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The relational artwork and the antagonismNilsson, Emilie January 2010 (has links)
Udgangspunktet for at skrive denne opgave er interessen for at undersøge,hvorvidt det lykkes den relationelle kunst at indtage en kritisk position idagens samfund. I en verdensorden, hvor kapitalismens varegørelse kan synesat have indoptaget kunstens kritiske potentiale, kan det være svært atforestille sig den position, hvorfra kunsten skulle have en reel politisk ogsocial betydning. Ikke desto mindre er det min grundlæggende antagelse, atkunsten har og altid vil have en priviligeret mulighed for at opfordrebeskueren til at stille spørgsmålstegn ved det bestående.På baggrund af en kritisk tekstanalyse af Nicolas Bourriauds essaysamlingEsthetique Relationelle (1998) hvor blandt andre teoretikerne Claire Bishop,Stewart Martin og Grant Kester inddrages til en nuanceret diskussion. Samtgennem en analyse af værkerne It is What it Is, Conversations About Iraq og TheAmerican War. –Argumenterer jeg for, at den relationelle æstetik ikke formårat skabe en reel kritik af de sociale og politiske diskurser som omgiver os alle.Der efterlades dog et lille håb for kritikken idet Bishop, inspireret af denBelgiske teoretiker Chantal Mouffe, introducerer ideen om antagonismen sommulig kritikbærer. / The primary foundation for writing this thesis originates from my interestin, whether or not there exists a critical potential, within the art form ofrelational aesthetics. In a World order, where capitalism seems to overshadowthe critical potential within the arts, it can be difficult to imagine the position,from where art could have a significant influence in changing political andsocial issues. Regardless, it is my fundamental belief, that art will always havea privileged possibility of urging the viewer to question the existing.Grounded in a critical text analysis of Nicolas Bourriuads’ essay collection,Estetique Relationelle (1998), where, amongst other theorists, Clare Bishop,Stewart Martin and Grant Kester are implicated for a nuanced discussion.Accompanied by an analysis of the two relational works; It is What it Is,Conversations About Iraq and The American War, -This thesis argues thatrelational aesthetics does not succeed in creating a real critique of the socialand political structures that surrounds us.Though, Bishop, inspired by the Belgian theorist Chantal Moueffe,introduces the idea of the antagonism as a possible critique carrier, and herebyleaves a fragment of hope for critique.
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Caractérisation de l'impact de la croissance en biofilm sur l'activité probiotique de souches du genre Lactobacillus / Characterization of the impact of biofilm growth on the activity of probiotic strains of the genus LactobaccillusAoudia, Nabil 13 February 2014 (has links)
Une approche in vitro a consisté à étudier la formation de biofilm de souches d’origine du genre Lactobacillus d’intérêt probiotique. Nous nous sommes également attachés à évaluer l’impact de conditions de stress mimant l’environnement intestinal sur la formation du biofilm pour l’ensemble de ces souches. Les effets antagonistes des surnageants de cultures en biofilm ou en planctonique contre des agents pathogènes alimentaires ont été appréhendés. Non seulement toutes les souches testées forment des biofilms mais ce mode de croissance génère un effet antagoniste accentué pour certaines d’entre elles. Parmi les critères de sélection des bactéries à intérêt probiotique, les effets immunomodulateurs des probiotiques sont souvent recherchés. L. casei ATCC334 connue pour ses effets anti-inflammatoires a été retenue pour notre étude. A l’aide du modèle de lignée cellulaire THP-1 et en présence de LPS, le surnageant de culture de L. casei ATCC334 cultivée en biofilm s’est avéré présenter un effet anti-inflammatoire bien supérieur à celui des cultures planctoniques. Une approche utilisant des techniques biochimique et immunologique a permis d’identifier un des principes actifs responsable de l’effet anti-inflammatoire de cette souche. L’utilisation du modèle poisson zèbre a permis de montrer la colonisation de l’intestin des larves et de confirmer le rôle anti-inflammatoire de L. casei ATCC334 avec une diminution de la production des interleukines pro-inflammatoires et une augmentation de la production d'IL-10. Le recrutement des macrophages fluorescents mesuré en cytométrie de flux est également atténué chez la larve nourrie auparavant par le probotique en présence d’un agent inflammatoire. Le résultat majeur de cette étude est l’identification de la protéine GroEL qui contribue de façon significative à l’effet anti-inflammatoire de la souche L. casei ATCC334 lorsque qu’elle est cultivée en biofilm. / An in vitro approach was used to study biofilm formation by bacterial strains with probiotic properties and belonging to the Lactobacillus genus. We also evaluated the impact of stress conditions mimicking the intestinal environment on biofilm formation for all of these strains. The antagonistic effects of supernatants from cultures in biofilm or planktonic conditions against food-borne pathogens were apprehended. This growth mode generates an antagonistic effect accentuated for some of them. Among the selection criteria of interest probiotic bacteria, the immunomodulatory effects of probiotics are often sought. L. casei ATCC334 known for its anti-inflammatory effects was selected for our study. Using the model cell line THP-1 and in the presence of LPS, the culture supernatant of L. casei ATCC334 grown in biofilm was found to have an anti-inflammatory effect much greater than planktonic cultures. An approach using immunological and biochemical techniques has allowed the identification of the active substances responsible for the anti-inflammatory effect of this strain. Using the zebrafish model, we showed the colonization of the gut of the larvae and confirmed the anti-inflammatory role of L. casei ATCC334 with a decreased production of pro-inflammatory interleukins, and increased IL-10 production. Recruitment of fluorescent macrophages measured by flow cytometry was also mitigated in larvae fed previously by probotic in the presence of an inflammatory agent. The major result of this study is the identification of the GroEL protein that contributes significantly to anti-inflammatory effect of the strain L. casei ATCC334 when it is grown in biofilm.
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L'Afrique dans l'antagonisme Est-Ouest de 1970 à 1991 / Africa in the East-West antagonism 1970-end 1991Sess, Gnagne Antoine 14 December 2009 (has links)
Marginalisée et cantonnée jusqu’alors à la périphérie de la guerre froide, l’Afrique devient dans les années 1970, l’enjeu de rivalités entre les grandes puissances. Et pour cause. Les nombreuses faiblesses et l’intérêt stratégique du continent ainsi que les changements qui affectent le monde dans les années 1970 offrent aux deux grands l’occasion de s’y affronter. L’initiative de cet affrontement revient à l’Urss et à ses alliés qui, profitant de l’effacement relatif des Occidentaux, s’introduisent successivement en Afrique australe et dans la Corne de l’Afrique faisant de l’Afrique Subsaharienne un terrain de l’expansionnisme soviétique. Ces rivalités influencent considérablement la vie politique, économique et sociale du continent. De sorte que la fin de ce conflit entraîne un bouleversement du paysage politico-stratégique de la période de guerre froide et la perte de la valeur stratégique du continent. / Previously marginalized and relegated to the periphery of the cold war, Africa became in the 1970 s, the challenge of competition between major powers. And for good reason. The many weaknesses and the strategic interest of the continent and the changes that affect the world in the 1970 s offer two major an opportunity to confront each other. The initiative of this confrontation is for the USSR and allies who, taking advantage of erasure of western, introduce successively in the southern Africa and Horn of Africa and transform sub-saharan Africa in an area of soviet expansionism. This competition has considerable influence on political, economic and social point of the continent. So that the end of this conflict leads to a disruption.
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Facteurs de variation de la biodisponibilité du zinc, ajouté sous forme organique ou inorganique, chez deux espèces monogastriques en croissance (poulet et porcelet)Schlegel, Patrick 24 September 2010 (has links) (PDF)
Le zinc est un élément essentiel, un métal polluant et une ressource non renouvelable. Les phytates sont identifiés comme facteur alimentaire principal qui limite la biodisponibilité du Zn chez le monogastrique. Le Zn sous forme organique (DZNO) est supposé moins interagir avec les phytates que celui de forme inorganique (DZNI). La biodisponibilité du Zn alimentaire a été étudiée en fonction des phytates chez le rat, le poulet et le porcelet pour mieux comprendre les mécanismes liés à cette interaction. Les expériences in vivo et les méta-analyses ont permis de mettre en évidence que : 1) L'absorption de DZNO est améliorée par rapport à DZNI, en présence de phytate de sodium qui suggère une protection, de DZNO contre cet antagoniste. 2) La biodisponibilité de DZNO n'est pas améliorée par rapport à DZNI chez le poulet et le porc nourri avec des aliments contenant des phytates d'origine végétale. L'antagonisme des phytates végétales agit sur le Zn natif seulement. 3) L'antagonisme des phytates végétales sur la biodisponibilité du Zn est plus prononcé chez le porc que chez le poulet. Contrairement au porc, le pH gastrique faible chez le poulet serait capable de valoriser le Zn natif, initialement lié aux phytates. 4) Pour une supplémentation optimale du Zn chez le porc, nous suggérons, en plus de la teneur en Zn native, la prise en compte d'une nouvelle variable " P phytique non hydrolysé ". Celle-ci tient compte de l'activité phytasique végétale et microbienne de l'aliment. La supplémentation en Zn peut ainsi être adaptée en fonction du potentiel antagoniste des phytates non hydrolysées. La capacité naturelle du poulet à valoriser le zinc natif limite la marge de progrès.
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Syntheses of chalcones and 2-aminopyrimidines and their evaluation as monoamine oxidase inhibitors and as adenosine receptor antagonists / Sarel Johannes RobinsonRobinson, Sarel Johannes January 2013 (has links)
Background and rationale -
Parkinson’s disease is a neurodegenerative disorder characterised by reduced levels of
dopamine in the brain. The cause of Parkinson's disease is still unknown; however several
theories pertaining to the etiology exist. Current treatment mainly aims at dopamine
replacement, with agents such as levodopa and dopamine agonists that provide patients
with symptomatic relief. This relief is unfortunately only temporary as the progression of the
disease is not halted. Furthermore, these therapies are associated with a range of side
effects and novel approaches to the treatment are thus urgently required. Adenosine A2A
receptor antagonists recently emerged as a promising non-dopaminergic alternative, not
only as symptomatic treatment, but also as potential neuroprotective therapy.
Adenosine A2A receptors are co-localised with dopamine D2 receptors in the striatum and
other nuclei of the basal ganglia. Adenosine A2A stimulation decreases the affinity of
dopamine for the D2 receptor, and increase cyclic AMP (cAMP) levels. The stimulation of
dopamine D2 receptors, in contrast, decreases cAMP levels and therefore these receptors
(A2A and D2), act in an opposing manner. Adenosine A2A antagonism will thus have similar
effects as dopamine D2 agonism and will reduce the postsynaptic effects of dopamine
depletion to give symptomatic relief. There are also several mechanisms where by
adenosine A2A antagonists may be neuroprotective, for example by preventing glutamate
excitotoxicity, that may cause damage to dopaminergic neurons. A number of adenosine A2A
antagonists have already reached clinical trials and promising results were obtained,
especially when combined with levodopa. Consequently, A2A antagonists are realistic
prospects that have therapeutic potential in diseases with dopaminergic hypofunction, like
Parkinson's disease. Many of the current A2A antagonists contain an amino-substituted
heterocyclic scaffold, such as an aminopyrimidine. The primary aim of this study was the
design, synthesis and evaluation of 2-aminopyrimidine derivatives as adenosine A2A receptor
antagonists.
Monoamine oxidase B (MAO-B) inhibitors are also promising candidates for the symptomatic
treatment of Parkinson's disease, since MAO-B is the enzyme primarily responsible for the catabolism of dopamine in the brain. Irreversible inhibitors of MAO-B, such as selegeline and
rasagiline, have been used clinically for the treatment of Parkinson's disease. This type of
inhibition comes with certain disadvantages as it may take up to several weeks after
termination of treatment for the enzyme activity to recover. Reversible inhibitors in contrast
will have much better safety profiles seeing that they will not inactivate the enzyme
permanently and allow for competition with the substrate.
When dopamine is oxidized by MAO, toxic metabolic by-products, such as hydrogen
peroxide (H2O2) forms, and this is believed to be a possible cause of Parkinson's disease.
MAO-B inhibitors will therefore not only provide symptomatic relief but may also alter the
progression of the disease by preventing the formation of these byproducts. Promising MAOB
inhibitory activities have been reported for chalcones, and since the intermediates
obtained in the synthesis of aminopyrimidines in this study are chalcones, a secondary aim
of this study was the screening of selected chalcone intermediates as inhibitors of MAO–B.
Results -
Design and synthesis: A series of 2-aminopyrimidines were designed using known active
structures and literature pharmacophores. A molecular modelling study (Discovery Studio
3.1, Accelrys) was further done to investigate the feasibility of these compounds as potential
adenosine A2A antagonists. All of the designed aminopyrimidines were successfully docked
in the binding site of the adenosine A2A receptor. Binding orientations and observed
interactions with important residues in the active site were similar to those observed for
known A2A antagonists. It was therefore concluded that these compounds may be potential
A2A antagonists and the designed compounds were thus synthesised. Structures were
primarily confirmed with nuclear magnetic resonance spectroscopy and mass spectrometry.
MAO-B inhibition studies: Selected chalcones were evaluated using a fluorometric assay
and kynuramine as substrate. The compounds were potent and selective inhibitors of the
MAO-B enzyme with IC50 values ranging between 0.49-7.67 μM. (2E)-3-(3-Chlorophenyl)-1-
(5-methyl-2-furyl)prop-2-en-1-one (1c) was the most potent compound with an IC50 value of
0.49 μM and was approximately 60 times more selective towards MAO-B than MAO-A.
Some preliminary structure activity relationships were derived, for example, phenyl
substitution with an electron withdrawing chlorine group generally resulted in better activity
than substitution with electron donating methoxy groups. Further investigation of structure
activity relationships are however required as a very small series of chalcones were
screened.
Reversibility studies and mode of inhibition: A dilution assay was used to determine whether
compound (1c) binds reversibly or irreversibly to the MAO-B enzyme. This was done by measuring the recovery of enzymatic activity after a large dilution of the enzyme-inhibitor
complex. The results from the reversibility studies showed that the inhibition of the most
potent compound (1c) is reversible as the catalytic activities are recovered to approximately
80% and 50% respectively, compared to the control measured in the absence of an inhibitor.
For the mode of inhibition, sets of Lineweaver–Burk plots were constructed. The Lineweaver-
Burk plots intersected on the y-axis which indicates that compound 1c is a competitive inhibitor
of the MAO-B enzyme.
In vitro adenosine A2A assays: Radioligand binding assays were used to determine the
affinity of the synthesised 2-aminopyrimidines for the adenosine A2A receptor. This assay
was performed with the radioligand [3H]NECA in the presence of N6-cyclopentyladenosine
(CPA). Compounds 2a - 2h showed moderate to weak affinity in the assay, while promising
affinities were observed for compounds 2j - 2n, which all exhibited Ki values below 55 nM.
The compound with the highest affinity was 4-(5-methylfuran-2-yl)-6-[3-(piperidine-1-
carbonyl)phenyl]pyrimidin-2-amine (2m) with a Ki value of 5.76 nM, which is comparable to
the Ki value of 2.10 nM obtained for the known amino-substituted heterocyclic adenosine A2A
antagonist, ZM 241385. The higher affinities of compounds (2j – 2n) could, at least in part,
be explained by the molecular modellling studies. In the docking experiments an additional
hydrogen bond interaction was observed between the amide carbonyl and tyrosine 271
indicating that this structural feature is a major contributing factor to the improved affinity
observed for these derivatives.
In vivo adenosine A2A assays: The haloperidol induced catalepsy assay was used to
determine whether the two compounds with the highest affinity for the adenosine A2A
receptor (2m and 2k) are antagonists of the A2A receptor. These compounds caused a
statistically significant reduction in catalepsy, which clearly illustrate that they are adenosine
A2A antagonists.
The objectives of this study as set out were thus successfully realised and promising results
were obtained. During this study, several novel 2-aminopyrimidines and chalcones were
synthesised, and the respective adenosine A2A antagonistic and monoamine oxidase
inhibitory activities for all of the screened compounds were determined for the first time. / Thesis (MSc (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2013
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Syntheses of chalcones and 2-aminopyrimidines and their evaluation as monoamine oxidase inhibitors and as adenosine receptor antagonists / Sarel Johannes RobinsonRobinson, Sarel Johannes January 2013 (has links)
Background and rationale -
Parkinson’s disease is a neurodegenerative disorder characterised by reduced levels of
dopamine in the brain. The cause of Parkinson's disease is still unknown; however several
theories pertaining to the etiology exist. Current treatment mainly aims at dopamine
replacement, with agents such as levodopa and dopamine agonists that provide patients
with symptomatic relief. This relief is unfortunately only temporary as the progression of the
disease is not halted. Furthermore, these therapies are associated with a range of side
effects and novel approaches to the treatment are thus urgently required. Adenosine A2A
receptor antagonists recently emerged as a promising non-dopaminergic alternative, not
only as symptomatic treatment, but also as potential neuroprotective therapy.
Adenosine A2A receptors are co-localised with dopamine D2 receptors in the striatum and
other nuclei of the basal ganglia. Adenosine A2A stimulation decreases the affinity of
dopamine for the D2 receptor, and increase cyclic AMP (cAMP) levels. The stimulation of
dopamine D2 receptors, in contrast, decreases cAMP levels and therefore these receptors
(A2A and D2), act in an opposing manner. Adenosine A2A antagonism will thus have similar
effects as dopamine D2 agonism and will reduce the postsynaptic effects of dopamine
depletion to give symptomatic relief. There are also several mechanisms where by
adenosine A2A antagonists may be neuroprotective, for example by preventing glutamate
excitotoxicity, that may cause damage to dopaminergic neurons. A number of adenosine A2A
antagonists have already reached clinical trials and promising results were obtained,
especially when combined with levodopa. Consequently, A2A antagonists are realistic
prospects that have therapeutic potential in diseases with dopaminergic hypofunction, like
Parkinson's disease. Many of the current A2A antagonists contain an amino-substituted
heterocyclic scaffold, such as an aminopyrimidine. The primary aim of this study was the
design, synthesis and evaluation of 2-aminopyrimidine derivatives as adenosine A2A receptor
antagonists.
Monoamine oxidase B (MAO-B) inhibitors are also promising candidates for the symptomatic
treatment of Parkinson's disease, since MAO-B is the enzyme primarily responsible for the catabolism of dopamine in the brain. Irreversible inhibitors of MAO-B, such as selegeline and
rasagiline, have been used clinically for the treatment of Parkinson's disease. This type of
inhibition comes with certain disadvantages as it may take up to several weeks after
termination of treatment for the enzyme activity to recover. Reversible inhibitors in contrast
will have much better safety profiles seeing that they will not inactivate the enzyme
permanently and allow for competition with the substrate.
When dopamine is oxidized by MAO, toxic metabolic by-products, such as hydrogen
peroxide (H2O2) forms, and this is believed to be a possible cause of Parkinson's disease.
MAO-B inhibitors will therefore not only provide symptomatic relief but may also alter the
progression of the disease by preventing the formation of these byproducts. Promising MAOB
inhibitory activities have been reported for chalcones, and since the intermediates
obtained in the synthesis of aminopyrimidines in this study are chalcones, a secondary aim
of this study was the screening of selected chalcone intermediates as inhibitors of MAO–B.
Results -
Design and synthesis: A series of 2-aminopyrimidines were designed using known active
structures and literature pharmacophores. A molecular modelling study (Discovery Studio
3.1, Accelrys) was further done to investigate the feasibility of these compounds as potential
adenosine A2A antagonists. All of the designed aminopyrimidines were successfully docked
in the binding site of the adenosine A2A receptor. Binding orientations and observed
interactions with important residues in the active site were similar to those observed for
known A2A antagonists. It was therefore concluded that these compounds may be potential
A2A antagonists and the designed compounds were thus synthesised. Structures were
primarily confirmed with nuclear magnetic resonance spectroscopy and mass spectrometry.
MAO-B inhibition studies: Selected chalcones were evaluated using a fluorometric assay
and kynuramine as substrate. The compounds were potent and selective inhibitors of the
MAO-B enzyme with IC50 values ranging between 0.49-7.67 μM. (2E)-3-(3-Chlorophenyl)-1-
(5-methyl-2-furyl)prop-2-en-1-one (1c) was the most potent compound with an IC50 value of
0.49 μM and was approximately 60 times more selective towards MAO-B than MAO-A.
Some preliminary structure activity relationships were derived, for example, phenyl
substitution with an electron withdrawing chlorine group generally resulted in better activity
than substitution with electron donating methoxy groups. Further investigation of structure
activity relationships are however required as a very small series of chalcones were
screened.
Reversibility studies and mode of inhibition: A dilution assay was used to determine whether
compound (1c) binds reversibly or irreversibly to the MAO-B enzyme. This was done by measuring the recovery of enzymatic activity after a large dilution of the enzyme-inhibitor
complex. The results from the reversibility studies showed that the inhibition of the most
potent compound (1c) is reversible as the catalytic activities are recovered to approximately
80% and 50% respectively, compared to the control measured in the absence of an inhibitor.
For the mode of inhibition, sets of Lineweaver–Burk plots were constructed. The Lineweaver-
Burk plots intersected on the y-axis which indicates that compound 1c is a competitive inhibitor
of the MAO-B enzyme.
In vitro adenosine A2A assays: Radioligand binding assays were used to determine the
affinity of the synthesised 2-aminopyrimidines for the adenosine A2A receptor. This assay
was performed with the radioligand [3H]NECA in the presence of N6-cyclopentyladenosine
(CPA). Compounds 2a - 2h showed moderate to weak affinity in the assay, while promising
affinities were observed for compounds 2j - 2n, which all exhibited Ki values below 55 nM.
The compound with the highest affinity was 4-(5-methylfuran-2-yl)-6-[3-(piperidine-1-
carbonyl)phenyl]pyrimidin-2-amine (2m) with a Ki value of 5.76 nM, which is comparable to
the Ki value of 2.10 nM obtained for the known amino-substituted heterocyclic adenosine A2A
antagonist, ZM 241385. The higher affinities of compounds (2j – 2n) could, at least in part,
be explained by the molecular modellling studies. In the docking experiments an additional
hydrogen bond interaction was observed between the amide carbonyl and tyrosine 271
indicating that this structural feature is a major contributing factor to the improved affinity
observed for these derivatives.
In vivo adenosine A2A assays: The haloperidol induced catalepsy assay was used to
determine whether the two compounds with the highest affinity for the adenosine A2A
receptor (2m and 2k) are antagonists of the A2A receptor. These compounds caused a
statistically significant reduction in catalepsy, which clearly illustrate that they are adenosine
A2A antagonists.
The objectives of this study as set out were thus successfully realised and promising results
were obtained. During this study, several novel 2-aminopyrimidines and chalcones were
synthesised, and the respective adenosine A2A antagonistic and monoamine oxidase
inhibitory activities for all of the screened compounds were determined for the first time. / Thesis (MSc (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2013
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La métaphysique dans la sculpture de Jean Tinguely : mécanique, contradiction et métamorphose comme principes générateurs / Metaphysics in sculptural work of Jean Tinguely : mechanical, contradiction and metamorphosis as generator principlesRolez, Anaïs 23 January 2015 (has links)
L'objet de cette thèse est l'étude de la part métaphysique dans l’oeuvre sculptée de Jean Tinguely (Fribourg 1925 - Berne1991). La problématique majeure est celle de l'aspect contradictoire d'une oeuvre à la fois anti-académique issue de l'influence dadaïste mais dont la dimension métaphysique la rapproche d'une tradition spéculative de l'art. L'étude de lasculpture de Jean Tinguely se fait sous deux axes principaux : l'art comme jeu plaisant et l'art comme pourvoyeur devérité. / The topic of this PhD thesis is the study of the metaphysical aspect of the sculptural work of Jean Tinguely (Fribourg 1925 –Bern 1991). The main argument is the contradictory conception of a work which is anti-academic in the dadaist attitude,but which metaphysical dimension makes it close to the speculative tradition in art. The study of the sculptural work of JeanTinguely follows two main perspectives: art as pleasant game and art as purveyor of truth.
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Couplage entre interactions antagonistes et mutualistes et dynamiques éco-évolutives des communautés / Interplay between antagonistic and mutualistic interactions and ecoevolutionary dynamics of communitiesGeorgelin, Ewen 14 October 2014 (has links)
Les communautés écologiques présentent une diversité importante d'organismes et d'interactions. Comprendre le fonctionnement de ces différents types d'interactions constitue l'un des enjeux majeurs de l'écologie des communautés. Cependant, une large majorité des travaux s'intéressant à ces questions s'est focalisée sur les différents types d'interactions séparément. Cette thèse cherche à comprendre comment le couplage entre différents types d'interactions affecte la dynamique des communautés naturelles. Au travers d'une approche théorique, des modèles simples de communautés comprenant deux types d'interactions sont construits. Ces communautés sont constituées de trois espèces : une espèce basale, plante, interagissant avec un antagoniste, herbivore et un mutualiste, pollinisateur. Nous décrivons comment l'effet indirect entre interactions antagonistes et mutualistes affecte les dynamiques écologiques et évolutives des communautés face à une perturbation. Nous montrons que la relation entre pollinisateurs et herbivores à des conséquences importantes pour le maintien éco-Évolutif de la communauté et pour sa stabilité. Nous étudions ensuite la dynamique évolutive de traits particuliers, qui sont impliqués dans chaque type d'interactions. Certains traits attractifs ou de défense des plantes, affectent à la fois les interactions avec les pollinisateurs et les herbivores. Nous montrons comment les pressions de sélection opposées dues à la pollinisation et à l'herbivorie modifient l'évolution de ces traits et peuvent amener à la diversification des plantes. / Ecological communities involve an amazing diversity of organisms and interactions. Understanding how this diversity of interaction types (competition, mutualism or predation) affects the ecological and evolutionary dynamics of natural systems is an important challenge of community ecology. However, a large majority of works in community ecology theory considers interaction types separately. This thesis focus on the interplay between antagonism and mutualism. With a theoretical approach, small community models, including antagonistic and mutualistic interactions are built. These communities contain three species : one basal species (a plant) with an antagonist (herbivore) and a mutualistic species (pollinator). First, we study how the indirect effect between the two interaction types affects the ecological and evolutionary dynamics of communities in the currency of a disturbance. Second, we study the evolutionary dynamics of special traits, that are involved in each interaction type. Attractive traits or defensive traits of plants affect both interaction with pollinators and herbivores. We depict how the opposite selective pressures due to pollination and herbivory modify the evolution of these traits and show that they can lead to evolutionary diversification of plants. Following this diversification, the coevolutionary emergence of complex interaction networks is studied.
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Étude des mécanismes de répression transcriptionnelle du gène de la proopiomélanocortine par les glucocorticoïdes : implication de Nur77/NGFI-B, un récepteur nucléaire orphelinMartens, Christine 11 1900 (has links)
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal. / Le récepteur nucléaire orphelin NGFI-B s'est démarqué des autres récepteurs nucléaires par sa capacité à lier I'ADN sous la forme de monomère. L'importance de ce facteur de transcription a été mise en évidence par son rôle dans l'apoptose des cellules T et par son implication à tous les niveaux de l'axe hypothalamo-hypophyso-surrénalien (axe HHS). Le stress induit une cascade neuroendocrinienne qui débute, au niveau de l'hypothalamus, par la sécrétion de CRH qui induit l'expression de NGFI-B dans les cellules corticotrophes de l'hypophyse, et NGFI-B à son tour induit la transcription du gène de la proopiomélanocortine (POMC) en liant un élément de réponse aux facteurs Nur, le NurRE. Cet élément de réponse a la particularité de lier des dimères de Nur77. La POMC est le précurseur de l'ACTH qui est le stimulus majeur de la synthèse des glucocorticoïdes. Les glucocorticoïdes activent ou répriment la transcription de différents gènes importants pour le métabolisme en liant un récepteur nucléaire (GR). Une surexpression de glucocorticoïdes peut avoir des conséquences néfastes sur l'organisme. Aussi régulent-ils leur propre synthèse en exerçant une rétro-inhibition de l'axe HHS en inhibant l'expression et la sécrétion du CRH et de la POMC/ACTH. Les glucocorticoïdes inhibent la transcription de la POMC induite par le CRH en agissant au niveau du NurRE en antagonisant l'activité transcriptionnelle de NGFI-B. Le but de cette étude consistait à déterminer les mécanismes qui sont sous-jacents à l'antagonisme transcriptionnel entre NGFI-B et GR. Nous avons émis l'hypothèse qu'une interaction protéine/protéine directe ou indirecte (séquestration d'un cofacteur commun aux deux récepteurs nucléaires) entre NGFI-B et GR est impliquée dans la répression de la transcription de la POMC. Afin de vérifier cette hypothèse nous avons utilisé des techniques qui permettent d'étudier la nature des interactions entre deux protéines. Ainsi, nous avons démontré une interaction directe entre NGFI-B et GR via leurs domaines de liaison à l'ADN. Cette interaction s'applique aux autres membres de la famille Nur. Nous avons également démontré que GR interagit avec NGFI-B sous la forme de monomère. En parallèle, nous avons observé que l'activité transcriptionnelle de NGFI-B est stimulée par des coactivateurs de la famille SRC et par CBP. Nous avons observé que les dimères ont une capacité plus grande à recruter les coactivateurs que les monomères. Certains résultats expérimentaux suggèrent que l'antagonisme transcriptionnel entre NGFI-B et GR puisse s'appliquer à la régulation de la transcription du gène codant pour le CRH. De plus, il a été démontré que dans les cellules T, les glucocorticoïdes bloquent l'apoptose induite par l'activation du TCR en antagonisant l'activité transcriptionnelle de NGFI-B. Ceci reflète l'importance de l'identification de ce nouveau mécanisme d'action des glucocorticoïdes. De plus, ce mécanisme est similaire à celui qui avait été démontré dans le contrôle de ['expression des gènes impliqués dans la réponse inflammatoire et/ou immunitaire où GR antagonise l'activité transcriptionnelle de NF-KBetAP-1.
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Les formes de la binarité dans l'oeuvre de Martín Kohan : une écriture de l'antagonismeRamirez Cifola, Cécile 08 November 2013 (has links) (PDF)
L'œuvre de Martín Kohan (Buenos Aires, 1967), écrivain prolifique à la notoriété grandissante au sein de la littérature argentine contemporaine, est l'objet de ce travail de recherche. Nous abordons le corpus - constitué par l'essentiel de l'œuvre : huit romans sur les neuf publiés à ce jour, La pérdida de Laura (1993), El informe. San Martín o el otro cruce de los Andes (1997), Los cautivos. El exilio de Echeverría (2000), Dos veces junio (2002), Segundos afuera (2005), Museo de la Revolución (2006), Ciencias morales (2007), Cuentas pendientes (2010); et deux recueils de nouvelles, Muero contento (1994), et Una pena extraordinaria (1998), principalement - sous l'angle de l'antagonisme, motif essentiel de l'univers fictionnel de Kohan, non seulement sur le plan de la diégèse mais également sur celui de la forme. Ce travail part de l'observation d'une constante au sein d'un corpus pourtant très varié : un rapport dichotomique, fait d'incompréhension et parfois de violence, entre la culture populaire ou la culture de masse, et la culture lettrée. La première partie de la thèse en propose une analyse systématique dans les cinq romans qui abordent explicitement ce type de conflit sous les modalités les plus diverses. La deuxième partie explore d'autres procédés qui tendent à confirmer le rôle structurant de l'antagonisme au sein de l'œuvre : si la mise à mal de l'union amoureuse semble exprimer la fatalité du malentendu, la dévalorisation des personnages du " milieu " et de la figure du consensus d'une part, et l'aspect revigorant des conflits menés à leur dernière extrémité d'autre part, révèlent l'aspect positif et particulièrement dynamique de l'antagonisme. La dernière partie se consacre aux implications de ce motif, omniprésent au point de représenter une nécessité : sur le plan politique - car sans être réaliste, la littérature de Kohan met en action la révolution marxiste en élaborant des figures de contre-pouvoir - ; sur le plan littéraire, où l'antagonisme montre toute sa fécondité. Le rapport hypertextuel, établi notamment avec des textes qui font autorité dans la littérature nationale, en est une expression essentielle ; mais la dichotomie est aussi une composante qui se manifeste à tous les niveaux de l'écriture, de l'unité minimale du mot à l'architecture complexe des romans. À la lutte entre personnages fait écho celle - défi formel le plus ambitieux - qui se joue entre le fond et la forme, source d'inépuisable ambivalence qui constitue l'une des spécificités les plus intéressantes de cet écrivain brillant.
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