Structures de la cabuamine et de la vincorine

Cabuamine is identified as O-methyl-hydrogeno akuammine.     

Action de la chlorhexidine sur l'expression de la virulence de Candida albicans

Candida albicans is an opportunistic yeast. Its pathogenicity is linked to the susceptibility of the host surface as well as to particular factors of the strain: adhesion, filamentous growth and secretion of proteolytic enzymes. Chlorhexidine digluconate is an antiseptic with fungicidal properties. The action of the antiseptic on the growth of the yeast shows a minimal inhibitory concentration (MIC) at 50 μg·mL⁻¹ and a minimal fungicidal concentration (MFC) at 100 μg·mL⁻¹. The consequences of antiseptic treatment are studied using two indicators of pathogenicity: filamentation and the secretion of acid proteinase. Concerning the morphological indicator, a complete inhibition of filamentation for antiseptic concentration far below the MIC is observed; concerning the biochemical indicator, the results show a maintenance of proteolytic activity for concentration equal to the MIC and a disappearance of this activity between the MIC and the MFC. Concerning the proteolytic activity, Skim Milk (Difco) was substituted for bovine serum albumin with success. This mixture of casein allows to use a cheaper and more easily available substrate.     

Controle de la chaine de biosynthese de la threonine chezE. coli

Resume Le travail décrit dans cet article s'appuie sur la théorie du contrôle du métabolisme et a pour but la mesure des coefficients de contrôle des différentes étapes sur le flux de production de thréonine. Le coefficient de contrôle d'une étape sur un flux mesure quantitativement la réponse du flux aux variations de l'étape. Cette notion est donc particulièrement importante aussi bien dans les situations pathologiques (diminution de l'activité d'une étape) qu'en biotechnologies où au contraire les étapes sont amplifiées.La mesure des coefficients de contrôle des étapes d'une chaîne métabolique permet donc de connaître celle(s) dont l'amplification doit entraîner une augmentation concomitante du flux.Nous avons appliqué ces concepts à l'étude de la voie de biosynthèse de la thréonine à partir de l'aspartate.La voie de la biosynthèse de la thréonine à partir de l'aspartate est constituée de cinq étapes catalysées par cinq activités enzymatiques: l'aspartokinase (AK), l'aspartate semi-aldéhyde déshydrogénase (ASA-DH), l'homosérine déshydrogénase (HDH), l'homosérine kinase (HK) et la thréonine synthase (TS).La mesure du coefficient de contrôle de la première étape (AK, insensible à la rétro-inhibition par la thréonine dans la souche étudiée) a montré qu'elle était faiblement contrôlante. L'étude a révélé la présence d'une inhibition jusqu'alors inconnue de l'homosérine kinase par la lysine.Un début de modélisation de cette chaîne de biosynthèse permet d'expliquer les résultats expérimentaux.

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This paper deals with the application of the metabolic control theory, especially the measurement of control coefficients, to the threonine pathway inE. coli. The control coefficient of a step on a metabolic flux quantitatively assesses the flux response to the step variations. This concept is particularly relevant both in pathological situations (decrease in the activity of an enzymatic step in the metabolism) and in biotechnologies, where, on the contrary steps are amplified.Measurement of the control coefficients of the steps of a metabolic network makes it possible to know those whose amplification should lead to a simultaneous increase in the fluxes.We have applied these concepts to threonine biosynthesis from aspartate inE. coli. The threonine pathway starting from aspartate involves five steps catalyzed by five enzyme activities: aspartokinase (AK), aspartate-semialdehyde-dehydrogenase (ASA-DH), homoserine dehydrogenase (HDH), homoserine kinase (HK) and hreonine synthetase activity (TS).Measurement of the control coefficient of the first step (AK, insensitive to threonine inhibition in the studied strain) has shown that it controls threonine production weakly. Our study has revealed a hitherto unknown inhibition of homoserine kinase activity by lysine.Mathematical modeling of this metabolic pathway has been undertaken to better understand our experimental results.

     

Influence de la cure chirurgicale de la varicocele sur la qualite du sperme

The aim of this study was to assess the efficacy of surgical varicocèle repair in terms of sperm quality. We have performed a retrospective study including 62 patients. All of them underwent clinical evaluation. A sperm analysis has been done before and after surgical repair. Before sugery, the spermogram was normal in only 11.3%. Oligospermia was found in 62.1 % of cases while 6.5% of patients had azoospermia. Abnormalities like microcephalia were encountered in 36.8% of cases. All patients underwent surgical varicocele repair. They were followed up every three months up to 18 months. A significant improvement of sperm count was found in 18 cases, with a pregnancy rate of 6.45%. Alterations of sperm quality was most severe in older patients. We think that as far as natural history of varicocele is not well established, the duration of its evolution is well correlated with the severity of sperm alterations. So, need for precocious diagnosis in order to lessen the risk of infertility.     

Place de la scintigraphie osseuse dans la maladie de Paget

The clinical and laboratory signs, as well as the imaging and course of Paget's disease of bone, are now well known. This chronic and usually benign disease is characterized by excessive remodelling of bone tissue, associated with an increase, sometimes considerable, of osteoclast resorption and osteoblast formation activities. The bone scan is a fundamental examination to establish initial mapping of the localizations of the disease. This examination has a greater sensitivity than X-rays for the flat bones. Through three clinical cases, we present the bone scan aspect, the various localizations and the diagnosis difficulties of the disease, especially when a context of neoplasm is present.     

Estudio preliminar de la efectividad de la terapia asistida con perros en personas de la tercera edad

IntroductionAnimal-assisted therapy is increasingly present in several educational and health areas. The aim of this study is to assess the effectiveness of such interventions in the elderly population living in residential settings.Materials and methodsA 12-week dog-assisted intervention program was designed, with 16 participants from a nursing home divided into an experimental group and a control group.ResultsSeveral physical and psychological variables were assessed before and after the intervention. While there were no significant differences in the control group, the experimental group improved significantly after participating in the program.DiscussionThe results support the hypothesis that animal-assisted interventions may be beneficial for residents in elderly care homes.     

Contribution à la connaissance de la faune marine de la côte belge

Summary The difference of phototropism and phototaxis of both molluscs influenced their fixation.The orientation of both molluscs is towards the incoming light-direction, less pronounced when the light-intensity to the center of the tile is decreasing. The density of the populations of oysters is increasing towards the center of the tiles by decreasing light-intensity, the density of the Crepidula-population decreasing towards the center of the collector.The competition of both organisms in relation to space, is, under the opposed influence of the light, less than described in the literature.Theoretically it is possible to separate Crepidula and oyster-fixation, using this property.Statistical analysis corroborated our observations.     

Evolution de la temperature de l'oxygene dissous et de la transparence dans la baie Nord du lac Tanganika

Resume Nous décrivons dans ce travail l'évolution de la température de l'oxygène dissous et de la transparence dans le bassin N. du lac Tanganika.La température de l'eau ne subit des fluctuations intéressantes au cours de l'année que dans les 100 premiers mètres de la surface. Les eaux du Tanganika offrent une temperature élevée jusqu' à ses plus grandes profondeurs; à 1.400 m. la température de l'eau est encore de 23.35° C. La température des eaux superficielles dépend de l'insolation journalière et les variations saisonnières n'affectent qu'une épaisseur d'eau d'une centaine de mètres. La couche oxygénée de l'eau est très faible par rapport aux énormes profondeurs du lac. Dans le bassin N. elle varie au cours de l'année entre les extrêmes de 45 m. et de 115 m.; la plupart du temps la limite de l'oxygène dissous se situant à 75–80 m de profondeur.Les eaux superficielles sont fortement oxygénées, leur teneur en oxygène dissous oscille autour de 100% de satuation, jusqu'au thermocline elles sont encore oxygénées à 80–90%.Le thermocline est toujours plus haut que la limite de l'oxygène dissous et ne présente absolument pas une barrière biologique comme c'est le cas dans la plupart des lacs des régions tempérées.La transparence des eaux du lac Tanganika est considérable, elle atteint souvent 20 m; la moyenne au cours de l'année se situant aux environs de 15 m.

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Summary The author describes the temperature, oxygen and transparency conditions in the Northern basin of Lake Tanganyika.The fluctuations in the temperature of the waters in the course of the year is of interest only down to a depth of 100 m.The temperature of water in Lake Tanganyika is high even in the greatest depths; at 1.400 m depth the temperature of the water is still 23.35° C. The temperature of surface water depends on the daily solar radiation. The influence of seasonal variations is felt only down to a depth of about one hundred meters.The oxygenated layer of water is very thin in comparison with the very great depth of the lake. In the northern basin, this layer varies in thickness between 45 and 115 m, the limit of dissolved oxygen being at a depth of about 75 m most of the time.The oxygen concentration in superficial waters is very high and nearly reaches the saturation point. Down to the thermoclinal point, the concentration is still 80–90 % The thermocline is always higher than the limit of dissolved oxygen, it does not at all constitute a biological barrier as it does in most lakes in temperate climates. The waters of Lake Tanganyika are very transparent, their transparency often reaches the depth of 20 m, the average for the year being 15 m.

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Centre de Recherches du Tanganika (Uvira) Institut pour la Recherche Scientifique en Afrique Centrale I.R.S.A.C.