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Structural Remodeling (structural + remodeling)

Distribution by Scientific Domains

Medical Sciences	87%
Life Sciences	12%

Selected Abstracts

Effect of Electrical and Structural Remodeling on Spatiotemporal Organization in Acute and Persistent Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2002
JOSEPH G. AKAR M.D.
Spatiotemporal Organization in Atrial Fibrillation.Introduction: Atrial fibrillation (AF) may originate from discrete sites of periodic activity. We studied the effect of structural and electrical remodeling on spatiotemporal organization in acute and persistent AF. Methods and Results: Atrial effective refractory periods (AERPs) were recorded from five different sites at baseline and after pacing in acute AF (n = 8 dogs) and persistent AF (n = 8). Four persistent AF dogs subsequently were cardioverted to sinus rhythm to allow AERP recovery. Periodicity was quantified by calculating power spectra on left atrial electrograms obtained from a 64-electrode basket catheter. Left atrial size was measured by intracardiac echocardiography and structural changes were assessed by electron microscopy. Mean AERPs decreased after pacing in acute (128 ± 16 msec to 108 ± 29 msec, P < 0.001) and persistent AF (135 ± 16 msec to 104 ± 24 msec, P < 0.0001). AERP recovery was established after 7 days of sinus rhythm. Structural changes were mild in acute AF, severe in persistent AF, and remained severe after AERP recovery. A single dominant frequency was identified in 94% of acute AF bipoles, 57% in persistent AF, and 76% after AERP recovery. Average correlation coefficient was 0.82 among acute AF bipoles, 0.63 in persistent AF, and 0.73 after AERP recovery. Conclusion: Transition from acute to persistent AF is associated with loss of spatiotemporal organization. A single dominant frequency recruits the majority of the left atrium in acute AF. Persistent AF, however, is associated with structural remodeling and dominant frequency dispersion. Recovery of refractoriness only partially restores spatiotemporal organization, indicating a major role for structural remodeling in the maintenance of persistent AF. [source]

Electrical and Structural Remodeling in Left Ventricular Hypertrophy,A Substrate for a Decrease in QRS Voltage?

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2007
Ljuba Bacharova M.D., M.B.A., Ph.D.
Electrical remodeling in advanced stages of cardiovascular diseases creates a substrate for triggering and maintenance of arrhythmias. The electrical remodeling is a continuous process initiated already in the early stages of cardiological pathology. The aim of this opinion article was to discuss the changes in electrical properties of myocardium in left ventricular hypertrophy (LVH), with special focus on its early stage, as well as their possible reflection in the QRS amplitude of the electrocardiogram. It critically appraises the classical hypothesis related to the QRS voltage changes in LVH. The hypothesis of the relative voltage deficit is discussed in the context of supporting evidence from clinical studies, animal experiments, and simulation studies. The underlying determinants of electrical impulse propagation which may explain discrepancies between "normal" ECG findings and increased left ventricular size/mass in LVH are reviewed. [source]

Microstructural status of ipsilesional and contralesional corticospinal tract correlates with motor skill in chronic stroke patients

HUMAN BRAIN MAPPING, Issue 11 2009
Judith D. Schaechter
Abstract Greater loss in structural integrity of the ipsilesional corticospinal tract (CST) is associated with poorer motor outcome in patients with hemiparetic stroke. Animal models of stroke have demonstrated that structural remodeling of white matter in the ipsilesional and contralesional hemispheres is associated with improved motor recovery. Accordingly, motor recovery in patients with stroke may relate to the relative strength of CST degeneration and remodeling. This study examined the relationship between microstructural status of brain white matter tracts, indexed by the fractional anisotropy (FA) metric derived from diffusion tensor imaging (DTI) data, and motor skill of the stroke-affected hand in patients with chronic stroke. Voxelwise analysis revealed that motor skill significantly and positively correlated with FA of the ipsilesional and contralesional CST in the patients. Additional voxelwise analyses showed that patients with poorer motor skill had reduced FA of bilateral CST compared to normal control subjects, whereas patients with better motor skill had elevated FA of bilateral CST compared to controls. These findings were confirmed using a DTI-tractography method applied to the CST in both hemispheres. The results of this study suggest that the level of motor skill recovery achieved in patients with hemiparetic stroke relates to microstructural status of the CST in both the ipsilesional and contralesional hemispheres, which may reflect the net effect of degeneration and remodeling of bilateral CST. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source]

Stress and hippocampal plasticity: implications for the pathophysiology of affective disorders

HUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue S1 2001
Bruce S. McEwen
Abstract The hippocampal formation, a structure involved in declarative, spatial and contextual memory, is a particularly sensitive and vulnerable brain region to stress and stress hormones. The hippocampus shows a considerable degree of structural plasticity in the adult brain. Stress suppresses neurogenesis of dentate gyrus granule neurons, and repeated stress causes atrophy of dendrites in the CA3 region. In addition, ovarian steroids regulate synapse formation during the estrous cycle of female rats. All three forms of structural remodeling of the hippocampus are mediated by hormones working in concert with excitatory amino acids (EAA) and N -methyl- D -aspartate (NMDA) receptors. EAA and NMDA receptors are also involved in neuronal death that is caused in pyramidal neurons by seizures and by ischemia and prolonged psychosocial stress. In the human hippocampus, magnetic resonance imaging studies have shown that there is a selective atrophy in recurrent depressive illness, accompanied by deficits in memory performance. Hippocampal atrophy may be a feature of affective disorders that is not treated by all medications. From a therapeutic standpoint, it is essential to distinguish between permanent damage and reversible atrophy in order to develop treatment strategies to either prevent or reverse deficits. In addition, remodeling of brain cells may occur in other brain regions. Possible treatments are discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source]

The Role of Cardiac Tissue Alignment in Modulating Electrical Function

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2007
CHIUNG-YIN CHUNG M.S.
Introduction:,Most cardiac arrhythmias are associated with pathology-triggered ion channel remodeling. However, multicellular effects, for example, exaggerated anisotropy and altered cell-to-cell coupling, can also indirectly affect action potential morphology and electrical stability via changed electrotonus. These changes are particularly relevant in structural heart disease, including hypertrophy and infarction. Recent computational studies showed that electrotonus factors into stability by altering dynamic properties (restitution). We experimentally address the question of how cell alignment and connectivity alter tissue function and whether these effects depend on the direction of wave propagation. Methods and Results:,We show that cardiac cell arrangement can alter electrical stability in an in vitro cardiac tissue model by mechanisms both dependent and independent of the direction of wave propagation, and local structural remodeling can be felt beyond a space constant. Notably, restitution of action potential duration (APD) and conduction velocity was significantly steepened in the direction of cell alignment. Furthermore, prolongation of APD and calcium transient duration was found in highly anisotropic cell networks, both for longitudinal and transverse propagation. This is in contrast to expected correlation between wave propagation direction and APD based on electrotonic effects only, but is consistent with our findings of increased cell size and secretion of atrial natriuretic factor, a hypertrophy marker, in the aligned structures. Conclusion:,Our results show that anisotropic structure is a potent modulator of electrical stability via electrotonus and molecular signaling. Tissue alignment must be taken into account in experimental and computational models of arrhythmia generation and in designing effective treatment therapies. [source]

Heterogeneous Regional Endocardial Repolarization is Associated with Increased Risk for Ischemia-Dependent Ventricular Fibrillation after Myocardial Infarction

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003
Michael H. Swann M.SC.
Introduction: The aim of this study was to investigate whether the characteristics of endocardial ventricular repolarization are associated with differential risk for sudden death. Prolonged surface QT interval is associated with increased arrhythmic risk after myocardial infarction (MI), but the underlying mechanism of QT prolongation and its relation to lethal arrhythmias are unclear. Methods and Results: Ventricular fibrillation (VF) risk was assessed in 12 dogs 1 month after anterior MI during an exercise test coupled with brief circumflex coronary occlusion. Susceptible dogs (n = 5) developed VF during the brief ischemic episode, whereas resistant dogs did not (n = 7). Surface QT interval was measured at rest. Endocardial electroanatomic catheter maps of left ventricular repolarization were obtained in four unique regions identified by echocardiography and compared between groups. Compared to resistant dogs, susceptible dogs were characterized by prolonged surface QT intervals (240 ± 10 msec vs 222 ± 7 msec, P = 0.04). In addition, they had lower baroreflex sensitivity (9.7 ± 1.5 msec/mmHg vs 28 ± 9.8 msec/mmHg, P < 0.01) and a tachycardic response to acute ischemia suggesting higher propensity for stronger sympathetic reflexes. Surface QT interval prolongation in susceptible dogs was due to a marked heterogeneity of endocardial left ventricular repolarization (239 ± 42 msec, basal anterior wall vs 197 ± 35, lateral wall; P < 0.001). Resistant animals had no regional differences in endocardial repolarization. Conclusion: Sympathetic activation following MI not only produces adverse structural remodeling but also contributes to adverse electrophysiologic remodeling resulting in heterogeneous ventricular repolarization and in a myocardial substrate conducive to lethal reentrant arrhythmias. (J Cardiovasc Electrophysiol, Vol. 14, pp. 873-879, August 2003) [source]

Effect of Electrical and Structural Remodeling on Spatiotemporal Organization in Acute and Persistent Atrial Fibrillation

Mechanisms of Cardiac Fibrosis in Hypertension

JOURNAL OF CLINICAL HYPERTENSION, Issue 7 2007
Javier Díez MD
Changes in the composition of cardiac tissue develop in hypertensive patients with left ventricular hypertrophy (ie, hypertensive heart disease) and lead to structural remodeling of the myocardium. One of these changes is related to the disruption of the equilibrium between the synthesis and degradation of collagen types I and III molecules, which results in an excessive accumulation of collagen types I and III fibers within the myocardium. Myocardial fibrosis is the consequence of a number of pathologic processes mediated by mechanical, neurohormonal, and cytokine routes. The clinical relevance of fibrosis is that it may contribute to heart failure and other cardiac complications in patients with hypertensive heart disease. This brief review focuses on the mechanisms of hypertensive myocardial fibrosis. [source]

Doppler ultrasound assessment of posterior tibial artery size in humans

JOURNAL OF CLINICAL ULTRASOUND, Issue 5 2006
Manning J. Sabatier PhD
Abstract Purpose. The difference between structural remodeling and changes in tone of peripheral arteries in the lower extremities has not been evaluated. The purpose of this study was to (1) evaluate the day-to-day reproducibility and interobserver reliability (IOR) of posterior tibial artery (PTA) diameter measurements and (2) evaluate the effect of posture on PTA diameter at rest (Drest), during 10 minutes of proximal cuff occlusion (Dmin), and after the release of cuff occlusion (Dmax), as well as range (Dmax , Dmin) and constriction [(Dmax , Drest)/(Dmax , Dmin) × 100] in vivo. Methods. We used B-mode sonography to image the PTA during each condition. Results. Day-to-day reliability was good for Drest (intraclass correlation coefficient [ICC] 0.95; mean difference 4.2%), Dmin (ICC 0.93; mean difference 5.4%), and Dmax (ICC 0.99; mean difference 2.2%). The coefficient of repeatability for IOR was 70.5 ,m, with a mean interobserver error of 4.7 ,m. The seated position decreased Drest (2.6 ± 0.2 to 2.4 ± 0.3 mm; p = 0.002), increased Dmin (2.1 ± 0.2 to 2.4 ± 0.2 mm; p = 0.001), and decreased Dmax (3.1 ± 0.4 to 2.8 ± 0.3 mm; p < 0.001) compared with the supine position. The seated position also decreased arterial range (Dmax , Dmin) from 0.9 ± 0.2 to 0.5 ± 0.1 mm (p = 0.003) and increased basal arterial constriction from 57 ± 19% to 105 ± 27% (p = 0.007). Conclusions. The system employed for measuring PTA diameter yields unbiased and consistent estimates. Furthermore, lower extremity arterial constriction and range change with posture in a manner consistent with known changes in autonomic activity. © 2006 Wiley Periodicals, Inc. J Clin Ultrasound 34:223,230, 2006 [source]

Objective assessments of allergic and nonallergic rhinitis in young children

ALLERGY, Issue 10 2009
B. L. K. Chawes
Background:, Allergic and nonallergic rhinitis are common childhood disorders. Objective:, To study nasal eosinophilia and nasal airway patency in young children with allergic and nonallergic rhinitis to assess the pathology behind such diagnoses. Methods:, We investigated 255 children at six years of age from the Copenhagen Prospective Study on Asthma in Childhood birth cohort assessing rhinitis history, specific immunoglobulin E relevant to rhinitis symptoms, nasal eosinophilia and nasal airway patency by acoustic rhinometry before and after decongestion. Associations were studied in a multivariate graphical model corrected for gender, height and nasal steroid usage. Results:, Allergic rhinitis was significantly and directly associated with irreversible nasal airway obstruction (reduced decongested nasal airway patency) (P = 0.004), whereas nonallergic rhinitis was not. Both allergic rhinitis (P = 0.000) and nonallergic rhinitis (P = 0.014) were directly and significantly associated with nasal eosinophilia, but this association was stronger for allergic rhinitis. Conclusion:, Allergic rhinitis and nonallergic rhinitis are of different pathologies as suggested from their different associations not only to allergy but importantly also to irreversible nasal airway obstruction and eosinophilic inflammation. Allergic rhinitis was significantly associated with nasal eosinophilia and irreversible nasal airway obstruction suggesting chronic inflammation and structural remodeling of the nasal mucosa in children at the age of 6 years. Nonallergic rhinitis exhibited no change in the nasal airway patency, but some nasal mucosal eosinophilia albeit less than children with allergic rhinitis. [source]

Obesity, Insulin Resistance, and Microvessel Density

MICROCIRCULATION, Issue 4-5 2007
Jefferson C. Frisbee
ABSTRACT The growing incidence and prevalence of the overweight/obese condition across developed economies worldwide has an enormous impact on increasing the risk for the development of impaired glycemic control or insulin resistance and ultimately peripheral vascular disease (PVD) in afflicted individuals. This places an enormous economic and social burden on these societies, in terms of additional health care costs and lost productivity and through a reduction in the quality of life of the individual owing, in part, to the progressive PVD. Characterized by an inability of the vascular systems to adequately perfuse tissues and organs relative to their metabolic demand, PVD is in part a function of a structural remodeling of the microvascular networks such that the density of microvessel and capillaries within tissues is reduced below that under normal conditions, with the potential for profound negative impacts on the processes of mass transport and exchange. The review discusses the severity of the obesity "epidemic" from the perspective of PVD and the effects of the development of the obese, insulin-resistant condition on tissue/organ microvessel density. Additional material is reviewed that addresses ameliorative treatments, primarily exercise training, on blunting microvessel loss in the obese, insulin-resistant individual, and on potential mechanistic contributors that warrant considerable future investigation. [source]

Ion channel remodeling in gastrointestinal inflammation

NEUROGASTROENTEROLOGY & MOTILITY, Issue 10 2010
H. I. Akbarali
Abstract Background,Gastrointestinal inflammation significantly affects the electrical excitability of smooth muscle cells. Considerable progress over the last few years have been made to establish the mechanisms by which ion channel function is altered in the setting of gastrointestinal inflammation. Details have begun to emerge on the molecular basis by which ion channel function may be regulated in smooth muscle following inflammation. These include changes in protein and gene expression of the smooth muscle isoform of L-type Ca2+ channels and ATP-sensitive K+ channels. Recent attention has also focused on post-translational modifications as a primary means of altering ion channel function in the absence of changes in protein/gene expression. Protein phosphorylation of serine/theronine or tyrosine residues, cysteine thiol modifications, and tyrosine nitration are potential mechanisms affected by oxidative/nitrosative stress that alter the gating kinetics of ion channels. Collectively, these findings suggest that inflammation results in electrical remodeling of smooth muscle cells in addition to structural remodeling. Purpose,The purpose of this review is to synthesize our current understanding regarding molecular mechanisms that result in altered ion channel function during gastrointestinal inflammation and to address potential areas that can lead to targeted new therapies. [source]

Electrophysiological Remodeling in Human Atrial Fibrillation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7p2 2003
DAVID R. VAN WAGONER
Atrial fibrillation (AF) is a progressive disease characterized by cumulative electrophysiological and structural remodeling of the atria. Cellular electrophysiological studies have revealed marked reductions in the densities of the L-type voltage-gated Ca2+ current, ICa,L, the transient outward K+ current, ITO, and the ultra-rapid delayed rectifier K+ current, IKur, in atrial myocytes from patients in persistent or permanent AF. The density of the muscarinic K+ current (IKACh) is also reduced, however the inward rectifier K+ current (IK1) density is increased. The net shortening or lengthening of the action potential is dependent on the balance between changes in inward and outward currents. The prominent reduction in ICa,L appears to be sufficient to explain the observed decreases in action potential duration and effective refractory period that are characteristic of the fibrillating atria. Earlier studies have shown that calcium overload and perturbations in calcium handling play prominent roles in AF induced atrial remodeling. More recently, we have shown that AF is associated with evidence of oxidative injury to atrial tissue, and suggested that oxidative stress may directly contribute to the pathophysiology of AF. It is anticipated that insights gleaned from mechanistic studies will facilitate the development of improved pharmacological approaches to treat AF and to prevent the progression of arrhythmia. (PACE 2003; 26[Pt. II]:1572,1575) [source]

New Pharmacological Strategies for the Treatment of Atrial Fibrillation

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2009
Alexander Burashnikov Ph.D.
Atrial fibrillation (AF) is a growing clinical problem, increasing in prevalence as the population of the United States and countries around the world ages. Intensive research aimed at improving prevention, diagnosis, and treatment of AF is ongoing. Although the use and efficacy of catheter ablation-based approaches in AF treatment have increased significantly in the last decade, pharmacological agents remain the first-line therapy for rhythm management of AF. Currently available anti-AF agents are generally only moderately effective and associated with extracardiac toxicity and/or a risk for development of life-threatening ventricular arrhythmias. Included among current investigational strategies for improving the effectiveness and safety of anti-AF drugs is the development of (1) Agents that produce atrial-specific or predominant inhibition of IKur, IK-ACh, or INa; (2) "Upstream therapies" that effect nonion channel targets that reduce atrial structural remodeling, hypertrophy, dilatation, inflammation, oxidative injury, etc; (3) Derivatives of "old" anti-AF drugs with an improved safety pharmacological profile; and (4) Gap junction therapy aimed at improving conduction without affecting sodium channels. This review focuses on new pharmacological approaches under investigation for the treatment of AF. [source]

Mediators of structural remodeling in peripheral spondylarthritis,

ARTHRITIS & RHEUMATISM, Issue 12 2009
Bernard Vandooren
First page of article [source]

Transition of nuclear proteins and chromatin structure in spermiogenesis of Sepia officinalis,

MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 3 2007
F. MartÍnez-Soler
Abstract During spermiogenesis of Sepia officinalis histones are directly substituted by a molecule of precursor protamine, which is later transformed into the protamine through a deletion of the amino terminal end. In the present work, it is shown that the pattern of spermiogenic chromatin condensation consists of a phase of "patterning" and a phase of "condensation." In the phase of patterning, three structural remodelings are produced in the chromatin structure: [somatic-like chromatin,,,18 nm granules,,,25 nm fibers,,,44 nm fibers]. The first remodeling of the chromatin into granules of 18 nm takes place without the entrance of specific proteins in the spermiogenic nuclei. The second remodeling [granules of 18 nm,,,fibers of 25 nm] is due to the entrance of the precursor protamine and its interaction with the DNA,histone complex. The third remodeling [fibers of 25 nm,,,fibers of 44 nm] occurs simultaneously with the disappearance of histones from the chromatin. In the phase of condensation, the fibers of 44 nm coalesce among themselves to form progressively larger aggregates of chromatin. In this phase there are no substantial variations in the nuclear proteins, so that the condensation of the chromatin must respond to posttranscriptional changes of the precursor protamine (dephosphorylation, deletion of the amino-terminal end). Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source]