The avian embryo to study development of the cardiac conduction system.

The avian embryo has long been a popular model system in developmental biology. The easy accessibility of the embryo makes it particularly suitable for in ovo microsurgery and manipulation. Re-incubation of the embryo allows long-term follow-up of these procedures. The current review focuses on the variety of techniques available to study development of the cardiac conduction system in avian embryos. Based on the large amount of relevant data arising from experiments in avian embryos, we conclude that the avian embryo has and will continue to be a powerful model system to study development in general and the developing cardiac conduction system in particular.

The epicardium as modulator of the cardiac autonomic response during early development.

The cardiac autonomic nervous system (cANS) modulates heart rate, contraction force and conduction velocity. The embryonic chicken heart already responds to epinephrine prior to establishment of the cANS. The aim of this study was to define the regions of the heart that might participate in modulating the early autonomic response to epinephrine. Immunofluorescence analysis reveals expression of neural markers tubulin beta-3 chain and neural cell adhesion molecule in the epicardium during early development. In addition, expression of the ß2 adrenergic receptor, the receptor for epinephrine, was found in the epicardium. Ex-ovo micro-electrode recordings in hearts with inhibition of epicardial outgrowth showed a significantly reduced response of the heart rate to epinephrine compared to control hearts. This study suggests a role for the epicardium as autonomic modulator during early cardiac development.

The sinus venosus myocardium contributes to the atrioventricular canal: potential role during atrioventricular node development?

The presence of distinct electrophysiological pathways within the atrioventricular node (AVN) is a prerequisite for atrioventricular nodal reentrant tachycardia to occur. In this study, the different cell contributions that may account for the anatomical and functional heterogeneity of the AVN were investigated. To study the temporal development of the AVN, the expression pattern of ISL1, expressed in cardiac progenitor cells, was studied in sequential stages performing co-staining with myocardial markers (TNNI2 and NKX2-5) and HCN4 (cardiac conduction system marker). An ISL1+/TNNI2+/HCN4+ continuity between the myocardium of the sinus venosus and atrioventricular canal was identified in the region of the putative AVN, which showed a pacemaker-like phenotype based on single cell patch-clamp experiments. Furthermore, qPCR analysis showed that even during early development, different cell populations can be identified in the region of the putative AVN. Fate mapping was performed by in ovo vital dye microinjection. Embryos were harvested and analysed 24 and 48 hrs post-injection. These experiments showed incorporation of sinus venosus myocardium in the posterior region of the atrioventricular canal. The myocardium of the sinus venosus contributes to the atrioventricular canal. It is postulated that the myocardium of the sinus venosus contributes to nodal extensions or transitional cells of the AVN since these cells are located in the posterior region of the AVN. This finding may help to understand the origin of atrioventricular nodal reentrant tachycardia.

[Infants with an unexplained event: management of brief resolved unexplained events revised]. / Zuigelingen met een kortdurend, onverklaard incident.

In this article, the new Dutch pediatric guideline Brief Resolved Unexplained Event is discussed, which replaces the old guideline Apparent Life Threatening Event. The main goal of the new guideline is identification of a group of low-risk infants who need not be admitted to the hospital and in which only limited diagnostic workup is indicated. Three fictional cases are presented to highlight the major changes in management of infants who present with an unexplained event. Application of the new guideline will likely result in less clinical admissions and diagnostic testing in these patients.

Anatomical perspective on radiofrequency ablation of AV nodal reentry tachycardia after Mustard correction for transposition of the great arteries.

A case of radiofrequency catheter ablation of atrioventricular (AV) nodal reentry tachycardia, in a patient with transposition of the great arteries after venous rerouting according to Mustard, is described. An electroanatomical map of the His and AV nodal region was created from inside the systemic venous atrium. Retrograde mapping of the pulmonary venous atrium was performed and the arterial catheter retracted to a position in close proximity to the venous catheter inside the intraatrial baffle. This position was chosen to deliver radiofrequency current.

[An infant with a complicated infection of the umbilicus]. / Een zuigeling met een gecompliceerde navelontsteking.

BACKGROUND: An umbilical infection (omphalitis) is frequent in de neonatal period. The infection usually presents as a relatively mild cellulitis. However, in rare cases omphalitis has a complicated course. CASE DESCRIPTION: A 20-day-old infant was referred to our Emergency Department with a fever and red umbilicus. Our diagnosis was "omphalitis" and after taking cultures we started with flucloxacillin and gentamicin intravenously. Upon clinical deterioration, we added ceftazidime and performed an ultrasound of the abdomen. A urachal remnant was found. The umbilical swab was positive for Staphylococcus aureus, which we treated with flucloxacillin monotherapy until the infiltrate disappeared on ultrasound. CONCLUSION: A patient with an omphalitis should be referred to the pediatrician. Clinical admission, obtaining cultures and starting antibiotic treatment is necessary. A large number of health care providers are involved in the care during the neonatal period. Therefore, broad knowledge about prevention and early identification of this disease is important.

The Role of Cell Tracing and Fate Mapping Experiments in Cardiac Outflow Tract Development, New Opportunities through Emerging Technologies.

Whilst knowledge regarding the pathophysiology of congenital heart disease (CHDs) has advanced greatly in recent years, the underlying developmental processes affecting the cardiac outflow tract (OFT) such as bicuspid aortic valve, tetralogy of Fallot and transposition of the great arteries remain poorly understood. Common among CHDs affecting the OFT, is a large variation in disease phenotypes. Even though the different cell lineages contributing to OFT development have been studied for many decades, it remains challenging to relate cell lineage dynamics to the morphologic variation observed in OFT pathologies. We postulate that the variation observed in cellular contribution in these congenital heart diseases might be related to underlying cell lineage dynamics of which little is known. We believe this gap in knowledge is mainly the result of technical limitations in experimental methods used for cell lineage analysis. The aim of this review is to provide an overview of historical fate mapping and cell tracing techniques used to study OFT development and introduce emerging technologies which provide new opportunities that will aid our understanding of the cellular dynamics underlying OFT pathology.

Disruption of RHOA-ROCK Signaling Results in Atrioventricular Block and Disturbed Development of the Putative Atrioventricular Node.

The RHOA-ROCK signaling pathway is involved in numerous developmental processes, including cell proliferation, differentiation and migration. RHOA is expressed in the atrioventricular node (AVN) and altered expression of RHOA results in atrioventricular (AV) conduction disorders in mice. The current study aims to detect functional AVN disorders after disturbing RHOA-ROCK signaling in chicken embryos. RHOA-ROCK signaling was inhibited chemically by using the Rho-kinase inhibitor compound Y-27632 in avian embryos (20 experimental and 29 control embryos). Morphological examination of control embryos show a myocardial sinus venosus to atrioventricular canal continuity, contributing to the transitional zone of the AVN. ROCK inhibited embryos revealed lateralization and diminished myocardial sinus venosus to atrioventricular canal continuity and at the severe end of the phenotype hypoplasia of the AVN region. Ex ovo micro-electrode recordings showed an AV conduction delay in all treated embryos as well as cases with first, second (Wenkebach and Mobitz type) and third-degree AV block which could be explained by the spectrum of severity of the morphological phenotype. Laser capture microdissection and subsequent qPCR of tissue collected from this region revealed disturbed expression of HCN1, ISL1, and SHOX2. We conclude that RHOA-ROCK signaling is essential for normal morphological development of the myocardial continuity between the sinus venosus and AVN, contributing to the transitional zone, and possibly the compact AVN region. Disturbing the RHOA-ROCK signaling pathway results in AV conduction disturbances including AV block. The RHOA-ROCK inhibition model can be used to further study the pathophysiology and therapeutic strategies for AV block. Anat Rec, 302:83-92, 2019. © 2018 Wiley Periodicals, Inc.

RHOA-ROCK signalling is necessary for lateralization and differentiation of the developing sinoatrial node.

AIMS: RHOA-ROCK signalling regulates cell migration, proliferation, differentiation, and transcription. RHOA is expressed in the developing cardiac conduction system in chicken and mice. In early development, the entire sinus venosus myocardium, including both the transient left-sided and the definitive sinoatrial node (SAN), has pacemaker potential. Later, pacemaker potential is restricted to the right-sided SAN. Disruption of RHOA expression in adult mice causes arrhythmias including bradycardia and atrial fibrillation, the mechanism of which is unknown but presumed to affect the SAN. The aim of this study is to assess the role of RHOA-ROCK signalling in SAN development in the chicken heart. METHODS AND RESULTS: ROCK signalling was inhibited chemically in embryonic chicken hearts using Y-27632. This prolonged the immature state of the sinus venosus myocardium, evidenced by up-regulation of the transcription factor ISL1, wide distribution of pacemaker potential, and significantly reduced heart rate. Furthermore ROCK inhibition caused aberrant expression of typical SAN genes: ROCK1, ROCK2, SHOX2, TBX3, TBX5, ISL1, HCN4, CX40, CAV3.1, and NKX2.5 and left-right asymmetry genes: PITX2C and NODAL. Anatomical abnormalities in pulmonary vein development were also observed. Patch clamp electrophysiology confirmed the immature phenotype of the SAN cells and a residual left-sided sinus venosus myocardium pacemaker-like potential. CONCLUSIONS: RHOA-ROCK signalling is involved in establishing the right-sided SAN as the definitive pacemaker of the heart and restricts typical pacemaker gene expression to the right side of the sinus venosus myocardium.

Variation in coronary anatomy in adult patients late after arterial switch operation: a computed tomography coronary angiography study.

BACKGROUND: The arterial switch operation is the current treatment for transposition of the great arteries. Long-term outcome mainly depends on the patency of the transferred coronary arteries. This study assessed the presence of abnormal coronary findings and neoaortic root dilation late after arterial switch operation. METHODS: In 30 adult patients after arterial switch operation (22 men, 22 ± 3 years), computed tomography angiography was performed to assess the coronary anatomy and abnormal coronary findings, defined as significant stenosis, interarterial coronary course, and acute angled coronary origins. Neoaortic root dimensions and coronary takeoff height were also assessed. RESULTS: The most common coronary anatomy pattern was found in 24 of 30 patients. Variant anatomy patterns were seen in 6 patients (5 with aberrant circumflex artery, 1 with a single ostium). The prevalence of abnormal coronary findings was higher in patients with variant coronary pattern as compared with patients with common coronary pattern (100% and 29%, respectively; p = 0.003). In particular, an acute angle of the coronary origin was frequently observed. In patients with an acute angle, larger dimensions of the aortic annulus (p = 0.016) and the sinus of Valsalva (p = 0.002) were observed. Moreover, a higher takeoff of the right (p = 0.030) and left (p = 0.002) coronary ostium was noted in patients with acute angles. CONCLUSIONS: Abnormal coronary findings were frequently observed in adult patients after arterial switch operation, especially in patients with a variant coronary anatomy pattern. Neoaortic root dilation and a higher coronary takeoff may explain part of the pathophysiology. Long-term follow-up is needed to determine the clinical significance of these findings.

[A vomiting neonate]. / Een brakende zuigeling.

A 24-days-old male neonate presented with vomiting directly after feeding. Physical examination showed a prominent peristaltic wave, indicating an obstruction of the pylorus. This diagnosis was confirmed with a capillary bloodgas measurement and ultrasound examination. A Ramstedt procedure was performed without complications.

Quantitative polymerase chain reaction-based analysis of podocyturia is a feasible diagnostic tool in preeclampsia.

Preeclampsia is a significant cause of maternal and fetal morbidity and mortality worldwide. A clinically useful screening test that can predict development of preeclampsia at an early stage is urgently needed. The detection of podocyturia by immunohistochemistry after cell culture has been noted as a reliable marker for preeclampsia. However, this method is laborious and carries the risk of cell culture contamination. The aim of this study was to investigate the diagnostic value of quantitative polymerase chain reaction as a rapid method to detect preeclampsia. Clean-catch urine samples were collected from preeclamptic (n=35), healthy pregnant (n=34), and healthy nonpregnant (n=12) women. Furthermore, a control group of women with gestational hypertension (n=5) was included. Quantitative polymerase chain reaction analysis was performed for podocyte-specific markers. Receiver operating characteristic curve analyses were performed. Significantly elevated mRNA levels of nephrin, podocin, and vascular endothelial growth factor were detected in preeclamptic women compared with healthy pregnant and healthy nonpregnant controls. In addition, significantly elevated levels of nephrin mRNA were detected in urine of preeclamptic women compared with women with gestational hypertension. A positive correlation (ρ=0.82; P<0.0001) was observed between nephrin and vascular endothelial growth factor mRNA levels in preeclamptic women. Receiver operating characteristic curve analyses demonstrated a strong ability of this method to discriminate between the different study groups. Quantitative polymerase chain reaction analysis of podocyte-specific molecules in urine samples is a rapid and reliable method to quantify podocyturia. We demonstrate that this method distinguishes preeclamptic patients from healthy controls and women with gestational hypertension. This method may be a tool for the detection of preeclampsia at an earlier stage, thereby preventing maternal and fetal morbidity and mortality.