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A Vialle

Publications and source records attributed to A Vialle.

8 recordsLinked to original sources
PubMed1986

Creatine kinase: reassessment of optimal concentrations for adenosine-5'-diphosphate and magnesium.

Whereas univariate studies led to an European agreement for the choice of optimal reagent concentrations of 2 mmol/L for ADP and 10 mmol/L for Mg2+ for determining creatine kinase (EC 2.7.3.2) activity in serum, whatever its isoenzyme pattern, the results of our bivariate study led us to recommend higher optimal concentrations: 4.1 to 4.7 mmol/L for ADP and 22 mmol/L for Mg2+. The zone of maximal activity was in fact a broad plateau such that more than 99% of maximal enzyme activity was attained at ADP concentrations between 3 and 5 mmol/L and Mg2+ concentrations between 17 and 26 mmol/L. Under these new conditions the maximum activity measured was modestly increased (about 10%) over the previously recommended method but the assay could be expected to be more resistant to the variations of ADP and Mg2+ concentrations. It may become necessary to modify the European recommended method.

Adenosine Diphosphate↗
PubMedDate not supplied

Evaluation of EMIT-TOX Enzyme Immunoassay for the analysis of benzodiazepines in serum: usefulness and limitations in an emergency laboratory.

The EMIT-TOX Enzyme Immunoassay for benzodiazepines was evaluated. Reproducibility, linearity, accuracy, sensitivity, and interferences were tested and found to be in good agreement with the manufacturer's specifications. Furthermore, the reactivity of 15 benzodiazepines were studied. According their differential reactivity, the 15 benzodiazepines can be classified into three groups: good reactivity similar to diazepam (potassium clorazepate, prazepam, estazolam, medazepam, flunitrazepam, nitrazepam); medium reactivity (clobazam, clonazepam, bromazepam, chlordiazepoxide, triazolam); and low reactivity (oxazepam, ethyl loflazepate, lorazepam). A possible structure/reactivity relationship is discussed. It is concluded that this kit is well adapted for the rapid detection of most benzodiazepines, but in no way can the EMIT technique permit quantitative results without clinical information.

Anti-Anxiety Agents↗
PubMedDate not supplied

[Enzyme calibrators: principle and practical use].

Results of catalytic activities of enzymes are highly dependent on the measurement procedures and on local conditions. Thus, only poorly marked improvement of interlaboratory comparability of results have been observed in clinical enzymology. To solve this problem, SFBC and IFCC have proposed to use "validated enzyme calibrators". Standardised operating procedures adapted to 37 C have been developed by IFCC for the most commonly used enzymes in clinical chemistry, and will be soon published. Reference materials which have been certified with these SOPs can be used as calibrators for a set of measurement methods which exhibit the same analytical specificity. Calibrators must be commutable, a property that must be checked experimentally. It is possible to produce stable and commutable materials for the calibration of a set of methods. Interest of this approach has been demonstrated for several enzymes. Results of two studies presented here show that the comparison of results to the upper limit of reference ranges does not improve the interlaboratory comparability of results in contrast to the calibration of different methods by a common calibrator which allowed to reach an interlaboratory CV close to 4% for ALT and gammaGT.

Calibration↗
PubMedDate not supplied

Calcium channel modulators and susceptibility to ischaemic ventricular fibrillation: modification of cellular calcium overload.

The effects of the calcium channel modulators, Bay k 8644, infused i.v. at a rate of 2.5 micrograms/kg/min, and diltiazem, injected i.v. in a dose of 0.5 mg/kg, on the susceptibility to fibrillation induced by ischaemia, were investigated in anaesthetized, open-chest pigs. Ischaemia was produced, under ventricular pacing at constant high rate (180 beats/min), by transient complete occlusion of the left anterior descending coronary artery, near its origin. It was maintained till the triggering of fibrillation. The propensity to fibrillation was judged from the time elapsing between the onset of occlusion and the onset of fibrillation (time to fibrillation). In addition to the surface electrocardiogram, conduction time and monophasic action potential were recorded in the ventricular contractile fibres, as were dP/dtmax in the left ventricle and blood pressure in the carotid artery. At the end of a 10 min infusion, Bay k 8644 lowered to a large extent (about 40%) the time to fibrillation, which returned to its control values within the following 20 min. Conversely, diltiazem increased the time to fibrillation by a factor 4 or 5 at 5 min after its administration. This time to fibrillation remained substantially increased 25 min later. These changes were not associated with alterations in conduction time or monophasic action potential duration in the absence of ischaemia, but with significant alterations in myocardial contractility and blood pressure: in the direction of an increase with Bay k 8644 and of a decrease with diltiazem. These results are in agreement with the enhancement by Bay k 8644 and the prevention by diltiazem of cell calcium overload which is at present recognized as being the essential determinant of the fibrillatory process.

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