Ractopamine hydrochloride (RAC) has been used in the pig production industry for over 30 years. RAC is a beta-adrenergic agonist which is supplemented in the feed during the last 28 days prior to harvesting in finisher pigs to modify the pig's metabolism such that nutrients are redirected to favour muscle accretion rather than adipose deposition, and hence improve growth efficiencies, feed utilisation and carcass revenues. The objective of this study was to investigate the effect of dietary ractopamine (Paylean®) supplementation at levels of 0, 5, and 10 mg.kg-1 (hereafter referred to as 0-RAC, 5-RAC, and 10-RAC respectively) on animal growth performance, efficiency and carcass characteristics including daily voluntary feed intake, feed efficiency, absolute daily growth rate (ADG) and daily live weight gain, and backfat thickness for the last 27 days in finishing gilts. In this 27-day study, a homogenous group of 71 grower gilts (LW = 43 ± 1 kg) were pre-selected at a source farm. The gilts were then housed in similar and equally sized group pens at the Hatfield experimental facility of the University of Pretoria and fed a standard maize-soya oilcake based grower ration formulated to contain 0.94% standardised ileal digestible Lys (1.05% total Lys) and 14.01 MJ ME kg-1 during the 28 day pre-adaptation phase. From these gilts, individuals were weighed and 58 gilts selected (average LW = 68.7 ± 4.3 kg), and placed into individual pens and the same diet for 7 days (adaptation phase), afterwhich they were assigned to 1 of 3 treatments in a completely randomized block design with 19, 19, and 20 replicate pens per treatment. The pigs were then fed a standard maize-soya oilcake finisher (treatment) diet containing either 0-RAC, 5-RAC or 10-RAC for 27 d before harvesting. All treatment diets were formulated to contain 1.02% standardised ileal digestible Lys (1.13% total Lys) and 13.96 MJ ME kg-1. Individual pig LW, P2 thickness and pen feed disappearance were recorded weekly to determine LW changes, ADG, ADFI, and G:F. After 27 d on trial, gilts were slaughtered and carcass measurements were recorded at 24 h post-mortem. Overall, RAC supplementation did not affect ADFI or P2 (P > 0.05) but did influence LW (P = 0.049) and overall G:F (P = 0.012) after d27. At d15-d21 and d22-27, only a tendency (P = 0.169, 0.104 respectively) for a linear decrease in G:F with RAC supplementation was found. RAC also affected HCY (P= 0.045) and CCY (P = 0.045) but not fat depth, meat depth or fat % (P > 0.05). These results indicate that RAC may have small but beneficial effects in modern pig production, but further research is required to optimize concentrations and duration of supplementation in modern lean pig genotypes. / Dissertation (MSc (Agric))--University of Pretoria, 2016. / Animal and Wildlife Sciences / MSc (Agric) / Unrestricted

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23468号 / 医博第4775号 / 新制||医||1053(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 竹内 理, 教授 山下 潤, 教授 戸口田 淳也 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Stimulation of β-adrenergic receptor (β-AR) induces cardiac myocyte apoptosis. Integrins, a family of cell-surface receptors, play an important role in the regulation of cardiac myocyte apoptosis and ventricular remodeling. Cleavage of extracellular domain of β1 integrin, also called integrin shedding, is observed during cardiac hypertrophy and progression to early heart failure. Here we show that stimulation of β-AR induces β1 integrin fragmentation in mouse heart. To examine the role of intracellular domain of β1 integrin in cardiac myocyte apoptosis, a chimeric receptor consisting of the cytoplasmic tail domain of β1A integrin and the extracellular/transmembrane domain of the interleukin-2 receptor (TAC-β1) was expressed in adult rat ventricular myocytes (ARVM) using adenoviruses. TAC-β1 increased the percentage of apoptotic ARVM as measured by TUNEL-staining assay. TAC-β1-induced apoptosis was found to be associated with increased cytosolic cytochrome c and decreased mitochondrial membrane potential. TAC-β1 increased caspase-8 activity. Z-IETD-FMK, a specific caspase-8 inhibitor, significantly inhibited TAC-β1-induced apoptosis. TAC-β1 expression also increased cleavage of Bid, a pro-apoptotic Bcl-2 family protein. These data suggest that shedding of β1 integrin may be a mechanism of induction of apoptosis during β-AR-stimulated cardiac remodeling.

La voie β-adrénergique (β-AR)/AMPc est cruciale pour l’adaptation de la fonction cardiaque. Dans l’insuffisance cardiaque (IC), cette signalisation est perturbée et une part importante des patients meurt de troubles du rythme. Classiquement, les effets inotrope et lusitrope positifs de l’AMPc sont attribués à la phosphorylation par la protéine kinase AMPc dépendante (PKA) des protéines clés du couplage excitation–contraction (CEC). L’AMPc active aussi le facteur d’échange Epac, impliqué dans l’hypertrophie cardiaque et le contrôle de l’homéostasie calcique. Une cible d’Epac est la CaMKII, une kinase modulée par le Ca2+ et la calmoduline qui phosphoryle aussi les protéines clés du CEC, et dont l’activation est pro-arythmique.Les phosphodiestérases (PDEs) de type 3 et 4 sont majeures pour dégrader l’AMPc et contrôler l’homéostasie calcique et le CEC. Les inhibiteurs de PDE3 sont de puissants cardiotoniques mais leur utilisation est limitée par leurs effets pro-arythmiques. De plus, l’invalidation de gènes codant pour PDE4 conduit à des arythmies ventriculaires. Mon travail a permis d’identifier les perturbations de l’homéostasie calcique responsables de la survenue d’arythmies lorsque l’activité des PDE3 et des PDE4 est diminuée. Mes résultats montrent que les inhibiteurs de PDEs exercent des effets inotropes via PKA, mais suscitent des vagues de Ca2+ pro-arythmiques impliquant la PKA et la CaMKII activée en partie via Epac. Ceci suggère l'utilisation potentielle d'inhibiteurs de CaMKII comme compléments aux inhibiteurs de PDEs pour limiter leurs effets délétères, une hypothèse que j’ai pu vérifier dans un modèle porcin plus proche du patient. / The β-adrenergic pathway (β-AR)/cAMP is crucial for the adaptation of the cardiac function upon stress. In heart failure (HF), this signaling pathway is disrupted and a significant proportion of patients dies of cardiac arrhythmias. Classically, the inotropic and lusitropic effects of cAMP are attributed to the phosphorylation by the cAMP-dependent protein kinase (PKA) of the key proteins of the excitation-contraction coupling (ECC). cAMP also activates the exchange factor Epac, which is involved in cardiac hypertrophy and controls intracellular Ca2+ homeostasis. Epac activates CaMKII, another kinase modulated by Ca2+ and calmodulin which phosphorylates the same key proteins of the ECC, and is involved in arrhythmogenesis.Phosphodiesterases (PDEs) type 3 and 4 are crucial enzyme to degrade cAMP and to control Ca2+ homeostasis, thus ECC. PDE3 inhibitors are potent cardiotonic drugs but their use is limited by their pro-arrhythmic effects. Furthermore, the invalidation of genes encoding PDE4 results in ventricular arrhythmias. My work allowed characterizing the perturbations of Ca2+ homeostasis which lead to arrhythmias when PDE3 and PDE4 activities are decreased. My results show that PDE inhibitors exert inotropic effects via PKA, but evoke pro-arrhythmic Ca2+ waves via both PKA and CaMKII, the latter being activated in part via Epac. Altogether, these results suggest the potential use of CaMKII inhibitors as adjuncts to PDEs inhibitors to limit their deleterious effects, a hypothesis I also tested in a porcine model closer to the patient.

<p>Chicken fetuses exposed to chronic hypoxia suffer from growth retardation and</p><p>induces an overall sympathetic activity, including elevation of the concentration</p><p>of circulating catecholamines. Simultaneously, hypoxic fetuses display a</p><p>lowered β-adrenoreceptor (βAR) density in myocardial tissue. In vertebrates,</p><p>β1AR and β2AR are the most important signalling pathways for acute elevation</p><p>of cardiac performance. The aim of this study was to see how chronic hypoxia</p><p>affects the level of messenger RNA (mRNA) for the β1AR in the fetal chicken</p><p>heart at different developmental ages. The broiler chicken is a suitable model</p><p>organism for studying the progression of heart failure because the fast growth</p><p>rate requires a large increase in blood perfusion at the end of fetal development.</p><p>The β1AR sequence of the broiler chicken is 1587 bp and located on</p><p>chromosome 6. When running a PCR for quantification of the sequence,</p><p>primers for almost the whole sequence failed (1404 bp) and so did primers of</p><p>1193 bp; instead primers of 692 bp of the sequence were used and made</p><p>quantification possible. Similar results were obtained from both the heart and</p><p>liver of day 15 fetal chickens. The PCR product was cloned into a TOPO vector</p><p>and sent for sequencing, to enable the making of a probe for a northern blot</p><p>analysis of the mRNA in the fetal chicken hearts.</p>

Chicken fetuses exposed to chronic hypoxia suffer from growth retardation and induces an overall sympathetic activity, including elevation of the concentration of circulating catecholamines. Simultaneously, hypoxic fetuses display a lowered β-adrenoreceptor (βAR) density in myocardial tissue. In vertebrates, β1AR and β2AR are the most important signalling pathways for acute elevation of cardiac performance. The aim of this study was to see how chronic hypoxia affects the level of messenger RNA (mRNA) for the β1AR in the fetal chicken heart at different developmental ages. The broiler chicken is a suitable model organism for studying the progression of heart failure because the fast growth rate requires a large increase in blood perfusion at the end of fetal development. The β1AR sequence of the broiler chicken is 1587 bp and located on chromosome 6. When running a PCR for quantification of the sequence, primers for almost the whole sequence failed (1404 bp) and so did primers of 1193 bp; instead primers of 692 bp of the sequence were used and made quantification possible. Similar results were obtained from both the heart and liver of day 15 fetal chickens. The PCR product was cloned into a TOPO vector and sent for sequencing, to enable the making of a probe for a northern blot analysis of the mRNA in the fetal chicken hearts.

Previous studies have suggested that phosphodiesterase (PDE) hydrolysis of cyclic adenosine monophosphate (cAMP) is important in the generation of specific and segregated cAMP signals within cells. The purpose of this study was to determine if PDE compartmentation was important in cardiac ventricular myocytes. Therefore, we investigated the effects of β-adrenergic (β-AD) stimulation with isoproterenol in the presence of cilostamide, a PDE3 inhibitor, or Ro 20-1724, a PDE4 inhibitor, on unloaded cell shortening, L-type calcium currents and intracellular calcium levels in freshly dissociated adult rat ventricular myocytes. PDE3 inhibition resulted in a 216 ± 17 % (n=8) increase in unloaded cell shortening after ten minutes of isoproterenol exposure, whereas isoproterenol produced a statistically smaller increase of 155 ± 12 % (n=8) in the presence of PDE4 inhibition. There was a non-significant trend for PDE4 inhibition to produce larger increases in calcium currents (179 ± 17 % (n=4) of controls) than PDE3 inhibition (155 ± 10 % (n=6) of controls). Both PDE3 and PDE4 inhibitors had similar effects on isoproterenol-stimulated increases of calcium transient amplitude with values of 209 ± 14 % (n=8) and 185 ± 12 % (n=8), respectively. Determination of sarcoplasmic reticulum (SR) calcium load using caffeine pulse experiments demonstrated that PDE4 inhibition and isoproterenol superfusion produced a statistically larger increase in SR-calcium loading (139 ± 9 % (n=6)) than PDE3 inhibition and isoproterenol superfusion (113 ± 9 % (n=6)). These results suggest that PDE3 may be active in proximity to the contractile apparatus of cardiac myocytes, whereas PDE4 may be localized in a domain consisting of the L-type calcium channel and junctional SR. Consequently, our study provides functional evidence for differential localization of PDE isoforms in cardiac myocytes. / Thesis (Master, Physiology) -- Queen's University, 2008-01-18 10:14:29.671 / CIHR OGS OGSST

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京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22073号 / 農博第2365号 / 新制||農||1072(附属図書館) / 学位論文||R1||N5227(農学部図書室) / 京都大学大学院農学研究科食品生物科学専攻 / (主査)教授 井上 和生, 教授 保川 清, 教授 谷 史人 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Acute cold exposure is a significant stressor activating heat production by shivering after the prolonged exposure cellular oxidative stress increases. Chronic exposure to cold lasting at least 2 weeks leads to the development of cold acclimatization. The main thermogenic role is taken over by non-shivering thermogenesis taking place in brown adipose tissue, which significantly increases its weight due to cold. Cardiac hypertrophy, hypertension and impaired renal function are frequently observed pathologies of acclimatization at 4-5 řC. Our laboratory recently introduced a model of mild chronic cold acclimatization at 8 řC, during which no damage to the heart or kidneys occurs and has proven cardioprotective effect on reducing infarct size. Hence, the influence of this cold acclimatization model on the other cellular and molecular processes needs to be investigated. The cardioprotective effect of cold acclimatization includes changes in β-AR signaling, activation of anti-apoptotic pathways or augmentation of the antioxidant system. The aim of this thesis was to investigate the effect of cold acclimation and subsequent reacclimation on proteins regulating Ca2+ levels in the rat heart (SERCA2 and phospholamban) and on the stimulation of regulatory proteins β-arrestin 1/2 and protein kinase PDPK1. The...