Abstract
Though description has been made on the phagocytosis and the fate after pigment accumulation of histiocytes in the first (I. Influence of adminstration of polyvinyl pyrolidon) and second (II. Influence of administration of cell activating agent) reports, the change of the picture of each individual accumulated granule and its state in the digesting vacuole have not been clarified yet. In the present study, detailed observations have been made with the electron microscope to allow a general consideration.
The phagocytosis of histiocytes has been studied by various workers. However, no one has ever imagined that the pigment granules, which have once accumulated in the cytoplasm of a histiocyte, would be excreted into the outside of the cell. In reality, in the present study, no finding which supports the extracellular excretion has been obtained in the normal animal. When pigment absorptive and cell activating agents had been administered to animals, however, the mode of their accumulation in histiocytes was quite different. It was found that, in such cases, the pigment accumulated in the cell, could be partially excreted extracellularly by protrusion and isolation from the cell by the help of the unstainable giant vacuoles which appeared in the cell. Here, the state in the digesting vacuole will be described in detail, attention being centered on the appearance of unstainable giant vacuoles.
As was stated in the first and second reports, the sepia accumulated in the cytoplasm is swollen when either P. V. P., B. A. L. or sodium thiosulfate has been injected. Here a question arises: is each individual sepia granule really swollen? It is equally probable that each accumulated granule appears to have been swollen accompanying the dilatation of digesting vacuoles. This state is not clear with the light microscope. However, it can be clearly observed with the electron microscope. The size of each sepia granule was almost similar and no marked difference was found between the normal findings and those obtained when either P. V. P, B. A. L. or sodium thiosulfate was administered.
Next the state of the E. R. and digesting vacuole in the cell was compared. When P. V. P is injected, the cytoplasm is extremely swollen, the digesting vacuoles in the cytoplasm are connected with the adjacent digesting vacuoles, and at last, large unstainable giant vacuoles are produced. When B. A. L. is injected, the cell is activated from the early stage, E. R. is rapidly dilated, and at the same time the digesting vacuole is markedly dilated. After sodium thiosulfate, the digesting vacuole and E. R. are similarly dilated, though the appearance of vacuoles is considerably delayed. This time the dilatation of E. R. is quite characteristic and the state of the dilatation is clearly presented in the photographs. It is supposed that this dilatation of E. R. is prerequisite for the appearance of the unstainable giant vacuole and that it plays an important part in excreting the intracellulary accumulated granules.
Next the time course of the dilatation of E. R. was observed. As time elapses, from the 24th to the 48th hour, E. R. and digesting vacuoles are dilated and large vacuoles are formed after 72 hours. This large vacuole has been referred to as unstainable giant vacuole, because its shape and significance are different from those of the usual giant vacuole. In most instances, sepia is not accumulated in the inner wall of this unstainable giant vacuole and, if it is, the accumulation is slight. The characteristic finding of the inner wall of the vacuole is the trace of accumulated sepia which is clearly proved. Many free granules become observable in the state of E. R. and digesting vacuole is quite different from that of the accumulation. The number of these unstainable giant vacuoles is decreased after 120 hours. This closely coincides with the unstainable giant vacuole of the cell described by Seki and others.
