A system for the evaluation of temperature changes in living tissue at a dimensional level of a single cell is described. A glass micropipette the tip of which is filled with semiconducting glass (Rech et al. 1992), is used as a microsensor. The changes of conductivity of the sensor due to variations of temperature are evaluated by electronic circuitry based on the measurement of an AC current of sinusoidal waveform flowing through the sensor. Temperature changes in the range of 0.01 K can be detected in this way.
Ligand-gated ionic channels are integral membrane proteins that enable rapid and selective ion fluxes across biological membranes. In excitable cells, their role is crucial for generation and propagation of electrical signals. This survey describes recent results from studies performed in the Department of Cellular Neurophysiology, Institute of Physiology ASCR, aimed at exploring the conformational dynamics of the acetylcholine, glutamate and vanilloid receptors during their activation, inactivation and desensitization. Distinct families of ion channels were selected to illustrate a rich
complexity of the functional states and conformational transitions these proteins undergo. Particular attention is focused on structure-function studies and allosteric modulation of their activity. Comprehension of the fundamental principles of mechanisms involved in the operation of ligand-gated ion channels at the cellular and molecular level is an essential prerequisite for gaining an insight into the pathogenesis of many psychiatric and neurological disorders and for efficient development of novel specifically targeted drugs.
We proposed a temperature sensitive microelectrode for rapid measurements of temperature at the cellular level. In principle, the electrical impedance of the tip of the microelectrode changes with temperature. We designed an impulse measurement system (STEP) sensitive to the above changes of impedance. The system is based on a presettable negative input impedance of the current to a voltage converter. We compared the efficiency of the new STEP with the currently used RAMP system. We found following advantages of the STEP system: i) the danger of high voltage oscillations which could mechanically destroy the microelectrode tip is eliminated; ii) this system provides the opportunity to set the maximum sensitivity of the system according to the measured temperature interval. Moreover, the STEP method makes it possible to measure the resistance by using a sinusoidal stimulation signal which has to be preliminarily compensated by a rectangular signal. The shortest sampling period of the new system represents 0.1 ms with a resolution higher than 0.1 K and sensitivity better than 30 mV/K.
A microelectrode technique is described for simultaneous measurements of biopotentials and small and rapid ionic changes using double-barrel ion-selective coaxial microelectrodes (ISCM) evaluated by computer analysis.