Freezing of boar spermatozoa: fertilizing capacity with concentrated semen and a new thawing procedure

Characterization of the ICSI-mediated gene transfer method in the production of transgenic pigs

Understanding the behavior of transgenes introduced into oocytes or embryos is essential for evaluating the methodologies for transgenic animal production. We investigated the expression pattern of a transgene transferred to porcine eggs by intracytoplasmic sperm injection-mediated gene transfer (ICSI-MGT) or pronuclear microinjection (PN injection). The introduction of the EGFP gene by ICSI-MGT yielded significantly more embryos with non-mosaic transgene expression (P < 0.01). In the ICSI-MGT group, 61.5% (24/39) of the embryos were EGFP-positive in all their component blastomeres at the morula stage, while fewer than 10% of such embryos were EGFP-positive in the PN-injection group. Using three types of transgenes, ranging from 3.0 to 7.5 kb in size, we confirmed that approximately one in four fetuses obtained by ICSI-MGT was transgenic, suggesting that ICSI-MGT is a practical method for transgenic pig production. Southern blot analysis of 12 transgenic fetuses produced by ICSI-MGT revealed that the number of integrated transgene copies varied from 1 to 300, with no correlation between transgene size and the number of integrated copies. Fluorescence in situ hybridization analysis revealed that the transgenes were randomly integrated into a single site on the host chromosomes. Together, these data indicate that multiple-copy, single-site integration of a transgene is the primary outcome of ICSI-MGT in the pig and that ICSI-MGT is less likely than PN injection to cause transgene integration in a mosaic manner.

Fertilization outcome could be regulated by binding of oviductal plasminogen to oocytes and by releasing of plasminogen activators during interplay between gametes

OBJECTIVE

To detect plasminogen and plasminogen activators (PA) in oviduct and oocytes and to clarify the role of the plasminogen/plasmin system on mammalian fertilization.

DESIGN

Experimental prospective study.

SETTING

Mammalian reproduction research laboratory.

ANIMAL(S)

Oviducts and ovaries from porcine and bovine females were collected at slaughterhouse. A total of 52 oviducts and 2,292 oocytes were used. Boar and bull ejaculated spermatozoa were also used.

INTERVENTION(S)

Plasminogen concentration in oviductal fluid (OF) through the cycle was measured. Immunolocalization of plasminogen and PAs in oocytes was carried out before and after fertilization. Porcine and bovine oocytes were in vitro fertilized, with plasminogen and plasmin added to the culture medium at different concentrations.

MAIN OUTCOME MEASURE(S)

Plasminogen concentration in OF. Plasminogen and PAs immunolocalization in oocytes. Penetration and monospermy rates, number of spermatozoa in the ooplasma and on the zona pellucida (ZP) after IVF.

RESULT(S)

Oviductal fluid contains about 92 μg/mL of plasminogen. The mature oocyte shows immunoreactivity toward plasminogen and toward PAs on its oolemma and ZP. After fertilization, plasminogen and PAs immunolabeling decreases in the oocyte, suggesting its conversion into plasmin. When exogenous plasminogen is added to the IVF medium, sperm entry into the oocyte is hampered, suggesting that the role of plasminogen activation during fertilization is to reduce the number of (or to select) penetrating spermatozoa.

CONCLUSION(S)

The plasminogen/plasmin system is activated during gamete interaction and regulates the sperm entry into the oocyte.

Cysteine addition on short-term cooled boar semen preservation and its relationship with swine field fertility

Artificial insemination is routinely used in the swine industry to reduce the costs of production through to increase the efficiency of the refrigerated boar semen process. The objective of this study was to evaluate the effect of different levels of cysteine (CYS) added to the Beltsville Thawing Solution (BTS) extender semen during cooling for up to 72 hours. Ejaculated from three boars were collected with the gloved-hand technique and semen aliquots were diluted in BTS as follow: BTS only (BTS), BTS + 0.1mM cysteine (CYS0.1), BTS + 0.5mM cysteine (CYS0.5), BTS + 1.0mM cysteine (CYS1.0), BTS + 2.5mM cysteine (CYS2.5), BTS + 5.0mM cysteine (CYS5.0), BTS + 10.0mM cysteine (CYS10.0), and BTS + 20.0mM cysteine (CYS20.0). Evaluation of sperm integrity were analyzed using 0.5mg/ml propidium iodide (plasma membrane), 100µg/ml isothiocynate-conjugated Pisum sativun agglutinin (acrosomal membrane) and 153µM 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide (mitochondria potential) after semen dilution at specific times (0, 24, 48 and 72 hours). Additionally, we also evaluated the effects of 5.0 mM CYS addition in the BTS extender on the maintenance of sperm quality and their influence on fertility in the swine production. After artificial insemination, animals were evaluated based on the estrous return and the number of piglet's born. Cysteine at concentrations of 10.0 and 20.0mM resulted in more pronounced reductions even at the time zero. Semen viability decreased to levels below 10% at these high levels of CYS in the first 24 hour of storage at 17ºC. At the end of the storage time, less than 65% of sperm cells had intact plasma membrane in all groups. The sperm viability decreased significantly when the semen was added at high concentrations of CYS (time "0"; CYS10.0 and CYS20.0; p<0.05), when compared to the other CYS concentrations. The BTS (10.20±0.39) treated group showed a lower rate of estrus return when compared to other (BTSCYS; 86.05±039), and it showed also the highest total number of piglets borne per treatment (12.71±3.38 vs. 9.00±3.38, respectively). In conclusion, the addition of CYS in the BTS semen extender did not maintain spermatic viability of boar cooled spermatozoa and it results in a higher percentage of return to estrus and lower number of piglets borne.

The creation of transgenic pigs expressing human proteins using BAC-derived, full-length genes and intracytoplasmic sperm injection-mediated gene transfer

In most transgenic (Tg) animals created to date, a transgene consisting of the minimum promoter region linked to a cDNA has been used. However, transgenes on small plasmids are susceptible to the position effect, increasing the difficulty of controlling transgene expression. In this study, we attempted to create Tg pigs by intracytoplasmic sperm injection-mediated gene transfer (ICSI-MGT) using two large genomic transgenes derived from a bacterial artificial chromosome (BAC) containing the full genomic region encoding two human proteins, type I collagen and albumin. The production efficiencies (Tg piglets/live offspring) of type I collagen and albumin Tg pigs were 11.8% (6/51) and 18.2% (2/11), respectively. In all of the Tg pigs examined by real-time PCR analysis, tissue-specific expression of the transgene was confirmed (type I collagen: skin, tendon, vessels, genitalia; albumin: liver). The production of human proteins derived from BAC transgenes was also confirmed. Fluorescence in situ hybridization analysis indicated that the BAC transgenes transferred into porcine oocytes by ICSI-MGT were integrated into single or multiple sites on the host chromosomes. These data demonstrate that Tg pigs expressing human proteins in a tissue-specific manner can be created using a BAC transgenic construct and the ICSI-MGT method.

International Conference on Boar Semen Preservation (ICBSP): the first 25 years

The International Conference on Boar Semen Preservation (ICBSP) has been in existence for 25 years. During that time, six conferences have been held in Europe and North America. Each conference has sought to communicate research advances in pig semen technology and artificial insemination (AI). Clearly, the conference has been a catalyst for the advancement of various improvements in semen preservation and AI. In addition, the conference has served to initiate collaboration among scientists worldwide. A summary of problems that remain to be investigated and solved in swine semen technology is provided.

Changes in sperm membrane and ROS following cryopreservation of liquid boar semen stored at 15 °C

Boar semen is occasionally transferred to different locations in liquid form at 15 °C for cryopreservation. However, the use of frozen boar semen is limited due to the high susceptibility of boar sperm to cold shock. The aim of this study was to help improve the quality of frozen boar semen by determining the changes in sperm membrane and ROS during the cryopreservation processes of 15 °C-stored boar semen. Semen was collected from ten Duroc boars and transferred to our laboratory in liquid form stored at 15 °C. After cooling to 5 °C and freezing-thawing, conventional sperm parameters (total motility, progressive motility, and normal morphology), plasma membrane integrity, acrosomal membrane status, and intracellular ROS were evaluated. Sperm function, as assessed by conventional parameters, was unaffected by cooling but was decreased by freezing-thawing (P<0.05). However, the cooling and freezing-thawing processes led to damages in the sperm plasma membrane, and the cooling process caused increase in mean PNA (peanut agglutinin)-fluorescence intensity in viable acrosome-intact sperm (P<0.05). In ROS evaluation, the cooling process decreased intracellular (·)O(2) and H(2)O(2) in viable sperm (P<0.05), while the freezing-thawing process increased intracellular H(2)O(2) (P<0.05) without change in intracellular (·)O(2) in viable sperm. Our results suggest that, in liquid boar semen stored at 15 °C, cooling may be primarily responsible for the destabilization of sperm membranes in viable sperm, while freezing-thawing may induce reductions in sperm function with increase in membrane damage and H(2)O(2).

Recovery, Preparation, Storage and Utilization of Spermatozoa for Fertility Preservation in Cancer Patients and Sub-Fertile Men

Sperm cryopreservation is an important part of an infertility program for patients undergoing infertility treatments, fertility assurance for vasectomy cases, and for fertility preservation due to cancer or other medical conditions. With recent developments in reproductive technology, even men with severely impaired sperm parameters can benefit from cryopreservation as procedures such as intra-cytoplasmic sperm injection (ICSI) require only a few sperm to achieve fertilization and pregnancy. The increasing success of cancer treatment and concerted efforts to ensure quality of life after successful treatment have placed great emphasis on the need to preserve the reproductive capability of young men. It is a highly effective method of protecting male fertility potential, and involves collection, freezing, and long-term storage of sperm. Based on the etiological condition of the patients, sperm can be collected by ejaculation or by surgical retrieval from epididymis or testes. The option to bank sperm should be offered systematically to all patients who may benefit. However, this is not a standard of practice yet; it may be overlooked due to lack of physician awareness regarding the need for fertility preservation and the effectiveness of this option, and/or overestimating the limitations of poor baseline sperm quality leading physician to view cryopreservation as futile. Failure to offer cryopreservation ignores the only possible reproductive option available to certain patients.

Single layer centrifugation with androcoll-p can be scaled-up to process larger volumes of boar semen

The objective of this study was to scale-up the procedure for Single Layer Centrifugation (SLC) through Androcoll(TM)-P, as a preliminary step towords processing the whole ejaculate. The first experiment compared Single Layer Centrifugation using 4.5 mL and 15 mL extended ejaculate (SLC-4.5 and SLC-15, resp.), assessing sperm quality by objective motility analysis, morphology, viability, and the production of reactive oxygen species (ROS). In the second experiment, SLC-4.5 was compared to Single Layer Centrifugation with 25 mL extended ejaculate (SLC-25) using motility analysis and morphology. In both experiments, normal morphology and linear motility were significantly higher in the SLC-selected samples than in the uncentrifuged controls (P < .001), whereas total motility and membrane integrity were unchanged. Although ROS production was higher in the SLC-selected samples than in the controls (P < .01), this might have been due to the presence of antioxidants in seminal plasma in the latter. In conclusion, there was no difference in sperm quality between SLC-4.5 and SLC-15 samples, or between SLC-4.5 and SLC-25 samples, indicating that the SLC method can be scaled-up successfully.

The HSP90AA1 sperm content and the prediction of the boar ejaculate freezability

In a previous study we reported that the immunolabelling of GLUT3, HSP90AA1, and Cu/ZnSOD proteins on boar sperm did not show differences between good and poor freezability ejaculates, in terms of a qualitative analysis based on location and reactivity of these proteins at 17 degrees C and at 240 min post-thaw. Since predicting the ejaculate freezability is considerably important in sperm cryopreservation procedures, the objective of the present study was to quantify the expression of these three proteins in good and poor freezability ejaculates. For this purpose, 10 ejaculates from 9 Piétrain boars were cryopreserved and their sperm quality assessed in the three main steps of the freezing process (17 degrees C, 5 degrees C, and 240 min post-thaw). After this assessment, the 10 ejaculates were clustered for freezability on the basis of their sperm progressive motility and membrane integrity at 240 min post-thaw. From the whole ejaculates, only four good and four poor freezability ejaculates displaying the most divergent values were selected for a western blot assay using sperm samples coming from the three mentioned freezing steps. Protein levels through densitometry were significantly different between good and poor freezability ejaculates for Cu/ZnSOD at 240 min post-thaw (P <or= 0.01) and for HSP90AA1 at 17 degrees C and 5 degrees C (P <or= 0.05). This last finding claims the introduction of tests based on molecular markers in spermatozoa to accurately predict the freezability of ejaculates in order to promote the use of frozen semen on artificial insemination programmes.

Extracellular signal-regulated kinases (ERKs) pathway and reactive oxygen species regulate tyrosine phosphorylation in capacitating boar spermatozoa

The extracellular signal-regulated kinase (ERK) family of the mitogen-activated protein kinase (MAPK) pathway is identified for the first time in boar sperm and is associated with capacitation and tyrosine phosphorylation (tyr-P). Reactive oxygen species (ROS) modulate this signal transduction. Western immunoblotting detected the ERK pathway components RAF1, MEK1/2, and ERK1/2 in extracts from fresh boar spermatozoa and determined that their phosphoprotein profiles differed in a capacitation-dependent fashion. Capacitation was accompanied by appearance of two new ERKs (158 and 161 kDa) and disappearance of others. Capacitation was verified with increased tyr-P, which was inhibited by a 30-min pre-exposure of fresh boar sperm to a xanthine/xanthine oxidase ROS-generating system prior to the capacitating incubation; ROS pre-exposure also affected the phosphorylation of RAF1, MEK1/2, and ERK1/2. Preincubating sperm with inhibitors of the ERK components with or without the ROS generator affected subsequent capacitation. Inhibiting ERK1/2 inhibited tyr-P of capacitated boar spermatozoa proteins of 172, 97, and 66 kDa (P ≤ 0.04); with ROS, this inhibition increased (P < 0.002) and tyr-P of 111 kDa declined (P < 0.028). Pre-exposure to ROS plus MEK1/2 inhibitor prevented capacitation-induced tyr-P of proteins of 187 (P < 0.01) and 112 kDa (P < 0.04) versus capacitation with or without ROS. Therefore, ERK1/2 components of the MAPK pathway significantly regulate boar sperm capacitation, and RAF1 and MEK1/2 may have some lesser influence through crosstalk with different pathways. ROS affect RAF1, MEK1/2, and ERK1/2 and could influence the sequential events of boar sperm capacitation.

Deep intra-uterine artificial inseminations using cryopreserved spermatozoa in beluga (Delphinapterus leucas)

Artificial insemination (AI) with liquid-stored spermatozoa and sperm cryopreservation using directional freezing (DF) have been successful in the beluga. This study built on this foundation to develop a deep intra-uterine AI technique with frozen-thawed semen in beluga. Forty-two ejaculates from one male were cryopreserved using DF technology and subsequently used for 10 insemination attempts with seven females. Percentage pre- and post-thaw progressive motility and viability were (mean +/- SD) 73.0 +/- 12.2, 38.4 +/- 8.8, 88.0 +/- 0.1, and 59.3 +/- 15.7%, respectively. A series of GnRH injections (3 x 250 microg, IV, 1.5 to 2 h apart) were used to induce ovulation, once a growing follicle >2.5 cm in diameter was visualized via trans-abdominal ultrasonography. Artificial insemination was performed at 30.1 +/- 3.8 h post-initial GnRH injection with semen deposited in the uterine horn, 92.6 +/- 16.2 cm beyond the genital opening using a flexible endoscope. The external cervical os (cEOS) was located beyond a series of 5 to 10 vaginal rings, 44.8 +/- 9.3 cm from the external genital opening. The internal bifurcation of the uterus was 27 +/- 6.8 cm beyond the cEOS. Ovulation occurred at 8.5 +/- 7.6 h post-AI. Two of 10 inseminations (20%) resulted in pregnancy. The first pregnancy resulted in twins; both calves were born 442 d after AI, with one surviving. The second pregnancy is ongoing. These findings represent the first successful application of AI using frozen-thawed semen in beluga, and are important examples of how assisted reproductive technologies can provide tools for the global management of threatened species.

A novel method for detection of chromosomal integrity in cryopreserved livestock spermatozoa using artificially fused mouse oocytes

PURPOSE

The aim of the present study was to investigate the effect of mouse oocyte volume on the efficiency of chromosomal analysis in livestock spermatozoa.

METHODS

Oocytes were injected with bull, ram, boar and dog sperm heads, and then fused with enucleated mouse oocytes.

RESULTS

The increment of oocyte volume increased the rates of morphologically normal oocytes after sperm injection, which induced much higher rates of overall chromosome detection in bull, ram and dog spermatozoa. The recipient oocyte volume did not affect the chromosomal integrity. Furthermore, in bull, the chromosomal integrity detected by fused mouse oocytes was similar to that derived from a homologous system. On the other hand, chromosomal plates of boar spermatozoa could not be detected despite the use of fused oocytes.

CONCLUSION

These data indicate that fused mouse oocytes improved the efficiency of chromosome detection in bull, ram and dog spermatozoa.

Preservation of beluga (Delphinapterus leucas) spermatozoa using a trehalose-based cryodiluent and directional freezing technology

A beluga (Delphinapterus leucas) sperm preservation method was developed for use in genome banking and AI. In Study 1, glycerol-based cryodiluents (modified BF5F and modified Platz Diluent Variant (PDV)) were unable to maintain adequate progressive motility using straws (fast and slow freezing rate (FR)) or pellets (slow FR). Neither freezing method nor FR affected in vitro sperm characteristics (P > 0.05), but retention of prefreeze progressive motility following thawing was greater (P < 0.05) for BF5F (21%) than PDV (15%). In Study 2, examining the effects of straw freeze–thawing using BF5F with glycerol (1 and 3%, v/v) or trehalose (46 and 91 mM) on sperm characteristics, samples cryopreserved in trehalose exhibited superior (P < 0.05) in vitro parameters compared with their glycerol-treated counterparts. In Study 3, compared with a straw method, directional freezing using 91 mM trehalose enhanced (P < 0.05) sperm characteristics, with samples retaining 38%, 75% and 61% of their prefreeze progressive motility, curvilinear velocity and viability, respectively. A higher (P < 0.05) proportion of motile spermatozoa displayed rapid velocity after directional (21 ± 1%) compared with straw (12 ± 3%) freezing. Systematic development of a cryodiluent and the use of directional freezing resulted in beluga spermatozoa exhibiting adequate post-thaw quality for genome banking and use in AI.

Superfine open pulled straws vitrification of porcine blastocysts does not require pretreatment with cytochalasin B and/or centrifugation

The present study investigated the in vitro development of and cytoskeletal disruption suffered by in vivo-derived porcine blastocysts subjected to superfine open pulled straws (SOPS) vitrification. Blastocysts were either untreated prior to SOPS vitrification or were subjected to one of the following three pretreatment protocols: (1) centrifugation (12 min, 13 000g); (2) 25 min equilibration with 7.5 μg mL–1 cytochalasin B; or (3) equilibration with cytochalasin B followed by centrifugation. After 24 h culture, fresh (n = 32) and vitrified–warmed (n = 188) blastocysts were evaluated by stereomicroscopy, with survival and hatching rates recorded. Some blastocysts were stained with 4′,6′-diamidino-2-phenylindole and processed for cytoskeletal evaluation. Three cytoskeletal patterns were identified: Grade I, intact cytoskeleton; Grade II, gross maintenance of integrity, but with some clumps of actin within the cytoplasm; and Grade III, a highly disrupted cytoskeleton. There were no differences in the survival, hatching and cell death rats, total cell number or cytoskeletal integrity between the different vitrification groups. Cell death was greater for vitrified blastocysts than for fresh blastocysts (3.6 ± 0.4% v. 0.4 ± 0.7%, respectively; P < 0.05) and the percentage of blastocysts with a Grade I cytoskeletal pattern was lower for vitrified compared with fresh blastocysts (60.8% v. 92%, respectively; P < 0.05). The vitrified–warmed blastocysts that hatched during culture exhibited a Grade I cytoskeletal pattern. In conclusion, successful SOPS vitrification of porcine blastocysts does not require pretreatment with cytochalasin B and/or centrifugation.

Flow cytometric evaluation of boar semen by the sperm chromatin structure assay as related to cryopreservation and fertility

Boar semen from a heterospermic mating trial and semen cryopreserved by various methods were evaluated by the flow cytometric sperm chromatin structure assay (SCSA), which measures the susceptibility of sperm nuclear DNA to acid-induced denaturation in situ. Spermatozoa were treated with a pH 1.4 buffer and then stained with the metachromatic dye acridine orange. Acridine orange intercalated into double-stranded DNA (native) fluoresces green while single-stranded DNA (denatured) fluoresces red when excited with 488 nm light. The ratio of red to total fluorescence provides an index of normality/abnormality. The SCSA data on neat boar semen or semen in either Kiev-Merck or Pursel-Johnson extender and frozen directly on dry ice blocks or plunged into LN2 did not differ within individual boars. Therefore, chromatin structure, as measured by the SCSA, was not influenced differently by these 2 methods of semen cryopreservation. When semen from 6 boars was mixed in equal sperm numbers in six 3-way combinations and inseminated into at least 3 Duroc gilts per combination, 4 of the 6 combinations yielded 2 litters, while the remaining 2 combinations yielded 3 litters. The SCSA correctly predicted both the high and low fertility boars based on a ratio of offspring as deviated from the theoretical percentage. Thus, the SCSA was found to be a valuable adjunct method for evaluating boar semen quality.

Vitrification and warming of in vivo-derived porcine embryos in a chemically defined medium

The aim of this study was to design a protocol for vitrification and warming of porcine embryos in a chemically defined medium. A total of 663 morulae and blastocysts were collected from weaned crossbred sows (Large White-Landrace) 5 to 6 d after estrus and vitrified with the Superfine Open Pulled Straw method. In Experiment 1, embryos were vitrified using as a basic medium TCM-199-HEPES supplemented with 20% newborn calf serum (NBCS) or with 0, 0.1%, 0.5%, or 1% polyvinyl alcohol (PVA). Nonvitrified embryos were used as a fresh control group. Survival and hatching rates were evaluated after 72 h of in vitro culture to assess embryo viability. In addition, some hatched blastocysts derived from morulae and blastocysts were processed to determine the total cell number and the cell proliferating index as measures of their quality. Within each stage of embryo development, the different vitrification groups and the fresh control group showed similar high embryo survival (range, 70.5+/-7.1% to 84.9+/-8.1% and 85.3+/-8.1% to 98.4+/-8.2% for morulae and blastocysts, respectively) and hatching rate (range, 46.3+/-10.1% to 66.7+/-11.2% and 73.7+/-11.3% to 89.4+/-11.2% for morulae and blastocysts, respectively) and quality after in vitro culture. In Experiment 2, embryos were vitrified using 0.1% PVA and warmed with TCM-199-HEPES-0.13 M sucrose supplemented with 20% NBCS or either 0 or 0.1% PVA. Nonvitrified embryos were used as a fresh control group. As in Experiment 1, no significant differences were detected in embryo survival (range, 67.9+/-6.6% to 74.5+/-6.6% and 91.9+/-7.0% to 99.5+/-6.3% for morulae and blastocysts, respectively) and hatching rate (range, 47.0+/-7.2% to 64.8+/-9.9% and 89.4+/-7.4% to 98.2+/-6.9% for morulae and blastocysts, respectively) and quality among the warming groups or among vitrified and fresh control embryos. In both experiments, the developmental embryo stage influenced the survival and hatching rates, as well as the number of cells (P<0.01), with the blastocyst stage yielding the best results. In conclusion, PVA can be used as a substitute for serum in vitrification and warming solutions without detrimental effects on the in vitro development of in vivo-derived porcine morulae and blastocysts.

Seasonality, estrous cycle characterization, estrus synchronization, semen cryopreservation, and artificial insemination in the Pacific white-sided dolphin (Lagenorhynchus obliquidens)

The reproductive physiology of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, was characterized to facilitate the development of artificial insemination (AI) using cryopreserved spermatozoa. Specific objectives were to: 1) describe reproductive seasonality of the Pacific white sided dolphins; 2) describe urinary LH and ovarian steroid metabolites during the estrous cycle; 3) correlate LH and ovarian steroidal metabolite patterns to ultrasound-monitored follicular growth and ovulation; and 4) assess the efficacy of synchronizing estrus, sperm collection/cryopreservation, and intrauterine insemination. Ovulations (64%, n=37) and conceptions (83%, n=18) occurred from August to October. Peak mean serum testosterone (24 ng/ml), cross-sectional testicular area (41.6 cm2), and sperm concentration (144.3×107 sperm/ml) occurred in July, August, and September respectively. Spermatozoa were only found in ejaculates from July to October. Estrous cycles (n=22) were 31 d long and were comprised of a 10 d follicular and 21 d luteal phase. Ovulation occurred 31.2 h after the onset of the LH surge and 19.3 h after the LH peak. Follicular diameter and circumference within 12 h of ovulation were 1.52 and 4.66 cm respectively. Estrus synchronization attempts with altrenogest resulted in 17 (22%) ovulatory cycles with ovulation occurring 21 d post-altrenogest. Ten AI attempts using cryopreserved semen resulted in five pregnancies (50%). The mean gestation length was 356 days (range 348–367). These data provide new information on the Pacific white-sided dolphin's reproductive physiology and collectively enabled the first application of AI in this species.

Selection of boar spermatozoa using centrifugation on a glycidoxypropyltrimethoxysilane-coated silica colloid

Use of sperm separation methods such as density gradient centrifugation for selecting the best spermatozoa for animal breeding is constrained by the problem of dealing with the large volumes of ejaculate produced by the males of some species, such as boars. The purpose of this study was to compare density gradient centrifugation (DGC) with centrifugation on a single layer of colloid (SLC) for the preparation of ejaculated boar spermatozoa using Androcoll(TM)-P. There was no difference between the two techniques in terms of sperm motility or duration of motility after selection, and sperm motility was retained for at least 24 h longer in the centrifuged sperm preparations than in controls (uncentrifuged aliquots). Sperm motility was significantly better (P<0.001) in the centrifuged sperm preparations (means +/- sd: SLC 79.6 +/- 8.1% and DGC 74.2 +/- 12.0%) than in the uncentrifuged controls (62.9 +/- 12.7%). The mean yield of motile spermatozoa for SLC was 67.5 +/- 25.6%, and for DGC it was 59.6% +/- 22.3% (not significant, ns). Sperm survival was significantly increased by colloid centrifugation (control 3.1 +/- 0.3 days, SLC 5.5 +/- 0.79 days, DGC 5.75 +/- 0.62 days; P<0.001 for uncentrifuged versus centrifuged; SLC vs. DGC, ns). Moreover, boar spermatozoa could be stored for 24 h before centrifugation without any detrimental effect on sperm motility or duration of motility. In a further experiment, larger volumes of ejaculate were processed easily on a modified SLC, indicating that this method may be practical for processing large volumes of boar ejaculates.

Cellular biophysics during freezing of rat and mouse sperm predicts post-thaw motility

Though cryopreservation of mouse sperm yields good survival and motility after thawing, cryopreservation of rat sperm remains a challenge. This study was designed to evaluate the biophysics (membrane permeability) of rat in comparison to mouse to better understand the cooling rate response that contributes to cryopreservation success or failure in these two sperm types. In order to extract subzero membrane hydraulic permeability in the presence of ice, a differential scanning calorimeter (DSC) method was used. By analyzing rat and mouse sperm frozen at 5 degrees C/min and 20 degrees C/min, heat release signatures characteristic of each sperm type were obtained and correlated to cellular dehydration. The dehydration response was then fit to a model of cellular water transport (dehydration) by adjusting cell-specific biophysical (membrane hydraulic permeability) parameters L(pg) and E(Lp). A "combined fit" (to 5 degrees C/min and 20 degrees C/min data) for rat sperm in Biggers-Whitten-Whittingham media yielded L(pg) = 0.007 microm min(-1) atm(-1) and E(Lp) = 17.8 kcal/mol, and in egg yolk cryopreservation media yielded L(pg) = 0.005 microm min(-1) atm(-1) and E(Lp) = 14.3 kcal/mol. These parameters, especially the activation energy, were found to be lower than previously published parameters for mouse sperm. In addition, the biophysical responses in mouse and rat sperm were shown to depend on the constituents of the cryopreservation media, in particular egg yolk and glycerol. Using these parameters, optimal cooling rates for cryopreservation were predicted for each sperm based on a criteria of 5%-15% normalized cell water at -30 degrees C during freezing in cryopreservation media. These predicted rates range from 53 degrees C/min to 70 degrees C/min and from 28 degrees C/min to 36 degrees C/min in rat and mouse, respectively. These predictions were validated by comparison to experimentally determined cryopreservation outcomes, in this case based on motility. Maximum motility was obtained with freezing rates between 50 degrees C/min and 80 degrees C/min for rat and at 20 degrees C/min with a sharp drop at 50 degrees C/min for mouse. In summary, DSC experiments on mouse and rat sperm yielded a difference in membrane permeability parameters in the two sperm types that, when implemented in a biophysical model of water transport, reasonably predict different optimal cooling rate outcomes for each sperm after cryopreservation.

Distinct effects of boar seminal plasma fractions exhibiting different protein profiles on the functionality of highly diluted boar spermatozoa

The aim of this study was to evaluate how different protein profiles of seminal plasma (SP) fractions affect sperm functionality in vitro. Ejaculates from three boars were separated into six fractions. The fractions differed from each other in their sperm content, in their total SP protein content, and their spermadhesin PSP-I/PSP-II and heparin-binding protein (HBP) concentrations. Spermatozoa were mainly recovered in fraction 2 (sperm-rich fraction, >1800 x 10(6) spermatozoa/ml), whereas the pre-sperm fraction 1 and the post-sperm fractions 4-6 contained low numbers of spermatozoa (<500 x 10(6)/ml). Except in fraction 2, the total SP protein concentration and the concentration of both, spermadhesin PSP-I/PSP-II and the HBPs increased with fraction order. Distinct time-dependent effects were observed on motility characteristics and membrane integrity of highly diluted boar spermatozoa upon incubation with a 10% dilution of the SP from each fraction. The highest sperm viability was recorded after exposure for 5 h to fraction 2, followed by fractions 1 and 3. The percentages of motile spermatozoa also differed significantly among fractions after 5 h of incubation. Spermatozoa incubated with SP of fractions 1-3 showed the highest percentage motility. We conclude that different SP fractions exert distinct effects on the functionality of highly diluted boar spermatozoa. Fractions 1-3 appear to promote sperm survival, whereas fractions 4-6 seem to be harmful for preserving the physiological functions of highly diluted boar spermatozoa.

Pre-fertilization zona pellucida hardening by different cross-linkers affects IVF in pigs and cattle and improves embryo production in pigs

Zona pellucida (ZP) hardening (resistance to proteolysis) has been classically identified as a post-fertilization event that contributes to the block to polyspermy. Di-(N-succinimidyl)-3,3′-dithiodipropionate (DSP), a permeable amine-reactive cross-linker, was recently shown to induce pre-fertilization ZP hardening and to improve porcine IVF productivity. The objectives of this study were to investigate i) how DSP affects pre-fertilization ZP hardening and IVF in cattle, ii) if a non-permeable amine-reactive cross-linker such as bis(sulfosuccinimidyl) suberate (BS3) affects ZP hardening and IVF in cattle and pigs, and iii) whether DSP or BS3, if improvement in IVF productivity was demonstrated in either species, affectsin vitroembryo development. Bovine and porcinein vitromatured oocytes were incubated with the cross-linkers (0.06, 0.3, and 0.6 mg/ml) for 30 min. Then they were subjected to ZP digestion or IVF. In cattle, both DSP and BS3 induced ZP hardening and decreased the penetration rate, although monospermy, penetration, or male pronuclear formation was not affected. In pigs, BS3 treatment induced ZP hardening, decreased penetration and male pronuclear formation, and increased monospermy. IVF productivity only improved when porcine oocytes were exposed to DSP. When porcine zygotes derived from this treatment were further culturedin vitro, the cleavage and blastocyst formation rates increased. These results support the idea that mechanisms involved in the prevention of polyspermic fertilization in cattle and pigs have different efficiencies, and ZP hardening induced by DSP cross-linker may be useful for improving porcine embryo production.

Reactive oxygen species and boar sperm function

Boar spermatozoa are very susceptible to reactive oxygen species (ROS), but ROS involvement in damage and/or capacitation is unclear. The impact of exposing fresh boar spermatozoa to an ROS-generating system (xanthine/xanthine oxidase; XA/XO) on sperm ROS content, membrane lipid peroxidation, phospholipase (PL) A activity, and motility, viability, and capacitation was contrasted to ROS content and sperm function after cryopreservation. Exposing boar sperm (n = 4-5 ejaculates) to the ROS-generating system for 30 min rapidly increased hydrogen peroxide (H2O2) and lipid peroxidation in all sperm, increased PLA in dead sperm, and did not affect intracellular O2- (flow cytometry of sperm labeled with 2',7'-dichlorodihydrofluorscein diacetate, BODIPY 581/591 C11, bis-BODIPY-FL C11, hydroethidine, respectively; counterstained for viability). Sperm viability remained high, but sperm became immotile. Cryopreservation decreased sperm motility, viability, and intracellular O2- significantly, but did not affect H2O2. As expected, more sperm incubated in capacitating media than Beltsville thawing solution buffer underwent acrosome reactions and protein tyrosine phosphorylation (four proteins, 58-174 kDa); which proteins were tyrosine phosphorylated was pH dependent. Pre-exposing sperm to the ROS-generating system increased the percentage of sperm that underwent acrosome reactions after incubation in capacitating conditions (P < 0.025), and decreased capacitation-dependent increases in two tyrosine-phosphorylated proteins (P < or = 0.035). In summary, H2O2 is the major free radical mediating direct ROS effects, but not cryopreservation changes, on boar sperm. Boar sperm motility, acrosome integrity, and lipid peroxidation are more sensitive indicators of oxidative stress than viability and PLA activity. ROS may stimulate the acrosome reaction in boar sperm through membrane lipid peroxidation and PLA activation.

Effects of oviductal fluid on the development, quality, and gene expression of porcine blastocysts produced in vitro

In mammals, fertilization and early pre-implantation development occur in the oviduct. Previous results obtained in our laboratory have identified specific molecules in the oviduct that affect porcine sperm-egg interactions. The aim of the present study was to determine whether the contact between oocytes and oviductal fluid also affect embryo development, quality, and gene expression. In vitro matured porcine oocytes were exposed to bovine oviductal fluid (bOF) for 30 min prior to fertilization. Cleavage and blastocyst development rates were significantly higher from bOF-treated oocytes than from untreated oocytes. Blastocysts obtained from bOF-treated oocytes had significantly greater total cell numbers than those obtained from untreated oocytes. Using real-time PCR, grade 1 (very good morphological quality) and grade 2 (good morphological quality) blastocysts were analyzed for gene transcripts related to apoptosis (BAX, BCL2L1), mitochondrial DNA (mtDNA) transcription/replication (POLG, POLG2, and TFAM), blastomere connection and morula compaction (GJA1), and blastocyst formation and pluripotency (POU5F1). We found that the entire set of genes analyzed was differentially expressed between grade 1 and 2 blastocysts. Furthermore, bOF treatment reduced the ratio of BAX to BCL2L1 transcripts and enhanced the abundance of TFAM transcripts in grade 2 blastocysts. Not only do these findings demonstrate that factors within the bOF act on porcine oocytes both quickly and positively, but they also suggest that such factors could promote embryo development and quality by protecting them against adverse impacts on mtDNA transcription/replication and apoptosis induced by the culture environment.

Effects of HSPA8, an evolutionarily conserved oviductal protein, on boar and bull spermatozoa

Previous studies have shown that a soluble protein fraction derived from preparations of apical plasma membrane (APM) of the oviductal epithelium enhances the in vitro survival of mammalian spermatozoa. Here, we show that the survival enhancing property of the soluble protein fraction seems to depend significantly upon heat shock 70 kDa protein 8 (HSPA8 previously known as HSPA10). The following findings in the present study enabled us to draw this conclusion: first, using proteomic analysis, we identified a subset of 70 kDa oviductal surface proteins that bound to spermatozoa, one of which was HSPA8. Second, pre-treatment of the soluble protein fraction with anti-HSPA8 antibody reduced the 24 h (at 39 degrees C) sperm survival enhancement effect normally induced by the presence of 200 microg/ml soluble APM proteins. Third, complementary experiments showed that substituting the soluble protein fraction with bovine recombinant HSPA8 (0.5-2 microg/ml) also elicited the sperm survival effect. Finally, we also tested the effect of bovine recombinant HSPA8 on bull spermatozoa and found similar, dose-responsive, sperm survival promoting effects. The conserved nature of HSPA8 between mammalian species suggests that this protein may represent a common biological mechanism for the maintenance of sperm survival in the oviduct.