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At least 901 records · Page 50Linked to original sources
PubMed1991

Retinal early receptor potential in retinitis pigmentosa: correlations with visual field and fluorangiography estimates.

The flash induced electroretinogram (ERG) and early receptor potential (ERP) were recorded in a population of patients with definite diagnosis of retinitis pigmentosa in the context of a study protocol including a complete diagnostic screening. ERPs were evoked by full-field 20-joule stimuli (5 stimuli at 10 min of interval in dark adaptation); recording was by skin electrodes positioned at the inferior orbital margin; amplifiers were set at 10-10,000 Hz. The flash ERG was absent or markedly abnormal in all cases, even at an early stage of development of the retinitis, while ERPs (with a normal morphology, latency of the R1 component increased and a reduced amplitude compared to normal controls) could be identified unambiguously in all cases. The amplitude reduction was highly correlated with the severity of the disease as determined by kinetic perimetry and fluorangiography.

Adult↗
PubMed1996

Hyperbaric oxygen treatment for macular edema in retinal vein occlusion: relation to severity of retinal leakage.

Twelve subjects with macular edema in retinal vein occlusion received hyperbaric oxygen treatment. Median visual acuity improved from 20/100 to 20/25 (p = 0.002). Clinically significant improvement (2 lines or more) was achieved in 10 cases (83%). Evaluation of the inward permeability coefficient of the blood-retinal barrier using vitreous fluorophotometry showed no significant alteration in the permeability. Studies of larger groups of vein occlusion patients are required to better understand and characterize the visual changes after the oxygen treatment. Moreover, further follow-up is required before conclusions can be reached about the long-term effect of this treatment.

Aged↗
PubMed1997

Retinal capillary hemodynamics and VEP/pressure tolerance: evidence of retinal microcirculatory compromise in treated glaucomatous eyes.

Measurements of retinal leukocyte velocity were made in single eyes of 6 glaucomatous adults and 9 normal subjects at each of 4 discrete levels of IOP elevation assigned according to the characteristics of prior pattern-evoked cortical potential pressure tolerance measurements. Glaucomatous eyes failed to demonstrate any stabilization in retinal leukocyte velocity at pressures above 45 mm Hg, with velocities 33% lower than normal for a comparable degree of IOP elevation (p < 0.012). Even at baseline IOP, leukocyte velocity was 27.2% slower in the treated glaucomatous eyes than in normal control eyes (p < or = 0.013), despite comparable baseline IOP levels in both groups.

Adrenergic beta-Antagonists↗
PubMed2005

Reductions in serum vitamin A arrest accumulation of toxic retinal fluorophores: a potential therapy for treatment of lipofuscin-based retinal diseases.

PURPOSE: Excessive accumulation of lipofuscin is observed in numerous degenerative retinal diseases. A toxic vitamin A-based fluorophore (A2E) present within lipofuscin has been implicated in the death of RPE and photoreceptor cells. Here, we used an animal model that manifests accelerated lipofuscin accumulation (ABCA4-/- mutant) to evaluate the efficacy of a therapeutic approach based on reduction of serum retinol. METHODS: N-(4-hydroxyphenyl)retinamide (HPR) potently and reversibly reduces serum retinol. The interaction of HPR with retinol binding protein (RBP) and transthyretin was studied by spectrofluorometry and size-exclusion chromatography. To assess the effects of HPR on visual cycle retinoids and A2E biosynthesis, HPR was chronically administered to ABCA4-/- mice. Mice were evaluated using biochemical, electrophysiological, and morphologic techniques. RESULTS: Administration of HPR to ABCA4-/- mice caused immediate, dose-dependent reductions in serum retinol and RBP. Chronic administration produced commensurate reductions in visual cycle retinoids and arrested accumulation of A2E and lipofuscin autofluorescence in the RPE. Physiologically, HPR treatment caused modest delays in dark adaptation. Chromophore regeneration kinetics, light sensitivity of photoreceptors, and phototransduction processes were normal. Histologic examinations showed no alteration of retinal cytostructure or morphology. CONCLUSIONS: These findings demonstrate the vitamin A-dependent nature of A2E biosynthesis and validate a novel therapeutic approach with potential to halt the accumulation of lipofuscin fluorophores in the eye.

ATP-Binding Cassette Transporters↗
PubMed1993

Diffusible, retinal factors stimulate the barrier properties of junctional complexes in the retinal pigment epithelium.

The retinal pigment epithelium lies at the interface between the neural retina and the choriocapillaris where it forms a blood-retinal barrier. Barrier function requires a polarized distribution of plasma membrane proteins and 'tight' tight junctions. During chicken embryogenesis, these features develop gradually. Although terminal junctional complexes are established by embryonic day 4, the distribution of the Na+/K(+)-APTase is not polarized in all cells of the epithelium until embryonic day 11. Similarly, the tight junctions of early embryos are leaky, but become tight by hatching (embryonic day 21). We used primary cell culture to examine the molecular basis of this gradual induction of polarized function. Pigment epithelium harvested from embryonic day 7, and cultured on filters, formed monolayers coupled by junctional complexes. The distribution of the Na+/K(+)-ATPase was non-polarized and the tight junctions were leaky with a transepithelial electrical resistance of 20-30 omega cm2. To isolate diffusible factors that stimulate the transepithelial electrical resistance, neural retinas from embryonic day 7, 14 or 16 embryos were incubated at 37 degrees C in base medium for 6 hours. The conditioned medium was added to the apical chamber of freshly cultured pigment epithelium. The distribution of the Na+/K(+)-ATPase became basolateral, and the electrical resistance gradually increased two to three times over 6 days. The increase in electrical resistance corresponded to a decrease in the rate of [3H]inulin diffusion across the monolayer. The effectiveness of the conditioned medium increased steadily with increasing age of the neural retina. Rather than increased production of an active factor, apparently different active factors were produced at different ages.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

Acid-sensing ion channel 2 is important for retinal function and protects against light-induced retinal degeneration.

pH variations in the retina are thought to be involved in the fine-tuning of visual perception. We show that both photoreceptors and neurons of the mouse retina express the H+-gated cation channel subunits acid-sensing ion channel 2a (ASIC2a) and ASIC2b. Inactivation of the ASIC2 gene in mice leads to an increase in the rod electroretinogram a- and b-waves and thus to an enhanced gain of visual transduction. ASIC2 knock-out mice are also more sensitive to light-induced retinal degeneration. We suggest that ASIC2 is a negative modulator of rod phototransduction, and that functional ASIC2 channels are beneficial for the maintenance of retinal integrity.

Acid Sensing Ion Channels↗
PubMed1998

Two novel mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in X-linked retinitis pigmentosa (RP3). Mutations in brief no. 172. Online.

Recently a new gene called RPGR (retinitis pigmentosa GTPase regulator) was isolated in Xp21.1 and found to be mutated in patients with RP3 type X-linked retinitis pigmentosa. Two new mutations, the first a single base pair deletion and the other a two base pairs deletion, have been found in one Spanish and one Italian family.

Carrier Proteins↗
PubMed1999

Mutations of the retinal specific ATP binding transporter gene (ABCR) in a single family segregating both autosomal recessive retinitis pigmentosa RP19 and Stargardt disease: evidence of clinical heterogeneity at this locus.

Stargardt disease (STGD) is an autosomal recessive macular dystrophy of childhood characterised by bilateral loss of central vision over a period of several months. STGD has been mapped to chromosome 1p22.1 and recently ascribed to mutations in the retinal specific ATP binding transporter gene (ABCR). The fundus flavimaculatus with macular dystrophy (FFM), an autosomal recessive condition responsible for gradual loss of visual acuity in adulthood (second to third decade) has also been mapped to the same locus. However, a gene for autosomal recessive retinitis pigmentosa with distinctive features of choriocapillaris atrophy at an advanced stage (RP19) has been mapped to the genetic interval encompassing the STGD gene on chromosome 1p (D1S435-D1S236), raising the question of whether, despite striking differences in clinical course and presentation, RP19 and STGD might be allelic disorders at the ABCR locus. In a family segregating RP and STGD in two first cousins, we found that heterozygosity for a splicing mutation in the ABCR gene (1938-1 G-->A) resulted in STGD while hemizygosity for this splice mutation resulted in RP, and when studying the RP patient's parents, we found a maternal non-contribution with apparent segregation of a null allele ascribed to a partial deletion of the ABCR gene. The present study shows that, despite striking clinical differences, RP19 and STGD are allelic disorders at the ABCR locus.

ATP-Binding Cassette Transporters↗
PubMed2001

Calcium channel blocker D-cis-diltiazem does not slow retinal degeneration in the PDE6B mutant rcd1 canine model of retinitis pigmentosa.

PURPOSE: D-cis-diltiazem, a calcium channel blocker, has been reported to enhance photoreceptor survival in the rd mouse, a model of retinitis pigmentosa (RP) resulting from mutation of the PDE6B gene. We tested the hypothesis that diltiazem treatment would similarly rescue the canine rcd1 model of RP, which is also caused by a null mutation in the PDE6B gene. METHODS: D-cis-diltiazem was delivered orally twice daily to rcd1 affected dogs beginning at 4 weeks of age; untreated age-matched rcd1 dogs served as controls. At 14 weeks, electroretinograms (ERG) were performed on all animals; 14 dogs were euthanized at this age, and 2 dogs at 25 weeks of age. Eyes were enucleated, fixed, and processed for routine histological examination. RESULTS: No significant differences were found in ERG or histopathologic parameters between diltiazem-treated and untreated rcd1 dogs. Neither rcd1 group showed a rod b-wave; ERGs evoked by single white flashes (dark- or light-adapted) and flicker were also identical between groups. Similarly, treated and untreated animals did not differ in the degree of preservation of the photoreceptor layer, confirmed in cell counts within the outer nuclear layer. CONCLUSIONS: Treatment of rcd1 affected dogs with D-cis-diltiazem did not modify the photoreceptor disease when results were assessed using either ERG or histopathologic criteria. The positive photoreceptor-rescue effect of calcium channel blockers reported in the rd mouse was thus not generalizable to another species with retinal degeneration due to mutation in the PDE6B gene. Caution needs to be exerted in extrapolation to the comparable human forms of RP.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2001

Mutation of human retinal fascin gene (FSCN2) causes autosomal dominant retinitis pigmentosa.

PURPOSE: To characterize the clinical features of 14 Japanese patients with autosomal dominant retinitis pigmentosa (ADRP) who were found to have a mutation in the FSCN2 gene. METHODS: Mutation screening by single-strand conformation polymorphism (SSCP) was performed in 120 unrelated patients with ADRP, 200 unrelated patients with autosomal recessive retinitis pigmentosa (ARRP), and 100 patients with simplex RP (SRP). The DNA fragment that showed abnormal mobility on SSCP was sequenced. The clinical features of these patients were determined by visual acuity, slit lamp biomicroscopy, electroretinography, fluorescein angiography, and kinetic visual field testing. RESULTS: A novel 208delG mutation in the FSCN2 gene was identified in 14 patients from four unrelated families with ADRP. The ophthalmic findings were typical of RP. CONCLUSIONS: The findings show that a 208delG mutation in the FSCN2 gene produces ADRP. This mutation was found in 3.3% of the patients with ADRP in Japan, which suggests that it may be relatively common in Japanese patients with ADRP.

Adult↗
PubMed2002

Two novel mutations of the retinitis pigmentosa GTPase regulator gene in two Chinese families with X-linked retinitis pigmentosa.

OBJECTIVE: To detect mutations of the retinitis pigmentosa GTPase regulator (RPGR) gene in two Chinese X-linked retinitis pigmentosa families. METHODS: Fragments of exons 1-19 of the RPGR gene were amplified with intronic primers, using genomic DNA as template. The polymerase chain reaction (PCR) products were analysed by single-strand conformation polymorphism (SSCP) and direct sequencing. Mutations were identified by comparing DNA sequences of the patients with those of the normal controls. RESULTS: Two novel mutations, c1536delC and E332X, were identified in exons 12 and 9 of the RPGR gene in both families. Each mutation was the first mutation found in their respective exons. Both mutations were predicted to cause premature termination, which resulted in truncated proteins without normal functions of the RPGR products. CONCLUSIONS: Both mutations are the genetic basis of the pathogenesis in the respective families. Our data might be helpful in analysing the function of the RPGR protein.

Carrier Proteins↗
PubMed1992

[Krypton laser therapy. Use in secondary serous detachment of the retinal pigment epithelium and in multiple idiopathic serous detachments of the retinal pigment epithelium].

Two variants of serious detachments of the retinal pigment epithelium (RPE) are demonstrated with reports of typical cases: (1) secondary serous detachment of the RPE; (2) idiopathic serous detachment of the RPE (pigment epithelium detachment not associated with any other retinal or choroidal disease). Fluorescein angiographic criteria for differential diagnosis and the resulting different techniques of krypton laser coagulation are portrayed: (a) focal krypton laser coagulation of the total area of the pigment epithelium detachment; (b) circular, one-row laser coagulation at the detachment borders. The advantages of circular, one-row laser coagulation of idiopathic serous RPE detachment over coagulation of the total area of the RPE detachment are described: first, these are fewer scotomas following coagulation; second, fewer laser foci are required; and third, the risk of subretinal bleeding is lower. These findings emphasize the efficiency of circular, one-row laser coagulation at the detachment borders in the treatment of idiopathic serous RPE detachments.

Adult↗
PubMed1992

Retinal periphlebitis and retinal pigment epithelium changes associated with multiple sclerosis: a report of two cases.

Two patients with definite MS and no significant visual loss are presented, because of the marked bilateral sheathing of retinal veins, and diffuse pigmentary changes in the first patient, and the previously unreported paravenous pigmentation with bone corpuscular configuration in the second patient. The lesions in the second patient are similar to paravenous retinitis pigmentosa. We assume that the RPE lesions may be secondary to perivasculitis, which is not uncommonly seen in MS patients.

Adult↗
PubMed1989

[Erythrocyte aggregation and retinal vein occlusion. Preliminary data for a randomized study on the efficacy of anti-erythrocyte aggregation (troxerutin) in retinal vein occlusion].

Erythrocyte aggregation (EAg) is one of the principal determinants of blood viscosity at low shearing rates (slow flow). The retinal venous circulation, characterised by a slow circulatory rate and a high resistance to flow, creates a favourable environment for the formation of erythrocyte aggregates. EAg and other laboratory parameters (haematocrit, fibrinogen, plasma proteins, clotting) were measured in 64 patients presenting with retinal vein occlusion (RVO) and 64 controls matched for age, sex, risk factors (HT, diabetes, smoking) and concomitant vascular disease. Statistical analysis of the results demonstrated a significant difference between the RVO group and the control group for fibrinogen (p = 0.03) and erythrocyte aggregation (p = 0.00003 for the aggregation index at 10 sec and p = 0.0002 for the threshold of partial dissociation). The rise in the fibrinogen level alone cannot explain the increased erythrocyte aggregation. These results demonstrate that the increased EAg largely explains the hyperviscosity reported by other authors and suggest that it plays an important role in the pathogenesis of RVO.

Adult↗
PubMed1989

Early differentiation of retinal ganglion cells: an axonal protein expressed by premigratory and migrating retinal ganglion cells.

A monoclonal antibody, RA4, was developed that recognizes retinal ganglion cell axons in the mature retina. Between embryonic days 3 and 9, the RA4 antigen was associated with cell bodies in certain regions of the retina in addition to the ganglion cell axons. The RA4-positive cells were of 3 types: an apolar cell adjacent to the ventricular surface, a bipolar cell that spanned the thickness of the retina, and a monopolar cell in the ganglion cell layer. Evidence suggests that these cells are premigratory and migrating retinal ganglion cells. The expression of the RA4 antigen is the earliest indicator of ganglion cell differentiation yet reported. The existence of RA4-positive apolar cells along the outer surface of the retina suggests that the ganglion cell phenotype is expressed as soon as the cell becomes postmitotic. Approximately 20% of the migrating ganglion cells were in pairs. The paired cells most likely arose from the terminal division of a germinal cell. One possibility suggested by these data is that a ganglion cell-specific germinal cell arises from a pluripotent germinal cell. Immunoblots and other analyses revealed the RA4 antigen to be a 140 kDa cytoplasmic protein in the retina. RA4 also recognized many long tract axons in the brain. In the brain, the RA4 epitope was observed on proteins with at least 7 different molecular weights. Evidence suggests that different cell types may express the RA4 antigen with slightly different molecular weights.

Animals↗
PubMedDate not supplied

[A hormone-sensitive stage in the development of the retinal pigment epithelium in Hunter rats with hereditary retinal dystrophy].

The sensitivity of the retinal pigment epithelium (RPE) to the melanotropic effects of alpha-MSH and dbcAMP was assayed in an organ culture of the eye scleral part in the Hunter rats with inherited retinal dystrophy. The melanin synthesis was estimated by liquid scintillation on the RPE isolated enzymatically after 48-h cultivation. One eye from every animal was cultivated in a medium without natural components and with the hormone or dbcAMP (experiment), while the other in a hormone-free medium (control). The melanin synthesis was estimated by 14C-thiouracil incorporation. The result was expressed as a cpm/microgram DNA (experiment) to cpm/microgram DNA (control) ratio. In addition, the index of labelled nuclei was determined using 3H-thymidine autoradiography in the central RPE zone of the eyes from young rats of the same litter. The experiments with alpha-MSH confirmed the earlier data according to which the RPE of the 3 day old Hunter rats were insensitive to melanotropic hormones. This was not due to defects in the cytoplasmic melanin-synthesizing system, since under the influence of dbcAMP the melanin synthesis in the RPE increases more than four-fold as compared with the control; dbcAMP stimulates also the total protein synthesis, as estimated by 3H-leucine incorporation. The RPE of the 4 day old rats proved to be sensitive to alpha-MSH: the melanin synthesis increases more than twice suggesting the healthy state of the RPE membrane melanotropic receptors. alpha-MSH also stimulates the total protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Retinal light damage reduces autofluorescent pigment deposition in the retinal pigment epithelium.

Lipofuscin in the retinal pigment epithelium (RPE) is thought to be derived from phagocytosed photoreceptor outer segment disc membranes. Based on this hypothesis, one would predict that the rate of lipofuscin deposition in the RPE would be proportional to the density of photoreceptor cells in the retina. In previous studies it was demonstrated that specific loss of photoreceptor cells due to a genetic defect resulted in a substantial decrease in the rate of age-related lipofuscin accumulation in the RPE. In order to confirm that this decreased RPE lipofuscin deposition was directly related to reduced photoreceptor cell density, experiments were conducted to determine whether light-induced photoreceptor cell destruction affected RPE lipofuscin content. The effects of retinal light damage on RPE autofluorescent pigment accumulation resulting from both normal aging and vitamin E deficiency were examined. Starting immediately after weaning, albino Fisher 344 rats were fed diets either containing or lacking vitamin E. All animals were maintained on a 12 hr/12 hr light/dark cycle. During the light phases of the cycles, the cage illuminance for one-half the animals in each dietary group was 750 lux, while the remaining rats were exposed to a light level of 15 lux. Illumination was provided by 40 watt cool-white fluorescent lamps. After 17 weeks, rats in both dietary groups that were maintained under the higher light intensity had substantially reduced photoreceptor cell densities relative to animals in the same dietary group maintained under dim light conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗