Peter Satir

Membrane renewal after dibucaine deciliation of Tetrahymena. Freeze-fracture technique, cilia, membrane structure.

Abstract Axenic late log phase cultures of Tetrahymena pyriformis DN-B3 are deciliated by treatment with dibucaine. Deciliation occurs first at the anterior end of the cell and then progresses posteriorly. Concomitantly, all mature mucocysts are induced to discharge by the drug. The exact point of scission of each cilium is found to be a very localized region, between two specialized membrane arrays: the ciliary necklace and the ciliary patches, situated at the base of the cilium. Isolated cilia retain the patches, while the necklaces remain with the deciliated bodies. The cell membrane seals over the stubs. The new ciliary membrane then grows out above the necklace without the patches, which do not generally appear for several hours. Membrane renewal is therefore asynchronous, with bulk growth preceding the formation of specialized intramembrane particle arrays. During regrowth, the cilia also first return at the anterior end of the cell. This suggests that underlying gradients, perhaps related to Ca2+, are significant in the deciliation process.

Ionophore-mediated calcium entry induces mussel gill ciliary arrest

Lateral cilia of freshwater mussel gills, which normally beat with metachronal rhythm, are arrested pointing frontally by perfusion with 6.25 to 12.5 millimolar calcium and 10(-5) molar A23187, a calcium ionophore. Arrest does not occur in either calcium or ionophore and monovalent cations alone. Activity returns with continued perfusion in potassium chloride or calcium chloride, and more slowly in sodium chloride, after removal of ionophore. These results support the hypothesis that a local rise in internal calcium causes ciliary arrest.

Ciliary activity in the mouse oviduct as studied by transmission and scanning electron microscopy

Abstract The mouse oviduct is covered by dense tracts of ciliated cells interspersed at random with occasional non-ciliated cells. Correlation between scanning electron microscopy and thin section images indicates that in the isolated fimbria most cilia are short (5 µm) and inactive, resting at the end of a uterad-directed effective stroke. These cilia terminate in a 9S−2 tip, the microtubules ending in an electron-dense plaque underneath the cell membrane. At the tip of the cilium a crown of fine extracellular hairs is attached to the ciliary membrane. In the ampulla and isthmus the ciliated cells decrease progressively in number and appear to lie in crypts.

Partition coefficient of membrane particles in the fusion rosette

Abstract In freeze fracture of the Tetrahymena fusion rosetts, the fracture can pass to either side of an intercalated particle by a stochastic process, dependent only on relative bond strength to either side of the intercalation. Any given freeze fracture particle can be found on either the A or B fracture face, with a chance measured by the particle partition co-efficient (Kp).

The termination of the central microtubules from the cilia of Tetrahymena pyriformis

In frayed axonemes of cilia isolated from Tetrahymena pyriformis, observed in negative stain, the central apparatus remains intact, stabilized in part by the sheath projections that encircle the two singlet central microtubules. The projections terminate ca. 1.5 +/- 0.5 micron before the microtubules themselves end. The microtubules are capped together at their tips by a distinct structure, the central pair cap. The cap, ca. 50 nm across and 90 nm long, consists of a stack of two disks and a ball, similar in shape to a finial. The cap is the only part of the axoneme that extends to the distalmost point of the ciliary membrane and, therefore, it may be of significance in length determination or in shaping the ciliary tip.

Microvilli and cilia: surface specializations of mammalian cells

Publisher Summary This chapter discusses the surface specializations of mammalian cells—microvilli and cilia. The apical surface of an epithelial cell of the mammalian body faces the external environment. This surface can be distinguished from the junctional surfaces, where a cell is in contact with neighboring homologos or heterologos cells, and from the basal surface, which faces the internal or coelomic world and rests against a basement membrane. In a stratified epithelium, the outermost layer of cells possesses the apical surface differentiations, while the potential of the inner layers is unexpressed. The apical border might be defined for most epithelia as being that part of the plasma membrane to the lumenal side of the tight junction, the structure that prevents free exchange of material from the apical to the basal side of the epithelium. The plasma membrane of the apical surface of an epithelial cell is exposed to an environment that is different from that present at other cell surfaces. Physiological demands on this surface lead to significant molecular specialization of the membrane. Such specialization involves enzymatic and specific structural modification. The most prominent structures found as part of the apical surfaces of epithelial cells are microvilli and cilia. These determine the histotypes of cells in a complex epithelial tissue.