Abstract-Oxidative stress stimulates both growth and apoptosis in cardiac myocytes in vitro. We investigated whether oxidative stress mediates hypertrophy and apoptosis in cyclically stretched ventricular myocytes. Neonatal rat ventricular myocytes cultured on laminin-coated silastic membranes were stretched cyclically (1 Hz) at low (nominal 5%) and high (nominal 25%) amplitudes for 24 hours. Stretch caused a graded increase in superoxide anion production as assessed by superoxide dismutase (SOD)-inhibitable cytochrome c reduction or electron paramagnetic resonance spectroscopy. The role of reactive oxygen species (ROS) was assessed using the cell-permeable SOD/catalase mimetics Mn(II/III)tetrakis(1-methyl-4-peridyl) (MnTMPyP) and EUK-8. Stretch-induced increases in protein synthesis ( 3 Hleucine incorporation) and cellular protein content were completely inhibited by MnTMPyP (0.05 mmol/L) at both low and high amplitudes of stretch. In contrast, while MnTMPyP inhibited basal atrial natriuretic factor (ANF) mRNA expression, the stretch-induced increase in ANF mRNA expression was not inhibited by MnTMPyP. In contrast to hypertrophy, only high-amplitude stretch increased myocyte apoptosis, as reflected by increased DNA fragmentation on gel electrophoresis and an Ϸ3-fold increase in the number of TUNEL-positive myocytes. Similarly, only high-amplitude stretch increased the expression of bax mRNA. Myocyte apoptosis and bax expression stimulated by high-amplitude stretch were inhibited by MnTMPyP. Both low-and high-amplitude stretch caused rapid phosphorylation of ERK1/2, while high-, but not low-, amplitude stretch caused phosphorylation of JNKs. Activation of both ERK1/2 and JNKs was ROS-dependent. Thus, cyclic strain causes an amplitude-related increase in ROS, associated with differential activation of kinases and induction of hypertrophic and apoptotic phenotypes.

Neuregulins (i.e. neuregulin-1 (NRG1), also called neu differentiation factor, heregulin, glial growth factor, and acetylcholine receptor-inducing activity) are known to induce growth and differentiation of epithelial, glial, neuronal, and skeletal muscle cells. Unexpectedly, mice with loss of function mutations of NRG1 or of either of two of their cognate receptors, ErbB2 and ErbB4, die during midembryogenesis due to the aborted development of myocardial trabeculae in ventricular muscle. To examine the role of NRG and their receptors in developing and postnatal myocardium, we studied the ability of a soluble NRG1 (recombinant human glial growth factor 2) to promote proliferation, survival, and growth of isolated neonatal and adult rat cardiac myocytes. Both ErbB2 and ErbB4 receptors were found to be expressed by neonatal and adult ventricular myocytes and activated by rhGGF2. rhGGF2 (30 ng/ml) provoked an approximate 2-fold increase in embryonic cardiac myocyte proliferation. rhGGF2 also promoted survival and inhibited apoptosis of subconfluent, serum-deprived myocyte primary cultures and also induced hypertrophic growth in both neonatal and adult ventricular myocytes, which was accompanied by enhanced expression of prepro-atrial natriuretic factor and skeletal ␣-actin. Moreover, NRG1 mRNA could be detected in coronary microvascular endothelial cell primary cultures prepared from adult rat ventricular muscle. NRG1 expression in these cells was increased by endothelin-1, another locally acting cardiotropic peptide within the heart. The persistent expression of both a neuregulin and its cognate receptors in the postnatal and adult heart suggests a continuing role for neuregulins in the myocardial adaption to physiologic stress or injury.

Neuregulins are a family of growth-promoting peptides known to be important in neural and mesenchymal tissue development. Targeted disruption of neuregulin (NRG)-1 or one of two of its cognate receptors, ErbB2 or ErbB4, results in embryonic lethality because of failure of the heart to develop. Although expression of NRGs and their receptors declines after midembryogenesis, both ErbB2 and ErbB4 are present in cardiac myocytes, and NRG-1 expression remains inducible in primary cultures of coronary microvascular endothelial cells from adult rat ventricular muscle. In neonatal rat ventricular myocytes, a soluble NRG-1, recombinant human glial growth factor-2, increased [(3)H]phenylalanine uptake and induced expression of atrial natriuretic factor (ANF) and sarcomeric F-actin polymerization. The effect of NRG-1 on [(3)H]phenylalanine uptake and sarcomeric F-actin polymerization was maximal at 20 ng/ml but declined at higher concentrations. NRG-1 activated p42/p44 mitogen-activated protein kinase (MAPK) [extracellular signal-regulated kinase (ERK)-2/ERK1] and ribosomal S6 kinase (RSK)-2 (90-kDa ribosomal S6 kinase), both of which could be inhibited by the MAPK/ERK kinase-1 antagonist PD-098059. NRG-1 also activated 70-kDa ribosomal S6 kinase, which was inhibited by either rapamycin or wortmannin. Activation of these pathways exhibited the same "biphasic" response to increasing NRG-1 concentrations. Wortmannin and LY-294002 blocked sarcomeric F-actin polymerization but not [(3)H]phenylalanine uptake or ANF expression, whereas PD-098059 consistently blocked both [(3)H]phenylalanine uptake and ANF expression but not actin polymerization. In contrast, rapamycin inhibited [(3)H]phenylalanine uptake and F-actin polymerization but not ANF expression. Thus NRG-ErbB signaling triggers multiple nonredundant pathways in postnatal ventricular myocytes.

Aortic aneurysm and acute aortic syndrome are not uncommon conditions. Management of acute aortic dissection and related syndromes requires a multidisciplinary approach with input from the patient, clinician, imager, surgeon, and anesthesiologist. This requires an integrated evaluation of pathophysiology, anatomy, and severity to enable appropriate therapy. This review includes discussion of essential anatomy of the aortic valve and the aorta that determines the candidacy for surgical repair. It also includes discussion of various imaging modalities, particularly echocardiography, cardiac computed tomography, and cardiac magnetic resonance angiography. The relative benefits and demerits of each of these techniques are reviewed. This paper is intended to help guide management decisions for patients with acute aortic dissection and related syndromes.

Patients with coronary artery disease or heart failure have been shown to be insulin resistant. Whether in these patients heart muscle participates in the insulin resistance, and whether reduced blood flow is a mechanism for such resistance is not known. We measured heart and skeletal muscle blood flow and glucose uptake during euglycemic hyperinsulinemia (insulin clamp) in 15 male patients with angiographically proven coronary artery disease and chronic regional wall motion abnormalities. Six age-and weightmatched healthy subjects served as controls. Regional glucose uptake was measured by positron emission tomography using [

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Although this is a preliminary study, the finding suggests a new therapeutic approach to a large proportion of GHD patients with CHF.

Abstract-British Indian Asian men aged Ͻ40 years have a twofold to threefold increased risk of death from coronary heart disease (CHD) compared with British whites. Epidemiological studies have suggested an association between glucose intolerance and hyperinsulinemia with premature CHD in Indian Asians. We tested the association of insulin action with myocardial infarction (MI) by using the hyperinsulinemic-euglycemic clamp in 17 MI patients: 8 Punjabi Sikhs (PSMIs), 9 British whites (BWMIs), and 17 control subjects (9 PSCs and 8 BWCs Key Words: myocardial infarction Ⅲ abdominal obesity Ⅲ nonesterified fatty acids Ⅲ insulin resistance P remature CHD mortality is higher in British Indian Asians than in British whites. 1 Increased mortality in Indian Asians is particularly marked in men aged 30 to 39 years, in whom the relative risk of death from CHD is 2, and in men aged 20 to 29, for whom the relative risk is 3, compared with age-matched whites.1 Conventional risk factors, including smoking, hypercholesterolemia, or hypertension, do not account for the higher cardiovascular mortality in this population group.2 In fact, the prevalence of these risk factors is generally reduced in Indian Asians compared with whites.2 Insulin resistance and its metabolic consequences are increasingly recognized as risk factors for CHD.3-11 However, the association of insulin action with MI has not been formally examined in Indian Asians or in British whites. We studied Punjabi Sikh (Indian Asian [PS]) survivors of premature MI for defects of insulin action. A comparable group of white MI survivors (BWMI) was also studied. Familial aggregation of defective insulin action was examined by investigating first-degree relatives of Sikh MI patients to search for early markers of MI. Methods SubjectsSeventeen male MI patients (8 PSMIs and 9 BWMIs) and 17 control subjects (9 PSCs and 8 BWCs) underwent the hyperinsulinemiceuglycemic clamp study to test the association of insulin action with MI. Fifty-one male MI patients (24 PSMIs and 27 BWMIs) and 53