310 ESSENTIAL FATTY ACIDS 



Figs. 12a and 12b, p. 300). Control animals having fat in the diet and grossly 

 exhibiting healthy skin and hair present an epidermis 2 to 3 cell layers in 

 thickness, a stratum corneum which is thin, wavy, and lacelike, the cell 

 outlines and nuclei being well delineated, a dermis with well-defined col- 

 lagen fibers, normal hair follicles, thin endothelial cells with large lumina 

 to the small vessels, and slight cellular infiltration. In the fat-deficient dog 

 presenting distinct abnormalities of the skin with marked desciuamation 

 and loss of hair, the stratum corneum is smudgy and indistinct and often 

 there is parakeratosis, the epidermis is greatly thickened with palisade 

 formation at the basilar layer with intracellular bridges evident, and the 

 dermis shows evidence of irregular collagen bundles, extensive edema, pres- 

 ence of cellular material, swollen endothelial cells with small lumina of the 

 vessels, increase in the cells of the hair follicles, plugging of the hair shafts, 

 degeneration of the hair, and enlarged sebaceous glands. Later the seba- 

 ceous glands become shrunken. When fat is added to the diet there is good 

 correlation between the amount and kind of dietary fat and a reversal in 

 the microscopic appearance of the skin. Changes similar to these have been 

 found in many human subjects, but heretofore no attempt has been made to 

 relate such changes to the dietary history. 



e. Summary 



On the basis of data obtained from studies with laboratory animals in- 

 cluding the dietary history, serum lipid values, especially for the diene and 

 tetraene fatty acids, and gross and histologic observations regarding the 

 skin have given leads for study of the human requirements for essential 

 fatty acids. 



4. Spectroscopic Study of Serum Lipids in Human Subjects 



In so far as is known, no sustained effort has been made to determine for 

 human subjects the highly unsaturated fatty acid levels of serum. Wiese,^^ 

 in work done at our laboratories under a contract sponsored by the Bureau 

 of Human Nutrition and Home Economics, U. S. Department of Agricul- 

 ture, adapted the spectrographic technique to a semimicro basis which 

 makes it possible to study the values for diene, triene, and tetraene fatty 

 acids on samples of serum on a clinical basis. Under the same contract, and 

 with this method of analysis, the serum levels of these fatty acids were de- 

 termined for 75 human subjects. ^^ The individuals studied were either 

 healthy adult subjects or hospitalized children who were considered to be in 

 a good nutritional state clinically, or children markedly underweight and 

 appearing malnourished. The EW^. values at 2350 A. (diene fatty acids) 



62 H. F. Wiese and A. E. Hansen, J. Biol. Chem. 202, 417 (1953). 



63 A. E. Hansen and H. F. Wiese, Federation Proc. 11, 446 (1952). 



