[Morphological phase-contrast cinematographic studies on the behavior of bone marrow cells in vitro. X. Myeloblasts and monoblasts].

The myeloblast is nearly of the same size as the lymphozyte and has the same nucleus cytoplasma ratio of 0.7 but differs from it in its morphology, its high frequency of multiplication, and by its kinetic behaviour. By phase contrast observation the transformation of the myeloblast into the promyelocyte has been seen several times. The myeloblast like the lymphocyte is able to move although at a much slower speed. By locomotion the myeloblast, and likewise the lymphocyte can move between blood and bone marrow. Of the granulocytopoietic series only the promyelocyte and the myelocyte with their nuclear cytoplasm relation of 0.3 are found in the bone marrow. The monoblast but is about twice its size, and moves less often. Apart from its transformation into promonocyte, monocyte and histiocyte, the monoblast may evalue in another way: it grows into a cell of doubled size with the same nucleus cytoplasm ratio 0.7 in whose cytoplasm are seen a lot of big granules. The cell may now be characterized as a tissue macrophage or mastcell. In consequence a frequently multiplying basophilic cell with a coarse nuclear structure and nucleoli, grows from a diameter of 6.5 to one of 13.0 mum without marked morphologic change apart from becoming alpha-NA-Esterase positive and acquiring big lysosomes. When this haemocytoblast is small (K 1/4 to K 1/2), it can be triggered into the granulocytopoietic series, when it is bigger (K 1/2 to K1) into the monocytopoietic series, or in the size K1 to K2 by erythropoietin into the erythropoietic series. If no triggering takes place, the cell degenerates after having granulated. The lymphopoietic system is not connected to this system of stem cells committed to the granulocytopoietic, the monocytopoietic and the erythropoietic series. Therefore we postulate a dual haematopoietic system. In acute leukemias the spread of size of cells and nuclei is wider and kinetically active stem cells are rarer. Only leukemic promyelocytes are in locomotion vividly, in contrast to the normal ones. In leukemic myeloblasts there are fewer mitoses than in normal ones, but in leukemic promyelocytes and monoblasts the mitotic frequency is not reduced.