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  • 1
    ISSN: 1432-0428
    Keywords: Axonal flow ; diabetic neuropathies ; hypothermia ; motor neurones ; streptozotocin-diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study measured the velocity of fast orthograde axonal transport of incorporated 3H-proline in motoneurones of the sciatic nerve in control rats and in rats with streptozotocin-induced diabetes of 3 weeks duration. Sciatic nerve and abdominal cavity temperatures were monitored throughout the period of measurement of transport velocity, and the rats were warmed to minimise hypothermia at both sites. There was marked abdominal and sciatic nerve hypothermia immediately after operation, and this effect was more intense in diabetic rats than in control rats. In steady state, abdominal cavity temperature (mean±SEM) was 38.1±0.1 °C in both control and diabetic rats, and the sciatic nerve temperatures were 37.8±0.1 °C in controls and 37.1±0.3 °C in diabetic rats. The difference was not statistically significant. The velocities of orthograde axonal transport for the fastest molecules containing 3H-proline were 14.0±0.9 (SEM)mm/h for controls and 13.9±1.1 (SEM)mm/h for diabetic rats. Thus, no velocity difference was observed. The findings are discussed in relation to measurements of fast orthograde transport velocity in experimental diabetes in other studies. It is suggested that, where velocity deficits have been seen in diabetic rats, nerve hypothermia should be considered as a contributory factor.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 72 (1983), S. 117-130 
    ISSN: 1432-1424
    Keywords: surface charge ; surface concentration ; calcium channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Calcium ions affect the gating of Ca currents. Surface charge is involved but to what extent is unknown. We have examined this, using isolated nerve cell bodies ofHelix aspersa and the combined microelectrode-suction pipette method for voltage-clamp and internal perfusion. We found that Ba and Sr currents produced by substitution of these ions for extracellular Ca ions are activated at less positive potentials than Ca currents. Mg ions do not permeate the Ca channel and changes in [Mg]0 produce shifts in the activation-potential curves that are comparable to the effects of changes in [Ba]0 or [Sr]0. Inactivation of Ba currents also occurs at less positive potentials. Perfusion intracellularly with EGTA reduced inactivation of Ca currents as a function of potential, but did not shift the inactivation-potential curve. Hence, Ca current-dependent inactivation which is blocked by intracellular EGTA probably does not involve a similar change of intracellular surface potential. The voltage shifts of activation and inactivation produced by extracellular divalent cations used singly or in mixtures can be described by the Gouy-Chapman theory for the diffuse double layer with binding (Gilbert & Ehrenstein, 1969; McLaughlin, Szabo & Eisenman, 1971). From the surface potential values and the Boltzman distribution, we have computed surface concentrations that predict the following experimental observations: 1) saturation of current-concentration relationships when surface potential is changing maximally; 2) the increase in peak current when Ca ions are replaced by Sr or Ba ions; and 3) the greater inhibitory effect of Mg onI Ba thanI Ca. Theory indicates that surface charge cannot be screened completely even at 1m [Mg]0 and thus that Ca channel properties must be evaluated in the light of surface charge effects. For example, after correction for surface charge effects the relative permeabilities of Ca, Ba and Sr ions are equivalent. In the presence of Co ions, however, Ca ions are more permeable than Ba ions suggesting a channel binding site may be involved.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 78 (1984), S. 163-168 
    ISSN: 1432-1424
    Keywords: rat ventricle ; isolated single cell ; volrage-clamp ; internal perfusion ; Na current ; extracellular pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Effects of extracellular pH on the sodium current (I Na) of single rat ventricular cells were examined under conditions of voltage clamp and internal perfusion. In this way, pH i was controlled while pH o was changed. The combined suction pipette-microelectrode method was used. The suction pipette passed current and perfused the cell's interior; the microelectrode measured membrane potential. Increasing extracellular H+ depressedI Na and slowed inactivation. The current-voltage curves forI Na and Slowed inactivation. The current-voltage curves forI Na were shifted to positive and negative potentials at low and high pH o , respectively. Similar potential shifts were observed in both the conductance voltage curve and the steadystate inactivation voltage curve (h ∞). Conduction was also depressed at low pH o . The shifts were probably due to surface charge effects, while the impaired conduction was probably due to protonation of a site in the Na channel.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 21 (1975), S. 353-374 
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary In a giant neuron ofAplysia californica, permeabilities and conductances obtained by measuring net fluxes of Na+, K+ and Cl− with ion-specific microelectrodes were compared with those obtained by measuring transmembrane current and potential changes when the three ions were varied in the external solution. Net fluxes were measured with ion-specific microelectrodes, after blocking metabolic processes, thus allowing movement of ions down their electrochemical gradients. Permeabilities and conductances obtained from the “chemical” measurements (i.e., ion-specific electrodes) were generally comparable to the values obtained from “electrical” measurements. Where discrepancies occurred, they could be explained by showing that some of the assumptions necessary to use the “electrical” method were not quantitatively true in this system. The absolute magnitudes of the permeabilities are significantly less than those found in many axonal preparations. There is also a relatively highP Na/P K ratio. The selectivity of the membraneagainst ions such as Tris+ and MeSO 3 − is not good, Tris+ being nearly as permeable as Na+ and MeSO 3 − about one-half as permeable as Cl−. These properties may be characteristic of somal membranes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 560 (1989), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 130 (1932), S. 777-777 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE interaction of two haploid cells of opposite sex to produce the diplophase is a phenomenon well known in heterothallic species of the Hymenomycetes and of the smut and rust fungi. Buller1 has recently shown that a diploid mycelium of Coprinus lagopus, on coming into contact ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The source of Galactic cosmic rays (with energies up to 1015 eV) remains unclear, although it is widely believed that they originate in the shock waves of expanding supernova remnants. At present the best way to investigate their acceleration and propagation is by ...
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the ‘first stars’, which may have formed before galaxy formation began. Direct measurements are ...
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles (cosmic rays). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate ...
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Biophysics and Biomolecular Structure 22 (1993), S. 173-198 
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
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