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G Haudecoeur

Publications and source records attributed to G Haudecoeur.

At least 19 recordsLinked to original sources
PubMed1992

Effect of Bay K 8644 on the magnitude of isoflurane and halothane contracture of skeletal muscle from patients susceptible to malignant hyperthermia.

Isoflurane has a lesser ability than halothane to induce contracture in malignant hyperthermia (MH) muscle in vitro. This does not necessarily imply that isoflurane is not as potent an MH trigger as halothane in vivo. A hypothesis was tested that in vitro treatment with Bay K 8644, an activator of both the dihydropyridine receptors as well as the sodium channels of the T-tubules, potentiates isoflurane-induced MH-susceptible skeletal muscle contracture. In addition to the usual halothane-caffeine test, other muscle bundles were exposed to 10 microM Bay K 8644-halothane and equipotent anesthetic concentrations (expressed in multiple minimum alveolar concentration [MAC]) of isoflurane either alone or combined with Bay K 8644. In 14 MH-susceptible muscle bundles, the mean maximum contracture induced by 2 MAC isoflurane was 0.20 +/- 0.22 g (mean +/- SD), and this value was significantly less than that obtained with 2 MAC halothane (0.68 +/- 0.40 g). Bay K 8644 did not induce muscle contracture on its own but consistently enhanced both the 0.5 MAC isoflurane and halothane to the same maximal isometric tension (1.09 +/- 0.35 g and 1.11 +/- 0.37 g, respectively). Such an effect was not observed in the MH-nonsusceptible group. Under the conditions of this in vitro study, 0.5 MAC isoflurane appears to be as potent as halothane in inducing muscle contracture in skeletal muscle bundles from individuals susceptible to MH.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Is resting membrane potential a possible indicator of viability of muscle bundles used in the in vitro caffeine contracture test?

In 22 patients susceptible to and 34 patients not susceptible to malignant hyperthermia, we examined which muscle conditions may influence the degree of sensitivity of skeletal muscle to the in vitro caffeine contracture test: predrug resting membrane potential, predrug twitch tension, and maximum contracture induced by 32 mM caffeine in two caffeine tests performed respectively at 30 and 75 min after biopsy. No differences in the measured variables were observed between the first and the second caffeine tests in the 34 patients susceptible to malignant hyperthermia. The first caffeine test was found to be positive in all of the 22 patients susceptible to malignant hyperthermia. However, in eight patients, the second caffeine test was negative and the muscle fibers were found to be significantly depolarized. Resting membrane potential was -73.4 +/- 7.9 mV before the first caffeine test and -65.8 +/- 8.8 mV before the second test. We suggest that when time-induced partial depolarization of malignant hyperthermia-susceptible fibers occurs, fibers may become less sensitive to caffeine.

Caffeine↗
PubMed1991

Effects of calcium-free solution, calcium antagonists, and the calcium agonist BAY K 8644 on mechanical responses of skeletal muscle from patients susceptible to malignant hyperthermia.

The purpose of this investigation was to determine if alteration in the function of the dihydropyridine receptor may in turn modify halothane-induced contractures in muscle bundles from patients susceptible to malignant hyperthermia (MH). The effects of Ca(2+)-free Krebs Ringer (KR) solution, 5 microM verapamil, 5 microM nifedipine, and 10 microM of the Ca2+ agonist BAY K 8644 on halothane-induced contracture were therefore investigated. The halothane-induced contracture was prevented in the absence of extracellular Ca2+ and significantly reduced in the presence of verapamil or nifedipine. BAY K 8644 significantly enhanced the 0.5-, 1.0-, and 1.5-vol % halothane-induced contracture in MH-susceptible muscle bundles. When BAY K 8644 was dissolved in Ca(2+)-free KR solution, no contracture was observed in MH-susceptible muscle bundles. These results on cut MH-susceptible human muscle bundles support the hypothesis that halothane-induced contracture in MH can be modified by the binding of Ca2+ agonists or antagonists to the dihydropyridine receptor. The role of Ca2+ entry phenomena remains unclear, but the results suggest that extracellular Ca2+ is required to reprime or to bind to some sites of the dihydropyridine receptors.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

Diltiazem and nifedipine reduce the in vitro contracture response to halothane in malignant hyperthermia-susceptible muscle.

The effects of diltiazem (1 microM) and nifedipine (1 microM) were examined separately on the in vitro halothane tests for malignant hyperthermia (MH) susceptibility. Eighteen patients with MH susceptibility were diagnosed as MH-susceptible (MHS) according to the protocol of the European MH Group. In addition, halothane tests were carried out in the presence of either diltiazem (ten patients) or nifedipine (eight patients). These two calcium channel blockers significantly reduced the halothane contracture. Furthermore, in five of the ten MHS patients tested in the presence of diltiazem as well as in five of the eight MHS patients tested in the presence of nifedipine the halothane contracture test could be classified as negative. It is concluded that the presence of clinical concentrations of either diltiazem or nifedipine in the muscle bath affects the in vitro discrimination for MH susceptibility to halothane.

Depression, Chemical↗
PubMed1990

Clinical concentrations of verapamil affect the in vitro diagnosis of susceptibility to malignant hyperpyrexia.

We examined the effects of verapamil on the in vitro caffeine and halothane tests for malignant hyperpyrexia (MH) susceptibility. Ten consecutive MH-susceptible patients were investigated according to the protocol of the European MH group. Additional tests were carried out in the presence of verapamil 10(-6) mol litre-1. In four of the 10 patients, the halothane contracture response following pretreatment with verapamil was classified as positive to halothane. In contrast, in nine of the 10 patients, contracture tests of muscle in the presence of verapamil were classified as negative to caffeine. It is advised that verapamil should be discontinued before performing a contracture test.

Caffeine↗
PubMed1990

Use of the calcium agonist BAY K 8644 for in vitro diagnosis of susceptibility to malignant hyperthermia.

We have studied the effects of the calcium agonist BAY K 8644 on the in vitro halothane test in 10 malignant hyperthermia-susceptible (MHS), 12 MH "equivocal" to halothane (MHEh), 30 MH non-susceptible (MHN) and 10 control patients. BAY K 8644 potentiated the halothane-induced contracture in muscle strips from both MHS and MHEh patients. The drug produced a more obvious difference in contracture responses between the MHEh group compared with the MHN and control groups.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1989

The association between the neuroleptic malignant syndrome and malignant hyperthermia.

The neuroleptic malignant syndrome (NMS) is an uncommon but dangerous complication of treatment with neuroleptic drugs. A primary defect in skeletal muscle has been suggested in view of similarities in the clinical presentations of NMS and anaesthetic-induced malignant hyperthermia (MH). The in vitro halothane-caffeine contracture tests are the most reliable method of identifying individuals susceptible to MH. The aim of this study was to define if a relationship exists between NMS and MH susceptibility. Hence, the in vitro halothane and caffeine contracture tests were performed on muscle tissue obtained from eight NMS, ten MH-susceptible and ten control patients. The results, which are expressed in accordance with the criteria of the European MH Group, defined the eight NMS subjects as MH non-susceptible. The response to halothane and caffeine exposure of skeletal muscle from NMS and control subjects was the same and significantly different from that of muscle from patients susceptible to MH. Furthermore, muscle from subjects in NMS and control group responded similarly to increasing concentrations of chlorpromazine. These results do not point towards an association between NMS and MH.

Adult↗
PubMed1983

[Inhibition, by an amphiphilic substance, niflumic acid, of the inward rectification of the crustacean muscle fiber].

Agents such as TEA+ or CS+ ions, these last ions instead of K+ ions in poor K extracellular solution, known to reduce or abolish the inwardly rectifying channel in many preparations produced no effect in crayfish muscle membrane By contrast, poor Cl extracellular solution (Cl- ions were replaced by CH3OSO3- ions) blocked the inward current activated by hyperpolarizing pulses and produced an increase of the resting potential. Niflumic acid is a agent which inhibited the inward going rectification of the crayfish muscle membrane. Apparent dissociation constant of niflumic acid with membrane sites was equal to about 6 X 10(-8) M; this value corresponds to that given by Cousin & Motais (1979) concerning translocation of Cl- ions in the membrane of red cells. Activation of the inward going rectification in the crayfish membrane is responsible of an inward current carried by Cl- ions.

Animals↗
PubMed1983

[Modification of the affinity of actomyosin calcium sites by anions].

ATP hydrolysis-pCa and isometric tension-pCa relationships were determined for isolated myofibrils under a variety of ionic conditions i.e. in presence of Cl- ions (normal conditions), in presence of CH3COO- or CH3OSO3- (ions replacing all or a part of Cl- ions). In all ionic conditions, these relationships have a S-shape. For each ionic condition, the relationships between isometric tension or ATP hydrolysis and pCa were parallel, but the isometric tension-pCa was shifted towards a smaller value of pCa. The relation between ATP hydrolysis and pCa has been analysed by means of the enzymatic reaction described by Michaelis-Menten. The analysis of isometric tension-pCa relationship can be also described by using the consecutive scheme of reaction for the co-operative action of two Ca2+ ions in the process of tension activation given by Ashley & Moisescu (1977) for barnacle myofibrils. The dissociation constant (k1) equal to the one that we determined for the ATP hydrolysis probably corresponds to the Ca2+ binding site of troponin (M1). This association (M1-Ca) would lead to the phosphorylation of the second site (M2) localized on myosin, which can bind a Ca2+ ion. In presence of CH3COO-, ATP hydrolysis (V) was increased with no change of the affinity of the first site for the Ca2+ ion. At the opposite, V did not change but the affinity of M1 site was decreased in presence of CH3OSO3-. CH3OSO3- must be considered as a competitive inhibitor whereas CH3COO- must be considered as an activator ion of the ATP hydrolysis reaction. In all cases, the relationship between isometric tension and ATP hydrolysis was hyperbolic.

Acetates↗
PubMed1982

[The effect of tetraethylammonium and the decrease in the extracellular chloride concentration on membrane depolarization and contraction of skeletal muscle fiber induced by a hyperpotassium solution].

1.--The tetraethylammonium (TEA) effects on K+ contracture and membrane depolarization are compared in both crab and frog skeletal muscle fibres. 2.--The mechanical tension of the contracture is reduced by the TEA in frog skeletal muscle fibre; it is increased in crab skeletal fibre. 3.--When no mechanical phenomenon is observed in frog skeletal muscle, the amplitude and the velocity of membrane depolarization induced by an increase of outward K+ concentration is reduced by the TEA. These effects are in opposition in crab muscle fibre. 4.--In crab muscle fibre, the results obtained tend to show that the C1-ions are not distributed on each side of the membrane according to Donnan equilibrium.

Animals↗
PubMed1978

[Effects of hypertonic solutions on the excitation-contraction coupling of the skeletal muscle fibre of the crab. II. Ultrastructural aspects (author's transl)].

Experiments were performed to investigate the modifications of electrical activity and the loss of contraction by examination of the ultrastructure. These alterations were obtained with a control physiological solution (artificial sea water, ASW) which was made hypertonic by adding sucrose, glycerol, choline chloride or urea. 1. Under these conditions, the ultrastructural results show that: a) all those substances induce a modification of the coupling junction (either diad or triad). This modification can explain the inhibition of the mechanical phenomenon; b) sucrose (Figs. 6C and 6D) and glycerol (Figs. 4A and 4B) induce alterations of the surface membrane and of the tubular system (less important with glycerol). They can explain the decrease of the resting potential and the abolishment or the modification of the action potential; c) in contrast, choline chloride (Figs. 7A to 7E) and urea (Figs. 9A to 9F) only modify the organisation of the coupling junction. The action potential is maintained. 2. A short exposure of the fibre in an isotonic sucrose solution (Figs. 5A to 5D) deeply modifies the tubular system, particularly, in cutting it off from the sarcolemma. 3. Choline chloride and urea produce similar changes in the ultrastructure but as urea is not ionized, it can be added to the ASW to investigate the electrical phenomenon which cannot be modified by contraction.

Animals↗