Last 7 days
Bookmark and Share    
See detailMOLECULAR TOOLS APPLIED TO THE STUDY OF MICROCYSTIN-PRODUCING CYANOBACTERIA IN BELGIAN WATERBODIES
Lara, Yannick ULg

Doctoral thesis (2014)

‘Blooms’, an increasing worldwide phenomenon, are adversely affecting surface water resource, including reservoirs and lakes, used for drinking water supplies, recreation, crop, irrigation and fisheries ... [more ▼]

‘Blooms’, an increasing worldwide phenomenon, are adversely affecting surface water resource, including reservoirs and lakes, used for drinking water supplies, recreation, crop, irrigation and fisheries. These amenities are affected by recurrent mass proliferations of cyanobacteria. The latter are responsible for the production of a wide range of bioactive compounds, including potent toxins (cyanotoxins). These comprise neurotoxins, cytotoxins, inflammatory agents, and hepatotoxins. Microcystins (MCs), hepatotoxins and tumour promoters are the most documented of the cyanotoxins. The microcystin synthetase gene cluster (mcy) involved in MC biosynthesis consists of a succession of non-ribosomal peptide synthase (NRPS) and polyketide synthetase (PKS) genes. The main producers of MCs are Anabaena, Microcystis, and Planktothrix. However, it is not possible to distinguish a toxic from a non-toxic strain on the basis of their morphology. In the present study, molecular tools were used, optimized and developed to (i) characterize the 16S rRNA gene diversity of planktonic cyanobacteria, (ii) to detect the cyanobacteria responsible for the production of MCs, (iii) to identify the MCs producing taxa, and (iv) to determine the environmental factors that influence the dynamic of toxic and non-toxic genotypes in Belgian freshwaters. Eighty-nine strains were isolated and their 16S rRNA genes sequenced. The 16S rRNA gene diversity was studied in 32 samples by denaturing gradient gel electrophoresis (DGGE). In order to evaluate the contribution of this work to the study of the molecular diversity of cyanobacteria in Belgian waterbodies, 114 (strains and DGGE) sequences obtained during this PhD thesis were compared to Belgian sequences obtained by others. As a result, 14 previously undiscribed operational taxonomic units (OTUs) were found in the present study. For polymerase chain reaction (PCR) detection of the mcyA/B/E genes, the DNA from a total of 162 environmental samples was extracted. The three genes were found together in 64.2% of the samples, whereas the mcyB alone was detected in 95.1% of the samples. In order to identify the mcyE-carriers present in the freshwaters, a restriction fragment length polymorphism (RFLP) was performed on the mcyE gene. The presence of potentially toxic Microcystis was observed in most of the cases.To bypass the constraint of bacterial cultivation, a combination of whole genome amplification (WGA) and enzyme-linked immunoassay (ELISA) was tested on individual colonies of members of two cyanobacteria, Microcystis and Woronichinia, directly from the natural environment. Sequences of 3 different housekeeping genes (ftsZ, gltX, and recA), of 3 mcy genes, and the Internal Transcribed Spacer (ITS) were analyzed for 11 colonies of Microcystis. MCs were detected and quantified by ELISA in 7 of the 11 Microcystis colonies tested, in agreement with the detection of mcy genes. Sequence types (ST) based on the concatenated sequences of housekeeping genes from cyanobacterial colonies from Belgian water bodies appeared to be endemic when compared to those of strains described in the literature. One colony belonged to a yet undiscovered lineage. A similar protocol was used for 6 colonies of the genus Woronichinia, a taxon that is very difficult to cultivate in the laboratory. The 16S rRNA analysis confirmed the colony identification based on morphology. In addition, we obtained for the first time new genetic data for this genus, such as the rpoC1 gene sequences and the sequences and secondary structures of the ITS. The first discovery of NRPS and PKS DNA sequences in Woronichinia colonies highlights the need for further study of this widely occurring genus, to better assess its ability to produce MCs and/or related metabolites. For the first time, in this study, we were able to simultaneously monitor one toxic and one non-toxic genotype of M. aeruginosa using real time qPCR technology during a monitoring of 2 years. Both toxic and non-toxic genotypes dynamics appeared influenced by the photoperiod. In addition, the dynamic of the toxic genotype was influenced of light intensity. The results obtained during this PhD research show the need to characterize toxic cyanobacteria in freshwaters, as well as the conditions that influence MCs concentration dynamics. We showed that factors controlling the dynamics of toxic and non-toxic genotypes are complex. Nevertheless, detection tools can be developed to better understand these widely occurring phenomena. Therefore, efforts should go on in this field with collaborations between the scientists and the authorities. [less ▲]

Detailed reference viewed: 34 (10 ULg)
Full Text
See detailBiologie de la reproduction et analyse du déterminisme et de la différenciation du sexe à des stades précoces chez le tilapia du Nil, Oreochromis niloticus
Gennotte, Vincent ULg

Doctoral thesis (2014)

La reproduction des poissons téléostéens se caractérise par une diversité des types de sexualité (gonochorisme vs hermaphrodisme) et des systèmes de déterminisme du sexe (génétique et/ou environnemental ... [more ▼]

La reproduction des poissons téléostéens se caractérise par une diversité des types de sexualité (gonochorisme vs hermaphrodisme) et des systèmes de déterminisme du sexe (génétique et/ou environnemental), ainsi que par une plasticité du contrôle génétique et endocrinien de la différenciation sexuelle incomparables parmi les autres vertébrés. Le tilapia du Nil (Oreochromis niloticus) est un cichlidé gonochorique possédant un système chromosomique de déterminisme sexuel à homogamétie femelle XX/XY, complété par un déterminisme environnemental, les hautes températures pouvant modifier le développement phénotypique du sexe. L’intérêt porté à cette espèce en aquaculture à conduit au développement de différentes techniques de contrôle du sexe (par traitement hormonal) permettant la production de poissons présentant différentes combinaisons de phénotype/génotype sexuels (mâles XX, XY, YY, femelles XX, XY et YY). Ces derniers constituent des outils majeurs de l’étude du déterminisme et de la différenciation du sexe et soulèvent de nombreuses questions concernant les interactions génotype/phénotype sexuels chez cette espèce. Au regard de ces considérations, nous nous sommes fixés 2 objectifs principaux : 1. Déterminer l’influence du génotype sexuel sur certains aspects liés à la biologie reproductive chez le tilapia du Nil tels que la qualité du sperme, les taux de stéroïdes sexuels (testostérone, T ; 17β-œstradiol, E2 ; 11-cétotestostérone, 11KT) et les comportements agressifs. Le génotype sexuel ne semble pas avoir d’influence sur la qualité gamétique des mâles, puisqu’aucune différence n’est observée entre les individus XX, XY et YY, alors que paradoxalement, les taux de 11KT sont plus élevés chez les mâles XX. De la même manière, les femelles présentent des taux croissants d’E2 chez les individus XX, XY et YY. Ces différences de taux de stéroïdes sexuels pourraient être liées aux taux d’agressivité (évalué par la quantification de huit comportements agonistiques dans des confrontations mâle-femelle) plus élevés des mâles XX et des femelles XY et YY et engendrer des perturbations des comportements reproducteurs. Des recherches complémentaires sont nécessaires d’une part, pour évaluer l’effet du génotype sur la qualité des gamètes des femelles et d’autre part, pour déterminer si les modifications phénotypiques observées sont liées à l’expression du génotype sexuel ou à des perturbations engendrées par les traitements hormonaux d’inversion sexuelle administrés durant la période de différenciation des gonades. 2. Explorer les mécanismes du déterminisme et de la différenciation à des stades précoces du développement. Grâce à la mise au point d’une technique d’inversion sexuelle ciblant les périodes embryonnaire et larvaire (avant 10 jpf) par des expositions courtes (4h) d’embryons âgés d’un jpf à des androgènes (11KT, 17α-méthyltestostérone), un inhibiteur de l’aromatase (Fadrozole) ou un œstrogène (17α-éthynylœstradiol), nous avons confirmé l’existence d’une période sensible de la différenciation sexuelle avant le développement des gonades. Les voies de différenciation phénotypique semblent être différentes en fonction du génotype, puisque la masculinisation des embryons XX est moins efficace (max 10%) que la féminisation d’embryons XY (max 91%). De la même manière, un probable effet chromosomique rend inefficace la féminisation d’embryons YY. La féminisation des individus XY est concomitante avec une augmentation des taux de T et d’E2 et d’expression de l’aromatase cérébrale à 4 jpf qui pourrait indiquer un rôle précoce du cerveau dans la différenciation sexuelle. Dans l’ensemble, nos résultats nous permettent de suggérer, d’une part, que les premiers événements moléculaires de la différenciation sexuelle du tilapia sont initiés avant la formation des gonades, et d’autre part, que chez les individus sexuellement inversés, des différences sexuelles peuvent apparaître dans le cerveau avant ou en même temps que le développement des gonades et induire des modifications comportementales à l’âge adulte. La question du rôle possible du cerveau dans la différenciation des gonades reste ouverte. [less ▲]

Detailed reference viewed: 102 (32 ULg)
Full Text
Peer Reviewed
See detailPREVENTION OF INCISIONAL HERNIA AFTER MIDLINE LAPAROTOMY FOR ABDOMINAL AORTIC ANEURYSM TREATMENT: A RANDOMIZED CONTROLLED TRIAL
Muysoms, F; Vierendeels, T; Huyghe, M et al

Conference (2014, September 11)

Background: The incidence of incisional hernias (IH) after open abdominal aortic aneurysm (AAA) repair is high. Prophylactic mesh augmentation (PMA) during laparotomy closure has been proposed in high ... [more ▼]

Background: The incidence of incisional hernias (IH) after open abdominal aortic aneurysm (AAA) repair is high. Prophylactic mesh augmentation (PMA) during laparotomy closure has been proposed in high-risk patients. Methods: A multicenter prospective randomized controlled study was conducted on patients undergoing elective repair of AAA through midline laparotomy (Clinical.Trials.gov: NCT00757133). In the study group a retro-muscular PMA was performed with a large-pore polypropylene mesh (Ultrapro™, width 7.5 cm). The primary endpoint was the incidence of IH at 24 months. Results: Between February 2009 and January 2013, 120 patients were recruited at 8 Belgian centers. Patients' characteristics at baseline were similar between the groups. Operative and postoperative characteristics showed no difference in morbidity or mortality. A highly significant reduction of IH incidence was found after PMA compared to conventional closure, respectively 0% (CI: 0 % - 5.5%) versus 27.6% (CI: 16.7% - 40.9%) (P<0.0001; Fisher's exact test). The estimated "freedom of IH" curves (Kaplan-Meier estimate) were significantly different across study arms (X2=18.93, P<0.0001; Mantel-Cox test). No adverse effects were observed, apart from an increased mean (SD) time to close the abdominal wall for PMA: 46.2 min (18.6) versus 29.6 min (18.5) (P<0.001; Mann-Whitney U test). Conclusion: Prophylactic retro-muscular mesh augmentation of a midline laparotomy in AAA patients is safe and effectively prevents the development of IH, with an extra time investment of 17 minutes. [less ▲]

Detailed reference viewed: 19 (0 ULg)
Full Text
See detail1. Implantation des cultures
Eylenbosch, Damien ULg; Hiel, Marie-Pierre ULg; Meza Morales, Walter ULg et al

in Bodson, Bernard; Destain, Jean-Pierre (Eds.) Livre Blanc - Céréales (2014, September 11)

Detailed reference viewed: 10 (3 ULg)
Full Text
See detailLivre Blanc Céréales
Bodson, Bernard ULg; Destain, Jean-Pierre ULg

Book published by Gembloux Agro-Bio Tech (2014)

Detailed reference viewed: 10 (6 ULg)
Full Text
See detail2. Variétés - 2. Escourgeon et orge d'hiver fourragers
Monfort, Bruno; Mahieu, Olivier; Couvreur, Luc et al

in Bodson, Bernard; Destain, Jean-Pierre (Eds.) Livre Blanc céréales (2014, September 11)

Detailed reference viewed: 7 (0 ULg)
Full Text
See detail4. Qualité des froments en 2014: une récolte prometteuse et puis la douche froide
Sinnaeve, Georges; Gofflot, Sébastien; Chandelier, Anne et al

in Bodson, Bernard; Destain, Jean-Pierre (Eds.) Livre Blanc Céréales (2014, September 11)

Detailed reference viewed: 8 (1 ULg)
Full Text
See detail2. Variétés - 1. Froment d'hiver
Meza Morales, Walter ULg; Couveur, Luc; Eylenbosch, Damien ULg et al

in Bodson, Bernard; Destain, Jean-Pierre (Eds.) Livre Blanc Céréales (2014, September 11)

Detailed reference viewed: 7 (3 ULg)
Full Text
See detailWeakening of Jupiter’s main auroral emission in response to magnetospheric hot plasma injections
Badman, Sarah; Bonfond, Bertrand ULg; Fujimoto, M. et al

Conference (2014, September 11)

We present images of Jupiter’s northern UV aurorae taken by the Hubble Space Telescope as part of a large observing campaign in January 2014. The high time resolution observations allow the dynamics of ... [more ▼]

We present images of Jupiter’s northern UV aurorae taken by the Hubble Space Telescope as part of a large observing campaign in January 2014. The high time resolution observations allow the dynamics of the different components of the aurorae to be observed. Particular features of interest are large regions of diffuse emission, which occurred equatorward of the main oval, enveloping the auroral footprint of Ganymede. These diffuse, low latitude emissions are caused by the injection of hot plasma from the outer magnetosphere, a process which has previously been related to interchange between the flux tubes from the outer magnetosphere and outward-moving flux tubes loaded with iogenic plasma. Over the two-week observing interval the auroral signatures of two large injection events were observed, while the main oval generally decreased in intensity. We suggest that the overall dimming of the main oval results from the weakening of the corotation-enforcement currents that drive the main emission, following the replacement of the radially-stretched, mass-loaded flux tubes by more dipolar flux tubes containing rarefied hot plasma. [less ▲]

Detailed reference viewed: 9 (2 ULg)
Full Text
See detailHighlights of the 2014 Jupiter observing campaign by multi - spectral remote sensing using space telescopes
Kimura, T.; Badman, S.; Tao, C. et al

Conference (2014, September 11)

From January to April 2014, two observing campaigns by multi-wavelength remote sensing from X-ray to radio were performed to uncover energy transport process in Jupiter’s plasma environment using space ... [more ▼]

From January to April 2014, two observing campaigns by multi-wavelength remote sensing from X-ray to radio were performed to uncover energy transport process in Jupiter’s plasma environment using space telescopes and ground-based facilities. These campaigns were triggered by the new Hisaki spacecraft launched in September 2013, which is an extremely ultraviolet (EUV) space telescope of JAXA designed specifically for planetary observations. In the first campaign in January, Hubble Space Telescope made imaging of far ultraviolet (FUV) aurora with a high special resolution (0.08”) through two weeks while Hisaki continuously monitored aurora and plasma torus emissions in EUV wavelength with a high temporal resolution (1 min<). We discovered new magnetospheric activities from the campaign data: e.g., internally-driven type auroral brightening associated with hot plasma injection, and plasma and electromagnetic filed modulations in the inner magnetosphere externally driven by the solar wind modulation. The second campaign in April was performed by Chandra X-ray Observatory, XMM newton, and Suzaku satellite simultaneously with Hisaki. Relativistic auroral accelerations in the polar region and hot plasma in the inner magnetosphere were captured by the X-ray space telescopes simultaneously with EUV monitoring of aurora and plasma torus. In this presentation, we show remarkable scientific results obtained these campaigns mainly focusing on Jupiter’s aurora. [less ▲]

Detailed reference viewed: 10 (1 ULg)
Full Text
See detailOrigin and properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface: a first-principles hybrid functional study.
Fontaine, Denis ULg

Doctoral thesis (2014)

Complex oxides exhibit a wide range of physical properties making them very attractive for future electronic and device applications. Although more and more studied, additional scientific investigations ... [more ▼]

Complex oxides exhibit a wide range of physical properties making them very attractive for future electronic and device applications. Although more and more studied, additional scientific investigations are required, especially in oxide interfaces, where new and amazing phenomena can arise. A prototypical example is the LaAlO3-SrTiO3 interface that appear to be conducting, magnetic or even supra-conducting while these properties are not present in the LaAlO3 and SrTiO3 bulk insulator compounds. The conductivity arises from the formation of a highly localized electron gas at the interface which exhibits a different behavior than the one at semiconductor interfaces. Even nowadays, its exact origin, intrinsic versus extrinsic, is still intensively debated. The existence of an electric field in LaAlO3 used as a key feature of models based on an intrinsic origin is highly controversial. In these models, the closing of the band gap with increasing LaAlO3 film thicknesses finally results to a Zener breakdown and to the metal/insulator transition. In this Ph.D. thesis we aim to investigate the various consequences of the presence of an electric field in LaAlO3 through first-principles calculations in pristine LaAlO3-SrTiO3 interfaces. First, using both experimental and theoretical structural distortions in LaAlO3, we predicted a lattice expansion via an electrostrictive effect, supporting the existence of an electric field in LaAlO3. Second, the metal/insulator transition was tuned with regards to the intensity of the electric field in the film, which was controlled by the composition of a solid solution between LaAlO3 and SrTiO3. The theoretical results match the experimental one where, nevertheless, extrinsic origin mechanisms are allowed and defects are present. These two works are in favors of an intrinsic origin of the electronic gas observed in LaAlO3-SrTiO3 heterostructures. In addition, a relationship between the sheet carrier density and spatial extension of the gas was established and thus setting an intrinsic threshold to the sheet carrier concentration. At lower density the electrons are strictly localized close to the interface while above this value the carriers start to spill into the SrTiO3 substrate. [less ▲]

Detailed reference viewed: 5 (2 ULg)
Full Text
Peer Reviewed
See detailEffects of concentrate level on milk production and traffic of grazing cows milked by a mobile automatic milking system on pasture
Lessire, Françoise ULg; Hornick, Jean-Luc ULg; Dufrasne, Isabelle ULg

in Hopkins, Alan; Collins, Rosemary; Fraser, Marieacia (Eds.) et al EGF at 50: The future of European Grasslands (2014, September 10)

Cows milked by an automatic milking system in pastures were assigned in 2 groups receiving different amounts of concentrates (2.1 kg vs 4.1 kg). The effect of concentrates’ level on milk yield (MY) and ... [more ▼]

Cows milked by an automatic milking system in pastures were assigned in 2 groups receiving different amounts of concentrates (2.1 kg vs 4.1 kg). The effect of concentrates’ level on milk yield (MY) and returns to the robot was assessed. Concentrates’ level had a positive influence on daily milk production over the grazing period as cows of low concentrates group produced 21.43 ± 0.62 kg compared with 24.33 ± 0.62 kg in high concentrates group. However this effect was modulated subsequently to grass quality and availability. Regarding daily voluntary returns to the robot, high concentrates group showed higher frequency (3.66 ± 0.05, compared with 3.22 ± 0.04 in low concentrates group) demonstrating positive impact of complement distribution on cows’ traffic. [less ▲]

Detailed reference viewed: 22 (5 ULg)
Full Text
Peer Reviewed
See detailEffects of mild heat stress periods on milk production, milking frequency and rumination time of grazing cows milked by an automatic milking system
Lessire, Françoise ULg; Hornick, Jean-Luc ULg; Dufrasne, Isabelle ULg

Poster (2014, September 10)

Grazing dairy cows milked by an automatic system (AS) experienced mild heat stress (HS) periods, twice during the summer. The daily temperature humidity index (THI) during these periods were higher than ... [more ▼]

Grazing dairy cows milked by an automatic system (AS) experienced mild heat stress (HS) periods, twice during the summer. The daily temperature humidity index (THI) during these periods were higher than 72. Milk production, as well as milking frequency, rumination time and milk fat to protein ratio (F/P) during these periods were compared to adjacent periods with mean THI of 61. The daily milking frequency, the total number of visits to AS and the milk production were significantly higher in HS periods (2.12 vs 1.97, 2.99 vs 2.69, and 19.7 vs 18.5 kg milk per cow, respectively). There were significant interactions between times and periods for milking frequency and number of visits, while the daily rumination time was significantly lower (339 vs 419 min) and the F/P in milk tended to be decreased (1.17 vs 1.23). These results could be explained by changes in cow behaviour during HS periods. [less ▲]

Detailed reference viewed: 28 (2 ULg)
Full Text
See detailAnalyse de la variabilité naturelle du climat : application à l’aide des ondelettes
Mabille, Georges ULg

Doctoral thesis (2014)

Ce travail a pour but de mettre en évidence des cycles méconnus et cachés de la transformée de Fourier dans les séries temporelles liées au climat. Les périodes recherchées, à l’aide de l’outil ondelettes ... [more ▼]

Ce travail a pour but de mettre en évidence des cycles méconnus et cachés de la transformée de Fourier dans les séries temporelles liées au climat. Les périodes recherchées, à l’aide de l’outil ondelettes développé à l’Institut de Mathématique de l’Université de Liège, sont de l’ordre de quelques dizaines de mois. [less ▲]

Detailed reference viewed: 27 (15 ULg)
Full Text
Peer Reviewed
See detailCFD Comparison of hydrodynamics between BIOSTAT® Cultibag STR and standard Stirred Cell Culture Bioreactors
Calvo, Sébastien ULg; Delafosse, Angélique ULg; Crine, Michel ULg et al

Poster (2014, September 10)

Single-use bioreactors have been increasingly used for animal cell cultures on microcarriers in screening experiments. Because of their manufacturing process, the shape of these kinds of vessels such as ... [more ▼]

Single-use bioreactors have been increasingly used for animal cell cultures on microcarriers in screening experiments. Because of their manufacturing process, the shape of these kinds of vessels such as the BIOSTAT® Cultibag STR one, is limited. For example, technical constraints on weld seams limit angles to 30° and no baffle may be installed. The shape of standard re-usable vessels may thus not be exactly reproduced and the flow structure may thus significantly differs from the flow structure in standard bioreactors. [less ▲]

Detailed reference viewed: 6 (2 ULg)
Full Text
Peer Reviewed
See detailPressure-impulse diagram of a beam under explosion - Influence of the indirectly affected part
Hamra, Lotfi ULg; Demonceau, Jean-François ULg; Denoël, Vincent ULg

in Landolfo, Raffaele; Mazzolani, Frederico (Eds.) Proceeding of the 7th European conference on steel and composite structures (Eurosteel 2014) (2014, September 10)

The paper studies the structural response of a beam subjected to a close-field local internal blast loading. In the literature, the pressure-impulse (p-I) diagram is commonly used to design elements or ... [more ▼]

The paper studies the structural response of a beam subjected to a close-field local internal blast loading. In the literature, the pressure-impulse (p-I) diagram is commonly used to design elements or structures for a given blast loading. The p-I diagram is a spectrum representing the level sets of damage or required ductility for a given structural system, nonlinear beam in this paper. This representation is much appreciated because a simple reading for the actual pressure p and impulse I of the considered load indicates the ductility demand of the structural system. Recent works of quasi-static behaviour have indicated the crucial need to account for the membrane effects taking place in the extreme loading of frame beams. This paper will thus extend the state-of-art features, establishing thus the p-I diagram for a beam including the lateral restraints offered by the rest of the structure, the development of non-linear membrane action and also, the M-N interaction that develops in the plastic hinges. [less ▲]

Detailed reference viewed: 66 (21 ULg)
Full Text
Peer Reviewed
See detailEvidence for Holocene bottom-currents erosion in the Western Gulf of Corinth, Greece
Beckers, Arnaud ULg; Beck, Christian; Hubert, Aurelia ULg

Poster (2014, September 10)

The Gulf of Corinth, Greece, is connected to the Ionian Sea through a 62 m deep sill. Strong tidal currents have been measured above this sill, what could potentially induce bottom-current erosion in the ... [more ▼]

The Gulf of Corinth, Greece, is connected to the Ionian Sea through a 62 m deep sill. Strong tidal currents have been measured above this sill, what could potentially induce bottom-current erosion in the Gulf. Seismic reflexion data allowed us to identify this present-day expected seafloor erosion in a wide area, as well as erosional unconformities and a wide channel between 100 and 300 m below sea level. These features highlight the possible occurrence of strong bottom-currents since the last sea level rise. [less ▲]

Detailed reference viewed: 12 (0 ULg)