網膜色素上皮細胞の病的反応に関する実験的研究

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  • Experimental Studies on the Retinal Pigment Epithelium
  • モウマク シキソ ジョウヒ サイボウ ノ ビョウテキ ハンノウ ニ カンスル

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Part I and II<BR>Elect r o n Microscopic Studies on the Phagocytic Activity, and Proliferation of the Retinal Pigment Epithelial Cells<BR>Phagocytic and proliferative activities of the retinal pigment epithelial cells (RPE cells)of the albino and pigmented rabbits were studied under electron microscope. Polystyrene spheres of various sizes (6μm and 1μm in diamete r) and homologous erythrocytes, suspended in a saline solution, were injected into the subretinal space through the choroid by micropipett. The following results were obtained.<BR>1) Phagocytic activity Following inje ction the small spheres ( 1μm in diameter) were filled between the sensory retina and the retinal pigment epithelium. Six hours after injection, they were enclosed by the microvilli of the RPE cells, and then, they were engulfed into the cells. The phagocytosis of the large spheres (6μm in diameter) into the cells were begun observe in 12 hours later after injection. All of the particles, injected into the subretinal space, were engulfed by the RPE cells and disappeared completely from the space within 24 hours. At that time, the cytoplasma of the each epithelial cells was filled with the spheres, to which lysosomes in the cells fused and surrounded. Only a few of erythrocytes, which were a similar size in diameter to the larger spheres, were phagocytized into the cytoplasma on the third day. From our these experiments, it clarified that the RPE cells showed remarkable phagocytic activity to the particles injected into the subretinal space, however, in phagocytic process, the microvilli of the cells seemed to be capable of selecting a size and a property of the material to be engulfed.<BR>2) Cell proliferation and migration On the third day, many proliferated cells, which seemed to be originated from the pigment epithelial cells, appeared over the pigment epithelium. On the 5th day, these cells became rather slender in shape and increased to multilayers from 2 to 5 cell layers. Desmosome like structure were seen as the intercellular junctional complex between the proliferated cells. The cell nuclei were irregular in shape and deeply indented, and the rough surfaced endoplasmic reticulums were prominent in the 1 lcytoplasm. Each proliferative cells also contained many polystyrene spheres, especially in the cells located at the apical area. Mitotic figures of the RPE cells were to some extent detected at the basal layer, but such incidence were rare. In the pigmented rabbits, these proliferated cells located at the apical area container many melanin granules, and in the cells located at the basal area numerous premelanoso. mes in various stages were observed in their cytoplasm. In the experiment of erythrocytes injection, proliferation of the RPE cells was rarely seen, however, migration of many macrophages in to the subietinal space were frequ ently observed. On the 5th day, macrophages which engulfed the polystyrene spheres were seen in and beneath the Bruch's membrane. These observations showed the retinal pigment epithelial cells have marked proliferative activity and migratory nature of them.<BR>3) Fibrous metaplasia (Production of collagen fibers)The proliferated cells seemed to be originated from the pigment epithelium which became spindle form in shape, spreading long processes, produced collagenous fibrils outside of the cells. These cells resembled the fibroblast in appearance. The observations revealed the fibrous metaplasia of the retinal pigment epithelial cells. It may be considered dubious that the RPE cells can produce collagenous fiber, but such fact is feasible when it is considered that the RPE cell originates from the neuroepithelial tissue. Collagenous fiber in the vitreous body are also considered to be produced by nonpigmented ciliary epithelium which originates in same tissue. It clarified in our observations that the pigment epitheli al cells of the retina show the active pathologic reactions

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