bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of low-density lipoprotein particle size by high-performance gel-filtration chromatography
Authors: Scheffer Peter G , Bakker Stephan J L , Heine Robert J , Teerlink Tom 
Published: January 2020

AbstractWe describe a new technique for measuring LDL size by high-performance gel-filtration chromatography (HPGC). LDL was subjected to chromatography, and the column effluent was monitored at 280 nm. The retention time of the LDL peak was used to calculate the LDL diameter. We compared the HPGC method with gradient gel electrophoresis (GGE) on 2–10% nondenaturing polyacrylamide gels. In a group of 60 non-insulin-dependent diabetes mellitus patients, LDL size as measured by HPGC and GGE was highly correlated (r = 0.88, P &lt;0.001). Good reproducibility, high precision, and the possibility of analyzing large series of samples are the main advantages of the automated HPGC method. Within-run and between-run CV for LDL size measured by HPGC were &lt;0.1% and 0.2%, respectively. There was a significant inverse association between LDL size measured by HPGC and the logarithm of plasma triglycerides (r = −0.84, P &lt;0.001), and a significant positive association with the LDL free cholesterol/protein ratio (r = 0.89, P &lt;0.001).
Approach to maintaining comparability of biochemical data during long-term clinical trials
Authors: Cull Carole A , Manley Susan E , Stratton Irene M , Neil H Andrew W , Ross Iain S , Holman Rury R , Turner Robert C , Matthews David R 
Published: January 2020

Abstract
Our objective was to design a structured approach to maintaining comparability of biochemical data during a long clinical trial. Maintaining the comparability of clinical and biochemical data obtained in long-term studies is essential, even though analytical methods in the laboratory may be changed, conventions on specimen handling and storage revised, calibration procedures updated, quality-control systems replaced, and secular changes may occur. The United Kingdom Prospective Diabetes Study (UKPDS), a large randomized control trial investigating therapy for type 2 diabetes, was the setting for the study. Data were collected from 5102 subjects randomized since 1977. Our techniques included quality control, external quality assurance, direct comparison of laboratory methods when updating assays and statistical techniques for the detection of unsuspected changes in assay bias, laboratory comparisons of new with old assay methodologies, the realigning of data to current methods, the use of a suitable reference population for long-term monitoring, and rules to aid decision-making about clinical vs statistical significance. Procedures by which comparability of data is assured should be specified for all long-term trials and, where possible, comparison with reference methods should be detailed to allow results from different laboratories to be compared.
Significance of various parameters derived from biological variability of lipoprotein(a), homocysteine, cysteine, and total antioxidant status
Authors: Cobbaert Christa , Arentsen Johannes C , Mulder Paul , Hoogerbrugge Nicoline , Lindemans Jan 
Published: January 2020

AbstractAnalytical and biological components of variability and various derived indices have been determined for lipoprotein(a) [Lp(a)], homocysteine (Hcy), cysteine (Cys), and total antioxidant status (TAOS) in ostensibly healthy adult Caucasians and in stable outpatients with an increased serum Lp(a). In healthy Caucasians, average intraindividual biological CVs (CVb) were 20.0% for Lp(a), 9.4% for Hcy, 5.9% for Cys, and 2.8% for TAOS, CVbs being similar in men and women. In the outpatient group, CVbs were comparable for Hcy, Cys, and TAOS, but significantly lower for Lp(a) (7.5% vs 20.0%; P &lt;0.0001). Moreover, a significant inverse relation between both biological and analytical CVs (CVa) and serum Lp(a) concentrations was demonstrated. We conclude that average CVa and CVb values, and hence average derived indices, are adequate for Hcy, Cys, and TAOS, whereas individual values should be used for Lp(a).
Immunological measurement of transforming growth factor-beta 1 (TGF-β1) in blood; assay development and comparison
Authors: Kropf Jürgen , Schurek Josef O , Wollner Antje , Gressner Axel M 
Published: January 2020

Abstract
Development of a new, sensitive immunoassay for measuring transforming growth factor beta 1 (TGF-β1) is described and compared with four commercially available TGF-β1 immunoassays. Preanalytical conditions were evaluated. The nonlinearity found in serum or plasma is due to masking of TGF-β1 by binding proteins in blood. Mixing TGF-β1 with latency-associated peptide or α2-macroglobulin at physiological concentrations suppressed most of the TGF-β1 signal. Plasma fibronectin showed no effect, even at concentrations exceeding its physiological range. Equilibrium concentrations computed from a model system confirmed the experimental results. Dilutional nonlinearity could be markedly reduced by an appropriately designed activation procedure that minimized the effects of reassociation between TGF-β1 and its binding partners during restoration of a neutral pH. Plasma should be used for measuring TGF-β1 in blood. Because serum TGF-β1 is highly significantly correlated with the platelet count, probably most of the TGF-β1 is released by platelet degranulation.
Improved purification of human bone sialoprotein and development of a homologous radioimmunoassay
Authors: Karmatschek Markus , Maier Ina , Seibel Markus J , Woitge Henning W , Ziegler Reinhard , Armbruster Franz P 
Published: January 2020

AbstractBone sialoprotein (BSP) is a phosphorylated skeletal glycoprotein. Here we describe a new procedure for the purification of BSP involving wide-pore reversed-phase HPLC, and the development of a homologous RIA for human BSP. The immunoassay showed linearity between 3 and 120 μg/L, a lower detection limit of 0.7 μg/L, and a mean recovery rate of 99.4%. Intraassay variation was 7.0% (mean = 10.9 μg/L) and 6.1% (mean = 38.8 μg/L), and interassay variation was 9.2% (mean = 11.1 μg/L) and 9.4% (mean = 39.0 μg/L). No cross-reactivity was detected with osteocalcin, osteonectin, or bone alkaline phosphatase. Preliminary clinical evaluation in healthy controls (n = 90) showed a mean serum BSP concentration of 12.1 ± 5.0 μg/L (±SD). BSP was significantly increased in patients with Paget disease of bone, primary and secondary hyperparathyroidism, and also in subjects with renal failure without skeletal involvement. Impairment of hepatic function did not affect serum BSP concentrations.
Intramuscular administration of 5α-dihydrotestosterone heptanoate: changes in urinary hormone profile
Authors: Coutts Sarah B , Kicman Andrew T , Hurst Derek T , Cowan David A 
Published: January 2020

Abstract
A recommended confirmatory procedure for detecting 5α-dihydrotestosterone (DHT) doping in male athletes proposed the use of the urinary concentration ratio of DHT to epitestosterone (EpiT) as the primary marker and those of 5α-androstane-3α,17β-diol (5α-Adiol) to EpiT, luteinizing hormone (LH), and 5β-androstane-3α,17β-diol (5β-Adiol) as secondary markers. Here we investigate the effects on these markers of intramuscular administration of DHT heptanoate (250 mg) to six healthy men. Within 24 h of administration all four markers greatly exceeded the published discrimination limits, remaining above these limits for 10–14 days. All ratios returned to basal values by day 28. In contrast to results after percutaneous administration, 5β-Adiol excretion decreased, probably as a consequence of greater suppression of testicular steroidogenesis. Results were largely in agreement with those obtained after percutaneous administration, although probably augmented by the larger dose and the different route of delivery.
Comparison of NCEP performance specifications for triglycerides, HDL-, and LDL-cholesterol with operating specifications based on NCEP clinical and analytical goals
Authors: Fallest-Strobl Patricia C , Olafsdottir Elin , Wiebe Donald A , Westgard James O 
Published: January 2020

Abstract
The National Cholesterol Education Program (NCEP) performance specifications for methods that measure triglycerides, HDL-cholesterol, and LDL-cholesterol have been evaluated by deriving operating specifications from the NCEP analytical total error requirements and the clinical requirements for interpretation of the tests. We determined the maximum imprecision and inaccuracy that would be allowable to control routine methods with commonly used single and multirule quality-control procedures having 2 and 4 control measurements per run, and then compared these estimates with the NCEP guidelines. The NCEP imprecision specifications meet the operating imprecision necessary to assure meeting the NCEP clinical quality requirements for triglycerides and HDL-cholesterol but not for LDL-cholesterol. More importantly, the NCEP imprecision specifications are not adequate to assure meeting the NCEP analytical total error requirements for any of these three tests. Our findings indicate that the NCEP recommendations fail to adequately consider the quality-control requirements necessary to detect medically important systematic errors.
Development and validation of sensitive method for determination of serum cotinine in smokers and nonsmokers by liquid chromatography/atmospheric pressure ionization tandem mass spectrometry
Authors: Bernert John T , Turner Wayman E , Pirkle James L , Sosnoff Connie S , Akins James R , Waldrep Mary K , Ann Qinghong , Covey Thomas R , Whitfield Wanda E , Gunter Elaine W , Miller Barbara B , Patterson Donald G , Needham Larry L , Hannon W Harry , Sampson Eric J 
Published: January 2020

Abstract
We describe a sensitive and specific method for measuring cotinine in serum by HPLC coupled to an atmospheric pressure chemical ionization tandem mass spectrometer. This method can analyze 100 samples/day on a routine basis, and its limit of detection of 50 ng/L makes it applicable to the analysis of samples from nonsmokers potentially exposed to environmental tobacco smoke. Analytical accuracy has been demonstrated from the analysis of NIST cotinine standards and from comparative analyses by both the current method and gas chromatography/high-resolution mass spectrometry. Precision has been examined through the repetitive analysis of a series of bench and blind QC materials. This method has been applied to the analysis of cotinine in serum samples collected as part of the Third National Health and Nutrition Examination Survey (NHANES III).
Subnanogram-concentration measurement of buprenorphine in human plasma by electron-capture capillary gas chromatography: application to pharmacokinetics of sublingual buprenorphine
Authors: Everhart E Thomas , Cheung Polly , Shwonek Peter , Zabel Karen , Tisdale Eileen C , Jacob Peyton , Mendelson John , Jones Reese T 
Published: January 2020

AbstractWe describe a sensitive and specific method for the measurement of buprenorphine in human plasma. The method involves a structural analog as an internal calibrator, careful control of pH during sample extraction to maximize drug recovery, and back-extraction into acid followed by reextraction to eliminate endogenous interferences. After evaporation, sample residues are derivatized with heptafluorobutyric anhydride and analyzed by separation on a fused-silica polymethylsiloxane capillary column and electron-capture detection. Calibration curves were linear in the ranges 0.1–2.0 μg/L and 2.0–20 μg/L, with within-run CVs of 9.7% at 0.1 μg/L to 5.0% at 20 μg/L, and total CVs of 15.9% at 0.1 μg/L to 6.5% at 10 μg/L. The limit of quantification was 0.1 μg/L. The method was utilized in studies to determine the absolute bioavailability of sublingual doses of 2 mg of buprenorphine in 1 mL of 300 mL/L ethanol and the bioequivalence of sublingual 8-mg tablet and 300 mL/L ethanol solution formulations.
IMP-dehydrogenase inhibition in human lymphocytes and lymphoblasts by mycophenolic acid and mycophenolic acid glucuronide
Authors: Griesmacher Andrea , Weigel Günter , Seebacher Gernot , Müller Mathias M 
Published: January 2020

AbstractInosine 5′-monophosphate dehydrogenase (IMP-DH) activities were measured in human lymphocytes (exhibiting type I IMP-DH activity) and human lymphoblasts (exhibiting type II IMP-DH activity) in the presence of various amounts of mycophenolic acid (MPA) (0–20 μmol/L) and MPA glucuronide (MPAG) (0–200 μmol/L). Moreover, the influences of human serum albumin (HSA) and human plasma on the MPA- and MPAG-mediated effects were investigated. In the presence of water, 2.5 μmol/L MPA decreased the IMP-DH activity measured in lymphocytes by 60%, whereas in lymphoblasts a 80% inhibition was detectable. In the presence of ≥10 μmol/L MPA, lymphocytic as well as lymphoblastic IMP-DH activities were reduced in a similar manner. The concentration of MPAG required for 50% inhibition was for both cell types &gt;25 μmol/L and &lt;50 μmol/L, respectively. MPAG (200 μmol/L) reduced lymphocytic as well as lymphoblastic IMP-DH activity by ∼80%. With 100 g/L HSA or human plasma as diluent, the inhibitory effects of MPA and MPAG were significantly (P &lt;0.05) diminished, whereas HSA concentrations ≤25 g/L only slightly influenced the inhibition of IMP-DH activity by MPA and MPAG. In summary, it can be clearly demonstrated that not only MPA but also MPAG contributes to the inhibition of both IMP-DH isoenzymes, which might be relevant for the immunosuppressive properties of mycophenolate mofetil in transplant patients.
Calibration of ion-exchange HPLC measurements of glycohemoglobin: effect on interassay precision
Authors: Gerlo Erik , Gorus Frans 
Published: January 2020

Abstract
To investigate the effect of calibration with lyophilized calibrators on the interassay precision of glycohemoglobin (glyHb) measurements, we used an ion-exchange HPLC system equipped with a Pharmacia Mono S® HR 5/5 column. Calibration of analytical runs substantially increased interassay variation (CV), from 1.7% to 4.4% and from 0.9% to 3.2% for control samples with low (6.5%) and high (14%) glyHb percentages, respectively. Standardization of glyHb results, though essential for interlaboratory comparisons, should not be done at the expense of assay precision, as may occur with thoughtless use of lyophilized calibrators. We therefore recommend the use of carefully determined conversion factors for standardization of glyHb results obtained with ion-exchange HPLC systems that are capable of excellent long-term interassay precision.
Glycohemoglobin filter assay for doctors’ offices based on boronic acid affinity principle
Authors: Frantzen Frank , Grimsrud Kjersti , Heggli Dag-Erik , Faaren Arne Ludvig , Løvli Trond , Sundrehagen Erling 
Published: January 2020

Abstract
We present a new filter assay for the determination of glycohemoglobin as a unique application of the boronic acid affinity principle. With the use of a water-soluble blue-colored boronic acid derivative and a specific precipitation method for hemoglobin, total hemoglobin including bound boronic acid is precipitated and collected on a filter strip before quantification. Hemoglobin and boronic acid are quantified by a dual-wavelength reflectometric measurement, and the result is reported directly as percent glycohemoglobin. The test is simple, quick, and designed as a doctors’ office test for the monitoring and management of diabetes. The imprecision of the assay is &lt;4% over the range 3–18% Hb A1c, and the method is linear up to at least 20% Hb A1c. Comparisons with four well-established glycohemoglobin methods yielded correlation coefficients ranging from 0.94 to 0.99, with slopes from 0.94 to 1.01.
Stability of long-chain and short-chain 3-hydroxyacyl-CoA dehydrogenase activity in postmortem liver
Authors: Hale Daniel E , Cornell John E , Bennett Michael J 
Published: January 2020

Abstract
Inherited enzyme defects in mitochondrial fatty acid oxidation (FAO) are associated with acute metabolic crisis and sudden death. Necropsy findings may be subtle, yielding no diagnosis and precluding genetic counseling. Preliminary identification of an FAO disorder requires the use of sophisticated tools (e.g., GC/MS) and specific body fluids, and the diagnosis rests on molecular analysis or enzyme assay. At present, confirmation of long-chain or short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency relies on measurement of enzyme activity. Here, we report our examination of the effect of storage temperature (25, 4, −20, and −70 °C) and the postmortem interval on enzyme activities in rat and human liver. Enzyme activity decreases 50% in 30 h in samples stored at 25 °C, whereas 55 h at 4 °C is required to reach this value; freezing minimizes this loss. Regardless of rate of degradation, however, the short-chain to long-chain activity ratio remains constant—which should make it possible to differentiate postmortem degradation from enzyme deficiency.
Rapid screening method for detecting mutations in the 21-hydroxylase gene
Authors: Oriola Josep , Plensa Isabel , Machuca Isabel , Pavía Carles , Rivera-Fillat Francisca 
Published: January 2020

AbstractImpaired synthesis of adrenal steroid hormones because of steroid 21-hydroxylase deficiency is one of the most common inborn errors of metabolism. To expedite molecular diagnosis in families with 21-hydroxylase deficiency, we have designed a rapid strategy to determine nine of the most common mutations in the 21-hydroxylase gene. According to the mutation to be detected, we apply either of two simple strategies: digestion with adequate restriction enzyme or use of the amplification-created restriction site (ACRS) approach and subsequent restriction analysis. Both procedures are rapid and, being nonradioactive, are safer to perform; moreover determination of zygosity in the analyzed mutations requires only one tube per mutation.
Antioxidative enzyme activities in human erythrocytes
Authors: Andersen Helle Raun , Nielsen Jesper B , Nielsen Flemming , Grandjean Philippe 
Published: January 2020

AbstractReliable and standardized methods are necessary to determine the expression of antioxidative enzymes and their role in maintaining health. In addition, the variability of the enzyme activities within the general population caused by age, gender, and life-style factors must be described. This study describes methodological conditions that are suitable for analyzing copper–zinc superoxide dismutase (CuZn-SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and glutathione reductase (GR) in human erythrocytes with a high degree of reproducibility. Intervals for the enzyme activities have been established in a randomly selected population of 220 individuals between 20 and 89 years of age. An age-related decrease was observed in CuZn-SOD and GR activities, whereas no age-related changes were demonstrated for GSH-Px and CAT. The GSH-Px activity was positively associated with the intake of dietary supplements and negatively correlated with tobacco consumption. These factors probably account for the fact that women tended to have higher GSH-Px activity.
Clinical and technical evaluation of ACS™BR serum assay of MUC1 gene-derived glycoprotein in breast cancer, and comparison with CA 15-3 assays
Authors: Bon Gijsbert G , von Mensdorff-Pouilly Silvia , Kenemans Peter , van Kamp Gerard J , Verstraeten Rob A , Hilgers Jo , Meijer Sybren , Vermorken Jan B 
Published: January 2020

AbstractThe mucin glycoprotein-detecting assay CA 15-3 is a valuable tool for monitoring the course of disease in breast cancer patients. Assays of CA 15-3 are based on the use of two MAbs to polymorphic epithelial mucin (PEM). We evaluated the technical and clinical performance of the Chiron ACSTM BR, an automated competitive chemiluminescence assay using a single MAb, B27.29, and compared the assay’s results with those of the Centocor CA 15-3 RIA, the Abbott IMx CA 15-3, and the Boehringer Mannheim Enzymun-Test CA 15-3. The study population consisted of 253 healthy women, 66 patients with benign breast disease, 168 breast cancer patients, and 76 patients with other carcinomas. In the technical evaluation, we assessed the precision and linearity on dilution of the ACS BR assay. Cutoff values (upper limits of values seen in healthy subjects) were determined for all four assays. Agreement between the assays was studied by linear regression analysis. The ACS BR assay gave within- and between-assay CVs of 2.2% and 3.9%, respectively. Three samples from healthy women gave discordant values by ACS BR and were not included in the calculations. All four assays exhibit a highly similar pattern when monitoring breast cancer disease; the closest agreement of values was obtained between ACS BR and Centocor CA 15-3. We conclude that the ACS BR assay is a fast and reliable immunoassay for measuring PEM in serum. Although it detects a slightly different epitope on the PEM molecule than is targeted in other assays, for cancer serum samples it agreed better with the original Centocor CA 15-3 assay than did the other two CA 15-3 assays tested.
Precipitation methods for high-density lipoprotein cholesterol measurement compared, and final evaluation under routine operating conditions of a method with a low sample-to-reagent ratio
Authors: Demacker Pierre N M , Hessels Marja , Toenhake-Dijkstra Helga , Baadenhuijsen Henk 
Published: January 2020

Abstract
We evaluated six precipitation methods for high-density lipoprotein cholesterol (HDL-chol) determination: the heparin/Mn2+precipitation reagent method (Hep), two variants of the phosphotungstic acid/Mg2+ method (Tung-L and Tung-B), the dextran sulfate 50 000/Mg2+ method (Dex), the PEG 6000 method (PEG), and the PEG 6000/dextran sulfate 15 000 (PEG/Dex) method. The Tung-B and PEG/Dex precipitation methods have a low sample/precipitation reagent volume ratio (&lt;0.4). The Tung-B, Dex, PEG, and PEG/Dex methods gave similar values, averaging within 0.1 mmol/L of each other, showing that the precipitation selectivity of these methods is comparable. The precipitation efficiency of Tung-B and Peg/Dex, however, was superior. Ultrafiltration of the supernatants was needed only at triglyceride concentrations &gt;16.4 mmol/L (undiluted sample) or &gt;28.0 mmol/L (sample diluted twofold); however, ultrafiltration without dilution was the most accurate method. Results of Tung-B under routine conditions (33 technicians) agreed well with those of the PEG method for 406 normo- and hyperlipidemic plasma samples. By comparison with the HDL-chol method from the Centers for Disease Control and Prevention, the Tung-B method showed a total error of 10.6%, which fulfills the criteria of the National Cholesterol Education Program for HDL-chol analysis. In conclusion, with motivated personnel, Tung-B is a reliable, cost-effective method for routine HDL-chol analysis.
Positive interference in lithium determinations from clot activator in collection container
Authors: Sampson Maureen , Ruddel Mark , Albright Suzanne , Elin Ronald J 
Published: January 2020

Abstract
We describe positive interference with the ion-selective electrode determination of lithium (Lytening 2Z analyzer; Dade) when blood is collected in a 10-mL plain red-top plastic Vacutainer Plus Tube® (Becton Dickinson) containing a silica clot activator and silicone surfactant (prod. no. 36–7820). We evaluated both the original tube (blue-labeled) and a new tube formulated to contain less silicone surfactant (striped-labeled). We determined that the interference is from either the silica clot activator or the silicone surfactant used to fix the silica to the tube and is inversely related to the volume of blood in the tube. Long-term intermittent exposure of the Li ion-selective electrode to the silica clot activator or surfactant results in decreased Li values—in terms of both the positive interference by the silica clot activator or surfactant and the actual Li determinations. Moreover, this long-term interference with the Li ion-selective electrode for patients’ specimens is undetected by the Dade control material (QCLytes).