Enteric nerves in diabetic rats: increase in vasoactive intestinal polypeptide but not substance P

The distribution of vasoactive intestinal polypeptide (VIP) and substance P-like immunoreactivities was studied by immunohistochemistry in the myenteric plexus and circular muscle layer of the ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin. A consistent increase was observed in fluorescence intensity of VIP-like immunoreactivity in the nerve fibers, and intensely stained cell bodies were significantly more frequent in the myenteric plexus of the ileum (p less than 0.001) from diabetic animals. Some varicosities of VIP-like immunoreactive fibers in the myenteric plexus appeared to be enlarged. Vasoactive intestinal polypeptide-like immunoreactivity was increased and VIP-like immunoreactive nerves appeared thicker in the circular muscle layer of both diabetic ileum and proximal colon. The VIP levels were measured biochemically in tissue consisting of the smooth muscle layers and myenteric plexus. A significant increase in the VIP content per centimeter of intestine was found in both the ileum (p less than and proximal colon (p less than 0.01) from diabetic rats. In contrast, no apparent change in substance P innervation was observed immunohistochemically in the myenteric plexus and circular muscle layer of either diabetic ileum or proximal colon when compared with controls. The results are discussed in relation to the symptoms of autonomic neuropathy of the gut in diabetes.     

The ultrastructural bases for coordination of intestinal motility

The electrical control activity (slow waves) of dog small intestine is characterized by phase locking of potential changes in a frequency plateau in the upper intestine. In the distal intestine, phase locking does not occur, though frequencies of each segment are pulled up (increased) by adjacent, more proximal segments. This suggests poorer coupling in the distal compared to the proximal intestine. Electron microscopic studies of the intestine revealed no differences in appearance or number of nexuses (found only in circular muscle) or of intermediate contacts (found in both muscle layers) in duodenum and upper jejunum as compared with ileum. Thus, differences in cell to cell contacts could not explain poorer coupling in the ileum. No difference in innervation of these two regions was observed. However, evidence was obtained that circular muscle cells of the ileum, unlike those of the duodenum, are not oriented perpendicularly to the longitudinal muscle layer. This could provide a structural basis for poorer coupling and for the observed phase lag of potentials around the circumference of the ileum.     

Neurotensin-like immunoreactivity after intestinal resection in the rat.

Neurotensin is a tridecapeptide located mainly in the distal small intestine. The present study was carried out in order to investigate the neurotensin response after proximal small intestinal resection in the rat. After resection, the median plasma concentration of neurotensin like immunoreactivity (NTLI) was unchanged compared with sham operated rats. Intragastric instillation of fat increased the plasma concentration of NTLI from 45 pmol/l (34-63) in sham operated rats to 92 pmol/l (46-121) in resected rats. No significant increase in the plasma concentration of NTLI was found after intragastric instillation of amino acids or glucose. The tissue concentration of NTLI increased significantly in the jejunum and ileum after proximal small intestinal resection, while the number of immunoreactive neurotensin cells was unchanged. This study shows that the adaptive responses in the distal small intestine after proximal small intestinal resection also involve the neurotensin producing cells.     

Serotoninergic neurons in human fetal intestine: an immunohistochemical study

The distribution of 5-hydroxytryptamine-like immunoreactivity was studied in whole-mount preparations of intestine from human fetuses. Immunoreactive nerve cell bodies were located in the myenteric plexus and were occasionally found in the submucous plexus; they were often seen to have long processes. Varicose fibers were found in the ganglia and internodal strands of the myenteric and submucous plexuses, in the deep muscular plexus of the circular muscle, and in the walls of some small mesenteric blood vessels immediately outside the intestine. This study provides evidence for the presence of serotoninergic nerves in the human intestine.     

Zinc absorption following massive small-bowel resection in the rat

Zinc absorption was evaluated six weeks after massive small-bowel resection in rats. Forty rats were divided into four groups. Ten were subjected to proximal small-bowel resection, 10 to distal resection, and 20 served as pair-fed controls. Intestinal perfusion studies were performed using a recirculation technique. Twenty ml of a solution containing 10 g/ml of zinc as zinc sulfate, isotonic sodium chloride, and polyethylene glycol 5 g/liter was perfused for 2 hr through 10 cm of remaining bowel in resected animals and comparable segments in control animals. Zinc uptake was determined and expressed per 0.1 g mucosal dry weight. In control animals, zinc absorption was greatest in the ileum. Animals undergoing distal bowel resection had a compensatory increase in zinc absorption in the proximal small intestine. However, animals undergoing proximal resection did not demonstrate an increase in zinc absorption in the distal bowel. The proximal small intestine appears capable of increasing its capacity for zinc absorption in the response to distal small-bowel resection.     

Distribution of nitric oxide synthase-containing nerves in the aganglionic intestine of mutant rats: A histochemical study

We examined the distribution of nerves containing nitric oxide synthase in the intestine of congenitally aganglionic rats, using a reduced nicotinamide adenine dinucleotide phosphate diaphorase histochemical method for whole-mount and cryostat specimens. A constricted intestinal segment extends from the terminal ileum to the anus in this mutant. No nerve elements with the activity were found in the affected terminal ileum, cecum, and proximal colon. Although intrinsic ganglionic neurons were absent along the constricted intestine, nerve fibers with the activity were found in both the submucous and intermuscular layers distal to the proximal colon. These fibers increased in density towards the rectum, forming hypertrophic nerve bundles and unusual fiber networks. However, positive fibers were never seen within the circular and longitudinal musculature of the constricted lesion. Some of these hypertrophic nerve bundles were continuous with ectopic ganglia that were situated in the adventitial connective tissue around the lower rectum and in the submucosa near the anus. The hypertrophic nerve bundles seemed to have an extrinsic origin; some of them may have originated from ectopic ganglia. These results suggest that the defective distribution of nerves containing nitric oxide synthase may be involved in the pathogenesis of congenital colonic aganglionosis.     

Intestinal bypass. Bacteriological studies from different parts of the small intestine in rats

Forty-five rats were divided into four groups according to type of operation: 1) end-to-side jejunoileal bypass (ES), 10 rats; 2) end-to-end jejunoileal bypass (EE), 10 rats; 3) jejunoileal resection (R), 10 rats; and 4) no operation, 15 rats. The luminal contents from the proximal jejunum and distal ileum, in groups 1 and 2 also from the proximal and distal part of the excluded small intestine, were examined bacteriologically 5-11 months after operation. The total number of aerobic and anaerobic microbes in the jejunum was equal in all groups. The number of aerobic bacteria in the ileum was significantly higher in the ES group than in the R and U groups. The number of bacteria capable of producing gas in glucose-supplemented media was increased both in the jejunum and ileum after ES bypass. Enterobacteriaceae and Bacteroides were commonly present in the ileum after both types of bypass but were not cultured in jejunal contents. The proximal part of the excluded intestinal segment in groups 1 and 2 contained very low numbers of microbes, whereas the flora of its distal part was similar to that of the ileum in continuity in group 1. Thus, the most marked changes of the intestinal flora occurred after ES bypass in the region of the anastomosis and distal to this.     

Cells in the intestinal system of holothurians (Echinodermata) express cholecystokinin-like immunoreactivity

The presence of cholecystokinin (CCK), originally isolated from porcine small intestine, has been reported in a diversity of invertebrates ranging, from cnidarians to protochordates, but so far, not in echinoderms. We have used immunohistochemical techniques to demonstrate the presence of cells expressing CCK-like immunoreactivity in the intestine of three species of sea cucumber: Holothuria mexicana, H. glaberrima, and Stichopus badionotus. The immunoreactivity was observed within the cytoplasm of these cells, in what appeared to be granular or vesicle-like structures. The cell bodies were present in the outer connective tissue layer of the intestine and had a neuronal appearance, sending an axon-like structure into the circular muscle and internal connective tissue. A plexus of fibers expressing CCK-like immunoreactivity was found overlying the muscle layer. Contractility of H. mexicana intestinal strips was studied under partially isometric conditions. CCK and related peptides induced relaxation of the basal muscle tension, and of tension induced by ACh application, suggesting a role for this agent in the intestinal physiology of holothurians.     

Neurochemical coding in the small intestine of patients with Crohn''s disease.

BACKGROUND: There have been conflicting results regarding the effect of Crohn's disease on the neurochemical composition of the enteric nervous system. AIMS: To examine the effect of Crohn's disease on the neurochemical composition of enteric nerve fibres and cell bodies using whole mount preparations of human ileum. METHODS: Whole wall ileum from seven normal subjects and nine patients with Crohn's disease was used to investigate the neurochemical composition of neurones and nerve fibres in the myenteric plexus, circular muscle, and serosa layer of ileum using immunohistochemical techniques. RESULTS: Increased tyrosine hydroxylase, 5-hydroxytryptamine, and neuropeptide Y immunoreactivity was exclusively seen in the myenteric plexus. There was increased neurofilament immunoreactivity in the myenteric plexus and nerve fibres of the circular muscle layer, and thick bundles of immunoreactive nerve fibres in the serosa layer. Increased vasoactive intestinal polypeptide, nitric oxide synthase, and pituitary adenylate cyclase activating peptide immunoreactivity was seen in the myenteric plexus and nerve fibres of the circular muscle layer, and aggregates of inflammatory cells in the serosa layer of the afflicted segment of Crohn's ileum. In addition, there was a chaotic display of nerve fibres containing some of the neuroactive substances with a high frequency of enlarged varicosities in the myenteric ganglia and/or nerve fibres of the circular muscle layer of Crohn's ileum. CONCLUSION: Results show quantitative as well as qualitative changes in the neurochemical composition of enteric nerve fibres and nerve cell bodies of Crohn's ileum. These changes and the presence of nitric oxide synthase and peptides immunoreactive inflammatory cells in the serosa layer suggest that nerve-immune interactions may have a significant role in the process of the inflammatory changes seen in Crohn's ileitis.     

Smooth muscle adaptation after intestinal transection and resection

Changes in motor function occur in the intestinal remnant after intestinal resection. Smooth muscle adaptation also occurs, particularly after extensive resection. The time course of these changes and their interrelationship are unclear. Our aim was to evaluate changes in canine smooth muscle structure and function during intestinal adaptation after transection and resection. Twenty-five dogs underwent either transection (N=10), 50% distal resection (N=10), or 50% proximal resection (N=5). Thickness and length of the circular (CM) and longitudinal (LM) muscle layers were measured four and 12 weeks after resection.In vitro length-tension properties and response to a cholinergic agonist were studied in mid-jejunum and mid-ileum. Transection alone caused increased CM length in the jejunum proximal to the transection but did not affect LM length or muscle thickness. A 50% resection resulted in increased length of CM throughout the intestine and thickening of CM and LM near the anastomosis. Active tension of jejunal CM increased transiently four weeks after resection. Active tension in jejunal LM was decreased 12 weeks after transection and resection. Sensitivity of CM to carbachol was similar after transection and resection. It is concluded that: (1) Structural adaptation of both circular and longitudinal muscle occurs after intestinal resection. (2) This process is influenced by the site of the intestinal remnant. (3) Only minor and transient changes occur in smooth muscle function after resection. (4) Factors other than muscle adaptation are likely involved in the changes in motor function seen following massive bowel resection.Supported by the VA Merit Review Program.     

Regional variation in canine intestinal muscle mass and function

Our aim was to investigate the contribution of variations in intestinal muscle morphology or function to regional differences in motor propertiesin vivo. We quantitated intestinal muscle thickness and surface area along the canine gut and compared thein vitro contractile properties of the jejunum and ileum. The thickness and cross-sectional surface area of both circular and longitudinal muscle demonstrated a parabolic distribution along the intestine, with the greatest values occurring in the proximal and distal regions. The terminal ileum had the greatest circular (885±194 μm) and longitudinal muscle (367±135 μm) thickness. Circular muscle was 2.5–3 times thicker than longitudinal muscle at all points. Passive tension was similar in muscle strips from the mid-jejunum, mid-ileum, and terminal ileum (2.8±0.8, 2.5±0.4, and 2.3±0.8 vs 2.5±0.5, 1.9±0.5, and 2.8±1.0, longitudinal and circular, respectively). Active and total tension, however, were significantly greater in longitudinal than circular muscle in mid-jejunum (active; 8.5±1.4 vs 5.6±1.2,P<0.05 and total 11.3±1.7 vs 8.1±1.2) and in mid-ileum (active 9.5±1.6 vs 5.8±1.2 and total 12.0±1.6 vs 7.7±1.2). Values for each layer were similar in both sites. In contrast, in the terminal ileum, longitudinal and circular muscle strips demonstrated similar active (10.1±1.7 vs 9.0±2.7 NS) and total tension (12.4±2.0 vs 11.9±3.4 NS). Dose-response curves to carbachol (10^?8–10^?2 M) were similar in all these regions. We conclude (1) there are regional variations in muscle mass but contractile properties are similar in jejunum and ileum; and (2) the unique motor properties of the terminal ileum may be related more to differences in muscle morphology and neural input than intrinsic function.     

Peptidergic innervation of the human esophageal smooth muscle

Studies were performed to define the peptidergic nature of intramural nerves in the human esophagus. Cryosections of uninvolved surgically resected tissues from 14 individuals were studied by immunofluorescence for the localization of 10 neuropeptides. Myenteric neurons showed bombesin-, calcitonin gene-related peptide-, galanin-, substance P-, vasoactive intestinal polypeptide-, leucine-enkephalin-, methionine-enkephalin-, neuropeptide Y-, and somatostatin-like immunoreactivity. Submucous neurons had all the above except neuropeptide Y, methionine-enkephalin, leucine-enkephalin, and bombesin. Both groups of neurons received nerve terminations positive for calcitonin gene-related peptide, galanin, neuropeptide Y, substance P, and vasoactive intestinal polypeptide. Myenteric neurons additionally received terminations positive for neuropeptide Y, methionine-enkephalin, and somatostatin. All muscle layers had varicose fibers that reacted for calcitonin gene-related peptide, galanin, neuropeptide Y, and substance P. Longitudinal and circular muscle received few nerves reactive for leucine-enkephalin, whereas methionine-enkephalin was localized in a few nerve endings in the circular muscle. Somatostatin- and bombesin-reactive nerves occurred in longitudinal muscle. No cholecystokinin-reactive nerves were found. This study extends the results of previous studies and shows the previously undescribed presence of calcitonin gene-related peptide- and galanin-reactive nerves in the human esophagus and identifies neuropeptides that may serve as motor, sensory, and modulatory neurotransmitters of esophageal nerves.     

Glucose transport by rat small intestine after extensive small-bowel resection

In rats 50 cm of proximal or distal small intestine were resected, preserving duodenum and terminal ileum. Glucose transport was studied 5–6 weeks later, using everted gut sacs from duodenum, ileum, and also from a midgut segment consisting of intestine located preresection at mid-small intestine. Sham-operated animals served as controls: The inner (serosal) fluid medium in sacs from duodenum and midgut gained glucose; ileal sac serosal medium lost glucose. Proximal resection resulted in significant growth of duodenal and midgut mucosa. Duodenal transport specific activity (transport per gram dry mucosa) decreased from control values, but mucosal growth compensated so sac transport capacity (transport per centimeter sac length) remained unchanged. Midgut transport specific activity remained unchanged, thus sac transport capacity directly mirrored increased mucosal mass. Ileal sac serosal medium now accumulated glucose; there was no mucosal growth. Transport specific activity and sac transport capacity of ileum increased in parallel. After distal resection there was no alteration of either duodenal and midgut mucosal masses or transport specific activities, hence sac transport capacities remained unchanged. Ileal sac serosal medium also accumulated glucose, but now both transport specific activity and mucosal mass increased. The resultant increased sac transport capacity was identical to that of ileum after proximal resection. In all sacs from control and resected animals uphill [¹⁴C]glucose concentration differences developed between medium and mucosa. Activity of the mucosal uptake process, assessed in terms of a ratio of mucosal intracellular fluid radioactivity to mucosal medium radioactivity, usually mirrored altered transport specific activity. This indicates that the increased undercoats tissue mass that accompanied increased mucosal mass did not critically affect transport. The most striking findings were: (1) decreased duodenal transport specific activity after proximal resection with mucosal growth compensating; and (2) identical adaptations of ileal segment transport capacities after either proximal or distal small-bowel resections, although mechanisms differed. The present study provides a base for further examinations of carrier-mediated hexose transport after extensive loss of small intestine.     

Influence of diet complexity on intestinal adaptation following massive small bowel resection in a preclinical model

AIMS: To investigate the effect of dietary complexity on intestinal adaptation using a preclinical model. METHODS: Four-week-old piglets underwent a 75% proximal small bowel resection or transection operation (control). Post-operatively, animals received either pig chow (n = 15), polymeric formula (n = 9), polymeric formula plus fiber (n = 6), or elemental formula (n = 7). RESULTS: The weight gain of all groups was reduced compared with controls that were fed the same diet. Animals that had a resection, which were fed elemental formula, had significantly reduced weight gain compared with the other groups (4.7 4.2 vs 30.7 7.1 kg chow and 11.5 1.3 kg polymeric formula). Villus height was increased in the jejunum, ileum and terminal ileum of resected animals compared with controls in animals fed with pig chow, polymeric formula and elemental formula. The animals that had a resection had a significant reduction in the transepithelial conductance (10.4 5.5 vs 25.4 6.5 mS/cm2) and 51Chromium-EDTA flux (2.8 1.9 vs 4.8 4.9 microL/h per cm2) compared with the controls. CONCLUSIONS: A complex diet was found to be superior to an elemental diet in terms of the morphological and functional features of adaptation following massive small bowel resection.     

Anatomic and clinical aspects of the junction of the ileum with the large intestine

Summary The termination of the ileum at its junction with the large intestine looks like a papilla and, therefore, has been called the ileal papilla. The ileal papilla projects into the large intestine for a distance of 2 to 3 cm and can be misinterpreted as having a valvular configuration when it is distorted after death. An anatomic muscular mechanism, the ileal pylorus, can be demonstrated within the ileal papilla and terminal ileum. It consists of longitudinal and circular muscle fibers which open and close the starshaped ileal orifice, respectively. Although the clinical significance of the ileal pylorus remains to be fully elucidated, it appears advisable to preserve this muscular mechanism whenever possible. Read at the meeting of the American Proctologic Society, Boston, Massachusetts, June 16 to 18, 1969. Supported in part by the Detroit General Hospital Research Corporation.     

Changes in Distribution of Three Isoforms of Nitric Oxide Synthase in Ulcerative Colitis

Background: Nitric oxide (NO) has an important role both in normal physiology and pathological events of the colon. Our aim was to study possible changes of the three nitric oxide synthases in ulcerative colitis (UC). Methods: Tissue samples from normal colon and least and moderately affected regions of ulcerative colitis colon were obtained at surgery and immunostained for NOS-1, NOS-2, NOS-3, and GAP-43, a marker of nerve fibers. Quantitative analysis of NOS-1 immunoreactivity was performed on the circular muscle layer. Results: NOS-1-immunoreactive fibers in the muscularis mucosae disappeared in least affected and moderately affected UC colon. Quantitative analysis of NOS-1-immunoreactive nerve fibers in the circular muscle showed no differences between normal and diseased colon. NOS-2 immunoreactivity appeared apically in the epithelial cells. In normal colon some specimens showed immunoreactivity in lower parts of crypts. NOS-2 immunoreactivity increased according to the severity of UC. NOS-3 immunoreactivity was exclusively localized in the vascular endothelium. The difference in NOS-3 staining intensity between the lamina propria and submucosa observed in normal tissue disappeared in moderately affected UC colon. The number of NOS-3-immunoreactive vascular profiles increased in the lamina propria of UC colon. Conclusions: All three NOS isoforms show specific changes in UC colon.     

Ganglion cell changes in experimental stenosis of the gut

Teflon mesh was wrapped around the terminal ileum of dogs to cause a partial obstruction. Both smooth muscle layers became thickened in the gut proximal to the constriction, but the circular muscle was more hypertrophied than the longitudinal. The cells in Auerbach's plexus were stained by an indoxyl esterate technique in 100mu sections and counted. The number of ganglion cells related to muscle mass was decreased above the constriction. Although some ganglion cells increased in size there was no evidence of any increase in number.     

The localization of the site(s) of neurotensin release in man and dog

The major source of neurotensin in the gut is the ‘N’ cell and this is found in the highest density in the ileum. The ingestion of food, particularly fat, causes the biphasic release of neurotensin-like immunoreactivity (NTLI) into the circulation. The early peak occurs sooner than expected if it is due to the presence of chyme in the ileum, suggesting that the early release of neurotensin is due to a more proximal concentration of N cells or that neurotensin is released from the ileum by a more proximal stimulus. This paper investigates the site(s) of neurotensin release by studying: three groups of patients with various resections of the small intestine and the fashioning of duodenostomies, jejunostomies and ileostomies; and the dog with chronic gastric, duodenal and ileal fistulae, and following ileal resection. The results indicate that the jejunum and ileum are critical in the release of neurotensin following fat stimulation and that the stomach and duodenum have no direct role. The stimulation of the jejunum by fat causes the early rise of plasma NTLI by releasing neurotensin from the ileum. If chyme is prevented from passing to the distal jejunum the magnitude of the early peak is diminished and the second, later, peak is abolished. The second peak of plasma NTLI is due to the direct luminal stimulation of the distal jejunum and ileum by the products of fat digestion. Ileal resection completely abolishes any release of plasma NTLI in response to fat. It was concluded that the source of neurotensin released by the ingestion of food is the ileum. The release of neurotensin from the distal gut is dependent upon a signal from the proximal to the distal gut. The identity of the signal is unknown, but it is either neural or humoral and previous studies suggest a cholinergic-dependent reflex.     

Abnormalities of peptide-containing nerve fibers in infantile hypertrophic pyloric stenosis

The distributions of nerve cells and fibers with immunoreactivity for the peptides enkephalin, gastrin-releasing peptide, neuropeptide Y, somatostatin, substance P, and vasoactive intestinal peptide were examined in specimens of myenteric plexus and external muscle from the pylorus of 20 infants with hypertrophic pyloric stenosis. These were compared with peptide distributions in pyloric samples from unaffected infants and adults. In the normal pylorus the circular muscle was richly supplied with fibers reactive for enkephalin, neuropeptide Y, substance P, and vasoactive intestinal peptide. In pyloric stenosis, these immunoreactive fiber bundles were either missing or less than 5% of normal. In contrast, there were reactive cell bodies and nerve fibers in the myenteric plexuses of both normal and affected specimens. In the samples from cases of stenosis, swollen nerve fibers that appeared to be in the process of degeneration were frequently encountered. It is concluded that infantile hypertrophic pyloric stenosis is associated with a loss of peptide immunoreactivity in nerve fibers in the circular muscle, although the same peptides are still revealed in fibers and in nerve cell bodies in the myenteric plexus.     

Effect of small bowel resection on the intestinal surface acid microclimate in the rat

The effect of extensive (65%) proximal and middle small bowel resection on the intestinal surface acid microclimate (ISAM) of the remaining ileum in the rat was examined and the results were compared to those of sham-operated rats. ISAM pH measurements were performed in vivo using a pH microelectrode; incubation was performed in Krebs-Ringer phosphate buffer (pH 7.40 +/- 0.02). In the resected rats, ISAM pH of 6.03 +/- 0.07 and 7.22 +/- 0.03 were recorded in the proximal and distal part of the remaining ileum, respectively. In the sham-operated rats, ISAM pH of 6.04 +/- 0.07, 6.98 +/- 0.03 and 7.28 +/- 0.02 were recorded in the proximal jejunum and in the proximal and distal part of the corresponding ileal segment. ISAM pH was significantly lower (p less than 0.01) in the proximal part of the remaining ileum of the resected rats as compared to the corresponding part in the sham-operated rats but was similar in distal ileum. In fact, the ISAM pH of the proximal part of the remaining ileum of resected rats was as acidic as that of the jejunum of the sham-operated rats. These results clearly demonstrate that adaptation in the ISAM occurs in the remaining ileum following extensive resection of proximal and middle small intestine.