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Takashi Mikawa - One of the best experts on this subject based on the ideXlab platform.
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Purkinje Fibers of the avian heart express a myogenic transcription factor program distinct from cardiac and skeletal muscle
Developmental Biology, 2001Co-Authors: Kimiko Takebayashisuzuki, Linda B Pauliks, Yelena Eltsefon, Takashi MikawaAbstract:Abstract A rhythmic heart beat is coordinated by conduction of pacemaking impulses through the cardiac conduction system. Cells of the conduction system, including Purkinje Fibers, terminally differentiate from a subset of cardiac muscle cells that respond to signals from endocardial and coronary arterial cells. A vessel-associated paracrine factor, endothelin, can induce embryonic heart muscle cells to differentiate into Purkinje Fibers both in vivo and in vitro. During this phenotypic conversion, the conduction cells down-regulate genes characteristic of cardiac muscle and up-regulate subsets of genes typical of both skeletal muscle and neuronal cells. In the present study, we examined the expression of myogenic transcription factors associated with the switch of the gene expression program during terminal differentiation of heart muscle cells into Purkinje Fibers. In situ hybridization analyses and immunohistochemistry of embryonic and adult hearts revealed that Purkinje Fibers up-regulate skeletal and atrial muscle myosin heavy chains, connexin-42, and neurofilament protein. Concurrently, a cardiac muscle-specific myofibrillar protein, myosin-binding protein-C (cMyBP-C), is down-regulated. During this change in transcription, however, Purkinje Fibers continue to express cardiac muscle transcription factors, such as Nkx2.5, GATA4, and MEF2C. Importantly, significantly higher levels of Nkx2.5 and GATA4 mRNAs were detected in Purkinje Fibers as compared to ordinary heart muscle cells. No detectable difference was observed in MEF2C expression. In culture, endothelin-induced Purkinje Fibers from embryonic cardiac muscle cells dramatically down-regulated cMyBP-C transcription, whereas expression of Nkx2.5 and GATA4 persisted. In addition, myoD, a skeletal muscle transcription factor, was up-regulated in endothelin-induced Purkinje cells, while Myf5 and MRF4 transcripts were undetectable in these cells. These results show that during and after conversion from heart muscle cells, Purkinje Fibers express a unique myogenic transcription factor program. The mechanism underlying down-regulation of cardiac muscle genes and up-regulation of skeletal muscle genes during conduction cell differentiation may be independent from the transcriptional control seen in ordinary cardiac and skeletal muscle cells.
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skeletal muscle specific myosin binding protein h is expressed in Purkinje Fibers of the cardiac conduction system
Circulation Research, 1997Co-Authors: Tatiana N Alyonycheva, Leona Cohengould, Christiana Siewert, Donald A Fischman, Takashi MikawaAbstract:Abstract Heart contraction is coordinated by conduction of electrical excitation through specialized tissues of the cardiac conduction system. By retroviral single-cell tagging and lineage analyses in the embryonic chicken heart, we have recently demonstrated that a subset of cardiac muscle cells terminally differentiates as cells of the peripheral conduction system (Purkinje Fibers) and that this occurs invariably in perivascular regions of developing coronary arteries. Cis regulatory elements that function in transcriptional regulation of cells in the conducting system have been distinguished from those in contractile cardiac muscle cells; eg, 5′ regulatory sequences of the desmin gene act as enhancer elements in skeletal muscle and in the conduction system but not in cardiac muscle. We hypothesize that Purkinje fiber differentiation involves a switch of the gene expression program from that characteristic of cardiac muscle to one typical of skeletal muscle. To test this hypothesis, we examined the expression of myosin binding protein-H (MyBP-H) in Purkinje Fibers of chicken hearts. This unique myosin binding protein is present in skeletal but not cardiac myocytes. A site-directed polyclonal antibody (AB105) was generated against MyBP-H. Immunohistological analysis of the myocardium mapped the AB105 antigen predominantly to A bands of myofibrils within Purkinje Fibers. Western blot analysis of whole extracts from the ventricular wall of adult chicken hearts revealed that the AB105 epitope was restricted to a single protein of ≈86 kD, the same size as MyBP-H in skeletal muscle. Biochemical properties of the Purkinje fiber 86-kD protein and RNase protection analyses of its mRNA indicate that Purkinje fiber 86-kD protein is indistinguishable from skeletal muscle MyBP-H. The results provide evidence that skeletal muscle MyBP-H is expressed in a subset of cardiac muscle cells that differentiate into Purkinje Fibers of the heart.
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terminal diversification of the myocyte lineage generates Purkinje Fibers of the cardiac conduction system
Development, 1995Co-Authors: Robert G Gourdie, Tatsuo Mima, Robert P Thompson, Takashi MikawaAbstract:The rhythmic contraction of the vertebrate heart is dependent on organized propagation of electrical excitation through the cardiac conduction system. Because both muscle- and neuron-specific genes are co-expressed in cells forming myocardial conduction tissues, two origins, myogenic and neural, have been suggested for this specialized tissue. Using replication-defective retroviruses, encoding recombinant beta-galactosidase (beta-gal), we have analyzed cell lineage for Purkinje Fibers (i.e., the peripheral elements of the conduction system) in the chick heart. Functioning myocyte progenitors were virally tagged at embryonic day 3 of incubation (E3). Clonal beta-gal+ populations of cells, derived from myocytes infected at E3 were examined at 14 (E14) and 18 (E18) days of embryonic incubation. Here, we report that a subset of clonally related myocytes differentiates into conductile Purkinje Fibers, invariably in close spatial association with forming coronary arterial blood vessels. These beta-gal+ myogenic clones, containing both working myocytes and Purkinje Fibers, did not incorporate cells contributing to tissues of the central conduction system (e.g. atrioventricular ring and bundles). In quantitative analyses, we found that whereas the number of beta-gal+ myocyte nuclei per clone more than doubled between E14 and E18, the number of beta-gal+ Purkinje fiber nuclei remained constant.(ABSTRACT TRUNCATED AT 250 WORDS)
Robert G Gourdie - One of the best experts on this subject based on the ideXlab platform.
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why do we have Purkinje Fibers deep in our heart
Physiological Research, 2014Co-Authors: David Sedmera, Robert G GourdieAbstract:Summary Purkinje Fibers were the first discovered component of the cardiac conduction system. Originally described in sheep in 1839 as pale subendocardial cells, they were found to be present, although with different morphology, in all mammalian and avian hearts. Here we review differences in their appearance and extent in different species, summarize the current state of knowledge of their function, and provide an update on markers for these cells. Special emphasis is given to popular model species and human anatomy.
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epicardium derived cells are important for correct development of the Purkinje Fibers in the avian heart
Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2006Co-Authors: Robert G Gourdie, Ismail Eralp, Heleen Lievenema, Maurits C E F Wijffels, Arnoud Van Der Laarse, Marco C Deruiter, Ad J J C Bogers, Nynke M S Van Den Akker, Martin J SchalijAbstract:During embryonic development, the proepicardial organ (PEO) grows out over the heart surface to form the epicardium. Following epithelial-mesenchymal transformation, epicardium-derived cells (EPDCs) migrate into the heart and contribute to the developing coronary arteries, to the valves, and to the myocardium. The peripheral Purkinje fiber network develops from differentiating cardiomyocytes in the ventricular myocardium. Intrigued by the close spatial relationship between the final destinations of migrating EPDCs and Purkinje fiber differentiation in the avian heart, that is, surrounding the coronary arteries and at subendocardial sites, we investigated whether inhibition of epicardial outgrowth would disturb cardiomyocyte differentiation into Purkinje Fibers. To this end, epicardial development was inhibited mechanically with a membrane, or genetically, by suppressing epicardial epithelial-to-mesenchymal transformation with antisense retroviral vectors affecting Ets transcription factor levels (n = 4, HH39-41). In both epicardial inhibition models, we evaluated Purkinje fiber development by EAP-300 immunohistochemistry and found that restraints on EPDC development resulted in morphologically aberrant differentiation of Purkinje Fibers. Purkinje fiber hypoplasia was observed both periarterially and at subendocardial positions. Furthermore, the cells were morphologically abnormal and not aligned in orderly Purkinje Fibers. We conclude that EPDCs are instrumental in Purkinje fiber differentiation, and we hypothesize that they cooperate directly with endothelial and endocardial cells in the development of the peripheral conduction system. Anat Rec Part A, 2006. © 2006 Wiley-Liss, Inc.
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differentiation of cardiac Purkinje Fibers requires precise spatiotemporal regulation of nkx2 5 expression
Developmental Dynamics, 2006Co-Authors: Brett S Harris, Laura Spruill, Angela M Edmonson, Mary S Rackley, Woodrow D Benson, Terrence X Obrien, Robert G GourdieAbstract:Nkx2-5 gene mutations cause cardiac abnormalities including deficits of function in the atrioventricular conduction system (AVCS). In the chick, Nkx2-5 is elevated in Purkinje fiber AVCS cells relative to working cardiomyocytes. Here, we show that Nkx2-5 expression rises to a peak as Purkinje Fibers progressively differentiate. To disrupt this pattern, we over-expressed Nkx2-5 from embryonic day 10 as Purkinje Fibers are recruited within developing chick hearts. Over-expression of Nkx2-5 caused inhibition of sMHC, a late Purkinje fiber marker but did not affect Cx40 levels. Working cardiomyocytes over-expressing Nkx2-5 in these hearts ectopically up-regulated Cx40, but not sMHC. Isolated embryonic cardiomyocytes over-expressing Nkx2-5 also displayed increased Cx40 and suppressed sMHC. By contrast over-expression of a human NKX2-5 mutant did not effect these markers in vivo or in vitro, suggesting one possible mechanism for clinical phenotypes. We conclude that a prerequisite for normal Purkinje fiber maturation is precise regulation of Nkx2-5 levels.
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Epicardium-derived cells are important for correct development of the Purkinje Fibers in the avian heart
The Anatomical Record Part A: Discoveries in Molecular Cellular and Evolutionary Biology, 2006Co-Authors: Ismail Eralp, Robert G Gourdie, Maurits C E F Wijffels, Arnoud Van Der Laarse, Marco C Deruiter, Ad J J C Bogers, Nynke M S Van Den Akker, Heleen Lie-venema, Martin J SchalijAbstract:During embryonic development, the proepicardial organ (PEO) grows out over the heart surface to form the epicardium. Following epithelial-mesenchymal transformation, epicardium-derived cells (EPDCs) migrate into the heart and contribute to the developing coronary arteries, to the valves, and to the myocardium. The peripheral Purkinje fiber network develops from differentiating cardiomyocytes in the ventricular myocardium. Intrigued by the close spatial relationship between the final destinations of migrating EPDCs and Purkinje fiber differentiation in the avian heart, that is, surrounding the coronary arteries and at subendocardial sites, we investigated whether inhibition of epicardial outgrowth would disturb cardiomyocyte differentiation into Purkinje Fibers. To this end, epicardial development was inhibited mechanically with a membrane, or genetically, by suppressing epicardial epithelial-to-mesenchymal transformation with antisense retroviral vectors affecting Ets transcription factor levels (n = 4, HH39-41). In both epicardial inhibition models, we evaluated Purkinje fiber development by EAP-300 immunohistochemistry and found that restraints on EPDC development resulted in morphologically aberrant differentiation of Purkinje Fibers. Purkinje fiber hypoplasia was observed both periarterially and at subendocardial positions. Furthermore, the cells were morphologically abnormal and not aligned in orderly Purkinje Fibers. We conclude that EPDCs are instrumental in Purkinje fiber differentiation, and we hypothesize that they cooperate directly with endothelial and endocardial cells in the development of the peripheral conduction system
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terminal diversification of the myocyte lineage generates Purkinje Fibers of the cardiac conduction system
Development, 1995Co-Authors: Robert G Gourdie, Tatsuo Mima, Robert P Thompson, Takashi MikawaAbstract:The rhythmic contraction of the vertebrate heart is dependent on organized propagation of electrical excitation through the cardiac conduction system. Because both muscle- and neuron-specific genes are co-expressed in cells forming myocardial conduction tissues, two origins, myogenic and neural, have been suggested for this specialized tissue. Using replication-defective retroviruses, encoding recombinant beta-galactosidase (beta-gal), we have analyzed cell lineage for Purkinje Fibers (i.e., the peripheral elements of the conduction system) in the chick heart. Functioning myocyte progenitors were virally tagged at embryonic day 3 of incubation (E3). Clonal beta-gal+ populations of cells, derived from myocytes infected at E3 were examined at 14 (E14) and 18 (E18) days of embryonic incubation. Here, we report that a subset of clonally related myocytes differentiates into conductile Purkinje Fibers, invariably in close spatial association with forming coronary arterial blood vessels. These beta-gal+ myogenic clones, containing both working myocytes and Purkinje Fibers, did not incorporate cells contributing to tissues of the central conduction system (e.g. atrioventricular ring and bundles). In quantitative analyses, we found that whereas the number of beta-gal+ myocyte nuclei per clone more than doubled between E14 and E18, the number of beta-gal+ Purkinje fiber nuclei remained constant.(ABSTRACT TRUNCATED AT 250 WORDS)
Michael R. Rosen - One of the best experts on this subject based on the ideXlab platform.
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alpha1 adrenergic receptor modulation of repolarization in canine Purkinje Fibers
Journal of Cardiovascular Electrophysiology, 1994Co-Authors: Michael R. RosenAbstract:INTRODUCTION: Alpha 1-adrenergic receptor stimulation increases contractility and prolongs repolarization. These effects are modulated by alpha 1-adrenergic receptor-mediated inhibition of transsarcolemmal potassium currents. METHODS AND RESULTS: We used standard microelectrode techniques to study the actions of 4-aminopyridine (4-AP), which blocks the transient outward current, I(to), and WAY-123,398, which blocks the delayed rectifier, Ik, on canine Purkinje fiber action potential prolongation induced by phenylephrine. At a basic cycle length of 1 second, phenylephrine (0.1 to 10 microM) dose-dependently prolonged action potential duration at 90% repolarization (APD90) from 331 +/- 10 msec to 400 +/- 12 msec (P < 0.05) at phenylephrine, 10 microM. Phenylephrine did not change phase 1 or plateau height. 4-AP (0.1 mM) decreased phase 1 magnitude, shifted plateau height to more positive potentials (from 0.1 +/- 1.8 mV to 14.3 +/- 1.1 mV [P < 0.05]), and shortened APD90 from 318 +/- 9 msec to 294 +/- 8 msec (P < 0.05). 4-AP did not block phenylephrine effects on APD90, which increased, at 10 microM phenylephrine, from 294 +/- 8 msec to 342 +/- 6 msec (P < 0.05). In contrast, WAY-123,398 (0.1 microM) prolonged APD90 from 360 +/- 6 msec to 452 +/- 6 msec (P < 0.05), and had no effect on plateau height. In the presence of WAY-123,398, phenylephrine no longer increased APD90. CONCLUSION: (1) Agents that block I(to) shorten APD in Purkinje Fibers; and (2) the alpha-agonist mediated increase of APD in canine Purkinje Fibers can be explained by inhibition of Ik.
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Developmental changes in the muscarinic stimulation of canine Purkinje Fibers.
Journal of Pharmacology and Experimental Therapeutics, 1990Co-Authors: Michael R. Rosen, Susan F. Steinberg, Peter DaniloAbstract:Acetylcholine (ACh) hyperpolarizes adult canine Purkinje Fibers and induces a decrease in their automaticity. In Purkinje Fibers from young dogs, there is a biphasic effect on automaticity, which increases at low and decreases at high ACh concentrations. We used standard microelectrode techniques to study these actions of ACh. In Fibers from young dogs, 10(-10) to 10(-9) M ACh increased automaticity and 10(-5) M ACh decreased automaticity. The decrease was blocked by the M2 muscarinic blocker AFDX-116, whereas the increase was blocked by the predominant M1 blocker pirenzepine. The M2 agonist oxotremorine never increased automaticity. Rather, it decreased automaticity and hyperpolarized adult and young Fibers, the former more than the latter. The hyperpolarization and biphasic effect on automaticity of ACh in Fibers from young dogs failed to occur after treatment with pertussis toxin, suggesting that these effects are dependent on a pertussis toxin-sensitive G protein. These electrophysiologic studies suggest that postsynaptic M1 and M2 muscarinic processes modulate the automatic response of Purkinje Fibers from young dogs and that the postsynaptic M1 pathway is no longer seen in the adult.
B A Dupuis - One of the best experts on this subject based on the ideXlab platform.
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droperidol exerts dual effects on repolarization and induces early afterdepolarizations and triggered activity in rabbit Purkinje Fibers
Journal of Pharmacology and Experimental Therapeutics, 1993Co-Authors: M M Adamantidis, P Kerram, J F Caron, B A DupuisAbstract:This study was designed to clarify discrepancies concerning the effects of droperidol on cardiac repolarization. Myocardial electrical activity was recorded by using microelectrode technique in rabbit Purkinje Fibers and guinea pig ventricular muscle. In Purkinje Fibers stimulated at 60 pulses/min, low concentrations (0.01-0.3 microM) of droperidol increased in a dose-dependent fashion action potential duration (APD) without altering the other parameters. At 1 and 3 microM, droperidol led to the reversal of the prolonging effect. The highest concentrations used (10 and 30 microM), produced shortening in APD at 50% repolarization concomitantly with a significant decrease in Vmax, action potential amplitude and resting membrane potential. Inexcitability occurred in 4 of 15 preparations exposed to 30 microM. In 8 of 15 Purkinje Fibers, the prolonging effect induced by low concentrations was so important that APD exceeded the 1000-msec period of basal stimulation and early afterdepolarizations (EADs) and triggered activity developed. In guinea pig ventricular muscle, these effects were notably less pronounced. Prolongation of action potential showed a reverse use-dependence (i.e., much greater at the lowest stimulation frequencies), whereas Vmax depression was use-dependent. Decreasing extracellular K concentration from 4.0 to 2.7 mM enhanced the incidence of EADs in Purkinje Fibers, whereas elevating the K concentration from 2.7 to 5.4 mM abolished them completely and shortened drastically APD. EADs were also eliminated by increasing magnesium concentration from 1 to 5 mM. Addition of isoproterenol favored EADs, whereas these were suppressed at plateau level by exposure to 0.3 microM nifedipine. The results indicate that in rabbit Purkinje Fibers, droperidol exerts a dual effect on repolarization, prolongation with low concentrations with development of EADs and subsequent triggered activity. These abnormalities were suppressed at high concentrations concomitantly with a marked depression of other characteristics. These observations suggest multiple ionic channel activities and further studies are required to precise the underlying mechanisms at channel level.
A Mugelli - One of the best experts on this subject based on the ideXlab platform.
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Histamine and abnormal automaticity in barium- and strophanthidin-treated sheep Purkinje Fibers
Agents and Actions, 1990Co-Authors: E Cerbai, S Amerini, A MugelliAbstract:We used intracellular microelectrodes to study the effects of histamine on both normal and abnormal automaticity in sheep Purkinje Fibers. Histamine, dimaprit and 4-methylhistamine caused a similar reduction of the action potential duration in driven Purkinje Fibers. Histamine (10^−6 M ) induced spontaneous activity in previously quiescent preparations more often than did equimolar concentrations of dimaprit and 4-methylhistamine. The effects of histamine on automaticity were enhanced in the presence of barium. In fact histamine, at concentrations which were unable to induce automaticity in normal preparations, induced it in the presence of barium. In Purkinje Fibers manifesting barium-induced automatic activity, histamine (10^−7–10^−6 M ) significantly increased the average number of spontaneous action potentials and shortened the time of their appearance. In the same range of concentrations, histamine dose-dependently increased the amplitude of the barium-induced oscillatory afterpotentials (OAP), which are considered an electrophysiological manifestation of calcium overload. Histamine (10^−6–10^−4 M ) increased the OAP amplitude of strophanthidin-treated Purkinje Fibers, eventually inducing triggered extrabeats. All these previously described effects were selectively blocked by cimetidine (10^−5 M ). It is concluded that histamine may induce cardiac arrhythmias under conditions of calcium overload and that this effect may be due to induction or enhancement of oscillatory afterpotentials.
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Histamine and abnormal automaticity in barium- and strophanthidin-treated sheep Purkinje Fibers.
Agents and actions, 1990Co-Authors: E Cerbai, S Amerini, A MugelliAbstract:We used intracellular microelectrodes to study the effects of histamine on both normal and abnormal automaticity in sheep Purkinje Fibers. Histamine, dimaprit and 4-methylhistamine caused a similar reduction of the action potential duration in driven Purkinje Fibers. Histamine (10-6 M) induced spontaneous activity in p previously quiescent preparations more often than did equimolar concentrations of dimaprit and 4-methylhistamine. The effects of histamine on automaticity were enhanced in the presence of barium In fact histamine, at concentrations which were unable to induce automaticity in normal preparations, induced it in the presence of barium. In Purkinje Fibers manifesting barium-induced automatic activity, histamine (10-7--10-6M) significantly increased the average number of spontaneous action potentials and shortened the time of their appearance. In the same range of concentrations, histamine dose-dependently increased the iological manifestation of calcium overload. Histamine (10-6--10-4M) increased the OAP amplitude of strophanthidin -treated Purkinje Fibers, eventually inducing triggered extrabeats. All these previously described effects were selectively blocked by cimetidine (10-5 M). It is concluded that histamine may induce cardiac arrhythmias under conditions of calcium overload and that this effect may be due to induction or enhancement of oscillatory afterpotentials.
