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PubMed1975

The effect of ultraviolet radiation on the electrical conductivity of human bone.

The electrical conductivity of intact bone, collagen and apatite mineral was determined in the region of moderately high fields. After exposure to ultraviolet (UV) radiation the conductivity of the specimens was redetermined. Following exposure marked decreases in electrical conductivity occurred in all specimens. The possible modes of interaction of UV radiation with bone are discussed. It is suggested that protonic conduction may be an important mode of charge transport in bone.

Apatites↗
PubMed2006

Anisotropic ion diffusivity in intervertebral disc: an electrical conductivity approach.

STUDY DESIGN: Investigation of the transport behavior of ions in intervertebral disc using an electrical conductivity method. OBJECTIVES: To determine the electrical conductivity and ion diffusivity of nucleus pulposus and anulus fibrosus in 3 major directions (axial, circumferential, and radial). SUMMARY OF BACKGROUND DATA: Knowledge of diffusivity of small molecules is important for understanding nutrition supply in intervertebral disc and disc degeneration. However, little is known on the anisotropic behaviors of ion diffusivity and of electrical conductivity in intervertebral disc. METHODS: Electrical conductivity measurement was performed on 24 axial, circumferential, and radial anulus fibrosus specimens and 24 axial nucleus pulposus specimens from bovine coccygeal discs. The diffusivity of Na and Cl were estimated by the analysis of conductivity data. RESULTS: The electrical conductivity (mean +/- standard deviation; n = 24) of the bovine anulus fibrosus was 4.70 +/- 1.08 mS/cm in the axial, 2.86 +/- 0.83 mS/cm in the radial, and 4.38 +/- 1.25 mS/cm in the circumferential direction. For nucleus pulposus, the electrical conductivity (mean +/- standard deviation; n = 24) was 8.95 +/- 0.89 mS/cm. The mean value for nucleus pulposus was significantly higher than that of anulus fibrosus (t test, P < 0.05). For anulus fibrosus, the conductivity in the radial direction was significantly lower than in axial or circumferential directions. Similar trends were found for both Na and Cl diffusivities. Both electrical conductivity and ion diffusivity were highly sensitive to water content. CONCLUSIONS: Electrical conductivity and ion diffusivity of anulus fibrosus are anisotropic.

Animals↗
PubMed2003

Electrical conduction through linear porphyrin arrays.

Electrical conduction measurements were made on two extreme types of directly linked porphyrin arrays by using nanoelectrodes. One type is the directly linked Zn(II)porphyrin arrays, consisting of 48 Zn(II)porphyrin moieties (Z48), and the other type is the completely flat, tape-shaped Zn(II)porphyrin arrays, consisting of eight Zn(II)porphyrin units (T8). The I-V curve for Z48 exhibits the diode-like behavior and the hysteresis depending on the voltage sweep direction presumably due to the conformational heterogeneity arising from the dihedral angle distribution in Z48. On the other hand, the I-V curve for T8 is nearly symmetric without any hysteresis, leading to the higher conductivity and the smaller band gap. These results illustrate that the stronger pi-electron conjugation in T8, as compared with that of Z48, results in better electrical conduction.

Biomimetic Materials↗
PubMed2007

Electrically conductive biodegradable polymer composite for nerve regeneration: electricity-stimulated neurite outgrowth and axon regeneration.

Normal and electrically stimulated PC12 cell cultures and the implantation of nerve guidance channels were performed to evaluate newly developed electrically conductive biodegradable polymer composites. Polypyrrole (PPy) doped by butane sulfonic acid showed a significantly higher number of viable cells compared with PPy doped by polystyrenesulfonate after a 6-day culture. The PC12 cells were left to proliferate for 6 days, and the PPy-coated membranes, showing less initial cell adherence, recorded the same proliferation rate as did the noncoated membranes. Direct current electricity at various intensities was applied to the PC12 cell-cultured conductive membranes. After 7 days, the greatest number of neurites appeared on the membranes with a current intensity approximating 1.7-8.4 microA/cm. Nerve guidance channels made of conductive biodegradable composite were implanted into rats to replace 8 mm of sciatic nerve. The implants were harvested after 2 months and analyzed with immunohistochemistry and transmission electron microscopy. The regenerated nerve tissue displayed myelinated axons and Schwann cells that were similar to those in the native nerve. Electrical stimulation applied through the electrically conductive biodegradable polymers therefore enhanced neurite outgrowth in a current-dependent fashion. The conductive polymers also supported sciatic nerve regeneration in rats.

Absorbable Implants↗
PubMedDate not supplied

[Anisotropic electric conductivity of bacterial suspensions induced by external electric field].

The anisotropy of electrical conductivity of suspensions of such bacteria, as E. coli, Serratia marcescens, Pseudomonas fluorescens induced by a sinusoidal external electric field and relaxation of the anisotropy after switching off the field were investigated. On the basis of the experimental relationships the anisotropy of electrical polarizability and coefficient of rotational diffusion of the cells were evaluated. The anisotropy of electrical polarizability and coefficient of the rotational diffusion obtained are in a good agreement with the available data of other methods.

Bacterial Physiological Phenomena↗
PubMed2002

Electrical conductivity of lumbar anulus fibrosis: effects of porosity and fixed charge density.

STUDY DESIGN: Experimental investigation of the electrical conductivity of normal and trypsin-treated lumbar anulus fibrosis specimens. OBJECTIVES: To measure the electrical conductivity of intervertebral disc tissues and to study the effects of tissue porosity (volume fraction of water) and fixed charge density on the electrical conductivity of anulus fibrosis in physiologic saline. SUMMARY OF BACKGROUND DATA: Specific electrical conductivity is one of the material properties of intervertebral discs. Their value depends on ion concentrations and ion diffusivities within the tissue, which in turn are functions of tissue composition and structure. To our knowledge, the electrical conductivity of intervertebral discs has not been studied. Investigation of the electrical conductivity of intervertebral discs and understanding of their relationship to tissue porosity and fixed charge density will provide insights into electromechanical phenomena (e.g., streaming potential) and ion transport in intervertebral discs. METHODS: A total of 35 porcine lumbar anulus fibrosis specimens were divided into two groups: one control group (n = 10) and one trypsin-treated group (n = 25). The specimens in the control group were subjected to one-dimensional free swelling in phosphate-buffered saline (pH 7.4), and electrical conductivity and porosity (water content) were measured over a period of about 45 minutes. The specimens in the treated group were immersed in a trypsin solution (372 U/mL phosphate-buffered saline) for 45 minutes at room temperature, and the electrical conductivity and porosity were measured after treatment. The electrical conductivity was correlated to tissue porosity for the control and treated specimens. The influences of porosity and fixed charge density were studied. RESULTS: The average value for control specimens was 5.60 +/- 0.89 mS/cm (mean +/- SD; n = 10) before swelling and 9.11 +/- 0.90 mS/cm (mean +/- SD; n = 10) after swelling. Tissue porosity increased from 0.74 +/- 0.03 (mean +/- SD; n = 10) before swelling to 0.83 +/- 0.02 (mean +/- SD; n = 10) after swelling. The trypsin treatment reduced anulus fibrosis porosity by 3.6% (P < 0.05) and conductivity by 13% (P < 0.05) compared to those for control specimens after swelling. No significant changes werefound in wet and dry tissue densities between control and treated groups. There was a significant, linear correlation between conductivity and porosity for control anulus fibrosis specimens (R2 = 0.87; 86 measurements). CONCLUSIONS: Measured electrical conductivity was sensitive to tissue porosity, but not to fixed charged density for anulus fibrosis specimens in phosphate-buffered saline.

Animals↗
PubMed1981

Studies on the phenomenon of latent propagated sensation along the channels. I. The discovery of a latent PSC and a preliminary study of its skin electrical conductance.

By combining electrical impulse stimuli with mechanical ones, we are able to trace out a new line of feeling, coincident with the classical channel course. Impulse stimulation was carried out at the Jing point of the Large Intestine or Stomach channel, namely Shangyan or Lidui. With a small rubber nipple, light taps were applied on the skin along the lines perpendicular to the channel and crossing over the acupuncture points; a specific propagational numb feeling at the points of the channel could be found. By linking up these points of specific feeling, an imaginary line which is exactly the classical Large Intestine or Stomach channel can be traced out. This line is called the "latent propagational sensation line along the channels" because, unless through tapping, no prominent sensation of propagation could be felt. Employing an impulsive electrical generator and an all-wave commutating circuit linked to a micro-ammeter, the skin conductance was measured over the latent PSC of the Large Intestine channel lying between the wrist and 5 cm above the elbow joint. Results were compared to those locations of 1 cm apart from the channel course, i.e. the control sites devoid of acupuncture points or channels. At most acupuncture points or any site of the channel course on all of the 10 subjects under examination, there was greater electrical conductance maxima than there was at control sites. This fact indicates that not only the acupuncture points, but the entire course of latent PSC are also of higher electrical conductance.

Acupuncture Therapy↗
PubMed2004

Basic study of new diagnostic modality according to non-invasive measurement of the electrical conductivity of tissues.

The purposes of this study were to estimate the electrical conductivity of tissues by non-invasively measuring the electrical bio-impedance, to develop a new method for tissue diagnosis, i.e., electrical impedance tomography (EIT). Tissue models were first designed taking into consideration the distribution of the fat tissue, muscle and bone in the human forearm, and then the intra-tissue distributions of electrical potential and field, and the electrical impedance in the models was theoretically analyzed by the three-dimensional finite element method. The electrical impedance of both forearms was measured in healthy human subjects, and estimated the electrical conductivity of individual local tissues. The results of the analysis showed that the distributions of electrical potential and field were affected by the presence of fat tissue but not by the presence or absence of bone. In addition, as a result of calculation of the electrical resistance of the extracellular fluid (Re) in each model, it was found that the value of bio-impedance was influenced by the presence of fat tissue, and the value of bio-impedance was increased by the intervention of a fat layer. The electrical conductivity estimated by fitting the observed values to the values obtained by finite element analysis was 0.40 S/m and 0.15 S/m for male muscle and fat tissue, and 0.35 S/m and 0.11 S/m for female muscle and fat tissue, respectively. The sex difference in the slope of linear approximation in the estimation of electrical conductivity of the males and females was thought to be due to sex differences in the properties and structure of fat tissue. These results suggest that local tissues can be diagnosed differentially and electrically by percutaneous measurement of local bio-impedance and subsequent estimation of the electrical conductivity of each tissue.

Adult↗
PubMed1979

[Water in keratin: electrical conductivity measurements].

Measurements of electrical conductivity of keratin fibers show that, for weak hydration (0-5%) interaction between water and protein is strong. This decreases the probability of charges-exchange taking place between them. During the first percentages of elongation, an increase of the percentage of "intermediate water" appears.

Electric Conductivity↗
PubMed2004

Tetrapolar measurement of electrical conductivity and thickness of articular cartilage.

A tetrapolar method to measure electrical conductivity of cartilage and bone, and to estimate the thickness of articular cartilage attached to bone, was developed. We determined the electrical conductivity of humeral head bovine articular cartilage and subchondral bone from a 1- to 2-year-old steer to be 1.14+/-0.11 S/m (mean+/-sd, n =11) and 0.306+/-0.034 S/m, (mean+/-sd, n =3), respectively. For a 4-year-old cow, articular cartilage and subchondral bone electrical conductivity were 0.88+/-0.08 S/m (mean+/-sd, n =9) and 0.179+/-0.046 S/m (mean+/-sd, n =3), respectively. Measurements on slices of cartilage taken from different distances from the articular surface of the steer did not reveal significant depth-dependence of electrical conductivity. We were able to estimate the thickness of articular cartilage with reasonable precision (<20% error) by injecting current from multiple electrode pairs with different inter-electrode distances. Requirements for the precision of this method to measure cartilage thickness include the presence of a distinct layer of calcified cartilage or bone with a much lower electrical conductivity than that of uncalcified articular cartilage, and the use of inter-electrode distances of the current injecting electrodes that are on the order of the cartilage thickness. These or similar methods present an attractive approach to the non-destructive determination of cartilage thickness, a parameter that is required in order to estimate functional properties of cartilage attached to bone, and evaluate the need for therapeutic interventions in arthritis.

Animals↗
PubMed1987

Lateral electrical conduction along a phosphatidylcholine monolayer.

Lateral electrical conduction due to lipid-monolayers spread on the surface of pure water was observed under both d.c. and a.c. electrical fields. An apparent specific electrical conductivity is evaluated as high as approximately equal to 4.10(-2) mho/cm for the monolayer-water system of L-DPPC at 25 degrees C. Arrhenius plots of the apparent conductance show a deflection at a temperature corresponding to a crystalline-to-fluid phase transition of the surface monolayer. From the magnitude and temperature dependence of conductance and a comparison of results with those obtained by use of deuterated water, it is concluded that enhanced protonic conduction mediated by a network consisted of polar head groups of phosphatidylcholines and water molecules may be brought about near the lipid/water interface.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

Electrical conduction within the cerebrovasculature of stroke-prone spontaneously hypertensive rats.

Alterations in electrical conductivity between smooth muscle cells (SMCs) can alter the spread and effectiveness of electromechanical SMC contraction. We attempted to determine whether alterations in pressure-dependent constriction (PDC) occurring in relation to stroke development within the middle cerebral arteries (MCAs) of Wistar-Kyoto stroke-prone hypertensive rats (SHRsp) were associated with changes in electrical conductivity between the SMCs. Current was injected into nonpressurized MCAs, using a suction electrode. The conducting distance along the length of the MCA where the amplitude of the membrane potential deflection (electronic potential) produced by current injection declined to 1/e (length constant) was used to measure conductivity. PDC to a 100 mmHg pressure step was measured with a pressure myograph. A loss of PDC in the MCAs of SHRsp preceded stroke development. Heptanol (4 mM), a gap junction communication inhibitor, reversibly inhibited conductivity and PDC in the MCA of prestroke SHRsp. The ability of heptanol to reversibly inhibit PDC was likely not related to it's ability to alter electrical conduction. The length constant of electrical conduction in the MCAs was about 0.75 mm and didn't differ between MCA sampled from pre-versus post-stroke SHRsp or Sprague-Dawley rats. It was concluded that alterations in electrical conductivity along the MCA could modify the spread of PDC, but such changes do not contribute to the loss of PDC within the MCA of poststroke SHRsp.

Animals↗
PubMed1990

Thermoregulatory effects and electrical conductivity in vagina of cow during oestrous cycle.

Measurement of vaginal temperature and electrical conductivity of cervicovaginal mucus were conducted in 20 dairy cows and were related to the phase of the oestrus cycle. Temperature and electrical conductivity in the anterior part of the vagina changed in synchronicity with phases of the oestrous cycle. About 12 hours before ovulation, the vaginal temperature increased from 37.94 +/- 0.33 degrees C to 39.00 +/- 0.64 degrees C, as compared to the pre-oestrus value. The occurrence of oestrus was accompanied by an increase in electrical conductivity of mucus in the anterior part of the vagina from 7.60 +/- 0.33 mS to 12.00 +/- 0.54 mS. Vaginal temperature dropped to 38.50 +/- 0.29 degrees C, and electrical conductivity dropped to 10.00 +/- 0.55 mS at ovulation time. Rises in vaginal temperature and electrical conductivity in the anterior part of the vagina were additional symptoms of oestrus and were followed by decrease in these values, indicating ovulation in cows.

Animals↗
PubMed2003

Finite element analysis of hepatic radiofrequency ablation probes using temperature-dependent electrical conductivity.

BACKGROUND: Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed. METHODS: The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion. RESULTS: The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion. CONCLUSION: Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100 degrees C.

Electric Conductivity↗
PubMed1990

Influence of EA on the electrical conductance in the marginal area of the acute ischemic myocardium in the rabbit.

AMI was produced by occlusion of LVB for 30 min in the rabbit, lengthening the conductive time of myocardium in the ischemic area and resulting in asynchronous activation state of myocardium. EA could facilitate the conductance of electric activation in the ischemic marginal area and make the activation of myocardial cells in this area synchronous which is of importance in blocking the formation of reentrant circuit. The finding suggests that EA possesses an antiarrhythmic effect.

Action Potentials↗
PubMed1983

Somatic cell count, electrical conductivity, and serum albumin concentration for detecting bovine mastitis.

Cell concentration, electrical conductivity, and serum albumin concentration of milk were evaluated for predicting infection status of quarters in three herds. Probability of misclassifying quarters was lowest for cell concentration. For discriminating quarters infected with Staphylococcus aureus from quarters free from infection, probability of misclassification for cell concentration ranged from 8 to 20% among herds. For electrical conductivity probability of misclassification ranged between 22 and 32%, whereas for serum albumin the range among herds was from 15 to 48%. Among herds there was also considerable variation of the trait, which minimized the probability of misclassification. Cell concentrations for the three herds were 158, 200, and 251 x 10(3) cells/ml whereas for electrical conductivity counts were 4.6, 5.8, and 6.5 mS/cm. For electrical conductivity and serum albumin comparisons within cow by differences and ratios from different quarters yielded little advantage over absolute estimations. For a single sampling, cell concentration provided the most accurate prediction of quarter infection status. We suggest that 200 x 10(3) cells/ml should be the threshold above which quarters are considered likely to be infected with a major pathogen.

Animals↗