Distribution of interstitial cells of Cajal in tunica muscularis of the canine rectoanal region

Electrical and mechanical activity of the circular muscle layer in the rectoanal region of the gastrointestinal tract undergoes considerable changes in the site of dominant pacemaking activity, frequency, and waveform shape. The present study was performed to determine whether changes in the structural organization of the circular layer or in the density, distribution, and ultrastructure of interstitial cells of Cajal (ICC) could account for this heterogeneity in electrical and mechanical activities. Light microscopy revealed that the structural organization of the circular muscle layer underwent dramatic morphological changes, from a tightly packed layer with poorly defined septa in the proximal rectum to one of discrete muscle bundles separated by large septae in the internal anal sphincter. Kit immunohistochemistry revealed a dense network of ICC along the submucosal and myenteric borders in the rectum, whereas in the internal anal sphincter, ICC were located along the periphery of muscle bundles within the circular layer. Changes in electrical activity within the circular muscle layer can be partially explained by changes in the structure of the muscle layer and changes in the distribution of ICC in the rectoanal region of the gastrointestinal tract.     

Unique distribution of interstitial cells of Cajal in the feline pylorus

The feline gastrointestinal (GI) tract is an important model for GI physiology but no immunohistochemical assessment of interstitial cells of Cajal (ICC) has been performed because of the lack of suitable antibodies. The aim of the present study was to investigate the various types of ICC and associated nerve structures in the pyloric sphincter region, by using immunohistochemistry and electron microscopy to complement functional studies. In the sphincter, ICC associated with Auerbach’s plexus (ICC-AP) were markedly decreased within a region of 6–8 mm in length, thereby forming an interruption in this network of ICC-AP, which is otherwise continuous from corpus to distal ileum. In contrast, intramuscular ICC (ICC-IM) were abundant within the pylorus, especially at the inner edge of the circular muscle adjacent to the submucosa. Similar distribution patterns of nerves positive for vesicular acetylcholine transporter (VAChT), nitric oxide synthase (NOS) and substance P (SP) were encountered. Quantification showed a significantly higher number of ICC-IM and the various types of nerves in the pylorus compared with the circular muscle layers in the adjacent antrum and duodenum. Electron-microscopic studies demonstrated that ICC-IM were closely associated with enteric nerves through synapse-like junctions and with smooth muscle cells through gap junctions. Thus, for the first time, immunohistochemical studies have been successful in documenting the unique distribution of ICC in the feline pylorus. A lack of ICC-AP guarantees the distinct properties of antral and duodenal pacemaker activities. ICC-IM are associated with enteric nerves, which are concentrated in the inner portion of the circular muscle layer, being part of a unique innervation pattern of the sphincter. This study was supported by operating grants from the Canadian Institutes of Health Research (to J.D.H. and N.E.D.) and from the Canadian Association of Gastroenterology (to L.W.C.L.).     

Interstitial cells in the primate gastrointestinal tract

Kit immunohistochemistry and confocal reconstructions have provided detailed 3-dimensional images of ICC networks throughout the gastrointestinal (GI) tract. Morphological criteria have been used to establish that different classes of ICC exist within the GI tract and physiological studies have shown that these classes have distinct physiological roles in GI motility. Structural studies have focused predominately on rodent models and less information is available on whether similar classes of ICC exist within the GI tracts of humans or non-human primates. Using Kit immunohistochemistry and confocal imaging, we examined the 3-dimensional structure of ICC throughout the GI tract of cynomolgus monkeys. Whole or flat mounts and cryostat sections were used to examine ICC networks in the lower esophageal sphincter (LES), stomach, small intestine and colon. Anti-histamine antibodies were used to distinguish ICC from mast cells in the lamina propria. Kit labeling identified complex networks of ICC populations throughout the non-human primate GI tract that have structural characteristics similar to that described for ICC populations in rodent models. ICC-MY formed anastomosing networks in the myenteric plexus region. ICC-IM were interposed between smooth muscle cells in the stomach and colon and were concentrated within the deep muscular plexus (ICC-DMP) of the intestine. ICC-SEP were found in septal regions of the antrum that separated circular muscle bundles. Spindle-shaped histamine⁺ mast cells were found in the lamina propria throughout the GI tract. Since similar sub-populations of ICC exist within the GI tract of primates and rodents and the use of rodents to study the functional roles of different classes of ICC is warranted.     

Role of Interstitial Cells of Cajal and their relationship with the enteric nervous system.

The term 'Interstitial cells of Cajal' (ICC) designates several groups of mesenchymal cells present along the gastro-intestinal tract (GI), in close association with smooth muscle cells and elements of the enteric nervous system (ENS). For years, transmission electron microscopy (TEM) has been the only reliable tool to study ICC. Whilst TEM remains the golden standard for identification of ICC, the observation that the tyrosine kinase receptor c-kit plays a crucial role in their development recently resulted in numerous immunohistochemical studies and also led to a better characterization of their roles. ICC form extensive networks of electrically coupled cells and certain groups of ICC are currently regarded as the source of the spontaneous slow waves of the gut musculature (pacemaker cells). Other ICC appear to be involved in the transduction of the relaxation of smooth muscle triggered by nitric oxide. Abnormal distribution of ICC has been reported in several human diseases and abnormal functioning of ICC might actually be involved in many disorders of GI transit. This review addresses (1) the morphology and relationships of ICC along the GI tract in man and mouse, mainly based on data from immunohistochemistry and confocal microscopy, (2) the emerging role of ICC in the pathophysiology of human diseases, like infantile hypertrophic pyloric stenosis (a common disorder with a dysfunction of the pyloric sphincter), Hirschsprung's disease (aganglion-osis coli) and intestinal pseudo-obstruction, (3) developmental issues, (4) recent reports suggesting a possible link between ICC and gastrointestinal stromal tumors.     

Telocytes express PDGFRα in the human gastrointestinal tract

Telocytes (TC), a cell population located in the connective tissue of many organs of humans and laboratory mammals, are characterized by a small cell body and extremely long and thin processes. Different TC subpopulations share unique ultrastructural features, but express different markers. In the gastrointestinal (GI) tract, cells with features of TC were seen to be CD34‐positive/c‐kit‐negative and several roles have been proposed for them. Other interstitial cell types with regulatory roles described in the gut are the c‐kit‐positive/CD34‐negative/platelet‐derived growth factor receptor α (PDGFRα)‐negative interstitial cells of Cajal (ICC) and the PDGFRα‐positive/c‐kit‐negative fibroblast‐like cells (FLC). As TC display the same features and locations of the PDGFRα‐positive cells, we investigated whether TC and PDGFRα‐positive cells could be the same cell type. PDGFRα/CD34, PDGFRα/c‐kit and CD34/c‐kit double immunolabelling was performed in full‐thickness specimens from human oesophagus, stomach and small and large intestines. All TC in the mucosa, submucosa and muscle coat were PDGFRα/CD34‐positive. TC formed a three‐dimensional network in the submucosa and in the interstitium between muscle layers, and an almost continuous layer at the submucosal borders of muscularis mucosae and circular muscle layer. Moreover, TC encircled muscle bundles, nerve structures, blood vessels, funds of gastric glands and intestinal crypts. Some TC were located within the muscle bundles, displaying the same location of ICC and running intermingled with them. ICC were c‐kit‐positive and CD34/PDGFRα‐negative. In conclusion, in the human GI tract the TC are PDGFRα‐positive and, therefore, might correspond to the FLC. We also hypothesize that in human gut, there are different TC subpopulations probably playing region‐specific roles.     

Enteric motor neurons form synaptic-like junctions with interstitial cells of Cajal in the canine gastric antrum

Morphological studies have shown synaptic-like structures between enteric nerve terminals and interstitial cells of Cajal (ICC) in mouse and guinea pig gastrointestinal tracts. Functional studies of mice lacking certain classes of ICC have also suggested that ICC mediate enteric motor neurotransmission. We have performed morphological experiments to determine the relationship between enteric nerves and ICC in the canine gastric antrum with the hypothesis that conservation of morphological features may indicate similar functional roles for ICC in mice and thicker-walled gastrointestinal organs of larger mammals. Four classes of ICC were identified based on anatomical location within the tunica muscularis. ICC in the myenteric plexus region (IC-MY) formed a network of cells that were interconnected to each other and to smooth muscle cells by gap junctions. Intramuscular interstitial cells (IC-IM) were found in muscle bundles of the circular and longitudinal layers. ICC were located along septa (IC-SEP) that separated the circular muscle into bundles and were also located along the submucosal surface of the circular muscle layer (IC-SM). Immunohistochemistry revealed close physical associations between excitatory and inhibitory nerve fibers and ICC. These contacts were synaptic-like with pre- and postjunctional electron-dense regions. Synaptic-like contacts between enteric neurons and smooth muscle cells were never observed. Innervated ICC formed gap junctions with neighboring smooth muscle cells. These data show that ICC in the canine stomach are innervated by enteric neurons and express similar structural features to innervated ICC in the murine GI tract. This morphology implies similar functional roles for ICC in this species.     

The digestive tract of the amberjack Seriola dumerili, Risso: a light and scanning electron microscope study

The histology of the digestive tract of the amberjack ( Seriola dumerili , Risso) was studied using light and scanning electron microscopy. The anterior oesophagus mucosa displays primary and secondary folds lined with a stratified squamous epithelium with fingerprint-like microridges which is substituted, on the top of the oesogaster folds, by a simple columnar epithelium with short microvilli. Only primary folds are present in the stomach. The anterior portion is rich in simple tubular glands, whereas the oesogaster and the pyloric region are devoid of them. Pyloric caeca and anterior and middle intestine mucosa display the same pattern of folding. The dominant cell type is the enterocyte, which exhibits larger and thinner microvilli in the caeca than in the intestine. The columnar epithelium of the rectum is replaced, in the anal sphincter, by a stratified flattened epithelium. Goblet cells are numerous throughout the whole length of the tract with the exception of the initial part of the oesophagus, the oesogaster, the stomach and the anal sphincter. Mucosubstances have been shown to vary in the different regions of the gut: acid mucines are found in the oesophagus, pyloric stomach, caeca, intestine and rectum, whereas neutral mucosubstances dominate in the anterior portion of the stomach. The muscularis is well developed throughout the length of the tract: two layers of striated muscle at the oesophageal level; two layers of smooth muscle in the stomach wall and three at the intestinal level.     

Homeostatic and injury‐induced microglia behavior in the aging brain

Microglia cells are essential for brain homeostasis and have essential roles in neurodegenerative diseases. Aging is the main risk factor for most neurodegenerative diseases, and age‐related changes in microglia may contribute to the susceptibility of the aging brain to dysfunction and neurodegeneration. We have analyzed morphology and dynamic behavior of neocortical microglia in their physiological environment in young adult (3‐month‐old), adult (11‐ to 12‐month‐old), and aged (26‐ to 27‐month‐old) C57BL/6J‐Iba1‐eGFP mice using in vivo 2‐photon microscopy. Results show that surveying microglial cells in the neocortex exhibit age‐related soma volume increase, shortening of processes, and loss of homogeneous tissue distribution. Furthermore, microglial process speed significantly decreased with age. While only a small population of microglia showed soma movement in adult mice, the microglia population with soma movement was increased in aged mice. However, in response to tissue injury, the dynamic microglial response was age‐dependently diminished. These results provide novel insights into microglial behavior and indicate that microglial dysfunction in the aging brain may contribute to age‐related cognitive decline and neurodegenerative diseases.     

Relationship between interstitial cells of Cajal, fibroblast-like cells and inhibitory motor nerves in the internal anal sphincter

Interstitial cells of Cajal (ICC) have been shown to participate in nitrergic neurotransmission in various regions of the gastrointestinal (GI) tract. Recently, fibroblast-like cells, which are positive for platelet-derived growth factor receptor ?? (PDGFR??⁺), have been suggested to participate additionally in inhibitory neurotransmission in the GI tract. The distribution of ICC and PDGFR??⁺ cell populations and their relationship to inhibitory nerves within the mouse internal anal sphincter (IAS) are unknown. Immunohistochemical techniques and confocal microscopy were therefore used to examine the density and arrangement of ICC, PDGFR??⁺ cells and neuronal nitric-oxide-synthase-positive (nNOS⁺) nerve fibers in the IAS of wild-type (WT) and W/W ^v mice. Of the total tissue volume within the IAS circular muscle layer, 18% consisted in highly branched PDGFR??⁺ cells (PDGFR??⁺-IM). Other populations of PDGFR??⁺ cells were observed within the submucosa and along the serosal and myenteric surfaces. Spindle-shaped intramuscular ICC (ICC-IM) were present in the WT mouse IAS but were largely absent from the W/W ^v IAS. The ICC-IM volume (5% of tissue volume) in the WT mouse IAS was significantly smaller than that of PDGFR??⁺-IM. Stellate-shaped submucosal ICC (ICC-SM) were observed in the WT and W/W ^v IAS. Minimum surface distance analysis revealed that nNOS⁺ nerve fibers were closely aligned with both ICC-IM and PDGFR??⁺-IM. An even closer association was seen between ICC-IM and PDGFR??⁺-IM. Thus, a close morphological arrangement exists between inhibitory motor neurons, ICC-IM and PDGFR??⁺-IM suggesting that some functional interaction occurs between them contributing to inhibitory neurotransmission in the IAS.     

Development of c‐kit immunopositive interstitial cells of Cajal in the human stomach

Interstitial cells of Cajal (ICC) include several types of specialized cells within the musculature of the gastrointestinal tract (GIT). Some types of ICC act as pacemakers in the GIT musculature, whereas others are implicated in the modulation of enteric neurotransmission. Kit immunohistochemistry reliably identifies the location of these cells and provides information on changes in ICC distribution and density. Human stomach specimens were obtained from 7 embryos and 28 foetuses without gastrointestinal disorders. The specimens were 7–27 weeks of gestational age, and both sexes are represented in the sample. The specimens were exposed to anti‐c‐kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined by using anti‐neuron specific enolase and the differentiation of smooth muscle cells (SMC) was studied with anti‐α smooth muscle actin and anti‐desmin antibodies. By week 7, c‐kit‐immunopositive precursors formed a layer in the outer stomach wall around myenteric plexus elements. Between 9 and 11 weeks some of these precursors differentiated into ICC. ICC at the myenteric plexus level differentiated first, followed by those within the muscle layer: between SMC, at the circular and longitudinal layers, and within connective tissue septa enveloping muscle bundles. In the fourth month, all subtypes of c‐kit‐immunoreactivity ICC which are necessary for the generation of slow waves and their transfer to SMC have been developed. These results may help elucidate the origin of ICC and the aetiology and pathogenesis of stomach motility disorders in neonates and young children that are associated with absence or decreased number of these cells.     

Function of the anal sphincters following anterior resections of rectum

The purpose of the present work is to evaluate the function of the anal sphincter following anterior resections of the rectum. Our data have shown that the anorectal reflex did not depend on the presence of the rectal mucosa. The external anal sphincter contraction involves a reflex which is initiated by stretch receptors in the levator ani muscle. The internal anal sphincter relaxation is likely a local reflex involving nerve pathways not yet completely defined.     

Development of the enteric nervous system,smooth muscle and interstitial cells of Cajal in the human gastrointestinal tract

The generation of functional neuromuscular activity within the pre-natal gastrointestinal tract requires the coordinated development of enteric neurons and glial cells, concentric layers of smooth muscle and interstitial cells of Cajal (ICC). We investigated the genesis of these different cell types in human embryonic and fetal gut material ranging from weeks 4–14. Neural crest cells (NCC), labelled with antibodies against the neurotrophin receptor p75^NTR, entered the foregut at week 4, and migrated rostrocaudally to reach the terminal hindgut by week 7. Initially, these cells were loosely distributed throughout the gut mesenchyme but later coalesced to form ganglia along a rostrocaudal gradient of maturation; the myenteric plexus developed primarily in the foregut, then in the midgut, and finally in the hindgut. The submucosal plexus formed approximately 2–3 weeks after the myenteric plexus, arising from cells that migrated centripetally through the circular muscle layer from the myenteric region. Smooth muscle differentiation, as evidenced by the expression of -smooth muscle actin, followed NCC colonization of the gut within a few weeks. Gut smooth muscle also matured in a rostrocaudal direction, with a large band of -smooth muscle actin being present in the oesophagus at week 8 and in the hindgut by week 11. Circular muscle developed prior to longitudinal muscle in the intestine and colon. ICC emerged from the developing gut mesenchyme at week 9 to surround and closely appose the myenteric ganglia by week 11. By week 14, the intestine was invested with neural cells, longitudinal, circular and muscularis mucosae muscle layers, and an ICC network, giving the fetal gut a mature appearance.A.S.W. is funded by a PhD studentship awarded to A.J.B. by the Child Health Research Appeal Trust.     

Interstitial cells of Cajal,macrophages and mast cells in the gut musculature: morphology,distribution, spatial and possible functional interactions

• ? Introduction
• ? Identification of the cells
  • ‐ ICC
  • ‐ Macrophages
    • ‐ Activation
    • ‐ Identification
  • ‐ Mast cells
    • ‐ Activation
    • ‐ Identification
• ? Cell distribution
  • ‐ ICC in rodent gastrointestinal tract
  • ‐ ICC in human gastrointestinal tract
  • ‐ Macrophages in rodent gastrointestinal tract
  • ‐ Macrophages in human gastrointestinal tract
  • ‐ Mast cells in rodent gastrointestinal tract
  • ‐ Mast cells in human gastrointestinal tract
• ? Inflammation
  • ‐ Models of inflammation
    • ‐ LPS administration
    • ‐ Surgical anastomosis
    • ‐ Ileal obstruction
    • ‐ Post‐operative ileus
    • ‐ Helminth infections
  • ‐ Inflammatory bowel disease
  • ‐ Achalasia
• ? Diabetes mellitus
  • ‐ NOD/LtJ mice
  • ‐ STZ‐DM rats
• ? Conclusions

Interstitial cells of Cajal (ICC) are recognized as pacemaker cells for gastrointestinal movement and are suggested to be mediators of neuromuscular transmission. Intestinal motility disturbances are often associated with a reduced number of ICC and/or ultrastructural damage, sometimes associated with immune cells. Macrophages and mast cells in the intestinal muscularis externa of rodents can be found in close spatial contact with ICC. Macrophages are a constant and regularly distributed cell population in the serosa and at the level of Auerbach’s plexus (AP). In human colon, ICC are in close contact with macrophages at the level of AP, suggesting functional interaction. It has therefore been proposed that ICC and macrophages interact. Macrophages and mast cells are considered to play important roles in the innate immune defence by producing pro‐inflammatory mediators during classical activation, which may in itself result in damage to the tissue. They also take part in alternative activation which is associated with anti‐inflammatory mediators, tissue remodelling and homeostasis, cancer, helminth infections and immunophenotype switch. ICC become damaged under various circumstances – surgical resection, possibly post‐operative ileus in rodents – where innate activation takes place, and in helminth infections – where alternative activation takes place. During alternative activation the muscularis macrophage can switch phenotype resulting in up‐regulation of F4/80 and the mannose receptor. In more chronic conditions such as Crohn’s disease and achalasia, ICC and mast cells develop close spatial contacts and piecemeal degranulation is possibly triggered.     

A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation. The involuntary action of the external anal sphincter: histologic study.

The histologic changes in the external anal sphincter after internal anal sphincter excision were studied in 20 dogs. An external sphincter biopsy was taken before internal sphincterectomy and 2 weeks and monthly thereafter for 10 months. The excised material was studied microscopically after being stained with hematoxylin and eosin, Verhoeff-van Gieson and succinic dehydrogenase. 70% of external sphincter specimens before internal sphincter excision showed smooth muscle fibers scattered between the striated fibers. These smooth fibers could be responsible for the resting tone of the external sphincter. After internal sphincter excision, characteristic histologic changes could be identified in the external sphincter. From the 2nd week to the 5th month after excision, the external sphincter showed degenerative and hypertrophic changes. From the 6th to the 10th month, there were regeneration of the striated muscle fibers and increase in the number of smooth fibers so that by the 10th month a 'compound' muscle of striated and smooth fibers was identified. Two theories were put forward to explain the smooth fiber preponderance in the external sphincter after internal sphincter excision: mutant and replacement theories. The increased nonstriated element in the external sphincter seems to be a structural-functional adaptation so that the external sphincter takes on the involuntary function of the excised muscle.     

A qualitative and quantitative study on the enkephalinergic innervation of the pig gastrointestinal tract.

Enkephalins are involved in neural control of digestive functions such as motility, secretion, and absorption. To better understand their role in pigs, we analyzed the qualitative and quantitative distribution of enkephalin immunoreactivity (ENK-IR) in components of the intestinal wall from the esophagus to the anal sphincter. Immunohistochemical labelings were analyzed using conventional fluorescence and confocal microscopy. ENK-IR was compared with the synaptophysin immunoreactivity (SYN-IR). The results show that maximal ENK-IR levels in the entire digestive tract are reached in the myenteric plexuses and, to a lesser extent, in the external submucous plexus and the circular muscle layer. In the longitudinal muscle layer, ENK-IR was present in the esophagus, stomach, rectum, and anal sphincter, whereas it was absent from the duodenum to the distal colon. In the ENK-IR plexuses and muscle layers, more than 60% of the nerve fibers identified by SYN-IR expressed ENK-IR. No ENK-IR was observed in the internal submucous plexus and the mucosa; the latter was found to contain ENK-IR endocrine cells. These results strongly suggest that, in pigs, enkephalins play a major role in the regulatory mechanisms that underlie the neural control of digestive motility.     

Physiology and pathophysiology of the interstitial cell of Cajal: from bench to bedside. I. Functional development and plasticity of interstitial cells of Cajal networks

Interstitial cells of Cajal (ICC) are the pacemaker cells in gastrointestinal (GI) muscles. They also mediate or transduce inputs from enteric motor nerves to the smooth muscle syncytium. What is known about functional roles of ICC comes from developmental studies based on the discovery that ICC express c-kit. Functional development of ICC networks depends on signaling via the Kit receptor pathway. Immunohistochemical studies using Kit antibodies have expanded our knowledge about the ICC phenotype, the structure of ICC networks, the interactions of ICC with other cells within the tunica muscularis, and the loss of ICC in some motility disorders. Manipulating Kit signaling with reagents to block the receptor or downstream signaling pathways or by using mutant mice in which Kit or its ligand, stem cell factor, are defective has allowed novel studies of the development of these cells within the tunica muscularis and also allowed the study of specific functions of different classes of ICC in several regions of the GI tract. This article examines the role of ICC in GI motility, focusing on the functional development and maintenance of ICC networks in the GI tract and the phenotypic changes that can occur when the Kit signaling pathway is disrupted.     

Anal sphincteric neurogenic injury in asymptomatic nulliparous women and fecal incontinence

While anal sphincter neurogenic injury documented by needle electromyography (EMG) has been implicated to cause fecal incontinence (FI), most studies have been uncontrolled. Normal values and the effects of age on anal sphincter motor unit potentials (MUP) are ill defined. The functional significance of anal sphincter neurogenic injury in FI is unclear. Anal pressures and EMG were assessed in 20 asymptomatic nulliparous women (age, 38 ± 5 yr; mean ± SE) and 20 women with FI (54 ± 3 yr). A computerized program quantified MUP duration and phases. These parameters and MUP recruitment were also semiquantitatively assessed by experienced electromyographers in real time. Increasing age was associated with longer and more polyphasic MUP in nulliparous women by quantitative analysis. A higher proportion of FI patients had prolonged (1 control, 7 patients, P = 0.04) and polyphasic MUP (2 controls, 9 patients, P = 0.03) at rest but not during squeeze. Semiquantitative analyses identified neurogenic or muscle injury in the anal sphincter (11 patients) and other lumbosacral muscles (4 patients). There was substantial agreement between quantitative and semiquantitative analyses (κ statistic 0.63 ± 95% CI: 0.32-0.96). Anal resting and squeeze pressures were lower (P ≤ 0.01) in FI than controls. Anal sphincter neurogenic or muscle injury assessed by needle EMG was associated (P = 0.01) with weaker squeeze pressures (83 ± 10 mmHg vs. 154 ± 30 mmHg) and explained 19% (P = 0.01) of the variation in squeeze pressure. Anal sphincter MUP are longer and more polyphasic in older than younger nulliparous women. Women with FI have more severe neurogenic or muscle anal sphincter injury, which is associated with lower squeeze pressures.     

Distribution of the intermediate filament nestin in the muscularis propria of the human gastrointestinal tract

The intermediate filament nestin is expressed in neural stem cells, neuroectodermal tumors and various adult tissues. In the gastrointestinal (GI) tract, nestin has been reported in glial cells. Recently, nestin has been reported in interstitial cells of Cajal (ICC) and in gastrointestinal stromal tumors, thought to derive from ICC. Here we investigated nestin immunoreactivity (-ir) in the normal human GI tract, with emphasis on Kit-ir ICC. Two different antibodies specific for human nestin and multicolor high-resolution confocal microscopy were used on material from our human GI tissue collection. The staining pattern of both nestin antibodies was similar. In labeled cells, nestin-ir appeared filamentous. Most intramuscular ICC in antrum and all myenteric ICC (ICC-MP) in small intestine were nestin-ir, while nestin-ir was not detected in deep muscular plexus ICC. In the colon, some - but not all - ICC-MP and most ICC in the circular musculature were nestin-ir while nestin-ir was not detected in ICC in the longitudinal musculature and in the submuscular plexus. In addition, many Kit-negative cells were nestin-ir in all regions. Neurons and smooth muscle cells were consistently nestin negative, while most S100-ir glial cells were nestin-ir. In addition, nestin-ir was also present in some CD34-ir fibroblast-like cells, in endothelium and in other cell types in the mucosa and serosa. In conclusion, nestin-ir is abundantly present in the normal human GI tract. Among a number of cell types, several, but not all, subpopulations of Kit-ir ICC were nestin-ir. The functional significance of nestin in the GI tract remains obscure.     

The intrinsic myenteric innervation of the hind-gut and accessory muscles of defaecation in the cat

Summary The anatomy and intrinsic innervation of the colon, rectum, internal anal sphincter, ano-coccygeus and recto-coccygeus have been studied in the cat with cholinesterase and catecholamine-fluorescence histochemical techniques. A variable pattern of intrinsic innervation by acetylcholinesterase-positive and adrenergic nerves along the length of the large bowel is described and is related to segmental variations in motor activity. A variation in the distribution of non-specific cholinesterase within the muscle layers is also described. Adrenergic nerves in proximal colon are arranged in the usual peri-ganglionic manner but there is also a rich direct adrenergic innervation of the longitudinal muscle in distal colon and rectum, and of circular muscle in lower rectum and internal anal sphincter. This distribution has not been reported in other species. Direct adrenergic innervation of muscle cells has been confirmed at ultrastructural level after treatment with 5-hydroxydopamine. Adrenergic neurones have not been detected in cat bowel. The ano- and recto-coccygeus muscles and internal anal sphincter possess a dense innervation of adrenergic and cholinesterase-positive nerves. It is suggested that the variation in intrinsic innervation along the large bowel should be considered in the interpretation of pharmacological and physiological experiments on this part of the gut.This work was supported by a grant from the King's College Hospital Voluntary Research Trust. We wish to thank Dr. J. P. Tranzer and F. Hoffman-La Roche & Co. Ltd., Basle, for the gift of 5-hydroxydopamine.We also thank Miss M. K. Egan and Mr. K. J. Davies for their technical assistance.