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Ionic channels in cells and model systems
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Book Ionic Channels in Cells and Model Systems.
Reviews
R. LATOKRE (ed.). Plenum
This book is a compendium of lectures given in Santiago, Chile during November 1984. It contains 430 pages divided into 26 chapters which cover a particularly wide spectrum of topics connected with ion channels both experimental and theoretical. Like most books of this type it suffers from an uneven level of treatment but it is difficult to imagine any one author dealing confidently with such diverse topics. The declared aim is to produce a tutorial guide for graduate students taking their first steps in this field. The reference lists are geneous but, in my opinion, the treatment is in many cases so short as to rule it out as a graduate student primer. I see the book rather as a stimulating refresher course for research workers in neighbouring fields as it does convey the rapid progress currently being made under the impact of new techniques such as patch clamping, optical detection methods. incorporation of intact channels into liposomes or planar lipid membranes and channel protein sequencing by DNA recombinant techniques. The first section entitled “Methodologies” contains a chapter by Osvaldo Alvarez describing the theory of the fluctuations expected from a two-state (open or shut) channel which is as clearly expressed as I have seen. This section also includes three chapters on optical methods. The first by Ana Garcia describes a measurement of Tl+ ion flux through channels incorporated in liposomes by fluorescent quenching, the second by Brian Salzberg and others describes attempts to detect trans-membrane voltage differences using fluorescent dyes and the third by Eduardo Rojas and others describes the optical detection of ATP release using the Luciferin-Luciferase reactijon. In each case the present problems as well as the hoped-for advantages of the techniques are described. Another interesting chapter is that by George Eisenman and John Dani who attempt to explain the current versus voltage characteristic of the acetylcholineactivated channel using the simplest barrier model with two barriers flanking one binding site but in which the barriers fluctuate as has been suggested by Peter LIuger and others. Using only the simplest two-state representation of the fluctuation very complex behaviour is predicted including a dependence of conductivity on ion concentration usually taken as a sign of multiple occupation of the channel. Too often one reads of models of ion channel behaviour that depend upon rigid and almost crystalline structures which totally disregard the thermally activated mechanical motions of proteins measured by NMR or inelastic neutron scattering. The second section entitled “Channels in Biological Membranes” contains descriptions of mechanotransducing channels, ion channels in plant protoplants. channels in kidney epithelial cells, channels in photoreceptors, calcium channels in muscle fibres and electrophysiological studies of endocrine cells. A graphic example of the fruitful impact of new techniques is given by Juan Bacigalupo, who describes
Press, New York (1986). f69.50.
the fluctuating single channel conductance measured by patch clamping the membrane of the photoreceptor of the ventral eye of Limulus. Macroscopic studies have shown that the conductance of the membrane varies with the voltage across the membrane. Single channel recording shows that the current versus voltage curve of each channel is in fact linear and that the measured change in membrane conductance is due to a marked dependence on membrane voltage of the probability of each channel being open. The third section describes experiments on channels reconstituted into liposomes or planar lipid bilayers and includes a general introduction to the topic by Christopher Miller. I found particularly interesting a study by Robert French and others of the BTX modified sodium channel incorporated into planar lipid membranes. Single channel behaviour is observed and a study of the effect of TTX, STX and other STX derivatives with net charges ranging from 0 to 2 showed that the binding of these toxins is indeed voltage-dependent, as had been established earlier, but that the voltage dependence was the same for all the toxins no matter what their charge. This indicates that the common voltage-dependent step must in some manner proceed in parallel with toxin binding. This chapter also illustrates another advantage of lipid bilayer incorporation in that the conductance of the BTX modified sodium channels may be studied in the complete absence of the calcium ion because, unlike many biological membranes, the lipid bilayers remain stable in its absence. The fourth section deals with ion channel modulation by “second messengers” and includes chapters by Irwin Levitan on metabolic regulation of channels, by Werner Loewenstein on the regulation of the cell-to-cell channel by phosphorylation, by Illani Atwater and John Rinzcl on the beta-cell bursting pattern and intracellular calcium and by Benjamin Suarez-Isla and Stanley Papoport on the changes observed in muscle cells that are cocultured with spinal chord neurons. Finally there is a section which contains a chapter on an attempt to correlate structure to function for the acetylcholine channel by Francisco Barrantes and a comprehensive chapter on the amiloride-sensitive epithelial sodium channels by Dale Benos which includes single channel data obtained by patch clamping and data obtained after incorporation of the channels into planar lipid membranes. The last chapter by Gerald Ehrenstein and Richard FitzHugh concerns an interesting attempt to model the chain of events which follows the fertilization of sea urchin eggs and leads to the observed release of free calcium. The book is well produced, clearly illustrated and contains a sensible index and for the reasons given above I believe it will earn a place in many departmental libraries.
D. T. EDMONDS
Book Ionic Channels in Cells and Model Systems.
Reviews
R. LATOKRE (ed.). Plenum
This book is a compendium of lectures given in Santiago, Chile during November 1984. It contains 430 pages divided into 26 chapters which cover a particularly wide spectrum of topics connected with ion channels both experimental and theoretical. Like most books of this type it suffers from an uneven level of treatment but it is difficult to imagine any one author dealing confidently with such diverse topics. The declared aim is to produce a tutorial guide for graduate students taking their first steps in this field. The reference lists are geneous but, in my opinion, the treatment is in many cases so short as to rule it out as a graduate student primer. I see the book rather as a stimulating refresher course for research workers in neighbouring fields as it does convey the rapid progress currently being made under the impact of new techniques such as patch clamping, optical detection methods. incorporation of intact channels into liposomes or planar lipid membranes and channel protein sequencing by DNA recombinant techniques. The first section entitled “Methodologies” contains a chapter by Osvaldo Alvarez describing the theory of the fluctuations expected from a two-state (open or shut) channel which is as clearly expressed as I have seen. This section also includes three chapters on optical methods. The first by Ana Garcia describes a measurement of Tl+ ion flux through channels incorporated in liposomes by fluorescent quenching, the second by Brian Salzberg and others describes attempts to detect trans-membrane voltage differences using fluorescent dyes and the third by Eduardo Rojas and others describes the optical detection of ATP release using the Luciferin-Luciferase reactijon. In each case the present problems as well as the hoped-for advantages of the techniques are described. Another interesting chapter is that by George Eisenman and John Dani who attempt to explain the current versus voltage characteristic of the acetylcholineactivated channel using the simplest barrier model with two barriers flanking one binding site but in which the barriers fluctuate as has been suggested by Peter LIuger and others. Using only the simplest two-state representation of the fluctuation very complex behaviour is predicted including a dependence of conductivity on ion concentration usually taken as a sign of multiple occupation of the channel. Too often one reads of models of ion channel behaviour that depend upon rigid and almost crystalline structures which totally disregard the thermally activated mechanical motions of proteins measured by NMR or inelastic neutron scattering. The second section entitled “Channels in Biological Membranes” contains descriptions of mechanotransducing channels, ion channels in plant protoplants. channels in kidney epithelial cells, channels in photoreceptors, calcium channels in muscle fibres and electrophysiological studies of endocrine cells. A graphic example of the fruitful impact of new techniques is given by Juan Bacigalupo, who describes
Press, New York (1986). f69.50.
the fluctuating single channel conductance measured by patch clamping the membrane of the photoreceptor of the ventral eye of Limulus. Macroscopic studies have shown that the conductance of the membrane varies with the voltage across the membrane. Single channel recording shows that the current versus voltage curve of each channel is in fact linear and that the measured change in membrane conductance is due to a marked dependence on membrane voltage of the probability of each channel being open. The third section describes experiments on channels reconstituted into liposomes or planar lipid bilayers and includes a general introduction to the topic by Christopher Miller. I found particularly interesting a study by Robert French and others of the BTX modified sodium channel incorporated into planar lipid membranes. Single channel behaviour is observed and a study of the effect of TTX, STX and other STX derivatives with net charges ranging from 0 to 2 showed that the binding of these toxins is indeed voltage-dependent, as had been established earlier, but that the voltage dependence was the same for all the toxins no matter what their charge. This indicates that the common voltage-dependent step must in some manner proceed in parallel with toxin binding. This chapter also illustrates another advantage of lipid bilayer incorporation in that the conductance of the BTX modified sodium channels may be studied in the complete absence of the calcium ion because, unlike many biological membranes, the lipid bilayers remain stable in its absence. The fourth section deals with ion channel modulation by “second messengers” and includes chapters by Irwin Levitan on metabolic regulation of channels, by Werner Loewenstein on the regulation of the cell-to-cell channel by phosphorylation, by Illani Atwater and John Rinzcl on the beta-cell bursting pattern and intracellular calcium and by Benjamin Suarez-Isla and Stanley Papoport on the changes observed in muscle cells that are cocultured with spinal chord neurons. Finally there is a section which contains a chapter on an attempt to correlate structure to function for the acetylcholine channel by Francisco Barrantes and a comprehensive chapter on the amiloride-sensitive epithelial sodium channels by Dale Benos which includes single channel data obtained by patch clamping and data obtained after incorporation of the channels into planar lipid membranes. The last chapter by Gerald Ehrenstein and Richard FitzHugh concerns an interesting attempt to model the chain of events which follows the fertilization of sea urchin eggs and leads to the observed release of free calcium. The book is well produced, clearly illustrated and contains a sensible index and for the reasons given above I believe it will earn a place in many departmental libraries.
D. T. EDMONDS