Human retinal epithelial cells dividing in culture have been radiolabelled with tritiated thymidine and subsequently transplanted and identified on Bruch's membrane of owl monkey by autoradiography. Such cells have been followed from 2 hours to 7 days after transplantation. The transplant cells reattach within 2 hours to the basement membrane left on Bruch's membrane after the host epithelial cells have been removed by suction after trypsinization. Within 6 to 24 hours they form a layer on Bruch's membrane with junctional complexes between cells and an apical-basal polarity characteristic of such cells in culture or after retinal detachment. After 2 to 7 days multilayers form by continued mitosis but no transplant cells invade the choroid as long as Bruch membrane is intact. Within this time macrophages begin to appear in the choriocapillaris under the transplant. These cells migrate through Bruch's membrane and between the transplant cells but have not been seen phagocytizing transplant cells. Reattachment of the neural retina to the transplant layer has not been attempted but seems technically possible.

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The fine structure of an unusual cell, the ‘Stäbchendriisenzellen’ (the so‐called foliaceous or rodlet cells of several authors), associated with the endothelium of the vascular system of marine and freshwater fishes was studied in the goldfish Carassius auratus (L.). The bulbus arteriosus was fixed with either a 6 % solution of buffered glutaraldehyde or with one part of a 3 % solution of lanthanum nitrate plus two parts of a 3 % solution of buffered glutaraldehyde and then post‐fixed in a 1.2% solution of osmium tetroxide. Electron micrographs of the vascular tissue show four cell forms which appear to be phases in the life cycle of the endothelium‐associated cell. Two of the phases are not encased and are characterized by their inclusions: in one cell these are crystalline, while in the second, they are amorphous and granular. In the other phases the cell is encased partially or completely within an apparently contractile fibrous wall surrounded by the plasmalemma. In the encased phases, the arrangement and condition of the cell organelles appears to have been changed, and in the fully‐encased phase mitochondrial activity seems to have decreased. This apparent change in the mitochondrial activity is accompanied by a thickening of the mitochondrial membrane from 48 to 109 Å. The micrographs seem to indicate that this cell in question behaves as a foreign body and, in some way, may be interacting with the epithelial tissue of the bulbus arteriosus.

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NYTwo-dimensional gel (2-D) electrophoresis coupled to fluorography was used to obtain the [ 35Sl-methionine labeled protein profiles of cultured human retinal pigment epithelial cells. These patterns revealed about 250 polypeptides in the largely acidic isoelectric focusing 2-D profile and approximately 200 in the mainly basic nonequilibrium pH gradient electrophoresis 2-D profile. The isolation of a detergentresistant cytoskeletal preparation revealed an enriched content of intermediatesized (7-10 nm) filaments as shown by electron microscopy. Two-dimensional analysis (acidic isoelectric focusing, 2-D) of the cytoskeletal preparation showed about 30 major proteins including non-muscle actin, which had their counterparts in the total retinal pigment epithelium protein profile. These studies have begun to establish the subcellular local (filaments) and identity of some of the currently visualized 450 different retinal pigment epithelium proteins.