Arboriculture Biologique : 11 années d'expérimentation en vergers de pêchers et pommiers

Un programme de recherche a été conduit en arboriculture biologique pendant 11 ans (1994-2004) à l'unité expérimentale INRA (Institut National de la Recherche Agronomique) de Gotheron dans le Sud-Est de la France, en partenariat avec Agribiodrôme (F-26150 Die), asssociation de développement de l'Agriculture Biologique (AB) en Drôme, et le GRAB (Groupe de Recherche en Agriculture Biologique, F-84911 Avignon). Les objectifs étaient : (i) acquérir des références en arboriculture biologique ; (ii) identifier et analyser les verrous techniques de la production de pêches et pommes biologiques, afin d'optimiser la conduite des vergers AB et/ou de proposer de nouvelles expérimentations ; (iii) évaluer à long terme l'impact du mode de production pour le sol et la communauté d'arthropodes du verger. Le suivi longitudinal réalisé dans les 3 vergers expérimentaux de pêchers et pommiers a permis de souligner certaines contraintes en culture pérenne AB, notamment pour la conduite du sol (entretien de la fertilité, enracinement limité par le travail du sol sur le rang pour limiter les adventices) et la protection du verger. Probablement en rapport avec une fertilisation modérée et une conduite de la protection favorable à des régulations naturelles, certains ravageurs ne se sont pas développés : acariens phytophages, pucerons du pêcher,... D'autres bio-agresseurs ont pu être contrôlés par l'utilisation de méthodes biotechnique ou microbiologique : confusion sexuelle (tordeuse orientale), virus de la granulose (carpocapse),... En revanche, la maîtrise de certains bio-agresseurs a nécessité l'utilisation d'importantes quantités de matières actives présentant des effets non intentionnels (cuivre contre la cloque du pêcher, soufre contre la tavelure du pommier) et/ou a été insuffisante (puceron cendré du pommier, maladies de conservation du pêcher). Le suivi de la teneur en nitrates de la solution du sol à différentes profondeurs a permis d'établir que le risque de lessivage, et donc de pollution par les nitrates, était nul pour notre stratégie de fertilisation et notre situation. Enfin, l'étude de la communauté des arthropodes dans le verger de pommiers AB (2001-2003) a mis en évidence une biomasse plus élevée et un cortège d'auxiliaires de structure différente (prédominance de prédateurs polyphages) par rapport à d'autres vergers conduits en conventionnel. En raison d'une efficacité limitée et/ou d'effets non intentionnels de la lutte directe contre les bio-agresseurs en verger, il est donc important de concevoir et de gérer le verger AB afin de limiter le recours aux intrants phytosanitaires : variétés, distances de plantation, architecture de l'arbre, aménagement de l'environnement du verger, prophylaxie,..

Soil nitrogen in an organic apple orchard

Introduction The lack of vigour of an organic apple orchard (Smoothee cultivar) planted in 1994 pointed out the management of tree nitrogen supply in this orchard. Serious damages due to Dysaphis plantaginea, the rosy aphid, were also noted on trees. As tree vigour and therefore aphid population levels are related to nitrogen nutrition, the monitoring of soil nitrogen availability was necessary to analyse the causes of these problems. Besides, the aim was to optimise the orchard organic nitrogen fertilisation. Materials and methods From 1994 to 1998, the fertilisation management mainly consisted in compost supply (10 t.ha-1). From 1999 to 2001, autumn compost supply was reduced to 5 t.ha-1, complemented with organic quickly mineralised fertilisers in spring (2 x 20 kg.ha-1 N). Lysimeters have been installed (density of 32 lysimeters per ha) in the orchard at 80 cm from trees in the areas under irrigation emitters; at 35 cm depth in 1999, at 35 cm and 50 cm depth in 2000 and 2001. These lysimeters allowed to sample the soil solution and to measure its nitrate content each week along the vegetative period. Growth of the trees, yield, fruit quality and pests were monitored. Soil and leaf analyses were performed in order to evaluate their nitrogen status. Results During the first year of the experiment (1999), nitrate content in soil solution was low and slightly varied among the tested places. In 2000 and 2001, the orchard homogeneity and the very low risk for nitrate leaching were assessed, as nitrate content in soil solution was comprised between 5 and 15 ppm, and remained lower at 50 cm than at 35 cm depth. Analyses of soil samples before and after the vegetative period led to the same conclusions: soil nitrate content varied between 20 and 30 kg.ha-1 at the end of winter, 15 and 25 kg.ha-1 in autumn. These results suggested that soil nitrate content was low enough to limit nitrate leaching, but sufficient to ensure an appropriated nitrate availability for the apple trees (Bussi and Gojon, 1997). The soil C/N ratio increased (from 8.6 in 1998 to 9.8 in 2001), as a result of the soil organic matter increase due to compost supplies. In our soil conditions, a close to 10 C/N ratio, as measured in 2001, appears to be an adequate level (Delas and Molot, 1983). Leaf nitrogen content decreased from 23.7 g.kg-1 in 1999 to 20.4 g.kg-1 in 2001, and fruit nitrogen content from 2.45 g.kg-1 in 1999 to 1.69 g.kg-1 in 2001; nevertheless these N content remained quite suitable for apple production (Sharples, 1980). Yield varied from 15 to 23 t.ha-1 according to the year, and first choice fruit represented 51 to 75 % of the total harvest. These yield fluctuations were mostly a consequence of the serious damages caused by the rosy aphid. Damages by rosy aphid were serious in 1998 and 2000. In 1998, damages might have been favoured by high soil nitrate content, as a consequence of the 10 t.ha-1 compost yearly applied. In 2000, results showed that trees were not overfertilised, which excluded a stimulation effect of nitrogen. Weather in spring 2000 was wet and hot, which was likely to favour the increase of aphid populations, despite pest management before blooming. Conclusion Soil solution and soil nitrate content are useful tools to check the adequacy of organic fertilisation. They may allow to quickly detect excess or lack of nitrogen fertilisation, in order to correct it. Leaf and fruit nitrogen contents are diagnostic elements to evaluate the nitrogen fertilisation effectiveness in organic apple orchard. In our conditions, the optimisation of nitrogen fertilisation was simultaneous of an effective control of the rosy aphid in 1999 and 2001. However, rosy aphid damages in 2000 were serious, suggesting that this problem is most probably related to multi-factorial causes. References Bussi, C., Gojon, A. (1997). Nitrate reductase activity in leaves of peach trees. J. Hort. Sci., 72 (3), 347-353. Delas, J. and Molot, C. (1983). Effet de divers amendements organiques sur les rendements du maïs et de la pomme de terre cultivés en sol sableux. Agronomie, 3 (1), 19-26. Sharples, R.O. (1980). The influence of orchard nutrition on the storage quality of apples and pears grown in the United Kingdom. In : Mineral Nutrition of Fruit Trees, 17-28

Prolonged Mechanical Ventilation Induces Cell Cycle Arrest in Newborn Rat Lung

Rationale: The molecular mechanism(s) by which mechanical ventilation disrupts alveolar development, a hallmark of bronchopulmonary dysplasia, is unknown. Objective: To determine the effect of 24 h of mechanical ventilation on lung cell cycle regulators, cell proliferation and alveolar formation in newborn rats. Methods: Seven-day old rats were ventilated with room air for 8, 12 and 24 h using relatively moderate tidal volumes (8.5 mL.kg-1). Measurement and Main Results: Ventilation for 24 h (h) decreased the number of elastin-positive secondary crests and increased the mean linear intercept, indicating arrest of alveolar development. Proliferation (assessed by BrdU incorporation) was halved after 12 h of ventilation and completely arrested after 24 h. Cyclin D1 and E1 mRNA and protein levels were decreased after 8-24 h of ventilation, while that of p27Kip1 was significantly increased. Mechanical ventilation for 24 h also increased levels of p57Kip2, decreased that of p16INK4a, while the levels of p21Waf/Cip1 and p15INK4b were unchanged. Increased p27Ki

Microglia Are Mediators of Borrelia burgdorferi–Induced Apoptosis in SH-SY5Y Neuronal Cells

Inflammation has long been implicated as a contributor to pathogenesis in many CNS illnesses, including Lyme neuroborreliosis. Borrelia burgdorferi is the spirochete that causes Lyme disease and it is known to potently induce the production of inflammatory mediators in a variety of cells. In experiments where B. burgdorferi was co-cultured in vitro with primary microglia, we observed robust expression and release of IL-6 and IL-8, CCL2 (MCP-1), CCL3 (MIP-1α), CCL4 (MIP-1β) and CCL5 (RANTES), but we detected no induction of microglial apoptosis. In contrast, SH-SY5Y (SY) neuroblastoma cells co-cultured with B. burgdorferi expressed negligible amounts of inflammatory mediators and also remained resistant to apoptosis. When SY cells were co-cultured with microglia and B. burgdorferi, significant neuronal apoptosis consistently occurred. Confocal microscopy imaging of these cell cultures stained for apoptosis and with cell type-specific markers confirmed that it was predominantly the SY cells that were dying. Microarray analysis demonstrated an intense microglia-mediated inflammatory response to B. burgdorferi including up-regulation in gene transcripts for TLR-2 and NFκβ. Surprisingly, a pathway that exhibited profound changes in regard to inflammatory signaling was triggering receptor expressed on myeloid cells-1 (TREM1). Significant transcript alterations in essential p53 pathway genes also occurred in SY cells cultured in the presence of microglia and B. burgdorferi, which indicated a shift from cell survival to preparation for apoptosis when compared to SY cells cultured in the presence of B. burgdorferi alone. Taken together, these findings indicate that B. burgdorferi is not directly toxic to SY cells; rather, these cells become distressed and die in the inflammatory surroundings generated by microglia through a bystander effect. If, as we hypothesized, neuronal apoptosis is the key pathogenic event in Lyme neuroborreliosis, then targeting microglial responses may be a significant therapeutic approach for the treatment of this form of Lyme disease

Sox17 Promotes Cell Cycle Progression and Inhibits TGF-β/Smad3 Signaling to Initiate Progenitor Cell Behavior in the Respiratory Epithelium

The Sry-related high mobility group box transcription factor Sox17 is required for diverse developmental processes including endoderm formation, vascular development, and fetal hematopoietic stem cell maintenance. Expression of Sox17 in mature respiratory epithelial cells causes proliferation and lineage respecification, suggesting that Sox17 can alter adult lung progenitor cell fate. In this paper, we identify mechanisms by which Sox17 influences lung epithelial progenitor cell behavior and reprograms cell fate in the mature respiratory epithelium. Conditional expression of Sox17 in epithelial cells of the adult mouse lung demonstrated that cell cluster formation and respecification of alveolar progenitor cells toward proximal airway lineages were rapidly reversible processes. Prolonged expression of Sox17 caused the ectopic formation of bronchiolar-like structures with diverse respiratory epithelial cell characteristics in alveolar regions of lung. During initiation of progenitor cell behavior, Sox17 induced proliferation and increased the expression of the progenitor cell marker Sca-1 and genes involved in cell cycle progression. Notably, Sox17 enhanced cyclin D1 expression in vivo and activated cyclin D1 promoter activity in vitro. Sox17 decreased the expression of transforming growth factor-beta (TGF-β)-responsive cell cycle inhibitors in the adult mouse lung, including p15, p21, and p57, and inhibited TGF-β1-mediated transcriptional responses in vitro. Further, Sox17 interacted with Smad3 and blocked Smad3 DNA binding and transcriptional activity. Together, these data show that a subset of mature respiratory epithelial cells retains remarkable phenotypic plasticity and that Sox17, a gene required for early endoderm formation, activates the cell cycle and reinitiates multipotent progenitor cell behavior in mature lung cells

Bezlotoxumab for Prevention of Recurrent Clostridium difficile Infection

BACKGROUND Clostridium difficile is the most common cause of infectious diarrhea in hospitalized patients. Recurrences are common after antibiotic therapy. Actoxumab and bezlotoxumab are human monoclonal antibodies against C. difficile toxins A and B, respectively. METHODS We conducted two double-blind, randomized, placebo-controlled, phase 3 trials, MODIFY I and MODIFY II, involving 2655 adults receiving oral standard-of-care antibiotics for primary or recurrent C. difficile infection. Participants received an infusion of bezlotoxumab (10 mg per kilogram of body weight), actoxumab plus bezlotoxumab (10 mg per kilogram each), or placebo; actoxumab alone (10 mg per kilogram) was given in MODIFY I but discontinued after a planned interim analysis. The primary end point was recurrent infection (new episode after initial clinical cure) within 12 weeks after infusion in the modified intention-to-treat population. RESULTS In both trials, the rate of recurrent C. difficile infection was significantly lower with bezlotoxumab alone than with placebo (MODIFY I: 17% [67 of 386] vs. 28% [109 of 395]; adjusted difference, −10.1 percentage points; 95% confidence interval [CI], −15.9 to −4.3; P<0.001; MODIFY II: 16% [62 of 395] vs. 26% [97 of 378]; adjusted difference, −9.9 percentage points; 95% CI, −15.5 to −4.3; P<0.001) and was significantly lower with actoxumab plus bezlotoxumab than with placebo (MODIFY I: 16% [61 of 383] vs. 28% [109 of 395]; adjusted difference, −11.6 percentage points; 95% CI, −17.4 to −5.9; P<0.001; MODIFY II: 15% [58 of 390] vs. 26% [97 of 378]; adjusted difference, −10.7 percentage points; 95% CI, −16.4 to −5.1; P<0.001). In prespecified subgroup analyses (combined data set), rates of recurrent infection were lower in both groups that received bezlotoxumab than in the placebo group in subpopulations at high risk for recurrent infection or for an adverse outcome. The rates of initial clinical cure were 80% with bezlotoxumab alone, 73% with actoxumab plus bezlotoxumab, and 80% with placebo; the rates of sustained cure (initial clinical cure without recurrent infection in 12 weeks) were 64%, 58%, and 54%, respectively. The rates of adverse events were similar among these groups; the most common events were diarrhea and nausea. CONCLUSIONS Among participants receiving antibiotic treatment for primary or recurrent C. difficile infection, bezlotoxumab was associated with a substantially lower rate of recurrent infection than placebo and had a safety profile similar to that of placebo. The addition of actoxumab did not improve efficacy. (Funded by Merck; MODIFY I and MODIFY II ClinicalTrials.gov numbers, NCT01241552 and NCT01513239.

Hypoxia induces a pro-tumoral inflammation in brain tumors

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Hypoxia induces macrophage polarization and re-education towards an M2 phenotype in glioblastoma

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Impact du débruitage par intelligence artificiel sur les radiomics extrait d’examen PET au FDG

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