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Reserve Capacity (reserve + capacity)
Selected AbstractsImpaired cardiac functional reserve in type 2 diabetic db/db mice is associated with metabolic, but not structural, remodellingACTA PHYSIOLOGICA, Issue 1 2010A. Daniels Abstract Aim:, To identify the initial alterations in myocardial tissue associated with the early signs of diabetic cardiac haemodynamic dysfunction, we monitored changes in cardiac function, structural remodelling and gene expression in hearts of type 2 diabetic db/db mice. Methods:, Cardiac dimensions and function were determined echocardiographically at 8, 12, 16 and 18 weeks of age. Left ventricular pressure characteristics were measured at 18 weeks under baseline conditions and upon dobutamine infusion. Results:, The db/db mice were severely diabetic already at 8 weeks after birth, showing elevated fasting blood glucose levels and albuminuria. Nevertheless, echocardiography revealed no significant changes in cardiac function up to 18 weeks of age. At 18 weeks of age, left ventricular pressure characteristics were not significantly different at baseline between diabetic and control mice. However, dobutamine stress test revealed significantly attenuated cardiac inotropic and lusitropic responses in db/db mice. Post-mortem cardiac tissue analyses showed minor structural remodelling and no significant changes in gene expression levels of the sarcoplasmic reticulum calcium ATPase (SERCA2a) or ,1-adrenoceptor (,1-AR). Moreover, the phosphorylation state of known contractile protein targets of protein kinase A (PKA) was not altered, indicating unaffected cardiac ,-adrenergic signalling activity in diabetic animals. By contrast, the substantially increased expression of uncoupling protein-3 (UCP3) and angiopoietin-like-4 (Angptl4), along with decreased phosphorylation of AMP-activated protein kinase (AMPK) in the diabetic heart, is indicative of marked changes in cardiac metabolism. Conclusion:, db/db mice show impaired cardiac functional reserve capacity during maximal ,-adrenergic stimulation which is associated with unfavourable changes in cardiac energy metabolism. [source] Optimal CBM of tie lines between control areas in a deregulated environmentELECTRICAL ENGINEERING IN JAPAN, Issue 1 2009Hideaki Kuraishi Abstract In order to keep power supply reliability at a certain level, electric power utilities have a certain amount of reserve capacity. When no generator outage or no unexpected large power demand occurs, however, the reserve capacity is regarded as surplus facility. To reduce the reserve capacity, some margin is reserved in tie lines between utilities. This margin is called the capacity benefit margin (CBM). In this study, a method of calculating optimal CBM in tie line under deregulated environment is described and two kinds of optimal CBM are proposed. As a result, it is shown how the deregulation affects the optimal CBM by using numerical simulation for the IEE Japan West 30 test system. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 35, 48, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20654 [source] Cerebral vasomotor reactivity of bilateral severe carotid stenosis: is stroke unavoidable?EUROPEAN JOURNAL OF NEUROLOGY, Issue 2 2006A. Y. Gur We evaluated the cerebral hemodynamic features of severe bilateral carotid stenosis by assessing and comparing cerebral vasomotor reactivity (VMR) in the middle cerebral (MCA) and vertebral arteries (VA) by transcranial Doppler and the Diamox (1 g acetazolamide i.v.) test. VMR was evaluated by recording the percentage differences in peak systolic blood flow velocity in each MCA and VA at baseline and by the Diamox test. Twenty-eight symptomatic (SCAS) and 31 asymptomatic (ACAS) patients with bilateral severe (>70%) internal carotid artery stenosis were studied. The mean MCA VMR% was 29 ± 26.9% in SCAS and 43.2 ± 26.8% in ACAS patients (P < 0.01). Their respective mean VA VMR% was 30.2 ± 36.5% and 39.6 ± 24.4% (P = NS). VMR% of the symptomatic MCA side in SCAS patients was significantly lower than the opposite side (20.5 ± 31.1% and 39.2 ± 37.9% respectively; P < 0.03). In contrast, the VA VMR% of both sides in SCAS patients remained similar (28.1 ± 39.3% and 34.6 ± 47.9% respectively; P = NS). VMR% of the MCA and VA in ACAS patients was also similar for both sides of bilateral carotid stenosis. The cerebral hemodynamic features differ between SCAS and ACAS patients with bilateral carotid occlusive disease in the anterior part of the circle of Willis. An independent cerebral vascular reserve capacity of the posterior circulation is proposed. [source] Dimensioning of data networks: a flow-level perspectiveEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2009Pasi Lassila Traditional network dimensioning formulations have applied the Erlang model where the connections reserve capacity in the network. Until recently, tractable stochastic network models where the connections share the capacity in the network did not exist. The latter are becoming increasingly important as they can be applied to characterise file transfers in current data networks (e.g. IP networks). In particular, they can be utilised for dimensioning of networks with respect to the file transfer performance. To this end, we consider a model where the traffic consists of elastic flows (i.e. file transfers). Flows arrive randomly and share the network resources resulting in stochastically varying transmission rates for flows. Our contribution is to develop efficient methods for capacity planning to meet the performance requirements expressed in terms of the average transmission rate of flows on a given route, i.e. the per-flow throughput. These methods are validated using ns2 simulations. We discuss also the effects of access rate limitations and how to combine the elastic traffic requirements with those of real-time traffic. Finally, we outline how the methods can be applied in wireless mesh networks. Our results enable a simple characterisation of the order-of-magnitude of the required capacities, which can be utilised as a first step in practical network planning and dimensioning. Copyright © 2008 John Wiley & Sons, Ltd. [source] Does arm length indicate cognitive and functional reserve?INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 5 2005Seul-Ki Jeong Abstract Background This study aimed to examine whether arm length and height were associated with cognitive and functional abilities. Methods Screening interviews were conducted in 235 community dwelling individuals aged 65 and over. The assessment scales included the Korean version of modified Mini-Mental State Examination (K-mMMSE) for cognition, and the Korean Instrumental Activities of Daily Living (K-IADL) for functional ability. All the participants were examined clinically and a diagnosis of dementia was ascertained. Anthropometric measurements included total arm span and height. Results Both arm length and height correlated significantly with the cognitive and functional scales. In the multivariate regression models, their associations were significant, independent of age, sex, education, and other variables. Shorter arm length was also significantly associated with dementia; while, height lost significance after an adjustment for the potential confounders. Conclusions Arm length and height could indicate cognitive and functional ability. Arm length, which was known to be less prone to degenerative processes, might be more stable as an indicator for cognitive and functional reserve capacity than height. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Role of the Kidneys in HypertensionJOURNAL OF CLINICAL HYPERTENSION, Issue 9 2005L. Gabriel Navar PhD The devastating long-term consequences of high blood pressure include stroke, heart disease, atherosclerosis, renal disease, and other end-organ damage. From a physiologic perspective, it is not apparent why the propensity for hypertension is so widespread in the general population. Clearly, an adequate arterial pressure is essential for perfusion of the tissues to provide adequate oxygenation and nutrition to the brain and other critical organs. Although the various microcirculatory beds have the capability to adjust vascular resistance to autoregulate blood flow, systemic arterial pressure is usually maintained at levels greater than required for requisite tissue perfusion. The myriad of neurohumoral mechanisms designed to protect against decreases in systemic arterial pressure provide a reserve capacity for increased perfusion when there are increased tissue demands. The unfortunate consequence of having these powerful physiologic control mechanisms is that they may be inappropriately activated in certain circumstances or by genetically determined traits, leading to hypertension and cardiovascular injury. Evidence continues to accumulate indicating that the kidney not only is victim to hypertension-related injury, but also contributes as a villain to the hypertensinogenic process. [source] Boys live dangerously in the wombAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2010Johan G. Eriksson The growth of every human fetus is constrained by the limited capacity of the mother and placenta to deliver nutrients to it. At birth, boys tend to be longer than girls at any placental weight. Boy's placentas may therefore be more efficient than girls, but may have less reserve capacity. In the womb boys grow faster than girls and are therefore at greater risk of becoming undernourished. Fetal undernutrition leads to small size at birth and cardiovascular disorders, including hypertension, in later life. We studied 2003 men and women aged around 62 years who were born in Helsinki, Finland, of whom 644 had hypertension: we examined their body and placental size at birth. In both sexes, hypertension was associated with low birth weight. In men, hypertension was also associated with a long minor diameter of the placental surface. The dangerous growth strategy of boys may be compounded by the costs of compensatory placental enlargement in late gestation. In women, hypertension was associated with a small placental area, which may reduce nutrient delivery to the fetus. In men, hypertension was linked to the mothers' socioeconomic status, an indicator of their diets: in women it was linked to the mothers' heights, an indicator of their protein metabolism. Boys' greater dependence on their mothers' diets may enable them to capitalize on an improving food supply, but it makes them vulnerable to food shortages. The ultimate manifestation of their dangerous strategies may be that men have higher blood pressures and shorter lives than women. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source] Childhood, adolescence, and longevity: A multilevel model of the evolution of reserve capacity in human life historyAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2009Barry Bogin The grandmother hypothesis (GH) of Hawkes et al. ([1998]: Proc Natl Acad Sci USA 95: 1336,1339) finds that selection for lower adult mortality and greater longevity allow for the evolution of prolonged growth in human beings. In contrast, other researchers propose that the evolution of the human childhood and adolescent stages of life history prolonged the growth period and allowed for greater biological resilience and longevity compared with apes. In this article, the GH model is reanalyzed using new values for some of its key variables. The original GH set the age at human feeding independence at 2.8 years of age (weaning) and used demographic data from living foragers to estimate average adult lifespan after first birth at 32.9 years. The reanalysis of the GH uses age 7.0 years (end of the childhood stage) as the minimum for human feeding independence and uses data from healthier populations, rather than foragers, to derive an estimate of 48.9 years for average adult life span. Doing so finds that selection operated to first shorten the infancy stage (wean early compared with apes), then prolong the growth period, and finally result in greater longevity. The reanalysis provides a test of the reserve capacity hypothesis as part of a multilevel model of human life history evolution. Am. J. Hum. Biol. 2009. © 2009 Wiley-Liss, Inc. [source] Adaptations in placental nutrient transfer capacity to meet fetal growth demands depend on placental size in miceTHE JOURNAL OF PHYSIOLOGY, Issue 18 2008P. M. Coan Experimental reduction in placental growth often leads to increased placental efficiency measured as grams of fetus produced per gram of placenta, although little is known about the mechanisms involved. This study tested the hypothesis that the smallest placenta within a litter is the most efficient at supporting fetal growth by examining the natural intra-litter variation in placental nutrient transfer capacity in normal pregnant mice. The morphology, nutrient transfer and expression of key growth and nutrient supply genes (Igf2P0, Grb10, Slc2a1, Slc2a3, Slc38a1, Slc38a2 and Slc38a4) were compared in the lightest and heaviest placentas of a litter at days 16 and 19 of pregnancy, when mouse fetuses are growing most rapidly in absolute terms. The data show that there are morphological and functional adaptations in the lightest placenta within a litter, which increase active transport of amino acids per gram of placenta and maintain normal fetal growth close to term, despite the reduced placental mass. The specific placental adaptations differ with age. At E16, they are primarily morphological with an increase in the volume fraction of the labyrinthine zone responsible for nutrient exchange, whereas at E19 they are more functional with up-regulated placental expression of the glucose transporter gene, Slc2a1/GLUT1 and one isoform the System A family of amino acid transporters, Slc38a2/SNAT2. Thus, this adaptability in placental phenotype provides a functional reserve capacity for maximizing fetal growth during late gestation when placental growth is compromised. [source] The Reserve Capacity Model as a Framework for Understanding Psychosocial Factors in Health DisparitiesAPPLIED PSYCHOLOGY: HEALTH AND WELL-BEING, Issue 1 2009Linda C. Gallo Substantial research has identified a robust, linear association between socioeconomic status (SES) and health, across many different populations and outcomes. Among myriad influences, psychosocial factors may contribute to SES-related gradients in health. In the current manuscript, we describe the Reserve Capacity Model (Gallo & Matthews, 2003) as a potential framework through which to examine psychosocial pathways in health disparities. The model posits that SES is connected to health, in part through associations with stress and concomitant negative emotions, and their subsequent links with bio-behavioral functioning. In addition, low SES may predict enhanced emotional and physiological reactivity to stress due to a deficiency in resilient psychosocial resources (i.e. "reserve capacity") and limited opportunities to replenish resource reserves. In addition, resources might represent a direct mediational pathway from SES to health. We describe several studies in which we have examined various tenets of the Reserve Capacity Model, and comment on future research directions to better understand the roles of psychosocial variables in health disparities. [source] | ||||||||||||||||