Search PubMed⌕ Search

Biomedical subjects

H Ohkuma

Publications and source records attributed to H Ohkuma.

At least 91 records · Page 5Linked to original sources
PubMed1991

[Detection of destruction of anionic sites in the outer blood-retinal barrier and damage caused by iron].

We studied the alteration of the anionic charge in the outer blood-retinal barrier in ocular siderosis by electron microscopy using the cationic probe, polyethyleneimine (PEI). The eyes of four days after injection of iron powder and control rabbit eyes demonstrated numerous PEI-positive sites at the basement membrane of the retinal pigment epithelium, collagen fiber of Bruch's membrane, and the basement membrane of the choriocapillaris. Seven days after injection of iron powder, no change was observed in the retina by light microscopy, but PEI positive sites at the basement membrane of the retinal pigment epithelium were decreased. At 14 days, it was seen that the outer layer of the retina disappeared and was replaced by pigment containing macrophages and Müller cells. Berlin blue reaction became positive in some of those macrophages and retinal pigment epithelia. PEI positive sites decreased. At 28 days, the retina was completely disorganized, and became thin, while the retinal pigment epithelium proliferated and became double layered. Berlin blue reaction was strongly positive in pigment-laden macrophages and retinal pigment epithelium. PEI-positive sites became scarce. As a result of these methods, anionic sites decreased, despite negative iron reaction of 7 days after injection of iron powder. It was shown that in ocular siderosis at an early stage, the barrier function of anionic sites between choroid and retina decreased before histological change.

Animals↗
PubMed1990

[Subependymoma of the septum pellucidum. MRI features and its usefulness in planning surgery].

A 61-year-old female was referred because of headache and gait disturbance. A computed tomography (CT) scan revealed a midline isodense mass lesion. The limit of the tumor was equivocal even after administration of contrast medium. Magnetic resonance imaging (MRI) study, however, clearly showed the relationship between the tumor and the surrounding structures, such as the corpus callosum, the ventricular cavities. The tumor had originated from the region of the septum pellucidum and positioned just beneath the corpus callosum from the genu to the splenium with the roof of the third ventricle pushed downward. The tumor was totally extirpated via the interhemispheric paratranscallosal route. The tumor was typical subependymoma. The post-operative course was uneventful. Transient psychiatric disturbance and inability to retain recent memory were observed and the former subsided in several weeks. CT and MRI characteristics of subependymoma are summarized and the usefulness of MRI to locate tumors and to plan proper surgical approaches are emphasized.

Cerebral Ventricle Neoplasms↗
PubMed1990

[A role of the retinal pigment epithelium in the involution of subretinal neovascularization].

We clarified a role of the retinal pigment epithelium (RPE) in the regression of experimentally induced subretinal neovascularization (SRN) in monkey. Eight eyes of 5 rhesus monkeys were used in this study. Two weeks after intense krypton laser photocoagulation to the posterior pole of the fundus, 0.5M l-ornithine hydrochloride solution 0.03 ml was injected intravitreously for the purpose of selective RPE damage. After ornithine injection, SRN continued without any evidence of spontaneous regression over 8 weeks following photocoagulation. Histopathologically, SRN developed with wide lumen in the subretinal space accompanied with serous detachment of the sensory retina, and new vessels were not enveloped completely by the proliferating RPE cells. We already showed that experimentally induced subretinal neovascularizations naturally regress spontaneously by envelopment of RPE cells 5 to 8 weeks after photocoagulation. Our results suggested that SRN persist actively without regression due to incomplete enclosure by RPE by selective damage of RPE at the active stage of SRN. We have confirmed that the RPE cells played an important role at the involution stage of SRN.

Animals↗
PubMed1990

[Endophthalmitis induced by herpes simplex virus, a study on early phase].

We studied the early phase of herpetic endophthalmitis to clarify the process of necrotizing retinitis by herpes simplex virus type-1 (HSV-1) and viral localization in the retina. A clone, isolated from HSV-1 Miyama for its high yield on Vero cells, was inoculated on mono-layers of Vero cells. Two days after inoculation, the cells were frozen-and-thawed once and were centrifuged. The supernatant was diluted with Hanks' balanced saline solution. The viral suspension 1.5 x 10(5) pfu/ml) was injected intravitreally to colored rabbits for 0.1 ml. All rabbits showed exudative iritis from 1 to 2 days after inoculation, vitreal opacities from 2 to 4 days and retinal exudates from 2 to 6 days. These exudates initially considered of necrotic materials of the inner nuclear layer. These fused with one another gradually and formed massive exudates which spread to the whole retinal layer, causing retinal necrosis. Viral particles were found in the nuclei of the inner nuclear layer at first, and later in the nuclei of Müller cells, ganglion cells and axon of the nerve fiber. These findings indicated that retinal lesion occurred primarily in viral replication of the inner nuclear layer.

Animals↗
PubMed1990

[An immunoperoxidase study of early phase experimental retinitis induced by herpes simplex virus].

Herpes simplex virus type 1 (HSV-1) was intravitreally inoculated in domesticated rabbits, and retinitis was observed with the ABC-method using peroxidase-conjugated antibody. Trypsin digestion was used for antigen visualization. Three days after inoculation, although cell degeneration was not found in the retina, DAB was deposited on the inner limiting membrane and the nerve fiber layer, which corresponded to the basal side of Müller cells. These findings indicated that viral antigen was already present in the retina at this early stage. Four or five days after inoculation, numerous variously sized exudative retinal lesions were seen. In the small exudative foci, DAB deposition was restricted to only in the nuclei of the nerve cells of the inner nuclear layer, while it extended to the outer and inner retinal layer in the large exudative foci. These results suggested that when HSV-1 was injected intravitreally it invaded from the basal side of Müller cells to the inner nuclear layer, where it replicated. The virus spread to the outer nuclear layer and ganglion cells as infection proceeded.

Animals↗
PubMed1990

[Destruction of anionic sites in blood-retinal barrier after retinal photocoagulation].

The retinal pigment epithelial cells (RPE) have "tight junctions" at the apical side of the lateral wall between neighbouring cells and form physiological blood-retinal barriers. Recently, in addition to physiological barriers, charged barriers, consisting of anionic sites of cell membrane and its basement membrane, have been discussed. We performed weak retinal photocoagulation in rabbit eyes in order to break their charged barriers, and examined the repair process using a cationic probe, polyethyleneimine (PEI). Two days after photocoagulation, RPE cells were broken down and choriocapillaries were occluded with thrombi, and their anionic sites were lost. At one week after photocoagulation, structural reconstruction started from the edge of the photocoagulation area. In this area, proliferated RPE cells covered Bruch's membrane, but their charged barrier did not recover. Two weeks after photocoagulation, proliferated RPE cells covered Bruch's membrane over the entire photocoagulated area, and they obtained anionic charge. The present study revealed that retinal damage induced by weak laser photocoagulation was repaired within two weeks after photocoagulation with respect to the charged barrier.

Animals↗
PubMed1990

[Effect of intravitreal gas on the destruction of anionic sites in the outer blood-retinal barrier].

The present work was undertaken to evaluate the effect of sulfur hexafluoride (SF6) injected intravitreously in rabbit eyes. The alterations of the outer blood retinal barrier that was composed of anionic sites, using a cationic probe, polyethyleneimine (PEI). We injected 0.5 ml of 100% SF6 or 0.5 ml of air into the vitreous cavity of rabbit eyes, and the 0.5% PEI-saline solution was given intravenously at 2, 4, 7, or 14 days after the injection. Control eyes demonstrated numerous PEI-positive sites at the basement membrane of the RPE, collagen fiber of Bruch's membrane, and basement membrane of choriocapillaries. Until seven days after SF6 injection, PEI-positive sites decreased, but had increased at 14 days to control levels, while in air-injected eyes, they had recovered at seven days. SF6 in the vitreous was absorbed in seven days and air in three days. While gas was present in the vitreous, the charge barrier of the outer retina and choroid decreased, but when the gas was absorbed, the charge barrier recovered. The result showed that the decrease of charge barrier was a reversible change.

Animals↗
PubMed1990

[Optic nerve finding in experimental retinitis induced by herpes simplex virus].

We reported histological changes and viral localization of HSV-1 in the optic nerve by the ABC-method and electron microscopy, after intravitreal inoculation. There was neither histological change nor antigen deposition on the specimen of 3 days after inoculation. Some series of antigen-positive sites were successively found along the nerve fiber from the lamina cribrosa to the optic chiasma in the optic nerve on 4 days after inoculation. Round cell infiltration were also found around these sites, and these changes increased on the 8th day. Antigen-positive cells were mainly considered to be oligodendroglia and astrocytes. These results suggested that HSV-1 infected the optic nerve fiber via the retina. On the way to be the brain by axonal transport, they would infiltrate to the glial cells, where they could replicate and spread to neighbouring glial cells.

Animals↗
PubMed1990

[Dye laser photocoagulation treatment for experimental subretinal neovascularization. 1. Histopathological findings of healing process].

To clarify the healing process of subretinal neovascularization (SRN) histopathologically following laser photocoagulation treatment, we performed laser photocoagulation for experimental SRNs produced in rhesus monkey eyes. To produce long-lasting SRNs, 0.5M 1-ornithine hydrochloride solution was injected intravitreously 2 weeks after photocoagulation. These SRNs were treated a 590nm dye laser, and examined clinically and histopathologically at 24 hours, 2 weeks, 3 months. Histopathologically, new vessels in the subretinal space were coagulated intensely and disappeared during the course of healed lesion. In these lesions, the retinal pigment epithelial cells proliferated in the subretinal space after the disappearance of the SRNs and covered the scar tissue. In strongly coagulated lesions, glial cells were related to the formation of scar tissue. These results showed that closure of new vessels was necessary for the healing of SRNs by photocoagulation and proliferation of the retinal pigment epithelial cells and glial cells occurred during their healing process.

Animals↗
PubMed1990

[Dye laser photocoagulation treatment for experimental subretinal neovascularization. 2. Histopathological findings of unsuccess lesions].

We observed the histopathological process in unhealed lesions following photocoagulation treatment for experimental subretinal neovascularization (SRN) in rhesus monkey eyes. Long-lasting SRNs were produced experimentally by the method which we previously reported. These SRNs were treated by a 590nm dye laser beam, and were examined clinically and histopathologically. Lesions in which insufficient photocoagulation treatment was performed showed serous fluid accumulation and fluorescein angiography revealed remaining neovascularization. In these lesions abundant patent neovascularization was seen with proliferation of spindle-shaped fibroblast-like retinal pigment epithelial (RPE) cells in the subretinal space. These metaplastic RPE cells produced matrix and abundant collagen fiber around the cells. The above results showed that insufficient photocoagulation induced neovascularization and proliferation of RPE cells in the subretinal space and promoted the formation of fibrovascular membrane.

Animals↗
PubMed1990

[Disturbance of inhibitory capacity of endothelial cell for platelet adhesion or aggregation following experimental subarachnoid hemorrhage].

Time sequential changes of the endothelial cells of feline basilar arteries after experimental subarachnoid hemorrhage (SAH) were studied morphologically and functionally under the scanning electron microscope (SEM). Experimental SAH was induced by the two-hemorrhage method, and the basilar artery was removed at 1 hour, or 2, 4, 7, or 14 days respectively after the 1st cisternal blood injection. At each stage, morphological changes of the luminal surface and endothelial cells of the basilar artery were observed by SEM. In another group, adenosin diphosphate (ADP) was infused through the right vertebral artery at the various stages mentioned above, for the purpose of activating platelets, and the basilar artery was then removed. The platelet adhesion or aggregation on the luminal surface was observed quantitatively also by SEM, for evaluating the inhibitory capacity of the endothelial cells upon platelet adhesion or aggregation after SAH. The fold formation of the arterial luminal surface and the ballooning of the endothelial cells were observed initially at 1 hour and 2 days respectively after the 1st cisternal blood injection. The latter findings became most remarkable during the 4 to 7 days after the said blood injection. They were accompanied by intercellular gap formation. None of these findings were seen, however, in the specimens taken 14 days after the said blood injection. In the group with pre-sacrificing ADP infusion, adhesion or aggregation of platelets on the arterial luminal surface was scarcely seen before the second day, but became remarkable 4 to 7 days after the 1st cisternal blood injection, and were reduced by the time 14 days had passed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Early effects of sodium iodate shown by detection of the destruction of anionic sites in outer blood-retinal barrier].

In order to demonstrate the early effect of sodium iodate (NaIO3) on retinal pigment epithelium (RPE), Bruch's membrane and choriocapillaries, we examined the alteration of their anionic sites using a cationic probe, polyethyleneimine (PEI). We injected 10 microliters of 3% NaIO3 solution into the vitreous of pigmented rabbits and after thirty minutes or one hour, administered 0.5% PEI intravenously. In the eyes injected with intravitreously saline solution or without injection, PEI-positive particles (diameter 15-20 nm) were located in a row on both sides of the basement membrane of the RPE and choriocapillaries and periodically at the collagen fiber of inner and outer collagenous zone of Bruch's membrane. However no particle was observed on the cell membrane of the basal infolding of the RPE. Thirty minutes after injection of NaIO3, PEI particle positive sites were reduced at the basement membrane of the RPE. One hour after injection they reduced in number but remained at the basement membrane of choriocapillaris and collagens in Bruch's membrane. We showed the early effect of NaIO3 to the RPE by examining the alterations of the anionic sites.

Animals↗
PubMed1990

[The role of retinal pigment epithelium in the early stage of development of subretinal neovascularization].

In order to evaluate the role of retinal pigment epithelium (RPE) in the early stage of experimental subretinal neovascularization, we severely damaged RPE cells before the development of subretinal neovascularization. Three adult rhesus monkeys were used in this study. One mol/l l-ornithine hydrochloride saline solution was injected intravitreously at 2 weeks before intense krypton laser photocoagulation on the retina at the posterior pole, and clinical and histopathological course were studied at 1 to 28 days after photocoagulation. As a result, no evidence of new vessel formation could be observed clinically throughout the entire course. Histopathologically, at 3 days after photocoagulation, slight proliferation of RPE cells was identified by electron microscopy at the margin of the laser lesions, and budding of vascular endothelial cells derived from choroidal microvessels was observed in the choroid. However, no newly-formed vessels extended into the subretinal space at 7 days or more after photocoagulation. These results confirmed our hypothesis that proliferated RPE cells had inductive effect on the growth of endothelial cells in the early stage of development of subretinal neovascularization.

Animals↗
PubMed1990

[The process of occlusion and re-construction of the choriocapillaries following dye laser photocoagulation].

In order to elucidate the histopathological changes in the choriocapillaries following laser photocoagulation, moderate laser burns were performed on monkey retinas by an orange dye laser beam (595nm). Immediately after photocoagulation, the choriocapillaries were occluded by the intraluminal thrombus, however, the basement membrane of the endothelial cells remained. The newly-formed immature endothelial cells began to migrate along the pre-existing basement membrane toward the center from the edge of the lesion after 3 days. They formed new vascular lumens by coupling of intercellular junctions at 5 days. At 7 days, newly-formed capillaries were formed beneath the Bruch's membrane. After more than 7 days, the choriocapillaries in the lesion were re-constructed and required an almost normal structure with wide patent lumens, basement membrane, pericytes and fenestrations. It was showed that choriocapillaries occluded by moderate laser photocoagulation were re-constructed by the process of re-endothelialization along the preexisting basement membrane.

Animals↗
PubMed1989

[Pathologic response of the retinal pigment epithelium. The effect of mucopolysaccharide in the subretinal space to phagocytosis. Part 5].

Previously we reported that retinal pigment epithelial cells (RPE) showed different phagocytotic activity according to the charge characteristics of the surface of polystyrene particles which were injected into the subretinal space of albino rats. In this study we examined whether subretinal mucopolysaccharide controls RPE phagocytosis or not, using positive or negative charged particles (3 microns in diameter). The technique of ruthenium red staining, a cationic dye, was employed with special efforts to detect the relationship between acid mucopolysaccharide and particles at the electron microscopic level. Six hours after injection of the positive charged particles, the ruthenium red staining revealed fine granular electron-dense materials, coating the surfaces of many small substances surrounding polystyrene particles which were not yet phagocytized by RPE. On the other hand, there was no staining of negative ones which were already phagocytized by RPE. At 24 hours, no staining was observed on the surface of either particles. These findings suggest that an anionic property of mucopolysaccharide in the subretinal space controls the phagocytosis of RPE.

Animals↗
PubMed1989

Choroidal vascular repair following orange dye laser photocoagulation.

In order to evaluate the effect of laser photocoagulation on choroidal vessels, moderate laser burns were performed on monkey fundi with a dye orange beam (595 nm) at various intervals for a period of 60 days. After photocoagulation, choroidal vascular casts were prepared by injection of Mercox resin into the carotid arteries, and then observed by scanning electron microscopy. Immediately after photocoagulation, filling defects of the choriocapillaris and medium-sized choroidal vessels were seen in all lesions. By three to five days, restoration of the choroidal microcirculation in the laser lesions had begun. At seven to ten days, filling defects of the choriocapillaris had gradually become undemarcated. By 2 weeks, the sites of the former filling defects were occupied by a loose network of capillaries. At 60 days, the laser lesions had been entirely replaced by newly formed choriocapillaris, composed of narrower lumina and showing a more irregular lobular pattern than normal choriocapillaris.

Animals↗