scholarly journals Characterization of embryonic cardiac pacemaker and atrioventricular conduction physiology in Xenopus laevis using noninvasive imaging

2004 ◽  
Vol 286 (6) ◽  
pp. H2035-H2041 ◽  
Author(s):  
Heather L. Bartlett ◽  
Thomas D. Scholz ◽  
Fred S. Lamb ◽  
Daniel L. Weeks
Keyword(s):  
Xenopus Laevis ◽  
Congenital Heart ◽  
Morphological Changes ◽  
Heart Defects ◽  
Cardiac Pacemaker ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Model Organisms ◽  
Morphological Evidence ◽  
Video Images

Congenital heart defects often include altered conduction as well as morphological changes. Model organisms, like the frog Xenopus laevis, offer practical advantages for the study of congenital heart disease. X. laevis embryos are easily obtained free living, and the developing heart is readily visualized. Functional and morphological evidence for a conduction system is available for adult frog hearts, but information on the normal properties of embryonic heart contraction is lacking, especially in intact animals. With the use of fine glass microelectrodes, we were able to obtain cardiac recordings and make standard electrophysiological measurements in 1-wk-old embryos ( stage 46). In addition, a system using digital analysis of video images was adapted for measurement of the standard cardiac intervals and compared with invasive measurements. Video images were obtained of the heart in live, pharmacologically paralyzed, stage 46 X. laevis embryos. Normal values for the timing of the cardiac cycle were established. Intervals determined by video analysis ( n = 53), including the atrial and ventricular cycle lengths (473 ± 10 ms and 464 ± 19 ms, respectively) and the atrioventricular interval (169 ± 5 ms) were not statistically different from those determined by intrathoracic cardiac recordings. We also present the data obtained from embryos treated with standard medications that affect the human conduction system. We conclude that the physiology of embryonic X. laevis cardiac conduction can be noninvasively studied by using digital video imaging. Additionally, we show the response of X. laevis embryonic hearts to chronotropic agents is similar but not identical to the response of the human heart.

Complete Heart Block after open Heart Surgery in Children with Congenital Cardiac Diseases Feasibility of more waiting time before PPM administration

2021 ◽  
Vol 4 (11) ◽  
pp. 01-06
Author(s):  
Akbar Molaei
Keyword(s):  
Heart Block ◽  
Congenital Heart ◽  
Heart Surgery ◽  
Complete Heart Block ◽  
Heart Defects ◽  
Open Heart Surgery ◽  
Cardiac Conduction ◽  
Cardiac Diseases ◽  
Open Heart ◽  
Cardiac Disorders

Introduction: Congenital cardiac disorders are the most prevalent congenital disorders which require interventional or surgical treatments. The most common causes of complete heart block (CHB) are degeneration of cardiac conduction system, acute myocardial infarction and congenital cardiac disorders. CHB after congenital heart surgery is of paramount importance which causes post-operation death and heart failure. Application of a pacemaker is a standard treatment for CHB. The purpose of this paper is to study the frequency of early postoperative CHB in patients with congenital cardiac diseases and also the need for temporary (TPM) and permanent (PPM) pacemakers. Materials and methods: This descriptive-analytical and cross-sectional study was conducted on children with congenital heart defects who had undergone open-heart surgery in Tabriz’s Shahid Madani Hospital from 2011 to 2016. Patients with early postoperative CHB were included in the study. Those who had improved on their own and those who needed TPM and PPM were identified and at the end, the frequency of CHB and the need for TPM and PPM were assessed. Results: Of the 2100 operated patients, 109 patients developed early postoperative heart block. The frequency of early CHB after open heart surgery was 5.19%. Of the 109 patients, 69 patients (63.3%) with early postoperative CHB needed TPM, 9 patients needed PPM and 22 patients improved without pacemaker. Conclusion: The prevalence of early CHB in patients operated for congenital cardiac diseases was 5.19%. The need for TPM was high and most of the patients had improved cardiac rhythm with no need for PPM or TPM.

CONGENITAL HEART BLOCK DUE TO A LESION IN THE CONDUCTION SYSTEM

PEDIATRICS ◽  
1970 ◽  
Vol 45 (4) ◽  
pp. 640-650
Author(s):  
Cirilo Sotelo-Avila ◽  
Harvey S. Rosenberg ◽  
Dan G. McNamara
Keyword(s):  
Heart Block ◽  
Congenital Heart ◽  
Complete Heart Block ◽  
Fibrous Tissue ◽  
Postmortem Examination ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Fibrous Body ◽  
Congenital Complete Heart Block ◽  
Bundle Of His

The cardiac conduction system of an infant with congenital complete heart block was studied at postmortem examination by subserial sections of the interatrial and interventricular septa. A localized area of necrosis in the central fibrous body interrupted the penetrating portion of the bundle of His. The cardiac structure was intact, with no abnormality other than the lesions in the fibrous tissue. The lesion is interpreted as the result of an acquired inflammation late in intrauterine life, with damage localized to the cardiac central fibrous body.

Abstract 2722: Large Scale Mutation Discovery Screen Identifies Functionally Variant UGDH Alleles in Patients with Atrioventricular Valve Defects

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Jeroen Bakkers ◽  
Sonja Chocron ◽  
Victor Gouriev ◽  
Kelly Smith ◽  
Ronald Lekanne dit Deprez ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Congenital Heart Defects ◽  
Congenital Heart ◽  
Large Scale ◽  
Heart Defects ◽  
Glucose Dehydrogenase ◽  
Model Organisms ◽  
Missense Mutations ◽  
Coding Regions

Background: Congenital heart defects are the most common birth defects. Although genetic dispositions are believed to cause CHDs, only few genes have been identified that harbour mutations causing such defects. Studies in model organisms have identified many essential genes for cardiac development. UDP-glucose dehydrogenase (UGDH) enzymatic activity is required for the signal transduction of FGF and Wnt ligands and zebrafish jekyll/ugdh mutations lack AV valves. Methods and Results: From literature candidate genes were selected that are essential for AV canal-, septum-, and valve formation. By large scale sequencing we analysed the coding regions of 36 candidate genes in 192 patients with reported AVSDs. As a result we identified 457 genetic variations of which 207 variants are in flanking non-coding regions, 156 variants are in coding regions but silent and 94 variants are non-synonymous variants that alter the protein sequence. Comparison with the available databases such as HapMap and screening 350 control individuals resulted in the validation of 49 non-synonomous missense mutations in 23 genes only present in the patient group. These included novel GATA4 missense mutations (R285C and M224V) located in the highly conserved DNA binding domains, which by in vitro analysis significantly reduce transcriptional activity of the protein. Three patients with mitral valvar prolapse and mitral regurgitation were identified with novel missense mutations in the UDP-glucose dehydrogenase (UGDH) gene (R141C and E416D). In vitro experiments demonstrated a negative affect on enzyme activity and stability by a change in protein conformation. Furthermore, experiments in zebrafish jekyll/ugdh mutants showed that UGDH R141C and UGDH E416D couldn’t rescue the defects in AV formation demonstrating an inactivating effect of these missense mutations in vivo. Conclusions: A model organism based candidate gene screen in CHD patients resulted in the identification of novel functional missense mutations in the UGDH gene not previously implicated in congenital heart defects.

scholarly journals HAND1 loss-of-function within the embryonic myocardium reveals survivable congenital cardiac defects and adult heart failure

2019 ◽  
Vol 116 (3) ◽  
pp. 605-618 ◽  
Author(s):  
Beth A Firulli ◽  
Rajani M George ◽  
Jade Harkin ◽  
Kevin P Toolan ◽  
Hongyu Gao ◽  
...  
Keyword(s):  
Heart Failure ◽  
Gene Dosage ◽  
Diastolic Heart Failure ◽  
Heart Defects ◽  
Conduction System ◽  
Cardiac Conduction ◽  
Bhlh Transcription Factor ◽  
Loss Of Function ◽  
Regulatory Pathways ◽  
Morphological Alterations

Abstract Aims To examine the role of the basic Helix-loop-Helix (bHLH) transcription factor HAND1 in embryonic and adult myocardium. Methods and results Hand1 is expressed within the cardiomyocytes of the left ventricle (LV) and myocardial cuff between embryonic days (E) 9.5–13.5. Hand gene dosage plays an important role in ventricular morphology and the contribution of Hand1 to congenital heart defects requires further interrogation. Conditional ablation of Hand1 was carried out using either Nkx2.5 knockin Cre (Nkx2.5Cre) or α-myosin heavy chain Cre (αMhc-Cre) driver. Interrogation of transcriptome data via ingenuity pathway analysis reveals several gene regulatory pathways disrupted including translation and cardiac hypertrophy-related pathways. Embryo and adult hearts were subjected to histological, functional, and molecular analyses. Myocardial deletion of Hand1 results in morphological defects that include cardiac conduction system defects, survivable interventricular septal defects, and abnormal LV papillary muscles (PMs). Resulting Hand1 conditional mutants are born at Mendelian frequencies; but the morphological alterations acquired during cardiac development result in, the mice developing diastolic heart failure. Conclusion Collectively, these data reveal that HAND1 contributes to the morphogenic patterning and maturation of cardiomyocytes during embryogenesis and although survivable, indicates a role for Hand1 within the developing conduction system and PM development.

Functional and morphological evidence for a ventricular conduction system in zebrafish and Xenopus hearts

2003 ◽  
Vol 284 (4) ◽  
pp. H1152-H1160 ◽  
Author(s):  
David Sedmera ◽  
Maria Reckova ◽  
Angela deAlmeida ◽  
Martina Sedmerova ◽  
Martin Biermann ◽  
...  
Keyword(s):  
Polysialic Acid ◽  
Conduction System ◽  
Model Organisms ◽  
Morphological Evidence ◽  
Apical Region ◽  
Atrioventricular Canal ◽  
Organ Systems ◽  
Ventricular Activation ◽  
Activation Times ◽  
Ventricular Conduction

Zebrafish and Xenopus have become popular model organisms for studying vertebrate development of many organ systems, including the heart. However, it is not clear whether the single ventricular hearts of these species possess any equivalent of the specialized ventricular conduction system found in higher vertebrates. Isolated hearts of adult zebrafish ( Danio rerio) and African toads ( Xenopus laevis) were stained with voltage-sensitive dye and optically mapped in spontaneous and paced rhythms followed by histological examination focusing on myocardial continuity between the atrium and the ventricle. Spread of the excitation wave through the atria was uniform with average activation times of 20 ± 2 and 50 ± 2 ms for zebrafish and Xenopus toads, respectively. After a delay of 47 ± 8 and 414 ± 16 ms, the ventricle became activated first in the apical region. Ectopic ventricular activation was propagated significantly more slowly (total ventricular activation times: 24 ± 3 vs. 14 ± 2 ms in zebrafish and 74 ± 14 vs. 35 ± 9 ms in Xenopus). Although we did not observe any histologically defined tracts of specialized conduction cells within the ventricle, there were trabecular bands with prominent polysialic acid-neural cell adhesion molecule staining forming direct myocardial continuity between the atrioventricular canal and the apex of the ventricle; i.e., the site of the epicardial breakthrough. We thus conclude that these hearts are able to achieve the apex-to-base ventricular activation pattern observed in higher vertebrates in the apparent absence of differentiated conduction fascicles, suggesting that the ventricular trabeculae serve as a functional equivalent of the His-Purkinje system.

scholarly journals Transient Nodal signalling in left precursors coordinates opposed asymmetries shaping the heart loop

2019 ◽  
Author(s):  
Audrey Desgrange ◽  
Jean-François Le Garrec ◽  
Ségolène Bernheim ◽  
Tobias Holm Bønnelykke ◽  
Sigolène M. Meilhac
Keyword(s):  
Congenital Heart ◽  
Morphological Changes ◽  
Heart Defects ◽  
Matrix Composition ◽  
Mouse Heart ◽  
Heart Tube ◽  
Random Generator ◽  
Downstream Effectors ◽  
Heart Looping ◽  
Insight Into

SummaryThe secreted factor Nodal has been shown to be a major left determinant. Although it is associated with severe congenital heart defects, its role in heart morphogenesis has remained poorly understood. Here, we report that Nodal is transiently active in precursors of the mouse heart tube poles, before the morphological changes of heart looping. In conditional mutants, we show that Nodal is not required to initiate asymmetric morphogenesis. We provide evidence of a heart-specific random generator of asymmetry that is independent of Nodal. Using 3D quantifications and simulations, we demonstrate that Nodal functions as a bias of this mechanism: it is required to amplify and coordinate opposed left-right asymmetries at the heart tube poles, thus generating a robust helical shape. We identify downstream effectors of Nodal signalling, regulating asymmetries in cell proliferation, cell differentiation and extra-cellular matrix composition. Our work provides novel insight into how Nodal regulates asymmetric organogenesis.

scholarly journals Mechanosensitive Pathways in Heart Development: Findings from Chick Embryo Studies

2021 ◽  
Vol 8 (4) ◽  
pp. 32
Author(s):  
Maha Alser ◽  
Samar Shurbaji ◽  
Huseyin C. Yalcin
Keyword(s):  
Chick Embryo ◽  
Heart Development ◽  
Congenital Heart ◽  
Morphological Changes ◽  
Heart Defects ◽  
Genetic Regulation ◽  
The Body ◽  
Embryonic Chick ◽  
Chemical Treatments ◽  
Developing Heart

The heart is the first organ that starts to function in a developing embryo. It continues to undergo dramatic morphological changes while pumping blood to the rest of the body. Genetic regulation of heart development is partly governed by hemodynamics. Chick embryo is a major animal model that has been used extensively in cardiogenesis research. To reveal mechanosensitive pathways, a variety of surgical interferences and chemical treatments can be applied to the chick embryo to manipulate the blood flow. Such manipulations alter expressions of mechanosensitive genes which may anticipate induction of morphological changes in the developing heart. This paper aims to present different approaches for generating clinically relevant disturbed hemodynamics conditions using this embryonic chick model and to summarize identified mechanosensitive genes using the model, providing insights into embryonic origins of congenital heart defects.

Ultrastructural Study of a differentiating human colon carcinoma cell line

1990 ◽  
Vol 48 (3) ◽  
pp. 208-209
Author(s):  
Sylvie Polak-Charcon ◽  
Mehrdad Hekmati ◽  
Yehuda Ben Shaul
Keyword(s):  
Cell Line ◽  
Morphological Changes ◽  
Secretory Granules ◽  
Human Colon ◽  
Cell Types ◽  
Culture Conditions ◽  
Morphological Evidence ◽  
Human Colon Carcinoma Cell ◽  
Colon Cell

The epithelium of normal human colon mucosa “in vivo” exhibits a gradual pattern of differentiation as undifferentiated stem cells from the base of the crypt of “lieberkuhn” rapidly divide, differentiate and migrate toward the free surface. The major differentiated cell type of the intestine observed are: absorptive cells displaying brush border, goblet cells containing mucous granules, Paneth and endocrine cells containing dense secretory granules. These different cell types are also found in the intestine of the 13-14 week old embryo.We present here morphological evidence showing that HT29, an adenocarcinoma of the human colon cell line, can differentiate into various cell types by changing the growth and culture conditions and mimic morphological changes found during development of the intestine in the human embryo.HT29 cells grown in tissue-culture dishes in DMEM and 10% FCS form at late confluence a multilayer of morphologically undifferentiated cell culture covered with irregular microvilli, and devoid of tight junctions (Figs 1-3).

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