ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The role of the Na+-Ca2+exchanger as a major determinant of cell Ca2+is well defined in cardiac tissue, and there has been much effort to develop specific inhibitors of the exchanger. We use a novel system to test the specificity of two putative specific inhibitors, KB-R7943 and SEA0400. The drugs are applied to electrically stimulated heart tubes from control mouse embryos or embryos with the Na+-Ca2+exchanger knocked out. We monitored effects of the drugs on Ca2+transients. Both drugs depress the Ca2+transients at low concentrations even in the absence of any Na+-Ca2+exchanger. KB-R7943 and SEA0400 are not completely specific and should be used with caution as Na+-Ca2+exchange inhibitors.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Heart morphogenesis comprises 2 major consecutive steps, viz. chamber formation followed by septation. Septation is the remodeling of the heart from a single-channel peristaltic pump to a dual-channel, synchronously contracting device with 1-way valves. In the human heart, septation occurs between 4 and 7 weeks of development. Cardiac looping and chamber formation bring the contributing structures into position to engage in septation. Cardiomyocytes that participate in chamber formation do not materially contribute to septation. The (re)discovery of the role of extracardiac mesenchymal tissue in atrioventricular septation, the appreciation that the formation of the right atrioventricular connection is more than a mere rightward expansion of the atrioventricular canal, the awareness that myocardium originating from the so-called anterior heart field regresses after its function as outflow-tract sphincter ceases, and the recent finding that the myocardialized proximal portion of the outflow-tract septum becomes the supraventricular crest have all significantly enhanced our understanding of the morphogenetic processes that contribute to septation. The bifurcation of the ventricular conduction system is the landmark that separates the contribution of the atrioventricular cushions and the outflow-tract ridges to septation and that divides the muscular ventricular septum in inlet, trabecular, and outlet portions.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Several proteins including connexin40 (Cx40) and connexin43 (Cx43) form gap junctions between cells of the heart; they may be found separately or may be coexpressed. These connexins form channels with differing conductance and permeability properties. Cx40 and Cx43 are each required for normal electrical conduction between cells in different regions of the heart. We hypothesized that the major difference between these connexins might be in their selective intercellular passage of small molecules such as second messengers, which can be assessed using biologically inert fluorescent probes. Therefore, we designed experimental paradigms to quantitate the permeability properties of these cardiac connexins using simultaneous measurement of junctional conductance (gj) by the double whole-cell patch-clamp technique and intercellular transfer of Lucifer Yellow (LY) by fluorescence microscopy. These studies were performed in HeLa cells stably transfected with Cx40 or Cx43 or cotransfected with both connexins. We found that homotypic Cx43 channels were about 5 times more permeable to LY than homotypic Cx40 channels (flux of ≈1560 versus ≈300 molecules/channel per second). Channels between heterotypic (Cx40-Cx43) cell pairs and between pairs of coexpressing cells exhibited intermediate LY permeability. The permeability ratio for LY relative to monovalent cation (K+) ranged from 0.0025 for Cx40 to 0.028 for Cx43. These permeability ratios suggest that the connexins are highly selective for solutes in the size and charge range of many second messengers. Moreover, the data indicate that coexpression of connexins does not generate unique permeability characteristics, but rather results in an intermediate permeability for solutes involved in metabolic/biochemical coupling.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Although recent investigations have suggested that a Rho-kinase–mediated Ca2+sensitization of vascular smooth muscle contraction plays a critical role in the pathogenesis of cerebral and coronary vasospasm, the upstream of this signal transduction has not been elucidated. In addition, the involvement of protein kinase C (PKC) may also be related to cerebral vasospasm. We recently reported that sphingosylphosphorylcholine (SPC), a sphingolipid, induces Rho-kinase–mediated Ca2+sensitization in pig coronary arteries. The purpose of this present study was to examine the possible mediation of SPC in Ca2+sensitization of the bovine middle cerebral artery (MCA) and the relation to signal transduction pathways mediated by Rho-kinase and PKC. In intact MCA, SPC induced a concentration-dependent (EC50=3.0 &mgr;mol/L) contraction, without [Ca2+]ielevation. In membrane-permeabilized MCA, SPC induced Ca2+sensitization even in the absence of added GTP, which is required for activation of G-proteins coupled to membrane receptors. The SPC-induced Ca2+sensitization was blocked by a Rho-kinase inhibitor (Y-27632) and a dominant-negative Rho-kinase, but not by a pseudosubstrate peptide for conventional PKC, which abolished the Ca2+-independent contraction induced by phorbol ester. In contrast, phorbol ester–induced Ca2+sensitization was resistant to a Rho-kinase inhibitor and a dominant-negative Rho-kinase. In primary cultured vascular smooth muscle cells, SPC induced the translocation of cytosolic Rho-kinase to the cell membrane. We propose that SPC is a novel messenger for Rho-kinase–mediated Ca2+sensitization of cerebral arterial smooth muscle and, therefore, may play a pivotal role in the pathogenesis of abnormal contraction of the cerebral artery such as vasospasm. The SPC/Rho-kinase pathway functions independently of the PKC pathway.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

We previously reported the identification of a locus on mouse chromosome 6 that confers almost total resistance to atherogenesis, even on a hypercholesterolemic (LDL receptor–null) background. 5-Lipoxygenase (5-LO) is the rate-limiting enzyme in leukotriene synthesis and was among the chromosome 6 locus candidate genes that we examined. The levels of 5-LO mRNA were reduced about 5-fold in a congenic strain, designated CON6, containing the resistant chromosome 6 region derived from the CAST/Ei strain (CAST), as compared with the background C57BL/6J (B6) strain. 5-LO protein levels were similarly reduced in the CON6 mice. Sequencing of the 5-LO cDNA revealed several differences between CON6 and the B6 strain. To test the whether 5-LO is responsible for the resistant phenotype, we bred a 5-LO knockout allele onto an LDL receptor–null (LDLR−/−) background. On this background, the mice bred poorly and only heterozygous 5-LO knockout mice were obtained. These mice showed a dramatic decrease (>26-fold;P<0.0005) in aortic lesion development, similar to the CON6 mice. Immunohistochemistry revealed that 5-LO was abundantly expressed in atherosclerotic lesions of apoE− /−and LDLR−/−deficient mice, appearing to colocalize with a subset of macrophages but not with all macrophage-staining regions. When bone marrow from 5-LO+/−mice was transplanted into LDLR−/−, there was a significant reduction in atherogenesis, suggesting that macrophage 5-LO is responsible, at least in part, for the effect on atherosclerosis. These results indicate that 5-LO contributes importantly to the atherogenic process and they provide strong presumptive evidence that reduced 5-LO expression is partly responsible for the resistance to atherosclerosis in CON6 mice.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Intrauterine growth retardation (IUGR) is associated with vascular complications leading to hypoxia and abnormal fetal development. The effect of IUGR on l-arginine transport and nitric oxide (NO) synthesis was investigated in cultures of human umbilical vein endothelial cells (HUVECs). IUGR was associated with membrane depolarization and reduced l-arginine transport (Vmax= 5.8±0.2 versus 3.3±0.1 pmol/&mgr;g protein per minute), with no significant changes in transport affinity (Km=159±15 versus 137±14 &mgr;mol/L). l-Arginine transport wastrans-stimulated (8- to 9-fold) in cells from normal and IUGR pregnancies. IUGR was associated with reduced production of l-[3H]citrulline from l-[3H] arginine, lower nitrite and intracellular l-arginine, l-citrulline, and cGMP. IUGR decreased hCAT-1 and hCAT-2B mRNA, and increased eNOS mRNA and protein levels. IUGR-associated inhibition of l-arginine transport and NO synthesis, and membrane depolarization were reversed by the NO donorS-nitroso-N-acetyl-l,d-penicillamine. In summary, endothelium from fetuses with IUGR exhibit altered l-arginine transport and NO synthesis (l-arginine/NO pathway), reduced expression and activity of hCAT-1 and hCAT-2B and reduced eNOS activity. Alterations in l-arginine/NO pathway could be critical for the physiological processes involved in the etiology of IUGR in human pregnancies.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Expression of the zinc finger transcription factor early growth response gene-1 (Egr-1) is triggered rapidly after mechanical vascular injury or after a precipitous drop in ambient oxygen, whereupon it induces the expression of diverse gene families to elicit a pathological response. Initially characterized as an early response transcriptional activator, the role of Egr-1 in more chronic forms of vascular injury remains to be defined. Studies were designed to examine whether Egr-1 induction may serve as a causal link between early preservation injury and delayed vascular consequences, such as coronary allograft vasculopathy (CAV). The preservation and transplantation of heterotopic murine cardiac allografts strongly induce Egr-1 expression, leading to increased expression of its downstream target genes, such as intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and platelet-derived growth factor A chain. Expression of these Egr-1–inducible gene targets is virtually obliterated in homozygous Egr-1–null donor allografts, which also exhibit attenuated parenchymal rejection and reduced CAV as long as 60 days. Congruous data are observed by treating donor hearts with a phosphorothioate antisense oligodeoxyribonucleotide directed against Egr-1 before organ harvest, which blocks subsequent expression of Egr-1 mRNA and protein and suppresses the late development of CAV. These data indicate that Egr-1 induction represents a central effector mechanism in the development of chronic rejection characterized by CAV. Blocking the expression of this proximal transcription factor solely at the time of organ harvest elicits beneficial delayed consequences for the cardiac allograft.

ISSN:0009-7330    

出版商:OVID    

年代:2002

数据来源: OVID