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Cardiac Conduction System (cardiac + conduction_system)
Selected AbstractsCardiac expression patterns of endothelin-converting enzyme (ECE): Implications for conduction system developmentDEVELOPMENTAL DYNAMICS, Issue 6 2008David Sedmera Abstract The spatiotemporal distribution of the endothelin-converting enzyme (ECE) protein in the embryonic chick heart and the association of this polypeptide with the developing cardiac conduction system is described here for the first time. Further, we show how cardiac hemodynamic load directly affects ECE level and distribution. Endothelin (ET) is a cytokine involved in the inductive recruitment of Purkinje fibers. ET is produced by proteolytic cleavage of Big-ET by ECE. We generated an antibody against chick ECE recognizing a single band at ,70 kD to correlate the cardiac expression of this protein with that reported previously for its mRNA. ECE protein expression was more widespread compared to its mRNA, being present in endothelial cells, mesenchymal cells, and myocytes, and particularly enriched in the trabeculae and nascent ventricular conduction system. The myocardial expression was significantly modified under experimentally altered hemodynamic loading. In vivo, ET receptor blockade with bosentan delayed activation sequence maturation. These data support a role for ECE in avian cardiac conduction system differentiation and maturation. Developmental Dynamics 237:1746,1753, 2008. © 2008 Wiley-Liss, Inc. [source] Developmental expression and comparative genomic analysis of Xenopus cardiac myosin heavy chain genesDEVELOPMENTAL DYNAMICS, Issue 4 2005Robert J. Garriock Abstract Myosin heavy chains (MHC) are cytoskeletal motor proteins essential to the process of muscle contraction. We have determined the complete sequences of the Xenopus cardiac MHC genes, ,-MHC and ventricular MHC (vMHC), and have characterized their developmental expression profiles. Whereas ,-MHC is expressed from the earliest stages of cardiac differentiation, vMHC transcripts are not detected until the heart has undergone chamber formation. Early expression of vMHC appears to mark the cardiac conduction system, but expression expands to include the ventricle and outflow tract myocardium during subsequent development. Sequence comparisons, transgenic expression analysis, and comparative genomic studies indicate that Xenopus ,-MHC is the true orthologue of the mammalian ,-MHC gene. On the other hand, we show that the Xenopus vMHC gene is most closely related to chicken ventricular MHC (vMHC1) not the mammalian ,-MHC. Comparative genomic analysis has allowed the detection of a mammalian MHC gene (MyH15) that appears to be the orthologue of vMHC, but evidence suggests that this gene is no longer active. Developmental Dynamics 233:1287,1293, 2005. © 2005 Wiley-Liss, Inc. [source] Zebrafish IRX1b in the embryonic cardiac ventricle,DEVELOPMENTAL DYNAMICS, Issue 4 2004Elaine M. Joseph Abstract The synchronous contraction of the vertebrate heart requires a conduction system. While coordinated contraction of the cardiac chambers is observed in zebrafish larvae, no histological evidence yet has been found for the existence of a cardiac conduction system in this tractable teleost. The homeodomain transcription factor gene IRX1 has been shown in the mouse embryo to be a marker of cells that give rise to the distinctive cardiac ventricular conduction system. Here, I demonstrate that zebrafish IRX1b is expressed in a restricted subset of ventricular myocytes within the embryonic zebrafish heart. IRX1b expression occurs as the electrical maturation of the heart is taking place, in a location analogous to the initial expression domain of mouse IRX1. The gene expression pattern of IRX1b is altered in silent heart genetic mutant embryos and in embryos treated with the endothelin receptor antagonist bosentan. Furthermore, injection of a morpholino oligonucleotide targeted to block IRX1b translation slows the heart rate. Developmental Dynamics 231:720,726, 2004. © 2004 Wiley-Liss, Inc. [source] Wnt11 and Wnt7a are up-regulated in association with differentiation of cardiac conduction cells in vitro and in vivoDEVELOPMENTAL DYNAMICS, Issue 4 2003Jacqueline Bond Abstract The heart beat is coordinated by a precisely timed sequence of action potentials propagated through cells of the conduction system. Previously, we have shown that conduction cells in the chick embryo are derived from multipotent, cardiomyogenic progenitors present in the looped, tubular heart. Moreover, analyses of heterogeneity within myocyte clones and cell birth dating have indicated that elaboration of the conduction system occurs by ongoing, localized recruitment from within this multipotent pool. In this study, we have focused on a potential role for Wnt signaling in development of the cardiac conduction system. Treatment of embryonic myocytes from chick with endothelin-1 (ET-1) has been shown to promote expression of markers of Purkinje fiber cells. By using this in vitro model, we find that Wnt11 are Wnt7a are up-regulated in association with ET-1 treatment. Moreover, in situ hybridization reveals expression, although not temporal coincidence of, Wnt11 and Wnt7a in specialized tissues in the developing heart in vivo. Specifically, whereas Wnt11 shows transient and prominent expression in central elements of the developing conduction system (e.g., the His bundle), relative increases in Wnt7a expression emerge at sites consistent with the location of peripheral conduction cells (e.g., subendocardial Purkinje fibers). The patterns of Wnt11 and Wnt7a expression observed in vitro and in the embryonic chick heart appear to be consistent with roles for these two Wnts in differentiation of cardiac conduction tissues. Development Dynamics 227:536,543, 2003. © 2003 Wiley-Liss, Inc. [source] Natriuretic peptides in relation to the cardiac innervation and conduction systemMICROSCOPY RESEARCH AND TECHNIQUE, Issue 5 2002Magnus HanssonArticle first published online: 10 SEP 200 Abstract During the past two decades, the heart has been known to undergo endocrine action, harbouring peptides with hormonal activities. These, termed "atrial natriuretic peptide (ANP)," "brain natriuretic peptide (BNP)," and "C-type natriuretic peptide (CNP)," are polypeptides mainly produced in the cardiac myocardium, where they are released into the circulation, producing profound hypotensive effects due to their diuretic, natriuretic, and vascular dilatory properties. It is, furthermore, well established that cardiac disorders such as congestive heart failure and different forms of cardiomyopathy are combined with increased expression of ANP and BNP, leading to elevated levels of these peptides in the plasma. Besides the occurrence of natriuretic peptides (NPs) in the ordinary myocardium, the presence of ANP in the cardiac conduction system has been described. There is also evidence of ANP gene expression in nervous tissue such as the nodose ganglion and the superior cervical ganglion of the rat, ganglia known to be involved in the neuronal regulation of the heart. Furthermore, in the mammalian heart, ANP appears to affect the cardiac autonomic nervous system by sympathoinhibitory and vagoexcitatory actions. This article provides an overview of the relationship between the cardiac conduction system, the cardiac innervation and NPs in the mammalian heart and provides data for the concept that ANP is also involved in neuronal cardiac regulation. Microsc. Res. Tech. 58:378,386, 2002. © 2002 Wiley-Liss, Inc. [source] Three-dimensional anatomy of the conduction system of the early embryonic rabbit heartTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2006Florence Rothenberg Abstract The complete embryonic cardiac conduction system is difficult to view in three dimensions, primarily because there has not been a marker of all segments of the normal system throughout all stages of development. Imaging of the conduction system components within the atria has been particularly controversial because different markers reveal different pathways that may or may not represent conduction system components. The conduction system of the adult and embryonic rabbit, however, can be labeled in its entirety with the neurofilament marker, NF-160. The conduction system of rabbit embryos at several stages of development spanning cardiac septation was therefore investigated. Optical mapping of the electrical signature of the conduction system previously revealed a close correlation between the cardiac activation patterns and the anatomy as shown by serial sections. The 3D relationship between the components of the conduction system could only be inferred from the 2D sections. The sections were consequently reconstructed using a commercial software program (AutoQuant). This is the first demonstration of the three-dimensional complete normal rabbit embryonic cardiac conduction system at several stages of development. © 2005 Wiley-Liss, Inc. [source] Spatiotemporal pattern of commitment to slowed proliferation in the embryonic mouse heart indicates progressive differentiation of the cardiac conduction systemTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2003David Sedmera Abstract Patterns of DNA synthesis in the developing mouse heart between ED7.5,18.5 were studied by a combination of thymidine and bromodeoxyuridine labeling techniques. From earliest stages, we found zones of slow myocyte proliferation at both the venous and arterial poles of the heart, as well as in the atrioventricular region. The labeling index was distinctly higher in nonmyocardial populations (endocardium, epicardium, and cardiac cushions). Ventricular trabeculae showed lower proliferative activity than the ventricular compact layer after their appearance at ED9.5. Low labeling was observed in the pectinate muscles of the atria from ED11.5. The His bundle, bundle branches, and Purkinje fiber network likewise were distinguished by their lack of labeling. Thymidine birthdating (label dilution) showed that the cells in these emerging components of the cardiac conduction system terminally differentiated between ED8.5,13.5. These patterns of slowed proliferation correlate well with those in other species, and can serve as a useful marker for the forming conduction system. Anat Rec Part A 274A:773,777, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||