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D V Rai

Publications and source records attributed to D V Rai.

10 recordsLinked to original sources
PubMed2006

Impedance of goat lens as a function of frequency at DC voltages 0, 50, 100, 200 mV.

Impedance characteristics of lens tissue has been studied using the AC impedance system (EG&G PARC, model 318) at different low voltage excitations using a Cole-Cole Plot. The extracellular resistance (Re), intracellular resistance (Ri), depressed angle (theta), total impedance (/Z/), and phase angle (phi) of the tissue were measured. The impedance locus between the real part (Z') and imaginary part (Z'') of the complex impedance of lens was examined at discrete frequencies ranging from 10 mHz to 10 Hz. A decrease in extra-cellular resistance (Re) and increase in distribution of the factor (alpha) of 56.8 KOmega, 48.1 KOmega, 32.8 KOmega, 13.4 KOmega, and 0.40, 0.43, 0.46, 0.53 were found at 0 mV, 50 mV, 100 mV, and 200 mV, respectively. The total impedance (/Z/) and phase angle (phi) were also evaluated and the observed frequency dependent for the frequency range was tested as a function of excitation voltage. An attempt has been made to explain the effect of voltage stress on lens impedance.

Animals↗
PubMed1999

Effect of low voltage on electrical properties of eye lens.

In the present study, the Cole-cole plot of lens tissue has been drawn using AC impedance system (EG and G PARC Model 318) in the frequency range 10 mHz to 10 Hz at low voltage stress. The impedus locus between real part (Z') and imaginary part (Z") of complex impedance of lens was examined. Results showed that the extracellular resistance (Re), distribution factor (alpha) and depressed angle (theta) were significantly varied at experimental low voltages. An attempt has been made to explain the electrical data of voltage-tissue interaction on the basis of solid state biophysics.

Animals↗
PubMed1998

Impedance of goat eye lens at different DC voltages.

A computer assisted AC impedance system is used to measure the DC voltage-current (V-I) characteristics and AC impedance of a goat eye lens using a two-probe Ag-AgCl electrode system. The measurement of the V-I characteristics shows that when a DC voltage from 0 mV to 30 mV is applied, the resultant current decreases from an initial value of 0.58 microA to 0.006 microA. However, when the voltage is increases beyond 30 mV, the current increases and reaches a value of 0.9 microA at 100 mV. The data on the frequency response (0.01-10 Hz) of the impedance of lens tissue show an inverse relationship with frequency. The effect of various DC voltages, namely 0, 30, 50, 100 and 200 mV, on the impedance of the eye lens is also investigated over a frequency range of 0.01-10 Hz. The measurement results for both V-I characteristics and AC impedance further suggest the presence of a 30 mV voltage compartment in the goat eye lens.

Animals↗
PubMed1997

Impedance of a goat eye lens.

The complex electrical impedance of a goat eye lens is studied in the frequency range 10 mHz-10 Hz at room temperature, using a computer-controlled AC impedance system. AC impedance software (model 368, version 2.2) is employed to determine the total impedance and capacitance of the eye lens at various frequencies. A Cole-Cole plot of the eye lens material is drawn between the real component of impedance Z' and the imaginary component Z" for each excitation frequency that shows a perfect arc of a-semicircle, with its centre lying below the abscissa at an angle of 35 degrees. The half-angle phi between R(0) and R infinity is found to be 55 degrees, which mathematically demonstrates the selective permeability of the eye lens. Using graphical analysis of the Cole-Cole plot, characteristic frequency fc and distribution factor alpha are observed to be 1 Hz and 0.77, respectively. At characteristic frequency, capacitance and total impedance are found to be 1.14 microF and 9.08 k omega. The effect of electrode polarisation on capacitance is corrected, based on Fricke's power function. The observed electrical parameters are then used to explain the multiple current path through various tissue compartments. Further, an attempt is made to explain the results on the basis of a possible dipolar model.

Animals↗
PubMed1997

Escape mutants of foot-and-mouth disease virus selected by monoclonal antibodies directed to a trypsin-sensitive neutralization epitope.

Five monoclonal antibodies (MoAbs) against Indian reference/vaccine strain of foot-and-mouth disease (FMD) virus subtype A22 (IND17/77) and a guinea pig antibody against a synthetic peptide representing amino acids (aa) 136-151 of VP1 polypeptide of A22 virus were used in the study. All the antibodies either failed to react or showed a reduced reactivity with trypsin-treated (TT)-146 S virus particles in enzyme-linked immunosorbent assay (ELISA), and could neutralize the infectivity of the reference virus. The antibodies were hence identified as specific to a trypsin-sensitive neutralizable antigenic site of the virus. Using the antibodies we isolated mutants which showed either no or reduced reactivity with the homologous as well as heterologous antibodies in ELISA. The mutants could not be neutralized with the respective antibodies but were efficiently neutralized with the serum from vaccinated cattle (BVS). These results indicated that the antibodies elicited in cattle following vaccination protected them adequately against the mutants selected and that the trypsin-sensitive neutralizable antigenic site of FMD A22 virus as identified by the MoAbs may not be dominant in eliciting a neutralizing antibody response in vaccinated cattle.

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PubMed1996

Comparison of a radioactive and non-radioactive method for sequencing foot and mouth disease virus isolates.

The authors compare the radioactive method of detecting foot and mouth disease virus sequence products with a non-radioactive, silver stain sequencing method. The latter was found to compare favourably to the radioactive technique for detecting such products. The silver stain sequencing method was simple and did not require expensive specialised equipment. This new approach will be particularly useful in developing countries, since the method does not depend on the availability of fresh radioactive isotopes and is also safer and considerably cheaper.

Animals↗
PubMed1996

Near ultraviolet radiation induced changes in goat lens.

The possibility that the ultraviolet radiation from sunlight and other ambient sources as a major causative factor for the onset of cataract processes and photolytic changes of the eye lens constituents was studied. Normal goat lenses exposed in vitro to near UV radiation in the region of 315-400 nm (UV-A) revealed distinct morphological changes in the ultrastructure, increase in the inorganic elements; C, H, N, and a sharp shift in the intrinsic fluorescence spectra. UV exposure resulted in an alteration in the lambda max of the excitation spectra, a red shift in the emission absorption maxima and also an increase in the absolute fluorescence intensity. Scanning electron microscopic study showed a significant increase in the interfibrillar distances of the lens structural proteins. It is argued that the UV light induced covalent modifications of the lens proteins and their aggregations might have occurred due to the generation of photolytic products which then lead to oxidative damages.

Animals↗
PubMed1986

Biophysical characterization of osteoporotic bone.

A number of biophysical and biochemical parameters have been measured in normal and osteoporotic animals and their bones. Rats have been fed normal and calcium- and phosphorus-deficient diets (through mineral content) from the weaning period to maturity (greater than 125 days). The experiments were performed after attaining this age. Biochemical parameters considered for comparison included: red blood cells (RBC), white blood cells (WBC), Hb, serum calcium and phosphorus, blood pH, PCO2, and PO2. Bones obtained after sacrificing mature animals were used for obtaining data regarding infrared, fluorescence, and X-ray spectra, and transmission electron micrographs, and were also subjected to spectrochemical analysis. It was found that the two sets of results show differences in most of the above-mentioned parameters, which correlates well with the loss of calcium and phosphorus metabolism and the corresponding increase in the amorphous-to-crystalline ratio. It is hoped that these data will be useful in characterizing the osteoporotic bone and will suggest the mechanism for reversal by external stimulations.

Animals↗
PubMed1979

On the solid state of bone.

Photovoltaic effect (infrared and visible light) is observed in bone and its two major components, collagen and apatite, at room temperature. A dimunition in the magnitude of photovoltage is observed after exposure to ultraviolet light in all the cases. The drift mobility of the charge carriers is obtained by measuring I versus V relationships in sandwich samples and relating them to the permittivity of the medium. Lifetime of the injected carriers is measured in the usual way. The data are consistent with the hypothesis that the effects are due to protonic conduction phenomena.

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