bluuebunny/crossref_metadata_2025_split huggingface dataset:
Technique for gas-chromatographic measurement of volatile alkanes from single-breath samples.
Authors: Zarling E J , Clapper M 
Published: January 2020

Abstract
For detection of small quantities of alkanes that are present in expired breath, these gases have hitherto been concentrated, either by passing large volumes of breath through a liquid-nitrogen-cooled precolumn or by use of a closed collection system. Here, we describe a technique for analyzing small volumes of gas from single-breath samples from humans, in which no precolumn is required. Results are linearly related to sample concentrations of ethane, propane, butane, and pentane in the range 0 to 13 nmol per liter of air (r = 0.999). Within-run coefficients of variation were less than 15%. Breath samples could be stored for as long as 10 h without loss of the alkanes. We also report alkane concentrations in samples of alveolar gas and total breath collected from normal subjects. This technique appears to be well suited for measuring alkane concentrations in single-breath samples.
Turbidimetric determination of transthyretin (prealbumin) with a centrifugal analyzer.
Authors: Hamlin C R , Pankowsky D A 
Published: January 2020

Abstract
We describe a simple, rapid turbidimetric method for measuring transthyretin in human serum by use of a centrifugal analyzer (Cobas-Bio) and commercially available antiserum. The immunoturbidimetric reaction is monitored at 340 nm for 180 s, and the changes in absorbance after the antiserum is added are used to prepare a stable standard curve. The range of measurement is 10 to 520 mg/L. The CV for between-day precision was less than 5.0% for normal and low controls. Bilirubin up to 310 mumol/L and hemoglobin up to 225 mumol/L did not interfere, but triglycerides greater than 2.3 mmol/L falsely depress the results. The normal reference interval for adults, derived from data on subjects 20 to 65 years old (both sexes), is 193 to 376 mg/L. Concentrations are lower in children (67-302 mg/L) and in adults 65 or more years old (113-292 mg/L).
Rate nephelometry and radial immunodiffusion compared for measuring serum prealbumin.
Authors: Goldsmith B M , Munson S 
Published: January 2020

Abstract
We compared a rate-nephelometric method and a radial immunodiffusion (RID) assay for measurement of prealbumin (transthyretin) in 55 samples of serum from healthy children. The mean prealbumin concentration as measured by the Beckman Auto ICS nephelometer was 188 mg/L (range 128-350); the mean by RID was 221 mg/L (range 125-419). This difference was statistically significant by Student's t-test (p less than 0.05), but the correlation coefficient (r) was 0.95. To determine a reference interval for prealbumin in children by the Auto ICS method, we assayed samples from 93 healthy children between the ages of one day and 18 years (55 boys, 38 girls). The mean was 191 mg/L, the reference interval (mean +/- 2 SD) 109-273 mg/L. There was no significant difference in prealbumin concentrations between girls and boys (Student's t-test, p greater than 0.05). Evidently the Beckman Auto ICS method measures prealbumin in serum rapidly and accurately.
Clinical application of a sensitive non-isotopic immunometric assay of thyrotropin.
Authors: Sheppard M C , Black E G 
Published: January 2020

Abstract
We have evaluated an immunometric assay of thyrotropin (TSH) based on enhanced chemiluminescence signal; its detection limit is 0.06 milli-int. unit/L. Values in 101 clinically euthyroid subjects with normal thyroid hormone concentrations ranged from 0.39 to 6.83 milli-int. units/L. TSH in 15 hypothyroid patients ranged from 10.3 to greater than 200 milli-int. units/L, whereas in 31 hyperthyroid subjects with increased concentrations of free thyroxin and free triiodothyronine, TSH was undetectable serum of all but one subject. Of 32 clinically and biochemically euthyroid patients with goiter, two had undetectable serum TSH and six had values below the normal range. In 19 clinically euthyroid patients from an intensive-care unit, TSH was undetectable in two and below the normal range in another two. This immunometric chemiluminescence assay distinguishes thyrotoxic from euthyroid subjects, but caution is required in interpreting TSH values alone in subjects with goiter or nonthyroidal illness.
Liquid-chromatographic method for determination of homovanillic acid in plasma, with electrochemical detection.
Authors: Zumárraga M , Andia I , Bárcena B , Zamalloa M I , Dávilla R 
Published: January 2020

Abstract
We describe a sensitive, simple method for measuring homovanillic acid in human plasma. The method is based on liquid chromatography with electrochemical detection. Sensitivity was 125 pg of homovanillic acid per injection. Samples were deproteinized and extracted with organic solvent before chromatography. Quantification was by the standard-additions technique. Analytical recovery of added HVA was 44.8 (SD 6.2%). We confirmed specificity by using serial amperometric detectors.
Automated enzymatic measurement of lecithin, sphingomyelin, and phosphatidylglycerol in amniotic fluid.
Authors: Bradley C A , Salhany K E , Entman S S , Aleshire S L , Parl F F 
Published: January 2020

Abstract
We describe methods for automated enzymatic measurement of lecithin, sphingomyelin, and phosphatidylglycerol in amniotic fluid. Phospholipase C (EC 3.1.4.3) and sphingomyelin phosphodiesterase (EC 3.1.4.12) are reacted with lecithin and sphingomyelin, respectively, to liberate phosphocholine. Phosphocholine is then reacted with alkaline phosphatase, choline oxidase, peroxidase, and 4-aminoantipyrine to form a colored complex, for which the absorbance at 500 nm is measured with a centrifugal analyzer. Phosphatidylglycerol is hydrolyzed by phospholipase D (EC 3.1.4.4) to form glycerol, which is subsequently reacted with ATP and NAD+ in the presence of glycerol kinase and glycerol-3-phosphate dehydrogenase to yield NADH. The absorbance of the NADH formed is measured at 340 nm. These methods provide a simple, rapid, and accurate alternative to thin-layer chromatography for determination of phospholipids in amniotic fluid for assessment of fetal lung maturity.
Measurement of acetylcholinesterase in erythrocytes in the field.
Authors: Magnotti R A , Eberly J P , Quarm D E , McConnell R S 
Published: January 2020

Abstract
We describe here a field method we developed for colorimetry of erythrocytic acetylcholinesterase (EC 3.1.1.7) in capillary blood samples. Three stable, premixed assay reagents and de-ionized water (but no centrifuge or balance) are required. This method, adapted for a microplate format, is essentially that of Ellman et al. (Biochem Pharmacol 1961;7:88-95) as modified by George and Abernethy (Clin Chem 1983;29:365-8). Assays were quantified and corrected for hematocrit by using a battery-powered colorimeter with a silicon carbide (blue) light-emitting-diode source. Advantages over existing field methods include better portability, ruggedness, greater precision, and lower cost per sample.
Determination of delta-aminobutyric acid and other amino acids in cerebrospinal fluid of pediatric patients by reversed-phase liquid chromatography.
Authors: Goldsmith R F , Earl J W , Cunningham A M 
Published: January 2020

Abstract
The reversed-phase liquid-chromatographic system described here is capable of resolving the neurotransmitter amino acids aspartic acid, glutamic acid, and gamma-aminobutyric acid (GABA) plus 21 other amino acids in cerebrospinal fluid (CSF) in a single analysis. The amino acids, derivatized with o-phthalaldehyde, are separated in 65 min. Concentrations of glutamine less than or equal to 600 mumol/L can be measured at the same time as GABA greater than or equal to 10 nmol/L. Using this method, we have determined reference intervals for amino acids, including GABA, in CSF in a group of pediatric patients who underwent lumbar puncture before myelography, and who were subsequently shown to have normal myelograms. These intervals are generally lower than those previously reported for childhood, but we believe this results from a more rigid selection of the control group. In addition, artifactual increases in concentrations of free neurotransmitters, caused by breakdown of amino acid conjugates, are minimized by (a) immediate freezing of the CSF samples to prevent enzyme-mediated changes, (b) omission of a deproteinization step, and (c) precolumn derivatization to reduce on-column breakdown of amide and peptide forms.
Determining methemoglobin in blood by zero-crossing-point first-derivative spectrophotometry.
Authors: Taulier A , Levillain P , Lemonnier A 
Published: January 2020

Abstract
We determined methemoglobin in blood by zero-crossing-point first-derivative spectrophotometry. After lysis of erythrocytes, hemoglobin was converted into oxyhemoglobin and the first derivative spectrum was recorded between 405 and 425 nm. At the exact point where the first-derivative spectrum of oxyhemoglobin was zero ("zero-crossing point"), the first-derivative value of oxyhemoglobin and methemoglobin mixture was proportional to the methemoglobin concentration. The standard curve was linear for all proportions of methemoglobin. Within-assay precision (CV) was 3.4% for a 20% methemoglobin content. Correlation with results by the Evelyn and Malloy method was very good for high proportions of methemoglobin (greater than 10%), but the proposed technique was far better for low methemoglobin percentages because of its linearity, its high sensitivity, and its low detection limit.
Liquid-chromatographic determination of five orally active cephalosporins--cefixime, cefaclor, cefadroxil, cephalexin, and cephradine--in human serum.
Authors: McAteer J A , Hiltke M F , Silber B M , Faulkner R D 
Published: January 2020

Abstract
We report an isocratic "high-performance" liquid-chromatographic (HPLC) procedure for measurement of five orally administered cephalosporins (cefixime, cefaclor, cefadroxil, cephalexin, and cephradine) in 0.1 mL of human serum. Serum protein is precipitated with acetonitrile, the sample is centrifuged, and the supernate is evaporated under nitrogen. The residue is reconstituted in 0.1 mL of mobile phase, and 50 to 80 microL of this is injected onto a reversed-phase Altex Ultrasphere Octyl (C8) column. The five cephalosporins are resolved by elution with a pH 2.6 mobile phase of methanol/monobasic phosphate buffer (20/80) by vol), flow rate 2 mL/min. The column effluent is monitored at 240 nm. Cefixime serves as the internal standard for the analysis of the four other compounds, cephalexin as the internal standard for cefixime. We used two standard curves for all compounds: a low-range curve for concentrations commonly observed clinically and a higher-range curve for higher concentrations. The former were linear from 1.0 to 10 mg/L for cefaclor, cefadroxil, cephalexin, and cephradine and from 0.1 to 1 mg/L for cefixime. The high-concentration curves were linear from 1 to 10 mg/L for cefixime and from 10 to 100 mg/L for the other compounds. The detection limits were 0.1 mg/L for cefixime, 1 mg/L for the other cephalosporins. Mean within-run and day-to-day CVs were always less than 15% for all compounds studied.
A latex agglutination assay for D dimer: evaluation and application to the diagnosis of thrombotic disease.
Authors: Hillyard C J , Blake A S , Wilson K , Rylatt D B , Miles S , Bunch R , Elms M J , Barnes A , Bundesen P G 
Published: January 2020

Abstract
Although latex agglutination assays have been used for some years to diagnose thrombotic disorders, only recently has it been possible to measure specifically the products of fibrin breakdown in the presence of fibrinogen degradation products, by using monoclonal antibodies. We have evaluated a preparation of latex particles coupled to the monoclonal antibody DD-3B6/22, which is specific for cross-linked fibrin degradation products (XDP) and allows accurate discrimination between normal and pathological conditions. Of samples from 515 apparently healthy volunteers, 97.7% failed to agglutinate the latex; the normal reference interval for XDP determined by enzyme immunoassay was less than 78-320 micrograms/L. The use of different anticoagulants with or without the addition of a protease inhibitor had no significant effects on the results of the latex assay. The latex preparation provides a useful, rapid diagnostic tool for assaying small numbers of samples or as an emergency test.
Identification and analysis of nine metabolites of cyclosporine in whole blood by liquid chromatography. 1: Purification of analytical standards and optimization of the assay.
Authors: Lensmeyer G L , Wiebe D A , Carlson I H 
Published: January 2020

Abstract
We describe an extraction and an isocratic "high-performance" liquid-chromatographic (HPLC) separation of cyclosporine (CsA) and nine metabolites (M1, M8, M17, M18, M21, M25, M26, M203-218, and MUNDF1) from whole blood. Metabolites (for standards) were purified from human bile with liquid-liquid and solid-phase extractions, chromatographed on a cyanopropyl (CN) semipreparative HPLC column, and further purified on octyl, CN, and silica columns. The identity of each metabolite was verified with authentic standards on three chemically different HPLC columns and on the basis of cross-reactivity data from radioimmunoassay. For the routine analytical method, 1 mL of whole blood is diluted, hemolyzed, and applied to a Bond Elut CN (500 mg) cartridge to extract CsA, metabolites, and cyclosporin C, the internal standard. Interferences are removed by using four wash solutions and an additional cartridge of octyldecyl sorbent introduced prior to elution. Analytes are separated on a Zorbax CN analytical column maintained at 58 degrees C, with detection at 214 nm. Analytical recovery, as tested with three lots of CN sorbent, ranged from 47% to 95% for the 10 cyclosporines. Between-run CVs are less than 10% at 200 micrograms/L (concentration of each compound) and the standard curves are linear to 1500 micrograms/L. We also report a study of the separation mechanisms.
Criteria for essential fatty acid deficiency in plasma as assessed by capillary column gas-liquid chromatography.
Authors: Siguel E N , Chee K M , Gong J X , Schaefer E J 
Published: January 2020

Abstract
To develop criteria for deficiency of essential fatty acids (EFA), we used capillary-column gas-liquid chromatography to determine fatty acids (percentage of total fatty acids) in plasma obtained in the fasting state from 56 reference subjects and from 10 patients with intestinal fat malabsorption and suspected EFA deficiency. Fatty acid evaluations (percentage of total fatty acids) that allowed for a clear distinction (P less than 0.01) between reference subjects and patients, based on values two standard deviations below or above the reference mean, included values for linoleic acid (18:2w6) below 27%, and values for palmitic acid (16:0), palmitoleic acid (16:1w7), oleic acid (18:1w9), vaccenic acid (18:1w7), and Mead acid (20:3w9) exceeding 21%, 2.6%, 23.3%, 2.1%, and 0.21%, respectively. Ratios of total EFA to total non-EFA of less than 0.60 and of Mead acid to arachidonic acid of greater than 0.025 also served to identify patients, and were not found in reference subjects. Significant inverse correlations between percentages of plasma EFA and plasma mono-unsaturated fatty acids were noted. Our reference-interval data can be used to assess normality of plasma EFA status.
Liquid chromatography and fluorescence polarization immunoassay methods compared for measuring flecainide acetate in serum.
Authors: Straka R J , Hoon T J , Lalonde R L , Pieper J A , Bottorff M B 
Published: January 2020

Abstract
We analyzed 99 patients' serum samples for concentrations of a new antiarrhythmic agent, flecainide acetate, by fluorescence polarization immunoassay (FPIA) and "high-performance" liquid chromatography (HPLC). Within-day and between-day coefficients of variation at concentrations in the low and high ends of the therapeutic range were less than 7% for HPLC and less than 9% for FPIA. There was no statistical difference in the mean (+/- SD) concentrations of the clinical serum samples measured by the two methods (607 +/- 334 micrograms/L by HPLC, 602 +/- 344 micrograms/L by FPIA), but results by each differed by a mean of 0.13%. FPIA and HPLC measurements correlated significantly (r = 0.98, P less than 0.05), and were linearly related (slope = 0.970, intercept = 13 micrograms/L) as assessed by orthogonal regression. Both assay methods produced similar concentration measurements and were sufficiently accurate and precise to be used in therapeutic drug monitoring.
Time-resolved immunofluorometric assay of alpha-fetoprotein in serum and amniotic fluid, with a novel detection system.
Authors: Chan M A , Bellem A C , Diamandis E P 
Published: January 2020

Abstract
We describe a new "sandwich"-type nonisotopic immunoassay of alpha-fetoprotein (AFP) in serum and amniotic fluid. In the assay, AFP binds to a monoclonal antibody immobilized in a microtiter well and to a polyclonal soluble biotinylated antibody. A fluorescent product is created on the solid-phase after adding streptavidin labeled with a new Eu3+ chelate, 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA), and excess Eu3+. The fluorescent complex, monoclonal antibody-AFP-polyclonal antibody-biotin-streptavidin-BCPDA-Eu3+, is quantified by nitrogen laser excitation at 337.1 nm, the emission at 615 nm being monitored in an especially designed gated fluorometer working in a time-resolved mode. This assay of AFP has a broad dynamic range (up to 1 mg/L), and is precise and accurate. The detection limit is approximately 0.1 microgram/L. Results agree well with those obtained by established techniques.
Simultaneous determination of neopterin and creatinine in serum with solid-phase extraction and on-line elution liquid chromatography.
Authors: Werner E R , Fuchs D , Hausen A , Reibnegger G , Wachter H 
Published: January 2020

Abstract
This is a method for the simultaneous determination of neopterin, a product of interferon-gamma-activated macrophages, and creatinine in serum. Acidified, but not deproteinized serum is applied to a 4-propylbenzene sulfonic acid-modified silica sorbent cartridge, which quantitatively retains the analytes but not the serum proteins. The retained analytes are then eluted from the cartridge directly onto the liquid-chromatography column. Elution from the cartridge is facilitated by a pulse of 0.4 mol/L, pH 6.8 potassium phosphate buffer. On isocratic elution from an octadecylsilica column with potassium phosphate buffer (15 mmol/L, pH 6.0), neopterin is detected by its native fluorescence, creatinine by ultraviolet absorption. Detection limits are 0.5 nmol/L for neopterin, 1 mumol/L for creatinine at a sample volume of 100 microL. The standard curve is linear over the range of concentrations encountered in sera. For both neopterin and creatinine in serum, concentrations so measured agree well with results by established methods.
New assay of apolipoproteins A-I and B by rate nephelometry evaluated.
Authors: Maciejko J J , Levinson S S , Markyvech L , Smith M P , Blevins R D 
Published: January 2020

Abstract
We evaluated new, commercially available reagents for assaying apolipoproteins (apo) A-I and B by rate nephelometry (INA). Our initial linearity studies for apoA-I indicated that use of the commercial diluent resulted in incomplete immunoreactivity. Subsequent revision of the calibration line by the manufacturer compensated for this and improved the linearity for the apoA-I assay. We observed good linearity for the apoB assay. The within-run CVs were less than 4.0% and the between-run CVs were less than 5.5% for both assays. Results were 109% for apoA-I and 101% for apoB as compared with those measured for IUIS-WHO reference materials from the Centers for Disease Control. Recovery averaged 103% for apoA-I and 105% for apoB, for duplicate assays of three concentrations of purified apoA-I and low-density lipoprotein (LDL). Assaying sera from 45 patients, we demonstrated a good correlation between INA and radial immunodiffusion for both apoA-I (r = 0.92) and apoB (r = 0.95). Correlations between apoA-I and high-density lipoprotein cholesterol, and between apoB and LDL cholesterol compared favorably with previous reports. We conclude that these assays are accurate, precise, and easily automated for clinical application.
Evaluation of the Hitachi 704 automatic analyzer.
Authors: Lentjes E G , Harff G A , Backer E T 
Published: January 2020

Abstract
We evaluated the analytical performance of the Hitachi 704 automatic analyzer. The spectrophotometer showed a linearity of response at 340 nm up to 2.8 A. Photometric imprecision measured bichromatically at 340 and 376 nm was 0.49% at 0.16 A, 0.14% at 0.46 A, and 0.17% at 0.76 A. Imprecision of the sample probe was 0.4% for 5, 10, and 20 microL, and the volume delivered deviated -2.4%, -4.4%, and -4.2% from these preset volumes, respectively. Imprecision of the reagent probe over the range 50 to 500 microL ranged from 0.14% to 0.29%; volume delivered deviated from +1.7% to +4.4%). At equilibrium, the temperature in the cuvets was 29.8 (SD 0.05) degree C as measured by cresol red spectrophotometry. No sample carryover was detected. Reagent carryover was detected when a bilirubin assay was preceded by a total protein assay and when lactate dehydrogenase was measured after alanine aminotransferase. Imprecision for nine tests at three concentrations ranged from 1.1% to 4.4%. Comparison of methods with the SMAC II as reference method showed good results. Precision was better than reported for the Hitachi 705 automatic analyzer.
Gas-chromatographic determination of ethanol in blood with 0.53-mm fused-silica open tubular columns.
Authors: Penton Z 
Published: January 2020

Abstract
Several 0.53 mm (i.d.) fused-silica open tubular columns were evaluated for the gas-chromatographic determination of ethanol and other volatiles in blood by both headspace and liquid injection. These columns offer the advantages of fused-silica technology without requiring expensive modification of the instrument for capillary. Methyl silicone columns of various lengths and film thicknesses were examined and also a polyethylene glycol column. The merits of each column are discussed and relative retention times are given.
Routine urinalysis (dipstick) findings in mass screening of healthy adults.
Authors: Carel R S , Silverberg D S , Kaminsky R , Aviram A 
Published: January 2020

Abstract
We present results of simple urinalysis examinations (dipstick) in a large (approximately 21,000 people) working population. In about 10% of the screened individuals at least one abnormality was found. In men the most common finding was proteinuria (4.9%). Hematuria was found in 2.6% and glycosuria in 0.6%. The most prevalent finding in women was hematuria (8.1%), followed by proteinuria (3.9%) and glycosuria (0.6%). Only about 1% of the examinees had two or more abnormalities in their urine examinations. These findings attest to the utility and practicability of incorporating urine testing into various screening and clinical examinations.
Interference of the chemotherapeutic agent etoposide with the direct phosphotungstic acid method for uric acid.
Authors: Matheke M L , Kessler G , Chan K M 
Published: January 2020

Abstract
A 62-year-old woman receiving chemotherapy with etoposide showed discrepant uric acid values as measured by a direct phosphotungstic acid (PTA) method (150 mg/L) compared with a uricase technique (40 mg/L). After ultrafiltration, the positive interference for the direct PTA method was retained in the protein fraction, but not in the filtrate. Adding exogenous etoposide to drug-free serum confirmed this interference for the direct PTA method, but not for the uricase procedure or a PTA technique preceded by dialysis. Decisions for aggressive patient management are often based on the magnitude of hyperuricemia. We do not recommend that the direct phosphotungstic acid method be used to measure uric acid in patients receiving etoposide.