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At least 811 records · Page 45Linked to original sources
PubMed1999

Long-term survival of retinal cell cultures on retinal implant materials.

The aim of the present study was to evaluate cell adhesion and cell survival of mammalian retinal neurons on different materials used for the production of multi-photodiode arrays (MPDAs) intended for implantation in the subretinal space of patients suffering from progressive photoreceptor cell loss. The survival rates of different types of retinal neurons and glia cells were monitored by conventional histochemical techniques and immunocytochemistry up to 4 weeks. Whereas most of the materials tested showed good biocompatibility, cell survival of retinal glia and neurons was markedly reduced on titanium nitride (TiN), especially for culturing periods longer than 2 weeks. The effect was not mediated by diffusible factors released from TiN material. In conclusion, most of the materials tested in this study are suitable for the production of functional MPDAs and no complications are to be expected from long-term implantations of them in the subretinal space.

Animals↗
PubMed2001

Rat retinal progenitor cells and a retinal pigment epithelial factor.

Retinal progenitor cells were isolated from explants of neonatal rat retinas and characterized by transmission electron microscopy and reverse transcriptase-polymerase chain reaction and by their response to an isolated retinal pigment epithelial cell cell factor. The isolated progenitor cells demonstrated nuclei with abundant euchromatin typical of progenitor cells and showed the presence of nestin and opsin message. A protein ( approximately 67 kDa) isolated from conditioned media of cultured rat RPE cells promoted the survival of isolated retinal progenitor cells.

Animals↗
PubMed1991

Replacement of leucine-93 by alanine or threonine slows down the decay of the N and O intermediates in the photocycle of bacteriorhodopsin: implications for proton uptake and 13-cis-retinal----all-trans-retinal reisomerization.

We report that the replacement of Leu-93 in bacteriorhodopsin by Ala (L93A) or Thr (L93T) slows down the photocycle by approximately 100-fold relative to wild-type bacteriorhodopsin. Time-resolved visible absorption spectroscopy and resonance Raman experiments, respectively, show the presence of long-lived O-like and N-like intermediates in the photocycles of the above mutants. We infer the existence of an equilibrium between the N and O intermediates in the photocycles of these mutants. The L93A and L93T mutants exhibit normal proton pumping under continuous illumination, suggesting that the decay of the N and/or O intermediate, and consequently, proton translocation, can be accelerated by the absorption of a second photon. Since the 13-cis----all-trans reisomerization of retinal is completed during the decay of the N and O intermediates, we conclude that the interaction of Leu-93 with retinal is important in this phase of the photocycle. This conclusion is supported by a recent structural model of bacteriorhodopsin that suggests that Leu-93 is near the C-13 methyl group of retinal.

Alanine↗
PubMed2005

Toxicity of indocyanine green (ICG) in combination with light on retinal pigment epithelial cells and neurosensory retinal cells.

PURPOSE: To evaluate the toxicity of indocyanine green (ICG) in combination with light. METHODS: Human retinal pigment epithelial cells (ARPE-19) and rat neurosensory retinal cells (R28) were treated with four different concentrations of ICG in combination with light exposure. Cell viability, mitochondrial function, and DNA synthesis were measured. RESULTS: All concentrations of ICG with 10 min of light exposure caused a significant decrease in mitochondrial dehydrogenase activity in R28 and ARPE-19 cells. ICG without light exposure did not decrease mitochondrial dehydrogenase activity. In both cell lines, [(3)H]thymidine incorporation was increased when treated with ICG with or without light. R28 cells did not show any significant decrease in cell viability. CONCLUSIONS: The duration of light was a significant factor in ICG toxicity. ICG needs to be used with caution as it decreases the mitochondrial dehydrogenase activity and increases the DNA synthesis in retinal cells, markers for cell toxicity and dysfunction.

Animals↗
PubMed1995

Role of retinal metabolism in methanol-induced retinal toxicity.

Methanol is a toxicant that causes systemic and ocular toxicity after acute exposure. The folate-reduced (FR) rat is an excellent animal model that mimics characteristic human methanol toxic responses. The present study examines the role of the methanol metabolites formaldehyde and formate in the initiation of methanol-induced retinal toxicity. After a single oral dose of 3.0 g/kg methanol, blood methanol concentrations were not significantly different in FR rats compared with folate-sufficient (FS) (control) rats. However, FR rats treated with 3.0 g/kg methanol displayed elevated blood (14.6 mM) and vitreous humor (19.5 mM) formate levels and abnormal electroretinograms (loss of b-wave) 48 h postdose. FR rats pretreated with disulfiram (DSF) prior to 3.0 g/kg methanol treatment failed to display these symptoms. Formaldehyde was not detected in blood or vitreous humor with or without DSF treatment, suggesting that formate is the toxic metabolite in methanol-induced retinal toxicity. Additionally, creating a blood formate profile (14.2 mM at 48 h) similar to that observed in methanol-treated rats by iv infusion of pH-buffered formate does not alter the electroretinogram as is observed with methanol treatment. These data suggest that intraretinal metabolism of methanol is necessary for the formate-mediated initiation of methanol-induced retinal toxicity.

Animals↗
PubMed1978

Disruption of blood-retinal barrier at the retinal pigment epithelium after systemic urea injection.

Electron microscopic studies were done on the structural alterations of retinal pigment epithelial cells occurring under osmotic stress utilizing rhesus monkeys and lanthanum nitrate as a tracer. Fluorescein fundus angiography revealed leaking points of fluorescein from the choroid to the retina, and various degenerative alterations of the retinal pigment epithelial cells were observed in these leaking areas. Some cells included many vacuoles in their cytoplasm, but diffusion of lanthanum from the choroid to the outer segment of visual cell was obstructed by the tight junctions between the retinal pigment epithelial cells. Other cells were severely damaged with ruptured membranes. Abundant tracer material diffused through the cytoplasm into the subretinal space. Other cells were broken down in an isolated manner and here marked extravasation of lanthanum into the subretinal space was observed.

Animals↗
PubMed1998

Retinal thickness variation in the diabetic patient measured by the retinal thickness analyser.

AIM: To evaluate the potential of the retinal thickness analyser (RTA) as an objective tool for assessment and follow up of diabetic macular oedema. METHODS: A prototype of the RTA that operates on the principle of laser slit biomicroscopy was used. Retinal thickness was obtained in 41 eyes of 41 diabetic patients. The clinical diagnosis was cystoid macular oedema (CMO) in 10 eyes, clinically significant macular oedema (CSMO) without retinal cysts in 21 eyes, and "dry" macula following grid pattern laser treatment in 10 eyes. The control group consisted of 46 eyes of age matched healthy volunteers. RESULTS: In normal eyes (46 eyes), the foveal thickness measured was 178 (SD 44) microns and the macular thickness around the fovea was 311 (51) microns. The eyes with CMO displayed the largest foveal thickening, 875 (287) microns (390% increase compared with normal values). The average thickness of the fovea in the non-cystoid CSMO group was 427 (175) microns (144% increase compared with normal fovea). The average thickness of the foveal centre in eyes judged as having "dry" macula after laser treatment was 315 (71) microns (77% increase compared with normal value and a 26% decrease in thickness compared with the CSMO eyes). Statistically significant differences were found in central thickness between these four groups (p = 0.0001). The average thickness at 500 microns surrounding the fovea was 566 (202) microns in the CSMO eyes compared with 311 (51) microns in normal eyes (80% increase). The "dry" macula group (after undergoing laser treatments) had an average thickness of 414 (94) microns (27% decrease compared with CSMO eyes and a 33% increase compared with eyes of healthy controls). CONCLUSIONS: RTA is a system for quantifying macular thickness and imaging of macular pathology. The system can be a useful tool for diagnosis of macular diseases and for evaluation of the effect of treatment modalities.

Adult↗
PubMed1990

Comparison of non-mydriatic retinal photography with ophthalmoscopy in 2159 patients: mobile retinal camera study.

OBJECTIVE: To determine whether non-mydriatic Polaroid retinal photography was comparable to ophthalmoscopy with mydriasis in routine clinic screening for early, treatable diabetic retinopathy. DESIGN: Prospective study of ophthalmoscopic findings according to retinal camera screening and ophthalmoscopy and outcome of referral to ophthalmologist. SETTING: Outpatient diabetic clinics of three teaching hospitals and three district general hospitals. PATIENTS: 2159 Adults selected randomly from the diabetic clinics, excluding only those registered as blind or those in wheelchairs and unable to enter the screening vehicle. MAIN OUTCOME MEASURES: Numbers of patients and eyes correctly identified by each technique as requiring referral with potentially treatable retinopathy (new vessel formation and maculopathy) and congruence in numbers of microaneurysms, haemorrhages, and exudates reported. RESULTS: Camera screening missed two cases of new vessel formation and did not identify a further 12 but indicated a need for referral. Ophthalmoscopy missed five cases of new vessel formation and indicated a need for referral in another four for other reasons. Maculopathy was reported in 147 eyes with camera screening alone and 95 eyes by ophthalmoscopy only (chi 2 = 11.2; p less than 0.001), in 66 and 29 of which respectively maculopathy was subsequently confirmed. Overall, 38 eyes received laser treatment for maculopathy after detection by camera screening compared with 17 after ophthalmoscopic detection (chi 2 = 8.0; p less than 0.01). Camera screening underestimated numbers of microaneurysms (chi 2 = 12.9; p less than 0.001) and haemorrhages (chi 2 = 7.4; p less than 0.01) and ophthalmoscopy underestimated hard exudates (chi 2 = 48.2; p less than 0.001). CONCLUSIONS: Non-mydriatic Polaroid retinal photography is at least as good as ophthalmoscopy with mydriasis in routine diabetic clinics in identifying new vessel formation and absence of retinopathy and is significantly better in detecting exudative maculopathy.

Adolescent↗
PubMed2004

Retinal pH reflects retinal energy metabolism in the day and night.

The extracellular pH of living tissue in the retina and elsewhere in the brain is lower than the pH of the surrounding milieu. We have shown that the pH gradient between the in vitro retina and the superfusion solution is regulated by a circadian (24-h) clock so that it is smaller in the subjective day than in the subjective night. We show here that the circadian changes in retinal pH result from a clock-mediated change in the generation of H+ that accompanies energy production. To demonstrate this, we suppressed energy metabolism and recorded the resultant reduction in the pH difference between the retina and superfusate. The magnitude of the reduction in the pH gradient correlated with the extent of energy metabolism suppression. We also examined whether the circadian-induced increase in acid production during the subjective night results from an increase in energy metabolism or from the selective activation of glycolysis compared with oxidative phosphorylation. We found that the selective suppression of either oxidative phosphorylation or glycolysis had almost identical effects on the dynamics and extent of H+ production during the subjective day and night. Thus the proportion of glycolysis and oxidative phosphorylation is maintained the same regardless of circadian time, and the pH difference between the tissue and superfusion solution can therefore be used to evaluate total energy production. We conclude that circadian clock regulation of retinal pH reflects circadian regulation of retinal energy metabolism.

Animals↗
PubMed2005

Trypan blue: effect on retinal pigment epithelial and neurosensory retinal cells.

PURPOSE: To evaluate the toxicity of trypan blue on retinal cells in vitro. METHODS: Human retinal pigment epithelial cells (ARPE-19) and rat neurosensory retinal cells (R28) were grown in tissue culture and treated with four different concentrations of trypan blue (0.1%, 0.05%, 0.025%, and 0.0125%), in combination with surgical light exposure (0, 5, or 10 minutes). Cell viability, mitochondrial function, and DNA synthesis were measured by trypan blue dye-exclusion assay, mitochondrial dehydrogenase assay, and tritiated [3H] thymidine incorporation, respectively. RESULTS: ARPE-19 and R28 cells exposed to trypan blue with or without illumination did not show any significant decrease, either in cell viability by the dye-exclusion assay or in [3H] thymidine incorporation. R28 cells exposed to 0.1% trypan blue with and without light showed a significant reduction of mitochondrial dehydrogenase activity (P <0.05). ARPE-19 cells exposed to trypan blue, with or without light, did not show any significant decrease in mitochondrial dehydrogenase activity. CONCLUSIONS: This study suggests that rat neurosensory retina (R28) cells are more sensitive than human RPE (ARPE-19) cells to trypan blue. ARPE-19 cells showed no evidence of toxicity with any of the three assays, but R28 cells showed evidence of toxicity with the mitochondrial dehydrogenase assay at the higher doses and light-exposure times studied. Clinical studies must be conducted to determine the safety and efficacy of staining of the inner limiting membrane with trypan blue.

Animals↗
PubMedDate not supplied

Neither intraocular grafts of retinal cell homogenates nor live non-retinal neurons produce behavioral recovery in rats with light-damaged retinas.

Previously we have observed that fetal retinal cells grafted to the subretinal space of blind rats produced a functional recovery as determined by testing the visual inhibition of the startle response. Following those studies, we performed experiments to test whether the injection itself, cell by-products, or unrelated neural cells could also produce an effect. Visual function was tested by examining the inhibitory effect of a brief light flash (300 lx) on the acoustic startle response to an immediately following intense noise burst in light blinded Fischer 344 rats. Animals were tested before and after grafts of fetal retinal cell homogenates, dissociated perinatal cerebellar cells, and sham injections in the subretinal space. Behavioral testing continued every 2 wk for 14 wk after the graft. In the pretests, the light flash inhibited the startle response, maximal at intervals of 40-70 ms with recovery thereafter. In contrast, after exposure for 4 wk to fluorescent light (300 lx) and a rest in a normal 12/12 h light/dark environment the rats showed reflex facilitation to the light, maximal at an interval of 110 ms, followed by a late period of reflex inhibition. The light flash had no effect on other rats that had been blinded by bilateral enucleation. Light blinded animals receiving either cerebellar grafts or retinal cell homogenates were no different in performance from their sham injected control animals. The present data suggest that neither subretinal injections of neural cells nor non-specific neurochemical factors are able to elicit a positive behavioral response in visually impaired animals.

Animals↗
PubMed1995

jun-B gene expression in rat retinal cells following focal retinal injury.

We examined jun-B gene expression in the rat retina after a focal retinal injury by in situ hybridization. 30 min after producing a penetrating retinal wound, the retina showed the expression of jun-B mRNA intensively in the inner nuclear layer (INL) and relatively sparsely in the ganglion cell layer. The double-labeled retina by immunocytochemistry and in situ hybridization demonstrated that jun-B mRNA within the INL surrounded S-100 protein immunoreactive cytoplasm in the middle sublayer of the INL. These results suggest that the jun-B expression is induced mainly in Müller cells following retinal damage.

Animals↗
PubMed1997

Phenotypic analysis of retinal leukocyte infiltration during combined cyclosporin A and nasal antigen administration of retinal antigens: delay and inhibition of macrophage and granulocyte infiltration.

Nasal antigen administration successfully suppresses a model of organ-specific autoimmune disease, experimental autoimmune uveoretinitis (EAU), when administered prior to immunisation. We have previously shown that nasal antigen therapy for active disease or in primed, sensitised animals does not reliably or consistently suppress histological disease. However, when nasal antigen administration is combined with cyclosporin A (CsA) therapy, rod outer segment destruction (target organ) is reduced despite the presence of clinical and histological leukocytic infiltration of the eye. In this study, two colour flow cytometric phenotypic analysis of retinal and choroidal leukocytic infiltration of animals treated with either CsA alone, combined therapy with CsA and inhalational tolerance therapy with retinal antigens or sham treated controls was performed. There was no clinical difference between the two treated groups. Flow cytometric phenotypic analysis was performed in all groups at both maximal clinical disease and during resolution of clinical signs. Although the cell number within the infiltrate was reduced in combined treated group, CD4+ IL-2R+ T cells were still present in large numbers, in contrast to the markedly reduced numbers of ED7+ (macrophages/granulocytes) cells infiltrating during height of disease. In the CsA-nasal antigen treated group, when clinical inflammation had subsided, an increase in both macrophages and granulocyte numbers in the chorioretina was observed. The cell numbers were always less than CsA-only treated animals. Despite the late cellular influx of monocytes/macrophages, rod outer segment (ROS) integrity as determined histologically, was maintained. Nasal antigen administration of retinal antigens in CsA-only treated animals (combined therapy group) protects against target organ damage without inhibiting activated T cell traffic to the eye. These results suggest that recruitment of macrophages to the target tissue is central to autoimmune target organ damage, the mechanisms of which are discussed.

Administration, Intranasal↗
PubMed1982

Orientation of retinal in bacteriorhodopsin as studied by cross-linking using a photosensitive analog of retinal.

The photosensitive m-diazirinophenyl analog of retinal (Fig. 1, II) bound to bacterio-opsin at Lys-216 and regenerated a chromophore with lambda max at 470 nm. Photolysis of the complex at 365 nm resulted in covalent cross-linking of the retinal analog to the bacterio-opsin in greater 30% yield. Investigation of the sites of cross-linking between the 3H-labeled retinal analog and the protein showed the peptide fragment (amino acid residues 190-248) to be the main radioactively labeled product. Stepwise Edman degradation showed Ser-193 and Glu-194 to be the predominant sites of cross-linking. These results show that the chromophore in bacteriorhodopsin is inclined towards helix 6 and towards the exterior of the cell. These data also provide information on the approximate angle that the chromophore makes with the plane of the membrane and they require a modification of the current secondary structure model for bacteriorhodopsin.

Amino Acid Sequence↗
PubMed1984

Retinal microincarceration with penetrating diathermy in the management of giant retinal tears.

A technique for repair of giant retinal breaks with detachment involves the performance of lensectomy-sector iridectomy, vitrectomy, and scleral buckling behind the equator. Total fluid-gas exchange is performed while the patient is turned to the prone position on a rotating table. Penetrating diathermy is used to fix the retina and to create retinal microincarceration while air is simultaneously injected into the eye.

Adolescent↗
PubMed1977

[Retinal adhesion after retinal detachment surgery (author's transl)].

The effect of cryotherapy was studied in experimentally detached retinas under conditions similar to those in retinal detachment surgery. When cryotherapy was applied to the pigment epithelium and to the retina and the retina was reattached, a strong adhesion developed, characterized by the occurrence of true cell junctions between pigment epithelium and retinal cells. When only the pigment epithelium was treated, the adhesion after reattachment appeared weak due to the absence of microvillous interdigitations normally present between pigment epithelium and retina.

Animals↗
PubMed1993

Differential permeance of retina and retinal pigment epithelium to water: implications for retinal adhesion.

Water movement from the vitreous to the choroid would tend to maintain retinal apposition, if the retina were less permeable than the retinal pigment epithelium (RPE). We used a rabbit model, to test the relative permeability of retina and RPE to tritiated water. The retina was found less permeable than the RPE. This result suggests the presence of a hydrostatic pressure gradient across the retina which could enhance apposition of retina to the RPE.

Animals↗