 12 hours during the oestrus. Significant changes (P < 0.05) in vestibular resistance were detected, registering high variation among individuals. Maximum resistance data was reached between 12 and 24 hours after ovulation time in 83 per cent of the sows. Crystallisation samples were classified into three different patterns according to the fern-like crystal degree. Arborisation peak occurred from 48 to 36 hours before the moment of ovulation, when vestibular resistance values increased gradually. In the optimal insemination moment, vestibular resistance increased significantly (P < 0.05) and vestibular mucus showed a low crystallisation pattern (P < 0.05). Combining several methods to measure genital mucus changes may predict the ovulation time and the best insemination moment.

237 PROTEIN-TYROSINE PHOSPHORYLATION AND CALCIUM UPTAKE IN BOAR SPERM SUBPOPULATIONS AFTER DIFFERENT DISCONTINUOUS PERCOLL GRADIENT CENTRIFUGATIONS

Semen is composed of an heterogeneous population of sperm with varying degrees of structural and functional differentiation. To optimize in vitro fertilization (IVF), different selection methods have been used to isolate sperm subpopulations with high fertilizing capacity. The aim of this study was to evaluate protein-tyrosine phosphorylation (P-Tyr) and calcium uptake in boar sperm subpopulations from the same ejaculate. Spermatozoa from fertile and normozoospermic boars were treated by 2-step discontinuous gradient centrifugation consisting of 3 different combinations of isotonic Percoll (45/60, 60/75, and 45/90%). An aliquot of semen was kept without centrifugation as a control group. Immunofluorescence was employed to determine the localization of proteins phosphorylated in tyrosine residues (Tardif et al. 2001 Biol. Reprod. 65, 784–792). In order to measure intracellular free [Ca2+], spermatozoa treated as described above were incubated with 2.5 μM Fura-2AM in a noncapacitating medium (Tardif et al. 2003 Biol. Reprod. 68, 207–213) for 45 min at 37°C. Then, spermatozoa were resuspended in TALP medium (Rath et al. 1999. J. Anim. Sci. 77, 3346–3352), incubated (5% CO2, 38.5°C) for a further 10 min and then analysed in a fluorescence spectrofluorometer during 30 min with excitation wavelength set at 340–380 nm and emission held at 510 nm. The calculation of intracellular free [Ca2+] was performed according to the equation of (Grynkiewicz et al. 1985 J. Biol. Chem. 260, 3440–3450). The results showed that Percoll treatment increased the percentage of cells with P-Tyr v. control group (P < 0.01). Among Percoll groups, 45/90% showed the highest pattern of cells with signal in equatorial region, acrosome, and tail. As was observed with P-Tyr results, the intracellular free Ca2+ concentration (nM) was different between control group and spermatozoa treated with Percoll gradient (P < 0.01). Among Percoll groups, 45/90% showed the highest levels in calcium uptake and 45/60 showed the lowest levels (299.26; P < 0.01). In conclusion, it could be stated after Percoll centrifugation that sperm subpopulations have different abilities to protein-tyrosine phosphorylation and calcium uptake that could be related to different levels of in vitro fertility. Supported by Fundación Séneca 08752/PI/08.

236 PROTEIN TYROSINE PHOSPHORYLATION IN BOAR SPERM DURING CO-CULTURE WITH OVIDUCTAL EPITHELIAL CELLS

Essentials steps of the capacitation are coordinated in the caudal isthmus of the oviduct, where sperm are stored in intimate contact with the epithelium. A crucial event involved in capacitation is the protein tyrosine phosphorylation. The aim of this study was to characterise the different protein tyrosine phosphorylation patterns in boar sperm after the co-culture with oviducal epithelial cells (POEC). Epithelial cells were stripped from the oviducts of cycling sows and cultivated for 7 days on Petri dishes. Sperm (with and without treatment by discontinuous gradient of isotonic Percoll) were added and co-incubated for 1 h. Six different samples were analysed by indirect immunofluorescence to determine the localization of proteins phosphorylated in tyrosine residues (Tardif et al. 2001 Biol. Reprod. 65, 784–792): ejaculated control, ejaculated bound and unbound POEC, sperm washed through Percoll, and sperm Percoll-washed bound and unbound POEC. Four patterns were determined according to their surface distribution: nonphosphorylated spermatozoa, head and/or tail phosphorylated, equatorial segment phosphorylated, equatorial segment, and head and/or tail phosphorylated. Sperm without any treatment showed lower tyrosine phosphorylation levels than sperm washed through Percoll (66.90% v. 1.90%; P < 0.01). The most common tyrosine phosphorylation distribution in sperm adhesion to POEC was located in equatorial segment (57.78%; P < 0.01). A significant difference regarding head phosphorylation (P < 0.01) was found between sperm bound to oviductal epithelium and unbound sperm (0.00% v. 4.75%). Binding to POEC occurred mainly in sperm with nonphosphorylated heads and tails, whereas higher proportions of equatorial segment and head and/or flagellum phosphorylated cells were found in unbound population (50.25% v. 83.75%; P < 0.01). The data of this study showed differences in the sperm-POEC binding in relation to protein tyrosine phosphorylation patterns, indicating a selective function in the sperm-oviductal epithelial cells interaction. Supported by Fundación Séneca 08752/PI/08.