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Exhaustion
Kinds of Exhaustion Selected AbstractsEXHAUSTION OF MORPHOLOGIC CHARACTER STATES AMONG FOSSIL TAXAEVOLUTION, Issue 2 2000Peter J. Wagner Abstract., Frequencies of new character state derivations are analyzed for 56 fossil taxa. The hypothesis that new character states are added continuously throughout clade history can be rejected for 48 of theses clades. Two alternative explanations are considered: finite states and ordered states. The former hypothesizes a limited number of states available to each character and is tested using rarefaction equations. The latter hypothesizes that there are limited possible descendant morphologies for any state, even if the character has infinite potential states. This is tested using power functions. The finite states hypothesis explains states: steps relationships significantly better than does the ordered states hypothesis in 14 cases; the converse is true for 14 other cases. Under either hypothesis, trilobite clades show appreciably more homoplasy after the same numbers of steps than do molluscs, echinoderms, or vertebrates. The prevalence of the exhaustion pattern among different taxonomic groups implies that worker biases are not to blame and instead implicates biological explanations such as intrinsic constraints or persistent selective trends. Regardless of the source of increased homoplasy, clades appear to exhaust their available character spaces. Nearly all examined taxa show significant increases in proportions of incompatible character pairs (i.e., those necessarily implying homoplasy) as progressively younger taxa are added to character matrices. Thus, a deterioration of hierarchical structure accompanies character state exhaustion. Exhaustion has several implications: (1) the basic premise of cladistic analyses (i.e., that maximum congruence reflects homology rather than homoplasy) becomes increasingly less sound as clades age; (2) sampling high proportions of taxa probably is needed for congruence to discern homoplasy from homology; (3) stratigraphic data might be necessary to discern congruent homoplasy from congruent homology; and (4) in many cases, character states appear to have evolved in ordered patterns. [source] Burnout and physical and mental health among Swedish healthcare workersJOURNAL OF ADVANCED NURSING, Issue 1 2008Ulla Peterson Abstract Title.,Burnout and physical and mental health among Swedish healthcare workers Aim., This paper is a report of a study to investigate how burnout relates to self-reported physical and mental health, sleep disturbance, memory and lifestyle factors. Background., Previous research on the possible relationship between lifestyle factors and burnout has yielded somewhat inconsistent results. Most of the previous research on possible health implications of burnout has focused on its negative impact on mental health. Exhaustion appears to be the most obvious manifestation of burnout, which also correlates positively with workload and with other stress-related outcomes. Method., A cross-sectional study was conducted, using questionnaires sent to all employees in a Swedish County Council (N = 6118) in 2002. The overall response rate was 65% (n = 3719). A linear discriminant analysis was used to look for different patterns of health indicators and lifestyle factors in four burnout groups (non-burnout, disengaged, exhausted and burnout). Results., Self-reported depression, anxiety, sleep disturbance, memory impairment and neck- and back pain most clearly discriminated burnout and exhausted groups from disengaged and non-burnout groups. Self-reported physical exercise and alcohol consumption played a minor role in discriminating between burnout and non-burnout groups, while physical exercise discriminated the exhausted from the disengaged group. Conclusion., Employees with burnout had most symptoms, compared with those who experienced only exhaustion, disengagement from work or no burnout, and the result underlines the importance of actions taken to prevent and combat burnout. [source] Role Stress, Exhaustion, and Satisfaction: A Cross-Lagged Structural Equation Modeling Approach Supporting Hobfoll's Loss SpiralsJOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 6 2010Daniel ÖRtqvist This study applies Hobfoll's notion of loss spirals to argue for a reciprocal relationship between role stress and 2 of its most commonly studied consequences: exhaustion and satisfaction. By means of structural equation modeling and a cross-lagged design of 116 business managers, the researchers found support for a relationship between role stress and exhaustion. They also found that satisfaction influences role stress, a relationship that the existing literature has not examined. The study contributes a more complex understanding of the relationship between role stress and its modeled outcomes than has been achieved previously. [source] Organizational Justice and Individuals' Withdrawal: Unlocking the Influence of Emotional ExhaustionJOURNAL OF MANAGEMENT STUDIES, Issue 3 2010Michael S. Cole abstract This study examined the relationships between organizational justice and withdrawal outcomes and whether emotional exhaustion was a mediator of these linkages. Data were obtained from 869 military personnel and civil servants; using structural equation modelling techniques, we examined an integrative model that combines justice and stress research. Our findings suggest that individuals' justice perceptions are related to their psychological health. As predicted, emotional exhaustion mediated the linkages between distributive and interpersonal (but not procedural and informational) justice and individuals' withdrawal reactions. Results showed that distributive and interpersonal justice negatively related to emotional exhaustion and emotional exhaustion negatively related to organizational commitment which, in turn, negatively influenced turnover intentions. These findings were observed even when controlling for the presence of contingent-reward behaviours provided by supervisors and individuals' psychological empowerment. [source] Work Relationships in Telephone Call Centres: Understanding Emotional Exhaustion and Employee WithdrawalJOURNAL OF MANAGEMENT STUDIES, Issue 4 2002Stephen Deery This paper examines the nature of employment and the conditions of work in five telephone call centres in the telecommunications industry in Australia. Call centre work typically requires high levels of sustained interpersonal interaction with customers which can lead to burnout and employee withdrawal. Customer service staff can also become targets of customer hostility and abuse. In addition, this form of work tends to involve extensive employee monitoring and surveillance with little job discretion or variety of tasks. The paper draws upon survey data from 480 telephone service operators to identify the factors that are associated with emotional exhaustion and the frequency of absence amongst the employees. A modelling of the data using LISREL VIII revealed that a number of job and work-setting variables affected the level of emotional exhaustion of employees. These included interactions with the customer, a high workload and a lack of variety of work tasks. Moreover, higher rates of absence were associated with emotional exhaustion. [source] The mediating effect of burnout on the relationship between structural empowerment and organizational citizenship behavioursJOURNAL OF NURSING MANAGEMENT, Issue 3 2010STEPHANIE GILBERT MSc gilbert s., laschinger h.k.s. &leiter m (2010) Journal of Nursing Management18, 339,348 The mediating effect of burnout on the relationship between structural empowerment and organizational citizenship behaviours Aim, We used Kanter's (1977) structural empowerment theory to examine the influence of structural empowerment and emotional exhaustion on healthcare professionals' use of organizational citizenship behaviours directed at the organization (OCBO) and peers (OCBI). Background, Organizational citizenship behaviours (OCB) are discretionary behaviours that are not rewarded directly by the organization but have been linked to positive outcomes, such as increased job satisfaction and lower turnover intentions. Promoting OCB can help employees and organizations flourish despite current challenges in the healthcare system. Structural empowerment may influence the frequency and type of OCB by reducing burnout. Method, We conducted multiple mediated regression analyses to test two hypothesized models about relationships between empowerment, emotional exhaustion and two types of OCB (OCBI and OCBO) in a sample of 897 healthcare professionals in five Canadian hospitals. Results, Emotional exhaustion was found to be a significant mediator of the relationship between empowerment and OCBO. The predicted mediation of the empowerment/OCBI relationship by emotional exhaustion was not supported. Conclusions, Exhaustion was an important mediator of empowering working conditions and OCBO, but was not significantly related to OCBI. Empowerment was significantly related to both OCBO and OCBI. Implications for nursing management, Promoting empowerment among healthcare workers may decrease burnout and promote OCB. Specific managerial strategies are discussed in the present study. [source] Exhaustion of Industrial Property Rights from the German PerspectiveTHE JOURNAL OF WORLD INTELLECTUAL PROPERTY, Issue 2 2001Johann Pitz First page of article [source] Resource management in open Linda systemsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2003Ronaldo Menezes Abstract Coordination systems, in particular Linda, have established themselves as important tools for the development of applications to open systems such as the Internet. This paper shows how to tackle a forgotten, but crucial problem in open coordination systems: memory management. As with any system which intends to be of wide use and because memory is a finite resource, coordination systems must address the problems of memory exhaustion. This paper first explores the orthogonality between coordination and computation in order to make it clear that the problem of memory exhaustion in coordination systems cannot be solved using garbage collection schemes implemented at the computation language,a garbage collection scheme must exist in the coordination environment as well. Following the explanation on orthogonality, the paper will focus on describing a garbage collection scheme for the Linda family of coordination systems. It is expected that the solution in Linda can be adapted to other coordination systems as long as they are based on tuple space communication. Copyright © 2003 John Wiley & Sons, Ltd. [source] Cardiovascular function in the heat-stressed humanACTA PHYSIOLOGICA, Issue 4 2010C. G. Crandall Abstract Heat stress, whether passive (i.e. exposure to elevated environmental temperatures) or via exercise, results in pronounced cardiovascular adjustments that are necessary for adequate temperature regulation as well as perfusion of the exercising muscle, heart and brain. The available data suggest that generally during passive heat stress baroreflex control of heart rate and sympathetic nerve activity are unchanged, while baroreflex control of systemic vascular resistance may be impaired perhaps due to attenuated vasoconstrictor responsiveness of the cutaneous circulation. Heat stress improves left ventricular systolic function, evidenced by increased cardiac contractility, thereby maintaining stroke volume despite large reductions in ventricular filling pressures. Heat stress-induced reductions in cerebral perfusion likely contribute to the recognized effect of this thermal condition in reducing orthostatic tolerance, although the mechanism(s) by which this occurs is not completely understood. The combination of intense whole-body exercise and environmental heat stress or dehydration-induced hyperthermia results in significant cardiovascular strain prior to exhaustion, which is characterized by reductions in cardiac output, stroke volume, arterial pressure and blood flow to the brain, skin and exercising muscle. These alterations in cardiovascular function and regulation late in heat stress/dehydration exercise might involve the interplay of both local and central reflexes, the contribution of which is presently unresolved. [source] Cerebral oxygenation decreases but does not impair performance during self-paced, strenuous exerciseACTA PHYSIOLOGICA, Issue 4 2010F. Billaut Abstract Aim:, The reduction in cerebral oxygenation (Cox) is associated with the cessation of exercise during constant work rate and incremental tests to exhaustion. Yet in exercises of this nature, ecological validity is limited due to work rate being either fully or partly dictated by the protocol, and it is unknown whether cerebral deoxygenation also occurs during self-paced exercise. Here, we investigated the cerebral haemodynamics during a 5-km running time trial in trained runners. Methods:, Rating of perceived exertion (RPE) and surface electromyogram (EMG) of lower limb muscles were recorded every 0.5 km. Changes in Cox (prefrontal lobe) were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxyhaemoglobin (,[O2Hb], ,[HHb]). Changes in total Hb were calculated (,[THb] = ,[O2Hb] + ,[HHb]) and used as an index of change in regional blood volume. Results:, During the trial, RPE increased from 6.6 ± 0.6 to 19.1 ± 0.7 indicating maximal exertion. Cox rose from baseline to 2.5 km (,,[O2Hb], ,,[HHb], ,,[THb]), remained constant between 2.5 and 4.5 km, and fell from 4.5 to 5 km (,,[O2Hb], ,,[HHb], ,,[THb]). Interestingly, the drop in Cox at the end of the trial coincided with a final end spurt in treadmill speed and concomitant increase in skeletal muscle recruitment (as revealed by higher lower limb EMG). Conclusion:, Results confirm the large tolerance for change in Cox during exercise at sea level, yet further indicate that, in conditions of self-selected work rate, cerebral deoxygenation remains within a range that does not hinder strenuous exercise performance. [source] Low-volume muscle endurance training prevents decrease in muscle oxidative and endurance function during 21-day forearm immobilizationACTA PHYSIOLOGICA, Issue 4 2009T. Homma Abstract Aim:, To examine the effects of low-volume muscle endurance training on muscle oxidative capacity, endurance and strength of the forearm muscle during 21-day forearm immobilization (IMM-21d). Methods:, The non-dominant arm (n = 15) was immobilized for 21 days with a cast and assigned to an immobilization-only group (Imm-group; n = 7) or an immobilization with training group (Imm+Tr-group; n = 8). Training comprised dynamic handgrip exercise at 30% of pre-intervention maximal voluntary contraction (MVC) at 1 Hz until exhaustion, twice a week during the immobilization period. The duration of each exercise session was 51.7 ± 3.4 s (mean ± SE). Muscle oxidative capacity was evaluated by the time constant for phosphocreatine recovery (,offPCr) after a submaximal handgrip exercise using 31phosphorus-magnetic resonance spectroscopy. An endurance test was performed at 30% of pre-intervention MVC, at 1 Hz, until exhaustion. Results:,,offPCr was significantly prolonged in the Imm-group after 21 days (42.0 ± 2.8 and 64.2 ± 5.1 s, pre- and post-intervention respectively; P < 0.01) but did not change for the Imm+Tr-group (50.3 ± 3.0 and 48.8 ± 5.0 s, ns). Endurance decreased significantly for the Imm-group (55.1 ± 5.1 and 44.7 ± 4.6 s, P < 0.05) but did not change for the Imm+Tr-group (47.9 ± 3.0 and 51.7 ± 4.0 s, ns). MVC decreased similarly in both groups (P < 0.01). Conclusions:, Twice-weekly muscle endurance training sessions, each lasting approx. 50 s, effectively prevented a decrease in muscle oxidative capacity and endurance; however, there was no effect on MVC decline with IMM-21d. [source] Cerebral oxygenation decreases during exercise in humans with beta-adrenergic blockadeACTA PHYSIOLOGICA, Issue 3 2009T. Seifert Abstract Aim:, Beta-blockers reduce exercise capacity by attenuated increase in cardiac output, but it remains unknown whether performance also relates to attenuated cerebral oxygenation. Methods:, Acting as their own controls, eight healthy subjects performed a continuous incremental cycle test to exhaustion with or without administration of the non-selective beta-blocker propranolol. Changes in cerebral blood flow velocity were measured with transcranial Doppler ultrasound and those in cerebral oxygenation were evaluated using near-infrared spectroscopy and the calculated cerebral mitochondrial oxygen tension derived from arterial to internal jugular venous concentration differences. Results:, Arterial lactate and cardiac output increased to 15.3 ± 4.2 mm and 20.8 ± 1.5 L min,1 respectively (mean ± SD). Frontal lobe oxygenation remained unaffected but the calculated cerebral mitochondrial oxygen tension decreased by 29 ± 7 mmHg (P < 0.05). Propranolol reduced resting heart rate (58 ± 6 vs. 69 ± 8 beats min,1) and at exercise exhaustion, cardiac output (16.6 ± 3.6 L min,1) and arterial lactate (9.4 ± 3.7 mm) were attenuated with a reduction in exercise capacity from 239 ± 42 to 209 ± 31 W (all P < 0.05). Propranolol also attenuated the increase in cerebral blood flow velocity and frontal lobe oxygenation (P < 0.05) whereas the cerebral mitochondrial oxygen tension decreased to a similar degree as during control exercise (delta 28 ± 10 mmHg; P < 0.05). Conclusion:, Propranolol attenuated the increase in cardiac output of consequence for cerebral perfusion and oxygenation. We suggest that a decrease in cerebral oxygenation limits exercise capacity. [source] Free radical generation and oxidative stress with ageing and exercise: Differential effects in the myocardium and liverACTA PHYSIOLOGICA, Issue 4 2000Bejma Reactive oxygen species and other oxidants are implicated in the mechanisms of biological ageing and exercise-induced tissue damage. The present study examined the effects of ageing and an acute bout of exercise on intracellular oxidant generation, lipid peroxidation, protein oxidation and glutathione (GSH) status in the heart and liver of young adult (8 month, N=24) and old (24 month, N=24) male Fischer 344 rats. Young rats ran on treadmill at 25 m min,1, 5% grade until exhaustion (55.4 ± 2.7 min), whereas old rats ran at 15 m min,1, 5% until exhaustion (58.0 ± 2.7 min). Rate of dichlorofluorescin (DCFH) oxidation, an indication of intracellular oxidant production, was significantly higher in the homogenates of aged heart and liver compared with their young counterparts. In the isolated heart and liver mitochondria, ageing increased oxidant production by 29 and 32% (P < 0.05), respectively. Acute exercise increased oxidant production in the aged heart but not in the liver. When nicodinamide dinucleotide phosphate (reduced), adenosine diphosphate and Fe3+ were included in the assay, DCFH oxidation rate was 47 and 34% higher (P < 0.05) in the aged heart and liver homogenates, respectively, than the young ones. The age differences in the induced state reached 83 and 140% (P < 0.01) in isolated heart and liver mitochondria, respectively. Lipid peroxidation was increased in the aged liver and exercised aged heart, whereas protein carbonyl content was elevated only in the aged heart (P < 0.05). Although our data using DCFH method probably underestimated cellular oxidant production because of time delay and antioxidant competition, it is clear that oxidative stress was enhanced in both heart and liver with old age. Furthermore, aged myocardium showed greater susceptibility to oxidative stress after heavy exercise. [source] Does aerobic fitness influence microvascular function in healthy adults at risk of developing Type 2 diabetes?DIABETIC MEDICINE, Issue 4 2005A. R. Middlebrooke Abstract Aim To investigate whether aerobic fitness is associated with skin microvascular function in healthy adults with an increased risk of developing Type 2 diabetes. Methods Twenty-seven healthy normal glucose-tolerant humans with either a previous diagnosis of gestational diabetes or having two parents with Type 2 diabetes and 27 healthy adults who had no history of diabetes were recruited. Maximal oxygen uptake was assessed using an incremental exercise test to exhaustion. Skin microvascular function was assessed using laser Doppler techniques as the maximum skin hyperaemic response to a thermal stimulus (maximum hyperaemia) and the forearm skin blood flow response to the iontophoretic application of acetylcholine (ACh) and sodium nitroprusside. Results Maximal oxygen uptake was not significantly different in the ,at-risk' group compared with healthy controls. Maximum hyperaemia was reduced in those ,at risk' (1.29 ± 0.30 vs. 1.46 ± 0.33 V, P = 0.047); however, the peak response to acetylcholine or sodium nitroprusside did not differ in the two groups. A significant positive correlation was demonstrated between maximal oxygen uptake and maximum hyperaemia (r = 0.52, P = 0.006 l/min and r = 0.60, P = 0.001 ml/kg/min) and peak ACh response (r = 0.40, P = 0.04 l/min and r = 0.47, P = 0.013 ml/kg/min) in the ,at-risk' group when expressed in absolute (l/min) or body mass-related (ml/kg/min) terms. No significant correlations were found in the control group. Conclusions In this ,at-risk' group with skin microvascular dysfunction maximal oxygen uptake was not reduced compared with healthy controls. However, in the ,at-risk' group alone, individuals with higher levels of aerobic fitness also had better microvascular and endothelial responsiveness. [source] Household Unemployment and the Labour Supply of Married WomenECONOMICA, Issue 270 2001Paul Bingley A recent reform to the UK unemployment insurance (UI) system has reduced the duration of entitlement from 12 to six months. The UI and welfare systems interact in the UK in such a way that exhaustion of UI for married individuals has potentially large disincentive effects on the labour supply of spouses. A model of labour supply is estimated for married women allowing for endogenous unemployment durations of husbands and wives. We distinguish between transfer programme induced incentive effects; correlation between labour supply and wages within couples; complementarity between the leisure times of spouses; and a discouraged worker effect. [source] Can Growth Ease Class Conflict?ECONOMICS & POLITICS, Issue 1 2002E. Somanathan This paper proposes a theory that links labor supply to wage growth and economic growth, and the conflict of interest between capital and labor. During the early stages of industrialization of a country, "surplus" labor drawn from the traditional sector of the economy is available to the modern capitalist sector at a constant or only slowly rising wage. As industrialization proceeds, this labor surplus vanishes, leading to wages rising in tandem with the growth of output. As long as there is surplus labor, workers in the modern capitalist sector, who are organized, have little interest in growth as it does not raise wages. The effect of growth is external to them, simply drawing more workers into the capitalist sector and enabling the entrants to receive rents. So capitalist-sector workers would like to redistribute income regardless of the adverse effect on growth. Once the economy grows enough for the subsistence sector to vanish, further growth raises wages. Hence, this change in the structure of the economy leads to a reduction in the intensity of the labor,capital conflict. The dual economy model implies that growth rates rise over time and fall after the exhaustion of the labor surplus which is consistent with the stylized fact of economic growth. [source] Overreachers: Hyperbole, the "circle in the water," and Force in 1 Henry 6ENGLISH LITERARY RENAISSANCE, Issue 3 2003Michael Harrawood Overreachers: hyperbole, the "circle in the water," and the imposition of force in Henry VI, Part One This essay considers Joan of Arc's "Glory is like a circle in the water," speech from Henry VI, Part One. My argument is that the circle in the water,a model for the former English victories which now Joan claims will disperse to nothing,is both a figure for and a model of what the period called "overreaching." An examination of Joan's verbal tactics in this brief speech leads me first to a historical claim that Shakespeare, through Joan, deliberately sophisticates (by weakening) the model of Tamburlainian speech which constituted his chief competition in the amphitheaters. The circle in the water simile gets its power by thematizing the pathos of its own eventual exhaustion; and unlike Tamburlaine the power of the early English histories is derived from a series of ego surges that lead ultimately to failed and exhausted verbal performers. This historical claim leads to an examination of contemporary theories about hyperbolical speech and about the personal risks of using hyperbole in public speech performances. [source] Bioavailability of solid and non-aqueous phase liquid (NAPL)-dissolved phenanthrene to the biosurfactant-producing bacterium Pseudomonas aeruginosa 19SJENVIRONMENTAL MICROBIOLOGY, Issue 9 2001Marta García-Junco The biodegradation of phenanthrene by the biosurfactant-producing strain Pseudomonas aeruginosa 19SJ was investigated in experiments with the compound present either as crystals or dissolved in non-aqueous phase liquids (NAPLs). Growth on solid phenanthrene exhibited an initial phase not limited by dissolution rate and a subsequent, carbon-limited phase caused by exhaustion of the carbon source. Rhamnolipid biosurfactants were produced from solid phenanthrene and appeared in solution and particulate material (cells and phenanthrene crystals). During the carbon-limited phase, the concentration of rhamnolipids detected in culture exceeded the critical micelle concentration (CMC) determined with purified rhamnolipids. The biosurfactants caused a significant increase in dissolution rate and pseudosolubility of phenanthrene, but only at concentrations above the CMC. Externally added rhamnolipids at a concentration higher than the CMC increased the biodegradation rate of solid phenanthrene. Mineralization curves of low concentrations of phenanthrene initially dissolved in two NAPLs [2,2,4,4,6,8,8-heptamethylnonane and di(2-ethylhexyl)phthalate] were S-shaped, although no growth was observed in the population of suspended bacteria. Biosurfactants were not detected in solution under these conditions. The observed mineralization was attributed not only to suspended bacteria, but also to bacterial populations growing at the NAPL,water interface, mineralizing the compound at higher rates than predicted by abiotic partitioning. We suggest that rhamnolipid production and attachment increased the bioavailability of phenanthrene, so promoting biodegradation activity. [source] Severe functional impairment and elevated PD-1 expression in CD1d-restricted NKT cells retained during chronic HIV-1 infectionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2009Markus Moll Abstract Invariant CD1d-restricted NKT cells play important roles in regulating both innate and adaptive immunity. They are targeted by HIV-1 infection and severely reduced in number or even lost in many infected subjects. Here, we have investigated the characteristics of NKT cells retained by some patients despite chronic HIV-1 infection. NKT cells preserved under these circumstances displayed an impaired ability to proliferate and produce IFN-, in response to CD1d-restricted lipid antigen as compared with cells from uninfected control subjects. HIV-1 infection was associated with an elevated expression of the inhibitory programmed death-1 (PD-1) receptor (CD279) on the CD4, subset of NKT cells. However, blocking experiments indicated that the functional defects in NKT cells were largely PD-1-independent. Furthermore, the elevated PD-1 expression and the functional defects were not restored by anti-retroviral treatment, and the NKT cell numbers in blood did not recover significantly in response to treatment. The functional phenotype of NKT cells in these patients suggests an irreversible immune exhaustion due to chronic activation in vivo. The data demonstrate a severe functional impairment in the remaining NKT-cell compartment in HIV-1-infected patients, which limits the prospects to mobilize these cells in immunotherapy approaches in patients. [source] Activation drives PD-1 expression during vaccine-specific proliferation and following lentiviral infection in macaquesEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 5 2008David Abstract Recent data supports that increased expression of PD-1, a negative regulator of immune function, is associated with T cell exhaustion during chronic viral infection. However, PD-1 expression during acute infection and vaccination has not been studied in great detail in primates. Here, we examine PD-1 expression on CD3+ T cells following DNA vaccination or lentiviral infection of macaques. Ex vivo peptide stimulation of PBMC from DNA-vaccinated uninfected macaques revealed a temporal increase in PD-1 expression in proliferating antigen-specific CD8+ T cells. Following the initial increase, PD-1 expression steadily declined as proliferation continued, with a concomitant increase in IFN-, secretion. Subsequent examination of PD-1 expression on T cells from uninfected and lentivirus-infected non-vaccinated macaques revealed a significant increase in PD-1 expression with lentiviral infection, consistent with previous reports. PD-1 expression was highest on cells with activated memory and effector phenotypes. Despite their decreased telomere length, PD-1hi T cell populations do not appear to have statistically significant uncapped telomeres, typically indicative of proliferative exhaustion, suggesting a different mechanistic regulation of proliferation by PD-1. Our data indicate that PD-1 expression is increased as a result of T cell activation during a primary immune response as well as during persistent immune activation in macaques. Supporting Information for this article is available at www.wiley-vch.de/contents/jc_2040/2008/37857_s.pdf [source] The ratio between dendritic cells and T,cells determines the outcome of their encounter: Proliferation versus deletionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2005Abstract Dendritic cells (DC) either induce T,cell tolerance or contribute to the initiation and modulation of T and B,cell responses. Since many of the variables determining the thresholds of naive T,cell priming were defined in vitro using a homogeneously matured DC population, we here focused on partially mature DC which might reflect the occurrence of tumor-infiltrating and thymic DC. To predict how those DC regulate the induction of antigen-specific T,cell proliferation and T,cell tolerance, we co-cultured ovalbumin-pulsed murine DC at different ratios with antigen-specific DO11.10 transgenic T,cells. Whereas partially mature DC at a DC/T,cell ratio of 1,:,10 supported proliferation, a DC/T,cell ratio of 1,:,2 induced proliferation arrest in naive CD4+ T,cells. The acquisition of the NK cell inhibitory markers NK1.1 and KLRG on T,cells exposed to high numbers of DC suggests a role for these molecules in the protection of antigen-responsive T,cells from exhaustion by overstimulation. Mechanistically, abortive T,cell proliferation upon encounter of high numbers of partially mature DC is caused by an apoptosis-related pathway, suggesting that excessive antigen density without sufficient costimulation results in activation-induced cell death. [source] Inverse correlation between IL-7 receptor expression and CD8 T cell exhaustion during persistent antigen stimulationEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2005Abstract Persistence is a hallmark of infection by viruses such as HIV, hepatitis B virus, hepatitis C virus and LCMV. In the case of LCMV, persistence may often be associated with exhaustion of CD8+ T cells. We demonstrate here that persistent antigen suppressed IL-7R, expression and this correlated with T cell exhaustion and reduced expression of the anti-apoptotic molecule B cell leukemia/lymphoma 2 (Bcl-2). In contrast, exposure to short-lived antigen only temporarily suppressed IL-7R, expression, failed to induce T cell exhaustion, and primed T cells. Persistent antigen also suppressed IL-7R, expression on primed T cells and this correlated with exhaustion of a previously stable primed T cell population. These findings suggest that antigen longevity regulates T cell fate. [source] EVOLUTION OF INTRINSIC GROWTH RATE: METABOLIC COSTS DRIVE TRADE-OFFS BETWEEN GROWTH AND SWIMMING PERFORMANCE IN MENIDIA MENIDIAEVOLUTION, Issue 6 2006Stephen A. Arnott Abstract There is strong evidence that genetic capacity for growth evolves toward an optimum rather than an absolute maximum. This implies that fast growth has a cost and that trade-offs occur between growth and other life-history traits, but the fundamental mechanisms are poorly understood. Previous work on the Atlantic silverside fish Menidia menidia has demonstrated a trade-off between growth and swimming performance. We hypothesize that the trade-off derives from the competing metabolic demands associated with growth and swimming activity. We tested this by measuring standard metabolic rate (MSTD), maximum sustainable metabolic rate (MACT) and metabolic scope of laboratory-reared silversides originating from two geographically distinct populations with well-documented differences in genetic capacity for growth. The fast-growth genotype had a significantly greater MSTD than the slow-growth genotype, but a similar MACT when swum to near exhaustion. The scope for activity of the fast-growth genotype was lower than that of the slow-growth genotype. Furthermore, the fast-growth genotype eats larger meals, thereby incurring a greater postprandial oxygen demand. We conclude that a metabolic trade-off occurs between growth and other metabolic demands and that this trade-off provides a general mechanism underlying the evolution of growth rate. [source] EXHAUSTION OF MORPHOLOGIC CHARACTER STATES AMONG FOSSIL TAXAEVOLUTION, Issue 2 2000Peter J. Wagner Abstract., Frequencies of new character state derivations are analyzed for 56 fossil taxa. The hypothesis that new character states are added continuously throughout clade history can be rejected for 48 of theses clades. Two alternative explanations are considered: finite states and ordered states. The former hypothesizes a limited number of states available to each character and is tested using rarefaction equations. The latter hypothesizes that there are limited possible descendant morphologies for any state, even if the character has infinite potential states. This is tested using power functions. The finite states hypothesis explains states: steps relationships significantly better than does the ordered states hypothesis in 14 cases; the converse is true for 14 other cases. Under either hypothesis, trilobite clades show appreciably more homoplasy after the same numbers of steps than do molluscs, echinoderms, or vertebrates. The prevalence of the exhaustion pattern among different taxonomic groups implies that worker biases are not to blame and instead implicates biological explanations such as intrinsic constraints or persistent selective trends. Regardless of the source of increased homoplasy, clades appear to exhaust their available character spaces. Nearly all examined taxa show significant increases in proportions of incompatible character pairs (i.e., those necessarily implying homoplasy) as progressively younger taxa are added to character matrices. Thus, a deterioration of hierarchical structure accompanies character state exhaustion. Exhaustion has several implications: (1) the basic premise of cladistic analyses (i.e., that maximum congruence reflects homology rather than homoplasy) becomes increasingly less sound as clades age; (2) sampling high proportions of taxa probably is needed for congruence to discern homoplasy from homology; (3) stratigraphic data might be necessary to discern congruent homoplasy from congruent homology; and (4) in many cases, character states appear to have evolved in ordered patterns. [source] Exercise Heat Stress does not Reduce Central Activation to non-exercised Human Skeletal MuscleEXPERIMENTAL PHYSIOLOGY, Issue 6 2003Julian Saboisky In this study we measured the central activation ratio (CAR) of the leg extensors and the elbow flexor muscles before and after exhaustive exercise in the heat to determine whether exercise-induced hyperthermia affects the CNS drive to exercised (leg extensors) and/or non-exercised (forearm flexors) muscle groups. Thirteen subjects exercised at fixed intensities representative of a percentage of peak power output (PPO) for 10 min periods (50%, 40%, 60%, 50%) and then at 75% PPO until exhaustion in ambient conditions of 39.3 ± 0.8 °C and 60.0 ± 0.8% relative humidity. Before and immediately following exercise subjects performed a series of maximal voluntary contractions (MVCs) with the leg extensors (exercised muscles) and forearm flexors (non-exercised muscles). The degree of voluntary activation during the sustained MVCs was assessed by superimposing electrical stimulation to the femoral nerve and the biceps brachii. Exercise to exhaustion increased the rectal temperature from 37.2 ± 0.2 to 38.8 ± 0.2 °C (P < 0.0001). The mean heart rate at the end of exercise to exhaustion was 192 ± 3 beats min,1. Leg extensor voluntary force was significantly reduced from 595 ± 143 to 509 ± 105 N following exercise-induced hyperthermia but forearm flexor force was similar before and after exercise. The CAR of the leg extensors decreased from 94.2 ± 1.3% before exercise to 91.7 ± 1.5% (P < 0.02) following exercise-induced hyperthermia. However, the CAR for the forearm flexors remained at similar levels before and after exercise. The data suggest that the central nervous system selectively reduces central activation to specific skeletal muscles as a consequence of exercise-induced hyperthermia. [source] Horn size predicts physical performance in the beetle Euoniticellus intermedius (Coleoptera: Scarabaeidae)FUNCTIONAL ECOLOGY, Issue 4 2005S. P. LAILVAUX Summary 1In many animals, the size of secondary sexual ornaments is known to be related to the probability of victory in fights between males, and hence to fighting ability. However, few studies have attempted to link fighting ability to any physical performance measures. 2Here we show that horn size in the dung beetle Euoniticellus intermedius accurately predicts two types of whole-organism performance, independent of body size, that are likely to play an important role in male contests: the force required to pull a beetle out of a tunnel, and the distance the beetle was able to run before exhaustion (maximum exertion). 3Body length is also a statistically significant predictor of pulling force, but not of exertion, suggesting that horn size is a more reliable predictor of performance than body size alone, a result that is consistent with a previous finding that horn size becomes more important in determining victory in male,male contests as body size increases. 4This study is the first to establish direct links between whole-organism performance abilities, male armaments and fighting ability in the same species. Our findings suggest that physiological performance capacities are important factors underlying the evolution of signal expression in E. intermedius, and should be considered in future studies of the evolution of animal signalling. [source] Postradiation nasopharyngeal necrosis in the patients with nasopharyngeal carcinoma,HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 6 2009Yi-Jun Hua MD Abstract Background Radiation-induced nasopharyngeal necrosis is a consequential late effect in the patients with nasopharyngeal carcinoma (NPC). Patients with NPC who have been treated with high-dose radiotherapy are at risk of developing postradiation nasopharyngeal necrosis (PRNN). However, the analysis of PRNN with a significant cohort of patients has not been reported in English-language literature. In this study, we aimed to evaluate PRNN in 28 patients with NPC. Methods From June 2006 to December 2007, 28 patients were diagnosed with PRNN with pathologic evidence. Surgical procedure of endoscopy-guided debridement and systemic anti-inflammatory treatments were conducted for the patients. Their clinical features, treatment procedures, and outcomes were analyzed retrospectively. Results Clinical symptoms such as foul odor and headache were alleviated in all, 8 patients were cured of their PRNN, 9 patients with exposed internal carotid artery died of sudden nasopharyngeal massive bleeding, and 3 patients died of exhaustion (cachexia). Conclusion PRNN is an important consequential late effect of radiotherapy in the patients with NPC. Internal carotid artery erosion is a severe situation and acts as an independent prognostic factor for the patients. Diagnosis of PRNN could be made after ruling out the persistent-recurrent NPC proven by pathologic examination. Surgery is effective for improving the quality of life and for curing PRNN. © 2009 Wiley Periodicals, Inc. Head Neck, 2009 [source] Effectiveness of Supportive Educative Learning programme on the level of strain experienced by caregivers of stroke patients in ThailandHEALTH & SOCIAL CARE IN THE COMMUNITY, Issue 1 2010R. Oupra RN MSc MNS PhD Abstract In Thailand, the crude death rate from stroke is 10.9/100 000 population and increasing. Unlike Western countries where community rehabilitation programmes have been established to provide services following the acute stage of stroke recovery, there is no stroke rehabilitation team in the community in Thailand. Therefore, family caregivers are the primary source for ongoing care and support. While family members accompany patients during their hospitalisation, they receive little information about how to assist their relatives, and as a result feel inadequately trained, poorly informed and dissatisfied with the support that is available after discharge. Family caregivers report that they suffer both physically and psychologically and find themselves overwhelmed with strain, experiencing burden and exhaustion. This study aimed to develop and implement a nurse-led Supportive Educative Learning programme for family caregivers (SELF) of stroke survivors in Thailand and to evaluate the effect of the SELF programme on family caregiver's strain and quality of life. This was a non-randomised comparative study with concurrent controls, using a two-group pre-test and post-test design. A total of 140 stroke survivors and 140 family caregivers were recruited; 70 patients/caregiver pair in each group. Caregivers of patients admitted to the intervention hospital following an acute stroke received the intervention, while caregivers of patients admitted to the comparison hospital received the usual care provided at the hospital. The data were collected prior to discharge of the patients and after 3 months. The family caregivers in the intervention group had a significantly better quality of life than the comparison group (GHQ-28 at discharge t = 2.82, d.f. = 138, P = 0.006; and at 3 months t = 6.80, d.f. = 135, P < 0.001) and they also reported less strain (Caregiver Strain Index at discharge t = 6.73, d.f. = 138, P < 0.001; and at 3 months t = 7.67, d.f. = 135, P < 0.001). This research demonstrated that providing education and support to the family caregiver of stroke survivors can reduce caregiver strain and enhance their quality of life. [source] Quality of working life and turnover intention in information technology workHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2008Christian Korunka High turnover has been a major issue in information technology (IT) organizations. A conceptual model to explain turnover was developed and tested in two national samples of IT and IT manufacturing work. The model postulates that quality of working life mediates the relations between job/organizational characteristics and turnover intention. The American sample consisted of 624 IT employees of five IT organizations. The Austrian sample consisted of 677 employees from an international IT production company (IT manufacturing work). A similar questionnaire was used in both studies. The model was tested with path analysis. A core model with main pathways between job demands and supervisory support to emotional exhaustion, and between emotional exhaustion and job satisfaction to turnover intention was confirmed in the national samples and in subsamples of demographics and job types. © 2008 Wiley Periodicals, Inc. [source] HR practices perceptions, emotional exhaustion, and work outcomes: A conservation-of-resources theory in the Chinese contextHUMAN RESOURCE DEVELOPMENT QUARTERLY, Issue 1 2008Li-Yun Sun The conservation-of-resources theory provided the theoretical underpinning for the relationship among HR practices perceived by employees, emotional exhaustion, and work outcomes ( job satisfaction and job performance). To fully understand the underlying mechanism of the relationship, the study examined (1) the main and interactive effects of HR practices and employee age on emotional exhaustion and (2) the mediating effect of job satisfaction on the relationship between emotional exhaustion and job performance. Data were obtained from manufacturing workers in a privately owned company in the People's Republic of China. Empirical results lent strong support for the main, moderated, and mediated effects mentioned previously. However, contrary to our hypotheses the research result indicated that the relationship between low-commitment HR practices and emotional exhaustion was stronger for older employees than for younger ones. This contrasting finding demonstrated the criticality of an organization's commitment to employees, particularly to older employees, which further supported and enriched the conservation-of-resources theory in the Chinese context. [source] | ||||||||||||||||||||||||||||||||||