bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunoradiometric assay of endotoxin in serum.
Authors: Leibowitz A I , Vladutiu A O , Nolan J P
Published: January 2020

We describe an immunoradiometric assay for the specific detection and quantitation of endotoxin from Escherichia coli 026, with use of 125I-labeled antibody. The sensitivty of this assay is 1 microgram/L.E. coli 026 endotoxin was detected in serum of rats for as long as 24 h after intraperitoneal injection of 0.1 mg of endotoxin per 100 g body weight. The assay is specific for the O-polysaccharide portion of this endotoxin, as confirmed by results after protein digestion and oxidation of the endotoxin, as well as by failure to detect endotoxin in serum after similar injections of E. coli 0127 and Salmonella typhosa 0901 endotoxins.
Hydrolysis of glutathione by human liver gamma-glutamyltransferase.
Authors: Shaw L M , Newman D A
Published: January 2020

We studied the catalytic hydrolysis of glutathione by human liver gamma-glutamyltransferase [(gamma-glutamyl)-peptide:amino acid gamma-glutamyltransferase, EC 2.3.2.2]. Glutamate production from glutathione was maximal at pH 7.4 (37 degrees C). Kinetically, the liver enzyme is similar to human kidney gamma-glutamyltransferase: their respective Km values with glutathione as substrate are similar (0.096 x 10(-3) mol/L and 0.097 x 10(-3) mol/L, respectively). S-Methylglutathione was hydrolyzed at a slightly higher rate than glutatione by liver gamma-glutamyltransferase. From these findings and other established properties of liver and kidney gamma-glutamyltransferase we propose that human liver is an important site of glutathione catabolism and that gamma-glutamyltransferase in liver catalyzes the first step of the catabolism of glutathione and glutathione conjugates in this organ.
A model program for education and training of clinical chemists.
Authors: Trawick W G
Published: January 2020

Some general guidelines can help in the assessment of clinical chemistry training and training programs. A clinical chemist must be, first of all, a good chemist, but to this must be added other knowledge and skills. A program that begins with a bachelor's degree in chemistry equivalent to the American Chemical Society's standards is proposed for the clinical chemistry technologist. The model provides more flexibility as the education proceeds toward the doctoral and postdoctoral levels and as the opportunities and responsibilities become increasingly more diverse. An essential portion of the training at all levels is experience in a clinical laboratory. It is strongly recommended that this be started early and be continued throughout the program. Certification by an independent agency (National Registry in Clinical Chemistry or American Board of Clinical Chemistry) is strongly recommended as a final step in all plans.
Hemoglobinuria and hematuria: accuracy and precision of laboratory diagnosis.
Authors: Bee D E , James G P , Paul K L
Published: January 2020

Five methods of assessing blood in urine were studied and compared: sedimentation count, hemacytometry, "Clini-lab" reagent strip and "N-Multistix" and "ChemStrip-8" dipsticks. The minimum sensitivity of two commercially available urine dip-stick procedures for blood was established. The study includes method association, assay variation among and within technologists, accuracy, precision, and sensitivity. Our results demonstrate generally poor association between results by the dip-stick procedures and the hemacytometer or sedimentation count. Results by the last two procedures also showed very poor association with each other.
Serum cortisol and 11 deoxycortisol by liquid chromatography: clinical studies and comparison with radioimmunoassay.
Authors: Canalis E , Caldarella A M , Reardon G E
Published: January 2020

We describe a liquid-chromatographic procedure for separating and measuring cortisol and 11-deoxycortisol in serum. We quantitated these steroids in patients who were undergoing various tests of pituitary and (or) adrenal function and compared the results with those obtained by two radioimmunoassays done in two different laboratories. Results of 48 tests done in 37 functionally normal humans are presented. Cortisol values for sera collected in the morning as determined by liquid chromatography were (mean +/- SD) 134 +/- 54 micrograms/L. Serum cortisol concentrations increased from 136 +/- 65 to 321 +/- 80 micrograms/L 60 min after injecting synthetic corticotropin and increased from 107 +/- 46 to 242 +/- 31 micrograms/L after insulin-induced hypoglycemia. Serum cortisol decreased from 142 +/- 49 to 26 +/- 20 micrograms/L after oral administration of metyrapone, while 11-deoxycortisol increased from less than 10 to 210 +/- 53 micrograms/L. Serum cortisol measured less than 10 micrograms/L the morning after oral ingestion of dexamethasone. Results of the dynamic tests of adrenal function correlated well with previously reported studies. However, the cortisol values obtained by our technique were generally lower than those obtained by radioimmunoassay, possibly owing to lack of specificity of the latter methods used here for comparison. In contrast, values for 11-deoxycortisol were the same by both methods. The present studies confirm the usefulness of liquid chromatography for measuring these two steroids in serum during tests of pituitary and adrenal function. Future refinements of the technique should continue to increase its clinical applications.
Improved radioimmunoassay for 11-deoxycortisol (compound S) in plasma.
Authors: Demers L M , Ebright L , Derck D D
Published: January 2020

We describe a radioimmunoassay for 11-deoxycortisol (Compound S) that involves preliminary chromatography on Sephadex LH-20, to isolate 11-deoxycortisol from crossreacting structurally related steroids. Pools with means of 3.4, 12.9, and 69.9 micrograms/L gave intra-assay coefficients of variation of 9.7, 9.6, and 11.4%, respectively; pools with means of 4.6, 27, and 95 micrograms/L gave inter-assay CV's of 10.1, 9.7, and 6.2%, respectively. A normal range (mean +/- 2SD) of 0.5 to 12.0 micrograms/L was obtained. This procedure is useful for the specific determination of 11-deoxycortisol, commonly determined in blood as part of the metyrapone test for assessing pituitary corticotropin reserve.
Determination of 4-O-methylated catecholamine metabolites in urine by mass fragmentography.
Authors: Muskiet F A , Fremouw-Ottevangers D C , Nagel G T , Wolthers B G
Published: January 2020

We describe the determination of the 4-O-methylated catecholamine metabolites 4-methoxy-3-hydroxyphenylacetic acid (iso-HVA), 4-methoxy-3-hydroxyphenylmandelic acid (iso-VMA) and 4-methoxy-3-hydroxyphenylethylene glycol (iso-MOPEG) in urine with use of mass fragmentography and deuterated internal standards. Normal values, expressed in terms of creatinine, are given as a function of age. Urinary excretion values during neuroblastoma, pheochromocytoma, and parkinsonism treated with L-DOPA, and during the intravenous administration of dopamine are discussed. For normal persons, the mean percentages (+/- SD) of 4-O-methylated metabolites relative to their 3-O-methylated analogs were 6.29 +/- 2.79% (iso-HVA/HVA), 0.70 +/- 0.57% (iso-VMA/VMA), and 0.77 +/- 0.53% (iso-MOPEG/MOPEG). We observed no significant changes in these parameters for the patients studied and conclude that the determination of 4-O-methylated catecholamine metabolites for these patients does not add information to the results obtained from their quantitatively more important 3-O-methylated analogs.
Spurious hyperbilirubinemia in uremic patients on propranolol therapy.
Authors: Stone W J , McKinney T D , Warnock L G
Published: January 2020

Chronic, low-grade, unexplained increases of total serum bilirubin concentration were observed in 16 of 132 (12%) chronic dialysis patients. Cessation of antihypertensive medication in four patients resulted in disappearance of hyperbilirubinemia. Propranolol was the only antihypertensive drug common to all 16 patients. Daily dosage varied among the patients, but the mean dose was 308 mg (+/- 51 SEM). Serial determinations of sera from individual patients given different doses and from the group as a whole demonstrated a linear relationship between propranolol dose and apparent total serum bilirubin concentration with continuous-flow analysis. When serum specimens from uremic patients receiving propranolol were treated with diazotized fulfanilic acid and examined spectrophotometrically, an absorbance peak distinct from but overlapping that of bilirubin was consistently demonstrated. The material producing the peak disappeared when the drug was stopped, did not dialyze, and was not reproduced by the in vitro addition of propranolol to uremic serum. We postulate that a metabolite(s) of propranolol is retained in uremic serum and interferes with the bilirubin determination.
Evaluation of two assays of functional surfactant in amniotic fluid: surface-tension lowering ability and the foam stability index test.
Authors: Statland B E , Freer D E
Published: January 2020

We characterize two assays of total amniotic fluid surfactant that are based on function: the surface-tension lowering ability of extracts of amniotic fluid lipid (I) and the foam stability index test (II). I is determined on chloroform extracts of amniotic fluid. II is defined as the highest ethanol volume fraction of an amniotic fluid-ethanol mixture that will permit a stable foam to form after 30 s of vigorous shaking. The relationship of I to disaturated phosphatidylcholine concentrations (after osmium tetroxide treatment of the amniotic fluid lipid extract) is in the expected theoretical form of a hyperbolic function. The relation between values for II and disaturated phosphatidylcholine concentrations showed a consistent bias, suggesting that components other than disaturated phosphatidylcholine contribute to stable foam formation. Phosphatidylclycerol concentrations did not appear to account for this bias. The relation between I to II values suggest that both assays measure total surfactant. I, II, and concentration of disaturated phosphatidyl choline are all excellent indicators of fetal pulmonary maturity. From a practical standpoint, the foam stability index test is the most efficient approach to routine assessment of fetal pulmonary status.
Comparison of two micromethods for determination of lipoprotein cholesterol in plasma.
Authors: Kupke I R , Zeugner S , Gottschalk A
Published: January 2020

We compared the results obtained by a micromethod for the determination of plasma lipoprotein cholesterol, in which electrophoresis is used to separate the lipoprotein fractions (beta-, pre-beta-, and alpha-lipoproteins), with those determinations with ultracentrifugation (low-density, very-low-density, and high-density lipoproteins). Precision of determination (coefficient of variation, CV, %) was the same for beta- and low-density lipoproteins (1.6%), and for pre-beta- and very-low-density lipoproteins (3.7%); however, determination of alpha-lipoprotein cholesterol was more precise (1.4%) than that of high-density lipoprotein cholesterol (3.1%). Analytical recovery of lipoprotein cholesterol was the same for both methods (98--100%) and the results were closely correlated (r = 0.943). The procedure has been used to determine the cholesterol content of plasma lipoprotein fractions of apparently healthy adults (both sexes). Lipoprotein cholesterol concentrations in our population sample compare well with those reported for other groups of similar age, in particular Stanford long-distance runners.
Evaluation of the DuPont aca amylase method.
Authors: Balkcom R M , O'Donnell C M , Amano E
Published: January 2020

The dilution/activity curve for the DuPont aca kinetic amylase (EC 3.2.1.1) method is linear to approximately six times the upper limit of the expected range. Total reaction time on the aca is 4.3 min; however, there is a nonlinear rate of change in absorbance for at least the first 8 min, which is consistent with a lag phase. The within-run and day-to-day coefficients of variation were 2.4% at 100 U/L and 3.6% at 114 U/L, respectively. There was no interference by marked hemolysis (hemoglobin 4 g/L) or by glucose concentrations of 10--50 g/L. Comparisons by the split-sample method between the Amylochrome procedure and the aca procedure gave correlation coefficients of 0.992 for serum and 0.989 for urine. A second comparison, between the AutoAnalyzer I method and the aca, gave correlation coefficients of 0.998 for serum and 0.909 for urine. The expected range for serum was 18--106 U/L and for urine 2--33 U/2 h.
Evaluation of the BMC glucose oxidase/peroxidase-4-aminophenazone-phenol procedure for glucose as adapted to the Technicon SMAC.
Authors: Purcell G V , Behenna D B , Walsh P R
Published: January 2020

We evaluated the analytical performance of Trinder's glucose oxidase (EC 1.1.3.4)/peroxidase (EC 1.11.1.7) 4-aminophenazone-phenol method for the quantification of serum glucose as adapted to the Technicon SMAC. Our results correlated well with those by the routine SMAC glucose oxidase/peroxidase 3-methyl-2-benzothiazolinone hydrazone-N,N-dimethylaniline method (y = 1.02x - 49.4; r = 0.99) and the glucose oxidase oxygen-rate method (y = 0.99x + 14; r = 0.99) with the Beckman Glucose Analyzer. Sample-to-sample interaction was less than 1%. Ascorbic acid or uric acid in concentrations as high as 200 mg/L were without demonstrable effect on results for glucose. Intra- and inter-assay precisions (CV) were 1.6 and 2.3%, respectively. The upper limit of linearity was about 5 g/L. Adaptation of the Trinder method for glucose to the SMAC is simple and provides an analytically acceptable and economical alternative to the methods ordinarily used with the SMAC.
Improvements in and clinical utility of a continuous-flow method for routine measurement of dialyzable (ultrafiltrable) calcium.
Authors: Toffaletti J , Bowers G N
Published: January 2020

We describe modifications to the original continuous-flow procedure for dialyzable calcium (Clin. Chem. 23: 1258, 1977) needed to make the method more suitable for routine clinical laboratory use. The modifications simplify the continuous-flow (AutoAnalyzer) manifold, decrease baseline noise, increase the sensitivity, and permit use of a less-expensive fluorometer. Bias due to variation in serum processing is minimized by use of serum samples minimally exposed to air and a pH 7.40 buffer in place of the routinely processed sera and pH 7.30 buffer used formerly. Day-to-day precision (CV) during the past year for samples that included three different lots of quality-control sera was 2 to 3%. The analysis requires 200 micro L of serum, collected with minor additional precautions. We find that dialyzable calcium can be dependably measured in the routine service laboratory and show how this information is clinically more useful than is information on total calcium in serum.
Liquid-chromatographic measurement of endogenous and exogenous glucocorticoids in plasma.
Authors: Frey F J , Frey B M , Benet L Z
Published: January 2020

The therapeutic response to and side effects of glucocorticoids will be better recognized and the recovery of the adrenals during the tapering of therapy with steroids better evaluated if endogenous and exogenous glucocorticoids are separately assessed. We describe a specific method for simultaneously measuring the concentrations of cortisone, cortisol, prednisone, and prednisolone in plasma by "high-pressure" liquid chromatography. The steroids, together with an internal standard, dexamethasone, are extracted from 1 mL of plasma with methylene chloride-ether, washed with acid and base, and separated isocratically on a normal-phase silica column with a mobile phase consisting of methylene chloride/tetrahydrofuran/methanol/glacial acetic acid (96.85/1/2.1/0.05 by vol) at a flow rate of 1.3 mL/min. The steroids are detected at 254 nm and quantitated by peak-height measurements; their retention times range from 6 to 20 min. The lower limits for routine detection of all four compounds is 10 microgram/L. The analytical recoveries are about 75%; the intra-day variability (CV) is 1 to 9%, and the inter-day variability 2 to 11%. Of 26 drugs and 20 steroids tested, only theophylline presents an interference problem.
Direct determination of lead and cadmium in blood and urine by flameless atomic absorption spectrophotometry.
Authors: Lagesson V , Andrasko L
Published: January 2020

We describe procedures for direct determination of lead and cadmium in blood and urine by flameless atomic absorption spectrophotometry. Before analysis, the samples are pre-ashed in microboats in an ordinary laboratory oven. In this way, many samples can be prepared and pre-ashed simultaneously. We find the procedures presented in this work to be rapid, accurate, and precise.
Pre-renal azotemia mimicking chronic renal failure in a hypotensive patient.
Authors: Darm J R , Bhagavan N V , Scottolini A G
Published: January 2020

A 56-year-old Samoan man with a documented history of hypertension, who presented with atrial fibrillation and hypotension, quickly developed renal failure with a serum urea nitrogen of 1.370 g/L and a serum creatinine of 92 mg/L. After hydration of the patient, the creatinine value became normal in two days, the urea nitrogen in four days. The urinary creatinine output during the first 24 h of hospitalization was 3.7 g. This case illustrates the rapidity with which unusually large amounts of creatinine (more commonly seen in chronic renal failure) can accumulate and be excreted in pre-renal failure. It also reaffirms the usefulness of the urea nitrogen/creatnine ratio in evaluating the causes of azotemia.
Creatine kinase measurement in the 1977 CAP Enzymology Survey: anomalies explained.
Authors: Handschuh G J , Donovan K L
Published: January 2020

In the recently published results of the 1977 College of American Pathologists Enzymology Survey, Some anomalous results were obtained in measuring the creatine kinase (EC 2.7.3.2) activity of the samples. The cause of these anomalies was discovered to be an arginine kinase (EC 2.7.3.3) contaminant in one of the enzyme pools used to make the samples. The contaminant shows cross reactivity with creatine phosphate and is activated by dithioerythritol but not the other commonly used thiol activators.
A new assay for diaphorase activity in reagent formulations, based on the reduction of thiazolyl blue.
Authors: Boethling R S , Weaver T L
Published: January 2020

This new assay procedure for diaphorase eliminates problems of high blank rates and nonlinear kinetics associated with other methods. The dye thiazolyl blue tetrazolium bromide is reduced in the presence of NADH and diaphorase to yield a colored formazan, which as maximum absorbance at 560 nm.
Assay of urinary 4-hdyroxy-3-methoxymandelic (vanillylmandelic) acid by liquid chromatography with electrochemical detection.
Authors: Morrisey J L , Shihabi Z K
Published: January 2020

We describe a method for the assay of urinary 4-hydroxy-3-methoxymandelic acid (vanillylmandelic acid) based on separation on a microparticulate reversed-phase column and direct electrochemical detection. The method can be used after extraction from urine or by direct urine injection after 100-fold dilution.
Thin-layer agarose electrophoresis of lactate dehydrogenase isoenzymes in serum: a note on the method of reporting and on the lactate dehydrogenase isoenzyme-1/isoenzyme-2 ratio in acute myocardial infarction.
Authors: Leung F Y , Henderson A R
Published: January 2020

We assessed the clinical efficacy of a thin-layer agarose electrophoresis assay for lactate dehydrogenase isoenzyme estimation in the diagnosis of acute myocardial infarction. From a population of 228 patients admitted to the Coronary Care Unit with suspected acute myocardial infarction, all 101 positive cases (confirmed by clinical presentation and electrocardiographic changes) were correctly identified with lactate dehydrogenase isoenzyme-1 percentage of total activity above the reference range and with a lactate dehydrogenase isoenzyme-1/isoenzyme-2 ratio of 0.76 or above. This ratio was between 0.45 and 0.74 for 250 healthy subjects. No falsely negative, but 12 falsely positive results were obtained from this Coronary Care Unit population, to give a sensitivity of 100% and a specificity of 90.5% for the ratio test.
New saccharogenic determination of alpha-amylase in serum and urine.
Authors: van Leeuwen L
Published: January 2020

I describe a new kinetic enzymatic saccharogenic method for assaying alpha-amylase in human serum and urine. alpha-Amylase liberates maltose from starch. This is successively acted on by alpha-glucosidase, mutarotase, and glucose dehydrogenase. The resulting conversion of NAD+ to NADH, measured at 340 nm, during a 20-min incubation reflects amylase activity. Endogenous glucose is destroyed before measurement of amylase activity is begun.
Enzyme-linked immunosorbent choriomammotropin assay.
Authors: Dittmar D , Monji N , Cid A , Malkus H , Castro A
Published: January 2020

We have devloped an enzyme-linked immunosorbent assay for determining choriomammotropin (human placental lactogen) in serum. Unlabeled hormone competes with choriomammotropin-beta-galactosidase conjugate for antibody bound to polystyrene tubes. The entire assay can be performed in 2.5 h with good precision. The coefficient of variation for one sample with a mean concentration of 5.6 mg/L, assayed 10 times on the same day, was 5.7%. The coefficient of variation for nine samples (3.5 to 9.0 mg/L) assayed on five different days was 7.9%. Forty-eight clinical samples were assayed (y) and compared with results obtained by radial immunodiffusion (x). The resulting regression equation was: y = 1.05x + 0.78; r = 0.91.
Electron-capture gas-liquid chromatographic determination of ethosuximide and desmethylmethsuximide in plasma or serum.
Authors: Wallace J E , Schwertner H A , Hamilton H E , Shimek E L
Published: January 2020

We describe the determination of ethosuximide and desmethylmethsuximide, simultaneously or separately, in 50 to 100 microliter of plasma or serum. Derivatives of ethosuximide and desmethylmethsuximide formed by reaction with pentafluorobenzoyl chloride are extremely sensitive to the electron-capture detector of a gas-liquid chromatograph. The sample, with added internal standard and ammonium sulfate as a pH-adjusting and salting-out agent, is extracted with ethyl acetate/benzene (20/80 by vol). The extract is evaporated and the derivatives are formed. Analytical recoveries of ethosuximide and desmethylmethsuximide exceed 99%, and the relative standard deviation (CV) between analyses is usually less than 4.0%. alpha-Methyl-alpha-propylsuccinimide is used as the internal standard for ethosuximide, 2-phenylsuccinimide as the internal standard for desmethylmethsuximide.
Analysis for urinary catecholamines by liquid chromatography with amperometric detection: methodology and clinical interpretation of results.
Authors: Moyer T P , Jiang N S , Tyce G M , Sheps S G
Published: January 2020

A method is presented for the quantitative analysis of urinary unconjugated norepinephrine, epinephrine, and dopamine as discrete entities. The procedure requires initial purification of the specimen on aluminum oxide and a boric acid-gel. We used "high-performance" reversed-phase paired-ion chromatography, with a flow-through amperometric cell as the detector. The CV was 6% for determination of norepinephrine, 11% for epinephrine, and 6% for dopamine monitored at physiologic concentrations of these compounds in urine. In a population study, urine specimens from 117 normal pediatric and adult subjects, 85 hypertensive patients, and 22 patients with surgically proved pheochromocytoma were analyzed. The specificity of the method for detection of pheochromocytoma was 100%, with a sensitivity of 97%.
Gel isoelectric focusing method for specific diagnosis of familial hyperlipoproteinemia type 3.
Authors: Warnick G R , Mayfield C , Albers J J , Hazzard W R
Published: January 2020

We describe a gel isoelectric focusing procedure for resolving into at least five bands the arginine-rich protein of very-low-density lipoproteins, and use the method in diagnosis of hyperlipoproteinemia type 3. We find that deficiency of one band, designated E3, relative to E2, expressed as an E3/E2 ratio less than or equal to 0.3, is specifically associated with hyperlipoproteinemia type 3 as diagnosed by traditional criteria in a large family study. In addition, we used the procedure to test 47 referral samples with demonstrable beta-migrating very-low-density liproprotein grouped by very-low-density lipoprotein cholesterol/total triglyceride ratios of greater than or equal to 0.3, from 0.25 to 0.3, and less than 0.25. All 24 of the first group, three of six in the second, and only one of 17 in the third had E3/E2 ratios of less than or equal to 0.3. Also, two normolipidemic children, without detectable lipoprotein abnormalities but related to subjects with hyperlipoproteinemia type 3, had E3/E2 ratios of less than or equal to 0.3. Use of our procedure improves the specificity of diagnosis and allows sensitive detection of asymptomatic subjects who may be at risk of developing the disorder.
Single- and coupled-enzyme nylon tube reactors for routine determination of pyruvate and lactate in serum.
Authors: Sundaram P V , Hinsch W
Published: January 2020

We describe the use of a continuous-flow clinical analyzer with an immobilized coupled-enzyme nylon tube reactor and an immobilized single-enzyme nylon tube reactor for routine estimation of lactate and pyruvate in serum. These reactors are incorporated into the flow system of a modified continuous-flow analyzer (Technicon AutoAnalyzer). Results for serum lactate and pyruvate by this method are compared with those by corresponding methods in which the same enzymes are used in solution, either automatically (pyruvate) or manually (lactate) performed. Routine clinical laboratory determinations with use of the coupled-enzyme system lactate dehydrogenase and alanine aminotransferase, co-immobilized in the nylon tube reactor for estimation of lactate, and lactate dehydrogenase reactors for estimation of pyruvate give reliable and reproducible results with high precision at low cost.
Enzyme immunoassay of carbamazepine with a centrifugal analyzer.
Authors: Lacher D A , Valdes R , Savory J
Published: January 2020

We describe a rapid enzyme immunoassay for carbamazepine with a centrifugal analyzer (Rotochem IIA-36). Reagent costs are reduced fourfold while good precision and sensitivity are maintained. Sample volume is 10 microliter, and as many as 28 patients' sera can be measured during an assay time of 225 s. Assay temperature is 30 degrees C, the wavelength 340 nn. Linearity is excellent for a carbamazepine concentration range of 1 to 12 mg/L; analytical recovery is quantitative. Results correlate well with those by liquid- and gas-liquid chromatography. Absorbance rates for each carbamazepine concentration are acquired by a multi-point kinetic rate program and a computer program provides a logit-log transformation of absorbance rate vs. concentration data for final calculations in the assay. Hemoglobin interference precludes analysis of severely hemolyzed specimens.
Phthalate interference in gas-chromatographic determination of long-chain fatty acids in plasma.
Authors: Geisler C , Swanson A R , Zieve L , Anders M W
Published: January 2020

Phthalates leached from plastic tubing or other plastic devices may interfere with gas-chromatographic determination of long-chain fatty acids in plasma. In the case of hospitalized patients who have received infusions or had blood drawn through plastic tubing, gas chromatography/mass spectrometry may be required for accurate determination of such fatty acids.
Improved indirect and direct radioimmunoassay for carcinoembryonic antigen.
Authors: Kumar M S , Carl K J , Deodhar S D
Published: January 2020

Values obtained by the indirect and the direct assays for carcinoembryonic antigen by use of the "CEA Roche" method and reagents differ significantly. In 32 samples the latter method gave values almost twofold those obtained by the former. The mean ratio for direct/indirect was 1.9 +/- 0.6. Analytical recovery experiments on samples to which known amounts of the antigen had been added showed a similar disparity. A simple modification of these two procedures, involving addition of normal human plasma (containing less than 2.0 microgram of the antigen per liter) to standards, eliminated this discrepancy. In the indirect method, standards were added to normal human plasma, then extracted with perchloric acid before assay. In the direct assay normal human plasma instead of goat serum, was added to standards. With these modifications the analytical recoveries of added CEA by the indirect and direct methods were 87 +/- 17% and 99.7 +/- 8%, respectively, and the mean ratio between two methods was 1.2 +/- 0.4.
Effect of protein on titrimetry of bicarbonate, titratable acid, and ammonium in urine.
Authors: Litkowski L J , Wilson T L
Published: January 2020

Measurement of bicarbonate, titratable acid (HTA+) and ammonium in the urine can facilitate clinical evaluation of acid-base status. Sequential measurement of these three components by titrimetric techniques is well established, but possible interference by proteinuria has not been examined. We report the influence on these analyses of albumin and globulin, two proteins commonly observed in urine in renal disease states. The presence of these proteins in urine affects the measurement of NH4+, and to a less extent that of HTA+. The magnitude of the effect depends on the concentration and the kind of protein present. Proteins do not influence the measurement of HCO3-.
Antibodies to native DNA: detection by immunoperoxidase assay and determination of their immunoglobulin classes.
Authors: Vladutiu A O , Palumbo D A , Asirwatham J E
Published: January 2020

Antinuclear antibodies are almost always found in sera of patients with systemic lupus erythematosus. To differentiate antinuclear antibodies from antibodies to DNA in the recently described Crithidia luciliae assay, we developed an immunoperoxidase technique for detecting antibodies to native, double-stranded DNA and compared results by it with those by the Farr assay. Smears of cultured Crithidia luciliae were incubated with human sera, peroxidase-labeled anti-human IgG serum, and diaminobenzidine. The peroxidase stain was examined by conventional light microscopy, which facilitated differentiation between the kinetoplast and the nuclear staining. The Crithidia assay appeared to be specific for double-stranded DNA antibodies, seemed to be more sensitive than the Farr assay, and allowed us to determine the immunoglobulin classes of antibodies to native DNA. Some patients with systemic lupus erythematosus had only IgM or IgA antibodies to DNA.
Secondary hypertriglyceridemia and hyperlipoproteinemia in patients with primary asymptomatic gout.
Authors: Naito H K , Mackenzie A H
Published: January 2020

We carefully selected 30 men with primary gout, rendered asymptomatic by therapy, to examine the frequency and type of hyperlipidemia and hyperlipoproteinemia, with the objective of determining whether serum uric acid, alcohol intake, liver function, kidney function, and (or) drugs were participating in the secondary lipid disorder. Sixty-one age- and sex-matched men were used as controls. About 73% of the gout patients had hypertriglyceridemia, 1.6-fold the frequency found in the control group. Types IV and IIb lipoprotein electrophoretic patterns were most prevalent in the gout group. Neither alcohol intake nor hyperuricemia, per se, seems to be the cause of the lipid and lipoprotein disorder and cannot be related to liver or kidney dysfunctions. Obesity was the major underlying factor associated with the lipidemia. The study suggests that diet and, possibly, defective clearance of triglycerides may be etiologic factors associated with the abnormal serum triacylglycerol (triglyceride) and lipoprotein concentrations in these individuals.
Acetate intolerance and an inhibitor of acetate utilization in hemodialysis patients.
Authors: Egan J D , Wells I C
Published: January 2020

Diminished ability to utilize acetate (acetate intolerance) developed in a male patient on chronic hemodialysis after five years of maintenance dialysis. His ability to utilize lactate was also subnormal. We studied acetate metabolism in vitro by isolating lymphocytes from the patient's blood before dialysis and measuring their ability to convert [1-14C]acetate to 14CO2. His cells metabolized acetate only 35% as well as did lymphocytes from normal adults. The inhibition appeared when the patient's lymphocytes were cultured, and the ability of normal lymphocytes to oxidize acetate decreased after they had been incubated in the patient's plasma. We conclude that an inhibitor of acetate utilization is present in the plasma and in (or on) the cells of this acetate-intolerant patient. The diminished ability of the patient to utilize lactate and the presence of normal concentrations of pyruvate, citrate, and ketone bodies in his blood suggest that the inhibitor functions at the cell surface to impede the entrance of acetate into the cells. The inhibitor appears to be dialyzable; its nature is unknown. Its accumulation in the plasma of chronic hemodialysis patients has not been thus far associated with any deleterious effects other than prolonging the metabolic acidosis of such patients.
Liquid chromatographic analysis of disopyramide and its mono-N-dealkylated metabolite.
Authors: Lima J J
Published: January 2020

We describe a rapid, sensitive, and specific "high performance" liquid chromatographic analysis for disopyramide and its mono-N-dealkylated metabolite in serum, urine, and saliva. We used a mu-Bondapak CN column and an acetate buffer mobile phase containing methanol. Retention times for the two compounds and the internal standard, p-chlorodisopyramide, were 3.4, 4.1, and 6.3 min, respectively. The lower limits of sensitivity for drug and metabolite were 50 and 80 micrograms/L, respectively, with maximum coefficients of variation of 4.6 and 12%, respectively. Currently used antiarrhythmic drugs did not interfere with the analysis of disopyramide, and the pharmacokinetics of the drug, obtained from studies of one subject, agree well with reported values.
Incorrect least-squares regression coefficients in method-comparison analysis.
Authors: Cornbleet P J , Gochman N
Published: January 2020

The least-squares method is frequently used to calculate the slope and intercept of the best line through a set of data points. However, least-squares regression slopes and intercepts may be incorrect if the underlying assumptions of the least-squares model are not met. Two factors in particular that may result in incorrect least-squares regression coefficients are: (a) imprecision in the measurement of the independent (x-axis) variable and (b) inclusion of outliers in the data analysis. We compared the methods of Deming, Mandel, and Bartlett in estimating the known slope of a regression line when the independent variable is measured with imprecision, and found the method of Deming to be the most useful. Significant error in the least-squares slope estimation occurs when the ratio of the standard deviation of measurement of a single x value to the standard deviation of the x-data set exceeds 0.2. Errors in the least-squares coefficients attributable to outliers can be avoided by eliminating data points whose vertical distance from the regression line exceed four times the standard error the estimate.
Automated measurement of total cholesterol and triglycerides, in "tandem," on the discrete sample analyzer, Gilford System 3500.
Authors: Smith L , Lucas D , Lehnus G
Published: January 2020

We have developed an automated procedure on a discrete sample analyzer, Gilford System 3500, which alternately measures both total serum cholesterol and triglyceride concentrations as a "tandem" procedure. We used Dow Diagnostic's fully enzymatic, colorimetric reagents and aqueous standards to calculate unknowns ratiometrically. Cholesterol and then triglyceride reagent are dispensed into alternate cups; the produced color at 500 nm is measured after an ambient temperature incubation of 20 min. Reagent and sample carryover is less than 1.6%. Correlation coefficients of 0.997 for comparison for both automated tests with the manual methods at 30 degrees C and a typical CV of less than 2.0% show this "tandem" procedure to be reliable and accurate.
The elution profile of vitamin D2 metabolites from sephadex LH20 columns.
Authors: Hay A W , Jones G
Published: January 2020

A metabolite of vitamin D2 in the tissues of primates fed this vitamin co-migrates to a significant extent with 24,25-dihydroxyvitamin-D3 on columns of Sephadex LH20, with chloroform/n-hexane (60/40 by vol) as eluent. In individuals receiving vitamin D2 and in individuals with scant exposure to sunlight this metabolite, which we believe to be 25,26-dihydroxyvitamin-D2, may yield falsely higher concentrations of apparent 24,25-dihydroxyvitamin-D3 if separation on LH20 is used.
Spectral analysis of urinary reactions: a preliminary study based on a novel concept.
Authors: Wilding P , Bullock D G , Kricka L J , Morriss P , Holder R L
Published: January 2020

The concept of spectral analysis of urinary reactions (a range of simple chemical tests combined with pattern analysis) is described. A preliminary study in which we used 10 nonspecific tested on untimed urine specimens from 20 controls and 20 diabetics, matched for age and sex, suggested that a combination of these tests could be used to separate diabetics from healthy subjects. This combination, however, did not prove satisfactory for a further group of 13 diabetics. Closer examination revealed that factors such as therapy and glycosuria affected the results of these tests. This approach, which should extend the usefulness of urinalysis, may prove viable when larger groups, and possibly a different set of tests, are used to establish a more robust combination of tests.
Maltotetraose as a substrate for enzyme-coupled assay of amylase activity in serum and urine.
Authors: Whitlow K J , Gochman N , Forrester R L , Wataji L J
Published: January 2020

The use of maltotetraose ss a new substrate for the enzyme-coupled determination of amylase activity in biological fluids was developed by Beckman Microbics. We evaluated a manual and a centrifugal analyzer version of the method in comparison with two commonly used manual starch-dye amylase techniques: Roche Amylochrome and Pharmacia Phadebas. Both maltotetraose amylase procedures proved to be rapid and precise, and results correlated satisfactorily with the starch-dye methods for serum and urine samples.
Immunochemical determination of human immunoglobulins: use of kinetic turbidimetry and a 36-place centrifugal analyzer.
Authors: Finley P R , Williams R J , Lichti D A , Griffith F , Thies A C
Published: January 2020

We describe the measurement of human immunoglobulins IgG, IgA, and IgM in diluted sera, with diluted commercial monospecific antisera, with use of a 36-place centrifugal analyzer (RotoChem IIa; American Instrument Co., Silver Spring, MD 20920). The assay involves a two-point kinetic turbidimetric technique. The changes in absorbance at 340 nm between 10 and 255 s are taken for standard curve construction with use of a computer-generated cubic least-squares fit. Patients' samples are quickly calculated from the stored curve. Multiple time-interval readings are taken to observe the reaction kinetics. The lowest detectable concentrations are: IgG, 5 mg/L; IgA, 20 mg/L; and IgM, 20 mg/L. Correlation with radial immunodiffusion was excellent. Precision, accuracy, linearity, and sensitivity were very acceptable. Antigen or antibody excess can be easily detected. The accuracy of the proposed method when measuring idiotypic monoclonal proteins is greater than radial immunodiffusion. Up to 30 patients' samples can be analyzed at one time, and calculation of test results by use of the computer program is efficient and rapid.
Radioimmunoassay of 17 alpha-hydroxyprogesterone in saliva, parotid fluid, and plasma of congenital adrenal hyperplasia patients.
Authors: Walker R F , Read G F , Hughes I A , Riad-Fahmy D
Published: January 2020

We report a radioimmunoassay sensitive enough to determine 17 alpha-hydroxyprogesterone concentrations in 200 microliter of parotid fluid or mixed whole saliva. Because the correlation of concentrations in matched samples of parotid fluid and saliva was excellent (r = 0.98), we exclusively used saliva, which is easier to collect, in later studies. The assay is specific; saliva samples assayed with and without thin-layer chromatographic purification showed no significant difference. The assay is also precise, and has a lower limit of sensitivity of 4 pg per assay tube. In 14 patients having congenital adrenal hyperplasia from a C21-hydroxylase enzyme deficiency, all of whom were receiving cortisol replacement therapy, the range in 17 alpha-hydroxyprogesterone concentrations observed in saliva (67-26,300 pmol/L) was about 20-fold that seen in 32 healthy children (90-1520 pmol/L). The close correlation (r = 0.91) between 17 alpha-hydroxyprogesterone concentrations in matched samples of saliva and plasma from these patients indicates that determination of steroids in saliva could well replace determination in plasma. This concept is supported by 17 alpha-hydroxyprogesterone concentrations monitored throughout 24 h from one patient and following stimulation with synthetic corticotropin in another patient.
Measurement of aspartate aminotransferase activity: effects of oxamate.
Authors: Rej R
Published: January 2020

Oxamate, a potent inhibitor of lactate dehydrogenase, is shown also to inhibit aspartate aminotransferase activity, both in human serum and in purified isoenzymes of human origin. The inhibition was competitive with respect to 2-oxoglutarate for both isoenzymes. The apparent Ki was 29 mmol/L for the cytoplasmic enzyme and 17 mmol/L for the mitochondrial enzyme. Noncompetitive inhibition was found between oxamate and aspartate. At saturating concentrations of substrate (2-oxoglutarate greater than or equal to 15 mmol/L, L-aspartate greater than or equal 150 mmol/L) oxamate inhibited the mitochondrial enzyme but had less effect on the cytoplasmic isoenzyme. Oxamate at 40 mmol/L inhibited the enzyme in serum by 11 and 9% in assays containing 2-oxoglutarate at 6.7 and 15 mmol/L, respectively. This concentration of oxamate inhibited enzyme activity in serum by 5% more than did the same concentration of Cl- (itself an inhibitor). Oxamate (less than or equal to 30 mmol/L) had no measurable effect on the stability or activity of porcine malate dehydrogenase. Until the effects of its inhibitory properties are considered, addition of oxamate to suppress lactate dehydrogenase-mediated side reactions in the assay of aspartate aminotransferase cannot be recommended.
A Liquid-Chromatographic Analysis for Indomethacin in Serum
Authors: Soldin Steven J , Gero Terese
Published: January 2020

We describe a "high-performance" liquid-chromato-graphic assay for measuring indomethacin in 100 µL of serum. The procedure involves an ethylene dichloride extraction of indomethacin and internal standard (2,5-diphenyloxazole) from serum. The organic phase is separated and evaporated, and the residue dissolved in a 40/60 (by vol) mixture of potassium phosphate buffer (10 mmol/L, pH 3.0) and acetonitrile. An aliquot of this solution is injected into the chromatograph. We used a µ-Bondapak C-18 column with the above-mentioned buffer system as mobile phase, a flow rate of 3.0 mL/min, and a column temperature of 40 °C. Indomethacin and the internal standard are detected by their absorbance at 200 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis for indomethacin in serum at concentrations > 100 µg/L. Analytical recovery for indomethacin was 66-68%, and the method affords good day-to-day precision (CV <11 %).
Fixed-time kinetic assay of plasma ammonia, with NADPH as cofactor, with a centrifugal analyzer.
Authors: Li P K , Shull B C
Published: January 2020

We describe a fixed-time, enzymatic, reaction-rate procedure for determining plasma ammonia with a centrifugal analyzer (Rotochem IIA/36; American Instrument Co., silver Spring, MD 20910), with NADPH as cofactor. The reaction is based on that of da Fonseca-Wollheim's modification [J. Clin. Chem. Clin. Biochem. 11, 421 (1973)] of the Kirstein reaction, which depends on the catalytic amination of alpha-ketoglutarate by the action of glutamate dehydrogenase with NADPH as the cofactor instead of NADH. Use of NADPH minimizes interference from endogenous reactions such as that between lactate dehydrogenase and pyruvate. This method permits shortened preincubation time and thus improves both specificity and precision. This assay requires 100 microliter of freshly collected heparinized plasma, gives quantitative analytical recovery, and the standard curve is linear to 430 mumol/L. Data are presented comparing results with those by two other enzymatic ammonia procedures.
Predictive values of thyroxine, thyrotropin, and triiodothyronine concentrations in serum.
Authors: Homburger H A , Hewan-Lowe K
Published: January 2020

The predictive values of total thyroxine, thyrotropin, and total triiodothyronine concentrations in serum for clinically apparent and subclinical hypothyroidism and hyperthyroidism were determined by retrospective analysis of clinical cases chosen from the frequency distributions of hormone test results. Very low total thyroxine concentrations, less than 25 microgram/L, were specific for hypothyroidism. Most subclinical hypothyroid cases had intermediate or low total thyroxine concentrations, 35-60 microgram/L, with moderately increased thyrotropin concentrations, greater than 12 milli-int. units/L. Thyrotropin cut-off concentrations were identified that had predictive values greater than 90% for classifying untreated and hormone-treated hypothyroid cases. Above-normal total thyroxine concentrations, regardless of absolute value, were not specific for hyperthyroidism, because binding-protein alterations related to estrogen taking were prevalent and produced occasional marked increases in serum total thyroxine. Nevertheless, cut-off concentrations for serum total thyroxine and total triiodothyronine were identified that had a predictive value greater than 90% for hyperthyroidism, without necessitating measurement of the capacities or concentrations of hormone-binding proteins.
Microchemical analysis for 13 constituents of plasma from healthy children.
Authors: Cheng M H , Lipsey A I , Blanco V , Wong H T , Spiro S H
Published: January 2020

Normal values for 13 chemical constituents of plasma were estimated from results for 837 presumably healthy children. Ninety microliters of specimen was analyzed for lactate dehydrogenase, aspartate aminotransferase, alkaline phosphatase, inorganic phosphorus, total calcium, total cholesterol, total proteins, albumin, uric acid, urea nitrogen, alanine aminotransferase, total bilirubin, and glucose. We used two Abbott ABA-100 Bichromatic Analyzers interfaced directly to the ABA Data Management System. For each test age- and sex-related variations were assessed and normal values were estimated for six different age groups.
Enzyme immunoassay of estrogen-like substances in plasma, with polyethylene glycol as precipitant.
Authors: Osterman T M , Juntunen K O , Gothoni G D
Published: January 2020

We devised an enzyme immunoassay for plasma estrogen-like substances in pregnancy, using estriol covalently linked to horseradish peroxidase. Free and bound steroid were separated by use of polyethylene glycol reagent. The assay satisfies the normal criteria of specificity and precision. Results obtained by radioimmunoassay and enzyme immunoassay agreed well. Our assay is particularly applicable in smaller clinical laboratories to routine determination of plasma estriol in pregnancy.