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At least 163 records · Page 9Linked to original sources
PubMed2000

The use of electrochemically grown polymers on metallized electrodes to reduce electrode fouling in biological matrices.

The use of electrochemically grown polymers has expanded dramatically in the last couple of years, and they are now well established as membranes for immobilizing components. The evidence here for their anti-fouling properties is good. The poly(1,3-diaminobenzene)-covered electrodes performed well in the buffer, urine, plasma and serum samples, but not so well in the blood. The Ru/Rh/Pt, Rh/Rh and the Pt-on-glassy carbon electrodes covered with poly(1,3-diaminobenzene) were the best electrodes in the blood. The Pt disc seemed to exhibit the largest irrepeatability in most of the biological matrices.

Aniline Compounds↗
PubMed2001

Defibrillation efficacy comparing a subcutaneous array electrode versus an "active can" implantable cardioverter defibrillator and a subcutaneous array electrode in addition to an "active can" implantable cardioverter defibrillator: results from active can versus array trials I and II.

INTRODUCTION: Placement of implantable cardioverter defibrillators (ICDs) has been simplified by using the shell of a pectorally implanted ICD as a defibrillation electrode in combination with an endocardial right ventricular defibrillation lead. However, a sufficiently low defibrillation threshold (DFT) cannot be obtained in a few patients. Therefore, alternative approaches were systematically tested in the Active Can versus Array Trial (ACAT). METHODS AND RESULTS: In the first of two prospective randomized studies, the DFT of a subcutaneous left dorsolateral array anode introduced from a pectoral incision was compared to that of a standard active can anode in 68 patients. Intraoperatively, the DFT was determined twice in each patient using either the active can or, in patients with a subcutaneous array lead, once with all three fingers and once omitting the middle finger of the array. The second prospective randomized study included 40 patients. DFT also was determined twice in each patient using an active can in a left pectoral position as anode alone and combined with a left dorsolateral array electrode with two fingers. In ACAT I, stored energy at DFT decreased from 13.1+/-7.7 J (active can) to 9.6+/-6.1 J (three-finger array lead) (P = 0.04), impedance decreased from 53+/-8 ohms to 40+/-6 ohms (P < 0.0001). Omitting the middle finger of the array lead, stored energy at DFT increased by 0.9 J (P = 0.47) and impedance by 2 ohm (P < 0.0001). In ACAT II, DFT and impedance using an active can device were significantly lower when a two-finger array lead was added that decreased stored energy at DFT from 10.1+/-5.2 J to 6.9+/-3.9 J (P = 0.001) and impedance from 56+/-5 1 to 42+/-5 l (P < 0.0001). CONCLUSION: In combination with a right ventricular defibrillation electrode, a left pectoral subcutaneous array lead improves defibrillation efficacy if used instead of, or in addition to, a left pectoral active can ICD device. Implantation of the array lead can be simplified by using two instead of three fingers, without a significant loss of defibrillation efficacy.

Adult↗
PubMed1996

The influence of location of electrode on muscle fiber conduction velocity and EMG power spectrum during voluntary isometric contraction measured with surface array electrodes.

A surface array electrode was used to investigate muscle fiber conduction velocity (MFCV) and EMG power spectrum during voluntary isometric contraction of m. biceps brachii. The mean power frequency (MPF) and the total power (TP) at various locations of the muscle were obtained from the power spectrum. MFCVs at various locations of the muscle were measured directly using the averaging method. The values of MPF, TP and MFCV were identified with respect to the electrode locations on the m. biceps brachii. MPF was shown as high near the end-plate and low near the tendon of the muscle during contraction of 40% of isometric maximum voluntary contraction (MVC). TP showed low value near the end-plate and the tendon of the muscle fiber and different values at different location setting electrode during voluntary isometric contraction. TP at each location on the muscle surface increased when the contraction levels increased in the contractions range of 20 to 60% MVC. MFCVs showed a high value near the end-plate and the tendon of the muscle during the contraction of 40% MVC. These results indicated that MPF, TP and MFCV at different locations on the muscle were different along the length of the muscle fiber.

Adult↗
PubMed2003

Problems in assessments of amalgam electrodes for standardising or certifying the corresponding ion selective electrodes.

The primary method for standardizing or certifying an Mz+-ISE (Ion Selective Electrode for Mz+ where Mz+ = alkali or alkaline-earth cation) implies comparing the latter with the corresponding M-Amalgam electrode in the cell Pt/M-Amalgam/Mz+ Solution/Mz+ ISE/Pt, whose potential difference is obviously independent of Mz+ concentration. Assessment of the potential of the M-Amalgam electrode requires the precise determination of the mole fraction x of the M metal in amalgam, which is customarily performed by decomposing an M-Amalgam sample in excess HCl and titrating the HCl excess with standard NaOH solution. There arises the problem of choosing the correct end-point in pH-metric titrations of strong acids with carbonate-contaminated NaOH standard solutions, which is of frequent occurrence both in research and routine laboratory practice. This topic is either overlooked or insufficiently treated in textbooks: thus the interpretation of the above experimental pH-metric titration curves is often misled and the results may be affected by significant errors. Some recent misleading suggestions are here re-analyzed critically in order to focus correct, recommended methodological schemes.

Hydrogen-Ion Concentration↗
PubMed2004

[Electrochemical behavior of daunorubicin at Co/GC ion implantation modified electrode and the application of the electrode].

AIM: To study the electrochemical behavior of daunorubicin at Co/GC ion implantation modified electrode. METHODS: With Co/GC ion implantation modified electrode as working electrode, daunorubicin was determined by voltammetry in 0.05 mol x L(-1) Na2HPO4-KH2PO4 (pH 6.82) solution. RESULTS: A sensitive reductive peak of daunorubicin was obtained by linear sweep voltammetry. The peak potential was -0.60 V (vs SCE). The peak current was proportional to the concentration of daunorubicin over the range of 2.84 x 10(-8) - 1.42 x 10(-6) mol x L(-1) and 1.42 x 10(-6) - 1.28 x 10(-5) mol x L(-1) with the detection limit of 1.42 x 10(-8) mol x L(-1). The reduction wave was applied to the determination of daunorubicin. The electrochemical behavior and reaction mechanism were studied by linear sweep and cyclic voltammetry. CONCLUSION: The reduction process was quasi-reversible with adsorption characteristics.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

[Statistical analysis of the replacement circuit of the electrode- biological object-electrode system in electric stimulation of the heart].

Methods of topology and numerical parameters determination of electrode-bioobject-electrode equivalent circuit system was developed for electrocardiostimulants (ECS) operating under voltage source regime. It was established that in designing of ECS of the kind the rated value of load impedance be 200-300 omega. Empirical histograms and distribution law curves of RC-parameters of the mentioned equivalent circuit took into account the variability of these parameters both in patients and depending on the position of electrode heart as well.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Temporary pacing leads in cardiac surgery. A comparison of multifilament braided electrode and localized solitary stainless steel electrode.

The standard braided wire lead used for temporary pacing following open heart surgery may be rendered ineffective by high current thresholds. In this study braided leads were compared with a lead incorporating a localised stainless steel electrode in 17 patients undergoing routine cardiac surgical procedures. Each patient acted as his own control. The localised electrode lead gave significantly lower current and voltage thresholds compared to the braided lead, this difference being apparent both on the day of operation and prior to lead removal (p less than 0.0005). Use of a lead incorporating a localised electrode is therefore less likely to be restricted by difficulties in capture and sensing.

Adult↗
PubMed1985

Determination of some cardiac drugs using an ionselective chloride electrode and a silver electrode.

To determine hydrochlorides of butobendin, carbocromen, hexobendin, lidocaine, procainamide, todrazoline in pharmaceutical preparations, two analytical techniques were applied: the direct potentiometric method (from a standard curve) using an ion-selective chloride electrode and the method of potentiometric titration using a silver electrode as well as an ion-selective chloride electrode (indirect method). A statistical analysis has been carried out, and statistical tests were applied to compare the methods used.

Cardiovascular Agents↗
PubMed1981

[Comparison of the blink-reflex obtained using needle electrodes and surface electrodes (author's transl)].

The electrically released Blink-Reflex was registered on four channels simultaneously using needle- and surface-electrodes. 17 healthy volunteers were examined. The latencies of the R1-, R2- and R2'-components are comparable using both recording technics. The amplitudes of the reflex components however show great variation using as well needle- and surface electrodes. The amplitudes didn't turn out to be more stable using surface electrodes. For the clinical use this result implies that both recording technics produce comparable latencies and therefore can be used alternatively according to the special necessities of examination.

Adult↗
PubMed1980

Sampling membrane potential, membrane resistance and electrode resistance with a glass electrode impaled into a single cell.

A method is demonstrated to measure membrane resistances and membrane potentials of single cells during impalement by a single glass microelectrode. The intention was to develop a procedure which would provide data almost continuously. Therefore, a frequency-dependent voltage divider network has been chosen to represent the basic electrical properties of the electrode and cell membrane, and used to explore its voltage response to a current stimulus, consisting of two rectangular pulses of different widths. It can be shown that the resolution of the method can be improved by inverting this stimulus so that each polarization becomes a relaxation and vice versa. In order to generate, analyze and display this signal continuously, a device has been designed which has been called 'Electrophysiological Monitor, (E1M2)'. E1M2 provides a current stimulus as input into a standard bridge network and can analyze the summed response of the electrode and cell by a set of sample-hold amplifiers. It then decodes and displays the data continuously, as membrane potential (Em), input resistance of the cell (Rinp) and the electrode resistance (Re) respectively. From Rinp the membrane resistance (Rm) can be deduced. The validity of the method has been examined by measuring these parameters in frog muscle cells. Technical design considerations, the accuracy and possible pitfalls with the suggested procedure are discussed.

Animals↗
PubMed1989

The cone electrode: a long-term electrode that records from neurites grown onto its recording surface.

A novel long-term recording electrode combines neural regeneration with a standard wire recording technique. The electrode consists of an insulated gold wire fixed inside a hollow glass cone. A piece of sciatic nerve is placed in the glass cone before implantation in cortex of rat. Cortical neurites grow into the sciatic nerve in the cone from surrounding neurons and their electrical activity is recorded via the wire (or wires) in the cone. This activity increases in amplitude over the first few weeks after implantation and remains stable until termination of the experiment many months later. Activity of both single and multi units has been recorded. The cone electrode opens unique opportunities for studies of neurite growth in vivo, for plasticity studies on a captive set of neurites, for studying the neural correlates of behavior and motor learning, and for accessing the central nervous systems of patients with severe paralysing and communicative disorders.

Animals↗
PubMedDate not supplied

Microiontophoresis electrode location by neurohistological marking: Comparison of four native dyes applied from current balancing electrode channels.

INTRODUCTION: The re-establishment of electrode position after microiontophoresis with multi-barrelled electrodes has always been a complicated and mostly inaccurate procedure. The present report describes a new method for 'on line' neurohistological marking of each recording position during experimental sessions in which in vivo microiontophoresis was combined with extracellular single unit recording. METHODS: We tested the effectiveness of four native dyes: pontamine sky blue (PSB), methylene blue (MB), cresyl violet (CV) and toluidine blue (TB). They were ejected from the continuous balancing channels of multi-barrelled microelectrodes during iontophoresis in place of the usual sodium chloride solution. RESULTS: The present results are based on observations obtained from 66 neuronal recordings and 42 labelled sites in the rat neocortex. Results indicate that none of the tested native dyes altered the spontaneous firing rate of the neurons, nor did they have any influence on the applied bioactive compounds. Recording positions were detected as small, labelled spots in brain slices (2-12 microm in diameter) at the end of the recording tracks. Labelling was successful with MB and PSB, but not with CV or TB. In addition, MB provided good labelling with a low net ejection current. DISCUSSION: The present results suggest that using native dyes, especially MB, instead of sodium chloride in current balancing channels during in vivo microiontophoresis provides fast and accurate confirmation of electrode placement. This method saves the experimenter the time consuming further application of secondary labelling procedures after such experiments. Moreover, the MB-labelling we describe here is focal, enabling a more accurate verification of the site of recording and/or application of various neuroactive compounds. In addition, MB labelled accurately and reliably and with very low ejection currents, presumably due to its smaller molecular weight and higher relative mobility.

Animals↗
PubMed1994

Substrate-purging enzyme electrodes. Peroxidase/catalase electrodes for H2O2 with an improved upper sensing limit.

A substrate-purging enzyme electrode carrying a sensing enzyme and a substrate-purging catalyst on its surface is proposed and was examined theoretically and experimentally. Since the substrate-purging catalyst partially consumes the substrate without consuming a cosubstrate, the sensitivity of the enzyme electrode is lowered while the maximum response remains unchanged leading to a raising of the upper sensing limit. Thus, by coating it with a cross-linked film of catalase and albumin, the upper sensing limit of a peroxidase-incorporated polypyrrole membrane electrode as an H2O2 sensor was raised by approximately 2 orders of magnitude.

Biosensing Techniques↗
PubMed2003

An analogy of an ion-selective electrode sensor based on the voltammetry of microcrystals of tetracyanoquinodimethane or tetrathiafulvalene adhered to an electrode surface.

The voltammetry of solid 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetrathiafulvalene (ITF) at an electrode-microparticle-aqueous (electrolyte) interface generates characteristic current-potential profiles associated with solid-solid-phase transformations. During the reactions, electrolyte ions are included into the TCNQ (cations) and TTF (anions) lattice sites as part of the charge neutralization process. Consequently, electrolyte ion concentration is associated with the reversible potential of the TCNQ0/- and TTF0/+ reactions, making these processes candidates for the development of novel voltammetric cation and anion sensors, respectively. Electrode potential-analyte ion concentration dependence studies exhibited highly reproducible potential shifts of 45 (+/- 1) mV/decade change in ion analyte concentration for both the TCNQ cation sensor and the TTF anion sensor. When presented with mixed-analyte solutions, both ion-sensing systems exhibited a degree of ion selectivity. Ion selectivity trends may be modeled using equations based on a Nicolsky-type selectivity relationship, in accordance with the concept that these are the voltammetric analogies of potentiometric ion-selective membrane electrodes.

Journal Article↗
PubMed2004

DNA-modified carbon paste electrode applied to the study of interaction between rifampicin (RIF) and DNA in solution and at the electrode surface.

Rifampicin (RIF) is an antibiotic widely used against tuberculosis and a DNA intercalator. The interaction of RIF with double-stranded (ds) and single-stranded (ss) calf thymus DNA was studied in solution as well as at the electrode surface by means of transfer voltammetry using differential pulse as stripping mode with carbon paste electrode (CPE) at 0.2M acetate buffer at pH 5.0 and at 0.2M phosphate buffer pH 7.4. Differentiations in the above-mentioned interaction at different pH values are presented and compared in order to optimize the detection of Rifampicin (RIF).

Animals↗
PubMed2005

An electrode configuration technique using an electrode matrix arrangement for FES-based upper arm rehabilitation systems.

An upper limb electrical stimulation technique has been developed which features a novel self-configuration approach, to obtain an ideal wrist response from the patient. The system uses an analogue de-multiplexer in conjunction with an electrode matrix so that different electrode sites can be tested using only one channel of stimulation. A twin axis goniometer is attached to the patient's wrist and flex sensors are attached to the patient's fingers so that the control algorithm can assess the wrist response. A data acquisition unit logs the data for further analysis. A clinical investigation on healthy subjects was conducted to test the proposed system. The results show a high variation in hand response across different subjects. In addition, for all subjects tested an ideal response was found which shows some justification for the use of the proposed technique.

Algorithms↗
PubMedDate not supplied

Visually evoked potentials evoked by moving unidimensional noise stimuli: effects of contrast, spatial frequency, active electrode location, reference electrode location, and stimulus type.

We determined the relative importance of electrode derivation, stimulus type, spatial frequency and contrast in determining the relative size of the late negative and early positive responses of motion elicited VEPs. Seven subjects aged 22-48 years with normal vision were tested binocularly. Motion onset and motion reversal were employed as modes of stimulus presentation. For both, pseudo-random one-dimensional noise patterns whose peak power was at 5.2, 2.6, 1.3, 0.325 and 0.1625 cycles per degree (cpd) were stimuli. Contrasts were 70% and 5%. Active electrodes were placed at Oz, 5 cm to the left of Oz, 5 cm to the right of Oz and a frontal midline position (Fpz) and referenced to linked mastoids. Transient motion reversal elicited a prominent positive response present in all subjects and at low contrasts. Motion onset VEPs have a complex waveform which may be either predominantly positive or negative. The most important variables in determining whether a prominent positivity or negativity is present in the motion onset VEP are the contrast and the spatial frequencies. Data such as these are first efforts in developing recommendations for the motion VEP.

Acoustic Stimulation↗