Biomedical subjects

Jan C Behrends

Publications and source records attributed to Jan C Behrends.

5 recordsLinked to original sources

PubMed2006

High-resolution electrophysiology on a chip: Transient dynamics of alamethicin channel formation.

Microstructured planar substrates have been shown to be suitable for patch clamp recording from both whole cells and isolated patches of membrane, as well as for measurements from planar lipid bilayers. Here, we further explore this technology with respect to high-resolution, low noise single-channel recording. Using solvent-free lipid bilayers from giant unilamellar vesicles obtained by electro-swelling, we recorded channels formed by the peptaibol alamethicin, a well-studied model system for voltage-dependent channels, focusing on the transient dynamics of single-channel formation upon application of a voltage step. With our setup, we were able to distinctly resolve dwell times well below 100 mus and to perform a thorough statistical analysis of alamethicin gating. Our results show good agreement with models that do not rely on the existence of non-conducting preaggregate states. Microstructured apertures in glass substrates appear promising with respect to future experiments on cellular ion channels reconstituted in suspended lipid membranes.

Alamethicin↗

PubMed2006

Microchip technology for automated and parallel patch-clamp recording.

The patch-clamp technique is the state-of-the-art technology for the study of a large class of membrane proteins called ion channels. Ion channels mediate electrical current flow, have crucial roles in cellular physiology, and are important drug targets. However, patch clamping is a laborious process requiring a skilled experimenter and is, therefore, not compatible with the high throughput needed in drug development. The solution for automated and parallel patch-clamp measurements that is provided by microchip technology is presented here.

Animals↗

PubMed2003

Microstructured apertures in planar glass substrates for ion channel research.

We have developed planar glass chip devices for patch clamp recording. Glass has several key advantages as a substrate for planar patch clamp devices. It is a good dielectric, is well-known to interact strongly with cell membranes and is also a relatively in-expensive material. In addition, it is optically neutral. However, microstructuring processes for glass are less well established than those for silicon-based substrates. We have used ion-track etching techniques to produce micron-sized apertures into borosilicate and quartz-glass coverslips. These apertures, which can be easily produced in arrays, have been used for high resolution recording of single ion channels as well as for whole-cell current recordings from mammalian cell lines. An additional attractive application that is greatly facilitated by the combination of planar geometry with the optical neutrality of the substrate is single-molecule fluorescence recording with simultaneous single-channel measurements.

Animals↗

PubMed2002

Whole cell patch clamp recording performed on a planar glass chip.

The state of the art technology for the study of ion channels is the patch clamp technique. Ion channels mediate electrical current flow, have crucial roles in cellular physiology, and are important drug targets. The most popular (whole cell) variant of the technique detects the ensemble current over the entire cell membrane. Patch clamping is still a laborious process, requiring a skilled experimenter to micromanipulate a glass pipette under a microscope to record from one cell at a time. Here we report on a planar, microstructured quartz chip for whole cell patch clamp measurements without micromanipulation or visual control. A quartz substrate of 200 microm thickness is perforated by wet etching techniques resulting in apertures with diameters of approximately 1 microm. The apertures replace the tip of glass pipettes commonly used for patch clamp recording. Cells are positioned onto the apertures from suspension by application of suction. Whole cell recordings from different cell types (CHO, N1E-115 neuroblastoma) are performed with microstructured chips studying K(+) channels and voltage gated Ca(2+) channels.

Animals↗

PubMed2001

Repetitive activation of postsynaptic GABA(A )receptors by rapid, focal agonist application onto intact rat striatal neurones in vitro.

GABA(A) receptor-mediated Cl(-) currents were evoked by rapid and short (0.75-1.5 ms), focal iontophoretic applications of GABA to proximal dendrites of cultured striatal neurones. The mean amplitude (232 +/- 21.0 pA) was in the range of large miniature inhibitory postsynaptic currents (mIPSCs), while the 10-90% rise times (3.4 +/- 0.20 ms) and the time constants of decay (60.0 +/- 8.4 ms) were three times slower. Responses to paired-pulse application of GABA at inter-pulse intervals (IPIs) of 30, 100 and 300 ms showed no depression of the second response (R2) relative to the first (R1). At short IPIs, at which R1 and R2 showed temporal summation, the net amplitude of R2 (R2(net)) was partially occluded. Lowering the iontophoretic intensity during paired-pulse application at an IPI of 30 ms reduced R1 by 69.5 +/- 3.3%, while occlusion of R2(net) decreased significantly, indicating that the receptor occupancy had been lowered. During the course of ten pulses of GABA at 10 Hz, responses declined by 8.7 +/- 3.9%, which probably reflects slow cumulative desensitization. In conclusion, rapid focal iontophoresis of exogenous GABA onto GABA(A) receptors does not result in activity-dependent depression of the postsynaptic response. This result suggests that fast desensitization is unlikely to occur during repetitive GABA(A) receptor-mediated synaptic transmission in striatal neurones.

Animals↗