Sperm penetration

Although suppression of FSH and LH is the primary mechanism by which combined oral contraceptives prevent ovulation, there are other mechanisms by which these hormones work to prevent pregnancy. Other mechanisms include reduced penetration of the egg by sperm, reduced implantation of fertilized eggs, thickening of cervical mucus to prevent sperm penetration into the upper genital tract, and slowed tubal motility, which may delay transport of sperm.1 Thus, in... 

Summarized in Table 2 is the sperm penetration in cervical mucus data as a function of molecular structure for various polysaccharides, with the following observations ... 

Hydroxyethyl cellulose (A) or a mixture of carboxymethyl cellulose/ polyvinyl pyrrolidone (B) did not affect sperm penetration. These polymers do not contain a hydrophobic moiety. 

Cationic polymer C (hydroxyethyl cellulose with a cationic moiety without a hydrophobic group) has a minor effect on sperm penetration. 

Cationic/hydrophobe modified hydroxyethyl celluloses, (E) and (F), eliminate sperm penetration, even though they are not spermicidal. These DCEs physically impede sperm penetration, without affecting motility. 

TABLE 2. Molecular Structure Effects on Sperm Penetration [12],... 

Item Polymer Class Sperm Penetration in Cervical Mucus (% of Control)... 

The effect in (E) and (F) is primarily hydrophobe related, not cationic concentration related. (C) has a much higher cationic content than (E), but sperm penetration in the presence of (C) is significantly higher than (E). 

Ability to inhibit sperm penetration in cervical mucus [the Modified One End Test (MOET)]... 

A series of DCE-based formulations containing Igepal CO-630 Special (N9) and dextran sulfate (DS) were evaluated for in vitro contraceptive testing. Also included in the screening tests were placebos, N9, two commercial spermicidal products (Conceptrol and KY Plus), vaginal moisturizer products (KY Jelly and Replens ), and saline. Test results are summarized in Table 6. The N9-containing products exhibited similar spermicidal activity, as illustrated by the minimum effective concentration (MEC). Samples without N9 did not have spermicidal activity. DCE placebo vehicle inhibits sperm penetration into the cervical mucus, illustrated by the very low MOET values after 1 10 and 1 160 dilutions. This activity has not been reported for anionic or nonionic polymer vehicles. There are no striking differences... 

Interaction with the cervical mucus has been anticipated to be highest with cationic species [58], such as benzalkonium chloride, chlorhexidene, and vantocil (polyhexamethylene biguanide). A clear exception is the water-soluble sulfated polystyrene derivative (ORE 13904) [23]. In general, sperm penetration is lower for water-soluble cationic polymers than for anionic or nonionic polymers [59]. 

DCEs are not spermicidal. However, DCEs effectively impede sperm penetration (impedance). Incorporation of N9 facilitates impedance and confers cidal properties. 

Combination OCs - Combination OCs inhibit ovulation by suppressing the gonadotropins, FSH, and LH. Additionally, alterations in the genital tract, including cervical mucus (which inhibits sperm penetration) and the endometrium (which reduces the likelihood of implantation), may contribute to contraceptive effectiveness. 

Estrogenic effect. Hexane extract of the fruit, at a concentration of 5 nM, inhibited the binding of mibolerone and methyl-trienolone to androgen receptors "" Fertility effect. Tetrahydrofuran extract of the fruit, administered orally to hamster at a concentration of 9 mg/mL, reduced sperm penetration " . Zona-free hamster oocytes, pretreated with 0.6 mg/mL of St. John s wort at a concentration of 0.06 mg/mL, resulted... 

The acrosome reaction is the loss of the acrosomal and plasma membranes in the acrosome region and the release of acrosin, hyaluronidase and other enzymes that disperse the cumulus complex and allow the sperm to penetrate the zona pellucida. After capacitation and the acrosome reaction, sperm penetrate the extracellular cumulus matrix and bind with zona protein 3, a heavily glycosylated protein of the zona pellucida. The first segment of the sperm to make contact with the oolemma is usually the inner acrosomal membrane, followed by the postacrosomal region. The plasma membrane of the sperm attaches to microvilli on the oolemma. Sperm-egg fusion is apparent from reduced movement of the sperm tail (Yanagimachi, 1970,1988 Takano et al.,... 

Eggert-Kruse W, Leinhos G, Gerhard I, Tilgen W, Runnebaum (1989) Prognostic value of in vitro sperm penetration into hormonally standardized human cervical mucus. Fertil Steril, 61 317-323. 

C. L. Joyce, S. R. Mack, R. A. Anderson, and L. J. D. Zaneveld. Effect of hyaluronidase, -glucuronidase and P-N-acctylglucosaminidase inhibitors on sperm penetration of the mouse oocyte. BioL Reprtrd. Jt5 336 (1986). 

The m - and subsequent hydrolytic products of m -acrosin are not as susceptible to inhibition with these carbohydrates as is m -acrosin (53). These data provide evidence for a model for the penetration of ZP by sperm by a sequential binding, hydrolysis, and subsequent rebinding that would be necessary for sperm penetration of the ZP. 

H5. Hartshorne, G. M., Preovulatory follicular fluid relationships to ovarian stimulation protocol, fertilization, and sperm penetration in vitro. Fertil. Steril. 52,998—1005 (1989). 

The hostility of the thickened cervical mucus to sperm penetration has been used as a means to achieve contraception, and low-dose oral contraceptives depend largely on this condition for their effectiveness in fertility controlJ Sequential oral contraceptives do not affect mucus and like estrogen, may even increase sperm penetration. 

Katz, D. Slade, D. Nakajima, S. Analysis of preovulatory changes in cervical mucus hydration and sperm penetrability. Adv. Contraction 1997, 13 (2-3), 143-151. 

There have been only limited studies in humans and only rare anecdotal evidence of St. John s wort s effects on reproduction and lactation. A study using hamster oocytes incubated in either 0.06 or 0.6 mg/mL of hypericum extract for 1 hour showed normal sperm penetration at the lower concentration, whereas no penetration occurred at the higher concentration. Sperm incubated in the same concentrations for 1 week demonstrated sperm DNA... 

Tsukui S, Noda Y, Fukuda A, Matsumoto H, Tatsumi K, Mori T. Blocking effect of sperm immobilizing antibodies on sperm penetration of human zonae pellucidae. J In Vitro Fert Embryo Transf 1988 5 123-8. 

Intrauterine device—A device inserted in the uterus to prevent pregnancy, either through spermicidal action (copper device) or thickening cervical mucus to inhibit sperm penetration and migration (progesterone device). 

The union of ovum and spermatozoon is not a process in which the sperm penetrates by virtue of its mechanical properties, but one in which a particularly intimate arul specific biochemical reaction plays the chief role. 

Mammalian fertilization is the result of a precisely regulated series of cellular interactions. This process can be divided into a number of component stages, including the following (i) the early events that precede egg fusion, consisting of the preliminary event of sperm capacitation, sperm penetration of the cumulus oophorus, zona pellucida adhesion, initiation and completion of acrosome reactions, penetration of the zona pellucida, egg plasma membrane contact and fusion and (ii) the late events that occur within the egg that consist of sperm nuclear decondensation followed by pronuclear consolidation and syngamy. 

Sperm penetrate the zona pellucida only after completion of the acrosome reaction. A similar process occurs in nonmammalian species, where sperm must penetrate the vitelline coat. In abalone this is accomplished by release of lysin, an acrosomal protein that disperses the vitelline coat by a noncatalytic mechanism (Lewis et al., 1982 Shaw et al., 1993). In contrast, the generally accepted model for mammalian sperm penetration of the zona pellucida is the acrosin hypothesis in which proteolysis of zona pellucida matrix glycoproteins by acrosin, the acrosomal serine esterase, plays a trailblazing role in the sperm penetration process (Yanag-... 

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