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Results for “Microelectrodes”

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At least 523 records · Page 29Linked to original sources

PubMed1979

The effect of cell excision and microelectrode perforation on membrane resistance measurements of Nitella translucens.

The effect of cell excision and microelectrode perforation on the membrane resistance measurements of Nitella translucens was determined by direct experiment. From the results it is concluded that perforation has no effect on cells as short as 1 cm. Current leakage though the node of an excised cell has however to be given some consideration. The method used for determining the resistance recovery to insertion has a wide application and its simplicity will encourage its use in other biological systems.

Cell Membrane↗

PubMed1986

Microelectrode measurement of cell membrane potential in isolated hepatocytes attached to collagen.

Isolated spherical rat hepatocytes attached to collagen-coated cover slips generate a mean membrane potential (Em) of -78 +/- 9 mV as measured with high-resistance microelectrodes. The recordings were biphasic and were stable for upto 20 minutes. The correlation between external potassium concentration and Em was not linear. Several potassium-channel blockers did not effect the membrane potential. Addition of ouabain added to the incubation solution slowly depolarized the cells. The results indicate a high potassium permeability of the isolated spherical hepatocytes attached to collagen.

Animals↗

PubMed1987

Microelectrode studies of potential difference responses to changes in stromal K+ in bullfrog cornea.

The effects of changing stromal K+ were studied using microelectrodes in an in vitro preparation of frog cornea. The intracellular potential (V0) responded in two opposite ways under short-circuit conditions: (1) depolarization (normal response) when stromal K+ was increased from 4 to 20 or to 79 mM, about 30 mV per 10-fold K+ concn. change; (2) a hyperpolarization (anomalous response) of 10 mV maximum when stromal K+ was increased from 0 to 4 mM. The increase from 4 to 20 or 79 mM decreased or even reversed the short-circuit current (Isc). The transepithelial conductance (gt) increased when K+ was increased to 79 mM but no change occurred in the apical membrane fractional resistance (fRo). Increase of stromal K+ from 0 to 4 mM increased Isc and minimally changed gt and fRo. Ouabain (10(-3) M) abolished the anomalous responses, that is, the increases in V0 and Isc when stromal K+ was increased from 0 to 4 mM. These results are interpreted in terms of two K+ conductive pathways in the basolateral membrane of the corneal epithelium, a Nernstian conductance and an electrogenic (Na+ + K+)-ATPase pump transporting more Na+ than K+ ions per cycle. The normal or anomalous potential difference responses to changes in stromal K+ appear to depend on the relative resistance of the two pathways at the time stromal K+ is changed.

Animals↗

PubMed1991

Effect of phloretin on the carrier-mediated electrically silent ion fluxes through the bilayer lipid membrane: measurements of pH shifts near the membrane by pH microelectrode.

The effect of phloretin on the carrier-mediated electrically silent ion fluxes through the bilayer lipid membrane (BLM) was studied. The measurements were carried out according to our conventional technique, i.e. electrical potential recording in the presence of a protonophore, and by a new method--direct measurements of pH shifts in the unstirred layers of the BLM by pH microelectrode. Both techniques gave similar results. It was shown that the addition of phloretin increased the rate of cation/H+ exchange induced by nigericin and decreased the rate of anion/OH(-)-exchange induced by tributyltin. The effect of phloretin was higher in the presence of cholesterol in the BLM. Cholesterol decreased the nigericin- and tributyltin-induced fluxes under our experimental conditions. The application of an external voltage to the membrane had no effect on the ion fluxes thereby showing that these fluxes were electroneutral. The most probable explanation of these results bases on the effect of the membrane dipole potential on the electroneutral fluxes of ions. The possible mechanism of the dipole potential effect on the carrier-mediated electrically silent ion fluxes was discussed in terms of two competing hypotheses--the translocation through the membrane or the reactions at the membrane surface being the rate-limiting steps of the whole transport process.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗

PubMed1991

Measurements of local pH changes near bilayer lipid membrane by means of a pH microelectrode and a protonophore-dependent membrane potential. Comparison of the methods.

Shifts of pH near the bilayer lipid membrane (BLM) were measured in the absence of pH difference between bulk solutions by two methods, i.e. pH microelectrode and membrane potential recordings in the presence of a protonophore. A quantitative agreement of the results of both methods was obtained. The kinetics of the generation of potential induced by the addition of ammonium chloride was accounted for by the time of the diffusion through the unstirred layers. The thickness of the unstirred BLM layers was determined in the experiment.

Diffusion↗

PubMed1993

Effect of ultrasound on the pH profiles in the unstirred layers near planar bilayer lipid membranes measured by microelectrodes.

A pH shift in the unstirred layers (USLs) near a planar lipid bilayer membrane was induced by the diffusion of acetic acid along a concentration gradient. By means of a microelectrode technique it was shown that ultrasound decreases the thickness of the USL and that this reduction was much more pronounced on the side facing the ultrasound transducer than on the opposite side of the membrane. The effect depending on sound frequency and pressure is caused by the unidirectional fluid flow built up between transducer surface and membrane, the so-called quartz wind. Theoretical considerations based on the equations of the acoustic streaming near interfaces combined with the diffusion equation allow to predict the thickness of the USL if the sound field parameters are known.

Acetates↗

PubMed1988

Giant proteoliposomes prepared by freezing-thawing without use of detergent: reconstitution of biomembranes usually inaccessible to patch-clamp pipette microelectrode.

When sarcoplasmic reticulum membrane vesicles or synaptosomes were mixed with sonicated phospholipid vesicles and subjected to freezing-thawing, giant vesicles of up to 50 microns in diameter were formed. When the biomembrane vesicles were labeled with a covalently binding fluorescent dye, the resultant giant vesicles were fluorescent, thereby suggesting that the freezing-thawing process induces fusion of phospholipid and biomembrane vesicles. When membranes of the giant proteoliposomes thus prepared were studied using the patch-clamp technique, potassium channels of the biomembranes were detectable. The present method of the giant proteoliposome preparation is simple and rapid, and provides a system suitable for the study of ion channels of various biomembranes usually inaccessible to a patch-pipette microelectrode.

Animals↗

PubMed1982

Differential voltammetric measurement of catecholamines and ascorbic acid at surface-modified carbon filament microelectrodes.

Triple-barrel carbon filament microelectrodes were chemically and electrochemically oxidized to allow resolution of ascorbic acid from catecholamines during differential pulse voltammetric scans. The contribution of current from DOPAC to the catecholamine signal was minimized by this treatment. These electrodes exhibit linearity over a wide range of concentrations and long-term response stability.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1983

On the possibility of simultaneously recording from two cells with a single microelectrode in the hippocampal slice.

Unusual cellular elements have been recorded intracellularly in the CA1 region of the rat hippocampal slice. The elements appear, by all electrophysiological criteria except one, to be glia. However, unlike glia, they can fire action potentials. We suggests that these recordings represent cases of artifactual coupling of two cells by a recording microelectrode. The results have implications for the interpretation of dye injection experiments in the hippocampal CA1 region.

Action Potentials↗

PubMed1996

A chronic microelectrode investigation of the tonotopic organization of human auditory cortex.

We investigated the functional organization of human auditory cortex using a new chronic microelectrode technique. Tonotopic mapping data was obtained at the single unit level for the first time in humans. All sound-driven units were noted to have frequency-dependent response patterns. The majority of units (73%) demonstrated sharply tuned excitatory best-frequency responses. Twenty seven percent of units showed wide receptive fields, representing excitatory responses to almost the entire range of frequencies presented. A tonotopic pattern was observed with best frequencies systematically increasing as more medial-caudal recording sites were sampled.

Acoustic Stimulation↗

PubMed1976

A glass-insulated "Elgiloy" microelectrode for recording unit activity in chronic monkey experiments.

A glass-coated microelectrode made of a stiff cobalt--nickel alloy is described. The thickness of the glass coating and the length of the uninsulated tip can be varied as desired. The electrode is stiff enough to insert through the relatively tough dura of the monkey in chronic experiments. Further, the recording site can be marked by electrolytic deposition of iron and the Prussian blue reaction.

Alloys↗

PubMed1977

Development of the single microelectrode current and voltage clamp for central nervous system neurons.

The development of a single microelectrode clamping circuit for central nervous system preparations is presented. The efficacy of the circuit in both current and voltage clamp modes is demonstrated by investigating the membrane properties of cat spinal motoneurons. Results are compared with those obtained using conventional techniques and reveal that this technique can be more readily applied to central nervous system neurons. The constraints invovled in employing this system to study time-varying events are also discussed.

Animals↗

PubMed1979

A microdrive for use with glass or metal microelectrodes in recording from freely-moving rats.

A new subminiature microdrive assembly is described for electrophysiological recording from behaving rats. This very small, lightweight system allows excellent precision in electrode placement and can maintain stable recordings over extended periods. Since the electrode is nonrotating, tissue damage is minimized. Either metal or glass microelectrodes may be used with the system, offering the possibility of iontophoresis for cell marking or neuropharmacological manipulations.

Animals↗

PubMed1981

A ball-joint manipulator for microelectrode recording.

The conventional technique for single unit recording involves insertion of microelectrodes into the brain along an axis which is perpendicular to the cross-sectional plan of a recording chamber. Thus, only tissue that lies within the projection of the recording chamber can be reached. This limitation is overcome by use of a ball-joint manipulator which enables insertion of electrodes into the brain at a wide range of tilt angles. Construction of the ball-joint manipulator and the method by which the stereotactic location of the electrode recording tip is determined are described in the present note.

Animals↗

PubMed1986

A microelectrode for depth recording in awake animals.

The manufacture is described of a metal, glass-coated microelectrode for single-cell recording from deep structures of the brain during behavioral testing. It is thin, long, and straight, and has excellent electrical properties.

Animals↗

PubMed1987

A sputtered gold microelectrode in combination with a multibarrelled micropipette: a low impedance extracellular recording electrode with the facility of iontophoresis.

The manufacture of a metal film electrode on a multibarrelled micropipette is described. Gold film is sputtered onto the external surface of a multibarrelled micropipette and subsequently insulated. Gold film exposed at the tip operates as an extracellular recording microelectrode and the micropipettes may be used for iontophoresis of drugs or marker dyes. This method may be used to produce electrodes with increased numbers of iontophoresis channels at the tip without altering the low impedance and good recording characteristics of the metal film (recording) electrode.

Animals↗

PubMed1989

Intra-operative unit recordings in the human dorsal horn with a simplified floating microelectrode.

The authors report on the development, for studies in man, of a tungsten, glass-coated, light and simple microelectrode, that is implanted by hand in open operative conditions under the microscope and floats freely with the moving target tissue. This technique has provided limited but nevertheless satisfactory unit activity isolations. Intra-operative unit recordings were obtained from the dorsal horns of 2 spastic and 2 neurogenic pain patients. In the latter, dorsal horn deafferentation hyperactivities after a peripheral and a centro-peripheral lesion were recorded, characterized by a continuous, spontaneous and unalterable high frequency hyperactivity.

Electrodes, Implanted↗

PubMed1988

Microelectrode studies on the acid microenvironment beneath adherent macrophages and osteoclasts.

Osteoclasts and activated macrophages in culture were shown to generate an acidic microenvironment specifically in the attachment zone between the cell and the base of the culture dish. Measurements using pH microelectrodes revealed that osteoclasts, when firmly attached, could achieve a pH fall of about 1 unit min-1 to a limit value of pH 3.0 or less. Activated macrophages produced a slower fall of 0.5-2 pH units h-1 and a limit value of pH 3.6-3.7 was generally detected. The method of activation was relatively unimportant, but where macrophages formed clumps the pH effect was reinforced. Osteoclasts were also examined in situ in osteoporotic bone fragments in rabbit ear chambers, using a combination H+ and Ca2+ double-barrelled electrode. The pH readings reached a lower limit of 4.7 and the calcium concentration rose to a maximum of 40 mM in the erosion sites. In vivo such acid conditions would favor the direct extracellular action of secreted lysosomal proteinases in the degradation of collagen by both cell types.

Animals↗