The role played by a parathyroid hormone-like peptide (PLP) in the pathogenesis of hypercalcemia associated with malignancy has been examined. Elevated circulating levels of PLP were found more frequently in hypercalcemic cancer patients. A reduction of tumor burden in two of these patients resulted in concomitant decreases in both plasma calcium and plasma PLP. Immunoneutralization of endogenous PLP in a rat model of malignancy associated hypercalcemia resulted in a rapid and sustained reversal of the biochemical abnormalities manifest in the disease state. These studies, therefore, provided strong evidence for a role for PLP in the pathogenesis of hypercalcemia associated with neoplasia. The frequent association of squamous cell carcinoma with hypercalcemia and elevated circulating PLP levels prompted examination of a keratinocyte model of tumor progression for evidence of dysregulated PLP expression. Increased constitutive production of PLP, accompanied by resistance to previously identified regulatory agents, was demonstrated in the progression to the malignant phenotype. Finally, a potential autocrine or paracrine role for PLP in keratinocyte cell growth was suggested by the demonstration of functional adenylate cyclase-linked PLP receptors on an established keratinocyte cell line. These studies have therefore provided important insights into the role played by PLP as both an endocrine factor involved in the pathogenesis of malignancy associated hypercalcemia and as a potential autocrine/paracrine factor in keratinocyte homeostasis.

Oral sorbent therapy, as an adjunct or a replacement for dialysis therapy, is one area of research with great potential. If successful it can help kidney failure patients avoid a "life on the machine" existence. For the past twenty years the major problem was in finding an effective oral sorbent for urea. The use of oral microcapsules containing a urease-silica adduct and ion exchanger zirconium phosphate, though successful in reducing urea levels, resulted in a number of problems including a negative calcium balance. In this thesis it is demonstrated that the use of microcapsules containing a urease-zeolite preparation may be a potential route to urea removal. The use of zeolite ion exchangers, and zeolite W in particular, can alleviate the above mentioned problems of zirconium phosphate. In addition, the use of enzyme envelopes on zeolite support, which replaces silica, can reduce the amount of ingested material by at least 25%. The present "in vitro" study shows that the microcapsules remove up to 80% of urea in less than one hour. Preliminary "in vivo" experiments on Sprague-Dawley uraemic rats treated with ingested microcapsules indicate reductions in urea level and a lengthening of survival times compared to controls.

The pathologic effects of sex steroids on the hypothalamic arcuate nucleus of adult rats were examined using numbers of reactive microglia and astrocytic granules as quantitative indices of neuropathology. / Microglial and astrocytic reactions were observed in adult female rats entering a state of "persistent estrus" following a single injection of 2 mg estradiol valerate (EV) or exposure to continuous illumination. Lower doses of EV failed to elicit both the persistent estrus state and significant glial responses. In EV-treated animals, a hypothalamic lesion could be prevented by prior ovariectomy or by pituitary-ovarian suppression with medroxyprogesterone acetate indicating that an ovarian factor is responsible for the neuropathological changes. This ovarian product is probably estradiol since dose-related enhancement of glial reactivity occurs in male rats treated with multiple injections of EV. / Arcuate pathology developed spontaneously in "senile persistent estrus" female and aging male rats. In females, but not in males, early gonadectomy suppressed age-related arcuate glial reactivity. Conceivably, estrogen withdrawal or EV-treatment respectively retards or accelerates histologic aging of the female gonadotropic hypothalamus. / Testosterone treatment occasionally elicited mild arcuate glial responses, possibly through prior aromatization to estradiol. In contrast, 5 (alpha)-dihydrotestosterone (a non-aromatizable androgen) appeared to suppress astrocytic granule counts below control values. / The EV-induced persistent estrus rat may serve as a useful model for Clover disease of the ewe and the human polycystic ovarian syndrome.

Closure of bone defects that do not heal spontaneously require some form of bone inducing agent in order to ensure complete repair. Autogenous bone is the clinical gold standard for the management of these types of defects. Present research is aimed at finding acceptable alternatives to harvesting autogenous bone grafts in patients for obvious reasons. Recent literature supports that demineralized bone matrix (DBM) is osteoinductive, although this is not the case for all commercially available forms of DBM. / An in vivo study was conducted which attempted to evaluate the healing of critical sized defects in New Zealand white rabbit calvarium using various grafting materials. By combining demineralized bone matrix and a poloxamer gel carrier, a putty-like material that is surgically convenient can be delivered to these defects and allowed to heal.

Background. Therapeutic angiogenesis in cardiovascular disease aims at improving myocardial function by increasing blood flow to ischemic myocardium that is not amenable to traditional forms of revascularization. This study hypothesizes that using the Omental graft to wrap the ischemic heart will lead to formation of multiple collateral anastomoses between surrounding systemic arteries and the coronary arteriolar system of right and left coronary arteries. / Results. Left ventricular end diastolic pressure was reduced in the group treated with revascularized Omental graft compared to vehicle group. Ejection fraction was also improved in revascularized group then infarcted group. Measurements of the myocardial infarction area showed more reduction in the MI area of the revascularized group than in the vehicle group, however this difference did not reach statistical significances. In comparison between free and pedicle Omental grafts, the free Omentum was shown to be superior over the pedicle in terms of cardiac function EF% (41.3 +/- 0.75 Vs. 35.6 +/- 0.75, P = 0.01), and infarction size (36.2 +/- 6.6 Vs. 39.5 +/- 13, P = NS). All different Omental grafts showed the ability to form a neovascularization between the ischemic myocardium and the surrounding structures.

Subcortical band heterotopia (SBH) is a rare neuronal migration disorder, characterized by bilateral bands of neurons abnormally located in the cerebral white matter. It occurs mostly in females, 80% of whom harbor mutations in the DCX (Xg22.3-q23) gene. / To determine whether males and females with SBH have a similar clinical spectrum and genetic basis, we analyzed and compared the clinical, imaging, and molecular features in 30 males and 60 previously reported females with SBH. / The range of clinical phenotypes in males with SBH overlapped that in females. However, MRI studies revealed that some SBH subtypes such as incomplete posterior SBH, diffuse SBH with posterior predominance and pachygyria-SBH were more frequently or exclusively observed in males. Conversely, diffuse SBH and diffuse SBH with anterior predominance were more frequent in females. The preponderance in males of either the mildest or the most severe SBH subtypes correlated with the overrepresentation of normal/borderline intelligence and severe mental retardation respectively. Conversely, females who had SBH of intermediate severity exhibited mostly mild or moderate mental retardation. Mutations in DCX were detected in 33% of males; 8% had mutations of the LIS1 (17p13.3) gene and 4% a partial trisomy of chromosome 9p. / These studies demonstrate that SBH in males is a clinically and genetically heterogeneous, mostly sporadic syndrome, and suggest other genetic mechanisms such as mutations in the non-coding regions of the DCX or LIS1 genes; functional, somatic or germline mosaicism; and mutations of other genes.

A physical surgical simulator, the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS) is used to examine the acquisition of laparoscopic skills, as well as to determine a summative evaluation of these skills. The cumulative summation method (CUSUM) is used to characterize individual and group learning curves for a MISTELS task. To examine transfer of learning in laparoscopy, novice laparoscopists were randomized to either practice a basic psychomotor task (peg board transfer) or to a no-practice control group. After forty iterations, the novices performed a more complex task (suturing); those who practiced the basic task significantly improved their complex task performance. Finally, using the receiver operator curve (ROC), the summative evaluation score for MISTELS was determined by maximizing the sensitivity and specificity of this training instrument. Using these findings, individualized training programs can be developed to teach essential laparoscopic skills prior to entering the operating room.

Sutural distraction osteogenesis (SDO) has been proposed as a novel approach for cleft palate closure in an effort to avoid the shortcomings of traditional surgical repair. In this thesis, we present data that confirms that attempted distraction of the palatomaxillary suture (PMS) achieves cleft closure preferentially by alveolar arch collapse, and not by intended SDO. To that end, we have designed a novel custom-fit intraoral splint that successfully prevents maxillary collapse while facilitating cleft defect approximation via sutural distraction. Preservation of maxillary dimensions was confirmed via intraoral measurements and craniometrics. New bone deposition secondary to SDO was quantified with histomorphometry and microCT, while the effects of distraction on the PMS and palatal bone were assessed with histology and Dual-energy Xray Absorptiometry (DXA). In summary, approximation of palatal defects via SDO in a canine model without maxillary collapse is possible, and may be a promising therapeutic approach for the repair of cleft palates in human infants.

The biggest challenge to islet transplantation is preserving cell mass and function. It is known that the stresses encountered during islet isolation have deleterious effects on beta-cell physiology. The nature of these effects, however, are incompletely known, partly due to the heterogeneity of islet preparations. Using a combination of laser capture microdissection and microarray technology, we therefore sought to determine the beta-cell specific events that occur as a result of islet isolation and in vitro culture. Our data shows that islet isolation and in vitro culture induce a large inflammatory response that is NF-kB dependent and involves the upregulation of several pro-inflammatory cytokines such as IL-8, IL-1 and MCP-1. Furthermore, several transcription factors involved in ß-cell differentiation, such as NeuroD1, NKX2.2, and MafA were decreased, providing insight into mechanisms of beta-cell dedifferentiation. Therefore, therapies aimed at targeting NF-kB and re-expressing transcription factors necessary to beta-cell function should be explored further. / Le stress subi durant l'isolation des îlots de Langerhans a des effets négatifs sur la physiologie des cellules bêta. Nous avons tenté de déterminer les événements survenant suite à une isolation d'îlots et de leur culture in vitro grâce à la capture et découpage laser et la puce à gènes. Nos résultats démontrent que l'isolation d'îlots et leur culture in vitro produisent une importante réponse inflammatoire. Cette réponse dépend de la protéine NF-kB et implique une augmentation de plusieurs cytokines pro-inflammatoires, incluant IL-8, IL-1, et MCP-1. Aussi, plusieurs facteurs de transcription essentiels dans la différenciation des cellules bêta comme NeuroD1, NKX2.2, et MafA ont diminué, suggérant que les cellules bêta se dédifférencient après leur isolation et culture in vitro. Par conséquent, les thérapies visant NF-kB et la réexpression des facteurs de transcription nécessaires à la fonction des cellules bêta devraient être explorées plus en détails.

Mutant quaking viable mice (qkV) develop a tremor phenotype in their hind limbs 10 days after birth, likely resulting from severe myelination defects. Genetically, quaking viable mice contain a deletion in the promoter/enhancer region of the quaking gene. The quaking gene is alternatively spliced, producing QUAKING isoforms that differ in their C-terminal amino acid sequence. The QKI-5 isoform is nuclear, whereas the QKI-6 and QKI-7 isoforms are predominantly cytoplasmic. The QKI isoforms contain a single KH RNA-binding domain, which suggests a role in RNA metabolism. Although the dysmyelinating phenotype of the mutant mice suggests a role in myelination, the function of the protein remains largely unknown. The objective of this thesis is to characterize the role of the RNA binding proteins QKI in the differentiation of glial cells and their involvement in the process of myelination. Moreover, this study describes the quaking viable defects and how the isoforms contribute to the observed phenotype. [...] / Les protéines liant l’ARN jouent un rôle central afin de contrôler l’expression génique, l’épissage alternatif et la localisation des ARN messagers. Pour qu’une cellule se différencie, les gènes doivent être régulés au niveau de leur expression et de la localisation de leurs ARNm. Un des phénomènes physiologique de différentiation au niveau du système nerveux est la myélinisation des axones. En vulgarisant, la gaine de myéline serait l’isolant entourant le fil électrique étant l’axone. [...]