ARTICLE

STUDIES ON CILIA : II. Examination of the Distal Region of the Ciliary Shaft and the Role of the Filaments in Motility

Peter Satir ¹

¹ From the Whitman Laboratory, University of Chicago, Chicago, Illinois

Termination of peripheral filaments of the axoneme of gill cilia of fresh-water mussels (Elliptio or Anodonta) occurs in characteristic fashion: (a) subfiber b of certain doublets ends leaving a single simplified tubular unit; (b) the wall of the unit becomes thick and may even obliterate the interior; and (c) the filament drops out of the 9 + 2 pattern. The order in which doublets begin simplifying is also characteristic. This may be determined by numbering the filaments, those with the bridge being 5–6, with the direction of numbering determined by the apparent enantiomorphic configuration (I to IV) of the cross-section. Shorter filaments can be identified in simplifying tips with mixed double and single peripheral units. In this material, laterofrontal cirri show a morphological specialization in the region where individual cilia simplify. The cilia studied run frontally from the body of the cirrus and point in the direction of effective stroke. The longest filaments (Nos. 3, 4, 5, 6, 7) appear as the doublets at the bottom of the cross-section, nearest the surface of the cell of origin. Above them, and above the central pair, a dark band (a section of a dense rod) runs through the matrix. The remaining filaments are the single units. Effective-pointing frontal and lateral ciliary tips end in a fashion similar to laterofrontal tips, although no dense band is present. For all effective-pointing tips studied, the order in which the peripheral filaments end appears to be Nos. (9, 1), 8, 2, 7, 6, 3, 4, 5. However, recovery-pointing lateral tips show a different order: Nos. 7, 6, 8, 5, 9, 4, 1 (3, 2), although the longer filaments are still at the bottom of the cross-section. In simple models of ciliary movement involving contraction of the peripheral filaments, filaments at the top of the cross-section should be longer, if any are. Such models are not supported by the evidence here. These results can be interpreted as supporting sliding-filament models of movement where no length change of peripheral filaments occurs.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

• Lindemann, C. B., Macauley, L. J., Lesich, K. A. (2005). The Counterbend Phenomenon in Dynein-Disabled Rat Sperm Flagella and What It Reveals about the Interdoublet Elasticity. Biophys. J 89: 1165-1174 [Abstract] [Full Text]  
• Wells, W. A. (2005). Cilia get arms for bending. JCB 168: 350-351 [Full Text]  
• Criswell, P. S., Asai, D. J. (1998). Evidence for Four Cytoplasmic Dynein Heavy Chain Isoforms in Rat Testis. Mol. Biol. Cell 9: 237-247 [Abstract] [Full Text]  
• Criswell, P., Ostrowski, L., Asai, D. (1996). A novel cytoplasmic dynein heavy chain: expression of DHC1b in mammalian ciliated epithelial cells. J. Cell Sci. 109: 1891-1898 [Abstract]  
• Brokaw, C. J. (1972). Flagellar Movement: A Sliding Filament Model: An explanation is suggested for the spontaneous propagation of bending waves by flagella. Science 178: 455-462 [Abstract]  
• Behnke, O., Forer, A. (1966). Intranuclear Microtubules. Science 153: 1536-1537 [Abstract]  

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents