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See detailTrend analysis in ecological status and macrophytic characterization of watercourses: case of the Semois-Chiers basin, Belgium Wallonia
Sossey Alaoui, Khadija ULg; Rosillon, Francis ULg; Tychon, Bernard ULg

in Journal of Water Resource and Protection (2015), Vol.7 No.13 2015

In order to analyze the distribution and evolution of the aquatic vegetation and ecological status of the Semois-Chiers basin (Semois sub-basin and Chiers sub-basin), macrophyte surveys were conducted at ... [more ▼]

In order to analyze the distribution and evolution of the aquatic vegetation and ecological status of the Semois-Chiers basin (Semois sub-basin and Chiers sub-basin), macrophyte surveys were conducted at 48 sites in 2007 and 2013. Environmental parameters were also measured in order to characterize the waterbodies in terms of physico-chemical properties and anthropogenic pressure. The two-way clustering and indicator value (INDVAL) methods were used to assess groups of sites according to their macrophytic composition and species communities. The results showed a clear difference between streams in the Lorraine area (calcareous watercourses) and in the Ardennes (siliceous). Within each natural region, those with natural vegetation of high ecological status were separated from those dominated by resistant species. The Macrophytical Biological Index for Rivers (IBMR), was calculated for the sites visited in 2010 and 2013 and the results show a trend towards an increase of IBMR values of polluted sites. For the latter, the Wilcoxon test was performed to assess the significance of the difference in quality between 2010 and 2013. This showed a statistically significant difference (p-value= 0.035). Our results showed similarities with previous data, as well as some differences. The differences observed might indicate a gradual change in the composition of the vegetation in the study area, caused by changes in environmental conditions. They could also reflect a lack of information about the ecology of certain groups of plants, mainly bryophytes and macroalgae that were not considered in previous studies. Despite the measures implemented under the EU’s Water Framework Directive (WFD), the current vegetation of the Semois river differs little from that observed in 1996. There is a slight improvement in the headwaters of a Semois river, described in previous studies as polytrophic and devoid of vegetation, with the appearance of macrophytic species. In some parts of the Chiers sub-basin, however, resistant species observed in 1999 persist. [less ▲]

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See detailThe executive functioning in normal aging: Impact of the cognitive reserve
Simon, Jessica ULg; Gilsoul, Jessica ULg; Collette, Fabienne ULg

Poster (2015, September 04)

There exists a large inter-individual variability regarding the effects of aging on cognition. According to Stern (2009), people who developed a high level of reserve are more resilient to the effects of ... [more ▼]

There exists a large inter-individual variability regarding the effects of aging on cognition. According to Stern (2009), people who developed a high level of reserve are more resilient to the effects of aging that individuals with lower cognitive reserve. In this study, we describe the impact of cognitive reserve on executive functions in normal aging. Ninety healthy participants aged from 60 to 80 years were recruited. We assessed the three major executive functions: Inhibition (Stroop test, Hayling test, TAP Incompatibility subtest), Shifting (TAP Flexibility subtest, Plus-Minus task), and Updating (Letter-Number Sequencing subtest from MEM III, Letter memory task, 2-back task). Cognitive reserve was measured by questionnaires assessing educational level, occupation, leisure activities and physical activity across the life. Multiple linear regressions (p<0.05) adjusted for age, quality of sleep, processing speed showed that elderly with a high level of reserve have better performance on updating. We also assessed the effect of each factor of cognitive reserve separately after adjustment for the other. We observed that people with high level of education have better performance on flexibility (TAP Flexibility subtest and composite score) and on updating (Letter-Number Sequencing subtest, Letter memory and composite score). However, we didn’t observe any significant effect of the other factors of cognitive reserve. These results suggest that the cognitive reserve is related to abilities in some executive tests. [less ▲]

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See detailLe licenciement du travailleur qui introduit une plainte pour cause de harcèlement
Linguelet, Renaud ULg

in Revue de Jurisprudence de Liège, Mons et Bruxelles (2015)

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See detailA Comparative Study of Models for Shear Strength of Reinforced Concrete Deep Beams
Liu, Jian ULg; Mihaylov, Boyan ULg

Scientific conference (2015, September 03)

The shear behaviour of deep reinforced concrete beams has been a focus of experimental and analytical studies since the early 1950s, resulting in different approaches for predicting the shear strength of ... [more ▼]

The shear behaviour of deep reinforced concrete beams has been a focus of experimental and analytical studies since the early 1950s, resulting in different approaches for predicting the shear strength of deep beams. This paper compares the main modelling assumptions of these approaches and summarizes the results from validation studies available in the literature. Based on these comparisons, a two-parameter kinematic theory (2PKT) and a mechanical model by Zararis are selected for further evaluation with the help of test series with different experimental variables. It is shown that both approaches predict the trends in beam series with varying shear-span-to-depth ratios, even though the mechanical model overestimates the shear strength of beams without web reinforcement. It is also shown that the two models differ significantly in capturing the effect of transverse reinforcement and the size effect in shear. While the 2PKT accounts for sliding shear failures which limit the effectiveness of transverse reinforcement beyond a certain reinforcement ratio, the mechanical model predicts a monotonic increase of shear strength with the ratio. The 2PKT is also shown to capture the size effect in shear observed in two series of tests well, while the mechanical model neglects this effect. [less ▲]

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See detailLa fonction publique régionale wallonne: Réflexions et balises pour un projet de recherche prospective
Claisse, Frédéric ULg; Guyot, Jean-Luc

Scientific conference (2015, September 03)

Évolution du cadre institutionnel, contraintes budgétaires, transferts de compétences, instauration de nouveaux modes de gestion, vieillissement du personnel, recomposition du métier de fonctionnaire ... [more ▼]

Évolution du cadre institutionnel, contraintes budgétaires, transferts de compétences, instauration de nouveaux modes de gestion, vieillissement du personnel, recomposition du métier de fonctionnaire : tels sont quelques-uns des défis, tendances lourdes ou incertitudes auxquels la fonction publique régionale sera confrontée à plus ou moins brève échéance. Pour répondre à ce questionnement, l’IWEPS a décidé de développer une réflexion prospective sur le(s) futur(s) du SPW et des OIP à l’horizon 2030-2040. La présentation se centrera sur la méthodologie du projet, les variables et composantes de l’analyse systémique et de la base prospective. [less ▲]

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See detailUne féminité en métamorphose: Représentation de la féminité noire dans le cinéma black-British
Herbert, Emilie ULg

Conference (2015, September 03)

Le long-métrage "Burning an illusion", réalisé par Menelik Shabazz, met en scène l'éveil politique d'une jeune femme noire, Pat (Cassie McFarlane) lorsqu'elle fait l'expérience du racisme et de la ... [more ▼]

Le long-métrage "Burning an illusion", réalisé par Menelik Shabazz, met en scène l'éveil politique d'une jeune femme noire, Pat (Cassie McFarlane) lorsqu'elle fait l'expérience du racisme et de la violence dans les rues de Londres. "Burning an illusion" est l'un des premiers films black British à prendre pour personnage principal une femme et Shabazz décrit la conscientisation politique de Pat en termes ouvertement féminins : sa transformation intellectuelle passe en effet par une métamorphose physique. A travers une africanisation de son apparence (son maquillage disparaît, ses vêtements changent et ses cheveux, soigneusement lissés au début du film, reprennent leur apparence naturelle), Pat manifeste son rejet des codes de beauté occidentaux qui annihilent les femmes noires en imposant la blancheur comme point de référence. Ce long-métrage, réalisé en 1981, met en avant une notion développée par un féminisme noir qui s'éveille à la même époque en Grande-Bretagne : celle de la (re)conquête de la féminité noire à travers la création d'une identité black British fluide qui reconnaît la nature fragmentée des identitées hybrides, racialisées et genrées (Mirza, 1997). L'analyse d'un corpus de plusieurs films du mouvement du black British Cinema des années 1980 et 90 à travers une approche intersectionnelle, féministe et de genre nous permettra de comprendre ce processus de redéfinition de la féminité noire, jusqu'alors rendue invisible au sein du cinéma britannique blanc (Bourne, 2001). Les films étudiés encouragent en effet la revalorisation de la beauté naturelle du corps féminin noir, permettant ainsi son mouvement d'objet à sujet (Weekes, 1997), en passant par un processus de métamorphose physique. Le corps y est fragmenté (Coly, 2010) afin d'en déconstruire l'image socialement et culturellement produite (Jordan-Zachery, 2013) et de créer ainsi une nouvelle syntaxe qui permet d'articuler et de comprendre le corps féminin noir différemment (Doane, 1981). [less ▲]

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See detailFragility Analysis of a Steel Building in Fire
Gernay, Thomas ULg; Elhami Khorasani, Negar; Garlock, Maria

in Usmani, Asif; Lu, Yong; Das, Purnendu (Eds.) Proceedings of the First International Conference on Structural Safety under Fire & Blast - CONFAB 2015 (2015, September 03)

Community resilience to extreme events is an issue of increasing concern in our interconnected and urbanized societies. This work provides a framework to evaluate the response of a community of buildings ... [more ▼]

Community resilience to extreme events is an issue of increasing concern in our interconnected and urbanized societies. This work provides a framework to evaluate the response of a community of buildings to fire following earthquake, a potentially highly destructive cascading multi-hazard event. In a previous part of the work, a model has been developed to predict the probability of ignition in a building due to an earthquake. Given an ignition in a building, the probability of the structure exceeding certain limit states must be evaluated in order to quantify the expected damage loss. Adopting an approach similar to that used in seismic engineering, fragility functions can be developed for structures subjected to fire. The methodology is described here for a prototype nine-story steel frame building. In developing the fragility functions, uncertainties in the fire model, the heat transfer model and the thermo-mechanical response are considered. In addition several fire scenarios at different locations in the building are studied. The demand on and capacity of the system are assessed probabilistically in terms of critical temperature. The developed fire fragility functions yield the probability of exceedance of predefined damage states as a function of the fire load in the building. Future works will aim to implement fire fragility functions into a GIS based risk assessment software platform for assessment of the expected risk and cost associated with fire following earthquake for a community of buildings. [less ▲]

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See detailWildflowers sown at field margins have positive and negative effects on pests and parasitoids
Hatt, Séverin ULg; Uyttenbroeck, Roel ULg; Chevalier Mendes Lopes, Thomas ULg et al

Conference (2015, September 03)

Wildflower strips are sown at field margins throughout Europe to support insect conservation in agricultural areas. Among other insects, parasitoids may favor a biological regulation of pests. On an ... [more ▼]

Wildflower strips are sown at field margins throughout Europe to support insect conservation in agricultural areas. Among other insects, parasitoids may favor a biological regulation of pests. On an experimental field of the research platform AgricultureIsLife in Gembloux (University of Liège, Belgium), three replications of five wildflower seed mixtures were sown in strips adjacent to crops in spring 2013. Insect pests and their parasitoids were pan-trapped in spring 2014 in both wildflower strips and oilseed rape crops and identified at the species level. Flower species and cover were monitored in the strips using 1 m² quadrats, before mowing. Meligethes spp. were found abundantly in crops when oilseed rape was blooming. Meligethes’ parasitoids occurred later and their abundance was positively correlated with that of Meligethes in the flower strips. At the crop ripening stage, weevils Ceutorhynchus spp. occurred and were followed by an increase in abundance of their parasitoids in both crops and flowers. Positive as well as negative correlations were found between the abundance of these pests, their parasitoids and different flower species blooming at this time. The link between these results with flower species’ functional traits will be discussed. [less ▲]

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See detailLa Banque de Données des Epiclèses Grecques (BDEG) dans le cadre des Humanités numériques : questions théoriques et méthodologiques.
Lebreton, Sylvain ULg

Poster (2015, September 03)

Quiconque est un peu familier avec les textes grecs antiques peut aisément prendre la mesure de la richesse, en nombre et en diversité, des épiclèses (épithètes cultuelles) que les anciens Grecs ont ... [more ▼]

Quiconque est un peu familier avec les textes grecs antiques peut aisément prendre la mesure de la richesse, en nombre et en diversité, des épiclèses (épithètes cultuelles) que les anciens Grecs ont attribuées à leurs divinités. Cette importance, tant quantitative que qualitative, fait de ces dénominations un vecteur extrêmement pertinent pour l'étude du polythéisme hellénique, en même temps qu'elle constitue un défi analytique de premier ordre. Compte tenu de cette abondance, de la masse documentaire mise à contribution (surtout si l'on envisage le monde grec antique dans son ensemble), mais aussi de la complexité des relations entre les différentes composantes de la « société des dieux » des anciens Grecs, une telle étude peut tirer grand profit du recours à des outils de traitement quantitatif des données. Ce constat est à l'origine de la création, il y a une dizaine d'années, de la Banque de Données des Epiclèses Grecques (BDEG), dans le cadre du LAHM (ex-Crescam, UMR 6566 CReAAH) de l'Université Rennes 2 (https://epiclesesgrecques.univ-rennes1.fr/accueil.php). Le projet est toujours en cours de développement et constitue de ce fait une étude de cas potentiellement intéressante dans le cadre d'une réflexion sur les Humanités numériques dans le champ de l'Antiquité. En effet, la confrontation avec la réalité des données documentaires (en l'occurrence principalement littéraires et épigraphiques), les progrès dans la réflexion sur le traitement quantitatif et les évolutions des outils numériques ont rendu nécessaire l'évolution de la BDEG depuis sa création. On s'attachera donc à présenter certains pans de cette évolution – passés, en cours et à venir – en insistant sur les problèmes méthodologiques qu'ils posent du point de vue des Humanités numériques. [less ▲]

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See detailWhy are flux avalanches deflected by a metallic layer?
Brisbois, Jérémy ULg

Poster (2015, September 03)

Sudden avalanches of magnetic flux bursting into a superconducting sample are deflected from their trajectories when they encounter a conductive layer deposited on top of the superconductor. Remarkably ... [more ▼]

Sudden avalanches of magnetic flux bursting into a superconducting sample are deflected from their trajectories when they encounter a conductive layer deposited on top of the superconductor. Remarkably, in some cases the flux is totally excluded from the area covered by the conductive layer. Even if this phenomenon has been known for a few years, there is currently no theoretical model describing it. Moreover, the question whether the deflection would also be observed for a single vortex entering the region covered by a metallic layer is still unanswered. In this work we use the magneto-optical imaging (MOI) technique, based on the Faraday effect, to show that a conductive layer (Cu) can repel flux avalanches triggered in an underlying superconducting film (Nb) (see figure). We present a simple classical model that accounts for the deflection of a single vortex and considers a magnetic monopole approaching a semi-infinite conductive plane. This model suggests the important role played in the avalanche deflection by electromagnetic braking, arising from the eddy currents induced by the moving vortex in the metal. Moreover, we have found a decrease of the vortex damping coefficient due to the metallic sheet at large vortex velocities, correcting early theoretical descriptions where a linear behaviour was proposed. [less ▲]

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See detailImportance des résidus lysine 70 et tryptophane 154 sur la structure, la stabilité, la carbonatation et l'activité de la béta-lactamase OXA-10 de Pseudomonas aeruginosa
Baurin, Stéphane ULg

Doctoral thesis (2015)

SUMMARY : This thesis was conducted to highlight the biochemical and structures impact of conserved residues of the beta-lactamase OXA-10 isolated from P. aeruginosa. The beta-lactamase OXA-10 production ... [more ▼]

SUMMARY : This thesis was conducted to highlight the biochemical and structures impact of conserved residues of the beta-lactamase OXA-10 isolated from P. aeruginosa. The beta-lactamase OXA-10 production is one of the main responsible to the beta-lactam antibiotics resistance of Pseudomonas strains. This work is subdivided in five chapters. The first is focused on the organization of class D beta-lactamase in sub classes. We have created by identity analysis, 21 sub classes that reflect an easy discrimination between proteins variability and mutants. This methodology is able to organize the enzymes as function of a parental enzyme but also based on the substrate profiles. The second chapter regroups the studies that target the importance of the residue tryptophan 154 carried by the Omega loop. The substitution of the residue tryptophan 154 by an alanine, a glycine or an phenylalanine leads to a large decrease of i) the catalytic activity, ii) of the affinity toward to CO2 and iii) on the enzyme stability. The structural data show an absence of lysine 70 modification and a large modification of the hydrogen network throughout the mutants structures. The various complexes resolved by R-x diffraction of the W154A mutant indicate that the deacylation rate is the most impacted. The third chapter makes an analogy between the available structural informations of others proteins characterized by a carboxylation modification. Others serine enzymes known to be not modified were also integrated in the analysis. The data reveal that the presence of a tryptophan residue seems to be necessary. We notice the presence of a large hydrophobic area with various shape near of the modified lysines. The calculation of the theoretical pKa values of the lysines seems to indicate a large decrease of the values that lead to an unprotonated form at physiological pH. The fourth chapter describes, the role of the lysine 70. The substitution of the lysine by a cysteine or a glutamate leads to a large decrease of the catalytic activity and an absence of carboxylation. At the opposite, the protein stability is not impacted, and an increase of stability is observed for the K70C mutant. The structural data show that the overall fold and structures localization are conserved. The complex obtained with the nitrocefin proves that the mutant is always able to react with the beta-lactams compounds and show that the deacylation step is rate limiting. Finally, the last chapter regroups the effect of pH on the structure, the dimerization, the stability and the catalytic activity. The data show that in the tested conditions the OXA-10 beta-lactamase is in a dimeric form at physiological pH. The addition of CO2, leads the formation of a more compact enzyme form. At high pH (10), the monomer is observed, while a fast equilibrium between the monomer and the dimer is observed between the pH 7.5 and 10. The enzyme is characterized with similar stability as function of pH. The addition of CO2 leads an increase of the stabilities. In tested conditions, the OXA-10 beta-lactamase is characterized by two optimum pH in presence or not of CO2. The CO2 addition leads to a large increase of the catalytic constant. The biophysics' studies reveal that in absence of CO2, subtle modifications are observed as function of pH, but that the addition of CO2 leads theirs disappearance. [less ▲]

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See detailImpact of a one-day preventive voice program for teachers : A longitudinal study
Remacle, Angélique ULg; Gerber, Silvain; David, Claire et al

Conference (2015, September 02)

I. INTRODUCTION Teachers are professional voice users, i.e. people who rely on a consistent, special, or appealing voice quality to achieve their job. If afflicted with dysphonia or aphonia, they would ... [more ▼]

I. INTRODUCTION Teachers are professional voice users, i.e. people who rely on a consistent, special, or appealing voice quality to achieve their job. If afflicted with dysphonia or aphonia, they would generally loose motivation at work and seek alternative employment [1]. Teachers represent the largest group of professionals complaining of dysphonia: they represent 20% to 25% of the treatment-seeking workers [2, 3]. Voice disorders impact both physical and psychological health. They represent a public health problem, since they have considerable economic consequences in terms of treatment and replacement of professionals who suffer from these problems [4]. Moreover, they have been shown to interfere with quality of life, emotional state, job satisfaction, performance and attendance [4, 5]. Finally, a teacher’s dysphonia adversely impacts students’ comprehension and learning [6]. These negative effects of teachers’ voice disorders motivate to develop prevention programs and test their efficacy. This study aims to evaluate the impact over a five-month period of a one-day prevention program for female teachers. This program includes both direct and indirect methods. II. METHODS A. Participants Twenty-two female kindergarten and elementary schoolteachers with less than 5 years of experience participated in this study. Half of them (test group) took part in a one-day prevention program in October, while the other half (control group) received no counseling on the use of the voice. B. Assessments For each participant, five sustained /a/ vowels and the reading of a text were recorded (1) at two times of the workday (morning and evening), and (2) at three times of the year: October (T0), December (T1) and February (T2). For the sustained vowels, we measured maximum phonation time (MPT), mean fundamental frequency (F0), values of jitter, shimmer and harmonics-to-noise ratio (HNR). For the texts, we measured mean F0, standard deviation in F0 and intensity, and parameters related to speech rate (number of syllables per second, number of pauses and mean duration of pauses). For each parameter, a repeated-measures ANOVA (2 groups * 2 times of day * 3 times of year) was carried out. Participants also completed a questionnaire on voice use and comfort at the three test sessions. III. RESULTS A. Time of day effect The main effect of time of day showed an increase in the mean F0 of the vowels and the text following a workday (p<.01). MPT and HNR also increased (p<.01), while jitter and shimmer decreased at the end of the day (p<.05). The speech rate measures showed that the teachers tended to pause less often while reading the text at the end of the day, and their pauses were shorter (p<.05). B. Time of year effect The main effect of time of year showed an increase in the mean F0 of the vowels and the text during the year (p<.01), with the highest values observed in December (T1). The speech rate measures also showed an increase in the number of syllables per second (p<.01) and a tendency for speakers to pause less often later in the year. C. Group effect Several acoustic parameters showed that voice changed during the day and during the year in significantly different ways in the two groups. Thus, the MPT increased more during the year for the control group than for the test group. The elevation of mean F0 during the day increased to a similar degree for both groups between T0 and T1, but continued to increase until T2 for the control group, while it decreased for the test group. Jitter and shimmer decreased significantly following a workday for both groups at T0, and this decrease was more marked for the test group at T1 and T2. Finally, analysis of the questionnaires showed a very strong deterioration in teachers’ self-evaluations of vocal comfort and control at T1; nevertheless there were significantly fewer complaints from the group that received the prevention program. IV. DISCUSSION AND CONCLUSION For both groups, the changes in the observed parameters suggested an increase in vocal fatigue and hyperfunctional phonation during the day and during the year. The results showed greater vocal deterioration in December than at the other points in the school year (October and February). For several acoustic parameters, the comparison of the two groups showed a less severe vocal deterioration for subjects who received the preventive program. Moreover, the questionnaires showed that the prevention program had a significantly positive impact on the changes in the teachers’ perception during the year. These results encourage to offer such preventive interventions to teachers before or during their career, since they have a positive impact on teachers’ perception and vocal comfort. V. REFERENCES [1] Titze IR, Lemke J, Montequin D. (1997). Populations in the U.S. workforce who rely on voice as a primary tool of trade: A preliminary report. Journal of Voice, 11(3), 254-259. [2] Van Houtte, E., Van Lierde, K., D'Haeseleer, E., & Claeys, S. (2010). The prevalence of laryngeal pathology in a treatment-seeking population with dysphonia. Laryngoscope, 120(2), 306-312. [3] Remacle, A., Petitfils, C., Lejeune, L., Finck, C., & Morsomme, D. (2014). Quel est le profil professionnel des patients consultant en phoniatrie ? 70e Congrès de la Société Française de Phoniatrie, Paris, France. (October 13, 2014). [4] Roy, N., Merrill, R. M., Thibeault, S., Parsa, R. A., Gray, S. D., & Smith, E. M. (2004). Prevalence of voice disorders in teachers and the general population. Journal of Speech, Language, and Hearing Research, 47(2), 281-293. [5] Chen, S. H., Chiang, S.-C., Chung, Y.-M., Hsiao, L.-C., & Hsiao, T.-Y. (2010). Risk factors and effects of voice problems for teachers. Journal of Voice, 24(2), 183-190. [6] Morsomme, D., Minel, L., & Verduyckt, I. (2011). Impact of teachers’ voice quality on children’s language processing skills. Vocologie: Stem en Stemstoornissen, 4, 9-15. [less ▲]

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See detailMilk biomarkers to detect ketosis and negative energy balance using MIR spectrometry
Grelet, Clément ULg; Bastin, Catherine ULg; Gelé, Marine et al

Conference (2015, September 02)

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See detailIn vivo quantification of dopaminergic terminals loss in Parkinson’s Disease rat model: comparison between [18F]FMT and [18F]FDOPA.
Becker, Guillaume ULg; Bahri, Mohamed Ali ULg; Michel, Anne et al

Poster (2015, September 02)

Objectives: Rat models of Parkinson’s disease (PD), such as unilaterally lesioned rats with 6-hydroxydopamine (6-OHDA), are useful to evaluate novel antiparkinsonian therapies. MicroPET imaging, using L-3 ... [more ▼]

Objectives: Rat models of Parkinson’s disease (PD), such as unilaterally lesioned rats with 6-hydroxydopamine (6-OHDA), are useful to evaluate novel antiparkinsonian therapies. MicroPET imaging, using L-3,4-dihydroxy-6-[18F]-fluoro-phenylalanine ([18F]FDOPA) allows longitudinal evaluations of DA terminals loss. However, chemical structure of [18F]FDOPA leads to suboptimal PET imaging. 18F-fluoro-m-tyrosine ([18F]FMT) is an effective PET tracer to evaluate DA terminals integrity and L-aromatic amino acid decarboxylase (AAAD) metabolic pathway. So far, there are no available quantitative PET studies comparing the two methods in hemiparkinsonian rats. In this study, we compare imaging data provided by [18F]FMT PET and [18F]FDOPA PET in 6-OHDA-lesioned rats. Methods: 10 µg of 6-OHDA were injected into the right medial forebrain bundle (MFB) of male Sprague-Dawley rats (n=8). As control, sham-treated rats (n=8) were injected with vehicle only but otherwise treated identically. Striatal DA presynaptic activity was assessed by dynamic PET with both [18F]FMT and [18F]FDOPA. Structural T2-weighted brain images were acquired on a 9.4T MRI and were used for co-registration. After normalization on a MRI template, kinetic analysis was performed by “Patlak Reference” model, using PMOD software. Six days after the last PET scan, rats were sacrificed, and striatum were rapidly removed for striatal DA and metabolites quantification. Results: Striatal accumulation was observed for both tracers. However, while the administration of [18F]FDOPA required two peripheral inhibitors (benserazide and entacapone), only benserazide is needed with [18F]FMT. As consequence of the 6-OHDA-lesion, significant decrease of both [18F]FMT and [18F]DOPA accumulation was recorded in the striatum ipsilateral to the lesion. Lesioned rats had dramatically reduced uptake constant Ki in the ipsilateral striatum compared to the contralateral striatum (p<0.001 for [18F]FMT and p<0.05 for [18F]DOPA) and to the ipsilateral striatum of sham-treated rats (p<0.001 for both tracers). The DA content in the ipsilateral striatum was significantly lower (p<0.001) than in the contralateral striatum in the 6-OHDA-injected group, whereas such difference was not measured with the sham group. This indicate that [18F]FMT PET is as effective as [18F]DOPA PET to quantify loss of DA presynaptic function in unilaterally 6-OHDA lesioned rats. Conclusions: Our results are in agreement with data reporting correlation between these two tracers in a Non-human primate model of PD. The sensitivity of the data quantification obtained in this study, confirms the interest to pursue longitudinal investigations with [18F]FMT to monitor dopaminergic dysfunction in a more progressive preclinical model of PD. [less ▲]

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See detailLes pouvoirs du Chef de l'Etat dans le recours aux opérations extérieures
Behrendt, Christian ULg

Scientific conference (2015, September 02)

27e Cours international de Justice constitutionnelle, Aix-en-Provence, Institut Louis Favoreu, Université Paul Cézanne Aix-Marseille, 2 septembre 2015

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See detailProgenitor potential of nkx6.1-expressing cells throughout zebrafish life and during beta cell regeneration.
Ghaye, Aurelie P.; Bergemann, David ULg; Tarifeño Saldivia, Estefania ULg et al

in BMC biology (2015), 13

BACKGROUND: In contrast to mammals, the zebrafish has the remarkable capacity to regenerate its pancreatic beta cells very efficiently. Understanding the mechanisms of regeneration in the zebrafish and ... [more ▼]

BACKGROUND: In contrast to mammals, the zebrafish has the remarkable capacity to regenerate its pancreatic beta cells very efficiently. Understanding the mechanisms of regeneration in the zebrafish and the differences with mammals will be fundamental to discovering molecules able to stimulate the regeneration process in mammals. To identify the pancreatic cells able to give rise to new beta cells in the zebrafish, we generated new transgenic lines allowing the tracing of multipotent pancreatic progenitors and endocrine precursors. RESULTS: Using novel bacterial artificial chromosome transgenic nkx6.1 and ascl1b reporter lines, we established that nkx6.1-positive cells give rise to all the pancreatic cell types and ascl1b-positive cells give rise to all the endocrine cell types in the zebrafish embryo. These two genes are initially co-expressed in the pancreatic primordium and their domains segregate, not as a result of mutual repression, but through the opposite effects of Notch signaling, maintaining nkx6.1 expression while repressing ascl1b in progenitors. In the adult zebrafish, nkx6.1 expression persists exclusively in the ductal tree at the tip of which its expression coincides with Notch active signaling in centroacinar/terminal end duct cells. Tracing these cells reveals that they are able to differentiate into other ductal cells and into insulin-expressing cells in normal (non-diabetic) animals. This capacity of ductal cells to generate endocrine cells is supported by the detection of ascl1b in the nkx6.1:GFP ductal cell transcriptome. This transcriptome also reveals, besides actors of the Notch and Wnt pathways, several novel markers such as id2a. Finally, we show that beta cell ablation in the adult zebrafish triggers proliferation of ductal cells and their differentiation into insulin-expressing cells. CONCLUSIONS: We have shown that, in the zebrafish embryo, nkx6.1+ cells are bona fide multipotent pancreatic progenitors, while ascl1b+ cells represent committed endocrine precursors. In contrast to the mouse, pancreatic progenitor markers nkx6.1 and pdx1 continue to be expressed in adult ductal cells, a subset of which we show are still able to proliferate and undergo ductal and endocrine differentiation, providing robust evidence of the existence of pancreatic progenitor/stem cells in the adult zebrafish. Our findings support the hypothesis that nkx6.1+ pancreatic progenitors contribute to beta cell regeneration. Further characterization of these cells will open up new perspectives for anti-diabetic therapies. [less ▲]

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