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  • 1
    Digitale Medien
    Digitale Medien
    Responses of electroreceptors (ampullae of lorenzini) of Skates to electric and magnetic fields (1976)
    Springer
    Journal of comparative physiology 106 (1976), S. 127-136 
    Details
    ISSN: 1432-1351
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary 1. The single nerve fibre responses of ampullae of Lorenzini to electric and magnetic stimulation were studied in the Black Sea Skates,Trygon pastinaca andRaja clavata. 2. Thresholds for electric stimulation were in the range 1·10−10 – 1·10−8 A/mm2. 3. Electrical coupling between receptors associated with different ampullar canals was found to exist (Fig. 2). 4. The receptors responded only to a changing magnetic field, the constant field being without effect (Fig. 3, 4). 5. The minimum thresholds for magnetic stimulation were 0.8 and 20 Gs/ sec for dorsal and mandibular receptors, respectively. 6. Receptor thresholds to magnetic stimulation were found to be dependent on the length of the ampullar canal and sensitivity to electric current (Fig. 7). 7. The character of the responses depended on both the direction of the magnetic field and the position of the receptor (Fig. 6). 8. The mechanism of the magnetic field effect was analyzed. 9. Skates can possibly perceive the magnetic field of the earth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00620494
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  • 2
    Digitale Medien
    Digitale Medien
    On the relationship between the number of negative slope regions in the voltage-current curve of the Hodgkin-Huxley model and its parameter values (1995)
    Springer
    Biological cybernetics 73 (1995), S. 149-154 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract.  We consider the problem of the existence of a negative slope region (NSR) in the voltage-current curve of the neuronal membrane and the relationship between this phenomenon and the membrane parameters. For the Hodgkin-Huxley model it is proposed to determine the dependence of the number of NSR on the values of the maximal sodium (g¯Na) and potassium (g¯K) conductances. The method is suggested for constructing the boundaries on the (g¯Na, g¯K) plane, in passing through which the number of NSR changes to 1. Using the method we partition the (g¯Na, g¯K) plane into the regions corresponding to the curves with the different number of NSR. This number can be changed from 0 to 2 in changing the values of g¯Na and g¯K over the physiologically possible range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004220050171
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  • 3
    Digitale Medien
    Digitale Medien
    Effects of Various Ions on the Resting and Action Potentials of the Giant Nerve Cells of the Leech Hirudo medicinalis (1967)
    [s.l.] : Nature Publishing Group
    Nature 214 (1967), S. 1351-1352 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The ganglion was isolated in physiological saline3 and its connective tissue capsule was opened in order to expose the nerve cells and their glia. Two or three microelectrodes were inserted into the two nerve cells to record changes in the potential of the membrane and the transmembrane current. ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/2141351b0
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  • 4
    Digitale Medien
    Digitale Medien
    Functional states of an excitable membrane and their dependence on its parameter values (1993)
    Springer
    Biological cybernetics 70 (1993), S. 157-161 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract The property of an excitable membrane of a nerve cell to change the type of electrical activity has been examined with the change of the value of applied current (I). The dependence of this property on the values of the membrane parameters is determined. Two different functional states depending on the values of the membrane parameters are considered. For one of the states a change in the value of I is accompanied by a change in the type of activity (damped periodic oscillations jump to undamped periodic oscillations or vice versa). For the other state the type of activity remains phasic (damped periodic oscillations) for each value of I. For the mathematical model of a membrane we have considered the problem of obtaining the boundary, partitioning the parameter space into the regions to which these functional states correspond. We suggest a mathematical set of this problem and give its algorithm. These boundaries have been constructed for two different variable parameters of the model. A good agreement between the boundaries and the experimental values of sodium and potassium conductances for different excitable membranes has been obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00200829
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  • 5
    Digitale Medien
    Digitale Medien
    On the relationship between the number of negative slope regions in the voltage-current curve of the Hodgkin-Huxley model and its parameter values (1995)
    Springer
    Biological cybernetics 73 (1995), S. 149-154 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract We consider the problem of the existence of a negative slope region (NSR) in the voltage-current curve of the neuronal membrane and the relationship between this phenomenon and the membrane parameters. For the Hodgkin-Huxley model it is proposed to determine the dependence of the number of NSR on the values of the maximal sodium (gNa) and potassium (gK) conductances. The method is suggested for constructing the boundaries on the (gNa, gK) plane, in passing through which the number of NSR changes to 1. Using the method we partition the (gNa, gK) plane into the regions corresponding to the curves with the different number of NSR. This number can be changed from 0 to 2 in changing the values of gNa and gK over the physiologically possible range.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00204053
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  • 6
    Digitale Medien
    Digitale Medien
    Partition of the Hodgkin-Huxley type model parameter space into the regions of qualitatively different solutions (1992)
    Springer
    Biological cybernetics 66 (1992), S. 413-418 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract We have examined the problem of obtaining relationships between the type of stable solutions of the Hodgkin-Huxley type system, the values of its parameters and a constant applied current (I). As variable parameters of the system the maximal Na+(gNa),K+(gK) conductances and shifts (Gm, Gh, Gn) of the voltage-dependences have been chosen. To solve this problem it is sufficient to find points belonging to the boundary, partitioning the parameter space of the system into the regions of the qualitatively different types of stable solutions (steady states and stable periodic oscillations). Almost all over the physiological range of I, a type of stable solution is determined by the type of steady state (stable or unstable). Using this fact, the approximate solution of this problem could be obtained by analyzing the spectrum of eigenvalues of the Jacobian matrix for the linearized system. The families of the plane sections of the boundary have been constructed in the three-parameter spaces (I, gNa,gK), (I, Gm, Gh), (I, Gm, Gn).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00197721
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  • 7
    Digitale Medien
    Digitale Medien
    Method for constructing the boundary of the bursting oscillations region in the neuron model (2000)
    Springer
    Biological cybernetics 82 (2000), S. 493-497 
    Details
    ISSN: 1432-0770
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Informatik , Physik
    Notizen: Abstract. We examine the problem of constructing the boundary of bursting oscillations on a parameter plane for the system of equations describing the electrical behaviour of the membrane neuron arising from the interaction of fast oscillations of the cytoplasma membrane potential and slow oscillations of the intracellular calcium concentration. As the boundary point on the parameter plane we consider the values at which the limit cycle of the slow subsystem is tangent to the Hopf bifurcation curve of the fast subsystem. The method suggested for determining the boundary is based on the dissection of the system variables into slow and fast. The strong point of the method is that it requires the integration of the slow subsystem only. An example of the application of the method for the stomatogastric neuron model [Guckenheimer J, Gueron S, Harris-Warrick RM (1993) Philos Trans R Soc Lond B 341: 345–359] is given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004220050602
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  • 8
    Digitale Medien
    Digitale Medien
    Neuropharmacological analysis of synaptic transmission in the Lorenzinian ampulla of the skate Raja clavata (1991)
    Springer
    Journal of comparative physiology 168 (1991), S. 639-646 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Lorenzinian ampulla ; Discharge frequency ; Electroreception ; Neurotransmitter ; Primary synapse ; Amino acids ; l-glutamate ; l-aspartate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Dissected ampullae of Lorenzini of the skate (Raja clavata) were studied with the aim of determining the synaptic transmitter between electroreceptor cell and afferent fibre. Resting activity and stimulus-evoked activity in response to electrical pulses were recorded in single afferent units at constant perfusion with normal and test solutions containing different putative neurotransmitters. Presynaptic transmitter release was blocked by Mg2+ (up to 50 mM) to investigate the effects of the test substances upon the postsynaptic membrane. l-Glutamate (l-GLU) and l-aspartate (l-ASP), both at concentrations between 10-7 and 10-3 M, enlarged strongly resting and stimulus-evoked discharge frequency in the afferent fibre. If transmission was blocked by high Mg2+, resting discharge frequency could be restored by l-GLU or l-ASP. The glutamate agonists quisqualate (10-8–105 M) and N-methyl-D-aspartate (10-5–10-3 M) enlarged spontaneous activity in the afferent fiber. The same was found for kainic acid (10-9–10-5 M). Taurine at concentrations between 10-5 and 10-3 M caused a concentration-dependent decrease in afferent activity. The same was found for gammaaminobutyric acid (GABA; 10-5–10-4 M), and for the catecholamines adrenaline and noradrenaline, both in concentrations between 10-5 and 10-3 M. Serotonine (10-5–10-3 M) and dopamine (10-5-10-3 M) had no effect on resting or evoked activity in the Lorenzinian ampulla afferents. Acetylcholine (ACh; 10-4 M) enlarged discharge frequency in those units with initial rates lower than 22–25 Hz, but diminished discharge frequency in fibres with initial activity higher than 25 Hz. When synaptic transmission was blocked by high Mg2+ solution, perfusion with additional ACh did not restore resting activity in the afferent fibre. The results suggest that the most probable transmitter in the afferent synapse of the ampullae of Lorenzini is l-GLU or l-ASP, or a substance of similar nature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00224354
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  • 9
    Digitale Medien
    Digitale Medien
    Effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata (1991)
    Springer
    Journal of comparative physiology 168 (1991), S. 647-652 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Electroreceptors ; Lorenzinian ampulla ; Afferent synapse ; Neurotransmitters ; Pharmacology ; Amino acid antagonists
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary 1. The effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata were studied. 2. At concentrations of 10-3 to 10-6 M, l-glutamic acid diethylester (GDEE) and l-glutamic acid dimethylester (GDME) decreased the resting afferent discharge frequency as well as the electrically evoked activities and depressed the responses to application of excitatory amino acids. 3. d-α-Aminoadipic acid (AA) and 2-amino-4 phosphonobutyric acid (APB) had practically no effect either on resting afferent discharge or on evoked afferent activity. 4. 2-Amino-5-phosphonovaleric acid (APV) reduced the resting afferent discharge and electrically evoked activity in the afferent fibres. APV blocked N-methyl-d-aspartate (NMDA) induced responses at a lower concentration than those induced by aspartate. 5. Responses caused by NMDA were Mg2+-dependent; those to quisqualate (Q) application depended to a lesser degree on the Mg2+ concentration. 6. Cis-2,3-piperidinedicarboxylic acid (PDA) blocked both the resting afferent discharge and the electrically evoked activity; it also reversibly blocked the postsynaptic, amino acid-induced responses. The l-glutamate (l-GLU) response was more resistant to the blockade than the l-aspartate (l-ASP) response. 7. Both kynurenic acid (KEN) and γ-d-glutamylglycine (DGG) reduced the resting and evoked activities in the afferent fibres. l-ASP was more resistant to blockade by KEN than l-GLU. 8. These observations suggest a prominent physiological role of quisqualate-, kainate- and NMDA-preferring receptors in the ampullae of Lorenzini of Raja clavata.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00224355
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  • 10
    Digitale Medien
    Digitale Medien
    Some functional characteristics of the electroreceptors (the ampullae of lorenzini) of elasmobranchs (1973)
    Springer
    Cellular and molecular life sciences 29 (1973), S. 293-294 
    Details
    ISSN: 1420-9071
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Выводы Исследовались свойства злектрорецепторных волокон черноморских скатов. Обнаружены фазные и тонические волокна. Показано, что одни рецепторы(тии I) возбуждаются при катодических толчках тока, а другие (тип П)-при анодических.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01926484
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