bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isotope dilution/mass spectrometry of serum cholesterol with [3,4-13C]cholesterol: proposed definitive method.
Authors: Pelletier O , Wright L A , Breckenridge W C 
Published: January 2020

Abstract
We describe a new gas-chromatographic/mass-spectrometric (GC/MS) isotope-dilution method for determination of serum cholesterol. The method has been fully optimized and documented to provide the high accuracy and precision expected for a Definitive Method. In the presence of [3,4-13C]cholesterol, cholesteryl esters in serum are hydrolyzed under optimum conditions and the entire cholesterol pool is extracted and derivatized to silyl ethers. The cholesterol derivatives are resolved from other sterols by gas-liquid chromatography on a fused silica column, and selected ions characteristic of cholesterol and the [3,4-13C]cholesterol are monitored with a GC/MS quandrupole system. We estimated the cholesterol content of samples by bracketing each sample with standards of comparable cholesterol concentration that also contained the [3,4-13C]cholesterol. The procedure was highly reproducible (CV less than 0.5%), better accuracy and precision being obtained with [3,4-13C]cholesterol than with heptadeuterated cholesterol. Mean values per gram of dry serum for one serum pool assayed by this method and that of the National Bureau of Standards differed by 0.5%. We conclude that the method satisfies the criteria for a Definitive Method.
Deproteinizing methods evaluated for determination of uric acid in serum by reversed-phase liquid chromatography with ultraviolet detection.
Authors: Sakuma R , Nishina T , Kitamura M 
Published: January 2020

Abstract
We evaluated six deproteinizing methods for determination of uric acid in serum by "high-performance" liquid chromatography with ultraviolet detection: those involving zinc hydroxide, sodium tungstate, trichloroacetic acid, perchloric acid, acetonitrile, and centrifugal ultrafiltration (with Amicon MPS-1 devices). We used a Toyosoda ODS-120A reversed-phase column. The mobile phase was sodium phosphate buffer (40 mmol/L, pH 2.2) containing 20 mL of methanol per liter. Absorbance of the eluate was monitored at 284 nm. The precipitation method with perchloric acid gave high recoveries of uric acid and good precision, and results agreed with those by the uricase-catalase method of Kageyama (Clin Chim Acta 1971;31:421-6).
Improved procedure for determining glutathione in plasma as an index of myocardial oxidative stress.
Authors: Curello S , Ceconi C , Cargnoni A , Cornacchiari A , Ferrari R , Albertini A 
Published: January 2020

Abstract
Glutathione plays an important role in the detoxification processes of electrophilic metabolites of xenobiotics and oxygen free radicals, such that release of reduced and oxidized glutathione into the plasma is considered a reliable index of oxidative stress. However, reduced glutathione in plasma undergoes spontaneous autoxidation, with mixed disulfide formation. We developed a new, simple, quick method to overcome this problem by treating the blood, immediately after collection, with thiol reagents. We add 5,5'-dithiobis(2-nitrobenzoic acid) and N-ethylmaleimide to the blood before determination of total and oxidized glutathione, respectively. We find the proposed assay useful for investigating oxidative stress in clinical situations.
Improved liquid-chromatographic assay of labetalol in plasma.
Authors: Luke D R , Matzke G R , Clarkson J T , Awni W M 
Published: January 2020

Abstract
This is an assay for labetalol in plasma by "high-performance" liquid chromatography, with 5-(2-[4-(4-chlorophenyl)ethyl]) salicylamide hemihydrate as the internal standard. Plasma samples (500 microL) are extracted with acetonitrile, evaporated under nitrogen, reconstituted in the mobile phase, and injected onto a PRP-1 (Hamilton) column packed with particles of poly(styrene-divinylbenzene) copolymer. Fluorescence, enhanced by post-column introduction of NH4OH, was measured in the effluent (excitation wavelength 340 nm, emission wavelength 418 nm). Retention times for labetalol and the internal standard were 1.99 and 3.32 min, respectively. Inter- and intraday CVs for high and low concentrations of the drug were less than 7.5%. The assay standard curve is linear from 1 to 250 micrograms/L. Some commonly co-administered drugs were tested and did not interfere.
Effect of two anticoagulants on leukocyte yield and function, and on lysosomal enzyme activity.
Authors: Branum E , Cummins L , Bartilson M , Hopper M , Pruett S , O'Brien J F 
Published: January 2020

Abstract
We compared acid citrate-dextrose (ACD-B) and heparin to determine which anticoagulant better preserves leukocytes for lysosomal enzyme assays if processing was done immediately or delayed for 24 h or more. Twenty normal subjects had blood drawn into tubes containing either ACD-B or heparin. The leukocytes were isolated by sedimentation in dextran (50 g/L) less than 2, 24, 48, and 72 h later. The most apparent difference was that cell counts indicated a 30% reduction in the number of leukocytes for ACD-B and a 95% reduction for heparin-treated cells at 48 h. The neutrophil function assay indicated that leukocyte processing must be done in less than 24 h regardless of the anticoagulant used, and that heparin is to be preferred. A comparison of heparin and ACD-B for maintenance of the activity of arylsulfatase A (EC 3.2.6.1) and hexosaminidase (EC 3.2.1.50) indicates that there is no effect of anticoagulant. However, at 48 h after venipuncture, there is an 80% reduction in the number of heparin-treated samples that are suitable for use in the assay. Those laboratories doing lysosomal enzyme tests on mailed specimens, which are most often greater than 24 h old, should use ACD-B as anticoagulant.
One-point recalibration of heterogeneous enzyme immunoassays with non-linear calibration curves.
Authors: Meyer H D , Keller H 
Published: January 2020

Abstract
We have investigated one-point recalibration of heterogeneous enzyme immunoassays involving nonlinear calibration curves. By using a factor determined from a single standard we updated calibration curves obtained earlier by means of multiple-point determination. The prerequisite for this method is a reproducible working procedure, i.e., as ensured by a fully mechanized system. In our investigations with Enzymun-Test system ES 600 (Boehringer Mannheim) we determined alpha 1-fetoprotein, carcinoembryonic antigen, digoxin, ferritin, thyroxin-binding globulin, triiodothyronine, and thyroxin in human serum pools over a period of two weeks with both full calibration and one-point recalibration. Comparisons of the results thereby obtained show that the means of the concentrations and the CVs for the alternative calibration procedures differed negligibly, even if we used reagents exposed to different temperatures for different periods of time. With the one-point recalibration procedure presented here, therefore, one can considerably reduce the time and effort spent on calibration.
Improved determination of selenium in serum by Zeeman atomic absorption spectrometry.
Authors: Morisi G , Patriarca M , Menotti A 
Published: January 2020

Abstract
We have improved Zeeman atomic absorption spectrometric determination of selenium in serum by using an acidic solution of Ag + Cu + Mg as a matrix modifier and performing the charring step in flowing O2. Under these conditions, we could calibrate serum results with selenium standards in bovine albumin solutions. Mean analytical recovery was 98%, and the CV was 1.8% within runs, 2.9% between runs. Analysis of Reference Materials from the U.S. National Bureau of Standards (SRM 909 and RM 8419) yielded the values of 106 (SD 2.4) and 15 (SD 1.6) microgram/L, respectively, in good agreement with the expected values (106 and 16, respectively). The method--being reliable and relatively simple and rapid--is suitable for use in epidemiological screenings. Mean selenium concentrations in serum sampled from 274 adults in central Italy were 90 (SD 15) microgram/L. For 11-year-old children, these values were lower and showed a tendency to sex-related difference: 82 (SD 9.9) microgram/L for 97 boys, 78 (SD 9.3) microgram/L for 90 girls.
Two dry-reagent systems evaluated for determinations of enzyme activities.
Authors: Hafkenscheid J C , van der Ven-Jongekrijg J 
Published: January 2020

Abstract
We evaluated the Kodak Ektachem DT60/DTSC and the Boehringer Mannheim Reflotron for measuring activity concentrations of six enzymes. The Ektachem CVs for low concentrations of aspartate aminotransferase and alanine aminotransferase were high. As compared with the Ektachem and a routine "wet-chemistry" system, values for aspartate aminotransferase and alanine aminotransferase were lower as measured by the Reflotron, because no pyridoxal 5'-phosphate is included in the Reflotron slides. Activity concentrations of gamma-glutamyltransferase and creatine kinase measured with the Ektachem and with the routine procedure did not agree well, possibly because the Ektachem gave too-high results for the enzyme activities. Assays of several commercial test sera indicated that test results by the dry-chemistry and routine procedures are not interconvertible. This contrasts with our previous experience, in which between-test agreement for several analytes was acceptable.
Albumin Cooperstown: a serum albumin variant with the same (313 Lys----Asn) mutation found in albumins in Italy and New Zealand.
Authors: Huss K , Putnam F W , Takahashi N , Takahashi Y , Weaver G A , Peters T 
Published: January 2020

Abstract
Albumin Cooperstown is an electrophoretically fast genetic variant (alloalbumin) inherited in a family in New York State. To determine the structural change, we separated the alloalbumin from normal albumin A by "high-performance" liquid chromatography, reduced and carboxymethylated it, and cleaved it with CNBr. Isoelectric focusing showed that the substitution was in fragment CB4 (residues 299 to 329). The variant CNBr fragment from the albumin of two siblings was purified by liquid chromatography. Automated sequence analysis established the substitution of lysine-313 by asparagine (313 Lys----Asn), which corresponds to mutation of a single nucleotide base. The same substitution has recently been reported in albumin variants in Italy and New Zealand. This provides the first evidence for independent mutations at a single site within the structure of the mature albumin molecule. Because of the significance of albumin for study of protein evolution, clinical chemists are asked to be on the alert for cases of bisalbuminemia.
Heterophilic antibodies: a problem for all immunoassays.
Authors: Boscato L M , Stuart M C 
Published: January 2020

Abstract
We verified that antibody-binding substances in serum that interfere in two-site immunoassays involving murine antibodies are heterophilic antibodies. Incubation of serum containing heterophilic antibodies and a murine monoclonal antibody to human choriogonadotropin (hCG) leads to formation of a series of soluble immune complexes. We investigated the recognition of hCG by reagent antibody in the presence of heterophilic antibodies and found this recognition to be diminished. Consequently, about 30% of serum samples containing heterophilic antibodies falsely appear to contain increased concentrations of hCG. The effect on analyte recognition probably results from steric inhibition of hCG binding to complexed antibody. Heterophilic antibodies detected with a murine antibody also bound immunoglobulin from several other species but did not bind all of those tested.
Effect of lot-to-lot variability in filter paper on the quantification of thyroxin, thyrotropin, and phenylalanine in dried-blood specimens.
Authors: Slazyk W E , Phillips D L , Therrell B L , Hannon W H 
Published: January 2020

Abstract
We prepared whole-blood pools to contain various concentrations of phenylalanine (Phe), thyroxin (T4), and thyrotropin (TSH) and applied them to six different lots of Schleicher & Schuell Grade 903 filter paper, two of which represented extremes for serum-absorbancy. Individual measured T4 values showed minimal overlap among all pools for each individual filter-paper lot and for all lots combined, but Phe values overlapped considerably among the high-concentration pools within and among lots. Individual TSH values also showed considerable overlap among the high-concentration pools for all lots combined, but little overlap within each lot. Maximum differences in mean observed values among lots ranged from 6% to 36% for all analytes. Assay results from hemolyzed blood specimens generally were lower than from intact-cell blood specimens for T4 and TSH, but slightly higher for Phe. Maximum among-lot differences in mean values ranged from 13% to 29% for all analytes when each tested lot was used for assay calibration. Lot-to-lot differences in measured values were not strongly related to serum absorbancy values. We conclude that routinely encountered within- and among-lot filter paper variability, as measured by serum-absorbancy, is not alone sufficient to cause gross quantification errors in neonatal screening programs.
Rate and delta checks compared for selected chemistry tests.
Authors: Lacher D A , Connelly D P 
Published: January 2020

Abstract
We compared delta and "rate" check methods for 12 selected chemistry tests. Rate checks were determined by dividing delta checks by inter-specimen interval time. The delta and rate check methods were based on differences and percent change of untransformed and absolute value-transformed values. The distribution of delta differences was not symmetrical for calcium, alkaline phosphatase, aspartate aminotransferase, or phosphorus, which led to different check limits between untransformed and absolute value-transformed methods. The dispersion of rate checks was large. The interval time between two consecutive tests was multimodal, which probably reflected adherence to fixed testing protocols.
Enzyme-linked immunosorbent assay of CA-125 in serum of patients with endometriosis: efficacy in diagnosis.
Authors: Kang J O , Hudak W A , Keller N , Criswell B S 
Published: January 2020

Abstract
We used an enzyme-linked immunosorbent assay to quantify CA-125, a cancer antigen, in serum of patients with endometriosis. Concentrations of CA-125 in 103 patients with untreated endometriosis significantly (P less than 0.005) exceeded those for 31 controls with no evidence of disease: 9.1 (SD 12.3) vs 2.2 (SD 3.2) arb. units/mL. Values for patients with treated endometriosis were lower (2.3, SD 2.6, arb. units/mL, n = 9) than those for patients with untreated endometriosis. The mean concentrations of CA-125 in different stages of untreated endometriosis were 4.8 (SD 4.5), 7.1 (SD 9.9), 9.8 (SD 13.2), and 10.8 (SD 13.0) arb. units/mL for Stages I, II, III, and IV, respectively. The differences between controls and each stage were statistically significant (for all stages: P less than 0.05). We also assayed serum sampled from controls and patients with untreated endometriosis during menstruation (Group A) and during nonmenstruation (Group B). The efficacy of the present assay for concentrations of CA-125 in serum of patients with endometriosis was greater for Group B than for Group A. Evidently, determination of CA-125 in serum by the present assay may assist in such diagnosis.
Electroimmuno- and immunonephelometric assays of apolipoprotein A-I by using a mixture of monoclonal antibodies.
Authors: Pruvot I , Fievet C , Durieux C , Vu Dac N , Fruchart J C 
Published: January 2020

Abstract
The use of mixtures of well-defined monoclonal antibodies may represent a step forward in the standardization of immunochemical assays. We developed and optimized working conditions for using such a mixture to determine apolipoprotein A-I in human sera by two independent techniques (electroimmuno- and immunonephelometric-assays). Six monoclonal antibodies, each addressed to distinct epitopes located at the surface of apolipoprotein A-I, were used in combination to permit a reproducible measurement of the protein, without prior delipidation of samples. Parallel standard curves for a high-density lipoprotein subfraction (HDL3, the primary standard) and a reference serum (the secondary standard) were obtained. Within- and between-run coefficients of variation were acceptable for both methods. Apolipoprotein A-I concentrations, as measured in 60 subjects selected to present a large range of apolipoprotein content by electroimmunoassay (y1) and immunonephelometric assay (y2) with monoclonal antibodies, compared well with those measured by the same techniques but with polyclonal antibodies (x): r1 = 0.96, r2 = 0.99; y1 = 1.19x - 0.11 g/L, y2 = 0.98x. Comparison of results obtained by electroimmunoassay and immunonephelometric assay performed with monoclonal antibodies was also good: r = 0.96; y2 = 1.08y1 + 0.13 g/L.
Laboratory and clinical evaluation of an assay of thrombin-antithrombin III complexes in plasma.
Authors: Hoek J A , Sturk A , ten Cate J W , Lamping R J , Berends F , Borm J J 
Published: January 2020

Abstract
We evaluated a recently developed commercial assay for quantifying thrombin-antithrombin III (TAT) complexes in human plasma. The assay is precise (within-assay CV less than 10%, between-assay CV less than 13%), and sensitive (detection limit 0.7 micrograms of TAT per liter of plasma). Measurements for healthy volunteers yielded a normal reference (95 percentile) interval of 0.8 to 5.0 micrograms/L (n = 50, mean 2.1 micrograms/L, range 1.1 to 7.5 micrograms/L). TAT concentrations were increased in 25 of the 41 patients who fulfilled the clinical criteria of disseminated intravascular coagulation (DIC, overall mean 15.8 micrograms/L) and in 30 of the 35 patients with deep-vein thrombosis of the leg (overall mean 9.4 micrograms/L). We assessed the accuracy of the TAT assay by comparison with established criteria for the laboratory diagnosis of DIC involving various cutoff values for antithrombin III, factor V, fibrinogen, platelet count, fibrin/fibrinogen degradation products, and activated partial thromboplastin time. The low specificity of the TAT assay with regard to some of these criteria indicates that the latter are probably insensitive.
Intra-individual variation of serum thyroxin and triiodothyronine in pregnancy.
Authors: Hölzel W G , Deschner W 
Published: January 2020

Abstract
The mean concentrations of triiodothyronine (T3) and thyroxin (T4) in serum were increased in pregnancy, the increases for individuals remaining stable for week 16 to week 40 of gestation. For this period biological intra-individual variations of T3 and T4 in serum were estimated and compared with those of non-pregnant women. The average biological intra-individual CVs for T3 and T4 were of the same order for pregnant and non-pregnant women (6.9-8.4%). The ratios of the biological intra-individual CVs to the biological group CVs were 0.5 to 0.6. Individual values were normally distributed. There was no increase of the intra-individual variation with the lapse of time between two consecutively observed values. The estimated average biological intra-individual CVs were used to derive decision-making criteria in monitoring thyroid function during the 2nd and 3rd trimester of gestation.
Estradiol-17 beta quantified in serum by isotope dilution-gas chromatography-mass spectrometry: reversed-phase C18 high-performance liquid chromatography compared with immuno-affinity chromatography for sample pretreatment.
Authors: Thienpont L M , Verhaeghe P G , Van Brussel K A , De Leenheer A P 
Published: January 2020

Abstract
Here, isotope dilution-gas chromatography-mass spectometry is used as a reference technique for determining the concentration of estradiol-17 beta in candidate human serum Reference Material. The accuracy of assigned concentrations in biologic materials is not only determined by instrumental performance, it also depends greatly on the selectivity of the procedure for isolating the analyte from the biological matrix, an issue which we consider insufficiently addressed in the literature. We introduced reversed-phase C18 high-performance liquid chromatography as a fractionation procedure in addition to the commonly used solvent extraction and column chromatography on Sephadex LH-20. The validity of this approach as part of a Reference Method for measurement of estradiol-17 beta by isotope dilution-gas chromatography-mass spectrometry was investigated by comparison with immuno-affinity chromatography, which on theoretical grounds is generally considered as highly selective.
An alternative method for assaying cerebrospinal fluid protein in the presence of methotrexate.
Authors: Kasper L M , Moorehead W R , Oei T O , Markanich M 
Published: January 2020

Abstract
Therapeutic concentrations of methotrexate can cause significant positive interference in cerebrospinal fluid (CSF) protein values when assayed in the Du Pont aca. Conversely, our modified turbidimetric method, in which trichloroacetic acid (TCA) plus a sample blank containing dilute hydrochloric acid is used in place of TCA, exhibits little or no interference from methotrexate. This was verified by assaying solutions that contained a constant amount of protein (approximately 430 mg/L) and various amounts of methotrexate (0.0-2.3 x 10(-4) mol/L) by both the Du Pont aca and the manual turbidimetric method. As expected, the aca results showed increasing protein values with increasing methotrexate, whereas the manual method gave results approximating the expected protein value irrespective of the methotrexate concentration.
Falsely high high-density lipoprotein triglyceride values by the heparin-manganese precipitation method.
Authors: Simo I E , Kiss Z , Ooi T C 
Published: January 2020

Abstract
Recent evidence indicates that high-density lipoprotein triglyceride (HDL-Tg) may be a predictor of coronary artery disease. We examined three methods for HDL-Tg measurement, comparing results obtained by measurement of Tg in the supernate after heparin-manganese chloride (heparin-Mn) precipitation of EDTA-treated plasma (I) with results obtained after preparative ultracentrifugation (II and III). In II, we used heparin-Mn precipitation of low-density lipoprotein (LDL) from the infranate after ultracentrifugation at d 1.006 to remove very-low-density lipoprotein (VLDL). In III, we performed sequential flotation ultracentrifugation at d 1.006 and 1.063, then measured Tg in the d greater than 1.063 fraction. Method I gave significantly higher HDL-Tg results than II and III, which gave essentially identical results. The difference in results between I and II was not caused by the presence of heparin or manganese chloride, because these were used in both methods. Prior removal of VLDL in II and III resulted in lower HDL-Tg values, and subsequent removal of LDL by precipitation or ultracentrifugation did not alter final HDL-Tg values. The higher values obtained in I were the result of the presence of VLDL-rich unsedimented precipitate in the supernate.