bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of a reversed-phase evaporation vesicle formulation for a homogeneous liposome immunoassay.
Authors: Canova-Davis E , Redemann C T , Vollmer Y P , Kung V T
Published: January 2020

Complement-mediated release of enzyme molecules from reversed-phase evaporation vesicles serves as the basis of the sensitive homogeneous immunoassay reported here. We found it necessary to co-entrap the substrate glucose 6-phosphate with the bacterial enzyme glucose-6-phosphate dehydrogenase (EC 1.1.1.49) to protect enzyme activity during liposome preparation. Enzyme can be released specifically from these liposomes by incubation with antibody and complement. the enzyme is not merely available to substrate but is actually physically free of the liposomes. Inhibition of this complement-mediated lysis by theophylline is the basis for the homogeneous liposome immunoassay described. The assay results vary linearly with theophylline concentrations in plasma in the clinically relevant range, and serum components do not interfere. The reagents in the assay kit are stable for at least seven months when stored at 5 degrees C. No nontheophylline compounds reacted significantly with the antiserum used. The assay can be run in a kinetic format, with either ultraviolet or colorimetric detection.
Discriminative ability of tests for free and total thyroid hormones in diagnosing thyroid disease.
Authors: Wilke T J , Eastment H T
Published: January 2020

We assessed the sensitivity, specificity, predictive value of a positive result, and efficiency of tests for total thyroxin, free thyroxin index, free thyroxin, total triiodothyronine, free triiodothyronine index, and free triiodothyronine in serum from 1619 consecutive new patients with suspected thyroid dysfunction. Multivariate discriminant analysis was also used. Free thyroxin index and free thyroxin were clearly the most sensitive indicators of hypothyroidism. In contrast, all of these tests identified hyperthyroidism with similar efficiencies. By stepwise discriminant analysis, the free thyroxin index was the most efficient test for distinguishing between euthyroidism and hyperthyroidism and between euthyroidism and hypothyroidism. The combination of tests for total thyroxin, free thyroxin index, triiodothyronine, and free triiodothyronine was optimal for separating euthyroidism, hyperthyroidism, and hypothyroidism. We conclude that the free thyroxin index, despite the introduction of newer technologies, is still the best thyroid hormone test for screening for thyroid disease.
Fluorescence polarization immunoassay for ethosuximide evaluated and compared with two other immunoassay techniques.
Authors: Stewart C F , Bottorff M B
Published: January 2020

We evaluated a new fluorescence polarization immunoassay (FPIA) for ethosuximide in the Abbott TDx and compared results with those by two other ethosuximide immunoassays, EMIT (Syva Co.) and aca (DuPont). The FPIA assay produced within- and between-day CVs of less than 5% at the low, medium, and high ranges of the standard curve. For the ethosuximide FPIA assay the standard curve was stable during the 47 days of the study. By all three methods, we analyzed 100 serum and plasma samples from patients who were receiving ethosuximide. The coefficient of determination (r2) for TDx versus EMIT was 0.973 (slope, 0.96; intercept, -0.80); for TDx vs aca it was 0.985 (slope, 1.00; intercept, -2.44); both relationships were statistically significant (p less than 0.05). Values for patient's specimens were significantly lower by the TDx than by the aca or EMIT methods (p less than 0.05).
Diagnostic quality of laboratory tests as evaluated by graphic comparison of "first test" data, with Reye's syndrome "workup" assays as a model.
Authors: Meites S , Bubis S
Published: January 2020

In the absence of predictive values for quantitative tests ordered in particular diseases, we approximated the comparative diagnostic merit of such tests by graphically reviewing hospital experience with those diseases. As a model, we examined the usefulness of the five chemical tests most commonly ordered on admission as part of the "Reye's workup": aspartate and alanine aminotransferases, NH3, prothrombin time, and glucose. We expressed the data as multiples of the upper reference limit (URL) for each of these liver-function tests, setting the URL high enough to overcome method- and age-related differences. Graphs of "first test" data from 141 patients show the great sensitivity of the two aminotransferase assays for Reye's syndrome: only 2% of the results fall below their URL, whereas about 32% of NH3 determinations and 27% of prothrombin times fall below their URL. Thus measuring the aminotransferases apparently is at least 10 times more useful than the other three analytes as "first tests." Current record keeping does not provide a ready means for assessing the specificity of these tests to determine the number of false positives, but does provide useful data for assessing sensitivity and false negatives.
Plasma apolipoproteins in Tangier disease, as studied with two-dimensional electrophoresis.
Authors: Visvikis S , Dumon M F , Steinmetz J , Manabe T , Galteau M M , Clerc M , Siest G
Published: January 2020

Tangier disease is characterized by a deficiency of high-density lipoproteins and of their major protein constituent, apolipoprotein (apo) A-I. We used high-resolution two-dimensional electrophoresis to examine the principal plasma apolipoproteins (A-I, A-II, A-IV, E, C-II, and C-III) of three persons with Tangier disease, one homozygous patient and his two heterozygous children, comparing the patterns with those for healthy subjects. Characteristic abnormalities were found in the distribution of the isoproteins of apo A-I, there being a normal concentration of pro apo A-I but dramatically decreased concentrations of the other apo A-I isoproteins. We also found hitherto-undescribed polypeptide abnormalities in apo C-III: sialylated and nonsialylated forms of apo C-III appear as double spots having the same isoelectric points but different molecular masses. No other substantial difference was detected in the polypeptide distribution of the other plasma apolipoproteins.
Interference by platelets in the electrophoretic determination of enolase isoenzymes in plasma.
Authors: Viallard J L , Ven Murthy M R , Borocco S , Dastugue B
Published: January 2020

Serum and plasma gave different electrophoretic patterns when enolase isoenzymes were evaluated by electrophoresis on cellulose acetate. Plasma isoenzyme bands were more intense, and there was an additional one (band P) that was not present in serum. We show that, under the conditions of electrophoresis, some of the residual platelets in the plasma are ruptured, releasing intracellular enolases and consequently leading to intensification of the isoenzyme bands. The band P originated from the remaining unruptured platelets. Thus plasma samples must be platelet-free for determination of enolase isoenzyme to be reliable.
Precipitation of serum proteins by the lectin from wheat-germ.
Authors: Schreiber W E , Whitta L
Published: January 2020

We investigated the composition of the precipitate that forms when wheat-germ lectin derived from Triticum vulgaris is added to serum. A number of serum proteins are precipitated, representing about 2.5% of the total serum protein. This study demonstrates that the interaction of this lectin with the bone isoenzyme of alkaline phosphatase is not specific.
Se, Zn, Mg, Ca, K, cholesterol, and creatine kinase concentrations in men during the 12 days after an acute myocardial infarction.
Authors: Speich M , Chappuis P , Robinet N , Gelot S , Arnaud P , Nguyen V G , Nicolas G , Rousselet F
Published: January 2020

We determined concentrations of selenium, zinc, magnesium, calcium, potassium, total and high-density lipoprotein cholesterol, and total creatine kinase (EC 2.7.3.2) in plasma (P) and (or) erythrocytes (E) of 32 men at the time of hospital admission for acute myocardial infarction and then on subsequent days 2, 3, 6, 10, and 12. During these 12 days, only P-selenium and high-density lipoprotein cholesterol concentrations remained unchanged. For the other variables, individual comparison of means indicated the dates of significant changes in concentration (p less than 0.05).
Quantification of two different types of apolipoprotein A-I containing lipoprotein particles in plasma by enzyme-linked differential-antibody immunosorbent assay.
Authors: Koren E , Puchois P , Alaupovic P , Fesmire J , Kandoussi A , Fruchart J C
Published: January 2020

We describe a method for measuring apolipoprotein A-I (ApoA-I) associated and unassociated with apolipoprotein A-II (ApoA-II) in plasma. To directly determine associated ApoA-I, we coated microtiter plates with antibody to ApoA-II, blocked the nonspecific binding sites, and incubated the plate with plasma, immobilizing the lipoprotein particles containing both ApoA-II and ApoA-I. The unbound constituents of plasma were washed away, peroxidase-labeled antibody to ApoA-I was added, the plate rewashed, peroxidase substrate added, and the resulting color measured. ApoA-I unassociated with ApoA-II was evaluated by subtracting the concentration of associated ApoA-I from the total ApoA-I concentration. The method is specific, rapid, and precise. Within- and between-assay CVs were 5.6 and 9.8%, respectively. Analytical recovery of ApoA-I was 94%. The average normolipidemic concentration of ApoA-I associated with ApoA-II in 50 women was 790 mg/L; in 50 men, it was 788 mg/L. The corresponding values for unassociated ApoA-I were 644, 577 mg/L. Both lipoprotein forms of ApoA-I were detected in all major density classes, but were most abundant in high-density lipoproteins. The technique is applicable to measurement of any two apolipoproteins that occur in both associated and unassociated forms in plasma.
Determination of neopterin in serum and urine.
Authors: Werner E R , Bichler A , Daxenbichler G , Fuchs D , Fuith L C , Hausen A , Hetzel H , Reibnegger G , Wachter H
Published: January 2020

Concentrations of neopterin, a product of activated macrophages, in serum from 662 apparently healthy individuals (ages 1 to 97 years, median 22 years) were measured by radioimmunoassay and the results statistically analyzed. Consistent with prior investigations on the urinary excretion of neopterin, we found no significant sex dependence, but values for subjects younger than 18 or older than 75 years were significantly higher. Renal clearance of neopterin in nine healthy individuals was 218 (SD 44) mL/min, which suggests that the kidneys have an active role in neopterin excretion. Results for neopterin concentrations measured in serum by RIA and "high-performance" liquid chromatography (HPLC) are consistent, but for urinary neopterin the concordance between methods was weak. Therefore, the RIA should be used only for measuring neopterin in serum. In comparison of the clinical utility of serum neopterin and urinary neopterin/creatinine concentrations, in patients with gynecological tumors, the latter values (measured by HPLC) discriminated slightly better between patients with favorable and unfavorable prognoses.
On the albumin-dependence of measurements of free thyroxin. II. Patients with non-thyroidal illness.
Authors: Csako G , Zweig M H , Benson C , Ruddel M
Published: January 2020

We studied the relation between thyroxin-binding proteins and free thyroxin (FT4) measurements by five radioimmunoassays (RIA) and an FT4 index (FT4I) in patients with non-thyroidal illness (NTI). The one-step FT4 RIAs and the FT4I frequently failed to identify the true FT4 status (as determined by equilibrium dialysis) of NTI patients. In these patients, falsely low FT4 results with one-step RIAs and FT4I were associated with decreasing total T3 and T4 concentrations, which, furthermore, paralleled decreasing serum albumin concentrations. All NTI patients with "low T3, low T4 syndrome" had subnormal albumin concentration. The two-step RIAs and equilibrium dialysis showed normal FT4 concentrations in most patients with NTI. However, sera from a subset of NTI patients with "low T3 syndrome" gave above-normal FT4 results with these methods. From their predictably poor performance in the presence of a subnormal albumin concentration, we conclude that the one-step FT4 RIAs and FT4I are inappropriate for testing the thyrometabolic status of NTI patients.
Measurement of corticotropin in unextracted plasma: comparison of a time-resolved immunofluorometric assay and an immunoradiometric assay, with use of the same monoclonal antibodies.
Authors: Dobson S , White A , Hoadley M , Lovgren T , Ratcliffe J
Published: January 2020

We describe a time-resolved immunofluorometric assay (IFMA) for corticotropin in unextracted human plasma, based on the use of two monoclonal antibodies: europium-labeled antibody 1A12 and antibody 2A3 coated onto microtiter wells. We compared the results of this assay with those of an immunoradiometric assay (IRMA) performed with the same antibodies working ranges (CV less than 10%) were 25 to 1000 ng/L and 22 to 1000 ng/L for the IFMA and IRMA, respectively, and both assays had comparable detection limits (IFMA 4.0 +/- 1 ng/L, IRMA 3.5 +/- 0.8 ng/L). Results by both assays for 130 patients' samples containing corticotropin within the range 3-100 ng/L and greater than ng/L correlated well (r = 0.88 and 0.92, respectively), and samples with corticotropin in the range 80-624 ng/L gave results that paralleled those for the standard curve. Corticotropin concentrations in apparently healthy subjects were consistent with those reported previously. The IFMA is a simple, precise, and robust assay that can be completed within one day. Its nonisotopic label is stable for at least 50 weeks.
Properties of alkaline phosphatase isoenzymes in plasma of preterm and term neonates.
Authors: Crofton P M
Published: January 2020

The isoenzymes of alkaline phosphatase (EC 3.1.3.1) in plasma of 37 preterm and 21 term neonates two weeks postpartum have been studied with regard to electrophoretic mobility, sialic acid content, inhibition properties, heat lability, molecular mass, and binding to lectins. Term infants generally had a single form of alkaline phosphatase present in significant amounts, identified by the above criteria as originating in bone. All the preterm neonates had two alkaline phosphatase isoenzymes in plasma, namely, bone- and fetal-type intestinal alkaline phosphatase. Liver-, placental-, and adult-type intestinal alkaline phosphatase were not detected in any of the plasma samples.
Validation and application of a liquid-chromatographic/enzymatic assay for individual bile acids in the serum of rats.
Authors: Thompson M B , Blair P C , Morris R W , Neptun D A , Deyo D F , Popp J A
Published: January 2020

A liquid-chromatographic technique with a post-column enzymatic reaction and fluorescence detection was validated for analysis of individual bile acids in the serum of rats. Extraction recoveries averaged 91.1% (SD 6.9%) for all bile acids. The assay was sensitive (minimum detection of 16.8 pmol per 100-microL injection), linear (r greater than 0.999 for concentrations ranging between 45 and 112,500 pmol per 100-microL injection), and reproducible (mean CVs for three different concentrations of standards and a serum pool ranged from 4.4% to 12.2%). In rats treated for three days with either neomycin, carbon tetrachloride, alpha-naphthylisothiocyanate, or total bile-duct ligation (five animals per group), total concentrations of bile acids were significantly increased (P less than 0.004). Concentrations of 16 of 17 individual bile acids differed significantly between groups (P less than 0.04). Examination of the relative concentrations (percent of total) of individual bile acids by canonical discriminant analysis placed each animal into the appropriate treatment or control group. Use of this technique in toxicological studies can help detect and identify specific types of disruptions in the enterohepatic circulation of bile acids.
Inhibitory effect of disulfiram (Antabuse) on alcohol dehydrogenase activity.
Authors: Carper W R , Dorey R C , Beber J H
Published: January 2020

We investigated the effect of disulfiram (Antabuse) on the activity of alcohol dehydrogenase (EC 1.1.1.1) in vitro. We observed a time-dependent inhibition of this dehydrogenase by disulfiram and diethyldithiocarbamate similar to that obtained for aldehyde dehydrogenase (EC 1.2.1.3). These results suggest a possible explanation for various side effects observed in the clinical use of Antabuse.
Multiple drugs of abuse in urine detected with a single reagent and fluorescence polarization.
Authors: Colbert D L , Childerstone M
Published: January 2020

We describe a simple polarization fluoroimmunoassay for the detection of several commonly abused drugs in urine. The single reagent used, prepared by mixing four different antisera and three fluorescein-labeled derivatives, produces a polarization signal that is the average of the individual signals of the derivatives. One adds urine to the pre-mixed reagent, incubates at room temperature for a few minutes, then measures fluorescence polarization. The presence of any of several abused drugs, at concentrations of 1 mg/L or more, noticeably decreases the average signal. Although other combinations are possible, the present assay detects the presence of a cocaine metabolite, amphetamine, and (or) several barbiturates.
Bence Jones proteinuria in multiple sclerosis.
Authors: Pezzoli A , Pascali E
Published: January 2020

We report our findings of Bence Jones proteins (monoclonal free light chains of immunoglobulins) in concentrated urines of patients with multiple sclerosis, by using agarose electrophoresis and immunofixation. The lack of such findings in urines from healthy subjects and patients with other neurological disorders should stimulate further investigation.
Sensitivity of the direct oxalate oxidase assay of urinary oxalate improved.
Authors: Buttery J E , Pannall P R
Published: January 2020

The direct colorimetric method for urinary oxalate has been modified to improve its sensitivity. Oxalate is precipitated overnight with calcium chloride and ethanol, the precipitate is redissolved, and the oxalate is measured by use of oxalate oxidase (EC 1.2.3.4), methylbenzothiazolinone hydrazone, and dimethylaniline. The color developed is more intense, analytical recovery averages 102%, and the overall imprecision is less than 5%. To assess the accuracy of the method, we used a gas-chromatography comparison method and control sera. Interference from ascorbate is negligible. The modified method retains its simplicity and is less expensive.
Chemiluminescence immunoassay for somatomedin C in serum.
Authors: Tode B , Messeri G , Bassi F , Pazzagli M , Serio M
Published: January 2020

To select the best tracer for use in a competitive immunoassay, we conjugated human somatomedin C (SmC) to various chemiluminescent compounds via two different synthetic pathways. Naphthylhydrazides and arylhydrazides, used as the labels, were incorporated via their imidate or their succinimide esters. Conjugating the carboxy terminal of (amino ethyl)ethyl-isoluminol to SmC via a succinimide linkage supplied the most sensitive detection limit and the most immunoreactive conjugate. We developed an immunoassay based on the use of this conjugate, and evaluated dextran-coated charcoal, second-antibody precipitation, and solid-phase immunoprecipitation for separating bound and free label. This chemiluminescent method has a detection limit of 16 pg per tube, and it is accurate and precise. Correlation studies with a conventional radioimmunoassay (x) for SmC gave the following regression equation: y = 0.66x + 3.76 (r = 0.953, n = 30); the slight discrepancies between the two methods are probably ascribable to the use of different antibodies. We thus propose this chemiluminescence immunoassay as an inexpensive and sensitive alternative to radioimmunoassay for measuring SmC in serum or in extracts of serum.
Specific immunoradiometric assay of insulin-like growth factor I with use of monoclonal antibodies.
Authors: Scott M G , Cuca G C , Petersen J R , Lyle L R , Burleigh B D , Daughaday W H
Published: January 2020

We identified two monoclonal antibodies that bind spatially distinct epitopes on insulin-like growth factor I (IGF-I). Using these two antibodies, we developed a simultaneous, two-site immunoradiometric assay (IRMA) specific for IGF-I. This IRMA has no detectable cross reactivity with insulin, proinsulin, prolactin, or somatotropin, and less than 2% crossreactivity with IGF-II. The assay response varies linearly with IGF-I concentrations of 0-800 micrograms/L in serum; the detection limit is about 10 micrograms/L. A comparison of 26 IGF-I serum values from the IRMA and from a previously reported IGF-I specific RIA gave a correlation coefficient of 0.96 with no substantial bias (slope = 1.10). IGF-I values for serum, as an aid in assessing growth abnormalities, are easily (only three pipetting steps) obtained in less than 4 h.
Radioimmunoassay of tumor necrosis factor in serum.
Authors: Teppo A M , Maury C P
Published: January 2020

We present a double-antibody radioimmunoassay for determination of the concentration of tumor necrosis factor (TNF) in serum. TNF in serum competes with a fixed amount of 125I-labeled TNF for the binding sites of specific rabbit antibodies. The bound TNF is precipitated with Sepharose-bound anti-rabbit IgG, then centrifuged, and the radioactivity of the pellets is counted. The detection limit of the assay is 7 ng/L (B0-3 SD). Bound radioactivity in the range of 10% to 90% of the B0 counts corresponds to TNF concentrations of 26 to 10,000 ng/L. Of 40 sera from healthy subjects, 21 (53%) contained TNF concentrations greater than 7 ng/L (range 8-40 ng/L). Some patients with parasitic or neoplastic disease and patients with septic shock had highly increased TNF values. Three of the 14 sera (21%) from patients with rheumatoid arthritis had TNF concentrations greater than 40 ng/L.
Computer-aided infrared analysis of urinary calculi.
Authors: Berthelot M , Cornu G , Daudon M , Helbert M , Laurence C
Published: January 2020

We have created a library of 497 digitized infrared spectra of 58 components of urinary calculi and of their usual binary and ternary mixtures. We tested the operation of the "Birsy" search program (Bruker Analytische Messtechnik) with this library for the interpretation of infrared spectra of 50 urinary calculi, selected from both classical and difficult cases. This program correctly identifies the two first components 98% of the time and the third (minor) component 70% of the time. Using this program, those without training or experience in infrared analysis can routinely use the infrared method of analysis of urinary calculi.
Four methods compared for measuring des-carboxy-prothrombin (PIVKA-II).
Authors: Widdershoven J , van Munster P , De Abreu R , Bosman H , van Lith T , van der Putten-van Meyel M , Motohara K , Matsuda I
Published: January 2020

PIVKA-II (Protein Induced by Vitamin K Absence) is abnormal des-carboxylated prothrombin, which is present in vitamin K deficiency or in patients using warfarin. With a sensitive method for PIVKA-II, biochemical vitamin K deficiency can be established before clinical symptoms occur. We give an overview of methods used to detect PIVKA-II, and four selected methods are inter-compared: (a) measuring total factor II including PIVKA-II by using Echis carinatus snake venom as an activator of prothrombin; (b) measuring PIVKA-II by using snake venom as an activator of factor II after adsorption of functional factor II onto barium sulfate; (c) electrophoresis-immunofixation method; and (d) enzyme immunoassay. We found d to be the most sensitive and reliable method for PIVKA-II.
Antimony accumulation in hair during treatment of leishmaniasis.
Authors: Dorea J G , Costa J M , Holzbecher J , Ryan D E , Marsden P D
Published: January 2020

We used instrumental neutron activation analysis (INAA) to determine antimony in small quantities of hair from individuals living in an area of endemic leishmaniasis. The groups studied were 12 patients undergoing treatment with N-methylglucamine antimoniate, 34 patients who had received such treatment a year ago, and 17 control subjects (untreated) who were living in the same area. Patients receiving treatment showed mean and median (12.13, 2.9 micrograms/g) values for antimony in hair that significantly exceeded those in either controls (1.01, 0.4 microgram/g) or patients one year after treatment (1.54, 1.0 microgram/g). We conclude that INAA can be useful in monitoring and differentiating such exposure to antimony in patients under treatment.
An alternative explanation for the changes in erythrocyte fatty acids observed in diabetes mellitus.
Authors: Taylor A J , Jennings P E , Barnett A H , Pandov H I , Lawson N
Published: January 2020

Fatty acids in erythrocyte membranes and plasma were determined by capillary gas-liquid chromatography in 27 controls and 44 subjects with insulin-dependent diabetes mellitus. Significant decreases in stearic acid (P less than 0.00003) and arachidonic acid (P less than 0.001) and significant increases in palmitic acid (P less than 0.00003) were observed in erythrocytes from diabetic patients. The stearic:oleic acid ratios and arachidonic:linoleic acid ratios in erythrocytes were significantly lower in diabetic patients than in controls (P less than 0.0003 and less than 0.0007, respectively). The relative concentration of palmitic acid in plasma (as a percentage of the sum of the five major fatty acids) was increased in diabetic patients, as compared with controls (P less than 0.0125). We observed no other significant differences in fatty acids in plasma, making it unlikely that changes in fatty acids in erythrocyte membranes in diabetic patients can be accounted for simply by alterations in the fatty acids in plasma. We propose that impaired metabolic control associated with diabetes mellitus may interfere with the maintenance of fatty acid profiles in erythrocyte membranes against the concentration gradients in plasma.
Chemiluminescence immunoassay of thyrotropin with acridinium-ester-labeled antibody evaluated and compared with two other immunoassays.
Authors: Bounaud M P , Bounaud J Y , Bouin-Pineau M H , Orget L , Begon F
Published: January 2020

A new chemiluminometric immunoassay of thyrotropin (TSH) involves antibody labeled with acridinium ester ("Magic Lite System," Ciba Corning Diagnostic Corp.). The assay is rapid, with two incubations totaling 2.5 h, requires two standards per run, and takes 10 s per sample for the quantification step. Analytical performance, within- and between-run reproducibilities, and linearity were excellent. The detection limit is 0.04 milli-int. unit/L. Results correlated well with those obtained by immunoradiometric assay (RIA-gnost hTSH, Hoechst-Behring) and immunofluorometric assay (hTSH Delfia, LKB): r = 0.975. TSH measurements in 32 euthyroid subjects ranged from 0.4 to 4.8 milli-int. units/L (mean 1.35 milli-int. units/L). TSH values for 51 hypothyroid and subclinically hypothyroid patients ranged from 2 to 65 milli-int. units/L. TSH values for 33 hyperthyroid patients (less than 0.14 milli-int. unit/L, less than 0.04 milli-int. unit/L in 16 of the 33) were clearly lower than for most untreated euthyroid subjects. For 169 other individuals whose thyroid function was being routinely assessed. TSH ranged from 0.4 to 4.8 milli-int. units/L, three had TSH less than 0.14 milli-int. unit/L, and four had TSH between 0.14 and 0.4 milli-int. unit/L. This system is as efficient and reliable for screening for thyroid function as the two comparison systems.
Fructosamine: structure, analysis, and clinical usefulness.
Authors: Armbruster D A
Published: January 2020

Glucose molecules are joined to protein molecules to form stable ketoamines, or fructosamines, through glycation, a nonenzymatic mechanism involving a labile Schiff base intermediate and the Amadori rearrangement. The amount of fructosamine in serum is increased in diabetes mellitus owing to the abnormally high concentration of sugar in blood. The concentration of fructosamine in serum thus reflects the degree of glycemic control attained by the diabetic patient and is useful in monitoring the effectiveness of therapy in diabetes over a period of several weeks, in a manner analogous to the determination of glycated hemoglobin. Of the analytical approaches used to measure fructosamine, affinity chromatography with m-aminophenylboronic acid and the nitroblue tetrazolium reduction method appear to be the most practical means for clinical chemists to assay fructosamine quickly, economically, and accurately. Fructosamine values can readily distinguish normal individuals and diabetic patients in good glycemic control from diabetics in poor control. Unlike glycated hemoglobin, which reflects the average blood sugar concentration over the past six to eight weeks, fructosamine reflects the average blood sugar concentration over the past two to three weeks. Thus a clinical advantage is that fructosamine responds more quickly to changes in therapy, thereby allowing for improved glycemic control. Used in conjunction with determinations of blood sugar and (or) of glycated hemoglobin, or by itself, the fructosamine assay can provide clinically useful information for the detection and control of diabetes.
An enzymic assay for the specific determination of methanol in serum.
Authors: Vinet B
Published: January 2020

This method for the specific determination of methanol in serum is based on the following two reactions: (formula; see text) Alcohol oxidase is not specific: it converts all lower alcohols to their corresponding aldehydes; however, formaldehyde dehydrogenase is specific and thus the transformation of NAD+ to NADH (which is used to monitor the reaction) proceeds only if methanol is originally present in the sample. The method was automated with a Roche COBAS FARA centrifugal analyzer. The calibration curve is linear between 0.6 and 12 mmol/L. The detection limit is about 0.6 mmol/L. The CV is 4.6% for a concentration of 3 mmol/L. When 55 serum specimens known to be free of methanol were supplemented with known amounts of methanol and analyzed by the enzymatic method, the results correlated well (r = 0.987) with the true values, the regression equation being: y = 1.016x + 0.661, where x represents the true values. Results are not affected by other alcohols that may be present in serum, by methanol metabolites, or by some commonly prescribed drugs. The major advantage of this new assay is that it can be used 24 h a day in any clinical chemistry laboratory.
31P nuclear magnetic resonance study of variations in intra-erythrocytic ATP concentration and pH induced by surgical trauma.
Authors: Monti J P , Martinez S , Braguer D , Courtina C , François G , Crevat A
Published: January 2020

Variations in intracellular pH and ATP concentrations in erythrocytes were studied in patients undergoing a mild surgical intervention. Intra-erythrocytic pH was decreased at the end of the operation; ATP concentrations concomitantly increased, but not highly significantly. These variables returned to their initial values by 20 h after the end of surgery.
Chemical factors important to calcium nephrolithiasis: evidence for impaired hydroxycarboxylic acid absorption causing hyperoxaluria.
Authors: Cowley D M , McWhinney B C , Brown J M , Chalmers A H
Published: January 2020

An investigation of variables important to calcium stone formation in urine indicated significantly increased daily excretion of calcium and oxalate and decreased excretion of ascorbate and citrate by recurrent calcium stone formers. In addition, urine volume, sodium, mucopolysaccharide, and protein were also significantly increased. We compared the uptake of citrate and ascorbate from the gut into the blood in normal controls and stone formers. These studies indicated significantly depressed absorption of both these hydroxycarboxylic acids in recurrent calcium stone formers. We also found that concurrent administration of citrate inhibited ascorbate absorption and increased urinary oxalate excretion after an ascorbate load in normal subjects and stone formers. These findings suggest a mechanism that explains hyperoxaluria in stone patients on the basis of a malabsorption of citrate, ascorbate, and possibly other hydroxycarboxylic acids.
Improved separation of fetal hemoglobin by mini-column chromatography.
Authors: Morin L G , Barton E G
Published: January 2020

We present chromatographic conditions for separating and measuring fetal hemoglobin on a 5-cm column of Sephadex CM-50. A distinct fetal band is evident, even when present at less than 1% of total hemoglobin. Precision (CV) of better than 5% is achievable.
Value and limitations of a highly sensitive immunoradiometric assay for thyrotropin in the study of thyrotroph function.
Authors: Caldwell G , Gow S M , Sweeting V M , Beckett G J , Seth J , Toft A D
Published: January 2020

Using a highly sensitive and specific immunoradiometric assay for thyrotropin, we studied thyrotroph function in 232 new patients referred to a thyroid clinic and in 13 patients after treatment for hyperthyroidism. Significant thyrotroph responsiveness to thyroliberin (thyrotropin-releasing hormone, TRH) was found in all patients with values for basal thyrotropin greater than 0.1 milli-int unit/L. In no overtly hyperthyroid patient was any increment in thyrotropin recorded at 20 min after thyroliberin administration. In seven patients, four subclinically hyperthyroid and three who had received treatment, increments in thyrotropin from undetectable basal values were recorded, consistent with incomplete thyrotroph suppression. By use of assays with even higher sensitivity, one may be able to distinguish these patients from overtly hyperthyroid patients.
Transient hyperphosphatasemia of infancy and early childhood: clinical and biochemical features of 21 cases and literature review.
Authors: Stein P , Rosalki S B , Foo A Y , Hjelm M
Published: January 2020

Clinical and biochemical features of transient hyperphosphatasemia of infancy and early childhood are reviewed in 21 patients we have studied and in a further 93 cases reported in the literature. The diagnosis is suggested by the finding of an increased activity of alkaline phosphatase (EC 3.1.3.1) in plasma, typically more than fivefold the adult upper reference limit, in a child under five years of age, without evidence of liver or bone disease. The condition is confirmed by the presence of a characteristic pattern of alkaline phosphatase isoenzymes and by the normalization of the enzyme's activity in plasma within approximately three months. The etiology of the condition and possible mechanisms of the enzyme increase are discussed.
Early diagnosis of acute myocardial infarction by rapid analysis of creatine kinase isoenzyme-3 (CK-MM) sub-types.
Authors: Wu A H , Gornet T G , Wu V H , Brockie R E , Nishikawa A
Published: January 2020

We compared the clinical sensitivity, specificity, and diagnostic efficiency of measuring creatine kinase-3 (MM) isoenzyme sub-types (CK, EC 2.7.3.2) with the measurement of CK-2 (MB) isoenzymes for the diagnosis of acute myocardial infarction. Serial blood collections at 3-h intervals from 35 patients with acute myocardial infarction were examined. In attempts to reperfuse their coronary arteries, some of these patients were treated with pharmacological thrombolysis (streptokinase, tissue plasminogen activator), with or without coronary angioplasty. The infarction patients were divided into two groups: patients who were successfully treated with thrombolytic agents (i.e., they achieved coronary reperfusion), and patients who were treated unsuccessfully or who were not treated acutely. We also examined blood from 34 non-infarction patients. We measured CK-3 sub-types by both anion-exchange liquid chromatography and a modified high-voltage electrophoresis method, and CK-2 by immunoprecipitation. Our results show that during the first few critical 3 to 9 h after onset of chest pain, measurement of CK-3 sub-types has the highest diagnostic efficiency; in contrast, CK-2 has the highest efficiency during the 10- to 21-h time intervals. Thus early diagnosis of acute myocardial infarction can be based on rapid assays of CK-3 sub-types.
Two-stage transformation systems for normalization of reference distributions evaluated.
Authors: Linnet K
Published: January 2020

In two-stage transformation systems for normalization of reference distributions, the asymmetry is first corrected, and any deviation of kurtosis is then adjusted. The simulation studies reported here show that these systems have previously been assessed too optimistically because the sample variation of the transformation parameters was neglected. Applying a goodness-of-fit test to transformed values shows that one should accept gaussianity only for p-values greater than 0.15 instead of those greater than 0.05. Further, the calculated 90% confidence intervals of reference limits should be expanded by 25%. When the correct level of significance is used, only real reference distributions that deviate moderately from the gaussian form are normalized. Calculation of confidence intervals demonstrated that 50 to 450 subjects are needed for a precise parametric estimation of the 95% reference interval. For the nonparametric approach, 125 to 700 reference subjects are necessary. The larger sample sizes are needed when distributions show pronounced skewness.
Cholesteryl ester transfer activity in plasma measured by using solid-phase-bound high-density lipoprotein.
Authors: Sparks D L , Frohlich J , Cullis P , Pritchard P H
Published: January 2020

We studied the ability of lipid-transfer factors in plasma to promote transfer, to endogenous lipoproteins, of [3H]cholesteryl ester from high-density lipoprotein (HDL) covalently bound to Sepharose 4B beads. After incubation for 2 h at 37 degrees C, 12 to 14% of the [3H]cholesteryl ester had been transferred to the lipoproteins of the plasma, in the proportions 57% to HDL and 43% to low- and very-low-density lipoproteins. This process was a function of the amount of plasma present and was stimulated by addition of partly purified lipid-transfer protein. Transfer also depended on the concentration of donor HDL but was independent of the amount of acceptor lipoprotein. This simple evaluation of cholesteryl ester transfer does not require removal of lipoproteins from the plasma before incubation.
Percentile estimates of reference values for total protein and albumin in sera of premature infants (less than 37 weeks of gestation).
Authors: Zlotkin S H , Casselman C W
Published: January 2020

We measured the concentrations of total protein and albumin in sera of 281 well-fed premature infants, gestational ages 22-36 weeks, and calculated reference values from the 10th to 90th percentiles. The mean serum albumin concentration (27.6 +/- 4.4 g/L, mean +/- SD) and total protein concentration (49.2 +/- 6.7 g/L) at a postnatal age of 14.5 days were lower than reference values for full-term infants. We detected a significant positive correlation between albumin concentration and gestational age (r = 0.34, p less than 0.01) and total protein concentration and gestational age (r = 0.43, p less than 0.01). Even though albumin values were low, generalized edema was not present. We conclude that values for total protein and albumin in the preterm infant are lower than in the full-term infant but are an expected physiological response to premature birth.
Distribution of cyclosporine in blood of a renal-transplant recipient with type V hyperlipoproteinemia.
Authors: Verrill H L , Girgis R E , Easterling R E , Malhi B S , Mueller W F
Published: January 2020

A patient with severe type V hyperlipoproteinemia and chronic end-stage renal disease received a renal transplant and therapy with cyclosporine. Concentrations of the drug in plasma as determined by liquid chromatography appeared extraordinarily high for the dose ingested. When we measured the drug in the plasma, plasma cleared by ultracentrifugation, leukocytes, erythrocytes, and whole blood, we found that the high concentrations of cyclosporine were associated with the chylomicrons that always were present in this patient's blood. Cyclosporine added directly to this patient's plasma was less associated with the plasma lipids. Isolated lymphocytes and kidney slices incubated with plasma from this patient bound no more drug than when incubated with nonhyperlipemic plasma containing cyclosporine at a normal therapeutic concentration. We conclude that the cyclosporine associated with the chylomicrons in this patient was not biologically available to either lymphocytes or kidney tissue. We strongly recommend the use of chylomicron-cleared plasma for therapeutic drug monitoring of cyclosporine in type V hyperlipoproteinemic patients.
Quinine directly determined in serum or urine by separation fluoroimmunoassay.
Authors: Sidki A M , Al-Abdulla I H , Rowell F J
Published: January 2020

We developed and validated a magnetizable solid-phase fluoroimmunoassay for directly determining quinine in serum or urine. We prepared the immunogen by coupling quinine hemisuccinate to keyhole-limpet hemocyanine, using this to immunize three sheep, and coupling the antisera to magnetizable solid-phase particles to facilitate separation of bound antigen from interfering components of serum or urine. We tested the stability of two fluorescein-labeled derivatives of quinine--one prepared by direct conjugation of quinine to dichlorotriazenyl aminofluorescein, the other by conjugating quinine hemisuccinate to fluorescein thiocarbamyl ethylenediamine. The latter was unstable. Using the former label and an 30-min incubation, we saw no interference by quinidine (an enantiomer of quinine) or other antimalarial drugs at their therapeutic concentrations.
Fast kinetic method for methemoglobin developed and adapted for quantification of hemoglobin in whole blood.
Authors: Cummings R H , Pardue H L
Published: January 2020

We studied the kinetics of the reaction of cyanide with methemoglobin (mHb), used the information to develop a fast kinetic method for quantifying methemoglobin, then used that method to quantify hemoglobin (Hb) in whole blood based on the reaction with ferricyanide to produce mHb. Reaction conditions for mHb and cyanide are adjusted to give pseudo-first-order behavior with an apparent rate constant that increases linearly with cyanide concentration, decreases linearly with pH, and follows an Arrhenius-type relationship with temperature. Absorbance change, computed from kinetic data with a curve-fitting method, varies linearly with mHb concentration. Although the reactions are monitored most reliably with stopped-flow mixing, cyanide concentration was used to decrease reaction velocities to be compatible with centrifugal mixing. Kinetic results (y) for Hb in blood by both mixing methods correlate well with equilibrium results (x): y = 1.000x + 0.02 mmol/L, Syx = 0.06 mmol/L with stopped-flow mixing; y = 1.03x + 0.12 mmol/L, Syx = 0.07 mmol/L with centrifugal mixing; r = 0.96 and n = 21 in each case.
Estimating fat in feces by near-infrared reflectance spectroscopy.
Authors: Koumantakis G , Radcliff F J
Published: January 2020

We describe use of near-infrared reflectance spectroscopy (NIRRS) to estimate the amount of fat in feces, for diagnosis of steatorrhea. After sample homogenization, the spectrum of the fecal homogenate is scanned over the near-infrared region. Assay of 94 samples of feces having a known concentration of fat showed the appropriate wavelengths for the NIRRS procedure to be 1734, 1778, 1818, 2270, and 2310 nm. The reflectance output of 47 fecal samples subsequently measured at these wavelengths was used to compute the reflectance scaling factors (F values) by the instrument's microprocessor. Assay of fat content in a further 124 fecal samples, by both hydrolysis/titration (J Biol Chem 1949;177:347) and the NIRRS procedure at the wavelengths and corresponding F values previously determined, gave results that correlated highly satisfactorily. However, the NIRRS procedure demonstrated much better precision.
Detecting errors in blood-gas measurement by analysis with two instruments.
Authors: Metzger L F , Stauffer W B , Krupinski A V , Millman R P , Cembrowski G S , Pack A I
Published: January 2020

We performed a two-stage prospective evaluation of the error detection capabilities of duplicate analysis of blood-gas specimens. In the first stage we analyzed 1601 specimens with a Corning Model 175 blood-gas analyzer as the test instrument and a Corning Model 178 analyzer as the reference instrument, and in the second stage we analyzed 1544 specimens with two Model 178 analyzers. In each stage the designated reference instrument underwent troubleshooting whenever an analytical error was detected; the test instrument underwent troubleshooting only when error conditions were indicated by means other than duplicate analysis. An error was considered to have occurred if the difference between the duplicate analyses exceeded 0.02 (for pH), 0.53 kPa, i.e., 4 mmHg (pCO2), or 7% (pO2). The number of specimens for which errors were detected was 97 (6.1%) in the first stage, 23 (1.5%) in the second. For each analyte more errors were detected with the Model 175 analyzer (of older design) than with the newer Model 178 analyzer. Furthermore, in certain periods associated with the use of particular electrodes there were very high error rates for individual analytes: 8% for pCO2, 18% for pO2. We conclude that duplicate analysis should be considered as a possible required standard for error detection.
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

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

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.