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.

Influence of ejaculation frequency on seminal parameters.

Abstract: Several factors have been shown to influence semen parameters, one of which is sexual abstinence; a clinical criteria included in the semen evaluation to provide maximum sperm quality. The aim of the present study was to assess the effect of a daily ejaculation frequency on conventional and functional semen parameters. Semen samples were collected daily over a period of two weeks of which every second sample per person was processed and analyzed according to the World Health Organization guidelines. Furthermore, mitochondrial function, intracellular reactive oxygen species production and sperm DNA fragmentation were evaluated by flow cytometry. Total sperm count and seminal volume per ejaculation declined and remained decreased for the duration of the daily ejaculation period. However, conventional parameters such as sperm concentration, motility, progressive motility, morphology, vitality and functional parameters such as sperm plasma membrane integrity, mitochondrial membrane potential and DNA fragmentation was not significantly affected and remained similar to the initial measurement throughout the daily ejaculation period. Despite intra- and inter individual variations, the average values of the basic semen parameters remained above the WHO (2010) reference values throughout the daily ejaculation period. Interestingly, a decreasing trend in intracellular ROS production was observed, although statistically not significant. The study shows that an extended 2 week period of daily ejaculation does not have major clinical effects on conventional and functional seminal parameters.

Founders' Lecture. Human spermatozoa: fruits of creation, seeds of doubt.

Abstract: Deoxyribonucleic acid damage in the male germline is associated with defective fertilisation, impaired embryonic development, reduced implantation, abortion and childhood disease. Oxidative stress and the retention of excess residual cytoplasm by the spermatozoa are frequently associated with the induction of such damage. The redox cycling of xenobiotics by oxido-reductases in the germline, the patient's age, the incidence of genital tract infections and Sertoli cell dysfunction are all possible contributors to DNA damage in germ cells. Collateral peroxidation of unsaturated fatty acids in the sperm plasma membrane generally ensures that spermatozoa experiencing severe oxidative DNA damage cannot participate in the process of fertilisation. The adaptive termination of pregnancy through the selective vulnerability of genes involved in placentation may also help prevent the vertical transmission of damaged DNA. However, the ultimate safeguard against this form of damage will be to understand the biochemical basis of oxidative stress in human spermatozoa, so that the underlying causative mechanisms can be addressed in a logical manner.

Effect of cholesterol on the motility and plasma membrane integrity of frozen equine spermatozoa after thawing.

Abstract: The aim of the present study was to investigate the cryoprotectant properties of cholesterol after incorporation into the plasma membranes of equine spermatozoa. A cholesterol-methyl-beta-cyclodextrin complex was used to alter sperm plasma membrane cholesterol content. Ejaculates from six stallions were centrifuged in a non-fat skimmed milk glucose-sucrose extender (MK) or a modified Tyrode's medium (TALP). The sperm pellets were resuspended in the appropriate extender with or without added cholesterol (0.125 mmol cholesterol-methyl-beta-cyclodextrin complex l(-1)) and incubated at 24 degrees C for 15 min. After incubation, the aliquots were centrifuged and the sperm pellets were resuspended in lactose-EDTA-egg yolk freezing extender, frozen in static nitrogen vapour and stored at -196 degrees C. The straws were thawed and the motility and plasma membrane integrity of the spermatozoa were analysed. Addition of cholesterol to the incubation extenders improved the mean percentages of motile, progressively motile and rapidly motile spermatozoa in both the MK and TALP extenders containing cholesterol compared with extenders without cholesterol (P < 0.05). The percentage of spermatozoa with intact plasma membranes was higher in samples incubated in extenders containing cholesterol than in those without cholesterol (P < 0.05). The results of this study indicate that cyclodextrins can be used to incorporate cholesterol into equine sperm plasma membranes and that cholesterol incorporation imparts protection to the spermatozoa during cryopreservation.

PSP‐I/PSP‐II spermadhesin exert a decapacitation effect on highly extended boar spermatozoa

Abstract: PSP-I/PSP-II heterodimer is a major protein of boar seminal plasma that is able to preserve, in vitro, the viability, motility and mitochondrial activity of highly-extended boar spermatozoa. However, a relationship between the protective effects of the heterodimer and sperm capacitation is still unclear. The present study investigated the effect of the PSP-I/PSP-II (1.5 mg/mL) on membrane stability, intracellular calcium concentration ([Ca(2+)](I)) and plasma membrane and acrosome integrity of highly extended boar spermatozoa. Boar spermatozoa were diluted to 1 x 10(6) spermatozoa/mL and incubated at 38 degrees C in Phosphate-buffered saline (PBS) for 10, 30, 60, 120 and 300 min or in modified Tris-buffered medium (mTBM) for 10, 20, 30, 60 and 120 min. After each incubation time, the membrane stability (using Merocyanine-540/Yo-Pro-1), elevation of [Ca(2+)](I) (using Fluo-3-AM/PI) and the sperm plasma membrane and acrosome integrity (using SYBR-14/PI/PE-PNA) were evaluated by flow cytometry. As expected, exposure of the spermatozoa to the PSP-I/PSP-II preserved the plasma membrane and acrosome integrity compared to non-exposed spermatozoa in both media PBS and mTBM (p < .01). The evaluation of membrane stability showed no differences in the percentages of viable sperm with instable plasma membrane in the presence of the PSP-I/PSP-II compared to controls irrespective of the dilution media. The evaluation of the [Ca(2+)](I) levels showed that while spermatozoa incubated in mTBM and exposed to PSP-I/PSP-II had lower [Ca(2+)](I) than controls (39.08% vs. 47.97%, respectively; p < .05), no differences were observed in those samples incubated in PBS. However, a temporal evaluation of the samples showed that a similar proportion of live spermatozoa were able to achieve high levels of [Ca(2+)](I) and membrane instability independent of the presence of PSP-I/PSP-II. In conclusion, PSP-I/PSP-II exert a non-permanent decapacitation effect on highly extended boar spermatozoa that is related with a delay in the increase of [Ca(2+)](I) levels.

Membrane stability and mitochondrial activity of human-ejaculated spermatozoa during in vitro experimental infection with Escherichia coli, Staphylococcus haemolyticus and Bacteroides ureolyticus

Abstract: Summary The aim of the study was to examine an in vitro effect of the three bacterial strains (Escherichia coli, Staphylococcus haemolyticus and Bacteroides ureolyticus) on ejaculated spermatozoa with reference to sperm membrane integrity and mitochondrial activity. The study was carried out on swim-up-separated spermatozoa from 12 normozoospermic volunteers. Sperm plasma membrane stability was evaluated by the LIVE/DEAD Sperm Viability Kit and by the merocyanine 540 test. Mitochondrial activity was evaluated using the JC-1 test as well as the NADH-dependent NBT assay. The percentage of dead cells was significantly higher in spermatozoa treated with B. ureolyticus as compared to that of control spermatozoa (P < 0.01). All the bacterial strains applied affected sperm plasma membrane architecture measured by M540 test (P < 0.01). Moreover, the presence of E. coli or B. ureolyticus was connected with significant decrease in both the number of cells with high mitochondrial transmembrane potential (ΔΨm) and the cells with normal oxidoreductive function of mitochondria (P < 0.05 as compared to untreated cells). To conclude, the contact of bacteria with ejaculated spermatozoa can be a reason for severe injury of sperm membrane stability and mitochondrial activity with potential consequences for male fertility.