bluuebunny/crossref_metadata_2025_split huggingface dataset:
A technique for determining the probability of abnormality.
Authors: Grannis G F , Lott J A 
Published: January 2020

Abstract
Histograms of the results of quantitative clinical laboratory analyses are usually broadly skewed because some of the patients have normal values with respect to the analyte being measured while values for others are below or above normal. We describe a technique for calculating the maximum possible number of individuals in a patient population who will give normal values and, by difference, the minimum possible number of those who will give below-normal and above-normal values. The technique permits estimation of the probability that any given result represents a member of a particular subpopulation, as well as selection of decision limits for patient classification, and estimates the degree of change required for a subject with a normal value to start giving below- or above-normal values.
Simultaneous liquid-chromatographic determination of 12 common sedatives and hypnotics in serum.
Authors: Kabra P M , Koo H Y , Marton L J 
Published: January 2020

Abstract
We present a method for simultaneously determining 12 hypnotics and sedatives (primidone, methyprylon, phenobarbital, butabarbital, butalbital, ethchlorvynol, pentobarbital, amobarbital, phenytoin, glutethimide, secobarbital and methaqualone) in 200 microliter of serum. Serum proteins are precipitated with an acetonitrile solution containing 5-(4-methylphenyl)-5-phenylhydantoin, the internal standard. The drugs are eluted from a reversed-phase column with a mobile phase consisting of an acetonitrile/phosphate buffer, at a flow rate of 3.0 ml/min. The eluted drugs are detected by their absorption at 195 nm; their quantities are estimated from their peak heights. Each analysis requires no longer than 30 min at the optimum column temperature of 50 degrees C. The lower limit of detection for all of these drugs is less than 10 ng/sample for drug standard. A sensitivity of 1.0 mg/liter of serum is attained routinely for each of the drugs. Analytical recoveries for the 12 drugs varied from 94 to 112%, with good day-to-day precision (CV between 3.8 and 10.4%). Of more than 35 drugs tested for possible interference, only ethotoin interferes with the analysis of phenobarbital.
Time--concentration studies by high-performance liquid chromatography of metabolites removed during hemodialysis.
Authors: Knudson E J , Lau Y C , Veening H , Dayton D A 
Published: January 2020

Abstract
Reversed-phase high-performance liquid chromatography was used to study the efficiency of hemodialysis. The method, previously used to study uremic hemodialysate, was also found useful for analyzing other uremic biofluids, such as serum and urine. Samples of blood (centrifuged to obtain cell-free serum) and hemodialysate were simultaneously collected from selected patients at regular intervals during the entire 6-hour hemodialysis treatment. These samples were filtered through membranes to remove particulates and proteins and were then analyzed by use of a 60-cm muBondapak-C18 column, an aqueous sodium acetate/methanol gradient, and detection at 254 nm. The identification of components in the eluate was based on retention times, ultraviolet absorption spectra, and mass spectra. From the amounts of several metabolites in the various physiological fluid pools during hemodialysis, we concluded that they mostly originate from tissue fluids. We also observed that the concentrations of most components in serum and hemodialysate fluctuated regularly with time.
Gas-chromatographic determination of nanogram amounts of enantiomers of nortilidine, a main metabolite of tilidine, in biological specimens.
Authors: Hengy H , Vollmer K O , Gladigau V 
Published: January 2020

Abstract
We report a specific and sensitive method for determination of the individual optical isomers of nortilidine, a main metabolite of tilidine, with the aid of a nitrogen-sensitive detector. With N-trifluoroacetyl-L-leucyl chloride as chiral reagent, the diastereomeric derivatives of the nortilidine enantiomers could be separated and quantified in the nanogram range. Under these conditions, the enantiomers of bisnortilidine, another main metabolite of tilidine, were also separated. Investigations in rats with the enantiomers of tilidine and nortilidine indicated that no racemization occurs during N-demethylation in the organism. After oral and intravenous administration of 50 mg of tilidine.HCI to a human volunteer, identical concentrations of nortilidine enantiomers were found in the plasma.
Cross reactivity of digitoxin and spironolactone in two radioimmunoassays for serum digoxin.
Authors: Müller H , Bräuer H , Resch B 
Published: January 2020

Abstract
We measured the cross reactivity of two medications--digitoxin and spironolactone--in two digoxin radioimmunoassay (liquid and solid-phase) kit procedures. Both tests showed similar average percentages of cross reactivity with digitoxin (7.2 and 8.9% for intravenous, and 11.9 and 10.9% for oral administration), but no cross reactivity with spironolactone or its metabolites after equal intravenous or oral doses.
Comparative determination of phenytoin by spectrophotometry, gas chromatography, liquid chromatography, enzyme immunoassay, and radioimmunoassay.
Authors: Castro A , Ibanez J , DiCesare J L , Adams R F , Malkus H 
Published: January 2020

Abstract
Sera from patients being treated with phenytoin were analyzed for the drug by spectrophotometry, gas chromatography, radioimmunoassay, enzyme immunoassay, and liquid chromatography. The essay values obtained were intercompared statistically. Enzyme immunoassay and liquid chromatography appear to be attractive alternatives to the more traditional methods of spectrophotometry and gas chromatography. Our radioimmunoassay data correlated poorly with results by the four other methods.
Micromethod for determination of creatinine in biological fluids by high-performance liquid chromatography.
Authors: Soldin S J , Hill J G 
Published: January 2020

Abstract
We describe a procedure for the rapid and specific measurement of creatinine, in which it is separated from other compounds in serum or urine by paired-ion chromatography and is quantified by measuring its absorbance at 200 nm. The procedure can be done on as little as 10 microliter of serum. Between-day precision studies for concentrations of 13 and 62 mg/liter yielded coefficients of variation of 6.9 and 2.2%, respectively. Analytical recovery of various amounts of creatinine added to plasma exceeded 95% in all cases. The proposed procedure was compared with the continuous-flow procedure by analyzing a series of serum and urine specimens by both methods. There was excellent agreement for urine specimens, but with serum the results by the present method were significantly (P less than 0.001) lower.
High-performance liquid-chromatographic assay for chloramphenicol in biological fluids.
Authors: Thies R L , Fischer L J 
Published: January 2020

Abstract
We describe a method for measuring chloramphenicol by high-performance liquid chromatography. The assay involves a single extraction of the biological sample with ether, evaporation of the extract, and chromatography of the residue, redissolved in methanol. A reversed-phase column with an eluting solvent of methanol/water (30/70 by vol) is used. Chloramphenicol is eluted from the column in about 4 min and is well separated from the internal standard (mephenesin), which is eluted at 5.5 min. Absorption of the effluent at 278 nm is monitored and measured. As little as 0.1 microgram of the antibiotic can be analyzed after its extraction from a 0.1-ml sample. The method is suitable for rapid and specific analysis for the drug in plasma, urine, cerebrospinal fluid, and other biological fluids.
Two-point determination of plasma ammonia with the centrifugal analyzer.
Authors: Bruce A W , Leiendecker C M , Freier E F 
Published: January 2020

Abstract
A simple, convenient, and rapid method for determining ammonia in plasma by the glutamate dehydrogenase reaction is described for the centrifugal analyzer. The measuring principle is fixed-time, with NADH as the coenzyme. ADP is added to stabilize glutamate dehydrogenase and prevent interference from endogenous plasma ADP. The reaction is linear to 400 mumol of ammonia per liter. The plasma sample volume is 100 microliter and the whole procedure takes only 25 min, including the 15-min preincubation. The normal range for venous plasma was 44 +/- 13.5 (SD) mumol of ammonia per liter.
Simple, rapid method for determination of propionic acid and other short-chain fatty acids in serum.
Authors: Hillman R E 
Published: January 2020

Abstract
A semimicro method for measuring propionic and other short-chain fatty acids in serum is presented. The procedure requires as little as 200 microliter of serum. Data are provided for premature infants, children, adults, and patients with propionicacidemia.
N-Ethylmaleimide prevents destruction of corticotropin (ACTH) in plasma.
Authors: Jubiz W , Nolan G 
Published: January 2020

Abstract
Addition of N-ethylmaleimide, an inhibitor of proteolytic enzymes, to samples for plasma corticotropin determinations prevents destruction of the hormone at room temperature for at least 72 h. A concentration of 125 mg per liter of blood is effective. N-Ethylmaleimide is not so effective in preventing corticotropin degradation in whole blood. Use of the inhibitor should make plasma corticotropin determinations more practical and reliable.
An interlaboratory study of measurement of aspartate aminotransferase activity with use of purified enzyme materials.
Authors: Burtis C A , Sampson E J , Bayse D D , McKneally S S , Whitner V S 
Published: January 2020

Abstract
The Center for Disease Control (CDC), the New York State Department of Health (NYSDH), the College of American Pathologists, and 23 manufacturers of diagnostic products participated in an interlaboratory study of aspartate aminotransferase (EC 2.6.1.1) methodologies. Six different lyophilized materials were prepared and characterized and then distributed to 293 laboratories for aspartate aminotransferase measurements. The specimens included one human serum; four catalytic concentrations of the cytoplasmic isoenzyme, two purified from human erythrocytes, and two from porcine heart; and one matrix bovine serum albumin (30 g/liter) blank. The purified isoenzymes were prepared in the matrix. We present data on Michaelis parameters (Km and Vmax), Arrhenius plots, activation with pyridoxal 5-phosphate, vial-to-vial variability, and stability on reconstitution. The 281 responses showed that most of the laboratories used NADH-detection methods (91.1%), monitored at 340 nm (79.4%), and reported results in U/liter (89.4%). The percentage of laboratories reporting use of reaction temperatures of 30 and 37 degrees C was evenly divided, i.e., 42.7 and 42%, respectively. Analytical values reported by participating laboratories were categorized by reporting temperature, instrument, and method. Results were most consistent for a selected group of laboratories that supplemented optimized reaction solutions with pyridoxal 5-phosphate.
Factors affecting measurement of total alkaline phosphatase activity in human serum, especially wavelength accuracy.
Authors: Lott J A , Turner K , Scott J 
Published: January 2020

Abstract
Serum alkaline phosphatase estimations by the Selected Method [Clin. Chem. 21, 1988 (1975)] are very sensitive to small errors in the wavelength setting of the spectrophotometer. With a setting error as small as 3 nm, results can be too low by as much as 23%. The product of the reaction, 4-nitrophenol, can be prepared in very pure form and can be used to check both the wavelength and absorbance accuracy of a spectrophotometer. The molar absorptivity for 4-nitrophenol obtained in the instrument being used should be used in calculating alkaline phosphatase activities.
Biochemical properties of tartrate-resistant acid phosphatase in serum of adults and children.
Authors: Lam W K , Eastlund D T , Li C Y , Yam L T 
Published: January 2020

Abstract
Spectrophotometry of total acid phosphatase activity in children's sera showed an average value of 22.4 +/- 2.9 and 7.4 +/- 0.8 U/liter, for the hydrolysis of p-nitrophenyl phosphate and alpha-naphthyl phosphate, respectively. Analyses of "band 5b", after electrophoresis on acrylamide gel, gave even higher values. The values for children's sera were much higher than those for sera from adults. The multiplicity of acid phosphatases in sera of children and adults was studied by electrophoresis on acrylamide gel and by chromatography on CM-Sepharose. Both methods showed the major acid phosphatase in children's sera to be an acid pyrophosphatase, band 5b. Its catalytic properties are indistinguishable from the enzyme previously isolated from the spleen of leukemic reticuloendotheliosis.
Use of a programmable desk-top calculator for the statistical quality control of radioimmunoassays.
Authors: Cernosek S F , Gutierrez-Cernosek R M 
Published: January 2020

Abstract
We have developed an interactive statistical quality-control system for the small- to medium-sized radioimmunoassay laboratory, which can be used in a programmable desk-top calculator instead of the medium- or large-scale computer systems usually required. The design of this quality-control system is modeled after the suggestions of Rodbard and has three components. The first component evaluates the relationship between the measured response variable of the radioimmunoassay and the precision (or variance) of these measurements. This derived relationship is then used in the second component of the system as the basis for the weighting function used to calculate an interative, weighted, least squares regression of the logit-log transformation of the dose-response curve. The third component uses the quality-control parameters statistically calculated from the linearized dose-response curve to monitor whether the assay is "in-control". The calculator tabulates the means and confidence limits for the various parameters and can plot the statistical quality-control charts. The major benefit of this statistical quality-control system is that it allows the real-time computation and plotting of quality-control data with a programmable desk-top calculator.
Hexosaminidase A in amniotic fluid of Tay-Sachs fetuses.
Authors: Geiger B , Navon R , Arnon R 
Published: January 2020

Abstract
Hexosaminidase A is present in relatively low concentrations in cell-free amniotic fluids from pregnancies with Tay-Sachs fetuses. This isoenzyme was determined by an immunological procedure, radial immunodiffusion, by which hexosaminidase A can be directly and specifically detected, even in the presence of excess amounts of hexosaminidase B. No hexosaminidase A could be detected by the same procedure in Tay-Sachs fetal tissues, implying that this isoenzyme in the amniotic fluid originates from the mother.
Simultaneous determination of phosphatidylglycerol and the lecithin/sphingomyelin ratio in amniotic fluid.
Authors: Gotelli G R , Stanfill R E , Kabra P M , Farina F A , Marton L J 
Published: January 2020

Abstract
We describe a single-dimension thin-layer chromatographic method by which one can simultaneously determine the lecithin/sphingomyelin ratio and the proportion of phosphatidylglycerol in amniotic fluid. The phospholipids are conveniently detected by an improved molybdenum-blue spray reagent, which immediately produces blue spots on a white background. The stained phospholipids are stable for at least 90 min after spraying, and densitometry results in symmetrical peaks that are easily quantitated.
Improved methods for isolating cortisol metabolites from neonatal urine.
Authors: Derks H J , Drayer N M 
Published: January 2020

Abstract
Urine was collected from newborns, children, and adults who had received a tracer dose of [3H] cortisol. The free and different types of conjugated cortisol metabolites were separated by ion-exchange chromatography. A modified Amberlite XAD-2 procedure was used, which enabled quantitative extraction of the extremely polar cortisol metabolites from urine from newborns. Large differences between the ion-exchange chromatographic patterns for neonates and adults were observed. Urine from neonates was shown to contain quantitatively important amounts of an as-yet-unidentified conjugate that was absent from urine from adults. The effects of three different hydrolytic methods on the neonatal steroid conjugates were studied and it was found that the unknown conjugate in urine from the newborn could be hydrolyzed by solvolysis only.
Biochemical characterization of an aryl acetic ester hydrolase isolated from human monocytes.
Authors: Lam W K , Taft E , Yam L T 
Published: January 2020

Abstract
A carboxylic-ester hydrolase was isolated from the leukocytes of a patient with myelomonocytic leukemia. Its relative molecular mass as estimated by sucrose density-gradient sedimentation is about 70 000. The purified enzyme is specific for acetyl esters of aromatic alcohols. It is inhibited by fluoride, but insensitive to eserine or p-chloromercuriphenylsulfonate. Hydrolysis of 1-naphthyl acetate was optimal above pH 6.0; of o-nitrophenyl acetate, above 8.0. The common catalytic site for the two types of substrates on the enzyme was confirmed by competitive inhibition data.
Effect of temperature on plasma renin samples.
Authors: Fyhrquist F , Puutula L 
Published: January 2020

Abstract
Plasma renin activity was measured in parallel in Na2EDTA-contained plasma samples after storage at -20, 4, and 24 degrees C, and in the lyophilized state. In peripheral venous plasma from 22 hypertensive patients, the activity (range, 0.08-46.7 microgram/liter per hour) remained stable during three days of storage at 4 degrees C, but decreased to a variable extent when plasma was kept at 24 degrees C: in one day by 9.2%, two days by 25.6%, and three days by 74.0%. Values were the same for samples handled at room temperature and chilled to 4 degrees C within 3 h and parallel samples immediately cooled in an icebath and kept at 4 degrees C. Freezing (-20 degrees C) and thawing of plasma was associated with a 22% mean increase in activity (range, 0-83%). Lyophilization resulted in a smaller increase of plasma renin activity (mean 12%, range 0-46%). Blood for renin analysis need not be cooled immediately, but must be cooled to 4 degrees C within 2-3 h. It then is stabe for at least three days. Freezing or lyophilization appears to be associated with some cold activation of "prorenin."
A melting-point-of gallium apparatus for thermometer calibration.
Authors: Sostman H E , Manley K A 
Published: January 2020

Abstract
We have investigated the equilibrium melting point of gallium as a temperature fixed-point at which to calibrate small thermistor thermometers, such as those used to measure temperature in enzyme reaction analysis and other temperature-dependent biological assays. We have determined that the melting temperature of "6N" (99.999% pure) gallium is 29.770 +/- 0.002 degrees C, and that the constant-temperature plateau can be prolonged for several hours. We have designed a simple automated apparatus that exploits this phenomenon and that permits routine calibration verification of thermistor temperature probes throughout the laboratory day. We describe the physics of the gallium melt, and the design and use of the apparatus.
Rapid assessment of isoenzymes by high-performance liquid chromatography.
Authors: Schlabach T D , Alpert A J , Regnier F E 
Published: January 2020

Abstract
We describe the rapid profiling of isoenzymes by use of microparticulate anion-exchange chromatography supports and a continuous, post-separation enzyme detector in a high-performance liquid chromatograph. Chromatographic analysis and enzyme detection are fully automated and provide excellent reproducibility. Factors affecting the isoenzyme profile and detector response characteristics are assessed. Lactate dehydrogenase and creatine kinase isoenzymes in tissue extracts, control materials used as electrophoretic standards, and serum were profiled by this method to establish the resolution and reliability of the method. We show the clinical use of this method in detecting changes in these isoenzymes in serum associated with acute myocardial infarction.
Automated system for fractionation of blood samples.
Authors: Lee N E , Genung R K , Johnson W F , Mrochek J E , Scott C D 
Published: January 2020

Abstract
We describe a prototype system for preparing multiple fractions of blood components (plasma, washed erythrocytes, and hemolysates) by use of automated techniques. The procedure is based on centrifugal separation and sample transfer by induced pressure differentials in a blood-processing vessel (rotor) that has been designed to process 24 samples simultaneously. Erythrocytes are sedimented against the outer walls of individual sample chambers, and plasma is siphoned, by imposition of either a slight positive or negative pressure, into individual reservoirs in a collection ring. Cells are washed in situ; samples of washed cells, either packed or in saline solution, can be recovered. Cellular hemolysates are automatically prepared and transferred to individual, commercially available collection vials, ready for immediate analysis or for storage in liquid nitrogen. The system has potential application in any biomedical area in which many samples are to be expeditiously analyzed and in which one or more of the blood fractions will be used. A separate unit has been designed and developed for the semiautomated cleaning of the rotor.
Improved approach to sequential addition immunoassay.
Authors: Lasky F D , Al Razi J , Karmen A 
Published: January 2020

Abstract
In the usual sequential addition enzyme immunoassays for drugs, the activity of the drug-labeled enzyme decreases continuously with time as more of it is bound to antibody. Sensitivity also decreases; the activity immediately after mixing is the most sensitive indicator of drug concentration. The reaction of enzyme-drug with antibody can be stopped by saturating the antibody with a larger quantity of unlabeled drug, which reacts with the antibody faster than does the enzyme-labeled drug. When drug is added soon after the reaction starts, the enzyme activity is stabilized and the sensitivity to small quantities of antigen is increased. This approach, with modification, should be applicable to sequential immunoassays in which other kinds of labels are used. The enzyme activity can be measured for a longer time, with the predictable increase in precision, as well as the ability to detect smaller quantities, to use less reagent, and to use end-point rather than kinetic assays.
Comparison of three radioligands, selenium-75, lodine-125, and tritium, in the radioimmunoassay of methotrexate.
Authors: Paxton J W , Rowell F J , Cree G M 
Published: January 2020

Abstract
Radioimmunoassays for methotrexate are described, involving use of a rabbit antiserum to a conjugate of the drug and bovine serum albumin and the drug labeled with tritium, selenium-75, or iodine-125. Of the two gamma emitters, the 75Se-labeled drug was prepared by the Radiochemical Centre, Amersham, England and the 125I-labeled drug in the laboratory, by the Chloramine T iodination technique. The stability of labels with both methods allows use of the faster, cheaper, and simpler gamma-counting techniques, with results available after 3 h. All three methods have acceptable sensitivity, accuracy, precision, and reproducibility, and are specific for methotrexate, with no significant interference from naturally occurring folates or leucovorin. The assays in which the gamma emitters are used have significant practical advantages over the beta emitter and are much better suited to automation and clinical application. The main advantage of 75Se=labeled methotrexate is its longer half-life, 121 days, as compared with 60 days for 125I.