bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological variation of lipids and lipoproteins in fingerstick blood
Authors: Kafonek S D , Donovan L , Lovejoy K L , Bachorik P S 
Published: January 2020

Abstract
The biological variability of total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and calculated low-density lipoprotein cholesterol (LDL-C) was determined in three serial (monthly) capillary and venous specimens from 83 subjects. The analytes were quantified with a desktop analyzer. We saw no differences in the coefficient of biological variability (CVb) between capillary and venous specimens for any analyte (TC, 5.2%; TG, 14.7%; HDL-C, 7.2%; LDL-C, 5.4%). The average analytical variability (CVa) for each analyte, determined in quality-control pools, was; TC, 5.0%; TG, 5.2%; HDL-C, 5.8%; and LDL-C, 7.5%. Compared with standardized laboratory measurements, the desktop analyzer exhibited a significant (P &lt; 0.001) positive bias for all analytes (average bias: TC, 5%; TG, 16%; HDL-C, 6%; and LDL-C, 2.4%). Thus, the biological variation of lipids and lipoproteins was the same in fingerstick and venous samples, and the desktop analyzer showed inherently greater analytical variability.
Immunoreactive elastase I: clinical evaluation of a new noninvasive test of pancreatic function
Authors: Stein J , Jung M , Sziegoleit A , Zeuzem S , Caspary W F , Lembcke B 
Published: January 2020

Abstract
We have evaluated the diagnostic value of the fecal elastase test in comparison with the secretin-pancreozymin test in the diagnosis of exocrine pancreatic insufficiency. Pancreatic elastase was measured immunologically. Immunoreactive elastase activity in spot stools from controls ranged from 136 to 4440 microgram/g; 95% of all values were within 175 to 1500 microgram/g. The elastase assay CVs ranged from 3.3% to 6.3% (intraassay) and from 4.1% to 10.2% (interassay). The output of elastase correlated well with those of amylase, lipase, and trypsin, yielding respective correlation coefficients of 0.83, 0.82, and 0.84 in controls and 0.86, 0.91, and 0.91 in patients with impaired pancreatic function. In contrast to fecal chymotrypsin, the test results were unaffected by pancreatic enzyme replacement therapy. These results indicate that fecal immunoreactive elastase may be recommended as a new, noninvasive tubeless test of pancreatic function.
Rapid competitive PCR determination of relative gene expression in limiting tissue samples
Authors: Jiang Y H , Davidson L A , Lupton J R , Chapkin R S 
Published: January 2020

Abstract
Reverse transcriptase (RT)-PCR is widely used to study gene transcription in many biological systems. Despite the development of a variety of procedures, quantification of RT-PCR products remains difficult, particularly when processing a large number of samples. Therefore, we developed a novel alternative PCR technique that we term "rapid competitive PCR" (RC-PCR), designed to study the relative expression of specific genes in a large number of small tissue biopsies. RC-PCR is characterized by measuring relative gene expression at the mRNA level of two or more samples with a nonradioactive assay based on competitive PCR amplification between identical sequences of internal standard and target cDNA. Only a single reaction tube per sample is used in this technique, and it was validated by comparing RC-PCR of protein kinase C zeta and alpha expression in rat colonic mucosa samples with competitive RT-PCR analysis (requiring 6-8 reaction tubes per sample). We conclude that RC-PCR is a simple, rapid, highly sensitive technique that is capable of detecting less than twofold differences in mRNA expression.
Technical performance evaluation of BM/Hitachi 747-200 serum fructosamine assay
Authors: Lin M J , Hoke C , Ettinger B , Coyne R V 
Published: January 2020

Abstract
The technical performance of serum fructosamine assay as a short-term index of diabetic control was evaluated by using the BM/Hitachi 747-200 Automatic Analyzer (Boehringer Mannheim Corp). Intra- and interassay precisions (CV) were &lt;2%. Linearity was confirmed up to 1000 micromol/L. Lipemia, produced artificially or from hypertriglyceridemia in vivo, did not interfere with measurement of serum fructosamine concentration. However, hemoglobin (Hb) interfered with measurement substantially at concentrations &gt;15.5 micromol/L, and bilirubin interfered substantially at concentrations &gt;68.4 micromol/L. A normal reference range of up to 282 micromol/L (mean +/- 2SD = 242 +/- 40) was derived from results obtained from 228 nondiabetic subjects. In 222 diabetic subjects, serum fructosamine concentration correlated well with fasting glucose concentration (r = 0.74) and with Hb A1c concentration (r = 0.80). This automated fructosamine assay has the advantages of technical simplicity, low cost, and reduced analytical time compared with the Hb A1c method.
Effect of cortisol on percentage of non-sex-hormone-bound steroid: implications for distribution of steroids on binding proteins in serum
Authors: Cooke R R , McIntosh J E , Murray-McIntosh R P 
Published: January 2020

Abstract
We previously observed that in men concentrations of serum testosterone (T) not bound to sex-hormone-binding globulin (n-SHBGT) decreased as concentrations of cortisol increased in early morning. This led us to investigate in vitro the influence of several steroids on protein-bound T. Steroids were added to late-evening sera containing low concentrations of cortisol. Changes were measured in percent T or estradiol not bound to SHBG (%n-SHBGT or %n-SHBGE). Results were compared with computer simulations of a mass action model describing current understanding of steroid binding to serum proteins. In vitro measurements confirmed changes observed in vivo. Cortisol at 600 nmol/L reduced %n-SHBGT to 61% +/- 5% of basal, but this was reversed with cortisol at 2000 nmol/L. Progesterone reduced %n-SHGBT less, and dexamethasone had no effect. Free T rose with added cortisol. Increasing estradiol to 900 nmol/L caused an increase in %n-SHBGT. The %n-SHBGE rose with added cortisol (121% +/- 5% of basal with cortisol at 1000 nmol/L). Simulation predicted all behaviors except the marked initial decrease in %n-SHBGT as cortisol concentrations increased and the absolute values of %n-SHBGT and %n-SHBGE. A possible explanation for the former is that T is displaced from corticosteroid-binding globulin (CBG) by added cortisol, more T is bound to CBG than expected, and T displaced from CBG associates with SHBG rather than albumin. Alternatively, current understanding about steroid binding to serum proteins has other major deficiencies.
Determination of blood lead by electron-capture negative chemical ionization gas chromatography-mass spectrometry
Authors: Baird G S , Fitzgerald R L , Aggarwal S K , Herold D A 
Published: January 2020

Abstract
An electron-capture negative chemical ionization (NCI) gas chromatography-mass spectrometry (GC-MS) method for determination of lead (Pb) in blood samples is described. Extraction of Pb from the sample does not involve hot digestion but is based on treatment at ambient temperature. The blood sample is supplemented with a known amount of internal standard (204Pb) for isotope dilution and is treated with concentrated nitric acid. After adjusting the pH to 7, the Pb is extracted into toluene as the pyrrolidine-dithiocarbamate chelate. Samples are then derivatized with 4- fluorophenylmagnesium bromide to form Pb(FC6H4)4. The use of NCI offers enhanced sensitivity (by 75-fold better than previously used electron ionization), gives good precision and accuracy, and has no observable memory effect. The isotope dilution GCoff methodology typically agreed within 2-3% of expected values for the College of American Pathologists blood Pb specimens and the National Institute of Standards and Technology Standard Reference Material 955a.
Use of flameless atomic absorption spectroscopy in immune cytolysis for nonradioactive determination of killer cell activity
Authors: Borella P , Bargellini A , Salvioli S , Cossarizza A 
Published: January 2020

Abstract
We describe here a novel method to evaluate natural killer (NK) cytolytic activity by use of flameless atomic absorption spectroscopy (GF-AAS). This technique may be adopted for use in laboratories equipped with electrothermal atomic absorption spectrometers. Nonradioactive Cr as Na2CrO4 was used to label target cells (K562), and cell lysis was evaluated by measuring Cr released after 4 h of incubation with the effectors. We selected 520 micrograms/L as the optimal dose for labeling targets, between 12 and 20 h as the optimal incubation time, and 10(4) cells as the optimal target size. Advantages of this method include: (a) exclusion of radioactive tracer, with no risk for workers; (b) limited costs; (c) high sensitivity and reproducibility; (d) possibility to store samples; and (e) better control of Cr used for labeling cells due to well-determined, fixed Cr concentrations in the range of nontoxic and linear cellular uptake. Comparison with data obtained by conventional 51Cr labeling of targets killed by the same effectors was excellent, yielding comparable results and corroborating the method.
Rapid diagnosis of homocystinuria and other hypermethioninemias from newborns' blood spots by tandem mass spectrometry
Authors: Chace D H , Hillman S L , Millington D S , Kahler S G , Adam B W , Levy H L 
Published: January 2020

Abstract
We report a new method for the diagnosis of homocystinuria and other hypermethioninemias from dried blood spots on newborn screening cards, based on isotope-dilution tandem mass spectrometry. The mean concentration of methionine in 909 unaffected newborns was 19 micromol/L (CV 44%). The variability of results was reduced when the concentration of methionine was expressed relative to that of another amino acid in the same specimen. The mean ratio of methionine to leucine plus isoleucine for these same newborn blood spots was 0.16 (CV 25%). In newborn samples from a collection categorized by a Guthrie bacterial inhibition assay as true positive, unaffected, or falsely positive for hypermethioninemias, the ratio of methionine to leucine for each true-positive specimen was at least 2.5 times greater than for respective age-matched unaffected blood specimens. The ratio for falsely positive samples did not differ from that for unaffected blood samples. We predict that the ratio of methionine to leucine plus isoleucine determined by tandem mass spectrometry will successfully detect hypermethioninemias with very low rates for false positives and false negatives.
Detection and identification of 6-methylmercapto-8-hydoxypurine, a major metabolite of 6-mercaptopurine, in plasma during intravenous administration
Authors: Keuzenkamp-Jansen C W , van Baal J M , De Abreu R A , de Jong J G , Zuiderent R , Trijbels J M 
Published: January 2020

Abstract
6-Mercaptopurine, a hypoxanthine antimetabolite, is used in the treatment of acute lymphoblastic leukemia (ALL) in children. Extensively metabolized before it exerts cytotoxic action, it is catabolized into 6-mercapto-2,8-dihydroxypurine (thiouric acid), which is excreted by the kidneys. We describe a metabolite of 6-mercaptopurine, 6-methylmercapto-8-hydroxypurine, whose presence has not been previously reported in plasma. This compound was found in high concentrations in plasma during high-dose 6-mercaptopurine infusions (1300 mg/m2 in 24 h). This previously unknown compound was identified by reversed-phase HPLC with absorbance detection and by gas chromatography-mass spectrometry. The pathways leading to 6-methylmercapto-8-hydroxypurine in vivo are not yet fully understood. In a group of 17 patients treated with four courses of high-dose 6-mercaptopurine infusions according to the ALL-8 treatment protocol of the Dutch Childhood Leukemia Study Group, the steady-state concentrations of 6-methylmercapto-8-hydroxypurine in plasma were one-fifth of the parent drug concentrations, with wide interindividual variation. The formation of high concentrations of 6-methylmercapto-8-hydroxypurine in plasma, especially during the infusion, probably indicates another catabolic pathway of high-dose 6-mercaptopurine, apart from its conversion into thiouric acid.
Delivering clinical laboratory services to intensive care units
Authors: Steffes M W , Gillen J L , Fuhrman S A 
Published: January 2020

Abstract
In response to the pressures of cost reduction, we established and evaluated a carefully integrated program to deliver clinical laboratory services more promptly and efficiently to the intensive care units (ICUs). The new protocol reduced the steps and turnaround time from ordering tests by physicians to reporting results by as much as 80% on all ICUs, permitting significant reductions in personnel (exceeding $400,000 per year). For the surgical ICU there were also fewer blood collections (mean preprotocol: 7.0 per patient per 24 h; mean last 12 months: 6.0; P= 0.002). The volume of blood collected fell from 8.1 to 3.5 mL per collection, primarily following an emphasis on small containers. Consequently, the amount of blood taken from each surgical ICU patient decreased from 56 to 21 mL per 24 h (P &lt;0.001).
VIDAS D-dimer: fast quantitative ELISA for measuring D-dimer in plasma
Authors: Pittet J L , de Moerloose P , Reber G , Durand C , Villard C , Piga N , Rolland D , Comby S , Dupuy G 
Published: January 2020

Abstract
VIDAS D-dimer (bioMérieux) is a new quantitative ELISA for D-dimer determination designed for the VIDAS automated system. The test contains single-dose, ready-to-use reagents and is completed within 35 min. Quantitative results are obtained from a calibration curve stored in the software of the system and expressed as fibrinogen equivalent units. The two-step capture/tag test relies on two complementary monoclonal anti-D-dimer antibodies, the second one being labeled with alkaline phosphatase. The upper limit of the measuring range is 1000 micrograms/L and the lower detection limit is &lt;50 micrograms/L, which is below the lower limit of the reference interval (68-494 micrograms/L). Reproducibility (CV) within and between runs ranges from 5% to 7%. There is no interference from heparin, bilirubin, hemoglobin, fibrinogen degradation products, or plasma turbidity. Comparison with a conventional ELISA (y) gave good correlation (r= 0.91, n= 579) and comparable results (y= 1.35x - 148, S(y/x)= 750), especially for D-dimer concentrations ranging from 0 to 1000 micrograms/L (y= 1.09x - 10.6, r= 0.88, S(y/x)= 170).
Serum prostate-specific antigen measured in children from birth to age 18 years
Authors: Randell E W , Diamandis E P , Ellis G 
Published: January 2020

Abstract
We measured prostate-specific antigen (PSA) in serum from 94 cord- blood samples, from 44 newborns, and from 330 children up to age 18 years, using a highly sensitive "third generation" PSA assay on the IMMULITE (Diagnostic Products Corp.) analyzer. The serum was that remaining after cross-matching for blood transfusion. Most children were hospitalized for special care or surgery. We found detectable concentrations of PSA (&gt; or = 0.003 micrograms/L) in many cord sera and in sera from both male and female neonates. PSA was more frequently detectable in cord and newborn sera from males than from females, but there was considerable overlap in values between the sexes, negating any possible usefulness of PSA for assigning male gender to newborns with ambiguous genitalia. PSA decreased to undetectable concentrations in most prepubertal males and females but became detectable around the age of puberty in males. We speculate that the presence of detectable PSA in cord and newborn sera results from androgenic stimulation of prostatic tissue in males or from stimulation of breast or other tissue by prolactin or progesterone in females.
Relation between number of apolipoprotein(a) kringle 4 repeats and mobility of isoforms in agarose gel: basis for a standardized isoform nomenclature
Authors: Marcovina S M , Hobbs H H , Albers J J 
Published: January 2020

Abstract
The size of apolipoprotein(a) [apo(a)] varies from 187 to 648 kDa because of interallelic differences in the number of kringle 4-encoding sequences in the apo(a) gene. Plasma apo(a) isoform sizes were determined by a high-resolution sodium dodecyl sulfate-agarose gel electrophoretic method, followed by immunoblotting. The relation between the number of apo(a) kringle 4-encoding sequences in the apo(a) gene, as assessed by pulsed-field gel electrophoresis and genomic blotting, and the mobility of apo(a) isoforms in agarose gel was evaluated in 29 individuals who had 48 expressed apo(a) isoforms that contained between 12 and 41 kringle 4 repeats. The log of the kringle number was linearly related to the distance the isoform migrated on the agarose gel (r= 0.999). A nomenclature is proposed to designate apo(a) isoforms by the respective number of kringle 4 repeats.
Measurement of sugar probes in serum: an alternative to urine measurement in intestinal permeability testing
Authors: Fleming S C , Duncan A , Russell R I , Laker M F 
Published: January 2020

Abstract
The percentage dose of lactulose and mannitol excreted in urine after oral ingestion is used as a noninvasive method of assessing small intestinal permeability. The collection of incomplete or inaccurately timed urine samples can lead to errors in estimation of sugar probe molecules. We describe an HPLC method for the simultaneous determination of lactulose and mannitol in serum after oral ingestion of test sugars. We applied the test to healthy volunteers and to subjects undergoing jejunal biopsy for suspected gluten-sensitive enteropathy. The ratio of concentrations of lactulose and mannitol in serum discriminated well between subjects with a normal biopsy and those with villous atrophy, discrimination being best at 90 min postdose. The results agree well with lactulose:mannitol ratios determined in urine (r= 0.88), and the two methods can be used interchangeably. The determination of mannitol and lactulose in serum provides an acceptable alternative to urine collection and may be particularly useful in young children. It also reduces the time spent on the investigation from 5 h to 90 min.
Low-density lipoprotein oxidation, antioxidants, and atherosclerosis: a clinical biochemistry perspective
Authors: Jialal I , Devaraj S 
Published: January 2020

Abstract
Cardiovascular disease is the leading cause of mortality in westernized populations. An increased concentration of plasma low-density lipoprotein (LDL) cholesterol constitutes a major risk factor for atherosclerosis. Several lines of evidence support a role for oxidatively modified LDL in atherosclerosis and for its in vivo existence. Antioxidants have been shown to decrease atherosclerotic lesion formation in animal models and decrease LDL oxidation; the evaluation of LDL oxidation in vivo is therefore very important. However, there is a paucity of methods for direct measurement of LDL oxidation. Of the direct methods currently available, the preferred ones seem to be the measurement of F2-isoprostanes, autoantibodies to epitopes on oxidized LDL, and the assessment of antioxidant status. Of the indirect measures, the most uniformly accepted procedure is examining the oxidative susceptibility of isolated LDL by monitoring conjugated diene formation.
Reference intervals for plasma apolipoprotein A-1 determined with a standardized commercial immunoturbidimetric assay: results from the Framingham Offspring Study
Authors: Contois J , McNamara J R , Lammi-Keefe C , Wilson P W , Massov T , Schaefer E J 
Published: January 2020

Abstract
We have evaluated a commercially available, standardized immunoturbidimetric assay of apolipoprotein (apo) A-I, the major protein constituent of high-density lipoproteins (HDL). We determined the reference ranges of plasma apo A-I concentration for white men and women and related these values to the risk of coronary heart disease (CHD). The mean between-run CV for this assay was 2.9%. As determined with individuals participating cycle 4 of the Framingham Offspring Study, the mean (+/- SD) apo A-I concentration was 13% lower in 1879 men (1.34 +/- 0.23 g/L) than in 1939 women (1.54 +/- 0.28 g/L) (P&lt;0.001). An apo A-I concentration of 1.20 g/L roughly corresponded to the 25th percentile value in men and the 5th percentile in women, and subjects with a concentration below this value were significantly more likely to have CHD than subjects wit a higher concentration (P&lt;0.001).
Assay of prostate-specific antigen from whole blood spotted on filter paper and application to prostate cancer screening
Authors: Hoffman B R , Yu H , Diamandis E P 
Published: January 2020

Abstract
We report the measure of prostate-specific antigen (PSA) from extracts of blood dried on filter paper. Five 3-mm (diameter) paper discs containing approximately 25 microL of dried whole blood were punched from the filter paper and extracted with 500 microL of buffer. Recovery of PSA was &gt; 92%. Imprecision of the filter paper procedure was &lt;10% when corresponding whole-blood concentrations were &gt;0.35 micrograms/L. PSA recovery was unaffected whether blood was applied to the filter as one 85-microL aliquots, two 43-microL aliquots, or three 28-microL aliquots. PSA is contained in the plasma fraction. Variation in hematocrit from 0.61 to 0.31 caused &lt;+/-10% change in filter paper PSA. Regression analysis showed: filter paper PSA = 0.86 whole-blood PSA - 0.02; Sy/x = 0.44. Men (153) without prostate cancer gave a 95th percentile of 4.8 micrograms /L. PSA in filter paper dried blood was stable for &gt;1 month at -20 to 37 degrees C and showed no loss of recovery after being mailed to a hot climate. We conclude that the filter paper procedure can reliably distinguish normal from increased concentrations of PSA and that it could facilitate screening to detect occult prostate cancer in large-scale mail-in programs to centralized laboratories.
Quantitative immunoassay for complexes of prostate-specific antigen with alpha2-macroglobulin
Authors: España F , Sánchez-Cuenca J , Estellés A , Gilabert J , Griffin J H , Heeb M J 
Published: January 2020

Abstract
We have developed two ELISAs for quantifying complexes of prostate-specific antigen (PSA) with alpha2-macroglobulin (alpha2M), using partially purified PSA:alpha2M complex as the calibrator. One ELISA was designed to evaluate )SA:alpha2M complex in fluids containing a huge excess of PSA over the amount of complex (semen-derived fluids), the other for use in fluids containing an excess of alpha2M over PSA (blood plasma). The range of the assays was 2-1000 micrograms/L for PSA complexed to alpha2M; the detection limit was 3 micrograms/: Intra- and interassay CVs were 7-13% and 11-17%, respectively, at complexed PSA concentrations of 6-500 micrograms/L. Seminal fluid from healthy men (n = 60) contained 5.2 +/- 2.6 micrograms/L PSA complexed with alpha2M. Prostatic and seminal vesicle fluids contained 6.5 +/- 2.9 ad 0.3 +/- 0.2 mg/L PSA complexed to alpha2M, respectively. When purified PSA was incubated with citrated plasma, between 45% and 65% of the added PSA was recovered as free PSA, whereas approximately 25% formed complexes with alpha2M, 10% complexed with alpha1-antichymotrypsin, and only 0.1-6% was complexed with protein C inhibitor. Of 30 patients with prostate disease, 20 showed detectable plasma PSA:alpha2M complexes; however, the potential diagnostic significance of this complex requires further investigation.