Glomerular Filtration

Maddox, David A.; Deen, William M.; Brenner, Barry M.

doi:10.1002/cphy.cp080113

Cited by 22 publications

(47 citation statements)

References 545 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both hydraulic and plasma oncotic pressures are shown on the y axis. The values provided in Figure 2 are typical of those observed in rats, which were first directly measured by Brenner et al (7) and subsequently confirmed in many studies in rats (8) and squirrel monkeys (9). P GC averages just ,50 mmHg in normal rats and is nearly constant along the glomerular capillary network, a value significantly higher than in systemic capillaries.…”

Section: Glomerular Transcapillary Hydraulic and Oncotic Pressures Dsupporting

confidence: 79%

“…Using the value of S obtained for rat glomeruli, the calculated value of k is approximately 2500 nl/min per mmHg per cm 2 . This value is one to two orders of magnitude greater than reported for other capillary beds (8), and this allows for the high rate of glomerular filtration despite a net driving pressure of ,10 mmHg, on average, along the capillary.…”

Section: Glomerular Transcapillary Hydraulic and Oncotic Pressures Dmentioning

confidence: 69%

“…The oncotic pressure profile is highly nonlinear and is a consequence of (1) the greater local ultrafiltration pressure near the afferent end of the capillary leading to more rapid translocation of fluid and (2) the exponential relationship between the plasma protein concentration and the plasma oncotic pressure (8). In fact, under equilibrium conditions, the exact Dp curve cannot be determined.…”

Section: Glomerular Transcapillary Hydraulic and Oncotic Pressures Dmentioning

confidence: 99%

See 2 more Smart Citations

The Glomerulus

Pollak

Quaggin

Hoenig

et al. 2014

Clinical Journal of the American Society of Nephrology

142

View full text Add to dashboard Cite

The glomerulus, the filtering unit of the kidney, is a unique bundle of capillaries lined by delicate fenestrated endothelia, a complex mesh of proteins that serve as the glomerular basement membrane and specialized visceral epithelial cells that form the slit diaphragms between interdigitating foot processes. Taken together, this arrangement allows continuous filtration of the plasma volume. The dynamic physical forces that determine the single nephron glomerular filtration are considered. In addition, new insights into the cellular and molecular components of the glomerular tuft and their contribution to glomerular disorders are explored.Clin J Am Soc Nephrol 9: 1461-1469, 2014. doi: 10.2215/CJN.09400913 The GlomerulusThe glomerulus, the filtering unit of the kidney, is a specialized bundle of capillaries that are uniquely situated between two resistance vessels ( Figure 1). These capillaries are each contained within the Bowman's capsule and they are the only capillary beds in the body that are not surrounded by interstitial tissue. Therefore, a unique support structure is needed to maintain flow in these essential capillary units. In fact, all of the major components of the filter itself are unique compared with related structures in other capillary beds. The proximal component layer of the glomerular filter itself is a fenestrated endothelium, characterized by the presence of individual fenestrae on the order of 70-100 nm in diameter. These cells drape the luminal aspect of the capillary and permit filtration. The second layer of the filter, the glomerular basement membrane (GBM), is a complex mesh of extracellular proteins, including type IV collagen, laminins, fibronectins, and proteoglycans. The distal layer of the glomerular filter is composed of the visceral epithelial cells, or podocytes. These remarkable cells help to create the filtration slit diaphragm and serve as support to help sustain the integrity of the free-standing capillary loops. A third cell type, the mesangial cells, also contributes to the integrity of the glomerular tuft and the dynamic nature of filtration. Together, this elegant structure permits the formation of the primary glomerular filtrate that enters a space delimited by the visceral and parietal epithelial cells before modification during transit through the tubule.

show abstract

Section: Glomerular Transcapillary Hydraulic and Oncotic Pressures Dsupporting

confidence: 79%

Section: Glomerular Transcapillary Hydraulic and Oncotic Pressures Dmentioning

confidence: 69%

Section: Glomerular Transcapillary Hydraulic and Oncotic Pressures Dmentioning

confidence: 99%

See 1 more Smart Citation

The Glomerulus

Pollak

Quaggin

Hoenig

et al. 2014

Clinical Journal of the American Society of Nephrology

142

View full text Add to dashboard Cite

show abstract

“…This is especially true for interactions between a pore and flexible, asymmetric, and/or highly charged molecules. In a biological context, these issues have been dealt with most thoroughly in glomerular filtration (for review, see Maddox et al, 1992), which involves the pressure-driven flow of solution through channels about 0.2 m long and 10 nm in diameter, roughly comparable to the dimensions of aqueous channels in plasmodesmata. However, at 0.003 MPa, the pressure differential is far less than for SE/CC unloading.…”

Section: Molecular Sizesmentioning

confidence: 99%

“…Subject to the foregoing reservations, experimental and theoretical treatments of hindered diffusion Deen, 1988a, 1988b;Maddox et al, 1992) allow a rough estimate of the plasmodesmal channel size available for cell-to-cell post-phloem movement in wheat grains. Assuming an absence of interaction between solute and pore and a R s of 2.6 nm as the largest mobile tracer, these sources indicate that the channel would have to be about 1.5x this radius, or a diameter of approximately 8 nm, to allow appreciable mobility of such a large solute.…”

Section: Post-phloem Pathwaymentioning

confidence: 99%

Sieve Tube Unloading and Post-Phloem Transport of Fluorescent Tracers and Proteins Injected into Sieve Tubes via Severed Aphid Stylets

Fisher

Cash-Clark²

2000

Plant Physiology

View full text Add to dashboard Cite

A variety of fluorescent tracers and proteins were injected via severed aphid stylets into the sieve tubes of wheat (Triticum aestivum L.) grains to evaluate the dimensions of plasmodesmal channels involved in sieve element/companion cell (SE/CC)unloading and post-phloem transport. In the post-phloem pathway, where diffusion is the predominant mode of transport, the largest molecule to show mobility was 16-kD dextran, with a Stokes radius of 2.6 nm. This suggests that the aqueous channels for cell-to-cell transport must be about 8 nm in diameter. Even the largest tracer injected into the sieve tubes, 400-kD fluorescein-labeled Ficoll with a Stokes radius of about 11 nm, was unloaded from the SE/CC complex. However, in contrast to smaller tracers (≤3 kD, with a Stokes radius ≤ 1.2 nm), the unloading of fluorescein-labeled Ficoll and other large molecules from the SE/CC complex showed an irregular, patchy distribution, with no further movement along the post-phloem pathway. Either the plasmodesmal channels involved in SE/CCunloading are exceptionally large (perhaps as much as 42 nm in diameter), with only a very small fraction of plasmodesmata being conductive, or the larger tracers damage the plasmodesmata in some way, enlarging smaller channels.

show abstract