PATHOLOGY OF MICE IRRADIATED AFTER 

 INJECTION OF CYSTEAMINE 

 (P MERCAPTOETHYLAMINE) 



M. A. Gerebtzoff and Z. M. Bacq, 

 Laboratory of Anatomy and Laboratory of Pathology of Liege University 



There is no doubt that cysteamine injected into mice before a lethal 

 irradiation, confers protection. But the site of this action is unknown. In 

 what organs does the protection appear ? And does it protect the cells 

 themselves or a factor necessary to their regeneration ? In an attempt to 

 obtain an answer to these questions, we have studied the lesions in three 

 radio-sensitive organs (spleen, thymus and intestinal epithelium) and in the 

 liver ; the importance of this organ in regeneration has been stressed by 

 Maisin and his co-workers. We have compared C57 mice subjected to 

 700 r with or without an injection of 3mg of cysteamine just before the 

 irradiation. The detailed results are published elsewhere^. Only the main 

 observations will be described here. For every organ listed above, we have 

 measured the degeneration due to the primary action of X-rays, as seen 

 6 hours after irradiation, and the regeneration observed 3 to 6 days later. 



{]) Spleen 



(a) Degeneration— In the lymph nodes of the spleen, the spread of nuclear 

 pycnosis is smaller in mice treated with cysteamine than in control animals. 

 The relation between the intact surface and the total surface of the nodes is, 

 in the mean, 0-151 for untreated mice and 0-371 for treated mice. The 

 difference is quite significative, {b) Regeneration — Four days after irradia- 

 tion, pycnotic nuclei are very rare in treated animals, but still numerous in 

 some nodes of controls. In these, elimination of degenerated cells and 

 regeneration are slower. 



(2) Thymus 



(a) Degeneration— The difference in pycnotic areas is not significative. 

 Pycnosis is massive in both groups of mice, {b) Regeneration — Count of 

 mitosis for 10 microscopic fields gives 48 mitosis for controls and 60 for 

 treated animals. But a statistic study of the results shows that this difference 

 is not quite significant. 



We attribute the uncertain action of cysteamine on thymus to the strong 

 radio-sensitivity of this organ. 



(3) Intestine 



{a) Degeneration— There is no difference between treated and untreated 

 mice. {b) Regeneration— The number of mitotic nuclei is 61 for controls, 

 83 for treated animals. The difference is significant and regeneration is 

 more intense after an injection of cysteamine, 



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