THE PITUITARY BODY 



the rapid, dramatic changes which can be induced by an- 

 terior pituitary extract; however, this is hardly proof, as the 

 author suggests, that the mechanisms involved are differ- 

 ent. Extracts containing thyrotropic hormone probably facil- 

 itate the survival and growth of transplants as has again 

 been reported by Eitel (1936). According to Koch, Schreiber, 

 and Schreiber (1937), the peripheral growth of a transplant 

 of the thyroid in the guinea pig is facilitated, if thyroid and 

 pituitary tissue are transplanted together. 



For some years it has been known that the rate of mitotic 

 division of thyroid epithelium may be greatly increased in a 

 mammal like the guinea pig, if anterior pituitary extract 

 (thyrotropic hormone) be injected. An enormous change was 

 reported by Kippen and Loeb (1935), who injected anterior 

 pituitary extract into immature guinea pigs and removed the 

 thyroid gland 48 hours later. In comparison with the normal 

 thyroid in which was found an average of about 150 mitotic 

 figures, the thyroid of injected animals contained as many as 

 190,000 mitotic figures. The effects observed by Bastenie 

 and Zylberszac (1937) were clear cut but much less pro- 

 nounced. These authors also injected colchicine (about 0.8 

 mg. per kg. body-weight) to bring out clearly the action of 

 thyrotropic hormone on mitotic division. "^ Guinea pigs 

 weighing 220-250 gm. were used. In thyroid tissue from con- 

 trol animals 6.3 mitotic figures per 100 follicles were found. 

 The number increased to 16.8 after the injection of thyro- 

 tropic hormone. However, if both thyrotropic hormone and 

 colchicine were injected, 1 19 mitotic figures — in the prophase 

 for the most part — were found in 100 follicles. 



Halpern (1935) investigated the action of anterior pitui- 

 tary extract or KI on the appearance of the mitochondria 

 and Golgi apparatus of epithelium of the thyroid of rats 

 2.5-3 months old. 



' Bastenie and Zylberszac mention two interpretations of the manner in which 

 colchicine acts: it may bring about an increased rate of karyokinesis (Dustin) or it 

 may arrest karyokinesis before the process is completed (Allen and others). 



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