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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.
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TL;DR: It is shown that short incubations with cyclodextrin, a cholesterol removal agent, just before stimulation promote acrosomal exocytosis, and cholesterol efflux facilitates Rab3A association to sperm plasma membrane, indicating that cholesterol plays a direct role in the calcium-dependent exocyTosis associated with acrosome reaction.
58 citations
TL;DR: Evidence is included that the sperm and egg plasma membranes fuse to establish the single continuous zygote membrane which, consequently, is a mosaic, contrary to the general hypothesis of Tyler.
Abstract: An earlier paper showed that in Saccoglossus the acrosomal tubule makes contact with the egg plasma membrane. The present paper includes evidence that the sperm and egg plasma membranes fuse to establish the single continuous zygote membrane which, consequently, is a mosaic. Contrary to the general hypothesis of Tyler, pinocytosis or phagocytosis plays no role in zygote formation. Contact between the gametes is actually between two newly exposed surfaces: in the spermatozoon, the surface was formerly the interior of the acrosomal vesicle; in the egg, it was membrane previously covered by the egg envelopes. The concept that all the events of fertilization are mediated by a fertilizin-antifertilizin reaction seems an oversimplification of events actually observed: rather, the evidence indicates that a series of specific biochemical interactions probably would be involved. Gamete membrane fusion permits sperm periacrosomal material to meet the egg cytoplasm; if an activating substance exists in the spermatozoon it probably is periacrosomal rather than acrosomal in origin. The contents of the acrosome are expended in the process of delivering the sperm plasma membrane to the egg plasma membrane. After these membranes coalesce, the sperm nucleus and other internal sperm structures move into the egg cytoplasm.
57 citations
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.
57 citations
TL;DR: In this paper, a freeze-fracture examination of the sperm plasma membrane has revealed that small areas or patches free of intramembranous paarticles (IMPs) appear in the membrance during sperm preincubation, and these IMP−free areas expand drastically in response to Ca2+ when the LC conccentration in the medium is reduced at the time Ca 2+ is added to the medium.
Abstract: When guinea pig spermatozoa are preincubated for 1 hr in Ca2+−free medium containing a low concentration of lysolecithin (LC, 85 μg/ml) and then exposed to 2 mM Ca2+ by diluting the preincubation medium with an equal volume of LC−free, 4 mM Ca2+−containing medium, the majority of the spermatozoa undergo acrosome reaction promptly. On the other hand, when the preincubated spermatozoa are exposed to 2 mM Ca2+ without reducing the original concentration of LC in the medium, none of them undergo acrosome reaction. These spermatoza can acrosome−react if they are transferred to an LC−free medium. These results and those of some other experiments suggest that in the presistent presence of a high concentration of LC in the medium, exogenous Ca2+ essential for the acrosome reaction either does not penetrate the sperm plasma membrane or, if it does, it cannot alter the membrane for the acrosome reaction, at least under the experimental conditions employed. Freeze−fracture examination of the sperm plasma membrane has revealed that small areas or patches free of intramembranous paarticles (IMPs) appear in the membrance during sperm preincubation, and these IMP−free areas expand drastically in response to Ca2+ when the LC conccentration in the medium is reduced at the time Ca2+ is added to the medium. In contrast, IMP−free areas remain unchanged even after exposure of spermatozoa to Ca2+ if the concentration of LC remains at its original level of 85 μg/ml.
57 citations
TL;DR: The obtained data of in vitro experiments show that melatonin is 40-fold less efficient than Trolox in achieving the 50% reduction in LPO, and its antioxidative role in vivo is probably of minor importance.
Abstract: The ability of melatonin to suppress experimentally induced lipid peroxidation (LPO) in sperm membrane was investigated in 41 samples of infertile men. Iron/ascorbate (0.04/0.2 mmol)-induced LPO was measured by the formation of malondialdehyde (MDA) using the thiobarbituric acid method. Sperm incubated in the presence of melatonin (2-6 mmol) exhibited a concentration-dependent decrease of MDA generated from hydroperoxide of the sperm plasma membrane in the presence of promoter system. Addition of 6 mmol of melatonin significantly reduced the rate of lipid peroxidation in sperm of unselected donors (mean +/- SE in control samples = 26.4 +/- 2.9 vs. 6.5 +/- 1.1 nmol MDA/108 sperm in melatonin-treated samples; n = 16, p <. 005). Inhibitory effect of melatonin was also significant in the presence of 0.015 mmol of ferrous ions (20.5 +/- 1.7 vs. 7.9 +/- 1.6 nmol MDA/108 sperm in melatonintreated samples; n = 7, p <. 02) and 0.005 mmol of ferrous ions (20.2 +/- 2.8 vs. 9.9 +/- 2.4 nmol MDA/ 108 sperm; n = ...
57 citations