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L. E. FRANKLIN

Summary.

A lamella of granular endoplasmic reticulum was found to be associated with the outer surface of the Golgi apparatus of golden hamster spermatids during the period of acrosome production. The morphological situation during this period has some features in common with those reported in other cell types during the production of secretory granules, including lysosomes. Thus, the observations are compatible with the view that the acrosome is a specialized lysosome.

Stacked lamellae which resemble annulate lamellae were also found to be associated with the Golgi apparatus of some spermatids. The morphological variations observed are consistent with the possibility that annulate lamellae may in some cases undergo conversion into granular endoplasmic reticulum.

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PRUDENCE TALBOT and L. E. FRANKLIN

Hamster spermatozoa incubated in heat-pretreated blood serum release 55 to 60% of their total hyaluronidase activity by the end of 1 hr of incubation; little increase in activity is found in the incubation medium at later time intervals up to 4 hr (Rogers & Morton, 1973; Talbot & Franklin, 1974b). This release occurs well before and independently of a normal acrosome reaction, i.e. detachment of the acrosome from motile spermatozoa as observed with phase-contrast microscopy (Talbot & Franklin, 1974b). Vesiculation between the outer acrosomal membrane and plasma membrane does not occur before the surge of hyaluronidase release which takes place between time zero and 1 hr of incubation (Talbot & Franklin, 1974b).

Lewis & Ketchel (1972a, 1973) demonstrated that the release of hyaluronidase from rabbit spermatozoa incubated in postovulatory uterine fluid is "related to the completion

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PRUDENCE TALBOT, L. E. FRANKLIN and E. N. FUSSELL

Epididymal spermatozoa of the golden hamster can undergo the acrosome reaction and subsequently penetrate eggs in vitro in a variety of heat-pretreated blood sera (Yanagimachi, 1970; Barros & Garavagno, 1970).

This report describes the effect of varying sperm concentration on the acrosome reaction and sperm penetration of eggs in vitro using heat-pretreated (60°C for 1 hr) blood sera. The relationship between sperm concentration and occurrence of the acrosome reaction was examined in the blood sera of five mammalian species, including baboon, chimpanzee, hamster, rhesus monkey and rabbit (rabbit anti-hamster sperm-immune serum). Two additional experiments examined the relationship between sperm concentration and capacitation, i.e. the capacity, as classically defined, of spermatozoa to penetrate eggs (Text-fig. 3).

Stock sperm suspensions were collected in normal saline from lacerated cauda epididymidis. The sperm concentration of the stock suspension was determined turbidimetrically from a previously prepared standard concentration curve. The calculated standard error for this

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C. BARROS, A. M. VLIEGENTHART and L. E. FRANKLIN

The mechanisms for the prevention of polyspermy in mammalian eggs appear to be associated with the development of the so-called `zona reaction' (Braden, Austin & David, 1954) and with the development of a vitelline surface block to polyspermy (Austin & Braden, 1956). The time required for the development of the zona reaction has been estimated to be not less than 10 min and not more than 1½ to 2 hr (Braden et al., 1954).

Hamster eggs recovered from mated females show a low incidence (1·6%) of polyspermy (Austin & Braden, 1956) while eggs fertilized in vitro show a high incidence, often as high as 100% (Yanagimachi & Chang, 1964; Barros & Austin, 1967; Barros, 1968b; Yanagimachi, 1969).

It has not been established whether the high incidence of polyspermy in vitro is due to the penetration of several spermatozoa at the same time or to a continuous flow of spermatozoa