bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increasing Gap Junction Coupling Reduces Transmural Dispersion of Repolarization and Prevents Torsade de Pointes in Rabbit LQT3 Model
Authors: QUAN XIAO‐QING , BAI RONG , LIU NIAN , CHEN BO‐DI , ZHANG CUN‐TAI 
Published: August 2007

Introduction:
Increased transmural dispersion of repolarization (TDR) contributes importantly to the development of torsades de pointes (TdP) in long QT syndrome (LQTS). Intercellular electrical coupling via gap junctions plays an important role in maintaining TDR in both normal and diseased hearts. This study examined the effects of antiarrhythmic peptide AAP10, a gap junction enhancer, on TDR and induction of TdP in a rabbit LQT3 model.
Methods and Results:
An arterially perfused rabbit left ventricular preparation and sea anemone toxin II (ATX‐II, 20 nM) were used to establish a LQT3 model. Transmural ECG as well as action potentials from both endocardium and epicardium were simultaneously recorded. Changes in nonphosphorylated connexin43 (Cx43) were measured by immunoblotting. Compared with the control group, the QT interval, TDR, early afterdepolariztion (EAD), R‐on‐T extrasystole, and TdP increased sharply with augmented nonphosphorylated Cx43 in the LQT3 group (P < 0.001 for both). Interestingly, compared with the LQT3 group, 500 nM AAP10 reduced QT interval, TDR (P < 0.001 for both), and prevented EAD, R‐on‐T extrasystole, and TdP (P = 0.003, P = 0.001, P = 0.02) with a parallel decrease in nonphosphorylated Cx43 in the presence of ATX‐II (P < 0.001).
Conclusion:
Gap junction enhancer AAP10 is capable of abbreviating the QT interval, reducing TDR, and suppressing TdP in a rabbit LQT3 model probably via its effect by preventing dephosphorylation of Cx43. These data suggest that increasing intercellular coupling may reduce TDR and, therefore, prevent TdP in LQTS.
Validation of the Frequency Spectra Obtained from the Noncontact Unipolar Electrograms During Atrial Fibrillation
Authors: LIN YENN‐JIANG , HIGA SATOSHI , KAO TSAIR , TSO HAN‐WEN , TAI CHING‐TAI , CHANG SHIH‐LIN , LO LI‐WEI , WONGCHAROEN WANWARANG , CHEN SHIH‐ANN 
Published: August 2007

Introduction:
Noncontact mapping (NCM) can record virtual unipolar electrograms (Egs) from multiple sites simultaneously; therefore, it has the potential to perform simultaneous frequency mapping during atrial fibrillation (AF). The aim of this study was to validate the frequency spectra of the noncontact unipolar Egs in both atria.
Methods:
This study enrolled 12 patients (age = 61 ± 16 years) with paroxysmal or persistent AF who underwent catheter ablation guided by NCM. Noncontact and contact unipolar Egs were recorded simultaneously. The cross‐correlation of the Eg morphology, activation time difference of the time‐domain signals, and resultant frequency spectra were compared via dominant frequency (DF) and magnitude‐squared coherence (MSC).
Results:
A total of 159 sites were analyzed during AF. The variables that independently predicted a higher correlation between the contact and noncontact electrogram morphology were a smaller activation timing difference P < 0.01), smaller distance of the mapping sites to the array center (P = 0.01), and higher atrial voltage (P = 0.03). However, the average MSC of the frequency band within the physiologic range of AF (2 to 15 Hz) was only affected by the activation timing difference (P = 0.002). The DF value between the contact and noncontact unipolar signals correlated well with each other throughout the right atria and left atria in 94% of the mapping sites (r = 0.87, P < 0.001).
Conclusion:
The accuracy of the noncontact unipolar Eg morphology decreased when the mapping sites harbored a smaller atrial voltage and longer distance to the array center. The DF difference between the contact and noncontact unipolar Eg was not affected by the distance to the array center.
Focal Arrhythmia Confined Within the Coronary Sinus and Maintaining Atrial Fibrillation
Authors: KNECHT SÉBASTIEN , O'NEILL MARK D. , MATSUO SEIICHIRO , LIM KANG‐TENG , ARANTES LEONARDO , DERVAL NICOLAS , KLEIN GEORGES J. , HOCINI MÉLÈZE , JAÏS PIERRE , CLÉMENTY JACQUES , HAÏSSAGUERRE MICHEL 
Published: August 2007

Introduction: The coronary sinus (CS) is a complex structure comprising a mesh of circumferential muscular fibers with oblique connections to both atria. We describe further evidence for the clinical importance of CS arrhythmogenicity in maintaining atrial fibrillation (AF) in humans. Methods: Since January 2004, following a sequential approach, the CS and the inferior left atrium were ablated in 144 patients with symptomatic drug refractory AF. Patients were included for analysis when this step resulted in the electrical dissociation of the CS from both atria with restoration of sinus rhythm, but with continued arrhythmic activity in the CS. The electrophysiologic mechanism of the confined arrhythmia was considered as focal activity (automaticity or triggered activity) by the presence of electrograms spanning less than 75% of the cycle length in the CS. Results: After restoration of sinus rhythm, four male patients (3% of the patients, three persistent and one permanent AF) were identified in whom arrhythmia continued within the CS. Repetitive activity confined to the disconnected CS was inconsistent in occurrence, as well as in duration (1 sec to 15 min) and cycle length (from 158 to 380 ms). For all four patients, electrogram mapping of the entire CS was compatible with a focal mechanism. In two patients, bursts alternating with slow dissociated activity suggested automaticity. In one patient, local activity consistently coupled to the previous sinus beat favored triggered activity. Conclusions: This study provides evidence that the CS may be a potential source of focal rapid activity maintaining AF.
Autonomic and Pharmacological Responses of Idiopathic Ventricular Tachycardia Arising from the Left Ventricular Outflow Tract
Authors: YAMAWAKE NORIYOSHI , NISHIZAKI MITSUHIRO , HAYASHI TATSUYA , NIKI SAORI , MAEDA SHINGO , TANAKA YASUAKI , FUJII HIROYUKI , ASHIKAGA TAKASHI , SAKURADA HARUMIZU , HIRAOKA MASAYASU 
Published: August 2007

Background: It is well recognized that the mechanism of idiopathic ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT) is mostly due to cyclic AMP‐mediated triggered activity. The mechanism of VT arising from the left ventricular outflow tract (LVOT) has not been well clarified whether it is the same as VT of RVOT. Methods: We studied autonomic modulations and pharmacological interventions on VT/premature ventricular contractions (PVCs) from LVOT to explore its possible mechanism in six patients (age: 49 ± 14, three males). None of them had structural heart diseases. Results: Isoproterenol application easily induced VT and/or PVCs from LVOT. Valsalva maneuvers suppressed isoproterenol‐induced VT in two and PVCs in two, and carotid sinus massage (CSM) suppressed PVCs in one patient. Adenosine triphosphate inhibited both VT and PVCs in all six patients. Propranolol, lidocaine, and procainamide eliminated VT/PVCs in four, three, and four patients, respectively. Verapamil terminated VT in one and PVCs in another one patient, but aggravated PVCs to VT in one patient. Conclusion: The results suggest that the mechanism of VT from LVOT is mostly due to cAMP‐mediated triggered activity as similar to that in VT from RVOT.
Radiofrequency Ablation of Complex Fractionated Atrial Electrograms (CFAE): Preferential Sites of Acute Termination and Regularization in Paroxysmal and Persistent Atrial Fibrillation
Authors: SCHMITT CLAUS , ESTNER HEIDI , HECHER BIRGIT , LUIK ARMIN , KOLB CHRISTOF , KARCH MARTIN , NDREPEPA GJIN , ZRENNER BERNHARD , HESSLING GABRIELE , DEISENHOFER ISABEL 
Published: August 2007

Introduction: Complex fractionated atrial electrograms (CFAE) have been described as a new target for ablation of atrial fibrillation (AF). This prospective study evaluates the acute effects of CFAE ablation in patients with paroxysmal or persistent AF and analyzes the preferential anatomic sites where these effects occur. Methods and Results: Ablation of CFAE was performed in 66 symptomatic patients (mean age of 58 ± 12 years) with paroxysmal (n = 36) or persistent AF (n = 30). Termination or regularization of AF during ablation of CFAE was achieved in 56 of 66 patients (84%), with termination in 28 of 66 patients (42%) and regularization of AF in 28 of 66 patients (42%). Ablation of CFAE showed no effect in 10 of 66 patients (16%). Termination of AF occurred at 53 sites and AF regularization at 81 sites. The preferential sites of AF termination or regularization were found around the pulmonary veins (termination n = 15; regularization n = 22), at the anterior wall (termination n = 14; regularization n = 19) and at the interatrial septum (termination n = 8; regularization n = 17). Conclusion: Termination or regularization of AF was achieved acutely in 84% of patients by ablation of CFAE. The preferential sites of AF termination or regularization were found around the pulmonary veins, at the anterior wall of the LA and at the interatrial septum. These findings may have implications for future ablation concepts.
Novel Electrode Design for Potentially Painless Internal Defibrillation Also Allows for Successful External Defibrillation
Authors: JAYANTI VENKU , ZVIMAN MENEKHEM M. , NAZARIAN SAMAN , HALPERIN HENRY R. , BERGER RONALD D. 
Published: August 2007

Background: Implantable cardioverter defibrillators (ICDs) save lives, but the defibrillation shocks delivered by these devices produce substantial pain, presumably due to skeletal muscle activation. In this study, we tested an electrode system composed of epicardial panels designed to shield skeletal muscles from internal defibrillation, but allow penetration of an external electric field to enable external defibrillation when required. Methods and Results: Eleven adult mongrel dogs were studied under general anesthesia. Internal defibrillation threshold (DFT) and shock‐induced skeletal muscle force at various biphasic shock strengths were compared between two electrode configurations: (1) a transvenous coil placed in the right ventricle (RV) as cathode and a dummy can placed subcutaneously in the left infraclavicular fossa as anode (control configuration) and (2) RV coil as cathode and the multielectrode epicardial sock with the panels connected together as anode (sock‐connected). External DFT was also tested with these electrode configurations, as well as with the epicardial sock present, but with panels disconnected from each other (sock‐disconnected). Internal DFT was higher with sock‐connected than control (24 ± 7 J vs. 16 ± 6 J, P < 0.02), but muscle contraction force at DFT was greatly reduced (1.3 ± 1.3 kg vs. 10.6 ± 2.2 kg, P < 0.0001). External defibrillation was never successful, even at 360 J, with sock‐connected, while always possible with sock‐disconnected. Conclusion: Internal defibrillation with greatly reduced skeletal muscle stimulation can be achieved using a novel electrode system that also preserves the ability to externally defibrillate when required. This system may provide a means for painless ICD therapy.
Price and yield effects of spill‐overs in international agricultural research: evidence from ICRISAT and Australia
Authors: Brennan John P. , Bantilan M.C.S. 
Published: August 2007

AbstractInternational agricultural research aimed at improving productivity in developing countries also has spill‐over effects on developed countries. Research that affects the supply of commodities is also likely to affect the world price of tradeable commodities. In this paper, the effects of spill‐overs to Australia from successful cost‐reducing research into sorghum and chickpeas at die International Crops Research Institute for the Semi‐Arid Tropics (ICRISAT) aimed at developing countries are assessed. Genetic materials developed and distributed through ICRISAT are used in Australia to increase productivity. The price‐reducing effects of successful research are incorporated into the analysis of spill‐over impacts on productivity. The net effects on welfare for producers and consumers of sorghum and chickpeas in Australia and the Rest of the World (ROW) are identified. The consequences of the impacts are discussed and the implications for further funding of international agricultural research are also discussed.
Technical efficiency and CO2abatement policies in the Dutch glasshouse industry
Authors: Lansink Alfons Oude 
Published: August 2007

AbstractThis paper develops a short‐run microeconomic simulation model of the Dutch glasshouse industry in order to investigate the relation between technical efficiency and marginal abatement costs of CO2emission. The model is also used to determine the effects of an emission tax and systems of tradable and non‐tradable quota for groups of firms with different rates of technical efficiency. The results show that marginal abatement costs are very responsive to changes in technical efficiency. Furthermore, it is found that firms with a low technical efficiency are faced with a higher profit reduction under different abatement policies than firms with a high technical efficiency.
Productivity growth in pre‐ 1990 Mongolian agriculture: spiralling disaster or emerging success?
Authors: Bayarsaihan T. , Coelli T.J. 
Published: August 2007

AbstractThe reasons for the spectacular collapse of so many centrally‐planned economies are a source of ongoing debate. In this paper, we use detailed farm‐level data to measure total factor productivity (TFP) changes in Mongolian grain and potato farming during the 14‐year period immediately preceding the 1990 economic reforms. We measure TFP growth using stochastic frontier analysis (SFA) and data envelopment analysis (DEA) methods. Our results indicate quite poor overall performance, with an average annual TFP change of – 1.7% in grain and 0.8% in potatoes, over the 14‐year period. However, the pattern of TFP growth changed substantially during this period, with TFP growth exceeding 7% per year in the latter half of this period. This suggests that the new policies of improved education, greater management autonomy, and improved incentives, which were introduced in final two planning periods in the 1980s, were beginning to have a significant influence upon the performance of Mongolian crop farming.
On export rivalry and the greening of agriculture–the role of eco‐labels
Authors: Basu Arnab K. , Chau Nancy H. , Grote Ulrike 
Published: August 2007

AbstractWhy do some countries have eco‐labelling programs and others do not? In this paper, we provide both theoretical arguments and empirical evidence suggesting that the answer to this question can shed new light on three questions that have taken center‐stage in the trade and environment debate: (i) does trade exacerbate the exploitation of the environment; (ii) are countries competing in export markets engaged in a race to the bottom in environmental performance; and (iii) do market‐based environmental instruments benefit the rich and hurt the poor?
A household hedonic model of rice traits: economic values from farmers in West Africa
Authors: Dalton Timothy J. 
Published: August 2007

AbstractNew crop varieties often have been promoted in developing countries based upon superior yield vis‐a‐vis locally available varieties. This research presents a hedonic price model for upland rice by drawing upon the input characteristics and consumer good characteristics model literature. Model specification tests determine that a combination of production and consumption characteristics best explains the willingness to pay for new upland rice varieties. The household model specification determined that five traits explain the willingness to pay for new rice varieties: plant cycle length, plant height, grain colour, elongation/ swelling and tenderness. Yield was not a significant explanatory variable of the willingness to pay for seed. The implications of this model are two‐fold. First, varietal development and promotion must include post‐harvest characteristics in addition to production traits when determining which varieties to promote for official release. Secondly, non‐yield production characteristics such as plant height and cycle length are significant factors in producer's assessments of the value of a new variety. Overall, this paper provides an alternative explanation for limited adoption of modern upland rice varieties in West Africa: varietal evaluation programs have focused too narrowly on yield evaluation and have not promoted varieties with superior non‐yield characteristics than locally available varieties.
The economic determinants of cereal crop diversity on farms in the Ethiopian highlands
Authors: Benin S. , Smale M. , Pender J. , Gebremedhin B. , Ehui S. 
Published: August 2007

AbstractIn less favoured areas such as the highlands of Ethiopia, farmers manage risk through land allocation to crops and varieties since they cannot depend on market mechanisms to cope. They also grow traditional varieties that are genetically diverse and have potential social value. Supporting the maintenance of crop and variety diversity in such locations can address both the current needs of farmers and future needs of society, though it entails numerous policy challenges. We estimate a model of crop and variety choice in a theoretical framework of the farm household model to compare the determinants of crop and variety diversity, revealing some of these policy considerations. Farm physical features and household characteristics such as wealth and labour stocks have large and significant effects on both the diversity among and within cereal crops, varying among crops. Policies designed to encourage variety diversity in one cereal crop may have opposing effects in another crop. Trade‐offs between development‐related factors and diversity in this resource‐poor system are not evident, however. Market‐related variables and population density have ambiguous effects. Education positively influences cereal crop diversity. Growing modern varieties of maize or wheat does not detract from the richness or evenness of these cereals on household farms.
Farm size and the determinants of productive efficiency in the Brazilian Center‐West
Authors: Helfand Steven M. , Levine Edward S. 
Published: August 2007

AbstractThis paper explores the determinants of technical efficiency, and the relationship between farm size and efficiency, in the Center‐West of Brazil. This is the region where agricultural production and total factor productivity have grown the fastest since 1970. It is also a region characterised by unusually large farms. Technical efficiency is studied with Data Envelopment Analysis and county level data disaggregated by farm size and type of land tenure. The efficiency measure is regressed on a set of explanatory variables which includes farm size, type of land tenure, composition of output, access to institutions and indicators of technology and input usage. The relationship between farm size and efficiency is found to be non‐linear, with efficiency first falling and then rising with size. Type of land tenure, access to institutions and markets, and modern inputs are found to be important determinants of the differences in efficiency across farms.
May the pro‐poor impacts of trade liberalisation vanish because of imperfect information?⋆
Authors: Boussard J. M. , Gérard F. , Piketty M. G. , Christensen A. K. , Voituriez T. 
Published: August 2007

AbstractIn this paper, we try to evaluate changes in welfare gains and their distribution due to trade liberalisation when imperfect information is considered. The results of two versions of a computable general equilibrium (CGE) model, using the GTAP database and representing goods as well as capital flows, are compared. In the first version, a standard world CGE approach is followed. In the second version, we included risk aversion, imperfect information and production lag in the agricultural sector. After a brief description of the two versions, changes in welfare, represented by the income of two types of household (middlelow and middle‐high) in three regions (Europe, United States, Rest of the World) after agricultural trade liberalisation are presented. Theoretical and political consequences of the results are discussed.
Measuring market integration in the presence of transaction costs–a threshold vector error correction approach
Authors: Meyer Jochen 
Published: August 2007

AbstractApplied econometric analyses of market integration based on price data alone have been criticised because they neglect the role of transaction costs. To meet this objection, threshold vector error correction models are used. Threshold models can account for the effects of transaction costs in price transmission without directly relying upon information about these costs, which are often unavailable. It is argued that threshold models that are based on two thresholds provide results that are economically more intuitive than those obtained from one‐threshold models. However, to this point no adequate econometric test is available for threshold significance in a two‐threshold model; such tests are only available for the one‐threshold model. In this paper a restricted two‐threshold model is developed in which the significance of the thresholds can be tested. This model is therefore amenable to economic interpretation and statistical inference. The model is used to estimate market integration in the European pig market.
Analysis of the Colorado potato beetle protection system in Finland
Authors: Heikkilä Jaakko , Peltola Jukka 
Published: August 2007

AbstractInvasive species, including plants, insects and other pests, are a serious threat to agricultural production and to the environment in general. Finland has traditionally had a favourable situation concerning invasives, partly due to its isolated geographical location. The situation may now be changing and one of the currently increasing threats is the Colorado potato beetle (CPB). Finland has designed a CPB protection policy incorporating a protected zone, which is commonly used to deal with invasive plant pests in other European countries. Within this zone, the randomly occurring CPB invasions are collectively fended off, to prevent the establishment of a permanent pest population and to minimise potential damage. This paper evaluates the economics of the current protection programme, comparing this to a hypothetical situation in which the current pre‐emptive policy is abandoned and control relies on producers' individual reactive protection measures. The annual random pest invasions are modelled in a static stochastic framework. To date the pest has not been able to establish a permanent population in Finland. According to our analysis, the currently exercised pre‐emptive policy is the cost‐efficient choice at this point. The relatively low expected invasion magnitude is one of the key factors supporting the efficiency of the current system. Another reason is the fairly small damage incurred. However, when the invasions become larger and more frequent or the pest strains more cold‐resistant, the future situation may change.