Trials were performed in sheep and rats to elucidate the pathogenesis of the myocardial lesions in gousiekte. In the first trial the macro- and lightmicroscopical lesions and myofibre morphometrical changes were studied in ten sheep exposed daily to Pachystigma pygmaeum at 10 g/kg live body weight for 23 to 31 days. All the treated animals either died or were euthanased in extremis between 31 and 51 days after the commencement of dosing. In the second trial the myocardial ultrastructural lesions were studied in six sheep dosed with Fadogia homblei at a dosage rate of 10 g/kg per day live body weight for 22 to 23 days. All the treated animals either died or were euthanased in extremis between 34 and 57 days after the commencement of dosing. The main objective of the third trial was to compare the myocardial lesions in rats exposed to pavetamine with lesions recorded in sheep exposed to P. pygmaeum and F. homblei plant material. Seven rats were injected intraperitoneally with pavetamine at a dosage rate of 5 mg/kg on day 0 and three were killed on day 6. The remaining four were injected with a second dose of pavetamine at a dosage rate of 3 mg/kg on day 27 and euthanased on day 42. In the sheep exposed to P. pygmaeum pulmonary oedema and hydropericardium were present in eight, hydrothorax in four and ascites in two cases. In two sheep cardiac dilatation was associated with subendocardial pallor (fibrosis) and transmural myocardial mottling. Myofibre hypertrophy was recorded in all the sheep, myofibre necrosis and replacement fibrosis occurred in seven animals the latter being particularly evident in animals with medium to long latent periods. A mononuclear cellular infiltration that varied from mild to severe was evident in all the cases and endocardial thickening, which is an indication of cardiac dilatation, was present in seven animals. Myofibre atrophy occurred in eight animals and was the most striking lesion in a sheep with a short latent period. “Typical” gousiekte lesions, characterised by myofibre necrosis and atrophy, replacement fibrosis and an associated round cell infiltration in the subendocardial region, were present in eight of the sheep. “Atypical” lesions, characterised by hypertrophy of myofibres with multifocal coagulative necrosis or myofibre atrophy, were recorded in two sheep, both of which had short latent periods. The myofibre diameter and nuclear area in the affected animals differed statistically from those of the controls (larger) and anisocytosis and anisonucleosis were particularly striking in sheep with intermediate to long latent periods. The most striking ultrastructural lesions included breakdown of myofibrils, involving in particular what appeared to be thick (myosin) filaments; selective proliferation of organelles such as mitochondria and sarcoplasmic reticulum in areas previously occupied by myofibrils; excessive folding of the myofibre sarcolemma; and advanced myocardial injury characterised by complete loss of myofibrils with loss of intercellular connections and necrosis of myocardial cells. No lesions were present in the rats exposed to a single dose of pavetamine, although they became anorexic and lost weight. Rats exposed to pavetamine twice became anorexic within two to three days after the first exposure and regained weight within a few days (on about day 7). However, they kept on losing weight after the second exposure and continued to do so until termination of the experiment. As a general rule the myocardial lesions were mild in the rats dosed twice with pavetamine. Transmural multifocal myocardial necrosis, with an associated round cell infiltration and replacement fibrosis, was the most striking light- microscopical lesion. The lesions were comparable with “atypical” lesions in ruminants. Ultrastructural lesions in degenerative/necrotic fibres included karyolysis, swelling of the mitochondria and focal lysis of myofilaments. In rats exposed to pavetamine twice there was statistical evidence of myofibre atrophy. Based on the information emanating from this study and previous research the following deductions are made to explain the pathogenesis of the myocardial lesions: 1. Pavetamine has a prolonged effect on the myocardium owing to inhibition of protein synthesis, and also influences the energy production system, which affects the function of myocytes. The structure of the myocytes is not affected during the early stages of the latent period but eventually myofibre hypertrophy, atrophy, degeneration and necrosis are seen. 2. Replacement fibrosis in the subendocardial region is a sequel to the effect of pavetamine on myofibres and the consequence of ischaemia owing to impaired myocardial perfusion of, particularly, the subendocardial region, as a result of decreased myocardial contraction, increased diastolic pressure, tachycardia and myofibre hypertrophy. 3. Cardiac dilatation is a compensatory mechanism, a result of the myofibre damage inflicted by pavetamine and ischaemia (pathological dilatation). 4. Lesions in animals with gousiekte represent a final common pathway of cellular damage rather than a manifestation of a specific type of heart disease. Animals may die during any stage in the development of the lesions. “Atypical” lesions represent a manifestation of the disease in a progression that terminates with dilated cardiomyopathy if the animal does not die during the early stages. These deductions provide an explanation, for the first time, for the latent period between ingestion of the plant and the onset of illness in gousiekte. They also explain the wide range of lesions seen in experimental cases. It furthermore demonstrate that the “typical” lesions of gousiekte are not pathognomonic, and that the absence of “typical” lesions does not rule out a diagnosis of gousiekte in situations where exposure to the causative plants and the clinical history support such a diagnosis. / Thesis (PhD)--University of Pretoria, 2008. / Paraclinical Sciences / unrestricted

No description available.

Original published work submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Medicine (Internal Medicine) 18 October, 2017. / The very first coronary artery balloon angioplasty is reported to have been performed by Gruntzig in 1977.1 Subsequently to this, over the past 40 years, there have been significant advances in coronary angiography and intervention. Coronary artery interventional techniques have evolved and improved significantly. There have been considerable device developments, new generation stents and novel antiplatelet therapy which have all proved to reduce the incidence of the primary periprocedural complications associated with percutaneous coronary intervention (PCI). [No abstract provided. Information taken from introduction] / LG2018

Myocardial infarction (MI), a late-stage event of many cardiovascular diseases (CVD), results in cardiomyocyte death, myeloid cell recruitment to promote cellular debris removal and excessive cardiac remodeling affecting architecture and function, which can ultimately lead to heart failure. Currently, the use of biomaterials to intervene on the hostile post-MI environment and promote myocardial healing is being investigated to restore cardiac function. It has been shown that an injectable collagen matrix improves cardiac repair by altering macrophage polarization, reducing cell death and enhancing angiogenesis, leading to a reduction in infarct size and improved cardiac function when delivered at 3 hours post-MI. MicroRNAs (miRNA) “fine tune” gene expression by negatively regulating the translational output of target messenger RNA (mRNA). As such, miRNAs present interesting therapeutic opportunities for the treatment of MI. However, the delivery of miRNA mimics and/or inhibitors can be complicated by degradation and off target effects. The objectives of this thesis were to determine how the matrix may regulate endogenous miRNAs and to explore the biomaterial’s ability to deliver therapeutic miRNAs. It was shown that matrix treatment of MI mouse hearts resulted in altered expression of 119 miRNAs, some of which had functions linked to the beneficial effects of matrix treatment. Of particular interest, miR-92a was down-regulated within the infarct and peri-infarct cardiac tissue 2 days after matrix treatment (delivered at 3-hours post-MI) compared to PBS treatment. In in vitro cultures, the matrix down-regulated miR-92a levels in macrophages but did not significantly alter miR-92a expression in endothelial cells, circulating angiogenic cells or fibroblasts. In addition, using an in vitro model system, it was shown that the matrix may have the potential to deliver functional therapeutic miRNAs to cells; however further experimental optimisation is required to confirm these results. Therefore, collagen matrix treatment may be a promising approach to regulate and/or deliver miRNAs for protecting the myocardial environment and improving function of the infarcted heart.

Cardiac-specific troponins (Tns) are sensitive and specific markers of myocardial injury that have been shown to be predictive of outcomes in many cardiac and noncardiac conditions. We sought to determine whether normal cardiac Tn concentrations obtained during the first 24 hours following blunt chest trauma would predict good cardiac outcomes. A PubMed/MEDLINE search was performed to identify prospective studies in patients with blunt chest trauma in which serial cardiac TnT or TnI values were measured within 24 hours of admission and clinical outcomes assessed. Ten studies qualified for review. Studies that used the lower reference limit of Tn as the cutoff for cardiac injury showed 100% negative predictive value (NPV) for developing cardiac complications, whereas studies using higher Tn cutoffs showed wider variation in NPV (50%-98%). Cardiac Tn measured within 24 hours using the lower reference limit (LRL) as the cutoff appears to have excellent NPV for clinically significant adverse cardiac events. This could allow for early discharge after a 24-hour observation period in otherwise uncomplicated blunt chest trauma patients and avoid the need for more expensive cardiac imaging and additional resource utilization.

The mechanisms responsible for myocardial dysfunction in the setting of sepsis remain undefined. Fas ligation with its cognate ligand (FasL) induces apoptosis and activates cellular inflammatory responses associated with tissue injury. We determined whether interruption of Fas/FasL interaction by cardiac-specific expression of soluble Fas (sFas), a competitive inhibitor of FasL, would improve myocardial dysfunction and inflammation in a lipopolysacharide (LPS)-induced mouse model of sepsis. Wild-type (WT) and sFas transgenic mice were injected intraperitoneally with 10 mg/kg LPS or with an equivalent volume of saline. At 18 h after LPS administration, echocardiographic evaluation revealed a significant decrease in left ventricular fractional shortening in the WT mice, whereas the fractional shortening was preserved in the sFas mice. Activation of nuclear factor-kappa B (NF-κB) and the increase in the transcript levels of proinflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 resulting from LPS treatment were attenuated in the myocardium of sFas mice. sFas expression also inhibited LPS-induced upregulation of Toll-like receptor 4 (TLR-4) and inducible nitric oxide synthase (iNOS), and formation of peroxynitrite in the myocardium. LPS-induced increase in caspase-3/7 activity and apoptotic cell death were suppressed in sFas mice compared with WT mice. LPS-induced lung injury and increase in lung water content were also significantly reduced in sFas mice. These data indicate that neutralization of FasL by expression of sFas significantly preserves cardiac function and reduces inflammatory responses in the heart, suggesting that Fas/FasL signaling pathway is important in mediating the deleterious effects of LPS on myocardial function.

Resistin, an adipocyte-derived hormone, is thought to represent a link between obesity and insulin-resistant diabetes. The potential role of resistin as a cardioprotective agent has not been explored. Our hypothesis is that resistin has a cardioprotective effect that is mediated by the resistin receptor-coupled activation of PI3K/Akt/PKC/KATP dependent pathways. Our studies demonstrated that pretreatment of mouse hearts with 10 nM resistin for 5 min protected the heart against I/R injury in a mouse heart perfusion model. When mouse hearts were subjected to 60 min of LAD ligation followed by 4 h of reperfusion, resistin pretreatment (33 μg/kg) for 30 min or 24 h before ligation was able to significantly reduce the infarct size/risk area. The protective effect of resistin was abolished by wortmannin, as well as by an Akt inhibitor, triciribine. Resistin's protective effect was absent in Akt kinase-deficient mutant mice. The protective effect was also blocked by chelerythrine, a PKC inhibitor, and εV1-2, a PKCε inhibitor. Finally, the protective effect was blocked by 5-hydroxydecanoate, which blocks the opening of mitoKATP channels. Resistin-induced Akt phosphorylation in HL-1 cells was inhibited by wortmannin and triciribine. Resistin also induced PKCε phosphorylation, which was blocked by triciribine. These studies demonstrate that resistin's cardioprotective effect is mediated by PI3K/Akt/PKC dependent pathways. In addition to cardiomyocytes, resistin also induced Akt phosphorylation in endothelial cells and smooth muscle cells, suggesting that resistin receptors are present in these cells. The effect of resistin on apoptosis was assessed in hearts subjected to 30 min of ischemia and 3 h of reperfusion. There were significantly fewer in situ oligo ligation-positive myocyte nuclei in mice treated with resistin. Our results show that resistin can dramatically reduce apoptosis and infarct size, thus protecting the heart against I/R injury.

Background: Transplantation of marrow stromal cells (MSC) has been shown to improve heart perfusion and cardiac function after ischemia. Erythropoietin (EPO) is capable of inducing angiogenesis and inhibiting cell apoptosis. The aim of this study was to investigate the effect of EPO on the therapeutic potency of MSC transplantation in a rat model of myocardial infarction. Methods: MSC viability was detected by MTT andflow cytometry following culture in serum-free medium for 24 h with or without EPO. Release of vascular endothelial growth factor (VEGF) by MSC incubated with different doses of EPO was assayed using ELISA. Immediately after coronary ligation, autologous MSC (3 × 10 6 cells) were injected into the ischemic myocardium (MSC and MSC-EPO groups). EPO (3,000 U/kg body weight) was injected daily for 3 consecutive days starting 1 day prior to ligation. The same EPO dose was also injected for consecutive 3 days starting 15 days after surgery (EPO and MSC-EPO groups). Control animals were injected saline solution for the same time period. Cardiac function was assessed by echocardiography 2 and 21 days after surgery, respectively. Western blot and immunohistological assessments were performed to examine the effects of treatments. Results: In vitro, EPO inhibited MSC apoptosis induced by serum-free medium and increased vascular endothelial growth factor (VEGF) release by MSC. In vivo, cardiac infarct size was significantly smaller, cardiac function significantly improved, and capillary density obviously higher in the MSC and EPO groups than in the control group. Combined treatment with EPO infusion and MSC transplantation demonstrated a further decrease in infarct size, a further improvement in cardiac function, and a further increase in capillary density compared with MSC or EPO alone. Furthermore, a higher ratio of phosphorylated Akt to total Akt was measured by Western blot; Bcl-2 was upregulated and Bax was downregulated by immunohistochemistry in the MSC-EPO group compared to the other three groups. Conclusion: Transplantation of MSC combined with EPO infusion is superior to MSC monotherapy for angiogenesis and cardiac function recovery.

We postulated that combining erythropoietin (EPO) infusion with bone marrow mesenchymal stem cells (MSC) delivery may give better prognosis in a rat infarcted heart. Acute myocardial infarction (MI) model was developed by coronary artery ligation. Animals were grouped (n = 18) to receive intramyocardial injection of 30 μl saline solution without cells (EPO and control groups) or with 3 × 106 MSC from transgenic green fluorescent protein (GFP)+ male mice (MSC and MSC-EPO groups). The animals received either 5000 U/kg body weight EPO (EPO and MSC-EPO groups) or saline solution (MSC and control groups) for 7 days after MI. Cardiac functions were measured by echocardiography and cardiac tissue was harvested for immunohistological studies 3 weeks after surgery. We observed regeneration of MSC in and around the infarcted myocardium in MSC and MSC-EPO groups. Capillary density was markedly enhanced with significantly smaller infarct size and reduced fibrotic area in MSC-EPO group as compared with other three groups. A smaller left ventricular (LV) diastolic dimension and a higher LV fractional shortening were observed in MSC-EPO group than in other three groups. Transplantation of MSC combined with cytokine EPO is superior to either of the monotherapy approach for angiomyogenesis and cardiac function recovery.

Experiments were performed to test the postulate that exercise training (ExT) improves the blunted renal excretory response to acute volume expansion (VE), in part, by normalizing the neural component of the volume reflex typically observed in chronic heart failure (HF). Diuretic and natriuretic responses to acute VE were examined in sedentary and ExT groups of rats with either HF or sham-operated controls. Experiments were performed in anesthetized (Inactin) rats 6 wk after coronary ligation surgery. Histological data indicated that there was a 34.9 ± 3.0% outer and 42.5 ± 3.2% inner infarct of the myocardium in the HF group. Sham rats had no observable damage to the myocardium. In sedentary rats with HF, VE produced a blunted diuresis (46% of sham) and natriuresis (35% of sham) compared with sham-operated control rats. However, acute VE-induced diuresis and natriuresis in ExT rats with HF were comparable to sham rats and significantly higher than sedentary HF rats. Renal denervation abolished the salutary effects of ExT on renal excretory response to acute VE in HF. Since glomerular filtration rates were not significantly different between the groups, renal hemodynamic changes may not account for the blunted renal responses in rats with HF. Additional experiments confirmed that renal sympathetic nerve activity responses to acute VE were blunted in sedentary HF rats; however, ExT normalized the renal sympathoinhibition in HF rats. These results confirm an impairment of neurally mediated excretory responses to acute VE in rats with HF. ExT restored the blunted excretory responses as well as the renal sympathoinhibitory response to acute VE in HF rats. Thus the beneficial effects of ExT on cardiovascular regulation in HF may be partly due to improvement of the neural component of volume reflex. Copyright © 2006 the American Physiological Society.