Olav Øyvind Pedersen

Destruction of Müller cells in the adult rat by intravitreal injection of d,l-α-aminoadipic acid. An electron microscopic study

Abstract Four hours after intravitreal injection of 100 μg d,l -α-aminoadipic acid to adult rats, the Muller cells developed morphological changes indicating cellular dysfunction. The changes in these cells varied from a loss of electron density and vacuolization of the cytoplasm to frank necrosis. The retinal pigment epithelium, photoreceptors, and the retinal neurons were at this time, as judged by electron microscopy, not significantly affected. The study indicates that d,l -α-aminoadipic acid can be used as a scientific tool to destroy selectively the Muller cells.

PSEUDO-EXFOLIATION MATERIAL ON THE ANTERIOR LENS SURFACE. DEMONSTRATION AND EXAMINATION OF AN INTERFIBRILLAR GROUND SUBSTANCE

Peroxidase did not penetrate into the capsule of cataractous lenses with or without pseudo‐exfoliation (PE). Neither did this tracer penetrate into the PE material itself, indicating that the PE fibrils are embedded in a ground substance which is impenetrable to peroxidase. Staining with alcian blue and ruthenium red showed that this ground substance is structurally heterogeneous. Acid mucopolysaccharides and/or glycoproteins are probably present. The fibrils are coated by a material with affinity to ruthenium red. This applies also to the fibrils of the amorphous layer. Their diameter is only about 1/3 of the fibrils of the PE material on the lens surface. Rounded membrane‐covered bodies are present, partly in groups, in the PE material. Morphologically, they resemble the mucopolysaccharide‐containing lysosomal vacuoles found in systemic mucopolysaccharidoses. Observations supporting the conception of similarities between PE material and amyloid are pointed out. The pathogenesis of the PE material is discussed.

ELECTRON MICROSCOPIC STUDIES ON THE BLOOD-AQUEOUS BARRIER OF PROSTAGLANDIN-TREATED RABBIT EYES: II. Iris

The distribution of intravenously injected horseradish peroxidase in the iris of prostaglandin (E1 and E2)‐treated rabbit eyes, has been studied with the electron microscope. Peroxidase was demonstrated in the stroma of all parts of the iris. The tracer was found throughout interendothelial clefts of iris vessels, indicating that these vessels had become permeable to peroxidase. The distribution of peroxidase in the iris epithelium indicates that the posterior epithelial cells are girdled by zonula® occludentes.

Electron microscopic studies on the blood-aqueous barrier of prostaglandin-treated rabbit eyes. I. Iridial and ciliary processes.

Prostaglandins E1 and E2 were applied topically to rabbit eyes. Structures related to the blood‐aqueous barrier in the iridial and ciliary processes, as well as the permeability of the ciliary epithelium to the protein tracer horseradish peroxidase, were studied with the electron microscope. Marked morphological changes, including dilations of the intercellular spaces and separation of the two epithelial cell layers, were found in the epithelium of the iridial processes. Only minor structural changes were found in the epithelium of the ciliary processes. Leakage of peroxidase through the intercellular spaces of the epithelium was demonstrated in the iridial processes and in the anterior parts of the ciliary processes. In the ciliary vessels of the same regions, opening of interendothelial gaps, platelet aggregations, microthrombi, and haemorrhages were found. In a previous in vitro study on the effects of prostaglandins on the movement of peroxidase in the ciliary epithelium, no structural changes of the epithelium were found, and the epithelial diffusion barrier to peroxidase was found to be intact. It is assumed that the breakdown of this barrier in vivo is secondary to vascular changes.

Toxic effects of dl-α-aminoadipic acid on müller cells from rats in vivo and cultured cerebral astrocytes

Subcutaneous injection of dl -α-aminoadipic acid (2 mg/g body wt) on 9-day-old rats gave a reproducible retinal lesion which was manifested by morphological changes in the Muller cells four hr after the injection. These cells appeared swollen and with a less electron dense cytoplasma. After 24 and 48 hr, however, these morphological changes had completely disappeared both on the light- and electron microscopic level. All other parts of the retina were likewise unaffected by the lesion When cultured cerebral astrocytes were exposed to 1 m m - dl -α-aminoadipic acid, visible changes in cell morphology were observed after 1 2 1 hr. These changes consisted of swelling of the cells leading to a less dense cytoplasma. The cells appeared more round and their processes normally seen had regressed. After changing the culture medium, however, the cells recovered their normal configuration

An electron microscopic study of the permeability of intraocular blood vessels using lanthanum as a tracer in vivo

Abstract In the present work lanthanum has been used as an electron microscopic tracer to study intraocular blood vessel permeability in vivo. Aqueous solutions of lanthanum were injected intravenously in rabbits. The eyes were enucleated 30 or 60 min later. Lanthanum was detected as irregular electron-dense deposits in the vascular lumen of intraocular blood vessels. In normal eyes, the tracer did not permeate the endothelium of blood vessels in iris, ciliary processes, choroid, or retina. Conjunctival application of prostaglandin E 1 (25 μg) 15 min before lanthanum injection, induced leakage of the tracer from blood vessels in the anterior parts of the ciliary processes and their iridial extensions. Leakage occurred through gaps between endothelial cells. Blood vessels showing increased permeability to lanthanum were readily detected, as heavy deposits of tracer material had accumulated in their walls. In the present work, lanthanum has been found to be a suitable tracer to study intraocular blood vessel permeability in the experimental animal. The technique is direct and simple, and the tracer is easily visualized in the electron microscope.

IN VITRO STUDIES ON PEROXIDASE MOVEMENT IN THE EPITHELIUM OF PROSTAGLANDIN‐TREATED RABBIT CILIARY BODIES

The movement of horseradish peroxidase (HRP) in the epithelium of isolated rabbit iris/ciliary body preparations, has been studied with the electron microscope. HRP was applied at the stromal side of the epithelium, and was left for 60 and 120 min. The distribution pattern of HRP found in the epithelium of the iridial and ciliary processes is consistent with in vivo studies, i.e. the progression of HRP is blocked at the site of the zonula occludens of the superficial epithelium. The HRP distribution pattern found in the iris epithelium indicates that also the superficial epithelial cells of this epithelium are girdled by zonulae occludentes.

THE PERMEABILITY OF THE RABBIT CILIARY EPITHELIUM TO HORSERADISH PEROXIDASE IN EXPERIMENTAL UVEITIS An electron microscopic study

Experimental uveitis has been produced in two groups of albino rabbits by a single intravitreal injection of antigen. The animals in group I were immunized by injection of 10 mg of human serum albumin, whereas those belonging to group II received 50 mg of the same antigen. To study the blood‐aqueous barrier to proteins in the ciliary body of these eyes, horseradish peroxidase has been used as a cytochemical tracer by electron microscopy. The tracer was injected intravenously at different time intervals (1–30 min) before enucleation.

Peroxidase diffusion in the rabbit ciliary body in experimental uveitis. A light microscopic study.

Experimental uveitis has been produced in albino rabbits by injection of human serum albumin into the vitreous body. To study the blood‐aqueous barrier in the ciliary body in experimental uveitis, horseradish peroxidase has been used as a cytochemical tracer by light microscopy.

A light and electron microscopic study of the permeability of the rabbit iris vessels to horseradish peroxidase in experimental uveitis.

Experimental uveitis has been produced in two groups of albino rabbits by a single intravitreal injection of antigen. The animals in group I were immunized by injection of 10 mg of human serum albumin, whereas those belonging to group II received 50 mg. To study the blood‐aqueous barrier to proteins in the iris vessels of these eyes, horseradish peroxidase has been used as a protein tracer by light and electron microscopy. The tracer was injected intravenously at different time intervals (1–30 min) before enucleation.