Abstract
SUMMARY In~rganic-~~P, injected into yolks of eggs incubated to produce embryos of different ages, was incorporated into all phospholipid fractions in both whole chick embryo and embryo brain. Specific activity values compared between individual phospholipids of the same incubation age and in eggs injected at the same time did not vary more than twofold between one another. Biologically prepared pho~phatidyl-~~P choline and phosphatid~l-~~P ethanolamine, when injected into yolks of eggs, gave a very different pattern of incorporation into embryo brain from that given by inorganic 32P. When the labeled choline phosphatide was injected, a phosphatidyl choline fraction was isolated whose specific activity was 30-40 times greater than those of other phospholipid fractions. Phosphatidyl-mP ethanolamine injection gave a qualitatively similar result. Glycerol-1 ,3-14C and acetate-1-14C were incorporated to a much lesser extent than in~rganic-~~P. The hypothesis is advanced that as the embryo develops, de novo synthesis from inorganic phosphate decreases and intact phospholipid is transferred from the yolk to the embryo and its organs.
Highlights
Prepared pho~phatidyl-~c~hPoline and phosp hatid ~ l - ~e~thPanolamine, when injected into yolks of eggs, gave a very different pattern of incorporation into embryo brain from that given by inorganic 32P
Allowing for all the errors in counting and phosphorus determination, the normalized specific activity values fall within 5% of the most accurate value which could be determined for each sample
At various subsequent times of incubation, the phospholipids were extracted from yolk, whole embryo, and brain and analyzed
Summary
The sources of fertile eggs and chemicals are indicated in the preceding paper [7]. I n addition, carrier-free sodium p h ~ sphate - ~w~ aPs purchased from Nuclear Consultants Corp., Glendale, Calif. The aqueous KC1 solution was evaporated a t 40" to half or less of its original volume and diluted to a known volume for analysis of Pi and total P Duplicate aliquots of this solution were mixed with a n appropriate amount of activated carbon. An effort was made to complete the injec- ethanolamine fraction (as well as other phospholipid tion within a few hours and after all the eggs were in- fractions) contained negligible amounts of 14C The injection solution was diluted 1000-fold and a 1 fraction These low levels of 14Cincorporation prevented ml aliquot was counted a t the same time as the isolated the biological preparation of doubly-labeled phosphoexperimental samples.
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