bluuebunny/crossref_metadata_2025_split huggingface dataset:
Association between urinary N-acetyl-beta-glucosaminidase and its isoenzyme patterns and microangiopathy in type 1 diabetes mellitus
Authors: Agardh C D , Agardh E , Isaksson A , Hultberg B 
Published: January 2020

Abstract
Urinary N-acetyl-beta-glucosaminidase (NAG) and its isoenzymes (NAG A and NAG B) in samples from 87 type 1 diabetic patients and 40 apparently healthy reference subjects were studied with enzyme immunoassays. The diabetic patients had higher concentrations of urinary NAG than did the control subjects (P less than 0.01), but the isoenzyme pattern did not differ. There was a positive correlation between metabolic control (Hb A1c concentrations) and total NAG (P less than 0.01), NAG A (P less than 0.01), and NAG B (P less than 0.001). The diabetic patients were divided into three groups, depending on the degree of retinopathy. Subjects with severe forms of retinopathy did not have increased concentrations of urinary NAG unless they had concomitant nephropathy. The isoenzyme pattern was similar irrespective of degree of retinopathy or nephropathy. The results indicate that concentrations of urinary NAG are positively correlated to the degree of nephropathy, whereas there is no such correlation to the degree of retinopathy.
Studies on the measurement of protein S in plasma
Authors: Bovill E G , Landesman M M , Busch S A , Fregeau G R , Mann K G , Tracy R P 
Published: January 2020

Abstract
The anticoagulant factor Protein S circulates in two major forms, free and bound to C4b binding protein (C4BP). We report a monoclonal antibody-based enzyme-linked immunosorbent assay of human Protein S that is sensitive (detection limit 30 ng) and free of notable competition from other vitamin K-dependent proteins. We demonstrate assay sensitivity to Protein S-C4BP complex, as well as to free Protein S by (a) results of immunoaffinity chromatography involving the assay antibody; (b) parallelism between the standard curve and a plasma dilution curve, including dilutions greater than 100-fold; (c) lack of effect of added C4BP on Protein S values; and (d) reactivity in the assay by high-molecular-mass plasma Protein S in gel permeation studies. These latter studies also indicate that uncomplexed Protein S has an apparent molecular mass of approximately 150,000 Da, attributable to either polymerization or conformational considerations. Inter- and intra-assay CVs were 9.8% and 5.1%, respectively, and 90% of Protein S added to plasma was recovered. Reference ranges (mean and SD) for total Protein S in middle-aged normal subjects were 16.6 (1.9) mg/L for men (n = 54) and 16.0 (3.0) mg/L for women (n = 38). In the polyethylene glycol precipitation method, the reference values for free Protein S were 5.4 (1.6) mg/L for men and 4.4 (1.1) mg/L for women.
Monoclonal antibody-based discrepancies between two-site immunometric tests for lutropin
Authors: Pettersson K , Ding Y Q , Huhtaniemi I 
Published: January 2020

Abstract
We compared five two-site immunometric assays (including three commercially available kits) for measuring lutropin (LH) in serum. Four of the assays involved monoclonal antibodies directed against the alpha-beta dimer, intact LH; these assays measured significantly lower concentrations of LH in 19 (out of 83) samples than did a commercial method not involving such antibodies. In five serum samples, two of the intact LH assays failed to detect any significant immunoreactivity above the detection limit. Findings of normal in vitro LH bioactivity in these samples did not confirm the low immunoreactivity of the intact LH assays. The inability of these assays to detect bioactive LH creates confusion in daily, routine testing as well as in research monitoring of bio/immuno ratios. The data presented here confirm our previous findings (Clin Chem 1991;37:333-40) and emphasize the need to avoid the use of monoclonal antibodies specific for the intact LH dimer.
Atrial natriuretic peptide assayed after immunoextraction with magnetic iron particles
Authors: Török A , Penke B 
Published: January 2020

Abstract
We investigated a new method for the immunoextraction of atrial natriuretic peptide (ANP) from plasma. Anti-ANP antibody was coupled to magnetizable iron particles by various coupling methods; both carboxyl terminal and amine terminal iron particles were examined. Introducing a chemical spacer between the iron particles and the antibody improved binding with ANP. The most efficient and reliable immunoextraction involves coupling the ANP antibody to amine terminal iron particles with bis-succinimidyl-suberate. Analytical recovery of ANP from this antibody-coupled suspension was 104% (SD 7.8%). We measured extracted samples by RIA. Standards were included in the extraction step. The detection limit of the assay was 3 ng/L. Patients' samples were assayed after both immunoextraction (y) and Sep-Pak C18 extraction (x); ANP values obtained with these methods correlated highly significantly y = 1.02x - 5.57 ng/L [r = 0.9302, n = 19, SE intercept = 5.7 (not significant), SE slope = 0.10 (P less than 0.0001)]. The method presented is potentially a reliable, efficacious immunoextraction method for ANP.
Pentobarbital quantification in the presence of phenobarbital by fluorescence polarization immunoassay
Authors: Earl R , Sobeski L , Timko D , Markin R 
Published: January 2020

Abstract
We developed a method for measuring pentobarbital in samples that also contain phenobarbital. The phenobarbital is destroyed by adding sodium hydroxide and then heating at 95 degrees C for 60 min. Pentobarbital is not affected by this pretreatment and can then be measured with an Abbott TDx barbiturates kit. Using this method, we obtained an average analytical recovery of 98% of added pentobarbital and a correlation of y = 0.953x + 3.4 vs HPLC. The intra-assay CV was 3.7% at 25.8 mg/L; the interassay CV was 6.2% at 16.1 mg/L. Other long-acting barbiturates, e.g., hexobarbital, are also effectively destroyed by this alkali pretreatment. Other short-acting barbiturates, e.g., secobarbital, are not removed and would produce an interference.
Plasma renin activity and plasma prorenin assays
Authors: Sealey J E 
Published: January 2020

Abstract
Sensitivity and accuracy are essential features of an assay of plasma renin activity (PRA) because the normal concentration of PRA is only 1 pmol/L, and subnormal concentrations have diagnostic relevance. Conditions for blood collection need to be standardized but the conditions are not difficult for outpatients. For routine diagnostic purposes blood should be collected from ambulatory (ideally, untreated) patients on moderate sodium intake. To avoid irreversible cryoactivation of plasma prorenin (which is present in 10-fold greater concentrations than renin), samples should be processed at room temperature and stored completely frozen. Cryoactivation occurs when plasma is liquid at temperatures less than 6 degrees C. PRA is commonly measured with an enzyme kinetic assay in which angiotensin I (Ang I) is formed by the reaction of plasma renin with endogenous renin substrate (angiotensinogen). The Ang I so formed is measured by RIA; results are expressed as an hourly rate (micrograms/L formed per hour). This method, which is provided by most commercial kits, has the potential for unlimited sensitivity because the step for Ang I generation can be prolonged as long as necessary, so that enough Ang I forms to be measured accurately. Unfortunately, that sensitivity is not always exploited. Dilution of plasma during pH adjustment should be kept to a minimum. The Ang I generation step should last at least 3 h. The step should last 18 h for samples with PRA less than 1.0 micrograms/L per hour, to eliminate the errors inherent in the measurement and subtraction of immunoreactive Ang I in the untreated plasma (blank subtraction). These changes actually simplify PRA measurements because they eliminate the need for ice in the clinic and reduce by almost half the number of samples to be assayed by RIA. I also describe the method for measurement of plasma prorenin, which may be an important marker for patients with diabetes mellitus who subsequently develop vascular complications.
Abbreviated kinetic profiles in area-under-the-curve monitoring of cyclosporine therapy
Authors: Grevel J , Kahan B D 
Published: January 2020

Abstract
Abbreviated kinetic profiles can reduce the number of phlebotomies and drug assays, and thereby the cost of area-under-the-curve (AUC) monitoring. In the present investigation, we used two independent data sets: group 1, 101 AUC profiles from 77 stable renal-transplant patients, which included a 5-h sample in addition to the usual 0-, 2-, 4-, 6-, 10-, 14-, and 24-h samples; and group 2, 100 profiles from 50 stable renal-transplant patients before and after a change in their daily oral dose of cyclosporine. Group I demonstrated a fair correlation between cyclosporine trough concentrations and the AUC calculated from a complete set of seven concentrations (r2 = 0.820 and 0.758 for the 24- and 0-h samples, respectively). Stepwise multiple linear-regression analysis revealed that the abbreviated set of three time points (2, 6, and 14 h) explained 96% of the variance in AUC values calculated from the full set of seven samples; additional time points increased the accuracy only slightly. For group 2, we examined the difference between the observed and the predicted concentrations by linear extrapolation; the error in the observed AUC value, compared with the predicted value calculated from seven time points (-13.2% to -1.2%), was similar to the error from just three time points (-11.5% to 4.5%). Abbreviated AUC profiles involving three time points used with a model equation seem to provide a reliable alternative to full seven-point profiles.
New method for isolating and quantifying intermediate and beta-very-low-density lipoprotein cholesterol
Authors: Wikinski R L , Schreier L E , Rosental S B 
Published: January 2020

Abstract
We describe a new method, useful to clinical laboratories, for assessing intermediate density (IDL) or beta-very-low-density (beta-VLDL) lipoprotein cholesterol. The technique involves selective precipitation properties of the qualitative Wieland and Seidel post-electrophoretic method that immobilizes IDL and beta-VLDL in the beta-zone of an agarose slide (Clin Chem 1973;19:1139-41). In our method, we separate low-density lipoprotein (LDL) in a second electrophoretic step, in which LDL moves toward the anode, and then quantify the cholesterol of the above lipoproteins remaining in the precipitate band at the beta-zone. Replicate within-run precision (CV) of 15 aliquots of a sera pool was 10.1%. The correlation with sequential ultracentrifugation of 30 samples was r = 0.96 (P less than 0.001). Serum reference values for 30 normal individuals are 57 +/- 7.0 mg/L. Seven phenotype III hyperlipoproteinemic patients had the highest concentrations of IDL or beta-VLDL cholesterol in serum, 1620 +/- 346 mg/L.
Use of immunoglobulin heavy-chain and light-chain measurements in a multicenter trial to investigate monoclonal components: I. Detection
Authors: Jones R G , Aguzzi F , Bienvenu J , Bianchi P , Gasparro C , Bergami M R , Perinet A , Bernon H , Penn G M , Keller I 
Published: January 2020

Abstract
We assessed the combined use of serum protein electrophoresis (SPE) and nephelometric measurement of immunoglobulin heavy- and light-chain components for detecting serum monoclonal immunoglobulins (monoclonal components, MC) in 4788 unselected samples from 4173 patients. MC were detected in 514 samples from 390 patients. In 356 these were detected by SPE; the other 34 had a normal SPE pattern but an abnormal kappa:lambda light-chain ratio (KLR). Only 208 of the 356 (58%) samples with bands by SPE had abnormal KLRs. Samples with MC concentrations greater than 5 g/L had a higher proportion of abnormal KLRs (75%) than those with concentrations less than 5 g/L (42%). The KLR was abnormal in 13% of samples in which no MC were visible by SPE or immunofixation electrophoresis (IFE). Compared with quantitative measurements of immunoglobulin heavy and light chains, high-quality SPE remains the method of choice for the detection of MC. Quantitative methods, however, are able to detect additional MC, especially those containing free light chains, and in the absence of SPE and IFE will detect about 75% of MC present at greater than 5 g/L.
Efficient extraction of basic, neutral, and weakly acidic drugs from plasma for analysis by gas chromatography-mass spectrometry
Authors: Brooks K E , Smith N B 
Published: January 2020

Abstract
We describe a method for efficiently extracting basic, neutral, and weakly acidic drugs from plasma for toxicological analysis by gas chromatography-mass spectrometry (GC/MS). The 2-mL plasma sample is diluted with an equal volume of saturated NaCl containing triethylamine, 10 mmol/L, and then extracted twice with 4 mL of an equivolume solution of dichloromethane/acetone. The organic (top) phases are combined, then mixed with 1 mL of water, 200 mg of NaHCO3, and 100 microliters of acetic anhydride. This mixture is then heated at 75 degrees C until the solvents have boiled off and aqueous acetylation is complete (less than 30 min). After addition of 1 mL of water and 2 g of NaCl, the sample is extracted twice with 2 mL of dichloromethane/acetone (2/1 by vol). The combined extracts are dried and then subjected to thin-layer chromatography on a blank Toxi-Lab Toxi-A chromatogram with 1-chlorobutane as the developing solvent (about 6 min). After the lipids have migrated with the mobile phase, the drugs are eluted from the origin with acetone/triethylamine (29/1 by vol), evaporated, and reconstituted in injection solvent. With this procedure drugs are recovered relatively quickly (less than 2 h) and the GC/MS total ion chromatograms are very clean. Studies with 13 basic, neutral, and weakly acidic drugs showed that all except theophylline were extracted with recoveries of at least 75%.
High-performance liquid-chromatographic method compared with a modified radioimmunoassay of cotinine in plasma
Authors: Perkins S L , Livesey J F , Escares E A , Belcher J M , Dudley D K 
Published: January 2020

Abstract
Cotinine is a sensitive and specific biochemical marker of exposure to cigarette smoke. We describe a simple solid-phase extraction of cotinine from plasma before quantification by HPLC. Extraction recovery was 97.9% +/- 11.0% for plasma concentrations of 5-400 micrograms/L. Baseline separation of cotinine and caffeine was achieved within 11 min of injection onto a C18 reversed-phase column. The mobile phase was citric acid/dibasic potassium phosphate (30 mmol/L each, pH 6.0) containing 100 mL of acetonitrile per liter. Within-day and day-to-day precision (CV) were 4.7% and 8.4%, respectively. We also describe a modification of the Nicotine Metabolite RIA kit (Diagnostic Products Corp.) for quantifying cotinine in plasma. Recovery of cotinine from supplemented plasma was within 10% of the expected value with this RIA kit. Interassay precision averaged 8.1% for samples in the range 50-400 micrograms/L; intra-assay precision averaged 3.6% at 230 micrograms/L and 8.7% at 53 micrograms/L. Correlation between the two methods was RIA = 1.13 HPLC + 14.8 (n = 128, r = 0.957, P less than 0.001). Both methods are technically simple to perform.
Determination of intact parathyrin by immunoradiometric assay evaluated in normal children and in patients with various disorders of calcium metabolism
Authors: Saggese G , Baroncelli G I , Bertelloni S 
Published: January 2020

Abstract
We report the reference values for intact parathyrin (PTH) measured by a two-site immunoradiometric assay (IRMA) during childhood. The study has been carried out in 215 healthy children and adolescents, ages 2.0 to 18.7 years. Some patients with altered mineral homeostasis were also studied to assess the sensitivity of the method in a clinical setting. Mean intact PTH concentrations were 30.8 (SD 9.6) ng/L; the median was 28.5 ng/L. Normal reference values were 16.0-59.0 ng/L (95% confidence interval). The distribution of intact PTH values was nongaussian. We found no significant variations between males and females and no age-related variations. The IRMA used was sufficiently sensitive to detect differences in PTH concentrations between healthy children and patients with hypocalcemia or hypercalcemia.
Serum Catalase: Reversibly Formed Charge Isoform of Erythrocyte Catalase
Authors: Góth László 
Published: January 2020

Abstract
The different electrophoretic mobilities of erythrocyte and serum catalase (EC 1.11.1.6) were confirmed and the causes responsible for their differences were examined. The presence of a catalase-binding protein in serum that could form a complex with erythrocyte catalase was excluded by incubating serum proteins with erythrocyte catalase. No new unequivocal catalase bands representing a catalase-binding protein were detected. The erythrocyte and serum catalase proved to be charge isoforms: their molecular masses, estimated by gel permeation chromatography or polyacrylamide gel electrophoresis in a nondenaturing system, were very similar, whereas their electrophoretic mobilities were different. Assay of serum catalase by gel permeation and hydrophobic chromatography yielded a product with the same electrophoretic mobility as that of erythrocyte catalase. Different dilution of erythrocyte catalase with human sera led to a gradual decrease of its mobility, 20-fold or greater dilution yielding the same results as for serum catalase. Similarly, when serum catalase was diluted 20-fold or more with 60 mmol/L phosphate buffer, it migrated similarly to erythrocyte catalase. I detected no effect of dialyzable serum ligands, NADPH, or protection of SH groups on the electrophoretic mobility of either catalase isoform. I conclude that formation of charge isoforms of catalase is caused by a reversible, conformational modification due to matrix effect of serum.
Factors Influencing the Accuracy of the National Reference System Total Cholesterol Reference Method
Authors: Bernert John T , Akins James R , Cooper Gerald R , Poulose Abraham K , Myers Gary L , Sampson Eric J 
Published: January 2020

Abstract
Previous comparisons between the Reference and Definitive Methods for measuring serum cholesterol have demonstrated a small but persistent positive bias in the Reference Method, averaging about +1.6%. Here we describe the results of further investigations designed to better characterize the nature of this bias. Analysis of a well-characterized model serum sample (SRM 909) suggests that more than half of the difference in cholesterol values determined by the two methods is the result of small contributions from cholesterol precursor sterols and phytosterols, which are also measured for the Reference Method. An additional significant contribution may be from cholesterol oxidation products, particularly 7-hydroxycholesterol isomers, which are active in the Liebermann-Burchard reaction. The 7-hydroxycholesterol in SRM 909, most of which appeared to be already present in the serum rather than formed during saponification, may account for as much as 20% of the observed difference between the methods. Contributions from other possible sources, including impurities in the cholesterol standard and incomplete saponification of cholesteryl esters, are very small. Because the observed bias is both quite small and consistent among samples, the cholesterol Reference Method continues to meet all of the requirements generally expected for a dependable and effective Reference Method.
Analytical Performance of EMITTM Cyclosporine Assay Evaluated
Authors: Dasgupta Amitava , Saldana Sylvia , Desai Manju 
Published: January 2020

Abstract
We evaluated the EMITTM Cyclosporine Assay (Syva Co., Palo Alto, CA), using the Cobas-Mira analyzer to assess the precision, accuracy, and analytical recovery from whole-blood samples supplemented with cyclosporine. We also performed comparative analysis of whole-blood samples containing cyclosporine from liver and kidney transplant patients by using EMIT, HPLC, and RIA (IncStar Cyclo-Trac, SP assay). Before assay by EMIT or RIA, cyclosporine was extracted from whole blood with methanol. For the HPLC method, whole blood containing cyclosporine was hemolyzed with 300 mL/L acetonitrile in water; cyclosporine was extracted from the hemolysate with acetonitrile. The within-run and between-run CVs for the EMIT assay of cyclospoprine were 9.9% (means = 72.6, SD = 7.2 μg/L; n = 20) and 13.5% (means = 75.0, SD = 10.1 μg/L; n = 26) for the low control; 3.5% (means = 194.7, SD = 6.8 μg/L; n = 20) and 8.1% (means = 189.0, SD = 15.3 μg/L; n = 26) for the medium control; and 7.0% (means = 332.5, SD = 23.3 μg/L; n = 20) and 7.1% (means = 340.0, SD = 24.2 μg/L; n = 24) for the high control (Bio-Rad, whole-blood controls). Analytical recovery of cyclosporine from drug-supplemented samples averaged 99% for EMIT, 104% for HPLC, and 90% for RIA over a concentration range of 50-500 μg/L. Analysis of 196 specimens by HPLC (x) vs EMIT (y) gave the following regression statistics: y = 1.27x + 16.44; IncStar‘s RIA (x‘) vs EMIT: y = 1.12x‘ - 2.50; HPLC vs RIA: x‘ = 1.10x + 23.87.
PCR-Based Method to Create a Specific Mutation as a Reference for Oligomelting
Authors: Gudnason Vilmundur , Humphries Steve 
Published: January 2020

Abstract
In screening selected populations for known mutations in genes relevant to risk for hyperlipidemia, atherosclerosis, and coronary artery disease, one gene we have examined is the low-density-lipoprotein receptor (LDLR) gene in patients with familial hypercholesterolemia (FH), which has a frequency of 1:500 in most populations(1). More than 30 mutations in this gene have been described, with gross alterations accounting for about 2-6& of defects in the populations investigated (2), leaving the majority to be point mutations. Some mutations create a change of a recognition site for a restriction enzyme, allowing direct detection; the remainder can be detectedby the oligomelting technique with allele-specific oligonucleotides(ASOs) (3). One problem in using ASOs to screen for mutations is the unavailability of a DNA samplefrom a patient with the mutation to use as a positive control in the test. To overcome this problem, we have used a polymerase chain reaction (PCR)-based method to create mutations of interest, using primers containingthe mutated DNA sequence [this method is frequently used to create new restriction sites in PCR fragments via 3' mutated primers (4)].
Sensitive, Selective, and Rapid Procedure for Quantifying Cocaine in Urine
Authors: Vasiliades John 
Published: January 2020

Abstract
Cocaine metabolism produces two major metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME) (1-4). BE is the metabolite ordinarily used to identify cocaine misuse in urine (5). However, determination of EME and cocaine in urine can provide valuable and important forensic information as to the source of BE and the time of cocaine ingestion (4-7). Laboratories should therefore be able to provide information on EME and cocaine when requested, in addition to BE. We have already described a sensitive and selective procedure for EME analysis in urine (8). We now present a rapid and sensitive procedure for the identification and quantification of cocaine in urine.