Mating modifies the expression of crucial oxidative-reductive transcripts in the pig oviductal sperm reservoir: is the female ensuring sperm survival?

Background

Mating induces large changes in the female genital tract, warranting female homeostasis and immune preparation for pregnancy, including the preservation of crucial oxidative status among its pathways. Being highly susceptible to oxidative stress, sperm survival and preserved function depend on the seminal plasma, a protection that is removed during sperm handling but also after mating when spermatozoa enter the oviduct. Therefore, it is pertinent to consider that the female sperm reservoir takes up this protection, providing a suitable environment for sperm viability. These aspects have not been explored despite the increasing strategies in modulating the female status through diet control and nutritional supplementation.

Aims

To test the hypothesis that mating modifies the expression of crucial oxidative-reductive transcripts across the entire pig female genital tract (cervix to infundibulum) and, particularly in the sperm reservoir at the utero-tubal junction, before ovulation, a period dominated by estrogen stimulation of ovarian as well as of seminal origin.

Methods

The differential expression of estrogen (ER) and progesterone (PR) receptors and of 59 oxidative-reductive transcripts were studied using a species-specific microarray platform, in specific segments of the peri-ovulatory sow reproductive tract in response to mating.

Results

Mating induced changes along the entire tract, with a conspicuous downregulation of both ER and PR and an upregulation of superoxide dismutase 1 (SOD1), glutaredoxin (GLRX3), and peroxiredoxin 1 and 3 (PRDX1, PRDX3), among other NADH Dehydrogenase Ubiquinone Flavoproteins, in the distal uterus segment. These changes perhaps helped prevent oxidative stress in the area adjacent to the sperm reservoir at the utero-tubal junction. Concomitantly, there were a downregulation of catalase (CAT) and NADH dehydrogenase (ubiquinone) oxidoreductases 1 beta subcomplex, subunit 1 (NDUFB1) in the utero-tubal junction alongside an overall downregulation of CAT, SOD1, and PRDX3 in the ampullar and infundibulum segments.

Conclusions

Natural mating is an inducer of changes in the expression of female genes commanding antioxidant enzymes relevant for sperm survival during sperm transport, under predominant estrogen influence through the bloodstream and semen. The findings could contribute to the design of new therapeutics for the female to improve oxidative-reductive balance.

Proteomics in fresh and preserved pig semen: Recent achievements and future challenges

Proteins in semen, either in spermatozoa (SPZ) or seminal plasma (SP), are directly involved in molecular processes and biological pathways regulating sperm function, including fertilizing ability. Therefore, semen proteins are candidates of choice for biomarkers discovery for fertility and for sperm (dys)function. Mass spectrometry (MS)-based proteomics has opened up a new era for characterizing and quantifying the protein profile of SP and SPZ, as well as for unveiling the complex protein interactions involved in the activation of sperm functionality. This article overviews existing literature on MS-based proteomics regarding porcine semen, with a specific focus on the potential practical application of the results achieved so far. The weaknesses of current studies and the perspectives for future research in MS-based pig semen proteomics are also addressed.

Seminal Plasma Cytokines Are Predictive of the Outcome of Boar Sperm Preservation

Background: Boar seminal plasma is rich in cytokines, which could influence the capability of spermatozoa to tolerate preservation. Objectives: To evaluate the involvement of boar seminal plasma cytokines in the changes experienced by boar spermatozoa during their storage, either in liquid or frozen state. Materials and Methods: In two separated experiments, semen samples from healthy and fertile boars were split in two aliquots, one centrifuged twice (1,500 ×g for 10 min) to harvest seminal plasma, whereas the other was either commercially extended (3 × 10⁷ sperm/mL) and liquid-stored at 17°C during 144 h (n = 28, Experiment 1) or frozen-thawed using a standard 0.5 mL protocol (n = 27, Experiment 2). Sixteen cytokines were quantified using Luminex xMAP®. Sperm attributes (CASA-evaluated total and progressive motility; flow cytometry-evaluated sperm viability, production of intracellular H₂O₂ and O 2 • - and levels of lipid peroxidation in viable spermatozoa) were evaluated either at 0, 72, or 144 h of liquid storage (Experiment 1) or before freezing and at 30- and 150-min post-thawing (Experiment 2). Results: Multiple linear regression models, with Bayesian approach for variable selection, revealed that the anti-inflammatory TGF-β2, TGF-β3, IL-1Ra, and IL-4 and the pro-inflammatory IL-8 and IL-18, predicted changes in sperm motility for liquid-stored semen while the anti-inflammatory IFN-γ was included in the models predicting changes in all sperm attributes for cryopreserved semen. Conclusion: Specific boar seminal plasma cytokines would contribute to modulate the structural and metabolic changes shown by spermatozoa during preservation, either in liquid or frozen state.

Extracellular vesicles isolated from porcine seminal plasma exhibit different tetraspanin expression profiles

Seminal extracellular vesicles (EVs) include exosomes (ø 40–120 nm) and microvesicles (MVs, ø 120–1000 nm), which would be involved in multiple functional reproductive roles. The study aimed to establish which EV subtypes are present in pig semen, using a high-resolution flow cytometer to explore differences in their tetraspanin expression profile. The EVs were isolated from 12 pig ejaculates using serial ultracentrifugation and characterized by dynamic light scattering and electron microscopy for size and morphology as well as for tetraspanin expression using flow cytometry with Carboxyfluorescein succinimidyl ester (CFSE) and antibodies against CD9, CD63 and CD81. Pig semen contained a heterogeneous EV-population regarding size and morphology. Flow cytometric analysis demonstrated that the proportion of EVs expressing CD63 and CD9 was higher in MVs (P < 0.001 and P < 0.05, respectively) than in exosomes, while the opposite was true for CD81; higher (P < 0.001) in exosomes than in MVs. In conclusion, (1) the new generation of flow cytometers are able to accurately identify EVs and to gate them in two size-different populations named exosomes and MVs. (2) Tetraspanins CD9, CD63 and CD81 are present in both seminal EVs, albeit with exosomes and MVs differing in expression profiles, suggesting dissimilar cargo and binding affinity.

Levels of activity of superoxide dismutase in seminal plasma do not predict fertility of pig AI-semen doses

Superoxide dismutase (SOD) is a major antioxidant enzyme in boar seminal plasma (SP). This study evaluated how SP-SOD affected sperm attributes when semen of boars of various breeds, included in commercial artificial insemination (AI)-programs, was extended and liquid-stored at 17 °C for AI; as well as their in vivo fertility (farrowing rate and litter size of 10,952 AI-sows). SP-SOD-activity was assessed in 311 ejaculates (100 boars) while sperm motility (by CASA), viability and intracellular H₂O₂ generation in viable spermatozoa (by flow cytometry) were measured at 0 and 72 h of liquid storage. SP-SOD activity was not affected by breed but differed (P < 0.001) between boars (n = 50), ranging from 1.16 ± 0.11 to 7.02 ± 0.75 IU/mL. Semen AI-doses (n = 44) hierarchically grouped (P < 0.001) with low SP-SOD activity showed lower (P < 0.05) sperm motility and intracellular H₂O₂ at 72 h of liquid storage. Fertility did not differ between AI-boars (n = 39) hierarchically grouped (P < 0.001) with high or low SP-SOD activity. In conclusion, SP-SOD activity is boar dependent and positively related with sperm functionality of liquid-stored semen AI-doses. However, this positive effect is not reflected on in vivo fertility post-AI.

The Proteome of Pig Spermatozoa Is Remodeled During Ejaculation

Proteins are essential for sperm function, including their fertilizing capacity. Pig spermatozoa, emitted in well-defined ejaculate fractions, vary in their functionality, which could be related to different sperm protein composition. This study aimed (i) to update the porcine sperm proteome and (ii) to identify proteins differentially expressed in mature spermatozoa from cauda epididymis and those delivered in separate ejaculate fractions. Ejaculates from nine mature and fertile boars were manually collected in three separate portions: the first 10 ml of the sperm-rich ejaculate fraction (SRF), the rest of the SRF and the post-SRF. The contents of cauda epididymides of the boars were collected post-mortem by retrograde duct perfusion, generating four different semen sources for each boar. Following centrifugation, the resulting pellets of each semen source were initially pooled and later split to generate two technical replicates per source. The resulting eight sperm samples (two per semen source) were subjected to iTRAQ-based 2D-LC-MS/MS for protein identification and quantification. A total of 1,723 proteins were identified (974 of Sus scrofa taxonomy) and 1,602 of them were also quantified (960 of Sus scrofa taxonomy). After an ANOVA test, 32 Sus scrofa proteins showed quantitative differences (p < 0.01) among semen sources, which was particularly relevant for sperm functionality in the post-SRF. The present study showed that the proteome of boar spermatozoa is remodeled during ejaculation involving proteins clearly implicated in sperm function. The findings provide valuable groundwork for further studies focused on identifying protein biomarkers of sperm fertility.

The Effect of Oxidative Stress on Thawed Bulk-Sorted Red Deer Sperm

The aims of this study were to assess the effects of the sex-sorting process on post-thaw sperm quality as well as on induced oxidative stress damage (H2 O2 0 mm = H000; H2 O2 50 mm = H050; H2 O2 100 mm = H100) and the protective action of reduced glutathione (GSH) and Trolox, when comparing sorted (BSS) and non-sorted (NS) red deer spermatozoa incubated at 37°C. Sperm samples from three stags were collected by electroejaculation and frozen. Immediately after thawing, sperm motility was higher (p < 0.05) for NS (59% ± 3.3) than BSS (36.9% ± 5.8) sperm. Furthermore, the percentage of apoptotic sperm was higher (p < 0.05) for BSS (21.6% ± 5.0) than NS sperm (14.6% ± 1.2). The presence of H2 O2 increased DNA damage in NS (H000 = 4.1% ± 0.9; H050 = 9.3% ± 0.7; and H100 = 10.9% ± 2.3), but not in BSS sperm. However, in the presence of oxidant, GSH addition improved (p < 0.05) sperm motility in both groups of sperm samples as compared to their controls (NS: 44.5 ± 4.8 vs 21.1 ± 3.9 and BSS: 33.3 ± 8.1 vs 8.9 ± 1.8). These results demonstrate that the sperm-sorting process induces sublethal effects, albeit selecting a sperm population with a chromatin more resistant to oxidative stress than that in non-sorted sperm. Moreover, addition of GSH at 1 mm may be a good choice for maintaining the quality of stressed sperm samples, unlike Trolox, which inhibited sperm motility.

Egg yolk and glycerol requirements for freezing boar spermatozoa treated with methyl β-cyclodextrin or cholesterol-loaded cyclodextrin

Egg yolk (EY) and glycerol are common constituents of extenders used for sperm cryopreservation. It has been demonstrated that using cholesterol-loaded cyclodextrins (CLC) improves sperm cryosurvival in several species. However, standard freezing extenders might not be the most appropriate for CLC-treated sperm. This study evaluated the EY and glycerol requirements for freezing CLC-treated boar spermatozoa. Semen samples from 34 ejaculates coming from 4 boars were used. Each ejaculate was split into three aliquots: one was used untreated (control), and the other two were treated with 1 mg of CLC or methyl-β-cyclodextrin/120 × 10⁶ sperm for 15 min at 22 C prior to cryopreservation. Our results indicated that reducing the concentration of EY was detrimental for sperm viability after thawing (31.57 ± 2 vs. 19.89% ± 2 for 20 and 10% EY, respectively; P <0.05), even in semen treated with CLC. On the other hand, it was observed that the traditional concentration of glycerol (3%) was not the appropriate for freezing CLC-treated sperm (61.10 ± 3 vs. 47.87% ± 3 viable sperm for control and CLC-treated sperm, respectively; P <0.05). Thus, CLC-treated sperm showed a higher tolerance to high glycerol concentrations (5%) in terms of sperm viability (59.19% ± 3) than non-treated sperm (45.58% ± 3; P<0.05). Therefore, it could be necessary to modify the freezing extenders for CLC-treated sperm. Nevertheless, additional studies will be needed to evaluate alternative cryoprotectants and to determine the effect of high glycerol concentrations on sperm functionality.

Exploring child maltreatment and its relationship to alcohol and cannabis use in selected Latin American and Caribbean countries

OBJECTIVES

Research from developed countries shows that child maltreatment increases the risk for substance use and problems. However, little evidence on this relationship is available from developing countries, and recognition of this relationship may have important implications for substance demand reduction strategies, including efforts to prevent and treat substance use and related problems. Latin America and the Caribbean is a rich and diverse region of the world with a large range of social and cultural influences. A working group constituted by the Inter-American Drug Abuse Control Commission and the Center for Addiction and Mental Health in June, 2010 identified research on this relationship as a priority area for a multinational research partnership.

METHODS

This paper examines the association between self-reported child maltreatment and use in the past 12 months of alcohol and cannabis in 2294 university students in seven participating universities in six participating countries: Colombia, El Salvador, Jamaica, Nicaragua, Panama and Uruguay. The research also considers the possible impact of religiosity and minimal psychological distress as factors contributing to resiliency in these samples.

RESULTS

The results showed that experience of maltreatment was associated with increased use of alcohol and cannabis. However, the effects differed depending on the type of maltreatment experienced. Higher levels of religiosity were consistently associated with lower levels of alcohol and cannabis use, but we found no evidence of an impact of minimal psychological distress on these measures.

CONCLUSIONS

This preliminary study shows that the experience of maltreatment may increase the risk of alcohol and cannabis use among university students in Latin American and Caribbean countries, but that higher levels of religiosity may reduce that risk. More work to determine the nature and significance of these relationships is needed.

Seminal plasma proteins as modulators of the sperm function and their application in sperm biotechnologies

Seminal plasma (SP) is known to play an important role in mammalian fertilization. However, the variability found in its composition among species, males and even fractions of the same ejaculate has made difficult to completely understand its effect in sperm function. Proteins are one of the major SP components that modulate sperm functionality. During the last years, intensive work has been performed to characterize the role of these proteins. They have been found to influence sperm capacitation, formation of the oviductal sperm reservoir and sperm-oocyte interaction. Sperm biotechnologies, such as sperm cryopreservation and flow cytometric sex-sorting, that involve a substantial dilution of the SP are detrimental to sperm quality. Attempts to improve the outcome of these biotechnologies include the restoration of SP, which has produced contradictory results. To overcome this variability, different research groups have proposed the application of isolated SP proteins. Herein, we will review the current knowledge in the role of the major SP proteins as modulators of sperm functionality. Furthermore, we will discuss the possible applications of the SP proteins in sperm cryopreservation and flow cytometric sex-sorting.

Pentoxifylline added to freezing or post-thaw extenders does not improve the survival or in vitro fertilising capacity of boar spermatozoa

This study evaluated whether pentoxifylline added to freezing and thawing extenders influenced the function of boar spermatozoa. In Experiment 1, pooled ejaculated sperm-rich fractions were frozen in 0.5 ml straws after dilution in extender supplemented with pentoxifylline to a final concentration of 0, 2, 4, 8, 16 or 32 mM. The addition of 4, 8, 16 and 32 mM pentoxifylline to the freezing extender significantly decreased the progressive and total motility of spermatozoa. The percentage of viable spermatozoa with intact acrosomes as well as the penetration rate and the efficiency of fertilisation were significantly lower in pentoxifylline-treated groups compared with the untreated control. In Experiment 2, a pool of three straws with ‘good’ post-thaw sperm quality parameters and another three straws with ‘poor’ sperm quality were diluted in extender with 0, 1, 2, 4, 8, 16 or 32 mM pentoxifylline. Post-thaw samples with both ‘good’ and ‘poor’ sperm quality with 0, 2, 4, 8 and 16 mM were used to assess IVF parameters. The addition of pentoxifylline to post-thaw extender did not improve the post-thaw motility or viability of spermatozoa compared with the control. The in vitro penetration was higher (P<0.05) than the control for oocytes fertilised with spermatozoa that were thawed and incubated in extender with 4, 8 and 16 mM pentoxifylline. However, no differences were observed in the efficiency of fertilisation. We conclude that pentoxifylline, as a supplement added to the freezing extender, has a deleterious effect and that it does not improve the survival or in vitro fertilising efficiency of frozen–thawed boar spermatozoa when added after thawing.

Pre-pubertal Di(2-ethylhexyl) Phthalate (DEHP) Exposure of Young Boars Did Not Affect SpermIn vitroPenetration Capacity of Homologous Oocytes Post-puberty

Di(2-ethylhexyl) phthalate (DEHP), a plastic softener used in polyvinylchloride (PVC) products (e.g., plastic bags and medical equipment), has been reported to have toxic effects on animal reproduction and is considered an environmental hazard based, mostly, on rodent studies. However, the doses used in these studies are often considerably higher than that presumed in human exposure. In the present study we used young boars as model animals to assess the effects of pre-pubertal DEHP exposure on the ability of spermatozoa to penetrate homologous oocytes in vitro. Eight pairs of cross-bred male boar siblings were used. One brother in each pair became, at random, the test animal exposed to DEHP per os, three times a week, from 3 to 7 weeks of age while the other acted as the control, i.e., placebo-exposed. Semen was collected and frozen between 8 and 9 months of age and stored until spermatozoa were evaluated for their ability to in vitro penetrate in vitro-matured homologous oocytes post-thaw. Both the penetration rate and the number of spermatozoa per oocyte were considered within expected ranges for frozen boar semen of good quality. Penetration rate did not significantly differ (p > 0.05) between the groups with DEHP-exposed: 50%; control: 59%, which could be owing to a large variation between boars, and between replicates. The number of spermatozoa in the ooplasm was low and similar (p > 0.05) between the groups with DEHP-exposed: 1.5 and the control: 1.7. Under the conditions of the present experiment, pre-pubertal exposure to DEHP does not seem to cause a deleterious effect on the in vitro fertilizing ability of frozen spermatozoa post-puberty.

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.

Improving the efficiency of insemination with sex-sorted spermatozoa

The sorting of X- and Y-chromosome-bearing spermatozoa by flow cytometry is nowadays one of the most apt assisted-reproduction technologies in livestock production. Potential economic and biological benefits, as well as those related to easier management of herds, have been reported arising out of the application of this technique, especially in cattle. Yet, the sex-sorting procedure induces damage to spermatozoa, affecting their function and fertilizing ability. Different species present varying degrees of susceptibility to damage from the sorting process and each has its own requirements for sex-sorted insemination procedures. Thus, several new protocols and strategies have been designed for the handling of sorted spermatozoa, with the main objective of optimizing their fertilizing ability and the consequent application of flow-cytometric sex-sorting technology. This article reviews current advances in this technology, pointing out the components to be improved before this technology may be widely applied in different domestic species.

The physiological roles of the boar ejaculate

During ejaculation in the boar, sperm cohorts emitted in epididymal cauda fluid are sequentially exposed and resuspended in different mixtures of accessory sex gland secretion. This paper reviews the relevance of such unevenly composed fractions of seminal plasma (SP) in vivo on sperm transport and sperm function and how this knowledge could benefit boar semen processing for artificial insemination (AI). The firstly ejaculated spermatozoa (first 10 ml of the sperm-rich fraction, SRF [P1]) remain mainly exposed to epididymal cauda fluid and its specific proteins i.e. various lipocalins, including the fertility-related prostaglandin D synthase; than to prostatic and initial vesicular gland secretions. P1-spermatozoa are hence exposed to less bicarbonate, zinc or fructose and mainly to PSP-I spermadhesin; than if they were in the rest of the SRF and the post-SRF (P2). Since the P1-SP is less destabilizing for sperm membrane and chromatin, P1-spermatozoa sustain most in vitro procedures, including cryopreservation, the best. Moreover, ejaculated firstly, the P1-spermatozoa seem also those deposited by the boar as a vanguard cohort, thus becoming overrepresented in the oviductal sperm reservoir (SR). This vanguard SR-entry occurs before the endometrial signalling of SP components (as PSP-I/PSP-II and cytokines) causes a massive influx of the innate defensive PMNs to cleanse the uterus from eventual pathogens, superfluous spermatozoa and the allogeneic SP. The SP also conditions the mucosal immunity of the female genital tract, to tolerate the SR-spermatozoa and the semi-allogeneic conceptus. These in vivo gathered data can be extrapolated into procedures for handling boar spermatozoa in vitro for AI and other biotechnologies, including simplified cryopreservation.

Localization and expression of spermadhesin PSP-I/PSP-II subunits in the reproductive organs of the boar

The epithelial localization and expression of the spermadhesin PSP-I and PSP-II subunits were determined in the testis, ductus epididymes (caput, corpus and cauda), seminal vesicles and bulbourethral glands of mature boars, using immunohistochemical, western blotting and RT-PCR methods. Immunohistochemistry showed positive labelling for PSP-I and PSP-II antibodies in the epithelium of seminal vesicles in all males tested. Positive immunolabelling, but with variable intensity, was also present in the epididymal epithelium (caput, corpus and cauda), although varying largely among segments and boars. Immunoreactivity was nearly or completely absent in the seminiferous epithelium and the bulbourethral gland, although SDS-PAGE and western blotting revealed the presence of PSP-I and PSP-II immunoreactive bands in all the tissue extracts, including the testis and the bulbourethral gland. mRNA amplification by RT-PCR using primers specific for PSP-I and PSP-II showed a trend similar to that observed for western blotting, i.e. intensity variation between tissues (even between segments of the same epididymis) and among boars. Our results indicate that the seminal vesicles are the main source of PSP-I and PSP-II spermadhesins, although epididymal segments, testis and the bulbourethral gland also participate in the expression of both proteins.

Improving the fertilizing ability of sex sorted boar spermatozoa

The sex sorting of spermatozoa by flow cytometry induces damage, since sperm cells are highly diluted, affecting their functionality and fertilizing ability. In this work it was investigated whether the concentration of sex sorted spermatozoa by the sedimentation method, rather than centrifugation, in combination with the presence of the seminal plasma protein PSP-I/PSP-II heterodimer may improve their fertilizing ability. Spermatozoa were sorted by flow cytometry and collected in BTS with 10% of seminal plasma (group C: control) or with 1.5mg/mL of PSP-I/PSP-II heterodimer (group H). Collected spermatozoa from each medium were split into two aliquots. One aliquot of each group was centrifuged (800 x g/5 min) just after sorting and stored 16-18 h at 17 degrees C (groups Cc and Hc) at 6 x 10(6)sperm/mL. The second aliquot was directly stored at 17 degrees C for 16-18 degrees C (group Cs and Hs). After storage the supernatant was discarded and the sedimented pellet adjusted to 6 x 10(6)sperm/mL. Membrane integrity, acrosome status and motility characteristics of spermatozoa from all groups were assessed. Post-weaning pre-ovulatory sows were inseminated by laparoscopy into the oviduct with 0.3 x 10(6) sex sorted spermatozoa to assess their ability to penetrate oocytes in vivo. Putative zygotes were collected 18 h after insemination by washing the oviduct. Penetration and monospermic rates were evaluated. After 16-18 h of storage, centrifuged spermatozoa collected with 10% seminal plasma or 1.5 mg/mL PSP-I/PSP-II heterodimer after sex sorting showed lower (p<0.05) percentages of membrane integrity, motility and fertilization than sedimented spermatozoa. Overall, the presence of 10% seminal plasma or PSP-I/PSP-II heterodimer did not affect the results. However, a positive effect of PSP-I/PSP-II heterodimer (p<0.05) was observed in sedimented spermatozoa. Hence, our results indicate that the sedimentation method in the presence of PSP-I/PSP-II heterodimer improves the in vivo fertilizing ability of sex sorted boar spermatozoa.

Adjustments on the cryopreservation conditions reduce the incidence of boar ejaculates with poor sperm freezability

The objective of the present study was to evaluate the effectiveness of different cryopreservation conditions (CCs) for freezing and thawing boar ejaculates, focusing on those having sub-optimal sperm freezability. Using a split-ejaculate technique, single ejaculates from 53 boars were diluted in lactose-egg yolk extender, containing a final glycerol concentration (GLY) of 2 or 3%, packaged in 0.5 mL straws and were cooled at rates of -10, -40 or -60 degrees C/min (cooling rate: CR). Thereafter, the frozen sperm samples were thawed by warming them at rates of approximately 1200 or approximately 1800 degrees C/min (warming rate: WR). Frozen-thawed sperm samples were assessed for the sperm motility (CASA system) and flow cytometric analysis of plasma and acrosomal membranes integrity. Cooling rate had no influence (P>0.05) on sperm quality parameters, however GLY and WR independently affected (P<0.05) all assessed sperm parameters. Evaluating the combined effect of GLY and WR (four different CCs resulting of a 2 x 2 factorial design), the best post-thaw quality results were achieved for sperm samples frozen with 3% glycerol and thawed at 1800 degrees C/min (CC4). However, there was a significant interaction (P<0.001) between CC and ejaculate for all post-thaw sperm quality assessments. Therefore, ejaculates were classified in three different populations according to the post-thaw sperm quality achieved using control CC (CC1: 2% of glycerol and approximately 1200 degrees C/min of warming). The effectiveness of CCs was different (P<0.05) in the three ejaculate populations. Spermatozoa from ejaculates considered as "good" freezers were relatively unaffected (P>0.05) by the modifications in the CCs, whereas those from "moderate" and, mainly, "bad" freezers were very sensitive (P<0.05). In conclusion, optimization of the CCs - GLY and WR - can improve the cryosurvival of spermatozoa in some ejaculates, particularly in those having poor sperm freezing ability.

Cryosurvival and in vitro fertilizing capacity postthaw is improved when boar spermatozoa are frozen in the presence of seminal plasma from good freezer boars

The study evaluated the protective effect of seminal plasma (SP) added to freezing extender against cryopreservation injuries to boar spermatozoa. Pooled sperm-rich fractions collected from 9 fertile boars were frozen in 0.5-mL straws after being extended in a conventional freezing extender either alone or supplemented with 5% of SPs (SP1-SP4) collected from the sperm-rich fractions (diluted 1:1, vol/vol, in Beltsville Thawing Solution extender) from 4 boars (1-4) with known sperm cryosurvival (poor, moderate, and good sperm freezers). Cryopreservation injuries were assessed in terms of postthaw sperm motility (assessed by computer-assisted sperm analysis), viability (plasma membrane and acrosome integrity assessed simultaneously by flow cytometry), membrane lipid peroxidation (malondialdehyde [MDA] production), and the ability of thawed spermatozoa to fertilize in vitro-matured homologous oocytes. The addition of SP from good sperm freezers (SP3 and SP4) improved (P < .01) the motility and viability of thawed spermatozoa without any influence on MDA production. Moreover, SP from good sperm freezers also increased (P < .05) the percentage of penetrated (SP3) and polyspermic oocytes (SP4) with respect to the control. Neither the total amount of SP proteins, protein profiles, nor antioxidant capacity of the different SPs were related to the various cryosurvival/fertilizing capacities of the processed spermatozoa.

Differences in SCSA outcome among boars with different sperm freezability

Spermatozoa from some boars sustain the process of cryopreservation poorly and yield poor fertility after artificial insemination. Poor freezability has not been disclosed using conventional semen analyses. A defective chromatin can, if present in a substantial number of spermatozoa, affect the fertilizing ability of spermatozoa. Here we tested the hypothesis that nuclear DNA instability could explain differences in freezability among boars, and complement or supersede conventional tests for sperm quality such as sperm motility or membrane assessments. Frozen-thawed (FT) spermatozoa from a total of 44 stud boars were assessed by the sperm chromatin structure assay (SCSA), in relation to computer-assisted sperm analysis-derived sperm motility variables and sperm viability (triple fluorescent microscopic staining), including three experiments. The first trial, including 24 boars, evaluated the relationship between the sperm motility and viability with levels of DNA integrity. The SCSA showed that most spermatozoa had intact DNA [levels of DNA fragmentation index (%DFI) ranging from 0.63% to 11.85%] significantly correlated (albeit weakly) with current sperm quality variables. The second trial, on 15 boars, assessed the influence of two different thawing rates (20 s at 37 degrees C vs. 8 s at 70 degrees C) and the post-thaw incubation times (0, 30, 150 and 300 min) at 37 degrees C on FT-boar sperm quality. The highest sperm survival (p < 0.05) and the lowest DNA damage (p < 0.01) were achieved when thawing was carried out at 70 degrees C for 8 s, without any change during the first 150 min of incubation. Finally, the third experiment studied if differences in sperm freezability showed by stud boar semen, as 'good' or 'bad' freezers by conventional analyses, could be attributed to differences in chromatin structure. All SCSA parameters were low, but significantly (p < 0.05-0.001) higher for 'bad' freezers, showing they had less homogeneous sperm chromatin than the 'good' freezers. The results indicate that SCSA outcome complements conventional assessment of FT-boar spermatozoa, disclosing differences in their ability to sustain freezing and thawing. However, the low overall DNA damage observed in FT spermatozoa seems to have poor biological significance.

Challenges in Pig Artificial Insemination

Semen extended in a liquid state, together with conventional artificial insemination (AI), is the sole sperm technology used by the pig industry. Sperm technologies known for many years, such as cryopreservation, and others developed during recent years, such as sperm sexing, have not yet been integrated into commercial use. Moreover, there has recently been an explosion of new technologies, such as sperm mediated gene transfer or encapsulated spermatozoa which need additional supportive techniques before they can be economically applied to pig breeding. The speed with which the aforementioned sperm technologies are accepted and utilized by the pig industry depends on the availability of efficient insemination procedures. Therefore, AI is entering a new dimension where it will be converted into a tool for the efficient application of current and new sperm technologies. Some new insemination procedures have been recently developed. This review examines the suitability of available insemination procedures for the efficient application of current, emergent and future sperm technology to the pig industry.

Factors influencing boar sperm cryosurvival1

Optimal sperm cryopreservation is a prerequisite for the sustainable commercial application of frozen-thawed boar semen for AI. Three experiments were performed to identify factors influencing variability of postthaw sperm survival among 464 boar ejaculates. Sperm-rich ejaculate fractions were cryopre-served using a standard freezing-thawing procedure for 0.5-mL plastic straws and computer-controlled freezing equipment. Postthaw sperm motility (assessed with a computer-assisted semen analysis system) and viability (simultaneously probed by flow cytometry analysis after triple-fluorescent stain), evaluated 30 and 150 min postthaw, were used to estimate the success of cryopreservation. In the first experiment, 168 unselected ejaculates (1 ejaculate/boar), from boars of 6 breeds with a wide age range (8 to 48 mo), were cryopreserved over a 12-mo period to evaluate the predictive value of boar (breed and age), semen collection, transport variables (season of ejaculate collection, interval between collections, and ejaculate temperature exposure), initial semen traits, and sperm quality before freezing on sperm survival after freezing-thawing. In Exp. 2, 4 ejaculates from each of 29 boars, preselected according to their initial semen traits and sperm quality before freezing, were collected and frozen over a 6-mo period to evaluate the influence of interboar and intraboar ejaculate variability in the survival of sperm after cryopreservation. In Exp. 3, 12 ejaculates preselected as for Exp. 2, from each of 15 boars with known good sperm cryosurvival, were collected and frozen over a 12-mo period to estimate the sustainability of sperm cryosurvival between ejaculates over time. Boar and semen collection and transport variables were not predictive of sperm cryosurvival among ejaculates. Initial semen traits and sperm quality variables observed before freezing explained 23.2 and 10.9%, respectively, of the variation in postthaw sperm motility and viability. However, more that 70% of total variance observed in postthaw sperm quality variables among ejaculates was explained by boar. This indicates that boar is the most important (P < 0.001) factor explaining the variability among ejaculates in sperm cryosurvival, with most (14 of the 15 boars in Exp. 3) showing consistent (P > 0.05) sperm cryosurvival over time.

Immunolocalization and possible functional role of PSP-I/PSP-II heterodimer in highly extended boar spermatozoa

PSP-I/PSP-II heterodimer is a major protein of boar seminal plasma which is able to preserve, in vitro, the viability, motility, and mitochondrial activity of highly extended boar spermatozoa for at least 5 hours. However, little is known about the binding pattern of the heterodimer to the sperm plasma membrane and its eventual relation with the maintenance of the sperm functionality. The present study investigated the effect of exposing highly extended boar spermatozoa (1 million/mL) to 1.5 mg/mL of PSP-I/PSP-II for 0.5, 5, and 10 hours at 38 degrees C on sperm characteristics and the changes in PSP-I/PSP-II localization as a result of both the addition of PSP-I/PSP-II to the extender and the incubation time. Exposure of the spermatozoa to PSP-I/PSP-II preserved sperm viability, motility, and mitochondrial activity when compared to nonexposed spermatozoa. This protective effect lasted for 10 hours (P < .05). After immunolabeling of highly extended semen with rabbit monospecific polyclonal antibody against PSP-I/PSP-II, the percentage of immunopositive spermatozoa declines over time from 71% (0.5 hours) to 49% (10 hours). However, more than 80% of spermatozoa remained labeled during the 10-hour incubation period if PSP-I/PSP-II was added. Scanning electron microscopy revealed 4 different binding patterns. The heterodimer was mainly localized to the acrosomal area, being redistributed to the postacrosomal area or lost during in vitro incubation. In conclusion, the protective effect of the heterodimer appears to be related to its adhesion to the acrosomal area, and the loss of this protective effect coincides with a stepwise redistribution of PSP-I/PSP-II during incubation.

Dissimilarities in sows’ ovarian status at the insemination time could explain differences in fertility between farms when frozen-thawed semen is used

Deep intrauterine insemination (DUI) offers a suitable alternative for the commercial use of frozen-thawed boar semen. The present study evaluated how the ovarian status at DUIs of frozen-thawed spermatozoa (1 x 10(9) spz/dose, two DUIs, 30-31 and 36-37 h after detection of oestrus) in 179 sows would explain differences in fertility between two farms with similar, but not equal, reproductive management (experiment 1). A further experiment investigated whether an increase in sperm number per AI-dose (1 versus 2 x 10(9) spz/dose, two DUIs, 30-31 and 36-37 h after detection of oestrus, on 228 sows) could minimize this effect (experiment 2). Ovaries were checked by transrectal ultrasonography at the time of DUI and sows were classified into three categories: F-: ovarian pre-ovulatory follicles were visible during two examinations; O-: ovulation visible during one examination; and C-sows: corpora hemorragica visible during the two examinations. Overall farrowing rates differed (P < 0.01) between farms (70.1 versus 51.2%, farms A and B, respectively). Distribution of sows among ultrasonography categories also differed (P < 0.05) between farms (17.5, 72.2 and 10.3% were classified as F-, O- and C-sows in farm A, versus 40.2, 29.3 and 30.5% in farm B). Nevertheless, farrowing rates and litter sizes within categories did not vary between farms (P > 0.05). In addition, a two-fold increase in the number of spermatozoa per DUI improved (P < 0.05) fertility in F- and C-sows, but not in O-sows. In conclusion, the interval DUI-to-ovulation provides a major explanation for fertility differences between farms when frozen-thawed spermatozoa are used.

Strategies to improve the fertility of frozen-thawed boar semen for artificial insemination

Although cryopreservation of boar semen for artificial insemination (AI) was developed 35 years ago, cryopreservation conditions and AI strategies are still considered sub-optimal. AI with excessive numbers of frozen-thawed sperm (5-6 x 10(9) cells), still does not achieve fertility levels similar to AI using liquid semen because of reduced sperm survival. Frozen-thawed (FT) spermatozoa have therefore not been the preferred option for commercial breeding programmes. However, substantial progress has been made regarding boar sperm cryopreservation. Adjustment of cooling and re-warming rates to biophysical properties of boar spermatozoa, new sperm package systems and the achievement of accurately consistent freezing of large numbers of samples using programmable freezers have contributed to post-thaw survival rates above 50%, a threshold similar to that used for bull AI-semen. Moreover, these post-thaw sperm survival rates are consistent within a large population of boars selected for sperm freezability potential, as occurs with AI-bull sires. When such post-thaw boar semen is deposited intra-utero, acceptable fertility (in terms of farrowing rates and litter size) is obtained. Currently, the most effective application of FT-semen for AI is achieved using deep uterine-AI (DUI) which allows placement of a minimal semen dose (in volume 0.5 to 10 mL and sperm number 0.5 to 1 x 10(9) total spermatozoa) into the anterior 1/3 of one uterine horn, with levels of fertility close to AI with liquid semen. However, owing to their shorter life span, FT-boar spermatozoa require an AI-to-ovulation interval not longer than 4-6 h, making peri-ovulatory AI a pre-requisite to obtain the highest possible fertility. Spontaneous ovulation most often occurs when two-thirds of oestrus has passed. Estimation of the duration of oestrus, taking into account the weaning-to-oestrus interval, is helpful when establishing appropriate AI-schedules. However, as the length of oestrus varies within and between farms, different AI strategies should be established a priori. The development of bio-sensors for spontaneous ovulation will widen the use of AI with frozen-thawed frozen semen.

Does multivariate analysis of post-thaw sperm characteristics accurately estimate in vitro fertility of boar individual ejaculates?

The objective of this study was to determine if a multivariate pattern analysis of frozen-thawed sperm characteristics of boar semen of unknown fertility, thus identifying groups of ejaculates as "good" or "bad" freezers, would estimate their fertilizing potential in an in vitro embryo production (IVP) system. Frozen-thawed spermatozoa from a single ejaculate collected from 46 boars were evaluated for sperm motility and kinematic patterns, for sperm viability and for early changes in sperm membrane stability. All data generated were used for a multivariate pattern analysis (PATN; CSIRO, Canberra, Australia) which objectively classified all ejaculates within a data set in to one of two groups, categorised as "good" (n = 25) or "bad" (n = 21) according with their freezability. In vitro matured oocytes were exposed to 2000 or 4000 frozen-thawed spermatozoa per oocyte for 6h and then cultured in embryo culture medium for either 6h (assurance of fertilization) or 7 days (to collect data on embryo development). Rates of sperm oocyte penetration and of embryo development significantly (p < 0.05) increased in a sperm:oocyte ratio-dependent manner. A similar pattern was observed when sperm characteristics were grouped. Indeed, ejaculates classified as "good" showed significantly (p < 0.05) higher rates of oocyte penetration, cleavage and of blastocyst formation than those classified as "bad". However, variation was still present among individuals (ejaculates, boars) in their ability to produce blastocysts in vitro. It is therefore concluded that despite the presence of a relationship for ejaculates with good semen quality post-thaw (thus grouped as "good") to higher IVP-results, the presence of individual variation does not allow for an accurate estimation of in vitro fertility based solely on the frozen-thawed semen quality parameters of a single ejaculate from a given boar.

Influence of seminal plasma PSP-I/PSP-II spermadhesin on pig gamete interaction

The seminal plasma PSP-I/PSP-II spermadhesin is able to preserve, in vitro, the viability of highly extended boar spermatozoa, suggesting it might be used as a suitable ameliorator for the damaging effects of sperm handling, including in vitro fertilization. However, little is known about the ligand capability of PSP-I/PSP-II as regards the zona pellucida (ZP) or its possible role in gamete interaction. The present study evaluated the effect of the presence of PSP-I/PSP-II (1.5 mg/ml) during in vitro oocyte maturation and also during co-incubation of frozen-thawed boar spermatozoa with either immature (IM) or in vitro matured (IVM) oocytes, either enclosed by cumulus cells or denuded. Exposure of the gametes to the heterodimer during in vitro gamete co-incubation showed a significant blocking effect of sperm penetration rates and a decreased number of spermatozoa per oocyte in both IM and IVM denuded oocytes. Such an effect was not present in cumulus-enclosed oocytes, suggesting the effect could be mediated by exposed ZP receptors. In addition, when PSP-I/PSP-II was added to the IVM medium, oocyte maturation rates were significantly reduced. In conclusion, the results suggest that PSP-I/PSP-II, when present in vitro, blocks sperm–ZP binding.

Piglets born after non-surgical deep intrauterine transfer of vitrified blastocysts in gilts

The aims of this study were: (1) to evaluate the effect of the number of previous estrus of recipient gilts on effectiveness of intrauterine insertion of a flexible catheter designed for non-surgical deep intrauterine catheterization during diestrus in pigs; and (2) to determine the farrowing rate and the litter size after non-surgical deep intrauterine embryo transfer (ET) of porcine blastocysts vitrified by the open pulled straw (OPS) method. In experiment 1, 27 large white hyperprolific gilts (LWh) with 2-6 previous estrus were used. Intrauterine insertions of the flexible catheter were carried out at day 5.5-6 of the estrous cycle (D0=onset of estrus). During insertions, no or only moderate reactions were observed in 88.9% of gilts and was not related (P >0.05) to the number of estrus prior to the insertion periods. The number of the estrus had a significant effect (P <0.05) on the difficulties found during the procedure. In the 100% of gilts with two estrus (N=6) it was not possible to insert the flexible catheter through the cervix. In gilts with three or more estrus, it was possible to pass the cervix and to progress along a uterine horn in 80.9% of the cases. In 86.7% of the gilts, the tip of the flexible catheter achieved the second or third quarter of the uterine horn. In experiment 2, following non-surgical deep intrauterine transfer of 20 vitrified/warmed blastocysts, 9 Meishan recipients (42.9%) farrowed an average of 5.4 +/- 0.8 piglets (range 3-9) of which 0.6 +/- 0.3 piglets (range 0-2) were born dead. In conclusion, this study shows that it is possible to obtain birth of piglets following non-surgical deep intrauterine embryo transfer (ET) of vitrified/warmed blastocysts. Non-surgical deep intrauterine ET and OPS vitrification methods are promising procedures to be used together for the introduction of new genetic material in a farm.

Hoechst 33342 stain and u.v. laser exposure do not induce genotoxic effects in flow-sorted boar spermatozoa

Sex selection by flow cytometry/cell sorting involves the staining of spermatozoa with Hoechst 33342 in combination with the impact of a u.v. laser beam, two potentially mutagenic agents. A phenotypic and cytogenetic study of lymphocytes of piglets born after insemination with spermatozoa stained with Hoechst 33342 and from piglets obtained from stain-sorted spermatozoa was performed to evaluate the genotoxic effect of Hoechst 33342 staining and u.v. laser irradiation on the offspring. Lymphocytes from piglets born after insemination with unstained spermatozoa, but from the same ejaculate, were used as a control group. Peripheral blood lymphocytes from these piglets were cultured following a standard cell culture protocol. Cells were then collected by centrifugation, subjected to hypotonic solution and fixed and dropped onto slides. Sister chromatid exchanges (SCEs) and chromosome aberrations (CAs: including chromosome and chromatid breaks) per cell were scored in 50-s division metaphase spreads from each donor. Reproductive parameters and litter performance of all inseminations performed were also recorded in all groups. Data were analyzed by ANOVA. No significant increase (P> 0.05) of SCE and CA frequencies were observed in piglets born from stained spermatozoa or from stain-sorted spermatozoa with respect to controls (untreated sperm). The results indicated that no mutagenic effect on spermatozoa, expressed as increases in the incidence of abnormalities in the resulting offspring and also as increases in SCE and CA frequencies on lymphocytes from these individuals, was induced by the staining of boar spermatozoa with Hoechst 33342, nor by combination of staining with laser impact during flow cytometry.

In vitro development following one-step dilution of OPS-vitrified porcine blastocysts

The objective of this experiment was to compare the in vitro survival and hatching rates of OPS-vitrified porcine blastocysts obtained after conventional (three-step dilution) or direct (one-step dilution) warming procedures. Expanded blastocysts were collected by laparotomy from weaned crossbred sows (n=7) on Day 6 of the cycle (D0: onset of estrus). Vitrification was performed as described by Berthelot et al. [Cryobiology 41 (2000) 116] using 17% (v/v) ethylene glycol and 17% (v/v) dimethyl-sulfoxide in the second vitrification medium. Conventional warming was carried out by plunging straws containing embryos in 800 microl of TCM199 Hepes containing 20% new born calf serum (TCM-NBCS) and 0.13 M sucrose for 1 min. Embryos were then transferred to another well with the same medium for 5 min, washed in TCM-NBCS with 0.075 M sucrose for 5 min and transferred to TCM-NBCS for 5 min. In one-step dilution, embryos were placed in 400 microl TCM-NBCS containing 0.13 M sucrose. To evaluate in vitro development, embryos warmed by conventional (n=59) or direct (n=58) procedures were cultured for 96 h. Non-vitrified embryos were used as controls (n=20). No significant (P>0.05) differences were observed in the in vitro development of vitrified and non-vitrified embryos. The survival and hatching rates obtained by three-step dilution (84.8 and 71.2%, respectively) and one-step dilution (86.2 and 74.1%, respectively) procedures were not different (P>0.05). The average diameter of expanded blastocysts from each donor was significantly different (P<0.001) among embryo donors. The embryo diameter or the interactions among the factors evaluated did not affect (P>0.05) the embryo survival and hatching of the vitrified/warmed blastocysts. However, the donor of embryos had a significant effect (P<0.001) on these parameters, confirming previous experiments. This experiment shows that porcine embryo vitrification and one-step dilution are promising procedures to be used under field conditions. However, the good results obtained in vitro must be confirmed also by in vivo experiments.

Vitrification of porcine embryos at various developmental stages using different ultra-rapid cooling procedures

In this study, three different vitrification systems (open pulled straw: OPS; superfine open pulled straw: SOPS; and Vit-Master technology using SOPS: Vit-Master-SOPS) were compared in order to investigate the influence of cooling rate on in vitro development of vitrified/warmed porcine morulae, early blastocysts, or expanded blastocysts. Embryos were obtained surgically on Day 6 of the estrous cycle (D0 = onset of estrus) from weaned crossbred sows, classified and pooled according their developmental stage. A subset of embryos from each developmental stage was cultured to evaluate the in vitro development of fresh embryos; the remaining embryos were randomly allocated to each vitrification system. After vitrification and warming, embryos were cultured in vitro for 96 h in TCM199 with 10% fetal calf serum at 39 degrees C, in 5% CO(2) in humidified air. During the culture period, embryos were morphologically evaluated for their developmental progression. The developmental stage of embryos at collection affected the survival and hatching rates of vitrified/warmed embryos (P < 0.001). The vitrification system or the interaction of vitrification system and developmental stage had no effect on these parameters (P > 0.05). Vitrified expanded blastocysts showed the best development in vitro (P < 0.001), with survival and hatching rates similar to those of fresh expanded blastocysts. The hatching rate of fresh morula or early blastocyst stage embryos was higher than their vitrified counterparts. In conclusion, under our experimental conditions, cooling rates greater than 20,000 degrees C/min, as occurs when SOPS or Vit-Master-SOPS systems are used, do not enhance the efficiency of in vitro development of vitrified porcine embryos.

Transfer of vitrified blastocysts from one or two superovulated Large White Hyperprolific donors to Meishan recipients: reproductive parameters at Day 30 of pregnancy

The present study was designed to determine the effect of pooling embryos from two donors on the reproductive success of transfer of vitrified/warmed porcine blastocysts. Intact blastocysts were collected from superovulated Large White Hyperprolific gilts (n = 24) on Days 5-5.5 after artificial insemination. Embryos were recovered by flushing the uterine horns, and unhatched blastocysts were selected. Vitrification and warming were performed as described by Berthelot et al. [Cryobiology 41(2000) 116]. To evaluate in vitro development, 37 vitrified/warmed blastocysts were cultured, non-vitrified embryos (n = 48) were used as controls. Embryo transfers were conducted in asynchronous (-24 h) Meishan gilts (n = 20). Twenty vitrified/warmed blastocysts were surgically transferred into one uterine horn. Ten recipients received embryos from one donor (Group 1) and the other 10 transfers were performed with mixed embryos from two donors (Group 2). Pregnancy was assessed ultrasonographically at Day 25 after estrus and recipients were slaughtered at Day 30 after transfer. In vitro survival rate of the vitrified/warmed blastocysts was lower (P < 0.01) than that from control embryos (73.0% versus 93.7%). The pregnancy rate for Group 1 (70%) was not different (P > 0.05) than that from Group 2 (90%). No significant differences were detected between Groups 1 and 2 for in vivo embryo development (number fetuses/transferred embryos in pregnant recipients) or in vivo embryo survival (number viable fetuses/transferred embryos in pregnant recipients). However, the in vivo efficiency (number viable fetuses/total transferred embryos) was higher (P < 0.05) when transfers were performed with embryos from two donors (19.5% versus 30.5%). These results indicate that pooling embryos from two donors increases the in vivo efficiency after transfer of vitrified/warmed porcine blastocysts.

Fluorescence in situ hybridization in diluted and flow cytometrically sorted boar spermatozoa using specific DNA direct probes labelled by nick translation

Successful evaluation of X- and Y-chromosome-bearing sperm separation technology using flow cytometry-cell sorter is of great importance. Fluorescence in situ hybridization (FISH), which allows for the detection of specific nucleic acid sequences on morphologically preserved spermatozoa, is an ideal method for quantitatively and qualitatively assessing the purity of sorted sperm samples. In this study specific pig DNA direct probes for small regions of chromosomes 1 and Y were used. Chromosome 1 was labelled in green and used as internal control to detect a lack of hybridization, whereas chromosome Y was labelled in red. Nick translation was used as the labelling method for the preparation of these probes. Spermatozoa, unsorted and sorted for high and low Y-chromosome purity from ejaculates of five boars, were fixed on slides and two-colour direct FISH was performed for chromosomes 1 and Y. About 500 non-sorted and 200 sorted spermatozoa per sample were scored. The proportion of Y-chromosome-bearing spermatozoa was determined by the presence of a red fluorescent signal on the sperm head and the proportion of X-chromosome-bearing spermatozoa was determined by subtraction. The efficiency of the hybridization procedure was established as near 98% on sorted and unsorted samples. The results of this study confirm that direct FISH using specific pig DNA probes labelled by nick translation provides a useful tool for laboratory validation of sperm separation by flow sorting technology. Moreover, the ease of nick translation and the quality of the fluorescent signal obtained using this method makes this procedure the most appropriate method for labelling pig DNA probes to be used for direct FISH on pig spermatozoa.

Influence of follicle size on the penetrability of immature pig oocytes for homologous in vitro penetration assay

In order to improve the performance of homologous in vitro penetration (hIVP) assays using immature oocytes to assess the penetrating ability of boar sperm, the present study was designed to evaluate the influence of oocyte and follicle size on the penetrability of immature pig oocytes obtained from slaughterhouse ovaries. Nonatretic antral follicles were isolated, measured with a computerized image analysis system and grouped according to their diameter: Group 1 (0.40-0.99 mm), Group 2 (1.00-2.19 mm), Group 3 (2.20-2.79 mm), and Group 4 (2.80-6.50 mm). After sperm coincubation and before penetrability evaluation, the immature oocytes were classified into four size categories according to their diameter excluding zona pellucida: <105, 105-109, 110-114, and > or =115 microm. As regards follicle size, the highest viability and penetrability were obtained with oocytes from follicles >2.20 mm (P>0.05). Regarding oocyte size, significant differences (P<0.05) were observed for all parameters evaluated between oocytes with a diameter above or below 110 microm. However, our results revealed that such differences were due to follicle size rather than oocyte diameter, since oocytes with the same diameter but from different follicle size groups showed different penetration rates. With increasing follicle size, the percentage of penetrated oocytes increased (P<0.05). Finally, our results showed that the greater penetrability of immature oocytes from larger follicles is not due to variations in the thickness of the zona pellucida. There were no significant differences in zona pellucida thickness between oocytes from the four follicular size groups. In summary, these results indicate that follicle size directly affects the penetrability of immature pig oocytes used in hIVP.

Relationship between antral follicle size, oocyte diameters and nuclear maturation of immature oocytes in pigs

We designed the present study to examine the possible relationship between oocyte, antral follicle size and the nuclear heterogeneity of immature pig oocytes, in order to study the heterogeneity of oocyte populations in ovaries obtained from slaughterhouses. Previously, we carried out an initial experiment to determine, by histological analysis, the effectiveness of the macroscopic criteria (MC) used to screen atretic and nonatretic antral follicles. We recovered 239 follicles by mechanical dissection, measured them with a computerized image analysis system, and classified them into five size categories according to their diameter (FD): Group 1 (0.40-0.99 mm), Group 2 (1.00-2.19 mm), Group 3 (2.20-2.79 mm), Group 4 (2.80-3.59 mm) and Group 5 (3.60-6.50 mm). In relation to histological analysis, the results showed that MC is an effective method to select atretic and nonatretic antral follicles from 0.40 to 6.50 mm in diameter (overall accuracy was 80.75%, with sensitivity and specificity rates of 79.33 and 82.20%, respectively). In a second experiment, we recovered 454 nonatretic follicles, then measured and classified them as mentioned above. We removed oocytes individually from follicles and measured their size (oocyte diameter without and with zona pellucida, OD and TOD, respectively). Finally, we evaluated the relationship between OD, FD and nuclear maturation of immature oocytes (germinal vesicles (GV) Stages 0, I, II, III and IV; diakinesis, prophase I, and metaphase I). Overall OD was 101.77 +/- 0.65, 109.19 +/- 0.45, 113.55 +/- 0.50, 116.92 +/- 0.46 and 117.13 +/- 0.47 microm (Groups 1, 2, 3, 4, and 5, respectively). Differences in OD between groups were significant (P < 0.01), although from 2.80 to 6.50 mm follicles, the oocytes were not different in size. There was a certain heterogeneity in OD within each follicular group. Although we observed a certain degree of nuclear variability, regardless of FD or OD, the present study showed a clear progression in GV when FD increased from 0.40 to 6.50 mm. A positive correlation (r2 = 0.4248; P > 0.05) was established mainly between the nuclear stage and oocyte diameter.

Viability and fertility of rabbit spermatozoa diluted in Tris-buffer extenders and stored at 15 degrees C

Artificial insemination (AI) in rabbits is not extensive in the breeding programs of the rabbit meat industry. A limiting factor is related to the semen preservation. In order to improve the use of AI, two experiments have been conducted to evaluate sperm viability and fertility of rabbit semen chilled and stored at 15 degrees C after dilution in Tris-based extenders. In Experiment 1, pooled semen samples were diluted 1:10 (semen/extender) in four different Tris-based extenders (Tris-citric-glucose (TCG), TES-Tris-glucose (TTG), Tris-citric-fructose (TCF) and TES-Tris-fructose (TTF)) and stored at 15 degrees C. Sperm viability was evaluated at 0, 24, 48, 72 and 96 h following dilution for total sperm motility (TSM), forward progressive motility (FPM), plasma membrane integrity (PMI) and acrosome integrity (NAR). Viability of spermatozoa declined with time of storage (P<0.05), irrespective of the extender used. There were interactions between extender and time of storage (P<0.05) in all viability parameters evaluated. After 96 h of storage, TCG provided the highest sperm viability (P<0.05) and TTG the lowest (P>0.05). In Experiment 2, a field trial was conducted at a commercial farm to evaluate the conception and farrowing rates of rabbit spermatozoa extended in TCG. After synchronization of oestrous and induction of ovulation, 3713 does with different physiological conditions (nulliparous, primiparous, lactating and re-breeding) were inseminated one time (15x10(6) sperm per doses) with semen stored at 0 (n: 1275), 24 (n: 1503) and 48 h (n: 935) at 15 degrees C. Overall conception and farrowing rates were 77.1+/-0.7 and 70.4+/-0.7, respectively, and the mean litter size was 7.6+/-0.1. Fertility results were unaffected by the time of semen storage (P>0.05). Regardless of time of semen storage, fertility results were affected by the physiological conditions of does (P<0.05). Nulliparous and lactating does showed the highest fertility and primiparous the lowest. In summary, these results indicate that Tris-buffer extenders are effective for preserving viability and fertilizing capability of rabbit spermatozoa stored at 15 degrees C.

Effect of the oxygen transfer coefficient on xylitol production from sugarcane bagasse hydrolysate by continuous stirred-tank reactor fermentation

The effect of the oxygen transfer coefficient on the production of xylitol by bioconversion of xylose present in sugarcane bagasse hemicellulosic hydrolysate using the yeast Candida guilliermondii was investigated. Continuous cultivation was carried out in a 1.25-L fermentor at 30 degrees C, pH 5.5, 300 rpm, and a dilution rate of 0.03/h, using oxygen transfer coefficients of 10, 20, and 30/h. The results showed that the microbial xylitol production (11 g/L) increased by 108% with the decrease in the oxygen volumetric transfer coefficient from 30 to 20/h. The maximum values of xylitol productivity (0.7 g/[L.h]) and yield (0.58 g/g) were obtained akLa 20/h.

Infectious diseases in Mazzaella laminarioides (Rhodophyta): estimating the effect of infections on host reproductive potential

Very little is known about the potential effects of endophytic infections on the host in algae, especially in terms of fitness. In this study, we report a first attempt at quantifying the effects of the endophytes Endophyton ramosum (Chlorophyta) and Pleurocapsa sp. (Cyanophyta) on the reproductive potential of their host Mazzaella laminarioides (Rhodophyta). Density of reproductive structures and spore germination rates was compared between infected and non-infected fronds. It was found that differences in density of reproductive structures between infected and non-infected fronds were not significant, which suggests that the level of maturity of the host is unaltered by the endophytes. On the other hand, carpospore germination rates significantly decreased when produced by fronds infected by the cyanobacterium Pleurocapsa sp. Thus, in the general context of host fitness, we discuss the fact that only some of the components of the reproductive output of M. laminarioides are negatively affected by the endophytes.