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 7.5 +/- 1.5 mm to 16 +/- 4 mm and their distance from 4.1 +/- 0.2 mm to 7.9 +/- 0.3 mm; luminal contents were alternatively shaken off the haustral wall, whirled around the lumen or left to settle. We also suspended the row of haustra between two taeniae inside a frame and attached flaps of taeniae and haustral folds to strain gauges to record their mechanical activity; both taeniae and haustral folds produced an undulating baseline tension; during rolling, folds produced phasic contractions at 17 +/- 2 cycles min-1 which propagated distally across haustral septa; rolling constantly shuffled around glass beads placed inside the haustra. When we stimulated the intramural nerves to the caecum through bipolar electrodes, all contractile activity was temporarily inhibited and haustral septa flattened; a rebound contraction then propagated aborally from the caecal pole and swept the glass beads ahead of it. Thus, tonic contractions of taeniae shift caecal contents back and forth across haustral septa; expansion of haustra triggers haustral rolling which shuffles contents; both these movements produce local flow within and between haustra which might enhance the separation of solid and liquid colonic contents.

Contraction and accommodation of guinea pig duodenum in vitro.

Because duodenal resistance to gastric emptying depends in part on duodenal capacity, we examined the changes of duodenal diameter, length, and luminal pressure that occur in response to injection of bolus volumes. Filling the duodenum led to a powerful, nonpropagating contraction of the duodenum. After the end of filling, sequential duodenal segments widened and duodenal pressure and length returned to baseline; i.e., there was accommodation. Accommodation was volume dependent and ceased at volumes greater than or equal to 1.2 ml. The entire duodenum unfolded almost immediately and the initial increase of pressure and length was abolished when the duodenal musculature was inhibited by exposure to tetrodotoxin or to Ca(2+)-free solution. Pressures and pressure accommodation were larger, occurred earlier, and lasted longer when the duodenal musculature was stimulated by exposure to carbachol. Filling of the duodenum from the distal end led to rapid distribution of the bolus through the duodenum and to accommodation similar to that seen with proximal filling. However, phasic duodenal contractions were less powerful on distal than on proximal injection. Spontaneous phasic contractions of the duodenum were accompanied by a similar sequence of changes in duodenal configuration as was observed with filling. We conclude that 1) the duodenum adjusts the tension of its walls at small volumes, and beyond this is fairly rigid; 2) filling the duodenum triggers contraction responses similar to those that occur with spontaneous contractions; and 3) the direction from which the duodenum is filled does not affect its accommodation. We postulate that the filling response of the duodenum may critically affect gastric emptying.

Motility changes in opossum esophagus from experimental esophagitis.

We assessed how acute inflammation affects the contractile activity of the esophageal body. Two models of esophagitis were used: nine opossums had an esophageal perfusion of 100 meq hydrochloric acid for 2 hr and were studied at 24 hr. Ten had the perfusion for 4 h and their esophagitis were studied in vitro after 72 hr. Comparisons were made in all instances to animals who had esophageal saline perfusion for identical periods. All acid-perfused animals developed gross and histologic evidence of mucosal inflammation; in three animals, inflammatory changes extended into the submucosa and the muscularis propria. Manometric recordings in the acid-perfused animals revealed esophageal shortening, frequent failure of primary peristalsis and frequent occurrence of spontaneous contractions. Recordings of isometric tension of muscle in vitro revealed spontaneous contractions in strips from the mucosa and from the circular and from the longitudinal muscle. The amplitude of contractions in response to electrical stimulation was decreased, but the duration of contractions was increased largely because of a prolonged recovery phase. These changes in mechanical response occurred with stimulus parameters directed at both the muscle and the intrinsic nerves. We conclude that esophageal inflammation can lead to an increased irritability and decreased stimulus response of the smooth muscle of the esophagus even where it is not directly involved in an inflammatory response. These changes correspond to the functional abnormalities of the esophagus seen in patients with reflux esophagitis.