Sampling strategies for tropical forest nutrient cycling studies: a case study in São Paulo, Brazil

The precise sampling of soil, biological or micro climatic attributes in tropical forests, which are characterized by a high diversity of species and complex spatial variability, is a difficult task. We found few basic studies to guide sampling procedures. The objective of this study was to define a sampling strategy and data analysis for some parameters frequently used in nutrient cycling studies, i. e., litter amount, total nutrient amounts in litter and its composition (Ca, Mg, Κ, Ν and P), and soil attributes at three depths (organic matter, Ρ content, cation exchange capacity and base saturation). A natural remnant forest in the West of São Paulo State (Brazil) was selected as study area and samples were collected in July, 1989. The total amount of litter and its total nutrient amounts had a high spatial independent variance. Conversely, the variance of litter composition was lower and the spatial dependency was peculiar to each nutrient. The sampling strategy for the estimation of litter amounts and the amount of nutrient in litter should be different than the sampling strategy for nutrient composition. For the estimation of litter amounts and the amount of nutrients in litter (related to quantity) a large number of randomly distributed determinations are needed. Otherwise, for the estimation of litter nutrient composition (related to quality) a smaller amount of spatially located samples should be analyzed. The determination of sampling for soil attributes differed according to the depth. Overall, surface samples (0-5 cm) showed high short distance spatial dependent variance, whereas, subsurface samples exhibited spatial dependency in longer distances. Short transects with sampling interval of 5-10 m are recommended for surface sampling. Subsurface samples must also be spatially located, but with transects or grids with longer distances between sampling points over the entire area. Composite soil samples would not provide a complete understanding of the relation between soil properties and surface dynamic processes or landscape aspects. Precise distribution of Ρ was difficult to estimate.

Effects of the removal of shelterwood on the foliar nutrient conceentrations of Norway spruce (Picea abies(L.)Karst.) on drained peatlands

Tiivistelmä: Neulasten pääravinnepitoisuuksien muutokset turvekankaan alikasvoskuusikossa ylispuuhakkuun jälkeen

Nutrient leaching potential following application of papermill lime-sludge to an acidic clay soil

This experiment was carried out under greenhouse conditions with soil pots during 210 days, to evaluate the effect of calcitic papermill lime-sludge application (at the rates 0, 773, 1.547, and 2.320 mg kg-1 or respective equivalents to control, 2, 4, and 6 t ha-1), on chemical composition of soil leachate and its effects on eucalypt growth and yield. Highest soil leachate pH, SO4, and Na concentrations occurred in the 4 and 6 t ha-1 treatments. Soil leachate nitrate concentrations decreased with increasing lime-sludge rate. Soil leachate phosphate remained low (below the detection limit) in all treatments until 120 days, while the concentration increased in the lime-sludge treatments at 210 days (last sampling) in about 600 mg L-1. Lime-sludge decreased leachate Mg concentration, but had no significant effect among rates. Soil leachate Ca, K, B, Cu, Fe, and Zn did not change significantly for any lime-sludge application rates. The maximum NO3, Ca, Mg, K, and Na concentrations in the soil leachate occurred at 60 days after lime-sludge application (leaching equivalent to 1 pore volume), but for pH and SO4, the maximum occurred at 210 days (leaching equivalent to 4 pore volumes). Lime-sludge application decreased the concentration of exchangeable Al in the soil. Plant diameter growth and dry matter yield were increased with increasing lime-sludge rate. Beneficial effects on mineral nutrition (P, K, Ca, B, and Zn) of eucalypts were also obtained by the application of 4 and 6 t ha-1 of lime-sludge.

A receptor-like kinase mutant with absent endodermal diffusion barrier displays selective nutrient homeostasis defects.

The endodermis represents the main barrier to extracellular diffusion in plant roots, and it is central to current models of plant nutrient uptake. Despite this, little is known about the genes setting up this endodermal barrier. In this study, we report the identification and characterization of a strong barrier mutant, schengen3 (sgn3). We observe a surprising ability of the mutant to maintain nutrient homeostasis, but demonstrate a major defect in maintaining sufficient levels of the macronutrient potassium. We show that SGN3/GASSHO1 is a receptor-like kinase that is necessary for localizing CASPARIAN STRIP DOMAIN PROTEINS (CASPs)--major players of endodermal differentiation--into an uninterrupted, ring-like domain. SGN3 appears to localize into a broader band, embedding growing CASP microdomains. The discovery of SGN3 strongly advances our ability to interrogate mechanisms of plant nutrient homeostasis and provides a novel actor for localized microdomain formation at the endodermal plasma membrane.

New insights into the role of microRNAs in pancreatic ß-cell maturation and plasticity

Le diabète est une maladie chronique caractérisée par une élévation du taux de sucre dans le sang aussi appelé « glycémie » reflétant un état pathologique. L'élévation de la glycémie au long cours a des répercussions délétères sur nombreux de nos tissus et organes d'où l'apparition de complications sévères chez les sujets diabétiques pouvant atteindre les yeux, les reins, le système nerveux, le système cardiovasculaire et les membres inférieurs. La carence en une hormone essentielle à notre organisme, l'insuline, est au coeur du développement de la maladie. L'insuline induit la captation du glucose circulant dans le sang en excès suite à une prise alimentaire riche en glucides et favorise son utilisation et éventuellement son stockage dans les tissus tels que le foie, le tissu adipeux et les muscles. Ainsi, l'insuline est vitale pour réguler et maintenir stable notre niveau de glycémie. Les cellules bêta du pancréas sont les seules entités de notre corps capables de produire de l'insuline et une perte de fonctionnalité associée à leur destruction ont été mises en cause dans le processus pathologique du diabète de type 2. Cependant la pleine fonctionnalité et la maturation des cellules bêta n'apparaissent qu'après la naissance lorsque le pancréas en développement a atteint sa masse adulte définitive. Enfin, une fois la masse des cellules bêta définitive établie, leur nombre et volume restent relativement constants au cours de la vie adulte chez un sujet sain. Néanmoins, au cours de périodes critiques les besoins en insuline sont augmentés tel qu'observé chez les femmes enceintes et les personnes obèses qui ont une perte de sensibilité à l'insuline qui se traduit par la nécessité de sécréter plus d'insuline afin de maintenir une glycémie normale. Dans l'hypothèse où la compensation n'a pas lieu ou n'est pas aboutie, le diabète se développe. Le processus de maturation postnatale ainsi que les événements compensatoires sont donc des étapes essentielles et de nombreuses questions sont encore non résolues concernant l'identification des mécanismes les régulant. Parmi les acteurs potentiels figurent de petites molécules d'ARN découvertes récemment appelées microARNs et qui ont été rapidement suggérées très prometteuses dans l'identification de nouvelles cibles thérapeutiques dans le cadre du diabète et d'autres pathologies. Les microARNs vont réguler l'expression de notre génome sans en modifier la séquence, phénomène également appelé épigénétique, ce qui résulte en des différences de comportement et de fonction cellulaires. Les microARNs sont donc susceptibles de jouer un rôle clé dans l'ensemble des processus biologiques et notre environnement associé à nos prédispositions génétiques peuvent grandement modifier leur niveau et donc leur action, qui à son tour se répercutera sur notre état physiologique. En effet nous avons identifié des changements de microARNs dans les cellules d'îlots pancréatiques de modèles animaux (rats et souris) associés à un état de résistance à l'insuline (grossesse et obésité). Par le biais d'expériences in vitro sur des cellules bêta extraites de rats et conservées en culture, nous avons pu analyser de plus près l'implication des microARNs dans la capacité des cellules bêta à sécréter de l'insuline mais aussi à se multiplier et à survivre au sein d'un environnement toxique. Ainsi, nous avons identifié des microARNs qui participent positivement à la compensation des cellules bêta, sous la direction d'hormones telles les estrogènes ou d'une hormone libérée par l'intestin au cours de la digestion (l'inerétine GLP1) et qui est largement utilisée comme agent thérapeutique dans la médication contre le diabète. Dans un second temps nous avons utilisé une stratégie similaire afin de déterminer le rôle de microARNs préalablement détectés comme étant changés au cours du développement postnatal des cellules bêta chez le rat. Cette étude a également mené à l'identification de microARNs participant à la maturation et à l'expansion de la masse des cellules bêta sous l'influence de la composition du régime alimentaire et des besoins en insuline adéquats qui en dépendent. Ces études apportent la vision de nouveaux mécanismes moléculaires impliquant les microARNs et démontrant leur importance pour le bon fonctionnement des cellules bêta et leur capacité d'adaptation à l'environnement. -- Les cellules bêta sont une composante des îlots pancréatiques de Langerhans et sont des cellules hautement différenciées qui ont l'unique capacité de sécréter de l'insuline sous l'influence des nutriments suite à une prise alimentaire. L'insuline facilite l'incorporation de glucose dans ses tissus cibles tels le foie, le tissu adipeux et les muscles. Bien que les besoins en insuline soient relativement constants au cours de la vie d'un individu sain, certaines conditions associées à un état de résistance à l'insuline, telles la grossesse ou l'obésité, requièrent une libération d'insuline majorée. En cas de résistance à l'insuline, une dysfonction des cellules bêta plus ou moins associée à leur mort cellulaire, conduisent à une sécrétion d'insuline insuffisante et au développement d'une hyperglycémie chronique, caractéristique du diabète de type 2. Jusqu'à présent, les mécanismes moléculaires sous- jacents à la compensation des cellules bêta ou encore menant à leur dysfonction restent peu connus. Découverts récemment, les petits ARNs non-codant appelés microARNs (miARNs), suscitent un intérêt grandissant de par leur potentiel thérapeutique pour la prise en charge et le traitement du diabète. Les miARNs sont de puissants régulateurs de l'expression génique qui lient directement le 3'UTR de leurs ARN messagers cibles afin d'inhiber leur traduction ou d'induire leur dégradation, ce qui leur permet de contrôler des fonctions biologiques multiples. Ainsi, nous avons pris pour hypothèse que les miARNs pourraient jouer un rôle essentiel en maintenant la fonction des cellules bêta et des processus compensatoires afin de prévenir le développement du diabète. Lors d'une première étude, une analyse transcriptomique a permis l'identification de miARNs différemment exprimés au sein d'îlots pancréatiques de rattes gestantes. Parmi eux, le miR-338-3p a démontré la capacité de promouvoir la prolifération et la survie des cellules bêta exposées à des acides gras saturés et des cytokines pro-inflammatoires, sans altérer leur propriété sécrétrice d'insuline. Nous avons également identifié deux hormones reconnues pour leurs propriétés bénéfiques pour la physiologie de la cellule bêta, l'estradiol et l'incrétine GLP1, qui régulent les niveaux du miR-338-3p. Ce miARN intègre parfaitement les voies de signalisation de ces deux hormones dépendantes de l'AMP cyclique, afin de contrôler l'expression de nombreux gènes conduisant à son action biologique. Dans un projet ultérieur, notre objectif était de déterminer la contribution de miARNs dans l'acquisition de l'identité fonctionnelle des cellules bêta en période postnatale. En effet, directement après la naissance les cellules bêta sont reconnues pour être encore immatures et incapables de sécréter de l'insuline spécifiquement en réponse à l'élévation de la glycémie. Au contraire, la réponse insulinique induite par les acides aminés ainsi que la biosynthèse d'insuline sont déjà fonctionnelles. Nos recherches ont permis de montrer que les changements de miARNs corrélés avec l'apparition du phénotype sécrétoire en réponse au glucose, sont régis par la composition nutritionnelle du régime alimentaire et des besoins en insuline qui en découlent. En parallèle, le taux de prolifération des cellules bêta est considérablement réduit. Les miARNs que nous avons étudiés coordonnent des changements d'expression de gènes clés impliqués dans l'acquisition de propriétés vitales de la cellule bêta et dans la maintenancé de son identité propre. Enfin, ces études ont permis de clairement démontrer l'importance des miARNs dans la régulation de la fonction des cellules bêta pancréatiques. -- Beta-cells are highly differentiated cells localized in the pancreatic islets and are characterized by the unique property of secreting insulin in response to nutrient stimulation after meal intake. Insulin is then in charge of facilitating glucose uptake by insulin target tissues such as liver, adipose tissue and muscles. Despite insulin needs stay more or less constant throughout life of healthy individuals, there are circumstances such as during pregnancy or obesity which are associated to insulin resistance, where insulin needs are increased. In this context, defects in beta-cell function, sometimes associated with beta-cell loss, may result in the release of inappropriate amounts of insulin leading to chronic hyperglycemia, properly defined as type 2 diabetes mellitus. So far, the mechanisms underlying beta- cell compensation as well as beta-cell failure remain to be established. The recently discovered small non-coding RNAs called microRNAs (miRNAs) are emerging as interesting therapeutic targets and are bringing new hope for the treatment of diabetes. miRNAs display a massive potential in regulating gene expression by directly binding to the 3'UTR of messenger RNAs and by inhibiting their translation and/or stability, enabling them to modify a wide range of biological functions. In view of this, we hypothesized that miRNAs may play an essential role in preserving the functional beta-cell mass and permitting to fight against beta-cell exhaustion and decompensation that can lead to diabetes development. In a first study, global profiling in pancreatic islets of pregnant rats, a model of insulin resistance, led to the identification of a set of differentially expressed miRNAs. Among them, miR-338- 3p was found to promote beta-cell proliferation and survival upon exposure of islet cells to pro- apoptotic stimuli such as saturated fatty acids or pro-inflammatory cytokines, without impairment in their capacity to release insulin. We also discovered that miR-338-3p changes are driven by two hormones, the estradiol and the incretin GLP1, both well known for their beneficial impact on beta- cell physiology. Consistently, we found that miR-338-3p integrates the cAMP-dependent signaling pathways regulated by these two hormones in order to control the expression of numerous genes and execute its biological functions. In a second project, we aimed at determining whether miRNAs contribute to the acquisition of beta-cell identity. Indeed, we confirmed that right after birth beta-cells are still immature and are unable to secrete insulin specifically in response to elevated concentrations of glucose. In contrast, amino acid-stimulated insulin release as well as insulin biosynthesis are already fully functional. In parallel, newborn beta-cells are proliferating intensively within the expanding pancreas. Interestingly, we demonstrated that the miRNA changes and the subsequent acquisition of glucose responsiveness is influenced by the diet composition and the resulting insulin needs. At the same time, beta-cell proliferation declines. The miRNAs that we have identified orchestrate expression changes of essential genes involved in the acquisition of specific beta-cell properties and in the maintenance of a mature beta-cell identity. Altogether, these studies clearly demonstrate that miRNAs play important roles in the regulation of beta-cell function.

Steady-state equilibrium phase inversion recovery ON-resonant water suppression (IRON) MR angiography in conjunction with superparamagnetic nanoparticles. A robust technique for imaging within a wide range of contrast agent dosages.

PURPOSE: To investigate the ability of inversion recovery ON-resonant water suppression (IRON) in conjunction with P904 (superparamagnetic nanoparticles which consisting of a maghemite core coated with a low-molecular-weight amino-alcohol derivative of glucose) to perform steady-state equilibrium phase MR angiography (MRA) over a wide dose range. MATERIALS AND METHODS: Experiments were approved by the institutional animal care committee. Rabbits (n = 12) were imaged at baseline and serially after the administration of 10 incremental dosages of 0.57-5.7 mgFe/Kg P904. Conventional T1-weighted and IRON MRA were obtained on a clinical 1.5 Tesla (T) scanner to image the thoracic and abdominal aorta, and peripheral vessels. Contrast-to-noise ratios (CNR) and vessel sharpness were quantified. RESULTS: Using IRON MRA, CNR and vessel sharpness progressively increased with incremental dosages of the contrast agent P904, exhibiting constantly higher contrast values than T1 -weighted MRA over a very wide range of contrast agent doses (CNR of 18.8 ± 5.6 for IRON versus 11.1 ± 2.8 for T1 -weighted MRA at 1.71 mgFe/kg, P = 0.02 and 19.8 ± 5.9 for IRON versus -0.8 ± 1.4 for T1-weighted MRA at 3.99 mgFe/kg, P = 0.0002). Similar results were obtained for vessel sharpness in peripheral vessels, (Vessel sharpness of 46.76 ± 6.48% for IRON versus 33.20 ± 3.53% for T1-weighted MRA at 1.71 mgFe/Kg, P = 0.002, and of 48.66 ± 5.50% for IRON versus 19.00 ± 7.41% for T1-weighted MRA at 3.99 mgFe/Kg, P = 0.003). CONCLUSION: Our study suggests that quantitative CNR and vessel sharpness after the injection of P904 are consistently higher for IRON MRA when compared with conventional T1-weighted MRA. These findings apply for a wide range of contrast agent dosages.

Autoinduction of 2,4-diacetylphloroglucinol biosynthesis in the biocontrol agent Pseudomonas fluorescens CHA0 and repression by the bacterial metabolites salicylate and pyoluteorin.

The antimicrobial metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) contributes to the capacity of Pseudomonas fluorescens strain CHA0 to control plant diseases caused by soilborne pathogens. A 2, 4-DAPG-negative Tn5 insertion mutant of strain CHA0 was isolated, and the nucleotide sequence of the 4-kb genomic DNA region adjacent to the Tn5 insertion site was determined. Four open reading frames were identified, two of which were homologous to phlA, the first gene of the 2,4-DAPG biosynthetic operon, and to the phlF gene encoding a pathway-specific transcriptional repressor. The Tn5 insertion was located in an open reading frame, tentatively named phlH, which is not related to known phl genes. In wild-type CHA0, 2, 4-DAPG production paralleled expression of a phlA'-'lacZ translational fusion, reaching a maximum in the late exponential growth phase. Thereafter, the compound appeared to be degraded to monoacetylphloroglucinol by the bacterium. 2,4-DAPG was identified as the active compound in extracts from culture supernatants of strain CHA0 specifically inducing phlA'-'lacZ expression about sixfold during exponential growth. Induction by exogenous 2,4-DAPG was most conspicuous in a phlA mutant, which was unable to produce 2, 4-DAPG. In a phlF mutant, 2,4-DAPG production was enhanced severalfold and phlA'-'lacZ was expressed at a level corresponding to that in the wild type with 2,4-DAPG added. The phlF mutant was insensitive to 2,4-DAPG addition. A transcriptional phlA-lacZ fusion was used to demonstrate that the repressor PhlF acts at the level of transcription. Expression of phlA'-'lacZ and 2,4-DAPG synthesis in strain CHA0 was strongly repressed by the bacterial extracellular metabolites salicylate and pyoluteorin as well as by fusaric acid, a toxin produced by the pythopathogenic fungus Fusarium. In the phlF mutant, these compounds did not affect phlA'-'lacZ expression and 2, 4-DAPG production. PhlF-mediated induction by 2,4-DAPG and repression by salicylate of phlA'-'lacZ expression was confirmed by using Escherichia coli as a heterologous host. In conclusion, our results show that autoinduction of 2,4-DAPG biosynthesis can be countered by certain bacterial (and fungal) metabolites. This mechanism, which depends on phlF function, may help P. fluorescens to produce homeostatically balanced amounts of extracellular metabolites.

Biomass and nutrient cycling in pure and mixed stands of native tree species in southeastern Bahia, Brazil

The objective of this paper is to study selected components of the nutrient cycle of pure and mixed stands of native forest species of Atlantic Forest in southeastern Brazil. Tree diameter, height, above-ground biomass, and nutrient content were determined in 22-year-old stands. Litterfall, litter decomposition, and nutrient concentration were evaluated from August 1994 to July 1995. The following species were studied: Peltogyne angustiflora, Centrolobium robustum, Arapatiella psilophylla, Sclerolobium chrysophyllum, Cordia trichotoma, Macrolobium latifolium. The litter of a natural forest and a 40-year-old naturally regenerated second-growth forest was sampled as well. The mixed-species outmatched pure stands in height, stem volume and total biomass (29.4 % more). The greatest amount of forest litter was observed in the natural forest (9.3 Mg ha-1), followed by the mixed-species stand (7.6 Mg ha-1) and secondary forest (7.3 Mg ha-1), and least litterfall was measured in the pure C. robustum stand (5.5 Mg ha-1). Litterfall seasonality varied among species in pure stands (CV from 44.7 to 91.4 %), unlike litterfall in the mixed-tree stand, where the variation was lower (CV 31.2 %). In the natural and second-growth forest, litterfall varied by 57.8 and 34.0 %, respectively. The annual rate of nutrient return via litterfall varied widely among forest ecosystems. Differences were detected between forest ecosystems in both the litter accumulation and quantity of litterlayer nutrients. The highest mean nutrient accumulation in above-ground biomass was observed in mixed-species stands. The total nutrient accumulation (N + P + K+ Ca + Mg) ranged from 0.97 to 1.93 kg tree-1 in pure stands, and from 1.21 to 2.63 kg tree-1 in mixed-species stands. Soil fertility under mixed-species stands (0-10 cm) was intermediate between the primary forest and pure-stand systems. The litterfall rate of native forest species in a mixed-species system is more constant, resulting in a more continuous decomposition rate. Consequently, both nutrient availability and quantity of organic matter in the soil are higher and the production system ecologically more sustainable.

Organic material decomposition and nutrient dynamics in a mulch system enriched with leguminous trees in the Amazon

The new techniques proposed for agriculture in the Amazon region include rotational fallow systems enriched with leguminous trees and the replacement of biomass burning by mulching. Decomposition and nutrient release from mulch were studied using fine-mesh litterbags with five different leguminous species and the natural fallow vegetation as control. Samples from each treatment were analyzed for total C, N, P, K, Ca, Mg, lignin, cellulose content and soluble polyphenol at different sampling times over the course of one year. The decomposition rate constant varied with species and time. Weight loss from the decomposed litter bag material after 96 days was 30.1 % for Acacia angustissima, 32.7 % for Sclerolobium paniculatum, 33.9 % for Iinga edulis and the Fallow vegetation, 45.2 % for Acacia mangium and 63.6 % for Clitoria racemosa. Immobilization of N and P was observed in all studied treatments. Nitrogen mineralization was negatively correlated with phenol, C-to-N ratio, lignin + phenol/N ratio, and phenol/phosphorus ratios and with N content in the litterbag material. After 362 days of field incubation, an average (of all treatments), 3.3 % K, 32.2 % Ca and 22.4 % Mg remained in the mulch. Results confirm that low quality and high amount of organic C as mulch application are limiting for the quantity of energy available for microorganisms and increase the nutrient immobilization for biomass decomposition, which results in competition for nutrients with the crop plants.

Short and long-term effects of tillage systems and nutrient sources on soil physical properties of a Southern Brazilian Hapludox

Soil tillage promotes changes in soil structure. The magnitude of the changes varies with the nature of the soil, tillage system and soil water content and decreases over time after tillage. The objective of this study was to evaluate short-term (one year period) and long-term (nine year period) effects of soil tillage and nutrient sources on some physical properties of a very clayey Hapludox. Five tillage systems were evaluated: no-till (NT), chisel plow + one secondary disking (CP), primary + two (secondary) diskings (CT), CT with burning of crop residues (CTb), and CT with removal of crop residues from the field (CTr), in combination with five nutrient sources: control without nutrient application (C); mineral fertilizers, according to technical recommendations for each crop (MF); 5 Mg ha-1 yr-1 of poultry litter (wetmatter) (PL); 60 m³ ha-1 yr-1 of cattle slurry (CS) and; 40 m³ ha-1 yr-1 of swine slurry (SS). Bulk density (BD), total porosity (TP), and parameters related to the water retention curve (macroporosity, mesoporosity and microporosity) were determined after nine years and at five sampling dates during the tenth year of the experiment. Soil physical properties were tillage and time-dependent. Tilled treatments increased total porosity and macroporosity, and reduced bulk density in the surface layer (0.00-0.05 m), but this effect decreased over time after tillage operations due to natural soil reconsolidation, since no external stress was applied in this period. Changes in pore size distribution were more pronounced in larger and medium pore diameter classes. The bulk density was greatest in intermediate layers in all tillage treatments (0.05-0.10 and 0.12-0.17 m) and decreased down to the deepest layer (0.27-0.32 m), indicating a more compacted layer around 0.05-0.20 m. Nutrient sources did not significantly affect soil physical and hydraulic properties studied.

Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil

The ability of a soil to keep its structure under the erosive action of water is usually high in natural conditions and decreases under frequent and intensive cultivation. The effect of five tillage systems (NT = no-till; CP = chisel plowing and one secondary disking; CT = primary and two secondary distings; CTb = CT with crop residue burning; and CTr = CT with removal of crop residues from the field), combined with five nutrient sources (C = control, no nutrient application; MF = mineral fertilizers according to technical recommendations for each crop; PL = 5 Mg ha-1 y-1 fresh matter of poultry litter; CM = 60 m³ ha-1 y-1 slurry cattle manure; and SM = 40 m³ ha-1 y-1 slurry swine manure) on wet-aggregate stability was determined after nine years (four sampled soil layers) and on five sampling dates in the 10th year (two sampled soil layers) of the experiment. The size distribution of the air-dried aggregates was strongly affected by soil bulk density, and greater values of geometric mean diameter (GMD AD) found in some soil tillage or layer may be partly due to the higher compaction degree. After nine years, the GMD AD on the surface was greater in NT and CP compared to conventional tillage systems (CT, CTb and CTr), due to the higher organic matter content, as well as less soil mobilization. Aggregate stability in water, on the other hand, was affected by the low variation in previous gravimetric moisture of aggregates, which contributed to a high coefficient of variation of this attribute. The geometric mean diameter of water-stable aggregates (GMD WS) was highest in the 0.00-0.05 m layer in the NT system, in the layers 0.05-0.10 and 0.12-0.17 m in the CT, and values were intermediate in CP. The stability index (SI) in the surface layers was greater in treatments where crop residues were kept in the field (NT, CP and CT), which is associated with soil organic matter content. No differences were found in the layer 0.27-0.32 m. The effect of nutrient sources on GMD AD and GMD WS was small and did not affect SI.

Cilengitide combined with standard treatment for patients with newly diagnosed glioblastoma with methylated MGMT promoter (CENTRIC EORTC 26071-22072 study): a multicentre, randomised, open-label, phase 3 trial.

BACKGROUND: Cilengitide is a selective αvβ3 and αvβ5 integrin inhibitor. Data from phase 2 trials suggest that it has antitumour activity as a single agent in recurrent glioblastoma and in combination with standard temozolomide chemoradiotherapy in newly diagnosed glioblastoma (particularly in tumours with methylated MGMT promoter). We aimed to assess cilengitide combined with temozolomide chemoradiotherapy in patients with newly diagnosed glioblastoma with methylated MGMT promoter. METHODS: In this multicentre, open-label, phase 3 study, we investigated the efficacy of cilengitide in patients from 146 study sites in 25 countries. Eligible patients (newly diagnosed, histologically proven supratentorial glioblastoma, methylated MGMT promoter, and age ≥18 years) were stratified for prognostic Radiation Therapy Oncology Group recursive partitioning analysis class and geographic region and centrally randomised in a 1:1 ratio with interactive voice response system to receive temozolomide chemoradiotherapy with cilengitide 2000 mg intravenously twice weekly (cilengitide group) or temozolomide chemoradiotherapy alone (control group). Patients and investigators were unmasked to treatment allocation. Maintenance temozolomide was given for up to six cycles, and cilengitide was given for up to 18 months or until disease progression or unacceptable toxic effects. The primary endpoint was overall survival. We analysed survival outcomes by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00689221. FINDINGS: Overall, 3471 patients were screened. Of these patients, 3060 had tumour MGMT status tested; 926 patients had a methylated MGMT promoter, and 545 were randomly assigned to the cilengitide (n=272) or control groups (n=273) between Oct 31, 2008, and May 12, 2011. Median overall survival was 26·3 months (95% CI 23·8-28·8) in the cilengitide group and 26·3 months (23·9-34·7) in the control group (hazard ratio 1·02, 95% CI 0·81-1·29, p=0·86). None of the predefined clinical subgroups showed a benefit from cilengitide. We noted no overall additional toxic effects with cilengitide treatment. The most commonly reported adverse events of grade 3 or worse in the safety population were lymphopenia (31 [12%] in the cilengitide group vs 26 [10%] in the control group), thrombocytopenia (28 [11%] vs 46 [18%]), neutropenia (19 [7%] vs 24 [9%]), leucopenia (18 [7%] vs 20 [8%]), and convulsion (14 [5%] vs 15 [6%]). INTERPRETATION: The addition of cilengitide to temozolomide chemoradiotherapy did not improve outcomes; cilengitide will not be further developed as an anticancer drug. Nevertheless, integrins remain a potential treatment target for glioblastoma. FUNDING: Merck KGaA, Darmstadt, Germany.

Nutrient supply by mass flow and diffusion to maize plants in response to soil aggregate size and water potential

Nutrients are basically transported to the roots by mass flow and diffusion. The aim of this study was to quantify the contribution of these two mechanisms to the acquisition of macronutrients (N, P, K, Ca, Mg, and S) and cationic micronutrients (Fe, Mn, Zn, and Cu) by maize plants as well as xylem exudate volume and composition in response to soil aggregate size and water availability. The experiment was conducted in a greenhouse with samples of an Oxisol, from under two management systems: a region of natural savanna-like vegetation (Cerradão, CER) and continuous maize under conventional management for over 30 years (CCM). The treatments were arranged in a factorial [2 x (1 + 2) x 2] design, with two management systems (CER and CCM), (1 + 2) soil sifted through a 4 mm sieve and two aggregate classes (< 0.5 mm and 0.5 - 4.0 mm) and two soil matric potentials (-40 and -10 kPa). These were evaluated in a randomized block design with four replications. The experiment was conducted for 70 days after sowing. The influence of soil aggregate size and water potential on the nutrient transport mechanisms was highest in soil samples with higher nutrient concentrations in solution, in the CER system; diffusion became more relevant when water availability was higher and in aggregates < 0.5 mm. The volume of xylem exudate collected from maize plants increased with the decrease in aggregate size and the increased availability of soil water in the CER system. The highest Ca and Mg concentrations in the xylem exudate of plants grown on samples from the CER system were related to the high concentrations of these nutrients in the soil solution of this management system.