The Alestle - Vol. 67 No. 47 - 07/22/2015

Vol. 67 No. 4

An Extremal Problem for Characteristic Functions

Suppose E is a subset of the unit circle T and Hinfinity C Linfinity is the Hardy subalgebra. We examine the problem of finding the distance from the characteristic function of E to znHinfinity. This admits an alternate description as a dual extremal problem. Precise solutions are given in several important cases. The techniques used involve the theory of Toeplitz and Hankel operators as well as the construction of certain conformal mappings

Towards optimisation of surface enhanced photodynamic therapy of breast cancer cells using gold nanoparticle-photosensitiser conjugates

Gold nanoparticles (AuNPs; ca. 4 nm) were synthesised and functionalised with a mixed monolayer of polyethylene glycol (PEG) and one of two zinc phthalocyanines (ZnPcs), the difference between the two molecules was the length of the carbon chain that connects the Pc to the gold core. The chain was composed of either three (C3Pc) or eleven (C11Pc) carbon atoms. The C11Pc photosensitiser displayed higher fluorescence emission intensity than the C3Pc in solution. By contrast, the C3Pc photosensitiser exhibited higher fluorescence when bound to the surface of the AuNPs than the C11Pc, despite the shorter carbon chain which was expected to quench the fluorescence. In addition, the C3Pc nanoparticle conjugates exhibited an enhancement in the production of singlet oxygen (1O2). The metal-enhanced 1O2 production led to a remarkable photodynamic efficacy for the treatment of human breast cancer cells

L'environnement : une priorité pour l'agriculture : traiter et recycler les déchets

L'Institut de Recherche pour le Développement (IRD) a pour objectif la conduite de recherches avec des partenaires scientifiques des pays du Sud sur des thèmes importants pour le développement de ces pays. Depuis une quinzaine d'années, la dépollution et la valorisation des déchets agricoles et agro-industriels constituent l'un des trois principaux thèmes de recherche des microbiologistes regroupant leurs activités au sein d'un Programme de l'IRD intitulé "Utilisation de la biodiversité microbienne pour la valorisation des ressources tropicales". Ces recherches sont orientées d'une part vers les activités microbiennes anaérobies et la méthanisation, et d'autre part vers les processus microbiens dits de "fermentation en milieu solide" (FMS) impliquant principalement des champignons et des groupes bactériens tels que les bactéries lactiques. Ces deux orientations conditionnent le classement en trois grands groupes des résidus agricoles et agro-industriels pouvant constituer une source de pollution importante dans les pays du Sud et du Nord. Différents exemples de projets de recherche achevés ou en cours sont résumés en indiquant pour chacun d'eux (1) la nature du problème, (2) l'approche microbiologique du problème et (3) l'état de la valorisation pratique de ces résultats. Les recherches à l'IRD sur la méthanisation de sous-produits agricoles et agro-industriels tropicaux ont initialement été orientées vers la biodépollution. Les premiers travaux ont utilisé des consortiums microbiens non définis provenant de différents écosystèmes et adaptés aux produits à dépolluer. Ce n'est que récemment qu'un inoculum caractérisé a été utilisé avec succès. Ces travaux ont débouché soit sur la valorisation en milieu industriel, soit sur des essais en cours à l'échelle pilote... (D'après le résumé d'auteur

Fate predetermination of cardiac myocytes during zebrafish heart regeneration

Adult zebrafish have the remarkable ability to regenerate their heart upon injury, a process that involves limited dedifferentiation and proliferation of spared cardiomyocytes (CMs), and migration of their progeny. During regeneration, proliferating CMs are detected throughout the myocardium, including areas distant to the injury site, but whether all of them are able to contribute to the regenerated tissue remains unknown. Here, we developed a CM-specific, photoinducible genetic labelling system, and show that CMs labelled in embryonic hearts survive and contribute to all three (primordial, trabecular and cortical) layers of the adult zebrafish heart. Next, using this system to investigate the fate of CMs from different parts of the myocardium during regeneration, we show that only CMs immediately adjacent to the injury site contributed to the regenerated tissue. Finally, our results show an extensive predetermination of CM fate during adult heart regeneration, with cells from each myocardial layer giving rise to cells that retain their layer identity in the regenerated myocardium. Overall, our results indicate that adult heart regeneration in the zebrafish is a rather static process governed by short-range signals, in contrast to the highly dynamic plasticity of CM fates that takes place during embryonic heart regeneration

Chicory increases acetate turnover, but not propionate and butyrate peripheral turnovers in rats

Chicory roots are rich in inulin that is degraded into SCFA in the caecum and colon. Whole-body SCFA metabolism was investigated in rats during food deprivation and postprandial states. After 22h of food deprivation, sixteen rats received an IV injection of radioactive 14C-labelled SCFA. The volume of distribution and the fractional clearance rate of SCFA were 0·25-0·27 litres/kg and 5·4-5·9%/min, respectively. The half-life in the first extracellular rapidly decaying compartment was between 0·9 and 1·4min. After 22h of food deprivation, another seventeen rats received a primed continuous IV infusion of 13C-labelled SCFA for 2h. Isotope enrichment (13C) of SCFA was determined in peripheral arterial blood by MS. Peripheral acetate, propionate and butyrate turnover rates were 29, 4 and 0·3μmol/kg per min respectively. Following 4 weeks of treatment with chicory root or control diets, eighteen fed rats received a primed continuous IV infusion of 13C-labelled SCFA for 2h. Intestinal degradation of dietary chicory lowered caecal pH, enhanced caecal and colonic weights, caecal SCFA concentrations and breath H2.The diet with chicory supplementation enhanced peripheral acetate turnover by 25% (P=0·017) concomitant with an increase in plasma acetate concentration. There were no changes in propionate or butyrate turnovers. In conclusion, by setting up a multi-tracer approach to simultaneously assess the turnovers of acetate, propionate and butyrate it was demonstrated that a chronic chicory-rich diet significantly increases peripheral acetate turnover but not that of propionate or butyrate in rat

Dissecting T Cell Contraction In Vivo Using a Genetically Encoded Reporter of Apoptosis

SummaryContraction is a critical phase of immunity whereby the vast majority of effector T cells die by apoptosis, sparing a population of long-lived memory cells. Where, when, and why contraction occurs has been difficult to address directly due in large part to the rapid clearance of apoptotic T cells in vivo. To circumvent this issue, we introduced a genetically encoded reporter for caspase-3 activity into naive T cells to identify cells entering the contraction phase. Using two-photon imaging, we found that caspase-3 activity in T cells was maximal at the peak of the response and was associated with loss of motility followed minutes later by cell death. We demonstrated that contraction is a widespread process occurring uniformly in all organs tested and targeting phenotypically diverse T cells. Importantly, we identified a critical window of time during which antigen encounters act to antagonize T cell apoptosis, supporting a causal link between antigen clearance and T cell contraction. Our results offer insight into a poorly explored phase of immunity and provide a versatile methodology to study apoptosis during the development or function of a variety of immune cells in vivo