Organization of the boar spermatozoan plasma membrane: evidence for separate domains (subdomains) of integral membrane proteins in the plasma membrane overlying the principal segment of the acrosome

1987 ◽  
Vol 88 (3) ◽  
pp. 343-349
Author(s):  
R.N. Peterson ◽  
M. Gillott ◽  
W. Hunt ◽  
L.D. Russell
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Acrosome Reaction ◽  
Freeze Fracture ◽  
High Specificity ◽  
Sperm Head ◽  
Integral Membrane Proteins ◽  
Indirect Immunofluorescence Microscopy ◽  
Acrosomal Membrane ◽  
Acidic Phospholipids

Indirect immunofluorescence microscopy and freeze-fracture have been used to identify overlapping subdomains at the peripheral rim of the sperm-head plasma membrane (PM) and the margin of the outer acrosomal membrane (OAM) comprising the principal segment of the acrosome of the boar spermatozoon. An array of ridge-like structures (spaced 12–16 nm centre-to-centre), originally observed on the OAM by Aguas & Pinto da Silva, lies just beneath an area of the PM that is sparsely populated with large intramembranous particles compared to that of other regions of the head PM. This region has a high specificity for the lectin arachis hypogaea (peanut agglutinin). We suggest that the OAM at the rim of the sperm head may be rich in acidic phospholipids and that the close apposition of this membrane with a region of the PM relatively poor in integral membrane proteins may provide sites for initiating the acrosome reaction.

scholarly journals Membrane particle changes attending the acrosome reaction in guinea pig spermatozoa

1977 ◽  
Vol 74 (2) ◽  
pp. 561-577 ◽  
Author(s):  
DS Friend ◽  
L Orci ◽  
A Perrelet ◽  
R Yanagimachi
Keyword(s):  
Plasma Membrane ◽  
Guinea Pig ◽  
Acrosome Reaction ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Phosphatidylcholine Liposomes ◽  
Acrosomal Membrane ◽  
Large Particles ◽  
Fracture Appearance ◽  
Preparatory Stage

To examine the freeze-fracture appearance of membrane alterations accompanying the preparation of sperm membranes for fusions-the first preparatory stage occurring before physiological release of the acrosomal content, the second afterward-we induced the acrosome reaction in capacitated guinea pig spermatozoa by adding calcium to the mixture. The most common features observed before fusion of the acrosomal and plasma membranes were the deletion of fibrillar intramembranous particles from the E-fracture faces of both membranes, and the clearance of globular particles from the P face of the plasma membrane-events taking place near the terminus of the equatorial segment. Large particles, >12nm, remained not far from the cleared E-face patches. The P face of the outer acrosomal membrane is virtually clear from the outset. In addition, when fusion was completed, occasional double lines of large particles transiently embossed the P face of the plasma membrane (postacrosomal) side of the fusion zone. Behind the line of fusion, another series of particle-cleared foci emerged. We interpreted these postfusion membrane clearances as a second adaptation for sperm-egg interaction. Induction of the acrosome reaction in media containing phosphatidylcholine liposomes resulted in their apparent attachment, incorporation, or exchange in both the originally and secondarily cleared regions. Our observations support the concepts that membranes become receptive to union at particle- deficient interfaces, and that the physiologically created barren areas in freeze-fracture replicas may herald incipient membrane fusion.

Bimodal redistribution of surface transmembrane glycoproteins during Ca2+-dependent secretion (acrosome reaction) in boar spermatozoa

1989 ◽  
Vol 93 (3) ◽  
pp. 467-479
Author(s):  
A.P. Aguas ◽  
P.P. da Silva
Keyword(s):  
Plasma Membrane ◽  
Acrosome Reaction ◽  
Freeze Fracture ◽  
Secretory Process ◽  
Membrane Domains ◽  
Cytoplasmic Vesicle ◽  
Acrosomal Membrane ◽  
Freeze Fracture Electron Microscopy ◽  
Boar Spermatozoa

We used the acrosome reaction of boar sperm cells to study the dynamics of surface transmembrane glycoproteins (TMG) during a secretory process. The acrosome reaction is the Ca2+-dependent fusion of a large cytoplasmic vesicle (the acrosome) with the overlying segment of the plasma membrane (acrosomal cap) that leads to the release of the acrosomal enzymes. After triggering the acrosome reaction in vitro (2 mM-CaCl2 in the presence of 10 microM-A23187), we used freeze-fracture electron microscopy to follow the topographical rearrangement of a population of acrosomal-cap large intramembrane particles that correspond to transmembrane proteins that bind wheat germ agglutinin. We found that these TMG move in the direction of either one of two opposite poles, proximal and distal, of the acrosomal cap. This bimodal movement of the TMG reorganizes the acrosomal cap into three extensive domains. The first two, on the apical rim and on the equator, are membrane domains to which the TMG are directed and where they accumulate. The third, a large in-between area of protein clearing, corresponds to the region from which TMG were preferentially located before displacement induced by the Ca2+ effect. The topography of these new membrane domains of the acrosomal cap becomes coincident with that of the structural domains of the subjacent acrosomal membrane. Mirroring of the acrosomal membrane by the plasma membrane is followed by fusion between the two membranes, formation of an exquisite labyrinth of hybrid-membrane tubules, followed by fission and release of the acrosomal contents through intertubular fenestrae.

Image Analysis of Intramembrane Particles in Freeze-Fractured Biomembranes Using Computer Simulation Techniques

1975 ◽  
Vol 33 ◽  
pp. 214-215
Author(s):  
D.J. Benefiel ◽  
R.S. Weinstein
Keyword(s):  
Membrane Proteins ◽  
Freeze Fracture ◽  
Integral Membrane Proteins ◽  
Systematic Evaluation ◽  
Intramembrane Particles ◽  
Modeling Methods ◽  
Simulation Techniques ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron ◽  
Computer Simulation Techniques

Intramembrane particles (IMP or MAP) are components of most biomembranes. They are visualized by freeze-fracture electron microscopy, and they probably represent replicas of integral membrane proteins. The presence of MAP in biomembranes has been extensively investigated but their detailed ultrastructure has been largely ignored. In this study, we have attempted to lay groundwork for a systematic evaluation of MAP ultrastructure. Using mathematical modeling methods, we have simulated the electron optical appearances of idealized globular proteins as they might be expected to appear in replicas under defined conditions. By comparing these images with the apearances of MAPs in replicas, we have attempted to evaluate dimensional and shape distortions that may be introduced by the freeze-fracture technique and further to deduce the actual shapes of integral membrane proteins from their freezefracture images.

Membrane changes associated with mucus production by intestinal goblet cells

1978 ◽  
Vol 33 (1) ◽  
pp. 301-316
Author(s):  
J.G. Swift ◽  
T.M. Mukherjee
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Membrane Fusion ◽  
Thin Section ◽  
Structural Organization ◽  
Freeze Fracture ◽  
Goblet Cells ◽  
Mucus Production ◽  
Membrane Reorganization ◽  
Membrane Changes

Changes in the structural organization of membranes of mucous bodies and the plasma membrane that occur during mucus production in goblet cells of rat rectum have been studied by thin-section and freeze-fracture techniques. Immature mucous bodies are bounded by a trilaminar membrane and fracture faces of the membrane have randomly distributed intramembrane particles. During maturation, mucous bodies become packed tightly together and changes in the structure of their membranes include (1) fusion of apposing membranes of adjacent bodies to form a pentalaminar structure, (2) a reduction in the density of particles on membrane fracture faces, and (3) exclusion of particles from regions of membrane apposition. Some trilaminar membranes of mucous bodies fuse with the lumenal plasma membrane to form a pentalaminar structure. Sites of apposition between mucous body membranes and the lumenal plasma membrane are seen as particle-cleared bulges on fracture faces of the plasma membrane. Our results indicate that membrane reorganization associated with mucous production in goblet cells includes a reduction and redistribution of some membrane proteins and that membrane fusion occurs between portions of membranes from which proteins have been displaced.

Capacity of goat epididymal spermatozoa to undergo the acrosome reaction and subsequent fusion with the egg plasma membrane

1993 ◽  
Vol 5 (3) ◽  
pp. 239 ◽  
Author(s):  
H Harayama ◽  
H Kusunoki ◽  
S Kato
Keyword(s):  
Plasma Membrane ◽  
Acrosome Reaction ◽  
Morphological Changes ◽  
Glass Tube ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
Acrosomal Membrane ◽  
Sperm Penetration ◽  
Epididymal Spermatozoa ◽  
Caput Epididymidis

The capacity to undergo the acrosome reaction and subsequent fusion with the egg plasma membrane was examined in goat epididymal spermatozoa. Spermatozoa from the proximal and distal caput and distal cauda were preincubated in a sealed glass tube for induction of the acrosome reaction, and their viability, acrosome morphology and penetrability into zona-free hamster eggs were determined. A simplified triple-stain technique revealed that most of the preincubated live spermatozoa in the samples from the distal caput and distal cauda epididymides underwent morphological changes that indicated the occurrence of the acrosome reaction. Electron microscopic examination revealed that the outer acrosomal membrane of many spermatozoa in these samples showed fusion at multiple sites to the plasma membrane. However, the rates of acrosome-reacted cells in the proximal caput spermatozoa were still lower. The sperm penetration assay demonstrated that the penetration rates of distal caput and distal cauda spermatozoa preincubated for 2 h were 93% and 74% respectively, whereas proximal caput spermatozoa scarcely penetrated into eggs. These results indicate that increasing numbers of goat spermatozoa improve in the functions related to the acrosome reaction and subsequent fusion with the egg plasma membrane during their transit through the caput epididymidis.

How does sperm meet egg?--in a marsupial

1994 ◽  
Vol 6 (4) ◽  
pp. 485 ◽  
Author(s):  
WG Breed
Keyword(s):  
Acrosome Reaction ◽  
Small Region ◽  
Sperm Head ◽  
Sminthopsis Crassicaudata ◽  
Acrosomal Membrane ◽  
Wide Range ◽  
A Cell ◽  
Inner Acrosomal Membrane ◽  
Head Morphology ◽  
Range Of Variation

Australian marsupials exhibit a wide range of variation in sperm head morphology, and in thickness of the zona pellucida around the oocyte, suggesting interspecfic differences in the processes of sperm-egg interaction. The observations described here are largely based on the dasyurid Sminthopsis crassicaudata. They show that in oestrous females, after mating, a coagulum forms in the lateral vaginae and, within an hour of insemination, numerous spermatozoa congregate in the isthmus of the oviduct in which the vanguard population undergoes transformation with the head rotating on its axis with the tail to form a T-shape. Once oocytes are released, a few spermatozoa migrate to the higher reaches of the oviduct where sperm-zona binding occurs by way of the plasmalemma over the acrosomal region. The acrosome reaction takes place here and, as the egg rotates, the tail of the spermatozoon becomes parallel to the head. A small region of acrosome sometimes appears to remain intact at this time because spermatozoa with partly intact acrosomes have been found within the zona matrix. In some of these, electron-dense bridges between part of the inner and outer acrosomal membranes which may act as stabilizing structures, were also seen. The zona matrix is tightly packed around the penetrating spermatozoon, but that close to the acrosomal region becomes less electron-dense and more filamentous. Once incorporated into the egg, the spermatozoon lacks a cell membrane around the tail but vesicles close to the sperm head may, at least in part, be remnants of an inner acrosomal membrane. How generally applicable these observations are to other Australian marsupials remains to be determined.

Membrane fusion events in the Ca2+/ionophore-induced acrosome reaction of ram spermatozoa

1986 ◽  
Vol 81 (1) ◽  
pp. 43-63 ◽  
Author(s):  
J.E. Flechon ◽  
R.A. Harrison ◽  
B. Flechon ◽  
J. Escaig
Keyword(s):  
Plasma Membrane ◽  
Acrosome Reaction ◽  
Morphological Changes ◽  
Anterior Part ◽  
Freeze Fracture ◽  
Calcium Ionophore ◽  
Limited Area ◽  
Ionophore A23187 ◽  
Early Effect ◽  
Effect Of Treatment

An acrosome reaction was induced in ejaculated ram spermatozoa by treatment with calcium and the ionophore A23187. Samples were fixed at different times after initiation of induction, and the morphological changes within the head membranes that took place as exocytosis occurred were studied in freeze-fracture replicas. Reacted acrosomes appeared in individual spermatozoa within the calcium/ionophore-treated population at different times after the start of treatment; the first cells had reacted by 10 min, whereas some took more than 40 min to react. No changes were observed in control populations. An early effect of treatment (seen in most cells within 10 min) was the appearance of particle-free ‘clearings’ in the plasma membrane over the entire acrosomal region, with aggregation of intramembranous particles between and around these ‘clearings’. At the same time, there was an increase in the number of large particles (greater than or equal to 10 nm) within the plasma membrane over the ‘lunula’ of the equatorial segment and the anterior part of the post-acrosomal region. Fusion of the plasma and outer acrosomal membranes began in a limited area at the border between the anterior and equatorial segments of the acrosome. It then spread, following arborescent pathways, sideways along this border and forwards towards the apex of the head. This labyrinthic propagation resulted in an ‘acrosomal cap’ increasingly fenestrated towards its posterior margin. Fusion propagation over the equatorial segment was inhibited, apparently as a result of the highly ordered structure of the membranes in this region.

scholarly journals THE ACROSOME REACTION IN MYTILUS EDULIS

1965 ◽  
Vol 25 (2) ◽  
pp. 243-248 ◽  
Author(s):  
Lumiko Niijima ◽  
Jean Dan
Keyword(s):  
Plasma Membrane ◽  
Mytilus Edulis ◽  
Outer Surface ◽  
Sperm Cell ◽  
Acrosome Reaction ◽  
Outer Wall ◽  
Acrosomal Membrane ◽  
General Organization

The intact acrosome of the Mytilus edulis spermatozoon consists of a conical vesicle, the basal side of which is deeply invaginated so that the whole vesicle forms a sheath around a very slender axial rod, about 2.7 µ long, inserted in a tube passing through the nucleus. The annular base of the acrosomal vesical is filled with a homogeneous substance; the outer wall of the vesicle is lined with a somewhat irregular layer of a particulate substance interspersed with very fine tubular elements, and its lumen is nearly filled by a strand of material which extends from the inner tip of the invagination to the apex of the acrosome. The lumen of the invagination appears empty except for the rod and a delicate sleeve-like structure which surrounds it. The plasma membrane of the sperm cell lies in immediate contact with the acrosomal membrane over its whole outer surface. In its general organization, this molluscan acrosome shows a rather close homology with that of the annelid Hydroides.

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