FLUORESCEIN AS INDICATOR OF BRAIN INJURY 



373 



S?+++ 



12 16 20 24 28 32 36 40 



Days after irradiation 

 Fig. 3. Summaiy of results obtained using fluorescein staining as a criterion of 

 damage in rats. The time of onset and intensity of fluorescein staining are different for 

 diflferent doses of irradiaton. 



1 St a ppearance of 



histologic lesior 



•- — 



1st appearance of fluorescenc 



01 1 10 100 



Days after irradiation 



Fig. 4. .\ log-log plot of the time of first appearance of fluorescence as a function 

 of dose, illustrating the definite relationship between dose and time of onset of recog- 

 nizable changes (staining with fluorescein). 



Microscopic examination of the same brains that were examined for fluo- 

 rescence, as well as of brains from companion rats from whom the tissue 

 was removed and fixed without pre\ious freezino, demonstrated that a 

 lesion is seen earlier and at lower doses with fluorescein staining than with 

 light microscopy. Alter a dose of 8.000 rad. a fluorescein-stained lesion was 

 clearly demonstrated during the 2nd and 3rd weeks postirradiation without 

 subsequent clearly demonstrable microscopic e\idence of damage. 



