ONTOGENIC DEVELOPMENT OF MEMBRANE-LIPIDS IN THE CHICK OPTIC LOBE

The developmental profiles of the lipid composition and their de novo synthesis and remodelling in the optic lobe of the chicken were studie d. The P-32 incorporation to phospholipids showed an active de novo sy nthesis mainly of phosphatidylinositol and of a particular fraction of phosphatidylcholine during the early stages of the embryo development , concomitantly with the beginning of synaptogenesis. This de novo syn thesis of phospholipids strongly increased at hatching. On the other h and, phosphatidylnositol presented an active lipid exchange (acylation -deacylation) in the early stages of embryogenesis, indicating a stron g incorporation of C-14-arachidonic acid during this period, followed by a fast drop in specific activity. Two different fractions of phosph atidylcholine were isolated by high-performance thin-layer chromatogra phy with a different profile of fatty acid composition, disclosing the ir different physicochemical behavior, metabolic activities and evolut ion during embryogenesis. P-32 incorporation into phosphatidylethanola mine remained very low during the earliest stages of embryogenesis, sh owing an increase when the process of synaptogenesis began, until hatc hing, when radioactivity reached a plateau. C-14- arachidonic acid inc orporation into phosphatidylethanolamine was minimal. Furthermore, the phosphatidylethanolamine pool was progressively enriched in its ethan olamine plasmalogen throughout the development. Chromatographic analys is of lipid extracts showed the presence of cerebroside traces after 1 6 days of embryo incubation. At hatching, a remarkable increase in non -hydroxylated cerebrosides was observed concurrently with the appearan ce of hydroxylated ones. These glycosphingolipids, as well as the sulf atides, were markedly increased in the lipid extracts of optic lobes o f adult animals, indicating the progressive development and maturity o f the myelin sheath.