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Biomedical subjects

N Nao-i

Publications and source records attributed to N Nao-i.

At least 19 recordsLinked to original sources
PubMed1997

Progressive retinitis-encephalitis due to ganciclovir-resistant cytomegalovirus associated with aplastic anemia.

A 29-year-old woman with aplastic anemia who complained of visual disturbances and pain in the right eyeball was diagnosed as having cytomegalovirus (CMV) retinitis based upon the characteristic retinal changes and isolation of CMV. She received treatment with ganciclovir (GCV), and the retinitis initially responded for several months. However, the patient was found to have CMV lesions in the left eye followed by neurological symptoms. The CMV isolated just before her death was approximately 20 times more resistant to GCV than that isolated previously, suggesting that the GCV-resistant CMV had developed during the long-term treatment with GCV.

Adult↗
PubMed1997

Different responsiveness to nitric oxide-cyclic guanosine monophosphate pathway in cholinergic and tachykinergic contractions of the rabbit iris sphincter muscle.

PURPOSE: In the rabbit iris sphincter muscle, sodium nitroprusside (SNP), a nitric oxide (NO) donor, inhibits cholinergic contraction but does not affect tachykinergic contraction in vitro. The objectives of the current study were to clarify the mechanism for the different responsiveness to NO in cholinergic and tachykinergic muscular contractions, and to examine whether the mechanism for NO-induced inhibition of cholinergic muscular contraction is operative in vivo. METHODS: Iris sphincter muscle was dissected from the rabbit eye pretreated with or without endotoxin (lipopolysaccharide, LPS) in vivo. Cyclic guanosine monophosphate (cGMP) content in the iris sphincter muscle was determined by radioimmunoassay. The motor activity of the ring-shaped iris sphincter muscle was measured isometrically. Sodium nitroprusside, carboxy-2-phenyl-4,4,5,5,-tetramethyl-imidazoline-1-oxyl-3-oxide (C-PTIO, a scavenger of NO radicals), and 8-bromo cGMP (a permeable cGMP analogue) were administered between the first and second administrations of carbachol and neurokinin A, both of which had caused sustained contraction in the iris sphincter muscle. RESULTS: Sodium nitroprusside inhibited the contraction of the iris sphincter muscle caused by carbachol but had no effect on the contraction caused by neurokinin A. Application of C-PTIO significantly reduced SNP-induced cGMP accumulation in the muscle, as well as the SNP-induced inhibition of muscular contraction caused by carbachol. Neither carbachol nor neurokinin A influenced SNP-induced cGMP accumulation in the muscle. Induction of 8-bromo-cGMP significantly diminished the muscular contraction caused by carbachol but not that caused by neurokinin A. In vivo pretreatment of the eye with LPS increased, in a time-dependent manner, the cGMP accumulation in the iris sphincter muscle, which was significantly inhibited by pretreatment of NG-nitro-L-arginine methyl ester (an inhibitor of NO synthesis) in vivo. CONCLUSIONS: These results demonstrate that in rabbits the increase in cGMP accumulation induced by NO in the iris sphincter muscle is involved in the cholinergic contraction but not in the tachykinergic contraction, suggesting that different sensitivities to cGMP are essential for the different responsiveness to NO. Furthermore, the results of this study showed that the NO-cGMP pathway is operative in vivo and regulates iris sphincter muscle tone, at least when the eyes are infected with bacteria.

Animals↗
PubMed1996

Ultrasound biomicroscopic findings of acute angle-closure glaucoma in Vogt-Koyanagi-Harada syndrome.

PURPOSE: We studied a case of Vogt-Koyanagi-Harada syndrome with transient shallow anterior chamber and increased intraocular pressure as initial manifestations. METHODS: We examined the patient using ultrasound biomicroscopy and speculated on the mechanisms of increased intraocular pressure. RESULTS: Ultrasound biomicroscopic examinations revealed the swollen ciliary body with anterior rotation and supraciliary space at the time of increased intraocular pressure. CONCLUSIONS: We confirmed that the swollen ciliary body with anterior rotation and supraciliary space caused transient angle-closure glaucoma in this patient with Vogt-Koyanagi-Harada syndrome.

Acute Disease↗
PubMed1996

Retinitis pigmentosa with recurrent vitreous hemorrhage.

We observed recurrent vitreous hemorrhage in two patients with retinitis pigmentosa: a 41-year-old female and a 49-year-old male. At age 41, the first patient had diffuse capillary dilatation, macular microaneurysms, and paramacular macroaneurysms in the right eye. At age 47, similar retinal vascular lesions and disc neovascularization developed in the left eye followed by recurrent vitreous hemorrhage. The retinal microvascular changes and vitreous hemorrhages subsided spontaneously during the ensuring 4 years. In the second case, recurrent vitreous hemorrhage developed in the right eye. Funduscopy and fluorescein angiography at age 49 revealed no angiopathy. However, 2 years later we detected retinal neovascularization in the macula and an avascularity in the peripheral retina in the right eye. Subretinal exudate or retinal detachment was consistently absent in both cases.

Adult↗
PubMed1996

Electrical responses from locally detached retina and its recovery after reattachment.

Alterations in the focal electroretinogram (FERG) after experimental retinal detachment and spontaneous reattachment in albino rabbits were studied. Retinal detachments of two disc diameters were produced by injecting balanced salt solution into the subretinal space. FERGs were obtained under direct fundus visualization by an infrared television fundus camera with a light stimulator. The preoperative b-wave amplitude and implicit time were 0.52 +/- 0.07 microV and 59.7 +/- 3.8 ms (mean +/- SD), respectively. Thirty minutes after retinal detachment, the amplitude decreased significantly to 0.05 +/- 0.09 microV (p < 0.0001). The next day, we confirmed retinal reattachment ophthalmoscopically and the amplitude recovered to 0.30 +/- 0.07 microV. Then it gradually increased to 0.54 +/- 0.07 microV 7 days after the operation. The implicit time increased significantly to 66.6 +/- 4.1 ms 30 min after retinal detachment (p < 0.01), was maximal the day after surgery (69.9 +/- 4.9 ms), and thereafter shortened. However, the implicit time did not recover completely and was significantly delayed compared with preoperatively even 28 days postoperatively (65.4 +/- 3.4 ms, p < 0.01). These data suggest that functional abnormalities persist in the reattached rabbit retina, even following a brief retinal detachment.

Animals↗
PubMed1996

Nitric oxide-sensitive and -insensitive contractions of the isolated rabbit iris sphincter muscle.

PURPOSE: The rabbit iris sphincter muscle is innervated by cholinergic and tachykinergic nerves that regulate its tone. To clarify the involvement of nitric oxide (NO) in the postsynaptic regulation of the rabbit iris sphincter muscle tone, the authors examined the effects of NO-related agents on the cholinergic contraction induced by carbamylcholine (carbachol) and the tachykinergic contraction induced by neurokinin A. METHODS: The motor activity of the ring-shaped rabbit iris sphincter muscle was measured isometrically. Sodium nitroprusside (SNP, a NO donor) was administered between the first and second administrations of carbachol and neurokinin A, each of which induced sustained contraction. The effects of carboxy-2-phenyl-4,4,5,5,-tetramethyl-imidazoline-l-oxyl-3-oxide (carboxy-PTIO, a scavenger of NO radicals), NG-monomethyl-L-arginine (L-NAME, an inhibitor of NO formation from L-arginine), and methylene blue (an inhibitor of soluble guanylate cyclase) on contractions induced by carbachol and neurokinin A also were studied. Cyclic guanosine monophosphate (GMP) content in the muscle was determined by radioimmunoassay. RESULTS: Sodium nitroprusside inhibited carbachol-induced contractions of the iris sphincter muscle in a concentration-dependent manner but had no effect on neurokinin A-induced muscle contractions. Carboxy-PTIO and methylene blue significantly diminished the inhibitory effect of SNP on carbachol-induced contractions. L-NAME had no effect on contractions induced by either carbachol or neurokinin A. Sodium nitroprusside alone increased cyclic GMP accumulation in a concentration-dependent manner. CONCLUSIONS: This study showed that SNP inhibited cholinergic contractions mainly through a cyclic GMP-dependent mechanism but did not affect the tachykinergic contractions, indicating that cholinergic contraction is NO sensitive, whereas tachykinergic contraction is NO insensitive. These findings suggest that in rabbits, the cholinergic and tachykinergic responses have distinct features for the fine adjustment of the iris sphincter muscle tone.

Animals↗
PubMed1996

[A case of morning glory syndrome associated with contractile movement of the optic disc and subretinal neovascularization].

We report a rare case of morning glory syndrome with choroidal neovascular membrane and contractile movement of the optic disc. A 12-year-old healthy boy was first seen in April 1992 with a chief complaint of transient visual loss in his left eye for 3 months. The diagnosis of morning glory syndrome was made by the characteristic optic nerve head. His visual acuity was 1.2 in both eyes. In August 1994, retinal hemorrhage associated with choroidal neovascular membrane was observed in the macula of his left eye, resulting in a decrease of visual acuity to 0.4. In October 1994, we observed contractile movement in the morning glory optic disc. Using a scanning laser ophthalmoscope (SLO), we could observe the disc contracting for approximately 2 seconds and then dilating again over a 20-second period. The contractile movement was not evoked by exposure to a strong light or by the Valsalva maneuver. However, it seemed to be induced by digital massage of the eyeball.

Child↗
PubMed1995

Effects of adenosine on chick retinal pigment epithelium: membrane potentials and light-evoked responses.

We examined the effects of adenosine, a putative mediator of neuroprotection during cerebral ischemia, on the electrophysiological characteristics of retina-retinal pigment epithelium-choroid preparations obtained from 1-7 day-old chick and maintained in vitro. Our experiments produced the following results. First, superfusion of the retinal surface with adenosine (0.1 mM) increased the trans-tissue potential. The trans-epithelial (but not the trans-retinal) potential was also increased to the same magnitude with a time-course similar to that of the trans-tissue potential. Second, adenosine produced a depolarization of the epithelial basal plasma membrane with a concomitant decrease in its basal membrane resistance. Third, the trans-epithelial (but not the trans-retinal) c-wave in response to a light stimulus was augmented by adenosine. Adenosine reduced the hyperpolarization of the epithelial basal membrane, but had no effect on the extracellular concentration of K+ in the subretinal region. Fourth, the light-peak that was elicited with a 300 s light stimulus was also depressed by adenosine. Fifth, when 4,4'-diisothiocy anostilbene-2,2'-disulfonate (DIDS), a relatively selective inhibitor of Cl- channels, was perfused at 50 microM on the choroidal surface, adenosine-induced increases in the trans-tissue potential and the c-wave were both abolished. These results suggest that adenosine increased the Cl- conductance of the basal plasma membrane of the retinal pigment epithelium and thereby augmented the standing potential as well as the light-elicited membrane potentials of the retinal pigment epithelium, which seems to be involved in the pathophysiology of retinal ischemia.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1995

Thallium-201 uptake in eosinophilic granuloma of the frontal bone: comparison with technetium-99m-MDP imaging.

An 11-yr-old female presented with a 6-wk history of left upper lid tenderness and left eye lacrimation. Left lateral supraorbital mass and left preauricular lymph node were the only significant physical examination findings. On skull x-ray, a left frontal bone defect was noted. CT and MRI showed a soft-tissue mass in the area of the bone defect. Bone scintigraphy exhibited peripheral uptake within the central photon deficient area. With 201TI SPECT, high uptake was noted on early and delayed images. Diagnosis of eosinophilic granuloma was performed by biopsy. Since thallium uptake was seen in the area where photon deficiency was exhibited by 99mTc-MDP scintigraphy, we speculate that thallium SPECT could detect eosinophilic granuloma when radiographic skeletal survey or radionuclide bone scan are equivocal. It could also rule out multiple bone involvement and recurrence or regrowth after therapy.

Child↗
PubMed1994

[Interferon-induced retinal changes].

Fifty patients treated with interferon for chronic type C hepatitis, chronic type B hepatitis and renal cell carcinoma were examined for retinal complications. Retinal hemorrhages or cotton wool spots were observed in 23 (46%) of the patients. Retinal hemorrhages without cotton wool spots were found in 14 patients, cotton wool spots without retinal hemorrhages in 5 patients, and both hemorrhages and cotton wool spots in four patients. These findings were potentially reversible. There was one case of branch retinal artery occlusion and one case with microaneurysm. Red blood cell count decreased significantly in the patients with retinopathy compared with those without retinopathy (p < 0.05%). Patients with diabetes, hypertension, retinal arterial sclerosis, and anemia were at risk for retinopathy.

Carcinoma, Renal Cell↗
PubMed1994

[Effect of intraocular irrigating solution on flicker electroretinogram during cataract surgery in humans].

We studied the effects of intraocular irrigating solutions on the 30Hz flicker electroretinogram (ERG) during extracapsular cataract surgery in 45 eyes of 35 patients. The effects of two commercially available irrigating solutions. S-MA2 (Opeguard MA) and DE-057 (BSS Plus) were compared. After irrigation and aspiration (I/A) of the residual cortex with S-MA2, ERG amplitude increased to 111.2 +/- 5.8% of the pre-I/A amplitude. It significantly increased to 116.9 +/- 7.0% at the end of operation (p < 0.05) compared with before I/A. After I/A with DE-057, ERG amplitude increased to 109.5 +/- 5.3% of the pre-I/A amplitude. It significantly increased to 115.7 +/- 6.5% at the end of operation (p < 0.05) compared with before I/A. After I/A with S-MA2, ERG peak time was significantly prolonged to 103.9 +/- 0.8% of the pre-I/A peak time (p < 0.01). It was significantly shortened to 101.5 +/- 0.9% at the end of the operation (p < 0.001) compared with after I/A. After with DE-057, ERG peak time was significantly prolonged to 104.2 +/- 1.2% of the pre-I/A peak time (p < 0.01). It was significantly shortened to 101.3 +/- 1.22% at the end of the operation (p < 0.05). There were no statistical differences between changes of amplitude and peak time with S-MA2 and those with DE-057. We speculated that a drop in the retinal temperature during I/A in the anterior chamber and an increment of the photopic ERG amplitude during light adaptation with the operating microscope caused these ERG changes.

Adolescent↗
PubMed1993

[Effect of intraocular irrigating solution on electroretinogram during pars plana vitrectomy].

The effects of intraocular irrigating solutions on the human retina are not known. We recorded 30 Hz-flicker electroretinograms (ERGs) during vitrectomy, and examined the effects of perfusate S-MA2 and DE-057 on the human ERG. The amplitude of the 30 Hz-flicker ERGs were not significantly different for the two irrigating solutions. The peak latency of the 30 Hz-flicker ERG was increased 14 +/- 4.4% (mean +/- SE) during irrigation with S-MA2, compared with the preoperative peak latency. Replacement of S-MA2 by DE-057 increased the peak latency by 37 +/- 5.8% (p < 0.01). Since the peak latency of the 30 Hz-flicker ERG became shorter after replacement of DE-057 by S-MA2, these effects were reversible (p < 0.01).

Aged↗
PubMed1992

Outcome of White pump shunt surgery for neovascular glaucoma in Asians.

We compared the effect of seton (White pump shunt) surgery (16 eyes) with that of trabeculectomy and 5-fluorouracil (31 eyes) in treating 38 Asian patients with medically uncontrollable neovascular glaucoma. We found the probability of long-term success (intraocular pressure < or = 26 > or = 5 mm Hg) of seton surgery (53.0% at 3 years) to be similar to that obtained following trabeculectomy with adjunctive 5-fluorouracil (45.4% at 3 years). However, 3 years postoperatively, the probability of the preservation of visual acuity was significantly greater following trabeculectomy than seton surgery (67.1% vs 23.1%; P < .05). In addition, the prevalence of postoperative complications was higher with the seton procedure (P < .001). The loss of endothelial cells 6 months postoperatively was more marked with seton surgery than with trabeculectomy, whether the shunt device touched the cornea (P < .000001) or not (P < .0005). In conclusion, White's pump shunt was effective in lowering the IOP of eyes with neovascular glaucoma. However, care must be taken to prevent postoperative complications, the incidence of which exceeded those observed following trabeculectomy with adjunctive 5-fluorouracil.

Adult↗
PubMed1992

[Effect of metoclopramide, dopamine receptor blocker, on the EOG light peak].

We studied the effects of metoclopramide hydrochloride (MTCL), a D2-selective dopamine receptor antagonist, on the electro-oculograms (EOGs) in 10 eyes of 5 healthy volunteers and on the electroretinograms (ERGs) in 6 eyes of 3 volunteers. MTCL was given intravenously after 15 minutes of dark adaptation. The L/D ratio of EOG was 2.13 +/- 0.14 (mean +/- SE) before the administration of MTCL. After the administration of MTCL, the dark-adapted EOG amplitudes increased transiently. MTCL significantly depressed the L/D ratio to 1.60 +/- 0.07 (p less than 0.01). The a- and b-wave amplitudes of the flash ERG decreased by 12% and 11% respectively. However, the OP2 and OP3 amplitudes of oscillatory potential increased by 23% and 19% respectively. The implicit times of all waves mentioned above tended to be prolonged. This study shows that a blockade of D2-dopamine receptor supresses the EOG light peak. Further investigations are needed to clarify the exact mechanism of this effect.

Adult↗
PubMed1990

Effects of cAMP and IBMX on the chick retinal pigment epithelium. Membrane potentials and light-evoked responses.

cAMP is known to alter electrical measures of retinal pigment epithelial (RPE) function (standing potential and DC ERG. To locate the origin of these effects, studies were performed on in vitro preparations of chick retina-RPE-choroid and RPE-choroid, which were separately perfused with cAMP or db-cAMP on the retinal (apical) and choroidal (basal) tissues surfaces. Similar studies were performed using the phosphodiesterase inhibitor IBMX. cAMP and db-cAMP produced essentially identical results. cAMP placed in the retinal or choroidal baths hyperpolarized the RPE basal membrane, increased the apparent basal membrane resistance (Rba), and decreased the ERG c-wave. Experiments in RPE-choroid preparations suggested that these effects of cAMP were not secondary to effects on the neural retina. Effects were observed at 1.0 microM and increased with concentration (1.0 microM-500 microM), with choroidal application producing smaller effects than retinal. The c-wave decrease with retinal cAMP was due principally to the increase in Rba. However, the light-evoked subretinal K+ ([K+]0) decrease, measured with K(+)-specific microelectrodes, showed a small reduction that may have contributed to the c-wave change and that explained an observed decrease in slow PIII. Retinal cAMP also led to a small decrease in ERG a-wave amplitude, which in view of the effects on [K+]0, is consistent with a small reduction in the light response of photoreceptors. The cAMP-induced hyperpolarization of the RPE basal membrane may result from a decrease in basal membrane anion conductance. The results of retinal or choroidal perfusion with IBMX (0.1 mM) in the retina-RPE-choroid preparation were similar and were complicated by effects on photoreceptors. IBMX increased the amplitude of the light response of photoreceptors as indicated by an increase in amplitude of the light-evoked [K+]0 decrease and the a-wave of the ERG. IBMX also produced a transient increase in dark-adapted [K+]0 that altered the membrane potentials of the RPE and obscured any direct effects of IBMX on the RPE. However, IBMX perfusion of the RPE-choroid suggested that the effect on the RPE was similar to that of cAMP perfusion. The IBMX-induced increase in the photoresponse also led to increases in other components of the DC ERG, including the c-wave, fast oscillation and light peak.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Effects of melatonin on the chick retinal pigment epithelium: membrane potentials and light-evoked responses.

The indolamine hormone melatonin, synthesized in the retina, is thought to participate in modulating day-night cyclic variations in photoreceptor and retinal pigment epithelium (RPE) function. It has also been shown to alter the electrical activity of the RPE of the mammalian eye (Dawis and Niemeyer, 1985, Soc. Neurosci. 11, 1079:1988, Clin. Vis. Sci. 3, 109-118: Textorius and Nilsson, 1987, Doc. Ophthalmol, 65, 97-111). To determine the origin of such electrical effects studies were performed on in vitro preparations of both chick retina-RPE-choroid and RPE-choroid. In retina-RPE-choroid preparations choroidal perfusion with melatonin (2.10(-6) M) hyperpolarized the basal membrane, increased its apparent resistance, and diminished the amplitude of the c-wave of the electroretinogram (ERG). Retinal perfusion with melatonin (2.10(-6) M) first depolarized the RPE apical membrane and increased its apparent resistance and this gave way to a basal membrane hyperpolarization accompanied by an increase in basal membrane resistance. Both phases were accompanied by c-wave decreases. Experiments in RPE-choroid preparations suggested that the choroidal effect of melatonin was independent of the neural retina, while the retinal effect was more complex and probably included a neural retinal component. Retinal or choroidal melatonin (2.10(-6) M) had little or no effect on the amplitude of the light peak of the DC ERG. These results show that chick RPE membrane potentials and resistances at either the apical or basal membrane can be affected by melatonin directly, or indirectly via effects on other cells.

Animals↗
PubMed1987

Effects of glucose and fructose added to the intraocular irrigating solutions on the rabbit ERG in vitro.

The addition of various concentrations of glucose to intraocular irrigating solutions for the retina was studied electrophysiologically using an in vitro eye-cup in the pigmented rabbit. Comparison of b-wave amplitudes demonstrated that, glucose at a concentration of 20 mM/l yielded the highest values. With this concentration, the b-wave amplitude was markedly enhanced to 250% at 90 minutes. With 5 mM/l glucose (normogycemic) solutions, the b-waves were decreased to below 20% at 60 minutes. A 40 mM/l glucose solution also increased the b-waves but to a lesser extent than 20 mM/l. These results might be due to the detrimental effects of osmolarity. However, under hypoxic conditions the amplitudes of b-waves obtained with 40 mM/l glucose solutions were greater than those with 20 mM/l glucose solutions. The addition of 10 mM/l fructose to the control solution had no remarkable effects suggesting that fructose is not a direct energy source for the in vitro retina.

Animals↗