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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0886-1544
    Keywords: flagella ; asymmetric beating ; sea urchin ; Ciona ; Chlamydomonas ; switching mechanism ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Time-averaged data covering six to ten beat cycles for ATP-reactivated spermatozoa of a sea urchin and Ciona, and from a uniflagellate mutant of Chlamydomonas, were analyzed to obtain parameters of oscillation and mean shear angle at each point along the flagellum. The mean shear angles usually show a sharp change near the base of Ihc flagellum. This sharp basal change in angle is correlated with perceived asymmetry in the development times of principal and reverse bends when these bends are measured directly from the asymmetric bending patterns, without subtracting out the mean shear angle. The asymmetry in development times was previously considered to be evidence against a “biased baseline” mechanism for asymmetric bending waves, in which completely symmetric bending waves develop and propagate on a curved flagellum. Our analysis now shows that the asymmetry in development times can be fully explained by the presence of a sharp static bend near the base of the flagellum, which can confuse the determination of the times of initiation of new bends at the base of the flagellum. Our reinterpretation of these data removes previous objections to the “biased baseline” mechanism for the regulation of bending wave asymmetry by calcium, and supports other evidence favoring a biased baseline mechanism, rather than a “biased switching” mechanism.
    Additional Material: 9 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 185-189 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 347-353 
    ISSN: 0886-1544
    Keywords: axoplasmic transport ; flagella ; microtubule ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The generation of bending waves by microtubules in squid nerve axoplasm has been modelled using appropriately modified versions of computer programs developed previously for simulation of flagellar bending waves. The results confirm that a constant longitudinal force directed along the axis of the microtubule is sufficient to cause the generation of regular oscillations and propagated bending waves when the forward gliding movement of the microtubule is obstructed. No control mechanism is required to modulate the active force-generating system. In order to obtain bending waves similar to those observed experimentally, it was necessary to use a model for the force-generating system in which the active force decreases with increasing sliding velocity. If the elastic bending resistance of axoplasmic microtubules is similar to that of microtubules in sperm terminal filaments, the longitudinal force per unit length generated by the axoplasmic microtubules must be of the same order of magnitude as the force generated by dynein arms along the doublet microtubules of eukaryotic flagella.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 137-141 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
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  • 6
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 239-244 
    ISSN: 0886-1544
    Keywords: sperm ; nucleotide analog ; kinetics ; Stronglyocentrotus purpuratus ; reactivation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The 2-substituted ATP analog 2-Chloro ATP was tested for its capacity to support axonemal movement. The movement of sea urchin axonemes reactivated with 2-CI ATP appeared very similar to that with ATP. Detailed waveform analysis indicated that bend angle and shear amplitude were not significantly different for ATP and 2-CI ATP. Although wavelength differs at particular nucleotide concentrations, if normalized to the beat frequency, it is similar for ATP and 2-CI ATP. The main difference in the movement with the two analogs was seen in beat frequency and sliding velocity. The Vmax for beat frequency and mean sliding velocity was lower for 2-CI ATP. The apparent Km for beat frequency and sliding velocity was much lower for 2-CI ATP. The ratio of these two effects, that is, (Vmax/Km) is higher for 2-CI ATP. Thus 2-CI ATP is a good substrate for axonemal movement. The significantly lower Km of 2-CI ATP was also demonstrated by its ability to support oscillatory motion at concentrations below that for ATP. The observations identify the structures and conformation of substrate necessary to support axonemal movement.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 123-130 
    ISSN: 0886-1544
    Keywords: calmodulin ; motility ; spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The asymmetry of ATP-reactivated flagellar bending waves of Triton-demem-brated sea urchin spermatozoa has been measured over a range of free Ca2+ ion concentrations from 10-9 to 10-4 M. Detailed examination of the gradual response of asymmetry to Ca2+ ion concentration over this wide range indicates the presence of two Ca2+ sensors. A high-affinity sensor operates at Ca2+ concentrations near 10-7.5 M. A lower-affinity sensor operates at Ca2+ concentrations above 10-6 M, in the typical range for calmodulin-mediated responses. Incubation of demembranated sperm flagella at high Ca2+ concentrations to release calmodulin is required to enable these Ca2+ responses to be observed. This treatment also causes a decrease in the apparent affinity of the flagella for cal-modulin, as determined by measuring the increase in asymmetry in response to addition of exogenous calmodulin at low Ca2+ concentration.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 0886-1544
    Keywords: Ciona ; flagella ; motility ; tyrosine kinase ; cAMP-dependent kinase ; spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A specific peptide inhibitor of the cyclic AMP (cAMP)-dependent protein kinase (PKI-peptide) is a very effective inhibitor of the cAMP-dependent activation of motility of Ciona spermatozoa, when the PKI-peptide is present at the beginning of incubation of demembranated spermatozoa with cAMP and ATP. Under conditions where approximately 120 sec is required for full activation of motility, the window of sensitivity to the PKI-peptide lasts for only 25-30 sec. Examination of sperm pellet proteins labeled with 32P ATP during activation reveals a major 25 kDa phosphoprotein and 2 minor phosphoproteins whose phosphorylation is highly sensitive to inhibition by the PKI-peptide and essentially complete during this early phase. These sperm proteins appear to be immediate substrates for cAMP-dependent protein kinase, and phosphorylation of one or more of these appears to be required, but not sufficient, for activation of motility. The phosphorylation of other proteins is reduced or eliminated when PKI-peptide is present at the beginning of incubation, but is unaffected by later addition of PKI-peptide. Some of these substrates appear to be likely candidates for axonemal proteins that must be phosphorylated during the later stages of incubation in order to complete the activation process. This selection is based upon a high degree of inhibition by inclusion of PKI-peptide or other inhibitors at the start of the incubation process, on near-completion of their phosphorylation by the end of the 2 min incubation period required for activation of motility, and evidence that these proteins are phosphorylated during in vivo activation of motility. Although these observations suggest the presence of a second kinase activity that is upregulated by the initial activation of the cAMP-dependent protein kinase, assays using exogenous substrates have not yet been able to identify such a kinase activity. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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