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At least 19 recordsLinked to original sources
PubMed1992

Determination of body composition in growing rats by total body electrical conductivity.

Total body electrical conductivity (TOBEC), measured with an Em-Scan SA-1 analyzer, was evaluated as a means of estimating fat-free mass and total body water content noninvasively in small laboratory animals. Ninety-four rats whose weight ranged from 5.53 to 170.84 g at 0-50 days of age were studied. The animals were killed by intraperitoneal injection of a pentobarbital overdose. After weight, crown-rump length (CRL) and TOBEC were measured, and the animals were minced with scissors and desiccated to constant weight in a convection oven. Fat was extracted by multiple bathings in petroleum ether followed by Soxhlet extraction. Fifty-four rats were used to determine the relation between fat-free mass (FFM), total body water (TBW), and TOBEC# (E) by regression analysis. The best correlations were observed between FFM and (E x CRL)1/2 (r = 0.995, p less than 0.0001). Forty rats were used to determine the predictive value of TOBEC estimates. With this instrument, TOBEC tended to underestimate FFM by an average of 3.9% and TBW by 5.3%. Accuracy was questionable for animals smaller than 13 g and TOBEC did not provide useful estimates of total body fat. Subject to these limitations, TOBEC instruments should prove to be useful for sequential in vivo estimations of body composition during growth and development of small animals.

Animals↗
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↗
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↗
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↗
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↗
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↗
PubMed1992

The electrical conductivity of phospholipid films as an iodine-sensing mechanism.

The d.c. electrical conductivity of dry phospholipid films is increased by some 8-11 orders of magnitude by the adsorption of iodine vapor. The conductivity of these films has been found to increase as a function of iodine 'vapor pressure' and the quantitative relationship between electrical conductivity and the adsorbed iodine has been determined. Films composed of phospholipids with unsaturated hydrocarbon chains are some three orders of magnitude more electrically conductive than are films of phospholipids containing saturated hydrocarbon chains. Optical spectroscopic measurements show the development of absorption bands centered near 294 nm and 365 nm, upon iodine adsorption. These bands are much more intense for unsaturated phospholipids than for saturated ones. X-ray diffraction studies show that exposure to iodine decreases the thickness of phospholipid bilayers containing unsaturated hydrocarbon chains but does not change the thickness of bilayers containing only saturated chains. The electrical response of the lipid films, upon exposure to iodine, suggests their possible use as iodine sensors.

Biosensing Techniques↗
PubMed1991

Identification of subclinical mastitis with a hand-held electrical conductivity meter.

A hand-held, commercially available instrument for measuring the electrical conductivity of milk (the Milk Checker) has been examined for its usefulness and accuracy in detecting subclinical and clinical mastitis. Foremilk from uninfected quarters had an electrical conductivity of 5.4 to 5.6 millisiemens (mS)/cm. Milk from cows with subclinical Staphylococcus aureus infections had a higher milk conductivity (7.1 to 7.5 mS/cm) but milk from cows with subclinical S uberis infections showed no increase in conductivity (5.3 to 5.6 mS/cm). However, experimental S uberis infections could be detected by a 50 per cent increase in the electrical conductivity of foremilk two milkings before visible signs of mastitis were apparent. The equipment could be a useful advisory/veterinary tool but is unlikely to be used routinely in the milking parlour.

Animals↗
PubMed1991

Variation in somatic cell count, California mastitis test, and electrical conductivity among various fractions of ewe's milk.

Variation of three estimates of udder inflammation (SCC, California mastitis test, and electrical conductivity) among the foremilk, machine milk, and hand stripping samples were studied. Foremilk and hand stripping milks were taken from each individual teat; machine milk was taken from the entire udder. For this experiment a total of 30 Manchega ewes were subjected to machine milking during the 9th wk of lactation. Samples were taken in duplicate during two milkings on consecutive mornings. Significant differences were observed in the SCC and electrical conductivity, but not in California mastitis test, between foremilk and stripping milk. The stripping fraction had higher SCC (70 +/- 12%) and lower electrical conductivity (difference = .52 +/- .03 mS/cm) than did the foremilk fraction in both healthy and mastitic udders. Machine milk, foremilk, and stripping milk fractions in udders where both halves were healthy were compared. The electrical conductivity values for the machine milk were intermediate and significantly different from conductivity of foremilk and stripping fractions. The log SCC of the machine milk did not differ from that of the foremilk fraction but was significantly less than the stripping milk.

Animals↗
PubMed1990

Slotted resonator: principles and applications for high-frequency imaging and spectroscopy on electrically conducting samples.

The electric equivalent of an Alderman-Grant slotted resonator is analyzed in terms of two one-turn solenoids interconnected by a slotted cylinder resonator. The homogeneity of the magnetic RF field is probed using NMR imaging techniques and found to be comparable to that of a saddle-shaped coil. The dielectric losses of the slotted resonator are intrinsically low and much smaller than the inductive losses. Inductive losses are found to be proportional to the sample conductivity and to the fourth power of the sample diameter.

Electric Conductivity↗
PubMed1992

Electrical conductivity of milk: measurement, modifiers, and meta analysis of mastitis detection performance.

The physics, physiology, and pathology of electrical conductivity of milk are described. Based on a meta analysis, the use of electrical conductivity as a mastitis detection tool is discussed. Most reports were based on subclinical mastitis data. The gold standards of the different reports are discussed. With an overall sensitivity of 66% and an overall specificity of 94%, the predictive value of a positive electrical conductivity test remains low in a low prevalence population. The use of on-line systems for clinical mastitis detection is discussed. On-line systems that combine multiple data and perform multifactorial analyses will be of interest to the dairy industry.

Animals↗
PubMedDate not supplied

[The electric conductivity indices of the skeletal muscles in the dynamics of the posttraumatic period].

In order to determine the time of inflicting mechanical trauma, values of electric conduction of skeletal muscles were measured taking into consideration postmortem interval and temperature of an object tested. Electric conduction of traumatized and intact muscles was determined within 0, 6, 12, 24, 48 and 72 hr of posttraumatic period directly after death (the 1st series of observations) and in different postmortal periods. The results of investigations disclose presence of certain time-course changes in parameters of electric conductivity of skeletal muscles depending on time of posttraumatic period.

Animals↗
PubMed1975

[Effect of various factors on the electric conductivity of mixed milk].

The authors evaluated the method of the determination of the electric conductivity of purchased milk for the estimation of the hygienic aspects of milk quality and for mass diagnosis of the inflammatory diseases of dairy cow mammary glands. The variability coefficient of duplicates varied from 1.37 to 3.09%. The study of the dependence of milk conductivity measurement on milk temperature revealed a statistically highly significant positive correlation between the values of these two factors. In the temperature range from 30 degrees C to 35 degrees C the coefficients of correlation ranged from 0.951 to 0.996. Furthermore, interference caused by milk acidity was examined during a five-day incubation of samples at 25 degrees C. A statistically significant difference was observed from the third hour of incubation (P less than 0.05) and a statistically highly significant difference from the fourth hour of incubation (P less than 0.01). The evaluation of the diagnostic value of the method of the measurement of electric conductivity in purchased milk revealed a positive correlation to the content of chloride ions (r = 0.69) and to the number of the cellular elements of milk (r = 0.33).

Animals↗
PubMed1975

[Influence of some factors on the electric conductivity of mixed milk].

The authors evaluated the method of the determination of the electric conductivity of purchased milk for the estimation of the hygienic aspects of mlik quality and for mass diagnosis of the inflammatory diseases of dairy cow mammary glands. The variability coefficient of duplicates varied from 1.37 to 3.09%. The study of the dependence of milk conductivity measurement on milk temperature revealed a statistically highly significant positive correlation between the values of these two factors. In the temperature range from 30 degrees C to 35 degrees C the coefficients of correlation ranged from 0.951 to 0.996. Furthermore, interference caused by milk acidity was examined during a five-day incubation of samples at 25 degrees C. A statistically significant difference was observed from the third hour of incubation (P less than 0.05) and a statistically highly significant difference from the fourth hour of incubation (P less than 0.01). the evaluation of the diagnostic value of the method of the measurement of electric conductivity in purchased milk revealed a positive correlation to the content of chloride ions (r = 0.69) and to the number of the cellular elements of milk (r = 0.33).

Acids↗
PubMed1976

Electrical conductivity in lipid bilayer membranes induced by pentachlorophenol.

Electrical conductivity induced in thin lipid bilayer membranes by pentachlorophenol has been studied. The membranes were formed from phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl glycerol and various amounts of cholesterol. The position and the magnitude of the maximum of the conductivity vs. pH curve depend on the type of lipids and cholesterol content. At low pentachlorophenol concentrations and low pH the concentration dependence of conductivity is quadratic and becomes linear at higher pH. Above 10(-5) M of pentachlorophenol the concentration dependence of the membrane conductivity tends to saturate. Presence of pentachlorophenol enhances membrane transport of nonactin-K+ complex. Increase of cholesterol content increases pentachlorophenol induced conductivity in all membranes and shifts the conductivity toward lower pH. For phosphatidyl choline the largest rate of change of membrane conductivity with cholesterol occurs at 1:1 phospholipid to cholesterol molar ratio. Pentachlorophenol is found to be a class II uncoupler and the experimental results are consistent with the hypothesis that the membrane permeable species are dimers formed by combination of neutral and dissociated pentachlorophenol molecules. Several schemes of membrane conduction, including dimer formation in the aqueous phase as well as at the membrane-water interface have been considered. Arguments are given in favor of the formation of dimers within the membrane surface.

Electric Conductivity↗
PubMed1979

A PCO2 surface electrode working on the principle of electrical conductivity.

A PCO2 electrode working on the principle of electrical conductivity is described. The calibration curve can be linearized according to the formula G = Go + b square root PCO2. This linearity has been tested in the PCO2 range of 0.93-9.33 kPa (7--70 Torr). For the experiments electrodes are used which have conductivity values of about 50 nS and drifts of maximally 5%/h at a PCO2 of 5.33 kPa (40 Torr). The response time (T90) is about 20 s. The temperature sensitivity is 2.4 nS/1 K between 298 K-310 K. The standard error of the measurements is sigma = 0.33 nS. With these electrodes tissue PCO2 can be measured on the surface of various organs.

Carbon Dioxide↗
PubMed1976

The effect of the phase transition on the hydration and electrical conductivity of phospholipids.

Adsorption isotherms for various saturated phosphatidylcholines have been obtained. Lipids above and below their phase transition temperature differ only in the amount of water adsorbed and not in the nature of their adsorption isotherms. Cholesterol has an effect similar to that of increasing unsaturation in the hydrocarbon chains. Decreasing the length of the hydrocarbon chains for lipids below their phase transition temperature has no effect on the isotherms. If the chain length is short enough so that the lipids are above their transition temperature, however, a large increase in water adsorption occurs. All of the phospholipids exhibit a rapid increase of electrical conductivity for a few water molecules adsorbed per lipid molecule. All of the phospholipids show a saturation in conductivity at greater amounts of adsorbed water; the shape of the saturation region depends on whether the lipids are above or below their phase transition temperature. The activation energy for the electrical conductivity process depends on whether the hydrated lipids are in the "liquid-like" of the crystalline state, being lower for phospholipids in the liquid-like state. If the lipids are hydrated above their phase transition temperatures, their activation energies are lower than if they are hydrated below the transition temperature. Cholesterol lowers the activation energy. The phosphatidylcholines can be characterized by different activation energies, depending both upon their physical state and the presence of unsaturation in their hydrocarbon chains.

Binding Sites↗