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Biomedical subjects

M Völker

Publications and source records attributed to M Völker.

12 recordsLinked to original sources
PubMed2006

Intravitreal bevacizumab (Avastin) for occult choroidal neovascularization in age-related macular degeneration.

BACKGROUND: The purpose of the study is to report data on short-term safety of intravitreal bevacizumab treatment and its effect on visual function, central retinal thickness, and angiographical changes of occult choroidal neovascularization due to age-related macular degeneration. METHODS: A consecutive interventional case series of 30 patients with active subfoveal occult choroidal neovascularization secondary to age-related macular degeneration was followed after one intravitreal injection of 1.25 mg bevacizumab at baseline and subsequent injections following standardized criteria. At baseline and follow-up visits patients had visual acuity assessment, intraocular pressure measurement, fluorescein angiography, and optical coherence tomography imaging. RESULTS: No serious ocular or systemic adverse events were identified. A significant increase of intraocular pressure or signs of retinal toxicity or endophthalmitis were not detected in any patient. Optical coherence tomography revealed significant decrease (p < 0.001) in central retinal thickness after 1 week, 4 weeks, and 12 weeks, respectively. Fluorescein leakage decreased within 1 week and improvement was maintained at week 12 in the majority of patients. Visual acuity improved or remained stable in 29 of 30 patients; improvement of 3 or more lines was seen in 14 of 30 patients; one patients showed improvement of 6 lines. No patient had severe vision loss of 6 lines or more; moderate vision loss of 3 lines was seen in one patient. Re-injections of bevacizumab according to standard criteria were performed one to two times during the follow-up period of 12 weeks with a re-injection interval of 4 to 18 weeks (median 8 weeks). CONCLUSIONS: Short-term results suggest that intravitreal injection of bevacizumab is well tolerated and for the majority of patients with occult choroidal neovascularization in AMD results in improvement of visual acuity, decrease in central retina thickness, and reduction of angiographic leakage of the lesion. Bevacizumab as intravitreal treatment may provide a novel therapeutic option for selected patients with exudative AMD. Randomized prospective multicenter trials seem justified to further evaluate long term effects and impact of intravitreal bevacizumab on different subtypes of AMD compared to established therapies.

Aged↗
PubMed2006

Verteporfin photodynamic therapy induced apoptosis in choroidal neovascular membranes.

AIM: To evaluate the impact of verteporfin photodynamic therapy (PDT) on the induction of apoptosis in choroidal neovascular membranes (CNV) secondary to age related macular degeneration. METHODS: Retrospective review of 22 surgically excised CNV. 12 of these patients had been treated with PDT 3-146 days previously. Apoptotic cells were detected with the TUNEL technique and compared to the expression of CD34 (endothelial cells, EC), CD105 (activated endothelial cells), Ki-67 (proliferation marker), and cytokeratin18 (retinal pigment epithelial cells, RPE). RESULTS: CNV excised 3 days after PDT were characterised both by collapsed and patent vessels. The EC displayed a statistical significant positive TUNEL reaction when compared to the remaining treated CNV (p < 0.001) and untreated CNV (P = 0.002). The proliferative activity was reduced. CNV excised 1-5 months after PDT displayed a patent vascularisation and high proliferative activity. All membranes either treated or untreated disclosed only sporadic TUNEL positive cells within the stroma and the RPE. CONCLUSIONS: Verteporfin PDT leads to selective and effective damage of EC within CNV. Both patent and occluded vessels were lined by apoptotic EC. This finding and the increased expression of proliferation marker at later time points suggest that revascularisation after PDT is caused by angiogenesis rather than recanalisation.

Aged↗
PubMed2006

[Bevacizumab for treatment of macular edema secondary to retinal vein occlusion].

Application of VEGF inhibitors represents a treatment option for macular edema secondary to retinal vein occlusion that targets the disease at the causal molecular level. First reports on intravitreal injections of bevacizumab show promising morphological and functional effects and demonstrate that bevacizumab is a potent antiedematous agent in this context. A significant reduction of the central retinal thickness followed by a rapid improvement of visual acuity may be achieved within days. In a pilot study with a review period of 3 months, we found a significant improvement of one or more lines in 93% and four or more lines in 27% of eyes. This was associated with a concomitant significant reduction in central retinal thickness, which, however, was not sustained by a single injection (64% reduction after 1 month and 28% after 3 months). No relevant adverse events were noted. The duration of action after intravitreal bevacizumab administration is currently unknown. Reinjections will be necessary to maintain a lasting beneficial effect. Prospective, controlled long-term studies are mandatory to develop standardized treatment protocols that allow a safe and effective application of this off-label therapy.

Angiogenesis Inhibitors↗
PubMed2006

Karyotype differentiation in Chromaphyosemion killifishes (Cyprinodontiformes, Nothobranchiidae). II: cytogenetic and mitochondrial DNA analyses demonstrate karyotype differentiation and its evolutionary direction in C. riggenbachi.

African killifishes of the genus Chromaphyosemion show a high degree of phenotypic and karyotypic diversity. The latter is especially pronounced in C. riggenbachi, a morphologically defined species restricted to a small distribution area in Cameroon. This study presents a detailed reconstruction of karyotype differentiation within C. riggenbachi using conventional Giemsa staining and sequential chromosome banding as well as a phylogenetic analysis based on part of the mitochondrial (mt) cytochrome b gene from eleven populations. The cytogenetic analysis revealed differences in chromosome morphology, banding patterns and/or diploid chromosome number (2n) among all populations examined. Diploid number ranged from 2n = 20 to 2n = 36 and varied mainly among populations, while C-banding patterns and NOR phenotypes showed fixed differences among populations as well as some variability within populations. The mtDNA analysis disclosed five clearly differentiated haplotype groups. Mapping the karyotype data onto the mtDNA dendrogram revealed a decrease in 2n from the most basal to the most derived groups, thus demonstrating a reduction of 2n during their evolutionary history. Our results indicate that karyotype differentiation involved Robertsonian fusions as well as non-Robertsonian processes. Causes of the high karyotypic variability may include an elevated chromosomal mutation rate as well as certain features of the ecology and mating system that could facilitate the fixation of chromosomal rearrangements. The pattern of karyotype and haplotype differentiation and the results of previous crossing experiments suggest incipient speciation in C. riggenbachi.

Africa↗
PubMed2004

[Optical coherence tomography in the diagnosis and follow-up of patients with uveitic macular edema].

BACKGROUND: Optical coherence tomography (OCT) is a relatively new, noninvasive method and has been well established as an effective diagnostic procedure for the investigation of several macular diseases. Knowledge about the efficacy of OCT in the diagnosis and follow-up of macular edema in uveitis patients is still limited. PATIENTS AND METHODS: In the first part of the study, OCT was performed in 22 eyes of 18 patients with anterior or intermediate uveitis who showed angiographic and fundoscopic evidence of macular edema. The OCT results were compared with the visual acuity and fundoscopic and angiographic appearance of macular edema. In the second part of the study, the same patients were followed over a period of approximately 5 months (+/-2 months) and OCT was repeated at different time points during treatment of uveitic macula edema. RESULTS: OCT investigation also showed clear evidence of macular edema in all eyes and was not compromised by a low or medium degree of optical haze. Furthermore, OCT investigation revealed marked differences in the individual degree of macular edema (foveal heights 168-810 microm). Diffuse macular edema ( n = 4 ) and different types of cystoid macular edema (several distinguished cysts n = 6, partially or completely confluent cysts n = 11, one marked cyst n = 1) were observed. During the follow-up of the patients, OCT results, visual acuity, and fundoscopic appearance of the macula showed a comparable behavior. In some eyes, a stable visual acuity was accompanied by changes of foveal edema demonstrated by OCT. CONCLUSION: Optical coherence tomography is a safe and highly effective method in the diagnosis of macular edema in uveitis associated with low or medium haze of the optical media. Furthermore, OCT investigation seems to be useful in the follow-up of uveitic macular edema under treatment.

Fluorescein Angiography↗
PubMed1997

Förster energy transfer in ultrathin polymer layers as a basis for biosensors.

A method of detecting the binding of analyte molecules to biospecific receptors, like antibodies, is described. Förster energy transfer is used in connection with monomolecular organic films. The films are built up from pre-polymerized materials using the Langmuir-Blodgett or self-assembly techniques. Fluorescent dyes (as energy transfer donors) as well as reactive groups for covalent immobilization of protein receptors are integrated into the polymers. Several different methods for immobilizing biomolecules are described, including the use of protein A and the biotin/streptavidin couple. The studies suggest that the combination of Förster transfer and ultrathin organic films can be used for the construction of biosensors working either by displacement or by competitive assays. The mannose/concanavalin A, digoxin/antibody, and mouse immunoglobulin G/antibody systems are investigated. Further, a simplified meter optimized for measuring the fluorescence ratio at two wavelengths is described.

Antibodies↗
PubMed1997

Proliferative response of cultured human tenon's capsule fibroblasts to platelet-derived growth factor isoforms.

BACKGROUND: Although platelet-derived growth factor (PDGF) has been thought to be critical in the wound-healing response of Tenon's capsule fibroblasts after glaucoma filtration surgery, no information is currently available concerning the proliferative effect of PDGF isoforms on this cell type. The aim of the present study was to evaluate the proliferative effect of PDGF-AB heterodimer and PDGF-AA and -BB homodimers on cultured human Tenon's capsule fibroblasts. METHODS: Human Tenon's capsule fibroblasts, cultured under serum-free conditions, were stimulated with PDGF-AA, -AB and -BB isoforms in concentrations ranging from 1 to 100 ng/ml. Cell numbers were determined on days 1, 3, 5 and 7, using a cell counter. RESULTS: Addition of PDGF-AB and -BB led to a dose-dependent increase in cell proliferation. A maximal response (79.9% over control) was obtained after 7 days with 30 ng/ml of PDGF-BB, with an EC50 of 8.9 ng/ml. The maximal increase in cell proliferation caused by PDGF-AB (30 ng/ml) was 54.9%, with an EC50 of 12.5 ng/ml. Stimulation with PDGF-AA revealed a significant effect only with concentrations higher than 30 ng/ml. CONCLUSION: Our results indicate that PDGF-AB and -BB isoforms are potent stimulators of proliferation of human Tenon's capsule fibroblasts, suggesting that PDGF-AB and -BB isoforms play an important role in the wound-healing response after glaucoma filtration surgery.

Anticoagulants↗
PubMed1997

[Lens coloboma and lens dislocation in Stickler (Marshall) syndrome].

BACKGROUND: Both, Stickler and Marshall syndrome are dominantly inherited, connective tissue disorders with highly variable individual manifestations. Probably, both syndromes represent the same entity with occasional partially different clinical manifestations. PATIENT: We are reporting on a female patient with typical ocular and systemic manifestations of both syndromes: high myopia, glaucoma and goniodysgenesis, submucosal cleft palate, sensorineural hearing loss, and "flat" mid-face. Additionally, we observed subluxation of the ocular lens in one eye which was previously described in only a few cases. In our case, subluxation was combined with nasal coloboma of the lens and congenital cataract. This represents the first report of coloboma of the ocular lens as a manifestation of Stickler (Marshall) syndrome. In both children of the patient manifestations of the syndrome were present (high myopia, cleft palate, sensorineural hearing loss). CONCLUSION: Coloboma and subluxation of the lens have to be regarded as possible manifestations of the Stickler (Marshall) syndrome. The syndrome(s) should be included in the differential diagnosis of ectopia lentis-associated systemic diseases.

Abnormalities, Multiple↗
PubMed1995

[Glaucoma in Marfan syndrome: position-dependent measurement of intraocular pressure as a diagnostic criterium].

PATIENT: A 35-year-old female patient with Marfan's syndrome presented with fast progressive reduction of visual acuity (hand movements) of her right eye and lens-related glaucoma on both eyes. On examination, subluxation of the lens and nuclear cataract were seen on both eyes. Diurnal pressure curve showed great fluctuations in pressure with normal IOP in the morning and elevated pressure in the evening. Pressure measurement revealed great fluctuations depending on positioning. Because of cataractous lens in the right eye blocking the visual axis and uncontrollable, phacogenic glaucoma removal of the lens by cryoextraction was necessary. Visual acuity increased to 0.5 and IOP was normal after three weeks. To improve safety of topical medication of lens-related glaucoma in Marfan's syndrome regular measurement of IOP at different times of the day is especially important. Measurement of IOP at different positions seems to be an effective provocation test in cases of phacogenic glaucoma in Marfan's syndrome. Examination of all members of a family with Marfan's syndrome should include regular measurement of IOP at different times of the day. In suspected cases, measurement of IOP at different positions that may provoce IOP-increase could be useful in the early detection of lens-related glaucoma.

Adult↗
PubMed1993

[Clinical electroretinography: standard protocol and normal values].

The International Standard of Clinical Electroretinography serves as standard protocol for recording electroretinographic responses in order to facilitate worldwide comparisons of examinations. To promote its distribution and acceptance throughout the German speaking countries, we established normal values for the five standard responses and added a German translation of the International Standard in the appendix. To determine normal values for electroretinographic data we suggest to use percentiles instead of parameters based on a Gaussian distribution. Patient-related (age, sex) and -unrelated (interstimulus-interval, diurnal rhythm) parameters proved to influence the data values significantly. With these variables taken into account one can increase the clinical value of electroretinography in terms of a greater reliability and predictiveness of data.

Adolescent↗
PubMed1989

A 16 kDa protein co-isolating with gap junctions from brain tissue belonging to the class of proteolipids of the vacuolar H+-ATPases.

A 16 kDa protein from an enriched gap junction preparation was isolated from bovine brain tissues. N-terminal amino acid microsequencing of the first 20 amino acids showed a complete homology with a recently published sequence of a proteolipid from a vacuolar H+-ATPase from chromaffin granules. Incubation of the brain gap junction preparation with 14C-N,N'-dicyclohexylcarbodiimide showed a significant binding of this compound to the 16 kDa protein, indicating that a proton binding site also occurs within that particular protein. The data suggest that this 16 kDa protein, which has also been described in gap junction preparations from various other tissues, belongs to the proton transporting ATPase.

Amino Acid Sequence↗