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  • 11
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 11 (1988), S. 235-247 
    ISSN: 0886-1544
    Schlagwort(e): video-enhanced contrast microscopy ; transverse fibers ; transport ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Wound healing in Swiss 3T3 cultures was investigated with video-enhanced contrast (VEC) microscopy. The formation of protrusions at the leading edge of cells along wounds was investigated in detail during the spreading stage, which usually lasted from 1 to 4 hr postwounding. Lamellipodia exhibited a continuous rearward, or centripetal, transport of a variety of cellular constituents at rates of ∼0.26 μm/sec from the leading edge. The lamellipodia were also the sites of lateral migration as well as extension and retraction of actin microspikes. Actin fibers oriented transversely to the direction of movement were also observed to transport centripetally at similar rates. These fibers may in part give rise to large actin fibers forming at the interface between the base of the lamellipodia and the lamellae. Beads 0.5 μm in diameter attached to the dorsal surfaces of lamellipodia also transported centripetally at rates of ∼0.21 μm/sec. Thus there is an apparent correlation between transport of a variety of structures within lamellipodia and with surface movements of lamellipodia.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 14 (1989), S. 527-543 
    ISSN: 0886-1544
    Schlagwort(e): immunofluorescence ; video-enhanced contrast microscopy ; protrusions ; lamellipodia ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The formation of lamellipodia in migrating cells involves dynamic processes that occur in a cyclic manner as the leading edge of a cell slowly advances. We used video-enhanced contrast microscopy (VEC) to monitor the motile behavior of cells to classify protrusions into the temporal stages of initial and established protrusions (Fisher et al.: Cell Motility and the Cytoskeleton 11:235-247, 1988), and to monitor the fixation of cells. Multiple parameter fluorescence imaging methods (DeBiasio et al.: Journal of Cell Biology 105:1613-1622, 1987; Waggoner et al.: Methods in Cell Biology, Vol. 30, Part B, pp. 449-478, 1989) were then used to determine and to map accurately the distributions of actin, myosin and microtubules in specific types of protrusions. Initial protrustions exhibited no substructure as evidenced by VEC and actin was diffusely arranged, while myosin and microtubules were absent. Newly established protrusions contained diffuse actin as well as actin in microspikes. There was a delay in the appearance of myosin into established protrusions relative to the presence of actin. Microtubules were found in established protrusions after myosin was detected, and they were oriented parallel to the direction of migration. Actin and myosin were also localized in fibers transverse to the direction of migration at the base of initial and established protrusions. Image analysis was used to quantify the orientation of actin fibers relative to the leading edge of motile cells. The combined use of VEC, multiple parameter immunofluorescence, and image analysis should have a major impact on defining complex relationships within cells.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 3 (1983), S. 151-165 
    ISSN: 0886-1544
    Schlagwort(e): actin ; villin ; fluorescence ; energy transfer ; polymerization ; microfilament ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: We have investigated the Ca2+-dependent interactions of villin, a protein of the intestinal microvillar core, with actin by monitoring resonance energy tranfer between fluorescently labeled actin subunits. In the presence of elevated free Ca2+(∼20 μM), villin affects both the nucleation and the elongation phases of actin polymerization. Consistent with previous reports, villin stimulates the nucleation process and will form stable nuclei under depolymerization conditions. Compared to the control, the net rate of polymerization is slightly inhibited at low con-centrations of villin (villin/actin ∼ 1:400) but is stimulated at higher concentrations (villin/actin 〉 1:100). Villin also significantly increases the critical concentration of actin polymerization. Addition of either villin or villin-actin complexes induces depolymerization of preassembled actin filaments. This villin-induced depolymerization is reversible upon removal of free Ca2+ or upon the addition of phalloidin. The exchange of actin subunits at steady state is inhibited at low concentrations of villin (villin/actin ∼ 1:200) but is stimulated at higher concentrations (villin/actin ∼ 1:50). None of the above effects is observed at 〈 10-8 M free [Ca2+].
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 14
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 11 (1988), S. 64-82 
    ISSN: 0886-1544
    Schlagwort(e): D.d. α-actinin ; actin ; gelation ; fluorescence photobleaching recovery ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Dictyostelium discoideum α-actinin (D.d.α-actinin) is a calcium and pH-regulated actin-binding protein that can cross-link F-actin into a gel at a submicromolar free calcium concentration and a pH 〈7 [Fechheimer, et al., 1982]. We examined mixtures of actin and D.d. α-actinin at four pH and calcium concentrations that exhibited various degrees of gelation or solation. The macroscopic viscosities of these mixtures were measured by falling ball viscometry (FBV) and compared to the translational diffusion coefficients measured by gaussian spot and periodic-pattern fluorescence photobleaching recovery (FPR) of both the actin filaments and D.d. α-actinin. A homogeneous, macroscopic gel was not composed of a static actin network. Instead, the filament diffusion coefficient decreased to ∼65% of the control value. If the D.d. α-actinin concentration was increased, the solution became inhomogeneous, consisting of domains of higher actin concentration. These domains were often composed of a static actin network. The mobility of D.d. α-actinin consisted of a major fraction that freely diffused and a minor fraction that appeared immobile under the conditions employed. This suggested that D.d. α-actinin binding to the actin filaments was static over the time course of measurement (∼5 sec). Under solation conditions, there was no apparent interaction of actin with D.d. α-actinin. These results demonstrate that (1) actin filaments need not be cross-linked into an immobile, static array in order to have macroscopic properties of a gel, (2) interpretation of the rheological properties of actin:α-actinin gels are complicated by spatial heterogeneity of the filament concentration and mobility; and (3) a fraction of D.d. α-actinin binds statically to actin in undisturbed gels. The implications of these results are discussed in relation to cytoplasmic structure and contractility.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 15
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 10 (1988), S. 1-1 
    ISSN: 0886-1544
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 10 (1988), S. 28-37 
    ISSN: 0886-1544
    Schlagwort(e): cytomatrix ; cytoplasmic ground substance ; ratio imaging ; fluorescence photobleaching recovery ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The compartmentalization of eukaryotic cells by internal membranes and the subcellular localization of endogenous macromolecules by specific binding mechanisms are familiar concepts. In this report we present evidence that the cytoplasmic ground substance, which surrounds and contains the membranebound compartments, may also be compartmentalized by local differentiations of its submicroscopic structure that sort subcellular particles on the basis of size. The subcellular distribution of size-fractionated, fluorescent tracer particles was studied in living cells by ratio imaging and fluorescence recovery after photobleaching (FRAP). Large and small particles showed different distributions within the cytoplasmic volume, suggesting that the large particles were relatively excluded from some domains. While the structural basis for this phenomenon is not yet understood in detail, ratio imaging of large and small particles can be used as an empirical tool to identify cytoplasmic compartments for further study. The cytoplasmic diffusion coefficient (Dcyto) and % mobile fraction of the large particles showed considerable spatial variation over the projected area of the cell, while Dcyto and % mobile fraction of the small particles did not. A model is presented to account for this difference. Based on this model, a method is proposed by which FRAP can be used to detect sol-gel transitions in the cytoplasmic ground substance of living cells.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Fresenius' Zeitschrift für analytische Chemie 343 (1992), S. 38-38 
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 141 (1989), S. 410-419 
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Addition of mitogens to quiescent cells results in rapid ionic changes in the cytoplasm, including pH. We studied the changes in cytoplasmic pH in single Swiss 3T3 cells upon serum stimulation using fluorescence ratio imaging microscopy. Quiescence was attained using two approaches, serum deprivation of subconfluent cells and confluence. All measurements were made in the presence of bicarbonate and the absence of other organic buffers. We also used BCECF coupled to dextran to avoid several artifacts associated with using BCECF-AM, including leakage and phototoxicity. Analysis of the changes in cytoplasmic pH demonstrated a dramatic heterogeneity in the responses of single cells. There were six basic classes of responses, (1) a fast alkalinization, reaching a maximum pH in ∼2-5 min; (2) a slow alkalinization, reaching a maximum pH in 10-20 min; (3) a very slow alkalinization, not reaching a plateau pH within the measurement time; (4) no apparent change in pH during the measurement time; (5) an early transient acidification, followed by either a fast or slow alkalinization; and (6) an acidification, followed by alkalinization and then by a decrease to some intermediate pH. Subconfluent cells exhibited greater heterogeneity in response than confluent cells, with no single dominant class of response. The dominant (55%) response for confluent cells was a gradual alkalinization of ∼0.01 pH units/min. A larger proportion (52%) of subconfluent cells exhibited an early transient acidification compared to confluent cells (7%). A significant proportion of both types of cells (23% subconfluent, 36% confluent) exhibited no change in cytoplasmic pH upon stimulation. In general, the kinetics of changes in cytoplasmic pH were significantly different from the published results with population averaging methods.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 19
    Digitale Medien
    Digitale Medien
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 3 (1975), S. 181-191 
    ISSN: 0091-7419
    Schlagwort(e): Life Sciences ; Molecular Cell Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: The changes in birefringence in the rigor to relax transition of single Triton-extracted rabbit psoas muscle fibers have been investigated. The total birefringence of rigor muscle fibers was dependent on sarcomere length and ranged from (1.46 ± 0.08) × 10-3 to (1.60 ± 0.06) ± 10-3 at sarcomere lengths from 2.70 μm to 3.40 μm. An increase in total birefringence was measured dependent on sarcomere length when 55 single fibers were relaxed from the rigor state with Mg-ATP. Pyrophosphate relaxation produced a smaller increase in retardation when compared to Mg-ATP. The expected change in intrinsic birefringence during the rigor to relax transition was calculated assuming a hinge function of the subfragment 2 moiety of myosin. The changes in birefringence during isometric contraction and relaxation have been discussed in relation to possible structural changes.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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