Stress and strain analysis of contractions during ramp distension in partially obstructed guinea pig jejunal segments

Abstract

Previous studies have demonstrated morphological and biomechanical remodeling in the intestine proximal to an obstruction. The present study aimed to obtain stress and strain thresholds to initiate contraction and the maximal contraction stress and strain in partially obstructed guinea pig jejunal segments. Partial obstruction and sham operations were surgically created in mid-jejunum of male guinea pigs. The animals survived 2, 4, 7, and 14 days, respectively. Animals not being operated on served as normal controls. The segments were used for no-load state, zero-stress state and distension analyses. The segment was inflated to 10 cmH2O pressure in an organ bath containing 37°C Krebs solution and the outer diameter change was monitored. The stress and strain at the contraction threshold and at maximum contraction were computed from the diameter, pressure and the zero-stress state data. Young’s modulus was determined at the contraction threshold. The muscle layer thickness in obstructed intestinal segments increased up to 300%. Compared with sham-obstructed and normal groups, the contraction stress threshold, the maximum contraction stress and the Young’s modulus at the contraction threshold increased whereas the strain threshold and maximum contraction strain decreased after 7 days obstruction (P<0.05 and 0.01). In conclusion, in the partially obstructed intestinal segments, a larger distension force was needed to evoke contraction likely due to tissue remodeling. Higher contraction stresses were produced and the contraction deformation (strain) became smaller.

Interdependency between mechanical parameters and afferent nerve discharge in hypertrophic intestine of rats

“…2). This is consistent with previously observed increased muscle contraction force (3,30,36) and may reflect changes in the enteric reflex function. Functionally, the increased contraction force in the hypertrophic intestinal segment may serve to overcome the resistance to flow through the partial obstruction.…”

“…The change in nerve and ganglia morphology and function will also have an impact on smooth muscle contractile activity due to intrinsic stretch sensitive neural reflexes (18). During distension we and others found increased muscle force and hyposensitivity to stretch (36). Whereas the force relates to the increased muscle mass, the sensitivity will relate to mechanoreceptor and nerve function.…”

“…However, when the motor response was normalized with respect to tissue wet weight, a remarkable reduction of contractile efficiency was observed postobstruction (2). Furthermore, from our previous study it was demonstrated that the pressure and stress thresholds of distension-induced contractility were increased in the partially obstructed jejunal segment (36).…”

Mechanical experimentation of the gastrointestinal tract: a systematic review

“…The effect of partial obstruction on the active behaviour of the small intestine was studied in guinea pigs (Zhao et al. 2011a , b ), while Zhao and Gregersen ( 2015 ) studied the effect of ageing on the passive material response of the organ in rats.…”

“… 2008 , 2013b , 2019 ), guinea pigs (Zhao et al. 2011a , b ), mice (Lu et al. 2012 ) and pigs (Terry et al.…”