| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1987: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1986: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Our study of these two years gave the following results.
(1) Yolk sac hemopoiesis and circulating erythroblasts of yolk sac origin
Hemopoiesis in the yolk sac of the mouse embryo begins at 8 days of gestation, after the formation of vitellin vessels, erythtopoiesis appears to be active at 10 days. The hemopoietic foci contain primitive erythroblasts of various stages of development, and among them there exist small number of large, immature, hemopoietic cells with nuclei over 8 um in diameter. Such immature hemopoietic cells resembling late angioblasts are present in the peripheral circulation of a 10-day embryo.
(2)Liver hemopoiesis and spleen hemopoiesis
At 11 days of gestation, hepatic tissues contain immature hemopoietic cells which resemble late angioblasts on the basis of their nuclear and nucleolar appearance. Such hemopoietic cells measure larger than 8 um nuclear diameter and can be seen in the liver unitl 15 days of gestation. Then the immature hemopoietic cells appear in the splenic cords, and the cells can be seen in the spleen even at 2 days after birth.
(3)Spleen hemopoiesis and lymphocytes
At 16 days of gestation, immature hemopoietic cells and small lymphocytes first appear and then the spleen become predominantly erythroietic. The fetal spleen is the possible source of B-lymphocyte population before the bone marrow hemopiesis.
(4)Megakaryopoiesis
Yolk sac vitelline vessels contain a few free megakaryopoietic cells. Yolk sac megakaryopoietic cells, which are significantly smaller in cell size than bone marrow megakaryopoietic cells, can be classified into three types: YM1, YM2, and YM3. Most of the hepatic megakaryopoietic cells of an 11-day embryo have ultrastructural features similar to those of YM1 or YM2 cells.
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