Changes in glucose uptake rate and in the energy status of PC-12 cells acutely exposed to hexavalent chromium,an established human carcinogen

In the 1920s, Otto Warburg reported a striking metabolic shift in solid tumors: contrary to their normal counter parts, which exhibited a nearly pure respiratory metabolism, where cancer cells relied strongly on lactic fermentation for energy production, even in the presence of ample oxygen. This metabolic shift, later named the Warburg effect, is now viewed as a nearly universal cancer phenotype. To investigate whether it is operating in hexavalent chromium (Cr(VI))-induced carcinogenesis, PC-12 cells were exposed to low Cr(VI) concentrations and effects determined on the rates of glucose uptake, lactate production and oxygen consumption, critical indicators of the type of energy metabolism adopted by the cells. Further, the influence on the cells’ energy charge, an important parameter in the evaluation of the cellular physiological state was assessed. In the presence of ample oxygen, concentration-dependent, statistically significant decreases in the energy charge were detected, which were accompanied by an increased glucose uptake rate. This enhanced uptake may constitute the first step in a compensatory mechanism aimed at counteracting the decrease in energy charge. Although these changes may be too small to exert an impact in the cellular functions, they may provide insight into the initial steps of Cr(VI)-induced carcinogenesis.     

Biogeochemistry and cycling of zinc and copper in a dyked seasonally flooded savanna

There is very little information on the cycling of heavy metals in natural savannas. Venezuelan flooded savannas are characterised by acid soils with redox conditions which might induce Zn and Cu solubilisation. In those flooded savannas a network of small dykes has been constructed to control floods. The biomass accretion after dyking and the abundance of clay particles in the vertisols, dominant in the overflow plains, might be responsible for an increase in nutrient uptake and immobilisation. Due to the redox and pH conditions prevailing during flooding, some questions arise on the fate of the heavy metals. Are they significantly lost as soluble and particulate forms, which in turn, can induce a potential risk of microelement deficiency? Or, on the contrary, are heavy metal inputs in precipitation waters retained somewhere in the terrestrial pools of the watershed allowing for an adequate micronutrient economy? By using input-output budgets, which consider the total atmospheric input and total output in stream runoff (soluble and particulate) for zinc and copper we concluded that in Mantecal flooded savannas, a net accumulation of micronutrient in soils is actually occurring through organic and inorganic complexes, a process that is counterbalanced by the losses of particulates through erosion.     

Application of the electrochemical speciation of heavy metals in tracking groundwater pollution

The application of the electrochemical speciation of heavy metals in tracking groundwater is presented. Three fractions interchangeable, associated to the organic materials and associated to the matter in suspension of the metals Zn, Cd, Pb and Cu by means of the anodic stripping voltammetry were determined. The parameters of the determination were: electrodeposition potential ‐1.2 V, time of deaerating with nitrogen 300 s, time of the electrolysis 90 s (with stirring) and the rest time 40 s. The core of this work was to determine the validity of this scheme of electrochemical speciation in the pursuit of the follow‐up of groundwater pollution caused by heavy metals after the breakdown of the mining raft at the River Guadiamar Basin (Andalusia, Spain).     

Green fuel production: processes applied to microalgae

The continuous increase in world energy demand will lead to an energy crisis due to the limited availability of fossil fuels. Furthermore, the use of this energetic resource is responsible for the accumulation of greenhouse gases in atmosphere that is associated with several negative effects on environment. Therefore, it is worth to search for different energy supplies that are renewable and environmentally friendly—carbon neutral fuel. Microalgae are photosynthetic microorganisms that can achieve high oil contents. This oil is suitable for producing biodiesel; thus, microalgae are considered a promising sustainable energetic resource that can reduce the dependence on fossil fuel. Biodiesel production from microalgae includes several steps, such as cell cultivation and harvesting, oil extraction and biodiesel synthesis. Although several attempts have been made to improve biodiesel yields from microalgae, further studies are required to improve biodiesel production rates and to reduce the associated costs. This review shows the recent developments on biodiesel production from microalgae, emphasizing two process concepts: (1) indirect route, in which, after a facultative cell wall disruption method, microalgal oil is recovered in an appropriate solvent and then converted into biodiesel through transesterification and (2) direct route, in which biodiesel is produced directly from the harvested biomass. High biodiesel yields are obtained when both routes are preceded by a cell wall disruption method. In the indirect route, it is possible to apply three different types of solvents to recover microalgal oil. Although there are several concerns about the application of organic solvents, the most promising and cost-effective alternative for lipid recovery is n-hexane. Comparing direct and indirect routes, this study demonstrates that although further studies are required to optimize biodiesel production from microalgae, the available information proposes that the direct route is the most efficient.     

Phytoremediation of bauxite-derived red mud by giant reed

In 2010 the pond dam of an aluminium manufacturing plant in Hungary broke and flooded many towns with toxic red mud. At least 10 people were dead and over 150 hospitalized. Bauxite residue is often referred as red mud due to the colour of the bauxite ore and iron oxides. Red mud is separated during the refining process. The production of 1 t of alumina generally results in the creation of 1–1.5 t of red mud. Red mud is toxic for the environment due to high alkalinity, salinity and trace metals. Here, we used the plant Arundo donax L. (giant reed) to uptake trace metals and decrease salinity and pH of red mud. We measured plant toxicity, trace metal availability and biomass production. Results show a 25 % decrease in electrical conductivity of red mud and a 6 % decrease in electrical conductivity of mud-polluted soil. Giant reed cultivation decreases available Cd, Pb, Co, Ni and Fe. Biomass of giant reed seedlings in red mud and mud/control soil mixture was increased by 40.4 and 47.2 %, respectively, comparing with control soil. Our findings show that giant reed is promising to decontaminate soils contaminated by red mud.     

The surgeonfish, Acanthurus bahianus, has crossed the Amazon–Orinoco outflow barrier

Dispersal varies among species according to different biological and environmental factors. It is known that there is strong genetic division between the Ocean Surgeonfish (Acanthurus tractus) and the Barber Surgeonfish (Acanthurus bahianus) in the Caribbean and southern Atlantic biogeographic provinces with relation to the Amazon–Orinoco outflows. We analyzed cytb gene sequence diversity from 149 individuals collected at five localities around Cuba between October 2006 and February 2010. As expected, most individuals had haplotypes identical or closely related to those previously reported for the Caribbean. However, south Atlantic lineage haplotypes were also found in all surveyed localities with frequencies around 5 %. This finding suggests that A. bahianus has dispersed in recent times across the Amazon–Orinoco barrier, probably because environmental perturbations have aided dispersal.     

The interspecific relationship between prevalence of blood parasites and sexual traits in birds when considering recent methodological advancements

Hamilton and Zuk (Science 218:384–387, 1982) supported their influential hypothesis of parasite-mediated sexual selection based on a positive interspecific correlation between the prevalence of blood parasites and the expression of male displays in birds. However, subsequent studies provided mixed support for this relationship after considering several confounding factors. Here, we revisit this fundamental prediction by refining the analyses through implementation of recent methodological advancements. First, we distinguish between prevalence data obtained through microscopic and molecular tools, as PCR-based detection methods may be more sensitive for detecting infection. Second, we use quantitative estimates of both acoustic and visual signals of males, in which color measurements adopt the perspective of avian vision. Third, applying modern phylogenetic comparative approaches, we correct for phylogenetic inertia as well as heterogeneity in sampling effort. Fourth, we distinguish between prevalence transition states, as we compare species with and without evidence of infection and also monitor changes in parasite prevalence only in species in which blood parasites are detected. We show that given the considerable variation among populations, the repeatability of prevalence at the within-species level is modest. We failed to detect a strong interspecific relationship between the prevalence of blood parasites and sexual traits. However, we found that an evolutionary increase from zero to non-zero prevalence is likely to be accompanied by an increase in trait expression in males, but further increase from non-zero prevalence to a higher level of infection tends to be associated with a reduced degree of trait elaboration. Our results provide some support to the Hamilton and Zuk hypothesis, but the relationship between blood parasites and male displays varies among traits depending on degree of infection.     

Automated method for the determination of total arsenic and selenium in natural and drinking water by HG-AAS

A multicommutated flow system was designed and evaluated for the determination of total arsenic and selenium by Hydride Generation Atomic Absorption Spectrometry (HG-AAS). It was applied to the determination of arsenic and selenium in samples of natural and drinking water. Detection limits were 0.46 and 0.08 μg l⁻¹ for arsenic and selenium, respectively; sampling frequency was 120 samples h⁻¹ for arsenic and 160 samples h⁻¹ for selenium. Linear ranges found were 1.54–10 μg l⁻¹ (R = 0.999) for arsenic and 0.27–27 μg l⁻¹ (R = 0.999) for selenium. Accuracy was evaluated by spiking various water samples and using a reference material. Recoveries were in the range 95–116%. Analytical precision (s _r (%), n = 10) was 6% for both elements. Compared with the Standard Methods, APHA, 3114B manual method, the system consumes at least 10 times less sample per determination, and the quantities of acid and reducing agent used are significantly lower with a reduction in the generation of pollutants and waste. As an additional advantage, the system is very fast, efficient and environmentally friendly for monitoring total arsenic and selenium levels in waters.     

Plant diversity partitioning in Mediterranean croplands: effects of farming intensity, field edge, and landscape context

Farmland biodiversity is affected by factors acting at various spatial scales. However, most studies to date have focused on the field or farm scales that only account for local (alpha) diversity, and these may underestimate the contribution of other diversity components (beta diversity) to total (gamma) farmland diversity. In this work, we aimed to identify the most suitable management options and the scale at which they should be implemented to maximize benefits for diversity. We used a multi-scale additive partitioning approach, with data on plant diversity from 640 plots in 32 cereal crop fields from three agricultural regions of central Spain that differed in landscape configuration. We analyzed the relative contribution to overall plant diversity of different diversity components at various spatial scales and how these diversity components responded to a set of local (application of agri-environment schemes [AES] and position within the field) and landscape (field size and landscape connectivity and composition) factors. Differences in species composition among regions and then among fields within regions contributed most to overall plant diversity. Positive edge effects were found on all diversity components at both the field- and regional scales, whereas application of AES benefited all diversity components only at the field scale. Landscape factors had strong influences on plant diversity, especially length of seminatural boundaries, which increased species richness at both the field and the regional scales. In addition, positive effects of percentage of nonproductive land-uses in the landscape were found on all diversity components at the regional scale. Results showed that components that contributed most to overall plant diversity were not benefited by current AES. We conclude that agri-environmental policies should incorporate and prioritize measures aimed at the maintenance of seminatural boundaries and patches of nonproductive habitats within agricultural landscapes, through landscape planning, cross-compliance, or high nature-value farmland programs. These options will help to conserve overall plant diversity at regional scales, as well as the spillover of plant species from such seminatural elements into crops, especially in Mediterranean areas that still harbor extensive farming and relatively complex landscapes.