Assessment of Some Morphofunctional Characteristics of Flow-Cytometrically Sorted and Stained Boar Spermatozoa

Veterinary Research Communications -     

Relationship Between Motility and Membrane Integrity of Boar Spermatozoa in Media Varying in Osmolality

A study was conducted to evaluate the relationship between boar sperm motility and membrane integrity following exposure to media with 150–1120 mOsm. Total sperm motility was defined as the percentage of spermatozoa that had any form of motility was subjectively assessed under a light microscope. Sperm cell damage was expressed as a loss of membrane integrity as measured by a combination of fluorescent stains, carboxyfluorescein diacetate (CFDA) and propidium iodide (PI), and Hoechst 33258 (H33258). There were no significant differences between sperm motility and membrane-intact spermatozoa, as measured by CFDA-PI and H33258, in media with 250 and 300 mOsm. In anisosmotic conditions, a higher amount of membrane-intact spermatozoa than motile spermatozoa was observed. In hypo-osmotic conditions (150 mOsm), a high proportion of spermatozoa had curled or coiled tails and most of them retained their entire membrane integrity, as detected by CFDA-PI. In media with 350–1120 mOsm, some spermatozoa accumulated PI in the head region and CFDA in the mid-piece. These spermatozoa fluoresced blue at the lower region of the head, as detected by H33258. The ATP content in spermatozoa exposed to hypo- and hyperosmotic conditions was markedly reduced. There was no recovery of sperm motility on returning the spermatozoa to isosmotic conditions after 10 min incubation in anisosmotic conditions, indicating that the spermatozoa suffered an almost complete and irreversible loss of motility. This irreversible loss of motility may be a consequence of reduced ATP production in spermatozoa subjected to anisosmotic conditions. The results of this study demonstrate that plasma membrane integrity assessment in combination with sperm motility, using a range of media varying in osmolality, can give valuable information about the status and function of different sperm membranes, which might be relevant for semen preservation.     

Effectiveness of in vitro Methods for Predicting in vivo Fertilizing Capacity of Boar Spermatozoa Cryopresemed with 2% or 4% Glycerol1

Contents: Thirteen ejaculates from each of two boars that were greatly different in post-thaw sperm quality were frozen in either 2 or 4% glycerol (final concentration/split-sample). Frozen-thawed sperm were evaluated in vitro, for motility, acrosomal integrity (NAR), plasma membrane integrity (PMI), and for sperm penetration (SPA) of zona-free hamster eggs. To evaluate in vivo fertilizing capacity, 52 sows were inseminated once, 30–34 hours after onset of estrus. Ova were recovered from the reproductive tract 2–4 days following insemination and evaluated for cleavage and sperm binding. The two boars differed significantly for all in vivo and in vitro parameters. Motility and PMI were higher (P < 0.05) for sperm frozen with 4% than 2% glycerol whereas NAR was higher with 2% glycerol. Higher numbers of sperm were bound to eggs in vivo for sperm frozen with 4% than with 2% glycerol (P < 0.05). The fertilization rate for sperm frozen with 4% glycerol was not significantly higher than the fertilization rate for sperm frozen with 2% glycerol (P = 0.12). On the basis of these data, 4% rather than 2% glycerol may be close to optimum when freezing boar semen in straws. However, more extensive in vivo fertility testing is required to confirm this trend. Low correlations were observed between in vitro (and in vivo) evaluation of sperm quality and fertility when the effect of boar and glycerol concentrations was kept constant. Inhalt: Die Brauchbarkeit von in vitro-Methoden für die Voraussage der in vivo-Befruch-tungskapazität von Eberspermatozoen nach Tiefgefrierung mit 2% oder 4% Glycerin Von 2 Ebern, die sich in der Qualität ihres Auftauspermas deutlich unterschieden, wur-den je 13 Ejakulate mit 2% oder 4% Glycerinanted (Endkonzentration — split sample) tiefgefroren. Die aufgetauten Samenproben wurden in vitro nach Motilität, akrosoma-ler Integrität (NAR), Plasmamembran-Integrität (PMI) und im Spermapenetrationstest (SPA) am zonafreien Hamstereiüberprüft. Zur Beurteilung der Befruchtungskapazität in vivo wurden 52 Sauen 30–34 h nach Brunstbeginn einmalig besamt. 2–4 Tage nach der Besamung wurden die Eier aus dem Genitaltrakt gewonnen und auf Teilung und auf Anheftung von Samenzellen an der Zona pellucida beurteilt. Die beiden Eber wa-ren in allen In vitro- und In vivo-Parametern signifikant verschieden. Motilitat und PMI waren besser (p <0,05) für Spermien, die in 4% Glycerin konserviert waren, NAR bes-ser in 2%igem Glycerin. Nach Konservierung in 4% Glycerin waren mehr Spermien an der Eihülle angeheftet als nach 2% Glycerin (p < 0,05). Aber die Befruchtungsraten waren nach 4% und 2% Glycerinkonservierung praktisch nicht verschieden (p = 0,12). Auf der Grundlage dieser Ergebnisse ist zu folgern, daβ die Tiefgefrierkonservierung von Pelletsperma mit 4% Glycerin günstiger ist als mit 2% Glycerin; dieser Trend muβ jedoch in umfangreicheren In vivo-Fertilitätstests noch bestätigt werden. Wenn die Ef-fekte Eber und Glycerinkonzentration konstant gehalten wurden, dann wurden nur niedrige Korrelationen zwischen In vitro- und In vivo-Beurteilung von Spermaqualität und Fruchtbarkeit erhalten.     

The Effects of Hoechst 33342 Staining and the Male Sample Donor on the Sorting Efficiency of Canine Spermatozoa

The aim of this study was to evaluate the influence of Hoechst 33342 (H‐42) concentration and of the male donor on the efficiency of sex‐sorting procedure in canine spermatozoa. Semen samples from six dogs (three ejaculates/dog) were diluted to 100 × 10⁶ sperm/ml, split into four aliquots, stained with increasing H‐42 concentrations (5, 7.5, 10 and 12.5 μl, respectively) and sorted by flow cytometry. The rates of non‐viable (FDA+), oriented (OS) and selected spermatozoa (SS), as well as the average sorting rates (SR, sorted spermatozoa/s), were used to determine the sorting efficiency. The effects of the sorting procedure on the quality of sorted spermatozoa were evaluated in terms of total motility (TM), percentage of viable spermatozoa (spermatozoa with membrane and acrosomal integrity) and percentage of spermatozoa with reacted/damaged acrosomes. X‐ and Y‐chromosome‐bearing sperm populations were identified in all of the samples stained with 7.5, 10 and 12.5 μl of H‐42, while these two populations were only identified in 77.5% of samples stained with 5 μl. The values of OS, SS and SR were influenced by the male donor (p < 0.01) but not by the H‐42 concentration used. The quality of sorted sperm samples immediately after sorting was similar to that of fresh samples, while centrifugation resulted in significant reduction (p < 0.05) in TM and in the percentage of viable spermatozoa and a significant increase (p < 0.01) in the percentage of spermatozoa with damage/reacted acrosomes. In conclusion, the sex‐sorting of canine spermatozoa by flow cytometry can be performed successfully using H‐42 concentrations between 7.5 and 12.5 μl. The efficiency of the sorting procedure varies based on the dog from which the sperm sample derives.     

Percentage of Ubiquitinated Spermatozoa does not Correlate with Fertilizing Capacity of Thawed Bovine Semen

In the spermatozoa of some species, the ubiquitin–proteasome system detects altered proteins and tags them for elimination by the proteasome. In some species' ejaculates, a high proportion of ubiquitinated spermatozoa (i.e. those having ubiquitin bound to the altered or damaged membrane proteins) has been related to infertility. The aim of this study was to assess whether the percentage of ubiquitinated spermatozoa relates to fertility of dairy bulls and whether ubiquitination increases during protein remodelling that occurs during in vitro spermatic capacitation. Thirty‐two frozen semen straws from four high‐fertility (ReproMax^®) and four normal‐fertility (Normal) Holstein‐Friesian sires were evaluated. Ubiquitinated and capacitated spermatozoa were quantified by sperm ubiquitin tag immunoassay and chlortetracycline stain, respectively. Fertilizing capacity of sires was assessed by in vitro fertilization. No differences were found between Normal and ReproMax^® sires with regard to the observed percentage of ubiquitinated spermatozoa (42.97 ± 3.69% and 49.68 ± 9.27%, respectively; p > 0.05). Additionally, no differences were found in the percentage of ubiquitinated spermatozoa as a consequence of spermatic capacitation in either Normal (42.97 ± 3.69% before capacitation vs 44.67 ± 7.5% after; p > 0.05) or ReproMax^® sires (49.68 ± 9.27% before vs 45.05 ± 7.51% after; p > 0.05). The percentage of ubiquitinated spermatozoa in a thawed sperm samples did not correlate with its in vitro fertilizing capacity; thus, this assay does not prove useful to detect in vivo fertility differences between sires. Additionally, protein degradation occurring during remodelling of the spermatozoon plasma membrane during the capacitation process does not seem to involve the ubiquitin–proteasome system.     

Effects of Dilution Rate on the Motility and Acrosome Morphology of Boar Spermatozoa Stored at 15 °C

The objective of this investigation was to establish the optimal extent of dilution for storage of boar spermatozoa at 15°C in Kiev diluent. The dilution titers used for the sperm-rich fraction of ejaculates from 8 boars ranged from 1:2 to 1:50. Seminal doses were stored for 10 days. Motility and acrosome morphology were evaluated after 1, 3, 5, 7, and 10 days of storage. The percentages of motile spermatozoa after 24 and 72 hours of storage were significantly higher for dilution rates between 1:7 and 1:11 than for dilution rates lower than 1:7 or higher than 1:11 (p < 0.05). The percentages of spermatozoa with normal acrosomes after 24, 72, and 120 hours of storage were significantly higher for dilution rates between 1:8 and 1:11 than for dilution rates lower than 1:8 or higher than 1:11 (p < 0.01 ).     

Assessing in vivo Fertilizing Capacity of Liquid-Preserved Boar Semen According to the 'Hanover Gilt Model'

The goal of this study was to determine the ability of the Hanover gilt model to assess in vivo fertilizing capacity of preserved sperm and to consider whether any modifications to this model were needed. This model evaluates the fertilizing capacity of semen based on the fertilization rate, the rate of normal embryos and the accessory sperm count of 3–5‐day embryos. Its distinguishing characteristics are the use of one‐time insemination of sperm in reduced numbers, of spontaneously ovulating gilts and of ovulation detection through ultrasound examination of ovaries. Reduced sperm numbers allow for an accurate evaluation of the fertilizing potential of different semen treatments, thereby avoiding the compensatory effect of doses calibrated to maximize fertility. The model's usefulness was assessed in a trial run designed to compare the fertilizing capacity of liquid boar semen diluted into two different extenders. The diluent, the boar and the backflow, had no significant effect on any of the parameters studied. Gilts inseminated less than 24 h before ovulation had a significantly higher (p < 0.01) fertilization rate and accessory sperm cell count (p < 0.05) than those inseminated more than 24 h before ovulation. Very good/good embryos from homogeneous litters (only very good/good embryos were present) had a significantly higher (p < 0.01) accessory sperm count than those from heterogeneous litters (at least one embryo was of a different quality and/or oocytes were present). Both very good/good and degenerated/retarded embryos from heterogeneous litters had low accessory sperm numbers. This suggests that accessory sperm count is significantly related to the quality of the litter, but not to the quality of the embryo within gilts. It can be concluded that the Hanover gilt model is sensitive enough to show fertility differences (in this study, those associated with in vivo ageing of semen), while using relatively few gilts and little time.     

In vitro Fertilizing Capacity of Deep Frozen Boar Semen Packaged in 0.5 and 5 ml Straws

The aim of this study was to evaluate the straw size effect used for freezing on the in vitro fertilizing capacity. Twenty-one ejaculates from seven fertile boars were frozen under controlled conditions in 0.5 and 5 ml straws. Thawed semen was compared to fresh semen. For fresh and thawed semen in 0.5 and 5 ml straws, the results were: 92.18, 77.38 and 79.04% sperm penetration; 80.68, 66.89 and 69.33% monospermy; 11.51, 10.49 and 9.74% polyspermy; 86.19, 47.14 and 47.02% motility and 75.52, 48.19 and 46.81% normal apical ridge (NAR), respectively. Analysis of variance and test of multiple comparisons showed that under the conditions employed, penetration, monospermy, motility and NAR were significantly reduced by freezing–thawing, but polyspermy was much less affected. The results obtained suggest that frozen boar semen is adequate for in vitro fertilization. In addition freezing in 5 ml straws did not have any detrimental effect on either penetration, monospermy, polyspermy, motility and NAR, in comparison with freezing in 0.5 ml straws.     

精液冷却过程中应激蛋白90对猪精子活动力的影响

公猪的精子对冷休克高度敏感,在迅速冷却时失去活力,称之为“冷休克”,而应激蛋白90(HSP90)外源的低表达阻碍细胞周期和减弱冷休克反应。对受精来说,精子运动性是一个重要的参数,HSP90和精子运动有很大的联系。因此,研究猪精子冷却过程中HSP90与精子运动力的关系是很必要的。Geldanamycin(GA)是一种特效的HSP90抑制剂(抗生素),能快速和选择性地抑制HSP90的活性。研究使用此种抗生素抑制HSP90功能,评价HSP90对猪精子活动力的影响。1材料与方法1.1供试精液试验用猪精液采自长白猪和约克夏猪,采取手握法采集精液。精液过滤、离心后,…     

芝麻酚对猪精液冷冻保存效果的影响

为了探究芝麻酚对猪精液冷冻保存效果的影响,用手握法采集成年杜洛克公猪精液,预处理后添加不同浓度芝麻酚(0,0.05,0.10,0.15,0.20和0.25g/L)的冷冻稀释液进行稀释,冷冻-解冻后检测猪精子活率、质膜完整性(低渗肿胀试验)、线粒体活性、顶体完整性、DNA完整性以及超氧化歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)和谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)活性等。结果显示:当芝麻酚添加浓度为0.20g/L时,解冻后精子活率、线粒体活性、质膜完整率和顶体完整率为最高,相比较于对照组,分别提高了12.67%、19.07%、18.78%和14.09%(P0.05);MDA含量最低为2.04nmol/mL(P0.05);SOD和GSH-Px酶活最高为73.04U/mL和237.59U/I(P0.05)。当芝麻酚添加浓度为0.25g/L时,DNA完整性最高为72.46%(P0.05)。当芝麻酚添加浓度为0.15g/L时,CAT酶活最高为3.44U/mL(P0.05)。结果表明:与对照组相比较,在猪精液冷冻稀释液中添加适当浓度的芝麻酚能显著提高解冻后猪精子活率、功能完整性和抗氧化能力(P0.05),且当芝麻酚的浓度为0.2g/L时对猪精子冷冻保存效果最好。研究结果表明,芝麻酚作为一种天然抗氧化剂,对猪精子冷冻保存具有良好的效果。     

In vitro Evaluation of the Quality and Fertilizing Capacity of Boar Semen Frozen in 0.25 ml straws

Twenty-two boar ejaculates were frozen in 0.25 ml straws using a controlled cooling rate, then evaluated in vitro in order to assess: (i) the extent to which a range of semen evaluation parameters accurately characterize sperm quality, (ii) the value of quality assessment in the characterization of long-term sperm survival and fertility and (iii) the suitability of the cryopreservation protocol used for yielding semen with good quality and fertilizing capacity. Motility with or without caffeine, plasma membrane integrity (PMI) evaluated with both propidium iodide (PI) and Hoechst 33258, and acrosome morphology were studied, the ejaculates being then classified into five quality groups. A thermoresistance test and a homologous in vitro fertilization test were applied to selected ejaculates of these groups. Caffeine-stimulated motility and PMI evaluated with PI provided better estimations of semen quality than the other tests of motility, PMI, or acrosome morphology, but this quality assessment could not reveal differences in fertilizing capacity or thermoresistance among ejaculates. Over 43% spermatozoa survived cryopreservation in 19 of the 22 ejaculates, with inter-boar and inter-ejaculate variability in the freezing success being observed. The fertilizing capacity, however, was seriously affected by the process regardless of the semen quality. It is concluded that caffeine-stimulated motility and PMI evaluated with PI give accurate information on sperm quality, but important aspects to the valuation of semen such as thermoresistance and fertilizing capacity are not revealed by this quality study. Moreover, the approach of selecting suitable protocols of cryopreservation does not appear to be sufficient for guaranteeing systematically good quality and fertilizing capacity in the frozen-thawed semen.     

In vitro Fertilizing Capacity of Frozen-thawed Bull Spermatozoa Selected by Single-layer (Glycidoxypropyltrimethoxysilane) Silane-coated Silica Colloidal Centrifugation

Barriers to the use of density gradient centrifugation for preparing animal spermatozoa for artificial insemination (AI) include the scarcity of animal-specific formulations and the daunting prospect of processing large volumes of ejaculate in small aliquots (1.5 ml extended semen). Recently, new colloid formulations have been tested in vitro in a modified procedure, centrifugation on a single layer of colloid. The present study investigated the fertilizing ability during in vitro fertilization (IVF) of frozen-thawed bovine spermatozoa following centrifugation through a single layer of glycerolpropylsilane (GS)-coated silica colloid with a species-specific formulation (patent applied for; treatment, T). Controls (C) included centrifugation through gradients of either the same colloid (C1) or Percoll™ (C2). Sperm recovery surpassed 50% for both C1–C2 and T (n.s.). Mean values of various parameters of computerized analysis of sperm motility did not differ between T and C1 (n.s.), and only the proportions of path straightness and linearity were lower in T vs C2 (p < 0.05). In T, the mean (±SD) percentages of fertilization rate, blastocyst development rate and the total number of blastomeres were 58.1 ± 23.3%, 24.5 ± 14.3% and 94.6 ± 23.4%, respectively. The proportions did not differ significantly from controls (C1/C2). Therefore, centrifugation through a single layer of colloid offers an alternative method to density gradient centrifugation for selection of viable, potentially fertile frozen-thawed bull spermatozoa. This single-layer technique is gentle, versatile and convenient because it facilitates scaling-up the process of sperm preparation to allow larger numbers of spermatozoa (for instance, whole ejaculates) to be processed for AI.     

Studies on Motility and Fertility of Cooled Stallion Spermatozoa

This study on extended, cooled stallion spermatozoa aimed to compare the ability of three extenders to maintain sperm motility during 24 h of preservation, and to describe pregnancy and foaling rates after artificial insemination (AI) of stallion spermatozoa stored and transported in the extender chosen from the in vitro study. After 6 and 24 h of preservation, motility, both subjective and evaluated by the motility analyzer (total, progressive and rapid), was lower in non-fat, dried skim milk-glucose than in both other extenders: dried skim milk-glucose added to 2% centrifuged egg yolk, and ultra high temperature treated skim milk-sugar-saline solution added to 2% centrifuged egg yolk (INRA82-Y). Rapid spermatozoa and sperm velocity parameters, after 24 h, were significantly higher in INRA82-Y. In the fertility trial, semen collected from three Maremmano stallions, diluted in INRA82-Y, and transported in a refrigerated Styrofoam box, was used to inseminate 56 mares of the same breed. Pregnancy rates after the first cycle and per breeding season were significantly higher for the 31 mares inseminated in three AI centres (54.8 and 80.6%, respectively) than for the 25 mares inseminated at the breeder's facilities (28.0 and 52.0%). Foaling rates were not significantly different between the AI centres mares (54.8%) and the other mares (44.0%). In conclusion, INRA82-Y yielded satisfactory pregnancy and foaling rates, especially when employed in the more controlled situation of an AI centre, and can therefore be included among those available for cooled stallion semen preservation.     

Analysis of In vitro Fertilizing Capacity to Evaluate the Freezing Procedures of Boar Semen and to Predict the Subsequent Fertility

A porcine in vitro fertilization (IVF) system and seminal quality parameters of frozen–thawed boar semen were used to assess the effectiveness of two different thawing rates of frozen boar semen, and to address the question of whether differences between fertility of ejaculates could be predicted in a limited field trial. In the first experiment, two thawing procedures were analysed (37°C, 30 s; 50°C, 12 s) and no differences in sperm quality were found. However, when the procedure was 50°C, 12 s the IVF results showed a higher number of sperm per penetrated oocyte and a near 10 points higher rate of pronuclear formation. In the second experiment, the fertility results obtained in the limited field trial show to be efficient enough for application in a commercial use, especially for three of the employed boars (fertility ≥80%). In this limited study, the conventional seminal parameters are not accurate enough to discriminate good and bad boars in relation to fertility. On the contrary, parameters of in vitro penetrability are more precise to predict subsequent fertilities. As conclusion, the IVF fertilization system seems to be a good tool to evaluate the quality of frozen–thawed boar semen previous to its commercial way, to verify the bank semen storage quality and a good way to assay new sperm freezing procedures, as it is the more precise evaluating method in estimating the potential fertilizing ability.     

Evaluation of a side population of canine lymphoma cells using Hoechst 33342 dye

Cancer stem cell (CSC) research has increased exponentially to gain further insight into the mechanisms underlying both carcinogenesis and chemotherapy resistance. The present study was performed to explore the potential value of a side population (SP) assay for identifying and characterizing putative CSCs among canine lymphoma cells. Canine lymphoma cells from cell lines and clinical samples were subjected to the SP assay consisting of Hoechst 33342 staining and subsequent flow cytometric analysis. The SP assay revealed various amounts of a SP fraction among the canine lymphoma cells. The percentages of SP were not affected by inhibitors of membrane transporters, verapamil hydrochloride, or fumitremorgin C. Most of the canine lymphoma cells expressed high levels of Bmi-1 and membrane transporter proteins such as ABCG2 and phosphorylated (p)-glycoprotein. This investigation lays the groundwork for further studies of the biological behaviors and molecular characteristics of CSCs in cases of canine lymphoma.     

葡萄籽原花青素对猪精液冷冻保存效果的研究

在猪精液冷冻基础液中分别添加0μg/mL,10μg/mL,20μg/mL,30μg/mL,40μg/mL,50μg/mL的葡萄籽原花青素,通过对冷冻-解冻后猪精子的动力学参数、生理参数以及生化参数的检测,旨在研究其对猪精液冷冻保存效果的影响。结果表明,当葡萄籽原花青素添加浓度为20μg/mL和50μg/mL时,解冻后精子活力、活率、顶体完整率、线粒体活性、质膜完整性和酶活性都显著高于对照组(P0.05),但是两组间比较差异不显著(P0.05)。与对照组和其他实验组相比,当葡萄籽原花青素添加浓度为40μg/mL时,精子畸形率降低了9.30%,精子活力、活率、顶体完整率、线粒体活性和质膜完整性分别提高了12.59%、11.78%、14.27%、12.53%和11.96%(P0.05)。当葡萄籽原花青素的添加量为40μg/mL时,MDA的量最低为1.16nmol/mg,SOD和GSH-Px酶活性最大分别为77.36U/mg、35.21U/mg。结果显示,在猪精液稀释液中添加一定浓度的葡萄籽原花青素,可以显著提高冷冻-解冻后猪精子品质和抗氧化能力。当葡萄籽原花青素的添加量为40μg/mL时,其对猪精子冷冻保存效果最好。