Hypertrophic pyloric stenosis: ultrastructural abnormalities of enteric nerves and the interstitial cells of Cajal

Presence of in vitro electrical activity in the ileum of horses with enteric nervous system pathology: equine dysautonomia (grass sickness)

Equine dysautonomia (grass sickness) is a frequently fatal disease of horses characterised by intestinal stasis. Interstitial cells of Cajal (ICC) are the pacemakers and mediators of neurotransmission in the gastrointestinal tract. Impaired ICC-mediated control of motility has been implicated in intestinal disorders in laboratory mammals, humans and in equine grass sickness. The aim of this study was to compare the in vitro electrical properties of ileum from grass sickness cases with horses free from gastrointestinal disease. Intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations of equine ileum, superfused in vitro. Samples were taken from six horses with grass sickness and from eight horses free from gastrointestinal disease, all euthanised on humane grounds. Ileal tissues were processed for haematoxylin and eosin histology, and c-Kit immunohistochemistry. Membrane potential oscillations were recorded in the ileal preparations from four of the six horses with grass sickness and from all of the normal horses. A waxing and waning pattern of the membrane potential oscillation activity was noted in some cells. In comparison to the normal horses, the membrane potential oscillations in grass sickness horses had a significantly reduced frequency (P = 0.0001) and increased duration (P = 0.0002). Immunohistochemistry revealed the presence but reduction of ICC in grass sickness. Histological assessment of the same tissues used for analysis of the ICC showed the depletion and pathology of the enteric neurons in grass sickness. Therefore, the majority of ileal preparations from grass sickness-affected horses exhibited prominent membrane potential oscillation activity suggesting that, although the neural elements are damaged severely, the ICC-mediated pacemaker function remains intact.

Pathology of interstitial cells of Cajal in relation to inflammation revealed by ultrastructure but not immunohistochemistry

The role of interstitial cells of Cajal associated with Auerbach's plexus (ICC-AP) in the pathophysiology of inflammation-induced abnormalities in gut motor activity is poorly understood. Therefore we applied a well-described model of inflammation (infection by Trichinella spiralis) to the mouse small intestine where the structure and function of ICC-AP are best known. Electron microscopic evaluation revealed that 1 to 3 days after infection, selective and patchy damage to the ICC processes occurred, thereby disrupting contacts between these ICC and smooth muscle cells as well as ICC and nerves, which was associated with disordered electrical activity and abnormal peristalsis. Ten to 15 days after infection, damage to ICC-AP was maximal and now involving the cell body and major processes. Marked synthetic activity and regrowth of their processes occurred from day 3 onward and recovery was completed at day 40 after infection. No changes to the network of ICC-AP were seen with c-Kit immunohistochemistry. From day 1 after infection, macrophages infiltrated the AP area, making close contact including peg-and-socket-like junctions with smooth muscle cells and ICC-AP but up to day 6 after infection without any sign of phagocytosis. By day 6 after infection, lymphocytes entered the musculature forming close contacts with ICC-AP. This was not associated with damage to ICC-AP but with proliferation of rough endoplasmic reticulum. From day 23 onward, immune cells withdrew from the musculature except macrophages, resulting in a markedly increased population of macrophages in the AP area at day 60 after infection.

The interstitial cells of Cajal and a gastroenteric pacemaker system

In spite of a claim by Kobayashi (1990) that they do not correspond to the cells originally depicted by CAJAL, a particular category of fibroblast-like cells have been identified in the gut by electron microscopy (Faussone-Pellegrini, 1977; Thuneberg, 1980) and by immunohistochemistry for Kit protein (Maeda et al., 1992) under the term of the "interstitial cells of Cajal (ICC)". Generating electrical slow waves, the ICC are intercalated between the intramural neurons and the effector smooth muscular cells, to form a gastroenteric pacemaker system. ICC at the level of the myenteric plexus (IC-MY) are multipolar cells forming a reticular network. The network of IC-MY which is believed to be the origin of electrical slow waves is morphologically independent from but associated with the myenteric plexus. On the other hand, intramuscular ICC (IC-IM) usually have spindle-shaped contours arranged in parallel with the bulk smooth muscle cells. Associated with nerve bundles and blood vessels, the IC-IM possess receptors for neurotransmitters and such circulating hormones as cholecystokinin, suggesting their roles in neuromuscular and hormone-muscular transmissions. In addition, gap junctions connect the IC-MY and IC-IM, thereby realizing the electrically synchronized integrity of ICC as a pacemaker system in the gut. The smooth muscle cells are also coupled with ICC via gap junctions, and the functional unit thus formed enables rhythmically synchronized contractions and relaxations. It has recently been found that a lack of Kit-expressing cells may induce hyper-contractility of the tunica muscularis in vitro, whereas a decrease in Kit expression within the muscle wall causes dysmotility-like symptoms in vivo. The pacemaker system in the gut thus seems to play a critical role in the maintenance of both moderate and normal motility of the digestive tract. A loss of Kit positive cells has been detected in several diseases with an impaired motor activity, including diabetic gastroenteropathy. Pathogenesis of these diseases is thought to be accounted for by impaired slow waves and neuromuscular transmissions; a pacemaker disorder may possibly induce a dysmotility-like symptom called 'gastroenteric arrhythmia'. A knowledge of the structure and function of the ICC and the pacemaker system provides a basis for clarifying the normal mechanism and the pathophysiology of motility in the digestive tract.

Deficiency of interstitial cells of Cajal in the small intestine of patients with Crohn's disease

OBJECTIVE

Interstitial cells of Cajal are critical for the generation of electrical slow waves that regulate the phasic contractile activity of the tunica muscularis of the GI tract. Under certain pathophysiological conditions loss of interstitial cells of Cajal may play a role in the generation of certain motility disorders. The aim of the present study was to determine if there is an abnormality in the density or distribution of interstitial cells of Cajal from patients with Crohn's disease.

METHODS

Small intestines from control subjects and patients with Crohn's disease were examined using immunohistochemistry and antibodies against the Kit receptor, which is expressed in interstitial cells of Cajal within the tunica muscularis of the GI tract. The density and distribution of interstitial cells of Cajal were assessed in the longitudinal and circular muscle layers and in the myenteric and deep muscular plexus regions of Crohn's and control tissues.

RESULTS

Tissues from Crohn's disease patients showed an almost complete abolition of interstitial cells of Cajal within the longitudinal and circular muscle layers and a significant reduction in numbers at the level of the myenteric and deep muscular plexuses.

CONCLUSIONS

In tissues from Crohn's disease patients, the density of interstitial cells of Cajal was reduced throughout the tunica muscularis in comparison to control small intestines. The disturbance of intestinal motility that occurs in patients with Crohn's disease may be a consequence of the loss of or defects in specific populations of interstitial cells of Cajal within the tunica muscularis.

Physiology and pathophysiology of the interstitial cell of Cajal: from bench to bedside. II. Gastric motility: lessons from mutant mice on slow waves and innervation

The stomach harbors a network of interstitial cells of Cajal (ICC) associated with Auerbach's plexus as well as intramuscular ICC within the muscle layers that make close apposition contact with nerve varicosities. ICC are critical for slow-wave generation, making ICC the pacemaker cells of the gut, allowing rhythmic peristaltic motor patterns in the mid- and distal stomach. ICC also play a role in neurotransmission, but its importance relative to direct muscle innervation is still under investigation. The role of ICC in many control functions of gastric motility in humans needs further examination. The pathophysiology of ICC in disease can be partially assessed by immunohistochemistry and electron microscopy on tissue samples. Electrogastrogram measurements may also play a role, but this technique needs further refinement. Communication between ICC and muscle may involve electrical coupling, metabolic coupling through gap junctions, or secretion of nitric oxide or carbon monoxide.

In vivo visualization of pyloric mucosal hypertrophy in infants with hypertrophic pyloric stenosis: is there an etiologic role?

OBJECTIVE

Infantile hypertrophic pyloric stenosis (IHPS) is a common condition which presents in infants at 2-12 weeks of postnatal life, and whose cause remains obscure. Multiple associated abnormalities have been recognized within the external hypertrophied pyloric muscle layer, but the internal component of the pyloric mucosa has received scant attention in the literature to date. Our purpose in this study was to show that pyloric mucosal redundancy is a constant finding in infants with IHPS, to discuss its possible cause, and to explore the hypothesis of a relationship between pyloric mucosal redundancy and the development of IHPS.

MATERIALS AND METHODS

We identified 102 consecutive infants with surgically confirmed IHPS and determined the thickness of the pyloric mucosa compared with the thickness of the surrounding hypertrophied muscle. Fifty-one infants who did not have pyloric stenosis served as controls.

RESULTS

Mean mucosal thickness in patients with IHPS approximated mean muscle thickness, with a ratio of 0.89. In infants with IHPS, the pyloric mucosa constitutes approximately one third of the cross-sectional diameter of the pyloric mass and fills and obstructs the pyloric canal.

CONCLUSION

Mucosal redundancy is a constant associated finding in IHPS. Although the origin of the redundancy and a cause-and-effect relationship are difficult to establish, our findings support the hypothesis that hypergastrinemia may be implicated in the pathogenesis of IHPS, and suggest that mucosal thickening could be implicated as one of the initiating factors in its development.

A reduction in interstitial cells of Cajal in horses with equine dysautonomia (grass sickness)

Equine dysautonomia (grass sickness) is a common, frequently fatal disease of horses characterised by dysfunction of the gastrointestinal tract. Interstitial cells of Cajal are the c-Kit-immunoreactive cells responsible for the generation of pacemaker activity in gastrointestinal smooth muscle. Impairment of this pacemaker action has been implicated in several motility disorders in humans and laboratory mammals. The aim of this study was to test the hypothesis that changes in interstitial cells of Cajal may be involved in the pathophysiology of the intestinal dysfunction observed in equine grass sickness. Interstitial cells of Cajal were identified using immunohistochemical labelling with an anti-c-Kit antibody and their density was assessed using a semi-quantitative grading system. Segments of ileum were examined from 24 horses free from gastrointestinal disease and compared to tissues from 28 horses with grass sickness. Segments of the pelvic flexure region of the large colon were examined from 13 horses free from gastrointestinal disease and compared to tissues from 10 horses with grass sickness. In horses with grass sickness, interstitial cells of Cajal were significantly decreased in both the myenteric plexus and circular muscle regions of both ileum and pelvic flexure compared to normal animals. Therefore, it is possible that the decline in interstitial cells of Cajal may be an important factor in the development of intestinal dysmotility observed in grass sickness.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.

Long-term effects of pyloromyotomy on pyloric motility and gastric emptying in humans

OBJECTIVE

The aim of this study was to determine the long term effects of pyloromyotomy for infantile hypertrophic pyloric stenosis (IHPS) on gastric emptying and pyloric motility.

METHODS

Concurrent measurements of gastric emptying and antropyloroduodenal pressures were performed in six volunteers (aged 24-26 yr) who had had pyloromyotomy performed in infancy because of IHPS, and in six normal subjects. Subjects were studied on 2 days, once sitting and once in the left lateral position. Gastric emptying of 300 ml 25% dextrose labeled with 20 MBq 99mTc sulfur colloid was measured. Antropyloroduodenal motility was evaluated with a sleeve/multiple sidehole manometric assembly, which was also used to deliver an intraduodenal triglyceride infusion at 1.1 kcal/min for 60 min, starting 30 min after ingestion of the dextrose.

RESULTS

In both body positions, gastric emptying and intragastric distribution of the drink did not differ between the two groups. In both groups and postures, the amount emptied was less during intraduodenal lipid infusion. The number (p<0.01) and amplitude (p<0.02) of isolated pyloric pressure waves (IPPWs) was greater in the control subjects, whereas basal pyloric pressure was greater in the pyloromyotomy subjects (p<0.02). In both groups, the rate of gastric emptying in the sitting position was related to the number of IPPWs (r> or =0.40, p<0.05), but not to basal pyloric pressure.

CONCLUSIONS

These results indicate that, in adults who have had pyloromyotomy for IHPS in infancy, patterns of pyloric motility are abnormal; pyloric tone is higher, whereas the number and amplitude of phasic pyloric pressure waves are less. In contrast, the overall rate of gastric emptying of a nutrient liquid meal is normal. These observations are consistent with the concept that the stomach has the capacity to compensate for changes in pyloric motility to minimize effects on gastric emptying.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.

Guide to the identification of interstitial cells of Cajal

The interstitial cell of Cajal, abbreviated ICC, is a specific cell type with a characteristic distribution in the smooth muscle wall throughout the alimentary tract in humans and laboratory mammals. The number of publications relating to ICC is rapidly increasing and demonstrate a rich variation in the structure and organization of these cells. This variation is species-, region-, and location-dependent. We have chosen to define a "reference ICC," basically the ICC in the murine small intestine, as a platform for discussion of variability. The growing field of ICC markers for light and electron microscopy is reviewed. Although there is a rapidly increasing number of approaches applicable to bright field and fluorescence microscopy, the location of markers by electron microscopy still suffers from inadequate preservation of ultrastructural detail. Finally, we summarize evidence related to ICC ultrastructure under conditions differing from those of the normal, adult individual (during differentiation, in pathological conditions, transplants, mutants, and in cell culture).

Ultrastructural characterization of the interstitial cells of Cajal

Recent studies on the interstitial cells of Cajal (ICC) have determined ultrastructural criteria for the identification of these previously enigmatic cells. This review deals with the electron microscopic findings obtained by the author's research group in different tissue regions of the gut in mice, rats and guinea-pigs, comparing these with reports from other groups in different species and in humans. ICC are characterized by the following morphological criteria: numerous mitochondria, abundant intermediate filaments and large gap junctions which connect the cells with each other and with smooth muscle cells. Due to their location in the gut and the specific species, the ICC are markedly heterogeneous in appearance, ranging from cells closely resembling smooth muscle cells to those similar to fibroblasts (Table 1). Nevertheless, the above-mentioned morphological features are shared by all types of ICC and serve in identifying them. Recent discoveries on a significant role of c- kit in the maturation of the ICC and their specific immunoreactivity to anti-c-Kit antibody have confirmed the view that the ICC comprise an independent and specific entity of cells. This view is reinforced by the findings of the author's group that the ICC characteristically possess vimentin filaments and are stained with the zinc iodide-osmium tetroxide method which provides a staining affinity similar to methylene blue, the dye used in the original work by Cajal, (1911). Developmental studies indicate that the ICC are derived from a non-neuronal, mesenchymal origin. This paper further reviews advances in the physiological studies on the ICC, in support of the hypothesis by THUNEBERG (1982) that they function as a pacemaker in the digestive tract and a mediator transmitting impulses from the nerve terminals to the smooth muscle cells.

Control systems of gastrointestinal motility are immature at birth in dogs

Networks of interstitial cells of Cajal (ICC) in the myenteric plexus (Myp) or circular muscle (CM) function as pacemakers for gastrointestinal slow waves. ICC in contact with muscle and closely associated with nerves in the CM may mediate inhibitory neurotransmission. We wondered if ICC in Myp and CM and their connections are immature at birth and mature first in the proximal gut in association with nerves. Tissues from lower esophageal sphincter (LES), pylorus (PYL), small intestine (SI) and colon (CO) of 18 term fetal dogs taken from six females were fixed and prepared for ultrastructural examination and studied. Ganglia were present where expected in the Myp and submucous plexus (SMP). ICC cells were present in the Myp of PYL, SI and CO and appeared to have normal relationships to the outer border of CM as in adults. ICC in CM were found associated with nerves in the LES and in PYL, but not in SI or CO. However, axons in CM were everywhere usually free of glial covering, indicating ongoing migration or development. No organized deep muscular plexus (DMP) in SI or submuscular plexus (SP) in colon was present. Visible gap junctions were absent everywhere except for very rare ones between circular muscle cells. We conclude that at birth the neural and ICC networks of CM are more immature in intestine and colon than in oesophagus and stomach. Development of nerve and ICC of CM in oesophagus and stomach apparently precedes that in the remaining gut. However networks in these regions have not achieved adult organization and ICC and smooth muscle cells are anatomically poorly coupled. These findings suggest the reasons that gut motility at birth will not be adult in pattern are because ICC, nerve and muscle control systems are not fully differentiated. Further developmental delays in ICC and nerve maturation could have serious consequences for feeding of infant animals.

Ontogeny of interstitial cells of Cajal in the human intestine

BACKGROUND/PURPOSE

Interstitial cells of Cajal (ICC) recently have been identified as intestinal pacemaker cells. Abnormalities in ICC are increasingly recognized in a number of neonatal disorders such as infantile hypertrophic pyloric stenosis, Hirschsprung's disease, and transient intestinal pseudo-obstruction. The aim of this study was to determine the fetal and postnatal differentiation and development of ICC in the human gastrointestinal tract to aid interpretation of pathological specimens.

METHODS

Specimens of human gastrointestinal tract from (1) fetuses (9 to 17 weeks' gestation; n = 12), (2) premature and full-term neonates with non-gut motility-related disorders, (age 26 to 59 weeks' gestation; n = 13), and (3) children (age 4 months to 13 years; n = 7) were immunohistochemically stained with antibodies to c-kit(a marker for ICC) and protein gene product 9.5 (PGP9.5, a marker for neural tissue).

RESULTS

(1) C-kit-positive ICC were present throughout the gut in all specimens including those from the earliest gestational ages. C-kit and PGP9.5 immunoreactivities were present in different cell populations. (2) The distribution of ICC varied with gestational age and with region of the gut. (3) Maturation of ICC networks continues postnatally in a region-specific manner.

CONCLUSIONS

ICC are present from an early stage in human gut development. Interpretation of apparent abnormalities in ICC distribution as being of pathological significance should be tempered by the knowledge that ICC networks continue to develop postnatally and that ICC development varies throughout the gut.

An immunohistochemical study of interstitial cells of Cajal (ICC) in the equine gastrointestinal tract

The interstitial cells of Cajal (ICC) are c-kit immunoreactive cells of the gastrointestinal tract which are suggested to have a role in the control of intestinal motility. Cells with c-kit immunoreactivity have not been previously described in the gastrointestinal tract of the horse. Immunoreactivity for c-kit was revealed using immunohistochemical labelling with an anti-c-kit polyclonal antibody. Sections of normal gastrointestinal tissue were examined from 13 anatomically defined sites from stomach to small colon taken from horses free from gastrointestinal disease. Three types of c-kit immunoreactive cells were identified: spindle-shaped cells in the region of the myenteric plexus, stellate or bipolar cells in the circular muscle layer, and round cells in the submucosa. The round cells were shown to be mast cells with the use of toluidine blue staining, whereas the other c-kit immunoreactive cells did not exhibit metachromasia and were classified as ICC. This study will serve as a basis for future pathological studies in the horse.

Smooth muscle cell hypertrophy versus hyperplasia in infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is characterized by hypertrophy of the pyloric muscle. It is not clearly understood whether pyloric muscle enlargement is due to hypertrophy (increase in cell size) or hyperplasia (increase in cell number). In the present study, we investigated proliferative activity as well as size and number of smooth muscle cells to understand the mechanism of pyloric muscle enlargement in IHPS. Full thickness muscle biopsy specimens were obtained from 18 IHPS patients at pyloromyotomy and from 11 age-matched controls. Formalin-fixed paraffin sections were immunostained with MAb MIB-1, which stains cells in the proliferating phase of the cell cycle. The proliferative index (PI) was calculated as the percentage of positive cell nuclei. Smooth muscle cell number per bundle and cell size were measured with an image analyzer. The mean PI in IHPS (9.6 +/- 5.7%) was significantly higher than that of controls (1.3 +/- 1.2%) (p < 0.01). There was a significant inverse correlation between PI and age at operation. Smooth muscle cell number per bundle in IHPS (240.6 +/- 129.4) was significantly greater than that of the controls (134.1 +/- 49.8) (p < 0.05). Smooth muscle cell size in IHPS (298.5 +/- 59.0 microm2) was also significantly greater than that of controls (154.3 +/- 21.5 microm2) (p < 0.01). Our findings suggest that hypertrophy-and hyperplasia as well-play important roles in increasing pyloric smooth muscle mass in IHPS.

The changing presentation of pyloric stenosis

Metabolic abnormalities described in pyloric stenosis are now rare, probably because of prompter recognition of the disease. This report reviews the trend in presentation over three decades. All infants treated for pyloric stenosis during three mid-decade target periods were reviewed. Comparison between the 1975 group and the 1985 group and between the 1995 group and previous decades were designed to identify the impact of ultrasonography, since this modality has only been available in the last decade. Parameters included age at diagnosis and incidence of water and electrolyte imbalance as measures of delay in presentation. Two hundred eighty-three patients were reviewed. Mean age (weeks) at presentation was 5.4+/-3.0 in 1975, 4.6+/-2.0 in 1985, and 3.4+/-1.3 in 1995 (P < .05, ANOVA). Overall, 88% had no electrolyte anomalies on admission. There was no statistical difference in frequency of abnormal results between the three decades. Total and postoperative hospitalization was significantly shorter in the recent period: in 1985, 5.34 and 4.36 days; in 1985, 4.48 and 3.4 days; and in 1995, 3.8 and 2.8 days. These data show that pyloric stenosis is now recognized earlier than in previous decades. The availability of ultrasonography cannot solely be credited for earlier diagnosis, since this trend was already apparent before its introduction. The "classic" metabolic derangements associated with pyloric stenosis have been highly uncommon for the past three decades.

Regional and transmural density of interstitial cells of Cajal in human colon and rectum

The interstitial cells of Cajal (ICC) are thought to play an important role in the control of gut motility. The regional and transmural pattern of distribution of ICC in the normal human colon and rectum was evaluated with immunohistochemistry using an anti-c-kit antibody. The transmural distribution of ICC was constant throughout the whole colon, the density of ICC was significantly greater at the myenteric plexus than at either the longitudinal or circular muscle layers, and in the rectum the transmural distribution was more even. Regionally, at the myenteric plexus, the transverse colon had a significantly greater density of ICC compared with the right colon (P = 0.038), left colon (P = 0.006), and rectum (P = 0.008). The pattern of distribution of ICC identified in this study is consistent with the proposed roles of ICC as colorectal pacemakers, intermediaries of the neural control of muscle activity, and coordinators of colorectal muscle activity. The highest density of ICC was at the myenteric plexus of the transverse colon, which is the proposed region of pacemaking activity.

Distribution of the interstitial cells of Cajal in the human anorectum

The interstitial cells of Cajal are proposed to have a role in the control of gut motility. The aim of this study was to establish the distribution of interstitial cells of Cajal in the wall of the normal human anorectum. Interstitial cells of Cajal express the proto-oncogene c-kit. Interstitial cells of Cajal were identified in the colon by immunohistochemical staining, using a rabbit polyclonal anti-c-kit antibody. Anorectal tissue was obtained at surgical resection for carcinoma of the colorectum. Density of interstitial cells of Cajal was graded. Statistical analysis was performed using chi2 tests. In the longitudinal and circular muscle layers of the rectum interstitial cells of Cajal were seen in the bulk of the muscle layer. In the intermuscular plane interstitial cells of Cajal encased the myenteric plexus. Interstitial cells of Cajal were found at the inner margin of the circular muscle and in association with neural elements of the submuscular plexus. Within the internal anal sphincter interstitial cells of Cajal were infrequently scattered among the muscle fibres. The density of interstitial cells of Cajal in the internal anal sphincter was significantly lower than that observed in the circular muscle layer of the rectum (P = 0.014). In conclusion, interstitial cells of Cajal are evenly distributed in the layers of the muscularis propria of the rectum, but have a lower density in the internal anal sphincter.

Neural injury, repair, and adaptation in the GI tract. IV. Pathophysiology of GI motility related to interstitial cells of Cajal

Our understanding of the physiological roles played by interstitial cells of Cajal (ICC) in relation to gastrointestinal (GI) motility is still rudimentary. Nevertheless, studies into the pathophysiology of ICC are emerging at a rapid pace. Caution should be exercised, however, in assuming correlations between changes in Kit immunoreactivity, findings of ultrastructural abnormalities in ICC, and the pathophysiology and symptoms of the patients. Recent studies have revealed reduced numbers or the absence of ICC in small intestine and colon that do not exhibit normal peristaltic activity. Furthermore, important evidence is emerging that motor abnormalities in newborns may be associated with delayed maturation of the ICC network. These preliminary clinical studies provide plausible hypotheses toward the pathophysiology of certain motor disorders and strongly encourage basic scientific studies directed toward discovering the intrinsic properties of ICC as well as obtaining a deeper understanding of the physiological roles played by these cells.

Increased insulin-like growth factor and platelet-derived growth factor system in the pyloric muscle in infantile hypertrophic pyloric stenosis

BACKGROUND

Infantile hypertrophic pyloric stenosis (IHPS) is characterized by hypertrophy of the pyloric muscle. The etiology of IHPS is unknown. The growth of smooth muscle cells (SMC) is regulated by several growth factors. Insulin-like growth factor (IGF) and platelet-derived growth factor (PDGF) act synergistically to stimulate SMC proliferation. The effects of IGF-I and PDGF are mediated via their receptors.

METHODS

Full-thickness muscle biopsy specimens were obtained from eight IHPS patients (age range, 14 to 46 days) at pyloromyotomy and from eight age-matched controls without gastrointestinal disease at autopsy performed within 4 hours after death. Indirect three-step immunohistochemistry was performed using anti-IGF-I, IGF-I receptor alpha (IGF-IR alpha), IGF-IR beta, PDGF-BB and PDGF receptor (PDGF-R) antibodies and visualized by peroxidase staining.

RESULTS

The most striking difference between tissues from IHPS patients and controls was the marked increase in IGF-I, IGF-IR alpha, IGF-IR beta and PDGF-R in the hypertrophic circular muscle layer, and, to a lesser degree, in the longitudinal muscle in pyloric stenosis.

CONCLUSION

The findings suggest that the upregulated local IGF and PDGF systems may play a role in the development of pyloric muscle hypertrophy in IHPS.

Disorders of the oesophagus and stomach in infants

Pathological processes and disease entities in the upper gastrointestinal (GI) tract, specifically those of the oesophagus and the stomach in infancy, have received a disproportionately small amount of attention until recently when appreciation of their pathophysiology and concordant importance in terms of symptomatology has been highlighted. This is probably a phenomenon secondary to improved diagnostic yield from the recent technical advances in areas such as infant endoscopy and a shift in opinion regarding the pathophysiological origin of ubiquitous symptoms of infancy such as feeding disorders, colic and irritability. In addition, the apparently complex interactions of various aetiological factors such as pH-independent gastro-oesophageal reflux (GOR), cow's milk protein intolerance (CMPI), Helicobacter pylori gastritis and upper GI motor disorders have in the past 1-2 years become underlined in terms of aetiopathogenesis and have radically changed thinking regarding diagnosis and therapy of infants with apparent upper-GI-associated symptoms. The contribution to comprehension of infant upper GI disorders of inflammatory paradigms and ontogeny of the upper GI tract is also a recent area worthy of mention. The recent advances in all of these areas and their contribution to the understanding, and subsequent diagnosis and therapy, of upper GI symptoms and their explanation by way of aetiopathogenesis will be explored in this chapter.

Role of the interstitial cells of Cajal in the control of gut motility

BACKGROUND

The interstitial cells of Cajal (ICCs) are a population of cells in the gastrointestinal tract which have a role in the control of gut motility.

METHOD

A comprehensive review of the scientific literature was undertaken to assess current understanding of the morphology, structure, identification, distribution, development and function of these cells.

RESULTS AND CONCLUSIONS

ICCs have an important role in the control of gut motility. Experimental evidence from animal studies suggests roles as pacemakers and coordinators of gut motor activity, and as intermediaries in the neural control of motility. With an increasing understanding of the distribution and behaviour of these cells in the healthy or diseased human gastrointestinal tract, there is the potential to develop novel therapeutic approaches to diseases that have gut dysmotility as a contributory factor.

Lack of intestinal pacemaker (C-KIT-positive) cells in infantile hypertrophic pyloric stenosis

The pathogenesis of infantile hypertrophic pyloric stenosis (IHPS) is not well understood. Recent studies have shown that the protonocogene c-kit is essential for the development or maintenance of autonomic gut motility, and also show that the c-kit gene protein product (C-KIT) positive cells in the mammalian gut are responsible for intestinal pacemaker activity. This study examines cells in the pyloric muscles of 23 patients (16 with IHPS, 7 controls) for the presence of the C-KIT (C-KIT+), using immunohistochemical techniques with antihuman C-KIT sera. In the controls, many C-KIT immunoreactive (IR+) cells were observed in the muscle layers. The myenteric plexuses were demarcated by a moderate number of C-KIT-IR+ cells. However, in the IHPS patients, C-KIT-IR were either absent or significantly reduced. No C-KIT-IR+ cells were found around the myenteric plexuses. These findings suggest that a lack of c-kit expression (as an indicator of intestinal pacemaker activity) in the hypertrophic pyloric smooth muscles may be an important factor in the pathogenesis of IHPS.