Concentrations of heavy metals (Cu, Zn, Cd, Pb and As) were measured in water, sediment and two fish species,
Sparus aurata and
Solea senegalensis, from the estuary of Tinto and Odiel rivers in ...Huelva (Spain), one of the most metallic polluted estuaries in Europe.
As a forward step to understand metal bioavailability and assess the potential impact on aquatic biota, a study of heavy metal speciation of sediments and water were achieved. High levels of total and dissolved Zn and Cu were found in water and high pollution of Zn, Pb, As and Cu were found in sediments. Availability of metals was established as following ranking: Cd
>
Zn
>
Cu
>
Pb in both water and sediment. In addition, the effect of this pollution was studied by evaluation of metal bioaccumulations and correlations obtained between metal levels in fractions of water and sediment and metal levels in fish tissues. High Cu and Zn levels were observed in liver tissue of both species, in according with higher total content and more available metals in water and sediment. Correlations among metal content in tissues and different fractions of metal in water for
S. aurata and sediment for
S. senegalensis were found.
The coupled transport of Cu(II), Cd(II) and Ni(II) ions through a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as carrier dissolved in toluene has been ...studied. Once the optimal conditions of extraction of each metal were established, a comparative study of the transport kinetics for these metals was performed by means of a kinetic model involving two consecutive irreversible first-order reactions. The kinetic parameters (apparent rate constants of the metal extraction and re-extraction reactions (k ₁, k ₂), the maximum reduced concentration of the metal in the liquid membrane ( graphic removed ), the time of the maximum value of R o ( t max) and the maximum entry and exit fluxes of the metal through the liquid membrane ( graphic removed and graphic removed ) of the extraction and stripping reactions were evaluated and results showed good agreement between experimental data and theoretical predictions. Complete transport through the membrane took place according to the following order: Cd(II)>Cu(II)>Ni(II), with similar kinetic parameters obtained for Cu(II) and Cd(III). The transport behaviour of Ni(II) was different to that of Cu(II) and Cd(III), probably due to the different stoichiometry of the nickel complex compared to those of the other metal ions and the different chemical conditions required for its formation. The influence of the sample salinity on the transport kinetics was studied. k ₁ values decreased slightly when the feed solution salinity was increased for Cu(II) and Ni(II), but not for Cd(II). Values of k ₂ were practically unaffected. The proposed BLM was applied to the preconcentration and separation of metal ions (prior to their determination) in water samples with different saline matrices (CRM, river water and seawater), and good agreement with the certified values was obtained.
The transfer and separation of Cu(II) ions across a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as the mobile carrier dissolved in toluene has been ...investigated and optimised. The system was applied to the preconcentration of copper from natural waters prior to analysis by flame atomic absorption spectroscopy. The flux of copper across the membrane has been studied, and characterised as a function of analytical variables such as the carrier concentration, volume of organic phase, pH of feed and strip receiving solutions, stirring rate and temperature of solutions. The preconcentration yield at optimum conditions was 100.54±0.94%, even with a high saline matrix (30
g
l
−1 NaCl), with good precision (1.49%). A preconcentration factor of approximately 18 times could be obtained. The detection limit of a blank sample was 0.24
μg
l
−1 of Cu.
The method was validated using a certified reference material (TMDA-62) and was applied successfully to the analysis of copper in two samples of seawater collected from the coast of Huelva (Spain). The relative errors were 2.42% for CRM and 0.48 and 3.66%, for seawaters (obtained between the results of the proposed and DPASV methods), respectively.
In this work, a bulk liquid membrane method has been applied for Ni enrichment and separation from natural waters. The carrier-mediated transport was accomplished by pyridine-2-acetaldehyde ...benzoylhydrazone dissolved in toluene as a complexing agent. The preconcentration was achieved through pH control of source and receiving solutions via a counterflow of protons. The main variables were optimized by using a modified simplex technique. High transport efficiencies (101.2 ± 1.8-99.7 ± 4.2%) were provided by the carrier for nickel ions in a receiving phase of 0.31 mol L-¹ nitric acid after 9-13 h depending on sample salinity. The precision of the method was 2.05% (without a saline matrix) and 4.04% (with 40 g L-¹ NaCl) at the 95% confidence level and the detection limit of the blank was 0.015 μg L-¹ Ni for detection by atomic absorption spectroscopy. The applicability of the method was tested on certified reference and real water samples with successful results, even for saline samples. The relative errors were -0.60% for certified reference materials and ranged from -0.39 to 2.90% and from 0.3 to 11.05% for real samples, obtained by comparison of inductively coupled plasma mass spectrometry and adsorptive cathodic stripping voltammetry measurements, respectively.
Hypothalamic astrocytes can respond to metabolic signals, such as leptin and insulin, to modulate adjacent neuronal circuits and systemic metabolism. Ghrelin regulates appetite, adiposity and glucose ...metabolism, but little is known regarding the response of astrocytes to this orexigenic hormone. We have used both in vivo and in vitro approaches to demonstrate that acylated ghrelin (acyl-ghrelin) rapidly stimulates glutamate transporter expression and glutamate uptake by astrocytes. Moreover, acyl-ghrelin rapidly reduces glucose transporter (GLUT) 2 levels and glucose uptake by these glial cells. Glutamine synthetase and lactate dehydrogenase decrease, while glycogen phosphorylase and lactate transporters increase in response to acyl-ghrelin, suggesting a change in glutamate and glucose metabolism, as well as glycogen storage by astrocytes. These effects are partially mediated through ghrelin receptor 1A (GHSR-1A) as astrocytes do not respond equally to desacyl-ghrelin, an isoform that does not activate GHSR-1A. Moreover, primary astrocyte cultures from GHSR-1A knock-out mice do not change glutamate transporter or GLUT2 levels in response to acyl-ghrelin. Our results indicate that acyl-ghrelin may mediate part of its metabolic actions through modulation of hypothalamic astrocytes and that this effect could involve astrocyte mediated changes in local glucose and glutamate metabolism that alter the signals/nutrients reaching neighboring neurons.
A global assessment of arsenic (As), nickel (Ni), cobalt (Co) and chromium (Cr) was performed in environmental samples from an important industrial bay. Different fractions of water, sediments and ...tissues from four species of fish were analysed. Samples were collected from selected sampling sites during four consecutive samplings in spring and autumn seasons, in order to evaluate concentrations and their possible correlations among the aquatic compartments. While a higher availability of Cr and Ni was found in water, Co and As were the most available elements in sediments. In fish, the liver was the tissue with the highest proportion of As and Co, and gills showed the highest concentrations of Ni and Cr. Significance differences were observed among sites showing the pollution sources. In sediments, high correlations were found between total Co content and the most available fractions. Total Ni content highly correlated with the oxidisable fraction, while Cr total content tightly correlated with the least available fractions. Quality guideline values for sediments were frequently exceeded. In sediments and biota, concentrations were slightly higher than in other ecosystems, indicating that maritime, industrial and urban activities are affecting this type of ecosystem with great anthropogenic influence.
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