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The study reports on the presence of connections between the visual receptor outer segments and the apical villi on the retinal pigment epithelium in the human eye. The mechanisms underlying sensory retinal adhesion to the pigment epithelium, recognition and attachment of visual receptor outer segments to the pigment epithelium during phagocytosis, and communication and transport of substances between the two layers of retina have been difficult to define, and molecular connections between the two layers of retina could play an important role in these processes.

Electron spin resonance (ESR) spectroscopy has been used in an attempt to observe free radicals which may be connected to the aging processes. Isolated lipofuscin particles from the human brain, which may act as traps for reactive ESR centers, have been studied. The lipopigments exhibit ESR signals which were attributed to metal ions. Both high-spin ferric iron and copper (II) complexes were observed. The copper resonance showed axial symmetry and the observed ESR parameters (A parallel = 185 gauss, g parallel = 2.25 and g perpendicular = 2.066) indicate that the copper ions are of the "non-blue" type (so-called "type 2"). The data suggest that the copper ions might be ligated to two nitrogen and two oxygen atoms. Ceroid particles from the brains of dogs with end-stage "canine ceroid lipofuscinosis" yield similar resonances involving metal complexes. The concentration of the copper ions in the lipopigments seems to increase slightly towards the end stage of life. Retinal pigment epithelial cells from the eyes of dogs with canine ceroid lipofuscinosis were grown in vitro and examined with ESR when the cells reached confluency and then after being maintained confluent for 2 weeks. The spectra indicate an accumulation of metal ions due to this "aging". Phase-contrast microscopy reveals an increase in perinuclear dense bodies during the time in confluency. A weak ESR signal, compatible with an "oxygen-centered" radical, was also found to increase slightly during the "aging" period.

A technique that permits removal of viable retinal pigment epithelial (RPE) explants of determined size from Bruch's membrane, and the transfer of such explants with maintained apico-basal polarity to cell culture dishes is presented. The RPE is a polarized tissue where the apical surface is involved in the interchange of material between the choroid and sensory retina and in phagocytosis of visual receptor outer segments. The maintenance of this polarity is of importance in studies aimed at elucidating these functions on pure RPE explants in early primary culture. No previous work has presented a method that permits this maintenance. The possibility of standardizing the size of these explants should facilitate quantitative studies on phagocytosis and uptake of markers and labelled compounds. The described dissection procedure is also currently used to separate the RPE as a pure cell population from surgically removed chorio-retinal biopsies for cell culture purpose.

The alterations in surface morphology in human retinal pigment epithelium in explant culture was studied by scanning electron microscopy. After 14 days in culture, large areas of the epithelium showed well preserved surface villi. In some zones, however, the density of the finger-like villi were reduced and the shorter villi became more visible. The short villi are lamellar in structure and constitute systems of communicating membranous folds and not isolated structures as previously believed. Most of the tall finger-like villi were found to have their bases on the top of these folds. Dead cells followed 2 different pathways of degeneration. Some showed large ruptures in the membrane, followed by expulsion of organelles and finally detachment of the cell from Bruch's membrane. With other cells, a progressive disintegration of the cell membrane was observed. The first type of degeneration occurred most frequently in dilated, single cells, whereas the latter type was found in larger areas of necrosis.

Addition of increased amounts of serum and a protein (peroxidase from horseradish) to the culture medium caused structural alterations in previously confluent cultures composed of cells from the human retinal pigment epithelium and choroid. The alterations consisted in the formation of bi- and multi-layered strands, plaques and nodular structures and in the detachment of cells with formation of nude areas. These alterations resemble the frequently observed reactive alterations at the chorio-retinal junction in eyes with inflammation, trauma, retinal detachment and certain degenerative disease processes as the senile disciform macula degeneration.

In recent years several investigators have described the histologic findings made in the external eye muscles in biopsies or necropsies in cases of chronic progressive external ophthalmoplegia. 2,4,7,8,12,13 The authors cited agree that the changes are of the type usually seen in skeletal muscles in progressive muscular dystrophy, and they are of the opinion that chronic progressive external ophthalmoplegia is closely related to progressive muscular dystrophy and represents a particular type of this disease with preponderant or selective affection of the extrinsic eye muscles. Further support for this view is found in the concomitant occurrence of dystrophic changes in skeletal muscles in some cases. 4,7,8 The previously generally accepted opinion that progressive external ophthalmoplegia is primarily an affection of the nuclei of the eye muscle nerves appears to rest on insufficient evidence, as discussed by Kiloh and Nevin, 7 Schwarz and Liu, 13 and Adams, Denny-Brown, and Pearson. 1 The