Coenzyme Q10 improves the quality and in vitro fertility of post-thawed buffalo (Bubalus bubalis) semen via its antioxidative effect

This study aimed to determine the effects of Coenzyme Q10 (CoQ10) in the freezing medium on functional and oxidative stress parameters and in vitro fertilization (IVF) rate of buffalo sperm. Collected samples were relocated to the laboratory for initial evaluation, gentle dilution in extenders, cooling (4°C, 2 h), equilibration (4°C, 4 h), packaging (straws, 0.5 mL), programmable freezing, and thawing (37°C, 30 s). Statistical analysis depicted that adding CoQ10 (100 μM) in a freezing medium caused a significant augmentation in total motility (%), average path, and straight-line velocities (μm/sec) of buffalo sperm than control. Adding CoQ10 (100 μM) improved sperm progressive motility, rapid velocity, and functional parameters (%) compared to the control and 10 μM of CoQ10. Moreover, CoQ10 in a freezing medium caused a significant augmentation in seminal plasma catalase (U/mL) and glutathione reductase (GSH; nmol/109 ) at 100 μM than control and other treatments. CoQ10 inclusion (100 μM) ameliorates seminal plasma superoxide dismutase (U/mL), glutathione-S-transferase (GST; nmol/mL/min) fructose (μg/mL), and ATP (nmol/million) than control. Furthermore, CoQ10 at 100 μM improved seminal plasma glutathione peroxidase (μM) levels than control, 10 μM, and 20 μM. Lastly, hydrogen peroxide (H2 O2; nM) production was significantly lower at 100 μM than at control and 10 μM. CoQ10 (100 μM) caused a significant augmentation in the un-capacitated pattern followed by a reduction in the capacitated pattern, and apoptosis-like changes (%) than control, and other treatments, whereas viability was increased than control and other treatments. CoQ10 (100 μM) significantly improved the IVF rate in comparison with control, CoQ10 at 10 μM, and 20 μM groups. In conclusion, the addition of CoQ10 (100 μM) in the freezing medium can improve the quality and in vitro fertility of post-thawed buffalo semen via its antioxidative effect. Further studies are needed to evaluate the effect of CoQ10 on the in vivo fertility of buffalo bull semen.

DNA integrity and methylation changes of mouse spermatozoa following prolonged incubation

Sperm quality can be affected by different factors including the length of incubation time between sperm preparation and intracytoplasmic sperm injection. Here, we have evaluated the level of DNA methylation and expressions of related genes in mice spermatozoa. The spermatozoa were divided into three groups: fresh, spermatozoa incubated at room temperature (RT) and 37°C for 24 hr. The sperm chromatin structure assay was used to determine the DNA fragmentation index (DFI), and DNA methylation was analysed by flow cytometry. The expression levels of DNA methylation-related genes were determined by quantitative real-time PCR (qRT-PCR). According to the results, we observed significantly higher sperm progressive motility and viability in the group incubated at RT compared to the spermatozoa incubated at 37°C (p < 0.05). Spermatozoa incubated at 37°C had a higher DFI compared to the other groups (p < 0.05), but the DNA methylation level significantly decreased (p < 0.05). qRT-PCR analysis showed increased Dnmt-1 expression in spermatozoa after 24-hr incubation at 37°C. However, there were significantly higher expression levels of Dnmt-3l, Dnmt-3a and Dnmt-3b after incubation at both RT and 37°C compared to the fresh group (p < 0.05). The 24-hr incubation period affected both sperm DNA methylation and integrity. This study indicated that incubation at RT resulted in better sperm quality.

Semen cryopreservation in Bactrian camel (Camelus bactrianus) using SHOTOR diluent: Effects of cooling rates and glycerol concentrations

Experiments were conducted with a final goal of providing a suitable protocol for cryopreservation of Bactrian camel semen. In Experiment I, the effect of average cooling rate (slow cooling: 0.14 versus fast cooling: 0.55 degrees C/min) on the viability of chilled semen was evaluated. In Experiment II, the effect of different concentrations of glycerol (4, 6 and 8%) on the post-thaw viability of frozen sperm was investigated. In Experiment III, the efficiency of SHOTOR diluent was compared with IMV buffers for the cryopreservation of camel semen. Viability parameters including progressive forward motility (PFM), plasma membrane integrity and percentage of live spermatozoa were assessed. Progressive forward motility of sperm cooled at the faster rate was superior after incubating for 24h at 4 degrees C compared to that cooled at the slower rate (P<0.05). Post-thaw viability of Bactrian camel sperm was better using a final glycerol concentration of 6% compared to 4 and 8% (P<0.05). Progressive forward motility of frozen-thawed sperm was greater using SHOTOR diluent (29.9%) compared to IMV buffers (4.2%, P<0.05). In conclusion, semen cryopreservation in Bactrian camel is feasible when it is extended in SHOTOR diluent, cooled within 1h (average cooling rate: 0.55 degrees C/min) to 4 degrees C, and then exposed to glycerol, at the final concentration of 6%.

Fertility of bull sperm frozen and stored in clarified egg yolk-Tris-glycerol extender

Egg yolk-Tris-glycerol extender, which is widely used in commercial artificial insemination (AI), was modified by replacing the 20% egg yolk (vol/vol) with a supernatant from egg yolk centrifuged at 50,000 x g for 2 h and then used to cryopreserve bull sperm. Preliminary studies showed that 20% egg yolk interfered with biochemical assays, which could be overcome by centrifugation. In Experiment 1, semen from 4 Holstein bulls was frozen in the experimental Tris extender and compared with the whole milk-glycerol control. A total of 2256 first services resulted in 72.6% 60- to 90-d nonreturns for the control and 71.0% for the Tris extender. In Experiment 2, semen from 10 Holstein bulls was frozen in the experimental Tris extender. Half of the semen was used immediately and half was stored in liquid nitrogen for 1 yr before distribution. The nonreturn rates based on 8878 first services for 7 bulls that completed both parts of the trial were 70.9% initially and 71.6% 1 yr later. This time trend difference of 0.7% was comparable to 0.6% for the AI mean for Holstein sires used at the same time. These fertility results and previous laboratory studies indicate that the conventional egg yolk-Tris-glycerol might be simplified for cryopreserving bull sperm. The experimental Tris extender also was suitable for making biochemical measurements.

Role of sperm motility and acrosome integrity in the filtration of bovine semen

In this study, the role of sperm motility and acrosome integrity in filtration of bovine semen was investigated. In Experiment 1, the treatment of semen with formaldehyde, hyperosmotic buffer, heating and direct freezing immobilized the spermatozoa completely but their acrosomal status varied significantly (P < 0.01). The immotile spermatozoa, of any kind, did not pass through the Sephadex ion-exchange column at room temperature. In Experiment 2, semen samples possessing different percentages of immobilized spermatozoa (0, 50, 75 and 100%) were filtered through the Sephadex ion-exchange column. The immotile/dead spermatozoa were removed proportionately to their number in the semen by Sephadex ion-exchange column. The type and number of immotile spermatozoa in semen had no effect (P > 0.05) on the post-filtration recovery rate of motile spermatozoa. Filtered spermatozoa exhibited higher (P < 0.01) motility (> 90%), progressive motility (> 70%) and normal acrosomes (> 95%) than non-filtered spermatozoa. In conclusion, sperm motility seems to be more important than acrosome integrity for semen filtration, and the Sephadex ion-exchange column can remove the known quantities of different kinds dead/immotile spermatozoa.

Effect of filtration on post-thaw quality of bull semen

Semen from 4 Holstein bulls was diluted in 4 different extenders, filtered with Sephadex ion-exchange column, and frozen in liquid nitrogen. Sperm motility, progressive motility, path velocity, progressive velocity and the percentage of normal acrosomes of filtered and nonfiltered semen were recorded before and after freezing. Semen characteristics were significantly influenced by extender, filtration and freezing. Before and after freezing, motility measurements and the percentage of normal acrosomes were higher (P < 0.001) in filtered than in nonfiltered spermatozoa. Post-thaw recovery rate of motile spermatozoa was higher in filtered semen than nonfiltered (68 vs 39%, P < 0.0001). The reduction in motility, progressive motility and the percentage of normal acrosomes during freezing and thawing processes were significantly lower (P < 0.0001) in filtered semen (34, 34 and 4%, respectively) than nonfiltered (59, 54 and 15%, respectively). Post-thaw viability of spermatozoa was significantly affected by extender, filtration and time (P < 0.0001). Immediate (0 h) post-thaw motility of nonfiltered semen (29%) was similar to 4-h post-thaw motility of filtered semen (25%; P > 0.05). In conclusion, bull spermatozoa recovered by Sephadex ion-exchange filtration showed better post-thaw viability.

Effect of preincubation of human spermatozoa in milk on penetration of zona-free hamster oocytes: comparison to TEST yolk

PURPOSE

To investigate the effect of preincubation of human sperm in milk on their ability to penetrate zona-free hamster oocytes, 27 ejaculates were studied. Each ejaculate was divided into two portions and incubated in either milk or TEST yolk (TESTY) for 22-24 hr at 5 degrees C prior to processing for the sperm penetration assay.

RESULTS

Spermatozoa preincubated in milk penetrated a significantly (P < 0.05) higher percentage of oocytes (mean +/- SE; 74.4 +/- 6.3) than spermatozoa preincubated in TESTY (66.8 +/- 6.6). Statistically, no significant differences were noted for penetration index or postincubation sperm motility between the two media.

CONCLUSION

Preincubation of sperm in milk therefore appears to enhance their ability to penetrate zona-free hamster oocytes, compared to TESTY preincubation. Since milk is natural, simple, inexpensive, readily available, and can be easily processed, it should be the medium of choice for sperm preincubation.

Differential effects of butylated hydroxytoluene analogs on bull sperm subjected to cold-induced membrane stress

Previous reports established that butylated hydroxy toluene (BHT) minimized cold-induced membrane rupture in sperm from several species. No data regarding the specificity of its effect is available. In this study 25 BHT analogs were tested for their effect on bovine sperm membrane stability. Fourteen were membrane lytic at 25 degrees C and 6 were neither membrane lytic nor membrane stabilizing. The remaining 5 compounds, a family of 2,6-tert-butyl phenols with substitutions at position 4 of hydrogen, methyl (BHT), ethyl, butyl, hexyl, or octyl, afforded effective membrane protection to cold shock. Since membrane protection is a function of both the ability of a compound to partition into the membrane and a molecule's effectiveness once there, an analysis of each analog's membrane partitioning, assessed by measuring the cellular analog/cholesterol ratio, showed the following extents of transfer for the analogs: ethyl = butyl greater than methyl = hydrogen greater than hexyl greater than octyl. Thus, an optimum chain length exists for partitioning from micellar donors into cells. A separate experiment established that all analogs, when incorporated in equivalent amounts, protect equally plasma and mitochondrial membranes from cold shock. No effect on acrosomal membrane stability was noted. BHT, but not the other analogs, reduced sperm motility. Addition of egg yolk to extender containing BHT analog protected sperm motility from cold shock but had little effect on membrane stabilization. Analysis of sperm membrane compartments revealed that little to no analog was partitioned into the outer acrosomal membrane or the plasma membrane overlying the acrosome, but rather was localized in other portions of the sperm. We conclude that (a) the effective BHT analogs, if partitioned into the membrane, are indistinguishable with regard to their capacity to eliminate cold-induced membrane lysis; (b) membrane-linked events (e.g., motility) are uniquely disrupted by a subset of this analog family; and (c) when concentrations of egg yolk and BHT analogs are carefully controlled, unique synergistic effects are noted.

Measurement and manipulation of cytoplasmic free calcium of ram and boar spermatozoa using quin 2

The highly selective fluorescent Ca2+ indicator 'quin 2' has been loaded into ram and boar spermatozoa as the acetoxymethyl ester, 'quin 2/AM', which is hydrolysed and trapped in the cytoplasm. Loadings of several mM were not toxic to spermatozoa as judged by motility. Fluorescence measurements (mean +/- S.E.M.) indicated a normal cytoplasmic free-calcium concentration, [Ca2+]i, of 193 nM +/- 0.2 (n = 10) for ejaculated ram sperm, 175 nM +/- 3.9 (n = 10) for cauda epididymal boar sperm and 105 nM +/- 10 (n = 10) for the caput sperm. After cold shock ejaculated ram and cauda epididymal boar sperm did not retain quin 2, due presumably to structural damage. However, cold shocked caput boar sperm could be readily loaded with quin 2 and had a [Ca2+]i similar to control sperm. Sodium azide, propranolol and caffeine did not affect the [Ca2+]i of ram and boar sperm, however theophylline, dibutyryl c-AMP and La3+ significantly reduced it. The inhibitors rotenone and antimycin A, and the uncouplers 2,4-DNP and CCCP caused a transient elevation of [Ca2+]i, most likely resulting from release of mitochondrial calcium. The increased [Ca2+]i following addition of the ionophore A23187, was highly pH dependent in ram spermatozoa and it was critical to increase the pH of the medium above 7.5; the increase in [Ca2+]i was apparently not dependent on the oxidative metabolism of the sperm as addition of the uncouplers 2,4-DNP and CCCP had no effect on [Ca2+ )i. Addition of filipin to ram and boar sperm resulted in a large increase in [Ca2+]i but addition of filipin to ionophore-treated sperm caused [Ca2+]i to fall well below control levels.

Susceptibility of epididymal boar sperm to cold shock and protective action of phosphatidylcholine

Rapidly cooling (cold shocking) washed cauda boar sperm irreversibly reduced motility and respiration and greatly increased the uptake of 45Ca2+; the plasma membranes were removed and the acrosomes detached from nuclei. The motility, respiration, and calcium uptake of the less mature caput sperm were largely unaffected; and there was little damage to the ultrastructure. This indicates that boar sperm becomes less resistant to cold shock as they mature in the epididymis. The oxygen uptake, glucose breakdown, and lactic acid production of control caput sperm was less than that of cauda sperm. This suggest that the maturation of sperm in the epididymis of the boar involves an increase in both the glycolytic and oxidative phases of glucose metabolism. The presence of 2.0 mg/ml phosphatidylcholine (lecithin) in the medium prevented ultrastructural damage to cauda sperm on cold shock, and motility and respiration were maintained at levels similar to those of control sperm. Although the presence of phospholipid reduced the large calcium influx following cold shock, it was still greater that that of control sperm. The "protective" effect against cold shock was not maintained after rewashing the sperm free of phosphatidylcholine prior to cold shock, indicating a fairly "loose" interaction of the phospholipid with boar sperm membranes that was easily disrupted.

Lipid deficient extender for bovine spermatozoa: its development and use in measuring freezing-induced lipid loss

To facilitate the measurement of lipid losses from spermatozoa due to freezing, three low-lipid seminal extenders containing lactose, bovine serum albumin, or soybean protein were evaluated as potential cryoprotectants. All extenders were formulated to have an osmotic pressure within the range of 270 to 330 mosmol and a pH of 6.8 to 7.0. Soybean protein (Promine-D) maintained the highest post-thaw motility of spermatozoa with similar survival for spermatozoa frozen in ampules and straws. The extender derived from testing several components consisted of Tris(hydroxymethyl) aminomethane (245 mM), and citric acid monohydrate (78mM), as the buffering compounds; and fructose (69 mM), glycerol (7% vol/vol), and Promine-D (1.5% wt/vol). Post-thaw sperm motility of approximately 40% was not different from the Tris-egg yolk control. Fertility of fresh rabbit semen treated with the extender was normal. After freeze-thawing, protected spermatozoa contained more lipid (1.61 versus 1.20 mug/10-6 sperm) and lost less glutamic oxaloacetic transaminase enzyme (102 versus 108 Karmen units) than when Promine-D was not incorporated. However, even with protection by soybean protein, spermatozoa lipid content decreased from 2.43 to 1.61 mug/10-6 sperm after one freeze-thawing. The lipid status of spermatozoa frozen and thawed in conventional bull seminal extenders containing large amounts of lipids is unknown.