bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved preparation of hepatic microsomes for in vitro diagnosis of inherited disorders of the glucose-6-phosphatase system
Authors: Coughtrie M W , Blair J N , Hume R , Burchell A 
Published: January 2020

Abstract
Disruption of microsomal membranes after freezing liver samples can undermine the reliability of in vitro enzymatic diagnosis of the type 1 glycogen storage diseases. However, freezing of biopsy material is necessary if biopsy samples are to be safely transported to the place of assay. We have therefore examined several different methods (each of which could easily be carried out in routine hospital laboratories) of preparing and freezing liver tissue before analysis for glucose-6-phosphatase (EC 3.1.3.9) enzyme activity, and determination of microsomal intactness. Our study showed that homogenizing fresh liver, and centrifuging the homogenate at 10,000 x g for 10 min at 4 degrees C, followed by freezing the resulting supernatant material at -80 degrees C, provided the optimum source of material for subsequent preparation of microsomes for analysis of glucose-6-phosphatase activity. We also demonstrated that 1-naphthol UDP glucuronosyltransferase (EC 2.4.1.17) activity could be used to assess microsomal intactness in cases of type 1a glycogen storage disease, where mannose-6 phosphatase activity cannot be used.
Choriogonadotropin-mediated thyrotoxicosis in a man
Authors: Cain Heather J , Pannall Peter R , Kotasek Dusan , Norman Robert J 
Published: January 2020

Abstract
A 38-year-old man with a metastatic gonadotropin-secreting tumor of unknown primary origin presented with both clinical and biochemical findings of hyperthyroidism in association with markedly increased concentrations of human choriogonadotropin (hCG) in plasma. After chemotherapy, the concentrations of both hCG and free thyroxin decreased and the patient became euthyroid. We discuss the rare occurrence of this presumably hCG-driven hyperthyroidism in men and compare it with the relatively more common eumetabolic hyperthyroidism associated with choriocarcinoma in women.
Quantitative fluorometric screening test for fecal porphyrins
Authors: Pudek Morris R , Schreiber William E , Jamani Azim 
Published: January 2020

Abstract
We describe a fluorometric method for screening and quantifying porphyrins in stool. A small sample of stool is extracted with concentrated HCI and is diluted 200-fold in 3 mol/L HCI before analysis. An excitation scan is done from 350 to 450 nm, monitoring emission at 603 nm. Total porphyrin is estimated at the isosbestic point for coproporphyrin and protoporphyrin (402.5 nm). Monitoring emission at 603 nm eliminates interference from chlorophyll, obviating the need for extraction with ether. The position of the excitation peak gives some indication of the nature of the porphyrins in the stool. The acid extract can be injected directly into an HPLC system for fractionation studies. Our method correlates well with the spectrophotometric method developed by Lockwood et al. (Clin Chem 1985;31:1163-7). However, in our method, the sample is easier to process and the assay has higher sensitivity than their assay. The reference interval for porphyrin in healthy individuals by the fluorometric method is less than 300 nmol/g dry weight. We can detect as little as 1 nmol of porphyrin per gram (dry weight) of stool. Results of the method vary linearly with stool porphyrin concentrations as great as 4000 nmol/g dry weight. The within-run imprecision of the method is 3%.
Single-spin density-gradient ultracentrifugation vs gradient gel electrophoresis: two methods for detecting low-density-lipoprotein heterogeneity compared
Authors: Dormans Tom P J , Swinkels Dorine W , de Graaf Jacqueline , Hendriks Jan C M , Stalenhoef Anton F H , Demacker Pierre N M 
Published: January 2020

Abstract
Single-spin density-gradient ultracentrifugation (DUC) has proven to be a reproducible method for detection of low-density-lipoprotein (LDL) heterogeneity. Recently another method has been described for this: gradient gel electrophoresis (GGE) of serum, a method that might be more suitable for screening. To gain insight into the relationship of GGE to DUC and into their reproducibility, we determined LDL heterogeneity by DUC and GGE in 41 healthy individuals. In 90.2% (n = 37) of the subjects, the number of LDL subfractions found by both methods agreed. In addition, the density and the relative migration distance of the predominant LDL subfraction observed with the respective methods showed a strong correlation (Pearson correlation, r = 0.85, P less than 0.0001). Although it was not possible to compare for all aspects of LDL heterogeneity, these data suggest that GGE is a valid method of analysis for LDL heterogeneity. In screening programs, it may be necessary to store samples. Therefore, we studied in 24 sera the influence of storage at -80 degrees C for one, four, and 12 weeks on the LDL subfraction distribution detected by each method. LDL heterogeneity was maintained during storage under these conditions.
Five treatment procedures evaluated for the elimination of ascorbate interference in the enzymatic determination of urinary oxalate
Authors: Inamdar Kalpana V , Raghavan Keddy G , Pradhan Dinkar S 
Published: January 2020

Abstract
We evaluated the efficacies of five treatment procedures for eliminating ascorbate interference in the enzymatic determination of urinary oxalate. Aliquots of urine samples, containing different amounts of added ascorbate and oxalate, were individually subjected to ferric chloride, sodium nitrite, sodium periodate, charcoal, or ascorbate oxidase treatment to eliminate ascorbate interference. Oxalate contents of the urine samples were then determined by a banana oxalate oxidase-horseradish peroxidase-linked assay with 3-methyl-2-benzothiazolinone hydrazone and 3-(dimethylamino)benzoic acid as chromogens. Only those urine samples treated with ascorbate oxidase or charcoal consistently gave recovery of oxalate close to 100%. Treatment with other reagents, though improving the recovery of oxalate, gave inconsistent results. On the basis of these data, we describe procedures for simply and reliably assaying oxalate by using banana oxalate oxidase.
Age- and sex-related differences for the urinary excretion of norepinephrine, epinephrine, and dopamine in adults
Authors: Gerlo Erik A M , Schoors Danny F , Dupont Alain G 
Published: January 2020

Abstract
Using a specific high-performance liquid-chromatographic method, we measured norepinephrine, epinephrine, and dopamine in 24-h urine collections from 459 men and 497 women, ages 17 to 88 years. We found a significant negative correlation between age and the 24-h excretion of dopamine in men and women (P less than 0.001). Epinephrine excretion decreased with age in men (P less than 0.001). No age dependence was observed for norepinephrine (P greater than 0.2). The excretion of all three catecholamines, expressed in nmol/24 h, was significantly greater in men than in women. The differences, however, were small. With data expressed in nmol/g of creatinine, only epinephrine excretion was greater in men; norepinephrine and dopamine excretions were slightly greater in women. Also, expressed in these units, urinary excretion of norepinephrine in both sexes and of epinephrine in women was significantly positively related with age; urinary excretion of dopamine was significantly inversely related to age in women, but not in men. Reference values are provided for age-independent variables in both sexes.
Defects in diagnostic kits for determination of urate in serum
Authors: Whitehead T P , Bevan E A , Miano L , Leonardi A 
Published: January 2020

Abstract
Certain diagnostic kits that measure serum urate by the Barham and Trinder principle of enzymic liberation of oxygen and its combination with chromogens can give results for urate in fresh serum that are approximately 20% lower than results from serum stored at ambient temperature for 72 h. In fresh serum, antioxidants compete with chromogen for liberated peroxyl-oxygen. We postulate that during storage the interfering antioxidant substances are destroyed. In some diagnostic kits, L-ascorbate oxidase is added to the reaction, eliminating some but not all of this effect. We discuss defects of several commercially available kits for determination of serum urate and recommend comparing results of these kits with results from the phosphotungstic acid method as a precaution against falsely low results.
Quantification of virus-specific antibodies in cerebrospinal fluid and serum: sensitive and specific detection of antibody synthesis in brain
Authors: Reiber Hansotto , Lange Peter 
Published: January 2020

Abstract
Specific antibody synthesis in brain could be detected with maximal sensitivity by combining an advanced enzyme immunoassay with a sophisticated evaluation method that involves calculating the ratio between the cerebrospinal fluid (CSF)/serum quotients for specific antibodies (Qspec) and total IgG (QIgG). This Antibody Index (AI = Qspec/QIgG) discriminates between a blood-derived and a pathological, brain-derived specific antibody fraction in CSF and takes into account individual changes in blood/CSF barrier function. For local synthesis of polyclonal IgG in the central nervous system (QIgG greater than QLim), we propose the correction AI = Qspec/QLim (QLim represents that IgG fraction in CSF originating only from blood, calculated from the individual albumin quotient of a single patient). The normal reference range for the AI was between 0.7 and 1.3 (n = 250 control patients for each antibody species). Values of AI greater than or equal to 1.5 indicated a local specific antibody synthesis in the central nervous system. Sensitivity and precision were greatest if we analyzed the virus-specific antibodies in CSF and serum simultaneously with an enzyme immunoassay in continuous concentrations (arbitrary units) instead of titer steps. We have applied the method successfully to antibodies to measles, rubella, herpes simplex, varicella-zoster, human immunodeficiency virus (HIV), and cytomegalovirus, and to anti-Toxoplasma or -Borrelia antibodies. Clinical relevance is demonstrated for an acute zoster virus infection (monospecific response), chronic diseases such as HIV encephalitis with acute opportunistic Toxoplasma infection, and multiple sclerosis (secondary polyspecific response).
Determination of serum cholesterol by isotope dilution mass spectrometry with a benchtop capillary gas chromatograph/mass spectrometer: comparison with the National Reference System's Definitive and Reference Methods
Authors: Eckfeldt John H , Lewis Linda A , Belcher John D , Singh Jasbir , Frantz Ivan D 
Published: January 2020

Abstract
We developed an isotope dilution mass spectrometric cholesterol method with [25,26,27-13C]cholesterol as internal standard and a benchtop gas chromatograph/mass spectrometer (GC/MS) that is much easier and less time consuming than previously described Reference and Definitive Methods for cholesterol. The internal standard, cholesterol standards, and unknown specimen are delivered volumetrically with an automated dilutor and the saponifying reagent. After saponification, extraction, and derivatization, specimens are injected into a benchtop quadrupole MS with an autosampler. Unknown cholesterol concentrations are calculated automatically by comparing the peak area ratio of the m/z = 368, 371 ion pair with the ratios for the cholesterol standards (0 to 12.93 mmol/L). We found within-run and day-to-day (overall) imprecision of 0.44% and 0.95%, respectively, when specimens were assayed singly. In several lyophilized and frozen Standard Reference Material (SRM) pools, cholesterol results with our GC/MS method averaged 0.4% less than the National Institute for Standards and Technology definitive GC/MS result performed about three years earlier. Our GC/MS results averaged 1.3% and 2.0% less than results by the National Reference System (NRS) Abell-Levy-Brodie-Kendall (ALBK) results from clinical specimens and the SRM pools, respectively. These results are consistent with the previously reported bias between the NRS Reference and Definitive Methods and the 0.1% per year decrease in cholesterol concentrations in SRM pools as determined by GC/MS analysis. These results further emphasize the small but consistent bias between cholesterol results by isotope dilution mass spectrometry and the ALBK Reference Method, the latter being the basis for the National Cholesterol Education Program guidelines and population reference values.
Effect of weight loss on serum lipoprotein(a) concentrations in an obese population
Authors: Corsetti James P , Sterry Judith A , Sparks Janet D , Sparks Charles E , Weintraub Michael 
Published: January 2020

Abstract
To assess the distribution of serum concentrations of the atherogenic lipoprotein(a) [Lp(a)] in an obese population and the possible effects of weight reduction, we determined Lp(a) in 52 white, moderately obese subjects (16 men and 36 women). The subjects were participating in a weight-reduction program of diet, exercise, and behavior modification plus combination anorectic drug therapy (fenfluramine and phentermine). This placebo-controlled, double-blind study lasted 104 weeks. We also determined concentrations of fasting insulin, triglycerides, total cholesterol, high-density lipoprotein cholesterol, apolipoprotein (apo) A-I, low-density lipoprotein cholesterol, and apo B. Results showed the following: a highly skewed, nongaussian distribution of serum Lp(a) values in the obese population, virtually identical to that reported for healthy adults; no clinically significant change in Lp(a) concentrations with weight loss; and further evidence of normalization of insulin, lipid, and lipoprotein concentrations with weight loss.
Massive overdoses with sustained-release lithium carbonate preparations: pharmacokinetic model based on two case studies
Authors: Friedberg Richard C , Spyker Daniel A , Herold David A 
Published: January 2020

Abstract
Clinically significant delayed absorption after lithium overdose has been reported previously without adequate explanation. We have studied two patients after they took massive intentional lithium overdoses. The first patient presented shortly after ingesting 74 g of lithium carbonate. Pharmacokinetic analysis with a multicompartmental model of 29 serum lithium concentrations during 300 h (including hemodialysis) established absorption and elimination kinetics. Lithium absorption was both slow (peak concentration 33 h after the initial overdose) and delayed (a second peak occurred at 148 h, 30 h after initiation of oral tube feedings). The delayed absorption of a large fraction of lithium implicated a gastrointestinal drug reservoir. Study of the pharmacokinetics in a second patient, who ingested 98 g of lithium carbonate, provided additional evidence of an endogenous reservoir. This patient's medical management was guided by experience gained from the initial case. Appropriate management for a predicted endogenous drug reservoir may have shortened intensive care and hospitalization. In treating overdoses of sustained-release drug preparations, clinically significant delayed absorption triggered by enteral fluids must be considered as a contributor to delayed absorption.
Modified enzyme-based colorimetric assay of urinary and plasma oxalate with improved sensitivity and no ascorbate interference: reference values and sample handling procedures
Authors: Wilson David M , Liedtke Robert R 
Published: January 2020

Abstract
The measurement of oxalate in urine and plasma continues to be difficult, particularly in the presence of ascorbate. We have modified and validated a colorimetric assay involving the use of oxalate oxidase (EC 1.2.3.4). Modification of an HPLC spectrophotometric detector improved sensitivity (to as much as 1000-fold that of conventional spectrophotometers) and allowed measurement of oxalate concentrations less than 1 mumol/L. This provided more than enough sensitivity for measurement of normal concentrations of plasma oxalate. We established reference values for oxalate concentrations in urine and plasma, studied sample handling, and established conditions to avoid ascorbate interference in urine and plasma measurements. Mean analytical recovery of [14C]oxalate from plasma to the filtrate was 86 (SD 10)%; recovery of unlabeled oxalate from filtrate was 87 (SD 9)%. Urinary oxalate excretion rates in apparently healthy controls were 0.11-0.46 mmol/24 h. Plasma concentrations in control subjects were 2.5 (SD 0.7) mumol/L, similar to concentrations determined by recent gas chromatographic and isotope dilution methods. Frozen and acidified urine samples showed no interference from ascorbate when excess ascorbate was avoided. Ingestion of 2 g of ascorbate daily did not increase urinary oxalate in healthy control subjects, but during storage ascorbate was converted to oxalate in all conditions tested.
Isocratic reversed-phase HPLC method to measure pyrimethamine extracted from plasma of infants treated for toxoplasmosis
Authors: Zytkovicz T H , Salter J , Hennigan L , Timperi R , Maguire J , Hoff R 
Published: January 2020

Abstract
An isocratic HPLC method for measuring pyrimethamine extracted from infant plasma is reported. The method is an improvement over previously published methods by requiring lower volumes of plasma (100 microL) and having increased sensitivity to pyrimethamine at 210 nm. The procedure, which entails a basic organic extraction and subsequent HPLC chromatography of the reconstituted extract, can detect 1.4 ng and quantify 4.0 ng of pyrimethamine per 40-microL injection, with two analyses per 100-microL sample. Analytical recovery of pyrimethamine added to plasma at 10, 50, and 125 ng/100 microL averaged 80%, 92%, and 101%, respectively (n = 20). Within- and between-day CVs were less than 7%. Studies of various plasma samples from adults and infants (n = 15) revealed no interference from other plasma peaks with the analyte of interest.
Serum profiles of steroid hormones in patients with Cushing's syndrome determined by a new HPLC/RIA method
Authors: Ueshiba H , Segawa M , Hayashi T , Miyachi Y , Irie M 
Published: January 2020

Abstract
We developed a method for simultaneously measuring steroid hormones in very small volumes of serum, using a combination of high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA). By this method, aldosterone, cortisol, 11-deoxycortisol, estrone, estradiol, androstenedione, dehydroepiandrosterone, deoxycorticosterone, 17-hydroxyprogesterone, testosterone, pregnenolone, and progesterone could be determined in a single 100-microL aliquot of serum from normal adults and patients with Cushing's syndrome. The steroid profile associated with Cushing's syndrome caused by adrenal adenoma was quite distinct from that associated with the syndrome caused by adrenal hyperplasia. Serum concentrations of androstenedione, dehydroepiandrosterone, estrone, estradiol, 17-hydroxyprogesterone, pregnenolone, and testosterone were significantly higher in patients with adrenal hyperplasia than in those with an adenoma. We compared the results of this HPLC/RIA method with those of 125I RIAs. The use of a HPLC/RIA system to obtain an accurate and sensitive profile of a range of serum steroids, as described here, obviates the need for large volumes of blood.
Predictive, error-compensating kinetic method for enzymatic quantification of creatinine in serum
Authors: Bacon B L , Pardue H L 
Published: January 2020

Abstract
Here we describe an error-compensating kinetic-based method for the enzymatic quantification of creatinine in serum. The method, which has a large linear range and very low dependency on experimental variables that influence enzyme activity, is based on the use of creatinine amidohydrolase in a four-step coupled reaction sequence to generate a product that is monitored photometrically. We collected data for absorbance vs time during two to four half-lives of each reaction and fit a first-order model to the data to compute the total absorbance change that would be measured if the reaction were monitored to completion. Computed values of absorbance change agreed well with measured values and varied linearly with creatinine concentration in the sample throughout the range examined: 44 to 1326 mumol/L. A twofold change in enzyme activity in the final reaction mixture (3.3 to 6.6 kU/L) produced changes of only 12% and 4% for creatinine concentrations of 44 and 353 mumol/L, respectively. Results (y) for 39 serum samples that contained creatinine concentrations between 20 and 1800 mumol/L agreed well with liquid-chromatographic results (x), yielding linear least-squares statistics of y = (1.03 +/- 0.01) x + (5 +/- 5) mumol/L (r = 0.995, Sy.x = 37 mumol/L). We conclude that the predictive kinetic approach is a robust method for the quantification of creatinine in serum.
Measurement of the ratio of lecithin to sphingomyelin in amniotic fluid by fast atom bombardment mass spectrometry
Authors: Shimizu A , Ashida Y , Fujiwara F 
Published: January 2020

Abstract
We describe a fast atom bombardment mass spectrometric method to determine the ratio of lecithin to sphingomyelin in amniotic fluid. Between m/z 400 and 1000, amniotic fluid extracts showed clear peaks for only sphingomyelin and lecithin. The molecular species of fatty acid in the phospholipids were analyzed quantitatively and quickly in a small volume of the extracts. The dipalmitoyllecithin/palmitoylsphingomelin ratio, determined by the proposed method, showed a reasonable correlation to the lecithin/sphingomyelin ratio measured by thin-layer chromatography. This method allows rapid and sensitive measurement of these phospholipids.
Computerized approach to monitoring aminoglycosides
Authors: Leal T , Parez J J , Vanbinst R , Wallemacq P E 
Published: January 2020

Abstract
Aminoglycosides are still used extensively in the treatment of nosocomial infections with Gram-negative bacteria. However, the treatment is associated with several adverse effects. Aminoglycosides monitoring is therefore essential to prevent toxic accumulations and to reach therapeutic concentrations. A computer program, PHARMONITOR, has been developed to optimize aminoglycosides monitoring, responding to the demands of most clinical daily situations. This program, based on a one-compartment open pharmacokinetics model, is developed for IBM PC-compatible computers, using D-Base III+. It can calculate t1/2, Vd, Cldrug, Cpmax, and the theoretical optimal dose and interval and also evaluates the creatinine clearance. The program has been conceived to allow maximal speed, flexibility, and reliability by the use of (e.g.) a linear least-squares analysis, the possible reference to previous protocols, the extensive use of keywords to classify and recall patients according to their pathologies, the development of messages recommending maximal dose or minimal dosing interval, and increasing the safety of the analysis. We consider the program a valuable tool for adjusting aminoglycoside dosage in individuals.