Biomedical subjects
N Nao-i
Publications and source records attributed to N Nao-i.
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.
[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.
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.
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.
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.
[The ERG C-wave during adaptation to the dark and the light in the pigmented rabbit].
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[Studies on the clinical differences between low-tension glaucoma and high-tension glaucoma (preliminary report)].
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Paradoxical enhancement of the ERG c-wave by a small dose of sodium iodate.
The early effects of sodium iodate (NaIO3) on the ERG c- and b-waves were studied in rabbits. When 30 mg NaIO3/kg body weight was administered intravenously, the c-wave amplitude decreased and was replaced by a potential of opposite polarity. However, the administration of 20 mg/kg of NaIO3 enhanced the c-wave remarkably. Twenty min after administration, the mean c-wave amplitude significantly increased (P less than 0.001) to 211 +/- 6.2% of the pre-administration amplitude, whereas that of the control was 108 +/- 13.0%. The b-wave amplitude showed no significant changes. When 10 mg/kg of NaIO3 was administered, the enhancement of the c-wave was not remarkable. These effects were similar in both pigmented and albino rabbits. A lower blood concentration of NaIO3 applied to the basal side of the retinal pigment epithelium (RPE) may initially affect only the basal membrane of the RPE resulting in the decrease in the basal membrane resistance (Rba). This would explain the transient increase in the c-wave amplitude with 20 mg NaIO3/kg.
A new polyvinyl alcohol hydrogel as a scleral buckling material.
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Resorption of subretinal fluid by transepithelial flow of the retinal pigment epithelium.
The efficiency of flow through the retinal pigment epithelium (RPE) was calculated by studying the postoperative course of the subretinal fluid after nondrainage surgery of rhegmatogenous retinal detachment. In ten eyes of ten patients the preoperative volume of the subretinal fluid, area of the RPE participating in resorption of the fluid, elapsed time until resorption of the fluid, and efficiency of the flow were studied using B-scan ultrasonography. The flow through the RPE was 261 microliter/cm2 per day and could drain more than 50% of the vitreous volume to the choroidal circulation. These data coincide well with early reattachment of neural retina in nondrainage surgery. No statistically significant difference in this flow was seen between young and old patients.
Some problems involved in employing the ERG c-wave in pharmacological experiments: conditioning in pigmented rabbits.
The large inter- and intra-individual variations in ERG c-waves have prevented the application of the component in pharmacological experiments on the retinal pigment epithelial function. We examined some of the problems involved in employing the c-wave in pharmacological experiments using rabbit retinas. 1) Under our experimental conditions, the c-wave amplitudes in some rabbits reached equilibrium under intermittent stimuli, while in others they increased with time and did not reach a constant level in 3 h. 2) The c-wave amplitudes of the right and left eyes were similar, indicating that the contralateral eye can be used as a control during local administration of drugs. 3) The c-wave amplitude under 50 lux light had smaller inter-individual variations than that in the dark. This may be a useful indicator of the retinal pigment epithelium function when drugs are administered systemically.
Effects of low molecular weight dextran in intraocular irrigating solutions on ERG B-wave.
We examined effects of low molecular weight dextran in intraocular irrigating solutions on in vitro ERGs of the rabbit. A significant difference in ERG b-wave amplitude was observed between dextran-free and 3-4% dextran-added solutions. The b-wave amplitudes were well maintained and even enhanced to 120% of the presubstitution level after 90 minutes incubation with 4% dextran-added solution (15 mM/L bicarbonate, 290 M0sm/kg). It is suggested that low molecular weight dextran might be a useful or, at least, non-toxic agent in intraocular irrigating solutions for maintaining the retinal function with respect to ERG b-wave.
[Drainage of subretinal fluid by the retinal pigment epithelium: their role in reattachment of the retina].
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[The ERG C-wave during adaptation to the dark in pigmented rabbit].
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Toxic effect of fluorouracil on the rabbit retina.
We conducted electrophysiologic tests of the toxic effects of fluorouracil on 26 albino rabbit eyes. Fluorouracil concentrations of 10(-7) g/ml, 10(-6) g/ml, and 10(-5) g/ml produced no significant changes in the b-wave amplitudes of the electroretinogram. A concentration of 10(-4) g/ml, however, reduced the b-wave amplitude to 62% +/- 7.3% of the original value after 60 minutes. A concentration of 10(-3) g/ml decreased the value even further, to 41% +/- 12% of the original value. At this concentration the a-wave appeared to be enhanced, probably because the ascending phase of the b-wave was delayed. A concentration of 5 X 10(-3 g/ml resulted in disappearance of the b-wave within approximately three minutes, but removal of the test solution and replacement with a fluorouracil-free medium produced recovery of the b-wave amplitude to 89% +/- 9.9% of the original value within 55 minutes.
Multifocal electroretinograms in normal subjects.
Multifocal electroretinography (ERG), developed by Sutter in 1992, is a method of recording the spatial distribution of focal ERG in a short time period using multi-input stimulation. Using this technique, we can detect the spatial extent and severity of damage to the macula. In this study, we recorded multifocal ERGs from 20 eyes of 20 normal subjects and analyzed the topographical properties of responses. In every subject, a negative wave followed by a positive wave could be recorded and we named them the N1-wave and the P1-wave, respectively. The amplitudes of the N1-wave and the P1-wave were the largest in the fovea, and they became smaller with eccentricity. In the P1-wave amplitude, the greatest intersubject variability was observed at the fovea. The N1 and P1 latencies were shorter in the upper retina than in the lower retina. The amplitude was larger in the upper retina than in the lower retina, which suggests the functional superiority of the upper retina. There was no statistical difference in latency and amplitude between the nasal and the temporal retina. We found no statistical difference between the responses of the papillomacular bundle and those of the temporal retinal area. The mapping obtained by multifocal ERG was useful as objective perimetry.
Effect of intraocular irrigating solution on flicker electroretinogram during cataract surgery in human eye.
The effects of two commercially available intraocular irrigating solutions, Opeguard MA and BSS Plus, were studied during extracapsular cataract surgery in 45 eyes of 35 patients. After irrigation and aspiration of the residual cortex with Opeguard MA or BSS-Plus, the ERG amplitude increased, respectively, to 111.2+/-5.8% and 109.5+/-5.3% of the preirrigation amplitudes. The increases reached significance (116.9+/-7.0% and 115.7+/-6.5%; both P < .05) at the end of surgery compared with pre-irrigation ERG amplitudes. After irrigation with Opeguard MA or BSS-Plus, the ERG peak times were significantly prolonged to 103.9+/-0.8% and 104.2+/-1.2%, respectively, of the preirrigation peak times (both P < .01). The ERG peak times significantly shortened to 101.5+/-0.9% and 101.3+/-1.22%, respectively, at the end of surgery (P < .001 and P < .05) compared with just after irrigation. Although we have previously shown that Opeguard MA maintained amplitude and implicit time of 30 Hz flicker ERG during vitrectomy better than BSS-Plus, there were no statistically significant differences between the changes in amplitude and peak time with Opeguard MA and BSS-Plus during cataract surgery. We speculate that a drop in the retinal temperature during irrigation and aspiration in the anterior chamber and an increase in the photopic ERG amplitude during light adaptation with the operating microscope caused these ERG changes.