Studies on erythropoiesis 1. Studies on cell size of erythroid cells from anemic animal

For the purpose to look into the regulatory mechanism of erythropoiesis, changes in the cell volume and the cell size of the erythroid cells have been observed in peripheral blood and marrow from normal and phenylhydrazine induced anemic rabbits. And the following results have been obtained: 1. After the injection of phenylhydrazine hydrochloride a hemolytic anemia can be induced with a marked increase in the reticulocyte number. The cell volume increases with the advance of anemia but it is never proportional to the increase of reticulocyte number. The MCV reaches the value twice the normal but it never exceeds the threshold. 2. In bone marrow the smaller sized orthochromatic cells are reduced extremely in number or obliterated in anemic animals. As there is not any marked difference in cell size of polychromatic erythroblasts between normal and anemic animals, the large red cells of anemic animal will be formed by denuc1eation of the polychromatic erythroblasts. 3. The percentage of basophilic erythroblasts is increased in anemic animal suggesting an accelerated differentiation-division of proerythroblasts to basophilic ones. 4. The data strongly support the denuc1eation at polychromatic stage in emergency but not at the younger stages than polychromatic erythroblast. Data also suggest that in severe anemia an accelerated cell division occurs, especially in the stage from proerythroblast to basophilic erythroblast.