In-vivo force, frequency, and velocity of dog gastrointestinal contractile activity

Structural breakdown of starch-based foods during gastric digestion and its link to glycemic response: In vivo and in vitro considerations

The digestion of starch-based foods in the small intestine as well as factors affecting their digestibility have been previously investigated and reviewed in detail. Starch digestibility has been studied both in vivo and in vitro, with increasing interest in the use of in vitro models. Although previous in vivo studies have indicated the effect of mastication and gastric digestion on the digestibility of solid starch-based foods, the physical breakdown of starch-based foods prior to small intestinal digestion is often less considered. Moreover, gastric digestion has received little attention in the attempt to understand the digestion of solid starch-based foods in the digestive tract. In this review, the physical breakdown of starch-based foods in the mouth and stomach, the quantification of these breakdown processes, and their links to physiological outcomes, such as gastric emptying and glycemic response, are discussed. In addition, the physical breakdown aspects related to gastric digestion that need to be considered when developing in vitro-in vivo correlation in starch digestion studies are discussed. The discussion demonstrates that physical breakdown prior to small intestinal digestion, especially during gastric digestion, should not be neglected in understanding the digestion of solid starch-based foods.

Computer-assisted method for the analysis of postprandial gastrointestinal motility in conscious dogs

A fully automated system to quantify different parameters of gastrointestinal motility and gastroduodenal co-ordination in conscious dogs was designed and built around a personal technical computer (HP 9816). Online it performs sampling of contractions on four different sites of the digestive tract for two dogs simultaneously, data reduction, drift correction and storage of data on hard disk. Offline it performs baseline determination, peak detection, calculation of motility parameters such as amplitude and interval, plus co-ordination between gastric and duodenal motility and presentation of the results in both tabular and graphic form. To illustrate the possibilities and advantages of the computer analysis the early postprandial motor patterns for antrum, duodenum and jejunum were quantified during the first hour after administration of a small test meal.

Actions of cholecystokinin octapeptide on smooth muscle of isolated dog intestine

Adult dogs were anesthetized and segments of small intestine were isolated and perfused via a mesenteric artery with Krebs-bicarbonate solution. Muscle responses along the circular and longitudinal axes were monitored with extraluminal strain gauge transducers. Agonists were administered as intraarterial bolus injections in volumes not exceeding 0.1 ml. Antagonists were dissolved in the Krebs perfusion solution. The C-terminal octapeptide of cholecystokinin (CCK-OP) produced dose-related tonic and phasic contractions of smooth muscle along the transverse axis and tonic and phasic relaxations along the longitudinal axis of the muscle segments. Smooth muscle responses to CCK-OP were reduced by atropine sulfate (0.1 mug/ml) and minimally affected by hexamethonium (10 mug/ml) perfusion. Tetrodotoxin (TTX, 5 ng/ml) selectively reduced muscle responses to dimethylphenylpiperazinium (0.5 mug) and CCK-OP (0.2 mug) but failed to alter responses to bethanechol (BeCh, 5 mug). Higher concentrations of TTX (10 ng/ml) abolished responses to CCK-OP. Depolarizing doses of nicotine (500 mug) selectively antagonized responses to 5-hydroxytryptamine (5HT, 5 mug) and CCK-OP (0.2 mug) but did not alter responses to BeCh (5 mug). Perfusion with tetraethylammonium (1 mg/ml) reduced muscle responses to depolarizing doses of nicotine and abolished the nicotine-induced antagonism of 5HT and CCK-OP. The intestinal smooth muscle response to CCK-OP in the dog is mediated through a neurogenic mechanism. CCK-OP interacts with a nonnicotinic receptor on postganglionic cholinergic neural elements in this preparation.

Intraluminal pressure of the small intestine of the unanesthetized dog

Intraluminal pressure recordings have been performed in 14 unanesthetized dogs via a Mann-Bollman fistula by means of an air-filled balloon catheter system and a water-filled catheter system. The dynamic response is adequate for studying intraluminal pressures of the small intestine. Resting pressures in the proximal, middle and distal jejunum averaged approximately 6 mm Hg above atmosphere and no appreciable differences were noted between the different areas. The contraction time of simple, monophasic waves was fairly constant (approximately 1.0 s in duration) and usually unrelated to amplitude of the wave. Propulsion of intraluminal contents occurred in the absence of complex (type III) waves. A pressure wave in a proximal segment of jejunum was temporally related to a wave occurring 5 cm distally. The mean intervals between the proximal and distal contractions were: 0.42 s in the proximal jejunum; 0.74 s in the middle jejunum; 1.56 s in the distal jejunum; 2.79 s in the ileum. These time lags have a log normal distribution. The length of the physiologic segment in the jejunum of the dog varied from 1.0-8.0 cm and was usually 2-4 cm.