bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iohexol in Serum Determined by Capillary Electrophoresis
Authors: Shihabi Z K , Constantinescu M S 
Published: January 2020

Abstract
Iohexol, a nonionic compound used as a contrast medium for angiography and as a measure of the glomerular filtration rate, was quantified in serum by capillary electrophoresis. Comparable results were obtained for serum samples deproteinized with acetonitrile or analyzed directly after 50-fold dilution with borate buffer. Serum samples were electrophoresed for 2.6 min at 12 kV in a borate buffer with detection at 254 nm and with 3-isobutyl-1-methylxanthine as internal standard. Acetonitrile deproteinization gave a greater sensitivity than did sample dilution. Between-run CVs were between 4.7% and 6.7%, and within-run CVs were between 2.5 and 3.2%. Analytical recoveries were 95-105%. Results of the method compared well with those by high-performance liquid chromatography (slope 0.96, intercept 0.005 g/L). This method demonstrates the potential of capillary electrophoresis for rapid and simple quantification of small molecules.
Development of Monoclonal Antibodies for an Assay of Cardiac Troponin-I and Preliminary Results in Suspected Cases of Myocardial Infarction
Authors: Bodor G S , Porter S , Landt Y , Ladenson J H 
Published: January 2020

Abstract
To improve the specificity of biochemical markers of myocardial infarction (MI), we have developed a double monoclonal "sandwich" enzyme immunoassay to measure cardiac troponin-I (cTnI) in serum. We produced eight IgG monoclonal antibodies against human cardiac troponin-I (cTnI) and tested them against human and animal (canine, bovine, and rabbit) troponins. Five antibodies were cardiac-specific; none of the antibodies were species-specific. Two of the five cTnI-specific monoclonal antibodies were utilized in an immunoassay. Standards were made by adding purified human cTnI to affinity-stripped cTnI-free human sera to cover the range 0-100 micrograms/L for cTnI. The dose-response curve was nonlinear but reproducible. Total assay imprecision (CV) varied between 11% and 21%. The upper limit of the reference range (nonparametric 95% interval) was established as 3.1 micrograms/L by measuring cTnI concentration in sera of 159 hospitalized patients without evidence of cardiac disease. Purified human skeletal TnI up to 10,000 micrograms/L did not affect the assay (calculated cross-reactivity &lt; 0.1%). Diagnostic sensitivities of creatine kinase MB isoenzyme (CK-MB) and cTnI were evaluated retrospectively in 49 consecutive patients with proven MI. In the 30 patients for whom sufficient information was available to establish an accurate time course, CK-MB was more sensitive during the first 4 h after the onset of chest pain, but thereafter the sensitivities were similar up to 48 h. However, cTnI is more cardiac-specific than is CK-MB and remains increased longer than does CK-MB.
Ratio of Creatine Kinase 2 Mass Concentration to Total Creatine Kinase Activity not Altered by Heavy Physical Exercise
Authors: Ordóñez-Llanos J , Serra-Grima J R , Mercé-Muntañola J , González-Sastre F 
Published: January 2020

Abstract
Serum creatine kinase isoenzyme 2 concentrations (CK 2 mass) were measured in marathon runners during training and 1 and 2 days after a race and compared with values from 36 acute myocardial infarction (AMI) patients whose total CK and (or) CK 2 activities were similar to those of runners in the basal state. During training, runners had CK and CK 2 activities 53% and 43% above reference values, respectively, and 36% had CK 2 activity &gt; 5% of total CK. Nine runners (26%) showed CK 2 mass values &gt; 6 micrograms/L but &lt; or = 10 micrograms/L; 35 of the AMI subjects, despite having CK activities similar to those of runners, had values &gt; 10 micrograms/L. The ratio of CK 2 mass to total CK activity was significantly (P &lt; 0.0002) different between sexes for runners. At 1 and 2 days after racing, 100% of CK and CK 2 activities and 71% and 57% of the percentages of CK 2 activity, respectively, were abnormally high; 57% and 43% of CK 2 mass values were &gt; 10 micrograms/L, being comparable with those observed for the AMI group. Basal CK 2 mass values of the runners appeared only slightly higher than that for sedentary subjects, but after exercise half the subjects presented increased values similar to those observed for AMI subjects. The ratio of CK 2 mass to total CK activity appeared unaltered by exercise in all but one of the samples assayed, indicating its utility in evaluating CK 2 mass increases originating in skeletal muscle.
Effects of Angiotensinase Inhibitors on Plasma Protein Binding and IC50 Determinations of Renin Inhibitors
Authors: Dayton B D , Stein H H , Cohen J , Baker W R , Boyd S A , Condon S L , Donner B G , Fung A K , Luly J R , Rosenberg S H 
Published: January 2020

Abstract
To establish whether the use of proteinase inhibitors in the routine determination of in vitro plasma renin activity overestimates the potency of renin inhibitors in vivo, we examined the effects of phenylmethylsulfonyl fluoride and 8-hydroxyquinoline sulfate on the binding to plasma proteins and the respective IC50 values (50% inhibiting concentrations) of three renin inhibitors. All three renin inhibitors, A-64662, A-65317, and A-74273, bound (&gt; 60%) to plasma proteins at both pH 6.0 and 7.4, with slightly greater binding at pH 7.4. Phenylmethylsulfonyl fluoride (1.45 mmol/L) had no significant effect on the protein binding at either pH 6.0 or 7.4; 8-hydroxyquinoline sulfate (3.4 mmol/L) caused a modest dissociation (10-30%) of the renin inhibitors from plasma proteins at both pH values; and the effects of both proteinase inhibitors together were similar to those of 8-hydroxyquinoline alone. At pH 7.4, phenylmethylsulfonyl fluoride increased the potencies of the three renin inhibitors slightly (&lt; or = 43%), whereas IC50 values determined in the presence of 8-hydroxyquinoline decreased by 1.5- to 3.7-fold. The greatest increase in potency occurred with the most hydrophilic compound, and with both angiotensinase inhibitors the effect was no greater than that of 8-hydroxyquinoline alone. The results show that any dissociation of the hypotensive activity measured in vivo from the plasma renin activity measured in vitro is not simply an artifact in the plasma renin activity assay stemming from the use of these angiotensinase inhibitors, especially if only phenylmethylsulfonyl fluoride is used.
Pre-Beta High-Density Lipoprotein Determined by Immunoblotting with Chemiluminescent Detection
Authors: O'Kane M J , Wisdom G B , McEneny J , McFerran N V , Trimble E R 
Published: January 2020

Abstract
We describe a novel assay of pre-beta high-density lipoprotein (HDL), a unique apolipoprotein A-I (apo A-I)-containing lipoprotein particle. The pre-beta and alpha lipoproteins are separated by electrophoresis in agarose and transferred onto a membrane by capillary blotting. The membrane blot is sequentially incubated with sheep anti-human apo A-I antiserum and then with a conjugate of rabbit anti-sheep immunoglobulin and horseradish peroxidase. Chemiluminescence formed by the peroxidase-catalyzed oxidation of luminol in the presence of an enhancer is captured on photographic film, and the pre-beta HDL band is quantified by transmission densitometry. The assay is calibrated with standards prepared from a reference serum diluted in 9 mol/L urea. Within-batch precision (CV) at pre-beta HDL concentrations of 22.1 and 44.3 mg/L was 7% and 4.9% respectively. Pre-beta HDL contained 1.6% (0.65-2.6%, mean and range) of total serum apo A-I in 30 normolipidemic subjects.
Abbott IMx and Serono MAIAclone Assays Compared for Lutropin Determinations in Urine
Authors: Weiss P , Zech H , Schönholzer H P , Fritzsche H 
Published: January 2020

Abstract
The urinary lutropin (luteinizing hormone; LH) profiles of 20 patients were determined in 10 consecutive urine samples (n = 200) with a manual technique (MAIAclone, Serono; y) and a fully automated (Abbott IMx; x) technique. For 132 single determinations within the range of detection, the regression line was y = 1.39 x - 0.07 (r = 0.85). Retrospective analysis of the LH profiles obtained by the IMx yielded the classification "not pregnant" (negative) in 14 cases, of which 13 were correctly classified; 6 profiles were classified as "pregnant" (positive), which correlated with the clinical findings in 4 cases. Nine of the LH profiles analyzed with the MAIAclone method were classified as negative, which was correct in seven cases. Retrospective analysis of 11 LH profiles established with the MAIAclone assay gave positive results, which agreed with the clinical outcome in three cases. The diagnostic sensitivity of the IMx and MAIAclone methods was 87% and 47%, respectively; diagnostic specificity was 80% and 60%, respectively. In smaller series (&lt; or = 40 samples), the IMx method has considerable advantages over the MAIAclone method in cost and convenience, because standard curves can be stored and assays can be performed as single determinations.
Interlaboratory Study of the IFCC Method for Alanine Aminotransferase Performed with Use of a Partly Purified Reference Material
Authors: Schiele F , Muller J , Colinet E , Siest G , Arzoglou P , Brettschneider H , Calam D H , Ceriotti F , Férard G , Frei J 
Published: January 2020

Abstract
We present the results of a study on performance of a reference material for alanine aminotransferase (ALT, EC 2.6.1.2) and the corresponding IFCC-approved method in an interlaboratory trial involving 13 laboratories. The ALT material was partly purified from pig heart (specific activity, 150 kU/g) and was essentially free of six potentially contaminating enzyme activities, including aspartate aminotransferase (EC 2.6.1.1). The partly purified ALT was lyophilized in a triethanolamine-buffered matrix, pH 6.4, containing bovine serum albumin and saccharose. Under these conditions, the predicted yearly loss of activity was 0.02% at 4 degrees C and &lt; 0.01% at -20 degrees C. The final blank-corrected results of the accepted set of data gave a mean (SD) of 128.5 (5.1) U/L. The among-laboratory SD was 4.6 U/L and the within-laboratory SD was 2.0 U/L. The certified ALT catalytic concentration in the reconstituted material was 129 U/L with a 0.95 confidence interval of +/- 4 U/L.
Apolipoprotein B Quantified by Particle-Concentration Fluorescence Immunoassay
Authors: Hallaway B J , Rastogi A , Kottke B A 
Published: January 2020

Abstract
We have developed a particle-concentration fluorescence immunoassay (PCFIA) for estimating apolipoprotein (apo) B concentrations in plasma. A two-step antigen-detection system with a polyclonal antibody to apo B bound to carboxyl-polystyrene particles binds the antigen, and a fluorescein-labeled monoclonal antibody detects the bound apo B. Narrow-cut low-density lipoproteins (d = 1.03-1.05 kg/L) were used as the primary standard. The assay compares well with the enzyme-linked immunosorbent assay. The PCFIA gives parallel responses with low-density lipoprotein, very-low-density lipoproteins, and plasma samples, and can be fully automated and completed in 3 h. In a pilot study of patients with diabetes, coronary artery disease (CAD), or both, we found statistically significant differences in apo B concentrations for patients with both CAD and diabetes compared with those for patients with diabetes alone or for control subjects (P &lt; 0.01).
Standardization of Glycohemoglobin Determinations in the Clinical Laboratory: Three Years of Experience
Authors: Bodor G S , Little R R , Garrett N , Brown W , Goldstein D E , Nahm M H 
Published: January 2020

Abstract
Measurement of glycohemoglobin has been recommended for the long-term assessment of glycemic control in diabetic patients. Because different analytical methods measure different glycohemoglobin species, it has been difficult to compare results between laboratories. Here we report 3 years of experience with calibration of an affinity chromatography method for measuring total glycohemoglobin (GHb). Calibration was achieved by including in each assay three hemolysate calibrators for which values for HbA1c and GHb had been determined by repeated analyses by high-performance liquid chromatography (HPLC) and affinity chromatography, respectively. Calibration improved interassay precision (CV = 3.20-7.90% and &lt; 5.0% before and after the introduction of calibration, respectively) and eliminated lot-to-lot variability. In 91 samples, HbA1c was estimated by the calibrated affinity chromatography assay and measured by an ion-exchange HPLC method. Estimated and HPLC-measured HbA1c showed no clinically significant differences during 36 months. The high degree of long-term precision, the disappearance of lot-to-lot variability, and the excellent comparability between analytical methods measuring different species of glycated hemoglobins demonstrate the advantages of calibration.
Relation Between Magnesium and Potassium Concentrations in Myocardium, Skeletal Muscle, and Mononuclear Blood Cells
Authors: Reinhart R A , Broste S K , Spencer S , Marx J J , Haas R G , Rae P 
Published: January 2020

Abstract
Potassium and magnesium were measured in 26 cardiac surgery patients (right atrial appendage), 23 autopsy subjects (right atrial appendage, left ventricular free wall, and skeletal muscle), and 9 healthy volunteers (mononuclear blood cells) to determine whether there was a relation between these two ions in the tissues measured. In the cardiac surgery patients, the potassium and magnesium concentrations were 46.35 +/- 3.89 and 4.40 +/- 0.58 (mean +/- SD, mumol/g wet weight tissue), respectively, and were significantly correlated (r = 0.54, P = 0.005). In the autopsy group, the respective concentrations were: for right atrial appendage, 30.54 +/- 10.18 and 3.66 +/- 0.70 mumol/g (r = 0.38, P = 0.14); left ventricular free wall, 60.69 +/- 17.93 and 7.74 +/- 1.73 mumol/g (r = 0.92, P = 0.0001); and skeletal muscle, 93.05 +/- 20.49 and 8.64 +/- 2.06 mumol/g (r = 0.91, P = 0.0001). In the healthy volunteer group, the results for potassium and magnesium in mononuclear blood cells were 42 +/- 9.9 and 3.99 +/- 0.70 fmol/cell, respectively (r = 0.94, P = 0.0001). Thus, potassium and magnesium concentrations were significantly correlated in all the tissues measured.
Spuriously Low Concentrations of Serum Iron Measured with Generation 14 Kodak Ektachem Slides: Prevalence, Possible Causes, and Partial Improvement with Generation 16 Slides
Authors: Kempinaire A , Laureys M , Goedhuys W , Demeulemeester L , Sevens C , Smeyers-Verbeke J , Cooreman W , Neels H , Gorus F K 
Published: January 2020

Abstract
For sera with iron (Fe) concentrations &lt; 4 mumol/L, Kodak Ektachem slides Generation (GEN) 14 (without ascorbic acid) yielded systematically lower results for Fe than did liquid Ferrozine-based reagents from Baker containing ascorbic acid (10 g/L, final concentration) and adapted to Cobas-Bio. During an 8-month comparison period, outliers (defined as [Fe]Cobas - [Fe]Kodak &gt; 4 mumol/L) were seen in 21 of the 8731 sera (0.24%) tested, corresponding to &lt; 5% of the sera with [Fe]Kodak &lt; 4 mumol/L. In vitro addition of ascorbic acid and (or) Fe identified at least two types of outliers: type 1 (approximately 70%), characterized by [Fe]Kodak &gt; 0.4 mumol/L, by (supra)normal Fe recovery in Kodak slides in the presence or absence of ascorbic acid (10 g/L), and by between-method differences in serum Fe (Cobas - Kodak) that were significantly correlated with serum Zn content (P &lt; 0.0004); and type 2 (approximately 30%), tentatively ascribed to contamination by EDTA, with serum Fe by Kodak &lt; 0.4 mumol/L and Fe recovery near 0%, both of which could be significantly and dose-dependently increased by addition of ascorbic acid (5-20 g/L). For both types of outliers, flameless atomic absorption spectrometry (AAS) yielded results that were significantly higher than concentrations by Kodak with GEN 14. Use of GEN 16 slides (containing ascorbic acid) improved concordance of Kodak results with Cobas, and hence with flameless AAS, for both types of outliers; abolished Zn dependency of results; and increased Fe results in sera with type 2 outliers, although these remained substantially lower than by Cobas. However, like other ascorbic acid-containing reagents, GEN 16 slides were more sensitive to interference by dextran-bound Fe, as assessed during in vitro addition experiments and comparisons involving samples from Fe-dextran-treated patients. GEN 16 slides are hence expected to more frequently overestimate the physiologically available protein-bound Fe in hemodialysis patients. In hospital laboratories, this new interference will probably arise more frequently than the spuriously low results with GEN 14, hence warranting further efforts in optimizing Fe slides.
The Two mRNAS Encoding Rat Intestinal Alkaline Phosphatase Represent Two Distinct Nucleotide Sequences
Authors: Engle M J , Alpers D H 
Published: January 2020

Abstract
Rat duodenal mucosa contains two mRNAs (2.7 and 3.0 kb) encoding intestinal alkaline phosphatase (IAP), but the mechanism for their production has not been clear. By means of the polymerase chain reaction (PCR), we isolated a fragment that identifies a second rat IAP (rIAP-II), differing from the rIAP-I sequence in the coding and 3' untranslated regions and encoding a COOH-terminal sequence predicted to be hydrophilic. By means of probes unique to each sequence, rIAP-I identified the 2.7-kb mRNA, and rIAP-II the 3.0-kb mRNA. The different structures and differential regulation of the mRNAs after fat feeding demonstrate the presence of two rat IAP transcripts.
Differential Release of Human Intestinal Alkaline Phosphatase in Duodenal Fluid and Serum
Authors: Deng J T , Hoylaerts M F , Van Hoof V O , De Broe M E 
Published: January 2020

Abstract
Human intestinal alkaline phosphatase (IAP) can be released by the enterocyte into duodenal fluid as a mixture of three isoforms. A proportion of the enzyme is associated with triple-layered membrane vesicles (vesicular IAP). Although, occasionally, free hydrophilic IAP dimers are present, the remaining enzyme usually consists of a mixture of hydrophobic IAP dimers and more complex hydrophobic IAP structures of larger size, both entities being identified as "intestinal variant" alkaline phosphatase (VAR IAP). The hydrophobicity of VAR IAP stems exclusively from its attached glycosyl-phosphatidylinositol (GPI) anchor. Both vesicular IAP and VAR IAP are converted to hydrophilic enzyme upon removal of the GPI tail by phospholipase D (PLD) present in duodenal fluid. The IAP released into the vascular bed consists mainly of VAR IAP; vesicular IAP is absent. The enzyme characteristics of VAR IAP partially purified from duodenal fluid and from serum are identical. In plasma, VAR IAP appears to associate with (lipo)protein complexes and is thus protected from further degradation by plasma PLD. Such complex formation may explain why, in the serum of a healthy reference population, VAR IAP was more abundant than hydrophilic dimeric IAP.
Amplified Enzyme-Linked Immunoassay of Human Proinsulin in Serum (Detection Limit: 0.1 pmol/L)
Authors: Dhahir F J , Cook D B , Self C H 
Published: January 2020

Abstract
We describe an amplified enzyme-linked immunoassay of human proinsulin in serum that detects intact proinsulin and both the 32/33 and 65/66 split forms. The method uses the IgG fraction of a polyclonal antibody raised in a guinea pig against intact proinsulin, which we used to coat plastic microtiter plates. A sandwich was formed with proinsulin by using a monoclonal antibody against C-peptide labeled with alkaline phosphatase. We quantified the reaction by using the enzyme amplification procedure, which detected as little intact proinsulin as 0.1 pmol/L. We found no cross-reactivity with C-peptide in the assay, and decreased recovery attributable to the presence of insulin could be demonstrated only with a 30-fold excess of this hormone over proinsulin.
Simultaneous Determinations of Liver- and Bone-Type Alkaline Phosphatase by Curve-Fitting of Inhibition Kinetic Data. I. Development and Evaluation of an Absorbance-Based Method
Authors: Fitzpatrick Carol P , Pardue Harry L 
Published: January 2020

Abstract
We describe an approach for the simultaneous determination of isoenzymes of alkaline phosphatase (EC 3.1.3.1) based on the kinetic behavior of inhibition reactions. Data for absorbance vs time, collected while enzymes are being inhibited, are fitted with suitable models to obtain results related to activities of the individual isoenzymes. The primary focus is on two-component mixtures of the bone and liver isoenzymes of alkaline phosphatase, but some results are reported for three- and four-component mixtures. Factors studied include choices of inhibitors, buffers, pH, ionic strength, substrate concentration, kinetic models, data ranges, data densities, and data-processing approaches and programs. Criteria used to select optimal conditions include measurement times, detection limits, useful range, and agreement between expected and computed results for mixtures of isoenzymes. For two-component mixtures, a linear least-squares fit of isoenzyme content computed with the curve-fitting method (y) v a comparison method (x) gave y = 0.96 (+/- 0.05)x + 3.8 (+/- 3)% with r = 0.97 and standard error of the estimate of 9.4% for a range from 15 to 300 U/L. The pooled relative standard deviation (CV) for results was about 5%. Results were degraded for three- and four-component samples.
Simultaneous Determinations of Liver- and Bone-Type Alkaline Phosphatase by Curve-Fitting of Inhibition Kinetic Data. II. Development and Evaluation of a Fluorescence-Based Method
Authors: Fitzpatrick Carol P , Pardue Harry L 
Published: January 2020

Abstract
We describe a kinetic method for the determination of alkaline phosphatase (ALP) isoenzymes, based on fluorescence detection of 4-methylumbelliferone. Several different buffer-inhibitor combinations and substrate concentrations were evaluated. Best results were obtained for inhibition with 2.9 mol/L urea in amino-2-methyl-1-propanol buffer. With this combination, normal concentrations of bone- and liver-type ALP could be determined from kinetic data during an 8-min measurement period. We computed initial velocities from parameters for first-order fits during 1.2 half-lives of the response for liver-type ALP. A linear least-squares fit of initial velocities (y) determined in this way vs results obtained with a comparison procedure (x) gave good correlations. We also estimated total signal changes, delta S, from first-order fits during four half-lives. Isoenzyme content correlated well with parameters computed from the first-order fits. Values for standard errors of the estimates represent 5% and 3% of median responses for activities and isoenzyme content, respectively. When compared with an absorbance-based method described previously, this method had threefold shorter measurement times, but imprecisions were 1.6- to 1.8-fold larger.