Biomedical subjects

Sharlene M Day

Publications and source records attributed to Sharlene M Day.

7 recordsLinked to original sources

PubMed2026

Social Determinants of Health and Clinical Outcomes in Hypertrophic Cardiomyopathy.

IMPORTANCE: Area-based indicators of social determinants of health (SDOH) are associated with higher risk for acquired heart disease, but their impact on conditions with a strong genetic etiology, such as hypertrophic cardiomyopathy (HCM), is not well understood. OBJECTIVE: To determine the association of area-based SDOH with clinical outcomes in patients with HCM. DESIGN, SETTING, AND PARTICIPANTS: This multicenter, prospective cohort study was conducted among US adult patients with HCM from 5 sites in the Sarcomeric Human Cardiomyopathy Registry (a multicenter prospective registry of patients with HCM) who were followed up for a median (IQR) period of 2.15 (0.15-5.82) years. Data were entered from 2015 to March 2024, and data analysis was completed from March 2024 to June 2025. EXPOSURES: Patients' residential addresses were geocoded at the zip code level and linked to the American Communities Survey to estimate area-based (1) median household income and (2) social deprivation index (SDI), which ranges from 0 to 100, with higher scores indicating a more deprived area. MAIN OUTCOMES AND MEASURES: Multivariate models, adjusting for age at diagnosis, body mass index, hypertension, and sex, were used to estimate the independent association of area-based median household income and SDI with heart failure (HF), ventricular arrhythmias (VA), and an overall composite outcome (VA, HF, atrial fibrillation, stroke, and death). RESULTS: Among 4431 US adult patients with HCM, median (IQR) age at HCM diagnosis was 51.3 (38.9-61.6) years, and 1862 patients (42.0%) were female. Median (IQR) area-based household income was $80 000 ($60 000-$110 000), and median (IQR) SDI was 25 (10-55). Adjusted hazard ratios comparing the lowest income group to the highest income group were 2.07 (95% CI, 1.77-2.42; P < .001) for HF, 1.31 (95% CI, 0.97-1.78; P = .08) for VA, and 1.52 (95% CI, 1.36-1.69; P < .001) for the overall composite outcome. Adjusted hazard ratios comparing the highest SDI (ie, more deprived) group to the lowest SDI group were 1.48 (95% CI, 1.29-1.70; P < .001) for HF, 1.55 (95% CI, 1.15-2.09; P = .004) for VA, and 1.36 (95% CI, 1.22-1.50; P < .001) for the overall composite outcome. CONCLUSIONS AND RELEVANCE: In this multicenter cohort study, residing in an area with lower median household income or worse SDI were each independently associated with adverse clinical outcomes in patients with HCM. These findings suggest that despite the genetically determined nature of HCM, place of residence is associated with patient outcomes.

Humans↗

PubMed2006

Histidine button engineered into cardiac troponin I protects the ischemic and failing heart.

The myofilament protein troponin I (TnI) has a key isoform-dependent role in the development of contractile failure during acidosis and ischemia. Here we show that cardiac performance in vitro and in vivo is enhanced when a single histidine residue present in the fetal cardiac TnI isoform is substituted into the adult cardiac TnI isoform at codon 164. The most marked effects are observed under the acute challenges of acidosis, hypoxia, ischemia and ischemia-reperfusion, in chronic heart failure in transgenic mice and in myocytes from failing human hearts. In the isolated heart, histidine-modified TnI improves systolic and diastolic function and mitigates reperfusion-associated ventricular arrhythmias. Cardiac performance is markedly enhanced in transgenic hearts during reperfusion despite a high-energy phosphate content similar to that in nontransgenic hearts, providing evidence for greater energetic economy. This pH-sensitive 'histidine button' engineered in TnI produces a titratable molecular switch that 'senses' changes in the intracellular milieu of the cardiac myocyte and responds by preferentially augmenting acute and long-term function under pathophysiological conditions. Myofilament-based inotropy may represent a therapeutic avenue to improve myocardial performance in the ischemic and failing heart.

Amino Acid Substitution↗

PubMed2005

Dystrophic heart failure blocked by membrane sealant poloxamer.

Dystrophin deficiency causes Duchenne muscular dystrophy (DMD) in humans, an inherited and progressive disease of striated muscle deterioration that frequently involves pronounced cardiomyopathy. Heart failure is the second leading cause of fatalities in DMD. Progress towards defining the molecular basis of disease in DMD has mostly come from studies on skeletal muscle, with comparatively little attention directed to cardiac muscle. The pathophysiological mechanisms involved in cardiac myocytes may differ significantly from skeletal myofibres; this is underscored by the presence of significant cardiac disease in patients with truncated or reduced levels of dystrophin but without skeletal muscle disease. Here we show that intact, isolated dystrophin-deficient cardiac myocytes have reduced compliance and increased susceptibility to stretch-mediated calcium overload, leading to cell contracture and death, and that application of the membrane sealant poloxamer 188 corrects these defects in vitro. In vivo administration of poloxamer 188 to dystrophic mice instantly improved ventricular geometry and blocked the development of acute cardiac failure during a dobutamine-mediated stress protocol. Once issues relating to optimal dosing and long-term effects of poloxamer 188 in humans have been resolved, chemical-based membrane sealants could represent a new therapeutic approach for preventing or reversing the progression of cardiomyopathy and heart failure in muscular dystrophy.

Animals↗

PubMed2004

Macrovascular thrombosis is driven by tissue factor derived primarily from the blood vessel wall.

Leukocytes and leukocyte-derived microparticles contain low levels of tissue factor (TF) and incorporate into forming thrombi. Although this circulating pool of TF has been proposed to play a key role in thrombosis, its functional significance relative to that of vascular wall TF is poorly defined. We tested the hypothesis that leukocyte-derived TF contributes to thrombus formation in vivo. Compared to wild-type mice, mice with severe TF deficiency (ie, TF(-/-), hTF-Tg+, or "low-TF") demonstrated markedly impaired thrombus formation after carotid artery injury or inferior vena cava ligation. A bone marrow transplantation strategy was used to modulate levels of leukocyte-derived TF. Transplantation of low-TF marrow into wild-type mice did not suppress arterial or venous thrombus formation. Similarly, transplantation of wild-type marrow into low-TF mice did not accelerate thrombosis. In vitro analyses revealed that TF activity in the blood was very low and was markedly exceeded by that present in the vessel wall. Therefore, our results suggest that thrombus formation in the arterial and venous macrovasculature is driven primarily by TF derived from the blood vessel wall as opposed to leukocytes.

Animals↗

PubMed2004

Parvalbumin corrects slowed relaxation in adult cardiac myocytes expressing hypertrophic cardiomyopathy-linked alpha-tropomyosin mutations.

Hypertrophic cardiomyopathy mutations A63V and E180G in alpha-tropomyosin (alpha-Tm) have been shown to cause slow cardiac muscle relaxation. In this study, we used two complementary genetic strategies, gene transfer in isolated rat myocytes and transgenesis in mice, to ascertain whether parvalbumin (Parv), a myoplasmic calcium buffer, could correct the diastolic dysfunction caused by these mutations. Sarcomere shortening measurements in rat cardiac myocytes expressing the alpha-Tm A63V mutant revealed a slower time to 50% relengthening (T50R: 44.2+/-1.4 ms in A63V, 36.8+/-1.0 ms in controls; n=96 to 108; P<0.001) when compared with controls. Dual gene transfer of alpha-Tm A63V and Parv caused a marked decrease in T50R (29.8+/-1.0 ms). However, this increase in relaxation rate was accompanied with a decrease in shortening amplitude (114.6+/-4.4 nm in A63+Parv, 137.8+/-5.3 nm in controls). Using an asynchronous gene transfer strategy, Parv expression was reduced (from approximately 0.12 to approximately 0.016 mmol/L), slow relaxation redressed, and shortening amplitude maintained (T50R=33.9+/-1.6 ms, sarcomere shortening amplitude=132.2+/-7.0 nm in A63V+PVdelayed; n=56). Transgenic mice expressing the E180G alpha-Tm mutation and mice expressing Parv in the heart were crossed. In isolated adult myocytes, the alpha-Tm mutation alone (E180G+/PV-) had slower sarcomere relengthening kinetics than the controls (T90R: 199+/-7 ms in E180G+/PV-, 130+/-4 ms in E180G-/PV-; n=71 to 72), but when coexpressed with Parv, cellular relaxation was faster (T90R: 36+/-4 ms in E180G+/PV+). Collectively, these findings show that slow relaxation caused by alpha-Tm mutants can be corrected by modifying calcium handling with Parv.

Actin Cytoskeleton↗

PubMed2004

Murine thrombosis models.

Due to exciting advances in molecular biology, the laboratory mouse has become an important and frequently used model for studying thrombosis. This article reviews several experimental approaches that have been used to study arterial, venous, and microvascular thrombosis in mice. The advantages and limitations of different models are examined. Related topics of mouse anesthesia, phlebotomy, and in vitro hemostasis testing are also reviewed.

Anesthesia↗

PubMed2003

Chronic iron administration increases vascular oxidative stress and accelerates arterial thrombosis.

BACKGROUND: Iron overload has been implicated in the pathogenesis of ischemic cardiovascular events. However, the effects of iron excess on vascular function and the thrombotic response to vascular injury are not well understood. METHODS AND RESULTS: We examined the effects of chronic iron dextran administration (15 mg over 6 weeks) on thrombosis, systemic and vascular oxidative stress, and endothelium-dependent vascular reactivity in mice. Thrombus generation after photochemical carotid artery injury was accelerated in iron-loaded mice (mean time to occlusive thrombosis, 20.4+/-8.5 minutes; n=10) compared with control mice (54.5+/-35.5 minutes, n=10, P=0.009). Iron loading had no effect on plasma clotting, vessel wall tissue factor activity, or ADP-induced platelet aggregation. Acute administration of dl-cysteine, a reactive oxygen species scavenger, completely abrogated the effects of iron loading on thrombus formation, suggesting that iron accelerated thrombosis through a pro-oxidant mechanism. Iron loading enhanced both systemic and vascular reactive oxygen species production. Endothelium-dependent vasorelaxation was impaired in iron-loaded mice, indicating reduced NO bioavailability. CONCLUSIONS: Moderate iron loading markedly accelerates thrombus formation after arterial injury, increases vascular oxidative stress, and impairs vasoreactivity. Iron-induced vascular dysfunction may contribute to the increased incidence of ischemic cardiovascular events that have been associated with chronic iron overload.

Adenosine Diphosphate↗