Recherche et caractérisation de sols résistants aux Pythium spp. en Amazonie brésilienne

Aux environs de la ville de Manaus (Amazonie brésilienne), les sols sont localisés dans deux écosystèmes: ‘terra firme’ recouverte de foret vierge ou cultivée et ‘varzea’, zones submergées chaque année et cultivées. 160 échantillons de sol ont été prélevés dans ccs deux zones, puis analysés afin de déterminer leur capacité de fonte des semis, causée par les Pythium spp.; 76 de ces sols semblaient non infestés, ou ne l'étaient que faiblement. Afin de déterminer leur réceptivité vis‐à‐vis des Pythium spp., les 76 sols ont été inoculés avec 10% d'un sol infesté naturellement, et la capacité d'infection a étéévaluée aprés des incubations de 4, 8, 12 et 16 semaines par tests biologiques sur jeunes plants de concombre. L'aptitude à supprimer les Pythium spp. n'est apparue que dans les écosystèmes ‘terra firme'et non dans les ‘varzeas’ submergés. La fréquence des sols pouvant supprimer la maladie semblait décroitre en fonction de la mise en culture: 82% dans les sols de foret vierge; 67% dans les sols de pépinières forestiéres; 53% dans les forets gérées; 31% dans les sols forestiers mis en culture avec des cultures variées; 7% dans les sols forestiers mis en culture et portant des cultures maraichères. On a constaté trois types d'aptitude à supprimer les Pythium spp. aprés inoculation des sols: (1) résistance apparaissant rapidement et se maintenant à un niveau élevé et constant (jusqu'à 16 semaines); (2) résistance initiate élevée, mais non durable; (3) résistance initialement faible, mais croissante avec le temps. Une partie de cette dynamique semble etre sous controle microbien. Le développement agricole autour de Manaus ainsi que les systèmes de culture intensifs peuvent rapidement modifier les écosystèmes microbiens des sols et nuire à leur capacité naturelle à supprimer les Pythium spp. Copyright © 1987, Wiley Blackwell. All rights reserve

Surveying activated sludge changes during acclimation with artificial wastewater

Many processes in the chemical and pharmaceutical industries generate wastewater containing organic toxic compounds and other kinds of xenobiotics. Usually, biological treatments are used to degrade a great quantity of these substances. However, most of the time, the microorganisms are not adapted and the treatment can be blocked. Therefore, the first step to make a continuous reactor operative is the acclimation, i.e., the adaptation of the microorganisms to a specific substrate. During this particular step of the process there is a selection and a multiplication of specialized microorganisms and physiological transformations can occur in their metabolic system. Furthermore, combining image processing techniques have already been successfully used to elucidate the activated sludge morphological changes for both aggregated and filamentous bacteria contents, during such processes. The experimental set-up is composed of an aerated reactor and a clarifier. The sludge is recycled from the clarifier by a peristaltic pump. The complete mixing inside the reactor is guaranteed by the diffusion of air from its bottom. The reactor was inoculated with biomass collected from a wastewater treatment plant and fed with an artificial wastewater based on meat extract. During acclimation, chemical parameters were measured in the influent, reactor and effluent, in order to verify the stability of the process. To complete the evaluation of the process, microscopy acquisition and image processing and analysis techniques were performed for aggregates and filamentous bacteria characterization for bright field, Gram and poly-β-hydroxybutyrate (PHB) staining images. The information extracted from those images allowed for aggregates and filamentous bacteria contents inspection, identification of PHB storing microorganisms and, gram-positive and gram-negative filamentous bacteria recognition. Figure 1 presents activated sludge samples at the beginning and at the end of the acclimation phase. It was found in this study that biomass changes during the acclimation phase could be effectively monitored, combining image analysis information and chemical parameters

Multiple shells driven by disk winds: ALMA observations in the HH 30 outflow

We present archive Atacama Large Millimeter/Submillimeter Array (ALMA) Band 6 observations of the $^{13}$CO (J=2-1) and $^{12}$CO (J=2-1) molecular line emission of the protostellar system associated with HH 30. The $^{13}$CO molecular line shows the accretion disk while the molecular outflow is traced by the emission of the $^{12}$CO molecular line. We estimated a dynamical mass for the central object of $0.45\pm0.14$ M$_\odot$, and a mass for the molecular outflow of $1.83\pm0.19\times10^{-4}$ M$_\odot$. The molecular outflow presents an internal cavity as well as multiple outflowing shell structures. We distinguish three different shells with constant expansion ($\sim4-6$ km s$^{-1}$) and possible rotation signatures ($\leq0.5$ km s$^{-1}$). We find that the shells can be explained by magnetocentrifugal disk winds with launching radii $R_\mathrm{launch}\lesssim4$ au and a small magnetic lever arm $\lambda\sim1.6-1.9$. The multiple shell structure may be the result of episodic ejections of the material from the accretion disk associated with three different epochs with dynamical ages of $497\pm15$ yr, $310\pm9$ yr, and $262\pm11$ yr for the first, second, and third shells, respectively. The outermost shell was ejected $187\pm17$ yr before the medium shell, while the medium shell was launched $48\pm14$ yr before the innermost shell. Our estimations of the linear and angular momentum rates of the outflow as well as the accretion luminosity are consistent with the expected values if the outflow of HH 30 is produced by a wide-angle disk wind

Hall Effect of Spin Waves in Frustrated Magnets

We examine a possible spin Hall effect for localized spin systems with no charge degrees of freedom. In this scenario, a longitudinal magnetic field gradient induces a transverse spin current carried by spin wave excitations with an anomalous velocity which is associated with the Berry curvature raised by spin chirality, in analogy with anomalous Hall effects in itinerant electron systems. Our argument is based on a semiclassical equations of motion applicable to general spin systems. Also, a microscopic model of frustrated magnets which exhibits the anamalous spin Hall effect is presented.Comment: 5 pages, title and presentation style are changed, accepted for publication in Phys. Rev. Let

Inactivation of aPKCλ Reveals a Context Dependent Allocation of Cell Lineages in Preimplantation Mouse Embryos

BACKGROUND:During mammalian preimplantation development, lineage divergence seems to be controlled by the interplay between asymmetric cell division (once cells are polarized) and positional information. In the mouse embryo, two distinct cell populations are first observed at the 16-cell stage and can be distinguished by both their position (outside or inside) and their phenotype (polarized or non-polarized). Many efforts have been made during the last decade to characterize the molecular mechanisms driving lineage divergence. METHODOLOGY/PRINCIPAL FINDINGS:In order to evaluate the importance of cell polarity in the determination of cell fate we have disturbed the activity of the apical complex aPKC/PAR6 using siRNA to down-regulate aPKClambda expression. Here we show that depletion of aPKClambda results in an absence of tight junctions and in severe polarity defects at the 16-cell stage. Importantly, we found that, in absence of aPKClambda, cell fate depends on the cellular context: depletion of aPKClambda in all cells results in a strong reduction of inner cells at the 16-cell stage, while inhibition of aPKClambda in only half of the embryo biases the progeny of aPKClambda defective blastomeres towards the inner cell mass. Finally, our study points to a role of cell shape in controlling cell position and thus lineage allocation. CONCLUSION:Our data show that aPKClambda is dispensable for the establishment of polarity at the 8-cell stage but is essential for the stabilization of cell polarity at the 16-cell stage and for cell positioning. Moreover, this study reveals that in addition to positional information and asymmetric cell divisions, cell shape plays an important role for the control of lineage divergence during mouse preimplantation development. Cell shape is able to influence both the type of division (symmetric or asymmetric) and the position of the blastomeres within the embryo

L-Ilf3 and L-NF90 Traffic to the Nucleolus Granular Component: Alternatively-Spliced Exon 3 Encodes a Nucleolar Localization Motif

Ilf3 and NF90, two proteins containing double-stranded RNA-binding domains, are generated by alternative splicing and involved in several functions. Their heterogeneity results from posttranscriptional and posttranslational modifications. Alternative splicing of exon 3, coding for a 13 aa N-terminal motif, generates for each protein a long and short isoforms. Subcellular fractionation and localization of recombinant proteins showed that this motif acts as a nucleolar localization signal. Deletion and substitution mutants identified four arginines, essential for nucleolar targeting, and three histidines to stabilize the proteins within the nucleolus. The short isoforms are never found in the nucleoli, whereas the long isoforms are present in the nucleoplasm and the nucleoli. For Ilf3, only the posttranslationally-unmodified long isoform is nucleolar, suggesting that this nucleolar targeting is abrogated by posttranslational modifications. Confocal microscopy and FRAP experiments have shown that the long Ilf3 isoform localizes to the granular component of the nucleolus, and that L-Ilf3 and L-NF90 exchange rapidly between nucleoli. The presence of this 13 aminoacid motif, combined with posttranslational modifications, is responsible for the differences in Ilf3 and NF90 isoforms subcellular localizations. The protein polymorphism of Ilf3/NF90 and the various subcellular localizations of their isoforms may partially explain the various functions previously reported for these proteins

Outpatient chemotherapy with gemcitabine and oxaliplatin in patients with biliary tract cancer

This phase II study was conducted to determine the efficacy and toxicity of a gemcitabine (GEM) and oxaliplatin (OX) chemotherapy protocol in patients with unresectable biliary tract cancer (BTC). Patients were treated with GEM 1000 mg m−2 (30 min infusion) on days 1, 8, 15, and OX 100 mg m−2 (2 h infusion) on days 1 and 15 (gemcitabine and oxaliplatin (GEMOX-3 protocol), repeated every 28 days. The data were collected according to the Simon 2-stage design for a single centre phase II study (α=0.05; β=0.2). Primary end point was response rate; secondary end points were time-to-progression (TTP), median survival, and safety profile. Thirty-one patients were enrolled in the study between July 2002 and April 2005. Therapeutic responses were as follows: partial response in eight patients (26%, 95% confidence interval (CI) 14–44), stable disease in 14 patients (45%, 95%CI 29–62), resulting in a disease control rate of 71%. Nine patients (29%, 95%CI 16–47) had progressive disease. Median TTP was 6.5 months. Median overall survival was 11 months. Common Toxicity Criteria (CTC) Grade 3–4 toxicities were transient thrombocytopenia (23%), peripheral sensory neuropathy (19%), leucopenia (16%), and anaemia (10%). In conclusion the GEMOX-3 protocol is active and well tolerated in patients with advanced BTC. It can be applied in an outpatient setting with three visits per month only