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PubMed1978

[Polarographic measurements of PO2 with a 95% response time of 7-10 msec (author's transl)].

A fast PO2 tracing with 95% delay times of 15-20 msec in routine is necessary for measurement of the PO2 jumps in the expired air, particularly for the precise measurement of the so-called dead-air plateau. A Clark type PO2 electrode has been developed which has the demanded property. This electrode has four characteristic features: (1) a glasscoated Pt cathode with a tip diameter of 0.3 mm (diameter of the Pt wire = 0.1 mm); (2) a differential screwdrive for feeding the cathode 50 micrometer per turn; (3) a 0.2- to 0.3-micrometer-thin polytetrafluorethylene membrane, and (4) a special polishment of the surface of the cathode. The electrode has a 95% response time of 15-20 msec in routine when tracing PO2 changes from 150 to 750 mm Hg. About 30% of the prepared electrodes have response times of 7-10 msec. The output of the electrode in air is stable within the first 3 h (deviation smaller than 0.2%) and then decreases within 10 h approximately 1% per hour. The response times are constant for more than 48 h. The output of the electrode is linear from 0 to 760 mm Hg PO2. Within the accuracy of measurement the output is independent of PCO2.

Electrodes↗
PubMed1987

Novel cholinesterase expression in the HuH-7 cell line.

On polyacrylamide gradient gel electrophoresis, normal serum cholinesterase was separated into seven isozymes (I-VII from the anodic to the cathodic side). The enzyme of the conditioned medium of the HuH-7 cell line, established from a human hepatoma, had two main isozymes. The one migrating faster was located slightly to the cathodic side of band II of the normal serum enzyme, and the other, a slower one, electrophoresed at the same position as that of band VI of the normal serum enzyme. Aside from these two isozymes, a faint band with enzyme activity sometimes appeared at a position just cathodic or very close to the position of band I of the normal serum isozymes. The effect of some inhibitors and activators on both the normal serum enzyme and the enzyme of the conditioned medium was similar, but lectin-binding properties of the two enzymes were different with Ricinus communis agglutinin I, concanavalin A and wheat germ agglutinin. These results suggest that the difference in sugar moieties of both enzymes is expressed in D-galactose, D-mannose and N-acetylglucosamine.

Carcinoma, Hepatocellular↗
PubMed1986

Comparison of the defibrillation threshold and the upper limit of ventricular vulnerability.

To examine the relationship between the defibrillation threshold and the strength of shocks that induce ventricular fibrillation during the vulnerable period, we determined the defibrillation threshold in 22 open-chest dogs using epicardial defibrillation electrodes with the cathode at the ventricular apex and the anode at the right atrium. We also determined whether there was an upper limit of shock strength that induces fibrillation in the vulnerable period by giving shocks of various energy through these same electrodes during the repolarization phase of paced rhythm. The above determinations were also made with the anode at the ventricular apex and the cathode at the right atrium in eight of the dogs and with the cathode at the ventricular apex and the anode at the left atrium in another eight of the dogs. In all dogs for all electrode configurations, there was an upper limit to the shock strength that induced ventricular fibrillation during the vulnerable period. Depending on the electrode combination, this upper limit of ventricular vulnerability either was not significantly different from or was slightly lower than the defibrillation threshold. The correlation coefficient between the two was highly significant for all three electrode configurations. These results support the hypothesis that successful defibrillation with epicardial electrodes requires a shock strength that reaches or exceeds the upper limit of ventricular vulnerability and that shocks slightly lower than the defibrillation threshold fail because they reinitiate ventricular fibrillation by stimulating portions of the myocardium during their vulnerable period.

Animals↗
PubMed1986

Hematologic effects of the high-energy endocardial ablation technique.

Ablation of atrioventricular conduction is now widely accepted in the management of supraventricular arrhythmias. Reports of high temperatures, high pressures, and gas production suggest that there may be adverse effects on the blood, the electrode, and the cardiovascular system. In this investigation, using samples of fresh, heparinized pig blood, we measured hemolytic damage, the liberated gas volume and composition, and electrode erosion associated with high-energy electrical ablation. The blood was tested in a 10 liter tank at room temperature. Impulses of 10 to 400 J were applied to new USCI No. 6F bipolar pacing electrodes using both positive and negative polarities. Voltage and current waveforms were recorded. The volume of gas liberated with cathodal electrodes was 0.50 microliter/J up to 50 J and 0.29 microliter/J above 100 J. It was composed predominantly of hydrogen and nitrogen, with carbon dioxide and oxygen. With positive electrodes, the gas volume was linearly related to energy at 4.34 microliter/J up to 200 J and also contained carbon monoxide. The hemolysis was directly proportional to impulse energy for both cathodal and anodal electrodes, being 1.37 microliter/J and 4.48 microliters/J, respectively. Electrode erosion was substantial but clinically acceptable. We conclude that there are marked differences in the energy conversion processes and, where the same energy can achieve a comparable clinical effectiveness, there are advantages in using a cathodal electrode polarity. It is also advisable to use lower energies.

Animals↗
PubMed1995

Improved defibrillation threshold with a new epicardial carbon electrode compared with a standard epicardial titanium patch.

BACKGROUND: Recent studies show that depending on the type of shock morphology used, 5% to 15% of patients requiring implantable defibrillators cannot be treated with a nonthoracotomy system. In these cases, an epicardial patch-based system becomes necessary. In this study, we investigated a newly developed epicardial carbon electrode as an alternative to a standard epicardial titanium patch. METHODS AND RESULTS: A tubular epicardial braided carbon electrode of 7F diameter and 14-cm length applied in a U-shape to the epicardium was compared with a standard left ventricular epicardial 15-cm2 titanium mesh patch (CPI Inc). As cathode, a CPI endocardial lead, a Medtronic lead, or a carbon-platinum-iridium prototype electrode was used. Ventricular fibrillation was induced with a 60-Hz generator and allowed to continue for 10 seconds before a shock was given. Two different biphasic shock waveforms (3.2/2- and 6/6-millisecond) were delivered by the six electrode configurations. Eight dogs (weight, 24.5 +/- 1.3 kg) underwent an up-down defibrillation protocol. The order of testing the epicardial electrodes, the endocardial cathodes, and the waveform was randomized. With the epicardial carbon electrode, the mean defibrillation threshold (DFT) energy decreased 39% to 56% and the voltage decreased 24% to 35% compared with the titanium patch: from 8.3 +/- 2.5 to 4.9 +/- 3.6 J with the CPI lead and the 3.2/2-millisecond waveform, from 6.2 +/- 2.5 to 2.9 +/- 2.1 J with the carbon-platinum-iridium prototype, and from 6.4 +/- 3.4 J to 3.5 +/- 2.6 J with the Medtronic lead (P < or = .05). The DFT determinations with the 6/6-millisecond biphasic waveform showed a similar trend with slightly higher values. CONCLUSIONS: Compared with a titanium patch, the new braided epicardial electrode significantly decreases the defibrillation energy requirements. This effect can be maximized by using an endocardial carbon-platinum-iridium prototype as cathode and a short duration biphasic waveform.

Animals↗
PubMed2003

Electric fields and MAP kinase signaling can regulate early wound healing in lens epithelium.

PURPOSE: To use lens epithelial cell monolayer wounds as a model system for the aberrant cell migration underlying posterior capsule opacification (PCO) and to investigate the effects of an applied physiological electric field (EF) on monolayer wound healing. METHODS: Scratch wounds were made in cultured bovine lens epithelial monolayers, and the wounds were exposed to an EF, with or without U0126 treatment (an inhibitor of active extracellular signal-regulated kinase [ERK 1/2]). Serial wound images were taken and wound areas were measured. Western blot analysis and immunocytochemical staining for ERK 1/2 in the wounded monolayers were performed. RESULTS: An applied EF of a given polarity influenced the healing of lens epithelial monolayer wounds. Wounds facing the anode healed at normal rates, those facing the cathode closed much more slowly. U0126, an inhibitor of mitogen-activated protein kinase (MAPK) signaling, inhibited wound healing, with or without exposure to an EF. Western blot analysis showed that both wounding and application of an EF enhanced the activation of ERK 1/2 independently and that U0126 completely inhibited these activations of ERK 1/2 in monolayers. Immunocytochemical staining showed an asymmetric activation of ERK 1/2 in EF-exposed wounds, with much weaker fluorescence in cathode-facing wounds, which could contribute to differentially directed wound-healing rates in an EF. CONCLUSIONS: Exposure to an EF inhibited the healing of lens epithelial monolayer wounds facing the cathode. ERK signaling pathways were involved in healing of lens epithelial monolayer wounds and in the EF-directed migration of the wound edge. It may be possible to use an applied EF to regulate the aberrant migration of lens epithelial cells that results in PCO after cataract surgery.

Animals↗
PubMed1988

Short term efficacy of applied electric fields in the repair of the damaged rodent spinal cord: behavioral and morphological results.

The short term effects of electric fields applied exogenously to the contused rat spinal cord were studied in a blind experiment. A DC field using 3 microA was applied to the dorsal cord when the lesion was made, and rats were behaviorally tested weekly for up to 3 weeks on an inclined plane. The results show that the "cathode rostral" orientation group of animals performed statistically significantly better on the inclined plane than either the "anode rostral" or the "no current" group. Counts of axons in the dorsal funiculi rostral to the lesion in the "cathode rostral" group were statistically significantly greater than in other groups. The greater number of axons rostral to the lesion site coupled with the superior behavioral performance of the "cathode rostral" group suggest that this treatment may provide an environment suitable for axonal growth and can facilitate functional recovery in the damaged mammalian spinal cord.

Animals↗
PubMed2006

Endoscopic transsphenoidal pituitary surgery with intraoperative magnetic resonance imaging.

OBJECTIVE: The two most recent significant advances in pituitary surgery have been the endonasal endoscopic approach and intraoperative magnetic resonance imaging (IMRI). Each provides improved visualization of intra- and parasellar anatomy with the goal of attaining a complete resection. The combination of the two techniques has not been previously reported in the literature. METHODS: We performed endoscopic, endonasal resection of pituitary macroadenomas in 15 patients using the Polestar N-10 (0.12T) IMRI (Odin Medical Technologies, Inc., Newton, MA). Eleven patients had nonfunctioning tumors, three had acromegaly, and one had a medication-resistant prolactinoma. The effect of the magnetic field on the cathode ray tube screen and the image quality of the IMRI images were assessed. The presence of residual tumor on IMRI was noted and then re-examined with the endoscope. RESULTS: Although the Polestar N-10 is a low Tesla magnet, the IMRI caused significant distortion of the cathode ray tube screen regardless of the viewing angle. This was overcome with the use of a wall-mounted plasma screen. IMRI images were obtained in all cases and were of sufficiently high quality to demonstrate adequate decompression of the optic chiasm and the removal of all suprasellar tumor. In three cases, residual tumor was found with IMRI that was resected endoscopically before the completion of surgery. In four other cases, potential residual tumor was examined endoscopically and found to be normal postoperative change. In eight cases no residual intrasellar tumor was seen on the IMRI. Preresection visual deficits improved in all cases and the insulin-like growth factor levels normalized in two of three cases. There were no delayed cerebrospinal fluid leaks. CONCLUSION: Combining intraoperative endoscopy and IMRI is feasible and distortion of the cathode ray tube screen can be overcome with the use of either a plasma or liquid crystal display screen. Each technology provides complementary information, which can assist the surgeon in safely maximizing the extent of resection. In this small series using a low-field magnet, rates of residual tumor following endoscopic transsphenoidal surgery were less than have been reported following microscope-based transsphenoidal surgery.

Adenoma↗
PubMed1987

Spinal neurite reabsorption and regrowth in vitro depend on the polarity of an applied electric field.

Retraction and regrowth of frog neural tube neurites have been studied in vitro in control cultures and in the presence of a small, continuously applied electrical field. In control cultures, some degree of retraction was seen in 39% of neurites while 7% were reabsorbed completely. Reabsorption of anodal-facing neurites was at least twice as common, with 67% showing some retraction and 17% almost totally reabsorbed. Cathodal-facing neurites were spared from retraction. Following extreme reabsorption of anodal-facing neurites, reversal of the electric field promoted regeneration in 47% (9/19) of cases studied. growth cone morphology also was determined by the polarity of the applied field. Anodal-facing growth cones had fewer filopodia than cathodal-facing growth cones sharing the same cell body. Field reversal induced a polarity-specific change in filopodia number on individual growth cones: a shift from anodal to cathodal increased filopodia numbers and vice versa. Some possible mechanisms involved and the significance of these results are discussed.

Animals↗
PubMed1989

Nerve growth in the absence of growth cone filopodia and the effects of a small applied electric field.

Nerve orientation may involve a biasing of the distribution of tension at the growth cone. Chemical and electrical guidance cues cause more filopodia to appear on one side of the growth cone and this may determine turning behaviour. In a small applied electric field, filopodia predominate on the cathodal side of the growth cone and nerves turn towards the cathode. Removing all filopodia by treatment with cytochalasin D did not prevent nerves from continued slow growth and nerves still oriented towards the cathode. It is concluded that nerves can perform some types of orienting behaviour in the complete absence of filopodia.

Actins↗
PubMed1990

Nerve growth in a small applied electric field and the effects of pharmacological agents on rate and orientation.

The rate of growth and orientation of embryonic Xenopus nerves exposed to pharmacological agents, to an applied electric field or to both simultaneously were studied. The adenyl cyclase activator forskolin (100 microM) induced a threefold increase in the rate of elongation, as did an electric field alone. Together, their effect in augmenting rate of growth was additive, but only at a concentration of 50 microM forskolin. The normal pattern of faster growth towards cathode than anode was not present in nerves treated with the lectin concanavalin A, which also inhibits normal turning behaviour towards the cathode. Nerve orientation towards the cathode and augmented rates of growth were found in the presence of forskolin or ganglioside GM1. It is suggested that a combined approach of drug treatment and an applied electric field may be useful in promoting nerve regeneration.

Animals↗
PubMed2003

Hemoglobin function in deep-sea and hydrothermal-vent endemic fish: Symenchelis parasitica (Anguillidae) and Thermarces cerberus (Zoarcidae).

Deep-sea hydrothermal vents probably provide the harshest physico-chemical conditions confronting metazoan animals in nature. Given the absence of information on hemoglobin (Hb) function in hydrothermal-vent vertebrates, and the complex molecular and functional adaptations observed in hydrothermal-vent invertebrates, we investigated the oxygenation reactions of Hbs from the vent-endemic zoarcid Thermarces cerberus and the deep-sea anguillid Symenchelis parasitica from adjacent habitats. Electrophoretically cathodic and anodic isoHbs from S. parasitica exhibit radical differences in O(2) affinity and pH and organic phosphate (ATP) sensitivities, reflecting a division of labor as in other 'class II' fish that express both Hb types. Remarkably, the cathodic Hb (I) lacks chloride sensitivity, and the anodic Hb (II) shows anticooperativity near half-saturation at low temperature. T. cerberus isoHbs exhibit similar affinities and pH sensitivities ('class I' pattern) but much higher O(2) affinities than those observed in Hbs of the temperate, shallow-water zoarcid Zoarces viviparus, which, unless compensated, reveals markedly higher blood O(2) affinities in the former species. The temperature sensitivity of O(2) binding to T. cerberus Hbs and the anodic S. parasitica Hb, which have normal Bohr effects, is decreased by endothermic proton dissociation, which reduces the effects of ambient temperature variations on O(2) affinity. In the cathodic S. parasitica Hb, similar reduction appears to be associated with endothermic conformational changes that accompany the oxygenation reaction.

Adaptation, Physiological↗
PubMed2002

Macroradiography using conventional radiographic X-ray equipment.

Macroradiography is a radiographic imaging technique used to increase the size of the image relative to that of the object. Macroradiographic images suffer degradation due mainly to geometric unsharpness (U(g)). U(g) results from the finite size of the focal spot of the X-ray tube. Specialized equipment with a small effective focal spot size (Eff FSS) is generally used to perform macroradiography. The specialized nature of the equipment means macroradiographic examinations are not commonly undertaken. Macroradiographic examinations can also be performed on conventional radiographic equipment because the Eff FSS varies in the X-ray beam along the cathode-anode axis. Calculations and measurements of FSSs at different positions along the cathode-anode direction of the X-ray beam have been made. A simple technique of angling the X-ray tube 10 degrees towards the cathode reduces the Eff FSS in one dimension while still maintaining a vertical central ray. Reduced beam coverage results from this technique and an increase in radiographic exposure is required to compensate for the anode heel effect. Macroradiographic images of line pair phantoms and a hand-wrist phantom, at various tube angles, have been obtained to compare image detail.

Mathematics↗
PubMed2003

Attenuated total reflection surface-enhanced infrared absorption spectroscopy of carboxyl terminated self-assembled monolayers on gold.

A new recipe for surface-enhanced infrared absorption (SEIRA) active island Au films with improved adhesion in aqueous solution, low resistivity, and enhancement of the infrared (IR) absorption of about 300 was developed. The Au films prepared were utilized in studies of the ionization of self-assembled monolayers of 11-mercaptoundecanoic acid in Na2SO4 aqueous solutions by attenuated total reflection surface-enhanced infrared absorption (ATR-SEIRA) spectroscopy. It was found that the carboxyl end groups of the self-assembled monolayer turn into carboxylate anions on going from anodic to cathodic potentials or from acidic to alkaline pH. The water molecules close to the self-assembled monolayer in acidic solutions or at anodic potentials are preferentially aligned with their dipole moments parallel to the interface. This type of alignment can be ascribed to the dipole-dipole interaction between the carboxyl groups and the water molecules. On the other hand, in alkaline solutions or at cathodic potentials the structure of water close to the self-assembled monolayer is essentially bulk-like, with randomly oriented water molecules. This observation suggests that in alkaline solutions or at cathodic potentials the charge of the carboxylate anions is almost completely compensated for by strongly adsorbed counter cations. As a result, the electric field close to the surface of the ionized self-assembled monolayer is weak and has little influence on the orientation and hydrogen bonding of the water molecules.

Carbon Dioxide↗
PubMed2005

Exposure of human leukemic cells to direct electric current: generation of toxic compounds inducing cell death by different mechanisms.

Treatment with direct electric current (DC) influences the growth of several cancer cells. In this work, we evaluated the effects of DC treatment on the human leukemic cell line HL60. Human cells were separately treated in the presence of the cathode or the anode or without contact with the electrodes. In all systems, DC-treated cells presented an impaired ability to proliferate. Growth inhibition was dependent on the generation of soluble products of electrolysis. Cathodic treatment of HL60 cells predominantly induced lysis, whereas treatment without contact with electrodes did not induce alterations in cell viability. In contrast, cell stimulation by the anode resulted in irreversible membrane damage, as demonstrated by trypan blue and 7-aminoactinomycin staining. Analysis of these cells by transmission electron microscopy indicated that necrosis is a major mechanism inducing cell death. In addition, apoptotic-like cells were observed under light microscopy after anodic treatment. Accordingly, DNA from anodic-treated cells presented a typical pattern of apoptosis. Apoptotic cell death was only generated after the treatment of HL60 cells in conditions in which the generation of chloride-derived compounds was favored. These results indicate that the nature of the products from cathodic or anodic reactions differently influences the mechanisms of cell death induced by DC-derived toxic compounds.

Cell Death↗
PubMedDate not supplied

The effect of electric field on callus induction with rape hypocotyls.

The influence of electric field treatment on dedifferentiation and calli formation on rape hypocotyls was investigated. Segments, 10 mm long, of the upper part of rape (Brassica napus L., cv. Góczański) hypocotyls were stimulated by different combinations of voltage/time (1.5 V/120 h, 3 V/3 h, 10 V/15 min and 30 V/30 s) under in vitro conditions. With all electric field treatments, segments oriented with their apical part towards the cathode produced more calli as compared to control (non-treated with electric field). Under opposite orientation slight inhibition of callus growth was observed. As the strongest effect on callus growth was observed after treatment with 30 V/30 s, this electric field treatment was selected for following analyses: the incorporation of [14C]-2,4-D (2,4-dichlorophenoxyacetic acid) and [14C]-BAP (benzylaminopurine) from the culture medium, changes in ACC (1-aminocyclopropane-1-carboxylic acid) level and the redox activity in apical and bottom parts of hypocotyls during 18 d of culture. In contrast to changes in fresh weight, electric field treatment (30 V/30 s) stimulated a higher accumulation of 2,4-D and BAP in basal parts of hypocotyls than in apical ones. Moreover, orienting the apical part towards the cathode resulted in lower uptake of hormones as compared with the opposite orientation. The ACC concentration increased, especially in the basal parts of hypocotyls, independently on electric field application. However, the highest level was observed after electric field treatment with orientation of the apical part towards the anode. The distribution of oxidative substances (measured as the amount of ferric ions) between the apical and bottom part of hypocotyls was not changed when the apical parts were oriented towards the cathode. Under these conditions a decrease in apical and an increase in basal parts was observed during culture. Opposite orientation influenced the redistribution of oxidative substances from the first day of electric field treatment. Based on these results we suggest that electric field action can be connected with its influence on specific concentration of oxidative substances and hormone distribution in cells.

Brassica napus↗
PubMedDate not supplied

2,4-dichlorophenol degradation by an integrated process: photoelectrocatalytic oxidation and E-Fenton oxidation.

A new reactor system was designed for an integrated process involving photoelectrocatalytic oxidation (PECO) and electro-Fenton (E-Fenton) oxidation. Its efficiency was evaluated in terms of 2,4-dichlorophenol (2,4-DCP) degradation in aqueous solution. In this process, a TiO2 electrode and an iron (Fe) electrode were used as anodes in parallel, while graphite felt (GF) was used as a cathode. When an electrical current is applied between the anodes and the cathode, the iron anode can release Fe2+ and the GF cathode can generate H2O2 continuously in the reaction solution. Under UV-A illumination, while a H2O2-assisted PECO reaction occurs on the surface of the TiO2 photo anode, an E-Fenton reaction takes place in the solution. The experimental results demonstrated that 2,4-DCP degradation in aqueous solution was greatly enhanced because of the interaction between the two types of reactions. Moreover, the effect of pH as an important factor was investigated. It was found that the combined reaction becomes less pH sensitive than the typical E-Fenton reaction and may be suitable for application in a wide pH range.

Catalysis↗
PubMed2003

Voltammetric method based on an ion-pairing reaction for the determination of trace amount of iodide at carbon-paste electrodes.

Carbon-paste electrodes (CPEs) were studied to elucidate the cathodic stripping voltammetric determination of iodine. At an accumulation potential of 1.0 V (vs. SCE), iodide was preconcentrated on CPEs via an ion-pairing reaction, followed by oxidation to iodine. Then a linear scan voltammogram was recorded after 10 s of quiescent time by a cathodic potential scan from 0.7 V to 0.1 V at a scan rate of 100 mV s(-1). A cathodic peak current was obtained at about 0.38 V. Various experiment parameters such as the acidity, chloride concentration, accumulation potential, accumulation time, concentration of cetyltrimethylammonium bromide (CTAB) and scan rate, were optimized to analyze the iodide by employing linear-scan stripping voltammetry. Under the optimal conditions, calibration curves were obtained over a wide concentration range of the iodide ion from 8 x 10(-9) mol L(-1) to 5 x 10(-6) mol L(-1) with a detection limit of 2 x 10(-9) mol L(-1) at an accumulation time of 3 min. The effect of interfering species was evaluated and the procedure was applied to an iodide analysis in table salt, with good results.

Journal Article↗