236 Colchicine 



In the Langerhans' islets of the pancreas, pituitary stimulation 

 9-' '>" and pregnancy increase the number ot mitoses, as detected by 

 colchicine. 



It is surprising. to find no paper dealing ^vith mitotic stimulation 

 in the interstitial (Leydig) cells ot the testes. In guinea pigs injected 

 with chorionic gonadotropins, these cells increase in number, but 

 colchicine failed to detect mitoses. It was concluded that the hor- 

 mone-secreting cells originated from ordinary connective cells.^^ 

 Further work on this tissue is obviously needed. ^'^ 



9.5: Regeneration and Hypertrophy 



The problem which was under study in the laboratory of A. P. 

 Dustin, Sr., since about 1920 and which led to the discovery of the 

 properties of colchicine was that of the regulation of growth and 

 mitotic activity in pluricellular animals. In vertebrates, for instance, 

 cell division takes place only in some tissues, and then in an orderly 

 way. While in the adult, nerve cells become incapable of any mitosis, 

 other organs, such as the liver and the kidney, while nearly devoid 

 of any mitotic activity in normal conditions, may grow rapidly by 

 cellular multiplication after surgical excision. In the rodents, and 

 in ]jarticular the rat, large portions of the liver may be removed 

 surgically. The remaining cells start to divide at once, and regenera- 

 tion of the normal liver mass is remarkably rapid. -^ The exact de- 

 terminism of this cellular growth is unknown. This was one of the 

 first subjects to be studied with the help of colchicine as a tool for 

 a better analysis of mitotic activity. i»- -•'• -i- -- Hence, the work which 

 had been initiated in order to understand better such problems as 

 regenerative growth led indirectly to the discovery of a new tool, 

 colchicine, which was rapidly put to use in several countries. ^^^ ^^' ^^' *^ 

 The problems of cellular division in wound healing, which is closely 

 related to regeneration, will be considered in the next section of this 

 chapter. This work deserves special attention, for important results 

 aj)pear to have been often overlooked. Once again, colchicine was 

 taken up with enthusiasm as a new tool; new discoveries were made 

 possible, but only in a few instances w\as the study pursued long 

 enough to come near a solution of the problems.^i This field ap- 

 pears today as one of the most promising for futvne research. 



9.5-7.- Liver. In the rat, as much as 68 per cent of the liver 

 parenchyma may be removed surgically. After an initial period of 

 edematous swelling lasting about 24 hours, cell division takes place. 

 This type of growth has been extensively studied, for it lends itself 

 to quantitative estimations of the numbers of new cells formed each 

 day.'-^ The duration of mitosis was found to be between 48 and 53 

 minutes. After colchicine, many arrested mitoses are visible. Their 



