im') 



p. COLDIIABER 



UJ 

 < 



O 



a: 

 o 



>- 



X 



< 

 o 



UJ 



Hydroxyproline- H found in media hydrolyzates of 

 parathyroid extract-treated cultures vs. controls 

 (DPM/ml whole media hydrolyzate) 

 500 



1200 - 



900 - 



PTE r0.5U/AfLJ+50% Or, 



^ 600 - 



O 



X 



d 300 



Q. 

 O 



DAYS 



Fig. 28B. Graph of hydroxyproline-H'' (DPM/ml whole media hydroly- 

 zate) found in media of parathyroid extract-treated cultures versus controls. 

 Note that peak release of labeled collagen occurs in media collected on the 

 4th day, which corresponds roughly to the period of most rapid bone resorption, 

 as visualized morphologically or as measured by determining the calcium level 

 in the media. (Data reproduced from Stern et ah, 1963rt, 1963/?.) 



form, but was recoverable both as small peptides and as the free 

 amino acid. 



Effect of Vitamin A 



It is well known that hypervitaminosis A can intensify bone re- 

 sorption in vivo, leading to bone deformities and fractures in the 

 rat (Barnicot and Datta, 1956). Although Barnicot's experiment con- 

 cerning the intracerebral implantation of combined fragments of 

 parietal bone and parathyroid gland tissue has been widely ac- 



