Wick Electrode Research Articles

Direkte spektroskopische Analyse von Spurenelementen in ZnSe-Proben im rotierenden Gleichstrombogen unter Anwendung eines homogenen Magnetfeldes und von Zusatzsubstanzen

An emission spectroscopic method was developed for the simultaneous determination of the trace elements Ag, Al, Cr, Cu, Fe, Ga, In, Mg, Mn, Ni, Pb and Ti in ZnSe samples. The sample to be analysed (about 10 mg) is vaporized directly from the anode and excited by a rotating d.c. arc using a homogeneous magnetic field. The influence of elements with lower ionization potential on the plasma was investigated, too. These additives (NaCl, KCl) were introduced into the plasma by means of a wick electrode (cathode). The calibration is carried out on the basis of mixtures of oxides of the trace elements with spectroscopically pure ZnSe powder. Analytical detection limits of the trace elements investigated were in the region of ppm and sub-ppm corresponding to absolute amounts of 10 ng and lower.

Modification of retrograde degeneration in transected spinal axons of the lamprey by applied DC current

In the spinal cord of the lamprey, regeneration of giant reticulospinal axons occurs following transection. We show that partial degeneration of the proximal axonal segment, or "die-back," also occurs following spinal transection and it precedes regenerative outgrowth. The die-back during the first 5 days post-transection is reduced significantly by application of a 10-microA DC current across the site of transection, with the cathode distal to the lesion. Reversing the polarity of the applied current (cathode proximal to the lesion) increases the extent of axonal die-back relative to the sham-treated controls. Following spinal transection, saline-filled wick electrodes were implanted in the body musculature on either side of the lesion. Electrically treated animals received current across the lesion for 5 days, while the sham-treated controls received no current. After 5 days, several giant axons in each preparation were injected intracellularly in the spinal cord with the dye Lucifer Yellow. The extent of axonal die-back in the proximal cord stump was determined in the filled fibers by measuring the distance of the axon end from the site of lesion. The mean distances of axonal die-back were as follows: controls, 1750 microns +/- 45 SEM; cathode-distal, 740 microns +/- 33 SEM; cathode-proximal, 2820 microns +/- 60 SEM. These differences between the treatment groups proved to be significant using the Wilcoxon rank sum test. We propose that die-back is caused by the entry of cations driven into the cut surface of the cord by the endogenous injury current. The applied DC current interacts with the endogenous current of injury to either decrease or increase the flow of cations into the cord, depending on the direction of applied current flow across the lesion. This in turn causes a corresponding reduction or enhancement of the axonal die-back.

Enhanced spinal cord regeneration in lamprey by applied electric fields.

After a weak, steady electric current of approximately 10 microamperes was imposed across the completely severed spinal cord of the larval lamprey Petromyzon marinus, enhanced regeneration was observed in the severed giant reticulospinal neurons. The current was applied with implanted wick electrodes for 5 to 6 days after transection (cathode distal to lesion). The spinal cords were examined 44 to 63 days after the operation by means of intracellular fluorescent dye injections and electrophysiology. Extracellular stimulation of whole cords showed that action potentials in most of the electrically treated preparations were conducted in both directions across the lesion, but they were not conducted in either direction in most of the sham-treated controls. In most of the electrically treated animals, processes from giant axons with swollen irregular tips, indicating active growth, were seen in or across the lesion. Only a few of the sham-treated controls showed these features. It is possible that these facilitated regenerative responses were mediated by the effects of the artificially applied electric fields on the natural steady current of injury entering the spinal lesion.

Corneal wick electrode for recording bright flash electroretinograms and early receptor potentials.

We developed a corneal wick electrode that is free of photovoltaic artifact when used with a bright flash strobe and is convenient for routine clinical application. The corneal wick electrode is employed for bright flash electroretinogram (ERG) recordings and for research measurements of the early receptor potential. The wick electrode gives accurate, stable, reproducible recordings with an amplitude comparable to that obtained with standard contact lens electrodes.

Separation of the total TQ-ST deflection intoits component TQ and ST deflections using a mobile epicardial wick electrode in porcine myocardial ischemia

Summary Simultaneous DC- and AC-coupled epicardial electrocardiograms (ECGs) were recorded from a mobile epicardial wick electrode during myocardial ischemia in a total of seven open-chest pigs and were used to separate the total TQ-ST deflection into its component TQ and ST deflections. A wick epicardial electrode made of a steel wire tipped with a high density polyurethane foam saturated with normal saline (+KCl, 4 mEq/L) was swept swiftly back and forth across the ischemic border. Relatively rapid passage of the epicardial wick electrode into and out of the zone of ischemia allowed the electrocardiographic baseline to remain constant using both the AC- and DC-coupled systems; the deviation of the electrocardiographic baselines were usually within ±0.5 mV. Total TQ-ST deflection, TQ segment depression, ST segment elevation, and the ratio of ST segment elevation to TQ segment depression (ST/TQ ratio) were calculated for each system. Reproducibility of results was excellent. Strong correlations were observed between DC- and AC-coupled systems for total TQ-ST deflection (r=+0.994, p

Pacemaker activity in the circular smooth muscle of frog stomach

Wick and pressure electrode recording were used to locate the sites where spontaneous activity originates in isolated bundles of the circular smooth muscle layer of frog stomach. In long bundles up to three pacemaker regions were found to be active. Electrical activity of pacemaker regions as recorded with pressure electrodes is characterized by a distinct prepotential which has not been observed to precede action potentials of other regions of the bundle. Pacemaker sites are up to 8 mm away from each other. They appear to be spatially fixed and do not shift with time. When pacemaker regions were excised, we did not observe spontaneous activity in the remaining segments. Stimuli which usually induce activity in latent pacemaker regions are ineffective in such segments. Along the circumference of intact muscle rings of the stomach also three pacemaker regions have been located. Pacamaker frequency increases in aboral direction and is one per minute in the fundus region and 6 per min in the pyloric region.

Fast light-evoked potential from leaves.

When a leaf is illuminated with an intense flash of light, an elec trical response with a time course in milliseconds can be recorded. This re sponse was obtained between two wick electrodes placed at different positions on top of the leaf, with the entire leaf uniformly illuminated by the flash. During the first millisecond or so, the electrode nearer the apex of the leaf always became negative with respect to an electrode at the base, which indi cates that the voltage-generating source is fixed longitudinally in the leaf.

Electrical Activity in the Radial Nerve Cord and Ampullae of Sea Urchins*

ABSTRACT A single shock applied through wick electrodes to the isolated radial nerve cord of a sea urchin produces a recordable potential in the cord. The potential is conducted along the cord at a velocity of between 14 and 20 cm./sec. The potential is complex and graded. Two components of the potential can be identified and have different thresholds to stimulation, conduction velocities and amplitudes. They are believed to represent two classes of fibres. The potential is conducted decrementally along the cord and normally cannot be recorded at distances greater than 60 mm. from the stimulus. The amplitude of the potential decays logarithmically falling to half after 7 mm. spread. There is no facilitation of amplitude or distance of spread. Potentials initiated simultaneously at either end of the isolated nerve cord collide and partially occlude each other. Stimulation of a side branch of the nerve cord evokes potentials recordable from only ipsilateral neighbouring side branches and the whole cord. However, contractions of the contralateral ampullae following stimulation of lateral branches reveal spread of the excitation beyond the region of recordable potentials. A single shock to a cord still attached to the test causes contraction of the associated ampullae. One ampulla will contract several times after a single shock, a period of relaxation following each contraction. Electrical activity recorded from the ampullae, and lasting many seconds after the single shock, corresponds with their contractions. The activity is believed to be muscle action potentials. Evidence of a feedback from damaged tube feet to the cord, suppressing ampulla response to cord stimulation, was found.

Method For Recording Electrical Activity of the Isolated Heart

The simultaneous recording of electrical activity from two sites on an isolated mammalian heart by a simple and effective method is described. The use of agarfilled polyethylene tubing containing cotton wick electrodes offers distinct advantages compared to the usual platinum hook electrodes.

CRAB AXONS SHOWING A PROLONGED REPOLARIZATION PHASE.

A FURTHER type of response from isolated crab axons has been recorded by a new technique. The method is to thread an isolated axon through two holes in a fine polythene tube. The axon outside the tube is treated with isotonic sucrose solution and then raised into paraffin oil. Inside the tube test solutions can be flowed over the axon membrane. The effect is to produce an isolated ‘node’ of excitable membrane. Non-polarizable potassium chloride wick electrodes provide stimulating and recording connexions on each side of the ‘node’. This method gives the normal variety of responses from different fibres1. In one type of fibre, when bathed by normal sea-water, the action potential shows a very prolonged repolarization phase of 25 msec with two discrete segments of 1 msec and of 24 msec, and during the later segment a supernormality develops, that is, during the falling phase of the first action potential a second action potential can be elicited by a weaker stimulus. The absolute refractory period extends for a period of 2 msec, up to the end of the first phase of the repolarization. Following this for 3—5 msec a period of typical subnormality leads to the period of supernormality which can last as long as 30 msec (Figs. 1 and 2 a and b).

Effect of nicotine on the synapse of the central nervous system.

The effect of nicotine on synaptic transmission in the frog and cat spinal cord was studied. Both a regular wick electrode and a microelectrode of the Ling-Gerard type were used. The reflex activity of the bullfrog spinal cord is facilitated by 0.01% nicotine solution, but is depressed and abolished by 0.1% solution. In the cat, intravenous administration of 150 mg/kg fails to block reflex activity, but topical application does block. The intracellular potential, of both frog and cat motoneurones, shows no change in the synaptic potential after application of the drug, but the spike appears after a shorter synaptic delay and one or more additional spikes appear. When the synaptic delay becomes sufficiently short, however, all spikes suddenly disappear, leaving the still unchanged synaptic potential. Occasionally the synaptic delay is again increased just before the spike potentials disappear. The excitability of a frog motoneurone was measured, by a recording microelectrode, before and after nicotine application. The drug first increased and then decreases excitability. Epinephrine can restore a reflex discharge depressed or abolished by nicotine. It is concluded that high concentrations of nicotine block synaptic transmission in the central nervous system, acting on the cell body but not on the synaptic potential.

Midbrain Response to Electrical Stimulation of the Optic Nerve

Evoked potentials to electrical stimulation of the optic nerve were recorded by a wick electrode and also with a KCl-filled microelectrode from the optic tectum of the carp. 1. The potential consisted of two positive spikes of about 1 msec. in duration, a positive deflection of a few msec. and a negative one of about 10 msec. The latter was followed by a second negative deflection when the stimulus was sufficiently strong. 2. The negative deflections, especially the second, were facilitated at first, but depressed later by topical application of d-tubocurarine. The second negative deflection was augmented by strychnine. All the positive components were not affected by these drugs. 3. The negative deflection could not follow repetitive stimulation at a rate higher than about 60 cps., but the positive components could. 4. When a microelectrode was inserted into the optic tectum, the negative deflections reversed their sign at a certain depth. The depth of phase reversal was a little deeper with the second deflection. The positive components showed no phase reversal. 5. By simultaneous recording of the action potential of the opti nerve and the evoked potential it was confirmed that the two precedin; positive spikes of the evoked potential are of presynaptic origin. 6. Based on the findings stated above it was inferred that the firs negative deflection represented synaptic potentials at receiving cells, an_??_ that polysynaptic excitation produced the second negative deflection.

Relation Between Resting and Action Potential in the Frog Eye.

It has been observed that the magnitude (b-wave) of the action potential elicited from the excised frog eyeball in response to a light stimulus varies with the magnitude of the resting potential,1 other conditions remaining constant. It has further been reported2 that the above direct relation was consistently observed in the dark-adapted eyes of intact curarized frogs.These observations imply that the sensitivity of the retina, measured by the retinal electric response to a constant intensity, constant duration light stimulus, is determined by the resting potential as well as by the state of adaptation.3 The theoretical importance of this implication indicates the necessity for quantitative data.Method. Experiments were performed on two types of frog eye preparations: (1) excised but intact eyeballs of frogs (Rana pipiens) and (2) excised enucleated eyeballs. Electrical contact with the eyes was made through agar impregnated wick electrodes connected to calomel half cells. Resting potentials were measure...

Influence of Local Applications of Potassium Chloride on Action Current of the Mammalian Heart.

In experiments previously reported, it was found that application to the surface of the heart (cat, dog, rabbit) of squares of filter paper soaked in M/10 or M/5 KC1 solutions, produced changes in the electrocardiogram similar to those which follow various types of injury to the heart, except that the potassium effects quickly subsided following removal of the solution. Generally accepted views of the action of potassium ions in the heart and elsewhere suggest that the electrocardiographic changes produced by the application of potassium to the surface of the heart result from the reversible extinction of the action current at the point of application. Potassium chloride has in fact been employed to abolish electrical activity at selected regions in muscle and thus to permit recording of monophasic action currents. We have performed a series of experiments to determine whether potassium has a similar effect when applied to the surface of the heart, and found that we could obtain monophasic action currents from the surface of the dog's heart by use of potassium chloride, in M/10, M/5, or isotonic solutions. Electrograms were obtained by wick electrodes soaked in Ringer's solution placed on the anterior surface of the heart, one on the right and one on the left ventricle The wicks led to silver-silver chloride electrodes, and these were connected to a 100,000 ohm potentiometer from which one-fifth of the potential was recorded by an amplifier-type electrocardiograph (Cardiette). Sensitivity was approximately 2 mm per millivolt. After controls were taken, first one and then the other electrode was replaced by a wick soaked in the potassium solution. This procedure yielded monophasic records, and when the leads were arranged so that the spike was upright, the monophasic wave from the right ventricle was upright, while that from the left ventricle was inverted (Fig. 1).

Avitaminosis B1 and Pigeon Brain Potentials

Since vitamin B1 lack disturbs the normal carbohydrate metabolism of brain, it was desirable to follow its influence on brain potentials. Pigeons were standardized on a stock diet for 30 days, then on a diet of polished rice and salt.1 Although deficient in other nutritional elements, only vitamin B1 lack could play a role within the time limits, for typical beri-beri symptoms (opisthotonus) developed in 30–40 days. A small portion of the calvarium over the occipital portion of one cerebral hemisphere was removed under nembutal (30 mg/kg, sufficient to relax the rigid muscles) and the exposed brain kept moist and warm with Ringer. Potentials were led off (different electrode on exposed brain; indifferent on bone over opposite hemisphere) with Ag-AgCl wick electrodes,2 amplified and recorded with a crystograph. When desired, 2–5 mg of crystalline vitamin B1 were injected intramuscularly, administered orally, or both. At the conclusion of the experiment, the scalp was sewn together. Despite the absence of a...