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PubMed1997

Advantages of HCO3 solution with low sodium concentration over standard lactate solutions for acute peritoneal dialysis.

The aim of this study was to identify the advantages of a bicarbonate solution with a low sodium concentration. Twelve children (3 days-6 years) with acute renal failure (ARF), positive fluid balance, and lactate acidosis (> 40 mg/dL) were treated by automated peritoneal dialysis (APD) with frequent exchanges of small fill volumes of a hypertonic solution. For Day 1 we used PD1/PD4 Dianeal (3.86%) (Baxter). After 24 hours we switched to a HCO3 solution: 38 mmol/L, Na 128 mmol/L. As the control group, we studied retrospectively the last 12 children of the previous period who were treated with APD. The age distribution was 4 days to 4 years. No significant differences were found between the groups for serum creatinine, blood urea nitrogen, and fluid overload (Day 1 to Day 4). Although the values for lactate and Na were not different before the start of the study (Day 1) and after 24 hours of Dianeal (Day 2), they were significantly lower in the study group on Day 4 [HCO3 53 (23-83), Na 148 (137-136) mEq/L] than in the control group [lactate 148 (137-156), Na 154 (142-165) mEq/L]. A low sodium concentration results in higher sodium extraction, which is important for patients with fluid overload. Low sodium concentrations in APD are needed because the peritoneal membrane "sieves" the sodium during short dwells. HCO3 dialysis is a logical choice for patients with lactate acidosis, resulting in a significant lower serum lactate and increase of BE after 48 hours of treatment.

Acute Kidney Injury↗
PubMedDate not supplied

Cardioplegia for heart transplantation: unmodified UW solution compared with Stanford solution.

Clinical practice and laboratory studies have demonstrated the efficacy of cold crystalloid cardioplegia for donor heart protection. Efforts to increase the margin of safety for protection led us to compare unmodified University of Wisconsin (UW) solution to the dextrose, mannitol-based Stanford (ST) solution. A canine model of heart transplantation with antegrade hypothermic cardioplegic arrest and 6 hours of 4 degrees C ischemic storage was used. An oxygenated blood-primed isolated heart preparation was used for reperfusion and myocardial mechanics and energetics studies of the working heart. Six of 6 UW and 4 of 6 ST hearts reached the working phase. Computer-assisted analysis of pressure-volume loops generated at varying flows measured by tri-axial sonomicrometry and high-fidelity micromanometry showed no significant differences in function between the ST and UW groups by maximum elastance (UW, 4.2 +/- 1.1; ST, 4.0 +/- 0.7), preload recruitable stroke work (UW, 43.7 +/- 7.3; ST, 43.4 +/- 8.7), or slope of log-linear end-diastolic pressure-volume curve (UW, 0.057 +/- 0.01, ST, 0.061 +/- 0.01). Specimens for determination of myocardial water content were taken after cardioplegic arrest, after storage, after reperfusion, and after the working phase. There was a significant increase in tissue water after reperfusion in both groups (UW, 75.7% +/- 0.5% to 81.6% +/- 0.2%, p = 0.0001; ST, 76.5% +/- 0.4% to 83.4% +/- 0.3%, p = 0.0002), which persisted after the working phase (UW, 81.5% +/- 0.9%, p = 0.0002; ST, 82.6% +/- 0.1%, p = 0.0003). Both groups exhibited postreperfusion increase in myocardial water content, but this edema was significantly less marked in the UW group (p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed2004

Kinetic precipitation of solution-phase polyoxomolybdate followed by transmission electron microscopy: a window to solution-phase nanostructure.

This study aimed to elucidate the structural nature of the polydisperse, nanoscopic components in the solution and the solid states of partially reduced polyoxomolybdate derived from the [Mo132] keplerate, [(Mo)Mo5]12-[Mo2 acetate]30. Designer tripodal hexamine-tris-crown ethers and nanoscopic molybdate coprecipitated from aqueous solution. These microcrystalline solids distributed particle radii between 2-30 nm as assayed by transmission electron microscopy (TEM). The solid materials and their particle size distributions were snap shots of the solution phase. The mother liquor of the preparation of the [Mo132] keplerate after three days revealed large species (r=20-30 nm) in the coprecipitate, whereas [Mo132] keplerate redissolved in water revealed small species (3-7 nm) in the coprecipitate. Nanoparticles of coprecipitate were more stable than solids derived solely from partially reduced molybdate. The TEM features of all material analyzed lacked facets on the nanometer length scale; however, the structures diffracted electrons and appeared to be defect-free as evidenced by Moiré patterns in the TEM images. Moiré patterns and size-invariant optical densities of the features in the micrographs suggested that the molybdate nanoparticles were vesicular.

Journal Article↗
PubMed1999

Effects of solute methoxylation on glass-forming ability and stability of vitrification solutions

The effects of replacing hydroxyl groups with methoxyl (OCH(3)) groups in the polyols ethylene glycol (EG), propylene glycol (PG), glycerol, and threitol were studied by differential scanning calorimetry (DSC) during cooling of aqueous solutions to -150 degrees C and subsequent rewarming. For 35% (w/w) PG, 40% EG, and 45% glycerol, a single substitution of a terminal hydroxyl group with a methoxyl group reduced the critical cooling rate necessary to avoid ice on cooling (vitrify) from approximately 500 to 50 degrees C/min. This reduction was approximately equivalent to increasing the parent polyol concentration by 5% (w/w). The critical warming rate calculated to avoid formation of ice on rewarming (devitrification) was also reduced by methoxyl substitution, typically by a factor of 10(4) for dilute solutions. Double methoxylation (replacement of both terminal hydroxyls) tended to result in hydrate formation, making these compounds less interesting. An exception was threitol, for which substituting both terminal hydroxyls by methoxyls reduced the critical rewarming rate of a 50% solution by a factor of 10(7) without any hydrate formation. These glass-forming and stability properties of methoxylated compounds, combined with their low viscosity, enhanced permeability, and high glass transition temperatures, make them interesting candidate cryoprotective agents for cryopreservation by vitrification or freezing. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Physicochemical Properties of 2-Vinylpyridine Telomers Possessing Multihydrocarbon Chains in Aqueous Solution and at the Silica/Aqueous Solution Interface.

Physicochemical properties of multialkylated surfactants of partially quaternized 2-vinylpyridine telomers having multihydrocarbon side chains (nRm-2VPQ: n, number of chains; m, alkyl chain length) in aqueous solutions were investigated. The critical micelle concentration (cmc) and surface tension at the cmc were 13 µmol dm(-3) and 52 mNm(-1) for 2.1R(8)-2VPQ, 7.1 µmol dm(-3) and 37 mNm(-1) for 2.5R(12)-2VPQ, and 4.7 µmol dm(-3) and 40.0 mNm(-1) for 3.4R(12)-2VPQ, respectively. The aggregation numbers at the cmc determined by the light scattering method were 4 +/- 1 for 2.1R(8)-2VPQ, 45 +/- 10 for 2.5R(12)-2VPQ, and 11 +/- 1 for 3.4R(12)-2VPQ. Thus, the number of chains and the alkyl chain length of the telomers affected the micellar properties in aqueous solutions. At the interface of the silica/aqueous solution, the adsorbed amounts of the telomers increased sharply at their low concentrations and reached a plateau by forming a monolayer and a subsequent bilayer. Silica suspensions also showed a dispersion-flocculation-redispersion sequence with the telomer concentration, where the maximum sedimentation rate was influenced by the number of chains and the alkyl chain length of the telomers. Copyright 1999 Academic Press.

Journal Article↗
PubMed1993

Evaluation of the effect of thymoxamine solution 0.5% on mydriasis induced by ibopamine solution 1%.

The effects of thymoxamine 0.5% solution and of a placebo solution (mannitol) on the mydriasis induced by ibopamine 1% solution were evaluated in 8 healthy volunteers and 12 patients with eye diseases. One drop of ibopamine was instilled into each eye and 30 min later 1 drop of thymoxamine was instilled into one eye and 1 drop of placebo into the contralateral eye. Pupillary diameter was measured before and 30 min after the instillation of ibopamine, immediately before the treatment with thymoxamine and placebo and 30, 60 and 90 min after the instillation of thymoxamine or of placebo. Within 30 min of treatment, ibopamine had produced a statistically and clinically significant mydriatic effect. In eyes treated with thymoxamine, prompt reversal of mydriasis was observed, the baseline diameter being observed within 60 min. No difference in the time-course of the mydriatic effect was detected between healthy subjects and patients. The pupillary response to thymoxamine was not influenced by the colour of the iris. The tolerability of ibopamine and of thymoxamine was good. No local or systemic adverse events were seen or reported.

Adult↗
PubMed1986

Activity coefficients of salts in highly concentrated protein solutions. II. Potassium salts in isoionic bovine serum albumin solutions.

Mean activity coefficients of different potassium salts KX (X = F-, Cl-, Br-, I-, NO3-, SCN-) have been measured in concentrated isoionic bovine serum albumin (BSA) solutions, by use of the EMF method with ion-exchange membrane electrodes. These solutions may be regarded as simple model systems for the cytoplasm of living cells as far as the influence of the macromolecular component on the activity coefficients of the salts is concerned. Two series of measurements have been carried out: (a) varying the amount of salt from 0.01 to 0.5 molal and maintaining the BSA concentration constant at 20 wt% and (b) varying the protein concentration up to 25 wt% and keeping the salt concentration constant at 0.1 molal. For all salts studied, the mean activity coefficients in the protein-salt solutions increase as the salt concentration rises, when the protein concentration is maintained constant. In the series of measurements (b) the activity coefficients of all salts change linearly with the protein concentration. Marked qualitative differences, however, were observed depending on the anion species, which could be interpreted in terms of specific ion binding of X- to the protein molecule. By taking into account BSA-bound 'non-solvent' water, the results were analyzed in terms of numbers of anions bound per BSA molecule. Comparison with the results of Scatchard, obtained at low protein concentrations, showed only a very small electrostatic effect of the BSA-(X-)v polyions on the activity coefficient of the salts at higher protein and salt concentrations.

Kinetics↗
PubMed2005

Self-assembly in evaporated polymer solutions: influence of the solution concentration.

Amorphous polymers were dissolved in chlorinated organic solvents and deposited on thin horizontal substrates. The solutions with various concentrations of polymers were deposited and evaporated under ambient conditions in a slow air current. Self-assembled oriented mesoscopically scaled patterns were observed. The patterns were studied with optical and atomic force microscopy. The concentration of the solution exerts a decisive influence on the mesoscopic cell characteristic dimension. Cell dimensions grow linearly with the polymer solution concentration for all kinds of tested polymers, chlorinated solvents and substrates. The dependence could be explained by a physical mechanism, based on the mass transport instability occurring under the intensive evaporation of the solvent. In situ FTIR study of the process was performed first. It was established with FTIR spectroscopy that film porosity is not due to water droplet condensation under evaporation.

Journal Article↗
PubMed2003

The primary electroviscous effect, free solution electrophoretic mobility, and diffusion of dilute prolate ellipsoid particles (minor axis = 3 nm) in monovalent salt solution.

The principal objective of the present work is the modeling of the primary electroviscous effect of charged prolate ellipsoid models of low axial ratio. Other transport properties examined include (free solution) electrophoretic mobilities and translational diffusion constants. A numerical boundary element method is employed to solve the coupled Poisson, low Reynolds number Navier-Stokes, and ion transport equations. The methodology is first applied to the primary electroviscous effect of spheres with a centrosymmetric charge distribution and excellent agreement with independent theory is obtained. Specific model studies are also carried out for prolate ellipsoid models with axial ratios less than 4 and a minor axis equal to 3 nm. Most studies are carried out in aqueous NaCl solution (2 to 50 mM) at 20 degrees C for a range of different particle charges, although limited results are also presented in LiCl and KCl solution. The primary electroviscous effect for weakly charged prolate ellipsoids is smaller than that of a sphere under similar conditions. These studies are also carried out at high absolute particle charge. A comparison is made between the primary electroviscous effect and electrophoretic mobilities of prolate ellipsoids and corresponding spherical models.

Journal Article↗
PubMed2002

Development and validation of an integrated computational approach for the study of ionic species in solution by means of effective two-body potentials. The case of Zn2+, Ni2+, and Co2+ in aqueous solutions.

In this paper we have developed an effective computational procedure for the structural and dynamical investigation of ions in aqueous solutions. Quantum mechanical potential energy surfaces for the interaction of a transition metal ion with a water molecule have been calculated taking into account the effect of bulk solvent by the polarizable continuum model (PCM). The effective ion-water interactions have been fitted by suitable analytical potentials, and have been utilized in molecular dynamics (MD) simulations to obtain structural and dynamical properties of the ionic aqueous solutions. This procedure has been successfully applied to the Co2+-H2O open-shell system and, for the first time, Co-oxygen and Co-hydrogen pair potential functions have been determined and employed in MD simulations. The reliability of the whole procedure has been assessed by applying it also to the Zn2+ and Ni2+ aqueous solutions, and the structural and dynamical properties of the three systems have been calculated by means of MD simulations and have been found to be in very good agreement with experimental results. The structural parameters of the first solvation shells issuing from the MD simulations provide an effective complement to extended X-ray absorption fine structure (EXAFS) experiments.

Journal Article↗
PubMed2005

Synthesis and characterization of [PtIn6](GeO4)2O and its solid solution [PtIn6](GaO4)(2-x)(GeO4)xOx/2 (0 < or = x < or = 2): gradual color change of the solid solution from black (x = 0) to yellow (x = 2) as a consequence of quantum dot effect.

A new phase [PtIn6](GeO4)2O, a filled variant of [PtIn6](GaO4)2, and the solid solution [PtIn6](GaO4)(2-x)(GeO4)xOx/2 (0 < or = x < or = 2) were prepared and characterized. Single-crystal structure refinements show that [PtIn6](GeO4)2O is isotypic with the mineral, sulfohalite Na6FCl(SO4)2, and crystallizes in the space group Fmm (Z = 4) with a = 1006.0(1) pm. The building units of [PtIn6](GeO4)2O are isolated [PtIn6]10+ octahedra and (GeO4)4- tetrahedra, and the isolated O2- ions occupy the centers of the In6 octahedra made up of six adjacent PtIn6 octahedra. The lattice parameter of the solid solution [PtIn6](GaO4)(2-x)(GeO4)xOx/2 (0 < or = x < or = 2) varies gradually from a = 1001.3(1) pm at x = 0 to a = 1006.0(1) pm at x = 2, and the color of the solid solution changes gradually from black (x = 0) to red (x = 1) to yellow (x = 2). The cause for the gradual color change was examined by performing density functional theory electronic structure calculations for the end members [PtIn6](GaO4)2 and [PtIn6](GeO4)2O. Our analysis indicates that an oxygen atom at the center of a In6 octahedron cuts the In 5p/In 5p bonding interactions between adjacent [PtIn6]10+ octahedra thereby raising the bottom of the conduction bands, and the resulting quantum dot effect is responsible for the color change.

Color↗
PubMedDate not supplied

Structural properties of double-stranded helical poly (gamma-benzyl-D-L-glutamate) in solution. Comparison with some solution properties of linear gramicidin.

The double-stranded helical conformations of alternating PBD-LG found in the solid state have been studied in infrared, circular dichroism, and NMR techniques in solution in methylene chloride, chloroform dioxane, and collidine. The infrared and CD properties of the solutions, transconformations between single- and double-stranded helices and transconformations within the family of double helices, support the hypothesis that the conformation in solution is the same as that found after evaporation of the solvent, namely the pi pi DL 7.2, pI pI DL 9.0, and pi pi DL 10.8 helices, depending on the solvent. An attempt to identify the conformation of linear gramicidin is made on the basis of the CD spectra and the infrared frequencies conformation relationship established for PBD-LG. However, owing to the great number of different conformations observed for the antibiotic, no firm conclusion can yet be drawn, except for the probable existence of the double antiparallel helical structure.

Benzyl Compounds↗
PubMed2007

Gas-phase ions of solute species from charged droplets of solutions.

Charged droplets, produced by electrostatic dispersion of solutions of amino acids and peptides are driven by a potential difference a countercurrent to a flow of heated nitrogen bath gas. Evaporation of solvent from those droplets increases surface charge density, resulting in subdivision into smaller charged droplets. Each smaller droplet repeats that sequence until the ultimate result is a dispersion of solvent-free solute ions in the bath gas. Surprisingly, mass spectrometric analyses of the final ion-bath gas mixtures showed that the relative abundances of the desolvated ions were substantially higher when the nitrogen bath gas contained vapor of a polar solvent species than when no such solvent vapor was present. Adding solvent vapor to the background bath gas can certainly not increase, but must decrease, the net rate of solvent evaporation from the charged droplets. Consequently, the observed enhancement of ion formation by the presence of solvent vapor in the bath gas constitutes persuasive evidence that the observed solute ions cannot have been produced by the charged residue mechanism originally suggested by Dole et al. [Dole M, et al. (1968) J Chem Phys 49:2240-2249 and Dole M, Rheude A, Mack LL (1970) J Chem Phys 52:4977-4986]. It is therefore concluded that electrospray ions are most likely produced by the ion evaporation mechanism of Iribarne and Thomson [Iribarne JV, Thomson BA (1975) J Chem Phys 64:2287-2294]. Moreover, and probably as important, this observed signal enhancement constitutes a welcome increase in detection sensitivity.

Journal Article↗
PubMedDate not supplied

A comparison of solute-transport solution techniques and their effect on sensitivity analysis and inverse modeling results.

Five common numerical techniques for solving the advection-dispersion equation (finite difference, predictor corrector, total variation diminishing, method of characteristics, and modified method of characteristics) were tested using simulations of a controlled conservative tracer-test experiment through a heterogeneous, two-dimensional sand tank. The experimental facility was constructed using discrete, randomly distributed, homogeneous blocks of five sand types. This experimental model provides an opportunity to compare the solution techniques: the heterogeneous hydraulic-conductivity distribution of known structure can be accurately represented by a numerical model, and detailed measurements can be compared with simulated concentrations and total flow through the tank. The present work uses this opportunity to investigate how three common types of results--simulated breakthrough curves, sensitivity analysis, and calibrated parameter values--change in this heterogeneous situation given the different methods of simulating solute transport. The breakthrough curves show that simulated peak concentrations, even at very fine grid spacings, varied between the techniques because of different amounts of numerical dispersion. Sensitivity-analysis results revealed: (1) a high correlation between hydraulic conductivity and porosity given the concentration and flow observations used, so that both could not be estimated; and (2) that the breakthrough curve data did not provide enough information to estimate individual values of dispersivity for the five sands. This study demonstrates that the choice of assigned dispersivity and the amount of numerical dispersion present in the solution technique influence estimated hydraulic conductivity values to a surprising degree.

Bromides↗
PubMedDate not supplied

[Impulse photoconductivity of solutions of ohlorophyll and its analogs. III. Photoconductivity of hexanol solutions of chlorophyll a in the presence of n-benzoquinone. Kinetic and temperature measurements].

It is shown that an increase deltasigma of electroconductivity of chlorophyll "a" (Chlalpha) solution in hexanole in the presence of n-benzoquinone (Q) under impulse illumination of solution is proportional to flash intensity: deltasigma=1(0,99+/-0,07). Dependence deltasigma on solution temperature is of an exponential character with the activation energy Esigma=0,30+/-0,01 ev. In the temperature range studied (248--298 degrees K) the ratio between the recombination velocity constant and the mobility of ion-radicals Chlalpha+ and Q-(Kp/mu) is shown to be equal (8+/-1)X 10(-8) cm-v. The activation energy for the dissociation of coulomb pair (Chlalpha+Q-) into free ion-radicals Epiapproximately0,1 ev is evaluated. The value of total mobility of negative and positive ion-radicals is calculated from the date obtained and literature ones: mu=(1,0+/-0,2)X10(-5) cm2/v-sec.

Chlorophyll↗
PubMedDate not supplied

[A compact form of DNA in solution. III. Influence of the ion composition of the solution on the compactization process of double-stranded DNA in the presence of peg].

The data showing the features of the DNA compactization process in PEG-containing solutions of chlorides of different alkaline metals (LiCl, KCl, RbCl and CsCl) and an ammonium salt (CH3-(CH2)17-N-(CH3)3Br) are presented. The data indicate that the formation of a compact form of the double-stranded DNA in PEG-containing water-salt solutions depends not only on the PEG concentration and ionic strength but on tha cation nature as well. The compactization occurs most easily in the presence of Na+-ions. This indicates a specific character of interaction between Na+-ions and DNA phosphate groups which may be due to an optimum structural fit between the hydrated Na+-ions and orientation of the phosphate groups in the DNA molecule. The nature of forces involved in the processes of the intramolecular compactization and intermolecular aggregation of double-stranded DNA molecules in water-salt solution is discussed. The difference between the effect of Na+ and that of K+-ions on the compactization process at the ionic strengths close to physiological values makes it possible to suggest that the changes of the tertiary structure of double-stranded DNA which accompany its function in vivo may take place under conditions of a decreased water activity at the expense of relatively slight changes in ion composition of the water surrounding DNA.

Binding Sites↗
PubMed1992

Magnesium, adenosine triphosphate, and catecholamine complexes: application of new means of identifying solute-solute interactions of biological significance using NMR chemical shift data.

The interaction of magnesium ions with biomolecular species is fundamental to the regulation of many biological processes. A mathematical technique to investigate such interactions is described. The concept of a pseudo-formation curve is discussed and the relevance and applicability of such constructions to the study of solute-solute interactions is outlined. Analysis of curves based on the published variation of chemical shift data of various nuclei of adrenaline and dichloroisoprenaline in aqueous solution, in the presence of increasing concentration of the complex Mg-ATP, is described. Unambiguous indentification of specific interactions and the stability of the species produced is shown to be feasible. Some variation of the values of formation constants deriving from different nuclei reflects the significance of molecular environmental factors on the parameters used.

Adenosine Triphosphate↗
PubMed1992

[Mannitol solution (M-400) vs. mannitol solution combined with allopurinol in the prevention of post-transfusion acute renal failure].

Evaluation on the incidence of Acute Renal Failure (ARF) from a total of 41 corpse renal graft receptors, 20 of which received perfusion with mannitol solution at 400 mOsm/kg (Group 1) and 21 the same mannitol solution plus allopurinol (Group 2). No significant differences were present between both groups when they were analyzed for ARF incidence (15% vs 23.8%); overall incidence was 19.5%. 24-hour initial diuresis was shown to be an excellent predictor for long-term graft functionality. We can conclude that the addition of mannitol to the perfusion solution contributes decisively to reduce post-transplantation ARF, while addition of allopurinol does not have further beneficial effects.

Acute Kidney Injury↗