Minipodia, the Adhesive Structures Active in Locomotion and Endocytosis of Amoebae

Andrzej Grebecki ； Lucyna Grebecka ； Anna Wasik

《Acta Protozoologica》 40卷4期 (2001/12) Pp. 235-247

並列摘要

Amoeba proteus cells, strains A and C(subscript t), with well pronounced motor polarity (the polytactic and orthotactic forms) develop dense coats of discrete minipodia which anchor them to the glass substratum. The scanning electron microscopy demonstrates that minipodia are surface microprotrusions about 0.5 µm thick and up to 8 µm long, covering mainly the middle-anterior area of the ventral cell surface. They are few at the frontal zone and absent at the tail region. It means that the dense felt of discrete minipodia is located in the same region which has been earlier described as the zone of most efficient adhesion of a directionally moving amoeba. The cells without stable motor polarity and those which adhere to the glass without moving, or just start locomotion, lack areas covered by discrete minipodia; instead, minipodia are grouped in rosette contacts, which have the form of papillae composed of supporting platforms with crones of minipodia projected from them. The cells detached from the substratum by simple experimental procedures: radiate heterotactic forms produced by mechanical shocks, anucleate fragments obtained by microdissection, and amoebae in course of cation-induced pinocytosis, neither have separate minipodia nor rosette contacts. In contrast, during phagocytosis amoebae strongly adhere and produce dense sheaths of discrete minipodia extending along the whole surface up to the tail, except the naked front enclosing the phagosome. It was demonstrated by staining with the fluorescein-conjugated phalloidin that both types of adhesive structures: the discrete minipodia as well as the rosette contacts are very rich in the cytoskeletal F-actin.

並列關鍵字

adhesive organelles ； Amoeba proteus ； amoeboid movement ； minipodia ； rosette contacts