950 



ADVENTURES IN RADIOISOTOPE RESEARCH 



from plasma phosphatide. A few hours after the administration of labelled 

 phosphate, the milk phosphatides are only slightly active, while the 

 milk inorganic P shows a strong activity. This is a decisive argument 

 against the above view. The high activity already found for the milk 

 inorganic P in the early stages of the experiment, is only compatible 

 with the assumption that the milk inorganic P is derived from the plasma 

 inorganic P. The latter acquires a high activity soon after subcutaneous 

 injection of labelled sodium phosphate. 



As a further example we may mention the origin of the phosphorus 

 compounds in the chick embryo(^^\ 0.1 cm^ physiological sodium chloride 

 solution containing traces of labelled sodium phosphate was injected 

 into fertihzed eggs. Several days after incubation, the phosphatides and 

 other phosphorus compounds were isolated in turn from the embryo 

 and the yolk, their activity and their phosphorus content being deter- 

 mined. As seen in Table 8, the specific activity of the embryo phosphatide 

 P is very different from that of the yolk phosphatide P. 



Table 8. — Specific Activity of P Extracted 

 FROM THE Hen's Egg Incubated for 18 Days 



While the yolk is scarcely active, the phosphatides extracted from 

 the embryo are found to have a very strong activity. The phosphatide 

 molecules present in the embryo must obviously have been newly synthe- 

 sized. Similar considerations apply to the protein phosphorus present 

 in the embryo. 



REACTION PATH 



The path taken by organically bound phosphate radicals in glycolytic 

 processes was investigated by using labehed compounds prepared under 

 the action of enzymes present in muscle juice or yeast. When labelled 

 adenyl phosphate was added to fresh muscle pulp in which glycolysis 

 occurred, no formation of active inorganic phosphate was found to take 



