LIPID STORAGE UNDER ABNORMAL CONDITIONS 679 



ethenoid acids or a single di- or polyethenoid acid as the unsaturated acid 

 component. Since the presence of palmitic or stearic acid to the extent of 

 about 50% of the total acid content seems to be well established, the high 

 iodine number can be reconciled only with the second alternative given 

 above, namely that unsaturated acids containing more than one unsatu- 

 rated linkage must be present to a considerable extent in the mixed lecithin 

 acids. In addition to oleic acid, linoleic, linolenic, arachidonic, and clup- 

 anodonic acids, other unsaturated acids have been isolated from various 

 lecithin preparations. It is quite possible that lecithins are unable to 

 function without the presence of a certain proportion of the highly unsatu- 

 rated acids in the molecules. For a further discussion of the composition of 

 the lecithin molecule and its fatty acid composition, the reader is referred to 

 pages 408 to 426 of Volume I. 



When the essential fatty acids (linoleic, linolenic, and arachidonic) are 

 absent from the diet, not only does malnutrition develop, but a failure of 

 growth ensues, and fatty livers develop. 571 ' 822 Burr and Burr 838 also noted 

 lesions in the kidneys, which were sometimes fatal. It is not certain whether 

 or not the pathological effect is similar to that resulting from choline 

 deficiency, but this would seem probable. Smedley-MacLean and Nunn 839 

 have reported that essential fatty acid-deficient rats, likewise, have an im- 

 paired ability to lay down depot fat. Moreover, although fat absorption is 

 not reduced out of porportion to the size of the animals, phosphorylation of 

 fats (and lecithin synthesis) in the intestinal mucosa is at a subnormal level. 840 

 Presumably the phospholipid turnover in the liver is decreased, due to 

 inability to synthesize phospholipids, with the result that fat metabolism 

 and fat transport are blocked. Hence, fatty acids accumulate in this or- 

 gan. Fatty livers, which originate because of an essential fatty acid de- 

 ficiency, are readily explained by a failure in the biosynthesis of phospho- 

 lipid in the absence of the highly unsaturated fatty acid which is needed for 

 incorporation into this molecule. 



(e) Fatty Livers Resulting from an Excess of Cholesterol. Best and Rid- 

 out 579,841 confirmed the findings of Schonheimer and Yuasa, 842 of Bailey, 843 

 and of Sperry and Stoyanoff 844 that the administration of cholesterol in 

 moderate amounts to rats results in fatty livers. These livers contain in- 



838 G. O. Burr and M. M. Burr, /. Biol. Chem., 86, 587-621 (1930). 



839 1. Smedley-MacLean and L. C. A. Nunn, Biochem. J., 84, 884-902 (1940). 



840 R. H. Barnes, E. S. Miller, and G. O. Burr, /. Biol Chem., 140, 773-778 (1941). 



841 C. H. Best and J. H. Ridout, Am. J. Physiol, 105, 6P (1933). 



842 R. Schonheimer and D. Yuasa, Z. physiol. Chem., 180, 5-16 (1929). 



843 C. H. Bailey, J. Exptl. Med., 28, 69-85 (1916). 



844 W. M. Sperry and V. A. Stoyanoff, J. Nutrition, 9, 131-155 (1935). 



