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Pathophysiologic Role (pathophysiologic + role)
Selected AbstractsFocal Atrial Fibrillation: Experimental Evidence for a Pathophysiologic Role of the Autonomic Nervous SystemJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2001PATRICK SCHAUERTE M.D. Focal AF and Autonomic Nerves.Introduction: Focal paroxysmal atrial fibrillation (AF) was shown recently to originate in the pulmonary veins (PVs) and superior vena cava (SVC). In the present study, we describe an animal model in which local high-frequency electrical stimulation produces focal atrial activation and AF/AT (atrial tachycardia) with electrogram characteristics consistent with clinical reports. Methods and Results: In 21 mongrel dogs, local high-frequency electrical stimulation was performed by delivering trains of electrical stimuli (200 Hz, impulse duration 0.1 msec) to the PVs/SVC during atrial refractoriness. Atrial premature depolarizations (APDs), AT, and AF occurred with increasing highfrequency electrical stimulation voltage. APD/AT/AF originated adjacent to the site of high-frequency electrical stimulation and were inducible in 12 of 12 dogs in the SVC and in 8 of 9 dogs in the left superior PV (left inferior PV: 7/8, right superior PV: 6/8; right inferior PV: 4/8). In the PVs, APDs occurred at 13 ± 8 V and AT/AF at 15 ± 9 V (P < 0.01; n = 25). In the SVC, APDs were elicited at 19 ± 6 V and AT/AF at 26 ± 6 V (P < 0.01; n = 12). High-frequency electrical stimulation led to local refractory period shortening in the PVs. The response to high-frequency electrical stimulation was blunted or prevented after beta-receptor blockade and abolished by atropine. In vitro, high-frequency electrical stimulation induced a heterogeneous response, with shortening of the action potential in some cells (from 89 ± 35 msec to 60 ± 22 msec; P < 0.001; n = 7) but lengthening of the action potential and development of early afterdepolarizations that triggered APD/AT in other cells. Action potential shortening was abolished by atropine. Conclusion: High-frequency electrical stimulation evokes rapid ectopic beats from the PV/SVC, which show variable degrees of conduction block to the atria and induce AF, resembling findings in patients with focal idiopathic paroxysmal AF. The occurrence of the arrhythmia in this animal model was likely due to alterations in local autonomic tone by high-frequency electrical stimulation. Further research is needed to prove absolutely that the observed effects of high-frequency electrical stimulation were caused by autonomic nerve stimulation. [source] Pathophysiologic role of myocardial apoptosis in post-infarction left ventricular remodelingJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002Antonio Abbate Left ventricular (LV) remodeling and heart failure (HF) complicate acute myocardial infarction (AMI) even weeks to months after the initial insult. Apoptosis may represent an important pathophysiologic mechanism causing progressive myocardiocyte loss and LV dilatation even late after AMI. This review will discuss the role of apoptosis according to findings in animal experimental data and observational studies in humans in order to assess clinical relevance, determinants, and mechanisms of myocardial apoptosis and potential therapeutic implications. More complete definition of the impact of myocardiocyte loss on prognosis and of the mechanisms involved may lead to improved understanding of cardiac remodeling and possibly improved patients' care. Mitochondrial damage and bcl-2 to bax balance play a central role in ischemia-dependent apoptosis while angiotensin II and ,1 -adrenergic-stimulation may be major causes of receptor-mediated apoptosis. Benefits due to treatment with ACE-inhibitors and ,-blockers appear to be in part due to reduced myocardial apoptosis. Moreover, infarct-related artery patency late after AMI may be a major determinant of myocardial apoptosis and clinical benefits deriving from an open artery late post AMI (the "open artery hypothesis") may be, at least in part, due to reduced myocardiocyte loss. © 2002 Wiley-Liss, Inc. [source] Voxel-based morphometry of sporadic epileptic patients with mesiotemporal sclerosisEPILEPSIA, Issue 4 2010Angelo Labate Summary Purpose:, In refractory temporal lobe epilepsy (rTLE), gray matter (GM) abnormalities are not confined to the hippocampus but also are found in extrahippocampal structures. Very recently we observed in mild TLE (mTLE) with or without mesiotemporal sclerosis (MTS), GM reductions in regions outside the presumed epileptogenic focus. To date, there are no studies that directly investigate whether whole-brain GM volume differs between rTLE and mTLE. Herein, we used optimized voxel-based morphometry (VBM) to identify GM abnormalities beyond the hippocampus in both rTLE and mTLE with evidence of MTS. Methods:, Brain magnetic resonance imaging (MRI) and optimized VBM were performed in 19 unrelated patients with mTLE, 19 patients with rTLE, and 37 healthy controls. MRI diagnosis of MTS was based on the atrophy of the hippocampal formation and/or mesiotemporal hyperintensity on fluid-attenuated inversion recovery (FLAIR) or T2 images, or both. Results:, No patients (rTLE and mTLE) had generalized tonic,clonic or complex partial seizures for at least 3 weeks before scanning. Both mTLE and rTLE patients showed GM volume reduction of the bilateral thalamus, left hippocampus, and sensorimotor cortex compared with controls. No significant GM difference was found between rTLE and mTLE groups. Discussion:, In both rTLE and mTLE, VBM shows GM reductions not confined to the hippocampus involving mainly the thalamus bilaterally. This finding together with the lack of significant GM differences between the two TLE groups supports the hypothesis that mTLE and rTLE might lie along a biologic continuum, suggesting a pathophysiologic role of the thalamus in partial epilepsy. [source] MicroRNA-195 suppresses tumorigenicity and regulates G1/S transition of human hepatocellular carcinoma cells,HEPATOLOGY, Issue 1 2009Teng Xu Growing evidence indicates that deregulation of microRNAs (miRNAs) contributes to tumorigenesis. Down-regulation of miR-195 has been observed in various types of cancers. However, the biological function of miR-195 is still largely unknown. In this study we aimed to elucidate the pathophysiologic role of miR-195. Our results showed that miR-195 expression was significantly reduced in as high as 85.7% of hepatocellular carcinoma (HCC) tissues and in all of the five HCC cell lines examined. Moreover, introduction of miR-195 dramatically suppressed the ability of HCC and colorectal carcinoma cells to form colonies in vitro and to develop tumors in nude mice. Furthermore, ectopic expression of miR-195 blocked G1/S transition, whereas inhibition of miR-195 promoted cell cycle progression. Subsequent investigation characterized multiple G1/S transition-related molecules, including cyclin D1, CDK6, and E2F3, as direct targets of miR-195. Silencing of cyclin D1, CDK6, or E2F3 phenocopied the effect of miR-195, whereas overexpression of these proteins attenuated miR-195-induced G1 arrest. In addition, miR-195 significantly repressed the phosphorylation of Rb as well as the transactivation of downstream target genes of E2F. These results imply that miR-195 may block the G1/S transition by repressing Rb-E2F signaling through targeting multiple molecules, including cyclin D1, CDK6, and E2F3. Conclusion: Our data highlight an important role of miR-195 in cell cycle control and in the molecular etiology of HCC, and implicate the potential application of miR-195 in cancer therapy. (HEPATOLOGY 2009.) [source] Evidence for an endothelium-derived hyperpolarizing factor in the superior mesenteric artery from rats with cirrhosisHEPATOLOGY, Issue 5 2000Eric Barriere In cirrhosis, in splanchnic arteries, endothelium-dependent relaxation may persist even if overactive nitric oxide synthase (NOS) and cyclooxygenase (COX) are inhibited. In normal arteries, a significant endothelium-dependent relaxation to acetylcholine persists after NOS/COX inhibition. This relaxation is caused by smooth muscle cell (SMC) membrane hyperpolarization, which is sensitive to a combination of the potassium channel blockers apamin and charybdotoxin, and is mediated by an endothelium-derived hyperpolarizing factor (EDHF). The aim of this study was to detect EDHF and evaluate its pathophysiologic role in isolated superior mesenteric arteries from cirrhotic rats. Arterial rings were obtained and exposed to Nw -nitro-L-arginine (L-NNA, a NOS inhibitor) and indomethacin (a COX inhibitor). Acetylcholine-induced membrane potential responses and concentration-response curves to the relaxant of acetylcholine were obtained with and without apamin plus charybdotoxin. Acetylcholine-induced responses were measured in certain rings from endothelium-denuded arteries. Contractions caused by the ,1 -adrenoceptor agonist phenylephrine were obtained in cirrhotic and normal rings with and without apamin and charybdotoxin. Significant acetylcholine-induced, endothelium-dependent, apamin- and charybdotoxin-sensitive, SMC membrane hyperpolarization and relaxation were found. An apamin- and charybdotoxin-sensitive hyporesponsiveness to the contractile action of phenylephrine was found in cirrhotic rings. In conclusion, in cirrhotic rats, in the superior mesenteric artery exposed to NOS/COX-inhibitors, an EDHF exists that may replace NOS/COX products to induce endothelium-dependent arterial relaxation. [source] Increased collagen and aggrecan degradation with age in the joints of Timp3,/, miceARTHRITIS & RHEUMATISM, Issue 3 2007Solmaz Sahebjam Objective To investigate the in vivo effect of an imbalance between metalloproteinases and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs), in mouse articular cartilage. Methods Hind joints of Timp3,/, and wild-type mice were examined by routine staining and by immunohistochemical analysis using antibodies specific for type X collagen and for the neoepitopes produced on proteolytic cleavage of aggrecan (, VDIPEN and , NVTEGE) and type II collagen. The neoepitope generated on cleavage of type II collagen by collagenases was quantitated in sera by enzyme-linked immunosorbent assay. Results Articular cartilage from Timp3 -knockout animals (ages ,6 months) showed reduced Safranin O staining and an increase in ,VDIPEN content compared with cartilage from heterozygous and wild-type animals. There was also a slight increase in , NVTEGE content in articular cartilage and menisci of Timp3,/, animals. Chondrocytes showed strong pericellular staining for type II collagen cleavage neoepitopes, particularly in the superficial layer, in knockout mice. Also, there was more type X collagen expression in the superficial zone of articular cartilage, especially around clusters of proliferating chondrocytes, in the knockout mice. More type II collagen cleavage product was found in the serum of Timp3,/, mice compared with wild-type animals. This increase was significant in 15-month-old animals. Conclusion These results indicate that TIMP-3 deficiency results in mild cartilage degradation similar to changes seen in patients with osteoarthritis, suggesting that an imbalance between metalloproteinases and TIMP-3 may play a pathophysiologic role in the development of this disease. [source] Induction of triggering receptor expressed on myeloid cells 1 in murine resident peritoneal macrophages by monosodium urate monohydrate crystalsARTHRITIS & RHEUMATISM, Issue 2 2006Yousuke Murakami Objective Triggering receptor expressed on myeloid cells 1 (TREM-1) is a cell surface molecule that was recently identified on monocytes and neutrophils. TREM-1 has been implicated in the early inflammatory responses induced by microbes, but its pathophysiologic role in nonmicrobial inflammation remains unknown. In the present study, we investigated the role of TREM-1 in acute inflammation induced by monosodium urate monohydrate (MSU) crystals. Induction of TREM-1 expression by MSU crystal,stimulated murine resident peritoneal macrophages and infiltrating leukocytes in a murine air-pouch model of crystal-induced acute inflammation was determined. The biologic role of TREM-1 in crystal-induced cytokine production by resident peritoneal macrophages was also investigated. Methods TREM-1 expression by resident peritoneal macrophages and infiltrating leukocytes in a murine air-pouch model was determined by quantitative real-time polymerase chain reaction, Western blot analysis, and flow cytometry. Cytokine production by resident peritoneal macrophages after incubation with MSU crystals in the presence or absence of an anti,TREM-1 agonist antibody was determined by enzyme-linked immunosorbent assay. Results TREM-1 expression by resident peritoneal macrophages was significantly induced after stimulation with the crystals. Maximum expression of TREM-1 transcripts and protein occurred at 1 and 4 hours after exposure to the crystals, respectively. Costimulation of resident peritoneal macrophages with MSU crystals and an anti,TREM-1 agonist antibody synergistically increased the production of both interleukin-1, and monocyte chemotactic protein 1 compared with stimulation with the crystals alone. MSU crystals also induced TREM-1 expression in infiltrating leukocytes in a murine air-pouch model of crystal-induced acute inflammation. Conclusion These findings suggest that rapid induction of TREM-1 expression on resident peritoneal macrophages and neutrophils by MSU crystals may contribute to the development of acute gout through enhancement of inflammatory responses. [source] Accelerated plasminogen activator inhibitor may prevent late restenosis after coronary stenting in acute myocardial infarctionCLINICAL CARDIOLOGY, Issue 3 2003Teruo Inoue M.D. Abstract Background: Although acceleration of plasma plasminogen activator inhibitor-1 (PAI-1) level after emergent coronary angioplasty in acute myocardial infarction (AMI) has been documented, its pathophysiologic role is still unknown. Hypothesis: This study was designed to elucidate the role of PAI-1 in the development of restenosis after primary coronary stenting in AMI. Methods: We selected for this study 66 patients with AMI, who underwent primary coronary stenting for infarct-related coronary artery lesions in an emergent situation. In all patients, plasma PAI-1 level was measured at admission, and at 3 h, 24 h, 48 h, and 1 month after coronary stenting. Results: At admission, the PAI-1 level was equivalent in 24 patients who experienced restenosis and in 42 patients without restenosis (28 ± 4 vs. 29 ± 4 ng/ml). In patients with restenosis, the levels did not change during the course after coronary stenting. In patients without restenosis, however, the level significantly increased at 3 h (48 ± 9 ng/ml, p < 0.001), 24 h (42 ± 9, p < 0.01), and 48 h (38 ± 7, p < 0.05) after coronary stenting, and was restored to the level equivalent to that at admission (27 ± 2 ng/ml) 1 month after coronary stenting. The PAI-1 level at 3 h after coronary stenting in patients without restenosis was significantly higher (p < 0.05) than the level (33 ± 6 ng/ml) in patients with restenosis. Multiple logistic regression analysis indicated that the PAI-1 level 3 h after coronary stenting was an independent predictor of restenosis (Wald x2 = 3.826, p = 0.019, odds ratio 0.921, 95% confidence interval 0.866-0.961). Conclusion: Accelerated PAI-1 after coronary stenting in patients with AMI may protect against the development of late restenosis. [source] | ||||||||||