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Biomedical subjects

S Okisaka

Publications and source records attributed to S Okisaka.

At least 19 recordsLinked to original sources
PubMed1992

Diode laser iridotomy in rabbit and human eyes.

We investigated the use of an infrared diode laser to perform iridotomies in 20 eyes of ten rabbits and 40 eyes of 24 patients with primary angle-closure glaucoma. We used a two-stage method with initial circular stretch burns and subsequent penetrating multiple burns. The iris was perforated in one session and remained patent through ten months in rabbits, and seven to nine months in humans. Transitory clinical complications included intraocular pressure increase of more than 10 mm Hg (20%, eight of 40 eyes), corneal endothelial changes (5%, two of 40 eyes), clouding of lens surface (60%, 24 of 40 eyes), localized cataract (5%, two of 40 eyes), and pupillary distortion (70%, 28 of 40 eyes). No retinal damage was observed. Diode laser can be used for peripheral iridotomy.

Acute Disease↗
PubMed1992

Formation of capillary-like tubes by vascular endothelial cells cocultivated with keratocytes.

This report describes an in vitro system that could be useful for investigating corneal neovascularization. When isolated bovine capillary endothelial cells (CEC) were cocultivated with rabbit corneal keratocytes, capillary-like cords extended actively from the endothelial cells in the multilayers of the keratocytes. The developing cords continued to elongate, branch out, and anastomose with each other, forming a capillary-like network by the 12th day of coculturing. Electron microscopic observation revealed that the cords were tubular structures composed of three to seven endothelial cells in the multilayers of keratocytes, and that a basal lamina-like matrix was situated at the abluminal face of the endothelial cells. The growth of cellular cords from the cloned CEC also occurred when CEC were seeded onto a cell-free extracellular matrix that had been synthesized by keratocytes. Keratocyte-conditioned medium alone did not stimulate proliferation of CEC. These observations clearly indicate that the formation of capillary-like structures by CEC depended upon the presence of an extracellular matrix produced by keratocytes, rather than upon the keratocytes themselves or any other keratocyte byproduct. This simple in vitro experimental system is proposed as a useful tool for studying corneal neovascularization.

Adrenal Cortex↗
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↗
PubMed1992

[Linearity and nonlinearity of pattern ERG and pattern VECP].

To investigate the linearity and nonlinearity of both pattern electroretinogram (P-ERG) and pattern visually evoked cortical potential (P-VECP), a checkerboard pattern was presented to normal subjects with the reversal rate of transient and steady-state condition. Using a personal computer (BASIC) system, we made simulated waves (linear model) at 3 to 15 rev/s stimuli summated from an original wave evoked at 1 rev/s stimulation. Both simulated P-ERGs and P-VECPs were found to be different from the original ones, and the nonlinear component, which was interpreted as the difference between the original and simulated waves, was thought to increase with the increment of pattern reversal rate. However the 2 nd harmonic component of the original wave drastically decreased at above 7.5 rev/s stimulation. Thus, it is concluded that the nonlinearity of both P-ERG and P-VECP does not correlate with those 2 nd harmonic components.

Adult↗
PubMed1992

[In vitro formation of endothelial cells into capillary-like cords is promoted by keratocytes].

When isolated bovine capillary endothelial cells were co-cultivated with rabbit corneal keratocytes, capillary-like cords extended actively from the capillary endothelial cells in multilayers of keratocytes. The developing cords continued to elongate, branch out and anastomose with each other, forming a capillary-like network by the 12th day of co-culturing. Electron microscopic observation revealed that the cords had tubular structures, which were composed of 3-8 endothelial cells in the multilayers of keratocytes, and that a basal-like matrix was situated on the outer surface of the endothelial cells. The roles of keratocytes in the cord formation by capillary endothelial cells were discussed. This simple in vitro experimental system is proposed as a useful tool in the study of corneal neovascularization.

Animals↗
PubMed1992

[The tension of zonule and aging changes of ciliary bodies].

The zonular tension was studied in thirty fixed autopsy eyes (7 eyes under 30 years old, 15 eyes seventh decade and 8 eyes over 85 years old) by pulling the lens backward, and the surface structure of the ciliary body was studied histopathologically following the removal of zonular fibers. The tension for breaking zonules was 49.1 +/- 8.0 gm in younger age group, and 35.3 +/- 8.2 gm in older age group. The zonules in the younger age group was statistically stronger than those in the older age group (p less than 0.01). This breaking occurred at the region adjacent to the ciliary body in the younger age group, but at the region adjacent to the lens in the older age group. The internal surface of the pars plicata and the anterior pars plana was characterized by regular meridional ridges and grooves in the younger age group but was irregular in older age group. In the older age group, grooves among the ridges were wide. In the posterior pars plana, spine-like structure was observed learning parallel toward the lens along the course of zonular fibers. These ageing changes of zonules and ciliary body may depend on the load for the accommodation.

Accommodation, Ocular↗
PubMed1992

Photocoagulation with continuous wave ND:YAG laser for neovascular maculopathy.

Twenty-two eyes in 22 cases of neovascular maculopathy were treated with continuous wave (CW) Nd:YAG laser and followed up for 6 to 24 months. The effect of the treatment was evaluated by repeated visual acuity testing, fundus photography, fluorescein angiography and automated static perimetry. In 91% of the patients visual acuity remained unchanged or improved. Fluorescein angiography revealed that the neovascularization disappeared in 91% of the patients. In 40% of the patients the central visual field showed improvement by automated static perimetry. These results indicate that CW Nd:YAG laser photocoagulation is useful for the treatment of neovascular maculopathy.

Aged↗
PubMed1991

Luminance-unbalanced pattern onset-offset electroretinogram and visual evoked cortical potential.

The effects of a luminance-unbalanced pattern onset-offset mode of stimulation on electroretinograms and visual evoked cortical potentials were investigated. With the use of originally devised software, only offset luminance was varied from 14.7 to 62.3 cd/m2. A vertical grating pattern (1.5 c/deg, 38.8 cd/m2 mean luminance, 0.95 contrast) was presented for 260 ms and was absent for 260 ms to normal subjects. With an increase in the luminance level of the offset pattern from the lowest level, the amplitude of the onset electroretinogram increased by degrees, while that of the offset electroretinogram gradually decreased. Conversely, onset visual evoked cortical potential responses decreased gradually, and offset visual evoked cortical potentials increased correspondingly. Furthermore, the spatial tuning of the onset pattern electroretinogram was already ambiguous, even when there was only a 4-cd/m2 difference between onset and offset pattern luminances. Thus, luminance control is indispensable for pattern onset-offset stimulation.

Adult↗
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

[Mitotic activity of rabbit corneal epithelium in vitro].

It is difficult to maintain corneal epithelial cells for several passages in culture. At a first step to establish a culture system for corneal epithelium, the authors evaluated factors which seemed to be involved in the growth kinetics and mitotic activity of rabbit corneal epithelium in vitro. First of all, to compare the growth kinetics of peripheral and central epithelium, we measured the areas and distances of the epithelium that outgrew from peripheral and central explants in culture. The peripheral corneal epithelium grew 1.2-to 1.6-fold better than the central corneal epithelium. However, there was no significant difference between them. Secondly, we evaluated the effects of epidermal growth factor (EGF), cholera toxin (CTX) and insulin, which were contained in supplemented hormonal epithelial medium (SHEM) developed by Jumblatt et al, on the mitotic activity of rabbit corneal epithelium. Among these drugs, only EGF had the ability to increase the epithelial cell number after 10 days of incubation. By contrast, CTX which elevated the level of cyclic AMP inhibited the proliferation of the epithelium.

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↗
PubMed1990

[Quantitative analysis of collagen fiber in keratoconus].

In order to identify the direct pathogenic factors involved in the stromal thinning of keratoconus, quantitative analysis of keratocytes, collagen fibers and collagen lamellae in keratoconus cornea was performed histologically by light and electron microscopy. Both normal and keratoconus corneas showed a similar cell density of keratocytes in the central stroma, therefore the total number of keratocytes in keratoconus cornea might be smaller than that of controls, because of the thinning of stroma in the keratoconus. The collagen lamellae in keratoconus corneas showed a significant decrease in number compared with controls. There was a direct relationship between the stromal thickness and number of collagen lamellae. On the other hand, there was no statistical significance between normal and keratoconus corneas in terms of the thickness of collagen lamellae. These results suggest that the thinning of the cornea in keratoconus might occur as the result of a defect of some collagen lamellae due to a disorganization during the process of collagen lamellae formation.

Adolescent↗
PubMed1990

[Photocoagulation with free-running mode Nd: YAG laser on neovascular maculopathy].

Seventeen eyes in 14 cases of early neovascular maculopathy were treated with free-running mode Nd: YAG laser and followed up for 7 to 56 months by examination of visual acuity, fluorescein angiography and static perimetry. Obliteration of subretinal neovascularization could be achieved with both mild and moderate photocoagulation. Retinal sensitivity after moderate photocoagulation decreased moderately. Damaged retinal sensitivity after mild photocoagulation recovered one month later. Two out of 11 eyes in which only the neovascular membrane was treated showed recurrent neovascularization adjacent to the treated lesion 6 months and 9 months after photocoagulation. One out of 6 eyes received mild photocoagulation on the neovascular membrane and the surrounding area showed recurrent neovascularization adjacent to the treated lesion 6 months after photocoagulation. Retinal hemorrhage occurred in one out of 14 eyes that received mild photocoagulation and in one out of three moderately photocoagulated eyes. The recurrent neovascularization occurred in two eyes with retinal hemorrhage and in one mild burned eye without retinal hemorrhage. Recurrent neovascularization may correlate with retinal hemorrhage.

Adult↗
PubMed1990

Retinal pigment epithelial cells in culture secrete angiogenic inhibitors: in vitro study.

Conditioned medium wherein bovine retinal pigment epithelial cells have been cultured (RPE-CM) inhibited proliferation of the capillary endothelial cells (CEC) of the bovine adrenal gland. The RPE-CM was fractionated into three fractions; molecular weight of more than 30 kilo Daltons (kDa) (30 kDa fraction), between 10 and 30 kDa (10 kDa-30 kDa fraction), and less than 10 kDa (10 kDa fraction). Each fraction was tested for its effect on the proliferation, morphology and movement of the CEC. The proliferation of CEC was inhibited in the more than 30 kDa fraction and less than 10 kDa fraction, but not in the 10 kDa-30 kDa fraction. The RPE-CM changed morphology of the CEC into slender shape. This morphological change was observed only in the more than 30 kDa fraction, and the CEC in the other fractions maintained normal morphology. When the CEC proliferation was arrested by hydroxyurea, RPE-CM and the more than 30 kDa fraction did not change morphology. Unfractionated RPE-CM and the more than 30 kDa fraction which changed the morphology of the CEC also inhibited movement of the CEC, such as the migration of cells from a confluent cell layer and single cell movement. These findings suggested that the RPE in culture secrete soluble anti-angiogenic factors into the medium.

Adrenal Glands↗
PubMed1990

[A case of necrotizing scleritis with angiitis of papilla].

A case of a 66-year-old woman suffering from polymyalgia rheumatica with necrotizing scleritis followed central retinal artery occlusion in the left eye was studied clinico-pathologically. The left eye was enucleated because of severe pain in spite of the steroid therapy, and was examined histopathologically. The necrotic granulomatous changes of the deep sclera in the ciliary body and peripheral fundus were observed. Lymphocytes, plasma cells and epitheloid cells infiltrated in the central retinal artery at the papilla. It seemed that subconjunctival injection of steroid had induced scleral necrosis. When scleritis is very severe, it might be suggested that systemic steroid should be given in large suppressive doses.

Female↗
PubMed1989

[The role of the cytoskeletal components in cell culture in collagen gel as a model system of vitreous contraction].

We previously reported a cell culture system in artificial collagen gel as a model system of vitreous contraction. In this report, the epithelium cultured in the collagen gel elongated and induced gel contraction. The motile cytoskeletal components were thought to be important for morphological changes of the cells and the gel contraction. In order to examine the relationship between the cytoskeletal components and morphological changes of the cells and gel contraction, colchicine and cytochalasin B, known to be inhibitors for microtubules and microfilaments respectively, were added to the gels and the culture media. Bovine lens epithelia were cultured in the gels and the media containing 0-1000 nM colchicine or 0-10 microM cytochalasin B. Both inhibitors arrested the elongation of the cells and the contraction of the gels. These results suggested that the cell movement caused by the functions of microtubules and microfilaments were related to the vitreous contraction.

Animals↗
PubMed1989

[Pattern reversal electroretinogram--effect of check size, luminance, field size and defocusing].

Using a high water-content soft-contact-lens electrode we recorded pattern electroretinograms (P-ERGs) of subjects responding to reversal checkerboard stimuli and the stimulus parameters were varied in order to investigate normal P-ERG properties. The P-ERG varied with changing luminance, field size and defocusing parameters in the same way as P-VECP, but differed from P-VECP with changes in the check size parameter. These results suggest that the spatial tuning observed in P-VECP could not be discerned in this P-ERG study. It cannot be denied that P-ERG is distorted by P-VECP, which has a larger amplitude at about 100 ms after stimulation. In the future it will be necessary to investigate the origin of P-ERG under experimental conditions separating contrast-related response from luminance-related response.

Adult↗