ISSN:0002-9106    

DOI:10.1002/aja.1001740302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001740303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractDuring fertilization in mammals, the male and female gametes undergo a form of highly complex cell‐cell recognition whereby a nonspecific initial binding is followed by a species‐specific penetration of the zona pellucida. Recent data from many species have demonstrated the involvement of surface carbohydrates in regulating fertilization at both these stages. The potential benefits as well as drawbacks of three major techniques used so far are discussed, and the need for a cautious interpretation of the data is emphasized. During capacitation, the carbohydrate components of the entire surface of spermatozoa undergo striking changes which may be linked to the concurrent metabolic events within motile spermatozoa, leading to the appearance of egg‐specific glycoconjugates in a time‐dependent manner. A multiple set of glycoproteins on the sperm surface, possessing oligosaccharides synthesized by the lipid‐linked pathway, are probably required during different stages of fertilization, including sperm‐oocyte fusion. The oviductal glycosaminolycans may also be involved in regulating the timing and species specificity of mammalian fertilization by masking the sperm receptor sites on the zona and triggering the physiological acrosome reaction. Future biochemical and highresolution localization studies involving specific probes for surface glycoconjugates, glycosyltransferases, and hydrolytic enzymes should greatly aid our understanding not only of the role of the individiual surface macromolecules but also of the surface domains to which they ar

ISSN:0002-9106    

DOI:10.1002/aja.1001740304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractMammalian spermatozoa undergo changes in morphology, composition, and function during transit through the epididymis. These changes correlate with acquisition by sperm of the ability to fertilize ova. It has been found that sperm from the cauda epididymidis, but not those from the caput epididymidis, are able to bind to the zona pellucida. This would imply a modification in sperm surface characteristics. Biochemical and immunological studies have demonstrated changes in sperm surface composition during epididymal maturation. These changes involve addition of epididymal maturation. These changes involve addition of epididymal secretory products to the sperm surface, loss or alteration of existing sperm surface molecules, and possibly the unmasking of preexisting molecules or epitopes. Several laboratories have studied the epididymal secretory proteins in the rat, but a consensus has not been reached on the identification, characterization, source, and sperm surface association of these proteins. Monoclonal antibodies are beginning to be used to characterize sperm surface components and sperm maturation antigens. They are proving to be valuable tools for the dissection of epididymal maturation when used in conjunction with biochemical and physiological approaches.

ISSN:0002-9106    

DOI:10.1002/aja.1001740305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThe mammalian acrosome reaction is an exocytotic process that can be analyzed by the technique of freeze‐fracture; only sperm cells capacitatedin vitroor treated to elicit the acrosome reactionin vitrohave been studied, and all pictures published are from material fixed before freezing. All the authors point out the appearance of particle‐free areas in the plasma membrane of the acrosomal region during capacitation and before any fusion. This is interpreted as an increase in membrane fluidity as suggested by studies on membrane lipid composition in guinea‐pig sperm. We have recently described the induced acrosome reaction in ram spermatozoa. Fusion starts at the limit of the anterior and equatorial segments and progresses forward in the anterior segment along ramified paths, resulting in a fenestration gradient of the acrosomal cap. Fusion propagation may be controlled by fluidity increase in the plasma membrane of the anterior segment, and it is probably inhibited in the equatorial segment by the ordered structure of the acrosomal mem

ISSN:0002-9106    

DOI:10.1002/aja.1001740306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThe inner acrosomal membrane (IAM) develops during the spermatid stage of differentiation as that portion of the Golgi‐derived acrosome granule that tightly associates with the condensing sperm nucleus. In some mammalian species, an electron‐dense proteinaceous material accumulates between the IAM and the nuclear envelope, collectively comprising the “perforatorium.” Evidence, including its partial purification and its structural resistance to detergents and sonlcation, suggests that the IAM is an unusually resiliant membrane. Dense paracrystalline arrays of intramembranous particles, a lack of lectin‐mediated receptor modulation, and its lack of participation in sperm‐egg fusion suggest that the IAM lacks the same degree of fluidity as the egg surface plasmalemma. Observations using monoclonal antibodies, however, suggest that some specific antigenic modulations may be possible within the IAM. Its structural rigidity is of obvious mechanical value during sperm penetration through the zone pellucida. An additional role as a scaffold for putative zona lysin material remains controversial. Biochemical evidence suggests that acrosin, for example, is not entirely soluble and that some remains sperm‐associated, depending on the conditions of acrosome disruption. Nevertheless, morphological studies do not agree on acrosin's specific localization to the IAM. Currently there is only very limited information concerning the localization of the other acrosomal enzymes to the IAM. Another possible role for the IAM in some species may be in recognizing the zona pellucida. Evidence for this derives from the observation that fucoidin, a fucose heteropolysaccharide, inhibits guinea pig sperm‐zona binding, and bound fucoidin can be localized to the IAM and equatorial regions of the living acrosomereacted spermatozoa. Finally, the IAM may have a role in early recognition/adhesion w

ISSN:0002-9106    

DOI:10.1002/aja.1001740307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractSeveral lines of evidence suggest that decapacitation of sperm occurs normally in the male reproductive tract, and as a result the acrosome is stabilized and the acrosome reaction is controlled. Since the defining experiments in 1951, where decapacitation was reversed in the female reproductive tract by capacitation, investigations have pursued the molecular events of this process. This review attempts to examine critically the older literature and compare that perspective with the current theories. The theories for decapacitation of sperm include the possible role of a peptide decapacitation factor, a glycoprotein‐mediated steroid transfer to the sperm, masking of a galactosyl transferase by some macromolecule‐containing carbohydrate, preclusion of calcium influx by a binding protein, and sperm interaction with the acrosome stabilizing factor. Although these theories are diverse, there are some unifying aspects. However, there remain some major unanswered questions. For example, although we point to some circumstantial evidence that infers a single decapacitation factor, this needs to be further substantiated. It is concluded that with the purification of a macromolecule involved in capacitation, specific proposals on the mechanism of capacitation, and new tools to evaluate the capacitation process, it is likely that another decade will not pass without emergence of a unifying molecular theory of sperm capacitat

ISSN:0002-9106    

DOI:10.1002/aja.1001740308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThis review deals with exogenous molecules that stimulate the acrosome reaction (AR) of mammalian sperm in vitro, presumably by acting at the sperm surface. Such molecules may exert their effect(s) by stimulating capacitation and/or by stimulation or initiation of the AR, and they are probably present at one of three putative in vivo sites (also discussed here) for the AR of a fertilizing sperm: the oviductal fluid, the cumulus oophorus matrix, and the zona pellucida. The molecules discussed include serum albumin, hydrolytic enzymes (particularly proteases); hormones including biogenic amines, estradiol, and arachiodonic acid metabolites; sulfur‐containing β‐amino acids; glycosaminoglycans such as hyaluronic acid; and a zona pellucida glycoprotein. Possible mechanisms to explain the effects of these molecules are also discussed. Several conclusions and suggestions are offered in this review: (1) There is more than one site for the AR of a fertilizing sperm in vitro, depending on experimental conditions and species, but the site(s) at which the AR of a fertilizing sperm occur(s) in vivo is/are still a matter of disagreement; (2) there are a number of molecules that can stimulate or initiate the AR in vitro, and such molecular duplication may also exist in vivo to ensure fertility; and (3) synergistic interaction between some of those exogenous molecules may occur in the stimulation of capacitation and the stimulation or initiation of th

ISSN:0002-9106    

DOI:10.1002/aja.1001740309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractThe cortices of a number of mammalian eggs are not strucurally homogeneous but are polarized. In mouse ova the plasma membrane is a mosaic; the cytoplasm overlying the meiotic spindle is devoid of cortical granules and consists of a filamentous layer containing actin. Functionally, this cortical polarity may be related to the restriction of sperm‐egg interaction and fusion to a specific region of the ovum cortex and to dynamic changes of the egg cortex during fertilization, including cortical granule exocytosis, polar body formation, and fertilization cone development. The origin of cortical polarity in mammalian oocytes and its possible relation to components of the cytoskeletal system and meiotic apparatus are discussed and compared with cortical features of eggs of other vertebrates and invertebrate

ISSN:0002-9106    

DOI:10.1002/aja.1001740310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractFreeze‐fracture studies on mammalian oocytes have been hampered by the relatively small numbers of cells available at a given time as well as by difficulties encountered in effectively freezing these large, watery cells. We have nevertheless pursued this area because of the benefits of visualizing membrane faces involved in various fusion reaction by the freezefracture method. Our observations indicate no overall change in intramembranous particle (IMP) distribution before and after sperm penetration, although the question of possible alterations of these structures at the precise locus of sperm attachment remains open. Preliminary statistical analysis indicates that there is a much higher IMP density on the P face than on the E face of the plasma membrane and that the microvillar membranes bear more IMPs than those of the intermicrovillus regions. Probes of lipid subclasses were used to determine the distribution of cholesterol and anionic lipid in the egg plasma membrane. Filipin and tomatin showed extensive complex formation in microvillus as well as nonmicrovillus regions, whereas anionic lipids (using polymyxin B) have been difficult to detect on the oocyte surface. These results are discussed relative to current views of membrane fusion mechanism

ISSN:0002-9106    

DOI:10.1002/aja.1001740311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY