bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on Centrifugation: Application to Centrifuge Development
Authors: Roberts Thomas , Smith Mathew , Roberts Barry 
Published: January 2020

Abstract
This report outlines the background to the development of an automated, serial, discrete centrifuge, reporting on the criteria considered essential in such an instrument. We established the criteria by examining the detailed logistics of centrifuge operation in a hospital laboratory. The mean sample load per run, using six centrifuges, was 13.6 samples, and the user-selectable cycle time ranged from 00:01:10 to 00:12:33 (hours:minutes:seconds) with a fixed g value of 1050. During the laboratory working window, (0900–1700), only 50% of the centrifuge capacity was utilized and more than one-third of the sample workload was delayed for &gt;5 min because the centrifuges were not emptied promptly. In addition, 35% of the sample workload was centrifuged for less than the time prescribed in the operational specifications. Based on these findings, we designed a new continuous, serial centrifuge to overcome some of the deficiencies noted in the logistics study. The centrifuge operates continuously, nominally treating 150 samples/h, with a cycle time of 5 min at 1000g. The cycle time and g value are variable between limits, and their selection governs the throughput rate. Each sample is centrifuged separately in individual rotors mounted in a sturdy carousel with a periphery that traverses a load/unload station. There is no sample delay because of operator absence, and the capacity is fully utilized. The centrifuge can operate in a stand-alone capacity or has the capability of being integrated into a sample preparation system or as a direct front end for high-throughput analyzers.
Biochemical and Molecular Genetic Characteristics of the Severe Form of Tyrosine Hydroxylase Deficiency
Authors: Bräutigam Christa , Steenbergen-Spanjers Gerry CH , Hoffmann Georg F , Dionisi-Vici Carlo , van den Heuvel Lambert PWJ , Smeitink Jan AM , Wevers Ron A 
Published: January 2020

AbstractBackground: Tyrosine hydroxylase (TH) catalyzes the rate-limiting step in the biosynthesis of the catecholamines dopamine, norepinephrine, and epinephrine. Recently, mutations were identified in cases of autosomal recessive dopa-responsive dystonia and infantile parkinsonism. We describe a patient with severe symptoms and a new missense mutation in TH.Methods: Relevant metabolites in urine and cerebrospinal fluid were measured by HPLC with fluorometric and electrochemical detection. All exons of the TH gene were amplified by PCR and subjected to single-strand conformation polymorphism analysis. Amplimers displaying aberrant migration patterns were analyzed by DNA sequence analysis.Results: The patient presented with severe axial hypotonia, hypokinesia, reduced facial mimicry, ptosis, and oculogyric crises from infancy. The major metabolite of dopamine, homovanillic acid, was undetectable in the patient’s cerebrospinal fluid. A low dose of l-dopa produced substantial biochemical but limited clinical improvement. DNA sequencing revealed a homozygous 1076G→T missense mutation in exon 10 of the TH gene. The mutation was confirmed with restriction enzyme analysis. It was not present in 100 control alleles. Secondary structure prediction based on Chou-Fasman calculations showed an abnormal secondary structure of the mutant protein.Conclusions: We describe a new missense mutation (1076G→T, C359F) in the TH gene. The transversion is present in all known splice variants of the enzyme. It produces more severe clinical and biochemical manifestations than previously described in TH-deficient cases. Our findings extend the clinical and the biochemical phenotype of genetically demonstrated TH deficiency.
Capillary Electrophoresis for Detection of Inherited Disorders of Purine and Pyrimidine Metabolism
Authors: Adam Tomáš , Friedecký David , Fairbanks Lynette D , Ševc̆ík Juraj , Barták Petr 
Published: January 2020

Abstract
Background: Measurement of purine and pyrimidine metabolites presents complex problems for separations currently performed by HPLC and thin-layer chromatography in clinical practice. We developed a novel capillary electrophoresis method for this purpose.
Methods: Separations were performed in 60 mmol/L borate-2-amino-2-methyl-1-propanol-80 mmol/L sodium dodecyl sulfate (pH 9.6) at 35 °C.
Results: The conditions reported allowed separation of all diagnostic metabolites from major urinary constituents in an analysis time of 3 min and with a separation efficiency of 220 000 theoretical plates/m. The clinically important metabolites were detectable at concentrations of 0.85–4.28 μmol/L. The method was linear over the range 5–500 μmol/L (r &gt;0.99). The within-run and intra- and interday imprecision (CV) was &lt;5%. Characteristic abnormalities were detected in the electropherograms of urine samples from patients with purine and pyrimidine enzyme deficiencies. We provide the electrophoretic and spectral characteristics of many intermediates in purine and pyrimidine metabolism and describe common artifacts from medication and ultraviolet-absorbing compounds.
Conclusion: Capillary electrophoresis is a valuable screening tool in the detection of inborn errors of purine and pyrimidine metabolism.
Recombinant Human Tissue Transglutaminase ELISA for the Diagnosis of Gluten-sensitive Enteropathy
Authors: Sárdy Miklós , Odenthal Uwe , Kárpáti Sarolta , Paulsson Mats , Smyth Neil 
Published: January 2020

AbstractBackground: Tissue transglutaminase (TGc) has recently been identified as the major, if not the sole, autoantigen of gluten-sensitive enteropathy (GSE). We developed and validated an ELISA based on the human recombinant antigen and compared it to existing serological tests for GSE [guinea pig TGc ELISA and endomysium antibody (EMA) test].Methods: Human TGc was expressed in the human embryonic kidney cell line 293-EBNA as a C-terminal fusion protein with the eight-amino acid Strep-tag II allowing one-step purification via streptavidin affinity chromatography. We carried out ELISA assays for IgA antibodies against TGc using calcium-activated human and guinea pig TGc. The sera were also tested on monkey esophagus sections by indirect immunofluorescence for IgA EMA. We examined 71 serum samples from patients with GSE (38 with celiac disease, 33 with dermatitis herpetiformis), including 16 on therapy, and 53 controls.Results: The human TGc could be expressed and purified as an active enzyme giving a single band on a Coomassie-stained gel. The mean intra- and interassay CVs for the human TGc ELISA were 3.2% and 9.2%, respectively. The area under the ROC curve was 0.999. The specificity and sensitivity were 98.1% (95% confidence interval, 95.7–100%) and 98.2% (95.9–100%), respectively.Conclusions: The human TGc ELISA was somewhat superior to the guinea pig TGc ELISA, and was as specific and sensitive as the EMA test. The human TGc-based ELISA is the method of choice for easy and noninvasive screening and diagnosis of GSE.
Comparison of Serum and Plasma Methylmalonic Acid Measurements in 13 Laboratories: An International Study
Authors: Pfeiffer Christine M , Smith S Jay , Miller Dayton T , Gunter Elaine W 
Published: January 2020

Abstract
Background: Detection of cobalamin deficiency is increasingly important, and methylmalonic acid (MMA) appears to be a useful marker. Information on interlaboratory variation and on methodological differences for MMA in serum and plasma is limited.
Methods: Using gas chromatography/mass spectrometry, 13 laboratories participated in a 2-day analysis of 8 serum and 11 EDTA-plasma specimens. Results were analyzed for imprecision, recovery, and differences among laboratories and methods.
Results: The mean among-laboratory imprecision (CV) was 19% and 21% for serum and plasma samples, respectively, and 9.3% and 7.8% for serum and plasma samples with added MMA, respectively. The mean within-laboratory (among-run) CV was 13% for both serum and plasma samples and 5.2% and 4.9% for serum and plasma samples with added MMA. Within-method imprecision was the same or higher than among-method imprecision. The mean among-laboratory recovery of MMA was 105% and 95% in serum and plasma, respectively. Most laboratories showed a proportional bias relative to the consensus mean of up to 15%. Two laboratories reported results that on average were almost 30% higher than the consensus mean.
Conclusions: No method differences were found, but significant among-laboratory imprecision was found in the present study. Improvements are needed to reduce the analytical imprecision of most laboratories, and attention must be focused on calibration issues. Differences among laboratories can be improved by introducing high-quality reference materials and by instituting external quality assessment programs.
Thyroid Function during Pregnancy
Authors: Fantz Corinne R , Dagogo-Jack Samuel , Ladenson Jack H , Gronowski Ann M 
Published: January 2020

AbstractBackground: This Case Conference reviews the normal changes in thyroid activity that occur during pregnancy and the proper use of laboratory tests for the diagnosis of thyroid dysfunction in the pregnant patient.Case: A woman in the 18th week of pregnancy presented with tachycardia, increased blood pressure, severe vomiting, increased total and free thyroid hormone concentrations, a thyroid-stimulating hormone (TSH) concentration within the reference interval, and an increased human chorionic gonadotropin (hCG) β-subunit concentration.Issues: During pregnancy, normal thyroid activity undergoes significant changes, including a two- to threefold increase in thyroxine-binding globulin concentrations, a 30–100% increase in total triiodothyronine and thyroxine concentrations, increased serum thyroglobulin, and increased renal iodide clearance. Furthermore, hCG has mild thyroid stimulating activity. Pregnancy produces an overall increase in thyroid activity, which allows the healthy individual to remain in a net euthyroid state. However, both hyper- and hypothyroidism can occur in pregnant patients. In addition, two pregnancy-specific conditions, hyperemesis gravidarum and gestational trophoblastic disease, can lead to clinical hyperthyroidism. The normal changes in thyroid activity and the association of pregnancy with conditions that can cause hyperthyroidism necessitates careful interpretation of thyroid function tests during pregnancy.Conclusion: Assessment of thyroid function during pregnancy should be done with a careful clinical evaluation of the patient’s symptoms as well as measurement of TSH and free, not total, thyroid hormones. Measurement of thyroid autoantibodies may also be useful in selected cases to detect maternal Graves disease or Hashimoto thyroiditis and to assess risk of fetal or neonatal consequences of maternal thyroid dysfunction.
Tetrahydropalmatine Poisoning: Diagnoses of Nine Adult Overdoses Based on Toxicology Screens by HPLC with Diode-Array Detection and Gas Chromatography–Mass Spectrometry
Authors: Lai Chi-Kong , Chan Albert Yan-Wo 
Published: January 2020

Abstract
Background: Tetrahydropalmatine (THP) is a neuroactive alkaloid with analgesic and hypnotic action. Its analysis is important because cases of human poisonings have emerged as a result of unregulated use of some proprietary biopharmaceuticals containing purified THP. Methods: We established analytical parameters for HPLC with diode-array detection (HPLC-DAD) and gas chromatography–mass spectrometry (GC-MS) for the detection of THP in serum and urine. Nine acutely THP-poisoned adults were thus screened over 16 months. Results: All patients recovered quickly after mild neurological disturbance. In general, THP was metabolized rapidly and excreted as polar metabolites in urine. Serum THP was measured in five cases and found to be &lt;0.1–1.2 mg/L (&lt;0.3–3.4 μmol/L). Paired analyses of urine with and without glucuronidase treatment clarified the disposition of THP. Our GC–MS method with trimethylsilane derivatization identified O-desmethyl metabolites. With a uniform solid-phase extraction, the HPLC-DAD procedure detected intact glucuronide metabolites. Conclusion: Intact glucuronide metabolites of THP are sensitive markers for THP exposures. Our methods and findings provide practical tools and information for surveillance of intoxication caused by excessive THP intake.
Study of Calcium Metabolism in Idiopathic Hypercalciuria by Strontium Oral Load Test
Authors: Vezzoli Giuseppe , Caumo Andrea , Baragetti Ivano , Zerbi Simona , Bellinzoni Piera , Centemero Antonella , Rubinacci Alessandro , Moro GianLuigi , Adamo Donatella , Bianchi Giuseppe , Soldati Laura 
Published: January 2020

AbstractCalcium excretion and absorption were evaluated in hypercalciuric calcium stone formers by the study of Sr2+ excretion and absorption after an oral load. Ca2+ stone formers (n = 140) were studied, and the results were compared in the 83 of them who had idiopathic hypercalciuria and in the 57 who had Ca2+ excretion within reference values. Hypercalciuric patients showed increased renal Sr2+ clearance (CRE; 5.26 ± 0.358 vs 3.29 ± 0.277 mL/min; P &lt;0.001), whereas Sr2+ absorption [assessed as the area under the serum concentration–time curve (AUC)] was increased at 30 and 60 min (1.53 ± 0.087 vs 1.21 ± 0.071 mmol · L−1 · min; P &lt;0.05), but not at 240 min after the load. In hypercalciuric patients, the AUCs were positively correlated with urinary Sr2+ fractional excretion (P &lt;0.001). Conversely, in normocalciuric patients plasma parathyroid hormone (PTH) was negatively correlated with the AUCs (P &lt;0.01) and CRE (P &lt;0.05), whereas 1,25-dihydroxyvitamin D plasma concentrations normalized to PTH were positively correlated with the AUCs (P &lt;0.05). The results of Sr2+ load tests suggest that in the hypercalciuric population, Ca2+ absorption is altered predominantly in the duodenum and that the normal regulation exerted by calciotropic hormones on tubular and enteral Ca2+ handling is lost.
Quantitative Study of the Variability of Hepatic Iron Concentrations
Authors: Emond Mary J , Bronner Mary P , Carlson Timothy H , Lin Masami , Labbe Robert F , Kowdley Kris V 
Published: January 2020

Abstract
Background: The hepatic iron concentration (HIC) is widely used in clinical practice and in research; however, data on the variability of HIC among biopsy sites are limited. One aim of the present study was to determine the variability of HIC within both healthy and cirrhotic livers.
Methods: Using colorimetric methods, we determined HIC in multiple large (microtome) and small (biopsy-sized) paraffin-embedded samples in 11 resected livers with end-stage cirrhosis. HIC was also measured in multiple fresh samples taken within 5 mm of each other (“local” samples) and taken at sites 3–5 cm apart (“remote” samples) from six livers with end-stage cirrhosis and two healthy autopsy livers.
Results: The within-organ SD of HIC was 13–1553 μg/g (CV, 3.6–55%) for microtome samples and 60–2851 μg/g (CV, 15–73%) for biopsy-sized samples. High variability of HIC was associated with mild to moderate iron overload, because the HIC SD increased with increasing mean HIC (P &lt;0.002). Livers with mean HIC &gt;1000 μg/g exhibited significant biological variability in HIC between sites separated by 3–5 cm (remote sites; P &lt;0.05). The SD was larger for biopsy-sized samples than for microtome samples (P = 0.02).
Conclusion: Ideally, multiple hepatic sites would be sampled to obtain a representative mean HIC.
Nitrogen Dioxide Formation during Inhaled Nitric Oxide Therapy
Authors: Sokol Gregory M , Van Meurs Krisa P , Wright Linda L , Rivera Oswaldo , Thorn William J , Chu Pamela M , Sams Robert L 
Published: January 2020

Abstract
Background: Nitrogen dioxide (NO2) is a toxic by-product of inhalation therapy with nitric oxide (NO). The rate of NO2 formation during NO therapy is controversial.
Methods: The formation of NO2 was studied under dynamic flows emulating a base case NO ventilator mixture containing 80 ppm NO in a 90% oxygen matrix. The difficulty in measuring NO2 concentrations below 2 ppm accurately was overcome by the use of tunable diode laser absorption spectroscopy.
Results: Using a second-order model, the rate constant, k, for NO2 formation was determined to be (1.19 ± 0.11) × 10−11 ppm−2s−1, which is in basic agreement with evaluated data from atmospheric literature.
Conclusions: Inhaled NO can be delivered safely in a well-designed, continuous flow neonatal ventilatory circuit, and NO2 formation can be calculated reliably using the rate constant and circuit dwell time.
Automated Homogeneous Immunoassay for Gentamicin on the Dimension Clinical Chemistry System
Authors: Wei Tie Q , Chu Victor P , Craig Alan R , Duffy James E , Obzansky David M , Kilgore Daniel , Masulli Ignazio S , Sanders Connie M , Thompson John C 
Published: January 2020

Abstract
Background: Monitoring of the concentration of gentamicin in serum and plasma during therapy is widely recommended and practiced in hospitals. Our aim was to develop a homogeneous immunoassay based on particle-enhanced turbidimetric inhibition immunoassay technology to quantify gentamicin on the Dimension® clinical chemistry system.
Methods: Assay performance was assessed on each of the Dimension models in a 15-instrument interlaboratory comparison study. A split-sample comparison (n = 1171) was also performed between the gentamicin methods on the Dimension system and the Abbott®TDx® analyzer, using multiple reagent and calibrator lots on multiple instruments.
Results: The Dimension method was linear to 25.1 μmol/L (12.0 μg/mL) with a detection limit of 0.63 μmol/L (0.3 μg/mL). Calibration was stable for 30 days. The within-run imprecision (CV) was &lt;1.3%, and total imprecision ranged from 1.8% to 3.2% between 4.2 μmol/L (2.0 μg/mL) and 16.7 μmol/L (8.0 μg/mL) gentamicin. Linear regression analysis of the results on the Dimension method (DM) vs the Abbott TDx yielded the following equation: DM = 0.98TDx − 0.42; r = 0.987. Minimal interference was observed from structurally related compounds such as sagamicin, netilmicin, and sisomicin.
Conclusion: The monoclonal antibody used in this method has similar reactivities toward the individual gentamicin subspecies C1, C1a, and C2, thus providing analytical recovery not significantly dependent on relative subspecies concentrations.
Defect in Dimethylglycine Dehydrogenase, a New Inborn Error of Metabolism: NMR Spectroscopy Study
Authors: Moolenaar Sytske H , Poggi-Bach Jo , Engelke Udo FH , Corstiaensen Jacqueline MB , Heerschap Arend , de Jong Jan GN , Binzak Barbara A , Vockley Jerry , Wevers Ron A 
Published: January 2020

AbstractBackground: A38-year-old man presented with a history of fish odor (since age 5) and unusual muscle fatigue with increased serum creatine kinase. Our aim was to identify the metabolic error in this new condition.Methods: We used 1H NMR spectroscopy to study serum and urine from the patient.Results: The concentration of N,N-dimethylglycine (DMG) was increased ∼100-fold in the serum and ∼20-fold in the urine. The presence of DMG as a storage product was confirmed by use of 13C NMR spectroscopy and gas chromatography–mass spectrometry. The high concentration of DMG was caused by a deficiency of the enzyme dimethylglycine dehydrogenase (DMGDH). A homozygous missense mutation was found in the DMGDH gene of the patient.Conclusions: DMGDH deficiency must be added to the differential diagnosis of patients complaining of a fish odor. This deficiency is the first inborn error of metabolism discovered by use of in vitro 1H NMR spectroscopy of body fluids.
Near-Patient Test for C-Reactive Protein in General Practice: Assessment of Clinical, Organizational, and Economic Outcomes
Authors: Dahler-Eriksen Bjarne Steen , Lauritzen Torsten , Lassen Jens Flensted , Lund Erik D , Brandslund Ivan 
Published: January 2020

AbstractBackground: The benefits of near-patient, point-of-care tests have not been fully examined. We have assessed the clinical, organizational, and economic outcomes of implementing a near-patient test for C-reactive protein (CRP) in general practice.Methods: In a randomized crossover trial during intervention periods, general practitioners (GPs) were allowed to measure CRP within 3 min, using NycoCard® CRP. During control periods, they had to mail blood samples for CRP measurements to the hospital laboratory and received test results 24–48 h later. Twenty-nine general practice clinics participated (64 GPs), and 1853 patients were included in the study. Results were evaluated at both the level of participating GPs and the level of included patients.Results: For participating GPs, the overall use of erythrocyte sedimentation rates (ESRs) decreased by 8% (95% confidence interval, 1–14%) during intervention periods, and the number of blood samples mailed to the hospital laboratory decreased by 6% (1–10%). No reduction in the prescription of antibiotics was seen. The proportion of study patients having a follow-up telephone consultation was reduced from 63% to 53% (P = 0.0001), and patients with CRP concentrations &gt;50 mg/L had their antibiotic treatments started earlier when CRP was measured in general practices (P = 0.0161).Conclusion: The implementation of the near-patient CRP test was cost-effective mainly on the basis of a reduction in the use of services from the hospital laboratory by GPs. If the implementation is followed by education and clinical guidelines, opportunities exist for additional reduction in the use of ESR and for a more appropriate use of antibiotics.
Comparison of Three Different Plasma Homocysteine Assays with Gas Chromatography–Mass Spectrometry
Authors: Ubbink Johan B , Delport Rhena , Riezler Reiner , Vermaak WJ Hayward 
Published: January 2020

Abstract
Background: Various methods are available to measure plasma total homocyst(e)ine (tHcy) concentrations, but whether plasma tHcy assays may be used interchangeably is not known.
Methods: Results from three different methods [HPLC with fluorescence detection, enzyme immunoassay (EIA), and fluorescence polarization immunoassay (FPIA)] to determine fasting (n = 163) and post-methionine load (n = 80) plasma tHcy concentrations were compared with those obtained by gas chromatography–mass spectrometry (GC-MS). Difference plots on non-transformed and log-transformed data were used to assess the agreement between HPLC and GC-MS, EIA and GC-MS, and FPIA and GC-MS.
Results: The closest agreement between methods was observed between GC-MS and FPIA for fasting tHcy concentrations, with 95% of the FPIA values between 19% above and 24% below the corresponding GC-MS results. Post-methionine load tHcy concentrations measured by EIA showed the least agreement with GC-MS, with 95% of values measured by EIA ranging between 52% above and 16% below the GC-MS values. With respect to GC-MS, the above-mentioned methods showed a negative bias for fasting tHcy concentrations, but a positive bias for both immunoassays for post-methionine load tHcy concentrations.
Conclusions: The agreement among methods is insufficient to allow them to be used interchangeably. The intermethod differences emphasize the need for standardization of plasma tHcy assays.