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  • 1975-1979  (2)
  • 1960-1964
  • Microelectrode measurements  (1)
  • Negative capacitance amplifiers  (1)
  • 1
    Electronic Resource
    Electronic Resource
    A quasi-totally shielded, low-capacitance glass-microelectrode with suitable amplifiers for high-frequency intracellular potential and impedance measurements (1978)
    Springer
    Pflügers Archiv 378 (1978), S. 141-148 
    Details
    ISSN: 1432-2013
    Keywords: Microelectrode techniques ; High-frequency microelectrode recording ; Intracellular impedance measurements ; Negative capacitance amplifiers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The fabrication of a new glass microelectrode for high-speed recording is reported. It consists of a Ling-Gerard microelectrode which is slit into a “spacer” capillary with the tip slightly protruding. Except for the ultimate tip (of ∼30 μm length) the entire assembly is coated with silver and insulated. After proper insertion into the cell the electrode provides a shield, which extends from the surface of the cell membrane up to the input of the amplifier. This electrode has two advantages: 1. it eliminates all capacitive pickup of bath potentials which is of paramount importance in impedance measurements and 2. if used in conjunction with negative capacitance amplifiers, it allows more faithful high-frequency recordings, than was possible with the conventional techniques, because the capacitance neutralization can be properly set even though the non-ideal transmission properties of the electrode tips are not known. Test experiments using a rapid amplifier circuit of own design show that the electrode assembly allows error-free phaseshift measurements of up to 30 kHz to be obtained with electrodes of 20 MΩ or risetimes (10–90%) of squarewave pulses of 10 to 12 μs. The corresponding time constants of 5 to 6 μs indicate that the time resolution of the new technique is superior to the apparent time resolution of the conventional techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584447
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The potential and resistance profile of Necturus gallbladder cells (1977)
    Springer
    Pflügers Archiv 371 (1977), S. 109-117 
    Details
    ISSN: 1432-2013
    Keywords: Transepithelial salt transport ; Intracellular electrical potential ; Cytoplasmic resistivity ; Microelectrode measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Necturus gallbladders were mounted in a modified Ussing chamber and the open circuit potential as well as the IR drop in response to transepithelial current were recorded while passing 2.7 molar KCl-filled microelectrodes in steps of 2–7 μm from the mucosal compartment across the cell into the subepithelial space and back. Using high-resistance electrodes the intracellular electrical potential was found to be independent of the depth of penetration of the electrode into the cell. It averaged −57.9 ±4.5 mV (n=39) with reference to the mucosal solution. Similarly, the resistance between microelectrode tip and mucosal solution was independent of the depth of insertion, indicating that the major part of the IR drop in response to transepithelial currents of 100 μA/cm2 density occured at the cell membranes and that the IR drop inside the cytoplasm was negligibly small. The latter result agrees with quantitative estimates based on the cytoplasmic resistivity of other cells. Using low-resistance microelectrodes the existence of intracellular potential gradients could be simulated. The simultaneous resistance measurements, however, revealed that initial low potential readings must be interpreted as incomplete or leaky impalements. We conclude that active solute and water transport across Necturus gallbladder epithelium does not generate significant intracellular potential gradients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580778
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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