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PubMed1982

Extracts of electric lobe and electric organ from Torpedo californica increase the total number as well as the number of aggregates of chick myotube acetylcholine receptors.

Saline extracts prepared from the electric lobe, the electromotor nerves, and the electric organ (the electromotor system) of Torpedo californica increase the number of ACh receptors on uninnervated chick myotubes in culture, while extracts from T. californica liver or skeletal muscle do not. The extracts also increase the ACh sensitivity of treated myotubes, indicating that newly synthesized receptors are functional. The active substance(s) is heat sensitive but not trypsin sensitive. Gel filtration on Bio-Gel P-150 shows that the activity is associated with a peak of low (less than 5,000-dalton) molecular weight activity. Labeling studies with rhodamine-conjugated alpha-bungarotoxin show that, in addition to their effect on receptor number, these extracts also cause aggregation of prelabeled ACh receptors on the myotube surface.

Animals↗
PubMed1982

Preliminary studies of magnetic field facilitation of electric conduction in electrically switched "on" dye films that may be room-temperature superconductors.

Some organic dyes of a double diazo structure, pressurized into thin films, show trapping of magnetic flux at room temperature, suggestive of the behavior of type 2 superconductors. Some also show switching from low to high electrical conductivity at a voltage threshold, like amorphous inorganic semiconductors. An applied magnetic field facilitates switching, as well as current flow after switching, in a dye that traps magnetic flux but not in a dye of almost similar structure that does not trap magnetic flux. For best results, the magnetic field should be applied before switching and in a direction perpendicular to current flow. The magnetic field effects observed in the dye films at room temperature may be analogous to "anomolous" magnetic phenomena observed in metallic superconductors and/or in superconducting Josephson junctions at low temperatures. The implied possibility of superconductive mechanisms of biomagnetic effects, and apparent relation to the electrical switching seen in wet melanin, give the findings biological relevance.

Coloring Agents↗
PubMed1994

Electric treatment of human melanoma skin lesions with low level direct electric current: an assessment of clinical experience following a preliminary study in five patients.

In this study we have investigated the effects of negative low level direct electric current electrotherapy (current: 1 milliampere; treatment time: 30 minutes) in metastatic or primary melanoma skin lesions. After 12 applications in five patients, tumour regression was observed in all evaluable melanoma skin lesions; four of them were classified as partial responses. This study shows that locally applied electrotherapy with a negative low level direct electric current is an effective treatment that results in reduction of tumour mass of human melanoma skin lesions, and it is possible that it has a positive influence on the course of the metastatically disseminated melanoma. No serious side effects were observed.

Adult↗
PubMedDate not supplied

Electric current perception study challenges electric safety limits.

Although a key parameter for safety regulations, the electric current perception threshold is not sufficiently established yet. Present knowledge suffers from a lack of women's data, small numbers of data on investigation of men and investigated samples non-representative for the general population. With measurement at 708 adults aged between 16 and 60 years (349 men and 359 women) these deficiencies could be overcome. The results are important. They show that the perception variability among the general population is 100-fold higher than estimated so far and that the currently used estimate of the threshold is more than 10-fold too high. Besides this, it could be shown that there are an over-proportion of more sensitive women compared with men indicating the need for revision of the present assumptions on gender-specific differences in electrosensibility. The results show that the existing assumptions on safety limits and remaining safety factors need serious review. In any case, relaxation of safety requirements is not justified.

Adolescent↗
PubMed1998

Alternate indices of electric and magnetic field exposures among Ontario electrical utility workers.

Epidemiologic studies examining the risk of cancer among occupational groups exposed to electric fields (EF) and or magnetic fields (MF) have relied on traditional summaries of exposure such as the time weighted arithmetic or geometric mean exposure. Findings from animal and cellular studies support the consideration of alternative measures of exposure capable of capturing threshold and intermittent measures of field strength. The main objective of this study was to identify a series of suitable exposure metrics for an ongoing cancer incidence study in a cohort of Ontario electric utility workers. Principal components analysis (PCA) and correlational analysis were used to explore the relationships within and between series of EF and MF exposure indices. Exposure data were collected using personal monitors worn by a sample of 820 workers which yielded 4247 worker days of measurement data. For both EF and MF, the first axis of the PCA identified a series of intercorrelated indices that included the geometric mean, median and arithmetic mean. A considerable portion of the variability in EF and MF exposures were accounted for by two other principal component axes. The second axes for EF and MF exposures were representative of the standard deviation (standard deviation) and thresholds of field measures. To a lesser extent, the variability in the exposure variable was explained by time dependent indices which consisted of autocorrelations at 5 min lags and average transitions in field strength. Our results suggest that the variability in exposure data can only be accounted for by using several exposure indices, and consequently, a series of metrics should be used when exploring the risk of cancer owing to MF and EF exposure in this cohort. Furthermore, the poor correlations observed between indices of MF and EF reinforce the need to be take both fields into account when assessing the risk of cancer in this occupational group.

Animals↗
PubMed2006

Investigating the permanent electric dipole moment of beta-lactoglobulin fibrils, using transient electric birefringence.

Amyloid fibrils, which are polymeric assemblies of protein molecules, have been intensively studied on a structural level, yet due to complications such as the disorder within the molecules, several aspects of their structure remain mysterious. Similarly, the kinetics of assembly are not well understood. Here we investigate the electric dipole moment of beta-lactoglobulin fibrils, a model amyloid fibril system, by applying the technique of transient electric birefringence. This moment appears to be large, and comparable to the total moment of the constituent protein monomers if they were joined in a chain, head-to-tail, without changing conformation, suggesting an ordered joining of monomers in the fibril. Such an ordered assembly may have implications for the assembly mechanism of beta-lactoglobulin fibrils in particular, and amyloid fibrils in general.

Amyloid↗
PubMed1999

Reversing-Pulse Electric Birefringence of Montmorillonite K10 in Aqueous Media: Electric Moments, Field Orientation, and Changes in Sign and Profile of Signals Observed in the Low-Field Region.

The reversing-pulse electric birefringence (RPEB) of a montmorillonite K10 (MK-10) sample was measured at 25 degreesC and 633 nm in aqueous suspensions in the concentration range 0.005-0.145 g/L in the 0-200 V/cm region. The sign of the RPEB signals was negative and the profile was associated with a deep dip in the reverse process in all cases at weak fields lower than the sign-inversion point, Esi. Above Esi, the sign became positive, whereas the signal profile usually showed a hump in the buildup process and a larger hump in the reverse process. A complex signal pattern appeared at the highest MK-10 concentration (0.145 g/L). For the multicomponent equilibrium system, theoretical RPEB expressions were derived in terms of three electric dipole moments: the permanent moment, the fluctuating counterion polarizability (varsigma3) with ionic relaxation time (tauI) along the symmetry axis, and the covalent polarizability anisotropy (Deltaalpha'). Analysis of profiles of the observed RPEB signals showed that the MK-10 particle possesses no permanent dipole moment. The ratio varsigma3/Deltaalpha' was less than -1, and tau1 was comparable with the overall rotational relaxation time tau of the disklike MK-10 particle. RPEB signals at 0.145 g/L were analyzed with the two-state equilibrium theory and the MK-10 particle was found to form thin platelike aggregates with partially overlapping surfaces. The field-strength dependence of the steady-state birefringence was fitted with SUSID orientation functions. The field orientation mechanism of MK-10 particles in aqueous media was discussed. Copyright 1999 Academic Press.

Journal Article↗
PubMed2000

Polarization of the Electrical Double Layer. Time Evolution after Application of an Electric Field.

Electrophoresis is one of the electrokinetic phenomena most widely investigated, both from a fundamental point of view and as a research tool in academia and industry. However, the dependence between electrophoretic mobility and zeta potential is, in a general case, far from simple, because of the many physical processes involved. In this work, we first describe qualitatively and (in some cases) quantitatively the time behavior of the dipole moment induced in the electrical double layer by an applied electric field. Further, a simple relationship is deduced between the dipole moment and the electrophoretic mobility. Through the analysis of the time dependence of the former, it is possible to resolve the different contributions to the stationary values of the mobility. Three characteristic relaxation times are distinguished in the time evolution of the dipole moment: tau(H) (the time needed for hydrodynamic flows to be established), tau(MW) (time for ionic electromigration to develop), and tau(VD) (after this time, diffusion flows are established in the system, and the double layer polarization is complete). This means that different mechanisms are operating on the double layer for different times after the application of the field, and that computing the mobility at such different times is equivalent to calculating the steady-state electrophoretic mobility under different approximations. A comparison is shown between estimated and computed mobility values as functions of time and of zeta potential, confirming the validity of the asymptotic calculations. Copyright 2000 Academic Press.

Journal Article↗
PubMed1982

Comparison of electrical field plethysmography with electrical impedance plethysmography.

As a means for assessing cardiac function, electrical field plethysmography (EFP) has been shown to have some features quite different from electrical impedance plethysmography (EIP). Here the two techniques are compared by using the two systems simultaneously on a subject and also with independent use in different electrode configurations. The results conform with the view that EIP is related primarily to volumetric changes of the aorta, whereas EFP is affected predominantly by changes in cardiac dimensions and orientation. Because of this difference, the standard time differential formula used for EIP is not applicable for the computation of cardiac output from the EFP waveforms. An alternative method of computation based on the amplitude of the EFP waveform is suggested.

Cardiac Output↗
PubMed2003

Use of psi(alpha)-ETOs in the unified treatment of electronic attraction, electric field and electric field gradient multicenter integrals of screened Coulomb potentials over Slater orbitals.

In this study, using complete orthonormal sets of Psi(alpha)-ETOs (where alpha=1, 0, -1, -2, ...) introduced by the author, a large number of series expansion formulae for the multicenter electronic attraction (EA), electric field (EF) and electric field gradient (EFG) integrals of the Yukawa-like screened Coulomb potentials (SCPs) is presented through the new central and noncentral potentials and the overlap integrals with the same screening constants. The final results obtained are valid for arbitrary locations of STOs and their parameters.

Algorithms↗
PubMed1975

Electrical properties of squid axon membrane. II. Effect of partial degradation by phospholipase A and pronase on electrical characteristics.

Passive electrical characteristics of perfused squid axon membrane are investigated. In a previous publication, we reported that the capacitance of intact squid axon membrane is partly frequency dependent. We extended the same measurement to perfused axons. We found that the electrical characteristics of perfused axon membrane are essentially the same as those of intact axons. In this work, we investigated the effects of phospholipase A and pronase on the membrane capacitance. Phospholipase A is known to block the sodium activation and pronase to eliminate the sodium inactivation. Phospholipase A is found to increase the frequency dependent as well as the frequency independent capacitances. Our tentative conclusion is that this enzyme perturbs the lipid structure and decreases its thickness. Pronase is found to increase the frequency dependent capacitance slightly while the capacitance of the lipid layer remains unaltered. Although voltage clamp data indicate that the pronase disrupts the excitatory mechanism extensively, this enzyme has relatively little effect on the overall membrane capacitance.

Animals↗
PubMed2005

Electrically induced anisotropy in a colloidal dispersion of nanospheres as measured by electric birefringence.

Electrically induced birefringence experiments were performed on dispersions consisting of sulfate latex nanospheres of two different sizes and charges dispersed in an electrolyte solution, at various ionic strengths. The induced birefringence was found to have an important contribution increasing as a quadratic power law of the volume fraction of the spheres. This shows that interparticle interactions play a role in the observed birefringence. The data were analyzed, using a theory from Hafkenscheid and Vlieger [Physica 75 (1974) 57], in terms of the changes of the interparticle separations in the directions parallel and perpendicular to the applied electric field.

Journal Article↗
PubMed1974

Passive electrical properties of toad urinary bladder epithelium. Intercellular electrical coupling and transepithelial cellular and shunt conductances.

The electrical resistances of the transcellular and paracellular pathways across the toad urinary bladder epithelium (a typical "tight" sodium-transporting epithelium) were determined by two independent sets of electrophysiological measurements: (a) the measurement of the total transepithelial resistance, the ratio of resistance of the apical to the basal cell membrane, and cable analysis of the voltage spread into the epithelium; (b) the measurement of the total transepithelial resistance and the ratio of resistances of both cell membranes before and after replacing all mucosal sodium with potassium (thus, increasing selectively the resistance of the apical membrane). The results obtained with both methods indicate the presence of a finite transepithelial shunt pathway, whose resistance is about 1.8 times the resistance of the transcellular pathway. Appropriate calculations show that the resistance of the shunt pathway is almost exclusively determined by the zonula occludens section of the limiting junctions. The mean resistance of the apical cell membrane is 1.7 times that of the basal cell membrane. The use of nonconducting materials on the mucosal side allowed us to demonstrate that apparently all epithelial cells are electrically coupled, with a mean space constant of 460 microm, and a voltage spread consistent with a thin sheet model.

Animals↗
PubMed2005

Development of the female voxel phantom, NAOMI, and its application to calculations of induced current densities and electric fields from applied low frequency magnetic and electric fields.

This paper outlines the development of a 2 mm resolution voxel model, NAOMI (aNAtOMIcal model), designed to be representative of the average adult female. The primary medical imaging data were derived from a high-resolution MRI scan of a 1.65 m tall, 23 year old female subject with a mass of 58 kg. The model was rescaled to a height of 1.63 m and a mass of 60 kg, the dimensions of the International Commission on Radiological Protection reference adult female. There are 41 tissue types in the model. The application of NAOMI to the calculations of induced current densities and electric fields from applied low frequency magnetic and electric fields is described. Comparisons are made with values from the male voxel model, NORMAN. The calculations were extended from 50 Hz up to 10 MHz. External field reference levels are compared with the ICNIRP guidelines.

Adult↗
PubMed2005

A compact electric potential sensor array for the acquisition and reconstruction of the 7-lead electrocardiogram without electrical charge contact with the skin.

Conventional electrocardiogram (ECG) systems make use of separate electrical connections to the arms and legs. These use a 'long baseline' for the voltage reference potential which in the case of precordial ECG leads is provided using a Wilson central terminal (WCT) wiring configuration. The aims of this project were (a) to construct compact, non-invasive surface ECG sensor arrays which would operate without the need for a WCT reference, (b) to obtain high quality precordial ECGs showing fine differences in ECG detail between small adjacent areas of the chest and (c) to reconstruct, from a compact array of four sensors, ECGs which closely match to the conventional 7-lead ECG system, but without the need for multiple wires and long baselines. In this paper, we describe two sensor array configurations which have been constructed using electric potential sensors (EPSs). We show high quality precordial ECGs obtained from small areas of the surface of the chest and show the different angular vectors (leads) in the frontal cardiac plane constructed using signals from the array elements. We suggest that these ECG arrays, which are simple to apply, should prove to be a valuable tool in providing useful information about the state of the heart.

Amplifiers, Electronic↗
PubMed1992

Electrically induced protoplast fusion using pulse electric fields for dielectrophoresis.

The formation of protoplast chains in suspensions of isolated pea (Pisum sativum cv Ran 1) mesophyll protoplasts induced by electric fields was studied. The chain formation induced by a sine-wave field (2 V, peak to peak; 500-0.1 kHz) was compared to that induced by an alternating pulse field (1 V, amplitude; 0.1-0.4 kHz). An increased number of dielectrophoretically paired protoplasts, formation of protoplast chains in the presence of CaCl(2) up to 5 mm, and protoplast fusion in the presence of 3 mm CaCl(2) were found when the pulse field was applied. The present results suggest the possibility of electrically induced protoplast fusion at cation concentrations that prevent fusion when sine-wave fields are applied.

Journal Article↗
PubMed2006

On the calculation of the electrostatic potential, electric field and electric field gradient from the aspherical pseudoatom model.

Accurate, yet simple and efficient, formulae are presented for calculation of the electrostatic potential (ESP), electric field (EF) and electric field gradient (EFG) from the aspherical Hansen-Coppens pseudoatom model of electron density [Hansen & Coppens (1978). Acta Cryst. A34, 909-921]. They are based on the expansion of |r' - r|(-1) in spherical harmonics and the incomplete gamma function for a Slater-type function of the form R(l)(r) = r(n) exp(-alpha ). The formulae are valid for 0 < or = r < or = infinity and are easily extended to higher values of l. Special treatment of integrals is needed only for functions with n = l and n = l + 1 at r = 0. The method is tested using theoretical pseudoatom parameters of the formamide molecule obtained via reciprocal-space fitting of PBE/6-31G** densities and experimental X-ray data of Fe(CO)(5). The ESP, EF and EFG values at the nuclear positions in formamide are in very good agreement with those directly evaluated from density-functional PBE calculations with 6-31G**, aug-cc-pVDZ and aug-cc-pVTZ basis sets. The small observed discrepancies are attributed to the different behavior of Gaussian- and Slater-type functions near the nuclei and to imperfections of the reciprocal-space fit. An EF map is displayed which allows useful visualization of the lattice EF effects in the crystal structure of formamide. Analysis of experimental 100 K X-ray data of Fe(CO)(5) yields the value of the nuclear quadrupole moment Q((57)Fe(m)) = 0.12 x 10(-28) m(2) after taking into account Sternheimer shielding/antishielding effects of the core. This value is in excellent agreement with that reported by Su & Coppens [Acta Cryst. (1996), A52, 748-756] but slightly smaller than the generally accepted value of 0.16 +/- 5% x 10(-28) m(2) obtained from combined theoretical/spectroscopic studies [Dufek, Blaha & Schwarz (1995). Phys. Rev. Lett. 25, 3545-3548].

Journal Article↗
PubMed1980

The below-elbow myo-electric prosthesis. A comparison of the Otto Bock myo-electric prosthesis with the hook and functional hand.

The place of the myo-electric prosthesis in below-elbow amputees has been reviewed. Forty-three patients were seen and all possessed both a myo-electric prosthesis and a standard artificial limb. Nearly half the patients used the newer device almost all the time at work and many of these wore it for the majority of their waking hours. Its use at work was mainly related to the patient's type of job and here in turn there was concern about damaging the device. It is suggested that acceptance would be further increased if greater attention were paid to the durability of the arm and its glove. Criteria for prescription and future developments are discussed.

Adult↗