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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 detailL'accord institutionnel d'octobre 2011 et sa mise en oeuvre constitutionnelle et législative
Behrendt, Christian ULg

Conference given outside the academic context (2012)

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See detailAbundance estimates of southern right whales (Eubalaena australis) in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els ULg; Cammareri, Alejandro

Poster (2012, March 27)

Aerial surveys were conducted to estimate the abundance of southern right whales in Bahía San Antonio, a bay located in the north-western region of the San Matías Gulf (40°50¿S 64°50¿W), Rio Negro ... [more ▼]

Aerial surveys were conducted to estimate the abundance of southern right whales in Bahía San Antonio, a bay located in the north-western region of the San Matías Gulf (40°50¿S 64°50¿W), Rio Negro, Patagonia Argentina. The transect for the realization of aerial surveys was designed using the program DISTANCE 6.0 and consisted out of 14 North-South (up to S 40.9°) parallel transect lines with a 2.5km separation, covering a total surface of 418km² (mean coverage probability=0.78). Transect length was chosen according to the safety restrictions of the pilot. Surveys were conducted in good weather conditions and calm sea state (Beaufort 3 or less) using a high-wing Cessna 152 with a flat window. Due to the small size of the aircraft, only one person could fly besides the pilot; observations where therefore made from one side only. Average speed and height of the aircraft was kept constant over the surveys at 90kn (166km/h) and 700ft (213m) respectively. When a group of southern right whales was sighted, data were taken on location (using a Garmin GPSmap 60csx), time and group size. The downward angle to the group perpendicular to the aircraft¿s track was then measured using a hand-held clinometer (Suunto PM5/360PC). Perpendicular distances were calculated by the means of trigonometry using the aircraft¿s altitude and the declination angle to the sighting. Due the flat windows of the aircraft a left truncation distance was set at 150m. Perpendicular distances were also right-truncated at 10% of the observations. The uniform cosine model was chosen in the view of the minimum AIC to model the detection function of southern right whales in the study area. The estimates of g(0)=(s+t)/(s+d) resulted in a correction factor of 0.392 ± 0.456 In total, 7 aerial surveys were conducted in the beginning of August and September 2009, September, October and November 2010, and August, September 2011, resulting in a total flight time effort of 12.4h. In total, 200 whales were seen in 119 whale groups, equally distributed over the entire bay. Group sizes ranged between 1-5 animals with a mean group size of 1.7 animals (SD=0.83). Results show a peak of averagely 136 ± 63 whales in the bay during the month of September, with less than half the amount of whales present in adjacent months. September being the peak month for right whale presence accords to data from other regions in the country. The aerial surveys resulted in the first estimates of southern right whale abundance in this north Patagonian bay and indicate a marked peak during September. Nevertheless, data obtained over the other months remain scarce. More aerial surveys should be conducted to accurately determine the evolution of southern right whale abundance in the study area. [less ▲]

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See detailRegard du G1000 sur les propositions de réformes de l'État belge d'écolo j et Jong Groen
Dodeigne, Jérémy ULg

Conference given outside the academic context (2012)

Detailed reference viewed: 51 (2 ULg)
See detailMercury in blood of free-ranging seals Phoca vitulina from the North Sea: Time-trend and association with environmental factors
Das, Krishna ULg; Brochoire, Charlène ULg; Chambosse, Mélanie et al

Conference (2012, March 27)

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment ... [more ▼]

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment. Recently, development of monitoring programs and non-invasive sampling techniques, including seal catches allowed blood sampling on a regular basis together with measurements of blubber thickness, body mass, sex and body length. Concentrations of total mercury (T-Hg) and other trace elements (Cd, Pb, Zn, Cu, Fe) as well as ∂13C and ∂15N values were determined by mass spectrometry in blood of 75 wild harbour seals caught in the German Wadden Sea between 1997 and 2011. ∂13C and ∂15N mean values (-17.5‰ and 18.1 ‰ respectively) were strongly similar to that measured previously in the muscle of stranded harbour seals from the Wadden Sea. In contrast, ∂15N mean value was strikingly higher than that recorded in grey seals (Halichoerus grypus) from Scotland (14.1 ‰ respectively; Habran et al. submitted.) while ∂13C values remained similar between the two seal species. These values confirmed the high trophic position of the harbour seal in the North Sea. In contrast to Cd and Pb, T-Hg in blood harbour seals reached concentrations as high as 2.1 μg.g-1 dry weight (10 times higher than the 0.21 μg.g-1 dry weight recorded for grey seals from Scotland) but depended on several factors including ∂15N values, age group and the body mass. T-Hg was detected in juveniles confirming maternal transfer to offspring and time-trend revealed no decrease of T-Hg in blood of harbour seals these last 15 years. [less ▲]

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See detailEnergie et climat : historique et perspectives
Ozer, Pierre ULg

in La ville : air, eau, terre, feu. Éléments pour un Plan Régional de Développement Durable économe en ressources (2012)

On le sait, la Conférence de Copenhague a été un échec. En effet, quelques chefs d'Etat –à savoir les européens et américains pour le monde industrialisé– et la Chine, l'Inde, le Brésil et l'Afrique du ... [more ▼]

On le sait, la Conférence de Copenhague a été un échec. En effet, quelques chefs d'Etat –à savoir les européens et américains pour le monde industrialisé– et la Chine, l'Inde, le Brésil et l'Afrique du Sud pour les pays émergents ont doublé le processus de négociations des Nations Unies (dans l'obscurantisme le plus total et sans concertation avec les pays en développement) pour arriver à une note qui tient sur deux pages. Ce texte ne comporte plus de trace d'engagement de réduction de GES pour 2020 ou 2050, pas même volontaire. Une aide financière sera dégagée pour aider les pays pauvres à faire face aux conséquences du changement climatique. Quel sera le montant de cette aide ? Sera-t-elle additionnelle ou détournée des fonds d'aide au développement ? De qui viendra-t-elle et à qui profitera-t-elle ? Et pour quoi faire ? Nul ne le sait. Quant à la réduction de la déforestation et aux contraintes d'émissions de GES pour les secteurs aérien et maritime (annoncés comme des conditions sine qua non d'accord par les européens), pas un mot... Autant dire que le résultat final de ce grand rendez-vous n'est guère étincelant... Directement après ladite Conférence, j’écrivais dans une carte blanche « A quoi sert la science, si le politique se borne à cultiver, pour des raisons économiques dans le court terme, la science de l'inconscience ? » (Ozer 2010). Arriverons-nous à trouver un accord dans les mois ou les années à venir ? Ou devrons-nous subir brutalement les conséquences de ce changement climatique ? Car on peut négocier à l’infini entre délégations, mais on ne négociera jamais avec la physique de l’atmosphère. [less ▲]

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See detailMensonge et vérité sur la vibrotonie
Bruyère, Olivier ULg

Scientific conference (2012, March 27)

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See detailEvaluation de la diversité des pucerons et de leurs ennemis naturels en cultures maraîchères dans l’est de la Chine
Chevalier Mendes Lopes, Thomas ULg; Bosquée, Emilie ULg; Polo Lozano, Damien ULg et al

in Entomologie Faunistique = Faunistic Entomology (2012), 64(3), 63-71

The aim of this study was to evaluate the diversity and abundance of aphids and aphidophagous beneficials in courgettes and potato fields in the Shandong province, East of China. The assessment of aphid ... [more ▼]

The aim of this study was to evaluate the diversity and abundance of aphids and aphidophagous beneficials in courgettes and potato fields in the Shandong province, East of China. The assessment of aphid and related beneficial populations was conducted between May 9th and June 13th, 2011, using yellow traps and in situ observations on plants. A total of 53,206 insects were trapped and 35,144 observed on the plants. Aphids widely predominated in the traps and exerted a strong pressure on both crops early in the season. Two main species were identified on the plants, namely Aphis gossypii on the courgettes and Myzus persicae on the potatoes. Ladybirds were the most abundant aphidophagous predators, especially Coccinella septempunctata on the courgettes and Propylea japonica on the potato fields, the first one being earlier than the second. Only few hoverflies and lacewings were captured. Microhymenoptera appeared later in the season. The Aphidius gifuensis species represented the majority of trapped Braconidae, while the family Aphelinidae contained the largest number of individuals in the aphidiphagous. [less ▲]

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See detailEverybody knows what IRT is... (really?)
Magis, David ULg

Conference (2012, March 27)

Item response theory (IRT) is not only a famous acronym, it also covers a broad range of statistical and psychometric models, methods, and applications in psychology and educational science. However, IRT ... [more ▼]

Item response theory (IRT) is not only a famous acronym, it also covers a broad range of statistical and psychometric models, methods, and applications in psychology and educational science. However, IRT looks somewhat misunderstood or even esoteric to the non-statisticians and non-psychometricians. The main goal of this talk is to briefly and clearly present the main aspects of traditional IRT: objectives, assumptions, basic models, and basic estimation methods. As a secondary purpose, extensions of IRT to more complex situations (polytomous data, multidimensional and hierarchical models, computerized adaptive testing, differential item functioning, nonparametric IRT) are briefly outlined. This talk will be as little technical as possible, focusing on the main concepts and applications of this theory. [less ▲]

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See detailIntraocular Lenses with Functionalized Surfaces by Biomolecules in Relation with Lens Epithelial Cell Adhesion
Huang, Yi-Shiang ULg

Conference (2012, March 27)

A cataract is pathology opacity of the lens or capsule of the eye, causing impairment of vision or even blindness. In 1998, it was estimated that worldwide 19.4 million people were bilaterally blind from ... [more ▼]

A cataract is pathology opacity of the lens or capsule of the eye, causing impairment of vision or even blindness. In 1998, it was estimated that worldwide 19.4 million people were bilaterally blind from age-related cataract. Surgery, with lens extraction and intraocular lens implantation, is still the only currently available treatment. More than 1.3 million cataract operations were performed in the USA in 1998 at a cost of $3.5 billion. The most common complication after implantation of intraocular lenses (IOLs) is the posterior capsular opacification (PCO) or secondary cataract. This is the result of lens epithelial cells (LECs) proliferation and their transition to mesenchymal cells. In 1997, a Sandwich theory was proposed to elucidate the developmental process of PCO. According to this model, an IOL with higher affinity to LECs will induce a less PCO. In our research, the pHEMA (Poly(2-hydroxyethyl methacrylate)) based acrylic hydrophilic polymer is subjected to the surface modification by conjugating with the bioactive peptides. The RGD sequence, known for its excellent biocompatibility, is designed to stimulate the biointegration between the LECs and the polymer implant. Our research program will focus on the evaluation of the physical, mechanical and biological properties of the lens before and after peptide grafting. These diverse tests include contact angle measurements, Atomic Force Microscopy (AFM), x-ray photoelectron spectroscopy (XPS), FTIR/ATR, Scanning Electron Microscopy (SEM), and the MTS cytotoxicity assay. [less ▲]

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See detailMEMS packaging is crucial for system performance and reliability
Saint-Mard, Michel; Stoukatch, Serguei ULg

Scientific conference (2012, March 27)

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See detailRecognition of emotions in facial images
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

Report (2012)

This document reports about some work done in the field of emotions classification in facial images.

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See detailA medicina do Egito greco-romano revelada pelos papiros
Marganne, Marie-Hélène ULg; Macedo, Gabriel ULg

Scientific conference (2012, March 26)

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See detailSeasonal Variation in Abundance and Time-Budget of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els ULg; Cammareri, Alejandro; Holsbeek, Ludo et al

Poster (2012, March 26)

The abundance and time-budget of bottlenose dolphins (Tursiops truncatus) was assessed in Bahía San Antonio, Patagonia (Argentina) in the years 2009 and 2010. A total of 366.4 boat-based survey hours ... [more ▼]

The abundance and time-budget of bottlenose dolphins (Tursiops truncatus) was assessed in Bahía San Antonio, Patagonia (Argentina) in the years 2009 and 2010. A total of 366.4 boat-based survey hours resulted in 64 contact hours with a total of 88 dolphin groups. Mark-recapture abundance estimations, based on 63 identified dolphins, resulted in a corrected maximum estimate of 97 and 83 individuals during winter, and a minimum of 34 and 38 individuals during autumn of 2009 and 2010 respectively. Between 25% and 68% of the population consisted of unidentifiable individuals depending on the season, indicating the high presence of juveniles and calves. Behavioural data indicated that the dolphin¿s time-budget consisted mainly out of resting and feeding, variable over the seasons. Dolphins increased their time feeding and socializing during winter and spring, whereas feeding dropped to a minimum in autumn. During summer, the dolphins spent up to 46% of their time diving, a behaviour presumably associated with a tail out/peduncle-dive foraging strategy. Based on these data, we assume more prey availability during winter and spring (main food source being pelagic fish) and a notable decrease in prey availability during summer with benthic prey species being the main food source. In autumn, even less prey items might be available. Furthermore, the increase in social behaviour during winter and spring combined with a peak in the presence of calves during these seasons, suggests the existence of a mating and calving season. These estimates of abundance are in line with the sizes of other coastal populations of bottlenose dolphins elsewhere in the world, and fit the occupancy patterns described for other coastal areas with small resident communities. The study furthers suggests that dolphins specifically use the study area to rest and feed, and to give birth and raise their young, specifically during winter and spring. [less ▲]

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