Dextran sulfate sodium inhibits alanine synthesis in caco-2 cells

To understand and characterize the pathogenic mechanisms of inflammatory bowel disease, dextran sulfate sodium (DSS) has been used to induce acute and chronic colitis in animal models by causing intestinal epithelium damage. The mechanism of action of DSS in producing this outcome is not well understood. In an effort to understand how DSS might impact epithelial cell metabolism, we studied the intestinal epithelial cell line Caco-2 incubated with 1% DSS over 56 hours using (1)H NMR spectroscopy. We observed no difference in cell viability as compared to control cultures, and an approximately 1.5-fold increase in IL-6 production upon incubation with 1% DSS. The effect on Caco-2 cell metabolism as measured through changes in the concentration of metabolites in the cell supernatant included a three-fold decrease in the concentration of alanine. Given that the concentrations of other amino acids in the cell culture supernatant were not different between treated and control cultures over 56 hours suggest that DSS inhibits alanine synthesis, specifically alanine aminotransferase, without affecting other key metabolic pathways. The importance of alanine aminotransferase in inflammatory bowel disease is discussed.     

Creativity as flexible cognitive control.

Creative individuals have been described in terms suggestive of greater automatic processing (e.g., defocused attention, looser associations) and greater controlled processing (e.g., greater abilities to focus while working on a creative task). Both views cannot be correct from a static ability-related perspective. On the other hand, both views could be correct if creative individuals are better able to modulate the functioning of their cognitive control system in a context-sensitive manner. The present study (N = 50) assessed individual differences in creativity in terms of original responses on the Torrance Test of Creative Thinking (Torrance, 1974) and also in terms of creative behavior on the Creative Achievement Questionnaire (Carson, Peterson, & Higgins, 2005). The same participants performed a color–word Stroop task. Creative individuals were neither more nor less capable of overriding cognitive conflicts on incongruent (relative to congruent) Stroop trials. On the other hand, creative individuals displayed more flexible cognitive control, as defined by greater cognitive control modulation from trial to trial. Implications for theories of creativity and its underlying processing basis are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative Analysis of Exo- and Endonuclease Activities of APE1-like Enzymes

Apurinic/apyrimidinic (AP)-endonucleases are multifunctional enzymes that are required for cell viability. AP-endonucleases incise DNA 5′ to an AP-site; can recognize and process some damaged nucleosides; and possess 3′-phosphodiesterase, 3′-phosphatase, and endoribonuclease activities. To elucidate the mechanism of substrate cleavage in detail, we analyzed the effect of mono- and divalent metal ions on the exo- and endonuclease activities of four homologous APE1-like endonucleases (from an insect (Rrp1), amphibian (xAPE1), fish (zAPE1), and from humans (hAPE1)). It was found that the enzymes had similar patterns of dependence on metal ions’ concentrations in terms of AP-endonuclease activity, suggesting that the main biological function (AP-site cleavage) was highly conserved among evolutionarily distant species. The efficiency of the 3′-5′ exonuclease activity was the highest in hAPE1 among these enzymes. In contrast, the endoribonuclease activity of the enzymes could be ranked as hAPE1 ≈ zAPE1 ≤ xAPE1 ≤ Rrp1. Taken together, the results revealed that the tested enzymes differed significantly in their capacity for substrate cleavage, even though the most important catalytic and substrate-binding amino acid residues were conserved. It can be concluded that substrate specificity and cleavage efficiency were controlled by factors external to the catalytic site, e.g., the N-terminal domain of these enzymes.     

Supramolecular Systems Based on Novel Amphiphiles and a Polymer: Aggregation and Selective Solubilization

Supramolecular systems based on novel triazole-containing and pyrimidine-containing amphiphiles bearing OH-groups and a hydrophilic polymer (polyethyleneimine, PEI) were fabricated. Aggregation threshold of individual amphiphile solutions and a surfactant/polymer binary mixture were determined to be equal to 2 and 0.05 mM, respectively, using tensiometry and conductometry techniques. It was found, that PEI addition to surfactant aqueous solutions induces the transition from open to closed association mode accompanying the decrease of mean hydrodynamic diameter of particles (D _H) from 100 nm to D _H ≤ 5 nm. Polymer addition to the system results in the leveling of pH decrease with surfactant concentration and increase of the electrokinetic potential values from 10 mV up to 40 mV. It was established that solubilization capacity of the supramolecular system formed could be increased by transition from surfactant individual solutions to the amphiphile/polymer binary system. The solubilization properties of the system strongly depend on the nature of the hydrophobic guest solubilized and differ by two orders of magnitude for hydrophobic azodye and lipophilic oxime.     

Oxidation of Fine Tantalum Particles: Metastable Intermediates and Multistep Kinetics

Oxidation of Metals - The metastable tantalum suboxides have been found to be a cause of complicated oxidation behaviour of fine tantalum particles when heated in air at moderate temperatures. Fine...     

Improvement of enzyme electrocatalysis using substrate containing electroactive polymers. Towards limiting efficiencies of bioelectrocatalysis

Direct electrocatalysis by the enzymes in the absence of any freely diffusing mediators requires proper orientation of the protein macromolecule on the electrode surface. We report a conception on how to improve efficiency of bioelectrocatalysis using electroactive polymers containing analogues of the enzyme substrates (usually acting as artificial donors-acceptors). Indeed, substrate analogues having affinity to terminal redox groups of the enzymes can anchor them in an optimal orientation upon immobilization. The improvement of bioelectrocatalysis using such electroactive polymers is reported for different enzymes: hydrogenases and cellobiose dehydrogenase. Highly efficient electrocatalysis by hydrogenases was determined by thermodynamics of the catalyzed reaction confirming the direct bioelectrocatalysis. For hydrogenases immobilized over viologen substituted conducting polymers the limiting performance characteristics in bioelectrocatalysis have been achieved.     

2′‐Bispyrene‐Modified 2′‐O‐Methyl RNA Probes as Useful Tools for the Detection of RNA: Synthesis,Fluorescent Properties,and Duplex Stability

The synthesis and properties two series of new 2′‐O‐methyl RNA probes, each containing a single insertion of a 2′‐bispyrenylmethylphosphorodiamidate derivative of a nucleotide (U, C, A, and G), are described. As demonstrated by UV melting studies, the probes form stable complexes with model RNAs and DNAs. Significant increases (up to 21‐fold) in pyrene excimer fluorescence intensity were observed upon binding of most of the probes with complementary RNAs, but not with DNAs. The fluorescence spectra are independent of the nature of the modified nucleotides. The nucleotides on the 5′‐side of the modified nucleotide have no effect on the fluorescence spectra, whereas the natures of the two nucleotides on the 3′‐side are important: CC, CG, and UC dinucleotide units on the 3′‐side of the modified nucleotide provide the maximum increases in excimer fluorescence intensity. This study suggests that these 2′‐bispyrene‐labeled 2′‐O‐methyl RNA probes might be useful tools for detection of RNAs.     

土库曼斯坦阿姆河第二天然气处理厂集气工艺优化

土库曼斯坦阿姆河第一天然气处理厂集气装置在实际运行过程中存在气液分离器分离乳化油效果不明显、段塞流捕集器容量偏小、上游来液含较多乳化油严重影响下游凝析油稳定装置的平稳运行等问题,为避免类似问题的发生,有必要对即将投产的阿姆河第二天然气处理厂集气装置的工艺进行优化。从优化段塞流捕集器形式、增加分离缓冲设备和优化布局等因素综合考虑,采取了以下5项优化措施：①分别设置高低含硫天然气集气系统以满足下游酸气处理工艺要求;②采用新型高效段塞流捕集器提高气液分离效率;③增设缓冲沉降罐减小乳化油对下游装置的影响;④优化了设备平面布置增加操作舒适性;⑤完善安全放空系统,保证系统本质安全。优化后的集气装置能实现原料气气液高效分离、计量,对高低含硫系统硫化氢含量进行监测并对气量实现实时调配,确保了系统平稳高效可靠运行。     

Features of Retinal Neurogenesis as a Key Factor of Age-Related Neurodegeneration: Myth or Reality?

Age-related macular degeneration (AMD) is a complex multifactorial neurodegenerative disease that constitutes the most common cause of irreversible blindness in the elderly in the developed countries. Incomplete knowledge about its pathogenesis prevents the search for effective methods of prevention and treatment of AMD, primarily of its “dry” type which is by far the most common (90% of all AMD cases). In the recent years, AMD has become “younger”: late stages of the disease are now detected in relatively young people. It is known that AMD pathogenesis—according to the age-related structural and functional changes in the retina—is linked with inflammation, hypoxia, oxidative stress, mitochondrial dysfunction, and an impairment of neurotrophic support, but the mechanisms that trigger the conversion of normal age-related changes to the pathological process as well as the reason for early AMD development remain unclear. In the adult mammalian retina, de novo neurogenesis is very limited. Therefore, the structural and functional features that arise during its maturation and formation can exert long-term effects on further ontogenesis of this tissue. The aim of this review was to discuss possible contributions of the changes/disturbances in retinal neurogenesis to the early development of AMD.     

Controlled copolymerization of acrylonitrile with methyl acrylate and dimethyl itaconate via ARGET ATRP mechanism

The peculiarities of controlled copolymerization of acrylonitrile with methyl acrylate and dimethyl itaconate in the presence of copper-based catalytic system were investigated. It was shown that the polymerization proceeds in a controlled mode in accordance with ARGET ATRP mechanism. The increase of molecular weights in a strict agreement with theoretically predicted values is observed. The formation of copolymers was confirmed by NMR and MALDI TOF MS analysis. The introduction of mentioned monomers to acrylonitrile results in slight decrease of the polymerization rate. The performed calorimetric investigations showed the smoothing of exothermic effect of the oxidative stabilization of formed copolymers.