			Home About us Contact

Longitudinal Strips (longitudinal + strip)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Tension and stress in the rat and rabbit stomach are location- and direction-dependent

NEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2005
J. Zhao
Abstract, Distension studies in the stomach are very common. It is assumed in pressure,volume (barostat) studies of tone and tension in the gastric fundus that the fundus is a sphere, i.e. that the tension in all directions is identical. However, the complex geometry of the stomach indicates a more complex mechanical behaviour. The aim of this study was to determine uniaxial stress,strain properties of gastric strips obtained from rats (n = 12) and rabbits (n = 10). Furthermore, we aimed to study the gastric zero-stress state since the stomach is one of the remaining parts of the gastrointestinal tract where residual strain studies have not been conducted. Longitudinal strips (in parallel with the lesser curvature) and circumferential strips (perpendicular to the lesser curvature) were cut from the gastric fundus (glandular part) and forestomach (non-glandular part). The residual stress was evaluated as bending angles (unit: degree per unit length and negative when bending outwards). The residual strain was computed from the change in length between the zero-stress state and no-load state. The stress,strain test was performed using a tensile test machine. The thickness and width of each strip were measured from digital images. The strips data were compared with data obtained in the intact stomach in vitro. Most residual stresses and strains were bigger in the glandular part than in the forestomach, and in general the rat stomach had higher values than the rabbit stomach. The glandular strips were stiffer than the forestomach strips and the longitudinal glandular strips were stiffer than the circumferential glandular strips (P < 0.05). The gastric strips were stiffer in rats than in rabbits (P < 0.01). The data obtained in the intact rat stomach confirmed the strips data and indicated that those were obtained in the physiological range. In conclusion, the biomechanical properties of the gastric strips from the rat and rabbit are location-dependent, direction-dependent and species-dependent. The assumption in physiological pressure,volume studies that the stomach is a sphere with uniform tension is not valid. Three-dimensional geometric data obtained using imaging technology and mechanical data are needed for evaluation of the stomach function. [source]

MICROMECHANICS: SIMULATING THE ELASTIC BEHAVIOR OF ONION EPIDERMIS TISSUE

JOURNAL OF TEXTURE STUDIES, Issue 1 2006
JIMMY LOODTS
ABSTRACT A generic modeling approach is introduced that allows for dynamical simulations of cellular biological tissue. It is derived from the discrete element approach in the sense that the tissue is discretized such that histological aspects like cell geometry and the cellular arrangement within the tissue can be fully incorporated into the model. This makes dynamical simulations of arbitrarily shaped cellular tissues feasible in an elegant and a robust way. The validity of this simulation technique is demonstrated by a case study on the unicellular epidermis layer of onion (Allium cepa). The parameters of a two-dimensional model are determined using published stress,strain data from a tension test on longitudinal strips. The model is then validated quantitatively against the data for transversal strips. [source]

Functional alterations of mesenteric vascular bed, vas deferens and intestinal tracts in a rat hindlimb unloading model of microgravity

AUTONOMIC & AUTACOID PHARMACOLOGY, Issue 2 2004
G. De Salvatore
Summary 1 Prolonged bed rest or exposure to microgravity may cause several alterations in autonomic nervous system response (ANSR). 2 Hindlimb unloading (HU) rats were used as an animal model of simulated microgravity to investigate ANSR changes. The experiments were carried out to investigate the effects of simulated microgravity on the autonomic nervous response of the perfused mesenteric vascular bed (MVB), vas deferens and the colon and duodenum from 2-week HU rats. 3 In MVB preparations of HU rats, the frequency-dependent increases in perfusion pressure with perivascular nerve stimulation (PNS; 8,40 Hz) were inhibited, whereas the noradrenaline (NA) concentration-dependent (1,100 ,m) perfusion pressure increases were potentiated. The latter most probably reflected up-regulation of , -adrenergic receptor function. Relaxant responses of NA-precontracted MVB to PNS (4,30 Hz) or isoprenaline were not different between control and HU preparations, while vasodilation induced by the endothelial agonist ACh was reduced. 4 Transmural stimulation (2,40 Hz) induced frequency-dependent twitches of the vas deferens which were reduced in vas deferens of HU rats, while the sensitivity to NA-induced contraction was significantly increased. 5 In the gastroenteric system of HU rat, direct contractile responses to carbachol or tachykinin as well as relaxant or contractile responses to nervous stimulation appeared unchanged both in the proximal colon rings and in duodenal longitudinal strips. 6 In conclusion, HU treatment affects peripheral tissues in which the main contractile mediators are the adrenergic ones such as resistance vessels and vas deferens, probably by reducing the release of neuromediator. This study validates NA signalling impairment as a widespread process in microgravity, which may most dramatically result in the clinical phenotype of orthostatic intolerance. [source]

Effects of chronic treatment with vardenafil, a phosphodiesterase 5 inhibitor, on female rat bladder in a partial bladder outlet obstruction model

BJU INTERNATIONAL, Issue 7 2009
Seiji Matsumoto
OBJECTIVES To investigate whether vardenafil, a phosphodiesterase 5 (PDE-5) inhibitor, would protect the bladder from decompensatory changes in a 4-week rat bladder outlet obstruction (BOO) model, as evidence has been accumulating that PDE-5 inhibitors improve lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH). MATERIALS AND METHODS In all, 50 12-week-old female Sprague-Dawley rats were divided into five equal groups; group 1, sham operated vehicle control rats; group 2, BOO vehicle rats; group 3,5, BOO rats given oral vardenafil at 5, 20, 80 mg/L, respectively. Vardenafil was given in drinking water from the day of surgery. At 4-weeks after the introduction of BOO, vardenafil was washed-out by giving water for 24,48 h, and then the bladder was excised and dissected into four longitudinal strips for isometric organ-bath assay. Contractile responses of bladder strips to electrical field stimulation (EFS), carbachol and KCl was determined for each group. RESULTS BOO induced a significant increase in bladder weight in group 2 compared with group 1. Bladder weights of groups 3,5 were not significantly different from that of group 2. The contractile forces in response to EFS, carbachol and KCl in group 2 were 30.7,51.7% of those in group 1. Vardenafil treatment in groups 3,5 generally did not block the BOO-induced reduction of contractile force in the bladder strips. However, treatment with a high dose of vardenafil resulted in a significant increase in the contractile response to carbachol (78.4% group 5 vs 51.7% group 2). CONCLUSION Chronic treatment with a high dose of vardenafil protected the rat bladder from BOO-induced contractile dysfunction to carbachol. [source]