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  • 1
    Electronic Resource
    Electronic Resource
    Combined action of intraaxonal iodate and external sea anemone toxin ATX II on sodium channel inactivation of frog nerve fibres (1983)
    Springer
    Pflügers Archiv 398 (1983), S. 204-209 
    Details
    ISSN: 1432-2013
    Keywords: Node of Ranvier ; Voltage clamp ; Iodate ; Sea anemone toxin II ; Sodium channel inactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1. Voltage clamp experiments were done on single myelinated nerve fibres of the frog,Rana esculenta, with 10 mM TEA+ in the external solutions to block potassium channels. 2. Iodate (20, 40 or 100 mM KIO3) was applied to the axoplasmic side of the nodal membrane by diffusion from a cut internode. The effect of 20 mM started within a few minutes and reached a stationary value after ca. 20 min which was maintained for another 15 min. The size of the effect was independent of the iodate concentrations tested. Iodate action could not be reversed even after only a 2-min application. 3. When the effect was fully established, iodate increased the faster time constant of inactivation ca. 1.2 times, the slower one ca. 1.7 times. Iodate also induced a persistent (for seconds) INa component that was, at the end of a 15-ms pulse (I15ms), 6% of the early peak INa of the control. 4. Experiments with conditioning prepulses revealed a non-monotonich ∞-V curve in iodate with finiteh ∞ values throughout. Increasing [Ca2+]0 from 2 to 10 mM shifted peak INa(V) and I15ms(V) by 10–15 mV to more positive potentials. In contrast, as shown in previous experiments, I15ms induced by sea anemone toxin ATX II was nearly abolished (h ∞≈0) for 60〈V〈80 mV on increasing [Ca2+]0. Otherwise internal iodate and external ATX II produced very similar effects. 5. If 5 μM ATX II (which leads to near-saturating I15ms) was applied after iodate treatment the effects of both agents were additive. The rate of ATX II action was unchanged in the presence of iodate. 6. These results point to different mechanisms by which iodate and ATX II exert very similar effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657152
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  • 2
    Electronic Resource
    Electronic Resource
    Distinctly different rates of benzocaine action on sodium channels of Ranvier nodes kept open by chloramine-T and veratridine (1984)
    Springer
    Pflügers Archiv 402 (1984), S. 439-445 
    Details
    ISSN: 1432-2013
    Keywords: Node of Ranvier ; Veratridine ; Chloramine-T ; Benzocaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1. Single myelinated nerve fibres of the frog,Rana esculenta, were voltage clamped in a fast-exchange chamber in the presence of 10 mM TEA to block potassium channels. 2. After treatment with 0.6 mM chloramine-T for 1–4 min a sizeable INa component persisted even during a 14-s depolarizing impulse. Changing the perfusate to Ringer solution +1 mM benzocaine resulted in a fast reduction (half time ca. 0.06 s) of the persistent INa, comparable to the rate of block of peak INa during a series of short impulses before chloramine-T. 3. In the presence of 60 μM veratridine the peak INa was followed by a slow exponential (τs) reincrease of inward current, I s , that did not appreciably inactivate. Application of 0.25 mM benzocaine during a 14-s depolarizing impulse caused I s to decrease exponentially with a large time constant, τon of 4.3 s. Recovery on washout proceeded with τoff. 4. τon was little dependent on benzocaine concentration and was 4.5 s on the average in 1 mM. τon in 25 μM was insignificantly (15%) larger than in 1 mM if tested on the same fibre. After equilibration in 25 μM, 0.25 mM and 1 μM, I s (t=14s) was reduced to 0.69, 0.30, and 0.10, respectively, of the value without anaesthetic. 5. Cooling by only 4–5°C reduced I s and much increased τs. τon (1 mM benzocaine) increased almost in proportion to τs. 6. Tail currents during a series of pulses (1.1 s every 2.5 s) were reduced by 0.25 mM benzocaine clearly faster (τ′on = 1.3 s) than I s during a long pulse of the same amplitude. 7. It is concluded that channels kept open by veratridine cannot be blocked directly by benzocaine whose rate of I s inhibition is mainly determined by the rate with which alkaloid-modified channels close.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583945
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  • 3
    Electronic Resource
    Electronic Resource
    Rate of action ofAnemonia sulcata toxin II on sodium channels in myelinated nerve fibres (1982)
    Springer
    Pflügers Archiv 394 (1982), S. 313-319 
    Details
    ISSN: 1432-2013
    Keywords: Node of Ranvier ; Voltage clamp ; Sea anemone toxin II ; Sodium channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1. The effect ofAnemonia sulcata toxin II (ATX II) on single myelinated nerve fibres of the frog,Rana esculenta, was investigated. 2. ATX II promptly and reversibly increased the duration of action potentials; on applying 0.5 μM the timet 0,5, to reach half of the final effect was 2.6 s. In the presence of 10 mM tetraethylammonium the duration was very sensitive to ATX II and as little as 10 nM could be detected. 3. The underlying mechanism was a diphasic incomplete inactivation of sodium channels which, at 15°C, caused a sizeableI Na to persist after 15 ms depolarization (I 15 ms). 4. On applying 5 μM (1.25 μM) ATX II at ca. 15°C,I 15 ms developed with a sigmoid time course whoset 0.5 was 1.5s (2.6 s) and on washing declined in a near-exponential fashion with τoff = 6.1 s (6.4 s). Washing after a short (1–2 s) application led to a transient considerable increase inI 15 ms followed by a faster decline with τ′off 〈 τoff. 5. Cooling decreased the rate of action with aQ 10 of 1/t 0.5=1.9 and of 1/τoff = 2.0 (between 7 and 14°C). ATX I (up to 15 μM) was ineffective and did not antagonize ATX II. 6. Both rates of diffusional access and reaction seem to contribute to the rate of action. The results suggest a superficial binding site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583695
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  • 4
    Electronic Resource
    Electronic Resource
    Ionic channels through the axon membrane (a review) (1974)
    Springer
    European biophysics journal 1 (1974), S. 1-16 
    Details
    ISSN: 1432-1017
    Keywords: Selectivity ; Tetrodotoxin ; TEA ; Channel Density ; Gating Function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Ionic channels are discrete sites at which the passive movement of ions takes place during nervous excitation. Three types of channels are distinguished. 1. Leakage channels that are permanently open to various cations. 2. Na channels that open promptly on depolarization but slowly close again (inactivate) on sustained depolarization and that are predominantly permeable to Na+ ions. 3. K channels that on depolarization open after some delay but stay open and that are mainly passed by K+ ions. The selectivity sequence of the Na channels of the squid axon (or frog nerve) is as follows: Na+ ≈ Li+〉(T1+)〉NH+ 4≫K+〉 Rb+, Cs+; that of K channels is: (T1+)〉K+〉Rb+〉NH+ 4≫Na+, Cs+, Na channels are selectively blocked by tetrodotoxin (TTX) or saxitoxin (STX), K channels by tetraethylammonium ions (TEA). Either channel type is reversibly blocked when one drug molecule binds to one site per channel, the equilibrium dissociation constant of these reactions being about 3×10−9 MTTX (or STX) and 4×10−4 M TEA, respectively. Because of their specificity and high affinity, TTX and STX are used to “titrate” the Na channels whose density appears to be of the order of 100/Μm2. The “gates” of the channels operate as a function of potential and time but independent of the permeating ion species. Drugs (e.g. veratridine) and enzymes (e.g. pronase, applied intraaxonally) cause profound changes in the gating function of the Na channels without influencing their selectivity. This points to separate structures for gating and ion discrimination. The latter is thought to be, in part, brought about by a “selectivity filter” of which detailed structural ideas exist. Recent experiments suggest that the gates of the Na channels are controlled by charged particles moving within the membrane under the influence of the electrical field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01022556
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of temperature on the slowly changing sodium permeability of veratrinized nodes of ranvier (1969)
    Springer
    Pflügers Archiv 311 (1969), S. 73-95 
    Details
    ISSN: 1432-2013
    Keywords: Ranvierscher Schnürring ; Voltage Clamp ; Veratridin ; Temperatur ; Ranvier Node ; Voltage Clamp ; Veratridine ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary 1. The effect of veratridine-Ringer (10−5 g/ml; pH 8.1) of varying temperature on single nodes of Ranvier of frog motor fibres was studied by means of the double air gap method. 2. Nodes, once depolarized by veratridine at room temperature, repolarized or even hyperpolarized on cooling. The change in membrane potential markedly out-lasted the change in temperature. 3. Voltage clamp experiments revealed that repolarization was caused by a reduction ofP s , the veratridine-induced, slowly changing Na permeability. TheQ 10 of the steady state value ofP s was 3.3 between 8 and 22°C. 4. Cooling considerably increased the time constant, τ s , with whichP s changed on sudden displacement of membrane potential. TheQ 10 of 1/τ s was 3.9 between 8 and 23°C. 5. Fast changes in temperature induced steps in membrane current which were followed by slower phases of current change. A hypothesis is offered to explain these changes and the unusually high temperature coefficient of the stationary value ofP s .
    Notes: Zusammenfassung 1. Auf einer Doppelluftspalt-Brücke wurden isolierte motorische Froschnervenfasern unter dem Einfluß von Veratridin-Ringer-Lösung (10−5 g/ml; pH 8,1) bei verschiedenen Temperaturen untersucht. 2. Durch Veratridin bei Zimmertemperatur depolarisierte Schnürringe repolarisierten oder hyperpolarisierten bei Abkühlung. Selbst bei sprungartiger Temperaturänderung dauerte die Neueinstellung des Membranpotentials 1 min oder länger. 3. In Voltage Clamp Experimenten wurde festgestellt, daß die Repolarisation auf einer Abnahme vonP s , der durch Veratridin bedingten, langsam sich ändernden Na-Permeabilität, beruht. DerQ 10 des stationären Wertes vonP s betrug 3,3 (zwischen 8 und 22°C). 4. Abkühlung führte zu einer starken Zunahme von τ s , der Zeitkonstante, mit der sichP s bei einem Potentialsprung ändert. DerQ 10 von 1/τ s betrug 3,9 (zwischen 8 und 23°C). 5. Rasche Temperaturänderungen verursachten im Voltage Clamp rasche Änderungen des Membranstromes, auf die langsamere Stromphasen folgten. Es wurde eine Hypothese aufgestellt, welche diesen mehrphasischen Stromverlauf und die ungewöhnlich starke Temperaturabhängigkeit der stationärenP s erklären könnte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588063
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  • 6
    Electronic Resource
    Electronic Resource
    Chloramine-T effect on sodium conductance of neuroblastoma cells as studied by whole-cell clamp and single-channel analysis (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 129-136 
    Details
    ISSN: 1432-2013
    Keywords: Sodium channel ; Patch clamp ; Inactivation ; Chloramine-T ; Neuroblastoma cell ; Single-channel analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patch-clamp experiments were done on sodium channels of neuroblastoma cells (N1E-115) in the presence of tetraethylammonium ions to block potassium channels. In Ringer solution whole-cell records revealed a diphasic I Na inactivation with the fast (τ0) component being clearly larger than the slow (τ1 ≈ 3 τ0) component. In single-channel studies on inside-out patches the mean open time, ¯t0, turned out to be only a fraction of τ0 and almost independent of membrane potential. After external application of chloramine-T I Na inactivation of whole cells was delayed with both τ0 and τ1 increased, and incomplete, i.e. a persistent current component emerged. The latter was maximal at a more positive membrane potential than the peak current. Also, after chloramine-T treatment the peak I Na increased, particularly at weak depolarizations. In inside-out patches the equally effective internal application of chloramine-T led to bursting channel openings with mean burst times (¯tb) ≈ 6 ms, and gap times (¯tg) ≈ 20 ms, where gap is defined as a closure of ⩾ 1.5 ms. Within the bursts (¯to) was approximately 2 ms, again clearly shorter than τ0; the mean close time, ¯tc was approximately 0.5 ms. The single-channel conductance was approximately 13 pS and unaffected by chlopramine-T. Diphasic I Na inactivation and the fact that ¯to 〈 τ0 led to an extension of the model of Aldrich and Stevens [J Neurosci 7:418–431 (1987)], in which overall kinetics is determined by the openings rather than closures of the sodium channels. The extension comprises two inactivated states in series with the open state. Estimates are given of all rate constants of the transition between states that describe the single-channel results as well as whole-cell I Na (t), both in the control and in chloramine-T.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370461
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  • 7
    Electronic Resource
    Electronic Resource
    Faszinierende Phänomene in Tensidlösungen (1995)
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 29 (1995), S. 76-86 
    Details
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ciuz.19950290204
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  • 8
    Electronic Resource
    Electronic Resource
    Messungen zum Aggregationsverhalten perfluorierter AlkansäurenHerrn Prof. Dr. M. Seefelder/BASF zum 60. Geburtstag (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 451-481 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: With the use of various techniques an attempt was made to characterize the aggregates that exist in micellar surfactant solutions of salts of the perfluornonanoic acid. The cmc values of the investigated systems were determined by conductivity and surface tension measurements. Conclusions about the shape of the micellar aggregates were drawn from rheologic and electric birefringence measurements. For the lithium, the ammonium and the tetramethylammonium surfactants the existence of normal micelles with spherical shape and with all surfactant ions lying at the micellar surface was found. The perfluornonanoate surfactants with the ammonium counterions that are partially substituted by alkyl groups showed in all investigations a behaviour that was different from the normal case. It was postulated that these solutions contain emulsion-droplet-like giant micelles with the surfactant ions and counterions solubilized as ion pairs in the interior of the micelles. Some of these giant micelles do not have spherical shape; these solutions showed electric birefringence. In most cases the giant micelles disappeared at higher temperatures. Only normal small micelles with spherical symmetry could then be detected and the measured values were again in the range for values of normal C8-perfluordetergents. On the basis of the investigated systems reasons and models for the formation of giant micelles are discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820216
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  • 9
    Electronic Resource
    Electronic Resource
    Voltage clamp studies of veratrinized frog nodes (1965)
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 66 (1965), S. 91-98 
    Details
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1030660516
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