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PubMed1977

Effects of colchicine on phagosome-lysosome interaction in retinal pigment epithelium. II. In vitro observations on histio-organotypical retinal pigment epithelial cells of the pig (a preliminary report).

Phagocytic activity of histiotypical and organotypical retinal pigment epithelial cells was studied by SEM and EM. After a latent period polystyrene microspheres of different diameter were captured by newly formed microvilli. No mechanism of discrimination according to the size of microspheres was observed. After engulfment, microvilli of histiotypical cells decreased in length and finally disappeared. Lysosomes increased in number when compared to unstimulated cells and fused with many latex-containing phagosomes. Colchicine, when added at 5 X 10(-5) M to the medium, inhibits phagosome-lysome interaction, thus confirming in vivo observations.

Animals↗
PubMed1994

Regulation of the retinal interphotoreceptor matrix Na by the retinal pigment epithelium during the light response.

We examined the rabbit retinal pigment epithelium (RPE) for Na transport properties which would allow it to buffer undesirable changes in Na concentrations in the interphotoreceptor matrix (IPM) during light and dark cycles. The RPE is selectivity permeable to sodium. Open and short circuit transport studies with RPE indicate a circulating (choroid to retina and back) Na current which does not compromise the electrical integrity of the blood brain barrier but together with the Na permselectivity is of sufficient magnitude to buffer both upwards and downwards movements of IPM [Na] during light or dark responses.

Animals↗
PubMed1999

[Introduction of the lipofuscin-fluorophor A2E into the lysosomal compartment of human retinal pigment epithelial cells by coupling to LDL particles. An in vitro model of retinal pigment epithelium cell aging].

PURPOSE: Lipofuscin accumulates with age and in association with various retinal diseases. To investigate cellular effects of lipofuscin components in an in vitro RPE cell model, specific loading of the lysosomal compartment is required. Herein a major lipofuscin fluorophor was complexed to LDL and the subsequent subcellular localization of the retinoid was examined. METHODS: The lipofuscin component N-retinylidene-N-retinylethanolamine (A2-E) was synthesized and coupled to LDL. Human RPE cell cultures were loaded with the A2-E/LDL complex over 4 weeks. Thereafter, RPE cells were harvested by trypsinization and disrupted by nitrogen cavitation. After ultra-centrifugation, the postnuclear supernatant was fractionated on a self-generating gradient and fractions were analyzed by measuring marker enzyme activities of various cellular compartments. RESULTS: A2-Eaccumulated almost exclusively in the lysosomal compartment, as indicated by the identical peaks of the marker enzyme ss-hexosaminidase and the relative fluorescence of A2-E. Only a small amount of A2-E appeared to associate with the cell membrane, as shown by a minor peak of A2-E corresponding to the distribution of phosphodiesterase activity. The lysosomal marker enzyme was not present in the cytosolic fraction. CONCLUSIONS: The feeding of A2-E/LDL complexes to cultured RPE-cells proved to be highly effective in specific loading of the lysosomal compartment, providing a suitable in vitro cell culture model for RPE aging and the investigation of A2-E-effects on lysosomal functions in RPE cells. Such a model may contribute to the understanding of the pathogenesis of degenerative diseases of the outer retina associated with excessive lipofuscin accumulation, including age-related macular degeneration, Stargardt's disease and Best's disease.

Cells, Cultured↗
PubMed2005

Polyurethanes as potential substrates for sub-retinal retinal pigment epithelial cell transplantation.

Transplantation of cultured retinal pigment epithelial (RPE) cells under the failing macular is a potential treatment for age related macular degeneration. An important step in the development of this procedure is the identification of a suitable membrane on which to grow and transplant the cells. This paper evaluates the potential of using polyurethanes in this application since they possess several of the required properties, such as, flexibility, robustness, biostability and good biocompatiblilty although their hydrophobicity can limit cell adhesion. Three commercially available polyether urethanes (Pellethane, Tecoflex and Zytar) were evaluated in terms of their wettability using dynamic contact angle analysis and their ability to support a monolayer of functioning RPE cells (ARPE-19) . Furthermore Pellethane and Tecoflex were treated with a simple air plasma treatment and analysed as above. In the "as received condition" only a few RPE cells attached to the Pellethane and Tecoflex and remained clumped. RPE cells grew to confluence on the Zytar substrate by 7 days without further surface modification. Air gas plasma treatment of both Pellethane and Tecoflex increased the wettability of the surfaces and this resulted in the growth of a monolayer of well-spread RPE cells on both materials. Morphologically these cells grew with a normal 'cobblestone' phenotype. These results demonstrate the potential of these polyurethanes for this application.

Cell Line↗
PubMed2006

Melanin granule models for the processes of laser-induced thermal damage in pigmented retinal tissues. I. Modeling of laser-induced heating of melanosomes and selective thermal processes in retinal tissues.

The computer modeling was applied for investigation of the processes of laser-induced tissue damage. The melanin granule models for the processes of laser-induced thermal damage and the results of computer modeling of the optical, thermophysical, and thermochemical processes during selective laser interaction with melanoprotein granules (melanosomes) in retinal pigment epithelium are presented in this paper. Physical-mathematical model and system of equations are formulated which describe thermal interaction processes for "short" laser pulses of duration t (p)<10(-6) s and for " long' pulses of duration t(p) > 10(-6) s. Results of numerical simulation of the processes give the space-time distributions of temperature and degrees of thermodenaturation of the protein molecules inside and around melanosomes and in the volume of irradiated tissues. Energy absorption, heat transfer and thermochemical (thermodenaturation, coagulation) processes occurring during the interaction of laser pulses with pigmented spherical and spheroidal granules in heterogeneous tissues are theoretically investigated. The possibility for selective interaction of short laser pulses with pigmented granules is discussed which results in the formation of denaturation microregions inside and near the pigmented granules (granular thermodenaturation) without origination of a continuous macroscopic thermodenaturation lesion in tissue. Analytical model of heating of single spherical and spheroidal granule under laser pulse is presented. Simple equations for time dependencies of particle temperature are obtained. The presented results are of essential interest for laser applications in and can be used for investigation of laser interaction with pigmented tissues in different fields of laser medicine.

Computer Simulation↗
PubMed2003

CRALBP transcriptional regulation in ciliary epithelial, retinal Müller and retinal pigment epithelial cells.

Cellular retinaldehyde binding protein (CRALBP) functions in the visual cycle and mutations in the RLBP1 gene can lead to blindness. RLBP1 promoter analyses have been pursued in vitro as an approach to deciphering the mechanism controlling cell-specific expression of CRALBP. Reporter activity of wildtype and mutant RLBP1 promoter constructs suggest that CRALBP transcriptional regulation may be similar in the ciliary epithelium (CE) and retinal pigment epithelium (RPE) but different in Müller cells. Results in RPE cells refine the location of an RLBP1 enhancer element to within -1826 to -1749 bp and a repressor element to within -702 to -635 bp.

Base Sequence↗
PubMed1987

Retinal insulin receptors. 2. Characterization and insulin-induced tyrosine kinase activity in bovine retinal rod outer segments.

Bovine retinal rod outer segments (ROS) possess specific, high-affinity receptors for insulin. These receptors exhibit an insulin-stimulatable tyrosine-specific activity that is capable of phosphorylating the receptor's own beta-subunit and exogenous substrate. ROS insulin receptors exhibit heterogeneity in the apparent molecular weight of the receptor's alpha-subunit. In this regard, insulin receptors from this single cell type resemble insulin receptors obtained from whole retina, but are unlike receptors from brain and liver.

Animals↗
PubMed1999

Retinal damage by light in the golden hamster: an ultrastructural study in the retinal pigment epithelium and Bruch's membrane.

The mechanism of the toxicity of light on the retina remains unclear despite a large number of investigations. The purpose of this study is to identify and localize the ultrastructural changes and the site of the earliest damage after intense light exposure. Nine adult Syrian golden hamsters (Mesocricetus auratus) have been maintained under constant illumination with a high-pressure mercury lamp (HQJ R 80 W Deluxe, Osram, Berlin, light intensity 1000 lx) for 12 h, followed by an additional 3 h in the dark. Light damage is assessed by light and electron microscopy. Morphological evaluation reveals focal damage to the retinal pigment epithelial (RPE) cells in close proximity to less-affected RPE cells and normal photoreceptors. Collagen fibers in Bruch's membrane lose their parallel orientation. Occasionally, fusion of cell membranes of neighboring rod outer segments (ROS) is also observed. Continuous, 12 h exposure of hamsters to intense light results in initial focal damage to some RPE cells, such that severely damaged RPE cells are found adjacent to intact RPE cells. Only slight damage to the photoreceptors is evident, suggesting that the sequence of the pathological changes resulting from light begins with damage to the RPE cells and associated Bruch's membrane.

Animals↗
PubMed1999

Matrix and the retinal pigment epithelium in proliferative retinal disease.

In their normal state, RPE cell are strongly adherent to Bruch's membrane. Certain pathological conditions such as retinal detachment cause an injury-type response (probably augmented or induced by the local accumulation of a variety of substances which modulate cell behaviour) in which RPE begin to dissociate from the membrane. This RPE-Bruch's membrane separation may be mediated by proteins with counter-adhesive properties and proteolytic enzymes, partly derived from the RPE themselves. Concomitant with the RPE disassociation, the cells begin to lose tertiary differentiation characteristics and gain macrophage-like features. When the "free" RPE arrive at the surface of the neuroretina, they may attach to or create a provisional matrix. Some of the cells adopt a fibroblast-like phenotype. This phenotype is similar to that of the dermal fibroblast during cutaneous wound repair and the fibroblastic RPE synthesise the types of matrix components found in healing skin wounds. Many of these molecules in turn further modulate the activities of the cells via several families of cell surface receptors, while the RPE continue to remodel the new matrix with a range of proteolytic enzymes. The resulting tissue (or membrane) has many of the features of a contractile scar and is the hallmark of the condition known as proliferative vitreoretinopathy (PVR). Thus the development of PVR, and the resulting tractional distortion of the neuroretina, appears to be dependent on RPE-matrix interactions. The interactions present a number of potential therapeutic targets for the management of the disorder.

Animals↗
PubMed1989

Light-induced retinal degeneration in rdgB (retinal degeneration B) mutant of Drosophila: electrophysiological and morphological manifestations of degeneration.

Quantitative light and electron microscopy was used to monitor the extent of retinal degeneration as a function of age and temperature in the white-eyed rdgBKS222 mutant of Drosophila melanogaster. Parallel measurements of the electroretinogram (ERG) of the degenerating retina reveal a new phenomenon--the appearance of spike potentials following illumination with bright light. These spikes, which do not appear in the normal fly retina, have a relatively long duration (20-50 ms), regenerative properties, and a rate of occurrence which increases with increasing light intensity. The spikes differed from the light response in being more susceptible to CO2 and to cuts in the eye. The spikes completely disappeared at low extracellular Ca2+ levels which did not reduce the amplitude of the light response. The spike potentials become triphasic when the recording electrode is advanced to the level of the basement membrane. This suggests that the spike potentials originate from the photoreceptor axons as a result of synchronous opening of voltage-dependent channels in a large number of photoreceptor cells. The occurrence of spike potentials during the process of degeneration was studied. Two pahses can be distinguished: (1) Spike potentials appear in retinae of 2-3-day-old flies which display few morphological signs of degeneration. The frequency of appearance of spike potentials decreases in retinae of 14-16-day-old flies which show extensive degeneration of the R1-6 photoreceptor cells but no degeneration of the central R7,8 cells. (2) Spike potentials appear more frequently again in flies of 22-24 d of age. This is probably a consequence of degeneration of the remaining R7,8 photoreceptor cells. Temperature and the light-dark cycle had a critical effect on degeneration. Eight-day-old mutants raised at 19 degrees C in a normal light-dark cycle showed only little degeneration. Eight-day-old mutants raised at 24 degrees C showed only a slight degeneration when raised in the dark. However, the degree of degeneration was greatly enhanced in the mutants raised at 24 degrees C under a light-dark cycle regime. The combined electrophysiological and morphological study of the degeneration, as a function of age and temperature, revealed that (1) the degeneration process takes place even in darkness, but at a slow rate, while light greatly accelerates the degeneration. (2) The degeneration is negligible at 19 degrees C, even during light, in the first week after eclosion.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

Promotion of the release of 11-cis-retinal from cultured retinal pigment epithelium by interphotoreceptor retinoid-binding protein.

This study investigates whether the interphotoreceptor retinoid-binding protein (IRBP) is necessary for the release of 11-cis-retinaldehyde (RAL) or if the retinoid is constitutively released from the retinal pigment epithelium (RPE) following synthesis. The strategic location of IRBP in the interphotoreceptor matrix (IPM) and its retinoid-binding ability make it a candidate for a role in 11-cis-RAL release. Fetal bovine RPE cells were grown in permeable chambers, and their apical surfaces were incubated with medium containing either apo-IRBP, the apo form of cellular retinaldehyde-binding protein (CRALBP), the apo form of serum retinol-binding protein (RBP), or bovine serum albumin (BSA) or with medium devoid of binding proteins. [3H]-all-trans-Retinol (ROL) was delivered to the basal surface of the cells by RBP. High-performance liquid chromatography demonstrated that [3H]-11-cis-RAL was optimally released into the apical medium when apo-IRBP was present. The most surprising result was the diminished level of [3H]-11-cis-RAL when apo-CRALBP was in the apical medium. Circular dichroism demonstrated that CRALBP had not been denatured by the photobleaching required for endogenous ligand removal. Therefore, apo-CRALBP should have been able to bind [3H]-11-cis-RAL if it was constitutively released into the apical medium. In addition, when proteins other than apo-IRBP were present, or if the cells were incubated with medium alone, the observed decrease in apical [3H]-11-cis-RAL was concomitant with a buildup of intracellular [3H]-all-trans-retinyl palmitate and [3H]-all-trans-ROL in the basal culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Enantioselective binding of an 11-cis-locked cyclopropyl retinal. The conformation of retinal in bovine rhodopsin.

[formula: see text] The conformation of the retinal chromophore in rhodopsin is central for understanding the visual transduction process. The absolute twist around the 12-s bond of the chromophore in rhodopsin has been determined by studies with 11-cis-locked 11,12-cyclopropylretinal analogues (11S,12R)-2 and (11R,12S)-3, enantioselectively synthesized with the aid of an enzyme. The finding that enantiomer 2 binds to opsin while the other 3 does not defines the absolute sense of twist around the 12-s bond.

Animals↗
PubMed1988

[Abnormalities of retinal function (light sense) following idiopathic central serous chorioretinopathy and diffuse retinal epitheliopathy].

Although central serous retinopathy is considered a "benign" condition, it is associated in healed forms with frequent and troublesome impairment of visual function. The abnormalities are even more severe after diffuse retinal pigment epitheliopathy. Since Snellen visual acuity testing is a relatively imprecise index of visual function, it does not enable the subtle visual disturbances experienced by these patients to be fully appreciated. The authors evaluated visual function disorders by static automated perimetry and contrast sensitivity in 30 patients with healed central serous retinopathy and in five patients with diffuse epitheliopathy at a cicatricial stage. The results of this study are examined and discussed.

Adult↗
PubMed1994

Exogenous glycosaminoglycans induce complete inversion of retinal ganglion cell bodies and their axons within the retinal neuroepithelium.

Prior to forming an axon, retinal ganglion cells retain a primitive radial configuration while maintaining ventricular and vitreal endfeet attachments. During their subsequent differentiation, ganglion cells polarize their cell body and axon only along the vitreal surface. When the ventricular surfaces of intact retinas in organ culture were exposed to free chondroitin sulfate (CS) in solution, both the cell body and nerve fiber layers were repolarized to the opposite side of the neuroepithelium. However, the basal lamina remained in its usual position. Thus, the ability to initiate an axon is not restricted to the vitreal endfoot region of differentiating neurons, and in addition, the radial position at which the axon emerges can be mediated by the location and concentration of the extracellular CS milieu.

Animals↗
PubMed1986

Effect of imposed retinal image movements on colour vision at a heterochromatic boundary in a stabilized retinal image.

A stabilized image, including a straight-line boundary between two areas of different colour was displayed. Movements normal to itself were imposed on this boundary while other boundaries remained stabilized. Broad band filters giving red, yellow, green and blue were used in various pairs. Step movements, pulse movements and oscillatory movements (including sinusoidal, triangular and square wave forms) were applied in turn. Threshold movements to give perception of hue were measured for steps and pulses and signal/photon-noise ratios were calculated for a red/blue boundary. The ratio was found to be constant at a value of about 20 when the retinal illuminance (ER) varied between 5 td and 60 td. When ER was increased (up to 2000 td) the ratio increased rapidly. None of the colour appearances produced by moving the boundary exactly matched the corresponding appearances in an unstabilized image, though the nearest matches were obtained with oscillatory movements of frequency 2 Hz and displacement greater than 5'.

Color Perception↗
PubMed1983

The retinal toxicity of befunolol and other adrenergic beta-blocking agents: inhibition of phagocytic activity of cultured retinal pigment epithelial cells.

Effects of befunolol and other beta-blocking agents on the phagocytosis of cultured retinal pigment epithelial cells (RPE cells) from the chick embryo were investigated. Toxicity was evaluated as an ability of RPE cell phagocytosis of polystylene latex spheres (PS). After an incubation with beta-blockers, PS was added to the medium. The phagocytic reaction was terminated, and particle numbers in RPE cells were counted under an oil immersion microscope. Incubation with befunolol in a range of concentration of 10(-9)-10(-3) M resulted in a time- and dose-dependent inhibition of phagocytosis. Incubation with 10(-6) M befunolol inhibited phagocytic activity down to 60% of control. The same mode of action was observed in other beta-blockers. The inhibitory effect of befunolol at 10(-4) M or lower concentrations was reversible, while incubation with 10(-3) M for 24 h was irreversible.

Adrenergic beta-Antagonists↗
PubMed2005

Early detection of thinning of retinal nerve fiber layer in glaucomatous eyes by optical coherence tomography 3000: analysis of retinal nerve fiber layer corresponding to the preserved hemivisual field.

The retinal nerve fiber layer (RNFL) thickness was measured with the optical coherence tomography using version 3.0 software (OCT3000) in 153 eyes of 153 normal subjects. The mean of the average RNFL thickness over the entire 360 degrees in the control group was 92.5 +/- 12.9 microm which was significantly thinner than the normative data of 95.9 +/- 11.4 microm included with the OCT3000 (p < 0.01). The RNFL thickness decreased with increasing age (p < 0.01, r = -0.395). The RNFL thickness was also measured in 53 eyes of 53 patients with glaucoma whose superior (13 eyes) or inferior (40 eyes) perimetric hemifields were normal. Only the RNFL thickness corresponding to the preserved perimetric hemifields were measured by OCT3000 and scanning laser ophthalmoscopy (SLO). The RNFL thickness in the superior and inferior 30 degrees sectors, the maximum and average RNFL thickness in the superior (S(max) and S(avg)), and inferior quadrants (I(max) and I(avg)) were analyzed. The S(max), S(avg), I(max), I(avg), and the RNFL thickness in the superior (p < 0.05), superotemporal and inferotemporal sectors (p < 0.01) in the glaucoma patients without a nerve fiber layer defect (SLO) were significantly thinner than in the control subjects in same age. OCT3000 measurements showed that the RNFL thickness in glaucomatous eyes with normal perimetric visual fields and SLO was significantly thinner than the RNFL thickness in normal eyes.

Adult↗
PubMedDate not supplied

Cellular organization in retinal transplants using cell suspensions or fragments of embryonic retinal tissue.

We have investigated the cellular organization in two different types of retinal transplants using cell type-specific monoclonal antibodies. Both fragments and cell suspensions of E17-E19 Sprague-Dawley rat retina were transplanted to a subretinal site in congenic adult rat hosts. After a survival time of 28 days, the transplants were stained by immunocytochemistry with antibodies against rhodopsin, which stained rods; with antibodies against HPC-1, which stained amacrine cells and outer and inner plexiform layers; and with antibodies against vimentin, which stained Müller cell fibers and horizontal cells. In the host retina, the distribution of immunocytochemical staining was similar, irrespective of transplantation technique. In the transplants, the anti-rhodopsin staining showed that fragment transplants developed photoreceptors in rosettes, whereas in cell suspension transplants, this staining showed a scattered distribution of photoreceptors. The HPC-1 staining showed that regions corresponding to the inner nuclear layer surrounded both types of transplants and made large invaginations into them. In one case, using the cell suspension technique, fibres were found to run from the inner plexiform layer of the transplant to the outer plexiform layer of the host. The vimentin staining revealed a disorganized array of Müller cell fibres in both types of transplants, but with some concentration to the regions corresponding to the inner plexiform layer.

Animals↗