A method to reproduce pH and Eh environmental changes due to sediment resuspension.

During the last decades, metals have been released into coastal areas increasing the environmental and human health risks, however, resuspension events of trace metals polluted sediment could represent even more severe risks. Anoxic condition in the sediment is capable to stabilize the trace metals, due to the bonding with reduced anions. Although, the sediment resuspension can alter the potential redox and pH characteristics resulting in metals released from the water column. The climate change advance would impact directly on ocean chemistry, is expected the spatial increase of anoxic sites, mainly in coastal areas. Furthermore, it is mandatory and urgent to expand the knowledge over the process of sediment metals releasing in order to develop prediction and remediation tools for possible environmental impacts. This is a simple method of manipulating and simulating physicochemical alterations. The creation of microcosmos without oxygen allows the formation of a very reducible environment, common in coastal areas with low energy and high organic matter input. And further oxidation allows the assessment of the trace metals released to the water column and/or the new arrangement of these metals in different geochemical fractions. • The experimental procedure to assess trace metals mobility to potential redox and pH changes in sediment and water. • A method is suitable for a wild range of sediment characteristics.

A chemical status predictor. A methodology based on World-Wide sediment samples.

As a consequence of the limited resources of underdeveloped countries and the limited interest of the developed ones, the assessment of the chemical quality of entire water bodies around the world is a utopia in the near future. The methodology described here may serve as a first approach for the fast identification of water bodies that do not meet the good chemical status demanded by the European Water Framework Directive (WFD). It also allows estimating the natural background (or reference values of concentration) of the areas under study using a simple criterion. The starting point is the calculation the World-Wide Natural Background Levels (WWNBLs) and World-Wide Threshold Values (WWTVs), two indexes that depend on the concentration of seven elements present in sediments. These elements, As, Cd, Cr, Cu, Ni, Pb and Zn, have been selected taking into account the recommendations of the UNEP (United Nations Environment Programme) and USEPA (United States Environmental Protection Agency), that describe them as elements of concern with respect to environmental toxicity. The methodology has been exemplified in a case study that includes 134 sediment samples collected in 11 transitional water bodies from 7 different countries and 4 different continents. Six of the water bodies considered met the good chemical status demanded by the WFD. The rest of them exceeded the reference WWTVs, at least for one of the elements. The estuaries of the Nerbioi-Ibaizabal (Basque Country) and Cavado (Portugal), the sea inlet of Río San Pedro (Spain), the Sepetiba Bay (Brazil) and the Yucateco lagoon (Mexico) belong to that group.

Mercury speciation in sediments of a tropical coastal environment.

The speciation of mercury in tropical coastal areas, although scarcely studied, has presented an odd behaviour when compared with the results obtained in temperate environments. In this work, we measured the concentrations of mercury species (mercuric mercury, methyl-mercury and dimethyl-mercury) in the sediments of Sepetiba Bay (Brazil) and compared these with geochemical parameters. Twenty-eight sediment samples were extracted in an open microwave system and mercury speciation was carried out by ethylation, cryogenic focusing, gas chromatography and quartz furnace atomic absorption spectrometry. Fraction < 63 microm, organic carbon and total sulphur contents and redox potential were measured in order to outline the geochemical characteristics of the sediments. While mercuric mercury presented concentrations ranging between 22.65 and 134.61 ng g(-1), methyl-mercury concentrations ranged between < 2.0 and 4.4 ng g(-1). Only a few dimethyl-mercury concentrations were relatively high (up to 14.6 ng g(-1)). The results of mercuric mercury presented an unexpected positive correlation with sulphur contents showing that mercury is forming stable sulphide complexes, even under very reducing conditions. This would render mercury available for t he formation of methyl- or dimethyl-mercury that would be both fixed in the sediments and volatilised.

Chemical availability of mercury in stream sediments from the Almadén area, Spain.

The chemical speciation, fractionation and availability of mercury in sediments from a cinnabar mining area (Almadén, Spain) was studied with different extraction and analytical procedures, in order to determine the degree to which the ecosystem is harmed by this pollutant. Three total extraction procedures, a sequential extraction and the speciation of organo-mercury compounds were performed in nine sediment samples. In the study area, although concentrations of mercury can be extremely high (up to 1,000 mg kg(-1)), no organomercury compounds were detected (< 2 microg kg(-1) and the availability of this element seems restricted. One of the methods for total extraction presented considerably lower recovery in Almadén's sediments, yet the results were controlled with certified reference materials. This disagreement was attributed to the fact that the mercury is in a refractory form. Sequential extraction was able to show that most of the mercury is associated with sulfides (probably as metacinnabar) or in the residual refractory phase (probably as red cinnabar).

Molecular characterization of ROSIT, a renal osmotic stress-induced Na(+)-Cl(-)-organic solute cotransporter.

A gene family encoding many Na(+)- and Cl(-)-dependent organic solute cotransporters has recently been recognized. Among the cotransporters that have been characterized are those for neurotransmitters, amino acids, and organic osmolytes. Using polymerase chain reaction and mRNA derived from renal cortex, we isolated a new member of this gene family, ROSIT, a renal osmotic stress-induced transporter. The cDNA is 2,354 bp long with an open reading frame of 1,845 bp. The 615 deduced amino sequence shows ROSIT to be most clearly related to two orphan cDNAs of this family isolated from brain. Northern analysis showed the mRNA is normally expressed in renal cortex but not in brain, heart, colon, liver, stomach, or skeletal muscle. Moreover, hypernatremic rats displayed a marked increase in mRNA levels in renal cortex, renal outer medulla, and perhaps intestine. Heterologous expression of the cRNA in Xenopus laevis oocytes failed to reveal the function of this gene product when analyzed with isotope fluxes or electrophysiological measurements using a wide variety of organic solutes. Although its function remains unknown, ROSIT is likely to be involved in kidney reclamation of an organic osmolyte or osmolyte precursor required for adaptation to hypertonic stress.

Expression of GLUT-2 cDNA in human B lymphocytes: analysis of glucose transport using flow cytometry.

The molecular characterization of transport proteins is often limited by transient functional expression or the need for a simple method to select functional cDNA clones. We used a mammalian expression system to obtain long-term expression of GLUT-2, an isoform of glucose permease. Rat GLUT-2 cDNA was ligated into an EBV vector (pLPP) and transfected into B lymphocytes which lack GLUT-2. Northern and Western analyses confirmed expression of GLUT-2 protein in membranes of transfected cells. Two functional assays using flow cytometry were developed to distinguish GLUT-2 transfectants from control/pLPP transfectants. Uptake of NBD-glucosamine, a fluorescent analogue of glucose, was increased in GLUT-2 transfectants. In addition, when exposed to hypertonic glucose medium, GLUT-2 transfectants and control/pLPP transfectants exhibited a difference in forward-angle light scatter (FALS), an index of cell volume, indicating a difference in glucose permeability. Independent measurements of glucose uptake (isotopic) and cell volume (video microscopy) confirmed the flow cytometry observations. This expression system used in combination with flow cytometry is useful for studying the functional properties of glucose and other solute transporters.

Immediate early gene and HSP70 expression in hyperosmotic stress in MDCK cells.

The early genetic response to hyperosmotic stress remains to be elucidated in eukaryotes. We observed that hyperosmotic NaCl in Madin-Darby canine kidney cells increased levels of mRNA encoding the immediate early gene (IEG) transcription factors Egr-1 and c-fos at 2 h of treatment by two- and threefold, respectively. Sham treatment and hyperosmotic glycerol, and ineffective osmole, had no effect. Hyperosmotic NaCl, but not glycerol, also increased the mRNA level of the stress protein HSP70 by four- to fivefold at 2, 6, and 24 h. These changes occurred despite inhibition of total RNA transcription rate and DNA synthesis rate by NaCl. Neither NaCl nor glycerol treatment manifested significant cytotoxicity. NaCl, and to a lesser extent glycerol, suppressed protein synthesis, a phenomenon previously correlated with IEG superinduction. Therefore, hyperosmotic stimuli with different physiological effects result in differential expression of IEGs and the stress protein HSP70; induction of the former may govern the ensuing program of gene expression that culminates in the osmolyte response, while the latter may serve as a temporizing protective measure.