bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flash-Heater Ethylation of Some Antiepileptic Drugs
Authors: Friel Patrick , Troupin Allan S 
Published: January 2020

Abstract
We describe a modification of the MacGee method [Anal. Chem. 42, 421 ( 1970)] for rapid determination of phenytoin (diphenylhydantoin) in plasma by gas—liquid chromatography, in which an ethylating reagent is used instead of the more common methylating reagents. With this modification, several N-methylated antiepileptic drugs can be separated from their demethylated metabolites. Our results agree well with those of Butler and Waddell [Neurology 8, 106 ( 1958)], who showed that in patients receiving the N-methylated compounds mephenytoin and mephobarbital, the N-demethylated products, 5-ethyl-5-phenylhydantoin and phenobarbital are found in higher concentrations in plasma than are their respective parent drugs. The method is also useful for routine determinations of phenobarbital, primidone, and phenytoin in serum, cerebrospinal fluid, or saliva.
Simple Manual Procedure for Determination of Serum Triglycerides
Authors: Mendez Jose , Franklin Barry , Gahagan Harry 
Published: January 2020

Abstract
We describe a modified method for determining serum triglycerides (triacylglycerols), which is based on the heptane extraction procedure of Gottfried and Rosenberg [Clin. Chem. 19, 1077 (1973)] with the stable saponification, oxidation, and color development reagents of Neri and Frings [Clin. Chem. 19, 1201 (1973)]. This modified method eliminates one heating step, reduces saponification time to 5 min, absorbances are read at room temperature, and the calibration curve is linear to 3.0 g/liter. A sample comparison between the proposed method and the automated Block and Jarrett [Am. J. Med. Technol. 35, 1 (1969)] procedure showed no significant difference (r = 0.98). The coefficient of variation (47 duplicate samples) for the modified method was 6.3%. Further validation was obtained from analysis of quality-control samples; the proposed method gave equivalent values.
A Radioimmunoassay for Isoniazid
Authors: Schwenk Robert , Kelly Kenneth , Tse Kam S , Sehon Alec H 
Published: January 2020

Abstract
A sensitive radioimmunoassay is described, for measuring isoniazid in therapeutic and subtherapeutic concentrations. This radioimmunoassay was used in an exploratory clinical study to measure, as a function of time, the concentration of this drug in plasma of patients receiving isoniazid therapy.
Colorimetric Enzymatic Determination of Serum Total Carbon Dioxide, as Applied to the Vickers Multichannel 300 Discrete Analyzer
Authors: Norris Kenneth A , Atkinson Alan R , Smith William G 
Published: January 2020

Abstract
Phosphoenolpyruvate carboxylase (EC 4.1.1.31) has been used in developing a simple, inexpensive colorimetric assay for serum total carbon dioxide in an open system. The oxaloacetate formed by the action of the enzyme on bicarbonate and phosphoenolpyruvate is measured by use of the diazonium salt of Fast Violet B. Interferences from bilirubin, pyruvate, and drugs are negligible. Acetoacetate interference is significant only in highly ketotic samples, and a serum blank corrects for it. Serum protein interference is equivalent to 3.3 ± 1.25 mmol of CO2 per liter and hence is sufficiently constant to be corrected for by use of a serum standard or serum blank. The method has been applied to the Vickers M-300 and D-300 systems and within-batch standard deviations of ±0.1 to ±0.6 mmol/liter have been observed. Excellent correlation with orthodox techniques has been obtained.
Simultaneous Separation of Serum Creatine Kinase and Lactate Dehydrogenase Isoenzymes by Ion-Exchange Column Chromatography
Authors: Mercer Donald W 
Published: January 2020

Abstract
Lactate dehydrogenase isoenzymes were partially separated by use of a previously described column technique for creatine kinase [Clin. Chem. 20, 36 (1974)]. Extracts of lactate dehydrogenase-rich tissues were used to evaluate column resolution. Samples layered on mini-columns containing DEAE-Sephadex were eluted with Tris-buffered sodium chloride (100 and 200 mmol/ liter). Lactate dehydrogenase activity in column effluents was measured by the Wacker method, and their isoenzyme content was assessed by electrophoresis on polyacrylamide gel. Dehydrogenase isoenzymes 3, 4, and 5 were separated from isoenzymes 1 and 2, and the separation was tissue-specific and reproducible. The electrophoretic technique for isoenzymes 3, 4, and 5 gave values about 20% lower than did the column technique. Sera from 15 healthy laboratory technicians contained total lactate dehydrogenase, isoenzymes 1 and 2, and isoenzymes 3, 4, and 5 in the ranges 94 to 152, 34 to 64, and 38 to 75 U/liter, respectively. Activities of sera from 15 patients with acute myocardial infarction (total lactate dehydrogenase) ranged from 212 to 800 U/liter and lactate dehydrogenase isoenzymes 1 and 2 ranged from 138 to 628 U/liter. Lactate dehydrogenase and creatine kinase isoenzymes were rapidly and easily measured after being simultaneously separated. The procedure is specific and sensitive for following the post-infarct time course of changes in isoenzyme activities.
Interlaboratory Proficiency, Intermethod Comparison, and Calibrator Suitability in Assay of Serum Aspartate Aminotransferase Activity
Authors: Rej Robert , Fasce C F , Vanderlinde Raymond E 
Published: January 2020

Abstract
Sources of variation in assays of aspartate aminotransferase (EC 2.6.1.1) activity were examined in an interlaboratory survey and through an examination of materials used as calibration materials in these assays. Four highly stable lyophilized specimens containing human cytoplasmic enzyme, with activities of 0, 22, 46, and 96 U/liter at 30 °C and optimal substrate concentrations, were assayed by 319 laboratories. Mean values obtained on these specimens by laboratories using 2,4-dinitrophenylhydrazine kits varied among manufacturers and deviated from values expected from this procedure. The average coefficient of variation (CV) with these kits was &gt; 20%. Automated continuous-flow procedures with use of diazonium salt showed the best precision (av CV, &lt; 10%). However, the automated continuous-flow mAlate Dehydrogenase/Nadh Coupled Method Produced An Average Cv &gt; 20%. Results from each of the automated methods were related to a reference malate dehydrogenase/NADH coupled continuous kinetic assay method by temperature relationships alone. Mean values from manual diazonium salt procedures were 1.7-fold greater than similar reference values (av CV was 18%). The higher results were attributed to the use of poorly-defined units and to an artifact caused by chromophore stabilizers in this procedure when aqueous samples are used. The average CV in continuous kinetic methods varied among kit manufacturers, ranging from 6 to 28% for the specimen of highest activity. Variations in results were much larger at 366 nm than at 340 nm. Interassay relationships of these methods are presented. Concentrations of pyruvate in commercially available calibration materials differed between manufacturers, varied in stability, and deviated from the expected concentration. For some colorimetric assays the precision attained on reported absorbance values for the enzyme specimens was of the same order of magnitude as that for pyruvate standards. Other sources of error are revealed by the interlaboratory survey. The value of commercially available sources of enzyme activity as calibration or control materials was assessed by evaluating the following properties: activity at suboptimal concentrations of L-aspartate or 2-oxoglutarate, temperature effects, preincubation lability owing to aspartate and phosphate, pyridoxal phosphate saturation, contamination with glutamate dehydrogenase, and manufacturer's rated activity. These properties are compared to those of human cytoplasmic enzyme in a human serum matrix.
Modification of a Commercially Available Digoxin Radioimmunoassay Kit for Higher Precision
Authors: van der Vijgh W J F 
Published: January 2020

Abstract
The procedure prescribed for the Schwarz/Mann 125Idigoxin kit was modified with regard to pipetting and counting procedure. Incubation time with dextran-coated charcoal was also investigated. The modifications resulted in a significantly higher precision without introduction of a systematic error and the analysis time per eight-tube batch was decreased by 20 min.
High-Speed Quantitative Karyotyping by Flow Microfluorometry
Authors: Gray J W , Carrano A V , Moore D H , Steinmetz L L , Minkler J , Mayall B H , Mendelsohn M L , Van Dilla M A 
Published: January 2020

Abstract
We describe a new flow-system technique for highspeed quantitative karyotyping. Metaphase chromosomes are isolated from cells, stained with a DNA-specific fluorochrome, and individually measured for stain content at rates up to 105/min in a flow microfluorometer. The resulting distribution contains quantitative information about the relative frequency of occurrence and the chromosomal DNA content of the measured chromosomes. Such analyses of Chinese hamster chromosomes are in good agreement with independent results from scanning cytophotometry and with cytogenetic observations of the banded chromosomes. Analyses of two karyotypicaliy different clones of Chinese hamster M3-1 lines provide the quantitative characterization of two stable translocations. Initial data on human chromosomes are presented and agree well with results of scanning cytophotometry and suggest potential clinical applications as preparative and instrumental techniques improve.
Coagulation-Time Determination with Automatic Multivariable Analysis, by Use of a Miniature Centrifugal Fast Analyzer
Authors: Bostick W D , Bauer M L , Morton J M , Burtis C A 
Published: January 2020

Abstract
Use of a miniature Centrifugal Fast Analyzer for the parallel photometric monitoring of the coagulation process is shown to have a number of advantages. These include a choice of optical modes, virtually simultaneous initiation and observation of the coagulation process for a number of patient-plasma samples and an on-board control sample, small sample and reagent volume requirements, and automatic determination of a number of diagnostically useful variables (including relative fibrinogen content) from the data recorded in a single run. Also, the system is shown to give results that correlate well with those obtained by conventional techniques for determination of prothrombin time.
Simultaneous high-pressure liquid-chromatographic determination of some anticonvulsants in serum.
Authors: Adams R F , Vandemark F L 
Published: January 2020

Abstract
We describe procedures for simultaneously determining some anticonvulsants (phenobarbital, diphenylhydantoin, primidone, ethosuximide, methsuximide, carbamazepine) in serum by high-pressure liquid chromatography. The drugs, together with an internal standard, phenacetin, are adsorbed from serum onto charcoal and eluted from it with organic solvent. The eluate is analyzed isocratically on a reverse-phase column with a mobile phase consisting of acetonitrile/water (17/83 by volume). The eluted drugs are detected by their absorption at 195 nm, and quantities estimated from their peak areas as compared with those of extracted standards. Results are reproducible to about 6%. Sensitivities, for 0.5-ml serum samples, of 0.1 mg/liter for all the drugs analyzed except ethosuximide (0.5 mg/liter) are attained routinely. Correlation of results with gas chromatography was 0.912 for phenobarbital, 0.982 for diphenylhydantoin, 0.886 for primidone, and 0.966 for ethosuximide. Amobarbital and secobarbital interfere with the analysis; chlordiazepoxide, methaqualone, salicylate, diazepam, and oxazepam do not. Including extraction, analysis time for a single sample is 20 min.
Quantitative fractionation of alkaline phosphatase isoenzymes according to their thermostability.
Authors: PetitClerc C 
Published: January 2020

Abstract
Continuous monitoring of heat denaturation of a mixture of alkaline phosphatase isoenzymes at 60 degrees C and pH 7.5 permits the simultaneous direct identification and quantitation of three isoenzymes: the placental isoenzyme, the L-phenylalanine-sensitive intestinal isoenzyme, and the liver isoenzyme (hepatocytic). The isoenzyme that is principally of bone origin cannot be identified as such without the help of other diagnostic aids and the patient's medical history. All human tissues contain alkaline phosphatase, many organs more than one of the isoenzymes. Liver alkaline phosphatase, which constitutes 40-50% of normal serum alkaline phosphatase activity, was measured in the serum of persons with various liver diseases. Its activity exceeded normal in all types of liver disease; in 80% of cases this increase was accompanied by increased gamma-glutamyl-transferase activity, but the quantitative correlationship (r = 0.54) was not as good as expected if both enzymes come from the same source and are indices of liver dieases. Liver alkaline phosphatase activity increases in the blood early in liver disease, before most liver tests show abnormalities. The other major isoenzyme of normal serum probably represents a mixture of isoenzymes from bone and reticulo-endothelial and vascular tissues, which all contain the same "very heat-labile" alkaline phosphatase. Cord blood and children's sera contain mostly this very heat-labile isoenzyme.
Atypical increase in serum creatine kinase activity in hospital patients.
Authors: Sax S M , Moore J J , Giegel J L , Welsh M 
Published: January 2020

Abstract
We use an ion-exchange column-chromatographic technique for separating creatine kinase isoenzymes in serum, and occasionally observe what appears to be sustained increase in the MB fraction. Most patients whose sera show such behavior have myocardial disease, but not necessarily a recent myocardial infarction. Electrophoretic analysis of a small sampling of such sera revealed that the apparent MB migrates atypically, appearing distinctly between isoezymes MB and MM. In another electrophoretic system, the peak might easily be mistaken for MM. This unusual isoenzyme does not appear to be "macro" creatine kinase. In laboratories that use the ion-exchange technique, the possibility of a falsely positive MB value should be considered in subjects who show persistent increases together with normal or nearly normal values for total creatine kinase activity. A suitable electrophoretic method that clearly demonstrates this unusual isoenzyme should be used in such cases, for confirmation.
Use of cholesterol oxidase for assay of total and free cholesterol in serum by continuous-flow analysis.
Authors: Richmond W 
Published: January 2020

Abstract
Idescribe an assay for total cholesterol in serum, with use of the AutoAnalyzer ii (Technicon), in which cholesterol esters are saponified by alkali, cholesterol is held in aqueous micellar solution with a surfactant (Triton X-100) and oxidized by cholesterol oxidase, and the hydrogen peroxide produced is measured by chelation with Ti4+ and xylenol orange. An assay for free cholesterol in serum, based on similar principles, is also described, and the two can be run simultaneously on a dual-channel AutoAnalyzer II. Standard solutions of cholesterol in isopropanol have poorer carryover characteristics than sera, and therefore do not reach the same continuous-flow steady state as sera of equivalent concentrations. Consequent potential calibration errors are avoided by using micellar solutions of cholesterol containing albumin for standardization. The formation of cholesterol peroxide in solutions of cholesterol in isopropanol is demonstrated, and this constitutes another potential source of error in the calibration of enzymic cholesterol assays. In analyzing patients' sera, results of the total cholesterol assay correlate well with those of a mechanized method in which cholesterol esterase and cholesterol oxidase are used; an automated Abell method, calibrated with solutions of cholesterol in isopropanol, gave slightly higher values. Determinations of the ratio of free cholesterol to total cholesterol by our automated cholesterol exidase assays given values that agree well with published results in which digitonin precipitation is used.
Microcalorimetric determination of glucose in reference samples of serum.
Authors: Goldberg R N 
Published: January 2020

Abstract
Ireport a detailed series of microcalorimetric measurement of glucose concentrations in five reference samples of serum. The method utilized (a) calibration in the actual medium of analysis and (b) a correction for interferences owing to the nonspecificity of the enzyme hexokinase. The microcalorimetric results are compared with the tentative results of analyses obtained by the spectrophotometric hexokinase/glucose-6-phosphate dehydrogenase method and by isotope-dilution mass spectrometry. In most cases, the microcalorimetric results appear to be in agreement with the results obtained by these latter two methods. A discussion of the basis of the microcalorimetric measurements is presented.
Amino acid composition of human nail, as measured by gas-liquid chromatography.
Authors: Greaves M , Moll J M 
Published: January 2020

Abstract
We describe a quantitative method for determination of histidine and 16 other amino acids in a nail hydrolysate. This is based on the formation of trifluoroacetyl amino acid methyl esters and gas-liquid chromatographic analysis with use of two columns of mixed stationary phases. Histidine is determined as a triple derivative Nalpha-trifluroacetyl-Nim-carbethoxy methyl histidinate. The specificity and reproducibility of the method are illustrated. As little as 1 mg of amino acid per gram of nail can be determined, and 15 hydrolysates can be completely analyzed in 10 working days. Data obtained from multiple analyses of 10 nail hydrolysates by the method described closely parallel those obtained in another laboratory, in which an amino acid analyzer was used.
Direct enzymatic determination of urea in plasma and urine with a centrifugal analyzer.
Authors: Bretaudiere J P , Phung H T , Bailly M 
Published: January 2020

Abstract
A direct enzymatic micromethod (sample volume, 3mul) has been adapted to the centrifugal analyzer (ENI-GEMSAEC) for measurement of urea in plasma and urine. The method is based on urease (urea amidohydrolase, EC3.5.1.5)/glutamate dehydrogenase [l-glutamate:NAD(P)+oxidoreductase (deaminating), EC1.41.3] coupled reactions, and uses a two-point fixed-time (t(1)=20s,t(2)=50s)kinetic scheme for monitoring the rate of comsumption of NADH at 340 nm. Sensitivity and precision of the method are excellent,and results compare well with those from a commonly used continuous-flow method.
Cholesterol oxidase-based determination, by continuous-flow analysis, of total and free cholesterol in serum.
Authors: Lie R F , Schmitz J M , Pierre K J , Gochman N 
Published: January 2020

Abstract
We describe a continuous-flow, automated determination of total cholesterol in serum, which is based on enzymatic hydrolysis of cholesterol esters, oxidation of cholesterol by cholesterol oxidase, and colorimetric measurement of liberated perioxide with 4-aminoantipyrine, phenol, and peroxidase. Free cholesterol is determined with the same AutoAnalyzer II manifold and reagents, except that cholesterol esterase is omitted from the reagent. Cholesterol-in-serum materials that have been assayed by an established method are used for calibration. We found this approach to be necessary because primary cholesterol standards in organic solvents are incompatible with the aqueous reagent. Results of the enzymatic total cholesterol method correlated well with those by an AutoAnalyzer II method which involves an extraction with isopropanol and the Liebermann-Burchard color reaction (total cholesterol, g/liter, yenz= 0991xlb +0.05;r=0.996). Results of the enzymatic free cholesterol procedure agreed satisfactorily with one in which free cholesterol is precipitated as the digitonide and subsequently analyzed colorimetrically with the Liebermann-Burchard reaction (free cholesterol, %, yenz = 0.982xdig -0.7;r= 0.956).
Detection of inhibitors in reduced nicotinamide adenine dinucleotide by kinetic methods.
Authors: Howell B F , Margolis S , Schaffer R 
Published: January 2020

Abstract
Methods are described for detection of lactate dehydrogenase (LDH) inhibitors in preparations of reduced nicotinamide adenine dinucleotide. They are (a) comparison of values by kinetic methods with those measured for highly purified NADH and (b) examination of Lineweaver-Burk plots. Chromatographic inhomogeneities are correlated with deviant values for the kinetic constants of NADH preparations. Lineweaver-Burk plots that curve upward at the high concentrations or have a larger or smaller than normal slope may indicate the presence of inhibitor. As determined in bicarbonate buffer (0.11 mol/liter, pH 7.9) by use of 0.600 mmol/liter pyruvate and NADH freshly separated from impurities by chromatography on diethyl-aminoethyl-cellulose, the Km (apparent) of NADH at 25 degrees C has the value 8.11 +/- 0.71 mumol/liter (SD, n = 28) with LDH-1 (pig heart, 2.48 +/- 0.05 U per milliliter of reaction mixture, or 41.3 +/- 0.8 nmol/liter per second). Under similar conditions, the Km (apparent) of NADH has the value of 8.57 +/- 1.58 mol/liter (SD, n = 21) with LDH-5 (pig muscle, 1.77 +/- 0.03 U/ml of reaction mixture), or 29.4 +/- 0.6 nmol/liter per second). At infinite substrate concentrations with the same pH, buffer, and temperature, the Km (apparent) for NADH was 26.0 +/- 0.63 mumol/liter with LDH-1 and 23.2 +/- 4.6 mumol/liter with LDH-5.
Results for serum cholesterol and triglycerides by gas-liquid chromatography, as compared with a continuous-flow technique.
Authors: Watts R , Carter T , Taylor S 
Published: January 2020

Abstract
We assessed the usefulness of gas-liquid chromatography forthe routine and reference measurement of cholesterol and triglycerides (triacylglycerols). Compared with results obtained by an AutoAnalyzer II method, correlation was good with both serum specimens (triglycerides, r = 0.88; cholesterol, r = 0.90) and lipoprotein fractions isolated by ultracentrifugation (triglycerides, r = 0.98; cholesterol, r = 0.98). However, none of the comparisons was completely free of analytical bias, and in general the AutoAnalyzer method underestimated the cholesterol value and overestimated triglycerides. The obvious advantage of the AutoAnalyzer is its greater analytical speed, but the chromatographic method appeared to be more accurate and precise and to suffer less from interfering substances, and in addition gave information about the cholesterol ester and triglyceride composition. We expect gas-liquid chromatography to be of major importance in the calibration of other analytical methods.
Sarcolemmal membrane changes related to enzyme release in the imipramine/serotonin experimental animal model.
Authors: Silverman L M , Gruemer H D 
Published: January 2020

Abstract
We report specific findings in the imipramine/serotonin animal model that are consistent with sarcolemmal membrane alterations. Among these findings are cytoplasmic enzyme release, diminished uptake of alpha-aminoisobutyrate (an amino acid analog), decreased oxygen consumption in isolated rat diaphragm, and ribosuria. Furthermore, we describe for the first time the release of the MB isoenzyme of creatine kinase from a source other than cardiac tissue; that is, isolated diaphragms from imipramine/serotonin-treated animals release increased amounts of MB isoenzyme as compared to diaphragms from control animals. We believe the similarities between this animal model and the human disease (Duchenne muscular dystrophy) support a genetically determined generalized membrane abnormality in the pathogenesis of this form of muscular dystrophy.