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At least 1,225 records · Page 68Linked to original sources
PubMed1985

Microelectrode measurements from oxyntic cells in intact Necturus gastric mucosa.

The electrical properties of oxyntic cells were measured in intact isolated Necturus fundic mucosa by dissecting away the serosal muscle and connective tissue and impaling the oxyntic cells across their basolateral membranes. Their properties under resting [i.e., not secreting acid (10(-4) M serosal cimetidine)] and stimulated (10(-4) M histamine) conditions were compared with those of surface cells impaled across their apical membranes in a separate set of experiments. Histamine hyperpolarized the transepithelial potential by 6-10 mV and reduced the transepithelial resistance by approximately 40%. The basolateral membrane potential (Vcs) of both cell types was significantly hyperpolarized by histamine, that of oxyntic cells from a resting value of -50 to -59 mV (P less than 0.001) and that of surface cells from -50 to -54 mV (P less than 0.05). Histamine also hyperpolarized the apical membrane potential (Vmc) of the oxyntic cells; however, the Vmc of surface cells was significantly depolarized. The ratio of the apical to basolateral cell membrane resistances Ra/Rb (delta Vmc/delta Vcs resulting from transepithelial current pulses) of resting oxyntic cells was 1.1 and that of surface cells was 3.6. Stimulation did not affect the Ra/Rb of either cell type. A tenfold increase in serosal K+ concentration depolarized Vcs and increased Ra/Rb of resting and stimulated oxyntic cells, indicating a significant basolateral K+ conductance. The results are consistent with a purely passive role for surface cells and indicate that stimulation results in a simultaneous decrease of both the apical and basolateral membrane resistances of the oxyntic cells.

Animals↗
PubMed1979

Measurement of myocardial PCO2 with a microelectrode: its relation to coronary sinus PCO2.

A micro-PCO2 electrode, with dimensions of 1 x 10 mm, and a 63% response time of 14 s was inserted into the left ventricular myocardium of the pentobarbital-anesthetized dog. Continuous recordings were made of myocardial PCO2 (PmCO2), arterial PCO2 (PaCO2), and coronary sinus PCO2 (CSPCO2) during variation of respiratory rate. PmCO2 and CSPCO2 were compared at varying coronary flow. PmCO2 was similar to and closely followed changes in CSPCO2. The difference between PmCO2 and CSPCO2 was -0.52 +/- 3.63 (SD) mmHg, and PmCO2 exceeded PaCO2 by 20.69 +/- 5.12 mmHg. After coronary occlusion, PmCO2, rose promptly, but CSPCO2 was only slightly elevated until the occlusion was released, when a CO2 efflux into the coronary sinus occurred. It is concluded that the electrode measures extracellular PCO2 and that extracellular and myocardial PCO2 are essentially equal. PmCO2 rises rapidly following coronary occlusion.

Animals↗
PubMed1991

Carbonic acid buffer species measured in real time with an intracellular microelectrode array.

Carbonic acid buffer anions, HCO3- and CO3(2-), play an instrumental role in a host of vital processes in animal cells and tissues. Yet study of carbonic acid buffer species is hampered because no means are available to simultaneously monitor them at a cellular level in a rapid and dynamic fashion. An ion-selective cocktail, previously reported to measure changes in bicarbonate activity (alpha HCO3-), was instead shown to be principally selective for alpha CO3(2-). Ion-selective micropipettes (ISMs) based on this exchanger and consisting of a 3:1:6 (volume) mixture of tri-n-octylpropylammonium chloride, 1-octanol, and trifluoroacetyl-p-butylbenzene showed no significant interference from bicarbonate, chloride, phosphate, ascorbate, lactate, glutamate, acetate, or hydroxyl ions at concentrations expected in vivo. Intracellular and triple-barrel ISMs, consisting of a CO3(2-) sensitive, pH-sensitive, and reference barrel, were fabricated. Skeletal muscle cells (n = 17) were penetrated in vivo and showed values of 74 +/- 7 mV for membrane potential, 6.94 +/- 0.09 pHi, and 11 +/- 5 microM intracellular alpha CO3(2-), from which intracellular alpha HCO3- of 25 +/- 10 mM and CO2 tension of 120 +/- 55 Torr were calculated. All ion measurements reached a new steady state in 9 +/- 2 s after cell penetration. Thus measurements of intracellular alpha CO3(2-) and pH and associated levels of alpha HCO3(2-) and CO2 tension can be determined in biological tissues and cells with a spatial and temporal resolution previously unattainable.

Animals↗