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  • 1
    Electronic Resource
    Electronic Resource
    Periodic firing pattern in afferent discharges from electroreceptor organs of catfish (1995)
    Springer
    Pflügers Archiv 429 (1995), S. 378-385 
    Details
    ISSN: 1432-2013
    Keywords: Stimulus transduction ; Bursting ; Temperature dependence ; Calcium entry blockers ; Siluriformes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneous afferent activity was recorded from 26 single ampullary electroreceptive organs of freshwater catfish (Ictalurus nebulosus LeS) at various temperatures. Regular grouping of action potentials was apparent in this secondary sensory system at 35°C and occasionally at 30°C. Impulse groups consisted of up to seven impulses. The precise timing of impulse generation and the temporal sequence of impulses indicated that oscillating processes are involved. Expectation density functions were calculated for records of afferent activity obtained at various temperatures below 35°C. In the majority of records the function was periodic. Impulse grouping and expectation density functions became more distinct in units exhibiting extremely high thresholds (i.e. being insensitive) to electrical stimuli. The results suggest that the oscillations originate from the postsynaptic membrane. The temporal pattern of impulse generation within impulse groups of ampullary electroreceptor organs and of specific warm and cold receptors was compared and found to be similar. Application of cadmium and menthol, which both reduce calcium entry, suppressed spontaneous activity in normal and insensitive electroreceptor systems, attenuated the sensitivity of normal receptors and modified the periodic pattern. This indicates that calcium is implicated in sensory transduction and in postsynaptic mechanisms. The data suggest that an oscillating process is one component of signal transmission in ampullary electroreceptor organs of teleost fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374153
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ampullary electroreceptors in catfish (Teleostei): temperature dependence of stimulus transduction (1990)
    Springer
    Pflügers Archiv 417 (1990), S. 100-105 
    Details
    ISSN: 1432-2013
    Keywords: Catfish ; Ampullary electroreceptors ; Stimulus transduction ; Temperature dependence ; Calcium channels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The response properties of ampullary electroreceptors have been studied in the catfish Ictalurus nebulosus at skin temperatures between 5 and 35 °C. A unimodal relationship between spontaneous activity and temperature was obtained. Mean (±SEM) peak discharge rate was 57.3 ±1.8 impulses s−1 at 25 ° C; the receptors were active at 5 °C (15.0 impulses s−1) and at 35 °C (31.5 impulses s−1). There were no dynamic responses to temperature changes in either the warming or cooling direction. The shape of the frequency characteristic depended on temperature: the peak of the gain curve shifted to low frequencies at low temperatures. There was a concomitant change of the phase characteristic: the intersection at zero degree phase angle shifted to higher frequencies with an increase of temperature, thus increasing the lead at lower frequencies and decreasing the lag at higher frequencies. Latency after combined excitatory and inhibitory impulse stimulation was temperature dependent, ranging from 16.4 ms (5 °C) to 5.6 ms (35 °C). Application of the specific calcium channel blocker menthol (0.2 mM) suppressed spontaneous activity, the effect becoming more prominent at higher temperatures. Sensitivity to sinusoidal electrical stimulation was also impaired, but to a lesser degree and mainly at lower temperatures. We conclude that the filter properties of the receptor organ can be modelled by a band-pass filter in series with a latency, both of which are temperature dependent. These filter properties might be partially based on the activation kinetics of the tranduction channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370776
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Ionenselektive Coated Glass-Elektroden (1979)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 299 (1979), S. 115-118 
    Details
    ISSN: 1618-2650
    Keywords: Elektroden, ionenselektive ; coated glass, Carrier-PVC-Membran, Na, K, NH4, Ca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Na+-, K+-, NH 4 + - und Ca2+ selektive coated glass-Elektroden wurden entwickelt, bei denen eine ionenselektive Carrier-PVC-Membran auf eine ionenselektive Glasschicht aufgebracht wird, die über einen Innenelektrolyten mit der Ableitelektrode in Verbindung steht. Die Selektivität wird durch die aufgebrachte Carrier-PVC-Membran bestimmt, die zusätzlich Weichmacher zur Optimierung der Eigenschaften enthält.
    Notes: Summary Na+, K+, NH 4 + and Ca2+ selective electrodes have been developed by coating the ion-selective glass layer with a carrier PVC membrane. The glass is in contact with the conducting electrode through an inner electrolyte. The selectivity is determined by the PVC membrane, containing neutral carriers or electrically charged ligands and additionally plasticizers for optimizing the properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00518421
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Strömungsoptimiertes Multimeßsystem mit ionenselektiven Diskelektroden (1980)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 301 (1980), S. 410-413 
    Details
    ISSN: 1618-2650
    Keywords: Elektroden, ionenselektive ; Diskelektroden, strömungsoptimiertes Multimeßsystem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird ein strömungsoptimiertes Multimeßsystem mit ionenselektiven Diskelektroden vorgestellt, bei dem aufgrund stromlinienförmiger Erhebungen im Kanalsystem gegenüber den Carrier-PVC-Membranen in Verbindung mit einem stau- und totzonenarmen Strömungsverlauf eine trägheitsarme und präzise ionenselektive Analytik gewährleistet wird. In das Meßsystem lassen sich auch andere Sensoren wie pH-, gassensitive und Enzym-Elektroden einführen.
    Notes: Summary The proposed system ensures low-inertia and precise measurements by means of ion-selective disc electrodes. This is achieved by streamlined elevations in the channel system opposite to the carrier PVC membranes, caring for a flow low in stagnation and dead zones. Other sensors may also be used in this system, as e.g. pH-, gas-sensitive and enzyme electrodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00475748
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    Paper (German National Licenses)
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