Katsuyoshi Mizuno

Leber's Congenital Amaurosis

An early stage of Lebers congenital amaurosis, characterized by white spots or lines in the fundus, occurred in two children. Light microscopic examination of eyes obtained from one child, a 16-month-old Japanese girl, revealed subretinal deposits corresponding to the white spots and lines in the fundus deposits. Light and electron microscopic examination of the eye showed distinctive changes in the outer retinal layers and choroid, while the inner retinal layers were nearly normal. Characteristic early lesions of congenital amaurosis appeared to be produced by deposits consisting of loose outer segments and apical processes of the pigmental epithelial cell and macrophages. Undifferentiation in the nuclei of the photoreceptor cell, the inner segment, the pigment epithelial cell, and the choriocapillaris were likely characteristics of the early changes of congenital amaurosis.

Electron-Microscopic study of pseudo- exfoliation of the lens capsule

The lens, iris, and ciliary body from the eyes of patients with glaucoma with cataract were examined via electron microscopy, and the following results obtained. 1. Zonular bundles were encrusted with accumulations of pseudoexfoliative (PE) materials and fragmented zonular fibrils, especially on their lateral aspects. 2. PE materials ranged from 300 to 400 Å in width, consisting of several subunits about 100 Å wide. 3. Pigment epithelial cells of the iris and nonpigmented epithelial cells of the ciliary process occasionally contained many phagosomes engulfing pigment granules. 4. Near the ciliary process, degenerating zonular bundles were mostly replaced with PE materials and fragmented zonular fibrils, and a gradual transition was observed between them. Zonular bundles were encrusted with accumulations of pseudoexfoliative (PE) materials and fragmented zonular fibrils, especially on their lateral aspects. PE materials ranged from 300 to 400 Å in width, consisting of several subunits about 100 Å wide. Pigment epithelial cells of the iris and nonpigmented epithelial cells of the ciliary process occasionally contained many phagosomes engulfing pigment granules. Near the ciliary process, degenerating zonular bundles were mostly replaced with PE materials and fragmented zonular fibrils, and a gradual transition was observed between them. From the above findings, it is probable that PE material might be mainly composed of degenerated zonular fibrils, which are presumed to be digested with lysosomal enzymes.

Distribution and some properties of cathepsin D in the retinal pigment epithelium

Abstract Cathepsin D in the retinal pigment epithelium of the bovine eye was studied using standard enzymological techniques. In the bovine eye the retinal pigment epithelium revealed the highest specific activity, the activity being highest in the lysosomal fraction. The enzyme activity in the lysosomal extract of the retinal pigment epithelium was proportional to both the enzyme concentration and incubation time. When the enzyme was heated, the enzyme activity was lost completely. The initial rate of the tyrosine release was dependent on the concentration of the bovine serum albumin, exhibiting a hyperbolic saturation curve. The optimal pH of the enzyme was about 4·0. The enzyme activity was not affected by thiol agents.

Cycloscopy of Pseudoexfoliation

We examined patients eyes with pseudoexfoliation gonioscopically and cycloscopically. In almost all eyes with pseudoexfoliation, accumulation was found in the zonules and ciliary processes in addition to the lens surface and iris border. In the fellow eyes of unilaterally affected eyes, pseudoexfoliative deposits were found in the zonules and ciliary processes in more than one half of the cases, leading us to conclude that pseudoexfoliative deposits in the zonule and ciliary process may be an early and consistent characteristic of pseudoexfoliation and may be an integral part of the clinical picture of pseudoexfoliation.

A Scanning Electron Microscopic Study of Nylon Degradation by Ocular Tissue Extracts

A scanning electron microscopic study showed that the surface of the nylon used for corneoscleral wound closure was smooth, while the nylon suture thread used to fix the intraocular lens against the iris showed cracks and roughness on its surface. The surface of the nylon thread was also roughened after treatment with bovine iris-ciliary body extracts. The nylon-degrading factor in the extract was nondialyzable, heat-labile, active at acidic pH, and inhibited in part by leupeptin, suggesting that lysosomal enzymes may be a factor in this phenomenon. Of the bovine ocular tissues, ciliary body extract degraded the surface of the nylon thread most significantly. The nylon surface was moderately digested by the retinal pigment epithelial extract, and slightly eroded by the extracts from the iris, sensory retina, and choroid. Corneal and lenticular extracts did not affect the nylon surface. Nylon suture thread may be hydrolyzed by lysosomal enzymes and should be considered a late-degrading suture.

Lysosomal Enzymes in Subretinal Fluid

Samples of subretinal fluid (SRF) from patients with primary rhegmatogeneous retinal detachment of various duration were studied using standard enzymologic techniques. The protein content in SRF increased with the duration of detachment. The activities of lysosomal enzymes in SRF, which were acid phosphatase, β-glucuronidase, and cathepsin D, also increased with the duration of detachment. Especially cathepsin D, which was not detected in serum, was present in SRF. The activity of a nonlysosomal enzyme, i. e., lactic dehydrogenase, which was used as a marker of cell disruption and of serum transudation was the same as that of serum. Because lysosomal enzymes are known to be able to degrade cells and tissues, the enzymologic analysis of SRF contributes to our understanding of the pathology of primary rhegmatogeneous retinal detachment. Bericht über enzymatische Untersuchungen von subretinaler Flüssikeit (SRF) bei Patienten mit primär rhegmatogener Netzhautablösung unterschiedlicher Dauer. Der Proteingehalt in der SRF nahm mit der Dauer der Abhebung zu, ebenso die Aktivitäten der lysosomalen Enzyme (saure Phosphatase, β-Glucuronidase und Kathepsin D). Insbesondere fand sich in der SRF Kathepsin D, das im Serum nicht enthalten war. Die Aktivität eines nicht-lysosomalen Enzyms (Laktat-Dehydrogenase) war die gleiche wie im Serum. Da die lysosomalen Enzyme dafür bekannt sind, daß sie Zellen und Gewebe verändern, trägt die Analyse der Enzyme der SRF zum Verständnis der Pathologie der primär rhegmatogenen Netzhautablösung bei.

Distribution of acid lipase in the bovine retinal pigment epithelium.

Abstract Acid lipase in the retinal pigment epithelium of the bovine eye was studied biochemically using triglyceride as substrate. The retinal pigment epithelium revealed the highest specific activity, the activity being highest in the lysosomal fraction. The lysosomal distribution of acid lipase was supported by the evidence that other hydrolytic enzymes were also localized with highest specific activity in the lysosomal fraction prepared by differential pelleting. The optimal pH of the enzyme was 4–5. Acid lipase in the retinal pigment epithelium had maximum activity with glycerol tridecanoate as substrate. Specific activity of retinal pigment epithelium was about 10-fold higher than that of liver. The possible role of acid lipase in the retinal pigment epithelium was discussed.

Distribution and some properties of cathepsin B in the bovine eyes.

Abstract Cathepsin B in the bovine eye was studied biochemically using α- N -benzoyl- l -arginine amide as substrate. The highest specific activity of cathepsin B was observed in the ciliary body among bovine eye tissues, the activity being highest in the lysosomal fraction. The optimal pH of the enzyme in the ciliary body was about 5·1. The enzyme activity in the ciliary body was activated by thiol agents, and inhibited by p -chloromercuribenzoate, leupeptin and heavy metal ions.

Pigment Deposition in the Anterior Segment Caused by Melanocytoma of the Optic Disc

A 34-year-old Japanese woman had a melanocytoma of the optic disc with scattered pigment particles in the vitreous in the left eye in 1970. Fifteen years later, we noticed pigment dispersion on the posterior lens surface, iris root, and trabecular meshwork, which resembled findings often caused by ocular malignant melanoma. Because the melanocytoma of the optic disc had decreased in size and the number of dispersed pigment particles in the vitreous cavity was reduced, it appeared that the pigmented particles produced by partial necrosis of the melanocytoma had resulted in the pigmentation of the anterior segment.

Regional distribution of lysosomal enzymes in the retina and choroid of human eyes

Regional distribution of lysosomal enzymes in the retina and choroid of human eyes was studied biochemically. Specific activities of acid phosphatase, cathepsin D, and arylsulfatase in the retina and choroid varied by area were also studied. The macular area showed the highest activities in comparison to other areas.