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At least 19 recordsLinked to original sources

PubMed1977

Modifications of glass microelectrodes: a self-filling and a semifloating glass microelectrode.

A simple and inexpensive method for constructing a double capillary was developed for preparing a self-filling glass microelectrode. The modified method uses a thin capillary instead of a bundle of glass fibers and fuses it to the outer capillary wall with flame before pulling the latter with a puller. The validity of the new electrode was proven by measuring the proximal cell PD of the rat kidney slices (mean of the stable cell PDs lasting longer than 30 min,--69 mV). A semifloating electrode was modified from the original floating electrode to be applicable to the in vivo kidney preparation whose pulsatile and respiratory movements had hindered yielding a stable cell PD. This electrode is constructed simply by replacing the shaft of the Ling-Gerard glass microelectrode with a length of flexible silcone-rubber tubing. The cell PD recorded by this electrode is found to be more stable and can withstand minor tissue distortion in mammalian kidney cells in vivo and also in such a contractile tissue as the secretory coil of the eccrine sweat gland.

Animals↗

PubMed1979

Electrochemical properties of Na+- and K+-selective glass microelectrodes.

Electrochemical properties of Na+-selective glass microelectrodes were studied and compared with those of K+-selective glass microelectrodes. The selectivity of Na+-selective glass microelectrodes depended on the ion concentration of test solutions. With aging, resistance of Na+-selective microelectrodes increased and their selectivity for Na over K decreased. Na+-selective microelectrodes potential measured in NaCl solution remained constant with aging, while the potential measured in KCl solution decreased and became more positive. The changes in resistance and potential of Na+-selective microelectrodes may be due to the effects of the less mobile cation, i.e., H+ or K+ on the Na ion exchange in the Na-sensing region. The results indicate that Na+-selective microelectrodes must be used as soon after filling as possible. The selectivity of Na+-selective microelectrodes increased with increase of the sensitive exposed-tip length, whereas their response time became slow due to a large recessed volume, indicating requirement of an optimum exposed-tip length for intracellular applications. The changes in the properties of Na+-selective glass microelectrodes with aging contrasted with those of K+-selective glass microelectrodes in which resistance decreased and K+-selectivity increased. The K+-selective microelectrodes required aging before use for a high selectivity and low resistance. The K+-selective microelectrodes with low resistance after sufficient aging can be used without insulation to measure K+ and Na+ activities in aqueous solutions. The different properties between Na+- and K+-selective microelectrodes are understandable, because hydration of N+-selective glass is much less extensive than that of K+-selective glass.

Electric Conductivity↗

PubMed1978

A simple circuit for automatic continuous recording of microelectrode resitance.

Microelectrodes with tip diameters less than or equal to 0.5 micron used for intracellular recording sometimes give artefactual readings due to tip potentials. These appear to be caused by a change in the tip of the microelectrode upon impalement with a corresponding change in microelectrode resistance. A circuit is described which enables the resistance of the microelectrode to be continuously monitored throughout an experiment. The electrode is used as one half of a potential divider for an a.c. signal at 20 Hz with an amplitude of 20 mV. The other half of the potential divider is a 1000 Momega resistor. The a.c. signal across the microelectrode is approximately proportional to the microelectrode resistance in the range 0 --50 Momega. This signal is amplified, rectified and smoothed and then displayed on a chart recorder or other convenient meter.

Animals↗

PubMed1976

Physicochemical properties of a liquid ion exchanger microelectrode and its application to biological fluids.

Double-barreled potassium or chloride ion-selective microelectrodes were constructed using a liquid ion exchanger. Technical details of the fabrication of double-barreled microelectrodes, having a PD sensor as one barrel and an ionic sensor as the other, are described. The sensitivity of K+ or CI- ion-selective microelectrodes exhibited an approximately Nernstian response over a temperature range of 7 degrees-37 degrees C, and the electromotive force (EMF) was stable within +/- mV for a few hours. The rise time was less than 1 sec. The effect of pH on the electrode response was negligible over a physiological range of pH 5.6 to 7.8. The selectivity constants of the K+ microelectrode to other cations were 0.011 for Na+, 0.200 for NH+4, and less than 0.002 and 0.001 for Ca++ and Mg++, respectively, while that of the CI- microelectrode was 0.067 for HCO-3. Glucose or urea has no effect on the EMF. Protein has a significant effect on ion exchanger membrane only when the concentration of the tested ion is low and protein is high. On the basis of this background the determination of K+ and CI- activity was carried out both in vivo and in vitro on several biological samples, such as serum, tissue and cellular fluids, and other protein-containing fluids. The values obtained with the microelectrode were consistent with those obtained with the other conventional methods or with the current theory on electrolyte solutions. These results were taken to assure the practical application of these electrodes to biological studies in many fields.

Animals↗

PubMed1979

Carbon fibre microelectrodes.

A technique for making recording microelectrodes containing an ultrafine carbon fibre is described. This technique can be used for single- and multi-barrel microelectrodes. These microelectrodes not only have a very low signal-to-noise ratio comparable with that found in tungsten microelectrodes but are simpler to make. When used in a multi-barrel array for iontophoretic application of drugs the carbon fibre microelectrode has many advantages over a fluid electrolyte-filled recording barrel, including very high signal-to-noise ratio and relative immunity to spike distortion during application of iontophoretic current.

Animals↗

PubMed2026

Choice of Anesthesia in Microelectrode Recording-guided Deep Brain Stimulation Surgery for Parkinson's Disease (CHAMPION): A Noninferiority Randomized Controlled Trial.

BACKGROUND: Deep brain stimulation for Parkinson's disease is often performed under conscious sedation or general anesthesia. However, anesthetic agents may influence intraoperative microelectrode recording, and the optimal anesthesia method for microelectrode recording remains unclear. This study compared general anesthesia and conscious sedation in preserving microelectrode recording signal intensity during deep brain stimulation. METHODS: In this prospective, noninferiority randomized controlled trial, patients with Parkinson's disease (United Kingdom Brain Bank criteria) undergoing elective bilateral surgery were randomized 1:1 to the conscious sedation or the general anesthesia group. During surgery, a desflurane anesthetic titrated against the quality of the electrophysiologic signal was applied in the general anesthesia group, whereas patients in the conscious sedation group received dexmedetomidine anesthesia. The primary outcome was the proportion of patients with high-quality microelectrode recording (normalized root mean square greater than 2.0), assessed postoperatively off-line. Secondary outcomes included operation and recording duration, 6-month clinical efficacy, and complication rates. RESULTS: Of 188 randomized patients (94 general anesthesia, 93 conscious sedation), desflurane anesthesia was noninferior for high normalized root mean square proportion (89.4% vs . 90.3%; difference, -0.96%; 95% CI, -9.62 to 7.70). The general anesthesia group had shorter operative time (difference, -9.07 min; 95% CI, -13.99 to -4.14; P < 0.001). At 6 months, changes in Unified Parkinson's Disease Rating Scale score (difference, -2.50; 95% CI, -7.20 to 2.20; P = 0.297), levodopa equivalent daily dose (difference, -58.4 mg; 95% CI, -133.56 to 16.75; P = 0.128), and complication rates (general anesthesia: 10.9% vs . conscious sedation: 8.9%; P = 0.655) were comparable between the groups. CONCLUSIONS: General anesthesia is noninferior to conscious sedation for microelectrode-guided subthalamic nucleus deep brain stimulation, providing equivalent signal intensity and clinical outcomes while improving procedural efficiency, supporting its use as a valid clinical option.

Humans↗

PubMed1976

Measurement of current spread from microelectrodes when stimulating within the nervous system.

Tungsten stimulating microelectrodes have been tested in monopolar, bipolar and concentric configurations for the extent to which unwanted current spread occurred. Current spread from monopolar electrodes in close conformity with the predictions of the inverse square law, both in vitro in vivo. The bipolar and concentric configurations, tested only in vitro, had current-spread characteristics which did not follow the inverse square law so closely. The bipolar configuration gave little reduction in spread, compared wpith a monopolar electrode, but the concentric configuration did reduce the extent of stimulus spread. The extent of spread depends greatly upon a number of experimental variables, including the dimensions of the microelectrode tip. For studies requiring precise localization with low stimulus currents, it is advisable to determine the inverse square law constant for each experimental situation. For more generalized stimulation purposes within the mammalian C.N.S., employing monopolar microelectrodes of moderate tip size, brief pulses of 10 muA can be expected to stimulate myelinated axons with about 0.15 mm of the tip, and 100 muA WILL Stimulate with a radius of about 0.5 mm.

Animals↗

PubMed1979

Active and passive properties of rabbit descending colon: a microelectrode and nystatin study.

The electrical properties of the basolateral membrane of rabbit descending colon were studied with microelectrode methods in conjunction with the polyene antibiotic nystatin. Two problems were examined: (i) the relative distribution of tight junctional, apical membrane and basolateral membrane resistances, and (ii) the ionic basis of the basolateral membrane potential. Intracellular K+ activity (K+) was measured using liquid ion exchanger microelectrodes ((K+) = 76 +/- 2 MM) and was found not to be in equilibrium with the basolateral membrane potential. In order to measure membrane resistances and to estimate the selective permeability of the basolateral membrane, the apical membrane was treated with nystatin and bathed with a K2SO4 Ringer's solution which was designed to mimic intracellular K+ composition. This procedure virtually eliminated the resistance and electromotive force of the apical membrane. Shunt resistance was calculated by two independent methods based on microelectrode and transepithelial measurements. Both methods produced similar results (Rs = 691 +/- 63 omega cm2 and 770 +/- 247 omega cm2, respectively). These findings indicate that the shunt has no significant selectivity, contrary to previous reports. Native apical membrane resistance was estimated as 705 +/- 123 V cm2 and basolateral membrane resistance was 95 +/- 14 V cm2. To estimate basolateral membrane selectivity, the serosa was bathed in a NaCl Ringer's solution followed by a series of changes in which all or part of the Na+ was replaced by equimolar amounts of K+. From measures of bi-ionic potentials and conductance during these replacements, we calculated potassium permeability and selectivity ratios for the nystatin-treated colon by fitting these results to the constant field equations. By correcting for shunt conductance, it was then possible to estimate the selective permeability of the basolateral membrane alone. Selectivity estimates were as follows: PNa/PK = .08 and PCl/ PK = .07 (uncorrected for shunt) and PNa/PK = .04 and PCl/PK = .06 (basolateral membrane alone). In a second set of experiments, evidence for an electrogenic Na+ pump in the basolateral membrane is presented. A small ouabain-sensitive potential could be generated in the nystatin-treated colon in the absence of chemical or electrical gradients by mucosal, but not serosal, addition of NaCl. We conclude that this electrogenic pump may contribute to the basolateral membrane potential; however, the primary source of this potential is "passive": specifically, a potassium gradient which is maintained by an "active" transport process. An appendix compares the results of nystatin experiments to amiloride experiments which were conducted separately on the same tissues. The purpose of this comparison was to develop a comprehensive model of colonic transport. The analysis reveals a leak conductance in the apical membrane and the presence of an amiloride-insensitive conductance pathway.

Animals↗

PubMed1978

Biological and artificial ion exchangers: electrical measurements with glass microelectrodes.

Biological (stratum corneum) and artificial (cation-exchange resin beads, Bio-Rad AG 50W-X2) ion exchangers were impaled by glass microelectrodes filled with KCl solution. The electrical potential difference recorded in these structures in reference to the external bathing medium was shown to be dependent on the KCl concentration of both the external and the microelectrode filling solutions. The potentials were interpreted on the grounds of the fixed charge theory of membrane potentials as a consequence of two phase boundary potentials (Donnan potentials), one at the matrix-external solution interface and the other at the matrix-microelectrode solution interface. The contribution of a diffusion component for the recorded potential was considered.

Animals↗

PubMedDate not supplied

Tapered tungsten fine-wire microelectrode for chronic single unit recording.

A new fine-wire microelectrode made from tungsten wire is described. The electrode design provides for strength as well as flexibility due to the stiffness of tungsten wire and a gradually tapering profile. Unlike previously-used fine wire electrodes, microelectrodes of the new design can be singly implanted under electrophysiological control into deep brain structures of larger animals such as cats. The flexibility of the fine diameter terminal portion of the microelectrode permits stable recording from caudal brain stem single units during vigorous behavioral activity.

Animals↗

PubMed1977

Liquid and solid-state Cl- -sensitive microelectrodes. Characteristics and application to intracellular Cl- activity in Balanus photoreceptor.

When intracellular chloride activity (aiCl) was monitored with chloride-sensitive liquid ion exchanges (CLIX) microelectrodes in Balanus photoreceptors, replacement of extracellular chloride (Cl0) by methanesulfonate or glutamate was followed by a rapid but incomplete loss of aiCl. When propionate was used as the extracellular anion substitute, CLIX electrodes detected an apparent gain in aiCl, while a newly designed Ag-AgCl wire-in glass microelectrode showed a loss of aiCl under the same conditions. This discrepancy in Cl- washout when propionate replaced Cl0 is explained by the differences in selectivity of CLIX and Ag-AgCl electrodes for native intracellular anions and for the extracellular anion substitute which also replaces Cli and interferes in the determination of aiCl. Both electrodes indicate that ECl approximately Em when the cells are bathed in normal barnacle saline, and both electrodes showed the rate of Cl washout (tau approximately 5 min) to be independent of Cli when Cl0 was replaced by glutamate. Details of Ag-AgCl microelectrode construction are presented. These electrodes were tested and found to be insensitive to the organic anion substitutes used in this study. Selectivity data of CLIX electrodes for several anions of biological interest are described.

Animals↗

PubMed1979

The measurement of intracellular sodium activities in the bullfrog by means of double-barreled sodium liquid ion-exchanger microelectrodes.

A double-barreled Na+-selective microelectrode was constructed with monensin as a liquid ion exchanger. The HCl-treated monensin was dissolved in a solvent (Corning 477317) at 10% (weight/weight). Internal reference solution of its ionic barrel was mixture of 0.49 M NaCl and 0.01 M KCl, the pH being adjusted to 3 with 0.1 M citrate-HCl buffer, whereas that of the PD barrel was 0.5 M KCl. Average slope and selectivity ratio (Na+/K+) tested on 10 different microelectrodes were -57.5 +/- 1.87 mV/P(Na) (SEM) and 6.7 +/- 0.44, respectively. The electrical resistance was an order of 10(10) ohm and the response time was less than 10 sec. Using this microelectrode, a free flow micropuncture experiment was carried out in the bullfrog kidney and the intracellular Na+ activity as well as the membrane PD was determined on the proximal tubular cell. Average value (+/- SEM, n = 15) for the intracellular Na+ and K+ was 20.7 +/- 1.56 mEq/L and 61.2 +/- 1.16 mEq/L, respectively, and -68.7 +/- 0.88 mV for the peritubular membrane PD. There was a significant negative correlation between Na+ and K+ activities within the cell, i.e., the lower the ionic activity of cellular Na+ was, the higher the cellular K+, and vice versa, the sum of these two being kept nearly constant. The above finding may be somehow related to the isosmosis in the reabsorptive process across the proximal tubular epithelium.

Animals↗

PubMed1979

[Semiautomatic regulator for the preparation of microelectrodes for electrophysiology].

This paper describes an electronic device for making metallic microelectrodes to be used for electrophysiological experiments. These microelectrodes are endowed with a small tissue-electrode capacity and a high mechanical strength. The same microelectrodes are applicable for derivation of spikes as in the case of microstimulation of nervous structures during repeated penetrations.

Electrophysiology↗

PubMed1979

Electron microscopic studies of serially sectioned cat spinal alpha-motoneurons. I. Effects of microelectrode impalement and intracellular staining with the fluorescent dye "Procion Yellow".

Cat spinal alpha-motoneurons were studied in the light and electron microscope after intracellular recording and staining with the fluorescent dye Procion Yellow. Generally, the ultrastructural preservation of the stained neurons improved when the amount of dye delivered was decreased, and when the duration of the microelectrode impalement of the neuron as well as the time between the intracellular staining and the tissue fixation was kept as short as possible. Utilizing the optimal experimental procedure finally arrived at, about one-third of the stained neurons could be used for further quantitative morphometric analysis. With respect to synaptology and gross architecture these cells appeared to differ from control motoneurons mainly with regard to a focal disarrangement of the cell body periphery, probably a result of the microelectrode injury, and a certain degree of damage to some large boutons.

Animals↗

PubMed1976

pH-sensitive glass microelectrodes and intracellular pH measurements.

1. Some properties of the open-tipped, uninsulated, pH-sensitive glass microelectrode were examined in several electrical experiments. 2. Based on these observations, technical and theoretical problems were considered for application to the pH measurement in small cells. 3. The intracellular pH, (pH)i, of the epithelial cell in rat duodenum measured was approximately 7.0. A reduction in (pH)i was apparent (about 0.3) with the addition of 20 mM-glucose to the bathing fluid. 4. It was concluded that with certain limitations such uninsulated, open-tipped microelectrodes may be successfully utilized for intracellular pH measurements.

Animals↗

PubMed1977

A new solid-state microelectrode for measuring intracellular chloride activities.

Solid-state microelectrodes from measuring intracellular Cl activity (alphaiCl) were made by sealing the tips of tapered glass capillaries (tip diameter 0.3 mum), coating them under vacuum with a 0.2-0.3 mum thick layer of spectrscopic grade silver, and sealing them (except for the terminal 2-5 mum of the tip) inside tapered glass shields. 106 microelectrodes had an average slope of 55.0+/- 0.6 m V (S,E,) per decade c hange in alphaCl. Tip resistance was (77.1+/- 3.1) x 10(9) omega(n=30). Electrode response was rapid (10-20 s), was unaffected by HCO3, H2PO4, HPO42 or protein, and remained essentially unchanged over a 24-h period. AlphaiCl in frog sartorius muscle fibers and epithelial cells of bullfrog small intestine was measured in vitro. In both tissues, alphaiCl significantly exceeded the value corresponding to equlibrium ditribution of Cl across the cell membrane.

Animals↗

PubMed1975

A dual marking technique for microelectrode tracks and localization recording sites.

This paper describes techniques for marking both microelectrode tracks and exact recording loci using a combination of fast green dye and horseradish peroxidase (HRP). The procedure involves coating the exterior of HRP filled microelectrodes with fast green dye in order to identify electrode tracks, and ejecting HRP from the electrode to mark recording loci. Rapid, multiple marks can be made with this technique without harming the recording capabilities of the micropipette.

Animals↗

PubMed1979

Sodium-selective liquid ion-exchanger microelectrodes for intracellular measurements.

The sodium-selective ligand 1,1,1-tris[1(1)-(2(1)-oxa-4(1)-oxo-5(1)-aza-5(1)-methyl)dodecanyl]propane dissolved in 3-nitro-o-xylene containing a small amount of the lipophilic anion tetrachlorophenyl borate was used as a liquid ion-exchanger in sodium-selective microelectrodes. The microelectrodes gave rapid, stable responses that were linear functions of the logarithm of sodium activity. They were tested under conditions approximating those to be expected in the cell interior, and the results indicated that they can be used to measure intracellular sodium activity without significant interference from intracellular potassium.

Animals↗