Capillary network structure does not affect theoretical analysis of glomerular size selectivity

1995 ◽  
Vol 268 (5) ◽  
pp. F972-F979
Author(s):  
A. Remuzzi ◽  
B. Ene-Iordache
Keyword(s):  
Pressure Drop ◽  
Homogeneous Model ◽  
Wistar Rat ◽  
Size Selectivity ◽  
Membrane Pore ◽  
Heterogeneous Model ◽  
Glomerular Size ◽  
The Difference ◽  
Membrane Pore Size ◽  
Log Normal

Anatomical studies have demonstrated that the glomerular capillaries are complex and heterogeneous networks. Conventional models of glomerular size selectivity, however, are based on the assumption of simplified geometries. We developed a theoretical model of glomerular size-selective function based on the geometric data obtained in a previous reconstruction of a glomerular network from a normal Munich-Wistar rat. This heterogeneous model was compared with the homogeneous model conventionally used to calculate membrane selective parameters from the fractional clearance of two test solutes, neutral dextran and Ficoll. For both models we assumed a hypothetical log-normal distribution of pore sizes and calculated optimal membrane pore-size parameters using previously published values of fractional clearances. The difference between the sieving coefficients calculated with the two models was negligible, never exceeding 5.5%. Since the homogeneous model does not consider the pressure drop along the glomerular capillary, we also computed fractional clearances with the homogeneous model, assuming the same pressure drop as in the heterogeneous one. The differences in computed fractional clearances using the homogeneous model with and without a pressure drop were less than 1.2%. We concluded that models based on identical capillary networks can therefore be used for interpreting sieving coefficients for macromolecules.

Determination of glomerular size-selectivity in the normal rat with Ficoll.

1992 ◽  
Vol 3 (2) ◽  
pp. 214-228 ◽  
Author(s):  
J D Oliver ◽  
S Anderson ◽  
J L Troy ◽  
B M Brenner ◽  
W H Deen
Keyword(s):  
Pore Size ◽  
Size Selectivity ◽  
Membrane Pore ◽  
Charge Selectivity ◽  
Wide Range ◽  
Fractional Clearance ◽  
Glomerular Size ◽  
Molecular Sizes

Diffusion studies in vitro indicate that Ficoll behaves more like an ideal spherical molecule than does dextran, suggesting that Ficoll would be a better probe of glomerular pore size than the commonly used dextran. To examine the differences between these macromolecules in vivo, the fractional clearances of tritiated Ficoll and dextran were measured over a wide range of molecular sizes (Stokes-Einstein radius, rs, from 19 to 65 A) in normal euvolemic Munich-Wistar rats. Whole-kidney and single-nephron hemodynamic conditions were characterized through a combination of clearance and micropuncture measurements. The fractional clearance, or sieving coefficient (theta), for dextran significantly exceeded that of Ficoll at all molecular sizes examined, theta for dextran being approximately 10 times that for Ficoll for rs greater than 30 A. Thus, the results with Ficoll imply a more size-restrictive barrier than do the results with dextran. The values of theta for Ficoll approximated previously reported values for uncharged globular proteins. Although theta for Ficoll at rs = 35 A was much smaller than the corresponding value for dextran, it was still approximately 30 times greater than typical values of the filtrate-to-plasma concentration ratio reported for serum albumin (a polyanion) in the rat, in agreement with the concept that glomerular charge-selectivity normally plays an important role in the prevention of albuminuria. Three membrane-pore models were compared in their ability to represent the dextran and Ficoll sieving data. A lognormal pore-size distribution in parallel with a nonselective "shunt" pathway was found to be more effective than either an isoporous membrane with a shunt or a purely lognormal distribution. On the basis of these laboratory results and computations, Ficoll may be preferred over dextran in future studies of glomerular size-selectivity.

Size Selectivity of Diamond and Square Mesh Codends in Pelagic Herring Trawls: Only Small Herring Will Notice the Difference

1992 ◽  
Vol 49 (10) ◽  
pp. 2104-2117 ◽  
Author(s):  
Petri Suuronen ◽  
Russell B. Millar
Keyword(s):  
Relative Size ◽  
Mesh Size ◽  
The Other ◽  
Size Selectivity ◽  
The Difference ◽  
Catch Rates ◽  
Two Sides ◽  
High Catch

A twin codend trawl was fished in the northern Baltic to study the size selectivity of square mesh and diamond mesh codends of 36-mm nominal mesh size. For each codend, 15 hauls were completed with a small mesh (20 mm) codend deployed on the other side of the trawl. The relative size of the catches in the two sides of the trawl varied considerably from haul to haul (the separator section was not operating properly) and selection curves were estimated from each individual haul using a method that incorporated the differences in catching efficiency of the two sides. The length of 50% retention decreased with increased catch for both the diamond and square mesh codends, although in neither case was this relationship statistically significant. Selection curves fitted to the combined haul data were asymmetric. The square mesh codend retained significantly less small herring than the diamond mesh codend, and for larger herring the two codends had similar selectivity. In both codends, most escapes occurred at the front of the catch bulge, from the upper side of the codend. At high catch rates, mesh blockage was observed for several metres ahead of the catch bulge during the later part of the tow.

scholarly journals Optimization of protein fractionation by skim milk microfiltration: Choice of ceramic membrane pore size and filtration temperature

2016 ◽  
Vol 99 (8) ◽  
pp. 6164-6179 ◽  
Author(s):  
Camilla Elise Jørgensen ◽  
Roger K. Abrahamsen ◽  
Elling-Olav Rukke ◽  
Anne-Grethe Johansen ◽  
Reidar B. Schüller ◽  
...  
Keyword(s):  
Pore Size ◽  
Ceramic Membrane ◽  
Skim Milk ◽  
Protein Fractionation ◽  
Membrane Pore ◽  
Membrane Pore Size

Relationship between Cake Structure and Membrane Pore Size in Crossflow Filtration of Microbial Cell Suspension Containing Fine Particles

2001 ◽  
Vol 34 (12) ◽  
pp. 1524-1531 ◽  
Author(s):  
TAKAAKI TANAKA ◽  
YOSHINOBU YAMAGIWA ◽  
TETSUYA NAGANO ◽  
MASAYUKI TANIGUCHI ◽  
KAZUHIRO NAKANISHI
Keyword(s):  
Pore Size ◽  
Cell Suspension ◽  
Fine Particles ◽  
Microbial Cell ◽  
Crossflow Filtration ◽  
Membrane Pore ◽  
Membrane Pore Size

scholarly journals Increased Urine IgM and IgG2Levels, Indicating Decreased Glomerular Size Selectivity, Are Not Affected by Dalteparin Therapy in Patients with Type 2 Diabetes

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Ole Torffvit ◽  
Majid Kalani ◽  
Jan Apelqvist ◽  
Björn Eliasson ◽  
Jan W. Eriksson ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Physiological Saline ◽  
Diabetic Patients ◽  
Size Selectivity ◽  
Type 2 Diabetic Patients ◽  
Once Daily ◽  
Urinary Levels ◽  
Glomerular Size ◽  
Type 2 Diabetic

Fifty-four type 2 diabetic patients with neuroischemic foot ulcers were randomised to treatment with 5000 IU of dalteparin, (n=28), or physiological saline, (n=26), once daily until ulcer healing or for a maximum of 6 months. Thirty-three patients had normo-, 15 micro-, and 6 macroalbuminuria. The urinary levels of IgM and IgG2were elevated in 47 and 50 patients, respectively. Elevated urinary levels of IgM and IgG2indicate decreased glomerular size selectivity. Urine IgM levels were associated with IGF-1/IGFBP-1 and IGFBP-1 levels. Dalteparin treatment increased urinary levels of glycosaminoglycans (P<0.001) and serum IGFBP-1 (P<0.05) while no significant effects were seen in any of the other studied parameters. In conclusion, dalteparin therapy in patients with type 2 diabetes had no effects on urinary levels of albumin, IgM, or IgG2despite significantly increased glycosaminoglycans in urine. Elevated urinary levels of IgM and IgG2might be more sensitive markers of renal disease than albuminuria in patients with type 2 diabetes and antihypertensive therapy.

ACE inhibition and ANG II receptor blockade improve glomerular size-selectivity in IgA nephropathy

1999 ◽  
Vol 276 (3) ◽  
pp. F457-F466 ◽  
Author(s):  
Andrea Remuzzi ◽  
Norberto Perico ◽  
Fabio Sangalli ◽  
Giovanni Vendramin ◽  
Monica Moriggi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Iga Nephropathy ◽  
Ace Inhibitors ◽  
Ace Inhibition ◽  
Maximum Effect ◽  
Double Blind Study ◽  
Ang Ii ◽  
Size Selectivity ◽  
Double Blind ◽  
Glomerular Size

Protein trafficking across the glomerular capillary has a pathogenic role in subsequent renal damage. Despite evidence that angiotensin-converting enzyme (ACE) inhibitors improve glomerular size-selectivity, whether this effect is solely due to ANG II blocking or if other mediators also play a contributory role is not clear yet. We studied 20 proteinuric patients with IgA nephropathy, who received either enalapril (20 mg/day) or the ANG II receptor blocker irbesartan (100 mg/day) for 28 days in a randomized double-blind study. Measurements of blood pressure, renal hemodynamics, and fractional clearance of neutral dextran of graded sizes were performed before and after 28 days of treatment. Both enalapril and irbesartan significantly reduced blood pressure over baseline. This reduction reached the maximum effect 4–6 h after drug administration but did not last for the entire 24-h period. Despite transient antihypertensive effect, proteinuria was effectively reduced by both treatments to comparable extents. Neither enalapril nor irbesartan modified the sieving coefficients of small dextran molecules, but both effectively reduced transglomerular passage of large test macromolecules. Theoretical analysis of sieving coefficients showed that neither drug affected significantly the mean pore radius or the spread of the pore-size distribution, but both importantly and comparably reduced the importance of a nonselective shunt pathway. These data suggest that antagonism of ANG II is the key mechanism by which ACE inhibitors exert their beneficial effect on glomerular size-selective function and consequently on glomerular filtration and urinary output of plasma proteins.

scholarly journals Linear traveltime perturbation interpolation: a novel method to compute 3-D traveltimes

2015 ◽  
Vol 203 (1) ◽  
pp. 548-552 ◽  
Author(s):  
Jianzhong Zhang ◽  
Junjie Shi ◽  
Lin-Ping Song ◽  
Hua-wei Zhou
Keyword(s):  
Seismic Waves ◽  
Homogeneous Medium ◽  
Cell Boundary ◽  
Routine Method ◽  
Bilinear Interpolation ◽  
Linear Distribution ◽  
Heterogeneous Model ◽  
Computational Errors ◽  
Novel Method ◽  
The Difference

Abstract The linear traveltime interpolation has been a routine method to compute first arrivals of seismic waves and trace rays in complex media. The method assumes that traveltimes follow a linear distribution on each boundary of cells. The linearity assumption of traveltimes facilitates the numerical implementation but its violation may result in large computational errors. In this paper, we propose a new way to mitigate the potential shortcoming hidden in the linear traveltime interpolation. We use the vertex traveltimes in a calculated cell to introduce an equivalent homogeneous medium that is specific to the cell boundary from a source. Therefore, we can decompose the traveltime at a point on the cell boundary into two parts: (1) a reference traveltime propagating in the equivalent homogeneous medium and (2) a perturbation traveltime that is defined as the difference between the original and reference traveltimes. We now treat that the traveltime perturbation is linear along each boundary of cells instead of the traveltime. With the new assumption, we carry out the bilinear interpolation over traveltime perturbation to complete traveltime computation in a 3-D heterogeneous model. The numerical experiments show that the new method, the linear traveltime perturbation interpolation, is able to achieve much higher accuracy than that based on the linear traveltime interpolation.

scholarly journals Histologi Lumen Dan Endotelium Arteri Dorsal Penis Tikus Wistar (Rattus Novergicus) Yang Diinduksi Pakan Tinggi Lemak

2020 ◽  
Vol 7 (1) ◽  
pp. 73
Author(s):  
I Wayan Rosiana ◽  
I Gede Widhiantara
Keyword(s):  
Treatment Group ◽  
High Fat Diet ◽  
Wistar Rats ◽  
Wistar Rat ◽  
Lumen Diameter ◽  
Control Group ◽  
High Fat ◽  
Arterial Lumen ◽  
Male Wistar Rats ◽  
The Difference

This study aims to look at the histopathological picture of the dorsal arteries of the penis of the hiperlipidemic wistar rats (Rattus novergicus) induction by high-fat diet that seen in terms of lumen diameter and thickness of the arterial endotelium wall. Hyperlipidemia is a risk factor for ateriosclerosis in the penile arteries causing erectile dysfunction in men. This study is an experimental study with a randomized posttest only control goup design. The sample are  10 individuals adult male wistar rats aged 3-4 months with a range of body weight 150-200 grams. Before treatment, adaptation was carried out for 7 days. After that the sample rats in the treatment group were made hyperlidemic by feeding lard for 50 days. Then surgery is performed for histopathological preparations at the posttest. To determine the differences in endotelium thickness and arterial lumen diameter in the two groups, an independent t-test was used. Thick diameter data of the endotelium and dorsal arteries of the penis of the wistar rat between the lower treatment group and the control group. The difference that occurred was statistically significant (p <0.05). So it can be concluded that the provision of high-fat diet (hyperlipidemia) decreases the lumen diameter and endotelium thickness of dorsal arteries penis. Keywords: Dorsal arteries, high-fat diet, Wistar rats

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