Izchak Z. Steinberg
Electrical behavior of nerve cells
The Matthew Rosenhaus Professorial Chair of Biophysics
Tel, Fax: (972-8) 934-2302
I did my Ph.D. research under the guidance of Prof. E. Katzir at the Weizmann Institute. I returned to the Weizmann in 1963 and have been there since then. I spent periods of research at Cornell University (1961), Berkeley (1962), MIT (1975), Johns HopkinsUniversity (1980) and the NIH (1989 and 1991).
The generation of electric potential across the cell membrane is brought about and controlled by the flow of specific ions through channels implanted in the membrane. Each channel fluctuates between a state in which it is open and a state in which it isclosed. I am interested in the rules that govern these fluctuations, and have developed a method for analyzing whether or not the channels behave as a system that is at thermodynamic equilibrium. This method of analysis has recently been applied by experimentalists to the elucidation of the mode of action of ionic channels.
One of the ionic channels, which is of paramount importance in the control of the electric voltage of nerve cells, is the sodium conducting channel. Normally it inactivates and shuts down soon after it opens, thus ensuring that the cell behavior is under control. However, under the influence of some toxins or pathological action of enzymes, the inactivation process is disrupted. I have simulated on the computer the electric behavior of a nerve cell that contains such modified sodium channels and have obtained a detailed description of such behavior under a variety of conditions. The computed results can be matched to findings obtained by experimentalists, and there are indications that such channels might be involved inclinical pathological cases of muscle weakness.
Nerve cells usually extend a branching tree, or trees, of processes presumed to collect messages coming in from other nerve cells. The conduction of electric signals in such dendritic trees has therefore been of much interest over the years. Recently Ideveloped a mathematical description of the spread of electricity in dendritic structures. Among other things this study will make it possible to investigate the electric behavior of dendrites as a function of the morphology of the trees. Thus the functional significance of the details of the intricate typical structures of the branching dendrites may be elucidated.
Steinberg, I.Z. (1987): Frequencies of paired open-closed durations of ion channels: method of evaluation from single-channel recordings. Biophys.J., 52:47-55.
Steinberg, I.Z. (1988): Computer simulations of the effect of non-inactivating sodium channels on the electric behavior of excitable cells. J.Theor.Biol.,133:193-214.
Steinberg, I.Z. (1990): Computer simulations of electrical bistability in excitable cells due to non-inactivating sodium channels: space- and time-dependent behavior. J.Theor.Biol., 144:75-92.
Steinberg, I.Z. (1995): Analytical solution of the electrical behavior of branched passive dendritic trees. Biophys. J. 68A: 360.
|Examples of the voltage distributions over a model dendritic tree comprised of seven segments. Compatibility with the demands of the boundary conditions at all junctions and terminals is ensured by the mathematical treatment.|