The Physiology of Contractile Vacuoles X. Effects of High Hydrostatic Pressure on the Contractile Vacuole of a Suctorian

INTRODUCTION The effects of high pressure on living material are little understood and probably complicated. In a number of cases the tendency of cytoplasmic inclusions to become stratified by centrifuging is increased, and this is attributed to a decrease in protoplasmic viscosity (Marsland, 1942). High pressure is therefore considered to solate protoplasmic gels. In addition, high pressure affects contractile structures; at ordinary temperatures it increases the tension of muscle during contraction (Brown, 1934, 1936) and it temporarily increases the frequency of beat of certain cilia (Pease & Kitching, 1939). The effect of pressure on the rate of beat of tadpole heart tissue depends upon temperature; increased pressure causes a temporary increase in frequency at temperatures above 16 C, but a decrease below 14 C. (Landau & Marsland, 1952). It appears that several reactions or processes are differentially affected. It seems likely that all the effects mentioned, including the solation of protoplasmic gels, have a common basis in the folding of protein molecules. This might be caused either directly or perhaps indirectly, through some contraction-causing reaction in which ATP might be concerned.