Biomedical subjects

Michael Fejtl

Publications and source records attributed to Michael Fejtl.

3 recordsLinked to original sources

PubMed2004

Micro-electrode arrays in cardiac safety pharmacology: a novel tool to study QT interval prolongation.

Drug-induced QT interval prolongation is now a major concern in safety pharmacology. Regulatory authorities such as the US FDA and the European Medicines Agency require in vitro testing of all drug candidates against the potential risk for QT interval prolongation prior to clinical trials. Common in vitro methods include organ models (Langendorff heart), conventional electrophysiology on cardiac myocytes, and heterologous expression systems of human ether-a-go-go-related gene (hERG) channels. A novel approach is to study electrophysiological properties of cultured cardiac myocytes by micro-electrode arrays (MEA). This technology utilises multi channel recording from an array of embedded substrate-integrated extracellular electrodes using cardiac tissue from the ventricles of embryonic chickens. The detected field potentials allow a partial reconstruction of the shape and time course of the underlying action potential. In particular, the duration of action potentials of ventricular myocytes is closely related to the QT interval on an ECG. This novel technique was used to study reference substances with a reported QT interval prolonging effect. These substances were E4031, amiodarone, quinidine and sotalol. These substances show a significant prolongation of the field potential. However, verapamil, a typical 'false positive' when using the hERG assay does not cause any field potential prolongation using the MEA assay. Whereas the heterologous hERG assay limits cardiac repolarisation to just one channel, the MEA assay reflects the full range of mechanisms involved in cardiac action potential regulation. In summary, screening compounds in cardiac myocytes with the MEA technology against QT interval prolongation can overcome the problem of a single cell assay to potentially report 'false positives'.

Action Potentials↗

PubMed2003

The roboocyte: automated cDNA/mRNA injection and subsequent TEVC recording on Xenopus oocytes in 96-well microtiter plates.

Membrane-bound neurotransmitter receptors and ion channels are among the most numerous and important drug targets, and electrophysiological methods are the gold standard for the study of their functional properties and their response to drugs. However, electrophysiological measurements are usually performed one at a time by highly skilled individuals, and secondary functional screening is often hampered by this lack of throughput. Accordingly, the use of automated procedures to increase the efficiency of electrophysiological techniques is of great interest. Among the many different electrophysiological techniques that have been described, two electrode voltage clamp recording (TEVC) from Xenopus oocytes seems particularly suitable for the implementation of automated measurement systems. Here, we describe a workstation that was expressly developed for this purpose. The Roboocyte is the first (and the only currently available) instrument that automatically performs both cDNA (or mRNA) injection and subsequent TEVC recording on Xenopus oocytes plated in a standard 96-well microtiter plate. This paper describes the scientific background of the oocyte expression system for drug screening and the development of the Roboocyte. Then, some technical details of the Roboocyte system are presented and, finally, results obtained with the Roboocyte are discussed with regard to increased throughput compared with manually performed experiments. Further information can be obtained at www.roboocyte.com.

Animals↗

PubMed2002

A three-dimensional multi-electrode array for multi-site stimulation and recording in acute brain slices.

Several multi-electrode array devices integrating planar metal electrodes were designed in the past 30 years for extracellular stimulation and recording from cultured neuronal cells and organotypic brain slices. However, these devices are not well suited for recordings from acute brain slice preparations due to a dead cell layer at the tissue slice border that appears during the cutting procedure. To overcome this problem, we propose the use of protruding 3D electrodes, i.e. tip-shaped electrodes, allowing tissue penetration in order to get closer to living neurons in the tissue slice. In this paper, we describe the design and fabrication of planar and 3D protruding multi-electrode arrays. The electrical differences between planar and 3D protruding electrode configuration were simulated and verified experimentally. Finally, a comparison between the planar and 3D protruding electrode configuration was realized by stimulation and recording from acute rat hippocampus slices. The results show that larger signal amplitudes in the millivolt range can be obtained with the 3D electrode devices. Spikes corresponding to single cell activity could be monitored in the hippocampus CA3 and CA1 region using 3D electrodes.

Action Potentials↗