Electrophoresis of NADH-dependent oxidoreductase (diaphorase) in boar spermatozoa: Elektrophorese der NADH-abhängigen Oxydoreduktase (Diaphorase) in Eberspermatozoen

Two forms of NADH-dependent oxidoreductase (diaphorase [EC.1.6.99.-]) are established in boar spermatozoa. The first form is typical for soluble proteins with a varying electrophoretic profile, while the other form for sedimental proteins with a specific, slowly-moving fraction, which is not common for the soluble form. The two enzyme forms have a close isoelectric point (pI5.5-6.0) and they can not be inhibited by dicumarol 10(-5) mol l-1 and FAD 10(-4) mol l-1. The molecular mass of the soluble form of the enzyme is 28, 37, 46 and 67 kD, while of the sedimental form it is 220, 250 and 260 kD, respectively.     

A new and simple method to evaluate early membrane changes in frozen-thawed boar spermatozoa

Detection of early changes in the sperm plasma membrane during cryopreservation is of utmost importance when designing freezing protocols and has previously been studied in the pig species using annexin-V detection of phosphatidylserine translocation. In the present study we designed a new assay to detect these changes in boar spermatozoa, based on the slight increase of sperm membrane permeability occurring during the early stages of cryoinjury, using the combination of three fluorescent probes, SNARF-1, YO-PRO-1 and ethidium homodimer. Four ejaculates from five different boars were frozen-thawed and flow cytometrically (FC) evaluated as paired samples. One of the samples was assayed using the annexin-V/propidium iodide staining and the other sample was evaluated using the new triple staining. Using this combination of probes, four sperm subpopulations were easily detected: viable, with stable membranes (SNARF-1 positive cells), and three with compromised membranes, one of YO-PRO-1+/Eth- cells, one ethidium homodimer+ spermatozoa and, finally spermatozoa stained both with YO-PRO-1 and ethidium homodimer (YO-PRO-1+/Eth+). The latter three categories corresponded to dead spermatozoa, but with different degree of membrane damage, being YO-PRO+/Eth- an earlier stage of membrane destabilization, (manifested by an increase in membrane permeability, while still maintaining membrane integrity) than YO-PRO+/Eth+. A method agreement analysis between both methods was performed revealing good agreement, although the percentage of live cells was 9.44% larger for the triple stain than the annexin-V assay. The new assay stained all sperm sub-populations present in the sample, making it especially suitable for both fluorescence microscopy and flow cytometry, facilitating the exclusion of debris and egg-yolk particles when using FC.     

Controlled cooling during semen cryopreservation does not induce capacitation of spermatozoa from two portions of the boar ejaculate

Cryopreservation imposes dramatic changes in boar sperm survivability but it is as yet unclear which part of the process affects the spermatozoa the most. The present study monitored, along the entire process of cryopreservation, the stability (PMS) of the architecture of the lipid plasma membrane and its integrity (PMI), as well as the kinetics of the processed spermatozoa using two portions from the boar ejaculate (P1 = the first 10 mL of the sperm-rich fraction, SRF; P2 = the rest of the ejaculate), frozen in a recently developed package, the MiniFlatPack (MFPs, 0.5 x 10(9) sperm/dose). Evaluation was made at four specific stages, viz. S1 = after collection (suspended in Beltsville thawing solution, BTS); S2 = at 15 degrees C (suspended in lactose-egg yolk, LEY); S3 = at 5 degrees C (suspended in LEY plus glycerol); and S4 = post-thaw. Both sperm kinetics (using computer-assisted sperm analysis, CASA) and PMS [i.e. the degree of lipid disorder and of the exteriorization of phosphatidylserine (PS) in the plasma membrane, measured by flow cytometry using Merocyanine-540 (M-540), and Annexin-V (AV) respectively], as well as plasma membrane integrity [PMI, i.e. the degree of membrane damage, measured using Yo-Pro-1 or propidium iodide (PI)] were assessed after incubation in BTS at 38 degrees C. Moreover, spermatozoa were challenged by incubation in modified Brackett-Oliphant medium (mBO+) with 37 mm of bicarbonate at 38 degrees C for 30 min, and their PMS and PMI further explored. Total sperm motility was significantly higher in P1 than in P2 along the entire process (S1-S4; p < 0.01), decreasing significantly at S4 for both fractions (p < 0.0001). The proportion of spermatozoa showing linear motility (LinM) was similar between ejaculate portions (P1 and P2), with a significant increase post-thaw (S4; p < 0.0001). During cooling (S1-S3) but not post-thaw (S4), lateral head displacement (LHD) differed between portions and changed along the stages (p < 0.01). Sperm velocity differed between portions in S1 (p < 0.01), but remained similar, independently of the portion, thereafter (S2-S4). Both PMS and the total number of live spermatozoa remained similar between S1 and S3 while incubated in BTS for both ejaculate portions. Sperm mortality increased post-thaw (S4) in both portions but the degree of lipid disorder remained low in the live cells (1.28% for P1; 1.55% for P2). Exposure to mBO+, on the other hand, significantly increased membrane lipid disorder along cooling (S1-S3; p < 0.0001), increasing the percentages of dead spermatozoa, especially post-thaw (around 70%, both portions). PS-exteriorization (AV) was not evident along the cryopreservation process in control (BTS) samples and exposure to mBO+ only induced minor variations. The data showed that kinetics, PMS and PMI of boar spermatozoa suspended in BTS (S1), LEY (S2) or LEY plus glycerol (S3) were maintained during controlled cooling but were altered by thawing, showing more characteristics of cell injury than of sperm capacitation. The spermatozoa were able to capacitate but the bicarbonate challenge destabilized the plasma membrane during initial cooling and accelerated membrane changes post-thaw. We conclude that capacitation of boar spermatozoa does not occur during controlled cooling.     

Fertility and post-thawing characteristics of deep frozen boar spermatozoa

Eight-nine gilts were inseminated with deep frozen boar spermatozoa thawed in seminal plasma, filtrate of seminal plasma, skimmed milk and isotonic glucose solution. The most favourable fertility results were obtained when seminal plasma was used as thawing diluent. It was shown that a relationship exists between the post thawing acrosome morphology, the post thawing GOT-release and the fertility of frozen spermatozoa.     

Conventional slow freezing cryopreserves mouflon spermatozoa better than vitrification

This work examines the effectiveness of a TCG (Tris, citric acid, glucose, 6% egg yolk and 5% glycerol) and a TEST (TES, Tris, glucose, 6% egg yolk and 5% glycerol) sperm extender in the freezing of mouflon spermatozoa at slow cooling rates, using different pre‐freezing equilibration times (2–3 hr). It also examines the tolerance of mouflon spermatozoa to different concentrations of cryoprotectants (5, 10, 20% glycerol; 5%, 10%, 20% dimethyl sulfoxide; 6% polyvinylpyrrolidone) and/or sucrose (100, 300, 500 mm ). The highest quality (p < .01) thawed spermatozoa were obtained when using the TEST extender and an equilibration time of 3 hr. Sperm motility and membrane integrity were strongly reduced when using rapid freezing rates (60–85°C min^?1), independent of the concentration of cryoprotectants. The lowest sucrose concentration (100 mm ) provided the highest (p < .05) percentage of motile spermatozoa and live spermatozoa with an intact acrosome. Vitrified–warmed sperm variables were at their best when the spermatozoa was diluted in TCG–6% egg yolk + 100 mm sucrose and warmed at 60°C. Slow warming at 37°C strongly reduced (p < .05) sperm motility and viability. However, sperm vitrification returned lower fertility, sperm motility and sperm viability values than conventional sperm freezing.     

Monoclonal antibodies against boar acrosomal antigens labelling undamaged acrosomes of spermatozoa in immunofluorescence test

Monoclonal antibodies specific for acrosomal proteins were prepared and characterized. Two of these monoclonal antibodies, ACR.3 and ACR.11, reacted with the same molecular specificity of acrosomal antigens (18-20 kDa), antibody ACR.4 reacted with the 25-27 kDa antigens, and antibody ACR.2 reacted with several forms of boar acrosin (55, 53, 45, and 38 kDa). All monoclonal antibodies labelled the acrosomes of undamaged spermatozoa in immunofluorescence test. This test should be convenient as an immunological test of the sperm quality.     

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

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

Effect of storage in short--and long-term commercial semen extenders on the motility, plasma membrane and chromatin integrity of boar spermatozoa

For artificial insemination (AI) in pigs, preservation of liquid boar semen at 16-20 degrees C is still common practice as sperm cryopreservation remains suboptimal in this species. To meet the different needs of the swine industry, several extenders have been developed to preserve semen in liquid form for short--and long-term storage. In the present study, three different commercial extenders devised for short-term (BTS+) or long-term preservation (MR-A and X-Cell), were used to test whether storage of semen from four mature, fertile boars at 17 degrees C for 96 h would affect sperm characteristics relevant for fertility, such as motility, membrane integrity and chromatin stability. Computer-assisted sperm analysis, and stainings with the acylated membrane dye SYBR-14/propidium iodide, and acridine orange in connection with flow cytometry were used to evaluate these variables. Percentages of total motile spermatozoa decreased slightly, but significantly, after 72-96 h. While membrane integrity values varied during the period of study, no significant changes in either membrane integrity or chromatin stability were, however, registered. This suggests a customary 96-day storage at 17 degrees C in these extenders was too short an interval to cause losses of integrity in nuclear DNA in the boar population studied.     

Fennel (Foeniculum vulgare) provides antioxidant protection for boar semen cryopreservation

Boar semen is extremely vulnerable to cold shock and it is also sensitive to peroxidation due to the high content of unsaturated fatty acids in the plasma membrane. Antioxidants exert a protective effect on the plasma membrane of frozen boar sperm. Fennel has been shown to contain antioxidant substances. Therefore, this study was performed to evaluate the effect of different concentrations of fennel added to the freezing extender on boar semen quality and lipid peroxidation after thawing. Semen collected from four boars was cryopreserved in lactose-egg-yolk extender or in the same extender with varying concentration of fennel essences: low (LF); medium (MF); high (HF). Analysis of data clearly indicated that higher concentrations of fennel produced significant improvement in total motility. Moreover, when fennel was included in the extender, a dose-dependent tendency to increase sperm viability was observed. In contrast, the addition of fennel had no effect on acrosome integrity or hypoosmotic swelling test (HOST) compared with the control. Malondialdehyde (MDA) formation decreased significantly in fennel groups, yielding similar results for MF and HF. Fennel seems a new antioxidant for use in sperm cryopreservation, but its particular effects on sperm physiology must be further studied, especially the causes of motility stimulation and its effect on lipoxidation.     

Characterization of lectin receptors isolated from the outer acrosomal membrane of boar spermatozoa

The outer acrosomal membrane (OAM) of boar spermatozoa was isolated by homogenization and centrifugation through modified colloidal silica. Homogeneity of the isolated membrane fraction (OAM) was revealed by transmission electron microscopy. At least 10 protein components could be discriminated by SDS-PAGE electrophoresis of the OAM, with molecular weights ranging from 340 to 15 kdal. Radiolabelling of the externally disposed carbohydrate side-chains by [3H]borhydride reduction of the isolated membrane, oxidized by use of galactose oxidase, revealed one main galactoprotein with a reduced molecular weight of about 270 kdal. This was identified as the RCA-120 receptor protein by means of lectin-affinity chromatography, high resolution gelfiltration and SDS-PAGE. Screening of the Con A binding properties of the solubilized membrane components partially isolated by affinity chromatography and HPLC was performed by an enzyme-linked-lectin-assay (ELLA). Electrophoretic analysis including a Con A-peroxidase staining procedure allowed the identification of 4 Con A binding proteins of the OAM with molecular weights of 120, 110, 88 and 66 kdal.     

Capacitation status and in vitro fertility of boar spermatozoa: effects of seminal plasma, cumulus-oocyte-complexes-conditioned medium and hyaluronan

In the present study, the effects of seminal plasma (SP), cumulus-oocyte-complexes (COCs) conditioned medium (CCM) and hyaluronan (HA) on functional changes and in vitro fertilizing ability of porcine spermatozoa were examined. In in vitro fertilization (IVF) experiments, 10% (v/v) of exogenous SP in the fertilization medium prevented sperm penetration (using fresh-extended and frozen-thawed ejaculated spermatozoa). Analysis of frozen-thawed CCM revealed a HA content to levels of 30 ng/mL per incubated COC. Presence of frozen-thawed CCM did not, however, prove effective to increase (furthermore decreasing) oocyte penetration in vitro, and neither did supplementation with exogenous HA at the same concentration as that present in the CCM (secreted by COCs). Analysis of sperm capacitation using the chlortetracycline (CTC) assay showed that frozen-thawed CCM had no elevating effect on 'B-pattern' spermatozoa (implying capacitation-like changes) and that addition of 10% (v/v) SP held spermatozoa in the 'F-pattern' (intact) status. Dose of 500 microg/mL HA and freshly prepared CCM increased, however, the frequency of capacitated spermatozoa (B-pattern) without resulting in increased rates of 'AR-pattern' (acrosome-reacted) spermatozoa, compared with controls. The present results confirm the decapacitating effect of SP and suggest capacitating actions of HA (dose-related) and CCM (freshly prepared) on boar spermatozoa in vitro. The unclear effects of frozen-thawed CCM and a low dose of HA on penetration rates of boar spermatozoa call for further researches of their function in vivo.     

Effects of glycerol,equilibration time and antioxidants on post‐thaw functional integrity of bovine spermatozoa directly obtained from epididymis

This work aimed to evaluate the effect of stabilisation times, glycerol concentration, and the catalase and superoxide dismutase supplementation of diluent on parameters of frozen‐thawed spermatozoa from epididymis of Nelore bulls: Experiment 1: spermatozoa diluted in Tris‐egg yolk with glycerol (3%, 5% or 7%) and stabilisation times (0, 2 or 4 hr at 5°C); Experiment 2: Tris‐egg yolk only, Tris‐egg yolk with catalase (CAT, 50 or 100 U ml^?1) or superoxide dismutase (SOD, 50 or 100 U ml^?1). Frozen‐thawed spermatozoa were evaluated for kinetic parameters, plasma membrane and acrosome integrity, mitochondrial activity and IVF capacity. ALH and BCF were affected (p < .05) by glycerol at 3% after 4‐hr equilibration time and 7% after 2‐hr equilibration time. Glycerol 3% had lower (p < .05) iPM and iAc after 4 hr. Glycerol 5% had greater (p < .05) hPMM after 4 hr and iAc after 2 hr than at 0 hr. SOD 100 U ml^?1 had lower (p < .05) linearity and wobble compared to control group. No was observed differences to fertilisation rate (p < .05) among groups. In conclusion, glycerol 5% in Tris‐egg yolk extender for 4 hr is suitable for the preservation of sperm kinetics and membrane integrity. CAT (50 and 100 U ml^?1) or SOD (50–100 U ml^?1) had no beneficial effects on sperm kinetics, plasma and acrosomal membrane integrity, mitochondrial activity or the capacity for IVF of frozen‐thawed spermatozoa from epididymis of Nelore bulls.     

Ultrastructural features and pathogenesis of decapitated spermatozoa in a boar

Summary. A boar with decapitated spermatozoa was examined. The growth rate and libido were normal. The right testis was in the scrotum, but the left one was intra-abdominal. Ejaculated spermatozoa and tissue specimen from both testes were observed by light and electron microscopy. Only tailless heads and headless tails of spermatozoa were observed in the ejaculate. The ratio of heads to tails was about 1:4. Motility of the headless tails was about 25%. The proximal extremity in the tail was occupied by the proximal centriole. The basal plate could not be found in the head or in the tail. Pathogenesis of decapitated spermatozoa in the present case was analysed by investigating spermiogenesis in the scrotal testis. Since the pair of centrioles failed to approach the nucleus, mechanical connection between the proximal centriole and the nucleus did not seem to be established. In addition, the basal plate was not formed on the nuclear membrane. Since the ratio of tailless heads to headless tails was also 1:4 in the testis, it was concluded that the heads had already detached the tails in the testis.     

Supplemental effect of varying L-cysteine concentrations on the quality of cryopreserved boar semen

Cryopreservation is associated with the production of reactive oxygen species, which leads to lipid peroxidation of the sperm membrane and consequently a reduction in sperm motility and decreased fertility potential. The aim of this study was to determine the optimal concentration of L-cysteine needed for cryopreservation of boar semen. Twelve boars provided semen of proven motility and morphology for this study. The semen was divided into four portions in which the lactose-egg yolk （LEY） extender used to resuspend the centrifuged sperm pellet was supplemented with various concentrations of L-cysteine to reach 0 mmol L^-1 （group Ⅰ, control）, 5 mmol L^-1 （group Ⅱ）, 10 mmol L^-1 （group Ⅲ） and 15 mmol L^-1 （group Ⅳ）. Semen suspensions were loaded in straws （0.5 mL） and placed in a controlled-rate freezer. After cryopreservation, frozen semen samples were thawed and investigated for progressive motility, viability using SYBR-14/EthD-1 staining and acrosome integrity using FITC-PNA/EthD-1 staining. There was a significantly higher （P 〈 0.01） percentage of progressive motility, viability and acrosomal integrity in two L-cysteine-supplemented groups （group Ⅱ and group Ⅲ） compared with the control. There was a biphasic effect of L-cysteine, with the highest percentage of progressive motility, viability and acrosomal integrity in group Ⅲ. In conclusion, 5 or 10 mmol L^-1 was the optimum concentration of L-cysteine to be added to the LEY extender for improving the quality of frozen-thawed boar semen.     

速冻和缓慢冷冻法对精子运动特征的影响

目的了解冷冻方法对人精子运动特征的影响。方法精液标本进行速冻和缓慢冷冻保存,应用计算机精液分析仪进行精子运动特征分析。结果冷冻复温后精子运动能力与冷冻前精子运动能力比较明显下降(P<0.001,P<0.05);速冻与缓慢冷冻方法保存的精子运动参数相比较差异均无显著性(P>0.05)。结论冷冻保存易导致精子运动能力下降,速冻与缓慢冷冻方法对精子运动参数影响无明显差异。     

Monitoring the reactive oxygen species in spermatozoa during liquid storage of boar semen and its correlation with sperm motility,free thiol content and seasonality

Oxidative stress is an important factor affecting the quality of spermatozoa during liquid storage of boar semen; however, monitoring of reactive oxygen species (ROS) that provides direct insight into the oxidative status is not yet attempted. This study aimed to monitor ROS in boar sperm during liquid semen storage to determine its correlation with sperm motility and free thiol (SH) content, and seasonality. Ejaculate was collected from mature Duroc boars in a commercial farm in autumn and spring, diluted in Mulberry III extender, stored at 15°C, and examined daily for sperm ROS level, SH content and motility. The ROS levels in spermatozoa prepared during autumn and spring were constantly low until days 4 and 5 of storage, respectively, which thereafter progressively increased in association with the loss of sperm motility. The increased sperm ROS level correlated with the higher SH level and lower motility, which was accentuated from day 4 of storage and was higher in September, or early autumn. This study indicates that increased sperm ROS levels during liquid storage results in oxidative damage, causing loss of sperm motility, presumably through decreased sperm viability, suggesting that sperm ROS monitoring effectively evaluates the quality of boar semen.     

Potassium leakage: not the cause of gossypol induced anti-motility in spermatozoa

Gossypol induced a dose-dependent potassium leakage from boar spermatozoa suspended either in Krebs-Ringer phosphate buffer or in isotonic tris-HCl buffer. It had, however, practically no effect on the spermatozoal intracellular sodium ion content. As spermatozoal motility arrest was observed at a much lower gossypol concentration, the gossypol anti-motility effect does not seem to have stemmed from potassium leakage.     

A chemically ''defined'' diluent for cryopreservation of bovine spermatozoa

A chemically 'defined' extender for the cryopreservation of bovine spermatozoa was developed using commercially available lecithin as an additive to protect cells against freeze damage. The effectiveness of different media in preventing cryoinjury was evaluated by assessing motion activity immediately post-thaw and after 2 h incubation at 37 degrees C by means of automatic computer image analysis. The extender best suited to maintains swimming activity consisted of the zwitter ion buffer system HEPES-Tris/Citrate (HTC) supplemented with 0.9% lecithin. The effectiveness of this diluent was compared with that of an extender containing egg yolk used routinely in breeding stations. While immediately post-thaw sperm samples frozen in HTC showed a lower motion activity than those preserved in egg yolk diluent, the opposite result was obtained after 2 h incubation at 37 degrees C.     

In vitro effects of nonylphenol on motility,mitochondrial, acrosomal and chromatin integrity of ram and boar spermatozoa

The objective of this study was to determine the effects of nonylphenol (NP) on viability of ram and boar sperm in vitro. Ram or boar spermatozoa were exposed to 1, 10, 100, 250 and 500 μg NP ml^?1 for 1, 2, 3 or 4 h. Computer‐assisted sperm motility analysis (CASA) system was used to evaluate sperm motility characteristics. Flow cytometry was used to determine mitochondrial membrane potential (MMP) and chromatin integrity, while epifluorescent microscopy was used to determine sperm acrosomal status. Exposure of both species spermatozoa to 250 and 500 μg NP ml^?1 was detrimental to progressive motility (P < 0.05), and its adverse effect was significant at lower (100 μg NP ml^?1) concentration (P < 0.05). The percentages of ram and boar spermatozoa with high MMP declined drastically after exposures to ≥250 μg ml^?1 NP (P < 0.05). Unlike chromatin integrity, which did not appear to be altered by NP exposure, there were dose‐dependent NP effects (P < 0.05) on acrosomal integrity of both species at as low as 1 μg ml^?1 NP for boar spermatozoa and 10 μg ml^?1 NP for ram spermatozoa. These data show adverse effects of NP on ram and boar spermatozoa and thus its potential harmful effects on male reproduction as NP is found in fruits, vegetables, human milk, fish and livestock products.