Mechanisms of Electricity Conduction in Brain and Kidney Studied by Impedance Measurements and Chronopotentiometric Polarography
The change of specific tissue conductivity in rheoencephalography or electroanaesthesia presents several hitherto unsolvable problems. We cannot f.i. consider a possibility that the volume relations between brain,cerebrospinal fluid and blood may have changed simultaneously with a change of electrical properties of the glial compartment.Measurements at different frequencies could partially resolve the problem (RANCK 1963) but the limiting assum ptions still remain drastic. There appears to be a need for some additional measurement to supplement the electrical impedance measurements. Polarographic studies of qualitative differences between charge carriers seemed very promising in this respect. In the past these studies were limited mainly to one aspect of electrode reactions in the tissue namely to the oxygen reduction on cathode at −0.7 V. The polarographic half-wave potential of oxygen was considered as sufficient to characterize a specific qualitative aspect of one of the tissue depolarizers. However the electrochemical reactions that actually take place on uncovered polarized electrodes in the tissue are much more complex; it becomes necessary to measure both the anodic and cathodic electrode processes with pertinent time characteristics. The biological applications of chronopotentiometry are as yet very rare. The theoretical principles and first applications were described by MILGRAM (1970) in our laboratory. In this paper we are extending the applications to a dynamic study of hypoxia in brain and kidney with simultaneous measurements of tissue impedance in wide frequency range.
KeywordsImpedance Increase Tissue Impedance Toronto General Hospital Polarographic Study Average Dipole Moment
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