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Stanley Feldman - One of the best experts on this subject based on the ideXlab platform.

  • the effect of rate of stimulation on force of contraction in a partially paralyzed rat phrenic nerve hemidiaphragm preparation
    Anesthesia & Analgesia, 1997
    Co-Authors: Adrian J. England, Katrina M. Richards, Stanley Feldman
    Abstract:

    This study was performed to determine whether presynaptic receptor blockade could be differentiated from postsynaptic blockade by examining the effect of increasing rates of indirect stimulation on twitch height depression (THD) on partially paralyzed in vitro rat diaphragm preparations. We calculated the T200/T1 ratio (force of the 200th stimuli divided by the force of the first stimuli) at rates of 0.2 Hz, 0.5 Hz, 1 Hz, and 2 Hz using a drug concentration which provided approximately 20% THD during stimulation at 0.1 Hz. Markedly different T200/T1 ratios were demonstrated when Hexamethonium, a drug with predominantly presynaptic effects, was compared with alpha bungarotoxin, a drug with predominantly postsynaptic effects. These results were then compared with those from vecuronium, rocuronium, mivacurium, and tubocurarine. Both Hexamethonium and rocuronium caused a marked decrease in T200/T1 ratio at higher rates of stimulation; alpha bungarotoxin caused a slight increase in T200/T1 ratio at higher rates of stimulation. The T200/T1 ratios produced by vecuronium, mivacurium, and tubocurarine lay intermediate between Hexamethonium and alpha bungarotoxin. Significant differences in T200/T1 ratios were found when alpha bungarotoxin was compared with all other drugs at 2 Hz. Hexamethonium and rocuronium produced significant differences in T200/T1 ratio from those of all the other drugs at 1 Hz and 2 Hz. There were significant differences in the T200/T1 ratio found after Hexamethonium and rocuronium compared to alpha bungarotoxin at 0.5 Hz. No significant differences at any rate of stimulation were found between Hexamethonium and rocuronium. No difference was observed in the effect of vecuronium, mivacurium, and tubocurarine. We conclude that, if the observed effect is the result of Hexamethonium acting predominantly at presynaptic sites and alpha bungarotoxin acting predominantly at postsynaptic sites, the relative contribution of small doses of nondepolarizing drugs at each site can be differentiated by determining the T200/T1 ratio at rates of 1 Hz or 2 Hz. Our results are consistent with the suggestion that small doses of rocuronium have marked presynaptic activity, but that vecuronium, mivacurium, and tubocurarine have both pre- and postsynaptic effects.

  • Interaction of decamethonium with Hexamethonium or vecuronium in the rat : an isobolographic analysis
    Anesthesia and analgesia, 1995
    Co-Authors: Imre Redai, Katrina M. Richards, Adrian J. England, Stanley Feldman
    Abstract:

    We used isobolographic analysis to investigate the interaction of decamethonium with either Hexamethonium or vecuronium in the rat phrenic nerve hemidiaphragm preparation. EC50 values of decamethonium, Hexamethonium, and vecuronium were (mean +/- SEM) 47.36 +/- 9.58 microM, 4.27 +/- 0.53 mM, and 5.19 +/- 1.17 microM, respectively. Combinations of drugs in concentrations corresponding to the 1:2, 1:1, and 2:1 ratios of their EC50 values were used to determine three points of each isobole. Decamethonium and Hexamethonium showed antagonism: significant deviations from the line of additivity were found at EC50 ratios of 2:1 and 1:1 (P < 0.01 and P < 0.05, respectively) indicating that Hexamethonium is a potent antagonist of decamethonium. For decamethonium and vecuronium none of the three points on the isobole was significantly different from the corresponding point on the line of additivity. Hexamethonium is known to be a weak antagonist at the postsynaptic nicotinic acetylcholine receptor but a potent antagonist at the presynaptic nicotinic receptor. Vecuronium is a more potent antagonist at the postsynaptic nicotinic receptor but a much weaker antagonist at the presynaptic site. It was postulated that in the rat the primary site of action of decamethonium is at the presynaptic nerve terminal. Our findings suggest that presynaptic rather than postsynaptic potency of a nondepolarizing drug determines ability to antagonize the effect of a depolarizing drug in the rat.

Yu Fan - One of the best experts on this subject based on the ideXlab platform.

  • Hexamethonium bromide assisted synthesis of como graphene catalysts for selective hydrodesulfurization
    Applied Catalysis B-environmental, 2019
    Co-Authors: Yunfeng Guo, Tingting Huang, Yu Fan
    Abstract:

    Abstract A series of CoMo/graphene selective hydrodesulfurization (HDS) catalysts were prepared using the Hexamethonium bromide-assisted hydrothermal method, and the influences of the Hexamethonium bromide/Mo molar ratio and the CoMoS/MoS2 ratio on the HDS activity and selectivity were investigated. The results show that the kHDS value (2.76 × 10−7 mol g−1 s−1) of thiophene and the HDS selectivity factor (13.6) over the as-prepared catalysts were 1.3 times and 1.6 times greater than those over the CoMo/graphene prepared using the conventional impregnation method. The higher HDS activity and selectivity of the as-prepared catalysts result from the higher dispersion of Mo species and the higher CoMoS/MoS2 ratio compared to the CoMo/graphene prepared by impregnation. Among all the catalysts, the catalyst with a Hexamethonium bromide/Mo molar ratio of 6.0 presents the highest HDS selectivity due to its highest ratio of edge to corner Co atoms in CoMoS with a superior CoMoS/MoS2 ratio. The present investigation provides a route for developing highly selective HDS catalysts using graphene as support by adjusting the Hexamethonium bromide/Mo ratio to finely tune the morphology of the active phases.

  • Hexamethonium bromide-assisted synthesis of CoMo/graphene catalysts for selective hydrodesulfurization
    Applied Catalysis B: Environmental, 2019
    Co-Authors: Yunfeng Guo, Tingting Huang, Yu Fan
    Abstract:

    Abstract A series of CoMo/graphene selective hydrodesulfurization (HDS) catalysts were prepared using the Hexamethonium bromide-assisted hydrothermal method, and the influences of the Hexamethonium bromide/Mo molar ratio and the CoMoS/MoS2 ratio on the HDS activity and selectivity were investigated. The results show that the kHDS value (2.76 × 10−7 mol g−1 s−1) of thiophene and the HDS selectivity factor (13.6) over the as-prepared catalysts were 1.3 times and 1.6 times greater than those over the CoMo/graphene prepared using the conventional impregnation method. The higher HDS activity and selectivity of the as-prepared catalysts result from the higher dispersion of Mo species and the higher CoMoS/MoS2 ratio compared to the CoMo/graphene prepared by impregnation. Among all the catalysts, the catalyst with a Hexamethonium bromide/Mo molar ratio of 6.0 presents the highest HDS selectivity due to its highest ratio of edge to corner Co atoms in CoMoS with a superior CoMoS/MoS2 ratio. The present investigation provides a route for developing highly selective HDS catalysts using graphene as support by adjusting the Hexamethonium bromide/Mo ratio to finely tune the morphology of the active phases.

Sung Yell Kim - One of the best experts on this subject based on the ideXlab platform.

  • Neuromuscular Blocking Properties of beta-Bungarotoxin, Hexamethonium and Verapamil in the Rat Phrenic Nerve-Hemidiaphragm Preparation
    Korean Journal of Anesthesiology, 2001
    Co-Authors: Sung Yell Kim, Jeong Seok Lee, Sun Chong Kim, Sang Ho Kim, Yong Ik Kim, Soon Im Kim
    Abstract:

    Background: β-Bungarotoxin irreversibly changes the presynaptic membrane, Hexamethonium acts on the presynaptic nicotinic receptor, and verapamil blocks the ion channels on the presynaptic membrane. The effect of these drugs on twitch height and train of four (TOF) ratio were investigated, as well as the reversal effects of neostigmine, pyridostigmine or 4-aminopyridine (4-AP) on the partial neuromuscular blockade induced by these drugs. Methods: Square wave, 0.1 Hz supramaximal stimuli or 2 Hz, 0.2 ms train of four stimuli, was applied to the phrenic nerve-hemidiaphragm preparation of the rat, and the twitch height response was recorded mechanomyographically. The cumulative concentration effects and TOF ratios at each point of twitch depression after β-bungarotoxin, Hexamethonium or verapamil were measured. TOF ratios were observed at 75, 50 and 25% of the control twitch height value during observation of the concentration effect. The EC50 and EC95 of β-bungarotoxin, Hexamethonium or verapamil were calculated using an inhibitory sigmoid Emax model. The reversal effect of some doses of neostigmine, pyridostigmine or 4-aminopyridine to the partial neuromuscular block produced by EC50 of βbungarotoxin, Hexamethonium or verapamil was determined. Results: The EC50 and EC95 of β-bungarotoxin, Hexamethonium and verapamil were 0.0695 and 0.1160μg/ml, 1267.0 and 2033.5μg/ml and 29.45 and 37.99μg/ml respectively. TOF fade was marked with Hexamethonium or verapamil but small with β-bungarotoxin. Neostigmine or pyridostigmine did not reverse the partial neuromuscular block induced by β-bungarotoxin, Hexamethonium or verapamil. However, 4-AP produced a dose-dependent recovery of the twitch response (P < 0.05). Conclusions: β-Bungarotoxin, Hexamethonium and verapamil produced different degree of TOF fade, and this may be due to different sites of action of these drugs. 4-AP reversed effectively the partial

  • Studies of Interaction between Hexamethonium and Lidocaine, alpha-Bungarotoxin or Decamethonium in Vitro
    Korean Journal of Anesthesiology, 2001
    Co-Authors: Jeong Seok Lee, Sung Yell Kim, Dae Geun Jeon, Sae Jin Choi
    Abstract:

    Background: Interactions of neuromuscular blocking agents are antagonistic in a combination of depolarizing and nondepolarizing agents, additive in a combination of relative two compounds or synergistic in a combination of different two nondepolarizing agents. However, the interactions of neuromuscular blocking agents with a different site of action from each other have not been studied clearly. This study was designed to examine the interaction between Hexamethonium and lidocaine, α-bungarotoxin or decamethonium with markedly different pre and postsynaptic sites of action. Methods: Square wave, 0.1 Hz supramaximal stimuli or 2 Hz, 0.2 ms train of four (TOF) stimuli, was applied to the rat phrenic nerve-hemidiaphragm preparation, and the twitch height response was recorded mechanomyographically. The cumulative concentration effect and TOF ratio at each point of twitch depression after Hexamethonium, lidocaine, α-bungarotoxin or decamethonium given were measured. The EC50 and EC95 of Hexamethonium, lidocaine, α-bungarotoxin and decamethonium were calculated using an inhibitory sigmoid E model. In the experiment of each combination of two drugs, three points of the isobole for Hexamethonium-lidocaine, Hexamethonium-α-bungarotoxin and Hexamethonium-decamethonium were established using ratios of 1: 3, 1: 1 and 3: 1 of their EC50. Points on the line of theoretical additivity and 95% canfidence intervals were calculated according to Tallarida et al. TOF ratios were observed at 75, 50 and 25% of the control twitch height value during each combination ratio of their EC50. Results: Significant deviations of points on the isobole from the line of additivity to the left were found at all EC50 ratios of Hexamethonium-lidocaine (P

Adrian J. England - One of the best experts on this subject based on the ideXlab platform.

  • the effect of rate of stimulation on force of contraction in a partially paralyzed rat phrenic nerve hemidiaphragm preparation
    Anesthesia & Analgesia, 1997
    Co-Authors: Adrian J. England, Katrina M. Richards, Stanley Feldman
    Abstract:

    This study was performed to determine whether presynaptic receptor blockade could be differentiated from postsynaptic blockade by examining the effect of increasing rates of indirect stimulation on twitch height depression (THD) on partially paralyzed in vitro rat diaphragm preparations. We calculated the T200/T1 ratio (force of the 200th stimuli divided by the force of the first stimuli) at rates of 0.2 Hz, 0.5 Hz, 1 Hz, and 2 Hz using a drug concentration which provided approximately 20% THD during stimulation at 0.1 Hz. Markedly different T200/T1 ratios were demonstrated when Hexamethonium, a drug with predominantly presynaptic effects, was compared with alpha bungarotoxin, a drug with predominantly postsynaptic effects. These results were then compared with those from vecuronium, rocuronium, mivacurium, and tubocurarine. Both Hexamethonium and rocuronium caused a marked decrease in T200/T1 ratio at higher rates of stimulation; alpha bungarotoxin caused a slight increase in T200/T1 ratio at higher rates of stimulation. The T200/T1 ratios produced by vecuronium, mivacurium, and tubocurarine lay intermediate between Hexamethonium and alpha bungarotoxin. Significant differences in T200/T1 ratios were found when alpha bungarotoxin was compared with all other drugs at 2 Hz. Hexamethonium and rocuronium produced significant differences in T200/T1 ratio from those of all the other drugs at 1 Hz and 2 Hz. There were significant differences in the T200/T1 ratio found after Hexamethonium and rocuronium compared to alpha bungarotoxin at 0.5 Hz. No significant differences at any rate of stimulation were found between Hexamethonium and rocuronium. No difference was observed in the effect of vecuronium, mivacurium, and tubocurarine. We conclude that, if the observed effect is the result of Hexamethonium acting predominantly at presynaptic sites and alpha bungarotoxin acting predominantly at postsynaptic sites, the relative contribution of small doses of nondepolarizing drugs at each site can be differentiated by determining the T200/T1 ratio at rates of 1 Hz or 2 Hz. Our results are consistent with the suggestion that small doses of rocuronium have marked presynaptic activity, but that vecuronium, mivacurium, and tubocurarine have both pre- and postsynaptic effects.

  • Interaction of decamethonium with Hexamethonium or vecuronium in the rat : an isobolographic analysis
    Anesthesia and analgesia, 1995
    Co-Authors: Imre Redai, Katrina M. Richards, Adrian J. England, Stanley Feldman
    Abstract:

    We used isobolographic analysis to investigate the interaction of decamethonium with either Hexamethonium or vecuronium in the rat phrenic nerve hemidiaphragm preparation. EC50 values of decamethonium, Hexamethonium, and vecuronium were (mean +/- SEM) 47.36 +/- 9.58 microM, 4.27 +/- 0.53 mM, and 5.19 +/- 1.17 microM, respectively. Combinations of drugs in concentrations corresponding to the 1:2, 1:1, and 2:1 ratios of their EC50 values were used to determine three points of each isobole. Decamethonium and Hexamethonium showed antagonism: significant deviations from the line of additivity were found at EC50 ratios of 2:1 and 1:1 (P < 0.01 and P < 0.05, respectively) indicating that Hexamethonium is a potent antagonist of decamethonium. For decamethonium and vecuronium none of the three points on the isobole was significantly different from the corresponding point on the line of additivity. Hexamethonium is known to be a weak antagonist at the postsynaptic nicotinic acetylcholine receptor but a potent antagonist at the presynaptic nicotinic receptor. Vecuronium is a more potent antagonist at the postsynaptic nicotinic receptor but a much weaker antagonist at the presynaptic site. It was postulated that in the rat the primary site of action of decamethonium is at the presynaptic nerve terminal. Our findings suggest that presynaptic rather than postsynaptic potency of a nondepolarizing drug determines ability to antagonize the effect of a depolarizing drug in the rat.

Jeong Seok Lee - One of the best experts on this subject based on the ideXlab platform.

  • Neuromuscular Blocking Properties of beta-Bungarotoxin, Hexamethonium and Verapamil in the Rat Phrenic Nerve-Hemidiaphragm Preparation
    Korean Journal of Anesthesiology, 2001
    Co-Authors: Sung Yell Kim, Jeong Seok Lee, Sun Chong Kim, Sang Ho Kim, Yong Ik Kim, Soon Im Kim
    Abstract:

    Background: β-Bungarotoxin irreversibly changes the presynaptic membrane, Hexamethonium acts on the presynaptic nicotinic receptor, and verapamil blocks the ion channels on the presynaptic membrane. The effect of these drugs on twitch height and train of four (TOF) ratio were investigated, as well as the reversal effects of neostigmine, pyridostigmine or 4-aminopyridine (4-AP) on the partial neuromuscular blockade induced by these drugs. Methods: Square wave, 0.1 Hz supramaximal stimuli or 2 Hz, 0.2 ms train of four stimuli, was applied to the phrenic nerve-hemidiaphragm preparation of the rat, and the twitch height response was recorded mechanomyographically. The cumulative concentration effects and TOF ratios at each point of twitch depression after β-bungarotoxin, Hexamethonium or verapamil were measured. TOF ratios were observed at 75, 50 and 25% of the control twitch height value during observation of the concentration effect. The EC50 and EC95 of β-bungarotoxin, Hexamethonium or verapamil were calculated using an inhibitory sigmoid Emax model. The reversal effect of some doses of neostigmine, pyridostigmine or 4-aminopyridine to the partial neuromuscular block produced by EC50 of βbungarotoxin, Hexamethonium or verapamil was determined. Results: The EC50 and EC95 of β-bungarotoxin, Hexamethonium and verapamil were 0.0695 and 0.1160μg/ml, 1267.0 and 2033.5μg/ml and 29.45 and 37.99μg/ml respectively. TOF fade was marked with Hexamethonium or verapamil but small with β-bungarotoxin. Neostigmine or pyridostigmine did not reverse the partial neuromuscular block induced by β-bungarotoxin, Hexamethonium or verapamil. However, 4-AP produced a dose-dependent recovery of the twitch response (P < 0.05). Conclusions: β-Bungarotoxin, Hexamethonium and verapamil produced different degree of TOF fade, and this may be due to different sites of action of these drugs. 4-AP reversed effectively the partial

  • Studies of Interaction between Hexamethonium and Lidocaine, alpha-Bungarotoxin or Decamethonium in Vitro
    Korean Journal of Anesthesiology, 2001
    Co-Authors: Jeong Seok Lee, Sung Yell Kim, Dae Geun Jeon, Sae Jin Choi
    Abstract:

    Background: Interactions of neuromuscular blocking agents are antagonistic in a combination of depolarizing and nondepolarizing agents, additive in a combination of relative two compounds or synergistic in a combination of different two nondepolarizing agents. However, the interactions of neuromuscular blocking agents with a different site of action from each other have not been studied clearly. This study was designed to examine the interaction between Hexamethonium and lidocaine, α-bungarotoxin or decamethonium with markedly different pre and postsynaptic sites of action. Methods: Square wave, 0.1 Hz supramaximal stimuli or 2 Hz, 0.2 ms train of four (TOF) stimuli, was applied to the rat phrenic nerve-hemidiaphragm preparation, and the twitch height response was recorded mechanomyographically. The cumulative concentration effect and TOF ratio at each point of twitch depression after Hexamethonium, lidocaine, α-bungarotoxin or decamethonium given were measured. The EC50 and EC95 of Hexamethonium, lidocaine, α-bungarotoxin and decamethonium were calculated using an inhibitory sigmoid E model. In the experiment of each combination of two drugs, three points of the isobole for Hexamethonium-lidocaine, Hexamethonium-α-bungarotoxin and Hexamethonium-decamethonium were established using ratios of 1: 3, 1: 1 and 3: 1 of their EC50. Points on the line of theoretical additivity and 95% canfidence intervals were calculated according to Tallarida et al. TOF ratios were observed at 75, 50 and 25% of the control twitch height value during each combination ratio of their EC50. Results: Significant deviations of points on the isobole from the line of additivity to the left were found at all EC50 ratios of Hexamethonium-lidocaine (P