Search PubMed⌕ Search

Biomedical subjects

F V McCann

Publications and source records attributed to F V McCann.

At least 37 records · Page 2Linked to original sources
PubMed1974

Studies of impedance in cardiac tissue using sucrose gap and computer techniques. II. Circuit simulation of passive electrical properties and cell-to-cell transmission.

The impedance measured in a strip of heart tissue from the moth Hyalophora cecropia is fitted by circuit models of several configurations. The circuits include: (a) a single R-C circuit (b) a double R-C circuit (c) terminated transmission lines, and (d) a pattern of cells with cell-to-cell transmission paths. The last of these is found to give the best fit. Calculation of the model impedances and optimization of element values are performed by a computer. The possibility that the mechanism of cell-to-cell transmission may be capacitative rather than conductive is explored using values of capacitance derived from the circuit models to calculate the effect of capacitative coupling alone on signal transmission. The calculations show that sufficient voltage can be transmitted from the excited cell to an adjacent cell to effect excitation.

Animals↗
PubMed1973

Studies of impedance in cardiac tissue using sucrose gap and computer techniques. I. The influence of sucrose and oil as insulating media.

Impedances of cardiac cells of an insect were determined as a function of time to test the effects of sucrose and oil as insulating media in a gap arrangement. Impedance values are shown to increase markedly with time when sucrose is used as the insulating agent. Although impedance values are steady when oil is used, it is suggested that a layer of trapped electrolyte provides a shunt pathway and seriously impairs the validity of the measurements. A quick wash with sucrose followed by oil does not alleviate the situation but leaves a layer of sucrose trapped at the tissue-medium interface into which ions diffuse. The hypotheses (a) that the diffusion of intracellular K(+) into the sucrose would result in an increase in tissue impedance and (b) that a layer of trapped electrolyte under the oil film provides a shunt pathway are examined by computer analyses of a simple model.

Animals↗
PubMed1966

Curare as a neuromuscular blocking agent in insects.

Topical application of curare produced no effects on electrical activity in single flight-muscle fibers of the fly Sarcophaga. However, the intraabdominal injection of curare induced a neuromuscular block similar to that described for vertebrates. The general refractoriness of some insects to chemical agents may well be due to the method of application.

Animals↗