T he changes in brain constituents during development have been widely studied and data concerning lipids and other substances are now available. Some investigators have considered the possibility of correlating the maturation of the brain with the deposition of specific lipid fractions; but it is difficult to relate composition data to the functional development of the nervous system. An increase in the concentration of various lipids in the brain of different animal species during development has been demonstrated by many investigators, and these data have recently been reviewed by S perry (1963). The concentration of cholesterol increases sharply during brain development: F olch ‐P i (1955) found an increase of the order of 300‐400 per cent in mouse brain from birth to 90 days, and M andel and B ieth (1951) demonstrated a 300 per cent increase of cholesterol concentration during the development of the rat brain from newborn to adult age. M andel , B ieth and S toll (1949) demonstrated that the cholesterol content increases from 1 to 5‐4 mg in the brain of the chick embryo from the 10th to 19th day of incubation. Most investigators agree that cholesterol is present in mature brain only in the free form (C umings , 1957; D avison and W ajda , 1959) and L e B aron and F olch (1959) postulated that it is combined with the water soluble proteins in the myelin sheat. However, some investigators have found esterified cholesterol in developing brain. M andel et al. (1949) found cholesterol esters in the brain of chick embryo and A dams and D avison (1959) in the cord of the chick embryo and in foetal human brain. JOHNSON, M c N abb and R ossiter (1948) and B rante (1949) found some esterified cholesterol in the infant human brain, while C umings (1957) found trace amounts of cholesterol esters in adult white and infant grey matter. More recently C larenburg , C haikoff and M orris (1963) give values for cholesterol esters in the brain of the developing rabbit. However, there are no firm data on the changes in concentration of esterified cholesterol in the brain during development. We have, therefore, measured the sterol esters in the chick developing brain at different stages of embryonic and postnatal life. Recent investigations have shown that cholesterol is not the only sterol present in the developing brain, but there is a considerable amount of desmosterol (24‐dehydro‐cholesterol) in the brain of the chick embryo (F ish , B oyd and S tokes , 1962) and other animal species (P aoletti , F umagalli , G rossi and P aoletti ; 1965). Desmosterol is partially esterified in the chick brain and disappears from the brain during maturation (F umagalli , G rafnetter , G rossi and M organti , 1963).
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Grafnetter et al. (1965) studied this question.