TABLE I 

 Metabolic and Structural Changes Upon Fertilization of Sea Urchin Eggs: 



A. Carbohydrates and Energy Metabolism 



1. Respiration rate increase 



2. Increased pentose shunt activity 



3. Increased content of glycolytic esters 



B. Cofactor and Coenzyme Metabolism 

 1 . TPNH increase 



2 . Free Ca' 



+2 



increase 



3 . K increase 



-3 

 i* . PC, uptake increase 



C. Synthetic Metabolism 



1. Increased rates of protein synthesis 



2. Increased rates of RNA synthesis 



3. Increased rate of lipid synthesis 



D. Structural and Physical Changes 



1. Cortical granule breakdown 



2. Changes in subcellular localization of 

 enzymes 



3. Fertilization acid excretion 



4. Proteolytic activity increase 



5. Membrane potential 



6. Light-scattering change in cortex 



References 



41 , 42 (review) , 

 14, 6 



39, 40 



29, 43 



9, 12 



34 



44 



45, 46 



47-53, 3 

 54- 5b 

 57 



19, 58 (reviews) 



32, 33 

 59, 22 



60 

 15, 16 



13 



coenzymes (as evidenced by increased TPNH), 

 by lack of respiratory substrate (as evidenced 

 by increased content of glycolytic esters, respi- 

 ration rate, etc.), by unavailability of substrate 

 to enzyme (as evidence by both structural 

 changes in cortex and intracellular location of 

 enzymes, as well as the transient proteolytic 

 activity), or possibly by presence of a general 

 inhibitor (as suggested by acid excretion or 

 proteolytic activity). 



To decide between these alternatives, a 

 kinetic analysis has been used and will be 

 described in this paper. Such an analysis, 

 aimed at describing the temporal sequence of 

 the fertilization reactions, should yield infor- 

 mation on possible mechanisms of activation. 

 Hypotheses derived from the kinetic analysis 

 can then be tested, hopefully leading to elucida- 

 tion of any primary reaction or reaction series 



of fertilization. These studies should also pro- 

 vide rigorous testing of hypotheses. As an 

 example, if the recent hypothesis relating pro- 

 teolytic activity to the post-fertilization initia- 

 tion of protein synthesis is correct (3), the 

 transient activation of proteolytic activity should 

 occur before the activation of protein synthesis. 

 To date, we have concentrated on the kine- 

 tics, mechanism, and metabolic significance of 

 changes in coenzymes, carbohydrate and res- 

 piratory metabolism, acid excretion, and struc- 

 tural changes. The methods we have used 

 measure in vivo changes in cell suspensions, 

 using procedures developed at the Johnson 

 Foundation of the University of Pennsylvania 

 (4, 5). The basic equipment consists of awater- 

 jacketted glass cuvette, into which is placed a 

 concentrated suspension of eggs. From the side 

 of this cuvette, optical measurement of light- 



18 



