|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1993 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1992 : ¥1,500,000 (Direct Cost : ¥1,500,000)
Blood And Coelom Mononuclear Phagocytes Before Liver Hemopioesis : Circulating blood cells of a 10-day fetal mouse are primtive erythroblasts derived from yolk sac blood islands, and many mononuclear cells appar in the periphral blood. Free phagocytes with similar ultrastructural features also can be observed in intraembryonic peritoneal cavities, and the precursors of these phagocytes are not monocytes but mononuclear cells from yolk sac or mesenchyme.
Scavenger Macrohages in Fetal Liver : Livers of 12-day mouse embryos contain macrophages laden with large heterophagosomes in sinusoids. Macrophages, as scavengers, engulf circulationg primitive erythroblasts from the yolk sac as well as nuclei expelled from erythroblasts. Scavenger macrophages are seen in mitosis to migrate from sinusoids into hepatic cords, forming cell clusters designated as erythroblastic islets. Blood mononuclear cells are considered to be the precursors of the hepatic macrophages.
Thymus Macrophages : Monocytes as w
ell as macrohages laden with phagocytic inclusions first appear in the perivascular space or very close to blood vessels at the cortico-medullary junction of the 15-day-embryo thymus. The perivascular spaces contain many monocyte-like cells, and candidates of precursors of thymic macrophages are monocytes probably from the fetal liver.
Phagocytes In Fetal Spleen And Neonatal Bone Marrow : Spleen in fetal and early postnatal mice contains two kinds of phagocytes, scavenger macrophages and mast cells, and their phagocytotic activity is directed toward extruded erythrocytic nuclei, erythrocytes and dying hemopoietic cells. Neonatal femoral marrow cavity contains many polymorph nuclear leucocyte, showing early signs of cell degeneration. Not only free macrophages but fixed reticular cells engulf and digest apoptotic neutrophils in the hemopoietic compartment of bone marrow. The orign of spleen and bone marrow scavengers should be considered in relation to monocyte producion in the fetal liver.