Ritman, E. L.

We measured antral volumes and propulsion-retropulsion for individual peristaltic cycles using the dynamic spatial reconstructor in three female mongrel dogs. Our aim was to quantify the effect of intestinal perfusion of equicaloric, isotonic, and isomolar nutrients (maltose, 32.5 mg/100 ml; casein hydrolysate, 32.5 mg/100 ml; and oleic acid 15.5 mg/100 ml) at a rate of 10 ml/min in the upper small intestine on total antral volume and the propulsion-retropulsion function of the "antral pump." Isotonic saline was used as a control solution. Isotonic gastrografin (600 ml) was instilled intragastrically as a meal. A 6-channel perfused manometric assembly was used to record antral phasic pressure activity. Antral volume was significantly lower (P < 0.05) in response to fat perfusion compared with other nutrients or isotonic saline. The propulsion-retropulsion ratio was also significantly reduced (P < 0.05) in response to fat perfusion in the upper small intestine. Our study, therefore, indicates that the fraction of a liquid meal delivered to the antrum is determined, at least in part, by the upper small intestinal nutrients and also that the presence of fat in the small intestine alters the propulsion-retropulsion function of the antrum.

The constitutive equation with stress-dependent coefficients for laminated composite is derived and employed for iterative determination of myocardial fiber’s stiffness equation Ef = Kσf + C from myocardial strip’s stiffness equation Es = Ksσs + Cs. The strip’s stiffness constants Ks and Cs are estimated by the least-square curve fitting of the stress-strain data experimentally obtained from uniaxially stretching of strips of left ventricular heart wall excised from seven canine hearts. The values of K and C computed at selected fiber orientations across the thickness of the strip and using three, five, and ten-layer approximations are reported.