Sperm capacitation and the acrosome reaction are compromised in teratospermic domestic cats

Analysis of metabolic flux in felid spermatozoa using metabolomics and 13C-based fluxomics†

Spermatozoa from three feline species-the domestic cat (Felis catus), the cheetah (Acinonyx jubatus), and the clouded leopard (Neofelis nebulosa)-were analyzed using metabolomic profiling and 13C-based fluxomics to address questions raised regarding their energy metabolism. Metabolic profiles and utilization of 13C-labeled energy substrates were detected and quantified using gas chromatography-mass spectrometry (GC-MS). Spermatozoa were collected by electroejaculation and incubated in media supplemented with 1.0 mM [U13C]-glucose, [U13C]-fructose, or [U13C]-pyruvate. Evaluation of intracellular metabolites following GC-MS analysis revealed the uptake and utilization of labeled glucose and fructose in sperm, as indicated by the presence of heavy ions in glycolytic products lactate and pyruvate. Despite evidence of substrate utilization, neither glucose nor fructose had an effect on the sperm motility index of ejaculated spermatozoa from any of the three felid species, and limited entry of pyruvate derived from these hexose substrates into mitochondria and the tricarboxylic acid cycle was detected. However, pathway utilization was species-specific for the limited number of individuals (four to seven males per species) assessed in these studies. An inhibitor of fatty acid beta-oxidation (FAO), etomoxir, altered metabolic profiles of all three felid species but decreased motility only in the cheetah. While fluxomic analysis provided direct evidence that glucose and fructose undergo catabolic metabolism, other endogenous substrates such as endogenous lipids may provide energy to fuel motility.

Influence of the type of semen and morphology of individual sperm cells on the results of ICSI in domestic cats

The aim of this study was to analyze the influence of the type of spermatozoa and of different sperm abnormalities on fertilization and embryo development after ICSI in cats. In Exp I, ICSI was performed using urethral or epididymal spermatozoa collected from 7 tomcats. In Exp. II, epididymal spermatozoa from 16 cats were used for ICSI and an epididymal spermatozoon exhibiting no abnormalities or one with an abnormality was microinjected into an oocyte. Exp. I was performed in 14 replicates and Exp. II was performed in 20 replicates. In both experiments the number of cleaved oocytes, the number of embryos at the morula stage and the number of embryos at the blastocyst stage were evaluated at 24 h, and at 6 and 7 days after ICSI, respectively, and compared between experimental groups. No statistically significant differences (P > 0.05) were observed, either for Exp. I or for Exp. II. The average cleavage rate was 60.2%, morula rate 62.3% and blastocyst rate 19.2% in Exp. I and 51.6%, 66.8% and 25.8% in Exp. II, respectively. The study confirmed that both urethral and epididymal spermatozoa can be used for in vitro fertilization in cats and proved the usefulness of the ICSI method in the case of teratozoospermic males. The study showed that even in severe cases, when almost no normal spermatozoa can be found in the semen, it is possible to obtain embryos using abnormal sperm cells with the same chance of success as for normal spermatozoa.

Group management influences reproductive function of the male cheetah (Acinonyx jubatus)

Although the free-ranging cheetah is generally socially solitary, as many as 60% of males live in same-sex (usually sibling) coalitions. Under ex situ conditions, the cheetah experiences low reproductive success with only ~18% of males having ever produced young. Most male cheetahs (85%) are managed in captivity in coalitions, but with no data on the influence of social grouping on reproductive parameters. We examined the influence of singleton versus coalition management on various male cheetah physiological traits, including ejaculate quality and gonadal and adrenal hormone metabolite concentrations. We also assessed behaviour within coalitions for evidence of social hierarchy through initiation of interactions with group mates and relatedness to physiological traits. Ejaculate quality (including total motile and structurally normal spermatozoa per ejaculate) and androgen concentration profiles were higher (P<0.05) in coalition compared with singleton males. These results support the conclusion that testis function in the cheetah, specifically related to the development of normal, motile spermatozoa and androgen production, is influenced by management with same-sex conspecifics. The findings have implications for ex situ conservation breeding programs by suggesting that reproductive quality can be enhanced through group maintenance of cheetah males.

Effect of Foetal Bovine Serum on sperm motility, acrosome reaction and spermatic interaction to zona pellucida in alpacas (Vicugna pacos)

The use of foetal bovine serum (FBS) in cell culture media is quite common. However, little is known about the effect of FBS on sperm. The severe difficulties in alpaca reproduction demand the search of new methods for in vitro reproductive management. In the present study, we use for the first time FBS as a supplement in the culture medium for sperm in alpaca, and the effect of FBS on motility, acrosome reaction and sperm binding to the zona pellucida in this species was evaluated. A concentration of 10% v/v FBS was used. The sperm motility with FBS at the first hour was 32.8% (vs. control = 30.0%), whereas at the second hour sperm motility with FBS was 30.2% (vs. control = 28.8%). The acrosome reaction reached an average of 44.0% for treatment with FBS (vs. control = 30.1%). The sperm-zona pellucida binding assay showed that the samples incubated with FBS had an average of 2.7 bound sperm (vs. control = 1.7). Only a significant difference was observed for sperm motility at the first hour and for the acrosome reaction. It is concluded that FBS favours the capacitation of sperm in alpaca.

Transcriptional regulation of P63 on the apoptosis of male germ cells and three stages of spermatogenesis in mice

Infertility affects 10-15% of couples worldwide, and male factors account for 50%. Spermatogenesis is precisely regulated by genetic factors, and the mutations of genes result in abnormal spermatogenesis and eventual male infertility. The aim of this study was to explore the role and transcriptional regulation of P63 in the apoptosis and mouse spermatogenesis. P63 protein was decreased in male germ cells of P63^(+/-) mice compared with wild-type mice. There was no obvious difference in testis weight, sperm motility, and fecundity between P63^(+/-) and wild-type mice. However, abnormal germ cells were frequently observed in P63^(+/-) mice at 2 months old. Notably, apoptotic male germ cells and the percentage of abnormal sperm were significantly enhanced in P63^(+/-) mice compared to wild-type mice. Spermatogonia, pachytene spermatocytes and round spermatids were isolated from P63^(+/-) and wild-type mice using STA-PUT velocity sedimentation, and they were identified phenotypically with high purities. RNA sequencing demonstrated distinct transcription profiles in spermatogonia, pachytene spermatocytes, and round spermatids between P63^(+/-) mice and wild-type mice. In total, there were 645 differentially expressed genes (DEGs) in spermatogonia, 106 DEGs in pachytene spermatocytes, and 1152 in round spermatids between P63^(+/-) mice and wild-type mice. Real time PCR verified a number of DEGs identified by RNA sequencing. Gene ontology annotation and pathway analyzes further indicated that certain key genes, e.g., Ccnd2, Tgfa, Hes5, Insl3, Kit, Lef1, and Jun were involved in apoptosis, while Dazl, Kit, Pld6, Cdkn2d, Stra8, and Ubr2 were associated with regulating spermatogenesis. Collectively, these results implicate that P63 mediates the apoptosis of male germ cells and regulates three stages of spermatogenesis transcriptionally. This study could provide novel targets for the diagnosis and treatment of male infertility.

Normozoospermic versus teratozoospermic domestic cats: differential testicular volume, sperm morphometry, and subpopulation structure during epididymal maturation

Teratozoospermia (<40% morphologically normal spermatozoa/ejaculate) is a frequent phenomenon in feline species. This research was carried out to study the possible differences in testicular volume, differential sperm morphometric traits, and potential differences regarding the sperm subpopulational structure during epididymal sperm maturation in teratozoospermic feline donors. Epididymal sperm samples were collected from the caput (R1), corpus (R2), and cauda (R3) epididymidis in two donor groups (N: normozoospermic; T: teratozoospermic). Aliquots were assessed for concentration, viability, motility, and acrosomal integrity. Sperm morphometric descriptors from CASA-Morph analysis were analyzed by the Principal Component Analysis (PCA) and clustering analyses. Irrespective of the group analyzed, PCA revealed two Principal Components (PCs) for each epididymal region explaining more than the 93% of the variance. Surprisingly, the number of subpopulations remained constant in regions R1-R2-R3 irrespective of the donor group analyzed. However, the distribution of these subpopulations was found to be structurally different and strongly influenced by the epididymal region and the donor group. In conclusion, testicular morphometry and the sperm subpopulation structure were different in N and T donors. The alterations in subpopulations during epididymal maturation could be used as a potential clinical indicator of teratozoospermic individuals since an important influence of teratozoospermia on sperm subpopulation structure has been demonstrated.

Influence of living status (single vs. paired) and centrifugation with colloids on the sperm morphology and functionality in the clouded leopard (Neofelis nebulosa)

The objectives of the present study were to evaluate sperm characteristic of captive clouded leopards in Thailand and examine the structural and functional properties of sperm after selection with the single-layer centrifugation (SLC) method. Twenty-two ejaculates from 11 captive clouded leopards (four housed with access to a female in estrus, and seven housed singly) were collected and assessed for semen traits during 2013 to 2015. Twelve fresh ejaculates were chosen from seven males, and each was divided between two sperm preparation methods; (1) simple washing and (2) SLC. Cryopreservation was performed after semen preparation. Sperm qualities after selections including motility, progressive motility, sperm motility index, viability, acrosome integrity, DNA integrity, and morphology were evaluated in fresh, chilled, and frozen-thawed samples. In addition, sperm functionality after cryopreservation was tested by heterologous IVF using domestic cat oocytes. Sperm motility in the ejaculates was 52.5% to 91.3% (76.8 ± 2.0%, mean ± standard error). A high proportion of morphologically abnormal sperm (63.9 ± 2.0%) was observed, with the major abnormality being tightly coiled tail (13.5 ± 0.5%). An interesting observation was that males housed together with a female had a significantly higher proportion of sperm with intact acrosome (47.9 ± 3.4% and 38.4 ± 2.8%) and lower proportion of sperm with bent midpiece and droplet (7.1 ± 0.6% and 10.2 ± 0.5%) than the males living singly. The sperm motility index, intact acrosome, and sperm with normal tail in the fresh and chilled semen samples were improved by the SLC. In the postthawed semen, the SLC selected higher numbers of viable sperm (34.1 ± 2.2% and 27.9 ± 1.8%), sperm with intact acrosome (31.2 ± 2.1% and 24.3 ± 2.2%), and sperm with normal tail (34.2 ± 2.7% and 24.3 ± 2.7%) than simple washing. Also, the proportion of sperm with tightly coiled tail was lower in the SLC-processed than the simple washed samples (8.1 ± 3.1% and 13.5 ± 3.4%). The SLC-processed group had significantly higher penetration rate in heterologous IVF (29.4 ± 3.0%) than the simple washing group (15.8 ± 3.2%). In conclusion, ejaculates of clouded leopards living in Thailand demonstrated teratospermic characteristic similar to the previous reports from other continents. Single-layer centrifugation is a promising tool to select morphologically normal sperm of teratospermic donors. The successes of assisted reproductive technology could be enhanced by the improved quality of postthaw sperm in this species.

High incidence of 'Dag-like' sperm defect in the domestic cat

The occurrence of a high incidence of sperm tail defects in a male domestic cat resembling the known 'Dag-like' defect is reported. Sperm analyses were performed in ejaculated samples collected by an artificial vagina and in testicular and epididymal sperm cells after castration. The following alterations were observed using transmission electron microscope: heavily coiled sperm tails containing several axonemal units enclosed in the same common cell membrane; aberrations in the axonemal main structure; and swollen and unevenly distributed mitochondria in the midpiece. Abnormal modifications in the mitochondrial sheath were also found in sperm cells retrieved from testes and epididymides. Considering these findings, we can conclude that this is the Dag-like defect, described previously in other domestic species and a testicular origin may be involved.

Glycolytic enzyme activity is essential for domestic cat (Felis catus) and cheetah (Acinonyx jubatus) sperm motility and viability in a sugar-free medium

We have previously reported a lack of glucose uptake in domestic cat and cheetah spermatozoa, despite observing that these cells produce lactate at rates that correlate positively with sperm function. To elucidate the role of glycolysis in felid sperm energy production, we conducted a comparative study in the domestic cat and cheetah, with the hypothesis that sperm motility and viability are maintained in both species in the absence of glycolytic metabolism and are fueled by endogenous substrates. Washed ejaculates were incubated in chemically defined medium in the presence/absence of glucose and pyruvate. A second set of ejaculates was exposed to a chemical inhibitor of either lactate dehydrogenase (sodium oxamate) or glyceraldehyde-3-phosphate dehydrogenase (alpha-chlorohydrin). Sperm function (motility and acrosomal integrity) and lactate production were assessed, and a subset of spermatozoa was assayed for intracellular glycogen. In both the cat and cheetah, sperm function was maintained without exogenous substrates and following lactate dehydrogenase inhibition. Lactate production occurred in the absence of exogenous hexoses, but only if pyruvate was present. Intracellular glycogen was not detected in spermatozoa from either species. Unexpectedly, glycolytic inhibition by alpha-chlorohydrin resulted in an immediate decline in sperm motility, particularly in the domestic cat. Collectively, our findings reveal an essential role of the glycolytic pathway in felid spermatozoa that is unrelated to hexose metabolism or lactate formation. Instead, glycolytic enzyme activity could be required for the metabolism of endogenous lipid-derived glycerol, with fatty acid oxidation providing the primary energy source in felid spermatozoa.

Evidence for compromised metabolic function and limited glucose uptake in spermatozoa from the teratospermic domestic cat (Felis catus) and cheetah (Acinonyx jubatus)

Cheetahs and certain other felids consistently ejaculate high proportions (≥ 60%) of malformed spermatozoa, a condition known as teratospermia, which is prevalent in humans. Even seemingly normal spermatozoa from domestic cat teratospermic ejaculates have reduced fertilizing capacity. To understand the role of sperm metabolism in this phenomenon, we conducted a comparative study in the normospermic domestic cat versus the teratospermic cat and cheetah with the general hypothesis that sperm metabolic function is impaired in males producing predominantly pleiomorphic spermatozoa. Washed ejaculates were incubated in chemically defined medium containing glucose and pyruvate. Uptake of glucose and pyruvate and production of lactate were assessed using enzyme-linked fluorescence assays. Spermatozoa from domestic cats and cheetahs exhibited similar metabolic profiles, with minimal glucose metabolism and approximately equimolar rates of pyruvate uptake and lactate production. Compared to normospermic counterparts, pyruvate and lactate metabolism were reduced in teratospermic cat and cheetah ejaculates, even when controlling for sperm motility. Rates of pyruvate and lactate (but not glucose) metabolism were correlated positively with sperm motility, acrosomal integrity, and normal morphology. Collectively, our findings reveal that pyruvate uptake and lactate production are reliable, quantitative indicators of sperm quality in these two felid species and that metabolic function is impaired in teratospermic ejaculates. Furthermore, patterns of substrate utilization are conserved between these species, including the unexpected lack of exogenous glucose metabolism. Because glycolysis is required to support sperm motility and capacitation in certain other mammals (including dogs), the activity of this pathway in felid spermatozoa is a target for future investigation.

Effect of cryopreservation on sperm DNA integrity in patients with teratospermia

OBJECTIVE

To test whether sperm with abnormal head morphology are more likely to undergo DNA damage and/or chromatin modification during the process of freeze-thawing.

DESIGN

In this prospective study, the semen samples from forty-four men attending the infertility clinic were included. Samples were divided into aliquots to allow direct comparison of fresh and frozen spermatozoa from the same ejaculate. The sperm morphology and the sperm DNA damage were evaluated before and after cryopreservation. The relationship between sperm head abnormalities and freeze-thaw-induced DNA modification was assessed.

SETTING(S)

University hospital fertility center.

PATIENT(S)

Men attending infertility clinic for semen analysis.

INTERVENTION(S)

The normospermic and teratospermic semen samples were evaluated for DNA damage before and after cryopreservation by comet assay and acridine orange bindability test.

MAIN OUTCOME MEASURE(S)

Elucidation of association between sperm morphologic defect and cryodamage.

RESULT(S)

A threefold increase in the amount of DNA damage was observed in teratospermic samples compared with their normospermic counterparts, indicating a higher susceptibility of morphologically abnormal sperm to cryodamage.

CONCLUSION(S)

The susceptibility of morphologically abnormal sperm to DNA damage/chromatin modification during the freeze-thaw process is significantly higher than that of sperm with normal morphology.

Cryopreservation effects on domestic cat epididymal versus electroejaculated spermatozoa

Frozen-thawed epididymal spermatozoa have already been successfully used in artificial insemination in the domestic cat, proving to be a valuable resource for the reproduction of felid species, which are threatened with extinction. The aim of this study was to compare the effects of freezing and thawing on domestic cat semen collected by electroejaculation (EL) and from the epididymides (EP) and vasa deferentia. Ten adult cats were anesthetized, electroejaculated and immediately thereafter, orchiectomized. Epididymal spermatozoa were collected through the compression of caudae epididymidis and vasa deferentia. Spermatozoa were frozen-thawed following a single protocol. Sperm motility, sperm progressive status (0-5), plasma membrane integrity and morphology (light and transmission electron microscope) were assessed on two occasions, immediately after collection and after freezing and thawing. There were no significant differences between the electroejaculated and epididymal fresh or frozen-thawed spermatozoa for any of the variables. However, the incidence of acrosome defects after freezing and thawing increased by 19% based on light microscopy, whereas ultrastructural images revealed acrosome damages in most sperm cells. Since these acrosomal changes are known to affect sperm fertilising capacity, further studies are needed to optimize cryopreservation techniques for epididymal as well as electroejaculated domestic cat spermatozoa.

A short sperm–oocyte incubation time ZBA in the dog

The fertilising capacity of a semen sample can be predicted by evaluation of spermatozoa with in vitro tests. The zona pellucida binding assay (ZBA) accounts for several parameters and interprets the interaction between the spermatozoa and the oocyte. The present study was made in two parts. The aim of the first experiment was to evaluate whether the sperm binding capacity of oocytes varies between different oocyte pools. Each zona binding was made with oocytes from different bitches, using pooled frozen-thawed semen from the same two dogs. The sperm-oocyte complexes were incubated for 1h. There was a significant difference between the six replicates in the number of sperm bound to the zona pellucida (ZP), which indicates that the sperm binding capacity of the ZP differs between oocyte pools. The aims of the second experiment were to evaluate the effects of five different treatments of the spermatozoa on the ZBA, and to evaluate two different incubation times of the sperm-oocyte complexes. ZBAs were made with: fresh semen; semen kept chilled for 1 or 2 days prior to the ZBA; and with semen that had been frozen with or without Equex. The oocytes and spermatozoa were incubated for 1 or 4h. For fresh semen and for semen frozen without Equex, incubation for 1h resulted in a higher number of bound spermatozoa per oocyte than incubation for 4h (P<0.0001). When the effect of the different sperm treatments on the number of spermatozoa bound to the ZP was evaluated, it was found that this number was higher for fresh spermatozoa than for chilled or frozen-thawed spermatozoa both after 1 and 4h of co-incubation (P<0.0001). After 1-h incubation of the sperm-oocyte complexes, spermatozoa chilled for 1 day showed better zona binding capacity than spermatozoa chilled for 2 days, and spermatozoa frozen without Equex had a better zona binding capacity than spermatozoa frozen with Equex. Sperm motility and sperm plasma membrane integrity were higher in fresh than in chilled and frozen-thawed semen. The acrosome integrity was high in all groups of treated semen. In conclusion, 1-h incubation of the sperm-oocyte complexes seems to be sufficient for fresh and chilled semen. Further studies are required to establish the optimal incubation time for sperm-oocyte complexes when frozen-thawed semen is evaluated, as a comparison between semen frozen with Equex and semen frozen without Equex gave different results depending on whether the incubation time was 1 or 4h (in the present study), or 6h [Ström Holst B, Larsson B, Linde-Forsberg C, Rodriguez-Martinez H. Evaluating chilled and frozen-thawed dog spermatozoa using a zona pellucida binding assay.

Gamete cryopreservation in the domestic cat

Cryopreservation of gametes is an important tool for the improvement of assisted reproductive technologies. In-depth studies of spermatozoon and oocyte characteristics are required in order to define efficient protocols for the maintenance of viability, including fertilizing and developmental ability, of gametes after thawing. In the domestic cat, semen cryopreservation techniques still produce variable results, the cryopreservation of oocytes is at an experimental level and there have been only a few attempts at cryopreserving gonadal tissue. However, each procedure has generated promising results and has important implications, both for improving reproductive performance of valuable breeds of domestic cats and for conservation of biodiversity in endangered felids by reclamation of valuable male and female germplasm.

The impact and potential etiology of teratospermia in the domestic cat and its wild relatives

Teratospermia (production of >60% morphologically abnormal sperm/ejaculate) is relatively common among various species in the family Felidae, which is comprised of 37 species. Over two decades of research in this area have produced a significant understanding of the phenotypic expression, its impacts on sperm function and etiology. There is good evidence suggesting that a reduction in genetic diversity contributes to this phenomenon. Results to date demonstrate that spermatozoa from teratospermic donors are compromised in the ability to undergo capacitation and the acrosome reaction, penetrate the zona-pellucida, fertilize conspecific oocytes and survive cryopreservation. Recent studies also reveal abnormalities in chromatin integrity in sperm from teratospermic donors, which, interestingly, fails to impact fertilization or embryo development after intracytoplasmic sperm injection. Through planned inbreeding studies, we now have established that teratospermic cats also produce more spermatozoa by virtue of more sperm producing tissue, more germ cells per Sertoli cell and reduced germ cell loss during spermatogenesis. Overall, it now is clear that gain in sperm quantity is achieved at the expense of sperm quality, suggesting an extensive disruption of normal testicular function in teratospermic donors. Preliminary studies on testicular gene expression in teratospermic cats have also revealed abnormal expression patterns. These findings have markedly increased our understanding of testis biology in the teratospermic donor and reaffirm the value of cats, including wild species, as models for studying novel regulatory mechanisms controlling spermatogenesis and spermiogenesis.

Freezing of stored, chilled dog spermatozoa

The aims of this study were to find out if dog spermatozoa can be stored chilled for 1 or 2 days prior to freezing without a deterioration in post-thaw vitality and longevity, and to compare two extenders; the Uppsala Equex-2 (UE-2) and a TRIS egg yolk extender (EYT). Pooled dog semen was frozen immediately after collection, or was extended and stored at 4 degrees C for 1 or 2 days before freezing. Sperm motility and acrosome integrity were evaluated before freezing and for 6h post thaw at 38 degrees C, while sperm plasma membrane integrity was evaluated post thaw. There were no effects of pre-freeze storage time or extender on post-thaw motility or plasma membrane integrity, but a significant effect of extender (P < 0.0153) on post-thaw acrosomal integrity was found, UE-2 being better than EYT. There was a significant (P < 0.0001) negative effect of post-thaw storage time on acrosome integrity, but this was not influenced by pre-freeze storage time or extender. In conclusion, we found that dog spermatozoa can be frozen after 1 or 2 days of cold storage without significant deterioration in post-thaw motility, acrosome integrity or sperm plasma membrane integrity compared to when frozen immediately after collection. The UE-2 extender was superior to the EYT extender for freezing of cold stored dog spermatozoa.

Influence of glucose and fructose in the extender during long-term storage of chilled canine semen

The use of chilled, extended semen in dog breeding is becoming increasingly popular as preparation and transportation is less expensive and regulations are often less complicated than for frozen semen. Sugar is one of the main constituents in semen extenders, and glucose and fructose are metabolized in separate pathways by freshly ejaculated dog sperm. In this study, glucose, fructose or an equal mixture of both were used in an egg-yolk-tris (EYT) extender at two different concentrations (10 and 70 mM). EYT extender without sugar supplementation, providing only the glucose (3-4 mM) originating from the egg-yolk, served as a control. The longevity of the chilled semen at 5 degrees C was 23 days: the quality of physical and functional characteristics decreasing with time. Glucose and fructose had a strong influence on motility and movement patterns of chilled canine semen. The beneficial effect of 70 mM sugar concentrations compared to 10 mM and the control was pronounced, and maintained sperm motility > or = 70% for 8 days of storage, compared to for 4 days in the control extender. Fructose maintained higher sperm motility than did glucose and the mixture. VAP values were higher in sugar-supplemented extenders (P < 0.05). Neither type nor concentration of the two sugars influenced sperm plasma membrane, acrosome integrity or the acrosome reaction following ionophore challenge (ARIC). Sugar consumption by dog sperm varied between the different periods of storage and with sugar concentrations provided in the extenders. Glucose consumption by dog sperm was greater than fructose consumption when both sugars were present in equal amounts, indicating that dog sperm used glucose in preference to fructose. In conclusion, the major influence of the two sugars on chilled semen was to support motility. EYT extender supplemented with fructose at a concentration of 70 mM was found to be the best of the tested extenders for long-term preservation of chilled canine semen.

Acrosomal integrity and capacitation are not influenced by sperm cryopreservation in the giant panda

Sperm cryopreservation and artificial insemination are important management tools for giant panda breeding and the preservation of extant genetic diversity. This study examined the influence of freeze-thawing on sperm function, specifically capacitation. Sperm from nine giant pandas were assessed before and after rapid (- 40 and - 100 degrees C/min) cryopreservation by incubation in HEPES-buffered Ham's F10 medium with and without the capacitation accelerators, 3-isobutyl-1-methylxanthine (IBMX) and dibutyryl cyclic AMP (dbcAMP). At 0, 3 and 6 h of exposure, aliquots were assessed for sperm motility traits and capacitation, defined as the proportion of sperm with intact acrosomes following exposure to solubilised zonae pellucidae (ursid or felid) or calcium ionophore subtracted from the proportion of sperm with intact acrosomes before exposure. Although mean+/-S.E.M. sperm motility post-thaw (56.1 +/- 3.9% at 0 h) was less (P < 0.05) than pre-freeze (71.7 +/- 6.0%), there was no difference (P > 0.05) in the proportion of acrosome-intact sperm (fresh, 93.0 +/- 1.7% versus cryopreserved-thawed, 81.7 +/- 4.7% at 0 h). Incidence of capacitation was greater (P < 0.05) in fresh sperm incubated with capacitation accelerators IBMX and dbcAMP (9 h: 50.9 +/- 1.1) compared with fresh sperm incubated without accelerators (9 h: 41.2 +/- 1.1%). Frozen-thawed sperm preincubated without accelerators underwent capacitation (49.6 +/- 1.1%) to a greater extent (P < 0.05) compared with these fresh counterparts. Thawed samples with (9 h: 45.9 +/- 1.4%) and without accelerators (9 h: 41.2 +/- 1.1%) did not differ (P > 0.05) during the 9-h incubation. We conclude that giant panda spermatozoa (1) undergo capacitation in vitro with or without chemical accelerators and (2) withstand a rapid cryopreservation protocol, including retaining normal acrosomal integrity and functional capacitation ability.

The effect of Equex STM paste and sperm morphology on post-thaw survival of cat epididymal spermatozoa

Cryopreservation of epididymal spermatozoa is a potentially valuable tool for preserving genetic material from individuals of endangered species that die accidentally. Improvement of sperm-freezing protocols would increase the efficacy of gene banking from endangered felids, and the domestic cat can be used as a model for the wild felids. Addition of the detergent Equex STM paste to semen freezing extenders has been found to improve post-thaw survival and longevity of spermatozoa from various species but has never been tested for cat spermatozoa. Spermatozoa from cats with a high percentage of morphologically abnormal spermatozoa are more susceptible for cold injury and osmotic stress than spermatozoa from normozoospermic cats. Therefore, the aims of this study were to investigate: (a) if addition of Equex STM paste to a semen freezing extender would improve post-thaw sperm survival, and (b) if there is a relation between the percentage of morphologically normal spermatozoa and cryopreservation induced damage in cat epididymal spermatozoa. Spermatozoa harvested from epididymides of 10 male cats were frozen in a Tris egg yolk extender with or without the addition of Equex STM paste (0.5%, v/v). Sperm motility, membrane integrity and acrosomal status were evaluated immediately after harvesting, and at 0, 2, 4 and 6 h post-thaw. Sperm membrane integrity and acrosomal status were also evaluated after cooling to 4 degrees C, just before freezing. Cooling did not cause significant damage to the spermatozoa, whereas freezing damaged sperm membranes and acrosomes. Addition of Equex to the freezing extender had a significant positive effect on the percentage of intact acrosomes immediately after thawing (P > 0.05), but had a negative effect on the longevity of the spermatozoa; the percentages of membrane intact and motile spermatozoa being significantly lower in the presence of Equex than in the controls at 6h after thawing. The percentage of morphologically normal spermatozoa was not found to be correlated with either cryopreservation induced acrosome or plasma membrane damage, or with post-thaw motility (P > 0.05). The results clearly show that addition of Equex STM paste in the freezing extender protects the acrosomes of cat epididymal spermatozoa during the freezing--thawing process, but reduces the sperm longevity during in vitro incubation at 38 degrees C. Our results also indicate that the percentage of morphologically normal epididymal spermatozoa is not correlated with cryopreservation induced sperm damage using the described freezing protocol.

Quantity rather than quality in teratospermic males: a histomorphometric and flow cytometric evaluation of spermatogenesis in the domestic cat (Felis catus)

Teratozoospermia (ejaculation of <40% morphologically normal sperm) commonly occurs within the Felidae, including certain domestic cats, but the cellular and molecular mechanisms that give rise to this phenomenon remain unknown. This study quantified spermatogenesis to identify differential dysfunctions in teratospermic versus normospermic (>60% normal sperm/ejaculate) domestic cats. Sperm used were from electroejaculates and cauda epididymides. Testes from 10 normo- and 10 teratospermic males were obtained by castration and then evaluated by histomorphometry, flow cytometry, and testicular testosterone enzyme immunoassay. Some morphometric traits (tubular diameter, epithelium height, interstitial area, number of Leydig cells, and blood vessels per cross-section) as well as testicular testosterone concentrations were similar between groups, but testicular volume was greater in teratospermic males. Stage frequencies differed also between both cat populations, suggesting possible dysfunctions in spermiation. Quantification of cell populations in most frequent stages revealed more spermatogenic cells and fewer Sertoli cells per tubule cross-section as well as per tissue unit in teratospermic donors. Hence, the ratio of spermatogenic cells per Sertoli cell was elevated in the teratospermic cat. DNA flow cytometry confirmed higher total spermatogenic and meiotic transformations in teratospermic males. In summary, compared with normospermic counterparts, teratospermic cats have a higher sperm output achieved by more sperm-producing tissue, more germ cells per Sertoli cell, and reduced germ cell loss during spermatogenesis. Gains in sperm quantity are produced at the expense of sperm quality.

Normospermic versus teratospermic domestic cat sperm chromatin integrity evaluated by flow cytometry and intracytoplasmic sperm injection

Teratospermia (>60% of morphologically abnormal spermatozoa) is well documented in felids. Even morphologically normal spermatozoa from teratospermic ejaculates have reduced ability to undergo tyrosine phosphorylation, acrosome react, and bind and penetrate oocytes compared with normospermic (<40% abnormal spermatozoa) counterparts. However, it is unknown whether fertilization deficiencies originate at a nuclear level. This study examined whether fertilization failure also was attributable to abnormal sperm chromatin, using the sperm chromatin structure assay (SCSA), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI). Aliquots of unprocessed and swim-up-processed (to isolate morphologically normal spermatozoa) spermatozoa from teratospermic and normospermic domestic cats were analyzed by the flow cytometric SCSA. Swim-up-processed sperm were incubated with in vivo-matured oocytes or used for ICSI. Teratospermic ejaculates expressed more (P < 0.05) chromatin heterogeneity (abnormal chromatin structure) than their normospermic counterparts, both in unprocessed and swim-up-processed samples. Fertilization success in vitro was higher (P < 0.05) from normo- compared with teratospermic inseminates. Similar (P > 0.05) proportions of oocytes fertilized after ICSI using spermatozoa from normo- and teratospermic cats. Results reveal that teratospermia in the cat is expressed at the nuclear level as increased sperm chromatin heterogeneity, but ICSI showed that this does not apparently affect fertilization rates if the zona pellucida and oolemma can be bypassed.

Gonadotropin exposure, salt storage and storage duration affect penetration of domestic cat oocytes by homologous spermatozoa

Salt-stored domestic cat oocytes are routinely used to study sperm function in domestic and nondomestic felids. Our objectives were to assess the effects of in vitro maturation (IVM), salt storage and storage duration on penetration of domestic cat oocytes by homologous spermatozoa. In Experiment 1, domestic cat spermatozoa were coincubated with fresh immature oocytes, salt-stored (2-3 weeks) immature oocytes, or salt-stored (2-3 weeks) IVM oocytes matured in Minimum Essential Medium containing 0.1IU FSH and 0.1IU LH/ml (IVM1) or 0.5IU FSH and 2.2IULH/ml (IVM2). In Experiment 2, all oocytes were matured (IVM2) and inseminated fresh or after salt storage for 2-3 weeks, 2-3 months or 9 months. In Experiment 1, penetration of the outer zona pellucida (OZP) was greater (P<0.05) in salt-stored IVM2 oocytes than in salt-stored immature oocytes, whereas penetration of salt-stored IVM1 oocytes was intermediate (P>0.05). In Experiment 2, penetration of the OZP and inner zona pellucida (IZP) was higher (P<0.05) in fresh IVM2 oocytes than in salt-stored oocytes, and a higher (P<0.05) proportion of oocytes had IZP sperm after 2-3 weeks of storage than after 2-3 months. Penetration of the perivitelline space was higher (P<0.05) in fresh IVM2 oocytes than in oocytes stored for 2-3 weeks or 2-3 months. These results suggest that oocyte penetration is improved by IVM, but is impaired by exposure to salt-storage solution and prolonged storage duration.

Effects of Genistein Isoflavone (4',5',7-Trihydroxyisoflavone) and Dexamethasone on Functional Characteristics of Spermatozoa

Caudal epididymal spermatozoa were used to study the influence of genistein isoflavone and dexamethasone (dxm) on the functional characteristics of spermatozoa. The effects of genistein alone and in combination with dxm on sperm motility, sperm morphology, spontaneous acrosome reaction (AcR), and ionophore A23187-induced AcR were investigated. The FITC-PSA/Hoechst 33258 staining procedure was used to assess sperm cell viability and AcR status and thus to differentiate between true AcR and acrosome degeneration. The overall results indicated that (1) lower doses of genistein alone, or in combination with dxm, did not significantly influence sperm motility or sperm morphology; (2) ionophore A23187 induced AcR in rat spermatozoa; (3) there appeared to be no direct correlation between sperm motility and AcR, (4) higher doses of genistein, alone or in combination with dxm, significantly interfered with percentage sperm motility and caused significant detachment of sperm heads but did not cause morphological defects; and (5) higher doses of genistein caused significant decrease in sperm acrosome reactivity with long duration of exposure. In view of the fact that sperm capacitation and AcR are physiological prerequisites for successful fertilization of oocytes, the findings suggest that chronic exposure of spermatozoa to high doses of genistein could be associated with infertility problems through suppression/inhibition of AcR and sperm motility. Dexamethasone did not appear to influence the effect of genistein on the functionality of postspermatogenic spermatozoa.

Evaluation of the acrosome reaction and viability in buffalo spermatozoa using two staining methods: the effects of heparin and calcium ionophore A23187

In this study, we investigated the effect of heparin and calcium ionophore A23187 on in vitro induction of buffalo sperm acrosome reaction (AR). Two methods for detection of the AR and viability were employed. Fluorescein isothiocyanate-conjugated Arachis hypogea agglutinin (FITC-PNA) was used as a vital stain in combination with ethidium homodimer-1 (EthD-1) to determine the acrosome status of viable spermatozoa. In another experiment, trypan blue replaced EthD-1 to differentiate live and dead spermatozoa having undergone AR. The results from the two methods were significantly correlated (r > 0.9). Four different staining patterns were found in both methods. The FITC-PNA intensely labels the acrosome region of acrosome-intact spermatozoa. EthD-1 and trypan blue stained red and blue at the post-acrosomal region of dead spermatozoa, respectively. Spermatozoa incubated with heparin showed a significant increase ( p < 0.05) in the percentage of live acrosome-reacted sperm after 30 min incubation period. This trend continued and was significantly different over the entire incubation period when compared with the control group at the same interval. In the ionophore-treated group, the proportion of changes in live acrosome-intact and live acrosome-reacted spermatozoa was statistically significantly different ( p < 0.001) when compared with those treated with heparin at the same interval. The AR occurred sooner and to a greater extent when incubated with the ionophore but at 5 h of incubation the percentage of false acrosomal reaction was significantly higher than those in the control and heparin-treated groups. The results in this study indicated that the in vitro induction of AR by heparin and calcium ionophore evaluated by both methods could be used to assess sperm fertilizing capacity for in vitro fertilization of this species.

Creatine phosphokinase in domestic cat epididymal spermatozoa

Mammalian spermatozoa that have not completed final testicular sperm maturation have residual cytoplasm and increased creatine phosphokinase (CK) content. This study determined: (1) if CK could be detected by immunostaining cat spermatozoa from the caput, corpus, and cauda epididymis, (2) fluctuations in the proportions of spermatozoa with mature or immature CK-staining patterns during epididymal sperm transit, and (3) how well sperm maturity (as determined by a CK marker) correlated with testicular or epididymal dysfunctions associated with morphological sperm abnormalities. One epididymis was collected from each of 37 cats after orchiectomy and processed immediately to allow sperm morphology evaluations on a 'regional' basis. Sperm released from the contralateral epididymis were evaluated for motility, sperm membrane integrity, and immunostaining with CK-B antibodies. Proportions of spermatozoa with malformed or detached heads, proximal droplets and acrosomal or midpiece abnormalities decreased (P < 0.05) from the caput to the cauda epididymis. In contrast, proportions of spermatozoa that were motile, membrane-intact or with flagellar abnormalities or distal droplets increased (P < 0.05) from the caput to cauda region. Percentages of spermatozoa with an immature CK-staining pattern also decreased (P < 0.05) with epididymal transit (which differs from that reported for the human and stallion). There was no correlation (P > 0.05) between sperm morphology and the CK-staining patterns. In summary, the results reveal that some specific sperm malformations in the domestic cat are of testicular origin, whereas others develop during epididymal transit.

Seasonal analysis of semen characteristics, serum testosterone and fecal androgens in the ocelot (Leopardus pardalis), margay (L. wiedii) and tigrina (L. tigrinus)

Captive adult male ocelots (Leopardus pardalis, n = 3), margays (L. wiedii, n = 3) and tigrinas (L. tigrinus, n = 4) in two locations in southern Brazil were studied for 14 consecutive months to evaluate the effect of season on testicular function. Reproductive evaluations, including testicular measurements, electroejaculation and blood collection were conducted monthly. Fecal samples were collected weekly for androgen metabolite analysis to assess testicular steroidogenic activity. Ocelots had the highest number of motile spermatozoa in the ejaculate (114.7+/-15.8 x 10(6); P < 0.05), the highest percentage of morphologically normal spermatozoa (82.4+/-1.2%; P < 0.05) and the highest concentration of fecal androgens (1.71 vs. 0.14 microg/g; P < 0.05). Margays and tigrinas had lower numbers of motile spermatozoa (23.4+/-2.8 x 10(6), 74.2+/-8.9 x 10(6), respectively), lower percentages of morphologically normal spermatozoa (57.4+/-2.8, 59.2+/-3.5%, respectively), and lower fecal androgen concentrations (0.15+/-0.01, 0.23+/-0.01 microg/g, respectively). Serum testosterone concentrations were similar among the three species. Fecal androgen concentrations were not affected by season, with the exception of the ocelot where concentrations were higher (P < 0.05) in the summer. Ejaculates were collected throughout the year; however, peaks in average sperm production were observed during the summer for all species. In summary, this study has identified several species differences in male testicular traits among ocelots, margays and tigrinas. Results of longitudinal reproductive assessments suggest males of each species are capable of breeding throughout the year.

Sperm capacitation in vitro in the eld's deer

Sperm capacitation was examined in the endangered Eld's deer (Cervus eldi thamin). Sperm motility and viability (percentage of sperm cells with intact membranes) were assessed in vitro over time after attempting to induce capacitation in TALP alone and TALP supplemented with calcium (10 mM CaCl2), dibutyryl cAMP (1 mM dbcAMP), or fetal calf serum (20% FCS). Sperm aliquots were evaluated at 0, 3, 6, 9, and 12 h for motility, viability, and ability to acrosome react after exposure to calcium ionophore (A23187, CI; 10 microM) or lysophosphatidylcholine (LC; 100 microg/mL). Fresh sperm aliquots in TALP + 10 mM CaCl2 exposed to CI had fewer (P < 0.05) intact acrosomes than the TALP control (TALP alone) or dbcAMP and FCS treatments after 9 h. Mean (+/- SEM) percentage of intact acrosomes of spermatozoa incubated in medium with increased CaCl2 declined (P < 0.05) from 80.2 +/- 2.6% (0 h) to 49.7 +/- 7.3% after prolonged incubation (9 h). The proportion of capacitated fresh spermatozoa was not influenced by LC treatment. Capacitation was not induced (P > 0.05) by any of the presumptive sperm capacitators after freeze-thawing. Likewise, neither CI nor LC induced the acrosome reaction (AR) in these spermatozoa, suggesting that the freeze-thawing process may have caused membrane damage. Results revealed that the supplementation of medium with CaCl2 evokes capacitation in some spermatozoa. However, Eld's deer spermatozoa appear remarkably resistant to conventional stimulators of capacitation and the AR.

Induction of the acrosome reaction in dog sperm cells is dependent on epididymal maturation: the generation of a functional progesterone receptor is involved

In the current study we investigated the progesterone receptor exposure on the sperm from the testis and different parts of the epididymis, the relation to the sperm maturation stage, the functionality of the progesterone receptor and the capacity of sperm to undergo acrosome reaction. Exposed progesterone receptors on spermatozoa were detected using Progesterone-BSA conjugate labeled with fluorescein isothiocyanate (P-BSA-FITC) or a monoclonal antibody against progesterone receptor, C-262. Either progesterone or calcium ionophore was used to induce acrosome reaction. A high percentage (69 +/- 8%; mean +/- SD) of spermatozoa from the cauda epididymis showed P-BSA-FITC labeling at the onset of incubation, whereas only 0.1 +/- 1 and 4 +/- 2%, of spermatozoa from the testes, caput, and corpus epididymis, respectively, were labeled. There was no significant increase in P-BSA-FITC binding during the course of a 6 hr incubation. Treatment with either 10 microM progesterone or 5 microM calcium ionophore induced acrosome reaction in cauda epididymal sperm but not in testicular sperm, caput or corpus epipidymal sperm. It is concluded that the matured sperm of the dog from cauda epididymis and freshly ejaculated sperm demonstrate a functional membrane-bound progesterone receptor while less matured spermatozoa from the testicle, caput, and corpus epididymis fail to demonstrate such a receptor. Acrosome reaction of dog sperm can be induced using either progesterone or calcium ionophore; however, the maturation stages of spermatozoa influence this occurrence.

Effect of ejaculation intervals on semen quality in cats

The relationship between ejaculation intervals and semen quality in 4 male cats aged 3-5 years was investigated in this study. Semen was collected 10 times at intervals of every day, every other day, and every three days using an artificial vagina. Semen was collected consecutively twice on the day of semen collection, and the semen quality was examined. In semen collected every day, the number of sperm in the first collection decreased, and the frequency of immature sperm rapidly increased after the 4th day. In semen collected every other day and every three days, although the semen volume markedly varied among the animals on both first and second collections, the volume remained stable for each animal, the number of sperm was similar in the first and second collections, but was clearly larger in the first collection (p<0.01). Sperm motility and abnormality were stable among the various intervals and between the first and second collections in each animal.

Piecing together the puzzle of carnivore reproduction

Recent advances in feline and canine reproductive studies demonstrate how methodically piecing this information together is beginning to reap rewards for wildlife conservation programs. Non-invasive endocrinology can be used to monitor female reproductive function, time con-specific introductions or AI, and diagnose pregnancy. Sperm morphology characteristics and cell membrane function may be genetically inherited and differ between genetically diverse and inbred species/populations in felids. It is not clear if the same is true for the endangered red wolf. While standards exist for freezing feline and canine sperm, new information using fluorescent staining and zona penetration assays (ZPA) indicates that significant damage can occur during pre-freeze cooling, and may also be related to a species' genetic diversity. Posthumous gamete salvage from genetically valuable animals not only provides a means to study sperm and oocyte physiology but also to assist with genetic management of populations. Using the knowledge gained, IVM/IVF and ICSI have been successful in the domestic cat and AI has resulted in offspring in numerous non-domestic felids. However, understanding the processes of IVM/IVF is still not well understood in canids. New information reveals that sperm and the cumulus cells may be integral to oocyte maturation and that canine epididymal sperm are not capable of undergoing fertilization. The acquisition of knowledge and application of biotechnologies lags behind for non-domestic canid conservation programs.

Detection of calcium ionophore induced membrane changes in dog sperm as a simple method to predict the cryopreservability of dog semen

The sensitivity of dog sperm cells for extracellular Ca(2+)/Ca(2+)-ionophore challenge was compared to the detrimental effects of an optimized freeze/thawing protocol. Three sperm-rich fractions of ejaculates from 9 dogs were obtained, and one aliquot of each ejaculate was washed in a modified Tyrode's medium (HBT containing 0.1 mM Ca(2+)), without (control sample) and with 2.5 microM Ca(2+)-ionophore (induced sample) and incubated for 60 min at 38 degrees C in humidified atmosphere. Another aliquot from the same semen fractions was diluted, washed in a Tris buffer, and packed into 0.5-ml straws with a Tris buffer containing 7.5 vol % glycerol. The samples were stored for 1 week in liquid nitrogen after a computer-driven three-step freeze protocol and subsequently thawed for 50 sec in a 37 degrees C water bath and reconstituted into HBT. The acrosome integrity was determined using fluorescein-conjugated peanut agglutinin (PNA-FITC) as an acrosomal marker, while the vitality of the sperm cells was simultaneously assessed with the membrane impermeable DNA supravital stain ethidium homodimer 1 (EthD-1) using fluorescence microscopy and flow cytometry. The motility of frozen/thawed sperm samples was evaluated by microscopic as well as computerized motility analyses. Remarkably, the percentage sperm cells that underwent acrosome reactions induced by Ca(2+)-ionophore correlated very positively (r = 0.93) with the amount of acrosome damage observed in cryopreserved sperm samples. Furthermore, the degree of cellular damage induced by Ca(2+)-ionophore treatment correlated very negatively (r = -0.99) with the relative amount of sperm cells that remained motile after cryopreservation. Such clear correlations between Ca(2+)-ionophore induced acrosome reaction and motility parameters for frozen/thawed dog sperm cells were not found, suggesting that the generation of acrosome leakage and sperm immotility are two independent detrimental processes occurring during cryopreservation. From these results it can be concluded that Ca(2+)-ionophore treatment followed by simultaneous determination PNA-FITC and EthD-1 staining can be used to predict the cryopreservability of ejaculates from individual dogs used as donors.

Osmotic effects on feline spermatozoa from normospermic versus teratospermic donors

Effects of osmolality stresses on the sperm of normospermic (>60% normal sperm/ejaculate) versus teratospermic (<40% normal sperm) domestic cats and the normospermic leopard cat and the teratospermic clouded leopard were studied. Spermatozoa were exposed to various anisotonic solutions in a single step or returned to near isotonic conditions in a single step after exposure to anisotonic solutions. The percentage of sperm motility was measured subjectively, and dual fluorescent stains were used to assess membrane integrity by flow cytometry. The percentage of sperm motility declined (P < 0.05) in domestic cat sperm exposed to osmolalities <200 and >450 mOsm. Spermatozoa from all felines underwent marked (P < 0.05) membrane disruption following a hypotonic stress, but sperm from teratospermic donors experienced greater (P < 0.05) membrane disruption in response to decreased osmolality. While feline spermatozoa appeared to be highly resistant to hypertonic (600, 1200, and 2400 mOsm) conditions, with >85% of the cells maintaining intact membranes, severe membrane disruption occurred when cells were returned to isotonicity in a single step. There was no difference (P > 0.05) between a 1- and 5-min exposure to various anisotonic solutions. Similarly, sperm from normospermic and teratospermic domestic cats responded identically after exposure to ionic or nonionic solute. Results demonstrate that: (1) spermatozoa from teratospermic males are more vulnerable to a hypotonic stress than sperm from normospermic counterparts; (2) in response to small deviations in osmolality, feline sperm experience a more rapid decline in motility than membrane integrity; and (3) an abrupt return to isotonicity after a hypertonic stress causes extensive sperm membrane damage regardless of ejaculate quality.

Sensitivity of domestic cat (Felis catus) sperm from normospermic versus teratospermic donors to cold-induced acrosomal damage

Freeze-thawing cat sperm in cryoprotectant results in extensive membrane damage. To determine whether cooling alone influences sperm structure and viability, we compared the effect of cooling rate on sperm from normospermic (N; > 60% normal sperm per ejaculate) and teratospermic (T; < 40% normal sperm per ejaculate) domestic cats. Electroejaculates were divided into raw or washed (Ham's F-10 + 5% fetal calf serum) aliquots, with the latter resuspended in Ham's F-10 medium or Platz Diluent Variant Filtered without glycerol (20% egg yolk, 11% lactose). Aliquots were 1) maintained at 25 degrees C (no cooling; control), 2) cooled to 5 degrees C in a commercial refrigerator for 30 min (rapid cooling; approximately 4 degrees C/min), 3) placed in an ice slush at 0 degrees C for 10 min (ultrarapid cooling; approximately 14 degrees C/min), or 4) cooled to 0 degrees C at 0.5 degrees C/min in a programmable alcohol bath (slow cooling); and aliquots were removed every 4 degrees C. All samples then were warmed to 25 degrees C and evaluated for percentage sperm motility and the proportion of intact acrosomes using a fluorescein-conjugated peanut agglutinin stain. In both cat populations, sperm percentage motility remained unaffected (p > 0.05) immediately after exposure to low temperatures and after warming to 25 degrees C. However, the proportion of spermatozoa with intact acrosomes declined (p < 0.05) after rapid cooling ( approximately 4 degrees C/min) to 5 degrees C (N, 65.6%; T, 27.5%) or ultrarapid cooling ( approximately 14 degrees C/min) to 0 degrees C (N, 62.1%; T, 23.0%) in comparison to the control value (N, 81.5%; T, 77.5%). Transmission electron microscopy of cooled sperm revealed extensive damage to acrosomal membranes. In contrast, slow cooling (0.5 degrees C/min) to 5 degrees C maintained (p > 0.05) a high proportion of spermatozoa with intact acrosomes (N, 75.5%; T, 68.3%), which also remained similar (p > 0.05) between cat populations (N, 64.7%; T, 56.8%) through continued cooling to 0 degrees C. Results demonstrate that 1) rapid cooling of domestic cat sperm induces significant acrosomal damage without altering sperm motility, 2) spermatozoa from teratospermic males are more susceptible to cold-induced acrosomal damage than normospermic counterparts, and 3) reducing the rate of initial cooling markedly decreases sperm structural damage.

Circannual variations in intraovarian oocyte but not epididymal sperm quality in the domestic Cat

Ovaries and testes were collected throughout the year from domestic cats spayed and neutered at local veterinary clinics. Fresh oocytes recovered from minced ovaries were subjected to in vitro maturation and then stained to determine stage of maturation or were inseminated with conspecific sperm. The cauda and corpus regions of each epididymis were dissected into pieces and placed in medium; 30 min later, the epididymal tissue was removed, the medium centrifuged, and the sperm pellet resuspended. Samples were assessed for total sperm count and sperm motility traits, morphology, acrosomal integrity, and ability to penetrate cat oocytes in vitro. Fewer excellent (grade I) oocytes were recovered per ovarian pair during September-November (mean +/- SEM, 19.2 +/- 2.1%) than during January-July (36.8 +/- 3.6%, p < 0.05), while the remaining months had intermediate percentages of grade I oocytes (p > 0.05). A high percentage of oocytes recovered from November-April completed nuclear maturation (64.3 +/- 6.8%), which was different (p < 0.05) from the values for May-July (32.2 +/- 3.8%) and August-October (10.4 +/- 2.9%). Percentage of oocytes with bound sperm was lowest (p < 0.01) in September and October (32.0 +/- 3.1%) compared to February and March (91.4 +/- 1.7%). Percentage of oocytes with sperm within the perivitelline space was highest (p < 0.05) in May-August (33.8 +/- 4.6%) compared to all other months. In contrast, the period of highest (p < 0.01) fertilization (i.e., >/= 4-cell embryo formation) was March-April (51.7 +/- 3.1%) as compared to May-July (17.2 +/- 1.8%) or November-January (12.4 +/- 2.6%). Negligible numbers of oocytes recovered during August-October developed beyond the 2-cell stage (1.1 +/- 0.3%). Blastocyst development from cleaved embryos was highest during February-April (44.3 +/- 2.3%) and lowest during August-October (0.6 +/- 0.1%; p < 0.01). Sperm recovered from the epididymides throughout the year did not differ (p > 0.05) in concentration or in any of the motility, structural, or functional variables evaluated. In summary, cat oocyte nuclear maturation in vitro is depressed during August-October, and the ability to form cleaved embryos remains low even when the capacity to achieve nuclear maturation is relatively high (November-January and May-July). In contrast, male cats are capable of consistently producing viable, progressively motile sperm throughout the year.

Inhibition of domestic cat spermatozoa acrosome reaction and zona pellucida penetration by tyrosine kinase inhibitors

Spermatozoa from teratospermic domestic cats (> 60% morphologically abnormal spermatozoa per ejaculate) consistently exhibit lower levels of oocyte penetration in vitro than their normospermic (< 40% abnormal spermatozoa per ejaculate) counterparts. This could be caused by structural abnormalities or intracellular defects resulting in disruption of normal cellular functions. Spermatozoa from teratospermic cats also are compromised in the ability to capacitate and undergo the acrosome reaction (AR) in vitro. Further, we recently identified two tyrosine phosphorylated proteins (95- and 160-kDa) localized over the acrosome region in domestic cat spermatozoa. Phosphorylation of these proteins is reduced in teratospermic compared with normospermic ejaculates. To begin to understand the relationship between tyrosine phosphorylation and sperm function, we examined the effects of two protein tyrosine kinase inhibitors (tyrphostin RG-50864 and genistein) on (1) sperm motility; (2) protein tyrosine phosphorylation; (3) the ionophore A23187-induced AR; (4) the spontaneous and zona pellucida (ZP)-induced AR, and (5) the ability of spermatozoa from normospermic cats to penetrate conspecific ZP-intact oocytes. Over a wide range of concentrations, neither inhibitor affected sperm percentage motility during incubation (P > 0.05). Preincubation with either inhibitor reduced tyrosine phosphorylation of both (95- and 160-kDa) sperm proteins. Although both inhibitors blocked the ZP-induced AR, neither influenced the spontaneous AR nor the A23187-induced AR, suggesting that tyrosine phosphorylation may be involved in physiologic AR. No differences (P > 0.05) were observed in the ability of control or inhibitor-treated spermatozoa to bind to or penetrate the outer ZP layer. However, percentages of oocytes with treated spermatozoa in the inner ZP (tyrphostin, 8.7%; genistein, 20.4%) and perivitelline space (tyrphostin, 0%; genistein, 2.3%) were less (P < 0.001) than untreated controls (inner ZP, 62.7%; perivitelline space, 10.2%). These results (1) demonstrate that ZP-induced acrosomal exocytosis in domestic cat spermatozoa is regulated via a tyrosine kinase-dependent pathway and (2) suggest that defects in these signaling pathways may represent one of the causes for compromised sperm function in teratospermic males.