The spermatozoa of most invertebrates (e.g., sea urchins) and nonmammalian vertebrates (e.g., fishes and amphibians) have full capacity to fertilize eggs upon leaving the testis. Testicular spermatozoa of mammals, on the other hand, do not possess the ability to do so. Their fertilizing capacity develops as they pass through the epididymis (Young, 1931; Nishikawa and Waide, 1952; Blandau and Rumery, 1964; Bedford, 1966; Orgebin-Crist, 1967). This process, apparently “unique” to mammals, is referred to as the epididymal maturation of spermatozoa. Even after their maturation, however, spermatozoa require an additional phase of maturation or capacitation within the female genital tract before they are able to fertilize eggs (Austin, 1951, 1952; Chang, 1951a). Thus, epididymal maturation and capacitation are two extra steps that mammaliam spermatozoa must take before they can effect fertilization. In this chapter, I will discuss how mammalian spermatozoa prepare themselves for fertilization and how the spermatozoa and eggs interact during fertilization. The process and mechanisms of sperm transport in the female genital tract will not be dealt with extensively here. Readers are referred to Bishop (1961, 1969), Blandau (1969), Bedford (1970b, 1972b), Thibault (1972, 1973a), Zamboni (1972), Blandau and Gaddum-Rosse (1974), Hafez and Thibault (1975), Overstreet and Katz (1977), Overstreet and Cooper (1978, 1979b), Overstreet et al. (1978), Shalgi and Kraicer(1978), Cooper et al. (1979) and Hunter (1975, 1980). The rejection or elimination of extra spermatozoa by the fertilized egg, one of the most fascinating events in fertilization, will not be discussed here. Instead, readers are referred to the chapter by Dr. Wolf in this volume. The physiology of egg activation has been described and discussed to some extent by Gwatkin (1977) and Yanagimachi (1978a). There are numerous reviews dealing with general aspects of mammalian fertilization. The following are recommended to aid in grasping the outline of mammalian fertilization: Austin and Bishop (1957), Austin and Walton (1960), Austin (1961, 1968), Blandau (1961), Piko (1969), Thibault (1969), Bedford (1970a,b, 1972b), Gwatkin (1976, 1977), Yanagimachi (1977, 1978a), Bedford and Cooper (1978) and Hunter (1980).

Mechanisms of Fertilization in Mammals

Receptors for Ricinus communis agglutinin I (RCAI), concanavalin A (Con A), and wheat germ agglutinin (WGA) were localized on the zonae pellucidae and plasma membranes of hamster, mouse, and rat eggs with ferritin-lectin conjugates Intact eggs labeled with the ferritin conjugates showed dense concentrations of RCAI and WGA receptors in the outermost regions of their zonae pellucidae and sparse distributions of Con A receptors throughout the zonae Ferritin-lectin labeling was specific, since inhibitory saccharides effectively blocked labeling The asymmetric density of RCAI receptors across the zona was confirmed by ferritin-RCAI and fluorescein-RCAI labeling of mechanically isolated zonae pellucidae, indicating that the RCAI-binding sites are more densely distributed in the exterior zona regions Plasma membranes of rodent eggs contained RCAI, WGA, and Con A receptors These receptors were found to be more or less randomly distributed on surfaces of aldehyde-fixed eggs or on eggs labeled near 0 degrees C However, eggs incubated at 25 degrees C showed aggregated WGA- and Con A-binding site distributions on their plasma membranes This indicates that lectin-induced receptor redistribution occurs at this temperature The possibility that plasma membrane receptor mobility is a requirement for sperm-egg fusion is discussed

https://rupress.org/jcb/article-pdf/66/2/263/1387131/263.pdf

Ultrastructural localization of lectin-binding sites on the zonae pellucidae and plasma membranes of mammalian eggs.

Potential Value of Plants as Sources of New Antifertility Agents II

The molecular mechanisms used by the gonococcus to initiate infection exhibit gender specificity. The clinical presentations of disease are also strikingly different upon comparison of gonococcal urethritis to gonococcal cervicitis. An intimate association occurs between the gonococcus and the urethral epithelium and is mediated by the asialoglycoprotein receptor. Gonococcal interaction with the urethral epithelia cell triggers cytokine release, which promotes neutrophil influx and an inflammatory response. Similarly, gonococcal infection of the upper female genital tract also results in inflammation. Gonococci invade the nonciliated epithelia, and the ciliated cells are subjected to the cytotoxic effects of tumor necrosis factor alpha induced by gonococcal peptidoglycan and lipooligosaccharide. In contrast, gonococcal infection of the lower female genital tract is typically asymptomatic. This is in part the result of the ability of the gonococcus to subvert the alternative pathway of complement present in the lower female genital tract. Gonococcal engagement of complement receptor 3 on the cervical epithelia results in membrane ruffling and does not promote inflammation. A model of gonococcal pathogenesis is presented in the context of the male and female human urogenital tracts.

The Molecular Mechanisms Used by Neisseria gonorrhoeae To Initiate Infection Differ between Men and Women

Spermatozoa from bulls, boars, dogs, horses, mice, and men were examined using a fluorogenic stain consisting of the membrane-permeant substrate carboxyfluorescin diacetate (CFDA) and the relatively membrane-impermeant nuclear stain propidium iodide (PI). Three distinct populations of spermatozoa were discernible in samples from each species upon microscopic examination. Individual spermatozoa, presumed to be viable because of their motility, retained products of the fluorescein chromophore throughout the cell. A second population of spermatozoa in which the nuclei stained red with PI retained the green fluorescein fluorophore mainly in the acrosome. A third population, presumed to be degenerate spermatozoa, possessed only red fluorescent nuclei. These populations were quantified using dual parameter flow cytometry in 14 samples of cryopreserved bovine spermatozoa for which fertility and seminal quality data were available. Flow cytometric analyses were highly correlated with other seminal quality measurements. Sequential flow cytometric analyses provided the ability to rapidly quantitate changes in specific fluorescently stained populations. The ability to make rapid quantitative measurements should allow development of new and presumably more reliable information on the functional aspects of spermatozoa.

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Assessment of spermatozoal function using dual fluorescent staining and flow cytometric analyses.

Synthetic enzyme inhibitors as antifertility agents

Acrosin is a proteolytic enzyme extractable from sperm acrosomes and essential for penetration of the zona pellucida of the ovum by spermatozoa. It has properties in common with both trypsin and plasmin having an optimum pH of 8.0, hydrolyzing benzoyl arginme ethyl ester (BAEE) and tosyl arginine methyl ester (TAME) but not benzoyl tyrosine ethyl ester (BTEE), or acetyl tyrosine ethyl ester (ATEE), being stimulated by calcium ions and stable at pH 3.0. Acrosin differs from pancreatic trypsin in that it hydrolyzes BAEE more rapidly than TAME, is less effectively inhibited by ovomucoid and pancreatic trypsin inhibitor, has a higher molecular weight, undergoes rapid loss of activity even in the presence of calcium and produces fewer peptides on incubation with oxidized nbonuclease. One of two trypsin inhibitors isolated from guinea pig seminal vesicles inhibits acrosin and trypsin but not plasmin, whereas the other inhibits all three enzymes. Acrosin further differs from plasmin in that it has a different molecular weight and is more unstable. Inhibition by diisopropyl fluorophosphate and tosyl lysine chloromethyl ketone shows a similarity to trypsins and lack of inhibition by tosyl phenylalanine chloromethyl ketone indicates that acrosin is not chymotrypsin-like. The enzyme is also inhibited by soybean trypsin inhibitor. Acrosin appears to be a unique proteolytic enzyme and therefore deserves a specific name. Previously we described the purification of an acrosomal trypsin-like enzyme, acrosin, from epididymal sperm with a molecular weight of 55,000 (Polakoski et a!., 1971). The presence of such a proteolytic enzyme in sperm was first reported by Yamane (1935a, b) and shown to be trypsin-like by Buruiana (1956). Hartree and Srivastava (1965), and Srivastava, Adams, and Hartree (1965) showed that acrosomal extracts prepared from ram sperm removed the zona pellucida from rabbit ova in vitro. Stambaugh and Buckley (1968, 1969) confirmed these results using similar extracts prepared from epididymal rabbit sperm. These authors showed that the protease demonstrated to be localized in acrosomal extracts by Srivastava ci a!. (1965) was trypsin-like in nature and responsible for the removal of the zona. It is most likely the same enzyme studied by Buruiana (1956). In vitro fertilization was inhibited by soybean trypsin inhibitor (Stambaugh ci a!., 1969). Fertilization in vivo was inhibited by preincubation of capacitated sperm with pancreatic tryp

/pdf/properties-of-a-proteolytic-enzyme-from-rabbit-sperm-4o0q66yrdp.pdf

Properties of a Proteolytic Enzyme From Rabbit Sperm Acrosomes

/pdf/purification-of-a-proteolytic-enzyme-from-rabbit-acrosomes-4u4kas99r0.pdf

Purification of a Proteolytic Enzyme From Rabbit Acrosomes

Mammalian sperm acrosomal neuraminidases.

Acrosome extracts obtained by treatment of ejaculated rabbit and human sperm with detergents contain an enzyme which disperses the corona radiata of the rabbit ovum. The enzyme was designated corona penetrating enzyme, CPE. The effects of the extracts on the corona was not due to hyaluronidase or a trypsin-like enzyme (TLE) which are also associated with the sperm acrosome. CPE activity is destroyed by boiling. The enzyme is unstable at 4 or -20 C but is stable at -70 C or in the lyophilized form. DEAE-cellulose column chromatography of acrosomal preparations showed two protein components, only one possessing CPE activity. The fraction containing CPE was shown by disc electrophoresis to consist of two protein bands. This component dispersed the corona much faster than the crude acrosomal preparations. Although no TLE activity was present in the crude acrosomal extracts, TLE activity was found in the active CPE fraction after DEAE chromatography. This fraction removed the zona as well as the corona. Soybean trypsin inhibitor prevented the removal of the zona but not the corona by this preparation. Seminal plasma and partially purified decapacitation factor (DF), a substance from seminal plasma that renders sperm incapable of penetrating ova, inhibited CPE activity but not hyaluronidase or TLE. Acid-inactivated DF and uterine fluids did not inhibit CPE.

L. J. D. Zaneveld

Papers

Synthetic enzyme inhibitors as antifertility agents

Properties of a Proteolytic Enzyme From Rabbit Sperm Acrosomes

Purification of a Proteolytic Enzyme From Rabbit Acrosomes

Mammalian sperm acrosomal neuraminidases.

A Sperm Enzyme That Disperses the Corona Radiata and Its Inhibition by Decapacitation Factor