546 Energy Exchange and Enzyme Development During Embryogenesis 



Because of its unique relation to the mech- 

 anism of muscular contraction, ATPase has 

 been extensively investigated. Moog and 

 Steinbach ('45) showed that the ATPase 

 activity of early chick embryos is low but 

 rises on the sixth day, and an attempt was 

 made to correlate this with the development 

 of spontaneous muscular activity. Later, 

 Moog ('47) showed that the temporal pattern 

 of development of the enzyme was different 



in concentration of actomyosin, with which 

 it supposedly was associated, and this strong- 

 ly suggested that some of the ATPase in 

 muscle was not combined with actomyosin. 

 That this was true was then shown by Herr- 

 mann, Nicholas, and Vosgian ('49). The 

 demonstration by Kielley and Meyerhof 

 ('48) of two ATPases in muscle, one asso- 

 ciated with actomyosin, the other with cell 

 particulates, and the findings of Herrmann, 



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 < cr 



o 

 o "- 



Z z 



Ul - 



o 



0.9 



0.8 



0.5 



0.4 



0.2 



PREMOTILE EARLY 

 FLEXURE 



SINGLE 

 COIL 



DOUBLE 

 COIL 



EARLY 

 SWIM 



STRONG 

 SWIM 



Fig. 204. The relation between development of cholinesterase and neuromuscular activity in Amblystoma 

 punctatum. Ordinate denotes enzyme activity; abscissa, sequence of behavioral manifestations. (After 

 Sawyer, '43.) 



in brain, liver, and muscle, and this could 

 to some extent be correlated with the time 

 of functional differentiation of the various 

 organs. In the case of muscle, "the enzyme 

 reaches its maximum level on the very day 

 that the muscles are . . . called upon to 

 work in the business of hatching" (Moog, 

 '52). 



In the developing rat, correlation of 

 ATPase with functional differentiation is 

 more clearly indicated. Herrmann and Nich- 

 olas ('48a) showed that ATPase was at a 

 very low level tmtil the sixteenth day when, 

 coincident with the beginning of muscle 

 contractility, it rose sharply and continued 

 to increase for approximately three weeks 

 after birth. They fovmd in addition (Herr- 

 mann and Nicholas, '48b) that the rise in 

 ATPase did not run parallel with increase 



Nicholas, and Vosgian were taken as a 

 point of departure by deVillafranca ('53) 

 in a study of the course of development of 

 the two enzymes. The two ATPases can be 

 distinguished not only by their differential 

 location, but also by differences in pH op- 

 tima and ion activation. Although the two 

 enzymes begin to develop in activity at the 

 same time, that is, at the onset of contrac- 

 tility, as shown by Herrman and Nicholas, 

 the course of increase is different. Acto- 

 myosin ATPase increases more slowly, and 

 somewhat in parallel with the actomyosin 

 curve of Herrmann and Nicholas, while 

 particulate ATPase develops more rapidly. 

 The function of the actomyosin ATPase 

 seems quite clear; that of particulate ATPase 

 is more obscure. It may be suggested that 

 it operates for release of energy in general 



