bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of serum triglycerides by an accurate enzymatic method not affected by free glycerol.
Authors: Sullivan D R , Kruijswijk Z , West C E , Kohlmeier M , Katan M B 
Published: January 2020

Abstract
In this automated single-run enzymatic procedure for specific determination of triglycerides in serum, free glycerol is removed from the reaction mixture by pre-incubation with glycerol phosphate oxidase and peroxidase. The subsequent addition of lipase and the chromogen, 4-aminoantipyrine, results in the formation of color proportional to the amount of triglycerides in serum. Standards containing triolein in aqueous detergent are used to calibrate the method. For serum pools from the Centers for Disease Control with target values of 0.74, 1.41, and 2.63 mmol/L, the method produced biases of +0.01, -0.05, and 0.00 mmol/L, respectively (mean: -0.01 mmol/L or -0.4%). The mean coefficient of variation was 1.4% within and 2.5% between days; the combined CV, 2.9%. Ninety 6-microL serum samples can be analyzed per hour. The method is more accurate and precise than one based on an NADH-coupled enzyme system with separate addition of lipase.
Urinary creatine: biochemical indicator for evaluation of sickle cell crises.
Authors: Beyer C , Statius van Eps L W , Kastelein J J , Brandjes D P , Mairuhu W M , van den Ende A 
Published: January 2020

Abstract
In a patient with known sickle cell beta 0-thalassemia we measured serum lactate dehydrogenase (LD) activity and 24-h urinary creatine excretion rate as markers to evaluate sickle cell crises. We believe that a distinction based on biochemical findings can be made between hemolytic and painful vaso-occlusive sickle cell crises with muscular involvement. To assess hemolytic crises by objective biochemical measures, we have used assay of LD activity, and to assess painful crises with muscular involvement objectively, the 24-h urinary creatine excretion rate. We conclude that hemolytic crises are characterized by high serum LD activities. Furthermore, we conclude that--at least in this patient--painful crises are accompanied by high 24-h urinary creatine excretion rates. Our findings suggest that muscle involvement may play an important role in painful vaso-occlusive sickle cell crises.
Combined liquid chromatography/radioimmunoassay with improved specificity for serum digoxin.
Authors: Gault M H , Longerich L , Dawe M , Vasdev S C 
Published: January 2020

Abstract
This method for assaying digoxin in serum with improved specificity combines small-column extraction of serum, "high-performance" liquid chromatography, and RIA of the eluted fractions. Analytical recoveries of 1.0, 0.5, and 0.1 microgram/L standards were 95%, 93%, and 84%, respectively. The CVs for duplicates and replicates of sera with values of 0.5 to 1 microgram/L were 4 to 6%. Fifty-nine sera from 50 patients receiving digoxin were so studied. All digoxin metabolites appear to cross react with antibody to digoxin to various degrees. The most polar metabolites were quantitatively the most important, their average cross reactivity being 33%. For eight patients the value for digoxin by the present method was less than 60% of the RIA value. Sera from nine patients not taking digoxin but with falsely high digoxin values were also studied by the present method. The digoxin peak was well resolved from those for (a) digoxin metabolites (except dihydrodigoxin), (b) digitalis-like factors in neonates and in patients with renal failure or combined hepatic and renal failure, and (c) two cross reacting drugs and their metabolites.
Binding of Al by protein in plasma of patients on maintenance hemodialysis.
Authors: Cochran M , Patterson D , Neoh S , Stevens B , Mazzachi R 
Published: January 2020

Abstract
Gel filtration of plasma from hemodialysis patients, with use of reagents and apparatus with carefully minimized background Al concentrations, reproducibly showed a single peak for Al, corresponding exactly to the elution position of transferrin. The Al/transferrin molar ratio in adjacent fractions was constant (mean 0.126, SE 0.006) in replicate experiments. In contrast, the association of Al with albumin varied. Using both equilibrium dialysis and gel-filtration techniques, in the presence and absence of calcium or phosphate, we could demonstrate no significant binding of Al by human albumin at Al concentrations of 1 to 12 mumol/L. We saw no Al peak in pooled, concentrated, low-molecular-mass fractions of plasma gel-filtered on Sephadex G-50. Evidently, transferrin is the sole Al-binding protein in plasma of hemodialysis patients.
Phenols as enhancers of the chemiluminescent horseradish peroxidase-luminol-hydrogen peroxide reaction: application in luminescence-monitored enzyme immunoassays.
Authors: Thorpe G H , Kricka L J , Moseley S B , Whitehead T P 
Published: January 2020

Abstract
Certain phenol derivatives, including p-iodophenol and p-phenylphenol, enhance light emission from the horseradish peroxidase-catalyzed oxidation of cyclic diacyl hydrazides such as luminol. The light emission decays slowly (glowing for several minutes) and its intensity may be greater than 1000-fold that of the unenhanced reaction. The enhanced system enables rapid, sensitive assay of peroxidase conjugates. We describe its application in immunoassays for human choriogonadotropin, digoxin, and factor VIII-related antigen. Luminescent quantification of peroxidase labels has been directly incorporated into immunoassays based on beads, tubes, or microtiter plates, used in conjunction with photodetectors such as photomultiplier tubes or instant photographic film. Enhancement with phenol derivatives exceeds that achieved with 6-hydroxybenzothiazole derivatives and depends on pH and enhancer concentration. Emission spectra of phenol-enhanced and unenhanced reactions are remarkably similar, suggesting that the enhancers do not act as more efficient emitters but exert their action earlier in the complex reaction between peroxidase, oxidant, and luminol.
Three methods compared for determining phosphatidylglycerol in amniotic fluid.
Authors: Coapman-Hankin R A , Kiechle F L , Epstein E , Artiss J D , Zak B 
Published: January 2020

Abstract
Phosphatidylglycerol is one component of amniotic fluid that is unaffected by several of the reported interferences with conventional thin-layer chromatographic measurement of phospholipid. To compare a rapid immunological agglutination test, "Amniostat-FLM", with two-dimensional thin-layer chromatography, we determined phosphatidylglycerol by both methods in 41 amniotic fluid specimens obtained at 31 to 40 weeks of gestation. We also assayed phosphatidylglycerol in 14 of these specimens by an enzymic, colorimetric procedure. The agglutination test is rapid and simple but relatively insensitive; it yielded positive results for only seven of 23 specimens in which phosphatidylglycerol was detected by thin-layer chromatography. In 18 specimens in which no phosphatidylglycerol was detected by thin-layer chromatography, results by Amniostat-FLM were also negative; however, eight of these specimens, assayed by the enzymic method, had phosphatidylglycerol present. Apparently, the Amniostat-FLM detects phosphatidylglycerol only at concentrations exceeding 25 mumol/L, or more than 15% of the total phospholipid composition.
N-[(carbamoylmethyl)amino]ethanesulfonic acid improves phenotyping of alpha 1-antitrypsin by isoelectric focusing on agarose gel.
Authors: Chappell D J 
Published: January 2020

Abstract
The hereditary deficiency variants of alpha 1-antitrypsin that are associated with diseases such as emphysema are usually identified by use of isoelectric focusing on polyacrylamide gels. Agarose is a simpler, faster, safer, and more reliable medium for this, but resolution often is not as good. I describe a method in which the ultrathin agarose gel contains N-[(carbamoylmethyl)amino]ethanesulfonic acid as a "separator," to flatten the pH gradient and improve separation of the alpha 1-antitrypsin isoforms. The resolution obtained equals or surpasses that of conventional methods based on use of either polyacrylamide or agarose. Haptoglobin, which interferes with isoelectric focusing on polyacrylamide, does not interfere with this method; other advantages are also discussed.
Use of DNA immobilized on plastic and agarose supports to detect DNA by sandwich hybridization.
Authors: Polsky-Cynkin R , Parsons G H , Allerdt L , Landes G , Davis G , Rashtchian A 
Published: January 2020

Abstract
Cloned Salmonella DNA, which has been immobilized irreversibly on plastic and agarose solid supports, can form hybrids in both single-layer and "sandwich" hybridization protocols. In single-layer hybridization, 3 micrograms of immobilized DNA bound at least 30 fmol of a specific 800-base DNA sequence (equivalent to 8.5 ng, or the amount of that sequence present in 4 X 10(10) organisms). In a 4-h sandwich hybridization protocol, as little as 14 amol (equivalent to 8 pg, or the amount of that sequence present in 1 X 10(7) organisms) of a 1600-base sequence of DNA could be detected. The methods described should be applicable to use with any set of probes--not just from Salmonella--that fulfill the criteria specified. The ability to perform DNA hybridizations on solid-phase matrices such as those used for immunoassay should bring DNA hybridization into the realm of routine clinical laboratory procedures.
Fluorescence depolarization assay for quantifying alpha-amylase in serum and urine.
Authors: Hofman M , Shaffar M 
Published: January 2020

Abstract
We have developed a new method for quantifying alpha-amylase (EC 3.2.1.1) in serum and urine by fluorescence depolarization. Amylase in the sample catalyzes the hydrolysis of the substrate, a fluorescein-labeled amylose. This results in decreased fluorescence polarization, owing to the increased rate of rotation of the amylose fragment relative to the intact substrate. The TDx amylase assay is calibrated with six human-serum-based pancreatic amylase calibrators. Amylase activities are determined by interpolation from the calibration curve, which is stored in the TDx analyzer's memory. Results correlate well with those by the Du Pont aca assay and the Beckman "DRI-STAT" assay. Endogenous glucose does not interfere. CVs are less than 6%, and the reagents are stable in liquid form.
Particle concentration fluorescence immunoassay: a new immunoassay technique for quantification of human immunoglobulins in serum.
Authors: MacCrindle C , Schwenzer K , Jolley M E 
Published: January 2020

Abstract
A new fluorescence immunoassay technique, particle concentration fluorescence immunoassay (PCFIA), has been developed for quantifying the human immunoglobulins (IgA, IgM, and IgG). In these "two-site sandwich assays," the capture antibody is immobilized on small polystyrene spheres and the tracer is fluorescein-labeled antibody. Polystyrene particles less than 1 microm in diameter make up the solid phase, to which goat anti-human antibody for each respective assay is attached. Serum specimens are diluted (5000-fold for IgA or IgM, 20 000-fold for IgG) placed on the 96-well Pandex assay plate; and mixed with the solid phase and tracer (fluorescein-labeled goat anti-human IgA, IgM, or IgG), which are added automatically by the Pandex Screen Machine. This instrument incubates the reaction mixture for 17 min at ambient temperature, separates the bound and free label by filtration, washes the solid phase, and determines the total particle-bound fluorescence by front-surface fluorimetry or epifluorescence, calculates results, and generates detailed reports. Ninety-six specimens may be analyzed in 29 min or 960 specimens in 136 min. Results by PCFIA for IgA, IgM, and IgG in serum correlated well with those by rate nephelometry.
Simultaneous determination of total IgE and allergen-specific IgE in serum by the MAST chemiluminescent assay system.
Authors: Brown C R , Higgins K W , Frazer K , Schoelz L K , Dyminski J W , Marinkovich V A , Miller S P , Burd J F 
Published: January 2020

Abstract
We have developed a chemiluminescent immunoenzymometric system. The first commercial application of this chemiluminescent assay (CLA) is the measurement of total IgE and allergen-specific IgE in human serum. The CLA system is a second-generation adaptation of the MAST RIA allergy profiling system. The MAST CLA system assay protocol consists of three steps: overnight incubation of serum, a 4-h incubation with enzyme-labeled antibody, and a 30-min chemiluminescent reaction, which produces a visible image (immunograph) on high-speed Polaroid instant film. The densities of the bands produced on the film are quantified with an inexpensive microprocessor-controlled infrared transmittance densitometer. The novel luminogenic substrates used yield a constant light output for over 2 h with an intensity at least 10-fold greater than that of commercial chemiluminescent reagents. The MAST CLA system exhibits sensitivity, specificity, and precision equal to that of the MAST RIA system (r = 0.96 for 40 serum samples analyzed with 25 allergens). As many as 35 different allergens per sample can be quantified in a single assay. The MAST CLA system requires no standard curve or volume-dependent pipetting steps, incorporates both positive and negative controls for each sample, and quantifies allergen-specific IgE at picomolar concentrations.
The use of DNA probes in studies of human cytomegalovirus.
Authors: Spector S A , Spector D H 
Published: January 2020

Abstract
Hybridization assays provide a sensitive and rapid means for studying the molecular biology of viral replication and for identifying viral nucleic acid in biological specimens. Such assays are attractive because the detection of virus does not require intact virions or concomitant viral protein synthesis, both of which may be absent in a latently infected cell or in a virus-associated tumor. For molecular and clinical studies on human cytomegalovirus (HCMV), we have cloned and characterized subgenomic EcoRI fragments representative of the entire genome of HCMV strain AD169. To study the epidemiology of HCMV infections and to identify the presence of HCMV nucleic acid in urine, blood, Kaposi's sarcoma, and other tissues, we have used various hybridization techniques, including DNA dot/slot-blot hybridization, Southern blot hybridization, and in situ cytohybridization. These studies demonstrate how cloned molecular probes can be used to study the molecular biology, pathogenesis, and treatment of viral infections.
Endogenous digoxin-like immunoreactive factors: impact on digoxin measurements and potential physiological implications.
Authors: Valdes R 
Published: January 2020

Abstract
Various laboratories have reported endogenous digoxin-like immunoreactive factor(s) (DLIF) in blood from patients in renal failure or liver failure, from newborn infants, and from third-trimester pregnant women. Similar immunoreactivity has been detected in amniotic fluid, in cord blood, and in urine and serum from normal subjects. The factor(s) giving rise to this immunoreactivity cross react with antibodies used in many currently available immunoassays for digoxin, sometimes causing apparent digoxin concentrations exceeding the therapeutic range obtained for exogenous digoxin, with consequent errors in measurement and in subsequent clinical interpretation of digoxin results. Here, I summarize findings in our laboratory and those of others. DLIF evidently exist in three states in serum: tightly protein-bound, weakly protein-bound, and unbound (free). In normal subjects, greater than 90% of the total DLIF in serum is tightly but reversibly bound to serum proteins and is not readily detectable by direct measurement of digoxin in serum with conventional immunoassays. However, there seems to be a redistribution of the more weakly bound and unbound components in patients with renal failure, pregnant women, and newborns. The increased values detected in these groups are ascribable to increased amounts of weakly bound and unbound DLIF rather than to increased total DLIF. Carrier proteins may play a prominent role in the transport of these factors in blood. I discuss the potential physiological and pharmacological implications of detecting endogenous immunoreactive factors that cross react with antibodies to drugs.
Influence of oral contraceptives and pregnancy on constituents of the kallikrein-kininogen system in plasma.
Authors: Adam A , Albert A , Boulanger J , Genot D , Demoulin A , Damas J 
Published: January 2020

Abstract
We measured kininogens of low and high molecular mass along with prokallikrein activity in plasma of women with a normal menstrual cycle. We observed no difference between results for the follicular and luteal phases. We assayed the same constituents in women who were taking oral contraceptives (combined estroprogestative) and found that activity of prokallikrein and concentrations of low- and high-molecular-mass kininogens were significantly increased. Lastly, we studied the components of the kallikrein-kininogen system during pregnancy. We also observed a marked increase in their concentrations in plasma, despite a decrease in total proteins. Specifically, prokallikrein and kininogens increase continuously with gestational age, reaching their maxima around the eighth month of pregnancy. At that time, more than 50% of observed results fall outside the normal reference interval. Our observations are even more striking when prokallikrein and kininogens are expressed in units per gram of total proteins, to account for the hemodilution. After delivery, the concentrations of prokallikrein and low- and high-molecular-mass kininogens decline promptly, returning to normal within three days.
Heterogeneous enzyme immunoassay with electrochemical detection: competitive and "sandwich"-type immunoassays.
Authors: Wehmeyer K R , Halsall H B , Heineman W R 
Published: January 2020

Abstract
In these competitive and "sandwich"-type heterogeneous enzyme immunoassays, based on liquid chromatography with electrochemical detection, rabbit immunoglobulin G is used as a model compound. Alkaline phosphatase (EC 3.1.3.1), the labeling enzyme, catalyzes conversion of phenyl phosphate to phenol. After separation on an octyldecylsilane column, the enzyme-generated phenol is detected in a thin-layer cell at a carbon-paste working electrode. The detection limit for phenol is 5.0 nmol/L. The electrode response varies linearly with concentration over a range of three orders of magnitude. For the sandwich-type assay procedure the detection limit is 10 ng/L; the linearity ranges over four orders of magnitude. The detection limit of the competitive immunoassay is 5 micrograms/L. The dynamic range spans two orders of magnitude.
Use of protein-based standards in automated colorimetric determinations of fructosamine in serum.
Authors: Baker J R , Metcalf P A , Johnson R N , Newman D , Rietz P 
Published: January 2020

Abstract
We have developed an automated colorimetric assay for glycated serum proteins (or fructosamines), measuring the reducing activity of serum in alkaline solution (pH 10.35) at 37 degrees C. The calibrants were prepared from a synthetic fructosamine (1-deoxy-1-morpholinofructose), although secondary standards of glycated bovine albumin were more robust in routine application. Interference was appreciable only with icteric specimens (bilirubin greater than 60 mumol/L), and between-batch imprecision (CV) was less than 2%. The range of fructosamine concentrations measured in 502 healthy (nondiabetic) blood donors was 1.87-2.87 mmol/L. There were no significant (p greater than 0.05) age- or sex-related differences in this population sample. Fructosamine accurately reflected blood glucose control as evidenced by the significant correlation with glucose concentrations in fasting plasma (r = 0.82, p less than 0.001) and with glycated hemoglobin (HbA1c) (r = 0.87, p less than 0.01) in 115 patients with type 2 (non-insulin-dependent) diabetes mellitus. The test is simple and rapid to perform (75 samples per hour) and provides an alternative to HbA1c determinations for monitoring blood glucose control and assessing the effects of changes in diabetes management.
Bedside micro-method for measuring effective hepatic blood flow, with use of first-order galactose clearance pharmacokinetics.
Authors: Rypins E B , Sankary H , Wynn M J 
Published: January 2020

Abstract
Data from first-order galactose clearance were used to estimate "effective" hepatic blood flow in normal subjects and in patients with hepatic diseases. Galactose clearance was determined by infusing galactose intravenously at a constant rate and measuring its resulting steady-state concentration in blood. The infusion rate must not exceed the maximum rate of galactose clearance by the liver, the "galactose elimination capacity." With this constraint and within the physiological and pathophysiological limits of hepatic blood flow, a constant infusion at 50 mg/min results in steady-state concentrations ranging from 20 to 200 mg/L. To measure galactose within this range, we modified a YSI Model 23A glucose analyzer and, using an immobilized galactose oxidase (EC 1.1.3.9)/hydrogen peroxide electrode system, accurately measured galactose in water and blood. The galactose metabolic clearance rate was calculated for six normal rats and for a normal and a cirrhotic human subject. The speed of the analysis (40 s), the small sample required (25 microL), and the suitability of fresh whole blood as the sample make the method ideal for measuring hepatic blood flow in small laboratory animals as well as for determining at bedside the effective hepatic blood flow in humans.
Use of the serum copper/zinc ratio in the differential diagnosis of ovarian malignancy.
Authors: Lightman A , Brandes J M , Binur N , Drugan A , Zinder O 
Published: January 2020

Abstract
We measured copper and zinc in serum (n = 82) and tumor tissue (n = 41) from women with a palpable pelvic mass, admitted for suspected ovarian tumor. In serum, copper was increased and zinc decreased in the group (n = 40) subsequently proven to have a malignant ovarian tumor. The mean copper/zinc ratio in this group was 2.30 (SD 0.41), significantly (p less than 0.001) higher than for the benign group (n = 42), 1.43 (SD 0.22). In tumor tissue the concentrations of copper and zinc followed the same pattern, the copper/zinc ratio being significantly (p less than 0.001) higher in the malignant (0.158, SD 0.065) tumors than in the benign tissue (0.093, SD 0.04). We conclude that the Cu/Zn ratio in serum reliably (specifically) indicates the presence of advanced ovarian malignant tumor. The decreased concentrations of zinc and the increased concentrations of copper in serum do not seem to result from a shift of zinc into or release of copper out of the malignant tumor tissue.
Plasma cholinesterase phenotyping with use of visible-region spectrophotometry.
Authors: Abernethy M H , George P M , Herron J L , Evans R T 
Published: January 2020

Abstract
A method that overcomes the difficulties of the 240-nm benzoylcholine method for phenotyping plasma cholinesterases has been developed. After a timed reaction, under the same reaction conditions as in the classic procedure, choline is detected at 500 nm by use of choline oxidase coupled with the peroxidase/phenol/aminoantipyrine system. Cholinesterase activity measurements, calibrated by use of choline iodide as standard, are linearly related to results obtained with propionylthiocholine as substrate at 25 degrees C (y = 0.14x + 0.17, n = 30, r = 0.98). Results of differential inhibition with dibucaine and fluoride are virtually identical with those obtained by the ultraviolet method (y = 0.97x + 4.3, r = 0.995, and y = 0.93x - 0.5, r = 0.987, respectively) and give the same classification of homo- and heterozygotes for the usual, atypical, and fluoride-resistant variants. The new method has substantial advantages in that it eliminates the difficulties associated with measuring small changes in high absorbances at a suboptimal wavelength on a steep portion of the absorption curve.