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Biomedical subjects

N Papst

Publications and source records attributed to N Papst.

15 recordsLinked to original sources
PubMed1994

A new system for recording electroretinographical potentials in animals.

Electroretinography can provide meaningful evidence of oculotoxic changes. We describe a new recording system specially constructed for animal experiments. It meets the standards for electroretinographical investigations and recording systems set up by international committees. The recording apparatus has a resolution of 0.49 microV (amplitude) and 1 ms with a sensitivity range of +/- 1 mV full scale and a band-pass of 0.03 to 1,000 Hz. The signals are digitized and processed by a computer. The calibration symbol is faithfully represented as a rectangular impulse with an amplitude of 100 microV and a period of 100 ms. Normal values were calculated for 25-week-old albino Wistar rats. The normal range is defined as the mean +/- 2 SD for A and B wave parameters. These normal values can serve as reference values for future studies in oculotoxicity.

Animals↗
PubMed1989

[Retinotoxicity of intravitreous injection of cefmenoxime].

The semisynthetic third generation cephalosporin cefmenoxime was injected through the pars plana into the mid-vitreous in seven rabbit eyes. The drug dosage varied between 0.5 and 15 mg. Seven control eyes were injected only with 0.9% NaCl-solution. Electroretinography was performed before injection and 1 week post injection. The rabbits were anesthetized by intramuscular application of ketanine (Ketanest). Immediately after the second ERG the eyes were enucleated and prepared for both light and electron microscopy. Light microscopy showed only slight retinotoxic effects. Electron microscopy revealed beginning toxic necrosis of the outer segments of the photoreceptors following drug doses equal to or greater than 2 mg. Significant changes in the ERG were not noted in any of the treated eyes. The toxicity of cefmenoxime and other cephalosporins reported in the literature is discussed together with the clinical relevance of the findings.

Animals↗
PubMed1988

[New findings in Oguchi disease].

The authors report on clinical and electrophysiological studies of a patient with Type I Oguchi's disease. Numerous small pigmentations of the retinal pigment epithelium (RPE) causing focal disruption of the Oguchi reflex were observed, a phenomenon which has not previously been reported. Consistent with reports of pathologic changes in the RPE, an abnormal electro-oculogram (EOG) was recorded in this patient. On the basis of this information, the pigmentations were interpreted as dysplastic changes.

Adolescent↗
PubMed1986

[Pattern ERG in X-chromosome juvenile retinoschisis].

Typical electroretinographic findings in x-chromosomal juvenile retinoschisis are a normal a-wave and a reduced b-wave suggesting that the primary defect is located at the level of the bipolar cell layer whereas deeper retinal structures are not basically affected. The marked amplitude reduction in the pattern-ERG suggests to look for the origin of response in the inner retinal layer or in subsequent structures.

Child↗
PubMed1985

[Autosomal dominant infantile optic atrophy: ascending or descending degeneration?].

All patients with autosomal dominant infantile optic atrophy had a normal electro-oculogram (EOG) and a normal luminance electroretinogram (L-ERG). Patients with a typical blue sensitivity defect at the time of investigation had a normal pattern electroretinogram (P-ERG), while the visually evoked cortical potentials to pattern stimuli (P-VECP) showed a delayed latency and a decreased amplitude. Only in severe cases of the disease where the blue sensitivity defect was masked by a progressive concomitant colour blindness was there a reduced amplitude in the P-ERG. The P-VECP in these cases was not recordable. The findings suggest that the primary process in autosomal dominant infantile optic atrophy is in the optic nerve, the inner layers of the retina being affected secondarily.

Adult↗
PubMed1984

Pattern electroretinogram and visually evoked cortical potentials in glaucoma.

Electroretinograms (P-ERG) and cortical potentials (P-VECP) evoked by checkerboard patterns were examined in patients with defects of the ganglion cell and nerve fiber layers due to glaucoma. Only a few patients exhibited a prolonged latency in the P-VECP, whereas in the P-ERG all patients with papillary and visual field defects revealed a significantly attenuated amplitude. Since there is a substantial fluctuation in the assessment of papillary excavation and visual field, the P-ERG offers a further means of evaluating and follow-up of retinal function in glaucoma patients.

Aged↗
PubMed1984

The pattern evoked electroretinogram associated with elevated intraocular pressure.

Electroretinographic responses to pattern-reversal stimuli (P-ERG) were recorded in eight patients with protracted elevation of intraocular pressure. Pressures of bigger than 30 mm Hg result in marked amplitude reductions in the P-ERG. The observed changes probably reflect the impaired function of retinal ganglion cells caused by decreased oxygen supply.

Adult↗
PubMed1984

[Light and pattern ERG in advanced glaucoma].

Electroretinographic responses of 9 eyes severely affected by glaucoma showed a reduction in amplitude on stimulation with pattern reversal, but normal amplitudes following stimulation with light flashes. Thus, the pattern-reversal electroretinogram offers a further means of evaluating the function of retinal ganglion cells and their nerve fibers. In addition, the authors' results also suggest that flash and pattern-reversal electroretinograms are generated by different retinal structures.

Adult↗
PubMed1984

[Pattern and light electroretinograms in branch occlusions of the central retinal artery].

Electroretinographical responses to brightness (H-ERG, Ganzfeld illumination) and pattern reversal (M-ERG, illuminating an area of 20 degrees) were recorded in two cases of occlusion of the temporal inferior branch of the retinal artery. While the H-ERG exhibited essentially normal responses, the M-ERG was markedly disturbed. With central fixation the amplitude of response to pattern was decreased by more than 50 percent. With peripheral fixation (14 degrees) exposing most of the diseased part of the retina, the M-ERG was extinguished, whereas in the fellow eye pattern responses were present. The findings strongly support the notion that the M-ERG at least partly reflects the activity of retinal ganglion cells.

Arterial Occlusive Diseases↗
PubMed1982

Changes in pO2 induce retinal autoregulation in vitro.

Vascular autoregulation maintains stable retinal function in vivo in the face of changes in arterial pO2. We observed autoregulatory changes in the flow of perfusate through the isolated cat eye in response to changes in pO2. Hydrostatic perfusion pressure and all other variables of the perfusate, except for pO2, were kept constant. Throughout the experiments the viability of the eye was monitored by electroretinography. In nine short periods of hypoxia, pO2 of the perfusate was reduced by 12%-42% compared to the control. In eight of these experiments the flow rate of the perfusate increased significantly. Retinal vasodilation during hypoxia was also documented by indocyanine green angiography, monitored by TV, and photographed. In seven periods of hyperoxia, pO2 was raised by 7%-38%. In all cases the flow of the perfusate decreased. These changes in flow are interpreted as resulting from autoregulative vasodilation and vasoconstriction of the retinal vessels. The b-wave of the ERG increased and decreased parallel with pO2 of the perfusate. This indicates that autoregulation in vitro does not sufficiently compensate for changes in pO2. This is in contrast to our findings from a previous study in the anesthetized cat.

Animals↗