Electrical activity of the intestine of mice with hereditary megacolon and absence of enteric ganglion cells

Mice with a recessive gene which reduces the number of ganglion cells of the large intestine and produces megacolon similar to Hirschsprung's disease were studied. Electrical activity of the small bowel consisted of electrical slow waves and action potentials and showed no difference between the mice with megacolon and their normal siblings. Electrical slow waves and action potentials occurred in the large intestine of both normal and abnormal mice. The principal difference between normal mice and their abnormal siblings was increased incidence of discharge of action potentials associated with uncoordinated phasic contractions superimposed upon tonic contracture of the circular muscle layer of the distal aganglionic segment in the abnormal mouse. The distended colon of the abnormal mouse and the entire length of the normal bowel showed bursts of action potentials which accompanied peristaltic waves of circular muscle contraction. During propulsive motility in the rectum, activation of the circular muscle was preceded by coordinated contraction of the longitudinal muscle only in the normal bowel. Symptoms of megacolon can be accounted for by the absence of spontaneously active inhibitory neurons from the enteric plexuses of the distal segment of the large bowel.     

Development of interstitial cells of Cajal and pacemaking in mice lacking enteric nerves.

BACKGROUND & AIMS: Development of interstitial cells of Cajal (ICC) requires signaling via Kit receptors. Kit is activated by stem cell factor (SCF), but the source of SCF in the bowel wall is unclear and controversy exists about whether enteric neurons express the SCF required for ICC development. METHODS: Glial cell line-derived neurotrophic factor (GDNF) knockout mice, which lack enteric neurons throughout most of the gut, were used to determine whether neurons are necessary for ICC development. ICC distributions were determined with Kit immunofluorescence, and function of ICC was determined by intracellular electrical recording. RESULTS: ICC were normally distributed throughout the gastrointestinal tracts of GDNF-/- mice. Intracellular recordings from aganglionic gastrointestinal muscles showed normal slow wave activity at birth in the stomach and small intestine. Slow waves developed normally in aganglionic segments of small bowel placed into organ culture at birth. Quantitative polymerase chain reaction showed similar expression of SCF in the muscles of animals with and without enteric neurons. Expression of SCF was demonstrated in isolated intestinal smooth muscle cells. CONCLUSIONS: These data suggest that enteric neurons are not required for the development of functional ICC. The circular smooth muscle layer, which develops before ICC, may be the source of SCF required for ICC development.     

Ultrastructural changes in internal anal sphincter in neurogenic faecal incontinence.

The ultrastructural features of the internal anal sphincter (IAS) muscle were studied in biopsies from five patients with neurogenic anorectal incontinence and six control subjects undergoing anorectal excision for cancer, or for inflammatory bowel disease. In the patients with idiopathic neurogenic anorectal incontinence the internal anal sphincter showed loss of smooth muscle cells, disruption of the normal relationships of the remaining cells, stretching of elastic tissue, and increased collagen fibril content. These ultrastructural changes in the morphology of the internal anal sphincter, although probably not the primary cause of faecal incontinence, have functional relevance in the clinical syndrome, as shown by the reduction in resting anal canal pressure found in some patients with this syndrome.     

Aggressive systemic mastocytosis complicated by protein-losing enteropathy.

A 46-year-old woman was admitted to the hospital with complaints of chronic diarrhoea, vomiting and severe muscle weakness. Clinical examination showed a lethargic, malnourished, dehydrated patient with ascites and bilateral leg oedema. Laboratory evaluation revealed mild normochromic normocytic anaemia and severe hypoproteinaemia with hypoalbuminaemia. Upper gastrointestinal endoscopy showed a thickened, friable duodenal mucosa with multiple erosions. Colonoscopy revealed nodular, pseudopolypoid lesions with patchy erosions in the left hemicolon. Haematoxylin-eosin stained sections from biopsies of endoscopically abnormal bowel segments showed multi-focal aggregates of large, histiocyte-like cells with abundant pale cytoplasm in the lamina propria. These cells were negative on PAS, Ziehl-Neelsen, Giemsa and toluidine blue stains. Their immunophenotype was CD68 (+), c-kit/CD117 (+) and mast cell tryptase (+), which is consistent with mast cells. A trephine biopsy showed diffuse replacement of the bone marrow by atypical, monomorphic, frequently spindle-shaped mast cells. No associated haematopoietic malignancy was detected. The final diagnosis was aggressive systemic mastocytosis with involvement of the gastrointestinal tract complicated by protein-losing enteropathy. This association has not been reported previously. The patient has been treated with prednisolone and interferon-alpha and has since recovered.     

Tetany, malabsorption, and mastocytosis.

Mastocytosis is characterized by increased proliferation of mast cells. Two patients had systemic mastocytosis involving the skin and gastrointestinal tract, complicated by malabsorption and tetany. Absorption studies in these patients suggested that the entire small bowel was involved and that the defect was mild in the absence of diarrhea. Small bowel biopsies disclosed infiltration of the lamina propria and submucosa by mast cells, and gastrointestinal tract x-ray films showed nodular densities, edema, and thickening of the bowel wall. Tetany was due in part to combined hypocalcemia, hypomagnesemia, and hypokalemia. Diarrhea and malabsorption were due to mast cell infiltration of the bowel rather than to histamine. patients with signs of systemic mastocytosis should have careful evaluations and be followed up to prevent development of malabsorption and tetany.     

A theory of integrated gastrointestinal motor activity based on the chain oscillator model

Summary The present simple one-dimensional differential equation model of the excitable properties of smooth muscle cells (functional units) offers a qualitative simulation of stomach and small bowel, and perhaps the colon as well. In particular, it permits the conclusion that intrinsic properties of the smooth muscle cells, as manifested by connected functional units, constitute a sufficiently flexible and organized system to exhibit much of the basic behavior of stomach, small bowel and colon. In most circumstances, this chain oscillator model differs conceptually from other proposed explanations of gut behavior. It is the only model consistent with certain observed properties. Hopefully, it can be extended to a more complete system model in the future.     

Inhibition of acetylcholine induced intestinal motility by interleukin 1 beta in the rat.

BACKGROUND/AIMS: The fact that raised interleukin 1 beta (IL 1 beta) concentrations have been found in the colonic mucosa of rats with experimentally induced colitis and of patients with inflammatory bowel disease indicates that this cytokine may participate in the disturbed intestinal motility seen during inflammatory bowel disease. This study investigated whether IL 1 beta could change the contractility of (a) a longitudinal muscle-myenteric plexus preparation from rat jejunum, ileum, and colon and (b) isolated jejunal smooth muscle cells. METHODS: Isometric mechanical activity of intestinal segments was recorded using a force transducer. Moreover, smooth muscle cell length was measured by image analysis. RESULTS: Although IL 1 beta did not affect jejunal, ileal, and colonic basal contractility, it significantly reduced contractile response to acetylcholine (ACh). This significant inhibition was seen only after 90 or 150 minutes of incubation with IL 1 beta. Pretreatment with cycloheximide blocked IL 1 beta induced inhibition of ACh stimulated jejunal contraction, suggesting that a newly synthesised protein was involved in the effect. NW-nitro-L-arginine (a nitric oxide synthase inhibitor) did not prevent the inhibition induced by IL 1 beta. Blocking neural transmission with tetrodotoxin abolished the IL 1 beta effect on jejunal contractile activity, whereas IL 1 beta had no effect on isolated and dispersed smooth muscle cells. CONCLUSIONS: IL 1 beta inhibits ACh induced intestinal contraction and this inhibitory effect involves protein synthesis but is independent of nitric oxide synthesis. This effect does not involve a myogenic mechanism but is mediated through the myenteric plexus.     

Small bowel extracts in the inhibition of tumour growth.

Results presented in this paper confirm earlier experiments which showed that microsomal extract of small bowel, preincubated with tumour cells, resulted in complete inhibition of tumour growth. However, experiments in vitro have shown that this effect is due to direct cytotoxicity of the extract and that (a) it is not specific for the small bowel; (b) it is not specific for tumour cells; and (c) the activity is predominantly in the mitochondrial fraction.     

High-dose erythropoietin inhibits apoptosis and stimulates proliferation in neonatal rat intestine.

BACKGROUND: Erythropoietin (Epo) receptors are widely expressed in the small bowel of neonatal rats and evidence suggests Epo has important trophic effects in developing bowel. OBJECTIVE: To compliment in vitro data, we directly examine in vivo the hypotheses that systemic Epo treatment can promote cell division and enterocyte migration, and arrest apoptosis in the ileum of neonatal rats. DESIGN: Epo (5000 U/kg s.c.) or vehicle treatments were given to one week old Sprague-Dawley rats (n = 86) along with timed injections of the thymidine analog 5-bromo-2-deoxyuridine (BrdU, 50mg/kg s.c.) to label DNA synthesis and track newly proliferating cells. To characterize the time course of effects, animals were killed at scheduled times from 30 min to 24 h after treatment. BrdU-containing cells were immunostained and counted in intestinal crypts, villi, and muscle wall of ileum. Effects of Epo on apoptosis were analyzed by TUNEL staining. Calibrated measurements were made to determine the density or relative proportion of BrdU- and TUNEL-positive cells. RESULTS: Systemic high-dose Epo promoted cell division in intestinal smooth muscle and enterocytes, stimulated migration of intestinal epithelial cells, and arrested apoptosis of enterocytes at the villous tips. CONCLUSION: These data provide in vivo evidence that Epo functions trophically in developing intestine tissues.     

Strictures in Crohn's disease are characterised by an accumulation of mast cells colocalised with laminin but not with fibronectin or vitronectin

BACKGROUND/AIMS: Intestinal fibrosis and stricture formation is an unresolved problem in Crohn's disease. The aim of this study was to investigate whether mast cells accumulate in these tissues and whether their localisation is associated with extracellular matrix components. METHODS: Mast cells were visualised by immunohistochemical staining of the mast cell specific proteases chymase and tryptase. Their localisation in relation to extracellular matrix components was shown by immunohistochemical double labelling. RESULTS: In strictures in Crohn's disease, a striking accumulation of mast cells was seen particularly in the hypertrophied and fibrotic muscularis propria, with a mean (SEM) mast cell number of 81.3 (14.9) v 1.5 (0.9)/mm(2) in normal bowel (p<0.0005). All mast cells in the muscularis propria were colocalised with patches of laminin. In contrast, in the submucosa, laminin was exclusively found in the basal lamina of blood vessels where many adherent mast cells were seen. No colocalisation of mast cells was found with fibronectin or vitronectin. CONCLUSIONS: The large accumulation of mast cells in the muscle layer of strictured bowel suggests a functional role for these cells in the hypertrophic and fibrotic response of the smooth muscle cells. The colocalisation with laminin indicates a mechanism of interaction between smooth muscle cells and mast cells that may be important in the role of mast cells in the process of fibrosis.     

Gastrin-producing cells in ectopic gastric mucosa of developmental and metaplastic origins.

Immunocytochemical techniques using antigastrin antibody were employed to localize G cells in ectopic gastric mucosa of metaplastic and congenital origins and to compare their distribution with that in normal gastric mucosa. Five examples of Barrett's esophagus, 8 Meckel's diverticula, and 2 small bowel duplications were studied. Although G cells were absent in the gastric mucosa from all cases of Barett's esophagus, four Meckel's diverticula and one small bowel duplication contained G cells. In all instances of congenitally derived ectopic gastric mucosa where G cells were demonstrable, the gastric mucosa showed areas of antropyloric differentiation, whereas in the remaining cases the ectopic gastric mucosa was exclusively of the body-fundic type. It is concluded that the presence of G cells within ectopic gastric mucosa of Meckel's diverticula and small bowel duplications in foci of antropyloric differentiation reflects their developmental origin, whereas the absence of G cells in Barrett's esophagus is in keeping with its metaplastic derivation.     

Histopathology of cell mediated immune reaction in mouse colon--allograft rejection.

Grafts of mouse fetal colon, implanted beneath the renal capsule of adult hosts, have been used to study the growth and development of colonic isografts and the rejection of colonic allografts. Isografts grew normally and maintained a structure similar to normal colon. Grafts between strains with H2 histocompatibility differences were rejected by 13 days after transplantation. Early progressive infiltration of the grafts by lymphoid cells was followed by increasing damage to, and subsequent loss of, the epithelial cell layer and destruction of the underlying muscle, changes which parallel those seen in rejection of skin and small bowel. The increase in survival time which is seen in allografts between strains with H2 identity was longer in the colon than has been seen in the skin or small bowel; none of the allografts of colon were completely rejected before 30 days, and some remained viable at 50 days. Comparison of the appearances of rejection in the colon with those of ulcerative colitis and colonic Crohn's disease does not show the striking similarity which is seen between small bowel rejection and coeliac disease. Many of the individual features of these diseases are, however, present in the course of colonic rejection.     

Small bowel motility: Ready for prime time?

The primary function of the small bowel is the absorption of nutrients, and the motor patterns of the healthy bowel are intended to promote that function. The motor patterns of the small bowel are the result of close interaction between the enteric nervous system, extrinsic nerves, regulatory peptides, and the intestinal smooth muscle. The basic electrical rhythm governing intestinal contractions is determined by specialized pacemaker cells called the interstitial cells of Cajal. Diseases affecting any of these components may result in intestinal dysmotility and its associated symptoms. Although transit studies and intestinal manometry are helpful in the diagnosis of dysmotility, our understanding of pathophysiology is hampered by the difficulties involved in obtaining and analyzing intestinal tissue. Treatment of intestinal dysmotility relies on dietary manipulations and nutritional support (enteral or parenteral) because there is no drug therapy that can effectively enhance the propulsive function of the small bowel. Small bowel transplantation remains a life-saving intervention for patients who fail to respond to other therapies.     

Neuromuscular and vascular hamartoma of small bowel presenting as inflammatory bowel disease.

We present the case of a rare hamartomatous condition of the small intestine clinically mimicking inflammatory bowel disease. Disorganised fascicles of smooth muscle derived from both muscularis mucosae and propria, bundles of non-myelinated nerve fibres with groups of abnormal ganglion cells, and haemangiomatous vessels were present within the submucosa of a long segment of small intestine causing subacute obstruction.     

Met-RANTES inhibition of mucosal perfusion failure in acute intestinal transplant rejection - role of endothelial cell-leukocyte interaction

Acute rejection-induced microvascular injury results in graft dysfunction, ultimately leading to graft loss. Infiltration of T cells and monocytes as a consequence of an enhanced endothelial cell-leukocyte interaction appears to play an important role in this deleterious process. Recruitment of these pro-inflammatory cells to the vessel wall is mediated by chemokines such as RANTES. Heterotopic small bowel transplantation was performed in rats with the fully allogeneic Brown Norway-Lewis strain combination and, as a control, the syngeneic Lewis-Lewis strain combination. Intravital microscopy was performed from postoperative day 1-7 in both groups. The percentages of perfused villi and villus stasis, mucosal and muscular functional capillary densities, red blood cell velocities, and finally, firm adherence of leukocytes in postcapillary submucosal venules were assessed. Syngeneic small bowel transplantation revealed homogeneous perfusion of villi and muscle layers over the whole study period. Allogeneic small bowel transplantation showed a decline in perfusion from postoperative day 1 until complete failure on postoperative day 7. This was accompanied by a continuous increase in endothelial cell-leukocyte interaction which reached a plateau on postoperative day 5. Met-RANTES treatment at 200 microg/day for 5 days markedly attenuated both the decrease in functional capillary density and the increased endothelial cell-leukocyte interaction in rats following allogeneic small bowel transplantation. We conclude that blocking chemokine receptors, thereby limiting endothelial cell-leukocyte interaction, may constitute a useful therapeutic approach to the prevention of microcirculatory perfusion failure in acute transplant rejection.     

Bladder smooth muscle dysfunction in patients with irritable bowel syndrome.

Urodynamic studies were carried out on 30 patients with irritable bowel syndrome and 30 matched controls. Fifty per cent of the irritable bowel patients compared with only 13% of the control group had evidence of bladder dysfunction (p = 0.006). In the irritable bowel group detrusor instability was observed in 10 patients compared with only one control subject (p = 0.008). A steep cystometrogram occurred in five irritable bowel patients and three controls (NS). Detrusor instability was most common in patients with a bowel habit characterised by alternating constipation and diarrhoea. This is the first study to provide objective evidence that patients with irritable bowel syndrome may have a disorder of smooth muscle or its innervation that is not confined to the gastrointestinal system.     

Polymyositis associated with ulcerative colitis.

An elderly woman with chronic ulcerative colitis who developed proximal muscle weakness, increased serum creatine phosphokinase activity, and histological and electromyographic abnormalities characteristic of polymyositis is described. Treatment with corticosteroids and 5-acetylsalicylic acid was followed by a remission in bowel symptoms, improvement in muscle power, and reversal of electromyographic changes. An autoimmune link between the two disorders seems likely.     

Changes of smooth muscle contractile filaments in small bowel atresia

AIM: To investigate morphological changes of intestinal smooth muscle contractile fibres in small bowel atresia patients.METHODS: Resected small bowel specimens from small bowel atresia patients (n = 12) were divided into three sections (proximal, atretic and distal). Standard histology hematoxylin-eosin staining and enzyme immunohistochemistry was performed to visualize smooth muscle contractile markers α-smooth muscle actin (SMA) and desmin using conventional paraffin sections of the proximal and distal bowel. Small bowel from age-matched patients (n = 2) undergoing Meckel’s diverticulum resection served as controls.RESULTS: The smooth muscle coat in the proximal bowel of small bowel atresia patients was thickened compared with control tissue, but the distal bowel was unchanged. Expression of smooth muscle contractile fibres SMA and desmin within the proximal bowel was slightly reduced compared with the distal bowel and control tissue. There were no major differences in the architecture of the smooth muscle within the proximal bowel and the distal bowel. The proximal and distal bowel in small bowel atresia patients revealed only minimal differences regarding smooth muscle morphology and the presence of smooth muscle contractile filament markers.CONCLUSION: Changes in smooth muscle contractile filaments do not appear to play a major role in postoperative motility disorders in small bowel atresia.     

Gastrointestinal motility in pregnancy.

The gallbladder and gut should be viewed as hormonally responsive organs the normal physiology of which may be altered by the hormones of pregnancy. The gallbladder enlarges and empties sluggishly in response to meals during pregnancy. Small bowel transit is slowed, and the resting pressure of the lower esophageal sphincter is reduced. All these effects are reversed by delivery; motility reverts toward normal in the postpartum period. The rapid return of normal motility suggests that the effects of pregnancy are hormonally related. Most studies have demonstrated that progesterone, not estrogen, may be the hormone responsible. Although incompletely defined, one mechanism of the effects of pregnancy on motility may be progesterone-induced inhibition of the mobilization of intracellular calcium within smooth muscle cells.     

Abdominal distension in female patients with irritable bowel syndrome: exploration of possible mechanisms.

Abdominal distension is a common but little understood symptom of the irritable bowel syndrome. The authenticity of the symptom was confirmed by appreciable increases in girth measurement during the day in 20 patients with the irritable bowel syndrome compared with 20 control subjects. Objective corroboration of this finding was shown in the group with the irritable bowel syndrome by a highly significant increase in lateral abdominal 'profile' on computed tomography. Previously postulated mechanisms for distension--namely, retention of gas, depression of the diaphragm, and excess lumbar lordosis--were excluded by the radiological findings. Voluntary protrusion of the abdomen produced a completely different pattern on computed tomography to that observed in the irritable bowel syndrome. These observations suggest that abdominal distension may be related to changes in motility or tone of gastrointestinal smooth muscle.