The release of zinc and lead from mine tailings

Mining and processing of metal ores are important causes of soil and groundwater contamination in many regions worldwide. Metal contaminations are a serious risk for the environment and human health. The assessment of metal contaminations in the soil is therefore an important task. A common approach to assess the environmental risk emanating from inorganic contaminations to soil and groundwater is the use of batch or column leaching tests. In this regard, the suitability of leaching tests is a controversial issue. In the first part of this work the applicability and comparability of common leaching tests in the scope of groundwater risk assessment of inorganic contamination is reviewed and critically discussed. Soil water sampling methods (the suction cup method and centrifugation) are addressed as an alternative to leaching tests. Reasons for limitations of the comparability of leaching test results are exposed and recommendations are given for the expedient application of leaching tests for groundwater risk assessment. Leaching tests are usually carried out in open contact with the atmosphere disregarding possible changes of redox conditions. This can affect the original metal speciation and distribution, particularly when anoxic samples are investigated. The influence of sample storage on leaching test results of sulfide bearing anoxic material from a former flotation dump is investigated in a long-term study. Since the oxidation of the sulfide-bearing samples leads to a significant overestimation of metal release, a feasible modification for the conduction of common leaching tests for anoxic material is proposed, where oxidation is prevented efficiently. A comparison of leaching test results to soil water analyzes have shown that the modified saturation soil extraction (SSE) is found to be the only of the tested leaching procedures, which can be recommended for the assessment of current soil water concentrations at anoxic sites if direct investigation of the soil water is impossible due to technical reasons. The vertical distribution and speciation of Zn and Pb in the flotation residues as well as metal concentrations in soil water and plants were investigated to evaluate the environmental risk arising from this site due to the release of metals. The variations in pH and inorganic C content show an acidification of the topsoil with pH values down to 5.5 in the soil and a soil water pH of 6 in 1 m depth. This is due to the oxidation of sulfides and depletion in carbonates. In the anoxic subsoil pH conditions are still neutral and soil water collected with suction cups is in equilibrium with carbonate minerals. Results from extended x-ray absorption fine-structure (EXAFS) spectroscopy confirm that Zn is mainly bound in sphalerite in the subsoil and weathering reactions lead to a redistribution of Zn in the topsoil. A loss of 35% Zn and S from the topsoil compared to the parent material with 10 g/kg Zn has been observed. 13% of total Zn in the topsoil can be regarded as mobile or easily mobilizable according to sequential chemical extractions (SCE). Zn concentrations of 10 mg/L were found in the soil water, where pH is acidic. Electron supply and the buffer capacity of the soil were identified as main factors controlling Zn mobility and release to the groundwater. Variable Pb concentrations up to 30 µg/L were observed in the soil water. In contrast to Zn, Pb is enriched in the mobile fraction of the oxidized topsoil by a factor of 2 compared to the subsoil with 2 g/kg Pb. 80% of the cation exchange capacity in the topsoil is occupied by Pb. Therefore, plant uptake and bioavailability are of major concern. If the site is not prevented from proceeding acidification in the future, a significant release of Zn, S, and Pb to the groundwater has to be expected. Results from this study show that the assessment of metal release especially from sulfide bearing anoxic material requires an extensive comprehension of leaching mechanisms on the one hand and on weathering processes, which influence the speciation and the mobility of metals, on the other hand. Processes, which may change redox and pH conditions in the future, have to be addressed to enable sound decisions for soil and groundwater protection and remediation.

Inhibition of FcepsilonRI-dependent mediator release and calcium flux from human mast cells by sialic acid-binding immunoglobulin-like lectin 8 engagement

BACKGROUND: Sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of glycan-binding inhibitory receptors, and among them, Siglec-8 is selectively expressed on human eosinophils, basophils, and mast cells. On eosinophils, Siglec-8 engagement induces apoptosis, but its function on mast cells is unknown. OBJECTIVE: We sought to study the effect of Siglec-8 engagement on human mast cell survival and mediator release responses. METHODS: Human mast cells were generated from CD34+ precursors. Apoptosis was studied by using flow cytometry. Mast cell mediator release or human lung airway smooth muscle contraction was initiated by FcepsilonRI cross-linking with or without preincubation with Siglec-8 or control antibodies, and release of mediators was analyzed along with Ca++ flux. RBL-2H3 cells transfected with normal and mutated forms of Siglec-8 were used to study how Siglec-8 engagement alters mediator release. RESULTS: Siglec-8 engagement failed to induce human mast cell apoptosis. However, preincubation with Siglec-8 mAbs significantly (P < .05) inhibited FcepsilonRI-dependent histamine and prostaglandin D(2) release, Ca++ flux, and anti-IgE-evoked contractions of human bronchial rings. In contrast, release of IL-8 was not inhibited. Siglec-8 ligation was also shown to inhibit beta-hexosaminidase release and Ca++ flux triggered through FcepsilonRI in RBL-2H3 cells transfected with full-length human Siglec-8 but not in cells transfected with Siglec-8 containing a tyrosine to phenylalanine point mutation in the membrane-proximal immunoreceptor tyrosine-based inhibitory motif domain. CONCLUSION: These data represent the first reported inhibitory effects of Siglec engagement on human mast cells.

Catch Rates, Composition and Fish Size from Reefs Managed with Periodically-Harvested Closures

Periodically-harvested closures are commonly employed within co-management frameworks to help manage small-scale, multi-species fisheries in the Indo-Pacific. Despite their widespread use, the benefits of periodic harvesting strategies for multi-species fisheries have, to date, been largely untested. We examine catch and effort data from four periodically-harvested reef areas and 55 continuously-fished reefs in Solomon Islands. We test the hypothesis that fishing in periodically-harvested closures would yield: (a) higher catch rates, (b) proportionally more short lived, fast growing, sedentary taxa, and (c) larger finfish and invertebrates, compared to catches from reefs continuously open to fishing. Our study showed that catch rates were significantly higher from periodically-harvested closures for gleaning of invertebrates, but not for line and spear fishing. The family level composition of catches did not vary significantly between open reefs and periodically-harvested closures. Fish captured from periodically-harvested closures were slightly larger, but Trochus niloticus were significantly smaller than those from continuously open reefs. In one case of intense and prolonged harvesting, gleaning catch rates significantly declined, suggesting invertebrate stocks were substantially depleted in the early stages of the open period. Our study suggests periodically-harvested closures can have some short term benefits via increasing harvesting efficiency. However, we did not find evidence that the strategy had substantially benefited multi-species fin-fisheries.

Differential quantal release of histamine and 5-hydroxytryptamine from mast cells of vesicular monoamine transporter 2 knockout mice

The recent availability of mice lacking the neuronal form of the vesicular monoamine transporter 2 (VMAT2) affords the opportunity to study its roles in storage and release. Carbon fiber microelectrodes were used to measure individual secretory events of histamine and 5-hydroxytryptamine (5-HT) from VMAT2-expressing mast cells as a model system for quantal release. VMAT2 is indispensable for monoamine storage because mast cells from homozygous (VMAT2−/−) mice, while undergoing granule-cell fusion, do not release monoamines. Cells from heterozygous animals (VMAT2+/−) secrete lower amounts of monoamine per granule than cells from wild-type controls. Investigation of corelease of histamine and 5-HT from granules in VMAT2+/− cells revealed 5-HT quantal size was reduced more than that of histamine. Thus, although vesicular transport is the limiting factor determining quantal size of 5-HT and histamine release, intragranular association with the heparin matrix also plays a significant role.

Proteasome inhibition interferes with Gag polyprotein processing, release, and maturation of HIV-1 and HIV-2

Retrovirus assembly and maturation involve folding and transport of viral proteins to the virus assembly site followed by subsequent proteolytic cleavage of the Gag polyprotein within the nascent virion. We report that inhibiting proteasomes severely decreases the budding, maturation, and infectivity of HIV. Although processing of the Env glycoproteins is not changed, proteasome inhibitors inhibit processing of Gag polyprotein by the viral protease without affecting the activity of the HIV-1 viral protease itself, as demonstrated by in vitro processing of HIV-1 Gag polyprotein Pr55. Furthermore, this effect occurs independently of the virus release function of the HIV-1 accessory protein Vpu and is not limited to HIV-1, as proteasome inhibitors also reduce virus release and Gag processing of HIV-2. Electron microscopy analysis revealed ultrastructural changes in budding virions similar to mutants in the late assembly domain of p6gag, a C-terminal domain of Pr55 required for efficient virus maturation and release. Proteasome inhibition reduced the level of free ubiquitin in HIV-1-infected cells and prevented monoubiquitination of p6gag. Consistent with this, viruses with mutations in PR or p6gag were resistant to detrimental effects mediated by proteasome inhibitors. These results indicate the requirement for an active proteasome/ubiquitin system in release and maturation of infectious HIV particles and provide a potential pharmaceutical strategy for interfering with retrovirus replication.

Platelets modulate gastric ulcer healing: Role of endostatin and vascular endothelial growth factor release

Bleeding and delayed healing of ulcers are well recognized clinical problems associated with the use of aspirin and other nonsteroidal antiinflammatory drugs, which have been attributed to their antiaggregatory effects on platelets. We hypothesized that antiplatelet drugs might interfere with gastric ulcer healing by suppressing the release of growth factors, such as vascular endothelial growth factor (VEGF), from platelets. Gastric ulcers were induced in rats by serosal application of acetic acid. Daily oral treatment with vehicle, aspirin, or ticlopidine (an ADP receptor antagonist) was started 3 days later and continued for 1 week. Ulcer induction resulted in a significant increase in serum levels of VEGF and a significant decrease in serum levels of endostatin (an antiangiogenic factor). Although both aspirin and ticlopidine markedly suppressed platelet aggregation, only ticlopidine impaired gastric ulcer healing and angiogenesis as well as reversing the ulcer-associated changes in serum levels of VEGF and endostatin. The effects of ticlopidine on ulcer healing and angiogenesis were mimicked by immunodepletion of circulating platelets, and ticlopidine did not influence ulcer healing when given to thrombocytopenic rats. Incubation of human umbilical vein endothelial cells with serum from ticlopidine-treated rats significantly reduced proliferation and increased apoptosis, effects reversed by an antibody directed against endostatin. Ticlopidine treatment resulted in increased platelet endostatin content and release. These results demonstrate a previously unrecognized contribution of platelets to the regulation of gastric ulcer healing. Such effects likely are mediated through the release from platelets of endostatin and possibly VEGF. As shown with ticlopidine, drugs that influence gastric ulcer healing may do so in part through altering the ability of platelets to release growth factors.

An in vitro assay reveals essential protein components for the “catch” state of invertebrate smooth muscle

“Catch,” a state where some invertebrate muscles sustain high tension over long periods of time with little energy expenditure (low ATP hydrolysis rate) is similar to the “latch” state of vertebrate smooth muscles. Its induction and release involve Ca2+-dependent phosphatase and cAMP-dependent protein kinase, respectively. Molecular mechanisms for catch remain obscure. Here, we describe a quantitative microscopic in vitro assay reconstituting the catch state with proteins isolated from catch muscles. Thick filaments attached to glass coverslips and pretreated with ≈10−4 M free Ca2+ and soluble muscle proteins bound fluorescently labeled native thin filaments tightly in catch at ≈10−8 M free Ca2+ in the presence of MgATP. At ≈10−4 M free Ca2+, the thin filaments moved at ≈4 μm/s. Addition of cAMP and cAMP-dependent protein kinase at ≈10−8 M free Ca2+ caused their release. Rabbit skeletal muscle F-actin filaments completely reproduced the results obtained with native thin filaments. Binding forces >500 pN/μm between thick and F-actin filaments were measured by glass microneedles, and were sufficient to explain catch tension in vivo. Synthetic filaments of purified myosin and twitchin bound F-actin in catch, showing that other components of native thick filaments such as paramyosin and catchin are not essential. The binding between synthetic thick filaments and F-actin filaments depended on phosphorylation of twitchin but not of myosin. Cosedimentation experiments showed that twitchin did not bind directly to F-actin in catch. These results show that catch is a direct actomyosin interaction regulated by twitchin phosphorylation.

Comparison of hydrophilic and hydrophobic active molecules release from polymer-phospholipid complexes

Hypercoiling polymers can be suited for application to living systems because they are similar in structure to the protein-based lipid assemblies found at fluid interfaces within the body. This leads to a range of exciting possibilities, not only in membrane transport applications but also in biosensors, drug delivery and mechanistic studies of biological membrane function. This study is focused in the study of the stability and suitability of nanostructures made of a hypercoiling polymer for drug delivery applications. The polymer poly (styrene-maleic acid) (PSMA) was combined with the phospholipid dimyristoylphosphatidylcholine (DMPC) to form amphiphilic nanostructures. The stability and suitability of these polymer-phospholipid nanocarriers for hydrophobic and hydrophilic molecules load and release was analyzed by several techniques. It was found that several of the studied molecules had a substantial effect on the surface charge and stability of the nanocarrier. It was also demonstrated that two types of nanocarriers, chemically modified and unmodified, were able to control the release of the molecules, especially in the case of hydrophobic compounds. In addition, as the hydrophobicity increased the release slowed down. These clear nanocarriers have the potential to behave very favorably at interfaces such as the tear lipid film were transparency is a requirement, giving a new way of controlled drug release in the eye.

Comparative study of dexamethasone and vancomycin release behavior from stimuli-sensitive microgel aqueous dispersions

Stimuli-sensitive microgels of poly(N-isopropylacrylamide-co-acrylic acid) (designated as P(NIPAAm-co-AA)) were prepared through precipitation polymerization. Their capacity to load and release different drugs under different conditions, including physiological, in a controlled manner was analyzed. Two drugs were assayed and compared: dexamethasone and vancomycin. The prepared microgel particles show good thermosensitivity. In addition, the amount of cross-linker used in the preparation of the microgels does not greatly influence the drug-release capability of P(NIPAAm-co-AA)), but the amount of drug used to load the microgels did result in bigger amounts of drug released afterwards. These results imply potential application of prepared stimuli-sensitive microgel dispersions as drug-delivery systems and tissue engineering materials.

Standardized geo-referenced catch, fishing effort and length-frequency data for the Indian Ocean Bigeye Tuna, Thunnus obesus (1952-2014)

Geo-referenced catch and fishing effort data of the bigeye tuna fisheries in the Indian Ocean over 1952-2014 were analysed and standardized to facilitate population dynamics modelling studies. During this sixty-two years historical period of exploitation, many changes occurred both in the fishing techniques and the monitoring of activity. This study includes a series of processing steps used for standardization of spatial resolution, conversion and standardization of catch and effort units, raising of geo-referenced catch into nominal catch level, screening and correction of outliers, and detection of major catchability changes over long time series of fishing data, i.e., the Japanese longline fleet operating in the tropical Indian Ocean. A total of thirty fisheries were finally determined from longline, purse seine and other-gears data sets, from which 10 longline and four purse seine fisheries represented 96% of the whole historical catch. The geo-referenced records consists of catch, fishing effort and associated length frequency samples of all fisheries.

Development of nanostructured hydrogel for spatial and temporal controlled release of active compounds

L’utilisation de nanovecteurs pour la livraison contrôlée de principes actifs est un concept commun de nous jours. Les systèmes de livraison actuels présentent encore cependant des limites au niveau du taux de relargage des principes actifs ainsi que de la stabilité des transporteurs. Les systèmes composés à la fois de nanovecteurs (liposomes, microgels et nanogels) et d’hydrogels peuvent cependant permettre de résoudre ces problèmes. Dans cette étude, nous avons développé un système de livraison contrôlé se basant sur l’incorporation d’un nanovecteur dans une matrice hydrogel dans le but de combler les lacunes des systèmes se basant sur un vecteur uniquement. Une telle combinaison pourrait permettre un contrôle accru du relargage par stabilisation réciproque. Plus spécifiquement, nous avons développé un hydrogel structuré intégrant des liposomes, microgels et nanogels séparément chargés en principes actifs modèles potentiellement relargués de manière contrôlé. Ce contrôle a été obtenu par la modification de différents paramètres tels que la température ainsi que la composition et la concentration en nanovecteurs. Nous avons comparé la capacité de chargement et la cinétique de relargage de la sulforhodamine B et de la rhodamine 6G en utilisant des liposomes de DOPC et DPPC à différents ratios, des nanogels de chitosan/acide hyaluronique et des microgels de N-isopropylacrylamide (NIPAM) à différents ratios d’acide méthacrylique, incorporés dans un hydrogel modèle d’acrylamide. Les liposomes présentaient des capacités de chargement modérés avec un relargage prolongé sur plus de dix jours alors que les nanogels présentaient des capacités de chargement plus élevées mais une cinétique de relargage plus rapide avec un épuisement de la cargaison en deux jours. Comparativement, les microgels relarguaient complétement leur contenu en un jour. Malgré une cinétique de relargage plus rapide, les microgels ont démontré la possibilité de contrôler finement le chargement en principe actif. Ce contrôle peut être atteint par la modification des propriétés structurelles ou en changeant le milieu d’incubation, comme l’a montré la corrélation avec les isothermes de Langmuir. Chaque système développé a démontré un potentiel contrôle du taux de relargage, ce qui en fait des candidats pour des investigations futures.

Aquatic ecology monitoring: water quality, fish, fish catch, sanitation and disease vectors: monitoring No.9, 9th – 12th September 2011

The results reported on were from a monitoring survey No. 9 undertaken between 9th and 12th September 2011 during construction period of the Bujagali Hydropower Project (BHPP). Two pre-construction, baseline surveys in April 2000 and April 2006 were conducted and so far, during construction phase of the project, eight monitoring surveys have been undertaken i.e. in September 2007, April 2008, April 2009, October 2009, April 2010, September 2010, April 2011 and the present one, in September 2011. Since 2009 biannual monitoring surveys have been conducted at an upstream and a downstream transect of the BHPP with emphasis on the following aspects: water quality determinants biology and ecology of fishes and food webs fish stock and fish catch including economic aspects of catch and sanitation/vector studies (bilharzias and river blindness)in addition to the above mentioned studies, a soil pH survey was undertaken on 15th October 2011 in the area behind the reservoir whose filling started a week earlier. The findings of pH status in the catchment of the dam are also contained in this report.

Development of nanostructured hydrogel for spatial and temporal controlled release of active compounds

L’utilisation de nanovecteurs pour la livraison contrôlée de principes actifs est un concept commun de nous jours. Les systèmes de livraison actuels présentent encore cependant des limites au niveau du taux de relargage des principes actifs ainsi que de la stabilité des transporteurs. Les systèmes composés à la fois de nanovecteurs (liposomes, microgels et nanogels) et d’hydrogels peuvent cependant permettre de résoudre ces problèmes. Dans cette étude, nous avons développé un système de livraison contrôlé se basant sur l’incorporation d’un nanovecteur dans une matrice hydrogel dans le but de combler les lacunes des systèmes se basant sur un vecteur uniquement. Une telle combinaison pourrait permettre un contrôle accru du relargage par stabilisation réciproque. Plus spécifiquement, nous avons développé un hydrogel structuré intégrant des liposomes, microgels et nanogels séparément chargés en principes actifs modèles potentiellement relargués de manière contrôlé. Ce contrôle a été obtenu par la modification de différents paramètres tels que la température ainsi que la composition et la concentration en nanovecteurs. Nous avons comparé la capacité de chargement et la cinétique de relargage de la sulforhodamine B et de la rhodamine 6G en utilisant des liposomes de DOPC et DPPC à différents ratios, des nanogels de chitosan/acide hyaluronique et des microgels de N-isopropylacrylamide (NIPAM) à différents ratios d’acide méthacrylique, incorporés dans un hydrogel modèle d’acrylamide. Les liposomes présentaient des capacités de chargement modérés avec un relargage prolongé sur plus de dix jours alors que les nanogels présentaient des capacités de chargement plus élevées mais une cinétique de relargage plus rapide avec un épuisement de la cargaison en deux jours. Comparativement, les microgels relarguaient complétement leur contenu en un jour. Malgré une cinétique de relargage plus rapide, les microgels ont démontré la possibilité de contrôler finement le chargement en principe actif. Ce contrôle peut être atteint par la modification des propriétés structurelles ou en changeant le milieu d’incubation, comme l’a montré la corrélation avec les isothermes de Langmuir. Chaque système développé a démontré un potentiel contrôle du taux de relargage, ce qui en fait des candidats pour des investigations futures.

Clozapine Promotes Glycolysis And Myelin Lipid Synthesis In Cultured Oligodendrocytes.

Clozapine displays stronger systemic metabolic side effects than haloperidol and it has been hypothesized that therapeutic antipsychotic and adverse metabolic effects of these drugs are related. Considering that cerebral disconnectivity through oligodendrocyte dysfunction has been implicated in schizophrenia, it is important to determine the effect of these drugs on oligodendrocyte energy metabolism and myelin lipid production. Effects of clozapine and haloperidol on glucose and myelin lipid metabolism were evaluated and compared in cultured OLN-93 oligodendrocytes. First, glycolytic activity was assessed by measurement of extra- and intracellular glucose and lactate levels. Next, the expression of glucose (GLUT) and monocarboxylate (MCT) transporters was determined after 6 and 24 h. And finally mitochondrial respiration, acetyl-CoA carboxylase, free fatty acids, and expression of the myelin lipid galactocerebroside were analyzed. Both drugs altered oligodendrocyte glucose metabolism, but in opposite directions. Clozapine improved the glucose uptake, production and release of lactate, without altering GLUT and MCT. In contrast, haloperidol led to higher extracellular levels of glucose and lower levels of lactate, suggesting reduced glycolysis. Antipsychotics did not alter significantly the number of functionally intact mitochondria, but clozapine enhanced the efficacy of oxidative phosphorylation and expression of galactocerebroside. Our findings support the superior impact of clozapine on white matter integrity in schizophrenia as previously observed, suggesting that this drug improves the energy supply and myelin lipid synthesis in oligodendrocytes. Characterizing the underlying signal transduction pathways may pave the way for novel oligodendrocyte-directed schizophrenia therapies.

Effect of nitric oxide inhibitor and donor substances on the infammatory process caused by endodontic irrigants

Nitric oxide (NO) has been considered a key molecule in infammation. OBJECTIVE: The aim of this study was to evaluate the effect of treatment with L-NAME and sodium nitroprussiate, substances that inhibit and release NO, respectively, on tissue tolerance to endodontic irrigants. MATERIAL AND METHODS: The vital dye exudation method was used in a rat subcutaneous tissue model. Injections of 2% Evans blue were administered intravenously into the dorsal penial vein of 14 male rats (200-300 g). The NO inhibitor and donor substances were injected into the subcutaneous tissue in the dorsal region, forming two groups of animals: G1 was inoculated with L-NAME and G2 with sodium nitroprussiate. Both groups received injections of the test endodontic irrigants: acetic acid, 15% citric acid, 17% EDTA-T and saline (control). After 30 min, analysis of the extravasated dye was performed by light absorption spectrophotometry (620 nm). RESULTS: There was statistically signifcant difference (p<0.05) between groups 1 and 2 for all irrigants. L-NAME produced a less intense infammatory reaction and nitroprussiate intensifed this process. CONCLUSIONS: Independently of the administration of NO inhibitors and donors, EDTA-T produced the highest irritating potential in vital tissue among the tested irrigating solutions.