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  • 1
    Electronic Resource
    Electronic Resource
    Three-dimensional dynamics of pseudopod formation and the regulation of turning during the motility cycle of Dictyostelium (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 1-12 
    Details
    ISSN: 0886-1544
    Keywords: pseudopod extension ; amoebae ; uropod retraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Employing a newly developed computer-assisted system for visualizing and quantitating cell motility in three dimensions, we have examined the 3-dimensional changes in cell shape and the dynamics of pseuodopod extension during translocation of Dictyostelium amoebae. Amoebae exhibit a 3-dimensional behavior cycle with an average period of 1.5 min. The cycle includes a transient pseudopod extension phase in the x, y axis followed by a z-axis expansion phase. Anterior pseudopod extension in the x, y axis is accompanied by a decrease in height, not by uropod retraction. The increase in height is accompanied by uropod retraction. In the pseudopod extension phase in the x, y axes, pseudopods form either anteriorly or laterally, and either on or above the substratum. Pseudopods which initially form on the substratum in almost all cases continue to expand as the anterior end of the cell. In the case of lateral pseuodopods, anteriorization leads to a turn. Approximately half of anterior pseudopod and two-thirds of lateral pseudopods which initially form above the substratum are retracted. These results suggest that pseudopod-substratum interaction plays a fundamental role in the regulation of directionality and turning in the translocation phase of the 3-dimensional behavior cycle. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270102
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  • 2
    Electronic Resource
    Electronic Resource
    Behavior of Dictyostelium amoebae is regulated primarily by the temporal dynamic of the natural cAMP wave (1992)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 23 (1992), S. 145-156 
    Details
    ISSN: 0886-1544
    Keywords: Dictyostelium ; cAMP wave ; temporal mechanism ; chemotaxis ; pseudopod formation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The instantaneous velocity plots of Dictyostelium discoideum amoebae responding to natural waves and simulated temporal waves of cAMP with periods of 7 min are highly similar. This similarity has been used to deduce the dynamics of a natural wave crossing an amoeba, and the behavior of amoebae has been characterized during the different phases of a natural wave with a computer-assisted dynamic image analyzing system. During the first ∼150 sec of the front of a natural wave, cells move persistently toward the aggregation center, with high instantaneous velocity and a decreased frequency of lateral pseudopod formation. During the last 30 sec of the front of the wave and the first 30 sec of the back of the wave, there is a “freeze” in cell shape and a dramatic depression in cell motility, pseudopod formation, and intracellular particle movement. During the last 180 sec of the back of the wave, there is a rebound in pseudopod formation, but it is random in direction and leads to no net cellular translocation. The data suggest that all of the behavior of a cell but orientation during the translocation phase is mediated by the temporal dynamics of the wave. The data also suggest that orientation toward the aggregation center occurs early in the front of the wave and that, once oriented, cells move in a blind fashion during the translocation phase. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970230207
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  • 3
    Electronic Resource
    Electronic Resource
    Myosin IB null mutants of Dictyostelium exhibit abnormalities in motility (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 301-315 
    Details
    ISSN: 0886-1544
    Keywords: DMIB- cells ; F-actin ; cAMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cellular and intracellular motility are compared between normal Dictyostelium amoebae and amoebae lacking myosin IB (DMIB-). DMIB- cells generate elongated cell shapes, form particulate-free pseudopodia filled with F-actin, and exhibit an anterior bias in pseudopod extension in a fashion similar to normal amoebae. DMIB- cells also exhibit a normal response to the addition of the chemoattractant cAMP, including a depression in cellular and intracellular particle velocity, depolymerization of F-actin in pseudopodia, and a concomitant increase in cortical F-actin. DMIB- cells do, however, form lateral pseudopodia roughly three times as frequently as normal cells, turn more often, and exhibit depressed average instantaneous cell velocity. DMIB- cells also exhibit a decrease in the average instantaneous velocity of intracellular particle movement and an increase in the degree of randomness in particle direction. These findings indicate that if there is functional substitution for myosin IB by other myosin I isoforms, it is at best only partial, with myosin IB being necessary for maintenance of the normal rate and persistence of cellular translocation, suppression of lateral pseudopod formation and subsequent turning, rapid intracellular particle motility, and the normal anterograde bias of intracellular particle movement. Furthermore, it is likely that the behavioral abnormalities observed here for DMIB- cells underlie the delay in the onset of chemotactic aggregation, the increase in the time required to complete streaming, and the abnormalities in morphogenesis exhibited by DMIB- cells.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970200406
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  • 4
    Electronic Resource
    Electronic Resource
    Intracellular vesicle movement, cAMP and myosin II in Dictyostelium (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 11 (1990), S. 341-353 
    Details
    ISSN: 0192-253X
    Keywords: Vesicle movement ; myosin II ; cAMP ; Dictyostelium ; actin ; computer-assisted motion analysis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Dictyostelium amoebae were analyzed before and after rapid addition of 10-6 M cAMP for cellular motility, dynamic shape changes, and intracellular particle movement. Before cAMP addition, amoebae moved in a persistent anterior fashion and were elongate with F-actin localized predominantly in the anterior pseudopod. Intracellular particles moved rapidly and anteriorly. Within seconds after 10-6 M cAMP addition, cells stopped translocating, pseudopod formation ceased, intra-cellular particle movement was depressed, and F-actin was lost from the pseudopod and concomitantly relocalized in the cell cortex After 10 seconds, expansion zones reappeared but were small and no longer anteriorly localized. Vesicle movement partially rebounded but was no longer anteriorly directed. The myosin II null mutant HS2215 exhibited both depressed cellular translocation and vesicle movement. The addition of cAMP to HS2215 cells did not result in any detectable change in the random, depressed movement of particles. The results with HS2215 suggest that myosin II is essential for (1) rapid cellular translocation, (2) cellular polarity, (3) rapid particle movement, (4) anteriorly directed particle movement, and (5) the cAMP response. Electron micrographs suggest that at least half of the particles examined in this study contain in turn smaller membrane bound vesicles or multilameilar membrane bodies. The possible role of these vesicles is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020110505
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  • 5
    Electronic Resource
    Electronic Resource
    “Dynamic morphology system”: A method for quantitating changes in shape, pseudopod formation, and motion in normal and mutant amoebae of Dictyostelium discoideum (1988)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 37 (1988), S. 177-192 
    Details
    ISSN: 0730-2312
    Keywords: chemotoxins ; computer-assisted analyses ; actin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: An automated, video-driven system was used to measure approximately 30 parameters of cell motion and accompanying changes in shape. This “Dynamic Morphology System” is based upon the Expertvision Motion Analysis System and is driven by a SUN computer. With the aid of this system, amoebic movement and shape changes were compared for vegetative wild-type Dictyostelium discoideum amoebae and a motility mutant, Mo-1. The measured parameters included speed, angle change, bearing, length, width, roundness, boundary flow, and curvature; and cell behavior was visualized monitoring amoebic tracks, difference pictures, and a newly developed ring expansion plot. Wild-type cells remained elongated, moved continuously and retained polarity throughout migration. In contrast, Mo-1 did not translocate, was round rather than elongated, formed bulges rather than elongated pseudopods, and exhibited no polarity. In contrast to the anterior f-action distribution in wild-type cells, f-actin in Mo-1 was distributed evenly as a shell just under the entire plasma membrane, a distribution consistent with the lack of polar cytoplasmic expansion.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240370205
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