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Biomedical subjects
J P Wall
Publications and source records attributed to J P Wall.
Mechanical activity of muscular "patch pouches" from cat and rabbit stomachs.
With a newly developed preparation (the gastric patch pouch), we compared the mechanical response of the proximal with that of the distal stomach to volume loads, drugs, and stimulation by an electrical field. Squares, 2 X 2 cm, were cut from the anterior and posterior walls of stomachs from cats and rabbits; the corresponding edges of opposing squares were sewn together. A luminal balloon served to change pouch volume and to monitor pouch pressure. Filling increased the width more than the length of most pouches; this difference was particularly marked in pouches from the rabbit fundus. Filling led to an initial pressure peak, after which pressure declined to a new baseline pressure plateau; emptying led to an initial pressure nadir, pressure recovery, and baseline pressure plateau. The difference between initial pressure and plateau pressure was larger in proximal than in distal pouches: hence, baseline pressures rose more sharply on filling and declined more steeply on emptying of antral than of proximal pouches. Pressure waves occurred in all antral pouches of cats and in some antral pouches of rabbits. Carbachol enhanced the pressure waves and isoproterenol inhibited them. In the fundic pouches, these drugs altered primarily the baseline pressure. Electrical field stimulation caused a relaxation in fundic pouches and a suppression of rhythmic contractions in antral pouches. The onset and the duration of nervous inhibition was comparable in fundic and in antral pouches. The baseline pressure of pouches was not affected by the presence or by the absence of the mucosa. This novel preparation is suitable to demonstrate differences in the volume-pressure relationships of the muscle coat of the proximal and the distal stomach.
Adaptation, Physiological↗
Determinants of flow across isolated gastroduodenal junctions of cats and rabbits.
The resistance generated by the gastroduodenal junction was measured in isolated cat and rabbit preparations. Cannulas were tied into the antrum and duodenum. Yield pressures were determined by increasing the pressure in one of the cannulas until flow occurred. The junctional segment of the cat maintained a high yield pressure. Yield pressures were similar in the antroduodenal and the duodenogastric direction (12.5 +/- 5.7 vs. 14.8 5.8 cmH2O) and increased on both sides to the same degree following exposure of the preparation to 100 mM [K+] and to 10(-6) M carbachol. These experimental manipulations also led to the occurrence of pressure waves in the antral cannula. Yield pressures were diminished but not abolished by exposure of the preparation to 0 [Ca2+] solution or 10(-6) M isoproterenol. Junctional segments from the rabbit did not maintain a yield pressure. Resistance across the junctional segment of both species was also measured by channeling the outflow of one of the cannulas to a flowmeter. Over a wide range of pressures, flow rates across the junctional segment of the rabbit exceeded those across the junctional segment of the cat. Carbachol and 100 mM [K+] decreased the base-line flow and increased the amplitude of intermittent decreases of flow. Isoproterenol and 0 [Ca2+] had opposite effects. Inflation of a balloon decreased the flow rate across the rabbit but not the cat junctional segment. Flow rates across the junctional segment did not differ in the antroduodenal and duodenogastric direction. The gastroduodenal junction does not act as an unidirectional valve. Pyloric resistance relates to the structure of the pyloric segment and to phasic and tonic activity of its musculature.
Animals↗