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  • 1990-1994  (3)
  • 1955-1959
  • 1990  (3)
  • Life and Medical Sciences  (3)
  • supercritical fluid chromatography
  • 1
    Electronic Resource
    Electronic Resource
    Cyclical binding, processing, and functional interactions of neutrophils with leukotriene B4 (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 299-308 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Leukotrene (LT) B4 activates human polymorphonuclear neutrophils. (PMN) by binding to plasmalemmal receptors. It stimulates PMN to raise cytosolic calcium and degranulate. Both responses end within 15-30 sec. However, in 〈 15 sec, LTB4-treated PMN lose the ability to respond further to LTB4; decrease the affinity and number of high affinity receptors available for binding LTB4 sequester LTB4 in plasmalemma-associated sites that are inaccessible to a releasing buffei regi i men; and begin internalizing LTB4. Over the next 90 min, the cells increasingly internalize LTB4 and convert it to less potent metabolites; release the metabolites; recover LTB4 binding sites; and become fully sensitive to LTB4. Contrastingly, during the entire 90 min incubation with LTB4. PMN retained the capacity to bind and respond normally to a second stimulus platelet-activating factor. We therefore suggest the following model. LTB4 receptors, when ligand-bound, initiate function but rapidly lose this capacity as they lower their ligand binding affinity and sequester, internalize, or otherwise uncouple from transducing elements. These LTB4 receptor changes contribute to terminating PMN responses and producing a stimulus-selective state of desensitization. During the desensitization period, PMN progressively process and metabolize LTB4. This removes LTB4 from the environment, thereby allowing PMN to recover functional receptors for and sensitivity to the ligand.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041420212
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Inhibition of late endosome-lysosome fusion: Studies on the mechanism by which isotonic-K+ buffers alter intracellular ligand movement (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 145 (1990), S. 522-530 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Incubation of alveolar macrophages or hepatocytes in media in which Na+ is replaced by K+ (‘isotonic-K buffer’) inhibited the movement of internalized ligand from late endosomes to lysosomes (Ward et al.: journal of Cell Biology 110:1013-1022, 1990). In this study we investigate the mechanism responsible for the isotonic-K+ block in movement of ligand from late endosomes to lysosomes. We observed that iso-K+ inhibition of endosome-lysosome fusion is not unique to alveolar macrophages or hepatocytes but can be seen in a variety of cell types including J774 and Hela cells. The inhibition in intracellular ligand movement was time dependent with the maximum change occurring after 60 minutes. Once established the inhibition resulted in a prolonged and apparently permanent decrease in vesicle movement. Cells were able to recover from the effects of iso-K+ buffers over a time course of 5-10 minutes when placed back in Na+-containing media. The effect of iso-K+ buffers was independent of intracel-lular pH changes and appeared to involve cell swelling. When cells were incubated in iso-K+ buffers under conditions in which cell volume changes were reduced, intracellular ligand movement approached normal levels. Such conditions included replacing Cl- with the less permeant anion gluconate, and by addition of sucrose to isotonic-K+ buffers. Analysis of the mechanism by which changes in cell volume could alter intracellular movement ruled out changes in cyclic nucleotides. Ca2+, or microtubules. These results suggest that changes in cell shape or volume can alter intracellular transport systems by novel routes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041450319
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Time-resolved cryotransmission electron microscopy (1990)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 14 (1990), S. 6-12 
    Details
    ISSN: 0741-0581
    Keywords: Direct imaging ; Time-resolved cryo-TEM ; Transient microstructures ; Phospholipid mesophases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We describe a new technique, time-resolved cryotransmission electron microscopy (TRC-TEM), that can be used to study changes in microstructure occurring during dynamic processes such as phase transitions and chemical reactions. The sample is prepared on an electron microscope grid maintained at a fixed temperature in a controlled atmosphere. The dynamic process is induced on the grid by a change in pH, salt, or reactant concentration by rapid mixing with appropriate solutions. Alternatively, induction is by rapid change of specimen temperature, or by controlled evaporation of a volatile component. We call such procedures on-the-grid processing. The dynamic process is permitted to run for a defined time and then the thin-film specimen is thermally fixed by plunging into liquid ethane at its freezing point, producing a cryotransmission electron microscopy specimen. By repeating this procedure with varying delays between induction and sample fixation, we can observe transient microstructures. We demonstrate the use of TRC-TEM to study the intermediate structures that form during the transitions between Lα, III, and HII liquid crystalline phases in phospholipid systems. We also identify several other possible applications of the technique.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060140103
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    Paper (German National Licenses)
    Fulltext
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