Biomedical subjects

A De Hemptinne

Publications and source records attributed to A De Hemptinne.

15 recordsLinked to original sources

PubMed1989

Simulated ischemia and intracellular pH in isolated ventricular muscle.

Isolated guinea pig papillary muscles were subjected to an in vitro model of ischemia, consisting of superfusion arrest and immersion in paraffin oil, which results in restriction of substrate supply and metabolite washout. Intracellular pH (pHi) and surface pH (pHs) were measured with glass microelectrodes. Contractile force declined to 82% of the pre-"ischemic" value after 2 min and to 37% of the control value after 10 min. In addition, a shortening of the time to peak and duration of contraction was noted. The rate of force development decreased later than the rate of relaxation. After 10 min, pHi was acidified on average 0.08 pH unit, which is about one-third of the measured pHs change. Tripling the ischemic pHi change by reduction of the intracellular buffering power only slightly increased the rate of tension decline. Experimental pHi changes of similar magnitude, induced during normal superfusion, had a smaller effect on contractile force and failed to reproduce the characteristic changes in time course of the contraction. It is concluded that, in our condition of simulated ischemia, the intracellular acidification cannot account fully for the rapid decline in contractility.

Amiloride↗

PubMed1984

Single-unit pH-sensitive double-barreled microelectrodes for extracellular use.

The purpose of this study is to systematically describe the construction of pH-sensitive double-barreled microelectrodes for extracellular use. The most important advantages of these microelectrodes are as follows: the reference and the pH barrels are next to each other, and therefore the measured pH is not affected by asymmetric or slowly spreading direct current potential. The diameter of the tip of the microelectrodes is between 7 and 35 micron. These pH-sensitive microelectrodes are generally stable and Nernstian. They can be used repeatedly both in vivo and in vitro to measure tissue extracellular fluid pH. Some applications are described.

Animals↗

PubMed1983

Changes in brain ECF pH during metabolic acidosis and alkalosis: a microelectrode study.

We used pH-sensitive double-barreled microelectrodes to measure brain extracellular fluid (ECF) pH in anesthetized dogs during isocapnic infusion acidosis (HCl) and alkalosis (Na2CO3) of 45-60 min duration. The diameter of the tips of these electrodes varied from less than 1 to 27 micron and were placed 5 mm below the surface of the parietal cortex. In group I (metabolic acidosis, n = 5) mean plasma and brain ECF pH fell significantly by 0.221 and 0.025, respectively, with changes in brain ECF pH being 11.3% of those noted in plasma. In group II (metabolic alkalosis, n = 5) mean plasma and brain ECF pH rose significantly by 0.170 and 0.049, respectively, with changes in brain ECF pH being 28.8% of those noted in plasma. Mean arterial and sagittal venous PCO2 and cisternal cerebrospinal fluid (CSF) acid-base variables did not change significantly during acid or base infusion. We conclude that during transients of isocapnic metabolic acid-base perturbations ionic gradients exist between brain ECF and CSF and that changes in brain ECF pH measured by microelectrodes follow the changes in plasma pH. These pH changes may play an important role in respiratory adaptations of acute metabolic acidosis and alkalosis.

Acidosis↗

PubMed1979