Frederic S Michel

Frederic S Michel
University of the Witwatersrand | wits · Faculty of Health Sciences

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37
Publications
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476
Citations

Publications

Publications (37)
Article
Full-text available
Quercetin is known to reduce blood pressure (BP); however, its acute effects are unclear. We investigated the acute effects of quercetin on BP, aortic mechanical properties and vascular reactivity in female Sprague–Dawley (SD) rats. Hypertension was induced using L‐NAME (40 mg/kg/day). Quercetin (4.5 mg/kg) was administered intravenously. Mechanica...
Article
Full-text available
Hypertension drives the development of concentric left ventricular hypertrophy (LVH). However, the relative contribution of pentraxin‐3 (PTX‐3), a novel marker for inflammatory cardiovascular disease, in the hypertrophic response to pressure overload has not been adequately elucidated. We investigated the role of PTX‐3 in the development of LVH in...
Article
Background MicroRNAs have been implicated in the pathogenesis of cardiovascular disease. However, the contribution of microRNAs remain poorly understood in the context of hypertensive cardiac pathology. Aim We investigated the role of miR-146a-5p, -155-5p, and -29b-5p in the development of cardiac hypertrophy and dysfunction in male and female spo...
Article
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A patent foramen ovale (PFO) is associated with numerous clinical conditions. The most severe of these is cryptogenic stroke. This consensus statement aims to provide a clinical guideline on which patients should be offered PFO closure.
Article
Full-text available
Chronic inflammation causes dysregulated expression of microRNAs. Aberrant microRNA expression is associated with endothelial dysfunction. In this study we determined whether TNF-α inhibition impacted the expression of miRNA-146a-5p and miRNA-155-5p, and whether changes in the expression of these miRNAs were related to inflammation-induced changes...
Article
Objective: Estrogen deficiency is associated with left ventricular (LV) dysfunction in postmenopausal women and ovariectomized rats. Whether the relationship between estrogen deficiency and LV dysfunction is independent of cardiovascular disease (CVD) risk factors remains uncertain. This study assessed the effects of short-term and long-term estro...
Article
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Background High-grade inflammation may play a pivotal role in the pathogenesis of left ventricular (LV) dysfunction. Evidence to support a role of systemic inflammation in mediating impaired LV function in experimental models of rheumatoid arthritis (RA) remains limited. The aim of the present study was to determine the effects of high-grade system...
Article
Full-text available
Rheumatoid arthritis (RA) impacts arterial and diastolic function. This study examined whether arterial properties can determine diastolic function in RA. In 173 RA patients, arterial function measures including carotid femoral pulse wave velocity (PWV), central systolic and pulse pressure, pulse pressure amplification, and the magnitude and timing...
Article
We determined the role of high-grade inflammation on endothelial function and its association with biomarkers of endothelial dysfunction in collagen-induced arthritis. Sprague-Dawley rats were divided into a control (n = 12) or collagen-induced arthritis (CIA; n = 21) group. To induce arthritis, Bovine-type-II collagen emulsified in incomplete Freu...
Article
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The effect of hyperlipidemia on the cardiovascular system is uncertain in females. The aim of the present study was to determine whether administration of a lipogenic diet alters cardiovascular parameters in female rats. Fifty female Sprague-Dawley rats were assigned into 2 groups of rats receiving a standard or a high-fat, high-sucrose diet (HFHS)...
Conference Paper
Background Patients with rheumatoid arthritis (RA) experience an increased risk of developing heart failure with a preserved ejection fraction. Although there is some evidence to support a role of chronic inflammation in the pathogenesis of impaired left ventricular (LV) function in RA,¹ the direct effects of inflammatory cytokines on the LV functi...
Conference Paper
Full-text available
Background Patients with rheumatoid arthritis (RA) experience an increased frequency of heart failure with a preserved ejection fraction (HFpEF) (1). The treatment of HFpEF is currently suboptimal. Elucidation of the underlying pathophysiological mechanisms of HFpEF may provide potential targets for its management. Diastolic dysfunction often prece...
Article
Sodium (Na)-intake increases vascular reactivity. Whether low potassium (K)-intake affects vascular reactivity associated blood pressure (BP) changes is uncertain. This study aimed to determine whether Na-induced increases in BP and vascular reactivity are altered by low K-intake. Male Sprague-Dawley rats were assigned to three dietary groups for s...
Article
Background: Left ventricular (LV) diastolic dysfunction characterizes heart failure with a preserved ejection fraction. Although it is recognized that the renin-angiotensin-aldosterone-system (RAAS) decreases LV diastolic function, whether systemic angiotensinogen contributes to these effects is uncertain. Hence the aim was to determine the relati...
Article
Chronic β-adrenergic stimulation induces left ventricular (LV) remodelling in male but not in female spontaneously hypertensive rats (SHR). However the role of sex-steroids in mediating these effects has not been determined. The aim of the present study was to assess the impact of gonadectomy on isoproterenol (ISO)-induced LV remodeling in SHR. Gon...
Article
Objective: The aim of this work was to determine whether adrenergic-induced left ventricular (LV) dilation and eccentric remodeling in pressure-overload hypertrophy is sex specific. Methods and results: Chronic β-adrenoreceptor activation was produced in male and female spontaneously hypertensive rats (SHRs) by means of daily administration of i...
Article
Aims: The role of the adipokine, resistin in mediating increases in aortic stiffness is uncertain. We aimed to determine independent relations between circulating resistin concentrations and aortic pulse wave velocity (PWV) and wave reflection in a community-based sample with a high prevalence of untreated hypertension and obesity. Methods: Plas...
Article
Although the adipokine resistin may play a role in heart failure, the mechanisms of this effect are uncertain. Relations with left ventricular mass (LVM) and function are uncertain. In 739 randomly selected participants from a community sample (43.6% obese), we assessed relations between circulating resistin concentrations and LVM index (LVMI), LVM...
Article
Obesity causes an increased blood pressure (BP). This effect may be diminished in communities of African descent. However, the impact of obesity on ambulatory or aortic BP, which are enhanced in groups of African ancestry, has not been assessed. We aimed to determine the extent to which obesity is related to variations in office, ambulatory and aor...
Article
Full-text available
Objectives Whether a human immunodeficiency virus (HIV)-associated vasculitis in-part accounts for occlusive large artery disease remains uncertain. We aimed to identify the histopathological features that characterize large vessel changes in HIV sero-positive as compared to sero-negative patients with critical lower limb ischemia (CLI). Materials...
Article
Full-text available
Although the circulating renin-angiotensin system (RAS) is suppressed in salt-sensitive populations, the role of the intrarenal RAS in blood pressure (BP) control in these groups independent of the circulating RAS is uncertain. We evaluated the relationship between 24-hour urinary angiotensinogen excretion and either office (mean of 5 measurements;...
Article
A reduced testosterone concentration characterizes heart failure and independently predicts outcomes. Although testosterone replacement therapy may have non-cardiac-related therapeutic benefits in heart failure, whether reduced testosterone concentrations protect against adverse left ventricular remodelling (LV dilatation) is uncertain. We therefor...
Article
Full-text available
Background: Primary healthcare is the foundation of a country's healthcare system. Without an efficient and cost-effective programme, the level of healthcare offered across all levels of health management is adversely affected. Objective: To analyse the effectiveness of the management of hypertension and diabetes mellitus (DM) among two distinct...
Article
To determine whether increases in central aortic pulse pressure (PPc), but decreases in carotid-femoral pulse wave velocity (PWV) predict the presence of advanced peripheral arterial disease (PAD). Applanation tonometry and vascular ultrasound were employed to assess carotid-femoral PWV, PPc, and carotid intima media thickness (IMT) in 136 patients...
Article
Background: Although groups of African descent are particularly sensitive to blood pressure (BP) effects of salt intake, the role of obesity and insulin resistance in mediating this effect is uncertain. We determined whether obesity or insulin resistance is independently associated with urinary Na(+)/K(+)-BP relationships in a community sample of...
Article
Aim: We determined whether left ventricular hypertrophy (LVH) which exceeds that predicted from workload [inappropriate LV mass (LVM(inappr))] is associated with reduced left ventricle (LV) systolic chamber function independent of and more closely than absolute or indexed left ventricular mass (LVM). Methods: In 626 randomly selected adult parti...
Article
Although an increased aortic pulse wave velocity (PWV) may be employed to predict cardiovascular risk, the extent to which this may be limited by decreases in PWV in peripheral arterial disease (PAD) is uncertain. Applanation tonometry (SphygmoCor software) and vascular B-mode ultrasound were employed to assess carotid-femoral PWV and carotid intim...
Article
Full-text available
In high-Na(+), low-K(+) diets, which suppress renin release in salt-sensitive groups, the mechanisms maintaining increases in renin-angiotensin-aldosterone system activation downstream from renin and renin-angiotensin-aldosterone system-induced effects on blood pressure (BP) are uncertain. Whether circulating angiotensinogen concentrations (AGT) or...
Article
Experiments were designed to determine the modulation by nitric oxide (NO) and endothelium-dependent hyperpolarizations (EDHF-mediated responses) of endothelium-dependent contractions in renal arteries of normotensive and hypertensive rats. Rings, with or without endothelium, of renal arteries of 8-month-old Wistar Kyoto rats (WKY) and spontaneousl...
Article
Full-text available
Early manifestations of kidney disease occur in atherosclerosis and activation of TP (thromboxane A(2)) receptors is implicated in atherosclerotic, diabetes, and renal diseases. The purpose of the present study was to analyze, in isolated, perfused mouse kidneys, the participation of TP receptors in renal vasoconstrictions and vasodilatations. In k...
Article
The spontaneous tone of vascular smooth muscle is augmented in hypertension. The present study examined the role of nitric oxide (NO), cyclooxygenase (COX), thromboxane A(2)/prostanoid (TP) and PGE(2)/prostanoid (EP-1) receptors, reactive oxygen species, and large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels in the regulation of spontaneous...
Article
We analyzed the involvement of thromboxane (TX) A2/prostaglandin (PG) H2 (TP) receptor in ischemia-induced neovascularization in mice. Unilateral hindlimb ischemia was induced by right femoral artery ligature in male C57BL/6J mice (n=7 per group). Animals were then treated with or without TP receptor antagonist (S18886, 5 or 10 mg/kg per day; ramat...
Article
We analyzed the role of aldosterone in ischemia-induced neovascularization and the involvement of angiotensin II (Ang II) signaling in this effect. Ischemia was induced by right femoral artery ligature in mice treated or not with aldosterone (4.5 microg/day), aldosterone plus spironolactone (aldosterone receptor blocker; 20 mg/kg per day), or aldos...
Article
The aim of the study was to investigate in vivo arterial reactivity in the mouse hind limb using Orthogonal Polarisation Spectral (OPS) imaging, which delivers high-contrast images of vascular beds by visualizing red blood cells. After minimal skin invasion of anesthetized mice, the OPS probe was placed on the hind limb continuously superfused with...

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