The critical role of the nucleolus in cell differentiation and stem cell development - the concept as it applies to erythropoiesis.

There is evidence to suggest that nucleated red blood cells (normoblasts) are derived from a fixed reticulum cell lining that marrow sinusoids. The reticulum cell is transformed into a nucleolated stem cell which gives rise to a cluster of normoblasts by a special process of clonal division. The problem, which is paramount to myeloid development, is what happens to the large numbers of nuclei which are extruded from the normoblasts during the freeing of the haemoglobinised plastid. They seem to disappear without a trace, and in order to explain this phenomenon the hypothesis is made that the extruded nuclei are transformed into cells of the neutrophil series, and evidence is presented to support this viewpoint.