Quantitative levels, fatty acid composition and positional distribution of acyl groups in encephalic phosphoglycerides during embryonic development of the chick and duck.

l. Phosphatidylcholine (PC) was the major phospholipid fraction in the embryonic encephaIon, palmitic and oleic acids being the main acyl constituents. 2. These fatty acids were poorly represented in phosphatidylethanolamine (PE). whereas stearic, arachidonic and docosahexenoic acids had very high relative abundances. 3. The fatty acid composition of choline or ethanolamine phosphoglycerides from the embryonic encephalon did not show appreciable differences either during the developmental stages considered or between the two avian species. 4. The positional distribution of acyl groups in l.2-diacyl-sn-glycero-3-phosphocholines showed a clear predominance of saturated fatty acids bound to sn-I posItIon of the glycerol moiety. whereas the unsaturated fatty acids were predommantly located in the sn-2 position.