772 



SPERM. OVA, AND PREGNANCY 



strength (which completely inhibited mo- 

 tility, in vitro) fertilization occurred, al- 

 though at a low rate. Chang and Thorsteins- 

 son also studied the tolerance of sperm to 

 osmotic variation in relation to simulta- 

 neous changes in pH. In isotonic Krebs- 

 Ringer medium, rabbit sperm withstood 

 short exposure to acid or alkaline condi- 

 tions over a pH range of about 5.6 to 10.0, 

 based on observations of motility and con- 

 ception rate. Under hypo- or hypertonic 

 conditions, however, the upper limit of the 

 pH range tolerated was significantly de- 

 pressed. This work emphasizes once again 

 the unusual resistance or adaptation of the 

 mammalian germ cell to changes in ionic 

 environment. 



E. EFFECTS OF BIOLOGIC FLUIDS 



Some effects of certain biologic fluids 

 with which sperm come in contact have been 

 discussed in previous sections. It is clear, 

 for example, that seminal fructose serves 

 the gametes as glycolytic substrate at the 

 time of ejaculation; uterine fluid, or certain 

 of its components, aids in the capacitation 

 phenomenon of sperm during transport 

 through the genital tract. In studies of the 

 effect on fertilizing capacity, sperm have 

 been treated, in vitro, with seminal plasma, 

 urine, normal blood serum, and antisperm 

 serum, as well as with isolated products of 

 the female tract itself. 



The beneficial effect of seminal plasma 

 as sperm diluent, for example, was demon- 

 strated in the rabbit by Chang (1947b). 

 Tests on 33 rabbits showed the advantage 

 (percentage of fertilized eggs I of homolo- 

 gous plasma over saline when the does were 

 inseminated with a minimal number of 

 sperm. It was subsequently indicated that 

 heterologous plasma from human semen was 

 equally effective when used as a diluent for 

 rabbit sperm (Chang, 1949). Bull seminal 

 plasma, however, was injurious to rabbit 

 sperm and caused a significant reduction in 

 fertilizing capacity. It is not clear whether 

 the favorable action of plasma, when it 

 occurs, is due to a specific factor or set of 

 factors, or whether it is caused by a non- 

 specific action such as chelation by the 

 amino acid or polypeptide components pres- 

 ent. The role of chelating substances in 



extending the motility, metabolism, and 

 fertilizing capacity of sperm has been dem- 

 onstrated in several invertebrate and verte- 

 brate species (Lorenz and Tyler, 1951; 

 Tyler and Rothschild, 1951; Tyler and 

 Tanabe, 1952; Tyler, 1953; Rothschild and 

 Tyler, 1954). Such an effect was indeed sug- 

 gested by the work of Chang, since prepara- 

 tions of dead heterologous sperm were as 

 effective as seminal plasma in augmenting 

 fertility in the rabbit (Chang, 1949). These 

 findings may have some bearing on those 

 cases in which, it has been claimed, resus- 

 pension of human sperm in foreign plasma 

 improves motility and fertilizing capacity 

 (see Rozin, 1958). A possible detrimental 

 effect of seminal plasma on the fertilizing 

 capacity of sperm was indicated by the 

 demonstration of Chang (1957) that plasma 

 destroys or counteracts the capacitation re- 

 sponse of sperm within the rabbit genital 

 tract (see above). 



Although it is generally believed that 

 urine is harmful to spermatozoa, Chang and 

 Thorsteinsson (1958a) have shown that 

 rabbit sperm tolerate exposure to 50 per 

 cent urine for 10 to 15 minutes with no 

 disturbance in conception rate. A urine con- 

 centration of 75 per cent can seriously im- 

 pair sperm motility, in vitro, but even this 

 treatment does not prevent fertilization 

 when these same sperm are artificially in- 

 seminated into receptive does. 



As has long been known, normal blood 

 serum sometimes agglutinates spermatozoa, 

 usually in a head-to-head type of aggrega- 

 tion. This is regarded as a nonspecific ag- 

 glutination response, and the serum factor 

 which brings it about can be destroyed or 

 effectively reduced by heating to approxi- 

 mately 60°C. In an investigation of the 

 effects of sera on homologous and heterolo- 

 gous sperm, Chang (1947a) demonstrated 

 a complement-like agglutinating component 

 which generally was toxic to the sperm of 

 both its own and of other species; the one 

 exception was the factor in human serum 

 which was ineffective on human sperm. The 

 substance in rabbit serum was found chemi- 

 cally unstable, thermolabile, and nondialyz- 

 able. Such an agent was detectable in the 

 sera of man, bull, rabbit, guinea pig, and 

 rat; very little is known, however, concern- 



