THE GROWTH-PROMOTING HORMONE 



the Jensen-sarcoma grows slowly in hypophysectomized rats 

 and even begins to retrogress 1-3 weeks after transplanta- 

 tion. If, however, growth-promoting hormone is administered 

 to tumor-bearing, hypophysectomized rats, the sarcoma be- 

 gins promptly to grow. Tumor-growth parallels body-growth 

 to some extent. 



Hofbauer (1930) attributed a proliferation of the squamous 

 epithelium of the portio vaginalis of the cervix to the admin- 

 istration of implants or extracts of the pars glandularis of the 

 ox. He believed that the changes produced resembled a 

 leukoplakia. He stated that implants or extracts produced 

 the same effect after bilateral ovariectomy. Hofbauer's ex- 

 periments were performed in guinea pigs. 



The assay of growth-promoting extracts of the pars glandu- 

 laris. — Most attempts to assay the growth-promoting hor- 

 mone have been made in rats, although mice have also been 

 used by a few investigators. A more or less qualitative recog- 

 nition of the presence of the hormone in an extract can be 

 accomplished without much difficulty. For such a purpose 

 either young hypophysectomized rats of either sex or normal 

 adult female rats should be used. For clear-cut results a 

 greater number of the latter is required. If injections are to 

 be made only for a few days, as by the method of van Dyke 

 and Wallen-Lawrence (1930),'^ it is best to use at least twen- 

 ty rats; if injections are carried on for a period of 3 weeks, five 

 or six rats are sufficient (Evans and Simpson, 1931). Obvi- 

 ously it is necessary to make certain that no growth (hypo- 

 physectomized rats) or very slow growth (normal adult fe- 

 male rats) is taking place before any injections are made. It 

 is also necessary that all the conditions of the experiment 

 (diet, time of feeding, temperature, etc.) be kept as constant 

 as possible. Young animals, provided that they meet the 

 description given above, are more sensitive than old animals. 

 Animals which have never been injected probably respond 

 better than animals which have already been used for assay. 



'^ Also see Simon and Binder (1932). 



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