X-RAY MICROSCOPY 



Fig. 9. MRD (microradiograph) of a normal 

 rabbit liver in a case of indirect vital injection of 

 thorotrast. Section 10 n, 2 hours after injection, 

 approx. X80. 



Typical distribution of thorotrast in RES ele- 

 ments of liver lobules. 



All the microphotographs (called MRD) of this 

 article are reproductions of original microradio- 

 graphs, i.e. their ma.ximum white color corre- 

 sponds to the maximum absorption of X-rays in an 

 object, the maximvmi black to the minimum ab- 

 sorption. 



thorotrast and contains a little less thorium 

 (about 22% by volume). Disadvantages of 

 thorotrast are its slight radioactivity (half 

 life about 25 years) and the perpetual re- 

 tention in cells of RES. These drawbacks, 

 however, are mostly of no importance in 

 research with vital injections which last a 

 short time. 



Figures 9 and 10 present microradio- 

 graphs of the liver and spleen of rabbit and 

 dog (both normal) after vital injection of 

 thorotrast: 10 cc to rabbit and 15 cc to dog, 

 two hours before sacrificing the animals. One 

 may see rows of Kupffer cells in the liver 

 and histiocytes in the spleen packed with 

 thorotrast (Bohatirchuk) (21) (24). These 

 pictures suggest that the thorotrast impreg- 

 nation of RES cells may be used not only 



for the study of the morphology of RES ele- 

 ments but also for the examination of their 

 function. Thorotrast disappears completely 

 from the blood in 4 to 6 hours. If, for some 

 reason, thorotrast is contraindicated, one 

 may use the colloidal preparation of iodine: 

 iodocol sol (Mulford Colloid Laboratories, 

 Philadelphia, USA). A similar preparation 

 "iodsolen" was made in Germany (Schering 

 Co.) shortly before the war. Both these 

 preparations are not radioactive and are 

 excreted from the RES cells within 24 hours. 

 However, the x-ray opacity produced by 

 both colloids is very slight and may be de- 

 tected only in very soft microradiographs. 



In addition to liver and spleen small 

 quantities of thorotrast are found after vital 

 injection in the RES elements of lymphatic 

 glands, kidneys and lungs. However, the data 

 on these findings are very scanty. 



There are a few indications that iron 

 (Barclay) (6), bismuth (Lamarque) (82) 

 were found in the limgs of experimental 



Fig. 10. MRD of dog spleen, 24 hours after in- 

 direct vital injection of thorotrast, approx. X180, 

 10 M. 



Thorotrast within histiocytes. Observe that 

 OM is only in cytoplasm, nuclei remain black. 



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