Biomedical subjects

P Lechêne

Publications and source records attributed to P Lechêne.

4 recordsLinked to original sources

PubMed1994

Effects of acidosis and alkalosis on mechanical properties of hypertrophied rat heart fiber bundles.

Effects of alkalosis (pH 7.4) or acidosis (pH 6.8) on the intrinsic mechanical properties of control and pressure-overloaded rat hearts were studied in Triton X-100-treated left ventricular fiber bundles. In control bundles, Ca sensitivity [pCa required for one-half maximal response (pCa50)] was 5.520 +/- 0.012 at pH 7.1. Alkalosis increased it by 0.357 +/- 0.018 pCa unit, whereas acidosis decreased it by 0.365 +/- 0.014 pCa unit with no change in Hill coefficient. Maximal tension was decreased by acidic pH and increased by alkaline pH. Stiffness was measured by the response to quick length changes. Acidosis decreased maximal stiffness but increased the stiffness-to-force ratio, whereas alkalosis increased maximal stiffness but had no effect on stiffness-to-force ratio, suggesting that acidosis decreased the force generated per cross bridge. Alkalosis increased the time constant of tension recovery following a quick stretch from 10.6 +/- 0.66 to 17.45 +/- 1.83 ms, suggesting a decreased cross-bridge cycling rate. Pressure overload induced by thoracic aortic stenosis for 4-6 wk led to a 200% cardiac hypertrophy associated with a shift from fast to slow ventricular myosin. pCa50 of hypertrophied bundles was not different from control (5.541 +/- 0.012). Ca sensitivity was increased by 0.383 +/- 0.008 in alkaline medium and decreased by 0.325 +/- 0.009 in acidic medium. Stiffness-to-force ratio was decreased in acidic pH, and the time constant of tension recovery was increased from 31.0 +/- 0.4 to 34.9 +/- 0.25 ms by alkalosis. In hypertrophied bundles, maximal tension was decreased by acidic pH but not changed by alkalosis. These results show that in the small pH range of our study 1) pH changes have symmetrical effects on Ca sensitivity in both control and hypertrophied bundles, 2) a decrease or an increase in H+ concentration does not have symmetrical effects on the mechanics of the cross bridges, and 3) changes in the phenotype of contractile proteins induced by aortic stenosis do not influence Ca sensitivity, only moderately influence the response to pH changes, and mainly affect the cross-bridge cycling rate.

Acidosis↗

PubMed1992

A loudspeaker-driven system for rapid and multiple solution exchanges in patch-clamp experiments.

A new and inexpensive system allowing rapid and synchronized changes of solutions around a membrane patch or a cell under voltage-clamp conditions is described. Four plastic capillary tubings (OD 640 microns; ID 430 microns) were glued together horizontally and attached to a coil of a commercially available loudspeaker. Servo-control of the position of the coil allowed the mouth of any of the capillaries to be positioned near the pipette tip within 6 ms. A high flow speed of the test solution was crucial to achieve rapid solution exchange. At a flow speed of 5 cm/s, complete exchange of the external environment of a frog ventricular cell was achieved within 20-30 ms. The time course of solution change was found to be 3-5 times faster at the tip of an open patch pipette. To preserve the physical integrity of the cell, the cell was usually perfused by a control capillary at a slow velocity (0.2-0.4 cm/s) and test solutions flowing out of adjacent capillaries at high velocity (4-5 cm/s) were applied to the cell only for short periods. Determination of the three-dimensional contamination profile around the mouth of the control capillary allowed the optimal conditions for the use of the system to be established and possible sources of contamination to be avoided between adjacent capillaries with unmatched flow speeds. Successive and multiple changes in external solutions could be easily synchronized with voltage-clamp depolarizations to examine the time course of the effect of drugs on voltage-operated ion channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Effect of dietary salmon oil feeding on rat heart lipid status.

For 2 mo rats were fed a salmon oil diet (12.5%, wt/wt) supplemented with 4.5% (wt/wt) corn oil, a corn oil diet (17%, wt/wt) or a low fat diet (4.4%, wt/wt). Cardiac lipids were analyzed and fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was determined. Ventricular biopsies were taken for ultramicroscopic examination. Serum cholesterol, triglyceride, phospholipid and vitamin E concentrations were significantly lower in rats fed salmon oil than in those fed the other two diets, whereas serum transaminases and vitamin A were not significantly affected. Cardiac protein, phospholipid, triglyceride and cholesterol concentrations were unaffected by diet. Cardiac phospholipid composition remained unchanged and no significant changes in lyso-PC or lyso-PE levels were observed. However, the salmon oil diet produced a markedly lower n-6/n-3 ratio in both PE and PC than in the other two diets. This was the result of replacement of n-6 polyunsaturated fatty acids (PUFA), primarily 20:4n-6 with n-3 PUFA, primarily 22:6n-3. The unsaturation index of PC and PE was higher with the salmon oil diet than with the other two diets. Ventricular biopsies of rats fed salmon oil showed mild lipid accumulation associated with some lipofuscin-like material. It is suggested that, in rat heart, fish oil led to a moderate accumulation of lipids, the composition of which may include long-chain monounsaturated fatty acids and a degradative form of peroxidized lipids.

Animals↗

PubMed1986

A dual effect of cardiac glycosides on Ca current in single cells of frog heart.

The effects of cardiac glycosides (1 microM ouabain, 50 microM dihydrooubain, 1 microM strophanthidin) on Ca current (ICa) were investigated on Cs-loaded single frog ventricular cells using the whole-cell patch-clamp technique (9). Cardiac glycosides exert both inhibitory and stimulatory effects on ICa in 20 Cs Ringer solution, but have only a stimulatory effect in 0 Cs, when the Na,K pump is blocked. The inhibitory response seems related to the inhibition of the Na,K pump by glycosides. The stimulatory effect on ICa may contribute to the positive inotropic effect of cardiac glycosides.

Animals↗