974 ADVENTURES IN RADIOISOTOPE RESEARCH 



Scheme for the specific activity of phosphatides""^ 



Phosphatide transport in laying hens. 

 Plasma phosphate 



t I ' 



°^ Liver phosphate 



li 1 



CO T 



bo Liver phosphatide 



I 



d Plasma phosphatide 



t 



o 

 03 



Oh 

 CO 



Ovary phosphatide — > Yolk phosphatide 



Phosphatide transport in lactating goats. 

 Plasma phosphate 



^ Liver phosphate Milk gland phosphate 



CO 



Liver phosphatide Milk gland phosphatide 



Y 4 t 



Plasma phosphatide Milk phosphatide 



Effect of Irradiation with X-Rays on the Formation of Nucleic Acids 



The application of radioactive indicators proved to be an efficient 

 tool for the measurement of the change in the rate of formation of mole- 

 cular body constituents caused by administration of chemicals inducing 

 such interference or by irradiation with ionizing radiation which pro- 

 duces such interfering products iii situ. Such radiation may diminish 

 the growth rate, and we can expect that it might interfere with the rate 

 of formation of some cellular constituents already in the early or earliest 

 phase of the experiment and with that of deoxyribonucleic acid, a main 

 constituent of the cell nucleus. 



In a growing tumour, growth, and correspondingly, additional forma- 

 tion of deoxyribonucleic acid, may amount to about 1% in the course 

 of 2 hours. If this formation is suppressed by irradiation, the irradiated 

 tumour after the lapse of 2 hours can be expected to contain 1% less 

 deoxyribonucleic acid than do the controls. The distinction between 100 

 and 99 deoxyribonucleic acid molecules present in a tumour by means 

 of chemical analyses is a most difficult task. However, when applying 

 radioactive indicators such a difference can easily be measured. Radio- 

 active indicators permit us to distinguish between old and new mole- 

 cules, between those present before the start of the experiment and those 



