| Summary: | Rats of three different ages (7, 13, and 22 days) were given a single injection of acetate-1-14C, then sacrificed at intervals (4 hr, 2 days, 10 days, and 30 days). The fatty acids of brain gangliosides, glycerophosphatides, cerebrosides, and sulfatides were isolated and counted. Some were decarboxylated and the resultant carbon dioxide was counted.The data indicate that the palmitate of gangliosides and glycerophosphatides is made de novo from acetate, but that the stearate of these lipids is made by elongation of palmitate. The palmitate used for elongation is not the freshly synthesized acid but rather the acid recently liberated by breakdown of the complex lipids. Lignocerate also appears to be made by elongation, but it is possible that the stearate of cerebroside is made de novo. No qualitative difference was seen in the turnover curves or modes of biosynthesis in the three rat groups. The turnover rates for ganglioside fatty acids were similar to those for the phosphoglycerides. Turnover data for sphingosine in cerebrosides and sulfatides are presented.
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