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See detailOrigine biogénétique des triterpènes pentacycliques présents dans la sécrétion défensive de Platyphora Kollari (Chrysomelidae)
Ghostin, Jean; Laurent, Pascal ULg; Daloze, Désiré et al

Poster (2006)

Les chrysomèles sont des insectes phytophages brillement colorés qui représentent une des famille (Chrysomelidae) les plus importante de l'ordre des coléoptères. Etant aposématiques, ils sont facilement ... [more ▼]

Les chrysomèles sont des insectes phytophages brillement colorés qui représentent une des famille (Chrysomelidae) les plus importante de l'ordre des coléoptères. Etant aposématiques, ils sont facilement repérables par des prédateurs potentiels et ont, au cours de l'évolution, développé des mécanismes de défense chimique élaborés. La découverte de glycosides triterpéniques basés sur le squelette oléanane a soulevé le problème de leur origine biogénétique. En effet, il est bien connu que les insectes ne possèdent pas la squalène synthase, une enzyme indispensable à la formation des stéroïdes et des triterpènes pentacycliques. Dès lors, une biosynthèse de novo de ce type de dérivé est peu probable. Par ailleurs, l'analyse de la plante hôte des chrysomèles a montré que la séquestration des glycosides au départ de cette plante est également exclue. Une troisième possibilité serait que l'insecte utilise un précurseur provenant de son alimentation pour fabriquer ses substances défensives. Un tel précurseur pourrait être la b-amyrine identifiée chez différentes plantes hôtes des chrysomèles ou l'acide oléanolique dont la structure de base se retrouve au niveau des triterpènes défensifs. Enfin, l'analyse des plantes hôtes a montré que celles-ci contiennent à la fois de la b-amyrine et de l'a-amyrine dans un rapport 1,76/1. Cependant aucun glycoside triterpénique basé sur le squelette ursane n'a été isolé jusqu'à présent chez les chrysomèles, ce qui suggère un mécanisme de transport sélectif en faveur de la b-amyrine. Dans le cadre de ce travail, nous présenterons les synthèses d'a-amyrine, de b-amyrine et d'acide oéanolique trideutériés, ainsi que les résultats d'incorporation des deux premiers précurseurs chez Platyphora kollari. [less ▲]

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See detailOrigine biogénétique des triterpènes pentacycliques présents dans la sécrétion défensive de Platyphora Kollari (Chrysomelidae)
Ghostin, Jean; Laurent, Pascal ULg; Daloze, Désiré et al

Poster (2004)

Les chrysomèles sont des insectes phytophages brillamment colores qui, avec plus de 32000 espèces, représentent une des familles (Chrysomelidae) les plus importantes de 1'ordre des coléoptères. Etant ... [more ▼]

Les chrysomèles sont des insectes phytophages brillamment colores qui, avec plus de 32000 espèces, représentent une des familles (Chrysomelidae) les plus importantes de 1'ordre des coléoptères. Etant aposématiques, ils sont facilement repérables par des prédateurs potentiels et ont, au cours de 1'evolution, développé des mécanismes de défense chimique élaborés. La découverte de glycosides triterpéniques basés sur le squelette oléanane (comme par exemple le ligatoside B) dans les secrétions défensives de plusieurs espèces de Doryphorina (Platyphora, Desmogramma et Leptinotarsa) a soulevé le problème de leur origine biogénétique. En effet, il est bien connu que les insectes ne possèdent pas la squalène synthase, une enzyme indispensable à la formation des stéroïdes et des triterpènes pentacycliques. Des lors, une biosynthèse de novo de ce type de dériveé par les chrysomèles est peu probable. Par ailleurs, l’analyse de la plante hôte des chrysomèles a montre que la séquestration des glycosides au départ de cette plante est également exclue. Une troisième possibilité serait que 1'insecte utilise un précurseur provenant de son alimentation pour fabriquer ses substances défensives. Un tel précurseur pourrait être la la b-amyrine identifiée chez différentes plantes hôtes des chrysomèles ou 1'acide oléanolique dont la structure de base se retrouve au niveau des triterpènes défensifs. Enfin l’analyse des plantes hôtes a montré que celles-ci contiennent a la fois de la b-amyrine et de l’a-amyrine dans un rapport 1,76/1. Cependant, aucun glycoside triterpénique basé sur le squelette ursane n'a été isolé jusqu'à présent chez les chrysomèles, ce qui suggère un mécanisme de transport sélectif en faveur de la b-amyrine . Dans le cadre de ce travail, nous présenterons les synthèses d'a-amyrine, de b-amyrine et d'acide oléanolique trideutériés, ainsi que les résultats d'incorporation des deux premiers précurseurs chez Platyphora kollari. [less ▲]

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See detailOrigine de l'abstraction
Seba, Jean-Renaud ULg

in Artistes liégeois d'aujourd'hui (1980)

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See detailOrigine de la CISP et mise en application actuelle dans les pays Francophones
Jamoulle, Marc ULg

Scientific conference (1999)

The International Classification of Primary Care (ICPC), first (1987) and second (1998) editions have been elaborated by the WONCA International Classification Committee (WICC), an international group of ... [more ▼]

The International Classification of Primary Care (ICPC), first (1987) and second (1998) editions have been elaborated by the WONCA International Classification Committee (WICC), an international group of family doctors driven by WONCA, the world organisation of family doctors. We describe the story of ICPC and ICPC-2, their relationships to the International Classification of Disease and their utilisation in the episode of care processing. The ICPC French speaking users club (CISP-Club), on behalf of the WONCA International Committee, spreads information and training methods about research in general practice/family medicine through the use of IC?C. The CISP-Club manages also an Internet site for the Committee [less ▲]

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See detailOrigine de la vie : où, quand, comment ?.
Javaux, Emmanuelle ULg

Conference given outside the academic context (2010)

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See detailL’origine de la vie dans l’univers
Javaux, Emmanuelle ULg

Conference given outside the academic context (2007)

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See detailL'origine des hématites oolithiques exploitées durant la Préhistoire récente. Objectifs et méthodes d'un PCR
BILLARD, Cyrille; SAVARY; GOEMAERE, Eric et al

Poster (2011)

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See detailL'origine des mégalithes du Fond de Quarreux (Ardenne, Belgique)
Collard, Sébastien; Juvigné, Etienne ULg; Marion, Jean-Marc ULg et al

in Bulletin de la Société Géographique de Liège (2012), 58

Origin of megaliths of the Fond de Quarreux (Ardenne, Belgium). Distribution of megaliths was studied in the Ambleve valley throughout its gorge developed within the quartzites of the Cambrian-aged La ... [more ▼]

Origin of megaliths of the Fond de Quarreux (Ardenne, Belgium). Distribution of megaliths was studied in the Ambleve valley throughout its gorge developed within the quartzites of the Cambrian-aged La Venne Formation (Fond de Quarreux) in the south-eastern part of high Belgium. The high concentration of megaliths at this place can be essentially explained by mass movements which have occurred on the adjacent slopes in periglacial periods of cold Ocean Isotopic Stages in Quaternary times, and especially the coldest ones i.e. even O.I.S.#22 through #2. Stratigraphical studies of deposits in the Chefna and Ambleve valleys allowed us to place final periglacial deposits during the Younger Dryas. The critical shear stress and the critical unit stream power are used in order to evaluate the Ambleve River competence. It results that, under the present climatic conditions, this river cannot move boulders of more than 50 cm in diameter. Hence, it is concluded that ice rafting has been the main process responsible for carrying away the megaliths which have got the Ambleve river bed throughout the Quaternary Period. [less ▲]

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See detailOrigine des produits animaux et empreinte génétique
Portetelle, Daniel ULg; Mortiaux, Frédéric; Burny, Arsène et al

in Agricontact (1997), 294

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See detailL'origine des querelles entre Jean de Bavière et les Liégeois : l'affaire de Seraing en 1395
Kurth, Godefroid ULg

in Bulletin de la Classe des Lettres et des Sciences Morales et Politiques (1908), 9-10

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See detailOrigine des troubles morphosyntaxiques chez des enfants dysphasiques
Maillart, Christelle ULg

Doctoral thesis (2003)

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See detailOrigine du Solutréen: le rôle de l'Espagne
Otte, Marcel ULg; Noiret, Pierre ULg

in Zephyrus (2002), LV

The Solutrean "culture" of France should be separated in two clearly distinct elements. (1) The "Proto-Solutrean" and the "early" Solutrean are linked to the late phases of the Gravettian of the northern ... [more ▼]

The Solutrean "culture" of France should be separated in two clearly distinct elements. (1) The "Proto-Solutrean" and the "early" Solutrean are linked to the late phases of the Gravettian of the northern plains. (2) The "middle and late" Solutrean seem to have originated in Spain. A movement from North Africa, in the most arid phase, constitutes the most likely hypothesis to explain this expansion. [less ▲]

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See detailL’origine du télescope (I)
Manfroid, Jean ULg

Article for general public (2013)

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See detailL’origine du télescope (II)
Manfroid, Jean ULg

Article for general public (2013)

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See detailL'origine du verbe haver, terme de houillerie
Tilkin, Françoise ULg; Remacle, Louis

in Les dialectes de Wallonie (1989), 17

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See detailOrigine et dynamique des populations d’arbres des forêts denses humides d’Afrique Centrale, le cas de Lophira alata Banks ex Gaertn C.F. (Ochnaceae)
Biwole, Achille ULg

Doctoral thesis (2015)

The canopy of Central African rainforests is characterized by the abundance of light-demanding trees belonging to several species, suggesting that favorable conditions for their regeneration once ... [more ▼]

The canopy of Central African rainforests is characterized by the abundance of light-demanding trees belonging to several species, suggesting that favorable conditions for their regeneration once prevailed. Today this isn’t the case in light of the demographic structure of their populations, which shows a lack of regeneration. The appearance of such species in rainforests is the result of significant and sustainable openings in the forest canopy. Such events may have occurred with climatic changes and / or large-scale anthropogenic disturbances. The risk of their populations decline is increased by the fact that most of them are timber species. This is typically the case of Lophira alata Banks ex Gaertn C.F., which is one of the most important Central African trees harvested, and is considered vulnerable by the IUCN. In the current context where the preservation of the biodiversity and the integrity of the forest cover is a major concern, the present PhD aims to understand the history and ecological requirements of L. alata in order to propose the sustainable management strategies. The history of L. alata has been studied using an approach integrating both anthracology and archeology. We found a large body of evidences (pottery fragments, palm nuts and charcoal) in the forests soil of southern Cameroon indicating human occupation and widespread fires over two periods : 2200 - 1500 years BP, and around 300 years BP. The age of the most recent events coincides with the probable age of the tallest specimens of L. alata. To determine the light requirements of the species and to better define its regeneration strategy, a quantitative study on the guild of juveniles was conducted for two years. The results show that L. alata has both the characteristics of a pioneer species and those of a non-pioneer species. Indeed, at low irradiances (1% of full sunlight), the plants mortality rate was very low and their biomass showed no signs of decline, a behavior observed in all non-pioneer species. By contrast, the response of leaf traits, patterns of biomass allocation, and the maximum growth of plants in the intermediate (23-43% of the relative irradiance) and high (100%) irradiance levels, according to the population origins, are typical of all pioneer species. These results emphasize the importance of the population origins when studying the response to light and the need to define a more encompassing classification system. In terms of the dynamics of mature populations, environmental conditions affect the diameter growth of trees, with better growth being realized in the evergreen forest. Nevertheless, even under these favorable conditions, simulations of the exploitable stocks and their recovery rates indicated a significant decline during the first three cutting cycles, which could lead to a decline in economic activity associated with this species. Our results allowed us to suggest a set of recommendations for the sustainable management of L. alata. [less ▲]

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See detailOrigine et effet de la myéloperoxydase lors de la congélation du sperme d'étalon
Ponthier, Jérôme ULg

Doctoral thesis (2012)

Semen freezing allows worldwide commercialization of equine genetic. Despite improvement of techniques, semen of 20% of stallions remains unfreezable. Currently, post-thaw semen quality is only determined ... [more ▼]

Semen freezing allows worldwide commercialization of equine genetic. Despite improvement of techniques, semen of 20% of stallions remains unfreezable. Currently, post-thaw semen quality is only determined by progressive motility, but its definition is not standardised. Spermatozoa are highly differentiated cells and freezing lesions can occur on DNA, membrane, mitochondria or acrosome. Current research focuses on prediction of freezability, improvement of freezing extenders and prevention of Reactive Oxygen Species (ROS) effects. Under its O2 form, oxygen is inactive and oxidase or oxygenase enzymes are required to produce ROS. Two pathways of ROS production in semen are described: the intrinsic pathway reflecting ROS escaping from the spermatozoon mitochondria and the extrinsic pathway corresponding to ROS produced by inflammatory cells. ROS induce DNA fragmentation, lipid peroxidation, apoptosis and decreased motility of spermatozoa. Myeloperoxidase (MPO) is a pro-oxidant enzyme contained in and released by neutrophils during degranulation or after lysis. It is responsible for formation of hypochlorous acid, a strong oxidant, which could damage spermatozoa. However, MPO presence and effects have never been investigated in equine semen. The first aim was to assay presence of MPO in equine thawed semen and to determine a relation between MPO concentration and post-thaw semen parameters. 35 straws from different stallions were analyzed. Post-thaw spermatozoa and MPO concentrations, viability, morphology, progressive and total motility were determined. Our study showed that thawed semen contains large amounts of free MPO. High MPO concentration samples showed lower total and progressive motility. Higher proportion of acrosome reaction was observed in late examinations of the high MPO concentration group. As MPO was present in frozen semen and did interfere with its quality, timing and origin of its release was determined during the freezing process. Forty ejaculates were frozen with a classical procedure. MPO ELISA and MPO immunocytochemistries (ICC) were assayed in raw semen, centrifugation supernatant, and after cooling down to 4°C. Post-thaw MPO concentration and spermogram parameters were determined. MPO concentration increased after cooling and thawing when compared to fresh semen. As temperature decreased, MPO was higher in post-thaw poor quality samples. Non-sperm cells (NSC) showed various degrees of MPO-ICC, and were mostly epithelial cells with nuclear picnosis. Elastase, another neutrophil pro-inflammatory enzyme, was also assayed in post-thaw semen. In twenty ejaculates, NSC concentration was determined in fresh semen. Post-thaw motilities were determined by CASA; MPO and elastase concentrations were assayed by ELISA. Post-thaw elastase concentrations were low and there was no difference according to semen quality. NSC or MPO concentrations were not correlated to elastase concentration. NSC concentration was higher in unfreezable semen and correlated to post-thaw MPO concentration. To confirm MPO release by NSC during freezing, the effect of washing semen with density gradient centrifugation (DGC) was then assayed on NSC and MPO concentrations. NSC and MPO concentrations were assessed at each step and MPO localization was performed by ICC. DGC washing decreased NSC and MPO concentrations in post-thaw semen and NSC were mainly remaining in DGC supernatant. MPO concentration was correlated with NSC concentration in the upper layer of the DGC supernatant and in post-thaw semen. NSC were epithelial cells showing MPO-ICC staining. Fresh semen MPO concentration had no effect on fresh or post-thaw semen quality, while post-thaw semen concentrations were correlated with decreased motility. To understand these findings, concentration, activity and structure of MPO present in seminal plasma, sperm-rich pellet and post-thaw semen were assayed. Factor inducing MPO release was determined by adding or not glycerol in samples stored at 4°C or 20°C. Total MPO was high in seminal plasma and thawed semen and low in sperm-rich pellet. Active MPO was high in sperm-rich pellet and low in seminal plasma and post-thaw semen. MPO concentrations were correlated in post-thaw and in semen cooled at 4°C with or without glycerol. Active MPO in sperm-rich pellet and post-thaw progressive motility were highly negatively correlated. MPO present in fresh semen is mainly the native inactive enzyme subunit. To confirm our previous findings, effect of active MPO and fresh or frozen-thawed NSC was assayed on purified spermatozoa motility, mitochondrial potential, membrane and acrosome integrity. Highest MPO concentration tested (50ng/ml) decreased motility. However, highest MPO concentration did not affect mitochondrial potential, membrane or acrosome integrity. Thawed NSC did decrease motility and mitochondrial potential when compared to fresh NSC, suggesting a synergic effect between MPO and other products released by NSC after thawing. Temperature decrease during freezing process increases MPO concentration and post-thaw concentration is negatively associated to post-thaw motilities. ICC slides have shown MPO presence on epithelial keratinized and pycnotic cells while neutrophils were rarely observed. Semen washing with DGC decreases MPO and NSC concentrations in post-thaw semen as NSC and MPO concentrations were positively correlated. MPO present in seminal plasma is native and inactive form while MPO present in sperm-rich pellet is active and negatively correlated to the post-thaw progressive motility. Addition of active MPO in semen decreased motility but had no effect on acrosome integrity, despite what had previously been suggested. Thawed NSC addition to spermatozoa decreased mitochondrial potential, suggesting a synergic effect between MPO and other factors released by NSC. Further studies should investigate the origin of high inactive MPO concentrations in fresh semen. Other studies should be conduced about the origin of epithelial keratinized pyknotic NSC in fresh semen and the pathophysiological mechanism leading to their MPO release during freezing. Large scale studies should be conducted to confirm the use of NSC concentration in fresh semen or active MPO concentration in sperm rich pellet as freezability prognosis. Further studies should also investigate effect of MPO specific inhibitors. [less ▲]

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See detailOrigine et évolution du cannibalisme dans les populations animales : pourquoi manger son semblable ?
Alabi, Taofic; Patiny, Sébastien; Verheggen, François ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2009), 13

Le cannibalisme est issu d’une déformation linguistique de la terminologie Arawak (Amérindiens des Antilles) caribal qui signifie courageux. Christophe Colomb l’emploie pour désigner les Indiens des ... [more ▼]

Le cannibalisme est issu d’une déformation linguistique de la terminologie Arawak (Amérindiens des Antilles) caribal qui signifie courageux. Christophe Colomb l’emploie pour désigner les Indiens des Caraïbes réputés pour être des mangeurs d’hommes. Le cannibalisme est largement répandu au sein du règne animal. Sa pratique au sein de l’espèce humaine remonte au Paléolithique et persiste encore dans certaines sociétés actuelles, bien qu’elle ne répond pas exclusivement à des besoins alimentaires comme chez les autres espèces animales. Au regard de sa large distribution, il y a lieu de s’interroger sur les causes, origines et avantages évolutifs de ce comportement au sein du règne animal. Le cannibalisme est induit soit par des facteurs écologiques directement liés à une insuffisance des ressources alimentaires, à de fortes densités d’individus et à une hétérogénéité structurale de la population, soit par des facteurs sociaux comme des besoins de reproduction, ou des contraintes de soins parentaux face à une progéniture trop nombreuse. Les avantages de ce comportement sont les gains nutritionnel et énergétique, les gains de territoire pour vivre et se développer. Par contre, les inconvénients résident dans la réduction des effectifs et de la variabilité génétique de la population, ainsi que dans la possibilité de transmission de parasites, virus et de maladies. [less ▲]

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See detailOrigine et impact des risques biologiques, physiques et chimiques
Samb, Babacar; Schiffers, Bruno ULg

in Proceedings Bio-Scope - Atelier "Responsable Assurance Qualité Totale" (2003)

La préservation de la santé des consommateurs est devenue une préoccupation majeure en ce début de nouveau millénaire marqué par le poids de la société civile en général et des ligues de consommateurs en ... [more ▼]

La préservation de la santé des consommateurs est devenue une préoccupation majeure en ce début de nouveau millénaire marqué par le poids de la société civile en général et des ligues de consommateurs en particulier. Les exigences en termes de qualité sanitaire et de traçabilité, qui figurent non seulement dans des réglementations toujours plus strictes mais aussi dans des référentiels de qualité ou des cahiers de charge imposés aux producteurs, traduisent la volonté des consommateurs européens de savoir où, comment et quand les aliments qu'ils ont dans leur assiette ont été produits. [less ▲]

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