Protein osmotic pressure gradients and microvascular reflection coefficients

1997 ◽  
Vol 273 (2) ◽  
pp. H997-H1002 ◽  
Author(s):  
R. E. Drake ◽  
S. Dhother ◽  
R. A. Teague ◽  
J. C. Gabel
Keyword(s):  
Reflection Coefficient ◽  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Reflection Coefficients ◽  
Pressure Gradients ◽  
Fluid Filtration ◽  
The Mean ◽  
Osmotic Reflection Coefficient ◽  
New Equation ◽  
Osmotic Pressure Gradient

Microvascular membranes are heteroporous, so the mean osmotic reflection coefficient for a microvascular membrane (sigma d) is a function of the reflection coefficient for each pore. Investigators have derived equations for sigma d based on the assumption that the protein osmotic pressure gradient across the membrane (delta II) does not vary from pore to pore. However, for most microvascular membranes, delta II probably does vary from pore to pore. In this study, we derived a new equation for sigma d. According to our equation, pore-to-pore differences in delta II increase the effect of small pores and decrease the effect of large pores on the overall membrane osmotic reflection coefficient. Thus sigma d for a heteroporous membrane may be much higher than previously derived equations indicate. Furthermore, pore-to-pore delta II differences increase the effect of plasma protein osmotic pressure to oppose microvascular fluid filtration.

Measurement of osmotic reflection coefficient for small molecules in cat hindlimbs

1989 ◽  
Vol 256 (1) ◽  
pp. H282-H290 ◽  
Author(s):  
M. B. Wolf ◽  
P. D. Watson
Keyword(s):  
Skeletal Muscle ◽  
Reflection Coefficient ◽  
Small Molecules ◽  
Osmotic Pressure ◽  
Maximum Rate ◽  
Reflection Coefficients ◽  
Flow Rates ◽  
Perfusate Flow ◽  
Arterial Inflow ◽  
Osmotic Reflection Coefficient

Capillary osmotic reflection coefficients (sigma) for NaCl, urea, sucrose, and raffinose were measured in the isolated, perfused cat hindlimb using the osmotic transient technique. sigma were determined from the ratio of the maximum rate of transcapillary absorption [delta Jv(max)] to the increase in the osmotic pressure (25-35 mosmol/kg H2O) in the arterial inflow (delta pi a) produced by adding one of the molecules to an albumin-electrolyte perfusate containing isoproterenol (greater than 10(-7) M). delta Jv (max) was determined from organ weight and delta pi a from perfusate osmolalities. For each molecule, the delta Jv(max)/delta pi a ratio increased monotonically with perfusate flow rates (Q) to Q greater than 100 ml.min-1.100 g-1. This ratio was independent of the size of the delta pi a. Apparent sigma values were calculated by dividing these ratios by the capillary hydraulic capacity determined in other studies. At low Q, apparent sigma was comparable to the approximately 0.1 values found by others in skeletal muscle. At the highest Q, apparent sigma for these molecules were at least 0.5. These data are consistent with at least 50% of transcapillary water flow moving through a water-exclusive pathway.

Pulmonary microvascular reflection coefficients estimated with modified lymphatic washdown technique

1997 ◽  
Vol 272 (1) ◽  
pp. H382-H385 ◽  
Author(s):  
R. E. Drake ◽  
S. Dhother ◽  
J. C. Gabel
Keyword(s):  
Reflection Coefficient ◽  
Osmotic Pressure ◽  
Plasma Protein ◽  
Lung Tissue ◽  
Evans Blue ◽  
Filtration Rate ◽  
Blue Dye ◽  
Reflection Coefficients ◽  
Fluid Filtration ◽  
Tissue Protein

Many investigators have used the lymphatic protein washdown technique to estimate the pulmonary microvascular membrane reflection coefficient to protein (sigma d). With that technique, the investigator causes a high microvascular filtration rate then estimates sigma d from the lymph and plasma protein concentrations. However the lymph may contain protein washed from the lung tissue, and the tissue protein may cause investigators to underestimate sigma d. Plasma protein osmotic pressure (IIc) may cause investigators to underestimate sigma d because IIc opposes fluid filtration. To minimize the effect of IIc, we decreased IIc to 5.6 +/- 1.1 mmHg in five anesthetized sheep. We increased the microvascular filtration rate by increasing pulmonary microvascular pressure to 22 +/- 3 mmHg. Then we tagged plasma protein with Evans blue dye and estimated sigma d from the lymph and plasma dye concentrations. Because tissue protein was not tagged, it did not interfere with our sigma d estimate. Our sigma d estimate (0.79 +/- 0.08) was much higher than previous estimates in anesthetized animals.

Impact of hetastarch on the intestinal microvascular barrier during ECLS

2000 ◽  
Vol 88 (4) ◽  
pp. 1374-1380 ◽  
Author(s):  
Charles S. Cox ◽  
Michael Brennan ◽  
Steven J. Allen
Keyword(s):  
Reflection Coefficient ◽  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Life Support ◽  
Extracorporeal Life Support ◽  
Ringer Solution ◽  
Colloid Osmotic Pressure ◽  
Tissue Water ◽  
Protein Clearance ◽  
Osmotic Pressure Gradient

The effects of hetastarch on microvascular fluid flux were determined in anesthetized dogs undergoing extracorporeal life support (ECLS) with a roller pump and membrane oxygenator. ECLS with a lactated Ringer priming solution resulted in a decrease in microvascular protein reflection coefficient and an increase in transvascular protein clearance. Use of a 6% hetastarch priming solution attenuated the decrease in microvascular protein reflection coefficient and blunted the increase in transvascular protein clearance. Ileal tissue water increased in the group treated with the lactated Ringer priming solution compared with the group treated with 6% hetastarch. The effective plasma-to-interstitial colloid osmotic pressure gradient was greater in the group treated with hetastarch than in the group treated with lactated Ringer solution. Hetastarch decreases the edema associated with ECLS. The reduction in edema is due to the maintenance of the plasma-to-interstitial colloid osmotic pressure gradient and the reduction in the microvascular permeability to protein.

Freezing point depression of rat kidney slices during water diuresis and antidiuresis

1960 ◽  
Vol 199 (5) ◽  
pp. 915-918 ◽  
Author(s):  
George A. Bray
Keyword(s):  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Freezing Point ◽  
Rat Kidney ◽  
Freezing Point Depression ◽  
Water Diuresis ◽  
Outer Medulla ◽  
Kidney Slices ◽  
Outer Stripe ◽  
Osmotic Pressure Gradient

The freezing point depression of slices of rat kidney removed during water diuresis or antidiuresis has been investigated with a microcryoscopic method. The osmotic pressure gradient in the inner medulla first demonstrated by Wirz has been confirmed. The inner medulla was found to be hypertonic to plasma during water diuresis. Hypotonic tubules were present throughout the cortex and outer stripe of the outer medulla.

New Thermal Energy Converters Based on Polyelectrolyte Hydrogels

2014 ◽  
Vol 1037 ◽  
pp. 117-122 ◽  
Author(s):  
Ibragim Suleimenov ◽  
Andrei Falaleev ◽  
Dina Shaltykova ◽  
Sergei Panchenko ◽  
Grigoriy Mun
Keyword(s):  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Thermal Energy ◽  
Motion Equations ◽  
Mobile Ions ◽  
Local Value ◽  
Osmotic Pressure Gradient ◽  
Energy Converters

The theory of thermal energy converters based on polyelectrolyte hydrogels has been developed. The possibility of providing the circulation of a fluid in the contour by controlled variations of the local value of concentrations of the mobile ions that cause an osmotic pressure gradient was shown. On the basis of the solution of motion equations of the mobile ions the numerical estimates of parameters of proposed type of circulation contour are given.

Effect of hemolysis on reflection coefficient determined by endogenous blood indicators

1987 ◽  
Vol 62 (6) ◽  
pp. 2252-2257 ◽  
Author(s):  
M. B. Maron ◽  
C. F. Pilati ◽  
K. C. Maender
Keyword(s):  
Reflection Coefficient ◽  
Plasma Protein ◽  
Protein Concentration ◽  
Venous Pressure ◽  
Hemoglobin Concentration ◽  
Plasma Protein Concentration ◽  
Fluid Filtration ◽  
Lung Lobe ◽  
Before And After ◽  
Osmotic Reflection Coefficient

The osmotic reflection coefficient (sigma) can be estimated from the increases in hematocrit and plasma protein concentration that result from fluid filtration occurring in an isolated perfused organ. We determined what effect perfusion pump-induced hemolysis has on the value of sigma determined by this technique in both the isolated canine left lower lung lobe (LLL) and forelimb by comparing estimates of sigma obtained before and after correction for hemolysis. Hemolysis was corrected by using the slopes of the relationships between hematocrit and plasma hemoglobin concentration and between the plasma protein and hemoglobin concentrations to correct hematocrit and protein concentration to a state of zero hemolysis. Uncorrected estimates of sigma in the LLL were 1.19 +/- 0.14 (SE) at a venous pressure (Pv) of 12 Torr (n = 7) and 0.90 +/- 0.02 at a Pv of 19 Torr (n = 6). Both sets of LLL's yielded sigma values of 0.77 +/- 0.03 after hemolysis correction. In the forelimb (n = 5), uncorrected and corrected estimates of sigma of 0.99 +/- 0.03 and 0.85 +/- 0.01, respectively, were obtained. The latter values were similar to sigma's (0.88 +/- 0.01) determined by lymph analysis in five additional forelimbs. We conclude that hemolysis results in overestimates of sigma. After hemolysis correction, this technique yields similar results to those obtained from lymph analysis for the forelimb and from published values for the LLL.

scholarly journals Sodium Movement across Single Perfused Proximal Tubules of Rat Kidneys

1964 ◽  
Vol 47 (6) ◽  
pp. 1175-1194 ◽  
Author(s):  
Gerhard Giebisch ◽  
Ruth M. Klose ◽  
Gerhard Malnic ◽  
W. James Sullivan ◽  
Erich E. Windhager
Keyword(s):  
Pressure Gradient ◽  
Osmotic Pressure ◽  
Water Movement ◽  
Rat Kidney ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Colloid Osmotic Pressure ◽  
Concentration Difference ◽  
The Relationship ◽  
Osmotic Pressure Gradient

Using perfusion techniques in single proximal tubule segments of rat kidney, the relationship between net sodium movement and active transport of ions, as measured by the short-circuit method, has been studied. In addition, the role of the colloid-osmotic pressure gradient in proximal transtubular fluid and sodium movement has been considered. Furthermore, the limiting concentration gradient against which sodium movement can occur and the relationship between intratubular sodium concentration and fluid transfer have been investigated. Comparison of the short-circuit current with the reabsorptive movement of sodium ions indicates that this process is largely, perhaps exclusively, active in nature. No measurable contribution of the normally existing colloid-osmotic pressure gradient to transtubular water movement was detected. On the other hand, fluid movement across the proximal tubular epithelium is dependent upon the transtubular sodium gradient and is abolished when a mean concentration difference of 50 mEq/liter is exceeded.

The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 1 — Mean Quantities

1995 ◽  
Author(s):  
Scott P. Mislevy ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Gradient ◽  
Temperature Profile ◽  
Adverse Pressure Gradient ◽  
Surface Heat ◽  
Pressure Gradients ◽  
Surface Heat Transfer ◽  
Mean Temperature ◽  
The Mean

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6%. The acceleration parameter, K=vU¯∞2dU¯∞dx, was kept constant along the test section. Both surface heat transfer and boundary layer measurements were conducted. The boundary layer measurements were conducted with a three-wire probe (two velocity wires and one temperature wire) for two representative cases, K1=−0.51 × 10−6 and K2=−1.05 × 10−6. The surface heat transfer measurements were conducted for K values ranging from −0.045 × 10−6 to −1.44 × 10−6 over five divergent wall angles. The Stanton numbers of the cases with adverse pressure gradients were greater than that of the zero-pressure-gradient turbulent correlation in the low-Reynolds number turbulent flow, and the difference increased as the adverse pressure gradient was increased. The adverse pressure gradient caused earlier transition onset and shorter transition length based on Rex, Reδ*, and Reθ in comparison to zero-pressure-gradient conditions. As expected, there was a reduction in skin friction as the adverse pressure gradient increased. In the U+-Y+ coordinates, the adverse pressure gradients had a significant effect on the mean velocity profiles in the near-wall region for the late-laminar and early transition stations. The mean temperature profile was observed to precede the velocity profile in starting and ending the transition process, opposite to what occurred in favorable pressure gradient cases in previous studies. A curve fit of the turbulent temperature profile in the log-linear region for the K2 case gave a conduction layer thickness of Y+=9.8 and an average Prt=0.71. In addition, the wake region of the turbulent mean temperature profile was significantly suppressed.

The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 1—Mean Quantities

1996 ◽  
Vol 118 (4) ◽  
pp. 717-727 ◽  
Author(s):  
S. P. Mislevy ◽  
T. Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Pressure Gradient ◽  
Temperature Profile ◽  
Adverse Pressure Gradient ◽  
Surface Heat ◽  
Pressure Gradients ◽  
Surface Heat Transfer ◽  
Mean Temperature ◽  
The Mean

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6 percent. The acceleration parameter, K, was kept constant along the test section. Both surface heat transfer and boundary layer measurements were conducted. The boundary layer measurements were conducted with a three-wire probe (two velocity wires and one temperature wire) for two representative cases, K1 = −0.51 × 10−6 and K2 = −1.05 × 10−6. The surface heat transfer measurements were conducted for K values ranging from −0.045 × 10−6 to −1.44 × 10−6 over five divergent wall angles. The Stanton numbers of the cases with adverse pressure gradients were greater than that of the zero-pressure-gradient turbulent correlation in the low-Reynolds-number turbulent flow, and the difference increased as the adverse pressure gradient was increased. The adverse pressure gradient caused earlier transition onset and shorter transition length based on Rex, Reδ*, and Reθ in comparison to zero-pressure-gradient conditions. As expected, there was a reduction in skin friction as the adverse pressure gradient increased. In the U+−Y+ coordinates, the adverse pressure gradients had a significant effect on the mean velocity profiles in the near-wall region for the late-laminar and early transition stations. The mean temperature profile was observed to precede the velocity profile in starting and ending the transition process, opposite to what occurred in favorable pressure gradient cases in previous studies. A curve fit of the turbulent temperature profile in the log-linear region for the K2 case gave a conduction layer thickness of Y+ = 9.8 and an average Prt = 0.71. In addition, the wake region of the turbulent mean temperature profile was significantly suppressed.

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