CHAPTER 9 



Experimental Growth, in Animals 



9.1: Endocrinological Research 



One ot the most striking features of colciiicine, wliettier injected 

 into animais or acting upon tissue cultures,--^ is ttie accumuiation of 

 mitoses arrested at metaphase (Fig. 9.1) . Tiiis is a consequence of tlie 

 absence of spindle (cf. Cliapter 3) . The increase in the number of 

 mitotic cells was soon understood to be most useful for the analysis 

 of growth by cellular multiplication. Several lines of research were 

 started in the years 1934-36. At this time, the isolation and the 

 synthesis of hormones were proceeding rapidly, in particular, the 

 steroid hormones of the sexual glands. These substances have most 

 powerful physiological effects, the principal being to stimulate cells 

 to increase the rate of appearance of new mitoses. Now, ordinary 

 histological technicjues give only an instantaneous picture of the 

 state of the tissues at one given moment. If the cell divisions proceed 

 very .rapidly, there will be small chance of observing them in a micro- 

 scopic slide. Colchicine, by arresting all these rapid cellular changes, 

 would be able to let the mitoses progressively accumulate in a given 

 tissue. Counting would be easier, and easier also the localization of 

 regions of maximal growth. 



While several authors understood the uscfidness of colchicine as 

 a tool for the study of growth, the largest amotnit of work was done 

 in the field of endocrinology. Allen, Smith, and Gardner- are to be 

 credited with the publication, in 1937, of an excellent paper with 

 splendid photomicrographs that gave added impetus to research with 

 this new technique. They were studying the action of estrogens in 

 the mouse. After injecting the still chemically impure hormone of 

 that type at their disposal, "theelin," they observed that colchicine in- 

 creased tremendously the visible mitotic action in tissue sections. In 

 the vaginal epithelium, they mention "a most incredible number of 

 mitoses." * In a single transverse section of the vagina, controls in- 



* E. Allen, M. Smith, and W. V. Gardner, "Accentuation of the Growth Effect 

 of Theelin on Genital Tissues of the Ovariectomized Mouse by Arrest of Mitosis 

 With Colchicine," Amer. Jour. Anat., 61 (1937) , p. 324. 



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