Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Measurement of axonal membrane conductances and capacity by means of a varying potential control voltage clamp (1969)
    Springer
    The journal of membrane biology 1 (1969), S. 431-458 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A new mode of voltage clamping in the squid giant axon is introduced and its advantages are analyzed, tested, and utilized to investigate membrane conductances and capacity. This method replaces the constant command potentials of the standard voltage clamp with potentials which vary with time. Some of the advantages in using the varying potential clamp are: (1) slowly varying potentials generate practically pureI K ; (2) rapidly varying potentials generate practically pureI Na; (3) triangular waves generate, under proper conditions, pure capacity currents and easy-to-analyze leakage currents; (4) the method gives direct, on-line display of sodium or potassium I–V characteristics within milliseconds; (5) it enables rapid and accurateE Na andE K determinations; and (6) it enables simple and accurate determination ofC m. The method was utilized to study the effects of various ions on membrane conductances and the effects of ionic composition, ionic strength, and temperature on membrane capacity. Membrane capacity was found to be practically independent of frequency in the 200 to 2,000 Hz range. Replacement of external sodium by Ca++, by impermeable Tris+, or even by dextrose or sucrose (low ionic-strength solutions) had negligible effects onC m.C m showed a small, positive temperature coefficient of 1.39% per °C in the 3 to 21°C range, and little change with temperature in the 20 to 40°C range. Above 40°C, bothC m andg L increased considerably with temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869791
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Potassium ion accumulation in a periaxonal space and its effect on the measurement of membrane potassium ion conductance (1973)
    Springer
    The journal of membrane biology 13 (1973), S. 387-410 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Potassium currents of various durations were obtained from squid giant axons voltage-clamped in artificial seawater solutions containing sufficient tetrodotoxin to block the sodium conductance completely. From instantaneous potassium current-voltage relations, the reversal potentials immediately at the end of these currents were determined. On the basis of these reversal potential measurements, the potassium ion concentration gradient across the membrane was shown to decrease as the potassium current duration increased. The kinetics of this change was shown to vary monotonically with the potassium ion efflux across the membrane estimated from the integral over time of the potassium current divided by the Faraday, and to be independent of both the external sodium ion concentration and the presence or absence of membrane series resistance compensation. It was assumed that during outward potassium current flow, potassium ions accumulated in a periaxonal space bounded by the membrane and an external diffusion barrier. A model system was used to describe this accumulation as a continuous function of the membrane currents. On this basis, the mean periaxonal space thickness and the permeability of the external barrier to K+ were found to be 357 Å and 3.21×10−4 cm/sec, respectively. In hyperosmotic seawater, the value of the space thickness increased significantly even though the potassium currents were not changed significantly. Values of the resistance in series with the membrane were calculated from the values of the permeability of the external barrier and these values were shown to be roughly equivalent to series resistance values determined by current clamp measurements. Membrane potassium ion conductances were determined as a function of time and voltage. When these were determined from data corrected for the potassium current reversal potential changes, larger maximal potassium conductances were obtained than were obtained using a constant reversal potential. In addition, the potassium conductance turn-on with time at a variety of membrane potentials was shown to be slower when potassium conductance values were obtained using a variable reversal potential than when using a constant reversal potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868237
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Periaxonal surface calcium binding and distribution of charge on the faces of squid axon potassium channel molecules (1982)
    Springer
    The journal of membrane biology 70 (1982), S. 115-123 
    Details
    ISSN: 1432-1424
    Keywords: surface charge ; calcium binding ; potassium channel ; axon membrane ; surface potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The calcium binding constant associated with external surface charge in a position to influence the voltage sensing charges for potassium channel gating appears to be ∼30 molar−1, a value much larger than previously thought and in approximate agreement with that found for artificial membranes composed of the lipid brain phosphatidylserene. Fixed charge on the periaxonal membrane surface is distributed in such a way that much larger charges occur at a distance of at least 8 angstroms from the channel pore openings. The separation between the ion pathway and the channel gating charge appears to be greater than or equal to 8 angstroms. Periaxonal surface charge which is in a position to determine the surface potential for gating has a magnitude greater than or equal to one (negative) electronic charge per 182 square angstrom before calcium binding, which is reduced to −e/625 Å in a normal divalent ionic environment. With the normal divalent ionic composition of seawater the surface potential at a position to influence the gating voltage sensor is ∼−15 millivolts relative to the bulk external potential. The external surface potential is ∼−3 mV at the pore mouth. There appears to be a negligible amount of fixed charge on the axoplasmic surface in the vicinity of the ion channel opening. Further, our results confirm earlier measurements that have given a negligible amount of axoplasmic surface fixed charge whose field components would be in a position to influence the channel gating charges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870221
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Leakage Current Rectification in the Squid Giant Axon (1961)
    [s.l.] : Nature Publishing Group
    Nature 190 (1961), S. 883-885 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE total current which flows across the mem-X brane of the giant axon of the squid in response to stepwise changes in membrane potential in a voltage -clamp arrangement was shown1 to consist mainly of sodium and potassium ions plus a small unidentified component, termed leakage'. This component ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/190883a0
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Effects of Internal Sodium on Ionic Conductance of Internally Perfused Axons (1966)
    [s.l.] : Nature Publishing Group
    Nature 212 (1966), S. 614-616 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Isolated, cleaned axons from the stellate nerves of Loligo pealii were perfused internally4 with artificial axoplasmic solutions containing sodium and potassium fluorides and were perfused externally with artificial sea water (ASW) solution the ion concentration of which (expressed as mmolar) was ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/212614a0
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    An anatomical basis for the resistance and capacitance in series with the excitable membrane of the squid giant axon (1977)
    Springer
    Journal of neurocytology 6 (1977), S. 621-646 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To correlate periaxonal tissue layer resistance with Schwann cell layer anatomy, cross and longitudinal sections of giant axons ofLoligo pealei were examined by transmission electron microscopy. Measurements were made of the width and frequency of mesaxonal clefts entering the Schwann cell layer from the periaxonal space and leaving the cell layer adjacent to the basal lamina. The average mesaxonal cleft width is 10.5 nm. One cm2 of the giant axon surface is enclosed by a single cell layer containing about 690 000 Schwann cells. One cm2 of axon surface has a sheath mesaxonal area of 0.002 cm2 at the periaxonal surface and 0.016 cm2 at the basal lamina, the mesaxons branching frequently as they cross the sheath. The volume of the Schwann cell layer extracellular space was estimated to be roughly 1% of the Schwann cell layer volume. Several models were used to predict the resistance,R, across the Schwann cell layer. Assuming the mesaxonal clefts contain seawater, and can be lumped into volume conductors having simple geometries, then (normalized for one cm2 of axon surface)R was estimated to be between 0.4 and 0.9 Ω cm2. This value compares favourably with electrophysiological estimates of the periaxonal tissue resistance (current clamp value = 0.9 Ω cm2 and the voltage clamp value = 1.4 Ω cm2) as these electrically measured values include the resistance across the outer connective tissue layer as well as the Schwann cell layer. The value of the Schwann cell membrane capacity was estimated to be approximately 0.7 μF/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01176377
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Direct visualization of particle velocity distribution by pseudostereoscopic viewing of time-lapsed sequential images: Application to fast axonal transport (1984)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 4 (1984), S. 231-239 
    Details
    ISSN: 0886-1544
    Keywords: pseudostereoscopy ; particle speed distribution ; velocity distribution ; fast axonal transport ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We describe a simple method for direct visualization of the velocity distribution of particles moving against an immobile background. The technique involves pseudostereoscopic viewing of image pairs separated by an appropriate time interval in a sequential recording of the subject. Under these conditions, the positive or negative parallax arising from particle motion results in the binocular image of a particle being perceived as raised or lowered relative to an immobile background plane depending on its direction of movement, and with the degree of perceived elevation being proportional to its speed. In effect, the binocular optic axis becomes a velocity (speed) axis under these conditions. The technique is illustrated with examples of image pair sequences showing fast axonal transport in lobster and squid axons using video-enhanced differential interference contrast microscopy. However, the pseudostereoscopic method is quite generally applicable to both microscopic and macroscopic time-dependent phenomena. Particle speeds can be quantitated using standard procedures for measuring frame-to-frame particle displacements, or alternatively, by determination of parallax using stereogrammatic methods. It should be also readily adaptable for on-line monitoring of particle velocity distribution, particularly in video systems where frame buffers can be utilized to extract and present serial image pairs having any desired time separation from video-taped sequences.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970040402
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Internally perfused squid axons studied under voltage clamp conditionsSupported by National Science Foundation grant GB 332 and U. S. Public Health Service grant NB 04601.. II. Results. The effects of internal potassium and sodium on membrane electrical characteristics (1964)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 64 (1964), S. 429-443 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030640315
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Internally perfused squid axons studied under voltage clamp conditions. I. Method (1964)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 64 (1964), S. 423-428 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030640314
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    The relation of accommodation to current distribution in single muscle fibers (1956)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 48 (1956), S. 181-195 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030480203
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...