Low-resistance Coupling between Gland Cells. Some Observations on Intercellular Contact Membranes and Intercellular Space

Abstract

ALTHOUGH it is not possible at present to give a general definition of the cellular surface membrane, or even to define its spatial limits, the consensus now is that it is related to the structure which under the electron microscope appears as a three-layered complex, about 75 Å thick¹. The physiologist generally assumes that this structure represents the barrier which he finds, by indirect means, restricting the flux of ions at the cell boundary. The general idea about this diffusion barrier is that its resistance is uniformly high over all faces of a given cell. This idea derives chiefly from electrophysiological work with a rather special group of cells which, like skeletal muscle and nerve fibres, have adapted to transmit electrical signals without appreciable cross-talk between cell neighbors; or which, like blood and gamete cells, are normally unconnected. Indeed, in these elements, except for special synaptic contact regions^2–11 and certain neuroglia contacts¹², the surface resistance is in general high and, within the limits of resolution of the methods, distributed rather uniformly over the cell surface.