XII.C: Erythrocyte Egress

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XII.C.001

Erythrocyte Egress. Murine Marrow. Enucleate erythrocyte containing ribosomes and a few mitochondria (marrow reticulocyte) is in juxtaposition to marrow sinus wall. At this level, a large segment of adventitial reticular cell cytoplasm prevents most of the erythrocyte from juxtaposing to the abluminal surface of the endothelial lining cell. A probe at the right edge of the erythrocyte is in contact with endothelium and may show very early penetration of endothelial cell. In experimental models pharmacological doses of erythropoietin decreases adventitial cell cytoplasmic cover of the abluminal sinus wall and may improve access of the reticulocyte to the endothelial cell. Sinus lumen (L). (Transmission electron micrograph)

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XII.C.002

Erythrocyte Egress. Murine marrow. Enucleate erythrocyte containing ribosomes and a few mitochondria (marrow reticulocyte) is in juxtaposition to marrow sinus wall. At this level, the endothelial cytoplasm is attenuated, approaching a fenestra in thinness. The arrow points to an endothelial cell junction. Marrow cell egress is usually parajunctional. Sinus lumen (L). (Transmission electron micrograph)

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XII.C.003

Erythrocyte Egress. Murine marrow. Reticulocyte containing ribosomes and a few mitochondria (marrow reticulocyte) is in transit from hematopoietic cord to marrow sinus lumen (L). The endothelial cytoplasm is attenuated. An endothelial cell junction is evident to the right of migrating cell. Marrow cell egress occurs near endothelial cell junctions but penetrates the sinus endothelium by generating a pore in the endothelial cell. Note the spherical shape of the portion of the reticulocyte in the sinus limen and the flaccid shape of the reticulocyte cytoplasm still in the cord, a reflection of a transmembrane pressure gradient, known to exist from cord to sinus. (Transmission electron micrograph)

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XII.C.004

Erythrocyte Egress. Murine marrow. Marrow reticulocyte containing ribosomes and a few mitochondria (marrow reticulocyte) is in transit from hematopoietic cord to marrow sinus lumen(L). An endothelial cell junction is evident to the left of the migrating cell (arrow). Marrow cell egress occurs near endothelial cell junctions, but penetrates the sinus endothelium by generating a pore in the endothelial cell. (Transmission electron micrograph)

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XII.C.005

Erythrocyte Egress. Marrow reticulocyte containing ribosomes and a few mitochondria is in transit from hematopoietic cord to marrow sinus lumen (L). An endothelial cell junction is evident to the right of the migrating cell (arrow). Marrow cell egress occurs near endothelial cell junctions, but penetrates the sinus endothelium by generating a pore in the endothelial cell. (Transmission electron micrograph)