Visual parameters define the phase and the load of contractions in isolated guinea pig ileum.

How the movements of the intestinal walls relate to luminal pressures and outflow remains incompletely understood. We triggered the peristaltic reflex in the isolated ileum of the guinea pig and quantified wall movements through computerized measurements of diameter changes. Contractions developed as indentations close to the upstream end of the loop.

Changes in the position and angulation of incisura during contractions of the isolated cat stomach.

Contractions change the configuration of the lesser curvature of the stomach while they indent the greater curvature. We studied these lesser curvature changes by measuring the position and angle of the gastric incisura on still frames captured from videotapes of isolated cat stomachs suspended in physiologic solution. In response to filling with 100 mL Krebs' solution stomachs generated a tonic contraction of the fundus/body segment and gave rise to a peristaltic contraction that spread from the body and through the antrum to the pylorus.

Contractions move contents by changing the configuration of the isolated cat stomach.

To understand how contractions move gastric contents, we measured, in isolated cat stomachs, the effects of contractions on gastric length, diameters, pressures, and emptying. Movements of the stomach and of gastric contents were monitored by video camera and ultrasound and were related to mechanical events. Based on pressures, we defined the following four phases of contractions: 1) Po, a steady pressure associated with tonic contraction of proximal stomach; 2) P', a pressure wave during which the contraction indents the gastric body; 3) a pressure nadir while the contraction lifts the gastric sinus toward the incisura; and 4) a second pressure wave, P", as the contraction advances through the antrum.

Gastric contractions, secretions and injury in cold restraint.

The clinical syndrome of stress ulceration has been studied for years using rodent cold restraint stress models, although the pathogenesis of the characteristic focal gastric mucosal lesions produced in these models has been controversial. We used gastric strain gauges to characterize fully the gastric motility effects of a 4-h cold restraint protocol, and we determined the relationship of variations in gastric contents and in gastric contractions to the amount of gastric mucosal injury. Additionally, we examined rat stomachs histologically, and determined the location of focal haemorrhagic mucosal lesions on the mucosal rugae.

Volume shifts, unfolding and rolling of haustra in the isolated guinea pig caecum.

The large intestine extracts water from chyme and compacts chyme into faecal conglomerates; it is unclear what role the special pockets known as colonic haustra have in these events. Here we monitored the movements of haustra in isolated preparations of guinea pig caecum using videocamera and ultrasound and related them to contractions of muscle flaps and movements of glass beads in haustral pockets. We found that in partially filled caecal loops localized contractions of taeniae shift volume back and forth between adjacent haustra; volume unfolds haustral walls in a characteristic sweep with sequential intrahaustral folds popping out; cyclic contractions and relaxations of the fold then produce the caterpillar-like movement known as haustral rolling; ultrasound showed that haustral rolling made the haustral flow channel narrower and longer as haustral folds increase their height from 7.

Role of altered responsiveness of hypertrophic smooth muscle in manometric abnormalities of the obstructed opossum oesophagus.

The movements of the obstructed oesophagus are abnormal, but whether this relates to the disease causing the obstruction, to the altered load conditions or to abnormal neuromuscular functions in hypertrophic smooth muscle is unclear. In an opossum model of chronic oesophageal obstruction, we compared the mechanical responsiveness of hypertrophic smooth muscle in vitro to in vivo manometric function. Related to their greater thickness, strips of hypertrophic muscle generated greater force in response to electrical stimulation and to stretch than control strips.

Manometric responses of human duodenum during infusion of HCl, hyperosmolar saline, bile and oleic acid.

Duodenal motor activity is incompletely understood. The purpose of this study was to define the contractile patterns of the duodenum that occur in response to rate controlled injection of various solutions. In nine healthy volunteers we placed a six channel perfused catheter, and recorded pressure activity in the antrum, pylorus and duodenum.

Duodenum as a immediate brake to gastric outflow: a videofluoroscopic and manometric assessment.

Background & Aims: Duodenal infusion of HCl or lipid delays gastric emptying. The aim of this study was to assess whether this delay was in part caused by mechanical activity of the duodenum.

Methods: Synchronized videofluoroscopy and manometry was used in 8 volunteers (5 men and 3 women) to examine contractile and flow patterns during duodenal infusion of 0.

Haustral septations increase axial and radial distribution of luminal contents in glass models of the colon.

We used two glass models of the colon to test the hypothesis that luminal septations increase efficiency of flow. Each was a straight glass tube 4 cm in diameter and filled with water. One had four septations narrowing the lumen to 2 cm; the other had no septations.

Preservation of peristaltic reflex in hypertrophied ileum of guinea pig.

Chronic obstruction of the guinea pig ileum leads to distension and muscular hypertrophy, but how this affects passive biomechanical and nerve-mediated contractions and clearance known as peristaltic reflex is unclear. Ileum of controls had a diameter of 3.0 +/- 1.

Cecum of guinea pig is a reservoir and sigmoid is a high-resistance conduit.

We compared the filling responses of the cecum and the sigmoid of the guinea pig using volumes up to 60 ml and 2.5 ml, respectively. In the isolated cecum, each 1-cm increment of hydrostatic pressure above zero led to accommodation of 10 ml volume; in the sigmoid, the yield pressure (at which accommodation first occurred) was 6 cm H2O, and pressure increments up to 20 cm H2O produced volume increments of less than 0.

Dynamic imaging of obstructed opossum esophagus. From altered load to altered contractility.

We studied by barium contrast the dynamics of experimental obstruction in the opossum esophagus. Immediately after banding the gastroesophageal junction, entrapment of the bolus between the band and the peristaltic contraction led to esophageal bulging, forceful retropulsion of the bolus at the band, and the repeated triggering of peristaltic contractions by the retropelled bolus. In ensuing weeks, triggering of contractions became more difficult and contractions led to bizarre "corkscrew" movements of the increasingly distended and tortuous esophagus.

Strenuous exercise decreases motility and cross-sectional area of human gastric antrum. A study using ultrasound.

Gastric emptying in humans is delayed with strenuous exercise. We used ultrasound imaging in six healthy volunteers to determine whether changes in motility and configuration of the gastric outlet contribute to this delay. After fasting, all individuals ingested chicken broth and garbanzo beans.

The configuration of the human gastroduodenal junction in the separate emptying of liquids and solids.

Background: The stomach separately empties liquids and large particulate solids. The present study aimed to better define the mechanisms responsible for this separate emptying in humans.

Methods: Real-time ultrasound images of the gastroduodenal junction were tape-recorded in normal volunteers after they ingested a test meal consisting of beans and chicken broth.

Morphological changes of myenteric neurons in the partially obstructed opossum esophagus.

We have previously described a model of partial esophageal obstruction which leads to hypertrophic and degenerative changes in the smooth muscle cells. In the present communication we describe changes occurring in the myenteric plexus including increased thickness, varicosities and irregular angulations of nerve fiber bundles. The perikarya of myenteric neurons in the obstructed esophagus showed elongated mitochondria, dilated cisternae of the endoplasmic reticulum and increased numbers of secondary lysosomes and multimembranous dense bodies.

Infiltration of hypertrophic esophageal smooth muscle by mast cells and basophils.

Partial obstruction leads to chronic distension and muscular hypertrophy of the opossum esophagus. The smooth muscle cells of the circular muscle layer enlarge, become pleomorphic and are surrounded by an amorphous ground substance in the extracellular space. Here we describe the histological and ultrastructural features of a peculiar cellular infiltrate in the hypertrophic smooth muscle.

Clearance patterns of the isolated guinea pig duodenum.

To determine what role duodenal clearance plays in the resistance that the duodenum generates to gastric emptying, duodenal output in vitro was assessed under a variety of preload and after-load conditions. In the presence of an outflow resistance, duodenal output occurred in pulses related to contractions of the duodenum. Stroke volume (incremental output during a single contraction) and cumulative output increased both with the degree of duodenal filling and with pharmacological stimulation.