RESUMO
An edible Mushroom-Nafion modified glassy carbon electrode (M2N5-GCE) was prepared using a homogeneous mixture varying the concentrations of these, in addition to the origin of the mushroom (Shiitake, Lentinula edodes, M1 and Abrantes, Agariscus bisporus, M2) and applied to the As(III) determination by anodic stripping voltammetry. After choosing the optimal conditions in the preparation of the electrode, the second stage was to study the effects of various parameters such as supporting electrolyte, pH, accumulation potential, and time (Eacc, tacc). The optimum experimental conditions chosen were Britton Robinson buffer 0.01 mol L-1 pH:4.6; Eacc: -1.0 and tacc: 60 s obtaining a signal of oxidation of As(0) to As(III) about 0.08 V. Peak current was proportional to arsenic concentration over the 19.6-117.6 µg L-1 range, with a 3σ detection limit of 13.4 µg L-1. The method was validated using As(III) spiked tap water from the laboratory with satisfactory results (RE:3.0 %). Finally, the method was applied to the determination of As(III) in water samples from the Loa River (Northern Chile) in the presence of As(V) in a concentration >20 times higher (RE: 2.3 %).
Assuntos
Agaricales , Arsênio , Carbono , Eletrodos , Polímeros de Fluorcarboneto , Polímeros de Fluorcarboneto/química , Carbono/química , Arsênio/análise , Arsênio/química , Agaricales/química , Técnicas Eletroquímicas/métodos , Limite de Detecção , Concentração de Íons de Hidrogênio , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , EletroquímicaRESUMO
Microglia serve key functions in the central nervous system (CNS), participating in the establishment and regulation of synapses and the neuronal network, and regulating activity-dependent plastic changes. As the neuroimmune system, they respond to endogenous and exogenous signals to protect the CNS. In aging, one of the main changes is the establishment of inflamm-aging, a mild chronic inflammation that reduces microglial response to stressors. Neuroinflammation depends mainly on the increased activation of microglia. Microglia over-activation may result in a reduced capacity for performing normal functions related to migration, clearance, and the adoption of an anti-inflammatory state, contributing to an increased susceptibility for neurodegeneration. Oxidative stress contributes both to aging and to the progression of neurodegenerative diseases. Increased production of reactive oxygen species (ROS) and neuroinflammation associated with age- and disease-dependent mechanisms affect synaptic activity and neurotransmission, leading to cognitive dysfunction. Astrocytes prevent microglial cell cytotoxicity by mechanisms mediated by transforming growth factor ß1 (TGFß1). However, TGFß1-Smad3 pathway is impaired in aging, and the age-related impairment of TGFß signaling can reduce protective activation while facilitating cytotoxic activation of microglia. A critical analysis on the effect of aging microglia on neuronal function is relevant for the understanding of age-related changes on neuronal function. Here, we present evidence in the context of the "microglial dysregulation hypothesis", which leads to the reduction of the protective functions and increased cytotoxicity of microglia, to discuss the mechanisms involved in neurodegenerative changes and Alzheimer's disease.