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Main Classes (main + class)
Selected AbstractsCholinesterase and glutathione- S -transferase activities in freshwater invertebrates as biomarkers to assess pesticide contaminationENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2010Inęs Domingues Abstract Studies investigating the use of biomarkers in pesticide risk assessment have greatly increased in recent years; however, issues concerning the ecological meaning of enzymatic responses have proved controversial. Ideally a good biomarker response should be modulated by the environmental contaminants alone and demonstrate a predictable behavior towards certain types of toxins. As these premises are rarely observed, the present study aims to outline research that has contributed to an understanding of the behavior of two widely used biomarkers, cholinesterase and glutathione- S -transferase, describing environmental and biotic factors that affect their response in freshwater invertebrates. Studies were performed in the main classes of aquatic invertebrates with these biomarkers and conclusions were reached concerning their behavior towards the main classes of pesticides. Links between biomarker responses and conventional endpoints were evaluated so that ecological relevance could be attributed to enzymatic responses. Toxicity of mixtures was investigated, and cases of synergism and antagonism were pointed out as factors changing the expected toxicity of aquatic systems and leading to misinterpretations of biomarker responses. Finally, the use of biomarkers as a tool for biomonitoring and in situ assays was investigated, with discussion of advantages and disadvantages of their use. Environ. Toxicol. Chem. 2010;29:5,18. © 2009 SETAC [source] Overview of the use of antimicrobials for the treatment of bacterial infections in horsesEQUINE VETERINARY EDUCATION, Issue 8 2008E. F. Haggett Summary Use of antimicrobial drugs is central to the treatment of primary and secondary bacterial infection in horses. When selecting an antimicrobial to treat confirmed or suspected bacterial infection multiple factors should be considered, including: the likely infectious agent; distribution and dosage of selected drugs; mechanisms of action; and potential side effects. Many of these issues will be covered in subsequent articles in this series. The aim of this paper is to aid the clinician in the rational selection of antimicrobials by reviewing the mode of action, spectrum of activity, pharmacokinetics, pharmacodynamics, indications and potential side effects of the main classes of antimicrobial drugs. Extralabel use of drugs is common in veterinary medicine due to a lack of licensed products. This increases the importance of a thorough understanding of antimicrobials and their possible adverse effects. [source] What makes biochemical networks tick?FEBS JOURNAL, Issue 19 2004A graphical tool for the identification of oscillophores In view of the increasing number of reported concentration oscillations in living cells, methods are needed that can identify the causes of these oscillations. These causes always derive from the influences that concentrations have on reaction rates. The influences reach over many molecular reaction steps and are defined by the detailed molecular topology of the network. So-called ,autoinfluence paths', which quantify the influence of one molecular species upon itself through a particular path through the network, can have positive or negative values. The former bring a tendency towards instability. In this molecular context a new graphical approach is presented that enables the classification of network topologies into oscillophoretic and nonoscillophoretic, i.e. into ones that can and ones that cannot induce concentration oscillations. The network topologies are formulated in terms of a set of uni-molecular and bi-molecular reactions, organized into branched cycles of directed reactions, and presented as graphs. Subgraphs of the network topologies are then classified as negative ones (which can) and positive ones (which cannot) give rise to oscillations. A subgraph is oscillophoretic (negative) when it contains more positive than negative autoinfluence paths. Whether the former generates oscillations depends on the values of the other subgraphs, which again depend on the kinetic parameters. An example shows how this can be established. By following the rules of our new approach, various oscillatory kinetic models can be constructed and analyzed, starting from the classified simplest topologies and then working towards desirable complications. Realistic biochemical examples are analyzed with the new method, illustrating two new main classes of oscillophore topologies. [source] Neural connectivity in hand sensorimotor brain areas: An evaluation by evoked field morphologyHUMAN BRAIN MAPPING, Issue 2 2005Franca Tecchio Abstract The connectivity pattern of the neural network devoted to sensory processing depends on the timing of relay recruitment from receptors to cortical areas. The aim of the present work was to uncover and quantify the way the cortical relay recruitment is reflected in the shape of the brain-evoked responses. We recorded the magnetic somatosensory evoked fields (SEF) generated in 36 volunteers by separate bilateral electrical stimulation of median nerve, thumb, and little fingers. After defining an index that quantifies the shape similarity of two SEF traces, we studied the morphologic characteristics of the recorded SEFs within the 20-ms time window that followed the impulse arrival at the primary sensory cortex. Based on our similarity criterion, the shape of the SEFs obtained stimulating the median nerve was observed to be more similar to the one obtained from the thumb (same median nerve innervation) than to the one obtained from the little finger (ulnar nerve innervation). In addition, SEF shapes associated with different brain regions were more similar within an individual than between subjects. Because the SEF morphologic characteristics turned out to be quite diverse among subjects, we defined similarity levels that allowed us to identify three main classes of SEF shapes in normalcy. We show evidence that the morphology of the evoked response describes the anatomo-functional connectivity pattern in the primary sensory areas. Our findings suggest the possible existence of a thalamo-cortico-thalamic responsiveness loop related to the different classes. Hum Brain Mapp 24:99,108, 2005. © 2004 Wiley-Liss, Inc. [source] Redox-Based Resistive Switching Memories , Nanoionic Mechanisms, Prospects, and ChallengesADVANCED MATERIALS, Issue 25-26 2009Rainer Waser This review article introduces resistive switching processes that are being considered for nanoelectronic nonvolatile memories. The three main classes are based on an electrochemical metallization mechanism, a valence change mechanism, and a thermochemical mechanism, respectively. The current understanding of the microscopic mechanisms is discussed and the scaling potential is outlined.. [source] HPLC-MS of anthraquinoids, flavonoids, and their degradation products in analysis of natural dyes in archeological objectsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2007Izabella Surowiec Abstract LC with MS detection was optimized for sensitive and selective analysis of main classes of natural dyes used in ancient times for dyeing textiles , red anthraquinoids, yellow flavonoids, and known degradation products of flavonols , hydroxybenzoic acids. Fragmentation patterns of both negative and positive molecular ions for the above mentioned compounds were investigated. Three acquisition modes of MS analysis: scanning, SIM, and multiple reaction monitoring (MRM) in both positive and negative ion modes were optimized and compared with each other and with the UV-Vis diode-array detection. Even though in the applied chromatographic system formic acid was used in the mobile phase, SIM in the negative ion mode was the most selective and sensitive detection for all the investigated compounds when both mixtures of standards and analysis of extracts from archeological samples were concerned, with one exception , alizarin, for which MS detection in positive ion mode was more sensitive. Detection limits obtained with MS detection for all investigated compounds except quinizarin were lower than the ones obtained with the diode-array UV-Vis detection, making MS detection the most suitable tool for the analysis of natural dyes and their degradation products in extracts from archeological samples. [source] Instrumental measurement of orange juice colour: a reviewJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2005Antonio Jesús Meléndez-Martínez Abstract Colour of orange juice is provided by carotenoids, which belong to one of the main classes of natural pigments, although the colour of particular orange varieties, blood oranges, is mainly due to anthocyanins. Colour of food influences consumers' preferences. For orange juices, some studies have revealed that the colour of citrus beverages in general is related to the consumer's perception of the quality of these products. The USA attaches great importance to the objective evaluation of orange juice colour, to the point that this attribute is evaluated for the commercial classification of the product on the basis of its quality. Apart from the importance of orange juice colour in relation to the quality of the product, it is important to accurately measure this parameter since it has been demonstrated that colour measurements can be used to estimate the carotenoid content rapidly for quality control purposes. Owing to this factors, several techniques and instruments have been developed over the years. This review assesses these methods and the results gained from them. Copyright © 2005 Society of Chemical Industry [source] Exposure assessment of fetus and newborn to brominated flame retardants in France: preliminary dataMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2008Jean-Philippe Antignac Abstract Brominated flame retardants (BFR) are chemicals extensively used in many manufactured products to reduce the risk of fire, but also environmental pollutants. In order to assess the potential risk linked to these compounds in human, a French monitoring study was initiated to evaluate the exposure of fetus and newborn. A previously described multi-residue analytical method was used, for measuring the main classes of BFR (hexabromocyclododecane, tetrabromobisphenol-A, and tri- to deca-polybromodiphenylethers) in various biological matrices. These analyzed samples (maternal and umbilical serum, adipose tissue and breast milk) were collected on volunteer women during caesarean deliveries. Preliminary results obtained on 26 individuals (mother/newborn pairs) mainly demonstrated the presence of polybromodiphenylethers (PBDE) and tetrabromobisphenol A both in maternal and fetal matrices, and a possible risk of overexposure of newborns through breastfeeding. Contaminations levels were found globally in the ng/g lipid weight range, consistent with other published European data. Exposure results regarding highly brominated PBDE congeners (octa- to deca-BDE) appeared particularly informative and non-commonly reported, these compounds accounting for around 50% of the total PBDE load. Additional data collection and metabolism investigations are now on-going. A more complete statistical analysis related to this BFR exposition study will be provided in a next future. [source] Back-contact solar cells: a reviewPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2006Emmanuel Van Kerschaver Abstract Ever since the first publications by R.J. Schwartz in 1975, research into back-contact cells as an alternative to cells with a front and rear contact has remained a research topic. In the last decade, interest in back-contact cells has been growing and a gradual introduction to industrial applications is emerging. The goal of this review is to present a comprehensive summary of results obtained throughout the years. Back-contact cells are divided into three main classes: back-junction (BJ), emitter wrap-through (EWT) and metallisation wrap-through (MWT), each introduced as logical descendents from conventional solar cells. This deviation from the chronology of the developments is maintained during the discussion of technological results. In addition to progress on manufacturing these cells, aspects of cell modelling and module manufacturing are discussed and an outlook towards industrial implementation is presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] Neuro-fuzzy structural classification of proteins for improved protein secondary structure predictionPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2003Joachim A. Hering Abstract Fourier transform infrared (FTIR) spectroscopy is a very flexible technique for characterization of protein secondary structure. Measurements can be carried out rapidly in a number of different environments based on only small quantities of proteins. For this technique to become more widely used for protein secondary structure characterization, however, further developments in methods to accurately quantify protein secondary structure are necessary. Here we propose a structural classification of proteins (SCOP) class specialized neural networks architecture combining an adaptive neuro-fuzzy inference system (ANFIS) with SCOP class specialized backpropagation neural networks for improved protein secondary structure prediction. Our study shows that proteins can be accurately classified into two main classes "all alpha proteins" and "all beta proteins" merely based on the amide I band maximum position of their FTIR spectra. ANFIS is employed to perform the classification task to demonstrate the potential of this architecture with moderately complex problems. Based on studies using a reference set of 17 proteins and an evaluation set of 4 proteins, improved predictions were achieved compared to a conventional neural network approach, where structure specialized neural networks are trained based on protein spectra of both "all alpha" and "all beta" proteins. The standard errors of prediction (SEPs) in % structure were improved by 4.05% for helix structure, by 5.91% for sheet structure, by 2.68% for turn structure, and by 2.15% for bend structure. For other structure, an increase of SEP by 2.43% was observed. Those results were confirmed by a "leave-one-out" run with the combined set of 21 FTIR spectra of proteins. [source] In search of the wage-labour/service contract: new evidence on the validity of the Goldthorpe class schemaTHE BRITISH JOURNAL OF SOCIOLOGY, Issue 4 2000Geoffrey Evans ABSTRACT In this paper we examine new empirical evidence on the coherence and magnitude of the main classes in the Goldthorpe class schema. Particular attention is paid to issues that have recently been a source of academic dispute: the coherence and size of the service class and the distinction between the service class and intermediate classes. Using recently available British data collected by the Office for National Statistics we examine: (i) the extent to which measures of class-relevant job characteristics are empirically discriminated by the categories of the schema; (ii) the structure of a ,contract type' dimension of employment relations conceived of as a categorical latent variable; and (iii) the association between this latent variable and both the Goldthorpe class schema and a related measure,socio-economic group (SEG). We find that the data are consistent with the existence of a three category latent ,contract type' variable largely corresponding to the notions of service, intermediate and wage-labour contracts explicit in discussions of the theoretical rationale for the Goldthorpe schema. We further find a substantial degree of fit between the latent ,contract types' and the schema. However, the service class fault line appears to lie within class I and II of the schema rather than between them and the intermediate classes which suggests a revised, smaller service class would better capture the reality of the contemporary British occupational structure. [source] Supersoft X-ray sources and the progenitors of Type Ia supernovaeASTRONOMISCHE NACHRICHTEN, Issue 2 2010Ph. Podsiadlowski Abstract Supersoft X-ray sources have been proposed as one of the major channels to produce Type Ia supernovae (SNe Ia). However, the true nature of the progenitors has remained an unsolved problem. In this review I summarize the present status of our understanding of SN Ia progenitors, the main classes of progenitor models and recent observational constraints. At present, neither the single-degenerate nor the double-degenerate model can be ruled out, and indeed more than one channel may be required to explain the observed SN Ia diversity. Finally, I discuss the origin of the lightcurve peak , lightcurve width relation (the ,Phillips relation') and show that it is expected to depend on metallicity; this needs to be taken into account in high-precision cosmological applications (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Regulation of transgene expressionACTA OPHTHALMOLOGICA, Issue 2009P KOCH Purpose Regulation of the transgene expression in the targeted cells is of course of major importance when using gene therapy. Actually, we have a huge range of possibilities to regulate gene expression. Methods There are two main classes of promoters: constitutive and inducible promoters. Amongst constitutive promoters, we have two sub-forms: non-tissue and tissue specific promoters. The lasts allows us to better target the tissue or cells in which we want to express our gene of interest. On the other hand, inducible promoters have been widely developed recently and allow us to obtain a regulated expression, depending on different factors. Very recently, disease specific inducible promoters emerged for a more precise regulation. Results We will together examine more precisely the different possibilities offered by gene regulation in Gene Therapy. Thereafter, we will more specifically describe usable promoters in ocular inflammation. Finally we will examine the effects of some inflammatory, disease specific, promoters. Conclusion Regulation of transgene expression is one of the fundaments of efficient gene transfer. Recent developments actually allow us to play within the targeted cell(s) to obtain an expression in specific conditions. [source] Volatile Methyl Esters of Medium Chain Length from the Bacterium Chitinophaga Fx7914CHEMISTRY & BIODIVERSITY, Issue 9 2010Thorben Nawrath Abstract The analysis of the volatiles released by the novel bacterial isolate Chitinophaga Fx7914 revealed the presence of ca. 200 compounds including different methyl esters. These esters comprise monomethyl- and dimethyl-branched, saturated, and unsaturated fatty acid methyl esters that have not been described as bacterial volatiles before. More than 30 esters of medium C-chain length were identified, which belong to five main classes, methyl (S)-2-methylalkanoates (class A), methyl (S)-2,(,,1)-dimethylalkanoates (class B), methyl 2,(,,2)-dimethylalkanoates (class C), methyl (E)-2-methylalk-2-enoates (class D), and methyl (E)-2,(,,1)-dimethylalk-2-enoates (class E). The structures of the compounds were verified by GC/MS analysis and synthesis of the target compounds as methyl (S)-2-methyloctanoate (28), methyl (S)-2,7-dimethyloctanoate ((S)- 43), methyl 2,6-dimethyloctanoate (49), methyl (E)-2-methylnon-2-enoate (20a), and methyl (E)-2,7-dimethyloct-2-enoate (41a). Furthermore, the natural saturated 2-methyl-branched methyl esters showed (S)-configuration as confirmed by GC/MS experiments using chiral phases. Additionally, the biosynthetic pathway leading to the methyl esters was investigated by feeding experiments with labeled precursors. The Me group at C(2) is introduced by propanoate incorporation, while the methyl ester is formed from the respective carboxylic acid by a methyltransferase using S -adenosylmethionine (SAM). [source] | ||||||||||||||||