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At least 307 records · Page 17Linked to original sources
PubMed1982

Electric dichroism of deoxyribonucleic acid in aqueous solutions: electric field dependence.

The ionic strength and molecular weight dependence of the electric field dichroism of DNA, using native and sonicated calf thymus DNA, has been examined in the range of 0.09-1.0 mM NaCl solutions for molecular weights ranging from 1.24 x 10(5) to 44 x 10(5). The application of a classical theoretical analysis implies that the orientation results from an induced moment which appears to saturate at moderate fields of several killivolts per centimeter and that the induced moment is at least partly characteristic of that expected of a polyion whose charge is partially counterion compensated. The orientation leads to dichroism values which are in accord with other observations and are lower than expected for a B-form rod of DNA. These values, however, are not uniquely interpretable as resulting from base tilting.

DNA↗
PubMed2002

Functional electric stimulation-assisted rowing: Increasing cardiovascular fitness through functional electric stimulation rowing training in persons with spinal cord injury.

OBJECTIVES: To assess changes in peak functional aerobic power after a 36-session, progressive functional electric stimulation (FES) rowing hybrid training program for persons with spinal cord injury (SCI) and to examine the safety and acceptability of the ROWSTIM II device as well as the integrity of technical modifications to it. DESIGN: Repeated-measures training study, quasi-experimental design, within-person data comparison. SETTING: A university-based recreational physical activity facility for persons with physical disabilities. PARTICIPANTS: Six persons with level C7-T12 SCI (American Spinal Injury Association classes A-C). INTERVENTION: Progressive rowing training program, 30 minutes per session, 3 times a week for 12 weeks at 70% to 75% of pretest peak functional aerobic power during FES rowing on an open loop control, FES-assisted rowing machine. MAIN OUTCOME MEASURES: Total rowing distance, peak functional oxygen consumption, and peak oxygen pulse. RESULTS: Subjects completed between 22 to 36 sessions. After 3 months of training, rowing distance increased by 25% (P<.02), peak oxygen consumption by 11.2% (P<.001), and peak oxygen pulse by 11.4% (P<.01). Heart rate response to hybrid training did not change at the end of training, although peak heart rate with FES lower-extremity exercise increased significantly from pre- to posttraining (P<.01). CONCLUSIONS: Pre- and posttraining peak aerobic power values for ROWSTIM II training were comparable to previously reported values for hybrid cycle and upper-extremity exercise. We conclude that FES-assisted rowing is an effective, safe, and well-tolerated training system for persons with SCI.

Adult↗
PubMed1971

Studies on the electrical potential profile across rabbit ileum. Effects of sugars and amino acids on transmural and transmucosal electrical potential differences.

When isolated strips of mucosal rabbit ileum are bathed by physiological electrolyte solution the electrical potential difference (PD) across the brush border (psi(mc)) averages 36 mv, cell interior negative. Rapid replacement of Na in the mucosal solution with less permeant cations, Tris or choline, results in an immediate hyperpolarization of psi(mc). Conversely, replacement of choline in the mucosal solution with Na results in an abrupt depolarization of psi(mc). These findings indicate that Na contributes to the conductance across the brush border. The presence of actively transported sugars or amino acids in the mucosal solution brings about a marked depolarization of psi(mc) and a smaller increase in the transmural PD (Deltapsi(ms)). It appears that the Na influx that is coupled to the influxes of amino acids and sugars is electrogenic and responsible for the depolarization of psi(mc). Under control conditions Deltapsi(ms) can be attributed to the depolarization of psi(mc) together with the presence of a low resistance transepithelial shunt, possibly the lateral intercellular spaces. However, quantitatively similar effects of amino acids on psi(mc) are also seen in tissues poisoned with metabolic inhibitors or ouabain. Under these conditions Deltapsi(mc) is much smaller than under control conditions. Thus, the depolarization of psi(mc) might not account for the entire Deltapsi(ms), observed in nonpoisoned tissue. An additional electromotive force which is directly coupled to metabolic processes might contribute to the normal Deltapsi(ms).

Alanine↗
PubMed1985

Effects of diltiazem on electrical responses evoked spontaneously or by electrical stimulation in the antrum smooth muscle cells of the guinea-pig stomach.

In circular smooth muscle cells of the guinea-pig stomach (antrum), diltiazem (10(-6)-10(-5)M) blocked the overshooting spike potential generated either spontaneously or by electrical stimulation in the presence of 2 mM tetraethylammonium chloride, but did not block the slow wave and the abortive spike potential. The membrane was depolarized by high concentrations of diltiazem (more than 3 X 10(-6)M), and this depolarization was associated with an increase in the membrane resistance. The interval between slow waves was shortened to about 0.90 times the control (14.7s) by 10(-5)M diltiazem. Transmural nerve stimulation evoked an inhibitory junction potential (i.j.p.) and enhanced the subsequently generated slow wave. Tetrodotoxin (3 X 10(-7)M) blocked both responses but atropine (10(-6)M) blocked only the latter. Diltiazem (more than 10(-6)M) increased the amplitude of the i.j.p. and depressed the enhancement of the slow wave produced by transmural nerve stimulation, presumably due to depolarization of the membrane. The latency for the i.j.p. remained the same in the presence of diltiazem (10(-5)M). It is concluded that in the guinea-pig stomach, diltiazem blocks Ca-influx during the generation of the overshooting spike potential, but not the Ca-influx related to generation of the abortive spike potential or the slow wave. The cholinergic excitatory and the non-adrenergic, non-cholinergic inhibitory transmission may not be much affected by diltiazem.

Action Potentials↗
PubMed1988

Effect of electrical stimulation of the crossed olivocochlear bundle on temporary threshold shifts in auditory sensitivity. I. Dependence on electrical stimulation parameters.

1. This study examines the effect on auditory desensitization of electrically stimulating the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle. Auditory desensitization was induced by a loud high-frequency pure tone exposure and measured as temporary threshold shifts (TTS) in the sensitivity of the compound action potential recorded from the cochlea. COCB stimulation simultaneous with the loud sound exposure reduced the TTS. This reduction was contingent on the COCB stimulus being presented as a continuous burst for the entire duration (1 min) of the exposure. 2. The reduction in TTS could be abolished by prior administration of strychnine. The action of strychnine on these TTS effects of continuous COCB stimulation paralleled its action on the classical COCB effects elicited by pulsed short COCB trains. If the action of strychnine on the classical COCB effects was allowed to reverse, then continuous COCB stimulation reduced TTS as effectively as before. 3. The most effective COCB stimulus was found to be one that was presented at a high rate of stimulation simultaneous with the exposure. The COCB effect on TTS was also found to be a tonic one; smaller but significant reductions in TTS could still be obtained with the exposure presented 5 min after COCB stimulation though not when the delay was 10 min. The tonic reductions in TTS appeared to occur without any persisting changes at the cochlea. Normal cochlear responses remeasured in the delay between the stimulus and exposure were not altered. 4. It was hypothesized that the persisting effect responsible for TTS reductions did not occur at the cochlea but at some central site facilitated by antidromic action potentials along the COCB fibers. Subsequent exposure to loud sounds would activate the central site primed by the prior COCB stimulus. This hypothesis was tested by stimulating the COCB alone as before, but then lesioning the fibers before presenting the exposure. Persistent cochlear effects of the COCB stimulus should have still resulted in a reduction in TTS. However, if the persistent effect was at a more central location, lesioning the fibers would allow afferent input to act at the facilitated central location but would not allow subsequent expression of COCB effects at the cochlea. In this case, no reductions in TTS could be expected--precisely the results that were obtained in these experiments. Thus the COCB system appeared to have a "memory" component facilitated by prior stimulation and activated by a subsequent exposure.

Acoustic Stimulation↗
PubMed1982

Effects of the discrete pattern of electrical coupling on propagation through an electrical syncytium.

We used numerical integration techniques to simulate action potential propagation along one-dimensional strands of cells coupled with electrical junctions. We considered the standard case to be a series of cardiac cells (20 micrometer in diameter, 50 micrometers long) with intercellular coupling such that the effective longitudinal resistance was 200 omega cm. The membrane properties were represented by the model of Beeler and Reuter (1977) (Sharp and Joyner, 1980). By increasing Ri (and thus decreasing the space constant, L), we showed that effects due to the discrete cell length, delta X, became apparent when delta X/L was greater than about 0.2, producing an increased maximal dV/dt but a decrease in peak inward current. We also simulated the effects of a periodic spatial variation in Ri, representing a structure with groups of well-coupled cells but with minimal coupling between the groups. Even with a constant membrane model and cell size, variations in the spatial pattern of interconnection produced significant changes in action potential shape and velocity, with some patterns producing decremental conduction or propagation failure.

Action Potentials↗
PubMed1978

Influence of water temperature on the electric organ discharge (EOD) of the weakly electric fish Marcusenius cyprinoides (Mormyridae).

1. The influence of different water temperatures on the electric organ discharge (EOD) of a mormyrid fish Marcusenius cyprinoïdes was studied. The range of the water temperatures was fixed according to the seasonal temperature variations of the rivers in Central Africa, the natural habitat of this species. 2. The EOD activity was characterized using the following parameters: mean EOD rate, EOD pattern in the form of Interpulse Interval Histograms (IIH), IIH range, and shortest pulse interval. These parameters remained constant during control experiments at constant temperature (27 degrees C) for 4 days. 3. The mean EOD rate increases with increasing water temperatures. The lowest mean EOD rate is always found at 17 degrees C, the highest between 26 and 33 degrees C. The characteristics of the IIH are modified by stepwise temperature increases. These IIH show during high temperatures (26-33 degrees C) similar patterns to those previously observed during high level motor activity and excitement. The IIH range diminishes with stepwise temperature increases. The shortest pulse interval has a negative, linear correlation with water temperature. 4. The possible role of water temperature in the reproduction of the mormyrids is discussed. The high discharge rate of M. cyprinoïdes produced by high water temperatures during the rainy season could serve to improve the resolution of the electroreceptors during this period.

Animals↗
PubMed2002

The interaction of carbachol and strophantin on the electrical and mechanical events in electrically driven strips of guinea pig left atria.

We compared the electrophysiological and the mechanical actions of the cholinergic agonist carbachol (CARB) and the digitalis glycoside strophantin (STR) in a study on the electrically driven strips of guinea pig left atria. The respective control values for the resting membrane potential (RMP), action potential amplitude (APA), action potential duration at 20%, 50%, and 90% repolarization levels (APD20,50,90), and time to peak tension (TtPt) were of the order of 61.1 +/- 1.69 nmV, 104.64 +/- 1.28 mV, 28.5 +/- 1.22 msec, 51.0 +/- 1.51 msec, 106.91 +/- 3.81 msec, and 60.1 +/- 1.09 msec. Exposure to CARB (2 x 10(-7) M) rapidly reduced contractility, TtPt, APD, and APA to exceptionally lower levels within the initial 5 minutes and gradually caused a slight hyperpolarization in RMP. Strophantin (1 x 10(-7) M) caused contractility and RMP to increase slightly, APD and APA to reduce less markedly, but did not significantly affect TtPt. Under the influence of combined CARB/STR, the effect of CARB on the contraction amplitude (CA), TtPt, APD, and APA was attenuated and that on RMP was significantly potentiated (p < 0.05), whereas the effects of STR on CA, TtPt, APD, and APA were reversed (p < 0.05), and the effect on RMP was augmented. The action potential duration was less responsive to STR at all depolarization levels with respect to those of CARB and combined CARB/STR. Although the correlation between the time course of APD-20 and APD-90 for STR was poor, the correlation for CARB and combined CARB/STR was highly significant (r > 0.95). The correlation between the effects of CARB on CA and APD-90 was high but poor for the effect of combined CARB/STR. Striking to note is that the rate of induction of contractile changes with CARB (d(delta)/dt = 1.39 +/- 0.05%/sec), and its washout was more rapid (p < 0.05) in comparison to the rate of changes in APD-90 (0.98 +/- 0.05%/sec). This result, however, was not observed with combined CARB/STR. From the results we concluded that CARB and STR act as antagonists when used in combination, with the exception that only the effect on RMP was additive, with asignificant discordance between the rates of induction of effects on CA and APD-90, with the former being more rapid.

Action Potentials↗
PubMed2003

Effects of pH, temperature, and pre-pulsed electric field treatment on pulsed electric field and heat inactivation of Escherichia coli O157:H7.

This investigation was undertaken to study the inactivation of Escherichia coli O157:H7 by pulsed electric field (PEF) treatment and heat treatment after exposure to different stresses. E. coli O157:H7 cells exposed to different pHs (3.6, 5.2, and 7.0 for 6 h). different temperatures (4, 35, and 40 degrees C for 6 h), and different pre-PEF treatments (10, 15, and 20 kV/cm) were treated with PEFs (20, 25, and 30 kV/cm) or heat (60 degrees C for 3 min). The results of these experiments demonstrated that a pH of 3.6 and temperatures of 4 and 40 degrees C caused significant decreases in the inactivation of E. coli O157:H7 by PEF treatment and heat treatment (P < 0.05). Pre-PEF treatments, pHs of 5.2 and 7.0, and a temperature of 35 degrees C, on the other hand, did not result in any resistance of E. coli O157:H7 cells to inactivation by PEF treatment and heat treatment (P > 0.05).

Colony Count, Microbial↗
PubMed2003

[Intercavitary electrical stimulation of the gastrointestinal tract and mucosa with a stand-alone electric stimulator in the treatment of patients in the physicochemical stage of gallbladder disease].

The use of the SAE for the GIT and MC has a stimulating effect on the processes of bile production and secretion for patients with the physical and chemical stage of the gallstone disease. Over a short period of time the SAE for the GIT and MC normalizes the biliary tract motor functions removing the dissynergism of the biliary tract sphincter organ and restoring the sphincter motor functions. The SAE for the GIT and MC has a positive effect on major factors of bile concentration and components ratio aimed at the reduction of lithogenicity and its colloid stability improvement. The intracavitary electrical stimulation with the SAE for the GIT and MC both as a monotherapy and one of the complex anti-relapse methods is an efficient and simple method and has no side effects or complications. Therefore, it may be recommended for the treatment of patients with the physical and chemical stage of the gallstone disease.

Bile↗
PubMed1989

Effects of single application of a moisturizer: evaporation of emulsion water, skin surface temperature, electrical conductance, electrical capacitance, and skin surface (emulsion) lipids.

Effects of single application of an oil in water emulsion were studied on the forearm skin of 12 healthy volunteers. Five different non-invasive methods were used. Values were followed for 360 min after application of the emulsion, with the contralateral forearm as untreated control. The evaporation of emulsion water from the skin surface immediately rose to high values, but within 15 min returned to the original level. A parallel initial increase in conductance was observed; however, this was followed by a slightly increased level throughout the 360 min study. Electrical capacitance was also slightly increased throughout the study. Skin surface lipids, dominated by emulsion lipids, were increased, with high values for at least 120 min, followed by a gradual decline toward normal. Single application of emulsion is characterized by an initial evaporation phase, with evaporation of emulsion water, which lasts less than 15 min, followed by a lipidization phase, which lasts at least 360 min, dominated by the oil-constituent of the emulsion undergoing epidermal absorption. During the lipidization phase, epidermal hydration parameters are slightly but consistently improved.

Aged↗
PubMed1989

[Investigation of accidents by the Special Inspection for Electrical Electrical Medical Equipment].

The article reviews the responsibilities of the Special Inspection for Electrical Medical Equipment, STEM, with emphasis on investigations of accidents and near-accidents in connection with the use of technical equipment. It stresses the obligation to report to STEM immediately. The reported accidents for the period 1980-1988 are given in table 1, and are discussed. Norwegian statistics are compared with both American and Scandinavian data and reference is made to the international standardization on technical medical equipment.

Accident Prevention↗
PubMedDate not supplied

[The effect of acetylcholine on passive electrical properties and intercellular electrical communications in the sinoatrial node of the rabbit heart].

The effect of acetylcholine (ACH) on passive electric properties and intercellular coupling was studied using microelectrode technique in experiments on isolated preparations of the sinoatrial area of the rabbit's heart. The space constant of electrotonic decay (lambda delta) and input resistance (RBX) were measured. ACH was found to reduce lambda delta and increase RBX. Analysis of the experimental data, using the model of thin layer 3-dimensional syncytium, revealed that ACH of 10(-7) M, 10(-6) M and 10(-5) M increased the resistance of intracellular syncytium by factor of 1.25, 1.36 and 1.43, respectively, and decreased the resistance of the electrogenic membrane by factor of 1.13, 1.12 and 1.23, respectively. It is concluded that ACH increases the resistance of intercellular contacts in the sinoatrial node.

Acetylcholine↗
PubMed1987

Electrical impedance tomography; the construction and application to physiological measurement of electrical impedance images.

Electrical impedance tomography enables images of tissue resistivity to be produced from measurements made via an array of surface electrodes. Using the technique of Applied Potential Tomography (APT) an array of 16 electrodes placed around the trunk has been used to image gastric, respiratory and cardiac related events. Some of the advantages and disadvantages of the technique are considered and the possibility of improvement discussed. Some cardiac gated images are presented which show the movement of blood on systole so allowing cardiac output and lung perfusion to be displayed.

Algorithms↗
PubMed1985

[Experimental histopathological studies of electrical callus formation and mechanism of bone healing by direct micro-electrical current].

In order to get better understanding of the effects of electrical stimulation on bone healing processes, the author compared the healing processes of the femur in dogs between two groups: a stimulation group and a control group (non-stimulation group) which were experimentally prepared. These bone specimens were periodically extirpated and used for pathological examinations and X-ray micro-analysis. In the stimulation group, strong proliferation of osteoblasts and new trabecular formation in the bone marrow were observed at the 3rd day, and transition from fibrous to bony callus were noted at the 9th day; after the 3rd week bone remodeling was sparsely seen and bone healing period was shortened. In electromicroscopic observation, calcification of bone matrix and bone remodeling also seemed to be facilitated in this group. However, no marked differences in histological process of bone healing were observed between the stimulation group and the control group.

Animals↗
PubMed1978

Ultrastructural features and glycogen distribution in the electric organ of the electric ray Torpedo marmorata L.

The ultrastructural topography of glycogen in the electic organ of the fish Torpedo marmorata has been examined following Thiéry's method and the modified osmium tetroxide post-fixation of De Bruijn. Both methods reveal a high concentration of glycogen particles in the nerve terminals, particularly in pedunculate pouches issuing from the nerve endings and bulging into the intersyncytial area. A few sparse positive particles are scattered at random in the Schwann cells and in the cuff cells occasionally encapsulating the myelinated and ummyelinated subsynaptic axons. In the electric cell, glycogen occurs in the form of scattered particles homogenously distributed among all the cytoplasm. The structure and the size of glycogen granules in relation to the detection methods used and to previous parallel investigations are briefly discussed.

Animals↗
PubMedDate not supplied

[Is the electrical activity of the brain always electrical? (The factors that generate the potential of a metal electrode in direct contact with the brain)].

In the paper are analysed the factors creating slow potential changes of a metal electrode directly contacting with the living tissue. In the paper are presented the data according to which electrochemical tissue activity participates in creating the electrode potential besides the electrical activity. The paper carries a discussion character.

Animals↗