bluuebunny/crossref_metadata_2025_split huggingface dataset:
Free thyroxin by radioimmunoassay: evaluation of a new direct method involving a radiolabeled thyroxin analog.
Authors: Kubasik N P , Lundberg P A , Brodows R G , Hallauer G D , Same D G , Lindstedt G , Bengtsson C , Nyström E 
Published: January 2020

Abstract
We present here the first performance evaluation of a new direct method for free thyroxin (T4) in serum by radioimmunoassay, with use of coated tubes and a radiolabeled T4 analog (Diagnostic Products Corp.). The assay is precise and robust: within-run imprecision (CV), 3.1-6.6%; between-run imprecision, 4.0-7.9%; no demonstrable variation between technologists irrespective of experience with the method. No outliers were observed when we compared the free T4 results with serum total T4. Reference values are reported for a total of 1243 euthyroid subjects; there was no significant age effect on serum free T4 in women 26 to 72 years old. The biological variation was about +/- 35% of the mean (2 SD). Free T4 results are the same for serum and plasma. The assay performs well in hypothyroidism and hyperthyroidism, and distinguishes individuals with thyroid disease from normal individuals. Free T4 values in women taking oral contraceptives are normal. Depressed results were often observed in acute nonthyroidal illness and continuing pregnancy. These results were directly comparable with those of another commercial direct radiolabeled-T4 analog kit for free T4.
An equilibrium model of the oxygen association curve of normal human erythrocytes under standardized conditions.
Authors: Ryall R G , Story C J 
Published: January 2020

Abstract
Hemoglobin-oxygen association curves of human erythrocytes were measured in metabolically stable cells under the standardized conditions of extracellular pH 7.400, carbon dioxide tension 38 mmHg (approximately 5 kPa) and temperature 37 degrees C. A model of the oxygen association curve of normal erythrocytes was subsequently developed, based on assumed equilibrium reactions between hemoglobins (Hb), oxygen, and 2,3-diphosphoglycerate (DPG). Conditional equilibrium constants were determined for reactions leading to the formation of species designated Hb-O2 (K = 0.14 mmHg-1), Hb-(O2)4 (K = 0.44 X 10(-4) mmHg-4), Hb-DPG (K = 0.30 X 10(4) L mol-1) and Hb-O2-DPG (K = 0.61 X 10(2) L mol-1 mmHg-1) for unmodified hemoglobin, and Hb-O2 (K = 0.14 mmHg-1) and Hb-(O2)4 (K = 0.44 X 10(-4) mmHg-4) for glycosylated hemoglobin. This model provides a practical means of calculating the expected oxygen association curve for a sample of erythrocytes under standardized conditions, given the intracellular concentrations of hemoglobins and 2,3-diphosphoglycerate and the assumption that the hemoglobins in those cells function normally.
Temperature correction of blood-gas and pH measurements.
Authors: Ashwood E R , Kost G , Kenny M 
Published: January 2020

Abstract
We critically review formulas for temperature correction of pH, pCO2, and pO2 measurements in whole blood and the clinical usefulness of these formulas. We discuss both the theoretical derivation and experimental verification of temperature-induced changes. We recommend when to use and when not to use these formulas, based upon the clinical interpretation of these assays.
Monoclonal antibodies to human plasma low-density lipoproteins. I. Enhanced binding of 125I-labeled low-density lipoproteins by combined use of two monoclonal antibodies.
Authors: Mao S J , Patton J G , Badimon J J , Kottke B A , Alley M C , Cardin A D 
Published: January 2020

Abstract
Four monoclonal antibodies (IgG2b) to human plasma low-density lipoproteins (LDL) have been characterized. The binding affinities of each monoclonal antibody to 125I-labeled LDL were moderately high, ranging from 10(8) to 10(10) L/mol at 4 degrees C, but were reduced by at least 50-70% at 37 degrees C. The maximum binding of each monoclonal antibody was unique, ranging from 20 to 95% of total 125I-labeled LDL, suggesting that LDL particles were immunochemically heterogeneous. One antibody, LP-34, had both high and low binding affinities to LDL. Another, LP-47, exhibited high affinity for isolated LDL, yet reacted poorly with native LDL in plasma, indicating that the conformation of isolated LDL differs from that of native LDL in plasma. Unlike polyclonal serum antibodies, a mixture of four monoclonal antibodies failed to precipitate LDL, but did show a drastic increase in binding to LDL. We found that only two of our monoclonal antibodies were necessary for such synergistic enhancement. We propose that one of the monoclonal antibodies may serve as a catalytic reagent, and discuss the clinical significance of this finding.
Evaluation of accuracy of 20 different test kits for the enzymic determination of cholesterol.
Authors: Demacker P N , Boerma G J , Baadenhuijsen H , van Strik R , Leijnse B , Jansen A P 
Published: January 2020

Abstract
We evaluated the accuracy of 20 different test kits for the enzymic determination of cholesterol. Using a selected set of standards, we found mean values differing by -9.9 to + 10.7% from values obtained by the Abell-Kendall procedure. Nine kits gave values with a relative bias of less than 2.5%. In the case of the other 11 kits, recalculation with secondary serum standards resulted in values within 5% of the reference values. Depending on the kit used, two different commercially available standard solutions produced results differing by, at most, 8.7%. We obtained indirect evidence that use of esterase of bacterial origin is associated with low values. We ascribe the high values obtained with some kits to positive interference by stabilizers or unspecified compounds in the reagents.
Evaluation of the Coomassie Brilliant Blue G-250 method for urinary protein.
Authors: Lott J A , Stephan V A , Pritchard K A 
Published: January 2020

Abstract
The Coomassie Brilliant Blue G-250 method for protein in urine has been evaluated for analytical accuracy and clinical applicability. Extremely simple to perform, the test exhibits good precision and sensitivity. The color developed per gram of protein is protein-type dependent, so no single protein standard is completely satisfactory. Color intensity is linearly related to concentration up to 1500 mg/L when used with a manual bichromatic method. Accuracy was clinically acceptable for patients with a variety of protein-losing diseases, and for patients having received renal transplants; however, the method underestimates urinary light-chain proteins. In athletes and premature neonates, we observed increased protein excretion during periods of stress. The upper reference limit for protein excretion in healthy adults is about 120 mg/24 h.
Cystic fibrosis--its biochemical detection.
Authors: Heeley A F , Watson D 
Published: January 2020

Abstract
We examine critically the biochemical methods capable of detecting and monitoring the end-organ disease processes in patients with cystic fibrosis. Although the diagnosis of cystic fibrosis is never justified on the basis of the sweat salt test alone, the original filter-paper technic (Gibson-Cooke, Pediatrics 23:545-549, 1959) for determining Na+ and Cl- concentrations in sweat remains the most discriminating method. We discuss the contributions for neonatal screening of the so-called cystic fibrosis protein, associated decreased enzymic activities in the homo- and heterozygous state, and immunoreactive trypsin. Because evidence of either intestinal malabsorption or a pancreatic lesion must be sought, we review the use and interpretation of some tests of pancreatic dysfunction (meconium albumin, duodenal juice components, serum pancreatic isoamylase, and trypsinogen), both in establishing and in confirming the diagnosis of cystic fibrosis.
Quantification of high-density-lipoprotein cholesterol by precipitation with phosphotungstic acid/MgCl2.
Authors: Assmann G , Schriewer H , Schmitz G , Hägele E O 
Published: January 2020

Abstract
We evaluated the use of a modified phosphotungstic acid/MgCl2 precipitation procedure for the precipitation of apolipoprotein B-containing lipoproteins. Precipitation of these lipoproteins [very-low- and low-density lipoproteins, and lipoprotein (a)] is complete, with negligible coprecipitation of high-density lipoprotein subfractions (HDL1, HDL2, HDL3), even in hypertriglyceridemic sera. In comparison with ultracentrifugation, the precipitation method yields, on the average, values that are 0.17 mmol/L lower for cholesterol values but almost identical for apolipoprotein A-I and phosphatidylcholine. Looking for delta 3,5-cholestadiene formed from cholesterol in the precipitation residue, we used "high-performance" liquid chromatography and "high-performance" thin-layer chromatography and found none.
Liquid-chromatographic determination of 5-S-L-cysteinyl-L-dopa with electrochemical detection in urine prepurified with a phenylboronate affinity gel.
Authors: Kågedal B , Pettersson A 
Published: January 2020

Abstract
A phenylboronate affinity gel has been investigated for use in the prepurification of urine before "high-performance" liquid chromatography and electrochemical determination of 5-S-L-cysteinyl-L-dopa. At pH 5.6 this naturally occurring 5-S-cysteinyldopa was adsorbed on a phenylboronate column and was quantitatively eluted with trichloroacetate, pH 3.0. This pretreatment of urine before "high-performance" liquid chromatography produced satisfactory chromatographic separations, and the results were further improved when the purification procedure also included treatment on a cation exchanger. By using 5-S-D-cysteinyl-L-dopa--a diastereomer to 5-S-L-cysteinyl-L-dopa--as an internal standard, we have developed a practical routine method for the quantitative determination of urinary 5-S-L-cysteinyl-L-dopa. The precision (CV = 2.4%) and analytical recovery (96.9%, SD 5.3%) were satisfactory and the results obtained correlated well with a previously described method.
Mechanism of cefoxitin and cephalothin interference with the Jaffé method for creatinine.
Authors: Kroll M H , Elin R J 
Published: January 2020

Abstract
Some cepha antibiotics interfere positively in the Jaffé method for determining creatinine. The extent of this interference differs with the modification used, and its mechanism is unknown. We studied the spectrophotometric and thermodynamic properties of the reaction of picrate with creatinine and two cepha antibiotics, cefoxitin and cephalothin. The absorbance spectra of the chromophore produced by each of the three compounds when reacted with picrate were essentially identical, with an absorbance maximum at 485 nm. We determined the molar absorptivity, rate constant, and equilibrium constant for the reaction of the three compounds with picrate. The molar absorptivity was similar for creatinine and cefoxitin but about fourfold smaller for cephalothin. The rate constant and equilibrium constant for the reaction with picrate were respectively 20- and 10-fold greater for creatinine than for either of the two cepha antibiotics. Thus, these differences indicate the mechanism by which these two cepha antibiotics interfere with the Jaffé procedure for creatinine, and explain why the degree of interference depends on details of the procedure.
The "HemoQuant" test: a specific and quantitative determination of heme (hemoglobin) in feces and other materials.
Authors: Schwartz S , Dahl J , Ellefson M , Ahlquist D 
Published: January 2020

Abstract
We describe a new, specific, quantitative method for fecal blood, based on conversion of nonfluorescing heme to fluorescing porphyrins, that obviates serious deficiencies inherent in currently used tests. A two-reagent system is used to determine the two hemoglobin-related fractions that are found in feces. The hot citric acid extract includes only the variable fraction of porphyrins that have been preformed from heme in the intestinal tract; this often is the major fraction. Total hemoglobin is indirectly determined by reaction with heated oxalic acid:FeSO4 reagent, which converts the remaining heme to porphyrin without loss of the preformed porphyrins. A three-step purification procedure eliminates interfering materials. Analytical recovery of added hemoglobin is linearly related to concentration over a several-thousand-fold range. The assay is equally applicable to whole blood or to sub-microgram amounts of hemoglobin in the 8-mg (wet weight) fecal sample tested. Quality control by liquid chromatographic and fluorometric analysis documents fluorescence specificity of the heme-derived porphyrins.
Gas-liquid chromatographic determination of propylene glycol in plasma and urine.
Authors: Yu D K , Sawchuk R J 
Published: January 2020

Abstract
We describe a gas-chromatographic assay for propylene glycol in human plasma and urine. The method is sensitive enough to allow quantification of the compound at concentrations observed clinically. It requires no derivative preparation and takes only 13 min of chromatographic time.
Meaning of serum free-thyroxin values in nonthyroidal illnesses: seven methods compared.
Authors: Chan D W , Waud J M , Taylor E , Stem J , Drew H , Oropeza M , Sucupira M S 
Published: January 2020

Abstract
Serum free thyroxin (FT4) was determined in 40 patients with various nonthyroidal illnesses. We studied seven methods: (1) a free thyroxin index calculated from total T4 and triiodothyronine resin uptake; (2) a free T4 index determined by enzyme inhibitor assays (Abbott's "Tetrazyme" and "Thyrozyme"); (3) a free T4 index calculated from total T4 and thyroxin-binding globulin; (4) free T4 by equilibrium dialysis; (5) Amersham's free T4 RIA; (6) Clinical Assays' one-step free T4 RIA; and (7) Clinical Assays' two-step free T4 RIA. Approximately half of the free T4 results were in the euthyroid range and the other half in the hypothyroid range by methods 1, 2, 5, and 6. Results for free T4 by methods 3 and 7 were similar to those by equilibrium dialysis (method 4), the percentages of patients with results in the euthyroid range being 68%, 65%, and 76%, respectively.
Isotope dilution--mass spectrometry of thyroxin proposed as a reference method.
Authors: Möller B , Falk O , Björkhem I 
Published: January 2020

Abstract
We describe a highly accurate and specific method based on isotope dilution--mass spectrometry for assay of thyroxin in serum. A fixed amount of 2H2-labeled thyroxin is added to a fixed amount of serum. Thyroxin is isolated from the serum by an extraction--solvent-distribution method, converted into the N,O-bis(trifluoroacetyl)methyl ester, and subjected to combined gas chromatography--mass spectrometry. The amount of thyroxin is determined from recordings at m/e 799 and m/e 801. These two ions correspond to the M-184 peak in the mass spectrum of the derivative of unlabeled and 2H2-labeled thyroxin, respectively. With this derivative and with the specific gas-chromatographic conditions used, the "memory" effects observed in previous work were absent. The accuracy of the method was checked by analyses of serum samples without addition of internal standard and by different recovery experiments. The intra-assay variation (CV) was less than 2%, the interassay variation (CV) less than 3.5%. We suggest that this method may be used as a Reference Method. Results by the present method were compared with those by a commercial radioimmunoassay. To our knowledge this represents the first time that radioimmunoassay of thyroxin has been evaluated with a more nearly accurate method. There was excellent agreement between results by the two methods (r = 0.997). We conclude that radioimmunoassay of serum thyroxin is sufficiently accurate for use in clinical work.
Creatinine determined by "high-performance" liquid chromatography.
Authors: Ambrose R T , Ketchum D F , Smith J W 
Published: January 2020

Abstract
We describe a "high-performance" liquid-chromatographic procedure for determination of creatinine in serum. Creatinine is separated from other species by cation-exchange chromatography. Absorbance of the creatinine in the eluate is monitored at 234 nm. Results from this procedure on sera correspond closely to those of a manual Jaffé-reaction procedure involving use of a protein-free filtrate with additional cleanup of the sample with Lloyd's reagent. None of the 21 endogenous and exogenous substances that we screened interfered. The overall CV at 138 mumol of creatinine per liter is 1.35% and at 539 mumol/L is 0.72%.
Value of the anion gap in clinical diagnosis and laboratory evaluation.
Authors: Lolekha P H , Lolekha S 
Published: January 2020

Abstract
We report the incidence of normal (50.4%), increased (46.7%), and decreased (2.9%) anion gap among hospitalized patients in a retrospective study. The mean and range of increased anion gaps were 25 and 19-28 mmol/L. Values exceeding 30 mmol/L were uncommon and may indicate either acidosis or laboratory error. The most common causes of the increased anion gap among patients were chronic renal failure, congestive heart failure, malignant neoplasm, and diabetes mellitus. Increased anion gap in this study may be due to excess acids along with decreases in sodium, chloride, and carbon dioxide. The mean and range of decreased anion gap were 6 and 3-8 mmol/L. Anion-gap values less than 3 mmol/L were uncommon (one of 500 cases), and a high incidence of such values may indicate laboratory error. Nephrotic syndrome, liver cirrhosis, intestinal obstruction, and severe hemorrhage were the common disorders associated with decreased anion gap, which resulted from hypoalbuminemia and hyponatremia. Although most patients with decreased anion gap had hypoalbuminemia, hypoalbuminemic patients did not necessarily have decreased anion gap.
Interrelations of the various mathematical approaches to radioimmunoassay.
Authors: Fernandez A A , Stevenson G W , Abraham G E , Chiamori N Y 
Published: January 2020

Abstract
Equations used for calculation of radioimmunoassay data are derived and compared. We show that the equation developed by Fernandez and Loeb is the most general of these. Those of Ekins et al., Hales and Randle, and Rodbard et al. are all derived here from this basic equation by neglecting certain of its terms. The logit-log plot of Rodbard et al. is a logarithmic transformation of the linear Hales-Randle equation. The basic equation, derived here solely from the mass-action law, approaches linearity under certain conditions without complex mathematical transformations of analyte concentrations or observable parameters. Applications are also presented.
Determination of urinary normetanephrine and metanephrine by radial-compression liquid chromatography and electrochemical detection.
Authors: Orsulak P J , Kizuka P , Grab E , Schildkraut J J 
Published: January 2020

Abstract
A procedure has been developed for determining the O-methylated catecholamine metabolites, normetanephrine and metanephrine, in urine by use of radial-compression liquid chromatography followed by electrochemical detection. Normetanephrine and metanephrine are isolated from hydrolyzed urine by ion-exchange on small, commercially available, disposable columns and preconcentrated by solvent extraction. They are then separated by reversed-phase ion-pair chromatography, with use of a radial compression cartridge and radial compression module, and quantified with 3-methoxy-4-hydroxybenzylamine as internal standard. Normetanephrine, metanephrine, and the internal standard are separated from interfering peaks in about 15 min. The method is applicable to the relatively low amounts of normetanephrine (100-600 micrograms/24 h) and metanephrine (50-400 micrograms/24 h) found in normal subjects and patients with depressive disorders or hypertension. Within-day CVs ranged from 1.1 to 2.2% for normetanephrine and 1.2 to 6.9% for metanephrine; the corresponding between-day CVs were 4.9 and 5.7% over these ranges.
Cytoplasmic creatine kinase isoenzymes quantitated in tissue specimens obtained at surgery.
Authors: Urdal P , Urdal K , Strømme J H 
Published: January 2020

Abstract
Because previous reports have given inconsistent results, we re-examined the catalytic concentrations of cytoplasmic creatine kinase (CK) and of CK isoenzymes in 38 biopsies obtained from 19 different tissues. After homogenization and centrifugation many tissues showed high CK catalytic concentrations; 11 of them contained activity exceeding 50 U/g wet weight (Scandinavian recommended method). The highest specific activities were found in skeletal muscle (2400 U/g), brain (530 U/g), and myocardium (460 U/g). The separate isoenzyme activities were estimated by electrophoretic, anion-exchange chromatographic, immunoinhibiting, and radioimmunological methods. CK-BB was present in all tissues and, in fact, was the only cytoplasmic CK isoenzyme in 16 of the 19 tissues examined. CK-MM was the major isoenzyme of skeletal muscle and myocardium and was in addition observed in placenta, in trace amounts. CK-MB was present in high catalytic concentrations in myocardium (20% of total CK) and in low catalytic concentrations in skeletal muscle (1.1% of total CK).
Fetal lung maturity assessed by fluorescence polarization: evaluation of predictive value, correction for endogenous fluorescence, and comparison with L/S ratio.
Authors: Cox K H , Ross J B , Peterson A P , Benedetti T J 
Published: January 2020

Abstract
The steady-state polarization (or anisotropy) of the fluorescent dye 1,6-diphenyl-1,3-5-hexatriene in amniotic fluid samples and the lecithin/sphingomyelin ratio of the samples were correlated with development of respiratory distress syndrome in newborns. We found that clinical samples have a variable endogenous fluorescence that reduces the observed polarization (or anisotropy). This background is a major interference in the assessment of fetal lung maturity by the polarization method. Correction for this interference, by also measuring the blank fluorescence and anisotropy of the sample, provides a clinical tool with a lower coefficient of variation than that of the more time-consuming lecithin/sphingomyelin ratio. The clinical correlation for 17 cases of respiratory distress syndrome in a high-risk population (60 births; twins counted as a single birth) indicates that the two methods are equivalent for predicting immature fetal lung status.
Evaluation of an enzymic procedure for the measurement of acetaminophen.
Authors: Price C P , Hammond P M , Scawen M D 
Published: January 2020

Abstract
We evaluated a new method for measurement of acetaminophen. From acetaminophen, acetate and p-aminophenol are enzymically produced, and the latter product is determined colorimetrically by reaction with o-cresol and ammoniacal copper sulfate. The method is rapid and precise, and results compare well with those by spectrophotometric and liquid-chromatographic techniques. Major metabolites of acetaminophen, some commonly used drugs, or phenolic substances that may be present in patients with liver or renal disease do not interfere.