16 Karl Bernhard 



The working up of the remaining hpid fractions yielded 

 large amounts of sphingomyelin and lecithin. 



The above observations point to the importance of deu- 

 terium as a tool in investigating clinical problems, especially 

 in relation to lipoidosis. 



REFERENCES 



Block, K., Borek, E., and Rittenberg, D. (1946). J. biol. Chem., 



162, 441. 

 Bloom, W., and Kern, Ruth (1926). Arch, intern. Med., 39, 456. 



DISCUSSION 



Rittenberg: If I understand Dr. Bernhard correctly his half-time 

 for the steroid in this particular organ was 8 days? That is what I 

 observed for serum cholesterol in the human, and I wonder whether 

 the identity of the two figures may not indicate a mobile equilibrium 

 between the spleen and the circulating plasma cholesterol? 



Bernhard: Unfortunately we could not get enough blood from the 

 patient for the isolation of plasma cholesterol. After all, the cholesterol 

 content of the spleen was 9 per cent under these conditions. I think 

 there was certainly much more cholesterol in the spleen than in the 

 blood. I believe that there really is a synthesis in the spleen and not a 

 transfer of cholesterol from the blood to the tumour. 



Block: Some years ago Dr. Rittenberg and I did some experiments, 

 which were never published, in which the half-life time of various organs 

 of the rat was studied by administration of deuterio-acetate. A very 

 high deuterium concentration was found in the cholesterol of the spleen. 

 The values for the spleen were very similar to those in liver and in 

 plasma, so that Rittenberg's suggestion of a rapid equilibrium between 

 plasma and spleen cholesterol sounds very reasonable. 



