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ABSTRACT: The influence of nitric oxide (NO) on the myelinated nerve fiber and the impact of modification of SHgroups of axon and myelin
membrane proteins on the amplitude and propagation velocity of action potential (AP), amount of the membrane-bound calcium
(Camb2+, viscosity of the axon membrane, and saturation factor of phospholipid fatty acids (Sf) of myelin have been investigated.
We established that the decrease in the number of extracellular SH-groups in membrane proteins induced by p-chloromercuribenzoate (pCMB, 10−4 M), led to a decrease in the AP amplitude and a reversible desorption of Camb2+ but did not affect the axolemma viscosity and Sf. Nitric oxide (NO) caused a decrease in the AP amplitude and propagation
velocity, an increase in the axolemma viscosity and a decrease in Sf of myelin; it also induced a reversible desorption of
Camb2+. Pretreatment of the nerve fiber with pCMB weakened the NO-induced desorption of Pretreatment of the nerve fiber with K+-channel blocker tetraethylammonium (10−2 M) completely abolished the NO-induced change in the amount of Camb2+. We suppose that NO-mediated changes in axolemma viscosity, Sf of myelin and desorption of Camb2+ affect protein-lipid interactions in axolemma and myelin, which in their turn influence the propagation of AP.
Biochemistry (Moscow) Supplement Series A Membrane and Cell Biology 04/2012; 3(2):190-195.
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ABSTRACT: The myelinated nerve fibre is formed by an axon and Schwann cells or oligodendrocytes that sheath the axon by winding around it in tight myelin layers. Repetitive stimulation of a fibre is known to result in accumulation of extracellular potassium ions, especially between the axon and the myelin. Uptake of potassium leads to Schwann cell swelling and myelin restructuring that impacts the electrical properties of the myelin. In order to further understand the dynamic interaction that takes place between the myelin and the axon, we have modelled submyelin potassium accumulation and related changes in myelin resistance during prolonged high-frequency stimulation. We predict that potassium-mediated decrease in myelin resistance leads to a functional excitation block with various patterns of altered spike trains. The patterns are found to depend on stimulation frequency and amplitude and to range from no block (less than 100 Hz) to a complete block (greater than 500 Hz). The transitional patterns include intermittent periodic block with interleaved spiking and non-spiking intervals of different relative duration as well as an unstable regime with chaotic switching between the spiking and non-spiking states. Intermittent conduction blocks are accompanied by oscillations of extracellular potassium. The mechanism of conductance block based on myelin restructuring complements the already known and modelled block via hyperpolarization mediated by the axonal sodium pump and potassium depolarization.
Interface focus: a theme supplement of Journal of the Royal Society interface 02/2011; 1(1):86-100.
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ABSTRACT: With the laser interference microscopy (LIM) technique, one can measure phase height of cells—a variable proportional to the cell thickness and the difference in the refractive indices of the cell and the surrounding medium. This makes functional optical cell imaging possible, and estimation of shape, thickness, and area of erythrocytes feasible. In this paper, we studied changes in erythrocyte shape and volume with osmolarity and p H . Obtained from the LIM technique, erythrocyte phase heights and area values, as well as the hematocrit-measured erythrocyte volume, were used to estimate changes in the refractive index with osmolarity and p H . A comparison between the estimated refractive index with the refractive index, calculated in the assumption that it can only depend on the hemoglobin concentration in the cell, indicates that these two estimates are identical in the range of osmolarity (250–1000 mOsm) and p H (4.5–10.0) values. Thus, refractive index changes result exclusively from the changes in hemoglobin concentration with the changes in erythrocyte volume. Under these conditions, it is possible to estimate the amount of hemoglobin in an erythrocyte from its phase height and area, obtained from LIM.
Journal of Applied Physics 06/2009; · 2.17 Impact Factor
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ABSTRACT: This paper presents the results of a laser interference microscopy study of the morphology and dynamical properties of myelinated nerve fibres. We describe the principles of operation of the phase-modulated laser interference microscope and show how this novel technique allows us to obtain information non-invasively about the internal structure of different regions of a nerve fibre. We also analyse the temporal variations in the internal optical properties in order to detect the rhythmic activity in the nerve fibre at different time scales and to shed light on the underlying biological processes. We observe pronounced frequencies in the dynamics of the optical properties and suggest that the oscillatory modes have similar origin in different regions, but different strengths and mutual modulation properties.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 10/2008; 366(1880):3463-81. · 2.77 Impact Factor
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ABSTRACT: The paper describes a detailed mechanism-based model of a tripartite synapse consisting of P- and R-neurons together with a giant glial cell in the ganglia of the medical leech (Hirudo medicinalis), which is a useful object for experimental studies in situ. We describe the two main pathways of the glial cell activation: (1) via IP(3) production and Ca(2 +) release from the endoplasmic reticulum and (2) via increase of the extracellular potassium concentration, glia depolarization, and opening of voltage-dependent Ca(2 +) channels. We suggest that the second pathway is the more significant for establishing the positive feedback in glutamate release that is critical for the self-sustained activity of the postsynaptic neuron. This mechanism differs from the mechanisms of the astrocyte-neuron signaling previously reported.
Journal of Biological Physics 09/2008; 34(3-4):441-57. · 1.86 Impact Factor
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ABSTRACT: We studied the effect of spirochete Borrelia burgdorferi sensu lato cell membrane proteins on excitability of myelinated nerve fiber. It was found that cell surface proteins of spirochetes B. burgdorferi s. s. bind to Ranvier nodes of the axon and to Schwann cells. Binding of B. burgdorferi s. s. and B. garinii to the nerve fiber modulates the amplitude and conduction velocity of the action potential, while B. afzelii had no effect on these parameters. The decrease in the spike amplitude and conduction velocity during sorption of B. burgdorferi s. s. or cell wall proteins was accompanied by desorption of membrane-bound calcium.
Bulletin of Experimental Biology and Medicine 02/2007; 143(1):36-9. · 0.27 Impact Factor
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ABSTRACT: The paper presents results on the application of interference microscopy and wavelet-analysis for cell visualization and studies of cell dynamics. We demonstrate that interference imaging of erythrocytes can reveal reorganization of the cytoskeleton and inhomogenity in the distribution of hemoglobin, and that interference imaging of neurons can show intracellular compartmentalization and submembrane structures. We investigate temporal and spatial variations of the refractive index for different cell types: isolated neurons, mast cells and erythrocytes. We show that the refractive dynamical properties differ from cell type to cell type and depend on the cellular compartment. Our results suggest that low frequency variations (0.1-0.6 Hz) result from plasma membrane processes and that higher frequency variations (20-26 Hz) are related to the movement of vesicles. Using double-wavelet analysis, we study the modulation of the 1 Hz rhythm in neurons and reveal its changes under depolarization and hyperpolarization of the plasma membrane. We conclude that interference microscopy combined with wavelet analysis is a useful technique for non-invasive cell studies, cell visualization, and investigation of plasma membrane properties.
Journal of Biological Physics 11/2006; 32(3-4):191-208. · 1.86 Impact Factor
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ABSTRACT: We present the model of an ion channel, operating in a regime of self-organized criticality. It is suggested that complex cooperative dynamics takes place in the protein and the overall tension of it facilitates an open or closed state of the rigid gates in the pore-making domain. For the first time multifractal spectra of ion channel dynamics are presented. Our model well reproduces the multifractal properties of ion channel dwell time series and provides an insight on the origin of the long-term correlations in these series.
Chaos An Interdisciplinary Journal of Nonlinear Science 10/2006; 16(3):033129. · 2.08 Impact Factor
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ABSTRACT: This Letter combines a novel experimental approach to the study of intracellular processes with a newly developed technique for multimode time-series analysis. Experiments are performed on isolated pond snail (Lymnaea stagnalis) neurons. Local variations in the cellular refractive index as detected by laser interference microscopy are related to the processes in the cell. A wavelet analysis shows the presence of several identifiable modes in the membrane and intracellular dynamics, and a double-wavelet analysis reveals nonlinear interactions between the regulatory processes in the form of mutual frequency and amplitude modulations.
Physical Review Letters 07/2005; 94(21):218103. · 7.37 Impact Factor
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ABSTRACT: A novel method based on the maximum overlap wavelet transform of dwell time series is proposed. Information on local multifractal properties of the series, namely local Hurst exponents or Holder exponents, was obtained. The results confirm the presence of multifractality and intrinsic correlations in the Ca(2+)-activated K+ channel dwell time series. The data on the local multifractal structure of the series can be interpreted in terms of processes having self-organized criticality. The proposed approach allows one to widen the store of methods for the analysis of single ion channel activity.
Biofizika 49(6):1075-83. · 0.43 Impact Factor
