The effect of auxiliary conditions on intestinal unstirred layer diffusion modelled by numerical simulation

Lucas, Michael L.; Sood, L.; McGregor, Megan; Sattar, N.; Watt, Alexander; Taylor, Jennifer E.

doi:10.1016/s0022-5193(05)80724-6

Cited by 7 publications

(3 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The time for one-half of induced concentration or potential difference change to occur is affected by membrane permeability, fluid absorption, and less than instantaneous bulk phase concentration change. Variation in these parameters unassociated with the USL can be misconstrued as alterations in ␦ (Lucas et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

The Size of the Unstirred Layer as a Function of the Solute Diffusion Coefficient

Pohl

Saparov

Antonenko³

1998

Biophysical Journal

140

124

View full text Add to dashboard Cite

By monitoring the concentration distribution of several solutes that are diffusing at the same time under given mixing conditions, it was established that the unstirred layer (USL) has no clearly defined boundary. For the cases of solute permeation and water movement across planar bilayer lipid membranes, respectively, experiments carried out with double-barreled microelectrodes have shown that the thickness of the USL depends on which species is diffusing. Small molecules with a larger diffusion coefficient encounter an apparently thicker USL than larger molecules with a smaller diffusion coefficient. The ratio of the USL thicknesses of two different substances is equal to the third root of the ratio of the respective diffusion coefficients. This experimental finding is in good agreement with theoretical predictions from the theory of physicochemical hydrodynamics.

show abstract

Section: Discussionmentioning

confidence: 99%

The Size of the Unstirred Layer as a Function of the Solute Diffusion Coefficient

Pohl

Saparov

Antonenko³

1998

Biophysical Journal

140

124

View full text Add to dashboard Cite

show abstract

“…The more pronounced adaptation of SGLT1-mediated transport in the diabetic ileum may be related to the abnormally high level of luminal glucose in the distal small intestine in this condition (Debnam & Chowrimootoo, 1992 A physiologically more reasonable model of the unstirred layer (Lucas et al 1992) than the simple film model, with improvements in the formulation of the boundary conditions, identifies factors besides length which influence the time course of solute accumulation and hence of apparent UL thickness. The lack of effect of guar gum on delay but not half-times excludes both diffusion path alterations, the hitherto favoured explanation, and decreased convection as modes of fibre action.…”

Section: *Nutrition Researchmentioning

confidence: 99%

Epithelia & Membrane Transport

1994

The Journal of Physiology

View full text Add to dashboard Cite

University of Leeds, Leeds LS2 9JT ROMK1, a K' channel cloned from rat kidney, belongs to the superfamily of inwardly rectifying K' channels (Ho et al. 1993). These channels are thought to consist of two membrane-spanning segments, Ml and M2, flanking the putative pore region, H5, which is highly homologous between K' channels. We have carried out blocking studies to characterize the pore region.Xenopus laevis oocytes were injected with 50 nl ROMK1 cRNA (0'01 ng nl') and whole-cell K' currents were measured using the two-electrode voltage clamp technique. The bath solution contained 100 mm KCl, 1 mM MgCl2, 1 mM CaCl2 and was buffered to pH 7-4 with 10 mm Hepes-KOH.Ba2' and Cs' were added at concentrations ranging from 0-01 to 10 mm and 0 5 to 50 mm, respectively. All data are given as means + S.E.M. Both Ba2+ and Cs+ blocked the expressed K+ currents in a voltage-and concentration-dependent manner. Kd for Cs+ block was 2-3 + 0'3 mm at Em = -160 mV and 15-6 + 2-5 mM at Em = -100 mV (n = 4). The electrical distance was determined as a = 0-81 + 0-08 using 10 mm Cs+ (n = 7). Ba2+ blocks the K+ current almost completely at a concentration of 1 mm. The electrical distance for Ba2+ amounts to n= 0-29 + 0-02 (n = 12). Ba2+ blocks ROMK1 more potently than Cs+, which is required at 20-to 50-fold higher concentrations to block the current completely. Whereas Cs+ block is instantaneous, Ba2+ block develops in a timedependent manner. The time constant for the onset of Ba2+ block decreased upon hyperpolarization of Em and upon increasing the Ba2+ concentration.Both Cs+ and Ba2+ block ROMK1 in a voltage-dependent manner, indicating that these cations block the channel by binding to a site which senses the transmembrane potential within the ion conducting pathway. Site directed mutagenesis experiments in the H5 segment will reveal whether this region constitutes the pore.

show abstract

“…Thickness of CBL depends on: type of membrane and solutions used, temperature gradient, concentration and density, velocity of mechanical stirring of solutions, geometry and orientation of membrane and measurement cells with solutions in the gravitational field. Most of the spontaneously occurring membrane processes, in physicochemical and biological systems in particular, proceed in the presence of the CBL on both sides of the membrane [8][9][10][11][12][13][14][15][16]. The paper by Barry and Diamond [17] reviews the effects of boundary layers on membrane phenomena.…”

Section: Introductionmentioning

confidence: 99%

Untitled

Ślęzak

Grzegorczyn

Sieroń³

et al. 1999

Journal of Biological Physics

View full text Add to dashboard Cite

Non-equilibrium thermodynamic model equations for non-ionic and heterogeneous n-component solution transport in a m-membrane system are presented. This model is based on two equations. The first one describes the volume transport of the solution and the second the transport of the solute. Definitions of the hydraulic permeability, reflection and diffusive permeability coefficients of the m-membrane system and relations between the coefficients of the m-membrane system and the respective membranes of the system are also given. The validity of this model for binary and ternary solutions was verified, using a double-membrane cell with a horizontally mounted membrane. In the cell, volume and solute fluxes were measured as a function of concentration and gravitational configuration.

show abstract

The effect of auxiliary conditions on intestinal unstirred layer diffusion modelled by numerical simulation

Cited by 7 publications

References 22 publications

The Size of the Unstirred Layer as a Function of the Solute Diffusion Coefficient

The Size of the Unstirred Layer as a Function of the Solute Diffusion Coefficient

Epithelia & Membrane Transport

Untitled

Contact Info

Product

Resources

About