Movement of surface markers along the pinocytotic pseudopodia ofAmoeba proteus

Summary The movement of latex beads over pinocytotic pseudopodia produced byAmoeba proteus was recorded in the presence of 117.65 mM EGTA as an inducer of pinocytosis. The results show that all particles flow in the direction of pseudopodial growth, with a slightly higher velocity than the advancing frontal edge. This means that markers are removed from the base of a pinocytotic pseudopodium and gradually approach the pseudopodium tip. Two particles on the surface of the same pseudopodium can move at the same rate or differ slightly in the velocity of their forward flow. A bead can move even if another blocks the channel orifice. Retrograde particle movement has never been observed. Whether all latex spheres bound to pinocytotic pseudopodia flow with the laterally mobile plasma membrane fraction, which slides over submembranous contractile layer, or whether the whole cortical complex, the actin network and the plasma membrane, move together towards the invagination site is discussed.