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See detailLC method for the determination of R-timolol in S-timolol maleate: Validation of its ability to quantify and uncertainty assessment.
Marini Djang'Eing'A, Roland ULg; Chiap, Patrice ULg; Boulanger, Bruno ULg et al

in Talanta (2006), 68(4), 1166-1175

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel ... [more ▼]

This article presents the validation results of a chiral liquid chromatographic (LC) method previously developed for the quantitative determination of R-timolol in S-timolol maleate samples. A novel validation strategy based on the accuracy profiles was used to select the most appropriate regression model, to assess the method accuracy within well defined acceptance limits and to determine the limits of quantitation as well as the concentration range. The validation phase was completed by the investigation of the risk profiles of various acceptable regression models in order to ensure the risk of obtaining the future measurements outside the acceptance limits fixed a priori. On the other hand, the present paper also shows how data used in this validation approach can be used to estimate the measurement uncertainty. The uncertainty derived from beta-expectation tolerance interval (sigma(Tol)(2)), which is equal to the uncertainty of measurements as well as the expanded uncertainty (U(x)) using a coverage factor k=2 was estimated. The uncertainty estimates obtained from validation data were finally compared with those obtained from interlaboratory and robustness studies. [less ▲]

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See detailLC method for the simultaneous determination of R-timolol and other closely related impurities in S-timolol maleate: Optimization by use of an experimental design
Marini Djang'Eing'A, Roland ULg; Chiap, Patrice ULg; Boulanger, Bruno ULg et al

in Journal of Separation Science (2003), 26(9-10), 809-817

A liquid chromatography (LC) method using cellulose tris(3,5-dimethylphenylcarbamate) (5 mum) as chiral stationary phase (CSP) and a mixture of hexane, 2-propanol, and diethylamine as mobile phase was ... [more ▼]

A liquid chromatography (LC) method using cellulose tris(3,5-dimethylphenylcarbamate) (5 mum) as chiral stationary phase (CSP) and a mixture of hexane, 2-propanol, and diethylamine as mobile phase was developed for the simultaneous determination of R-timolol and other potential related substances in S-timolol maleate samples. An experimental design was elaborated in order to test the effects of the different selected factors. Three factors were studied simultaneously, namely the concentrations of 2-propanol and diethylamine as well as the column temperature. The effects of these factors were evaluated statistically. Optimal LC conditions were then deduced by applying a multicriteria decision making approach, namely Derringer's desirability function, for the responses of interest. The developed LC method was compared to the European Pharmacopoeia method and was applied to the determination of R-timolol and other related substances in several samples of S-timolol maleate from different sources. [less ▲]

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See detailLC-MS/MS multi-analyte method for mycotoxin determination in food supplements
Di Mavungu, Jose Diana; Monbaliu, Sofie; Scippo, Marie-Louise ULg et al

in Food Additives & Contaminants (2009), 26(6), 885-895

A multi-analyte method for the liquid chromatography-tandem mass spectrometric determination of mycotoxins in food supplements is presented. The analytes included A and B trichothecenes (nivalenol ... [more ▼]

A multi-analyte method for the liquid chromatography-tandem mass spectrometric determination of mycotoxins in food supplements is presented. The analytes included A and B trichothecenes (nivalenol, deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxyvalenol, neosolaniol, fusarenon-X, diacetoxyscirpenol, HT-2 toxin and T-2 toxin), aflatoxins (aflatoxin-B-1, aflaxoin-G(1) and aflatoxin-G(2)). Alternaria toxins (alternariol, alternariol methyl ether and altenuene), fumonisins (fumonisin-B-1, fumonisin-B-2 and fumonisin-B-3), ochratoxin A, zearalenone, beauvericin and sterigmatocystin. Optimization of the stimulataneous extraction of these toxins and the sample pretreatment procedure, as well as method validation were performed on maca (Lepidium meyenii) food supplements. The results indicated that the solvent mixture ethyl acetate/formic acid (95:5, v/v) n-hexane was applied as partial clean-up step to remove excess of co-extracted non-polar components. Further clean-up was performed on Oasis HLB(TM) cartidges. Samples were analysed using an Acquity UPLC system coupled to a Micromass Quattro Micro triple quadrupole mass spectrometer equipped with an electrospray interface operated in the positive-ion mode. Limits of detection and quantification were in the range of 0.3-30 ng g(-1) and 1-100 ng g(-1), respectively. Recovery yields were above 60% for most of the analytes, except for different food supplements such as soy (Glycine max) isoflavones, St John's wort (Hypericum perforatum), garlic (Allium sativum), Ginkgo biloba, and black radish (Raphanus niger) demonstrated the general applicability of the method. Due to different matrix effects observed in different food supplement samples, the standard addition approach was applied to perform correct quantitative analysis. In 56 out of 62 samples analysed, none of the 23 mycotoxins investigated was detected. Positive samples contained at least one of the toxins fumonisin-B-1, fumonisin-B-2, fumonisin-B-3 and ochratoxin A. [less ▲]

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See detailLC-SPE-NMR-MS analysis of Strychnos usambarensis fruits from Rwanda
Cao, Martine ULg; Tits, Monique ULg; Muganga, Raymond et al

in Planta Medica (2010, September), 76(12), 1241-1242

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See detailLC/MS/NMR analysis of isomeric divanilloylquinic acids from the root bark of Fagara zanthoxyloides Lam
Ouattara, Badiore; Angenot, Luc ULg; Guissou, Pierre et al

in Phytochemistry (2004), 65(8), 1145-1151

Gradient HPLC coupled to DAD/UV, MS/MS and NMR has been applied to the rapid structure determination of three new isomeric divanilloylquinic acids from Fagara zanthoxyloides collected in Burkina Faso: 3,4 ... [more ▼]

Gradient HPLC coupled to DAD/UV, MS/MS and NMR has been applied to the rapid structure determination of three new isomeric divanilloylquinic acids from Fagara zanthoxyloides collected in Burkina Faso: 3,4-O-divanilloylquinic acid, 3,5-O-divanilloylquinic acid and 4,5-O-divanilloylquinic acid. Furthermore these new compounds named burkinabins A-C could play a useful role in sickle cell disease, as the active agents of Fagara zanthoxyloides are said to be unidentified aromatic compounds with carboxylic acid grouping (Adesanya, S.A., Sofowora, A., 1983. Biological standardisation of Zanthoxylum roots for antisickling activity. Planta Med. 48, 27-33). (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailLCA et rééducation isocinétique : analyse critique
Croisier, Jean-Louis ULg

in Actes de la XXIIème Journée scientifique de l’AMISEK « Controverses en chirurgie et rééducation du genou » (2003, December)

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See detailLCAT activation properties of apo A-I CNBr fragments and conversion of discoidal complexes into spherical particles.
Vanloo, B.; Taveirne, J.; Baert, J. et al

in Biochimica et Biophysica Acta (1992), 1128(2-3), 258-66

We studied the substrate properties of the phospholipid-cholesterol-apolipoprotein complexes generated with apo A-I, apo A-I-CNBr fragments, apo A-II and apo A-IV for cholesterol esterification by the ... [more ▼]

We studied the substrate properties of the phospholipid-cholesterol-apolipoprotein complexes generated with apo A-I, apo A-I-CNBr fragments, apo A-II and apo A-IV for cholesterol esterification by the enzyme lecithin-cholesterol acyltransferase (LCAT). The kinetic parameters determined with the different complexes as substrates, showed that the complexes containing apo A-I and apo A-IV were about 40-times more efficient than those generated with the apo A-I fragments. In this system, the substrates containing apo A-II had the lowest efficiency. In spite of the differences in the kinetic parameters observed with the various apolipoprotein-lipid complexes, the cholesterol inserted in the complexes was esterified for more than 90% after 24 h in all systems studied. Based upon the results of the kinetic experiments, we followed the transformation of the discoidal complexes into spherical particles, due to the formation of a cholesteryl esters core, in the presence of low-density lipoproteins as an external source of cholesterol. We observed the formation of spherical particles by electron microscopy, after incubation of the discoidal complexes with LCAT for 24 h. The average percentage of cholesteryl esters in the converted particles was around 60% of the total cholesterol, varying between 40% for the apo A-I-CNBr-1-DPPC-cholesterol complex and up to 86% for the apo A-I-DPPC-cholesterol complex. The secondary structure of protein in the complexes was not significantly modified. However, the phospholipid phase transition disappeared, together with the parallel orientation of the phospholipid acyl chains with the helical segments of the apolipoproteins, as the phospholipids are organized in a monolayer at the surface of the spheres. [less ▲]

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See detailThe LCC15-MB human breast cancer cell line expresses osteopontin and exhibits an invasive and metastatic phenotype
Sung, V.; Gilles, Christine ULg; Murray, A. et al

in Experimental Cell Research (1998), 241(2), 273-84

We have characterized the LCC15-MB cell line which was recently derived from a breast carcinoma metastasis resected from the femur of a 29-year-old woman. LCC15-MB cells are vimentin (VIM) positive ... [more ▼]

We have characterized the LCC15-MB cell line which was recently derived from a breast carcinoma metastasis resected from the femur of a 29-year-old woman. LCC15-MB cells are vimentin (VIM) positive, exhibit a stellate morphology in routine cell culture, and form penetrating colonies when embedded in three-dimensional gels of Matrigel or fibrillar collagen. They show high levels of activity in the Boyden chamber chemomigration and chemoinvasion assays, and like other invasive human breast cancer (HBC) cell lines, LCC15-MB cells activate matrix-metalloproteinase-2 in response to treatment with concanavalin A. In addition, these cells are tumorigenic when implanted subcutaneously in nude mice and recolonize bone after arterial injection. Interestingly, both the primary lesion and the bone metastasis from which LCC15-MB were derived, as well as the resultant cell line, abundantly express the bone matrix protein osteopontin (OPN). OPN is also expressed by the highly metastatic MDA-MB-435 cells, but not other invasive or noninvasive HBC cell lines. Expression of OPN is retained in the subcutaneous xenograft and intraosseous metastases of LCC15-MB as detected by immunohistochemistry. Both VIM and OPN expression have been associated with breast cancer invasion and metastasis, and their expression by the LCC15-MB cell line is consistent with its derivation from a highly aggressive breast cancer. These cells provide a useful model for studying molecular mechanisms important for breast cancer metastasis to bone and, in particular, the implication(s) of OPN and VIM expression in this process. [less ▲]

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See detailLck dephosphorylation at Tyr-394 and inhibition of T cell antigen receptor signaling by Yersinia phosphatase YopH.
Alonso, Andres; Bottini, Nunzio; Bruckner, Shane et al

in Journal of Biological Chemistry (2004), 279(6), 4922-8

A key virulence factor for Yersinia pestis, the etiologic agent of plague, is the tyrosine phosphatase YopH, which the bacterium injects into host cells. We report that treatment of human T lymphocytes ... [more ▼]

A key virulence factor for Yersinia pestis, the etiologic agent of plague, is the tyrosine phosphatase YopH, which the bacterium injects into host cells. We report that treatment of human T lymphocytes with a recombinant membrane-permeable YopH resulted in severe reduction in intracellular tyrosine phosphorylation and inhibition of T cell activation. The primary signal transducer for the T cell antigen receptor, the Lck tyrosine kinase, was specifically precipitated by a substrate-trapping YopH mutant, and Lck was dephosphorylated at its positive regulatory site, Tyr-394, in cells containing active YopH. By turning off Lck, YopH blocks T cell antigen receptor signaling at its very first step, effectively preventing the development of a protective immune response against this lethal bacterium. [less ▲]

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See detailLC–SPE–NMR–MS analysis of Strychnos usambarensis fruits from Rwanda
Cao, Martine ULg; Muganga, Raymond; Nistor, Iolanda ULg et al

in Phytochemistry Letters (2012), 5(0), 170-173

The novelty of the present work lies in the characterization of akagerine and palicoside in Strychnos usambarensis fruits by a hyphenated analytical method combining high-performance liquid chromatography ... [more ▼]

The novelty of the present work lies in the characterization of akagerine and palicoside in Strychnos usambarensis fruits by a hyphenated analytical method combining high-performance liquid chromatography coupled with solid-phase extraction (SPE), mass spectrometry (HPLC–MS) and NMR spectroscopy. Akagerine was already known in S. usambarensis roots but palicoside is described for the first time in the species. [less ▲]

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See detailLD-based haplotype encoding scheme with iterative pruning principal component analysis (ipPCA) to retrieve population substructures
Chaichoompu, Kridsadakorn ULg; Fouladi, Ramouna ULg; Wangkumhang, Pongsakorn et al

Poster (2014, April 29)

Objective To identify and differentiate between subpopulations using a rich set of genetic markers, as using reduced sets of genetic markers for these purposes can become challenging, especially when ... [more ▼]

Objective To identify and differentiate between subpopulations using a rich set of genetic markers, as using reduced sets of genetic markers for these purposes can become challenging, especially when similar geographic regions are involved or when spurious patterns are likely to exist. Method Single Nucleotide Polymorphisms (SNPs) are commonly used to capture variations between populations and often genome-wide SNP data are pruned based on linkage disequilibrium (LD) patterns. Notably, haplotype composition and the pattern of LD between markers may vary between larger populations but may also play a role within more confined geographic regions. Indeed, knowledge about haplotypes in unrelated individuals can reveal useful information about genetic ancestry. Here, we use iterative pruning principal component analysis (ipPCA) [1] to identify and characterize subpopulations in an unsupervised way. As input data, either pruned genome-wide SNP data are used (using PLINK 1.9 with the "indep-pairwise" option, window size = 100k, r2 < 0.25) or multilocus haplotype information derived from the genome-wide SNP panel (using BEAGLE 3.3.2 to infer haplotype). These approaches are applied to real-life data from 992 Thai individuals [2]. Result Preliminary results indicate that ipPCA applied to pruned SNP data or ipPCA that explicitly uses multilocus information (haplotypes) give complementary information about population substructure for geographically confined populations such as the Thai samples in this study. Both methods address different aspects of population structure. Detailed simulation studies are needed to identify the optimal scenarios for haplotype-based ipPCA. Conclusion In this work, we propose to combine an LD-based haplotype encoding scheme with the ipPCA machinery to retrieve fine population substructures. Despite the complexities that are associated with haplotype inference, added value can be obtained when the LD structure between SNPs is exploited in the search for relevant population strata. References 1. Intarapanich, A., et al., Iterative pruning PCA improves resolution of highly structured populations. BMC Bioinformatics, 2009. 10: p. 382. 2. Wangkumhang, P., et al., Insight into the peopling of Mainland Southeast Asia from Thai population genetic structure. PLoS One, 2013. 8(11): p. e79522. [less ▲]

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See detailLDSO: A program to simulate pedigrees and molecular information under various evolutionary forces
Ytournel, F.; Teyssèdre, S.; Roldan, D. et al

in Journal of Animal Breeding & Genetics (2012), 129(5), 417-421

Simulations are a major tool to evaluate new statistical methods and optimize experimental designs in the genomic era. However, this can only be achieved when the simulations are close enough to reality ... [more ▼]

Simulations are a major tool to evaluate new statistical methods and optimize experimental designs in the genomic era. However, this can only be achieved when the simulations are close enough to reality, as well as diverse enough to be realistic. For mapping studies, it is thus critical to re-create as much as possible the forces generating linkage (mutation, random drift, changes in population sizes, selection and pedigree structure) and the mechanisms producing trait genetic architecture (additivity, dominance, epistasis). We present here a computer program (ldso) simulating these phenomena. Optional outputs provide statistics on the linkage disequilibrium (LD) structure and the identity by descent between chromosomal segments, facilitating further data analyses. Furthermore, ldso enables the simulation of genomic data in known pedigrees, which sticks as precisely as possible to recent population history and structures of the long-range LD, allowing optimization of fine-mapping strategies. © 2012 Blackwell Verlag GmbH. [less ▲]

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See detailLe _Syntactic Reference Corpus of Medieval French_: Structure, outils et exploitation
Mazziotta, Nicolas ULg

in Dister, Anne; Longrée, Dominique; Purnelle, Gérald (Eds.) 11es Journées internationales d'Analyse statistique des Données Textuelles (JADT) (2012)

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