Dynamic esophageal patency assessment: an effective method for prenatally diagnosing esophageal atresia.

BACKGROUND: Esophageal atresia is a major anomaly with a low prenatal detection rate. We propose a sonographic method termed dynamic esophageal patency assessment. OBJECTIVE: This study aimed to assess the feasibility and performance of the dynamic esophageal patency assessment in a high-risk population. STUDY DESIGN: A prospective study was conducted in a single tertiary fetal ultrasound unit for 12 months. The study group included pregnant women referred for a targeted scan because of one or more of the following: (1) polyhydramnios; (2) small or absent stomach; (3) vertebral, anal atresia, cardiac, tracheoesophageal fistula, renal, and limb abnormalities; (4) first-degree relative with esophageal atresia; and (5) genetic mutation associated with esophageal atresia. In addition to dynamic esophageal patency assessment, a comprehensive anomaly scan was carried out. The fetal esophagus was observed during swallowing. Cases that demonstrated uninterrupted fluid propagation through the esophagus were classified as normal. Cases that demonstrated interrupted fluid propagation, with the formation of a pouch, were classified as abnormal. Cases with unclear visualization of the esophagus or cases that failed to demonstrate either fluid propagation or a pouch were classified as undetermined. Dynamic esophageal patency assessment results were compared with postnatal findings, considered "gold standard." Test performance indices and intra- and interobserver agreements were calculated. RESULTS: For 12 months, 130 patients were recruited, and 132 fetuses were scanned. The median gestational age (interquartile range) at the time of scan was 31.4 weeks (29.0-35.3). Of 132 fetuses enrolled, 123 (93.2%) were normal, 8 (6%) were abnormal, and 1 (0.8%) was undetermined. Excluded from test performance analysis were 3 cases that were terminated without postmortem autopsy (1 was abnormal and 2 were normal), and a fourth case was excluded as it was classified as undetermined. The detection rate of esophageal atresia was 100%, with no false-positive or false-negative case. Sensitivity, specificity, and positive and negative predictive values of the dynamic esophageal patency assessment were 100%. The Kappa coefficient was 1 for both inter- and intraobserver agreements (P<.0001). The median time (interquartile range) required to complete the dynamic esophageal patency assessment was 6.00 minutes (3.00-13.25). CONCLUSION: The dynamic esophageal patency assessment is a feasible and highly effective method of ascertaining an intact esophagus and detecting esophageal atresia in suspected cases.

Esophageal atresia and tracheoesophageal fistula: prenatal sonographic manifestation from early to late pregnancy.

OBJECTIVE: Esophageal atresia and/or tracheoesophageal fistula (EA/TEF) remains one of the most frequently missed congenital anomalies prenatally. The aim of our study was to elucidate the sonographic manifestation of EA/TEF throughout pregnancy. METHODS: This was a retrospective study of data obtained from a tertiary center over a 12-year period. The prenatal ultrasound scans of fetuses with EA/TEF were assessed to determine the presence and timing of detection of three principal signs: small/absent stomach and worsening polyhydramnios, both of which were considered as 'suspected' EA/TEF, and esophageal pouch, which was considered as 'detected' EA/TEF. We assessed the yield of the early (14-16 weeks' gestation), routine mid-trimester (19-26 weeks) and third-trimester (≥ 27 weeks) anomaly scans in the prenatal diagnosis of EA/TEF. RESULTS: Seventy-five cases of EA/TEF with available ultrasound images were included in the study. A small/absent stomach was detected on the early anomaly scan in 3.6% of fetuses scanned, without a definitive diagnosis. On the mid-trimester scan, 19.4% of scanned cases were suspected and 4.3% were detected. On the third-trimester anomaly scan, 43.9% of scanned cases were suspected and 33.9% were detected. An additional case with an esophageal pouch was detected on magnetic resonance imaging (MRI) in the mid-trimester and a further two were detected on MRI in the third trimester. In total, 44.0% of cases of EA/TEF in our cohort were suspected, 33.3% were detected and 10.7% were suspected but, eventually, not detected prenatally. CONCLUSIONS: Prenatal diagnosis of EA/TEF on ultrasound is not feasible before the late second trimester. A small/absent stomach may be visualized as early as 15 weeks' gestation. Polyhydramnios does not develop before the mid-trimester. An esophageal pouch can be detected as early as 22 weeks on a targeted scan in suspected cases. The detection rates of all three signs increase with advancing pregnancy, peaking in the third trimester. The early and mid-trimester anomaly scans perform poorly as a screening and diagnostic test for EA/TEF. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Noggin regulates foregut progenitor cell programming, and misexpression leads to esophageal atresia.

Esophageal atresia (EA/TEF) is a common congenital abnormality present in 1 of 4000 births. Here we show that atretic esophagi lack Noggin (NOG) expression, resulting in immature esophagus that contains respiratory glands. Moreover, when using mouse esophageal organoid units (EOUs) or tracheal organoid units (TOUs) as a model of foregut development and differentiation in vitro, NOG determines whether foregut progenitors differentiate toward esophageal or tracheal epithelium. These results indicate that NOG is a critical regulator of cell fate decisions between esophageal and pulmonary morphogenesis, and its lack of expression results in EA/TEF.

A Simple and Easy Technique for Imaging the Fetal Esophagus in the First, Second, and Third Trimesters Using the Transverse Section of the Esophagus in the Area Behind the Heart as a Reference Point.

OBJECTIVE: To describe and evaluate a simple technique of imaging the fetal esophagus, using the echogenic transverse section of the esophagus in the area behind the heart as a reference point, in all the 3 trimesters of pregnancy. METHOD: This was a prospective cross-sectional study of ultrasound imaging of the esophagus in 2 groups of patients: the first group comprised women at 18 to 30 weeks' gestation (208 fetuses); the second group comprised women at 11 to 14 weeks' gestation (102 fetuses). Using a 3- to 5-MHz curvilinear transducer, the transverse section of the collapsed esophagus was imaged in the area behind the heart. The probe was rotated 90 degrees to identify the longitudinal section of the esophagus which was then traced along its entire length. RESULT: This study shows that the collapsed, echogenic, transverse section of the esophagus was persistently seen in the area behind the heart, in more than 99% of fetuses in both the groups. It was a useful starting point to image the longitudinal section of the esophagus in both the groups, particularly in the 18 - 30 week group. Using this technique, the entire length of the esophagus could be traced in 92.3% of 18 - 30 week fetuses and 88.23% of the 11 - 14 week fetuses. CONCLUSION: A collapsed transverse section of the esophagus was persistently and easily seen as a bright echogenic structure in the area behind the heart in more than 99% of fetuses in all 3 trimesters (in both the groups) and, therefore, was an ideal starting point to begin tracing the esophagus in its longitudinal axis.

Interkinetic nuclear migration in the tracheal and esophageal epithelia of the mouse embryo: Possible implications for tracheo-esophageal anomalies.

Interkinetic nuclear migration (INM) is a cell polarity-based phenomenon in which progenitor cell nuclei migrate along the apico-basal axis of the pseudostratified epithelium in synchrony with the cell cycle. INM is suggested to be at least partially cytoskeleton-dependent and to regulate not only the proliferation/differentiation of stem/progenitor cells but also the localized/overall size and shape of organs/tissues. INM occurs in all three of the germ-layer derived epithelia, including the endoderm-derived gut. However, INM has not been documented in the esophagus and respiratory tube arising from the anterior foregut. Esophageal atresia with or without trachea-esophageal fistula (EA/TEF) is a relatively common developmental defect. Transcription factors and signaling molecules have been implicated in EA/TEF, but the etiology of EA/TEF-which has been suggested to involve cell polarity-related mechanisms-remains highly controversial. In the present study, we first examined whether INM exists in the trachea and esophagus of mouse embryos at embryonic day 11.5 (E11.5), just after separation of the two tubes from the anterior foregut. By labeling the DNA-synthesizing stem cell nuclei with 5-ethynyl-2'-deoxyuridine, a nucleotide analogue, and statistically analyzing chronological changes in the distribution pattern of the labeled nuclei by using multidimensional scaling, we showed the existence of INM in both the esophagus and trachea, with differences in the INM magnitude and cycle pattern. We further showed morphological changes from the INM-based pseudostratified single layer to the stratified multilayer in the esophageal epithelium in association with a temporal loss/perturbation of AB polarity, suggesting a possible relation with the pathogenesis of EA/TEF.

Twin pregnancy complicated by esophageal atresia, duodenal atresia, gastric perforation, and hypoplastic left heart structures in one twin: a case report and review of the literature.

BACKGROUND: The antenatal diagnosis of a combined esophageal atresia without tracheoesophageal fistula and duodenal atresia with or without gastric perforation is a rare occurrence. These diagnoses are difficult and can be suspected on ultrasound by nonspecific findings including a small stomach and polyhydramnios. Fetal magnetic resonance imaging adds significant anatomical detail and can aid in the diagnosis of these complicated cases. Upon an extensive literature review, there are no reports documenting these combined findings in a twin pregnancy. Therefore we believe this is the first case report of an antenatal diagnosis of combined pure esophageal and duodenal atresia in a twin gestation. CASE PRESENTATION: We present a case of a 30-year-old G1P0 white woman at 22-week gestation with a monochorionic-diamniotic twin pregnancy discordant for esophageal atresia, duodenal atresia with gastric perforation, hypoplastic left heart structures, and significant early gestation maternal polyhydramnios. In this case, fetal magnetic resonance imaging was able to depict additional findings including area of gastric wall rupture, hiatal hernia, dilation of the distal esophagus, and area of duodenal obstruction and thus facilitated the proper diagnosis. After extensive counseling at our multidisciplinary team meeting, the parents elected to proceed with radiofrequency ablation of the anomalous twin to maximize the survival of the normal co-twin. The procedure was performed successfully with complete cessation of flow in the umbilical artery and complete cardiac standstill in the anomalous twin with no detrimental effects on the healthy co-twin. CONCLUSIONS: Prenatal diagnosis of complex anomalies in twin pregnancies constitutes a multitude of ethical, religious, and cultural factors that come into play in the management of these cases. Fetal magnetic resonance imaging provides detailed valuable information that can assist in management options including possible prenatal intervention. The combination of a cystic structure with peristalsis-like movement above the diaphragm (for example, "the upper thoracic pouch sign"), polyhydramnios, and progressive distention of the stomach and duodenum should increase suspicion for a combined pure esophageal and duodenal atresia.

Impaired VEGF Signaling in Lungs with Hypoplastic Esophageal Atresia and Effects on Branching Morphogenesis.

BACKGROUND/AIMS: Patients with esophageal atresia (EA) and tracheoesophageal fistula (TEF) often suffer chronic respiratory tract disease. We previously reported that primary lung maldevelopment caused by deficient branching of embryonal airways in experimental EA-TEF was induced by Adriamycin. In this study, we investigated the Vascular endothelial growth factor (VEGF) pathway in the developing lung in an EA-TEF rat model. We further analyzed the effect of recombinant VEGF treatment in vitro on branching morphogenesis of embryo lungs in experimental EA-TEF. METHODS: Pregnant rats received either Adriamycin or vehicle on E7, E8 and E9. Lungs were recovered at E15, E18 and E21. Expression of VEGF and receptors (Flk-1 and Flt-1) were assessed by quantitative PCR, immunohistochemistry and immunoblotting. E13 lungs were cultured for 72 hours with 50 ng/mL of recombinant rat VEGF in serum-free medium. The rates of increase in bud count and airway contour were evaluated. RESULTS: Our results showed a significant downregulation of VEGF during pseudoglandular and canalicular stages. In contrast, there were significantly higher levels of the Flt-1 receptor in the canalicular stage, which may represent a compensatory response to decreased VEGF. However, both variables returned to normal levels at the saccular stage. Exogenous VEGF treatment enhanced hypoplastic lung growth, evidenced by the increase in bud count and airway contour. CONCLUSIONS: A VEGF signaling defect possibly plays an important role in defective embryonic airway branching. Additionally, VEGF treatment may accelerate lung growth in EA-TEF lungs.

Lung maturity in esophageal atresia: Experimental and clinical study.

INTRODUCTION: Esophageal atresia and tracheoesophageal fistula (EA-TEF) survivors suffer respiratory morbidity of unclear pathogenesis. Defective lung morphogenesis has been described in the rat model. This study examined fetal lung growth and maturity in rats and patients with EA-TEF. METHODS: Pregnant rats received either adriamycin or vehicle. Control and adriamycin-exposed lungs, with and without EA-TEF, were weighed and processed for RT-PCR, DNA quantification, immunofluorescence and immunoblot analysis of TTF1, VEGF, Sp-B, and α-sma. Twenty human lungs were also processed for immunofluorescence and Alcian-blue staining. RESULTS: Lungs from fetuses with EA-TEF (E21) showed decreased total DNA; FGF7 and TTF1 mRNA expressions were upregulated at E15 and E18, respectively. Protein expression and immunofluorescent distribution of maturity markers were similar. Lungs from stillborns with EA-TEF showed decreased epithelial expression of Sp-B and VEGF whereas those from newborns tended to have less Sp-B and more VEGF and mucous glands. DISCUSSION: The lungs of rats with EA-TEF were hypoplastic but achieved near-normal maturity. Stillborns with EA-TEF exhibited an apparently disturbed differentiation of the airway epithelium. Newborns with EA-TEF demonstrated subtle differences in the expression of differentiation markers, and increased number of mucous glands that could influence postnatal respiratory adaptation and explain some respiratory symptoms of EA-TEF survivors.

The contribution of fetal MR imaging to the assessment of oesophageal atresia.

OBJECTIVE: Present challenges are to improve the diagnosis rate of oesophageal atresia (OA) and evaluate as completely as possible a fetus affected by OA, specifically the type of OA and the length of the gap. Our aim was to evaluate the accuracy of fetal MR imaging (fMRI) for diagnosis of OA. METHODS: We reviewed fMRI performed because of sonographic suspicion of an OA. The signs reviewed included stomach size, "pouch sign", bowing of the trachea and visualization of the lower oesophageal lumen. The fetuses were assigned by consensus as having or not having EA, as well as having a tracheaoesophageal fistula (TOF). All findings were correlated with postnatal data. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. RESULTS: Se, Sp, PPV and NPV of the technique were respectively 91%, 100%, 100% and 88%. The presence of the pouch sign yielded corresponding values of 82%, 100%, 100% and 78%. Mid-tracheal bowing was correlated positively with EA. The type of atresia was correctly evaluated in 90% of patients. CONCLUSION: fMRI is useful for the diagnosis of EA through the visualization of the oesophageal pouch or through associated signs such as tracheal bowing. Visualization of the lower oesophageal lumen seems to be a good sign of TEF. KEY POINTS: • Challenges are to improve the prenatal diagnosis of EA and associated malformations. • fMRI is able to diagnose EA through demonstration of the pouch sign. • Tracheal bowing is a promising indirect sign of EA. • Tracheoesophageal fistula can also be suspected thanks to fMRI. • Obstetrical US, fMRI and fetal CT are complementary for assessing associated malformations.

Oesophageal atresia and tracheo-oesophageal fistula.

Oesophageal atresia with tracheo-oesophageal fistula is a relatively common congenital anomaly occurring in around 1:2500 births. The aetiology and embryology of the condition remain unclear, whilst associations with other significant anomalies are common. Studies in rodent models are contributing to our understanding of the condition. Advances in surgical care and neonatal management have improved survival considerably to around 90%. Long-gap and isolated oesophageal atresia present significant management challenges. Post-operative and long-term complications including oesophageal stricture, gastro-oesophageal reflux and respiratory compromise however remain relatively common and continue to pose a challenge for the ongoing management of patients.

Maternal hyperthyroidism increases the prevalence of foregut atresias in fetal rats exposed to adriamycin.

PURPOSE: Gastrointestinal malformations such as esophageal atresia with tracheoesophageal fistula (EA/TEF) and duodenal atresia (DA) have been reported in infants born to hyperthyroid mothers or with congenital hypothyroidism. The present study aimed to test whether maternal thyroid status during embryonic foregut division has any influence on the prevalence of EA/TEF and DA in an accepted rat model of these malformations. METHODS: Pregnant rats received either vehicle or 1.75 mg/kg i.p. adriamycin on gestational days 7, 8 and 9. Transient maternal hyper or hypothyroidism was induced by oral administration of levothyroxine (LT4, 50 µg/kg/day) or propylthiouracil (PTU, 2 mg/kg/day), respectively, on days 7 to 12 of gestation. Plasma cholesterol, total T3, free T4 and TSH were measured at gestational days 7, 12, and 21. At the end of gestation, the mothers were sacrificed and embryo-fetal mortality was recorded. Fetuses were dissected to determine the prevalence of esophageal and intestinal atresias. RESULTS: At gestational day 12, mothers treated with LT4 or PTU had hyper or hypothyroid status, respectively; plasma cholesterol levels were similar. In the adriamycin-exposed fetuses from hyperthyroid mothers, the embryonal resorption rate and the prevalence of both EA/TEF and DA were significantly higher than in the other groups; maternal hypothyroidism during the same period did not have significant effect on the prevalence of atresias. CONCLUSIONS: Maternal hyperthyroidism during the embryonic window corresponding to foregut cleavage increased the prevalence of both EA/TEF and duodenal atresia in fetal rats exposed to adriamycin. This suggests that maternal thyroid hormone status might be involved in the pathogenesis of foregut atresias and invites further research on this likely clinically relevant issue in humans.

Altered Tbx1 gene expression is associated with abnormal oesophageal development in the adriamycin mouse model of oesophageal atresia/tracheo-oesophageal fistula.

INTRODUCTION: Oesophageal atresia/tracheo-oesophageal atresia (OA/TOF) frequently arises with associated anomalies and has been clinically linked with 22q11 deletion syndromes, a group of conditions due to Tbx1 gene mutation which include Di George syndrome. Tbx1 and Tbx2 genes modulate pharyngeal and cardiac development, but are also expressed in the developing foregut and are known to interact with key signalling pathways described in oesophageal formation including bone morphogenic proteins. The adriamycin mouse model (AMM) reliably displays OA/TOF-like foregut malformations providing a powerful system for investigating the disturbances in gene regulation and morphology involved in tracheo-oesophageal malformations. We hypothesised that foregut abnormalities observed in the AMM are associated with altered Tbx1 and Tbx2 gene expression. METHODS: Time-mated CBA/Ca mice received intra-peritoneal injection of adriamycin (for treated) or saline (for controls) on embryonic days (E)7 and 8. Untreated Cd1 embryos were used to establish normal expression patterns. Embryos harvested on E9-E11 underwent whole-mount in situ hybridization with labelled RNA probes for Tbx1 and Tbx2. Optical projection tomography was used to visualise expression in whole embryos by 3D imaging. RESULTS: Tbx1 expression was visualised in a highly specific pattern in the proximal oesophageal endoderm in normal and control embryos. In the AMM, extensive ectopic expression of Tbx1 was detected in the dorsal foregut and adjacent to the TOF. The focally restricted oesophageal expression pattern persisted in the AMM, but was posteriorly displaced in relation to the tracheal bifurcation. Tbx2 was widely expressed in the ventral foregut mesoderm of controls, lacking specific endoderm localisation. In the AMM, altered Tbx2 expression in the foregut was only seen in severely affected embryos. CONCLUSION: Highly specific Tbx1 expression in the proximal oesophageal endoderm suggests that Tbx1 may be an important regulator of normal oesophageal development. Altered Tbx1 expression in dorsal foregut and adjacent to the TOF in the AMM suggests that Tbx1 gene disruption may contribute to the pathogenesis of tracheo-oesophageal malformations.

Genetic and cellular mechanisms of the formation of esophageal atresia and tracheoesophageal fistula.

Foregut separation involves dynamic changes in the activities of signaling pathways and transcription factors. Recent mouse genetic studies demonstrate that some of these pathways interact with each other to form a complex network, leading to a unique dorsal-ventral patterning in the early foregut. In this review, it is discussed how this unique dorsal-ventral patterning is set prior to the foregut separation and how disruption of this patterning affects the separation process. Roles of downstream targets of these pathways in regulating separation at cellular and molecular levels would be discussed further. Understanding the mechanism of normal separation process will provide insights into the pathobiology of a relatively common birth defect, esophageal atresia with/without tracheoesophageal fistula.

Abnormal control of lung branching in experimental esophageal atresia.

PURPOSE: Esophageal atresia and tracheo-esophageal fistula (EA-TEF) result from abnormal division of the foregut into esophagus and trachea thus, it may influence airway branching and lung development. The present study examined lung morphogenesis in fetuses with EA-TEF focusing in the expression of FGF10 and its receptor FGFR2 IIIb. METHODS: Pregnant rats received either 1.75 mg/kg i.p. adriamycin or vehicle on E7, E8 and E9. Embryos were recovered at E15, E18 and E21 and lungs processed for immunohistochemistry and RT-PCR. Three groups were studied: control, adriamycin-exposed with EA-TEF, and adriamycin-exposed without EA-TEF. Comparisons were performed with Mann-Whitney or t tests (significance level, 5 %). RESULTS: Lung weight at E15 and E18 were significantly lower in adriaEA fetuses in which the relative mRNA levels of FGF10 were significantly higher. These differences disappeared near term. The receptor FGFR2 IIIb messenger was only significantly increased in adria noEA fetuses at E15. Immunohistochemical study was consistent with these findings. CONCLUSIONS: Abnormal expression of FGF10 during earlier stages of development, when the lungs are smaller than controls, suggests a compensatory response aimed at "catching up" delayed tracheobronchial branching. Whether similar changes take place in the human condition and influence respiratory physiology remain to be determined.

Surgical advances in the fetus and neonate: esophageal atresia.

This article focuses on selected topics in the diagnosis and management of patients with esophageal atresia (EA) with or without tracheoesophageal fistula. The current status of prenatal diagnosis and recent advances in surgical techniques, including thoracoscopic repair for short-gap EA and tension-induced esophageal growth for long-gap EA, are reviewed. Although no consensus exists among pediatric surgeons regarding the role of these procedures in the treatment of EA, one can reasonably expect that, as they evolve, their application will become more widespread in this challenging patient population.

The effect of adriamycin exposure on the notochord of mouse embryos.

The notochord has important structural and signaling properties during vertebrate development with key roles in patterning surrounding tissues, including the foregut. The adriamycin mouse model is an established model of foregut anomalies where exposure of embryos in utero to the drug adriamycin leads to malformations including oesophageal atresia and tracheoesophageal fistula. In addition to foregut abnormalities, treatment also causes branching, displacement, and hypertrophy of the notochord. Here, we explore the hypothesis that the notochord may be a primary target of disruption leading to abnormal patterning of the foregut by examining notochord position and structure in early embryos following adriamycin exposure. Treated (n = 46) and control (n = 30) embryos were examined during the crucial period when the notochord normally delaminates away from the foregut endoderm (6-28 somite pairs). Transverse sections were derived from the anterior foregut and analyzed by confocal microscopy following immunodetection of extracellular matrix markers E-cadherin and Laminin. In adriamycin-treated embryos across all stages, the notochord was abnormally displaced ventrally with prolonged attachment to the foregut endoderm. While E-cadherin was normally detected in the foregut endoderm with no expression in the notochord of control embryos, treated embryos up to 24 somites showed ectopic notochordal expression indicating a change in characteristics of the tissue; specifically an increase in intracellular adhesiveness, which may be instrumental in structural changes, affecting mechanical and signaling properties. This is consistent with disruption of the notochord leading to altered signaling to the foregut causing abnormal patterning and congenital foregut malformations.

Abnormal development of lung innervation in experimental esophageal atresia.

BACKGROUND/AIM: Patients with esophageal atresia and tracheo-esophageal fistula (EA-TEF) have chronic respiratory tract disease and deficient tracheal innervation. This study tests the hypothesis in rats with EA-TEF that deficient lung innervation could be one of the causes of respiratory disease. MATERIAL AND METHODS: Pregnant rats were treated with either 2 mg/kg i.p. adriamycin or vehicle on E7, E8 and E9. Lungs and tracheas were retrieved on E15, E18 and E21 (term: E22). Innervation was examined by regular (PGP 9.5 and GDNF) and whole-mount (PGP 9.5 and α-actin) immunohistochemistry. PGP 9.5 and GDNF mRNA were measured by real-time, quantitative RT-PCR and the levels of PGP 9.5 protein by immunoblot. Embryonic lung primordia harvested on E13 were cultured for 72 h and airway peristalsis was assessed under an inverted microscope. PGP 9.5 expression was then examined in explants by whole-mount immunohistochemistry and RT-PCR. Values were compared with non-parametric tests. RESULTS: Neural networks were present in both EA-TEF and control fetuses on E15, E18 and E21, but the neural network was obviously disorganized in whole-mount immunohistochemistry of EA-TEF. The pan-neural marker PGP 9.5 protein was increased at term whereas the neural chemo-attractant GDNF protein was unchanged. PGP 9.5 mRNA significantly increased from subnormal levels on E15 to very increased ones on E18 compared with controls. GDNF mRNA levels followed the same trend. Airway peristalsis of explanted embryonal lungs was similar in both groups. The neural networks were underdeveloped in these primordia, as assessed by whole-mount PGP 9.5 immunohistochemistry and RT-PCR. CONCLUSIONS: The development of respiratory tract innervation in adriamycin-induced EA-TEF was delayed and abnormally controlled in rats compared with controls. However, these deficiencies were apparently compensated for at term and had no effect on airway peristalsis. The possible significance of innervation anomalies for respiratory sequelae in EA-TEF patients deserves further investigation.

Embryology of the early foregut.

In embryology, no agreement exists how the early foregut differentiates into the respiratory tract and the intestinal tract. In particular, the formation of the early lung anlage as well as the process of separation of trachea and esophagus remains unclear. This process is explained in a rather schematic way and aims more to explain pathologic findings, whereas true embryologic investigations are extremely rare in this field. Here, scanning electron microscopy of the normal foregut development illustrates the steps, which finally leads to the development of larynx and trachea on the one hand, and pharynx and esophagus on the other hand. This study was performed in chicken embryos in accordance to the developmental stages described. As the main results from these illustrations show, we found no evidence for lateral foregut ridges inside the undivided foregut chamber and no fusion of lateral foregut components to form a trachea-esophageal septum.