bluuebunny/crossref_metadata_2025 huggingface dataset:
Interrelations of the various mathematical approaches to radioimmunoassay.
Authors: Fernandez A A , Stevenson G W , Abraham G E , Chiamori N Y
Published: January 2020

Equations used for calculation of radioimmunoassay data are derived and compared. We show that the equation developed by Fernandez and Loeb is the most general of these. Those of Ekins et al., Hales and Randle, and Rodbard et al. are all derived here from this basic equation by neglecting certain of its terms. The logit-log plot of Rodbard et al. is a logarithmic transformation of the linear Hales-Randle equation. The basic equation, derived here solely from the mass-action law, approaches linearity under certain conditions without complex mathematical transformations of analyte concentrations or observable parameters. Applications are also presented.
Determination of urinary normetanephrine and metanephrine by radial-compression liquid chromatography and electrochemical detection.
Authors: Orsulak P J , Kizuka P , Grab E , Schildkraut J J
Published: January 2020

A procedure has been developed for determining the O-methylated catecholamine metabolites, normetanephrine and metanephrine, in urine by use of radial-compression liquid chromatography followed by electrochemical detection. Normetanephrine and metanephrine are isolated from hydrolyzed urine by ion-exchange on small, commercially available, disposable columns and preconcentrated by solvent extraction. They are then separated by reversed-phase ion-pair chromatography, with use of a radial compression cartridge and radial compression module, and quantified with 3-methoxy-4-hydroxybenzylamine as internal standard. Normetanephrine, metanephrine, and the internal standard are separated from interfering peaks in about 15 min. The method is applicable to the relatively low amounts of normetanephrine (100-600 micrograms/24 h) and metanephrine (50-400 micrograms/24 h) found in normal subjects and patients with depressive disorders or hypertension. Within-day CVs ranged from 1.1 to 2.2% for normetanephrine and 1.2 to 6.9% for metanephrine; the corresponding between-day CVs were 4.9 and 5.7% over these ranges.
Cytoplasmic creatine kinase isoenzymes quantitated in tissue specimens obtained at surgery.
Authors: Urdal P , Urdal K , Strømme J H
Published: January 2020

Because previous reports have given inconsistent results, we re-examined the catalytic concentrations of cytoplasmic creatine kinase (CK) and of CK isoenzymes in 38 biopsies obtained from 19 different tissues. After homogenization and centrifugation many tissues showed high CK catalytic concentrations; 11 of them contained activity exceeding 50 U/g wet weight (Scandinavian recommended method). The highest specific activities were found in skeletal muscle (2400 U/g), brain (530 U/g), and myocardium (460 U/g). The separate isoenzyme activities were estimated by electrophoretic, anion-exchange chromatographic, immunoinhibiting, and radioimmunological methods. CK-BB was present in all tissues and, in fact, was the only cytoplasmic CK isoenzyme in 16 of the 19 tissues examined. CK-MM was the major isoenzyme of skeletal muscle and myocardium and was in addition observed in placenta, in trace amounts. CK-MB was present in high catalytic concentrations in myocardium (20% of total CK) and in low catalytic concentrations in skeletal muscle (1.1% of total CK).
Fetal lung maturity assessed by fluorescence polarization: evaluation of predictive value, correction for endogenous fluorescence, and comparison with L/S ratio.
Authors: Cox K H , Ross J B , Peterson A P , Benedetti T J
Published: January 2020

The steady-state polarization (or anisotropy) of the fluorescent dye 1,6-diphenyl-1,3-5-hexatriene in amniotic fluid samples and the lecithin/sphingomyelin ratio of the samples were correlated with development of respiratory distress syndrome in newborns. We found that clinical samples have a variable endogenous fluorescence that reduces the observed polarization (or anisotropy). This background is a major interference in the assessment of fetal lung maturity by the polarization method. Correction for this interference, by also measuring the blank fluorescence and anisotropy of the sample, provides a clinical tool with a lower coefficient of variation than that of the more time-consuming lecithin/sphingomyelin ratio. The clinical correlation for 17 cases of respiratory distress syndrome in a high-risk population (60 births; twins counted as a single birth) indicates that the two methods are equivalent for predicting immature fetal lung status.
Evaluation of an enzymic procedure for the measurement of acetaminophen.
Authors: Price C P , Hammond P M , Scawen M D
Published: January 2020

We evaluated a new method for measurement of acetaminophen. From acetaminophen, acetate and p-aminophenol are enzymically produced, and the latter product is determined colorimetrically by reaction with o-cresol and ammoniacal copper sulfate. The method is rapid and precise, and results compare well with those by spectrophotometric and liquid-chromatographic techniques. Major metabolites of acetaminophen, some commonly used drugs, or phenolic substances that may be present in patients with liver or renal disease do not interfere.
Macromolecular alkaline phosphatase and an immunoglobulin G that inhibited alkaline phosphatase in a patient's serum.
Authors: Nakagawa H , Umeki K , Yamanaka K , Kida N , Ohtaki S
Published: January 2020

Macromolecular alkaline phosphatase (EC 3.1.3.1) was found in the serum of a patient suffering from myasthenia gravis (adult type II) complicated with thymoma, and was shown by immunoelectrophoresis to be bound to immunoglobulins A and G (IgG). Placental alkaline phosphatase, complexed with either the patient's serum or IgG purified from the patient's serum, remained at the origin on electrophoresis, with significant loss of activity. Intestinal alkaline phosphatase, complexed with either the patient's serum or the patient's IgG, migrated to a position similar to that of the macromolecular alkaline phosphatase in the patient's serum on electrophoresis. About 50% of the placental alkaline phosphatase activity was inhibited with 0.1-0.2 g of the patient's IgG per liter, but 6.93 g of the IgG per liter was required for about 20% inhibition of the intestinal alkaline phosphatase activity. The complex of intestinal alkaline phosphatase with the patient's IgG was fairly heat stable. From these results, we concluded that the macromolecular alkaline phosphatase in the patient's serum consisted of intestinal alkaline phosphatase and IgG that was specific for placental alkaline phosphatase.
Some considerations of methodology and standardization of apolipoprotein A-I immunoassays.
Authors: Steinberg K K , Cooper G R , Graiser S R , Rosseneu M
Published: January 2020

Apolipoprotein A-I (apo A-I) is the major protein of high-density lipoprotein. Compelling evidence suggests that measurement of concentrations of apo A-I in serum may be useful in predicting and assessing ischemic heart disease. The following review of methods of isolation, characterization, and assay of apo A-I has been developed to assess the possibility of standardizing apo A-I immunoassays. We consider the properties of apo A-I that have an effect on its quantification, such as self-association, polymorphism, and stability characteristics. We attempt to review critically the various methods presented, but more information about the physicochemical properties of the protein is required before definitive recommendations can be made.
A new reagent strip (Visidex) for determination of glucose in whole blood.
Authors: Sherwood M J , Warchal M E , Chen S T
Published: January 2020

A new solid-phase reagent strip for determination of glucose in whole blood, Visidex, has been developed specifically for visual use in conjunction with a calibrated color scale. Two reagent pads are used, each formulated for a different portion of the range of clinical values, to maximize the visual resolution available to the user. Colorimetric examination of reacted reagent pads indicated that the label color blocks match closely the appearance of the reagent pads; that the reagent pads exhibit good precision; and that the colors of the reagent pads are independent of operator technique, sample volume (20-50 microL), and effects of potential interferents studied (although high concentrations of fluoride slightly inhibited color development). Glucose measurements obtained visually with the Visidex system correlated well with values obtained with a YSI Glucose Analyzer (for two separate studies, slope = 0.96 and 1.04, r = 0.99 and 0.96, and n = 172 and 543, respectively).
Improved measurement of acetylsalicylic acid esterase in serum.
Authors: Sørensen S
Published: January 2020

A fixed-time incubation method for measuring acetylsalicylic acid esterase was improved by using a higher concentration of the substrate, acetylsalicylic acid, and an activator, Ca2+. The enzymatic activity in serum was 25-fold that measured by earlier methods. Inhibition studies showed a pattern similar to that reported for cholinesterase. Use of cholinesterase inhibitor in sample tubes for determination of acetylsalicylic acid and salicylic acid is recommended.
Clinical evaluation of Eastman Kodak's Ektachem 400 Analyzer.
Authors: Kadinger C L , O'Kell R T
Published: January 2020

We evaluated the performance of the Kodak Ektachem 400 Analyzer in a 16-week clinical trial. We assessed four potentiometric tests and nine colorimetric tests for precision and correlation with results obtained some other commonly used instruments (Technicon SMA II and C800 System, Du Pont aca II, and Baker CentrifiChem). The comparison was favorable for all tests except albumin, sodium, and carbon dioxide. The reagents are stable. Little refrigerator storage space is needed. The computer system and the modular component design of the Ektachem 400 Analyzer make operation, troubleshooting, and preventive maintenance relatively easy.
Further evaluation of luminol-enhanced luminescence in the diagnosis of disorders of leukocyte oxidative metabolism: role of myeloperoxidase.
Authors: Cohen M S , Shirley P S , DeChatelet L R
Published: January 2020

Chemiluminescence can be used to identify defects in the oxidative metabolism of granulocytes. This procedure has recently been adopted for use with microliter quantities of whole blood, appropriate for prenatal or neonatal study. Although the contribution of myeloperoxidase to the chemiluminescence assay has been noted, the possible diagnostic confusion between chronic granulomatous disease of childhood (which is rare and severe) and myeloperoxidase deficiency (which is common and of little clinical consequence) has not been stressed. We report a father and his infant daughter whose cells emitted no light in the luminol-enhanced luminescence assay; both patients are totally peroxidase deficient. These results emphasize the hereditary nature of myeloperoxidase deficiency, and the possibility for erroneous diagnosis of chronic granulomatous disease of childhood based on the luminol-enhanced luminescence test.
Interlaboratory proficiency survey of high-density lipoprotein cholesterol measurement.
Authors: Warnick G R , Benderson J M , Albers J J
Published: January 2020

Proficiency surveys of Seattle-area laboratories suggest only slight improvement in overall performance in high-density lipoprotein (HDL) measurement between 1978 and 1982, although the reported workload for HDL has increased by 15%. The mean interlaboratory SD was 64 mg/L (ranging from 34 for a pool averaging 299 mg/L to 136 for a pool averaging 886 mg of HDL cholesterol per liter) in 1982, compared with 79 mg/L (range 48-155) in 1978-79. Of the individual laboratory results in the current survey, 39% deviated by more than 50 mg/L from target values as compared with 37% in 1978-79. The discrepant values were primarily ascribable to method inaccuracy: only 30% of laboratories in 1982 reported results that averaged within 30 mg/L of target values (vs 50% in 1978). For within-run precision, 80% of laboratories in 1982 had SDs of less than 30 mg/L, vs 70% in 1978. The 1982 survey included a lyophilized serum prepared by spray freezing and bulk lyophilization (Hyland Omega), identical to the pools used in the College of American Pathologists Comprehensive Chemistry Survey, and five pools of frozen plasma. Interlaboratory variation and biases for the Omega pool were similar to those for the frozen pools.
Clinical implications of differences between two recommended procedures for determination of aspartate aminotransferase.
Authors: Dols J L , van Zanten A P
Published: January 2020

We compared two officially recommended methods for determination of aspartate aminotransferase (EC 2.6.1.1): that of the International Federation of Clinical Chemistry (IFCC) and that of the Deutsche Gesellschaft für Klinische Chemie (DGKC). We used automated enzyme analyzers, initiating the reactions with 2-oxoglutarate. Normal values, 10-30 U/L (IFCC) and 7-18 U/L (DGKC), were apparently insensitive to intra-individual variations. Samples obtained from patients with heart disease showed a markedly different amount of activation with pyridoxal phosphate as compared with samples from other patient categories. Ratios for aspartate aminotransferase/alanine aminotransferase, as used in the differentiation of liver disease, can still be used with either method for determination of aspartate aminotransferase.
Development and analytical performance of automated tests for antithrombin III and plasminogen on the Du Pont aca analyzer.
Authors: Perry J F , Siefring G E , Reider M C , Coleman P L , Wehrly J A
Published: January 2020

We describe assays for functional antithrombin III (AT III) and plasminogen in plasma with the Du Pont aca discrete clinical analyzer. Both are two-stage kinetic assays, based on synthetic substrate methodologies, and require 20-microL sample volumes. In the AT III assay the sample is incubated with excess thrombin and heparin to form the functionally inactive AT III-thrombin complex. Residual thrombin is measured through its rate of hydrolysis of a lysine thioester and is inversely related to analyte concentration. In the plasminogen assay excess streptokinase is reacted with the sample to form an enzymatically active complex. The substrate hydrolysis rate of this complex is measured, which is linearly related to the concentration of plasminogen in the sample. Reaction conditions for both assays were optimized by univariate and response surface techniques. The assay for AT III has a range of 0 to 150% of the value for normal human plasma (% NHP) with a CV of 3% at 80% NHP. The plasminogen assay is linear from 25 to 200% NHP with a CV of less than 2% at 80% NHP. No significant interferences with either method by common blood components or drugs were found.
Radioenzymatic assay for direct measurement of plasma pyridoxal 5'-phosphate.
Authors: Camp V M , Chipponi J , Faraj B A
Published: January 2020

A radioenzymatic assay for measurement of pyridoxal 5'-phosphate (PLP) is described, based on the incubation of L-[3H]tyrosine (10(6) cpm, spec. acty. 1.88 Ci/mol) in the presence of the apoenzyme tyrosine decarboxylase (EC 4.1.1.25) from Streptococcus faecalis and PLP in phosphate buffer (0.1 mol/L, pH 5.5) at 37 degrees C for 60 min. The decarboxylated metabolite formed, [3H]tyramine, was selectively extracted into ethyl acetate, and the tritium radioactivity in the sample was determined by liquid scintillation counting. As little as 0.5 nmol of PLP can be detected per liter. The assay is specific, no cross reactivity having been noted for several compounds closely related to PLP. With this we could directly measure the concentrations of PLP in plasma without prior deproteinization and ether washing of the samples. Using the assay to determine plasma concentrations of PLP in healthy adult populations, we found results that were comparable with previously reported data.
Ultracentrifugation in swinging-bucket and fixed-angle rotors evaluated for isolation and determination of high-density lipoprotein subfractions HDL2 and HDL3.
Authors: Demacker P N , van Sommeren-Zondag D F , Stalenhoef A F , Stuyt P M , van't Laar A
Published: January 2020

We evaluated the density-gradient ultracentrifugation method in a swinging-bucket rotor (Anal Biochem 111, 149-157, 1981) in a slightly modified version for isolation and determination of high-density lipoprotein (HDL) subfractions. We prestained the serum with Coomassie Brilliant Blue R, which did not change the hydrated densities of the lipoproteins, and after only 2.2 X 10(8) gav . min obtained an equilibrium distribution of the lipoproteins along the gradient. The density distribution of the HDL of 120 sera obtained from apparently healthy persons and from patients with different types of hyperlipoproteinemia was bimodal. The HDL2 could be isolated in the density range 1.072-1.098 kg/L and the HDL3 at 1.100-1.176 kg/L, the latter fraction being more heterogeneous. At a solvent density of 1.100 we obtained similar results for HDL2-and HDL3-cholesterol by ultracentrifugation in two different fixed-angle rotors with tube angles of 15 degrees or 35 degrees. Independent of the rotor and the ultracentrifugation technique, subfractionation at d = 1.100 resulted in more distinct stained entities than ultracentrifugation at d = 1.125. In the swinging-bucket rotor procedure, interference by sinking pre-beta-lipoproteins was minimized because, having hydrated densities between 1.058 and 1.075, they could be removed without aspirating the HDL2. The method is both accurate and precise. For HDL2- and HDL3-cholesterol determined in a thawed frozen serum pool, CVs were 8.8 and 6.3%, respectively (n = 18).
Liquid-chromatographic quantification of piracetam.
Authors: Nalbandian R M , Kubicek M F , O'Brien W J , Nichols B , Henry R L , Williams G A , Goldman A I , Adams D , Teng C M
Published: January 2020

Piracetam, an analog of gamma-aminobutyric acid, absorbs maximally at 197 nm. Its molar absorptivity at 208 nm and pH 4.5 is 3576 (SD 251) L . mol-1 cm-1, approximately 45% of its absorptivity at 197 nm. Direct quantification of piracetam at 197 nm in biological extracts is complicated by the fact that many other compounds absorb between 190 and 220 nm due to carbon-nitrogen bonding. Chromatography of methanol extracts of serum and aqueous humor on a reversed-phase C-18 column developed isocratically with KH2PO4 (0.1 mol/L, pH 4.8) allows detection and quantification of 0.2 mmol of piracetam per liter. Under these conditions the retention time of piracetam is about 5 min. The detector response is linear for quantities between 5 and 15 nmol. The method is rapid, inexpensive, and convenient for the clinical laboratory.
An automated dry-slide enzymatic method evaluated for measurement of creatinine in serum.
Authors: Toffaletti J , Blosser N , Hall T , Smith S , Tompkins D
Published: January 2020

We evaluated an automated dry-slide enzymatic method involving creatinine iminohydrolase for measurement of creatinine in serum with the Kodak Ektachem analyzer. The means (and SD) for three commercially available quality-control sera, analyzed during eight weeks, were 9.7 (1.0), 16.6 (0.9), and 61 (2.1) mg/L. The regression equation for 105 samples measured with the Technicon SMAC (x) and Ektachem Analyzers (y) was: y = (0.89 +/- 0.007)x + (1.7 +/- 0.3) mg/L and for 170 samples measured with the Beckman Astra (x) and Ektachem analyzers (y): y = (1.00 +/- 0.005)x - (1.9 +/- 0.16) mg/L. Sixty-one samples from renal-transplant patients showed nearly the same agreement. The enzymatic method had no interference from substances that interfere with many Jaffé methods for creatinine, including acetoacetate. The drugs cephalothin and cephoxitin did not interfere, but 5-fluorocytosine interfered significantly with creatinine in the Ektachem method. Values for several ketone-positive sera were 5 to 10 mg/L higher by the Astra relative to the Ektachem. Grossly hemolyzed or lipemic samples were analyzed without difficulty. We conclude that this enzymatic method for creatinine in serum has the speed and precision necessary for routine clinical laboratory use and, except for one drug, the method appears to be specific for creatinine.
Deficiency of glycerol kinase (EC 2.7.1.30).
Authors: Eriksson A , Lindstedt S , Ransnäs L , von Wendt L
Published: January 2020

We describe the case of a 10-year-old boy who had been admitted on several occasions with a diagnosis of gastroenteritis. He had been severely ill, and on one occasion lost consciousness. He had a metabolic acidosis on these occasions. Examination of the urine by gas chromatography-mass spectrometry showed a large peak, identified as glycerol. The concentration of glycerol in the urine was 40-280 mmol/L and the concentration in plasma about 2 mmol/L. He was subjected to a fast of 21 h, at the end of which he expressed feelings of discomfort and nausea, began vomiting, and became somnolent. During this period the blood glucose concentration was only slightly decreased, the plasma glycerol concentration increased to 4.9 mmol/L, and the plasma lactate concentration increased to 3.8 mmol/L. During work on a bicycle ergometer for 35 min (40 W) he complained of muscle pain and became nauseated, but there was no significant increase in the concentration of plasma glycerol. The activity of glycerol kinase (EC 2.7.1.30) in leukocytes and cultured fibroblasts was less than 1% of the value for healthy subjects.
An enzymic radiochemical method for determining phosphatidylglycerol in amniotic fluid.
Authors: Siegel L , Walker S I , Robin N I
Published: January 2020

We describe an enzymic quantification of phosphatidylglycerol in amniotic fluid. Phosphatidylglycerol is hydrolyzed in alkali and the resulting glycerol is then enzymatically phosphorylated with adenosine 5'-[gamma-32P]triphosphate to yield glycero[32P]phosphate. After removal of excess [gamma-32P]ATP by charcoal, the radioactivity of the glycerophosphate is measured in a liquid scintillation counter. Triglyceride in the amniotic fluid is hydrolyzed by lipase before extraction and thus does not interfere with the analysis. This method is specific for phosphatidylglycerol. Preliminary studies suggest that a phosphatidylglycerol value greater than or equal to 10 nmol/mL correlates with fetal lung maturity.
Apoenzyme content of serum aminotransferases in relation to plasma pyridoxal-5'-phosphate concentration.
Authors: Westerhuis L W , Hafkenscheid J C
Published: January 2020

To investigate the considerable variation in stimulation of serum aminotransferase activities by pyridoxal-5'-phosphate added in vitro, we determined the pyridoxal-5'-phosphate content of plasma, using the tyrosine decarboxylase reaction together with the catalytic activities of alanine aminotransferase and aspartate aminotransferase, with and without pyridoxal-5'-phosphate supplementation, within a group of normal human individuals. We found a very significant inverse linear relationship between plasma pyridoxal-5'-phosphate concentration and stimulation of the activities of these enzymes in serum after supplementation with pyridoxal-5'-phosphate. We conclude that the degree of stimulation of the apoenzyme of the two serum aminotransferases clearly depends on the pyridoxal-5'-phosphate concentration in vivo.
Quantitative liquid-chromatographic estimation of bilirubin species in pathological serum.
Authors: Lauff J J , Kasper M E , Ambrose R T
Published: January 2020

Earlier we described a "high-performance" liquid-chromatographic procedure for separating the four distinct fractions of bilirubin (unconjugated, monoconjugated, diconjugated, and protein-bound) in pathological human serum (J. Chromatogr. 226: 391-402, 1981). We have modified the prechromatography precipitation of the serum globulins required in that method and have measured the bilirubin content of the precipitate spectrophotometrically. On average, the precipitate contained less than 10% of the total bilirubin in the serum samples. Adding the value obtained for the precipitate to that obtained by chromatography for the individual bilirubin fractions gave an estimate of the concentration of the total bilirubin in the sample. For 357 samples from 132 patients, this total value correlated well with that obtained by the Jendrassik-Gróf diazo procedure (slope = 1.00; r = 0.995, linear least-squares fit). The CV for the total and fractional bilirubin measurements was, on average, less than or equal to 5% for pathological sera. Serum sampled at different times from the same patient showed significant changes in the distribution of bilirubin among the four fractions.
Enzymic assay for phosphatidylcholine and sphingomyelin in serum.
Authors: Blaton V , De Buyzere M , Spincemaille J , Declercq B
Published: January 2020

We describe a method for the direct enzymatic determination of phosphatidylcholine and sphingomyelin in serum. Phospholipase C (EC 3.1.4.3) and sphingomyelinase (EC 3.1.4.12) are used to hydrolyze phosphatidylcholine and sphingomyelin, respectively, with high specificity; alkaline phosphatase (EC 3.1.3.1) is used to cleave inorganic phosphorus. The choline group, after oxidation with choline oxidase (EC 1.1.3.17), is detected with 4-aminoantipyrine. Alternatively, phosphorus is assayed with metavanadate. The excellent agreement between results of this modification of a procedure described by Artiss et al. (Microchem. J. 26: 1017, 1980) for amniotic fluid and of the conventional thin-layer chromatographic method makes this an attractive method for determination of both phospholipid subclasses in serum.
Ionized calcium in human milk determined with a calcium-selective electrode.
Authors: Allen J C , Neville M C
Published: January 2020

We measured the concentration of ionized calcium in human milk with a Radiometer ionized calcium analyzer at 37 degrees C. This instrument is designed to use simultaneous outputs from a pH electrode and a calcium ion-selective electrode to obtain the true ionized calcium in blood plasma. Because both the ionic strength and the pH of human milk differ significantly from that of plasma, we used a calibration curve that corrected for these variables. No other substances in milk interfered with the electrode response to Ca2+. The Ca2+ concentration of milk decreased and the pH increased as CO2 was lost to the atmosphere. Samples collected in glass capillaries, which minimized CO2 loss, contained 2.84 (SD 0.56) mmol of Ca2+ per liter at pH 6.98. We emphasize the importance of maintaining physiological CO2 concentrations when Ca2+ is being measured in milk.
Ferritin concentrations in plasma from capillary (finger prick) blood and venous blood compared.
Authors: Mejía L A , Viteri F E
Published: January 2020

Investigating the feasibility and validity of determining plasma ferritin concentration in blood obtained by finger prick, we studied 29 adults (ages 21-49 years) and 35 children (ages 14-66 months). Blood was sampled simultaneously in the same subject from both the antecubital vein (venous blood) and by finger pricking (capillary blood). The plasma was obtained by centrifugation. Ferritin concentration was determined by immunoradiometric analysis. Ferritin concentration in plasma from capillary blood was significantly higher than in venous plasma (p less than 0.01). This difference was more marked in children. The correlation between ferritin from the two blood sources was highly significant (r2 = 0.945 and 0.994 for samples from adults and children, respectively), and the slopes of the respective regression lines in both children and adults were significantly different from 1 (p less than 0.0001). We conclude that, despite the close association between the two procedures, the determination of ferritin concentration in capillary blood plasma overestimates the concentration of ferritin in venous blood plasma.
Chronic hyperamylasemia and chronic pelvic inflammatory disease.
Authors: Jacobs E , Jennette J C , Reavis R A
Published: January 2020

A 54-year-old woman with chronic pelvic inflammatory disease and pyelonephritis developed persistent hyperamylasemia with transient increases in the amylase-creatinine clearance ratio. Even though chronic pancreatitis was suspected clinically, at postmortem examination the pancreas was found to be normal. We suggest that the hyperamylasemia resulted from entry into the circulation of amylase produced within sequestered endosalpingeal epithelial cysts, possibly amplified by impaired renal clearance. Thus, the potential of the serum amylase assay as a sign of serous ovarian tumors is further indicated.
Inexpensive double-antibody fluoroimmunoassay for aminoglycoside antibiotics, phenytoin, and theophylline in serum.
Authors: Kurtz M J , Billings M , Koh T , Olander G , Tyner T , Weaver B , Stone L
Published: January 2020

We describe simple, clinically useful double-antibody fluoroimmunoassays for amikacin, gentamicin, tobramycin, theophylline, and phenytoin. The fluorescent tracers were prepared by conjugation to fluorescein isothiocyanate; the antisera were raised in rabbits. A simple filter fluorometer and disposable culture tubes are used. The tracer, sample, and first and second antibodies are combined and incubated at room temperature for 30 min. A precipitation-acceleration buffer is added, the samples are centrifuged, and the fluorescence of the supernate is measured directly in the assay tube without decantation. Interferences, usually negligible, can be corrected for by use of a sample blank. Results compare favorably in performance with various commercially available RIA and enzyme immunoassays.
Beta-carotene determined in serum by liquid chromatography with an internal standard.
Authors: Driskell W J , Bashor M M , Neese J W
Published: January 2020

We describe a procedure for quantitative determination of beta-carotene in human serum. The 0.1-mL serum sample is precipitated with ethanol containing the internal standard, dimethyl-beta-carotene, then extracted with hexane. This extract is injected onto a reversed-phase, "high-performance" liquid-chromatography column, and the carotenes are resolved and eluted with an acetonitrile/methylene chloride isocratic solvent system. They are quantified from the peak-height ratios of their absorbance at 450 nm. About 14 min is required for each chromatogram. The procedure has excellent precision and is appropriate for routine use in analysis of large numbers of samples. The method should be particularly useful for clinical studies on the relationship of serum beta-carotene and cancer incidence in human populations.
Serum LD-1 activity in suspected acute myocardial infarction.
Authors: Gerhardt W , Hofvendahl S , Ljungdahl L , Waldenström J , Tryding N , Pettersson T , Ohlsson O
Published: January 2020

We have studied the diagnostic value of measuring lactate dehydrogenase (LD) isoenzyme 1 in serum of 331 cases of suspected acute myocardial infarction (AMI). At a discriminatory level of 200 U/L (Scandinavian Committee on Enzymes, recommended method for the determination of LD) LD 1 verified the diagnosis in 96% of the AMI cases and excluded it in 96% of the not-AMI cases when samples were drawn 24-72 h after onset of pain. The correlation between 24-h S-LD-1 and 16-h S-CK B activities was 0.94 in the AMI cases. We found that quantitation of serum LD-1 is diagnostically more reliable than the serum LD-1/LD ratio.
Quantitative enzyme antigen immunoassay of acetylcholinesterase in amniotic fluid.
Authors: Nørgaard-Pedersen B , Hangaard J , Bjerrum O J
Published: January 2020

An enzyme immunoassay for acetylcholinesterase in amniotic fluid is described. Rabbit antiserum (IgG fraction) against human erythrocyte membrane acetylcholinesterase is first attached to microtitre plates. Samples containing acetylcholinesterase are added and the enzyme activity is then measured, with acetylthiocholine as substrate and Ellman's reagent as coupling salt. Results are comparable with those by qualitative determination of the enzyme after polyacrylamide gel electrophoresis, except for blood-contaminated amniotic fluids. One person can perform 200 enzyme analyses per day. Intra- and interassay coefficients of variation are less than 5% at concentrations from 15 to 450 arb. units/L. The mean catalytic concentration in 400 amniotic fluid samples was 21 arb. units/L (range 5 to 70 arb. units/L) with 1000 arb. units/L for a human serum pool as standard. All 39 cases of neural tube defects and two-thirds of cases with omphalocele and gastroschisis had abnormally high values, exceeding 75 arb. units/L.
Liquid-chromatographic determination of nadolol in plasma.
Authors: Gupta R N , Haynes R B , Logan A G , Macdonald L A , Pickersgill R , Achber C
Published: January 2020

We describe a liquid-chromatographic procedure for determining nadolol in plasma. After an analog of nadolol is added as internal standard, the plasma sample is passed through a disposable BondElut C18 column. After several column washes, nadolol and the internal standard are eluted with methanol, and the eluate is evaporated and reconstituted with the mobile phase (acetonitrile/water, perchloric acid, and tetramethylammonium hydroxide). An aliquot of the extract is chromatographed on a non-silica resin-base reversed-phase column. The peaks are detected by fluorescence (lambda ex = 265 nm and lambda em = 305). Drug and internal standard are well resolved, and only a few extraneous peaks appear. The standard curve ranges from 10 to 400 micrograms/L. We are using this procedure to determine steady-state concentrations of nadolol in patients receiving various dosages of nadolol along with other types of antihypertensive drugs.
Three commercial methods for serum ferritin compared and the high-dose "hook effect" eliminated.
Authors: Ng R H , Brown B A , Valdes R
Published: January 2020

We evaluated four commercial kits for measuring serum ferritin, based on three techniques: immunoradiometric assay, radioimmunoassay, and enzyme immunoassay. The kits evaluated were those manufactured by Abbott Laboratories, Clinical Assays, Corning Medical, and Ramco. Two of the immunoradiometric kits showed satisfactory results with respect to sensitivity and precision; they should be useful in diagnosing individuals with uncomplicated iron-deficiency anemia. One of the immunoradiometric assay kits, however, showed a high-dose "hook effect," beginning at 10 mg of ferritin per liter. We modified this kit to eliminate this effect, at least to ferritin concentrations of 33 mg/L. (We observed a ferritin value as high as 47 mg/L in one patient.) Results with all these kits did not inter-compare well for ferritin concentrations greater than 300 micrograms/L, a finding that casts further doubt on the controversial use of serum ferritin measurement in cases of iron overload.
Effects of whole blood storage on results for glycosylated hemoglobin as measured by ion-exchange chromatography, affinity chromatography, and colorimetry.
Authors: Little R R , England J D , Wiedmeyer H M , Goldstein D E
Published: January 2020

After storage of whole blood at either 4 or 20 degrees C, results for glycosylated hemoglobin by ion-exchange chromatography ("high-performance" liquid and mini-column chromatography), thiobarbituric acid colorimetry, and affinity chromatography were compared. At 4 degrees C, all methods gave acceptable results for samples stored for as long as a week. At 20 degrees C, the colorimetric and affinity methods also showed sample stability for a week or more. The ion-exchange methods were associated with a marked increase in values for glycosylated hemoglobin after a few days of storage. Evidently, care in details of sample collection and handling is especially important for ion-exchange methods, and the colorimetric and affinity methods have advantages over ion exchange in situations where long delays between sample collection and assay are unavoidable.
New statistical approach in biochemical method-comparison studies by using Westlake's procedure, and its application to continuous-flow, centrifugal analysis, and multilayer film analysis techniques.
Authors: Gerbet D , Richardot P , Auget J L , Maccario J , Cazalet C , Raichvarg D , Ekindjian O G , Yonger J
Published: January 2020

In this paper, we present an application of Westlake's method (Biometrics 32:741, 1976) in method-comparison studies in clinical chemistry. The techniques under study are continuous flow (CF), centrifugal analysis (CA), and multilayer film analysis (the Kodak Ektachem procedure KE). The experimental data are for plasma calcium and serum uric acid. It results from a particular regression procedure proposed by York (Can J Phys 44:1079, 1966) that the usual regression comparison technique (joint testing procedure) is irrelevant because it rejects the identity hypothesis for the three methods, whereas fixing a tolerable upper limit deviation, delta, between two methods would lead to the conclusion that, in 95% of cases, CF and KE results are equivalent for plasma calcium (delta less than or equal to 45 mumol/L) and CF is roughly equivalent to the other two methods for serum uric acid (delta less than or equal to 27 mumol/L).
Graded hemagglutination inhibition for quantification of human fetal hemoglobin.
Authors: Wolk M , Kieselstein M
Published: January 2020

We describe a hemagglutination system for quantification of fetal hemoglobin (HbF), especially at low concentrations. This system consists of three components: (a) sheep erythrocytes coated with purified HbF, (b) sheep antiserum of human HbF made specific for the gamma-chain, and (c) human blood lysate with a known concentration of HbF as the standard. We can measure the whole range of HbF proportions in human blood, from 100% down to 0.01%. Statistical analysis showed that our measurements agreed with those made by the methods of alkali denaturation and radial immunodiffusion. Reproducibility of the method is shown by the low CVs for six repeated measurements. Low concentrations of HbF not measurable by other methods are easily assayed. We offer examples of the clinical utility of data on low concentrations of HbF.
Variations of 1-deoxyglucose(1,5-anhydroglucitol) content in plasma from patients with insulin-dependent diabetes mellitus.
Authors: Yoshioka S , Saitoh S , Negishi C , Fujisawa T , Fujimori A , Takatani O , Imura M , Funabashi M
Published: January 2020

The concentration of 1-deoxyglucose(1,5-anhydroglucitol) in plasma from patients with insulin-dependent diabetes mellitus was measured by gas-liquid chromatography with an all-glass capillary column. Twenty-one plasma samples were obtained from 21 patients before insulin therapy, and 34 more from 13 patients receiving insulin therapy. 1-Deoxyglucose was generally not detectable in plasmas of diabetic patients before they received insulin; it was measurable in the patients who had received insulin, although its concentration was low compared with that of healthy subjects. We therefore suggest that the absence of 1-deoxyglucose in plasma is one of the markers of metabolic states of diabetes, perhaps reflecting a disturbed function of carbohydrate metabolism; its presence in plasma within a normal range may reflect the better control of diabetic patients.
Enzymic creatinine assay: a new colorimetric method based on hydrogen peroxide measurement.
Authors: Fossati P , Prencipe L , Berti G
Published: January 2020

We describe a new colorimetric method for measuring creatinine in serum and urine. Creatinine hydrolysis is catalyzed by creatinine amidohydrolase, and the creatine so produced is assayed in reactions catalyzed sequentially by creatine amidinohydrolase and sarcosine oxidase in a system that generates hydrogen peroxide. The hydrogen peroxide is measured at 510 nm in a reaction catalyzed by horseradish peroxidase, with 3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone as the chromogen. This series of reactions is complete in 30 min at room temperature. A blank sample measurement corrects for endogenous creatine. The standard curve is linear for creatinine concentrations as great as 2.21 mmol/L. Analytical recovery of creatinine in human sera and urine averaged 99.8%. Within-run and between-run precision studies gave CVs of less than or equal to 3.3 and less than or equal to 4.3% for a serum with a creatinine concentration of 69 mumol/L. Results by this method agree well (r greater than 0.99) with those by both the enzymic ultraviolet method of Wahlefeld and the fuller's earth/Jaffé method.
Potentiometry of Na+ in undiluted serum and urine with use of an improved neutral carrier-based solvent polymeric membrane electrode.
Authors: Anker P , Jenny H B , Wuthier U , Asper R , Ammann D , Simon W
Published: January 2020

We present an improved Na+-selective liquid membrane electrode for measurement of Na+ concentrations in both undiluted serum and urine. The values for urinary Na+ obtained with the ion-selective electrode agree well with those obtained with the flame photometer. The correlation gives a standard residual deviation of +/- 2.7 mmol/L over the Na+ range of 25-280 mmol/L. In serum, this direct potentiometry yields Na+ concentrations 5.4% (SD 1.1%) higher than those obtained by atomic spectrometry and a standard residual deviation of +/- 1.1 mmol/L. Correction of these values for the volumes of protein and lipid leads to potentiometric values 1.2% (SD 0.7%) lower than those by flame photometry (residual standard deviation: +/- 1.0 mmol/L). Other factors that possibly contribute to this discrepancy are discussed.
Human placenta as a convenient source of creatine kinase BB.
Authors: Steghens J P , Maire I , Mathieu M
Published: January 2020

We demonstrate that human placenta is a convenient source of creatine kinase isoenzyme BB. We compare the physicochemical and catalytic properties with those of other creatine kinase isoenzymes: purified human abdominal muscle MM and brain BB. We also describe a stabilizing medium for creatine kinase BB. Human placental and brain BB have similar catalytic properties, the respective Km values for creatine phosphate being 0.66 and 0.56 mmol/L and for adenosine diphosphate 89 and 70 nmol/L.
Quantitation of haptens by homogeneous immunoprecipitation. 2. Centrifugal analysis for tobramycin, phenobarbital, and theophylline in serum.
Authors: Wu J W , Bunyagidj C , Hoskin S , Riebe S M , Aucker J , White K , O'Neill S P
Published: January 2020

Our homogeneous immunoprecipitation inhibition assay (Clin. Chem. 28:659-661, 1982) is applied here to tobramycin, phenobarbital, and theophylline. Only 10-50 microL of test sample is needed. No sample treatment, dilution, or extraction is required. A test serum sample is simultaneously mixed with a drug conjugate and its specific antiserum in a centrifugal analyzer. The subsequent reaction and the measurement are completed in 3 min. Within-run and between-run CVs for clinically relevant concentrations were well below 10%. Results for patients' samples correlated well with those by enzyme immunoassay.
Immunoassay techniques with fluorescent phycobiliprotein conjugates.
Authors: Kronick M N , Grossman P D
Published: January 2020

We describe immunoassay techniques that take advantage of the novel properties of phycobiliprotein fluorescent dyes. These dyes, which can be isolated from a wide variety of algae, exhibit extremely high absorptivities, high quantum efficiencies, and excitation and emission bands across the visible spectrum. These stable, hydrophilic proteins can easily be linked to antibodies by conventional protein cross-linking reagents. One assay technique presented here demonstrates the use of phycobiliproteins in a solid-phase "sandwich" assay, which achieves picomolar sensitivity. In the other technique the unique spectral properties of phycobiliproteins are applied to fluorescence excitation transfer immunoassay.
Evaluation of multi-wavelength derivative spectra for quantitative applications in clinical chemistry.
Authors: Weiser W E , Pardue H L
Published: January 2020

We have used the quantitation of methemoglobin in the presence of a light-scattering suspension as a model to evaluate and compare the relative merits of zeroth-, first-, and second-derivative spectroscopy for problems in clinical chemistry. Data for second derivatives are most effective in nullifying the effect of the background spectrum; data for first derivatives are less effective; and data for absorbance (zeroth derivative) are least effective. In one set of experiments, variable amounts of the light-scattering component were added to a methemoglobin solution to increase the apparent absorbance up to about 230% of the absorbance of the original solution. Whereas computation with data for absorbance would have yielded errors approaching 100%, concentrations computed with second-derivative spectral data yielded a systematic error (bias) of only 0.5% and a relative standard deviation (CV) of 1.6%.
Optical fiber fluoroprobes in clinical analysis.
Authors: Sepaniak M J , Tromberg B J , Eastham J F
Published: January 2020

We used quartz optical fibers and laser excitation in developing single-fiber fluoroprobes, to be used to measure molecular fluorescence in minute volumes of body fluids. We illustrate and discuss the analytical capabilities of these fluoroprobes. Limits of detection for the anti-tumor drug doxorubicin are about 10(-7) mol/L, by either conventional fluorescence or sequentially excited fluoroscence modes of detection. We also report the results of preliminary in vivo measurements of doxorubicin in the interstitial fluids of human tumors, heterotransplanted in immune-deficient laboratory mice.
An improved micro-scale liquid-chromatographic assay for piperacillin in plasma and urine.
Authors: Jung D , Mahajan N K
Published: January 2020

An accurate, sensitive, and specific liquid-chromatographic method is described for measuring piperacillin in plasma and urine. Plasma samples deproteinized with two volumes of acetonitrile containing 1.2 mg of the internal standard, p-nitrobenzene sulfonamide, per liter are centrifuged. The clear supernate is evaporated under nitrogen, and the residue is reconstituted in 50 microL of the mobile phase (32/68 by vol acetonitrile/water, adjusted to pH 2.5 with 85% phosphoric acid), of which 10 microL is injected onto a reversed-phase (C-18) column. Urine samples are diluted 10-fold with distilled water, an equal volume of acetonitrile containing 3 mg of the internal standard per liter is added, and 20 microL is chromatographed. Stability studies indicate that storage conditions are critical for both plasma and urine. Piperacillin in plasma is stable at -70 degrees C for at least six weeks, but 100% of it is degraded during the same time at -20 degrees C. Piperacillin in urine is also stable at -70 degrees C for six weeks, but 20% is degraded during six weeks at -20 degrees C.
Anti-triiodothyronine autoantibodies interfere with two recently commercialized radioimmunoassays for free triiodothyronine.
Authors: Rodríguez-Espinosa J , Ordóñez-Lianos J , Gómez-Gerique J A , Mora J
Published: January 2020

We examined the effect of anti-triiodothyronine autoantibodies on results of RIA of free triiodothyronine with two commercial kits (Amersham International and Diagnostic Products Corp.). Both methods gave falsely high results because the 125I-labeled analogs used in these RIAs were bound by the autoantibodies.