THE "VESICLE IN A BASKET" A Morphological Study of the Coated Vesicle Isolated from the Nerve Endings of the Guinea Pig Brain, with Special Reference to the Mechanism of Membrane Movements

Five points are discussed regarding the vesicular structure isolated by fractionation techniques from the brain and liver of the guinea pig . 1 . One type of vesicle, fixed by OSO4 and shown in thin sections, is identified with the coated vesicle that has been observed in many varieties of tissues . 2. The vesicle contained in a spherical polygonal "basketwork" shown by the negative-staining techniques is identical with the coated vesicle shown in sections. 3 . Despite minute observation of this basketwork we could not confirm the existence of "hairlike projections" extending from the convex cytoplasmic surface of the vesicle . We are inclined to believe, therefore, that the hairlike projections are actually the superimposed visual images of the regular hexagons and pentagons of the network composing the basketwork . 4. We repeat the hypothesis originally advanced by Roth and Porter (1) that the "coating" of the coated vesicle plays a role in the mechanism of the infolding and fission of the membrane ; we suggest that these events are caused by the transformation of the regular hexagons (of the coating) into regular pentagons . 5 . Finally, we make a suggestion as to the nature of those vesicles which have on their surface subparticles which look like "elementary particles (2) ." 202 I N T R O D U C T I O N This article deals with the advanced hypothesis originally put forth by Roth and Porter (I) on the role of the "bristle coating" of "coated vesicles ." They suggested that when a coated vesicle appears to be formed by a pinocytosis of the apical plasmalemma, the "bristles (spines)" extending radially from the convex cytoplasmic side of the vesicle may be associated with the mechanism of infolding and pinching off. They stated that "such a mechanism using specific molecular spacing of the spines, can be envisioned to account for a gradual repulsion of the unattached ends of the spines and the consequent infolding of the membrane producing the pit, and the cytoplasmic vesicle ." Although pinocytotic vesicles seem to occur arbitrarily anywhere on cell surfaces, the cell does nonetheless acquire its essential nutrition. Hence, many cytologists have concentrated their attention upon the outer surfaces of the membranes to look for some special adsorbing apparatus that would on N ovem er 8, 2016 D ow nladed fom Published July 1, 1969