bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proposal for standardizing direct-reading biosensors for blood glucose
Authors: Fogh-Andersen Niels , D’Orazio Paul 
Published: January 2020

Abstract
Direct-reading glucose biosensors sense molality (glucose per unit water mass) in the sample. With aqueous calibration, a direct-reading glucose biosensor produces higher results in blood and plasma than methods measuring concentration, theoretically by the ratio of water concentrations in calibrator and sample. To confirm this, we measured glucose in 140 blood and 40 plasma samples with the direct-reading glucose sensor in the Chiron Model 860 Blood Gas and Critical Analyte System and with our routine method (ESAT 6660; Eppendorf). The Chiron instrument is calibrated with a 10 mmol/L (180 mg/dL) glucose calibrator (mass concentration of water = 0.99 kg/L). Assuming normal water concentrations of 0.84 and 0.93 kg/L in blood and plasma, respectively, we multiplied results from the Chiron sensor by 0.84/0.99 and 0.93/0.99 to obtain concentrations in blood and plasma. This conversion resulted in agreement of results with our routine method. An individual conversion based on hematocrit in each whole-blood sample was less satisfactory. To avoid confusion over variously measured and reported glucose results and reference values, we suggest standardization and reporting of whole-blood glucose results as equivalent plasma concentrations. This proposal may be conveniently achieved by using a commercially available reference material for glucose, NIST SRM 965.
Determination of gene dosage at the PMP22 and androgen receptor loci by quantitative PCR
Authors: Poropat Renee A , Nicholson Garth A 
Published: January 2020

Abstract
Although many genetic diseases are caused by the presence of point mutations in respective genes, an increasing number of diseases are known to be caused by gene copy number changes. We report the development of a rapid and reliable PCR-based method for quantitation of gene copy number with sufficient sensitivity to detect single copy changes without the use of radioactive or fluorescent labeling. The sensitivity of this technique has been demonstrated by the detection of the DNA duplication or deletion occurring in two inherited peripheral neuropathies, Charcot-Marie-Tooth type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP), that are caused by a reciprocal duplication or deletion event on chromosome 17p11.2–12. This method relies on the comparison of the amount of PCR product generated from a potentially duplicated or deleted target sequence with the amount of product generated from a disomic reference gene. The value of this ratio (target PCR product:reference PCR product) indicates whether the target sequence is duplicated, deleted, or unchanged. Using primers from within a duplicated or deleted region (PMP22 gene and EW401) and from within a reference region (NF1 gene), we tested 50 CMT1A, 30 HNPP, and 50 unaffected individuals for the presence of a DNA duplication or deletion. Target:reference ratios of 1.58, 1.02, and 0.56 were detected for the CMT1A, unaffected, and HNPP groups, respectively. Thus, differentiation of the three groups of individuals was on the basis of gene copy number. This technique was successfully used to detect the difference in the X chromosome copy number between males and females (target:reference ratios of 1.1 and 2.3, respectively). This approach to the detection of DNA duplications and deletions is sensitive, accurate, and has potential applications in the quantitation of changes in gene copy number associated with diseases characterized by such chromosomal alterations.
Serum protein electrophoresis by CZE 2000 clinical capillary electrophoresis system
Authors: Bossuyt Xavier , Schiettekatte Gilberte , Bogaerts Ann , Blanckaert Norbert 
Published: January 2020

Abstract
We compared the automated Paragon 2000 clinical capillary zone electrophoresis (CZE) system with two manual methods, agarose electrophoresis (AGE) and cellulose acetate electrophoresis (CAE). Reference intervals in healthy adults were determined for each method. When compared with AGE and CAE, CZE gave substantially higher reference values for the α1-globulin fraction. With CZE, within-run precision for fraction quantitation was between 0.5% (albumin) and 4.1% (α1-globulin). Total precision was between 0.8% (albumin) and 5.3% (β-globulin). Data obtained from CZE showed poor linear correlation with results obtained by AGE but good linear correlation with data from CAE. Analysis of serum from patients with inter alia inflammation, nephrotic syndrome, or polyclonal gammopathy showed that clinical information obtained by CZE is comparable with information obtained by AGE and CAE. We conclude that CZE offers a clinically reliable alternative to AGE and CAE and has the advantages of automation, higher precision, and faster turnaround time.
Standards of laboratory practice: cardiac drug monitoring
Authors: Valdes Roland , Jortani Saeed A , Gheorghiade Mihai 
Published: January 2020

AbstractIn this Standard of Laboratory Practice we recommend guidelines for therapeutic monitoring of cardiac drugs. Cardiac drugs are primarily used for treatment of angina, arrhythmias, and congestive heart failure. Digoxin, used in congestive heart failure, is widely prescribed and therapeutically monitored. Monitoring and use of antiarrhythmics such as disopyramide and lidocaine have been steadily declining. Immunoassay techniques are currently the most popular methods for measuring cardiac drugs. Several reasons make measurement of cardiac drugs in serum important: their narrow therapeutic index, similarity in clinical complications and presentation of under- and overmedicated patients, need for dosage adjustments, and confirmation of patient compliance. Monitoring may also be necessary in other circumstances, such as assessment of acetylator phenotypes. We present recommendations for measuring digoxin, quinidine, procainamide (and N-acetylprocainamide), lidocaine, and flecainide. We discuss guidelines for measuring unbound digoxin in the presence of an antidote (Fab fragments), for characterizing the impact of digoxin-like immunoreactive factor (DLIF) and other cross-reactants on immunoassays, and for monitoring the unbound (free fraction) of drugs that bind to α1-acid glycoprotein. We also discuss logistic, clinical, hospital, and laboratory practice guidelines needed for implementation of a successful therapeutic drug monitoring service for cardiac drugs.
Cardiac troponin T in patients with end-stage renal disease: absence of expression in truncal skeletal muscle
Authors: Haller Christlieb , Zehelein Jörg , Remppis Andrew , Müller-Bardorff Margit , Katus Hugo A 
Published: January 2020

AbstractIn patients with end-stage renal disease (ESRD), the serum concentration of cardiac troponin T (cTnT) may be increased without cardiac ischemia. One reason for this unexplained increase could be the extracardiac expression of cTnT. However, truncal skeletal muscle biopsies of five patients with ESRD showed no evidence of the expression of either cTnT mRNA (reverse transcription-PCR) or protein (immunoblot, immunofluorescence). We also measured the serum concentration of cTnT in 97 patients with ESRD. The serum cTnT concentration determined in both first and second generation cTnT assays was significantly lower P &lt;0.01 in patients with a low cardiac risk than in patients with positive indicators of coronary artery disease. The correlation between cTnT and indicators of coronary artery disease is consistent with the hypothesis that cTnT in the serum of patients with ESRD originates from the heart.
Serum creatine kinase activity is not a reliable marker for muscle damage in conditions associated with low extracellular glutathione concentration
Authors: Gunst Johan J , Langlois Michel R , Delanghe Joris R , De Buyzere Marc L , Leroux-Roels Geert G 
Published: January 2020

AbstractCreatine kinase (CK, EC 2.7.3.2) assays usually contain thiol-reducing compounds to restore the enzyme activity. In this study, we investigated the effect of endogenous extracellular glutathione on serum CK activity. We examined CK activity and glutathione concentrations in serum from 200 healthy subjects (107 males, 93 females) and 38 patients with multiple organ failure, muscle wasting, and low serum CK activity (&lt;50 U/L) (24 males, 14 females). Muscle damage was further evaluated using serum myoglobin concentrations and aldolase activity. In the overall group, serum glutathione concentrations correlated with serum CK activity (r = 0.791) but not with myoglobin concentrations and aldolase activity. In patients with multiple organ failure, low serum CK activities were accompanied by extremely low serum glutathione concentrations (&lt;0.5 μmol/L, P &lt;0.001). Endogenous glutathione can be regarded as a CK-preserving agent during the lifetime of the enzyme in the circulation (22 h on average). Serum CK activity should be interpreted with caution in patients with liver disease and multiple organ failure. In these conditions, the loss of CK activity due to extracellular glutathione depletion cannot be restored by the presence of thiol-reducing compounds in the CK assays.
Remnant lipoprotein cholesterol and triglyceride reference ranges from the Framingham Heart Study
Authors: McNamara Judith R , Shah Paulesh K , Nakajima Katsuyuki , Cupples L Adrienne , Wilson Peter W F , Ordovas Jose M , Schaefer Ernst J 
Published: January 2020

AbstractRemnants of triglyceride-rich lipoproteins of both intestinal and liver origin are considered atherogenic, but they have been difficult to isolate and measure. An assay has been developed that allows the measurement of remnant-like particle cholesterol (RLP-C) and triglyceride (RLP-TG). RLP-C and RLP-TG concentrations were measured in &gt;3000 fasting plasma samples obtained from participants in exam cycle 4 of the Framingham Offspring Study and stored at −80 °C. After exclusions, comparisons were made for 2821 samples (1385 women, 1436 men; mean age, 52 years). For women, the mean RLP-C and RLP-TG values were 0.176 ± 0.058 mmol/L (6.8 ± 2.3 mg/dL) and 0.204 ± 0.159 mmol/L (18.1 ± 14.1 mg/dL), respectively; for men, the mean values were 0.208 ± 0.096 mmol/L (8.0 ± 3.7 mg/dL) and 0.301 ± 0.261 mmol/L (26.7 ± 23.1 mg/dL), respectively. Women had significantly lower RLP-C and RLP-TG values (P &lt;0.0001) than men; premenopausal women had significantly lower values than postmenopausal women (P &lt;0.0001); and younger subjects (&lt;50 years) had significantly lower values than older individuals (P &lt;0.0001). The 75th percentile values for RLP-C and RLP-TG were 0.186 mmol/L (7.2 mg/dL) and 0.225 mmol/L (19.9 mg/dL), respectively, for women, and 0.225 mmol/L (8.7 mg/dL) and 0.346 mmol/L (30.6 mg/dL) for men. These data provide reference ranges for use in the evaluation of RLP-C and RLP-TG as potential indicators of risk for coronary heart disease.
Automated simultaneous quantification of the immunosuppressants 40-O-(2-hydroxyethyl)rapamycin and cyclosporine in blood with electrospray-mass spectrometric detection
Authors: Vidal Christian , Kirchner Gabriele I , Wünsch Gerold , Sewing Karl-Friedrich 
Published: January 2020

Abstract
A new analytical method to quantify 40-O-(2-hydroxyethyl)rapamycin (SDZ RAD) and cyclosporine (Cs) simultaneously in blood is presented. The combination of an on-line solid-phase extraction step with an HPLC system coupled to an electrospray mass spectrometer gave excellent specificity, sensitivity, and reproducibility. Aliquots of deproteinized blood samples were injected into the HPLC system and extracted on-line, using a conventional C18 guard column. The extract was eluted from the guard column in the backflush mode and injected into the liquid chromatography–mass spectrometry system. The calibration functions for SDZ RAD and Cs extracted from blood with added analyte were linear from 0.15 to 30 μg/L (r2 = 0.999) and from 1.5 to 1000 μg/L (r2 = 0.999), respectively. The CVs of peak areas were 6.2% at 10 μg/L SDZ RAD (n = 6) and 6.2% at 100 μg/L Cs (n = 6). Recovery ranged from 84.3% to 102.3% for SDZ RAD and from 81.7% to 92.2% for Cs. The lower limit of detection for both drugs was 0.05 μg/L. A rate of four samples per hour was maintained during the consecutive analysis of SDZ RAD and Cs in &gt;500 blood samples with one single extraction and analytical column. The method described is a powerful tool for the simultaneous determination of SDZ RAD and Cs in blood. It works without time-consuming sample preparation steps and with excellent reproducibility. Because of the detection performance of electrospray mass spectrometry, this system offers flexibility in the working range, which is essential for therapeutic drug monitoring under different conditions.
Cardiac troponin T in hemodialyzed patients
Authors: Ooi Daylily S , House Andrew A 
Published: January 2020

Abstract
We studied the extent and pattern of increased cardiac troponin T (cTnT) concentrations in 174 hemodialyzed patients. cTnT concentrations were above 0.10 and 0.20 μg/L in 29% and 10% of patients, respectively. In patients without acute coronary disease, the highest value observed was 3.2 μg/L. cTnT increased after dialysis in 10 of 12 patients, with a mean increase of 0.14 μg/L. In 125 patients with samples taken at 1-month intervals, 34% of patients showed differences &lt;20%, but 16% of patients had differences greater than twofold. Serum creatinine and urea, adequacy of dialysis, and duration on dialysis did not explain increased concentrations. Sixty percent of 57 diabetic patients had increased concentrations; the patients with multiple diabetic complications had the highest positivity. cTnT was increased in all eight patients with complications of neuropathy, retinopathy, coronary, and peripheral vascular disease; in 80% of patients with neuropathy; in 77% with peripheral vascular disease; in 73% with retinopathy; and in 70% with coronary artery disease.
Quantitation of bcl-2 protein in bladder cancer tissue by enzyme immunoassay: comparison with Western blot and immunohistochemistry
Authors: Eissa Sanaa , Seada Laila S 
Published: January 2020

Abstract
Apoptosis (programmed cell death) and the genes regulating this process (e.g., bcl-2), have recently become a focus of interest in the study of cancer development and progression. We adapted and evaluated a new enzyme immunoassay method (EIA) for quanitifying bcl-2 in cell lysates. The range of detection of the assay was 5–400 kilounits/L with inter- and intraassay CVs of 5.5–9.2% and 5.0–8.8%, respectively. The recovery of added bcl-2 protein to cell lysates was 96–104%. The concordance rates with Western blotting and immunohistochemistry were 97.5% and 93.7%, respectively. Bcl-2 concentrations were measured in the cell lysate of bladder tumors. The amount of bcl-2 in 158 bladder cancer (mean rank, 71.3 kilounits/g protein; range, 8.4–324 kilounits/g protein), was significantly higher than in nondiseased bladder tissues distant to the tumors (mean rank, 31.5 kilounits/g protein; range, 5–54.9 kilounits/g protein), P = 0.00001. Bcl-2 expression was correlated to tumor proliferative capacity, which was measured by DNA flow cytometry as the percentage of cells in the synthetic phase of the cell cycle. The enzyme immunoassay provides a rapid, quantitative, and reliable technique for measurement of bcl-2 in tumor tissue. The detection of substantial amounts of bcl-2 in invasive tumors (compared with nondiseased tissues) suggests that the assay should be a useful tool for investigating the prognostic value of bcl-2 in bladder tumors and for selecting patients for future anti-bcl-2 therapy.
Fluorometric determination of total retinyl esters in triglyceride-rich lipoproteins
Authors: Orth Matthias , Hanisch Monika , Kröning Gerd , Porsch-Özcürümez Mustafa , Wieland Heinrich , Luley Claus 
Published: January 2020

AbstractA time-consuming sample preparation and measuring procedure is required for the quantitation of retinyl palmitate by HPLC. We developed a fluorometric method for the determination of total retinyl esters in chylomicrons, chylomicron remnants, and VLDL. This method is precise, sensitive, rapid, simple, and particularly useful for large-scale studies of postprandial lipid metabolism. Because the turbidity of postprandial lipemic samples interferes with the fluorescence measurement, all samples were incubated for 10 min with a clearing buffer containing esterase and detergents. This buffer eliminates the turbidity and hydrolyzes all retinyl esters to retinol. The fluorescence signal (excitation wavelength, 330 nm; emission wavelength, 490 nm) was linear from 0.1 mg/L up to 4 mg/L retinyl palmitate, and the CVs were 3.6% within-run and 5.1% within-series. A first application studied postprandial lipoproteins, which were first separated by ultracentrifugation and then subjected to size exclusion chromatography. Fluorescence analysis revealed that the chylomicron density fraction contains large amounts of chylomicron remnants.
Sensitive enzymatic assay for erythrocyte creatine with production of methylene blue
Authors: Okumiya Toshika , Jiao Yufei , Saibara Toshiji , Miike Akira , Park Keunsik , Kageoka Takeshi , Sasaki Masahide 
Published: January 2020

Abstract
We developed a new, highly sensitive enzymatic method for quantifying creatine in erythrocytes, which comprises creatine amidinohydrolase, sarcosine oxidase, and peroxidase. In the present method, an N-methylcarbamoyl derivative of methylene blue, 10-N-methylcarbamoyl-3,7-bis(dimethylamino)phenothiazine (MCDP), was used as a sensitive chromogenic compound. Potassium ferrocyanide was used to prevent nonspecific oxidation of MCDP. The enzymatic method exhibited good analytical performance: precision, within-run CVs &lt;1.0% and between-day CVs &lt;2.0%; average analytical recovery, 99.3% ± 1.8%; detection limit, 1.0 μmol/L in hemolysate; and linearity, at least up to 500 μmol/L as creatine concentration in hemolysate. Excellent agreement was observed between the present method (y) and HPLC (x), y = 1.029x − 0.002 μmol/g hemoglobin, r = 0.9998, Sy‖x = 0.053 μmol/g hemoglobin (n = 110). No significant interference was produced by various compounds, including guanidino compounds, amino acids, and reducing materials. The reference intervals (mean ± 2 SD) for erythrocyte creatine obtained from 60 males and 60 females were (in μmol/g hemoglobin) 1.18 ± 0.52 (0.66–1.70) for males and 1.35 ± 0.49 (0.86–1.84) for females. Using this method, we documented changes in erythrocyte creatine in patients with various hemolytic conditions, including hemolytic anemia, liver cirrhosis, renal insufficiency, and chronic renal failure treated with hemodialysis with or without the administration of erythropoietin. We conclude that the use of MCDP allows sensitive measurement of erythrocyte creatine and that MCDP with potassium ferrocyanide can improve the sensitivity of assays that use peroxidase for detection of H2O2.
Transient 5-oxoprolinuria and high anion gap metabolic acidosis: clinical and biochemical findings in eleven subjects
Authors: Pitt James J , Hauser Simon 
Published: January 2020

AbstractWe describe biochemical and clinical features of 11 subjects (ages, 1.2–84 years, nine females and two males) with transient 5-oxoprolinuria (0.6–23.6 mol/mol of creatinine, reference range &lt;0.07). A variety of conditions preceded the onset of acidosis, and all had taken acetaminophen (paracetamol), although in therapeutic amounts in most subjects. Metabolic acidosis was documented in nine subjects, and all had an increased anion gap and abnormal liver functions. 5-Oxoproline was the major urinary organic acid in five subjects, whereas the rest had more complex profiles comprising 5-oxoproline and other organic acids, such as lactate, 3-hydroxybutyrate, and 4-hydroxyphenyl lactate. The 5-oxoproline was predominantly of the l-configuration. One subject died during an acidotic episode, and the rest recovered with no apparent long-term ill effects. Urinary 5-oxoproline was within the reference range in six subjects that were re-tested after the anion gap normalized. These findings suggest that acetaminophen, in association with other unidentified factors, is involved in the development of this condition through a mechanism of depletion of liver glutathione stores.
First direct assay for intact human proinsulin
Authors: Houssa Paule , Dinesen Bo , Deberg Michelle , Frank Bruce H , Van Schravendijk Chris , Sodoyez-Goffaux Françoise , Sodoyez Jean-Claude 
Published: January 2020

AbstractWe describe a sensitive two-site sandwich enzyme-linked immunosorbent assay for the measurement of intact human proinsulin in 100 μL of serum or plasma. The assay is based on the use of two monoclonal antibodies specific for epitopes at the C-peptide/insulin A chain junction and at the insulin B chain/C-peptide junction, respectively. Cross-reactivities with insulin, C-peptide, and the four proinsulin conversion intermediates were negligible. The detection limit in buffer was 0.2 pmol/L (3 standard deviations from zero). The working range was 0.2–100 pmol/L. The mean intra- and interassay coefficients of variation were 2.4% and 8.9%, respectively. The mean recovery of added proinsulin was 103%. Dilution curves of 40 serum samples are parallel to the proinsulin calibration curve. Proinsulin concentrations in 20 fasting healthy subjects were all above the limit of detection: median (range), 2.7 pmol/L (1.1–6.9 pmol/L). Six fasting non-insulin-dependent diabetes mellitus and five insulinoma patients had proinsulin concentrations significantly higher than healthy subjects: median (range), 7.7 pmol/L (3.2–18 pmol/L) and 153 pmol/L (98–320 pmol/L), respectively.
Monitoring ovarian function by the simultaneous time-resolved fluorescence immunoassay of two urinary steroid metabolites
Authors: Barnard Geoff , Kohen Fortune 
Published: January 2020

Abstract
We report the development of a novel time-resolved fluorescence immunoassay utilizing two different assay strategies for the simultaneous measurement of estrone-3-glucuronide (EG) and pregnanediol-3α-glucuronide (PG) in samples of early morning urine (EMU). The method for the measurement of EG involves the use of a labeled anti-idiotype as a surrogate antigen, whereas the other method (for the measurement of PG) is a regular competitive immunoassay using a labeled antigen. In addition, the procedure uses different lanthanide chelates as labels to monitor ovarian function in women. After washing the streptavidin-coated plate, we added 10 μL of undiluted urine or mixed standard to the coated wells, followed by the addition of 100 μL of assay buffer containing the labeled reactants (i.e., europium-labeled PG and samarium-labeled anti-idiotype recognizing the binding site of the antibody to EG). Subsequently, we added 100 μL of assay buffer containing the two biotinylated specific monoclonal anti-steroid glucuronide antibodies. After incubation for 1 h on a shaker at room temperature, we washed the plate and added 200 μL of enhancement solution to each well. We measured europium and samarium fluorescence, using a gated plate fluorometer with appropriate emission filters. The method demonstrates appropriate sensitivity and precision (all CVs, 5–8%) across the relevant working ranges for each analyte. The technique has been applied to serial EMUs collected from women with normal and stimulated menstrual cycles.