Showing papers on "Sperm plasma membrane published in 1984"
TL;DR: A peptide (resact) associated with the eggs of the sea urchin, Arbacia punctulata, which stimulates sperm respiration rates by 5-10-fold, was purified and its amino acid sequence was determined, and the protein appears to be the enzyme guanylate cyclase.
137 citations
TL;DR: It is proposed that this type of irreversible change within the sperm plasma membrane may contribute to the loss of motility and fertility suffered by spermatozoa after cooling and freezing and suggested that protective substances such as egg yolk may exert their effects by countering these deleterious changes, rather than by preventing their occurrence.
Abstract: In an effort to investigate the nature of the cellular injury caused when mammalian spermatozoa are cooled prior to cryopreservation, the occurrence of thermal phase transitions amongs the lipid components of the sperm plasma membrane was investigated by the use of freeze-fracture electron microscopy. The mechanisms by which glycerol and egg yolk exert protective effects during semen cooling and freezing were also examined. Ram and blackbuck spermatozoa, maintained at 30 degrees C prior to fixation at this temperature, exhibited randomly distributed intramembranous particles over the acrosomal, postacrosomal, and flagellar regions of the plasma membrane. In contrast, spermatozoa fixed at 5 degrees C after slow cooling to this temperature exhibited particle clustering over the postacrosomal region of the head as well as over the tail. These effects were not influenced by the presence of egg yolk or glycerol during the cooling procedure, although these substances protected the spermatozoa against loss of motility. Particle clustering over the sperm tail, induced by the slow cooling process, was found to be only partially reversible. The extensive areas of particle-free lipid, noted to result from the cooling procedure, were absent if the spermatozoa were rewarmed to 30 degrees C; however, the original distribution of particles was not restored and numerous small particle-free domains persisted. It is proposed that this type of irreversible change within the sperm plasma membrane may contribute to the loss of motility and fertility suffered by spermatozoa after cooling and freezing. Furthermore, it is suggested that protective substances such as egg yolk may exert their effects by countering these deleterious changes, rather than by preventing their occurrence.
135 citations
TL;DR: It is found that the major morphologically distinct regions (head, midpiece, and tail) of the plasma membrane of both testicular and ejaculated spermatozoa are also physically distinct as measured by C16dil diffusibility.
Abstract: An essential feature of the "fluid mosaic model" (Singer, S. J., and G. L. Nicolson , 1972, Science (Wash. DC)., 175:720-731) of the cell plasma membrane is the ability of membrane lipids and proteins to diffuse laterally in the plane of the membrane. Mammalian sperm are capable of overcoming free random diffusion and restricting specific membrane components, both lipid and protein, to defined regions of the sperm's surface. The patterns of these regionalizations evolve with the processes of sperm differentiation: spermatogenesis, epididymal maturation, and capacitation. We have used the technique of fluorescence recovery after photobleaching to measure the diffusion of the lipid analogue 1,1'- dihexadecyl 3,3,3',3'- tetramethylindocarbocyanine perchlorate ( C16dil ) on the different morphological regions of testicular and ejaculated ram spermatozoa. We have found: (a) that the major morphologically distinct regions (head, midpiece, and tail) of the plasma membrane of both testicular and ejaculated spermatozoa are also physically distinct as measured by C16dil diffusibility; (b) that despite regional differences in diffusibility there is exchange of this lipid analogue by lateral diffusion between the major morphological regions of the plasma membrane; and (c) that epididymal maturation results in changes in C16dil diffusibility in the different regions of the sperm plasma membrane. In particular, the plasma membranes of the anterior and posterior heads become physically distinct.
127 citations
TL;DR: Christen as discussed by the authors explored the relationship between the plasma membrane potential and activation of sperm motility and respiration, or induction of the acrosome reaction, was explored in sperm of the sea urchin Strongylocentrotus purpuratus.
62 citations
TL;DR: The data show a high degree of similarity between bull and ram, suggesting minimal differences between the two species as far as the structure and function of the sperm plasma membrane is concerned.
Abstract: The effects of gossypol acetic acid on the activity of Mg-ATPase and Ca-Mg-ATPase and on calcium uptake by plasma membranes from ram and bull spermatozoa were examined. The three parameters were almost completely inhibited by 10 microM gossypol for both ram and bull sperm. In order to assess the effects of higher gossypol concentrations isolated membrane vesicles were loaded with calcium by operating the ATP-dependent calcium pump after which gossypol was added and calcium uptake followed. At 10 microM gossypol, additional calcium uptake was 85% inhibited while at 40 microM a release of the accumulated calcium was observed. The inhibitory effect of 10 microM gossypol was almost completely reversible by simple dilution of gossypol-treated membranes, whilst at 40 microM the effect was only 50% reversible. The data show a high degree of similarity between bull and ram, suggesting minimal differences between the two species as far as the structure and function of the sperm plasma membrane is concerned.
31 citations
TL;DR: Results suggest the appearance of specific sugar moieties on the surface of the sperm plasma membrane which, in this particular species of mouse, are sialylated glycoproteins acting as ligands for specific receptors on thesurface of the egg.
Abstract: We have studied the molecular mechanisms of gamete interaction in vitro in the laboratory mouse, Mus musculus. In particular, we were interested in whether this interaction is similar to a lectin-hapten-mediated process. Inhibition of sperm-zona binding was examined using various concentrations (.25 mM to 50 mM) of different sugars (sialic acid α-methylmannose, glucose, fucose, galactose, and N-acetyl-glucosamine). Sperm-zona binding was significantly decreased when eggs were pretreated with 10 mM of sialic acid or α-methylmannose but not by other sugars tested. Furthermore, treatment of capacitated sperm with neuraminidase destroyed their ability to bind and fertilize eggs. We have also used a specific lectin for sialic acid from the horseshoe crab (Limulus polyphemus) to agglutinate mouse sperm. The lectin (.120 ng/ml) mediated agglutination of mouse sperm (105 sperm/ml) was routinely observed to increase from a 10% agglutination immediately following their isolation from the epididymis to 100% agglutination 90 minutes later. Collectively, these results suggest the appearance of specific sugar moieties on the surface of the sperm plasma membrane which, in this particular species of mouse, are sialylated glycoproteins acting as ligands for specific receptors on the surface of the egg. These are the first data to indicate that sperm-egg recognition and attachment is a lectin-hapten-mediated process in the mouse.
25 citations
TL;DR: The results indicate that the starting conditions to isolate and characterize the sperm membrane components that participate in the egg jelly induced permeability changes have been found.
Abstract: The acrosome reaction in sea urchin sperm is induced by a glycoprotein jelly surrounding the egg and is accompanied by changes in ion permeability of sperm plasma membrane. In an attempt to learn what membrane components are involved in the response to jelly, we have begun to reassemble sperm membrane components into artificial membranes and assay for permeability changes mimicking those that occur in sperm. Jelly in sea water at concentrations that induce the acrosome reaction did not significantly change 45Ca2+ uptake of sonicated unilamellar vesicles made with soybean lipid only (ratio jelly:control uptake = 1.08 +/- 0.36 SD, n = 21). Experiments with pure lipid planar bilayers made with soybean lipid or a lipid extract from sperm and held at various voltages, also did not reveal substantial permeability changes at comparable jelly concentrations. Thus, jelly by itself does not change the conductance of a pure lipid bilayer. In contrast, significant (P----0.0005, t test for two sample means) 45Ca2+ uptake was observed with vesicles made by cosonicating soybean phospholipids and Strongylocentrotus purpuratus sperm membranes isolated by the method of Cross, N. L. [1983, J. Cell Sci. 59, 13-25] (ratio jelly: control uptake = 1.51 +/- 0.75, n = 20, 16 positive out of 20 experiments). The calcium uptake response of the mixed vesicles was also species-specific: it did not occur with jelly from Arbacia punctulata (ratio Arbacia jelly: control = 1.18 +/- 0.51; ratio Strongylocentrotus jelly: control = 1.71 +/- 0.97, n = 10; P----0.025, paired t statistic). Vesicles made with soybean lipid and an octyl glucoside extract of sperm membranes also responded to jelly with increased 45Ca2+ uptake. Our results indicate that we have the starting conditions to isolate and characterize the sperm membrane components that participate in the egg jelly induced permeability changes.
25 citations
01 Jan 1984
TL;DR: The plasma membrane of the guinea-pig spermatozoon is divided into structural regions (macrodomians) closely correlating with the functional segments of the cell, and in each macrodomian, plasmalemmal, cytoplasmic, and functional diversities exist.
Abstract: Studied in extensive morphological detail, the plasma membrane of the guinea-pig spermatozoon (1–11) — like those of all other mammalian sperm — is divided into structural regions (macrodomians) closely correlating with the functional segments of the cell (2, 12–15). In each macrodomian, plasmalemmal, cytoplasmic, and functional diversities exist. Moreover, the membrane macrodomains themselves contain microdomains, thus contributing to further heterogeneity in the major vicinities of the cell. The parameters in which the primary sectors differ — that is, the acrosomal cap of the head, the equatorial and postacrosomal segments, and the midpiece, annulus, and principal-piece of the tail — involve many factors. These include the surface coat (morphology, antibody-specificity, lectin binding, surface-charge); the plasma membrane (intramembranous particle numbers and configurations, and the lining of the membrane); and possibly membrane sterol content, anionic-lipid asymmetry, and lipid-phase state. Similar forms of heterogeneity (6, 9) are provided in several internal organelles, particularly the nuclear envelope and the mitochondrion.
23 citations
TL;DR: Data show that changes in the monkey sperm plasma membrane during epididymal maturation occur in the distal corpus of the epididycumis.
Abstract: Changes in electronegative and electropositive surface charges and in lectin receptors (concanavalin A and wheat germ agglutinin) were investigated on sperm plasma membranes of the monkey (Macaca fascicularis) during epididymal transit and after ejaculation. Electronegative charges at pH 1.8, which were uniformly distributed on the whole plasma membrane of caput epididymal spermatozoa, increased mainly on the postacrosomal cap and the tail during epididymal passage. Electropositive charges at pH 9 were simultaneously found on the whole cell surface of caput epididymal spermatozoa with a stronger labeling on the acrosomal apex, the postacrosomal cap, and the tail. These charges disappeared during passage through the epididymis corpus. The surface distribution of lectin receptors varied inversely during epididymal transit with an increase in concanavalin A receptors and a decrease in wheat germ agglutinin receptors. These data show that changes in the monkey sperm plasma membrane during epididymal maturation occur in the distal corpus of the epididymis.
13 citations
01 Jan 1984
TL;DR: During passage through the epididymis, sperm achieve functional maturity, developing both the capacity for forward motility and for effecting fertilization of an ovum.
Abstract: Mammalian spermatozoa are released into the lumen of the seminiferous tubule after completing a prolonged and complex process of differentiation. Although the resultant cells are highly specialized in structure and function, they are immature, being neither motile nor capable of fertilizing an oocyte. After leaving the testis, sperm rapidly move into the epididymis where they remain for several days. During passage through the epididymis, sperm achieve functional maturity, developing both the capacity for forward motility and for effecting fertilization of an ovum (l–4).
9 citations
TL;DR: The adenylate cyclase activity of sperm membrane fragments isolated from Lytechinus pictus sperm according to Cross has been studied and two distinct fractions preferentially coming from the flagellar plasma membrane are obtained.
Abstract: The adenylate cyclase activity of sperm membrane fragments isolated from Lytechinus pictus sperm according to Cross [20] has been studied. Two distinct fractions preferentially coming from the flagellar plasma membrane are obtained. Surface I125-labeling experiments performed by Cross [20] indicate that these membranes are representative of the entire sperm plasma membrane. Both fractions are enriched in their adenylate cyclase activity: the specific activity of the top membranes is eightfold higher than in whole sperm, whereas that of the middle membranes is 15-fold higher. The cyclase seems to be associated with the membranes. Lytechinus pictus egg jelly has no effect or slightly inhibits the adenylate cyclase activity of the isolated sperm plasma membrane fragments. Mg++ and Na+ stimulated their cyclase activity about sevenfold at 2.5 mM Mn++ and 3.2 mM ATP. At this ATP to Mn++ ratio, high concentrations of Ca++ have a small stimulatory effect.
Journal Article•
TL;DR: Modifications in bull sperm plasmamembrane during epididymal passage were investigated by the use of four different lectins: Concanavalin A (Con A); Ricinus communis I (RCA1); Wheat germ agglutinin (WGA); Ulex europaeus agglUTinin I (UEA1).