Irmgard S. Wood

Trabecular Meshwork Cell Culture in Glaucoma Research:: Evaluation of Biological Activity and Structural Properties of Human Trabecular Cells In Vitro

The propagation of human trabecular cells in culture allows the study of the structural and functional properties of this distinct cell type under reproducible experimental conditions. Human trabecular cells can be effectively grown from dissected explants of trabecullar tissue, and the cultured cells can maintain the distinctive ultrastructural features of uncultured trabecular cells through at least five passages in vitro. The trabecular cell possesses a wide range of biochemical and structural properties that may be important for the maintenance of the aqueous outflow pathway. These properties include the growth of trabecular cells as an endothelial monolayer with a nonthrombogenic cell surface, the production of plasminogen activator, avid phagocytosis, and the ability to synthesize glycosaminoglycans, collagen, fibronectin, and other connective tissue elements. The presence of hyaluronidase and other lysosomal enzymes emphasizes that human trabecular cells are capable of metabolizing hyaluronic acid and other extracellular materials. Potential mechanisms of trabecular cell damage in vitro are examined by evaluating the effects of extended passage, peroxide exposure, and laser treatment on cellular morphology.

Experimental and Clinical Data on the Insertion of the Levator Palpebrae Superioris Muscle

Radiographic and electron microscopic evidence showed that the upper eyelid skin crease is formed by the insertion of the levator palpebrae superioris muscle into the septa between the orbicularis muscle into the septa between the orbicularis muscle bundles and not into the skin itself. Experiments on monkeys showed that the insertions of the aponeurosis and of Müllers muscle both contribute to normal eyelid elevation. No histologic evidence was found for a disinsertion of Müllers muscle in 20 cases of blepharoptosis. This, with other evidence discussed, supports the functional importance of the human aponeurotic insertions in eyelid elevation.

Salzmann's Nodular Degeneration of the Cornea

Eleven corneal specimens from nine patients with Salzmanns nodular degeneration of the cornea, together with all available clinical information, were collected for this study. The specimens were examined by light and electron microscopy. An antecedent keratitis was diagnosed by history and microscopic findings in every case. The corneal epithelium showed degenerative changes, its thickness varied, and in nodular areas it often consisted of only a single layer of flattened epithelial cells by light microscopy. Bowmans membrane was missing over the nodules, and in this zone there was excessive secretion of a basement membrane-like material. Hyaline degeneration of collagen, cellular debris, and electron-dense hyaline deposits were seen in the collagen of the nodules. The number of fibrocytes in the nodules varied from many that were active to a few that were degenerating. External irritation because of poor epithelial protection was interpreted as a causative factor, although other tissue repair mechanisms may also have played a role.

Radiation retinopathy as an experimental model for ischemic proliferative retinopathy and rubeosis iridis

We produced radiation retinopathy in capuchin monkeys and studied them with fluorescein angiography and light and electron microscopy. The animals were followed up from ten days to 3 1/2 years after radiation in order to determine whether this could provide an experimental model for other chronic ischemic-proliferative retinopathies, such as diabetes. The first change detected after radiation was the focal loss of capillary endothelial cells and pericytes. As the areas of acellular capillaries became confluent, cotton-wool spots became visible ophthalmoscopically. These increased in number and then faded away, leaving large areas of retinal capillary perfusion. Histologic studies showed occlusion first of the deeper, smaller retinal vessels and then gradually of the larger vessels. Intraretinal neovascularization as well as apparent recanalization then developed, but no new vessels extended through the internal limiting lamina into the vitreous. Rubeosis iridis with neovascular glaucoma developed 2 1/2 to 3 1/2 years postirradiation, and vitreous aspirate demonstrated a high level of angiogenic factor.

Retinal Phototoxicity from the Operating Microscope: The Role of Inspired Oxygen

The effect of the inspired oxygen concentration (FIO2) on the production of retinal phototoxicity by the operating microscope was studied in phakic rhesus monkeys. One eye of each monkey was exposed to light under conditions of 99% FIO2, and the other eye was exposed under 21% oxygen (O2). Three of four locations on each retina were exposed to light for durations varying from 1 1/2 to 20 minutes per exposure. Fundus photographs and fluorescein angiograms were obtained 24 to 72 hours after exposure. Animals were euthanatized for analysis of retinal histopathology at intervals from 2 weeks to 8 months after light exposure. Retinal phototoxic lesions were produced after an average of 5 minutes of light exposure under both 21 and 99% O2. O2 potentiated the light damage both clinically and histologically. Under both conditions, lesion size was directly related to the duration of light exposure (P less than 0.005). Lesions near threshold produced with 99% FIO2 were 1.6 to 6.9 (mean, 2.9) times larger than the corresponding lesions formed with 21% FIO2. Histologic damage was likewise more severe in lesions produced under high O2 conditions. Retinal repair occurred in lesions produced under high and low O2 conditions. Photoreceptor regeneration was nearly complete by 18 weeks, whereas retinal pigment epithelial (RPE) recovery lagged up to 1 1/2 months. The results of this study have important implications for clinical practice: the operating microscope can produce retinal phototoxicity rapidly, and O2 administered during ophthalmic procedures may potentiate the damage if appropriate precautions are not taken.

Clefts and microtubules of photoreceptor outer segments in the retina of the domestic cat

Transverse sections of cat photoreceptor outer segments, at several levels, were examined in the electron microscope. Rod disks usually had three shallow clefts. Single ciliary microtubules faced individual clefts and were observed close to the outer segment tip. Cone disks had a single cleft that deepened sclerally and subdivided the outer segment tip into two lobules. Ciliary microtubules also were positioned opposite the cleft in cone disks as far as the outer segment tip. The edge membrane of the clefts may be a preferred route for metabolic exchange between outer segment disks and cytoplasm.

Abnormal collagen fibrils in nanophthalmos: a clinical and histologic study

PURPOSE To report the successful treatment of choroidal detachment in a patient with nanophthalmos and to report histopathologic findings in this patients sclera. METHODS Choroidal detachment, secondary angle closure, and nanophthalmos were diagnosed using biomicroscopy, indirect ophthalmoscopy, and echography. Full-thickness sclerectomies in four quadrants were made on the right eye. Sclerae from these sclerectomies were studied ultrastructurally. RESULTS Best-corrected visual acuity improved to RE, 20/60 from 20/100 preoperatively; the anterior chamber deepened, and the choroidal detachment resolved. Histopathologic studies of each of the three scleral layers disclosed abnormal collagen fibrils that were frayed, split, and contained lightly stained cores. CONCLUSION New findings include the identification of collagen with lightly stained centers and identification of differences in collagen morphology in different areas of the sclera in a nanophthalmic eye.

Terminal course of nerve supply to Müller's muscle in the rhesus monkey and its clinical significance.

Electron microscopic, histochemical fluorescence, and pharmacologic evidence suggested that, in the rhesus monkey, Müllers muscle was not totally denervated either by cutting the levator palpebrae superioris muscle or by a Fasanella-Servat procedure. We examined the terminal course of the sympathetic nerve supply and the potential for preserving Müllers muscle in blepharoptosis surgery.

Pathology of iridectomy specimens in gyrate atrophy of the retina and choroid.

Gyrate atrophy of the retina and choroid is an autosomal recessive disease characterized by progressive retinal degeneration and ornithine aminotransferase deficiency. We report here the new histological findings and ultrastructural changes in 3 iridectomy specimens from 2 Finnish patients with gyrate atrophy. The iridectomy specimens were removed during routine cataract extraction and studied with a transmission electron microscope. The dilator muscle showed atrophy, abnormall mitochondria, and tubular aggregate type structures similar to those found in skeletal muscle. Degenerative changes such as extracted cellular matrix, dropout of cellular organelles, and dilated intercellular spaces were observed in the pigmented posterior epithelium and the anterior iris epithelium.

Degeneration of nerve terminals in cats following systemic epinephrine: depletion of tissue norepinephrine correlated with ultrastructural changes.

The drug 6-hydroxydopamine (6-OHDA) has been shown to cause degeneration of nerve terminals by direct observation with the electron microscope. This ability has been described as unique for 6-OHDA. Supralethal doses of epinephrine were given to four cats, three of which were pretreated with phenoxybenzamine (an alpha blocker used to protect the animal from epinephrines lethal effects) and iris and spleen capsule samples were examined with the electron miscroscope and assayed for norepinephrine content. A depletion of norepinephrine was found to coexist with ultrastructural evidence of nerve terminal degeneration when compared to control animals.