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AN ELECTRON MICROSCOPIC STUDY OF PINOCYTOSIS IN AMEBA : I. The Surface Attachment Phase

Philip W. Brandt Ph.D.¹ and George D. Pappas Ph.D.²

¹ From the Department of Anatomy and Ophthalmology, College of Physicians and Surgeons, Columbia University, New York. Dr. Brandt is a "Fight for Sight" Fellow, National Council to Combat Blindness, Inc., New York. Dr. Brandt submitted this work in partial fulfilment of the degree of Doctor of Philosophy, Anatomy Department, Columbia University
² From the Department of Anatomy and Ophthalmology, College of Physicians and Surgeons, Columbia University, New York.

The attachment to the surface of the ameba (Chaos chaos L. (Pelomyxa carolinensis, Wilson)) of two proteins, ribonuclease and ferritin, and two colloidal suspensions, thorium dioxide and gold, was studied in the electron microscope. The initial step in the pinocytosis of ferritin and thorium dioxide particles by amebas is shown to be the attachment of these substances to the "hairlike" extensions of the plasmalemma. Ribonuclease caused alterations in the structure of the plasmalemma, but on account of its relative lack of density, it could not be definitely localized. Colloidal gold did not appear to be active with respect to pinocytosis in amebas. Since molecules in solution and particles in suspension are taken up by the same mechanism, the first step of which is their attachment to the cell surface, it is suggested that a single mechanism underlies phagocytosis, pinocytosis, ropheocytosis, cytopempsis, and potocytosis.

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