The problem of the cell differentiation has been discussed from the view point of hemoglobin synthesis and the related functions of organellae in the erythroid series. Microspectrophotometry on the etythroblasts and denucleated cells reveal that the hemoglobin synthesis takes place most actively after the denucleation in the stage of reticulocytes. Morphologic observations show that the reticulocytes have mitochondria and the endoplasmic reticulum. Cytochemical studies lead to the conclusion that the endoplasmic reticulum is responsible for the globin synthesis for which the energy is supplied by the mitochondria which still retain the marked enzyme activities. The heme synthesis seems to be conducted by the mitochondria which are proven to have the ability to accumulate iron introduced intravenously.
The theory of the intranuclear hemoglobin synthesis is not so conclusive, because there are several evidences suggesting the penetration of hemoglobin from the cytoplasm into the nucleus in the course of the maturation of erythroblasts. Thus the anthor is of the opinion that the differentiation of red cells from their mother cells to the matured cells is led by the functional differentiation of the cytoplasmic organellae, mitochondria and endoplasmic reticulum, but not by the functional differentiation of nucleus.
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