Biomedical subjects

S Okisaka

Publications and source records attributed to S Okisaka.

At least 55 records · Page 3Linked to original sources

PubMed1995

[Clinical importance of inclusion cysts of nevi in bulbar conjunctiva].

We investigated 30 cases of nevi in bulbar conjunctiva histopathologically from 1980 to 1992. The patients' ages were between 5 and 85 years old (mean, 21 years). Investigated parameters of the tumors were the location, growth pattern, and the presence of inclusion cysts, melanin granules, goblet cells, and feeding vessels. Of 30 cases, 26 cases (87%) had inclusion cysts which were characteristic findings of conjunctival nevi. The mucous secretion from goblet cells may play an important role in the synthesis of inclusion cysts, but goblet cells were not found in 9 cases. This finding suggests that other secretory cells may be present. Four cases without inclusion cysts consisted of flat tumors. From this finding, the presence of inclusion cysts may be related to the growth of tumors. We conclude that the growth of the pigmented conjunctival tumors with inclusion cysts suggests a benign growth pattern. A periodical follow-up study or biopsy should be performed, if inclusion cysts are not found.

Adolescent↗

PubMed1995

[Comparative study on frequency-doubled Nd: YAG laser, krypton laser and diode laser photocoagulation for diabetic maculopathy].

Twenty six eyes of thirteen patients with diabetic maculopathy (Fukuda's classification AI, AII, BI) were treated with frequency-doubled Nd:YAG laser (6 eyes) or krypton laser (7 eyes) in one eye and diode laser (13 eyes) in the other eye. Group A was treated with frequency-doubled Nd: YAG laser and diode laser, and group B was treated with krypton laser and diode laser. The visual acuity, visual field (Octopus program 31) and fundus were examined at one month, 3 months, and 6 months after photocoagulation. Visual acuity was stable in all eyes. The central 30 degree visual sensitivity decreased more after diode laser treatment than after that of the other lasers. Krypton laser photocoagulation maintained the better visual function and was easy to use followed by frequency-doubled Nd: YAG laser. Because the appearance immediately after diode laser lesion was weaker than one hour after coagulation, it was difficult to get the proper power setting.

Adult↗

PubMed1995

[The effects of dopa and oxygen on RNA concentrations in cultured chick embryonal retinal pigment epithelial cells].

We measured RNA and DNA concentrations in cultured chick embryonal retinal pigment epithelial cells to investigate the effects of dopa and oxygen on DNA and RNA synthesis. RNA/DNA ratios were decreased by addition of 250 microM dopa. Decrease of RNA/DNA ratios was suppressed when the oxygen concentrations were reduced from 20% to 10%. Incubation with medium containing 100 microM dopa increased RNA/DNA ratios in 10% oxygen. Exposure of retinal pigment epithelial cells to 250 microM dopa caused the decrease of RNA concentrations in the retinal pigment epithelial cells, which was ameliorated by lowering oxygen concentrations. However, the addition of 100 microM dopa in 10% oxygen stimulated retinal pigment epithelial cells and seemed to increase RNA concentrations.

Animals↗

PubMed1994

A comparison between melanotic and amelanotic retinal pigment epithelial cells in vitro concerning the effects of L-dopa and oxygen on cell cycle.

Melanin precursors and free radicals, cytotoxic substances, are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L-dopa and oxygen on the cell cycle of melanotic retinal pigment epithelial (RPE) cells with amelanotic RPE cells because of the differences of tyrosinase activities between melanotic and amelanotic RPE cells. Flow cytometric DNA analysis of RPE cells exposed to L-dopa (100 microM and 250 microM) were conducted at several oxygen concentrations (20%, 10%, and 5%). The dose-dependent effect of L-dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic than in amelanotic RPE cells, and oxygen caused arrest in the G1 phase.

Animals↗

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↗

PubMed1994

[Influence of the yellow-tinted intraocular lens on spectral sensitivity].

One of the complaints of patients with aphakic eyes or pseudophakic eyes implanted with UV or non-UV intraocular lenses (IOLs) is chromatopsia. To determine the extent of color distortion, we measured the spectral sensitivity curve of normal subjects with visual acuity above 1.0 with correction, if any, including subjects implanted with the yellow-tinted IOL (UVCY IOL: HOYA Co.). We found that color sensitivity in the blue range (400-440 nm) declined rapidly with subjects age. We drew a regression line plotting age against sensitivity for 66 normal subjects. Sensitivity for pseudophakic eyes implanted with UVCY and UV IOLs at 400 nm corresponds to that of subjects in their early 20's. That of pseudophakic eyes implanted with non-UV IOLs and aphakic eyes corresponded to that of infants. In summary, compared to UV IOL and non-UV IOLs, the UVCY IOL was found to best approximate the color sensitivity of healthy eyes.

Adolescent↗

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↗

PubMed1993

[The effect of hyaluronic acid on proliferation and differentiation of capillary endothelial cells].

The effects of hyaluronic acid (HA) on capillary endothelial cells were studied in cell culture. The capillary endothelial cells were obtained from the bovine adrenal cortex. The proliferation of endothelial cells was inhibited by the addition of HA to the culture medium. Significant inhibition was observed consistently at concentrations of 100 micrograms/ml or greater. Capillary-like networks were formed by the differentiated endothelial cells in co-culture with rabbit corneal keratocytes and in type I collagen gels. They were inhibited by the addition of HA at a concentration of 200 micrograms/ml. The cell proliferation and differentiation were not significantly affected by different HA molecular weights.

Animals↗

PubMed1993

[Histological analysis of aging ciliary body].

The aging changes in human ciliary body were studied by histological analysis. Thirty four autopsy eyes were fixed in 2.5% formalin and 1.0% glutaraldehyde mixture. The age distribution was 12 eyes below 50 years of age 13 eyes between 60 and 70 years of age, and 9 eyes over 80 years of age. Serial sections of the ciliary body were made parallel to the limbus and vertical to the ciliary processes. From four areas (transitional portion between pars plana and pars plicata, posterior portion of pars plicata, middle portion of pars plicata, and anterior portion of pars plicata) a central section was selected. Histological analysis was done with the use of Azur II stained light microscopic pictures. The basement membrane of non-pigmented epithelium below 50 years of age was thinner than between 60 and 70 years of age. This finding may be related with lowering aqueous humor secretion with aging. Non-pigmented epithelium, blood vessels in the stroma, and muscle fibers in muscle tissue showed aging changes. The pigment epithelium, basement membrane, and muscle fibers in muscle tissue did not show aging changes in light microscopical analysis, but study of their fine structure is necessary.

Aged↗

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↗