bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid-chromatographic determination of indole-3-acetic acid and 5-hydroxyindole-3-acetic acid in human plasma.
Authors: Martínez E , Artigas F , Suñol C , Tusell J M , Gelpí E 
Published: January 2020

Abstract
We describe a "high-performance" reversed-phase liquid-chromatographic method for determination of indole-3-acetic acid (I) and 5-hydroxyindole-3-acetic acid (II) in human plasma. I is eluted at 1.0 mL/min with a mixture of 1-pentanesulfonic acid (pH 3.1), methanol, and water. It is detected by fluorometry. A mixture of citric acid/sodium phosphate solution (pH 4.8) and methanol, at 1.5 mL/min, is used to elute II, which is detected with an electrochemical cell. Platelet-poor plasma samples were pretreated with HCl, perchloric acid, and trichloroacetic acid for protein precipitation. Best results were obtained with the last (protein precipitation is incomplete with HCl, while recoveries of I are concentration dependent with perchloric acid). Analytical recoveries were 58% (SD 3.1%, CV 5.3%, n = 12) and 79% (SD 3.3%, CV 5.3%, n = 9) for I and II, respectively. Concentrations of I and II in plasma ranged from 0.61 to 3.32 (mean 1.54, SD 0.59, n = 15) mumol/L and from 33.0 to 102.6 (mean 51.8, SD 20.1, n = 16) nmol/L, respectively.
Immunonephelometry of apolipoprotein A-II in hyperlipoproteinemic serum.
Authors: Heuck C C , Erbe I , Frech K , Lohse P , Münscher G 
Published: January 2020

Abstract
Immunonephelometry of apolipoprotein A-II (apo A-II) in serum requires that factors responsible for nonspecific increases of light scattering be eliminated. Complete delipidation is not necessary for immunonephelometry of apo A-II; in fact, light scattering of immunocomplexes from delipidated HDL is greater than from isolated apo A-II. Therefore, using the isolated peptide as a standard does not suffice for measurements in serum. The concentration of protein influences the development of light scattering and must be considered in standardizing this measurement.
A nonlinear regression-kinetic method for quantification of serum triglycerides.
Authors: Hamilton S D , Skoug J W , Pardue H L 
Published: January 2020

Abstract
We report a new kinetic approach to the quantification of triglycerides (triacylglycerols) in human sera. The new approach combines a commercially available enzyme-reagent system with a multiple-linear-regression data-processing method. Values of absorbance collected at 3-s intervals between 20 and 305 s are fitted to a pseudo-first-order model to compute the total change in absorbance expected if the reaction were to proceed to equilibrium. The computed absorbance change varies linearly with triglyceride concentration between 3 and 20 mumol/L (after 250-fold dilution of sample). The pooled relative standard deviation was 7.2% for 23 serum samples with triglyceride concentrations between 3 and 20 mumol/L. Comparison of kinetic (y) and equilibrium (x) absorbance changes for the 23 sera gave a least-squares equation of y = 0.994x + 0.00066, confirming good agreement between the methods. The temperature coefficient is less than 0.2% per degree Celsius.
Sample preparation with ion-exchange resin before liquid-chromatographic determination of plasma catecholamines.
Authors: Frayn K N , Maycock P F 
Published: January 2020

Abstract
Estimation of plasma catecholamine concentrations by "high-performance" liquid chromatography, although increasingly used, still presents difficulties. We describe a method for clean-up of plasma samples on cation-exchange resin before they are extracted with alumina. This procedure eliminates many of the interfering compounds often present in plasma extracts prepared with the alumina treatment alone. The method can be adapted to use commercially available disposable cation-exchange columns.
Free erythrocyte protoporphyrin and zinc protoporphyrin measurements compared as primary screening methods for detection of lead poisoning.
Authors: Kaul B , Slavin G , Davidow B 
Published: January 2020

Abstract
We compared two commonly used primary screening methods (FEP and ZnP) for detecting Pb poisoning in children, used according to three major protocols. The results showed that FEP and ZnP values were comparable for only 36% of the children examined; 54% had FEP greater than ZnP and 10% had ZnP greater than FEP. One would identify approximately twice as many children with Pb greater than 300 micrograms/L by an FEP (500 micrograms/L cutoff) as with a ZnP (400 micrograms/L cutoff) screen. With a cutoff of 350, as compared with 500 micrograms/L for ZnP, one would perform 33% additional confirmatory blood Pb determinations with a 3% increased detection of Pb intoxication. If the number of false-negative Pb specimens is to be minimized, the cutoff "action level" for hematofluorometers should be lowered from the currently recommended 500 micrograms/L of whole blood to 350 micrograms/L. Our long experience and that of other laboratories leads us to recommend a revision of Centers for Disease Control risk categories and cutoff values, depending on whether FEP or ZnP is measured in combination with a patient's blood Pb concentration. Our finding of above-normal values for ZnP and FEP with Pb concentrations less than 300 micrograms/L indicates that iron deficiency constitutes an equally important public-health problem for children in New York City.
Cathodally migrating creatine kinase in sera of patients treated with theophylline, and its diagnostic implications.
Authors: Delahunty T J 
Published: January 2020

Abstract
Sera from 30 patients, selected only on the basis of having serum theophylline concentrations greater than or equal to 18 mg/L, were assayed for total creatine kinase (CK), isoenzyme CK-MB, and cathodally migrating CK (mCK-2). CK-MB was measured by ion-exchange chromatography. mCK-2 was detected by electrophoresis on agarose gel, with fluorometric scanning. The mCK-2 variant was found in 37% of these 30 patients. None of the patients in the mCK-2 group had CK-MB values exceeding the cutoff value associated with myocardial infarction, so extensive cardiac ischemia was considered unlikely. A review of the patients' records supported this conclusion, and no particular association with any specific disease was found among the mCK-2 group. Investigations with use of goat anti-CK-MM and anti-theophylline indicated that neither CK-MM nor theophylline were present in the mCK-2. Results of specific radioimmunoassay for CK-B subunit were negative. The mobility of the mCK-2 peak was unresponsive to 2-mercaptoethanol, suggesting that CK of mitochondrial origin was not present. These results provide insight into the clinical relevance of mCK-2 and some information concerning its composition.
Improved turbidimetric assay for lysozyme in urine.
Authors: Houser M T 
Published: January 2020

Abstract
I describe an improved turbidimetric assay for lysozyme in urine. This method is simple, reproducible, linear over a 100-fold concentration range, sensitive to concentrations as low as 10 micrograms/L, and only commercially available products are required. Evaluation of urinary lysozyme concentration with this assay demonstrated a within-run and between-run CV of 9.9% and 4.8%, respectively, for normal urine, minimal chemical interference, and a mean analytical recovery of 104.8%. There were differences in the rate of clearing and in the linearity of the assay with use of three commercial preparations of Micrococcus lysodeikticus, and significant differences in results when different lysozyme standards were used. Reference values were established by use of data on 169 healthy subjects, ages six months to 61 years. Clinical efficacy of the assay was demonstrated in children with renal disorders, especially those associated with chronic renal failure or tubular dysfunction.
Microsampling on the Technicon SMAC system.
Authors: Walmsley T A , Fowler R T , Abernethy M H 
Published: January 2020

Abstract
The sample volume needed for a Technicon SMAC continuous-flow analyzer has been reduced for routine operation. Two options are available: 141 microL for a 17-test profile, or 224 microL, which allows the direct-sampling assays for creatinine and iron to be included. The sample decrease is achieved by the sequential dialysis of creatinine and iron, an increased sample dilution from sixfold to ninefold, the strict minimization of diluted sample stream wastage, and development of more sensitive methods for glucose and alkaline phosphatase to allow greater use of the diluted sample stream. A glycine-containing diluent increases the sensitivity of the iron method by 25% and prevents the protein precipitation that plagues the continuous-flow analysis for iron in plasma. No deterioration in performance of the analyzer has been detected during nine months of routine operation at the reduced sample size. Added advantages are the decreased consumption of calibration materials and an increased ability to do repeat tests.
High creatine kinase MB isoenzyme activity associated with a rhabdomyosarcoma.
Authors: Hickman P E , Messina S , Trotter J M , Masarei J R 
Published: January 2020

Abstract
A 20-year-old man was found to have high plasma creatine kinase (EC 2.7.3.2) activity in association with a rhabdomyosarcoma of the prostate. There was a very high proportion of the MB isoenzyme. Clinical findings and changes in creatine kinase activity with time showed that this increase was not ascribable to myocardial disease. We believe that the high proportion of CK-MB, confirmed by a combination of electrophoretic and immunoinhibition studies, originated from the tumor.
Novel liposome composition for a rapid colorimetric test for systemic lupus erythematosus.
Authors: Janoff A S , Carpenter-Green S , Weiner A L , Seibold J , Weissmann G , Ostro M J 
Published: January 2020

Abstract
This test for systemic lupus erythematosus utilizes a novel liposome composition entrapping the cation-responsive red dye Arsenazo III. In dilutions of normal sera the liposome membranes undergo a rearrangement when divalent cations are added, resulting in the release of the encapsulated dye and the rapid formation of a stable blue cation-dye complex. Microliter amounts of sera from patients with active lupus stabilize the liposome preparation such that the vesicles remain intact in the presence of the added divalent cations and thus maintain their red color for extended periods. The assay requires 1-min incubations in sera at room temperature and can be performed with standard microtiter plates, allowing the screening of large numbers of serum samples in a short time. Moreover, the unique absorption spectra of the complexed and uncomplexed dye allow for quantification of results.
An internally referenced test strip immunoassay for morphine.
Authors: Litman D J , Lee R H , Jeong H J , Tom H K , Stiso S N , Sizto N C , Ullman E F 
Published: January 2020

Abstract
We describe an internally referenced immunochemical test-strip for use in the rapid detection of morphine. The method is based on the "enzyme-channelling" immunoassay technique, and a glucose oxidase-horseradish peroxidase enzyme pair is used to immunospecifically generate an insoluble, colored reaction product on the test-strip surface. Test strips are composed of two active surfaces, each of which contain co-immobilized glucose oxidase and antibody. The indicator pad contains antibody directed against the drug, and the color that develops on its surface is inhibited by the presence of drug in the sample. The reference pad contains anti-peroxidase and is used to set the assay detection limit and normalize for variations in temperature, timing, and sample interference. The 10-min assay protocol involves incubating the strip in sample, then incubating it in a developer solution containing glucose, a peroxidase chromogenic substrate, and a peroxidase conjugate of the analyte. The ratio of the color formed on the indicator pad to that formed on the reference pad is used to score the test as positive or negative for drug at a predetermined concentration.
Discrete automated chemistry system with tableted reagents.
Authors: Driscoll R C , Edwards R B , Liston M D , Love T W , Mazza J C , Trafton J E 
Published: January 2020

Abstract
An instrument/reagent system with tableted reagents has been developed for performing ultraviolet/visible photometric assays. Preformed disposable plastic cuvettes pass through a stationary track every 5 s, providing a maximum throughput of 698 tests/h. The photometric system consists of a single light source with a separate set of light guides for each of eight photometer stations; bichromatic readings are possible at any of seven wavelengths between 340 and 630 nm. Tablets for 30 different analytes have been developed, each of which contains all necessary components for a single determination. Tablets are dispensed from disposable dispensers into cuvettes under the direction of the system's microprocessor and are completely dissolved within 45 s by ultrasonic agitation. Sample volumes range from 2 to 20 microL. Test requests are selected on a cathode-ray tube display, and sample-container bar-code labels are automatically printed. Sample entry is totally random. The system is designed to provide reagent quality control and also serum and reagent blank corrections for each test. Examples of equilibrium, zero-order, and first-order kinetic assays are presented.
Rapid loss of lactate dehydrogenase isoenzyme activity in serum by cold-induced formation of immunoglobulin G-lactate dehydrogenase complex.
Authors: Wickus G G , Smith M J 
Published: January 2020

Abstract
Lactate dehydrogenase (LD; EC 1.1.1.27) activity in serum from a patient recovering from a myocardial infarction was extremely unstable when stored at 0 degree C. The activity of each LD isoenzyme except LD-1 decreased by at least 40% when serum was stored at 0 degree C for 4 h. The patient's erythrocyte LD activity had normal stability at lower temperatures, but LD from other sources, when added to the patient's serum, rapidly lost activity at 0 degree C. The patient's serum contained an immunoglobulin G that combined--at 0 degree C but not at 21 degrees C--primarily with LD isoenzymes containing one or more M subunits. Because this immunoglobulin-LD complex has no enzyme activity, we used 125I-labeled purified LD to study formation of the complex. NAD+ blocked the formation of immunoglobulin-LD complex but could not dissociate the complex and restore the LD activity.
Sex-dependent relation between ionized calcium in serum and blood pressure.
Authors: Fogh-Andersen N , Hedegaard L , Thode J , Siggaard-Andersen O 
Published: January 2020

Abstract
In an epidemiological study of 977 45-year-olds, both the mean concentration of ionized calcium in serum, [Ca2+]7.4, and arterial blood pressure were higher in men than in women. Among the men, there was a weak positive correlation between [Ca2+]7.4 and the systolic blood pressure, but no other significant correlation was found within each separate sex. Postmenopausal women had slightly increased [Ca2+]7.4 but normal blood pressure. Patients taking thiazide diuretics or beta-adrenergic blocking agents had normal [Ca2+]7.4.
Simultaneous on-line measurement of blood K+, Ca2+, Na+, and pH with a four-function ChemFET integrated-circuit sensor.
Authors: Sibbald A , Covington A K , Carter R F 
Published: January 2020

Abstract
On-line, simultaneous measurement of blood K+, Ca2+, Na+, and pH has been achieved by using a quadruple-function ChemFET (chemical-sensitive field-effect transistor) integrated-circuit sensor. Blood is withdrawn from the subject through an actively heparinized, dual-lumen cannula and passed into a flow-cell containing the sensor, in alternation with a calibration solution. A minicomputer controls the analysis system, logs data, and provides a continuous, graphic display of K+ and pH values.
Improved liquid-chromatographic determination of 3-methoxy-4-hydroxyphenylethyleneglycol in urine with electrochemical detection.
Authors: Shipe J R , Savory J , Wills M R 
Published: January 2020

Abstract
In this improved method for quantifying 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) in urine, after a multistep extraction of MHPG and internal standard (iso-MHPG) from 3.0 mL of urine, the compounds are separated on a C18 reversed-phase column and quantified by use of an electro-chemical detector. The isocratic chromatographic separation takes about 16 min. The mobile phase is phosphate buffer/acetonitrile (88/12 by vol), the flow rate 0.7 mL/min. Recycling the mobile phase and automating the sample injection make possible the unattended assay of more than 70 samples per day. The within-run precision of the method is excellent (CV 1.8%) at a mean concentration of 1.1 mg/L.
Enzyme-linked immunosorbent assay of retinol-binding protein in serum and urine.
Authors: Lucertini S , Valcavi P , Mutti A , Franchini I 
Published: January 2020

Abstract
This highly sensitive method for determining retinol-binding protein in human serum and urine is based on a double-antibody "sandwich"-type enzyme-linked immunosorbent assay. The assayable concentration range is 0.8-48 micrograms/L, the detection limit 0.2 micrograms/L. Within-assay coefficients of variation for 10 determinations at two different concentrations were 5.5 and 5.8%. The corresponding between-assay CVs were 7.9 and 9.2%. We saw no interference from any components of urine or serum. The mean urinary excretion by 30 healthy subjects, as determined by this method, was 101 micrograms/g of creatinine (SD 38.8). The concentration in serum averaged 43 mg/L (SD 12.1).
Sampling from a skewed population distribution as exemplified by estimation of the creatine kinase upper reference limit.
Authors: Miller W G , Chinchilli V M , Gruemer H D , Nance W E 
Published: January 2020

Abstract
Creatine kinase (EC 2.7.3.2) was measured in sera from 580 females, ages 1-77 years, and 550 males, ages 1-63 years. The distribution of results for male and female groups shows pronounced skewing toward higher values. The observed distribution of results could not be described by any of six mathematical formulas for skewed distributions, an indication of the unsuitability of such formulas to transform these data for parametric analysis. The range of 97.5 percentile estimates produced by six independent samples of 100, 200, and 400 observations randomly selected from a mathematical model defined by the adult female distribution showed progressive narrowing from the 150-380 U/L interval for the samples of 100 observations to 200-265 U/L for the samples of 400 observations; no further improvement was seen when 800 observations were used. The samples of 100 and 200 observations contained extreme value points that might appear as "outliers" but were shown to be valid members of the population distribution when larger sample sizes were collected.
Simultaneous determination of 25-hydroxy- and 1,25-dihydroxyvitamin D from a single sample by dual-cartridge extraction.
Authors: Kao P C , Heser D W 
Published: January 2020

Abstract
With this dual-cartridge system we extract 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] from a single serum sample by using a nonpolar octadecylsilanol silica cartridge to adsorb the vitamin D metabolites and other nonpolar substances; the polar substances wash through the cartridge. The eluted material is then applied to a second alkylamine cartridge, which adsorbs the relatively polar hydroxylated metabolites; the less-polar substances are washed from the second cartridge. Elution from the second cartridge purifies and also separates 25(OH)D and 1,25(OH)2D with analytical recoveries near 90%. The monohydroxyl metabolites are determined by "high-performance" liquid chromatography (HPLC); the dihydroxyl metabolites are further purified by HPLC and determined by radioreceptor assay according to established procedures. Mean (+/- SD) winter normal values (34 subjects of both sexes; blood drawn in mid-April) were 18 +/- 5 micrograms/L for 25(OH)D and 25 +/- 7 ng/L for 1,25(OH)2D. In nine laboratory volunteers, the mean increase in the serum 25(OH)D3 value 5 h after ingestion of 50 micrograms of 25-hydroxycholecalciferol (Calderol) was 9 (SD 4) micrograms/L.
Use of monoclonal antibodies in an enzyme immunoassay for factor VIII-related antigen.
Authors: Bradley L A , Franco E L , Reisner H M 
Published: January 2020

Abstract
Two monoclonal antibodies (MAb 53, MAb D7) were produced, each having specificity for Factor VIII-related antigen (FVIIIR:Ag), but exhibiting no inhibitory effect on either procoagulant activity or the ability of von Willebrand factor to agglutinate platelets in the presence of the antibiotic ristocetin. For quantification of FVIIIR:Ag, we used the antibodies in a competitive enzyme-linked immunosorbent assay (ELISA). Binding of either of the MAb's to solid-phase antigen was inhibited by free FVIIIR:Ag in the test sample. Dose-response curves for the reference standards were consistently linear (r2 greater than 0.990) and reproducible. The normal range of FVIIIR:Ag detected in plasma (normal defined as 1000 units/L) was similar to that reported for polyclonal heterologous antibodies in similar ELISA or immunoradiometric (IRMA) systems, and the assay was sensitive to 10 units of FVIIIR:Ag per liter. Inter- and intra-assay precision was good, coefficients of variation being less than 11%. Studies on patients showed good correlations between values measured by MAb ELISAS and IRMA (polyclonal rabbit antibody) over FVIIIR:Ag concentrations ranging from less than 10 to 2700 units/L (r = 0.971, p less than 0.001 for MAb 53; r = 0.938, p less than 0.001 for MAb D7). Both ELISAS could be used to quantify FVIIIR:Ag in other mammalian species. The assay is inexpensive and simple, and all reagents required for it are commercially available.
Development of a reference material for alkaline phosphatase.
Authors: Duncan P H , McKneally S S , MacNeil M L , Fast D M , Bayse D D 
Published: January 2020

Abstract
In developing a Reference Material for alkaline phosphatase, we studied the stability, kinetic properties, and commutability of separate preparations of the purified enzyme from human liver, intestine, bone, and placenta. The Michaelis constants (Km) for the preparations from liver, bone, and intestine agreed well with the Km values we obtained for five human serum specimens, whereas that for the placental isoenzyme differed significantly. The first three isoenzymes exhibited nearly identical response-surface patterns, which closely paralleled those observed for 12 human serum specimens (commutability), but not that of the placental isoenzyme. Thus, we believe that a reference material could equally well consist of either the bone, intestinal, or liver isoenzyme. All four isoenzymes were satisfactorily stable in temperature-accelerated degradation studies. We chose the liver isoenzyme as an appropriate reference material because liver tissue is easier to obtain than bone or intestine and the isoenzyme is abundant in liver, is easy to extract, and is the one most commonly increased in human serum. This material is stable at -20 degrees C, is free of interfering and degradative enzymes and, being of human origin, is commutable with the enzyme in human serum.
Association of an oxygen-sensitive lactate dehydrogenase isoenzyme, LDk, with LD-6 in serum of critically ill patients.
Authors: Onorato V A , Manly K F , Vladutiu A O 
Published: January 2020

Abstract
We measured a highly unusual, oxygen-sensitive lactate dehydrogenase, LDk, in the serum of six patients whose serum showed a band for LD-6 on routine agarose gel electrophoresis for LD isoenzymes. All these patients showed very high serum LDk activity, greatly exceeding the high values previously described in serum of patients with various malignant tumors. In two of the patients, LDk activity was low both before LD-6 was found in and after it disappeared from the serum, evidencing a correlation with LD-6. All of the six patients, five of whom died in the hospital, had severe hypotension. We suggest that hypoxia is responsible for the appearance of LD-6 in serum and that LD-6 is found in association with high LDk activity in serum of critically ill patients.