Showing papers on "Acrosome reaction published in 2007"

KSper, a pH-sensitive K + current that controls sperm membrane potential

Abstract: Mature mammalian spermatozoa are quiescent in the male reproductive tract. Upon ejaculation and during their transit through the female reproductive tract, they undergo changes that enable them to fertilize the egg. During this process of capacitation, they acquire progressive motility, develop hyperactivated motility, and are readied for the acrosome reaction. All of these processes are regulated by intracellular pH. In the female reproductive tract, the spermatozoan cytoplasm alkalinizes, which in turn activates a Ca2+-selective current (ICatSper) required for hyperactivated motility. Here, we show that alkalinization also has a dramatic effect on membrane potential, producing a rapid hyperpolarization. This hyperpolarization is primarily mediated by a weakly outwardly rectifying K+ current (IKSper) originating from the principal piece of the sperm flagellum. Alkalinization activates the pHi-sensitive IKSper, setting the membrane potential to negative potentials where Ca2+ entry via ICatSper is maximized. IKSper is one of two dominant ion currents of capacitated sperm cells.

Signalling pathways involved in sperm capacitation.

Abstract: After ejaculation, mammalian sperm have not yet acquired full fertilising capacity They will require a finite period of residence in the female reproductive tract before they become fertilisation competent The molecular, biochemical, and physiological changes that occur to sperm while in the female tract are collectively referred to as capacitation During capacitation, changes in membrane properties, enzyme activities, and motility render spermatozoa responsive to stimuli that induce the acrosome reaction and prepare spermatozoa for penetration of the egg investments prior to fertilisation These changes are facilitated by the activation of cell signalling cascades in the female reproductive tract in vivo or in defined media in vitro The purposes of this review are to consider some recent contributions towards our understanding of capacitation, to summarise open questions in this field, and to discuss future avenues of research

Proteomic changes in mammalian spermatozoa during epididymal maturation.

Abstract: Epididymal maturation is associated with the activation of a cAMP-induced tyrosine phosphorylation cascade, which is ultimately associated with the expression of capacitation-dependent sperm functions, such as hyperactivated movement and acrosomal exocytosis. As spermatozoa progress through the epididymis they first acquire the capacity to phosphorylate tyrosine on targets on the principal piece, followed by the midpiece. By the time these cells have reached the cauda epididymidis they can phosphorylate the entire tail from neck to endpiece. This particular pattern of phosphorylation is associated with the ontogeny of fully functional spermatozoa that are capable of fertilizing the oocyte. Proteomic analyses indicate that this change is associated with the phosphorylation of several mitochondrial proteins, creation of a mitochondrial membrane potential and activation of mitochondrial free radical generation. At least in rodent species, activation of sperm mitochondria appears to be a particularly important part of epididymal maturation.

Energy metabolism and sperm function

Abstract: Energy metabolism is a key factor supporting sperm function. Sustaining sperm motility and active protein modifications such as phosphorylation could be the reason why sperm require exceptionally more ATP than other cells. Many methods have been used to understand the relationship between energy metabolism and sperm function. These approaches have identified critical metabolic pathways that support specific processes during germ cell development and fertilisation. In round spermatids, lactate and pyruvate are the preferred substrates and the use of glucose is limited, however, during epididymal maturation sperm expand to use glycolysis. While the acrosome reaction requires lactate or pyruvate for ATP production by oxidative phosphorylation, gamete fusion requires glucose to produce NADPH by the pentose phosphate pathway. Sperm motility appears to be supported by relatively low ATP levels, but achievement of high ATP levels are essential for tyrosine phosphorylation linked to hyperactivation. Thus, each individual process and event requires a different substrate and metabolic pathway. Despite different preferences for energy substrates and metabolic pathways between species, analysis of knockout mice revealed that glycolysis is indispensable for mouse sperm function and that oxidative phosphorylation is not essential for male fertility. This suggests that glycolysis could compensate for the lack of oxidative phosphorylation and recover most sperm function. Spermatogenic cell-specific glycolytic enzymes may confer flexible use of substrates and adapt to unexpected conditions for substrates in the female reproductive tract.

CATSPER Channel-Mediated Ca2+ Entry into Mouse Sperm Triggers a Tail-to-Head Propagation

Abstract: Many Ca2+ channel proteins have been detected in mammalian sperm, but only the four CATSPER channels have been clearly shown to be required for male fertility Ca2+ entry through the principal piece-localized CATSPER channels has been implicated in the activation of hyperactivated motility In the present study, we show that the Ca2+ entry also triggers a tail-to-head Ca2+ propagation in the mouse sperm When activated with 8-Br-cAMP, 8-Br-cGMP, or alkaline depolarization, a CATSPER-dependent increase in intracellular Ca2+ concentration starts in the principal piece, propagates through the midpiece, and reaches the head in a few seconds The Ca2+ propagation through the midpiece leads to a Ca2+-dependent increase in NADH fluorescence In addition, CatSper1-mutant sperm have lower intracellular ATP levels than wild-type sperm Thus, a Ca2+ influx in the principal piece through CATSPER channels can not only initiate hyperactivated motility, but can also trigger a tail-to-head Ca2+ propagation that

Sperm Binding to the Zona Pellucida Is Not Sufficient to Induce Acrosome Exocytosis

Abstract: At fertilization, spermatozoa bind to the zona pellucida (ZP1, ZP2, ZP3) surrounding ovulated mouse eggs, undergo acrosome exocytosis and penetrate the zona matrix before gamete fusion. Following fertilization, ZP2 is proteolytically cleaved and sperm no longer bind to embryos. We assessed Acr3-EGFP sperm binding to wild-type and huZP2 rescue eggs in which human ZP2 replaces mouse ZP2 but remains uncleaved after fertilization. The observed de novo binding of Acr3-EGFP sperm to embryos derived from huZP2 rescue mice supports a ;zona scaffold' model of sperm-egg recognition in which intact ZP2 dictates a three-dimensional structure supportive of sperm binding, independent of fertilization and cortical granule exocytosis. Surprisingly, the acrosomes of the bound sperm remain intact for at least 24 hours in the presence of uncleaved human ZP2 regardless of whether sperm are added before or after fertilization. The persistence of intact acrosomes indicates that sperm binding to the zona pellucida is not sufficient to induce acrosome exocytosis. A filter penetration assay suggests an alternative mechanism in which penetration into the zona matrix initiates a mechanosensory signal transduction necessary to trigger the acrosome reaction.

Acrosomal exocytosis, a special type of regulated secretion.

Abstract: The acrosome is a single secretory granule present in the head of mammalian--and other animal groups--sperm. Secretion of this granule is an absolute requirement for physiological fertilization. Acrosome exocytosis is a synchronized and tightly regulated all-or-nothing process, with no recycling of membranes. In the last few years, it has been shown that acrosomal exocytosis is mediated by a molecular mechanism that is homologous to that reported in the secretion of neuroendocrinal cells. Moreover, because of its particular characteristics, acrosomal exocytosis is a unique mammalian model for the study of the different steps of the membrane fusion cascade. Combining results in intact and permeabilized sperm, the following sequence of events has been proposed. In resting sperm, SNARE proteins are locked in inactive cis complexes. Sperm activation causes a calcium increase in the cytoplasm that promotes the production of cAMP and activates Rab3A. Afterwards, NSF and alphaSNAP disassemble cis complexes and the free SNAREs are then able to reassemble in loose trans complexes. Membrane fusion is arrested at this stage until calcium is released from inside the acrosome by inositol 1,4,5-trisphosphate-sensitive calcium channels to trigger the final steps of membrane fusion, which require fully assembled trans SNARE complexes and the calcium sensor synaptotagmin. This working model is still incomplete and tentative. Its improvement will be important to share light on this and other processes of regulated exocytosis. Moreover, it will bring new perspectives into the field of sperm-related fertility and sterility.

Glycosylation related actions of glycodelin: gamete, cumulus cell, immune cell and clinical associations

Abstract: Glycodelin is an example of a glycoprotein whose complex-type glycans mediate biological actions in human reproduction and immune reactions. Being attached to an identical protein backbone, glycodelin oligosaccharides vary significantly from one reproductive tissue to another and have an effect on its own secretion and role in cell communication. For instance, uterine glycodelin-A inhibits sperm-oocyte interaction by binding on the sperm head. This is a glycosylation-dependent phenomenon, in which fucosyltransferase-5 plays a key role. Glycodelin-S from seminal plasma binds evenly around the sperm head and maintains an uncapacitated state in the spermatozoa, until the isoform is detached during sperm passage through the cervix. Glycodelin-F from follicular fluid and Fallopian tube binds to the acrosomal region of the sperm head, thereby inhibiting both the sperm-oocyte binding and premature progesterone-induced acrosome reaction. The cumulus cells surrounding the oocyte can capture glycodelin-A and -F from the surrounding environment and convert these isoforms to a cumulus cell isoform, glycodelin-C. It differs by glycosylation from the other isoforms, and it too attaches on the sperm head, with the highest density in the equatorial region. Glycodelin-C is capable of detaching the sperm-bound inhibitory isoforms so that the sperm-oocyte binding is enhanced. Glycodelin-A also has immunosuppressive actions directed to cellular, humoral and innate immunity. Although these actions depend mainly on the protein backbone, glycosylation also plays a part. Glycosylated glycodelin may be involved in the protection of spermatozoa against maternal immune reactions, and glycodelin also has apoptogenic activity. Some glycosylation patterns of glycodelin may mask its apoptogenic domain. This review updates the recent research and clinical associations of glycodelin, highlighting the role of glycosylation.

Evidence for the Involvement of Testicular Protein CRISP2 in Mouse Sperm-Egg Fusion

Abstract: CRISP2, originally known as Tpx-1, is a cysteine-rich secretory protein specifically expressed in male haploid germ cells. Although likely to be involved in gamete interaction, evidence for a functional role of CRISP2 in fertilization still remains poor. In the present study, we used a mouse model to examine the subcellular localization of CRISP2 in sperm and its involvement in the different stages of fertilization. Results from indirect immunofluorescence and protein extraction experiments indicated that mouse CRISP2 is an intraacrosomal component that remains associated with sperm after capacitation and the acrosome reaction (AR). In vitro fertilization assays using zona pellucida-intact mouse eggs showed that an antibody against the protein significantly decreased the percentage of penetrated eggs, with a coincident accumulation of perivitelline sperm. The failure to inhibit zona pellucida penetration excludes a detrimental effect of the antibody on sperm motility or the AR, supporting a specific participation of CRISP2 at the sperm-egg fusion step. In agreement with this evidence, recombinant mouse CRISP2 (recCRISP2) specifically bound to the fusogenic area of mouse eggs, as previously reported for rat CRISP1, an epididymal protein involved in gamete fusion. In vitro competition investigations showed that incubation of mouse zona-free eggs with a fixed concentration of recCRISP2 and increasing amounts of rat CRISP1 reduced the binding of recCRISP2 to the egg, suggesting that the proteins interact with common complementary sites on the egg surface. Our findings indicate that testicular CRISP2, as observed for epididymal CRISP1, is involved in sperm-egg fusion through its binding to complementary sites on the egg surface, supporting the idea of functional cooperation between homologous molecules to ensure the success of fertilization.

Semen-Coagulating Protein, SVS2, in Mouse Seminal Plasma Controls Sperm Fertility

Abstract: Mammalian seminal plasma is known to contain a decapacitation factor(s) that prevents capacitation and thus, the fertility of sperm. This phenomenon has been observed in experiments conducted in vitro that assessed the inhibition of epididymal sperm fertility by seminal plasma or by the purified decapacitation factor. However, the phenomenon of decapacitation has not yet been characterized in vivo. In the present study, we demonstrate that seminal vesicle protein secretion 2 (SVS2), which is a 40-kDa basic protein and a major component of the copulatory plug, enters the uterus and interacts with ejaculated sperm heads after copulation. The SVS2-binding region of sperm changed from the postacrosomal region to the equatorial segment, while the sperm migrated through the uterus and finally disappeared in the oviduct. Furthermore, SVS2 reduced the fertility of epididymal sperm. The sperm treated with SVS2 decreased the percentage of fertilized oocytes from 60% to 10%. The capacitation state was assessed by protein tyrosine phosphorylation and the comprehensiveness of the acrosome reaction. SVS2 functioned to maintain sperm in the uncapacitated state and to reverse capacitated sperm to the uncapacitated state. We found that the fertility of ejaculated sperm is associated with SVS2 distribution in the female reproductive tract. These results indicate that SVS2 functions as a decapacitation factor for mouse sperm.

Supplementation of the dilution medium after thawing with reduced glutathione improves function and the in vitro fertilizing ability of frozen-thawed bull spermatozoa.

Abstract: In this study, we evaluated the effects of glutathione (l-gamma-glutamyl-l-cysteinylglycine; GSH) supplementation of the thawing extender on bull semen parameters to compensate for the decrease in GSH content observed during sperm freezing. To address these questions fully, we used a set of functional sperm tests. These included tests of sperm motility assayed by computer-assisted semen analysis, membrane lipid packing disorder, spontaneous acrosome reaction, free radical production [reactive oxygen species (ROS) generation], sperm chromatin condensation, DNA fragmentation by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling and acridine orange staining measured by flow cytometry. Finally, the in vitro penetrability of in vitro matured oocytes and the in vitro production of embryos were evaluated. The main findings emerging from this study were that addition of GSH to the thawing medium resulted in: (i) a higher number of non-capacitated viable spermatozoa; (ii) a reduction in ROS generation; (iii) lower chromatin condensation; (iv) lower DNA fragmentation; (v) higher oocyte penetration rate in vitro and (vi) higher in vitro embryo production compared with control group. Nevertheless, GSH had no significant effect on motion parameters or the occurrence of the spontaneous acrosome reaction. Addition of GSH to the thawing extender could be of significant benefit in improving the function and fertilizing capacity of frozen bull spermatozoa.

Sperm phospholipases and acrosomal exocytosis.

Abstract: At the time of fertilization, the sperm cell undergoes regulated exocytosis in response to the oocyte-associated agonists progesterone and zona pellucida. An early response generated by agonist-receptor interaction in spermatozoa is the activation of mechanisms leading to Ca2+ influx, this ion being essential for the activation of phospholipases and for the fusion of the plasma membrane with the outer acrosomal membrane. Both a phosphoinositide-specific, and a phosphatidylcholine-specific phospholipase C are involved in the generation of a variety of diacylglycerol molecular species. Phospholipase D, on the other hand, does not seem to play a significant role in the generation of diacylglycerol. Hydrolysis of phospholipids by phospholipase A2 generates free fatty acids and lysophospholipids; these are important either as substrates for the generation of other metabolites (e.g., eicosanoids) or having a direct, essential action in the final stages of membrane fusion. There is still much work to be done in the future in order to characterize phospholipase isozymes and their regulation during acrosomal exocytosis in spermatozoa.

Milk Caseins Decrease the Binding of the Major Bovine Seminal Plasma Proteins to Sperm and Prevent Lipid Loss from the Sperm Membrane During Sperm Storage

Abstract: Milk is used as a medium for sperm preservation. Caseins, the major proteins of milk, appear to be responsible for the protective effect of milk on sperm. Recently, we have shown that egg yolk, which is also widely used to preserve semen, protects sperm functions by preventing the binding to sperm of the major proteins of bull seminal plasma (BSP proteins), thereby preventing BSP protein-mediated stimulation of lipid loss from the sperm membrane. In the present study, we investigated whether milk caseins protect sperm in the same manner as egg yolk. Bovine ejaculates were diluted with skimmed milk permeate (skimmed milk devoid of caseins) or permeate that was supplemented with caseins and stored at 4°C for 4 h. In the semen diluted with permeate, sperm viability and motility decreased in a time-dependent manner. However, in semen diluted with milk or permeate supplemented with caseins, sperm functions were maintained. In addition, lower amounts of the BSP proteins were associated with sperm in se...

Influence of hyaluronic acid synthesis and cumulus mucification on bovine oocyte in vitro maturation, fertilisation and embryo development

Abstract: During cumulus-oocyte complex (COC) maturation, cumulus expansion involves the deposition of mucoelastic compounds, especially hyaluronic acid, synthesised from glucose via the hexosamine biosynthesis pathway. The aim of the present study was to determine the effects of uridine monophosphate (UMP) and 6-diazo-5-oxo-L-norleucine (DON), inhibitors of hyaluronic acid synthesis, during bovine oocyte in vitro maturation (IVM) on cumulus expansion, glucose uptake, protein synthesis, cumulus cell number, meiotic maturation, cleavage rate and subsequent embryo development. A further aim of the study was to examine the effect of hyaluronic acid on sperm capacitation and acrosome reaction in relation to the capacity of COCs to be fertilised in vitro. A low correlation between glucose uptake and degree of cumulus expansion was observed. Total and partial inhibition of cumulus expansion was observed with DON and UMP, respectively, and was accompanied by a decrease in glucose uptake with DON. Total protein content and cumulus cell number per COC increased during IVM, but was unaffected by the presence of DON or UMP, as was oocyte meiotic maturation. Rates of cleavage and blastocyst development decreased in oocytes matured with DON and UMP, although this inhibition was reversed when the in vitro fertilisation (IVF) medium contained heparin. Hyaluronic acid induced capacitation and the acrosome reaction, and in IVF medium prevented the inhibition of cleavage and blastocyst development by DON in a similar fashion to heparin. Hyaluronic acid synthesis during cumulus mucification contributes to the penetration and fertilisation of bovine oocytes, most likely by facilitating the processes of capacitation and acrosome reaction. Mucification during IVM is independent of cumulus cell proliferation, COC protein content, oocyte meiotic maturation and subsequent developmental competence once fertilised.

Calmodulin and CaMKII in the sperm principal piece: evidence for a motility-related calcium/calmodulin pathway.

Abstract: Both cyclic AMP (cAMP)/protein kinase A (PKA) and calcium (Ca(2+)) signaling pathways are known to be involved in the regulation of motility in mammalian sperm. Calmodulin (CaM) is a ubiquitous Ca(2+) sensor that has been implicated in the acrosome reaction. In this report, we identify an insoluble pool of CaM in sperm and show that the protein, in addition to its presence in the acrosome, is found in the principal piece of the flagellum. These findings are consistent with, though not proof of, the presence of a pool of CaM in the fibrous sheath. The Ca(2+)/CaM-dependent protein kinase IIbeta (CaMKIIbeta), which is a downstream target of Ca(2+)/CaM, similarly localizes to the principal piece. In addition, we confirm earlier reports that a CaM inhibitor decreases sperm motility. However, we find that this inhibition can be largely reversed by stimulation of PKA if substrates for oxidative respiration are present in the medium. Our results suggest that the Ca(2+)/CaM/CaMKII signaling pathway in the sperm principal piece is involved in regulating sperm motility, and that this pathway functions either in parallel with or upstream of the cAMP/PKA pathway.

Syntaxin and VAMP association with lipid rafts depends on cholesterol depletion in capacitating sperm cells

Abstract: Sperm cells represent a special exocytotic system since mature sperm cells contain only one large secretory vesicle, the acrosome, which fuses with the overlying plasma membrane during the fertilization process. Acrosomal exocytosis is believed to be regulated by activation of SNARE proteins. In this paper, we identified specific members of the SNARE protein family, i.e., the t-SNAREs syntaxin1 and 2, and the v-SNARE VAMP, present in boar sperm cells. Both syntaxins were predominantly found in the plasma membrane whereas v-SNAREs are mainly located in the outer acrosomal membrane of these cells. Under non-capacitating conditions both syntaxins and VAMP are scattered in well-defined punctate structures over the entire sperm head. Bicarbonate-induced in vitro activation in the presence of BSA causes a relocalization of these SNAREs to a more homogeneous distribution restricted to the apical ridge area of the sperm head, exactly matching the site of sperm zona binding and subsequent induced acrosomal exocyto...

Expression of Hsp60 and Grp78 in the human endometrium and oviduct, and their effect on sperm functions

Abstract: BACKGROUND: Within the female genital tract, spermatozoa undergo a series of membranous and intracellular transformations to become competent at fertilizing the oocyte. In the bovine, previous studies have shown that two oviductal proteins, heat shock protein 60 (Hsp60) and glucose regulated protein 78 (Grp78), bind to spermatozoa and may be involved in this acquisition of fertilizing competence. METHODS: Immunohistochemical studies were performed on human endometrial and oviduct tissues to localize these two chaperones in the female genital tract. Human spermatozoa were incubated under capacitating conditions in the presence or absence of recombinant Hsp60 or Grp78. Following a 4-h incubation, the effects of these proteins were evaluated on sperm acrosomal integrity, motility, protein phosphotyrosine content and free intracellular calcium concentrations. RESULTS: Both chaperones were present in the uterus and oviduct epithelial cells and were shown to bind to human spermatozoa. Incubation with either exogenous Hsp60 or Grp78 did not affect sperm viability, motility or acrosomal integrity. Hsp60 partially prevented the increase in p81 phosphotyrosine content induced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine and both chaperones significantly increased the sperm intracellular calcium concentration. Moreover, the progesterone-induced increase in intracellular calcium was higher when sperm were pre-treated with either Hsp60 or Grp78. CONCLUSIONS: Our study suggests that these two proteins may affect human sperm intracellular signalling pathways and capacitation.

Relationship between sperm DNA damage, induced acrosome reaction and viability in ICSI patients.

Abstract: The DNA damage in human spermatozoa is a relevant predictor of prognosis in male infertility, whereby increased sperm DNA damage impairs the outcomes of artificial reproduction. Theoretically, DNA damage should alter the special cellular functions of human spermatozoa, and lead to diminished acrosome reaction with reduced fertilization rates. Nevertheless, intracytoplasmic sperm injection (ICSI) has been reported to alleviate such negative outcomes due to DNA damage. This study investigated the relationship between DNA fragmentation and acrosome reaction as well as viability in ICSI patients. The study enrolled 42 men undergoing ICSI due to poor sperm parameters. The DNA fragmentation indexes (DFI) were 4-10% in 38% of the cases, and > or = 10% in 19% of the cases. The results of both acrosome reaction and viability assays showed negative correlations with DFI values in all cases and especially in cases with fertilization rates 60%. There were no live deliveries in patients with high DFI levels (>10%). In conclusion, negative correlations were identified between increased DNA damage, and acrosome reaction and/or viability of human spermatozoa, especially in cases with reduced fertilization rates.

Seasonal changes in semen characteristics, composition of seminal plasma and frequency of acrosome reaction induced by calcium and calcium ionophore A23187 in Large White boars.

Abstract: This study attempted to explain the mechanisms regulating boar fertility by examining seasonal changes in semen characteristics, the composition of seminal plasma and responsiveness of sperm acrosomes to Ca(2+) and the Ca(2+) ionophore A23187 (Ca(2+)/A23187). Sperm-rich and sperm-poor fractions were separately collected from 3 mature fertile Large White boars once a month over a one-year period. During the period of study, ambient temperature and relative humidity were recorded for within the stall in which the boars were kept and the semen characteristics, composition of the seminal plasma of sperm-rich fractions, and occurrence of the acrosome reaction in response to Ca(2+) (3 mM)/A23187 (0.3 microM) were examined. The highest mean maximum and minimum ambient temperatures were recorded in August-September, whereas the lowest mean maximum and minimum ambient temperatures were recorded in December and January, respectively. There was a moderate peak in relative humidity from July to October. The lowest percentages of motile spermatozoa and of spermatozoa with intact acrosomes and highest percentage of spermatozoa with abnormal morphology and strongest agglutination were seen in August-September. The total protein and albumin concentrations were lowest in August-September. Testosterone levels increased gradually as day length decreased after the summer solstice (June) and peaked in October-November. The percentage of acrosome reactions in response to Ca(2+)/A23187 was highest with the quickest response in August-September, as shown by the shortest time required for 50% of relative acrosome reactions. The farrowing rates were lowest in these same 2 months. These results suggest that seasonal infertility in Large White boars may be due, at least in part, to a combination of low motility, abnormal morphology including acrosomal abnormality, and early occurrence of the acrosome reaction in response to stimulus, possibly resulting from a decrease in acrosomal stabilizing proteins in the seminal plasma during summer. These changes may be modulated by heat/humidity stress and/or photoperiod-regulated testosterone.

In vivo assessment of the human sperm acrosome reaction and the expression of glycodelin-A in human endometrium after levonorgestrel-emergency contraceptive pill administration

Abstract: sies RESULTS: Twenty-four and forty-eight hours after treatment, there were 145+ 39 3 10 6 and 173+ 68 3 10 6 sperm recovered from the uterus, respectively There were no differences between the AR rate and the endometrial glycodelin-A staining intensity in an LNG or placebo treated cycles The LNG in uterine flushing medium represented 138% of the values observed in serum 24 h after the LNG intake CONCLUSIONS: Twenty-four and forty-eight hours after administration of EC, neither the proportion of AR sperm, nor the glycodelin-A level was influenced by 15 mg of LNG LNG did not impair the cervical mucus either because viable spermatozoa were found in the genital tract 36–60 h after coitus and 24–48 h after LNG intake The mechanism of action of LNG as EC remains unknown

Effects of pentoxifylline treatment before freezing on motility, viability and acrosome status of poor quality human spermatozoa cryopreserved by the liquid nitrogen vapor method.

Abstract: The objective of the present study was to investigate the effects of the direct addition of pentoxifylline (PF) to the ejaculates of men with poor sperm quality before freezing on post-thaw sperm motility, viability, acrosome integrity, and agonist-induced acrosome reaction. Semen specimens from 16 infertile men with impaired sperm count and motility (oligoasthenozoospermia) were divided into two equal aliquots: one received no treatment (control) while the other was incubated with 5 mM PF (treated). Both aliquots were cryopreserved by the liquid nitrogen vapor method. Motility was assessed according to WHO criteria. Acrosome integrity and spontaneous and calcium ionophore-induced acrosome reactions were assessed with fluorescein isothiocyanate-conjugated peanut agglutinin combined with a supra-vital dye (Hoechst-33258). Cryopreservation impaired sperm motility (percentage reduction: 87.4 (interquartile range, IQ: 70.3-92.9) vs 89.1 (IQ: 72.7-96.0%)), viability (25.9 (IQ: 22.2-29.7) vs 25.6 (IQ: 19.7-40.3%)) and acrosome integrity (18.9 (IQ: 5.4-38.9) vs 26.8 (IQ: 0.0-45.2%)) to the same extent in both treated and control aliquots. However, PF treatment before freezing improved the acrosome reaction to ionophore challenge test scores in cryopreserved spermatozoa (9.7 (IQ: 6.6-19.7) vs 4.8 (IQ: 0.5-6.8%); P = 0.002). These data show that pre-freeze treatment of poor quality human sperm with pentoxifylline did not improve post-thaw motility or viability nor did it prevent acrosomal loss during the freeze-thaw process. However, PF, as used, improved the ability of thawed spermatozoa to undergo the acrosome reaction in response to calcium ionophore. The present data indicate that treatment of poor quality human sperm with PF may enhance post-thaw sperm fertilizing ability.

A carbohydrate-based mechanism of species recognition in sea urchin fertilization.

Abstract: In the present review, we describe a systematic study of the sulfated polysaccharides from marine invertebrates, which led to the discovery of a carbohydrate-based mechanism of sperm-egg recognition during sea urchin fertilization. We have described unique polymers present in these organisms, especially sulfated fucose-rich compounds found in the egg jelly coat of sea urchins. The polysaccharides have simple, linear structures consisting of repeating units of oligosaccharides. They differ among the various species of sea urchins in specific patterns of sulfation and/or position of the glycosidic linkage within their repeating units. These polysaccharides show species specificity in inducing the acrosome reaction in sea urchin sperm, providing a clear-cut example of a signal transduction event regulated by sulfated polysaccharides. This distinct carbohydrate-mediated mechanism of sperm-egg recognition coexists with the bindin-protein system. Possibly, the genes involved in the biosynthesis of these sulfated fucans did not evolve in concordance with evolutionary distance but underwent a dramatic change near the tip of the Strongylocentrotid tree. Overall, we established a direct causal link between the molecular structure of a sulfated polysaccharide and a cellular physiological event - the induction of the sperm acrosome reaction in sea urchins. Small structural changes modulate an entire system of sperm-egg recognition and species-specific fertilization in sea urchins. We demonstrated that sulfated polysaccharides - in addition to their known function in cell proliferation, development, coagulation, and viral infection - mediate fertilization, and respond to evolutionary mechanisms that lead to species diversity.

Effect of fatty acids on boar sperm motility, viability and acrosome reaction.

Abstract: Aim: The present study was undertaken to determine which fatty acids improve motility, viability, and increase acrosome reaction (AR) in boar spermatozoa. Methods: Boar spermatozoa were washed, swum-up and incubated at 37°C for 4 h in TALP medium supplemented with myristic, palmitic, stearic, lignoceric, oleic, linoleic, arachidonic, docosahexaenoic and palmitoleic acid. Sperm motility, viability and AR were evaluated during 4 h of incubation. Results: Results show that oleic and linoleic acid significantly improved (P < 0.05) the motility and viability of boar spermatozoa. The AR was significantly improved (P < 0.05) by oleic and arachidonic acid in almost all incubation periods. When combinations of oleic, linoleic and arachidonic acid were studied for motility, viability and AR, it was found that oleic plus linoleic acid significantly increased (P < 0.05) motility, whereas arachidonic plus oleic acid significantly increased (P < 0.05) AR. Conclusion: Unsaturated fatty acids, especially arachidonic acid, can improve boar sperm motility and AR. A combination of arachidonic and oleic acid is important for inducing boar sperm AR. (Reprod Med Biol 2007; 6: 235-239).