bluuebunny/crossref_metadata_2025_split huggingface dataset:
"Sandwich" enzyme immunoassay for placental alkaline phosphatase.
Authors: Millán J L , Stigbrand T 
Published: January 2020

Abstract
Alkaline phosphatase of the placental type in serum has been suggested as a "marker" for malignancy and pregnancy. We describe a highly sensitive enzyme-linked immunosorbent assay (ELISA) for the measurement of this enzyme in serum and ascitic fluid. The assay will detect as little as 0.4 microgram/L, significantly less than with a radioimmunoassay performed with the same reagents. It is highly specific; it does not measure even above-normal concentrations of the intestinal and liver isoenzymes of alkaline phosphatase. The assay is technically simple and allows the processing of many samples in less than 10 h. We measured this isoenzyme in serum of an adult control population. The upper limit of normality is 1.85 microgram/L. Interference by rheumatoid factor was eliminated. Concentrations of the analyte were increased in all pregnancy sera tested. Concentration and activity as measured by two different catalytic assays correlated well. Samples from cancer patients also showed a good correlation, with some exceptions. Possible reasons for these exceptions are discussed. The high sensitivity, specificity, and simplicity of this assay should make it a useful adjunct in monitoring cancer and pregnancy.
Centrifugal analysis with automated sequential reagent addition: measurement of serum calcium.
Authors: Liedtke R J , Kroon G , Batjer J D 
Published: January 2020

Abstract
We describe an automated method for calcium assay, for use with the Cobas-Bio centrifugal analyzer. Calcium is reacted with cresolphthalein complexone and the absorbance of the calcium--dye complex at 575 nm is measured. EDTA is then added to break up the calcium--dye complex and the absorbance at 575 nm is re-measured, to correct for endogenous color and turbidity. Day-to-day precision data, determined over four months, were as follows: mean = 92.9 mg/L, CV = 1.47%; n = 216; mean = 128.7 mg/L, CV = 1.72%; n = 216. Comparison of the Cobas-Bio method (y) with an atomic absorption spectrometric method (x) gave the following results: y = 1.012x--2.05, r = 0.991, Sy/x = 1.2, mean x = 92.63 mg/L, mean y = 91.69 mg/L, n = 74. Hemoglobin, bilirubin, or turbidity does not interfere. At the medical decision value (110 mg/L), the overall analytical error is 4.6 mg/L, which is less than the 5 mg/L allowable (95% confidence limit) error.
Reference values for ionized, complexed, and protein-bound plasma magnesium in men and women.
Authors: Speich M , Bousquet B , Nicolas G 
Published: January 2020

Abstract
Of the three magnesium fractions in plasma, free ionized magnesium (Mg2+) has the greatest biological activity. Accordingly, information concerning this form in plasma is of cardinal importance to investigations in biometry and human pathology. For this reason, we developed an indirect assay for ionized magnesium in which Mg2+ is determined as the difference between ultrafiltrable magnesium, as measured in plasma water after ultracentrifugation, and complexed magnesium, as obtained after fixation of the ionized and protein-bound magnesium on Amberlite IR-120(H) cation-exchange resin. All magnesium assays were performed by atomic absorption spectrometry. We used this methodology to compare ionized, complexed, and protein-bound plasma magnesium in 34 normal men and 12 normal women. Sex-related differences between the values for these fractions were not significant. Interesting preliminary results for cases of myocardial infarction prompt us to continue our investigations concerning these three states of plasma magnesium in cardiac pathology.
Determination of promethazine in serum by liquid chromatography.
Authors: Wallace J E , Shimek E L , Harris S C , Stavchansky S 
Published: January 2020

Abstract
We describe a procedure for the liquid-chromatographic determination of promethazine in low-nanogram concentrations in serum. Triflupromazine is used as the internal standard. The method is based on a single extraction of promethazine from serum with hexane and subsequent derivatization with trichloroethyl chloroformate. Analytical recovery of promethazine is about 90%. The lower limit of detection is 1 microgram/L when a 2.0-mL aliquot of serum is assayed. Our data illustrate the practicability of the method for bioavailability studies after oral or rectal administration of promethazine hydrochloride.
Ultramicro determination of serum triglycerides by bioluminescent assay.
Authors: Werner M , Gabrielson D G , Eastman J 
Published: January 2020

Abstract
The ultramicro (1-microL samples) assay of serum or plasma triglycerides that we describe here is potentially applicable to 1-nL samples and to isolated cells. This technically simple method involves only three reactions: (a) enzymic hydrolysis with lipase and alpha-chymotrypsin; (b) conversion by glycerol kinase of the liberated glycerol and of adenosine triphosphate added in excess to glycerol-1-phosphate and to adenosine diphosphate; and (c) assay of the residual adenosine triphosphate by the luciferin-luciferase reaction. The assay was optimized with respect to glycerol kinase, buffer, pH, temperature, and adenosine triphosphate. Performance characteristics compare well with those of traditional triglyceride assays.
Effect of serum lipids on radioimmunoassays of unconjugated estriol in serum.
Authors: Jawad M J , Wilson E A , Rayburn W F 
Published: January 2020

Abstract
Controversy regarding the presence of a circadian rhythm in unconjugated estriol in serum during pregnancy led us to study the possibility that the observed rhythms actually are the result of partitioning of estriol into serum lipids when these increase postprandially. Addition of triglycerides to purified estriol standards significantly decreased (p less than 0.001) apparent estriol as detected by radioimmunoassay after separation on dextran-coated charcoal and significantly increased (p less than 0.001) estriol as detected by radioimmunoassay after double-antibody separation. Compensation for individual nonspecific binding of standards nullified the effect of lipids only in systems involving dextran-coated charcoal separation, incubated for 1.0 h at 37 degrees C followed by 1.0 h at 4 degrees C. In contrast to other protocols, data obtained with this system revealed no significant circadian variation in serum estriol concentrations in normal pregnant women (CV, 4.3%). Evidently, reported variations in apparent serum estriol concentration are artifactual.
Liquid chromatography and fluorescence spectroscopy compared with a homogeneous enzyme immunoassay technique for determining quinidine in serum.
Authors: Drayer D E , Lorenzo B , Reidenberg M M 
Published: January 2020

Abstract
Sera from 67 cardiac patients being treated with quinidine were analyzed for this drug by both a homogeneous enzyme immunoassay (EMIT) and a fluorescence procedure (double-extraction method). Of these samples, 47 were also analyzed for quinidine and its major metabolite in serum, (3s)-3-hydroxyquinidine, by liquid chromatography. Results by the EMIT procedure correlated well with those by both the chromatographic and fluorescence procedures, but EMIT gave, on the average, 25% higher values for quinidine than did the chromatographic procedure. The EMIT procedure is therefore not totally specific. (3s)-3-Hydroxyquinidine and dihydroquinidine (a contaminant present in standard quinidine formulations) each show cross reactivity in the EMIT assay for quinidine. Nevertheless, the EMIT assay for quinidine is acceptable for clinical use because these two compounds are also pharmacologically active.
Biochemical findings in a case of mu-chain disease.
Authors: O'Reilly D S , Adjukiewicz A , Whicher J T 
Published: January 2020

Abstract
We report the 16th case of mu-chain disease. Unlike most previously reported cases, free mu-chains, but not Bence Jones protein, were present in the urine. The usefulness of immunofixation as a means of detecting free heavy chains in the serum is demonstrated.
Improved method for determination of high-density-lipoprotein cholesterol II. Enzymic determination of cholesterol in high-density lipoprotein fractions with a sensitive reagent.
Authors: Grillo F , Izzo C , Mazzotti G , Murador E 
Published: January 2020

Abstract
A reagent is described for the colorimetric enzymic determination of high-density-lipoprotein (HDL) cholesterol. The reagent can be used with HDL fractions isolated by the various methods of precipitation of low- and very-low-density lipoproteins we investigated. The considerable sensitivity obtained by use of Barham-Trinder's reaction allows the sample/reagent volume ratio to be decreased to 1:80, and major interferences thus eliminated. The response is linear from 100 to 2000 mg of HDL cholesterol per liter. The maximum CV obtained in precision tests was approximately 1% within series and approximately 3% between series. Most of the bilirubin interference is eliminated by adopting a reaction pH of 6.1. Because of its sensitivity, the reagent is particularly suitable for use with HDL fractions isolated after precipitation with polyethylene glycol 6000, which are characterized by a marked dilution. HDL cholesterol determination with the proposed reagent is accurate and precise. Values obtained are in line with those provided for by the Abell-Kendall method. The method can easily be automated.
Enzymic determination of branched-chain amino acids.
Authors: Rudolph H J , Gerbitz K D , Michal G , Wieland O H 
Published: January 2020

Abstract
Transamination of branched-chain amino acids to (alpha-oxoglutarate, catalyzed by leucine aminotransferase coupled to the glutamate dehydrogenase reaction, is used in an enzymic assay for determination of branched-chain amino acids in serum and tissue homogenates. The coefficients of variation of the method within-day and day-to-day are 2.4 and 6.5%, respectively. Analytical recovery of physiological concentrations of branched-chain amino acids added to serum is near 100%. Measurements in serum of healthy subjects revealed normal values similar to those found by use of other methods. During prolonged fasting the concentration of these amino acids in serum first increases, reaching a maximum by three days, followed by a successive decline.
Fluorometric liquid-chromatographic determination of serum cortisol.
Authors: Gotelli G R , Wall J H , Kabra P M , Marton L J 
Published: January 2020

Abstract
We describe a sensitive and specific liquid-chromatographic assay for serum cortisol, exploiting acid-induced fluorescence. Each analysis requires only 50 microL of serum, and chromatography is complete in 7 min. Analytical recovery of cortisol added to serum ranged from 90 to 105% and between-run precision (CV) from 6 to 8%. The lower limit of detection for cortisol is 10 micrograms/L, and linearity extends to 1600 micrograms/L. Numerous steroids and drugs tested did not interfere.
Clinical laboratory determination of phosphatidylglycerol: one- and two-dimensional chromatography compared.
Authors: Gross T L , Wilson M V , Kuhnert P M , Sokol R J 
Published: January 2020

Abstract
Reportedly, determination of several phospholipids in amniotic fluid, including phosphatidylglycerol and phosphatidylinositol, in addition to lecithin and sphingomyelin improves prediction of neonatal pulmonary function. In this study, we evaluated a two-dimensional technique for separating and measuring these phospholipids and compared it with a simpler one-dimensional procedure. The two-dimensional technique was adapted to readily available commercial plates, and a preheating step was introduced to avoid shattering of the plates during charring. The Rf values, reproducibility of each technique, and the correlation between them were examined. Even though the one-dimensional technique is faster and less expensive, we recommend the two-dimensional method for clinical use because of better precision (CV for phosphatidylglycerol 15% vs 21%) and clearer results when relatively little phosphatidylglycerol is present. The one-dimensional procedure is unreliable when blood or meconium are present. In addition, interfering compounds co-migrate with phosphatidylglycerol, phosphatidylethanolamine, and phosphatidylserine in the one-dimensional technique. Before any one-dimensional lipid separation is adopted for clinical use, it should be critically compared to the two-dimensional procedure.
Measurement of aspartate aminotransferase isoenzymes: six procedures compared.
Authors: Rej R , Bretaudiere J P , Graffunder B 
Published: January 2020

Abstract
Six procedures were evaluated for aspartate aminotransferase (EC 2.6.1.1) isoenzyme assay in human serum and tissue homogenates. Results of procedures based on immunochemical precipitation by use of antibodies directed against either the mitochondrial or (with greater precision) soluble isoenzyme correlated well with those by a differential kinetic assay involving both different pH conditions and adipate inhibition. Results with a DEAE-Sephadex ion-exchange chromatographic procedure correlated well with these techniques for specimens containing purified isoenzymes, but showed substantial positive bias for determination of the mitochondrial isoenzyme in human serum. An assay based on the differential effects of pH alone discriminated between the isoenzymes with less bias than did the chromatographic assay. Precision of the two differential pH assays was limited by significant reagent blank activity resulting from destruction of NADH at pH 6.0 or 6.2. An electrophoretic procedure in which diazonium salt is used to make oxalacetate visible was least accurate for measuring samples for which the isoenzyme composition was known.
Application of a sequence-specific radioimmunoassay for the carboxyl-terminal region of corticotropin.
Authors: Lazarus L H , DiAugustine R P , Khan M N , Jahnke G D , Erisman M D 
Published: January 2020

Abstract
The carboxyl terminal region of corticotropin (ACTH), (Ala34-Phe-Pro-Glu-Leu-Phe39), a region of the hormone conserved during evolution, served as an antigen for the production of a sequence-specific antiserum. In a radioimmunoassay, peptides that extend toward the amino terminal from Ala34, such as [Tyr,Gly]-ACTH34-39, ACTH18-39, and ACTH, had greater affinity for the antibody, which suggests that the antiserum recognizes the peptide bond preceding the alanyl residue. The assay readily detects 30 to 50 pmol of ACTH per liter with an incubation of only 3 h, and the antiserum cross reacts with larger molecular mass forms of the hormone. The amount of immunoreactive ACTH extracted by adsorption onto silicic acid from rat and human plasma was only 0.36 to 0.79 of that detected by a mid-region ACTH assay, which suggests proteolytic degradation at the carboxyl terminus of ACTH.
Parathyrin measured concurrently with free or total calcium in the differential diagnosis of hypercalcemia.
Authors: Boyd J C , Lewis J W , Slatopolsky E , Ladenson J H 
Published: January 2020

Abstract
We assessed the diagnostic utility of measuring C-terminal immunoreactive parathyrin (i-PTH) concurrently with free (CaF) or total (CaT) calcium in four groups of patients: (1) 91 patients with histologically proven primary hyperparathyroidism; (2) seven patients without histological evidence of hyperparathyroidism; (3) 70 patients with non-parathyroid malignancies with hypercalcemia; and (4) 28 similar patients without hypercalcemia. In patients in Group 1, the use of either calcium measurement along with i-PTH increased diagnostic accuracy from 95 to 99%. In Group 2, values consistent with primary hyperparathyroidism were obtained for 21% of samples with i-PTH assay alone, 29% with i-PTH and CaT, and 12% with i-PTH and CaF. Surprisingly, 36% of samples from both malignancy groups (3 and 4) had above-normal i-PTH values. In patients with malignancy and hypercalcemia (Group 3) the following percentages were classified as possibly being hyperparathyroid: 26% with i-PTH assay alone; 31% with i-PTH and CaT, and 24% with i-PTH and CaF. Our data indicate that (a) about a fourth of patients with nonparathyroid malignancies also have evidence of hyperparathyroidism as judged by this (and probably all other) i-PTH methods based on C-terminal antibody specificity and that (b) measuring CaF and i-PTH rather than CaT and i-PTH gives a small increase in diagnostic accuracy.
Metabolic abnormalities associated with diabetes mellitus, as investigated by gas chromatography and pattern-recognition analysis of profiles of volatile metabolites.
Authors: Rhodes G , Miller M , McConnell M L , Novotny M 
Published: January 2020

Abstract
Patterns of volatile metabolites in urine, as obtained by glass-capillary gas chromatography, were investigated by use of a nonparametric pattern-recognition method, in an effort to detect abnormalities associated with diabetes. We used threshold logic unit analysis on a data set consisting of normal subjects and those with diabetes mellitus, and could predict patterns for volatile metabolites as belonging to the proper class in 94.83% of the cases examined. In addition, a feature-extraction algorithm isolated those volatile constituents that are most useful in making the normal/diabetic classification. We used gas chromatography/mass spectrometry to identify important profile constituents. Finally, these same pattern-recognition methods indicated strong sex-related patterns in these volatiles.
Insulin degradation by human erythrocyte lysates.
Authors: Nerurkar S G , Gambhir K K 
Published: January 2020

Abstract
In vitro hemolysates of isolated human erythrocytes degrade 125I-labeled insulin. Ten- to 100-fold dilutions of the hemolysate give a proportionately decreased degradation of 125I-labeled insulin at 37 degrees C, while dilutions of up to eightfold do not. Like the control, diluted "Buffer G" containing 5 mmol/L Tris and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer alone, more than 500-fold dilutions of the hemolysate or boiled hemolysate (in buffer) caused negligible (less than 1%) degradation of the labeled insulin. We conclude that accurate insulin-binding data during erythrocyte insulin radioreceptor assay under optimum conditions (Clin. Chem. 23: 1590-1595, 1977) depend on avoiding or minimizing hemolysis.
Preincubation of serum aspartate aminotransferase with pyridoxal 5'-phosphate in the SMAC: comparison with revised DuPont aca method and recommended IFCC method.
Authors: Garber C C , Feldbruegge D H , Hoessel M 
Published: January 2020

Abstract
The method for continuous-flow assay of aspartate aminotransferase with the Technicon SMAC was modified to include preincubation of the serum enzyme with pyridoxal 5'-phosphate, to be consistent with the recommendations of IFCC and the Standards Committee of AACC. Preliminary estimates of the imprecision of the modified method on SMAC gave day-to-day standard deviations of 5.3 U/L at mean of 48 U/L (n = 66) and 6.2 U/L at 155 U/L (n = 61). Added bilirubin, sodium pyruvate, ascorbic acid, and endogenous lipids did not interfere. Comparison of results for 50 samples by this method with those by the manual IFCC method gave y = 1.1113x - 0.3 U/L, Sy/x = 4.4 U/L, and r = 0.997. Similar data are presented for the revised AST method for the DuPont aca discrete analyzer. Clinical data show that AST activities increase by as much as 200% when the serum is preincubated with pyridoxal 5'-phosphate.
Improved colorimetric assay for glycosylated hemoglobin.
Authors: Parker K M , England J D , Da Costa J , Hess R L , Goldstein D E 
Published: January 2020

Abstract
This colorimetric assay for glycosylated hemoglobin can be performed in 120 min with equipment available in most clinical laboratories. The glucose moiety of glycosylated hemoglobin is converted to 5-hydroxymethylfurfural by heating with oxalic acid for 60 min is an autoclave at 124 degrees C and 124 kPa (18 lb/in.2). The adduct formed by reacting 2-thiobarbituric acid with hydroxymethylfurfural is measured photometrically and results are expressed either as nanomoles of hydroxymethylfurfural or as fructose equivalents. Within-assay and between-assay coefficients of variation were less than 2% and less than 3%, respectively. Comparison of results for 50 patients' specimens as measured by the present assay and as analyzed for hemoglobin A1c by liquid chromatography showed excellent correlation (r = 0.98).
A homogeneous fluorescent immunoassay for human immunoglobulin M.
Authors: Worah D , Yeung K K , Ward F E , Carrico R J 
Published: January 2020

Abstract
We describe a homogeneous substrate-labeled fluorescent immunoassay for human IgM. In this competitive-binding method we use a fluorogenic substrate for Escherichia coli beta-galactosidase, N-(6-aminohexyl)-7-beta-galactosyl-coumarin-3-carboxamide, which is covalently coupled to IgM. The fluorescence emission intensity of the labeled IgM at 450 nm (with excitation at 400 nm) is negligible, but when beta-galactosidase is added, the acetal linkage of the galactosyl moiety is hydrolyzed and the product has a greatly enhanced fluorescence. Formation of this fluorescent product is inhibited when antibody specific for IgM is bound to the labeled protein. In competitive-binding reactions, IgM from the serum competes with the labeled IgM for antibody binding sites and consequently the fluorescence produced by the enzymic reaction is related to the IgM concentration. The working range of the assay is between 0.5 and 5.0 g of IgM per liter when a 50-fold predilution of the sera is used. The assay does not cross react significantly with immunoglobulins G or A.
New gas-liquid equilibration method: syringe tonometer.
Authors: Wallace W D , Cutler C A , Clark J S 
Published: January 2020

Abstract
This new apparatus for gas-liquid equilibration (tonometry) in a transportable vessel is designed for tonometry of blood or buffer solution in a specially designed syringe. Gas enters the syringe chamber through small holes in the tip of the syringe plunger and bubbles upward through the sample. The syringe plunger is a second chamber, which is used for warming and humidifying the gas before it enters the tonometer chamber. The entire syringe is housed in a transparent, temperature-controlled environment during equilibration. After equilibration, the sample is easily entered into a blood-gas analyzer. At most, gas-liquid O2/CO2 equilibration for 2.5 mL of buffer or blood requires less than 13 min. Comparisons with a standard thin-film tonometer show good agreement for pO2 and pCO2 over the range 0-93 kPa (0-700 mmHg) and 2-20 kPa (14-150 mmHg), respectively. The syringe tonometer eliminates contamination of the sample during transfer and transport to the analyzer, thus making tonometry more technique-independent. The apparatus is simple and easy to use, with definite advantages over existing methods of tonometry.
Two-hour assay for lutropin during ovulation.
Authors: Hay D L , Tasker P A , Johnston W I , Horacek I 
Published: January 2020

Abstract
A rapid lutropin assay with a 2-h incubation time and a second antibody/polyethylene glycol separation step is presented. Assay time is shortened by incubating at 37 degrees C and using relatively high concentrations of antibody and radioligand. The interval required for the antigen/antibody reaction varies directly with lutropin concentration, from 1 h for ovulation values to 8 h for low values. After a 2-h incubation, low concentrations have reached 80% of their equilibrium concentration. Separation of the bound fraction by use of combined second antibody/polyethylene glycol (50 g/L) gave one-third the nonspecific binding and as rapid a separation as with polyethylene glycol (180 g/L) alone. Optimal conditions for separating the immune complex were established, and separation was found to be independent of protein concentrations in urine or serum. This tested assay can detect increasing and ovulatory lutropin concentrations in urine or serum, but with some sacrifice in sensitivity.