The maturation of rat brain myelin.

Myelin fractions were prepared from brains of 9- to 90-day-old rats by continuous and discontinuous sucrose density gradient procedures. Total protein and lipid content of myelin showed little variation, but lipid composition changed significantly during maturation. Cholesterol, galactolipids, and ethanolamine glycerophosphatide plasmalogen increased whereas choline glycerophosphatide content decreased with increasing age. The changes in lipid composition were more marked in the myelin prepared by the discontinuous gradient technique. The significance of these lipid changes in relation to their organization in the myelin membrane is discussed.