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Biomedical subjects

I Wilmanns

Publications and source records attributed to I Wilmanns.

27 records · Page 2Linked to original sources
PubMed1978

Bandpass measurements in the electroretinographic electrode circuit.

In the experiments in this study band-pass measurements in electroretinographic electrode circuits were done for the first time, according to the information presently available to us. Our experiments show that in the much faster band-pass assessment by analysis of sawtooth and square waves no major error is involved. It may be concluded from our results that the recordings of ERG potentials are not changed by the characteristic properties of the electrode circuit in the frequency range of interest.

Adult↗
PubMed1978

Changes of the current pathways in the eye due to coating agents during electroretinography.

This study suggests a model by which we try to explain why coating agents habitually applied in electroretinography can change the amplitude of electroretinographic responses. The model is based on the results of experiments described in this paper. The accuracy of measurement in clinical and experimental electroretinography can be enhanced by applying this model.

Cellulose↗
PubMed1978

The influence of coating agents on the electrode circuit in electroretinography.

In electroretinography, coating agents are usually applied to improve the contact between the contact-lens electrode and the eye. These agents influence electroretinographic responses. In this experimental study we show that the characteristic properties of the electrode circuit are not influenced by the coating agent. Thus we conclude that these coating agents influence the eye itself. The mechanism of this interaction may be physical, or may be an unknown pharmacologic drug side effect.

Cellulose↗
PubMed1978

[Spatial arrangement and inner wall surface of ocular vessels. Scanning electronmicroscopy of vascular casts (author's transl)].

Vascular corrosion casts of the rabbit eye vessels were studied by scanning electron microscopy. Compared with light micrescopy, this method provides great depth of field and better contrast. Thus the pictures are more informative and documentation is easier. The high resolving power of scanning electron microscopy of suitable vascular casts allows the study of structures of the inner vessel wall. Such information could not be retrieved from these replicas until now.

Animals↗
PubMed1978

[EEG tracings in cerebral death (author's transl)].

In diagnosing electrocerebral silence (isoelectric tracing) the investigator must be sure to exclude the possibility of an artefact. With the methods available up to now for testing the proper functioning of electroencephalographic equipment it has not been possible entirely to avoid errors. A new method is described for the rapid and quantitatively exact testing of EEG equipment including electrodes and cables and the correct recording of isoelectric tracings.

Brain Death↗
PubMed1977

[A new method for calibration of electrophysiological recording systems (author's transl)].

The method described in this paper permits determination of amplification, band-pass properties, and electrode impedance in electrophysiological experimental setups. The battery powered test-signal generator drives square-wave current pulses through a 2 ohm resistance, which acts as a source of 100 muV p-p pulses. The 2 ohm resistor is wired in series with one of the electrode leads and remains there permanently. For calibration of the above-mentioned properties, one need only turn the generator on, without changing the measurement setup. By observing the shape of the square waves after passing through the system, it is possible to judge the band-pass characteristics of the entire system. Electrode impedance may be measured by putting a (variable) resistor in parallel with the preamplifier input. The test signal current is of the same order of magnitude as currents from biological signal sources. This method makes working with electrophysiological measurement systems which are used in electroretinography, electrooculography, and recording of visually-evoked cortical potentials in ophthalmology much easier.

Amplifiers, Electronic↗