bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of the conjugated polyene fatty acid, parinaric acid, in assaying fatty acids in serum or plasma.
Authors: Berde C B , Kerner J A , Johnson J D 
Published: January 2020

Abstract
We describe a method for rapidly assaying fatty acid concentrations in plasma or serum. This method is particularly appropriate for monitoring increased concentrations of fatty acids that may be present during intravenous lipid infusion, especially in neonates. Binding cisparinaric acid (9, 11, 13, 15-cis-trans-trans-cis-octadecatetraenoic acid) to albumin shifts the absorption spectrum of the acid. If fatty acids are present in serum, they will compete with parinaric acid for binding, changing the extent of this absorption shift. The measurement requires a spectrophotometer, 30 microL of serum or plasma, and knowledge of the sample's albumin concentration.
Turbidimetry of inorganic sulfate, ester sulfate, and total sulfur in urine.
Authors: Lundquist P , Mårtensson J , Sörbo B , Ohman S 
Published: January 2020

Abstract
We describe simple and precise methods for the determination of inorganic sulfate, ester sulfate, and total sulfur in urine. The methods are based on turbidimetry of sulfate as barium sulfate in the presence of a small amount of preformed barium sulfate and with polyethylene glycol as a stabilizing agent. Inorganic sulfate is directly determined, whereas ester sulfate is measured after removal of inorganic sulfate, followed by acid hydrolysis. Total sulfur is determined after wet oxidation of the sample with nitric acid and perchloric acid in the presence of vanadate as a catalyst. We also report excretion values for healthy persons on a self-selected diet. Men excrete significantly higher amounts of inorganic sulfate and total sulfur than women, but this sex-related difference becomes insignificant if excretion values are expressed relative to creatinine.
Assay for erythrocyte uroporphyrinogen I synthase activity, with porphobilinogen as substrate.
Authors: Ford R E , Ou C N , Ellefson R D 
Published: January 2020

Abstract
We describe a convenient, economical procedure for measuring uroporphyrinogen I synthase (EC 4.3 1.8) activity in erythrocytes, the results of which can be used to diagnose acute intermittent porphyria, in either its latent or acute stage. By limiting the test reaction sequence to the conversion of porphobilinogen to porphyrins, we eliminated several disadvantages of alternative methods in which delta-aminolevulinate is used as substrate. The latter assay was inhibited by lead; our procedure was not. Our procedure also gave greater porphyrin synthesis with less substrate. Erythrocytes of healthy women presented a mean activity of 12.4 nmol of porphyrin formed per liter per second; erythrocytes of healthy men presented a mean activity of 11.0 nmol/L per second. The within-run coefficient of variation (CV) for our assay was 1.8%; the between-run CV was 3.1%.
beta 2-Microglobulin clearance as measured by radioimmunoassay.
Authors: Woo J , Floyd M , Longley M A , Cannon D C 
Published: January 2020

Abstract
We describe a radioimmunoassay for beta 2-microglobulin (beta 2 mu) in serum and urine. We incubated aliquots of diluted samples at room temperature for 1 h with 125I-labeled beta 2 mu and a rabbit antiserum monospecific for human beta 2 mu, and separated the phases by the double-antibody technique. The logit-log transformed dose-response curve was linear in the range 2 to 64 ng, equivalent to 0.5 to 16 mg/L of serum and 0.5 to 320 mg/L of urine. Assay sensitivity was 2.4 ng of beta 2 mu. Validation studies included tests of precision, accuracy, antibody specificity, and parallelism of the dose-response curves for standard and unknown. In a study of 25 normal individuals, serum and urine beta 2 mu ranged from 1.1 to 2.3 mg/L and 40 to 360 micrograms/24 h; the clearance of beta 2 mu was 8 to 130 microL/min. In 21 renal allograft recipients tested one to five weeks after transplantation, serum and urine beta 2 mu ranged from 3.9 to 15.6 mg/L and 7.2 to 611 mg/24 h; beta 2 mu clearance was 0.60 to 33.3 mL/min. Values for both serum and urine correlated well with severity of allograft rejection.
Immunonephelometric assay of human apolipoprotein AI.
Authors: Lopes-Virella M F , Virella G , Evans G , Malenkos S B , Colwell J A 
Published: January 2020

Abstract
We report an immunonephelometric assay for apolipoprotein AI, which involves use of a laser nephelometer and an antiserum prepared in our laboratory. Coefficients of variation were 2.5% within-run, 6.3% between-run. Several types of manipulation of the samples (heating, delipidation, dissociation with urea), reportedly necessary for accurate determinations by radioimmunoassay or gel diffusion immunoassay, did not substantially affect results obtained with our technique. The assay is sensitive, reproducible, and simple, and appears suitable for routine use.
Two-site immunofluorometric assay for pregnancy-specific beta 1-glycoprotein (SP1).
Authors: Sykes A , Chard T 
Published: January 2020

Abstract
We describe an immunoassay for human pregnancy-specific beta 1-glycoprotein by use of fluorescein-labeled antibodies to this protein. The technique is generally similar to that of a "two-site" immunoradiometric assay but has the advantage of stability of tracer and avoidance of radiation hazard. However, the procedure requires relatively large quantities of antibody. Furthermore, the within-assay coefficient of variation (11.8%) is greater than that for radioimmunoassay (6.5%). This results from imprecision of the end-point detection, and some inherent difficulties in optimizing a "two-site" immunometric system. Concentrations of endogenous material as measured by the fluorometric assay are 1.9-fold higher than those obtained with radioimmunoassay, probably because the former detects multiple forms of this heterogeneous material.
Separation of serum prednisolone and prednisolone-21-hemisuccinate by extraction and their concurrent determination by radioimmunoassay.
Authors: Yanagibashi K , Mizuchi A , Yotsumoto H , Miyachi Y 
Published: January 2020

Abstract
We describe a simple, sensitive, and reliable radioimmunoassay for prednisolone and prednisolone-21-hemisuccinate in serum. The antiserum produced in rabbits to prednisolone-21-hemisuccinate/bovine serum albumin was specific for prednisolone and prednisolone-21-hemisuccinate. A simple dichloromethane extraction permitted the separation of prednisolone from prednisolone-21-hemisuccinate in the serum samples. Interference by cortisol, although not insignificant, is minimized in this assay. We used the method to measure prednisolone and prednisolone-21-hemisuccinate concentrations after a bolus injection of prednisolone-21-hemisuccinate into human beings and mice.
Measuring percent oxygen saturation of hemoglobin, percent carboxyhemoglobin and methemoglobin, and concentrations of total hemoglobin and oxygen in blood of man, dog, and baboon.
Authors: Dennis R C , Valeri C R 
Published: January 2020

Abstract
We used an automated four-wavelength spectrometer to measure the concentration of total hemoglobin, percent oxyhemoglobin, carboxyhemoglobin, and methemoglobin, and concentration of oxygen bound to hemoglobin in the blood of humans, dogs, and baboons under clinical and various experimental conditions. Measurements of total hemoglobin and methemoglobin with this simple method were comparable to those with standard spectrometric procedures. Carboxyhemoglobin measurements were comparable to those made with gas chromatography, and measurements of oxygen content were comparable to those made with the galvanic cell method. The new instrument is as accurate as the comparison methods used to evaluate it in all parameters, is reliable, and measurements take only 63 s per sample. In addition, it requires minimal operator training, infrequent need for calibration, and no sample preparation.
Nitrogen estimation in biological samples by use of chemiluminescence.
Authors: Ward M W , Owens C W , Rennie M J 
Published: January 2020

Abstract
We describe an apparatus modified for the chemiluminescent estimation of nitrogen in biological and clinical samples. Analytical characteristics have been assessed and results compared with those by the traditional Kjeldahl method. The chemiluminescence method, much faster and more sensitive than the traditional method, is at least as accurate, precise, and reproducible. Costs are low, and the method should find a place in laboratories needing, for example, rapid assessments of nitrogen balance in surgical patients and renal function in patients with renal failure, or estimations of small amounts of specific nitrogen-containing chemical substances in biological samples.
(University of Pennsylvania Case Conference): oligoclonal immunoglobulins in cerebrospinal fluid in multiple sclerosis.
Authors: Keshgegian A A , Coblentz J , Lisak R P 
Published: January 2020

Abstract
In the normal state, immunoglobulins are polyclonal. They migrate as a broad band on electrophoresis, reflecting the diversity of immunoglobulin species secreted by the many clones of immunoglobulin-producing cells. In lymphoproliferative disorders, monoclonal immunoglobulins are often found, migrating as electrophoretically homogeneous bands, reflecting the large amount of a single immunoglobulin being secreted by the single proliferating neoplastic clone. In certain neurological diseases, such as multiple sclerosis, the cerebrospinal fluid (CSF)2 often exhibits an oligoclonal immunoglobulin pattern consisting of several electrophoretically homogeneous bands in the gamma-globulin regin (Figure 1). We present two cases of neurological disease with an oligoclonal immunoglobulin pattern in the CSF electropherogram. In the discussion we consider the definition, etiology, and pathogenesis of multiple sclerosis, and laboratory tests that are useful in multiple sclerosis, emphasizing methods for the demonstration and interpretation of an oligoclonal immunoglobulin pattern.
Improved liquid-chromatographic determination of caffeine in plasma.
Authors: Blanchard J , Mohammadi J D , Conrad K A 
Published: January 2020

Abstract
We describe a rapid, specific, and sensitive liquid-chromatographic micro-method for caffeine in plasma. Each plasma sample can be assayed within about 15 min of its receipt. Samples are denatured with acetonitrile, centrifuged, and the supernate is chromatographed on a reversed-phase column. Only 100 microL of plasma is required, and concentrations as low as 0.3 mg/L can be measured accurately. Other xanthines and their metabolites do not interfere. The small sample required makes the procedure ideally suited for measuring caffeine in the plasma of infants and small animals as well as adults.
Evaluation of quality-control materials for high-density-lipoprotein cholesterol quantitation.
Authors: Warnick G R , Mayfield C , Albers J J 
Published: January 2020

Abstract
Commercial quality-control materials and frozen plasma and serum pools were evaluated for high-density lipoprotein (HDL) cholesterol quantitation by the heparin-Mn2+ and phosphotungstate-Mg2+ precipitation methods and by ultracentrifugal and electrophoretic methods. We evaluated among-day precision; inter-method differences in HDL cholesterol quantitation; lipid composition and electrophoretic mobility of th lipoprotein density fractions; and the effects of modifications in reagent concentration and temperature. Frozen plasma pools (in-house) and frozen serum pools (prepared by the Center for Disease Control) were determined to be suitable HDL controls. Also, a commercial lyophilized serum free of very-low-density lipoprotein (VLDL) to which VLDL is added in a diluent solution (Analytical Control) also appeared suitable as an HDL control material. Conventional lyophilized pools (Lyphochek Elevated, Monitrol I, Ortho Normal, Precilip) were less suitable as control materials because of poor between-day precision for one or both of the precipitation methods and, in some cases, because of large absolute differences observed between the HDL methods. A serum pool stabilized with ethylene glycol (Beckman Level I) was the least as appropriate as an HDL control material. Other lyophilized pools--Lipid Fraction Control (Hyland) prepared by a modified lyophilization process and Lipidophor (Immuno Diagnostika) prepared by lyophilization with a stabilizing agent--appear promising.
Relation between maternal weight and serum alpha-fetoprotein concentration during the second trimester.
Authors: Haddow J E , Kloza E M , Knight G J , Smith D E 
Published: January 2020

Abstract
Maternal serum alpha-fetoprotein concentrations are influenced by maternal weight during the second trimester. Heavier pregnant women have lower median values, apparently as a result of a diluting effect of larger blood volume. This phenomenon is of clinical interest because alpha-fetoprotein concentration in a pregnant woman's serum is one of the factors considered in assessing risk of poor outcome. A revision of the reference interval for alpha-fetoprotein to take body weight into account might improve its use as a diagnostic aid, especially in heavier women.
Liquid-chromatographic quantification of plasma phenylalanine, tyrosine, and tryptophan.
Authors: Neckers L M , Delisi L E , Wyatt R J 
Published: January 2020

Abstract
Phenylalanine, tyrosine, and tryptophan are isolated and quantified by "high-pressure" liquid chromatography, with fluorescence detection. An isocratic mobile phase and reversed-phase column are used to provide rapid and reproducible measurement of these amino acids in as little as 1 to 2 microL of human plasma.
Measurement of near-normal concentrations of erythrocyte protoporphyrin with the hematofluorometer: influence of plasma on "front-surface illumination" assay.
Authors: Schifman R B , Finley P R 
Published: January 2020

Abstract
Zinc protoporphyrin in erythrocytes increases in iron depletion. Because the hematofluorometer directly measures zinc protoporphyrin in whole blood, it may therefore be a useful screening instrument for detecting iron deficiency. We evaluated its performance with normal to slightly above-normal zinc protoporphyrin concentrations (0.2 to 2.0 mg/L) in erythrocytes, because this is a critical range for differentiating normal and iron-deficient individuals. There was excellent correlation (r2 = 0.900) between erythrocyte protoporphyrin as measured by an extraction procedure and as measured directly with the hematofluorometer. However, at these concentrations, plasma caused hematofluorometer readings to be spuriously high, by 2.4 to 89.4%, an effect due to the instrument's optical design. The effect can be eliminated by washing the cells free of plasma or by allowing erythrocytes to displace plasma by settling to the illuminated surface before the measurement. The interference does not affect the hematofluorometer's sensitivity, but abnormal results obtained for whole blood should be confirmed with more-specific tests, and interlaboratory precision may be influenced if whole-blood samples are used. A 1-min delay from sample placement to measurement decreased zinc protoporphyrin values by 2.6 to 36.9%. We also describe the use of cryopreserved control erythrocytes, for which the CV is 2.3% for a concentration of 0.96 mg per liter of erythrocytes, which are not affected by time of measurement, and which are stable for three months.
Evaluation of the IFCC-recommended procedure for serum aspartate aminotransferase as modified for use with the centrifugal analyzer.
Authors: Bruns D E , Savory J , Titheradge A C , Cross R E , Wills M R 
Published: January 2020

Abstract
The IFCC-recommended procedure for aspartate aminotransferase (EC 2.6.1.1) was adapted to the centrifugal analyzer and evaluated during five years. The main hindrance to widespread use of the recommended method is the need for pre-incubation with pyridoxal phosphate. The present method includes a 10-min pre-incubation with pyridoxal phosphate. Extensive evaluation of the method with and without this pre-incubation confirms earlier reports that it eliminates some significant errors, especially for samples from patients with cardiac disease. However, the pre-incubation can be briefer than the recommended 10 min and still provide acceptable results.
Extended clinical trial and evaluation of glucose determination with the Eastman Kodak Ektachem GLU/BUN Analyzer.
Authors: Bandi Z L , Fuller J B , Bee D E , James G P 
Published: January 2020

Abstract
We followed the "abbreviated precision protocol" of the National Committee for Clinical Laboratory Standards for the evaluation of precision, accuracy, and carryover in analyses for glucose with the "Ektachem." We analyzed 760 clinical samples by this technique, by the FDA Proposed Class Standard glucose reference method, and with the Beckman System I GLU/BUN Analyzer. Precision and accuracy were estimated for 500, 1000, 1200, 1500, and 3000 mg/L glucose concentrations in 100, 30, or 20 microL of serum or plasma. Potential interference of 19 compounds was evaluated. Random error (1.965 X SD) was 22, 30, 34, 40, and 88 mg/L. Systematic error was 8, 1.5, -2, -5, and -27 mg/L. Total analytical error was 30, 32, 36, 46, and 110 mg/L for analysis of 100 microL of serum at the above-stated glucose concentrations. The greatest interference (-39 mg/L) in the glucose (at 1200 mg/L) determination was caused by L-ascorbate (40 mg/L). Glucose concentrations as determined with the Ektachem were found to be linearly related to the expected concentration up to at least 5660 mg/L. Carryover was not statistically significant.
Urinary metanephrine radioimmunoassay: comparison with the colorimetric assay.
Authors: Raum W J , Swerdloff R S 
Published: January 2020

Abstract
A radioimmunoassay involving an 125I ligand has been developed and applied to the measurement of urinary metanephrine. To validate the clinical usefulness of this assay, we compared measurement of metanephrine by radioimmunoassay and of total urinary metanephrines by the Pisano colorimetric method. The radioimmunoassay is specific for metanephrine, whereas the colorimetric method measures both metanephrine and normetanephrine. We used both methods to determine urinary metanephrine or total metanephrines in subjects with essential hypertension, pheochromocytoma, the syndrome of multiple endocrine adenomatosis type 2, and normotensive volunteers. The mean and upper limit of normal (3 SD) for metanephrine by radioimmunoassay in our normotensive volunteers was 94.2 microgram/24 h and 229 microgram/24 h, respectively, which compares well with reported values of 87.6 microgram/24 h and 319 microgram/24 h by non-radioimmunoassay methods. Both radioimmunoassay and colorimetry accurately identified five patients with known pheochromocytoma. Good correlation (r = 0.993) was demonstrated between the two assays in a comparison of patients with essential hypertension and pheochromocytoma. We conclude that the radioimmunoassay is at least equivalent to the colorimetric methods in distinguishing pathological and normal catecholamine secretion, and is faster, more precise, and 1000-fold more sensitive.
A clinical evaluation of various delta check methods.
Authors: Wheeler L A , Sheiner L B 
Published: January 2020

Abstract
To evaluate the performance of delta check techniques, we analyzed 707 unselected pairs of continuous-flow test results, using three different delta check methods. If any of the test results (plus the urea nitrogen/creatinine ratio and the anion gap) failed one of the checks, the reason for the failure was sought by examining subsequent test results, retesting specimens, and (or) reviewing te patient's chart. Each delta check failure was accordingly classified as a true or false positive. The percentage of positives we judged to be true positives ranged from 5 to 29%. Each of the three methods had test types with low and high percentages of true positives. We conclude that with the delta check methods one can detect errors otherwise overlooked, but at the cost of investigating many false positives, because, in the population we studied, disease processes or therapy often caused large changes in a series of test results for a patient.
Day-to-day variation in serum ferritin concentration in healthy subjects.
Authors: Pilon V A , Howanitz P J , Howanitz J H , Domres N 
Published: January 2020

Abstract
We report our observations on day-to-day variation in serum ferritin, serum iron, total iron-binding capacity, and percent saturation of binding proteins with iron in 13 ostensibly healthy subjects during five weeks. The average intrasubject coefficients of variation were 14.5, 28.5, 4.8, and 28.0%, respectively. Precision studies on control samples showed greater within-assay and between-assay analytical variation for serum ferritin than for serum iron or total iron-binding capacity. Evidently, serum ferritin varies less in a given individual from day to day than do serum iron and percent iron saturation. Thus, a single measurement of serum ferritin may be a more reliable index of iron stores than an isolated determination of either serum iron or percent iron saturation.
Measurement of amniotic fluid surfactant.
Authors: Freer D E , Statland B E 
Published: January 2020

Abstract
Measurement of the production of surfactant is the most direct means of prenatally assessing fetal pulmonary maturity. We review assays which have evolved for measuring surfactant, classifying them into two general categories: biochemical quantitation and biophysical measurements. Biochemical quantitation assays include the amniotic fluid lecithin/sphingomyelin ratio and quantitation of lecithin and other surfactant phospholipids. Biophysical measurements include measurement of surface-tension-lowering ability of extracts of amniotic fluid lipid and evaluation of surface-tension-related properties such as foam stability and microviscosity. Assays of surfactant are subject to certain pre-analysis sources of variation over which the analyst has no control, such as variability in total in vivo amniotic fluid volume, incomplete in vivo mixing of surfactant with amniotic fluid, and presence of contaminating blood or meconium. We also examine other factors such as centrifugation speed and time, and storage of the amniotic specimen before analysis. These factors can dramatically affect analyses, and must be carefully controlled by the analyst. In general, both biochemical and biophysical approaches to surfactant analysis are useful diagnostically. When properly performed, both approaches give results that correlate well, both with each other and with clinical outcome. Because "mature" and "immature" values overlap, none of the assays can completely eliminate false predictions, whether of fetal maturity or fetal immaturity.
Concanavalin A binding of alpha-fetoprotein in amniotic fluid as an aid in the diagnosis of neural tube defects.
Authors: Buamah P K , Taylor P , Ward A M 
Published: January 2020

Abstract
Concanavalin A nonreactive alpha-fetoprotein was determined in samples of amniotic fluid from 16 abnormal pregnancies complicated by anencephaly (7), open spina bifida (6), intra-uterine death (1), anencephaly with exomphalos (1), or open spina bifida with exomphalos (1), and in amniotic fluid from 50 normal pregnancies with gestational age between 13 and 24 weeks. In all 16 cases with fetal malformations, the proportion of nonreactive alpha-fetoprotein was significantly decreased (median 5.3%) as compared with amniotic fluid from pregnancies with a normal outcome (median 39.7%). The results confirm that this measurement is useful in the diagnosis of neural tube defects, especially when the concentration of alpha-fetoprotein in amniotic fluid is normal or only slightly above normal and gestational age is uncertain.