Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Influence of pH on absorbance and CD-spectra of DNA in PEG-containing water-salt solutions has been studied. The changes in the spectra appeared due to disturbance of the DNA secondary structure upon acidification of the medium proir to or after DNA compactization. If acidification preceeds DNA compactization an intense negative band in the CD spectrum inherent to the compact particles is observed at pH values 7-4. The intensity of the band decreases with an increase of the acidity. The size of the compact particles as evaluated from the dependence of the apparent optical density on the wavelength value remains unchanged (about 1200 A). If the solution is strongly acidified (pH 4.0-2.8) and a considerable disturbance in the DNA secondary structure takes place a negative band in the CD spectrum completely disappears. If one acidifies a solution containing preformed DNA compact particles a decrease of the intensity of the CD negative band starts at lower pH values (less than 2.8). This process is accompanied by an increase of the size of the particles. Acidic "denaturation" of DNA within the compact particles (pH approximately 2.5) is followed by a dissappearance of the CD negative band and a considerable increase of the particle size. The data obtained indicate that the specific arrangement of DNA strands manifested in a CD negative band depends on the defects in the DNA secondary structure.
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PMID:[The compact form of DNA in solution. IV. The effect of secondary structure defectiveness on the arrangement of double-chained DNA molecules into compact particles]. 0 1

The influence of severe exocrine pancreatic disease on the acid-neutralizing capacity of the duodenum was studied in five patients with pancreatic insufficiency (PI) and six control subjects using duodenal perfusion-marker technique. Hydrochloric acid (0.1 N containing 1% PEG) was infused at constant rates (1.2, 4.5 and 7.0 ml/min) into the duodenum just distal to the duodenal bulb. Samples were aspirated from the tip of the duodenal perfusion tube located at the ligament of Treitz. All samples were analyzed for volume, pH, titrable acidity, PEG and [14C]PEG (gastric marker) determination. Patients with PI demonstrated significantly diminished ability to neutralize various acid loads as compared to controls who virtually completely neutralized acid loads in the range of maximal gastric acid secretion. Exogenous secretin did not significantly improve percent acid neutralized in PI. These data clearly indicate that patients with PI have significantly impaired ability to neutralize even small loads of acid in the duodenum.
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PMID:Impaired acid neutralization in the duodenum in pancreatic insufficiency. 3 15

The effects of two sources of dietary fiber on the characteristics of cecal contents were assessed directly with miniature swine cannulated to facilitate frequent collections of cecal digesta. The short-chain fatty acid (SCFA) concentrations increased and the pH decreased at the same time that meal constituents entered the cecum; PEG was used as a dietary marker. The bean diet resulted in higher concentrations of acetate and total SCFA in cecal digesta, lower concentrations of butyrate, a larger SCFA pool size, and a more acidic pH than did the bran diet. Thus, we conclude that SCFA concentrations and acidity of the digesta are directly related and that dietary fibers can affect simultaneously several variables that are implicated as factors influencing colonic health.
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PMID:High-fiber diets: influence on characteristics of cecal digesta including short-chain fatty acid concentrations and pH. 254 17

Chloralose may be used in a 10% solution as an anaesthetic in dogs. The solubility of chloralose was found to be much higher in polyethylene glycol-200 (PEG-200) than in either warm (body temperature) or cold saline (0.9% NaCl). The intravenous (i.v.) administration of chloralose in warm saline solution induced acidosis as a result of the increase in the level of metabolic acids. The acidity generated by chloralose in almost neutral saline was probably the result of increase in the base deficit in the animal. The infusion of PEG-200 (almost neutral) significantly reduced the base deficit without disturbing the PaO2 or PaCO2 in the arterial blood. The base deficit value was significantly lower after administration of chloralose solution in PEG-200 (almost neutral) than after administration in saline. The use of PEG-200 as a solvent for chloralose was advantageous in two ways. Firstly, it prevented the production of acids in anaesthetic solution and neutralized the blood metabolic acids generated by chloralose administration in saline. Secondly, the solubility of chloralose (10% w/v solution) in PEG-200 was very much higher than in warm or cold saline.
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PMID:The effect of polyethylene glycol-200 on metabolic acidosis induced by chloralose anaesthesia. 641 35

Poly(ethylene glycol) (PEG) in water is known to alter the structure and/or state of water to give a different polarity from that of pure water. We determined using the solvatochromic comparison method the dipolarity/polarizability (pi*), hydrogen bond (HB) accepting basicity (beta) and HB donating acidity (alpha) of aqueous solutions of PEGs of variegated molecular weights at different concentrations in order to understand the influence of the polymer on these properties of water. It was observed that PEG decreases alpha for water while it does not change pi* and beta appreciably in the range of the molecular weight and compositions studied.
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PMID:Dipolarity, hydrogen-bond basicity and hydrogen-bond acidity of aqueous poly(ethylene glycol) solutions. 1250 89

The aim of this study was to examine the stability of bovine serum albumin (BSA) in poly(DL-lactic acid-co-glycolic acid) (PLGA) microspheres upon addition of a new excipient, poly(ethylene glycol)-poly(L-histidine) diblock copolymer (PEG-PH). Poly(L-histidine) component can form an ionic complex with BSA under acidic conditions within a narrow pH range. To optimize the ionic complexation conditions for BSA with PEG-PH, the resulting complex sizes were monitored using the Zetasizer. PLGA microspheres containing BSA as a model protein were prepared by w/o/w double emulsion method. BSA stability in aqueous solutions and after release from PLGA microspheres was determined using circular dichroism (CD) spectroscopy for secondary structure analyses and fluorescence measurements for tertiary structure analyses. The release profile of BSA from the microspheres was monitored using UV spectrophotometry. The rate of PLGA degradation was monitored by gel permeation chromatography. The pH profile within microspheres was further evaluated by confocal microscopy using a pH-sensitive dye. Approximately 19 PEG-PH molecules and one BSA molecule coalesced to form an ionic complex around a pH range of 5.0-6.0. Plain BSA/PLGA and BSA/PEG-PH/PLGA microspheres had a mean size of 27-35 microm. PLGA microspheres with a BSA loading efficiency >80% were prepared using the double emulsion method. PEG-PH significantly improved the stability of BSA both in aqueous solutions and in PLGA microspheres. The release profiles of BSA from different formulations of PLGA microspheres were significantly different. PEG-PH effectively buffered the local acidity inside the microspheres and improved BSA release kinetics by reducing initial burst release and extending continuous release over a period of time, when encapsulated as an ionic complex. PLGA degradation rate was found to be delayed by PEG-PH. There was clear evidence that PEG-PH played multiple roles when complexed with BSA and incorporated into PLGA microspheres. PEG-PH is an effective excipient for preserving the structural stability of BSA in aqueous solution and BSA/PLGA microspheres formulation.
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PMID:Stability of bovine serum albumin complexed with PEG-poly(L-histidine) diblock copolymer in PLGA microspheres. 1626 69

In this third paper, varied types of polar stationary phases, namely silica gel (SI), cyano (CN)- and amino-propyl (NH2)-bonded silica, propanediol-bonded silica (DIOL), poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA), were investigated in subcritical fluid mobile phase. This study was performed to provide a greater knowledge of the properties of these phases in SFC, and to allow a more rapid and efficient choice of polar stationary phase in regard of the chemical nature of the solutes to be separated. The effect of the nature of the stationary phase on interactions between solute and stationary phases and between solute and carbon dioxide-modifier mobile phases was studied by the use of a linear solvation energy relationship (LSER), the solvation parameter model. The retention behaviour observed with sub/supercritical fluid with carbon dioxide-methanol is close to the one reported in normal-phase liquid chromatography with hexane. The hydrogen bond acidity and basicity, and the polarity/polarizability favour the solute retention when the molar volume of the solute reduces it. As with non-polar phases, the absence of water in the subcritical fluid allows the solute/stationary phase interactions to play a greater part in the retention behaviour. As expected, the DIOL phase and the bare silica display a similar behaviour towards acidic and basic solutes, when interactions with basic compounds are lower with the NH2 phase. On the CN phase, all interactions (hydrogen bonding, dipole-dipole and charge transfer) have a nearly equivalent weight on the retention. The polymeric phases, PEG and PVA, provide the most accurate models, possibly due to their better surface homogeneity.
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PMID:Characterisation of stationary phases in subcritical fluid chromatography with the solvation parameter model. III. Polar stationary phases. 1648 36

Double hydrophilic block copolymers PEG-b-PEI-linear with different PEI block lengths have been examined for CaCO3 mineralization at the air/water interface. The results demonstrated that either PEI length or the solution acidity had a significant influence on the morphogenesis of vaterite crystals at the air/water interface. A possible mechanism for the stratification of CaCO3 vaterite crystals has been proposed. Increasing either PEI length or the initial pH value of the solution will decrease the density of the PEG block anchored on the binding interface and result in exposing more space as binding interface to solution and favoring the subnucleation and stratification growth on the polymer-CaCO3 interface. In contrast, higher density of PEG blocks will stabilize the growing crystals more efficiently and inhibit subnucleation on the polymer-CaCO3 interface, and thus prevent the formation of stratified structures. This study provides an example that it is possible to access morphogenesis of calcium carbonate structures by a combination of a block copolymer with the air/water interface.
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PMID:Double hydrophilic block copolymer controlled growth and self-assembly of CaCO3 multilayered structures at the air/water interface. 1680 Jun 67

Many systems have been proposed for the encapsulation of bone marrow stromal cells (BMSCs) within degradable hydrogels. Here, we use a novel cyclic acetal-based biomaterial formed from 5-ethyl-5-(hydroxymethyl)-beta,beta-dimethyl-1,3-dioxane-2-ethanol diacrylate (EHD) and poly(ethylene glycol) diacrylate (PEGDA). A cyclic acetal-based hydrogel may be preferred as cyclic acetals hydrolytically degraded into diols and carbonyls as primary degradation products, which may not affect local acidity, unlike other widely investigated polymers. The EHD monomer and PEGDA polymer may be fabricated into a EH-PEG hydrogel by radical polymerization initiated by the ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED) system. The objective of this work is to determine whether the components utilized in the fabrication of EH-PEG hydrogels as well as the EH-PEG hydrogels permit BMSC viability, metabolic activity, and osteodifferentiation. Cell viability and metabolic activity were assessed after 30 min, 1 h, and 3 h of exposure to pertinent concentrations of the initiator system (10-20 mM). Osteodifferentiation was assessed by alkaline phosphatase and osteocalcin expression after a short exposure to the initiator system to simulate the encapsulation process. Lastly, cell viability was assessed immediately after encapsulation and after 7 days of culture within the EH-PEG hydrogels. Results indicate that the metabolic activity and viability of BMSCs are minimally affected, and that osteodifferentiation is not significantly affected by the APS-TEMED initiator system. Also, encapsulated BMSCs maintained viability within EH-PEG hydrogels for 7 days. This work demonstrates that the EH-PEG hydrogel is a viable option for the encapsulation and osteodifferentiation of BMSCs.
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PMID:Cyclic acetal hydrogel system for bone marrow stromal cell encapsulation and osteodifferentiation. 1802 39

A novel macroporous resin was prepared from an epoxy resin and triethylenetetramine (TETA) via a polymerization using micro-phase separation. In this novel method the polyethylene glycol (PEG-400) was used as solvent in the initial stage and a phase-separation reagent at later stage of the polymerization was firstly adopted. The resin was modified by sodium chloroacetate and the carboxyl groups were introduced. Its structure was characterized by Fourier transform-infrared spectra (FTIR) and scanning electron microscopy (SEM), respectively. The adsorption-desorption characteristics of the resin for Cu(II) in aqueous solution were investigated in detail using ICP-AES. The interaction between the metal ion and the resin was found to be depended upon the acidity of the medium. The prepared resin is strongly chelating and exhibits a chelating ability that can remove cupric ion in waste water treatment.
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PMID:Synthesis and characteristics of macroporous epoxy resin-triethylenetetramine polymer modified by sodium chloroacetate for copper chelation in aqueous solution. 1815 94


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