‘Temps replié, temps déployé temps dépassés? Au fil du texte de Under the Volcano

in Les Années 30 (1991), 13

Kinetic study of the aspartate/glutamate carrier in intact rat heart mitochondria and comparison with a reconstituted system.

in Biochimica et Biophysica Acta-Bioenergetics (1991), 1058

The homologous exchange of external [14C] aspartate/internal aspartate catalyzed by the aspartate/glutamate carrier of rat heart mitochondria was investigated using aspartate-loaded, glutamate-depleted ... [more ▼]

The homologous exchange of external [14C] aspartate/internal aspartate catalyzed by the aspartate/glutamate carrier of rat heart mitochondria was investigated using aspartate-loaded, glutamate-depleted mitochondria. An inhibitor-stop technique was developed for kinetic studies by applying pyridoxal phosphate. Direct initial rate determinations from the linear phase of [14C] aspartate uptake were insufficiently accurate at high external and/or low internal substrate concentrations. Therefore, the full time-course of [14C] aspartate uptake until reaching isotope equilibrium was fitted by a single exponential function and was used to calculate reliable initial steady-state rates. This method was applied in bisubstrate analyses of the antiport reaction for different external and internal aspartate concentrations. The kinetic patterns obtained in double reciprocal plots showed straight lines converging on the abscissa. This result is consistent with a sequential antiport mechanism. It implies the existence of a catalytic ternary complex that is formed by the translocator and substrate molecules bound from both sides of the membrane. The Km values for aspartate were clearly different for the external and the internal sides of the membrane, 216 +/- 23 microM and 2.4 +/- 0.5 mM, respectively. These values indicated a definite transmembrane asymmetry of the carrier. The same asymmetry became evident when investigating the isolated protein from bovine heart mitochondria after reconstitution into liposomes. In this case the Km values for external and internal aspartate were determined to be 123 +/- 11 microM and 2.8 +/- 0.6 mM, respectively. This comparison demonstrates a right-side out orientation of the carrier after insertion into liposomal membranes. The sequential transport mechanism of the aspartate/glutamate carrier, elucidated both in proteoliposomes and in mitochondria, also seems to be a common characteristic of other mitochondrial antiport carriers [less ▲]

Comparaison des températures mesurées en Belgique dans un site urbain (Uccle) et un site rural (Thimister) : Impact d'un changement de site sur une série de données thermométriques (Thimister)

in Publications de l'Association Internationale de Climatologie (1991), 4

A comparative study of long temperature series in an urban station and in a rural station situated in Belgium determine if warming detected in the urban station or temporay change in the rural station can ... [more ▼]

A comparative study of long temperature series in an urban station and in a rural station situated in Belgium determine if warming detected in the urban station or temporay change in the rural station can be generalized or not into the country. [less ▲]

Etude du processus d’enseignement. Implications pour la méthodologie des activités physiques et sportives

in Jonnaert, Philippe (Ed.) Les didactiques, similitudes et spécificités (1991)

Les principes et recommandations de notre enseignement de la Méthodologie des Activités Physiques et Sportives (Piéron, 1985) découlent en ligne directe des observations faites en classe et des critères ... [more ▼]

Les principes et recommandations de notre enseignement de la Méthodologie des Activités Physiques et Sportives (Piéron, 1985) découlent en ligne directe des observations faites en classe et des critères de réussite identifiés par les études de type processus-produit ainsi que par les comparaisons d'experts et de débutants (Piéron, 1988). Notre présentation comportera deux parties étroitement liées. Dans la première, nous rappellerons brièvement le modèle fondamental décrivant le fonctionnement de l'enseignement. Nous distinguerons les phases du déroulement de l'action pédagogique et en soulignerons les aspects spécifiques à l'enseignement des activités physiques. Dans la seconde, nous exposerons les objectifs et paradigmes de recherche utilisés dans l'observation systématique de l'enseignement et leurs implications dans le cadre de la méthodologie des activités physiques. [less ▲]

THE MUTATION LYS234HIS YIELDS A CLASS-A BETA-LACTAMASE WITH A NOVEL PH-DEPENDENCE

in Biochemical Journal (1991), 278(Part 3), 673-678

The lysine-234 residue is highly conserved in beta-lactamases and in nearly all active-site-serine penicillin-recognizing enzymes. Its replacement by a histidine residue in the Streptomyces albus G class ... [more ▼]

The lysine-234 residue is highly conserved in beta-lactamases and in nearly all active-site-serine penicillin-recognizing enzymes. Its replacement by a histidine residue in the Streptomyces albus G class A beta-lactamase yielded an enzyme the pH-dependence of which was characterized by the appearance of a novel pK, which could be attributed to the newly introduced residue. At low pH, the k(cat.) value for benzylpenicillin was as high as 50 % of that of the wild-type enzyme, demonstrating that an efficient active site was maintained. Both k(cat.) and k(cat.)/K(m) dramatically decreased above pH 6 but the decrease in k(cat.)/K(m) could not be attributed to larger K(m) values. Thus a positive charge on the side chain of residue 234 appears to be more essential for transition-state stabilization than for initial recognition of the substrate ground state. [less ▲]

Transcription des usages du sol par le modèle de potentiel

in Mappemonde (1991), 3

The paper deals with an application of the potential model to the urban environment of the city of Luxembourg. Specific loadings are assigned to urban and vegetable land uses, identified according to a ... [more ▼]

The paper deals with an application of the potential model to the urban environment of the city of Luxembourg. Specific loadings are assigned to urban and vegetable land uses, identified according to a supervised classification of remote sensed SPOT data. Then, the two sets of loadings are separately submitted to potential models and the resulting images are merged by chromatic synthesis to obtain a map of the residential environment of the town. [less ▲]

La Faute du graveur

Scientific conference (1991)

Le culte de la Persuasion. Peithô en Grèce ancienne

in Revue de l'Histoire des Religions (1991), 208

Variabilité spatiale et temporelle de l'enneigement du sol en Belgique

in Publications de l'Association Internationale de Climatologie (1991), 4(1991), 267-273

Abcès thyroïdien a streptocoque pneumoniae associé à un goitre nodulaire toxique. A propos d'un cas

in Annales de Chirurgie (1991), 45(5), 429-31

An unusual case of acute suppurative thyroiditis in association with toxic nodular goiter is reported by the authors. Surgical therapy was necessary due to the severity of the local and systemic ... [more ▼]

An unusual case of acute suppurative thyroiditis in association with toxic nodular goiter is reported by the authors. Surgical therapy was necessary due to the severity of the local and systemic inflammation induced by this association. [less ▲]