Search PubMed⌕ Search

Biomedical subjects

K Heimann

Publications and source records attributed to K Heimann.

At least 37 records · Page 2Linked to original sources
PubMed1999

[Repeat laser coagulation of subretinal neovascularization in age-related macular degeneration].

INTRODUCTION: Retinal laser coagulation (LC) of extrafoveal subretinal neovascularization (SRN) due to age-related macular degeneration (AMD) is the only sure therapy. Diagnostics, therapy and follow-up are presented in a case report. CASE REPORT: A 55-year-old woman had suffered from progressive reduction of visual acuity (with metamorphopsia) in both eyes (LE > RE) for 3 years. In the RE the visual acuity was 0.32 and in the LE 0.05. Funduscopy and fluorescein angiography revealed in both eyes the wet form of AMD. The extrafovealy located SRN of the RE was photocoagulated and had to be retreated three-times in 6 weeks due to persistence. For 8 months the findings in the RE have been stable. VA has been improved to 0.4 and no metamorphopsia has been found. CONCLUSION: Extrafoveal SRN should be treated by LC. Short-term follow-up (including FA) and in most cases several LCs are necessary to close the SRN and save the patients' reading vision.

Female↗
PubMed1999

Retinal pigment epithelial cells from Royal College of Surgeons dystrophic rats can take up melanin granules.

BACKGROUND: Many successful pigment epithelium transplantation studies involving pink-eyed Royal College of Surgeons (RCS) dystrophic rats showed highly pigmented transplanted cells forming a double layer with slightly pigmented cells, attached to Bruch's membrane. Since it is not clear whether transplanted pigmented cells can displace retinal pigment epithelial (RPE) host cells from Bruch's membrane, we suggested that RPE cells of RCS dystrophic rats can phagocytize melanin granules, possibly derived from perished transplanted cells. METHODS: In a series of three experiments, RPE cells of nine pink-eyed, 2 1/2-month-old RCS dystrophic rats were isolated by trypsinization and mechanical dissection and cultivated in Dulbecco's modified Eagles' medium. These cells were then fed with melanin granules, isolated from bovine RPE cells, double-trypsinized after phagocytosis and viewed by light and electron microscopy. We also transplanted iris pigment epithelial (IPE) cells of 20-day-old Long-Evans rats into the subretinal space of pink-eyed RCS dystrophic rats of the same age, shown in light-microscopic photography after 42 days. RESULTS: Living RPE cells were heavily pigmented after feeding with isolated melanin granules in all three experiments as viewed by light microscopy. In addition, we identified melanin granules phagocytized by dystrophic RPE cells in electron microscopy. After transplantation of pigmented IPE cells into the subretinal space of pink-eyed RCS dystrophic rats' eyes, a layer of slightly pigmented cells was seen on Bruch's membrane below the transplanted IPE cells, shown in light microscopy. CONCLUSION: We have shown by phagocytosis assay that dystrophic RPE cells can take up melanin granules in vitro. Our results assume that pigmented cells in transplantation studies, found as a monolayer, attached to Bruch's membrane, cannot automatically be identified as transplanted cells. Instead, the possibility of perished transplanted cells serving as melanin donors for RPE host cells must be taken into consideration.

Animals↗
PubMed1999

Ultrastructural localization of lipid peroxides as benzidine-reactive substances in the albino mouse eye.

BACKGROUND: Lipid peroxidation is considered to be a prominent feature of retinal degeneration and has also been proposed to be involved in the pathogenesis of age-related macular degeneration. Melanin protects against lipid peroxidation and takes part in the detoxification of lipid peroxides (LP). LP can be ultrastructurally detected as benzidine-reactive substances (BRS) using tetramethylbenzidine (TMB). Albino mice lack melanin. In the present study, LP were localized as BRS in the eyes of albino and pigmented mice. METHODS: Eye cups of an albino mouse lineage and of wild-type mice were fixed with 2% glutaraldehyde, incubated with 0.5 mg/ml TMB and embedded for electron microscopy. RESULTS: BRS were detected in the eyes of albino mice, but no reaction product was seen in pigmented eyes. BRS located in the retinal pigment epithelium (RPE) and in the choroid of the albino mouse; no BRS were found in intact rod outer segments (ROS). CONCLUSION: The lack of melanin in albino mice is associated with a higher level of lipid peroxidation in RPE and choroid. Melanin seems to protect against LP in RPE and choroid. A lack of melanin is not associated with lipid peroxidation in intact ROS. The present investigation demonstrates the significance of melanin in protection against LP in RPE and choroid.

Animals↗
PubMed1999

Tracing of benzidine-reactive substances in ROS, RPE and choroid after light-induced peroxidation.

BACKGROUND: A new method for the ultrastructural localization of lipid peroxides as benzidine-reactive substances (BRS) was recently developed in our laboratory. The aim of the present study was to localize BRS in the eye after intense light exposure. The light protocol was chosen to either hamper disc shedding or to induce a shedding peak. METHODS: Long-Evans rats were either kept under constant irradiation to enhance lipid peroxidation or under physiological light conditions. The light-induced peroxidation was carried out either by constant irradiation for 24 h or by constant irradiation for 20 h followed by a dark period of 4 h. The eye cups were fixed by glutaraldehyde, incubated with or without tetramethylbenzidine and embedded for electron microscopy. RESULTS: After constant irradiation for 24 h smooth nonlamellar BRS appear exclusively intracellularly over the complete rod outer segments (ROS). After the initiation of disc shedding smooth BRS are localized in the extracellular space of the ROS and extracellularly in the basal labyrinth of the retinal pigment epithelium (RPE). Fine-lamellar BRS emerge in vacuoles of the RPE, in the basal labyrinth and in the lumen of choroidal capillaries. CONCLUSION: Light conditions that trigger the disc shedding possibly activate a mechanism to extrude peroxidative damaged material over the complete ROS into the extracellular space to diminish peroxidative damage inside the ROS. Indigestible residual material from the ROS degradation in the phagosomes consists of membranous lipids associated with peroxidative damaged proteins. The residual material seems to be transported through Bruch's membrane into the choriocapillaris.

Animals↗
PubMed1999

Comparative study of ROS degradation by IPE and RPE cells in vitro.

BACKGROUND: The aim of this study was to compare the degradation of rod outer segments (ROS) in porcine iris pigment epithelial cells (IPE) and retinal pigment epithelial (RPE) cells by measuring the increase of lipofuscin-like fluorescence. METHODS: We measured the development of autofluorescence of lipofuscin-like material in living cells over a period of 4 weeks using an image-analyzing system comprising a light microscope, a filter set with an appropriate wavelength for the detection of lipofuscin-like autofluorescence and a silicon-intensified target camera connected to a computer. The lipofuscin-like fluorescence was quantified as the mean gray value of pixels over a defined area in the cell. In addition, ultrastructural examination of the cells was performed using transmission electron microscopy. RESULTS: We found that while both cell types had increased autofluorescence over time, the increase of lipofuscin-like fluorescence was significantly higher in IPE cells than in RPE cells. The ultrastructure of both cell types was similar and no accumulation of lipofuscin-like granules was observed. CONCLUSION: These findings suggest that although IPE cells are able to phagocytize ROS, their ability to degrade them may be lower than in RPE cells. The increase of lipofuscin-like fluorescence is not due to the accumulation of lipofuscin-like granules.

Animals↗
PubMed1999

Pars plana vitrectomy, endolaser coagulation of the retina and the ciliary body combined with silicone oil endotamponade in the treatment of uncontrolled neovascular glaucoma.

PURPOSE: Neovascular glaucoma develops on a background of ischemic ocular pathologies, such as diabetic eye diseases or central retinal vein occlusion. Development of neovascular membranes in the chamber angle leads to elevated intraocular pressure (IOP). Since cyclodestructive therapy or drainage surgery often fails, we have examined intense antiproliferative surgery as a treatment for advanced neovascular glaucoma. PATIENTS AND METHODS: Thirty-two patients with uncontrolled neovascular glaucoma (mean IOP 45.5 mmHg) subsequent to central retinal vein occlusion or advanced diabetic retinopathy underwent antiproliferative surgery, which comprised pars plana vitrectomy, panretinal laser treatment and direct laser coagulation of the ciliary processes, followed by silicone oil tamponade. Patients were followed up for a minimum of 1 year and as long as 3 years. RESULTS: One week following surgery the IOP was normal, ranging from 8 to 21 mmHg, in 52% of eyes (15/29). After 3 months the IOP was normal in 50% (16/32); after 6 months, in 59% (16/27); and after 1 year, in 72% (18/25). Of the 10 eyes that lost all sight after the surgery, 7 eyes had a history of central retinal vein occlusion. Hypotony was observed in 6% of the eyes (2/32) 3 months after surgery; after 6 months hypotony was present in 15% (4/27), and after 1 year hypotony was present in 12% (3/25). CONCLUSIONS: The theoretical premise of our surgical intervention (antiproliferative surgery) is that laser treatment interrupts the self-enhancing pathway of retinal ischemia, release of proliferative factors and increase in intraocular pressure. The silicone oil endotamponade prevents postoperative complications and supports the rapid regression of rubeosis iridis by separating the anterior from the posterior segment.

Aged↗
PubMed1999

Cellular transport of subretinal material into choroidal and scleral blood vessels: an electron microscopic study.

BACKGROUND: The fate of indigestible material injected into the subretinal space of rats was investigated. METHODS: The non-toxic dye Monastral Blue (MB), which cannot be digested within the lysosomal compartment, was injected transsclerally into the subretinal space of Long Evans and Wistar rats. After 5 and 12 days respectively the eyes were enucleated and examined by light and electron microscopy. Cryo sections were made of eyes 5 days after MB injection for the application of immunohistochemical techniques using markers for epithelial cells (cytokeratin) and macrophages (ED 1). RESULTS: Retina, choroid and sclera were not altered in their morphology in the circumference of the MB-containing bubble generated by subretinal injection. After both 5 and 12 days no injected material was found extracellularly in the subretinal space. Especially high amounts of MB were found, in particular 5 days after injection, in lysosomes and melanosomes of RPE cells as well as in cells between choroidal melanocytes. Cells containing MB were seen in contact with choroidal and scleral blood vessels. These MB-containing cells in the choroid and in the sclera were positive for macrophage antibodies. CONCLUSION: Subretinal injection was confirmed as a suitable method for placing fluids into the subretinal space without affecting the morphology of the retina. Subretinal injected material was shown to be incorporated into lysosomes and melanosomes of RPE cells. The injected material was subsequently transported through Bruch's membrane to be finally removed from the eye via choroidal and scleral veins, the process involving macrophages.

Animals↗
PubMed1999

Detection of mRNA for proteins involved in retinol metabolism in iris pigment epithelium.

BACKGROUND: To investigate in iris pigment epithelium (IPE) the expression of mRNA for proteins involved in retinol metabolism we used a semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) technique. METHODS: RNA was prepared from freshly isolated bovine IPE and retinal pigment epithelium (RPE) cells and reverse transcribed. The expression of mRNA for cellular retinaldehyde binding protein (CRALBP), p63 (RPE63), the presumed retinal pigment epithelial membrane receptor for retinoids, and 11-cis-dehydrogenase (11cisRDH) was determined by RT-PCR using specific primers. Semi-quantitative expression data were obtained by using a series of fivefold dilution of each cDNA with a fixed number of PCR cycles. RESULTS: Bovine IPE and RPE cells express mRNA for CRALBP, 11cisRDH, and RPE63. The mRNA expression for CRALBP and 11cisRDH is high and equal in both cell types. However, RPE63 mRNA expression in IPE cells is relatively low compared with the expression in RPE cells. CONCLUSIONS: The presence of mRNA for CRALBP, RPE63, and 11cisRDH suggests that IPE cells may be able to metabolize retinol.

Aldehyde Oxidoreductases↗
PubMed1999

Improvement of visual acuity in patients suffering from diabetic retinopathy after membrane differential filtration: a pilot study.

BACKGROUND: Membrane differential filtration is an extracorporeal treatment procedure which eliminates high molecular weight proteins and lipids from the blood. This pilot study was initiated to investigate the short-term effects on blood rheology and visual function in patients suffering from diabetic retinopathy. METHODS: Six patients with non-proliferative diabetic retinopathy, clinically significant macular edema (five patients, nine eyes) and inactive proliferative diabetic retinopathy (one patient, one eye) underwent a single treatment with a hollow fiber secondary plasma filter. The main parameter measured was visual acuity prior to and after treatment. Biochemical and rheological parameters (whole blood and plasma viscosity, and erythrocyte aggregation) were also measured. The mean follow-up was 25 (range 4-90) days after treatment. RESULTS: The mean improvement of visual acuity was 1.4 lines (SD 0.8 lines, p = 0.002) 24 h after therapy. This remained stable during the follow-up period. The rheological measures were significantly lowered. A significant reduction of total protein, fibrinogen, IgG, IgM, IgA, alpha-2-macroglobulin, total cholesterol, LDL and HDL was found. CONCLUSION: This study demonstrates the rheological impact of membrane differential filtration. It was shown that rheological changes correlated with clinical improvement in patients suffering from diabetic retinopathy with clinically significant macular edema.

Aged↗
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

[Current strategies for treatment of CMV retinitis in patients with AIDS].

BACKGROUND: CMV retinitis is the most common manifestation of active CMV infection in patients with AIDS. Before ganciclovir became available, the prognosis of CMV retinitis was very poor. Meanwhile a number of strategies for the management of CMV retinitis have evolved. To date no antiviral agent has proved effective in preventing reactivation of retinitis. Therefore the available antiviral agents delay rather than prevent relapse of CMV retinitis. Each relapse produces a more serious disease and retinitis becomes progressively less manageable. METHOD: A review of current therapeutic strategies for the treatment of CMV retinitis with regard to the challenge of clinical resistance is given. CONCLUSION: Effective treatment of clinically resistant CMV retinitis must consider the individual conditions. Thus, it is probable, that integration of both local and systemic therapies may be required to reduce the frequency of reactivation and thereby to decelerate the progression of the disease. Literature search in medline.

AIDS-Related Opportunistic Infections↗
PubMed1999

[Modification of vision by change in rheologic parameters in senile macular degeneration through membrane differential filtration--initial results of a randomized study].

BACKGROUND: Membrane differential filtration (MDF) is known to optimize rheological parameters by eliminating high molecular weight proteins und lipoproteins from the blood and was shown to influence ocular perfusion parameters. Following the hypothesis that these changes may influence the natural course of age-related macular degeneration (AMD) we tested their efficacy in improving visual function in these patients in a randomized trial. PATIENTS AND METHODS: 20 patients (36 eyes) were randomized into two groups. Ten patients (18 eyes) were treated with MDF and ten (18 eyes) served as controls. The first group was treated five times over a period of 21 weeks. In both groups 8/18 of the eyes showed subfoveolar subretinal neovascularisations. Main parameter of the study was visual acuity. Macular visual evoked potentials were also recorded. Plasmaviscosity, whole blood viscosity and erythrocyte aggregation were measured. RESULTS: The ten patients, treated repeatedly over a period of 21 weeks, showed a mean improvement 1.1 (SD 1.9) lines after 21 weeks, while the control group showed a deterioration of visual acuity (0.6 lines, SD 1.7). The macular visual evoked potentials showed an increase of 0.28 microV (SD 1.12) for the therapy group and a deterioration of 0.57 microV (SD 1.31) in the control group. The rheological parameters were lowered in all patients. CONCLUSIONS: We conclude that repetitive treatment with MDF is able to improve visual function in patients with AMD. Further research is necessary to show how to optimize the selection of patients and how to create an individual treatment strategy.

Aged↗
PubMed1999

[Vitreoretinal surgery in the treatment of neovascular glaucoma].

PURPOSE: Neovascular glaucoma develops on a background of ischemic ocular pathologies, such as diabetic eye diseases or central retinal vein occlusion. Development of neovascular membranes in the chamber angle leads to elevated intraocular pressure. Since treatment by cyclodestructive therapy or drainage surgery often fails, we have examined intense antiproliferative surgery as a treatment for advanced neovascular glaucoma. PATIENTS AND METHODS: Thirty-two patients with neovascular glaucoma subsequent to central vein occlusion or advanced diabetic retinopathy underwent antiproliferative surgery, which comprised vitrectomy, panretinal laser treatment and direct laser coagulation of the ciliary processes, followed by silicone oil tamponade. Patients were followed for a minimum of 1 year and as long as 3 years. RESULTS: After one week following surgery the intraocular pressure (IOP) was normal, ranging from 8 to 21 mm#Hg, in 52% (15/29 eyes), after 3 months the IOP was normal in 50% (16/32 eyes), after 6 months the IOP was normal in 59% (16/27 eyes) and after 1 year the IOP was normal in 72% (18/25 eyes). Of the 10 eyes that lost all sight after the surgery, 7 eyes had a history of central vein occlusion. Hypotony was observed in 6% (2/32) of the eyes 3 months following surgery; after 6 months hypotony was present in 15% (4/27) of the eyes and after 1 year hypotony was present in 12% (3/25) of the eyes. CONCLUSIONS: The theoretical premise of our surgical intervention (antiproliferative surgery) is based on the assumption that laser treatment interrupts the self enhancing pathway of retinal ischemia, release of proliferative factors and increase in intraocular pressure. The silicone oil endotamponade prevents postoperative complications and supports the rapid regression of rubeosis iridis by separating the anterior from the posterior segment.

Aged↗
PubMed1999

[A survey of clinically used drugs in PVR: a review].

Colchicine, corticosteroids, daunomycin, fluorouracil, heparin and retinoids have been used in man and show an effect in different stages of the development of PVR. In this survey the effect of each drug is described and the clinical studies are discussed. This survey shows that there are many drugs that in addition to surgery might influence the natural course of clinical PVR during different stages. However, the only drug for which a significant reduction in the number of reoperations has been demonstrated in a randomized prospective trial is daunomycin. Literature search by medline.

Animals↗
PubMed1999

Successful long-term implantation of electrically inactive epiretinal microelectrode arrays in rabbits.

BACKGROUND: In the ongoing discussion concerning the realization of an epiretinal prosthesis for electric stimulation of retinal ganglion cells, long-term fixation of such a device is a crucial question. We evaluated surgical techniques for implantation and fixation of electrically inactive microelectrode arrays (MA) into the retinas of rabbits and secondary tissue reactions to the implant. METHODS: Vitrectomy and laser coagulation of the prospective fixation area were performed in rabbits. Implantation of MAs was performed 3 weeks later in 10 animals. The MA was fixated using retinal tacks. The follow-up included ophthalmoscopy and electrophysiology. At the end of the follow-up, the enucleated eyes were processed for light microscopy using standard procedures and grinding techniques. RESULTS: Nine of 10 rabbits were implanted without serious complications. Clinical and electrophysiologic data through 6 months of follow-up did not indicate any adverse effect of the surgery, the implant, or the tack itself. No change in retinal architecture underneath the implant was found by light microscopy. In these cases, the implant was stable at its original fixation area. In three cases, mild cataract formation was observed, and in one case, a total retinal detachment was found. CONCLUSION: Tack fixation of electrode arrays for electric stimulation of the inner retinal surface seems to be a useful approach in long-term implantation of an epiretinal prosthesis.

Animals↗