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Lentle RG Janssen PW Asvarujanon P Chambers P Stafford KJ Hemar Y 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2008,178(3):257-268
Four types of contractile activity were identified and characterised in the isolated triple haustrated proximal colon of the
rabbit using high-definition spatiotemporal mapping techniques. Mass peristalses were hexamethonium-sensitive deep circular
contractions with associated taenial longitudinal contractile activity that occurred irregularly and propagated rapidly aborad,
preceded by a zone of local lumen distension. They were sufficiently sustained for each event to occupy the length of the
isolated colonic segment and the contraction persisted longer orally than aborally, the difference being more pronounced when
lumen contents were viscous. Haustra were bounded by deep even-spaced ring contractions that progressed slowly aborad (haustral
progression). Haustral formation and progression were hexamethonium-sensitive and coordinated across intertaenial domains.
Ripples were hexamethonium-resistant phasic circular contractions that propagated predominantly orad at varying rates. In
the presence of haustra, they were uncoordinated across intertaenial domains but were more coordinated when haustra were absent.
Fast phasic contractions were relatively shallow hexamethonium-resistant contractions that propagated rapidly in a predominantly
aborad direction. Fast phasic circular contractions were accompanied by taenial longitudinal muscle contractions which increased
in amplitude prior to a mass peristaltic event and following the administration of hexamethonium. On the basis of the concurrence
and interaction of these contractile activities, we hypothesise that dual pacemakers are present with fast phasic contractions
being modulated by the interstitial cells of Cajal in the Auerbach’s plexus (ICC-MY) while ripples are due to the submucosal
ICC (ICC-SM). Further, that ICC-SM mediate the enteric motor neurons that generate haustral progression, while the intramuscular
ICC (ICC-IM) mediate mass peristalsis. The orad movement of watery fluid was possibly due to ripples in the absence of haustra. 相似文献
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Psyllium husk, a highly viscous fiber, has beneficial effects for health, but has been reported to inhibit absorption of calcium. The present study found the effects of fiber viscosity on calcium, magnesium, and zinc absorption with partially degraded psyllium preparations to be one fifth viscosity (LD-HP) and one seventieth viscosity (HD-HP) using normal and ovariectomized rats. Magnesium absorption was reduced with ingestion of intact psyllium (50 g/kg diet) for 4 weeks but this reduced absorption was increased with lower viscous psyllium preparations. Moreover, the absorption in the HD-HP group was higher than in the control group (100 g cellulose/kg diet) in ovariectomized rats. Changes in calcium and zinc absorption were similar to those in magnesium absorption. Cecal pH was reduced only in rats fed HD-HP in both normal and ovariectomized rats. These results indicate that reduction of psyllium viscosity tends to counter inhibitory effects on mineral absorption. 相似文献
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Lentle RG Janssen PW Asvarujanon P Chambers P Stafford KJ Hemar Y 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(5):543-556
Longitudinal and radial movements during spontaneous contractions of isolated segments of terminal ileum of the brushtail
possum, a species of arboreal folivore, were studied using high definition spatiotemporal maps. Segments obtained from specimens
were continuously perfused with solutions of various apparent viscosities at 3 cm and 5 cm hydrostatic pressure. A series
of sustained tetrodotoxin-sensitive peristaltic events occurred during perfusion. The leading edge of each peristaltic event
progressed by a succession of rhythmic surges of circular contraction with concerted concurrent phasic longitudinal contractions.
Three types of peristaltic event were observed, with differing durations of occlusion and patterns of cyclic, in phase, circular
and longitudinal contractions. Each peristaltic event was preceded by a change of shade on the D map that indicated circumferential dilatation. Differences in the slopes of these phasic shade changes from those occurring
during peristalsis indicate that this distension is passive and likely results from aboral displacement of fluid. Tetradotoxin
insensitive longitudinal contraction waves of frequency 9.2 min−1 occurred during and in the absence of peristalsis, originating at a variety of sites, and propagating either in an orad or
aborad direction but predominantly in the latter. Perfusion with 1% guar gum, at 5 cm hydrostatic pressure caused the lumen
to become distended and the generation of peristaltic events to cease pending reduction of the hydrostatic head to 3 cm but
longitudinal contractile activity was preserved. Neither the frequencies nor the rates of progression of circular and longitudinal
contractile events, nor the temporal coordination between these events, varied with the apparent viscosity of the perfusate
or altered in a manner that could facilitate mixing. 相似文献
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