Determination of prostaglandin profiles in lipopolysaccharide‐challenged guinea pig spleen

We previously reported that splenic extract from lipopolysaccharide (LPS)‐challenged guinea pigs inhibits the exaggerated febrile response of splenectomized guinea pigs, suggesting that the spleen generates an inhibitory factor. Earlier results indicate that the factor is a lipid. In an effort to identify this factor, lipid fractions, isolated from splenic extracts of control and LPS‐challenged guinea pigs, were analyzed with emphasis on identifying and quantifying prostanoids, which according to current knowledge are the likely bioactive factors. Prostaglandins have been extensively implicated in central and peripheral thermoregulation, and thus these lipids were targeted for characterization in the spleen. Analysis was done on the splenic extracts using solid‐phase extraction, analytical and preparative thin‐layer chromatography (TLC) and high‐performance liquid chromatography–mass spectrometry (HPLC‐MS/MS). Four prostaglandins (PGs, 6‐keto‐PGF_1α, PGF_2α, PGE₂ and PGD₂) were identified and quantified. Our data shows that these PG levels are doubled in LPS‐treated guinea pig spleen compared with the control group. The methods used in this investigation to characterize PG in the spleen offer significant advantages over immunoassays previously used to identify and quantify PG in the spleen and other biological tissues. These methods will be utilized in further research needed to definitively characterize the role of splenic‐derived PG in modulation of the febrile response induced by LPS. Copyright © 2012 John Wiley & Sons, Ltd.     

Estimation of useful yields for electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS)

Useful yield for electrospray droplet impact/secondary ion mass spectrometry was estimated. The mixtures of C₆₀/rhodamine B and C₆₀/Aerosol OT were used as the samples for the positive and negative mode of operations, respectively. By assuming that (i) the desorption efficiencies are about the same for C₆₀, rhodamine B and Aerosol OT, and (ii) desorption of ionic compounds directly gives the secondary ion signals, the useful yields (i.e. total ions generated divided by the total molecules desorbed) for C₆₀ were estimated to be ~0.1. This value should be regarded as the upper limit because the neutralization of positive and negative ions in the plume and desorption of ionic compounds as neutral species are not taken into account. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Polyvinylpyrrolidone on the States of Water in Water-in-Oil Microemulsions with Betaine Surfactant

A water-in-oil (w/o) microemulsion was prepared with the zwitterionic surfactant dodecyl betaine (C₁₂BE), n-pentanol (C₅OH), n-heptane (C₇H₁₆) and water. Effects of polyvinylpyrrolidone (PVP) with different molecular weight on the state of water in w/o microemulsions at a given water/C₁₂BE molar ratio were investigated by FT-IR and differential scanning calorimetry (DSC). The experimental results showed that addition of PVP resulted in an increase of the content of the bound water in water pool of a w/o microemulsion, but a decrease of the amount of the bulky water. The higher the molecular weight of PVP, the more bound water; and the less bulk water. The change of the trapped water was not obvious due to the interference of C₅OH.     

Attainment of Emulsions with Liquid Crystal from Marigold Oil Using the Required HLB Method

Development of new formulations for topical use and cosmetic and pharmaceutical delivery agents has increased the complexity of emulsified systems. Liquid crystals, known since the nineteenth century are the third phase of an emulsion, being responsible for increasing its stability and the solubility of substances poorly soluble in water, or the oily phase, modulating the release of drugs imprisoned in its structure and promoting hydration of the skin surface. In the present work we developed oil/water emulsions, making use of Marigold oil (Calendula officinalis L) and ethoxylated fat alcohols as surfactant. The required HLB value for marigold oil was determined to be 6.0. The surfactants were associated in lipophilic/hydrophilic pairs. The lipophilic surfactants were Ceteth‐2 and Steareth‐2 and the hydrophilic surfactants were Steareth‐20, Ceteareth‐20, Ceteareth‐5, and Ceteth‐10. To identify the liquid crystalline phases, the emulsions were analyzed by polarized light microscopy. The physical stability was evaluated by rheology and zeta potential analysis. All emulsions presented lamellar liquid crystal structures. Results showed that this type of surfactant is able to produce liquid crystal in the system, with slight difference in appearance, influencing the physical stability, according to the methods applied.     

A single microcystin in a toxic Microcystis bloom from the river Río de la Plata (Argentina)

Microcystis is one of the most common bloom-forming cyanobacteria genera in diverse ecosystems. More than 80% of its strains are toxic, mainly due to their ability to produce metabolites known as microcystins (MC). Here we report on a M. aeruginosa bloom that appeared in the summer of 2001 at a site of the Río de la Plata, within the city of Buenos Aires. The symptoms in mice indicated that the bloom was hepatotoxic. LC-PDA analysis revealed a similar high concentration (0.9–1?mg?g^–1?d w) of just one MC in the bloom biomass during the 3-month study period. During this period most of the MC (ca. 98 %) was found intracellularly, and the content remained almost the same. The molecular mass of the bloom MC was 1036?Da, as deduced from LC-ESI-MS data. Fragment ion analysis by LC-IT-MS-MS allowed identifying 6 out of the 7 amino acids, as well as their position in the molecule. The molecular mass of the unidentified amino acid residue was 155?Da. According to the data obtained, the MC under study was MC-XR, X representing the unidentified amino acid. This is the first report both on the characterisation of MCs in an urban site of the Río de la Plata waters, and on an Argentinean bloom exhibiting only one MC variant.     

Photooxidation Of Arsenobetaine And Arsenocholine To Generate Arsines Previous To Icp-Oes Measurement

Abstract

A photolytic method, which uses UV irradiation (254 nm) and K₂S₂O₈ in alkaline media has been optimized for the speciation of arsenite, arsenate, monomethylarsonic and dimethylarsinic acid, arsenobetaine and arsenocholine. Under these conditions it is possible to obtain not only simple species from arsenobetaine and arsenocholine with good yields, but also to establish the optimum conditions to carry out the process on-line with HG-ICP/OES for the determination of these species.

The products obtained in the photolytic reaction are introduced into the reduction chamber to form arsines. According to the results obtained from the ICP measurements, the recoveries obtained are about 100% and the procedure has a good reproducibility.     

Programmed Temperature Vaporization Injection (PTV) in the Analysis by Gas Chromatography-Mass Spectrometry (GC-MS) of the Constituents of Landfill Gas

Abstract

Trace volatile compounds emitted from both domestic and industrial landfills have been identified by programmed temperature vaporization injection (PTV) coupled to gas chromatography with detection by ion-trap mass spectrometry (GC-ITD/MS). The PTV injection system has been developed using a combination of two six-port valves to achieve problems of interference in GC-MS while loading sample. A large volume of landfill gas was re-concentrated onto a sorbent trap, then rapidly liberated into the GC-ITD/MS system by programmed thermal desorption. Using this method, trace volatile compounds in gases from both domestic and industrial landfills such as aromatic hydrocarbons, terpenes, chlorinated hydrocarbons, and sulfur compounds can be identified and quantified.     

Effect of Abrasives on Three-Body Abrasive Wear Behaviour of Particulate-Filled Polyamide66/Polypropylene Nanocomposites

Polyamide66/polypropylene (PA66/PP) blend, graphite (Gr)-filled PA66/PP composite and nanoclay (NC)-filled PA66/PP nanocomposites were prepared by twin screw extrusion and injection molding. Three-body abrasive wear behaviour of the injection moulded composites was carried out using a rubber wheel abrasion wear tester. In this study, angular silica sand and quartz particles of size ranging from 200 to 250 μm were used as dry and loose abrasives. The tests were carried out for 150, 300, 450 and 600 m abrading distances at a constant load of 36 N. It was observed that inclusion of particulate fillers in PA66/PP have significant influence on wear under varied abrading distances for different abrasive particles. Further, it was found that NC-filled PA66/PP nanocomposite exhibited lower wear rate compared to Gr filled ones for different abrasive particles. In addition, the worn surfaces of the samples were examined by scanning electron microscopy (SEM) and the morphology was also discussed.     

Nanoindentation Experimental Approach and Numerical Simulation of Al/Cr Bilayer Films

The Al/Cr double-layer film structure samples (thickness, 1200 nm) were prepared by the magnetron sputtering method. To investigate the mechanical properties, the samples were measured by using a nanoindentation instrument. The test results showed the nonlinearity and different modes of the main mechanical properties by comparing the macro-scale structure samples with other samples of similar materials. Based on the test, the elastic modulus and hardness of thin film structures can be calculated by considering different loads to conduct multi-point indentations. Meanwhile, the relationships between the mechanical parameters can be investigated based on these Al/Cr double-layer film structure samples. To validate the test, numerical analysis was developed using a finite element method to simulate the loading and unloading process of indentation. The simulation results were compared with the results of experiments to illustrate the validity of both the test and simulation to a certain extent. The investigation builds not only an experimental basis for practical applications for future study, but also supplies a complementary means of verification for theoretical analysis.