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Lysinuric protein intolerance
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
The mechanisms by which hyperammonemia occur are not completely understood. Concentrations of ammonia are normal in the fasting state, but increase up to 500 μmolar postprandially [3, 11]. Persistent hyperammonemia may result from a large protein intake, prolonged fasting, or infection. The urinary excretion of orotic acid is usually elevated in patients [47, 48] even when they are receiving diets restricted in protein, and there is a major increase after the administration of a protein or alanine load [48]. Levels of orotic acid in urine are helpful in tailoring therapy. The concentration of urea in these patients is usually low.
Metabolic disorders
Published in Rachel U Sidwell, Mike A Thomson, Concise Paediatrics, 2020
Rachel U Sidwell, Mike A Thomson
The five enzymes involved in urea synthesis are: Carbamylphosphate synthetase (CPS)Ornithine transcarbamylase (OTC)Arginosuccinate synthetase (AS) (citrullinaemia)Arginosuccinate lyase (AL) (arginosuccinic acidaemia)Arginase (argininaemia)
Gastrointestinal tract and salivary glands
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The patient must stop taking a number of drugs (e.g. antibiotics and antacids) and is required to fast for 6 hours. The patient ingests carbon-13- or carbon-14-labeled urea either via capsule or a flavoured liquid. The labelled urea then diffuses through the mucosal gel layer of the gastric epithelia in which the bacteria reside. H. pylori splits the ingested urea into ammonia and labelled carbon dioxide via urease activity. The patient breaths out and the carbon dioxide is collected. The sample is then measured in a scintillation counter or infrared spectrophotometer in order to measure the amount of labelled carbon dioxide. This is an indirect measure of urease activity and subsequent presence of H. pylori. Figure 5.34a presents the process by which the results are collected for the breath test.
Effect of in vitro simulated digestion on the anti-Helicobacter Pylori activity of different Propolis extracts
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2023
Paolo Governa, Giulia Romagnoli, Paola Albanese, Federico Rossi, Fabrizio Manetti, Marco Biagi
The colorimetric urease activity assay kit (Sigma-Aldrich) was used to measure the inhibition of urease activity by DPE, galangin, and pinocembrin. This assay is based on the quantification of urease-produced ammonia, using the Berthelot method.54 Briefly, a suspension (1 x 106 CFU/mL) of the 10K clinical isolate was centrifuged (10000 x g for 3 min) and the pellet was used as the source of urease. DPE, galangin, and pinocembrin were used at the MBC found in the previous experiment. 90 µL of DPE (848.4 mg/L), galangin (37.5 mg/L), and pinocembrin (18.8 mg/L), diluted in the assay buffer (10 mM Na3PO4, pH 7.2) containing the 10K suspension pellet (1 x 106 CFU/mL), were added to the appropriate well in a 96-well plate. A standard curve was created by using decreasing NH4Cl concentration (final ammonia concentration 500 − 0 µM). The assay buffer was used as blank control, while the 10K suspension pellet (1 × 106 CFU/mL) in assay buffer was used as the positive control. 10 µL of urea was added to each well and incubated for 15 min at 37 °C. Then, 100 µL of reagent A was added to stop the urease reaction. After mixing, 50 µL of reagent B was added and incubated for 30 min in the dark. Finally, absorbance was measured at 670 nm using a Victor® NivoTM plate reader (PerkinElmer, Waltham, MA). Urease activity was calculated using the following formula: 670 is the absorbance at 670 nm, n is the dilution factor, Slope is the slope obtained by linear regression fitting of the standard curve, and t is the incubation time (15 min).
Potential interference of in vitro carbamylation on C-reactive protein laboratory measurement
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2023
Carolina dos Santos Stein, José Pedro Etchepare Cassol, Rafael Noal Moresco
In vitro carbamylation was induced using KOCN or urea. KOCN solutions were prepared in 0.1 mol/L phosphate-buffered saline (PBS; pH 7.4) to obtain final concentrations of 150 nM, 150 µM, and 150 mM. These experimental conditions were based on a previous study [15] that characterized the occurrence of carbamylation and the presence of homocitrulline. Urea solutions were tested at concentrations of 20, 100, and 500 mg/dL to reproduce a wide range of values associated with healthy and pathological conditions. After the addition of these solutions to a standard solution of CRP at a final concentration of 10 mg/L and a human serum pool spiked with the CRP standard solution, the samples were incubated at 37 °C for 24 h. All tests were conducted in replicates (n = 4). The serum pool was prepared from randomly selected samples of patients who had undergone routine laboratory tests at the University Hospital of Santa Maria, RS, Brazil. The study protocol was approved by the Institutional Ethics Committee (number 11559119.4.0000.5346). For the characterization of carbamylation, the standard solution of CRP at a final concentration of 10 mg/L was incubated at 37 °C for 24 h with PBS, KOCN, and urea at the highest concentrations, under conditions similar to those previously described. Assays were performed in triplicate. After incubation, the samples were dialyzed for 12 h in a dialysis tube containing a cellulose membrane (Membra-Cel® MD34, Sigma-Aldrich, St. Louis, MO, USA) against PBS to remove KOCN or urea excess.
What extreme laboratory values can be obtained that (some) patients can survive with?
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2022
Pim M. W. Janssens, Michiel W. Pot, Moniek Wouters, Henk J. van Leeuwen, Marcel M. G. J. van Borren
The approach to clinical plausibility of analytes in relation to disease and the compatibility of them with life is dependent on the kind of analyte. Many analytes are mere markers of disease processes. Patients will not die from them, only with them. Examples are most of the diagnostic enzymes measured in blood, heart marker proteins, compounds to monitor renal function and tumor markers. Analytes like these normally can reach certain limits in the circulation, however, in itself they do reflect, not determine the severity of the disease process and whether or not the patient will survive. A much different situation holds for analytes such as electrolytes, pH and hemoglobin. These analytes are compatible with life within certain limits because they directly influence the functioning of cells, tissues and organs. As a result, the body tightly regulates the concentration of the latter type of analytes by a process known as homeostasis [1]. Finally, there are a number of analytes that can be harmful when present at certain levels, mostly because they are waste products. Examples of these are bilirubin, urea and uric acid. Also, for these analytes monitoring the values is useful, as by their nature these analytes, especially at the extremes, may be detrimental to the body.