bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-performance liquid-chromatographic separation and fluorescence measurement of biogenic amines in plasma, urine, and tissue.
Authors: Davis T P , Gehrke C W , Gehrke C W , Cunningham T D , Kuo K C , Gerhardt K O , Johnson H D , Williams C H 
Published: January 2020

Abstract
We describe a high-performance liquid-chromatographic method for measuring histamine, norepinephrine, octopamine, normetanephrine, dopamine, serotonin, and tyramine in plasma (2 ml), brain (0.2 g), or urine. These amines are modifed by pre-column derivatization with o-phthalaldehyde, which stabilizes the molecules, facilitates extraction, and improves detection of nanogram amounts. Before separation, samples were neutralized with KOH and immediately derivatized and extracted into ethyl acetate, in which derivatives were stable for longer than 24 h. Interfering amino acids were removed from ethyl acetate by partitioning twice with Na2HPO4 buffer (pH 10.0). Separation was complete in about 90 min on a "mu Bondapak/phenyl" column, with which a stepwise gradient of methanol/phosphate buffer (pH 5.1) was used. A variable-wavelength fluorometer was used (exciting wavelength, 340 nm; emission wavelength, 480 nm). Amount and response were linearly related from 1 to 200 pmol. Precision (CV) for retention times was 1%, for derivatization and injection 2.5%. Analytical recoveries of the seven amines from 2 ml of plasma fortified with 200 pmol averaged 65% (CV approximately 8%). Data on rat-brain tissue samples are compared with results by the trihydroxyindole method. Application of the method to urine from normal persons and a patient with a brain tumor is demonstrated.
Determination of drugs in plasma by high-performance thin-layer chromatography.
Authors: Fenimore D C , Davis C M , Meyer C J 
Published: January 2020

Abstract
High-performance thin-layer chromatography was used to determine chlorpromazine, amitriptyline, nortriptyline, imipramine, desipramine, phenobarbital, and phenytoin in plasma, to demonstrate the utility of this technique for routine analysis. We quantitated the separated components by use of ultraviolet reflectance spectrometry with detection limits as low as 1 microgram/liter. Regressions of psychoactive agents extracted from plasma were linear over the range of 0 to 300 microgram/liter. The anti-convulsant drugs, phenobarbital and phenytoin, were determined over a range of 0 to 50 mg/liter. Analyses were rapid, reproducible, and well-suited to large-scale programs. Separated components also can be identified in situ by ultraviolet spectrophotometry.
Improved enzymatic assay of chloramphenicol.
Authors: Smith A L , Smith D H 
Published: January 2020

Abstract
We partly purified R-factor-encoded chloramphenicol acetyltransferase (EC 2.3.1.28) from a highly choloramphenicol-resistant mutant derived from Escherichia coli W677/R5. The preparation permitted rapid quanitation of chloramphenicol by use of [14C]acetylcoenzyme A, removing the diacetylated product by selective adsorption onto micropore filters. Succinyl and glucuronyl 3-hydroxyl esters of chloramphenicol were not active as substrates for the preparation, nor were they active as inhibitors. The enzyme was free of chloramphenicol reductase activity, and utilizes other biologically active chloramphenicol analogs. Other antibiotics, at concentrations commonly found in human sera, and blood preservatives, at concentrations 10-fold that found in blood-collection tubes, did not interfere with the enzymic quantitation of chloramphenicol. We conclude that this enzyme preparation permits rapid clinical quantitation of chloramphenicol.
Micro-scale extractive alkylation procedure for the gas-chromatographic measurement of theophylline in serum and saliva, with use of a nitrogen detector.
Authors: Joern W A 
Published: January 2020

Abstract
In this 10-min gas-chromatographic assay for theophylline, a 25-microliter portion of serum or saliva sample, 100 microliter of extraction reagent, and 1.0 ml of solvent were mixed, the solvent separated and evaporated, and an aliquot of the reconstituted extract injected into the gas chromatograph. At a concentration of 11 mg/liter, within-run precision (CV) was 3.6% and run-to-run 2.9%. At 22 mg/liter, within-run precision was 2.8%. Concentration and instrument response are linearly related between 2 and 40 mg/liter. The limit of detection was 0.4 mg/liter. Results correlated well (r = 0.98) with those by another micro-scale gas-chromatographic procedure. Analytical recovery was estimated to exceed 90%, and no interferences from other xanthines or related drugs were observed.
Spectrodensitometry of nanogram quantities of cholesterol.
Authors: Touchstone J C , Dobbins M F , Hirsch C Z , Baldino A R , Kritchevsky D 
Published: January 2020

Abstract
In studies of hydrolysis and synthesis of cholesterol esters by aortic enzymes, conventional methods (aside from isotope methodology) are too insensitive to measure reaction products when few aortas are used. High-performance thin-layer chromatography coupled with spectrodensitometry of plates charred after spraying with a cupric acetate-phosphoric acid reagent permitted quantitation of 10-ng amounts of cholesterol, cholesterol oleate oleate, and oleic acid. Linear calibration curves were obtained after spectrodensitometry of chromatograms containing 10-200 ng of lipid. The results were verified by radioassay.
A fluorogenic substrate for angiotensin-converting enzyme in plasma.
Authors: Russo F S , Persson A V , Wilson I B 
Published: January 2020

Abstract
A simple, sensitive, and reproducible assay for angiotensin-converting enzyme is described. It is based on the hydrolysis of the minimally fluorescent substrate p-nitrobenzyloxycarbonylglycyl-L-tryptophylglycine to the products p-nitrobenzyloxycarbonylglycine and the highly fluorescent L-tryptophylglycine. The L-tryptophylglycine was analyzed by fluorometry (lambda excitation = 285 nm; lambda emission = 350 nm). The mean value for human plasma (serum) is 16.5 nmol of substrate hydrolyzed per minute per milliter of plasma under the described assay conditions.
Analysis for salicylic acid in serum by high-performance liquid chromatography.
Authors: Blair D , Rumack B H , Peterson R G 
Published: January 2020

Abstract
We report a specific and sensitive quantitative assay for salicylate in serum or plasma. As little as 3 microliter of sample can be analyzed by an external standard procedure and larger volumes by diluting with the internal standard (o-methoxybenzoic acid). No extraction or derivatization is necessary and salicylic acid and the internal standard elute in 6 and 3.75 min, respectively. Peak-height ratios are linearly related to concentrations between 10 and 500 mg/liter. By comparison with an existing fluorometric method, our procedure is faster, more specific, and more sensitive.
Gas-liquid chromatographic determination of bupivacaine and lidocaine in plasma.
Authors: Zylber-Katz E , Granit L , Levy M 
Published: January 2020

Abstract
A modified gas-liquid chromatographic method for determining plasma concentrations of bupivacaine and lidocaine is described, with cyclizine as an internal standard. The extraction procedure requires no solvent evaporation, thus overcoming the problem of drug volatility. Concentrations as low as 0.1 mg/liter can be determined. The plasma sample is made alkaline and extracted into n-hexane, re-extracted into a small volume of an aqueous acid phase, and finally extracted into 50 microliter of methylene chloride after alkalinization. The final extract is assayed by gas chromatography on a 5% OV-17 column. The extraction scheme of the present method eliminates interferences by endogenous plasma constituents.
Spurious brain creatine kinase in serum from patients with renal disease.
Authors: Coolen R B , Herbstman R , Hermann P 
Published: January 2020

Abstract
Creatine kinase isoenzyme I(BB) is generally not detectable in normal serum, and its occurrence in serum has been documented in only a few disease states. In particular, increased activity of this isoenzyme has been reported in association with chronic renal failure, hemodialysis, and renal transplantation. The present study demonstrates that the apparent creatine kinase observed in the serum of such renal patients is an artifact, observed as a result of measuring creatine kinase isoenzymes by fluorescence. Our observations resemble those of McKenzie et al. [Clin. Chim. Acta 70, 333(1976)] concerning an artifact in the fluorometric determination of lactate dehydrogenase isoenzymes in the sera of patients with end-stage renal failure. The artifact binds to albumin, is not a protein, and occurs in some normal sera at very low concentrations. This artifact can be mistakenly identified as isoenzyme I in renal-disease patients if CK isoenzymes are determined fluorometrically.
Emergency determination of acetaminophen.
Authors: Meola J M 
Published: January 2020

Abstract
I describe a senstive colorimetric micromethod in which a pH 11.0 carbonate buffer is used to induce acetaminophen to react with Folin-Ciocalteau reagent at room temperature. These reagents and a simple solvent extraction favor formation of a stable indophenol dye with acetaminophen, giving this procedure a good degree of specificity. Results correlate well with those by liquid-chromatographic procedures, and day-to-day precision is less than 8%.
Detergent-containing glucose oxidase reagent for use with the Beckman glucose analyzer.
Authors: Bajema L L , Lee W , Zebelman A M , Kenny M A 
Published: January 2020

Abstract
We describe a modified glucose oxidase reagent for use in the polarographic determination of glucose with the Beckman "Glucose Analyzer." The reagent contains 1 mL/L of a surfactant (Brij-35 250 g/L solution) as the wetting agent instead of glycerol. Precipitation of components associated with the formulation recommended by Fischl et al. [Clin. Chem. 21, 760 (1975)] does not occur with this reagent. It can be used immediately after preparation. When compared to analytical performance of the commercially prepared reagent, the precision was unchanged by the modified reagent, but the upper limit of accurate response was diminished (7.5 g/L vs. 6.7 g/L). The modified reagent is less expensive than are commercially prepared reagents.
Discrete modular system for automation of radioimmunoassay of serum choriomammotropin.
Authors: Hammond G L , Leinonen P , Vihko R 
Published: January 2020

Abstract
We describe a discrete automated radioimmunoassay system for determining choriomammotropin (placental lactogen) in human serum. With the present system it can be measured in as many as 37 unknown sera (50 muL) and three quality-control sera, in duplicate, within 1.5 h. The time required for sample preparation, incubation (15 min), and separation of free and bound radioactivities (a 150 mL/L polyethylene glycol solution is superior to a twofold volume of absolute ethanol) is less than 45 min. The remaining time required is for counting and data processing. Intra-assay precision is 4.6% (CV). The modular approach endows the instrumentation with much flexibility, and consequently is suitable for automation of a wide range of assay protocols.
Removal of contaminating substances before gas-liquid-chromatographic determination of aldosterone in urine.
Authors: Graef V , Furuya E , Nishikaze O 
Published: January 2020

Abstract
This paper deals with removal of contaminants before gas-chromatographic determination of aldosterone in urine. Urine is incubated with beta-glucuronidase, which hydrolyzes all beta-glucuronides except aldosterone-18-glucuronide. The contaminants (the aglycones released and other methylene chloride-soluble substances) are extracted with methylene chloride. Solvolysis of the aqueous phase liberates aldosterone from aldosterone-18-glucuronide, which then is extracted with methylene chloride and oxidized by use of periodic acid. The resulting lactone can be easily separated by one-dimensional thin-layer chromatography and determined by gas-liquid chromatography.
Improved determination of serum theophylline by gas chromatography with use of a nitrogen-phosphorus detector.
Authors: Vinet B , Zizian L 
Published: January 2020

Abstract
We describe a method for the 7-min determination of theophylline in less than 100 muL of serum. The procedure requires no centrifugation or solvent evaporation after extraction. Butylation is done on the gas-chromatographic column by injecting the serum extract followed by a butylating mixture which contains 1-iodobutane as the alkylating agent. The method is precise, accurate, and free of interference. Results correlate well with those by ultraviolet spectrophotometry.
Quality of sweat test performance in the diagnosis of cystic fibrosis.
Authors: Shwachman H , Mohmoodian A 
Published: January 2020

Abstract
The sweat test, correctly performed, appears to be reliable, but results were found to be unreliable about half the time in 84 small community hospitals assessed. The reasons are inexperienced and untrained technicians, the infrequency of test performance, the use of unstandardized equipment, and the lack of appropriate standards. It behooves all clinical laboratory directors to re-examine and standardize their procedures and use the recommendations of the Cystic Fibrosis Foundation. Physicians should be made aware of the current situation and send their patients only to laboratories that perform the test reliably.
Homogeneous enzyme immunoassay of serum digoxin with use of a bichromatic analyzer.
Authors: Eriksen P B , Andersen O 
Published: January 2020

Abstract
We applied the Enzyme Multiplied Immunoassay Technique (EMIT; Syva Corp., Palo Alto, CA) for determination of serum digoxin to the ABA-100 bichromatic analyzer. Assay conditions were almost exactly as prescribed for the manual procedure, but the ABA-100 offers high automation, smaller reagent volumes, and shorter reaction time. Precision studies gave CV's of less than 10%. Sixty patients' samples, analyzed for digoxin by radioimmunoassay and this enzyme immunoassay, gave a correlation (r) of 0.941. Results obtained with the ABA-100 were apparently slightly higher. One kit provides reagents for 250 assays, as compared to 70 assays with the manual procedure. In an emergency situation a result will be available about 60 min after the patient's sample is received; one operator can analyze about 120 samples in 8 h.
A liquid-chromatographic analysis for ritalinic acid [alpha-phenyl-alpha-(2-piperidyl) acetic acid] in serum.
Authors: Soldin S J , Hill B M , Cahn Y P , Swanson J M , Hill J G 
Published: January 2020

Abstract
We describe a "high-performance" liquid-chromatographic assay for measuring ritalinic acid in 300 muL of serum. The procedure includes adsorption of ritalinic acid and internal standard (alpha,alpha-dimethyl-beta-emthylsuccinimide) from serum onto charcoal, from which both compounds are eluted with methanol. The methanol extract is evaporated, the residue dissolved in a 93/7 (by volume) mixture of potassium phosphate buffer (20 mmol/L, pH 3.8) and acetonitrile, and an aliquot of this solution is chromatographed. We used a mu-Bondapak C-18 column with the above-mentioned buffer system as mobile phase, a flow rate of 2.0 mL/min, and a column temperature of 40 degrees C. Ritalinic acid and internal standard are detected by their absorbance at 192 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis for ritalinic acid in serum at concentrations greater than 50 microgram/L. Analytical recoveries were greater than 73% and the method affords good day-to-day precision (CV, less than 12%).
Microviscosity of amniotic fluid phospholipids, and its importance in determining fetal lung maturity.
Authors: Blumenfeld T A , Cheskin H S , Shinitzky M 
Published: January 2020

Abstract
Fluorescence polarization measurements of microviscosity (apparent viscosity within the hydrophobic center of lipid bilayers) of amniotic fluid correlate well with lecithin/sphingomyelin ratios determined by thin-layer chromatography. In addition to lecithin, phosphatidylglycerol and phosphatidylinositol are important for determining fetal lung maturity, but the lecithin/sphingomyelin ratio gives no information concerning these other phospholipids. The microviscosity of sphingomyelin significantly exceeded that of lecithin over the temperature range 25--37 degrees C; values for phosphatidylglycerol, phosphatidylinositol, and phosphatidylserine were lower. Phosphatidylglycerol, phosphatidylinositol, and phosphatidylserine, added individually, significantly decreased the microviscosity of dispersions with lecithin/sphingomyelin ratios corresponding either to fetal lung immaturity or maturity. Phosphatidylglycerol caused the greatest decrease in both. Mixtures of the three phospholipids in the proportions found in term amniotic fluid decreased the microviscosity of fluids with either mature or immature lecithin/sphingomyelin ratios by 23--27%. When each was present in the proportion found in tracheal aspirate (twice that of term amniotic fluid), the decreases uere 46--50%. This technique quickly and precisely indicates not only fetal lung maturity but also the presence of important phospholipids other than lecithin and sphingomyelin.
Column chromatography and immunoassay compared for measuring the isoenzymes of aspartate aminotransferase in serum.
Authors: Sampson E J , Hannon W H , McKneally S S , McKenzie C , Miller S A , Whitner V S , Burtis C A 
Published: January 2020

Abstract
We compare a column-chromatographic method and a homogeneous immunoassay method for separately measuring the mitochondrial and cytoplasmic isoenzymes of aspartate aminotransferase. Analytical recovery for the two methods averaged 102% (SD, 2%) and 103% (SD, 4%), respectively, for 11 pools prepared by adding the purified isoenzymes to serum and 102% (SD 8.9%) and 89% (SD, 8.1%) for 26 unaltered specimens of human serum. In comparing the results of the immunoassay method (y) to the chromatographic method (x), our measurements agreed closely for the mitochondrial (y = 0.947 X + 7, r = 0.9991, standard error of estimate = 2.9 U/L) and cytoplasmic (y = 0.92x-6, r = 0.9995, standard error of estimate = 2.1 U/L) isoenzymes in pools prepared from the purified isoenzymes. Similar measurements of the 26 human serum specimens yielded the following results for least-squares evaluation; cytoplasmic isoenzyme y = 1.03x-11, r = 0.994, and standard error of estimate = 6.0 U/L; mitochondrial isoenzyme y = 0.75x+0, r = 0.927, and standard error of estimate = 3.9 U/L.
Rapid analysis for iodotyrosines and iodothyronines in thyroglobulin by reversed-phase liquid chromatography.
Authors: Alexander N M , Nishimoto M 
Published: January 2020

Abstract
We describe a 10-min reversed-phase "high-pressure' liquid-chromatographic procedure for measuring tyrosine, monoiodotyrosine, diiodotyrosine, 3,5-diiodothyronine, 3,5,3'-triiodothyronine, 3,3',5'-triiodothyronine, and thyroxine. Resolution and quantitation of a mixture of these amino acids were excellent on LiChrosorb (Altex) RP-8 with isocratic elution (1.5 mL/min) with acetonitrile/water/glacial acetic acid (50/49/1 by vol). As little as 100 ng of each iodoamino acid could be detected and quantitated with a conventional 1-cm, flow-through spectrophotometric (254-nm) detector coupled to a 10-mV strip-chart recorder. Analyses for monoiodotyrosine, diiodotyrosine, 3,5,3'-triiodothyronine, and thyroxine in hog and beef thyroglobulin hydrolysates (sequential digestion with pronase and aminopeptidase) agreed well with results by anion-exchange chromatography and by competitive radioassays. To prevent interference by tryptophan in the analysis for diiodotyrosine, we batch-separated the iodoamino acids by anion-exchange chromatography before the procedure. The procedure we describe seems generally useful for detection and quantitation of thyroid hormones, thyroid hormone metabolites, and iodotyrosines.
Ribonucleic acid in plasma from normal adults and multiple myeloma patients.
Authors: Hamilton T C , Smith A G , Griffin C A , Henderson R J 
Published: January 2020

Abstract
Reports of the presence of RNA in human plasma have been numerous, often suggesting that RNA in plasma is correlated with human disease. We critically examined the methods for determination of RNA in plasma. Lack of method specificity has caused previous workers to overestimate plasma RNA concentrations by more than 50-fold. To isolate RNA from plasma, we used both a phenol-chloroform extraction and a modified Schmidt-Thannhauser procedure. We show that RNA in plasma can be identified and quantified by alkaline hydrolysis of the plasma extract and subsequent separation of the resulting 2'- and 3'-mononucleotides by "high-performance" liquid chromatography. We could not detect RNA in plasma from either apparently healthy, normal adults or multiple myeloma patients, but found 1.1 mg/L in the plasma of a patient with Waldenström's macroglobulinemia. Our method is useful for the specific determination of RNA in plasma and will detect as little as 600 micrograms/L.
Enzymic determination of fructose in seminal plasma by initial rate analysis.
Authors: Anderson R A , Reddy J M , Oswald C , Zaneveld L J 
Published: January 2020

Abstract
We describe a spectrophotometric assay for fructose in seminal plasma. The method is based on reduction of fructose by a commercially available preparation of sorbitol dehydrogenase (EC 1.1.1.14), with the concomitant oxidation of NADH. The initial rate of NADH oxidation, which is proportional to the fructose content of seminal plasma, can be measured either with a recording spectrophotometer or by conventional two-point kinetic assay. The method was as accurate, precise, and sensitive as, and more specific and rapid than, currently used colorimetric (resorcinol) methods for fructose determination. Values (mmol/L) for fructose in seminal plasma from several species are: man, 9 +/- 2 (SD); cynamolgus monkey (Macaca fasicicularis)., 108 +/- 19; bull, 30 +/- 1; and rabbit, 13 +/- 4. These values agree with previously published results. We believe the method is appropriate for both research and clinical use.
Radiochemical method for measuring plasma clearance and urinary excretion of pteroylglutamic acid.
Authors: da Costa M , Rothenberg S P , Rosenberg Z 
Published: January 2020

Abstract
A radiochemical procedure is described for specific determination of pteroylglutamate in serum and urine. This method depends on denaturation of methyltetrahydrofolate with peroxide and measurement of the residual folate by a ligand-binding radioassay. The binding determinant for the radioassay is a folate-binding protein, partially purified from chronic myelogenous lekemia cells, that has low affinity for the reduced folates and thus will preferentially measure residual pteroylglutamate rather than any nondenatured residual methyltetrahydrofolate. We used this assay to measure the clearance from plasma and the urinary excretion of pteroylglutamate and a small fraction of serum folate that is stable to this oxidation procedure. The plasma clearance after intravenous injection is characterized by an initial rapid distribution phase followed by a second, slower metabolic phase; after about 2 h all of the administered pteroylglutamate has been cleared from the blood. The peak concentration of total folate in serum 1--2 min after administration of pteroylglutamate exceeded the sum of the endogenous stable and baseline serum folate, indicating that a reduced labile folate was released from the liver and perhaps from other tissues. This reduced folate had a slower metabolic clearance rate and was excreted to some extent in urine. Only 2.3 and 7.9% of the pteroylglutamate administered to two normal subjects was excreted as stable folate.