bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectrophotometric screening method for acetaminophen in serum and plasma.
Authors: Liu T Z , Oka K H 
Published: January 2020

Abstract
We describe a simple, economical procedure for rapidly detecting acetaminophen in serum or plasma. The method is based upon the reduction by the drug of ferric 2,4,6-tris(2-pyridyl)-s-triazine, at an acidic pH, to ferrous 2,4,6-tris(2-pyridyl)-S-triazine complex, which absorbs maximally at 593 nm. Absorbance and acetaminophen concentration are linearly related from 25 to 400 mg/L, and so therapeutic and toxic concentrations can be measured. The method is accurate; day-to-day CV's for two pooled control specimens (103 and 227 mg/L) were 4.4 and 6.6%. Correlation studies, with an established nitration method and with the free-radical diphenylpicrylhydrazyl dye method, showed correlation coefficients of 0.985 and 0.915, respectively. Of 25 commonly used drugs tested, only levodopa, oxyphenylbutazone, and phenylephrine interfere significantly. Interference from salicylate, salicylamide, and phenylbutazone was insignificant.
Metastable creatine kinase MM and complexes of creatine kinase BB and immunoglobulin G, "atypical" isoenzymes with similar electrophoretic mobility.
Authors: Homburger H A , Wold L , Jacob G L , O'Brien J 
Published: January 2020

Abstract
Metastable creatine kinase MM isoenzyme was isolated and partially purified from homogenates of myocardium and skeletal muscle by gradient elution on carboxymethyl cellulose. This variant isoenzyme migrated between the MM and MB isoenzymes on agarose electrophoresis, accounted for 3.5% of the total creatine kinase activity in each tissue, was not a macromolecule, and had stable electrophoretic mobility only in borate buffer (0.02 mol/L). By comparison, the creatine kinase isoenzymes with similar "atypical" electrophoretic mobility in serum specimens were complexes of the BB isoenzyme and immunoglobulin G. These complexes were measured by a radioimmunoassay specific for the creatine kinase B-subunit and eluted predominantly with the MB isoenzyme in a commercial anion-exchange reagent system.
A fully automated, continuous-flow radioimmunoassay for methotrexate.
Authors: Kamel R , Landon J , Forrest G C 
Published: January 2020

Abstract
We describe a fully automated continuous-flow radioimmunoassay for methotrexate. [125I]Histamine-labeled methotrexate was used as tracer. Anti-methotrexate serum was coupled to a magnetizable solid-phase and the bound and free fractions were separated with an electromagnetic field. The assay is precise (CV less than 2.5%) and rapid (30 samples per hour), incubation volume is small (about 160 micro L), and incubation brief (10 min). The accurate timing inherent in the system obviates the need to attain equilibrium, so that assay of each sample takes only 15 min. The assay is sensitive (1--100 microgram/L). There is no significant carryover between samples of high and low concentration. Results by the automated method correlated well with those by both a manual assay in which the same reagents and separation technique are used (r - 0.99) and a competitive protein-binding assay (r = 0.96).
Bilirubin binding by primary sites of human serum albumin, with suppression of secondary-site interference by use of a high salt concentration.
Authors: Rutkowski R B 
Published: January 2020

Abstract
A high (2.0 mol/L) NaCl concentration apparently suppresses the secondary-site binding of bilirubin by human serum albumin. Thus if an excess of bilirubin is added to human serum albumin or to neonatal serum in buffer containing 0.1 mol of tris(hydroxymethyl)aminomethane and 2.0 mol of NaCl per liter (pH 7.5), and the bilirubin not bound to albumin is removed by treatment with calcium carbonate, the bilirubin binding reserve of primary binding sites can be estimated from direct measurement of spectral absorbance at 468 nm. Hemolysis and conjugated bilirubin apparently do not interfere. In a comparison study with serum samples from neonates the method gave results that generally agreed with those obtained by a commercially available Sephadex G-25 column procedure. In serum samples from adults the calculated unbound unconjugated bilirubin (free bilirubin) values derived by using binding reserves determined by the proposed method correlated well with the free bilirubin concentrations measured by a peroxidase method, but were only about one-half the amounts obtained by the peroxidase method.
Monitoring clorazepate dipotassium as desmethyldiazepam in plasma by electron-capture gas--liquid chromatography.
Authors: Haidukewych D , Rodin E A , Davenport R 
Published: January 2020

Abstract
We describe a procedure for determing clorazepate dipotassium as its decarboxylated, pharmacologically active metabolite, desmethyldiazepam, in 100 microL of plasma, with use of electron-capture gas--liquid chromatography and with methylnitrazepam as the internal standard. The procedure is a one-tube, one-step extraction without derivative formation and is accurate, reproducible, and rapid. The sensitivity limit is 20 micrograms/L. Within-run and between-run CV's (concentration, 3.5 mg/L) were 2.9 and 3.5%, respectively. Within-run CV's for 1.5 and 1.0 mg/L concentrations were 3.9 and 4.3%, respectively. For a 1.0 mg/kg per day dose of clorazepate dipotassium, the mean steady-state concentration of desmethyldiazepam in plasma was 1.037 mg/L.
New perspectives in coagulation testing.
Authors: Fareed J , Messmore H L , Bermes E W 
Published: January 2020

Abstract
The field of coagulation testing has undergone some major technological and conceptual developments, which are briefly reviewed here. The assessment of coagulation parameters is no longer restricted to the study of clot formation and its dissolution. The understanding of the biochemical nature of coagulation processes, coupled with the development of new therapeutic agents in the treatment of hemostatic disorders, has brought about the development of fast, reliable, and clearly defined laboratory test procedures to evaluate the components of this system. The introduction of methods involving synthetic substrates has been very significant because many of the coagulation parameters can now be measured with a spectrophotometer or fluorometer, by methods that lend themselves to the automation found in most large clinical chemistry laboratories. In our laboratory, we use automated synthetic-substrate methods for antithrombin-III, plasminogen, and prothrombin, and are developing the synthetic-substrate assay equivalent of clot-based prothrombin time and partial thromboplastin. Immunological methods such as laser/rate nephelometry, enzyme-linked immunoassays, electroimmunodiffusion, and radioimmunoassays have been utilized to evaluate coagulation proteins. The relation of functional and immunological properties of these proteins to their physiological function is being studied. In coming years the testing of coagulation function will undergo some major changes and will require input from clinical chemists and other laboratory scientists to facilitate the technology transfer and proper standardization of new methods.
Use of electrochemical sensors for on-line monitoring of ionized calcium, potassium, and glucose in whole blood of living dogs.
Authors: Fogt E J , Eddy A R , Clemens A H , Fox J , Heath H 
Published: January 2020

Abstract
We report the development and evaluation of electrochemical sensors for continuous on-line measurement of whole-blood ionized calcium, potassium, and glucose in living animals. Ionized calcium and potassium are measured with ion-selective electrodes, by using a unique differential approach. A polarographic sensor coupled with a membrane with bound glucose oxidase is used in the glucose analyzer. The modular concept of instrument design permits one mainframe, computer, and pump system to house any analyzer module or a combination of modules. A small volume of venous blood (about 2 mL/h) is continuously withdrawn from the subject through a double-lumen catheter and pumped through the analyzer(s). Results of in vitro correlation studies and studies in normal dogs (including responses of ionized calcium, potassium, and glucose to various stresses) support the validity of the measurements.
Automated multiple flow-injection analysis in clinical chemistry: determination of total protein with Biuret reagent.
Authors: Shideler C E , Stewart K K , Crump J , Wills M R , Savory J , Renoe B W 
Published: January 2020

Abstract
We have examined the feasibility of the automated multiple flow-injection technique for application to clinical chemistry by adapting to this system the biuret method for the determination of total protein. Samples were discretely and rapidly introduced into a continuously flowing, nonsegmented reagent stream by means of an automatic sampler and high-pressure injection valve. Pumps operating at 1380-2070 kPa (200-300 psi) were utilized to introduce the biuret reagent and saline diluent into the system separately at flow rates of 72 and 47 microL/s, respectively. Use of 20-microL sample and a 3.0-s reaction-delay coil was adequately sensitive for analysis for total protein by this method. Samples were analyzed at a rate of 150/h with no detectable between-sample carryover. Within-run precision studies yielded relative standard deviations of 2.5% and less. Total protein values obtained by this method correlated well with those obtained by centrifugal analyzer and bubble-segmented continuous-flow biuret methods.
Monitoring serum valproic acid by gas chromatography with electron-capture detection.
Authors: Chan S C 
Published: January 2020

Abstract
I have developed a procedure to monitor, by gas chromatography with electron-capture detection, the concentration of valproic acid in serum. The valproic acid is derivatized into its phenacyl ester. The assay is very sensitive, measuring as little as 100 pg of valproic acid easily and accurately. Solvent extraction and concentration of the drug are not necessary; instead, one only has to precipitate the serum proteins. n-Octanoic acid is used as the internal standard. The peak-height ratio of phenacyl valproate to phenacyl octanoate is linearly related to concentration up to 200 mg of valproic acid per liter.
Kinetic immunoturbidimetric measurement of thyroxine binding globulin.
Authors: Spencer K , Price C P 
Published: January 2020

Abstract
We describe the extension of kinetic immunoturbidimetry to measurement of low-concentration proteins in serum, specifically thyroxine binding globulin. Method performance is superior to that of currently available direct assays for this protein by radioimmunoassay or the Laurell "rocket" techniques. The assay is rapid (1-min measurement period), economical, and results compare well with those by established techniques. The technique has wide applicability to instruments with kinetic measuring ability and could provide a useful support to other non-isotopic thyroid-function tests. The assay further emphasizes the sensitivity and usefulness of kinetic immunoturbidimetry for measuring low concentrations of proteins.
Monitoring 2-ethyl-2-phenylmalonamide in serum by gas-liquid chromatography: application to retrospective study in epilepsy patients dosed with primidone.
Authors: Haidukewych D , Rodin E A 
Published: January 2020

Abstract
We describe a procedure for determining 2-ethyl-2-phenylmalonamide (I) in serum of epilepsy patients dosed with primidone (II) for seizure control, by extracting the sample with chloroform under basic conditions, with use of an internal standard, 2-ethyl-2-(p-tolyl)malonamide, and without derivative formation. The sensitivity limit is 1.0 mg/L. Within-run CVs for 5, 10, and 30 mg/L concentrations were 3.5, 2.5, and 0.7%, respectively. For a 1.0 mg/kg body wt per day dose of II in patients co-medicated with phenytoin (Group A), the mean steady-state concentrations of I, II, and phenobarbital (III) were 0.72, 0.62, and 2.24 mg/L, respectively. For patients co-medicated with carbamazepine and phenytoin (Group B), I, II, and III concentrations were 0.68, 0.44, and 2.12 mg/L, respectively. Between these groups, only for II were the concentrations statistically different (t = 2.762; p &lt; 0.01). For Group A no correlation was found between II and III. For Groups A and B, the coefficients of correlation between I and III were 0.626 and 0.826, respectively.
Comparability of results by simplified methods for measuring serum lipoprotein cholesterol in a pediatric population.
Authors: Srinivasan S R , Foster T A , Berenson G S 
Published: January 2020

Abstract
We compared serum lipoprotein cholesterol concentrations in a randomly selected subsample (n = 406) population of children (ages 5 to 17 years), as measured by the heparin-Ca2+ and the heparin-Mn2+ precipitation methods. Statistical analysis showed significant differences between results by these methods, especially in values for VLDL- and HDL-cholesterol (mean difference: VLDL-cholesterol, -61 mg/L; HDL-cholesterol, + 108 mg/L). Lipoprotein electrophoretic data indicated that estimating VLDL-cholesterol from serum triglyceride concentrations invariably resulted in higher values for children with an extremely faint pre-beta-lipoprotein band. Among the HDL-subfractions, 14 to 20% of HDL2 was precipitated by heparin-Mn2+ despite the presence of 80 g of albumin per liter. Heparin affinity chromatography of HDL2 in the presence of Ca2+ and Mn2+ showed an interaction of apolipoprotein E-containing HDL2 subfraction only in conditions involving Mn2+. The heparin-Ca2+ procedure precipitated the equivalent of 2 g of beta- plus pre-beta-lipoprotein cholesterol per liter from serum, with no detectable apolipoprotein B in the supernate. We conclude that these precipitations are affected by cation specificity and by differences in lipoprotein makeup of a given individual or population group.
Spectrophotometric micro method for measurement of dialyzable calcium by use of cresolphthalein complexone and continuous-flow analysis.
Authors: Toffaletti J , Kirvan K 
Published: January 2020

Abstract
We adapted a method for dialyzable calcium from fluorometric detection by use of calcein to a more specific spectrophotometric determination with cresolphthalein complexone. The reagents are available commercially and perform satisfactorily with respect to noise level, drift, stability, and sensitivity. Construction of the continuous-flow manifold with commercially available components (injection blocks, coils, and dialyzer) and the use of a 9-mm pathlength flow cell in an AutoAnalyzer I colorimeter have permitted a sampling rate of 70/h, and decreased the volume of serum required to 130 microL. A comparison of 71 sera analyzed by the present and the calcein method gave means of 1.39 (SD 0.14) and 1.39 (SD 0.13) mmol/L, respectively. The regression equation was: present method = 1.016 calcein--0.022 mmol/L (r = 0.97). The CV for the new method, as determined from 46 randomized duplicate analyses, was &lt; 1%. The reference interval, as evaluated from results for 93 different individuals, was 1.26-1.43 mmol/L. We conclude that our methods is an improvement with respect to noise level, drift, specificity, detectability, and more general availability of instrumentation. Moreover, the smaller sample volume required makes possible the routine measurement of dialyzable calcium in pediatric samples.
Radioimmunoassay of human thyroglobulin with use of "thyroglobulin-free" plasma prepared by ultracentrifugation as diluent.
Authors: Ikekubo K , Jutton J , Schneider A B 
Published: January 2020

Abstract
We describe the preparation and evaluation of a new diluent for use in preparing standard curves for the radioimmunoassay of human thyroglobulin (TG). This diluent, "TG-free human plasma, allows measurement of TG in lower concentrations than with previous assay systems because the components of the standards are more similar to those of the samples. TG-free plasma was prepared by a modification of the differential centrifugation method of Edelhoch (J. Biol. Chem. 235:1326, 1960). Standard curves prepared by use of TG-free plasma and plasma obtained from thyroidectomized patients were identical. In our assay, plasma from patients who had undergone total thyroidectomy produced no displacement when 25 to 100 microL of plasma was assayed. Twenty-five normal subjects all had detectable TG concentrations, ranging from 4.0 to 25.7 microgram/L. Only 27 of 2000 determinations performed by this new method had undetectable values and 26 of these were from patients with total or near-total thyroidectomies. TG concentration determined by this assay may be more sensitive for finding recurrent thyroid malignancy.
Rapid sodium dodecyl sulfat/polyacrylamide gel electrophoresis of urinary proteins.
Authors: Cachera C , Mizon C , Fruchart J C , Mizon J , Tacquet A 
Published: January 2020

Abstract
We describe a procedure for the convenient separation of proteins by sodium dodecyl sulfate/polyacrylamide gel electrophoresis of urine from cases of renal disease. A precipitation method that requires no special apparatus was used to concentrate the urinary proteins; for electrophoretic separation we used a commercially supplied polyacrylamide/cellulose gel slab. This method seems to be valuable for investigation of proteinuria; we recommend it for routine use.
Cofactor in serum for high-affinity folate binding in milk.
Authors: Holm J , Hansen S I , Lyngbye J 
Published: January 2020

Abstract
Affinity-chromatographic purification of the folate-binding protein from whey of cow's milk results in the removal of a heat-resistant cofactor that is important in high-affinity folate binding (Biochim, Biophys. Acta 579: 479, 1979). Thus a shift from negative to positive cooperativity occurred in the presence of cofactor (Biochim, Biophys. Acta 579: 479, 1979). We demonstrate the presence of a similar cofactor in sera from men, pregnant women, and umbilical cords. Even highly diluted (10 000-fold) serum samples were active, and the cofactor was also present in erythrocyte hemolysates (10 000-fold diluted). The identity of the cofactor, which may act as an overall modulator of high-affinity folate binding, is still obscure.
Quantitation of serum gentamicin concentration by a solid-phase immunofluorescence method.
Authors: Tsay Y , Wilson L , Keefe E 
Published: January 2020

Abstract
We describe the use of a solid-phase immunofluorescence method (FIAX system) for measuring drug concentrations, specifically gentamicin, in serum or plasma. Antibody to gentamicin is immobilized on a polymeric surface. This Sampler is immersed in a mixture of serum standard or unknown and a buffered solution of fluorescent-labeled gentamicin. After 30 min, the fluorescence of the specifically bound labeled gentamicin is measured with a fluorometer. The assay detects gentamicin in concentrations as low as 50 mug/L. It is specific for gentamicin, cross reactivity to some other therapeutic drugs, except netilmicin and sisomicin, being low. Results by this assay compare well with those by a radioimmunoassay (r = 0.94) and a radioenzymic assay (r = 0.95). The assay is specific, economical, simply performed, requires little pipetting, and does not involve the use of radioisotopes.
Trimethoprim interferes with serum methotrexate assay by the competitive protein binding technique.
Authors: Hande K , Gober J , Fletcher R 
Published: January 2020

Abstract
Administration of Bactrim (a combination of trimethoprim and sulfamethoxazole) to a patient who also was receiving methotrexate caused a significant increase in apparent plasma methotrexate concentrations as determined by competitive protein binding assay with use of dihydrofolate reductase (EC 1.5.1.3) from Lactobacillus casei as the binding protein. This spurious increase was caused by trimethoprim in the patient's plasma. A plasma trimethoprim concentration of 0.1 mg/L inhibited binding of radiolabeled methotrexate to dihydrofolate reductase by 50%. In contrast, radioimmunoassay for methotrexate was not affected by concomitant administration of trimethoprim. The competitive protein binding assay for methotrexate should not be used in patients being treated with Bactrim or Septra (a similar combination). However, the L. casei competitive protein binding assay technique can be used to assay plasma trimethoprim concentrations with sensitivity to 0.02 mg of trimethoprim per liter.
Zinc concentrations in serum as related to myocardial infarction.
Authors: Lekakis J , Kalofoutis A 
Published: January 2020

Abstract
Zinc concentrations in serum from 99 patients with acute myocardial infarction were correlated with the incidence of further complications and with activities in serum of the "cardiac" enzymes aspartate aminotransferase and lactate dehydrogenase. A significantly subnormal zinc concentration was observed for the patients, the lowest values being observed on the second and third days after infarct, particularly in patients with serious complications. Moreover, a linear correlation was observed between zinc values and enzyme activities until the fourth day after infarct. We conclude that measurement of zinc in the serum may have diagnostic value for acute myocardial infarction, although its prognostic value is still speculative.
Photometric determination of glycosylation of hemoglobin in diabetes mellitus.
Authors: Subramaniam C V , Radhakrishnamurthy B , Berenson G S 
Published: January 2020

Abstract
We evaluated glycosylation of hemoglobin (HbA + HbA1) in 25 control subjects and in 133 diabetic patients who were in various stages of blood glucose control, by measuring ketoamine-linked hexoses in hemoglobin. These hexoses were converted by digestion with 10 mol/L acetic acid for 16 h at 100 +/- 5 degrees C to 5-hydroxymethylfurfuraldehyde, which was quantitated by reaction with 2-thiobarbituric acid. Glycosylation of hemoglobin was expressed as micromoles of hydroxymethylfurfuraldehyde per gram of globin protein (the "HMF index"). A mean HMF index of 1.67 (SD = 0.23) was obtained for controls; that for diabetic patients was 2.93 (SD 0.95). The index correlated well (r = 0.83, p &lt; 0.001) with average blood glucose concentration as measured during the preceding 16 weeks, over a wide range of glucose values (1 to 6 g/L). It correlated even better (r = 0.92, p &lt; 0.001) when corrected for variations in hemoglobin concentration. Thus measurement of ketoamine-linked hexoses of hemoglobin or HMF index provides an independent and useful alternative to the currently used methods that measure only HbA1 or HbA1c.
Direct, fixed-time kinetic assays for beta-hydroxybutyrate and acetoacetate with a centrifugal analyzer or a computer-backed spectrophotometer.
Authors: Li P K , Lee J T , MacGillivray M H , Schaefer P A , Siegel J H 
Published: January 2020

Abstract
In the course of studying the control of blood glucose in juvenile onset diabetics, we developed convenient methods for determining beta-hydroxybutyrate and acetoacetate. Here we describe fixed-time, enzymic, reaction-rate procedures for directly measuring these organic acids with a centrifugal analyzer (Rotochem IIA/36) or a computer-backed spectrophotometer (Gilford 102 system). In either case, the method requires only 20 micro L of plasma; is rapid, accurate, and precise; and analytical recovery is quantitative. Data are presented comparing results obtained with both instruments. Metabolic acidosis can be rapidly assessed and monitored with these methods, as illustrated by an example.