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Gasser R, Horn S, Köppel H
Discrimination by valinomycin K-selective surface microelectrodes of a sulphonylurea-sensitive and a distinct sulphonylurea-, barium-, TEA- and cinnamate-insensitive component of K-efflux from isolated pig coronary arteries during simulated ischaemia
Journal of Clinical and Basic Cardiology 1998; 1 (1): 43-51

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Fig. 1: K-Efflux in Koronararterien - Versuchsanordnung This Image - Fig. 2: K-Efflux in Koronararterien - Mikroelektroden Fig. 3: K-Efflux in Koronararterien Fig. 4: K-Efflux in Koronararterien Fig. 5: K-Efflux in Koronararterien Fig. 6: K-Efflux in Koronararterien Fig. 7: K-Efflux in Koronararterien Last Image
Figure/Graphic 2: K-Efflux in Koronararterien - Mikroelektroden
Simplified diagram of different microelectrode tips during simulated ischaemia. Hatched area represents paraffin oil (P.o.), area underneath, marked with oval rings, represents myocardial or smooth muscle tissue (T). Between tissue and P.o. one can see the artificially created reduced extra-cellular space (ARECS). a. Electrode tip bevelled in a 45° angle not yielding ideal contact with the tissue surface, thus making contact with the paraffin oil. Under these conditions the hydrophobic carrier will instantly escape from the tip and the electrode does not give further readings. b. Elec-trode tip bevelled in a 45° angle pushed too deeply into the tissue causing cell damage. Cells will be either damaged or destroyed causing a constant leak of K+(K+ ions represented by stippling) into the ARECS which, in turn, leads to faulty measurements: instead of ischaemia-induced K+ efflux caused by changed K+ conductance of the membrane the electrode measures changes resulting from damaged cells (c.f. Fig. 3). c. Electrode tip bevelled in a 90° angle (flat tip) ideally positioned in the ARECS. Only under these circumstances correct measurements of transmembrane K+ efflux induced by ischaemia are possible (c.f. Fig. 3). d. Ideally bevelled surface microelectrode, impaled too deeply into the tissue. Stippling represents K+ ions leaking from damaged tissue - readings will be misleading. e. Too fine-tipped microelectrode, pushed too deeply into the tissue. Leaking K+ from the damaged tissue like in b and d, represented by stippling and small arrows.
 
K-Efflux in Koronararterien - Mikroelektroden
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Figure/Graphic 2: K-Efflux in Koronararterien - Mikroelektroden
Simplified diagram of different microelectrode tips during simulated ischaemia. Hatched area represents paraffin oil (P.o.), area underneath, marked with oval rings, represents myocardial or smooth muscle tissue (T). Between tissue and P.o. one can see the artificially created reduced extra-cellular space (ARECS). a. Electrode tip bevelled in a 45° angle not yielding ideal contact with the tissue surface, thus making contact with the paraffin oil. Under these conditions the hydrophobic carrier will instantly escape from the tip and the electrode does not give further readings. b. Elec-trode tip bevelled in a 45° angle pushed too deeply into the tissue causing cell damage. Cells will be either damaged or destroyed causing a constant leak of K+(K+ ions represented by stippling) into the ARECS which, in turn, leads to faulty measurements: instead of ischaemia-induced K+ efflux caused by changed K+ conductance of the membrane the electrode measures changes resulting from damaged cells (c.f. Fig. 3). c. Electrode tip bevelled in a 90° angle (flat tip) ideally positioned in the ARECS. Only under these circumstances correct measurements of transmembrane K+ efflux induced by ischaemia are possible (c.f. Fig. 3). d. Ideally bevelled surface microelectrode, impaled too deeply into the tissue. Stippling represents K+ ions leaking from damaged tissue - readings will be misleading. e. Too fine-tipped microelectrode, pushed too deeply into the tissue. Leaking K+ from the damaged tissue like in b and d, represented by stippling and small arrows.
 
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