Abstract：
BACKGROUND:Blood concentrations of the calcineurin inhibitors (CNIs) cyclosporine and tacrolimus are currently measured to monitor immunosuppression in transplant patients. The measurement of calcineurin (CN) phosphatase activity has been proposed as a complementary pharmacodynamic approach. However, determining CN activity with current methods is not practical. We developed a new method amenable to routine use. METHODS:Using liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM-MS), we quantified CN activity by measuring the dephosphorylation of a synthetic phosphopeptide substrate. A stable isotope analog of the product peptide served as internal standard, and a novel inhibitor cocktail minimized dephosphorylation by other major serine/threonine phosphatases. The assay was used to determine CN activity in peripheral blood mononuclear cells (PBMCs) isolated from 20 CNI-treated kidney transplant patients and 9 healthy volunteers. RESULTS:Linearity was observed from 0.16 to 2.5 μmol/L of product peptide, with accuracy in the 15% tolerance range. Intraassay and interassay recoveries were 100.6 (9.6) and 100 (7.5), respectively. Michaelis-Menten kinetics for purified CN were Km = 10.7 (1.6) μmol/L, Vmax = 2.8 (0.3) μmol/min · mg, and for Jurkat lysate, Km = 182.2 (118.0) μmol/L, Vmax = 0.013 (0.006) μmol/min · mg. PBMC CN activity was successfully measured in a single tube with an inhibitor cocktail. CONCLUSIONS:Because LC-MRM-MS is commonly used in routine clinical dosage of drugs, this CN activity assay could be applied, with parallel blood drug concentration monitoring, to a large panel of patients to reevaluate the validity of PBMC CN activity monitoring.
journal_name
Clin Chemjournal_title
Clinical chemistryauthors
Carr L,Gagez AL,Essig M,Sauvage FL,Marquet P,Gastinel LNdoi
10.1373/clinchem.2013.213264subject
Has Abstractpub_date
2014-02-01 00:00:00pages
353-60issue
2eissn
0009-9147issn
1530-8561pii
clinchem.2013.213264journal_volume
60pub_type
杂志文章abstract：BACKGROUND:Different technologies, such as quantitative real-time PCR or microarrays, have been developed to measure microRNA (miRNA) expression levels. Quantification of miRNA transcripts implicates data normalization using endogenous and exogenous reference genes for data correction. However, there is no consensus ab...
journal_title：Clinical chemistry
pub_type： 杂志文章,评审
doi：10.1373/clinchem.2015.239459
更新日期：2015-11-01 00:00:00
abstract：:Determination of the concentration of erythrocyte folate by means of competitive protein binding assay critically depends on the extraction procedure applied. Results will be influenced by variable factors such as the in vitro age of the blood samples, the degree of hemolysis, the presence of ascorbic acid, and the pH...
journal_title：Clinical chemistry
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doi：
更新日期：1976-07-01 00:00:00
abstract：:Quantification of ethanol by a radiative energy attenuation (REA) technique was evaluated and compared with results by gas-liquid chromatography (GLC) and by the Du Pont aca. Within-assay CVs were less than 5.5%. Between-assay CVs ranged from 1.9% to 6.0% for serum and blood controls at concentrations of 0.5, 1.0, and...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1984-11-01 00:00:00
abstract：:We report the first solid-phase radioimmunoassay for triiodothyronine with use of antibody-coated tubes, which is designed specifically for the fully automated radioimmunoassay instrument, Micromedic Systems' "Concept 4 Automatic Radioassay." Antisera to triiodothyropropionic acid/bovine serum albumin were raised in r...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1977-05-01 00:00:00
abstract：:One currently observes many healthcare institutions rushing to reengineer and install information systems with the expectation of achieving enhanced efficiency, competitiveness, and, it is hoped, higher patient satisfaction resulting from timely, high-quality care. Unfortunately, information system concepts, design, a...
journal_title：Clinical chemistry
pub_type： 杂志文章,评审
doi：
更新日期：1995-09-01 00:00:00
abstract：:A modified fermentation procedure based on one described by Homer Smith in his textbook was used to eliminate glucose interference in the automated detrmination of inulin. The manifold of Fjeldbo and Stamey [J. Lab. Clin. Med. 72, 353 (1968)] was modified to enable us to insert the fermentation procedure without sacri...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1977-07-01 00:00:00
abstract：:The time-course of the contamination of exogenous hydrogen from cigarette smoke on postprandial breath hydrogen concentration was evaluated in 10 subjects, six regular smokers and four occasional smokers. Breath hydrogen values were determined by gas chromatography 10 min, 5 min, and immediately prior to smoking a fil...
journal_title：Clinical chemistry
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doi：
更新日期：1983-11-01 00:00:00
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doi：10.1373/clinchem.2005.057216
更新日期：2006-02-01 00:00:00
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journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1981-03-01 00:00:00
abstract：BACKGROUND:Coffee consumption has been associated with several risk factors for coronary heart disease, including increased cholesterol, increased blood pressure, and increased plasma total homocysteine (tHcy). tHcy is determined by several B-vitamins. However, reports about the association between coffee intake and B-...
journal_title：Clinical chemistry
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doi：10.1373/clinchem.2008.103465
更新日期：2008-09-01 00:00:00
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journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1980-09-01 00:00:00
abstract：:In iron deficiency, zinc protoporphyrin (ZPP) is produced instead of heme, and the ZPP concentration in erythrocytes is increased (normal < or = 40 mumol/mol heme). We investigated the relevance of ZPP for staging iron deficiency. ZPP was determined by hematofluorometry in samples from 103 patients. Nineteen patients ...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1994-05-01 00:00:00
abstract：:Haptoglobin is a hemoglobin-binding protein expressed by a genetic polymorphism as three major phenotypes: 1-1, 2-1, and 2-2. Most attention has been paid to determining haptoglobin phenotype as a genetic fingerprint used in forensic medicine. More recently, several functional differences between haptoglobin phenotype...
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doi：
更新日期：1996-10-01 00:00:00
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doi：10.1373/clinchem.2005.052456
更新日期：2005-11-01 00:00:00
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journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2016.260968
更新日期：2016-11-01 00:00:00
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journal_title：Clinical chemistry
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doi：10.1373/clinchem.2010.151688
更新日期：2011-03-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1976-02-01 00:00:00
abstract：:Seeking to minimize degradation of NADPH during storage, reagent preparation, and assays, we investigated the effects of pH, temperature, and ionic strength as well as the effects of phosphate and acetate. NADH was also included for comparison. Our results indicate that the rate of degradation of NADPH is proportional...
journal_title：Clinical chemistry
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doi：
更新日期：1986-02-01 00:00:00
abstract：:Demonstrable quality of laboratory services entails two parts. First, one needs a quality policy statement, identification of user needs, choice of measurement procedures, reference measurement system to provide traceability, control materials, and proficiency testing with materials having reference-measurement-assign...
journal_title：Clinical chemistry
pub_type： 杂志文章,评审
doi：
更新日期：1994-07-01 00:00:00
abstract：:We describe a gas-liquid chromatographic method for determining mephenytoin and its active metabolite, desmethylmephenytoin, in human serum. 5-Methyl-5-phenylhydantoin is used as the internal standard. The method involves extraction of the drugs by adsorption onto charcoal and off-column derivatization to their pentyl...
journal_title：Clinical chemistry
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doi：
更新日期：1979-01-01 00:00:00
abstract：BACKGROUND:Aberrant DNA hypermethylation of CpG islands occurs frequently throughout the genome in human colorectal cancer (CRC). A genome-wide DNA hypermethylation analysis technique using circulating cell-free DNA (cfDNA) is attractive for the noninvasive early detection of CRC and discrimination between CRC and othe...
journal_title：Clinical chemistry
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doi：10.1373/clinchem.2019.301804
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journal_title：Clinical chemistry
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doi：
更新日期：1982-03-01 00:00:00
abstract：:The Center for Disease Control (CDC), the New York State Department of Health (NYSDH), the College of American Pathologists, and 23 manufacturers of diagnostic products participated in an interlaboratory study of aspartate aminotransferase (EC 2.6.1.1) methodologies. Six different lyophilized materials were prepared a...
journal_title：Clinical chemistry
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doi：
更新日期：1978-06-01 00:00:00
abstract：:The concentration of the conjugated bile acid, cholylglycine, in serum is a sensitive and specific indicator of hepatic function. We describe a convenient, specific, and precise radioimmunoassay for cholylglycine, in which 125I-labeled cholylglycyltyrosine is used as tracer. In addition, a blocking agent in the buffer...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1981-10-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1982-12-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1978-01-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1984-06-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1988-06-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1986-10-01 00:00:00
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journal_title：Clinical chemistry
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doi：
更新日期：1976-06-01 00:00:00
