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Biomedical subjects

A Mizukawa

Publications and source records attributed to A Mizukawa.

15 recordsLinked to original sources
PubMed1999

[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 Descemet's 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 Descemet's membrane. After that, stromal swelling, decrease of keratocytes, breaking and disappearance of Bowman's membrane, epithelial edema, connective tissue accumulation beneath basal cells, and epithelial detachment occurred in the laser-damaged area.

Corneal Diseases↗
PubMed1998

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 Ganzfeld electroretinography (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.

Adult↗
PubMed1998

[Effect of ultraviolet-filtering contact lens on rabbit eyes after exposure to ultraviolet light].

We evaluated the protective effect of a newly designed soft contact lens (SCL) on rabbit eyes. This SCL absorbs the ultraviolet B light of wavelengths between 280 nm and 320 nm. Three weeks after resecting the nictitating membrane, the rabbit corneas were covered either by the new SCL or a conventional SCL. The eyes were exposed to ultraviolet light from two 15 W lamps placed 20 cm anteriorly for 3 hours. Another three hours after the exposure, the cornea was examined first with a slitlamp biomicroscope after staining with fluorescein and then by histopathological means after enucleation. Six eyes wearing the new SCL showed moderate superficial punctate keratopathy. Six eyes wearing conventional SCL showed severe superficial keratopathy or corneal erosion. These findings were in good agreement with the histopathological findings. The new ultraviolet-filtering SCL was thus effective in protecting the rabbit cornea under our experimental conditions.

Animals↗
PubMed1996

[Natural process of wound healing of photocoagulated retinal pigment epithelium in culture--observation of DNA synthesis by BrDu incorporation].

We examined the proliferation of retinal pigment epithelial (RPE) cells after krypton laser photocoagulation in culture. A pigmented monolayer of chick embryonic RPE cells was cultured on a collagen membrane placed on collagen gel. RPE cells were labeled with bromodeoxyuridine (BrDu) every 12 hours until 7 1/2 days after the photocoagulation and stained immunocytochemically with anti BrDu antibody. Immediately after the photocoagulation, RPE cells became detached at the burned lesion and the collagen membrane beneath the RPE layer was exposed. Some cells adjacent to the burned lesion showed DNA synthesis and subsequent mitosis between 12 to 24 hours after the photocoagulation. Cells with labeled nuclei migrated into the denuded burned area after 24 hours and covered the whole burned area within three days after the photocoagulation. DNA synthesis continued in these on the burned lesion after complete coverage of the lesion but stopped temporarily 3 1/2 to 4 1/2 days after the photocoagulation. Thereafter DNA synthesis increased again and continued until the end of the experiment. Such use of the cultured RPE cells might be useful in studying cellular reaction after photocoagulation.

Animals↗
PubMed1996

[Comparative study on diode laser (680 nm) and krypton laser mild photocoagulation--histological findings and therapeutic outcome for diabetic maculopathy].

A histopathological study of macaca monkey retina-choroid was carried out for one month after mild photocoagulation with a diode laser (680 nm) and a krypton laser (647 nm). Both lasers produced the same damage to the outer layer of retina and to the melanocytes of 1/3 of the inner choroid. Mild focal photocoagulation was done for 6 patients (12 eyes) with diabetic maculopathy. The patients were 41 to 67 years old, suffering from diabetes mellitus for 5 to 25 years. The grade of their retinopathy was Fukuda's classification AI, AII, and BI. AII eyes were tested before and 3-6 months after photocoagulation for corrected visual acuity, fluorescein angiography, and visual field sensitivity by Octopus automated static perimetry. Visual acuity was stable in all cases. Central sensitivity was better in 2 eyes and unchanged in 4 eyes in both types of laser photocoagulation. In cases of total loss, one eye was improved, 4 eyes were unchanged and one eye was worsened by diode laser photocoagulation and one eye was improved, 2 eyes were unchanged and 3 eyes were worsened by krypton laser photocoagulation. The diode laser (680 nm) might be as useful for ophthalmic laser treatment as the krypton laser.

Adult↗
PubMed1994

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.

Animals↗
PubMed1993

Histopathological study of pseudophakic bullous keratopathy developing after anterior chamber of iris-supported intraocular lens implantation.

Sixty corneal buttons excised from patients who developed pseudophakic bullous keratopathy after anterior chamber or iris-supported intraocular lens implantation were studied morphologically and statistically. The mean age of patients was 72.5 +/- 11.6 years. The mean interval between intraocular lens implantation and keratoplasty was 5.1 +/- 2.2 years. Degeneration and conversion of endothelial cells, abnormal proliferation of posterior collagenous layer, and edema of stroma and epithelium were noticed morphologically. Twenty-nine of the 60 specimens showed a surviving endothelial cell area of less than 50%. In these specimens a significant increase in the thickness of the central stroma was recognized compared with the other 31 specimens. The number of keratocytes in the 29 specimens had decreased significantly compared with the control. A linear regression study showed a significant relationship between the thickness of the stroma and the number of keratocytes. The keratocyte density decreased predominantly in the posterior part of the stroma.

Adult↗
PubMed1992

[Histopathological study on the pars plicata of cynomolgus monkey by the CW Nd:YAG laser].

The pars plicata of cynomolgus monkey eyes were coagulated by a continuous wave (CW) Nd:YAG laser contact system. the intraocular pressure and histopathological changes were observed during the following 3 months. the intraocular pressure decreased during the first week to a minimum level and returned gradually to the pre-coagulation level within 1-3 months. Immediately after photocoagulation, both pigment and non-pigmented epithelium of pars plicata were destroyed. Three weeks after the coagulation nonpigmented epithelium and capillaries showed regeneration. Three months after coagulation, the proliferation of non-pigmented epithelium was conspicuous and regenerating pigment epithelium was observed around the merging of the burned lesion. The CW-Nd:YAG laser contact photocoagulation induced localized destruction of ciliary processes. The regeneration of epithelium and capillaries might indicate that the function of ciliary body could recover to a certain extent and it may be comparatively easy to control the degree of coagulation. These findings suggest that it might be possible to apply CW-Nd:YAG laser photocoagulation to various types of glaucoma.

Animals↗
PubMed1991

Comparative histopathological study of free-running mode and continuous wave Nd:YAG laser photocoagulation of monkey retina and choroid.

The effects of free-running mode (FRM) or continuous wave (CW) Nd:YAG laser application on the retina and choroid of 12 monkeys were examined periodically up to 24 months by light and electron microscopes. FRM Nd:YAG laser produced severe choroidal hemorrhage even in mild burns, because of the extensive coagulation of melanocytes at the center of the burned lesion. The rupture of Bruch's membrane did not depend on the power of the laser. On the other hand, CW Nd:YAG laser rarely produced subretinal hemorrhage through the rupture of Bruch's membrane in the medium-grade and severe burns. However, choroidal hemorrhage was seen histologically even in mild CW burned lesions. In the healing stage of mild FRM burned lesions the retinal pigment epithelium (RPE) and choroidal fibroblasts showed different repair processes. FRM medium-grade burned lesions showed the proliferation of Müller cells, while CW burns showed the regeneration and proliferation of RPE, Müller cells and fibroblasts. Because of the difference in the repair processes evoked by these two modes of laser application, these findings suggest that CW Nd:YAG laser is preferable for the treatment of subretinal and choroidal disorders.

Animals↗
PubMed1991

[Histopathological study on the monkey retina and choroid by diode laser endophotocoagulation].

The fundi of three cynomolgus monkeys were coagulated using a diode laser endophotocoagulator. The histopathological changes of the retina and the choroid were investigated periodically up to 3 months. The damage of the retina extended into the outer plexiform layer following mild burn, into the inner nuclear layer with moderate burn and into the nerve fiber layer on severe burn. The pigment epithelium proliferated with multiple layer cells 1-3 months after the irradiation. The choriocapillaries were obstructed, regardless of the degree of burns, immediately after the irradiation, but recanaliculation was observed at the mild and moderate burns 1-3 months after the irradiation. The effects on the choroid were localized to the inner layer following mild burn, but the damage extended into the outer layer with moderate burns. Following severe burns obstruction of the medium size vessels was observed. The fibrous changes of the choroid increased in accordance with the degree of the burn. The damaged melanophore in the choroid recovered considerably 1 month after the mild burn. On the other hand, many macrophages still remained in moderate and severe burn lesions. These results suggested that diode laser photocoagulation might be effective for the treatment of the choroidal diseases rather than retinal diseases, because diode laser photocoagulation produced the considerable change in the choroid as well as in the retina.

Animals↗
PubMed1978

Fine structure of the Müller cell revealed by high-voltage electron microscopy.

The three-dimensional organization of Müller cells in the retina of various vertebrates was investigated by means of high-voltage electron microscope stereoscopy using 2-5 micrometer-thick Golgi preparations. The alveolar compartments constituted by thin lamellar processes of the Müller cell were seen in the outer and inner nuclear layers. The radial process of the Müller cell has many irregular appendages which attenuate into thin lamellae to invade the neuropile. The functional significance of the characteristic morphological features of the Müller cell is discussed.

Animals↗
PubMedDate not supplied

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.

Adult↗