scholarly journals A distributed solute model: an extended two-pore model with application to the glomerular sieving of Ficoll

2018 ◽  
Vol 314 (6) ◽  
pp. F1108-F1116 ◽  
Author(s):  
Carl M. Öberg ◽  
Joseph J. Groszek ◽  
Shuvo Roy ◽  
William H. Fissell ◽  
Bengt Rippe
Keyword(s):  
Size Distribution ◽  
Pore Radius ◽  
Molecular Size ◽  
Geometric Standard Deviation ◽  
Pore Model ◽  
Filtration Barrier ◽  
Small Pore ◽  
The Difference ◽  
A Charge ◽  
Nanopore Membranes

One of the many unresolved questions regarding the permeability of the glomerular filtration barrier is the reason behind the marked difference in permeability between albumin and polysaccharide probe molecules such as Ficoll and dextran of the same molecular size. Although the differences in permeability have been mainly attributed to charge effects, we have previously shown that this would require a highly charged filtration barrier, having a charge density that is ~10 times more than that on the albumin molecule. In this article, the classic two-pore model was extended by introducing size distributions on the solute molecules, making them conformationally flexible. Experimental sieving data for Ficoll from the rat glomerulus and from precision-made silicon nanopore membranes were analyzed using the model. For the rat glomerulus a small-pore radius of 36.2 Å and a geometric standard deviation (gSD) for the Ficoll size-distribution of 1.16 were obtained. For the nanopore membranes, a gSD of 1.24 and a small-pore radius of 43 Å were found. Interestingly, a variation of only ~16% in the size of the polysaccharide molecule is sufficient to explain the difference in permeability between albumin and Ficoll. Also, in line with previous data, the effects of applying a size distribution on the solute molecule are only evident when the molecular size is close to the pore size. Surely there is at least some variation in the pore radii, and, likely, the gSD obtained in the current study is an overestimation of the “true” variation in the size of the Ficoll molecule.

Response of alveolar epithelial solute permeability to changes in lung inflation

1980 ◽  
Vol 49 (6) ◽  
pp. 1032-1036 ◽  
Author(s):  
E. A. Egan
Keyword(s):  
Pore Radius ◽  
Alveolar Epithelium ◽  
Molecular Size ◽  
High Volume ◽  
Lung Inflation ◽  
Solute Permeability ◽  
Alveolar Epithelial ◽  
The Difference ◽  
Total Capacity ◽  
Inflation Volume

The relation between the solute permeability of th alveolar epithelium, characterized as a pore radius, and lung inflation was studied in anesthetized dogs. Pore radius was calculated from measurements of the rate of efflux of several radiolabeled solutes of known molecular size from alveolar saline. Individual animals were studied at two or more separate inflation volumes. The pore radius during the first volume studied averaged 20 A in high-volume animals (mean inflation 82% of capacity) and 15 A at lower volume (mean inflation, 47% of capacity). The difference was significantly P < 0.05. Lungs inflated to total capacity showed free solute movement across the lung epithelium. Increasing inflation volume in an animal always produced a larger pore radius. Decreasing the inflation volume did not produce a smaller pore radius; it remained the same or became larger. Volume induced increases in lung epithelial solute permeability do not reverse immediately at lower volumes, suggesting this phenomenon represents lung injury.

A distributed two-pore model: theoretical implications and practical application to the glomerular sieving of Ficoll

2014 ◽  
Vol 306 (8) ◽  
pp. F844-F854 ◽  
Author(s):  
Carl M. Öberg ◽  
Bengt Rippe
Keyword(s):  
Pore Radius ◽  
Diffusion Length ◽  
Wide Distribution ◽  
Analytic Solutions ◽  
Length Ratio ◽  
Pore Sizes ◽  
Filtration Barrier ◽  
Large Pore ◽  
Small Pore ◽  
Pore Area

In the present study, an extended two-pore theory is presented where the porous pathways are continuously distributed according to small- and large-pore mean radii and SDs. Experimental glomerular sieving data for Ficoll were analyzed using the model. In addition, several theoretical findings are presented along with analytic solutions to many of the equations used in distributed pore modeling. The results of the data analysis revealed a small-pore population in the glomerular capillary wall with a mean radius of 36.6 Å having a wide arithmetic SD of ∼5 Å and a large-pore radius of 98.6 Å with an even wider SD of ∼44 Å. The small-pore radius obtained in the analysis was close to that of human serum albumin (35.5 Å). By reanalyzing the data and setting the distribution spread of the model constant, we discovered that a narrow distribution is compensated by an increased mean pore radius and a decreased pore area-to-diffusion length ratio. The wide distribution of pore sizes obtained in the present analysis, even when considering electrostatic hindrance due to the negatively charged barrier, is inconsistent with the high selectivity to proteins typically characterizing the glomerular filtration barrier. We therefore hypothesize that a large portion of the variance in the distribution of pore sizes obtained is due to the molecular “flexibility” of Ficoll, implying that the true variance of the pore system is lower than that obtained using flexible probes. This would also, in part, explain the commonly noted discrepancy between the pore area-to-diffusion length ratio and the filtration coefficient.

Determination of the Size Distribution of Dissolved Organics in Effluents

1973 ◽  
Vol 8 (1) ◽  
pp. 1-15 ◽  
Author(s):  
L.A. Addie ◽  
K.L. Murphy ◽  
J.L. Robertson
Keyword(s):  
Size Distribution ◽  
Biological Treatment ◽  
Oxygen Demand ◽  
Molecular Size ◽  
Monitoring Systems ◽  
Clean Surface ◽  
Sephadex Column ◽  
Dissolved Organics ◽  
Molecular Size Distribution

Abstract The importance of removing the small amounts of residual organics is increasing as the sources of clean surface water decrease. Knowledge of the nature of these soluble residual organics will be needed in order to assess the type of treatment required for their removal. Residual organics in three different biological treatment plants were analyzed and compared. An attempt was made to characterize these organics by a molecular size distribution on a Sephadex column monitored by differential ultraviolet and refractive index detectors. The organic carbon and chemical oxygen demand of the fractions collected from the column was also determined. An investigation of some of the problems inherent in the monitoring systems was conducted.

Molecular Size Distribution of Lignin in Wood

Nature ◽  
1967 ◽  
Vol 214 (5086) ◽  
pp. 410-411 ◽  
Author(s):  
W. BROWN ◽  
S. I. FALKEHAG ◽  
E. B. COWLING
Keyword(s):  
Size Distribution ◽  
Molecular Size ◽  
Molecular Size Distribution

A Study of the Malpighian Tubules of the Pill Millipede, Glomeris marginata (Villers)

1974 ◽  
Vol 60 (1) ◽  
pp. 41-51
Author(s):  
PATRICIA ANNE FARQUHARSON
Keyword(s):  
Size Distribution ◽  
Fluid Transport ◽  
Molecular Size ◽  
Malpighian Tubules ◽  
Inverse Relation ◽  
Fluid Production ◽  
Molecular Size Distribution ◽  
Molecular Sieving ◽  
Tubule Fluid ◽  
Tubule Wall

1. Tubule fluid:medium ratios (TF/M) have been measured for inulin, glucose, LMWD and HMWD. These TF/M ratios were surprisingly high. 2. The tubule appears to act as a molecular filter; that is to say, molecules move through the tubule wall in inverse relation to their size. This is best illustrated using polyvinyl pyrrolidone as a tracer. The molecular size distribution of PVP fractions present in tubule fluid differs markedly from the molecular size distribution of PVP in the bathing Ringer. 3. No correlation can be made between the inulin and glucose TF/M and the rate of fluid production. However, the inverse relationship between TF/M and rate of fluid production for dextrans indicates a molecular sieving effect. 4. The significance of these results is discussed with reference to models of fluid transport.

scholarly journals Measurements in a highly polluted Asian mega city: observations of aerosol number size distribution, modal parameters and nucleation events

2005 ◽  
Vol 5 (1) ◽  
pp. 57-66 ◽  
Author(s):  
P. Mönkkönen ◽  
I. K. Koponen ◽  
K. E. J. Lehtinen ◽  
K. Hämeri ◽  
R. Uma ◽  
...  
Keyword(s):  
Size Distribution ◽  
Urban Areas ◽  
Geometric Mean ◽  
Formation Rate ◽  
Geometric Standard Deviation ◽  
Modal Parameters ◽  
Number Size Distribution ◽  
High Concentrations ◽  
Rural Sites ◽  
Aitken Mode

Abstract. Diurnal variation of number size distribution (particle size 3-800nm) and modal parameters (geometric standard deviation, geometric mean diameter and modal aerosol particle concentration) in a highly polluted urban environment was investigated during October and November 2002 in New Delhi, India. Continuous monitoring for more than two weeks with the time resolution of 10min was conducted using a Differential Mobility Particle Sizer (twin DMPS). The results indicated clear increase in Aitken mode (25-100nm) particles during traffic peak hours, but towards the evenings there were more Aitken mode particles compared to the mornings. Also high concentrations of accumulation mode particles (>100nm) were detected in the evenings only. In the evenings, biomass/refuse burning and cooking are possible sources beside the traffic. We have also shown that nucleation events are possible in this kind of atmosphere even though as clear nucleation events as observed in rural sites could not be detected. The formation rate of 3nm particles (J3) of the observed events varied from 3.3 to 13.9cm-3s-1 and the growth rate varied from 11.6 to 18.1nmh-1 showing rapid growth and high formation rate, which seems to be typical in urban areas.

scholarly journals Arctic smoke – aerosol characteristics during a record air pollution event in the European Arctic and its radiative impact

2007 ◽  
Vol 7 (1) ◽  
pp. 2275-2324 ◽  
Author(s):  
R. Treffeisen ◽  
P. Turnved ◽  
J. Ström ◽  
A. Herber ◽  
J. Bareiss ◽  
...  
Keyword(s):  
Air Pollution ◽  
Size Distribution ◽  
Climate Model ◽  
Atmospheric Stability ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Geometric Standard Deviation ◽  
Transfer Model ◽  
Climatic Effects ◽  
Pollution Event

Abstract. In early May 2006 a record high air pollution event was observed at Ny-Ålesund, Spitsbergen. An atypical weather pattern established a pathway for the rapid transport of biomass burning aerosols from agricultural fires in Eastern Europe to the Arctic. Atmospheric stability was such that the smoke was constrained to low levels, within 2 km of the surface during the transport. A description of this smoke event in terms of transport and main aerosol characteristics can be found in Stohl et al. (2007). This study puts emphasis on the radiative effect of the smoke. The aerosol size distribution was characterized as having an accumulation mode centered at 165–185 nm and almost 1.6 for geometric standard deviation of the mode. Nucleation and small Aitken mode particles were almost completely suppressed within the smoke plume measured at Ny-Ålesund. Chemical and microphysical aerosol information obtained at Mt. Zeppelin (474 m.a.s.l) was used to derive input parameters for a one-dimensional radiation transfer model to explore the radiative effects of the smoke. The daily mean heating rate calculated on 2 May 2006 for the average size distribution and measured chemical composition reached 0.55 K day−1 at 0.5 km altitude for the assumed external mixture of the aerosols but showing much higher heating rates for an internal mixture (1.7 K day−1). In comparison a case study for March 2000 showed that the local climatic effects due to Arctic haze, using a regional climate model, HIRHAM, amounts to a maximum of 0.3 K day−1 of heating at 2 km altitude (Treffeisen et al., 2005).

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