The role of glycosylation on voltage-dependent channel gating for the cloned human cardiac sodium channel (hH1a) and the adult rat skeletal muscle isoform (microl) was investigated in HEK293 cells transiently transfected with either hH1a or microl cDNA. The contribution of sugar residues to channel gating was examined in transfected cells pretreated with various glycosidase and enzyme inhibitors to deglycosylate channel proteins. Pretreating transfected cells with enzyme inhibitors castanospermine and swainsonine, or exo-glycosidase neuroaminidase caused 7 to 9 mV depolarizing shifts of V(1/2) for steady-state activation of hH1a, while deglycosylation with corresponding drugs elicited about the same amount of depolarizing shifts (8 to 9 mV) of V(1/2) for steady-state activation of microl. Elevated concentrations of extracellular Mg(2+) significantly masked the castanospermine-elicited depolarizing shifts of V(1/2) for steady-state activation in both transfected hH1a and microl. For steady-state activation, deglycosylation induced depolarizing shifts of V(1/2) for hH1a (10.6 to 12 mV), but hyperpolarizing shifts for microl (3.6 to 4.4 mV). Pretreatment with neuraminidase had no significant effects on single-channel conductance, the mean open time, and the open probability. These data suggest that glycosylation differentially regulates Na channel function in heart and skeletal muscle myocytes.
Résumé -Effet des cendres sur l'activité des porteurs d'oxygène dans la combustion du charbon en boucle chimique -L'application de la combustion en boucle chimique (CLC) aux combustibles solides est actuellement étudiée à l'Université du Kentucky, au Centre de Recherche de l'Energie Appliquée (CAER) dans le but de développer un procédé de gazéification/combustion en boucle chimique pressurisé (PCLC/G) afin de générer de l'électricité à partir de charbon. Un des principaux aspects de la combustion en boucle chimique de combustibles solides est la compréhension de l'effet des cendres sur la réactivité des porteurs d'oxygène (OCs). L'effet des cendres sur la capacité de transfert
The Moebius transformation maps straight lines or circles in one complex domain into straight lines or circles in another. It has been observed that the equations relating acoustic or mechanical impedance modifications to responses under harmonic excitation are in the form of the Moebius transformation. Using the properties of the Moebius transformation, the impedance modification that will minimize the response at a particular frequency can be predicted provided that the modification is between two positions. To prove the utility of this method for acoustic and mechanical systems, it is demonstrated that the equations for calculation of transmission and insertion loss of mufflers, insertion loss of enclosures, and insertion loss of mounts are in the form of the Moebius transformation for impedance modifications. The method is demonstrated for enclosure insertion loss by adding a short duct in a partition introduced to an enclosure. In a similar manner, it is shown that the length or area of a bypass duct in a muffler can be tuned to maximize the transmission loss. In the final example, the insertion loss of an isolator system is improved at a particular frequency by adding mass to one side of the isolator.
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