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PubMed1991

Effects of Vibrio cholerae recombinant strains on rabbit ileum in vivo. Enterotoxin production and myoelectric activity.

Previous studies have identified the effects of Vibrio cholerae and its enterotoxin, choleragen (CT A+B+), on the myoelectric activity of rabbit ileal loops in vivo. The response was defined as the migrating action potential complex, the single ring contraction that propels luminal contents aborad. In this study the same rabbit model is used to assess whether migrating action potential complex activity or fluid output is induced by recombinant strains of V. cholerae that produce no subunit of cholera toxin (CT A-B-) or only by the inactive binding subunit (CT A-B+). Three live strains were studied: El Tor wild-type N16961 (CT A+B+) and recombinant strains CVD106 (CT A-B+) and JBK70 (CT A-B-). Controls received sterile culture broth. Migrating action potential complex frequency in animals inoculated with CT A+B+ was significantly increased compared with that in all other experimental groups (P less than 0.01). Fluid output was also increased in animals inoculated with CT A+B+ compared with fluid output in all other groups (P less than 0.05). Migrating action potential complex frequency and fluid output in rabbits given CT A-B+ or CT A-B- did not differ from activity in controls. How these recombinant strains induce diarrhea is unknown, but the mechanism may involve bacterial colonization or production of an unknown toxin.

Animals↗
PubMed1995

Effect of intestinal tapering and lengthening on intestinal structure and function.

BACKGROUND: Intestinal lengthening (TL) is increasingly performed for the short bowel syndrome. Our aim was to evaluate the effect of TL on canine intestinal structure and function. METHODS: Two groups of 5 dogs had 75% distal intestinal resection. Twelve weeks later, serosal electrodes were placed in one group (RO) and tapering and lengthening of 10 to 15 cm distal intestine and electrode placement was performed in the other group (TL). Nutritional status and intestinal absorption, motility, and hormone release were assessed every 4 weeks for 12 weeks after the second procedure. RESULTS: The animals with the lengthening had diminished body weight (75% +/- 2% versus 81% +/- 4%, P < 0.05) and albumin levels (2.4 +/- 0.2 g/dL versus 2.9 +/- 0.5 g/dL, P < 0.05) and impaired absorption (stool fat 18% +/- 6% versus 10% +/- 3%, P < 0.05) compared with those that had undergone resection alone. The intestinal adaptive response was blunted in the TL group (villus height 328 +/- 90 microns versus 410 +/- 36 microns, P < 0.05). Transit time was prolonged 4 and 8 weeks (19 +/- 6 min and 18 +/- 5 min, respectively, versus 11 +/- 3 min, P < 0.05) after TL. Myoelectrical recordings showed a drop in slow wave frequency and impaired migration of Phase III of the migrating motor complex within the tapered and lengthened segments (P < 0.05). Both fasting and postprandial serum gastrin levels were two times greater in the TL group (P < 0.05). Enteroglucagon levels were increased after resection alone; this increase was attenuated by more than 50% in the TL group (P < 0.05). The somatostatin response to feeding was substantially greater in the TL animals. CONCLUSIONS: TL impairs nutritional status and intestinal absorption and adaptation following massive resection. The changes in absorption and transit may be related, in part, to motor disruption and hypergastrinemia. The impaired adaptation is possibly related to decreased enteroglucagon and increased somatostatin levels.

Animals↗
PubMed1995

Effect of cloned Salmonella typhimurium enterotoxin on rabbit intestinal motility.

We analysed the small intestine myoelectric responses of anesthetized New Zealand albino rabbits to Escherichia coli lysates containing an entertoxin cloned from Salmonella typhimurium. Migrating action potential complex, which consisted of rapid bursts of actions potentials and secretion of fluid, was observed only in ileal loops, injected with the enterotoxin-containing lysate. Migrating action potential complex produced by Stn usually propagated aborally, which was typical of cholera toxin, but orad or bidirectional propagation occurred from a single point of origin when activity was intense. Cell lysates from an E. coli clone containing vectors alone, as well as proximal control segments injected with phosphate-buffered saline, gave neither a change in motility nor fluid secretion. These results show that Stn caused dramatic changes in intestinal motility and substantial fluid production.

Action Potentials↗
PubMed1992

The isolated bowel segment (Iowa model II): motility across the anastomosis with or without mesenteric division.

In previous reports, anastomosis has been shown to disrupt the myoelectric activity of the bowel. However, these studies have failed to delineate the role of the extrinsic nerves. Using an isolated bowel segment (IBS) and an amesenteric bowel segment (ABS), motility was evaluated by myoelectric recording across a bowel anastomosis. Ten rats were divided equally into the experimental group with the IBS and the control group with the ABS. In the IBS group, an 8-cm segment of jejunum was divided, reanastomosed, and coapted to the liver margin (Iowa model II). In the ABS group, an 8-cm segment of jejunum was coapted to the liver margin without disruption of bowel continuity (Iowa model II variant). Two weeks later, bipolar electrodes were implanted in the IBS and ABS, and normal jejunum in both groups. Mesenteric division (MD) was performed 4 weeks later to eliminate extrinsic innervation. Myoelectrical recordings were taken 2 weeks before and after MD. In the control group with IBS, incoordination in the propagation of the migrating motor complex (MMC) and reduction in the frequency of slow waves (FSW) were observed across the anastomosis and were unchanged by MD. In the control group with the ABS, the MMC and FSW were identical to that in the normal jejunum and were unaffected by MD. In both groups postprandial inhibition of the MMC was the same as in the normal jejunum and was unaffected by MD. This study confirms that incoordination in propagation of the MMC and reduction in FSW occur across a bowel anastomosis, and elimination of extrinsic innervation does not affect the autonomy of these changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1995

Effects of novelty and conditioned fear on small intestinal and colonic motility and behaviour in the rat.

Novelty and conditioned fear were used to investigate the effects of psychological stress on fasting small intestinal and colonic myoelectric activity and their relation with behaviour in freely moving rats fitted with bipolar electrodes on proximal jejunum and colon. Rats in both novelty and conditioned fear groups spent a 15 min session in a novel box, where only rats in the fear group received unescapable, repeated foot shock (10 x 6 s, 0.5 mA). Behaviour in groups reexposed to the box on day 1 or day 7 indicated a profound difference in emotional state. Conditioned fear rats remained largely immobile, while novelty rats displayed active exploratory behaviour. Behaviour during conditioned fear did not differ significantly between rats reexposed to the box either 1 or 7 days after foot shock, while novelty animals appeared more aroused on day 7. Conditioned fear on day 1 caused a significant increase in colonic spike burst frequency compared to basal values in the home cage. A smaller but significant increase was found in novelty rats. In groups tested after 7 days, both novelty and conditioned fear resulted in small increases in colonic burst frequency that did not differ significantly from each other. No effects were found on the incidence of the fasting jejunal Migrating Motility Complex. Defecation was see only in conditioned fear rats, but did not differ quantitatively between day 1 and day 7. We conclude that, in the rat, colonic myoelectric spike burst activity is highly responsive to psychological stress, while the fasting pattern of small intestinal activity is more resistant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Changes in colonic motility following abdominal irradiation in dogs.

The purpose of the study was to compare colonic motor patterns before and after a single abdominal dose of X-rays in dogs. Recordings were made from five serosally implanted strain gauges at equidistant intervals along the colon in seven dogs (2 dogs also had 2 jejunal electrodes and 1 had ileal electrodes). Control recordings were made for 3 h in the fasted state and daily for 2 wk after an absorbed X-ray dose of 938 cGy was delivered to the abdomen. The duration of migrating colonic motor complexes decreased from 7.2 +/- 0.5 to 3.9 +/- 0.4 min while the mean amplitude fell from 10.3 +/- 0.6 to 1.8 +/- 0.2 g (P < 0.05). The rate of nonmigrating colonic motor complex occurrence increased from 0.6 +/- 0.1 to 1.2 +/- 0.2 per hour (P < 0.05). Colonic giant migrating contractions were rarely observed during control recordings (2 in 80 h of recording). In contrast, repetitive clusters of giant contractions were observed 5-8 days after exposure in five of seven dogs (1.5/h) and were associated with restlessness, whining, and passage of diarrheal stools (sometimes bloody) with nearly every occurrence. The basic colonic motility patterns were less disrupted than were jejunal myoelectric patterns at the same irradiation dosage. However, the study demonstrates the important role of colonic giant migrating contractions in pathological diarrheal states such as irradiation injury.

Abdomen↗
PubMed2001

Control of migrating motor activity in the colon.

One of the most significant developments in our approach to studying gastrointestinal motility over the past few years has been in the advent of genetic manipulation and the development of knockout animals. This means that it is possible to study motility patterns of specific regions of the gastrointestinal tract in which the development or synthesis of particular neurotransmitter substances or receptors has been prevented. The mouse has emerged as the model species for investigating the effects that genetic knockouts may have on gastrointestinal motility; therefore, an understanding of the mechanisms underlying the control of motility patterns of unaffected mice is crucial before we can apply this knowledge to knockout models. Major advances have been made in the past few years regarding the mechanisms underlying the generation of migrating motor complexes in the large bowel, particularly in the mouse colon.

Acetylcholine↗
PubMed1985

Contractile patterns and transit of fluid in canine terminal ileum.

Earlier recordings of intraluminal pressure from the terminal ileum and across the ileocolonic sphincter of dogs revealed, in addition to the usual interdigestive and digestive patterns, pressure waves that appeared to have propulsive potential. One of these, which we designated as a "prolonged propagated contraction" (PPC), was a wave of high amplitude; it had a duration much longer than the ileal slow wave and migrated rapidly through the ileum, often into the proximal colon. The other pattern was one of "discrete clustered contractions" (DCC); these were propagated bursts of rhythmic phasic waves, distinct from phase III of the interdigestive myoelectric complex. These migrated through the ileum more rapidly than did phase III. Our aims were to record the electrical and mechanical equivalents of these pressure events using only extraluminal sensors and to evaluate the capacity of these contractions to propel fluids. PPCs and DCCs were recorded by extraluminal strain gauges, and flow was assessed by recovery of a nonabsorbable marker. Phase III of the migrating motor complex propelled fluid through the ileum, but in addition DCCs and, especially, PPCs were able to empty the ileum. These latter contractions have similarities to the ileal "peristaltic rush" described by others, and we believe these waves are an important force for ileal emptying.

Animals↗
PubMed1999

Abnormalities of upper gut motility in patients with slow-transit constipation.

OBJECTIVE: To further delineate motor activity of the upper gastrointestinal tract in patients with slow-transit constipation. DESIGN: A prospective study comparing healthy volunteers with patients with a clinical diagnosis of slow-transit constipation. METHODS: Eighteen patients with clinical diagnosis of slow-transit constipation and 10 healthy controls were included in the study. Fasting antroduodenal motility was measured by perfusion manometry for at least one complete cycle of the migrating motor complex or a maximum of 300 min. Oesophageal manometry, gastric emptying and orocaecal transit time measurements were also performed. RESULTS: At least one complete cycle of the migrating motor complex was observed in all controls, but in only nine patients (P < 0.01 versus control). The migrating motor complex cycle was incomplete (n = 5) or phase 3 activity was absent (n = 4) in the other patients. The incidence of clustered contractions was significantly increased in slow-transit constipation (P = 0.05 versus controls). The area under the contraction curve during late phase 2 (1509+/-296 mmHg x s) in patients with a complete cycle was significantly smaller than that in controls (2997+/-614 mmHg x s; P = 0.05). Orocaecal transit time was not significantly different among patients and controls, but oesophageal motility was abnormal in five of 18 patients and gastric emptying was abnormal in eight of 15 patients. CONCLUSION: Abnormalities of upper gut motility occur frequently in patients with slow-transit constipation. Interdigestive antroduodenal motility is characterized by (i) absence or prolonged duration of the migrating motor complex, (ii) an increased number of clustered contractions, or (iii) a decreased motility during late phase 2 of the migrating motor complex.

Adult↗
PubMed1995

Contractile mechanisms of canine colonic propulsion.

We investigated the contractile mechanisms of propulsion in the dog colon. "Propagation index" indicating caudad or orad propagation of contractile states exhibited the strongest correlation with transit during both the fasting and the postprandial states. Other parameters, such as total duration of contractile states and area under contractions, also contributed to transit, but to a lesser degree. All parameters exhibited a stronger correlation with transit during the fasting than during the postprandial state. During the fasting state, the transit rate was faster in the proximal than in the middle colon. The transit rate was linear through the proximal and the middle colon during the postprandial state. In contrast to the phasic contractions and the contractile states, the giant migrating contractions were ultrapropulsive. We conclude that the propagation of contractile states in the colon is a major factor in the slow net distal propulsion of colonic contents. The individual phasic contractions may mainly produce mixing and agitation of colonic contents. Giant migrating contractions rapidly propel colonic contents over long distances.

Animals↗
PubMed2000

Myoelectric and motor activity after proctocolectomy and ileal pouch-anal anastomosis in dogs.

BACKGROUND: The aim of this study was to investigate the motor function of the ileoanal pouch and to evaluate its coordination with proximal small-intestine motility. METHODS: Proctocolectomy and ileal J pouch-anal anastomosis were performed in 12 dogs. Motility was recorded by serosal electrodes and strain gauge transducers. RESULTS: Transmission of the migrating motor complex (MMC) on the pouch appeared in only 37 of 109 measurements. On the ascending limb there was a constant irregular activity with no MMC detectable. Motility pattern of the pouch did not change postprandially. Spontaneous defecation always appeared independently from MMC transmission without an increase of electrical or mechanical activity or endoluminal pouch pressure. CONCLUSIONS: Ileal pouch motility is independent from motility patterns of the proximal intestine. Its random contractile activity might provide storage function and make the pouch act as a functional reservoir. Intrinsic pouch motility is not responsible for pouch evacuation under physiologic conditions.

Animals↗