Résumé

Les Fusarium spp, moisissures généralement mycotoxinogènes, sont responsables d’une pathologie majeure, la fusariose de l’épi chez le maïs. La production de mycotoxines du genre fumonisine dans les grains de maïs par certaines de ces espèces représente un risque potentiel non négligeable pour la santé des consommateurs. En absence des moyens chimiques efficaces de prévention, une des voies les plus prometteuses réside dans l’utilisation de l’antagonisme microbien. Le but de ce travail de thèse a été d’explorer la capacité des bactéries lactiques autochtones du maïs à contrôler la croissance de Fusarium verticillioides et proliferatum, les deux espèces les plus fréquentes parmi les producteurs de fumonisines. Les bactéries lactiques isolées de différents organes du maïs ont été criblées en vu d’évaluer leur activité « anti-Fusarium ». Parmi les 67 souches isolées, une souche L006 identifiée comme Pediococcus pentosaceus par des techniques phénotypiques et moléculaires s’est montrée particulièrement très active. Les métabolites « anti-Fusarium » produits par P. pentosaceus L006 sont des métabolites secondaires qui semblent agir en synergie avec l’acide lactique. La production de ces composés dans le milieu MRS est optimale en condition agitée à 200 rpm, à pH 5,5 et à 30°C pendant 120 h. L’étude de l’influence de ces entités sur la production de fumonisines en milieu liquide a mis en évidence une stimulation dans certaines conditions comme entre autres lorsque la souche fusarienne est co-inoculée simultanément avec la bactérie lactique ou inoculée dans une culture bactérienne de trois jours. Cependant, cette étude a démontré que ces entités sont généralement capables de réduire significativement l’accumulation de ces toxines aussi bien en milieu liquide que sur grains de maïs. L’étude de la réduction de la fumonisine B1 en milieu liquide acidifié a montré que P. pentosaceus L006 est capable d’éliminer par adsorption 75% de cette toxine. Ces résultats ouvrent des perspectives pour l’utilisation de la souche L006 de P. pentosaceus pour le biocontrôle des Fusarium spp en vue de la maîtrise de la contamination en fumonisines du maïs et de ses produits dérivés. / Fusarium spp. are generally mycotoxinogenic moulds responsible for a major disease on maize spikes. Production of mycotoxins such as fumonisins by some of these species is a threat for the consumers. As no chemical resources are available for preventing the risk of occurrence, one of the promising ways to limit the toxin accumulation is the use of microbial antagonism. The main goal of this doctoral project was to investigate the ability of maize autochthonous lactic bacteria to control the development of Fusarium verticillioides and proliferatum, the two main species producing fumonisins. Lactic bacteria isolated from different tissues of the plant have been screened in order to evaluate their “anti-Fusarium” activity. Among the 67 isolated strains, the L006 strain characterised as Pediococcus pentosaceus by phenotypic and molecular methods was particularly highly active. Anti-Fusarium metabolites produced by P. pentosaceus (L006) are secondary metabolites which probably act in synergy with lactic acid. The production of these entities in MRS medium is optimal in shaken cultures at 200 rpm, at pH 5.5 with a temperature of 30°C during 120 h. Study of the effects of these metabolites on the fumonisins production in liquid medium showed a stimulation in particular conditions such as co-inoculation of the Fusarium strain together with the lactic bacteria or inoculation in a three days old bacterial culture. However, this study demonstrated that these entities generally significantly inhibited the toxin accumulation when cultivated as well as in liquid medium or on maize grains. Studying the reduction of fumonisin B1 reduction in acidified liquid medium showed that P. pentosaceus (L006) was able to adsorb 75% of this toxin. These results open new perspectives for biocontrol of Fusarium spp. using the P. pentosaceus L006 strain to prevent contamination of maize and derived products by fumonisins.

Les présénilines PS1 et PS2 sont impliquées dans plusieurs fonctions cellulaires par l’intermédiaire de leur activité protéolytique ?-sécrétase qui clive de nombreux substrats y compris la protéine précurseur amyloïde (APP). Les mutations des présénilines, à l’origine des formes familiales de la maladie d’Alzheimer (MA), augmentent la production de peptides ß-amyloïde (Aß) qui s’accumulent dans le parenchyme cérébral et dans la paroi vasculaire, et affectent les signaux calciques de plusieurs types cellulaires. Le réseau vasculaire des patients atteints de la MA est affecté structurellement et fonctionnellement bien avant que ne se déclarent les troubles cognitifs. De plus, les pathologies cardiovasculaires sont des facteurs de risque majeurs pour les formes sporadiques de la MA. Comme les bases moléculaires de la vasculopathie liée à la MA ne sont pas établies, nous avons choisi les présénilines comme molécule cible dans le système vasculaire. Nous avons montré l’expression des présénilines et des protéines partenaires du complexe ?-sécrétase, Nicastrine, Aph-1 et Pen-2 dans les vaisseaux cérébraux et périphériques. L’ensemble génère une activité ?-sécrétase et la production de peptides Aß pathogènes dans les cellules musculaires lisses, soutenant l’hypothèse de l’origine vasculaire d’Aß dans la pathologie amyloïde. De plus, les mutations de PS1 dérégulent la signalisation calcique intracellulaire des artères cérébrales, en augmentant l’activité des canaux de libération du Ca2+ activés par l’IP3 (IP3R) et la recapture du Ca2+ par les pompes du réticulum sarco-endoplasmique Ca2+-ATPase (SERCA). La dérégulation de l’homéostasie calcique par les présénilines mutées pourrait avoir des conséquences sur la réactivité vasculaire des vaisseaux cérébraux. En conclusion, nous avons mis en évidence l’importance physiologique des présénilines dans le réseau vasculaire et l’ensemble de nos travaux permet de mieux comprendre comment les vaisseaux participent à l’apparition des symptômes cliniques de la MA que sont la surproduction d’Aß et l’hypoperfusion cérébrale. / Presenilins PS1 and PS2 are involved in several cellular functions through their ?- secretase proteolytic activity, which cleaves many substrates including the amyloid precursor protein (APP). Mutations in presenilins genes are responsible for the majority of familial forms of Alzheimer's disease (AD). Presenilins mutations increased production of ß-amyloid peptide (Aß) that accumulates in the brain parenchyma and the vascular wall, and affect calcium signals in several cell types. The vasculature of patients with AD is structurally and functionally affected before cognitive impairment appearance. In addition, cardiovascular diseases are major risk factors for sporadic forms of AD. As the molecular basis of the vasculopathy associated with AD is not established, we chose presenilins as target molecule in the vascular system. We showed the expression of presenilin and protein partners of ?-secretase complex, nicastrin, Aph-1 and Pen-2 in cerebral and peripheral blood vessels. Vascular wall generate a ?-secretase activity and production of pathogenic Aß peptides supporting the hypothesis of vascular origin of Aß in amyloid pathology. Furthermore, PS1 mutations disturb intracellular calcium signalling in cerebral arteries by first increasing channel activity of Ca2+ release activated by IP3 (IP3R) and second increasing reuptake of Ca2+ by Sarco/Endoplasmic Reticulum Ca2+-ATPase pump (SERCA). Dysregulation of calcium homeostasis by the mutant presenilins might affect vascular reactivity of cerebral vessels. In conclusion, we demonstrated the physiological importance of presenilins in the vascular network and our studies provide new insight on how cerebral blood vessels are involved in the onset of clinical symptoms of AD such as the overproduction of Aß and cerebral hypoperfusion.

: La TEP (Tomographie par Emission de Positons) est actuellement la technique d’imagerie la plus performante. Cependant sa résolution spatiale millimétrique interdit de déterminer avec certitude si les traceurs radiomarqués atteignent sélectivement leur cible moléculaire. Nous avons donc proposé d’utiliser un nouvel outil d’imagerie ex vivo pour apporter de nouvelles informations moléculaires grâce à la haute résolution des analyses par faisceaux d’ions. Les analyses PIGE (Particle Induced Gamma-ray Emission) et RBS (Rutherford Backscattering Spectrometry) permettent ainsi de quantifier les éléments chimiques d’un échantillon avec une résolution spatiale micrométrique. Nos travaux ont donc été fondés sur l’optimisation de ces techniques pour la détection de molécules marquées au 19F stable (FDG et peptide polyfluoré ciblant spécifiquement l’angiogenèse tumorale) au sein d’échantillons biologiques tels que des coupes tumorales ou des membranes vascularisées. / Abstract

Thesis (MPhill)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Background: Community-based placement of students provides an ideal opportunity to develop constructivist learning environments for learning. Students are placed in a low risk obstetric care facility where they required to interview, examine and manage uncomplicated pregnancies under supervision of a lecturer. Aims: The aim of this study was to investigate the appropriateness of using a validated Constructivist Learning Environment Survey (CLES) to gauge the perceptions of students in a community-based health sciences placement. A further aim of the study was to evaluate whether the learning environment was compliant with constructivism. Methods: An adapted CLES was administered to 99 students and 44 students were interviewed using the instrument scales as a schema. Results: The surveys were analysed and mean scores at or above 20 were obtained, where the 5 different scales would have a maximum score of 30 each. No gender or racial differences were elicited from the survey responses. Interview data supported the data of the survey that demonstrated the constructivist nature of the learning environment. Conclusion: The CLES appears to be an appropriate and useful instrument in evaluating a community-based constructivist learning environment in low-risk obstetric care. Practice Points: Learning environment research instruments developed for other settings may be appropriate to use in more specific training in health sciences education. The adapted CLES proved useful in evaluating a constructivist clinical learning environment.

To help address the knowledge gap between science and practice this study explores the possible positive benefits of using a more pedagogical effect size estimate when presenting statistical relationships. Traditional presentation has shown limitations with major downsides being that scientific findings are misinterpreted or misunderstood even by professionals. This study explores the possible effects of the non-traditional effect size estimate Common Language Effect Size (CLES) on different training outcomes for HR professionals. This study also explores the possible effect of cognitive system preference on training outcomes. Results show no overall effect of CLES on either training outcomes or cognitive system. A positive effect of CLES on training outcome is found at the subfactor level showing a significant effect. The results can be interpreted that non-traditional effect size estimates have a limited effect on training outcomes. This small but valuable piece to bridge the gap of knowledge is discussed.

The main purpose of this classroom action research was to improve student learning in a Health Science class in Thailand by using the Constructivist Learning Environment Survey (CLES) and a constructivist learning approach. This study combined quantitative and qualitative data and was conducted over one semester in four stages: 1) assessing the students' perceptions of their constructivist learning environment and determining students' pre-instruction conceptions about AIDS; 2) constructing an intervention based on constructivism theory in order to improving learning environments and students' learning outcomes; 3) implementing the intervention; and 4) evaluating the success of the intervention by re-assessing with the CLES. The Attitude Towards AIDS Questionnaire (ATAQ) was used to assess students' attitudes about AIDS. The students' cognitive achievement was assessed with the Students' Knowledge of AIDS Test (SKAT). Qualitative data were obtained from informal observation, focus group discussions, and student journals. The results indicated that the adapted Thai version of the CLES is appropriate for use in Health Science classes in Thailand's socio-cultural context because it was shown to be valid and reliable in both Actual and Preferred Forms. The results also revealed that the CLES and a constructivist learning approach can be used as effective tools in order to improve the learning environment of a Health Science class. This approach can improve students' knowledge and students' attitudes toward AIDS. The qualitative results supported the results from the questionnaires. This study suggests that teachers and health educators in Thailand can use the CLES to improve their learning environment and use a constructivist learning model to bring about improvement in students' achievement in their classes.

The principle focus of this study has been a reflection on my planning methodology since 1988. Teachers planning from 19882002 was predominantly individual and was aided by the gradual introduction of State and Commonwealth produced documents. These documents assisted in topic choices and assessment outcomes.Important influences transformed my planning. The first occurred in 1996 and the second in 2002. In 1996 I was involved in the production of a resource kit for teachers titled, Its Working Career and Work Education, Kindergarten to Year 8. During the compilation of this resource kit my planning incorporated the 1995, Teaching and Learning in Science Planning Guide, which resembled constructivism by building knowledge and understanding. In 2002 the curriculum in Tasmanian State Schools was transformed with the introduction of the Essential Learnings Framework 1 and 2. This curriculum innovation had implications on teachers planning methodology with a strong emphasis on collaborative planning.Studies and critiques of environmental units were undertaken in 2000, 2003 and 2004 to ascertain the effectiveness of my planning methodology. The underlying principles of constructivism provided a lens to improve perceived deficiencies in my classroom practice. The inclusion of the Constructivist Learning Environment Survey (CLES) assisted in making constructivism visible. A strong purpose therefore evolved from the study; a more effective planning methodology.

This longitudinal study explored the extent to which mathematics education lecturers' constructivist beliefs and aligned practices were communicated to students in a New Zealand primary pre-service teacher education degree programme. An integral part of this exploration was the identification of particular aspects of lecturers' practice that had a significant impact in enhancing the adoption of constructivist ideas on learning and constructivist-aligned teaching practices by student teachers. This goal had a practical focus on more effective course teaching within the chosen philosophical framework of constructivism. At a more theoretical level, there was a focus on the development of a constructivist approach to teacher education for teacher educators through the medium of mathematics education. A potential outcome of the development and widespread adoption of such a constructivist-aligned pedagogy within teacher education could be the significant furthering of a "reform" (or transformative) agenda in school education with its potential for enhanced learning by children. The methodology comprised both quantitative (survey) and qualitative (interview) techniques to collect information which allowed the capture of different but complementary data, so building a "rich" data set. The surveys were conducted using two leaming environment instruments underpinned by particular constructivist perspectives: one focusing on the overall nature of the learning environment at an individual level from a critical constructivist perspective, and the other focusing on the nature of interactions between teacher and student teachers at a classroom level from a socio-cultural constructivist perspective. / Surveys were conducted with the lecturers at the beginning and toward the end of the study, while the student teachers in these lecturers' classes were surveyed over a three year period. The interviews were semi-structured following an interpretative (evolving) research approach, with the "results" of ongoing data analysis being fed into later interviews. The interview data were analysed for personal perceptions and understandings rather than for generalisation and prediction with the intention of focusing on the identification of emergent themes. Interviews were conducted with lecturers at the beginning of the study and again toward its conclusion while student teachers were interviewed at the end of the study. The lecturers claimed constructivism as their underlying philosophical belief system and the initial surveys established baseline data on the actual nature of the lecturers' beliefs and how these were perceived by the student teachers. Similarly, the initial interviews explored the espoused beliefs and congruent practices of lecturers and student teachers. These two sets of data were compared to establish their congruence or otherwise. Further interviews with the lecturers focused on the survey data and my reconstruction of what the lecturers had said previously when interviewed. Later survey and interview data were also examined against the baseline data for evidence of change over the four years of the study. The data demonstrated that the student teachers perceived the existence of moderate to strong socio-cultural constructivist-aligned classroom environments when considered at a class (group) level, and a moderate alignment with critical perspectives at the individual (personal) level. / There was a high degree of consistency between staff and student teacher views, and the student teachers' views were consistent across the year groups (first, second and third years) and throughout the four years of the study. Lecturer practice(s) congruent with constructivism were the basis for student teacher change toward understanding and their adoption of constructivist ideas and aligned practices. Specific lecturer practices were identified as particularly effective in achieving such change. These effective lecturer practices may assist in establishing the foundations of a constructivist-aligned pedagogy for teacher education. The lecturers' modeling of the practices they were promoting for student teachers' practice was identified as a key element in promoting change. Indeed, the tension between traditional and transfornative approaches was exacerbated in situations where lecturers' promotion of a preferred practice was different from that which they enacted. The continuing existence of such situations and associated tensions has the potential to limit the extent of any change.

Der folgende Beitrag beschreibt die Situation der Fremdsprachenausbildung und -zertifizierung an den Instituts Universitaires de Technologie (IUT) in Frankreich. Die auf die Berufswirklichkeit ausgerichteten Ausbildungsziele und Kursinhalte unterscheiden sich von der externen Prüfung zur Zertifizierung. Die Prüfungsaufgaben einer Zertifizierungs-organisation für das Englische konzentrieren sich auf rezeptive Kenntnisse und Fertigkeiten, bieten aber den in den Fremdsprachenkursen ausgebildeten produktiven Fertigkeiten wenig Raum. Deshalb wird den IUT empfohlen, ein eigenes Zertifikat für die Sprachausbildung einzuführen, ein CLIUT (Certificat en langues pour les IUT). Das Zertifikat soll eine Fremdsprachenkompetenz bescheinigen, die auf die berufliche Verwendung der Fremdsprache ausgerichtet ist. Es wird jedoch vom Arbeitsmarkt nur dann anerkannt, wenn es mit einem transparenten Qualitätssicherungssystem verbunden wird und wenn es gelingt, die Niveaustufen nachprüfbar am Europäischen Referenzrahmen für Sprachen auszurichten. / La contribution ci-dessous essaie d’expliciter quelques pistes de réflexion présentées lors de la conférence plénière sur les certifications en langue du 34e congrès de l’APLIUT à Strasbourg. Il s’agira donc de s’attarder sur les considérations du Conseil d’administration de l’APLIUT (CA d’APLIUT : 2007). La 1ère partie présentera de manière succincte des exemples de mise en situation professionnelle des étudiants dans les cours de langues étrangères en IUT. L’application de cette méthode demande de développer des compétences plus complexes que celles développées dans un cours se limitant à des sujets du vécu quotidien. Il conviendra ensuite de se demander dans quelle mesure les effets souhaités de cette approche font l’objet des épreuves de certification recommandées par les Programmes Pédagogiques Nationaux (PPN) des DUT. En raison de l’incohérence entre les cours et les épreuves de certification, la question de la certification a l’air d’être sans issue. Du fait qu’à ce jour la recherche d’une certification validant l’enseignement dans les IUT n’a toujours pas abouti au résultat escompté, il faudrait peut-être envisager de créer une attestation propre destinée aux IUT. L’atteinte de cet objectif passe par l’aboutissement d’importants travaux préliminaires et également par la valorisation d’une certification grâce à un système d’assurance qualité, voir la 3e partie.