Abstract：
BACKGROUND:It has been postulated that changes in S-adenosylhomocysteine (AdoHcy), a potent inhibitor of transmethylation, provide a mechanism by which increased homocysteine causes its detrimental effects. We aimed to develop a rapid and sensitive method to measure AdoHcy and its precursor S-adenosylmethionine (AdoMet). METHODS:We used stable-isotope dilution liquid chromatography-electrospray injection tandem mass spectrometry (LC-ESI-MS/MS) to measure AdoMet and AdoHcy in plasma. Acetic acid was added to prevent AdoMet degradation. Solid-phase extraction (SPE) columns containing phenylboronic acid were used to bind AdoMet, AdoHcy, and their internal standards and for sample cleanup. An HPLC C(18) column directly coupled to the LC-MS/MS was used for separation and detection. RESULTS:In plasma samples, the interassay CVs for AdoMet and AdoHcy were 3.9% and 8.3%, and the intraassay CVs were 4.2% and 6.7%, respectively. Mean recoveries were 94.5% for AdoMet and 96.8% for AdoHcy. The quantification limits were 2.0 and 1.0 nmol/L for AdoMet and AdoHcy, respectively. Immediate acidification of the plasma samples with acetic acid prevented the observed AdoMet degradation. In a group of controls (mean plasma total Hcy, 11.2 mumol/L), plasma AdoMet and AdoHcy were 94.5 and 12.3 nmol/L, respectively. CONCLUSIONS:Stable-isotope dilution LC-ESI-MS/MS allows sensitive and rapid measurement of AdoMet and AdoHcy. The SPE columns enable simple cleanup, and no metabolite derivatization is needed. The instability of AdoMet is a serious problem and can be prevented easily by immediate acidification of samples.
journal_name
Clin Chemjournal_title
Clinical chemistryauthors
Gellekink H,van Oppenraaij-Emmerzaal D,van Rooij A,Struys EA,den Heijer M,Blom HJdoi
10.1373/clinchem.2004.046995subject
Has Abstractpub_date
2005-08-01 00:00:00pages
1487-92issue
8eissn
0009-9147issn
1530-8561pii
clinchem.2004.046995journal_volume
51pub_type
杂志文章abstract：:We describe the measurement of rheumatoid factor in human sera with a rate nephelometer. The National Reference Preparation for Rheumatoid Factors is used to calibrate the assay in International Units. We used Hyland Positive Control, Level I, as a secondary standard. The standard curve is exponential, but is linear w...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1979-11-01 00:00:00
abstract：:Optimal reaction conditions for assaying human lactate dehydrogenase pyruvate-to-lactate were determined for isoenzymes 1 and 5 at 25, 30, and 37 degrees C. Three of the nine different buffers examined--imidazole, triethanolamine, and N-tris(hydroxymethyl)-methyl-2-aminoethane sulfonic acid--are satisfactory. Beta-NAD...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1978-02-01 00:00:00
abstract：:A radioimmunoassay for barbiturates is shown to be equally sensitive to phenobarbital and its major urinary metabolite, p-hydroxyphenobarbital, in serum and urine. Interference by the metabolite can be essentially eliminated by selectively extracting phenobarbital into chloroform. The extraction efficiency of the meth...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1977-05-01 00:00:00
abstract：:Purified arylsulfatase A (EC 3.1.6.1) from human urine was radioiodinated under conditions that caused no significant loss of antigenic activity. We used this labeled arylsulfatase A (specific radioactivity 4-7.5 Ci/g) together with nonlabeled enzyme and rabbit antiserum produced against homogeneous enzyme to develop ...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1985-03-01 00:00:00
abstract：:This enzyme immunoassay procedure for pregnancy-associated plasma protein type A involves a "sandwich"-type system in microtitration plates. One can detect 0.27 mg of the protein per liter of serum, with a between-batch CV of 10.2%, and the antiserum used does not cross react with any of the other placentally derived ...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1984-11-01 00:00:00
abstract：:This method for determining aluminum in human serum involves electrothermal atomic absorption spectrophotometry. A longer drying time allows less pre-dilution of the sample, and the method also includes a flush cycle after atomization. Standard-addition methodology is used to eliminate matrix effects and the need for ...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1983-06-01 00:00:00
abstract：:A digestion procedure involving nitric acid is described for determination of aluminum in blood, serum, and plasma by graphite-furnace atomic absorption spectroscopy. Contamination was not a severe problem if all operations were performed in a dust-free atmosphere. Conditions for such determination of aluminum in bloo...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1982-11-01 00:00:00
abstract：:We review the present knowledge of telomeres and telomerase with special attention to their role in cell proliferation, cellular senescence, and human aging. We summarize the functional aspects of telomerase in cancer, as well as its role as a useful diagnostic and prognostic tumor marker, and discuss possible approac...
journal_title：Clinical chemistry
pub_type： 杂志文章,评审
doi：
更新日期：1997-05-01 00:00:00
abstract：:We adapted an inhibition assay for methotrexate, involving dihydrofolate reductase from bovine liver, for use with a discrete analyzer (the ABA-100). The analyzer was used both for dilution and a 5-min pre-incubation of the sample with NADPH--enzyme reagent, and for the assay itself. The standard curve was linear betw...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1980-02-01 00:00:00
abstract：:Carbohydrate-deficient transferrin (CDT) may now be the most valuable biological marker for diagnosis of alcohol abuse. We compared the diagnostic performance of two new CDT tests, Axis %CDT turbidimetric immunoassay (TIA) and Axis %CDT HPLC, against Specialty Laboratories' isoelectric focusing/immunoblotting/laser de...
journal_title：Clinical chemistry
pub_type： 临床试验,杂志文章
doi：
更新日期：1997-06-01 00:00:00
abstract：:Clinically relevant interassay precision profiles for thyrotropin (thyroid-stimulating hormone; TSH) were constructed with human serum pools measured over 4-8 weeks by six immunometric assays, in at least two different reagent lots. Functional sensitivities (the concentration at which the interassay CV is < or = 20%) ...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1995-03-01 00:00:00
abstract：BACKGROUND:Prostate-specific antigen (PSA) is a valuable prostatic cancer biomarker that is now widely used for population screening, diagnosis, and monitoring of patients with prostate cancer. Despite the voluminous literature on this biomarker, relatively few reports have addressed the issue of its physiological func...
journal_title：Clinical chemistry
pub_type： 杂志文章,评审
doi：
更新日期：2000-07-01 00:00:00
abstract：BACKGROUND:TMPRSS2:ERG fusions are promising prostate cancer biomarkers. Because they can occur in multiple forms in a single cancer specimen, we developed a quantitative PCR test that detects both type III and type VI TMPRSS2:ERG fusions. The assay is quantified from a standard curve determined with a plasmid-cloned t...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2008.108845
更新日期：2008-12-01 00:00:00
abstract：:We evaluated a method for quantifying high-density lipoprotein cholesterol in plasma, based on electrophoretic migration of the prestained (with Sudan Black III) sample through a discontinuous polyacrylamide++ gel and densitometric integration of the stain associated with each class of lipoprotein. With this method, o...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1985-11-01 00:00:00
abstract：:This simple polarization fluoroimmunoassay for detection of amphetamine in urine involves the use of a single reagent: suitably diluted antiserum plus fluorescein-labeled amphetamine as tracer. To this, one adds 10 microL of urine, incubates for a few minutes at room temperature, and measures the fluorescence polariza...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1985-07-01 00:00:00
abstract：:Estrogen receptor (ER) and progestin receptor (PR) concentrations in tumor biopsies are important predictive indicators of a clinical response to endocrine therapy of breast cancer. To assess interference of O.C.T. (optimum cutting temperature) embedding compound in assays of ER and PR by radioligand binding, we deter...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1989-12-01 00:00:00
abstract：:A convenient screening procedure for presence of drugs of abuse in urine consists of two steps: adsorption of the drugs from urine onto a paper loaded with cation-exchange resin and detection of the adsorbed drugs by direct radioimmunoassay. The first step can be performed in the field, the second in a central laborat...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1977-10-01 00:00:00
abstract：:We assessed the LKB "Delfia" (time-resolved dissociation-enhanced lanthanide fluoroimmunoassay) and the Amersham "Amerlite" (enhanced luminescent immunometry) assays of thyrotropin in serum. Both assays are sensitive (respective detection limits: 0.02 and 0.04 milli-int. unit/L) and have very good within- and between-...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1987-08-01 00:00:00
abstract：BACKGROUND:We used a difference in bias approach to evaluate the commutability of 4 frozen serum pools for 8 direct methods for measurement of HDL and LDL cholesterol (HDLC and LDLC). METHODS:Freshly collected nonfrozen sera from 138 diseased and 37 nondiseased patients and 4 frozen pools from the CDC Lipid Standardiz...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2015.240861
更新日期：2015-08-01 00:00:00
abstract：:We describe conditions for determining carboxypeptidase N (EC 3.4.17.3) activity by liquid chromatography. Serum (10 microL) is mixed with the artificial substrates hippuryl-L-arginine (30 mmol/L) and hippuryl-L-lysine (100 mmol/L) in 50 mmol/L 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1985-12-01 00:00:00
abstract：:Highly purified human lactate dehydrogenases I and V were assayed in 17 different buffers, at a variety of reaction pH's. Diethanolamine and 2-amino-2-methyl-1,3-propanediol provided the best measurements of the enzyme, assayed lactate-to-pyruvate. However, the commercial preparation of 2-amino-2-methyl-1,3-propanedio...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1976-11-01 00:00:00
abstract：:We describe a ratio gas-chromatographic method for determination of cortisol production rate by measuring the isotope dilution of urinary cortisol metabolites. The method was calibrated by analyzing [3H]tetrahydrocortisol and [3H]tetrahydrocortisone of known specific activities. Results are reasonably well reproducibl...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1977-03-01 00:00:00
abstract：BACKGROUND:Atherosclerosis is a complex, chronic disease that usually arises from the converging action of several pathogenic processes, including hypertension, hyperlipidemia, obesity, and the accumulation of oxidized LDL. Platelet-activating factor acetylhydrolase (PAF-AH) is a LDL- and HDL-bound enzyme that hydrolyz...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2004.036863
更新日期：2004-11-01 00:00:00
abstract：BACKGROUND:Growth differentiation factor 15 (GDF15), a stress-responsive cytokine produced in cardiovascular cells under conditions of inflammation and oxidative stress, is emerging as an important prognostic marker in individuals with and without existing cardiovascular disease (CVD). We therefore examined the clinica...
journal_title：Clinical chemistry
pub_type： 杂志文章,meta分析
doi：10.1373/clinchem.2012.190322
更新日期：2012-11-01 00:00:00
abstract：:We have improved the protocol for RNA quantification by using RNase protection. Instead of precipitation and extraction with phenol and chloroform, we use a faster and more reliable precipitation based on guanidinium thiocyanate (GdSCN). The internal standard is produced by in vitro transcription of a DNA template con...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1995-11-01 00:00:00
abstract：BACKGROUND:Galectin-3 has emerged as a potential useful novel biomarker for heart failure and cardiovascular disease (CVD). However, it remains unclear whether galectin-3 is associated with recurrent cardiovascular events during long-term follow-up of patients with stable coronary heart disease (CHD) after adjustment f...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2016.257550
更新日期：2016-10-01 00:00:00
abstract：BACKGROUND:Pompe disease (PD) is the first lysosomal storage disorder to be added to the Recommended Uniform Screening Panel for newborn screening. This condition has a broad phenotypic spectrum, ranging from an infantile form (IOPD), with severe morbidity and mortality in infancy, to a late-onset form (LOPD) with vari...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2016.259036
更新日期：2017-04-01 00:00:00
abstract：BACKGROUND:We explored the utility of multiplexed temperature gradient capillary electrophoresis (TGCE) as a screening tool for identifying genetic changes in the human mitochondrial genome. We examined changes in mitochondrial DNA (mtDNA) in nonmelanoma skin cancers (NMSCs), using TGCE to resolve genetic differences c...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：10.1373/clinchem.2004.040311
更新日期：2005-02-01 00:00:00
abstract：:The metabolism of the synthetic substrate 7-ethoxyresorufin is a selective measure of the activity of cytochrome P-448 monooxygenase, the subset of cytochrome P-450-mediated enzymes preferentially induced by polycyclic aromatic hydrocarbons and related compounds. 7-Ethoxycoumarin metabolism, on the other hand, reflect...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1981-09-01 00:00:00
abstract：:This time-resolved immunofluorometric assay (IFMA) developed for measurement of placental protein 5 (PP5) involves two antibodies: a monoclonal anti-PP5 antibody attached to a solid phase and an europium(III) chelate-labeled polyclonal anti-PP5 antibody as a tracer. The measuring range is 0.05-100 micrograms/L and the...
journal_title：Clinical chemistry
pub_type： 杂志文章
doi：
更新日期：1988-08-01 00:00:00
