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PubMed1979

Electrochemical investigations on the oxygen activation by cytochrome P-450.

The application of cytochrome P-450 in substrate conversion is complicated both due to the limited stability and the cofactor regeneration problems. To overcome the disadvantages of NADPH consumption the transfer of the reduction equivalents from an electrode into the cytochrome P-450-system was studied: 1. NADPH was cathodically reduced at a mercury pool electrode. By immobilization of NADP on dialdehyde Sephadex the reductive recycling was possible. 2. Different forms of reduced oxygen were produced by the cathode: a) The reaction of O2- with deoxycorticosterone yields a carboxylic acid derivative. In contrast the cytochrome P-450 catalyzed NADPH-dependent reaction with the same substrate gives corticosterone, O2- represents only an intermediate in the activation of oxygen and is not the "activated oxygen" species. b) Molecular oxygen was reduced to HO2- and H2O2, respectively. The interaction of adsorbed cytochrome P-450 on the electrode surface with the reduced oxygen species in the absence of NADPH was studied. The electrochemically generated peroxide seems to be more active than added H2O2. 3. In a model of electro-enzyme-reactor several substrates were hydroxylated by microsomal cytochrome P-450 with cathodically reduced oxygen which substitutes NADPH.

Animals↗

PubMed1980

Radioimmunoassay of trypsin-like substance in human serum.

A radioimmunological method for circulating trypsin-like substances was set up, using cathodic trypsin (isolated from human pancreas) as immunogen, reference standard and material to label, and bovine serum to stabilize the system. The assay scheme included a bound-free separation by polyethylene-glycol precipitation after a 1-h incubation at room temperature. Some relevant points emerged from the validation experiments: a) the assay proved simple and reliable, meeting both requirements of a prompt clinical response and of a high sensitivity level (1.5 ng/ml or less); b) evidence was added to the view that cathodic trypsinogen is the immunoassayable species present in the blood stream; c) the parallelism of the radioimmunological responses of cathodic trypsin and trypsinogen demonstrated that a self-consistent analytical information may be derived using either references; d) the absence of detectable amounts of trypsin-like substances in sera from totally-pancreatectomized patients (3 cases) indirectly confirmed the organ-specificity of the measurement; e) a "normal" level of 27 +/- 8 ng trypsin equivalent/ml (X +/- SD, n = 82) resulted: some much higher literature data, all related to a single radioimmunoassay system (RIA-Gnost trypsin kit, Hoechst, FRG), are seemingly explained by the different purity observed for the reference materials.

Humans↗

PubMedDate not supplied

Bone formation and impedance of electrical current flow.

The impedance to current flow to an electrically stimulated cathode did not change appreciably over a 12-week measurement period and did not support the hypothesis of a temporal relationship between bone formation and impedance to current flow in the region of the cathode. The use of an electrically stimulated titanium cathode at a current density of 0.33 microA/mm2 in this model of canine delayed union resulted in a significant bone formation when analyzed by quantitative and qualitative methods. Sequential quantitative radionuclide scanning correlated well with histologic appearance of bone formation and was a sensitive indicator of electrically induced osteogenesis.

Animals↗

PubMedDate not supplied

[Coincidence of the process of hydrogen-oxidizing bacterial culture and nutrient medium electrolysis].

The main factors limiting the possibility of organizing the cultivation of the hydrogen-oxidizing bacterium Alcaligenes eutropha Z-1 in combination with electrolysis were determined: accumulation of the oxidizing agents (hypochlorite, persulfate ions, hydrogen peroxide) in the process of electrolysis and deposition of microelements contained in the growth medium on the cathode. The limits for the susceptibility of the bacterium to the oxidizing agents were established. The rate of accumulation of the oxidizing agents and formation of the cathode deposit were found to depend on the current density, the pH and composition of a solution, and several other factors. The concentration of hypochlorite decreased if the content of chloride ions in the growth medium was reduced to approximately 10(-5) g/l; the concentrations of persulfate and hydrogen peroxide is decreased using a certain electrolysis regime and adding ferrous ions which reduce the oxidizing agents. The cathode deposit is dissolved by periodically reversing the current in the course of electrolysis.

Alcaligenes↗

PubMed1994

Binaural monopolar galvanic vestibular stimulation reduces body sway during human stance.

The influence of monopolar binaural galvanic stimulation of the vestibular system was studied on body sway. Subjects, with eyes closed, were standing on a hard support or on foam rubber. Their body sway was registered on a force platform at intervals of 50 s. Both polarities of direct current with intensity 1 mA were used as a galvanic stimulus during the whole recording interval. Changes of body sway amplitude and velocity were analyzed in situations with and without galvanic stimulation on two different support surfaces. In stance on the hard support, the cathodal polarization of labyrinths (in most subjects) reduced body sway velocity and decreased body sway slightly in the anteroposterior direction. Anodal polarization of labyrinths during 50 s did not affect the body sway parameters. The results on the foam rubber platform exhibited a significant reduction of body sway velocity induced by both anodal and cathodal polarization of the labyrinths. The decrease of body sway in the anteroposterior direction was also observed during cathodal polarization. The stabilizing effect of vestibular binaural monopolar stimulation on the upright stance was mainly observed in the postural control situation where the leg proprioceptive input was changed (stance on soft surface) and the role of vestibular input was more important.

Adolescent↗

PubMed1977

Diaphragm pacing. Evaluation of current waveforms for effective ventilation.

To evaluate the effectiveness of the configuration of the stimulating waveform on diaphragm pacing, we evaluated several different current forms: UDC-bipolar, UDC-monopolar cathodal, UDC-monopolar anodal, and ABDC. During stimulation with a pulse interval of 37 msec., a decrease in tidal volume was observed during the initial 30 hours with UDC-bipolar and UDC-monopolar anodal waveforms. Both UDC-monopolar cathodal and ABDC stimulation maintained the initial effectiveness for 6 hours. The decrease in tidal volume of UDC-monopolar anodal closely paralleled that of UDC-bipolar stimulation. Decreasing the pulse interval to 20 msec. caused a decrease in tidal volume with both UDC-monopolar cathodal and ABDC waveforms. Arterial oxygen tension (PaO2) in these experiments decreased to about 60 mm. Hg soon after the onset of unilateral diaphragm pacing. The concomitant decrease in tidal volume seen with UDC-bipolar stimulation could be avoided through the administration of oxygen to keep the animal's PaO2 about 100 mm. Hg. The amplitude of the evoked diaphragmatic action potentials decreased significantly under hypoxemia and returned to normal with hyperoxygenation. From these short-term experiments, our findings indicate that waveform configuration does influence the time of onset of diaphragm fatigue due to either an neuromuscular junction. Further, hypoxemia accelerates the occurrence of fatigue.

Acetylcholine↗

PubMed1995

Observation of ZnO particles grown by electrochemical reaction of Zn.

The electrochemical reaction of Zn is investigated by scanning electron microscopy and transmission electron microscopy. Zn films are used as anodes, loaded at DC voltages of 10-200 V in distilled water at 20 degrees C. Zn ions diffuse from the anode and are coupled with OH ions to form spindle-like ZnO particles of 1-2 microns on the cathode or on a permeable paper barrier placed between the anode and cathode. Formless layers, which are composed of fine ZnO crystallites of several nanometers or less in size, form on the cathode in the water at lower OH ion density before the growth of the spindles. They become spindle-shaped after only a few minutes of water bath treatment at 60 degrees C.

Electrochemistry↗

PubMed1979

Cross-reactions between serum proteins and water soluble liver tissue antigens of the nine-banded armadillo (Dasypus novemcinctus Linn.) and man.

Cross-reactions between serum proteins and water soluble liver antigens of the nine-banded armadillo (Dasypus novemcinctus Linn.) and man were studied by crossed immunoelectrophoresis (CIE). Armadillo serum tested with rabbit antiserum against human serum proteins gave twelve components in CIE. Nine of these cross-reacting proteins were identified and showed partial identity with the corresponding human proteins. The electrophoretic mobility of alpha 2-macroglobulin and Gc-globulin differed in the two species. An ultrasonicate of normal armadillo liver gave twenty-eight anodic and eight cathodic components in CIE. By absorption experiments with armadillo serum, twenty of the former and seven of the latter were shown to be liver tissue components. A combination of CIE and crossed-line immunoelectrophoresis (CLIE) revealed the presence of twelve anodic and six cathodic liver tissue components cross-reacting with man. A cathodic armadillo liver antigen called (CALA-17) showed partial identity with that of man both in tandem and fused rocket immunoelectrophoresis. The implications of the findings are discussed in relation to the use of armadillo-grown M. leprae for skin testing and other purposes in man.

Animals↗

PubMed1996

Instrumental effects on in situ electrochemical STM studies: an investigation of a current surge induced Pd deposit on HOPG.

Knowledge of instrumental complications is vital both in interpreting experimental observations and in achieving true results. In a study of palladium electrodeposition on highly ordered pyrolytic graphite by in situ electrochemical scanning tunnelling microscopy, some unexpected experimental artefacts caused by instrumental design and tip-surface interactions have been recognised. The electrodeposition system employed in our in situ studies has been found to be very sensitive to an initial cathodic current surge when the potentiostat control was applied to the electrodes at the measured open circuit potential. As a result, palladium and/or hydrogen were immediately deposited on the graphite surface within a small radius under the imaging tip. The cause of this current surge was investigated and found to be related to the performance of the potentiostat. The deposit was removed either by anodic potential sweeps or under positive local electric fields of the imaging tip. Further cathodic deposition was possible on the surge-induced deposit. Characterisation, by ex situ x-ray diffraction, atomic force microscopy, scanning transmission electron microscopy and high resolution electron microscopy, showed that the deposits were Pd. Use of the various techniques demonstrated their complementarity in studies of the structure and dimensions of surface deposits.

Electrochemistry↗

PubMed2000

Neurotrophins enhance electric field-directed growth cone guidance and directed nerve branching.

Neurotrophins play major roles in the developing nervous system in controlling neuronal differentiation, neurite outgrowth, guidance and branching, synapse formation and maturation, and neuronal survival or death. There is increasing evidence that nervous system construction takes place in the presence of dc electric fields, which fluctuate dynamically in space and time during embryonic development. These have their origins in the neural tube itself, as well as in surrounding skin and gut. Early disruption of these endogenous electric fields causes failure of the nervous system to form, or else it forms aberrantly. Nerve growth, guidance, and branching are controlled tightly during pathway construction and in vitro dc electric fields have profound effects on each of these behaviours. We have used cultured neurones to ask whether neurotrophins and dc electric fields might interact in shaping neuronal growth, given their coexistence in vivo. Electric field-directed nerve growth generally was enhanced by the simultaneous presentation of several neurotrophins to the growth cone. Under certain circumstances, more nerves turned cathodally, they turned faster, further, and in lower field strengths. Intriguingly, other combinations of dc electric field and neurotrophins (low field strength and neurotrophin 3 (NT-3) switched the direction of growth cone turning. Additionally, cathodally directed nerve growth was faster and directed branching was much more common when electric fields and neurotrophins interacted with neuronal growth cones. Given such profound changes in growth cone behaviour in vitro, neurotrophins and endogenous electric fields are likely to interact in vivo.

Animals↗

PubMed1999

Use of thiobacillus ferrooxidans in a coupled microbiological-electrochemical system for wastewater detoxification

We have developed a mixed system, electrochemical-microbiological, that can be used for detoxifying organic compounds present in wastewater. In this system, organic matter oxidation takes place at the anode of an electrochemical reactor while ferric iron reduction takes place at the cathode. We have used a growing culture of Thiobacillus ferrooxidans to regenerate the ferric ions consumed. The culture is used as the catholyte (solution in the cathode compartment) of the system and is therefore permanently subjected to an electric field. We have verified that, under our working conditions, the culture is able to oxidize ferrous ions for long periods of time (up to 15 days) depending on the intensity of the applied current. We have checked the performance of this system in methanol oxidation. Our results show that it decreases the energy cost by 35% when com- pared with the pure electrochemical system traditionally used. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1998

Effect of stimulator orientation on F-wave persistence.

Most electrodiagnosis texts advocate cathode distal stimulation (CDS) for nerve conduction, but suggest cathode proximal stimulation (CPS) for F waves, because of anodal block. We postulated that CDS and CPS elicit F waves of similar persistence. We studied 657 (207 median, 204 ulnar, 136 tibial, and 110 peroneal) nerves in 225 consecutive subjects. In the median nerve, CDS elicited F waves of slightly greater persistence than CPS. Stimulator orientation did not affect F-wave persistence in the remaining nerves.

Electric Stimulation↗

PubMed1999

Effect of ion modification of commonly used orthopedic materials on the attachment of human bone-derived cells.

Biomaterials which combine optimum properties of strength and biocompatibility are desirable in improving the long-term performance of implantable medical devices. Our study is aimed at developing technology designed to alter the outer atomic layers of a material to give the desired compatibility with the tissue while retaining the properties of the bulk substratum. Materials used in this study were titanium vanadium alloy (Ti-6Al-4V) and cobalt chromium molybdenum alloy (Co-Cr). Soda lime glass discs and polyethylene terephthalate (PET) acted as controls. A cathode of either Ti-6Al-4V or Co-Cr was used to simultaneously deposit and implant identified substrata. The attachment of human bone-derived cells (HBDC) to various materials was determined using radiolabeling or colorimetric assays. Results show that HBDC adhere preferentially to the unmodified surfaces of Ti-6Al-4V and Ti-6Al-4V on glass compared to the unmodified Co-Cr surfaces and to that of the Co-Cr on glass. Depositing Ti-6Al-4V on Co-Cr gives significantly better attachment of HBDC than when depositing Co-Cr onto Ti-6Al-4V. While cellular attachment to the created surfaces reflects that of the cathodic materials, it is not identical to these materials. Ion deposition/implantation is capable of creating permanent surfaces which reflect the adhesion of source materials not bulk substrata.

Alloys↗

PubMed2000

Cellular damage and altered carbohydrate expression in P815 tumor cells induced by direct electric current: an in vitro analysis.

Treatment with direct electric current (DC) can inhibit tumor growth in several systems. To evaluate the cellular reactions generated by this treatment, we stimulated mouse mastocytoma P815 cells with DC and examined their viability and ultrastructural characteristics, as well as the effect of DC on surface carbohydrate expression. DC treatment affected cell viability and caused marked alterations in vital structures of P815 cells. Alterations varied depending on the duration of stimulation and polarity of electrode. Anodic and cathodic treatments caused decrease in cell viability, although the latter was more effective in generating cell lysis. DC stimulation also induced changes such as membrane damage, alterations in cell shape and chromatin organization, mitochondrial swelling and condensation, cytoplasmic swelling, and matrix rarefaction. Stimulation of P815 cells without contact with electrodes produced no alterations, suggesting that this contact might be essential for the occurrence of the cellular modifications. DC treatment also altered the membrane distribution of anionic sites of P815 cells, as well as the surface carbohydrate exposition, involving a diminished binding of Concanavalin A to the cell surface after cathodic stimulation, and an increased binding of sialic acid- and fucose-specific lectins after anodic treatment. In this work we describe important cellular targets for the action of DC, which may contribute to the understanding of the mechanisms by which DC supresses several kinds of tumors.

Animals↗

PubMed2002

Electrokinetic transport of red blood cells in microcapillaries.

Electrokinetic flow of a suspension of erythrocytes (red blood cells, RBCs) in 20 num cylindrical fused-silica capillaries is examined in the present work. Flow direction anomalies are observed experimentally and tentatively explained by the development of a pH gradient between the cathode well and the anode well due to electrolysis reactions at the electrodes. This pH gradient alters the local zeta potentials of both the capillary and the RBC and thus the local electroendosmotic liquid flow (EOF) velocities and RBC electrophoretic (EP) velocities. The two velocities are opposite in direction but with EOF dominating such that the RBC moves toward the cathode, opposite to the anode migration observed in bulk conditions. The opposing zeta potentials also lead to RBC aggregation at the anode end for low fields less than 25 V/cm. As the electroendosmotic velocity decreases at the anode end due to decreasing pH, pressure-driven back flow develops to oppose the original EOF at the remaining portions of the capillary ensuring constant fluid flux. When the anode EOF velocity is smaller in magnitude than the EP velocity, reversal of blood cell transport is observed after a short transient time in which a pH gradient forms. RBC velocities and pH dependencies on electric field and MgCl(2) concentration are presented along with data showing the accumulation of charge separation across the capillary. Also, a short-term solution to the pH gradient formation is presented that could help thwart development of pH gradients in micro-devices at lower voltages.

Electrophoresis, Capillary↗

PubMedDate not supplied

Determination of Se(IV) and Se(VI) in Italian mineral waters.

This paper deals with determination of selenium and analysis of its speciation in some Italian mineral waters. Selenium was determined by differential pulse cathodic stripping voltammetry (DPCSV) even if square wave cathodic stripping voltammetry (SWCSV) was also taken into consideration. The selenium determined in the mineral waters here investigated is not over 600 ng L(-1); in three samples, it was found below the detection limit. Analysis of speciation revealed that Se(VI) is the highly prevailing form present: only two of the examined samples revealed a detectable amount (few ng L(-1)) of Se(IV). DPCSV made possible to detect, in two of the samples, the presence of a specie(s) able to interact with Se(IV). The apparent interaction constant for the adduct formation was evaluated and the species concentration determined. However, the nature of such compound(s) remains unknown.

Beverages↗

PubMed2006

Suppression of cortical spreading depression in migraine prophylaxis.

OBJECTIVE: Topiramate, valproate, propranolol, amitriptyline, and methysergide have been widely prescribed for migraine prophylaxis, but their mechanism or site of action is uncertain. Cortical spreading depression (CSD) has been implicated in migraine and as a headache trigger and can be evoked in experimental animals by electrical or chemical stimulation. We hypothesized that migraine prophylactic agents suppress CSD as a common mechanism of action. METHODS: Rats were treated either acutely or chronically over weeks and months, with one of the above migraine prophylactic drugs, vehicle, or D-propranolol, a clinically ineffective drug. The impact of treatment was determined on the frequency of evoked CSDs after topical potassium application or on the incremental cathodal stimulation threshold to evoke CSD. RESULTS: Chronic daily administration of migraine prophylactic drugs dose-dependently suppressed CSD frequency by 40 to 80% and increased the cathodal stimulation threshold, whereas acute treatment was ineffective. Longer treatment durations produced stronger CSD suppression. Chronic D-propranolol treatment did not differ from saline control. INTERPRETATION: Our data suggest that CSD provides a common therapeutic target for widely prescribed migraine prophylactic drugs. Assessing CSD threshold may prove useful for developing new prophylactic drugs and improving upon existing ones.

Animals↗

PubMed2026

Operando X-ray Spectroscopy Unveils Light-Driven Redox Selectivity for Photo-Assisted Li-S Batteries.

Photo-assisted lithium-sulfur batteries (PALSBs) can accelerate the sluggish redox kinetics of sulfur cathodes. However, the introduced light field inevitably complicates interfacial reactions, necessitating in situ evidence under realistic operating conditions. Here, we construct a TiO2/FePS3 (TF) p-n junction bifunctional photoelectrode and employ a multiphysics-coupled in situ x-ray spectroscopic technique to elucidate light-regulated catalysis from the interface into the bulk. Operando low-energy XPS identifies potential interfacial catalytic sites. High-energy operando XAFS is, for the first time, applied in PALSBs to track the K-edge position of catalytic centers throughout cycling. The results show that the reversible dynamic valence evolution synchronizes with the stepwise sulfur redox process, revealing that photogenerated carriers and electrocatalytic electrons act cooperatively to promote polysulfide conversion. DFT calculations corroborate, from thermodynamic and kinetic perspectives, that illumination strengthens polysulfide anchoring and lowers the energy barriers of key conversion steps, consistent with the operando spectroscopic observations. Benefiting from this photoelectrochemical co-regulation, the TF-based PALSB maintains excellent reversible capacity and cycling stability under high sulfur loading and low electrolyte content. This work establishes a characterization paradigm for the rational design of high-performance photo-assisted Li-S cathodes.

operando x‐ray spectroscopy↗