760 VII. LIPID DISTRIBUTION IN SPECIFIC TISSUES 



cholesterol levels were noted in areas of high psychic function, while the 

 highest values of this alcohol were found in the motor areas. Variations 

 in composition occurred in both sides of the brain. 



In general, the more active the portion of the nervous system examined, 

 the lower was the lipid content and the higher the protein level. The 

 highest lipid content was noted in the motor centers and the lowest in the 

 association areas. Cholesterol, cerebrosides, and saturated phospholipids 

 reached an especially low level in the association areas. Peripheral nerves 

 had the highest lipid content of the nervous system, while the spinal cord 

 presented a lower value and the brain had the lowest lipid content. 



d. The Effect of Diet on Brain Lipids. There is a general agreement 

 that the brain is one of the organs least influenced by diet. 310-312 This is 

 especially true in the case of brain lipids. Stoesser et al. 3n demonstrated 

 only minimal variations in the composition of rat brains. No differences in 

 the ratio of phosphatides to total lipids in the brain could be demonstrated 

 by Beauvallet 312 in the case of the adult or of the growing rat. 



However, McConnell and Sinclair 304 were able to introduce a certain 

 proportion of the unnatural fatty acid, elaidic, into the brain of the young 

 rat, either through the placenta or through the milk of its mother. How- 

 ever, the extent of elaidic acid substitution in the brain lipids was only about 

 one-fourth of that which obtained in the liver and muscle lipids of the same 

 animals. This indicates that the brain exhibits a greater degree of selec- 

 tion than do other tissues. 



Other experiments indicate that the composition of the brain lipids may 

 be influenced by diet. Changus and collaborators 313 found that radio- 

 active phosphorus could be incorporated into brain phospholipids, but 

 that the change in the brain components was slower than that for any of the 

 other tissues. The increase in uptake was progressive for 200 hours, after 

 a single dose, following which it decreased at a correspondingly slow rate 

 for four weeks. The rate of uptake was more rapid in the brains of young 

 animals than in those of older ones. The rate at which radiophosphorus 

 was taken up by brain phospholipids of mice was reduced by 25% by emo- 

 tional excitement or by direct electrical stimulation of the brain. 314 

 Torda 315 noted that the rate of phospholipid synthesis was markedly 

 decreased in mice during convulsions induced by electroshock or by 



«w C. Artom, G. Sarzana, and E. Segre, Arch, intern, physiol, 47, 245-276 (1938). 



311 A. V. Stoesser, K. A. Petri, and I. McQuarrie, Proc. Soc. Exptl. Biol. Med., 32, 761- 

 762 (1935). 



312 M. Beauvallet, Compt. rend. soc. bid., 144, 1596-1599 (1950). 



313 G. W. Changus, I. L. Chaikoff, and S. Ruben, /. Biol. Chem., 126, 493-500 (1938) 



314 R. M. C. Dawson, J. Physiol., 109, 21P-22P (1949). 

 316 C. Torda, Federation Proc, 12, 145 (1953). 



