Abstract

High levels of arsenic are found in many parts of the world and more than 100 million people may have been exposed to it. There is growing evidence to indicate that arsenic has a deleterious effect on the auditory system. This paper provides the general information of arsenic and its ototoxic effects.

Abstract

The upper Malwathu Oya is a seasonal river. The main livelihood of people living in the immediate vicinity of the river is paddy cultivation, and chronic kidney disease is reported among them. Farmers utilize different types of agricultural chemicals in their fields expecting bumper harvests. Several agricultural chemicals have been reported to contain toxic trace elements in Sri Lanka. Therefore, arsenic and cadmium might end up in the river water. The presence of these trace elements in the river water and sediments can result in their bioaccumulation in fish tissues. The main purpose of this study was to investigate the presence of two trace elements in water and sediments, as well as in fish tissues (gills, kidney, liver and muscle) of three food fish species, Etroplus suratensis, Anabas testudineus and Channa striata during cultivating and non-cultivating seasons of the year. Further, the level of bioaccumulation of two trace elements in fish tissues in relation to the contamination level of water and sediments was assessed. Data were gathered for 43 months. Arsenic and cadmium concentration in water showed a significant (P < 0.05) seasonal variation. Generally, the two trace elements in the river water were highest during the cultivating seasons than in other seasons. In all species, both trace elements in the gills highly depended on the concentration in the water. In all species, two trace elements in water and sediment did not significantly affect the levels in muscle tissue. Therefore, the trace element levels in the edible parts of these three fish were well below the maximum permissible levels of international institutions.

Abstract

Millions of people are exposed to arsenic through their drinking water and food, but the mechanisms by which it impacts embryonic development are not well understood. Arsenic exposure during embryogenesis is associated with neurodevelopmental effects, reduced weight gain, and altered locomotor activity, and in vitro data indicates that arsenic exposure inhibits stem cell differentiation. This study investigated whether arsenic disrupted the Wnt3a signaling pathway, critical in the formation of myotubes and neurons, during the differentiation in P19 mouse embryonic stem cells. Cells were exposed to 0, 0.1, or 0.5 μM arsenite, with or without exogenous Wnt3a, for up to 9 days of differentiation. Arsenic exposure alone inhibits the differentiation of stem cells into neurons and skeletal myotubes, and reduces the expression of both β-catenin and GSK3β mRNA to ∼55% of control levels. Co-culture of the arsenic-exposed cells with exogenous Wnt3a rescues the morphological phenotype, but does not alter transcript, protein, or phosphorylation status of GSK3β or β-catenin. However, arsenic exposure maintains high levels of Hes5 and decreases the expression of MASH1 by 2.2-fold, which are anti- and pro-myogenic and neurogenic genes, respectively, in the Notch signaling pathway. While rescue with exogenous Wnt3a reduced Hes5 levels, MASH1 levels stay repressed. Thus, while Wnt3a can partially rescue the inhibition of differentiation from arsenic, it does so by also modulating Notch target genes rather than only working through the canonical Wnt signaling pathway. These results indicate that arsenic alters the interplay between multiple signaling pathways, leading to reduced stem cell differentiation.

Abstract

The levels of six chemical elements (mercury, arsenic, lead, cadmium, zinc and copper) were examined in two species of Pacific salmon, genus Oncorhynchus, pink salmon (O. gorbuscha ), and chum salmon (O. keta ) that were caught in the Kuril waters in July 2013. Concentrations of toxic elements (Hg, As, Pb, Cd) in both species were shown to be below the maximum concentration limits of these trace elements for seafood. The concentrations of these elements were compared between wild salmon and hatchery salmon of the Pacific and Atlantic oceans.