Dynamiques et ruptures dans l'histoire des basses terres mayas. Questions et méthodes à partir du programme " La Joyanca " (Nord-ouest du Petén, Guatemala).

Les résultats qui sont présentés ici sont issus d'un programme ayant un double objectif. D'une part, en relation étroite avec les recherches archéologiques, il s'agissait de préciser la chronologie de l'occupation du site sur la longue durée et de reconstituer l'organisation locale de l'espace à l'époque maya. D'autre part, il a été pris pour hypothèse que l'analyse des formes contemporaines de colonisation pouvait aider, sur la base de la méthode régressive, à reconstituer les logiques agraires passées. Les premières recherches menées dans le nord-ouest du Petén livrent des résultats inattendus et relativement contradictoires. D'un côté, la corrélation entre les études sur les dynamiques contemporaines et les études géo-archéologiques tend à démontrer une relative stabilité à travers les siècles des potentialités et des processus agraires, en fonction des contraintes géomorphologiques, biogéographiques et pédologiques. D'un autre côté, les premières données paléoenvironnementales laissent entrevoir une occupation très ancienne, ce qui commence à être vérifié par les fouilles archéologiques

Historia del medio ambiente en la larga duracion y ocupacion del espacio en la region de la Joyanca, noroeste de Petén, Guatemala : primeros resultados

International audienceLas investigaciones arqueologicas desarrolladas entre 1999 y 2002 en el sitio arqueologico de la Joyanca han permitido el estudio de una ciudad de tamano medio. En el marco de este programa fueron desarrolladas investigaciones paleo-ambientales para intentar reconstituir las diferentes etapas de la ocupacion del sitio, al nivel de la pequena region y sus impactos sobre la organizacion del espacio de la ciudad. Este estudio fue dirigido en tres direcciones : estudio geomorfologico y fito-ecologico ; realizacion de sondeos ; estudio geomorfologico y pedologico

Lifestyle Modification Strategies to Counteract the World Epidemic Growth of Obesity and Diabetes

[no abstract available

Experimental demonstration of spectrally broadband Huygens sources using low-index spheres

Manipulating the excitation of resonant electric and magnetic multipole moments in structured dielectric media has unlocked many sophisticated electromagnetic functionalities. This invited article demonstrates the experimental realization of a broadband Huygens’ source. This Huygens’ source consists of a spherical particle that exhibits a well-defined forward-scattering pattern across more than an octave-spanning spectral band at GHz frequencies, where the scattering in the entire backward hemisphere is suppressed. Two different low-index nonmagnetic spheres are studied that differ in their permittivity. This causes them to offer a different shape for the forward-scattering pattern. The theoretical understanding of this broadband feature is based on the approximate equality of the resonant electric and magnetic multipole moments in both amplitude and phase in low permittivity spheres. This is a key condition to approximate the electromagnetic duality symmetry which, together with the spherical symmetry, suppresses the backscattering. With such a configuration, broadband Huygens’ sources can be designed even if magnetic materials are unavailable. This article provides guidelines for designing broadband Huygens’ sources using low-index spheres that could be valuable to a plethora of applications

Age-related Changes in Auditory Cortex Without Detectable Peripheral Alterations: A Multi-level Study in Sprague–Dawley Rats

International audienceAging is often considered to affect both the peripheral (i.e. the cochlea) and central (brainstem and thalamus-cortex) auditory systems. We investigated the effects of aging on the cochlea, brainstem and cortex of female Sprague-Dawley rats. The auditory nerve threshold remained stable between the ages of nine and 21 months, as did distortion product otoa-coustic emissions and the number of ribbon synapses between inner hair cells and nerve fibers. The first clear signs of aging appeared in the brainstem, in which response amplitude decreased, with thresholds remaining stable until the age of 15 months, and increasing slightly thereafter. The responses of primary auditory cortex neurons revealed specific effects of aging: at 21 months, receptive fields were spectrally narrower and the temporal reliability of responses to communication sounds was lower. However, aging had a null or even positive effect on neuronal responses in the presence of background noise, responses to amplitude-modulated sounds, and responses in gap-detection protocols. Overall, inter-animal variability remained high relative to the variability across groups of different ages, for all parameters tested. Beha-vioral performance for the modulation depth of amplitude modulation noise was worse in 21-month old animals than in other animals. Age-related alterations of cortical and behavioral responses were thus observed in animals displaying no signs of aging at the peripheral level. These results suggest that intrinsic, central aging effects can affect the perception of acoustic stimuli independently of the effects of aging on peripheral receptors

Macrophage metalloelastase (MMP-12) deficiency does not alter bleomycin-induced pulmonary fibrosis in mice

BACKGROUND: Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix in the interstitium resulting in respiratory failure. The role of remodeling mediators such as metalloproteinases (MMPs) and their inhibitors (TIMPs) in the fibrogenic process remains misunderstood. In particular, macrophage metalloelastase, also identified as MMP-12, is known to be involved in remodeling processes under pathological conditions. However, MMP-12 involvement in pulmonary fibrosis is unknown. Here we investigated fibrotic response to bleomycin in MMP-12 deficient mice. MATERIALS AND METHODS: C57BL/6 mice, Balb/c mice and MMP-12 -/- mice with a C57BL/6 background received 0.3 mg bleomycin by intranasal administration. 14 days after, mice were anesthetized and underwent either bronchoalveolear lavage (BAL) or lung removal. Collagen deposition in lung tissue was determined by Sircol™ collagen assay, MMP activity in BAL fluid was analyzed by zymography, and other mediators were quantified in BAL fluid by ELISA. Real time PCR was performed to assess gene expression in lung removed one or 14 days after bleomycin administration. Student t test or Mann & Whitney tests were used when appropriate for statistical analysis. RESULTS: The development of pulmonary fibrosis in "fibrosis prone" (C57BL/6) mice was associated with prominent MMP-12 expression in lung, whereas MMP-12 expression was weak in lung tissue of "fibrosis resistant" (Balb/c) mice. MMP-12 mRNA was not detected in MMP-12 -/- mice, in conformity with their genotype. Bleomycin elicited macrophage accumulation in BAL of MMP-12 -/- and wild type (WT) mice, and MMP-12 deficiency had no significant effect on BAL cells composition. Collagen content of lung was increased similarly in MMP-12 -/- and WT mice 14 days after bleomycin administration. Bleomycin elicit a raise of TGF-β protein, MMP-2 and TIMP-1 protein and mRNA in BAL fluids and lung respectively, and no significant difference was observed between MMP-12 -/- and WT mice considering those parameters. CONCLUSION: The present study shows that MMP-12 deficiency has no significant effect on bleomycin-induced fibrosis

Pressure support ventilation attenuates ventilator-induced protein modifications in the diaphragm

OnLine Journal Article Number : R116 The electronic version of this article is the complete one and can be found online at: http://ccforum.com/content/12/5/R116International audienceINTRODUCTION: Controlled mechanical ventilation (CMV) induces profound modifications of diaphragm protein metabolism, including muscle atrophy and severe ventilator-induced diaphragmatic dysfunction. Diaphragmatic modifications could be decreased by spontaneous breathing. We hypothesized that mechanical ventilation in pressure support ventilation (PSV), which preserves diaphragm muscle activity, would limit diaphragmatic protein catabolism. METHODS: Forty-two adult Sprague-Dawley rats were included in this prospective randomized animal study. After intraperitoneal anesthesia, animals were randomly assigned to the control group or to receive 6 or 18 hours of CMV or PSV. After sacrifice and incubation with 14C-phenylalanine, in vitro proteolysis and protein synthesis were measured on the costal region of the diaphragm. We also measured myofibrillar protein carbonyl levels and the activity of 20S proteasome and tripeptidylpeptidase II. RESULTS: Compared with control animals, diaphragmatic protein catabolism was significantly increased after 18 hours of CMV (33%, P = 0.0001) but not after 6 hours. CMV also decreased protein synthesis by 50% (P = 0.0012) after 6 hours and by 65% (P < 0.0001) after 18 hours of mechanical ventilation. Both 20S proteasome activity levels were increased by CMV. Compared with CMV, 6 and 18 hours of PSV showed no significant increase in proteolysis. PSV did not significantly increase protein synthesis versus controls. Both CMV and PSV increased protein carbonyl levels after 18 hours of mechanical ventilation from +63% (P < 0.001) and +82% (P < 0.0005), respectively. CONCLUSIONS: PSV is efficient at reducing mechanical ventilation-induced proteolysis and inhibition of protein synthesis without modifications in the level of oxidative injury compared with continuous mechanical ventilation. PSV could be an interesting alternative to limit ventilator-induced diaphragmatic dysfunction