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  • 1
    Electronic Resource
    Electronic Resource
    Direct Recording of K and Na Current–Potential Characteristics of Squid Axon Membrane (1969)
    [s.l.] : Nature Publishing Group
    Nature 224 (1969), S. 1116-1118 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] As step voltage clamp procedures have been applied to a wider range of membrane preparations, the tendency has been to infer from the current-potential (I-V) relations the late steady state (Iss) and transient maxima (Ip) currents, which usually give the potassium and sodium conductance ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2241116a0
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  • 2
    Electronic Resource
    Electronic Resource
    Patch voltage clamp of squid axon membrane (1975)
    Springer
    The journal of membrane biology 24 (1975), S. 265-279 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A small area (patch) of the external surface of a squid axon can be “isolated” electrically from the surrounding bath by means of a pair of concentric glass pipettes. The seawater-filled inner pipette makes contact with the axon and constitutes the external access to the patch. The outer pipette is used to direct flowing sucrose solution over the area surrounding the patch of membrane underlying the inner pipette. Typically, sucrose isolated patches remain in good condition (spike amplitude 〉90 mV) for periods of approximately one half hour. Patches of axon membrane which had previously been exposed to sucrose solution were often excitable. Membrane survival of sucrose treatment apparently arises from an outflow of ions from the axon and perhaps satellite cells into the interstitial cell space surrounding the axolemma. Estimate of the total access resistance (electrode plus series resistance) to the patch is about 100 kΩ (7 Ω cm2). Patch capacitance ranges from 10–100 pF, which suggests areas of 10−4 to 10−5 cm2 and resting patch resistances of 10–100 MΩ. Shunt resistance through the interstitial space exposed to sucrose solution, which isolates the patch, is typically 1–2 MΩ. These parameters indicate that good potential control and response times can be achieved on a patch. Furthermore, spatial uniformity is demonstrated by measurement of an axoplasmic isopotential during voltage clamp of an axon patch. The method may be useful for other preparations in which limited membrane area is available or in special instances such as in the measurement of membrane conduction noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868627
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  • 3
    Electronic Resource
    Electronic Resource
    Noise measurements in squid axon membrane (1975)
    Springer
    The journal of membrane biology 24 (1975), S. 281-304 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A small area (10−4 to 10−5 cm2 patch) of the external surface of a squid (Loligo pealei) axon was “isolated” electrically by means of a pair of concentric glass pipettes and sucrose solution to achieve a low extraneous noise measurement of spontaneous fluctuations in membrane potential and current. The measured “small-signal” impedance function of the isolated patch in seawater was constant at low frequencies and declined monotonically at frequencies beyond 100 Hz. It is shown that the power-density spectrum (PDS) of voltage noise, which generally reflects the current-noise spectrum filtered by the membrane impedance function, is equivalent to the power spectrum of current-noise up to frequencies where the impedance decline is significant (Fishman, 1973a, Proc. Nat. Acad. Sci. USA 70:876). This result is in contrast to an impedance resonance measured under uniform constant-current (internal axial wire) conditions, for which the voltage-noise PDS reflects the impedance resonance. The overdamped resonance in the patch technique is a consequence of the relatively low resistance (1 MΩ) pathways through the sucrose solution in the interstitial Schwann cell space which surround and shunt the high resistance (10–100 MΩ) membrane patch. Current-noise measurements during patch voltage clamp extend observation of patch ionconductance fluctuations to 1 kHz. Various tests are presented to demonstrate the temporal and spatial adequacy of patch potential control during current-noise measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868628
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  • 4
    Electronic Resource
    Electronic Resource
    Excess electrical noise during current flow through porous membranes separating ionic solutions (1975)
    Springer
    The journal of membrane biology 21 (1975), S. 291-309 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Spectral analysis of electrical noise from various artificial membrane systems suggests that excess noise of anf −n spectral form, wheren is approximately unity, is not primarily a bulk phenomenon simply dependent on the number of charge carriers. Measurements from aqueous and nonaqueous electrolytic resistors, comprised of several different ionic species, show only flat power density spectra under applied currents, even at extreme dilutions. Excess noise off −n form is observed under applied d-c current in single pore membranes, as previously reported, but is also seen in multipore and polymer mesh membranes. Calculations based on single pore membrane noise data are in significant variance with the bulk charge carrier model proposed by Hooge. These observations suggest that such excess noise occurs in conjunction with anisotropic constraints to ion flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01941073
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  • 5
    Electronic Resource
    Electronic Resource
    Potassium-Ion conduction noise in squid axon membrane (1975)
    Springer
    The journal of membrane biology 24 (1975), S. 305-328 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Spectral analysis (1–1000 Hz) of spontaneous fluctuations of potential and current in small areas of squid (Loligo pealei) axon shows two forms of noise:f −1 noise occurs in both excitable and inexcitable axons with an intensity which depends upon the driving force for potassium ions. The other noise has a spectral form corresponding to a relaxation process, i.e., its asymptotic behavior at low frequencies is constant, and at high frequencies it declines with a slope of −2. This latter noise occurs only in excitable axons and was identified in spectra by (1) its disappearance after reduction of K+ current by internal perfusion with solutions containing tetraethylammonium (TEA+), Cs+ or reduced [K i + ] and (2) its insensitivity to block of Na+ conduction and active transport. The transition frequency of relaxation spectra are also voltage and temperature dependent and relate to the kinetics of K+ conduction in the Hodgkin-Huxley formulation. These data strongly suggest that the relaxation noise component arises from the kinetic properties of K+ channels. Thef −1 noise is attributed to restricted diffusion in conducting K+ channels and/or leakage pathways. In addition, an induced K+-conduction noise associated with the binding of TEA+ and triethyldecylammonium ion to membrane sites is described. Measurement of the induced noise may provide an alternative means of characterizing the kinetics of interaction of these molecules with the membrane and also suggests that these and other pharmacological agents may not be useful in identifying noise components related to the sodium conduction mechanism which, in these experiments, appears to be much lower in intensity than either the normal K conduction or induced noise components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868629
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  • 6
    Electronic Resource
    Electronic Resource
    K+ conduction phenomena applicable to the low frequency impedance of squid axon (1979)
    Springer
    The journal of membrane biology 46 (1979), S. 1-25 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The observation of peaking in power spectra of K current noise in squid axon (Fishman, H.M., Moore, L.E., Poussart, D.J.M. 1975,J. Membrane Biol. 24:305) led to the calculation of a low frequency K conduction feature in the impedance (admittance) which was confirmed (Fishman, H.M., Poussart, D.J.M., Moore, L.E. & Siebenga, E., 1977,J. Membrane Biol. 32:255). This paper analyzes two physical phenomena, one within and the other outside of the excitable membrane, that might account for the low frequency impedance (admittance) feature. The accumulation of potassium ions in a space outside the axon in conjunction with diffusion through the Schwann cell layer produces a low-frequency mode that is similar in some respects to that observed experimentally. Alternatively, a hypothetical inactivation process, with a voltage-dependent time constant, associated with conduction in potassium channels gives a better account of the data. Either or both of these phenomena could be involved in producing the low-frequency impedance behavior in the squid axon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01959972
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  • 7
    Electronic Resource
    Electronic Resource
    Assessment of conduction properties and thermal noise in cell membranes by admittance spectroscopy (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 13 (1992), S. 87-100 
    Details
    ISSN: 0197-8462
    Keywords: membrane driving-point functions ; ion channels ; rapid admittance determinations ; channel conduction rate constants ; thermal noise ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Advances in the speed of signal processing enable application of a Fourier-synthesized function as a small perturbation (1 mV) superposed on voltage clamp steps to rapidly (〈1 sec) acquire cell membrane complex driving-point functions (impedance or admittance) in several frequency bands ranging from 1 Hz to 10 kHz. Curve fits of admittance models to these data yield a complete quantitative linear description of membrane conduction systems and their kinetics. Furthermore, the rate constants between microscopic states of an ion channel can be calculated from conductance parameters derived from model curve fits of membrane admittances. Additionally, the power spectrum of membrane thermal noise is obtainable from impedance determinations by use of the Nyquist relation. Consequently, rapid driving-point function determinations provide the most complete macroscopic assessment of membrane conduction properties presently available. Admittance determinations of the potassium conduction system in squid giant axon and the potassium conducting “inward rectifier” in snail neuron are used to illustrate the above points. 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250130709
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  • 8
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    Direct Recording of K and Na Current–Potential Characteristics of Squid Axon Membrane (1969)
    Springer Nature
    Details
    Publication Date: 1969-12-01
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 9
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    Calcium effects in the electrical excitability of ‘split’ frog skin (1968)
    Elsevier
    Details
    Publication Date: 1968-04-01
    Print ISSN: 0005-2736
    Electronic ISSN: 1879-2642
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Published by Elsevier
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  • 10
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    Direct and Rapid Description of the Individual Ionic Currents of Squid Axon Membrane by Ramp Potential Control (1970)
    Cell Press
    Details
    Publication Date: 1970-09-01
    Print ISSN: 0006-3495
    Electronic ISSN: 1542-0086
    Topics: Biology , Physics
    Published by Cell Press
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