Isomyosin expression in developing chicken atria: a marker for the development of conductive tissue?

Groot, I. de; Sanders, Edward B.; Visser, Saco de; Lamers, Wouter H.; Jong, F. De; Los, J. M.; Moorman, Antoon F.M.

doi:10.1007/bf00310091

Cited by 38 publications

(33 citation statements)

References 17 publications

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“…Because we examin ed mechan ical rather than electrical events, we cannot determine whether this effect resulted from mor e rapid electrical conduction or from differential changes in electrom echanical coupling. Although controversy remains as to whether the bundl e branches and distal Purkinje cells arise in situ in the ventricles or whether the bund le of His extends from its origin in the septum primum to produce the Purkinje network (13)(14)(15), there is no evidence of Purk inke cell precursors in the ventricle at stages as early as were examined in this study. Synchronous contra ction should be more effective than more peristaltic contraction, but only if there is atrioventricular valve competence.…”

Section: Resultsmentioning

confidence: 82%

Emulation of Conduction System Functions in the Hearts of Early Mammalian Embryos

Lloyd

Baldwin

1990

Pediatr Res

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Embry o culture. Whole embryo culture was performed as previously described (5). Wistar rat embryos were explanted on gestational d 9.5, d 0 being the day of positive vaginal smear.Embryos were explanted in Tyrode's solution, the decidual mass was removed, and Reichert's membrane was opened. Embryos were then placed in roller bottles containing heat-inactivated rat serum and cultured under an atmosphere of 90% N z , 5% Oz, and 5% COz as described by New (6). At explanation, embryos contain up to three somites and the primitive heart tube has not yet formed. Embryos were studied either at the five-to sevensomite stage (24 h in culture), at which stage the heart tube has formed but has not begun to loop, or at the 13-to IS-somite stage (36 h in culture), after cardiac looping is complete but before development of the atrial or ventricular septa.Wall motion recording. Embryos with prelooped or looped hearts were examined in Tyrode's solution using a Wild M5 microscope. Embryos were positioned and immobilized as shown in Figure I in a depression made in 9% agar. Embryos were maintained at 37.5 ± OSC by a thermostatically-controlled stage warming/cooling device (Sensortek, Clifton, NJ). Video-tape recordings of the embryonic hearts (at lOOx and 200 x magnification) were made using high-resolution closed circuit video and electronic processing to produce monochrome images of maximum contrast. For wall motion recording, these videotape recordings were played back on a 19-inch monitor. Fiber optic cables were placed over the video images of the proximal atrium, distal atrium, proximal ventricle, and proximal bulbus cordis as indicated in Figure I. The fiber optic cables were connected to photocell amplifiers that converted the changes in light intensity of the video image caused by wall motion to voltage signals, which were then recorded by a multichannel recorder at a paper speed of 50 mm /s. This apparatus has been described previously (7). Because of the nature of the opt ical system , the moment of peak wall motion is the most reliably detected point. Peak wall motion is also less affected by motion of adjacent structures than earliest motion would be, so position of the fiber optic cables was adjusted to optimize recording of peak wall motion. Cycle length was measured from the most proximal site recorded. Intervals between peak wall motion in the proximal and distal atrium (intra-atrial delay), distal atrium and proximal ventricle (atrioventricular delay), and proximal ventricle and proximal bulbus cordis (intraventricular delay) were measured to the nearest 5 ms as shown in Figure 2. Each measurement reported was the mean of five sequential contractions. Linear distance between recording sites was measured on the video screen and converted to JIm by reference to micrometer calibration recorded on each videotape at the same magnifications.Stat istical analysis. Intervals between maximum contraction within the atrium and ventricle and atrioventricular delay in prelooped and looped hearts were analyzed by analysis o...

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Section: Resultsmentioning

confidence: 82%

Emulation of Conduction System Functions in the Hearts of Early Mammalian Embryos

Lloyd

Baldwin

1990

Pediatr Res

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“…After the recordings, the isolated control or experimental hearts were photographed, fixed in Dent's fixative (80% methanol/20% DMSO), processed into paraffin, and serially sectioned at 8 m for immunohistochemical detection of early markers of ventricular conduction system (PSA-NCAM, clone 5A5, fresh ascites fluid, from Developmental Studies Hybridoma bank 15 and ␣-myosin heavy chain, clone 169-1A6, 16 shown to stain developing ventricular conduction system in the avian heart in a manner described by Sanders et al 17 Imaging was carried out on Leica TCS SP2 AOBS confocal microscope.…”

Section: Immunohistochemistrymentioning

confidence: 99%

Hemodynamics Is a Key Epigenetic Factor in Development of the Cardiac Conduction System

Rečková

Rosengarten

deAlmeida

et al. 2003

Circulation Research

173

180

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Abstract-The His-Purkinje system (HPS) is a network of conduction cells responsible for coordinating the contraction of the ventricles. Earlier studies using bipolar electrodes indicated that the functional maturation of the HPS in the chick embryo is marked by a topological shift in the sequence of activation of the ventricle. Namely, at around the completion of septation, an immature base-to-apex sequence of ventricular activation was reported to convert to the apex-to-base pattern characteristic of the mature heart. Previously, we have proposed that hemodynamics and/or mechanical conditioning may be key epigenetic factors in development of the HPS. We thus hypothesized that the timing of the topological shift marking maturation of the conduction system is sensitive to variation in hemodynamic load. Spatiotemporal patterns of ventricular activation (as revealed by high-speed imaging of fluorescent voltage-sensitive dye) were mapped in chick hearts over normal development, and following procedures previously characterized as causing increased (conotruncal banding, CTB) or reduced (left atrial ligation, LAL) hemodynamic loading of the embryonic heart. The results revealed that the timing of the shift to mature activation displays striking plasticity. CTB led to precocious emergence of mature HPS function relative to controls whereas LAL was associated with delayed conversion to apical initiation. The results from our study indicate a critical role for biophysical factors in differentiation of specialized cardiac tissues and provide the basis of a new model for studies of the molecular mechanisms involved in induction and patterning of the HPS in vivo. Key Words: chick embryo Ⅲ His-Purkinje system Ⅲ heart development Ⅲ optical mapping T he His-Purkinje system (HPS) is a specialized network of conduction tissues that ensures coordinated and reliable activation of the ventricular myocardium. Dysfunction of this essential network of specialized cardiac tissues is linked to ventricular arrhythmia and sudden cardiac death in both adults and children. To give a recent example, Purkinje fibers were mapped as the predominant origin of arrhythmias in human patients with recurrent idiopathic ventricular fibrillation. 1 The relationship between the anatomical structure of the HPS and its electrophysiological characteristics during the normal cardiac cycle has now been understood for nearly a century (summarized and put in perspective in Suma 2 ). After activation of the atria by the sinoatrial (SA) node, propagating electrical impulse exits from the atrioventricular (AV) node and is spread rapidly into the left and right ventricles via the bundle of His, its branched limbs and networks of Purkinje fibers ramifying from the bundle branches. The larger fascicles of the HPS (ie, the His bundle and bundle branches) are insulated from surrounding muscle as they course from the crest of the septum toward the ventricular apex. This insulation breaks down within the peripheral networks of Purkinje fibers, enabling direct electroton...

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“…Monoclonal primary antibodies against human ␣MyHC (Wessels et al, 1991), human ␤MyHC (Wessels et al, 1991), chicken ␣MyHC (De Groot et al, 1987), and chicken ␤MyHC (De Groot et al, 1987), and polyclonal primary antibody against all MyHC isoforms (L53) were used. The L53 polyclonal antibody was generated as described by Sanders et al (1984) and its specificity was characterised by Western blot analysis.…”

Section: Protein Immunohistochemistrymentioning

confidence: 99%

Species‐specific differences of myosin content in the developing cardiac chambers of fish, birds, and mammals

et al. 2002

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Key morphogenetic events during heart ontogenesis are similar in different vertebrate species. We report that in primitive vertebrates, i.e., cartilaginous fishes, both the embryonic and the adult heart show a segmental subdivision similar to that of the embryonic mammalian heart. Early morphogenetic events during cardiac development in the dogfish are long-lasting, providing a suitable model to study changes in pattern of gene expression during these stages. We performed a comparative study among dogfish, chicken, rat, and mouse to assess whether species-specific qualitative and/or quantitative differences in myosin heavy chain (MyHC) distribution arise during development, indicative of functional differences between species. MyHC RNA content was investigated by means of in situ hybridisation using an MyHC probe specific for a highly conserved domain, and MyHC protein content was assessed by immunohistochemistry. MyHC transcripts were found to be homogeneously distributed in the myocardium of the tubular and embryonic heart of dogfish and rodents. A difference between atrial and ventricular MyHC content (mRNA and protein) was observed in the adult stage. Interestingly, differences in the MyHC content were observed at the tubular heart stage in chicken. These differences in MyHC content illustrate the distinct developmental profiles of avian and mammalian species, which might be ascribed to distinct functional requirements of the myocardial segments during ontogenesis. The atrial myocardium showed the highest MyHC content in the adult heart of all species analysed (dogfish (S. canicula), mouse (M. musculus), rat (R. norvegicus), and chicken (G. gallus)). These observations indicate that in the adult heart of vertebrates the atrial myocardium contains more myosin than the ventricular myocardium. Anat Rec 268: 27-37, 2002.

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Isomyosin expression in developing chicken atria: a marker for the development of conductive tissue?

Cited by 38 publications

References 17 publications

Emulation of Conduction System Functions in the Hearts of Early Mammalian Embryos

Emulation of Conduction System Functions in the Hearts of Early Mammalian Embryos

Hemodynamics Is a Key Epigenetic Factor in Development of the Cardiac Conduction System

Species‐specific differences of myosin content in the developing cardiac chambers of fish, birds, and mammals

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