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PubMed1987

Pressure probe study of the water relations of Phycomyces blakesleeanus sporangiophores.

The physical characteristics which govern the water relations of the giant-celled sporangiophore of Phycomyces blakesleeanus were measured with the pressure probe technique and with nanoliter osmometry. These properties are important because they govern water uptake associated with cell growth and because they may influence expansion of the sporangiophore wall. Turgor pressure ranged from 1.1 to 6.6 bars (mean = 4.1 bars), and was the same for stage I and stage IV sporangiophores. Sporangiophore osmotic pressure averaged 11.5 bars. From the difference between cell osmotic pressure and turgor pressure, the average water potential of the sporangiophore was calculated to be about -7.4 bars. When sporangiophores were submerged under water, turgor remained nearly constant. We propose that the low cell turgor pressure is due to solutes in the cell wall solution, i.e., between the cuticle and the plasma membrane. Membrane hydraulic conductivity averaged 4.6 x 10(-6) cm s-1 bar-1, and was significantly greater in stage I sporangiophores than in stage IV sporangiophores. Contrary to previous reports, the sporangiophore is separated from the supporting mycelium by septa which prevent bulk volume flow between the two regions. The presence of a wall compartment between the cuticle and the plasma membrane results in anomalous osmosis during pressure clamp measurements. This behavior arises because of changes in solute concentration as water moves into or out of the wall compartment surrounding the sporangiophore. Theoretical analysis shows how the equations governing transient water flow are altered by the characteristics of the cell wall compartment.

Cell Compartmentation↗
PubMedDate not supplied

Water and electrolyte homeostasis in sheep without functional colons.

The regulatory role of the colon in water and electrolyte balance and the renal compensation which follows impairment of colonic function were assessed using sheep with ileorectal anastomosis (ILRAN sheep) on restricted and free water intake as experimental models. Faecal electrolyte loss sustained by the ILRAN group was eight to nine times greater than that in the control animals. When water was available ad lib., ILRAN sheep lost 2.81 and 0.51 more water per day via the faeces and urine, respectively, than the controls. Urine volume in the ILRAN sheep comprised largely electrolyte-free water and the renal retention of water was entirely secondary to the high degree of sodium reabsorption in these animals compared with the controls. On restricted water intake, the urine volume of the ILRAN sheep declined due to retention of electrolyte-free water and even greater absorption of sodium (and hence water by osmosis) by the kidney tubules. The latter observation was substantiated by a decrease in fractional excretion of sodium from 0.29 to 0.08% when water intake was restricted. Plasma aldosterone concentration was markedly elevated in the ILRAN sheep as a result of the excessive loss of sodium and water via the faeces. Activation of the renin-angiotensin-aldosterone sequence is believed to underlie the increased sensation of thirst (ILRAN sheep drank on average about 2.51 more water per day than the controls), the homeostatic response by the kidneys and the relatively lower plasma potassium in the ILRAN sheep compared to controls.

Animals↗
PubMed1978

A water purification system for laboratory use.

A water purification system is described, capable of producing Type I water upon demand at multiple locations up to 700 feet, from the purifying equipment. Tap water is initially treated employing reverse osmosis, followed by treatment with activated charcoal and mixed anion/cation exchange resins. The resultant Type I quality water is maintained by means of a recycling loop until removal upon demand. The current cost of producing water of this quality is $0.03 per liter, exclusive of capital and installation costs.

Dialysis↗
PubMedDate not supplied

Changes in refraction caused by induction of acute hyperglycemia in healthy volunteers.

PURPOSE: To determine whether the myopic changes and ocular hypotension after a glucose load are caused by hyperglycemia. METHODS: Oral glucose tolerance tests were conducted on seven healthy young subjects with normal vision. The changes in the hematologic parameters and the refractive system were measured periodically for 150 minutes after the glucose load. RESULTS: After the glucose load, there was an increase in plasma glucose level and the level of plasma osmosis, ocular hypotension, a myopic change in refractive power, shallowing of the anterior chamber, and a thickening of the lens. The degree of the myopic change exceeded the power of the residual accommodation. Normalization of the plasma glucose level led to a normalization of the intraocular pressure and a reversal of the myopic changes. CONCLUSIONS: These findings suggest that the myopic changes that accompanied hyperglycemia were caused by a thickening of the lens resulting from a decrease in the tension of the zonule fibers of Zinn, and were secondary to ocular hypotension. Hyperopia appeared to be caused by the reversal of the myopia after normalization of plasma glucose levels.

Accommodation, Ocular↗
PubMed1984

Combination of conventional and high-performance liquid chromatographic techniques for the isolation of so-called "uraemic toxins".

Using fluids from the artificial kidney as an example, a generally useful combination of separation techniques is described for the preparative isolation of biologically active subfractions from extremely heterogeneous and diluted biological fluids. Haemofiltrate (20 l) and dialysate (100 l), respectively, are desalted and concentrated in one step by reverse osmosis using membranes with a nominal cut-off of 500 Daltons. The retentate with high concentrations of "uraemic toxins" is fractionated by preparative ion-exchange chromatography (double column technique with detection at 206 nm) and size exclusion chromatography yielding large amounts of ninhydrin-positive subfractions which inhibit DNA synthesis of rat bone marrow and HeLa cells in vitro, respectively. These fractions were analyzed by reversed-phase and size exclusion high-performance liquid chromatography. Many of the isolated fractions were shown to contain peptides.

Animals↗
PubMed2003

Polarizability and complex conductivity of dilute suspensions of spherical colloidal particles with uncharged (neutral) polymer coatings.

The polarizability of polymer-coated colloidal particles, as measured via dielectric relaxation spectroscopy, reflects on the degree to which convection, diffusion, and electromigration deform the equilibrium double layer. With a polymer coating, convection and electro-osmosis are resisted by hydrodynamic drag on the polymer segments. The electro-osmotic flow near the underlying bare surface is therefore diminished. Characteristics of the particles and the adsorbed polymer can, in principle, be inferred by measuring the frequency-dependent polarizability. In this work, "exact" numerical solutions of the electrokinetic equations are used to examine how adsorbed polymer changes the particle polarizability and, hence, the conductivity and dielectric constant increments of dilute suspensions. For neutral polymer coatings, the conductivity and dielectric constant increments are found to be very similar to those of the underlying bare particles, so the response depends mostly on the underlying bare particles. These observations suggest that dielectric spectroscopy is best used to determine the underlying surface charge, with characteristics of the coating inferred from the electrophoretic or dynamic mobility, together with the hydrodynamic radius obtained from sedimentation or dynamic light scattering. Addressed briefly are the effects of added counterions and nonspecific adsorption. The electrokinetic model explored in this work can be used to guide experiments (frequency and ionic strength, for example) to either minimize or maximize the sensitivity of the complex conductivity to the coating thickness or permeability.

Journal Article↗
PubMed1983

Comparison of the physical properties and assembly pathways of the related bacteriophages T7, T3 and phi II.

To understand constraints on the evolution of bacteriophage assembly, the structures, electrophoretic mobilities (mu) and assembly pathways of the related double-stranded DNA bacteriophages T7, T3 and phi II, have been compared. The characteristics of the following T7, T3 and phi II capsids in these assembly pathways have also been compared: (1) a DNA-free procapsid (capsid I) that packages DNA during assembly; (b) a DNA packaging-associated conversion product of capsid I (capsid II). The molecular weights of the T3 and phi II genomes were 25.2 X 10(6) and 25.9 (+/- 0.2) X 10(6) (26.44 X 10(6) for T7, as previously determined), as determined by agarose gel electrophoresis of intact genomes. The radii of T7, T3 and phi II bacteriophages were indistinguishable by sieving during agarose gel electrophoresis (+/- 4%) and measurement of the bacteriophage hydration (+/- 2%) (30.1 nm for T7, as previously determined). Assuming a T = 7 icosahedral lattice for the arrangement of the major capsid subunits (p10A) of T7, T3 and phi II best explains these data and data previously obtained for T7. At pH 7.4 and an ionic strength of 1.2, the solid-support-free mu values (mu 0 values) of T7, T3 and phi II bacteriophages, obtained by extrapolation of mu during agarose gel electrophoresis to an agarose concentration of 0 and correction for electro-osmosis, were -0.71, -0.91 and -1.17(X 10(-4) cm2V-1 s-1. The mu 0 values of T7, T3 and phi II capsids I were -1.51, -1.58 and -2.07(X 10(-4] cm2V-1 s-1. For the capsids II, these mu 0 values were -0.82, -1.07 and -1.37(X 10(-4] cm2V-1 s-1. The tails of all three bacteriophages were positively charged and the capsid envelopes (heads) were negatively charged. In all cases the procapsid had a negative mu 0 value larger in magnitude than the negative mu 0 value for bacteriophage or capsid II. A trypsin-sensitive region in capsid I-associated, but not capsid II-associated, T3 p10A was observed (previously observed for T7). The largest fragment of trypsinized capsid I-associated p10A had the same molecular weight in T7 and T3, although the T3 p10A is 18% more massive than the T7 p10A. It is suggested that the trypsin-resistant region of capsid I-associated p10A determines the radius of the bacteriophage capsid.

Capsid↗
PubMed1986

Calcium oxalate precipitation in a flow system: an attempt to simulate the early stages of stone formation in the renal tubules.

This paper describes in vitro studies on the generation of supersaturation and the early stages of calcium oxalate (CaOx) precipitation using a reverse osmosis hollow-fiber membrane to simulate the precipitation processes occurring in the distal convoluted tubule and the collecting system of the kidney. The article reports on the preliminary results of using a plug-flow configuration to simulate the reabsorption of water and generation of supersaturation during the approximately three-minute biological residence time of the urine in the upper part of the urinary tract. The results suggest that microcrystallization of CaOx . 2H2O in the renal tubules may play a role in stone formation processes. A survey of the effect of various inhibitors of CaOx precipitation indicates that pyrophosphate, magnesium, glutamic acid, heparin and citric acid reduce the tendency of CaOx crystals formed to agglomerate in this system.

Calcium Oxalate↗
PubMed2001

Characterization of isolated fractions of dissolved organic matter from natural waters and a wastewater effluent.

Dissolved organic matter (DOM) was concentrated from natural waters and the effluent of a wastewater treatment plant using a portable reverse osmosis (RO) system. The humic acid (HA), fulvic acid (FA) and hydrophilic (HyI) fractions were isolated and purified by the XAD-8 resin combined with the cation exchange resin method. The FA fractions predominated in natural waters and accounted for 54-68% of the total amount of dissolved organic carbon (DOC), whereas the HA and HyI fractions constituted, respectively, 13-29 and 9-30% of the total DOC. The effluent of wastewater was almost devoid of HA and the HyI fraction exceeded FA. The elemental compositions of HA and FA were in the ranges typical for natural humic materials, but the HyI fractions did not exhibit humic character. 1H NMR spectra revealed that the HyI fractions were almost devoid of aromatic protons and the aliphatic region featured more sharp signals than HA and FA fractions, indicating that HyI fractions were consisted of more simple compounds and less complex mixtures. The aliphatic functional groups in these fractions of DOM samples followed the order HA < FA HyI. The rate of Cu complexation with the HyI fraction was faster than the rate with the HA or FA fraction of the Suwannee River DOM, implying that copper reacted with relatively weak ligands faster than with strong ligands.

Benzopyrans↗
PubMed2001

Stabilized landfill leachate treatment by combined physicochemical-nanofiltration processes.

Landfill leachate is a complex wastewater which the composition and concentration of contaminants are influenced by the type of waste deposited and the age of landfill. In the last years, several processes or process combinations were developed and tested to reach requirements for the discharge of leachate. Among the new processes, membrane processes are considered as promising: reverse osmosis is one of the most widely used treatment in the Northwestern European countries and nanofiltration is gained in popularity during the last 5 years. Successful application of membrane technology for the treatment of landfill leachates, requires efficient control of membrane fouling. Two organic membranes of nanofiltration were used for pilot-scale testing. Leachates were subject to several pretreatments (pH modification, prefiltration and coagulation with FeCl3) to remove potential foulants including dissolved organic and inorganic substances, colloidal and suspended particles. These pretreatments do not enhance the performances (retention and permeation flux) of membranes because the pH range and the presence of Fe3+ ions contribute greatly to change the characteristics of organic matter and the surface charges of membranes. However, the results show that nanofiltration is sufficient to eliminate refractory COD, the permeates have a COD lower than the requirements for discharge.

Adsorption↗
PubMed2001

Selective demineralization of water by nanofiltration application to the defluorination of brackish water.

Nanofiltration is generally used to separate monovalent ions from divalent ions, but it is also possible to separate ions of the same valency by careful application of the transfer mechanisms involved. Analysis of the retention of halide salts reveals that small ions like fluoride are the best retained, and that this is even more marked under reduced pressure when selectivity is greatest. The selectivity desalination of fluorinated brackish water is hence feasible and drinking water can be produced directly at much lower cost than using reverse osmosis by optimizing the pressure for the type of water treated.

Diffusion↗
PubMed2003

Use of surfactant modified ultrafiltration for perchlorate (Cl(O)(4-)) removal.

Determinations of perchlorate anion (ClO(4)(-)) transport and rejection were performed using a surfactant modified ultrafiltration (UF) membrane. Perchlorate anion (at a concentration of 100 microg/L of ClO(4)(-), spiked with KClO(4)) was introduced to the membrane as a pure component, in binary mixtures with other salts, cationic and anionic surfactants, and at various ionic strength conditions (conductivity). Also, a natural source water was spiked with perchlorate in the presence of cationic and anionic surfactants and used to determine the effects of a complex mixture (including natural organic matter (NOM)) on the observed rejection. All filtration measurements were performed at approximately the same permeate flow rate in order to minimize artifacts from mass transfer at the membrane interface. The objective of this study was to modify a negatively charged UF membrane in terms of the fundamental mechanisms, steric/size exclusion and electrostatic exclusion and to enhance perchlorate rejection, with synthetic water and a blend of Colorado River water and State Project water (CRW/SPW). Previous work suggested that perchlorate was dominantly rejected by electrostatic exclusion for charged nanofiltration (NF) and UF membranes (Rejection of perchlorate by reverse osmosis, nanofiltration and ultrafiltration (UF) membranes: mechanism and modeling. Ph.D. dissertation, University of Colorado, Boulder, USA, 2001). In that research, perchlorate rejection capability was quickly lost in the presence of a sufficient amount of other ions. However, this study showed that ClO(4)(-) was excluded from a (negatively) charged UF membrane with pores large with respect to the size of the ion. Although perchlorate rejection capability due to apparent electrostatic force was reduced in the presence of a cationic surfactant, a desired amount of the ClO(4)(-) was excluded by steric exclusion. The steric exclusion was due to decreasing membrane pore size caused by the adsorption of the cationic surfactant.

Filtration↗
PubMed2004

Direct and interacting toxicological effects on the waterflea (Daphnia magna) by natural organic matter, synthetic humic substances and cypermethrin.

Humic substances are the main component of dissolved organic matter in all aquatic ecosystems, comprising a variety of molecular structures and functional groups. They bind organic pollutants and metals, thereby decreasing the bioavailability and consequently the toxicity of these substances in most instances. Recent studies also describe direct interactions and effects on organisms. Current studies also show that in some cases mitigation effects are stronger at lower concentrations of natural organic matter (NOM) and that toxicity increases with increased NOM concentrations. We hypothetise that at higher concentrations the mitigating effects are overlayed by direct effects of NOM themselves, thus these aspects were investigated in combination. So, on the one hand, this study demonstrates direct effects on toxicological parameters and activities of transformation enzyme systems of Daphnia magna, provoked by two NOM and one synthetic humic-like substance, HS1500. On the other hand, capacities of NOM and synthetic HS1500 to mitigate effects of the insecticide cypermethrin were investigated. Taken together, mitigation effects were overlayed by direct own effects of the NOM and HS1500. The NOM used were isolates from Suwannee River (XAD, Spring 2000) and from streams of the Svartberget forest (reverse osmosis, Spring 2000). The HS1500 was synthetically produced by radicalic autoxidation of hydroquinones. Suwannee River NOM at concentrations between 50 and 100 mg/l, and HS1500 (10-50 mg/l), but not Svartberget NOM increased immobility and lethality of the daphnids. All elevated the activity of the soluble glutathione S-transferase from 0.5 mg/l (HS1500), 1.0 mg/l (Suwannee River NOM) and 10 mg/l (Svartberget NOM) onwards, the microsomal glutathione S-transferase did not react. The glutathione peroxidase tended to increase. In the single exposure, the insecticide cypermethrin increased all toxicological parameters, elevated soluble and tendentially microsomal glutathione S-transferase activity between 0.001 and 1.0 microg/l and tendentially increased glutathione peroxidase. In contrast to that, 50 mg/l of the NOM and HS1500 did not mitigate toxicological effects. HS1500 in combination with cypermethrin even increased immobility, compared to cypermethrin alone. Increase of the NOM or HS1500 concentrations in combination with cypermethrin did not increase mitigation as seen in the activity of soluble glutathione S-transferases, activities of microsomal glutathione S-transferase and glutathione peroxidase even decreased, relative to control, which can be a hint of enzyme disfunction or further damages in the cell. An increase of concentration did not increase mitigation. Mitigation was higher at lower NOM or HS1500 concentration, probably as a consequence of the direct effects caused by themselves. Consequently, direct effects are relevant for analysing the mitigation qualities.

Animals↗
PubMed1975

Pyrogenic reactions during haemodialysis caused by extramural endotoxin.

Between July 24 and Aug. 19, 1974, an outbreak of pyrogenic reactions occurred in patients at a private haemodialysis centre in a suburb of Washington, D.C. 49 reactions characterised by chills, fever, and hypotension occurred in twenty-three of the seventy patients dialysed during this period. No infections could be documented in any of the affected individuals. Despite the fact that only low levels of gram-negative bacterial contamination of the haemodialysis system were found, high levels of endotoxin contamination of dialysis fluid and endotoxaemia in patients experiencing overt reactions were recorded using the Limulus lysate test. The cause of these reactions was traced to an increase in endotoxin contamination of the tap water used to prepare dialysate, possibly caused by an increase in the algae levels in the local water source. The installation of a reverse osmosis system for water treatment may be a solution to the problem of endotoxin contamination of water used to prepare dialysis fluid.

Adult↗
PubMed1978

Osteomalacic dialysis osteodystrophy: Evidence for a water-borne aetiological agent, probably aluminium.

In patients maintained on regular haemodialysis in Newcastle upon Tyne the development of osteomalacia is substantially reduced when water used to prepare dialysate is deionised. After 1--4 years of dialysis, osteomalacia was evident in 15% of patients on deionised water in 70% of patients on softened water from the same source. The close association of dialysis encephalopathy and osteomalacia suggests a common aetiology. Both diseases occur in centres with a high tap-water aluminium content. Serum-aluminium concentrations were raised in patients undergoing regular haemodialysis in the Northern Region of England. Those using softened water had higher concentrations than those using deionised water. Patients on softened water who had encephalopathy or dementia had serum-aluminium concentrations similar to those of patients using the same water-supplies without symptoms of these diseases, but they had been treated for longer. The evidence that aluminium absorption from dialysate causes osteomalacia and encephalopathy is strong enough to justify the expense of treating water by deionisation, reverse osmosis, or both in centres where tap-water aluminium is high.

Adolescent↗
PubMed1987

Ultrafiltration with an isosmotic solution during long peritoneal dialysis exchanges.

The potential of a starch-derived glucose polymer (molecular weight 16,800) as an osmotic agent for peritoneal dialysis was evaluated. A dialysate isosmotic to uraemic serum (302 [SEM 1.3] mOsm/kg) containing 5% glucose polymer (9.4 mmol/l) was compared with hypertonic (332 [1.0] mOsm/kg) 1.36% glucose (76 mmol/l) solution for ultrafiltration, solute transport, and carbohydrate absorption over 6 h and 12 h peritoneal dialysis exchanges. Glucose polymer solution produced substantially greater net ultrafiltration than glucose, while maintaining stable dialysate osmolality throughout the exchanges. At 6 h and 12 h, 14.4% and 28.1% of glucose polymer had been absorbed, compared with 61.5% and 83.0% of glucose; thus, glucose polymer provided less than 50% of the calorie load of the glucose dialysate per unit volume of ultrafiltrate. There was a 7-9-fold increase in serum maltose with glucose polymer. This high-molecular-weight glucose polymer produced sustained ultrafiltration even when dialysate osmolality remained within the physiological range, by a mechanism resembling "colloid" osmosis. It is a safe and effective osmotic agent but its long-term effects need further study.

Adult↗
PubMed1997

Properties of electrolyte-filled glass microelectrodes: a model analysis.

A novel dynamic mathematical microelectrode model (a model of solvent and solute kinetics in electrolyte-filled microelectrodes) was deduced from experimental observations made on standard (single-barrelled, 3.0 M KCl-filled, approximately 10 M[ohm]) electrodes using (a) electrodiffusion, electro-osmosis, and continuity equations that were placed into the constraints of electrode geometry, and (b) handbook/textbook parameter values, only. The model proved to be able to faithfully reproduce all observed electrochemical and electrical electrode properties, i.e. even those that constituted no part of the model's experimental basis. In theoretical tests, the model shows, for the standard electrode that (a) inside the electrode, any profiles in electrical potential and electrolyte concentration are occurring at the most distal part (approximately 50 microm) of the tip region, (b) asymmetrical shifts in electrolyte concentration just inside the electrode tip opening are the true cause of the electrode's current rectification, and (c) strong transelectrode currents are producing water flows across the electrode orifice that may affect the volume of smaller and medium-sized cells. In further tests, the model shows, among other things, for non-standard electrodes that (a) decreasing the electrode electrolyte concentration will give rise to marked decreases in electrolyte leakage from the electrode, but only very minor changes in tip potential, and (b) increasing the surface charge of the electrode glass (increases in zeta potential) and/or decreasing the electrode electrolyte concentration will produce increases in electro-osmotic water transport, which may be desirable for the intracellular injection of water-soluble (electro-neutral) substances.

Electrochemistry↗
PubMed2000

NMR imaging investigations of drug delivery devices using a flow-through USP dissolution apparatus.

A system for performing NMR imaging experiments on drug delivery devices within a flow-through dissolution apparatus, USP Apparatus 4, has been developed. The system was used to image the physical changes that occur in solid dosage forms during dissolution in the flow-through apparatus. Simultaneous cumulative drug release measurements were also made. The NMR images obtained under these conditions and the drug release data provide a better understanding of the processes involved in the release of drugs from drug delivery systems based on diffusion, dissolution and osmosis mechanisms.

Drug Delivery Systems↗