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  • 1
    Electronic Resource
    Electronic Resource
    Pluripotent, cytokine-dependent, hematopoietic stem cells are immortalized by constitutive Notch1 signaling (2000)
    [s.l.] : Nature America Inc.
    Nature medicine 6 (2000), S. 1278-1281 
    Details
    ISSN: 1546-170X
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Hematopoietic stem cells give rise to progeny that either self-renew in an undifferentiated state or lose self-renewal capabilities and commit to lymphoid or myeloid lineages. Here we evaluated whether hematopoietic stem cell self-renewal is affected by the Notch pathway. Notch signaling ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/81390
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  • 2
    Electronic Resource
    Electronic Resource
    Frequency and orientation of pseudopod formation of Dictyostelium discoideum amebae chemotaxing in a spatial gradient: Further evidence for a temporal mechanism (1987)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 8 (1987), S. 18-26 
    Details
    ISSN: 0886-1544
    Keywords: chemotaxis ; cell motility ; cellular polarity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Amebae of Dictyostelium discoideum normally chemotax to aggregation centers by assessing the direction of outwardly moving, nondissipating waves of the chemoattractant cAMP. However, D. discoideum amebae can also assess the direction of a relatively stable spatial gradient. We demonstrate that amebae migrating towards the “source” of a stable, spatial gradient move faster, extend fewer pseudopodia, and turn less frequently than amebae migrating away from the “source” in the same spatial gradient. In addition, amebae extend lateral pseudopods in a polarized fashion from the anterior half of the cell, and do so as frequently towards the source as away from the source. However, those formed towards the source more often produce a turn than those formed away from the source. These results suggest that there may be two decision-making systems, one localized in the pseudopods, and one along the entire cell body; they support the suggestion that Dictyostelium amebae may employ a temporal mechanism to assess the direction of a spatial gradient of chemoattractant.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970080104
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  • 3
    Electronic Resource
    Electronic Resource
    Amebae of Dictyostelium discoideum respond to an increasing temporal gradient of the chemoattractant cAMP with a reduced frequency of turning: Evidence for a temporal mechanism in ameboid chemotaxis (1987)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 8 (1987), S. 7-17 
    Details
    ISSN: 0886-1544
    Keywords: cell motility ; sensory transduction ; slime mold ; pseudopod formation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In an aggregation territory of Dictyostelium discoideum, outwardly moving, nondissipating waves of the chemoattractant cAMP sweep across each ameba. At the front of each wave, an ameba experiences an increasing temporal and a positive spatial gradient of cAMP. At the back of a wave, an ameba experiences a decreasing temporal and a negative spatial gradient of cAMP. Employing a perfusion chamber, we have mimicked the temporal dynamics of these waves in the absence of a spatial gradient and demonstrated that the frequency of lateral pseudopod formation and the frequency of turning are dramatically affected by the direction and dynamics of the temporal gradient. In addition, since an ameba will move in a directed fashion up a shallow, nonpulsatile gradient of cAMP, we also mimicked the increasing temporal gradient generated by an ameba moving up a shallow spatial gradient. The frequency of lateral pseudopod formation and the frequency of turning were depressed. Together, these results demonstrate that amebae can assess the direction of a temporal gradient of chemoattractant in the absence of a spatial gradient and alter both the frequency of pseudopod extension and turning, accordingly. Although these results do not rule out the involvement of a spatial mechanism in assessing a spatial gradient, they strongly suggest that the temporal dynamics of a cAMP wave or the temporal gradient generated by an ameba moving through a spatial gradient may play a major role in chemotaxis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970080103
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Adaptation in the motility response to camp in dictyostelium discoideum (1988)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 9 (1988), S. 9-16 
    Details
    ISSN: 0886-1544
    Keywords: adaptation ; cAMP ; cell motility ; chemotaxis ; Dictyostelium discoideum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When developing amebae of Dictyostelium discoideum are treated with constant concentrations of cAMP above 10-8 M, the average rate of motility is depressed, with maximum inhibition at roughly 10-6 M. It is demonstrated that shifting the concentration of cAMP from 0 M to concentrations ranging from 10-8 to 10-6 M in a perfusion chamber results in the immediate inhibition of motility. After shifting from 0 M to 10-8 or 10-7 M, the rate of cell motility remains low, then rebounds to a higher level, exhibiting a standard adaptation response. No adaptation is exhibited after a shift from 0 M to 10-6 M, a concentration resulting in maximum inhibition. It is demonstrated that the level of inhibition and the extent of the adaptation period are dependent upon the concentration of cAMP after the shift, and that submaximal inhibition is additive. The characteristics of adaptation in this motility response are very similar to the characteristics of adaptation for the relay system and phosphorylation of the putative cAMP receptor.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970090103
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    Paper (German National Licenses)
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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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