Edad y crecimiento de Spondyliosoma cantharus (Sparidae) en el Golfo de Túnez

Age and the growth of the black seabream Spondyliosoma cantharus (Linnaeus, 1758) from the Gulf of Tunis were investigated using scales and otoliths. The length-weight relationship showed that the growth rates were isometric for females whereas males and the whole sample present a positive allometry. The monthly evolution in marginal increment data of scales and otoliths revealed that only one annulus is formed per year in April. Fish length and radii of the scales or otoliths were closely correlated. The von Bertalanffy growth equation was fitted on mean back-calculated length-at-age data, resulting in the parameter values L∞=35.4 cm, k=0.15 y–1 and t0=–0.19 y for scales and L∞=38.6 cm, k=0.10 y–1 and t0=–0.14 y for otoliths. Parameters estimated from scale and otoliths were significantly similar. However, taking into consideration the lower standard deviations of means for estimates based on otolith readings and the higher variance explained by the regression line fitted to otoliths, the latter seem to be more appropriate for ageing S. cantharus. The maximum age of the black seabream of the Gulf of Tunis is 10 years. Large discrepancies in growth parameters between geographic areas are the result of different growth patterns.Se han investigado la edad y el crecimiento de la cántara Spondyliosoma cantharus (Linnaeus, 1758) del Golfo de Túnez a partir de la lectura de las escamas y los otolitos. La relación talla-peso revela que las tasas de crecimiento son isométricas en las hembras, mientras que los machos y en toda la muestra existe una alometría positiva. La evolución mensual de los incrementos marginales de las escamas y los otolitos muestra que se forma un solo anillo anual en abril. La correlación entre la longitud de los peces y el radio de las escamas o los otolitos es muy elevada. La ecuación de crecimiento de von Bertalanffy se ha ajustado a la media talla-edad retrocalculada resultando en los siguientes valores para los parámetros de las escamas (L∞=35.4 cm, k=0.15 año–1, t0=–0.19 año) y los otolitos (L∞=38.6 cm, k=0.10 año–1, t0=–0.14 año). Los parámetros estimados a partir de las escamas y los otolitos resultaron significativamente similares. Sin embargo, teniendo en cuenta que las desviaciones estándar de las medias en las estimas son más bajas, y que la varianza explicada es mayor en la regresión ajustada a los otolitos, la lectura de los otolitos parece ser la más apropiada para datar la edad de S. cantharus. La edad máxima de la cántara del Golfo de Túnez es de 10 años. Las grandes diferencias en los parámetros de crecimiento entre áreas geográficas se deben a diferentes pautas de crecimiento

Functioning of the dimeric GABA(B) receptor extracellular domain revealed by glycan wedge scanning

The G-protein-coupled receptor (GPCR) activated by the neurotransmitter GABA is made up of two subunits, GABA(B1) and GABA(B2). GABA(B1) binds agonists, whereas GABA(B2) is required for trafficking GABA(B1) to the cell surface, increasing agonist affinity to GABA(B1), and activating associated G proteins. These subunits each comprise two domains, a Venus flytrap domain (VFT) and a heptahelical transmembrane domain (7TM). How agonist binding to the GABA(B1) VFT leads to GABA(B2) 7TM activation remains unknown. Here, we used a glycan wedge scanning approach to investigate how the GABA(B) VFT dimer controls receptor activity. We first identified the dimerization interface using a bioinformatics approach and then showed that introducing an N-glycan at this interface prevents the association of the two subunits and abolishes all activities of GABA(B2), including agonist activation of the G protein. We also identified a second region in the VFT where insertion of an N-glycan does not prevent dimerization, but blocks agonist activation of the receptor. These data provide new insight into the function of this prototypical GPCR and demonstrate that a change in the dimerization interface is required for receptor activation

Conception et optimisation d'un procédé extrapolable de purification d'acides hyaluroniques produits par culture microbienne

Hyaluronic acid (HA) is a biopolymer with mechanical and biological properties interesting the health and cosmetic areas. The industrial HA production is realized by implementation of streptococcus strains (group C or D). At the end of the production phase, a part of HA is free in a complex culture medium while the other remains associated to the cells in a capsule. The two main difficulties of the purification of HA lie, firstly, on the complexity of the production medium and, secondly, on the high requirements of the European Pharmacopoeia for such an application. The aim of this thesis was to provide an appropriate sequence of separation processes and a set of operating conditions for HA purification from a complex production medium which complies with the Pharmacopea. Initially, two original analytical methods for quantifying and evaluating the size of HA in complex environments have been developed in order to evaluate the performance criteria of the separation processes. Then, the HA extraction from the capsule, the elimination of cells, the purification and drying of HA were using classical separation processes and studied. The HA extraction by SDS or TCA showed that the HA bound to cells corresponds to 7 % of HA production. As a consequence, it was concluded that this step was not necessary. The cell separations from the culture medium by tangential microfiltration was unsuitable because of an excessive retention of HA (even at pore diameters higher than 0.22 µm) and a too fast membrane clogging. Good performances were observed with dead-end filtration using Celite. Then, the purification of HA by diafiltration (DF) with ultrafiltration membranes was considered. The operating conditions (PTM, feed rate, HA concentration and cutoff) allowing to maximize the permeate flow rate and the HA retention were selected from design of experiments methodology. The performances of purification by diafiltration (DF) in these conditions (yield, purity and productivity) were monitored. A method for predicting the performances according to the complex medium composition, based on the conventional mass balance equations and the DF permeate flow rate, was then proposed. This was done in order to facilitate the arrangement of the purification steps. In DF, the requirement of the pharmacopoeia in term of overall purity was obtained (> 95 %) but the proteins and nucleic acids levels were still above the threshold. This is why the adsorption of these molecules on activated carbon was studied as a function of temperature, ionic strength, pH and the type of activated carbon. The isotherm equations that better fitted the experimental data were selected and used combined to the equations of DF performances in order to find an appropriate chaining. Finally, the AH lyophilization and precipitation in organic solvent were compared. Both drying methods present less than 20 % moisture and preserve the properties of the moleculeL’acide hyaluronique (AH) est un polymère osidique aux propriétés mécaniques et biologiques d’intérêt pour le secteur de la santé et des cosmétiques. L’AH est produit à l’échelle industrielle par mise en oeuvre de souches de streptocoques groupe C et D. A l’issue de la production, une part de l’AH est libre dans le milieu de culture complexe, l’autre est associée à la capsule des cellules. La purification de l’AH est délicate en raison, d’une part, de la complexité des milieux de production et, d’autre part, des exigences de la pharmacopée européenne. L’objectif de cette thèse a été de proposer un enchaînement d’opérations et de conditions opératoires permettant une purification de l’AH à partir d’un milieu de production. Au départ, deux méthodes analytiques originales de quantification et d’évaluation de la taille de l’AH en milieux complexes ont été mises au point afin de pouvoir évaluer les critères de performance des procédés de séparation. Ensuite, quatre opérations permettant, premièrement l’extraction, deuxièmement l’élimination des cellules productrices d’AH, troisièmement la purification, et enfin, le séchage d’AH ont été établies. L’étude de l’extraction de la capsule d’AH assistée par SDS ou au TCA a permis d’établir que l’AH lié aux cellules ne représente que 7 % de l’AH produit. Il en a été déduit que cette étape n’est pas nécessaire. L’étude de la séparation des cellules du milieu de culture a montré que la microfiltration tangentielle n’est pas adaptée en raison, d’une part, d’une rétention trop élevée de l’AH (même avec des diamètres de pores supérieurs à 0,22 µm) et d’autre part, d’un colmatage trop rapide des membranes. Cette étape doit être réalisée par filtration frontale sur adjuvant de filtration (Célite). La purification de l’AH a été envisagée par diafiltration (DF) avec des membranes d’ultrafiltration. L’étude des conditions opératoires (PTM, débit d’alimentation, concentration en AH et seuil de coupure), par plan d’expériences, a permis de sélectionner des conditions qui maximisent le flux de perméat ainsi que la rétention d’AH. Ces conditions ont été appliquées en diafiltration au cours de laquelle les performances de séparation (rendement, pureté, productivité) ont été étudiées. Une méthodologie, basée sur les équations classiques de bilans de matière et de flux de perméat en DF, a alors été proposée. Cette démarche avait tout d’abord pour but de prédire lesdites performances en prenant en compte la composition complexe du milieu, de culture bactérienne mais aussi de faciliter l’agencement des étapes du procédé de purification. La diafiltration permet de satisfaire les exigences de pureté de la pharmacopée, mais pas les niveaux de certaines molécules (protéines et acides nucléiques). L’étude de l’adsorption de ces molécules sur charbon actif, en fonction de la température, de la force ionique, du pH et du type de charbon actif, a permis d’établir les conditions les plus favorables de l’élimination de ces molécules. Les équations classiques de modélisation des isothermes correspondant le mieux aux résultats expérimentaux ont été sélectionnées et utilisées avec les équations de performance en DF, afin d’associer au mieux ces deux étapes. Enfin, concernant le séchage de l’AH, deux méthodes, l’une par lyophilisation et l’autre par précipitation en solvant organique, ont été comparées. Ces dernières permettent d’obtenir moins de 20 % d’humidité et de conserver les propriétés des molécules d’A

Conception and optimization of an extrapolated process to purify hyaluronic acids by microbial culture

L’acide hyaluronique (AH) est un polymère osidique aux propriétés mécaniques et biologiques d’intérêt pour le secteur de la santé et des cosmétiques. L’AH est produit à l’échelle industrielle par mise en oeuvre de souches de streptocoques groupe C et D. A l’issue de la production, une part de l’AH est libre dans le milieu de culture complexe, l’autre est associée à la capsule des cellules. La purification de l’AH est délicate en raison, d’une part, de la complexité des milieux de production et, d’autre part, des exigences de la pharmacopée européenne. L’objectif de cette thèse a été de proposer un enchaînement d’opérations et de conditions opératoires permettant une purification de l’AH à partir d’un milieu de production. Au départ, deux méthodes analytiques originales de quantification et d’évaluation de la taille de l’AH en milieux complexes ont été mises au point afin de pouvoir évaluer les critères de performance des procédés de séparation. Ensuite, quatre opérations permettant, premièrement l’extraction, deuxièmement l’élimination des cellules productrices d’AH, troisièmement la purification, et enfin, le séchage d’AH ont été établies. L’étude de l’extraction de la capsule d’AH assistée par SDS ou au TCA a permis d’établir que l’AH lié aux cellules ne représente que 7 % de l’AH produit. Il en a été déduit que cette étape n’est pas nécessaire. L’étude de la séparation des cellules du milieu de culture a montré que la microfiltration tangentielle n’est pas adaptée en raison, d’une part, d’une rétention trop élevée de l’AH (même avec des diamètres de pores supérieurs à 0,22 µm) et d’autre part, d’un colmatage trop rapide des membranes. Cette étape doit être réalisée par filtration frontale sur adjuvant de filtration (Célite). La purification de l’AH a été envisagée par diafiltration (DF) avec des membranes d’ultrafiltration. L’étude des conditions opératoires (PTM, débit d’alimentation, concentration en AH et seuil de coupure), par plan d’expériences, a permis de sélectionner des conditions qui maximisent le flux de perméat ainsi que la rétention d’AH. Ces conditions ont été appliquées en diafiltration au cours de laquelle les performances de séparation (rendement, pureté, productivité) ont été étudiées. Une méthodologie, basée sur les équations classiques de bilans de matière et de flux de perméat en DF, a alors été proposée. Cette démarche avait tout d’abord pour but de prédire lesdites performances en prenant en compte la composition complexe du milieu, de culture bactérienne mais aussi de faciliter l’agencement des étapes du procédé de purification. La diafiltration permet de satisfaire les exigences de pureté de la pharmacopée, mais pas les niveaux de certaines molécules (protéines et acides nucléiques). L’étude de l’adsorption de ces molécules sur charbon actif, en fonction de la température, de la force ionique, du pH et du type de charbon actif, a permis d’établir les conditions les plus favorables de l’élimination de ces molécules. Les équations classiques de modélisation des isothermes correspondant le mieux aux résultats expérimentaux ont été sélectionnées et utilisées avec les équations de performance en DF, afin d’associer au mieux ces deux étapes. Enfin, concernant le séchage de l’AH, deux méthodes, l’une par lyophilisation et l’autre par précipitation en solvant organique, ont été comparées. Ces dernières permettent d’obtenir moins de 20 % d’humidité et de conserver les propriétés des molécules d’AHHyaluronic acid (HA) is a biopolymer with mechanical and biological properties interesting the health and cosmetic areas. The industrial HA production is realized by implementation of streptococcus strains (group C or D). At the end of the production phase, a part of HA is free in a complex culture medium while the other remains associated to the cells in a capsule. The two main difficulties of the purification of HA lie, firstly, on the complexity of the production medium and, secondly, on the high requirements of the European Pharmacopoeia for such an application. The aim of this thesis was to provide an appropriate sequence of separation processes and a set of operating conditions for HA purification from a complex production medium which complies with the Pharmacopea. Initially, two original analytical methods for quantifying and evaluating the size of HA in complex environments have been developed in order to evaluate the performance criteria of the separation processes. Then, the HA extraction from the capsule, the elimination of cells, the purification and drying of HA were using classical separation processes and studied. The HA extraction by SDS or TCA showed that the HA bound to cells corresponds to 7 % of HA production. As a consequence, it was concluded that this step was not necessary. The cell separations from the culture medium by tangential microfiltration was unsuitable because of an excessive retention of HA (even at pore diameters higher than 0.22 µm) and a too fast membrane clogging. Good performances were observed with dead-end filtration using Celite. Then, the purification of HA by diafiltration (DF) with ultrafiltration membranes was considered. The operating conditions (PTM, feed rate, HA concentration and cutoff) allowing to maximize the permeate flow rate and the HA retention were selected from design of experiments methodology. The performances of purification by diafiltration (DF) in these conditions (yield, purity and productivity) were monitored. A method for predicting the performances according to the complex medium composition, based on the conventional mass balance equations and the DF permeate flow rate, was then proposed. This was done in order to facilitate the arrangement of the purification steps. In DF, the requirement of the pharmacopoeia in term of overall purity was obtained (> 95 %) but the proteins and nucleic acids levels were still above the threshold. This is why the adsorption of these molecules on activated carbon was studied as a function of temperature, ionic strength, pH and the type of activated carbon. The isotherm equations that better fitted the experimental data were selected and used combined to the equations of DF performances in order to find an appropriate chaining. Finally, the AH lyophilization and precipitation in organic solvent were compared. Both drying methods present less than 20 % moisture and preserve the properties of the molecul

Erosion Infiltration in the Management of Molar-Incisor Hypomineralization (MIH) Defects

White spot lesions caused by enamel demineralization are frequently encountered in dental practice. Their management has always been an important issue in modern dentistry. However, the real dilemma was treating aesthetic demands with noninvasive or minimally invasive techniques preserving the natural tissues. The introduction of resin infiltration technique seems to provide an intermediary treatment modality between prevention and restorative therapy. This case report is aimed at reporting the management of MIH opacities in anterior teeth with resin infiltration technique

L-(+)-2-Amino-4-thiophosphonobutyric acid (L-thioAP4), a new potent agonist of group III metabotropic glutamate receptors: increased distal acidity affords enhanced potency.

International audienceL-2-Amino-4-phosphonobutyric acid (l-AP4), l-2-amino-4-thiophosphonobutyric acid (l-thioAP4), and l-2-amino-4-(hydroxy)phosphinylbutyric acid (desmethylphosphinothricin, DMPT) were synthesized from protected vinylglycine. They were tested as agonists at group III metabotropic glutamate receptors (mGluR) along with phosphinothricin (PT). DMPT and PT display a much lower potency at mGlu4 receptor (EC50 = 4.0 and 1100 microM, respectively) in comparison to l-AP4 (EC50 = 0.08 microM), whereas l-thioAP4 has a 2-fold higher potency (EC50 = 0.039 microM). Similar rank orders of potency were observed at mGlu6,7 and mGlu8 receptors. The higher potency of l-thioAP4 is due to its stronger second acidity compared to l-AP4. These pKa values of 5.56 and 6.88, respectively, were determined using 31P NMR chemical shift variations. The second distal negative charge of l-AP4/l-thioAP4 probably provides stronger binding to specific basic residues of the binding sites of group III mGluRs, which stabilizes the active conformation of the receptor

Activation of a Dimeric Metabotropic Glutamate Receptor by Inter-Subunit Rearrangement

International audienceAlthough many G protein-coupled receptors (GPCRs) can form dimers, a possible role of this phenomenon in their activation remains elusive. A recent and exciting proposal is that a dynamic inter-subunit interplay may contribute to GPCR activation. Here we examined this possibility using a dimeric metabotropic glutamate receptor (mGluR). We first developed a system to perfectly control their subunit composition, and show that mGluR dimers do not form larger oligomers. We then examined an mGluR dimer containing one subunit in which the extracellular agonist binding domain is uncoupled from the G protein-activating transmembrane domain (TMD). Despite this uncoupling in one protomer, agonist stimulation resulted in symmetric activation of either TMD in the dimer with the same efficiency. This, plus other data, can only be explained by an inter-subunit rearrangement as the activation mechanism. Although well established for other types of receptors such as tyrosine kinase or guanylate cyclase receptors, this is the first clear demonstration that such a mechanism may also apply to GPCRs

Fabrication and characterization of ZnO:Sb/n-ZnO homojunctions

International audienceAntimony-doped ZnO layers have been grown by metalorganic vapour-phase epitaxy on sapphire and ZnO substrates at high-temperature (950 °C) and low-pressure conditions (50 torr). Nitrous oxide and diethyl-zinc have been used as oxygen and zinc precursors, respectively. The incorporation of antimony has been obtained from the decomposition of triethylantimony doping molecules added in the gas phase. High Sb concentrations were measured from 1019 to 1021 at/cm−3 using secondary ion mass spectroscopy and depend on the nature and the orientation on the substrate. Low-temperature photoluminescence spectra of Sb-doped layers exhibit donor–acceptor pair transitions at 3.253 eV. Unlike Raman spectra of nitrogen-doped ZnO layers which show several local vibrational modes related to nitrogen incorporation, these modes were found to be absent in the antimony-doped ZnO layers. Transmission electron microscopy suggests that the incorporation of Sb is partly related to dislocations and other structural defects. All together, the characterizations suggest the formation of acceptor dopant–defect complexes, such as SbZn-2VZn. Finally, ZnO:Sb/n-ZnO homojunction diodes have been successfully elaborated on ZnO substrate. The current–voltage characteristics of the device exhibit a rectifying behaviour with a turn-on voltage of 3 V

Factors associated with knowledge level in adult type 1 diabetic patients

Background: The objective of the study is to determine the factors associated with the level of knowledge of Tunisian type 1 diabetic (T1D) patients in adulthood. Methods: This is a cross-sectional study including 93 T1D patients over 18 years old. The knowledge assessment was carried out by a questionnaire rated out of 20 points. The subjects with an „unsatisfactory” level of knowledge (score < 10/20) were compared with subjects whose level of knowledge was „satisfactory” according to their socio-demographic, clinical, and paraclinical characteristics. Results: The mean age of the patients was 37.2 ± 12.4 years. The level of knowledge was „unsatisfactory” in 21 patients (23%). After univariate analysis, an „unsatisfactory” level of knowledge was associated with a low level of education (p = 0.001), a poor socioeconomic level (p = 0.03), a poor glycemic control (p = 0.003) and the absence of self-monitoring (p = 0.002). After multivariate analysis, only a low level of education and a lack of practice of self-monitoring were associated with an „unsatisfactory” level of knowledge (respectively p = 0.03 and 0.03; adjusted OR [95% confidence interval] = 7.3 [1.2–43.5] and 13.7 [1.3–143.3]). Conclusions: The factors independently associated with the level of knowledge in adult T1D patients are the level of education and the practice of self-monitoring. This encourages better tailoring of educational messages to patients with low levels of education and suggests that a better level of knowledge ensures better self-management of diabetes. However, the relationship with the quality of glycemic control remains uncertain

CTAB turbidimetric method for assaying hyaluronic acid in complex environments and under cross-linked form

International audienc