Abstract
That cerebrosides may exist in small amounts in blood has been shown by the development and application of a titrimetric microprocedure for this group of lipids. 1 , 2 , 3 This method, slightly modified, has been employed on lipid extracts of blood, stroma and brain. The data indicate that in erythrocytes, stroma, and brain, much of the lipid which formerly was designated as neutral fat∗ is cerebroside, whereas in plasma only negligible amounts of cerebroside are present. Furthermore, there are indications that the cerebrosides may comprise a significant fraction of the blood lipids in certain pathological conditions.
Method. Procedure for hydrolysis: The procedure of Kirk 2 was modified to facilitate hydrolysis of the cerebrosides and filtration of the hydrolysate. Aliquot samples of the lipid extract and blanks for initial and total reduction values 2 are measured into 10 cc glass-stoppered graduated cylinders. The solvents are evaporated carefully in a boiling water bath. To each of the samples for initial reduction are added 3 cc of water, and to each of those for total reduction 2 cc of 6 N hydrochloric acid. The cylinders are stoppered tightly and heated for 15 minutes in a boiling water bath to emulsify the lipids and hydrolyze the cerebrosides. After cooling, 1 drop of phenol red, 0.5 cc of 4% zinc sulfate solution (ZnSO4.7H2O), and 2 cc of 0.1 N sodium hydroxide are added to each sample for initial reduction, after which they are diluted to 10 cc and filtered through a medium weight filter paper. To each sample hydrolyzed with hydrochloric acid are added 1 drop of phenol red indicator and, in succession, the following: 40% sodium hydroxide (drop by drop) until the solution turns pink; 1 N hydrochloric acid until a yellow color is evident; and 0.1 N sodium hydroxide until a pink color develops.
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