Effective and High-Throughput Analytical Methodology for the Determination of Lead and Cadmium in Water Samples by Disposable Pipette Extraction Coupled with High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (HR-CS GF AAS)

A new procedure for the preconcentration of trace amounts of free Pb and Cd by disposable pipette extraction (DPX) is proposed herein. Recycled cork is used as a biosorbent and the procedure is completely free of organic solvents. The cork was reduced to a powder and characterized by scanning electron microscopy. Several parameters that influence the preconcentration of Pb and Cd with DPX-cork, such as the sample pH, number of extraction cycles, biosorbent mass, and percentage of acid in the desorption step, were studied. The tolerance of DPX-cork with respect to 10 potential interfering ions was also evaluated. Coupled with the high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) technique, the sample preparation method allowed the analytical limits required for quality control (according to the permitted limits established by legislation) to be obtained. The limits of detection for the extraction of a 3.5-mL water sample were 200?ng L^?1 for Pb and 100?ng L^?1 for Cd. The relative standard deviations were around 7.5% for Pb and 8.0% for Cd. The optimized method was successfully applied to the determination of Cd and Pb in two certified reference materials (water and wastewater) and five water samples (collected from a mangrove, a creek, and the sea).     

Photoprotective and Antigenotoxic Effects of the Flavonoids Apigenin,Naringenin and Pinocembrin

This work evaluated the photoprotective and antigenotoxic effects against ultraviolet B (UVB) radiation of flavonoid compounds apigenin, naringenin and pinocembrin. The photoprotective efficacy of these compounds was estimated using in vitro photoprotection indices, and the antigenotoxicity against UVB radiation was evaluated using the SOS chromotest and an enzymatic (proteinase K/T4 endonuclease V enzyme) comet assay in UV‐treated Escherichia coli and human (HEK‐293) cells, respectively. Naringenin and pinocembrin showed maximum UV‐absorption peak in UVC and UVB zones, while apigenin showed UV‐absorption capability from UVC to UVA range. These compounds acted as UV filters reducing UV‐induced genotoxicity, both in bacteria and in human cells. The enzymatic comet assay resulted highly sensitive for detection of UVB‐induced DNA damage in HEK‐293 cells. In this work, the photoprotective potential of these flavonoids was widely discussed.     

Antifungal activity of Annona coriacea Mart. ethanol extracts against the aetiological agents of cryptococcosis

Cryptococcosis is an opportunistic disease with a worldwide distribution. This disease is caused by fungi of the genus Cryptococcus, and its treatment is limited to several antifungals. In this study, the antifungal, cytotoxic and mutagenic properties of ethanol extracts from the bark and leaves of Annona coriacea were evaluated against the standard Cryptococcus species and clinical yeast specimens. Both extracts of A. coriacea showed inhibitory activity of 1.5 mg/mL for all of the yeasts tested. The number of viable cells at the lowest tested concentration was 0.187 mg/mL. The extracts that were tested showed inhibitory activity and reduced the fungal growth of the Cryptococcus gattii species and Cryptococcus neoformans species complexes, suggesting that this plant may be an effective alternative treatment for cryptococcosis.     

Prospective study of a Bothrops jararacussu venom batch (Bj2015) – phospholipase A2 activity,immunogenicity, neurotoxicity,and myotoxicity parameters

Bothrops jararacussu venom’s (Bj2015) batch was biomonitored quarterly for one year to assess phospholipase A₂ (PLA₂) activity, immunogenicity, neurotoxicity, and myotoxicity. In silico models were applied to evaluate losses using decay model and recoveries by predictive trend analysis. Mice were immunized with Bj2015. Antibodies were detected by double-immunodiffusion and total protein and albumin were measured. Neuromuscular blockade-induced by 40 μg mL^?1 venom solution was carried out using mouse nerve phrenic-diaphragm preparation. Resulting muscles were submitted to light microscopy to evaluate the myotoxicity. PLA₂ activity of 0.1 mg mL^?1 Bj2015 was measured using 4-nitro-3-(octanoyloxy)benzoic acid as substrate. Over time, greater losses occurred in neurotoxicity than PLA₂, but not in myotoxicity and immunogenicity. Concluding, the neurotoxicity decrease can be related to enzymatic losses, including PLA₂. Depending on the purpose of use, the collected venom responds on a long time, avoiding unnecessary new collections, improving life quality of animals in captivity and increasing their longevity.     

Sensitization to Drug Treatment in Precursor B-Cell Acute Lymphoblastic Leukemia Is Not Achieved by Stromal NF-κB Inhibition of Cell Adhesion but by Stromal PKC-Dependent Inhibition of ABC Transporters Activity

Cell adhesion to stromal support and the associated intracellular signaling are central to drug resistance, therefore blocking both has been effective in increasing drug sensitization in leukemia. The stromal Ser/Thr protein kinase C (PKC) has been found to be important for conferring protection to leukemic cells. We aimed at elucidating the intracellular signals connected to cell adhesion and to stromal PKC. We found that NF-κB and Akt were up-regulated in mesenchymal stem cells (MSC) after binding of B-cell acute lymphoblastic leukemia (B-ALL) cells. Nevertheless, Akt inhibition did not induce B-ALL cell detachment. In spite of a clear activation of the NF-κB signaling pathway after B-ALL cell binding (up-regulation NF-κB1/2, and down-regulation of the IKBε and IKBα inhibitors) and an important reduction in cell adhesion after NF-κB inhibition, sensitization to the drug treatment was not observed. This was opposite to the PKC inhibitors Enzastaurin and HKPS, a novel chimeric peptide inhibitor, that were able to increase sensitization to dexamethasone, methotrexate, and vincristine. PLCγ1, Erk1/2, and CREB appear to be related to PKC signaling and PKC effect on drug sensitization since they were contra-regulated by HKPS when compared to dexamethasone-treated cells. Additionally, PKC inhibition by HKPS, but not by Enzastaurin, in MSC reduced the activity of three ABC transporters in leukemic cells treated with dexamethasone, a new indirect mechanism to increase sensitization to drug treatment in B-ALL cells. Our results show the validity of targeting the functional characteristic acquired and modulated during cell-to-cell interactions occurring in the leukemic niche.     

PLLA Based Composites with α-Tricalcium Phosphate and a PLLA-PEO Diblock Copolymer

Hybrid composites consisting of poly(L -lactide), PLLA, or blends of PLLA with a PLLA-poly(ethylene oxide) diblock copolymer (15–30 wt%), COP, as a biodegradable polymeric matrix and of bioactive α-tricalcium phosphate, α-TCP, microparticles as dispersed phase (25–40 wt-%) were prepared by melt extrusion and their thermal, mechanical and degradation behaviour was investigated. SEM analysis of surfaces broken in liquid N₂ showed a good dispersion of α-TCP in the polymer matrix. A lowering of the glass transition temperature of the polymer matrix and enhanced crystallization rates of PLLA, both from the melt and from the glassy state, were observed in the presence of COP. Ternary PLLA/COP/α-TCP composites containing about 10 wt-% of COP and 25–40 wt-% of α-TCP showed improved compressive strength and deformation at yield as compared to pure PLLA. Degradation experiments revealed that in simulated body fluid the presence of α-TCP particles promoted the formation of inorganic deposits of a poor crystalline apatitic phase on composite surfaces as compact sferoids.     

Stereoselective synthesis and conformational analysis of aromatic C‐thionucleosides

Tetrahydrothiophene derivatives 2a–2d , which are useful intermediates in the synthesis of C‐thionucleosides, were obtained by a tandem strategy that involves the base‐catalyzed conjugate addition of ethyl 2‐mercaptoacetate to trans‐cinnamaldehyde followed by cyclization. The solvent and the nature of the amine used as Lewis base influence the stereo‐ selectivity of the reaction. The reduction of each isolated derivative 2a–2d was performed with LiAlH₄ to afford C‐thionucleosides 3a–3d . The configuration and conformation of each diastereomer 2a–2d and 3a–3d was assigned by means of the analysis of vicinal proton–proton coupling constants. The X‐ray structure of 2d, 3a , and 3b confirmed the configuration assigned to each isomeric tetrahydrothiophenes. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:289–298, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20205     

Selenite Downregulates STAT3 Expression and Provokes Lymphocytosis in the Liver of Chronically Exposed Syrian Golden Hamsters

Arsenic is considered a worldwide pollutant that can be present in drinking water. Arsenic exposure is associated with various diseases, including cancer. Antioxidants as selenite and α-tocopherol-succinate have been shown to modulate arsenic toxic effects. Since changes in STAT3 and PSMD10 gene expression have been associated with carcinogenesis, the aim of this study was to evaluate the effect of arsenic exposure and co-treatments with selenite or α-tocopherol-succinate on the expression of these genes, in the livers of chronically exposed Syrian golden hamsters. Animals were divided into six groups: (i) control, (ii) chronically treated with 100 ppm arsenic, (iii) treated with 6 ppm α-tocopherol-succinate (α-TOS), (iv) treated with 8.5 ppm selenite, (v) treated with arsenic + α-TOS, and (vi) treated with arsenic + selenite. Urine samples and livers were collected after 20 weeks of continuous exposure. The urine samples were analyzed for arsenic species by atomic absorption spectrophotometry, and real-time RT-qPCR analysis was performed for gene expression evaluation. A reduction in STAT3 expression was observed in the selenite-treated group. No differences in PSMD10 expression were found among groups. Histopathological analysis revealed hepatic lymphocytosis in selenite-treated animals. As a conclusion, long-term exposure to arsenic does not significantly alter the expression of STAT3 and PSMD10 oncogenes in the livers of hamsters; however, selenite down-regulates STAT3 expression and provokes lymphocytosis.     

Threshold-based Quasi-static Brittle Damage Evolution

We introduce models for static and quasi-static damage in elastic materials, based on a strain threshold, and then investigate the relationship between these threshold models and the energy-based models introduced in Francfort and Marigo (Eur J Mech A Solids 12:149–189, 1993) and Francfort and Garroni (Ration Mech Anal 182(1):125–152, 2006). A somewhat surprising result is that, while classical solutions for the energy models are also threshold solutions, this is shown not to be the case for nonclassical solutions, that is, solutions with microstructure. A new and arguably more physical definition of solutions with microstructure for the energy-based model is then given, in which the energy minimality property is satisfied by sequences of sets that generate the effective elastic tensors, rather than by the tensors themselves. We prove existence for this energy-based problem, and show that these solutions are also threshold solutions. A by-product of this analysis is that all local minimizers, in both the classical setting and for the new microstructure definition, are also global minimizers.     

Stress relaxation behavior of PMMA/PS polymer blends

In this work, the stress relaxation behavior of PMMA/PS blends, with or without random copolymer addition, submitted to step shear strain experiments in the linear and nonlinear regime was studied. The effect of blend composition (ranging from 10 to 30 wt.% of dispersed phase), viscosity ratio (ranging from 0.1 to 7.5), and random copolymer addition (for concentrations up to 8 wt.% with respect to the dispersed phase) was evaluated and correlated to the evolution of the morphology of the blends. All blends presented three relaxation stages: a first fast relaxation which was attributed to the relaxation of the pure phases, a second one which was characterized by the presence of a plateau, and a third fast one. The relaxation was shown to be faster for less extended and smaller droplets and to be influenced by coalescence for blends with a dispersed phase concentration larger than 20 wt.%. The relaxation of the blend was strongly influenced by the matrix viscosity. The addition of random copolymer resulted in a slower relaxation of the droplets.