724 NITROGEN METABOLISM AND GROWTH 9 



three species of sea urchin, disappearing after 30 minutes. After seven hours 

 proteolytic activity is resumed and continues to increase to the pkiteus stage. 

 Perlman and Gustafson (1948) imply that antigen appearance does not occur 

 during the cleavage period. The pioneering study of Ephrussi and Rapkine (1928) 

 suggested a continuous utilization of protein during early development. That not 

 all of the disappearing protein is being diverted into other nitrogenous compounds 

 is apparent from the study of Hutchens et al. (1942) who describe substantial 

 amounts of ammonia production up to the pluteus stage in A. punctulata. Orstrom 

 (1937, 1941) describes production of ammonia and oxidation of amino acids to 

 keto acids. 



Kavanau (1953) also investigated the effects of lithium vegetalization upon 

 the free amino acids. He found that "the general effect is to damp or retard the 

 changes which normally occur. This would be consistent with an inhibition of 

 carbohydrate metabolism by Li'' for it suggests a greater utilization of protein 

 for energy". 



Hultin (1950b), investigating protein precursors, found that '^NH^Cl was 

 taken up initially at the same rate by unfertilized and fertilized eggs. However, 

 the unfertilized eggs became rapidly saturated, whereas the fertilized eggs 

 continued to take up the salt throughout the duration of the experiment, to 50 h. 

 The highest rate of uptake occurred in insoluble proteins, probably including 

 mitochondria and microsomes. Incorporation of the isotope occurred also in 

 water soluble proteins continuously to 50 h., with a somewhat more rapid rate 

 after 25 h. This, he felt, might be correlated with antigen formation at this time 

 as described by Perlman and Gustafson (1948). Less extensive experiments with 

 '^N-labeled glycine showed a distribution of the isotope during the same period 

 of development approximately parallel with that resulting from ^-''NH^Cl ad- 

 ministration. 



Although the interesting approach of Ranzi and his co-workers has application 

 as well to later stages of development, some of their conclusions have a bearing 

 on the processes of development prior to gastrulation. Ranzi has given attention 

 to the form of protein molecules and its correlation with morphogenesis. His 

 criteria for the alteration of the protein molecule consist of (j) concentration of 

 ammonium sulfate required for precipitation; (2) viscosity changes as measured 

 by the Ostwald viscosimeter, (j) flow birefringence, {4) optical density, (5) diazo 

 reaction, OH" reactions and change in immimological properties. Ranzi and 

 Citterio (1955) describe five protein fractions related to different stages of 

 development, of which four correspond to peaks in the salting-out curve of the 

 adult frog (0-25%; 25-45%; 45-70%; 70-85% saturation of (NH4)2S04; the 

 fifth consists of proteins which remain in solution in ainmonium sulfate of 85% 

 saturation). The four precipitable fractions are fibrillar or folded filamentous 

 particles; only the fraction which remains in solution in 85% saturation ammonium 

 sulfate consists of globular particles. Ranzi (1951) assigns to the change in form 

 of protein molecides from fibrillar to globidar a significant role in the "formation 

 of intercellular spaces", presumably including blastulation. He also points out 

 that LiCl vegetalization in both sea urchin and frog causes increased viscosity of 

 proteins (euglobulin a and b), whereas KSCN, an animalizing agent, causes a 



