It is uncertain whether clinically useful information of otolith function can be well characterized by vestibular-evoked-myogenic-potentials (VEMPs), i.e., electromyogenic activity recorded from sternomastoid muscles in response to brief loud auditory clicks. We aimed to assess the utility of VEMP testing in the differential diagnosis of dizziness (81 dizzy patients, 12 normals). We found that: (1) VEMP was reliably elicited from all controls and from 96% of patients without loss of vestibular function; (2) in patients with documented unilateral peripheral vestibular disorders, VEMP could reveal loss of otolith function that usefully facilitated diagnoses; and (3) such otolith function loss was independent of canal function loss revealed by caloric testing. We conclude that the VEMP-test is clinically useful to assess vestibular (otolith and/or inferior vestibular nerve) function, providing information complementary to that obtained from caloric testing (horizontal semicircular canal and/or superior vestibular nerve function).

Normal bone marrow is composed of hematopoietic and non-hematopoietic cells. The later have also been termed stromal cells or mesenchymal cells. These cells were originally thought to provide an appropriate matrix for hematopoietic cell development, but recent examination of these cell populations suggests a much broader spectrum of activity, including the generation of bone, cartilage, tendon, fat and muscles including myocardium. / Cellular cardiomyoplasty (CCM) based on adult bone marrow stromal cells (MSCs) is a novel means of augmenting cardiomyocyte number and contractile function of the failing heart targeting the basic pathophysiology of heart failure. / Chapter I of this thesis briefly reviews the therapy of congestive heart failure and cellular cardiomyoplasty based on MSCs. The concept of MSCs for cardiomyoplasty and previous work conducted in our laboratory will be reviewed. Chapter II focuses on the fate of systemically implanted MSCs, in order to examine whether MSCs may participate in myocardial growth and injury in the post-natal immature hearts. / With the purpose of searching for universal donors for clinical application of MSC cardiomyoplasty, in chapter III we use a vast histocompatibility mismatch pig-to-rat model to examine the unique immune tolerance of MSCs. Chapter IV consists of closing remarks.

Diaphragmatic myotubes are known to constitutively express CCR1, a chemokine receptor in the C-C chemokine family, when cultured in vitro. It has been shown that CCR1 and its ligand CCL3 (MIP-1α) are directly involved in muscle repair responses in vitro. Furthermore, in vivo experiments, carried out in the MDX mouse model of muscular dystrophy, showed that these molecules were up-regulated in the dystrophic diaphragm muscle thus suggesting a role for CCR1 in inflammation and muscle healing. In this study, indeed, the role of CCR1 was investigated, with focus on inflammatory cell infiltration within the injured muscle using the freeze injury murine model. This study suggested that there is no significant difference in muscle regeneration or infiltration between CCR1-/- mice and their wild-type controls. There was also no difference in the muscle force between the knockout and their controls at 3, 7, and 14 days post injury. Investigation of individual infiltrating cell (macrophage, CD4 T-cells, CD8 T-cells) populations in the injured tissue yielded no significant difference. These data suggest that, although CCR1 has been found to play a role in myoblast proliferation and migration in vitro, it does not seem to have any apparent effect on muscle regeneration in vivo in the context of the freeze-injury model. / In vitro, les myotubes diaphragmatiques expriment de façon constitutive CCR1, le récepteur de la famille des chemokines C-C. Il a été démontré que CCR1 et son ligand, CCL3 (MIP-1α), sont directement impliqués dans le processus de la réparation musculaire in vitro. De plus, des études in vivo dans la souris MDX ont démontré que l'expression de ces molécules augmente dans le diaphragme dystrophique. Ceci suggère un rôle pour CCR1 dans l'inflammation et la réparation musculaire. Dans cette étude, le rôle de CCR1 a été étudié avec un focus sur l'infiltration des cellules dans le muscle blessé suite à une blessure par congélation dans le modèle animal. Cette étude suggère qu'il n'y a aucune différence dans la réparation musculaire et l'infiltration cellulaire entre la souris CCR1 -/- et le contrôle. De plus, il n'y a aucune différence significative dans la force musculaire entre ces deux modèles à 3,7 et 14 jours suite à la blessure. L'étude individuelle des populations cellulaires (macrophages, cellules T CD4+ et CD8+) n'a montré aucune différence significative. Nos résultats suggèrent que malgré le rôle de CCR1 dans la prolifération et la migration de myoblastes in vitro, CCR1 n'est pas implique dans cette régénération post-traumatique in vivo.

Background. The incidence of osteoporotic fractures increases by 1-3% per year of age. Nine to twelve percent of patients that have suffered a primary hip fracture will have a fracture of the contralateral hip within 5 years. Our objective is to identify predictive factors of contralateral hip fractures among men and women over 55 years of age. / Methods. A case control study with matched pairs was conducted, through a retrospective chart review of patients admitted for hip fractures at the Jewish General Hospital (JGH) and the Montreal General Hospital (MGH) between 1992 and 2004. / Results. Contralateral hip fractures were most strongly associated with the use of mobility aid (OR= 5.69, CI 95% (3.20-10.14)). No other risk factors could be identified as predictors, probably due to missing data. / Conclusion. This study confirms the use of mobility aid as a predictor of contralateral hip fractures. Future prospective risk studies may further optimize the diagnostic accuracy for predicting contralateral hip fractures.

During development cartilage originates as condensations of primordial mesenchymal cells which go through a strict program whereby these cells differentiate into chondrocytes, undergo hypertrophy, and are subsequently replaced by osteoblasts. A zebrafish mutant termed gonzo has been isolated which displays a phenotype similar to human chondrodysplasias. Recently it was shown that this phenotype is due to a mutation in the zebrafish equivalent of a mammalian serine protease termed SKI-1 or Site-1 protease (S-1P). This enzyme is a member of the prohormone convertase family of subtilisin-like proteases which are known to play a critical role in controlling the processing of sterol regulatory element binding proteins and in the Unfolded Protein Response (UPR). The goal of this research project is to explore the expression and the function of S-1P in chondrocyte differentiation in vitro. / In this study, the chondrogenic mouse cell line ATDC5 which recapitulates the steps of cartilage development when cultured in the presence of insulin was used. Result showed that 10 mug/mL of insulin is the optimum concentration to be used to induce chondrogenesis in ATDC5 cells. This was shown by Alcian Blue staining and glycosaminoglycan quantification, where cells induced by 10 mug/mL of insulin produced highest amount of glycosaminoglycan. Using RT-PCR, it was shown that S-1P is constitutively expressed in ATDC5 cells both induced and non-induced with insulin. S-1P was also shown to be expressed in ATDC5 cells induced by ascorbic acid and a combination of ascorbic acid and insulin. Using Real Time-PCR, the expression levels of S-1P in the presence of insulin, ascorbic acid and the combination of both differentiation inducers was determined. The expression levels of type I collagen (early-phase chondrocyte differentiation expressing gene), type II collagen and aggrecan (mature chondrocyte matrix genes) and type X collagen (hypertrophic chondrocyte matrix gene) were also analyzed. / The effect of the inhibition of S-1P on the expression levels of cartilage related components was studied by inhibiting S-1P using an R134E prosegment mutant (pro-SKI-1), which has been shown a potent cellular inhibitor of S-1P. The DNA of the pro SKI-1 variant was subcloned into pIRES-EGFP (provided by Dr. Nabil Seidah) and transfected into ATDC 5 cells. Stably transfected cells were selected and the expression of S-1P and other cartilage components were quantitatively evaluated by studying the transfected cells using Real Time-PCR. Functional inhibition of S-1P was confirmed using an artificial substrate reporter construct adapted for specific cleavage by this protease. / Overall the results showed that inhibition of S-1P activity had drastic effects in chondrogenesis---the expression of cartilage components (Aggrecan, Collagen I, Collagen II and Collagen X) were significantly lowered. Inhibition of S-1P seemed to prevent the chondrogenesis process in ATDC 5 cells.

Current therapies for diabetes mellitus are insufficient to prevent the devastating complications associated with this disease. A novel approach for the treatment of diabetes is the restoration of an insulin-producing beta-cell mass through the stimulation of endogenous progenitor cells. Thus, the aim of this thesis was to determine if pharmacological initiation of islet neogenesis and subsequent beta-cell mass expansion will lead to the reversal of hyperglycaemia in a response that is under homeostatic regulation and has efficacy in humans. / A pentadecapeptide fragment of Islet Neogenesis Associated Protein (INGAP 104-108), was administered to normoglycaemic hamsters and was found to result in an expanded beta-cell mass as measured by immunohistochemical morphometric analysis. This expansion was shown to occur through the transformation of duct- and acinar-associated progenitors. In order to determine if this therapeutic approach would be effective in mammals other than hamsters, INGAP 104-108 was administered to normoglycaemic mice, dogs and monkeys, hyperglycaemic mice, and to human pancreatic tissue cultures. / INGAP104-108 administration led to a dose-dependent increase of beta-cell mass in mice, with similar trends observed in dogs. Similarly, administration of INGAP104-108 to normoglycaemic monkeys for 90 days resulted in profound areas of islet neogenesis. Administration of INGAP104-108 to diabetic mice resulted in restoration of euglycaemia and a dramatic increase in beta-cell mass. Furthermore, INGAP104-108 administration to cultured human acinar tissue, led to the formation of insulin-producing islet-like structures. These results suggest that INGAP 104-108 therapy has the ability to reverse a diabetic state and could be effective in humans. However, it was necessary to determine whether the continual stimulation of islet neogenesis through INGAP 104-108 administration is a safe therapeutic approach. / The beta-cell mass dynamics of euglycaemic mice administered INGAP 104-108 at various doses for 31 or 90 days were determined. beta-cell mass was greatly increased at 31 days of therapy, though by 90 days of therapy there was no difference in total beta cell mass between all treatment groups. However, there were marked instances of islet neogenesis in mice treated with INGAP104-108 for 90 days. This elevation in islet neogenesis was tempered by decreased beta-cell replication and increased beta-cell apoptosis, resulting in no overall difference in total beta-cell mass. These results suggest that inherent homeostatic regulation persisted to maintain a net beta-cell mass that matched the physiological need, even in the setting of continual induction of islet neogenesis. / INGAP104-108 therapy has been shown to expand the insulin-producing beta-cell mass in a safe homeostatic manner and reverse diabetic hyperglycaemia. These findings suggest that a novel pharmacological agent for the successful stimulation of beta-cell mass expansion is within reach, enabling new therapeutic modalities for the treatment of diabetes.

There is tremendous enthusiasm for the utilization of angiogenesis as a therapeutic modality for atherosclerotic arterial disease. Augmentation of physiological neo-vascularization in cardiovascular disease can be achieved through different pathways. Marrow stromal cells may serve as an ideal cellular vehicle for the in vivo delivery of therapeutic proteins or production of these proteins by the cells themselves. The use of autologous marrow stromal cells is highly desirable since marrow stromal cells are abundant and available in all human of all ages and they are easy to harvest and reimplant without the fear of rejection. Our primary data showed that marrow stromal cells injected locally into ischemic animals promote angiogenesis. Exploring various routes of delivery is important for developing these cells as a novel therapeutic tool for treatment. We found that injecting these cells intravenously in high doses has a beneficial effect in restoring blood flow into the ischemic area in the ischemic hind limb animal model. Implantation of these cells into distant organs did not show any local or remote effects.

Fetal tracheal occlusion (TO) has been investigated as a treatment option for lung hypoplasia secondary to Congenital Diaphragmatic Hernia (CDH). While it has been shown to promote larger lungs, it is unclear whether TO stimulates mature lung growth or simply induces alveolarization without concomitant bronchial development, a distinction with important clinical implications. We employed the Nitrofen rat model of CDH to investigate the effect of TO on fetal lung branching through morphometric examination, lung casting, lung histology and comparison of two molecular markers involved in lung growth. Nitrofen administration retarded lung growth through decreased lung branching and delayed molecular marker expression profiles. TO did not promote lung branching as manifest by unchanged gross branching, although TO and the stress of in utero surgery may induce late lung maturation.

Minimally invasive surgeons are performing increasingly complex and time-consuming procedures on increasingly frail patients. Understanding the complex physiologic consequences of pneumoperitoneum is therefore of critical importance. This is especially true in the field of live laparoscopic donor nephrectomy where a thorough understanding of the effects of pneumoperitoneum on renal perfusion and function is mandated. A systematic review of the literature is undertaken and reveals that both renal perfusion and function are decreased during pneumoperitoneum. Next, a porcine model is established and used to compare the effects of aggressive fluid hydration (28cc/kg/h) versus maintenance fluid hydration (5cc/kg/h). We demonstrate that renal perfusion is preserved with aggressive fluid hydration. Finally, a noninvasive fluid administration algorithm based on esophageal Doppler stroke volume measurements is assessed. Using this technique, renal perfusion is preserved during pneumoperitoneum, using less fluid (10cc/kg/h) than a bolus group (25cc/kg/h). Fluid administration via the esophageal Doppler is a noninvasive way to target individual hemodynamics to maintain renal perfusion during pneumoperitoneum.

Calcium phosphate-based materials have become the first choice for surgeons when they look for a synthetic material for the repair and augmentation of bone. Numerous studies and commercial use over the last three decades have made these materials popular options. These materials are not without their negative aspects, and properties such as poor in vivo resorption and low setting pH are well documented. Magnesium phosphates represent a poorly investigated group of materials with chemical structures similar to those of the calcium phosphates.In this thesis we investigate magnesium phosphates for use as inorganic materials for bone repair. We demonstrated that heat-treatment of magnesium phosphate created a cement reactant, which upon mixing with citric acid or sodium phosphate solutions set to form a cement. Investigation into alternate applications for the cement showed the cement could be dip-coated onto titanium rods. The dip coating formulations were also tested for their ability to release bioactive compounds, showing a relationship between initial burst and sustained release with powder-to-liquid ratio. In vitro testing of the cement showed good biocompatibility with osteoblast-like cells, inducing the expression of osteoblast markers. Preliminary in vivo data showed good material resorption and osteoconduction compared to brushite by four weeks time.Our results demonstrate that magnesium phosphate can be used in bone repair applications. Further study and development may lead to them becoming a viable alternative to calcium phosphates. / Les matériaux à base de phosphate de calcium sont devenus le premier choix pour les chirurgiens quand ils choisissent un matériau synthétique pour la réparation et l'augmentation osseuse. De nombreuses études et d'utilisation commerciale au cours des trois dernières décennies ont fait de ces matériaux une option populaire. Ces matériaux ne sont pas sans désavantages, et les propriétés telles que une résorption lente in vivo et une faible mise en pH sont bien documentés. Les phosphates de magnésium représente un groupe de matériaux peu étudié avec des structures chimiques similaires à celles des phosphates de calcium. Dans cette thèse, nous avons examine les phosphates de magnésium pour l'utilisation en taut que matériaux inorganiques pour la réparation osseuse. Nous avons démontré que le traitement thermique du phosphate de magnésium crée un réactif de ciment, qui apres mélange avec de l'acide citrique ou de solutions de phosphate de sodium forment un ciment. Enquête sur les demandes de remplacement pour le ciment ont démontré que le ciment pourrait être enduit (revêti) sur des tiges de titane. Les formulations de revêtement ont également été testés pour leur capacité à libérer des composés bioactifs, démontrant une relation entre l'éclatement initial et à la libération prolongée avec un rapport poudre-liquide. Des essais in vitro ont démontré que ce ciment a une bonne biocompatibilité avec des cellules ostéoblastiques, ce qui induit l'expression des marqueurs ostéoblastiques. Les données préliminaires in vivo ont montré une bonne résorption du matériel et une ostéoconduction comparable par rapport à brushite par quatre semaines. Nos résultats démontrent que le phosphate de magnésium peut être utilisé dans des applications de réparation osseuse. Une étude plus poussée et le développement de ce matériau pourra le conduire à une alternative viable aux phosphates de calcium.