Particle Movement in Heliozoan Axopods Associated with Lateral Displacement of H ighly Ordered Membrane Domains

Abstract

Freeze-fracture studies reveal that extrusive organelles displaying saltatory particle movements in centrohelidian axopod are attached to highly ordered domains within the plasma membrane. It is postulated that the motive force for lateral displacement of these membrane domains with the adhering organelle is located immediately underneath the plasma membrane being either part of the peripheral membrane proteins or attached filaments alined parallel to the axopodial micro­ tubules. The attachment domain is interpreted organelle discharge by membrane fusion.

Motility occurring in association with the surface of the Chlamydomonas flagellum.

“…Bardele (6) suggests that both intracellular and extracellular particle movements occurring within the Heliozoan axopodium involve the lateral displacement of highly ordered membrane domains. He postulates that the motive force for these movements may result from the activity of contractile proteins attached to both the cytoskeletal array of microtubules within the axopodium and the ordered membrane domains.…”

Pseudopod formation and membrane production during prey capture by a heliozoon (feeding by Actinophrys, II)

“…Previous workers drew attention to peculiar extrusomes in heliozoa and implicated these in the process of prey adherence [Bardele, 1976;Davidson, 19761. It is clear that some extrusomes discharge their contents at this stage in Actinophrys.…”

“…Third, the prey of heliozoa, unlike that of rhizopod amoebae, adheres to the surface of the predator. Small bodies, extrusomes, which lie immediately under the plasma membrane of heliozoa have been implicated in the process of prey adhesion [Bardele, 1976;Davidson, 1976; Suzaki, Shigenaka, Watanabe, and Toyohara, 19801. This paper describes the ultrastructural aspects of prey adhesion and enclosure by Actinophrys sol. It attempts to shed some light on the subcellular events underlying the peculiar aspects of phagocytosis in this organism.…”

Handbook of Stable Strontium

“…The circle of IMPs immediately peripheral to the rosette is sometimes present as a distinct IMP structure (b type), but sometimes appears as a diffuse granular zone or can be completely absent (120). Plasma membrane attachment sites for mucocysts in Tetrahymena (152,154,157), conicysts in actinopods (158), and kinetocysts in heliozoans (159) are also characterized by rosettes.…”