834 



SPERM, OVA, AND PREGNANCY 



to Austin and Bishop (1958) there are 

 changes in the optical properties of the 

 acrosomes of rabbit, rat, and hamster sper- 

 matozoa as they traverse the female repro- 

 ductive tract. When a sperm reaches the egg 

 in the ampulla, the acrosome is detached, 

 exposing the perforatorium. Austin and 

 Bishop propose that the acrosome is the 

 carrier of the enzyme hyaluronidase which 

 allows the sperm to depolymerize the hy- 

 aluronic acid jelly of the cumulus oophorus. 

 The exposed perforatorium, then, may be a 

 carrier of a lysin which may alter the physi- 

 cal characteristics of the zona pellucida so 

 that the sperm may pass through it. There 

 has been much speculation on the impor- 

 tance of capacitation in fertilization, but 

 there is little significant evidence to support 

 the various theories proposed (Chang, 

 1955a, b, and 1959b; Strauss, 1956). 



C. SPERM-EGG INTERACTING SUBSTANCES 



The phenomenon of agglutination by "egg 

 water" has been observed and described 

 many times for the spermatozoa of echino- 

 derms, annelids, molluscs, ascidians, cyclo- 

 stomes, fish, and amphibia (Rothschild, 

 1956; Tyler, 1957) . The compound in the egg 

 water responsible for tlie effect is derived 

 from a jelly-like membrane which is secreted 

 on the egg by the follicular cells. On ovula- 

 tion the jelly gradually dissolves in sea water 

 and composes the fertilizin first described by 

 Lillie (1919). Experiments with inverte- 

 brate eggs have demonstrated that fertilizin 

 is responsible for the specific sperm-agglu- 

 tinating power and for the initial specific 

 adherence of the sperm to the egg. One of 

 the interesting chapters in biology has been 

 the attempt to characterize the biologic and 

 chemical properties of these interacting 

 substances. 



Whether sperm-egg interacting substances 

 are present in the fluids forming the en- 

 vironment of ovulated mammalian eggs has 

 been very little investigated. Recently 

 Bishop and Tyler (1956) and Thibault and 

 Dauzier (1960) have reported the presence 

 of fertilizin in the eggs of rabbits, mice, and 

 cows. The reaction was found to be pri- 

 marily species specific and its source is 

 believed to be the zona pellucida. 



Much more experimental testing must be 



done to amplify knowledge in the field of 

 interacting substances of mammalian eggs 

 and spermatozoa. 



D. SPERM PENETRATION OF THE 

 VITELLINE MEMBRANE 



The penetration of a spermatozoon into 

 the ooplasm in vitro has been observed on so 

 few occasions in mammals that it is not yet 

 possible to give an accurate account of this 

 phenomenon. Pincus (1930) records a slight 

 bulging of the ooplasm in rabbit eggs at the 

 point where the head of the sperm made con- 

 tact with the vitelline membrane. Because 

 of the opacity of the egg cytoplasm, no fur- 

 ther i^rogress of the head could be observed. 

 Studying rat, mice, and hamster eggs, Austin 

 (195ibj and Austin and Braden (1956) de- 

 scribed a more or less passive penetration 

 of the ooplasm by the fertilizing spermato- 

 zoon, as if the ooplasm "pulled" the entire 

 sperm into its substance or "phagocytized" 

 it. Austin (1951b) and Austin and Bishop 

 (1957) ascribed some peculiar property to 

 the head of the sperm which results in its 

 being "absorbed" into the vitellus. The in- 

 vestigations of Dan (1950) on the changes 

 in the acrosome of the sea urchin at the time 

 of sperm penetration of the egg have an in- 

 teresting bearing on this problem. She be- 

 lieved that as the spermatozoon swims ac- 

 tively through the jelly layer of the egg, the 

 acrosome responds to the chemical stimula- 

 tion of the egg jelly by a localized break- 

 down of its membrane. By the time the 

 spermatozoon reaches the vitelline mem- 

 brane a few seconds later, it carries at its 

 tip a labile mass of lysin with which it effects 

 penetration of the ooplasm. 



The observations of Austin are at variance 

 with those made by others also in the rat and 

 in which it appeared that ooplasmic pene- 

 tration was accomplished primarily by the 

 activities of the flagellum of the fertilizing 

 sperm (Blandau and Odor, 1952). Although 

 discontinuous, the forward progression of 

 the spermatozoon into the ooplasm seemed 

 to depend on a propulsive type of undulating 

 movement of the tail which forced the head 

 forward a distance of 10 to 20 /x at a time. 

 While that portion of the flagellum within 

 the ooplasm was retarded in its amplitude 

 of motion by the viscosity of the egg cyto- 



