bluuebunny/crossref_metadata_2025_split huggingface dataset:
Indirect vs direct measurement of magnesium and zinc in erythrocytes.
Authors: Deuster P A , Trostmann U H , Bernier L L , Dolev E 
Published: January 2020

Abstract
We evaluated three methods (two indirect and one direct) for determining the magnesium (Mg) and zinc (Zn) content of erythrocytes, to compare methodologic differences and to establish a method suitable for use in field studies. For the indirect methods, erythrocytes in whole blood were lysed by adding either de-ionized water (I) or nitric acid, 2 mol/L (II). For the direct method (III), erythrocytes were isolated by density centrifugation, washed, then digested in concentrated HNO3. Mg and Zn concentrations were measured by atomic absorption spectrophotometry in plasma and whole blood for the indirect methods, and in the pellet for the direct method. Hematocrit and hemoglobin were measured, and erythrocytes were sized and counted on all samples. Within-run CVs for the three methods ranged from 2.2% with method III for Mg to 5.4% with method I for Zn. CVs for reproducibility of the analytical procedures ranged from 2.6% with method II for Zn to 4.2% with method I for the two cations. Analytical recoveries of added Mg and Zn ranged from 93.8 to 104.7%. When values for the three methods were compared, those by method I were significantly (p less than 0.05) lower than those by methods II and III. Values obtained by method II were 100.1% for Mg and 102.4% for Zn of those by the direct method. Thus, the indirect method with 2 mol/L HNO3 lysing solution provides a reproducible, reliable, accurate, and simple technique for measuring Mg and Zn in erythrocytes.
Radioimmunoassay of somatomedin-C in filter paper discs containing dried blood.
Authors: Mitchell M L , Hermos R J , Moses A C 
Published: January 2020

Abstract
We describe a simple radioimmunoassay (RIA) for estimating concentrations of somatomedin-C (Sm-C) in dried blood on filter paper. A single 3.2-mm blood spot specimen on filter paper is eluted overnight into buffer containing antibody and 125I-labeled Sm-C. The following day, bound and free hormones are separated by addition of goat anti-rabbit gamma globulin in 60 g/L polyethylene glycol solution. The correlation between values obtained for such blood-spot discs and the corresponding wet plasma is highly significant (r = 0.90, p less than 0.001). The relative concentrations (arbitrary units) of Sm-C as determined for specimens on filter paper from mothers and infants, and for cord bloods, are similar to those reported by others using acidified serum.
Evaluating the clinical effectiveness of amniotic fluid assays in predicting respiratory distress syndrome in the neonate.
Authors: Amenta J S , Brocher S C , Serenko-Aber A L 
Published: January 2020

Abstract
Amniotic fluid phospholipids from 346 patients' specimens were quantified and evaluated against the clinical outcome (i.e., respiratory distress syndrome or normal respiratory function). Concentrations of lecithin, sphingomyelin, phosphatidylglycerol, and the lecithin/sphingomyelin reflectance ratio were evaluated by ordered frequency distribution and stepwise discriminant function analysis. The lecithin/sphingomyelin ratio was the best single test for discriminating between respiratory distress syndrome and normal pulmonary function in the fetus, slightly superior to lecithin assay alone. A combination of lecithin/sphingomyelin ratio and lecithin concentration, however, appeared to optimize the discriminant function, although the clinical significance of this test combination remained marginal. High concentrations of phosphatidylglycerol were correlated with high concentrations of lecithin, and virtually ruled out respiratory distress syndrome. Absence of phosphatidylglycerol was not diagnostic. High concentrations of sphingomyelin increased the probability of respiratory distress syndrome. We suggest the following stepwise series of tests to optimize diagnosis: phosphatidylglycerol concentration, sphingomyelin concentration, and finally lecithin-sphingomyelin ratio.
Increased lactate dehydrogenase in serum in measles infection.
Authors: Sugaya N , Takeuchi Y , Kanno T 
Published: January 2020

Abstract
We determined lactate dehydrogenase (LD; EC 1.1.1.27) in serum from 75 sequential measles patients and 105 control patients. In the measles patients, LD was increased to 1147.9 +/- 43.8 (mean +/- SE) U/L, markedly more than in the control group (517.2 +/- 15.0 U/L, p less than 0.001). Both LD-3 and LD-4 isoenzymes were increased, but the concentration of LD-5 was normal. Patients with high LD values (greater than 1500 U/L) had longer hospital stays than did those with lower values (p less than 0.01). Our results suggest that increased LD in serum is a common finding in measles infection and presumably originates from lymphocytes.
Immunoassay of rheumatoid factor by latex particle counting.
Authors: Borque L A , Cambiaso C L , Masson P L 
Published: January 2020

Abstract
We assayed rheumatoid factor by instrumental latex particle counting. The calibration curve ranged from 12.5 to 500 int. units/mL. Maximal within- and between-assay CVs were 5 and 11%, respectively. Analytical recoveries ranged from 92.4 to 108%, and the relation between results and dilutions was linear in the range of 15 to 400 int. units/mL. Correlation with an enzyme-linked immunoassay (ELISA, Cordia kit) was r = 0.934 (n = 58), with turbidimetry r = 0.825 (n = 100), and with the Waaler-Rose test r = 0.834 (n = 73). Of 260 blood donors, 95% gave a value less than 10 kilo-int. units/L, which was taken as the upper normal limit. In a population of patients with rheumatoid arthritis (n = 47), 87.2% had rheumatoid factor greater than 10 kilo-int. units/L.
D-mannose as a preservative of glucose in blood samples.
Authors: Nakashima K , Takei H , Nasu Y , Andoh Y 
Published: January 2020

Abstract
We evaluated whether any monosaccharides inhibit glycolysis in erythrocytes and discovered that D-mannose does. In the presence of D-mannose, glucose can be accurately measured by either the hexokinase procedure or the glucose oxidase procedure. In comparison studies with other glucose preservatives, we found that after 2 h at room temperature glucose decreased by 21 (SD 13) mg/L in D-mannose-treated blood, 93 (SD 10) mg/L in sodium fluoride-treated blood, 28 (SD 21) mg/L in ice-cooled blood, and 144 (SD 28) mg/L in control blood (no preservative treatment). Because D-mannose acted in the early phase of glycolysis, it was a more effective preservative than sodium fluoride; moreover, its use did not preclude measurement of sodium and potassium in the blood samples. D-Mannose did not interfere with other routine chemical tests except for the assay of creatine kinase involving coupled enzymes hexokinase/glucose-6-phosphate dehydrogenase. Creatine kinase could be correctly assayed in the presence of D-mannose by using glucokinase instead of hexokinase. D-Mannose can be used with or without anticoagulant and is compatible with most types of multi-channel automated analyzers.
New immunochemical method for rapid detection of human choriogonadotropin in urine.
Authors: Shoham Z , Katz E , Blickstein I , Katz Z , Zosmer A , Dgani R , Lancet M 
Published: January 2020

Abstract
We describe a visual assay for rapid detection of choriogonadotropin (hGC) in human urine, and evaluate a pregnancy test kit that is based on this assay and designed for use by the general public. The assay involves the formation of an antibody-antigen complex between the anti-hGC antibodies coated on the membrane protein of Staphylococcus aureus bacteria, prestained with hematoxylin, and the hGC concentrated on a column of Sepharose-concanavalin A. The test was calibrated to detect as little hGC as 0.9 (SD 0.15) int. unit/mL. The kit, clinically tested with 448 urine samples, was 99.6% accurate. Simple to perform, the test gives highly reliable results as early as five days after the missed menstrual period.
Effect of tetrasodium EDTA on enzymatic determinations of urinary oxalate.
Authors: Thode J , Amyx C , Valdes R , Kessler G 
Published: January 2020

Abstract
We studied the effects of pretreating urine samples with tetrasodium EDTA (TEDTA) before measuring urinary oxalate with an enzymatic kit (Sigma). Mean analytical recovery of added oxalic acid was only 49% (SD +/- 13%) when the assay was performed as recommended by the manufacturer, but treating samples with TEDTA improved recoveries (96 +/- 10%). In 20 unselected 24-h urine samples assayed with and without TEDTA treatment, the mean oxalate concentrations were significantly (P less than 0.001) different: 15.6 +/- 8.7 and 12.2 +/- 7.9 mg/L, respectively. TEDTA-treated urine samples stored for 14 days at -20 degrees C lost 20% of their oxalate concentration. Use of TEDTA simplifies sample preparation by eliminating the alkalinizing step needed to dissolve EDTA or disodium EDTA.
Total cholesterol in serum determined by isotope dilution/mass spectrometry, with liquid-chromatographic separation.
Authors: Takatsu A , Nishi S 
Published: January 2020

Abstract
We describe an accurate, precise method for determination of total serum cholesterol by isotope dilution/mass spectrometry (IDMS) with liquid-chromatographic separation. After adding [3,4-13C]cholesterol to serum and hydrolyzing the cholesterol esters, we extract the total cholesterol. "High-performance" liquid chromatography (HPLC) is used to separate the extracted cholesterol for measurement by electron-impact mass spectrometry with use of a direct-insertion device. To evaluate the specificity and the accuracy of this method, we also studied the conventional IDMS method, which involves converting cholesterol to the trimethylsilyl ether and assay by gas chromatography-mass spectrometry with use of a capillary column. The coefficient of variation for the HPLC method was a little larger than that for the conventional method, but mean values by each method agreed within 1% for all sera tested.
A model for assessing interference.
Authors: Kroll M H , Ruddel M , Blank D W , Elin R J 
Published: January 2020

Abstract
Most studies of analytical interference indicate the magnitude but not the type of interference. We developed a model for interference that assesses the magnitude of the following types of interference: independent of analyte concentration, dependent on analyte concentration, and a combination of the two. The experimental design for the model is an orthogonally arranged matrix with progressively increasing concentrations of analyte and interfering agent. Multiple regression with these independent variables (concentration of analyte, concentration of interfering agent, and the product of the two) is used to determine the magnitude, direction, and significance of each type of interference. Applying the model to study interference by hemoglobin with determinations of creatinine, direct bilirubin, and total bilirubin showed that hemoglobin interferes with determination of creatinine independent of the analyte concentration, interferes with total bilirubin dependent on the analyte concentration, and interferes with direct bilirubin by a combination of these two.
Mechanism of interference with the Jaffé reaction for creatinine.
Authors: Kroll M H , Roach N A , Poe B , Elin R J 
Published: January 2020

Abstract
We investigated the mechanism of the Jaffé reaction for determination of creatinine by studying the spectrophotometric, kinetic, and equilibrium properties of the reaction of picrate with creatinine and with cyclic and aliphatic ketones. Absorbance spectra for the reaction products of picrate with all the ketones were superimposable with that of creatinine (Amax, 490 nm). Cyclic ketones not containing nitrogen had a molar absorptivity less than half that of creatinine and equilibrium constants approximately 0.01 that of creatinine. Aliphatic ketones, except for benzylacetone, had molar absorptivities similar to that of creatinine, but all of these compounds had equilibrium constants approximately a tenth or less that of creatinine. The common structure for all of the compounds reacting with picrate is the carbonyl group. The variable magnitude of interference for aliphatic and cyclic ketones is ascribable to the different rate constants, molar absorptivities, and equilibrium constants as compared with creatinine. Structures adjacent to the carbonyl group significantly affect the absorptivity and equilibrium constant, but steric hindrance is the major factor affecting the rate of reaction. We postulate that the carbonyl group is required for the Jaffé reaction, and we suggest a mechanism for the reaction.
Plasma protein glycation as measured by fructosamine assay.
Authors: Mosca A , Carenini A , Zoppi F , Carpinelli A , Banfi G , Ceriotti F , Bonini P , Pozza G 
Published: January 2020

Abstract
The fructosamine test for assessing control of glucose in blood has been extensively evaluated, but some questions remain regarding its validity. From the analytical and clinical evaluation we present here, we conclude that: the test is sensitive to variations in the composition of the sample protein; the fructosamine reaction is almost completely unaffected by labile fractions; the concentrations of fructosamine correlate well with the degree of glycation of total serum proteins, especially with glycated albumins and glycated immunoglobulins, as determined by affinity chromatography; the correlation with glycated hemoglobin (Hb A1c), measured as the stable fraction, is very poor, in diabetics treated with insulin (r = 0.373), or with oral hypoglycemic agents (r = 0.390); and (e) fructosamine and Hb A1c are, in fact, expressions of different periods of metabolic control and therefore have different clinical meanings.
A monoclonal antibody that specifically inhibits human salivary alpha-amylase.
Authors: Gerber M , Naujoks K , Lenz H , Wulff K 
Published: January 2020

Abstract
Our monoclonal antibody 88E8 specifically binds to and inhibits human salivary alpha-amylase (EC 3.2.1.1) and cross reacts negligibly with the pancreatic isoenzyme, inhibiting it by less than 1%, as compared with about 90% for the salivary isoenzyme. The antibody binds the S1 and S2 types of salivary alpha-amylase, but no pancreatic alpha-amylase isoenzyme forms. A pancreatic alpha-amylase assay involving 88E8 is under development, with alpha-glucosidase as auxiliary enzyme and p-nitrophenyl-maltoheptaoside as substrate; we give preliminary data on this assay. The assay has to be done by substrate start, because the antibody interacts very slowly with the enzyme in the presence of substrate. Assay results for pancreatic alpha-amylase correlate well with those for isoamylase assayed with use of an inhibitor from wheat-germ.
Interpreting results of coulometry and immunoprecipitation in diagnosing iron disorders.
Authors: Rettmer R L , Labbé R F , Huebers H A , Brown W P , Josephson B M , Finch C A 
Published: January 2020

Abstract
Concentration of iron in plasma, total iron-binding capacity (TIBC), and transferrin saturation are often determined by standard spectrophotometric methods, but iron concentration may be quantified by immunoprecipitation or, electrochemically, by controlled-potential coulometry. Because these iron assays do not all measure the same form(s) of iron, we studied subjects in various states of iron nutriture: normal adults, iron-deficient patients, thalassemia patients with unsaturated transferrin or oversaturated transferrin, and patients with idiopathic hemochromatosis. The spectrophotometric and coulometric methods detected essentially all non-heme iron in plasma; results correlated well but showed a negative bias toward the coulometric method. Results by an immunoprecipitation procedure, which measures only transferrin-bound iron, correlated well with those obtained coulometrically but were slightly higher than the latter. The characteristics of the various methods for iron must be understood by the clinical laboratory if diagnosis of iron disorders is to be accurate.
Three commercial kits and one liquid-chromatographic method evaluated for determining 25-hydroxyvitamin D3 in serum.
Authors: Lindbäck B , Berlin T , Björkhem I 
Published: January 2020

Abstract
The accuracy of three commercial kit methods and one liquid-chromatographic (HPLC) method for determining 25-hydroxyvitamin D3 in serum was evaluated by using isotope dilution-mass spectrometry as a reference technique. The kit methods were based on radioimmunoassay and radioreceptor assay. Serum samples were analyzed from male and female volunteers, some of whom had been exposed to ultraviolet B light or given vitamin D3 orally. Results obtained with the three commercial kits were less accurate than those by HPLC. The agreement between the HPLC method and the comparison method was relatively good: r = 0.99; slope = 1.23; intercept = -2.9 micrograms/L. We conclude that methods based on HPLC should be preferred in routine clinical work and that the accuracy of the three commercial kits tested is not sufficient for their intended use.
Quality-control scheme for blood glucose measured outside the laboratory.
Authors: Forest J C , Rousseau F , Carrier R , Hivon P , Gosselin M 
Published: January 2020

Abstract
We propose a quality-control (QC) scheme to evaluate the performance of blood glucose estimates made with a reflectometer in hospital wards or at home. We constructed a chart illustrating the comparison by regression analysis of the results of 254 reflectometer readings (y) and simultaneous capillary blood glucose analyses in the laboratory (x). Arbitrary acceptance limits around the regression line (y = 0.5 + 0.87x; r = 0.97, Sy/x = 0.8 mmol/L) were established, based on the mean +/- 2 SD of the reflectometer readings of a series of classes of 1.1 mmol/L interval, made with the results from the laboratory analyzer. Each ward using a reflectometer is provided with the QC chart, and the first blood glucose estimation with the reflectometer on each working shift is controlled by re-assay in the laboratory. If the reflectometer reading is outside the limits, the next glucose estimation is also re-assayed. If two consecutive readings are outside the limits, the reflectometer procedure is considered to be failing, the instrument's readings are not used for medical decisions, and remedial action is taken. The chart can also be used as a teaching tool for training the patients or the nurses and to evaluate individual performance.
Melatonin secretion in humans assessed by measuring its metabolite, 6-sulfatoxymelatonin.
Authors: Bojkowski C J , Arendt J , Shih M C , Markey S P 
Published: January 2020

Abstract
Comparing a direct radioimmunoassay for 6-sulfatoxymelatonin (aMT6s) with an established gas chromatographic/mass spectrometric method for 6-hydroxymelatonin, we found a good correlation r = 0.94 (P less than 0.001, n = 100). aMT6s was stable, both in urine and plasma samples, without preservative, for at least two years at -20 degrees C and for five days at room temperature. Urinary excretion of aMT6s showed considerable inter-individual differences; however, the aMT6s excretion of any one individual was consistent over a four-day period, as assessed by continuous collection from 18 normal volunteers. Total 24-h urinary excretion of aMT6s was significantly correlated with the area under the curve of the respective profiles for plasma melatonin (r = 0.75, P = 0.0002) and plasma aMT6s (r = 0.70, P = 0.0005) for 22 healthy volunteers. At 24:00 h and 03:00 h, sampling plasma at 30-s intervals provided no evidence for episodic secretion (in short pulses) of either melatonin or aMT6s.
Highly sensitive two-site immunoradiometric assay of parathyrin, and its clinical utility in evaluating patients with hypercalcemia.
Authors: Nussbaum S R , Zahradnik R J , Lavigne J R , Brennan G L , Nozawa-Ung K , Kim L Y , Keutmann H T , Wang C A , Potts J T , Segre G V 
Published: January 2020

Abstract
We have developed a highly sensitive, two-site immunoradiometric assay (IRMA) for human parathyrin (PTH) that is specific for the intact, secreted, biologically active 84-amino-acid peptide. This assay has several technical advantages: it does not detect even high concentrations of inactive carboxyl-terminal fragments, results are available within 24 h, and the detection limit for intact hormone is low (1 ng/L). The assay readily measures concentrations of PTH in all healthy subjects and distinguishes these values from low or undetectable PTH values observed in clinical situations in which PTH secretion is expected to be suppressed. We found complete separation of results from 37 patients with surgically proven hyperparathyroidism and those from 23 patients with hypercalcemia associated with malignancy, the latter having PTH values at or below the lower limits of normal for this assay. The sensitivity, specificity, and rapid turnaround time of this two-site IRMA should advance the laboratory evaluation of patients with disorders of calcium metabolism.
Specificity of sensitive assays of thyrotropin (TSH) used to screen for thyroid disease in hospitalized patients.
Authors: Spencer C , Eigen A , Shen D , Duda M , Qualls S , Weiss S , Nicoloff J 
Published: January 2020

Abstract
Thyrotropin (TSH) concentrations were measured in 1580 hospitalized patients and 109 normal persons. Using the mean +/- 3 SD limits of the log values for the controls (0.35-6.7 milli-int. units/L), the proportion of abnormal TSH results in the hospitalized patients was 17.2%. TSH was undetectable (less than 0.1 milli-int. unit/L) in 3.1% of patients, suggesting hyperthyroidism, and high (greater than 20 milli-int. units/L) in 1.6%, suggesting hypothyroidism. On follow-up of 329 patients, 62% with abnormal TSH (less than 0.35 or greater than 6.7 milli-int. units/L) and 38% with normal TSH concentrations, only 24% of those with undetectable TSH had thyroid disease: 36% of them were being treated with glucocorticoids and 40% had nonthyroidal illness (NTI). Although half the patients with TSH greater than 20 milli-int. units/L had thyroid disease, 45% of patients had high TSH values associated with NTI. TSH concentrations usually returned towards normal when patients' therapy with glucocorticoids was discontinued or they recovered from NTI. TSH test sensitivity appeared good when the mean +/- 3 SD limits of the reference population were used, i.e., no cases of hyper- or hypothyroidism, as identified by free thyroxin index (FT4I), were missed. However, TSH test specificity was inferior to that of the FT4I test (90.7% vs 92.3%), although specificity could be improved to 97.0% if the wider TSH reference limits of 0.1 to 20 milli-int. units/L were used--limits considered pathological if applied to outpatients. Evidently, different reference intervals for TSH are needed for hospitalized and nonhospitalized patients. We conclude that a "sensitive TSH assay" is not a cost-effective thyroid screening test for hospitalized patients as compared with the FT4I.