摘要:

Mechanical stretch is thought to play an important role in remodeling atrial and ventricular myocardium and may produce substrates that promote arrhythmogenesis. In the present work, neonatal rat ventricular myocytes were cultured for 4 days as confluent monolayers on thin silicone membranes and then subjected to linear pulsatile stretch for up to 6 hours. Action potential upstrokes and propagation velocity (&THgr;) were measured with multisite optical recording of transmembrane voltage of the cells stained with the voltage-sensitive dye RH237. Expression of the gap junction protein connexin43 (Cx43) and the fascia adherens junction protein N-cadherin was measured immunohistochemically in the same preparations. Pulsatile stretch caused dramatic upregulation of intercellular junction proteins after only 1 hour and a further increase after 6 hours (Cx43 signal increased from 0.73 to 1.86 and 2.02% cell area, and N-cadherin signal increased from 1.21 to 2.11 and 2.74% cell area after 1 and 6 hours, respectively). This was paralleled by an increase in &THgr; from 27 to 35 cm/s after 1 hour and 37 cm/s after 6 hours. No significant change in the upstroke velocity of the action potential or cell size was observed. Increased &THgr; and protein expression were not reversible after 24 hours of relaxation. Nonpulsatile (static) stretch produced qualitatively similar but significantly smaller changes than pulsatile stretch. Thus, pulsatile linear stretch in vitro causes marked upregulation of proteins that form electrical and mechanical junctions, as well as a concomitant increase in propagation velocity. These changes may contribute to arrhythmogenesis in myocardium exposed to acute stretch.

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

In brain, the regulatory mechanism of the endothelial reactivity to nitric oxide and endothelin-1 may involve Ca2+, cytoskeleton, and vasodilator-stimulated phosphoprotein changes mediated by the cGMP/cGMP kinase system.1Endothelium of human brain capillaries or microvessels is used to examine the interplay of endothelin-1 with the putative vasorelaxant 2-arachidonoyl glycerol, an endogenous cannabimimetic derivative of arachidonic acid. This study demonstrates that 2-arachidonoyl glycerol counteracts Ca2+mobilization and cytoskeleton rearrangement induced by endothelin-1. This event is independent of nitric oxide, cyclooxygenase, and lipoxygenase and is mediated in part by cannabimimetic CB1 receptor, G protein, phosphoinositol signal transduction pathway, and Ca2+-activated K+channels. The induced rearrangements of cellular cytoskeleton (actin or vimentin) are partly prevented by inhibition of protein kinase C or high levels of potassium chloride. The 2-arachidonoyl glycerol–induced phosphorylation of vasodilator-stimulated phosphoprotein is mediated by cAMP. These findings suggest that 2-arachidonoyl glycerol may contribute to the regulation of cerebral capillary and microvascular function.

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Host genetic responses that characterize enteroviral myocarditis have not yet been determined. The injurious and inflammatory process in heart muscle may reflect host responses of benefit to the virus and ultimately result in congestive heart failure and dilated cardiomyopathy. On the other hand, host responses within the myocardium may secure the host against acute or protracted damage. To investigate the nature of modified gene expression in comparison with normal tissue, mRNA species were assessed in myocardium using cDNA microarray technology at days 3, 9, and 30 after infection. Of 7000 clones initially screened, 169 known genes had a level of expression significantly different at 1 or more postinfection time points as compared with baseline. The known regulated genes were sorted according to their functional groups and normalized expression patterns and, subsequently, interpreted in the context of viremic, inflammatory, and healing phases of the myocarditic process.

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Endothelial cells (ECs) actively regulate the extravasation of blood constituents. On stimulation by vasoactive agents and thrombin, ECs change their cytoskeletal architecture and small gaps are formed between neighboring cells. These changes partly depend on a rise in [Ca2+]iand activation of the Ca2+/calmodulin-dependent myosin light chain kinase. In this study, mechanisms that contribute to the thrombin-enhanced endothelial permeability were further investigated. We provide direct evidence that thrombin induces a rapid and transient activation of RhoA in human umbilical vein ECs. Under the same conditions, the activity of the related protein Rac was not affected. This was accompanied by an increase in myosin light chain phosphorylation, the generation of F-actin stress fibers, and a prolonged increase in endothelial permeability. Inhibition of the RhoA target Rho kinase with the specific inhibitor Y-27632 reduced all of these effects markedly. In the presence of Y-27632, the thrombin-enhanced permeability was additionally reduced by chelation of [Ca2+]iby BAPTA. These data indicate that RhoA/Rho kinase and Ca2+represent 2 pathways that act on endothelial permeability. In addition, the protein tyrosine kinase inhibitor genistein reduced thrombin-induced endothelial permeability without affecting activation of RhoA by thrombin. Our data support a model of thrombin-induced endothelial permeability that is regulated by 3 cellular signal transduction pathways.

ISSN:0009-7330    

出版商:OVID    

年代:2000

数据来源: OVID