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At least 991 records · Page 55Linked to original sources
PubMed2000

Effect of resin surface charge on gastric mucoadhesion and residence of cholestyramine.

Previous studies performed on excised gastric tissue and in healthy volunteers revealed that the ion exchange resin, cholestyramine, exhibits mucoadherent behaviour. This study was designed to elucidate whether surface charge affected this behaviour. Gamma scintigraphy was performed on fasted normal subjects following oral administration of cholestyramine or the cationic exchanger Amberlite(R) IRP-69, either uncoated or polymer-coated to mask their charge. Subjects were fed after 4 h. The initial gastric emptying of all formulations was similar (T(50) values (mean+/-S.E.M.): cholestyramine=85.86+/-9.16 min; IRP-69=76.09+/-9.23 min; polymer-coated cholestyramine=72.0+/-12.64 min; polymer-coated IRP-69=70.25+/-10.57 min: P=0.724). However, after 3 h the emptying pattern of cholestyramine was slower than that of IRP-69. This resulted in greater retention times than IRP-69 (AUC(0-6) values (relative units)=15,200+/-1093 versus 9452+/-811; cholestyramine versus IRP-69: P=0.0004). This effect was reduced by polymer-coating the cholestyramine. Serial images showed that cholestyramine was trapped in the oropharyngeal region and subsequently displaced by the meal, resulting in higher levels of activity remaining at 6 h. Thus, cholestyramine exhibited prolonged gastric residence via mucoadhesion and was distributed throughout the stomach. The surface charge of the resin was found to have a contributory role. These materials may have potential for the delivery of drugs in the topical treatment of the gastric mucosa, for example in the eradication of Helicobacter pylori.

Adolescent↗
PubMed1979

Production of L-serine by Sarcina albida.

Conditions for the production of microbial L-serine hydroxymethyltransferase and for the conversion of glycine to L-serine were studied. A number of microorganisms were screened for their abilities to form and accululate L-serine from glycine, and Sarcina albida was selected as the best organism. Enzyme activity in this organism as high as 0.12 U/ml could be produced in shaken cultures at 30 degrees C in a medium containing glucose, ammonium sulfate, glycine, yeast extract, and inorganic salts. L-Serine was produced most efficiently by shaking cells at 30 degrees C in a reaction mixture containing 20% glycine, 5 X 10(-3) M formaldehyde, and 3 X 10(-4) M pyridoxal phosphate in yields of 22 mg of broth in 5 days. L-Serine was easily isolated in 84% yields by ion-exchange resin.

Bacteria↗
PubMed2005

Removal of lipopolysaccharides from protein-lipopolysaccharide complexes by nonflammable solvents.

During the recovery of recombinant proteins from gram negative bacteria, many of the methods used to extract proteins from cells release lipopolysaccharides (LPS, endotoxin) along with the protein of interest. In many instances, LPS will co-purify with the target protein due to specific or non-specific protein-LPS interactions. We have investigated the ability of alkanediols to effect the separation of LPS from protein-LPS complexes while the complexes are immobilized on ion exchange chromatographic resins. Proteins were complexed with fluorescently labeled LPS and bound to ion exchange resin. Alkanediol washes of the resins were preformed and the proteins eluted. Column eluates were monitored for LPS and protein by fluorescence and UV spectroscopy, respectively. Alkanediols were effective agents for dissociating LPS from protein-LPS complexes. The efficiency of LPS removal increased with increasing alkanediol chain length. The 1,2-alkanediol isomers were more effective than terminal alkanediol isomers in the separation of LPS from protein-LPS complexes, while the separation of LPS from protein-LPS complexes was more efficient on cation exchangers than on anion exchangers. In addition, it was noted during these investigations that the 1,2-alkanediols increased the retention time of the proteins on the ion exchange resins. Alkanediols provide a safer alternative to the use of other organics such as alcohols or acetonitrile for the separation of LPS from protein due to their lower toxicity and decreased inflammability. In addition, they are less costly than many of the detergents that have been used for similar purposes.

Boron Compounds↗
PubMed2000

Determination of glufosinate ammonium and its metabolite (AE F064619 and AE F061517) residues in water by gas chromatography with tandem mass spectrometry after ion exchange cleanup and derivatization.

An analytical method for the determination of glufosinate ammonium and its principal metabolites, AE F064619 and AE F061517, in water of two different hardnesses (5 and 30 DH, French hardness) has been developed and validated. Samples were spiked at different levels (0. 05 and 0.5 microgram/L) and were purified by column chromatography on ion-exchange resins. After derivatization with glacial acetic acid and trimethylarthoacetate mixture, the derivatives were quantified by using capillary gas chromatography with an ion-trap tandem mass spectrometric detector. Analytical conditions for MS/MS detection were optimized, and the quantification was carried out on the areas of the most representative ions. The limit of quantification was validated at 0.05 microgram/L for each compound. The mean recovery value and the relative standard deviation (n = 20) were 92.0% and 17. 8% for glufosinate ammonium, 90.2% and 15.8% for AE F064619, and 89. 7% and 12.7% for AE F061517.

Acetates↗
PubMed2005

Improved separation methods for the recovery of (82)Sr from irradiated targets.

(82)Rb is a short-lived positron-emitting isotope (T(1/2)=75 s) that is increasingly being used in PET to study blood flow through the heart and brain. This isotope is supplied to physicians in the form of a generator where the parent isotope, (82)Sr, is immobilized onto an ion exchange column allowing the (82)Rb to be eluted with isotonic saline as required. (82)Sr is manufactured by the proton irradiation of molybdenum, rubidium chloride or rubidium metal targets followed by complex separations to recover the (82)Sr. A number of inorganic ion exchange materials were evaluated for their ability to remove (82)Sr from simulated target solutions and compared with currently used organic ion exchange resins. Sodium nonatitanate was identified as a replacement for current resins as a potential material that would simplify target processing and improve the yield of (82)Sr from each target.

Chromatography, Ion Exchange↗
PubMed1991

Determination of pyridoxamine 5'-phosphate in human blood plasma.

Pyridoxamine 5'-phosphate in 18 microliters of human capillary blood plasma is determined by catalytic amplification using the apoenzyme of aspartate aminotransferase. Prior isolation from interfering substances is accomplished by employment of a cation exchange resin in batch operation. The procedure consists of the following stages. Stage I, denaturation of proteins. Trichloroacetic acid is used to precipitate plasma proteins and liberate any bound coenzyme. Dilute NaCl is added to expand the volume thus minimizing coenzyme entrapment in the precipitate. Stage II, isolation of the coenzyme. A sulfonated polystyrene ion exchange resin is used inside a centrifugal filter. Pyridoxamine 5'-phosphate in the supernatant from Stage I adsorbs to the resin. Pyridoxal 5'-phosphate, other organic phosphates, and Pi are removed by centrifugation. Rinsing with dilute NaBH4 destroys traces of pyridoxal 5'-phosphate and washes off residual inhibitors. Pyridoxamine 5'-phosphate is then desorbed with NaOH and Tris buffer and recovered by centrifugation. Stage III, reconstitution and assay. The desorbate from Stage II is incubated with excess apoenzyme. Specific activity of the reconstituted enzyme is measured. Interpolation from a standard curve relating enzyme specific activity and pyridoxamine 5'-phosphate concentration yields the plasma level of the cofactor. Approximately 3 h are required to carry out the procedure. Much of the coenzyme was found not be assayable if plasma was refrigerated overnight or if whole blood was left standing at room temperature for a few hours. The degradation was arrested with freezing at -80 degrees C. In a 13-day experiment involving a healthy subject, sharp rises of plasma pyridoxamine 5'-phosphate were found to occur in response to small doses of oral vitamin B6.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Purified haemoglobin preparations in the evaluation of HbA1c determination by ion exchange chromatography.

The use of ion exchange resins for the estimation of HbA1c in clinical samples rests on the assumption that HbA1c is effectively and efficiently separated from other N-terminally modified haemoglobins and from HbA0. To test this assumption, we applied highly purified preparations of HbA(1a+1b, HbA1c and HbA0 to ion exchange minicolumns, using conditions of application simulating actual blood samples and the first and second elution buffers provided by the manufacturer. The authenticity and purity of the applied haemoglobin preparations were documented by high performance liquid chromatography, gel electrophoresis and carbohydrate content. About 40% of the applied HbA(1a+1b) eluted in the first fraction; 45% eluted in the second fraction, and 10% to 15% required 1 mol/L NaCl to elute from the column. Of the applied HbA1c, 65-80% eluted where expected in the second fraction, about 20% required 1 mol/L NaCl to elute from the column, and the remainder eluted with HbA(1a+1b). Some 3-6% of pure HbA0 applied to minicolumns emerged in the second fraction, with the remainder eluting as expected after making the buffer 1 mol/L in NaCl. The results indicate that the fraction eluting from ion exchange minicolumn chromatography that is designated 'HbA1c' contains HbA(1a+1b), and that a substantial portion of the HbA1c in an applied sample does not elute in this fraction.

Chromatography, High Pressure Liquid↗
PubMed1975

Analysis of urinary mucopolysaccharides using small ion exchange columns.

Methods are presented for the small scale column chromatography of urinary mucopolysaccharides. After isolation by cety pyridinium chloride mucopolysaccharides are applied to a small column of ion exchange resin and eluted by 2 M-sodium chloride. Colorimetric assays on this elutate allow clinically significant disease states to be detected.

Chemical Precipitation↗
PubMed1980

A hexokinase from fish liver with wide specificity for nucleotides as phosphoryl donor.

The liver of rainbow trout contains two hexokinases (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) designated C and D from the elution pattern in DEAE-cellulose column chromatography. Hexokinase D has been purified about 50-fold from the liver of rainbow trout by chromatography with DEAE-cellulose and Sephadex G-200, and by isoelectric focusing. The properties of hexokinase D were similar to those of mammalian hexokinase III with respect to the Km values for ATP and glucose and the substrate inhibition by glucose at high concentration. However, the enzyme showed a wide specificity for nucleotides as the phosphoryl donor. Although it has been reported that the only effective nucleotide as the phosphoryl donor for hexokinase from various origin in ATP, and that ADP, a reaction product, inhibits the enzyme, hexokinase D from the rainbow-trout liver was found to be able to form glucose 6-phosphate (Glc-6-P) from glucose and various nucleotides such as ATP, ADP, CTP, GTP, UTP and UDP. The reaction products from ADP and glucose, Glc-6-P and AMP, were identified by chromatography on ion-exchange resin column and paper. The enzyme D was not inhibited by ADP but was strongly inhibited by AMP, which is a reaction product from ADP.

Animals↗
PubMed1986

HPLC assay of phenylalanine and tyrosine in blood spots on filter paper.

Blood spots on filter paper are used to screen for phenylketonuria. We have developed a high pressure liquid chromatographic assay of phenylalanine and tyrosine after elution of these amino acids from filter paper. The analysis time is 20 min. The amino acids are separated using an ion-exchange resin with post-column ortho-phthalaldehyde derivatization and subsequent fluorescence detection. Other common amino acids do not interfere. The assay is linear from 20 pmol to at least 2,000 pmol with a coefficient of variation of 3%. The assay is as accurate as the determination of phenylalanine by ion-exchange ninhydrin-reactive methods currently in use, but is 100 times more sensitive. The method has the advantages of avoiding venipuncture, is cost effective, has a high sensitivity, and a rapid turnaround.

Adult↗
PubMed1980

125I-labeled gonadoliberin and high specific activity and immunoreactivity: method of iodination and rapid separation.

We describe optimum conditions for iodinating gonadoliberin with use of relatively large proportions of Na 125I. Products of the iodination are separated on an anion-exchange resin (Amberlite IRA-400). The 125I-labeled gonadoliberin thus obtained has a high specific activity (1400 to 1590 Ci/g); because of the conditions of iodination, we believe that the predominant species of the labeled decapeptide is the mono-iodinated one. Our separation and purification of the labeled substance on ion-exchange resin is rapid, economical, and less cumbersome than the use of a Biogel P-2 column. There is no adsorption of the labeled hormone onto the resin, as evidenced by analytical recovery studies with tritium-labeled gonadoliberin. Paper-strip chromatoelectrophoresis showed no free Na 125I or radiolabeled damaged peptide fragments after purification on the resin. When antiserum was used at a concentration 32-fold that used in the regular assay procedure, only 4% of the radioactivity remained in the free form, indicating the high immunoreactivity of the labeled hormone.

Anion Exchange Resins↗
PubMed1982

In vitro adsorption of oxalic acid and glyoxylic acid onto activated charcoal, resins and hydrous zirconium oxide.

Patients suffering from primary hyperoxaluria show elevated plasma concentrations of oxalic acid and glyoxylic acid. The in vitro adsorption of these compounds into activated charcoal, a series of neutral and ion exchange resins and onto hydrous zirconium oxide has been investigated. Hydrous zirconium oxide was the most effective sorbent studied for the removal of both oxalic acid and glyoxylic acid. In batch experiments, the zirconium oxide was capable of binding 5.5 mu mol oxalic acid and 8 mu mol glyoxylic acid per gram sorbent using 0.5 gram sorbent and 50 ml of solutions with initial concentrations of 100 mu mol . L-1 and an ionic composition resembling that of plasma. Recirculation of 2 L of the same solutions through 12 gram of a mixture of hydrous zirconium oxide and alumina for 6 hours at a flow rate of 12 ml . min-1, resulted in a final concentration of 70 mu mol . L-1 of oxalic acid and 50 mu mol . L-/ of glyoxylic acid.

Adsorption↗
PubMed1968

Rapid assay of labeled free fatty acids in mixtures of labeled lipids.

The fatty acids in lipid mixtures are adsorbed on dehydrated hydroxy-charged ion exchange resin, the other lipids are removed by washing with solvent, and the adsorbed fatty acids are released with quaternary ammonium base for counting. All manipulations are carried out directly in scintillation vials.

Carbon Isotopes↗