bluuebunny/crossref_metadata_2025_split huggingface dataset:
Azorubin in Aqueous and Methanolic Solutions
Authors: Friedman Howard S 
Published: January 2020

Abstract
A study of the spectrophotometric characteristics of azorubin in varying proportions of methanol and water has been presented.
The absorbence of azorubin in water was found to vary from 73 to 90 per cent of that in methanol, over a concentration range of 0.001 to 0.025 mg. per 2 ml. of test solution.
The absorbence of azorubin was found to be linear over the same range of concentration, and over the range from 0.1 to 10 mg. per 100 ml. of serum, using a final test dilution of 1 to 8.
The strong probability of the artefactual nature of "direct" and "total" serum bilirubin values has been demonstrated.
Glycylglycylglycine as a Synthetic Standard for Serum Protein Determination
Authors: Klein Bernard 
Published: January 2020

Abstract
Glycylglycylglycine was investigated as a reference standard for use in serum protein measurement by the biuret reaction. The tripeptide-biuret solution has a molar absorptivity of 96 at 565 nm, and absorbances at both 550 nm and 565 nm are proportional to concentration. By a manual reference procedure, the 550-nm absorbance of 1.0 g of tripeptide was equivalent to that given by 1.72 ± 0.03 g of human serum albumin or 1.43 ± 0.03 g of bovine serum albumin. By the Technicon N14b automated procedure, the absorbance of 1.0 g of tripeptide at 550 nm was equivalent to that of 1.81 ± 0.02 g of human serum albumin or 1.89 ± 0.03 g of bovine serum albumin. Results for serum protein analyses over the range 4.0 to 9.0 g/dl, when tripeptide or serum albumin was used to prepare calibration curves, showed mean differences of 0.15 g/dl in the manual mode and 0.08 g/dl in the automated mode.
Ion-Exchange Chromatography of Amino Acids in Sweat Collected from Healthy Subjects during Sauna Bathing
Authors: Gitlitz Peter H , Sunderman, F William , Hohnadel David C 
Published: January 2020

Abstract
Amino acids were measured by ion-exchange liquid chromatography in sweat samples obtained from 22 healthy men during sauna bathing. Amino acids were also measured in plasma (collected before breakfast) and urine (24-h collections) from the same subjects. Serine, ornithine, citrulline, and aspartic acid were present in sweat in mean concentrations &gt;10-fold their mean concentrations in plasma. In contrast, glutamine, cystine, α-aminobutyric acid, and α-aminoadipic acid were present in sweat in mean concentrations that were &lt;0.2 times their mean concentrations in plasma. Concentrations of specific amino acids in sweat bore no apparent relationship to their concentrations in urine. Thus, citrulline was abundant in sweat, whereas only traces of citrulline were found in urine. Conversely, glutamine, taurine, cystine, and several other amino acids were abundant in urine but were present in very low or undetectable concentrations in sweat samples. This study indicates that the physiological mechanisms controlling excretion of amino acids in sweat differ fundamentally from those regulating renal excretion of amino acids.
Measurement of Glucose-6-phosphate Dehydrogenase and 6-Phosphogluconate Dehydrogenase Activites in Erythrocytes by Use of a Centrifugal Analyzer
Authors: Nicholson John F , Bodourian Selma H , Pesce Michael A 
Published: January 2020

Abstract
We describe an accurate automated method for measuring activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in erythrocytes with a centrifugal analyzer. Blood is collected in microhematocrit tubes, centrifuged, and the erythrocytes are lysed with digitonin. Glucose-6-phosphate dehydrogenase activity is determined by mixing the hemolysate with glucose-6-phosphate, NADP+, and 6-phosphogluconate dehydrogenase #{ 233} (EC 1.1.1.44) in triethanolamine—EDTA buffer at pH 7.6, and measuring the rate of NADPH production for 3 min. Under these conditions 2 mol of NADPH are produced per mole of glucose-6-phosphate oxidized, ensuring the accuracy of the method and increasing its sensitivity. Activity is referred to hemoglobin, measured as cyanmethemoglobin. Activity of glucose-6-phosphate dehydrogenase added to hemolysates was well accounted for. Results obtained by our method and by the method of Bishop [J. Lab. Clin. Med. 68, 149 (1966)] are virtually identical. Our method requires a small amount of blood and is accurate and rapid; thus it is well suited for use in surveying large populations for glucose-6-phosphate dehydrogenase deficiency. A simple modification of the method may be used to determine the activity of 6-phosphogluconate dehydrogenase.
Palmitic Acid Content of Amniotic Fluid Lecithin as an Index to Fetal Lung Maturity
Authors: Russell Paul T , Miller W J , McLain C R 
Published: January 2020

Abstract
A method is described for evaluating functional maturity of the fetal lung by measuring the palmitic acid content of amniotic fluid lecithin. The proportion of palmitic acid in total lecithin fatty acids correlated well (r = .87) with the pulmonary status of the newborn in the neonatal period. Palmitic acid values of less than 20% correlated with respiratory distress in 21 of 24 pregnancies; values greater than 20% correlated with pulmonary maturity in 39 of 40 pregnancies. Blood in the amniotic fluid does not adversely affect the validity of values for palmitic acid. Advantages of this method for predicting fetal maturity are discussed.
Routine Micromethod for Determination of Oxalic Acid in Urine by Atomic Absorption Spectrophotometry
Authors: Menachè R 
Published: January 2020

Abstract
The method of Gitelson et al. was modified to a microscale procedure and adapted for atomic absorption spectrophotometry. Oxalic acid in urine is precipitated with excess of calcium ions at pH 5. The excess of calcium present in the supernate and the total calcium added and present in the urine at pH 2 are determined by atomic absorption spectrophotometry. The oxalic acid present in the precipitate is calculated indirectly from the difference between the two determinations of calcium. This method is useful for routine determination of urinary oxalic acid.
Pyruvate as Substrate in the Determination of Serum Lactate Dehydrogenase Isoenzyme Activity
Authors: McKenzie Doris , Henderson A R 
Published: January 2020

Abstract
Lactate dehydrogenase isoenzyme activity is usually assessed, after the isoenzymes have been separated, by reactions involving lactate as the substrate. We describe a method for their assessment with pyruvate as the substrate. Precision is adequate as compared to the conventional methodology. Application of this type of approach (measurement of a decrease in fluorescence) to determination of other serum isoenzymes is briefly described.
Increased Synthesis of Lactate Dehydrogenase "H" Subunit by a Malignant Tumor
Authors: Henderson Arthur R , Ahmad Dildar , McKenzie Doris 
Published: January 2020

Abstract
In a patient with a rapidly growing malignant teratoma in the anterior mediastinum, the only biochemical abnormality detected at first was an abnormally high serum lactate dehydrogenase (EC 1.1.1.27) activity, almost 50% of the activity being present in lactate dehydrogenase isoenzyme-1 (LD1). At the time of death, the total lactate dehydrogenase activity had increased still further, 77% of it being in the LD1 fraction. Both the tumor and its hepatic metastases were shown to have a supranormally active LD1 fraction. These patterns appear to be attributable to an increased synthesis of the "H" subunit by the tumor.
Standardization of Serum Ceruloplasmin Concentrations in International Enzyme Units with o-Dianisidine Dihydrochloride as Substrate
Authors: Lehmann H Peter , Schosinsky Karl H , Beeler Myrton F 
Published: January 2020

Abstract
We describe a method for calculating the absorptivity (in terms of substrate consumed) of the colored solution obtained when o-dianisidine dihydrochloride is oxidized by ceruloplasmin. By oxidizing o-dianisidine dihydrochloride with known amounts of hydrogen peroxide we could determine that the molar reacting ratio of o-dianisidine to hydrogen peroxide is 2:1. So calculated, absorptivity is 9.6 ml µmol-1 cm-1, the figure used to estimate ceruloplasmin oxidase activity in terms of International Units.
Parameters Affecting a Rapid Method In Which Sephadex Is Used to Determine the Percentage of Free Thyroxine in Serum
Authors: Levinson Stanley S , Rieder Sidney V 
Published: January 2020

Abstract
In this method, Sephadex is used to assess the percentage of free thyroxine in undiluted sera. We demonstrate that if temperature and amount of Sephadex are kept constant, reproducibility is excellent. When Sephadex is exposed to serum, equilibration between thyroxine and thyroxine-binding components of the system is instantaneous. Because it is so rapid, it is not possible to measure the true physiological fraction of free thyroxine in serum with any free-thyroxine-binding resin, but the method does give an accurate measure of fluctuations in percentage of free thyroxine, as indicated by the high correlation with values for percentage of free thyroxine as determined by equilibrium dialysis and by the appropriate response to additions of exogenous thyroxine and dilution of the serum.
Evaluation of a New Device for Rapidly Separating Serum or Plasma from Blood
Authors: Mathies James C 
Published: January 2020

Abstract
I have evaluated the suitability of a new device for the rapid and efficient separation of cell-free serum or plasma from whole blood. Thirty-four clinical chemistry procedures were used in the analysis of 750 paired blood samples. One sample from each pair was processed by double centrifugation, the other by single centrifugation with the new device. Differences between means for the paired samples were evaluated by Student's t-test. At a significance level of P ≤ 0.05, only uric acid, lactate dehydrogenase, lactate dehydrogenase isoenzyme 2, and CO2 show a statistically significant difference between the two separation procedures. These differences do not appear to be of sufficient magnitude to preclude use of the device in the clinical chemistry laboratory.
Sources of Error in Determining Lead in Blood by Atomic Absorption Spectrophotometry
Authors: Kopito Louis E , Davis Michael A , Shwachman Harry 
Published: January 2020

Abstract
203Pb was used to monitor sample-preparation techniques used in four atomic absorption methods for determination of lead in blood. Sources of error and their magnitude were identified and measured for each of the following analytical procedures: precipitation with trichloroacetic acid, separation with ammonium pyrrolidine dithiocarbonate into methyl isobutyl ketone, digestion with acids, and coprecipitation with bismuth and direct analysis after a "nonextraction" procedure. The determination of lead in blood supplemented with inorganic lead was compared with that of naturally bound lead obtained from experimentally poisoned animals. Because of differences in in vivo and in vitro lead binding, recovery of added inorganic lead may not accurately reflect the fate of endogenous lead in some analytical procedures.
New Method for Rapid Determination of Carboxyhemoglobin by Use of Double-Wavelength Spectrophotometry
Authors: Ramieri Alfred , Jatlow Peter , Seligson David 
Published: January 2020

Abstract
We have developed a simple method for rapid determination of carboxyhemoglobin concentration in blood, by use of double-wavelength spectrophotometry. The absorbance of both oxyhemoglobin and reduced hemoglobin are instrumentally nulled out in this procedure, so that the absorption signal reflects HbCO and only a single spectrophotometric reading is required. This procedure is accurate in the range encountered in ambulatory persons as well as in the "toxic" range. Results correlated well with the dithionite reduction procedure. The stability of carboxyhemoglobin in solution was investigated and concentrations of carbon monoxide in groups of smokers and nonsmokers were determined.
Use of the Carbon Rod Atomizer for Direct Analysis of Lead in Blood
Authors: Kubasik Norman P , Volosin Michael T 
Published: January 2020

Abstract
A method is described for direct analysis of lead in blood utilizing the carbon rod atomizer. Aliquots of whole blood are analyzed without pre-treatment. Results are comparable to those for a similar non-flame technique in which whole blood samples were prediluted with "Triton X-100." The small sample volumes required and the minimal sample preparation further diminish the possibility of spurious contamination.
Faster and Easier Radioimmunoassay of Digoxin
Authors: Drewes Patricia A , Pileggi Vincent J 
Published: January 2020

Abstract
We describe an improved radioimmunoassay method for serum digoxin, with 125I as tracer, to eliminate the problems that endanger the validity of this assay: apparent instability of tracer, time-dependence of charcoal separation of free and bound fractions, and influence of sample-to-sample differences on results. Principal innovations leading to a more rugged and reliable test are the use of (a) a stable [125I] tyros ine-methyl-ester of digoxin, (b) ammonium sulfate to separate bound and free fractions, (c) a fresh serum pool for the standard curve, and (d) individual specimen blanks. Results compare favorably with those of the properly-controlled, original tritium method of Smith et al. [New Engi. J. Med. 281, 1212 (1969)] in terms of digoxin values, while the method excels it in convenience and speed. Between-run precision is 11% (CV) over the range of interest (mean, 2.7 µg/liter), sensitivity is 0.2 µg/liter, and recovery of added digoxin averages 102%.
Dual-Precipitation Method for Lipoprotein Quantitation: Improvement by Membrane Ultrafiltration of Lipemic Samples
Authors: Wilson Dana E , Done Gregory A 
Published: January 2020

Abstract
Plasma lipoproteins can be measured by the clinical laboratory after the major lipoprotein classes have been separated by two precipitation steps, one of which is the aggregation of very-low-density lipoproteins (VLDL) by the detergent, sodium dodecyl sulfate. Lipoprotein concentrations are expressed in terms of the cholesterol concentration within each class. However, incomplete removal of aggregated VLDL has led to serious analytical errors in a few lipemic subjects. We tested the efficacy of a membrane ultrafiltration step in removal of aggregated VLDL in three patients with plasma triglyceride concentrations of 540 to 12 560 mg/dl. Preliminary membrane ultrafiltration to remove the aggregated VLDL improved the precision of the method and is recommended for the analysis of grossly lipemic samples.
Multivariate Analysis of Serum Protein Assays in Chronic Hepatitis and Postnecrotic Cirrhosis
Authors: Agostoni Angelo , Marasini Bianca , Stabilini Roberto , Del Ninno Ersilio , Pontello Mirella 
Published: January 2020

Abstract
Pre-albumin, albumin, orosomucoid, α-antitrypsin, α-macroglobulin, β1A-globulin, IgG, IgA, and IgM were assayed in the serum of patients with chronic persistent hepatitis, chronic aggressive hepatitis, and postnecrotic cirrhosis. When results were evaluated by multivariate analysis, a good discrimination was obtained, especially between chronic aggressive hepatitis and postnecrotic cirrhosis.
Gas-Liquid Chromatographic Procedure for Measurement of Methylphenidate Hydrochloride and Its Metabolite, Ritalinic Acid, in Urine
Authors: Wells Rhondda , Hammond Keith B , Rodgerson Denis O 
Published: January 2020

Abstract
A gas-liquid chromatographic procedure has been developed for measuring methylphenidate and its metabolite, ritalinic acid, in urine. The unchanged drug is extracted into chloroform from alkalinized urine together with an internal standard, diphenhydramine. The solvent is removed, the residue dissolved in ethanol, and aliquots are injected into a gas-chromatographic column containing 3% OV-17. Ritalinic acid is recovered from the urine by lyophilizing the aqueous phase remaining after the unchanged methylphenidate is extracted into chloroform. The ritalinic acid is methylated with diazomethane to form methylphenidate, which is then assayed as described. Recovery of methylphenidate added to normal urine was quantitative and reproducible (CV, 3.2%). Ritalinic acid added to drug-free urine was recovered with an efficiency of 90-98%, but somewhat less reproducibly (CV, 12.8%). No interfering substances were found in normal urines. Between 35-98% of a single therapeutic (10 mg) dose given to hyperkinetic children could be recovered from the urine collected during the 6 h immediately after the dose. Only a small proportion was excreted as the unchanged drug (0.8-11.0%), the remainder being excreted as ritalinic acid.
Detection and Measurement of Total Bilirubin in Serum, with Use of Surfactants as Solubilizing Agents
Authors: Pearlman Frederick C , Lee Robert T Y 
Published: January 2020

Abstract
We describe a new method for measuring total bilirubin in serum. Nonionic, cationic, or anionic surfactants can be used as solubilizing agents to promote the diazo coupling of indirect-reacting bilirubin. A representative surfactant—azobilirubin system is illustrated, in which absorbance is maximum at 560 nm and linear to a concentration of 200 mg of bilirubin per liter. At pH 2.5 and in the presence of Du ponol (an anionic surfactant), bilirubin is completely coupled within 6 mm at 37 °C. All ingredients required for an assay are combined in two dry reagents, which are stable for a year at room temperature. Sensitivity is comparable to that of procedures routinely used in clinical laboratories; precision, linearity, and stability of the reagents in solution are excellent. Results for fresh sera correlated well with those obtained by the Jendrassik—Grof method. Hemolysis is minimized and turbidity eliminated.
Mechanism of Interference by Uric Acid in the Glucose Oxidase/Peroxidase Method for Serum Glucose
Authors: Chinh Nguyen H 
Published: January 2020

Abstract
Uric acid lowers the value for glucose as determined by the "GOD-Perid" method. To localize the interference by uric acid, we investigated each step of the reaction. Bleaching of the final color is the only source of such interference.
Advantages and Disadvantages of Nephelometric Measurement of Serum Lipids
Authors: Baer Daniel M 
Published: January 2020

Abstract
Several technical difficulties diminish the usefulness of serum triglyceride estimation by the method of Stone and Thorp [Clin. Chim. Acta 14, 812 (1966)]. An artificial and somewhat unstable material is used in the standardization. Falsely elevated readings caused by scratched cuvettes are a frequent problem. Conventional quality-control procedures cannot be used because stable preparations are not available. Specimen stability is a greater problem than with conventional chemical methods. In spite of these difficulties, the method can be useful, if its limitations are recognized, in measurements made on nonfasting individuals.
Development and Application of a Radioimmunoassay for Plasma Glucagon
Authors: Sperling Mark A , DeLamater Paul V , Kazenelson Mirtha , Fiser Robert H , Fisher Delbert A 
Published: January 2020

Abstract
We report sensitive radioimmunoassay procedures for glucagon-like immunoreactivity and for pancreatic glucagon, with use of antisera generated in rabbits by the injection of glucagon covalently coupled to thyroglobulin. Optimum assay conditions were determined. These assays have absolute limits of sensitivity of 10 to 20 pg, an intra-assay coefficient of variation of 8%, and an inter-assay coefficient of variation of up to 22%. In human infants 30 minutes after birth, glucagon concentration was 227 ± 27 pg/ml (SEM), and glucagon-like immunoreactivity increased sharply with oral feeding. In children and adolescents, plasma glucagon concentrations during fasting, the increase in response to arginine stimulation, and the suppression after oral glucose loading were similar to values previously reported in adults. Problems inherent in the methodology for measuring plasma glucagon are discussed.
Measurement of IgG and Albumin Content of Cerebrospinal Fluid, and its Interpretation
Authors: Ganrot Karin , Laurell Carl-Bertil 
Published: January 2020

Abstract
A high correlation (r = 0.85) normally exists between the concentration of albumin and of IgG in cerebrospinal fluid (CSF). The correlation is still better (r = 0.96) if the concentrations of the two proteins are also measured in plasma and the CSF/ plasma ratios compared for albumin and IgG. The scatter diagram for these ratios in persons without disease of the nervous system is most useful as a reference when differentiating between local IgG production in the subarachnoid space and an increase in CSF protein for other reasons. The analysis can be performed on less than 0.1 ml of CSF, in contrast to agarose-gel electrophoresis, for which 5-10 ml is necessary.
Comparative Study of a Micro-Scale Test for Lead in Blood, for Use in Mass Screening Programs
Authors: Cooke Richard E , Glynn Kathryn L , Ullmann William W , Lurie Nicole , Lepow Martha 
Published: January 2020

Abstract
A procedure suitable for the mass screening of children for an undue body burden of lead was tested on 170 clinic patients. Capillary finger-prick blood, collected on filter paper, was analyzed for lead with an atomic absorption spectrophotometer with the Delves cup attachment. This method of analysis had first been judged to be accurate after a laboratory evaluation in which results were compared with those obtained by a dithizone procedure. In the present study, both capillary and venous bloods were obtained from the patients. Venous bloods were also analyzed by the filter paper disk method and by an atomic absorption spectrophotometric procedure requiring a 5-ml sample. Results show that the screening method described here will reliably identify those children with a significantly supranormal blood lead. Both sample collection and laboratory analysis are easier.
Evaluation of Glucose-6-Phosphate Dehydrogenase from Leuconostoc mesenteroides in the Hexokinase Method for Determining Glucose in Serum
Authors: Bondar Richard J L , Mead Donna C 
Published: January 2020

Abstract
The hexokinase (EC 2.7.1.1)/glucose-6-phosphate dehydrogenase (I) (EC 1.1.1.49) method of glucose analysis is highly accurate, precise, and sensitive when I from Leuconostoc mesenteroides and NAD+ are used. Coefficients of variation ranged from 0.68 to 8.9% for glucose standards between 0.56 and 27.7 mmol/liter. Recovery was 103 ± 10% for glucose standards added to sera of known glucose content. Although no substances investigated interfere with the test system when present at their normal or likely concentrations in serum, final reaction mixtures containing mannose (&gt;0.28 mmol/liter), fructose (3.7 mmol/liter), or 2-deoxy-D-glucose (4.01 mmol/liter) inhibit the analysis. With all constituents lyophilized, the reagent mixture is stable for at least a year at 4 °C and for five days at 40 °C. Within-day reproducibility averaged 0.83%; day-to-day precision was 1.3%. We compared results of hexokinase/glucose procedures by using I from yeast (with NADP+) and from L. mesenteroides (with either NAD+ or NADP+ as coenzyme); there was complete correlation over a serum glucose range of 4 to 12 mmol/liter (72 to 217 mg/dl). Use of NAD+ with I from L. mesenteroides is advantageous because of the decreased cost and greater stability of the coenzyme.
Urinary Excretion of Non-nitrogenous Organic Acids by Healthy Infants and Children
Authors: Aksu Asian , Morrow Grant , Barness Lewis A 
Published: January 2020

Abstract
We have quantitated 14 non-nitrogenous organic acids in the urine of infants and children. Excretion values are calculated as total milligrams per day, milligrams per kilogram body weight per day, and milligrams per milligram of urinary creatinine. The correlation with creatinine excretion is high; thus, meaningful data can be obtained from casual samples of urines.