bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specificity of human beta-choriogonadotropin assays for the hormone and for an immunoreactive fragment present in urine during normal pregnancy.
Authors: Schroeder H R , Halter C M 
Published: January 2020

Abstract
We evaluated four high-purity commercial preparations of human choriogonadotropin (hCG; Boehringer-Mannheim, Calbiochem, Cambridge, and Radioassay Systems) by two radioimmunoassays and one radioreceptor procedure. Their specific activities were less than half that of the first International Reference Preparation of hCG for immunoassay. In addition, a fragment that was immunoreactive in radioimmunoassays for hCG with antisera to the beta-subunit conformational determinant was isolated from crude hCG (Roussel Corp.). The fragment adsorbed to concanavalin A and exhibited a relative molecular mass of 12 000 by gel filtration. In a study with 94 urines from women three to 24 weeks pregnant, the fragment contributed more than 70% of the immunoreactivity detected by the above radioimmunoassays for hCG in 70% of the samples. The fragment was present in urine throughout pregnancy, but was not detected in the serum of any of seven pregnant women tested.
Liquid-chromatographic profiling of endogenous fluorescent substances in sera and urine of uremic and normal subjects.
Authors: Mabuchi H , Nakahashi H 
Published: January 2020

Abstract
Endogenous fluorescent substances increase in serum during uremia. We have used "high-performance" liquid chromatography to profile these fluorescent substances in both uremic and normal body fluids. The fluorescence excitation and emission maxima we used were 322 and 415 nm, respectively. Of the numerous fluorescent substances found in uremic body fluids and in normal urine, some were also detectable in normal serum, but at relatively weak fluorescence intensities.
Immunoadsorption to improve gas chromatography/high-resolution mass spectrometry of estradiol-17 beta in plasma.
Authors: Gaskell S J , Brownsey B G 
Published: January 2020

Abstract
We describe a new, highly selective procedure for the determination of estradiol-17 beta in plasma. Samples are extracted with a micro-cellulose-coupled antiserum to estradiol-17 beta. Conversion of the extracted steroid to the bis(trimethylsilyl) ether is followed by gas chromatography/high-resolution mass spectrometry with selected ion monitoring. Precise quantification is achieved through the use of [2H3]estradiol-17 beta as internal standard.
Rapid quantification of C-reactive protein by centrifugal analysis.
Authors: Melamies L 
Published: January 2020

Abstract
I describe a rapid, simple immunoturbidimetric method for determining C-reactive protein in serum. With the Instrumentation Laboratory Multistat III microcentrifugal analyzer, quantitative results are obtained automatically after a few minutes of reaction time. Within-run and between-run coefficients of variation ranged from 2.5 to 12.7% at C-reactive protein concentrations of 55 to 69 and 14 to 25 mg/L, respectively, normal values being less than 10 mg/L. Comparison with the commercially available radial immunodiffusion method (y) yields the regression equation y = 1.011x - 2.112 (r = 0.979, n = 100).
Determination of urinary oxalate with commercially available oxalate oxidase.
Authors: Buttery J E , Ludvigsen N , Braiotta E A , Pannall P R 
Published: January 2020

Abstract
For this direct colorimetry of urinary oxalate, commercially available oxalate oxidase (EC 1.2.3.4) is used. The urine is first diluted, to diminish the effect of interfering substances. Analytical recovery of oxalate from urines with five different oxalate concentrations (0.4 to 2.0 mmol/L) ranged from 92 to 109% (mean 99%). The within-day and between-day precision (CV) of the method for a wide range of oxalate concentrations averaged better than 10%. There is good correlation (r = 0.977) between this enzymatic method (y) and the chemical method of Hodgkinson and Williams (x) [Clin Chim Acta 36: 127-132, 1972], the regression equation being y = 1.014x + 0.061. Urines with added ascorbate give falsely increased results. The proposed method is inexpensive and simple to perform.
Improved separation and quantification of the "middle molecule" b4-2 in uremia.
Authors: Faguer P , Man N K , Cueille G , Di Giulio S , Funck-Brentano J L 
Published: January 2020

Abstract
The plasma of uremic patients usually contains high concentrations of the so-called middle molecules (molecular mass, 300 to 1500 Da), which exert various toxic effects. Among these numerous substances, only one, named peak b4-2, has been correlated with uremic neuropathy. We describe our improvement of a two-stage chromatographic method, gel permeation followed by anion-exchange chromatography (J. Chromatogr. 146: 55-65, 1978), for separation and quantification of b4-2 in body fluids. In analyzing more than 300 samples from 43 uremic patients and 12 healthy subjects, we found a linear correlation between peak area at 254 nm and b4-2 concentration in the range 0.8 to 32 mg/L. The coefficient of variation, including data acquired during seven changes of columns, was 9%. Analysis time (80 min) was shorter than required with other methods. Our results confirm previous data for urinary b4-2 excretion by healthy subjects and for b4-2 removal rate in uremic patients undergoing hemodialysis or hemofiltration. Patients treated with continuous ambulatory peritoneal dialysis have a higher b4-2 excretion than do healthy subjects, suggesting a higher production of this solute in uremic patients.
Solid-phase radioimmunoassay of fragment D of human fibrinogen by use of a low-affinity monoclonal antibody.
Authors: Kennel S J , Lankford P K 
Published: January 2020

Abstract
Increased concentrations of plasmin-catalyzed degradation products of fibrin and fibrinogen in body fluids have been correlated with many disease states. We have developed monoclonal antibodies that react with one of these products, fragment D. Antibodies binding fragment D but not fibrinogen were found to have low affinity constants (Ka = 10(7) L/mol). A double monoclonal-antibody assay was developed in which a specific antibody attached to Sepharose beads is used to concentrate fragment D selectively from a test sample. Fragment D bound to the washed beads was then quantified with a high affinity (Ka = 10(10) L/mol) monoclonal antibody that reacts equally well with fragment D and fibrinogen. This solid-phase assay is shown to be specific and about 10-fold more sensitive than a standard liquid-phase competition radioimmunoassay in which the same antibody was used.
Interlaboratory study of the proficiency of cholinesterase phenotyping.
Authors: Evans R T , Wardell J , Rapier C 
Published: January 2020

Abstract
We report the results of a proficiency survey into the accuracy of cholinesterase (EC 3.1.1.8) phenotyping undertaken by 12 laboratories over a three-year period, during which 21 samples of nine different genotypes were analyzed. Specimens from patients who were homozygous for the atypical variant AA or from UA and AF heterozygotes were identified without difficulty, but the less-well-recognized combinations AJ and AK were detected by only two and three laboratories, respectively. Some degree of difficulty was also experienced in differentiating among UU, UF, and FS specimens. Clinically significant ascription errors occurred on 11 occasions. We recommend that detailed studies of cholinesterase status be undertaken only by laboratories experienced in the assay, those likely to be able to produce accurate results and offer appropriate advice.
Creatine kinase response surfaces explored by use of factorial experiments and simplex maximization.
Authors: Fast D M , Sampson E J , Whitner V S , Ali M 
Published: January 2020

Abstract
We conducted a five-component, five-level response-surface experiment to optimize the pH and the concentrations of magnesium, creatine phosphate, adenosine diphosphate, and buffer in an assay for creatine kinase. Under optimal conditions, creatine kinase activity was about 5% greater than that obtained with a previously reported assay (Clin Chem 23: 1569, 1977). We also applied a simplex maximization algorithm to the response-surface equation to locate areas of maximum sensitivity. Reaction conditions for two such areas were found, each yielding approximately 11% more activity than with the previously reported method.
Clinical evaluation of the liquid-chromatographic determination of urinary free cortisol.
Authors: Nakamura J , Yakata M 
Published: January 2020

Abstract
We recently reported (Clin. Chem. 28: 1497-1500, 1982) a liquid-chromatographic method for quantifying free cortisol in urine. We have since evaluated the clinical utility of our method by assaying cortisol in urine from normal subjects, patients, and subjects undergoing endocrine tests. We found that, in contrast with plasma cortisol, urinary cortisol is not bound to protein. It shows some correlation with 17-hydroxycorticosteroids in urine, but is independent of creatinine excretion. The amount of cortisol excreted daily by a particular individual was found to be fairly constant during nine or 10 days. Normal values determined for 203 apparently healthy individuals were 35.8 (SD 18.7) micrograms/day, with no significant sex-related differences but a tendency for a gradual decrease of cortisol excretion with age. We also report urinary cortisol excretion by patients with pituitary-adrenal disorders and some other diseases, and the pattern of response to dexamethasone and metyrapone administration.
External quality assessment of assays for cortisol in plasma: use of target data obtained by gas chromatography/mass spectrometry.
Authors: Gaskell S J , Collins C J , Thorne G C , Groom G V 
Published: January 2020

Abstract
We describe procedures for measuring cortisol in plasma and serum by isotope dilution and mass spectrometry. A method that incorporated solvent extraction, derivatization, and gas chromatography/high-resolution mass spectrometry provided data of good precision; interassay CVs were generally 3 to 4% for the concentration range of 100-650 nmol/L. Replacing solvent extraction with extraction on a column of Lipidex 1000 or extraction by immunoadsorption yielded data in excellent agreement with the first method. Plasma and serum pools were analyzed to provide target data for use in the U.K. National External Quality Assessment Scheme for cortisol assays. Routine laboratory assays, as judged by comparison with mass-spectrometric data, were generally positively biased except for analysis of a charcoal-stripped plasma supplemented with cortisol. The results emphasize the importance of using unadulterated plasma or serum pools in assessments of steroid assay procedures.
Osmometry of CO2 in gas samples.
Authors: Oh M S , Kee C S , Uribarri J , Carroll H J 
Published: January 2020

Abstract
Measurement of solute concentrations in biologic fluids by an osmometric technique has been described previously. Here, we describe an osmometric technique for measuring CO2 in gas samples. A solution of NaOH is injected into a graduated syringe containing the gas sample and CO2 is trapped in the reaction: 2NaOH + CO2 leads to Na2CO3 + H2O. The decrease in osmolality of the NaOH solution allows estimation of pCO2 in the original gas sample.
Variations in amylase isoenzymes and lipase during acute pancreatitis, and in other disorders causing hyperamylasemia.
Authors: Leclerc P , Forest J C 
Published: January 2020

Abstract
We compare the clinical value of assay of amylase (EC 3.2.1.1) isoenzymes with that of lipase (EC 3.1.1.3) in serum from patients with proven acute pancreatitis or with hyperamylasemia from other causes. In the former group we measured amylase, lipase, and isoamylases daily. Lipase and P(pancreas)-type isoamylases reached the highest mean values on the first day of an attack of acute pancreatitis (day one). Lipase declined rapidly, and by day four its mean activity was about the same as that of amylase and lower than that of the P-type isoamylases. Great inter-individual variations were found among patients with a similar clinical course. Of the 85 samples analyzed, amylase activity for 36 declined to within reference limits, but 18 of the 36 had high lipase activity, 18 had high P-type isoamylases activity, and 31 had P3 isoenzyme, which is not detectable in normal sera. Determination of isoamylases is a more sensitive index to acute pancreatitis than lipase assay and may be particularly useful when pancreatitis is suspected despite a normal total amylase activity. In the group of patients with hyperamylasemia from other origins, three had macroamylasemia, one had mumps, one had abdominal trauma without pancreatic injury, and one had pelvic inflammatory disease. The specific pattern of macroamylase on electrophoresis permitted a precise diagnosis of macroamylasemia; normal lipase had only ruled out pancreatitis. In the three other cases, lipase and isoamylases excluded pancreatic involvement.
125I-labeled radioimmunoassay kits for progesterone evaluated for use in an vitro fertilization program.
Authors: Blight L F , White G H 
Published: January 2020

Abstract
We have evaluated two commercially available 125I radioimmunoassay kits (Diagnostic Products Corp., DPC; and Radioassay Systems Laboratories, RSL) for measurement of serum or plasma progesterone, to determine their suitability for use in in vitro fertilization programs. Both kits were suitably rapid for program requirements. Results by both were linear with concentration up to 60 nmol/L, and both had acceptable lower detection limits of 0.3 nmol/L. Kit-determined progesterone concentrations (y) for 100 patients' samples correlated well with results by our existing 3H radioimmunoassay method (y = 1.11x + 0.2, r = 0.965 for the DPC kit; y = 1.01x + 1.4, r = 0.974 for the RSL kit). Mean analytical recovery for the RSL kit was 116%, that for the DPC kit, 202%. Within-batch precision, expressed as the mean CV for three concentrations of progesterone, was 6.5% for the RSL kit, and 16.4% for the DPC kit; between-day CV was 8.1% for the RSL kit, 17.7% for the DPC kit. We conclude that the RSL kit provides a rapid, precise, and accurate assay for serum progesterone, suitable for use in a fertilization program, but do not recommend the DPC kit for either this purpose or the more general purpose of tracking menstrual cycles.
Pseudocholinesterase/high-density lipoprotein cholesterol ratio in serum of normal persons and of hyperlipoproteinemics.
Authors: Jain R , Kutty K M , Huang S N , Kean K 
Published: January 2020

Abstract
The proposed complementary risk factor, pseudocholinesterase/high-density lipoprotein cholesterol ratio, was significantly higher in patients with type IIb and IV hyperlipoproteinemias then in controls. In contrast, the established risk factor, total cholesterol/high-density lipoprotein cholesterol ratio, was significantly higher in patients with type IIa and IV hyperlipoproteinemias. Discriminant analysis indicated that prediction of risk for coronary heart disease on the basis of lipoprotein phenotypes can be improved by about 20% when both the above factors are assessed concurrently. On the basis of earlier studies in humans and animals, we also suggest that the proposed risk factor may provide a better understanding of events leading to enhanced risk for coronary heart disease as a consequence of nutrition and of abnormal metabolism of lipids and lipoproteins.
Reflectance digital matrix photometry.
Authors: Neeley W E , Zettner A 
Published: January 2020

Abstract
We have designed and constructed a digital matrix photometer for quantitative measurement of reflected light of small chromophoric areas or colored spots. The areas are divided conceptually into small subunits in which the reflected light is measured. This is done through stepwise scanning with a photodiode array. The sum of the individual reflectance measurements is related to the total amount of an analyte in the spot. We have found that this technique makes possible accurate and precise quantitation of light-absorbing substances in small areas of different sizes, shapes, and internal irregularity measuring as little as 1 mm across.
Simultaneous determination of phenytoin and phenobarbital in serum or plasma by substrate-labeled fluorescent immunoassay.
Authors: Dean K J , Thompson S G , Burd J F , Buckler R T 
Published: January 2020

Abstract
This assay system for simultaneously determining phenytoin and phenobarbital in serum and plasma is based on the substrate-labeled fluorescent immunoassay technique. A beta-galactosylcoumarin derivative of phenobarbital and a 4-methylcoumarin phosphodiester derivative of phenytoin are used as substrate labels for Escherichia coli beta-galactosidase and Crotalus atrox phosphodiesterase I, respectively. The smallest measurable concentrations are about 1.6 mg/L for phenytoin, 2.7 mg/L for phenobarbital. Within-run coefficients of variation are about 5% for phenytoin and 2% for phenobarbital, about 6% for both between-runs. Results for phenytoin and phenobarbital in serum and plasma correlate well with those determined by the Ames TDA (r = 0.944 and 0.986, respectively) and Syva's EMIT (r = 0.977 and 0.969, respectively) assays.
Direct spectrophotometric assay for angiotensin-converting enzyme in serum.
Authors: Ronca-Testoni S 
Published: January 2020

Abstract
The appropriate conditions for determining angiotensin-converting enzyme in human serum with use of 2-furanacryloyl-L-phenylalanylglycylglycine as substrate are described. The method, a modification of that reported by Holmquist et al. (Anal. Biochem. 95:540-548, 1979) for purified rabbit lung enzyme, is based on the blue shift of the absorption spectrum that occurs upon hydrolysis of the substrate into furanacryloyl-L-phenylalanine and glycylglycine. The Km value for the substrate is 0.31 mmol/L. Some kinetic properties determined by this method are similar to those previously reported for the purified serum enzyme. Results by the present assay and Cushman's modified method correlate closely (r = 0.995). The normal reference interval for 42 adult donors was 43-137 U/L (mean 90 U/L, SD 23 U/L). The within-run and between-run CVs ranged from 3.0 to 4.1%. Its rapidity, simplicity, sensitivity, and precision make the proposed method very suitable for routine work, clinical investigation, and kinetic and structural studies of the serum enzyme.
Kinetic measurement of total amylase and isoamylase activities with a centrifugal analyzer.
Authors: de Rijke D , Kreutzer H J 
Published: January 2020

Abstract
We evaluated a new kinetic assay for alpha-amylase (Phadebas IsoAmylase Test), using modified starch as the substrate and a CentrifiChem 400 centrifugal analyzer system. We determined isoamylase activities by using a selective inhibitor. Results were compared with those obtained with the chromogenic Phadebas dyed-starch technique. The method for total amylase appeared to be rapid and precise (CV = 4%) and results correlated well with the chromogenic method. Samples with activities up to 3000 arb. units/L can be analyzed without dilution. Glucose and pyruvate interfere with the assay, but hemoglobin and bilirubin do not. Pancreatic (P) and salivary (S) isoamylase activity can be determined with acceptable precision (CVP = 8%, CVS = 10%) by an automated routine procedure with commercially available reagents.
Interference from renal dialysis patients' specimens in a direct method for serum iron.
Authors: Bunting P S , Aggarwal M 
Published: January 2020

Abstract
In a direct-measuring, sample-blank procedure for serum iron we obtained spuriously high results for renal hemodialysis patients. These spurious results were found to be the result of protein precipitating out of solution owing to anticoagulation of these patients with heparin during hemodialysis. Two methods are described for circumventing this interference: adjusting the pH of the buffer and adding sodium dodecyl sulfate (lauryl sulfate). We prefer the latter procedure for reasons which are discussed, and optimized conditions are described for it. The effects on results by this latter method of bilirubin, hemolysis, and turbidity are described. The method is also evaluated for precision and accuracy, and it is recommended for routine use. A significant "protein effect" (due to viscosity) is noted, which has implications for calibration of the American Monitor KDA instrument.
Boehringer immunoinhibition procedure for creatine kinase-MB evaluated and compared with column ion-exchange chromatography.
Authors: ter Welle H F , Baartscheer T , Fiolet J W 
Published: January 2020

Abstract
In determination of creatine kinase isoenzyme MB (CK-MB), the Boehringer immunoinhibition method gives a high and variable blank activity as compared with column-chromatography. Thus a correction must be applied. Furthermore, a second correction of 1% of total creatine kinase activity is necessary to compensate for nonspecific creatine phosphate-dependent activity. As a consequence, two immunoinhibition determinations--one for CK-MB and one for blank activity--and a determination of total creatine kinase are required. Use of the manufacturer's diagnostic criteria, on the basis of which suspected myocardial infarction is confirmed or eliminated, leads to a high frequency of false-negative conclusions.
Bioluminescent assay for total bile acids in serum with use of bacterial luciferase.
Authors: Styrélius I , Thore A , Björkhem I 
Published: January 2020

Abstract
This simple, rapid, sensitive kinetic bioluminescent method for the assay of bile acids in serum involves use of 3 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) in combination with a new, commercially available NADH Monitoring Reagent (LKB-Wallac) containing a low activity of NADH:FMN-oxidoreductase and a high activity of bacterial luciferase. Interfering dehydrogenases in serum are inactivated in the test tube with trichloroacetic acid before the assay. The standard curve is linear for concentrations of bile acids up to about 300 mumol/L. With a sample volume of 20 microL, the detection limit is about 0.2 mumol/L. The within-run precision (CV) is about 10%, both at high and low concentrations of bile acids in serum. Correlation is good (r = 0.996) between results by this method and an enzymatic method based on spectrophotometry. However, the latter method is considerably less sensitive, and it is less precise at low concentrations of bile acids.
Determination of nifedipine in serum or plasma by reversed-phase liquid chromatography.
Authors: Bach P R 
Published: January 2020

Abstract
Therapeutic concentrations of nifedipine in serum or plasma were measured by reversed-phase liquid chromatography, with detection by ultraviolet absorbance at 235 nm. In the procedure a disposable reversed-phase extraction column is used. A 1-mL sample is required. The method is sensitive to 3 micrograms of nifedipine per liter and the standard curve is linear to at least 400 micrograms/L. Coefficients of variation at 100 micrograms/L were 2.2% within-run, 2.8% between-run. The method has been used to determine nifedipine in patients involved in a test of its efficacy in treating muscular dystrophy.