§ 5.222 PROTEIN METABOLISM 203 



if the apparent difference in nitrogen excretion in the intermoult 

 and moulting periods may be taken as vaHd. 



The intermoult period is characterized by secretion of the 

 moult-inhibiting hormone, MIH, and the lack of any Y-organ 

 secretion. Removal of the eyestalk, or even of the sinus gland, 

 allows the Y-organ to come slowly into action. Normal moulting 

 occurs when the secretion of MIH stops naturally and the moult- 

 promoting hormone, MPH, from the Y-organ becomes active 

 (§4.211 and Table 24). 



From this it appears that during intermoult, the amount of protein 

 catabolism, probably accompanied by steady synthesis, is restrained 

 by MIH (as has been postulated) since lack of MIH results in 

 increased catabolism. During moulting, catabolism and N-excretion 

 are practically inhibited ; since this cannot be attributed to the lack 

 of MIH, it may perhaps be correlated with the presence of MPH 

 from the Y-organ, which was absent during the intermoult period 

 but is now active. The lack of excretion at this stage is accompanied 

 by evidence of transfer of proteins to the new integument, and is a 

 process so clearly related to moulting that it might well be under 

 the control of the moult-promoting hormone. 



5.222 Increase in protein synthesis 



Insecta. Evidence from both Periplaneta (Bodenstein, 1953) 

 and Calliphora shows that removal of either the median neuro- 

 secretory CELLS OF THE BRAIN or of their stored products in the 

 CORPORA CARDIACA rcsults in reduced protein synthesis ; in Peri- 

 planeta this is show^n rather indirectly by the disappearance of 

 urates from the fat bodies, and their re-formation after re- 

 implantation of the corpora cardiaca. In Calliphora an effect upon 

 protein synthesis is deduced from the reduction or cessation of 

 growth of the ovaries, accessory glands, oenocytes and corpora 

 allata after ablation of the neurosecretory cells (E. Thomsen, 1952 

 and 1956). The effect is similar to that of keeping the flies on a 

 protein-free diet of sugar and water. The effect of removing the 

 corpus cardiacum is similar to, but not so profound as, removing 

 the source of the neurosecretion. 



The removal of the corpora allata of Carausiiis is followed by 

 an increase in amino acids in the tissues, which is interpreted as 



