Abstract
1. In a series of young adult albino rats weighing around 200 g, variations in mitochondrial number in blood lymphocytes were observed in relation to the processes of regeneration of the lymphatic tissue, the Flemming's secondary nodules in particular, after total body X-irradiation in a dose of 600 r.
2. Immediately after irradiation, there occurred a sharp drop of both the lymphocyte count and the average number of mitochondria per lymphocyte in the blood. The mesenteric lymph nodes and splenic white pulp were severely depleted of lymphocytes through a massive destruction of these cells. The Flemming's secondary nodules had disappeared within several days.
3. During the regenerative processes of the lymphatic tissue, an extensive new formation of Fl emmin g's secondary nodules in the mesenteric lymph nodes and spleen was observed almost coincident with a remarkable transient elevation of the average number of mitochondria in blood lymphocytes, during the period between the 14th and 22nd days after irradiation.
4. These findings provide a strong evidence to support the view that a marked rise in mitochondrial number of blood lymphocytes takes place as a consequence of extensive new formation of Flemming's secondary nodules in the lymphoid organs, which, in turn, indicates an increase in production and delivery of lymphocytes from these organs to the blood.
