Increase In Water Permeability Research Articles

The Effects of Tillage on Soil Water Content in Dry Areas

Abstract Annual rainfall is less than 500 mm of rainfall in the dry farming regions in order to be stored in the soil processing. At the time, and is provided with a sufficient number of the version of weed control, leveling a good soil is obtained, the temperature of the soil evaporation will be blocked, and capillarity corruption prevented erosion. Some dry land farming areas is 7-8 times a year. As a result of the false and incorrect versions of the soil organic matter content decreases, due to the heavy traffic and rainfall feeds into and hardens. Also, the more time the soil impermeable layer consists of the processing of terrain plow deep, it's broken, you need to increase water permeability changes in the ground. Our country's (Turkiye) Southeastern Anatolia region, especially during the period of erroneous releases summer soil cultivation of pistachios to crack and evaporate the water accumulated in the profile. In this region, the soil is less to prevent evaporation and mulch practices are required to do. Usually in the winter and spring to gain ground in both the water and the soil is completely dry in order to struggle for and type weeds, cracks and prevent evaporation of water to close the land sliding. In our region the soil structure and the orchards slope, vegetation, depending on the year, to a loss of between 40-100 tons per hectare. Soil processing by lose ground is important for quantities of soil and water losses in every year. The importance of the land in agricultural production processing topics, manufacturers, increases productivity with timely and accurate processing of applications on soil. In addition to the increase in the efficiency of handling soil erosion by the soil protection and control of soil water contents are benefits such as to conservation. In this study, tillage, reduced tillage in dry farming areas, mulching and soil moisture content will rely upon.

Controlling water permeability of composite films of polylactide acid, cellulose, and xyloglucan

ABSTRACTTo test the hypothesis that the introduction of a hydrophilic hemicellulose would affect viscoelastic properties and increase water permeability, xyloglucan (XG) was adsorbed onto the surface of microcrystalline cellulose (MCC) in water dispersion prior to the extrusion of 79–80 wt % polylactide acid (PLA), 20 wt % MCC, and 0–1 wt % XG. For comparison, composites of PLA, MCC, and non‐absorbed XG were produced. Analysis of thermal properties showed no differences for glass‐transition or melting temperatures, but the crystallinity of the films increased with the addition of MCC and XG. Storage modulus of the composite materials increased with XG content; however, at higher humidities storage modulus decreased, probably because of lower interfacial adhesion. Water permeability through the films increased more with the addition of XG adsorbed to the MCC than with the MCC and XG simply mixed in the same amounts. © 2014 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41219.

Observations on the water distribution and extractable sugar content in carrot slices after pulsed electric field treatment

The impact of pulsed electric field (PEF) processing conditions on the distribution of water in carrot tissue and extractability of soluble sugars from carrot slices was studied. Time domain NMR relaxometry was used to investigate the water proton mobility in PEF-treated carrot samples. Three distinct transverse relaxation peaks were observed in untreated carrots. After PEF treatment only two slightly-overlapping peaks were found; these were attributed to water present in the cytoplasm and vacuole of carrot xylem and phloem tissues. This post-treatment observation indicated an increase in water permeability of tissues and/or a loss of integrity in the tonoplast. In general, the stronger the electric field applied, the lower the area representing transverse relaxation (T2) values irrespective of treatment duration. Moreover an increase in sucrose, β- and α-glucose and fructose concentrations of carrot slice extracts after PEF treatment suggested increases in both cell wall and vacuole permeability as a result of exposure to pulsed electric fields.

A mechanistic approach to explain the relation between increased dispersion of surface modified cellulose nanocrystals and final porosity in biodegradable films

Nano-rod reinforced materials for example with cellulose nanocrystals (CNC) has shown great potential. It is common to optimize the compatibility between cellulose, polymer and solvent in order to improve material properties. Here we show that increased compatibility will give more porous films, which from many points of view can be a drawback, e.g. an increased porosity in the material can decrease mechanical and barrier properties. It was hypothesized that the addition of higher amounts of a rod-like nano-filler, i.e. up to 20wt% to a composite material will cause the nano-rods to overlap, lock the system and introduce pores and cavities to the final material. In order to investigate the hypothesis, nano-composite films consisting of the matrix materials polylactide acid (PLA) or poly(lactide-co-glycolide) (PLGA) and the nano-filler cellulose nanocrystals were produced via solvent casting and the morphology, density and water permeability were studied for the produced films. The addition of both unmodified and modified CNC to the matrix polymers resulted in materials where pores and cavities were present, which was more evident for the modified CNC that was more homogeneous dispersed into the matrix. The presence of pores in the films resulted in decreased density and increased water permeability. The solvent casted films were hot-melt pressed to reduce the amounts of pores and cavities but density and water permeability measurements for the pressed films showed that it was difficult to remove all cavities using melting and pressing procedure.

Effect of potassium sorbate on antimicrobial and physical properties of starch–clay nanocomposite films

Using fresh foods which undergo the least processing operations developed widely in recent years. Active packaging is a novel method for preserving these products. Active starch–clay nanocomposite films which contained potassium sorbate (PS) at a level of 0, 5, 7.5 and 10g PS/100g starch were produced and their physical, mechanical and antimicrobial properties were evaluated. In order to evaluate antimicrobial properties of films Aspergillus niger was used. The results showed that 5% of the PS did not produce antimicrobial property in the film, but by increasing the content of the additive in film formulation, antimicrobial effect increased. PS increased water permeability and elongation at break of the films, but decreased tensile strength. The rate of PS migration into the semi-solid medium in starch–nanocomposites was lower than starch films. This shows that nanocomposite films could retain their antimicrobial property for longer time.

Preparation of low-pressure water softening hollow fiber membranes by polyelectrolyte deposition with two bilayers

The layer-by-layer (LBL) polyelectrolyte deposition was applied on polyethersulfone (PES) hollow fiber ultrafiltration membrane to prepare nanofiltration (NF) membrane for low pressure water softening application for the first time. The effects of polyelectrolyte type and molecular weight (MW), deposited bilayer number, polyelectrolyte solution pH and supporting electrolyte concentration on the performance of resultant membranes were studied thoroughly.Experiments revealed that the pH of the polyelectrolyte solution and supporting electrolyte concentration presented the most notable effects. For weak poly-cations, Poly(ethylenimine) (PEI) and Poly(allylamine hydrochloride) (PAH), the solution pH affected the membrane performance significantly, and high water permeability and divalent cation rejection were obtained at optimum pH values. Using a low concentration of supporting electrolyte at underneath layers was proved to be an effective way to increase water permeability while maintaining high salt rejection. A salt water flux (SWP) of 12LMH/bar and 94% Mg2+ rejection was obtained by depositing only two bilayers of PSS/PAH polyelectrolytes on the PES substrate, while for the 3000ppm mixed salt solution, the water permeability was 11LMH/bar with Mg2+ and Ca2+ rejection as high as 90%. These promising results demonstrate that LBL technique is potentially applicable for preparing low-pressure water softening hollow fiber membranes.

Beta-1 integrin is important for the structural maintenance and homeostasis of differentiating fiber cells

β1-Integrin is a heterodimeric transmembrane protein that has roles in both cell–extra-cellular matrix and cell–cell interactions. Conditional deletion of β1-integrin from all lens cells during embryonic development results in profound lens defects, however, it is less clear whether this reflects functions in the lens epithelium alone or whether this protein plays a role in lens fibers. Thus, a conditional approach was used to delete β1-integrin solely from the lens fiber cells. This deletion resulted in two distinct phenotypes with some lenses exhibiting cataracts while others were clear, albeit with refractive defects. Analysis of “clear” conditional knockout lenses revealed that they had profound defects in fiber cell morphology associated with the loss of the F-actin network. Physiological measurements found that the lens fiber cells had a twofold increase in gap junctional coupling, perhaps due to differential localization of connexins 46 and 50, as well as increased water permeability. This would presumably facilitate transport of ions and nutrients through the lens, and may partially explain how lenses with profound structural abnormalities can maintain transparency. In summary, β1-integrin plays a role in maintaining the cellular morphology and homeostasis of the lens fiber cells.

Use of Steel Slag as Coarse Aggregate for the Production of Pervious Concrete

Pervious concrete is a type of concrete with significantly increased water permeability, ensuring increased rates of drainage of rainfall. The high porosity is achieved by removing a large percentage of fine aggregates from the mix. The present paper is an approach for the addition of steel slag as a substitute for coarse aggregates in pervious concrete. More specifically, three types of aggregates have been used: steel slag, construction and demolition wastes and conventional limestone aggregates. The produced pervious concretes are compared for their properties, such as water permeability, compressive strength and abrasion behaviour. Also this paper contains the study of the porosity analysis of these pervious concrete mix designs by using porosity profiles produced from X-ray CT Scanning. According to the results of this paper, it is observed that the incorporation of industry by-products or of Construction and Demolition (C&D) wastes leads to better abrasion behaviour, and to the increase, in some cases, of the compressive strength and of the water permeability.

A novel deletion mutation of the arginine vasopressin receptor 2 gene in a Japanese infant with nephrogenic diabetes insipidus.

Arginine vasopressin (AVP) is released from the posterior pituitary. It controls water balance homeostasis. It binds to arginine vasopressin receptor 2 (AVPR2) on the basolateral membrane of the kidney collecting duct and triggers activation of Gs proteins, which leads to increases in intracellular cAMP and the activity of protein kinase A. These increases cause trafficking of aquaporin-2 (AQP2) water channels to the apical membrane of collecting duct cells, resulting in increased water permeability and antidiuresis. The AVPR2 gene encodes a 7-transmembrane-spanning G protein-coupled receptor, which is located on chromosome Xq28. AVPR2 mutations, which are typically loss-of-function mutations, explain approximately 90% of cases of hereditary nephrogenic diabetes insipidus (NDI) (OMIM 304800). NDI is characterized by an inability to concentrate urine, resulting in excessive urine production, dehydration and thirst. Administration of exogenous AVP cannot restore the normal balance of water in most patients with AVPR2 mutations. We describe a Japanese infant with NDI who has a novel deletion mutation of the AVPR2 gene.

The ultrafiltration coefficient: this old 'grand inconnu' in dialysis

Although a wide range of physical principles capable of separating different solutes exist in biochemistry (such as affinity, or size as well as charge retaining columns and others), the removal of uraemic solutes has been almost exclusively performed up to the present with membrane-based systems. Sir Thomas Graham, in the second half of the 1800s, defined the method of separating various fluids by diffusion through a membrane with the term ‘dialysis’[1]. Galen in the second century of our era already claimed that the skin resembles a sieve and ‘sweating purifies the body, … by low-effort exercise, baths and the summer heat’ [De Symptomatum Causis Libri III, Claudii Galeni Opera Omnia (II)][2], and ancient Romans used the skin as a natural membrane to rid their bodies of poisonous urinal substances in the Therms and public baths. Well into the 20th century, artificial kidneys, based on membrane devices were adopted and the pioneer work by Abel, Rowntree and Turner [3], as well as that of Haas [4], was followed by the rotatory drum dialyser of Willem Kolff [5] and the vertical drum one of Nils Alwall [6]. Finally, the hollow fibre dialysers gained adepts and a widespread use of cuprophane membranes for a very long period of time (from the 1970s to the 1990s) has been followed by the introduction of high-flux membranes that have invaded most of the dialysis units worldwide to the present. It became quite clear from the very beginning that membranes differ in their clearance capacities of the different solutes, basically depending on thickness and pore size. However, increasing the pore size and reducing thickness is almost forcedly associated to a water permeability increase. The open dialysate circuit settings used during the era of low-permeability membranes had to be secured by the addition of ultrafiltration controllers, which closed the dialysis circuit [7], and are mandatory when using high-flux membranes (highly permeable to water) particularly if convective techniques are utilized. Defining water permeability of a dialyser was considered important from the beginning and is even more important with the high-flux dialysers. Water permeability of a dialyser was defined by its ultrafiltration coefficient, which is displayed in the notice of the given dialyser. The coefficient of ultrafiltration (KUF) was first defined by the amount of fluid (V) in mL crossing the dialyser membrane per time (T) in hours and pressure (P) in mmHg: KUF=VT×P The perception that renal physicians have of KUF has changed over time. Senior nephrologists considered KUF as a constant and took it into account in dialysis prescription in the low-permeability era [8]; it was common to hear comments on the different KUF or ‘slope’ of one dialyser in regard to another one in clinics and the consequences that this might have to the treatment and to the patient. Among senior physicians, only those particularly interested on the topic knew that KUF was not always a constant as its value may vary over a certain range of filtration rate. Young nephrologists, who have only lived the ultrafiltration controller era, have just ignored KUF. They simply did not need it. Nevertheless, the importance of KUF of the early times has remained in many aspects, including the approval of new devices by the regulatory agencies such as the US Food and Drugs Administration (FDA) [9] or its equivalent in Europe, the European Medicines Agency (EMA), a prerequisite to use them in clinics in all these countries. Indeed, the recent randomized, controlled trials on haemodiafiltration [10–12] and particularly that of Maduell et al. [12] providing evidence that high convective volume may improve survival has given a renewed protagonism to KUF, as it influences the convective capacities of the dialysis setting. KUF remains, though, the old ‘grand inconnu’. In the present editorial comment, we want to present a refurbished KUF to society, going in-depth into the factors influencing KUF and its calculation, and then coming back with as simple as possible methods to obtain it for easy clinical use.

Aquaporin Water Channels in the Mammary Gland: From Physiology to Pathophysiology and Neoplasia

Aquaporins are membrane proteins that play fundamental roles in water and small solute transport across epithelial and endothelial barriers. Recent studies suggest that several aquaporin proteins are present in the mammary gland. Immunohistochemical techniques have confirmed the presence of aquaporin 1 (AQP1) and AQP3 water channels in rat, mouse, bovine and human mammary glands. Studies suggest that in addition to AQP1 and AQP3 AQP4, AQP5 and AQP7 proteins are expressed in different locations in the mammary gland. Aquaporins play key roles in tumor biology and are involved in cell growth, migration and formation of ascites via increased water permeability of micro-vessels. Emerging evidence suggests that expression of these proteins is altered in mammary tumors and in breast cancer cell lines although it is not yet clear whether this is a cause or a consequence of neoplastic development. This review analyzes the expression and potential functional roles of aquaporin water channels in the mammary gland. The physiological mechanisms involved in the transport of water and small solutes across mammary endothelial and epithelial barriers are discussed in the context of milk production and lactation. This paper also reviews papers from the recent cancer literature that implicate aquaporins in mammary neoplasia.

Microstructural changes in sclera under thermo‐mechanical effect of 1.56 µm laser radiation increasing transscleral humor outflow

Pores in the sclera are a candidate pathway for aqueous transport and therefore can be utilized to decrease the intraocular pressure (IOP) in glaucomatous eyes. Since pore formation is a well-known mechanism for stress relaxation in solids, laser-induced creation of pores in cartilage increases hydraulic permeability and promotes tissue regeneration. The aim of this paper is to demonstrate the thermo-mechanical effect of non-destructive laser irradiation on microstructural changes in sclera, in particular pore formation, resulting in substantial increase of water permeability of eye tissues that can be a novel approach to normalize the IOP. Experiments were performed ex vivo on eight eyes of four mini-pigs and in vivo on eight eyes of four rabbits using pulse repetitive laser radiation of 1.56 µm in wavelength. Twenty laser spots of 0.6 mm in diameter with laser settings (power 0.9 W, pulse duration of 200 milliseconds, pulse repetition rate of 2 Hz) resulting in substantial increase of sclera hydraulic permeability were applied on the sclera at 1-2 mm from the eye limb. Sclera and underlying structures (choroid and ciliary body) of the rabbits' eyes were examined histologically in 1 and 45 days after laser irradiation, atomic force microscope (AFM) was applied before and after laser irradiation. Histological and AFM examinations have clearly recognized laser-assisted stable structural alterations: rarefication of the collagen structure in the laser irradiated zone and formation of sub-micron pores. Laser-induced alterations in the structure of ciliary bodies were small in size and mainly reversible. We have proposed a possible mechanism of the arising pores stabilization due to formation of small stable gas bubbles in sclera tissue. It is shown, for the first time, that thermo-mechanical effect of pulse repetitive laser irradiation results in pores formation in sclera. That can be a basis of a novel, safe, and effective technique for IOP normalization due to enhancing of uveoscleral outflow under non-destructive laser irradiation of the sclera.

Soil hydrological function at different vegetation restoration stages in purple soil slopelands in Hengyang

采用空间代替时间序列方法, 对衡阳紫色土丘陵坡地不同植被恢复阶段土壤层的水文效应进行研究。结果表明: (1)从裸露地、草坡、灌草、灌丛至乔灌恢复阶段, 土壤蓄水性与渗透性显著增加(<i>P</i><0.05); (2)Horton入渗模型对各植被恢复阶段的入渗过程拟合效果较好(<i>R</i>²≥0.765), 有较好的适用性; (3)土壤理化性状、植被根系显著影响土壤的渗透性能, 植被根系提高土壤入渗性能的实质是: ≤1 mm细根可有效改善土壤的理化性状; (4)基于主成分分析, 从裸露地、草坡、灌草、灌丛至乔灌恢复阶段, 土壤综合水文效应显著提高(<i>P</i><0.05)。此研究结果将丰富该地区植物生态学与恢复生态学的内容, 并为衡阳紫色土丘陵坡地生态系统的恢复与重建提供重要依据。

A novel thin film composite forward osmosis membrane prepared from PSf–TiO2 nanocomposite substrate for water desalination

In this work, polysulfone (PSf)–titanium dioxide (TiO2) nanocomposite substrates were prepared by incorporating different amounts of TiO2 nanoparticles (ranging from zero to 1wt%) into PSf matrix. The nanocomposite substrates so prepared were then characterized with respect to hydrophilicity, overall porosity, surface roughness and cross-sectional morphology. It was found that both hydrophilicity and porosity of the substrate were increased upon addition of TiO2. In addition, long finger-like structures were developed by increasing the TiO2 loading, leading to water permeability enhancement. In order to fabricate thin film nanocomposite (TFN) membranes for forward osmosis (FO) application, a thin polyamide layer was formed by interfacial polymerization of 1,3-phenylendiamine and 1,3,5-benzenetricarbonyl trichloride on the top surface of PSf–TiO2 nanocomposite substrates. Under the conditions for FO performance evaluation (10mM NaCl concentration in feed solution, 0.5 and 2.0M NaCl concentration in draw solution, and both active layer facing the feed solution (AL–FS) and active layer facing the draw solution (AL–DS) orientations), the TFN membrane prepared using PSf substrate embedded with 0.5wt% TiO2 nanoparticles (denoted as TFN0.5) exhibited the most promising results by showing high water permeability and low reverse solute flux. In comparison with control TFC membrane, the water flux of TFN0.5 membrane was improved by 86–93%, depending on the membrane orientation and draw solution concentration. The increase in water permeability can be attributed to decrease in structural parameter which resulted in decreased internal concentration polarization (ICP). Although further increase in TiO2 nanoparticles loading to 0.75 and 1wt% could result in higher water permeability, their FO performances were compromised by a significant increase in reverse solute flux. Based on the results obtained in this work, it can be concluded that adding an appropriate amount of TiO2 nanoparticles into PSf substrate could potentially improve the performance of TFC membrane during FO applications.

Effects of free volume in thin‐film composite membranes on osmotic power generation

For the first time, the effects of free volume in thin‐film composite (TFC) membranes on membrane performance for forward osmosis and pressure retarded osmosis (PRO) processes were studied in this work. To manipulate the free volume in the TFC layer, a bulky monomer (i.e., p‐xylylenediamine) was blended into the interfacial polymerization and methanol immersion was conducted to swell up the TFC layer. Results from positron annihilation lifetime spectroscopy (PALS) show that p‐xylylenediamine blending and methanol induced swelling enlarge and broaden the free volume cavity. In addition, the performance of TFC membranes consisting of different free volumes were examined in terms of water flux, reverse salt flux, and power density under high pressure PRO operations. The TFC‐B‐5 membrane (i.e., a TFC membrane made of blending monomers) with a moderate free volume shows the highest power density of 6.0 W/m2 at 9 bar in comparison of TFC membranes with other free volumes. After PRO operations, it is found that the free volume of TFC layers decreases due to high pressure compression, but membrane transport properties in terms of water and salt permeability increase. Interestingly, the membrane performance in terms of resistance against high pressures and power density stay the same. A slow positron beam was used to investigate the microstructure changes of the TFC layer after PRO operations. Compaction in free volume occurs and the TFC layer becomes thinner under PRO tests but no visible defects can be observed by both scanning electronic microscopy and PALS. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4749–4761, 2013

Mercury increases water permeability of a plant aquaporin through a non-cysteine-related mechanism

Water transport across cellular membranes is mediated by a family of membrane proteins known as AQPs (aquaporins). AQPs were first discovered on the basis of their ability to be inhibited by mercurial compounds, an experiment which has followed the AQP field ever since. Although mercury inhibition is most common, many AQPs are mercury insensitive. In plants, regulation of AQPs is important in order to cope with environmental changes. Plant plasma membrane AQPs are known to be gated by phosphorylation, pH and Ca²⁺. We have previously solved the structure of the spinach AQP SoPIP2;1 (Spinacia oleracea plasma membrane intrinsic protein 2;1) in closed and open conformations and proposed a mechanism for how this gating can be achieved. To study the effect of mercury on SoPIP2;1 we solved the structure of the SoPIP2;1-mercury complex and characterized the water transport ability using proteoliposomes. The structure revealed mercury binding to three out of four cysteine residues. In contrast to what is normally seen for AQPs, mercury increased the water transport rate of SoPIP2;1, an effect which could not be attributed to any of the cysteine residues. This indicates that other factors might influence the effect of mercury on SoPIP2;1, one of which could be the properties of the lipid bilayer.

An experimental study of improved oil recovery through fines-assisted waterflooding

Abstract Permeability decline during waterflooding by varying water composition, in particular with low salinity or high pH water, has been observed in numerous laboratory studies. This has been explained by the lifting, migration and subsequent plugging of pores by fine particles. Recently, mathematical models have been presented to investigate the concept of using this permeability decline for mobility control during a waterflood. Now, these models need to be tested against observations during a core flood test. This paper presents a systematic laboratory study to investigate the underlying physics mechanisms for improved oil recovery as a consequence of injecting low-salinity water. Three sister plugs of Berea sandstone were used in the experiments. The first plug was subjected to single-phase waterflood for permeability measurements with varying salinities from 4 (high-salinity) to 0 (low-salinity) g/L NaCl. Core permeability decreased from 495 to 60 md, confirming the effect of changing water composition on permeability. The second plug saturated with high-salinity water was subjected first to primary oil flood (using Soltrol) to the connate water saturation and then to a benchmark waterflood using the same water. The oil recovery was noted and the core was restored to the connate water by a secondary oil flood. Finally, low-salinity waterflood was carried out and oil recovery was recorded. Experimental observations were interpreted using a numerical model. In order to check the reproducibility of the observations, the same experimental procedure was applied on the third plug. Results confirmed the reproducibility of the observations. Significant decrease in water relative permeability by approximately 50% and some decrease in residual oil saturation by about 5% were observed during the low-salinity waterflood in comparison with the high-salinity waterflood. Treatment of the low-salinity coreflood data by a numerical model reveals the decrease in water relative permeability with increasing water saturation at high water saturations. This observation is explained by the expansion of rock surface exposed to low-salinity water during the increase of water saturation. The laboratory data matched by the numerical model shows a high surface exponent value (nA=30), which is explained by a sharp surface area rise at high water saturations. The abnormal behavior of water relative permeability in response to low-salinity waterflood has resulted from matching water permeability increase at low water saturations and decrease at high saturations.

Multilayered polyamide membranes by spray-assisted 2-step interfacial polymerization for increased performance of trimesoyl chloride (TMC)/m-phenylenediamine (MPD)-derived polyamide membranes

A spray-assisted, 2-step interfacial polymerization (IP) of trimesoyl chloride (TMC)/m-phenylenediamine (MPD) was proposed for the preparation of polyamide (PA) membranes. In the first step, TMC/hexane solutions were sprayed onto MPD-impregnated polysulfone (PSf) supports for 10–60s, followed by a second step where the first-step membranes made contact with the TMC/hexane solutions. It is noteworthy that water permeability was increased with spray time in the first step of the 2-step IP, showing approximately doubled values at the spray time of 20–30s, compared with 1-step PA/PSf composite membranes, while NaCl rejections were practically unchanged. With longer spray time (30–60s), water permeability decreased while NaCl rejection remained at the same level. A characterization of 1- and 2-step PA membranes, including FE-SEM and ATR-FTIR, revealed the formation of multilayered ridge-and-valley structures of polyamide from the spray-assisted IP steps, and it is suggested that the increased water permeability have been caused by the increased interfacial surface area of the 2-step PA membranes.

Insight into the role of amphiphilic pluronic block copolymer as pore-forming additive in PVDF membrane formation

The use of additives in the polymer dope solutions is one of the most powerful strategies to control the pore structure of poly(vinylidene fluoride) (PVDF) membranes for various applications. In present work, the effects of amphiphilic pluronic block copolymer as an additive on PVDF membrane formation has been studied and a membrane formation mechanism involving pluronic has been proposed. The surface tension–concentration curve reveals that no micelles are formed in pluronic/N-methyl-2-pyrrolidone (NMP) solutions while the thermodynamics and kinetics are found to be similar for the systems containing pluronic and polyethylene glycol (PEG), respectively. The membranes prepared with pluronic as the additive exhibit larger surface pore, porosity, and macrovoids than that with PEG, indicating that pluronic has a stronger pore-forming ability. Instead of the commonly used concept of instantaneous or delayed demixing, it is believed that the stronger pore-forming ability of pluronic is caused by the hydrophobic–hydrophobic interaction between pluronic and PVDF that delays the solidification process. Since pluronic is not completely stable in PVDF membrane matrix, the membranes are soaked in 2-propanol (IPA) to purposely wash out pluronic. The loss of pluronic after IPA-treatment causes an increase in water permeation and a decrease in rejection, indicating that the presence of pluronic on the membrane pore surface can narrow down the pore size. By adding lithium chloride as a second additive, the growth of macrovoids is suppressed. Moreover, the resultant membranes exhibit both higher permeability and selectivity.

Characterization of Three Vasopressin Receptor 2 Variants: An Apparent Polymorphism (V266A) and Two Loss-of-Function Mutations (R181C and M311V)

Arginine vasopressin (AVP) is released from the posterior pituitary and controls water homeostasis. AVP binding to vasopressin V2 receptors (V2Rs) located on kidney collecting duct epithelial cells triggers activation of Gs proteins, leading to increased cAMP levels, trafficking of aquaporin-2 water channels, and consequent increased water permeability and antidiuresis. Typically, loss-of-function V2R mutations cause nephrogenic diabetes insipidus (NDI), whereas gain-of-function mutations cause nephrogenic syndrome of inappropriate antidiuresis (NSIAD). Here we provide further characterization of two mutant V2Rs, R181C and M311V, reported to cause complete and partial NDI respectively, together with a V266A variant, in a patient diagnosed with NSIAD. Our data in HEK293FT cells revealed that for cAMP accumulation, AVP was about 500- or 30-fold less potent at the R181C and M311V mutants than at the wild-type receptor respectively (and about 4000- and 60-fold in COS7 cells respectively). However, in contrast to wild type V2R, the R181C mutant failed to increase inositol phosphate production, while with the M311V mutant, AVP exhibited only partial agonism in addition to a 37-fold potency decrease. Similar responses were detected in a BRET assay for β-arrestin recruitment, with the R181C receptor unresponsive to AVP, and partial agonism with a 23-fold decrease in potency observed with M311V in both HEK293FT and COS7 cells. Notably, the V266A V2R appeared functionally identical to the wild-type receptor in all assays tested, including cAMP and inositol phosphate accumulation, β-arrestin interaction, and in a BRET assay of receptor ubiquitination. Each receptor was expressed at comparable levels. Hence, the M311V V2R retains greater activity than the R181C mutant, consistent with the milder phenotype of NDI associated with this mutant. Notably, the R181C mutant appears to be a Gs protein-biased receptor incapable of signaling to inositol phosphate or recruiting β-arrestin. The etiology of NSIAD in the patient with V266A V2R remains unknown.