Radiation Dose in Autoradiography 



123 



graphs, but the general form should be equally suitable for 

 work with counters. 



In general the concentration in an organ of an element 

 applied at time will follow a curve similar to Fig. 1. The 

 dose will be due to the total concentration of tracer, only a 

 fraction of which is utilized in producing the autoradiograph. 

 Figs. 2, 3 and 4 show photomicrographs of cells and auto- 

 radiographs of tissue cultures of avian fibroblasts (Felc and 

 Spear, 1950a) grown in plasma containing ^^p (Pelc and 



fC-c) 



Fig. 1. Uptake and excretion of tracer (assumed to be stable) 



as a function of time (t). 



Spear, 1950b). The distribution of ^^P in the cells after 

 fixation in 80 per cent alcohol and washing (Fig. 2) is fairly 

 general, and it is safe to assume that a more even distribution 

 would have been obtained if the water soluble phosphorus 

 compounds had been retained. After extraction with 5 per 

 cent trichloracetic acid at 15°C. a more detailed autoradio- 

 graph appears (Fig. 3). This trend is even more marked after 

 extraction with normal hydrochloric acid for 10 minutes at 

 60 °C. when mainly phosphorus compounds situated in the 

 cell nuclei are retained (Fig. 4). The radiation dose given 



