bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term retrospective control procedures for monitoring analytical performance of laboratory instruments.
Authors: Gozzo M L , Barbaresi G , Giocoli G , Zappacosta B , Zuppi C
Published: January 2020

We propose a statistical procedure for long-term quality-control of laboratory instruments, including daily, day-to-day, and monthly evaluations. The procedure is based on the unique and unequivocal interpretation of five results for control sera by calculation of a Reliability Index and further manipulations of this unitless parameter. This method, which we have tested during the past two years, allows for monitoring analytical performance and making comparisons with results of interlaboratory surveys. The monthly analytical variability, expressed as "total error," is an indicator of the clinical usefulness of analytical results.
Effect of sample dilution on measurements of free (unbound) hormones.
Authors: Geiseler D , Ritter M
Published: January 2020

We describe the influence of sample dilution on the measurement of free or non-protein-bound hormones in serum or plasma. The concentration of free hormone in the sample will alter after dilution or addition of binding reagents. The extent of this equilibrium perturbation depends on the binding properties of the endogenous carrier proteins, which vary from sample to sample and from sample to reference standard. As examples, we demonstrate the different changes in concentrations of free thyroxin and free cortisol after dilution, both experimentally and by theoretical modeling of the hormone-protein distribution. We also show how this systematic error can be minimized in the design of free hormone assays.
A two-site immunoradiometric assay with magnetizable particles: human liver ferritin as a model.
Authors: Al-Shawi A , Dawnay A , Landon J
Published: January 2020

Using human liver ferritin as a model, we have developed a two-site immunoradiometric assay. Sample (or standard) is incubated with excess rabbit antiserum and 125I-labeled specific sheep antibodies directed against different antigenic determinants until equilibrium is reached. Then excess sheep anti-rabbit immunoglobulin G serum, covalently linked to magnetizable particles, is added. The radioactivity bound to these particles is directly proportional to the amount of ferritin present. The assay is reproducible and precise throughout the clinically important range for ferritin in serum. Late addition of second antibodies coupled to magnetizable particles is a novel, simple, rapid, and universally-applicable separation technique for two-site immunoradiometric assays. By this approach, the first immunological reaction can occur in liquid phase, which shortens the reaction time, maximizes sensitivity, and avoids the need for continuous mixing, as compared with methods in which one of the first antibodies is immobilized on a solid phase.
Clinical significance and partial biochemical characterization of lactate dehydrogenase isoenzyme 6.
Authors: Ketchum C H , Robinson C A , Hall L M , Grizzle W E , Maclaren N K , Riley W J , Trost C
Published: January 2020

We report nine patients with a sixth band, migrating cathodic to lactate dehydrogenase 5, appearing on routine electrophoresis for serum lactate dehydrogenase (LD, EC 1.1.1.27). Eight of these patients died during their hospitalization. Acidosis, hypotension, and sepsis were the common clinical conditions preceding the band's appearance. In several cases the band appeared transiently. We examined tissue samples from two of the cases, finding LD-6 in liver and skeletal muscle but not in heart. In randomly selected autopsy tissues, LD-6 was detected consistently in liver and skeletal muscle, sometimes in spleen, kidney, and adrenal tissue, but never in heart. Biochemical studies indicate that the LD-6 isoenzyme is not an artifact or an immunoglobulin complex, is larger than the other LD isoenzymes, contains an M-subunit but not an H-subunit, has an isoelectric point in the pH range of 9.0-9.6, and is more heat stable than LD-5.
Direct potentiometric determination of sodium ion in blood. I. Potentiometric response in simple sodium chloride solutions.
Authors: Bijster P , Vink K L
Published: January 2020

We measured the emf of NaCl solutions (120-160 mmol/L) with a home-built cell in steady-state and with some commercial direct potentiometric analyzers about 20 s after the sample is introduced into the instrument. We compared the results with the theoretical sodium ion activity calculated according to different thermodynamic theories. The slope of the calibration graph was calculated with and without correction for the influence of NaCl concentration on the liquid junction potential of the calomel reference electrode. We conclude that different theories used to calculate the sodium ion activity in the concentration range investigated give almost the same results; furthermore, introduction of the liquid junction potential leads to a more nernstian-like slope of the calibration graph. Measurement of identical NaCl solutions with various commercial analyzers showed different displayed concentrations, presumably because of differences in junction structure, measuring time, and concentration of calibration solutions.
Determination of enteroglucagon in plasma for detection of celiac disease in children.
Authors: Kilander A F , Stenhammar L , Lindstedt G , Lundberg P A
Published: January 2020

To evaluate the plasma enteroglucagon assay as a test for the detection of celiac disease, we have determined basal and postprandial concentrations of enteroglucagon in plasma of children who underwent small-intestinal biopsy because of suspected celiac disease. In the 14 children with untreated celiac disease both basal [81 (SD 33) pmol/L] and postprandial [129 (SD 26) pmol/L] concentrations of enteroglucagon were significantly higher (p less than 0.001) than in the 45 children with other gastrointestinal disorders [24 (SD 9) pmol/L, and 50 (SD 22) pmol/L, respectively] and in the 15 children without gastrointestinal disorders [14 (SD 10) pmol/L, and 35 (SD 8) pmol/L, respectively]. All children with celiac disease had either basal or postprandial plasma enteroglucagon concentrations exceeding the mean + 2 SD of the results for the children with other gastrointestinal disorders. Eight of 10 children with celiac disease in whom both concentrations were measured had increased values for both. In our study the sensitivity for detection of celiac disease was 100% and the specificity 97%. Evidently determination of plasma enteroglucagon concentration is effective in diagnosing celiac disease, thereby improving the selection of patients for small-intestinal biopsy.
Radioimmunoassay of apolipoprotein B with use of monoclonal antibodies.
Authors: Maynard Y , Roden D C , Tikkanen M J , Schonfeld G , Ladenson J H
Published: January 2020

We describe a double-antibody radioimmunoassay for apolipoprotein B with use of monoclonal antibodies. Values for 32 patients with various lipid disorders, obtained with use of one of the monoclonal antibodies (464B1B6), were similar to those obtained with use of a polyclonal antiserum. When we used another monoclonal antibody (465C3D1) the values were significantly lower. Monoclonal antibody 464B1B6 recognized apolipoprotein B determinants in the very-low-density-lipoprotein and low-density-lipoprotein fractions of plasma in a similar fashion as in unfractionated plasma, but monoclonal 465C3D1 gave lower values with the fractionated plasma. For precipitation of the antibody-apolipoprotein complex to be complete, use of polyethylene glycol was necessary with one of the monoclonal antibodies but not with the other. The interassay CV was 12.3% and 11.6% for the assays with the monoclonal antibodies. Analytical recoveries ranged from 85 to 94%. Owing to variations in the B50 from one preparation of standard to another, we found it necessary to normalize the results to those of a serum pool. We conclude that certain monoclonal antibodies can be used effectively in radioimmunoassays for apolipoprotein B in plasma and may help in the standardization of these assays.
Solid-phase chemiluminescence immunoassay for progesterone in unextracted serum.
Authors: De Boever J , Kohen F , Vandekerckhove D , Van Maele G
Published: January 2020

We describe a simple, solid-phase chemiluminescence immunoassay for progesterone in 10 microL of unextracted serum ("direct" assay). Danazol at pH 8.0 is included (100 ng per tube) to displace progesterone from binding proteins in serum. A progesterone-11 alpha-hemisuccinyl-aminobutylethyl isoluminol conjugate serves as the chemiluminescent ligand marker and homologous antiprogesterone IgG covalently coupled to "Immunobeads" is the immunoadsorbant. After the binding reaction, bound and free ligand are separated by centrifugation and the chemiluminescence yield of the bound label is determined. The sensitivity, specificity, precision, and accuracy of the method are similar to those of a conventional radioimmunoassay for progesterone in which a radioligand of tritiated progesterone and serum extraction are used. Progesterone values obtained by this procedure agreed well (r = 0.987) with those obtained by radioimmunoassay. We conclude that the chemiluminescence immunoassay for progesterone in unextracted serum is analytically valid and offers a convenient alternative to radioimmunoassay.
Measurement of gliclazide in plasma by radial compression reversed-phase liquid chromatography.
Authors: Charles B G , Ravenscroft P J
Published: January 2020

We describe a rapid, specific, and precise analysis for gliclazide in plasma by radial compression, reversed-phase, "high-performance" liquid chromatography. Gliclazide and the internal standard, 3-chlorogliclazide, are eluted after 4.4 and 6.8 min, respectively. Only 100 microL of plasma and minimal sample workup are required. The limit of detection for gliclazide in plasma is 0.5 mg/L (1.55 mumol/L) at 229 nm. Precision (CV) of the assay for 10 and 1 mg of gliclazide per litre is 2.1% and 6.4%, respectively.
Effects of sample preparation on concentrations of cyclosporin A measured in plasma.
Authors: Yatscoff R W , Rush D N , Jeffery J R
Published: January 2020

Because cyclosporin A rapidly changes its distribution in blood with changes in temperature, sample preparation affects results for it as measured in plasma. If whole blood is stored at either 4 degrees C or room temperature, results for cyclosporin A in the plasma are lower than in whole blood stored at 37 degrees C and centrifuged at this temperature. Re-equilibration of the former to 37 degrees C before cells are removed increases the analytical recovery of cyclosporin A in plasma; the optimal equilibration interval is 30 min. Use of such re-equilibration, followed by immediate centrifugation at room temperature, increases values obtained for cyclosporin in plasma by 60 to 65% over those determined after non-temperature-standardized collection procedures, but does not significantly improve the correlation between values for plasma and whole blood. Hematocrit and concentrations of cyclosporin A in plasma are inversely related. Correction for hematocrit improves the correlation between results for plasma and whole blood.
Enzyme immunoassay for pregnancy-associated plasma protein-A.
Authors: MacDonald D J , Mehta H C , Mack D S , Duffy T , Glen A C
Published: January 2020

This enzyme immunoassay procedure for pregnancy-associated plasma protein type A involves a "sandwich"-type system in microtitration plates. One can detect 0.27 mg of the protein per liter of serum, with a between-batch CV of 10.2%, and the antiserum used does not cross react with any of the other placentally derived proteins. A reference interval for the last trimester of pregnancy is presented. The procedure described is suitable for studying the behavior of this protein during pregnancy.
Two-dimensional electrophoresis and "ultrasensitive" silver staining of cerebrospinal fluid proteins in neurological diseases.
Authors: Harrington M G , Merril C R
Published: January 2020

Cerebrospinal fluid (CSF) proteins, as resolved by two-dimensional electrophoresis and made visible by silver staining, have been examined in patients with various neurological diseases and normal volunteers. The patterns for 15 of 20 patients with Parkinson's disease showed a protein (Mr 25 000) with charge similar to albumin, which was not seen in the patterns for any of 91 normal volunteers. Patterns for 21 of 22 multiple sclerosis patients showed novel immunoglobulin light chain proteins, also not present in the CSF of any normal volunteers. Quantitative analysis by computer-assisted densitometry in Parkinson's disease and multiple sclerosis showed that 20 of 68 and 33 of 85 proteins, respectively, were significantly altered as compared with proteins in the normal population. This ability to characterize both Parkinson's disease and multiple sclerosis molecularly provides a broad baseline for improved clinical diagnosis and may serve as an aid in exploring the underlying pathophysiology. These studies illustrate the potential of applying this methodology in the study of neurological diseases.
An attempt to resolve all the various proteins in a single human cell type by two-dimensional electrophoresis: I. Extraction of all cell proteins.
Authors: Klose J , Zeindl E
Published: January 2020

A concept is presented for estimation of the total number of different proteins in a single human cell type (exemplified here by Hep cells) by use of two-dimensional electrophoresis (2DE). This concept includes three problems, the first, investigated in this study, being the transfer of all protein species of the cells into a sample useful for separation by 2DE. Five different extraction media containing--in various combinations--urea, Nonidet P-40, Zwittergent, mercaptoethanol, dithiothreitol, and sodium dodecyl sulfate were used step by step in three different extraction procedures to extract the cell proteins. The amount of radiolabeled proteins in each extract was measured. Each extract was subjected to 2DE. From the total mass of cell proteins, 99.99% could be extracted in two steps: 96% were extracted with urea/beta-mercaptoethanol solution, the remaining 4% with sodium dodecyl sulfate/urea/beta-mercaptoethanol solution. A special class of proteins assumed to be present in the latter fraction was not detected. Thus this fraction can be omitted from the further analysis of all cell proteins by 2DE. Protein classes that possibly remain undetected by the described extraction procedures are mentioned.
Two-dimensional gel pattern of proteins synthesized de novo in lymphoid organs of the mouse.
Authors: Pluschke G , Lefkovits I
Published: January 2020

Mice were injected intravenously with 1 mCi of [35S]methionine, and serum and tissue were sampled 4 h later. Serum and lymphoid and non-lymphoid tissues had all incorporated enough labeled methionine to allow radiofluorographic detection on two-dimensional gels of proteins synthesized de novo and, by comparing radiofluorographs, we could distinguish spots peculiar to a given tissue from others more ubiquitous. We selected a protein of 17-kDa apparent molecular mass and pl about 4 to demonstrate tissue specificity. All patterns obtained for thymus samples yielded this spot; in all other immunologically relevant sites it was missing or weak. It also was not detected on gels previously obtained from lymphocyte subpopulations biosynthetically labeled in vitro. The labeling method described here will be especially helpful for characterizing cell populations that cannot be radiolabeled under cell-culture conditions. In contrast to detection methods that detect all proteins of a sample, in vivo labeling allows specific recognition of de novo synthesized proteins. Therefore it will facilitate comparison and detection of proteins produced by an animal in response to a given treatment.
Advantages of separations on "giant" two-dimensional gels for detection of physiologically relevant changes in the expression of protein gene-products.
Authors: Young D A
Published: January 2020

"Giant" 2-D gel electrophoretic protein separations (Methods Enzymol 91, part I, 190-214, 1983) offer a significant increase in resolving power over the usual methods. The increased capacity (good resolution up to 1 mg and as much as 10 mg of sample can be applied) and the improvement in resolution reveal some 3000 individual proteins when whole-cell extracts from diverse sources are separated on broad-range (pH 4.5-7.5) isoelectric-focusing (IEF) gels, and an additional 2000 when non-equilibrium and lower pH range IEF gels are also run. When applied to several types of steroid target cells, the giant-gel methods have allowed detection, among the minor protein species not resolved on standard-size gels, of a group of rapidly evolving (within the first 30 min or so) adrenal glucocorticoid inductions. These are likely mediators of the characteristic hormone effects. The giant gels have also greatly expanded the range of changes in protein gene-products in response to heat shock, growth factors, and retrovirus-induced malignant transformation, and should substantially enlarge the number of protein polymorphisms useful in genetic studies for linkage mapping.
Normal reference interval for thyrotropin response to thyroliberin: dependence on age, sex, free thyroxin index, and basal concentrations of thyrotropin.
Authors: Erfurth E M , Nordén N E , Hedner P , Nilsson A , Ek L
Published: January 2020

We measured the thyrotropin response (delta TSH) to 200 micrograms of thyroliberin in 131 subjects without thyroid dysfunction or other disease and with basal values for thyroid function that were within the normal reference intervals for our laboratory. By univariate and multivariate statistical methods we found delta TSH to be significantly influenced by the basal concentration of thyrotropin (TSH0) and the free thyroxin index (FT4I). When the effects of variations in TSH0 and FT4I were eliminated, delta TSH in men under 40 years of age did not differ from that in women. A decrease in delta TSH with increasing age was found in men but not in women. Thus a reference interval for delta TSH should consider TSH0, FT4I, and, in men, age. On the basis of multiple linear regression analysis, we constructed a formula for delta TSH reference intervals that takes into account individual values for TSH0 and FT4I. The formula should be applicable for women, regardless of age, up to 77 years and for men under 40 years. For older men a correction for the age-related decrease in delta TSH must be applied.
Performance characteristics and diagnostic value (vs other tests) of two radioimmunoassay kits for estimating free triiodothyronine in serum.
Authors: Wilke T J , Sheedy T J , Hirning D A
Published: January 2020

We compared the clinical value of "Amerlex" (Amersham International) and "Pre-release Coat-A-Count" (Diagnostic Products Corp.) radioimmunoassay kits for free triiodothyronine with that of triiodothyronine, triiodothyronine/thyroxin-binding globulin ratio, and free triiodothyronine index in patients with thyroid disease, pregnant women, oral contraceptive users, thyroxin-binding globulin-deficient subjects, and patients receiving phenytoin. Assay of free triiodothyronine in hyperthyroidism provided diagnostic information similar to that from the indirect indices, whereas the free triiodothyronine index was the most sensitive index of hypothyroidism. With respect to diagnostic value, free triiodothyronine assay was comparable with the free triiodothyronine index and superior to triiodothyronine assay and the triiodothyronine/thyroxin-binding globulin ratio in correcting for alterations in thyroid-hormone binding capacity. In neither kit for free triiodothyronine was the equilibrium between bound and free hormone significantly disturbed during assay. Overall, as a diagnostic index of thyroid status, free triiodothyronine is as good as the free triiodothyronine index and better than either triiodothyronine or the triiodothyronine/thyroxin-binding globulin ratio.
Quantitation of lactate by a kinetic method with an extended range of linearity and low dependence on experimental variables.
Authors: Hamilton S D , Pardue H L
Published: January 2020

We report conditions and characteristics of a new kinetic method for measuring lactate. Using a multiple linear regression method, we fit data for absorbance and for rate of change of absorbance to a modified rate form of the Michaelis-Menten equation. The principal objective of the fitting process is to compute the total absorbance change, delta A infinity, that would be measured if the reaction were monitored from the point of mixing to equilibrium. For data collected at 1-s intervals from 5 to 200 s, the fitting process gives values of delta A infinity that vary linearly with lactate concentration from 10.6 to 180 mumol/L in the reaction cell after 150-fold dilution of samples. For a range of enzyme activities that produced a 20% change in the initial rate, the regression-kinetic treatment yielded results with no detectable systematic error. The mean within-day CV was 2.1% for an average concentration of 14.4 mmol/L; the day-to-day CV was 5.2% for 3.90 mmol/L. For 25 samples of canine plasma with lactate concentrations from 2 to 26 mmol/L, comparison of results obtained with the regression-kinetic method (y) with results obtained with a commercially available equilibrium method (x) gave a least-squares equation of y = 1.01x - 10 mumol/L.
Immunonephelometry of apolipoprotein A-II in plasma.
Authors: Rosseneu M , Vinaimont N , Musliner T A , Bernier D , Herbert P N , Belpaire F
Published: January 2020

A quantitative assay based on endpoint immunonephelometry was developed for human apolipoprotein A-II (apoA-II) in plasma or serum. Dilution of plasma samples with a 0.1 mol/L solution of sodium cholate enhanced the quantification. We used either purified apoA-II as the primary standard or plasma as a secondary standard. Results correlated well (r = 0.90) with those by a double-antibody radioimmunoassay for 63 serum samples from both normal and hyperlipemic individuals. The interassay coefficient of variation for the immunonephelometric assay was 7% within a working range between 0.05 and 0.7 microgram of apoA-II per sample (corresponding to a 1500-fold final dilution of serum). No extraction of samples with organic solvent is necessary if the triglyceride concentration is less than 4 g/L.
Determination of inorganic sulfate in plasma with a centrifugal analyzer.
Authors: Pascoe P J , Peake M J , Walmsley R N
Published: January 2020

Turbidimetry of inorganic sulfate, after precipitation with barium sulfate, can be done simply in a Cobas Bio centrifugal analyzer. Polyethylene glycol is used as the precipitate-stabilizing agent. Reproducibility of precipitation is enhanced by the presence of BaSO4 particles, which function as seed nuclei. There is no interference by normal or above-normal concentrations of phosphate, heparin, bilirubin, hemoglobin, or erythrocyte contents, or by lipemia (triglyceride concentrations up to 6.5 mmol/L). Analytical recovery of added inorganic sulfate was found to be quantitative. Precision is similar to that for other methods for inorganic sulfate in plasma. This method is suitable for the rapid, routine analysis of plasma inorganic sulfate, and it is simple and less expensive to perform than alternative methods.
Effect of contrast media on radioimmunoassay of beta-endorphin in cerebrospinal fluid.
Authors: Fang V S , Fessler R G , Rachlin J R , Brown F D
Published: January 2020

An effect of metrizamide, a contrast medium, on results of beta-endorphin radioimmunoassay was examined. We found that 1, 5, and 10 microL of the medium added to 100 microL of standard containing 0 to 500 pg of beta-endorphin shifted the standard curve to the left in proportion to the metrizamide concentration. Three other contrast media showed a similar effect at low concentrations of beta-endorphin. This effect of contrast media artificially increased results in radioimmunoassay of beta-endorphin in cerebrospinal fluid, the mean overestimate being 121.9% (range, 0 to 435%). For plasma samples, this effect of contrast media resulted in an average 11.7% overestimate of beta-endorphin (range, -16% to 41%). These observations bring into question the validity of a previous suggestion that an increase in beta-endorphin in cerebrospinal fluid after intracerebral electrical stimulation is the mechanism for stimulation-produced analgesia.
Sources of error in determinations of carnitine and acylcarnitine in plasma.
Authors: Fishlock R C , Bieber L L , Snoswell A M
Published: January 2020

Radioactive and nonradioactive L-carnitine and acyl-L-carnitine were used to evaluate the washing procedures used during the determination of free, total, short-chain, and long-chain acylcarnitine in human and sheep plasma. The volume of fluid trapped by the protein precipitated by perchloric acid is approximately 24% of the total fluid volume and thus contains 24% of free carnitine and short-chain acylcarnitine. Washing twice with distilled water removes about 25% of the long-chain acylcarnitine along with the trapped free carnitine and short-chain acylcarnitines. Washing the pellet twice with a 60 g/L solution of perchloric acid completely removes the trapped free carnitine and short-chain acylcarnitine but does not remove the bound long-chain acylcarnitines. Thus washing with perchloric acid is essential for accurate measurement of long-chain acylcarnitines in plasma samples.
Differentiating two forms of plasma lipase by use of media with different ionic strengths.
Authors: Arzoglou P L , Férard G , Métais P
Published: January 2020

Three different techniques of lipase (EC 3.1.1.3) determination (titrimetry, nephelometry, and enzyme immunoassay) were used to investigate an interesting effect of ionic strength on enzyme activity. Both activation in the presence of NaCl (140 mmol/L) and strong immunoinhibition were observed for lipase from plasma of subjects with acute pancreatitis. Another type of lipase, not associated with pancreatitis and only weakly immunoinhibited, showed maximum activity in the presence of 80 mmol/L NaCl. The pancreatitis-type lipase was activated by 140 mmol/L NaCl solution only if colipase and sodium deoxycholate were also present, which suggests that these components are cofactors in the activating effect and confirms the specificity of this property. These findings can be exploited to improve the diagnosis of acute pancreatitis.
Changes in sodium and uric acid concentrations in plasma during the menstrual cycle.
Authors: Mira M , Stewart P M , Gebski V , Llewellyn-Jones D , Abraham S F
Published: January 2020

Hormonal changes during the menstrual cycle are well documented, but many other biochemical variables have not been studied. We find that in the luteal phase of the menstrual cycle the concentrations of sodium and uric acid are significantly lower. The changes may be of significance for the determination of the normal reference interval.
Progress report on a national quality-control survey of triiodothyronine and thyroxin assay.
Authors: Zucchelli G C , Pilo A , Chiesa M R , Piro M A
Published: January 2020

In January 1980, a national external quality-control survey was organized to evaluate assays for triiodothyronine (T3) and thyroxin (T4). Currently, about 150 laboratories are involved. Each participant has received and assayed 100 quality-control samples during four periods of about six months each. The average analytical performance achieved by the participants in each six-month period was estimated by computing the average between-laboratory agreement (CVT), the overall average bias, and the average laboratory imprecision. During the 2.5 years of the survey, analytical performance has improved for both assays (CVT decreased from 17.0 to 15.7% for T3 and from 13.1 to 12.7% for T4). Analysis of survey results according to the method/kit used (mean kit bias and kit imprecision for the nine kits most used by participants) showed that the analytical reliability of the T4 assay is generally better than that observed for T3, mainly because of the larger systematic differences among T3 kits.
An international comparison of vitamin D metabolite measurements.
Authors: Jongen M J , Van Ginkel F C , van der Vijgh W J , Kuiper S , Netelenbos J C , Lips P
Published: January 2020

An international 19-laboratory survey was organized to compare assays for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D in plasma. Each participant received two ethanolic standard solutions of each metabolite and eight plasma samples. Each laboratory used its usual procedures. Mean interlaboratory coefficients of variation (CVs) for the eight plasma samples were 35%, 43%, and 52% for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D, respectively. Average CVs for the standard solutions were 27%, 23%, and 25%, respectively. Of the eight plasma samples, five had the same concentration for one of the metabolites. One sample was diluted to 0.6 times its original concentration and three samples were fortified with one or more of the metabolites under investigation. Fourteen of 18 laboratories (78%) could distinguish between the five unchanged samples and the modified ones with their 25-hydroxyvitamin D assay. Nine of 12 (75%) could distinguish the modified samples from the other samples with the 24,25-dihydroxyvitamin D assay. Only eight of 15 (53%) could do this their 1,25-dihydroxyvitamin D assay. Values from different laboratories evidently cannot be intercompared without making an actual comparison of the assay procedures. Furthermore, in case of clinical applications of these assays, each laboratory should establish its own reference values and should continually use an internal reference sample to assess the precision of the procedures.
Profile of creatine kinase isoenzymes in skeletal muscles of marathon runners.
Authors: Apple F S , Rogers M A , Sherman W M , Costill D L , Hagerman F C , Ivy J L
Published: January 2020

The proportion of creatine kinase (CK; EC 2.7.3.2) isoenzyme MB activity was increased in skeletal muscle biopsies obtained from five long-distance runners, both 2 h before (mean 7.7%, SD 2.4%) and 30 min after (mean 7.2%, SD 1.2%) a marathon race, as compared with that in biopsies from five nonrunners (controls less than or equal to 1.0%). Further, mitochondrial CK and CK-BB isoenzymes were present in homogenates of the runners' skeletal muscle samples but not in those of the nonrunners. However, there were no substantial differences in the mean total CK activities per gram (wet wt.) of muscle tissue among premarathon samples, postmarathon samples, and nonrunners' samples (3148, 3365, and 3049 U/g, respectively). We conclude that the metabolically active gastrocnemius muscle of long-distance runners is qualitatively similar to the heart muscle in its CK isoenzyme composition.
Early detection of myocardial infarction by an immunoradiometric procedure for creatine kinase MB.
Authors: Dods R F
Published: January 2020

I investigated the diagnostic efficacy of the Embria-CK immunoradiometric assay (IRMA) in detecting myocardial infarction, using a single blood sample drawn at hospital admission 0 to 10 h after the onset of chest pain and serial testing over a 24- to 48-h interval after hospital admission. The sensitivity, specificity, and efficiency for hospital admission samples were 87.5, 83.3, and 85.0%, respectively, and for serial testing, 100, 79.2, and 87.5%, respectively. The diagnostic efficacy was comparable to that of electrophoresis and significantly better than the Du Pont CK-MB method.
Direct analysis for urinary protein with biuret reagent, with use of urine ultrafiltrate blanking: comparison with a manual biuret method involving trichloroacetic acid precipitation.
Authors: Eckfeldt J H , Kershaw M J , Dahl I I
Published: January 2020

We describe a method for measuring urinary protein with a centrifugal analyzer. Biuret reagent is used, and blanking with an ultrafiltrate of urine eliminates interferences from the nonprotein, biuret-positive chromogens in urine. We compare results by this new method with those by a manual method in which trichloroacetic acid precipitation and biuret reagent are used. The new method shows good precision and excellent correlation (r = 0.997) with the manual method. The ease and convenience of this assay should make this a useful method for the routine clinical laboratory.
Neutral carrier electrode for continuous measurement of blood Ca2+ in the extracorporeal circulation.
Authors: Anker P , Ammann D , Meier P C , Simon W
Published: January 2020

A neutral-carrier-based Ca2+-selective electrode exposed to whole blood exhibited an EMF-stability better than 0.13 mV (approximately 1% change of the initial activity) during 3.7 to 6.6 h. It has been used successfully to monitor ionic Ca2+ in the extracorporeal circulation during administration of calcitonin to dogs. Data simulation shows that the apparent concentration of ionic Ca2+ is affected by the concentration of Na+. A variation in [Na+] by +/- 5 mmol/L from a value of 143 mmol/L used for the calibration leads to uncertainties of +/- 0.8% in the Ca2+ concentration and +/- 0.2% in the Ca2+ activity if 3 mol/L KCl is used as the reference electrode solution. When an isotonic solution was used as reference electrolyte, errors of +/- 0.8% and +/- 1.7%, respectively, were observed.
A densitometer based on a microcomputer and TV camera, for use in the clinical laboratory.
Authors: Tracy R P , Young D S
Published: January 2020

We describe a microcomputer-based densitometer that includes a television camera for the analysis of one- and two-dimensional electrophoresis gels. The hardware configuration is a modification of that described by Mariash et al. (Anal Biochem 212: 388-394, 1982). The video signal is digitized by a commercially available interface, yielding 1 of 64 greyscale values for each pixel examined. The operator controls the region being analyzed through the use of a joystick and video monitor. We have optimized the linear response range (0-1.5 A) and have written a relatively simple control program ("GELSCAN 5.0"). For analyses of one-dimensional gels, the required operator decisions include the start and finish points of the gel, the width of the scan (analogous to slit size), and the level of background correction. The digital information may be stored on disk, displayed by one of several graphic routines, and analyzed for total scan and individual peak absorbance values. Similar analyses may be done with two-dimensional gel spots.
Effect of use of gel-barrier sampling tubes on determination of some antiepileptic drugs in serum.
Authors: Bergqvist Y , Eckerbom S , Funding L
Published: January 2020

We evaluated the effect on drug concentration of the duration of sample storage in three different tubes for blood collection: SST (Becton Dickinson), AutoSep (Terumo), and Microvette (Sarstedt), all of which contain an inert barrier (e.g., gel) for cleaner separation of serum from coagulum during centrifugation. With two of the tubes (SST and AutoSep) we examined samples taken from patients undergoing treatment with phenobarbital, phenytoin, and carbamazepine. We found significant decrease in the drug, concentration after 24 h with the serum standing over the gel barrier in the SST tubes for phenobarbital and both the SST and AutoSep tubes for carbamazepine. Adding aqueous drug solutions or serum samples supplemented with the above drugs in therapeutic concentrations to the three types of tubes resulted in a more pronounced decrease of concentration in the SST and Auto-Sep tubes than in the Microvette tubes.
Acetaldehyde-hemoglobin adducts: an unreliable marker of alcohol abuse.
Authors: Homaidan F R , Kricka L J , Clark P M , Jones S R , Whitehead T P
Published: January 2020

Acetaldehyde reacts with hemoglobin in vitro to produce acetaldehyde-hemoglobin adducts, but we could not detect these in the blood of 20 alcoholics, either by cation-exchange chromatography or agar gel electrophoresis. Thus, contrary to previous reports, this test is not a reliable marker of alcohol abuse. Nuclear magnetic resonance and gas chromatographic-mass spectroscopic analysis of acetaldehyde revealed the presence of aldehydic impurities. Formation of adducts in vitro may thus result from the reaction of hemoglobin with these impurities or with acetaldehyde condensation products (aldol) or from acetaldehyde condensation/dehydration products (crotonaldehyde).
Enzymic colorimetric determination of phosphatidylglycerol in amniotic fluid.
Authors: Artiss J D , McGowan M W , Strandbergh D R , Epstein E , Zak B
Published: January 2020

We describe a procedure for the enzymic, colorimetric determination of phosphatidylglycerol in amniotic fluid. After extraction into chloroform:methanol (2:1 by vol) and evaporation, the phospholipid-containing residue is redissolved in a non-ionic detergent, which thus provides an aqueous sample. The subsequent enzymic reaction sequence involves phospholipase-catalyzed hydrolysis of glycerol from its phospholipid. Subsequent enzyme-catalyzed reactions phosphorylate this glycerol and oxidize the resulting glycerol phosphate to produce hydrogen peroxide, which is reacted to produce an intense red chromogen in the peroxidase-catalyzed coupling of 4-aminoantipyrine and 2-hydroxy-3,5-dichlorobenzenesulfonate. When used in conjunction with previously reported enzymic techniques for determination of lecithin and sphingomyelin, this procedure may provide an accurate and precise "lung profile" for assessment of fetal lung maturity.
Iodination of thyroliberin by use of Iodogen.
Authors: Butler S R , Lam R W , Fisher D A
Published: January 2020

In this method of labeling thyroliberin for radioimmunoassay, 1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril (Iodogen) is used as oxidant. By cation-exchange chromatography and in response to antibody, thyroliberin so labeled behaved similarly to that produced by the conventional Chloramine-T method. Major advantages of the Iodogen method are its reliability, simplicity, and higher yield of stable RIA label in its most convenient (diiodinated) form.
Effects of storage temperature and time before centrifugation on ionized calcium in blood collected in plain vacutainer tubes and silicone-separator (SST) tubes.
Authors: Toffaletti J , Blosser N , Kirvan K
Published: January 2020

We studied the stability of ionized calcium and pH in samples stored at either room temperature or 4 degrees C, in centrifuged and uncentrifuged blood-collection tubes and in centrifuged tubes containing a silicone-separator gel (SST tubes). At room temperature, in uncentrifuged blood from healthy individuals, mean ionized calcium usually increased no more than 10 mumol/L per hour; at 4 degrees C it did not change detectably for 70 h. This stability was fortuitous, however: the concentrations of both hydrogen and lactate ions in these samples increased, apparently with offsetting effects on the concentration of ionized calcium. Blood stored for 70 h at 4 degrees C in centrifuged SST tubes, although showing a slightly greater change in ionized calcium, had less change of pH and no change in the ionized calcium corrected to pH 7.4. In 11 heparinized whole-blood samples from eight patients in intensive care, the mean change per hour in ionized calcium and pH after storage at room temperature was +10 mumol/L and -0.04 units, respectively.
Interrelationships among body mass, thyrotropin, thyroid hormones, and thyroid-hormone binding proteins in healthy 70-year-old men.
Authors: Edén S , Jagenburg R , Lindstedt G , Lundberg P A , Mellström D
Published: January 2020

In a previous study of a representative population of 460 men of age 70, we found that the free thyroxin (free T4) concentration was negatively correlated to body mass. In the present study we analyzed other indicators of thyroid function in relation to body mass and body mass index in 181 individuals without any disease or medication influencing thyroidal homeostasis or body mass. There was a significant negative relationship between body mass and body mass index and free T4, total T4, and 3,3',5'-triiodothyronine (rT3). Thus, individuals with high body mass normally had lower circulating concentrations of these hormones than lean individuals, whereas there was no such relationship for thyrotropin or 3,5,3'-triiodothyronine (T3). The thyroid-hormone binding proteins (thyroxin-binding globulin, prealbumin, and albumin) did not correlate with body mass or body mass index. As expected, thyroxin-binding globulin correlated with T4, T3, and rT3, but not with free T4 or thyrotropin. Concentrations of serum albumin correlated with T3 and rT3 concentrations but not with free T4, T4, or thyrotropin concentrations. Thyrotropin concentrations correlated negatively with free T4, T4, and rT3, but not with T3, indicating that circulating T4 plays the dominant role in feedback regulation of thyrotropin in healthy individuals.
Transferability studies for the AACC reference method and the IFCC method for measurement of alkaline phosphatase activity.
Authors: Tietz N W , Rinker A D , Burtis C , Duncan P , Ervin K , Ewen L , Hørder M , Mathieu M , Petitclerc C , Grisley D
Published: January 2020

We present the results of measurements of alkaline phosphatase activity from interlaboratory transferability studies conducted by 12 laboratories in five countries. The variability, as demonstrated by within-day precision (CV less than or equal to 2.6%), between-day precision (CV less than or equal to 3.6%), and between-lab precision (CV less than or equal to 6.3%) establishes the transferability of this method for alkaline phosphatase. Some common errors encountered in enzyme measurements that affect the accuracy and precision of the measurements are listed.
Removal of a component interfering with phosphatidylglycerol estimation in the "Helena" system for amniotic fluid phospholipids.
Authors: Spillman T , Cotton D B , Lynn S C , Bretaudiere J P
Published: January 2020

A simple " prechromatography " step removes a component of amniotic fluid ("pseudo PG") that otherwise co-chromatographs with phosphatidylglycerol in the system for amniotic fluid analysis developed by Touchstone et al. (Lipids 15: 61-62, 1980) and incorporated into the Helena "Fetal-Tek" kit. The final positions of the major phospholipids are practically unchanged but the faster migrating, more neutral components are swept into a tight band near the solvent front, providing improved general resolution. The resulting change in the ratio of "phosphatidylglycerol" to sphingomyelin ("PG"/S) is as much as 0.5 for some specimens, but no change is seen for others. In 20% of the 73 cases examined, including four of the six fluids associated with respiratory distress syndrome, the PG initially reported was found to be "pseudo PG" and was completely removed by the prechromatography step. This step produces a negligible decrease in the lecithin to sphingomyelin (L/S) ratio in amniotic fluid.
Screening for macroamylase in a community hospital.
Authors: Isham C A , Ridgeway N A , Hedrick R , Cate J C
Published: January 2020

We evaluated the polyethylene glycol precipitation test (Gastroenterology 83: 378-382, 1982), looking for macroamylase in the serum of 66 patients whose values for serum amylase were above normal. Three patients (4.5%) were identified by this method as having macroamylase , and this was confirmed by gel-filtration chromatography and electrophoresis. We find this to be the test of choice as a screening procedure for macroamylasemia because of its speed, simplicity, and apparent reliability. Diagnosis of macroamylasemia is important in preventing needless treatment and investigation for pancreatitis.
Relationship of potassium and magnesium concentrations in serum to cardiac arrhythmias.
Authors: Boyd J C , Bruns D E , DiMarco J P , Sugg N K , Wills M R
Published: January 2020

Low concentrations of potassium and magnesium in serum have been implicated in cardiac arrhythmias; the importance of mild hypokalemia or hypomagnesemia is uncertain. To investigate possible associations among use of diuretics, the concentration of these ions in serum, and the onset of clinically important arrhythmias, we reviewed records of 103 patients admitted to our Coronary Care Unit during three months and found mild to moderate hypokalemia and hypo- magnesemia in 18 and 24%, respectively. The significant correlation between the concentrations of magnesium and potassium in serum at admission (r = 0.27, p less than 0.007) remained constant in patients, whether they were receiving diuretics or not. Potassium concentrations were significantly lower (p less than 0.05) in patients receiving diuretics (3.93 mmol/L) than in those who were not (4.21 mmol/L), but the mean concentrations of magnesium did not differ significantly. Except for myocardial infarction, no single variable or combination of variables was highly predictive of cardiac arrhythmias in these patients. We conclude that there is no strong predictive relationship between mildly decreased concentrations of magnesium or potassium in serum and onset of cardiac arrhythmias.
Values of the U.S. National Reference Serum for human antibodies to native DNA obtained with commercial immunoassays for anti-DNA in systemic lupus erythematosus.
Authors: Berne B H , Galland K T , Welton R C
Published: January 2020

The Arthritis Foundation and the Centers for Disease Control have recently prepared a "U.S. National Reference Serum" for human antibodies to native DNA. We tested this serum with 13 commercial assays for antibodies to native DNA, to permit comparisons of the values obtained in each test. Titers ranged from 10 to 2560 in Crithidia luciliae immunofluorescence assays. The serum produced 794 int. units/mL in the Cordis ELISA assay, 136 Amersham units/mL in a radioimmunoassay, and 88 FIAX units in a fluorometric immunoassay. These results can be used for interlaboratory comparisons of differing methodologies for measuring anti-DNA.
Six approaches to routine quantification of human monoclonal immunoglobulin M compared.
Authors: Pontet F , Auget J L , Rousselet F
Published: January 2020

Six routine techniques for the determination of monoclonal IgM are compared: standard electrophoresis, the Technicon AIP system, Hyland laser nephelometry, Beckman Immunochemistry System, Behring laser nephelometry, and radial immunodiffusion. The data are evaluated by use of a nonparametric statistical analysis of variance by ranks (Friedman test) and Wilcoxon's test. The 27 sera containing monoclonal IgM that we studied yielded different results by the various techniques. Sera from a "reference" population of 15 subjects having above-normal polyclonal IgM yielded identical results for all techniques. These statistical findings agree with the biophysical mechanisms involved in the various ways of quantifying IgM. We conclude that these different systems are equivalent for estimating polyclonal IgM, but cannot (and should not) yield identical values when used in monoclonal IgM evaluations. Results for monoclonal IgM must be interpreted in terms of the molecular forms and immunological specificities of the assayed IgM.
Estimation of free thyroxin with a new thyroxin analog and a porous-glass solid phase.
Authors: Witherspoon L R , Shuler S E , Gilbert S S
Published: January 2020

We evaluated a new thyroxin analog-based assay for free thyroxin (FT4) (Corning Medical), finding it technically simple and precise (between-assay CVs of 3.3 and 4.2% for FT4 concentrations of 12 and 25 ng/L, respectively). We measured FT4 in a total of 325 serum samples from euthyroid patients; patients receiving replacement thyroxin; patients receiving estrogens or who were pregnant; hyperthyroid, hypothyroid, and non- thyroidally ill patients; and patients receiving salicylates, phenytoin, or heparin. This assay clearly identified hyper- and hypothyroid patients, and produced similar results in euthyroid patients with above-normal, normal, or low concentration of thyroxin-binding globulin. Results in some non-thyroid-illness patients and patients receiving salicylates or phenytoin were low compared with euthyroid patients receiving no medications, but the diagnostic accuracy of the Corning FT4 assay exceeded that of another analog-based assay (Amersham) in these particular groups. We believe the new Corning analog FT4 assay offers an attractive alternative to other commercial FT4 systems.