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At least 1,081 records · Page 60Linked to original sources
PubMed1981

A piezoelectric device to aid penetration of small nerve fibers with microelectrodes.

A small piezoelectric device for cell penetration is described. It retracts the micropipette slowly by electrostriction, and pushes it very fast (less than 5 microsecond) forward by short-circuiting the transducer. The design, operation circuit, and performance under test conditions are described. Penetration examples from small nerve fibers (less than 5 micrometer) show that membrane puncture occurs only with the fast forward push. Cells are not noticeably damaged, even if the device is repeatedly operated after cell penetration.

Animals↗
PubMed1981

A high voltage electrometer for recording and iontophoresis with fine-tipped, high resistance microelectrodes.

A high voltage electrometer is described which incorporates a controlled current source, direct current monitoring, balance bridge, electrode resistance, and capacitance compensation test circuits. This device is suitable for making biophysical measurements and iontophoresing dyes or enzymes through extremely fine micropipettes with impedances an order of magnitude higher than conventional micropipettes. Such electrodes are useful for recording from the small neurons of the central nervous system in vivo.

Animals↗
PubMed1982

Recording of spontaneous activity with photoetched microelectrode surfaces from mouse spinal neurons in culture.

A matrix of photoetched gold conductors integrated into the floor of a tissue culture chamber has been used to record from mammalian spinal cord neurons grown on the insulation layer of the multielectrode plate. Spontaneous activity has been monitored from tissue microfragments less than 150 micrometers in diameter and from thin sheets of spinal cell aggregates. Maximum spike amplitudes of 360 microV with signal-to-noise ratios of 8:1 have so far been achieved and the spontaneous activity maintained for several days. Recording electrode impedances measured between 4 and 7 M omega at 1 kHz. Conductor tips were deinsulated with laser pulses that formed shallow craters 2 micrometers deep and 12 micrometers in diameter. Addition of colloidal gold or platimum black was not necessary to achieve satisfactory recordings.

Animals↗
PubMed1991

Measurements of the extracellular potassium concentrations in the isolated rabbit retina with different kinds of potassium-sensitive microelectrodes.

When the dark-adapted isolated rabbit retina has been superfused from one side with a plasma-saline mixture containing 3.5 mM potassium, the extracellular potassium concentration within the dark-adapted retina was significantly higher (4.5-6.1 mM) than the potassium of the superfusate, when measured with an electrode filled with Corning 477317. The substantial difference between the [K+]0 of the perfusate and the [K+]0 within the retina is difficult to explain and could be an instrumental artefact. To probe this possibility measurements have now been repeated using 2 different K+ electrodes, one filled with Corning 477317 and the other filled with a valinomycin-based ion exchanger. With the latter electrodes there was practically no gradient between the [K+]0 in the retina (3.2-4.0 mM) and the potassium concentration of the superfusate. It is thus evident that the earlier enigmatic values for [K+]0 relate to the use of Corning 477317-filled K+ electrodes. When, however, changes in [K+]0 were induced by a light stimulus, the measured magnitudes of change in [K+]0 were the same with the 2 types of electrode.

Animals↗
PubMed1991

Calibration of ion-selective microelectrodes for use with high levels of interfering ions.

Ion-selective electrodes are often used in solutions which contain interfering ions. Calibration under these conditions is usually achieved by the fixed interference method, in which the concentration of the test ion is varied in a fixed background of interfering ion. The present paper describes a method for analyzing fixed interference calibration data which allows the Nicolski coefficients to be extracted using commercially available computer software. The method produces an accurate numeric description of the calibration curve. It also enables an accurate correction for the situation where the experimental level of interfering ion is not identical to that of the standard solutions.

Calibration↗
PubMed1993

Principles of voltammetry and microelectrode surface states.

In vivo voltammetry is approaching the end of its second decade as a technique to explore extracellular concentrations in the brain. The issues of selectivity and sensitivity, which caused considerable discussion and confusion in the early 1980s, are now resolved. It is clear that in vivo voltammetry and dialysis are complimentary tools to understand neurotransmitter dynamics. The two chief advantages of voltammetry compared to dialysis, improved temporal resolution and reduced tissue damage, make this technique exceptionally well suited for providing information which is complementary to that obtained by single-unit recording and is uniquely capable of providing information on the short-term regulation of extracellular levels of biogenic amines.

Animals↗
PubMedDate not supplied

Filling of microelectrodes: an expedient solution.

Micropipettes of small diameter filled with an electrolyte solution have been used widely to record electrophysiological potentials. Filling micropipettes is a major problem for many researchers. We describe an expedient and reliabel method of solving this problem by using parts that can be easily found in any research laboratory. Among the most important parts are; a vacuum pump, two stands, a container, tubes and a few clamps. The filling of these micropipettes can then be easily done by using negative pressure through the fine tip. With the drop in pressure distilled water or an electrolyte is forced downward inside the pipette thus filling the electiode tip.

Electrolytes↗