Migration of Erythropoietic and Prebursal Stem Cells from the Early Chicken Embryo to the Yolk Sac
The early chicken embryo elaborates a primitive red cell population which is succeeded by definitive red cells. The primitive erythrocytes are known to be derived from the yolk sac. After day 7 of incubation their place in the circulation is taken by the definitive erythrocytes (1). The cellular origin of the precursors of the definitive red cells has been unknown. Recently it has been studied in quail-chick chimeras, demonstrating that stem cells formed within the early embryo replace yolk sac stem cells in their erythropoietic function (2). Both types of stem cells were observed to have similar potentialities in erythropoiesis. However, yolk sac and intraembryonic stem cell contributions to erythropoiesis are quantitatively different. The yolk sac stem cells give rise to all or most primitive erythrocytes and to declining proportions of definitive erythrocytes, while the intraembryonic stem cells give rise to definitive erythrocytes in an increasing number and only to a minimal amount of primitive erythrocytes. However, the period during which yolk sac stem cells give off an erythroid progeny has not been determined precisely.
KeywordsStem Cell Lymphoid System Peripheral Blood Erythrocyte Embryo Part Area Vasculosa
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