bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short- and long-term biological variation in analytes in urine of apparently healthy individuals.
Authors: Shephard M D , Penberthy L A , Fraser C G 
Published: January 2020

Abstract
Intra-individual, interindividual, and analytical components of variation for each of 10 urine analytes were estimated from results obtained on analysis of urine specimens from 10 apparently healthy young men. In spot urines, urea and osmolality showed strong individuality, but intra-individual variances were larger than interindividual variances for sodium, urate, phosphate, and glucose. Urea and osmolality displayed strong individuality in daily urines, whereas sodium (when results were expressed in output terms), urate, potassium, and total protein (when results were expressed in concentration units) had intra-individual variances larger than interindividual variances. In monthly urines, calcium and glucose, in concentration terms, and phosphate, in output terms, exhibited strongest individuality. Analytical variance was a significant percentage of the total variance for total protein and glucose; the analytical methods we used for these analytes were probably unsatisfactory. A series of analytical goals for imprecision, based on biological variation, were derived. Although these goals may not be applicable in all clinical situations, they represent the beginning of a data base in the literature.
Centrifugal analysis for plasma kallikrein activity, with use of the chromogenic substrate S-2302.
Authors: Ito R , Statland B E 
Published: January 2020

Abstract
The amidolytic activity of activated kallikrein in plasma can be measured by use of the chromogenic substrate, S-2302 (H-D-Pro-Phe-Arg-pNA). Plasma prekallikrein was activated to kallikrein by exposure to 50 mg/L dextran sulfate in acetone/water (35/65 by vol) at 0 degrees C for 15 min. The acetone slows anti-kallikrein activity and increases the kallikrein activity by 30%. The 37 degrees C reaction mixture contained 0.54 mmol of S-2302 substrate per liter of Tris buffer (pH 7.5 at 37 degrees C). We monitored the change in absorbance at 405 nm for 60 s. The specificity of the substrate for kallikrein was demonstrated by using plasma deficient in prekallikrein (Fletcher trait) diluted with pooled normal human plasma. We recommend collecting blood specimens with sodium citrate as the anticoagulant and with use of a double-syringe technique and all-plastic containers. Plasma kallikrein activity with Chromozym-PK (Bz-Pro-Phe-Arg-pNA) as substrate (y-axis) compared with S-2302 as substrate (x-axis) gave the relation: y = 0.28x + 0.82 (r = 0.94). Day-to-day analytical variation was 2.4% for a pooled plasma with a mean value of 85.9 mukat/L. The mean (and 2 SD) for 50 healthy adults was 86.4 (32.4) mukat/L.
Test of radioimmunoassay validity in the presence of an isotope effect.
Authors: Xing S , Zheng S , Cekan S Z 
Published: January 2020

Abstract
An isotope effect, manifested as delayed elution of the labeled moiety, was detected in CO-chromatography of testosterone with [1,2,6,7-3H]testosterone on Celite. The isotope effect was smaller for [1,2-3H]testosterone and even smaller, but still significant, for [7-3H]testosterone. Because of the isotope effect, the test of validity of a testosterone radioimmunoassay had to be modified. Instead of testing the constancy of values for specific activity in individual chromatographic fractions, the slopes of specific activities exhibited by mixtures of plasma testosterone (pooled specimens of plasma from men and from women) with [1,2-3H]testosterone were compared with that yielded by authentic testosterone mixed with the same tracer. Because the slopes were statistically indistinguishable, the assay of testosterone in these materials appears to be valid. We suggest that comparison of the slopes of specific activities be used as the basis of validity tests whenever such an isotope effect is present.
Positive interference by danazol in a testosterone radioimmunoassay kit procedure.
Authors: Sharp A M , Fraser I S , Robertson S , Turtle J R 
Published: January 2020

Abstract
We describe a problem in measuring serum testosterone concentrations in the serum of women who are taking danazol. The Diagnostic Products Corporation testosterone radioimmunoassay gives very high apparent testosterone concentrations in these women and the value obtained depends on the volume of serum extracted per assay tube. Chromatography of the serum extracts on Sephadex LH-20, but not on Celite, before radioimmunoassay reduced these high apparent testosterone concentrations to less than that found in normal women.
Prostatic acid phosphatase as measured with two radioimmunoassay kits in the detection of prostatic adenocarcinoma.
Authors: Brody J P , Savory J , Sturgill B C , Lehman M R , Wills M R 
Published: January 2020

Abstract
Serum prostatic acid phosphatase concentration was measured with two commercially available radioimmunoassay kits. Results were compared with histological evidence of prostatic adenocarcinoma obtained at autopsy in 33 patients. The serum assay did not differentiate significantly (p greater than 0.1) between patients with adenocarcinoma and those without. We conclude that the test, at least as performed by use of these kits, is of little value in the detection of occult disease.
Preparation of whole blood for liquid scintillation counting.
Authors: Moore P A 
Published: January 2020

Abstract
Liquid scintillation counting of 3H-labeled whole-blood samples is severely impaired owing to quenching by blood pigments. In this study, dry oxidation and chemical solubilization followed by decolorization were the two general methods used to eliminate color quenching. Three blood volumes were examined: 0.25, 0.50, and 1.0 mL. Dry oxidation yielded complete recoveries of 3H label with counting efficiencies greater than 30% for up to 1.0 mL of blood. Although blood volumes larger than 0.25 mL can be used with chemical solubilization and decolorization, treatment of 0.25 mL of blood gave the highest counting efficiencies, with count rates comparable to those for 1.0-mL samples.
Radioenzymic measurement of norepinephrine, epinephrine, and dopamine: stability, enzymic activity, and sensitivity.
Authors: Saar N , Bachmann A W , Gordon R D 
Published: January 2020

Abstract
We investigated factors affecting sensitivity and reproducibility of radioenzymic (catechol-O-methyltransferase) measurement of plasma catecholamines. There was no apparent deterioration of catecholamine during storage at -20 degrees C for 240 days. Accuracy and sensitivity of the assay depended mostly on the method of transferase preparation; its preparation by adjusting the pH to 6.8 before fractionation with ammonium sulfate resulted in an unsuitable enzyme with a relatively high background-radioactivity count, particularly for neorepinephrine and dopamine.
Effect of serum dilution on apparent unbound bilirubin concentration as measured by the peroxidase method.
Authors: Ahlfors C E 
Published: January 2020

Abstract
I studied the effects of serum dilution and oxidation of albumin-bound bilirubin on the accuracy of results by the peroxidase method for assessing bilirubin-albumin binding. The apparent concentration of unbound bilirubin decreases with dilution of bilirubin-enriched serum or defatted-albumin solutions, the effect being more marked with serum. The decrease in apparent unbound bilirubin does not appear to be due to slow oxidation of albumin-bound bilirubin. Instead, the bilirubin-albumin complex has a much lower apparent dissociation rate constant (K-1) in serum (0.0033 [SD 0.0002] s-1) than in solutions of defatted-albumin (0.017 [SD 0.006] s-1), causing the dissociation of the complex to be rate-limiting when serum is analyzed at the currently recommended 40-fold dilution and peroxidase concentration (0.11 mu mol/L). In addition, dilution appears to enhance bilirubin binding by serum but not by defatted-albumin solutions. Decreasing the serum dilution and peroxidase concentration may significantly improve the accuracy of the peroxidase test. The actual correlation between clinical bilirubin toxicity and specific unbound bilirubin concentrations, however, remains to be determined.
Standardization of immunochemical determinations of serum albumin.
Authors: Keyser J W , Fifield R , Watkins G L 
Published: January 2020

Abstract
When we compared four commercially available preparations of human serum albumin with the human serum standard IFCC 74/1 by radial immunodiffusion, by immunoprecipitation turbidimetry, by laser nephelometry, and by "rocket" immunoelectrophoresis, three of the preparations gave almost "theoretical" results with the immunoprecipitation turbidimetric method. Results by the other three methods tended inconsistently to be low. Four pools of normal human serum were also analyzed for albumin by these four immunochemical methods, again with IFCC 74/1 as the reference standard. The results were virtually identical with those obtained by fractionation with 1.8 mol/L sodium sulfate and determination of protein nitrogen in the filtrate. We suggest that a combination of (a) fractionation of a pool of normal human serum in this way and (b) critical comparison with selected commercial preparations of human serum albumin will permit standardization of the serum albumin determination.
Volume of blood removed for analytical purposes during hospitalization of low-birthweight infants.
Authors: Nexø E , Christensen N C , Olesen H 
Published: January 2020

Abstract
Iatrogenic hazards may be induced by blood sampling in very-low-birthweight neonates. We report the number and types of analyses performed on 20 neonates with a birthweight below 1500 g during their first four weeks of hospitalization. Blood was sampled one to 13 times per infant per day on 382 of the 435 total days of hospitalization. The average blood loss was 7 to 51 mL per kilogram of body weight per four weeks--that is, from 5 to 45% of the calculated total blood volume. Of the blood removed, about 25% was in excess of the need for analytical procedures. Of the analyses, 40% were for acid-base, sodium, and potassium analyses--analyses for which transcutaneous methodology has been or is being developed. We conclude that because of the risks for low-birthweight neonates, procedures for blood sampling and analysis should periodically be reviewed, so as to minimize the number of samplings and the amount of blood removed.
A bioluminescence micromethod for measuring chloramphenicol in serum.
Authors: Boeckx R L , Brett E M 
Published: January 2020

Abstract
Bioluminescence provides a sensitive analytical approach for the measurement of low concentrations of ATP and can be used to monitor any reaction in which ATP is consumed or synthesized. We describe a quick, sensitive method involving bioluminescence for the quantitation of chloramphenicol in serum. Chloramphenicol acetyl transferase catalyzes the acetylation of chloramphenicol in the presence of acetyl coenzyme A. ATP is consumed when the acetylation reaction is coupled to the acetyl coenzyme A synthetase reaction. Residual ATP is then assayed with the firefly luciferin-luciferase reaction. The procedure can be completed in less than 1 h and requires as little as 20 microliter of serum. The response of the assay is linear with concentration through a range of 2 to 20 mg/L and shows good correlation with a gas-chromatographic method (r = 0.978) and a radioenzymic method (r = 0.985). No significant interference was found from five other antibiotics tested. The small sample requirement makes the assay especially applicable to infant and pediatric monitoring, where the effects of toxicity are greatest.
Improved method for quantitation of B apoprotein in plasma lipoproteins by electroimmunoassay.
Authors: Reardon M F , Poapst M E , Uffelman K D , Steiner G 
Published: January 2020

Abstract
The B apoprotein occurs in a wide range of plasma lipoproteins, which are heterogenous both with respect to size and to composition. Immunochemical recognition of the apoprotein is influenced by the nature of the particle in which the apoprotein is found, presumably due to the masking of the antigenic sites by lipoprotein lipid. Consequently, it is difficult to provide suitable standards for use in routine electroimmunoassay procedures of the B apoprotein, particularly for triacylglycerol-rich lipoproteins. We have devised a procedure whereby lipoprotein samples, independent of their initial size and composition, are reduced, by use of a bacterial lipase, to a common size and composition, which is almost identical to that of the standard. This permits an assay that may be easily used routinely. It provides a far more reliable estimate of the absolute B apoprotein mass in plasma lipoproteins of the very-low- and low-density lipoprotein spectrum than has been previously available.
Colorimetric method for free fatty acids in serum validated by comparison with gas chromatography.
Authors: Brunk S D , Swanson J R 
Published: January 2020

Abstract
We compared results by a simplified colorimetric copper-soap method for serum free fatty acids (Clin, Chem. 19: 419, 1973, modified) with those by a gas--liquid chromatographic method. The modified method requires only 100 microliters of sample, its standard curve is linear from 0.1 to 4.0 mmol/L (reference interval for adults: 0.2 to 0.8 mmol/L), and it is suitable for use with newborns. Comparison with the gas--liquid chromatographic method (n = 51) over a wide concentration range gave a correlation coefficient of 0.989. Between-run CVs varied from 4 to 10%, analytical recoveries from 97 to 104%. Triglycerides, salicylates, hemoglobin, and anticoagulants (except citrate) do not interfere, but bilirubin and phospholipids give small positive interferences. The colorimetric assay is used, along with other routine tests, to assess lipid status and estimate kernicterus risk in neonatal intensive-care patients receiving lipid nutrition parenterally.
Automated discrete kinetic method for erythrocyte acetylcholinesterase and plasma cholinesterase.
Authors: Lewis P J , Lowing R K , Gompertz D 
Published: January 2020

Abstract
We describe an automated kinetic method for erythrocyte acetylcholinesterase (EC 3.1.1.7) and plasma cholinesterase (EC 3.1.1.8) based on Ellman's colorimetric method. Quinidine sulfate is used as an inhibitor of plasma cholinesterase during the measurement of erythrocyte acetylcholinesterase activity, obviating the need for washing the erythrocytes before lysis. Results by this method are compared with those obtained by the electrometric delta pH method of Michel. To emphasize the need for measuring both erythrocyte acetylcholinesterase and plasma cholinesterase activity in workers exposed to organophosphate pesticides, we present a study of serial activities of both enzymes in a person accidentally exposed to demeton-S-methyl.
Aluminum concentrations in serum of hemodialysis patients.
Authors: Gorsky J E , Dietz A A 
Published: January 2020

Abstract
Aluminum has been implicated in the etiology of the progressive dialytic encephalopathy. Data are presented on samples taken from patients on maintenance hemodialysis, during treatment. Aluminum was determined by electrothermal atomic absorption spectroscopy. Hemodialysis had no significant effect on serum aluminum concentrations, which ranged from 27 to 254 micrograms of Al per liter (1.00 to 9.42 mumol/L). Isolated ultrafiltration removed part of the serum aluminum, but most remained bound to a nonfiltrable component. These results are evaluated in the light of present knowledge concerning dialysis dementia.
Determination of testosterone in plasma from men by gas chromatography/mass spectrometry, with high-resolution selected-ion monitoring and metastable peak monitoring.
Authors: Finlay E M , Gaskell S J 
Published: January 2020

Abstract
Highly specific methods are described for determining testosterone in plasma or serum from men. Extract fractions obtained by selective isolation procedures are converted to tert-butyldimethylsilyl (TBDMS) oximes/TBDMS ethers or methyl oximes/TBDMS ethers and analyzed by gas chromatography/mass spectrometry in the high-resolution selected-ion monitoring or metastable peak-monitoring modes. [2H3]Testosterone and unlabeled 17-epitestosterone are used as the respective internal standards. When we applied the two procedures to analysis of samples of pooled plasma and serum used for external quality assessment of routine assays, the results agreed well. Interlaboratory values for mean concentrations obtained by routine immunoassays (y) consistently exceeded values obtained by our technique (x), although the values closely correlated (r = 0.997; y = 1.008x + 0.564 nmol/L).
Fluorescence polarization immunoassay. II. Analyzer for rapid, precise measurement of fluorescence polarization with use of disposable cuvettes.
Authors: Popelka S R , Miller D M , Holen J T , Kelso D M 
Published: January 2020

Abstract
This instrument, developed for quantitating fluorescence polarization immunoassays, automatically measures both polarization components and computes a polarization value corrected for background and optical bias. An electronically switched liquid crystal provides a nonmechanical means of rotating the plane of polarization in the excitation optics. The electronic design features digital integration and microprocessor controlled functions. Readings are made in disposable 12 X 75 mm round culture tubes. in less than 10 s. Results are precise to 0.001 polarization unit, linear from 10(-7) to 10(-10) mol of fluorescein per liter, and correlate well with those obtained with other "high-performance" instrumentation.
Evaluation of a method for enzymic radiochemical assay of tobramycin and amikacin in serum.
Authors: McKnight R P , Willis J E 
Published: January 2020

Abstract
This enzymic radiochemical procedure for measuring tobramycin and amikacin in serum is based on the transfer of the 14C-acetyl group from [14C]acetyl-coenzyme A to the 6' nitrogen atom of the drug by the enzyme kanamycin 6'-acetyltransferase (EC 2.3.1.55). The transfer, stoichiometric and quantitative, is complete after 10-min incubation at 37 degrees C. The labeled acetylaminoglycoside is adsorbed onto phosphocellulose paper discs, which are washed to removed any unreacted [14C]acetyl-coenzyme A. The radioactivity is then eluted into liquid scintillation counting vials and counted for 1 min each. The assay detects as little as 2 ng of either drug and the standard curve is linear into the toxic range of concentrations. Most of the commonly administered aminoglycosides act as substrates in the assay, except for the C1 component of gentamicin C complex. Neither hemolysis, lipemia, nor icterus interfere with the assay. Results compare favorably with those determined by radioimmunoassay and a microbiological method.
Direct spectrophotometry of total bile acids in serum.
Authors: Mashige F , Tanaka N , Maki A , Kamei S , Yamanaka M 
Published: January 2020

Abstract
In this simple and direct method for determining total bile acids in serum, the serum was mixed with sodium pyruvate, a lactate dehydrogenase blocker, and bile acids were then measured spectrophotometrically after the following enzyme reaction. Bile acids are converted to 3-oxo bile acids with 3 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) with concomitant reduction of NAD+ to NADH. The hydrogen in the NADH generated is transferred by diaphorase (EC 1.6.4.3) to nitrotetrazolium blue to yield diformazan 540 nm). Analytical recovery of the various bile acids in serum averaged 96.2%. The CV for the day-to-day variation was 4.3%. Normal values are less than 7 mumol/L. Total serum bile acids were estimated by this method in 118 fasting patients with various liver diseases. This determination is clearly shown to be useful as a liver-function test.
Usefulness of serum nucleotide pyrophosphatase and phosphodiesterase I activities in classifying liver disease.
Authors: Haugen H F , Ritland S , Blomhoff J P , Solberg H E , Skrede S 
Published: January 2020

Abstract
Nucleotide pyrophosphatase and phosphodiesterase I activities were determined in sera from 126 patients with different types of liver disease and in two additional groups of patients with intra- and extrahepatic cholestasis, respectively. Both activities probably represent the same enzyme, and were positively correlated with alkaline phosphatase, lipoprotein X, and several other tests reflecting cholestasis. Also, we found by discriminant analysis that tests for cholestasis frequently replaced the results of both enzymes. In some groups of liver disease, nucleotide pyrophosphatase and phosphodiesterase I were correlated with the concentrations of prealbumin and albumin. The sensitivity of phosphodiesterase I (and nucleotide phosphatase) is rather low when compared with alkaline phosphatase, and we do not recommend it for use in the clinical routine. Nevertheless, it appears to be of potential value for studies on classification of liver diseases, adding information to a panel of 20 commonly used "liver tests" by appearing in some of the best four test-sets for distinguishing between groups of liver disease by discriminant analysis.
Spectrophotometry of tissue thromboplastin in cerebrospinal fluid.
Authors: Hische E A , Tutuarima J A , van der Helm H J 
Published: January 2020

Abstract
We describe a two-stage method for measuring thromboplastin in cerebrospinal fluid, based on the amidolytic determination of the generation rate of Factor Xa. We investigated the effect of variations in the duration of incubation, and in pH, temperature, and concentrations of calcium, buffer, and prothrombin complex (source of Factors VII and X). Optimal assay conditions are specified. The detection limit is 6 units/L and the results indicate an upper limit of normal of 14 units/L. The coefficients of variation were 7.7% within-day and 9.2--16.0% day-to-day, depending on the concentration.
Use of receiver operating characteristic curves to evaluate the clinical performance of analytical systems.
Authors: Robertson E A , Zweig M H 
Published: January 2020

Abstract
The usefulness of an analytical system in patient care is ultimately judged not by its analytical performance but by its clinical performance, i.e., its ability to separate apparently similar patients into two subgroups, one of which has a particular clinically important condition and another subgroup which does not. This clinical performance can be studied with the tools of signal detectability theory, originally developed to analyze the performance of radar and data-transmission systems. Each classification made by an analytical system may be categorized as a true-positive, true-negative, false-positive, or false-negative decision. For laboratory tests the proportion of decisions in each category depends on the biological overlap between the two subgroups, the analytical performance of the system, and the decision level chosen. The clinical performance of the analytical system for all possible decision levels is represented by the receiver operating characteristic curve, which plots the true-positive rate against the false-positive rate. The use of these curves permits comparison of alternative analytical techniques at equal true-positive rates and at all possible decision levels. These comparisons show the effect of analytical improvements on clinical performance.