bluuebunny/crossref_metadata_2025_split huggingface dataset:
Double-antibody fluorescence immunoassay of tobramycin.
Authors: Karnes H T , Gudat J C , O'Donnell C M , Winefordner J D 
Published: January 2020

Abstract
This heterogeneous assay for tobramycin involves fluorescein-labeled tobramycin, which competes with native unlabeled tobramycin for anti-tobramycin binding sites. Bound and free labeled antigen are separated by precipitation with a second antibody. Fluorescence intensity of the resuspended precipitate is inversely proportional to native tobramycin concentration. Background interference was consistently about 10% of the total fluorescence precipitated. Assay sensitivity was sufficient to detect nanogram quantities of tobramycin per assay tube. Correlation coefficients (r) were 0.96 and 0.98 for comparisons of this assay with a microbiological assay and a radioimmunoassay, respectively. Mean analytical recovery was 101% and the CV was less than 10% throughout the therapeutic range.
Radioassay for cobalamin (vitamin B12) requiring no pretreatment of serum.
Authors: Houts T M , Carney J A 
Published: January 2020

Abstract
We describe a radioassay for cobalamin (vitamin B12) in human serum or plasma that requires no boiling or other pretreatment of the sample. Normal chicken serum covalently coupled to magnetizable particles is used as the binding agent. The assay is performed at pH 12.9, at which pH all cobalamin in human serum is released from its binding proteins, whereas the binding agent maintains a high affinity for cobalamin (Ka 1.7 x 10(10) L/mol). Under these assay conditions the binding protein shows a specificity for cobalamin similar to that of purified intrinsic factor. The assay is simple, rapid, and precise, and results correlate well with those of the Euglena gracilis microbiological assay and an intrinsic-factor binding assay.
Rapid immunochemical identification of enterococci with use of a centrifugal analyzer after a brief antigen-extraction step.
Authors: Levinson S S 
Published: January 2020

Abstract
The precipitin reaction between antigens from enterococci and group-specific antisera was monitored turbidimetrically with a centrifugal analyzer. Linear standard curves (absorbance vs antigen concentration) were developed for studying optimal conditions for enzymic extraction of the antigen by use of an enzyme-containing filtrate from Streptomyces albus. This extraction was optimized by adding to the filtrate 1 mg of lysozyme per milliliter and incubating the bacteria for 40 min at 52 degrees C. The assay was adjusted so that detection of enterococci was indicated by positive absorbance changes near 0.1 A. When the concentration of bacteria from which the antigen was extracted was within a standardized range, non-enterococci produced no positive absorbance changes. Reproducibility of standard antigen and antisera solutions was excellent during three months. The procedure provides an objective, well-controlled means for identifying clinically important enterococci from pure cultures in about 1 h. In contrast, current methods involving biochemical media require as long as 48 h.
Four methods for determining albumin in azotemic sera evaluated.
Authors: Gulyassy P F , Depner T A , Ma W K 
Published: January 2020

Abstract
The methods most commonly used for determination of albumin in serum depend on its binding of dyes. The binding of many drugs as well as of several dyes is impaired in azotemic sera from patients with renal failure. We therefore evaluated four methods used to measure albumin concentration in sera of patients with various degrees of renal failure, comparing results with those by the most specific method, radial immunodiffusion. The automated bromcresol green, manual immediate bromcresol green, cellulose acetate electrophoresis, 2-(4'-hydroxyazobenzene)benzoic acid binding, and Na2SO3 precipitation/biuret methods were evaluated. The correlations with results of radial immunodiffusion for azotemic sera differed from method to method but were approximately the same for each method, as in previous published reports for samples from a heterogeneous population of patients. The ratios of serum albumin concentration by these methods to albumin concentration as measured by radial immunodiffusion ranged from 0.96 to 1.13 for 29 to 41 normal and azotemic sera, but none of the ratios showed any variation beyond random scatter over a range of serum creatinine from 6.0 to 180 mg/L. Thus the choice of method to apply to azotemic sera will depend on the relative importance of accuracy, speed, cost, and technical complexity.
Liquid-chromatographic analysis for urinary porphyrins.
Authors: Ford R E , Ou C N , Ellefson R D 
Published: January 2020

Abstract
Urinary porphyrins are separated, according to number of carboxyl groups, in a system consisting of a mu-Bondapak C18 stationary phase and a mobile phase of methanol and aqueous sodium phosphate (pH 3.5) in a linear gradient. The specimen is prepared simply by adjusting the pH of a 5-mL sample to 2.0 and removing solids by centrifugation. The eluted porphyrins are measured fluorometrically. Naturally occurring non-porphyrin fluorescent substances are eluted ahead of the porphyrins. Chromatography requires about 20 min, and a re-establishment of initial conditions requires an additional 15 min.
Activation of human creatine kinase isoenzymes by pH and various sulfhydryl and chelating agents.
Authors: Nealon D A , Pettit S M , Henderson A R 
Published: January 2020

Abstract
We report the effect of serum pH and of the presence or absence of mercaptoethanol, N-acetyl-L-cysteine, monothioglycerol, ethylenediaminetetraacetate, and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetate on the activation of the human creatine kinase isoenzymes. At the serum pH giving maximal enzyme stability and minimal assay lag phase (Nealon et al., Clin. Chem. 26: 1165-1169, 1980) thiol activation of CK-1 and CK-3 is nearly maximal with monothioglycerol in an optimized creatine kinase assay (Szasz et al., Clin. Chem. 22: 650-656, 1976). However, CK-2 is maximally activated at pH 8.5, a pH at which this isoenzyme is least stable on storage and its assay lag phase is prolonged. These findings suggest irreconcilable problems in the storage, activation, and assay of CK-2.
Rapid liquid-chromatographic determination of metformin in plasma and urine.
Authors: Charles B G , Jacobsen N W , Ravenscroft P J 
Published: January 2020

Abstract
We describe an analysis for metformin in plasma and urine by use of cation-exchange "high-performance" liquid chromatography. The assay requires only 0.5 mL of sample and involves pretreatment with trichloroacetic acid containing an internal standard (1-propylbiguanide), followed by centrifugation and injection into the chromatograph. The column eluent is monitored at 230 nm. Metformin and 1-propylbiguanide give retention times of 8 and 10 min, respectively. Within-day and between-day precision (CV) for the assay of plasma containing 2 mg (1.2 X 10(-5) mol) of metformin hydrochloride per liter was 3.6 and 3.9%, respectively. Similar precision was obtained for urine. The limit of detection is about 0.1 mg (6.0 X 10(-7) mol) of metformin hydrochloride per liter. Several commonly used drugs, including other oral hypoglycemic agents, do not interfere with this method.
Liquid-chromatographic determination of 4-aminopyridine in serum, saliva, and urine.
Authors: Uges D R , Bouma P 
Published: January 2020

Abstract
We have developed "high-performance" liquid-chromatographic methods for determining 4-aminopyridine, an acetylcholine-releasing drug, in serum, saliva, and urine. As little as 1 microgram/L can be detected by extracting the alkalinized sample plus the internal standard (3,4-diaminopyridine) into dichloromethane, mixing the organic phase with 1-pentanol, evaporating the dichloromethane, and injecting the residue onto a reversed-phase column, where it is eluted with acetonitrile/methanol/aqueous ammonium carbonate, with detection at 245 nm. Analytical recoveries from serum averaged 86.7%. The CV at 50 micrograms/L was 2.9% (n = 8). For urine samples containing very high concentrations of 4-aminopyridine, we mixed urine and potassium carbonate in an automatic injector vial, extracted the drug into dichloromethane, centrifuged, and injected an aliquot of the extract into the chromatograph. Analytical recoveries averaged 92%, and the CV was about 2% for drug concentrations of 0.1-8 mg/L of urine.
Analysis for 1,25-dihydroxyvitamin D in human plasma, after a liquid-chromatographic purification procedure, with a modified competitive protein-binding assay.
Authors: Jongen M J , van der Vijgh W J , Willems H J , Netelenbos J C 
Published: January 2020

Abstract
1,25-Dihydroxyvitamin D in plasma is measured by competitive protein-binding assay after isolation from plasma. The present method is improved, as compared with those hitherto described, with regard to receptor preparation, isolation of vitamin D metabolites from plasma, and procedure for the competitive protein binding. Receptor preparation from healthy rather than rachitic chicks, together with a fast isolation procedure, results in a high yield of active receptor protein: 12 animals provide receptor for about 4000 incubations. No loss of binding activity was observed during one year. 1,25-Dihydroxyvitamin D is isolated from plasma by a single extraction and a one-step chromatographic purification. Analytical recovery for the entire procedure averaged 78.1% (SD 4.7%). Other vitamin D metabolites (25-hydroxyvitamin D and 24,25-dihydroxyvitamin D) can also be separated with this procedure. The main features of the modified binding assay are the use of a stabilized cytosol receptor and dextran-coated charcoal instead of polyethylene glycol. The smallest detectable amount in the binding assay is 1-2 pg (2.4-4.8 fmol). Intra- and interassay CVs are 7.0% and 4.8%, respectively. 1,25-Dihydroxyvitamin D concentrations in plasma of 20 healthy subjects averaged 51.7 (SD 10.8) ng/L [124 (SD 26) pmol/L]. Three anephric patients showed values of 3, 6, and 7 ng/L (7, 14, and 17 pmol/L).
Agar gel electrophoretic determination of glycosylated hemoglobin: effect of variant hemoglobins, hyperlipidemia, and temperature.
Authors: Aleyassine H , Gardiner R J , Blankstein L A , Dempsey M E 
Published: January 2020

Abstract
We investigated the effect of temperature, variant hemoglobins, and hyperlipidemia on determination of glycosylated hemoglobin by an electrophoretic method (Clin. Chem. 26: 1598-1602, 1980). We found that: (a) temperature variations ranging from 4 to 30 degrees C were without effect on results obtained by electrophoresis; (b) concurrent determination of glycosylated hemoglobin by electrophoresis and column-chromatography in blood specimens from 150 diabetic patients yielded almost identical mean values for both procedures when operations were carried out at 22 degrees C; (c) electrophoretic determination of glycosylated hemoglobin in whole-blood hemolysate was not affected by concentration of triglycerides; and (d) unlike column-chromatographic procedures, which underestimate the percentage of glycosylated hemoglobin in patients with hemoglobin S and C, the electrophoretic method accurately determined the proportion of glycosylated hemoglobin in these hemoglobinopathies. Evidently, electrophoresis on agar gel is an excellent alternative to cation-exchange column-chromatographic methods for glycosylated hemoglobin.
Low results for inorganic phosphorus with the SMAC continuous-flow analyzer.
Authors: Robertson E A , Elin R J , Johnson E 
Published: January 2020

Abstract
Serum inorganic phosphorus concentrations as measured with the SMAC are lower than those found with other methods. To resolve this problem we analyzed patients' specimens and performed analytical recovery studies with four different systems (SMAC, AutoAnalyzer II, aca, and the Fiske--SubbaRow method). With the SMAC, results for patients' specimens are significantly lower (p less than 0.0001) than with any of the other three methods. The SMAC recovered only about 87% of the added inorganic phosphorus. The value assigned to SMAC Reference I for inorganic phosphorus was 0.876 of the value obtained when the material was analyzed by the reference method. Thus there is a significant systematic error in the SMAC method for inorganic phosphorus determination, attributable to an erroneous inorganic phosphorus concentration assigned the SMAC calibration material by the supplier (Technicon).
Esterolytic method for determination of heparin in plasma.
Authors: Kapke G F , Feld R D , Witte D L , Owen W G 
Published: January 2020

Abstract
This assay for heparin is based on the heparin-accelerated rate of alpha-thrombin III. The rate or product formation from the residual active thrombin is inversely proportional to plasma heparin content. The assay can be performed manually, but our results were obtained with a discrete analyzer, the ABA-100. The assay is insensitive to concentrations of antithrombin III in plasma. Precision studies gave CVs of less than 10%. This assay was compared to the Dade Protopath heparin assay and a correlation coefficient of 0.90 was obtained (n = 62). The correlation between activated partial thromboplastin times and heparin concentrations (r = 0.67) was calculated frm results on 78 plasma specimens from 10 patients.
Characterization of a spectrophotometric assay for angiotensin converting enzyme.
Authors: Ryder K W , Jay S J , Jackson S A , Hoke S R 
Published: January 2020

Abstract
Although serum angiotensin converting enzyme (EC 3.4.15.1) activity has generally been shown to be increased in patients with sarcoidosis, considerable variation in the diagnostic usefulness of this test has been reported. We investigated the possibility that this variation may be the result of inhibition of the widely used spectrophotometric assay by various substances. We also prospectively examined the predictive value of measurements of this enzyme in serum from 100 patients being evaluated for sarcoidosis. The following did not significantly affect the results: storage at 4 or 25 degrees C for one week, hemoglobin, lipoproteins, or corticosteroid medications. Bilirubin, at concentrations of 20 mg/L of serum or move, significantly inhibited the assay. Sera with increased activity showed nonlinear reaction rates during the usual 60-min reaction interval, This was corrected by shortening the reaction time to 30 min. We found a predictive value of 88% when the serum angiotensin converting enzyme test was applied to the diagnosis of active sarcoidosis.
Kinetic measurement of guanine deaminase in serum with a centrifugal analyzer.
Authors: Nishikawa Y , Fukumoto K 
Published: January 2020

Abstract
We describe an enzymic, one-step kinetic method for determination of guanine deaminase (guanase, EC 3.5.4.3) in serum with a centrifugal analyzer. A combined enzyme-substrate system consists of the enzymes xanthine oxidase, catalase, and aldehyde dehydrogenase, the coenzyme NAD+, the substrate guanine, and ethanol in tris(hydroxymethyl)methylamine buffer, with KCl added as activator for aldehyde dehydrogenase. The method requires only 40 microL of sample. Guanase activity in 28 samples can be determined within 10 min by setting a 4-min lag period. The increase in absorbance at 340 nm is linearly proportional to the activity of guanase to 60 U/L. Within-run precision (CV) was 1.32 to 4.50% over the range studied. Day-to-day precision corresponds to CVs of 4.8 to 7.2% over the same range of guanase activity. The reference interval, as calculated from data on 25 healthy humans, was 0 to 1.02 U/L. The enzymic automated method shows good correlation with Caraway's (Clin. Chem. 12: 187, 1966) method (r = 0.949).
Simultaneous measurement of estrogen and progesterone receptors in tumor cytosols with use of 125I-labeled estradiol and of 3H-R5020.
Authors: Thibodeau S N , Freeman L , Jiang N S 
Published: January 2020

Abstract
We describe a dual-isotope assay for measuring the concentration of estrogen receptors and progesterone receptors in tumor cytosols. The concentrations of these receptors are derived from separate Scatchard-plot analyses of a single dextran-coated charcoal assay that incorporates both radioiodinated estradiol and tritiated R5020 as the labeled ligands. The two isotopes, radioiodine and tritium, are easily measured with a liquid-scintillation counter. The concentrations of estrogen and progesterone receptors derived from the dual-label assay are identical to values derived from the respective single-label assays. Moreover, values obtained from an assay with dextran-coated charcoal that incorporates radioiodinated estradiol are identical to those obtained from an assay in which tritiated estradiol is used as the labeled ligand. The dual-isotope assay requires both less time and less tissue.
Albumin and beta 2-microglobulin radioimmunoassays applied to monitoring of renal-allograft function and in differentiating glomerular and tubular diseases.
Authors: Woo J , Floyd M , Cannon D C 
Published: January 2020

Abstract
Blood and urine were samples daily from 11 renal-allograft recipients from one to six weeks after the transplant. Clearances of both albumin (Calb) and beta2-microglobulin (C beta 2 mu) were significantly increased in all 11 patients. Five patients (Group I) with acute allograft rejection showed markedly increased Calb and moderately increased C beta 2 mu, concurrent with decreased creatinine clearance (CCr). Five other patients (Group II) with no evidence of rejection demonstrated episodes of grossly increased C beta 2 mu with minimally increased but stable Calb and normal CCr. One patient had no evidence of rejection nor indications of glomerular or tubular proteinuria. While changes in serum beta 2-microglobulin concentration closely paralleled those of serum creatinine in the Group II patients, the results diverged in the Group I patients because the increase in serum beta 2-microglobulin exceeded that of serum creatinine and preceded the increased in creatinine by one to five days, suggesting that measurement of serum beta 2-microglobulin might afford earlier indication of the nature and extent of renal damage in the allograft recipients.
Hydrophobic compounds interfere in radioimmunoassay for basic protein in myelin.
Authors: Macklin W B , Lees M B , Cohen S R , Ayella S B 
Published: January 2020

Abstract
Hydrophobic compounds influenced the accuracy of the radioimmunoassay for myelin basic protein when lipids (stearic acid, phosphatidylcholine, cholesterol, cerebroside, sulfatide, or GM1 ganglioside) or proteolipids (white-matter proteolipid apoprotein, kidney proteolipid apoproteins, or heart proteolipid apoproteins) were added to a known amount of basic protein and the samples assayed. All of these interfere with the assay, but the direction of the error depends on the quantity added: low concentrations of lipid decrease apparent basic protein, high concentrations enhance it. Obviously, results of basic-protein assays must be interpreted carefully.
The role of organic volatile profiles in clinical diagnosis.
Authors: Zlatkis A , Brazell R S , Poole C F 
Published: January 2020

Abstract
The organic volatile constituents of biological fluids contain clinically useful diagnostic information for the recognition of metabolic disorders in man. To gain access to this information, it was necessary to develop the methodology for reproducibly stripping the trace concentrations of volatiles from biological fluids (dynamic headspace, gas phase-stripping, solvent extraction, and the transevaporator technique), to separate the complex extracts by high-resolution capillary column gas chromatography, and to develop computer-aided data-handling and pattern-recognition techniques for analyzing the immense amount of information generated. The normal and pathological organic volatiles identified by gas chromatography--mass spectrometry in urine, serum, and breast milk are tabulated. Clinical applications of the above techniques to the study and diagnosis of diabetes mellitus, respiratory virus infection, renal insufficiency, and cancer are described.
Immunochemical determination of CK-MB isoenzyme in human serum: a radiometric approach.
Authors: Usategui-Gomez M , Wicks R W , Farrenkopf B , Hager H , Warshaw M 
Published: January 2020

Abstract
The presence of creatine kinase isoenzyme MB (CK-MB) in human serum is an indicator of myocardial injury. In this assay for CK-MB, reagent containing both rabbit antibodies to CK-MM and 125I-labeled sheep antibodies to CK-BB is added to the patient's serum and incubated for 1 h at ambient temperature. Goat anti-rabbit immunoglobulin, conjugated to a mixture of amylose and polyvinylidene fluoride floccules, is then added. After a 15-min incubation, the mixture is centrifuged, isolating the two M-subunit-containing isoenzymes as insoluble complexes. Because the B-subunit portion of MB is labeled with 125I, the radio-activity in the pellet will be proportional to the amount of MB present. The discarded supernate contains excess sheep 125I-labeled BB antibodies, free or bound to BB isoenzyme if it is present. The preparation and characterization of the isoenzymes and antibodies is explained. Concentrations of CK-MB is sera of patients with and without an acute myocardial infarction were assayed in serial specimens obtained in 103 consecutive admissions to a coronary care unit. The performance of this radiometric procedure compared well with CK-MB electrophoresis, giving a sensitivity of 100% and a specificity of 92%.
High-molecular-mass alkaline phosphatase in serum and bile: nature and relationship with lipoprotein-X.
Authors: Crofton P M , Smith A F 
Published: January 2020

Abstract
Using immunoelectrophoresis and other techniques, we have demonstrated an association between lipoprotein-X and (a) alkaline phosphatase and (b) other enzymes originating from the hepatocyte membrane, namely gamma-glutamyltransferase and leucine aminopeptidase. The high-molecular-mass forms of these enzymes, in both serum and bile, were precipitated by lipoprotein-X antiserum but not by antisera to other plasma proteins. The activity of high-molecular-mass alkaline phosphatase in serum was positively correlated with lipoprotein-X and with lipoprotein-X-associated alkaline phosphatase, both assessed semi-quantitatively. On the other hand, many sera possessed high activities of high-molecular-mass alkaline phosphatase but no detectable lipoprotein-X. Incubation of serum with conjugated bile salts and with synthetic detergents, at concentrations which did not dissociate the high-molecular-mass enzymes, caused parallel alterations in the electrophoretic mobility of serum lipoprotein-X and its associated enzyme activity. Incubation of normal dialyzed hepatic bile with normal, lipoprotein-X-negative serum produced an alteration in electrophoretic mobility of biliary lipoprotein and its associated enzyme activity from anodal to cathodal in agar gel. Digestion with papain had a variable effect on the different enzymes in the complex, without affecting the lipoprotein moiety. Leucine aminopeptidase was removed most readily from the complex to give the low-molecular-mass form present in normal serum; gamma-glutamyltransferase dissociated somewhat less readily, and alkaline phosphatase was completely resistant to dissociation from the complex. These results are discussed in the light of current knowledge, and a hypothesis is proposed for the nature of the high-molecular-mass enzymes in serum and bile.