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Embryos of the toad, Bufo arenarum, Hensel, taken during early stages of development were used to survey the [U-14C]glycerol and 32P lipid labeling. When precursors were supplied at the time of oogenesis, large differences in specific activities of phospholipid were observed. Using 32P, a steep rise as a function of development was evidenced. Triglycerides contained much higher proportions of [U-14C] glycerol than phospholipids when administered to the female toad along with a pituitary homogenate. However, lack of [U-14 C] glycerol uptake into lipids was observed when cell-free homogenates of eggs at different stages of development ranging from unfertilized oocyte to midgastrula were incubated in unsupplemented amphibian Ringer. At the later stage, significant de novo biosynthesis of lipids from glycerol began to be measurable, whereas during cell cleavage intracellular redistribution of preformed phosphoglycerides was used for membrane assembly.

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