820 XIII. ESSENTIAL FATTY ACIDS 



acid content of the diet. According to Richardson et al.^^'^ methyl arachi- 

 donate and methy] linoleate are equally effective in the treatment of the 

 dermatitis produced by vitamin Be deficiency. 



In a comprehensive study of skin structure as related to diet, Hansen 

 et al.^^^ proved that the absence of fat in the diet of dogs brings about 

 definite alterations in the epidermis and dermis, including the hair follicles, 

 the sebaceous glands, and the capillaries. Wiese and Hansen^^^ observed 

 that the nutritional status of dogs which were maintained on different levels 

 and kinds of fat could be assessed from the level of serum linoleate and serum 

 arachidonate. In a later study, Hansen and associates'^^ stated that die- 

 tary fat supplies a factor necessary for the maturation of epithelial, seba- 

 ceous, and sudoriparous cells. When fat is absent from the diet of either 

 puppies or adult dogs, distinct skin abnormalities occur, which can be 

 recognized both microscopically and macroscopically. When EFA are 

 available, the changes in the stratum corneum, the collagen structure, and 

 the cellular infiltration of the dermis, the changes in hair follicles, in seba- 

 ceous glands, and in sudoriparous glands are all related to changes in the 

 epidermis. The most rapid restoration of the normal microscopic struc- 

 ture was noted when the dietary fat was high in unsaturated fatty acids. 

 WilHamson'^^ reported that the epidermis of rats on a fat-free diet became 

 thicker and more differentiated than that of normal rats. The stratum 

 granulosum became especially distinct, and the horny layer thickened. 



The specificity of the skin picture in EP'A deficiency Avas demonstrated 

 by Ramalingaswami and Sinclair^"'' in rats; the histologic picture of the 

 skin in EFA deficiency closely resembled that of phrynoderma, whereas 

 the microscopic skin changes in vitamin A deficiency bore only a slight 

 resemblance to this condition. 



(5) Pregnancy and Lactation 



There is considerable evidence that the level of dietary fat may be of 

 considerable importance in physiologic functions such as pregnancy and 

 lactation. It is now certain that at least a portion of the beneficial effect 

 of fats on pregnancy and lactation is to be ascribed to their content of EFA. 

 Evans and collaborators-"'-"- were the first to prove that normal repro- 

 duction is impossible when the EFA are absent from the diet. The addl- 

 es H. F. Wiese and A. E. Hansen, Texas Repts. Biol. Med., 9, 516-544, 545-554 (1951 ). 

 "9R. WilUamson, Biochem. J., 35, 1003-1005 (1941). 



200 V. Ramalingaswami and H. M. Sinclair, Brit. J. Dermatol, 65, 1-22 (1953). 



201 H. M. Evans, S. Lepkovsky, and E. A. Murphy, ./. Biol. Chem., 106, 431-440 (1934). 



202 H. M. Evans, S. Lepkovskv, and E. A. IMurphv, J. Biol. Chem., 106, 441-444 

 (1934). 



