Lymphocytokaryorrhectic Effects of Adrenocortical Steroids 119 



During the period of acute hormone action, there is an inhibition of 

 mitosis which lasts for several hours and is followed by a resumption of cell 

 division until there is a reeonstitution of lymphatic organs characteristic of 

 the age and sex of the animal. 11 This effect of lymphocytokaryorrhexis, dis- 

 solution of cells and inhibition of mitosis and growth of lymphocytes, lasts 

 for only a short time following a single increase in the concentration of 

 lymphocytokaryorrhectic hormones at the cell site. 2 



CHRONIC EFFECTS OF CORTISOL ON LYMPHATIC TISSUE 



Persistent Cortisol effects can be produced only when animals are treated 

 at closely spaced intervals with either ACTH or appropriate steroid hor- 

 mones. ls Similarly, constant stress must be maintained to establish prolonged 

 reduction of lymphatic tissue. 18 During the period of chronic Cortisol treat- 

 ment, very little lymphocytorrhexis is observed. The lymphocytes are 

 pycnotic and hyperchromatic and have scant cytoplasm (Fig. 9-12). No evi- 

 dence of homoplastic or heteroplastic growth of lymphocytes is seen in 

 chronically treated animals. However, following either acute or chronic 

 treatment of lymphatic tissue with lymphocytokaryorrhectic hormones, both 

 the reticuloendothelial cells and the most immature reticular lymphocytes 

 appear to be highly resistant to the destructive effects of these hormones 

 (Fig. 9-1 2). (i - I5 Thus, since progenitive cells resist lymphocytokaryorrhectic 

 action, a seed bed of germinative cells is retained for repopulation. 



REPOPULATION OF LYMPHATIC TISSUE 



Reeonstitution of lymphatic tissue has been investigated following pro- 

 longed treatment with Cortisol and subsequent hormone withdrawal and 

 following hormone treatment and then adrenalectomy. 1 - At the termination 

 of the experiments, lymphatic organs were removed, weighed, and sectioned 

 for histologic study. The lymph nodes become more rapidly reconstituted 

 than the thymus which is very slow in the rate of its return following cortisol- 

 or ACTH-induced involution. 18 This is also true following various stressful 

 stimuli. Of most interest here is the fact that within hours following cessa- 

 tion of hormone treatment, there appears to be an increase in mean cell 

 size in the lymph nodes (Fig. 9-13). At this time one sees little evidence of 

 mitosis and heteroplasia. Rather, it appears that lymphocytes may become 

 and remain pycnotic for some time and return to their previous states when 

 the hormone level diminishes. 15 Reeonstitution, therefore, is accomplished 

 in part from these surviving cells. 



