Effet des systèmes de semis direct sous couverture végétale (SCV) sur le stockage de carbone et la marcofaune d'un sol ferrallitique (Cerrados, Brésil)

Les sols représentent un compartiment important de carbone (environ 1500 Gt), équivalent à trois fois la quantité stockée dans la biomasse terrestre et deux fois la quantité stockée dans l'atmosphère. Toute modification d'utilisation ou de gestion des terres entraîne généralement des variations dans les stocks de carbone (C) du sol. Ces modifications affectent aussi la macrofaune du sol (densité, biomasse, diversité) qui affecte elle-même la dynamique du C du sol. Les systèmes de semis direct sous couverture végétale (SCV), sans travail du sol et avec deux cultures par an, ont été largement adoptés dans les Cerrados (région centrale du Brésil) au cours des 10 dernières années. Ils ont remplacé les monocultures traditionnelles de soja avec jachère, sous travail du sol conventionnel (CT). L'objectif de cette étude est d'examiner comment les pratiques SCV affectent la dynamique du C et la macrofaune du sol (Rio Verde, Etat de Goias). Les stocks de C et la macrofaune d'un Sol ferrallitique argileux ont été étudiés, en mode synchronique, dans sept parcelles: une savane arborée de Cerrado (CER), un système conventionnel CT de 25 ans après défrichement de la savane arborée, cinq parcelles en SCV âgées de 1, 5, 8, 11 et 13 ans derrière cultures en systèmes CT depuis 24, 20, 17, 14 et 12 années. Chaque parcelle est donc cultivée depuis 25 ans. On constate que le taux moyen annuel de stockage du C est compris, selon le mode de calcul, entre 1,3 et 1,6 MgC ha-1, ce qui est dans la gamme des valeurs observées pour les SCV dans différentes zones du Brésil (0,4 à 1,7 MgC ha-1 an-1). Comparée à la savane arborée, la macrofaune du sol dans les systèmes cultivés a été très modifiée. Dans la parcelle CT, la densité, la biomasse et la biodiversité sont faibles et nettement inférieures aux valeurs relevées pour les parcelles CER et SCV. Avec l'âge croissant des SCV, la densité de la macrofaune augmente jusqu'à 8 ans puis diminue ensuite tandis que la biomasse augmente continuellement en raison d'une forte croissance de celle des larves de Coléoptères Scarabeidae. Ces modifications de densités et biomasses de macrofaune sont discutées en relation avec la dynamique du C du sol (décomposition, minéralisation et protection physique)

Bioquímica plasmática de jundiás alimentados com dietas contendo farelos vegetais submetidos a tratamento para remoção de fatores antinutricionais.

O objetivo deste trabalho foi avaliar a bioquímica plasmática de jundiás alimentados com dietas contendo farelos vegetais submetidos ou não a tratamento para remoção de fatores antinutricionais.Organizado por: Sílvio Ricardo Maurano; AQUACIÊNCIA 2012

Agrominerais como fontes de fósforo e potássio para a cultura do milheto.

A elevada demanda pelas plantas e conseqüente consumo de fertilizantes fosfatados e potássicos ocasionam a dependência brasileira sempre crescente da importação de fertilizantes, e alertam para a necessidade do uso de fontes alternativas de nutrientes. Objetivando avaliar o efeito de cinco rochas potássicas e uma rocha fosfática na produção de matéria seca do milheto foi conduzido um experimento em casa de vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras (UFLA). Foram utilizados dois solos (textura argilosa e textura arenosa) e os tratamentos consistiram de: tratamento completo, com (T1) e sem calagem (T2), completo sem cálcio (Ca) e magnésio (Mg) (T3), testemunha absoluta (T4), tratamentos com cinco rochas potássicas (com e sem calagem) e tratamento com rocha fosfática com e sem calagem (T5 a T16). Nos tratamentos com calagem, utilizou-se calcário dolomítico, visando elevar a saturação por bases para 55%. As doses de rochas foram ecomendadas baseadas na aplicação de 10 ton ha-1. A semeadura do milheto foi realizada após o período de incubação da mistura solo + calcário + rochas (20 dias) mantendo-se 15 plantas por vaso. O delineamento experimental foi inteiramente casualizado, com 4 repetições. Para os dois solos, os tratamentos T1, T2 e T3 apresentaram maior produção de matéria seca da parte aérea, sendo que no solo argiloso, o tratamento com rocha fosfática com e sem calagem foi superior aos demais tratamentos com rochas

4-aminopyridyl-based lead compounds targeting CYP51 prevent spontaneous parasite relapse in a chronic model and improve cardiac pathology in an acute model of Trypanosoma cruzi infection.

BackgroundChagas disease, caused by the protozoan Trypanosoma cruzi, is the leading cause of heart failure in Latin America. The clinical treatment of Chagas disease is limited to two 60 year-old drugs, nifurtimox and benznidazole, that have variable efficacy against different strains of the parasite and may lead to severe side effects. CYP51 is an enzyme in the sterol biosynthesis pathway that has been exploited for the development of therapeutics for fungal and parasitic infections. In a target-based drug discovery program guided by x-ray crystallography, we identified the 4-aminopyridyl-based series of CYP51 inhibitors as being efficacious versus T.cruzi in vitro; two of the most potent leads, 9 and 12, have now been evaluated for toxicity and efficacy in mice.Methodology/principal findingsBoth acute and chronic animal models infected with wild type or transgenic T. cruzi strains were evaluated. There was no evidence of toxicity in the 28-day dosing study of uninfected animals, as judged by the monitoring of multiple serum and histological parameters. In two acute models of Chagas disease, 9 and 12 drastically reduced parasitemia, increased survival of mice, and prevented liver and heart injury. None of the compounds produced long term sterile cure. In the less severe acute model using the transgenic CL-Brenner strain of T.cruzi, parasitemia relapsed upon drug withdrawal. In the chronic model, parasitemia fell to a background level and, as evidenced by the bioluminescence detection of T. cruzi expressing the red-shifted luciferase marker, mice remained negative for 4 weeks after drug withdrawal. Two immunosuppression cycles with cyclophosphamide were required to re-activate the parasites. Although no sterile cure was achieved, the suppression of parasitemia in acutely infected mice resulted in drastically reduced inflammation in the heart.Conclusions/significanceThe positive outcomes achieved in the absence of sterile cure suggest that the target product profile in anti-Chagasic drug discovery should be revised in favor of safe re-administration of the medication during the lifespan of a Chagas disease patient. A medication that reduces parasite burden may halt or slow progression of cardiomyopathy and therefore improve both life expectancy and quality of life

Blocking Zika virus vertical transmission.

The outbreak of the Zika virus (ZIKV) has been associated with increased incidence of congenital malformations. Although recent efforts have focused on vaccine development, treatments for infected individuals are needed urgently. Sofosbuvir (SOF), an FDA-approved nucleotide analog inhibitor of the Hepatitis C (HCV) RNA-dependent RNA polymerase (RdRp) was recently shown to be protective against ZIKV both in vitro and in vivo. Here, we show that SOF protected human neural progenitor cells (NPC) and 3D neurospheres from ZIKV infection-mediated cell death and importantly restored the antiviral immune response in NPCs. In vivo, SOF treatment post-infection (p.i.) decreased viral burden in an immunodeficient mouse model. Finally, we show for the first time that acute SOF treatment of pregnant dams p.i. was well-tolerated and prevented vertical transmission of the virus to the fetus. Taken together, our data confirmed SOF-mediated sparing of human neural cell types from ZIKV-mediated cell death in vitro and reduced viral burden in vivo in animal models of chronic infection and vertical transmission, strengthening the growing body of evidence for SOF anti-ZIKV activity

O trabalho da representação da memória social

Este artigo objetiva a analisar os bens culturais não tombados, através dos conceitos da memória social e idéias do patrimônio cultural, como silêncios das classes subalternas pela história oficial dominante no Brasil para construção de identidades

Carbon and Nitrogen Stocks in Integrated Crop Livestock

Soil organic matter (SOM) is recognized as an important characteristic of sustainable agricultural systems in the tropics and temperate regions. It is considered an integrated characteristic of physical, chemical and biological soil conditions and has been used as a soil quality index in different land uses and management practices (Lal 2011). Environmental, social, and financial imbalances have occurred, requiring producers to become more efficient. A system of intercropping grain crops with forages can provide enough forage in the dry season to maintain nutritional quality of livestock and even promote weight gain (Castro Filho et al. 1991). An integrated crop-livestock system (ICLS) that includes a crop phase and a pasture phase in rotation has strong potential for sustainable beef and grain crop production (Salton et al. 2011). Perennial pastures can contribute to soil C sequestration. Several studies have shown significant soil organic C accumulation with well-managed grazing of pastures (Maia et al. 2009; Salton et al. 2011). However, there are few studies that compare the efficiency of different grasses to maintain productivity and promote an increase in soil organic C and stocks. We hypothesized that an ICLS with maize cultivated under no-tillage in rotation with grazed pasture (Urochloa P. Beauv. spp. (syn. Brachiaria (Trin.) Griseb. spp.) would result in accumulation of soil organic C and N compared with continuously grazed, degraded pasture or with conventionally tilled monoculture production of maize. Our objective was to evaluate the stocks of soil organic C and N under alternative land uses from the prevailing degraded pasture condition in Sao Paulo state of Brazil

Produtividade e características morfoanatômicas de cultivares de Urochloa brizantha em sistemas silvipastoris.

O objetivo deste trabalho foi avaliar a produtividade e aspectos morfoanatômicos de forrageiras da espécie Urochloa brizantha cv. Marandu, Xaraés e Piatã cultivadas em sistemas silvipastoris com diferentes densidades arbóreas

Enantioselective inhibition of the SARS-CoV-2 main protease with rhenium(i) picolinic acid complexes

Infections of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have triggered a global pandemic with millions of deaths worldwide. Herein, the synthesis of functionalized Re(i) tricarbonyl complexes as inhibitors of the SARS-CoV-2 main protease, also referred to as the 3-chymotrypsin-like protease (3CL(pro)), is presented. The metal complexes were found to inhibit the activity of the enzyme with IC50 values in the low micromolar range. Mass spectrometry revealed that the metal complexes formed a coordinate covalent bond with the enzyme. Chiral separation of the enantiomers of the lead compound showed that one enantiomer was significantly more active than the other, consistent with specific binding and much like that observed for conventional organic small molecule inhibitors and druglike compounds. Evaluation of the lead compound against SARS-CoV-2 in a cell-based infection assay confirmed enantiospecific inhibition against the virus. This study represents a significant advancement in the use of metal complexes as coordinate covalent inhibitors of enzymes, as well as a novel starting point for the development of novel SARS-CoV-2 inhibitors