Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 131-146.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 139-153). Also available in electronic version. Access restricted to campus users.

Childhood depression is a widespread, stable disorder, and recurring disorder (Kovacs, Feinberg, Crouse-Novak, Paulauskas, & Finkelstein, 1984). Cognitive-Behavioral therapy is an empirically supported intervention for the treatment of depression (Weersing & Weisz, 2002; Weisz, McCarty, & Valeri, 2006). CBT for depression is often comprised of cognitive, behavioral, problem-solving, and relational interventions (McCarty & Weisz, 2007). While it is evident that CBT as a whole is efficacious, there exists a dearth of knowledge concerning the specific components within CBT, which contribute to symptom reduction in youth (Kazdin & Weisz, 1998; Kennard et al., 2009). Therefore, the manner in which CBT accomplishes change is not well understood (Shirk & Karver, 2006). Specifically, while cognitive theories assert that interventions targeted at modifying negative cognitions reduce depression (Beck, 1967), few studies, particularly with regards to depressed youth, have addressed this (Stice, Rohde, Seeley, & Gau, 2010). As such, this hypothesis concerning the role of depressogenic cognitions as mediators between certain CBT interventions and symptom reduction remains unsubstantiated (Weersing, Rozenman, & Gonzales, 2009). The current study assessed whether higher levels of cognitive, behavioral, problem solving, and relational components were associated with lower levels of post-treatment depression, as well as whether they were mediated through changes in the cognitive triad, a measure of depressogenic thinking. No studies have assessed the effectiveness of discrete interventions incorporated in CBT treatments for depression in youth, further examining whether noted changes in depression are mediated through cognitions, specifically the cognitive triad. Participants included 40 depressed females, aged 9 to 14, assessed using self-report measures and a diagnostic interview for depression, who engaged in treatment using a manualized group CBT treatment protocol. Results from hierarchical linear models indicated that higher participant cognitive triad scores and higher relational interventions were associated with lower post-treatment depression scores. However, subsequent analyses revealed that higher aggregated behavioral-problem-solving interventions scores were associated with lower post-treatment depression scores, while higher aggregated cognitive-relational intervention scores were associated with higher post-treatment depression scores. Implications, limitations, and recommendations for further areas of research are discussed. / text

Cigarette smoking is a major risk factor in the development of age-related chronic obstructive pulmonary disease (COPD) with chronic airway inflammation as a key feature. Currently, no effective treatment can reduce the protracted inflammation in the lung of COPD. Further research on the inflammatory mechanisms would therefore be important in determining new potential therapeutic targets in COPD. Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter that plays an important role in pulmonary functions and inflammatory responses. The serotoninergic system including serotonin transporter (SERT), serotonin receptors (5-HTR) and its metabolic enzyme monoamine oxidase (MAO) have been reported to associate with cigarette smoking and/or COPD. Blockade of serotonin receptor 2A (5-HTR2A) with its selective antagonist ketanserin has been shown to improve lung function in COPD patients. In this study, we hypothesize that the serotoninergic system is involved in cigarette smoke-induced oxidative stress, inflammation and COPD. Exposure to cigarette smoke medium (CSM) caused the elevation of interleukin (IL)-8 levels in primary normal human bronchial epithelial (NHBE) cells and a human bronchial epithelial cell line (BEAS-2B) in vitro via activation of p38 and extracellular signal-regulated kinases 1 and 2 (ERK1/2) signaling pathway. Besides, CSM was found to disrupt the glutathione (GSH) system, resulting in the translocation of nuclear factor-erythroid 2 related factor 2 (Nrf2) to the nucleus. Knock-down of Nrf2 by small interference RNA (siRNA) blocked CSM-induced IL-8 release. Pretreatment with ketanserin was found to attenuate CSM-induced IL-8 release by inhibiting the p38, ERK1/2, and Nrf2 signaling pathways, and by partially restoring the GSH system. On the other hand, CSM reduced MAO activity in BEAS-2B, indicating a reduced catabolism of 5-HT. Furthermore, 5-HT was found to share the common p38 and ERK1/2 signaling pathway with CSM in IL-8 release. In the cigarette smoke-exposed rat model, the GSH system in the lung was found to be disrupted compared to the sham-air control, supporting our in vitro findings. Interestingly, we found an increased MAO-A activity in the lung of cigarette smoke-exposed rats in comparison to sham air-exposed rats. The increased MAO-A activity in the lung was associated with the reduction of 5-HT levels in bronchoalveolar lavage (BAL) and lung homogenates, while the increased metabolism of 5-HT may be involved in cigarette smoke-induced superoxide anion levels. On the other hand, serum, but not plasma level of 5-HT was elevated in cigarette smoke-exposed group, which may be due to platelet activation caused by cigarette smoke. In the clinical study, the elevated plasma 5-HT levels were found to be associated with an increased odds ratio for COPD and positively correlated with age in COPD patients. Furthermore, plasma 5-HT was also demonstrated to be a significant mediator on the relation between cigarette smoking and COPD. In summary, our study supports the hypothesis that the serotoninergic system contributes to cigarette smoke-induced oxidative stress, inflammation and COPD. The serotoninergic system (e.g. 5-HTR2A) may constitute potential therapeutic targets for the treatment of COPD, which is worthy for further investigation. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

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Deoxyribonucleic acid (DNA) replication in eukaryotic cells requires a highly complex series of protein-DNA interactions. Elucidation of the mechanisms by which DNA replication occurs is vital to the understanding of cellular growth. DNA polymerase alpha is an enzyme with a putative role in the replication of eukaryotic DNA. Modification by phosphorylation and dephosphorylation is one process by which enzymatic activity is regulated. The purpose of this research was to determine if a phosphorylation event could be of significance in the expression of DNA polymerase alpha activity. Evidence will be presented for the regulation of DNA polymerase alpha by phosphorylation. A highly purified DNA polymerase alpha fraction was prepared from Chinese hamster ovary cells. Purification procedure included ion-exchange chromatographies and affinity chromatography. Both the crude DNA polymerase alpha activity and the highly purified DNA polymerase alpha activity were stimulated six-fold by the addition of exogenous bovine cardiac muscle cyclic AMP-dependent protein kinase. Dephosphorylation of the highly purified DNA polymerase alpha fraction by alkaline phosphatase resulted in a concomitant decrease in DNA polymerase alpha activity. An endogenous protein kinase activity was detected in the highly purified DNA polymerase alpha fraction. Incubation of this fraction in a protein kinase reaction mixture including adenosine triphosphate (ATP) could stimulate DNA polymerase alpha activity to twelve-fold that observed in controls with no pre-incubation. The endogenous protein kinase activity in the highly purified DNA polymerase alpha fraction was utilized to indicate (1) the linear increase in DNA polymerase alpha activity with time of phosphorylation which was dependent on the presence of ATP, (2) the linear relationship between γ³²P-ATP incorporation and DNA polymerase alpha activity, and (3) the incorporation of labelled phosphate into DNA polymerase alpha as determined by SDS-PAGE analysis. Finally, the co-purification of the endogenous protein kinase with DNA polymerase alpha is presented. The significance of this research in relation to the heterogeneous nature reported for DNA polymerase alpha is discussed. It is speculated that the phosphorylational regulation of DNA polymerase alpha may play a role in the transformation of cells.

Both chronic psychosocial stress and chronic administration of corticosterone have been shown to alter serotonergic type 2A (5-HT2A) receptor activity. A non-invasive behavioural index of 5-HT2A receptor activity is the frequency of "wet dog shakes" (WDS) or serotonergic stereotypy. In addition to WDS, 5-HT2A receptors mediate effects on sexual behaviour in the rat, in particular, inhibition in the male and stimulation in the female. In the present series of experiments, the potential involvement of stress and corticosterone in the regulation of WDS and sexual behaviour in the male and female rat was investigated. In Experiments 1-4, chronic exposure to several different forms of psychosocial stress was found to facilitate female and inhibit male rat sexual behaviour while concurrently increasing the display of WDS in both sexes. In Experiment 5, nefazodone, an antidepressant with 5-HT2A antagonistic properties, blocked the effects of stress on WDS but not sexual behaviour in female rats. In Experiments 6-7, the corticosterone synthesis inhibitor, metyrapone, blocked the effects of stress on sexual proceptivity and WDS in female rats. Metyrapone blocked the effects of stress on WDS but not sexual behaviour in male rats. In Experiments 8-9, high doses of corticosterone administered chronically facilitated female and inhibited male rat sexual behaviour while concurrently increasing WDS in both sexes. In Experiments 10-11, the 5-HT2A antagonist ketanserin was found to completely attenuate the effects of corticosterone on sexual behaviour and WDS in both male and female rats. In Experiments 12-13, the acute administration of corticosterone was found to exert no effect on either sexual behaviour or WDS in male or female rats. The present results indicate that both chronic corticosterone treatment and exposure to chronic stress inhibit male and facilitate female sexual behaviour while concurrently increasing WDS behaviour. The stress-induced facilitation of WDS appears to be related to elevated corticosterone levels and is suggestive of increased 5-HT2A activity. Both corticosterone and stress exerted effects on sexual behaviour in the direction that would be predicted by increased 5-HT2A activity. While the effects of corticosterone on sexual behaviour appear to be mediated by 5-HT2A activity, the effects of stress on sexual behaviour do not appear to be related to either elevations in corticosterone levels or alterations in 5-HT2A activity.

This study aimed to examine whether trigeminal nerve injury induces chronic nociceptive behaviour and central sensitization (CS) in functionally identified medullary dorsal horn (MDH) nociceptive neurons in mice, and whether CS in acute and chronic orofacial pain models and nociceptive behaviour in the chronic model are affected by systemic administration of pregabalin. Infraorbital nerve injury induced chronic facial mechanical allodynia as well as MDH CS; acute noxious tooth pulp stimulation also induced MDS CS. Systemic administration of pregabalin attenuated the nerve injury-induced allodynia as well as the MDH CS in both the chronic and acute pain models. These findings reveal that MDH CS occurs in mouse models of acute and chronic orofacial pain and that pregabalin may prove useful clinically in acute and chronic orofacial pain states.