Related Experiment Videos
Megakaryocytopoiesis in the rat: response to thrombocytopenia induced by exchange transfusion
We have studied the megakaryocytopoietic response in rats to acute thrombocytopenia induced by exchange transfusion of platelet-poor blood. Our analysis included serial determinations of peripheral blood counts, the size and number of megakaryocytes in sections of humeral marrow, the numbers of megakaryocytic (CFU-Meg) and granulocyte-macrophage (CFU-GM) colony-forming cells in marrow and spleen, and the proportion of CFU-Meg and CFU-GM in DNA synthesis. With exchange transfusion, the platelet count fell to 11% of the control value (101,000 +/- 49,000/mm3; mean +/- SD) and returned to normal by day 3; rebound thrombocytosis (peak 1,720,000 +/- 246,000/mm3) was observed on days 4 and 5. The average size of marrow megakaryocytes increased significantly on days 2 and 3 compared with normal (p less than 0.01), but the numbers of recognizable megakaryocytes did not change through day 5. The numbers of splenic CFU-Meg and CFU-GM increased significantly (p less than 0.05) on days 2-4 and on day 2, respectively, after the exchange; however, the numbers of marrow progenitors, which account for over 95% of total body progenitors, remained unchanged throughout the duration of the study. The proportion of CFU-Meg in DNA synthesis (mean +/- SD) increased from a baseline value of 17% +/- 4% to 33% +/- 11% (p less than 0.02) and 35% +/- 6% (p less than 0.001) on days 1 and 2, respectively, and returned to control values thereafter. There were no changes in the cell cycle activity of CFU-GM. Thus, acute selective thrombocytopenia induced by exchange transfusion causes an enlargement of marrow megakaryocytes and an increase in the fraction of CFU-Meg in cell cycle. These changes, occurring in the absence of immunologically mediated events, are the direct result of lowered platelet count.
We have studied the megakaryocytopoietic response in rats to acute thrombocytopenia induced by exchange transfusion of platelet-poor blood. Our analysis included serial determinations of peripheral blood counts, the size and number of megakaryocytes in sections of humeral marrow, the numbers of megakaryocytic (CFU-Meg) and granulocyte-macrophage (CFU-GM) colony-forming cells in marrow and spleen, and the proportion of CFU-Meg and CFU-GM in DNA synthesis. With exchange transfusion, the platelet count fell to 11% of the control value (101,000 +/- 49,000/mm3; mean +/- SD) and returned to normal by day 3; rebound thrombocytosis (peak 1,720,000 +/- 246,000/mm3) was observed on days 4 and 5. The average size of marrow megakaryocytes increased significantly on days 2 and 3 compared with normal (p less than 0.01), but the numbers of recognizable megakaryocytes did not change through day 5. The numbers of splenic CFU-Meg and CFU-GM increased significantly (p less than 0.05) on days 2-4 and on day 2, respectively, after the exchange; however, the numbers of marrow progenitors, which account for over 95% of total body progenitors, remained unchanged throughout the duration of the study. The proportion of CFU-Meg in DNA synthesis (mean +/- SD) increased from a baseline value of 17% +/- 4% to 33% +/- 11% (p less than 0.02) and 35% +/- 6% (p less than 0.001) on days 1 and 2, respectively, and returned to control values thereafter. There were no changes in the cell cycle activity of CFU-GM. Thus, acute selective thrombocytopenia induced by exchange transfusion causes an enlargement of marrow megakaryocytes and an increase in the fraction of CFU-Meg in cell cycle. These changes, occurring in the absence of immunologically mediated events, are the direct result of lowered platelet count.