Taille de la population d’Avahi laniger dans la réserve d’Ambodiriana-Manompana, Nord-est de Madagascar

Avahi laniger est le seul lémurien nocturne appartenant à la famille des Indriidae qui habite les forêts humides de l’est de Madagascar (Mittermeier et. al., 2010) dont une partie disparaît chaque année (exploitation du bois, pratique du «tavy» ou culture sur brûlis) (Beaucent and Fayolle, 2011; Lehman and Wright, 2000). La fragmentation et la destruction de leur habitat ainsi que la chasse menacent la survie de nombreuses espèces de lémuriens incluant celle de A. laniger (Jenkins et. al., 2011; Rakotondravony and Rabenandrasana, 2011; Anderson, Rowcliffe and Cowlishaw, 2007). Nous avons réalisé, entre fin Avril et Mai 2012, une étude de densité de la population de A. laniger au sein de l’aire protégée de Manompana-Ambodiriana afin d’estimer la taille de la population totale et de déterminer l’impact du projet de conservation menée par l’Association de Défense de la Forêt d’Ambodiriana (ADEFA) qui recherche l’évolution démographique à moyen terme de cette espèce."LABEX" TULIP: (ANR-10-LABX-41), fct fellowship: (SFRH/BD/64875/2009)

c-Jun N-terminal kinase has a key role in Alzheimer disease synaptic dysfunction in vivo.

Altered synaptic function is considered one of the first features of Alzheimer disease (AD). Currently, no treatment is available to prevent the dysfunction of excitatory synapses in AD. Identification of the key modulators of synaptopathy is of particular significance in the treatment of AD. We here characterized the pathways leading to synaptopathy in TgCRND8 mice and showed that c-Jun N-terminal kinase (JNK) is activated at the spine prior to the onset of cognitive impairment. The specific inhibition of JNK, with its specific inhibiting peptide D-JNKI1, prevented synaptic dysfunction in TgCRND8 mice. D-JNKI1 avoided both the loss of postsynaptic proteins and glutamate receptors from the postsynaptic density and the reduction in size of excitatory synapses, reverting their dysfunction. This set of data reveals that JNK is a key signaling pathway in AD synaptic injury and that its specific inhibition offers an innovative therapeutic strategy to prevent spine degeneration in AD

Carrageenan-induced acute inflammation in the mouse air pouch synovial model. Role of tumour necrosis factor

We used the mouse air pouch model of inflammation to study the interaction between cytokines, prostaglandin E2 (PGE2) and cell migration during the various phases of acute local inflammation induced by carrageenan. In serum, the levels of interleukin 1 (IL-1), interleukin 6 (IL-6), tumour necrosis factor (TNF), serum amiloid-A (SAA) and Fe++ were never different from controls, indicating that no systemic inflammatory changes were induced. Locally the exudate volume and the number of leukocytes recruited into the pouch increased progressively until 7 days after carrageenan. The same was true for PGE2 production. We could not measure IL-1 but the production of IL-6 and TNF reached a maximum after 5-24 h then quickly decreased. Anti-TNF antibodies inhibited cell migration by 50% 24 h after treatment. Pretreatment with interleukin 10 (IL-10) inhibited TNF production almost completely and cell migration by 60%. Carrageenan-induced inflammation was modulated by anti-inflammatory drugs. Pretreatment with dexamethasone (DEX) or indomethacin (INDO) inhibited cell migration and reduced the concentration of TNF in the exudate. Production of PGE2 or vascular permeability did not correlate with the number of cells in the pouch. Local TNF seems to play an important role in this model, particularly for leukocyte migration in the first phase of the inflammatory process. In conclusion, the air pouch seems to be a good model for studying the regulation of the early events of local inflammation, particularly the role of cytokines and cell migration

Pathogenic Aβ A2V versus protective Aβ A2T mutation : early stage aggregation and membrane interaction

We investigated the effects of punctual A-to-V and A-to-T mutations in the amyloid precursor protein APP, corresponding to position 2 of A\u3b21\u201342. Those mutations had opposite effects on the onset and progression of Alzheimer disease, the former inducing early AD pathology and the latter protecting against the onset of the disease. We applied Static and Dynamic Light Scattering and Circular Dichroism, to study the different mutants in the early stages of the aggregation process, essential for the disease. Comparative results showed that the aggregation pathways differ in the kinetics and extent of the process, in the size of the aggregates and in the evolution of the secondary structure, resulting in fibrils of different morphology, as seen by AFM. Mutated peptides had comparable toxic effects on N2a cells. Moreover, as assessed by X-ray scattering, all of them displayed disordering effects on the internal structure of mixed phospholipids-gangliosides model membranes

Neutron Stars in a Varying Speed of Light Theory

We study neutron stars in a varying speed of light (VSL) theory of gravity in which the local speed of light depends upon the value of a scalar field $\phi$. We find that the masses and radii of the stars are strongly dependent on the strength of the coupling between $\phi$ and the matter field and that for certain choices of coupling parameters, the maximum neutron star mass can be arbitrarily small. We also discuss the phenomenon of cosmological evolution of VSL stars (analogous to the gravitational evolution in scalar-tensor theories) and we derive a relation showing how the fractional change in the energy of a star is related to the change in the cosmological value of the scalar field.Comment: 15 pages, 2 figures. Added solutions with a more realistic equation of state. To be published in PR

The Molecular Assembly of Amyloid A beta Controls Its Neurotoxicity and Binding to Cellular Proteins

Accumulation of beta-sheet-rich peptide (A beta) is strongly associated with Alzheimer's disease, characterized by reduction in synapse density, structural alterations of dendritic spines, modification of synaptic protein expression, loss of long-term potentiation and neuronal cell death. A beta species are potent neurotoxins, however the molecular mechanism responsible for A beta toxicity is still unknown. Numerous mechanisms of toxicity were proposed, although there is no agreement about their relative importance in disease pathogenesis. Here, the toxicity of A beta 1-40 and A beta 1-42 monomers, oligomers or fibrils, was evaluated using the N2a cell line. A structure-function relationship between peptide aggregation state and toxic properties was established. Moreover, we demonstrated that A beta toxic species cross the plasma membrane, accumulate in cells and bind to a variety of internal proteins, especially on the cytoskeleton and in the endoplasmatic reticulum (ER). Based on these data we suggest that numerous proteins act as A beta receptors in N2a cells, triggering a multi factorial toxicity

Estimation des densités et tailles de population du Microcèbe Roux du Nord de (Microcebus tavaratra) dans la région Loky-Manambato (Daraina)

La région Loky-Manambato dans le Nord de Madagascar, est connue pour abriter le propithèque à couronne dorée (Propithecus tattersalli), un lémurien emblématique et endémique de la région. Néanmoins cette région composée d’une dizaine de fragments forestiers de taille moyenne et encore relativement peu étudiés, abrite aussi le microcèbe roux du nord (Microcebus tavaratra). Malgré la gestion des forêts de cette région par l’ONG Fanamby depuis 2005, aucune étude n’avait encore été menée dans chacun des fragments forestiers de la région pour déterminer la présence et quantifier la taille des populations de microcèbes de chacun d’entre eux. Lors de notre étude nous avons tenté d’estimer les densités et les tailles des populations de M. tavaratra dans neuf des dix principaux fragments forestiers de la région. Dans ce but nous avons utilisé la méthode de «line transect distance-sampling». Nos résultats montrent que les densités de microcèbes sont relativement élevées, et varient de 28 à 325 ind/km² entre fragments forestiers de la région. Desétudes plus approfondies des données collectées seront nécessaires pour déterminer les variables environnementales responsables des différences de densité observées.FCT grant: (SFRH/BD/64875/2009); l’Institut Français de la Biodiversité, GDRI Madagascar, “Laboratoire d’Excellence” (LABEX) TULIP: (ANR -10-LABX-41)

Daraina sportive lemur (Lepilemur milanoii) density and population size estimates in most of its distribution range: the Loky-Manambato region.

The population of the Daraina sportive lemur (Lepilemur milanoii) is believed to be mostly confined to the Loky-Manambato region (Louis et al., 2006). Very little is known about L. milanoii and it is classified as “Data Deficient” by the IUCN (IUCN, 2013; Schwitzer et al., 2013). Despite the management of the area by the NGO Fanamby since 2005, no study had been conducted to determine the presence and the abundance of L. milanoii in the main forest fragments of the region. During the 2011 dry season we surveyed the ten main forest fragments of the Loky-Manambato region and estimated L. milanoii densities and population sizes using line transect distance sampling (Buckland, 2001) and the DISTANCE software (Thomas et al., 2010). The results suggest that sportive lemur densities are reasonably high in the region, but with important discrepancies between forest fragments, with densities ranging from 49.8 ind./km² in Antsaharaingy to 590.5 ind./km² in Ampondrabe. For the region Loky-Manambato we were able to estimate a population size of 52,000 individuals. This is the first estimate for the total population size and we argue that similar studies should be repeated to monitor environmental changes and anthropogenic pressures (hunting, deforestation, mining, etc.).FCT grant: (SFRH/BD/64875/2009); the Groupement de Recherche International (GDRI); "Laboratoire d’Excellence" (LABEX) entitled TULIP : (ANR-10-LABX-41); Rufford Small Grant Foundation grant: (10941-1)

On spontaneous scalarization

We study in the physical frame the phenomenon of spontaneous scalarization that occurs in scalar-tensor theories of gravity for compact objects. We discuss the fact that the phenomenon occurs exactly in the regime where the Newtonian analysis indicates it should not. Finally we discuss the way the phenomenon depends on the equation of state used to describe the nuclear matter.Comment: 41 pages, RevTex, 10 ps figures, submitted to Phys. Rev.

Survey of the critically endangered Perrier’s sifaka (Propithecus Perrieri) across most if its distribution range.

Propithecus perrieri (Perrier’s sifaka) is one of the most endangered lemur species due to its small and fragmented distribution range. Despite a Critically Endangered (CR) conservation and flagship species status, there are still many uncertainties regarding its actual distribution and its presence in some forests of its putative distribution range. We report the results of diurnal and nocturnal surveys carried out in 2012 across most forest fragments of its putative distribution range, namely the Ankarana National Park, the Analamerana Special Reserve and Andrafiamena-Andava-koera Protected Area. During our surveys the species was only observed in Andrafiamena and Analamerana protected areas.FCT fellowship: (SFRH/BD/64875/2009), Institut Français de la Biodiversité, the GDRI Madagascar, the “Laboratoire d'Excellence” (LABEX) entitled TULIP (ANR-10-LABX-41), Instituto Gulbenkian de Ciência, “Optimus Alive!” Biodiversity grant, The Rufford Small Grant for Nature Conservation: (ref. 10941-1), Département de Biologie Animale et Ecologie (D.B.A.E.), Faculté des Sciences, University of Mahajanga, the University of Antsiranana, and the Fanamby NGO (in particular S. Rajaobelina), Madagascar National Park, Analamerana Special Reserve, Ankarana National Park