604 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



Stoneburg 381 investigated the lipid composition of cell nuclei. He em- 

 ployed a new technic of Crossmon, 382 in which the nuclei are ejected from 

 the cells when small pieces of tissue are placed in 5% citric acid solution. 

 Since the lipids are not water-soluble, the application of this procedure 

 should not result in a loss of any of the lipids from the freed nuclei. The 

 data of Stoneburg 381 are summarized in Table 20. 



Table 20 

 Average Lipid Analysis of Cell Nuclei on a Dry Basis" 



Source of nuclei 



Beef Rabbit 



heart thigh Tumor Pus 



Category muscle muscle cells cells 



Number of tests 6 8 6 1 



Acetone-sol. lipids 



Neutral fat and fatty acids — — — — 



Amount, % 6.5 1.8 18.0 26.0 



Iodine number 126 80 — — 



Cholesterol, % 3.6 3.6 4.6 2.5 



Acetone-insol. lipids 



Phospholipid, % 15.7 4.0 11.5 



Phospholipid fatty acids — — — — 



Amount, % 9.8 3.0 7.5 12.0 



Iodine number 70 70 30 27 



Phospholipid : cholesterol ratio 3.9 1.3 2.3 5.0 



a Adapted from C. A. Stoneburg, J. Biol. Chem., 129, 189-196 (1939). 



The nuclei were shown to contain considerable amounts of lipids ; these 

 were predominantly phospholipids and cholesterol. The lipid concentra- 

 tions of the nuclei tend to conform to those of the tissue from which they 

 were obtained, but at a higher level. 



Unfortunately, the Crossmon technic for removing the nuclei could not 

 be applied to liver cells. However, by the application of a different proce- 

 dure for the separation of the nuclei, Williams and his co-workers 383 were 

 able to study the lipid composition of the nuclei of the liver cells of normal 

 rats and dogs, and of rats previously treated with p-dimethylaminoazo- 

 benzene (butter yellow). It was found that the lipid pattern of the cell 

 nuclei differed from that of the whole liver. The structural or essential 

 lipids were shown to comprise 12 to 14% of the dry weight of the nuclei; 



381 C. A. Stoneburg, /. Biol. Chem., 129, 189-196 (1939). 



382 G. Crossmon, Science, 85, 250 (1937). 



383 H. H. Williams, M. Kaucher, A. J. Richards, E. Z. Moyer, and G. R. Sharpless, 

 J. Biol. Chem., 160, 227-232 (1945). 



