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  • 1
    Electronic Resource
    Electronic Resource
    Splitting the ciliary axoneme: Implications for a “Switch-Point” model of dynein arm activity in ciliary motion (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 14 (1989), S. 345-358 
    Details
    ISSN: 0886-1544
    Keywords: cell motility ; microtubules ; mussel gill ; ATPase ; electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the presence of specific inhibitors of beat, 20 μM VO43- or pCa 4, mussel gill lateral (L) cilia can be arrested in two positions - “hands down” or “hands up” - at opposite ends of the stroke cycle. Cilia move to these positions by doublet microtubule sliding. Axonemes of arrested cilia, still tethered to the cell, are intact after demembranation and protease treatment. When reactivated by 4 mM ATP with inhibitors present, about 40% split apart. Splits are not random but occur preferentially between different specific doublets in the two opposite arrest positions. Several different related patterns of splitting are observed; for every pattern in “hands down” axonemes, there is a corresponding complementary split pattern in “hands up” axonemes. In some split patterns two doublets remain firmly attached to the central pair; these also differ depending on axonemal position. Although some of the patterns seen may be artifactual or difficult to explain, the complementary splitting patterns are predictable with simple assumptions by a “switch point” hypothesis of ciliary activity where, during each recovery stroke, doublets 6-8 have active dynein arms, while during each effective stroke, arms on doublets 1-4 become active, and arms 6-8 are turned off. Because of a difference between the patterns seen and the predictions, the status of the arms on doublet 9 is unresolved. The patterns also suggest that a spokecentral sheath attachment cycle may correlate with switching of arm activity during the generation of an asymmetric beat.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970140305
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  • 2
    Electronic Resource
    Electronic Resource
    Physical model of axonemal splitting (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 287-298 
    Details
    ISSN: 0886-1544
    Keywords: cilium ; flagellum ; motility ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A physical model developed to explain microtubule sliding patterns in the trypsintreated ciliary axoneme has been extended to investigate the generation of bending moments by microtubules sliding in an axoneme in which the dublets are anchored at one end. With sliding restricted, a bending moment is developed by the polarized shearing interaction between neighbouring doublets, effected by the activity of dynein arms on doublet N pushing N + 1 in a tipward ( + ) direction. In arrested axonemes in which arms on several contiguous doublets are active, the bending moment causes splitting of the 9 + 2 microtubule array into two or more sets of doublets. In the absence of special constraints, splitting depends only on breaking the circumferential interdoublet links most distorted by the bending moment. The analysis, which permits assignment of arm activity to specific microtubules in each of the observed patterns of splitting, indicates that the axoneme will split between doublet N and N + 1 if arms on doublet N are inactive and arms on either N + 1 or N-1 are active. To produce the observed major splits, dynein arms on the microtubules of roughly one-half of the axoneme are predicted to be active, in a manner consistent with the switch-point hypothesis of ciliary motion. Electron microscopic examination indicates that virtually every set of doublets in the split axonemes retains its cylindrical form. Maintenance of cylindrical symmetry can be ascribed to the mechanical properties of the unbroken links, which may resist both tensile and compressive stress, and to active dynein arms. © 1994 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270402
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  • 3
    Electronic Resource
    Electronic Resource
    The mechanochemical cycle of the dynein arm (1981)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 1 (1981), S. 303-327 
    Details
    ISSN: 0886-1544
    Keywords: cilia ; microtubules ; ATPase ; vanadate ; geometry of sliding ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A dynein arm attachment cycle produces sliding between adjacent doublet microtubules (N and N + 1) of cilia. In intact axonemes, in the absence of ATP, almost all arms appear attached at both ends (rigor). When ATP is added, most arms detach from doublet N + 1. In ATP and vanadate, the arms do not return to rigor, suggesting that ATP hydrolysis is required for re-extension and reattachment of the dynein arm, but not for detachment. Using solutions containing dynein to decorate dynein-less axonemal doublets, we confirm this interpretation. In the absence of ATP, both sides of each doublet decorate with arms. Addition of ATP, ATP and vanadate or AMP-PNP causes immediate arm detachment, but only in the first instance, where extensive ATP hydrolysis can occur, does decoration eventually reappear. Dynein decorates heterologous axonemal doublets and brain microtubules, as well as homologous doublets, suggesting that this mechanochemical cycle may have general applicability in microtubule-based cell motility.
    Additional Material: 111 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970010304
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