Nuclear elimination from the normoblast of fetal guinea pig liver as studied with electron microscopy and serial sectioning techniques.

Abstract

AbstractThe process of denucleation in normoblasts of fetal guinea pig liver was studied with electron microscopy employing serial sections. In the late normoblast the nucleus becomes eccentrically located in the cytoplasm. Continued maturation results in a nucleus which is protruding from the normoblast. Still later the nucleus separates from the remainder of the cell and is phagocytized by a reticular cell. Nuclei which have been extruded are surrounded by a narrow border of cytoplasm and possess a nuclear envelope, nuclear pores, and internal nuclear structure similar to that of normoblasts. The cytoplasmic border and nuclear structure are observed for some time after ingestion by reticular cells. Dissolution of nuclei inside the phagocytes is characterized by disappearance of the cytoplasmic border and nuclear envelope, loss of density of the chromatin, and appearance of dense particles in the interchromatin. It was concluded that under normal conditions, the sole mechanism of denucleation in definitive erythroblasts is extrusion. Mitochondria are partially degraded inside the late erythroblasts, forming a membranous residue which is later extruuded.