Three novel mutations of the RPGR gene exon ORF15 in three Japanese families with X-linked retinitis pigmentosa.

We describe three new mutations in a recently identified exon, ORF15, of the retinitis pigmentosa GTPase regulator gene (RPGR) in three unrelated Japanese families (Families 1-3) with X-linked retinitis pigmentosa (XLRP). The affected males had typical retinitis pigmentosa (RP), whereas the obligate carrier females showed a wide clinical spectrum, ranging from minor symptoms to severe visual disability. Some carrier females in Families 1 and 2 showed typical RP, most carriers manifested high myopia and astigmatism, and their corrected visual acuity was insufficient. They showed an impairment of cone function following the rod dysfunction and accompanied by refractive errors. Microsatellite analysis of Family 1 revealed that the RP in the family was linked to the RP3 locus. Although one patient in the family had no mutation in the previously published exons 1-19 including exon 15a, he had a single-nucleotide insertion in exon ORF15 (g.ORF15 + 753-754 insG). Likewise, patients in Families 2 and 3 had two-base insertion/deletion in the exon, i.e., g.ORF15 + 833-834delGG and g.ORF15 + 861-862insGG, respectively. These insertional/deletional mutations observed in the three families are all different and new, and are predicted to lead to a frameshift, resulting in a truncated protein. These findings may support the previous hypothesis that RPGR-ORF15 is a mutational hot spot.

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

The purpose of this study was to determine how changes in [HCO3-] alter the electrical properties of the retinal pigment epithelium (RPE). Experiments were conducted on the isolated chick retina-RPE-choroid preparation. The chamber holding the preparation allowed independent perfusion of the retinal and the choroidal surfaces. The light-evoked trans-tissue potential (TTP), the trans-epithelial potential (TEP), the trans-retinal potentials, and the intracellularly-recorded apical and basal membrane potentials were studied. Increasing the [HCO3-]0 in the choroidal bath from 25 to 40 mEq/1 led to an increase in the TTP and TEP. The same change in the retinal bath decreased the TTP because of a biphasic change of the RPE membrane potentials. There was also an increase in the amplitudes of the TEP, the c-wave and the slow PIII. The light-evoked subretinal K+ decrease was greater which is consistent with an increase in the photoreceptor light response. These observations indicated that the decrease of TTP resulted from a basal membrane hyperpolarization followed by an apical membrane depolarization induced by an increase in retinal [HCO3-]0. The relationship of these potential changes to the human bicarbonate responses is discussed.

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.

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.

[Multi-focal electroretinograms in normal subjects].

The multi-focal electroretinogram (multi-focal ERG), developed by Sutter (1992), is a method of recording the spatial distribution of focal ERG in a short time 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 multi-focal ERGs from 20 eyes of 20 normal subjects and analyzed the topographical property 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 P1-wave amplitude, the greatest inter-subject 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 functional superiority of the upper retina. There was no statistical difference of latency and amplitude between nasal and 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 multi-focal ERG was useful as objective perimetry.

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.

Autosomal dominant cone-rod dystrophy associated with a Val200Glu mutation of the peripherin/RDS gene.

OBJECTIVE: Mutations of the peripherin/RDS gene have been reported in several kinds of retinal dystrophy, and they show a variety of manifestations. The authors identified a novel Val200Glu mutation of the peripherin/RDS gene in a Japanese family with autosomal dominant cone-rod dystrophy (CRD). This report describes a genotype-phenotype correlation of the Val200Glu mutation. PATIENTS AND METHODS: Fifteen members of one Japanese family with autosomal dominant CRD were screened for mutations in the peripherin/RDS and ROM 1 genes. Clinical features were identified by visual acuity, visual field testing, fundus examination, and electroretinography. RESULTS: A Val200Glu mutation was found in all of the affected family members examined and was segregated with the disease. No patient had a mutation in the ROM 1 gene. Phenotypic characteristics of each affected member in this family showed intrafamilial similarity. Characteristic features included cone function more severely impaired than rod function and degenerative change in the macular region associated with peripheral retinal degeneration. CONCLUSION: The mutation at codon 200 of the peripherin/RDS gene causes both cone and rod degeneration. The Val200Glu mutation results in a type of autosomal dominant CRD.

A comparative study of intraocular irrigating solutions: effects on electroretinography readings during closed vitrectomy in humans.

The effects of intraocular irrigating solutions on electroretinography have been extensively studied in animal models, but effects on human electroretinography have not been reported. This study examined the effects of two commercially available irrigating solutions, S-MA2 (Opeguard MA) and DE-057 (BBS-Plus) on 30-Hz flicker electroretinography during closed vitrectomy in humans. Eight eyes of 8 patients were examined. All patients underwent a simple vitrectomy without treatment of proliferative membrane. For 30-Hz flicker electroretinography recording, a contact lens with a built-in light-emitting diode was sterilized and used as both a stimulus source and a recording electrode. Replacing S-MA2 with DE-057 decreased the electroretinography amplitude from 55.8 +/- 15.2 to 45.5 +/- 13.2 microV (mean +/- SEM). Changing the irrigation solution from DE-057 back to S-MA2 increased the amplitude from 45.5 +/- 13.2 to 59.9 +/- 17.3 microV. However, these changes were not statistically significant. Replacing S-MA2 with DE-057 significantly increased the peak time from 50.1 +/- 1.5 to 57.6 +/- 1.3 msec (p < 0.001). This change was reversible; after changing from DE-057 back to S-MA2, the peak time of flicker electroretinography significantly decreased from 57.6 +/- 1.3 to 49.0 +/- 2.1 msec (p < 0.01). Thus intraoperative 30-Hz electroretinography showed delayed peak time during irrigation with DE-057, as compared with S-MA2. The lower potassium concentration and higher glucose concentration of S-MA2, as compared with DE-057, may be the cause of such electroretinography changes.

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.

[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.

[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).

[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.