Flow dependence of nonelectrolyte absorption in the nephron

1979 ◽  
Vol 236 (2) ◽  
pp. F163-F174 ◽  
Author(s):  
D. W. Barfuss ◽  
J. A. Schafer
Keyword(s):  
Lower Bound ◽  
Solute Transport ◽  
Axial Flow ◽  
Solute Concentration ◽  
Solute Flux ◽  
Perfusion Rate ◽  
Volume Absorption ◽  
Flow Dependence ◽  
Solute Absorption ◽  
Glomerulotubular Balance

The axial flow dependence of nonelectrolyte absorption was examined in terms of a model incorporating interactions between net volume absorption and both saturable and nonsaturable solute absorption. The model solutions demonstrated that changes in transepithelial solute transport are produced by changes in the average luminal solute concentration. Even passive non-saturable solute absorption was shown to exhibit dependence on the perfusion rate, and, therefore, on the solute delivery rate, which could be incorrectly interpreted as demonstrating the presence of a saturable absorptive mechanism. For a unidirectional lumen-to-bath solute flux mediated in part by a saturable mechanism, the observed flux is dependent on the permeability of any parallel nonsaturable permeation pathway. This permeability also sets a lower bound on the luminal solute concentration which may be achieved during active net solute absorption by determining the rate of passive solute backleak. Extension of the model to incorporate dependence of net volume absorption on the delivery of nonelectrolytes predicted a relationship between perfusion rate and net volume absorption equivalent to approximately one-third of complete glomerulotubular balance.

Transport of solute in proximal tubules is modified by changes in medium osmolality

1986 ◽  
Vol 250 (2) ◽  
pp. F246-F255
Author(s):  
J. C. Williams ◽  
D. W. Barfuss ◽  
J. A. Schafer
Keyword(s):  
Solute Transport ◽  
Proximal Tubules ◽  
Time Dependent ◽  
Cell Swelling ◽  
Fluid Absorption ◽  
Volume Absorption ◽  
Straight Tubules ◽  
Rate Of Absorption ◽  
Solute Absorption ◽  
Convoluted Tubules

To examine the hypothesis that fluid absorption is driven by transepithelial osmotic differences, we measured such differences in proximal tubules perfused under oil and attempted to increase the rate of fluid absorption (Jv) and hence the absorbate-perfusate osmotic differences by lowering the osmolality of the perfusate. We were able to consistently increase Jv in this manner only in proximal straight tubules perfused with a simple perfusate that contained no bicarbonate or amino acids. With the simple perfusate, a small but significant increase in the absorbate-perfusate osmolality difference was seen with increased Jv, which is expected if the volume absorption is driven by a transepithelial osmotic difference. In addition, lowering the perfusate osmolality from 290 to 160 mosmol/kg H2O increased the rate of solute absorption from 79 +/- 7 to 91 +/- 8 posmol . min-1 . mm-1; this increase was partly accounted for by an increase in the rate of absorption of glucose from 6.6 +/- 0.9 to 9.5 +/- 1.1 pmol . min-1 . mm-1. In contrast, with the complete perfusate in proximal straight tubules there was little or no increment in Jv, no change in transepithelial osmolality differences, and a decrease in the rate of solute transport with hypoosmolality from 136 +/- 21 to 87 +/- 22 posmol . min-1 . mm-1. In proximal convoluted tubules, similar results were obtained, but a time-dependent decline of Jv complicated the interpretation of the results in the convoluted tubules. It is hypothesized that the observed changes in solute transport with hypotonic perfusate may be the result of changes in membrane permeability that are subsequent to cell swelling.

Claudin Tight Junction Proteins: Novel Aspects in Paracellular Transport

2008 ◽  
Vol 28 (6) ◽  
pp. 577-584 ◽  
Author(s):  
Constanze Will ◽  
Michael Fromm ◽  
Dominik Müller
Keyword(s):  
Tight Junction ◽  
Solute Transport ◽  
Molecular Mechanisms ◽  
Family Members ◽  
Transport Processes ◽  
Paracellular Transport ◽  
Solute Flux ◽  
Solute Fluxes ◽  
Essential Components ◽  
Renal Tubular

Claudins are essential components of the intercellular tight junction and major determinants of paracellular solute fluxes across epithelia and endothelia. Many members of this family display a distinct charge or size specificity, whereas others render the epithelium impermeable to transport. Due to intercellular localization, claudin-mediated transport processes are passive and driven by an electrochemical gradient. In epithelial tissues, claudins exhibit a temporal–spatial expression pattern corresponding with regional and local solute transport profiles. Whereas paracellular transport mechanisms in organs such as intestine and kidney have been extensively investigated, little is known about the molecular mechanisms determining solute transport in the peritoneum, and thus the determinants of peritoneal dialysis. Given the ubiquitous expression of claudins in endothelia and epithelia, it is predictable that claudins also contribute to pore formation and determination in the peritoneum, and that they are involved in solute flux. Therefore, we review the basic characteristics of claudin family members and their function as exemplified in renal tubular transport and give an outlook to what extent claudin family members might be of importance for solute reabsorption across the peritoneal membrane.

scholarly journals Flattening of Diluted Species Profile via Passive Geometry in a Microfluidic Device

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 839
Author(s):  
Michael Miles ◽  
Biddut Bhattacharjee ◽  
Nakul Sridhar ◽  
Apresio Kefin Fajrial ◽  
Kerri Ball ◽  
...  
Keyword(s):  
Solute Transport ◽  
Concentration Profile ◽  
Microfluidic Channel ◽  
Region Of Interest ◽  
Solute Concentration ◽  
Cross Sectional ◽  
Driven Systems ◽  
Solute Profile ◽  
Dynamics Simulations ◽  
Pressure Driven

In recent years, microfluidic devices have become an important tool for use in lab-on-a-chip processes, including drug screening and delivery, bio-chemical reactions, sample preparation and analysis, chemotaxis, and separations. In many such processes, a flat cross-sectional concentration profile with uniform flow velocity across the channel is desired to achieve controlled and precise solute transport. This is often accommodated by the use of electroosmotic flow, however, it is not an ideal for many applications, particularly biomicrofluidics. Meanwhile, pressure-driven systems generally exhibit a parabolic cross-sectional concentration profile through a channel. We draw inspiration from finite element fluid dynamics simulations to design and fabricate a practical solution to achieving a flat solute concentration profile in a two-dimensional (2D) microfluidic channel. The channel possesses geometric features to passively flatten the solute profile before entering the defined region of interest in the microfluidic channel. An obviously flat solute profile across the channel is demonstrated in both simulation and experiment. This technology readily lends itself to many microfluidic applications which require controlled solute transport in pressure driven systems.

scholarly journals Direct characterization of solute transport in unsaturated porous media using fast X-ray synchrotron microtomography

2020 ◽  
Vol 117 (38) ◽  
pp. 23443-23449 ◽  
Author(s):  
Sharul Hasan ◽  
Vahid Niasar ◽  
Nikolaos K. Karadimitriou ◽  
Jose R. A. Godinho ◽  
Nghia T. Vo ◽  
...  
Keyword(s):  
Solute Transport ◽  
High Speed ◽  
Three Dimensional ◽  
Concentration Field ◽  
Solute Concentration ◽  
Breakthrough Curves ◽  
Pore Scale ◽  
X Ray ◽  
Long Tails ◽  
Computed Microtomography

Solute transport in unsaturated porous materials is a complex process, which exhibits some distinct features differentiating it from transport under saturated conditions. These features emerge mostly due to the different transport time scales at different regions of the flow network, which can be classified into flowing and stagnant regions, predominantly controlled by advection and diffusion, respectively. Under unsaturated conditions, the solute breakthrough curves show early arrivals and very long tails, and this type of transport is usually referred to as non-Fickian. This study directly characterizes transport through an unsaturated porous medium in three spatial dimensions at the resolution of 3.25 μm and the time resolution of 6 s. Using advanced high-speed, high-spatial resolution, synchrotron-based X-ray computed microtomography (sCT) we obtained detailed information on solute transport through a glass bead packing at different saturations. A large experimental dataset (>50 TB) was produced, while imaging the evolution of the solute concentration with time at any given point within the field of view. We show that the fluids’ topology has a critical signature on the non-Fickian transport, which yet needs to be included in the Darcy-scale solute transport models. The three-dimensional (3D) results show that the fully mixing assumption at the pore scale is not valid, and even after injection of several pore volumes the concentration field at the pore scale is not uniform. Additionally, results demonstrate that dispersivity is changing with saturation, being twofold larger at the saturation of 0.52 compared to that at the fully saturated domain.

scholarly journals The Effect of Heterogeneity on Large Scale Solute Transport in the Unsaturated Zone

1989 ◽  
Vol 20 (1) ◽  
pp. 43-52 ◽  
Author(s):  
Georgia Destouni ◽  
Vladimir Cvetkovic
Keyword(s):  
Solute Transport ◽  
Random Fields ◽  
Unsaturated Zone ◽  
Large Scale ◽  
Control Flow ◽  
Stochastic Methods ◽  
Solute Flux ◽  
Physical Parameters ◽  
Conductivity Water ◽  
Simple Stochastic Model

The effect of natural heterogeneity on large scale solute transport in the unsaturated zone is investigated using stochastic methods. Several of the physical parameters that control flow and solute transport in the unsaturated zone are regarded as random fields. Specifically, the influence of spatial variability in recharge applied on the surface, saturated hydraulic conductivity, water content at saturation and depth to the groundwater table, on solute flux into the groundwater, is illustrated. It is shown that the prediction of solute penetration into the groundwater through the unsaturated zone is significantly affected by the natural variability in the physical parameters. A simple stochastic model for the estimation of large scale solute flux through the unsaturated zone, is provided.

scholarly journals Solute transport by suspended buoyant particles

2021 ◽  
Vol 249 ◽  
pp. 09002
Author(s):  
Iván Colecchio ◽  
Natalia Arze ◽  
Georgina Flores ◽  
Ana Quijandria ◽  
Alejandro Boschan
Keyword(s):  
Solute Transport ◽  
Solid Fraction ◽  
Light Transmission ◽  
Solute Concentration ◽  
Suspended Particles ◽  
Sharp Interface ◽  
Transmission Technique ◽  
Fingering Instability ◽  
Mass Discharge ◽  
Hele Shaw Cell

The transport of a colouring solute, driven by the buoyant displacement of microscopic suspended particles, and in the absence of net flow, is studied experimentally in a Hele Shaw cell. Initially, a sharp interface between a transparent fluid without particles and an underlying coloured suspension is obtained. From this situation, the suspended particles rise, carrying the solute in the form of a fingering instability across the interface, where a light transmission technique is used to measure the local solute concentration. This one attains an asymptotic value that increases with the solid fraction ϕ of suspended particles, and decreases with the distance to the interface. The solute mass discharge also increases with ϕ, always being relatively small (< 3%). The onset and development of the instability as the mechanism driving the transport of the solute is discussed.

scholarly journals A quadratic analytical solution of root pressure generation provides insights about bamboo and other species

2021 ◽  
Author(s):  
Dongmei Yang ◽  
Xiaolin Wang ◽  
Mengqi Yin ◽  
Yongjiang Zhang ◽  
Guoquan Peng ◽  
...  
Keyword(s):  
Analytical Solution ◽  
Fine Roots ◽  
Soil Water Potential ◽  
Quadratic Function ◽  
Solute Concentration ◽  
Solute Flux ◽  
Root Pressure ◽  
Single Root ◽  
Whole Plant ◽  
Complex Roots

We derived a steady-state model of whole root pressure generation through the combined action of all parallel segments of fine roots. This may be the first complete analytical solution for root pressure, which can be applied to complex roots/shoots. The osmotic volume of a single root is equal to that of the vessel lumen in fine roots and adjacent apoplastic spaces. Water uptake occurs via passive osmosis and active solute uptake (J_s^*, osmol s-1), resulting in the osmolal concentration Cr (mol·kg-1 of water) at a fixed osmotic volume. Solute loss occurs via two passive processes: radial diffusion of solute Km (Cr-Csoil), where Km is the diffusional constant and Csoil is the soil-solute concentration) from fine roots to soil and mass flow of solute and water into the whole plant from the end of the fine roots. The proposed model predicts the quadratic function of root pressure P_r^2+bP_r+c=0, where b and c are the functions of plant hydraulic resistance, soil water potential, solute flux, and gravitational potential. The present study investigates the theoretical dependencies of Pr on the factors detailed above and demonstrates the root pressure-mediated distribution of water through the hydraulic architecture of a 6.8-m-tall bamboo shoot.

Effect of indomethacin on papillary solute concentration in the potassium-deficient rat

1986 ◽  
Vol 250 (1) ◽  
pp. F97-F102
Author(s):  
Y. Takamitsu ◽  
R. T. Kunau
Keyword(s):  
Solute Transport ◽  
Plasma Flow ◽  
Solute Concentration ◽  
Potassium Deficiency ◽  
Base Line ◽  
Experimental Setting ◽  
Solute Addition ◽  
Multiple Factors

Administration of indomethacin or meclofenamate to normal rats increases renal papillary solute concentration primarily by enhancing solute addition. A reduction in papillary solute concentration is characteristic of potassium deficiency. Of the multiple factors probably responsible for this reduction, several can be influenced by indomethacin or meclofenamate. The present study examined the effect of indomethacin on papillary solute concentration in the potassium-deficient rat. Indomethacin increased papillary solute concentration in normal but not potassium-deficient rats when studied in the conscious hydropenic state. Since indomethacin could increase papillary plasma flow in the potassium-deficient rat, potentially negating any enhancement of solute transport into the papilla, papillary plasma flow and papillary Cl concentration were determined in anesthetized surgically manipulated rats. Base-line papillary Cl concentrations were reduced in this setting. Indomethacin increased papillary plasma flow only in potassium-deficient rats but increased papillary Cl concentration equivalently in normal and potassium-deficient rats. The ability of indomethacin to increase papillary solute concentration in the potassium-deficient rat seemingly depends upon the experimental setting.

scholarly journals Regulation of glomerulotubular balance. III. Implication of cytosolic calcium in flow-dependent proximal tubule transport

2015 ◽  
Vol 308 (8) ◽  
pp. F839-F847 ◽  
Author(s):  
Zhaopeng Du ◽  
Sheldon Weinbaum ◽  
Alan M. Weinstein ◽  
Tong Wang
Keyword(s):  
Proximal Tubule ◽  
Axial Flow ◽  
Cytosolic Calcium ◽  
Low Flow ◽  
Angiotensin Ii Receptor ◽  
Atpase Inhibitor ◽  
Flow Effect ◽  
Dependent Transport ◽  
Glomerulotubular Balance

In the proximal tubule, axial flow (drag on brush-border microvilli) stimulates Na+ and HCO3− reabsorption by modulating both Na/H exchanger 3 (NHE3) and H-ATPase activity, a process critical to glomerulotubular balance. We have also demonstrated that blocking the angiotensin II receptor decreases baseline transport, but preserves the flow effect; dopamine leaves baseline fluxes intact, but abrogates the flow effect. In the current work, we provide evidence implicating cytosolic calcium in flow-dependent transport. Mouse proximal tubules were microperfused in vitro at perfusion rates of 5 and 20 nl/min, and reabsorption of fluid ( Jv) and HCO3− ( JHCO3) were measured. We examined the effect of high luminal Ca2+ (5 mM), 0 mM Ca2+, the Ca2+ chelator BAPTA-AM, the inositol 1,4,5-trisphosphate (IP3) receptor antagonist 2-aminoethoxydiphenyl borate (2-APB), and the Ca-ATPase inhibitor thapsigargin. In control tubules, increasing perfusion rate from 5 to 20 nl/min increased Jv by 62% and JHCO3 by 104%. With respect to Na+ reabsorption, high luminal Ca2+ decreased transport at low flow, but preserved the flow-induced increase; low luminal Ca2+ had little impact; both BAPTA and 2-APB had no effect on baseline flux, but abrogated the flow effect; thapsigargin decreased baseline flow, leaving the flow effect intact. With respect to HCO3− reabsorption, high luminal Ca2+ decreased transport at low flow and mildly diminished the flow-induced increase; low luminal Ca2+ had little impact; both BAPTA and 2-APB had no effect on baseline flux, but abrogated the flow effect. These data implicate IP3 receptor-mediated intracellular Ca2+ signaling as a critical step in transduction of microvillous drag to modulate Na+ and HCO3− transport.

scholarly journals Solute Transport in the Element of Fractured Porous Medium with an Inhomogeneous Porous Block

Symmetry ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1028
Author(s):  
Bakhtiyor Khuzhayorov ◽  
Jabbor Mustofoqulov ◽  
Gafurjan Ibragimov ◽  
Fadzilah Md Ali ◽  
Bekzodjon Fayziev
Keyword(s):  
Porous Medium ◽  
Solute Transport ◽  
Solute Concentration ◽  
Graphical Form ◽  
Asymmetric Distribution ◽  
Nonlinear Kinetics ◽  
Kinetics Of Adsorption ◽  
Fractured Porous Medium ◽  
Slowing Down ◽  
Porous Block

In this paper, the problem of solute transport in a fractured-porous medium taking into account the non-equilibrium adsorption kinetic is studied. The solute transport in fractured-porous medium consisting of two fractures and a porous block between them located in a symmetric form is considered. The problem is then solved numerically by using the finite difference method. Based on the numerical results, the solute concentration and adsorption fields in the fractures and porous blocks are shown in graphical form. The effect of adsorption on the solute transport in a fractured-porous medium is then analyzed. In the case of different parameters in two zones, asymmetric distribution of the solute concentration and adsorption is obtained. The nonlinear kinetics of adsorption leads to an increase in the adsorption effects, conversely slowing down the rate of the distribution of concentration of the solute in the fluid.

Sign in / Sign up

Export Citation Format

Share Document