Some physiological and morphological effects of polylysine on Amoeba proteus

Abstract

The effect of polylysine on pinocytosis and the cell surface of Amoeba proteus was investigated. The intensity of the pinocytotic response was evaluated by a channel counting method, and the surface was examined by means of transmission and scanning electron microscopy. Cells treated with polylysine and then immersed in a protein pinocytosis inducer showed a higher intensity of channel formation during the initial stages of the cycle than cells not pretreated. This was considered to be an additive effect of the protein and the polymer, since the latter alone was demonstrated to induce pinocytosis. No influence of molecular weight of the basic polymer on this reaction could be demonstrated. As well as normal pinocytotic channels electron micrographs revealed the presence of fine channels, 20-50 nm in width, in the cytoplasm as a result of polylysine treatment. The polymer was visualized as dense surface aggregates, about 25.0 nm in diameter, associated with the extracellular material. This deposit was not seen on Amoeba dubia, which lacked a well-developed extracellular covering, and micro-channels failed to develop in this case. It has been demonstrated that when polylysine and a protein pinocytosis inducer were applied to the cell sequentially both compounds occupied the same channels. In view of the lack of effect of metabolic inhibitors on the formation of channels by polylysine it was concluded that this phenomenon is distinct from pinocytosis. It is proposed that this kind of channel formation can be explained in terms of the bridging of areas of membrane by the polymer-polysaccharide complex.