bluuebunny/crossref_metadata_2025_split huggingface dataset:
Liquid chromatography of codeine in plasma with fluorescence detection.
Authors: Tsina I W , Fass M , Debban J A , Matin S B 
Published: January 2020

Abstract
This analytical method for easier determination of codeine in human plasma is based on "high-performance" liquid chromatography for separation and the natural fluorescence of codeine for detection. Codeine is extracted from alkalinized plasma with a mixture of hexane and dichloromethane, and the extract is further purified and chromatographed. The method can be used for routine assay of codeine at the concentrations of 10 micrograms/L or greater in human plasma. As little as 4 micrograms/L can be detected. Coefficients of variation for the assay of codeine in the concentration range of 10 to 100 micrograms/L were 2.2-7.4% (n = 6). We used this method to establish a concentration/time profile for plasma from a human volunteer after a 60-mg oral dose of codeine sulfate.
Dry film for the enzymic determination of total cholesterol in serum.
Authors: Dappen G M , Cumbo P E , Goodhue C T , Lynn S Y , Morganson C C , Nellis B F , Sablauskas D M , Schaeffer J R , Schubert R M , Snoke R E , Underwood G M , Warburton C D , Wu T W 
Published: January 2020

Abstract
We have prepared a dry film for the enzymic determination of total serum cholesterol. It consists of a transparent support bearing a buffered gelatin layer, and a white reflective spreading layer that contains all of the necessary components for the detection of cholesterol. The method is based on (a) hydrolysis of cholesterol esters to cholesterol by cholesterol ester hydrolase (EC 3.1.1.13), (b) oxidation of cholesterol to cholest-4-en-4-one and hydrogen peroxide by cholesterol oxidase (EC 1.1.3.6), and (c) oxidation of a triarylimidazole leuco dye with hydrogen peroxide in the presence of peroxidase (EC 1.11.1.7) to produce a dye with maximum absorption at about 650 nm. For use over a wider range of concentration, the dye density is read at 540 nm. With reflection densitometry and appropriate mathematical transformation, readings and cholesterol concentrations are linearly related to 5500 mg/L. Results correlate well with those by the Abell-Kendall comparison method (slope 0.97, intercept 92.5, correlation coefficient 0.974, Sy.x = 250.7), and the method is precise (CV of 1.2-2.3% for a control fluid and patients' samples) and relatively free of interferences.
Simultaneous quantitation of quinidine, procainamide, and N-acetylprocainamide in serum by gas-liquid chromatography with a nitrogen-phosphorus selective detector.
Authors: Kessler K M , Ho-Tung P , Steele B , Silver J , Pickoff A , Narayanan S , Myerburg R J 
Published: January 2020

Abstract
We describe a single-run method for quantitating quinidine, procainamide, and N-acetylprocainamide, involving gas-liquid chromatography with a nitrogen-phosphorus selective detector. Within-run precision (CV) was 3% (x = 2 mg/L, n = 20), 6.9% (x = 4 mg/L, n = 10), and 1.5% (x = 8 mg/L, n = 8) for quinidine; 7.7% (x = 4 mg/L, n = 14), 1.6% (x = 8 mg/L, n = 16), and 2.3% (x = 12 mg/L, n = 12) for procainamide; and 6.3% (x = 5 mg/L, n = 6), 3.6% (x = 10 mg/L, n = 20), and 4.0% (x = 20 mg/L, n = 10) for N-acetylprocainamide.l Between-run precision was 3.0%(x = 2 mg/L, n = 20), 7.0% (x = 4 mg/L, n = 9), and 2.8% (x = 8 mg/L, n = 9) for quinidine; 4.7% (x = 4 mg/L, n = 10). 3.3% (x = 8 mg/L, n = 20), and 1.9% (x = 12 mg/L, n = 10) for procainamide; and 9.3% (x = 5 mg/L, n = 6), 4.3% (x = 10 mg/L, n = 20), and 3.8% (x = 20 mg/L, n = 10) for N-acetylprocainamide. Tube stoppers that contain a rubber plasticizer interfere with the technique. Clinical application and correlation with drug concentrations by this technique are discussed.
Homogeneous nonisotopic assay for phenytoin evaluated.
Authors: Dugan S , Bailey J , Wu J W , Hoskin S , Riebe S , Gifford J , O'Neill S P 
Published: January 2020

Abstract
We evaluated a new homogeneous immunoprecipitation assay for phenytoin in human serum. No sample dilution or pretreatment is required. The new method is based on spectrophotometry of the inhibition by free phenytoin of the precipitating reaction between anti-phenytoin antibody and a phenytoin-human serum albumin conjugate. A serum test sample is simultaneously mixed with the phenytoin-albumin conjugate and rabbit antiserum to phenytoin in a centrifugal analyzer, and the subsequent reaction is monitored at 3 min. Within-run and between-run coefficients of variation were well below 7%. The relation between results for patients' test sample as determined by immunoprecipitation assay (y) and an enzyme immunoassay (x) can be expressed as y = 1.10x + 1.1 (r = 0.966, n = 66).
Diagnostic performance of enzymes in the discrimination of myocardial infarction.
Authors: Werner M , Brooks S H , Mohrbacher R J , Wasserman A G 
Published: January 2020

Abstract
We apply rigorous statistical methods to assess the diagnostic value of creatine kinase, creatine kinase-MB, aspartate aminotransferase, lactate dehydrogenase, and alpha-hydroxybutyrate dehydrogenase in realistic circumstances. The trade-off between false positives and false negatives obtained with various decision rules is examined with the receiver-operator characteristic function and with discriminant analysis. During the three days after an infarction, lactate and alpha-hydroxybutyrate dehydrogenase can provide diagnostic thresholds of constant sensitivity and specificity. By contrast, sensitivity progressively decays for creatine kinase, creatine kinase-MB, and aspartate aminotransferase. The diagnostic uncertainty introduced by the infarction's varying age at hospitalization is evaluated by subjecting the mixed patient population to discriminant analysis. For some enzymes, repeating the same assay on the second day contributes to sensitivity, while adding a different assay on the first day enhances specificity. The effects of lower or higher infarction prevalences on sensitivity and specificity are most favorable when creatine kinase-MB is combined with lactate or alpha-hydroxybutyrate dehydrogenase. Adding a third assay is ineffective. The further differentiation according to infarction stage produces only 81% correct classifications, even when five different assays are used on two consecutive days. As a general strategy, we recommend the assay of two enzymes on two consecutive days.
beta 2-Microglobulin instability in pathological urine.
Authors: Davey P G , Gosling P 
Published: January 2020

Abstract
Urinary excretion of beta 2-microglobulin (beta 2M) is a widely used test of renal proximal tubular function. beta 2M is known to be unstable in normal urine with a pH less than 5.5. The results of a study of beta 2M excretion in patients receiving gentamicin suggested that beta 2M might be more unstable in pathological urine. A series of experiments was designed to define the extent, variability, and mechanism of its instability in pathological urine. It was unstable in pathological urine with a pH of 6.0 at 37 degrees C and pH 5.5 at room temperature, but this varied in urines from different patients. The instability was abolished by heating the urine to 80 degrees C. These results suggest that the most likely explanation for the instability is enzymic degradation. Because enzymuria will vary among patients, investigators should test the stability of beta 2M in urine from the patients they wish to study before trying to define conditions for urine collection.
Normalization and reproducibility of mass profiles in the detection of individual differences from urine.
Authors: Marcuson R , Burbeck S L , Emond R L , Latter G I , Aberth W 
Published: January 2020

Abstract
The mass profiles of urine samples and their reproducibility (coefficient of variation) obtained by field-ionization mass spectrometry (volcano source) depend upon the choice of normalization method. We compared six different normalization techniques in terms of improved reproducibility and sensitivity. Several simple procedures markedly improved reproducibility while preserving the high degree of sensitivity. Although these procedures gave similar and satisfactory results, others were clearly inferior and are not recommended for clinical profiling.
Improved micromethod for assay of serum angiotensin converting enzyme.
Authors: Neels H M , Scharpé S L , van Sande M E , Verkerk R M , Van Acker K J 
Published: January 2020

Abstract
We describe conditions for determining angiotensin converting enzyme (EC 3.4.15.1) in serum, by liquid chromatography. Serum (10 microL) is assayed with the artificial substrate hippuryl-glycyl-glycine (30 mmol/L) in a 50 mmol/L "HEPES" buffer solution with a high salt content (300 mmol of NaCl and 400 mmol of Na2SO4 per liter), at pH 8.0. The resulting enzymic activity is ninefold that of the currently popular spectrophotometric assay of Cushman and Cheung as modified by Lieberman (Am. J. Med. 59: 365-372, 1975). The hippuric acid end product is separated from the substrate by reversed-phase liquid chromatography and measured spectrophotometrically at 228 nm. o-Methyl hippuric acid is used as internal standard. The mean value for 100 normal control subjects was 317 (SD 96) nmol of hippuric acid released per milliliter of serum per minute. The enzyme activity is greater in newborns (p less than 0.05) and has a tendency to decrease with age. This partly automated method, which is optimized with regard to activity and detection, can be used in clinical routine.
Serum copper concentration and hepatic enzyme induction during long-term therapy with anticonvulsants.
Authors: Tutor J C , Fernandez M P , Paz J M 
Published: January 2020

Abstract
We evaluated hepatic enzyme induction by measuring urinary D-glucaric acid and serum gamma-glutamyltransferase in a group of 40 adult epileptics of both sexes who were receiving long-term treatment with phenobarbital and (or) phenytoin. Total concentrations of copper and ceruloplasmin in their serum and the oxidase activity of ceruloplasmin were significantly greater than in the control group. However, non-ceruloplasmin copper and specific oxidase activity of the ceruloplasmin (activity per gram) were unchanged. A highly significant relationship was found between gamma-glutamyltransferase and (a) copper (r = 0.682, p less than 0.001), (b) ceruloplasmin (r = 0.523, p congruent to 0.001), and (c) the oxidase activity of the ceruloplasmin (r = 0.598, p less than 0.001). There is also a significant correlation of hemopexin with ceruloplasmin (r = 0.531, p congruent to 0.001) and the oxidase activity of the ceruloplasmin (r = 0.598, p less than 0.001). These results suggest that hypercupremia in patients undergoing long-term anticonvulsant therapy is a direct result of hepatic enzyme induction caused by the drugs that induce synthesis of ceruloplasmin.
Homogeneous enzyme immunoassay for tobramycin evaluated and compared with a radioimmunoassay.
Authors: Woo J , Longley M A , Cannon D C 
Published: January 2020

Abstract
We evaluated a commercially available homogeneous enzyme immunoassay (EMIT, Syva Co.) for tobramycin against a reference radioimmunoassay (RIA) method. Between-assay precision (CV) was 2.9% at 6.2 mg/L and 3.0% for values in the range of 1.0-7.6 mg/L. Accuracy based on a recovery experiment (1.0-13.0 mg/L) yielded an analytical recovery of 88-112%. A correlation study with 75 sera from patients on tobramycin therapy showed that EMIT = 0.984 RIA - 0.0808, r = 0.993. Neither the EMIT nor the RIA procedure was affected by the presence of gentamicin, amikacin, and vancomycin. Absorbance data from the EMIT system calculated with the conventional RIA logit-log algorithm correlate well with results generated by the Syva data-handling system (logit-log = 1.077 Syva - 0.318, r = 0.998). A reagent stability study indicated that the EMIT reagents, once reconstituted, remain stable for at least 17 days when stored at refrigerated temperatures, or 11 days if stored at room temperature, thus enabling frequent "stat" assays without the need to prepare a calibration curve each time.
Liquid-chromatographic measurement of nitrazepam in plasma.
Authors: Kelly H , Huggett A , Dawling S 
Published: January 2020

Abstract
In this simple and rapid "high-performance" liquid-chromatographic method for determining nitrazepam in plasma, serum, or whole blood, the sample at pH 7.4 is extracted into diethyl ether with an internal standard (prazepam), chromatographed, and detected at 280 nm with a fixed-wavelength ultraviolet detector. A specimen, together with standards and a quality control, can be analyzed in duplicate within 90 min. The limit of sensitivity is 5 micrograms/L (nitrazepam and 7-acetamidonitrazepam) and 50 micrograms/L (7-aminonitrazepam), and no interferents have been found. This method has the advantages of a small sample requirement and complete resolution of nitrazepam and the above-mentioned major metabolites. We have used this method for analysis of therapeutic and overdose concentrations of nitrazepam, and to investigate the stability of the drug in blood.
Verapamil and calcium-stimulated enzyme efflux from skeletal muscle.
Authors: Anand R , Emery A E 
Published: January 2020

Abstract
An early and significant biochemical abnormality in Duchenne's muscular dystrophy is an increase in intracellular calcium. We have found that the "calcium-blocker" drug verapamil inhibits calcium-stimulated efflux of creatine kinase (EC 2.7.3.2) and lactate dehydrogenase (EC 1.1.1.27) in vitro from normal human skeletal muscle at therapeutic concentrations. Such a calcium blocker might therefore be useful in the treatment of Duchenne's muscular dystrophy.
Radioimmunoassay for phencyclidine (PCP) in serum.
Authors: Owens S M , Woodworth J , Mayersohn M 
Published: January 2020

Abstract
This accurate, sensitive radioimmunoassay for determining phencyclidine concentrations in serum specimens involves the use of anti-phencyclidine sera, 0.1 mL of serum specimen, an iodinated tracer, and a solid-phase separation. Phencyclidine metabolites do not show significant cross reactivity, but several phencyclidine analogs do cross react. Within-run coefficients of variation for human and dog serum ranged from 2.5 to 13% for concentrations from 2.0 to 500 micrograms/L. Day-to-day coefficients of variation for human and dog serum ranged from 4.3 to 16.7% for concentrations ranging from 2.0 to 90.0 micrograms/L. The sensitivity of the radioimmunoassay is less than 0.5 micrograms/L. Thirty serum specimens from two dogs given 1 mg of phencyclidine per kilogram body weight were analyzed by radioimmunoassay and a gas-chromatographic method. Nonparametric statistical comparison and linear regression showed that results from the two procedures correlate well (r2 = 0.952). Concentration-time data from the two dogs are presented to illustrate the utility of the radioimmunoassay for examining phencyclidine disposition.
Unpredictable fluctuations in transcutaneous pCO2 from capillary blood gas determinations.
Authors: Kost G J , Chow J L , Kenny M 
Published: January 2020

Abstract
Transcutaneous pCO2 electrode response time was optimized by use of a new electrode filling solution composed of NaCl/NaHCO3 electrolyte buffer (100 and 20 mmol/L, respectively) in an equivolume mixture of glycerol and water. The 95% response time to a step change in pCO2 was 49.9 +/- 2.8 s (mean +/- SD) when there was no spacer between the membrane and glass of the electrode. Use of this filling solution during monitoring of severely ill premature infants with cardiopulmonary disease allowed identification of large, unpredictable transient changes in transcutaneous pCO2, and therefore presumably in arterial pCO2, that occurred during capillary blood gas sampling. The changes, which occurred in 19 of 20 samplings, ranged from -1.06 + 2.53 kPa (-8 to +19 Torr). The maximum relative change observed was +29%. These results indicate that the standard protocol for capillary blood collection induces significant transient fluctuations in blood gas tensions. We believe these fluctuations decrease the reliability of capillary pCO2 values for use in clinical management in patient populations similar to ours.
Urinary enzyme excretion by renal-transplant recipients in relation to interval after transplantation.
Authors: Jung K , Diego J , Scholz D , Schröder K , Strobelt V 
Published: January 2020

Abstract
We determined the urinary excretion of the enzymes aminopeptidase (EC 3.4.11.2), alkaline phosphatase (EC 3.1.3.1), gamma-glutamyltransferase (EC 2.3.2.2), and N-acetyl-beta-glucosaminidase (EC 3.2.1.30) in two groups of renal-transplant recipients at different times after transplantation (1.8 months and 52 months, respectively). Both groups of patients showed a higher rate of enzyme excretion than did a reference group of healthy persons. More aminopeptidase and N-acetyl-beta-glucosaminidase were excreted during the early period after transplantation than later. The time-dependence of urinary enzyme excretion was confirmed in six renal-transplant recipients studied during the course of 15 months after transplantation. There was a general correlation between the extent of urinary enzyme excretion and both the time after transplantation and the daily dose of prednisolone. Therefore, it is necessary to take into account this influence on the extent of urinary enzyme in renal-transplant recipients if urinary enzyme excretion is used as an indicator of renal disorder and especially as an early predictor of transplant rejection.
Release tags: a new class of analytical reagents.
Authors: Joppich-Kuhn R , Joppich M , Giese R W 
Published: January 2020

Abstract
Release tags are novel compounds made up of three molecular groups: "signal," "release," and "reactivity." The signal group is the detected part of the tag, the release group provides a site for specific covalent cleavage, and the reactivity group attaches the tag to a substance of interest. The general purpose of release tags is to function as molecular labels, analogous to radioisotopes. Release tags also extend the applicability of gas-phase electrophores as signal groups to the analysis of nonvolatile substances. These electrophores are measured with high sensitivity and specificity by gas chromatography with electron-capture detection (GC-ECD). Because extensive multiplicity is potentially available with GC-ECD electrophores, many analogous but distinctive release tags can be used simultaneously as labels in a given assay. In this paper, we use N-pentafluorobenzoylmethionylglycine-N-hydroxysuccinimide ester, our first GC-ECD release tag, to determine thyroxin in serum by a method called "labeling analysis," which involves the principle of isotope-derivative analysis.
A short-term in vitro drug-screening assay for cancer chemotherapy.
Authors: Chen S L , Snoga J R , Croft H 
Published: January 2020

Abstract
In this short-term in vitro assay for detection of tumor cell sensitivity to drugs, we have replaced the traditional soft-agar colony-forming assay with the measurement of DNA synthesis, to determine the cell renewal capability of the tumor cell population. The tumor cells are treated with drugs and cultured for five days. During the last 12--18 h of culture the cells are pulsed with [3H]thymidine, then harvested for scintillation counting. The effects of drugs are expressed as the percentage of DNA synthesis as compared with that of the control. When the % DNA synthesis is less than 40%, the drug is considered to be effective. So far we have studied tumor cells from multiple myeloma, non-Hodgkin's lymphoma, and carcinoma of lung, breast, ovary, stomach, and bladder. The overall negative predictive value is 1.0. The results are available within five days, compared with 21--28 days for completion of soft-agar assays; fewer cells are required; and the process is semiautomated.
Development of a multichannel electrochemical centrifugal analyzer.
Authors: Cho H K , Lee Y H , Couch R A , Jagadeesh J M , Olson C L 
Published: January 2020

Abstract
A new instrument has been developed that is similar in design and concept to the GeMSAEC centrifugal analyzer (Oak Ridge National Laboratory) except that electrochemical detection is used rather than optical detection. The present version has eight channels, each with its own detector. Problems of speed control and sampling synchronization are greatly minimized from those of a multichannel centrifugal analyzer having a single detector system. All eight sample compartments and polarographic cells are contained in a single Teflon rotor, 7.7 cm in diameter. The working electrodes are planar carbon electrodes. The initial application of the analyzer is in kinetic methods involving the rates of enzyme-catalyzed reactions. The initial system chosen was the glucose oxidase system. When the rotor is spun, the solution moves into the sample cell and up against the planar working electrode. The reaction starts and current is measured as a function of time at a constant applied voltage. The current output from each polarographic circuit is connected to a separate channel of a multiplexed analog-to-digital converter. The analyzer is controlled by a dedicated microcomputer system, which sets the polarographic cell voltages, collects the current-time data, and calculates the results.
An electrochemical assay system for peroxidase and peroxidase-couplers reactions based on a fluoride ion-selective electrode.
Authors: Siddiqi I W 
Published: January 2020

Abstract
A sensitive and accurate potentiometric reaction-rate method for the assay of peroxidase (EC 1.11.1.7) and peroxidase-coupled reactions is described. The technique is based on the peroxidase-catalyzed rupture of the covalent C--F bond in certain organo-fluoro compounds in the presence of H2O2 and the measurement of liberated F- by a fluoride ion-selective electrode. In a study screening 26 organo-fluoro compounds, 12 were susceptible to C--F bond rupture. However, analytically useful reaction kinetics were observed only with 4-fluoroaniline, 5-fluor-2-methylaniline, 4-fluorophenol, 2,3,5,6-tetrafluorophenol, pentafluorophenol, and 3-fluoro-DL-tyrosine. With this assay system, peroxidase activity as low as 25 mU/L could be precisely measured within 2 min. The reaction was coupled to glucose oxidase and cholesterol oxidase for the determination of glucose and cholesterol. Glucose oxidase activity in solution (to 2 U/L) was measured to demonstrate the feasibility of the assay for oxidase enzymes. Only a few microliters of sample is required and most determinations can be completed within minutes. The assay system offers broad applications and is especially attractive for use in enzyme immunoassays.
Statistical comparison of blood glucose as determined by several test-strip procedures and by a hexokinase procedure.
Authors: Stewart T C , Kleyle R M 
Published: January 2020

Abstract
We report a new statistical tool for comparing several dry-reagent strip procedures for whole blood glucose, which produce data in both digital and ordinal form, with results by the well-studied hexokinase-glucose-6-phosphate dehydrogenase procedure coupled to NAD+-NADH. Our use of "ordinal comparison unit" allows for a more equitable comparison of such data. These strip procedures produce biases of -2.21 to 1.74 ordinal comparison units over the range of glucose values corresponding to hypoglycemia and hyperglycemia, as compared with results by the hexokinase procedure, but they are essentially equivalent when compared with each other.
Improved enzymatic determination of total cholesterol in tissues.
Authors: Cho B H 
Published: January 2020

Abstract
In this improved method for rapid enzymatic determination of total cholesterol, the lipid extracts from tissues are dissolved in an equal volume of peroxide-free dioxane/isopropanol (50/50 by vol) solution, and are reacted directly with the aqueous enzymatic reagent, without further treatment. The presence of organic solvents, such as dioxane and isopropanol, does not interfere with enzymatic activity. This simpler procedure eliminates the tedious solubilization of tissue lipid extracts into an aqueous medium. The method is reproducible, and results correlate well with those by a chemical (FeCl3/H2SO4) method.