Drosophila Melanogaster as a Model System for Studies of Islet Amyloid Polypeptide Aggregation

Background: Recent research supports that aggregation of islet amyloid polypeptide (IAPP) leads to cell death and this makes islet amyloid a plausible cause for the reduction of beta cell mass, demonstrated in patients with type 2 diabetes. IAPP is produced by the beta cells as a prohormone, and proIAPP is processed into IAPP by the prohormone convertases PC1/3 and PC2 in the secretory granules. Little is known about the pathogenesis for islet amyloid and which intracellular mechanisms are involved in amyloidogenesis and induction of cell death. Methodology/Principal Findings: We have established expression of human proIAPP (hproIAPP), human IAPP (hIAPP) and the non-amyloidogenic mouse IAPP (mIAPP) in Drosophila melanogaster, and compared survival of flies with the expression driven to different cell populations. Only flies expressing hproIAPP in neurons driven by the Gal4 driver elavC(155,Gal4) showed a reduction in lifespan whereas neither expression of hIAPP or mIAPP influenced survival. Both hIAPP and hproIAPP expression caused formation of aggregates in CNS and fat body region, and these aggregates were both stained by the dyes Congo red and pFTAA, both known to detect amyloid. Also, the morphology of the highly organized protein granules that developed in the fat body of the head in hIAPP and hproIAPP expressing flies was characterized, and determined to consist of 15.8 nm thick pentagonal rod-like structures. Conclusions/Significance: These findings point to a potential for Drosophila melanogaster to serve as a model system for studies of hproIAPP and hIAPP expression with subsequent aggregation and developed pathology.Original Publication: Sebastian Schultz, Peter Nilsson and Gunilla Torstensdotter Westermark, Drosophila Melanogaster as a Model System for Studies of Islet Amyloid Polypeptide Aggregation, 2011, PLoS ONE, (6), 6. http://dx.doi.org/10.1371/journal.pone.0020221 Copyright: Public Library of Science (PLoS) http://www.plos.org/</p

Lethality and Developmental Delay in Drosophila melanogaster Larvae after Ingestion of Selected Pseudomonas fluorescens Strains

The fruit fly, Drosophila melanogaster, is a well-established model organism for probing the molecular and cellular basis of physiological and immune system responses of adults or late stage larvae to bacterial challenge. However, very little is known about the consequences of bacterial infections that occur in earlier stages of development. We have infected mid-second instar larvae with strains of Pseudomonas fluorescens to determine how infection alters the ability of larvae to survive and complete development.We mimicked natural routes of infection using a non-invasive feeding procedure to study the toxicity of the three sequenced P. fluorescens strains (Pf0-1, SBW25, and Pf-5) to Drosophila melanogaster. Larvae fed with the three strains of P. fluorescens showed distinct differences in developmental trajectory and survival. Treatment with SBW25 caused a subset of insects to die concomitant with a systemic melanization reaction at larval, pupal or adult stages. Larvae fed with Pf-5 died in a dose-dependent manner with adult survivors showing eye and wing morphological defects. In addition, larvae in the Pf-5 treatment groups showed a dose-dependent delay in the onset of metamorphosis relative to control-, Pf0-1-, and SBW25-treated larvae. A functional gacA gene is required for the toxic properties of wild-type Pf-5 bacteria.These experiments are the first to demonstrate that ingestion of P. fluorescens bacteria by D. melanogaster larvae causes both lethal and non-lethal phenotypes, including delay in the onset of metamorphosis and morphological defects in surviving adult flies, which can be decoupled

Bacterial Communities of Diverse Drosophila Species: Ecological Context of a Host–Microbe Model System

Drosophila melanogaster is emerging as an important model of non-pathogenic host–microbe interactions. The genetic and experimental tractability of Drosophila has led to significant gains in our understanding of animal–microbial symbiosis. However, the full implications of these results cannot be appreciated without the knowledge of the microbial communities associated with natural Drosophila populations. In particular, it is not clear whether laboratory cultures can serve as an accurate model of host–microbe interactions that occur in the wild, or those that have occurred over evolutionary time. To fill this gap, we characterized natural bacterial communities associated with 14 species of Drosophila and related genera collected from distant geographic locations. To represent the ecological diversity of Drosophilids, examined species included fruit-, flower-, mushroom-, and cactus-feeders. In parallel, wild host populations were compared to laboratory strains, and controlled experiments were performed to assess the importance of host species and diet in shaping bacterial microbiome composition. We find that Drosophilid flies have taxonomically restricted bacterial communities, with 85% of the natural bacterial microbiome composed of only four bacterial families. The dominant bacterial taxa are widespread and found in many different host species despite the taxonomic, ecological, and geographic diversity of their hosts. Both natural surveys and laboratory experiments indicate that host diet plays a major role in shaping the Drosophila bacterial microbiome. Despite this, the internal bacterial microbiome represents only a highly reduced subset of the external bacterial communities, suggesting that the host exercises some level of control over the bacteria that inhabit its digestive tract. Finally, we show that laboratory strains provide only a limited model of natural host–microbe interactions. Bacterial taxa used in experimental studies are rare or absent in wild Drosophila populations, while the most abundant associates of natural Drosophila populations are rare in the lab

Étude de la conductivité de composites poly(oxyde d’éthylène)/polypyrrole

Des composites semi-conducteurs à base de poly(oxyde d'ethylène) (POE) et de polypyrrole (PPy) ont été préparés, ils présentent des conductivités de 10-5 à 10-3 S/cm pour des teneurs en PPy ne dépassant pas 20% en poids.Des phénomènes de percolation modifiant brutalement la conductivité ont été observés aussi bien en faisant varier le taux de PPy qu'en faisant varier la température pour une teneur correspondant au seuil de percolation à froid que nous avons déterminé

Tenue en température de polypyrroles « dopés » tosylate en présence ou non de chlorures

Nous avons étudié le vieillissement thermique de polypyrrole (PPy) synthétisé à l'aide de tosylate ou de chlorure ferrique. Le PPy synthétisé à l'aide du tosylate ferrique est plus conducteur que celui synthétisé à l'aide du chlorure ferrique. Les deux polymères ont un comportement identique pour des traitements à 120°C, 140°C et 180°C. La dégradation du polypyrrole suit, en atmosphère oxydante, une cinétique du premier ordre après une période de stabilisation régie par la diffusion de l'oxygène au sein du matériau

Super-condensateurs polypyrrole/polypyrrole

Dans le cadre d'un projet Brite-Euram (Proposition 3286-Contrat BREU 0048), des supercondensateurs ont été montés en utilisant des électrodes à base de polypyrrole (PPY). Le PPY avait été synthétisé chez SOLVAY, possédait une capacité électrochimique supérieure à 100 Ah.kg-1 et une conductivité dans le domaine 40-50 S.cm-1. Des éléments boutons 2425 ont été montés avec des performances reproductibles. Ces éléments ont été cyclés plusieurs milliers de fois entre -1,5 et 1,5 volt, avec une capacité nominale de 7 farads sous 1 mA

Synthèse et caractérisation de particules composites modèles : carbone-polyparaphénylène

Au cours de ce travail, nous avons élaboré des particules composites à base de carbone et de polyparaphénylène (PPP). L'étude de diffraction X, ainsi que les déterminations de la taille et du potentiel zêta des particules, nous ont permis de déduire que le matériau obtenu est constitué d'un coeur de carbone et d’une couronne de PPP (core-schell)