Variations in the Mitotic Activity in Different Regions of Lymphoid Organs

I. Observations on the Thymolymphatic Organs of Young Mature Albino Rats

抄録

1. In a series of young mature albino male rats from a subline colony of the Wistarstrain weighing around 200g, cell counts and mitotic counts have been performed in sections from different regions of the thymolymphatic organs, at successive intervals from 2 to 8 hours after the subcutaneous injection of colchicine in a dose of 0.10mg per 100g of body weight.
2. Among different regions of the thymolymphatic organs, the highest mitotic activity was observed in the proliferating centers of Flemming's secondary nodules, not only in the mesenteric lymph node but also in the splenic white pulp, as well as in the Peyer's patches. Among the Flemming's nodules, those of the splenic white pulp appeared to be the most active.
3. In the mesenteric lymph nodes, the medullary cords also were found to be important sites of cell production, though much less active than the Flemmin g's nodules with respect to cell proliferation. On the other hand, the cortical lymphatic tissue other than the Flemming's nodules, including the so-called “solid secondary nodules” and “pseudo-secondary nodules”, did not appear to participate in cell production so actively as the medullary cords.
4. The thymic cortex, the superficial layer in par ticulare, showed high mitotic activity next to the proliferating centers of Flemming's nodules. Since, however, dividing cells were rather uniformly distributed in the thymus, the mitotic activity in this organ as a whole was estimated to be much greater than that in the mesenteric lymph nodes.
5. The splenic white pulp as well as Peyer's patches were found to participate in lymphocytopoiesis as actively as mesenteric lymph nodes.6. T he possible error in determination of the mitotic index in sections were discussed, which are due to the differences in nuclear size between resting and dividing cells.