Efeitos da escarificação na qualidade física de um latossolo vermelho distroférrico após treze anos de semeadura direta Effects of chiseling on physical quality of a dystroferric red latosol after thirteen years of no-tillage

O objetivo deste trabalho foi avaliar as alterações na qualidade física de um Latossolo Vermelho distroférrico provocadas pela escarificação, após 13 anos de semeadura direta. O experimento constituiu-se de dois tratamentos: escarificação do solo a 0,30 m de profundidade (SDE) e testemunha mantendo a semeadura direta (SD). Amostras de solo, com estrutura não deformada, foram coletadas nas profundidades de 0-0,15 m e 0,15-0,30 m, a partir das quais foram determinados a curva de retenção de água, a curva de resistência do solo à penetração, a densidade do solo e o "Intervalo Ótimo de Tensão da Água no Solo" (IOP). Os resultados mostraram que, na profundidade de 0-0,15 m, a escarificação promoveu modificações na porosidade do solo, mantendo condições adequadas de aeração em tensões matriciais menores do que 0,01 MPa. Por outro lado, no solo escarificado, constatou-se a maior ocorrência de limitações pela resistência do solo à penetração em tensões menores do que 1,5 MPa. Para a camada de 0,15-0,30 m, no tratamento SDE, a resistência do solo à penetração foi o limite superior do IOP. Os resultados deste estudo sugerem que, neste solo e sob esta condição de manejo, não é necessária a escarificação.<br>The objective of this study was to evaluate alterations in the physical soil quality of a Dystroferric Red Latosol (Typic Haplorthox) caused by chiseling, after thirteen years of no-tillage. The experiment consisted of two management systems: soil chiseling down to a 0.30 m depth (NTC) and no-tillage (NT). Undisturbed soil samples were collected at depths of 0-0.15 m and 0.15-0.30 m, and the soil water retention curve, the soil resistance to penetration curve, the soil bulk density, and the "Least Limiting Water Potential" (LLWP) were determined. The results showed that the chiseling caused modifications in soil porosity in the 0-0.15 m layer, maintaining appropriate aeration conditions in water matric potentials under 0.01 MPa. On the other hand, the strongest limitations by soil penetration resistance in matric potentials under 1.5 MPa were verified in the NTC soil management. In the 0.15-0.30 m soil layer under the NTC treatment, the soil penetration resistance was the upper limit of the LLWP. The results of the study indicate that under the present management condition, chiseling is not necessary in this soil

The effect of repeated physical exercise on hippocampus and brain cortex in stressed rats

Sensitivity of target cells to glucocorticoids is regulated by the expression of intracellular glucocorticoid receptor (GR), which mediates the effects of glucocorticoids. The level of GR and of its nuclear transporter protein 70 (Hsp70) were followed in hippocampus and brain cortex of adult Wistar rat males exposed to acute (immobilization, cold) and chronic (social isolation, isolation, and 15 min daily swimming) stress or their combinations. Changes in plasma levels of adenocorticotropic hormone and corticosterone were also studied. A significant decrease in cytosol GR and Hsp70 was observed after acute stress. Opposite to that, chronic stress led to negligible changes in both cytosol GR and Hsp70 levels. Isolation, as chronic psychosocial stressor, caused reduced responsiveness to novel acute stressors, judged by the cytosol GR and Hsp70 levels. This was not observed if chronic isolation was combined with 15 min daily swimming prior to acute exposure to immobilization. The data suggest that repeated physical exercise may, at least in some cases, diminish detrimental effects of chronic social isolation on limbic-hypothalamic-pituitary-adrenocortical axis, as judged by the levels of GR and Hsp70 in the Wistar rat brain.Cell Signaling World 2006 Conference, Jan 25-28, 2006, Luxembourg, Luxembour