NaCl Permeability Research Articles

Permeability and partition coefficient of aqueous sodium chloride in soft contact lenses

AbstractTransport of physiologic saline through soft contact lenses is important to on‐eye behavior. Using a specially designed Stokes‐diaphragm cell, we measure aqueous NaCl permeabilities through commercial soft contact lenses at 35°C. The permeabilities increase exponentially with the water content of the lenses spanning a range from 10−7 to 10−5 cm2/s. Equilibrium partition coefficients are obtained by the back‐extraction of lenses initially immersed in 1M aqueous NaCl. Partition coefficients also increase with lens water content but over a smaller range, from 0.1 to 0.7. Because the partition coefficient values are smaller than the water content of the lenses, ideal theory is not followed. Donnan exclusion, bound water, and excluded volume are proposed explanations. The diffusion coefficients of aqueous NaCl through soft contact lenses increase with increasing lens water content following free‐volume theory. Aqueous NaCl diffusivities in the lower water‐content lenses are smaller than the diffusion coefficient of NaCl in water by factors up to 100 indicating very tortuous diffusion paths. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Stagnant deoxygenated growth enhances root suberization and lignifications, but differentially affects water and NaCl permeabilities in rice (Oryza sativa L.) roots

It has been shown that rice roots grown in a stagnant medium develop a tight barrier to radial oxygen loss (ROL), whereas aerated roots do not. This study investigated whether the induction of a barrier to ROL affects water and solute permeabilities. Growth in stagnant medium markedly reduced the root growth rate relative to aerated conditions. Histochemical studies revealed an early deposition of Casparian bands (CBs) and suberin lamellae (SL) in both the endodermis (EN) and exodermis, and accelerated lignification of stagnant roots. The absolute amounts of suberin, lignin and esterified aromatics (coumaric and ferulic acid) in these barriers were significantly higher in stagnant roots. However, correlative permeability studies revealed that early deposition of barriers in stagnant roots failed to reduce hydraulic conductivity (Lp(r) ) below those of aerated roots. In contrast to Lp(r) , the NaCl permeability (P(sr) ) of stagnant roots was markedly lower than that of aerated roots, as indicated by an increased reflection coefficient (σ(sr) ). In stagnant roots, P(sr) decreased by 60%, while σ(sr) increased by 55%. The stagnant medium differentially affected the Lp(r) and P(sr) of roots, which can be explained in terms of the physical properties of the molecules used and the size of the pores in the apoplast.

Water and solute permeabilities of Arabidopsis roots in relation to the amount and composition of aliphatic suberin

Although it is implied that suberized apoplastic barriers of roots negatively correlate with water and solute permeabilities, direct transport measurements across roots with altered amounts and compositions of aliphatic suberin are scarce. In the present study, hydroponically grown Arabidopsis wild types (Col8 and Col0) and different suberin mutants with altered amounts and/or compositions (horst, esb1-1, and esb1-2) were used to test this hypothesis. Detailed histochemical studies revealed late development of Casparian bands and suberin lamellae in the horst mutant compared with wild types and esb mutants. Suberin analysis with gas chromatography and mass spectrometry (GC-MS) showed that the horst mutant had ∼33% lower amounts of aliphatic monomers than Col8 and Col0. In contrast, enhanced suberin mutants (esb1-1 and esb1-2) had twice the amount of suberin as the wild types. Correlative permeability measurements, which were carried out for the first time with a root pressure probe for Arabidopsis, revealed that the hydraulic conductivity (Lpr) and NaCl permeability (Psr) of the whole root system of the horst mutant were markedly greater than in the respective wild types. This was reflected by the total amounts of aliphatic suberin determined in the roots. However, increased levels of aliphatic suberin in esb mutants failed to reduce either water or NaCl permeabilities below those of the wild types. It was concluded that the simple view and the conventional assumption that the amount of root suberin negatively correlates with permeability may not always be true. The aliphatic monomer arrangement in the suberin biopolymer and its microstructure also play a role in apoplastic barrier formation.

Fundamental salt and water transport properties in directly copolymerized disulfonated poly(arylene ether sulfone) random copolymers

Water and sodium chloride solubility, diffusivity and permeability in disulfonated poly(arylene ether sulfone) (BPS) copolymers were measured for both acid and salt form samples at sulfonation levels from 20 to 40 mol percent. The hydrophilicity of these materials, based on water uptake, increased significantly as sulfonation level increased. The water permeability of BPS materials in both the salt and acid forms increases more than one order of magnitude as sulfonation level increases from 20% to 40%, while NaCl permeability increases by two orders of magnitude. The water and salt diffusivity and permeability were correlated with water uptake, consistent with expectations from free volume theory. In addition, a tradeoff was observed between water/salt solubility, diffusivity, and permeability selectivity and water solubility, diffusivity and permeability, respectively. This finding suggests a water/salt permeability/selectivity tradeoff, similar to that operative in gas separation polymers, in this family of polymers.

Surface modification of thin-film composite polyamide reverse osmosis membranes by coating N-isopropylacrylamide-co-acrylic acid copolymers for improved membrane properties

Commercial thin-film composite aromatic polyamide reverse osmosis membranes were modified by depositing N-isopropylacrylamide-co-acrylic acid copolymers (P(NIPAm-co-AAc)) on the membrane surface, and the modified membranes showed improved membrane properties. P(NIPAm-co-AAc) copolymers were synthesized by free radical copolymerization and their aqueous solutions of different concentrations were used to modify the polyamide membranes through in situ surface coating technique. The deposition of P(NIPAm-co-AAc) layer was shown to increase membrane surface hydrophilicity and surface charge at neutral pH, but offer additional resistance to water permeation. The effect of surface modification on membrane salt permeability was investigated through permeation tests with different salts under different pHs. The membrane modification was found to decrease the salt permeability of NaCl and Na2SO4 under neutral and alkaline conditions, and the decrease was significant for Na2SO4 that has divalent anions than for NaCl that has monovalent anions. The results of the fouling experiments with bovine serum albumin (BSA) aqueous solution and washing experiments with de-ionized water of different temperatures also revealed that the P(NIPAm-co-AAc) coating layer improved the fouling resistance to BSA and the cleaning efficiency. The phase transition of the coating layer under temperatures above its LCST would facilitate the removal of foulants located on the membrane surface.

Characterization of sodium chloride and water transport in crosslinked poly(ethylene oxide) hydrogels

Three series of crosslinked poly(ethylene oxide) (XLPEO) hydrogel materials were synthesized via UV-photopolymerization of aqueous solutions containing (1) poly(ethylene glycol) diacrylate (PEGDA) ( n = 10), (2) PEGDA ( n = 13), and (3) mixtures of PEGDA ( n = 13) and poly(ethylene glycol) acrylate (PEGA) ( n = 7), where n is the number of ethylene oxide groups. The water content in the prepolymerization mixture was varied from 0 to 80 wt.% and resulted in XLPEO hydrogels having equilibrium water contents ranging from 0.3 to 0.8 (v/v). These hydrophilic XLPEO hydrogels are highly water permeable. The NaCl transport properties of XLPEO were studied using direct permeation and kinetic desorption methods, and good agreement between these two methods was observed. Generally, NaCl permeability in XLPEO increased from less than 0.1–2 (×10 −6 cm 2/s) as prepolymerization water content increased from 0 to 80 wt.%. NaCl permeability also increased with increasing PEGDA chain length and was higher in samples prepared with PEGA in the prepolymerization solution, presumably due to decreases in effective crosslink density. There is a tradeoff between water permeability and water/salt selectivity: materials with high water permeability typically exhibit low water/salt selectivity, and vice versa. NaCl permeability and diffusivity were strongly correlated with free volume in the hydrogels. Free volume was characterized based on both equilibrium water content and positron annihilation lifetime spectroscopy (PALS). In these samples, the equilibrium water content was proportional to the fractional free volume from the PALS measurements.

Effect of tubular inhomogeneities on filter properties of thick ascending limb of Henle’s loop

We used a simple mathematical model of rat thick ascending limb (TAL) of the loop of Henle to predict the impact of spatially inhomogeneous NaCl permeability, spatially inhomogeneous NaCl active transport, and spatially inhomogeneous tubular radius on luminal NaCl concentration when sustained, sinusoidal perturbations were superimposed on steady-state TAL flow. A mathematical model previously devised by us that used homogeneous TAL transport and fixed TAL radius predicted that such perturbations result in TAL luminal fluid NaCl concentration profiles that are standing waves. That study also predicted that nodes in NaCl concentration occur at the end of the TAL when the tubular fluid transit time equals the period of a periodic perturbation, and that, for non-nodal periods, sinusoidal perturbations generate non-sinusoidal oscillations (and thus a series of harmonics) in NaCl concentration at the TAL end. In the present study we find that the inhomogeneities transform the standing waves and their associated nodes into approximate standing waves and approximate nodes. The impact of inhomogeneous NaCl permeability is small. However, for inhomogeneous active transport or inhomogeneous radius, the oscillations for non-nodal periods tend to be less sinusoidal and more distorted than in the homogeneous case and to thus have stronger harmonics. Both the homogeneous and non-homogeneous cases predict that the TAL, in its transduction of flow oscillations into concentration oscillations, acts as a low-pass filter, but the inhomogeneities result in a less effective filter that has accentuated non-linearities.

Electrokinetic and surface chemical characterizations of an irradiated microfiltration polysulfone membrane: Comparison of two irradiation doses

The effect of ionizing radiation on the surface and electrokinetic characteristic parameters for a porous membrane of pore size 0.2 μm is determined and correlated with the irradiation dose (10 and 80 J/kg). Changes in NaCl permeability and membrane system electrical resistance determined from diffusion and impedance spectroscopy measurements are consistent with the increase of membrane pore radii/porosity, in agreement with SEM micrographs and reported results. Low irradiation dose seems to clean the membrane surface of impurities, according to XPS results, but the increase of irradiation doses could affect surface roughness. Due to the relatively high pore radius, ion transport numbers are practically independent of radiation and dose, but irradiation slightly modifies the membrane solution interface by increasing its weakly electronegative character, which could be of interest in the ultrafiltration of proteins or macromolecules.

Multistability in tubuloglomerular feedback and spectral complexity in spontaneously hypertensive rats

Single-nephron proximal tubule pressure in spontaneously hypertensive rats (SHR) can exhibit highly irregular oscillations similar to deterministic chaos. We used a mathematical model of tubuloglomerular feedback (TGF) to investigate potential sources of the irregular oscillations and the corresponding complex power spectra in SHR. A bifurcation analysis of the TGF model equations, for nonzero thick ascending limb (TAL) NaCl permeability, was performed by finding roots of the characteristic equation, and numerical simulations of model solutions were conducted to assist in the interpretation of the analysis. These techniques revealed four parameter regions, consistent with TGF gain and delays in SHR, where multiple stable model solutions are possible: 1) a region having one stable, time-independent steady-state solution; 2) a region having one stable oscillatory solution only, of frequency f1; 3) a region having one stable oscillatory solution only, of frequency f2, which is approximately equal to 2f1; and 4) a region having two possible stable oscillatory solutions, of frequencies f1 and f2. In addition, we conducted simulations in which TAL volume was assumed to vary as a function of time and simulations in which two or three nephrons were assumed to have coupled TGF systems. Four potential sources of spectral complexity in SHR were identified: 1) bifurcations that permit switching between different stable oscillatory modes, leading to multiple spectral peaks and their respective harmonic peaks; 2) sustained lability in delay parameters, leading to broadening of peaks and of their harmonics; 3) episodic, but abrupt, lability in delay parameters, leading to multiple peaks and their harmonics; and 4) coupling of small numbers of nephrons, leading to multiple peaks and their harmonics. We conclude that the TGF system in SHR may exhibit multistability and that the complex power spectra of the irregular TGF fluctuations in this strain may be explained by switching between multiple dynamic modes, temporal variation in TGF parameters, and nephron coupling.

A dual-pathway ultrastructural model for the tight junction of rat proximal tubule epithelium.

A dual-pathway model is proposed for transport across the tight junction (TJ) in rat proximal tubule: large slit breaks formed by infrequent discontinuities in the TJ complex and numerous small circular pores, with spacing similar to that of claudin-2. This dual-pathway model is developed in the context of a proximal tubule model (Weinstein AM. Am J Physiol Renal Fluid Electrolyte Physiol 247: F848-F862, 1984) to provide an ultrastructural view of solute and water fluxes. Tubule model paramters (TJ reflection coefficient and water permeability), plus the measured epithelial NaCl and sucrose permeabilities, provide constraints for the dual-pathway model, which yields the small-pore radius and spacing and large slit height and area. For a small-pore spacing of 20.2 nm, comparable to the distance between adjacent particle pairs in apposing TJ strands, the small-pore radius is 0.668 nm and the large slit breaks have a height of 19.6 nm, occupying 0.04% of the total TJ length. This pore/slit geometry also satisfies the measured permeability for mannitol. The numerous small circular pores account for 91.25% of TJ NaCl permeability but only 5.0% of TJ water permeability. The infrequent large slit breaks in the TJ account for 95.0% of TJ water permeability but only 8.7% of TJ NaCl permeability. Sucrose and mannitol (4.6- and 3.6-A radius) can pass through both the large slit breaks and the small pores. For sucrose, 78.3% of the flux is via the slits and 21.7% via the pores; for mannitol, the flux is split nearly evenly between the two pathways, 50.8 and 49.2%. In this ultrastructural model, the TJ water permeability is 21.2% of the entire transepithelial water permeability and thus an order of magnitude greater than that predicted by the single-pore/slit theory (Preisig PA and Berry CA. Am J Physiol Renal Fluid Electrolyte Physiol 249: F124-F131, 1985).

NaCl osmotic perturbation can modulate hydration control in rabbit cornea

The corneal endothelium transports solute from the stroma to the aqueous humor, maintaining corneal hydration. Currently, little is known about how this active transport system is controlled. The purpose of this study is to investigate in greater detail the corneal response to small NaCl osmotic perturbations using a more refined automatic thickness measurement system in a search for response signatures of transport control. Adult New Zealand White rabbit corneas were debrided of their epithelium, excised and mounted in perfusion chambers. The endothelium, thus isolated, was bathed in isotonic Glutathione Bicarbonate Ringer's (GBR) solution and the bare anterior stroma was covered with silicone oil. Following stabilization in isotonic GBR, the endothelial perfusate was altered by ±15 mOsm or±45 mOsm for 1 hr and 45 min by addition or removal of NaCl and returned (reversal) to GBR for 1 hr and 45 min. An enhanced, automatic scanning specular microscope monitored stromal thickness. The effective membrane transport coefficients were determined from the stromal thickness vs. time curves using an established numerical model of corneal hydration dynamics. It was found that the small (±15 mOsm) NaCl perturbations of the rabbit corneal endothelium resulted in a rapid trans-endothelial stromal volume control response that was not reversible after return to GBR. Long after the expected dissipation of the induced transients, this thickness ‘controlling’ response ultimately resulted in a sustained net thinning of 14 μm following the hypotonic perturbation and reversal, and a net swelling of 16 μm following the hypertonic perturbation and reversal. Model calculations indicated that the change induced by the perturbation could be explained by an immediate and persistent reduction of the passive endothelial NaCl permeability by 26% for the −15 mOsm perturbation compared to the +15 mOsm perturbation. This change persisted even after return to GBR. In contrast, the larger (±45 mOsm) perturbations did not elicit a similar response consistently. Our data suggest that trans-endothelial fluid transport can be rapidly modulated to control stromal hydration in response to small NaCl osmotic stresses in a way that cushions the shock and reduces the change in corneal thickness. Moreover, this behavior is not reversible in the short term, and may assist the regulation of corneal hydration homeostatically.

Instantaneous and steady-state gains in the tubuloglomerular feedback system

The load of water and solute entering each nephron of the mammalian kidney is regulated by the tubuloglomerular feedback (TGF) mechanism, a negative feedback loop. Experiments in rats have shown that key variables of this feedback system may exhibit TGF-mediated oscillations. Mathematical modeling studies have shown that the open-feedback-loop gain is a crucial parameter for determining whether oscillations will emerge. However, two different formulations of this gain have been used. The first is the steady-state gain, a readily measurable quantity corresponding to the steady-state reduction in single-nephron glomerular filtration rate (SNGFR) subsequent to a sustained increased in ascending limb flow rate. The second is an instantaneous gain, a variable arising from theoretical considerations corresponding to the maximum reduction in SNGFR resulting from an instantaneous shift of the ascending limb flow column, with the assumption that the SNGFR response is also instantaneous. Here we show by an analytic argument how the steady-state and instantaneous open-feedback-loop gains for the ascending limb are related. In the case of no solute backleak into the ascending limb, the two formulations of gain are equivalent; however, in the presence of solute backleak, the instantaneous gain is larger in magnitude than the steady-state gain. With typical physiological parameters for the rat, calculations with a model previously devised by us show that the gains differ by 5-10%. Hence, experimental measurements of the steady-state gain may provide useful lower-bound estimates of the instantaneous gain of the feedback system in the normal rat. However, the gains may diverge significantly in pathophysiological states where ascending limb transport is compromised by abnormally high NaCl permeability.

Polyvinyl alcohol plasma deposited nylon 4 membrane for hemodialysis.

Polyvinyl alcohol (PVA) is a hydrophilic and blood compatible material, but it is easily hydrolyzed in aqueous solution. Various methods, including chemical crosslinking and gamma-ray irradiation, have been investigated by many researchers for overcoming the instability of PVA in aqueous solution. This study suggests a new hemodialysis membrane, which is prepared by plasma depositing vinylacetate (VAc) onto annealled nylon 4 membrane, followed by hydrolysis treatment. This improves the blood compatibility of nylon 4 and overcomes the hydrolysis problem of PVA. In addition to conventional plasma deposition, the plasma initiated interpenetrating network (IPN) method is also investigated. The new hemodialysis membranes prepared by both conventional plasma deposited VAc onto nylon 4 (PPVA/N4) and IPN polymer of plasma initiated VAc onto nylon 4 (PIPVA/N4 IPN) show significant improvement in blood compatibility. However, the solute permeabilities of PIPVA/N4 IPN membranes are higher than those of PPVA/N4 membranes. The permeabilities of NaCl, vitamin B12, and albumin for membranes prepared by IPN at 80 W, 30 sec plasma deposited conditions, i.e., the optimized conditions, are 3.614, 0.070, and 0.000 x 10(-5) cm2/min, respectively. The mole ratio of adsorbed fibrinogen to adsorbed albumin (the mole ratio F/A) for this membrane is 0.20, and it also shows excellent blood compatibility in this study.

In vitro perfusion of chinchilla thin limb segments: urea and NaCl permeabilities

We measured the urea and NaCl permeabilities (Purea and PNaCl, respectively) of the following nephron segments from chinchilla: the upper part of the long-loop descending limb (from outer medulla, LDLu), the middle part of the long-loop descending limb (from outer 30% of the inner medulla, LDLm), the lower part of the long-loop descending limb (from deep inner medulla, LDLl), and the thin ascending limb (from deep inner medulla, ATL). We found that Purea (x10(-5) cm/s) was relatively low in the LDLu (3.3), but that the value was larger in the inner medullary thin descending limb (16.8 for LDLm and 47.6 for LDLl). The ATL had an even higher value (170). Phloretin, 0.25 mM, added to the peritubular bath had no effect on Purea of these segments, suggesting that the rapid transport rate is not due to a phloretin-sensitive facilitated transport pathway like that seen in the inner medullary collecting duct. PNaCl (x10(-5) cm/s) also increased with distance along the length of the thin descending limb (LDLu, 11.7; LDLm, 41.2; LDLl, 98.4; and ATL, 321). Calculations from NaCl dilution potential measurements showed that LDLu was Na+ permselective, whereas LDLl and ATL were Cl- permselective. High solute permeabilities in the inner medullary thin descending limb contradict a major requirement of the passive model of urinary concentration developed previously (J. P. Kokko and F. C. Rector, Jr. Kidney Int. 2: 214-223, 1972; and J. L. Stephenson. Kidney Int. 2: 85-94, 1972).

Nylon 4/HEMA chemical homografted membrane

AbstractTo enhance the degree of grafting, homografting copolymerization of 2‐hydroxyethyl methacrylate (HEMA) onto nylon 4 using a chemical initiator has been attempted. The factors that affect the grafting copolymerization are the concentration of reactants, reaction time, and temperature. The dialysis permeabilities of solutes, water content, surface energy, mechanical properties, and blood compatibility of the membrane were investigated. Under the same reaction conditions, the degree of grafting by the homografting method is remarkably higher than of the heterografting method for the nylon 4–HEMA grafting system. The dialysis permeabilities of NaCl, vitamin B12, and ovalbumin of the homografted membrane with a 14.8% degree of grafting are 2.760, 0.392, and 0.073 × 10−5 cm2/min, respectively. These permeabilities are higher than the corresponding ones of ungrafted nylon 4 membrane. The mol ratios of adsorbed fibrinogen/albumin (F/A) of the heterografted membranes were found to decrease from 0.53 to 0.33, and the surface energy, to increase from 40.6 to 46.4 dyn/cm with the degree of grafting in the range of 12.5–29.9%, and their relationship is not remarkable for the homografted membranes for which the mol ratios of F/A are about 0.22–0.32 with the degree of grafting in the range of 14.8–103.8%. Observed from scanning electron micrographs of the membrane surface, denseness was found to be important to improve blood compatibility. Based on the dialysis permeabilities of solutes and the blood compatibility observed in this study, the homografted nylon 4/HEMA membrane can be considered as a hemodialysis material.

Nylon 4/PVA blend membrane for dialysis

AbstractTo improve the hydrophilicity and enhance the transport flux of nylon 4 membrane for dialysis, this study attempts to utilize blending nylon 4 with poly(vinyl alcohol) (PVA). The instability of PVA in water can be obtained more easily than by other methods, such as chemical, γ‐ray irradiated crosslinking, or high‐temperature treatment used by previous researchers. The effects of maturation time of the casting solution, nylon 4/PVA ratios, and casting solvent compositions on esterification of PVA, salt permeability, water content, partition coefficient, diffusivity, and mechanical strength of membrances are studied. The membrane, prepared by casting solution of nylon 4/PVA = 9/1 wt % formic acid with 24‐h maturation time, possesses permeabilities of NaCl and urea, 33.14 and 19.67 × 10−5 cm2/min, respectively.

Effect of varying salt and urea permeabilities along descending limbs of Henle in a model of the renal medullary urine concentrating mechanism

Modelling studies have played an important role in research on the mechanism of urine concentration and dilution by the medulla of the kidney ever since Hargitay and Kuhn (1951, Z. Elektrochem. 55, 539-558) first proposed that the parallel tubular structures in the kidney medulla must function as a "countercurrent multiplication" system. Present-day models, in keeping with our considerably improved understanding of most aspects of medullary structure-function relationships, have evolved into rather sophisticated systems of parallel tubes. In spite of this increasing complexity, it has remained the case that "model medullas" do not concentrate as well as the real kidney, especially in the inner medulla where only passive, diffusional transport occurs. Inasmuch as these models take into account the majority of contemporary ideas making up our global hypothesis about the functioning of this system, their failure to behave physiologically indicates that our understanding remains incomplete. The purpose of the present modelling study was to evaluate the implications of some recent measurements showing that permeabilities of NaCl (Ps) and urea (Pu) vary along the length of the descending thin limbs of Henle (Imai et al., 1988, Am. J. Physiol. 254, F323-F328), rather than being constant throughout this segment as had been assumed earlier. It was hoped that these newly measured values might explain, by a passive, diffusional process, the net solute addition at the bend of Henle's loop observed under some circumstances and heretofore attributed (though without any supporting experimental evidence) to active transport into the descending limb. The results of the present study show that whereas incorporation of the new values for Ps and Pu in the descending limbs of short nephrons does indeed improve the concentrating power of the model, these new values are nonetheless not sufficient to allow the model to build an osmolarity gradient that increases all the way through the inner medulla. This failing, which is common to virtually all modelling studies to date using measured values from rat kidneys, probably points to a key role for preferential exchange supposed by some to exist among certain tubule segments within vascular bundles in species whose kidneys have the highest concentrating power.

Plasma deposition modified nylon 4 membranes for hemodialysis

AbstractThe purpose of this research is to prepare high solute permeability membranes for hemodialysis by plasma depositing hydrophilic monomers onto chemically treated or O2 plasma etched Nylon 4 substrate. The factors that affect the performances of membranes, such as deposition conditions and chemical or plasma etching conditions, were studied. The monomers used in this study were 1‐vinyl‐2‐pyrrolidone (VP), 2‐Hydroxyethyl methacrylate (HEMA), and Methyl methacrylate (MMA). The permeabilities of NaCl, urea, vitamin B12, and albumin were measured, as were the water content, hydration, diffusivity, partition coefficient, and protein adsorption ratio of fibrinogen to albumin by membrane surface of plasma deposited membranes.The permeabilities of NaCl, urea, vitamin B12, and albumin of HEMA 5 w‐1 h plasma deposited onto chemical treated Nylon 4 membranes were 2.896 ± 0.192, 3.301 ± 0.325, 0.010 ± 0.007, and 0.000 x 10−5 cm2/min, respectively. The mole ratio of adsorbed fibrinogen to adsorbed albumin (F/A) is 0.26 ± 0.05, which is much lower than that of the pure Nylon 4 membrane (0.94 ± 0.06) and the Gambro® membrane (0.90 ± 0.15). The HEMA deposited membrane possesses the highest feasibility as hemodialysis material among those plasma deposited membranes considered.

Solvent drag measurement of transcellular and basolateral membrane NaCl reflection coefficient in kidney proximal tubule.

The NaCl reflection coefficient in proximal tubule has important implications for the mechanisms of near isosmotic volume reabsorption. A new fluorescence method was developed and applied to measure the transepithelial (sigma NaClTE) and basolateral membrane (sigma NaClcl) NaCl reflection coefficients in the isolated proximal straight tubule from rabbit kidney. For sigma NaClTE measurement, tubules were perfused with buffers containing 0 Cl, the Cl-sensitive fluorescent indicator 6-methoxy-N-[3-sulfopropyl] quinolinium and a Cl-insensitive indicator fluorescein sulfonate, and bathed in buffers of differing cryoscopic osmolalities containing NaCl. The transepithelial Cl gradient along the length of the tubule was measured in the steady state by a quantitative ratio imaging technique. A mathematical model based on the Kedem-Katchalsky equations was developed to calculate the axial profile of [Cl] from tubule geometry, lumen flow, water (Pf) and NaCl (PNaCl) permeabilities, and sigma NaClTE. A fit of experimental results to the model gave PNaCl = (2.25 +/- 0.2) x 10(-5) cm/s and sigma NaClTE = 0.98 +/- 0.03 at 23 degrees C. For measurement of sigma NaClbl, tubule cells were loaded with SPQ in the absence of Cl. NaCl solvent drag was measured from the time course of NaCl influx in response to rapid (less than 1 s) Cl addition to the bath solution. With bath-to-cell cryoscopic osmotic gradients of 0, -60, and +30 mosmol, initial Cl influx was 1.23, 1.10, and 1.25 mM/s; a fit to a mathematical model gave sigma NaClbl = 0.97 +/- 0.04. These results indicate absence of NaCl solvent drag in rabbit proximal tubule. The implications of these findings for water and NaCl movement in proximal tubule are evaluated.

Porous membrane of Bombyx mori silk fibroin: structure characterization, physical properties and application to glucose oxidase immobilization

Porous membranes of Bombyx mori silk fibroin were prepared by removal of polyethyleneglycol (PEG) from a silk fibroin-PEG mixed membrane in order to obtain high substrate permeability. The structure characterization of the porous membrane was investigated by means of 13C crosspolarization nuclear magnetic resonance (NMR) spectra and scanning electron microscopy. According to the NMR spectra obtained, the fraction of the Silk II, which exists as anti-parallel β-sheets in the porous silk fibroin membrane, was observed to be 60-65%. An increase of the permeabilities of glucose and NaCl by a factor of more than 20 was observed when the weight ratio of PEG to silk fibroin was increased to 3.0. The 1H-NMR spin-lattice relaxation times for water in the porous silk fibroin membranes were analyzed as two components, fast ( 14-26 msec) and slow (274-1385 msec), suggesting constrained motion of the water molecules in the NMR time scale in the silk fibroin membrane. The logarithmic permeability coefficients of glucose and NaCl decrease linearly with increasing relaxation rates of the slow components of the water. Glucose oxidase was immobilized with these porous membranes, and a sensing system for monitoring the glucose concentration was constructed. Detailed analysis of the output vs. glucose concentration data suggests that simultaneous reaction and diffusion control occur in these membranes.