PubMed Health⌕ Search

Biomedical subjects

W Sickel

Publications and source records attributed to W Sickel.

17 recordsLinked to original sources
PubMed2006

Effects of patent blue on human retinal function.

BACKGROUND: Dye solutions for intraoperative staining of epiretinal membranes and the internal limiting membrane improve the visualisation of these thin structures and facilitate their removal. Lately, the application of patent blue for staining of the internal limiting membrane has been proposed as an alternative to the standard procedures during macular hole surgery. In the present study we investigated the effects of patent blue 0.48% on human retinal function. METHODS: An isolated human retina preparation was perfused with a standard solution and the electroretinogram (ERG) was recorded repeatedly. After recording of stable ERG amplitudes the nutrient solution was substituted by a commercially available patent blue solution. The duration of retinal exposure to the dye solution was varied between 15 s and 4 min. Thereupon, the preparation was reperfused with standard solution for 2 h. The percentage of b-wave reduction after exposition was calculated. RESULTS: No effects on the human ERG were seen after 15 and 30 s of dye application. Reversible reductions of the b-wave amplitude were found for an exposure period of 60 and 120 s, respectively. After 4 min of patent blue application a persistant b-wave amplitude reduction by 40% was found. CONCLUSIONS: Patent blue affects human retinal function when applied for at least 1 min. However, no irreversible effects on the human ERG were seen even after 2 min of retinal exposure to patent blue. Thus, toxic effects on retinal function after intraoperative short-term application of patent blue 0.48% appear unlikely to occur.

Coloring Agents↗
PubMed2005

Retinal tolerance to dyes.

BACKGROUND: Dye solutions for intraoperative staining of epiretinal membranes and the internal limiting membrane improve the visualisation of these thin structures and facilitate their removal. In the present study the authors investigated the effects of indocyanine green 0.05%, trypan blue 0.15%, and patent blue 0.48% on bovine retinal function. METHODS: Bovine retina preparations were perfused with a standard solution and the electroretinogram (ERG) was recorded repeatedly. After recording of stable ERG amplitudes the nutrient solution was substituted by one of the dye solutions. The duration of retinal exposure to a dye solution was varied between 10 seconds and 2 minutes. Thereupon, the preparation was reperfused with standard solution for at least 115 minutes. The percentage of b-wave reduction after exposition was calculated. RESULTS: Reductions of the b-wave amplitude were found for each dye solution tested. The effects after application of patent blue and indocyanine green were completely reversible within the recovery time for an exposure period of 60 and 30 seconds, respectively. The application of trypan blue lead to a loss of the b-wave when the retina was exposed for 15 seconds or longer. This effect was only partly reversible within the recovery time. CONCLUSION: The ERG showed toxic effects of trypan blue after a short period of retinal exposure. The intraocular application of trypan blue should be limited to selected cases. However, intraocular application of indocyanine green and patent blue in a sufficient concentration and taking account of a short period of retinal exposure seems possible.

Animals↗
PubMed2001

Effects of protein tyrosine kinase inhibitor genistein on retinal function in superfused vertebrate retina.

The aim of this study was to evaluate safe concentrations of genistein for a potential intraocular application using the isolated retina technique on bovine retina preparations. Bovine retinas were isolated and perfused with an oxygen pre-equilibrated standard solution. The electroretinogram (ERG) was recorded as a transretinal potential using silver/silver-chloride electrodes. After recording of stable ERG amplitudes, genistein was added to the solution in different concentrations. The percentage of b-wave reduction under the drug was calculated. We also studied the influence of genistein on the a-wave amplitude. After the addition of aspartate, the b-wave amplitude was reduced continuously until unmasked a-wave amplitudes were reached. Genistein was then added to the aspartate containing perfusate. The percentage of a-wave amplitude reduction under the drug was calculated. Concentrations of 3.3 microMol/l and higher were found to reduce the b-wave amplitude. The a-wave amplitude was not changed by the applied concentrations. The ERG only showed toxic effects from genistein beyond concentrations that were found to inhibit endothelial cell growth in vitro. In previous studies, beneficial effects on trabecular meshwork cells were present for genistein concentrations which are distinctly higher than the maximum nontoxic concentration reported here. It was shown that the photoreceptor layer is not affected at the examined concentration range. Therefore, we attribute the toxic effects to postsynaptic interaction of genistein. Intraocular application of genistein in a sufficient concentration seems possible.

Animals↗
PubMed1999

Antibiotics and light responses in superfused bovine retina.

1. Our objective was to study effects of clindamycin and ciprofloxacin on the electroretinogram (ERG) of isolated bovine retinas. 2. Electroretinograms of isolated superfused bovine retinas were recorded under normal conditions and during application of clindamycin and ciprofloxacin. The b-wave reduction was plotted against the drug concentration. In several cases retinal oxygen uptake was also measured. Clindamycin was available only in a preparation containing benzyl alcohol. To differentiate between effects caused by the antibiotic and the alcohol, ERGs were also recorded under superfusion with benzyl alcohol. To record drug effects on photoreceptors synaptic transmission was blocked using 1 mM aspartate. 3. At concentrations between 0.3 and 10 mM clindamycin significantly reduced the amplitude of the b-wave of the ERG. A comparable reduction of retinal oxygen uptake was found at concentrations 10-fold higher. Clindamycin, 3 mM, did not affect the a-wave after preincubation with aspartate. Benzyl alcohol at concentrations of 0.3 and 1 mM did not affect the b-wave, whereas at higher concentrations the b-wave was found to be reduced. Considerable b-wave reductions were found with ciprofloxacin at concentrations of between 0.03 and 0.6 mM. All effects proved to be fully reversible and dose-dependent. 4. Ciprofloxacin and clindamycin did both alter neural function in the isolated superfused bovine retina. The nontoxic dosages found here differ considerably from results in rabbits after intravitreal injections. This is probably due to species differences.

Animals↗
PubMed1996

The triple flash electroretinogram and its significance in macular diseases. B-wave recovery as a diagnostic tool.

PURPOSE: The purpose of this study was to evaluate recovery data for the b-wave of the electroretinogram (ERG) elicited using multiple flash stimulation with increasing stimulus intervals in normal controls and in patients with macular diseases. The results will describe effects of age and macular disease and define indexes characterizing the recovery process. METHODS: Scotopic Ganzfeld flash ERGs were elicited using interstimulus intervals of 140, 280, and 560 ms. Relative b-waves were calculated as the ratio b140 ms/b560 ms and b280 ms/b560 ms, respectively. Responses obtained in 134 eyes of 134 normal controls served as reference data. Fifty-four patients with different macular diseases were also examined and their data compared to the reference data. RESULTS: Relative b-wave amplitudes correlated with interstimulus interval and with flash luminance, but not with age. All patients had a normal ERG when recorded following the standard of clinical electroretinography. A sigmoidal model was suggested, providing three indexes characterizing the b-wave recovery process. Relative b-waves and recovery indexes varied in age-related macular degeneration, central serous retinopathy, vitelliform macular degeneration, Stargardt's disease, and pattern dystrophy. CONCLUSION: The triple flash ERG reflects energy-yielding and -utilizing mechanisms. It proved to be more sensitive in detecting functional lesions in macular diseases than the standardized explorating procedure. The b-wave recovery model allows differentiation between two independent mechanisms contributing to the b-wave recovery process. One or more of the three characterizing indexes are affected in different macular diseases.

Adolescent↗
PubMed1994

Identification of fast spurts of pyridine nucleotide oxidation evoked by light stimulation in the isolated perfused vertebrate retina.

Transitory increases of ultraviolet transmission on stimulation with light were recorded simultaneously with electroretinogram on and off effects from isolated vertebrate retina. The spectral distribution of the optical light responses coincided with that of NADH reduction. The correlation of the optical, or respiratory, responses and the electrical responses were very close within a wide range of stimulus parameters, suggesting an interpretation in terms of supply and demand of energy with a tight coupling between the two kinds of evoked activity. Prerequisite to the response behaviour was the preservation of synaptic signal transmission from first- to higher-order retinal neurons.

Animals↗
PubMed1989

[Recording and analysis of the electrooculography using a personal computer. Initial experiences with normal probands and patients with diseases of the posterior eye segment and intraocular foreign bodies].

The electro-oculogram (EOG) is recorded by a personal computer and analyzed during the examination. If the results obtained with this method in normal subjects are compared with the conventional method (with which data recorded in analog form have to be measured manually), there is no significant difference. In patients with diseases of the posterior segment (e.g., posterior uveitis) or intraocular foreign bodies the results of computer and manual analysis are also practically identical. There are two computer analysis techniques: for subjects with almost normal EOGs the trigger-independent method is sufficiently accurate. In patients with pathologic EOGs, however, and in particular those with small potential differences, the trigger-related method is more likely to lead to correct results. The analysis path can be displayed on the computer monitor at any time, so that the examiner can always check whether it is correct. In contrast to manual analysis, the computer analysis cannot be influenced subjectively by the examiner. This considerably improves the comparability of examination results. A further advantage of computer analysis is its speed: the result is available immediately following the examination. It is a low-cost system which is easy to install and use, and thus suitable for routine clinical work.

Chorioretinitis↗
PubMed1984

Topical and temporal aspects of cortical responses to pattern reversal.

From elementary geometry cortical responses to foveally presented pattern reversal are described by a rotating electrical vector assumed to reflect sequential signal processing. The analysis allows one to predict waveshapes not actually recorded and provides information on the individual architecture of the visual cortex from two or three recordings.

Evoked Potentials, Visual↗
PubMed1979

[Liver involvement in lymphogranulomatosis].

Of 146 patients with lymphogranulomatosis biochemical parameters were tested for their diagnostic valency concerning the recognition of a liver infiltration. In patients with histologically proved affection of the liver the AP, GGTP, AAP, LAP and LDH show a significant increase in comparison to the enzyme values of the patients without any hepatic manifestation. In an increased result of 4 enzyme values with a probability of 85% muste be reckoned with a participation of the liver. The enzyme SGOT, SGPT, GDH, LDH-isoenzymes, choline esterase, beta-GC, the De Ritis quotient and the quotient (Formula: see text), on the other hand, do not give any additional differential-diagnostic information.

Acid Phosphatase↗
PubMed1979

[Bone changes in hemoblastoses and malignant lymphomas].

In haematological systemic diseases such as acute and chronic leukoses, malignant lymphomas, lymphogranulomatoses, osteomyelofibroses, polycythaemias and aplastic anaemias with a different proportion changes of the bones in form of osteoporoses, osteolytic processes and deformations of the vertebral bodies are to be found. The proof may be performed radiologically and histologically. In 461 patients with different haematological diseases absorption measurings of monoenergetic rays of a J-125-source were performed at the distal third of radius and ulna. It was shown that the bone mineral content of patients with proved bone destructions did not significantly differ from the normal group. The too peripherally located place of the measuring and also the late inclusion of the compacta into the changes is regarded as cause for the negative result.

Bone Diseases↗
PubMed1977

Regeneration of rhodopsin in frog rod outer segments.

1. Bleaching/regeneration cycles were performed in perfused frog retina while the optical transmittance at suitable wave-lengths was measured continously. Rhodopsin was identified from its spectral absorbance, its photosensitivity and from the kinetics of its regeneration. 2. In the absence of the pigment epithelium regeneration was complete when not more than 2-5% of the rhodopsin initially present had been bleached. However, the cycles could be repeated to a total of regenerated rhodopsin exceeding that explicable on the utilization of stored chromophores. The rate of regeneration was fast, with 0-12 min-1 rate constant, following first order reaction kinetics. Under these conditions the cycle does not seem to involve stages beyond metarhodopsin II. With the moderate bleaching intensities used, half-time 53 min, the Bunsen-Roscoe law was obeyed up to 15 min, indicating a capacity for the photoproducts to be accomondated in situ for subsequent regeneration. 3. It is concluded that only substantial bleaches, which exceed that capacity, result in hydrolysed chromophores. These surplus chromophores become esterified and are temporarily taken up by the pigment epithelium to be re-entered into the visual cycle as fast as they can be processed by the regenerative machinery of the rod outer segments.

Animals↗