bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relative value of three laboratory methods in the diagnosis of multiple sclerosis.
Authors: Bloomer L C , Bray P F 
Published: January 2020

Abstract
We compared three methods of analysis for IgG in cerebrospinal fluid, using samples from 158 patients with clinically suspected multiple sclerosis and from 200 neurological controls. The tests were: search for oligoclonal bands, calculation of rate of synthesis of IgG in the cerebrospinal fluid, and determination of the IgG/albumin ratio. Paired cerebrospinal fluid and serum samples were collected and their IgG and albumin concentrations measured. Oligoclonal bands were detected by electrophoresis on agarose. Positive results were obtained in 94, 75, and 67% of patients with probable or definite multiple sclerosis by the three respective methods. In contrast, for patients for whom the clinical diagnosis of multiple sclerosis was considered possible, positive results were obtained in 10, 43, and 13%, respectively. Evidently, detection of oligoclonal bands remains the best single test for the presence of abnormal IgG in suspected multiple sclerosis patients. A combination of the first two tests is most sensitive for both probable and definite multiple sclerosis (97%) and possible multiple sclerosis (50%). Some infectious or immunologic disorders can also produce these IgG abnormalities, but they can usually be distinguished from multiple sclerosis by other clinical and laboratory data.
Evaluation of a new free-thyroxin assay.
Authors: Wellby M L , Guthrie L , Reilly C P 
Published: January 2020

Abstract
The Amerlex Free Thyroxin (T4) Radioimmunoassay Kit (Amersham International Ltd.) is a new direct equilibrium radioimmunoassay for free T4 based on an antiserum with very high affinity for T4, and a unique 125I-labeled T4 analog as tracer. It is a very simple single-tube radioimmunoassay, making use of Amerlex particles to separate antibody-bound from free species. Interassay precision (CV) is 3.7% at 13 pmol/L and 2.3% at 30 pmol/L; within-assay precision is 4.2% at 21 pmol/L. The reference interval is 11-22 pmol/L. The assay did not misclassify any patients tested who had untreated myxedema or untreated thyrotoxicosis. The free T4 assay excelled both the free T4 index and the T4/T4-binding globulin ratio in correcting for increased thyroxin-binding globulin from pregnancy, and it was better than the index but not better than the ratio in correcting for increased thyroxin-binding globulin in users of oral contraceptives.
Improved simultaneous gas-chromatographic analysis for homovanillic acid and vanillylmandelic acid in urine.
Authors: Leiendecker-Foster C , Freier E F 
Published: January 2020

Abstract
We describe an improved gas-chromatographic method for the simultaneous quantitation of the catecholamine metabolites, homovanillic acid (3-methoxy-4-hydroxyphenylacetic acid) and vanillylmandelic acid (3-methoxy-4-hydroxymandelic acid). Our improvements in the method of Muskiet et al. (Clin. Chem. 23: 863, 1977) include a shorter program time and a longer silylation interval. Recovery and precision data obtained by this improved technique are similar to those of Muskiet et al. Vanillylmandelic acid results (y) were compared with those by the method of Pisano et al. (Clin. Chim. Acta 7: 285, 1962). The relation is expressed by the equation y = 0.52 + 1.05x (Sy . x = 2.33 mg/24 h and r = 0.997). Results for homovanillic acid (y) were compared with those by the method of Knight and Haymond (Clin. Chem. 23: 2007, 1977); the equation was y = 0.84 + 0.90x (Sy . x = 2.04 and r = 0.97). Retention times are also reported for several phenolic acids and other related compounds found in urine.
Liquid-chromatographic monitoring of 5-methyltetrahydrofolate in plasma.
Authors: Giulidori P , Galli-Kienle M , Stramentinoli G 
Published: January 2020

Abstract
The liquid-chromatographic measurement of 5-methyltetrahydrofolate in biological fluids is described. The sensitivity of the spectrophotofluorometric detector used allows direct evaluation of basal concentrations of the compound in plasma. Because it is resolved from the other common folates and from methotrexate, the procedure is suitable for monitoring it in plasma of patients receiving high-dose therapy with methotrexate.
Optimized assay for serum angiotensin-converting enzyme activity.
Authors: Hurst P L , Lovell-Smith C J 
Published: January 2020

Abstract
This optimized two-point kinetic assay for serum angiotensin-converting enzyme is based on the colorimetric determination of hippurate with cyanuric chloride/dioxan reagent. The hippurate is released from hippuryl-L-histidyl-L-leucine by angiotensin-converting enzyme in the presence of chloride ion. CVs for the method (within-run and between-run) ranged from 2.1 to 3.2%. Linearity extends up to 200 U/L. Results are unaffected by lipemia and icterus. Hemoglobin in concentrations greater than 1.5 g/L causes a slight negative interference. Reference intervals for men and women are 22-82 U/L and 25-69 U/L, respectively.
Separation and detection of lipoproteins in human serum by use of size-exclusion liquid chromatography: a preliminary report.
Authors: Busbee D L , Payne D M , Jasheway D W , Carlisle S , Lacko A G 
Published: January 2020

Abstract
Components of human serum can be separated on the basis of differences in relative molecular mass by using size-exclusion "high-performance" liquid chromatography. Lipoproteins in fractions of the eluate can be quantitated by conventional chemical and enzymatic methods. Alternatively, if lipoproteins in the serum are selectively prestained with diformazan dye, the column effluent can be monitored spectrophotometrically at 580 nm, so that only the lipoprotein components of serum are detected. Samples of purified low-density lipoproteins, so stained and analyzed, provide peak-area values that are proportional to their concentration as evaluated by chemical methods. With this technique, the various lipoprotein classes can be quickly separated and their concentration estimated. These techniques should prove useful in clinical and research laboratories.
Improved thin-layer chromatography of disaturated phosphatidylcholine in amniotic fluid.
Authors: Tsai M Y , Cain M , Josephson M W 
Published: January 2020

Abstract
We describe an indirect test of fetal lung maturity: the quantitation of disaturated phosphatidylcholine in amniotic fluid. The lipids in samples of amniotic fluid from 172 patients were reacted with osmium tetroxide, and disaturated phosphatidylcholine was then isolated by thin-layer chromatography. Interfering substances were retained by a pre-adsorbent layer. The charred disaturated phosphatidylcholine, quantitated by densitometry, was compared to standard dipalmitoyl phosphatidylcholine. Both within-run and between-run coefficients of variation were about 10%. Blood and meconium do not interfere. Six infants developed respiratory distress when disaturated phosphatidylcholine concentrations of amniotic fluid drawn within 72 h of delivery were less than 5.5 mg/L. A concurrently determined lecithin/sphingomyelin ratio falsely predicted lung maturity in one of these. In seven other samples for which lecithin/sphingomyelin ratios suggested lung immaturity but disaturated phosphatidyl-choline predicted maturity, none of the infants developed respiratory distress. In normal pregnancies, measurement of disaturated phosphatidylcholine in amniotic fluid appears to be a better predictor of fetal lung maturity than is measurement of the lecithin/sphingomyelin ratio. Further studies are needed to determine if this analysis is a better predictor in diabetic pregnancies.
Automated enzyme assays by use of a centrifugal analyzer with fluorescence detection.
Authors: Pearson K W , Smith R E , Mitchell A R , Bissel E R 
Published: January 2020

Abstract
The first commercially available centrifugal analyzer having fluorescence detection capability was used to develop kinetic fluorometric assays for several proteinases. The substrates were all synthetic oligopeptides incorporating 7-amino-4-trifluoromethylcoumarin, a molecule that can be detected either spectrophotometrically or fluorometrically. We thus compared the centrifugal analyzer spectrophotometric and fluorometric detection systems, finding fluorescence detection to be 50-fold more sensitive. We also compared the sensitivity of the fluorescence detector to that of a conventional spectrofluorometer by determining the minimum detection limit for each enzyme on both instruments; we found them to be similar in sensitivity. As an illustrative application, we measured the cathepsin B-like activity in serum samples from 55 women. The median enzyme activity of women taking oral contraceptives and pregnant women was increased two- and threefold, respectively, over the control group (about 5% CV within run, and 10% CV between runs).
Liquid-chromatographic determination of cimetidine, its known metabolites, and creatinine in serum and urine.
Authors: Ziemniak J A , Chiarmonte D A , Schentag J J 
Published: January 2020

Abstract
We describe a liquid-chromatographic procedure for determination of cimetidine, its hydroxymethyl-, sulfoxide-, and guanyl urea metabolites, and creatinine in patients serum and urine. SKF 92374 is used as the internal standard. Protein in 0.5 mL of serum or diluted urine is precipitated with 2 mL of acetonitrile, the organic and aqueous phases are separated by adding 0.3-0.5 g of anhydrous K2HPO4. The organic phase is evaporated, and 0.5 mL of 50 mmol/L HCl is added. This solution is washed with 3 mL of water-saturated isoamyl alcohol, the aqueous phase is extracted with 3 mL of methylene chloride and enough K2HPO4 to saturate the solution. The methylene chloride is evaporated, the residue reconstituted with 100 microL of mobile phase, and a 25-microL aliquot injected onto the chromatographic column (Dupont Sil). The mobile phase is acetonitrile/methanol/water/ammonium hydroxide (1000/50/50/2, by vol). The column effluent is monitored at 228 nm. Lower limits of detection ranged from 0.05 mg/L for cimetidine to 0.2 mg/L for guanyl urea. We determined cimetidine and its principal metabolites in the serum of a patient receiving cimetidine for the treatment of Zollinger-Ellison syndrome, and have assessed use of the assay in a clinical setting.
Analysis for paraquat by second- and fourth-derivative spectroscopy.
Authors: Fell A F , Jarvie D R , Stewart M J 
Published: January 2020

Abstract
We describe simple, precise methods, based on second and fourth-derivative spectroscopy, of analysis for paraquat in serum, plasma, or dialysis fluid. Plasma paraquat, after ion-pair extraction and dithionite reduction, yields a sharp, stable absorption peak at 396 nm. Derivative spectroscopy confers enhanced sensitivity (detection limit, 5 microgram/L) and improved rejection of spectroscopic interference by diquat, hemolysis, bilirubin, or lipemia. Derivative peak amplitudes are linearly related to paraquat dichloride concentration from 10 to 1000 microgram/L in plasma, and the methods are precise (CV 2.7-5.2% for 50 microgram/L concentration) and accurate. Results of derivative assays for 18 cases of paraquat poisoning correlate well with those by radioimmunoassay (r = 0.999). Derivative spectroscopy enables monitoring of paraquat concentrations in the plasma of poisoned patients during treatment by hemoperfusion or hemodialysis. A rapid assay developed for dialysis fluid (detection limit, 2 microgram/L) permits the efficacy of hemodialysis to be routinely assessed.
High-affinity binding of folate to a serum protein in chronic myelogenous leukemia: effect of binder concentration, pH, and temperature.
Authors: Holm J , Hansen S I , Lyngbye J 
Published: January 2020

Abstract
Serum from a patient with chronic myelogenous leukemia was subjected to anion-exchange chromatography on DEAE-Sepharose CL-6B. High-affinity binding of [3H]folate to front effluent, eluted at a low salt gradient, was studied in equilibrium-dialysis experiments (37 degrees C, pH 7.4). As suggested by the data, folate binding displayed positive cooperativity. Dilution of the binder solution resulted in a shift to a simple non-cooperative binding type and increased binding affinity. Furthermore, binding was inhibited at pH 5.0 and at low temperature (7 degrees C). This study demonstrates important similarities between high-affinity folate binding in milk and serum: positive cooperativity and dependence of binding affinity on concentration of binder. Identical mechanisms may underly these phenomena in milk and serum. The apparent relationship between binding type and concentration of binder shown herein seems to agree fairly well with recent observations on sera from groups of healthy persons.
Enzyme immunoassay and enzyme inhibition assay of methotrexate, with use of the centrifugal analyzer.
Authors: Pesce M A , Bodourian S H 
Published: January 2020

Abstract
Methotrexate was determined by the homogeneous enzyme immunoassay (EMIT) with the Multistat and CentrifiChem centrifugal analyzers and by the enzyme inhibition assay with use of the Multistat centrifugal analyzer. With both methods, the standard curve extends from 0.2 to 2.0 mumol/L and there is no interference from bilirubin in concentrations up to 100 mg/L. Moderately lipemic samples do not interfere with the EMIT method, but lower the values obtained with the enzyme inhibition assay. Hemoglobin concentrations as great as 1 g/L do not affect results for methotrexate obtained by the enzyme inhibition assay. With the EMIT assay, methotrexate values are lowered in samples containing hemoglobin in concentrations exceeding 750 mg/L. With the EMIT assay, the following compounds in concentrations of 1 mmol/L do not interfere: leucovorin, 5-methyl-tetrahydrofolate, 5-fluorouracil, and 6-mercaptopurine. When folic acid (100 mumol/L) was added to a serum that did not contain methotrexate, a response equivalent to 0.15 mumol/L was obtained. Methotrexate is stable for five days in serum stored at 23, 4, or -20 degrees C. Within-run precision (CV) for the enzyme inhibition method ranged from 4.7 to 8.1% and for the EMIT assay from 2.5 to 6.2%. Methotrexate concentrations in the serum of children receiving high-dose therapy were compared by three methods: competitive protein binding, EMIT, and enzyme inhibition assays. The correlation coefficients averaged 0.95.
Laser Doppler velocimetry vs heater power as indicators of skin perfusion during transcutaneous O2 monitoring.
Authors: Enkema L , Holloway G A , Piraino D W , Harry D , Zick G L , Kenny M A 
Published: January 2020

Abstract
Laser Doppler velocimetry (LDV) and heater power (HP) were compared as indicators of skin perfusion during transcutaneous oxygen tension (ptcO2) monitoring in adults. The LDV probe was fitted to a Radiometer ptcO2 attachment ring, which was fixed to the forearm. ptcO2, electrode temperature, HP, and LDV measurements were recorded continuously and simultaneously. LDV was more specific and sensitive to changes in cutaneous perfusion. Moreover, changes in perfusion were signalled four to 24 times faster by LDV than by HP. Changes in ptcO2 corresponded to changes in LDV more closely than to changes in HP in all experiments. HP was more specific and sensitive to changes in electrode and air temperatures. Once hyperemia was established at 44 degrees C and the electrode heater was turned off (HP = 0), LDV measurements frequently showed persistence of hyperemia (up to 25 min). Under these circumstances ptcO2 decreased linearly with decreasing electrode temperature in the range of 44-32 degrees C. LDV performance was referenced by monitoring velocity measurements taken on a cylinder revolving at known velocities. We conclude that LDV is a useful adjunct to ptcO2 monitoring and better than HP in assessing skin blood flow. It should enhance quality control of transcutaneous O2 monitoring.
Continuous-flow serum albumin determination by reaction with picrate ions, with use of a flow-through picrate ion electrode.
Authors: Diamandis E P , Papastathopoulos D S , Hadjiioannou T P 
Published: January 2020

Abstract
An automated potentiometric method for serum albumin determination by use of the picrate/albumin reaction is described. A continuous-flow system and a specially designed flow-through picrate ion electrode were used in making the measurements. Various factors affecting the reaction, such as pH, picrate ion concentration, and reaction time, were studied. Peak height in millivolts and albumin concentration were linearly related in the range 10-70 g/L. Both within-run and day-to-day, the CV for the method was about 2%. Analytical recovery of albumin added to serum samples ranged from 97.0 to 110.3%, averaging 102.2%. Results compare favorably with those by the established bromcresol green method. The proposed method is suitable for routine use and for screening tests.
Relation of age to isoenzyme pattern and total activity of amylase in serum.
Authors: Bossuyt P J , Van den Bogaert R , Scharpé S L , Van Maercke Y 
Published: January 2020

Abstract
Pancreatic and salivary isoenzymes of amylase were determined in serum from 70 subjects. Thin-layer gel/isoelectric focusing was used to separate the isoenzymes. Because other studies (J. Lab. Clin. Med. 90: 141-151, 1977) show that the major isoamylases have isoelectric points between 5.8 and 7.2, we focused the sera on polyacrylamide gel plates with a pH gradient from 5.5 to 8.5. The separated amylase fractions were made visible by direct incubation with a commercially available dye-starch polymer. Isoelectric focusing proved to be convenient, precise, and reproducible, and it can be used as a routine analysis to detect even slight changes in serum amylase distributions. We found that the isoamylase distribution is age dependent, whereas total amylase activity shows no correlation with age.
The Worthington "ultrafree" device evaluated for determination of ultrafiltrable calcium in serum.
Authors: Toffaletti J , Tompkins D , Hoff G 
Published: January 2020

Abstract
We evaluated a commercially-available disposable device ("Ultrafree," Worthington Diagnostics) for the anaerobic preparation of protein-free ultrafiltrates from serum for measurement of ultrafiltrable calcium. Sufficient filtrate for the analysis is obtained with 10 min from 0.2 to 0.4 mL of serum at room temperature. We assessed these ultrafilters with regard to permeability of calcium citrate, exclusion of proteins, frequency of leakage, and effect of temperature on results. Within-run and day-to-day coefficients of variation for human serum pools were 1.2 and 1.5%, respectively. Reference intervals (in mmol/L) for total (2.16-2.58), ultrafiltrable (1.44-1.67), dialyzable (1.25-1.41), and ionized (1.04-1.25) calcium have been determined for a healthy population of 69 women and 81 men, ages to 18 to 65 years. The device appears to be the most practicable yet available for use in making this measurement.
An optically clear hypercholesterolemic hypertriglyceridemic quality-control material prepared from animal lipid sources.
Authors: Proksch G J , Bonderman D P 
Published: January 2020

Abstract
A hyperlipidemic control serum can be simple prepared from animal lipid sources. Beta- and pre-beta-lipoproteins containing cholesterol and triglyceride are removed from porcine serum by treatment with dextran sulfate and calcium ions. A triglyceride-rich fraction containing only trace amounts of cholesterol is isolated from chicken egg-yolks. The two fractions are then combined in 40 mmol/L sodium bicarbonate to give the desired values for cholesterol and triglyceride. The preparation is stabilized against surface denaturation during long-term storage at 5 degrees C perhaps for as long as two years, by adding 0.25 g of Triton X-100 surfactant per liter, and against an accidental exposure to short-term freezing by adding 10 g of sucrose per liter. We used this solution as a diluent to reconstitute lyophilized bovine serum. The resulting product, having been prepared from only animal sources, is free of hepatitis-associated constituents, and is remarkably clear, homogeneous, and stable. Results obtained with it are precise.
Evaluation of pteroylglutamic acid and n-5-methyltetrahydrofolic acid reference standards in a new "No-Boil" radioassay for serum folate.
Authors: Theobald R A , Batchelder M , Sturgeon M F 
Published: January 2020

Abstract
Serum folate, pteroylglutamic acid standards, and N-5-methyltetrahydrofolate standards extract differently during sample preparation for radiometric assay. B/B0 values for each material were determined before and after an alkaline extraction procedure. Serum folate most closely resembled N-5-methyltetrahydrofolate standards in that it exhibited a slightly greater ability to displace iodinated folate derivative in competition for beta-lactoglobulin binder. Pteroylglutamic acid standards displaced folate derivative less well, so that serum folate values were lower than when N-5-methyltetrahydrofolate was used as the standard material.
A strategy for radioimmunoassay of plasma progesterone with use of a homologous-site 125I-labeled radioligand.
Authors: Corrie J E , Hunter W M , Macpherson J S 
Published: January 2020

Abstract
In this sensitive, specific 125I radioimmunoassay for plasma progesterone, an identical glucuronide bridge is used in the immunogen and radioligand. This apparently provides a system in which the bridge is poorly recognized and thereby avoids the excessively high affinity of the tracer for the antiserum and the consequent poor sensitivity that commonly is found in other homologous-bridge situations. The glucuronide bridge is potentially useful for attachment of other labeling probes.
Adsorbent treatment and immunoaffinity chromatography compared for removing estradiol-17 beta from plasma.
Authors: McBride J H , Davies R J 
Published: January 2020

Abstract
Removal of estradiol-17 beta from plasma by immunoaffinity chromatography on anti-estradiol antibodies coupled to Sepharose was investigated and compared with the use of charcoal adsorbent. Both methods completely removed added [3H]estradiol from pooled male plasma. In contrast to the adsorbent treatment, which caused marked changes in the biochemical composition of the plasma, immunoaffinity chromatography caused only minor perturbations. We discuss the advantages of using plasma, stripped of endogenous estradiol or other steroids by immunoaffinity chromatography, in construction of radioimmunoassay calibration curves.