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Myocardial Regions (myocardial + regions)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

Differential levels of tissue hypoxia in the developing chicken heart

DEVELOPMENTAL DYNAMICS, Issue 1 2006
Jamie Wikenheiser
Abstract Tissue hypoxia plays a critical role in normal development, including cardiogenesis. Previously, we showed that oxygen concentration, as assessed by the hypoxia indicator EF5, is lowest in the outflow tract (OFT) myocardium of the developing chicken heart and may be regulating events in OFT morphogenesis. In this study, we identified additional areas of the embryonic chicken heart that were intensely positive for EF5 within the myocardium in discrete regions of the atrial wall and the interventricular septum (IVS). The region of the IVS that is EF5-positive includes a portion of the developing central conduction system identified by HNK-1 co-immunostaining. The EF5 positive tissues were also specifically positive for nuclear-localized hypoxia inducible factor 1, (HIF-1,), the oxygen-sensitive component of the hypoxia inducible factor 1 (HIF-1) heterodimer. The pattern of the most intensely EF5-stained myocardial regions of the atria and IVS resemble the pattern of the major coronary vessels that form in later stages within or immediately adjacent to these particular regions. These vessels include the sinoatrial nodal artery that is a branch of the right coronary artery within the atrial wall and the anterior/posterior interventricular vessels of the IVS. These findings indicate that a portion of the developing central conduction system and the patterning of coronary vessels may be subject to a level of regulation that is dependent on differential oxygen concentration within cardiac tissues and subsequent HIF-1 regulation of gene expression. Developmental Dynamics 235:115,123, 2006. © 2005 Wiley-Liss, Inc. [source]

Assessment of Myocardial Viability with Dobutamine Stress Echocardiography in Patients with Ischemic Left Ventricular Dysfunction

ECHOCARDIOGRAPHY, Issue 1 2005
Siu-Sun Yao M.D.
The noninvasive assessment of myocardial viability has proved clinically useful for distinguishing hibernating and/or stunned myocardium from irreversibly injured myocardium in patients with chronic ischemic heart disease or recent myocardial infarction, with marked regional and/or global left ventricular (LV) dysfunction. Noninvasive techniques utilized for the detection of viability in asynergic myocardial regions include positron emission tomographic imaging of residual metabolic activity, single photon emission tomography (SPECT) of radioisotope uptake with thallium-201, low-dose dobutamine echocardiography assessment of inotropic reserve and myocardial contrast echocardiography for evaluation of microvascular integrity. Of these techniques, dobutamine stress echocardiography is a safe, widely available and relatively inexpensive modality for the identification of myocardial viability for risk stratification and prognosis. Low-dose dobutamine response can accurately predict improvement of dysfunctional yet viable myocardial regions, and thus identify a subset of patients whose LV function will improve following successful coronary revascularization. [source]

Electrophoretic variants of cardiac myosin heavy chain-, in Sprague Dawley rats

ELECTROPHORESIS, Issue 3 2004
Peter J. Reiser
Abstract Analysis of cardiac myosin revealed differences in gel electrophoretic migration patterns of the ,-isoform of myosin heavy chain, but not the ,-isoform, in Sprague Dawley rats. No differences in the migration patterns of the ,-or ,-isoforms were observed in other rat strains. Three electrophoretic migration patterns of the ,-isoforms were observed in individual rats: a slower migrating isoform alone (4% of all rats tested), a faster migrating isoform alone (55%), and both isoforms (41%). The isoform expression pattern was identical in all myocardial regions in each rat. Frequency of expression patterns suggests multiple gene sequences for ,-cardiac myosin heavy chain in Sprague Dawley rats. Sequence analysis of amplified regions of the Sprague Dawley and Brown Norway rat ,-myosin genes, specifically the 5'-untranslated region, exons 1,3, and associated introns, showed numerous single nucleotide polymorphisms in coding and noncoding regions, including putative regulatory sites in Sprague Dawley rats, but not in Brown Norway rats. All Sprague Dawley rats varied from Brown Norway rats and no heterogeneity was observed in Brown Norway rats. Several deletions and dimorphic positions were also observed. Dimorphic positions were evident on automated sequencing comparisons. The data indicate that at least two ,-myosin heavy chain isoforms exist in Sprague Dawley rats and these rats exhibit sequence diversity within that portion of the ,-myosin heavy chain gene reported in this study. [source]

Anti-ischemic effects of inotropic agents in experimental right ventricular infarction

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2009
M. HEIN
Background: Right ventricular (RV) function is an important determinant of survival after myocardial infarction. The efficacy of reperfusion therapy might be increased by the cardioprotective action of inotropic agents, which are used for symptomatic therapy in situations with compromised hemodynamics. Therefore, we used a porcine model of RV ischemia and reperfusion (IR) injury to study the influence of milrinone, levosimendan and dobutamine on the extent and degree of myocardial injury. Methods: IR injury was induced by temporary ligation of the distal right coronary artery for 90 min, followed by 120 min of reperfusion. Treatment was initiated 30 min after coronary artery occlusion. A bolus of milrinone (n=12; 50 ,g/kg) and levosimendan (n=10; 24 ,g/kg) was applied in different groups, followed by continuous infusion of the drugs at 0.5 and 0.2 ,g/kg/min, respectively. The effects on myocardial injury and inflammation were compared with a control (n=12) and a dobutamine group (n=10), where treatment was started with an infusion of 5 ,g/kg/min. Results: Milrinone and levosimendan reduced the resulting infarct size with respect to the area at risk (41.7±10.2%, 45.7±8.1%) when compared with the control group (58.3±6.1%). In contrast, dobutamine had no effect (55.8±7.7%). All drugs reduced the number of neutrophils infiltrating into the different myocardial regions and the circulating levels of interleukin-6. Increased levels of tumor necrosis factor , during reperfusion were only abated by milrinone and levosimendan. Conclusions: Cardioprotective properties of milrinone and levosimendan were demonstrated for the first time in a clinically relevant model of RV infarction. [source]