Showing papers on "Sperm plasma membrane published in 2006"
TL;DR: While the induction of oxidative stress in spermatozoa is causally involved in the aetiology of male infertility, the prospects of using such a strategy for male contraception is fraught with potential problems, should the suppression of fertility be incomplete and DNA-damaged spermatozosa gain access to the oocyte.
458 citations
TL;DR: These studies validate a methodology for investigating the origins of oxidative stress in the male germ line and demonstrate, for the first time, the significance of superoxide generation by human spermatozoa in the etiology of this condition.
Abstract: Context: Oxidative stress in the male germ line has been associated with poor fertility, impaired embryonic development, miscarriage, and childhood disease. Such stress is known to be associated with the peroxidation of unsaturated fatty acids in the sperm plasma membrane and oxidative DNA damage to both the nuclear and mitochondrial genomes. However, the source of the free radicals responsible for such damage is still unresolved. Objective: The objective of this study was to chemically validate the use of dihydroethidium (DHE) as a probe for detecting the generation of superoxide anion by human spermatozoa and to examine the relationship between this activity and defective sperm function. Method: DHE and SYTOX green were used in conjunction with flow cytometry and HPLC to investigate superoxide generation by human spermatozoa. Cause and effect relationships were established using menadione to artificially drive superoxide production by these cells. Results: HPLC, mass spectrometry, nuclear magnetic reson...
154 citations
TL;DR: The identification of a number of proteins that are actively released from the surface of mouse spermatozoa during capacitation in vitro are reported, including phosphatidylethanolamine binding protein 1 (PBP), and an unnamed protein product that is termed decapacitation factor 10 (DF10).
Abstract: Mammalian spermatozoa must undergo capacitation before acquiring the ability to fertilize the oocyte. This process is believed to be initiated following the release of surface-associated decapacitation factors that are elaborated by both the epididymis and the male accessory organs. Herein, we report the identification of a number of proteins that are actively released from the surface of mouse spermatozoa during capacitation in vitro. As anticipated, the addition of these factors back to suspensions of mouse spermatozoa was shown to suppress several correlates of the capacitation process. Specifically, they induced a significant, dose-dependent inhibition of the ability of spermatozoa to undergo a progesterone-induced acrosome reaction and to bind to the zona pellucida in vitro. Inhibition of these functions was associated with the suppression of tyrosine phosphorylation in the sperm plasma membrane but had no effect on the phosphorylation of internal proteins in either the sperm head or tail. This inhibitory activity was attributed to a subset of the isolated proteins compromising at least four putative decapacitation factors. These proteins were identified via tandem-mass spectrometry amino acid sequence analysis as plasma membrane fatty acid binding protein, cysteine-rich secretory protein 1 (CRISP1), phosphatidylethanolamine binding protein 1 (PBP), and an unnamed protein product that we have termed decapacitation factor 10 (DF10). Of these proteins, PBP was identified as a primary candidate for a decapacitation factor.
139 citations
TL;DR: The results suggest that the ferlin family members share a conserved mechanism to regulate cell-type-specific membrane fusion, which suggests that the C2 domains are involved in Ca2+ sensing and further supports their independent function.
Abstract: FER-1 is required for fusion of specialized vesicles, called membranous organelles, with the sperm plasma membrane during Caenorhabditis elegans spermiogenesis. To investigate its role in membranous organelle fusion, we examined ten fer-1 mutations and found that they all cause the same defect in membrane fusion. FER-1 and the ferlin protein family are membrane proteins with four to seven C2 domains. These domains commonly mediate Ca2+-dependent lipid-processing events. Most of the fer-1 mutations fall within these C2 domains, showing that they have distinct, non-redundant functions. We found that membranous organelle fusion requires intracellular Ca2+ and that C2 domain mutations alter Ca2+ sensitivity. This suggests that the C2 domains are involved in Ca2+ sensing and further supports their independent function. Using two immunological approaches we found three FER-1 isoforms, two of which might arise from FER-1 by proteolysis. By both light and electron microscopy, these FER-1 proteins were found to be localized to membranous organelle membranes. Dysferlin, a human homologue of FER-1 involved in muscular dystrophy, is required for vesicle fusion during Ca2+-induced muscle membrane repair. Our results suggest that the ferlin family members share a conserved mechanism to regulate cell-type-specific membrane fusion.
138 citations
TL;DR: It is shown that sperm hyperpolarize when external Na+ is replaced by N-methyl-glucamine, and results suggest that increases in cAMP content occurring during capacitation may inhibit ENaCs to produce a requiredhyperpolarization of the sperm membrane.
120 citations
TL;DR: The results corroborated the implication of lipid rafts and SGG in cell adhesion and strongly suggested that the enhanced ZP binding ability of capacitated sperm may be attributed to increased levels and a greater ZP affinity of lipidrafts in the sperm plasma membrane.
116 citations
TL;DR: Treatment strategies must be directed toward lowering of ROS levels to keep only a small amount necessary to maintain normal cell function, as spermatozoa are unable to repair the damage induced by excessive ROS as they lack the cytoplasmic enzymes required to accomplish the repair.
Abstract: The excessive generation of reactive oxygen species (ROS) by abnormal spermatozoa and contaminating leukocytes has been defined as one of the few etiologies for male infertility. Administration of antioxidants in patients with ‘male factor’ infertility has begun to attract considerable interest. The main difficulty of such an approach is our incomplete understanding of the role of free radicals in normal and abnormal sperm function leading to male infertility. Mammalian spermatozoa membranes are very sensitive to free radical induced damage mediated by lipid peroxidation, as they are rich in polyunsaturated fatty acids. Limited endogenous mechanisms exist to reverse these damages. ROS attacks the fluidity of the sperm plasma membrane and the integrity of DNA in the sperm nucleus. ROS induced DNA damage accelerate the germ cell apoptosis. Unfortunately spermatozoa are unable to repair the damage induced by excessive ROS as they lack the cytoplasmic enzymes required to accomplish the repair. Assessment of such oxidative stress status (OSS) may help in the medical treatment. Treatment strategies must be directed toward lowering of ROS levels to keep only a small amount necessary to maintain normal cell function.
108 citations
TL;DR: In the mouse, the removal of sperm plasma membrane and acrosome was not a prerequisite to produce offspring by ICSI, but it resulted in earlier onset of oocyte activation and better embryonic development.
Abstract: Direct injection of a single spermatozoon into an oocyte (ICSI) can produce apparently normal offspring. Although the production of normal offspring by ICSI has been successful in mice and humans, it has been less successful in many other species. The reason for this is not clear, but could be, in part, due to inconsistent activation of oocytes because of delayed disintegration of sperm plasma membrane within oocytes and incorporation of the acrosome containing a spectrum of hydrolyzing enzymes. In the mouse, the removal of sperm plasma membrane and acrosome was not a prerequisite to produce offspring by ICSI, but it resulted in earlier onset of oocyte activation and better embryonic development. The best result was obtained when spermatozoa were demembranated individually immediately before ICSI by using lysolecithin, a hydrolysis product of membrane phospholipids.
103 citations
TL;DR: Findings indicate that cryopreservation of human semen induces damages at different cellular levels, and some cryoinjuries are immediate although others seem to take place over time stored in liquid nitrogen.
86 citations
TL;DR: The results indicate that a triple combination of the fluorophores M540/Yo-Pro 1/H33342 is suitable for monitoring the status of membrane stability in frozen-thawed (FT) bull spermatozoa and a SU preselection method seems helpful in distinguishing relationships between sperm quality and fertility among bulls in a homogenous sire population.
85 citations
TL;DR: Existence of testis-expressed Snky-like genes in many animals, including humans, suggests conserved protein function and the characteristics of Drosophila Snky, acrosome function and sperm PMBD to membrane fusion events that occur in other systems are related.
Abstract: Fertilization typically involves membrane fusion between sperm and eggs. In Drosophila, however, sperm enter eggs with membranes intact. Consequently, sperm plasma membrane breakdown (PMBD) and subsequent events of sperm activation occur in the egg cytoplasm. We previously proposed that mutations in the sneaky (snky) gene result in male sterility due to failure in PMBD. Here we support this proposal by demonstrating persistence of a plasma membrane protein around the head of snky sperm after entry into the egg. We further show that snky is expressed in testes and encodes a predicted integral membrane protein with multiple transmembrane domains, a DC-STAMP-like domain, and a variant RING finger. Using a transgene that expresses an active Snky-Green fluorescent protein fusion (Snky-GFP), we show that the protein is localized to the acrosome, a membrane-bound vesicle located at the apical tip of sperm. Snky-GFP also allowed us to follow the fate of the protein and the acrosome during fertilization. In many animals, the acrosome is a secretory vesicle with exocytosis essential for sperm penetration through the egg coats. Surprisingly, we find that the Drosophila acrosome is a paternally inherited structure. We provide evidence that the acrosome induces changes in sperm plasma membrane, exclusive of exocytosis and through the action of the acrosomal membrane protein Snky. Existence of testis-expressed Snky-like genes in many animals, including humans, suggests conserved protein function. We relate the characteristics of Drosophila Snky, acrosome function and sperm PMBD to membrane fusion events that occur in other systems.
TL;DR: The findings indicate that this composite plant extract possesses potential contraceptive spermicidal activity in vitro, and shows the most promising results by complete sperm immobilization within 2 min after the application of the extract.
TL;DR: Binding of ouabain to Na+/K+ATPase induced sperm capacitation through depolarization of sperm plasma membrane and signaling via the tyrosine phosphorylation pathway without an appreciable increase in intracellular calcium.
Abstract: A heteromeric integral membrane protein, Na+/K+ATPase is composed of two polypeptides, alpha and beta, and is active in many cell types, including testis and spermatozoa. It is a well-known ion transporter, but binding of ouabain, a specific inhibitor of Na+/K+ATPase, to Na+/K+ATPase in somatic cells initiates responses that are similar to signaling events associated with bovine sperm capacitation. The objectives of the present study were to demonstrate the presence of Na+/K+ATPase in bovine sperm and to investigate its role in the regulation of bovine sperm capacitation. The presence of Na+/K+ATPase in sperm from mature Holstein bulls was demonstrated by immunoblotting and immunocytochemistry using a monoclonal antibody developed in mouse against the beta 1 polypeptide of Na+/K+ATPase. Binding of ouabain to Na+/K+ATPase inhibited motility (decreased progressive motility, average path velocity, and curvilinear velocity) and induced tyrosine phosphorylation and capacitation but did not increase intracellular calcium levels in spermatozoa. Furthermore, binding of ouabain to Na+/K+ATPase induced depolarization of sperm plasma membrane. Therefore, binding of ouabain to Na+/K+ATPase induced sperm capacitation through depolarization of sperm plasma membrane and signaling via the tyrosine phosphorylation pathway without an appreciable increase in intracellular calcium. To our knowledge, this is the first report concerning the signaling role of Na+/K+ATPase in mammalian sperm capacitation.
TL;DR: An overview is presented on the potential role of glycan-modifying enzymes in sperm maturation, namely glycohydrolases that cleave sugar residues and glycosyltransferases that add sugar residues to the existing glycoconjugates, in the epididymal luminal fluid that surrounds spermatozoa.
TL;DR: It is 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.
TL;DR: The gene for proprotein convertase subtilisin/kexin-like 4 (PCSK4), previously known as PC4, is primarily transcribed in testicular spermatogenic cells and its inactivation in mouse causes severe male subfertility.
Abstract: The gene for proprotein convertase subtilisin/kexin-like 4 (PCSK4, previously known as PC4) is primarily transcribed in testicular spermatogenic cells. Its inactivation in mouse causes severe male subfertility. To better understand the reproductive function of PCSK4, we examined its subcellular localization in the testicular epithelium via immunohistochemistry, and on intact sperm via indirect immunofluorescence and immunoelectron microscopy. PCSK4 was detected in the acrosomal granules of round spermatids, in the acrosomal ridges of elongated spermatids, and on the sperm plasma membrane overlying the acrosome. We also investigated PCSK4 relevance for sperm acquisition of fertilizing ability by comparing wild-type and PCSK4-null sperm for their abilities in capacitation, acrosome reaction, and egg binding in vitro. PCSK4-null sperm underwent capacitation at a faster rate; they were induced to acrosome react by lower concentrations of zona pellucida; and their egg-binding ability was only half that of wild-type sperm. These sperm physiologic anomalies likely contribute to the severe subfertility of PCSK4-deficient male mice.
TL;DR: These findings for the first time show the in vivo expression in insects of genes encoding beta-N-acetylhexosaminidases, the only molecules so far identified as involved in sperm/egg recognition in this class, whereas in mammals, the organisms where these enzymes have been best studied, only two types of polypeptide chains forming dimeric functional beta- N-acetyhexosamidases are present.
Abstract: Sperm surface beta-N-acetylhexosaminidases are among the molecules mediating early gamete interactions in invertebrates and vertebrates, including man. The plasma membrane of Drosophila spermatozoa contains two beta-N-acetylhexosaminidases, DmHEXA and DmHEXB, which are required for egg fertilization. Here, we demonstrate that three putative Drosophila melanogaster genes predicted to code for beta-N-acetylhexosaminidases, Hexo1, Hexo2, and fdl, are all expressed in the male germ line. fdl codes for a homolog of the alpha-subunit of the mammalian lysosomal beta-N-acetylhexosaminidase Hex A. Hexo1 and Hexo2 encode two homologs of the beta-subunit of all known beta-N-acetylhexosaminidases, which we have named beta(1) and beta(2), respectively. Immunoblot analysis of sperm proteins indicated that the gene products associate in different heterodimeric combinations forming DmHEXA, with an alphabeta(2) structure, and DmHEXB, with a beta(1)beta(2) structure. Immunofluorescence demonstrated that all the gene products localized to the sperm plasma membrane. Although none of the genes was testis-specific, fdl was highly and preferentially expressed in the testis, whereas Hexo1 and Hexo2 showed broader tissue expression. Enzyme assays carried out on testis and on a variety of somatic tissues corroborated the results of gene expression analysis. These findings for the first time show the in vivo expression in insects of genes encoding beta-N-acetylhexosaminidases, the only molecules so far identified as involved in sperm/egg recognition in this class, whereas in mammals, the organisms where these enzymes have been best studied, only two types of polypeptide chains forming dimeric functional beta-N-acetylhexosaminidases are present in Drosophila three different gene products are available that might generate numerous dimeric isoforms.
TL;DR: The protective effect of the heterodimer appears to be related to its adhesion to the acrosomal area, and the loss of this protective effect coincides with a stepwise redistribution of PSP-I/PSP-II during incubation.
Abstract: PSP-I/PSP-II heterodimer is a major protein of boar seminal plasma which is able to preserve, in vitro, the viability, motility, and mitochondrial activity of highly extended boar spermatozoa for at least 5 hours. However, little is known about the binding pattern of the heterodimer to the sperm plasma membrane and its eventual relation with the maintenance of the sperm functionality. The present study investigated the effect of exposing highly extended boar spermatozoa (11 million/mL) to 1.5 mg/mL of PSP-I/PSP-II for 0.5, 5, and 10 hours at 38 degrees C on sperm characteristics and the changes in PSP-I/PSP-II localization as a result of both the addition of PSP-I/PSP-II to the extender and the incubation time. Exposure of the spermatozoa to PSP-I/PSP-II preserved sperm viability, motility, and mitochondrial activity when compared to nonexposed spermatozoa. This protective effect lasted for 10 hours (P less than.05). After immunolabeling of highly extended semen with rabbit monospecific polyclonal antibody against PSP-I/PSP-11, the percentage of immunopositive spermatozoa declines over time from 71% (0.5 hours) to 49% (10 hours). However, more than 80% of spermatozoa remained labeled during the 10-hour incubation period if PSP-I/PSP-11 was added. Scanning electron microscopy revealed 4 different binding patterns. The heterodimer was mainly localized to the acrosomal area, being redistributed to the postacrosomal area or lost during in vitro incubation. In conclusion, the protective effect of the heterodimer appears to be related to its adhesion to the acrosomal area, and the loss of this protective effect coincides with a stepwise redistribution of PSP-I/PSP-II during incubation.
TL;DR: Evidence is provided for the presence of K(ATP) channels in mouse spermatogenic cells and sperm and the contribution of these channels to the capacitation-associated hyperpolarization is disclosed.
TL;DR: The results indicate that 1.0 M lactamide and acetamide have higher cryoprotective effects than 1.
Abstract: The rabbit is considered to be a valuable laboratory animal. We compared glycerol, lactamide, acetamide, and dimethylsulfoxide (DMSO) as cryoprotectants in egg-yolk diluent of ejaculated Japanese white rabbit spermatozoa for improvement of sperm cryopreservation methods. Rabbit semen was frozen with 1.0 M glycerol, lactamide, acetamide, or DMSO in plastic straws. Forward progressive motility and plasma membrane integrity of the post-thaw spermatozoa were examined. The rate of forward progressive motile spermatozoa in lactamide (37.8 +/- 3.0%) was significantly (P<0.05) higher than in glycerol (17.0 +/- 3.3%). In addition, the rates of sperm plasma membrane integrity in lactamide and acetamide (35.9 +/- 3.3% and 30.2 +/- 3.0%, respectively) were significantly (P<0.05) higher than in glycerol (17.0 +/- 2.6%). The results indicate that 1.0 M lactamide and acetamide have higher cryoprotective effects than 1.0 M glycerol for cryopreservation of Japanese white rabbit spermatozoa.
TL;DR: The results indicate that the manipulation of sperm plasma membrane cholesterol content affects porcine sperm viability and capacitation status and could therefore be useful to protect sperm from cold shock during cryopreservation by improving viability without promoting premature capacitation.
Abstract: Porcine sperm are extremely sensitive to the damaging effects of cold shock. It has been shown that cholesterol-binding molecules, such as 2-hydroxypropyl-beta-cyclodextrin (HBCD), improve post-cooling porcine sperm viability when added to an egg yolk-based extender, but also enhance sperm capacitation in other species. The objective of this study was to determine the effects of HBCD and cholesterol 3-sulfate (ChS) on porcine sperm viability and capacitation following cold shock or incubation under conditions that support capacitation using a defined medium. We report here that porcine sperm incubated in medium containing both HBCD and ChS have significantly improved viability following cold shock (10 min at 10 degrees C) when compared to sperm incubated without HBCD or ChS, or with either component alone. Treatment with HBCD plus ChS also completely inhibited the increase in protein tyrosine phosphorylation induced by the cold shock treatment or by incubation for 3 hr under conditions that support capacitation. Two assays of sperm capacitation, the rate of calcium ionophore-induced acrosome reactions and chlortetracycline (CTC) staining, were not significantly altered by HBCD and ChS following cold shock. However, 3-hr incubation with HBCD plus ChS or with 1 mM ChS alone decreased the percentage of sperm undergoing the induced acrosome reaction without significantly affecting viability when compared to the control. These results indicate that the manipulation of sperm plasma membrane cholesterol content affects porcine sperm viability and capacitation status and could therefore be useful to protect sperm from cold shock during cryopreservation by improving viability without promoting premature capacitation.
TL;DR: It is demonstrated that wombat spermatozoa are highly tolerant of cryopreservation when compared to koala sperm but that spermatozosa from both species show greatest post-thaw survival when frozen slowly in 14% glycerol.
TL;DR: Investigation of changes in protein composition of DRMs isolated from uncapacitated or capacitated mouse sperm suggests the physiological changes in sperm motility, ability to penetrate the zona pellucida (ZP), ZP responsiveness, and other capacitation‐dependent changes, may be due in part to a functional reorganization of plasma membrane microdomains.
Abstract: One of the hallmarks of mammalian sperm capacitation is the loss of cholesterol from the plasma membrane. Cholesterol has been associated with the formation of detergent insoluble membrane microdomains in many cell types, and sperm from several mammalian species have been shown to contain detergent-resistant membranes (DRMs). The change in cholesterol composition of the sperm plasma membrane during capacitation raises the question of whether the contents of DRMs are altered during this process. In this study, we investigated changes in protein composition of DRMs isolated from uncapacitated or capacitated mouse sperm. TX-100 insoluble membranes were fractionated by sucrose flotation gradient centrifugation and analyzed by Western and lectin blotting, and capacitation-related differences in protein composition were identified. Following capacitation, the detergent insoluble fractions moved to lighter positions on the sucrose gradients, reflecting a global change in density or composition. We identified several individual proteins that either became enriched or depleted in DRM fractions following capacitation. These data suggest that the physiological changes in sperm motility, ability to penetrate the zona pellucida (ZP), ZP responsiveness, and other capacitation-dependent changes, may be due in part to a functional reorganization of plasma membrane microdomains.
TL;DR: It is suggested that Hep(+) proteins (especially AQN 1, fraction II) on sperm could enable sperm binding to oviductal epithelium and thus participate in formation of the sperm ovidUCTal reservoir.
TL;DR: These remarkable differences in human SHBG expression in the testis, when compared to other mammals, force us to reconsider the functional significance of SH BG expression inThe testis in relation to male reproduction.
Abstract: The human sex hormone-binding globulin ( SHBG) gene contains at least two transcription units. A 4.3 kb human SHBG transcription unit encodes the precursor polypeptide, which is processed and secreted by hepatocytes as plasma SHBG. The proximal promoter of this transcription unit differs from the corresponding sequence in other mammals, in which it is also expressed in Sertoli cells. In particular, its proximal promoter sequence contains a binding site for USF transcription factors that represses its activity in Sertoli cells. Although human SHBG is not expressed in Sertoli cells, human SHBG transcripts containing an alternative exon 1 sequence are present in testicular germ cells. These are the products of an approximately 8 kb human SHBG transcription unit, and they appear to encode an SHBG isoform that is 4 - 5 kDa smaller than plasma SHBG. This sperm SHBG isoform accumulates between the outer acrosomal membrane and the sperm plasma membrane, and it is released during the capacitation reaction. These remarkable differences in human SHBG expression in the testis, when compared to other mammals, force us to reconsider the functional significance of SHBG expression in the testis in relation to male reproduction.
TL;DR: The α‐L‐fucosidase of Drosophila sperm plasma membrane appears to be potentially involved in gamete recognition by interacting with its glycoside ligands present on the egg surface at the site of sperm entry.
Abstract: Drosophila is emerging as a model organism to investigate egg fertilization in insects and the possible conservation of molecular mechanisms of gamete interactions demonstrated in higher organisms. This study shows that the spermatozoa of several species of Drosophila belonging to the melanogaster group have a plasma membrane associated alpha-L-fucosidase with features in common with alpha-L-fucosidases from sperm of other animals, including mammals. The enzyme has been purified and completely characterized in D. ananassae, because of its stability in this species. The sperm alpha-L-fucosidase is an integral protein terminally mannosylated, with the catalytic site oriented toward the extracellular space. It has a M(r) of 256 kDa and a multimeric structure made up by subunits of 48 and 55 kDa. Enzyme characterization included kinetic properties, pI, optimal pH, and thermal stability. A soluble form of the enzyme similar to the sperm associated alpha-L-fucosidase is secreted by the seminal vesicles. Synthetic peptides designed from the deduced product of the D. melanogaster gene encoding an alpha-L-fucosidase were used to raise a specific polyclonal antibody. Immunofluorescence labeling of spermatozoa showed that the enzyme is present in the sperm plasma membrane overlying the acrosome and the tail. Lectin cytochemistry analysis of the egg surface indicated that alpha-L-fucose terminal residues are present on the chorion with a strongly polarized localization on the micropyle. The alpha-L-fucosidase of Drosophila sperm plasma membrane appears to be potentially involved in gamete recognition by interacting with its glycoside ligands present on the egg surface at the site of sperm entry.
TL;DR: Data suggest PKDREJ to be a sperm plasma membrane protein presumably contributing to transmembrane signaling in mammalian spermatozoa and its putative role in mammalian fertilization.
Abstract: The mammalian polycystic kidney disease (PKD) gene family comprises eight members whose role in cell physiology is still poorly understood. Two of the founding members of the PKD family, PKD1 and PKD2, are responsible for the majority of cases of autosomal dominant polycystic kidney disease. The present study focuses on a PKD1 homologue, mouse polycystic kidney disease and receptor for egg jelly (PKDREJ) and its putative role in mammalian fertilization. To examine PKDREJ tissue distribution multiple-tissue Northern blot analysis was performed. We observed that PKDREJ expression is confined to mouse testis. A PKDREJ transcript was detected in spermatogenic cells by in situ hybridization with mouse testicular tissue. Upon heterologous expression PKDREJ was retained in intracellular membrane compartments and unlike PKD1 did not undergo cleavage in the G-protein-coupled receptor proteolytic site domain (GPS). Immunocytochemical experiments on isolated epididymal mouse spermatozoa using PKDREJ-specific polyclonal antibodies revealed that the protein is localized in the acrosomal region and on the inner aspect of the falciform-shaped head. To precisely characterize PKDREJ expression in the acrosomal region, transmission electron microscopy was performed. Immunogold labeling was only visible at the plasma membrane of the mouse sperm head. Collectively, these data suggest PKDREJ to be a sperm plasma membrane protein presumably contributing to transmembrane signaling in mammalian spermatozoa. Mol. Reprod. Dev. © 2005 Wiley-Liss, Inc.
01 Apr 2006
TL;DR: Chang and Austin this paper showed that fresh rabbit sperm cannot penetrate the zona pellucida immediately after ejaculation, and that sperm must remain within the female tract for a period before they are able to penetrate the eggs.
Abstract: Introduction Mammalian sperm are not able to fertilize eggs immediately after ejaculation. They acquire fertilization capacity after residing in the female tract for a finite period of time that varies depending on the species. In 1951, Chang (1951) and Austin (1951) independently demonstrated that such a period of time in the female tract is required for the sperm to acquire their fertilizing capacity. Both authors observed that freshly obtained rabbit sperm introduced into the Fallopian tubes shortly after ovulation were not able to penetrate the eggs; instead if sperm were introduced a few hours before ovulation, the majority of the eggs were later observed to be fertilized. This observation led them to conclude that freshly ejaculated sperm are incapable of penetrating the zona pellucida immediately, and that sperm must remain within the female tract for a period before they are able to penetrate the eggs. Following these original observations, many studies confirmed that the environment of the female tract induces a series of physiological changes in the sperm; these changes are collectively called ‘capacitation’. Inherent to these first observations was that capacitation state became defined using fertilization as end-point.
TL;DR: The findings reported in this article indicate that the sperm dysfunction associated to infertile varicocele coexists with decreased sperm plasma membrane fluidity and tyrosine phosphorylation, which represent potential new pathophysiological mechanisms underlyingvaricocele‐related infertility.
Abstract: Varicocele is a prevalent pathology among infertile men. The mechanisms linking this condition to infertility, however, are poorly understood. Our previous work showed a relationship between sperm functional quality and the ability of spermatozoa to respond to capacitating conditions with increased membrane fluidity and protein tyrosine phosphorylation. Given the reported association between varicocele, oxidative stress, and sperm dysfunction, we hypothesized that spermatozoa from infertile patients with varicocele might have a combined defect at the level of membrane fluidity and protein tyrosine phosphorylation. Semen samples from infertile patients with and without grade II/III left varicocele were evaluated for motion parameters (computer-assisted semen analysis [CASA]), hyperactivation (CASA), incidence and intensity of protein tyrosine phosphorylation (phosphotyrosine immunofluorescence and western blotting), and membrane fluidity (Laurdan fluorometry), before and after a capacitating incubation (6 hr at 37 degrees C in Ham's F10/BSA, 5% CO(2)). Spermatozoa from varicocele samples presented a decreased response to the capacitating challenge, showing significantly lower motility, hyperactivation, incidence and intensity of tyrosine phosphorylation, and membrane fluidity. The findings reported in this article indicate that the sperm dysfunction associated to infertile varicocele coexists with decreased sperm plasma membrane fluidity and tyrosine phosphorylation. These deficiencies represent potential new pathophysiological mechanisms underlying varicocele-related infertility.