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  • 1
    Electronic Resource
    Electronic Resource
    Irreversible reduction in potassium fluxes accompanies terminal differentiation of human myoblasts to myotubes (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 132 (1987), S. 57-64 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Potassium and sodium fluxes believed to be important in the cellular response to serum and growth factors have not been widely investigated in cells which have undergone terminal differentiation. In this study we have analyzed two main K+ transport systems - the ouabain-sensitive Na+/K+ pump and the bumetanide-sensitive transporter - in human muscle in vitro at two developmental stages: proliferating myoblasts and differentiated myotubes. Myoblast differentiation to myotubes was accompanied by a marked decrease in both the ouabain-sensitive and the bumetanide-sensitive K+ (Rb+) influxes. The addition of serum to the terminally differentiated myotubes had no effect on these K+ transporters. However, serum addition to serum-deprived, undifferentiated myoblasts produced a marked stimulation of these K+ fluxes.The bumetanide-sensitive K+ transporter in human myoblasts and myotubes has the following properties: (1) It carries 30% and 40% of the total K+ influx in myoblasts and myotubes, respectively. (2) It performs net efflux of K+ in the undifferentiated myoblasts and zero net flux (self-exchange) in terminally differentiated myotubes. (3) It is dependent on extracellular Na+ and Cl- in addition to K+. (4) In myoblasts, the Km value for K+ is 1.36 mM, similar to the Km for K+ of the Na+/K+ pump. (5) It is resistant to ouabain (up to 2 mM) and sensitive to furosemide (K0.5 = 5 × 10-6 M) and bumetanide (K0.5 = 10-7 M). These data indicate that following terminal differentiation of proliferating myoblasts to mitotically inactive myotubes there is an irreversible reduction of K+ fluxes with a change in the net flux of K+ carried by the bumetanide-sensitive transporter.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041320108
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    Paper (German National Licenses)
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  • 2
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    On evaluating parallel computer systems (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A workshop was held in an attempt to program real problems on the MIT Static Data Flow Machine. Most of the architecture of the machine was specified but some parts were incomplete. The main purpose for the workshop was to explore principles for the evaluation of computer systems employing new architectures. Principles explored were: (1) evaluation must be an integral, ongoing part of a project to develop a computer of radically new architecture; (2) the evaluation should seek to measure the usability of the system as well as its performance; (3) users from the application domains must be an integral part of the evaluation process; and (4) evaluation results should be fed back into the design process. It is concluded that the general organizational principles are achievable in practice from this workshop.
    Keywords: COMPUTER SYSTEMS
    Type: NASA-CR-185399 , NAS 1.26:185399 , RIACS-TR-85.3
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Systematic aspects of direct extrasolar planet detection (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Using the first optical observatory in space, the Hubble Space Telescope, images of possible extrasolar planets will have poor contrast against the background of diffracted and scattered starlight. The very long exposure time required to achieve an adequate signal-to-noise ratio will make their detection infeasible. For a future telescope, a 16-fold increase in either the smoothness of the collecting area of the optics would reduce the exposure time to a tolerable value, but the contrast would remain low and the required photometric precision high. In this situation, the feasibility of detection would be contingent on the careful identification and control of systematic errors.
    Keywords: ASTRONOMY
    Type: Bioastronomy - The next steps; Jun 22, 1987 - Jun 27, 1987; Balaton; Hungary
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Voyager observations of 1985U1 (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: During its discovery of the 75-km average diameter Uranian satellite 1985U1, between the epsilon ring and Miranda, Voyager was able to resolve this irregularly shaped satellite in sufficiently great detail to allow the determination of its size, shape, and photometric properties. It is presently noted that 1985U1's albedo, at between 0.07 and 0.09, is both substantially lower than those obtained for the large Uranian satellites and slightly higher than that of the Saturn moon, Phoebe. A V-system opposition magnitude of about +20.5 is conjectured.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 72; 79-83
    Format: text
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    NASA TECHNICAL REPORTS
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