bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aqueous primary standard for use in measuring cholesterol by the cholesterol oxidase method.
Authors: Abele J , Khayam-Bashi H 
Published: January 2020

Abstract
An aqueous primary standard is needed for measuring cholesterol by enzymatic procedures. Sodium deoxycholate solubilizes cholesterol in water. Crystalline cholesterol (1.00, 3.00, 4.00, and 5.00 g/L), added to a solution containing 150 g of this compound per liter of a 9 g/L saline solution, was measured by a cholesterol oxidase procedure, with a centrifugal analyzer. The solubilizer did not interfere. When compared to an isopropanol-based commercial cholesterol standard, the cholesterol standard in solubilizer showed excellent correlation (r = 0.986; m = 0.989). Day-to-day variation for the mixture during nine days was small (CV, 2.9% at 100 g/L, 3.7% at 3.00 g/L, and 1.8% at 4.00 g/L). Linearity was maintained up to 5.00 g/L. The cholesterol concentration in four reference sera so analyzed maintained CV's of less than 4%. The viscosity of the mixture was similar to that of serum. The standard mixtures, stored at room temperature for 360 days, remained stable. The solubilized cholesterol standard is shown to be suitable for use in the enzymatic procedure.
Monitoring diazepam and desmethyldiazepam concentrations in plasma by gas-liquid chromatography, with use of a nitrogen-sensitive detector.
Authors: Dhar A K , Kutt H 
Published: January 2020

Abstract
We describe a modified [from Anal. Chem. 36, 2099 (1964)] procedure for determining diazepam and its pharmacologically active metabolite, desmethyldiazepam, in plasma, with use of a nitrogen-sensitive detector in the gas-liquid chromatography. We used medazepam as the internal reference standard. Diazepam and desmethyldiazepam are converted to their respective benzophenones by mineral acid hydrolysis. With this procedure, as little as 100 muL of plasma can be used to determine the drug in concentrations as low as 10 microgram/L, accurately, reproducibly, and quickly. Within-run and between-run CVs for 100 microgram/L concentrations of the two compounds were 5 and 7%, respectively.
Effects of Ca, Mg, and EDTA on creatine kinase activity in cerebrospinal fluid.
Authors: Urdal P , Strømme J H 
Published: January 2020

Abstract
For one to obtain a precise estimate of creatine kinase (CK) activity in cerebrospinal fluid, the sample fraction is increased by about 10-fold over that used for serum. This increases the concentration of interfering substances, Ca being especially important. Therefore, the relationship between Ca, Mg, and EDTA was examined. Enzyme activity was maximal with 15 mmol of Mg per liter in the presence of 3 mmol of EDTA per liter, otherwise according to the (Scandinavian) recommended conditions for determination of CK activity in serum. These modifications increased the activity of CK by 35% for CK-MM and by 60% for CK-BB. Counteraction of Ca-induced inhibition was the main reason to this increase. We describe a practical and sensitive method for determining CK in cerebrospinal fluid.
Evaluation of two commercially available laser nephelometers and their recommended methods for measurement of serum immunoglobulin G.
Authors: Walsh R L , Coles M E , Geary T D 
Published: January 2020

Abstract
The Hyland and Behring laser nephelometer systems for assay of specific proteins are described. Immunoglobulin G was measured to assess the overall performance of the two systems. Intra-batch precision figures were comparable to those for the radial immunodiffusion method run routinely in our laboratory. There was no significant interference from turbid or lipemic specimens. Accuracy, ease of instrument operation, standard curve stability, linearity, and accessory equipment are discussed. Immunoglobulin G is measured rapidly, accurately, and precisely by either system.
Immobilized enzymes in continuous-flow analysis.
Authors: Werner M , Mohrbacher R J , Riendeau C J , Murador E , Cambiaghi S 
Published: January 2020

Abstract
Glucose oxidase, uricase, and urease were immobilized on the interior surface of activated polyamide tubing. The shelf-life of such enzyme bearing tubes was at least six months. The tubes were used for continuous-flow analysis of glucose, uric acid, and urea with conventional systems and with hybrid micro-scale systems in which modules of different manufacture were combined. The length of enzyme-bearing tube required for each system was ascertained empirically. Each tube could be used for several thousand assays, but glucose oxidase-bearing tubes were more stable than urease- or uricase-bearing tubes. Results for patients' samples correlated well with results obtained by accepted methods.
Determination of amniotic fluid phospholipids by thin-layer chromatography, with use of a hydrogen flame ionization detector.
Authors: Martin-Ponthieu A , Porchet N , Fruchart J C , Sezille G , Dewailly P , Codaccioni X , Delecour M 
Published: January 2020

Abstract
We describe a new specific method for measuring lecithin, sphingomyelin, and phosphatidylglycerol in amniotic fluid by thin-layer chromatography, with use of a hydrogen flame ionization detector. After extraction and acetone precipitation to isolate surface-active lecithin, the phospholipids are separated on a thin rod of refractory and chemically stable material, having an outer coating of a bonded, sintered partition medium. Two solvent systems are used to develop the chromatograms, chloroform/methanol/water to separate lecithin and sphingomyelin, tetrahydrofuran/methylal/methanol for phosphatidylglycerol. Then the rod is passed through an hydrogen flame; the resulting ions produced generate a current, which is amplified and fed to a potentiometric recorder. The height of integral curves was proportional to the area under each peak. For quantitation we used an internal standard (lysolecithin in the first system. phosphatidyldimethylethanolamine in the second). The method requires less than 5 mL of amniotic fluid; results are available within 6 h.
Quantitation of urinary porphyrins by use of second-derivative spectroscopy.
Authors: Jones K G , Sweeney G D 
Published: January 2020

Abstract
We describe a simple, rapid procedure for measuring porphyrins in urine. After acidification of a urine specimen with hydrochloric acid, the second derivative of the absorption spectrum is recorded in the region of the Soret band maximum. The amplitude of the deflection is linearly related to porphyrin concentration, and the point at which the second derivative minimum occurs provides an estimate of the ratio of uroporphyrin to coproporphyrin in the sample. Nonspecific interference is not significant and reproducibility is excellent. Porphyrin excretion was studied in 24-h urine collections from men and non-pregnant as well as pregnant women. Median daily porphyrin excretion (nmol) was: men, 65.0; non-pregnant women, 60.1; and third-trimester pregnant women, 175.0. Distribution of these data was significantly skewed; upper and lower 2.5 percentile limits are given.
Enzyme immunoassay for human ferritin.
Authors: Watanabe N , Niitsu Y , Ohtsuka S , Koseki J , Kohgo Y , Urushizaki I , Kato K , Ishikawa E 
Published: January 2020

Abstract
We describe an enzyme immunoassay with use of beta-D-galactosidase for quantitation of ferritin in human serum. The minimum detectable ferritin concentration is 0.25 microgram/L of serum, which is comparable to results obtained by radioimmunoassay. The correlation coefficient between values determined by enzyme immunoassay and radioimmunoassay was 0.95 (n - 1 = 85, p less than 0.001).
Erythrocyte protoporphyrin/heme ratio in the assessment of iron status.
Authors: Labbé R F , Finch C A , Smith N J , Doan R N , Sood S K , Madan N 
Published: January 2020

Abstract
The protoporphyrinemia of iron deficiency is well recognized. Clinically, information on the protoporphyrin/heme molar ratio in whole blood offers certain advantages over protoporphyrin measurement alone. A procedure for determining this ratio is reported. Protoporphyrin is extracted, solubilized, and measured fluorometrically. Heme (as hemin chloride) is precipitated with the blood proteins, the precipitate is dissolved in an alkaline/pyridine solvent, and the resulting bispyridine ferriprotoporphyrin is measured spectrophotometrically. The molar ratio of these two metabolites correlates well with values for plasma ferritin, plasma iron, transferrin saturation, hemoglobin, and hematocrit. In some cases the ratio increases detectably while the other variables, especially hematocrit and hemoglobin, remain normal. Evidently it is a more sensitive index to iron status. For healthy men and women, the mean ratio is 16.0 (SD, 5.3). The mean + 3 SD, or a ratio of 32, is distinctly abnormal, as shown by a confirmatory test. We validated the test by surveying routine blood specimens obtained from several population groups.
Improved radioimmunoassay of urinary estriol.
Authors: Jawad M J , Wilson E A , Kincaid H L 
Published: January 2020

Abstract
We report a rapid double-antibody radioimmunoassay for urinary estriol. Advantages over other current methods include: (a) 30-min hydrolysis; (b) total incubation time, 55 min; (c) assay unaffected by urinary glucose; (d) no degradation of estriol evident during hydrolysis; (e) superior (85%) analytical recovery of estriol conjugates; (f) linear standard curve by logit-log extrapolation; (g) good correlation (r = 0.83) with total estrogen determination by a generally accepted colorimetric method; (h) only 20 muL of urine required; and (i) the detection range is 1.9 to 100.5 mg/24-h urine.
DuPont aca III performance as tested according to NCCLS guidelines.
Authors: Garber C C , Westgard J O , Milz L , Larson F C 
Published: January 2020

Abstract
We evaluated the analytical performance of 10 representative channels on the new microprocessor-controlled DuPont aca III according to the guidelines (draft documents PSEP-2, 3, and 4) proposed by the Instrument Evaluation Subcommittee of the National Committee for Clinical Laboratory Standards. These guidelines were used for the experimental design and data analysis for the precision and accuracy testing, the latter by comparison with an aca II, with results of atomic absorption spectroscopy for calcium, and with the National Glucose Reference Method. From a 20-day replication study, we estimated within-run, between-run/within-day, between-run/between-day, and total standard deviations at three concentrations for each method. From duplicate analyses of 100 samples on the aca III, aca II, and other methods, we estimated the bias from the regression line at specific concentrations and total error from a tolerance limit about the regression line. Analytical performance of the aca III was judged acceptable because these estimated errors were small.
Metabolic balance of aluminum studied in six men.
Authors: Gorsky J E , Dietz A A , Spencer H , Osis D 
Published: January 2020

Abstract
The metabolism of aluminum was followed in patients who were receiving strictly controlled diets, either unaltered or supplemented with aluminum-containing antacids. Aluminum was determined by atomic absorption spectrophotometry with a graphite furnace. All food, water, and medications were analyzed, as were aliquots of urine and stool collected throughout six-day periods. Patients were usually studied for five consecutive six-day periods on the same diet and aluminum intake. This study included six patients who were studied for seven to 21 such six-day periods. During control periods, when the patients were receiving less than 5 mg of aluminum per day, the balance was usually slightly negative, but when the diet was supplemented with antacids to contain 1--3 g of aluminum per day, an average positive balance of 23 to 313 mg of aluminum per day was observed for the total time on the same intake. Consecutive six-day periods while a subject was receiving antacids might show either positive or negative balances, but the average retention for 18--84 days on antacids was always positive. Thus the potential effects of the storage of aluminum in the tissues must be considered in the chronic administration of antacids.
Measurement of acetate in human blood by gas chromatography: effects of sample preparation, feeding, and various diseases.
Authors: Tollinger C D , Vreman H J , Weiner M W 
Published: January 2020

Abstract
We measured acetate concentrations in whole blood, serum, and plasma by a modification of a previously described method involving vacuum distillation and gas chromatography. The mean acetate concentration of fresh venous plasma from 27 normal subjects was 51 +/- 5 mumol/L (95% confidence limits ranged from 0 to 103 mumol/L). The acetate concentrations of serum and plasma incubated for 2 h at either 4 degrees C or 27 degrees C were the same. The acetate concentration of whole blood incubated at 27 degrees C was significantly greater than that of blood incubated at 4 degrees C. This change may have resulted from the production of acetate by erythrocytes or from the hydrolysis of acetate esters. Storage of plasma at -20 degrees C for 24 h significantly increased acetate concentrations from 26 +/- 6 mumol/L to 63 +/- 4 mumol/L. After the subjects consumed a standard breakfast, venous plasma acetate concentrations increased from 58 to 97 mumol/L at 30 min. Acetate concentrations in arterial plasma exceeded those in venous plasma. Plasma acetate concentrations were not significantly altered in patients with malignancy or diabetes mellitus, but severe liver disease and severe acidosis were both associated with increased acetate concentrations. These preliminary observations suggest that plasma acetate concentrations may be altered in several disease states.
Myocardial infarction?--a conflict between electrocardiographic changes and biochemical data.
Authors: Borer W Z , Gottdiener J S , Papadopoulos N M 
Published: January 2020

Abstract
We present a case of hypovolemic shock accompanied by electrocardiographic changes classically associated with acute myocardial infarction. Prompt therapeutic intervention, which included correction of the hypovolemic shock, resulted in stabilization of the patient's clinical course, increased activities of the cardiac-specific enzymes in serum were not documented. Serial electrophoretic determinations of the isoenzymes of serum lactate dehydrogenase did not show the characteristic changes associated with myocardial infarction. Accurate determination of the serum isoenzymes provided valuable diagnostic information which, accompanied by the patient's clinical improvement, militated strongly against the occurrence of myocardial infarction.
Determination of ammonia and urea in urine and of urea in blood by use of an ammonia-selective electrode.
Authors: Georges J 
Published: January 2020

Abstract
I propose a single, quick method for measuring ammonia in urine and urea in plasma and urine. An ammonia-selective electrodie is used, set up on a microcell, which allows use of small sample volumes. Ammonia is measured directly after partial conversion of ammonium ions to NH3. Urea is measured after its hydrolysis by urease. With urine, the two procedures can be carried out successively in the same cell and on the same sample without changing the procedural conditions. Linear electrode response and accuracy have been checked for concentrations in the expected (normal) range.
Disopyramide determination by gas chromatography, liquid chromatography, and gas chromatography--mass spectrometry.
Authors: Vasiliades J , Owens C , Ragusa F 
Published: January 2020

Abstract
Disopyramide is determined in serum by gas chromatography with a nitrogen-selective detector, by liquid chromatography, and by gas chromatography--mass spectrometry. Comparable results are obtained with the three techniques, with a within-run and between-run precision of 5 to 10% (coefficient of variation). Least-squares analysis of data on patients' sera, analyzed first by gas chromatography (y) and then liquid chromatography (x), gave a slope of 1.12; y-intercept, -0.31; standard error of estimate, 0.46; and correlation coefficient, 0.94. Comparison of patients' sera by gas chromatography (y) and then by gas chromatography--mass spectrometry (x) gave a slope of 0.94; y-intercept, 0.42; standard error of estimate, 0.38; and correlation coefficient, 0.97. Interferences observed when using one technique--for example, gas chromatography--can be eliminated by analyzing the sample extract with one of the other techniques.
Quantitation of hemoglobin A1a+b and hemoglobin A1c by automated "high-performance" liquid chromatography.
Authors: Gruber C A , Koets M D 
Published: January 2020

Abstract
The glycosylated hemoglobins A1a+b and A1c have been rapidly and precisely quantitated in 5-micro L samples of human blood hemolysate (approximately 240 micrograms of hemoglobin) by cation-exchange column chromatography. Total chromatographic is 22.0 min. Proportions of Hb A1c range from 3.85 to 6.71% in normal individuals and from 4.23 to 19.90% in diabetic subjects. Within-day variation was 1.58 and 1.10% for mean Hb A1c proportions of 4.92 and 10.32%, respectively. Hb A1c and Hb A1 are stable in hemolysates stored at 4 degrees C for as long as seven days, and indefinitely under liquid nitrogen.
Cryoactivation of renin in plasma from pregnant and nonpregnant subjects, and its control.
Authors: Rowe J , Gallery E D , Györy A Z 
Published: January 2020

Abstract
Plasma renin activity increased by a mean of 7% from baseline values when blood from nonpregnant persons was kept at 0 degrees C for 5 h before incubation. Freezing chilled plasma and thawing it before incubation resulted in a mean increase of 11%. The same procedures used on plasma from normal pregnant women produced mean increases in plasma renin activity of 44 and 89%, respectively. If blood from pregnant women was kept at 0 degrees C for 5 h, and the plasma then separated, frozen, and thawed before incubation, the resulting mean increase in plasma renin activity from baseline values was 160%. We conclude that plasma from pregnant women should be handled at room temperature, or, if samples must be stored, they must be rapidly frozen, then thawed as rapidly as possible before incubation and assay if results are to be reproducible.
Effects of contaminant radioactivity on results of 125I-radioligand assay.
Authors: Witherspoon L R , Shuler S E , Garcia M M , Zollinger L A 
Published: January 2020

Abstract
Diagnostic radionuclide imaging procedures are often used in patients whose sera are later assayed by use of 125I-labeled radioligands; thus, it is important to identify those assays that potentially may be affected by contaminating radioactivity. Results obtained with assays in which specific separation methods (solid-phase primary antibody, second antibody) or small (10--25 micdo L) sample volumes are used are little affected by the presence of such contaminating radioactivity. Less-specific techniques (polyethylene glycol, charcoal, ion-exchange resin) segregate some of the contaminant activity into the bound fraction. The degree to which such activity is protein bound and the concentration of endogenous ligand then contribute to the resulting error in dose estimation. Samples for these assays should be screened for radioactivity before the assay is begun. Inclusion of nonspecific binding tubes for patients' samples when contamination is present permits the contaminating radioactivity to be evaluated and the patient's dose concentration to be more accurately estimated.
Centrifugal analyzer method for total bilirubin in serum by use of diazotized 2-chloroaniline-5-sulfonic acid.
Authors: Brody J P , Valdes R , Savory J 
Published: January 2020

Abstract
We describe two centrifugal analyzer methods for measuring total bilirubin in serum. Diazotized 2-chloroaniline-5-sulfonic acid is used in both. In the first procedure, ethylene glycol and methanol are used as an accelerator solvent; results correlate well with those by a Jendrassik and Grof method adapted to the centrifugal analyzer, but there is considerable hemolysis interference. In the second method, dimethyl sulfoxide is used with the ethylene glycol/methanol solvent and almost all hemolysis interference is eliminated. For either method, a 15-microliter sample is required. In the second method, instrument response is linearly related to concentration to 250 mg/L and the within-run precision (CV) is about 1%.
Gas-liquid chromatographic determination of mono- and diiodotyrosines in serum.
Authors: Davis L G , Sass N L , Manna B , Nusynowitz M L 
Published: January 2020

Abstract
A sensitivie, reliable gas-chromatographic assay for monoiodotyrosine and diiodotyrosine in human serum is reported. The oxazolidinone-heptafluorobutyric anhydride derivatives allow the quantitation of both compounds in the linear range of 0.2 to 7.6 mg/L of serum. Analytical recovery averaged 88%, and mean accuracy and within-run precision were 98 and 2%, respectively. Concentrations of monoiodotyrosine in serum as low as 20 microgram/L and of diiodotyrosine as low as 100 microgram/L can be detected. Normal serum contains no detectable concentration of either compound, but the method is applicable as a diagnostic tool in the early prediction of thyroid disease. Both compounds were detected in the serum of a hypothyroid subject whose normal thyroid hormone concentrations were being maintained by therapy with desiccated thyroid extract.
Reversed-phase liquid chromatographic separation of 3',5'-cyclic ribonucleotides.
Authors: Krstulovic A M , Hartwick R A , Brown P R 
Published: January 2020

Abstract
A rapid, reversed-phase "high-performance" liquid-chromatographic separation of the five naturally occurring cyclic ribonucleotides is described. The separation, optimized for the measurement of these compounds in biological samples, is short (25 min), sensitive (50-100 pmol), and requires no sample pre-concentration steps. We also report an alternative isocratic elution mode, optimized for a rapid and selective analysis for adenosine 3',5'-cyclic phosphate. The identity of chromatographic peaks in biological extracts is confirmed by several methods: retention times, co-chromatography with the reference compounds, absorbance ratios, enzymatic peak-shift with cyclic nucleotide phosphodiesterase, and stopped-flow ultraviolet-scanning techniques.
Four kits for plasma digoxin radioimmunoassay compared.
Authors: Bergdahl B , Molin L , Lindwall L , Dahlström G , Scherling I L , Bertler A 
Published: January 2020

Abstract
We evaluated four commercial radioimmunoassay kits for digoxin. We assayed a standard plasma containing digoxin, 2.0 microgram/L, and samples from patients receiving digoxin, with use of the kits and of a bioassay, the 86Rb-uptake inhibition technique. Intra-assay precisions differed significantly. Computer-calculated 95% confidence intervals for the radioimmunoassays averaged 0.4 to 0.6 microgram/L at the proposed toxic threshold of 2.0 microgram/L; the corresponding value of the 86Rb assay was 0.75 microgram/L. Digoxin in the standard plasma was overestimated with three of the kits (means: 2.40, 2.56, and 2.59 microgram/L) but was assayed accurately by the 86Rb technique and by one kit. This same kit gave a significantly lower mean (1.07 microgram/L) for the patients' samples then did the other three kits (1.32, 1.49, and 1.29 microgram/L), two of which also differed significantly in accuracy. The 86Rb assay measured glycoside activity corresponding to a mean digoxin concentration of 1.35 microgram/L. We conclude that the relatively low precision of digoxin assay and the variations in accuracy between kits from various vendors apparently deserve continual attention.