770 



SPERM. OVA, AND PREGNANCY 



of uncoupling agents which include sulf- 

 liyclryl-blocking agents, hormones {e.g., thy- 

 roxine), antibiotics, and surface-active sub- 

 stances (Mann, 1954, 1958bj. Other types 

 of environmental factors which induce pro- 

 found effects on sperm behavior involve di- 

 lution of the cell suspension, temperature 

 changes, ionizing radiation, and certain bio- 

 logic fluids and cell extracts. 



The action of such agents on sperm mo- 

 tility and metabolic activity, but not neces- 

 sarily on fertilizing capacity, is reviewed in 

 detail elsewhere (Hartman, 1939; Mann. 

 1954; Bishop, 1961) ; the effect on fertilizhig 

 capacity per se will be briefly presented 

 here. Alteration of the fertility rate by pre- 

 treatment of spermatozoa is, of course, an 

 established procedure. In an extreme sense, 

 this is accomplished by the extension of the 

 life span of sperm for purposes of artificial 

 insemination (Anderson, 1945; Emmens and 

 Blackshaw, 1956; Salisbury, 1957), or, con- 

 versely, the curtailment of survival by 

 spermicidal agents (Mann, 1958b; Jackson, 

 1959). 



A. DILUTION OF THE SPERM SUSPENSION 



Chang (1946a) drew attention to the di- 

 lution effect on mammalian sperm by dem- 

 onstrating that artificial insemination of 

 rabbits was successful with a given number 

 of sperm suspended in a small amount (0.1 

 ml.) of saline medium, whereas the same 

 number of sperm in a larger volume (1.0 

 ml.) failed to bring about fertilization. 

 Mann (1954) suggested that the dilution 

 effect in mammalian sperm might in part 

 be the same general type of response as that 

 occurring in invertebrate sperm, in which 

 the phenomenon has been extensively inves- 

 tigated (Gray, 1928; Hayashi, 1945; Roths- 

 child, 1948, 1956a, b; Rothschild and Tuft, 

 1950; Mohri, 1956a, b). The studies of 

 mamn:ialian sperm by Emmens and Swyer 

 (1948), Blackshaw (1953a), and White 

 (1953) indicate that some essential sub- 

 stance, or substances, is lost during dilution 

 of the sperm suspension. Such loss can be 

 partially counteracted by the addition to 

 the diluent of K+ (Blackshaw, 1953b; 

 White, 1953) or of seminal plasma or cer- 

 tain large molecular compounds (Chang, 

 1959). The nature of the loss, the protective 



effect of colloidal substances, and the in- 

 tracellular changes involved in the dilution 

 eft'ect in mammalian sperm are still obscure. 

 The alterations in the sperm are probably 

 not mere physical changes but rather chemi- 

 cal alterations wdiich involve the metabolic 

 state. The dilution phenomenon in inverte- 

 brate spermatozoa, for example, seems to in- 

 volve an activation of the cytochrome sys- 

 tem or other changes in respiratory pattern 

 induced by such factors as pH or copper 

 ions of sea water (Rothschild, 1950, 1956b). 

 Rothschild (1959) has shown an increase in 

 both the initial heat production and [pro- 

 longed heat production of bull sperm diluted 

 1:3 with balanced saline solution, compared 

 with the heat output of sperm in seminal 

 plasma. 



B. TEMPERATURE EFFECTS 



Numerous studies have indicated a direct 

 effect of temperature change on the overt 

 behavior and survival of spermatozoa, but 

 little attention has been directed toward the 

 possible effect on fertilizing capacity of pre- 

 treatment of the gametes. One earlier in- 

 vestigation (Young, 1929c) indicated that 

 exposure of guinea pig sperm in the epididy- 

 mis to 45°C. for 30 minutes reduced the fer- 

 tility rate, and treatment at 47°C. seriously 

 impaired motility; nevertheless, those em- 

 bryos which were produced by females in- 

 seminated with sperm treated at 45 to 46°C. 

 were apparently normal. Hagstrom and 

 Hagstrom (1959) recently demonstrated 

 that the fertilization rate of sea urchins is 

 enhanced by exposure of sperm to either 

 slight increases or decreases in temperature 

 before union of the gametes. The pro- 

 nounced temperature changes to which 

 sperm are exposed during vitrification are 

 of a far different order of magnitude and 

 are surprisingly well tolerated when prop- 

 erly controlled (see Artificial Insemination) . 



C. IONIZING RADIATION 



When very severe, irradiation can lead to 

 impairment of motility and metabolism in 

 animal spermatozoa; lower doses induce 

 change in nuclear components with conse- 

 ciuent abnormalities in development. Hert- 

 wig (1911) first demonstrated the paradoxi- 

 cal effect of fertilizing frog eggs with sperm 



