The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Martin Wehling - One of the best experts on this subject based on the ideXlab platform.
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Determination of rivaroxaban by different factor Xa specific Chromogenic Substrate assays: reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data ( P
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determination of rivaroxaban by different factor xa specific Chromogenic Substrate assays reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data (P < 0.0001). The robustness of the Chromogenic assay (method B) remains to be corroborated in interlaboratory comparisons.
Job Harenberg - One of the best experts on this subject based on the ideXlab platform.
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Determination of rivaroxaban by different factor Xa specific Chromogenic Substrate assays: reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data ( P
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determination of rivaroxaban by different factor xa specific Chromogenic Substrate assays reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data (P < 0.0001). The robustness of the Chromogenic assay (method B) remains to be corroborated in interlaboratory comparisons.
John F W Keana - One of the best experts on this subject based on the ideXlab platform.
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a Chromogenic Substrate for the continuous assay of mammalian phosphoinositide specific phospholipase c
Bioorganic & Medicinal Chemistry Letters, 1997Co-Authors: Aleksey V Rukavishnikov, Margret Ryan, Hayes O Griffith, John F W KeanaAbstract:Abstract The synthesis of a Chromogenic Substrate for mammalian PI-PLC, d,l - myo -inositol 4,5-bis(dihydrogen phosphate) 1-(4-nitrophenyl hydrogen phosphate) tetrasodium salt ( 13 ), is described. Phosphoinositol bisphosphate 13 (NPIP-P 2 ) is shown to be a Substrate for human PI-PLCδ 1 in a non-radioactive, continuous assay. © 1997 Elsevier Science Ltd.
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a Chromogenic Substrate for phosphatidylinositol specific phospholipase c 4 nitrophenyl myo inositol 1 phosphate
Chemistry and Physics of Lipids, 1991Co-Authors: M S Shashidhar, Hayes O Griffith, Johannes J Volwerk, John F W KeanaAbstract:Abstract A Chromogenic water-soluble Substrate for phosphatidylinositol-specific phospholipase C was synthesized starting from myo -inositol employing isopropylidene and 4-methoxytetrahydropyranyl protecting groups. In this analogue of phosphatidylinositol, 4-nitrophenol replaces the diacylglycerol moiety, resulting in synthetic, racemic 4-nitrophenyl myo -inositol-1-phosphate. Using this synthetic Substrate a rapid, convenient and sensitive spectrophotometric assay for the phosphatidylinositol-specific phospholipase C from Bacillus cereus was developed. Initial rates of the cleavage of the nitrophenol Substrate were linear with time and the amount of enzyme used. At pH 7.0, specific activities for the B. cereus enzyme were 77 and 150 μmol Substrate cleaved min −1 (mg protein) −1 at Substrate concentrations of 1 and 2 mM, respectively. Under these conditions, less than 50 ng quantities of enzyme were easily detected. The Chromogenic Substrate was stable during long term storage (6 months) as a solid at −20°C.
Christel Weiss - One of the best experts on this subject based on the ideXlab platform.
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Determination of rivaroxaban by different factor Xa specific Chromogenic Substrate assays: reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data ( P
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determination of rivaroxaban by different factor xa specific Chromogenic Substrate assays reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data (P < 0.0001). The robustness of the Chromogenic assay (method B) remains to be corroborated in interlaboratory comparisons.
Svetlana Marx - One of the best experts on this subject based on the ideXlab platform.
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Determination of rivaroxaban by different factor Xa specific Chromogenic Substrate assays: reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data ( P
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determination of rivaroxaban by different factor xa specific Chromogenic Substrate assays reduction of interassay variability
Journal of Thrombosis and Thrombolysis, 2011Co-Authors: Job Harenberg, Roland Krämer, Christina Giese, Svetlana Marx, Christel Weiss, Martin WehlingAbstract:Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific Chromogenic Substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25–900 ng/ml). The release of para-nitroaniline from the Chromogenic Substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data (P < 0.0001). The robustness of the Chromogenic assay (method B) remains to be corroborated in interlaboratory comparisons.