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Biomedical subjects

J R Clay

Publications and source records attributed to J R Clay.

61 records · Page 4Linked to original sources
PubMed1977

Random walk analysis of potassium fluxes associated with nerve impulses.

We present a novel recursion method for obtaining theoretical expressions for unidirectional single-file fluxes of ions through narrow membrane channels containing an arbitrary number of ion sites. The theory is applied to experimental tracer fluxes associated with nerve impulses from cephalopod giant axon membranes at various temperatures between 7 degrees and 27 degrees. The comparison between the theoretical and experimental one-way fluxes suggests that the potassium channel in nerve membrane contains three ion sites, which is consistent with the deduction by Hodgkin and Keynes that the potassium channel contains two or three sites on the basis of the ratio of tracer influx to tracer efflux. The analytical results in this paper provide a further test of the single-file model for nerve and other membrane preparations.

Action Potentials↗
PubMed1976

Theoretical model of the ionic mechanism of 1/f noise in nerve membrane.

A model is presented for the ionic mechanism of low frequency 1/f electrical noise which has been observed in axonal membranes. The model consists of narrow channels which open randomly throughout the membrane and remain open for only a short time compared with f-1max where fmax approximately 2 kHz is the maximum frequency for which 1/f noise is observed. The fluctuation in channel formation is coupled to low frequency normal mode vibrations in liquid crystals which have properties similar to nerve membranes. Ionic current flow through the channels is assumed to occur via single file diffusion. The diffusion process is regarded as a non-Markovian random walk on a one-dimensional lattice which is mathematically decomposed into its spatial and temporal components. This technique allows calculation of the mean and variance of the number of ions which flow through any single short-lived channel. The final result for the current noise power spectrum, S, is S(f) = (A + k/I/2)/f, where I is the mean membrane current and A and k are parameters which are independent of membrane voltage. The theoretical result is consistent with observations of 1/f noise in lobster axon by Poussart (1971, Biophys. J. 11:212.) on the dependence of S(f) on the mean steady-state current and the external potassium concentration. We also calculate the mean channel density and the Frank elastic constant of the membrane. This work is an extension of a macroscopic model of Lundström and McQueen (1974, J. Theor. Biol. 45:405.) who obtain a spectral density of the form S approximately /I/2/f.

Animals↗
PubMedDate not supplied

Tobacco cessation: a practical dental service.

Tobacco use is a complex addiction that must be addressed in all aspects of health care. Despite the deleterious and costly outcomes of tobacco use, Americans still are smoking and using smokeless tobacco. Dentists are trained to detect oral lesions and periodontal problems that are related to tobacco use. Dentists also are in a position to help prevent the initiation of tobacco use by children and adolescents through the use of positive anti-tobacco messages. Over the past decade, tobacco cessation strategies have been modified for practical use in the dental setting.

Child↗