BIOLOGY OF SPERMATOZOA 



771 



exposed to radium emanations. At lower 

 levels of treatment, abnormal young were 

 produced, increasing in percentage and se- 

 verity with increase in dosage. At high levels 

 of radiation, normal young developed. The 

 latter effect was attributed to the parthcno- 

 genetic development of eggs stimulated by 

 sperm incapable of participating in fertili- 

 zation. This was confirmed by Rugh (1939) 

 who found an increase in embryonic al)nor- 

 mality and death following fertilization by 

 sperm x-irradiated with doses from 15 to 

 10,000 r; sperm treated with 50,000 r, how- 

 ever, failed to enter the eggs and a high 

 proportion (91 per cent) of the partheno- 

 genetic young were viable. 



Since parthenogenesis is not readily in- 

 duced in mammals, no such paradoxical 

 effect is to be expected. Impairment of fer- 

 tilization and induction of embryonic ab- 

 normalities have, however, been caused by 

 x-irradiation of sperm in vitro. Irradiation 

 of rabbit and mouse sperm induced changes 

 as manifested by embryonic abnormalities 

 and chromosomal aberrations after fertili- 

 zation of normal eggs (Amoroso and Parkes, 

 1947; Bruce and Austin, 1956). y-Radiation 

 when administered at doses of 32,000 to 

 65,000 r from a radiocobalt source depressed 

 the motility of rabbit sperm (Chang, Hunt 

 and Romanoff, 1957). After treatment with 

 these high exposures, the sperm that were 

 able to reach the ova showed little if any 

 impairment in fertilizing cai^acity. How- 

 ever, even at a dosage of 800 r, blastocyst 

 formation was retarded, and at 6500 r it 

 was prevented altogether. Johansson (1946) 

 had reported similar findings in fowl; high 

 levels of x-irradiation (3000 to 12,000 r) 

 reduced motility of sperm, whereas rela- 

 tively low levels (600 to 1200 r) impaired 

 development. The w^ork of Edwards (1954- 

 1957) on the mouse indicates that irradia- 

 tion, either x-ray or ultraviolet (nonioniz- 

 ing), while permitting fertilization, can 

 render the male gamete incapable of taking 

 part in development. Comparable radiomi- 

 metic effects were obtained by treatment of 

 mouse sperm with either trypaflavine or 

 toluidine blue (Edwards, 1958). 



The effect of irradiation in mammalian 

 sperm may be similar to that suggested for 

 invertebrate sperm. At certain levels of x- 



irradiation the fertilizing capacity of sea 

 urchin sperm is reduced, and the cause has 

 been attributed to the formation in the 

 medium of hydrogen peroxide, produced by 

 splitting of water molecules and recombina- 

 tion of free radicals (Evans, 1947). It has 

 also been suggested that stable organic per- 

 oxides, rather than hydrogen peroxide, are 

 formed and that these are toxic to sperm, 

 possibly acting by the oxidation of enzy- 

 matic sulfhydryl groups (Barron, Nelson 

 and Ardao, 1948; Barron and Dickman, 

 1949; Barron, Flood and Gasvoda, 1949). 



D. IONIC AXD OSMOTIC EFFECTS 



Despite a mass of data concerning the 

 action of electrolytes and pH changes on 

 sperm motility, and recently on sperm heat 

 production (Rothschild, 1959), relatively 

 little has been done to assess the fertilizing 

 capacity of pretreated sperm. Although cer- 

 tain ions in excess seem to have unusually 

 detrimental effects on sperm survival, in 

 vitro — for example, calcium, manganese, 

 lithium, and chloride (Lardy and Phillips, 

 1943; MacLeod, Swan and Aitken, 1949) — 

 of more surprising interest is the general 

 resistance of sperm to nonbalanced saline 

 media (see Bishop, 1961 ). Rabbit sperm, for 

 instance, can tolerate 2.0 per cent NaCl for 

 many hours if brought gradually into the 

 hypertonic medium (Anderson, 1945), and 

 bull sperm retain motility for several hours 

 in isotonic KCl. Determinations of the de- 

 gree to which fertilizing capacity is affected 

 by such treatment might yield very signifi- 

 cant results. 



Chang and Thorsteinsson (19581)) have 

 made an important beginning with this aim 

 in view. They found that the fertilizing 

 capacity of rabbit sperm is unimpaired by 

 exposure for brief periods (10 to 20 min- 

 utes) before insemination in Krebs-Ringer 

 solutions of one-half or twice isotonic con- 

 centration. Of jiarticular interest was the 

 finding that motility, but not fertility, was 

 dein-essed by treatment with the hypertonic 

 medium ; one can assume that some re- 

 covery occui'red in the female tract. Beyond 

 the limits of this range of tonicity, fertiliz- 

 ing capacity was reduced, as judged by ob- 

 servation of recovered tubal eggs; yet even 

 witli solutions 0.1 oi' 4 times isotonic 



