24 



Ch. M. Lapiere 



into fractions of different density by flotation in liquids of different composition. 

 Using this technique they have been able to demonstrate that calcium metabolism is 

 partly related to the exchange properties of these different fractions with the body 

 fluid (RiCHELLE and Bronner, 1963). Hormones which are known to modify the 

 composition of bone affect these components at different rates (Richelle, 1964). 

 These results emphasize a difference in reactivity of the fractions of bone demonstrat- 

 ing the efficacy of the technique to investigate the metabolism and the organization 



Table 1. Calcium and Collagen in Bone Fractionated by Gradient Density 



' Between brackets, amount in mg. per fraction. 



Table 1. Distribution of calcium and collagen in total bone of sixty day old rats and in fractions obtained by 

 gradient density of ground bone (Upper values of each section in percent of the total and lower figures in mg. 



from 100 mg. of bone) 



Table 2. Specific Activity (S. A.) of the Collagen Hydroxyproline in Bone Fractionated by 



Gradient Density 



' S.A. of hydroxyproline in dpm//(M. 



^ Represent the factor by which the S.A. of the hydroxyproline of the total bo 

 obtain the real ,S.A. of the hydroxyproline in the fraction. 



Table 2. Explanation in the tcx 



be multiplied to 



The maximum relative specific activity of the collagen in the tr 

 framed inside of the heavv lines 



of the calcified tissues. Together with Richelle and Onckelinx we are applying this 

 technique of investigation to the study of bone collagen metabolism in rats. 



The particles of different density from diaphysal bone of 60 day old rats contain 

 different proportions of the total collagen and calcium (Table 1) in increasing amount 



