76 The Biochemistry of Semen 



explained by spontaneous and irreversible senile decay due to the 

 gradual disruption of cellular organization, exhaustion of food 

 reserve, depletion of energy, and autointoxication with the reaction 

 products accumulated during the period of activity. He showed that 

 it is possible to delay the decline of activity by replacing the sea- 

 water with egg-water; a similar effect has been later demonstrated 

 with solutions of the egg-surrounding jelly. In this respect, however, 

 egg-water cannot be looked upon as a very specific agent. Both 

 sperm motility and respiration can be extended, for instance, by the 

 addition of seminal plasma, and there are several indications that 

 this is due to proteins and their breakdown products in the seminal 

 plasma. Hayashi (1945, 1946) experimenting with Arbacia punctu- 

 lata, demonstrated the occurrence in the seminal plasma of a non- 

 dialysable constituent beneficial to the viability and fertilizing 

 capacity of spermatozoa. Wicklund (1949, 1952) demonstrated a 

 favourable influence of serum albumin on the fertiUzing capacity of 

 sea-urchin spermatozoa; she found that the fertilizing power of 

 washed or aged sperm of Psammechinus miliaris was retained much 

 longer following dilution with albumin solutions than with sea- 

 water. Tyler (1950) and Tyler and Atkinson (1950) found that the 

 life-span of sea-urchin sperm can be considerably extended by the 

 addition of certain peptides and amino acids. Tyler and Rothschild 

 (1951) examined the sperm metabolism of Arbacia punctulata and 

 Lytechinus in sea-water enriched with amino acids and noted that 

 under such experimental conditions the initial increase of respira- 

 tion characteristic of the 'dilution effect', was less pronounced but 

 the subsequent decline in activity .was considerably delayed, and the 

 total amount of oxygen consumed greatly increased. These facts, 

 coupled with evidence of non-utilization of the added amino acids, 

 indicated that the amino acids enabled the spermatozoa to make 

 fuller use of their endogenous substrate, probably by inducing the 

 formation of complexes with copper and other toxic heavy metals 

 commonly present in sea-water. This hypothesis has gained addi- 

 tional support from the results of further work on the detoxicating 

 effect of metal-chelating agents such as ethylenediamine tetra- 

 acetate (versene), diethyldithiocarbamate, a-benzoinoxime (cupron) 

 and 8-hydroxyquinoline (Tyler, 1953). Perhaps the beneficial action 

 of proteins (Metz, 1945; Wicklund, 1949) and of seminal plasma 



