scholarly journals Reflection coefficients of homopore membranes: effect of molecular size and configuration.

1979 ◽  
Vol 73 (1) ◽  
pp. 49-60 ◽  
Author(s):  
J S Schultz ◽  
R Valentine ◽  
C Y Choi
Keyword(s):  
Hydrostatic Pressure ◽  
Pore Size ◽  
Osmotic Pressure ◽  
Water Flow ◽  
Molecular Size ◽  
Reflection Coefficients ◽  
Osmotic Water ◽  
Molecular Rigidity ◽  
Flow Through ◽  
Osmotic Water Flow

Osmotic water flow through membranes with uniform defined pores was measured for a variety of macromolecular solutes. Water flow increased linearly with applied hydrostatic pressure, allowing the effective osmotic pressure of the solutes to be estimated by extrapolation. Reflection coefficients for each solute-membrane combination were calculated and correlated with the ratio of solute size to pore size. For the same mean molecular size, proteins were found to have larger reflection coefficients than dextrans. Molecular rigidity may play a role in this difference in behavior.

Bestimmung von Reflexionskoeffizienten an der Membran der Alge Valonia utricularis / Determination of Reflection Coefficients of the Membrane of the Algae Valonia utricularis

1970 ◽  
Vol 25 (5) ◽  
pp. 500-504 ◽  
Author(s):  
U. Zimmermann ◽  
E. Steudle
Keyword(s):  
Hydrostatic Pressure ◽  
Osmotic Pressure ◽  
Water Flow ◽  
Linear Dependence ◽  
Volume Flow ◽  
Reflection Coefficients ◽  
Valonia Utricularis ◽  
Flow Through ◽  
Zero Flow

A zero flow method of rapidly determining reflection coefficients of giant algae cells is described.Changes of the osmotic pressure in the outside medium caused a net volume flow through the cell membranes and consequently changes of the hydrostatic pressure inside the cell. By continously measuring the hydrostatic pressure it was possible, to determine the concentration outside the cell at which no volume flow occurs.The reflection coefficients of some non-electrolyts were determined on the membrane of the mediterranean algae Valonia utricularis with an error of 3 - 4% and are discussed on the basis of the pore model.The hydrostatic pressure inside Valonia cells decreased exponentially with time, when they were put into a hypertonic aequous solution. If a linear dependence of the volume (water) flow on the hydrostatic and osmotic pressure differences is supposed, it will be possible to calculate the volume (water) flow.

Importance of molecular size and hydrogen bonding in vasopressin-stimulated urea transport

1982 ◽  
Vol 243 (1) ◽  
pp. C27-C34 ◽  
Author(s):  
R. J. Petrucelli ◽  
P. Eggena
Keyword(s):  
Hydrogen Bonding ◽  
Water Flow ◽  
Transport Mechanism ◽  
Tritiated Water ◽  
Molecular Size ◽  
Urea Transport ◽  
Acid Transport ◽  
Glutaraldehyde Fixation ◽  
Osmotic Water ◽  
Osmotic Water Flow

We have employed a variety of urea and thiourea analogues to elucidate further the vasopressin-stimulated urea transport mechanism. In the urea series there was a progressive inhibition of tracer urea transport as cylindrical radius of analogue increased from 2.9 to 3.5 A. Above 3.8 A no inhibition was found. Thiourea analogues were more potent inhibitors for comparable cylindrical radii, and compounds greater than 3.8 A again were not inhibitory. Inhibition was comparable when the inhibitor was moving in the same or opposite directions. Urea transport and its inhibition were preserved in bladders fixed with glutaraldehyde. Osmotic water flow, tritiated water flow, and uric acid transport were not affected by any analogues tested. Analogues of urea and thiourea affected the transport of labeled methylurea and thiourea in a manner similar to their effect on urea. We therefore propose that the urea transport mechanism is a channel with a cylindrical radius between 3.5 and 3.8 A that is capable of interaction with the moving species by hydrogen bonding. This model can account for the selectivity of the vasopressin-stimulated urea transport, its inhibition by urea and thiourea analogues, the facilitated transport of urea, inhibition of tracer urea flux from either the cis or the trans position, and finally the preservation of the urea transport machinery following glutaraldehyde fixation.

Effect of hydrostatic pressure on ADH induced osmotic water flow in toad bladder

1982 ◽  
Vol 393 (3) ◽  
pp. 243-247
Author(s):  
Bernard Rosenbaum ◽  
Gerard Lombardo ◽  
Vincent A. DiScala
Keyword(s):  
Hydrostatic Pressure ◽  
Water Flow ◽  
Toad Bladder ◽  
Osmotic Water ◽  
Effect Of Hydrostatic Pressure ◽  
Osmotic Water Flow

Lack of solvent drag of NaCl and NaHCO3 in rabbit proximal tubules

1982 ◽  
Vol 243 (4) ◽  
pp. F342-F348 ◽  
Author(s):  
H. R. Jacobson ◽  
J. P. Kokko ◽  
D. W. Seldin ◽  
C. Holmberg
Keyword(s):  
Water Flow ◽  
Proximal Tubules ◽  
Reflection Coefficients ◽  
Solvent Drag ◽  
Nephron Segments ◽  
Osmotic Water ◽  
Pars Recta ◽  
Made In ◽  
Osmotic Water Flow

Using in vitro microperfusion of rabbit nephron segments we measured the effects of osmotically induced water flow on net transport of HCO3 and Cl. Measurements were made in superficial and juxtamedullary proximal convolutions and in superficial pars recta. In addition, measurements were taken in the presence and absence (hypothermia) of active transport. Using osmotic gradients of 25 mM raffinose in superficial and 50 mM in juxtamedullary segments, we observed increases in water flow equal to or greater than the normal rates of volume reabsorption observed in these tubule segments. However, there were no significant changes in HCO3 and Cl flux. This lack of significant solvent drag was seen both when osmotic water flow was in the lumen-to-bath direction and when osmotic flow was in the bath-to-lumen direction. The results of these studies suggest that solvent drag does not contribute significantly to NaCl and NaHCO3 reabsorption in proximal tubules. The lack of significant solvent drag of these salts can be interpreted as indicating either that osmotically induced transepithelial water flow in proximal tubules almost exclusively traverses transcellular pathways or that proximal tubule tight junction reflection coefficients for these salts are close to unity.

A FRACTAL MODEL FOR WATER FLOW THROUGH UNSATURATED POROUS ROCKS

Fractals ◽  
2018 ◽  
Vol 26 (02) ◽  
pp. 1840015 ◽  
Author(s):  
BOQI XIAO ◽  
XIAN ZHANG ◽  
WEI WANG ◽  
GONGBO LONG ◽  
HANXIN CHEN ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Pore Size ◽  
Capillary Pressure ◽  
Water Flow ◽  
Relative Permeability ◽  
Fractal Model ◽  
Water Phase ◽  
Porous Rocks ◽  
Proposed Model ◽  
Flow Through

In this work, considering the effect of porosity, pore size, saturation of water and tortuosity fractal dimension, an analytical model for the capillary pressure and water relative permeability is derived in unsaturated porous rocks. Besides, the formulas of calculating the capillary pressure and water relative permeability are given by taking into account the fractal distribution of pore size and tortuosity of capillaries. It can be seen that the capillary pressure for water phase decreases with the increase of saturation in unsaturated porous rocks. It is found that the capillary pressure for water phase decreases as the tortuosity fractal dimension decreases. It is further seen that the capillary pressure for water phase increases with the decrease of porosity, and at low porosity, the capillary pressure increases sharply with the decrease of porosity. Besides, it can be observed that the water relative permeability increases with the increase of saturation in unsaturated porous rocks. This predicted the capillary pressure and water relative permeability of unsaturated porous rocks based on the proposed models which are in good agreement with the experimental data and model predictions reported in the literature. The proposed model improved the understanding of the physical mechanisms of water flow through unsaturated porous rocks.

Polyclonal antibodies in study of ADH-induced water channels in frog urinary bladder

1991 ◽  
Vol 261 (3) ◽  
pp. F437-F442
Author(s):  
G. Valenti ◽  
G. Calamita ◽  
M. Svelto
Keyword(s):  
Urinary Bladder ◽  
Water Flow ◽  
Apical Membrane ◽  
Polyclonal Antibodies ◽  
Immune Serum ◽  
Frog Urinary Bladder ◽  
Hormonal Stimulation ◽  
Osmotic Water ◽  
Triton X ◽  
Osmotic Water Flow

It is now generally accepted that changes in water permeability in anti-diuretic hormone (ADH)-responsive target epithelial cells result from the insertion in the plasma apical membrane of new components that contain channels for water. The specificity of these channels suggests that they are formed by intrinsic proteins having access to both facies and spanning the whole membrane. We have previously shown that Triton X-100 apical extracts from ADH-stimulated frog urinary bladder contain some proteins inserted under hormonal stimulation. In the present study we have developed polyclonal antibodies using Triton X-100 extract as an immunogen. After considering the inhibitory effect exerted by the whole immune serum on the osmotic water flow, we used different adsorption steps to select, from the immune serum, antibodies to apical membrane proteins inserted in response to the hormone. Immunoblot analysis of these selected antibodies shows that they recognize seven to eight proteins, of which 55-, 35-, 26-, and 17-kDa proteins are always present. Antibodies to these four proteins, affinity purified on nitrocellulose sheets, inhibited ADH-induced osmotic water flow. Altogether these results strongly suggest that proteins of 55, 35, 26, and 17 kDa (or at least one of them) are likely to be involved in the mechanism of water transport.

scholarly journals A model of electrodiffusion and osmotic water flow and its energetic structure

2011 ◽  
Vol 240 (22) ◽  
pp. 1835-1852 ◽  
Author(s):  
Yoichiro Mori ◽  
Chun Liu ◽  
Robert S. Eisenberg
Keyword(s):  
Water Flow ◽  
Osmotic Water ◽  
Osmotic Water Flow
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