1000 ADVENTURES IN RADIOISOTOPE RESEARCH 



sodium, potassium, calcium, strontium, carbon 11, sulfur and so on 

 became available and found application in permeability and other stu- 

 dies. Skeleton metabolism could now be studied even applying calcium 

 and strontium. Both iron 55 and 59 were prepared. Ernest Lawrence 

 was most generous towards the few workers then applying radioactive 

 tracers and supplied them with radiophosphorus and a few other radio- 

 elements. When we learned that he had succeeded in preparing radio- 

 iron we were very anxious to obtain some. He told us, however, that 

 he had promised Whipple to put all the restricted amounts of radiorion 

 available at his disposal. This was a very wise decision in view of the 

 important work which the W' hipple — Hahn group carried out in following 

 resorption and incorporation of radioiron and therewith opening one of 

 the most beautiful chapters of the physiological and clinical application 

 of radioactive indicators. 



It looked for a while as if, when looking for suitable tracers for the 

 chief constituents of the living organism, for hydrogen, carbon, nitrogen 

 and oxygen, we would have to make use of stable rare isotopes of ^H, 

 ^^C, ^^N and ^^O which are also useful but very much more elaborate 

 and less sensitive to determine than the radioactive ones. Soon, however, 

 making use of the cyclotron, tritium (Alvarez and Cornog, 1939) and 

 the long living carbon 14 (Ruben and Kamen, 1940) were discovered. 

 To make them available in a sufficient amount the immense neutron 

 flux was necessary which alone the pile can supply. The fission products, 

 the most copious source of radioactive substances, does not contain the 

 above mentioned or other light elements. 



Isotopic indicators found application in all branches of biology in the 

 elucidation of a great variety of problems and were opening entirely 

 new approaches. One of these of special importance was the splitting 

 of dynamic equilibria so frequent in the living organism. The glucose 

 content of the circulation, for example, is the result of glucose taken 

 up or produced by the organism and that metabolised. An abnormally 

 high glucose level met in diabetes may be clue to a depressed utilization 

 or to enhanced formation of this compound. The application of isotopic 

 indicators permits to distinguish between the high glucose level due to 

 impaired metabolism and that due to increased formation. Some of these 

 investigations were carried out by studying glucose metabolism in tissue 

 slices. Hastings and associates^^Mncubated in a set of experiments liver 

 or muscle (diaphraghi) slices of the rat with ^^C labelled glucose in the 

 presence of non-labelled pyruvic acid. In another set of experiments 

 the tissue slices were incubated with non-labelled glucose and with i^C 

 labelled pyruvic acid. The first set of experiments aimed at the deter- 

 mination of glucose uptake by the liver or the muscle and its transfor- 

 mation into glycogen, fatty acids and other components. The last men- 

 tioned to obtain information about the amount of glucose built up 



