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  • Wiley Online Library  (111)
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  • 1
    In: Molecular Microbiology, March 2010, Vol.75(6), pp.1389-1401
    Description: Mechanisms of hydrogen peroxide generation in were investigated using a strain lacking scavenging enzymes. Surprisingly, the deletion of many abundant flavoenzymes that are known to autoxidize did not substantially lessen overall HO formation. However, HO production diminished by 25–30% when NadB turnover was eliminated. The flavin‐dependent desaturating dehydrogenase, NadB uses fumarate as an electron acceptor in anaerobic cells. Experiments showed that aerobic NadB turnover depends upon its oxidation by molecular oxygen, with HO as a product. This reaction appears to be mechanistically adventitious. In contrast, most desaturating dehydrogenases are associated with the respiratory chain and deliver electrons to fumarate anaerobically or oxygen aerobically without the formation of toxic by‐products. Presumably, NadB can persist as an HO‐generating enzyme because its flux is limited. The anaerobic respiratory enzyme fumarate reductase uses a flavoprotein subunit that is homologous to NadB and accordingly forms substantial HO upon aeration. This tendency is substantially suppressed by cytochrome oxidase. Thus cytochrome oxidase, which is prevalent among anaerobes, may diminish intracellular HO formation by the anaerobic respiratory chain, whenever these organisms encounter oxygen. These two examples reveal biochemical and physiological arrangements through which evolution has minimized the rate of intracellular oxidant formation.
    Keywords: Hydrogen Peroxide -- Physiological Aspects ; Escherichia Coli -- Physiological Aspects ; Cytochrome Oxidase -- Physiological Aspects;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 2
    In: Molecular Microbiology, July 2016, Vol.101(1), pp.62-77
    Description: When sulfur compounds are scarce or difficult to process, adapts by inducing the high‐level expression of sulfur‐compound importers. If cystine then becomes available, the cystine is rapidly overimported and reduced, leading to a burgeoning pool of intracellular cysteine. Most of the excess cysteine is exported, but some is adventitiously degraded, with the consequent release of sulfide. Sulfide is a potent ligand of copper and heme moieties, raising the prospect that it interferes with enzymes. We observed that when cystine was provided and sulfide levels rose, became strictly dependent upon cytochrome oxidase for continued respiration. Inspection revealed that low‐micromolar levels of sulfide inhibited the proton‐pumping cytochrome oxidase that is regarded as the primary respiratory oxidase. In the absence of the back‐up cytochrome oxidase, growth failed. Exogenous sulfide elicited the same effect. The potency of sulfide was enhanced when oxygen concentrations were low. Natural oxic‐anoxic interfaces are often sulfidic, including the intestinal environment where dwells. We propose that the sulfide resistance of the cytochrome oxidase is a key trait that permits respiration in such habitats. Toxic levels of intracellular sulfide arise either from the degradation of excess cysteine or from an influx of hydrogen sulfide itself. Sulfide inhibits the primary respiratory cytochrome oxidase, and continued respiration depends upon the presence of the secondary cytochrome oxidase. This scenario is likely common to sulfidic environments, such as the mammalian gut.
    Keywords: Sulfur Compounds ; Cytochromes ; Heme ; Respiration ; Enzymes ; Copper ; Hydrogen Sulfide ; Habitat ; Sulfide ; Oxygen ; Digestive Tract ; Cysteine ; Intestine ; Cytochrome Bd ; Escherichia Coli ; Cell Biology;
    ISSN: 0950-382X
    E-ISSN: 1365-2958
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  • 3
    Language: English
    In: Electroanalysis, September 2010, Vol.22(17‐18), pp.1989-1993
    Description: The method of linear cyclic voltammetry with hanging mercury drop eletctrode allows to follow the behaviour of aluminum nanoparticles in aqueous dispersions. The particles gradually react with the dispersion medium to form aluminum hydroxide over various intermediate aggregates depending on composition of the dispersing solution. Voltammetry shows adsorption at the electrode of some of the reaction intermediates and formation of aluminum amalgam when the bared metallic core contacts the electrode.
    Keywords: Linear Cyclic Voltammetry ; Hanging Mercury Drop Electrode ; Aluminum Nanoparticles Dispersion ; Aqueous Media ; Aluminum Amalgam ; Nanoparticles
    ISSN: 1040-0397
    E-ISSN: 1521-4109
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  • 4
    Language: English
    In: Cancer, 15 March 2004, Vol.100(6), pp.1230-1237
    Description: BACKGROUND: Ependymomas account for 3-5% of all intracranial malignancies and occur most often in children and young adults. These neoplasms continue to generate considerable controversy with regard to their rational clinical management. It has been shown that the histologic classification of ependymoma is a significant predictor of clinical outcome in patients with ependymoma.METHODS: Ependymomas from 258 patients who underwent microsurgery at a single institution were evaluated histologically to elucidate the prognostic utility of a recently proposed grading scheme. Pathologic and clinical data then were compared using univariate and multivariate analyses.RESULTS: Increasing grade of ependymoma malignancy was found to be associated strongly and independently with worse clinical outcomes in terms of both event-free survival and overall survival. The effect of radiotherapy also was found to be related to histologic grade and was more beneficial for patients who had anaplastic ependymomas and had undergone complete tumor removal.CONCLUSIONS: The application of a uniform diagnostic criteria for grading ependymomas highlighted the key role of tumor histology in clinical outcome in a cohort of patients who were treated in the microsurgical era. The recently proposed grading scheme is likely to be practically useful, reproducible, and clinically applicable.
    Keywords: Ependymoma ; Histology ; Malignancy Grade ; Prognosis ; Radiotherapy
    ISSN: 0008-543X
    E-ISSN: 1097-0142
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  • 5
    Language: English
    In: International Journal of Cancer, 01 November 2011, Vol.129(9), pp.2297-2303
    Description: Pilocytic astrocytoma (PA) is emerging as a tumor entity with dysregulated Ras/Raf/MEK/ERK signaling. Common genetic lesions observed in PA, which are linked to aberrant ERK pathway activity, include either inactivation, or gain‐of‐function mutations. To investigate the mutation spectrum within the proto‐oncogene encoding the Ser/Thr‐kinase B‐Raf in more detail, we analyzed 64 primary tumor samples from children with PA including two patients with neurofibromatosis type 1 (NF1). The well‐known mutation was found in 6/64 (9.38%) of our samples. For the first time, we report concomitant presence of a somatic mutation in an NF1 patient indicating that more than one Ras/ERK pathway component can be affected in PA. Furthermore, 2/64 (3.13%) of our samples carried a 3‐bp insertion in resulting in the duplication of threonine 599. This conserved residue is located within the activation segment and, if phosphorylated in a Ras‐dependent manner, plays a key role in Raf activation. Here, we demonstrate that this mutant (B‐Raf) and another B‐Raf mutant, which carries two additional threonine residues at this position, display an kinase activity and cellular MEK/ERK activation potential comparable to those of B‐Raf. Notably, replacement of threonines by valine residues had similar effects on B‐Raf activity, suggesting that the distortion of the peptide backbone by additional amino acids rather than the insertion of additional, potential phosphorylation sites destabilizes the inactive conformation of the kinase domain. We also demonstrate that B‐Raf and B‐Raf, but not B‐Raf, provoke drastic morphological alterations in human astrocytes.
    Keywords: Pilocytic Astrocytoma ; Neurofibromatosis Type 1 ; B‐Raf ; Insertion Mutagenesis ; Mapk Pathway
    ISSN: 0020-7136
    E-ISSN: 1097-0215
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  • 6
    In: Polymer Engineering & Science, October 2015, Vol.55(10), pp.2256-2269
    Description: Ideas concerning the use of a flat slot die with rollers in the technology of extrusion foaming of polymers are developed. Based on the experimental study of low‐density polyethylene foaming with isobutane, dependences of the cell density and foam density on the polymer solution viscosity, gap width between rollers, die temperature, and talc concentration have been analyzed. A model is formulated for estimating the intensity of coalescence of supercritical bubbles in an inhomogeneous field of flow velocities. The number density of supercritical nuclei formed in a polymer–gas solution in the limiting case of high pressure drop rate is estimated. The obtained simple estimations allow the results of experiments to be justified on a qualitative level. POLYM. ENG. SCI., 55:2256–2269, 2015. © 2015 Society of Plastics Engineers
    Keywords: Polymers – Production Processes ; Foamed Materials – Production Processes ; Polymer Processing Equipment – Design and Construction;
    ISSN: 0032-3888
    E-ISSN: 1548-2634
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  • 7
    In: Advanced Engineering Materials, May 2018, Vol.20(5), pp.n/a-n/a
    Description: It is shown experimentally that multipass TE leads to the saturation of mechanical properties in the billet. This fact indicates the occurrence of an ideal plastic state. An explanation for the hardening central zone of the billet during TE is offered.
    Keywords: High Pressure Torsion ; Ideal Plastic State ; Mechanical Properties ; Strain Distribution ; Titanium ; Twist Extrusion
    ISSN: 1438-1656
    E-ISSN: 1527-2648
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  • 8
    In: Polymer Engineering & Science, January 2014, Vol.54(1), pp.96-109
    Description: Operation of a flat slot die with rollers for the extrusion foaming of polymers, which has been originally designed by Benkreira et al. (., 19, 111 (2004)), is considered. The rotation of rollers makes it possible to independently control shear rate inside the die, in the bubble nucleation zone, thus influencing the cell density. In experimental studies of low‐density polyethylene foaming, the influence of the roller rotation speed on the cell density at variable isobutane and talc concentrations and die outlet area has been determined. Based on the fluctuational nucleation theory, a simple model is proposed for estimating the number density of supercritical nuclei formed at the nucleation stage and evaluating the cell density in the foam with allowance for bubble coalescence effects. POLYM. ENG. SCI., 54:96–109, 2014. © 2013 Society of Plastics Engineers
    Keywords: Molds (Forms) – Properties ; Plastics Extrusion – Equipment and Supplies ; Equipment Performance – Evaluation;
    ISSN: 0032-3888
    E-ISSN: 1548-2634
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  • 9
    Language: English
    In: Cancer, 15 August 2005, Vol.104(4), pp.825-832
    Description: BACKGROUND: In patients with glioblastoma, age 〈 50 years was identified as a consistent prognostic variable. In addition, the prognosis for these patients may be determined by a complex interaction between age and genetic alterations. The objective of the current study was the molecular analysis of glioblastomas from adult patients age 〈 50 years ("young adults").METHODS: The authors analyzed a set of 189 glioblastoma specimens. Fluorescence in situ hybridization was performed with a set of 10 chromosome probes (1p36, 1q25, centomere probe 7 [CEP7], 7p12/epidermal growth factor receptor gene (EGFR), CEP9, 9p21/p16, CEP10, 10q23/phosphatase and tesnin homolog gene (PTEN), 19p13, and 19q13).RESULTS: Patient age 〈 40 years was associated strongly with a favorable prognosis. Patients age 〉 or = 40 years frequently showed EGFR amplification, loss of 9p, loss of 10q, and gain of chromosome 19. The patients with - 19q were age 〈 40 years. The survival was shorter for patients with EGFR amplification, gain of chromosome 7, loss of 9p, loss of 10q, and gain of chromosome 19. In contrast, the patients who had tumors with gain of chromosome 9 or loss of 19q had more favorable outcomes. In a multivariate analysis, gain of chromosome 9 (P = 0.026) and loss of 10q23 (P = 0.007) reached the level of independent prognostic value. In addition, the prognostic value of molecular alterations in patients age 〈 40 years and patients age 〉 40 years were examined separately. Consequently, EGFR amplification, - 9p, and + 9 were significant for both age groups, whereas gain of chromosome 7 and loss of 10q showed clinical importance only among patients age 〉 40 years.CONCLUSIONS: Adult patients age 〈 50 years with glioblastoma had molecularly distinct disease, and the age-dependent heterogeneity seen on the chromosomal level also applied at the clinical level.
    Keywords: Glioblastoma ; Young Adults ; Molecular Analysis ; Prognosis
    ISSN: 0008-543X
    E-ISSN: 1097-0142
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  • 10
    Language: English
    In: ChemInform, May 2016, Vol.47(24), pp.no-no
    Description: Byline: Anatoly N. Vereshchagin(1), Michail N. Elinson(1), Alexander D. Korshunov(1), Mikhail P. Egorov(1) Keywords: spirocyclic compounds (heterocyclic compounds); pyrazole derivatives; cascade reactions, domino reactions, tandem reactions; ring closure reactions, annulation reactions ***** No abstract is available for this article. ***** Author Affiliation: (1)Zelinsky Inst. Org. Chem., Russ. Acad. Sci., Moscow 119991, Russia
    Keywords: Spirocyclic Compounds Heterocyclic Compounds ; Pyrazole Derivatives ; Cascade Reactions ; Domino Reactions ; Tandem Reactions ; Ring Closure Reactions ; Annulation Reactions
    ISSN: 0931-7597
    E-ISSN: 1522-2667
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