BACKGROUND: Hypoxic niches in solid tumors harbor therapy-resistant cells. Hypoxia-activated prodrugs (HAPs) have been designed to overcome this resistance and, to date, have begun to show clinical efficacy. However, clinical HAPs activity could be improved. In this study, we sought to identify non-pharmacological methods to acutely exacerbate tumor hypoxia to increase TH-302 activity in pancreatic ductal adenocarcinoma (PDAC) tumor models. RESULTS: Three human PDAC cell lines with varying sensitivity to TH-302 (Hs766t > MiaPaCa-2 > SU.86.86) were used to establish PDAC xenograft models. PDAC cells were metabolically profiled in vitro and in vivo using the Seahorse XF system and hyperpolarized 13C pyruvate MRI, respectively, in addition to quantitative immunohistochemistry. The effect of exogenous pyruvate on tumor oxygenation was determined using electroparamagnetic resonance (EPR) oxygen imaging. Hs766t and MiaPaCa-2 cells exhibited a glycolytic phenotype in comparison to TH-302 resistant line SU.86.86. Supporting this observation is a higher lactate/pyruvate ratio in Hs766t and MiaPaCa xenografts as observed during hyperpolarized pyruvate MRI studies in vivo. Coincidentally, response to exogenous pyruvate both in vitro (Seahorse oxygen consumption) and in vivo (EPR oxygen imaging) was greatest in Hs766t and MiaPaCa models, possibly due to a higher mitochondrial reserve capacity. Changes in oxygen consumption and in vivo hypoxic status to pyruvate were limited in the SU.86.86 model. Combination therapy of pyruvate plus TH-302 in vivo significantly decreased tumor growth and increased survival in the MiaPaCa model and improved survival in Hs766t tumors. CONCLUSIONS: Using metabolic profiling, functional imaging, and computational modeling, we show improved TH-302 activity by transiently increasing tumor hypoxia metabolically with exogenous pyruvate. Additionally, this work identified a set of biomarkers that may be used clinically to predict which tumors will be most responsive to pyruvate + TH-302 combination therapy. The results of this study support the concept that acute increases in tumor hypoxia can be beneficial for improving the clinical efficacy of HAPs and can positively impact the future treatment of PDAC and other cancers.

Many anticancer therapies, including radiotherapy, act by damaging the deoxyribosenucleic acid (DNA) that is fundamental to cell function and proliferation. H2AX is a histone protein associated with DNA that is phosphorylated to produce γH2AX in response to DNA double strand breaks (DSBs), the most lethal lesions caused in cancer cells. This thesis examines the translation of γH2AX detection assays to clinical situations in order to provide biomarkers of response that might help to guide the treatment of cancer patients. γH2AX immunohistochemistry was developed in preclinical xenograft models, and validated over a range of radiation doses and over time after irradiation. The method was prepared for translation to archived clinical biopsy and surgical specimens. The DSB Biomarkers Pilot Study was established in order to develop a method for γH2AX quantification in direct tumour cell specimens obtained using the clinical technique of fine needle aspiration (FNA) cytology. Eleven patients undergoing anticancer therapy were recruited to the study, and the method evaluated. The coefficient of variation of the measure was 49%. Non-invasive imaging for γH2AX would allow DNA damage to be quantified in all tumour sites, and on multiple occasions. An antibody-based nuclear medicine imaging agent was re-engineered using Fab fragments of the antibody. The novel agent demonstrated improved pharmacokinetics when compared to the whole antibody agent, but reduced target specificity. The findings further develop the potential to exploit DNA damage biomarker measurements in clinical oncology.

L'approche la plus courante en Mécanique des Fluides Numérique pour réaliser les simulations d'écoulement cardiovasculaire consiste à utiliser des méthodes numériques Body-fitted. Ces méthodes ont permis d'obtenir des simulations d'écoulement sanguin dans les artères qui sont précises et utiles. Toutefois, la génération du maillage body-fitted est une tâche qui demande beaucoup de temps et d'expertise à l'utilisateur.Les méthodes de Frontières Immergées sont des méthodes numériques alternatives qui ont l'avantage d'être plus simples d'emploi car elles ne requièrent aucune tâche de maillage de la part de l'utilisateur. Le travail présenté ici vise à évaluer le potentiel d'un méthode de Frontières Immergées à réaliser des simulations d'écoulement cardiovasculaire.Ce travail s'attache, dans un premier temps, à décrire les capacités de cette méthode numérique à rendre compte de l'imperméabilité et de la mobilité des parois sur des cas relativement simples mais représentatifs d'écoulements cardiovasculaires. Ensuite, des applications de la méthode à des cas d'écoulement cardiovasculaire plus complexes sont montrées. Il s'agira d'abord d'une simulation de l'écoulement dans un modèle rigide d'artère aorte. Puis, la simulation d'un écoulement à l'intérieur d'un ventricule cardiaque à paroi mobile sera montrée. / The most common approach in Computational Fluid Dynamics(CFD) for simulating blood flow into vessel is to make use of a body-fitted me-thod. This approach has lead to accurate and useful simulations of blood flowinto arteries. However, generation of the body-fitted grid is time consuming andrequires from the user an engineering knowledge.The Immersed Boundary Method has emerged as an alternate method whichdoes not require from the user any grid generation task. Simulations are done on astructured Cartesian grid which can be automatically generated. Here we addressthe question of the capability of an Immersed Boundary Method to cope withcardiovascular flow simulations.In particular, we assess the impermeable and moving properties of the wallwhen using the Immersed Boundary Method on simple but relevant vascular flowcases. Then, we show more complex and realistic cardiovascular flow simulations.The first application consists of blood flow simulation inside an aorta cross model.Then, the simulation of blood flow inside a cardiac ventricle with moving wall isshown.

abstract: A direct Magnetic Resonance (MR)-based neural activity mapping technique with high spatial and temporal resolution may accelerate studies of brain functional organization. The most widely used technique for brain functional imaging is functional Magnetic Resonance Image (fMRI). The spatial resolution of fMRI is high. However, fMRI signals are highly influenced by the vasculature in each voxel and can be affected by capillary orientation and vessel size. Functional MRI analysis may, therefore, produce misleading results when voxels are nearby large vessels. Another problem in fMRI is that hemodynamic responses are slower than the neuronal activity. Therefore, temporal resolution is limited in fMRI. Furthermore, the correlation between neural activity and the hemodynamic response is not fully understood. fMRI can only be considered an indirect method of functional brain imaging. Another MR-based method of functional brain mapping is neuronal current magnetic resonance imaging (ncMRI), which has been studied over several years. However, the amplitude of these neuronal current signals is an order of magnitude smaller than the physiological noise. Works on ncMRI include simulation, phantom experiments, and studies in tissue including isolated ganglia, optic nerves, and human brains. However, ncMRI development has been hampered due to the extremely small signal amplitude, as well as the presence of confounding signals from hemodynamic changes and other physiological noise. Magnetic Resonance Electrical Impedance Tomography (MREIT) methods could have the potential for the detection of neuronal activity. In this technique, small external currents are applied to a body during MR scans. This current flow produces a magnetic field as well as an electric field. The altered magnetic flux density along the main magnetic field direction caused by this current flow can be obtained from phase images. When there is neural activity, the conductivity of the neural cell membrane changes and the current paths around the neurons change consequently. Neural spiking activity during external current injection, therefore, causes differential phase accumulation in MR data. Statistical analysis methods can be used to identify neuronal-current-induced magnetic field changes. / Dissertation/Thesis / Doctoral Dissertation Biomedical Engineering 2019

The main objective of this thesis is to investigate the intrinsic optical signals (IOSs) with an ultra-high resolution optical coherence tomography system (UHROCT). In order to study the retinal IOSs evoked by visible light, an UHROCT and an Electroretinogram (ERG) system was combined. An animal model (chicken retina) based on its retinal avascularity and cone dominance, was selected. Imaging the chicken retina with OCT resulted in high contrast, high resolution (~3μm axial and ~5 μm lateral resolution) 2D and 3D volumetric tomograms, in which all retina layers were clearly distinguishable. Using the combined UHROCT and ERG system to image IOSs from the chicken retina exposed to visible light (7ms green flash) resulted in highly reproducible IOS recordings from all retinal layers for the first time. All inner retinal layers showed an initial increase and subsequently a decrease in the intensity of the backreflected imaging light within the first 100 ms after the onset of the stimulus. Outer segments of the photoreceptors also showed a decrease in the backreflected imaging light within 100 ms after the onset of the flash. All retinal layers showed a strong decrease in the backreflected light within 150 to 175 ms after the onset of the flash. Imaging the pupil dynamics of the chicken with a modified combined UHROCT and ERG system showed that part of the strong negative IOSs observed in all retinal layers resulted from the vignetting of the imaging beam due to the light induced pupil constriction. Thorough analysis of the pupil dynamics acquired with UHROCT showed a time dependent effect of the anesthesia agent on pupil constriction. Further experiments to investigate an anesthesia effects on retinal function showed significant changes in ERG components. Statistical analysis showed that Isoflurane anesthesia severely affects the inner retinal response. In conclusion, it was hypothesized that the fast IOSs within ~50-100 ms after the onset of the visual stimulus originated from the neuronal tissue in the retina and are related to tissue optical property changes as a result of the electrical signal propagation in the light activated retina. Longer term decreases in backreflected light are likely due to pupil changes.

The main objective of this thesis is to investigate the intrinsic optical signals (IOSs) with an ultra-high resolution optical coherence tomography system (UHROCT). In order to study the retinal IOSs evoked by visible light, an UHROCT and an Electroretinogram (ERG) system was combined. An animal model (chicken retina) based on its retinal avascularity and cone dominance, was selected. Imaging the chicken retina with OCT resulted in high contrast, high resolution (~3μm axial and ~5 μm lateral resolution) 2D and 3D volumetric tomograms, in which all retina layers were clearly distinguishable. Using the combined UHROCT and ERG system to image IOSs from the chicken retina exposed to visible light (7ms green flash) resulted in highly reproducible IOS recordings from all retinal layers for the first time. All inner retinal layers showed an initial increase and subsequently a decrease in the intensity of the backreflected imaging light within the first 100 ms after the onset of the stimulus. Outer segments of the photoreceptors also showed a decrease in the backreflected imaging light within 100 ms after the onset of the flash. All retinal layers showed a strong decrease in the backreflected light within 150 to 175 ms after the onset of the flash. Imaging the pupil dynamics of the chicken with a modified combined UHROCT and ERG system showed that part of the strong negative IOSs observed in all retinal layers resulted from the vignetting of the imaging beam due to the light induced pupil constriction. Thorough analysis of the pupil dynamics acquired with UHROCT showed a time dependent effect of the anesthesia agent on pupil constriction. Further experiments to investigate an anesthesia effects on retinal function showed significant changes in ERG components. Statistical analysis showed that Isoflurane anesthesia severely affects the inner retinal response. In conclusion, it was hypothesized that the fast IOSs within ~50-100 ms after the onset of the visual stimulus originated from the neuronal tissue in the retina and are related to tissue optical property changes as a result of the electrical signal propagation in the light activated retina. Longer term decreases in backreflected light are likely due to pupil changes.

De part le monde, nombre de personnes sont atteintes par pathologies cérébrales directement liées au vieillissement. Pour comprendre les mécanismes biologiques du vieillissement cérébral et développer de nouvelles thérapies, l’utilisation de modèles animaux pertinents est un atout décisif. Le primate Microcèbe, est un modèle de vieillissement cérébral normal et pathologique. Il présente avec l’âge des altérations cérébrales anatomiques accompagnées de déficits cognitifs, similaires à celles observées chez l’Homme. Chez certains individus, ces altérations sont plus sévères, avec une atrophie de l’hippocampe et la présence de plaques amyloïdes, suggérant l’existence d’un vieillissement cérébral pathologique. L’exploration fonctionnelle du vieillissement cérébral du Microcèbe a été réalisée grâce à l’imagerie par Tomographie par Émission de Positons (TEP). Celle-ci a été complétée par des études anatomiques et histologiques du cerveau et un suivi comportemental. Une thérapie par un agoniste de l’Insuline-like Growth Factor 1 (PEG-IGF-1) a été évaluée. Chez les animaux âgés, outre la présence d’une atrophie cérébrale, le métabolisme glucidique était réduit dans le cerveau et les sous structures d’intérêt (cortex frontal, hippocampe, noyaux caudés et cervelet). Ces altérations cérébrales n’ont pas pu être associées à des déffcits cognitifs et ne peuvent être expliquées par des altérations anatomo-histologiques. Le traitement par PEG-IGF-1 n’a pas modifié la consommation cérébrale de glucose. Néanmoins, il s’est accompagné de changements dans les paramètres de la torpeur journalière présente chez ce primate, suggérant une modulation de la gestion des ressources énergétiques. En conclusion, la mesure du métabolisme glucidique cérébral par imagerie TEP constitue un marqueur fonctionnel du vieillissement cérébral chez le Microcèbe. Ce marqueur peut être utilisé pour explorer de nouveaux aspects du vieillissement cérébral et/ou l’apparition de pathologies. Il pourrait également permettre d’évaluer l’effet de thérapies sur le fonctionnement cérébral / Worldwide populations affected by age-related brain pathology are becoming increasingly numerous. Using relevant animal models is a critical to understand biological mechanisms of brain aging and evluate therapy. The Mouse lemur primate is an animal model of normal and pathological brain aging. Indeed, it develops age-associated brain abnormalities linked with cognitive deficits remaining human age-associated brain alterations. Moreover, some older individuals display more severe alterations, as in particular atrophy of the hippocampus and cerebral amyloid plaques, suggesting a pathological brain aging. Positron Emission Tomography (PET) was used to quantify cerebral glucose metabolism quantification in mouse lemurs. This study was completed with anatomical, histological, and behavioral studies. Additionally, an insulin-like growth agonist (PEG- IGF-1) therapy was evaluated in aged mouse lemurs. In older animals, besides a cerebral atrophy, a glucose metabolism reduction appeared in the brain, and in particular in the frontal cortex, hippocampus, caudate nucleus, and cerebellum. These functional impairments were not associated with detectable cognitive deficits and could not be explained by anatomical or histological alterations. The PEG-IGF-1 treatment did not enhance cerebral glucose consumption. Nevertheless, it induced changes in the parameters of daily

La désignation est le geste de montrer un objet à une autre personne. La structure de la désignation est similaire à celle du discours verbal : la première personne « je » communique avec la seconde personne « tu » à propos de l'objet « il ». A partir de la description neuropsychologique d'un trouble acquis de la désignation, l'hétérotopagnosie ou incapacité à désigner le corps d'autrui, nous jetons les bases d'un nouveau modèle de la désignation impliquant la notion de seconde personne « tu ». Nous proposons et validons l'hypothèse que toute désignation implique de se représenter le point de vue de l'interlocuteur « tu » grâce à un référentiel hétérocentré. De plus, chez les patients hétérotopagnosiques comme chez les volontaires sains, désigner le corps d'autrui est plus difficile que désigner les objets. Nous expliquons ce phénomène par le fait que seul le corps humain vivant peut être à la fois sujet de communication et objet de communication. Poursuivant notre investigation sur la notion de seconde personne, nous montrons chez une patiente et chez les sujets sains que le corps des femmes est également plus difficile à désigner que celui des hommes. Les femmes seraient plus facilement considérées comme des sujets que les hommes. Enfin, nous avons recherché comment l'humain percevait la désignation réalisée par autrui comme témoignant d'une intention de communication à propos d'un objet. L'engagement dans une relation avec la seconde personne « tu » est nécessaire à cette compréhension. Au total, cette thèse apporte les premiers éléments expérimentaux sur les mécanismes de la relation de communication avec la seconde personne « tu ». / Pointing is used to communicate about an object with another person. This skill has a triadic structure similar to speech: the first person “I” communicate with the second person “you” about an object of interest “it”. From the neuropsychological description of an acquired deficit in pointing, heterotopagnosia which is the inability to point at another person's body parts, we build a new cognitive model involving the notion of a second person to explain pointing behaviour. We bring experimental evidence that pointing requires taking the addressee's perspective through the elaboration of a heterocentric reference frame. Furthermore, we show that in heterotopagnosic patients and in healthy subjects pointing at another person's body is more difficult than pointing at objects. We hypothesize that it is because only the living human body of other can be a subject to communicate with and an object to communicate about. In addition, we show that heterotopagnosic patients and healthy subjects find it more difficult to point at female body parts than at male ones, perhaps because women are more easily considered as subjects. Finally, we explore the behavioural and neural bases of the perception of pointing. We confirm that the relationship with the second person is necessary to understand the communicative intention of the addressee about the object. As a whole, this work provides the first cognitive and neural evidence for the notion of a second person in the brain.

No description available.

La navigation repose en majeure partie sur la vision puisque ce sens nous permet de rassembler des informations spatiales de façon simultanée et de mettre à jour notre position par rapport à notre environnement. Pour plusieurs aveugles qui se fient à l’audition, le toucher, la proprioception, l’odorat et l’écholocation pour naviguer, sortir à l’extérieur de chez soi peut représenter un défi considérable. Les recherches sur le circuit neuronal de la navigation chez cette population en particulier s’avèrent donc primordiales pour mieux adapter les ressources aux handicapés visuels et réussir à les sortir de leur isolement. Les aveugles de naissance constituent aussi une population d’intérêt pour l’étude de la neuroplasticité. Comme leur cerveau s’est construit en absence d’intrant visuel, la plupart des structures reliées au sens de la vue sont réduites en volume par rapport à ceux de sujets voyants. De plus, leur cortex occipital, une région normalement dédiée à la vision, possède une activité supramétabolique au repos, ce qui peut représenter un territoire vierge pouvant être recruté par les autres modalités pour exécuter diverses tâches sensorielles. Plusieurs chercheurs ont déjà démontré l’implication de cette région dans des tâches sensorielles comme la discrimination tactile et la localisation auditive. D’autres changements plastiques de nature intramodale ont aussi été observés dans le circuit neuronal de la navigation chez ces aveugles. Par exemple, la partie postérieure de l’hippocampe, impliquée dans l’utilisation de cartes mentales, est réduite en volume alors que la section antérieure est élargie chez ces sujets. Bien que ces changements plastiques anatomiques aient bel et bien été observés chez les aveugles de naissance, il reste toutefois à les relier avec leur aspect fonctionnel. Le but de la présente étude était d’investiguer les corrélats neuronaux de la navigation chez l’aveugle de naissance tout en les reliant avec leurs habiletés spatio-cognitives. La première étude comportementale a permis d’identifier chez les aveugles congénitaux une difficulté d’apprentissage de routes tactiles construites dans des labyrinthes de petite échelle. La seconde étude, employant la technique d’imagerie par résonance magnétique fonctionnelle, a relié ces faiblesses au recrutement de régions cérébrales impliquées dans le traitement d’une perspective égocentrique, comme le lobule pariétal supérieur droit. Alors que des sujets voyants aux yeux bandés excellaient dans la tâche des labyrinthes, ces derniers recrutaient des structures impliquées dans un traitement allocentrique, comme l’hippocampe et le parahippocampe. Par ailleurs, la deuxième étude a confirmé le recrutement du cortex occipital dans une tâche de navigation chez les aveugles seulement. Ceci confirme l’implication de la plasticité intermodale dans des tâches cognitives de plus haut niveau, comme la navigation. / Navigation is predominately based on vision as it gathers spatial information simultaneously and allows a continuous update of our position relative to space. For many blind people who rely mainly on auditive, haptic, proprioceptive, olfactive and echolocating cues to navigate, leaving outside their home can be a challenge. Research on the navigational neural network in this particular population is therefore crucial to better adapt resources for visually impaired people and free them from isolation. Congenitally blind subjects are also an interesting population for the study of neuroplasticity. As their brain was built without any visual input, most structures related to vision are reduced in volume compared to those of seeing subjects. Moreover, their occipital cortex, a region normally dedicated to vision, has a suprametabolic activity at rest, which could represent a virgin territory that can be recruited by other modalities to accomplish various sensory tasks. Recently some researchers have demonstrated the involvement of this region in sensory tasks such as tactile discrimination and auditive localisation. Other intramodal plastic changes have also been observed in the blind’s navigational neural network. The posterior part of hippocampus, involved in cognitive mapping, is reduced in volume while the anterior section is enlarged in blind subjects. Although some anatomical plastic changes have been observed in congenitally blind’s brain navigational system, their functional aspect remains to be elucidated. The purpose of this study was to investigate the neural correlates of navigation in congenital blindness and to link them with the blinds’ spatio-cognitive skills. The first behavioral study identified route learning difficulties in congenitally blind participants when they were ask to navigate inside small-scaled tactile mazes. Using functional magnetic resonance imagery in the second study, these problems were associated with the recruitment of brain regions involved in an egocentric perspective processing, such as right superior parietal lobule. While blindfolded seeing subjects excelled in the maze task, they recruited structures involved in allocentric processing, such as hippocampus and parahippocampus. Moreover, the second study confirmed the recruitment of occipital cortex in a navigation task for blind subjects only. This strengthens the involvement of crossmodal plasticity in higher level cognitive tasks, such as navigation.