Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Conductometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

[Ionic conductance of protein films at the temperatures -50-0 C].

Based on the analysis of the dielectric Maxwell's relaxation in a double-layer construction of protein and lavsan films an electrodeless method for measuring a. c. conductivity of protein films was developed. The conductivity of BSA films soaked in electrolyte solution was shown to retain its ionic character at subzero temperatures up to -50 degrees C in spite of an about 3-orders drop in the conductivity at 0 degrees C.

Animals↗
PubMedDate not supplied

Pulmonary mechanics in methacholine induced asthma.

We submitted eight asthmatics (age range 24-51 years) to progressively increasing doses of inhaled methacholine. Mechanical studies were done before and after each dose of methacholine and also after an inhalation of 240 micrograms of Ipratropium Bromide (IB). Recordings included: Thoracic gas volume at FRC (TGV), airways resistance (Raw), flow volume loops and static pressure/volume relationship (Pst/V). Exponential fitting of Pst/V curve was done according to previous studies, and maximal flow/static recoil curves were drawn with the data previously obtained. Considering the variation of SGaw as an index of airway reaction we found a good correlation between this parameter and MEF. Cdyn and the slope between MEF. The increase of TGV was in good correlation with SGaw as a percentage of control value. We could not find any significant variation in Specific Distensibility (Dsp) or Pst max. Our results support previous studies that have shown a insignificant modification of the elastic properties of the lung. The volume increases observed by plethysmography must be cautiously interpreted. We suggest that this modification may be the result of various factors, i.e. technical, mechanical (airways collapse, air trapping) and biological factors (surface forces, alveolar relaxation). Our data confirms the predominant central action of Ipratropium Bromide.

Adult↗
PubMed1979

Temperature dependence on the passive and dynamic electrical parameters of muscle cells.

Measurements of the temperature dependence in the range from 10 C to 30 C on the passive and dynamic electrical properties of single frog muscle cell following Arrhenius relation have been made. The propagated responses (V-t) and conduction velocity theta were analyzed following the H-H propagated cable equation. The ionic current-membrane potential relationship (I-t) was calculated from the phase-plane trajectory analysis (V-V) of the action potential curve (V-t). All the rate and time constants of the excitation and propagation processes kr, kNa, kK, tau Na, tau K, the negative conductance (-gNa) and the ionic conductances gNa, gK, influencing the evolution of the curves (V-t), (V-V) and (I-V) are correlated. The magnitudes of the resting (Vr) and action potential amplitude (Vs), the excitation potential (V*), the negative after potential (Vn), and the sodium equilibrium potential (VNa); the magnitudes of the maximum rate of rise and fall of the spike (V+) and (V-) and those corresponding to the inward INa and outward IK ionic currents, were analyzed. Two general classes of findings were obtained. One group of action potential parameters theta, V+, V-, Vn, kr, kNa, kK, tau Na, tau K, -gNa, gNa, gK, INa and IK is strongly temperature dependent with Q 10 S approximately 2 and energy of activation E approximately 10 kcal/mole. The other group of parameters, Gm (passive conductance), Cm (capacitance), tau, Vr, V*, Vs, and VNa are slightly temperature dependent, with Q10's lower than 1.4. This study contributes deeply to the analysis of temperature effects on the electrical cell responses to adequate stimuli. This temperature dependence analysis was designed to detect possible "masked" actions of microwave radiation on cell membrane functions.

Action Potentials↗
PubMedDate not supplied

[Conductometric method of studying hemocoagulation].

A conductometric method for studying flowing blood coagulation is proposed. Phases of conductograms characterizing the kinetics and intensity of blood cells aggregation, release of biologically active compounds, fibrin formation, its mechanical properties, retraction process and fibrinolysis of clot are analysed on the basis of their biophysical mechanisms.

Adult↗
PubMed1986

Microconductimetric assay of butyrylcholinesterase activity.

A conductimetric method for the assay of butyrylcholinesterase is described. A new conductimetric cell has been used which allows increased sensitivity. The physicochemical parameters (pH, buffer concentration) have been optimized. With 1 mM butyrylcholine, butyrylcholinesterase activities down to 2 x 10(-4) U ml-1 may be measured. Serum volumes needed for this assay are in the microliter range (1-5 microliters).

Animals↗
PubMed1979

The reaction of solvated electrons with cytosine, 5-methyl cytosine and 2'-deoxycytidine in squeous solution. The reaction of the electron adduct intermediates with water, p-nitroacetophenone and oxygen. A pulse spectroscopic and pulse conductometric study.

Using conductivity detection, pulse radiolysis experiments showed that solvent protonation of the electron adducts of cytosine, 5-methyl cytosine and 2'-deoxycytidine occurs with rate constants k greater than or equal to 2 x 10(4) M-1S-1. The protonated electron adducts transfer an electron to p-nitroactetophenone (PNAP) with rate constants ranging from 3.5 x 10(9) to 5.3 x 10(9) M-1S-1. The transfer is quantitative (G = 2.7), as shown by conductometric and spectroscopic measurements. In the presence of O2 no electron transfer to O2 takes place, implying that O2 adds to the protonated electron adduct radicals. No electron transfer from the H- and OH-adducts of the cytosine derivatives, either to PNAP or to O2, takes place near neutral pH. It is suggested that the differences in the reaction behaviour of the H-adduct radicals and the protonated electron adduct radicals towards PNAP can be accounted for if different radicals are formed by H-addition and protonation of the electron adduct. The H atoms most probably add to the C-5-C-6 double bonds, whereas the electron adducts are protonated at N-3 and/or 0-2.

Acetophenones↗