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.

Binding of porcine sperm plasma membrane proteins to sheep, hamster and mouse oocyte plasma membrane

Abstract: Four porcine sperm plasma membrane proteins were previously identified as putative ligands for the oocyte plasma membrane. The present study examined the binding of these proteins and two additional porcine sperm membrane proteins to oocytes from sheep, mice and hamsters as a first step in assessing potential conservation of these putative sperm ligands across species and across mammalian orders. Plasma membrane vesicles were isolated from porcine sperm, solubilised, and the proteins separated by one-dimensional gel electrophoresis. The 7, 27, 39 and 62 kDa porcine sperm protein bands demonstrating predominant binding of the porcine oocyte plasma membrane on ligand blots, a 90 kDa protein band demonstrating minor binding, and a 97 kDa protein band that did not bind the oocyte plasma membrane probe were electroeluted. Proteins were biotinylated, and incubated with zona-free oocytes. Bound biotinylated protein was labelled with fluorescent avidin and the oocytes examined with a confocal microscope. The 7 kDa, 27 kDa and the 39 kDa proteins bound to the sheep oocytes but not to a majority of the hamster or mouse oocytes. The 62 kDa protein bound to sheep oocytes and mouse oocytes but not to a majority of the hamster oocytes. The 90 kDa protein bound to oocytes from all three species. The 97 kDa protein, which did not recognise the porcine oocyte probe on a Western ligand blot, did not bind to oocytes from any species and served as a negative control. These observations are consistent with significant conservation of molecule and function among species within the same mammalian order. Hence, one species may be a good model for other species from the same order. Only limited conservation of binding activity of porcine sperm plasma membrane proteins to rodent oocytes was observed, suggesting a greater divergence either in molecular structure or in function among species from different orders.

Assessment of Progesterone‐Induced Acrosome Reaction by Biotinylated Monoclonal Antibody Probes

Abstract: PROBLEM: To develop an immunohistochemical assay for determination of acrosome-reacted human sperm and to study the effects of progesterone and cholesterol treatment on human sperm acrosome reaction. METHOD OF STUDY: Three distinct anti-sperm monoclonal antibodies were biotinylated and used as probes for assessment of acrosome reaction in a 30-min immunohistochemical assay. Progesterone and/or cholesterol were added to sperm preparation to influence the acrosome reaction in different experimental conditions. RESULTS: Percentages of acrosome-intact sperm decreased significantly during the 18-hr incubation. Acrosome reaction could be induced by progesterone as early as 2 hr after sperm incubation in human tubal fluid. The degree of progesterone-induced acrosome reaction was time dependent and the optimal effect was reached by adding 10 μg/ml progesterone for 30 min incubation. Progesterone-induced acrosome reaction was shown to be hormone-concentration dependent with 50% stimulation at 1 μg/ml. Cholesterol (1 μg/ml) was found to inhibit progesterone-induced acrosome reaction either by co-incubation with human sperm during capacitation, or by simultaneous incubation with progesterone during acrosome reaction induction. CONCLUSIONS: Assessment of human sperm acrosomal status by avidin-biotin immunohistochemical assay can be a routine in clinical laboratories for male infertility services. Cholesterol can inhibit progesterone-induced acrosome reaction, possibly by its modifications of sperm plasma membrane and/or interference of progesterone binding to its surface receptors.

[L-carnitine protects the motion parameters and mitochondrial function of human sperm in cryopreservation].

Abstract: Objective To study the effects of L-carnitine (LC) on cryopreserved human sperm. METHODS Ten semen samples were collected from normal sperm donors, each divided into six groups, fresh ejaculate (FE), non-LC cryopreservation (non-LC), and cryopreservation with LC at 1 mmol/L (LC-1), 2.5 mmol/L (LC-2), 5 mmol/L (LC-3) and 10 mmol/L (LC-4), respectively. The optimal concentration of LC was identified based on the motility and motion parameters of the post-thaw sperm. The plasma membrane integrity (PMI) of the sperm was assessed by eosin-nigrosin staining, their mitochondrial membrane potential (MMP) monitored by JC-1 assay, and the level of sperm ROS measured by the fluorescent probe DCFH-DA, followed by analysis of the mechanisms of LC protecting sperm against cryopreservation injury. RESULTS Compared with the sperm in the FE group, the post-thaw sperm in the non-LC and LC groups showed significantly decreased progressive motility, average path velocity (VAP), straight line velocity (VSP) and curvilinear velocity (VCP) (P < 0.05). In comparison with the non-LC group, the LC-3 group exhibited a remarkably higher percentage of progressively motile sperm (［41.9 ± 4.6］ vs ［47.0 ± 4.3］%, P = 0.0261) and VAP (［34.9 ± 2.6］ vs ［38.9 ± 4.2］ μm/s, P = 0.0152), indicating that the optimal concentration of LC was 5 mmol/L. Both PMI and MMP were significantly lower in the non-LC than in the FE group (［52.7 ± 5.7］ vs ［75.5 ± 5.4］%, P < 0.01 and ［44.5 ± 3.5］ vs ［57.3 ± 4.4］%, P < 0.01), but higher in the LC groups (［70.1 ± 8.2］% and ［50.3 ± 3.4］%) than in the non-LC group (P < 0.01 and P < 0.05). The level of sperm ROS, however, was markedly higher in the non-LC than in the FE group (［12.5 ± 3.9］ vs ［6.8 ± 2.4］, P < 0.01) but lower in the LC groups (［8.4 ± 5.3］%) than in the non-LC group (P = 0.05). CONCLUSIONS L-carnitine can improve the motility and motion parameters of cryopreserved human sperm by reducing sperm ROS, enhancing sperm mitochondrial membrane potential and protecting the sperm plasma membrane.

Plasma and acrosomal membrane lipid content of saltwater crocodile spermatozoa.

Abstract: This study describes the chemical lipid composition of the sperm plasma and acrosomal membranes of the saltwater crocodile Crocodylus porosus with the aim of providing new insights into sperm physiology, particularly that associated with their preservation ex vivo. The specific fatty acid composition of the sperm plasma and acrosomal membranes is documented. The mean (± s.d.) ratio of unsaturated to saturated membrane fatty acids within the plasma membrane was 2.57 ± 0.50, and was determined to be higher than a similar analysis of the lipids found in the acrosomal membrane (0.70 ± 0.10). The saltwater crocodile sperm plasma membrane also contained remarkably high levels of cholesterol (mean (± s.d.) 40.7 ± 4.5 nmol per 106 sperm cells) compared with the spermatozoa of other amniote species that have so far been documented. We suggest that this high cholesterol content could be conferring stability to the crocodile sperm membrane, allowing it to tolerate extreme osmotic fluxes and rapid changes in temperature. Our descriptive analysis now provides those interested in reptile and comparative sperm physiology an improved baseline database for interpreting biochemical changes associated with preservation pathology (e.g. cold shock and cryoinjury), epididymal sperm maturation and capacitation/acrosome reaction.

Functional Significance of Sperm Surface Mannosidase in Mammalian Fertilization

Abstract: Mammalian fertilization is the net result of a complex set of molecular events which enable the capacitated spermatozoa to recognize and bind to the egg’s extracellular coat, the zona pellucida (ZP). Sperm-egg interaction leading to fertilization is a species-specific carbohydrate-mediated event which depends on glycan-recognizing proteins (glycosyltransferases/ glycosidases/lectin-like carbohydrate-binding molecules) on the sperm plasma membrane (receptors) and their complementary glycan units (ligands) on homologous ZP. In this report, I have summarized our published and unpublished results on the sperm surface mannosidase, a hapten-binding enzyme thought to be involved in the initial sperm-egg interaction by binding to high mannose/hybrid-type glycans on ZP glycoconjugates. Evidence thus far available includes: (1) an a-D-mannosidase is present on the sperm plasma membranes of several species, including man; (2) high mannose/hybrid-type glycans (potential ligand sites) are present on mouse ZP2 and ZP3; (3) sperm-specific mannosidase is synthesized in the spermatogenic cells in a high molecular weight precursor form which undergoes proteolysis by a trypsin-like protease during spermatogenesis in the testis and sperm maturation in the epididymis; (4) the maturation-associated increase in sperm plasma membrane (PM) mannosidase correlates with the zona-binding ability of spermatozoa and (5) sperm surface mannosidase appears to have a receptor-like role in the mouse and rat. Taken together, these results are consistent with the proposed receptor-like role for the sperm surface mannosidase in sperm-egg interaction.