bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct spectrophotometric determination of alpha-amylase activity in salive, with p-nitrophenyl alpha-maltoside as substrate.
Authors: Gillard B K , Marksman H C , Feig S A 
Published: January 2020

Abstract
We describe a simple, direct kinetic method for determination of salivary alpha-amylase (1,4, alpha-D-glucan 4-glucanohydrolase, EC 3.2.1.1). The assay makes use of a well-defined substrate, p-nitrophenyl alpha-maltoside, which is hydrolyzed by alpha-amylase to a chromogenic product, p-nitrophenol. Activity is determined by directly monitoring the increase in absorbance of the reaction mixture. Amylase activity can be defined in international (IUB) units of micromoles of product/min per liter of saliva. For 22 healthy subjects, the mean +/- SD of amylase activity in mixed saliva was 2.77 +/- 1.12 U/liter. Activity and instrumental response were linearly related over the entire range tested (0.224 to 11.90 U/liter). The within-run precision (CV) over this range was better than 3% for all but the lowest activities. Values obtained with this assay correlate well with those obtained with a modified Nelson-Somogyi saccharogenic method (r = 0.979). The precision and simplicity of this assay suggest that it is the method choice for determining amylase activity in human saliva.
Influence of oleic acid on serum lipoprotein-X in vitro.
Authors: Muckle T J , Edwards J A , Auckland P 
Published: January 2020

Abstract
Lipoprotein-X is no longer detectable in serum by either the agar gel-electrophoresis/polyanion precipitation technique or immunoelectrophoresis with specific antiserum after in vitro addition of oleic acid. Evidence is presented which indicates that this ostensible loss is due not to its destruction, but rather to altered electrophoretic mobility. The findings suggest an explanation for the well known post-heparin "disappearance" of lipoprotein-X, and indicate that caution may be needed in the interpretation of such lipoprotein-X testing of sera from subjects with increased concentrations of lysolipids in their blood.
Urinalysis by use of multi-test reagent strips: two dipsticks compared.
Authors: Smith B C , Peake M J , Fraser C G 
Published: January 2020

Abstract
We compared Ames' "N-Multistix" with Boehringer's "Combur-8" ("Chemstrip-8") multi-test urine reagent strips by analysis of contrived urine specimens, testing accuracy, precision, specificity, and limits of detection of both products. Relative cost and ease of use were also examined. Each brand of urinary dipstick had specific advantages but it is unlikely that patient care would be adversely affected by preferential use of either product.
Immunoelectrophoretic quantitation of alpha-fetoprotein.
Authors: Pietrogrande M , Roffi L , Bassi A S , Vergani C 
Published: January 2020

Abstract
We describe an immunoelectrophoretic method for alpha-fetoprotein quantitation. The sensitivity of the method, which is easy to perform in the routine laboratory, is under the best conditions 50 mug/liter, but 83 mug/liter can always be detected. With this test, sera from patients with various hepatic diseases and from pregnancies can be tested.
Interconverting measurements of human lactate dehydrogenase activities in three buffers.
Authors: Buhl S N , Richards A H , Jackson K Y , Lubinski R , Vanderlinde R E 
Published: January 2020

Abstract
The lactate-to-pyruvate reaction for serum lactate dehydrogenase (LD) is most frequently assayed in one of three buffers, pyrophosphate (PPi), tris(hydroxymethyl)amino-methane (Tris), or 2-amino-2-methyl-1-propanol (AMP). We described interconverting results for serum samples and for highly purified LD isoenzymes I (dissolved in one of these matrixes) assayed in these buffers under optimized reaction conditions. The equation for converting results obtained for sera in Tris (x) to those in PPi(y) (both at 30 degrees C) is y = 0.74x+10 (n = 98). Since AMP is used extensively in Technicon procedures, we determined the LD activity of sera with an SMA 12/60, at 37 degrees C. The equation for convering these AMP results to results obtained in PPi at 30 degrees C is y = 0.45x-16 (n = 90). Very different equations were obtained with highly purified LD isoenzyme I maintained in two different matrixes and with both isoenzymes assayed in the same matrix. The matrix in which LD is dissolved and the proportion of various LD isoenzymes affect the magnitude of difference in observed LD activity under various conditions. Therefore, in clinical laboratories that use more than one analytical method or when conversion equations are used in the comparison of interlaboratory results, it is important to define the LD source, isoenzyme content, and the matrix, as well as the reaction conditions, and to use many samples with a wide range of activities when determining the conversion equations. For any changes in reagent source, substrate concentration, or alteration in procedure, a new normal range and new conversion equations should be determined.
Evaluation of current methods for creatine kinase isoenzyme fractionation.
Authors: Morin L G 
Published: January 2020

Abstract
I have evaluated electrophoretic, ion-exchange, kinetic, selective activation, and immunological methods of fractionating creatine kinase isoenzymes for diagnostic purposes. The last three were unsuitable. Electrophoretic methods had superior resolution and reliability, but were relatively insensitive when conventional film-drying techniques were used. With elution from the film, sensitivity was comparable to that of the ion-exchange methods. Electrophoretic methods require more skill than the other methods. Ion-exchange methods had acceptable resolution and reliability with potentially superior sensitivity; they require less skill than electrophoresis, but require about as much time. Batch operation of ion-exchange yielded superior efficiency and sensitivity, and was otherwise comparable to column operation.
Ultraviolet spectrometry of serum triglycerides by a totally enzymic method adapted to a centrifugal analyzer.
Authors: Wakayama J E , Swanson J R 
Published: January 2020

Abstract
We described a micromethod for determining serum triglycerides (triacylglycerols) with the centrifugal analyzer. This technique is based on the procedure of Bublitz and Kennedy [J. Biol. Chem. 211, 951 (1954)]. The enzymic hydrolysis requires 10 min at 30 degrees C. Twenty-six serum triglyceride assays can be done in about 30 min. Concentration and absorbance are linearly related up to 5.0 mmol/liter, but higher concentrations can be assayed by changing conditions slightly. Day-to-day reproducibility for the method was satisfactory (CV, 2.7 to 8.4%). Comparison of this method and two other methods for triglycerides, the automated Hantzsch condensation method and a commercial enzymic method (Calbiochem), gave correlation coefficients of 0.976 and 0.990, respectively. Results are unaffected by the presence of endogenous serum ADP, pyruvic acid, phosphatases, or ATPase.
Is lead poisoning still a problem?
Authors: Chisolm J J 
Published: January 2020

Abstract
Today, health professionals are concerned about whether asymptomatic or mildly symptomatic increases in lead absorption in preschool children is one of the important factors causing minimal brain dysfunction, which only becomes evident later during the school years. This concern arises, in part, because current screening data show that 5 to 10% of the children tested recently in the United States have a degree of increase in lead absorption sufficient to cause metabolic derangement in heme synthesis, but insufficient, with rare exception, to cause classical acute clinical symptoms of plumbism. These screening data are disturbing because similar increases in lead absorption in suckling (but not older) experimental animals have been shown in some studies to be followed by the delayed appearance of subtle deficits in learning ability and aberrations in behavior. Derangement of hemoglobin synthesis is the first adverse effect of increased lead absorption now detectable. Intervention on the basis of the first or critical effect of a toxic agent before more serious effects occur has advantages from the viewpoint of preventive medicine. Current CDC guidelines for prevention of childhood lead poisoning are based on this concept and recommend the use of micro-scale erythrocyte protoporphyrin tests in conjunction with micro blood lead tests for early detection of children with disturbed heme synthesis caused by lead.
Measurement of serum magnesium with a centrifugal analyzer.
Authors: Khayam-Bashi H , Liu T Z , Walter V 
Published: January 2020

Abstract
We show how serum magnesium can be determined with a centrifugal analyzer. The method is based upon a manual procedure involving magnesium/calmagite complex formation in an alkaline reagent mixture. The assay, performed at 30 degrees C, requires 5 mul of serum in a final reaction volume of 405 mul, including 350 mul of reagent mixture. The stable color produced at 1 min is measured at 520 nm. Linearity studies showed that Beer's law was followed to 50 mg/liter. Average analytical recovery was 97.3%. Within-day studies showed CV's of 3.36% and 1.09%, compared to day-to-day variations of 5.32% and 3.04% at 18.8 and 46.6 mg of magnesium per liter, respectively. Correlation studies with the manual method, the Du Pont aca (methylthymol blue compleximetric) procedure, and atomic absorption spectroscopy showed correlation coefficients of 0.996, 0.976, and 0.950, respectively. Results compare excellently with those by common present methods. The method is fast, economical, reliable, and applicable to small specimen volumes.
Alkaline phosphatase activity in the plasma of children and adolescents.
Authors: Fleisher G A , Eickelberg E S , Elveback L R 
Published: January 2020

Abstract
We determined plasma (serum alkaline phosphatase activity in 854 healthy students of the Rochester, Minnesota, public schools. Prepubertal girls had somewhat greater upper limits than did boys, and there was a low trend of increasing activity in both sexes. At the beginning of adolescence increasing activities were observed, which peaked at ages 11 to 12 years in girls and at ages 13 to 14 in boys. Adult values were not reached until six to eight years later. In 180 pairs of siblings, a significant intraclass correlation was noted. A possible role of alkaline phosphatase in the regulation of protein synthesis is suggested.
Evaluation of a semi-automated blood urea nitrogen analyzer.
Authors: Hanson D J , Bretz N S 
Published: January 2020

Abstract
We compared results for urea concentrations in plasma and serum as measured with the Kimble Blood Urea Nitrogen Analyzer method as the test method with those determined by continuous-flow analysis (AutoAnalyzer 1 method) as the comparison method. We evaluated accuracy and precision for patients' samples, National Bureau of Standards Standard Reference Material, College of American Pathologists Survey Validated Reference Materials, and College of American Pathologists Quality Assurance Service control materials. We found the test method to be more accurate and precise than the comparison method.
Separation of serum creatine kinase isoenzymes by ion-exchange column chromatography.
Authors: Klein B , Foreman J A , Jeunelot C L , Sheehan J E 
Published: January 2020

Abstract
We describe a practical, technically convenient DEAE-Sephadex chromatographic column and a three-fraction salt-gradient elution procedure, with which serum creatine kinase activity is rapidly and quantitatively separated into the isoenzyme components with excellent analytical recovery of the total activity applied. The homogeneity of the isoenzyme fractions was demonstrated by electrophoresis and rechromatography. Sera assessed by the Mercer fractionation [Clin. Chem. 20, 36 (1974)] and the present procedure showed excellent agreement.
Spectrofluorometry of free and protein-bound plasma tryptophan.
Authors: Woo J , Cano C , Cannon D C 
Published: January 2020

Abstract
We report a rapid, simple, and sensitive spectrofluorometric procedure for total serum or plasma tryptophan. Plasma deproteinization, tryptophan extraction, and pH optimization are all carried out with a buffered cellulose/ethanol reagent. The fluorescence is measured at an emission wavelength of 350 nm, on excitation of 290 nm. Tryptophan fluorescence relative to concentration is linear up to 50 mg/liter. The high precision, evidenced by a between-run coefficient of variation of 3.1%, negates the need for duplicate analysis of samples. Analytical recovery of tryptophan from plasma up to 50 mg/liter is 90-100%. We observed no significant difference between values for tryptophan in serum and plasma from the same individual. Assay of up to 32 samples requires 60 min. Commonly used anti-depressants have no detectable effect on tryptophan determination by this procedure.
D-Glucaric acid and gamma-glutamyltransferase as indices of hepatic enzyme induction in pregnancy.
Authors: Herzberg M , Tenenbaum E , Fishel B , Wiener M H 
Published: January 2020

Abstract
Increased activity of hepatic microsomal enzymes can be evaluated by measuring D-glucaric acid excretion in urine and gamma-glutamyltransferase (EC 2.3.2.2) activity in serum. Aside from diverse foreign compounds, endogenous steroid hormones have been shown to be normal substrates of the microsomal enzyme system. Because there is an increase in steroid production in pregnancy, we sought to determine whether these indices of induction increase during pregnancy. In 90 women in various stages of pregnancy, all with normal kidney function, we measured glucaric acid excretion in urine and activity of the transferase in serum and in urine. Glucaric acid increased markedly during pregnancy, from 14.4 +/- 2.1 in the first trimester to 23.5 +/- 2.8 mumol of D-glucaro-1,4-lactone per gram of creatinine in the third trimester. We saw no correlation between glucaric acid excretion and the transferase activity in serum or urine. Activity of gamma-glutamyl-transferase remains within normal limits throughout pregnancy, which leaves doubt as to the value of this measurement in evaluating enzyme induction owing to endogenous steroids.
Acid Phosphatase isoenzymes in Gaucher's Disease
Authors: Mercer Donald W , Peters Stephen P , Glew Robert H , Lee Robert E , Wenger David M 
Published: January 2020

Abstract
Acid phosphatase (EC 3.1.3.2) isoenzyme profiles of extracts of splenic tissue and serum from patients with Gaucher's disease were measured by a mini-column ion-exchange chromatographic method [Clin. Chem., 23, 000 (1977)]. Diagnosis of Gaucher's disease in the five patients studied was confirmed by demonstrating decreased (2.3 to 4.1 % of normal) glucocerebrosidase activity in the spleen. With p-nitrophenyl phosphate as substrate, in-creased acid phosphatase activity (three- to eight-fold normal) was demonstrated in spleen tissue from Gaucher's disease patients; isoenzyme profiles by the ion-exchange column technique showed acid phosphatase isoenzyme 5 to be the predominant isoenzyme. Comparison of acid phosphatase isoenzyme profiles from patients with Gaucher's disease and prostatic carcinoma revealed distinct differences in the activities of isoenzymes 2 and 5. The isoenzyme-5 measurement thus appears to provide a diagnostic test for Gaucher's disease that can be done rapidly and easily in the routine clinical chemistry labora-tory.
Photometry of Inulin and Polyfructosan by Use of a Cysteine/ Tryptophan Reaction
Authors: Waugh William H 
Published: January 2020

Abstract
Described are a macromethod for measuring 2 to 30 pg of polyfructoside in sample volumes of 0.5 ml and a mi¬cromethod for measuring 40 to 400 ng in 10-RI samples. The absorptivity of the cysteine/tryptophan color product is 2.5- to 10-fold those found with use of five other colorimetric methods for inulin. The method is highly specific for alkali-stable polyfructoside. Color, measured at 515 nm, was maximal on development at 56 °C for 25 min in dilute (57-58% by vol) sulfuric acid, after the addition of the combined cysteine hydrochloride/tryptophan reagent. Analytical recoveries of inulin and polyfructosan from plasma and urine were complete. With initial alkaline heating, the endogenous blank inulinoid values averaged 0.6 ± 0.47 (SD) mg/liter for plasma and 0.05 ± 0.024 mg/min for urine. The coefficient of variation of the macromethod was &lt;3%; that for the micromethod ranged from 1.3 to 6.3%. The micromethod appears adaptable to the determination of nanogram quantities of polyfruc¬toside in nanoliter volumes of biological fluids.
Amperometric Determination of Total Cholesterol in Serum, with Use of Immobilized Cholesterol Ester Hydrolase and Cholesterol Oxidase
Authors: Huang Hua-shan , Kuan Shia S , George G Guilbault 
Published: January 2020

Abstract
We describe an electrochemical method for simple, rapid, and economical assay of total serum cholesterol with use of immobilized cholesterol esterase (EC 3.1.1.13) and cholesterol oxidase (EC 1.1.3.6). A rotating porous cell was specially designed to hold the immobilized enzymes firmly and to allow the reaction mixture to pass through the en¬zyme layer easily, thus catalyzing the enzymatic trans¬formation quickly. Hydrogen peroxide resulting from the catalytic reactions was measured amperometrically at +0.60 V vs. a standard calomel electrode. The calibration curve for total serum cholesterol was linear from 0 to 5.00 g/liter. The method is specific, precise, and inexpensive. Our results correlate well with those obtained by the method of Abell et al. [Stand. Methods Clin. Chem. 2, 26 (1958)] , the correlation coefficient being 0.992. Ascorbic acid or bilirubin in concentrations up to 100 mg/liter do not interfere. The immobilized enzymes are stable, and the same immobilized-enzyme stirrer can be used for at least 200 accurate, reproducible assays.
The Gallium Melting-Point Standard: Its Role in Our Temperature Measurement System
Authors: Mangum B W 
Published: January 2020

Abstract
The latest internationally-adopted temperature scale, the International Practical Temperature Scale of 1968 (amended edition of 1975), is discussed in some detail and a brief description is given of its evolution. The melting point of high-purity gallium (stated to be at least 99.99999 % pure) as a secondary temperature reference point is evaluated. I believe that this melting-point tem-perature of gallium should be adopted by the various medical professional societies and voluntary standards groups as the reaction temperature for enzyme reference methods in clinical enzymology. Gallium melting-point cells are available at the National Bureau of Standards as Standard Reference Material No. 1968.
The Gallium Melting-Point Standard: Its Role in Manufacture and Quality Control of Electronic Thermometers for the Clinical Laboratory
Authors: Sostman Henry E 
Published: January 2020

Abstract
I discuss the traceability of calibration of electronic ther-mometers to thermometric constants of nature or to the National Bureau of Standards, from a manufacturer's basic standards through the manufacturing process to the user's laboratory. Useful electrical temperature sensors, their advantages, and means for resolving their disadvantages are described. I summarize our development of a cell for realizing the melting phase equilibrium of pure gallium (at 29.770 °C) as a thermometer calibration fixed point, and enumerate its advantages in the routine calibration veri-fication of electrical thermometers in the clinical chemistry laboratory.
Specific Conductivity of Urine and Sensitivity of Enzyme Immunoassay Methods of Analysis for Drugs of Abuse
Authors: Andersen Ole , Eriksen Peter Bonne 
Published: January 2020

Abstract
We studied the sensitivity of the EMIT® assays of amphet-amine, benzodiazepines (diazepam), methadone, opiates (morphine), and propoxyphene at different specific con-ductivities in urine. The specific conductivity was varied by adding NaCI. For a sensitivity of 0.5 mg of drug per liter, the urine must have a specific conductivity of less than about 35 mS/cm in all these assays except that for ben¬zodiazepine, for which it must be less than about 20 mS/cm.
High-performance liquid chromatography of pyruvic and alpha-ketoglutaric acids and its application to urine samples.
Authors: Liao J C , Hoffman N E , Barboriak J J , Roth D A 
Published: January 2020

Abstract
Pyruvic and alpha-ketoglutaric acids were quantitatively and rapidly converted to quinoxalones by a new method, to enhance their detectability in the ultraviolet. The quinoxalones were separated by reversed-phase chromatography with use of 10 micronm particles packed in a 30-cm (length) column. An aqueous solution of ammonium acetate and methanol was used for linear gradient elution. The urinary excretion of pyruvic and alpha-ketoglutaric acids by normal individuals, diabetic patients, and patients with renal dysfunction was determined.
Interference by p-hydroxyphenobarbital in the 125I-radioimmunoassay of serum and urinary phenobarbital.
Authors: Viswanathan C T , Booker H E , Welling P G 
Published: January 2020

Abstract
A radioimmunoassay for barbiturates is shown to be equally sensitive to phenobarbital and its major urinary metabolite, p-hydroxyphenobarbital, in serum and urine. Interference by the metabolite can be essentially eliminated by selectively extracting phenobarbital into chloroform. The extraction efficiency of the method for phenobarbital was 93+/-2% (SD) over the concentration range studied. Although cross reactivity between barbiturates and their metabolites may be less important in determining cases of barbiturates abuse or overdose, it may be extremely important if data on serum or urine are required for accurate estimates of drug disposition, or in establishing dose/response relationships.
Cholesterol determination in high-density lipoproteins separated by three different methods.
Authors: Lopes-Virella M F , Stone P , Ellis S , Colwell J A 
Published: January 2020

Abstract
We describe a simplified method for measuring high-density lipoprotein cholesterol in serum after very-low- and low-density lipoproteins have been precipitated from the specimen with sodium phosphotungstate and Mg2+. Values so obtained correlate well with values obtained with the heparin-Mn2+ precipitation technique (r = 0.95, CV less than 5% in 66% of the subjects studied and between 5 and 10% in the remaining ones) or by ultracentrifugal separation (r = 0.82, CV less than 5% in 80% of the subjects studied and between 5 and 10% in the remaining ones). Our precipitation technique is more appropriate for routine clinical laboratory use.
Proficiency testing: purification of lactate dehydrogenase 1 and results of its use as a reference material in the New York State program.
Authors: Buhl S N , Copeland W H , Fasce C F , Kowalski P , Richards A H , Vanderlinde R E 
Published: January 2020

Abstract
Highly purified human lactate dehydrogenase 1 has been used in an interlaboratory evaluation and improvement progran in clinical chemistry in New York State since 1971. Although there are difficulties in determining and assigning the most nearly accurate values for test samples in the absence of a reference method and a reference material, we have minimized these difficulties by using human lactate dehydrogenase preparations purified as we describe here and suspended in the same matrix, and by utilizing "reference laboratories" that routinely are doing multiple assays to determine the most nearly accurate value. The lactate dehydrogenase used in the program is stable for longer than 1.5 years. Conversion factors were used to convert all results to U/liter at 30 degrees C. Review of the data for 1972-75 shows a marked improvement in the accuracy of virtually all methods used to determine this enzyme.