Search PubMed⌕ Search

Biomedical subjects

E Adachi-Usami

Publications and source records attributed to E Adachi-Usami.

At least 55 records · Page 3Linked to original sources
PubMed1997

[Protective effect of nitric oxide on ischemic retina].

Nitric oxide (NO) is a free radical and was regarded as noxious to life. But recent studies show that NO is an important substance for transcellular signal transduction. It also seems to act as a neurotransmitter in the nervous system. In ischemic nerve tissue a release of glutamate is one of the critical factors that increase neuronal death, and some experiments suggest that NO may be involved in this process. Here we provide evidence that NO provides neuroprotection in ischemic retinas in vivo. Albino rabbits' eyes were subjected to 60 minutes of ischemia by raising intraocular pressure. Before ischemia the eyes were treated intravitreously with the NO-precursor L-arginine, the NO synthase-inhibitor nitro-L-arginine methyl ester hydrochloride (L-NAME), the NO-donor sodium nitroprusside (SNP), or solvent only. The amplitude of the b-wave was measured and the recovery ratio of the b-wave was analyzed hourly after reperfusion. The recovery ratio of b-wave in the eyes with L-arginine and with SNP increased more rapidly than in the controls, while the recovery ratio in the eyes with L-NAME increased in a way similar to that of the controls. These results suggest that NO plays a neuroprotective role in ischemic retina. It may be involved with S-nitrosylation of some proteins, including one of the glutamate receptors, the N-methyl-D-aspertate (NMDA) receptor.

Animals↗
PubMed1997

[Sensitivity loss of short wavelength sensitive cones in myopic eyes by blue-on-yellow perimetry].

A decrease of the short wavelength sensitive cone (S-cone) sensitivity has been reported in myopic eyes in addition to glaucoma and retinal diseases such as retinal detachment and diabetic retinopathy. In order to investigate early changes of visual function in myopic eyes, blue-on-yellow perimetry (B on Y) which could detect S-cone sensitivity and white-on-white perimetry (W on W) were measured with a computed perimeter program. Young subjects with good visual acuity, normal color vision, and normal intraocular pressure were selected. They had no other ophthalmoscopic abnormalities except for tigroid fundus. Mean deviations of W on W were reduced in mild and high myopic groups. In both tests, the sensitivities decreased as the refractive errors increased in all the tested areas (p < 0.0001). The sensitivity in B on Y decreased more remarkably than in W on W with an increase of refractive error (p < 0.05). We concluded that B on Y perimetry was significantly sensitive to identify early changes of visual function in myopic eyes.

Contrast Sensitivity↗
PubMed1997

Decreased contrast sensitivity in normal tension glaucoma determined by pattern visually evoked cortical potentials.

Little is known about the central visual function of patients with normal tension glaucoma (NTG). We estimated the contrast sensitivity of patients with NTG and normal subjects with the use of pattern visually evoked cortical potentials (PVECPs). PVECPs were recorded using checkerboard pattern reversal system display on television monitor of check size 15', 60' and frequency 3 reversals per second and contrast varied in 7 steps. Our results show that a significant delay of the P100 component for 60' check size in the NTG group was found at every contrast level (P < 0.05). Contrast threshold was determined as the value to obtain a criterion peak latency from a regression line calculated within a contrast range from 10% to 56%. The contrast threshold for both check sizes of the NTG group showed an increased threshold (P < 0.05). We conclude that contrast sensitivity decreased in NTG as determined by PVECP. The PVECP was a sensitive test for detecting the functional abnormalities of NTG.

Contrast Sensitivity↗
PubMed1997

Multifocal electroretinogram in myopia.

PURPOSE: To investigate early changes of retinal function in myopic eyes, patients with various degrees of myopia underwent multifocal electroretinography (multifocal ERG). METHODS: Thirty young patients (mean age, 26.1 years) were divided into three groups according to the degree of refractive error: emmetropia/low, medium, and high myopia. All groups were matched by sex and age. All subjects had good corrected visual acuities of better than 1.0 and normal color vision. No other ophthalmoscopic abnormalities except for tessellated fundus existed. Three grouping programs (all-traces, rings, and quadrants) were used, and all-traces grouping waveforms, six-ring grouping waveforms, and four-quadrant grouping waveforms were determined from 103 local responses. We studied the differences of amplitudes and latencies of the waves among the myopic groups and their relation to refractive error and axial length. RESULTS: Amplitudes were reduced and latencies were delayed as the refractive errors increased. The amplitudes in the peripheral areas were more reduced in the myopic groups. CONCLUSIONS: The reduced amplitude and delayed latency of each wave of multifocal ERG in myopia resulted primarily from cone function loss, which may occur even when the only noted retinal change is tessellated fundus.

Adult↗
PubMed1996

Retinal detachment in identical twins with Stickler syndrome type 1.

BACKGROUND: The high incidence of retinal detachment and its poor surgical prognosis in patients with Stickler syndrome are well known. However, the vitreoretinal relation to retinal detachment in this syndrome is uncertain. METHODS: Vitreoretinal examination with a binocular indirect ophthalmoscope and a Goldmann three mirror contact lens was performed on identical twin boys with Stickler syndrome. Each had retinal detachment in the left eye, and many aspects of their fundus findings were similar. The vitreous showed distinct abnormalities consistent with congenital vitreous anomaly of type 1 Stickler syndrome. The twins were followed up for 4 years after undergoing a successful operation to reattach their left retinas. RESULTS: Rhegmatogenous detachment with multiple tears occurred in the right eye of only one twin during the follow up period, despite the similar condition of their fundi. Although vitreous body was not present in most parts, slightly opaque vitreous cortex was attached to the retina near the ora serrata, and neither twin had posterior vitreous detachment during the follow up period. CONCLUSION: Multiple retinal tears appeared simultaneously in the right eye of one twin, indicating some tractional force had acted on the retina. It is believed that this force was caused by very thin vestigial vitreous cortex attached to the retina. Although these observations have been limited, vitreoretinal findings of the twins and their father were consistent and suggested presence of thin vitreous cortex attached to the retina without posterior vitreous detachment.

Abnormalities, Multiple↗
PubMed1996

[Sensitivity loss in short wavelength sensitive cones in myopic eyes].

To investigate early changes of visual function in high myopic eyes, the relative sensitivity of the short-wavelength sensitive cones (s-cones) was measured by flash-evoked cortical potentials and electroretinograms and their relation with refractive error and axial length of the eyes was studied. A Ganzfeld stimulus was employed. The subjects were all under 37 years of age and were divided into 3 groups according to the magnitude of the refractive error as follows; 1) emmetropia/low myopia group (10 eyes), between +0.50 D and -3.00 D; 2) medium myopia group (8 eyes), between -3.25 D and -6.00 D; and 3) high myopia group (10 eyes), over -6.25 D. Their corrected visual acuities were better than 1.0 and their color vision was normal according to Panel D-15 and SPPII. They had no other ophthalmological abnormalities except tigroid fundus. The s-cone sensitivity was significantly correlated with the refractive error and axial length (p < 0.001) and was reduced prior to ophthalmoscopic retinal changes in the medium and high myopia groups. This indicates that the site of s-cone sensitivity loss in myopia is in the retinal.

Adolescent↗
PubMed1995

Color vision and color pattern visual evoked cortical potentials in a patient with acquired cerebral dyschromatopsia.

We examined a 74-year-old man because of difficulty seeing green and the presence of prosopagnosia. His visual acuity was 0.8 in both eyes. He was not congenitally color blind, and there was no family history of color blindness. A left superior homonymous quadrantanopsia was found. The dyschromatopsia ws identical in both eyes. The patient showed red-green deficiency on testing with Ishihara plates a deutan defect with Tokyo Medical College plates, strong blue-yellow defects and medium red-green defects with Standard Pseudochromatic Plates II and a tritan defect with the Panel D-15. He failed the New Color separation test with scores of 160 and could not carry out the Farnsworth-Munsell 100-hue test, but his color naming test results were normal. Visual evoked cortical potentials to black-and-white checkerboard and color pattern reversal (Red and Blue-Green, Green and Red-Purple, Purple and Yellow-Green: isochromatic paired checks) stimuli were normal. Bilateral inferior occipital lesions were found by computed tomography and T2-weighted magnetic resonance imaging. Our findings suggested that luminance and color channels up to area 17 in our patient were intact. We believe that our patient's acquired cerebral dyschromatopsia is rare.

Aged↗
PubMed1995

Three cases of grouped pigmentation of the retina.

We examined three patients with congenital grouped pigmentation of the retina by means of electroretinography, electro-oculography and visually evoked cortical potentials. Two patients were affected bilaterally and 1 had a unilateral condition. Electrophysiological findings were normal in all patients, and no inheritance patterns for the disease were found in any of the patients' histories. Only 5 cases of this disease have been reported in Asian countries in recent years. We believe that our patients contribute to the sample of such cases regarding racial prevalence.

Adult↗
PubMed1994

Electrophysiological studies on light damage in the mouse retina after sodium iodate injection.

Acute experimental retinal degeneration was induced in 3-month-old mice with sodium iodate (NaIO3) injection to investigate the effect of bright light with electroretinography (ERG). Eight C 57 black male mice were anesthetized. The ERG was recorded before and 24 h after the injection of NaIO3. Next, only one eye of each mouse was exposed to a bright light of 3.0 x 10(4) lx white light for 30 min. Ten hours later, ERGs of both the light-exposed and the unexposed eye were recorded. The amplitudes and peak latencies of the a wave and b wave were measured. The ERG was recorded as both eyes were exposed to stimulating flashes that were given in an increasing order of 0.6 log unit steps from the dimmest flash to produce a detectable ERG. The ERG from the light-exposed eye showed a distinctly elevated threshold (approx 2.0 log), while the contralateral unexposed eye did not. The peak latencies of both waves were significantly prolonged by exposure to light. In conclusion, light exposure affected ERG thresholds in mice with experimentally induced acute retinal degeneration.

Animals↗
PubMed1994

Distribution of phosphate-activated glutaminase-like immunoreactivity in the retina of rodents.

The distribution of phosphate-activated glutaminase-like immunoreactivity was examined in the retinas of rodents. Intense glutaminase immunoreactivity was observed in many neuronal perikarya in the ganglion cell layer and inner nuclear layer including those of ganglion, bipolar and amacrine cells and possibly horizontal cells. Almost all bipolar cells containing protein kinase C were immunoreactive for glutaminase, suggesting that the majority of glutaminase immunoreactive bipolar cells were of the ON type. Intense glutaminase immunoreactivity was also found in the neuropil of the inner and outer plexiform layers and around the outer limiting membrane. Weak to moderate immunoreactivity was seen in the outer nuclear layer and photoreceptor inner and outer segments. Under electron microscopy, glutaminase immunoreactivity was seen in bipolar cell axons and amacrine cell processes in the inner plexiform layer. In the outer plexiform layer, immunoreactivity was found in the Müller cell processes, but not in the photoreceptor cell terminals. These results indicate that ganglion cells and ON type bipolar cells use glutaminase to produce transmitter glutamate and suggest glutaminase has additional roles in Müller cells. A population of amacrine cells and horizontal cells showed immunoreactivity to glutaminase.

Animals↗
PubMed1993

Accommodative response changes with age measured by pattern electroretinogram.

To evaluate whether the transient pattern electroretinogram reflects accommodation, we studied the amplitudes of the P-N component of transient pattern electroretinograms that were elicited in normal volunteers by reversing the checkerboard pattern. The stimuli were presented at a rate of three-reversals per second at a viewing distance of 20 cm. Each subject wore a lens that corrected for distance vision. The ophthalmic lenses were placed in front of the eye. A +12-diopter lens was used first, followed by lenses in decreasing 1-diopter steps, including minus lenses, until no response was recordable. The P-N amplitude was then plotted against increased accommodative stimulus. The graph showed a rapid increase to around 4 diopters, and then a slow decrease with increasing minus lens power. The gradually decreasing part of the graph became steeper under cycloplegic conditions. The amplitude of accommodative response was defined as the difference in diopters between the lens powers for eliciting an electroretinogram amplitude after cycloplegia was achieved and in the untreated pupil. The amplitude of accommodative response attenuated significantly in those subjects older than 40 years.

Accommodation, Ocular↗
PubMed1993

Electroretinographic effects of haloperidol on the mouse retina.

The effects of haloperidol on the electroretinogram were studied in mice injected intraperitoneally with haloperidol. A dose-related study was performed. A significant decrease in the amplitude of the b-wave was found in the mice injected with more than 20 mg/kg of haloperidol. However, the peak latency of the b-wave and the stimulus intensity required to elicit a b-wave of one half of the maximum b-wave amplitude remained unchanged. No significant changes were found in the a-wave. This change in the electroretinogram recovered 24 hours after the injection. These results suggest that functional change occurred at the retinal level after intraperitoneal injection of haloperidol.

Animals↗
PubMed1993

Early effects of sodium iodate injection on ERG in mice.

The electroretinogram (ERG) was recorded in 15 ICR albino mice before and 2, 4 and 24 h after injection of 40 mg/kg of NaIO3 and the results were compared with the corresponding ultrastructural findings. Both a- and b-wave amplitudes decreased at 2 h after injection and increased at 4 h to the levels before injection and further increased at 24 h after injection. The b-wave threshold intensity increased by 2.1 log units at 2 h after injection. Thereafter, it decreased once at 4 h and significantly increased at 24 h by 3.4 log units. Electron microscopic examination showed swollen cytoplasmic organelles of the retinal pigment epithelial cells at 4 h after injection. It was thus demonstrated that an early effect of NaIO3 on the electrical response of the mouse retina was more conspicuous than histopathological changes.

Animals↗
PubMed1993

Long-standing follow-up electroretinographic studies after surgical resection of optic nerve glioma.

We followed up electrophysiological findings in 2 patients who underwent optic nerve glioma resection. Case 1 showed a normal flash electroretinogram (ERG) 6 months after surgery. Case 2 showed a negative-type flash ERG and nonrecordable pattern ERG and flash visual-evoked cortical potentials 13 and 20 years after surgery. The flash ERG after surgical resection of the optic nerve was considered to be affected by the interruption of the central retinal artery during the surgery, and the preserved ERG suggested the possibility of developing the collateral circulation of the ciliary artery.

Child↗
PubMed1993

A case of Kearns-Shy syndrome with later onset.

We report a case of Kearns-Shy syndrome in a 44-year-old woman. She complained of bilateral ptosis, exotropia and gait disturbance. Diffuse chorioretinal degeneration and numerous punctate whitish spots were observed in both fundi. Eye movements were severely disturbed. An electroretinogram was almost nonrecordable, while visually evoked cortical potentials to pattern stimulation were normal. The dark adaptation curve showed an elevation of rod threshold. Besides such ophthalmological findings, muscle weakness, extinguished tendon reflex and healing difficulty were observed. Blood lactate, pyruvic acid and serum creatinine kinase were at high levels. A muscle biopsy showed ragged-red fibers and partial deficiency of cytochrome c oxidase. The patient is being treated with coenzyme Q, and we are now following up the therapeutic effects of this treatment.

Adult↗
PubMed1993

Correlation of electroretinographic changes with visual prognosis in central retinal artery occlusion.

Recent advances in the treatment of central retinal artery occlusion (CRAO) have resulted in a relatively good prognosis, but few studies have been reported. In the present study, electroretinography (ERG) was used to evaluate visual function recovery in 15 cases of CRAO. All patients were treated with ocular massage, intravenous urokinase and hyperbaric oxygenation. Of 15 cases, 8 had improved vision after treatment. A single flash ERG of 40 J from a xenon lamp was recorded before and during treatment. For ERG evaluation, the a- and b-wave amplitudes and the b/a wave amplitude ratio were analyzed. As control, the nonaffected eye of each patient was used. Before treatment, no significant difference was found in the a-wave amplitude between the two eyes, while a significant attenuation was found in the b-wave of the affected eye (p < 0.01). The b/a ratio was 0.73 +/- 0.04 (mean +/- SE) in the affected eye group and 1.08 +/- 0.03 in the nonaffected eye group. It was significantly higher (p < 0.01) in eyes with improved visual acuity (0.83 +/- 0.03) than in those with unimproved visual acuity (0.62 +/- 0.05). The b-wave amplitude increased in accordance with visual improvement. We could thus demonstrate the temporal changes of ERG before and after treatment and show their correlation with the visual prognosis in patients with CRAO.

Adult↗