Biomedical subjects

Sebastian Wolf

Publications and source records attributed to Sebastian Wolf.

32 records · Page 2Linked to original sources

PubMed2004

Selective staining by vital dyes of Müller glial cells in retinal wholemounts.

Müller glial cells within the retina may respond to different signaling molecules with an elevation of their intracellular free calcium. To prove the localization of the recorded calcium responses in Müller cells within acutely isolated retinal wholemounts, retinal pieces from adult animals and humans were exposed to different vital dyes just after the calcium imaging records were finished. The dyes, Mitotracker Orange, Mitotracker Green, Celltracker Orange, Celltracker Green, and monochlorobimane, are all selectively taken up by Müller glial cells, while neuronal cells remain largely devoid of the dyes. By using this method, it can be demonstrated that the free calcium alterations within the wholemounts indeed occur within Müller cells. Moreover, the cross-sectional areas of (dye-filled) Müller glial cell bodies, as well as of (dye-free) neuronal cell bodies, can be measured in retinal wholemounts, and the spatial densities of both types of cells can be determined. The vital dye loading of Müller cells may facilitate investigations of stimulus-induced alterations of retinal glial cell physiology and morphology.

Animals↗

PubMed2004

Peeling of the basal membrane in the human retina: ultrastructural effects.

PURPOSE: To study the effects of internal limiting membrane (ILM) peeling, usually performed in cases of macular hole formation, on the structural integrity of the human retina. DESIGN: Experimental study. MATERIAL: Two human donor eyes. METHODS: A human donor retina was subjected to ILM peeling shortly after enucleation, fixed, and studied by electron microscopy. MAIN OUTCOME MEASURES: Electron microscopic findings. RESULTS: Within the peeled area, and even at its margins, a substantial number of Müller (glial) cell endfeet and vitreal Müller cell processes was severely damaged. However, many glial cells remained intact, and the cell bodies of the injured cells showed no signs of destruction. CONCLUSIONS: We have shown that ILM peeling results in minor, but demonstrable, damage of the adjacent retina. Clinical studies are required to demonstrate unequivocally that ILM peeling does not induce functional deficits rather than improvement of visual function.

Basement Membrane↗

PubMed2004

Glial cell expression of hepatocyte growth factor in vitreoretinal proliferative disease.

The hepatocyte growth factor (HGF) has been crucially implicated in the development of proliferative retinal diseases; however, it is unclear whether retinal glial cells express or respond to HGF. Therefore, we examined the expression of HGF and of the receptor for HGF, c-Met, by immunohistochemical costaining with glial fibrillary acidic protein (GFAP) in epiretinal membranes of patients with proliferative vitreoretinopathy (PVR) and proliferative diabetic retinopathy (PDR), respectively. Furthermore, it was determined whether cells of the human retinal glial cell line, MIO-M1, secrete HGF protein, and whether HGF stimulates proliferation and chemotaxis, and secretion of the vascular endothelial growth factor (VEGF). Neuroretinas of patients with PVR express elevated mRNA level for HGF in comparison to control retinas. In epiretinal membranes of patients with PVR or PDR, immunoreactivity for HGF and for c-Met, respectively, partially colocalized with immunoreactivity for GFAP. Fetal bovine serum and basic fibroblast growth factor, but not heparin-binding epidermal or platelet-derived growth factors, evoked HGF secretion by cultured retinal glial cells. HGF displayed only a marginal effect on cell proliferation while it stimulated chemotaxis. HGF promoted the secretion of VEGF, via activation of the phosphatidylinositol-3 kinase. It is concluded that glial cells in epiretinal membranes express both HGF protein and c-Met receptors. The results suggest an autocrine/paracrine role of HGF in glial cell responses during proliferative vitreoretinal disorders as well as in retinal neovascularization, by stimulating of VEGF release.

Adolescent↗

PubMed2003

Identification of pollen-expressed pectin methylesterase inhibitors in Arabidopsis.

Pectin methylesterases (PMEs) play an essential role during plant development by affecting the mechanical properties of the plant cell wall. Previous work indicated that plant PMEs may be subject to post-translational regulation. Here, we report the analysis of two proteinaceous inhibitors of PME in Arabidopsis thaliana (AtPMEI1 and 2). The functional analysis of recombinant AtPMEI1 and 2 proteins revealed that both proteins are able to inhibit PME activity from flowers and siliques. Quantitative RT-PCR analysis indicated that expression of AtPMEI1 and 2 mRNAs is tightly regulated during plant development with highest mRNA levels in flowers. Promotor::GUS fusions demonstrated that expression is mostly restricted to pollen.

Arabidopsis↗

PubMed2003

Macular pigment density in healthy subjects quantified with a modified confocal scanning laser ophthalmoscope.

BACKGROUND: In the industrialized world age-related macular degeneration (ARMD) is the leading cause for legal blindness beyond the age of 65 years. Recent studies indicate that the density of the macular pigment (MP) may play a central role in the development and progression of age-related maculopathy (ARM). We present results of measurements of macular pigment density (MPD) with a modified confocal scanning laser ophthalmoscope and compare macular pigment density values obtained from reflectance and autofluorescence images in healthy subjects. METHODS: A modified confocal scanning laser ophthalmoscope (Heidelberg Engineering, Heidelberg) was optimised for fundus reflectance and autofluorescence images at 488 nm and 514 nm. For autofluorescence imaging a band pass barrier filter with a short wavelength cut off at 530 nm was used. MPD maps were obtained, and MPD was evaluated within two degrees around the foveal center. In this study we included 109 healthy subjects aged from 18-75 years. RESULTS: Average MPD ranged between 0.16 density units (D.U.) and 0.22 D.U. depending on the techniques used for the measurement. Using the reflectance method the mean MPD was 0.16+/-0.06 D.U., whereas a MPD of 0.22+/-0.07 D.U. resulted from autofluorescence images with the 530-nm barrier filter. CONCLUSIONS: This study demonstrates the good feasibility of MPD measurements with a modified confocal SLO. In agreement with previous studies we found higher macular pigment density values calculated from autofluorescence images than from reflectance images. We could not find any differences in MPD related to age and gender. Prospective longitudinal studies to verify the influence of MPD on the development and progression of ARM are needed.

Adolescent↗

PubMed2003

Age-related decrease of potassium currents in glial (Müller) cells of the human retina.

BACKGROUND: Age-dependent alterations have been investigated far less in retinal glial cells than in retinal neurons. We investigated age-dependent alterations of inwardly rectifying potassium (Kir) currents in Müller glial cells of the human retina. METHODS: Müller cells were isolated immediately post mortem from donors without a reported history of eye disease, and the amplitudes of Kir currents and of currents through high-voltage-activated (HVA) calcium channels were measured by whole-cell patch clamping. RESULTS: The amplitude of the Kir currents was lower in the cells from donors older than 50 years than in the cells of younger donors; the decrease was strongly correlated with the donor's age (p < 0.001). The current amplitude in the cells from donors older than 60 years was about 40% lower than the amplitude in the cells from donors younger than 50 years. The amplitude of the HVA currents was greater in the cells from donors older than 55 years than in the cells from younger donors; the increase, up to about 500%, was strongly age-dependent (p < 0.001). INTERPRETATION: The age-related decrease in Kir-current amplitude in Müller cells may reflect the neuron loss in the aged retina. Our findings also indicate that retinal glial cells have enhanced cytoplasmic calcium signals in the course of aging.

Adult↗

PubMed2003

Silicone oil-RMN3 mixture ("heavy silicone oil") as internal tamponade for complicated retinal detachment.

PURPOSE: To evaluate the efficacy and safety of a silicone oil-RMN3 mixture ("heavy silicone oil") as heavier as water internal retinal tamponade after vitrectomy for complicated retinal detachment. The relative density of the heavier-than-water silicone oil was 1.03 g/cm3, and the viscosity was 3,800 cSt. Heavy silicone oil is designed to tamponade the inferior retina in complicated retinal detachment. METHODS: Patients with a complicated retinal detachment involving the inferior part of the retina requiring internal tamponade with silicone oil were recruited for this prospective study. Inclusion criteria were retinal detachment secondary to proliferative vitreoretinopathy (stage > or = C2), inferior or posterior tears, or penetrating trauma. The heavy silicone oil was injected at the end of surgery after peeling of retinal membranes or retinotomy. Follow-up examinations were scheduled at 1, 3, 6 months, and 1 year after the initial surgery. RESULTS: A total of 33 eyes of 33 patients aged from 20 to 84 years (mean, 56 +/- 18 years) were treated with heavy silicone oil. Follow-up ranged from 12 to 16 months. Rhegmatogenous retinal detachment with significant proliferative vitreoretinopathy accounted for 17 cases, inferior holes for three, and trauma with retinal detachment for three. Initial visual acuity ranged from 20/50 to hand motions. Initial retinal reattachment was achieved in all cases. Complications included increased intraocular pressure in six eyes (18%), intraocular inflammation and synechia formation in one eye (3%), a central retinal artery occlusion after heavy oil removal in one eye, and scattered retinal hemorrhages during follow-up in two eyes (6%). Significant emulsification was not observed during intraocular tamponade with heavy silicone oil. At the last follow-up, all eyes had macular attachment, and 24 eyes had a visual acuity better than or equal to 20/400. CONCLUSIONS: The results of this prospective study show the good intraocular tolerance of heavy silicone oil as tamponade in complicated retinal detachment. Its specific gravity allows for sufficient tamponade of inferior retinal tears for at least 3 months without significant side effects.

Adult↗

PubMed2002

Patch-clamp recording of Müller glial cells after cryopreservation.

Human and other primate retinal Müller cells display dominating K(+) currents as well as other membrane conductances that may change in cases of retinal pathology. Because the use of human and primate tissue is limited by reasons of availability, a method for long-term storage of these cells is desirable. We describe a cryopreservation method in which isolated Müller cells are stored in liquid nitrogen. After thawing, the cells can be used for patch-clamp experiments immediately, without culturing. We show that the main electrophysiological properties are not altered by this method and that voltage- and ligand-gated currents can be recorded from cryopreserved cells even after 2-years storage.

Adenosine Triphosphate↗

PubMed2002

A new instrument for the quantification of macular pigment density: first results in patients with AMD and healthy subjects.

BACKGROUND: There is growing evidence that the development of age-related macular degeneration (AMD) is related to oxidative damage. This makes macular pigment (MP) an interesting target for research, as antioxidative quality is related to MP. As studies have shown that MP density (MPD) can be increased by dietary supplementation, MP may also offer a therapeutic or preventive approach to AMD. METHODS: Using scanning laser techniques, we quantified MPD in healthy subjects and patients with dry AMD. We introduce a modified scanning laser ophthalmoscope (SLO) which includes several advantages for the use in the clinical routine compared to the standard SLO. RESULTS: We examined 10 healthy subjects without ocular pathology and 10 patients with dry AMD (geographic atrophy). Eyes of patients with AMD had a significantly lower MPD (mean value 0.094+/-0.022 density units, DU) than healthy eyes (mean value 0.184+/-0.023 DU). CONCLUSIONS: It is possible to quantify MPD using a scanning laser ophthalmoscope in a clinical setting. The modified SLO offers several improvements with regard to the special requirements of the clinical situation. Using the new instrument, we were able to detect differences in MPD between patients with dry AMD and young healthy subjects. Further studies are needed to evaluate the reliability and reproducibility of the method.

Adolescent↗

PubMed2002

Angiographic findings in patients with exudative age-related macular degeneration.

PURPOSE: Exudative age-related macular degeneration (ARMD) is the leading cause for severe visual loss in the elderly. A series of clinical trials has established the efficacy of laser photocoagulation and photodynamic therapy (PDT) in special subgroups of patients with exudative ARMD. We analyzed the fluorescein and indocyanine green angiograms (ICG) of patients with exudative ARMD to characterize the nature of the CNV in order to estimate the percentage of patients amenable for one of the therapies. METHODS: Patients with acute symptoms related to exudative ARMD were recruited for the study. All patients underwent fluorescein and ICG angiography. We analyzed the type of the CNV (classic, occult, or mixed) and location relative to the fovea from the fluorescein angiograms. Additionally, we recorded the presence of a visible capillary network in the early ICG angiograms, as well as hot spots and plaque hyperfluorescence in the late ICG angiographic frames. RESULTS: We included 191 patients aged 53-92 years in the study. The angiograms revealed in 17 (9%) patients classic CNV (12 subfoveal), in 114 (60%) occult CNV, and in 60 (31%) mixed CNV. Of these 19 had a classic component >50%. In the early ICG angiograms a capillary network was visible in 50 eyes with occult CNV. Hot spots were present in 29 eyes and a hyperfluorescent plaque in 54 eyes. CONCLUSION: In total, only 18% of eyes included in our study were eligible for laser photocoagulation or for photodynamic therapy (PDT). These numbers highlight the deficiencies of current treatment modalities for exudative ARMD. For this reason, alternative treatment should be further investigated to offer better treatment to patients with exudative ARMD.

Aged↗

PubMed2002

[Treatment of Acute Central Retinal Artery Occlusion (CRAO) by Hyperbaric Oxygenation Therapy (HBO)--Pilot study with 21 patients].

BACKGROUND: Central retinal artery occlusion causes severe loss of vision. Treatment trials include massage of the globe, paracentesis, antiglaucomatous eye drops, haemodilution or lysis therapy, which in individual cases did improve the visual outcome, although in general the prognosis remains poor. In this study we applied hyperbaric oxygenation treatment additionally to haemodilution to overcome retinal ischaemia until spontaneous recanalisation of the central retinal artery occurs. PATIENTS AND METHODS: Patients with central retinal artery occlusion and onset of symptoms up to 12 h were included. Following initial ocular massage and application of antiglaucomatous eyedrops, hyperbaric oxygenation treatment was performed twice daily for up to three days. RESULTS: 21 patients could be included. The time lag between onset of symptoms and admission was between 4 and 12 h. Initial visual acuity ranged from light perception to 0.08. On discharge 19 patients reported on a subjective visual improvement which could be confirmed in 13 patients. In 9 patients an initial increase of visual acuity under hyperbaric oxygenation treatment could be observed which however was again reduced by at least one line on discharge. No patient experienced vision loss below admission vision. CONCLUSIONS: Hyperbaric oxygenation treatment seems to improve the visual outcome in central retinal artery occlusion. Major parameters for visual prognosis are the time lag from the onset of symptoms to the beginning of hyperbaric oxygenation treatment and the time lag until retinal reperfusion begins. Hyperbaric oxygenation treatment can compensate retinal ischaemia; however, the lack of glucose and accumulation of toxic metabolites is not addressed. A combination of hyperbaric oxygenation treatment with administration of glutamate antagonists or intravitreal glucose application might further improve the visual outcome.

Acute Disease↗

PubMed2002

Strabological results in patients with macular translocation surgery and counterrotation of the globe as a secondary procedure.

INTRODUCTION: Age-related macular degeneration is the most common cause of irreversible loss of visual acuity, including the ability to read, in elderly patients. One of the surgical treatment options is macular translocation with 360 degrees retinotomy. The orthoptic results of torsional muscle surgery as a second procedure are demonstrated. MATERIALS AND METHODS: Between January 1999 and December 2000, the macula was rotated upward by 12-45 degrees in 10 eyes following complete artificial detachment and a 360 degrees retinotomy. In these patients, torsional surgery was carried out as a second procedure. Depending on the resulting cyclotorsion, we performed surgery on the oblique muscles only in four patients with a cyclotropia of 12-20 degrees and a combination of oblique muscle surgery with surgery of two or four rectus muscles in the remaining six eyes (cyclotropia over 21 degrees ). The pre- and postoperative diagnostic techniques included visual acuity, reading vision and the orthoptic status. RESULTS: Due to the unilateral ectopia of the macula, all patients presented postoperative strabismus with a vertical deviation of 2-10 degrees and a subjective cyclotropia between 12 degrees and 40 degrees. After surgery on the oblique muscles, the patients showed a residual cyclotropia of 0-6 degrees. In patients in whom surgery on the oblique muscles was accompanied by rectus muscle surgery, the remaining cyclotorsion was 5-13 degrees. Four patients excluded the non-operated fellow eye, six patients experienced double vision under binocular conditions and thus required prescription of additional prism glasses. CONCLUSION: Macular translocation causes diplopia under binocular conditions because of the unilateral ectopia of the macular region with cyclotropia and vertical deviation. These problems can be resolved or reduced by oblique muscle surgery or in combination with additional surgery on the rectus muscles, depending on the range of the cyclotorsion. Performing the torsional surgery as a second procedure after macular rotation with an exact preoperative measurement of the subjective cyclodeviation appears to be useful.

Aged↗

PubMedDate not supplied

Femoral derotation.

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Child↗

PubMedDate not supplied

Fixation stability and macular light sensitivity in patients with diabetic maculopathy: a microperimetric study with a scanning laser ophthalmoscope.

BACKGROUND: In patients with diabetic maculopathy, evaluation of visual acuity alone may not represent central retinal function sufficiently. Despite good visual acuity, patients may suffer from visual disturbances like waviness, relative scotoma, loss of fixation and decrease of contrast sensitivity. The aim of the study was to assess localized light sensitivity in the central visual field and to determine fixation stability in patients with diabetic maculopathy with moderate visual loss in comparison to healthy controls. METHODS: Twenty-seven patients (mean age: 54 +/- 15; range 17-81 years) with diabetic maculopathy and 61 controls (mean age: 45 +/- 22; range 18-85 years) were included in the study. Light sensitivity was quantified by presenting stimuli with different light intensity with simultaneous real-time monitoring of the retina (intensity: 0-27.9 dB; size: Goldmann III, wavelength: 633 nm). Eye movements were controlled by semiautomatic fundus tracking. Fixation stability was quantified by measuring the area within 75% of all points of fixation. RESULTS: Fixation stability was significantly decreased in diabetic patients in comparison to controls (43 +/- 22 vs. 31 +/- 16 arc min, p < 0.01). There was a significant difference in macular light sensitivity in diabetic patients compared to controls (19.6 +/- 0.5 dB), both in mean difference (15.6 +/- 1.4 dB) and if affected with macular edema (16.1 +/- 4.5 dB), hard exudates (13.3 +/- 6.7 dB), nonperfusion areas (10.3 +/- 7.9 dB) and laser burns (3.0 +/- 6.1 dB). Temporal parts of the macula were more affected than other parts. No correlation was found between visual acuity and foveal light sensitivity and foveal fixation, respectively. CONCLUSION: Macular light sensitivity decreased progressively with the kind and severity of retinal alteration independent of visual acuity. The assessment of macular light sensitivity and stability of fixation with automatic threshold microperimetry may help to identify patients with diabetic maculopathy and could improve the management of diabetic maculopathy.

Adolescent↗