[Morphological characterization of the myelopoietic stem cell reserves in the human].

According to microkinomatographic observations made on single cells up to ten days in vitro, there are the following laws of growth in haematopoiesis: Small cells will increase in growth up to five times in size, with their morphologic and kinetic properties being preserved, the blood lymphocyte will grow to immunoblasts, the small pluripotent stem cell to bone-marrow histiocytes. When growing, the myelopoietic stem cell may be gradually deviated into all myelopoietic cell lines. Instead of bone-marrow histiocytes it may differentiate to promyelocytes, promonocytes or proerythroblasts, all having an equal nucleus size, when it is induced by serum factors. Apart from histiocytes these large cells are capable of differentiating to a clon of blood cells, such as granulocytes, monocytes or reticulocytes, by several successive divisions of maturity. Contrary to the stimulated lymphocyte, symmetric mitoses will frequently occur, when small pluripotent stem cells are growing to bone-marrow histiocytes to be no further differentiated. Occasionally, asymmetric divisions may also be observed, i.e. one of the daughter cells will differentiate into one of the myelopoietic lines, whereas the other one will remain a progenitor cell. Moreover, there are various pathological mitoses in all progenitor cell sizes, such as endomitosis, cytoplasm fusion after mitosis, nucleus fusion after cytoplasm conjunction or amitotic nucleus division without cytokinesis. They produce megacaryoblasts further differentiating to megacaryocytes by corresponding pathological mitoses. According to our vital observations the pluripotency of the haematopoetic stem cell is being lost step by step.