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Jörg Männer - One of the best experts on this subject based on the ideXlab platform.
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Functional Morphology of the Cardiac Jelly in the Tubular Heart of Vertebrate Embryos
Journal of Cardiovascular Development and Disease, 2019Co-Authors: Jörg Männer, T. M. YelbuzAbstract:The early embryonic Heart is a multi-layered tube consisting of (1) an outer myocardial tube; (2) an inner endocardial tube; and (3) an extracellular matrix layer interposed between the myocardium and endocardium, called “cardiac jelly” (CJ). During the past decades, research on CJ has mainly focused on its molecular and cellular biological aspects. This review focuses on the morphological and biomechanical aspects of CJ. Special attention is given to (1) the spatial distribution and fiber architecture of CJ; (2) the morphological dynamics of CJ during the cardiac cycle; and (3) the removal/remodeling of CJ during advanced Heart looping stages, which leads to the formation of ventricular trabeculations and endocardial cushions. CJ acts as a hydraulic skeleton, displaying striking structural and functional similarities with the mesoglea of jellyfish. CJ not only represents a filler substance, facilitating end-systolic occlusion of the embryonic Heart lumen. Its elastic components antagonize the systolic deformations of the Heart wall and thereby power the refilling phase of the ventricular tube. Non-uniform spatial distribution of CJ generates non-circular cross sections of the opened endocardial tube (initially elliptic, later deltoid), which seem to be advantageous for valveless pumping. Endocardial cushions/ridges are cellularized remnants of non-removed CJ.
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Functional Morphology of the Cardiac Jelly in the Tubular Heart of Vertebrate Embryos.
Journal of Cardiovascular Development and Disease, 2019Co-Authors: Jörg Männer, T. M. YelbuzAbstract:The early embryonic Heart is a multi-layered tube consisting of (1) an outer myocardial tube; (2) an inner endocardial tube; and (3) an extracellular matrix layer interposed between the myocardium and endocardium, called “cardiac jelly” (CJ). During the past decades, research on CJ has mainly focused on its molecular and cellular biological aspects. This review focuses on the morphological and biomechanical aspects of CJ. Special attention is given to (1) the spatial distribution and fiber architecture of CJ; (2) the morphological dynamics of CJ during the cardiac cycle; and (3) the removal/remodeling of CJ during advanced Heart looping stages, which leads to the formation of ventricular trabeculations and endocardial cushions. CJ acts as a hydraulic skeleton, displaying striking structural and functional similarities with the mesoglea of jellyfish. CJ not only represents a filler substance, facilitating end-systolic occlusion of the embryonic Heart lumen. Its elastic components antagonize the systolic deformations of the Heart wall and thereby power the refilling phase of the ventricular tube. Non-uniform spatial distribution of CJ generates non-circular cross sections of the opened endocardial tube (initially elliptic, later deltoid), which seem to be advantageous for valveless pumping. Endocardial cushions/ridges are cellularized remnants of non-removed CJ.
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Functional Morphology of the Cardiac Jelly in the Tubular Heart of Vertebrate Embryos
2019Co-Authors: Jörg Männer, T. M. YelbuzAbstract:The early embryonic Heart is a multi-layered tube consisting of (1) an outer myocardial tube; (2) an inner endocardial tube; and (3) an extracellular matrix layer interposed between myocardium and endocardium, called “cardiac jelly” (CJ). During the past decades, research on CJ has mainly focused on its molecular and cell biological aspects. This review focuses on the morphological and biomechanical aspects of CJ. Special attention is given to (1) the spatial distribution and fiber architecture of CJ; (2) the morphological dynamics of CJ during the cardiac cycle; and (3) the removal/remodeling of CJ during advanced Heart looping stages, which leads to the formation of ventricular trabeculations and endocardial cushions. CJ acts as a hydraulic skeleton displaying striking structural and functional similarities with the mesoglea of jellyfish. CJ not only represents a filler substance, facilitating end-systolic occlusion of the embryonic Heart lumen. Its elastic components antagonize the systolic deformations of the Heart wall and thereby power the refilling phase of the ventricular tube. Non-uniform spatial distribution of CJ generates non-circular cross sections of the opened endocardial tube (initially elliptic, later deltoid), which seem to be advantageous for valveless pumping. Endocardial cushions arise from non-removed remnants of the original CJ.
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Functional Morphology of the Cardiac Jelly in the Tubular Heart of Vertebrate Embryos
2019Co-Authors: Jörg Männer, T. M. YelbuzAbstract:The early embryonic Heart is a multi-layered tube consisting of (1) an outer myocardial tube; (2) an inner endocardial tube; and (3) an extracellular matrix layer interposed between myocardium and endocardium, called “cardiac jelly” (CJ). During the past decades, research on CJ has mainly focused on its molecular and cell biological aspects. This review focuses on the morphological and biomechanical aspects of CJ. Special attention is given to (1) the spatial distribution and fiber architecture of CJ; (2) the morphological dynamics of CJ during the cardiac cycle; and (3) the removal/remodeling of CJ during advanced Heart looping stages, which leads to the formation of ventricular trabeculations and endocardial cushions. CJ acts as a hydraulic skeleton displaying striking structural and functional similarities with the mesoglea of jellyfish. CJ not only represents a filler substance, facilitating end-systolic occlusion of the embryonic Heart lumen. Its elastic components antagonize the systolic deformations of the Heart wall and thereby power the refilling phase of the ventricular tube. Non-uniform spatial distribution of CJ generates non-circular cross sections of the opened endocardial tube (initially elliptic, later deltoid), which seem to be advantageous for valveless pumping. Endocardial cushions arise from non-removed remnants of the original CJ.
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how does the Tubular embryonic Heart work looking for the physical mechanism generating unidirectional blood flow in the valveless embryonic Heart tube
Developmental Dynamics, 2010Co-Authors: Jörg Männer, Armin Wessel, Mesud T YelbuzAbstract:The Heart is the first organ to function in vertebrate embryos. The human Heart, for example, starts beating around the 21st embryonic day. During the initial phase of its pumping action, the embryonic Heart is seen as a pulsating blood vessel that is built up by (1) an inner endothelial tube lacking valves, (2) a middle layer of extracellular matrix, and (3) an outer myocardial tube. Despite the absence of valves, this Tubular Heart generates unidirectional blood flow. This fact poses the question how it works. Visual examination of the pulsating embryonic Heart tube shows that its pumping action is characterized by traveling mechanical waves sweeping from its venous to its arterial end. These traveling waves were traditionally described as myocardial peristaltic waves. It has, therefore, been speculated that the Tubular embryonic Heart works as a technical peristaltic pump. Recent hemodynamic data from living embryos, however, have shown that the pumping function of the embryonic Heart tube differs in several respects from that of a technical peristaltic pump. Some of these data suggest that embryonic Heart tubes work as valveless “Liebau pumps.” In the present study, a review is given on the evolution of the two above-mentioned theories of early cardiac pumping mechanics. We discuss pros and cons for both of these theories. We show that the Tubular embryonic Heart works neither as a technical peristaltic pump nor as a classic Liebau pump. The question regarding how the embryonic Heart tube works still awaits an answer. Developmental Dynamics 239:1035–1046, 2010. © 2010 Wiley-Liss, Inc.
Christian S Wirkner - One of the best experts on this subject based on the ideXlab platform.
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Comparative morphology of the hemolymph vascular system in mygalomorphs (Araneae: Opisthothelae)
The Journal of Arachnology, 2019Co-Authors: Katarina Huckstorf, Christian S WirknerAbstract:Mygalomorphs are a well-known spider group; however, astonishingly little is known about their internal anatomy. As part of a comparative survey on the circulatory system in spiders, we conducted an examination of the hemolymph vascular system (HVS) and parts of the hemolymph lacunar system (HLS) in five mygalomorph spider species. Circulatory system features were investigated using micro-computer-tomography in combination with resin injection methods and serial sectioning. Data were visualized using a 3D-reconstruction software. The HVS consists of a Tubular Heart, which is situated along the dorsal midline of the opisthosoma. Anteriorly, the Heart gives rise to the anterior aorta. A posterior aorta system was not found. Three pairs of cardiac arteries originate laterally from the Heart and the branching pattern of these arteries is visualized and described here for the first time. The anterior aorta runs through the pedicel into the prosoma where it branches to supply the muscles and particularly the central nervous system. The data on mygalomorphs are discussed in comparison to the HVS in other Araneae.
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The hemolymph vascular system in Araneus diadematus with special focus on intraspecific variability in artery systems
Journal of Arachnology, 2016Co-Authors: Jens Runge, Christian S WirknerAbstract:Abstract The European garden spider, Araneus diadematus Clerck, 1757, is one of the most common spiders in central Europe. However, despite its abundance, comparatively little is known about its internal anatomy. We therefore conducted an examination of the hemolymph vascular system (HVS) of A. diadematus, as part of a comparative survey on the circulatory system in spiders. The HVS of A. diadematus was investigated using micro-computed-tomography and serial sectioning and visualized using 3D-reconstruction software. In order to examine the HVS for intraspecific variability, over 30 specimens were studied in detail. The HVS of A. diadematus consists of a Tubular Heart, which is situated along the dorsal midline of the opisthosoma. Anteriorly, the Heart gives rise to the anterior aorta and posteriorly to the posterior aorta. Three pairs of cardiac arteries originate from the dorso-lateral section of the Heart and the branching pattern of these arteries in A. diadematus is visualized and described here for ...
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8 Chilopoda – Circulatory system
Treatise on Zoology - Anatomy Taxonomy Biology. The Myriapoda Volume 1, 2011Co-Authors: Christian S Wirkner, Gero Hilken, Jörg RosenbergAbstract:The tracheal and circulatory systems are well developed in centipedes. These differ in this respect from hexapods, which possess a well developed tracheal system but a rather reduced circulatory system. The Tubular Heart, the most important pumping organ, runs the entire length of the trunk. Off the Heart in Scutigeromorpha and Scolopendromorpha, paired cardiac arteries emanate below every pair of ostia. Apart from the maxilliped arch, a mandibular arch can be found in Lithobius forficatus , formed by two arteries emanating from the anterior aorta uniting again underneath the foregut. The Heart tube in chilopods is surrounded by cells that were early on termed lymphatic glands or pericardial cells. In L. forficatus and in Strigamia maritima , the Heart is well innervated and the axons are covered by a myelin sheath. Two nerves emanating from the subesophageal ganglion connect to the dorsal Heart nerve close to the first pair of ostia. Keywords:centipedes; circulatory system; Heart; L. forficatus ; ostia; scolopendromorpha; scutigeromorpha
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morphology of the haemolymph vascular system in tanaidacea and cumacea implications for the relationships of core group peracarida malacostraca crustacea
Arthropod Structure & Development, 2008Co-Authors: Christian S Wirkner, Stefan RichterAbstract:Abstract Tanaidacea and Cumacea are crucial for understanding the phylogenetic relationships of “core group” peracarids. Here, the haemolymph vascular system in three tanaidacean and four cumacean species was studied on the basis of histological sections and 3D reconstruction. The circulatory organs in Tanaidacea include a Tubular Heart which extends through most of the thorax. It is extended into the cephalothorax by an anterior aorta. Haemolymph enters the Heart through one to two pairs of incurrent ostia. Up to five pairs of cardiac arteries emanate from the Heart to supply viscera in the body cavity. In the anterior cephalothorax, the aorta forms a pericerebral ring from which the arteries for the brain and the antennae branch off. In Cumacea, the Heart is shorter but more voluminous. In all cumaceans studied, five pairs of cardiac arteries supply the thoracopods and the pleon. The single pair of ostia is situated in the centre of the Heart. The anterior aorta runs into the anterior cephalothorax where it supplies the brain and antennae. This paper provides a general comparative discussion of all available data from the literature and the data provided herein. In certain details, the haemolymph vascular system of the Tanaidacea resembles that of Amphipoda, and some correspondences between Cumacea and Isopoda are pointed out. These findings might support a closer relationship between the latter two taxa while they show no support for an amphipod/isopod clade.
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Morphology of the haemolymph vascular system in Tanaidacea and Cumacea: – Implications for the relationships of “core group” Peracarida (Malacostraca; Crustacea)
Arthropod Structure & Development, 2007Co-Authors: Christian S Wirkner, Stefan RichterAbstract:Abstract Tanaidacea and Cumacea are crucial for understanding the phylogenetic relationships of “core group” peracarids. Here, the haemolymph vascular system in three tanaidacean and four cumacean species was studied on the basis of histological sections and 3D reconstruction. The circulatory organs in Tanaidacea include a Tubular Heart which extends through most of the thorax. It is extended into the cephalothorax by an anterior aorta. Haemolymph enters the Heart through one to two pairs of incurrent ostia. Up to five pairs of cardiac arteries emanate from the Heart to supply viscera in the body cavity. In the anterior cephalothorax, the aorta forms a pericerebral ring from which the arteries for the brain and the antennae branch off. In Cumacea, the Heart is shorter but more voluminous. In all cumaceans studied, five pairs of cardiac arteries supply the thoracopods and the pleon. The single pair of ostia is situated in the centre of the Heart. The anterior aorta runs into the anterior cephalothorax where it supplies the brain and antennae. This paper provides a general comparative discussion of all available data from the literature and the data provided herein. In certain details, the haemolymph vascular system of the Tanaidacea resembles that of Amphipoda, and some correspondences between Cumacea and Isopoda are pointed out. These findings might support a closer relationship between the latter two taxa while they show no support for an amphipod/isopod clade.
Angela B. Lange - One of the best experts on this subject based on the ideXlab platform.
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Neuropeptides Modulate the Heart of the Stick Insect Baculum extradentatum
Annals of the New York Academy of Sciences, 2009Co-Authors: Angela B. Lange, Amanda Calvin, Rosa Da SilvaAbstract:The dorsal vessel of the stick insect Baculum extradentatum consists of a Tubular Heart and an aorta that extends anteriorly into the head. Alary muscles, associated with the Heart, are anchored to the body wall with attachments to the dorsal diaphragm. Alary muscle contraction draws hemolymph into the Heart through incurrent ostia. Hemolymph exits the Heart through the excurrent ostia present on the dorsal vessel in thoracic and abdominal segments. FMRFamide-related peptides are present in axons of the segmental nerves that project to the dorsal vessel and in processes extending over the Heart and alary muscles. Immunoreactive processes are also localized to the valves of the incurrent ostia and excurrent ostia and to the lateral cardiac nerve and lateral cardiac neurons.
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Peptidergic control of the Heart of the stick insect, Baculum extradentatum
Peptides, 2008Co-Authors: Aiza Ejaz, Angela B. LangeAbstract:The dorsal vessel of the Vietnamese stick insect, Baculum extradentatum, consists of a Tubular Heart and an aorta that extends anteriorly into the head. Alary muscles, associated with the Heart, are anchored to the body wall with attachments to the dorsal diaphragm. Alary muscle contraction draws haemolymph into the Heart through incurrent ostia. Excurrent ostia lie on the dorsal vessel in the last thoracic and in each of the first two abdominal segments. Muscle fibers are associated with these excurrent ostia. Crustacean cardioactive peptide (CCAP)- and proctolin-like immunoreactivity is present in axons of the segmental nerves that project to the dorsal vessel, and in processes extending over the Heart and alary muscles. Proctolin-like immunoreactive processes are also localized to the valves of the incurrent ostia and to the excurrent ostia. Neither the link nerve neurons, nor the lateral cardiac neurons, stain positively for these peptides. Physiological assays reveal dose-dependent increases in Heart beat frequency in response to CCAP and proctolin. Isolating the dorsal vessel from the ventral nerve cord led to a change in the pattern of Heart contractions, from a tonic, stable Heart beat, to one which was phasic. The tonic nature was restored by the application of CCAP.
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Peptidergic innervation of the excurrent ostia of two orthopteroid insects
2007Co-Authors: Angela B. Lange, Rosa Da SilvaAbstract:The dorsal vessels of two Orthopteroid insects, the African migratory locust, Locusta migratoria, and the Vietnamese stick insect, Baculum extradentatum, were examined for their morphology. The dorsal vessels of both of these species consist of a Tubular Heart and an aorta that extends anteriorly into the head. Alary muscles, associated with the Hearts, are anchored to the body wall with attachments to the dorsal diaphragm. Alary muscle contraction draws haemolymph into the Heart through incurrent ostia. Excurrent ostia are present in both species with 7 pairs in the locust and 3 pairs in the stick insect. Each excurrent ostium is made up of a mass of cells that produce openings or slits that allow the haemolymph to exit the Heart and enter the perivisceral cavity directly without traveling through the aorta. Muscle fibers are associated with the excurrent ostia and these receive innervation from nerve processes containing proctolin-like immunoreactivity. These data indicate that the excurrent ostia are most likely under modulation from neuropeptides that might result in microcirculatory changes in these insects.
Stefan Richter - One of the best experts on this subject based on the ideXlab platform.
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morphology of the haemolymph vascular system in tanaidacea and cumacea implications for the relationships of core group peracarida malacostraca crustacea
Arthropod Structure & Development, 2008Co-Authors: Christian S Wirkner, Stefan RichterAbstract:Abstract Tanaidacea and Cumacea are crucial for understanding the phylogenetic relationships of “core group” peracarids. Here, the haemolymph vascular system in three tanaidacean and four cumacean species was studied on the basis of histological sections and 3D reconstruction. The circulatory organs in Tanaidacea include a Tubular Heart which extends through most of the thorax. It is extended into the cephalothorax by an anterior aorta. Haemolymph enters the Heart through one to two pairs of incurrent ostia. Up to five pairs of cardiac arteries emanate from the Heart to supply viscera in the body cavity. In the anterior cephalothorax, the aorta forms a pericerebral ring from which the arteries for the brain and the antennae branch off. In Cumacea, the Heart is shorter but more voluminous. In all cumaceans studied, five pairs of cardiac arteries supply the thoracopods and the pleon. The single pair of ostia is situated in the centre of the Heart. The anterior aorta runs into the anterior cephalothorax where it supplies the brain and antennae. This paper provides a general comparative discussion of all available data from the literature and the data provided herein. In certain details, the haemolymph vascular system of the Tanaidacea resembles that of Amphipoda, and some correspondences between Cumacea and Isopoda are pointed out. These findings might support a closer relationship between the latter two taxa while they show no support for an amphipod/isopod clade.
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Morphology of the haemolymph vascular system in Tanaidacea and Cumacea: – Implications for the relationships of “core group” Peracarida (Malacostraca; Crustacea)
Arthropod Structure & Development, 2007Co-Authors: Christian S Wirkner, Stefan RichterAbstract:Abstract Tanaidacea and Cumacea are crucial for understanding the phylogenetic relationships of “core group” peracarids. Here, the haemolymph vascular system in three tanaidacean and four cumacean species was studied on the basis of histological sections and 3D reconstruction. The circulatory organs in Tanaidacea include a Tubular Heart which extends through most of the thorax. It is extended into the cephalothorax by an anterior aorta. Haemolymph enters the Heart through one to two pairs of incurrent ostia. Up to five pairs of cardiac arteries emanate from the Heart to supply viscera in the body cavity. In the anterior cephalothorax, the aorta forms a pericerebral ring from which the arteries for the brain and the antennae branch off. In Cumacea, the Heart is shorter but more voluminous. In all cumaceans studied, five pairs of cardiac arteries supply the thoracopods and the pleon. The single pair of ostia is situated in the centre of the Heart. The anterior aorta runs into the anterior cephalothorax where it supplies the brain and antennae. This paper provides a general comparative discussion of all available data from the literature and the data provided herein. In certain details, the haemolymph vascular system of the Tanaidacea resembles that of Amphipoda, and some correspondences between Cumacea and Isopoda are pointed out. These findings might support a closer relationship between the latter two taxa while they show no support for an amphipod/isopod clade.
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The circulatory system in Mysidacea—Implications for the phylogenetic position of Lophogastrida and Mysida (Malacostraca, Crustacea)
Journal of Morphology, 2007Co-Authors: Christian S Wirkner, Stefan RichterAbstract:The morphology of the circulatory organs in Mysida and Lophogastrida (traditionally combined as Mysidacea) is revisited investigating species so far unstudied. In addition to classical morphological methods, a newly developed combination of corrosion casting with micro computer tomography (MicroCT) and computer aided 3D reconstructions is used. Lophogastrida and Mysida show a highly developed arterial system. The Tubular Heart extends through the greater part of the thorax and is connected with the ventral vessel via an unpaired descending artery. It is suggested that a distinct ostia pattern supports the monophyly of Mysidacea. The cardiac artery system is more complex in Lophogastrida than in Mysida, consisting of up to 10 pairs of arteries that supply the viscera. In both taxa, an anterior and posterior aorta leads off the Heart. In the anterior part of the cephalothorax the anterior aorta forms dilations into which muscles are internalized; these structures are called myoarterial formations. One of these myoarterial formations can also be found in all the other peracarid taxa but not in other Malacostraca. J Morphol., 2007. © 2007 Wiley-Liss, Inc.
Antoon F. M. Moorman - One of the best experts on this subject based on the ideXlab platform.
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Oxford Medicine Online - An evolutionary perspective on the origin of the cardiovascular system of vertebrates
Oxford Medicine Online, 2018Co-Authors: Roelof-jan Oostra, Bjarke Jensen, Antoon F. M. MoormanAbstract:The origin of the cardiovascular system of vertebrates is inferred from comparisons of basal chordates but must also encompass bewildering discrepancies. Basal chordates like lancelets (cephalochordates) have a vascular pattern similar to that of a vertebrate embryo, but without a recognizable Heart or myocardium. Instead, the ‘venous’ part of their circulation contains contractile vessels, located upstream and downstream of the liver. Tunicates (urochordates) have a Tubular Heart containing cardiomyocytes and enclosed by a pericardium. Their circulation is open and the dominant pacemaker activity can be at either end of the Heart tube, causing blood flow to reverse periodically. Recent molecular investigations have proved that urochordates rather than cephalochordates are the closest living relatives of vertebrates. This implies that the cardiovascular peculiarities of lancelets may be primitive ancestral qualities and that the original building plan of the vertebrate circulation featured a post-hepatic as well as a pre-hepatic cardiac pump.
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architectural plan for the Heart early patterning and delineation of the chambers and the nodes
Trends in Cardiovascular Medicine, 2004Co-Authors: Vincent M Christoffels, John B E Burch, Antoon F. M. MoormanAbstract:During folding of the embryo, lateroanterior visceral mesoderm forms the embryonic Tubular Heart at the midline, just ventral to the foregut. In mice, this nascent tube contains the future left ventricle and atrioventricular canal. Mesenchymal cells subsequently recruited to the cardiac lineage at the intake and the outflow of the tube will form the atria and the right ventricle and outflow tract, respectively. Shortly after its emergence, the embryonic Heart tube starts to loop, and the first signs of left ventricular chamber differentiation become visible on the outer curvature of the middle portion of the tube. Subsequently, the right ventricle differentiates cranially, and the atria caudally, while the inflow tract, atrioventricular canal, inner curvatures, and outflow tract form recognizable components flanking the chambers. The latter, nonchamber regions in turn provide signals for the formation of the cushion mesenchyme, are involved in remodeling of the Heart, and form the nodes of the conduction system. This review discusses how the patterning of the Heart tube relates to the localized differentiation of atrial and ventricular chambers, why some parts of the Heart do not form chambers, and how this relates to the formation of the conduction system.
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Regional expression of L-type calcium channel subunits during cardiac development.
Developmental Dynamics, 2004Co-Authors: Lourdes Acosta, Antoon F. M. Moorman, Hannelore Haase, Ingo Morano, Diego FrancoAbstract:The contraction of cardiomyocytes is initiated by the entrance of extracellular calcium through specific calcium channels. Within the myocardium, L-type calcium channels are most abundant. In the Heart, the main pore-forming subunit is the α1C, although there is a larger heterogeneity on auxiliary β subunits. We have analyzed the distribution pattern of different α1C and β subunits during cardiac development by immunohistochemistry. We observed homogeneous expression of α1C and β subunits within the early Tubular Heart, whereas regional differences are observed during the late embryogenesis. β2 and β4 show differential expression within the embryonic myocardium. α1CD1 displays only a transient enhanced expression in the ventricular conduction system. In adult Heart, the expression of the different calcium channel subunits analyzed is homogeneous along the entire myocardium except for α1CD1 that is practically undetectable. These findings suggest that β subunits might play a major role in conferring calcium handling heterogeneity within the developing embryonic myocardium, while α1C subunits might contribute just transiently. Developmental Dynamics 230:131–136, 2004. © 2004 Wiley-Liss, Inc.
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Cooperative action of Tbx2 and Nkx2.5 inhibits ANF expression in the atrioventricular canal: implications for cardiac chamber formation
Genes & Development, 2002Co-Authors: Petra E.m.h. Habets, Antoon F. M. Moorman, Marina Campione, Danielle E.w. Clout, Marian A. Van Roon, Merel Lingbeek, Maarten Van Lohuizen, Vincent M ChristoffelsAbstract:During Heart development, chamber myocardium forms locally from the embryonic myocardium of the Tubular Heart. The atrial natriuretic factor (ANF) gene is specifically expressed in this developing chamber myocardium and is one of the first hallmarks of chamber formation. We investigated the regulatory mechanism underlying this selective expression. Transgenic analysis shows that a small fragment of the ANF gene is responsible for the developmental pattern of endogenous ANF gene expression. Furthermore, this fragment is able to repress cardiac troponin I (cTnI) promoter activity selectively in the embryonic myocardium of the atrioventricular canal (AVC). In vivo inactivation of a T-box factor (TBE)- or NK2-homeobox factor binding element (NKE) within the ANF fragment removed the repression in the AVC without affecting its chamber activity. The T-box family member Tbx2, encoding a transcriptional repressor, is expressed in the embryonic myocardium in a pattern mutually exclusive to ANF, thus suggesting a role in the suppression of ANF. Tbx2 formed a complex with Nkx2.5 on the ANF TBE-NKE, and was able to repress ANF promoter activity. Our data provide a potential mechanism for chamber-restricted gene activity in which the cooperative action of Tbx2 and Nkx2.5 inhibits expression in the AVC.
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Multiple Transcriptional Domains, With Distinct Left and Right Components, in the Atrial Chambers of the Developing Heart
Circulation Research, 2000Co-Authors: Diego Franco, Marina Campione, Robert G. Kelly, Peter S. Zammit, Margaret Buckingham, Wouter H. Lamers, Antoon F. M. MoormanAbstract:Abstract—During Heart development, 2 fast-conducting regions of working myocardium balloon out from the slow-conducting primary myocardium of the Tubular Heart. Three regions of primary myocardium persist: the outflow tract, atrioventricular canal, and inflow tract, which are contiguous throughout the inner curvature of the Heart. The contribution of the inflow tract to the definitive atrial chambers has remained enigmatic largely because of the lack of molecular markers that permit unambiguous identification of this myocardial domain. We now report that the genes encoding atrial natriuretic factor, myosin light chain (MLC) 3F, MLC2V, and Pitx-2, and transgenic mouse lines expressing nlacZ under the control of regulatory sequences of the mouse MLC1F/3F gene, display regionalized patterns of expression in the atrial component of the developing mouse Heart. These data distinguish 4 broad transcriptional domains in the atrial myocardium: (1) the atrioventricular canal that will form the smooth-walled lower a...
