bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Detection of Ischemia-Induced Increases in Coronary Sinus Adenosine in Patients with Coronary Artery Disease
Authors: Feldman Marc D , Ayers Carlos R , Lehman Marcia R , Taylor Heidi E , Gordon Vicki L , Sabia Peter J , Ras Don , Skalak Thomas C , Linden Joel 
Published: January 2020

Abstract
Attempts to monitor coronary sinus adenosine as a clinical marker of myocardial ischemia in humans have been disappointing. Accordingly, procedures have been developed for detecting adenosine in blood collected from the human coronary sinus. Collection involves using a double-lumen metabolic catheter, which allows blood to be mixed with a stop solution at the catheter tip, thereby minimizing adenosine formation and degradation. A five-component stop solution almost completely arrests adenosine formation and degradation. Adenosine analysis is improved by using both boronate and C18 Sep-Pak columns to purify and concentrate adenosine in human plasma before HPLC. Plasma adenosine in the coronary sinus of patients with and without coronary artery disease, measured before and during peak atrial pacing, showed a twofold atrial pacing-induced increase in adenosine in the patients with coronary artery disease (n = 9, P less than 0.001) but no change in the patients with normal epicardial coronary arteries (n = 6). These preliminary results indicate that coronary sinus adenosine may provide an index of myocardial ischemia in patients with coronary artery disease.
Detection of Benzodiazepine Intake in Therapeutic Doses by Immunoanalysis of Urine: Two Techniques Evaluated and Modified for Improved Performance
Authors: Beck Olof , Lafolie Pierre , Hjemdahl Paul , Borg Stefan , Odelius Gudrun , Wirbing Peter 
Published: January 2020

Abstract
We evaluated the EMIT (enzyme-multiplied immuno technique) and FPIA (fluorescence polarization immunoassay) urine screening systems for detection of benzodiazepine intake. Healthy male volunteers were given single oral therapeutic doses of alprazolam (2 mg), chlordiazepoxide (25 mg), flunitrazepam (1 mg), lorazepam (3.75 mg), nitrazepam (5 mg), and triazolam (0.25 mg), after which urine was collected for the next 32 h. The EMIT method failed to detect the intake of flunitrazepam, lorazepam, and nitrazepam. FPIA did not detect the intake of chlordiazepoxide, flunitrazepam, lorazepam, nitrazepam, and triazolam. Modification of the EMIT method to include enzymatic hydrolysis did not significantly alter the results obtained with this method. A modification of the FPIA method to include enzymatic hydrolysis and a lower cutoff value improved the results considerably, so that we reliably detected all studied substances but flunitrazepam. We conclude that (a) both EMIT and FPIA techniques, when used as intended by the manufacturers, are unreliable for the detection of intake of therapeutic doses of these benzodiazepines, and (b) the described modification of the FPIA should provide a much improved tool for detection of benzodiazepine intake.
Two Automated Fully Enzymatic Assays for Lipase Activity in Serum Compared: Positive Interference from Post-Heparin Lipase Activity
Authors: Demanet C , Goedhuys W , Haentjens M , Huyghens L , Blaton V , Gorus F 
Published: January 2020

Abstract
The fully enzymatic Wako and Ektachem assays for pancreatic lipase in serum were found to yield precise (especially Ektachem) and consistent results that were significantly correlated (r = 0.995). Less good concordance was found with the turbidimetric aca method, results being on several occasions above normal by Wako or Ektachem but within the reference limit by the aca. Supplementation of aca packs with colipase generally increased lipase activities measured by the aca in these samples, thereby improving the correlation with Wako and Ektachem. In vitro addition experiments documented that both Wako and Ektachem were relatively insensitive to common chemical interferences. However, post-heparin lipase activities produced a positive interference in both assays, resulting in seemingly increased lipase activities that were suggestive of pancreatic disease. Substituting sodium glycocholate (6 mmol/L) for deoxycholic acid largely eliminated this positive interference in the Wako assay. Because Ektachem reagents cannot be modified in this way, we added sodium glycocholate (2-12 mmol/L) to sera; however, this failed to dissipate the in vivo effect of heparin on the Ektachem results.
Multianalyte Immunoassay Based on Spatially Distinct Fluorescent Areas Quantified by Laser-Excited Solid-Phase Time-Resolved Fluorometry
Authors: Kakabakos S E , Christopoulos T K , Diamandis E P 
Published: January 2020

Abstract
We describe a new multianalyte immunoassay principle and apply it to the simultaneous immunoassay of lutropin, follitropin, choriogonadotropin, and prolactin in serum. The method is based on the coating of distinct areas of polystyrene with analyte-specific antibodies. These antibodies react with the analyte and immobilize it in a specific area while another biotinylated antibody also reacts with the analyte to form a sandwich. After addition of streptavidin labeled with the fluorescent europium chelate of 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid, fluorescent areas are formed, the intensity of which is related to the amount of each analyte present in the sample. The fluorescent areas are quantified on the dry solid phase with laser-excited time-resolved fluorometric measurements. The assays developed are highly sensitive, precise, and accurate. We believe that this system shows potential for multianalyte immunoassay of diverse groups of compounds in disciplines such as endocrinology, infectious disease, hematology, and oncology.
Simultaneous Determination of Lactulose and Mannitol in Urine of Burn Patients by Gas-Liquid Chromatography
Authors: Shippee R L , Johnson A A , Cioffi W G , Lasko J , LeVoyer T E , Jordan B S 
Published: January 2020

Abstract
Ratios of lactulose/mannitol excretion in urine have been used to assess the extent of intestinal permeability in various disease and trauma conditions. Reported studies have used this technique to correlate altered gastrointestinal mucosal permeability to translocation of bacteria and endotoxin, leading to occult sepsis in burn patients. Enzymatic methods of analysis for urine concentrations of mannitol and lactulose were used in these studies. We have found that urine from patients with severe burns frequently contains compounds that interfere with the enzymatic methods. We describe using gas-liquid chromatography to determine mannitol and lactulose simultaneously in the urine of burn patients. To avoid the multiple peaks for the anomeric forms of the reducing sugars during precolumn trimethylsilyl derivatization, we converted the sugars to oximes before the silylation step. The method gave good recoveries of mannitol and lactulose added to burn patients' urine samples. Unlike the enzymatic methods, gas-liquid chromatography eliminates the effect of interfering compounds and allows for the simultaneous determination of both sugars in urine samples.
Specific Detection and Properties of Enzyme Hydrolyzing Phosphonate Ester in Serum
Authors: Han G Y , Fan X H , Jin X B , Wang D P 
Published: January 2020

Abstract
An enzyme capable of hydrolyzing 4-methylumbelliferyl phenylphosphonate to 4-methylumbelliferone and phenylphosphonic acid has been detected in human serum. It has a Km value of 1.72 x 10(-4) mol/L, has an optimum pH of 8.8-9.1 in Tris buffer, and shows maximum activity at 60 degrees C (30 min). The enzymic activity can be inhibited by Na3PO4, EDTA, and cysteine. We saw no effect of CuSO4, adenosine, thymidine, NaN3, diethyl p-nitrophenyl phosphate, p-chloromercuribenzoate, isopropyl fluorophosphate, or eserine on the enzymic activity. The enzyme cannot hydrolyze substrates of phosphodiesterase I or alkaline phosphatase. The enzyme is considered a phosphonate esterase.
Reference Intervals for 24-h Urinary Normetanephrine, Metanephrine, and 3-Methoxy-4-Hydroxymandelic Acid in Hypertensive Patients
Authors: Kairisto V , Koskinen P , Mattila K , Puikkonen J , Virtanen A , Kantola I , Irjala K 
Published: January 2020

Abstract
The urinary excretion of normetanephrine, metanephrine, and 3-methoxy-4-hydroxymandelic acid was quantified by HPLC in hypertensive patients who were being routinely investigated for the exclusion of pheochromocytoma. The data were used to calculate reference intervals for these analytes. Age- and sex-specific 95% reference intervals for 24-h urinary excretion were as follows (mumol/24 h): normetanephrine in men ages 16-35 years (n = 17) 0.7-3.4, in men older than 35 years (n = 121) 0.8-5.1, in women ages 16-35 years (n = 41) 0.5-2.1, and in women older than 35 years (n = 144) 0.6-3.3 mumol/24 h; metanephrine in men (n = 138) 0.3-2.0, and in women (n = 185) 0.2-1.3; and 3-methoxy-4-hydroxymandelic acid in men (n = 142) 10-54, and in women (n = 184) 9-38. Normetanephrine or metanephrine excretion rates or both exceeded the proposed reference intervals in seven of the eight patients with pheochromocytoma. Determination of 3-methoxy-4-hydroxymandelic acid excretion did not yield any additional diagnostic information.
Acyclic Adenine Nucleoside Phosphonates in Plasma Determined by High-Performance Liquid Chromatography with Fluorescence Detection
Authors: Naesens L , Balzarini J , De Clercq E 
Published: January 2020

Abstract
9-(2-Phosphonylmethoxyethyl)adenine (PMEA), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), and (R,S)-9-(3-fluoro-2-phosphonylmethoxypropyl)adenine (FPMPA) are selective antiviral agents with activity against a broad spectrum of DNA viruses and retroviruses. A highly sensitive method has been developed to determine concentrations of these compounds in human plasma. Plasma samples containing PMEA, HPMPA, or FPMPA were treated with chloroacetaldehyde to yield the corresponding highly fluorescent 1,N6-ethenoadenine derivatives. Chromatographic separation combined with excitation at 254 nm and fluorescence detection at 425 nm allowed quantification of PMEA, HPMPA, and FPMPA within a concentration range of 0.25-4000 mumol/L. This method proved useful in accurately determining low PMEA concentrations in sera from PMEA-treated monkeys and cats. The assay should be applicable to the quantification of PMEA, HPMPA, and FPMPA in plasma and urine of humans treated with any of these drugs.
Methylmalonic Acid Concentration in Serum Not Affected in Hepatic Disease
Authors: Hagelskjaer L , Rasmussen K 
Published: January 2020

Abstract
Accumulation of methylmalonic acid may provide an early clue to deficiency of cobalamin (vitamin B12) in tissue. Metabolic abnormalities involving precursors of methylmalonic acid are frequently observed in patients with hepatic diseases. To establish whether methylmalonic acid accumulates and thereby gives false-positive test results for cobalamin deficiency, we measured the concentration of methylmalonic acid in serum of patients with various hepatic diseases. Many of the patients had increased concentrations of cobalamin in serum. In serum from 70 patients, the mean concentration of methylmalonic acid (252, SE 25 nmol/L) did not differ significantly from that found in healthy subjects (211, SE 12 nmol/L). We conclude that the assay of methylmalonic acid in serum may be useful for evaluating cobalamin status in hepatic disease with functional cobalamin deficiency despite an artificially increased normal or high concentration of cobalamin in serum.
Advanced Glycosylation End Products in the Mesenteric Artery
Authors: MacDonald E , Lee W K , Hepburn S , Bell J , Scott P J , Dominiczak M H 
Published: January 2020

Abstract
We measured advanced glycosylation end products in the mesenteric artery of 37 patients (ages 29-82 years), 34 of whom were nondiabetic. Samples of arterial tissue were obtained during bowel resectioning. Advanced glycosylation end products were measured as collagen-linked fluorescence (excitation wavelength 370 nm, emission wavelength 440 nm) after collagenase digestion of tissue samples. Mean fluorescence of the arterial samples was 15 U/mg (range 5.3-27). Collagen fluorescence correlated with patients' age (r = 0.57; P less than 0.001). No difference in the collagen-linked fluorescence was observed between men and women (P = 0.63), hypertensive and normotensive patients (P = 0.44), smokers and nonsmokers (P = -0.52), and patients with and without symptomatic coronary heart disease (P = 0.7). This study demonstrates, for the first time, the relationship between collagen-linked fluorescence and patients' age in human arterial tissue ex vivo.
Elimination of Fibrinogen Interference in a Dye-Binding Method for Iron
Authors: Ooi D S , Perkins S L , Tokessy N E 
Published: January 2020

Abstract
Serum iron concentrations greater than 90 mumol/L were measured in samples from hemodialysis patients by a Ferrozine dye-binding method. Reanalysis by coulometry showed these results to be spuriously high. Turbidity resulting from precipitation of fibrinogen was identified as the source of the interference. High concentrations of heparin enhanced the effect. We conclude that the persistence of fibrinogen in serum samples from patients treated with anticoagulants is a potential interference in Ferrozine dye-binding methods performed without prior deproteinization. Adding guanidine.HCl to the acid buffer reagent is a simple way to eliminate this interference.
Method-Dependent Differences in Apparent Sodium Concentrations in Plasma after Exchange Transfusions with Citrated Blood
Authors: Schots J , De Raeve H , Boeyckens A , Umbrain V , Verbeek F , Gorus F K 
Published: January 2020

Abstract
Shortly after exchange transfusions (n = 7) with citrate-dextrose-phosphate (CDP)-treated blood, but not after regular transfusions (n = 9), sodium concentrations in plasma were significantly and paradoxically lower (3-10 mmol/L) by Ektachem 700 XR determination [with use of electrolyte reference fluid (ERF) generation 00] than by flame photometry. Similar between-method differences could also be generated by in vitro supplementation of plasma pools with CDP solution, with trisodium citrate, or to a lesser extent with Na2HPO4. For four potentiometric methods the analytical recovery of sodium added as CDP was significantly lower than by flame photometry. Within each potentiometric method the recovery was also less than the value for sodium added as NaCl. A significant association of sodium ions with citrate3- ions and, to a lesser extent, HPO4(2-) ions could theoretically account for at least part of the observations, conferring greater medical relevance to potentiometric measurements in this particular clinical situation.
Genetic Variants of Alpha 1-Antitrypsin and Hemoglobin Typed by Isoelectric Focusing in Preselected Narrow pH Gradients with Phastsystem
Authors: Jeppsson J O , Einarsson R 
Published: January 2020

Abstract
In this method for automatically running and staining isoelectric focusing (IEF) gels, pre-made dehydrated polyacrylamide gels were rehydrated before assays run with the PhastSystem (Pharmacia LKB Biotechnology). The typing of genetic variants of hemoglobin and alpha 1-antitrypsin in narrow pH gradients (pH 6.7-7.7 and 4.2-4.9, respectively) was simple, convenient, and reproducible. The clinically important variants of alpha 1-antitrypsin (ZZ and SZ) were identified from serum or dried blood on filter paper. The fast screening of abnormal hemoglobin samples (HbS) for cases in clinical medicine was easily performed. The total analysis time for the phenotyping with conventional protein staining was approximately 60 min.
Multisite Immunochemiluminometric Assay for Simultaneously Measuring Whole-Molecule and Amino-Terminal Fragments of Human Parathyrin
Authors: Klee G G , Preissner C M , Schryver P G , Taylor R L , Kao P C 
Published: January 2020

Abstract
The immunochemiluminometric assay described uses immobilized anti-human parathyrin (parathyroid hormone, hPTH)(1-44) and anti-hPTH(44-68) antisera and acridinium ester-labeled anti-hPTH(1-34) to simultaneously measure both intact hPTH and its amino-terminal fragments. Results by the assay correlate well with those by a cAMP-based bioassay and the Nichols Allegro immunoradiometric assay. The minimal detection limit is 0.08 pmol/L. The normal range is 1.0-5.0 pmol/L, and values are higher in older women. About 90% of study patients with surgically proven parathyroid adenomas had above-normal preoperative PTH concentrations, whereas patients with hypercalcemia of malignancy had normal or suppressed values. This assay was designed to detect both intact PTH and amino-terminal PTH fragments; however, chromatographic fractionation of pools of primary and secondary hyperparathyroid plasma showed virtually no amino-terminal fragment activity. Nonetheless, the design is important because the absence of carboxyl-terminal binding sites prevents interference by carboxyl-terminal fragments and because bioactive amino-terminal fragments will react in the assay if they are present in the patients' sera or if they are produced by in vitro proteolysis of intact PTH.
Immunoassay in Urine of a Specific Marker for Proximal Tubular S3 Segment
Authors: Verpooten G F , Nuyts G D , Hoylaerts M F , Nouwen E J , Vassanyiova Z , Dlhopolcek P , De Broe M E 
Published: January 2020

Abstract
Urinary intestinal alkaline phosphatase (EC 3.1.3.1; IAP) is a marker of the S3 segment of the human kidney proximal tubule. An accurate enzyme-antigen immunoassay (EAIA) with a high-affinity specific monoclonal antibody (IAP250) developed for this marker has a detection limit below the lowest IAP activity found in urine samples of normal subjects. The intra- and interassay CVs were less than 5%. Mean analytical recovery of pure IAP added to urine was 102% (SD 6%), and the EAIA results correlated well with immunoreactivity (measured by a sandwich ELISA), suggesting that the EAIA detected all of the IAP in urine. In healthy individuals (ages 20-80 years) the IAP concentrations, expressed as urinary creatinine ratios, ranged from 0.1 to 2.0 U/g (5-95 percentiles) without major differences related to sex and age. Workers exposed to mercury, which affects the S3 segment, showed an increased IAP elimination; abusers of analgesics, which affect more distal parts of the nephron, did not. As opposed to currently measured markers, the EAIA offers easy, accurate, and precise measurement of early alterations in the S3 segment.
International Federation of Clinical Chemistry Standardization Project for Measurements of Apolipoproteins A-I and B. II. Evaluation and Selection of Candidate Reference Materials
Authors: Albers J J , Marcovina S M , Kennedy H 
Published: January 2020

Abstract
The first phase of an international collaborative study for standardization of test systems for measuring apolipoprotein (apo) A-I and apo B demonstrated that uniformity of apo A-I and apo B measurements can be achieved if suitable common reference materials are used to calibrate the different systems. The objective of the second phase was to evaluate the linearity and parallelism or proportionality of the candidate reference materials selected in phase one and to determine whether any of them could be proposed as international reference materials. We evaluated the proposed reference materials with 37 test systems for apo A-I and 38 for apo B, involving 23 manufacturers and five research laboratories. Two lyophilized preparations were proposed for apo A-I, SP1 from Behringwerke AG and SP2 from Daiichi Pure Chemicals Co., and two liquid preparations were proposed for apo B, SP3 from Behringwerke AG and SP4 from Reagents Applications. The linearity of the candidate reference materials was compared with the linearity of a frozen serum pool or interim serum reference material distributed to all the participants and with that of a fresh serum pool prepared by each participant. SP1 and SP3 exhibited linearity and parallelism similar to that of the fresh frozen serum pool and had among-laboratory CVs less than or similar to those obtained on normolipidemic serum samples (approximately 6% for apo A-I and approximately 7% for apo B).
Marijuana Testing in Urine: Use of a Hexadeuterated Internal Standard for Extended Linearity, and Ion Trap vs Mass Selective Detector Gas Chromatograph/Mass Spectrometer Systems
Authors: Joern W A 
Published: January 2020

Abstract
The use of a hexadeuterated internal standard for the assay of the marijuana carboxy metabolite in urine resulted in two significant improvements. First, the linearity of the procedure was increased considerably because of the minimal chromatographic peak overlap of the internal standard and carboxy metabolite derivatives. Second, again because of minimal peak overlap, the same extract could be analyzed with similar results by both the ion trap detector and mass selective detector gas chromatograph/mass spectrometer systems.
Performance of an Immunoradiometric Assay of Erythropoietin and Results for Specimens from Anemic and Polycythemic Patients
Authors: Andre M , Ferster A , Toppet M , Fondu P , Dratwa M , Bergmann P 
Published: January 2020

Abstract
We evaluated a new commercially available two-site immunoradiometric assay (IRMA; BioMérieux 125I-EPO CoatRIA) for erythropoietin (EPO) in human serum. The precision (CV) was 4.1% intra-assay and 8% interassay for a serum pool with an EPO concentration of 17 int. units/L; the detection limit was 0.5 int. unit/L, one order of magnitude lower than by classical radioimmunoassay (RIA), although standardization of IRMA and RIA were similar. Results by both IRMA and RIA are compared for normal subjects, patients with nonrenal noninflammatory anemias, patients with beta-thalassemia major, hemodialysis patients, and patients with primary or secondary polycythemia. Values by IRMA compared well with those by RIA in the upper area of the range; IRMA and RIA values for EPO show parallel expected variations with the degree of anemia. However, because of its greater sensitivity and specificity, we consider the IRMA more appropriate than RIA for investigating patients with sub-normal EPO concentrations.
Design and Evaluation of an Anti-Evaporative Cover for Use with Liquid Containers
Authors: Burtis C A , Watson J S 
Published: January 2020

Abstract
We have designed an anti-evaporative cover for use with the sample and reagent cups and other liquid containers that are required in automated analytical systems. This cover, which is simple in design, consists of a baseplate and a cylindrical chimney. By increasing the height and decreasing the inner diameter of the chimney, evaporative losses can be reduced to less than 0.1%/h; thus, aliquots of sample and reagents can be allowed to remain in their cups and containers for several hours before an analytical error due to evaporation will be measurable. We have also modified a model that we previously developed and validated to estimate evaporative losses from open sample cups, to allow us to predict evaporative losses from cups and containers fitted with the new type of cover. This model confirms that the magnitude of the evaporative loss is inversely proportional to the resistance provided by the headspace above the sample in the cup and by the space defined by the chimney of the cover. With chimney heights ranging from 12 to 36 mm and their inner diameters from 1 to 4 mm, greater than 70% of the resistance to evaporation is provided by the cover.