896 XIV. NUTRITIONAL VALUE OF FATS 



activating" potencies of raw egg white and of avidin were directly propor- 

 tional to the biotin-binding activities of the two preparations. Thus 

 0.1 ng. of the purified avidin was found to be sufficient to combine with 

 only 0.2 m^ug. of biotin to nullify the growth-promoting action of 50 ng. 

 of oleic acid. 



(13) Fatty Acids as Growth Factors for Lower Organisms 



In a study of pathogenic fungi of the "dermatophj^te" genera, Tri- 

 chophyton, Epidermophyton, Microsporum, and Candida, Keeney^®' re- 

 ported that long-chain acids exhibited a fungicidal activity. Sodium pro- 

 pionate, sodium valerate, sodium caproate, sodium caprylate, sodium 

 caprate, and sodium undecylenate were all approximately equal in effec- 

 tiveness. Much less or no fungicidal action resulted when the fungi were 

 exposed to the short-chain members of the fatty acid series.'^'* Wyss and 

 co-workers-^^ also found that the long-chain saturated and unsaturated 

 fatty acids caused the greatest inhibition in growth of fungi, and killed 

 more spores than did those with a shorter chain length. 



Trager^^ reported that oleic acid can replace biotin in the growth of the 

 larvae of the yellow fever mosquito, Aedes aegypti. In the absence of 

 biotin, the larval growth was very slow, and metamorphosis did not occur. 

 However, when biotin was present to the extent of only 50 m/xg./ml. of 

 medium, excellent groA\i;h was obtained. Relatively low concentrations 

 of oleic acid or of an oil from hydrolyzed horse plasma, lecithin, or related 

 compounds, when used in place of biotin, supported larval growth compara- 

 ble with that obtained vnth. the lower effective doses of biotin. On the 

 other hand, oleic acid and Tween 80, either alone or with aspartic acid, 

 produced some gro\\'th response on the part of red bread mold (choline- 

 less Neurospora crassa), although Hodson-^^ v\'as unable to demonstrate 

 that biotin could be replaced completely. 



(14) Miscellaneous, Beneficial, and Harmful Effects of Fats 



Schweigert et al.^^^ pointed out that the isocaloric substitution of 10 

 or 20 parts of lard for sucrose in a purified ration reduced the incidence and 

 extent of carious lesions in the cotton rat (Sigmodon hispidus) in proportion 



»«2 E. L. Keeney, Bull. Johns Hopkins Hosp., 73, 379-390 (1943); /. Clin. Invest., 23, 

 929-930(1944). 



26^ O. Wyss, B. J. Ludwig, and R. R. Joiner, Arch. Biochem., 7, 415-425 (1945). 



2» A. Z. Hodson, /. Biol. Chem., 179, 49-52 (1949). 



"8 B. S. Schweigert, J. H. Shaw, M. Zepplin, and C. A. Elvehjem, J. Nutrition, 31, 439- 

 447(1946). 



