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PubMed2004

Sonoluminescence quenching of organic compounds in aqueous solution: frequency effects and implications for sonochemistry.

Solute-induced quenching of sonoluminescence (SL) is reported for aqueous solutions of two homologous series of methyl esters and ketones using low (20 kHz) and high (515 kHz) ultrasound frequencies. SL data at 20 kHz from aqueous solutions containing alcohols and carboxylic acids are also presented to compare with previously published results at 515 kHz. In addition to supporting the previous findings on the existence of stable and transient bubbles at 515 and 20 kHz, respectively, the results suggest that the hydrogen-bonding characteristics of the solutes also play a major role in the extent of SL quenching. An increase in the SL intensity at low concentrations for most of the solutes suggests that these solutes increase the number of "active" bubbles by hindering the coalescence of bubbles. It is concluded that the effect of the solutes on the SL signal from aqueous solutions at both frequencies is primarily due to the balance of two factors, namely, the incorporation of solute within the bubble, leading to SL quenching, and the prevention of coalescence of the bubbles, leading to SL enhancement. At the higher frequency, SL quenching by the solutes is the main influence on the emission yield. However, at the lower frequency, hindrance to coalescence by the solutes dominates at lower concentrations and leads to SL enhancement. The implications of these results for optimizing conditions for aqueous sonochemical reactions are discussed.

Journal Article↗
PubMed2001

Physicochemical determinants of passive membrane permeability: role of solute hydrogen-bonding potential and volume.

The relationship of solute structure with cellular permeability was probed. Two series of dipeptide mimetics consisting of glycine, alanine, valine, leucine, phenylalanine, and cyclohexylalanine with amino acids in the D-configuration were prepared. Partition coefficients for the peptidemimetics were obtained in the octanol/water (log P(octanol/water)), hydrocarbon/octanol (Delta log P), and heptane/ethylene glycol (log P(heptane/glycol)) systems in order to explore the contributions of solute volume, or surface area, and hydrogen-bond potential to the permeability of the solutes. Permeability coefficients were obtained in Caco-2 cell monolayers as a model of the human intestinal mucosa. The results were interpreted in terms of a partition/diffusion model for solute transport where membrane partitioning into the permeability-limiting membrane microdomain is estimated from the solvent partition coefficients. Neither log P(octanol/water) nor Delta log P alone correlated with cellular permeability for all the solutes. In contrast, log P(heptane/glycol) gave a qualitatively better correlation. With regard to solute properties, log P(octanol/water) is predominantly a measure of solute volume, or surface area, and hydrogen-bond acceptor potential, while Delta log P is principally a measure of hydrogen-bond donor strength. Log P(heptane/glycol) contains contributions from all these solute properties. The results demonstrate that both hydrogen-bond potential and volume of the solutes contribute to permeability and suggests that the nature of the permeability-limiting microenvironment within the cell depends on the properties of a specific solute. Collectively, these findings support the conclusion that a general model of permeability will require consideration of a number of different solute structural properties.

Caco-2 Cells↗
PubMed2005

Entropy-enthalpy compensations in solutions of dual character molecules with polymeric chromatographic liquid phases.

Careful gas chromatographic studies provide thermodynamic data for insights into solution processes in nonvolatile solvents. Using 24 solutes and five stationary phases, several entropy-enthalpy compensation effects in the thermodynamics of solution were identified. Despite solute structure differences, when excess enthalpy and entropy of solutions were examined, entropy-enthalpy compensation effects were found in solvents dominated by single types of interaction: squalane and, to some extent, methoxy poly(ethylene oxide) (PEO). The main reason for the absence of linearity in other solvents is pure solute state interactions in the reference state and the multicharacter nature of solvents. In this study, consideration of solute state interactions was removed through examination of the thermodynamics of transfer between solvent pairs. It was found that solute transfers from squalane to poly[methyl(trifluoropropyl)siloxane] (QF-1) and to poly(methylphenyl) (DC-550) also gave linear relationships. The former system contains a second correlation for ester type solutes. The transfer data for squalane to poly(methylsiloxane) (DC-200) had smaller ranges and were more scattered. The effects of derivatizing groups on the transfer enthalpy and entropy were treated as a summation of hydrocarbon cores with the derivative groups. The group properties of transfer then also show entropy-enthalpy compensation effects. Many solution effects could be explained on the basis of solvent composition and local interactions with solutes.

Journal Article↗
PubMed2005

The effect of surface-active solutes on bubble coalescence in the presence of ultrasound.

The sonication of an aqueous solution generates cavitation bubbles, which may coalesce and produce larger bubbles. This paper examines the effect of surface-active solutes on such bubble coalescence in an ultrasonic field. A novel capillary system has been designed to measure the change in the total volume resulting from the sonication of aqueous solutions with 515 kHz ultrasound pulses. This volume change reflects the total volume of larger gas bubbles generated by the coalescence of cavitation bubbles during the sonication process. The total volume of bubbles generated is reduced when surface-active solutes are present. We have proposed that this decrease in the total bubble volume results from the inhibition of bubble coalescence brought about by the surface-active solutes. The observed results revealed similarities with bubble coalescence data reported in the literature in the absence of ultrasound. It was found that for uncharged and zwitterionic surface-active solutes, the extent of bubble coalescence is affected by the surface activity of the solutes. The addition of 0.1 M NaCl to such solutes had no effect on the extent of bubble coalescence. Conversely, for charged surface-active solutes, the extent of bubble coalescence appears to be dominated by electrostatic effects. The addition of 0.1 M NaCl to charged surfactant solutions was observed to increase the total bubble volume close to that of the zwitterionic surfactant. This suggests the involvement of electrostatic interactions between cavitation bubbles in the presence of charged surfactants in the solution.

Air↗
PubMed1979

Microvascular and clinical effects of altered peritoneal dialysis solutions.

Blood flow in the peritoneum is one of the more important factors governing the efficiency of peritoneal dialysis. Yet there have been no previous studies which relate alterations and control of the peritoneal microcirculation to dialysis efficiency. Thus, we used closed-circuit television microscopy to quantitative the in vivo response (changes in diameter) to dialysis solutions of the small arteries on the mesothelial surface of the rat cecum and arterioles of the rat cremaster muscle. These responses were correlated wiht solute clearances from multiple peritoneal dialysis performed in humans. In the cremaster, a transient constriction was followed by a prolonged dilation. pH adjustments of the dialysis solution from 5.6 to 7.4 had no effect on the microvascular response and no effect on solute clearances during human peritoneal dialysis. In the cecum, dialysis solution caused a prolonged dilation which reached a maximum in about 10 min. Since dilation appears to be an important determinant of solute clearances during human peritoneal dialysis, the effects of a vasodilator, sodium nitroprusside, were determined. Sodium nitroprusside decreased the time to maximal dilation, which correlated clinically with an increased solute clearance during exchanges with this drug. Since nitroprusside increased clearances of the larger molecular weight solutes proportionally more than the smaller molecular weight solutes did, we hypothesize that nitroprusside increases solute clearances by both a vasodilatory effect and by an effect on vascular membrane permeability and area for solute exchange.

Animals↗
PubMed2004

Competition of hydrophobic and Coulombic interactions between nanosized solutes.

The solvation of charged, nanometer-sized spherical solutes in water, and the effective, solvent-induced force between two such solutes are investigated by constant temperature and pressure molecular dynamics simulations of model solutes carrying various charge patterns. The results for neutral solutes agree well with earlier findings, and with predictions of simple macroscopic considerations: substantial hydrophobic attraction may be traced back to strong depletion ("drying") of the solvent between the solutes. This hydrophobic attraction is strongly reduced when the solutes are uniformly charged, and the total force becomes repulsive at sufficiently high charge; there is a significant asymmetry between anionic and cationic solute pairs, the latter experiencing a lesser hydrophobic attraction. The situation becomes more complex when the solutes carry discrete (rather than uniform) charge patterns. Due to antagonistic effects of the resulting hydrophilic and hydrophobic "patches" on the solvent molecules, water is once more significantly depleted around the solutes, and the effective interaction reverts to being mainly attractive, despite the direct electrostatic repulsion between solutes. Examination of a highly coarse-grained configurational probability density shows that the relative orientation of the two solutes is very different in explicit solvent, compared to the prediction of the crude implicit solvent representation. The present study strongly suggests that a realistic modeling of the charge distribution on the surface of globular proteins, as well as the molecular treatment of water, are essential prerequisites for any reliable study of protein aggregation.

Journal Article↗
PubMed2006

Changes in thermodynamic quantities upon contact of two solutes in solvent under isochoric and isobaric conditions.

The changes in excess thermodynamic quantities upon the contact of two solutes immersed in a solvent are analyzed using the radial-symmetric and three-dimensional versions of the integral equation theory. A simple model mimicking a solute in water is employed. The solute-solute interaction energy is not included in the calculations. Under the isochoric condition, the solute contact always leads to a positive entropy change irrespective of the solute solvophobicity or solvophilicity. The energy change is negative for solvophobic solutes while it is positive for solvophilic ones. Under the isobaric condition, the contact of solvophobic solutes results in system-volume compression but that of solvophilic ones gives rise to expansion. Effects of the compression and expansion on the changes in enthalpy and entropy are enlarged with rising temperature. When the solute solvophobicity is sufficiently high, the entropy change (multiplied by the absolute temperature) can become negative due to the compression, except at low temperatures with the result of an even larger, negative enthalpy change. The expansion in the case of solvophilic solutes leads to a large, positive entropy change accompanied by an even larger, positive enthalpy change. The changes in enthalpy and entropy are strongly dependent on the temperature. However, the changes in enthalpy and entropy are largely cancelled out and the temperature dependency of the free-energy change is much weaker. The authors also discuss possible relevance to the enthalpy-entropy compensation experimentally known for a variety of physicochemical processes in aqueous solution such as protein folding.

Journal Article↗
PubMed1970

The coupling of solute fluxes in membranes.

Our previous description of solute drag on a synthetic membrane has been extended to include the solutes mannitol, sucrose, raffinose, inulin, and dextran. Labeled and nonlabeled forms of these solutes were used in pairs to quantitate solute flux interaction. Three membranes with pore sizes of 350, 80, and 20 A, respectively, have been utilized. It is shown that solute flux interaction occurs with all the solutes and that the extent of interaction is related directly to solute permeability, concentration, and molecular size. The magnitude of solute interaction is reciprocally related to the radii of the membrane pores, greater interaction occurring with small pored membranes. Solute drag is seen as an increased flux of tracer solute in the direction of the diffusion gradient of a second solute as well as a decreased tracer flux into the diffusion gradient. Values are given for self-diffusion and interaction coefficients as well as for a new coefficient, the "effectiveness coefficient."

Acetates↗
PubMed1991

Effects of changes in mucosal solution Cl- or K+ concentration on cell water volume of Necturus gallbladder epithelium.

An electrophysiologic technique was used to measure changes in cell water volume in response to isosmotic luminal solution ion replacement. Intracellular Cl- activity (aCl-i) was measured and net flux determined from the changes in volume and activity. Reduction of luminal solution [Cl-] from 98 to 10 mM (Cl- replaced with cyclamate) resulted in a large fall in aCl-i with no significant change in cell water volume. Elevation of luminal solution [K+] from 2.5 to 83.5 mM (K+ replaced Na+) caused a small increase in aCl-i with no change in cell water volume. Exposure of the Necturus gallbladder epithelium to agents that increase intracellular cAMP levels (forskolin and/or theophylline) induces an apical membrane electrodiffusive Cl- permeability accompanied by a fall in aCl-i and cell shrinkage. In stimulated tissues, reduction of luminal solution [Cl-] resulted in a large fall in aCl-i and rapid cell shrinkage, whereas elevation of luminal solution [K+] caused a large, rapid cell swelling with no significant change in aCl-i. The changes in cell water volume of stimulated tissues elicited by lowering luminal solution [Cl-] or by elevating luminal solution [K+] were reduced by 60 and 70%, respectively, by addition of tetraethylammonium (TEA+) to the luminal bathing solution. From these results, we conclude that: (a) In control tissues, the fall in aCl-i upon reducing luminal solution [Cl-], without concomitant cell shrinkage, indicates that the Cl- entry mechanism is electroneutral (Cl-/HCO3-) exchange. (b) Also in control tissues, the small increase in aCl-i upon elevating luminal solution [K+] is consistent with the recent demonstration of a basolateral Cl- conductance. (c) The cell shrinkage elicited by elevation of intracellular cAMP levels results from conductive loss of Cl- (and probably K+). (d) Elevation of cAMP inhibits apical membrane Cl-/HCO-3-exchange activity by 70%. (e) The cell shrinkage in response to the reduction of mucosal solution [Cl-] in stimulated tissues results from net K+ and Cl- efflux via parallel electrodiffusive pathways. (f) A major fraction of the K+ flux is via a TEA(+)-sensitive apical membrane K+ channel.

Animals↗
PubMed1994

The efficacy of various irrigation solutions in removing slime-producing Staphylococcus.

To determine which type of irrigation solution and which method of irrigation most effectively removes slime-producing Staphylococcus from implant surfaces, we performed experimental washings of bacteria-coated stainless steel screws with various solutions delivered by bulb syringe or by jet lavage. The quantity of bacteria remaining on the screw surface was determined after irrigation with 1 L of saline, 1 L of antibiotic solutions, or 1 L of saline containing a liquid soap. Antibiotic solutions tested included bacitracin, neomycin, and polymyxin/neomycin. We found that the use of power irrigation increased the removal of bacteria by a factor of at least 100 over bulb syringe irrigation of the same volume, no matter which solution was used. This effect ranged from a 100-fold improvement for neomycin, to a 285-fold effect for the polymyxin solution. The addition of antibiotic drugs to the irrigation solution had no significant effect on bacterial removal, and none of the antibiotic solutions were statistically different from saline alone in the amount of bacteria removed from the screws. The addition of a liquid soap solution dramatically increased the amount of bacteria removed by irrigation, reducing the residual bacteria per screw from a colony count of 3.5 x 10(4) for polymyxin (the best of the antibiotic solutions), to 4.38 x 10(3). This difference was statistically significant as judged by Student's t test, with p = 0.01. We have concluded that the use of power irrigation improves the ability to clean this pathogenic bacteria from metallic surfaces, and that the addition of antibiotic drugs to the irrigation solution does not.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMedDate not supplied

Efficacy of oral rehydration solutions in a rat model of secretory diarrhea.

Controversy continues regarding the ideal composition of glucose/electrolyte solutions used for oral rehydration of infants and children with acute diarrhea. We have used cholera toxin-treated rat small intestine as a model of secretory diarrhea to assess the efficacy of oral rehydration solutions by intestinal perfusion. All solutions tested reversed net water secretion but a hypotonic bicarbonate-free solution was more effective than other solutions, including the World Health Organization oral rehydration solution (p less than 0.003). Net sodium secretion persisted with all solutions tested but there was a significant linear relationship between sodium concentration of the solution perfused and net sodium transport (r = 0.75, p less than 0.05). Cholera toxin treatment alone and in combination with perfusion of oral rehydration solutions significantly reduced plasma sodium concentration and osmolality (p less than 0.05), the effects being most marked with low sodium solutions. Although direct parallelism between observations in this animal model of secretory diarrhea and human diarrheal disease has not been established as yet, the model may be useful in assessing clinical efficacy of new oral rehydration solutions and in systematic analysis of the relative benefits of their individual components.

Animals↗
PubMed1999

Effect of gum arabic in an oral rehydration solution on recovery from diarrhea in rats.

BACKGROUND: It has been shown that gum arabic, a soluble fiber, enhances water, electrolyte, and glucose absorption from oral rehydration solutions in jejunal perfusion of healthy rats and in animals with theophylline-induced secretion or chronic osmotic-secretory diarrhea. This report concerns a study of the effectiveness of an oral rehydration solution supplemented with gum arabic, during recovery from chronic osmotic secretory diarrhea in free-living rats. METHODS: Chronic diarrhea was induced in 60- to 80-g juvenile rats by providing a magnesium citrate-phenolphthalein solution as the sole fluid source for 7 days. This led to diarrhea characterized by dehydration, soft stools, increased cecal volume, decreased food and fluid intake and failure to gain weight. After 7 days of diarrhea, rats recovered for 24 hours with either tap water or an oral rehydration solution (90 mM Na, 111 mM glucose, 20 mM K, 80 mM chloride, 20 mM citrate) with or without 2.5 g/l gum arabic. RESULTS: Although all three solutions improved the diarrhea, optimal recovery from diarrhea was achieved with the gum arabic-supplemented oral rehydration solution. After 4 hours and 24 hours, rats drinking the gum arabic-supplemented solution gained more weight and had lower fecal output than rats receiving water or the rehydration solution without gum arabic. All three solutions normalized plasma osmolality after 24 hours. CONCLUSIONS: The positive effects of the gum arabic-supplemented rehydration solution on fluid and electrolyte absorption seen during jejunal perfusion also occurred during recovery from chronic osmotic secretory diarrhea, when free-living animals drank the solution ad libitum.

Animals↗
PubMed1991

The enhancement of myocardial protection through an acalcemic storage solution containing nicardipine, a potent calcium channel blocker. A basic study using rat ventricular myocytes.

Adult rat ventricular myocytes were used as a model system for investigating the direct effects of nicardipine, a potent calcium-channel blocker, on preservation of the heart during periods of simple cold storage. Cells were stored at 4 degrees C for 24 hr with an acalcemic storage solution. The superfusate then was exchanged with hypoxic Tyrode solution (1.8 mmol/L CaCl2). After 2 hr of hypoxia at 20 degrees C, cells were reoxygenated and simultaneously warmed to 37 degrees C. The addition of nicardipine to both the storage solution and Tyrode solution resulted in the highest percentage of viable cells (70.5%). Using either the storage solution or Tyrode solution containing the compound, the percentages of viable myocytes were 51.9% and 52.2%, respectively. In the absence of the drug in either solution, the percentage was 38.0%. The effect of diltiazem, another potent calcium-channel blocker, was examined using the same experimental procedure. The addition of diltiazem to Tyrode solution elevated the viability of ventricular myocytes, but addition to the storage solution showed no cardioprotective effect. Moreover, the addition of 8-bromo cyclic GMP to the storage solution resulted in a cardioprotective effect. These results suggested that nicardipine exerts a direct effect on myocardial protection in hypothermic and acalcemic storage solution and that the pharmacological effect of nicardipine depends on a mechanism other than its calcium-channel blocking action.

Animals↗
PubMed1996

Iterative refinement of the minimum norm solution of the bioelectric inverse problem.

Functional brain imaging based on the bioelectric scalp field depends on the solution of the inverse problem. The object is to estimate the current distribution in the cortex from a measured noisy scalp potential field. A minimum norm least squares solution is often used for this purpose. Although this approach leads to a unique solution, it represents only one of a set of feasible solutions. In particular, it leads to a solution in which current is found to be generated widely in the cortex. There are other feasible minimum norm solutions for which cortical current is generated only in a restricted region, and it is likely that in many cases, these solutions are of physiological importance. This study presents a method to uncover these solutions. It is based on the idea that a minimum norm solution can be used to define a region of interest, an ellipsoid, within which it is worthwhile to search for another feasible solution. The minimum norm approach is used iteratively and the ellipsoid shrinks. As it shrinks it provides evidence pointing to the location of the active cortical region. The method explicitly recognizes the role of measurement noise in defining feasible solutions. It is tested in a model of the human head that incorporates a realistic cortex in a three-shell sphere. The method improves the localization of cortical activity mimicking physiological processing.

Brain Mapping↗
PubMed1988

Calcium currents in single isolated smooth muscle cells from the rabbit ear artery in normal-calcium and high-barium solutions.

1. Ca2+ inward current was studied using the whole-cell patch clamp technique in single smooth muscle cells enzymatically isolated from the rabbit ear artery. Currents were studied in salt solutions containing either normal (1.5 mM) Ca2+ or high (110 mM) Ba2+. Outward currents were minimized by using a high-Na+ intracellular solution containing 10 mM-TEA. 2. In normal-Ca2+ solution, the threshold at which inward current could be evoked was -60 mV at a holding potential of -80 mV and -48 mV at a holding potential of -60 mV. At both holding potentials, the current showed little inactivation over 500 ms near threshold, and inactivated substantially but incompletely with larger depolarizations. In high-Ba2+ solution where currents were 5-10 times larger, current threshold, maximal peak amplitude and apparent reversal potential were shifted in a positive direction along the voltage axis. 3. Inward current in normal-Ca2+ solution was only fully available negative to -90 mV, was half-inactivated near -47 mV and was about 90% inactivated at -10 mV. A component of non-inactivating current was, however, present in both normal-Ca2+ and high-Ba2+ solutions even after conditioning pulses of 5 s duration to +30 mV. The inactivation-potential relationship was shifted in a positive direction in high-Ba2+ solution, and its position showed considerable variation between cells. 4. The inward current from a holding potential of -70 mV was reduced in normal-Ca2+ solution by about 50% by nifedipine (0.1 microM) in some cells at all test potentials, although at more-negative test potentials peak current was unaffected in some cells even at 10 microM. In some cells when the holding potential was -90 mV, the peak current amplitude was increased markedly by 10 microM-nifedipine. In high-Ba2+ solution, from negative holding potentials (-70 to -80 mV), nifedipine augmented peak current at test potentials negative to -10 mV and shifted the current threshold in a negative direction; current at potentials positive of -10 mV was reduced. Both effects were concentration dependent. The stimulatory effect of nifedipine was abolished and its inhibitory effect was enhanced when less-negative holding potentials were employed. Bay K 8644 (0.1 or 1 microM) approximately doubled current amplitude in normal-Ca2+ solution at a holding potential of -60 or -70 mV, and shifted maximal peak and threshold current in a negative direction. 5. Holding at more-negative potentials made available a component of current which activated and inactivated at more-negative potentials especially in high-Ba2+ solution.(ABSTRACT TRUNCATED AT 400 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1998

Brushing abrasion of eroded dentin after application of sodium fluoride solutions.

The aim of the present in vitro study was to evaluate the influence of sodium fluoride solutions on brushing abrasion of eroded dentin. Dentin specimens were prepared from 60 bovine incisors. The specimens were embedded in acrylic resin, ground flat, polished and subsequently covered with tape exposing an area of 1.8 mm x 10.0 mm in the center of the exposed dentin. The samples were alternatingly stored in a demineralizing solution (5 min) and a remineralizing solution (1 min) for 5 times. The erosive soft drink Sprite light(R) served as a demineralizing solution and artificial saliva was used as a remineralizing solution. Prior to storage in artificial saliva 15 specimens were each treated for 1 min with 250 and 2,000 ppm fluoride solution, respectively. Fifteen specimens were treated with distilled water instead of the fluoride solution (= eroded controls). The remaining samples were neither eroded with the soft drink nor fluoridated (= uneroded controls). After each immersion in artificial saliva the specimens were submitted to abrasion in a toothbrushing machine. After 5 demineralization-remineralization brushing cycles the total amount of tooth wear due to erosion and subsequent abrasion was profilometrically evaluated. Statistical analysis revealed the significantly lowest wear in the uneroded controls and the highest amount of abrasion in the eroded controls. Application of the fluoride solutions increased the wear resistance of the eroded dentin specimens, showing significantly better protection by the high-concentration compared to the low-concentration solution. The susceptibility to abrasion of the eroded dentin specimens treated with the high-concentration fluoride solution did not differ significantly from the uneroded dentin samples. It is concluded that application of 2,000 ppm sodium fluoride solutions immediately before toothbrushing significantly reduces abrasion of eroded dentin in vitro.

Animals↗
PubMed1992

Effect of a two-solution fluoride mouthrinse on remineralization of enamel lesions in vitro.

A previous study showed that a two-solution fluoride (F) rinse deposited significantly more loosely-bound F on the tooth surface than did a sodium fluoride (NaF) rinse with the same F concentration (12 mmol/L). In the present study, this experimental rinse was evaluated for its ability to cause remineralization of enamel lesions in an in vitro pH-cycling model. Caries-like lesions were formed in the enamel of extracted human molars by means of a pH 4 demineralizing solution. Fifty-one approximately 120-microns-thick sections containing lesions were randomly divided into (1) control, (2) NaF rinse, and (3) two-solution F rinse groups. With the cut surfaces protected, the control samples were immersed in a pH 7 remineralizing solution for 12 days, and twice daily the sections were also exposed to a pH 4 demineralizing solution for 30 min. Samples in the NaF group received an additional one-minute rinse with a NaF (12 mmol/L) solution twice daily. Samples in the two-solution rinse group received the rinse treatment with a 12 mmol/L F solution prepared by combination of a Na2SiF6 and phosphate-containing solution with a calcium solution just before use. The mineral contents of the lesions were assessed by quantitative microradiography. The results showed that (1) no significant de- or remineralization was detected in the controls; (2) a 46% decrease in mineral loss (delta Z) of the lesion was produced by the NaF rinses; and (3) a 94% decrease in delta Z and a 20-microns-thick, mineral-dense surface-coating were produced by the two-solution F rinse treatment.

Apatites↗
PubMedDate not supplied

Prefilter and postfilter cysteine/cystine and copper concentrations in pediatric parenteral nutrition solutions.

Pediatric amino acid products contain lower concentrations of methionine and require the addition of L-cysteine HCl just before infusion. Reports of a potential interaction between cysteine and copper, a routine addition to parenteral nutrition solutions, have appeared in the literature. This study serially evaluated cysteine/cystine and copper concentrations pre- and postfilter (0.22 microns) in two parenteral nutrition formulations prescribed for normal fluid (NF) or fluid-restricted (FR) pediatric patients. Solutions were infused via a peristaltic pump in vitro for 24 hours. Pre- and postfilter samples were obtained immediately after the infusion began (time 0) and at 1, 2, 3, 4, 8, 12, 16, 20, and 24 hours during the infusion. At 24 hours pre- and postfilter, cysteine/cystine were quantitated at 87.3% and 85% of the initial concentrations, respectively, for the NF solution and 92% and 91.5% for the FR solution. Pre- and postfilter copper was quantitated at 87.5% and 92.5% of the initial concentrations, respectively, for the NF solution and 88.2% and 95.2% for the FR solution. The 24 hour area under the curve for cysteine/cystine was 88.4% for the NF solution and 96.4% for the FR solution. For copper, the area under the curve for the NF solution was 99% and 96.7% for the FR solution. There was no visual evidence of incompatibility or precipitation. We conclude that copper-containing parenteral nutrition solutions with L-cysteine HCl added immediately before infusion are relatively stable after compounding and infusion over 24 hours.

Copper↗