The American journal of physiology
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Our aim in this study was to determine the effect of variations in intrabolus pressure on esophageal peristalsis. In five cats, intrabolus pressure was altered by increasing intragastric pressure to 20-45 mmHg by use of a pressure cuff to compress the abdomen. In each cat, increases in intragastric pressure were associated with comparable increases in pressure of the esophageal bolus while the bolus was in the distal esophagus during esophageal peristalsis. ⋯ The incidence of retrograde bolus escape was inversely related to the difference between peristaltic wave amplitude and intrabolus pressure. A pressure difference of greater than 20 mmHg prevented retrograde barium escape at all esophageal levels, whereas a difference of less than 20 mmHg was generally associated with retrograde escape of barium in the distal esophagus. We conclude that an increase in intrabolus pressure causes an increase in esophageal distension that is transduced into alterations of esophageal peristalsis by either a myogenic or neural mechanism.
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Specificity of amino acid transport in renal papilla: microinfusion of Henle's loops and vasa recta.
Amino acids can be reabsorbed distal to tips of Henle's loops and may be recycled between loops and vasa recta in rat papilla. Transport specificity was examined during continuous microinfusions of ascending Henle's loops and vasa recta with radiolabeled amino acids. Percent of recovered radiolabel as intact amino acid was also determined. ⋯ L-Phe (50 mM) in infusate inhibited appearance of L-Ala (2.5 mM) and D-Ala (10 mM) but not L-Glu(NH2) (42.6 microM) in ipsilateral urine. D-Asp (50 mM) inhibited appearance of L-Glu (1.5 mM), and beta-Ala (50 mM) inhibited appearance of Tau (78 microM) in ipsilateral urine. Thus some amino acids can move directly from vasa recta into tubules (probably descending thin limbs of Henle's loops) by a process showing significant specificity.