bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amidolytic kinetic assay of protein C by selective spectrophotometry in a centrifugal analyzer.
Authors: Kobayashi I , Amemiya N , Endo T , Motegi J , Kurihara A , Hamaoka S , Tamura K , Kume S 
Published: January 2020

Abstract
This rapid, simple amidolytic assay of protein C activity in whole plasma involves activation by protein C activator from the venom of Agkistrodon contortrix contortrix (Protac) and use of a Cobas Fara spectrophotometer programmed for kinetic assay. Plasma is incubated with activator venom in the presence or absence of antibody to human protein C in the instrument, chromogenic substrate (S-2366) is added, and the absorbance is measured at 405 nm. The difference between the absorbance of the sample plasma with and without antibody to human protein C correlated well with protein C antigen as assayed by enzyme-linked immunosorbent assay (ELISA) and the Laurell rocket technique in normal subjects, patients being treated with warfarin, and patients with liver cirrhosis or disseminated intravascular coagulation. Our mean value for protein C in normal subjects is 115.9 (SD 16.7)% for amidolytic activity, 103.0 (SD 17.4)% for ELISA, and 97.2 (SD 18.1)% for the rocket technique. The high value for normal subjects presumably includes some nonspecific amidolytic activity activated by the activator venom, as indicated by measurable activity in immuno-depleted protein C-deficient plasma. Within-run and between-run CVs were less than 5% at low, normal, and high concentrations of protein C amidolytic activity.
The stability of uric acid in ammonium hydroxide.
Authors: Ellerbe P , Cohen A , Welch M J , White E 
Published: January 2020

Abstract
We examined the stability of uric acid in dilute aqueous ammonium hydroxide solution by mass spectrometry. Uric acid decomposes in ammonium hydroxide even as dilute as 15 mmol/L when the mole ratio of ammonium hydroxide to uric acid is 50:1. There are at least four products of the decomposition, two of which have been identified as allantoin and urea. The slope of the decomposition curve indicates that uric acid is destroyed at an initial rate of 2-3% per hour. In ammonium hydroxide at a concentration of 1 mmol/L and a mole ratio of ammonium hydroxide to uric acid of less than or equal to 3.4, uric acid is not detectably decomposed. Evidently, any method for determination of uric acid that involves treating the analyte with ammonium hydroxide before analysis may destroy it. Therefore, a published method described as being "definitive" for uric acid (J Clin Chem Clin Biochem 1985; 23:129-35) could produce incorrect results because it involves storing the uric acid in 15 mmol/L ammonium hydroxide at a mole ratio of ammonium hydroxide to uric acid of greater than 120:1.
Assay of dipeptidyl peptidase IV in serum by fluorometry of 4-methoxy-2-naphthylamine.
Authors: Scharpé S , De Meester I , Vanhoof G , Hendriks D , van Sande M , Van Camp K , Yaron A 
Published: January 2020

Abstract
A new fluorometric assay for determining dipeptidyl peptidase IV (DPP IV; EC 3.4.14.5) was developed. The synthetic substrate glycyl-L-proline-4-methoxy-2-naphthylamide (20 mmol/L), Tris buffer (50 mmol/L, pH 8.3), and serum (20 microL) are mixed and incubated. The reaction is stopped with citrate (100 mmol/L, pH 4.0) and the released 4-methoxy-2-naphthylamine is measured fluorometrically. The mean value of DPP IV activity in serum for 64 healthy subjects was 58 (SD 16) mumol of 4-methoxy-2-naphthylamine released per liter of serum per minute. The proposed procedure is sensitive, rapid, and accurate and can easily be automated.
Evaluation of four commercially available assays for free thyroxin.
Authors: Ooi D S , Mahadevan M S , Greenway D C , Gertler S Z 
Published: January 2020

Abstract
We assessed two two-step and two analog assays for measuring free thyroxin (FT4) in serum: Clinical Assays' "GammaCoat Free/Total T4" (CA), Vitek's "KinetiCount Phase II Free T4" (VTK), Diagnostic Products Corporation's "Coat-a-Count Free T4" (DPC) kit (June 1987 version), and Amersham's "Amerlex-M Free T4" (AMX). The VTK assay is automated except for the initial pipetting step. Interassay results correlated well except for samples with abnormal serum albumin concentrations. FT4 values for hypoalbuminemic samples showed a highly significant (P less than 0.0001) correlation with serum albumin concentration in the DPC and AMX assays. The relationships are described by the equations y = 0.382albumin (g/L) + 0.81 pmol/L and y = 0.450albumin (g/L) - 3.20 pmol/L, respectively. When we used an equation derived from the Law of Mass Action to adjust FT4 values to values expected at an ideal albumin concentration, the observed correlation of albumin and FT4 was abolished completely in the DPC assay, and partly so in the AMX assay. The precision of CA was comparable with that of the analog assays; the CV for the VTK assay was approximately twice that for the other three assays.
Liquid-chromatographic determination of fleroxacin in serum and urine.
Authors: Awni W M , Maloney J A , Heim-Duthoy K L 
Published: January 2020

Abstract
This highly sensitive, accurate, and reproducible HPLC method for determining fleroxacin in human serum and urine makes use of a common C18 column, a fluorescence detector, and an internal standard. Serum samples require a simple extraction procedure; urine must be diluted. The method, which we have used extensively for pharmacokinetic assessment of fleroxacin in patients, measures concentrations as low as 5 micrograms/L.
Time-resolved pulsed fluorescence immunometric assays of carcinoembryonic antigen.
Authors: Dakubu S , Hale R , Lu A , Quick J , Solas D , Weinberg J 
Published: January 2020

Abstract
A time-resolved pulsed fluorescence immunometric assay (TR-PFIA) for carcinoembryonic antigen is described in which either Eu(III) or Tb(III) chelate is used as label. Described in detail is the assay involving the well-documented format of microtiter matrix and Eu(III) fluorescence enhanced with a beta-diketone and quantified in a commercial time-resolving fluorometer. We have also used the same basic assay, but one with a Tb(III) chelate as label, and we read the fluorescence signal directly off a surface without the application of enhancement solution. The Tb(III) fluorescence is then brought into solution by using an analog of dipicolinic acid in an enhancement solution. The latter approach demonstrates the scope of the methodology, which invokes the extra complexity of enhancement only when increased sensitivity might be required. The power and versatility of the enhancement methodology are demonstrated.
A reflectance photometer with a square photodiode array detector for use on multilayer dry-film slides.
Authors: Neeley W E 
Published: January 2020

Abstract
This semiautomated prototype reflectance photometer measures reflected light from multilayer dry-film slides. The instrument makes use of a square photodiode array detector, a Hewlett-Packard desktop computer, and a modified mechanical transport mechanism from an Ektachem DT60 analyzer. When 2 microL of serum is placed on a dry-film slide, a colored spot is formed. The slide is automatically transported to an incubation area and then to the photometer area. There the spot is illuminated with dual tungsten lamps, and the reflected light passes through an interference filter, where it is focused on a square photodiode array containing 10,000 individual detectors. The analog signal from each detector is digitized and transmitted to a computer for calculation of the percentage of reflectance. I used a series of algorithms to locate the spot, estimate spot area, correct for minor variations in sample volume, and compute the average reflectance from a central spot area. To evaluate the instrument's performance, I ran parallel glucose determinations in the Beckman Astra; results correlated well. The small sample size along with no dead sample volume makes the system useful for small sample volumes.
Increased urinary excretion of digoxin-like immunoreactive substance by insulin-dependent diabetic patients: a linkage with hypertension?
Authors: Giampietro O , Clerico A , Gregori G , Bertoli S , Del Chicca M G , Miccoli R , Lucchetti A , Cruschelli L , Navalesi R 
Published: January 2020

Abstract
Excretion of digoxin-like immunoreactivity (DLIS) was measured by RIA in timed overnight urine collections from 91 normotensive nondiabetic subjects and 104 normotensive insulin-dependent diabetic (IDDM) patients. The mean +/- SD DLIS excretion rate for the diabetic patients significantly exceeded that for the controls (73 +/- 41 vs 63 +/- 36 pg/min, P = 0.024). In both groups, the mean DLIS excretion rates for men were significantly higher (P = 0.0014, P = 0.006) than for women. In the controls, the DLIS excretion rate significantly correlated with the urinary excretion rate of creatinine (P less than 0.01), Na+ (P less than 0.05), and K+(P less than 0.05), and with the subjects' body weight (P less than 0.01), body mass index (P less than 0.05), and systolic blood pressure (P less than 0.05). In the diabetics, the DLIS excretion rate was significantly correlated with body weight (P less than 0.05) and with urinary excretion rates for albumin (P less than 0.01), creatinine (P less than 0.01), Na+ (P less than 0.05), and K+(P less than 0.05). Our data indicate that: (a) increased amounts of a cardiac glycoside-like substance (or a group of substances) are excreted in the urine of IDDM patients; (b) the urinary excretion of DLIS seems to depend on glomerular filtration rate and physiocochemical properties of glomerular membrane, as well as on subjects' body mass; and (c) because cardiac glycoside-like substances may increase peripheral vascular resistance, increased urinary excretion of DLIS by IDDM patients may indicate a tendency to develop hypertension.
Creatine kinase:aspartate aminotransferase activity ratio as an indicator of the source of an increased creatine kinase activity.
Authors: Dufour D R 
Published: January 2020

Abstract
Although measurements of creatine kinase isoenzyme 2 (CK-MB) are often used to diagnose acute myocardial infarction, their sensitivity and specificity are less than 100%. Because skeletal muscle contains more CK and less aspartate aminotransferase (AST) than cardiac muscle, the CK/AST ratio might provide a useful adjunct in evaluating the source of a supranormal value for CK. I established the following decision levels in a retrospective study of 342 patients: ratios less than 14 (if total CK was 300-1200 U/L), less than 20 (CK 1201-2000 U/L), or less than 25 (CK greater than 2000 U/L) suggested myocardial infarction, with a sensitivity of 95% and a specificity of 65%. In a validation study with 277 additional patients, liver disease and alcohol abuse caused erroneous results, leading to exclusion of 22% of these patients. In the remaining cases, sensitivity was 94%, specificity 90%. The CK/AST ratios changed little with time, suggesting that a single value would be adequate for evaluating patients with increased CK.
Concomitant purification of prostatic carcinoma tumor markers from human seminal fluid under nondenaturing conditions.
Authors: Rusciano D , Berardi A , Ceccarini C , Terrana B 
Published: January 2020

Abstract
We report a protocol for concomitant purification to homogeneity of both prostatic acid phosphatase [orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2] and prostate-specific antigen, from human seminal fluid. The method requires only two chromatographic steps: passage through an Affigel-Blue column and gel filtration HPLC. This is a fast, efficient procedure for purification of these two important tumor markers, which are specific for prostatic cancer.
Improved liquid chromatographic/immunoassay of digoxin in serum.
Authors: Stone J A , Soldin S J 
Published: January 2020

Abstract
This HPLC/immunoassay procedure measures digoxin in serum with no interference from digoxin metabolites or digoxin-like factors. We used solid-phase (C18 and Diol) extraction, a C18 column with a tetrahydrofuran/water mobile phase, and final quantification by fluorescence polarization immunoassay. Deslanoside and gitoxigenin were used as the internal standard and the retention-time marker, respectively. The average CV for 300-microL samples at digoxin concentrations between 0.9 and 3.9 nmol/L was 9.3%. Minimum column lifetime with daily use was three months. We also compared results, for 49 samples from patients taking digoxin, obtained with the Abbott "TDx FPIA digoxin I" and the present procedure. Discrepancies between the two methods were substantial for 20% of the samples.
Assay of pancreatic amylase with use of monoclonal antibodies evaluated.
Authors: Zaninotto M , Bertorelle R , Secchiero S , Plebani M , Burlina A 
Published: January 2020

Abstract
To evaluate a new method for measuring pancreatic amylase in serum, in which the salivary isoenzyme is inhibited with a specific monoclonal antibody, we determined the activity of pancreatic and salivary amylase in sera from 103 healthy subjects and from 114 hospitalized patients having a wide range of total amylase activities. CVs for the proposed method ranged from 0.8% to 5.1% (within day) and from 2.3% to 6.6% (day to day). Results correlated well with those obtained by the wheat-germ inhibition method (r = 0.998) and by electrophoresis on cellulose acetate. Analytical-recovery studies confirmed the good specificity of the monoclonal antibody for salivary amylase (97%) and its low cross-reactivity (0.6%) toward pancreatic amylase. The assay procedure presents a wide range of linearity (141-1817 U/L) and can easily be adapted to an automated kinetic system. We found the proposed method suitable for routine determinations of pancreatic amylase.
Autoantibodies to thyroxin and triiodothyronine in the immunoglobulin G fraction of serum.
Authors: Li Calzi L , Benvenga S , Battiato S , Santini F , Trimarchi F 
Published: January 2020

Abstract
Thyroid hormone antibodies (THAbs)--i.e., antibodies to thyroxin (T4) and triiodothyronine (T3)--are detected rarely in human serum, where they are searched for, possibly because of a quantitatively minimal interaction between thyroid hormones (the haptens) and serum IgGs (the antibodies). The weak binding could result from these facts: (a) there are already six physiological carrier proteins for thyroid hormones; (b) THAbs usually account for a very small fraction of the total serum IgGs; (c) THAbs may have--as reported in the literature--a relatively low affinity. To ascertain whether THAbs could pass undetected in serum, we measured antibodies to T3 and T4 in both the serum and the corresponding IgG fraction of six normal persons and 45 patients with various thyroid diseases (Graves' disease, idiopathic myxedema, Hashimoto's thyroiditis, subacute thyroiditis, tumors), using radioimmunoprecipitation. The prevalence of antibodies to T4 was 0/51 in both the sera and the IgG fractions; the prevalence of antibodies to T3 was 1/51 in both materials. Because all of the sera that tested THAb negative were confirmed to be so in the THAb assay of the IgG fraction, we conclude that the prevalence of serum THAbs is not underestimated and that autoimmunization against thyroid hormones is really a rare phenomenon.
Differential precipitation of isolated human plasma lipoproteins with heparin and manganese chloride.
Authors: Ruiz-Albusac J M , Velázquez E , Montes A 
Published: January 2020

Abstract
We studied the precipitation of isolated lipoproteins with heparin and MnCl2. Lipoproteins were isolated from human plasma by preparative ultracentrifugation and their free cholesterol was labeled. Each lipoprotein fraction was then precipitated at various pHs, with or without bovine serum albumin (60 g/L) present. Under no set of conditions was one class of lipoproteins completely separated from the other two. Specifically, under standard conditions for precipitation of serum lipoproteins (pH 7.4 and protein 60 g/L), 12% of the very-low-density lipoprotein (VLDL) and 8% of the low-density lipoprotein (LDL) remained in the supernatant liquid, and 30% of the high-density lipoprotein (HDL) was precipitated. These results indicate that, under these conditions, so-called HDL cholesterol may be a mixture of VLDL, LDL, and HDL, although the sum of the amount of these three fractions remaining in the supernate is fortuitously very close to the value for HDL cholesterol isolated by ultracentrifugation.
Specific 3H radioimmunoassay with a monoclonal antibody for monitoring cyclosporine in blood.
Authors: Ball P E , Munzer H , Keller H P , Abisch E , Rosenthaler J 
Published: January 2020

Abstract
A specific radioimmunoassay involving a mouse monoclonal antibody to cyclosporine has been developed for monitoring the parent drug in blood. Pretreatment with methanol removes cyclosporine from the erythrocytes. The limit of detection is about 12 micrograms/L, sample volume is 50 microL of blood, and within- and between-assay CVs are less than 7%. Assay results correlated well with those obtained by "high-performance" liquid chromatography (HPLC) for liver (n = 42), for heart (n = 64), for bone-marrow (n = 36), and for kidney (n = 140). For blood specimens obtained from patients treated with cyclosporine postoperatively for as long as 65 months, the mean RIA/HPLC ratio in all with transplant indications was close to 1. Therefore, the specific radioimmunoassay apparently can be used instead of HPLC to measure the parent drug in blood.
The chemistry of aluminum and silicon in relation to Alzheimer's disease.
Authors: Birchall J D , Chappell J S 
Published: January 2020

Abstract
Aluminosilicates have been identified at the core of senile plaques in Alzheimer's disease, and aluminum has been found within neurons bearing neurofibrillary tangles. Here we show that aluminum species interact with silicic acid, Si(OH)4--a normal component of plasma--to form aluminosilicate species solubilized by citrate. A switch in the binding of aluminum from silicate to phosphate at pH less than 6.6 calls attention to the strong binding of cationic aluminum species to proximate phosphate groups, as in the inositol phosphates, and to the potential effect on the activity of the phosphoinositide-derived intracellular messenger system. The chemistry may throw light on the debated relationship between aluminum and Alzheimer's disease.
A homogeneous, liposome-based signal amplification for assays involving enzymes.
Authors: Pinnaduwage P , Huang L 
Published: January 2020

Abstract
Exploiting the fact that phosphatidylethanolamine (PE) liposome can be stabilized by a membrane lipid or protein, and that destruction of this stabilizer leads to rapid lysis of the liposome, we have designed a liposome-based signal enhancement mechanism for assays that involve enzyme as the final read-out step. Stable liposomes with entrapped glucose-6-phosphate dehydrogenase (G6PDH) were prepared with unsaturated PE stabilized with 5 mol percent of ganglioside GM1. Addition of beta-galactosidase caused rapid (3-5 min) lysis of liposomes, revealing the latent G6PDH activity, owing to the enzymatic degalactosylation of GM1. We have used Microgenic's CEDIA assay for digoxin as an example. The magnitude of signal was 25 mA/min per microgram of digoxin per liter for the unamplified assay and 1000 mA/min per microgram of digoxin per liter for the liposome-enhanced assay--i.e., a 40-fold amplification. This simple, rapid, and homogeneous signal-amplification mechanism is likely to be useful in many enzyme-dependent assays, such as ELISA, CEDIA, gene-probe assays, and immunoliposome assays.
Quantitative X-ray diffraction analysis of urinary calculi by use of the internal-standard method and reference intensity ratios.
Authors: Wandt M A , Rodgers A L 
Published: January 2020

Abstract
The internal-standard method and the powder diffractometer have been applied here to the quantitative determination of urinary stone constituents by x-ray diffraction (XRD). Reference intensity ratios determined for six stone substances were used in the reduction of intensity data. Constituent concentrations calculated for 21 stones were compared with values obtained from an element-sensitive technique. We conclude that XRD analysis alone cannot be regarded as a routine technique for the quantitative characterization of uroliths, but that semiquantitative XRD analysis supplemented by accurate quantitative elemental data is more suitable for the precise determination of true stone composition.
Effects of reaction variables on nephelometric and turbidimetric responses for the immunochemical reaction of immunoglobulin G.
Authors: Skoug J W , Pardue H L 
Published: January 2020

Abstract
Here we report a kinetic study of the immunoprecipitin reaction involving immunoglobulins G, A, and M. We used stopped-flow mixing adapted for simultaneous monitoring of nephelometric and turbidimetric signals for some studies and centrifugal mixing for others. The variables having the most significant effects on the kinetic responses in the regions of excess antibody and excess antigen are polyethylene glycol concentration, ionic strength, and the ratio of antigen to antibody. We document effects of these variables on maximum velocities and signal changes over a fixed-time interval for both monitoring modes and on the maximum signal change for nephelometry. We use response-surface methodology to help identify interactive effects among these variables (polyethylene glycol, NaCl, and antibody concentrations) and to select the best combination to use to quantify antigen in all regions of the immunoprecipitin curve. We also observe that turbidimetric responses are more reproducible and much simpler than are nephelometric responses. Implications of these results for quantification of the immunoglobulins are discussed.
Kinetic turbidimetric method for the immunochemical quantification of immunoglobulins, including samples with excess antigen.
Authors: Skoug J W , Pardue H L 
Published: January 2020

Abstract
Here we describe a kinetic approach for quantification of the immunoglobulins (IgG, IgA, IgM) in all regions of the immunoprecipitin curve. We use centrifugal mixing and report results for maximum-velocity, two-point, and multipoint curve-fitting methods as well as the use of rate coefficients obtained from the curve-fitting process to differentiate among regions of excess antibody, equivalence, and excess antigen. We show that it is possible to quantify each immunoglobulin over a concentration range from a large excess of antibody to moderate excesses of antigen with a single set of measurements made on a single dilution of each sample. Results for standard additions of the immunoglobulins to pooled sera have relative standard deviations (coefficients of variation) in the range of 1% to 3%, with analytical recoveries in the range of 95% to 106%. Correlations among determined and reported values in individual sera are quite good, with slopes ranging from 0.86 to 1.03 and no intercepts differing from zero by more than two standard deviation units. Concentrations quantified in 14 pathological sera by the proposed method correlated well with concentrations quantified by a fluorescence immunoassay method.