Pressure and length adaptations in isolated cat stomach

Abstract

Correlations were made between the adaptation of gastric pressure and longitudinal muscle tension. Isolated cat stomachs were filled with physiological solution and longitudinal strips marked in five segments over the lesser and the greater curvature (LC and GC). Strip length changed the most in the proximal segments of GC. Volume changes led to triphasic changes in gastric pressure. On filling, there was a pressure peak and pressure accommodation to a new base-line pressure. On emptying there was an initial pressure nadir that was followed by a pressure recovery. When isolated longitudinal strips were stretched and released to their lengths at specific gastric volumes, they generated triphasic tension adaption and recovery. Strips from the proximal greater curvature generated the highest base-line tension, highest peak tension, and largest amplitude of tension adaptations. Addition of KCl, carbachol, or physostigmine increased base-line tension and tension adaptations in parallel, whereas atropine reduced them. Tetrodotoxin had no effect. The base-line tension of the isolated cat stomach is maintained by a tonic cholinergic neurosecretion but its tension adaptations do not require neural control.

Stomach stress and strain depend on location, direction and the layered structure

“…Tonic contraction of the proximal stomach (fundus) plays an important role in liquid emptying (Kelly, 1978;Paterson et al, 2000). The function of the fundus is traditionally studied by length-tension studies in muscle strips (Haffner and Stadaas, 1972;Milenov and Golenhofen, 1982;Schulze-Delrieu and Shirazi, 1987) and pressure-volume (barostat) studies of tone and tension Malagelada, 1985, 1987;Whitehead et al, 1997;Penning et al, 2001;Kuiken et al, 2002). In those studies they assumed that the organ is spherical, very thin-walled and in static force equilibrium, i.e., the inertial forces are zero.…”

Changes in the position and angulation of incisura during contractions of the isolated cat stomach

“…Still, volume affects the length of the lesser curvature to a much smaller extent than that of the greater curvature 21 . 22 , 24 –27 Contractions also affect the horizontal distance of the incisura to the pylorus, resulting if anything in a net movement of the incisura away from the pylorus. However, the incisura moves repeatedly and briefly back away from and towards the pylorus and this pattern of movement made it impossible for us to define net displacements at specific times of the contraction.…”

A novel 3D shape context method based strain analysis on a rat stomach model

“…The gastric configuration changes vary throughout the gastric contraction as increases in gastric tone that flatten and narrow the fundus, shorten the great curvature, affect the position of the incisura and redraw the borders between the proximal and distal stomach (SchulzeDelrieu et al, 1998;Schulze, 2006). The different geometric change of each gastric part (Schulze-Delrieu and Shirazi, 1987), from a mechanical point of view, could be caused by different gastric wall structures as well as particular mechanical properties in each gastric part. The non-uniform deformation features of the stomach were distinguished by using the present method as the deformation on the non-glandular part, the greater and lesser curvature part was significantly higher than that in the glandular part as well as the stiffer wall in the glandular part.…”

“…However, the stomach with its complex geometry in vivo experiences physiological loading with a complex deformation pattern, e.g. along and transverse to the direction of the gastric fibres (Schulze-Delrieu and Shirazi, 1987;Schulze-Delrieu et al, 1998;Schulze, 2006;Schwizer et al, 2002). Therefore, data from uni-axial testing cannot be extrapolated to analyse accurately physiological behaviour of the intact stomach.…”