Sperm plasma membrane

About: Sperm plasma membrane is a research topic. Over the lifetime, 1016 publications have been published within this topic receiving 49964 citations.

Lipid composition of the membrane released after an in vitro acrosome reaction of epididymal boar sperm

Abstract: Prior to fertilization, mammalian sperm must undergo the acrosome reaction, which involves modifications of the plasma and outer acrosomal membranes followed by vesiculation and release of the membranes. The membrane fraction that was released from caudal boar sperm undergoing an in vitro acrosome-like reaction was isolated and characterized with respect to density, marker enzymes and lipid composition. This membrane had a lower phospholipid/protein ratio (mg/mg) than the sperm plasma membrane, whereas both membranes had similar molar sterol/phospholipid ratios. The major phospholipid was sphingomyelin, followed by phosphatidylethanolamine and phosphatidylcholine, whereas in the plasma membrane the order was reversed; the two major phosphoglycerides contained alkylacyl and alkenylacyl species in addition to the diacyl species. The released membrane also contained lower amounts of cholesterol sulfate and unsaturated fatty acids than the plasma membranes. These results, in combination with our studies on the changes of the sperm membranes during maturation and acrosome reaction, will allow a better understanding of the mechanism of the sperm acrosome reaction.

Antimicrobial host defence peptide, LL-37, as a potential vaginal contraceptive

Abstract: STUDY QUESTION Does antimicrobial peptide, LL-37, inhibit sperm fertilizing ability? SUMMARY ANSWER Our results indicate that LL-37 inhibits mouse and human sperm fertilizing ability. WHAT IS KNOWN ALREADY LL-37, a cationic antimicrobial peptide, exerts its microbicidal effects through the disruption of microbial cytoplasmic membranes following its interaction with microbial surface anionic phospholipids. ALL-38 (an LL-37 close analogue: LL-37 + Ala at the N-terminus) is produced in the vagina 2-6 h post-intercourse from its precursor hCAP-18, a seminal plasma component. At this time, motile sperm have already swum into the uterine cavity, thus unexposed to ALL-38. Since sperm contain a substantial amount of acidic sulfogalactosylglycerolipid (SGG) on their surface, treatment of sperm with LL-37 may cause their membrane disruption in an analogous manner to that occurring on microbial membranes. STUDY DESIGN, SIZE AND DURATION Mouse/human sperm treated (2-30 min) with LL-37 in a physiological concentration range (up to 10.8 µM) were assessed for SGG-dependent LL-37 binding, and parameters relevant to fertilizing ability, namely motility and intactness of the sperm acrosome and plasma membrane. Ability of mouse sperm to fertilize eggs in vitro was also evaluated. Each study was performed with greater than or equal to three different sperm samples. The efficacy of LL-37 to inhibit sperm fertilizing ability in vivo was determined in female mice (n = 26 each for LL-37 treatment and no treatment), using sperm retrieved from 26 males. PARTICIPANTS/MATERIALS, SETTING, METHODS Human sperm samples were donated by fertile men. LL-37 was chemically synthesized and was biotinylated for sperm binding studies. Sperm motility was assessed by videomicroscopy and the acrosomal status by Coomassie blue staining of acrosome-intact mouse sperm or the exposure of CD46, an inner acrosomal membrane protein, of acrosome reacted human sperm. Sperm membrane permeabilization/disruption was assessed by the loss of hypo-osmotic swelling response, an incorporation of Sytox Green (a membrane impermeable fluorescent DNA dye), and electron microscopy. Mouse IVF was scored by the presence of two pronuclei in eggs 6 h post-insemination. Ability of mouse sperm to fertilize eggs in vivo was determined by the pregnancy outcome of female mice injected transcervically with sperm with or without LL-37. MAIN RESULTS AND THE ROLE OF CHANCE Biotinylated LL-37 bound to both mouse and human sperm and the binding was partially dependent on sperm surface SGG. Mouse and human sperm became immotile and underwent a premature acrosome reaction upon treatment with LL-37 at 3.6 and 10.8 µM, respectively. The initial action of LL-37 on both mouse and human sperm appeared to be through permeabilization/disruption of sperm surface membranes evidenced by the loss of hypo-osmotic swelling response, Sytox Green staining and electron microscopy revealing ultrastructural damage. Mouse sperm treated with 3.6 µM LL-37 lost the ability to fertilize eggs both in vitro and in vivo. All 26 female mice inseminated with sperm and LL-37 did not become pregnant. No apparent damage to the reproductive tract was observed as revealed by histological characterization in LL-37-inseminated mice and these females resumed fecundity following mating with fertile males. LIMITATIONS, REASONS FOR CAUTION Direct demonstration that LL-37 treated human sperm fail to fertilize eggs was limited by legal restrictions on obtaining human eggs for such use. WIDER IMPLICATIONS OF THE FINDINGS Our results reveal selective inhibitory effects of LL-37 on sperm fertilizing ability in mice without apparent impairment to the female reproductive tract. LL-37 is therefore a promising candidate to be developed into a vaginal contraceptive with microbicidal activity. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by Grand Challenges Explorations grant from the Bill & Melinda Gates Foundation (OPP1024509), Canadian Institutes of Health Research (MOP119438 & CCI82413) and International Collaboration and Exchanges NSFC of China (No.30611120525). There are no competing interests to declare.

Characterization of human semen α-l-fucosidases

Abstract: Human semen contains a large amount of alpha-L-fucosidase activity, the great majority of which is found in the seminal fluid. Immunocytochemical studies indicate that a small amount of semen fucosidase activity is present on the sperm plasma membrane, primarily in the posterior head region. Subcellular fractionation studies also indicate that sperm alpha-L-fucosidase is present in the plasma membrane-enriched fraction. Comparative characterization of human seminal fluid and sperm alpha-L-fucosidases indicates that seminal fluid alpha-L-fucosidase has a broad pH optimum curve with a number of near-equal maxima between pH 4.8 and 7.0 while sperm fucosidase has a major optimum between pH 3.4 and 4.0. Isoelectric focusing indicates that seminal fluid alpha-L-fucosidase contains three to six isoforms with isoelectric points (pI) of 5-7 while sperm fucosidase contains two distinct isoforms with pI values of 5. 2 +/- 0.2 and 7.0 +/- 0.2. Western blotting indicates that seminal fluid fucosidase contains a major protein band with a molecular mass ratio (M(r)) of approximately 56 kDa while sperm fucosidase contains a major protein band of approximately 51 kDa. The overall results indicate the presence of a low-abundance, plasma membrane-associated human sperm alpha-L-fucosidase, which is different in its properties from human seminal fluid alpha-L-fucosidase(s), and whose function is not yet known.

Severe antioxidase deficiency in human semen samples with pathological spermiogram parameters

Abstract: Spermatozoa of 103 ejaculates from infertile patients and fertile healthy individuals were separated from seminal plasma and purified on Percoll gradient to determine the activities of superoxide dismutase (SOD) and catalase (CAT) in seminal plasma as well as in spermatozoal supernatants after hypotonic disintegration of the sperm plasma membrane. Out of collected specimens, a subgroup of ejaculates from 40 individuals was examined whose female partners had developed malignant processes in the cervix uteri (oncological subgroup). All sperm samples were classified into normal and pathological semen samples according to WHO criteria. While no significant differences of SOD levels were detected in seminal plasma of patients with primary infertility, a catalase deficiency seemed to be associated with combined sperm pathology-oligoasthenoteratozoospermia (OAT). Liberated concentrations of both SOD and catalase were diminished by 10-70% in the oncological subgroup compared to normozoospermia. In four OAT samples obtained from infertile males of the oncological subgroup, total depletion from both antioxidases was observed. A lack of sufficient antioxidase protection in cases of severe sperm pathology (OAT) may also lead to cervical dysplasia.

Boar sperm membranes antigens. II. Reorganization of an integral membrane antigen during capacitation and acrosome reaction.

Abstract: The dynamics of the cell surface during the process of capacitation is impressively shown by means of a monoclonal antibody directed against the P86/5 antigen. This glycoprotein was located in the sperm plasma membrane using the colloidal gold method in combination with specimen preparation in toto. The antigen is absent at the rostral tip of non-capacitated spermatozoa, but forms clusters over the principal segment and the equatorial segment after induction of capacitation. This formation of microdomains with different properties may be a prerequisite for the onset of the acrosome reaction (AR). During AR the diffusion barrier for the P86/5 antigen breakes down and the antigen occupies now the rostral crescent-like area of the sperm head. These observations are discussed with respect to zona binding and induction of the AR in boar spermatozoa.