bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanism of false-negative urine cannabinoid immunoassay screens by Visine eyedrops.
Authors: Pearson S D , Ash K O , Urry F M 
Published: January 2020

Abstract
To drug-free urine specimens, we added the following drugs of abuse to give concentrations twice the cutoff value for positive test results: 11-nor-9-carboxy-delta-9-tetrahydrocannabinol (9-carboxy-THC), oxazepam, secobarbital, morphine, benzoylecgonine, amphetamine, or phencyclidine (PCP). Visine was then added. Although measured concentrations of several drugs were decreased in the presence of Visine, false-negative results were obtained only for 9-carboxy-THC for the EMIT-d.a.u. and TDx urine cannabinoid assays. Visine also decreased 9-carboxy-THC as measured by the Abuscreen assay. At low concentrations of Visine, false-negative cannabinoid results were attributable to the benzalkonium chloride ingredient of Visine. The added Visine was not detectable by routine urine analysis and had no effect on the activity of the glucose-6-phosphate dehydrogenase-drug conjugate used in the EMIT-d.a.u. assays. Moreover, analysis by gas chromatography/mass spectrometry showed no chemical modification or loss of 9-carboxy-THC in the Visine-adulterated urine specimens. However, Visine did increase the adhesion of 9-carboxy-THC to the borosilicate glass specimen containers. Results of ultrafiltration studies with Visine suggest that 9-carboxy-THC partitions between the aqueous solvent and the hydrophobic interior of benzalkonium chloride micelles, thereby reducing the availability of 9-carboxy-THC in antibody-based assays.
Enzymic urea assay: a new colorimetric method based on hydrogen peroxide measurement.
Authors: Lespinas F , Dupuy G , Revol F , Aubry C 
Published: January 2020

Abstract
We describe a new enzymic colorimetric method in which urea is measured in serum by use of a single reagent mixture. Ammonia produced by urea hydrolysis, catalyzed by urease, reacts with glutamate and ATP in the presence of glutamine synthetase. The ADP so produced is assayed in reactions catalyzed sequentially by pyruvate kinase and pyruvate oxidase in a system that generates hydrogen peroxide. The hydrogen peroxide is measured at 500 or 550 nm in a reaction catalyzed by horseradish peroxidase, with phenol/4-aminophenazone as the chromogen. The reaction is complete in 15 min at 37 degrees C. The standard curve is linear up to a urea concentration of 40 mmol/L. Precision is good; CVs ranged from 2.5% to 3.1%. Results by the present method compared well with those by a candidate Reference Method and are not subject to interferences from commonly used drugs and anticoagulants.
Separation and identification of urinary proteins and stone-matrix proteins by mini-slab sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
Authors: Fraij B M 
Published: January 2020

Abstract
Mini-slab electrophoresis on sodium dodecyl sulfate/polyacrylamide gel can be used to detect protein in unconcentrated urines containing more than 100 mg of protein per liter. Several urinary proteins--including albumin, transferrin, and the Tamm-Horsfall mucoprotein--precipitate, partly or totally, if urine samples are stored at 4 degrees C for one or two days. The present procedure permits identification of the albumin and transferrin in unconcentrated urines, thus avoiding their partial loss. Stone-matrix proteins in 10 mg or more of urinary calculi also could be detected. Albumin, transferrin, and Tamm-Horsfall mucoprotein accounted for greater than 40% of the total matrix protein in most of the urinary stones analyzed. The precipitation properties of these proteins and their high concentrations in stone matrix relative to those in urine suggest that they may play a role in stone formation and growth.
Immunocatalytic assay of pancreatic alpha-amylase in serum and urine with a specific monoclonal antibody.
Authors: Svens E , Käpyaho K , Tanner P , Weber T H 
Published: January 2020

Abstract
In this immunocatalytic assay for alpha-amylase (EC 3.2.1.1) of pancreatic origin, a highly specific monoclonal antibody coupled to plastic beads is used to extract pancreatic amylase from samples, leaving salivary amylase in solution. The catalytic activity of the bound pancreatic amylase is then determined with blocked p-nitrophenyl maltoheptaoside as substrate. The method shows no cross-reactivity with salivary amylase, analytical recovery is 89-109% for pancreatic amylase, and interassay imprecision is 7.1-7.7%. We used the method to determine pancreatic amylase in serum and urine from healthy controls and different patient groups. The reference intervals for 34 supposedly healthy controls were: serum, 10-48 U/L (mean 27 U/L); urine, less than 20-435 U/L (mean 104 U/L). Results by the present assay correlated well with a salivary amylase inhibition assay (Boehringer Mannheim). We conclude that the described immunocatalytic assay is clinically useful for detecting increased activities of pancreatic amylase in serum and urine.
Biological variability of 26 clinical chemistry analytes in elderly people.
Authors: Fraser C G , Cummings S T , Wilkinson S P , Neville R G , Knox J D , Ho O , MacWalter R S 
Published: January 2020

Abstract
Analytical, within-subject, and between-subject components of variation were estimated for 26 clinical chemistry analytes from duplicate analyses of 10 specimens collected from 27 healthy elderly subjects over a period of 20 weeks. Within-subject variations were similar to those generated previously by us in younger subjects. We conclude, therefore, that homeostasis is not compromised by age alone, and biological variability does not increase simply with age. All analytes except serum water had marked individuality, showing that conventional population-based reference values are of limited utility. The critical differences required for two results to be significantly (P less than or equal to 0.05) changed are not the same as those that prompt action by clinicians. Although heterogeneity of within-subject variation does exist, we believe that the critical differences generated will be useful in routine clinical decision making.
Immunoradiometric assay of corticotropin with use of avidin-biotin separation.
Authors: Zahradnik R , Brennan G , Hutchison J S , Odell W D 
Published: January 2020

Abstract
We have developed a "sandwich"-type immunoradiometric assay for corticotropin (ACTH), with a detection limit of 2 ng/L. Two antibodies are used: a mouse monoclonal antibody directed against ACTH[1-17] and labeled with 125I; and a purified polyclonal goat antibody directed against ACTH[34-39] and conjugated to biotin. We could separate 125I-labeled antibody bound to ACTH from 125I-labeled antibody not bound to ACTH by using an avidin-biotin bridge, with avidin bound to a polystyrene ball. This assay reacts with ACTH[1-39] but shows no reaction with ACTH fragments [1-24], [1-17], or [34-39], or with melanotropin, endorphins, or lipotropin. This assay is sensitive enough to detect ACTH in plasma of all normal adults. Concentrations measured in 94 adults between 0800 and 1000 hours were normally distributed on a log scale, with a mean of 19.5 ng/L and a 95% range of 7.1 to 53.8 ng/L. Dexamethasone given at 2300 hours to 14 adults suppressed ACTH to less than 4 ng/L in 13 of the subjects and to 8 ng/L in the 14th. Metyrapone given to 13 adults at 2300 hours increased ACTH to 245.3 ng/L (95% range, 90.1 to 667.7 ng/L). This assay accurately classified patients with disorders of the adrenal system.
Determination of the alkyl lysophospholipid derivative ET-18-OCH3, a new antineoplastic drug, in plasma.
Authors: Schaefer H G , Rohdewald P 
Published: January 2020

Abstract
We describe a sensitive method for measuring the concentration of the new antineoplastic drug ET-18-OCH3 in plasma. After plasma lipids are extracted, ET-18-OCH3 is separated from the excess of endogenous lipids by thin-layer chromatography and specific enzymatic hydrolysis of sphingomyelin by the action of sphingomyelinase. Analytical recovery after the complete isolation was 73.5% (CV = 9.8%, n = 15). [3H]-ET-18-OCH3 is used as internal standard. A densitometric method in which 8-anilino-1-naphthalenesulfonate, Mg salt, is used as fluorescent agent (excitation at 367 nm and emission greater than 390 nm) allows the sensitive determination of ET-18-OCH3 down to 0.1 mg/L (CV greater than 30%). The day-to-day CV is 25% for concentrations of 0.15 to 0.625 mg/L, 12% for 1.5 to 5.0 mg/L. Preliminary pharmacokinetic data reveal gastrointestinal absorption of ET-18-OCH3 after multiple oral administration.
Unreliable visual estimation of the incidence and amount of turbidity, hemolysis, and icterus in serum from hospitalized patients.
Authors: Glick M R , Ryder K W , Glick S J , Woods J R 
Published: January 2020

Abstract
We examined the frequency of occurrence for turbidity, hemolysis, or icterus in 2599 serum samples submitted for chemistry testing in an acute-care general hospital. Each specimen was compared visually with full-color photographs of adulterated serum, and designated as either "0" (containing no interferent), or trace, 1+, 2+, 3+, 4+, or 5+. Visible interferents (1+ or greater) were thought to be present in 838 (31%) of the specimens (icterus, 525; hemolysis, 244; lipemia, 69). To assess the accuracy of such visual grading, we determined the concentration of triglycerides, hemoglobin, or bilirubin in the specimens considered to be contaminated. There was little agreement between the actual concentration of each interferent and the assigned grade of turbidity, hemolysis, or icterus, confirming the unreliability of human visual estimation of these potentially interfering substances.
Correction of instrument- and reagent-based differences in determination of the International Normalized Ratio (INR) for monitoring anticoagulant therapy.
Authors: van Rijn J L , Schmidt N A , Rutten W P 
Published: January 2020

Abstract
As recommended by the World Health Organization, standardization of prothrombin time assays involves conversion of prothrombin times into International Normalized Ratios (INR). We investigated the effect of two different methods (Nycomed's Thrombotest, and Instrumentation Laboratory's PT-fibrinogen) and three coagulation instruments (Schnitger & Gross, KC-10, and ACL) on calculations of INR. The INR plots showed considerable scatter of individual values around the regression lines when the two different methods were compared. Systematic differences in the outcome of INR calculation were related to the use of the different coagulation instruments. Prothrombin times obtained with the different instruments were linearly correlated. We used the bias of these lines to correct results for both the patients' samples and the reference samples. This correction yielded INR values from the different instruments that agreed well.
Fluorescence polarization immunoassay of gentamicin or netilmicin in blood spotted on filter paper.
Authors: Fujimoto T , Tsuda Y , Tawa R , Hirose S 
Published: January 2020

Abstract
In this improved simple method for determination of aminoglycoside antibiotics in dried-blood spots on filter paper, gentamicin or netilmicin is recovered from the blood spot most effectively by incubation for 60 min in an ultrafiltration tube containing 500 microL of 0.5 mol/L Na2HPO4 buffer. The eluates from the paper are centrifuged, then transferred to an Abbott TDx cartridge for measurement of gentamicin or netilmicin by fluorescence polarization immunoassay. The dried sample on paper is stable for about eight days at ambient temperature. Intra-assay CVs for gentamicin and netilmicin are less than 8.5% and less than 6.1%, respectively. Analytical recovery of gentamicin and netilmicin from the paper exceeded 90%. This method permits simple blood collection and monitoring of the therapeutic concentration of gentamicin or netilmicin in serum, particularly that of newborn infants and small children.
Determination of trans-phylloquinone in children's serum.
Authors: Moussa F , Dufour L , Didry J R , Aymard P 
Published: January 2020

Abstract
By optimizing the conditions for determining trans-phylloquinone and its metabolite, K-2,3-epoxide, in serum through a two-step HPLC process combined with fluorometric detection after coulometric reduction, we have been able to develop a method applicable to small volumes of serum (200 to 500 microL). The limit of detection (signal-to-noise ratio of 3) was 15 ng/L for trans-phylloquinone, 30 ng/L for K-2,3-epoxide. The trans-phylloquinone concentrations measured by this method in serum from 82 children, ages one to six years, whose results were normal for overall coagulation tests, ranged from 40 to 880 ng/L (median 175 ng/L). We discuss these findings and compare them with vitamin K1(20) values reported for adults.
Indirect measurement of desferrioxamine and its chelated compounds aluminoxamine and ferrioxamine by Zeeman atomic absorption spectrometry.
Authors: D'Haese P C , Lamberts L V , De Broe M E 
Published: January 2020

Abstract
This indirect method for determination of desferrioxamine (DFO, deferoxamine, Desferal) and its chelated compounds ferrioxamine (FO) and aluminoxamine (AIO) in biological fluids involves metal chelate formation and solvent extraction, the metal being determined by Zeeman atomic absorption spectrometry (Zeeman-AAS). Special attention was paid to the pH and recovery of extraction, iron-aluminum interactions, extraction times and volumes, centrifugation rates, and instrument settings. Precautions were taken to avoid contamination with aluminum and iron and to prevent co-extraction of iron and aluminum not chelated to DFO. The addition calibration technique was used for standardization. Mean +/- SD recoveries of AIO and FO after extraction were respectively 98.3% +/- 3.7% and 101% +/- 3.7%. Sensitivity was 45 pg/0.0044 A.s for aluminum and 10 pg/0.0044 A.s for iron. Detection limits were 0.22 mumol/L for AIO, 0.06 mumol/L for DFO and FO.
Arginine pharmacokinetics in humans assessed with an enzymatic assay adapted to a centrifugal analyzer.
Authors: van Haeften T W , Konings C H 
Published: January 2020

Abstract
Arginine is used in supra-physiological concentrations as an insulin secretagogue, in both in vitro and in vivo studies. To investigate the pharmacokinetics of arginine in humans, we have developed a rapid, automated assay of arginine in serum, based on our manual enzymatic method (Clin Chim Acta 1988, 176; 185-94). The limit of linearity of the automated assay was an arginine concentration of 3 mmol/L. Within-run CVs for Ortho control sera with added arginine were 5.5%, 0.8%, and 0.7% at concentrations of 0.16, 1.30, and 2.50 mmol/L, respectively. After 30 min of primed continuous infusions with arginine at infusion rates of 3, 9, 15, and 21 mg/kg per minute, mean (+/- SEM) arginine concentrations in serum from eight volunteers were 1.17 +/- 0.08, 3.44 +/- 0.21, 6.84 +/- 0.58, and 9.25 +/- 0.39 mmol/L, respectively, well within the range of arginine concentrations shown (in vitro) to stimulate insulin secretion. Metabolic clearance of arginine was approximately 11 mL/kg body wt per minute. For the lowest three infusion rates, the half-life (t1/2) of arginine was approximately 15 min and the volume of distribution (Vd) was approximately 290 mL/kg. At the highest infusion rate, t1/2 was significantly increased (27.3 +/- 3.1 min), owing to an increased Vd (446 +/- 83 mL/kg).
Effects of in vivo and in vitro production of lactic acid on ionized, protein-bound, and complex-bound calcium in blood.
Authors: Toffaletti J , Abrams B 
Published: January 2020

Abstract
We have studied, both in vitro and in vivo, the quantitative effects of lactic acid production on concentrations of ionized calcium, bound calcium, pH, bicarbonate, and albumin. To do so, we examined the effects of addition of aqueous solutions of either hydrochloric acid, lactic acid, or lithium lactate to blood; we studied in vitro accumulation by storing blood sealed in tubes at room temperature for 5 h, then exposing the blood to air; and we induced in vivo production of lactic acid in healthy individuals who climbed stairs for 10 min. Lactic acid evidently affects the ionized, protein-bound, and complex-bound calcium concentrations in the following ways: (a) hydrogen ions from lactic acid bind to protein, which decreases protein-bound calcium; (b) lactate chelates calcium ions from free ionized calcium and protein-bound calcium about equally; and (c) the loss of a millimole of bicarbonate, either by exposure of blood to air or by respiratory alkalosis, results in the release of about 7 mumol of calcium ions, which re-equilibrate with both the protein-bound and ionized calcium. Because lactate apparently removes calcium ions directly from albumin, our study indicates that protein-bound calcium readily provides calcium ions that buffer changes in the concentration of ionized calcium.
Measurements of glutathione S-transferase B1 in plasma after birth asphyxia: an early indication of hepatocellular damage.
Authors: Beckett G J , Hussey A J , Laing I , Howie A F , Hayes J D , Strange R C , Faulder C G , Hume R 
Published: January 2020

Abstract
Concentrations of glutathione S-transferase (glutathione transferase; EC 2.5.1.18) B1 and B2 subunits (B1 and B2) and activity of alanine aminotransferase (ALT; EC 2.6.1.2) were measured in sequential plasma samples taken from 14 infants with birth asphyxia. Within 6 h of asphyxia, abnormal concentrations of B1 were found in 11 infants, whereas only seven infants showed abnormal ALT activities at this time. In plasma sampled 24 h after birth, values for ALT were abnormal in 10, whereas values for B1 were abnormal in six. Abnormal concentrations of B2 were found in relatively few of these infants, apparently because this monomer is poorly expressed in liver samples obtained up to 41 weeks after conception. We conclude that measurement of B1 may provide a useful index of hepatic impairment in birth-asphyxiated infants.
High-performance liquid chromatography/mass spectrometry: state of the art for the drug analysis laboratory.
Authors: Bowers L D 
Published: January 2020

Abstract
The combination of HPLC and mass spectrometry has great promise for the toxicology laboratory. In the past five years, significant progress has been made toward producing a reliable interface for these techniques. Thermospray, liquid ion evaporation, ion-spray, and the particle beam separator are all viable "second generation" approaches with significant advantages and disadvantages. I review the operation of these interfaces with an orientation to their use in the drug analysis laboratory. Thermospray, ion-spray, and liquid ion evaporation primarily supply information about molecular mass. The benefits and limitations of using tandem mass spectrometry to obtain additional structural information will also be discussed.
Effect of counting errors on immunoassay precision.
Authors: Klee G G , Post G 
Published: January 2020

Abstract
Using mathematical analysis and computer simulation, we studied the effect of gamma scintillation counting error on two radioimmunoassays (RIAs) and an immunoradiometric assay (IRMA). To analyze the propagation of the counting errors into the estimation of analyte concentration, we empirically derived parameters for logit-log data-reduction models for assays of digoxin and triiodothyronine (RIAs) and ferritin (IRMA). The component of the analytical error attributable to counting variability, when expressed as a CV of the analyte concentration, decreased approximately linearly with the inverse of the square root of the maximum counts bound. Larger counting-error CVs were found at lower concentrations for both RIAs and the IRMA. Substantially smaller CVs for overall assay were found when the maximum counts bound progressively increased from 500 to 10,000 counts, but further increases in maximum bound counts resulted in little decrease in overall assay CV except when very low concentrations of analyte were being measured. Therefore, RIA and IRMA systems based in duplicate determinations having at least 10,000 maximum counts bound should have adequate precision, except possibly at very low concentrations.
The between-run component of variation in internal quality control.
Authors: Linnet K 
Published: January 2020

Abstract
Design of control charts for the mean, the within-run component of variance, and the ratio of between-run to within-run components of variance is outlined. The between-run component of variation is the main source of imprecision for analytes determined by an enzymo- or radioimmunoassay principle; accordingly, explicit control of this component is especially relevant for these types of analytes. Power curves for typical situations are presented. I also show that a between-run component of variation puts an upper limit on the achievable power towards systematic errors. Therefore, when the between-run component of variation exceeds the within-run component, use of no more than about four controls per run is reasonable at a given concentration.
Influence of matrix on concentrations of somatotropin measured in serum with commercial immunoradiometric assays.
Authors: Felder R A , Holl R W , Martha P , Bauler G , Hellman P , Wills M R , Thorner M O 
Published: January 2020

Abstract
Using immunoradiometric assays (IRMAs) from Hybritech Inc. (H) and Nichols Institute Diagnostics (ND), we measured somatotropin (human growth hormone, hGH) in serum samples obtained every 20 min for 24 h from 10 prepubertal subjects with short stature. Results obtained with the ND reagents were 2.74 times greater than those obtained with the H reagents (P = 0.00001, r = 0.94, SEE = 3.9, n = 720). We therefore compared the IRMAs with the standard hGH RIA from the National Institutes of Health (NIH) National Hormone and Pituitary Program, using the genetically engineered hGH preparations (from Genentech Inc.) 22-kDa hGH and methionated 20-kDa hGH. We also assayed human pituitary hGH (NIH, lot no. AFP-4793B). Each hGH preparation was diluted in three diluent buffer systems: horse serum from H and from ND, and human serum. The RIA and H-IRMA gave superimposable standard curves for all hGH preparations in each diluent. The methionated 20-kDa hGH was not detected in the H-assay. Use of human serum matrix in the ND-IRMA shifted the standard curve as compared with the horse-serum matrix, giving equivalent binding at lower concentrations; i.e., serum hGH was overestimated in samples assayed against standards diluted in horse serum. Quality-control materials (Ciba-Corning) yielded disparate results in all three assays, yet human serum pools containing hGH gave similar results in the H and the NIH assays, and higher values in ND. When a human serum standard was used in the ND assay, both IRMAs gave similar results to the RIA assay for human serum samples. Reference intervals for hGH should be determined by each analytical laboratory, to prevent misdiagnosis of patients. Furthermore, quality-control material should be of human origin, because commercially supplied quality-control material does not react the same as human serum in some hGH assays.