| Abstract: | This study tries to give further insight into the mechanism and location of the physiological reduction of the bone marrow erythropoiesis during the first trimester (Trimenonreduction). Methods utilized included red blood values, bone marrow morphology, 3H-Thymidine Autoradiography, Feulgen-cytophotometry and 3H-, 14C-Thymidine double labelling techniques of bone marrow erythroblasts of healthy children of different age groups. Besides already known techniques we used especially a modification of the double labelling techniques, developed in our laboratories. We draw the following conclusions from our results: 1. Newborns have a higher rate of bone marrow erythropoiesis in comparison with normal controls of other ages. The reduction of the bone marrow erythropoiesis starts already in the first 2 days of life. 2. The reduction of the bone marrow erythropoiesis in the investigated infants in the second week of life was about to one fifth of values which proved to be normal for healthy older children. 3. This reduction is caused partially by prolongation of proliferation and maturation phases of erythroblasts, partially by a decrease of new erythroblast-formation from the stem cell pool. Medium values of DNA-synthesistime of infants with the highest reduction is double compared with values of healthy controls in vitro. 4. The decrease of cell proliferation and maturation during the reduction of the bone-marrow erythropoiesis includes all precursors and all phases of the cell cycle equally. In the first few days of life however it seems that the decrease of DNA synthesizing erythroblasts surpasses the reduction of maturing cells. 5. An ineffectiveness of erythropoiesis could not be found responsible for the reduction. 6. The reduction in erythropoiesis is seen in those steps in which other autors found stimulations by erythropoietin. Therefore this study supports the thesis, that the trimenonreduction is caused by a lack of erythropoietin stimulation. 7. The sequence of the trimenon reduction in humans is different from results found in animals. |
