Human sperm mitochondrial function related to motility: a flow and image cytometric assessment

Protective effects of benfotiamine on cyfluthrin-induced testicular damage and sperm characteristics during the prepubertal period

Cyfluthrin, a widely used synthetic pyrethroid insecticide, poses potential risks to both human health and the environment due to its extensive application in residential, agricultural, and outdoor settings. Conversely, benfotiamine, a fat-soluble derivative of vitamin B1, offers versatile therapeutic potential. This experimental study aimed to investigate the impact of cyfluthrin exposure during the prepubertal period on sperm characteristics and testicular tissue integrity in male rats, as well as to assess the protective effects of benfotiamine. A total of 32 4-week-old Wistar albino male rats were divided into four groups. Group I received daily oral gavage of 1 ml/kg/day of olive oil (control). Group II was administered cyfluthrin (54 mg/kg/day) dissolved in 1 ml of olive oil. Group III received both cyfluthrin (54 mg/kg/day) and benfotiamine (100 mg/kg/day) in olive oil. Group IV was given benfotiamine (100 mg/kg/day) in olive oil. After 5 weeks of treatment, the rats underwent evaluations for sperm motility, epididymal sperm density, and abnormal sperm rates. Additionally, their testicular tissues were examined histologically and immunohistochemically. This study underscores the potential hazards of cyfluthrin exposure on male reproductive health and highlights the protective role of benfotiamine in mitigating these effects. It emphasizes the importance of careful pesticide usage and dosage considerations to prevent potential public health issues, including infertility, associated with long-term exposure to pesticides like cyfluthrin.

How long can the sperm wait? Effect of incubation time on ICSI outcomes

In sperm processing for IVF/ICSI incubation times differ considerably both between and within assisted reproduction facilities. There is no established consensus on the optimal sperm incubation timings to maximize pregnancy rates, and the few studies addressing this association rely on manual and operator-dependent methods for time recording. The present retrospective cohort study includes 1169 ICSI cycles using fresh semen processed by swim-up. An operator-independent, radiofrequency-based system was used to record sperm incubation times: from sample collection to swim-up (T1, 0.35 ± 0.26); from swim-up to ICSI (T2, 3.30 ± 2.2); and total time from sample collection to ICSI (T, 3.66 ± 2.26). In oocyte donation cycles, we observed a significant negative effect of T1 on fertilization rate (FR; generalized linear modelling regression, coeff. -0.20, p = 0.001); however, after analysing all times by deciles and by adjusted logistic regression, none of the time intervals had a significant effect on pregnancy (biochemical, clinical, and ongoing) and live birth (LB) rates (p > 0.05 for all outcomes). In cycles using the patient's oocytes, we observed a negative effect of T2 (ordinal regression, coeff. -0.25, p = 0.011) and T (-0.33, p = 0.005) on the mean morphological score of the embryo cohort. In these cycles, a trend associating longer values of T with higher LB rates was identified (OR = 1.47, p = 0.050), although this difference is likely not clinically significant. In conclusion, while longer sperm incubation in vitro may impact slightly both FRs and embryo morphology after ICSI, no adverse effects were detected on the reproductive outcomes.

Characteristics and Cryopreservation of Semen of Sex-Reversed Females of Salmonid Fish

Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage-both short-term and long-term (cryopreservation)-that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma.

Evaluation of Sperm Mitochondrial Function: A Key Organelle for Sperm Motility

Introduction: The role of nutraceuticals in the treatment of male infertility, especially in the “idiopathic form”, remains the subject of significant debate. Many antioxidants improve sperm motility but the exact mechanism by which they act is still unclear. Although several studies have shown a correlation between sperm motility and mitochondrial function, the effects of antioxidant therapy on mitochondrial membrane potential (MMP) are poorly studied. The first aim of this review was to evaluate the efficacy of antioxidants on mitochondrial function and, consequently, on sperm motility in male infertile patients. Material and Methods: we performed a systematic search of all randomized controlled and uncontrolled studies available in the literature that reported sperm motility and MMP at baseline and after antioxidant administration in-vivo and in-vitro in patients with idiopathic asthenozoospermia. Pubmed, MEDLINE, Cochrane, Academic One Files, Google Scholar and Scopus databases were used. Results: Unexpectedly, among 353 articles retrieved, only one study met our inclusion criteria and showed a significant effect of myoinositol on both MMP and sperm motility. We then summarized the main knowledge on anatomy and metabolism of sperm mitochondria, techniques allowing to assess sperm mitochondria function and its relationships with low sperm motility. Finally, we paid special attention to the effect of antioxidant/prokinetic molecules for the treatment of asthenozoospermia. Conclusions: This is the first systematic review that has attempted to evaluate the effects of antioxidants on MMP and sperm motility. Although results are not conclusive due to the dearth of studies, the close relationship between mitochondria and sperm motility is clear. The investigation of this correlation could provide valuable information to be exploited in clinical practice for the treatment of male infertility.

Ultra-rapid cooling of ibex sperm by spheres method does not induce a vitreous extracellular state and increases the membrane damages

Sperm cryopreservation by ultra-rapid cooling based on dropping small volumes of sperm suspension directly into liquid nitrogen, has been successful in some wild ruminant species, including the Iberian ibex (Capra pyrenaica). In ultra-rapid cooling, the contents of these droplets are expected to enter a stable, glass-like state, but to the best of our knowledge no information exists regarding the presence or absence of ice formation in the extracellular milieu when using this technique. Different modifications to the extracellular milieu likely inflict different types of damage on the plasmalemma, the acrosome and mitochondrial membranes. The aims of the present work were: 1) to examine the physical state of the extracellular milieu after cryopreservation at slow and ultra-rapid cooling rates—and thus determine whether ultra-rapid cooling vitrifies the extracellular milieu; and 2) to compare, using conventional sperm analysis techniques and scanning and transmission electron microscopy, the damage to sperm caused by these two methods. Sperm samples were obtained by the transrectal ultrasound-guided massage method (TUMASG) from anesthetized Iberian ibexes, and cryopreserved using slow and ultra-rapid cooling techniques. Sperm motility (22.95 ± 3.22% vs 4.42 ± 0.86%), viability (25.64 ± 3.71% vs 12.8 ± 2.50%), acrosome integrity (41.45± 3.73% vs 27.00 ± 1.84%) and mitochondrial membrane integrity (16.52 ± 3.75% vs 4.00 ± 0.65%) were better after slow cooling (P<0.001) than after ultra-rapid technique. Cryo-scanning electron microscopy (Cryo-SEM) suggested that the vitrified state was not achieved by ultra-rapid cooling, and that the ice crystals formed were smaller and had more stretchmarks (P<0.001) than after slow cooling. Scanning electron microscopy revealed no differences in the types of damage caused by the examined techniques, although transmission electron microscopy showed the damage to the plasmalemma and mitochondrial membrane to be worse after ultra-rapid cooling. In conclusion ultra-rapid cooling provoked more membrane damage than slow cooling, perhaps due to the extracellular ice crystals formed.

Assessment of Oligo-Chitosan Biocompatibility toward Human Spermatozoa

The many interesting properties of chitosan polysaccharides have prompted their extensive use as biomaterial building blocks, for instance as antimicrobial coatings, tissue engineering scaffolds, and drug delivery vehicles. The translation of these chitosan-based systems to the clinic still requires a deeper understanding of their safety profiles. For instance, the widespread claim that chitosans are spermicidal is supported by little to no data. Herein, we thoroughly investigate whether chitosan oligomer (CO) molecules can impact the functional and structural features of human spermatozoa. By using a large number of primary sperm cell samples and by isolating the effect of chitosan from the effect of sperm dissolution buffer, we provide the first realistic and complete picture of the effect of chitosans on sperms. We found that CO binds to cell surfaces or/and is internalized by cells and affected the average path velocity of the spermatozoa, in a dose-dependent manner. However, CO did not affect the progressive motility, motility, or sperm morphology, nor did it cause loss of plasma membrane integrity, reactive oxygen species production, or DNA damage. A decrease in spermatozoa adenosine triphosphate levels, which was especially significant at higher CO concentrations, points to possible interference of CO with mitochondrial functions or the glycolysis processes. With this first complete and in-depth look at the spermicidal activities of chitosans, we complement the complex picture of the safety profile of chitosans and inform on further use of chitosans in biomedical applications.

Freezability biomarkers in bull epididymal spermatozoa

Sperm cryopreservation is an important tool for storing genetic traits and assisted reproduction techniques. Several studies have developed semen cryopreservation protocols. However, the sperm proteome is different between ejaculated and epididymal spermatozoa and little is known about cryopreservation effects on epididymal spermatozoa. Therefore, our study aimed to (i) investigate the differences of sperm parameters based on the freezing tolerance of spermatozoa and (ii) identify potential markers to predict the freezability of bull epididymal spermatozoa. Our preliminary study demonstrated that spermatozoa from individual bulls differ in cryopreservation freezability. We categorized spermatozoa into high freezing-tolerant spermatozoa and low freezing-tolerant spermatozoa group based on sperm motility after freezing/thawing. We evaluated several sperm functional parameters, including sperm motility/motion kinematics, sperm speed parameters, viability, mitochondrial activity, and capacitation status. Our results demonstrated that motility, sperm speed parameters, viability, and mitochondrial membrane potential had significant differences between the two groups but motion kinematics and capacitation status did not. In addition, the concentration of three proteins - glutathione s-transferase mu 5, voltage-dependent anion-selective channel protein 2, and ATP synthase subunit beta, differed between both groups. Thus, our research highlighted differences in bull epididymal spermatozoa freezability upon cryopreservation and these proteins might be useful markers to select high freezing-tolerant epididymal spermatozoa.

Mitochondrial membrane potential and reactive oxygen species in liquid stored and cryopreserved turkey (Meleagris gallopavo) spermatozoa

The extensive use of artificial insemination in turkeys has led to the development of in vitro semen storage. However, fertility rates from liquid stored and frozen/thawed turkey semen are still unsatisfactory. The aim of the study was to assess spermatozoa viability, mitochondrial membrane potential (MMP), and reactive oxygen species production (ROS) in liquid stored and cryopreserved turkey semen with the use of flow cytometry. Moreover, motility and adenosine triphosphate (ATP) content in sperm were monitored at the same time to link flow cytometry data with sperm movement and energetics. Liquid storage led to a decrease in sperm motility (80.6 vs. 55.6%, for fresh and stored for 48 h), live sperm with an intact MMP (59.9 vs. 30.5% for fresh and stored for 48 h), and a 20-fold decrease in ATP content after 24 h of storage. A 3-fold increase in ROS+ sperm was observed after 48 h of storage (9.3 vs. 26.8% for fresh and stored for 48 h). Semen equilibration before cryopreservation affected only ATP content. However, freezing/thawing led to a dramatic decrease in all of the studied semen quality parameters. A 5-fold decrease in live sperm with intact MMP (59.8 vs. 11.9%) and a 7-fold increase in sperm ROS+ (10.8 vs. 74.4%) were recorded between fresh and frozen/thawed semen. The results strongly suggested that a significant loss of MMP and a disturbance in sperm ATP production during semen storage can be the main reason for the decline in sperm motility. The disturbance of mitochondria activity during storage seems to be associated with the increase in oxidative stress in turkey semen. Turkey sperm mitochondria also appear to be very sensitive to cryodamage. Diminished energy production in turkey spermatozoa, visible as the low percentage of sperm with an intact MMP and low level of ATP after freezing/thawing, which is associated with high ROS generation, could be responsible for the low fertilizing ability of cryopreserved turkey semen.

Single-cell-based evaluation of sperm progressive motility via fluorescent assessment of mitochondria membrane potential

Sperm cells progressive motility is the most important parameter involved in the fertilization process. Sperm middle piece contains mitochondria, which play a critical role in energy production and whose proper operation ensures the reproductive success. Notably, sperm progressive motility is strictly related to mitochondrial membrane potential (MMP) and consequently to mitochondrial functionality. Although previous studies presented an evaluation of mitochondrial function through MMP assessment in entire sperm cells samples, a quantitative approach at single-cell level could provide more insights in the analysis of semen quality. Here we combine laser scanning confocal microscopy and functional fluorescent staining of mitochondrial membrane to assess MMP distribution among isolated spermatozoa. We found that the sperm fluorescence value increases as a function of growing progressive motility and that such fluorescence is influenced by MMP disruptors, potentially allowing for the discrimination of different quality classes of sperm cells in heterogeneous populations.

Influence of iodine in excess on seminiferous tubular structure and epididymal sperm character in male rats

Excess iodine induced public health problems are now emerging in many iodine sufficient regions for indiscriminate intake of iodine through various iodized products. It has been reported that excess iodine can disrupt overall male reproductive physiology by generating oxidative stress in the testis. However, information on the possible effect of iodine in excess on spermatozoa found less. In the present investigation flow cytometric techniques and scanning electron microscopy (SEM) have been used to study the spermatozoal functional as well as structural status under the influence of excess iodine; generation of ROS in the spermatozoa as evident by DCFDA, altered acrosomal integrity as observed by fluorescence lectin staining method and depolarized mitochondrial membrane potential (ΔΨ_m ) noticed by JC-1 staining. Ultrastructure of seminiferous tubule after excess iodine exposure indicated severe deterioration of seminiferous tubular surface architecture. Significant increase in spermatozoal DNA fragmentation and apoptotic sperms were found by acridine orange and Annexin V, respectively, however the plasma membrane integrity/viability was decreased as evident by propidium iodide staining in various incremental doses and durations under iodine excess. The study reveals that excess iodine could cause apoptosis of spermatozoal cells by inducing ROS that ultimately affects male fertility potential.

The effect of gentamicin on sperm motility and bacterial abundance during chilled sperm storage in the Booroolong frog

Antibiotics can inhibit bacterial contamination and extend sperm longevity during storage; a primary goal of captive facilities conducting biobanking and artificial fertilisation (AF). This study evaluated the effects of gentamicin on the short-term storage of Booroolong frog sperm. Sperm suspensions were obtained via either testis maceration, or as spermic urine, following hormonal induction of sperm-release. The effect of 0, 1, 2, 3 or 4mgmL^-1 gentamicin on bacterial abundance (CFUmL^-1) was determined and sperm motility assessed. In both testis macerate samples and spermic urine samples, gentamicin administered at intermediate-to-high doses (2, 3 & 4mgmL^-1) eliminated, or significantly reduced, bacterial abundance. Sperm samples obtained via testis maceration exhibited significantly lower sperm motility at the highest doses (3 & 4mgmL^-1). All remaining treatments (0, 1 & 2mgmL^-1) were statistically similar and maintained sperm motility >55%. Sperm samples obtained as spermic urine exhibited no difference in sperm motility or velocity when treated with gentamicin at any dose. While antibiotic treatment did not improve sperm longevity as predicted, this is the first study to demonstrate that antibiotic treatment can reduce bacterial abundance without compromising sperm motility in an anuran amphibian. Antibiotic supplementation may be an important tool for reducing pathogen transmission where sperm samples are transferred between captive institutions for biobanking and AF.

Apoptotic sperm biomarkers and their correlation with conventional sperm parameters and male fertility potential

PURPOSE

To investigate the relationship between sperm apoptotic biomarkers and patient clinical characteristics, conventional sperm parameters and fertility potential.

MATERIAL AND METHODS

Sperm analysis, phospholipid asymmetry, mitochondrial membrane potential (MMP) and DNA denaturation were assessed in 142 males of infertile couples. Seventy-three couples were allocated to the natural conception group, and 55 couples underwent IVF or ICSI.

RESULTS

DNA denaturation correlated positively with age and negatively with testicular volume (TV). MMP correlated negatively with BMI and FSH and positively with TV. Normal viable sperm correlated positively with TV and negatively with age, BMI and FSH. DNA denaturation was associated with a significantly lower natural pregnancy rate (OR 5.4, 95% CI:1.3-22, p = 0.011).

CONCLUSION

Sperm apoptosis is related to male age, BMI, testicular volume and FSH. Among the apoptotic markers, only DNA denaturation has been found to predict natural pregnancy better than conventional sperm parameters.

Characteristics of donkey spermatozoa along the length of the epididymis

In mammals, the epididymis has numerous interrelated functions including absorptive and secretory activity that affect luminal environment and cell membrane, and the maturation and storage of sperm. Spermatozoa acquire their motility and fertilizing ability during their passage through the epididymis and the motility of epididymal spermatozoa should be a balance between the maturation of flagellum and the inhibition of the flagellar machinery. In this study maturational change in sperm characteristics were evaluated in the epididymis of donkey. Spermatozoa collected from four portions of the epididymis (head, cranial corpus, caudal corpus, tail) were compared before and after ejaculation for viability, mitochondrial activity, kinetic parameters, and morphology. A significant increase in the mitochondrial activity along the epididymis was reported, suggesting a possible involvement in the motion mechanism. This should be corroborated by the significant correlation between mitochondrial activity and the total and progressive motility and the increase in velocities of spermatozoa recorded by computer-assisted sperm analysis. The percentage of most of the abnormal spermatozoa were similar in all tracts, with a great variability between jackasses. Only the bent midpiece percentage decreased significantly along epididymis. A significant increase in the percentage of distal cytoplasmic droplets (DCD), and a simultaneous decrease in the proximal cytoplasmic droplets (PCD), was found. The DCD fell down after ejaculation suggesting the late loss of the cytoplasmic residual (DCD) in the donkey, as hypothesized in the stallion. Because the prevalence of PCD were similar in both tail epididymal and ejaculated spermatozoa, a defect of the maturative process in the PCD sperm should be speculated.

Changes in sperm membrane and ROS following cryopreservation of liquid boar semen stored at 15 °C

Boar semen is occasionally transferred to different locations in liquid form at 15 °C for cryopreservation. However, the use of frozen boar semen is limited due to the high susceptibility of boar sperm to cold shock. The aim of this study was to help improve the quality of frozen boar semen by determining the changes in sperm membrane and ROS during the cryopreservation processes of 15 °C-stored boar semen. Semen was collected from ten Duroc boars and transferred to our laboratory in liquid form stored at 15 °C. After cooling to 5 °C and freezing-thawing, conventional sperm parameters (total motility, progressive motility, and normal morphology), plasma membrane integrity, acrosomal membrane status, and intracellular ROS were evaluated. Sperm function, as assessed by conventional parameters, was unaffected by cooling but was decreased by freezing-thawing (P<0.05). However, the cooling and freezing-thawing processes led to damages in the sperm plasma membrane, and the cooling process caused increase in mean PNA (peanut agglutinin)-fluorescence intensity in viable acrosome-intact sperm (P<0.05). In ROS evaluation, the cooling process decreased intracellular (·)O(2) and H(2)O(2) in viable sperm (P<0.05), while the freezing-thawing process increased intracellular H(2)O(2) (P<0.05) without change in intracellular (·)O(2) in viable sperm. Our results suggest that, in liquid boar semen stored at 15 °C, cooling may be primarily responsible for the destabilization of sperm membranes in viable sperm, while freezing-thawing may induce reductions in sperm function with increase in membrane damage and H(2)O(2).

Thiamine status in humans and content of phosphorylated thiamine derivatives in biopsies and cultured cells

Background

Thiamine (vitamin B1) is an essential molecule for all life forms because thiamine diphosphate (ThDP) is an indispensable cofactor for oxidative energy metabolism. The less abundant thiamine monophosphate (ThMP), thiamine triphosphate (ThTP) and adenosine thiamine triphosphate (AThTP), present in many organisms, may have still unidentified physiological functions. Diseases linked to thiamine deficiency (polyneuritis, Wernicke-Korsakoff syndrome) remain frequent among alcohol abusers and other risk populations. This is the first comprehensive study on the distribution of thiamine derivatives in human biopsies, body fluids and cell lines.

Methodology and Principal Findings

Thiamine derivatives were determined by HPLC. In human tissues, the total thiamine content is lower than in other animal species. ThDP is the major thiamine compound and tissue levels decrease at high age. In semen, ThDP content correlates with the concentration of spermatozoa but not with their motility. The proportion of ThTP is higher in humans than in rodents, probably because of a lower 25-kDa ThTPase activity. The expression and activity of this enzyme seems to correlate with the degree of cell differentiation. ThTP was present in nearly all brain and muscle samples and in ∼60% of other tissue samples, in particular fetal tissue and cultured cells. A low ([ThTP]+[ThMP])/([Thiamine]+[ThMP]) ratio was found in cardiovascular tissues of patients with cardiac insufficiency. AThTP was detected only sporadically in adult tissues but was found more consistently in fetal tissues and cell lines.

Conclusions and Significance

The high sensitivity of humans to thiamine deficiency is probably linked to low circulating thiamine concentrations and low ThDP tissue contents. ThTP levels are relatively high in many human tissues, as a result of low expression of the 25-kDa ThTPase. Another novel finding is the presence of ThTP and AThTP in poorly differentiated fast-growing cells, suggesting a hitherto unsuspected link between these compounds and cell division or differentiation.

The role of the mitochondrion in sperm function: is there a place for oxidative phosphorylation or is this a purely glycolytic process?

We review here the current knowledge related to the metabolic pathways used by spermatozoa to meet their high demands for ATP. This is discussed with special emphasis on one of their key roles, motility. We believe that the controversy among glycolytic and oxidative phosphorylation supporters is artificial and, as it happens in many other cell types, the source of ATP is multiple and depends on external inputs.

Effects of hCG as spermiation inducer on European eel semen quality

Fish sperm quality has traditionally been estimated by subjective evaluation of motility and sperm concentration. Alternative methods for evaluation of sperm quality have been developed in the last decade and enable estimation of spermatozoa head morphometry, membrane integrity and mitochondrial function. Weekly injections of human chorionic gonadotropin (hCG) induced spermiation in farmed male European eels. The milt volume increased from the 5th to 12th weeks. Sperm concentration significantly increased from the 5th week, reaching the highest values at the 8th week, while best motility results were registered at the 9th week of treatment. Coinciding with these intervals, the percentage of dead spermatozoa determined with Hoechst staining showed a reduction in the 8th to 11th weeks of treatment, while the percentage of mitochondrial functionality determined by JC-1 staining did not show a similar pattern. The automatic sperm morphology analysis (ASMA) of the spermatozoa head length, width, area and perimeter showed a significant growth from the 5th to 8th weeks. However, the analysis of isolated descriptive parameters may be difficult to understand because there is a variability in these parameters for each week, making knowledge of the growth kinetic complex. The global size of the spermatozoa head was calculated by applying principal component analysis (PCA), because this method establishes new components that make the interpretation of results easier, allowing a whole interpretation of the changes in the cell morphology. PC1 defines the global head size and shows a significant increase between the 5th and 8th weeks of treatment, showing shorter changes until 12th week. PC2 shows a significant increase in the spermatozoa width from the 5th to 7th weeks. Considering the results of the variations in the principal components defining European eel spermatozoa morphometry, it may be concluded that hCG maturative treatment produced thick cells during the first weeks of spermiation, and subsequent samplings showed an increase in cell width and length. These changes in sperm morphometry coincide with the highest sperm quality assessed as sperm motility and concentration, as well as with the best results obtained in previous studies reporting the best sperm quality between weeks 8 and 10 of hCG treatment. These results support the use of ASMA and Hoechst staining techniques as alternative methods for the evaluation of fish sperm quality.

Stimulation of bovine sperm mitochondrial activity by homeopathic dilutions of monensin

Mitochondrial activity is an important viability parameter of spermatozoa and is linked to sperm motility. Monensin is commonly used as an inhibitor for sperm mitochondrial activity in the laboratory. This study was conducted to evaluate the influence of some homeopathic dilutions of monensin on sperm mitochondrial activity. Fresh ejaculates from 6 mature bulls were used in the study. Samples of the semen were tested using a flow cytometer for mitochondrial activity and sperm viability using Rhodamine 123 and SYBR-14, respectively. The 9x dilution of monensin resulted in very highly significant (P<0.001) stimulation of mitochondrial activity. Monensin 5x, 7x, 8x and 13x caused highly significant (P<0.01) stimulation of the sperm mitochondrial activity. Other homeopathic dilutions of monensin (6x, 10x, 11x, 12x and 14x) also had a significant (P<0.05) stimulatory effect. The use of monensin did not have any negative effect on sperm viability. We conclude that some homeopathic dilutions of monensin increase mitochondrial activity of bovine spermatozoa without negative effect on sperm viability, the 9x dilution was the most effective. Further in vivo studies are required to estimate the effect of homeopathic dilutions of monensin on semen quality.

Fertility evaluation of frozen/thawed semen

In vitro semen analyses have been used for more than half a century to estimate the fertilizing potential of a semen sample. Unfortunately, none of the assays developed provide results that consistently correlate well with fertility. The reasons for this lack of consistency, due in part to the complexity of the spermatozoon itself, the collection of fertility data, and factors beyond control of the semen analyses themselves, are discussed. Different spermatozoal attributes that are necessary for a spermatozoon to fertilize an oocyte are presented and assays used to evaluate each attribute described. Although laboratory assay results do not correlate well with semen fertility, the importance of conducting laboratory assays on every semen sample used for artificial insemination or to attempt to determine causes for infertility, is discussed.

Anion exchanger 2 is essential for spermiogenesis in mice

Na+-independent anion exchangers (AE) mediate electroneutral exchange of Cl- for HCO3- ions across cell membranes, being involved in intracellular pH and cell volume regulation and in transepithelial hydroionic fluxes. Bicarbonate activation of adenylyl cyclase is known to be necessary for sperm motility and sperm capacitation, and a few studies have suggested a possible role of AE carriers in reproduction. Among the four AE genes identified in mammals thus far, only Ae2 (Slc4a2) has been determined to be expressed in the male reproductive system, especially in developing spermatozoa and in epididymal epithelium. Most AE genes drive alternative transcription, which in mouse Ae2 results in several Ae2 isoforms. Here, we generated mice carrying a targeted disruption of Ae2 that prevents the expression of the three AE2 isoforms (Ae2a, Ae2b1, and Ae2b2) normally found in mouse testes. Male Ae2-/- mice (but not female Ae2-/- mice) are infertile. Histopathological analysis of Ae2-/- testes shows an interruption of spermiogenesis, with only a few late spermatids and a complete absence of spermatozoa in the seminiferous tubules. The number of apoptotic bodies is increased in the seminiferous tubules and in the epididymis, which also shows squamous metaplasia of the epididymal epithelium. Our findings reveal an essential role of Ae2 in mouse spermiogenesis and stress the recently postulated involvement of bicarbonate in germ-cell differentiation through the bicarbonate-sensitive soluble-adenylyl-cyclase pathway.

Alterations in mitochondria membrane potential and oxidative stress in infertile men: a prospective observational study

OBJECTIVE

To evaluate the mitochondrial membrane potential (MMP) of spermatozoa and its correlation with semen parameters and production of reactive oxygen species (ROS) in infertile men and healthy donors.

DESIGN

Controlled prospective study.

SETTING

Male infertility clinic, Glickman Urological Institute, The Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Nineteen infertile men and 7 healthy volunteers.

INTERVENTION(S)

Standard semen analysis, assessment of MMP and ROS production in spermatozoa. The MMP was assessed by flow cytometry using the probe carbocyanine DiOC(6)(3) and ROS was measured with chemiluminescence assay using luminol.

MAIN OUTCOME MEASURE(S)

The results of MMP are reported as the median interquartile range (IQR) number of cells counted in different areas of fluorescence. Results of ROS measurement are expressed as x10(6) counted photons per minute per 20 million sperm (cpm).

RESULT(S)

The patients with abnormal semen parameters had a significantly lower MMP [1337.7 (1066.38, 1879.2)], and higher ROS [1.12 (0.26, 3.86)] than the donors [MMP: 2482.9 (2162.5, 3520.6)] and [ROS: 0.10 (0.01, 0.14)]. The MMP was positively correlated with sperm concentration (r = 0.62) and negatively correlated with the ROS produced (r = -0.45).

CONCLUSION(S)

Measuring MMP in spermatozoa provides useful information about a man's fertility potential. Increased ROS production by spermatozoa is associated with a decreased MMP.

Postnatal exposure of 2,2',3,3',4,6'-hexachlorobiphenyl and 2,2',3,4',5',6-hexachlorobiphenyl on sperm function and hormone levels in adult rats

Polychlorinated biphenyls (PCBs) are known to affect reproductive system in animals and in accidentally or occupationally exposed humans. Information is lacking on effects of non-dioxin like chlorinated biphenyls (CB) congeners on male reproduction. The aim of this study is to determine whether treatment of postnatal non-dioxin like CB congeners affects sperm function and hormone levels in rats. Male Sprague-Dawley rats received either 2,2',3,3',4,6'-hexachlorobiphenyls (CB 132) or 2,2',3,4',5',6-hexachlorobiphenyls (CB 149) by ip injection of 9.6 or 96 mg/kg at day 21. At 16 weeks, the animals were sacrificed; sperm quality and hormone levels were measured. Body weight, testis and cauda epididymis weights, sperm counts, ROS generation, acrosome reaction rate, serum thyroxine (T(4)), free T(4) and testosterone (TT) concentrations were unaffected. However, treatment of CB 132 and CB 149 caused decreases in sperm motility, curvilinear velocity (VCL), average path velocity (VAP), straight-line velocity (VSL), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF). Serum triiodothyronine (T(3)) level was significantly decreased in CB 132 9.6 mg/kg dose group compared with the controls. On the other hand, a significant decrease was found in free T(3) concentration both in 96 mg/kg of CB 132 and CB 149 groups. In summary, this study showed that CB 132 and CB 149 affects serum levels of triiodothyronine as well as sperm motility, velocity and capability of penetrating oocytes. The mechanism of action and potential effects on human warrant further investigation.

Assessment of sperm quality: a flow cytometric approach

For many years, scientists have sought to develop laboratory assays that accurately predict the fertilizing capacity of a semen sample. This goal, however, has proven elusive and will most likely be very difficult to achieve, due to the complex nature of the problem. Part of the problem results from the many attributes that a spermatozoon must possess to fertilize an egg, and how laboratory assays can evaluate all of these attributes simultaneously. The percentage of motile sperm in a sample is most commonly used to evaluate semen quality. This assay, however, is not highly correlated with the fertilizing capacity of semen samples. One reason motion assays do not correlate well with fertility is that we are evaluating only one of many attributes that a sperm must possess to fertilize an oocyte. One of the problems of measuring multiple sperm attributes is the time and cost required. Using flow cytometric assays, multiple sperm attributes, including cell viability, acrosomal integrity, and mitochondrial function, can be measured simultaneously in sperm cells. In addition, the ability of sperm to undergo capacitation and the acrosome reaction, as well as the chromosomal integrity of sperm can be measured using flow cytometry. Flow cytometry permits us to evaluate 50,000 sperm in less then 1 min and at reasonable cost. Although flow cytometry is a powerful tool for evaluating many sperm attributes, it cannot evaluate all of the attributes a sperm cell requires to fertilize an oocyte. Therefore, laboratory assays are also being developed to evaluate the ability of sperm: (1) to bind to the oocyte, by evaluating the ability of sperm to bind to the perivitelline membrane of the hen egg in vitro; (2) to undergo an acrosome reaction in vitro, after treatment with membrane destabilizing compounds; and (3) to penetrate oocytes in vitro. When data from multiple sperm assays are used, higher correlations with the fertilizing potential of a semen sample is achieved. For example, in a study conducted utilizing five stallions, the percentage of motile sperm in semen samples correlated poorly with fertility (r(2)=0.22), however, when data for sperm motility, viability and penetration rates into zona-free hamster oocytes were utilized together, these data explained 72% of the differences in the fertility of the stallions (r=0.849; [Theriogenology 46 (1996) 559]). Armed with a battery of tests, which evaluate many different sperm attributes, researchers should be able to more accurately estimate the fertilizing potential of semen samples.

Flow cytometric evaluation of antibiotic effects on viability and mitochondrial function of refrigerated spermatozoa of Nile tilapia

Improved techniques for storage and evaluation of fish sperm would enhance breeding programs around the world. The goal of this study was to test the effect of antibiotics on refrigerated sperm from Nile tilapia (Oreochromis niloticus) by use of flow cytometry with 2 dual-staining protocols for objective assessment of sperm quality. Concentrations of 1 x 10(9). sperm/mL were suspended in Ringer's buffer at 318 mOsmol/kg (pH 8.0). The fluorescent stains Sybr 14 (10 microM), propidium iodide (2.4 mM), and rhodamine 123 (0.13 microM) were used to assess cell viability and mitochondrial function. Three concentrations of ampicillin, gentamicin, and an antibiotic/antimycotic solution were added to fresh spermatozoa. Motility estimates and flow cytometry measurements were made daily during 7 d of refrigerated storage (4 degrees C). The highest concentrations of gentamicin and antibiotic/antimycotic and all 3 concentrations of ampicillin significantly reduced sperm viability. The highest of each of the 3 antibiotic concentrations significantly reduced mitochondrial function. This study demonstrates that objective sperm quality assessments can be made using flow cytometry and that addition of antibiotics at appropriate concentrations can lengthen refrigerated storage time for tilapia spermatozoa. With minor modifications, these protocols can be adapted for use with sperm from other species and with other tissue types.

Assessment of viability and mitochondrial function of equine spermatozoa using double staining and flow cytometry

An objective double-staining method was developed to evaluate viability and mitochondrial function of stallion spermatozoa using flow cytometry. Sperm viability was assessed by propidium iodide (PI) exclusion, and mitochondrial function was measured by the intensity of rhodamine 123 (R123) fluorescence. Flow cytometry estimates of sperm viability measured by PI were equivalent (P > 0.05) to estimates made using Hoechst 33258 stain and fluorescent microscopy (% dead: 25 +/- 2.4 vs 21.5 +/- 3.5). The use of both PI and R123 was validated by addition of various proportions of freeze-shocked (membrane damaged) cells to viable spermatozoa. There was a high correlation (r(2) = 0.996) between increased PI positivestained (dead) cells and the number of membrane-damaged spermatozoa added (% dead: 29 +/- 0.4, 44 +/- 1.4, 58 +/- 0.9, 75 +/- 0.7 and 91+/- 0.25 vs 0, 25, 50, 75 and 100% damaged cells, respectively). Optimal mitochondrial activity (OMA), as assessed by R123 uptake, was also reduced proportionally (r(2) = 0.976) by the percentage of membrane-damaged cells added (% OMA: 48 +/- 0.6, 37 +/- 1.7, 29 +/- 0.5, 16 +/- 1, 3.8 +/- 1.3 vs 0, 25, 50, 75 and 100% damaged cells, respectively). The mitochondrial inhibitors rotenone and monensin significantly depressed optimal mitochondrial activity (P < 0.001), and there was a significant positive correlation (r(2) = 0.959) between the dose of inhibitors added and the population of sperm cells exhibiting minimal R123 staining (4 -/+ 0.9, 12 -/+ 1.6, 14 -/+ 0.1 and 28 -/+ 2% for treatments with 0, 0.5, 1 and 2 x 10(-5) M rotenone and 0, 0.5, 1, and 2 x 10(-4) M monensin, respectively). Finally, it was shown that treatments containing identical proportions of membrane-damaged cells yielded similar results in terms of viability and mitochondrial activity, irrespective of whether the staining procedure was single or double (P > 0.05). The results of the double-staining method revealed that the percentage of spermatozoa with optimally functioning mitochondria was significantly correlated with the percentage of viable (PI negative) sperm cells (r(2) = 0.998). Flow cytometric analyses using this staining procedure provides reliable and rapid (10,000 cells/min) qualitative assessment of stallion semen.

Associated effects of divergent selection for residual feed consumption on reproduction, sperm characteristics, and mitochondria of spermatozoa

Eighteen generations of divergent selection for residual feed intake have been completed in two Rhode Island Red lines of domestic fowl. The high intake R+ line and the low intake R- line cocks used to sire Generation 19 of the selection experiment have been compared for associated responses on fertility, hatching, and sperm quality. Evaluations of sperm samples were based on volume, cell concentration, biochemical parameters (pH, uric acid and protein concentrations), and motility and morphology of spermatozoa. Finally, individual spermatozoa were analyzed by flow-cytometry (FCM) using Rhodamine 123 (Rh123) and nonyl-acrydine-orange (NAO) specific fluorochromes to assess, respectively, overall mitochondrial activity and overall mitochondrial content. Hatchability of incubated eggs was 20 points higher for the R- line, mainly because unfertilized eggs were only 6 vs 30% in the R+ line. Early embryo mortality was also twice as high in the R+ line (21%). The ratio of Rh123 to NAO fluorescence was identical for both lines. This result suggests that there was no difference in the energy producing potential of the individual mitochondria. Therefore, the difference seen for both dyes between the two lines might be attributed to a difference in the quantity of mitochondrial inner membranes present in the cell (with 17% less for the R+ line). In the R+ line, the poor performance at fertilization and during early embryonic development was associated with lower production of motile spermatozoa, possibly in relation to a lower quantity of mitochondria in spermatozoa from R+ cocks. Although the female contribution to the differences between lines was not explored separately, results suggest that selection for residual feed intake may have altered some cellular function related to the production of energy in the R+ line.

Comparison of the fertility of cryopreserved stallion spermatozoa with sperm motion analyses, flow cytometric evaluation, and zona-free hamster oocyte penetration

Stallion spermatozoa were cryopreserved in different extenders, and the correlations between laboratory assay results and sperm fertility were determined. Spermatozoa were cryopreserved in 1) a skim milk-egg yolk medium (CO); 2) a skim milk-egg yolk-sugar medium (SMEY); 3) CO after pretreatment with phosphatidylserine+cholesterol liposomes (CO + L); or 4) cooled to 5 degrees C without cryopreservation. The per cycle embryo recovery rates for mares inseminated with spermatozoa frozen in CO, SMEY, CO + L and spermatozoa cooled to 5 degrees C were 47, 42, 45 and 37%, respectively (P>0.05). The fertility rates of the 5 stallions used were 72, 71, 29, 25 and 16%, respectively (P<0.05). The percentage of motile spermatozoa immediately after thawing (42 to 47%) and after preparation for zona-free hamster oocyte penetration assays (27 to 35%) were not different across treatments (P>0.05). The percentages of motile spermatozoa after cryopreservation were not different across stallions (52 to 58%) initially but were different when spermatozoa were treated with 35 microM dilauroylphosphatidylcholine (PC12) to induce the acrosome reaction (17 to 42%; P<0.05). The percentages of viable spermatozoa and viable acrosome-intact spermatozoa ranged from 30 to 57% and 27 to 48%, respectively, across stallions. The percentages of penetrated hamster oocytes ranged from 19% to 55% and from 24% to 72% when spermatozoa were treated with 35 microM and 50 microM PC12, respectively. The number of spermatozoa penetrating each oocyte ranged from 0.21 to 1.16 sperm/oocyte and from 0.37 to 1.59 sperm/oocyte when spermatozoa were treated with 35 microM and 50 microM PC12, respectively. Analyses of single sperm parameters were not highly correlated with stallion fertility. However, a model utilizing data from flow cytometric analyses (percentage of viable spermatozoa), the percentage of motile spermatozoa, and hamster oocyte penetration (percentage of penetrated hamster oocytes) was highly correlated with stallion fertility (r = 0.85; P = 0.002).

Review: in vitro spermicidal tests

This review analyzes in vitro spermicidal tests that have been used to evaluate the spermicidal activity of contraceptive products. Special requirements and processes in numerous technologies were also reviewed. Nonoxynol-9 (N-9) was used as an example of a vaginally delivered spermicidal agent, and its spermicidal potency was compared by various spermicidal tests, such as Sander-Cramer, computer-assisted semen analysis, hypoosmotic swelling test, cervical mucus penetration test, and flow cytometry, and advantages and disadvantages of each test were specified. This provides an insight into the different aspects of sperm functionality on which each spermicidal agent exerts its activity. A rationale of the best combination of in vitro spermicidal tests, with particular emphasis on a simple and efficient strategy that targets the complete fertility control, was explained.

Interrelationships among fluorometric analyses of spermatozoal function, classical semen quality parameters and the fertility of frozen-thawed bovine spermatozoa

Cryopreserved spermatozoa from 8 bulls were used to examine the interrelationships among flow cytometric spermatozoal quality assessments and classical semen quality parameters and nonreturn rate estimates of fertility. The integrity of the sperm cell membrane and the functional capacity of the mitochondria were quantified by flow cytometry after concurrent staining with carboxydimethylfluorescein diacetate (CDMFDA), propidium iodide (PI), and rhodamine 123 (R123). For each sample a total of 10,000 stained spermatozoa were simultaneously quantified for the intensity of their green and red fluorescence. Three straws from each bull were each examined initially and following incubation at 37 degrees C for 3 hours to assess the rate of senescence. The proportion of spermatozoa retaining membrane integrity and having functional mitochondria, as determined by CDMFDA and R123 staining, were compared with classical semen quality assessments (sperm motility, acrosomal status, cellular and head morphology, presence of vacuoles/craters and cytoplasmic droplets) and with fertility (nonreturn to estrus rates). For individual ejaculates nonreturn rates, the range was from 61.8 to 78.8%, whereas the cumulative rates of several ejaculates for each bull ranged from 71.3 to 83.5%. The proportion of spermatozoa with functional membranes and mitochondria were positively correlated with the percentage of spermatozoa with normal morphology (r=0.82; P=0.01) and motility after 4 hours of incubation (r=0.78; P=0.02), but not with the estimates of fertility. The actual number of spermatozoa per straw staining with CDMFDA and R123 after 4 hours of incubation at 37 degrees C was correlated with the percentage of spermatozoa with normal morphology (r=0.73; P=0.04). Multiple regression equations indicated that combinations of semen quality measurements could be useful in estimating fertilizing potential.

Utility of light scatter in the morphological analysis of sperm

We were able to differentiate the morphologically diverse sperm nuclei of four animal species by using an Ortho flow cytometer to detect the forward light scatter from a red (helium-neon) laser. Cytograms depicting the axial light loss and forward red scatter signals revealed unique, but reproducible, sigmoid distributions that reflected not only interspecies differences in shape and size, but variations in particle refractive index and orientation within the flow cell at the time of analysis. Consequently, we were able to use regional gating of the light scatter cytogram to minimize the influence of orientation on the resolution of the fluorescence signal. We also observed that sperm enlarging as a result of chemically induced decondensation exhibit over time a biphasic shift (increase, then decrease) in light scatter at a species-dependent rate. These results suggest that, without any special adaptations to the flow cytometer, light-scatter parameters can be used to discriminate morphologically different sperm, to enhance the resolution of fluorescence measurements that may otherwise be confounded by variability in radial orientation, and to detect alterations in the rate of a biochemical/biophysical process such as decondensation.

Use of sperm viability and acrosomal status assays in combination with immunofluorescence technique to ascertain surface expression of sperm antigens

Sperm antigens are being sought for the development of prototype contraceptive vaccines. For vaccine-induced antisperm antibodies to inhibit the function of viable sperm, target antigens must be expressed on the sperm surface before, during or after the acrosome reaction. The purpose of this study was to develop an approach to detect accurately surface binding of antibodies to viable acrosome-intact or acrosome-reacted sperm, and to confirm sperm surface binding characteristics of a panel of antisperm monoclonal antibodies submitted to the World Health Organization Antifertility Vaccines Task Force. Monoclonal antibodies were tested using a combination of carboxyl-fluorescein diacetate (CoFDA) sperm viability, and rhodamine immunofluorescence assays to ascertain surface binding to viable membrane-intact human sperm, and, in parallel studies, with a combination of fluorescein isothiocyanate (FITC) conjugated Pisum sativum agglutinin (PSA) and rhodamine immunofluorescence assays to ascertain the acrosomal status of antibody-positive sperm. Only 14 out of 32 antibodies that were previously considered to be surface-reactive were confirmed to be positive with these methods. Five were positive on unfixed viable (CoFDA-labelled) fresh sperm in this study, and 9 different antibodies were positive on unfixed acrosome-reacted sperm. We conclude that this multifaceted approach is more accurate and informative than previous techniques used for detection of sperm surface antigens such as radioimmunoassay, standard immunofluorescence, sperm agglutination assays and enzyme-linked immunosorbent assays, which can give false positive results due to the presence of contaminating non-sperm cells, insoluble seminal plasma material, or permeabilized non-viable sperm. Furthermore, the combination of assays employed in this study does not depend on sperm motility, as do the immunobead and sperm immobilization assays, and provides information about the acrosomal status of antibody-positive cells.