Experiências de cataforese com suspensões da fracção argilosa do solo

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Nonlinear modeling of liming reaction and extractable base curves.

Modeling the response of soils to liming is important for understanding neutralization reactions and predicting lime residual effects. Models based on simple or quadratic polynomial equations are the most used due to their simplicity and ease of fitting; however, they fail to reproduce a realistic soil response to liming, indicating a decrease in pH as the lime dose is increased after reaching a maximum point. Thus, several nonlinear functions were tested and compared to polynomial models, using a dataset from a liming test conducted on a sandy clay loam soil in a farm. The best-fitting models for pH data were the Mitscherlich, three-parameter logistic, and MorganMercer-Flodin models. The best-fitting models for exchangeable Ca+2 + Mg+2 data were Skaggs et al., Gompertz, and Morgan- Mercer-Flodin. The use of the proposed T index, which ranks models based on their residual standard error and Akaike information criterion values, combined with constraints on extrapolation values, was useful for selecting models that are statistically robust and empirically coheren

Cholinergic Signaling Exerts Protective Effects in Models of Sympathetic Hyperactivity-Induced Cardiac Dysfunction

Cholinergic control of the heart is exerted by two distinct branches; the autonomic component represented by the parasympathetic nervous system, and the recently described non-neuronal cardiomyocyte cholinergic machinery. Previous evidence has shown that reduced cholinergic function leads to deleterious effects on the myocardium. Yet, whether conditions of increased cholinergic signaling can offset the pathological remodeling induced by sympathetic hyperactivity, and its consequences for these two cholinergic axes are unknown. Here, we investigated two models of sympathetic hyperactivity: i) the chronic beta-adrenergic receptor stimulation evoked by isoproterenol (ISO), and ii) the alpha(2A)/alpha(2C)-drenergic receptor knockout (KO) mice that lack pre-synaptic adrenergic receptors. In both models, cholinergic signaling was increased by administration of the cholinesterase inhibitor, pyridostigmine. First, we observed that isoproterenol produces an autonomic imbalance characterized by increased sympathetic and reduced parasympathetic tone. Under this condition transcripts for cholinergic proteins were upregulated in ventricular myocytes, indicating that non-neuronal cholinergic machinery is activated during adrenergic overdrive. Pyridostigmine treatment prevented the effects of ISO on autonomic function and on the ventricular cholinergic machinery, and inhibited cardiac remodeling. alpha(2A)/alpha(2C)-KO mice presented reduced ventricular contraction when compared to wild-type mice, and this dysfunction was also reversed by cholinesterase inhibition. Thus, the cardiac parasympathetic system and non-neuronal cardiomyocyte cholinergic machinery are modulated in opposite directions under conditions of increased sympathetic drive or ACh availability. Moreover, our data support the idea that pyridostigmine by restoring ACh availability is beneficial in heart disease

Succinate causes pathological cardiomyocyte hypertrophy through GPR91 activation

Background\ud Succinate is an intermediate of the citric acid cycle as well as an extracellular circulating molecule, whose receptor, G protein-coupled receptor-91 (GPR91), was recently identified and characterized in several tissues, including heart. Because some pathological conditions such as ischemia increase succinate blood levels, we investigated the role of this metabolite during a heart ischemic event, using human and rodent models.\ud \ud \ud Results\ud We found that succinate causes cardiac hypertrophy in a GPR91 dependent manner. GPR91 activation triggers the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), the expression of calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) and the translocation of histone deacetylase 5 (HDAC5) into the cytoplasm, which are hypertrophic-signaling events. Furthermore, we found that serum levels of succinate are increased in patients with cardiac hypertrophy associated with acute and chronic ischemic diseases.\ud \ud \ud Conclusions\ud These results show for the first time that succinate plays an important role in cardiomyocyte hypertrophy through GPR91 activation, and extend our understanding of how ischemia can induce hypertrophic cardiomyopathy.CAPESFAPEMIG (Pronex)INCT- Carbon NanotubesCNPqHHM

Influence of phosphorus-solubilizing microorganisms and phosphate amendments on pearl millet growth and nutrient use efficiency in different soils types.

Two greenhouse growth trials were performed to assess inoculation with phosphorus (P)-solubilizing microorganisms (PSM) in combination with alternative sources of phosphate in pearl millet (Pennisetum glaucum) cultivation: One using sandy soil and the other using clayey soil. The treatments comprised five P sources, with or without inoculation with PSM B119 (Bacillus megaterium) and B2084 (Bacillus subtilis) strains. Amendment of alternative sources (granulated, branned organomineral, and Bayovar rock) of P along with PSM inoculation produced more plant dry mass on sandy soil, which was not observed on clayey soil. Phosphorus use efficiency (PUE) did not differ between inoculated and non-inoculated treatments, and it was higher with the alternative P sources, compared to triple superphosphate (TSP) treatments. Available P content in the soil was higher with TSP, in sandy soil, and with PSM inoculation. Overall, acid and alkaline phosphatases and ?-glucosidase activity was higher in clayey soil, compared to sandy soil, which contains little organic matter; it was also higher with alternative P sources, compared to TSP, and in inoculation treatments, showing the potential of using PSM inoculation and alternative P sources to achieve higher sustainability and productivity in agriculture