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Pui Lan Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (Leaves 109-122). / Abstract --- p.i / Acknowledgements --- p.iii / Chapter Chapter1 --- Introduction / Chapter 1.1 --- A general introduction on mast cells --- p.1 / Chapter 1.2 --- Activation of mast cells --- p.6 / Chapter 1.3 --- Mediators of mast cells --- p.18 / Chapter 1.4 --- Usage of β-adrenoceptor agonists in asthma therapy --- p.26 / Chapter 1.5 --- Aim of this study --- p.32 / Chapter Chapter2 --- Materials and methods / Chapter 2.1 --- Chemicals --- p.42 / Chapter 2.2 --- Buffers and stock solutions --- p.43 / Chapter 2.3 --- Source of mast cells --- p.45 / Chapter 2.4 --- Animal sensitization --- p.45 / Chapter 2.5 --- Isolation of mast cells --- p.46 / Chapter 2.6 --- Procedure for the investigation of the effects of adrenoceptor agonists on histamine release from mast cells --- p.48 / Chapter 2.7 --- Procedure for the investigation of propranolol antagonism --- p.49 / Chapter 2.8 --- Histamine assay --- p.50 / Chapter 2.9 --- Data analysis --- p.50 / Chapter Chapter3 --- Results / Chapter 3.1 --- Establishment of experimental conditions --- p.53 / Chapter 3.2 --- The effects of β-agonists on immunologically induced histamine release from guinea pig lung mast cells --- p.54 / Chapter 3.3 --- The effects of β-agonists and two anti-allergic drugs on immunologically induced histamine release from guinea pig lung mast cells --- p.56 / Chapter 3.4 --- The effects of β2-agonists on histamine release induced by non-immunological agents from guinea pig lung mast cells --- p.56 / Chapter 3.5 --- Antagonism by propranolol on the effects of β2-agonists on histamine release from guinea pig lung mast cells --- p.57 / Chapter 3.6 --- The effects of β2-agonists on immunologically induced histamine release from rat peritoneal mast cells --- p.58 / Chapter 3.7 --- The effects of β2-agonists on immunologically induced histamine release from human lung mast cells --- p.58 / Chapter 3.8 --- "Comparison of the effects of β2-agonists on immunologically induced histamine release from mast cells isolated from the rat peritoneum, the guinea pig lung and the human lung" --- p.59 / Chapter Chapter4 --- Discussion / Chapter 4.1 --- The effects of β-agonists on immunologically induced histamine release from guinea pig lung mast cells --- p.89 / Chapter 4.2 --- The effects of β2-agonists and two anti-allergic drugs on immunologically induced histamine release from guinea pig lung mast cells --- p.97 / Chapter 4.3 --- The effects of novel β2-agonists on histamine release induced by non-immunological agents from guinea pig lung mast cells --- p.99 / Chapter 4.4 --- The study of propranolol --- p.100 / Chapter 4.5 --- The heterogeneity of mast cells --- p.103 / Chapter Chapter5 --- General conclusion --- p.107 / References --- p.109

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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed July 9, 2007). PDF text: xv, 147 p. : ill. UMI publication number: AAT 3249674. Includes bibliographical references. Also available in microfilm and microfiche formats.

"July 1999." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1999. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Daniel U. Thomson / The widespread use of beta adrenergic agonists in beef cattle production has been adopted by the beef industry in recent years to improve weight gain and feed efficiency at the end of the feeding period. During this feeding period, anecdotal reports of increased mortality during the timeframe in which beta agonists were being fed to cattle was also reported, and confirmed in epidemiologic studies. Additionally, adverse animal welfare events at abattoirs in cattle fed beta adrenergic agonists were reported in August 2013. The objectives of this dissertation were to investigate physiologic and management factors that may be associated with adverse effects of the use of beta adrenergic agonists in cattle. Two studies were conducted, one to establish normal Holter monitor registration values and evaluate the electrocardiographic effects of zilpaterol and ractopamine hydrochloride on finishing steers, and one to develop a model to investigate the physiologic effects of forced exercises in finished cattle, which was hypothesized to be a possible factor in reported adverse cattle welfare events in August 2013. Thirty steers were enrolled to evaluate the effect of ractopamine, zilpaterol or negative control on arrythmia and mean heart rate at 4 different time periods during a 28 day feeding period. Cattle fed ractopamine and zilpaterol had increased heart rate (P < 0.05) but no differences in arrythmia rates were found. Forty steers were enrolled in a study at a commercial feeding facility to develop a model for fatigue in cattle forced to run 1,540 m compared to control cattle walked 1,540 m. Blood lactate, cortisol, rectal temperature, heart rate was increased (P < 0.05), blood pH decreased (P < 0.01) and to have reduced locomotion, as measured by pedometers, during the 48 hour period following handling compared to controls. Additionally cattle that were fatter and forced to run had increased lactate (P =0.057) and lower blood pH (P < 0.01) than thinner cohorts. Cattle handling method is a factor in the health and welfare of cattle and the continued adoption of low stress handling methods throughout the beef industry should be pursued.

Physiologic β-adrenergic activation of PKA during the sympathetic “fight-or-flight” response increases calcium influx through CaV1.2 in cardiomyocytes, leading to increased cardiac contractility. The molecular mechanisms of β-adrenergic regulation of CaV1.2 in cardiomyocytes are incompletely known, but activation of PKA is required for this process. The second chapter of this dissertation describes our investigation of the functional PKA phosphorylation target for β-adrenergic regulation of CaV1.2. Recent data confirm that β-adrenergic regulation of CaV1.2 does not require any combination of PKA phosphorylation sites on α1C or β2B subunits. Proximity proteomic labeling methods led us to other potential PKA targets near the CaV1.2 complex, including Rad, a calcium channel inhibitor that changes its position within the calcium channel neighborhood after β-adrenergic stimulation. With expression of α1C, β2B, and Rad in a heterologous expression system, we reconstituted forskolin-PKA regulation of CaV1.2. By mutating potential PKA phosphorylation sites on Rad, we identified specific residues that are critical for this mechanism to occur and validated Rad as the functional PKA target for regulation of CaV1.2. In the third chapter, we probe the contribution of both CaV1.2 α1C and β subunits in β-adrenergic regulation. Previous results have shown that binding between α1C and β subunits is required for adrenergic stimulation of the calcium channel in the heart. Using transgenic mouse models, we demonstrate that this phenomenon requires a rigid IS6-AID linker in the α1C subunit, as introduction of glycines in this region increased flexibility of the linker and abolished a response to adrenergic agonists even though α1C was able to bind to β. The fourth chapter examines the role of the auxiliary β subunit in β-adrenergic regulation of CaV1.2. Binding of Rad to the β subunit is also necessary for this mechanism to occur. Although the β2B isoform is the predominant subunit in the heart, we show that transgenic mice with β3 or β4 replacing β2B in the heart are viable and still have normal β-adrenergic regulation of CaV1.2, indicating that this mechanism is universal to other voltage gated calcium channels that bind to β subunits and RGK proteins. The fifth chapter verifies that Rad is the PKA target in the heart. Using a knock-in mouse model with four PKA phosphorylation sites mutated to alanine, we definitively show that phosphorylation of Rad is necessary for β-adrenergic regulation of CaV1.2 in the heart. We investigate the importance of Rad phosphorylation on many levels. First, we study Rad’s role in regulating the calcium channel. Second, we observe the effect phosphorylation of Rad has on the calcium transient using isolated cardiomyocytes. Third, we examine cardiovascular function in vivo using radiotelemetry and echocardiograms. Finally, we assess the “fight-or-flight” response in an animal model with exercise capacity testing. Together, these findings conclusively show that in the heart, phosphorylation of Rad is the essential mechanism for the sympathetic nervous system control of calcium influx in both atrial and ventricular cardiomyocytes. Additionally, Rad modulates both heart rate and contractility in vivo. In the sixth chapter, we explore the mechanism of Rad modulation of CaV1.2 in depth using a flow-cytometry Förster resonance energy transfer (FRET) two-hybrid assay. We closely examine the roles of phosphorylation sites on both Rad’s N-terminus and C-terminus. By creating phosphomimetic mutations on Rad, we uncover the importance of phosphorylating the C-terminus for release of Rad from both the membrane and the β subunit. Taken together, these findings elucidate the mechanism behind β-adrenergic regulation of CaV1.2 in the heart – a longstanding query for over forty years in the cardiovascular ion channel field. At baseline, Rad “tunes” the amount of calcium influx into the cell by inhibiting a population of channels as a functional reserve. Upon adrenergic stimulation, Rad is phosphorylated, lessening its interaction with the membrane, and releasing inhibition of the calcium channel. The enhanced local calcium influx allows for additional calcium release into the cytoplasm through ryanodine receptors leading to increased contractility of the heart, a notable characteristic of the evolutionary survival mechanism— “fight-or-flight.”

Whereas first line therapy for chronic obstructive pulmonary disease (COPD) usually includes a short-acting bronchodilator, there are suggestions that these agents may increase the risk of cardiac arrhythmias. In this thesis, we first assessed the risks associated with short-acting beta-agonists (SABA), long-acting beta-agonists (LABA), ipratropium bromide (IB), and methyl xanthines (MX) within a cohort of COPD patients using the health databases of Saskatchewan. In order to confirm these findings and to address some methodological issues we then replicated this analysis within a larger cohort of patients using the health databases of Quebec. / Our first study cohort consisted of 6,018 adults aged 55 and older, newly treated with bronchodilator medications. We found that new users of both IB and LABA increased the risk of arrhythmia (RR 2.39 [95% CI 1.42-4.05] and (RR 4.55 [95% CI 1.43-14.45] respectively). When the cohort was restricted by excluding subjects who had recently either been hospitalised or experienced an exacerbation, the elevated risk associated with the new use of IB persisted (RR 3.65 [95% CI 1.72-7.74]), an effect was detected with new use of MX (RR 5.17 [95% CI 1.38-19.30]), but there was insufficient power to detect an effect associated with the new use of LABA. / Due to both power issues and the limited availability of LABA within the Saskatchewan data, we replicated the analysis in a larger new-user cohort of 76,661 Quebec adults aged 67 and over. This study confirmed our earlier results, with an elevated risk of arrhythmia associated with the new use of both IB and LABA (RR 1.43 [95% CI 1.08-1.88]) and (RR 1.54 [95% CI 1.00-2.36]) respectively, as well as with new use of SABA (RR 1.28 [95% CI 1.02-1.61]). Finally, using marginal structural models, we demonstrated that both exacerbations of COPD as well as minor non-event arrhythmias were moderate time-dependent confounders within this setting. / In conclusion, we found that new use of bronchodilators in COPD, particularly IB and LABA, was associated with an increase in the risk of cardiac arrhythmias. We also demonstrated the method by which the time-dependent confounder status of specific model covariates may be evaluated.

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