Fluid dynamics of gingival tissues (original) (raw)
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Serum proteins and aqueous outflow resistance
Experimental Eye Research, 1992
Purpose. Recent evidence shows that much of the protein in the anterior chamber aqueous humor enters diffusively through the root of the iris. The proximity of the protein entry point to the trabecular meshwork suggests that the protein content of the aqueous humor in the trabecular meshwork might be much higher than previously suggested. The authors were interested in investigating the possible hydrodynamic implications of these proteins.
The blood-aqueous barrier and its permeability for proteins of different molecular weight
Albrecht von Graefes Archiv f�r Klinische und Experimentelle Ophthalmologie, 1978
In aqueous humors and sera from 44 patients with cataracts, albumin, IgG, and c~-l-antitrypsin were measured using radial immunodiffusion. The mean concentrations of the three proteins were significantly smaller than values found in aqueous humors taken post mortem, but corresponded well to values found in cerebrospinal fluid. No statistically significant difference was found between men and women, normotensives and hypertensives, and patients with or without myopia of higher degree (> 6 diopters). A slight increase in protein concentrations in older patients and a relative decrease of e-l-antitrypsin is described. The aqueous humor-serum quotients of the different proteins showed a higher correlation than did the concentration of the proteins in aqueous humors. Zusammenfassung. Im Kammerwasser und Serum yon 44 an Cataract operierten Patienten wurden mit Hilfe der radialen Immundiffusion Albumin, IgG und e-l-Antitrypsin bestimmt. Die Mittelwerte waren gegenfiber Werten im KW, das post mortem gewonnen wurde, deutlich erniedrigt, stimmenjedoch gut mit den Normwerten des Liquor cerebrospinalis fiberein. Es fand sich kein statistisch gesicherter Unterschied zwischen M/innern und Frauen, Hypertonikern und Normotensiven, sowie Myopen (fiber 6 dptr) und Patienten mit nut geringen Brechungsfehlern. Es liel3 sich jedoch ein schwacher Anstieg der Proteinkonzentrationen im h6heren Alter sowie eine relative Verminderung von c~-l-Antitrypsin feststellen. Es besteht eine engere Korrelation zwischen den KW-Serum-Quotienten der einzelnen Proteine, als zwischen den Konzentrationen der Proteine im KW selbst.
Understanding Nonidealities of the Osmotic Pressure of Concentrated Bovine Serum Albumin
Journal of Colloid and Interface Science, 1998
Previously Vilker et al. (J. Colloid Interface Sci. 79(2), (1981)) reported the osmotic pressure of concentrated bovine serum albumin (BSA) up to 475 g/L in 0.15 M sodium chloride at pH 4.5, 5.4, and 7.4. The authors used a semiempirical model based on Donnan theory to predict the osmotic pressure with good agreement. However, the formal application of a three-term virial expansion with the coefficients determined from the potential energy of interaction between BSA molecules resulted in poor agreement with their data. In this study, modeling of the osmotic pressure was reexamined using a free-solvent model that considered average solute-solvent and microion-solute interactions in a mole fraction concentration variable. The resulting fits were excellent for all three pH. The model is designed with no fitted parameters; however, the model results were highly sensitive to the selected hydration and microion binding. Therefore the hydration was further regressed from its initial estimate of 1 g H 2 O/g BSA (based on water-17 O magnetic resonance studies of other globular proteins) to minimize the least-squares error between the predicted values and data. The resulting average hydration was determined to be 1.14 ؎ 0.03 g H 2 O/g BSA for all pH values. However, the standard error in hydration for each pH was no greater than ؎0.0063 g H 2 O/g BSA. These results demonstrate that solventsolute interaction and the concentration variable may be critical factors when evaluating osmotic pressure data of concentrated protein solutions.
Cell Biology International, 2006
How much does protein-associated water differ in colligative properties (freezing point, boiling point, vapor pressure and osmotic behavior) from pure bulk water? This question was approached by studying the globular protein bovine serum albumin (BSA), using changes in pH and salt concentration to alter its native structural conformation and state of aggregation. BSA osmotic pressure was investigated experimentally and analyzed using the molecular model of Fullerton et al. [Biochem Cell Biol 1992;70(12):1325]. Analysis yielded both the extent of osmotically unresponsive water (OUW) and the effective molecular weight values of the membrane-impermeable BSA solute. Manipulation of BSA conformation and aggregation by membrane-penetrating cosolutes show that alterations in pH and salt concentration change the amount of bulk water that escapes into BSA from a minimum of 1.4 to a maximum of 11.7 g water per g dry mass BSA.
The Effect of Molecular Weight on Passage of Proteins Through the Blood-Aqueous Barrier
Investigative Opthalmology & Visual Science
PURPOSE. To determine the effect of molecular weight (MW) on the concentration of plasmaderived proteins in aqueous humor and to estimate the plasma-derived and eye-derived fractions for each protein. METHODS. Aqueous humor and plasma samples were obtained during cataract surgery on an institutional review board-approved protocol. Protein concentrations were determined by ELISA and quantitative antibody microarrays. A total of 93 proteins were studied, with most proteins analyzed using 27 to 116 aqueous and 6 to 30 plasma samples. RESULTS. Plasma proteins without evidence of intraocular expression by sequence tags were used to fit a logarithmic model relating aqueous-plasma ratio (AH:PL) to MW. The log(AH:PL) appears to be well predicted by the log(MW) (P < 0.0001), with smaller proteins such as cystatin C (13 kDa) having a higher AH:PL (1:6) than larger proteins such as albumin (66 kDa, 1:300) and complement component 5 (188 kDa, 1:2500). The logarithmic model was used to calculate the eye-derived intraocular fraction (IOF) for each protein. Based on the IOF, 66 proteins could be categorized as plasma-derived (IOF<20), whereas 10 proteins were primarily derived from eye tissue (IOF >80), and 17 proteins had contribution from both plasma and eye tissue (IOF 20-80). CONCLUSIONS. Protein concentration of plasma-derived proteins in aqueous is nonlinearly dependent on MW in favor of smaller proteins. Our study demonstrates that for proper interpretation of results, proteomic studies evaluating changes in aqueous humor protein levels should take into account the plasma and eye-derived fractions.
Biophysical Journal, 1994
The nonideal osmotic pressure of bovine serum albumin (BSA) solutions was studied extensively by Scatchard and colleagues. The extent of pHand salt-dependent nonideality changes are large and unexplained. In 1992, Fullerton et al. derived new empirical expressions to describe solution nonideal colligative properties including osmotic pressure (Fullerton et al. 1992. Biochem. Cell Biol.70:1325-1331). These expressions are based on the concepts of volume occupancy and hydration force. Nonideality is accurately described by a solute/solvent interaction parameter /and an "effective" osmotic molecular weight A. This paper uses the interaction-corrected nonideal expressions for osmotic pressure to calculate the hydration /values and "effective" osmotic molecular weight of BSA, Ae, as a function of pH. Both factors vary in a predictable manner due to denaturing of the BSA molecule. Both contribute to an increase in osmotic pressure for the same protein concentration as the solution pH moves away from the isoelectric point. Increased nonideality is caused by larger hydration resulting from larger solventaccessible surface areas and by the decrease in "effective" osmotic molecular weight, Ae, due to segmental motion of denatured (filamentous) molecules.
AQP and the Control of Fluid Transport in a Salivary Gland
Journal of Membrane Biology, 2006
Experiments were performed with the perfused rat submandibular gland in vitro to investigate the nature of the coupling between transported salt and water by varying the osmolarity of the source bath and observing the changes in secretory volume flow. Glands were submitted to hypertonic step changes by changing the saline perfusate to one containing different levels of sucrose. The flow rate responded by falling to a lower value, establishing a new steady-state flow. The rate changes did not correspond to those expected from a system in which fluid production is due to simple osmotic equilibration, but were much larger. The changes were fitted to a model in which fluid production is largely paracellular, the rate of which is controlled by an osmosensor system in the basal membrane. The same experiments were done with glands from rats that had been bred to have very low levels of AQP5 (the principal aquaporin of the salivary acinar cell) in which little AQP5 is expressed at the basal membrane. In these rats, salivary secretion rates after hypertonic challenges were small and best modelled by simple osmotic equilibration. In rats which had intermediate AQP5 levels the changes in flow rate were similar to those of normal rats although their AQP5 levels were reduced.