This thesis begins with a brief overview of current strategies used in the synthesis of side-chain functionalizad polymers and materials. The discussion then focuses more explicitly on transition metal-based motifs and methodologies that are employed in polymer functionalization and continues with a more detailed overview of this field. The primary hypothesis that is addressed herein is that combining the versatility and strength of metal-ligand interactions with the efficiency and functional group tolerance of ROMP comprises a useful method of generating a variety of functionalized polymers and materials via side-chain metal coordination. Thus, the goal is to test this hypothesis by synthesizing functionalized polymers with a range of useful properties to demonstrate the relevance and importance of this methodology, by employing several different strategies to show the synthetic ease by which the materials can be realized. The strategies and methods discussed in the synthesis of side-chain functionalized polymers are divided into three subgroups: (1) pre-polymerization functionalization, in which all of the modifications take place on the monomer with polymerization as the last step, (2) post-polymerization functionalization, in which the polymer itself is subsequently modified, and (3) combinations of the first two strategies. It is shown that useful functional polymers and materials can be synthesized by any of the above strategies, and representative examples of each are given in both the introduction and in the body of work presented. Modes of functionalization are all based on transition metal coordination, and polymerizations are primarily carried out via ROMP. Metal coordination is shown to be a useful technique for functionalizing polymers, to creating supported emissive complexes, to modulating solution viscosity. Finally, conclusions are drawn regarding the various strategies presented herein, and potential future directions are discussed.

Cardiovascular disease is the main cause of death in the United States. Many of these conditions require the grafting or bypassing of compromised blood vessels. To this effect, biological vascular grafts (autografts and allografts) are the first line of action. However, when the patient lacks vasculature suitable for grafting use, several synthetic grafting options are available. The search for an inert biomaterial for vascular grafts has proven to be unsuccessful. This makes the interaction taking place on the blood-biomaterial interface critical for the success of the grafts. This thesis introduces a new bio-inspired approach to tackle the mechanical and biological challenges of vascular material design. The hypothesis of this research is that recombinant fibronectin protein can be stably incorporated onto elastin-mimetic polymers to increase endothelialization. Recombinant elastin, designed to recreate the mechanical properties of natural elastin as a candidate material for vascular graft fabrication, was used as a model surface. Recombinant fibronectin-functionalized elastin-mimetic polymer displayed significant improvement in cell adhesion. Quantification of surface bound recombinant fibronectin verified the concentration dependence of this cell adhesive behavior. Modified elastin-mimetic polymer also demonstrated an enhanced ability to support endothelial cell proliferation. Furthermore, the stability of recombinant fibronectin-modified polymers was assessed. These studies provide the foundation for fabricating elastin-mimetic vascular grafts with improved endothelialization and subsequent biological performance.

CD28 co-stimulation is required for the generation of naturally occurring regulatory T cells (nTregs) in the thymus through Lck-signaling. However, high level of CD28 suppresses the generation of induced Tregs (iTregs) from naïve CD4 T cells, although underlying mechanism(s) has not been defined. Here we investigated the role of CD28-mediated signaling pathways in the suppression of Treg generation. We used a series of transgenic (Tg) mice on CD28-deficient background that bears WT CD28 or mutated CD28 in its cytosolic tail incapable of binding to Lck, PI3K or Itk. Regardless of exogenous IL-2, strong CD28 costimulation suppressed iTreg generation through Lck signaling. Using a GVHD model to test the role of CD28-mediated iTreg suppression in T cell pathogenicity in vivo, we found that CD28-Lck T cells induced significantly less GVHD than T cells from CD28-WT mice. Furthermore, we found that the recipients of T cells from CD28-Lck mice generated significantly more iTregs than those with T cells from CD28-WT, which contribute to reduced graft-versus-host disease (GVHD) development in recipients of CD28-Lck T cells. These results indicate that CD28 costimulation can negatively regulate Treg generation and may provide an avenue for control of T-cell immunity or tolerance by regulating Tregs using the CD28 signal as a target. We went a step forward and investigated the therapeutic potential of antigen-specific iTregs in the prevention of GVHD. Donor hematopoietic stem cells and mature T cells are transplanted into a lymphopenic host to potentially cure many cancers and hematopoietic diseases like leukemia in bone marrow transplantation (BMT) or hematopoietic stem cell transplantation (HCT), but the frequent development of GVHD is the main drawback of this treatment. nTregs suppress the development of GVHD and may spare graft-versus-tumor effect. However, nTregs are a minor (~5%) subpopulation of CD4 helper T cells in healthy individuals, and using in vitro expanded nTregs is a common strategy to test their therapeutic potential in BMT. The concern of in vitro expanded nTregs may include their stability of Foxp3 (master regulatory gene for the development and function of regulatory T cell) expression and suppressive function, survival in vivo, and the non-selective suppression of the pre-activated nTregs. Antigen-specific activation of the regulatory T cells is important for optimal function. In this study, we used an alternative strategy to generate antigen-specific, iTregs and assessed their suppressive potential by comparing their effectiveness in preventing GVHD with polyclonal iTregs. We found that antigen-specific iTregs prevented GVHD lethality in recipients that expressed the target antigen, but were not protective of recipients who did not express the target antigen. Furthermore, antigen-specific iTregs were significantly more efficient than those polyclonal Tregs in the prevention of GVHD. These results reveal the therapeutic potential of antigen-specific iTregs to prevent GVHD efficiently and selectively, and provide the rationale to use antigen-specific iTregs in clinical HCT.

Thirty eligible patients are randomly assigned to two groups. The test group received PRP application around new implants, while in the control group no PRP treatment was made. The bone-to-implant contact region was analyzed in a clinical sample of 60 Digitized Panoramic Radiographs, 30 corresponding to immediate implant loading (Class-I) and 30 after an 8 month follow-up period (Class-II). This region was sampled by 1146 circular Regions-of-Interest (ROIs), resulting from a specifically designed segmentation scheme based on Markov-Random-Fields (MRF). From each ROI, 41 textural features were extracted, then reduced to a subset of 4 features due to redundancy and employed as input to Receiver-Operating-Characteristic (ROC) analysis, to assess the textural differentiation between two classes. / Σε αυτή την έρευνα για πρώτη φορά πραγματοποιήθηκε μια υπολογιστική μελέτη υφής για την εκτίμηση της διαφοροποίησης της υφής που συνδέεται με τις ιδιότητες του σχηματισμού των οστών, περιμετρικά του εμφυτεύματος μετά την χρήση πλάσματος πλούσιο σε αιμομετάλια (Platelet-Rich-Plasma), σε πανοραμικές ακτινογραφίες. Ο κύριος στόχος ήταν να ποσοτικοποιηθεί οποιαδήποτε διαφοροποίηση της υφής σε εικόνες πανοραμικής ακτινογραφίας σε μια περίοδο παρακολούθησης 8 μηνών, στην διεπαφή οστών-εμφυτεύματος, μεταξύ των δύο κατηγοριών (0 & 8 μήνες) και κατά συνέπεια να αξιολογηθεί οποιαδήποτε στατιστική διαφορά στα χαρακτηριστικά υφής των ακτινογραφιών μεταξύ των ομάδων ελέγχου και δοκιμασίας που μπορεί να αποδοθεί στη θεραπεία PRP. Η ανάλυση υφής σε συνδυασμό με τις ιδιότητες του σχηματισμού των οστών γύρω περιμετρικά του εμφυτεύματος πραγματοποιήθηκε με ROC ανάλυση.

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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Aims: This study uses radiological and clinical evaluations of the healing of endosseous titanium implants presented with different surface characteristics in the clinical situation (paper I-III) and experimentally to describe the early bone healing in maxillary sinus membrane elevation with and without the use of grafting material (paper IV). Material and methods: In paper I, 136 patients were treated with 394 dental implants – 199 were oxidized titanium implants (Nobel Biocare TiUnite) and 195 were turned titanium surface implants (Nobel Biocare Mark III). Implant survival rates were retrospectively investigated after a minimum of five months after functional loading of the implants. At the five-year follow-up (paper II), eight patients were deceased and 128 were invited. Twenty-five patients refrained from participating in the study. The remaining 103 patients (287 implants – 133 with a turned surface and 154 with an oxidized surface) were examined after at least five years of functional loading. Clinical examinations of bleeding on probing (BoP) and pocket depth (PD) were performed. Intraoral radiographs were used to assess marginal bone levels (MBLs). In paper III, 28 patients were subjected to autologous bone graft and delayed implant placement, with a total of 92 dental implants. Thirteen patients received 47 implants with a turned surface and 15 patients received 45 implants with an oxidized surface. After a minimum of five years of functional loading, all patients were clinically examined regarding PD and BoP. The MBL was measured in intraoral radiographs. Cone beam computed tomography (CBCT) was used to evaluate the apical bone level (ABL) of the implants and intra-sinus conditions. The experimental study (paper IV) used nine adult male tufted capuchin primates (Cebus apella). Eight animals were subjected to bilateral maxillary sinus membrane elevation using a lateral replaceable bone window technique. One oxidized dental implant was placed in the residual bone of the sinus floor, protruding into the maxillary sinus cavity on both sides. In four animals, one sinus was left without any additional treatment, while the contralateral sinus was filled with autologous bone grafts from the tibia. In two animals, the implants were inserted under the elevated sinus membrane on both sides. In two animals, the sinus membrane was totally removed bilaterally before placement of implants. The animals were euthanized after 10 (n=4) or 45 (n=4) days. One non-operated animal representing pristine tissue conditions served as the control. The maxillary sinuses with implants were retrieved and further processed to prepare light microscopic ground sections or decalcified sections for immunohistochemical analyses. Results: In paper I seven implants were lost in five patients – six in the maxilla and one in the mandible. All failed implants were Mark III turned implants. The overall implant survival rate was 98.2% with a survival rate of 96.4% for implants with turned surface after a minimum of five months after functional loading. In paper II, one additional oxidized implant failed, giving an overall cumulative survival rate of 94.7 and 99.4%, respectively, after at least five years of functional loading. There was no difference for BoP, PD, or MBL between turned and oxidized implants. A total of two implants, three oxidized and one turned, showed a PD > 3 mm, MBL > 4 mm, and BoP. However, none of these were associated with suppurative infection on examination. In paper III no difference was found between the two implants surfaces used in terms of PD, BoP, MBL, or ABL. Pathological reactions to the sinus membrane were seen in four of the patients (14%). Radiographic signs of sinus pathology were not correlated to either survival rate of the implants or any of the investigated parameters. In the experimental paper IV, bone formation started from the bottom of the sinus floor, sprouting into the granulation tissue along the implant surface under the elevated membrane irrespective of time and surgical technique. Bone formation was not seen in direct conjunction with the sinus membrane. A distinct expression of osteopontin was observed in the serous glands of deeper portion of the lamina propria in direct connection with the elevated sinus membrane and close to the implant within all groups. Conclusion: After more than five years of function in non-grafted patients, oxidized implants had a survival rate higher than turned implants, although this was not statistically significant. No difference was found in MBL, PD, or BoP. Grafting of the maxillary sinus floor with intra- orally harvested bone and delayed placement of either turned or oxidized implants resulted in equally high long-term survival rates, MBL, ABL, and BoP. Pathological findings in the maxillary sinus cavity, in terms of sinus membrane health, are few and not correlated to any of the other investigated parameters. In the experimental study bone formation after sinus membrane elevation with or without additional bone grafts started at the sinus floor and sprouted into the elevated space along the implant surface. Removal of the membrane resulted in less bone formation. The sinus membrane did not seem to present osteoinductive potential in sinus membrane elevation procedures.

The Fas pathway is critical for the maintenance of normal T cell homeostasis. Humans and mice with defects in this pathway exhibit the accumulation of large numbers of peripheral lymphocytes and lupus-like autoimmunity. A major feature of these organisms is the accumulation of non-NK TCRαβ+CD4-CD8- “double negative” (DN) T cells. While regulatory T cells (Tregs) with the DN phenotype have been extensively characterized in Fas-sufficient mice and humans, limited data exist on the role of DN T cells as Tregs in Fas-deficient animals. In fact, most of the literature suggests that the DN T cells accumulating in Fas-deficiency states are pathogenic, contributing to secondary lymph node enlargement and autoimmune disease. In this body of work, data are presented that illustrate that Fas-deficient lymphoproliferative (LPR) DN T cells can act as Tregs in an interferon γ (IFNγ)- and Fas ligand (FasL)-dependent fashion toward Fas-sufficient T cells. LPR DN T cells needed to be able to secrete and respond to IFNγ in order to upregulate surface FasL, in order to ameliorate GVHD mediated by CD4+ T cells in vivo and to suppress the proliferation of and kill activated CD4+ T cells in vitro. FcRγ, a key molecule involved in innate immune responses, can substitute for CD3ζ in the T cell receptor (TCR) of mouse and human T cells in certain circumstances; in doing so, it is essential for the regulatory function of TCR transgenic DN Tregs. FcRγ-deficient LPR mice were found to have exacerbated T cell accumulation and early mortality. We show that while FcRγ expression was required for LPR DN T cells to regulate CD4+ and CD8+ T cells responding to alloantigens in vitro and in vivo, it does not control autologous lymphoproliferation in LPR mice by supporting the function of a regulatory cell, nor does it affect the rate of proliferation of LPR T cells in vivo. Instead, FcRγ-expressing LPR CD4+, CD8+ and DN T cells were found to be undergoing apoptosis at a high rate in vivo, and in contrast to their FcRγ-deficient counterparts, FcRγ+ LPR DN T cells were capable of undergoing TCR restimulation-induced cell death (RICD). The data presented in this thesis therefore show that LPR DN T cells can exhibit IFNγ-, FasL- and FcRγ-dependent regulatory function, and also illustrate a previously unknown function for FcRγ in controlling the expansion of Fas-deficient T cells. The implications of these data for autoimmune lymphoproliferative syndromes, and normal T cell homeostasis, are discussed.

Roughly thirty percent of coronary artery bypass graft (CABG) patients develop atrial fibrillation (AF) in the five days following surgery, increasing the risk of stroke, prolonging hospital stay three to four days, and increasing the overall cost of the procedure. Current pharmacologic and nonpharmacologic means of AF prevention are suboptimal, and their side effects, expense, and inconvenience limit their widespread application. An accurate method for identifying patients at high risk for postoperative AF would allow these methods to be focused on the patients on which its utility would be highest. The main objective of this research was to develop a Bayesian network (BN) which could model/predict/assign risk of the occurrence of atrial fibrillation in CABG patients using retrospective data. A secondary objective was to develop an integrated framework for more advanced methods of feature selection and fusion for medical classification/prediction. We determined that the naïve Bayesian network classifier used with features selected by a genetic algorithm is a better classifier to use, given our cohort. The naïve BN allows for reasonable prediction despite being presented with patients with missing data points as might occur in the hospital. This classifier achieves a sensitivity of 0.63 and a specificity of 0.73 with an AUC of 0.74. Furthermore, this system is based on probabilities that are well understood and easily incorporated into a clinical environment. These probabilities can be altered based on the cardiologists prior knowledge through Bayesian statistics, allowing for online sensitivity analysis by doctors, to perceive the best treatment options. Contributions of this research include: - An accurate, physician-friendly, postoperative AF risk stratification system that performs even under missing data conditions, while outperforming the state of the art system, - A thorough analysis of previously examined and novel pre- and postoperative clinical and ECG features for postoperative AF risk stratification, - A new methodology for genetic algorithm-built traditional Bayesian network classifiers allowing dynamic structure through novel chromosome, operator, and fitness definitions, and - An integrated methodology for inclusion of doctor s expert knowledge into a probabilistic diagnosis support system.

This research project explores the creative and critical functions of editing in art, film and writing. The written component analyses the histories and discourses of 'cutting and splicing' to examine their various roles in processes of signification. The artistic practice uses more speculative and open-ended methods to explore the social 'languages' that inform our inter-subjective experiences. This project argues that editing is a creative methodology for making meaning, because it allows existing symbolic systems to be appropriated, revised and rewritten. By emphasising the operations of spacing, questioning and play, it also identifies editing as an essential tool for critically engaging with the potentials of art and theory.