BACKGROUND Postpubertal women with inherited long QT syndrome type 2 (LQT2) are at increased risk for polymorphic ventricular tachycardia (pVT) and sudden cardiac death (SCD), particularly during the postpartum period...
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BACKGROUND Postpubertal women with inherited long QT syndrome type 2 (LQT2) are at increased risk for polymorphic ventricular tachycardia (pVT) and sudden cardiac death (SCD), particularly during the postpartum period. OBJECTIVE To investigate whether sex hormones directly modulate the arrhythmogenic risk in LQTS. METHODS Prepubertal ovariectomized transgenic LQT2 rabbits were treated with estradiol (EST), progesterone (PROG), dihydrotestosterone (DHT), or placebo (OVX). RESULTS During 8 weeks of treatment, major cardiac events-spontaneous pVT or SCD-occurred in 5 of the 7 EST rabbits and in 2 of the 9 OVX rabbits (P < .05);in contrast, no events occurred in 9 PROG rabbits and 6 DHT rabbits (P < .01 vs PROG;P < .05 vs DHT). Moreover, EST increased the incidence of pVT (P < .05 vs OVX), while PROG reduced premature ventricular contractions, bigeminy, couplets, triplets, and pVT (P < .01 vs OVX;P < .001 vs EST). In vivo electrocardiographic monitoring, in vivo electrophysiological studies, and ex vivo optical mapping studies revealed that EST promoted SCD by steepening the QT/RR slope (P < .05), by prolonging cardiac refractoriness (P < .05), and by altering the spatial pattern of action potential duration dispersion. Isoproterenol-induced Ca2+ oscillations resulted in early afterdepolarizations in EST-treated hearts (4 of 4), while PROG prevented SCD by eliminating this early afterdepolarization formation in 4 of the 7 hearts (P = .058 vs EST;P < .05 vs OVX). Analyses of ion currents demonstrated that EST increased the density of I-Ca,I-L as compared with OVX (P < .05) while PROG decreased it (P < .05). CONCLUSION This study reveals the proarrhythmic effect of EST and the antiarrhythmic effect of PROG in LQT2 in vivo, outlining a new potential antiarrhythmic therapy for LQTS. KEYWORDS Long QT syndrome;Sex hormones;Arrhythmogenesis;Sudden cardiac death;Transgenic LQT2 rabbit model;Cardiac ion currents;Early afterdepolarization;In vivo electrophysiological study
To study the emission and diffusion pattern of mercury released from underground coal fire and spontaneous-ignited gangue hill, measurements were applied on the ambient air samples with 1.2m height to ground surface i...
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To study the emission and diffusion pattern of mercury released from underground coal fire and spontaneous-ignited gangue hill, measurements were applied on the ambient air samples with 1.2m height to ground surface in the peripheral area of a typical underground coal fire zone in central Inner Mongolia in north China (central coordinates: 39°30′44″ N/106°37′05″E , altitude:1246.82m, total peripheral area: 25000m2) in a 10mx10m grid and at the vicinity of a spontaneous-ignited gangue hill (central coordinates: 39°34′16 ″ N/106°38′ 06″ E , area: 12000m2) 6.7km apart. Both measurements gave a prevalent mercury concentration of 40- 50ng/m3. The ground vapor measured in the drilling hole-0.4m to the surface in the vicinity of the gangue hill also provided mercury concentration at the same level. The result indicates mild mercury pollution in the near-surface ambient air in the studied mining area, which may be ascribed to long-term accumulation of low-dosed gaseous mercury emission from the underground coal fire and spontaneous-ignited gangue hill other than acute real-time mercury emission. The consistency in the mercury concentration of ambient air at two studied area 6.7km apart may bring new issue on the range of mercury diffusion at a concentration 30 times higher than atmospheric background level (1.6-1.8ng/m3) and its potential regional environmental, ecological and public health threat.
Studies of Community-based question and answer services (cQA) have grown to be one of the emerging trends in Web information services. And one of the main tasks is to retrieve similar questions. To identify the fact t...
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Studies of Community-based question and answer services (cQA) have grown to be one of the emerging trends in Web information services. And one of the main tasks is to retrieve similar questions. To identify the fact that some questions with different expressions though may indeed have the same, or very similar, meaning, the similar questions are defined in syntactic, semantic and pragmatic aspects according to user retrieval intention. Five models including Language Model, Translation-based Language Model, Parser-based model, LDA and WordNet source-based model are selected as baselines. Integrated models which linearly combine WordNet, Stanford Parser and Language Model and further weighted by syntactic feature are proposed to integrate features of the three aspects. Experiment results show that our integrated models perform better than the basic models, especially when the linear combination of the WordNet model and the Stanford Parser model is weighted by syntactic information with proper noun phrases as representative. The integrated models are further verified by logistic analysis.
A modified ASTM G 65 rubber wheel test was employed in wet and dry conditions using 220 nm titania particles and 368 mu m sand particles, respectively. Both tests were conducted on WC-CoCr coatings produced with two p...
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A modified ASTM G 65 rubber wheel test was employed in wet and dry conditions using 220 nm titania particles and 368 mu m sand particles, respectively. Both tests were conducted on WC-CoCr coatings produced with two powders with different carbide grain sizes (conventional and sub-micron) to address the effect of carbide size and abrasive medium characteristics on the wear performance. The same spot before and after the wet abrasion wear testing was analyzed in detail using SEM to visualize wear mechanisms. It was shown that the wear mechanism depends on the relative size of the carbide and abrasive particles. Wear mechanisms in dry sand abrasion were studied by analyzing the single scratches formed by individual abrasive particles. Interaction of surface open porosity with moving abrasive particles causes formation of single scratches. By tailoring the carbide size, the wear performance can be improved.
A modified ASTM G 65 rubber wheel test was employed in wet and dry conditions using 220 nm titania particles and 368 mu m sand particles, respectively. Both tests were conducted on WC-CoCr coatings produced with two p...
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A modified ASTM G 65 rubber wheel test was employed in wet and dry conditions using 220 nm titania particles and 368 mu m sand particles, respectively. Both tests were conducted on WC-CoCr coatings produced with two powders with different carbide grain sizes (conventional and sub-micron) to address the effect of carbide size and abrasive medium characteristics on the wear performance. The same spot before and after the wet abrasion wear testing was analyzed in detail using SEM to visualize wear mechanisms. It was shown that the wear mechanism depends on the relative size of the carbide and abrasive particles. Wear mechanisms in dry sand abrasion were studied by analyzing the single scratches formed by individual abrasive particles. Interaction of surface open porosity with moving abrasive particles causes formation of single scratches. By tailoring the carbide size, the wear performance can be improved.
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