Soil Carbon and Nitrogen Dynamics After Pasture Installation in the Amazon Region

The objective of this paper is to present the soil carbon (C) and nitrogen (N) dynamics in a chronosequence made of a forest and pastures of different ages established in a Oxisol in the Western Brazilian Amazon Basin. The results of soil Carbon and Nitrogen stocks and gases fluxes were discussed. Stable 13C isotopic technique was used to calculate for a determinate age of pasture installation, the proportion of soil C remaining from the forest system and the proportion of soil C introduced by the grasses of the pasture system. The C lost from the original pool under the forest is 1.0 to 1.6 kg C m-2 concentrated during the first 5 years as pasture, and that the C fixed by the pasture (net fixation) is 1.7 to 2.3 kg C m-2 for the total period of 35 years. We agree with the assumption that cattle ranching would never be a profit-making venture as long as only the revenue from the sale of cattle is taken into account. But, now a days, the notions of taxes or refunds for C sequestration and land rehabilitation turn the management of areas that have already been converted to pasture a strategy for C sequestration

The Chemokine CCL2 Mediates the Seizure-enhancing Effects of Systemic Inflammation

Epilepsy is a chronic disorder characterized by spontaneous recurrent seizures. Brain inflammation is increasingly recognized as a critical factor for seizure precipitation, but the molecular mediators of such proconvulsant effects are only partly understood. The chemokine CCL2 is one of the most elevated inflammatory mediators in patients with pharmacoresistent epilepsy, but its contribution to seizure generation remains unexplored. Here, we show, for the first time, a crucial role for CCL2 and its receptor CCR2 in seizure control. We imposed a systemic inflammatory challenge via lipopolysaccharide (LPS) administration in mice with mesial temporal lobe epilepsy. We found that LPS dramatically increased seizure frequency and upregulated the expression of many inflammatory proteins, including CCL2. To test the proconvulsant role of CCL2, we administered systemically either a CCL2 transcription inhibitor (bindarit) or a selective antagonist of the CCR2 receptor (RS102895). We found that interference with CCL2 signaling potently suppressed LPS-induced seizures. Intracerebral administration of anti-CCL2 antibodies also abrogated LPS-mediated seizure enhancement in chronically epileptic animals. Our results reveal that CCL2 is a key mediator in the molecular pathways that link peripheral inflammation with neuronal hyperexcitability

Modelling Grass Productivity in the Brazilian Amazon

The Amazon Basin covers an area of 7 million km2, and the central part is almost entirely located within Brazilian territory. This region has the highest rates of deforestation in the world, and the total area deforested now exceeds 600,000 km2. Cattle pasture represents the largest single use (about 70%) of this once-forested land in most of the Brazilian Basin, with an estimated area of 20 million hectares. Our main objective was to simulate grass productivity in different forest to pasture chronosequences within the Brazilian Amazon

Structural alterations in the seminiferous tubules of rats treated with immunosuppressor tacrolimus

<p>Abstract</p> <p>Background</p> <p>Tacrolimus (FK-506) is an immunosuppressant that binds to a specific immunophilin, resulting in the suppression of the cellular immune response during transplant rejection. Except for some alterations in the spermatozoa, testicular morphological alterations have not been described in rats treated with tacrolimus. In the present study, we purpose to evaluate if the treatment with tacrolimus at long term of follow-up interferes in the integrity of the seminiferous tubules.</p> <p>Methods</p> <p>Rats aging 42-day-old received daily subcutaneous injections of 1 mg/kg/day of tacrolimus during 30 (T-30) and 60 (T-60) days; the rats from control groups (C-30 and C-60) received saline solution. The left testes were fixed in 4% formaldehyde and embedded in glycol methacrylate for morphological and morphometric analyses while right testes were fixed in Bouin's liquid and embedded in paraffin for detection of cell death by the TUNEL method. The epithelial and total tubular areas as well as the stages of the seminiferous epithelium and the number of spermatocytes, spermatids and Sertoli cells (SC) per tubule were obtained.</p> <p>Results</p> <p>In the treated groups, seminiferous tubules irregularly outlined showed disarranged cellular layers and loss of germ cells probably due to cell death, which was revealed by TUNEL method. In addition to germ cells, structural alterations in the SC and folding of the peritubular tissue were usually observed. The morphometric results revealed significant decrease in the number of SC, spermatocytes, spermatids and significant reduction in the epithelial and total tubular areas.</p> <p>Conclusion</p> <p>Tacrolimus induces significant histopathological disorders in the seminiferous tubules, resulting in spermatogenic damage and reduction in the number of Sertoli cells. A careful evaluation of the peritubular components will be necessary to clarify if these alterations are related to the effect of FK-506 on the peritubular tissue.</p

Alterações na matéria orgânica e nas características químicas de um Podzol hidromórfico sob pastagens cultivadas no Pantanal Sul-Mato-Grossense.

Estudou-se uma cronosseqüência de introdução de pastagens cultivadas em áreas com 10 e 20 anos de implantação, tendo uma área de Cerrado intacto como referência. Coletaram-se amostras até 40cm de profundidade ao longo de dois transectos, para cálculo dos estoques de C e N e determinações químicas. Também abriram-se trincheiras e coletaram-se amostras de solo até 1m de profundidade, para estudo das variações nos conteúdos de C e N no perfil. Após 10 anos de cultivo, o solo apresentou aumento no teor de bases trocáveis e na capacidade de troca catiônica, e diminuição da acidez. Entretanto, após 20 anos, os teores de bases trocáveis e a capacidade de troca catiônica diminuíram e a acidez aumentou, indicando tendência do sistema de retornar ao equilíbrio antigo. O fósforo apresentou diminuição nos teores em função do cultivo, porém, após 20 anos de cultivo os seus teores ainda eram satisfatórios. Observaram-se redução de 28% no conteúdo de C na camada de 0-40cm na área sob pastagem de 20 anos e alteração na proporção relativa das frações húmicas. No Cerrado intacto e na pastagem de 20 anos predominou a fração ácido fúlvico; sob pastagem de 10 anos, humina. Não se observou diferença significativa nos conteúdos de nitrogênio entre as áreas estudadas.bitstream/item/37423/1/BP29.pd