Addenda and corrigenda inserted on verso of back end paper. Includes: Publications and communications to learned societies (p. 4-5). Bibliography: leaves 272-286. Examines the acute myocardial uptake of drugs, particularly perindoprilat and enalaprilat in humans. The uptake of these agents is examined, together with the haemodynamic, metabolic and biochemical effects. In particular, the impact of these agents on angiotensin and bradykinin peptides both within the heart and peripherally is described. The acute effects of a range of cardioactive drugs upon the left ventricular force-interval relationship is examined.

Errata sheet inserted. Bibliography: leaves 99-102.

Left ventricular hypertrophy (LVH) in response to pressure overload is associated with increased cardiovascular morbidity and mortality, making its prevention an important therapeutic goal. The role of a calcineurin-dependent molecular pathway in the induction of pressure-overload LVH is controversial. The present study tested the hypothesis that, in the setting of LV pressure overload, activation of the systemic renin-angiotensin system was necessary for activation of this calcineurin pathway. Mild LV pressure overload was induced in male Wistar rats by abdominal aortic constriction (AAC) or transverse aortic arch constriction (TAC), producing well-matched pressure gradients of 37 ?? 8 and 35 ?? 15 mmHg, respectively. Tight transverse aortic arch constriction (TTAC) in additional animals produced a pressure gradient of 75 ?? 15 mmHg. Only AAC increased plasma renin concentration and activated the calcineurin pathway, indicated by increased nuclear NFAT3 content. Plasma renin concentration and nuclear NFAT3 content were unchanged in TAC and TTAC animals. AAC animals developed more LVH 21 days post-banding than TAC and TTAC animals: the slope of the relationship between LV/body weight ratio and systolic blood pressure was much steeper in AAC animals than the combined TAC and TTAC animals (20x10-6 versus 5x10-6, p<0.001). Treatment with the calcineurin inhibitor FK506 did not significantly alter the slope of this relationship in the combined TAC and TTAC animals (8x10-6), but FK506 abolished this relationship in AAC animals (-5x10-6, R =0.0003). These data indicate that activation of the calcineurin pathway occurs only in high-renin hypertension, providing an additional stimulus to LVH induction. Calcineurin plays no role in the induction of LVH in low-renin hypertension, which is much more common clinically.

Stretch of cardiac muscle is known to activate various physiological processes that result in changes to cardiac function, contractility and electrophysiology. To date, however, the precise relationship between mechanical stretch and changes in the electrophysiology of the heart remain unclear. This relationship, termed mechanoelectric feedback (MEF), is thought to underlie many cardiac arrhythmias associated with pathological conditions. These electrophysiological changes are observed not only in the whole heart, but also at the single cardiomyocyte level, and can be explained by the presence of stretch-activated ion channels (SACs). Most investigations of the actions of stretch have concentrated on these sacrolemmal ionic currents thought responsible for the proposed MEF-induced changes in contractility. While these studies have provided some useful insight into possible mechanisms, the inappropriate use of solutions and non-physiological degrees of stretch, may have caused somewhat misleading results. Currently, little is known about the involvement or contribution of non-selective or K+ selective SACs to the normal cardiac cycle. Here, I investigate the concept that stretch-induced changes in cardiac electrophysiology (MEF) are important in normal cardiac cycle and demonstrate the effects of stretch on the Frank-Starling mechanism (stretch induced increases in cardiac contractility) while pharmacologically manipulating stretch-activated ion currents. Experiments were conducted using a number of agents known to influence stretch-activated channels either in a positive or antagonistic manner. Results proved somewhat negative toward MEF theory with only substantial or pathological levels of stretch being able to elicit any electrophysiological change in the heart. Furthermore, where electrophysiological changes were associated with pathological stretch they were not consistently modulated by stretch-activated ion channel activators or blockers. Of equal importance was the observation that smaller levels of myocardial stretch associated with positive changes in contractility via the Frank-Starling mechanism were not associated with any electrophysiological changes in the Langendorff perfused heart (as observed by monophasic action potentials) nor in isolated muscle preparations (as observed through transcellular membrane potential recordings). As such, the present research undertaken in this thesis confirms an absence of electrophysiological changes with stretch except under extreme conditions suggesting that MEF is not a robust and necessarily repeatable phenomenon in the mammalian heart. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320476 / Thesis (Ph.D.) - University of Adelaide, School of Molecular and Biomedical Science, 2008

Thesis (Ph. D.)--Virginia Commonwealth University, 2006. / Prepared for: Dept. of Biostatistics. Bibliography: leaves 189-198. Also available online via the Internet.

Identifying the molecular and genetic pathways important for heart development and deciphering the causes of CHD are still a challenging puzzle. A newly identified piece of this puzzle is KLF13, a member of the Krüppel-like family of zinc-finger proteins, was found to be important for atrial septation and ventricular trabeculation of Xenopus embryos. The protein is expressed predominantly in the heart, binds evolutionarily-conserved regulatory elements on cardiac promoters, and activates cardiac transcription. In this study we examined KLF13 mechanism of action by investigating its transcriptional activity on the ANF promoter using a deletion/mutagenesis approach. We reported the identification of a new synergistic partnership between KLF13 and the individual cardiac transcription factors TBX5, NKX2.5, PEX1, and CATF1. Also, we localized KLF13’s transcriptional activation domain, the nuclear localization region/zinc-fingers, and the DNA binding zinc-fingers. This study will provide insight into the contribution of KLF13 to the development of CHDs.

Identifying the molecular and genetic pathways important for heart development and deciphering the causes of CHD are still a challenging puzzle. A newly identified piece of this puzzle is KLF13, a member of the Krüppel-like family of zinc-finger proteins, was found to be important for atrial septation and ventricular trabeculation of Xenopus embryos. The protein is expressed predominantly in the heart, binds evolutionarily-conserved regulatory elements on cardiac promoters, and activates cardiac transcription. In this study we examined KLF13 mechanism of action by investigating its transcriptional activity on the ANF promoter using a deletion/mutagenesis approach. We reported the identification of a new synergistic partnership between KLF13 and the individual cardiac transcription factors TBX5, NKX2.5, PEX1, and CATF1. Also, we localized KLF13’s transcriptional activation domain, the nuclear localization region/zinc-fingers, and the DNA binding zinc-fingers. This study will provide insight into the contribution of KLF13 to the development of CHDs.

Aging is characterized by a progressive impairment of cardiac structure and function. The cardiac remodeling involves loss of cardiac myocytes, reactive hypertrophy of the remaining cells, and increased extracellular matrix (ECM) and fibrosis in the aging heart. In contrast, exercise training not only improves cardiac function, but also reduces the risk of heart disease. However, the ability of exercise training to modulate ECM and remodeling in the aging heart remains unknown. Therefore, the purpose of this study was to determine the effects of exercise training on ECM remodeling in the aging heart. We hypothesized that (1) exercise training would attenuate age-related changes in left ventricle morphology including extramyocyte space and collagen contents, and (2) exercise training would ameliorate age-induced changes in ECM-related factors including MMPs, TIMPs, TNF-α, TGF-β1, and α-SMA in the heart. Three and 31 month old Fischer 344 × Brown Norway F1 hybrid rats were assigned to four groups: young sedentary (YS), young exercise-trained (YE), old sedentary (OS), and old exercise-trained (OE). Exercise training groups walked briskly on a treadmill for 45 min/day (12° incline) at 20m/min (young) or 10 m/min (old), 5 d/wk for 12 wk. We found that endurance exercise training might ameliorate the ageinduced increase in extramyocyte space and collagen contents of the left ventricle. Exercise training might protect against age-induced fibrosis by increasing MMP-2, MMP-14 in the soluble fraction and MMP-1, MMP-3, MMP-14 in the insoluble fraction of old rat hearts. Conversely, exercise training might reduce the fibrosis by decreasing TIMP-1 in the soluble fraction of old rat hearts. Further, exercise training reduced potential upstream pro-fibrotic mediators including TNF-α and TGF-β1 in the aging rat hearts. These results are the first to demonstrate that exercise training has a protective effect against age-induced extracellular collagen matrix remodeling in the aging heart, associated with increased MMP-1, -2, -3, -14 and decreased TIMP-1, TNF-α, and TGF- β1.

In order to understand the mechanical functions of the cardiac muscle it is important to first understand the microstructure of the tissue. Young et al. (1998) realized that quantitative three-dimensional information about the ventricular myocardium is necessary to analyze myocardial mechanics. They developed a technique using confocal fluorescence laser scanning microscopy to obtain three-dimensional images. While this method worked well in rebuilding the myocardial tissue image by image, it was quite extensive and costly. Costa et al. (1999) developed a method that was used to perform three-dimensional reconstruction as well. Their method, while less expensive and much less time consuming, required sheet assumptions and did not look directly at the cross-fiber plane. From Dr. Criscione's previous work on canines (Ashikaga et al., 2004), we found that the sheet structure can be accurately determined from cross-fiber sections without making any sheet assumptions. We have now expanded on those ideas and created a method to perform the quantitative histological investigation of the rat hearts in a way that is both timely and cost effective. We developed a processing method that preserves the orientation of the fiber and sheet angles. This method was carried out using plastic embedding since the dehydration process used in paraffin embedding has a tendency to grossly distort tissue. Once the heart was fixed in formalin, we then removed the septum and sliced it several times vertically. This allowed us to image the tissue at several depths and find an average fiber angle for each slice. Next, the specimen was hardened, and the sheet orientation was evaluated using polarized light. Once both fiber and sheet angles were obtained from several depths within the septum, we then constructed a three-dimension model of the wall. This method was both cost effective and less time consuming than previous ones and will be a method that can be used in the future to compare the myocardial tissue of diseased and healthy rat hearts so that we may better understand the mechanical functions of the heart as it remodels due to disease.

Thesis--Københavns universitet. / Includes bibliographical references.