A Comparative Study of the Lipids of the Vertebrate Central Nervous System

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Abstract
The concentration of water, cerebroside (glycosphingoside), free and total cholesterol, total phospholipin, monoaminophospholipin (phosphoglyceride) and lecithin (phosphatidyl choline) was determined in the spinal cords of a series of vertebrates including representatives of the cartilaginous and bony fishes, amphibians, reptiles, birds and mammals. From these figures was calculatedthe concentration of ester cholesterol, sphingomyelin (phosphosphingoside) and kephalin. As was previously found for brain, the spinal cords of each of the species studied contained negligibly small concentrations of cholesterol ester. The concentration of each lipid in the spinal cord was very similar for different individuals of the same species, but for different species within the same class the mean concentration of many of the lipids extended over a wide range. The concentration of total cholesterol, sphingolipid and myelin lipid was greater in the spinal cords of mammals than in the spinal cords of the lower vertebrates. Expressed as a percentage of ‘essential lipid‘, the concentration of cerebroside, cholesterol, sphingomyelin, sphingolipid and myelin lipid, but not of lecithin and kephalin, was greater in the spinal cord than in the brain. For the spinal cords of the species studied, the mean concentration of cerebroside expressed as a percentage of ‘essential lipid’ was negatively correlated with the mean concentration of sphingomyelin. The results are discussed in relation to the chemical nature of the lipids of the myelin sheath of a vertebrate nerve fibre.