Geometry of Valley Growth

Although amphitheater-shaped valley heads can be cut by groundwater flows emerging from springs, recent geological evidence suggests that other processes may also produce similar features, thus confounding the interpretations of such valley heads on Earth and Mars. To better understand the origin of this topographic form we combine field observations, laboratory experiments, analysis of a high-resolution topographic map, and mathematical theory to quantitatively characterize a class of physical phenomena that produce amphitheater-shaped heads. The resulting geometric growth equation accurately predicts the shape of decimeter-wide channels in laboratory experiments, 100-meter wide valleys in Florida and Idaho, and kilometer wide valleys on Mars. We find that whenever the processes shaping a landscape favor the growth of sharply protruding features, channels develop amphitheater-shaped heads with an aspect ratio of pi

Related RNAs in lepidopteran cells after in vitro infection with Hyposoter didymator virus define a new polydnavirus gene family

In the present study, we describe the isolation and the characterization of three different Hyposoter didymator virus (HdV) lepidopteran host-expressed genes, the products of which might interfere with the host physiology during parasitism. In this report, we study the expression of HdV genes in Sf9 cells infected with HdV since results indicate that the Sf9 model mimics to some extent the in vivo model and may be utilized to study expression of HdV genes in lepidopteran host cells. This system allowed us to isolate three HdV-specific cDNAs, termed M24, M27, and M40. cDNA nucleotide sequence analysis demonstrated significant regions of homology. The three cDNAs displayed repeated sequences arranged in tandem array that might have evolved through domain duplication. Similar to other previously described polydnavirus host-expressed genes, two intron positions have been found in the M24 leader region. The cDNAs corresponded to RNAs of 1.6, 1.6, and 2.3 kb that are also detected in parasitized Spodoptera littoralis larvae. They are encoded by different genes likely located on different HdV DNA molecules. Corresponding RNAs are detected early postinfection and remain detectable for at least 10 days postinfection. They encode secreted glycine- and proline-rich proteins. An antiserum raised against a baculovirus recombinant M24-encoded protein detected similar proteins in the culture medium of infected lepidopteran cells and in parasitized host hemolymph. We propose that the three cloned genes belong to an HdV gene family specifically expressed in parasitized lepidopteran hosts, (C) 1999 Academic Press

Members of the Hyposoter didymator Ichnovirus repeat element gene family are differentially expressed in Spodoptera frugiperda

BACKGROUND: The abundance and the conservation of the repeated element (rep) genes in Ichnoviruses genomes suggest that this gene family plays an important role in viral cycles. In the Ichnovirus associated with the wasp Hyposoter didymator, named HdIV, 10 rep genes were identified to date. In this work, we report a relative quantitative transcription study of these HdIV rep genes in several tissues of the lepidopteran host Spodoptera frugiperda as well as in the H. didymator wasps. RESULTS: The data obtained in this work indicate that, in the early phases of infection (24 hours), HdIV rep genes each display different levels of transcripts in parasitized 2(nd )instar or HdIV-injected last instar S. frugiperda larvae. Only one, rep1, is significantly transcribed in female wasps. Transcript levels of the HdIV rep genes were found as not correlated to their copy number in HdIV genome. Our results also show that HdIV rep genes display different tissue specificity, and that they are primarily transcribed in S. frugiperda fat body and cuticular epithelium. CONCLUSION: This work is the first quantitative analysis of transcription of the ichnovirus rep gene family, and the first investigation on a correlation between transcript levels and gene copy numbers in Ichnoviruses. Our data indicate that, despite similar gene copy numbers, not all the members of this gene family are significantly transcribed 24 hours after infection in lepidopteran larvae. Additionally, our data show that, as opposed to other described HdIV genes, rep genes are little transcribed in hemocytes, thus suggesting that they are not directly associated with the disruption of the immune response but rather involved in other physiological alterations of the infected lepidopteran larva

Is the blood B-cell subset profile diagnostic for Sjögren syndrome?

International audienc

Stability of bedforms in laminar flows with free surface: from bars to ripples

International audienceThe present paper is devoted to the formation of sand patterns by laminar flows. It focuses on the rhomboid beach pattern, formed during the backswash. A recent bedload transport model, based on a moving-grains balance, is generalized in three dimensions for viscous flows. The water flow is modelled by the full incompressible Navier–Stokes equations with a free surface. A linear stability analysis then shows the simultaneous existence of two distinct instabilities, namely ripples and bars. The comparison of the bar instability characteristics with laboratory rhomboid patterns indicates that the latter could result from the nonlinear evolution of unstable bars. This result, together with the sensibility of the stability analysis with respect to the parameters of the transport law, suggests that the rhomboid pattern could help improving sediment transport models, so critical to geomorphologists

Différences de connectivité effective entre des enfants dyslexiques et des enfants lecteurs normaux pendant une tâche de lecture de pseudomots : une étude par IRMf

International audiencePurpose.—This fMRI study investigated phonological and lexicosemantic processing in dyslexic and in chronological age- and reading level-matched children in a pseudoword reading task.Materials and methods.—The effective connectivity network was compared between the three groups using a structural model including the supramarginal cortex (BA 40; BA: Brodmann area), fusiform cortex (BA 37) and inferior frontal cortex (BA 44/45) areas of the left hemisphere.Results.—The results revealed differences in connectivity patterns. In dyslexic patients, in contrast with chronological age- and reading level-matched groups, no causal relationship was demonstrated between BA 40 and BA 44/45. However, a significant causal relationship was demonstrated between BA 37 and BA 44/45 both in dyslexic children and in the reading levelmatchedgroup.Conclusions.—These findings were interpreted as evidence for a phonological deficit in developmental dyslexiaBut.—Explorer par imagerie fonctionnelle d’activation cérébrale chez l’enfant les aires corticales et les circuits cérébraux impliqués dans le traitement phonologique et lexico sémantique d’une tâche de lecture.Matériel et methods.—Un réseau d’aires cérébrales interconnectées est examiné sur la base d’un modèle structural incluant les cortex supramarginal (aire 40 de Brodmann), fusiforme (aire 37de Brodmann) et frontal inférieur (aires 44/45 de Brodmann) de l’hémisphère gauche. La méthode de modélisation proposée permet d’évaluer une différence de connectivité effective des circuits engagés au cours d’une tâche de lecture de pseudomots entre des enfants dyslexiques et des enfants normaux lecteurs appariés en âge chronologique et lexical.Résultats.—Chez les patients dyslexiques, contrairement aux groupes témoins appariés par l’âge ou le niveau de lecture, aucune interaction causale n’a été démontrée entre les aires 40 et 44/45 de Brodmann qui constituent les noeuds du circuit d’assemblage phonologique. En revanche, une interaction significative a été retrouvée au niveau du circuit d’adressage lexico sémantique, entre les aires 37 et 44/45 de Brodmann, chez les enfants dyslexiques et les enfants appariés par le niveau de lecture.Conclusions.—Ces résultats confirment l’existence d’un déficit des processus phonologiques dans la dyslexie développementale

TOLL-LIKE RECEPTOR 9 DRIVES THE MATURATION OF B LYMPHOCYTES IN THE SALIVARY GLANDS OF PATIENTS WITH SJÖGREN’S SYNDROME

Oral Communication presented at the ";Forum des Jeunes Chercheurs";, Brest (France) 2011

In vivo stem cell tracking using scintigraphy in a canine model of DMD

One of the main challenges in cell therapy for muscle diseases is to efficiently target the muscle. To address this issue and achieve better understanding of in vivo cell fate, we evaluated the relevance of a non-invasive cell tracking method in the Golden Retriever Muscular Dystrophy (GRMD) model, a well-recognised model of Duchenne Muscular Dystrophy (DMD). Mesoangioblasts were directly labelled with 111In-oxine, and injected through one of the femoral arteries. The scintigraphy images obtained provided the first quantitative mapping of the immediate biodistribution of mesoangioblasts in a large animal model of DMD. The results revealed that cells were trapped by the first capillary filters: the injected limb and the lung. During the days following injection, radioactivity was redistributed to the liver. In vitro studies, performed with the same cells prepared for injecting the animal, revealed prominent cell death and 111In release. In vivo, cell death resulted in 111In release into the vasculature that was taken up by the liver, resulting in a non-specific and non-cell-bound radioactive signal. Indirect labelling methods would be an attractive alternative to track cells on the mid- and long-term

The ability of synovitis to predict structural damage in rheumatoid arthritis: A comparative study between clinical examination and ultrasound

Objectives: To evaluate synovitis (clinical vs ultrasound (US)) to predict structural progression in rheumatoid arthritis (RA). Methods: Patients with RA. Study design: Prospective, 2-year follow-up. Data collected: Synovitis (32 joints (2 wrists, 10 metacarpophalangeal, 10 proximal interphalangeal, 10 metatarsophalangeal)) at baseline and after 4 months of therapy by clinical, US grey scale (GS-US) and power doppler (PD-US); x-rays at baseline and at year 2. Analysis: Measures of association (OR) were tested between structural deterioration and the presence of baseline synovitis, or its persistence, after 4 months of therapy using generalised estimating equation analysis. Results: Structural deterioration was observed in 9% of the 1888 evaluated joints in 59 patients. Baseline synovitis increased the risk of structural progression: OR=2.01 (1.36-2.98) p<0.001 versus 1.61 (1.06-2.45) p=0.026 versus 1.75 (1.18-2.58) p=0.005 for the clinical versus US-GS versus US-PD evaluation, respectively. In the joints with normal baseline examination (clinical or US), an increased probability for structural progression in the presence of synovitis for the other modality was also observed (OR=2.16 (1.16-4.02) p=0.015 and 3.50 (1.77-6.95) p<0.001 for US-GS and US-PD and 2.79 (1.35-5.76) p=0.002) for clinical examination. Persistent (vs disappearance) synovitis after 4 months of therapy was also predictive of subsequent structural progression. Conclusions: This study confi rms the validity of synovitis for predicting subsequent structural deterioration irrespective of the modality of examination of joints, but also suggests that both clinical and ultrasonographic examinations may be relevant to optimally evaluate the risk of subsequent structural deterioration