Cryopreservation of ram semen with antioxidant supplemented soybean lecithin-based extenders and impacts on incubation resilience

The scope of this study was investigation the affects of various antioxidants on 1% soybean lecithin-based semen extenders for ram semen cryopreservation. Ejaculates, collected via electrically stimulated ejaculation, that have a thick consistency, rapid wave motion (3-5 on a 0-5 scale) and >75% initial motility were pooled. The pooled samples were split into four equal aliquots as 5 mM Methionine, 5 mM Cysteamine, 1 mM Cysteine and a sample of antioxidant-free control group. Each sample group was diluted to a ratio of 1/5 (semen/extender, v/v) as final concentration and two step dilution method was used for cryopreservation. Extender groups were assessed for sperm motility, plasma membrane functional integrity using hypoosmotic swelling test (HOST), damaged acrosome using FITC-Pisum sativum agglutinin (PSA-FITC) and DNA integrity using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Semen samples also incubated for 6 h in humidified air with 5% CO2 at 39 °C to evaluate post-thaw incubation resilience of semen characteristics. The results showed that freezing and thawing procedures had negative effects on motility (P < 0.05), plasma membrane integrity (P < 0.05) and acrosomal integrity (P < 0.05). After 6 h of incubation time, the Cysteine supplemented extender group yielded significantly higher results than other extender groups in terms of spermatological parameters. Furthermore MDA levels in the antioxidant groups were lower than control group (P < 0.05). Nevertheless, there were no significant differences among antioxidant groups.

Improved preimplantation development of bovine ICSI embryos generated with spermatozoa pretreated with membrane-destabilizing agents lysolecithin and Triton X-100

In cattle, intracytoplasmic sperm injection (ICSI) has a low efficiency. The acrosome content may be responsible for this effect because of the large amount of hydrolytic enzymes that are released within the oocyte. With the aim of removing the acrosome and destabilize the membranes, cryopreserved bovine spermatozoa were treated with lysolecithin (LL) and Triton X-100 (TX) at different concentrations. We evaluated the membrane integrity, the acrosome integrity, DNA integrity, and the variation of phospholipase C zeta. The rates of development (cleavage and blastocysts) were also evaluated along with pronuclear formation and the embryo quality. Spermatozoa incubated with LL and TX (0.01%, 0.02%, 0.03%, and 0.04%) decreased (P < 0.0001) sperm viability in a dose-dependent manner. The acrosome reaction was also increased (P < 0.0001) in all tested concentrations of LL and TX achieving 100% at 0.05% concentration in both treatments. Terminal deoxynucleotidyl transferase dUTP nick-end labeling assay reported an increase (P < 0.05) in DNA fragmentation only with the highest concentration of LL (0.06%), whereas all concentrations assessed of TX reported an increased respect to the control. Phospholipase C zeta expression decreased (P < 0.05) in spermatozoa treated with LL and TX at all concentrations tested. A higher cleavage rate was observed in ICSI-TX (66%) and ICSI-LL (65%) groups compared with the untreated control group (51%) and the blastocyst formation rate significantly increased in the ICSI-LL group (29%) compared with the control (21%). No differences were observed in the pronuclear formation and quality of the embryos. In conclusion, the destabilization of the plasma membrane and the release of the acrosomal content with LL and TX before ICSI improve the rate of embryonic development, without affecting the quality of the embryos produced by this technique.

Post-thaw ATP supplementation enhances cryoprotective effect of iodixanol in rat spermatozoa

BACKGROUND

Successful cryopreservation of rat spermatozoa from various strains still remains a challenge. The objective of this study was to determine if combinations of OptiPrep™ (iodixanol) and adenosine 5'-triphosphate (ATP) can improve rat sperm function during the cryopreservation procedure.

METHODS

Epididymal rat spermatozoa were frozen under different OptiPrep™ concentrations (0, 1, 2, 3 or 4 %) and were diluted with media supplemented with or without 2 mM ATP after thawing. Post-thaw sperm motility, acrosomal membrane integrity (AMI) and mitochondrial membrane potential (MMP) were then evaluated. In addition, the effect of different OptiPrep™ concentrations on fresh and cooled rat spermatozoa was tested via motility.

RESULTS

There was no effect of OptiPrep™ on motility of fresh and cooled spermatozoa. The supplementation of 1 and 2 % OptiPrep™ increased motility of frozen spermatozoa at 10 min after thawing, while it did not improve motility of spermatozoa at 3 h after thawing in the absence of ATP. During incubation of thawed spermatozoa, the ATP addition protected time-dependent decrease in motility after thawing in OptiPrep™-treated samples. OptiPrep™ had no effect on AMI and MMP in frozen-thawed spermatozoa but combinations of OptiPrep™ and ATP improved MMP in frozen-thawed spermatozoa.

CONCLUSIONS

Iodixanol has cryoprotective effects during rat sperm freezing without any toxic effect. Moreover, the combinations of iodixanol and ATP have a beneficial role in maintaining function of frozen-thawed rat spermatozoa for long period of incubation post-thaw.

[Evaluation of Indicators of Postejaculation Maturation of Spermatozoa of Bos taurus Using a Chlortetracycline Test]

Postejaculation maturation of spermatozoa (capacitation and acrosomal exocytosis) in bovine sperm was assessed using the method of staining with chlortetracycline and inhibitor analysis to identify the transition ways of calcium of intracellular depots under the influence of highly dispersed silica. It was shown that highly dispersed silica in a concentration of 0.001% stimulates capacitation but has no impact on the acrosome exocytosis in bovine sperm. Activated by highly dispersed silica, capacitation was inhibited in the presence of cytochalasin D and H-89 inhibitors, whereas nocodazole and Ro 31-8220 had no influence on this process. The joint action of theophylline and guanosine diphosphate stimulates an increase in the amount of capacitated sperm cells, similarly to highly dispersed silica; inhibitors cytochalasin D and H-89 restrict the capacitation of sperm activated by these compounds. At the same time, the joint effect of prolactin and guanosine triphosphate had no effect on the capacitation of spermatozoa; addition of nocodazole and Ro 31-8220 inhibitors did not alter the effect of prolactin and guanosine triphosphate on the capacitation of sperm. A hypothesis was put forward, according to which increase in the cryoresistance of spermatozoa of bulls under the influence of highly dispersed silica is, apparently, determined by the transition of Ca2+ between the intracellular stores in the direction from inositol triphosphate-sensitive to inositol triphosphate-insensitive intracellular stores of calcium. The obtained data allow us to expand the notion of the biochemical mechanisms of capacitation in the spermatozoa of bulls.

EFFECT OF SOLID MEDIUM DURING COOLED STORAGE ON STALLION SPERM PARAMETERS

BACKGROUND

Solid storage medium prevents cellular sedimentation, reduces metabolic demand via limiting movement, and avoids the modification of an extender composition in the sedimentary microenvironment. It has been proven to prolong spermatozoa viability in mammalians.

OBJECTIVE

This experiment aims to evaluate the effect of cool storage in solid phase extender on stallion sperms.

MATERIALS AND METHODS

Semen was collected from 10 Crioulo stallions (n=30) and submitted to treatments: control group (semen extender) and groups with gelatin addition in different concentrations (semen extender + 1%, 2% and 3%). Seminal analyses included motility, mitochondrial functionality, plasma membrane integrity, DNA and acrosome at 0; 24; 48 and 72 hours during cooled storage at 5 degree C.

RESULTS

Motility, mitochondrial functionality, plasma membrane and acrosome integrity declined during storage time, with no statistical difference between treatments. DNA integrity did not significantly change during storage period.

CONCLUSION

Solid medium was not harmful and did not improved stallion sperm parameters during cooled storage.

EFFECTS OF ORVUS ES PASTE ON THE MOTILITY AND VIABILITY OF YAK (BOS GRUNNIENS) EPIDIDYMAL AND EJACULATED SPERMATOZOA AFTER FREEZING AND THAWING

BACKGROUND

The addition of the detergent Orvus ES Paste (OEP) to semen freezing extenders has been observed to improve the post-thaw survival and longevity of spermatozoa from various species but has never been evaluated for yak spermatozoa.

OBJECTIVE

This study evaluated the effects of OEP on the post-thaw motility and viability of epididymal and ejaculated yak spermatozoa.

MATERIALS AND METHODS

Semen samples were frozen and thawed in semen freezing extender supplemented with 0 %, 0.375 %, 0.75 % or 1.5 % OEP. The motility and viability of frozen-thawed spermatozoa were evaluated before and after 3 h of incubation.

RESULTS

The addition of 0.75 % OEP to the freezing extender significantly improved the mean motility and viability values of both the epididymal and ejaculated spermatozoa immediately after thawing, but the beneficial effects on motility disappeared after 3h of incubation.

CONCLUSION

Our findings indicate that the addition of 0.75 % OEP is effective for the preservation of yak spermatozoa.

Effect of extracellular adenosine 5'-triphosphate on cryopreserved epididymal cat sperm intracellular ATP concentration, sperm quality, and in vitro fertilizing ability

Intracellular adenosine 5'-triphosphate (ATP) is essential for supporting sperm function in the fertilization process. During cryopreservation, damage of sperm mitochondrial membrane usually leads to compromised production of intracellular ATP. Recently, extracellular ATP (ATPe) was introduced as a potent activator of sperm motility and fertilizing ability. This study aimed to evaluate (1) levels of intracellular ATP in frozen-thawed epididymal cat sperm after incubation with ATPe and (2) effects of ATPe on epididymal cat sperm parameters after freezing and thawing. Eighteen male cats were included. For each replicate, epididymal sperm from two cats were pooled to one sample (N = 9). Each pooled sample was cryopreserved with the Tris-egg yolk extender into three straws. After thawing, the first and second straws were incubated with 0-, 1.0-, or 2.5-mM ATPe for 10 minutes and evaluated for sperm quality at 10 minutes, 1, 3, and 6 hours after thawing and fertilizing ability. The third straw was evaluated for intracellular ATP concentration in control and with 2.5-mM ATPe treatment. Higher concentration of intracellular sperm ATP was observed in the samples treated with 2.5-mM ATPe compared to the controls (0.339 ± 0.06 μg/2 × 10(6) sperm vs. 0.002 ± 0.003 μg/2 × 10(6) sperm, P ≤ 0.05). In addition, incubation with 2.5-mM ATPe for 10 minutes promoted sperm motility (56.7 ± 5.0 vs. 53.3 ± 4.4%, P ≤ 0.05) and progressive motility (3.1 ± 0.2 vs. 2.8 ± 0.4, P ≤ 0.05), mitochondrial membrane potential (36.4 ± 5.5 vs. 28.7 ± 4.8%, P ≤ 0.05), and blastocyst rate (36.1 ± 7.0 and 28.8 ± 7.4%, P ≤ 0.05) compared with the controls. In contrast, ATPe remarkably interfered acrosome integrity after 6 hours of postthawed incubation. In sum, the present finding that optimal incubation time of postthaw epididymal cat sperm under proper ATPe condition might constitute a rationale for the studies on other endangered wild felids regarding sperm quality and embryo development.

Anatase titanium dioxide nanoparticles in mice: evidence for induced structural and functional sperm defects after short-, but not long-, term exposure

Titanium dioxide (TiO 2 ) nanoparticles (TNPs) are widely used commercially and exist in a variety of products. To determine if anatase TNPs (ATNPs) in doses smaller than previously used reach the scrotum after entry in the body at a distant location and induce sperm defects, 100% ATNP (2.5 or 5 mg kg-1 body weight) was administered intraperitoneally to adult males for three consecutive days, followed by sacrifice 1, 2, 3, or 5 weeks later (long-) or 24, 48 or 120 h (short-term exposure). Transmission electron microscopy revealed the presence of ANTP in scrotal adipose tissues collected 120 h postinjection when cytokine evaluation showed an inflammatory response in epididymal tissues and fluid. At 120 h and up to 3 weeks postinjection, testicular histology revealed enlarged interstitial spaces. Significantly increased numbers of terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling-positive (apoptotic) germ (P = 0.002) and interstitial space cells (P = 0.04) were detected in treated males. Caudal epididymal sperm from the short-term, but not a long-term, arm showed significantly (P < 0.001) increased frequencies of flagellar abnormalities, excess residual cytoplasm (ERC), and unreacted acrosomes in treated versus controls (dose-response relationship). A novel correlation between ERC and unreacted acrosomes was uncovered. At 120 h, there were significant decreases in hyperactivated motility (P < 0.001) and mitochondrial membrane potential (P < 0.05), and increased reactive oxygen species levels (P < 0.00001) in treated versus control sperm. These results indicate that at 4-8 days postinjection, ANTP induce structural and functional sperm defects associated with infertility, and DNA damage via oxidative stress. Sperm defects were transient as they were not detected 10 days to 5 weeks postinjection.

Effect of the pH pre-adjustment in the freezing extender on post-thaw boar sperm quality

BACKGROUND

During freezing the selective precipitation of substances in the medium may provoke a pH shift and lead to sperm damage.

OBJECTIVE

To study the effect of the pH pre-adjustment in the freezing extender on post-thaw boar sperm quality.

METHODS

A total of 15 ejaculates from different boars were obtained and divided into six aliquots prior to a standard straw cryopreservation in freezing extender (lactose-egg yolk-glycerol-Orvus ES Paste) with different pH. After thawing, sperm quality (plasma membrane integrity, motility and acrosome status) were assessed at 30 and 90 minutes of post-thaw incubation at 37 degree C.

RESULTS

When the boar sperm were frozen in a freezing media with pH basic, and particularly at pH 8, it had higher post-thaw sperm quality.

CONCLUSION

The pre-adjustment at pH 8 of the freezing extender (lactose-egg yolk-glycerol-Orvus ES Paste) is able to improve the post-thaw boar sperm quality.

Increased chromatin fragmentation and reduced acrosome integrity in spermatozoa of red deer from lead polluted sites

Vertebrates are constantly exposed to a diffuse pollution of heavy metals existing in the environment, but in some cases, the proximity to emission sources like mining activity increases the risk of developing adverse effects of these pollutants. Here we have studied lead (Pb) levels in spermatozoa and testis, and chromatin damage and levels of endogenous antioxidant activity in spermatozoa of red deer (Cervus elaphus) from a Pb mining area (n=37) and a control area (n=26). Deer from the Pb-polluted area showed higher Pb levels in testis parenchyma, epididymal cauda and spermatozoa, lower values of acrosome integrity, higher activity of glutathione peroxidase (GPx) and higher values of DNA fragmentation (X-DFI) and stainability (HDS) in sperm than in the control area. These results indicate that mining pollution can produce damage on chromatin and membrane spermatozoa in wildlife. The study of chromatin fragmentation has not been studied before in spermatozoa of wildlife species, and the sperm chromatin structure assay (SCSA) has been revealed as a successful tool for this purpose in species in which the amount of sperm that can be collected is very limited.

Sperm proteases that may be involved in the initiation of sperm motility in the newt, Cynops pyrrhogaster

A protease of sperm in the newt Cynops pyrrhogaster that is released after the acrosome reaction (AR) is proposed to lyse the sheet structure on the outer surface of egg jelly and release sperm motility-initiating substance (SMIS). Here, we found that protease activity in the sperm head was potent to widely digest substrates beneath the sperm. The protease activity measured by fluorescein thiocarbamoyl-casein digestion was detected in the supernatant of the sperm after the AR and the activity was inhibited by 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), an inhibitor for serine or cysteine protease, suggesting the release of serine and/or cysteine proteases by AR. In an in silico analysis of the testes, acrosins and 20S proteasome were identified as possible candidates of the acrosomal proteases. We also detected another AEBSF-sensitive protease activity on the sperm surface. Fluorescence staining with AlexaFluor 488-labeled AEBSF revealed a cysteine protease in the principal piece; it is localized in the joint region between the axial rod and undulating membrane, which includes an axoneme and produces powerful undulation of the membrane for forward sperm motility. These results indicate that AEBSF-sensitive proteases in the acrosome and principal piece may participate in the initiation of sperm motility on the surface of egg jelly.

Rosmarinic acid improves function and in vitro fertilising ability of boar sperm after cryopreservation

During cryopreservation, oxidative stress exerts physical and chemical changes on sperm functionality. In the present study we investigated the antioxidant effect of rosmarinic acid (RA) on quality and fertilising ability of frozen-thawed boar spermatozoa. Ejaculates collected from mature boar were cryopreserved in lactose-egg yolk buffer supplemented with different concentrations of RA (0 μM, 26.25 μM, 52.5 μM and 105 μM). Motion parameters, acrosome and plasma membrane integrity, lipoperoxidation levels, DNA oxidative damage (8-hydroxy-2-deoxyguanosine base lesion) and in vitro fertilisation ability were evaluated. Total and progressive motility were significantly higher in experimental extenders with RA than in the control (P<0.05) at 0 and 120 min post-thawing. The plasma and acrosomal membrane integrity were improved by supplementation with 105 μMRA (P<0.05). Negative correlation between RA and malondialdehyde (MDA) concentration were determined (P<0.05). After thawing, the percentage of spermatozoa with oxidised DNA did not differ between extenders, however, at 120 and 240 min post-thawing, the samples supplemented with 105 μMRA showed the lowest DNA oxidation rate (P<0.05). The penetration rate was significantly higher on spermatozoa cryopreserved with 105 μMRA (P<0.05). The results suggest that RA provides a protection for boar spermatozoa against oxidative stress during cryopreservation by their antioxidant properties.

Do photoperiod and endocrine disruptor 4-tert-octylphenol effect on spermatozoa of bank vole (Clethrionomys glareolus)?

Photoperiod is an environmental signal that controls physiology and behavior of all organisms. Bank voles, which are seasonal breeders, are stimulated to reproduce by the long photoperiod associated with spring and summer. To date, physiology of bank vole spermatozoa has not been explored, although they constitute an interesting model for examining the relationship between photoperiod and xenoestrogen on spermatozoa function. In an attempt to evaluate the acute effect of 4-tert-octylphenol (OP) an in vitro system was used. Spermatozoa isolated from the cauda epididymidies of long-day (LD; 18 h light: 6 h darkness) and short-day (SD; 6 h light: 18 h darkness) bank voles were treated with two OP concentrations (10(-4) M and 10(-8)M, respectively). OP-treated spermatozoa were used for the examination of motility parameters (computer-assisted semen analyzer CEROS), acrosome integrity (Commassie blue staining), cAMP production (immunoenzymatic assay) and cell viability (flow-cytometry analysis). The study revealed the photoperiod-dependent effect of short OP-treatment on motility parameters of vole spermatozoa. In LD spermatozoa, an increase of velocities: (curvilinear velocity [VCL], average path velocity [VAP] straight line velocity [VSL]) and head activity (amplitude of the lateral head displacement, [ALH]) was found. Interestingly, in SD spermatozoa opposite effect on VCL, VAP, VSL and ALH was observed, however only after treatment with 10(-4)M OP. The dose-dependent influence of OP upon acrosome integrity, as well as cAMP levels, in relation to the reproductive status of voles was observed. Moreover, OP exposure affected spermatozoa morphology rather than spermatozoa viability.

Lipid modulation of calcium flux through CaV2.3 regulates acrosome exocytosis and fertilization

Membrane lipid regulation of cell function is poorly understood. In early development, sterol efflux and the ganglioside GM1 regulate sperm acrosome exocytosis (AE) and fertilization competence through unknown mechanisms. Here, we show that sterol efflux and focal enrichment of GM1 trigger Ca(2+) influx necessary for AE through CaV2.3, whose activity has been highly controversial in sperm. Sperm lacking CaV2.3's pore-forming α1E subunit showed altered Ca(2+) responses, reduced AE, and a strong subfertility phenotype. Surprisingly, AE depended on spatiotemporal information encoded by flux through CaV2.3, not merely the presence/amplitude of Ca(2+) waves. Using studies in both sperm and voltage clamp of Xenopus oocytes, we define a molecular mechanism for GM1/CaV2.3 regulatory interaction, requiring GM1's lipid and sugar components and CaV2.3's α1E and α2δ subunits. Our results provide a mechanistic understanding of membrane lipid regulation of Ca(2+) flux and therefore Ca(2+)-dependent cellular and developmental processes such as exocytosis and fertilization.

The effects of cooling rates and type of freezing extenders on cryosurvival of rat sperm

Cryopreservation of rat sperm is very challenging due to its sensitivity to various stress factors. The objective of this study was to determine the optimal cooling rate and extender for epididymal sperm of outbred Sprague Dawley (SD) and inbred Fischer 344 (F344) rat strains. The epididymal sperm from 10 to 12 weeks old sexually mature SD and F344 strains were suspended in five different freezing extenders, namely HEPES buffered Tyrode's lactate (TL-HEPES), modified Kreb's Ringer bicarbonate (mKRB), 3% dehydrated skim milk (SM), Salamon's Tris-citrate (TRIS), and tes/tris (TES). All extenders contained 20% egg yolk, 0.75% Equex Paste and 0.1 M raffinose or 0.1 M sucrose. The sperm samples in each extender were cooled to 4°C and held for 45 min for equilibration before freezing. The equilibrated sperm samples in each extender were placed onto a shallow quartz dish inserted into Linkam Cryostage (BCS 196). The samples were then cooled to a final temperature of -150°C by using various cooling rates (10, 40, 70, and 100°C/min). For thawing, the quartz dish containing the sperm samples were rapidly removed from the Linkam cryo-stage and placed on a 37°C slide warmer and held for 1 min before motility analysis. Sperm membrane and acrosomal integrity and mitochondrial membrane potential (MMP) were assessed by SYBR-14/Propidium iodide, Alexa Fluor-488-PNA conjugate and JC-1, respectively. The total motility, acrosomal integrity, membrane integrity and MMP values were compared among cooling rates and extenders. Both cooling rate and type of extender had significant effect on cryosurvival (P < 0.05). Sperm motility increased as cooling rate was increased for both strains (P < 0.05). Highest cryosurvival was achieved when 100°C/min cooling rate was used in combination with TES extender containing 20% egg yolk, 0.75% Equex paste and either 0.1M sucrose or raffinose (P < 0.05). This study showed that TES extender containing 0.1 M raffinose or sucrose with 70°C/min and 100°C/min cooling rate improved post-thaw motility of rat sperm.

Male contraceptive efficacy of Ricinus communis L. extract

ETHNOPHARMACOLOGICAL RELEVANCE

Ricinus communis L. (Rc), of Euphorbiaceae family is a widespread plant in tropical regions and it is used in traditional medicines as an antifertility agent in India and different parts of the world.

AIM OF THE STUDY

The aim of the present study is to revalidate the ethnobotanical knowledge by evaluating the activity of only crude stem bark extracts of Rc. In this study, effects of extracts on male contraceptive efficacy were experimented in vitro with human sperm sample. The work is based on primordial and contemporary therapeutic uses of this plant.

MATERIALS AND METHODS

In this study, dose of petroleum ether extract, ethyl acetate extract, acetone extract and lyophilised aqueous extract of Rc were added to fresh human semen in 1:1 volumetric ratio. As the aqueous extract showed a promising result in 1:1 ratio, therefore, the Hypo-osmotic swelling test (HOS), Nuclear chromatin decondensation test (NCD) and Acrosomal status and function test (AFT) were also carried out with the aqueous extract of Rc.

RESULTS

The sperm immobilisation effects of the extract appeared immediately in a dose-dependent manner when the samples were treated with four different extracts of this plant. At a concentration of 100mg/mL, 100% (p<0.001 and p<0.05) sperms lost their progressive motility. At a concentration of 300 mg/mL, 100% (p<0.001 and p<0.05) became immotile when treated with aqueous extract. There was 88% (p<0.001 and p<0.05) morphological deformities in sperm sample due the effect of aqueous extract when they were tested for HOS and 91% (p<0.05) sperms behaved against NCD as compared to control group. Also there was a distinct decline (p<0.05) in AFT with increase in dosage concentration.

CONCLUSION

The findings of the study revealed that aqueous stem bark extract of the plant showed dose dependent loss of sperm motility by influencing the morphological deformation, blockage in nuclear envelope and distinct declination in acrosomal status of spermatozoa. This research, thus, opens up scope for future exploration of bark of the plant as commercial source of new male contraceptive.

Identification of optimal concentrations and incubation times for the study of in vitro effects of Pb in ram spermatozoa

In vitro effects of lead (Pb) on ram (Ovis aries) spermatozoa were studied to establish a threshold level that affects sperm function. Spermatozoa were incubated between 15 and 180 min with Pb concentrations ranging from 0 to 5,000 ng/mL. Sperm motility, acrosome integrity, membrane functionality and sperm viability were all negatively affected by Pb and incubation time. Acrosome integrity was linearly affected by Pb levels at an incubation time of 30 min, and 50 ng/mL was the lowest Pb level producing such effect. These experimental conditions can be appropriate for in vitro studies of the mechanisms of action of Pb on spermatozoa.

The effects of 1,4-cyclohexanediol on frozen ram spermatozoa

In order to improve the quality of frozen spermatozoa of Yunnan semi-fine wool sheep, 1, 4-cyclohexanediol (1, 4-CHD) as a synthetic ice blocker was used for cryopreservation of ram spermatozoa in this study. Briefly, following collection by electric stimulation, equilibration at 5℃ following dilution with the freezing extender, and pre-freezing in liquid nitrogen vapor, the ram spermatozoa were preserved in liquid nitrogen for one month. In addition, the effects of osmolarity of the diluting extenders used for evaluation of frozen spermatozoa quality were also assessed. The results indicated addition of 1, 4-CHD could not increase the motility of ram spermatozoa after cryopreservation and thawing. With the elevation of the concentrations of 1, 4-CHD, the motility and moving velocity of frozen ram spermatozoa showed a steady decrease. Additionally, the presence of 1, 4-CHD cannot increase the percentage of frozen spermatozoa with intact acrosome and membrane. When the isotonic binding buffer was used to dilute the thawed spermatozoa, the percentage of cells labeled with propidium iodide (PI) after cryopreservation in the presence of 1, 4-CHD was significantly higher than that of spermatozoa frozen in the absence of 1, 4-CHD (P < 0.05). However, the percentage of frozen-thawed spermatozoa with exposed PS in the presence of 1, 4-CHD was significantly less than that of spermatozoa frozen in the absence of 1, 4-CHD (P < 0.01). When the basic extenders with an osmolarity of 404mOsm, 528mOsm, 648mOsm, or 853mOsm were used to dilute the frozen-thawed spermatozoa respectively, there is no significant difference between the four groups with respect to the moving velocity and membrane integrity (P > 0.05). In conclusion, the presence of 1, 4-CHD cannot improve the motility, moving velocity, acrosome staus, and membrane integrity of frozen ram spermatozoa. However, 1, 4-CHD may inhibit apoptosis caused by freezing and thawing.

Dose-response effects of estrogenic mycotoxins (zearalenone, alpha- and beta-zearalenol) on motility, hyperactivation and the acrosome reaction of stallion sperm

BACKGROUND

The aim of this study was to investigate the in vitro effects of the Fusarium fungus-derived mycotoxin, zearalenone and its derivatives alpha-zearalenol and beta-zearalenol on motility parameters and the acrosome reaction of stallion sperm. Since the toxic effects of zearalenone and its derivatives are thought to result from their structural similarity to 17beta-estradiol, 17beta-estradiol was used as a positive control for 'estrogen-like' effects.

METHODS

Stallion spermatozoa were exposed in vitro to zearalenone, alpha-zearalenol, beta-zearalenol or 17beta-estradiol at concentrations ranging from 1 pM - 0.1 mM. After 2 hours exposure, motility parameters were evaluated by computer-assisted analysis, and acrosome integrity was examined by flow cytometry after staining with fluoroscein-conjugated peanut agglutinin.

RESULTS

Mycotoxins affected sperm parameters only at the highest concentration tested (0.1 mM) after 2 hours exposure. In this respect, all of the compounds reduced the average path velocity, but only alpha-zearalenol reduced percentages of motile and progressively motile sperm. Induction of motility patterns consistent with hyperactivation was stimulated according to the following rank of potency: alpha-zearalenol > 17beta-estradiol > zearalenone = beta-zearalenol. The hyperactivity-associated changes observed included reductions in straight-line velocity and linearity of movement, and an increase in the amplitude of lateral head displacement, while curvilinear velocity was unchanged. In addition, whereas alpha- and beta- zearalenol increased the percentages of live acrosome-reacted sperm, zearalenone and 17beta-estradiol had no apparent effect on acrosome status. In short, alpha-zearalenol inhibited normal sperm motility, but stimulated hyperactive motility in the remaining motile cells and simultaneously induced the acrosome reaction. Beta-zearalenol induced the acrosome reaction without altering motility. Conversely, zearalenone and 17beta-estradiol did not induce the acrosome reaction but induced hyperactive motility albeit to a different extent.

CONCLUSIONS

Apparently, the mycotoxin zearalenone has 17beta-estradiol-like estrogenic activity that enables it to induce hyperactivated motility of equine sperm cells, whereas the zearalenol derivatives induce premature completion of the acrosome reaction and thereby adversely affect stallion sperm physiology. The alpha form of zearalenol still possessed the estrogenic ability to induce hyperactivated motility, whereas its beta stereo-isomere had lost this property.

Dephosphorylated NSSR1 is induced by androgen in mouse epididymis and phosphorylated NSSR1 is increased during sperm maturation

NSSR1 (Neural salient serine/arginine rich protein 1, alternatively SRp38) is a newly identified RNA splicing factor and predominantly expressed in neural tissues. Here, by Western blot analysis and immunofluorescent staining, we showed that the expression of dephosphorylated NSSR1 increased significantly during development of the caput epididymis. In adult mice, phosphorylated NSSR1 was mainly expressed in the apical side of epithelial cells, and dephosphorylated NSSR1 in caput epididymis was upregulated in a testosterone dependent manner. In addition, subcellular immunoreactive distribution of NSSR1 varied in different regions of the epididymis. With respect to the sperm, phosphorylated NSSR1 was detected in the mid-piece of the tail as well as the acrosome. Furthermore, NSSR1 was released from the sperm head during the capacitation and acrosome reaction. These findings for the first time provide the evidence for the potential roles of NSSR1 in sperm maturation and fertilization.

α-SNAP prevents docking of the acrosome during sperm exocytosis because it sequesters monomeric syntaxin

α-SNAP has an essential role in membrane fusion that consists of bridging cis SNARE complexes to NSF. α-SNAP stimulates NSF, which releases itself, α-SNAP, and individual SNAREs that subsequently re-engage in the trans arrays indispensable for fusion. α-SNAP also binds monomeric syntaxin and NSF disengages the α-SNAP/syntaxin dimer. Here, we examine why recombinant α-SNAP blocks secretion in permeabilized human sperm despite the fact that the endogenous protein is essential for membrane fusion. The only mammalian organism with a genetically modified α-SNAP is the hyh mouse strain, which bears a M105I point mutation; males are subfertile due to defective sperm exocytosis. We report here that recombinant α-SNAP-M105I has greater affinity for the cytosolic portion of immunoprecipitated syntaxin than the wild type protein and in consequence NSF is less efficient in releasing the mutant. α-SNAP-M105I is a more potent sperm exocytosis blocker than the wild type and requires higher concentrations of NSF to rescue its effect. Unlike other fusion scenarios where SNAREs are subjected to an assembly/disassembly cycle, the fusion machinery in sperm is tuned so that SNAREs progress uni-directionally from a cis configuration in resting cells to monomeric and subsequently trans arrays in cells challenged with exocytosis inducers. By means of functional and indirect immunofluorescense assays, we show that recombinant α-SNAPs — wild type and M105I — inhibit exocytosis because they bind monomeric syntaxin and prevent this SNARE from assembling with its cognates in trans. Sequestration of free syntaxin impedes docking of the acrosome to the plasma membrane assessed by transmission electron microscopy. The N-terminal deletion mutant α-SNAP-(160–295), unable to bind syntaxin, affects neither docking nor secretion. The implications of this study are twofold: our findings explain the fertility defect of hyh mice and indicate that assembly of SNAREs in trans complexes is essential for docking.

Spermicidal action of a protein isolated from ethanolic root extracts of Achyranthes aspera: an in vitro study

A previous study conducted in our department, showed that 50% ethanolic extract of the roots of Achyranthes aspera possess spermatotoxic effects. Preliminary studies also revealed that the active principle may be a protein. In this study a 58 kDa Achyranthes protein (Ap) was isolated from Achyranthes aspera using standard protocols and their effects on the rat sperm was studied in vitro in comparison with nonoxynol-9 (N-9). The sperm immobilization studies showed that about 150 μg of Ap was able to immobilize sperms completely within seconds at a lower concentration than N-9 (250 μg). The sperm revival test revealed that the spermicidal effect was irreversible. There was also a significant reduction in sperm viability and hypo-osmotic swelling in the Ap-treated and N-9 treated groups in comparison to the control. In the Ap and N-9 treated groups the number of acrosome reacted cells were found to be high and it also caused agglutination of the sperms indicating the loss of intactness of the plasma membrane which was further supported by the significant reduction in the activity of membrane bound 5' nucleotidase and acrosin enzyme. Hence this study showed that the protein isolated from the roots of Achyranthes aspera possess spermicidal activity in vitro and can act as a spermicide similar to that of nonoxynol 9. Ap also possessed spermicidal activity against human sperms in vitro.

[Effects of nonylphenol and cadmium on sperm acrosome reaction in vitro in mice]

OBJECTIVE

To study the effects of nonylphenol and cadmium on acrosome reaction in vitro in mouse spermatozoa.

METHODS

Sperm were collected from the vas deferens of mice, capacitated in vitro and stimulated with A23187 at 30 micromol/L to induce acrosome reaction. Then the sperm suspension was treated with nonylphenol at 10, 20, 30, 60 and 100 micromol/L or cadmium at 500, 2500 and 5 000 micromol/L, and the control group treated with the carrier solvent. Acrosome reaction of the sperm was analyzed by FITC-PSA staining.

RESULTS

Compared with the control group, nonylphenol significantly inhibited acrosome reaction at the concentration of > 60 micromol/L (P < 0.01), but not at < 30 micromol/L (P > 0.05), and the sperm survival rate was reduced with increased concentration of nonylphenol. However, cadmium exhibited no significant influence on either acrosome reaction (P > 0.05) or sperm survival rate at 500 - 5 000 micromol/L.

CONCLUSION

Nonylphenol and cadmium affect the spermatogenesis of mice in different ways; the former directly inhibits sperm acrosome reaction, while the latter has no direct effect on it.

The use of anti-VDAC2 antibody for the combined assessment of human sperm acrosome integrity and ionophore A23187-induced acrosome reaction

Voltage-dependent anion channel (VDAC) is mainly located in the mitochondrial outer membrane and participates in many biological processes. In mammals, three VDAC subtypes (VDAC1, 2 and 3) have been identified. Although VDAC has been extensively studied in various tissues and cells, there is little knowledge about the distribution and function of VDAC in male mammalian reproductive system. Several studies have demonstrated that VDAC exists in mammalian spermatozoa and is implicated in spermatogenesis, sperm maturation, motility and fertilization. However, there is no knowledge about the respective localization and function of three VDAC subtypes in human spermatozoa. In this study, we focused on the presence of VDAC2 in human spermatozoa and its possible role in the acrosomal integrity and acrosome reaction using specific anti-VDAC2 monoclonal antibody for the first time. The results exhibited that native VDAC2 existed in the membrane components of human spermatozoa. The co-incubation of spermatozoa with anti-VDAC2 antibody did not affect the acrosomal integrity and acrosome reaction, but inhibited ionophore A23187-induced intracellular Ca²⁺ increase. Our study suggested that VDAC2 was located in the acrosomal membrane or plasma membrane of human spermatozoa, and played putative roles in sperm functions through mediating Ca²⁺ transmembrane transport.

[Sperm immobilizing effect of leaves extracts of Cestrum parqui]

OBJECTIVE

The leaves extracts of Cestrum parqui were reported to have spermicidal activity. The current investigation identified the spermicidal component of the extracts and evaluated its spermicidal potential in vitro, particularly the effects on sperm motility and vitality.

METHODS

Sperms were prepared by discontinuous buoyant density gradient centrifugation and incubated with varying concentrations of extract from C. parqui (40-250 μg/ml) at 37°C and 5% CO(2). The mode of spermicidal action was evaluated by sperm motility and vitality at different intervals ranging from 5 to 240 minutes. Morphological changes in human spermatozoa after exposure to the extract were evaluated under transmission electron microscope.

RESULTS

A dose- and time-dependent effect of this extract on sperm motility and viability was observed. The mean effective concentration of extracts that induced irreversible immobilization was 250 μg/ml. Transmission electron microscope revealed a significant damage to sperm membrane in head and acrosomal membranes, notable swelling and disruption.

CONCLUSION

Our study indicates that this natural extract has potential spermicidal effect in vitro. It can adequately replace nonoxynol-9 in vaginal contraceptives to make them more vaginally safe and ecofriendly.