E. H. BETZ 



(i) Influence of cortisone and desoxycorticosterone acetate [D.C.A.) on haematopoietic 

 regeneration after a sub-lethal dose of X-rays 

 The experiments are made in order to see whether adrenocortical hor- 

 mones are able to inhibit the haematopoietic regeneration after a sublethal 

 irradiation (500 r). Former experiments have shown that rats submitted 

 to such a dose of X-rays regenerate very quickly the haematopoietic tissues 

 destroyed by the irradiation. 



Methods : Six groups of 12 albino rats each were used. The animals of the first 

 group are controls. They are irradiated with 500 r (Picker app., 250 kV. 18 mA, 

 filter 0-25mm Cu, F.D. 50cm output 90r/min.) The rats of the three following 

 groups are irradiated in the same way. After the irradiation, the animals are injected 

 daily with cortisone. The doses used were respectively 2-5, 5 and lOmg daily. 

 The rats of the two last groups are irradiated and injected daily with 3 or 5 mg of 



Figure 1. Femoral bone marrow of the rat, 15 days after 500 r ; extensive regeneration 

 of the myeloid tissues {200 X ) 



desoxycorticosterone acetate (D.C.A.). In each group, two animals are killed on 

 the sixth, eighth, tenth, twelfth and fifteenth days. Cervical lymph nodes, 

 spleen, thymus, femoral bone marrow are fixed in Helly's fluid, and studied 

 histologically. 



The control rats, which have been irradiated only, have an extensive 

 and early regeneration of thymus, spleen, lymph nodes and bone marrow. 

 The repair of the destroyed tissues starts on the fourth day after irradiation. 

 The daily injection of 2 • 5 mg of cortisone does not modify in any way the 

 histological picture of the haematopoietic tissues. 



Daily injection of 5mg of cortisone acetate to rats irradiated with 500 r 

 does not influence the regeneration of spleen, lymph nodes, or bone mar- 

 row ; the regeneration of the thymus only is inhibited by such a dose of 

 cortisone. On the contrary, the injection of lOmg of cortisone daily does 

 block the regeneration of spleen, lymph nodes and bone marrow as well as 

 the repair of thymus. The histological picture of the haematopoietic 



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