scholarly journals Ionic Mechanisms of the Cardiac Pacemaker Potential.

1996 ◽  
Vol 37 (5) ◽  
pp. 673-682 ◽  
Author(s):  
Akinori NOMA
Keyword(s):  
Cardiac Pacemaker ◽  
Pacemaker Potential ◽  
Ionic Mechanisms ◽  
Cardiac Pacemaker Potential

scholarly journals Estimating Contribution Of Individual Ionic Components To The Cardiac Pacemaker Potential

2009 ◽  
Vol 96 (3) ◽  
pp. 259a
Author(s):  
Yukiko Himeno ◽  
Chae Young Cha ◽  
Takao Shimayoshi ◽  
Yasuhiko Nakamura ◽  
Jian-Wu Wang ◽  
...  
Keyword(s):  
Cardiac Pacemaker ◽  
Pacemaker Potential ◽  
Ionic Components ◽  
Cardiac Pacemaker Potential

scholarly journals Cardiac Pacemaker Dysfunction Arising From Different Studies of Ion Channel Remodeling in the Aging Rat Heart

2020 ◽  
Vol 11 ◽  
Author(s):  
Aaazh M. Alghamdi ◽  
Mark R. Boyett ◽  
Jules C. Hancox ◽  
Henggui Zhang
Keyword(s):  
Ion Channels ◽  
Sinoatrial Node ◽  
Cardiac Pacemaker ◽  
Data Sets ◽  
Down Regulation ◽  
Aged Rat ◽  
Age Related ◽  
Aging Study ◽  
Ionic Mechanisms ◽  
Induced Changes

The function of the sinoatrial node (SAN), the pacemaker of the heart, declines with age, resulting in increased incidence of sinoatrial node dysfunction (SND) in older adults. The present study assesses potential ionic mechanisms underlying age associated SND. Two group studies have identified complex and various changes in some of membrane ion channels in aged rat SAN, the first group (Aging Study-1) indicates a considerable changes of gene expression with up-regulation of mRNA in ion channels of Cav1.2, Cav1.3 and KvLQT1, Kv4.2, and the Ca2+ handling proteins of SERCA2a, and down-regulation of Cav3.1, NCX, and HCN1 and the Ca2+-clock proteins of RYR2. The second group (Aging Study-2) suggests a different pattern of changes, including down regulation of Cav1.2, Cav1.3 and HCN4, and RYR2, and an increase of NCX and SERCA densities and proteins. Although both data sets shared a similar finding for some specific ion channels, such as down regulation of HCN4, NCX, and RYR2, there are contradictory changes for some other membrane ion channels, such as either up-regulation or down-regulation of Cav1.2, NCX and SERCA2a in aged rat SAN. The present study aims to test a hypothesis that age-related SND may arise from different ionic and molecular remodeling patterns. To test this hypothesis, a mathematical model of the electrical action potential of rat SAN myocytes was modified to simulate the functional impact of age-induced changes on membrane ion channels and intracellular Ca2+ handling as observed in Aging Study-1 and Aging Study-2. The role and relative importance of each individually remodeled ion channels and Ca2+-handling in the two datasets were evaluated. It was shown that the age-induced changes in ion channels and Ca2+-handling, based on either Aging Study-1 or Aging Study-2, produced similar bradycardic effects as manifested by a marked reduction in the heart rate (HR) that matched experimental observations. Further analysis showed that although the SND arose from an integrated action of all remodeling of ion channels and Ca2+-handling in both studies, it was the change to ICaL that played the most important influence.

Remembering William Chardack, MD, cardiac-pacemaker pioneer

2007 ◽  
Author(s):  
Andrew A. Gage ◽  
Anthony J. Federico
Keyword(s):  
Cardiac Pacemaker

Transvenous Cardiac Pacemaker Educational Resource

MedEdPORTAL ◽  
2015 ◽  
Vol 11 (1) ◽  
Author(s):  
Jmir Cousar ◽  
Michael Bohanske ◽  
Jeffery Hill
Keyword(s):  
Cardiac Pacemaker ◽  
Educational Resource

Hydrostibination of Alkynes: A Radical Mechanism

2020 ◽  
Author(s):  
Josh MacMillan ◽  
Katherine Marczenko ◽  
Erin Johnson ◽  
Saurabh Chitnis
Keyword(s):  
Density Functional ◽  
Activation Barrier ◽  
Closed Shell ◽  
Reaction Rates ◽  
Radical Mechanism ◽  
Neutral Radical ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Ionic Mechanisms ◽  
Terminal Acetylenes

The addition of Sb-H bonds to alkynes was reported recently as a new hydroelementation reaction that exclusively yields anti-Markovnikov <i>Z</i>-olefins from terminal acetylenes. We examine four possible mechanisms that are consistent with the observed stereochemical and regiochemical outcomes. A comprehensive analysis of solvent, substituent, isotope, additive, and temperature effects on hydrostibination reaction rates definitively refutes three ionic mechanisms involving closed-shell charged intermediates. Instead the data support a fourth pathway featuring neutral radical Sb<sup>II</sup> and Sb<sup>III</sup> intermediates. Density Functional Theory (DFT) calculations are consistent this model, predicting an activation barrier that is within 1 kcal mol<sup>-1</sup> of the experimental value (Eyring analysis) and a rate limiting step that is congruent with experimental kinetic isotope effect. We therefore conclude that hydrostibination of arylacetylenes is initiated by the generation of stibinyl radicals, which then participate in a cycle featuring Sb<sup>II</sup> and Sb<sup>III</sup> intermediates to yield the observed <i>Z</i>-olefins as products. This mechanistic understanding will enable rational evolution of hydrostibination as a methodology for accessing challenging products such as <i>E</i>-olefins.

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