Assessing the numerical accuracy of the impedance method

The impedance method has been used extensively to calculate induced electric fields and currents in tissue as a result of applied electromagnetic fields. However, there has previously been no known method for an a priori assessment of the numerical accuracy of the results found by this method. Here, we present a method which permits an a priori assessment of the numerical accuracy of the impedance method applied to physiologically meaningful problems in bioengineering. The assessment method relies on estimating the condition number associated with the impedance matrix for problems with varying shapes, sizes, conductivities, anisotropies, and implementation strategies. Equations have been provided which predict the number of significant figures lost due to poor matrix conditioning as a function of these variables. The results show that, for problems of moderate size and uncomplicated geometry, applied fields should be measured or calculated accurately to at least five or six significant figures. As resolutions are increased and material properties are more widely divergent even more significant figures are needed. The equations provided here should ensure that solutions found from the impedance method are calculated accurately.     

Method for studying the adaptation of Escherichia coli to the acidification of the medium

Apparatus permitting to regulate the growth rate of turbidostat culture of microorganisms has been worked out. The process of adaptation of culture microorganisms to the medium acidity has been investigated by the stabilization of growth rate method. The correlation coefficients between adaptation time and changes of acid concentration in medium have been determined. The effect of aeration and density of microorganisms on the parameters of adaptation process has been considered. The conclusion concerning prospects of the growth rate stabilization method application for studying the regularities of culture microorganisms adaptation to the action of the stress has been made.     

Electron microscope detection of biogenic amines in the medulla of the adrenal gland of the normoglycemic spiny mouse (Acomys cahirinus)

By means of a modification of the Reinecke salt method already described, characteristical amine containing granules have been demonstrated in the parenchymal cells of the adrenal medulla in normoglycemic spiny mice. By this method two types of granules have been discerned according to their different contrasts. The advantages of the modification method are discussed.     

Spectrophotometric quantitation of antioxidant capacity through the formation of a phosphomolybdenum complex: specific application to the determination of vitamin E

A spectrophotometric method has been developed for the quantitative determination of antioxidant capacity. The assay is based on the reduction of Mo(VI) to Mo(V) by the sample analyte and the subsequent formation of a green phosphate/Mo(V) complex at acidic pH. The method has been optimized and characterized with respect to linearity interval, repetitivity and reproducibility, and molar absorption coefficients for the quantitation of several antioxidants, including vitamin E. The phosphomolybdenum method, in combination with hexane monophasic extraction, has also been adapted for the specific determination of vitamin E in seeds. The results obtained with the proposed method were validated by comparison with a standard HPLC method. The phosphomolybdenum method is routinely applied in our laboratory to evaluate the total antioxidant capacity of plant extracts and to determine vitamin E in a variety of grains and seeds, including corn and soybean.     

An alternative method to the osmotic stressing polymers: the osmomanometer

Although stressing polymers have been widely and successfully used to determine the osmotic properties of solutes in aqueous media, the osmotic stress method presents some limitations. To overcome these drawbacks, an alternative and more direct method, which has been named the osmomanometer, is described in this letter. The osmotic pressure accessible by this method ranges typically from 1 to 30 kPa using a simple hydrostatic effect and can be extended to higher pressures by using pressurized gas. This method needs neither a pressure sensor nor calibration.     

A general method for the rapid measurement of enzyme precursors by the displacement of enzyme from antibody: the measurement of collagen proline hydroxylase precursor in cultured fibroblasts

A method has been developed for measuring inactive forms of an enzyme by displacing active enzyme from its antibody. The unbound enzyme is measured by an enzymatic assay. The method has been applied to the measurement of the precursor of collagen proline hydroxylase in cultured fibroblasts.     

A radioimmunoprecipitation method in the serodiagnosis of HIV infection: the development of the optimal conditions for its performance and the evaluation of the possibilities for its use

The optimum conditions for using the method of radioimmunoprecipitation (RIP) for the detection of human immunodeficiency virus (HIV) in serum samples have been established. Out of several available cell lines persistently infected with HIV, specially selected line 17 has been chosen. The characteristic feature of this is the high and stable (under the conditions of prolonged cultivation) accumulation of virus-specific proteins in infected cells. The optimum conditions for making the test and its evaluation have also been established. The data of literature on the advantages of the method of RIP over such traditional methods as the enzyme immunoassay and immunoblotting have been confirmed. Thus, the presence of specific antibodies in several serum samples registered as false negative has been established. The intertypical reactivity of two serotypes of the virus, HIV-1 and HIV-2, has been studied. Cross reactivity of antibodies with respect to the HIV gene gag, but not with respect to viral glycoproteids, has been established. Ideas on the expediency and prospects of using RIP for the serological control of HIV infection are presented.     

Use of the hummel and dreyer method for the study of nucleotide binding on chloroplast ATPase CF1

The study of the binding of the nucleotides ADP and ATP on the exchangeable sites of chloroplast ATPase CF1 has been carried out by the Hummel and Dreyer method applied to HPLC. It has been shown that this method was well fitted to the problem: rapidity of exchange, absence of noticeable modification after binding, presence of a constant concentration of ligand during the chromatography, which stabilizes these low affinity complexes. The dissociation constants of binding of ADP, ATP and of their magnesium salt complexes have been determined. In order to measure the simultaneous binding of ADP and ATP when present in mixture, we have modified the method by using an anion-exchange column in place of the gel filtration column: the two nucleotides were easily separated, while the binding on the protein was unchanged. The extension of this method to the reversed-phase chromatography could also be considered for the binding of hydrophobic ligands.     

A method for isolating intact mitochondria and nuclei from the same homogenate,and the influence of mitochondrial destruction on the properties of cell nuclei

1. An improved type of ground glass homogenizer for soft tissues has been described which brings about a high degree of cell disruption and liberation of nuclei without causing appreciable damage to mitochondria. The gentleness and effectiveness of the new homogenizer in respect to isolation of mitochondria have been ascertained by comparing the ATP-ase activities of mitochondria isolated in 0.25 M sucrose solution without pH adjustment using a previous type of homogenizer with those of mitochondria isolated under the same conditions with the aid of the new homogenizer. In these experiments sucrose of 0.25 molarity without pH adjustment has been used in order to maintain the mitochondria in a rather sensitive state so as to make slightly deleterious effects of homogenization readily apparent. 2. A new method is described for the isolation of morphologically intact mitochondria and cell nuclei from the same homogenate. In this procedure the pH of the homogenate in 0.44 M sucrose is maintained at 6.0-6.2 with citric acid during the homogenization. An alternative method employing 0.44 M sucrose plus 0.005 M CaCl(2) is given for the isolation of nuclei from tumor cells. However, the latter method does not produce unaltered mitochondria. 3. The alpha-ketoglutarate, malate, succinate, and hexanoate oxidases of the "intact" mitochondria isolated in 0.44 M sucrose adjusted to pH 6.0-6.2 with very dilute citric acid as described in this paper have been investigated, and it has been shown that the mitochondria compare favorably to those isolated in 0.25 M sucrose by a previously described method. 4. Mitochondria have been found to contain an enzyme which causes nuclei to lose their ability to form gels in dilute alkali. This enzyme is released from the mitochondria when the latter are disrupted. 5. Some properties of nuclei isolated by the new method have been briefly discussed.     

Application of the Free Energy Calculations to Study Drug-enzyme and Drug-dna Complexes

Applications of two free energy calculation approaches are presented to study drug-biomolecule complexes. The first method, the free energy perturbation (FEP) method and molecular dynamics simulations has been applied to study the JG-365 inhibitor bound to the HIV-aspartic protease. The FEP method has been applied to predict the consequence of replacing each of the seven peptide bonds in the JG-365 by trans-ethylene or fluoroethylene units. The necessary initial conformations of the inhibitor for "in water" perturbations have been found using neural network clustering approach applied to the long molecular dynamics trajectory of the inhibitor in water solution. The second method is applied to study binding free energies of some DNA-drug complexes and is based on analysis of long molecular dynamics trajectories by continuum solvent approach (MM/PBSA).     

A sensitive assay method for the measurement of S-adenosylmethionine in tissue

An assay method has been developed for the measurement of tissue levels of S-adenosylmethionine based upon the ability of this compound to activate tripolyphosphatase associated with S-adenosylmethionine synthetase beta prepared from rat liver. The method has been used to measure S-adenosylmethionine levels in rat liver after feeding rats on various concentrations of methionine in the diet. The results obtained by this method agree well with those measured by the spectrophotometric method. The limit of sensitivity of the assay was about 0.1 nmol of S-adenosylmethionine in an incubation volume of 0.1 ml (10(-6) M).     

Restriction endonucleases: the detection of new producer strains and the isolation of enzyme preparations]

The method for analysis of microorganisms for the presence of the modification-restriction systems has been developed. The method has permitted to detect more than 10 new producing strains of restrictases including microorganisms of Rhizobium genus. Some of them are promising for practical use. It has been shown that using selection of clones the strain productivity can be increased. The purification process for the majority of restrictases has been proposed. Some physical and catalytic properties of new enzymes have been studied.     

Development of a mouse model to estimate the potency of the diphtheria toxoid component of diphtheria-tetanus and diphtheria-tetanus-pertussis vaccines

A mouse model to estimate the potency of the diphtheria toxoid component in diphtheria-tetanus vaccines and diphtheria-tetanus-pertussis vaccines has been developed as an alternative to the conventional method of testing in guinea-pigs. Optimal conditions with regard to dose, route and period of immunization have been standardized. The maximum levels of antitoxin were detected five weeks after vaccination and the s.c. route was found to be optimal. Potency data have been compared with other studies in mouse models and with those obtained by the conventional method in guinea-pigs.     

Investigation into the production of bacteriostatic substances by fungi

A method is suggested for estimating the degree of potency and, to some extent, the specificity of bacteriostatic substances produced by fungi. It is based on the examination of several hundred fungi over a period of 2 years. It consists essentially of the placing of a few drops of the substance to be tested in the centre of a plate of bacteria-incorporated agar with the consequent production of a zone of inhibition which varies in width in proportion to the concentration of the bacteriostatic substance. The test is made against two representative types of bacteria— Bact. coli and Staph, aureus. The permissible technical latitude in the application of the test has been summarized. By using a standard inhibitor (mercuric chloride) the accuracy of the method has been statistically proved. This 'zonation' method has been compared with the standard 'dilution' method and close correlation has been established.     

Solvent effect on the stability of mannobiose conformers

The conformational equilibria of seven methyl β-D -mannobioside conformers have been studied theoretically in five solvents. The structure of each individual conformer has been refined by the PCILO quantum-chemical method from the seven distinct low-energy regions determined from (Φ, Ψ) maps calculated by a potential function method. The stability of the conformers in dilute solution has been evaluated by using a method that consists of electrostatic, dispersion, and cavity terms. The calculated abundance of conformers depends on the solvent and results indicate that the preponderant conformer in the solution may not be the one adopted by mannobiose in the crystalline form. Based on the determined abundance of conformers, thermodynamically averaged nmr parameters, dipole moment, and linkage rotation have been calculated. The solvation behavior of methyl β-D -mannobioside is compared to those previously estimated for cellobiose and maltose.     

Use of protein A in the immunosorbent analysis of antibodies to the tick-borne encephalitis virus

The results of the studies made with a view to developing the method for the determination of specific antibodies to the antigen of tick-borne encephalitis virus in human blood serum and liquor are presented. The method is based on the capacity of Staphylococcus aureus protein A to bind with Fc-region of immunoglobulins, which makes it possible to use this protein as the "second" system of antibodies. The conditions for the sorption of the antigen on polystyrene test tubes and for binding 125I-or horse radish peroxidase-labeled protein A preparations with antibodies have been determined, and the method has been approved in tests made on sera and liquor obtained from donors and tick-borne encephalitis patients.     

Quantitative immunoenzyme technic in the evaluation of specificity of the beta 1-g-globulin test in trophoblastic tumors]

The method of guantitative immunoenzymatic determination of beta 1-G-globulin (TSG) in the blood serum has been developed. The sensitivity of the method is 6 ng/ml TSG. It has been shown that elevated levels (12-100 ng/ml and higher) are usually observed in trophoblastic tumours of the uterus. The TSG ectopic synthesis is found to proceed in some tumours of the gastrointestinal tract and testicular teratoblastomas.     

Study of the parietal microflora in the rat intestine

The article deals with the adaptation of the existing method of the isolation of microorganisms from parietal mucin of the intestine of experimental animals (rats) with a view to ensure the methodological uniformity of investigations. The effectiveness of the method of sparing disintegration of parietal mucin taken from the mucous membrane of the gastrointestinal tract, specially developed for human biomaterial, and its adequacy for microbiological investigations of the digestive organs of rats have been confirmed. A certain similarity between the microbiocenosis of the parietal mucin in the intestine of humans and rats has been established.     

Bismuth citrate in the quantification of inorganic phosphate and its utility in the determination of membrane-bound phosphatases

This paper describes a rapid and sensitive method to determine inorganic phosphate, even in the presence of labile organic phosphate compounds and large quantities of proteins. The method eliminates the use of sodium arsenite, a highly toxic compound, substituting bismuth citrate for it to stabilize the phosphomolybdic acid complex formed during the interaction of inorganic phosphate and molybdate reduced by ascorbic acid. This method has also been adapted to microplates and has been used to determine the activities of Na/K ATPase and alkaline phosphatase of intestinal basolateral and luminal plasma membranes.