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  • 1
    ISSN: 1432-1106
    Keywords: Vestibular ; Ocular ; Optokinetic ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dynamic characteristics of the horizontal vestibulo-ocular reflex (HVOR), the optokinetic response (OKR), and their interactions were investigated in alert albino rabbits. For stimulation of the horizontal semicircular canals, the whole rabbit was rotated sinusoidally on a motor-driven turntable at peak-to-peak amplitudes of 5 ° to 30 ° over a frequency range of 1/30 to 1/2 Hz. Optokinetic stimulation was provided by a narrow vertical slit light source presented in front of the eye to be tested. The evoked horizontal eye movements were observed and measured by means of a closed circuit television system adapted to provide an analog signal proportional to the eye movement. The net HVOR was obtained by rotation of the turntable in darkness and the net OKR by rotation of the light source. Combining rotation of the turntable with a stationary light source immediately increased the gain and reduced the phase shift of the HVOR. The light source moving in phase with the turntable, but at twice the angular amplitude, reduced the gain and advanced the phase of the HVOR. Eye movement curves of the HVOR modified by a fixed or moving slit light could be reconstructed approximately by a linear combination of the net HVOR and OKR.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 148 (1968), 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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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 343 (1990), S. 567-570 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Plant cells, like many other cells, maintain their cytoplasmic free Ca2+ concentration between 1(T7 and 10~8 M (refs 17-19), probably by actively extruding Ca2+ from the cytoplasm towards the vacuole or out of the cell20"22. The Ca2+ concentration in the vacuole (0.1-10 mM) is therefore higher ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: TTX ; Purkinje cell ; Cerebellum ; Deafferentation ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Tetrodotoxin (TTX) is widely used to block the sodium dependent action potential in excitable cells to study their other ionic properties. TTX applied outside, selectively blocks voltage dependent sodium channels and is thought to have no other effects. We report here that TTX, applied to slices of rat cerebellum, suppressed sodium spikes of the Purkinje cells and induced firing in bursts of slower spikes. This activity was blocked by cobalt (2 mM) or cadmium (0.2 mM) in the medium as well as by hyperpolarizing currents showing that the slow spikes were due to voltage dependent calcium channels. The membrane potential was not significantly changed by TTX and the spikes during the bursts had the same threshold potentials and peak spike amplitudes as the voltage and Ca2+ dependent dendritic spikes evoked by injected current before adding TTX. This indicated that no marked changes in the membrane conductances were produced by the TTX. Unlike the burst firing induced by removing extracellular sodium, the TTX induced bursts were not followed by a large hyperpolarization. The same kind of results were obtained with extracellular recording in the in-vivo preparation with TTX applied topically or by pressure near the recording sites. TTX induced burst firing was not due to blocking afferent inhibitory input to the PC, since bicuculline (10-6 M) applied without TTX, produced only increased firing of fast action potentials and no bursts. The bursts could be arrested within 1 to 2 min by intravenously administering 2 mg/kg sodium pentobarbital, the blockage lasted from 5 to 15 min. These effects of TTX were not due to a contaminant as TTX from two different suppliers produced the same effects. A possible mechanism based on a decrease of intracellular free sodium is discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 10 (1972), S. 431-432 
    ISSN: 1741-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1615-6102
    Keywords: Ion channels ; Ion transport ; Cell membranes ; Patch clamp ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Conclusion Exciting innovations in the methodologies available for the study of ionic channels (notably in animal cells) have allowed hitherto impossible advances in the comprehension of both structure and function. In using channels like the Na channel and the AChR as examples of these strategies, we have tried to give a concise but up to date account of the current possibilities (in particular, the patch-clamp) for research in membrane physiology. That few of these techniques have been applied to plant cell membranes simply indicates the scope for advancement in the understanding of some problems fundamental to plant physiology. The mechanisms of transport involved in processes known to be important for the life of plant cells (e.g., regulation of cytoplasmic and vacuolar potential differences and pH, maintenance of vacuolar turgor pressure, accumulation of metabolites and their counterions, response to environmental stimuli) are relatively speaking, poorly characterized. In that ion fluxes through plasmalemma and tonoplast membranes are at least in part likely to be via ionic channels for all of these processes, an important step forward would be the application of patch-clamp techniques for the direct demonstration of a channel mechanism and the subsequent elucidation of their role.
    Type of Medium: Electronic Resource
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