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At least 217 records · Page 12Linked to original sources
PubMed2001

Retinal pigment epithelial tear after transpupillary thermotherapy for choroidal neovascularization.

PURPOSE: To describe two patients who developed a retinal pigment epithelial tear after transpupillary thermotherapy for choroidal neovascularization. METHOD: Case reports. RESULTS: Retinal pigment epithelial (retinal pigment epithelium) tear developed in 2 (8%) of 25 eyes after transpupillary thermotherapy for occult choroidal neovascularization associated with age-related macular degeneration. In both eyes, the retinal pigment epithelium tear developed between the treatment session and first post-treatment examination. In both eyes, the visual acuity was unchanged, but the complication of retinal pigment epithelium tear may result in decreased visual acuity when transpupillary thermotherapy is performed in an eye with good initial visual acuity. CONCLUSION: Retinal pigment epithelium tear appears to occur more frequently after transpupillary thermotherapy for poorly defined choroidal neovascularization than after conventional laser photocoagulation for poorly defined choroidal neovascularization.

Aged↗
PubMed1996

Paraproteinemias associated with serous detachments of the retinal pigment epithelium and neurosensory retina.

BACKGROUND: Serous retinal and retinal pigment epithelial detachments resembling central serous chorioretinopathy developed in three patients who had paraproteinemias. METHODS: The patients in this study were examined at two institutions, and their charts, photographs, and fluorescein angiograms were reviewed by the authors. Two patients had cryoglobulinemia and one had lgA, lgM benign gammopathy. RESULTS: These patients had decreased central visual acuity and metamorphopsia at the initial examination. All three patients were women. Two patients were taking systemic corticosteroids in tapering doses at the time of the initial examination. The multiple serous retinal pigment epithelial and retinal detachments were unilateral in one patient and bilateral in two patients. Two patients were treated with laser photocoagulation because of chronic visual loss and foveal detachments. At the most recent examination, each patient had visual acuity of 20/30 or better in both eyes and complete resolution of subretinal fluid. CONCLUSIONS: Patients with paraproteinemia may develop multiple serous detachments of the retinal pigment epithelium and of the neurosensory retina. The chorioretinopathy in these patients may have been related to their paraproteinemia, type A personality, corticosteroid use, or a combination of these factors. The final visual acuity in these three patients was good.

Adult↗
PubMed1996

Retinal pigment epithelial cell count, distribution, and correlations in normal human eyes.

PURPOSE: To determine the number of the retinal pigment epithelial cells, their regional distribution, and correlations with general variables in normal human eyes. METHODS: We examined 53 normal human donor eyes from individuals with a mean age of 58.6 +/- 18.8 years and an axial length of less than 27 mm. After opening the globes by a 16-mm corneoscleral trephination, up to 25 biopsy specimens of the retina and retinal pigment epithelium were obtained in four meridians. The retinal pigment epithelial cells and the retinal photoreceptors were counted on photographs taken from the apical retinal pigment epithelial surface and the inner photoreceptor segments. RESULTS: Total number of the retinal pigment epithelial cells was 3,556,290 +/- 490,700 (mean +/- S.D.; range, 2,130,500 to 4,653,200), and it was positively correlated with the number of rods and cones, the total area of the retina, the optic disk size, and the retinal pigment epithelial cell density but was independent of gender. The retinal pigment epithelial cell density decreased significantly (P < .001) from the fovea (4,220 +/- 727 cells/mm2) to the midperiphery (3,002 +/- 460 cells/mm2) and to the outer peripheral fundus regions (1,600 +/- 411 cells/mm2). In the retinal periphery, the retinal pigment epithelial cell density was the highest (P < .01) in the nasal fundus region compared with any other fundus quadrant. The retinal pigment epithelial cell density decreased by about 0.3% per year with increasing age. CONCLUSIONS: These data on the quantitative anatomy of the retinal pigment epithelium may be important for physiology and pathophysiology of the visual process, especially in evaluating the effects of aging.

Adolescent↗
PubMed1993

Mannitol, dextromethorphan, and catalase minimize ischemic damage to retinal pigment epithelium and retina.

We studied the recovery of retinal pigment epithelium and retinal function after 80 minutes of pressure-induced ischemia in rabbits. Just before restoring circulation, we gave intravenous mannitol (an osmotic agent and free-radical scavenger), dextromethorphan (an N-methyl-D-aspartate receptor antagonist), or catalase (an antioxidant enzyme). Mannitol has not previously been shown to be protective for retinal or retinal pigment epithelial ischemia. At 24 hours after reperfusion, the electroretinogram b-wave was reduced to 37% of preischemic amplitude in untreated eyes, but it recovered to 67% to 80% after treatment with all three agents. The c-wave was replaced by a negative slow PIII response in control eyes and in seven of 12 catalase-treated eyes, but it recovered by 58% to 82% in the remaining catalase-treated eyes and all the mannitol- and dextromethorphan-treated eyes. Histologic examination confirmed that retinal pigment epithelium as well as retina had been damaged by the ischemia. The effects of mannitol seem of special interest, since the drug has a dual mechanism of action and is clinically available.

Animals↗
PubMed2003

Ultrastructural analysis of hydraulic and abrasive retinal pigment epithelial cell debridements.

Differential changes in Bruch's membrane, choriocapillaris, retinal pigment epithelium, retina, and tapetum after hydraulic or abrasive debridement of the retinal pigment epithelium in the cat area centralis were documented by fluorescein angiography, histology, and transmission electron microscopy at 1-hour, 1-day, 3-day, 1-week, or 4-week time points. Abrasive debridement is associated with abnormal fluorescein angiography and incomplete ingrowth of retinal pigment epithelial cells. Transmission electron microscopy shows that abrasive debridement inflicts more long-lasting ultrastructural damage to Bruch's membrane, the choriocapillaris, tapetum, and retina than does hydraulic debridement. Because the retinal pigment epithelium can resurface abrasively debrided Bruch's membrane that is disorganized, split, reduplicated, or missing, we cannot correlate the ultrastructural appearance of Bruch's membrane with the likelihood of complete resurfacing of the debrided area. Primary choriocapillary or retinal damage in abrasive debridements may contribute to the poor outcome. Regions of retinal degeneration with no underlying retinal pigment epithelial cell monolayer were significantly larger in abrasive debridements at the 4-week than at the 1-week time point. Reduced resurfacing at the later time point suggests that not all cells resurfacing abrasively debrided areas survived over the longer term. This finding may mean that retinal pigment epithelial cells are not able to resurface completely and permanently areas showing geographic atrophy of the choriocapillaris.

Animals↗
PubMed1996

CD36 participates in the phagocytosis of rod outer segments by retinal pigment epithelium.

Mechanisms of phagocytosis are complex and incompletely understood. The retinal pigment epithelium provides an ideal system to study the specific aspects of phagocytosis since an important function of this cell is the ingestion of packets of membranous discs that are normally discarded at the apical ends of rod and cone cells during outer segment renewal. Here we provide evidence that rod outer segment phagocytosis by retinal pigment epithelium is mediated by CD36, a transmembrane glycoprotein which has been previously characterized on hematopoietic cells as a receptor for apoptotic neutrophils and oxidized low density lipoprotein. Immunocytochemical staining with monoclonal and polyclonal antibodies demonstrated CD36 expression by both human and rat retinal pigment epithelium in transverse cryostat sections of normal retina and in primary cultured cells. By western blot analysis of retinal pigment epithelial cell lysates, polyclonal and monoclonal antibodies to CD36 recognized an 88 kDa protein which comigrated with platelet CD36. Furthermore, the synthesis of CD36 mRNA by retinal pigment epithelium was confirmed by reverse transcriptase-PCR using specific CD36 oligonucleotides. The addition of CD36 antibodies to cultured retinal pigment epithelial cells reduced the binding and internalization of 125I-labeled rod outer segments by 60%. Immunofluorescence confocal microscopy confirmed that outer segment uptake was significantly diminished by an antibody to CD36. Moreover, we found that transfection of a human melanoma cell line with CD36 cDNA enabled these cells to bind and internalize isolated photoreceptor outer segments as seen by double immunofluorescent staining for surface bound and total cell-associated rod outer segments, and by measurement of cell-associated 125I-labeled rod outer segments. We conclude that the multifunctional scavenger receptor CD36 participates in the clearance of photoreceptor outer segments by retinal pigment epithelium and thus, participates in the visual process.

Aged↗
PubMed1985

Exocytosis by retinal pigment epithelial cells.

We observed cultured retinal pigment epithelial cells as they responded to the introduction of latex particles. The cells showed phagocytosis of particles 1 h after administration of latex and were filled with particles after 24 h. After 7 days, exocytosis of latex from basal plasma membrane was documented. Observation was repeated using a two-layer culture. 7 days after putting the retinal pigment epithelial layer containing latex particles on another layer without particles, we observed the appearance of latex particles in the lower layer that originally contained no particles. This demonstrated that cultured retinal pigment epithelial cells exocytose latex particles from basal cell membrane.

Animals↗
PubMed1994

Experimental transplantation of human retinal pigment epithelial cells on collagen substrates.

We studied the use of human retinal pigment epithelial cells cultured on a collagen support as a potential transplantation therapy to replace diseased or damaged retinal pigment epithelium. Using a transvitreal approach, we transplanted human retinal pigment epithelial cells attached to either a sheet of noncross-linked or cross-linked type I collagen into the subretinal space of New Zealand white rabbits, whose eyes lack pigment. Animals were killed after six weeks, and the eyes were fixed for light microscopy. The results demonstrated that, in eyes receiving the noncross-linked collagen support, a layer of pigmented donor retinal pigment epithelium was visible within the subretinal space, with a normal-appearing retina and no evidence of proliferative vitreoretinopathy or graft rejection. We believe this method may be applicable to replace dysfunctional retinal pigment epithelial cells in humans.

Animals↗
PubMed2001

Red pigment-concentrating hormone induces a calcium-mediated retraction of distal retinal pigments in the crayfish.

The octapeptide red pigment-concentrating hormone is capable of eliciting the aggregation of intracellular pigment granules in distal retinal pigment cells of isolated retinas of the crayfish Procambarus clarkii (Girard). The final level and the time course of pigment aggregation are dose dependent within a range of 10(-10) mol l(-1) to 10(-4) mol l(-1). The effect of red pigment-concentrating hormone is prevented by previous incubation with an anti- red pigment-concentrating hormone antibody; however, application of the antibody after the onset of the red pigment-concentrating hormone effect, does not prevent its full development. A similar effect to that elicited by red pigment-concentrating hormone is induced by the calcium ionophores ionomycin and A-23187. Red pigment-concentrating hormone evokes entry of 45Ca2+ to retinal cells. However, the red pigment-concentrating hormone-induced pigment aggregation persists in the presence of the calcium channel blocker verapamil and in Ca2+-free solutions. Caffeine and thapsigargin, known to release calcium from intracellular stores, elicit distal pigment aggregation, while ryanodine and dantrolene, blockers of intracellular calcium release, as well as the intracellular calcium chelator bapta-AM suppress the effect of red pigment-concentrating hormone. These results suggest that red pigment-concentrating hormone elicits distal retinal pigment aggregation by increasing intracellular calcium concentration, acting via a dual mechanism: (1) promoting calcium entry, and (2) releasing intracellular calcium.

Animals↗
PubMed1999

9-cis-retinoic acid in combination with retinal pigment epithelium induces apoptosis in cultured retinal explants only during early postnatal development.

Retinoic acid is one of the active metabolites of vitamin A and has profound effects on the development of the CNS including retina. Previously, we have shown that rod-specific apoptosis is induced in retinal explants from neonatal mice by exposure to 9-cis-retinoic acid (9CRA) when the retinal pigment epithelium (RPE) is present. In explants lacking RPE, it instead has a differentiation-promoting effect seen as an accelerated opsin expression on postnatal day 3. To investigate the long-term effect of 9CRA exposure, we have explanted retinas from neonatal C3H mice with or without RPE attached and placed in organ culture. After 19 or 48 h in culture or 7, 8 or 13 days in culture, the explants were either fixed for histochemical examination or frozen for assay of DEVDase activity. We found that long-term exposure to 9CRA caused a decrease in the number of cell layers in the outer nuclear layer (ONL) only in explants with the RPE attached. When explants with RPE attached were exposed to 9CRA only during the second postnatal week, neither an increase in DEVDase activity, TUNEL-positive cells, nor a decrease in cell layers of the ONL could be demonstrated, indicating that the retina was insensitive to the apoptosis-inducing effect of 9CRA after the first postnatal week. The absence of RPE in control explants resulted in a higher number of rosettes and the extrusion of cells into the subretinal space.

Aging↗
PubMed2004

Trypan blue induces apoptosis in human retinal pigment epithelial cells.

PURPOSE: To examine whether trypan blue dye induces apoptosis in human retinal pigment epithelium cells. DESIGN: Laboratory investigation. METHODS: Pure cultures of human retinal pigment epithelium cells were isolated. The cells were incubated with different concentrations of trypan blue (0.5%, 0.10%, and 0.05%) for either 5 or 30 minutes. The rate of retinal pigment epithelium cell apoptosis was assessed with Annexin V-PE staining and flow cytometry. RESULTS: Trypan blue induced a statistically significant amount of apoptosis in retinal pigment epithelium cells at all the concentrations (0.5%, 0.10%, and 0.05%) (P <.05). The increase in incubation time (from 5 to 30 minutes) led to an increase in the number of apoptotic retinal pigment epithelium cells. CONCLUSION: The incubation of retinal pigment epithelium cells with trypan blue increased the number of apoptotic retinal pigment epithelium cells in vitro. Our results suggest that decisions regarding the intravitreal application of trypan blue dye need to be made with caution.

Annexin A5↗
PubMed1987

Phosphorus-31 NMR spectroscopy of cultured human retinal pigmented epithelial cells.

Cultured human retinal pigmented epithelial cells were studied using phosphorus-31 nuclear magnetic resonance spectroscopy (P-31 NMR). Retinal pigmented epithelial cells from normal human donors were isolated and expanded using roller-bottle culture. The P-31 NMR spectrum of the intact living cells was obtained at 121 MHz by casting the cells in agarose threads and perfusing the threads with culture medium. The cells remained viable at 37 degrees C in the NMR magnet for at least 24 hr, as determined by the stability of the phosphorus spectrum and by trypan blue dye exclusion at the end of the experiments. The intact cell spectrum showed resonances from phosphorylethanolamine, phosphorylcholine, inorganic phosphate, phosphodiesters, phosphocreatine, ATP, NAD+, and UDP-N-acetylglucosamine, with phosphorylethanolamine, phosphorylcholine, and ATP being the major metabolites present. The resonances were assigned by making a perchloric acid (PCA) extract of the intact cells and running under high-resolution conditions. The PCA extract spectrum also detected sugar phosphates, ADP and UTP, with the latter being approximately 20% of the nucleotide pool. These studies provide the basis for the study of normal and diseased human RPE cells by NMR spectroscopic methods.

Cells, Cultured↗
PubMed2001

Combined hamartoma of the retina and retinal pigment epithelium associated with neurofibromatosis type-1.

BACKGROUND: Retinal tumors are occasionally seen in patients with neurofibromatosis type-1 (NF-1). These are usually astrocytic hamartomas or angiomas. Combined hamartoma of the retina and retinal pigment epithelium are tumors also described in NF-1, but this association has not been definitively established yet. METHOD: We report on a child with NF-1, who presented a combined hamartoma of the retina and retinal pigment epithelium in both eyes. RESULTS: The diagnosis of bilateral combined hamartoma of the retina and retinal pigment epithelium in our patient was performed on the basis of the ophthalmoscopic appearance of the lesions. NF-1 was diagnosed following the current international clinical criterion, supplemented by neuroimaging findings. CONCLUSION: Despite the extreme rarity of this association, we believe that it is not coincidental, as the presence of a hamartomatous retinal lesion in a patient with a systemic hamartomatous neuroectodermic disease would be, at least, rational. Thus, NF-1 must be excluded in patients with combined hamartoma of the retina and retinal pigment epithelium.

Child↗
PubMed2001

The phagocytosis of rod outer segments is inhibited by selected drugs in retinal pigment epithelial cell cultures.

The effects of tamoxifen, toremifene and chloroquine on the phagocytosis of rod outer segments by retinal pigment epithelium were evaluated in human retinal pigment epithelial cell line D407 and pig retinal pigment epithelial cell culture. Retinal pigment epithelial cells were exposed to different concentrations of tamoxifen (1-20 microM), toremifene (1-20 microM) and chloroquine (1-1000 microM), and challenged with FITC-labeled rod outer segments for 24 hr. The phagocytized (bound and ingested) rod outer segments were measured fluorometrically, and the effect of the drugs on the phagocytosis was determined. The cytotoxicity of the drugs was evaluated by measuring their effects on mitochondrial enzyme activities (WST-1-test). The results showed that the test compounds inhibited the phagocytosis of rod outer segments in both D407 and pig retinal pigment epithelial cells. The phagocytic activity was more sensitive to tamoxifen (EC(50) 7.2 microM for D407 cells and 3.6 microM for pig retinal pigment epithelial cells) and toremifene (EC(50) 6.2 microM and 3.1 microM respectively) than to chloroquine (EC(50) 77.2 microM for D407 cells). The inhibition of rod outer segment phagocytosis in both cell cultures started at lower dose levels of test compounds than the cytotoxicity indicated by the WST-1-test. The experiments were carried out both in serum-free medium and serum-containing medium. Serum seemed to be a critical factor in the medium and caused difficulties in the interpretation of the results.

Animals↗
PubMed1994

Lactate transport mechanisms at apical and basolateral membranes of bovine retinal pigment epithelium.

The isolated bovine retinal pigment epithelium actively transports lactate from the apical to the basal bath. Net short-circuit [14C]lactate flux in 20 mM lactate was 0.46 +/- 0.09 mu eq.cm-2.h-1 (n = 8). In open circuit, with a physiological lactate gradient, net [14C]lactate flux was 0.66-1.31 mu eq.cm-2.h-1 (n = 3). Lactate in the apical bath caused intracellular acidifications that were saturable, apparently stereospecific, and reduced in magnitude by several H-lactate cotransport inhibitors. In the basal bath, lactate caused intracellular alkalinizations that were dependent on the presence of Na. In short circuit, 20 mM lactate in both baths reversed the direction of net transepithelial 22Na transport from secretion to absorption, suggesting the presence of basolateral Na-lactate cotransport moving lactate out of the cells. Outwardly directed Na-lactate cotransport requires a lactate:Na stoichiometry > 1.4:1, consistent with the coupled movement of Na, lactate, and net negative charge across the basolateral membrane. Intracellular microelectrode recordings showed that basal lactate hyperpolarized and apical lactate depolarized the basolateral membrane. For lactate absorption, this is a novel arrangement of membrane proteins:luminal H-lactate cotransport and serosal electrogenic Na:(n)lactate cotransport. Lactate transport across the retinal pigment epithelium may play an important role in regulating retinal metabolism and subretinal space volume and composition.

Animals↗
PubMed1989

Transplanted retinal pigment epithelium modifies the retinal degeneration in the RCS rat.

Transplantation of dissociated retinal epithelial cells obtained from the retinas of normal, congenic pigmented strain of rats to Bruch's membrane and the subretinal space of dystrophic rats from the Royal College of Surgeon (RCS) strain can prevent photoreceptor cell degeneration in this retina for at least 4 months after transplantation. Host and transplant cells form close apposition with one another but can be distinguished by the presence of both phagosomes and melanin granules in the transplant and the absence of these inclusions in the host retinal epithelium. Transplanted cells show excessive amounts of phagosomal material within 48 hr after transplantation, implying that restoration of phagocytosis is responsible for the photoreceptor survival.

Animals↗