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ABSTRACT: The mouse visceral yolk sac (VYS) is widely known to play an important role as erythropoietic tissue during embryonic periods. Mouse VYS from embryonic days 9 to 12 was examined by light microscopy, electron microscopy and histochemical analysis with benzidine to detect the presence of hemoglobin with special reference to the development of VYS, the disappearance of the blood islands in VYS, and the appearance of a novel structure in the form of erythrocyte-like globules in VYS endodermal cells. The villous appearance of VYS became complicated by the development of VYS endodermal cells. The blood islands positive for the benzidine reaction were light microscopically detected on embryonic days 9, 10, and 11. They disappeared on embryonic day 12, however. Erythrocyte-like globules positive for the benzidine reaction were not observed in VYS endodermal cells on embryonic days 9, 10, and 11, but then appeared on embryonic day 12, by light and electron microscopy. Erythrocyte-like globules in VYS endodermal cells, which appear after the disappearance of blood islands in VYS, may participate in erythropoiesis during embryonic development.
Annals of Anatomy - Anatomischer Anzeiger 07/2003; 185(3):201-5. · 1.86 Impact Factor
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ABSTRACT: Hematological studies have revealed the importance of the visceral yolk sac (VYS) in the primitive erythropoiesis of mouse embryos at an early stage before day 12. We examined the possibility of the occurrence of extra-embryonic erythropoiesis at a stage later than embryonic day 12 by light and electron microscopic analyses. Surprisingly, a novel structure in the form of erythrocyte-like globules was observed in the VYS endodermal cells. They were consistently present in the VYS endodermal cells from embryonic day 12 until day 18 (birth is day 19), by immunocytochemical and enzyme histochemical analyses. They were immuno-positive for mouse erythrocyte antibody and also positive for the benzidine reaction showing the presence of hemoglobin. The erythrocyte-like globules were shown to be the erythrocytes present in the cytoplasm. These results indicated that erythropoiesis in the VYS endodermal cells continues from the early embryonic stage, as primitive erythropoiesis, until the late stage.
Annals of Anatomy - Anatomischer Anzeiger 10/2002; 184(5):425-9. · 1.86 Impact Factor
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ABSTRACT: It is well known that avian yolk sac is involved in both primitive and definitive erythropoiesis during embryonic development. Definitive erythropoiesis is first detected at about 4-5 days incubation and its maximum activity is reached between day 10 and 15 of incubation, ending between days 18 and 20 of incubation. We confirmed the definitive erythropoietic foci in the chicken yolk sac throughout the 5th to 19th day of incubation by histochemical light and electron microscopy. The definitive erythropoietic foci were observed in the yolk sac endodermal layer from day 5 until day 19, just before hatching. Ultrastructurally, definitive erythropoietic foci were observed extravascularly in the yolk sac endodermal cell layer in direct contact with the vitellolysis zone. These findings provide a basis for clarifying definitive erythropoiesis in vertebrates.
Italian journal of anatomy and embryology = Archivio italiano di anatomia ed embriologia 113(1):9-16.
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ABSTRACT: Light and electron microscopic examination of first-trimester and term human placental tissues were performed to identify erythrocytes containing hemoglobin in the villous trophoblast cell layer. Erythrocytes were not identified in chorionic villous epithelium at week 7 of gestation. These cells first appeared in the villous cytotrophoblast at week 8, and continued to be present in the villous cytotrophoblast until week 9, as shown by benzidine staining. At week 12 gestation, a cluster of erythrocytes was present in a villous syncytial sprout. At 40 and 41 weeks gestation, erythrocytes were located in the villous cytotrophoblast cell layer. Electron microscopic observations focused on the cytoplasm of villous cytotrophoblast at week 8, the syncytial sprout at week 12 and the cytotrophoblast cell layer at term, confirmed the presence of erythrocytes at an extravascular location, as observed by light microscopy.
Italian journal of anatomy and embryology = Archivio italiano di anatomia ed embriologia 112(3):191-8.
