bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of ampouled tonometered buffer solutions as a quality-control system for pH, pCO2, and pO2 measurement.
Authors: Maas A H , Veefkind A H , Van den Camp R A , Teunissen A J , Winckers E K , Jansen A P 
Published: January 2020

Abstract
In response to the need for an adequate quality-control system for blood-pH and blood-gas analyzers, we investigated the practical application of ampouled phosphate-bicarbonate-chloride solutions tonometered with mixtures of carbon dioxide, oxygen, and nitrogen. This system offers three discrete sets of pH, pCO2, AND PO2 values, which are consistent with normal and pathophysiologically high and low values. The stated values were based on the U.S. National Bureau of Standards scale for pH and on gas analysis for pCO2 and pO2. Influence of temperature, air contact, calibration gas, and storage was established. Internal and external quality control by means of these ampoules is presented. The system is stable, accurate, precise, and suitable for simultaneous quality control of pH, pCO2, and pO2 measurements.
Measurement of antitryptic activity of serum with a centrifugal analyzer.
Authors: Konings C H 
Published: January 2020

Abstract
The Selected Method [Clin. Chem. 20, 396 (1974)] for the enzymatic assay of alpha1-antitrypsin in serum has been adapted for use with the E.N.I.-GEMSAEC. With alpha-N-benzoyl-D,L-arginine-p-nitroanilide as substrate, the difference between the tryptic activity measured with and without addition of serum in the same run has been used to calculate the trypsin-inhibitory capacity. The rate of increase in absorbance at 400 nm of the p-nitroanilide formed, has been evaluated during a reaction time of 140 s. Results correlated well (r = 0.986) for 54 human sera analyzed as described here and by the Selected Method. The adaptation on GEMSAEC can be used in detecting alpha1-antitrypsin deficiency in the newborn.
Semiautomated spectrophotometry of total phospholipids in plasma.
Authors: Wootton D G 
Published: January 2020

Abstract
A one-stage semiautomated method for estimating total phospholipids in plasma is reported. The phospholipids are extracted into aqueous ethanol, combined with a Lewis acid, and the change in pH is monitored colorimetrically. The method, compared with the acid digestion method of Gomori [J. Lab. Clin. Med. 27, 955 (1942)], gives results that are about 0.25 mmol/liter lower, but seems to be a suitable and less hazardous alternative.
Gas-liquid chromatographic determination of nicotine and cotinine in plasma.
Authors: Hengen N , Hengen M 
Published: January 2020

Abstract
We report a procedure for determining nicotine and cotinine in plasma. Nicotine is extracted from 1 ml of plasma with diethyl ether, back extracted, and analyzed by gas-liquid chromatography with a nitrogen/phosphorus detector. Nicotine and its internal standard, modaline, had retention times of 1.9 and 2.9 min, respectively. Cotinine is then extracted from the same plasma with dichloromethane and similarly analyzed. Cotinine and its internal standard, lidocaine, had retention times of 3.8 and 4.9 min. Day-to-day reproducibilities (CV) within 14% for nicotine and within 6% for cotinine are attainable for the respective concentration ranges 1-100 microgram/liter and 1-200 microgram/liter. Nornicotine and related alkaloids do not interfere. The sensitivity was such that less than 0.1 microgram (0.62 nmol) of nicotine and 0.1 microgram (0.62 nmol) of nicotine and 0.1 microgram (0.57 nmol) of cotinine could be detected per liter.
Optimization of methods for aspartate aminotransferase and alanine aminotransferase.
Authors: Bergmeyer H U , Scheibe P , Wahlefeld A W 
Published: January 2020

Abstract
Conditions for accurate measurement of catalytic activity of aspartate aminotransferase and alanine aminotransferase in human serum have been reinvestigated. The basic variables (kind of buffer, buffer concentration, pH, ion effects, and the influence of pyridoxal-5-phosphate) can now be considered optimized. On this basis, the kinetic parameters of both aminotransferases were determined, i.e., Michaelis and inhibitor constants for substrates and reaction products. With a mathematical approach for two-substrate enzyme reactions the substrate concentrations were calculated from the viewpoints "most economical," "most convenient," and "lowest variability." Also the conditions for the indicator reactions have been newly defined with respect to a kinetic model. All calculated data were rechecked experimentally and it can be shown that both approaches fully agree. Furthermore, we show that the mathematical approach allows more precise recommendations for optimized methods. For technical reasons, the catalytic activity of aspartate aminotransferase in human serum can only be measured as a 0.96 fraction of its theoretical maximum velocity, the catalytic activity of alanine aminotransferase as a 0.91 fraction. The assay conditions for a Reference Method are finally described and recommendations are made for optimized routine methods for determination of the catalytic activity of these transferases in human serum.
Liquid-chromatographic procedure for tricyclic drugs and their metabolites in plasma.
Authors: Vandemark F L , Adams R F , Schmidt G J 
Published: January 2020

Abstract
We describe a procedure for determining amitriptyline and imipramine and their active metabolites nortriptyline and desipramine, respectively, at therapeutic concentrations in human plasma by use of liquid chromatography. The drugs are extracted at pH 10.5 into hexane/isoamyl alcohol, which is evaporated and the residue chromatographed. Protriptyline is used as the internal standard. As little as 10 microgram of each drug per liter could be detected in plasma, the limit being established by variability in drug-free plasmas. The day-to-day coefficient of variation for each drug at a concentration of about 100 microgram/liter was about 7%. Doxepin and diphenhydramine interfere with the analysis of amitriptyline. Total analysis time for a single sample is 20 min.
Kinetics of the reactions of unconjugated and conjugated bilirubins with p-diazobenzenesulfonic acid.
Authors: Landis J B , Pardue H L 
Published: January 2020

Abstract
We report the kinetics of the reactions of unconjugated bilirubin and conjugated bilirubin with p-diazobenzene sulfonic acid in aqueous media. Our studies confirm that each reaction proceeds in two steps and that the second step is catalyzed by sulfanilic acid. In the presence of an excess of p-diazobenzenesulfonic acid and in the absence of sulfanilic acid, the reaction for either unconjugated or conjugated bilirubin proceeds in two successive first-order steps, the second step being much the slower. This study emphasizes the first step in the reaction for each species and includes data on the effects of p-diazobenzenesulfonic acid, albumin, benzoate, and caffeine concentrations, pH in the range from 4 to 12, and temperature. Mechanisms proposed for reactions with and without caffeine are used to develop rate equations, and the kinetic data are used to evaluate rate constants, acid dissociation constants for the different bilirubin species, and formation constants for bilirubin-caffeine complex species that are proposed.
Improved micromethod for determination of underivatized clonazepam in serum by gas chromatography.
Authors: Edelbroek P M , De Wolff F A 
Published: January 2020

Abstract
We describe a gas-chromatographic micromethod, with use of a solid injection system and an electron capture detector, for determination of underivatized clonazepam in serum. Vigorous mixing of 100 microliter of serum with 20 microliter of borate buffer (pH 9.0) and 100 microliter of a cyclohexane/dichloromethane mixture (4/6 by vol) containing methyl nitrazepam as internal standard suffices to extract 86% of the clonazepam into the organic layer. We obtained a linear response curve for clonazepam in serum in the concentration range 5 to 150 microgram/liter. The lowest detectable concentration by our method is about 1 microgram/liter of serum. Interference by several anticonvulsant drugs, metabolites, and related compounds was investigated. The assay is simple, rapid, and suitable for clinical routine determination of clonazepam in serum in therapeutic concentrations. We illustrate the steady-state concentration of clonazepam in serum during chronic oral administration to 28 patients.
Drug screening by enzyme immunoassay with the American Monitor KDA.
Authors: Pearson J R 
Published: January 2020

Abstract
The methods for barbiturate, opiate, methadone, and amphetamine have been modified for use with the American Monitor KDA. The modification, which incorporates automatic correction for endogenous lysozyme activity, was evaluated by comparing results obtained with the KDA for human urine samples containing known amounts of drug(s) with results obtained with the procedure recommended by Syva for the Gilford 3500. There was 98% agreement bewteen the two systems. Six calibrators and 40 samples can be assayed for all four drugs in about 2.5 h. The procedure has proven to be reliable for screening urine samples obtained from clients at a methadone treatment center.
Additive, multiplicative, and mixed analytical errors.
Authors: Werner M , Brooks S H , Knott L B 
Published: January 2020

Abstract
Depending on the change in magnitude of analytical error occuring with change in concentration of analyte, two limiting types of error properties can be defined: additive and multiplicative. We investigated whether one of these two error types also characterizes the overall error of methods involving multiple procedural steps, or whether mixed error properties result in these cases. Using "open" quality-control data (i.e., and analyst identifies controls) from each of two hospitals and "blind" quality-control data from one hospital for 11 different assays, we found: (a) With current methodology, overall errors typically are mixed, though predominantly additive and multiplicative overall errors exist as well. (b) "Blinding" the quality-control system typically augments the multiplicative but not the additive error component.
Radioenzymatic assay of DOPA (3,4-dihydroxyphenylalanine).
Authors: Johnson G A , Gren J M , Kupiecki R 
Published: January 2020

Abstract
We modified the single-isotope radioenzymatic assay for catecholamines [Life Sci. 21, 625 (1977)] to assay 3, 4-dihydroxyphenylalanine (DOPA). DOPA decarboxylase is used to convert DOPA to dopamine, which concurrently is converted to [3H]-3-O-methyldopamine in the presence of catechol-O-methyltransferase and [methyl-3H]-S-adenosylmethionine and assayed radioenzymatically. For assay of plasma DOPA, 50 microliter of untreated plasma is added directly into the incubation mixture. A duplicate mixture containing an internal standard requires a second 50-microliter aliquot of plasma. Because the assay measures both DOPA and endogenous dopamine, two additonal aliquots of plasma must be assayed for dopamine in the absence of the decarboxylase by the differential assay; DOPA is estimated by difference. The assay is sensitive to 25 pg (500 ng/liter of plasma). Analysis of DOPA (DOPA plus dopamine) and the concurrent differential assay of catecholamines in at least 10 samples can be done in a single working day. Plasma DOPA concentrations for 42 normotensive adults were 1430 +/- 19 ng/liter (mean +/- SEM). In contrast, do-pamine concentrations for these same subjects averaged 23 +/- 20 ng/liter. Values for the 24 women subjects (15 10 +/- 62 ng/liter) significantly (P = 0.04) exceeded those for the men (1320 +/- 75 ng/liter).
Aspartate aminotransferase activity and isoenzyme proportions in human liver tissues.
Authors: Rej R 
Published: January 2020

Abstract
Aspartate aminotransferase (EC 2.6.1.1) activity and the distribution of its isoenzymes in human liver were examined. Rabbit antiserum against porcin soluble (i.e., non-mitochondrial) enzyme cross-reacted with the soluble enzyme of human origin and was used in an immunoprecipitation assay to quantitate the soluble and mitochondrial isoenzymes. These were separated by rapid, semiquantitative electrophoresis on cellulose acetate and by three other quantitative techniques: isoelectric focusing and anion-and cation-exchange chromatography. The mitochrondrial enzyme averaged 81% of the total activity in normal adult human liver (n = 4). Its contribution was dramatically reduced in single specimens of human fetal liver (56% of total activity) and hepatoblastoma tissue (38%). Total enzyme activities (mumol min-1 per gram of tissue) were: adult, 150; fetal, 38; tumor, 6. Total enzyme concentrations (micromoles of enzyme per kilogram of tissue) found were: adult, 10.8; fetal, 2.7; tumor, 0.4. The concentrations and isoenzyme distribution in human liver are compared to those in various animal model systems. Other methods for quantitative estimation of the isoenzymes and their adaptability for use in estimating concentrations in serum are reviewed.
Enzyme immunoassay and gas--liquid chromatography compared for determination of lidocaine in serum.
Authors: Pape B E , Whiting R , Parker K M , Mitra R 
Published: January 2020

Abstract
Lidocaine, an anti-arrhythmic drug, was quantitated in serum by a commercially supplied enzyme immunoassay procedure. Replicate analyses of serum controls resulted in a within-assay coefficient of variation of less than 5.0 and a between-assay coefficient of variation of less than 6.5. Regression analysis of 87 serum samples analyzed by this technique (y) and by gas-liquid chromatography (x) gave the equation y = 0.96x - 0.03 (r = 0.99). Clinical evaluation of the results indicates the enzyme immunoassay technique to be highly specific and sensitive for lidocaine.
Improved liquid chromatographic determination of placental estriol in urine.
Authors: Gotelli G R , Wall J H , Kabra P M , Marton L J 
Published: January 2020

Abstract
Placental estriol in urine can be determined, after enzymatic hydrolysis, by liquid chromatography. A single-step extraction technique results in rapid processing with minimal sample manipulation. Analytical recovery of estriol added to urine was 96 to 106%. Day-to-day precision (CV), established by 10 replicate analyses at a mean concentration of 15.9 mg of estriol per liter, was 3.7%.
Radioimmunoassay for urinary lysozyme in human serum from leukemic patients.
Authors: Peeters T L , Depraetere Y R , Vantrappen G R 
Published: January 2020

Abstract
We present a radioimmunoassay for lysozyme in human serum, based upon human lysozyme isolated from the urine of leukemic patients and antiserum prepared against this lysozyme in the goat. In the separation step, a second antibody is used. By properly adjusting the concentrations of unlabeled and 125I-labeled lysozyme and of the antibodies, maximal precision (SD, 0.04 mg/litre) was obtained in the range 0.00 to 2.00 mg/litre. In 20 normal volunteers the lysozyme concentration was 4.6 +/- 0.8 mg/litre (mean +/- SD), in 13 patients with monocytic leukemia 34.4 +/- 8.6 mg/litre. Correlation with lysoplate determinations was excellent in leukemic sera (r = 0.97) but was poor in normal sera (r = 0.35), possibly owing to the existence of isoenzymes.
High-performance liquid chromatography of quinidine in plasma, with use of a microparticulate silica column.
Authors: Peat M A , Jennison T A 
Published: January 2020

Abstract
We describe a routine method for determining plasma concentrations of quinidine by liquid chromatography. The procedure requires 1.0 ml of plasma (or serum) and involves internal standard addition, extraction with ether, and separation on a column of microparticulate silica. Day-to-day CV (15 days) was less than 5% and no deterioration in column performance has been observed during 12 months. Comparison with a fluorometric procedure gave a correlation coefficient of 0.995.
Modified micro-scale enzymatic method for plasma ammonia in newborn and pediatric patients; comparison with a modified cation-exchange procedure.
Authors: Wu J , Ash K O , Mao E 
Published: January 2020

Abstract
We modified two "kit" procedures for plasma ammonia to make them suitable for use with newborn and pediatric patients. Available methods either require too large a specimen, are insufficiently sensitive in the normal range, or are too cumbersome. One was an enzymatic (Sigma Chemical Co., St. Louis, Mo. 63178), the other a cation-exchange (Hyland, Costa Mesa, Calif. 92626) method. The modified micro-scale enzymatic method requires 100 microliter of plasma (CV at 38 micronmol/liter, 8%). Reagent costs per patient assay, including controls and standards, are currently $0.53. An assay run can be completed in 30 min. The modified cation-exchange method requires 200 microliter of plasma; the within-run CV is 12% for a concentration of 34.2 micronmol/liter. Reagents currently cost $0.74 per assay and each run requires less than 2 h to complete. The correlation coefficient for the two methods was 0.98.
Radial diffusion assay of NAD- and NADP-dependent oxidoreductases.
Authors: Shih J C , Teulings E P 
Published: January 2020

Abstract
With a radial diffusion assay we measured the activity of six NAD- and NADP-dependent oxidoreductases: alcohol, glucose-6-phosphate, hydroxysteroid, lactate and malate dehydrogenases, and glutathione reductase. The enzyme was allowed to diffuse for 24h in an agarose gel in which the substrate was incorporated, then reacted the pyridine nucleotide coenzyme. The size of an enzyme diffusion zone could be made visible by the change of the fluorescence of the coenzyme against the background when the coenzyme was either oxidized or reduced. The procedure for each enzyme is reported. The results indicate that this new technique may be applicable to all NAD- and NADP-dependent enzymes. Because of its simplicity and potentiality for screening many samples, we think this method has applications in the clinical laboratory and in nutrition studies.
Assay of vitamins D2 and D3, and 25-hydroxyvitamins D2 and D3 in human plasma by high-performance liquid chromatography.
Authors: Jones G 
Published: January 2020

Abstract
I describe a new assay that is capable of measuring vitamin D2, vitamin D3, 25-hydroxyvitamin D2, and 25-hydroxyvitamin D3 in 2 ml of plasma or serum. Plasma is extracted by the Bligh and Dyer technique [Can. J. Biochem. Physiol. 37, 911 (1959)], the lipid component is fractionated by two high-performance liquid-chromatographic systems based upon adsorption and reversed-phase chromatography, and each of the four vitamin D metabolites is measured by its absorbance at 254 nm. The method has a sensitivity limit of 0.5 mug/liter of plasma. The identity of metabolite peaks was confirmed by mass spectrometry, ultraviolet absorption spectrophotometry, and rechromatography, and there was good correlation (r=0.84) between plasma 25-hydroxyvitamin D as measured by the present method and by a protein binding assay developed in our laboratory. Mean concentrations of vitamin D and 25-hydroxyvitamin D in normal adults (n=25) in December were 2.2 +/- 1.1 (SD) and 16 +/- 3.9 (SD) mug/liter, respectively. 25-Hyroxyvitamin D2 made up 31% of the total 25-hydroxyvitamin D. Patients receiving pharmacological doses of vitamin D had values for vitamin D and 25-hydroxyvitamin D that were 10- to 100-fold normal. This method provides a rapid, reliable physico-chemical assay that appears to have advantages over existing protein binding assays and can be used to measure circulating vitamin D.
Simplified two-step column-chromatographic determination of taurine in urine.
Authors: Anzano M A , Naewbanij J O , Lamb A J 
Published: January 2020

Abstract
A two-step column-chromatographic procedure for accurate and rapid determination of taurine in urine is described. Sulfosalicyclic-acid deproteinized samples are chromatographed on a 0.9 X 10 cm column of cation-exchange resin (AG 50W-XB), with use of a pH 2.2 sodium citrate eluting buffer such that taurine and the more highly acidic compounds in urine are eluted in the void volume, and then on a 0.9 X 8 cm column of anion-exchange resin (AG 2-X8), from which taurine is preferentially eluted with 1 mol/liter acetic acid. The color developed with ninhydrin is directly proportional to taurine amounts as low as 0.01 mumol/sample. The method is highly reproducible, with analytical recoveries greater than 95%. The presence of 333 mumol of urea and 1 mumol of cysteic acid did not interfere in the analysis. When a mixture of C14-labeled amino acids other than taurine were co-chromatographed with taurine, less than 2% of the total counts loaded were located in the taurine fraction. Values for urinary taurine excretion by rats according to the present method agreed well with values obtained with an automated amino acid analyzer. Advantages of the present method for the determination of taurine are discussed.
D(-)-N-Methylglucamine buffer for pH 8.5 to 10.5.
Authors: Chromy V , Kulhánek V , Fischer J 
Published: January 2020

Abstract
A new amine buffer for the pH range 8.5 to 10.5 based on D(-)-N-methylglucamine and its hydrochloride is described. Important physical and chemical constants characterizing this buffer system have been determined: thermodynamic pKa = 9.52 (25 degrees C), buffer capacity = 0.055, dilution value pH 1/2 = -0.02, temperature coefficient dpKa/dT = 0.023, the heat of ionization delta H degrees = 36.93 kj mol-1. D(-)-N-Methylglucamine, which is available in highly purified form, is highly soluble in water. Thus one can prepare either buffer solutions or stable solid mixtures when combined with D(-)-N-methylglucaminium chloride. D(-)-N-Methylglucamine buffers are suitable for both biochemistry and pH control.
Radioimmunoassay of creatine kinase isoenzymes in human serum: isoenzyme BB.
Authors: Zweig M H , Van Steirteghem A C , Schechter A N 
Published: January 2020

Abstract
We describe a sensitive, specific radioimmunoassay for the BB isoenzyme of creatine kinase (CK-BB) in serum. A sequential saturation assay was used to achieve sufficient sensitivity to detect the isoenzyme in 100-microliter serum samples of all healthy persons and patients tested. Bound and free antigen were separated by a second antibody system. Large excesses of purified isoenzyme MM did not react in the assay. Cross reactivity of two preparations of CK-MB was only 1 to 7+. The 95th percentile of serum CK-BB in 208 healthy adults was 6.2 microgram/liter. Within-assay and between-assay precision ranged from 5.5 to 11.9% and 9.7 to 13.6%, respectively.
A solid-phase radioimmunoassay for vitamin B12 in serum, with use of radioiodinated tyrosine methyl ester of vitamin B12.
Authors: Endres D B , Painter K , Niswender G D 
Published: January 2020

Abstract
Although radioassays for vitamin B12 with use of any of several binding proteins have been available for many years, a radioimmunoassay for B12 has not been reported. We describe here such a radioimmunoassay, incorporating, for the first time, a radioiodinated tyrosine methyl ester of B12 as the radioactive tracer. Polypropylene tubes are coated with antiserum raised in a rabbit against B12/bovine serum albumin to simplify the separation of bound and free radioactivity. Factors affecting the preparation of coated tubes are described. The assay is accurate, sensitive, precise, and specific for vitamin B12. Accuracy of the assay is unaffected by the presence of denatured protein. The advantages of this radioimmunoassay over conventional radioassays are discussed.