It seems that C(4) grasses have structurally a superior photosynthate translocation and water distribution system by developing denser networks of small longitudinal and transverse veins, while keeping a constant density of large longitudinal veins. The bambusoid and panicoid C(3) grasses have a vascular system that is more similar to that in C(4) grasses than to that in the festucoid C(3) grasses.
Recently, we reported a novel ultrasound technique to assess the biomechanical properties of the oesophagus in humans. To investigate whether the oesophageal sensation induced by oesophageal distension correlates with wall tension, wall stress or wall strain, we studied 20 healthy subjects using a manometry catheter equipped with a high-compliance bag and a high-frequency intraluminal ultrasound probe. Oesophageal distensions were performed by injecting 1-20 mL water into the bag for 20-30 s. Subjects scored the nature (heartburn or chest pain) and severity of sensation in response to distension, before and after atropine (15 microg kg(-1), i.v.). Ultrasound images of oesophagus were digitized and measurements were made to calculate oesophageal wall tension, stress and strain during distensions. Subjects experienced mostly heartburn, not chest pain, in response to oesophageal distension. Oesophageal wall strain and bag pressures correlated best with the oesophageal sensation. Atropine reduced bag pressure but did not affect the distension induced heartburn and chest pain. We conclude that heartburn is a common sensation in response to oesophageal distension in normal subjects. A strong correlation between wall strain and oesophageal sensation suggests that the wall stretch is the stimulus for nociceptive mechanoreceptors of the oesophagus.
The effect of atropine, a smooth muscle relaxant, has often been determined as a change of compliance in the gastrointestinal (GI) tract. There are reports that atropine increases, decreases or has no effect on the compliance of the oesophagus in isovolumic distension studies (Barish et al. 1984;Richter et al. 1986;Paterson, 1991;Paterson et al. 1991a;Mayrand & Diamant, 1993;Mayrand et al. 1994). The compliance, however, is not an accurate measure of the wall stiffness. The elastic modulus, which is determined from the stress-strain relationship, is a more accurate measure of the wall stiffness. It has not been possible, however, to measure stress and strain in vivo in humans because previous methods could not measure wall thickness, luminal radius and pressure simultaneously. We recently developed a novel ultrasound technique that can measure all of the above-mentioned parameters simultaneously, in real time. Therefore, our technique allows accurate measurement of loading and deformation and subsequent computation of stress, strain and elastic modulus of the human oesophagus in vivo.The oesophagus consists of several layers, mucosa, submucosa and muscularis propria. The latter consists of circumferential and longitudinal muscle fibres. The muscle layer has both passive and active properties consistent with the Hill's three elements model and the non-muscle tissue has only passive properties. The active contraction of the muscle can be described by a combination of 'contractile element' in series with an 'elastic element'. The passive component can be described by a 'parallel element'. The goals of our study were to determine: (1) the effect of atropine on the stress-strain properties of the human oesophagus under isovolumic and isobaric test conditions, and (2) the active and passive components of the wall stress properties of the human oesophagus. Effect of atropine on the biomechanical properties of the oesophageal wall in humansTorahiko Takeda*, Ghassan Kassab †, Jianmin Liu*, Toshinaga Nabae* and Ravinder K. Mittal* Recently, we reported a novel ultrasound technique to assess biomechanical properties of the oesophagus in human subjects. In the present study, we use the technique, in combination with atropine, to determine the active and passive biomechanical properties of the oesophagus in normal healthy humans. A manometric catheter equipped with a high-compliance bag and a high-frequency intraluminal ultrasonography probe was used to record pressure and oesophageal geometry. Oesophageal distensions with either isovolumic (5-20 ml water) or with isobaric (10-60 mmHg) technique were performed. Intra-bag pressure and ultrasound images of the oesophagus were recorded simultaneously. Following injection of atropine (15 mg kg _1 , I.V.), the oesophageal distensions were repeated. The oesophageal wall compliance, circumferential wall tension, stress, strain and elastic modulus were calculated. Atropine resulted in an increase in the oesophageal wall compliance during isobaric distension, but no change in complia...
The nature of the photosynthetic pathways of Cyperaceae found in Japan were investigated on the basis of Kranz anatomy, the CO compensation concentration and previously reported data. Among 301 species (96% of all cyperaceous species recorded in the region), 58 species were classified as being C plants. These C species were scattered among the tribes Fimbristylideae, Lipocarpheae, Cypereae and Rhynchosporeae in the subfamily Cyperoideae. The genera Cyperus, Eleocharis and Rhynchospora included, in Japan, both C and C species within a single genus. Using these data, an analysis was made of the ecological characteristics and geographical distribution of the C and C species in Japan. Although cyperaceous species grow in markedly different environments, the majority were found in wet and aquatic areas (61%) or shaded areas, such as forest floors (20%). Most of the C species were also hygrophytes (58%) and forest-living species (25%), and C species growing in mesic and dry areas were relatively rare. The C species inhabited wet and aquatic (75%), mesic (13%) and dry areas (6%) and showed marked ecological characteristics with respect to soil-moisture conditions, unlike other C plants, although they were absent from shaded habitats. In order to determine the climatic factors that influence the relative floristic abundance of C and C members of the Cyperaceae in Japan, the ratios of number of C species to the total number of members of Cyperaceae (C percentage) in 16 representative locales were examined in terms of various climatic variables. There were strong positive correlations between the C percentage and temperature. Among the C groups of three subfamilies, there were different distributional trends for various temperature regimes. The C subfamily Caricoideae increased its relative contribution to the cyperaceous flora with a decrease in mean annual temperature, while the C subfamily Sclerioideae exhibited the opposite pattern. The C group of the subfamily Cyperoideae did not show any marked change in pattern along temperature gradients, unlike the two other C subfamilies, and seemed to be heterogeneous in terms of its response to temperature. The relationships between the C biochemical subtypes and ecological characteristics are also discussed.
The objectives of this study were to validate a novel ultrasound technique and to use it to study the circumferential stress-strain properties of the human esophagus in vivo. A manometric catheter equipped with a high-compliance bag and a high-frequency intraluminal ultrasonography probe was used to record esophageal pressure and images. Validation studies were performed in vitro followed by in vivo studies in healthy human subjects. Esophageal distensions were performed with either an isovolumic (5-20 ml of water) or with an isobaric (10-60 mmHg) technique. Sustained distension was also performed for 3 min in each subject. The circumferential wall stress and strain were calculated. In vitro studies indicate that the ultrasound technique can make measurements of the esophageal wall with an accuracy of 0.01 mm. The in vivo studies provide the necessary data to compute the Kirchhoff's stress, Green's strain, and Young's elastic modulus during esophageal distensions. The stress-strain relationship revealed a linear shape, the slope of which corresponds to the Young's modulus. During sustained distensions, we found dynamic changes of stress and strain during the period of distension. We describe and validate a novel ultrasound technique that allows measurement of biomechanical properties of the esophagus in vivo in humans.
After Billroth I PPPD, gastric emptying is delayed but recovers by 6 months after surgery. Tachygastria may play a part in the pathogenesis of delayed gastric emptying, but it can be treated with cisapride.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
334 Leonard St
Brooklyn, NY 11211
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.