70 research outputs found
Passive pericardial constraint protects against stretch-induced vulnerability to atrial fibrillation in rabbits
No full text© 2006 by the American Physiological Society.Atrial fibrillation is more common in conditions with elevated atrial pressure and can be induced experimentally with acute increases in atrial pressure. We examined the effect of increased atrial pressure with and without pericardial constraint to better separate the effects of increased pressure and atrial stretch. In Langendorff-perfused rabbit hearts with intact pericardium, after ligating the pulmonary and caval veins, intra-atrial pressures were increased in a stepwise manner by adjusting the pulmonary outflow cannula. Rapid burst pacing was applied to induce atrial fibrillation at increasing intra-atrial pressures from 0 to 24 cmH(2)O. The atrial refractory period was recorded at each pressure using a single extra stimulus. The protocol was repeated after the pericardium was removed. When the pericardium was intact, atrial stretch was limited by passive constraint, and sustained atrial fibrillation could not be induced despite atrial pressures in excess of 20 cmH(2)O. In contrast, when the pericardium was removed, atrial fibrillation could be reliably induced when atrial pressure exceeded 15 cmH(2)O. This suggests that the electrophysiological effects of acute atrial volume loading rely on atrial stretch rather than increased atrial pressure alone.Daniel M. Ninio and David A. Sain
Disability and poverty : a survey of World Bank poverty assessments and implications
No full textIn this paper the authors survey the World Bank poverty assessment literature to date on the relationship between disability and poverty.The authors find that using standard assumptions about the distribution of household consumption among household members and the typical way that poverty lines are set in World Bank poverty assessments, this relationship may not appear to be as quantitatively significant as common sense and anecdotal evidence would suggest.Their assessment is limited by the fact that household surveys which are used by the Bank to determine consumption and consumption-based poverty typically do not include any questions about the disability status of household members. Only in one region of the Bank's work, Europe and Central Asia, do the authors find poverty assessments with numeric poverty rates for households with disabled members. Other poverty assessments done in other regions of the Bank, in some cases, do provide data on disabled people in regard to employment, health, social assistance, or a related subject, but do not provide poverty rates per se. This literature is assessed in this work, and directions for further research the authors will undertake are indicated.Population Policies,,Access to Finance,Disability,Social Protections&Assistance
Population aging and the labor market : the case of Sri Lanka
No full textSri Lanka's population is predicted to age vary fast during the next 50 years, bringing a slowdown of labor force growth and after 2030its contraction. Based on a 2006 representative survey of old people in Sri Lanka, the paper examines labor market consequences of this process, focusing on retirement pathways and the determinants of labor market withdrawal. The paper finds that a vast majority of Sri Lankan old workers are engaged in the informal sector, work long hours, and are paid less than younger workers. Moreover, the paper shows that labor market duality carries over to old age: (i) previous employment is the most important predictor of the retirement pathway; (ii) older workers fall into two categories: civil servants and formal private sector workers, who generally stop working before they reach 60 because they are forced to do so by mandatory retirement regulations, and casual workers and the self-employed, who work until very old age (or death) due to poverty and insufficient income and who stop working primarily because of poor health; and (iii) the option of part-time work is used primarily by workers who held regular jobs in their prime age employment, but not by casual workers and self-employed.Labor Markets,Health Monitoring&Evaluation,Labor Policies,Work&Working Conditions,
Live longer, work longer : making it happen in the labor market
No full textThe objective of the paper is to summarize labor market implications of population aging and to discuss policy options to increase the employment of old workers. The paper argues that population aging and ensuing shrinking of the workforce will create a significant drag on the economies of developed, transition, and even some developing countries. Thus working longer is an imperative: unless countered by productivity increases, working longer, or both, population aging and ensuing shrinking of labor force will reduce economic growth and may jeopardize the economic well-being of some of the elderly. However, extending working lives has proven difficult, both because workers do not want to work longer and because employers are lukewarm about employment old workers. Among measures to motivate workers to work longer, the paper proposes providing retirement incentives and attractive, flexible working arrangements; and to stimulate employers to hire old workers, it argues for removing obstacles imposed by restrictive labor market institutions, for increasing human capital of workers via life-long learning, and for addressing age discrimination. Chances for extending working lives will also increase with improving health of old workers. The organization of the paper is as follows. Section 1 discusses the implications of population aging for economic growth. Section 2 examines factors that stand in the way of longer working lives - why workers opt for early exit from the labor market, and why employers are often lukewarm about employing old workers. In the policy part of the paper, Section 3 proposes possible measures to attract workers to work longer, and Section 4 describes how to remove institutional obstacles and introduce incentives that would make old workers more appealing to employers.Labor Markets,Health Monitoring&Evaluation,,Labor Policies,Work&Working Conditions
Dietary fish oil protects against stretch-induced vulnerability to atrial fibrillation in a rabbit model
No full textThe definitive version is available at www.blackwell-synergy.comIntroduction: Dietary fish oil is thought to reduce sudden cardiac death by suppressing ventricular arrhythmias but little is known about its impact on atrial arrhythmias. We examined the effect of dietary fish oil on the rabbit model of stretch-induced vulnerability to atrial fibrillation (AF). Methods and Results: Six-week-old rabbits were fed standard rabbit pellets supplemented with 5% tuna fish oil (n = 6) or supplemented with 5% sunflower oil (n = 6) for 12 weeks. Six rabbits raised on the standard diet were used as controls. In Langendorff-perfused hearts intraatrial pressures were increased in a stepwise manner and rapid burst pacing applied to induce AF at increasing intraatrial pressures until AF was sustained (>1 minute). Atrial refractory periods were recorded at each pressure. Increased atrial pressure resulted in a reduction in atrial refractory period and a propensity for induction of sustained AF. Higher pressures were needed to induce and sustain AF in the fish oil group compared with the sunflower oil and control groups. The stretch-induced drop in refractory period was also less marked in the fish oil group. Red blood cell, atrial, and ventricular omega-3 fatty acid levels were significantly higher in the fish oil group. The ratio of atrial n-6/n-3 polyunsaturated fatty acids was 13 ± 0.9 with sunflower oil and 1.5 ± 0.01 with fish oil (P < 0.001). Conclusions: Incorporation of dietary omega-3 fatty acids into atrial tissue reduces stretch-induced susceptibility to AF.Daniel M. Ninio, Karen J. Murphy, Peter R. Howe, and David A. Sain
The portability of pension rights : general principals and the Caribbean case
No full textThe portability of pension rights is an increasingly important issue in the Caribbean. The large and increasing flows of migrant workers, including both permanent and temporary migrants, the small size of the domestic economies and the process of regional integration and economic openness call for effective means to make pensions portable. This document presents a select survey of the literature on pension portability and reviews the progress made by the Caribbean countries as well as some remaining challenges in the light of the international experience.Pensions&Retirement Systems,Debt Markets,Emerging Markets,Gender and Law,Labor Markets
Indexing pensions
No full textPension indexation should anchor the parameters of the pension system to one or more economic and demographic variables to ensure that the system is implemented in a sustainable way, while minimizing distortions affecting important economic choices. Arguing that financial sustainability, incentive compatibility and consistency across multiple government programs are critical, the author examine the many linkages between the various parameters of pension schemes. Finally, the author turn to the cost of the insurance dimension of indexation, and suggest that option pricing techniques could be used to price indexation guarantees, and that this approach may suggest refinements to indexation practice not thus far implemented.Emerging Markets,Debt Markets,Pensions&Retirement Systems,Economic Theory&Research,Markets and Market Access
Learning Facial Expressions: From Alignment to Recognition
No full textInternational audienceOne of the main challenges in 'real-life' object recognition applications is keeping some invariance properties such as: translation, scaling, and rotation. However, trying to maintain such invariants can impair recognition capabilities, especially when the family of objects of interest has a large shape variability. We present a general family of shape metrics that generalizes Procrustes metric and within this framework learns the desired shape metric parameters from labeled training samples. The learnt distance retains invariance properties on one hand and emphasizes the discriminative shape features on the other hand. We show how these metrics can be incorporated in multi-class classification kernel SVMs. We demonstrate the merits of this approach on multi-class facial expressions recognition using the AR dataset. The results address some questions and cautions regarding the interpretation of classification results when using still images datasets collected in a controlled lab environment and their relevance for 'real-life' applications
An examination of the role of atrial stretch in the genesis of atrial fibrillation and the antiarrhythmic effects of dietary fish oil.
No full textThis thesis is submitted as a PhD by portfolio of publications. It explores the role of atrial stretch in the pathogenesis of atrial fibrillation and the modulating effect of dietary fish oil.
Atrial fibrillation is more common in conditions associated with atrial stretch. This relationship is thought to be due to changes in activity of stretch-sensitive ion channels and
alterations in calcium handling. Increasing atrial pressure in isolated rabbit hearts shortens atrial refractoriness and enhances the inducibility and sustainability of atrial fibrillation.
The first of the publications in this thesis¹ describes the effect of pericardial constraint on the isolated rabbit heart model which uses increasing atrial pressure as a surrogate for increasing stretch. Reproducing the original description of this model but with an intact pericardium, increasing atrial pressure did not result in the electrical changes seen with marked atrial
dilatation. When the pericardium was removed, the relationship between increasing atrial pressure and susceptibility to atrial fibrillation was restored.
The second publication² reports the effect of streptomycin and intracellular acidosis on the rabbit heart atrial fibrillation model. Stretch-activated channel blockers gadolinium and
Grammostola toxin have been shown to limit atrial fibrillation with stretch in the rabbit model. We further explored the role of the non-specific cation stretch-activated channel using
streptomycin. Streptomycin reduced the stretch-related vulnerability to atrial fibrillation without altering the drop in refractory period associated with stretch. We proposed that the drop in refractoriness might be related to activation of stretch-activated potassium channels. These channels have also been shown to be sensitive to intracellular pH. We therefore
investigated the interaction between intracellular pH and stretch in the induction of atrial fibrillation. Intracellular acidosis, induced with propionate, amplified changes in
refractoriness and inducibility of atrial fibrillation with stretch.
The third publication³ examines the effect of dietary fish oil on the rabbit model of atrial fibrillation. Changes in membrane fluidity and fatty acid composition could alter the stretch
response. We proposed that changing the phospholipid membrane composition could alter the mechano-electric feedback in this model. Comparing rabbits fed for 12 weeks with fish oil or
sunflower oil supplemented diets, we reported protection from the stretch induced vulnerability to atrial fibrillation in the fish oil fed rabbits. This was associated with an increase in n-3 omega fatty acids in the atrial tissue which was reflected in changes in erythrocyte membrane composition.
The last publication⁴ measured the effect of a 12 week dietary fish oil supplement on the heart rate variability of 46 overweight adults. This was a substudy of a larger randomised doubleblinded placebo controlled study of fish oil and exercise on cardiovascular health. Frequency domain analysis was performed before and after the 12-week intervention. Fish oil increased the high frequency component of heart rate variability in keeping with increased parasympathetic activity and improved autonomic function.
The outcome of this research has been to further the understanding of the complex interplay between stretch and atrial arrhythmias and to raise the possibility of using dietary fish oil to treat atrial fibrillation.Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 200
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