Fibronectin signals through integrin α5ß1 to regulate cardiovascular development in a cell type-specific manner.

Fibronectin (Fn1) is an evolutionarily conserved extracellular matrix glycoprotein essential for embryonic development. Global deletion of Fn1 leads to mid-gestation lethality from cardiovascular defects. However, severe morphogenetic defects that occur early in embryogenesis in these embryos precluded assigning a direct role for Fn1 in cardiovascular development. We noticed that Fn1 is expressed in strikingly non-uniform patterns during mouse embryogenesis, and that its expression is particularly enriched in the pharyngeal region corresponding with the pharyngeal arches 3, 4, and 6. This region bears a special importance for the developing cardiovascular system, and we hypothesized that the localized enrichment of Fn1 in the pharyngeal region may be essential for cardiovascular morphogenesis. To test this hypothesis, we ablated Fn1 using the Isl1(Cre) knock-in strain of mice. Deletion of Fn1 using the Isl1(Cre) strain resulted in defective formation of the 4th pharyngeal arch arteries (PAAs), aberrant development of the cardiac outflow tract (OFT), and ventricular septum defects. To determine the cell types responding to Fn1 signaling during cardiovascular development, we deleted a major Fn1 receptor, integrin α5 using the Isl1(Cre) strain, and observed the same spectrum of abnormalities seen in the Fn1 conditional mutants. Additional conditional mutagenesis studies designed to ablate integrin α5 in distinct cell types within the Isl1(+) tissues and their derivatives, suggested that the expression of integrin α5 in the pharyngeal arch mesoderm, endothelium, surface ectoderm and the neural crest were not required for PAA formation. Our studies suggest that an (as yet unknown) integrin α5-dependent signal extrinsic to the pharyngeal endothelium mediates the formation of the 4th PAAs.

Mesodermal expression of integrin α5ß1 regulates neural crest development and cardiovascular morphogenesis.

Integrin α5-null embryos die in mid-gestation from severe defects in cardiovascular morphogenesis, which stem from defective development of the neural crest, heart and vasculature. To investigate the role of integrin α5ß1 in cardiovascular development, we used the Mesp1(Cre) knock-in strain of mice to ablate integrin α5 in the anterior mesoderm, which gives rise to all of the cardiac and many of the vascular and muscle lineages in the anterior portion of the embryo. Surprisingly, we found that mutant embryos displayed numerous defects related to the abnormal development of the neural crest such as cleft palate, ventricular septal defect, abnormal development of hypoglossal nerves, and defective remodeling of the aortic arch arteries. We found that defects in arch artery remodeling stem from the role of mesodermal integrin α5ß1 in neural crest proliferation and differentiation into vascular smooth muscle cells, while proliferation of pharyngeal mesoderm and differentiation of mesodermal derivatives into vascular smooth muscle cells was not defective. Taken together our studies demonstrate a requisite role for mesodermal integrin α5ß1 in signaling between the mesoderm and the neural crest, thereby regulating neural crest-dependent morphogenesis of essential embryonic structures.

Fibronectin and integrin alpha 5 play requisite roles in cardiac morphogenesis.

Fibronectin and its major receptor, integrin α5ß1 are required for embryogenesis. These mutants have similar phenotypes, although, defects in integrin α5-deficient mice are milder. In this paper, we examined heart development in those mutants, in which the heart is formed, and discovered that both fibronectin and integrin α5 were required for cardiac morphogenesis, and in particular, for the formation of the cardiac outflow tract. We found that Isl1+ precursors are specified and migrate into the heart in fibronectin- or integrin α5-mutant embryos, however, the hearts in these mutants are of aberrant shape, and the cardiac outflow tracts are short and malformed. We show that these defects are likely due to the requirement for cell adhesion to fibronectin for proliferation of myocardial progenitors and for Fgf8 signaling in the pharyngeal region.

Essential roles of fibronectin in the development of the left-right embryonic body plan.

Studies in Xenopus laevis suggested that cell-extracellular matrix (ECM) interactions regulate the development of the left-right axis of asymmetry; however, the identities of ECM components and their receptors important for this process have remained unknown. We discovered that FN is required for the establishment of the asymmetric gene expression pattern in early mouse embryos by regulating morphogenesis of the node, while cellular fates of the nodal cells, canonical Wnt and Shh signaling within the node were not perturbed by the absence of FN. FN is also required for the expression of Lefty 1/2 and activation of SMADs 2 and 3 at the floor plate, while cell fate specification of the notochord and the floor plate, as well as signaling within and between these two embryonic organizing centers remained intact in FN-null mutants. Furthermore, our experiments indicate that a major cell surface receptor for FN, integrin α5ß1, is also required for the development of the left-right asymmetry, and that this requirement is evolutionarily conserved in fish and mice. Taken together, our studies demonstrate the requisite role for a structural ECM protein and its integrin receptor in the development of the left-right axis of asymmetry in vertebrates.

Simultaneous balloon aortic valvotomy and patent ductus arteriosus device closure in preterm newborn.

Multiple congenital heart disease in the small preterm newborn such as severe narrowing of aortic valve and patent ductus arteriosus (PDA) is a therapeutic challenge. We report successful transcatheter antegrade balloon dilatation of the aortic valve and device closure of the PDA in a 1700-gram preterm newborn. Meticulous planning and team work aids in such transcatheter intervention. .

Comparative Evaluation of Intrathecal Dexmedetomidine and Fentanyl as an Adjuvant for Combined Spinal-Epidural Analgesia for Labor.

Background: Combined spinal-epidural technique is a widely accepted and popular modality for labor analgesia. Opioids are being used as adjuvants since long time. Dexmedetomidine is a new drug that is being used as an intrathecal adjuvant. Aim: The study aims to compare the safety and efficacy of fentanyl and dexmedetomidine as intrathecal adjuvants in labor analgesia. Settings and Design: This was a continuous, prospective, randomized controlled trial with 120 parturients. Materials and Methods: After ethical approval and written consent, participants were divided randomly into two groups: Group A - bupivacaine 2.5 mg (0.5 mL diluted to 2 mL) + 20 µg of dexmedetomidine in 1 mL saline intrathecally (total volume: 3 mL) and Group B - bupivacaine 2.5 mg (0.5 mL diluted to 2 mL) + 15 µg of fentanyl in 1 mL saline intrathecally (total volume: 3 mL). Primary outcomes were satisfactory analgesia, mode of delivery, and neonatal outcome. Participants were monitored for the onset and duration of analgesia, degree of motor block, and maternal and fetal side effects. Results: A total of 108 parturients reported sufficient analgesia (Group A: 57; Group B: 51), and 74 patients delivered vaginally (Group A: 41; Group B: 44). The rates of normal vaginal delivery were higher in Group B. Group A reported earlier onset of analgesia (61.26 ± 18.23 s) that lasted for longer duration (124.16 ± 26.23 min) than in Group B. There were no serious side effects in any of the groups. Fetal ultrasound revealed attenuation of fetal heart rate variability. The heart rate of newborns was also found to be low in Group A. Conclusion: Chances of vaginal delivery are higher with intrathecal fentanyl as an adjuvant. Intensity and duration of analgesia are better with intrathecal dexmedetomidine.

The electrocardiogram in large pericardial effusion: the forgotten "P" wave and the influence of tamponade, size, etiology, and pericardial thickness on QRS voltage.

There are varying reports on the electrocardiogram in pericardial effusions. Some correlate low QRS voltage with tamponade and the size of the effusion while others do not. Low voltage also appears to vary with the etiology. There are no reports on the influence of pericardial thickness or changes in the P voltage. The authors studied 43 patients with large effusions of whom 26 had tuberculosis and the remaining had viral/idiopathic etiology. Pericardial thickness was measured at chest computed tomography. They found no correlation between the low QRS voltage and tamponade, size of the effusion, etiology, or pericardial thickness. Low voltage of the P wave and T-wave changes were more frequent than low QRS voltage.

Fibronectin and integrin alpha 5 play essential roles in the development of the cardiac neural crest.

Cardiac neural crest (CNC) plays a requisite role during cardiovascular development and defects in the formation of CNC-derived structures underlie several common forms of human congenital birth defects. Migration of the CNC cells to their destinations as well as expansion and maintenance of these cells are important for the normal development of the cardiac outflow tract and aortic arch arteries; however, molecular mechanisms regulating these processes are not well-understood. Fibronectin (FN) protein is present along neural crest migration paths and neural crest cells migrate when plated on FN in vitro; therefore, we tested the role of FN during the development of the CNC in vivo. Our analysis of the fate of the neural crest shows that CNC cells reach their destinations in the branchial arches and the cardiac outflow tract in the absence of FN or its cellular receptor integrin α5ß1. However, we found that FN and integrin α5 modulate CNC proliferation and survival, and are required for the presence of normal numbers of CNC cells at their destinations.

Bilateral herpes simplex-2 acute retinal necrosis with encephalitis in premature twins.

Acute retinal necrosis, caused by the herpes family of viruses, is a rapidly progressing ocular inflammatory disorder commonly reported in adults but rarely in children. The accepted diagnostic criteria include presence of 1 or more foci of retinal necrosis, rapid progression, circumferential spread, occlusive vasculopathy, and inflammation in the vitreous and anterior chamber. We report bilateral acute retinal necrosis with encephalitis due to herpes simplex virus (HSV-2) in newborn twins.

Correlation of sonographic findings and outcome in necrotizing enterocolitis.

BACKGROUND: There is little in the literature regarding the use of gray-scale and Doppler sonography of the bowel in necrotizing enterocolitis (NEC) and how findings depicted by this modality might assist in predicting outcome and influence management. OBJECTIVE: To correlate sonographic findings with outcome in NEC. MATERIALS AND METHODS: This was a retrospective analysis of clinical and abdominal ultrasonography (AUS) findings in NEC from January 2003 to December 2005. AUS findings were evaluated for portal venous gas, free gas, peritoneal fluid, bowel wall thickness, echogenicity, perfusion and intramural gas. Patients were categorized into two groups, according to their outcome. RESULTS: A total of 40 infants were identified who had AUS for NEC prior to any surgical intervention. Group A comprised 18 neonates treated medically and recovered fully, and group B comprised 22 neonates who required surgery or died. Free gas (six patients) and focal fluid collections (three patients) were only found in group B. Increased bowel wall echogenicity, absent bowel perfusion, portal venous gas, bowel wall thinning, bowel wall thickening, free fluid with echoes and intramural gas were seen in both groups, but more frequently in group B. Anechoic free fluid was seen more frequently in group A. Increased bowel perfusion was seen equally in both groups. CONCLUSION: An adverse outcome was associated with the sonographic findings of free gas, focal fluid collections or three or more of the following: increased bowel wall echogenicity, absent bowel perfusion, portal venous gas, bowel wall thinning, bowel wall thickening, free fluid with echoes and intramural gas. Sonographic findings are useful in predicting outcome and therefore might help guide management.