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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fast axonal transport (FAT) can be inhibited in neurones by the injection of DNase I3"5 and filamin3. DNase I depolymerizes microfilaments by disrupting the F-actin/G-actin equilibrium9, whereas filamin inhibits activation of the myosin ATPase10. However, due to difficulties in controlling ...
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  • 2
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 216 (1967), S. 1212-1214 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] I have studied the effect of transecting the sciatic nerve of a cat on the distribution in it of labelled axoplasmic proteins. If 3〉leucine-3H was injected into the vicinity of neurone cell bodies connected with axons in the sciatic nerve, the proteins within those axons were labelled, while the ...
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  • 6
    ISSN: 0886-1544
    Keywords: fast axonal transport ; mitochondria ; membrane receptors ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In living tissue, membrane-bound organelles, including mitochondria, move along parallel cytoplasmic pathways. Motion is directed and tends to be confined to a single path. Deviations from this single path motion are rare. When present, however, they tend to occur at points of intersection of cytoskeletal linear elements (LE). Such intersections are relatively uncommon in intact axons and extruded axoplasm. However, we have found that such intersections can be produced in extruded preparations by shear forces directed tangential to the axoplasmic surface.We have studied the detailed behavior of mitochondria in extruded squid axoplasm. Special attention was directed to the relationship between mitochondrial shape changes and orientation of cytoskeletal LE. The most striking of these changes in shape is branching. In this process, the mitochondrion transiently assumes a triradial (three-ended) shape. This appearance may be maintained for seconds to minutes before the normal cylindrical shape is resumed by absorption of either the newly formed end or, more commonly, one of the original ends. The frequency of branching appears to be dependent on the degree of cytoskeletal organization. It becomes more common as the number of apparent intersections between cytoskeletal LE increases. Further, the formation of new ends seems to occur along paths defined by cytoskeletal elements.These observations suggest that the mitochondrial membrane is multivalent. That is, it contains multiple sites capable of interacting with the axonal force generation apparatus. Furthermore, LE in the cytoskeleton may indicate the paths along which these interactions are permissible.
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  • 7
    ISSN: 0886-1544
    Keywords: fast axonal transport ; isolated axoplasm ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of AVEC-DIC microscopy and the application of this method to the study of fast axonal transport in isolated axoplasm extruded from the giant axon of the squid Loligo pealei provides a new paradigm for analyzing the intracellular transport of membranous organelles. The size of the axon, the number of transported particles, and the absence of permeability barriers like the plasma membrane in this preparation permit many experiments that are difficult or impossible to perform using other model systems. The use and features of this preparation are described in detail and a number of properties are evaluated for the first time. The process of extrusion is characterized. Particle movement is evaluated both in the interior of extruded axoplasm and along individual fibrils that extend from the periphery of perfused axoplasm. The role of divalent cations, particularly Ca2+, and the effects of elevated Ca2+ on axoplasmic organization and transport are analyzed. A series of pharmacological agents and polypeptides that alter cytoskeletal organization are used to examine the role of microfilaments and microtubules in fast transport. Finally, the effects of depleting ATP and of adding ATP analogues are discussed. The extruded axoplasm preparation is shown to be an invaluable model system for biochemical and pharmacological analyses of the molecular mechanisms of intracellular transport.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 9-21 
    ISSN: 0886-1544
    Keywords: neurofilament ; axoplasm ; axonal cytoskeleton ; giant axon ; squid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have used axoplasm from the squid giant axon to investigate the effects of anionic and cationic polypeptides on the mobility and organization of axonal neurofilaments (NFs). Intact cylinders of axoplasm were extruded from squid giant axons into an excess volume of artificial axoplasm solution. In a previous study on the mobility of NFs in extruded axoplasm, we showed that these polymers disperse freely and diffusively into the surrounding solution, thereby expanding the axoplasmic cross-sectional area [Brown and Lasek, 1993: Cell Motil. Cytoskeleton 26:313-324]. In the present study, we found that 83nm-long (“long-chain”) polylysine, a synthetic multivalent cationic protein, inhibited the radial expansion of isolated axoplasm and condensed the axoplasm, thereby reducing the cross-sectional area. Equivalent concentrations of a 7nm-long (“short-chain”) polylysine did not inhibit the expansion of axoplasm and did not cause the axoplasm to condense. Inhibition of the expansion of axoplasm by long-chain polylysine was dependent on the polylysine concentration; condensation of axoplasm was observed at concentrations of 0.01 mg/ml (0.27 μM) or greater. Electron microscopy of the condensed axoplasm showed that the NFs were aligned side-by-side and in parallel in closely-packed bundles. Equivalent concentrations of 91nm-long (“long-chain”) polyglutamate, a synthetic multivalent anionic protein, partially inhibited the expansion of axoplasm but did not cause the NFs to bundle and did not cause the axoplasm to condense. These studies indicate that cationic proteins bind tightly to the highly charged anionic surfaces of NFs and can link them together into compact bundles in a charge-dependent and length-dependent manner. The tightly packed organization of these cross-linked NFs differs from the normal loose organization of NFs in healthy axons. However, tightly bundled NFs are sometimes found in certain neuropathologies, such as giant axonal neuropathy.
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  • 9
    ISSN: 0886-1544
    Keywords: axon guidance ; chemotaxis ; haptotaxis substrate pathways ; development ; pattern biology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In multicellular organisms, guidance cues are either diffusible molecules or cellular or extracellular surfaces that are found in reproducible locations and that orient migrating cells and cell processes. The pattern of the guidance cues usually determines the complex in vivo migration routes of motile cells and cell processes. Within organisms, guidance cues are found to be organized in two general patterns: (a) broad gradients - such as diffuse chemotactic gradients; (b) discrete routes (substrate pathways) - such as chemotactic gradients confined to long channels, and such as the axon surface which represents a long specific highway for migrating Schwann cells.
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  • 10
    ISSN: 0886-1544
    Keywords: neurofilament ; plasma membrane ; axon ; squid giant axon ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Squid giant axons were used to obtain axonal cytoskeletons that had been separated from the confines of their plasma membranes. To remove the plasma membrane, axoplasm was extruded from the giant axon directly into an artificial axoplasm solution (AAS). This procedure produces a smooth axoplasmic cylinder in which neurofilaments (NFs) are the most prevalent cytological elements. The NFs scatter light strongly and thus dark-field light microscopy can be used to quantify the volume occupied by these polymers. Measurements of the widths of the dark-field images of the axoplasmic cylinders showed that the cross-sectional area of the NF population increased by 60-110% (n = 8) between 1-100 min after plasma membrane removal, and then continued to increase more slowly for many hours. After 1,000 min, the cross-sectional area was 75-160% (n = 8) larger than at 1 min. These light microscopic measurements of axoplasm suggest that the NF population disperses to occupy a continuously increasing volume after removal of the plasma membrane and immersion in AAS. This inference was confirmed by quantitative ultrastructural studies of NFs in axoplasmic cross-sections, which demonstrated that the spacing between the NFs increased between 1-1,000 min after plasma membrane removal. Comparison of the NF density distribution after 1,000 min with a theoretical distribution calculated using the Poisson theorem indicated that the NFs dispersed randomly. These studies on NFs in isolated axoplasm suggest that ordinary thermal forces of Brownian motion are sufficient to move axonal NFs apart independently and thereby to disperse them. We propose that, in the intact axon, the dispersive movements of the NFs spread the NF cytoskeleton radially and expansively to fill out the cylindrical space contained by the axonal plasma membrane and its surrounding connective tissue elements. © 1993 Wiley-Liss, Inc.
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