Differences in Proliferative Activity between Normoblasts and Pernicious Anemia Megaloblasts

The mitotic behavior of pernicious anemia and normal erythropoietic cells in vitro was studied by means of phase contrast microphotography and cinema-photograph. Direct measurements showed that the duration of mitosis is significantly shorter in megaloblasts than in normoblasts at every stage of maturation. Maturation induces an elongation of mitosis in both the normal and the pathologic series. The mitotic index being practically the same in normoblasts and megaloblasts, the weighted average generation time in megaloblasts, calculated according to the formula t_G = t_M/I_M, resulted in a shorter time than in normoblasts. This indicates that there is a higher than normal proliferative activity of p.a. cells since the generation time appears inversely proportional to the frequency by which new mitoses are entered in a cell population. The role of each single mitotic phase in shortening the total duration of mitoses has been investigated. Possible alterations in the mitotic mechanisms involved have been discussed.