To determine a possible role for NCX in myogenically active smooth muscle arterioles, studies were conducted by manipulation of extracellular Na+ levels and inhibition of the exchanger. Western blotting was performed for the identification of the NCX protein. Real-time PCR was performed to demonstrate the level of expression of mRNA, for the NCX isoforms. Antisense oligonucleotides against NCX mRNA were introduced in an isolated cremaster arteriole followed by functional studies after 24 hours. Level of expression of NCX was determined by western blotting. The data are consistent with the presence of NCX1 in the cremaster arterioles.

The relationship between cerebrovascular disease (CVD) risk factors and cognitive impairment or dementia has been widely studied with significant variability in findings between groups. We hypothesized that chronic small vessel injury in the form of arteriolar sclerosis, measured quantitatively using MRI to measure total white matter hyperintensity (WMH) volumes, would identify specific association of CVD risk factors and patterns of cognitive decline, associated with mild cognitive impairment of the cerebrovascular type, that represent the core features of vascular cognitive impairment in our cohort. A Cross-sectional analysis of clinical and quantitative MRI data on 114 subjects with normal cognitive function (n=52) and mild cognitive impairment (MCI; n=62) was performed. Quantitative total WMH volumes were examined in relation to potentially causative CVD risk factors and resultant test scores across cognitive domains using linear regression models adjusted for age, gender, and education. Among CVD risk factors analyzed, age (p< 0.001), education (p= 0.003), hypertension (p= 0.012), and hyperlipidemia (p= 0.008) demonstrated the strongest associations with WMH volumes. Conversely, diabetes, smoking, history of heart attacks, atrial fibrillation, and history of stroke that have shown associations with CVD pathology on imaging in other studies were not statistically associated with increased WMH in this cohort. WMH volumes were associated with decrease performance on the Trial Making Test type A & B and long delayed free recall on the California Verbal Learning Test. Our findings suggest similarities and yet differences in comparison to other studies. Hypertension and hyperlipidemia appear to represent common shared risks across geographically disparate groups. Our findings, like others, suggest CVD pathology impact processing speed and executive function and provide further evidence for CVD effects on short-term memory in those at risk for cognitive decline and the future development of dementia in our cohort.

Research into automatic retina image analysis has become increasingly important, not just in ophthalmology but also in other clinical specialities such as cardiology and neurology. In the retina, blood vessels can be directly visualised non-invasively in-vivo, and hence it serves as a "window" to cardiovascular and neurovascular complications. Biomarker research, i.e. investigating associations between the morphology of the retinal vasculature (as a means of revealing microvascular health or disease) and particular conditions affecting the body or brain could play an important role in detecting disease early enough to impact on patient treatment and care. A fundamental requirement of biomarker research is access to large datasets to achieve sufficient power and significance when ascertaining associations between retinal measures and clinical characterisation of disease. Crucially, the vascular changes that appear can affect arteries and veins differently. An essential part of automatic systems for retinal morphology quantification and biomarker extraction is, therefore, a computational method for classifying vessels into arteries and veins. Artery-vein classification enables the efficient extraction of biomarkers such as the Arteriolar to Venular Ratio, which is a well-established predictor of stroke and other cardiovascular events. While structural parameters of the retinal vasculature such as vessels calibre, branching angle, and tortuosity may individually convey some information regarding specific aspects of the health of the retinal vascular network, they do not convey a global summary of the branching pattern and its state or condition. The retinal vascular tree can be considered a fractal structure as it has a branching pattern that exhibits the property of self-similarity. Fractal analysis, therefore, provides an additional means for the quantitative study of changes to the retinal vascular network and may be of use in detecting abnormalities related to retinopathy and systemic diseases. In this thesis, new developments to fully automated retinal vessel classification and fractal analysis were explored in order to extract potential biomarkers. These novel processes were tested and validated on several datasets of retinal images acquired with fundus cameras. The major contributions of this thesis include: 1) developing a fully automated retinal blood vessel classification technique, 2) developing a fractal analysis technique that quantifies regional as well as global branching complexity, 3) validating the methods using multiple datasets, and 4) applying the proposed methods in multiple retinal vasculature analysis studies.

No description available.

La polyneuropathie sensitivomotrice héréditaire (PNSMH) est une maladie rare qui entraîne un ralentissement du développement moteur et mental, une déficience sensitivomotrice et des syndromes neuropsychiatriques, et qui s’accompagne souvent d’une agénésie du corps calleux. Par ailleurs, plusieurs évaluations rapportent une petite stature ou une masse corporelle anormalement basse chez les patients. La PNSMH est causée par des mutations perte de fonction du cotransporteur K⁺-Cl⁻ de type 3 (KCC3). Des évaluations cliniques détaillées et la caractérisation de souris inactivées pour Kcc3 (Kcc3ᴷᴼ) ont permis d’établir qu’un défaut d’export K⁺-Cl⁻ cause les atteintes neurologiques anatomiques et fonctionnelles dans la maladie. Chez les souris Kcc3ᴷᴼ, des manifestations extraneurologiques ont également été relevées : masse corporelle réduite, pression artérielle (PA) élevée, polydipsie et polyurie. Puisque la physiopathologie des désordres extraneurologiques découlant de la perte de fonction de KCC3 reste incomplètement décrite, mes travaux avaient pour objectif d’en comprendre les mécanismes sous-jacents en utilisant un modèle Kcc3ᴷᴼ. Une caractérisation initiale de notre lignée de souris Kcc3ᴷᴼ constitutive et systémique a montré des anomalies vasculaires et cardiaques accompagnant une élévation de PA diastolique. Cette lignée affichait également une polydipsie et une polyurie isoosmotique, de même qu’une réduction de masse corporelle et d’adiposité sans réduction d’apport alimentaire. Une caractérisation métabolique détaillée de notre modèle a ensuite permis de révéler des réductions de masse grasse et de masse maigre. Cette minceur résulte sûrement en partie des augmentations d’activité locomotrice et de dépense énergétique mesurées. Une nette amélioration de la tolérance au glucose a aussi été trouvée, ainsi que des concentrations réduites de triacylglycérols plasmatiques. Enfin, nous avons noté que notre modèle est résistant à l’obésité induite par une diète hyperlipidique et affiche une élévation concomitante de l’expression d’enzymes lipogéniques et lipolytiques dans le gras viscéral, engendrant potentiellement une dissipation calorique. En revisitant la fonction cardiovasculaire dans notre modèle par des méthodes de pointe, nous n’avons pas observé de changement de PA ni de différence de réactivité artériolaire en conditions basales, mais nous avons noté une élévation de distensibilité artériolaire passive. Chez notre modèle, nous n’avons pas non plus remarqué de sensibilité particulière de la PA au sel alimentaire, mais une excrétion urinaire fortement accrue de solutés sous diète hypersodée ainsi qu’une préférence marquée pour le sel. Ces observations sont compatibles avec un défaut de réabsorption hydrosodée par le rein pouvant d’ailleurs prévenir les élévations de PA. En somme, nos travaux ont permis de mieux comprendre les atteintes cardiométaboliques qui accompagnent le tableau neurologique d’un modèle murin de PNSMH. Nous avons notamment relevé des bénéfices inattendus dans le métabolisme glucidique et lipidique suivant l’inactivation de Kcc3. Nous soupçonnons également que l’absence de KCC3 dans le rein engendre une fuite ionique urinaire s’accentuant sous diète hypersodée et pouvant influencer la PA en limitant l’expansion volémique. Nos observations d’anomalies pléiotropiques liées à l’inactivation de Kcc3 font de ce gène une nouvelle cible pharmacologique potentielle et justifient la nécessité d’étudier l’anatomophysiologie cardiométabolique des patients atteints de PNSMH de façon plus approfondie. / Hereditary motor and sensory neuropathy (HMSN) is a rare disease that leads to delayed motor and mental development, loss of sensory and motor function and neuropsychiatric syndromes, and that is often accompanied by partial or complete agenesis of the corpus callosum. Additionally, several cases of short stature or low body weight have been reported in patients. HMSN is caused by loss-of-function mutations in K⁺-Cl⁻ cotransporter type 3 (KCC3). Detailed clinical reports and characterizations of mice inactivated for Kcc3 (Kcc3ᴷᴼ) have allowed to establish that defective K⁺-Cl⁻ export causes the anatomical and functional neurologic impairments in the disease. In Kcc3ᴷᴼ mice, extra-neurological abnormalities have also been noted: lower body weight, high blood pressure (BP), polydipsia and polyuria. Because the pathophysiology of extra-neurological traits arising from KCC3 loss of function remains incompletely described, my work aimed at understanding the mechanisms at play using a Kcc3ᴷᴼ model. An initial characterization of a constitutive and systemic Kcc3ᴷᴼ mouse line showed vascular and cardiac abnormalities along with a rise in diastolic BP. This model also showed polydipsia and iso-osmolar polyuria along with reduced body weight and adiposity but no decrease in food intake. A detailed metabolic characterization of our model further revealed reductions in fat and lean body masses. This leanness results certainly in part from increased locomotor activity and energy expenditure as measured. A marked improvement in glucose tolerance was also found in addition to lower plasmatic triglyceride concentrations. Lastly, we also demonstrated that our model is resistant to high-fat-diet-induced obesity and shows concomitant increase in expression of both lipogenic and lipolytic enzymes in visceral fat, thereby potentially generating caloric dissipation. When revisiting the cardiovascular function of our model with cutting-edge methods, we measured normal BP and arteriolar reactivity in baseline conditions. However, we noted an increase in passive arteriolar distensibility. In our model, we did not notice sensitivity of BP to dietary salt but found a marked increase in urinary solute excretion under high-salt diet and a strong preference for salt. These observations are consistent with a defect in hydromineral reabsorption by the nephron that may prevent BP from rising. In short, our work allowed to better understand the cardiometabolic characteristics that accompany the neurologic portrait of an HMSN mouse model. In particular, we noted unexpected benefits in carbohydrate and lipid metabolism upon Kcc3 inactivation. We also suspect that KCC3 ablation in the kidney leads to urinary hydromineral wasting that can be more salient under dietary salt loading and can influence BP by blunting extracellular volume expansion. The pleiotropic abnormalities arising from Kcc3 inactivation identify this gene as a new potential pharmacological target and argue for improving efforts at describing the cardiometabolic features of patients with HMSN.