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Biomedical subjects

R A Levis

Publications and source records attributed to R A Levis.

5 recordsLinked to original sources
PubMed1992

A method for exceptionally low noise single channel recordings.

We present a method whereby, with integrating electronics, quartz patch electrodes and a novel use of silicone oil, background noise levels as low as .083 pA RMS in a 5 kHz bandwidth (4-pole Butterworth filter) have been achieved in single channel patch clamp recordings. These approaches result in much higher signal to noise ratios for single channel recording than have previously been reported and should allow many investigators to significantly reduce noise at a constant bandwidth or to increase their recording bandwidths by several kHz.

Animals↗
PubMed1992

Constructing a patch clamp setup.

It should be obvious that there are many ways to construct clamp set-ups that are either equivalent or sufficient for the experiments planned. The hardware and electronics can be obtained from several manufacturers, as can analysis software. What we have presented here are guidelines primarily meant to point a new experimenter in the right direction and, we hope, to guide more experienced investigators toward techniques that can improve the resolution of their measurements.

Artifacts↗
PubMed1992

Glass technology for patch clamp electrodes.

Based on all of the properties of glass described here, it is obvious that no one glass can be recommended for all purposes and for all cells. Borosilicate glasses like 7760, 7052, and 7040 are good general purpose glasses for both single-channel and whole-cell recordings. They are good initial choices but, of course, must be checked for each cell type for problems associated with leaching of blockers, etc., from the glass. Corning 8161 is the best glass studied to date with respect to electrical and thermal properties but must be checked carefully for leachable components. If perforated-patch whole-cell recordings are to be used, 8161, KG-12, or some other high lead, low melting point glass are probably the best choices.

Data Collection↗
PubMed1988

Planar bilayer membranes made from phospholipid monolayers form by a thinning process.

We investigated the manner in which planar phospholipid membranes form when monolayers are sequentially raised. Simultaneous electrical and optical recordings showed that initially a thick film forms, and the capacitance of the film increases with the same time course as the observed thinning. The diameter of fully thinned membranes varies from membrane to membrane and a torus is readily observed. The frequency-dependent admittance of the membrane was measured using a wide-bandwidth voltage clamp whose frequency response is essentially independent of capacitative load. The membrane capacitance dominates the total admittance and the membrane dielectric is not lossy. The specific capacitance of membranes of several mixtures was measured. A schematic diagram of the formation of these membranes is presented.

Electric Conductivity↗