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Determination of villous rigidity in the distal ileum of the possum (Trichosurus vulpecula).

Lim YF, Lentle RG, Janssen PW, Williams MA, de Loubens C, Mansel BW, Chambers P - PLoS ONE (2014)

Bottom Line: We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV).Flow moved upward toward the tip on the upper portions of isolated villi on the surface facing the flow and downward toward the base on the downstream surface.The fluid in sites at distances greater than 150 µm below the villous tips was virtually stagnant indicating that significant convective mixing in the lower intervillous spaces was unlikely.

View Article: PubMed Central - PubMed

Affiliation: Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand.

ABSTRACT
We investigated the passive mechanical properties of villi in ex vivo preparations of sections of the wall of the distal ileum from the brushtail possum (Trichosurus vulpecula) by using a flow cell to impose physiological and supra-physiological levels of shear stress on the tips of villi. We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV). Ileal villi were relatively rigid along their entire length (mean 550 µm), and exhibited no noticeable bending even at flow rates that exceeded calculated normal physiological shear stress (>0.5 mPa). However, movement of villus tips indicated that the whole rigid structure of a villus could pivot about the base, likely from laxity at the point of union of the villous shaft with the underlying mucosa. Flow moved upward toward the tip on the upper portions of isolated villi on the surface facing the flow and downward toward the base on the downstream surface. The fluid in sites at distances greater than 150 µm below the villous tips was virtually stagnant indicating that significant convective mixing in the lower intervillous spaces was unlikely. Together the findings indicate that mixing and absorption is likely to be confined to the tips of villi under conditions where the villi and intestinal wall are immobile and is unlikely to be greatly augmented by passive bending of the shafts of villi.

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Relationship between displacement of points along the villous length with distance from the villous tip.The plot utilized data pooled from all villi*. Displacement is expressed as a percentage of total tip displacement (TD). The regression lines that best fitted the data obtained at each perfusion rate were all linear. * R2 values shown are for pooled data. R2 values for SLRs of individual villi were all above 0.8 at each flow rate. The dotted lines are 95% confidence intervals.
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pone-0100140-g007: Relationship between displacement of points along the villous length with distance from the villous tip.The plot utilized data pooled from all villi*. Displacement is expressed as a percentage of total tip displacement (TD). The regression lines that best fitted the data obtained at each perfusion rate were all linear. * R2 values shown are for pooled data. R2 values for SLRs of individual villi were all above 0.8 at each flow rate. The dotted lines are 95% confidence intervals.

Mentions: Curve fits of pooled data (CurveExpert v.1.4) from all flow rates showed that the variation of displacement (expressed as a percentage of TD) against distance down the villus was best fitted by a linear function (Fig. 7). At flow rates of 3.8, 7.6 and 15.3 mL/min significant linear regressions (Fig. 7) with R2 values of 0.73, 0.59, and 0.81 respectively were obtained. Moreover, the slopes of the linear fits at the three perfusion rates did not differ significantly on Student's t-test (d.f. = 29, T = 0.35, P>0.05 between 3.8 and 7.6 mL/min, d.f. = 24, T = 1.41, P>0.05 between 7.6 and 15.3 mL/min and d.f. = 13, T = 1.77, P>0.05 between 15.3 and 3.8 mL/min). Together these findings indicate that the villi were effectively rigid and did not bend at physiological or supra-physiological flow rates. Furthermore, the shafts of villi pivoted little around their bases. In regard to the latter finding it is important to note that the tension in the tightly mounted tissue (which was necessary to avoid movement of the entire mucosa on the probe) may have restricted such pivoting.


Determination of villous rigidity in the distal ileum of the possum (Trichosurus vulpecula).

Lim YF, Lentle RG, Janssen PW, Williams MA, de Loubens C, Mansel BW, Chambers P - PLoS ONE (2014)

Relationship between displacement of points along the villous length with distance from the villous tip.The plot utilized data pooled from all villi*. Displacement is expressed as a percentage of total tip displacement (TD). The regression lines that best fitted the data obtained at each perfusion rate were all linear. * R2 values shown are for pooled data. R2 values for SLRs of individual villi were all above 0.8 at each flow rate. The dotted lines are 95% confidence intervals.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4067314&req=5

pone-0100140-g007: Relationship between displacement of points along the villous length with distance from the villous tip.The plot utilized data pooled from all villi*. Displacement is expressed as a percentage of total tip displacement (TD). The regression lines that best fitted the data obtained at each perfusion rate were all linear. * R2 values shown are for pooled data. R2 values for SLRs of individual villi were all above 0.8 at each flow rate. The dotted lines are 95% confidence intervals.
Mentions: Curve fits of pooled data (CurveExpert v.1.4) from all flow rates showed that the variation of displacement (expressed as a percentage of TD) against distance down the villus was best fitted by a linear function (Fig. 7). At flow rates of 3.8, 7.6 and 15.3 mL/min significant linear regressions (Fig. 7) with R2 values of 0.73, 0.59, and 0.81 respectively were obtained. Moreover, the slopes of the linear fits at the three perfusion rates did not differ significantly on Student's t-test (d.f. = 29, T = 0.35, P>0.05 between 3.8 and 7.6 mL/min, d.f. = 24, T = 1.41, P>0.05 between 7.6 and 15.3 mL/min and d.f. = 13, T = 1.77, P>0.05 between 15.3 and 3.8 mL/min). Together these findings indicate that the villi were effectively rigid and did not bend at physiological or supra-physiological flow rates. Furthermore, the shafts of villi pivoted little around their bases. In regard to the latter finding it is important to note that the tension in the tightly mounted tissue (which was necessary to avoid movement of the entire mucosa on the probe) may have restricted such pivoting.

Bottom Line: We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV).Flow moved upward toward the tip on the upper portions of isolated villi on the surface facing the flow and downward toward the base on the downstream surface.The fluid in sites at distances greater than 150 µm below the villous tips was virtually stagnant indicating that significant convective mixing in the lower intervillous spaces was unlikely.

View Article: PubMed Central - PubMed

Affiliation: Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand.

ABSTRACT
We investigated the passive mechanical properties of villi in ex vivo preparations of sections of the wall of the distal ileum from the brushtail possum (Trichosurus vulpecula) by using a flow cell to impose physiological and supra-physiological levels of shear stress on the tips of villi. We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV). Ileal villi were relatively rigid along their entire length (mean 550 µm), and exhibited no noticeable bending even at flow rates that exceeded calculated normal physiological shear stress (>0.5 mPa). However, movement of villus tips indicated that the whole rigid structure of a villus could pivot about the base, likely from laxity at the point of union of the villous shaft with the underlying mucosa. Flow moved upward toward the tip on the upper portions of isolated villi on the surface facing the flow and downward toward the base on the downstream surface. The fluid in sites at distances greater than 150 µm below the villous tips was virtually stagnant indicating that significant convective mixing in the lower intervillous spaces was unlikely. Together the findings indicate that mixing and absorption is likely to be confined to the tips of villi under conditions where the villi and intestinal wall are immobile and is unlikely to be greatly augmented by passive bending of the shafts of villi.

Show MeSH
Related in: MedlinePlus