746 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



dates. 232 While these workers prepared 1300 to 1600 g. of a crude sphingo- 

 myelin-cerebroside mixture from beef brain, they were able to separate 

 approximately twice this amount from spinal cords. Johnson et al. Ml 

 suggest that sphingomyelin, together with cholesterol and cerebroside, 

 rather than lecithins and cephalins, form the basis of "myelin." 



Sphingomyelin prepared from the brain apparently has a different 

 composition from that obtained from other tissues. Thus, Thannhauser 

 and Boncoddo 233 proved that brain sphingomyelin, prepared in such a 

 manner as to exclude hydrolecithin, which had previously been an invari- 

 able contaminant in preparations made by the earlier procedures, contained 

 stearic, nervonic, and lignoceric acids. In contradistinction to this finding, 

 sphingomyelin from lung or spleen contained only palmitic and lignoceric 

 acids. Both spleen and brain sphingomyelin contained dihydrosphingo- 

 sine, as well as the usual unsaturated sphingosine. According to Carter 

 et al., 2U dihydrosphingosine is present in a higher concentration in spinal 

 cord than in brain. 



The phospholipid fatty acids in white and in gray matter have been 

 shown to differ in saturation. 235 Thus, the iodine value of the fatty acids 

 isolated from the phospholipids of frontal white matter was found to be 84, 

 as contrasted with a figure of 129 for the phospholipid fatty acids prepared 

 from frontal gray matter. 



A definite proportion of the phospholipids of beef brain has been shown 

 to consist of acetal phospholipids. Thannhauser and co-workers 236 were 

 able to demonstrate that these acetal phospholipids could be split cata- 

 lytically into aldehydes and glycerylphosphorylcolamine (glycerylphos- 

 phorylethanolamine) in the presence of mercury salts. Under these con- 

 ditions of hydrolysis, no migration of phosphoric acid was noted. The 

 compound was entirely of the a-configuration. Klenk and Bohm 224 also 

 reported that definite amounts of brain phospholipids consist of acetal 

 derivatives (plasmalogens) . The acetal phosphatides were found to occur 

 chiefly in the phosphatidylethanolamine fraction, in which the fatty acid : 

 aldehyde ratio was 2:1. In the case of phosphatidylserine, only small 

 amounts of the acetal compounds were found, corresponding to a fatty 



232 H. E. Carter, W. J. Haines, W. E. Ledyard, and W. P. Norris, /. Biol. Chem., 169, 

 77-82 (1947). 



233 S. J. Thannhauser and N. F. Boncoddo, /. Biol. Chem., 172, 141-147 (1948). 



234 H. E. Carter, W. P. Norris, F. J. Glick, G. E. Phillips, and R. Harris, J. Biol. 

 Chem., 170, 269-283 (1947). 



235 L. O. Randall, J. Biol. Chem., 124, 481-488 (1938). 



236 S. J. Thannhauser, N. F. Boncoddo, and G. Schmidt, /. Biol. Chem., 188, 423-426 

 (1951). 



