772 ADV^E^^rURES IN' RADIOISOTOPE RESEARCH 



Indications were also obtained that the degradation of cystein in the 

 hver is not a strictly unilateral process. (-^^ Not only is cystein split into 

 pyruvic acid and ammonia and hydrogen sulphide, but active cystein 

 is formed when active hydrogen sulphide is present. Only about i/g per 

 cent of the cystein molecules present are radioactive. 



Finally, mention is made here of the experiments by means of which 

 the formation of glycogen in liver sections was detected^^\ with pyruvic 

 acid serving as the substrate. Carbon originating from added radio- 

 actively labelled sodium bicarbonate was detected in 12 per cent of the 

 glycogen formed. The yield of radioactively labelled glycogen in vitro 

 was about the same as that detected in experiments in vivo. 



DETECTION OF THE FORMATION OF RADIOACTIVE -PHOSPHORUS- 

 CONTAINING DESOXYRIBONUCLEIC ACID IN SARCOMA SLICES 



In studying whether nucleic acid molecules are formed in vitro we have 

 shaken slices of freshly removed Jensen sarcoma, from rats, with 

 bicarbonate and Ringer's solution, which contained active sodium phos- 

 phate, for a period of 4 hr at 37° C. Warburg flasks were used in the 

 first experiments. In each flask were placed 2 gm of slices and 4 cm^ 

 of liquid. The Warburg apparatus was repeatedly filled with oxygen gas 

 (95% Og and 5% COg). At the end of the experiment the slices were 

 washed repeatedly with an inactive mixture of bicarbonate and R-inger's 

 solution. The shces were homogenized, a small portion was used for 

 determining the free P and its activity, and the remainder was given over 

 to the isolation of nucleic acid. The activity of the Ringer's solution at the 

 end of the experiment was also determined. We have since changed the 

 process, however, by introducing the slices into a 300 cm^ Erlenmeyer 

 flask and by replacing the bicarbonate solution, whose original pH of 

 7.6 had been disturbed in the course of the experiment, with rat's blood 

 or plasma. After the flasks had been placed in thermostats, the oxygen- 

 carbon dioxide mixture was first of all led through the flasks for 10 min 

 and the active phosphate, with a strength of several microcuries, was 

 then added. Blood has more often been used than plasma in order to 

 obtain a greater volume of liquid and to save the time required in sepa- 

 rating the plasma. 



^i>C. V. Smythey and T. Halliday, J. Biol. Chem. 144, 237 (1942). 



^2) J. M. Buchanan, A. B. Hastings and F. B. Nesbett, J.Biol. Chem. 145, 

 715 (1942). With regard to the formation of radioactively labelled acid-soluble 

 P compounds in muscle extract refer to J. K. Parnass, Bull. Soc. Chim. Biol. 

 Z. 21, 1058 (1939); M. O. Meyerhoff, Ibid. 21, 1094 (1939). 



