Ectopic Ganglia Research Articles

Complete adult neurogenesis within a Wallerian degenerating nerve expressed as an ectopic ganglion.

Neurogenesis in the adult peripheral nervous system remains to be demonstrated. We transplanted embryonic neural stem cells into a Wallerian degenerating nerve graft and observed development of a nodular structure consisting of neurons, glia, and Schwann cells. Histological analysis revealed a structure loosely resembling the spinal cord, including a synaptic network that formed along the neuron. Furthermore, the new axons reinnervated the paralysed muscle, forming both de novo and revived neuromuscular junctions. Reinnervation of the paralysed muscle resulted in significantly greater mean wet muscle weight and muscle fibre cross-sectional area on the cell transplantation side than on the surgical control side (body weight 0.071±0.011% vs. 0.051±0.007%, p=.006; area 355.6±345.2 vs. 114.0±132.0μm2 , p<.001). Electrophysiological experiments demonstrated a functional connection between the neurons and muscle; hence, we identified this nodule as an ectopic ganglion. Surprisingly, in green rat experiments, most of these glial cells, but none of the neurons, expressed enhanced green fluorescent protein, suggesting that the cells constituting the ectopic ganglion were derived from both transplanted stem cells and endogenous stem cells. Such adult neurogenesis in a peripheral nerve related to neural stem cell transplantation has not been reported previously, and these results form the basis for a novel regenerative medicine approach in paralysed muscle.

The clinical pathological analysis of intestinal neuronal dysplasia type B

Objective To investigate the clinicopathological features and diagnosis of intestinal neuronal dysplasia type B. Methods Between January 2004 and August 2014, 9 patients(5 males and 4 females) were treated for constipation and abdominal distention, and in all of them an intestinal neuronal dysplasia type B was confirmed histopathologically.The age of 9 patients ranged from 3 months to 1 year old(mean 7.8 months). The specimen of 9 patients was routinely taken by paraffin-embedded full-circumference sections of lesional bowel, hematoxylin and eosin and immunohistochemical staining were carried out on the specimen.The pathological morphology and quantitative of intestinal neurons and ganglia were retrospectively analyzed. Results Total of the 9 patients, the number and density of myenteric ganglia increased significantly increased in the lesional bowel, the pathological findings included giant nerve plexus, isolated and ectopic ganglia.In the proximal bowel, the number and density of myenteric ganglia were observed abnormal no giant nerve plexus, isolated and ectopic ganglia was observed.Combinated these pathological findings and symptoms, intestinal neuronal dysplasia type B was diagnosed. Conclusion The diagnosis of intestinal neuronal dysplasia type B relies on typical presentations of allied disorders of Hirschsprung's disease, giant ganglia, isolated and ectopic ganglia, and increasing the density of giant submucosal ganglia of pathologic morphology, meanwhile, excluding others primary etiologies. Key words: Intestinal neuronal dysplasia; Allied disorders of hirschsprung disease; Pathology; Diagnosis

Sonic hedgehog controls enteric nervous system development by patterning the extracellular matrix

The enteric nervous system (ENS) develops from neural crest cells that migrate along the intestine, differentiate into neurons and glia, and pattern into two plexuses within the gut wall. Inductive interactions between epithelium and mesenchyme regulate gut development, but the influence of these interactions on ENS development is unknown. Epithelial-mesenchymal recombinations were constructed using avian hindgut mesenchyme and non-intestinal epithelium from the bursa of Fabricius. These recombinations led to abnormally large and ectopically positioned ganglia. We hypothesized that sonic hedgehog (Shh), a secreted intestinal epithelial protein not expressed in the bursa, mediates this effect. Inhibition of Shh signaling, by addition of cyclopamine or a function-blocking antibody, resulted in large, ectopic ganglia adjacent to the epithelium. Shh overexpression, achieved in ovo using Shh-encoding retrovirus and in organ culture using recombinant protein, led to intestinal aganglionosis. Shh strongly induced the expression of versican and collagen type IX, whereas cyclopamine reduced expression of these chondroitin sulfate proteoglycans that are known to be inhibitory to neural crest cell migration. Shh also inhibited enteric neural crest-derived cell (ENCC) proliferation, promoted neuronal differentiation, and reduced expression of Gdnf, a key regulator of ENS formation. Ptc1 and Ptc2 were not expressed by ENCCs, and migration of isolated ENCCs was not inhibited by Shh protein. These results suggest that epithelial-derived Shh acts indirectly on the developing ENS by regulating the composition of the intestinal microenvironment.

Gut Epithelium‐derived Sonic Hedgehog Regulates the Extracellular Matrix During Formation of the Intestinal Nervous System

The enteric nervous system (ENS) is principally derived from vagal-level neural crest cells that migrate rostrocaudally along the entire length of the gastrointestinal tract, giving rise to neurons and glial cells in two ganglionated plexuses. Incomplete migration of vagal-derived enteric neural crest cells (ENCCs) leads to Hirschsprung disease (HD), a congenital disorder characterized by the absence of enteric ganglia along variable lengths of the distal intestine. Inductive interactions between gut epithelium and mesenchyme have been suggested to regulate the migration and differentiation of ENCCs. However, little is known about the function of epithelial derived factors, such as Sonic hedgehog (Shh), how they influence hindgut mesenchyme derived factors and how they regulate extracellular matrix expression during ENS development. Hindgut from 6 day old chicken embryo was cultured in the presence of Shh protein or Shh overexpressing RCAS-virus. In presence of Shh the hindgut is aganglionic, while in the presence of Shh inhibitor large, ectopic ganglia developed. Shh treatment strongly induced the expression of extracellular matrix versican and collagen type IX, whereas cyclopamine reduced the expression pattern of these inhibitory matrix molecules. These results indicate that versican and collagen IX is a candidate for mediating the effects of Shh on ENCC migration. Shh also inhibited the proliferation and promoted the differentiation of ENCCs. Abnormalities of NCC migration and extracellular pattern formation are characteristic of two human intestinal disorders, HD and intestinal neuronal dysplasia. Our results support an essential role for epithelial-mesenchymal interactions in these aspects of ENS development.

Sonic hedgehog controls enteric nervous system development by patterning the extracellular matrix.

The enteric nervous system (ENS) develops from neural crest cells that migrate along the intestine, differentiate into neurons and glia, and pattern into two plexuses within the gut wall. Inductive interactions between epithelium and mesenchyme regulate gut development, but the influence of these interactions on ENS development is unknown. Epithelial-mesenchymal recombinations were constructed using avian hindgut mesenchyme and non-intestinal epithelium from the bursa of Fabricius. These recombinations led to abnormally large and ectopically positioned ganglia. We hypothesized that sonic hedgehog (Shh), a secreted intestinal epithelial protein not expressed in the bursa, mediates this effect. Inhibition of Shh signaling, by addition of cyclopamine or a function-blocking antibody, resulted in large, ectopic ganglia adjacent to the epithelium. Shh overexpression, achieved in ovo using Shh-encoding retrovirus and in organ culture using recombinant protein, led to intestinal aganglionosis. Shh strongly induced the expression of versican and collagen type IX, whereas cyclopamine reduced expression of these chondroitin sulfate proteoglycans that are known to be inhibitory to neural crest cell migration. Shh also inhibited enteric neural crest-derived cell (ENCC) proliferation, promoted neuronal differentiation, and reduced expression of Gdnf, a key regulator of ENS formation. Ptc1 and Ptc2 were not expressed by ENCCs, and migration of isolated ENCCs was not inhibited by Shh protein. These results suggest that epithelial-derived Shh acts indirectly on the developing ENS by regulating the composition of the intestinal microenvironment.

Isolated intestinal neuronal dysplasia Type B (IND-B) in Japan: results from a nationwide survey.

Intestinal neuronal dysplasia Type B (IND-B) has been proposed to be an allied disorder of Hirschsprung's disease (ADHD). The original histological criteria included hyperganglionosis, giant ganglia, ectopic ganglion cells and an increased AChE activity in the lamina propria. The criteria for IND-B have been gradually revised. The present diagnostic criteria are [1] more than 20 % of the submucosal ganglia contain nine or more ganglion cells and [2] the patient is older than 1 year. To clarify the current status of IND-B in Japan, a nationwide retrospective cohort study was performed. Questionnaires were sent to 161 major institutes of pediatric surgery and gastroenterology in Japan. A total of 355 cases of ADHD were collected, including 18 cases of IND-B (5 %). Based on original criteria, 13 out of 18 cases were diagnosed as IND-B. However, only four cases met the current criteria. Three of the four patients (75 %) required pull-through operation. All of the patients exhibited giant ganglia and ganglioneuromatosis-like hyperplasia of the myenteric plexus. IND-B cases matching the current criteria are thought to be quite rare and they are associated with marked hyperplasia of the myenteric plexus. "True" IND-B is a rare and intractable disease.

Isolated adult hypoganglionosis resulting in toxic megacolon: A Case Report

Anahtar kelimeler: yetișkin; kolonda yalanci tikanma; Hischsprung hastaligi; rektosigmoid aganglionozisi Hypoganglionosis can be seen as an isolated form or associated with Hirschsprung’s disease (HD)2. Hypoganglionosis as an isolated disease accounts for 5% of neuronal intestinal malformations3. The differential diagnosis of the entities is mainly based on histological, immunohistochemical and electron microscopy fi ndings since their clinical features are similar4. Histologically, HD is defi ned as absence of intramural ganglia in the Meissner (submucosal) and Auerbach (myenteric) neural plexuses especially in the distal colon. IND is characterized by hyperganglionosis, giant ganglia and ectopic ganglia. In isolated hypoganglionosis (IH), the number of ganglia per a centimeter of bowel’s longitudinal axis is decreased and the distance between ganglia, as well as the plexus area, is increased4,5. There is very low or absent activity of acetyl cholinesterase (AchE) in the mucosa. These developmental anomalies are usually diagnosed in infancy or childhood, but there are studies reported in adults regarding these entities. Here, we report a case of IH in a 19 year–old male patient with sigmoid toxic megacolon.

Histopathologic Delineation of the Transition Zone in Short-Segment Hirschsprung Disease

Failure to completely resect the transition zone (TZ) between aganglionic and neuroanatomically normal bowel ("TZ pull-through") is considered one reason for postoperative obstructive symptoms in Hirschsprung disease (HD). Despite years of study, the proximal boundary of the TZ remains nebulous, complicated by discordant, often subjective, histopathologic definitions. In order to objectively delineate the TZ, transverse sections at 1 cm intervals from the rectums of 9 non-HD autopsy subjects and resections from 15 infants with short-segment HD were immunostained with Hu (ganglion cell bodies) and glucose transporter 1 (Glut1) (perineurium of extrinsic nerves), and 6 putative features of TZ were examined: (1) aganglionosis of ≥1/8th circumference; (2) myenteric or submucosal hypoganglionosis; (3) hypertrophic submucosal nerves; (4) Glut1+ submucosal innervation; (5) submucosal hyperganglionosis; and (6) "ectopic" ganglia in lamina propria, muscularis propria, or serosa. In non-HD controls, Glut1+ submucosal innervation, hypertrophic nerves, partial circumferential aganglionosis, and hypoganglionosis were absent or restricted to the distal 2 cm. In contrast, all 6 neuropathologic features of TZ were identified proximal to the aganglionic segment in the majority of HD resections, but the length of the TZ ranged from 0 to 12 cm, depending on which neuropathologic feature was considered. Excluding submucosal hyperganglionosis and ectopic ganglia, the TZ was generally ≤5 cm. Many features of TZ cannot be excluded intraoperatively with a biopsy or a full-circumference frozen section. However, partial circumferential aganglionosis, severe myenteric hypoganglionosis, and hypertrophic submucosal nerves can, and probably should, be assessed in full-circumference frozen sections of the proximal resection margin, to reduce the likelihood of TZ pull-through.

Variants of Hirschsprung disease

Variants of Hirschsprung disease are conditions that clinically resemble Hirschsprung disease, despite the presence of ganglion cells in rectal suction biopsies. The characterization and differentiation of various entities are mainly based on histologic, immunohistochemical, and electron microscopy findings of biopsies from patients with functional intestinal obstruction. Intestinal neuronal dysplasia is histologically characterized by hyperganglionosis, giant ganglia, and ectopic ganglion cells. In most intestinal neuronal dysplasia cases, conservative treatments such as laxatives and enema are sufficient. Some patients may require internal sphincter myectomy. Patients with the diagnosis of isolated hypoganglionosis show decreased numbers of nerve cells, decreased plexus area, as well as increased distance between ganglia in rectal biopsies, and resection of the affected segment has been the treatment of choice. The diagnosis of internal anal sphincter achalasia is based on abnormal rectal manometry findings, whereas rectal suction biopsies display presence of ganglion cells as well as normal acetylcholinesterase activity. Internal anal sphincter achalasia is either treated by internal sphincter myectomy or botulinum toxin injection. Megacystis microcolon intestinal hypoperistalsis is a rare condition, and the most severe form of functional intestinal obstruction in the newborn. Megacystis microcolon intestinal hypoperistalsis is characterized by massive abdominal distension caused by a largely dilated nonobstructed bladder, microcolon, and decreased or absent intestinal peristalsis. Although the outcome has improved in recent years, survivors have to be either maintained by total parenteral nutrition or have undergone multivisceral transplant. This review article summarizes the current knowledge of the aforementioned entities of variant HD.

A role for Pten in paediatric intestinal dysmotility disorders

The enteric nervous system (ENS) is a network of neurons and glia that lies within the gut wall. It is responsible for the normal regulation of gut motility and secretory activities. Hirschsprung's disease (HD) is a congenital defect of the ENS, characterised by an absence of ganglia in the distal colon. Intestinal neuronal dysplasia (IND) is a condition that clinically resembles HD, characterised by hyperganglionosis, giant and ectopic ganglia, resulting in intestinal dysmotility. Intestinal ganglioneuromatosis is characterised by hyperplasia and hypertrophy of enteric neuronal cells and causes chronic intestinal pseudo-obstruction (CIPO). Phosphatase and tensin homolog deleted on chromosome 10 (Pten) is a phosphatase that is critical for controlling cell growth, proliferation and cell death. A recent study of Pten knockout mice showed evidence of ganglioneuromatosis in the ENS suggesting a role for this protein in ENS development. Ganglioneuromatosis patients have also been shown to have a decreased level of Pten expression in the colon. The aim of our study was to investigate Pten expression in the ENS of HD and IND patients compared to normal controls. Resected tissue from 10 HD and 10 IND type B patients was fixed and embedded in paraffin wax. Normal control colon tissue was obtained from ten patients who underwent a colostomy closure for imperforate anus. Sections were cut and immunohistochemistry was carried out using a Pten antibody. Results were analysed by light microscopy. Staining showed that Pten was strongly expressed in ganglia of both the submucosal and myenteric plexus of normal and HD specimens from the ganglionic colon. Pten expression was significantly reduced in the giant ganglia in IND patients in both the myenteric and submucosal plexuses compared to the normal controls. Specimens from the aganglionic region of HD did not show Pten expression. To the best of our knowledge, this is the first study demonstrating a marked reduction of Pten expression in the myenteric and submucous plexuses of IND patients. Neuronal Pten deficiency in IND may disrupt the chemical pathway associated with the proliferation and development of neuronal cells forming mature ganglia and thus cause motility dysfunction.

39. The prevalence of intestinal neuronal dysplasia hirschsprung’s disease patients in Malaysia

Background Hirschsprung’s disease (HD) is due to malfunction of neural crest cell migration to the distal bowel, resulting in colonic aganglionosis. Hypoganglionosis and intestinal neuronal dysplasia (IND) are other neuronal causes of paediatric intestinal obstruction. These two entities have been reported to occur concurrently with HD. Their occurrence in the Malaysian HD population remains unknown. This knowledge is important to avoid the diagnostic pitfalls of transition zone evaluation, especially in intraoperative frozen section procedure. Aim To investigate the prevalence of hypoganglionosis and IND in resected bowel specimens for HD. Methods Thirty-nine resected bowel specimens from HD cases were retrieved from the archives of Pathology Department, Hospital Kuala Lumpur. The H&E stained sections from these cases were reviewed for the neuronal abnormalities stated above. Results Demographically, 79.4% of the patients were male. The age at operation ranged from 11 weeks to 4.9 years. Culturally, 66% were Malays, 17% Chinese, 12.8% indigenous Borneo ethnic group and 2.5% Indian. All of the cases had recto-sigmoid disease. Giant ganglia and hypoganglionosis were seen in 7 (17%) and 4 (10.3%) cases, respectively. In addition, an excess of small ganglions were present within the transtition zone of 24 cases (61.5%), while ectopic ganglia were observed in 2 cases. Conclusion IND is not uncommon in HD patients in Malaysia. This is important to appreciate, especially in the assessment of resection margins of HD.

Cystic adventitial degeneration: Ectopic ganglia from adjacent joint capsules

Cystic adventitial degeneration is a rare non-atherosclerotic cause of peripheral arterial occlusive disease, mainly seen in young men without other evidence of vascular disease. Diagnosis will be established by clinical findings and by ultrasound or angiography and can be treated by excision or enucleation of the affected arterial segment or by percutaneous ultrasound-guided aspiration. However, the etiology of adventitial cysts remains unknown. We report a case of cystic adventitial degeneration showing a connection between the joint capsule and the adventitial cyst, supporting the theory that cystic adventitial degeneration may represent ectopic ganglia from adjacent joint capsules.

Histochemical staining of rectal suction biopsies as the first investigation in patients with chronic constipation

Rectal suction biopsy (RSB) is the gold standard diagnostic procedure for disorders of bowel motility. This study describes our experience with RSB stained with histochemistry as the first diagnostic approach in a large series of patients presenting with chronic constipation. Between 1993 and 2005, 766 children underwent RSB for persistent chronic constipation. The specimens were snap frozen, sectioned and stained with conventional hematoxylin and eosin (H&E) and with nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) and acetylcholinesterase (AChE) histochemical stainings. Adequate amount of submucosa was present in 655 (85.5%) out of 766 cases and formed the basis of this study. RSB in 540 (82%) patients were reported as normal. Hirschsprung's disease was found in 47 (7.2%) patients with characteristic features of absence of ganglion cells, increased AChE activity in the lamina propria and muscularis mucosae, thick nerve fibers in the submucosa, and a lack of NADPH-d-positive fibers in muscularis mucosae. RSB in 59 (9%) patients presented features of intestinal neuronal dysplasia such as submucosal hyperganglionosis, giant ganglia, ectopic ganglia and increased AChE activity in lamina propria. Hypoganglionosis was suspected in nine (1.3%) children because of sparse or absent ganglion cells and low AChE and NAPDH-d activity in muscularis mucosae. Three patients (0.4%) developed bleeding following RSB, requiring diathermy of the bleeding point. Thus, we conclude that RSB is a simple and safe method when used as the first diagnostic approach in patients with chronic constipation. The combination of two histochemical stainings techniques provides a high level of accuracy in the diagnosis of intestinal dysganglionosis.

Intramucosal Ganglion Cells in Normal Adult Colorectal Mucosa

Intramucosal ganglion cells are incompletely understood. Reviewed were 100 normal specimens from colorectal biopsies of nonconstipated adults to firmly establish the existence of intramucosal ganglion cells in normal adult colorectal mucosa, determine whether intramucosal giant ganglia exist, and compare the prevalence of colorectal intramucosal ganglion cells between men and women. Fifty specimens from each gender were examined. Twenty specimens contained intramucosal ganglion cells, including 15 from women (75%) and only 5 from men (25%). Intramucosal ganglion cells occurred singly or in clusters. One woman had large disciform and globular clusters with 7 ganglion cells, resembling giant ganglia. Awareness of ganglion cells and large ganglia in normal mucosa is necessary to avoid potential confusion with ectopic ganglion cells and submucosal giant ganglia seen in adult intestinal neuronal dysplasia. Intramucosal ganglion cells in normal colorectal mucosa are particularly common in women. This disparity might contribute to colorectal neurophysiologic differences between genders.

Ectopic Ganglion Cyst Presenting as a Breast Lump: A Rare Case Report

We report a rare case of a breast lump in an 81-year-old woman. Initial investigations were inconclusive and excision biopsy of the lump was done. Histologically the mass proved to be a ganglion cyst. It is the only reported case of ectopic ganglion cyst in the literature that presented as a breast lump.

Sonic hedgehog regulates the position of the trigeminal ganglia

The trigeminal ganglia differentiate in part from specialized ectodermal structures in the embryonic head termed the trigeminal placodes. However, the signals which govern the migration of trigeminal precursors and the final morphology of the ganglia are poorly defined. Here, we show that notochord or floor plate tissue can induce the formation of ectopic sensory ganglia adjacent to the developing dorsal mesencephalon. Neurons within these ganglia coexpress the transcription factors Brn3a and Islet, which together characterize primary sensory neurons throughout the developing embryo. The ectopic ganglia originate from Pax3-expressing regions of the surface ectoderm that normally contribute to the ophthalmic trigeminal (op5), and can only be induced at developmental stages during which op5 precursors are present in the mesencephalic region. The migration of trigeminal precursors is also blocked by a local source of recombinant Shh, while in mouse embryos lacking Shh, these cells continue to migrate until they fuse into a single ganglion at the ventral midline. Together, these results suggest that Shh acts to arrest the migration of sensory precursors rather than to induce sensory neurons de novo. Consistent with this hypothesis, Shh induces the expression of the proteoglycan PG-M/versican in the cranial mesoderm, which has been previously implicated in the regulation of the movement of sensory neural precursors.

Intestinal neuronal dysplasia-like pathology in Ncx/Hox11L.1 gene-deficient mice

Background/Purpose:Ncx/Hox11L.1-deficient (Ncx-/-) mice specifically created by the authors had mega-ileo-ceco-colon (mega-ICC) with a caliber change in the proximal colon. The authors studied the nerve distribution in the bowel of these Ncx-/- mice to determine the cause of their bowel dysmotility. Methods: Four-week-old Ncx-/- mice (n = 10; 5 with mega-ICC, 5 without mega-ICC) were killed and the bowel harvested. Half of each specimen was snap frozen for AchE and NADPH-diaphorase histochemistry, and the other half were fixed with 10% formalin for H&E staining and immunohistochemistry using PGP9.5 antibody (a marker for neurons), C-kit antibody (a marker for intestinal pacemaker cells), and stem cell factor antibody (a marker for C-kit ligand). Age-matched wild-type normal mice (n = 5) served as controls. Results: In the ileum, cecum, and proximal colon from all Ncx-/- mice (irrespective of the association of mega-ICC), typical findings of human intestinal neuronal dysplasia (IND) ie, obvious hyperganglionosis in neuronal plexuses on PGP9.5 immunohistochemistry, ectopic ganglia in the mucosal and muscular layers on AchE histochemistry, and ghostlike ganglia on NADPH-diaphorase histochemistry were found. Likewise, in normal caliber distal colon from these mice, the distribution of ganglion cells, C-kit, and stem cell factor was normal. In control specimens, there was no ectopic ganglia or hyperganglionosis. Conclusions: These findings suggest that the Ncx/Hox11L.1 gene is required for the proper innervation of the enteric nervous system in mice, and our deficient strain may be useful as a model for studying IND in humans. J Pediatr Surg 36:1293-1296. Copyright © 2001 by W.B. Saunders Company.

Intestinal neuronal dysplasia: Results of treatment in 33 patients

Purpose: Intestinal neuronal dysplasia (IND) is a disease of the enteric nervous system, which clinically resembles Hirschsprung's disease. The authors reviewed their experience of IND over an 8-year period. Methods: Between 1992 and 1999, 418 patients underwent rectal suction biopsy for persistent constipation. Thirty-three (7.8%) patients had histologic evidence of IND. There were 26 boys and 7 girls (age range, 1 week to 10 years). The diagnosis of IND was based on the presence of hyperganglionosis of the submucous plexus and giant ganglia and at least one of the following features in rectal biopsies: (1) ectopic ganglia, (2) increased acetylcholinesterase (AChE) activity in the lamina propria, and (3) increased AChE nerve fibers around the submucosal blood vessels. All patients were started on laxatives with or without enemas after the diagnosis was made. Patients have been followed up from 1 to 8 years (mean, 2.4 years). Results: Twenty-one (64%) patients had a good response to conservative management and currently have normal bowel habits. Twelve patients (36%) underwent internal sphincter myectomy after failed conservative management. Seven of these patients now have normal bowel habits. Two patients are able to stay clean with regular enemas. Three patients who continued to have persistent constipation after myectomy and underwent resection of redundant and dilated sigmoid colon now have normal bowel habits. Conclusion: The majority of patients with IND can be treated successfully with conservative treatment. J Pediatr Surg 36:777-779. Copyright © 2001 by W.B. Saunders Company.

Ectopic CNS Projections Guide Peripheral Neuron Axons along Novel Pathways in Leech Embryos

Previous studies have indicated that the formation of stereotyped segmental nerves in leech embryos depends on the interactions between CNS projections and ingrowing afferents from peripheral neurons. Especially, CNS-ablation experiments have suggested that CNS-derived guidance cues are required for the correct navigation of several groups of peripheral sensory neurons. In order to directly test this hypothesis we have performed transplantations of CNS ganglia into ectopic sites in segments from which the resident ganglia have been removed. We find that the transplanted ganglia extend numerous axons distributed roughly equally in all directions. When these CNS projections reach and make contact with peripheral sensory axons they are used as guides for peripheral neurons to grow toward and into the ectopic ganglia even when this means following novel pathways that cross the midline and/or segmental boundaries. The peripheral sensory axons turn and grow toward the ectopic ganglia only when in physical contact with CNS axons, suggesting that diffusible chemoattractants are not a factor. These results demonstrate that the guidance cues provided by ectopic CNS projections are both necessary and sufficient to steer peripheral sensory neuron axons into the CNS.

Congenital colonic hypoganglionosis in murine trisomy 16--an animal model for Down's syndrome.

Human trisomy 21 (Down's syndrome) affects the development of multiple organ systems frequently including gastrointestinal anomalies such as Hirschsprung's disease. To elucidate the underlying morphogenetical mechanisms a murine model (trisomy 16 mouse) for Down's syndrome has been established. However, previous studies on trisomy 16 (TS 16) mice have been confined to non-enteric developmental disorders. Therefore, the aim of the present study was to assess the enteric nervous system and the morphology of the terminal colon in TS 16 mice during late intrauterine development. Immunohistochemical examination (protein gene product 9.5) revealed a reduction of myenteric ganglionic size and density as well as the presence of ectopic ganglia, thus resembling typical features of colonic hypoganglionosis and myenteric heterotopia. Enzyme histochemistry for NADPH-diaphorase showed a remarkable decrease of NADPH-positive neurons in TS 16 mice, whose sparse distribution was confined to a minor portion of the oligoneuronal myenteric ganglia. Electron microscopical studies of TS 16 mice confirmed the myenteric hypoganglionosis and, additionally, demonstrated the absence of submucosal neurons. Whereas neurons of controls were characterized by arborizing neuronal processes, neurons of TS 16 mice were reduced in size and exhibited only few and shortened cytoplasmic protrusions. Additionally, prominent bundles of parallel nerve fibers passed through the intermuscular zone and lacked the arborization pattern of normal neuropil. They were not observed in controls and resembled features of extrinsic nerves. Approximately one third of TS 16 mice developed a colonic dilatation proximally to an obstructed segment characterized by a pronounced hypoganglionosis. Although TS 16 mice did not develop complete aganglionosis, the abundance of nerve fiber bundles and the colonic dilatation were consistent with the morphological characteristics of Hirschsprung's disease. The findings suggest that even a hypoganglionosis characterized by ultrastructurally altered and NADPH-diaphorase-deficient neurons may be capable of provoking a functional intestinal obstruction. Similar abnormalities of the enteric nervous system as observed in TS 16 mice may also be present in such trisomy 21 patients who suffer from chronic intestinal motility disorders which are not caused by complete aganglionosis.