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See detailContribution à l’étude des peptides obliques impliqués dans des transconformations
Crowet, Jean-Marc ULg

Master's dissertation (2003)

The study of the amyloidogenic proteins is important to understand the transconformational processes. These proteins have a unique common feature : they undergo a conformational change leading to the ... [more ▼]

The study of the amyloidogenic proteins is important to understand the transconformational processes. These proteins have a unique common feature : they undergo a conformational change leading to the formation of highly structured fibrils that are mainly β conformed. These proteins are difficult to study experimentally due to their low solubility and their tendency to aggregate rapidly. Recently, tilted peptides have been detected in such proteins. These peptides are short fragments (11 to 18 residues) that adopt a tilted orientation when they interact with a hydrophilic/hydrophobic interface. This property is due to the presence of an asymmetric hydrophobicity gradient when they are helical. Those peptides are able to destabilize organized molecular systems. Amyloidogenic proteins containing such peptides are the PrP protein, the Aȕ peptide, and the bacterial prions Ure2p and Sup35p. The presence of such fragments in transconformational proteins has led to the hypothesis that tilted peptides could be implied in the conformational change of amyloidogenic proteins. These peptides could play a role through their destabilizing properties and/or their structural lability. The aim of this work was to detect tilted peptides among other amyloidogenic proteins by molecular modelling. One of the detected peptides is tested experimentally to evidence its lipid destabilizing properties. Five tilted peptides from four different proteins have been detected among 27 amyloidogenic proteins. The tilted fragment from the α-synuclein sequence, a protein involved in Parkinson disease, has been synthetized and tested for lipid fusion. The fusogenic assays pointed out its destabilizing properties. These results support the hypothesis that tilted peptides could be involved in transconformational processes. [less ▲]

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See detailLubrication by charged polymers
Raviv, Uri; Giasson, Suzanne; Kampf, Nir et al

in Nature (2003), 425(6954), 163-165

Long-ranged forces between surfaces in a liquid control effects from colloid stability [1] to biolubrication [2], and can be modified either by steric factors due to flexible polymers [3], or by surface ... [more ▼]

Long-ranged forces between surfaces in a liquid control effects from colloid stability [1] to biolubrication [2], and can be modified either by steric factors due to flexible polymers [3], or by surface charge effects [4]. In particular, neutral polymer 'brushes' may lead to a massive reduction in sliding friction between the surfaces to which they are attached [5-7], whereas hydrated ions can act as extremely efficient lubricants between sliding charged surfaces [8]. Here we show that brushes of charged polymers (polyelectrolytes) attached to surfaces rubbing across an aqueous medium result in superior lubrication compared to other polymeric surfactants. Effective friction coefficients with polyelectrolyte brushes in water are lower than about 0.0006-0.001 even at low sliding velocities and at pressures of up to several atmospheres (typical of those in living systems). We attribute this to the exceptional resistance to mutual interpenetration displayed by the compressed, counterion-swollen brushes, together with the fluidity of the hydration layers surrounding the charged, rubbing polymer segments. Our findings may have implications for biolubrication effects, which are important in the design of lubricated surfaces in artificial implants, and in understanding frictional processes in biological systems. [less ▲]

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See detailBulletin agrométéorologique - Août 2003
Tychon, Bernard ULg; De Longueville, Florence ULg; Ozer, Pierre ULg et al

in Bulletin Agrométéorologique (2003)

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See detailComportement des variétés de froment vis-à-vis de l'hiver 2002-2003
Couvreur, Luc; Herman, Jean-Luc; Vancutsem, Françoise ULg et al

in Livre Blanc: Céréales - Gembloux - Informations avant les semis (2003, September 09)

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See detailTraitement des semences de froment contre le piétin-échaudage
Moreau, Jean-Marc; Couvreur, Luc; Vancutsem, Françoise ULg

in Livre Blanc: Céréales - Gembloux - Informations avant les semis (2003, September 09)

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See detailMesures agri-environnementales (MAE) en froment d'hiver
Soete, Alice; Vancutsem, Françoise ULg; Bodson, Bernard ULg et al

in Livre Blanc: Céréales - Gembloux - Informations avant les semis (2003, September 09)

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See detailLe froment d'hiver
Vancutsem, Françoise ULg; Couvreur, Luc; Bodson, Bernard ULg et al

in Livre Blanc: Céréales - Gembloux - Informations avant les semis (2003, September 09)

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See detailAperçu de la qualité des froments d'hiver en 2003
Sinnaeve, Geoges; Lenartz, J.; Herman, Jean-Luc et al

in Livre Blanc: Céréales - Gembloux - Informations avant les semis (2003, September 09)

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See detailEstimation of surface soil organic matter by means of hyperspectral data analysis.
Touré, Souleymane; Tychon, Bernard ULg

Conference (2003, September 04)

This presentation shows results from two different hyperspectral instruments for the assessment of soil organic content of agricultural soils in southern Belgium.

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See detailPortable Holographic Marking Unit
Habraken, Serge ULg; vandormael, Denis; Holman, John, C.

Patent (2003)

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See detailDifferent mechanisms are implicated in ERBB2 gene overexpression in breast and in other cancers
Vernimmen, D.; Guéders, Maud ULg; Pisvin, Sonia ULg et al

in British Journal of Cancer (2003), 89(5), 899-906

The ERBB2 gene is overexpressed in 30% of breast cancers and this has been correlated with poor prognosis. ERBB2 is upregulated in other cancers such as prostate, pancreas, colon and ovary. In breast ... [more ▼]

The ERBB2 gene is overexpressed in 30% of breast cancers and this has been correlated with poor prognosis. ERBB2 is upregulated in other cancers such as prostate, pancreas, colon and ovary. In breast cancer cells, the mechanisms leading to ERBB2 gene overexpression are increased transcription and gene amplification. In these cancers, AP-2 transcription factors are involved in ERBB2 overexpression, and AP-2 levels are correlated with p185(c-erbB-2) levels. In this work, we wanted to know if the same molecular mechanisms are responsible for the ERBB2 upregulation in non-breast cancers. We compared ERBB2 gene copy number, p185(c-erbB-2) and mRNA levels with AP-2 levels in several ovary, prostate, colon and pancreas cancer cells. A moderate expression of erbB-2 mRNA and protein were observed in some cells without gene amplification. In contrast to breast cancer cells, AP-2 factors were absent or low in some non-breast cells which did express ERBB2. It is thus likely that AP-2 is not a major player in the increased levels of erbB-2 transcripts in non-breast cancer cells. The transcriptional activity of the ERBB2 promoter in colon and ovary cancer cells was estimated using reporter vectors. The results showed that the promoter regions involved in ERBB2 gene overexpression in breast cancer cells are different from those that lead to the gene upregulation in colon and ovary cancers. In conclusion, our results indicate that different transcriptional and post-transcriptional mechanisms are responsible for the increased levels of erbB-2 transcript and protein in breast and non-breast cancer cells. [less ▲]

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See detailSeparation of the retinal and central contribution to changes in visual performance after light exposure
Vandewalle, Gilles ULg

Master of advanced studies dissertation (2003)

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See detailElaboration d'outils intégrés de gestion des données topographiques et morphologiques pour la modélisation des crues et inondations
Detrembleur, Sylvain ULg

Master of advanced studies dissertation (2003)

L’activité de recherche dont bénéficie ce travail a consisté à poursuivre le développement du logiciel quasi-tridimensionnel de modélisation des écoulements de surface de la suite WOLF. Plus ... [more ▼]

L’activité de recherche dont bénéficie ce travail a consisté à poursuivre le développement du logiciel quasi-tridimensionnel de modélisation des écoulements de surface de la suite WOLF. Plus particulièrement, ce travail vise à développer et à rendre opérationnelle une filière automatique de traitement de données topographiques et morphologiques directement exploitables par WOLF2D. Ces algorithmes sont basés sur des approches hydrauliques ou sédimentaires, afin de générer une information complète sur grids réguliers organisés en blocs. Il s’agit d’exploiter des informations parcellaires, soit acquises par laser ou sonar multi-faisceaux, soit issues de campagnes plus classiques d’acquisition de profils en travers par méthodes topographiques. Une adaptation des lois classiques de frottement est également suggérée et traitée numériquement afin de tenir compte de ce nouveau type d’information très dense ainsi que des obstacles locaux constitués par les ouvrages d’art imposant des mises en charge et des pertes de charge locales. Le bien-fondé de ces développements est mis en lumière par le routage de grosses applications réelles pour lesquelles des campagnes complémentaires sur sites, l’exploitation de laisses de crue locales et des enquêtes de terrain permettent des comparaisons significatives. [less ▲]

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See detailExpression pattern of metalloproteinases and tissue inhibitors of matrix-metalloproteinases in cycling human endometrium
Goffin, Frédéric ULg; Munaut, Carine ULg; Frankenne, Francis et al

in Biology of Reproduction (2003), 69(3), 976-984

The cyclic growth, differentiation, and cell death of endometrium represents the most dynamic example of steroid-driven tissue turnover in human adults. Key effectors in these processes-matrix ... [more ▼]

The cyclic growth, differentiation, and cell death of endometrium represents the most dynamic example of steroid-driven tissue turnover in human adults. Key effectors in these processes-matrix metalloproteinases (MMPs) and their specific inhibitors (TIMPs)-are regulated by ovarian steroids and, locally, by cytokines. We used reverse transcription-polymerase chain reaction to evaluate the expression of both transcriptionally regulated molecules such as estrogen receptor-alpha, progesterone receptor, and prolactin and a large array of MMPs and TIMPs (MMP-1, -2, -3, -7, -8, -9, -11, -12, -19, -26, MT1-MMP, MT2-MMP, MT3-MMP, TIMP-1, -2, -3). Altogether, three distinct patterns of MMP and two patterns of TIMP expression were detected in cycling endometrium: 1). MMPs restricted to the menstrual period (MMPs-1, -3, -8, -9, -12); 2). MMPs and TIMPs expressed throughout the cycle (MMP-2, MT1-MMP, MT2-MMP, MMP-19, TIMP-1, and TIMP-2); 3). MMPs predominantly expressed during the proliferative phase (MMP-7, MMP-11, MMP-26, and MT3-MMP); and 4). TIMP-3, which, contrary to the other TIMPs, shows significant modulations, with maximum expression during the late secretory and menstrual phases. These specific patterns of MMP expression associated with each phase of the cycle may point to specific roles in the processes of menstruation, housekeeping activities, angiogenesis, tissue growth, and extracellular matrix remodeling. [less ▲]

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See detailStress echocardiography in horses: comparison of cardiac output during incremental dobutamine infusion in atropinised and non-atropinised ponies
Sandersen, Charlotte ULg; Detilleux, Johann ULg; Delguste, Catherine ULg et al

in Proceedings of the 42d Annual Congress of the British Equine Veterinairy Association (2003, September)

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See detailMoritella cold-active dihydrofolate reductase: Are there natural limits to optimization of catalytic efficiency at low temperature?
Xu, Y.; Feller, Georges ULg; Gerday, Charles ULg et al

in Journal of Bacteriology (2003), 185(18), 5519-5526

Adapting metabolic enzymes of microorganisms to low temperature environments may require a difficult compromise between velocity and affinity. We have investigated catalytic efficiency in a key metabolic ... [more ▼]

Adapting metabolic enzymes of microorganisms to low temperature environments may require a difficult compromise between velocity and affinity. We have investigated catalytic efficiency in a key metabolic enzyme (dihydrofolate reductase) of Moritella profunda sp. nov., a strictly psychrophilic bacterium with a maximal growth rate at 2degreesC or less. The enzyme is monomeric (M-r = 18,291), 55% identical to its Escherichia coli counterpart, and displays T-m and denaturation enthalpy changes much lower than E. coli and Thermotoga maritima homologues. Its stability curve indicates a maximum stability above the temperature range of the organism, and predicts cold denaturation below 0degreesC. At mesophilic temperatures the apparent K-m value for dihydrofolate is 50- to 80-fold higher than for E. coli, Lactobacillus casei, and T. maritima dihydrofolate reductases, whereas the apparent K-m value for NADPH, though higher, remains in the same order of magnitude. At 5degreesC these values are not significantly modified. The enzyme is also much less sensitive than its E. coli counterpart to the inhibitors methotrexate and trimethoprim. The catalytic efficiency (k(cat)/K-m) with respect to dihydrofolate is thus much lower than in the other three bacteria. The higher affinity for NADPH could have been maintained by selection since NADPH assists the release of the product tetrahydrofolate. Dihydrofolate reductase adaptation to low temperature thus appears to have entailed a pronounced trade-off between affinity and catalytic velocity. The kinetic features of this psychrophilic protein suggest that enzyme adaptation to low temperature may be constrained by natural limits to optimization of catalytic efficiency. [less ▲]

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