Atsushi Mizukawa

Apoptosis in retinal ganglion cell decrease in human glaucomatous eyes

Hematoxylin-eosin staining, the TUNEL method for in situ detection of the intranuclear DNA fragmentation, which indicates apoptosis, and electron microscopy were used to study the morphologic changes in specimens from the eyes of 8 patients with secondary glaucoma and 2 normal control eyes to evaluate our hypothesis that apoptosis causes a decrease in retinal ganglion cells in human glaucomatous eyes. The TUNEL method permits identification of intranuclear DNA fragmentation. Apoptosis was found in the ganglion cells of 2 glaucomatous eyes with recent sight loss, and in the ganglion cells of a control eye from a 95-year-old subject, taken at autopsy. Results of our study indicate that a decrease in retinal ganglion cells in glaucomatous eyes is caused by apoptosis. In addition, apoptosis resulting from aging must be considered in order to understand the reduction of retinal ganglion cells in the glaucomatous eyes of elderly patients.

Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation.

Twenty-two eyes of 11 cynomolgus monkeys were subjected to contact transscleral cyclophotocoagulation with a continuous-wave Nd:YAG laser. The right eye of each monkey was coagulated at the pars plicata region by the contact probe placed 1.0 mm from the limbus, while the left eye of each monkey was coagulated at the pars plana region by the contact probe placed 3.0 mm from the limbus. Physiological and morphological studies were carried out up to 6 months after the treatment. The postoperative intraocular pressure showed a significant decrease within 1 week, corresponding to the inflammation of the anterior chamber. A gradual increase of the intraocular pressure occurred from the 2nd week on and returned to the preoperative value 8 weeks after pars plicata coagulation. The pars plana coagulation group maintained the intraocular pressure lower than the preoperative value until the end of the observation period. Histopathological examinations were carried out by the use of tracer particle perfusion into the anterior chamber. The pathologic features of pars plicata coagulation were necrosis, followed by atrophy of the ciliary process. The tracer particles accumulated at the anterior portion of the space between the bundles of ciliary muscle. The pathologic features of pars plana coagulation were necrosis followed by extension of proliferative tissue into the vitreous. The surrounding extracellular space of the stroma was enlarged, and the ciliary muscles were separated from the sclera. The tracer particles accumulated at the enlarged extracellular space of the stroma and the opened suprachoroidal space. These results suggest that the decrease of the intraocular pressure after pars plicata cyclocoagulation resulted from the reduction of aqueous secretion, whereas that after pars plana cyclocoagulation resulted from enhancement of the uveoscleral outflow through the enlarged extracellular space from the anterior chamber into the suprachoroidal space.

Autoantibody Against Neuron-Specific Enolase Found in Glaucoma Patients Causes Retinal Dysfunction In Vivo

PURPOSE In our recent paper, we have reported the presence of serum autoantibody against neuron-specific enolase (NSE) in patients with glaucoma. The purpose of the present study was to investigate further the pathological effects of anti-NSE antibody on retina by comparing them with the effects induced by N-methyl-D-aspartate (NMDA). METHODS Either a glaucoma patients serum or purified anti-NSE antibody, or 10-40 mM NMDA was intravitreously administered into Lewis rat eyes, and electrophysiological, histopathological, and biochemical evaluations were performed. In addition, the neuroprotective effects of anti-glaucoma drugs, such as timolol, betaxolol, nipradilol, and isopropyl unoprostone, and a calcium antagonist were also studied using these animal models. RESULTS Electron microscopy revealed that intravitreal administration of a glaucoma patients serum, which immunoreacted with retinal 50 kDa in Western blot analysis, and purified anti-NSE antibody induced retinal ganglion cell apoptosis in rat eyes. Functionally, these eyes showed a significant decrease in electroretinogram (ERG) responses and a remarkable decrease in rhodopsin phosphorylation reaction. These changes were comparable to the effects observed after the intravitreal administration of 20 mM NMDA. Co-administration of nipradilol, an alpha- and beta-blocker, with anti-NSE antibody or 20 mM NMDA caused marked recovery of the affected ERG responses within 2 weeks. In contrast, administration of timolol or betaxolol showed no recovery effect on the ERG responses. Among these drugs, only betaxolol showed a recovery effect on NMDA-induced decrease of rhodopsin phosphorylation. Nilvadipine functioned beneficially on both impaired ERG and rhodopsin phosphorylation reactions observed in rat eyes injected intravitreously with anti-NSE antibody or NMDA. These effects of nilvadipine were not changed by the addition of endothelin-1. In contrast, isopropyl unoprostone had no effect on these functions. CONCLUSION These observations suggest that serum autoantibody against NSE found in some patients with glaucoma induces retinal dysfunction in vivo, similarly to NMDA.

Visual function in retinitis pigmentosa related to a codon 15 rhodopsin gene mutation

To determine the phenotype of a Japanese family in which retinitis pigmentosa cosegregates with a rhodopsin gene mutation, i.e. an asparagine-to-serine change at codon 15 (Asn-15-Ser), 5 affected and 5 unaffected members of one pedigree underwent several ophthalmic examinations as well as Ganzfeldelectroretinography (ERG) and multifocal ERG. Genomic DNA samples were analyzed by PCR amplification, sequencing and restriction enzyme digestion. A codon 15 rhodopsin gene mutation (Asn-15-Ser) was found in all affected members. The region of pigmentary degeneration was localized in the lower hemiretina, and visual field defects corresponded to the retinal pigmentary changes. Scotopic ERG amplitudes, rather than photopic ERG amplitudes, were reduced. Multifocal ERG revealed a low magnitude of response density, even for the upper hemiretina, which showed no bony corpuscle pigmentation. Visual function in sectorial retinitis pigmentosa associated with rhodopsin gene codon 15 mutation is on the basis of the rod-cone dystrophy, regardless of differences in phenotypic expression.

[Histopathological observations on bullous keratopathy after argon-laser iridotomy].

PURPOSE To elucidate histopathological mechanism of bullous keratopathy after argon-laser iridotomy (ALI). CASE AND METHOD The patient was a 60-year-old female who underwent penetrating keratoplasty because of bullous keratopathy after 2 years and 2 months of ALI. The corneal specimen was fixed with a mixture of 2.5% formalin and 1.0% glutaraldehyde, and examined under light and electron microscopes. FINDING AND CONCLUSION Laser-damaged endothelium produced a large amount of basement membrane-like material beneath Descemets membrane. At the next stage, the severely damaged endothelium lost its organellae and cell membranes, and fell off. The surrounding healthy endothelium migrated into the damaged area and produced a small amount of material like basement membrane which covered Descemets membrane. After that, stromal swelling, decrease of keratocytes, breaking and disappearance of Bowmans membrane, epithelial edema, connective tissue accumulation beneath basal cells, and epithelial detachment occurred in the laser-damaged area.