The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
S Heptinstall - One of the best experts on this subject based on the ideXlab platform.
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a whole blood assay of inhibition of platelet aggregation by glycoprotein iib iiia antagonists comparison with other aggregation methodologies
Thrombosis and Haemostasis, 1999Co-Authors: Robert F Storey, Robert G Wilcox, Jane A May, S HeptinstallAbstract:We have used a whole blood single-platelet counting assay (WB-SPC) that is sensitive to microaggregation for monitoring GPIIb/IIIa antagonists and have compared this with other methodologies. In vitro effects of the GPIIb/IIIa antagonist fradafiban on ADP-induced platelet aggregation were determined using WBSPC and PRP turbidimetry, comparing citrate and hirudin anticoagulation. Fradafiban was a more potent inhibitor of aggregation assessed by PRP turbidimetry compared to WBSPC. Citrate showed only a trend towards enhancing fradafiban potency (p = 0.087). Citrated blood from 8 patients with unstable angina, randomised to receive oral lefradafiban (the oral prodrug of fradafiban) or placebo, was studied before and during treatment using WBSPC, PRP turbidimetry, impedance aggregometry and Rapid Platelet Function Assay (RPFA, Accumetrics). RPFA, PRP turbidimetry and WBSPC measurements correlated well. Impedance aggregometry responses were oversensitive to GPIIb/IIIa blockade. WBSPC was most discriminating at high levels of inhibition and offered a rapid means of monitoring GPIIb/IIIa antagonist effect within the therapeutic range of inhibition.
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differential effects of glycoprotein iib iiia antagonists on platelet microaggregate and macroaggregate formation and effect of anticoagulant on antagonist potency implications for assay methodology and comparison of different antagonists
Circulation, 1998Co-Authors: Robert F Storey, Robert G Wilcox, S HeptinstallAbstract:Background—Citrated platelet-rich plasma (PRP) turbidimetry is used for assessing pharmacodynamic effects of glycoprotein (GP) IIb/IIIa antagonists in clinical trials. However, citrate can enhance the potency of at least eptifibatide (Integrilin), and turbidimetry is insensitive to microaggregate formation. We compared PRP turbidimetry, as a measure of macroaggregate formation, with single-platelet counting in both whole blood and PRP as a measure of microaggregate formation, using both citrate and hirudin anticoagulation. Methods and Results—Three GP IIb/IIIa antagonists, eptifibatide, MK-0852, and GR144053, were compared in PRP (turbidimetry) and whole blood (platelet counting with an Ultra-Flo 100 Platelet Counter), with ADP and collagen used as agonists. Compared with hirudin, citrate enhanced the potency of eptifibatide by up to 4-fold in both PRP and whole blood (P<0.0005), modestly enhanced MK-0852 potency (P=0.001), and had no effect on GR144053. Potency measured in PRP was 2- to 3-fold greater co...
Robert F Storey - One of the best experts on this subject based on the ideXlab platform.
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a whole blood assay of inhibition of platelet aggregation by glycoprotein iib iiia antagonists comparison with other aggregation methodologies
Thrombosis and Haemostasis, 1999Co-Authors: Robert F Storey, Robert G Wilcox, Jane A May, S HeptinstallAbstract:We have used a whole blood single-platelet counting assay (WB-SPC) that is sensitive to microaggregation for monitoring GPIIb/IIIa antagonists and have compared this with other methodologies. In vitro effects of the GPIIb/IIIa antagonist fradafiban on ADP-induced platelet aggregation were determined using WBSPC and PRP turbidimetry, comparing citrate and hirudin anticoagulation. Fradafiban was a more potent inhibitor of aggregation assessed by PRP turbidimetry compared to WBSPC. Citrate showed only a trend towards enhancing fradafiban potency (p = 0.087). Citrated blood from 8 patients with unstable angina, randomised to receive oral lefradafiban (the oral prodrug of fradafiban) or placebo, was studied before and during treatment using WBSPC, PRP turbidimetry, impedance aggregometry and Rapid Platelet Function Assay (RPFA, Accumetrics). RPFA, PRP turbidimetry and WBSPC measurements correlated well. Impedance aggregometry responses were oversensitive to GPIIb/IIIa blockade. WBSPC was most discriminating at high levels of inhibition and offered a rapid means of monitoring GPIIb/IIIa antagonist effect within the therapeutic range of inhibition.
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differential effects of glycoprotein iib iiia antagonists on platelet microaggregate and macroaggregate formation and effect of anticoagulant on antagonist potency implications for assay methodology and comparison of different antagonists
Circulation, 1998Co-Authors: Robert F Storey, Robert G Wilcox, S HeptinstallAbstract:Background—Citrated platelet-rich plasma (PRP) turbidimetry is used for assessing pharmacodynamic effects of glycoprotein (GP) IIb/IIIa antagonists in clinical trials. However, citrate can enhance the potency of at least eptifibatide (Integrilin), and turbidimetry is insensitive to microaggregate formation. We compared PRP turbidimetry, as a measure of macroaggregate formation, with single-platelet counting in both whole blood and PRP as a measure of microaggregate formation, using both citrate and hirudin anticoagulation. Methods and Results—Three GP IIb/IIIa antagonists, eptifibatide, MK-0852, and GR144053, were compared in PRP (turbidimetry) and whole blood (platelet counting with an Ultra-Flo 100 Platelet Counter), with ADP and collagen used as agonists. Compared with hirudin, citrate enhanced the potency of eptifibatide by up to 4-fold in both PRP and whole blood (P<0.0005), modestly enhanced MK-0852 potency (P=0.001), and had no effect on GR144053. Potency measured in PRP was 2- to 3-fold greater co...
Abolghasem Ataie - One of the best experts on this subject based on the ideXlab platform.
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influence of fe ba molar ratio on the characteristics of ba hexaferrite particles prepared by sol gel combustion method
Journal of Alloys and Compounds, 2005Co-Authors: A Mali, Abolghasem AtaieAbstract:Abstract Nano-crystalline particles of barium hexaferrite (BaFe 12 O 19 ) have been prepared by a sol–gel combustion technique using nitrate–citrate gels prepared from metal nitrates and citric acid solutions under various Fe/Ba molar ratios of 10, 11 and 12. The thermal decomposition process of the nitrate–citrate gels and as-burnt powders was investigated by XRD and DTA/TGA techniques. The results revealed that the nitrate citrate gels exhibit a self-propagating behavior after ignition and the single-phase barium hexaferrite formation temperature is significantly influenced by Fe/Ba molar ratio. The Fe/Ba molar ratio of 11 is more favorable for formation of barium hexaferrite. The SEM investigations revealed that the mean particle size of barium hexaferrite dramatically increases with increasing calcination temperature from 1000 to 1100 °C. The magnetic properties measured using a vibrating sample magnetometer (VSM) revealed that the sample synthesized under Fe/Ba molar ratio of 11, exhibits higher saturation magnetization in comparison with those synthesized under Fe/Ba molar ratios of 10 and 12.
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influence of the metal nitrates to citric acid molar ratio on the combustion process and phase constitution of barium hexaferrite particles prepared by sol gel combustion method
Ceramics International, 2004Co-Authors: A Mali, Abolghasem AtaieAbstract:A novel sol–gel combustion process was used to synthesize the ultrafine particles of barium hexaferrite. The nitrate–citrate gels were prepared from metal nitrates and citric acid solutions under various molar ratios of the metal nitrates to citric acid of 0.5, 1, 1.5 and 3 by sol–gel process. The results showed that the nitrate citrate gels exhibit a self-propagating behavior after ignition in air at room temperature. The thermal decomposition of nitrate–citrate gels and the phase evolution of calcined powder were investigated respectively by DTA/TG and XRD techniques. Scanning electron microscope was used to characterize the microstructure of the products. The results revealed that the formation temperature and the crystallite size of barium hexaferrite are influenced significantly by the molar ratio of the metal nitrates to citric acid. The formation temperature of barium hexaferrite decreases with increasing the molar ratio of the metal nitrates to citric acid. © 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Robert G Wilcox - One of the best experts on this subject based on the ideXlab platform.
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a whole blood assay of inhibition of platelet aggregation by glycoprotein iib iiia antagonists comparison with other aggregation methodologies
Thrombosis and Haemostasis, 1999Co-Authors: Robert F Storey, Robert G Wilcox, Jane A May, S HeptinstallAbstract:We have used a whole blood single-platelet counting assay (WB-SPC) that is sensitive to microaggregation for monitoring GPIIb/IIIa antagonists and have compared this with other methodologies. In vitro effects of the GPIIb/IIIa antagonist fradafiban on ADP-induced platelet aggregation were determined using WBSPC and PRP turbidimetry, comparing citrate and hirudin anticoagulation. Fradafiban was a more potent inhibitor of aggregation assessed by PRP turbidimetry compared to WBSPC. Citrate showed only a trend towards enhancing fradafiban potency (p = 0.087). Citrated blood from 8 patients with unstable angina, randomised to receive oral lefradafiban (the oral prodrug of fradafiban) or placebo, was studied before and during treatment using WBSPC, PRP turbidimetry, impedance aggregometry and Rapid Platelet Function Assay (RPFA, Accumetrics). RPFA, PRP turbidimetry and WBSPC measurements correlated well. Impedance aggregometry responses were oversensitive to GPIIb/IIIa blockade. WBSPC was most discriminating at high levels of inhibition and offered a rapid means of monitoring GPIIb/IIIa antagonist effect within the therapeutic range of inhibition.
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differential effects of glycoprotein iib iiia antagonists on platelet microaggregate and macroaggregate formation and effect of anticoagulant on antagonist potency implications for assay methodology and comparison of different antagonists
Circulation, 1998Co-Authors: Robert F Storey, Robert G Wilcox, S HeptinstallAbstract:Background—Citrated platelet-rich plasma (PRP) turbidimetry is used for assessing pharmacodynamic effects of glycoprotein (GP) IIb/IIIa antagonists in clinical trials. However, citrate can enhance the potency of at least eptifibatide (Integrilin), and turbidimetry is insensitive to microaggregate formation. We compared PRP turbidimetry, as a measure of macroaggregate formation, with single-platelet counting in both whole blood and PRP as a measure of microaggregate formation, using both citrate and hirudin anticoagulation. Methods and Results—Three GP IIb/IIIa antagonists, eptifibatide, MK-0852, and GR144053, were compared in PRP (turbidimetry) and whole blood (platelet counting with an Ultra-Flo 100 Platelet Counter), with ADP and collagen used as agonists. Compared with hirudin, citrate enhanced the potency of eptifibatide by up to 4-fold in both PRP and whole blood (P<0.0005), modestly enhanced MK-0852 potency (P=0.001), and had no effect on GR144053. Potency measured in PRP was 2- to 3-fold greater co...
A Mali - One of the best experts on this subject based on the ideXlab platform.
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influence of fe ba molar ratio on the characteristics of ba hexaferrite particles prepared by sol gel combustion method
Journal of Alloys and Compounds, 2005Co-Authors: A Mali, Abolghasem AtaieAbstract:Abstract Nano-crystalline particles of barium hexaferrite (BaFe 12 O 19 ) have been prepared by a sol–gel combustion technique using nitrate–citrate gels prepared from metal nitrates and citric acid solutions under various Fe/Ba molar ratios of 10, 11 and 12. The thermal decomposition process of the nitrate–citrate gels and as-burnt powders was investigated by XRD and DTA/TGA techniques. The results revealed that the nitrate citrate gels exhibit a self-propagating behavior after ignition and the single-phase barium hexaferrite formation temperature is significantly influenced by Fe/Ba molar ratio. The Fe/Ba molar ratio of 11 is more favorable for formation of barium hexaferrite. The SEM investigations revealed that the mean particle size of barium hexaferrite dramatically increases with increasing calcination temperature from 1000 to 1100 °C. The magnetic properties measured using a vibrating sample magnetometer (VSM) revealed that the sample synthesized under Fe/Ba molar ratio of 11, exhibits higher saturation magnetization in comparison with those synthesized under Fe/Ba molar ratios of 10 and 12.
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influence of the metal nitrates to citric acid molar ratio on the combustion process and phase constitution of barium hexaferrite particles prepared by sol gel combustion method
Ceramics International, 2004Co-Authors: A Mali, Abolghasem AtaieAbstract:A novel sol–gel combustion process was used to synthesize the ultrafine particles of barium hexaferrite. The nitrate–citrate gels were prepared from metal nitrates and citric acid solutions under various molar ratios of the metal nitrates to citric acid of 0.5, 1, 1.5 and 3 by sol–gel process. The results showed that the nitrate citrate gels exhibit a self-propagating behavior after ignition in air at room temperature. The thermal decomposition of nitrate–citrate gels and the phase evolution of calcined powder were investigated respectively by DTA/TG and XRD techniques. Scanning electron microscope was used to characterize the microstructure of the products. The results revealed that the formation temperature and the crystallite size of barium hexaferrite are influenced significantly by the molar ratio of the metal nitrates to citric acid. The formation temperature of barium hexaferrite decreases with increasing the molar ratio of the metal nitrates to citric acid. © 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.