943 resultados para Heat stress management


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Workplace stress associated with ongoing processes of organizational change is a major occupational and public health concern. It is also a costly economic issue—both public and private. In this paper a framework will be used that draws on Michel Foucault’s genealogies of the Self to suggest that the management of stress by professionals—in a workplace environment increasingly characterized by the practices of risk management—emerges as a key element of the choices and responsibilities that frame what it means to be professional. To be (a) professional means to be a person capable of making choices and accepting responsibilities that are framed by a duty of care to manage one’s health and well-being to maximize organizational performance and effectiveness. The article will examine the ways in which transformations in the organization and practice of teachers’ work have witnessed large numbers of teachers being seen, and seeing themselves, as stressed. These understandings of teacher stress have provoked a number of strategies designed to encourage individuals to take care of themselves—and to take care of themselves in ways that will make schools more effective. The authors are concerned with understanding the processes that are at work which make it possible to imagine that it is a professional duty of care to manage one’s life in such a way as to be both balanced and effective in contexts of uncertainty and risk.

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In diverse arenas there is much discussion about the dangerousness of contemporary lifestyles, including the stressful nature of work. These stresses associated with contemporary lifestyles and work are dangerous in so far as they are conceived as placing at-risk the emotional, physical and psychic health and wellbeing of large populations. In this paper I engage with debates about the stressful nature of teachers’ work, and the ways in which teacher health and wellbeing is constructed as being central to the task of delivering more effective schools. I am not so much concerned with the nature of teacher stress as an indication of individual physical, emotional or psychic health and wellbeing. Rather I am more concerned with understanding how it is that at this particular historical juncture the self can be so widely conceived in terms of stress. Moreover, what processes make it possible at this moment to link the success or otherwise of a massive institutional process of state regulated schooling to the health and wellbeing of teachers and the management of this health and wellbeing by school managers?

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To identify the mechanism underlying the exaggerated hyperglycemia during exercise in the heat, six trained men were studied during 40 min of cycling exercise at a workload requiring 65% peak pulmonary oxygen uptake (V˙o 2 peak) on two occasions at least 1 wk apart. On one occasion, the ambient temperature was 20°C [control (Con)], whereas on the other, it was 40°C [high temperature (HT)]. Rates of glucose appearance and disappearance were measured by using a primed continuous infusion of [6,6-2H]glucose. No differences in oxygen uptake during exercise were observed between trials. After 40 min of exercise, heart rate, rectal temperature, respiratory exchange ratio, and plasma lactate were all higher in HT compared with Con (P < 0.05). Plasma glucose levels were similar at rest (Con, 4.54 ± 0.19 mmol/l; HT, 4.81 ± 0.19 mmol/l) but increased to a greater extent during exercise in HT (6.96 ± 0.16) compared with Con (5.45 ± 0.18;P < 0.05). This was the result of a higher glucose rate of appearance in HT during the last 30 min of exercise. In contrast, the glucose rate of disappearance and metabolic clearance rate were not different at any time point during exercise. Plasma catecholamines were higher after 10 and 40 min of exercise in HT compared with Con (P < 0.05), whereas plasma glucagon, cortisol, and growth hormone were higher in HT after 40 min. These results indicate that the hyperglycemia observed during exercise in the heat is caused by an increase in liver glucose output without any change in whole body glucose utilization.

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Previous research has established Internet-based cognitive behavioural therapy (CBT) for panic disorder (PD) as effective in reducing panic severity and frequency. There is evidence, however, that such programs are less effective at improving overall end-state functioning, defined by a PD clinician severity rating of ≤2 and panic free. In order to test the effect on end-state functioning of the incorporation of stress management material within a CBT program for PD, 32 people with PD were randomised to either Internet-based CBT (PO1), Internet-based CBT plus stress management (PO2) or an Internet-based information-only control condition (IC). Both CBT treatments were more effective at posttreatment assessment than the control condition in reducing PD severity, panic and agoraphobia-related cognition, negative affect and self-ratings of health. PO2 was more effective than PO1 at posttreatment assessment on PD severity and general anxiety, although at 3-month follow-up these differences were no longer apparent. This study provides further support for the efficacy of Internet-based CBT for PD and suggests that although the incorporation of stress management material confers short-term advantages over a standard program, it is not associated with any longer term improvements on panic severity and related cognitions, negative affect, general wellbeing and end-state functioning.

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The temperature at the Banc d'Arguin can be very high, and may cause problems of heat regulation in waders originating from the Arctic or Antarctic. A formalin-fixed bar-tailed godwit Limosa lapponica mount exposed to the sun had a temperature of 45°C. The temperature of the mount was higher when placed in a lying position than when it was placed upright. Nevertheless observed bar-tailed godwits, dunlins Calidris alpina and Kentish plovers Charadrius alexandrinus in the high water roost were often lying on the hot sand, and most birds avoided contact with humid (cold) substrates. Only the dunlins stood in the water with their bill tucked under the scapular wing feathers. This behavioral trait is thought to conserve heat, and is also observed in the other bird species in the roosts. Heat stress is apparently not a problem for birds awaiting low tide. -M.Dean

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Incubation temperature (IT) was changed to evaluate if 6-wk-old birds become more tolerant to heat stress. After 13 d of incubation, 470 eggs were submitted to low (36.8degreesC), normal (37.8degreesC) and high (38.8degreesC) temperatures. At day 7 post-hatching, 144 birds were allocated to three rearing temperatures (48 birds/treatment): control/thermoneutral (35-24degreesC), high (33-30degreesC) or low (27-18degreesC) according to the age of the birds. Hsp70 levels in tissues of birds (1 d and 42 d), stress response (42 d) and performance were evaluated. High IT decreased brain (P < 0.01) and liver (P < 0.01) Hsp70 levels, whereas low IT decreased brain (P < 0.01) but increased heart (P < 0.01) Hsp70 levels in 1-d-old chicks. Birds incubated at a low temperature had higher (P < 0.05) feed intake (1-42d). High rearing temperature decreased feed intake (P<0.01) and liveweight (P<0.01). Colonic temperature was lower in birds incubated at a low temperature (P < 0.05) and higher in birds reared in a high temperature (P < 0.05) before heat stress. Birds reared in low temperature had higher increase in colonic temperature after heat stress (P < 0.05). Tissue Hsp70 levels were differently affected by rearing temperature, which affected broiler performance more than IT. Lower IT seemed to increase the sensitivity of birds to heat stress at market age.

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Hsp70 content (ng Hsp70 mu g total protein(-1)) in the liver and brain of control and adrenalectomized male rats was investigated by Western Blotting after heat stress (40 degrees C) or endotoxin-induced fever (E. coli lipopolysaccharide injection). The increase in rectal temperature was higher after heat stress than after LPS injection, Heat stress affected Hsp70 content of the liver, but not of the brain; however adrenalectomy did not influence any parameter. These results suggest that, under these circumstances, there is no relationship between the hypothalamic-pituitary-adrenal axis and Hsp70 synthesis in liver and brain. (C) 2000 Elsevier B.V. Ltd. All rights reserved.

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Stress response is a universal mechanism developed by all organisms to deal with adverse changes in the environment, which lead to the synthesis of heat shock proteins (Hsps). In this study, the effect of moderate (41degreesC) and severe (44degreesC) heat stress on Hsp70 transcript expression pattern was investigated during chicken embryogenesis. Acute exposure to severe heat stress for one hour resulted in a fifteen-fold increase in Hsp70 mRNA levels. The return of stressed embryos to normal incubation temperature resulted in Hsp70 mRNA levels five-fold higher than control after three hours and normal levels after six hours. Moderate heat stress did not induce enhancements on Hsp70 mRNA levels. The spatial expression of Hsp70 transcripts was detected in embryos under normal incubation conditions. Whole-mount in situ hybridization analysis showed that Hsp70 transcripts were constitutively present in somite and in distinct encephalic domains (predominantly in prosencephalon and mesencephalon areas) of the chicken embryo. These results showed that Hsp70 induction is dependent on incubation temperature conditions, suggesting that early chicken embryos may induce a quick emergence response to cope with severe heat stress by increasing Hsp70 mRNA levels.

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In order to evaluate the effects of broiler genotype and of heat exposure on performance, carcass characteristics, and protein and fat accretion, six hundred one-day-old male broilers were randomly assigned in a 2 x 3 factorial arrangement, according to the following factors: genetic group (selected and non-selected broilers) and pair-feeding scheme (Ad(32) - reared under heat stress and fed ad libitum; Ad(23) - reared at thermoneutrality and fed ad libitum; Pf(23) - reared at thermoneutrality and pair fed with Ad(32)), with a total of six treatments with four replicates of 25 birds each. Independent of pair-feeding scheme, selected broilers showed better feed conversion, higher carcass yield, and lower abdominal fat deposition rate. However, as compared to non-selected broilers, they reduced more intensively feed intake when heat exposed, which promoted significant breast-yield decrease, and more pronounced changes on carcass chemical composition. These findings allows concluding that, in both genetic groups, both environmental temperature and feed-intake restriction influence abdominal fat deposition rate and other carcass characteristics; however, the impact of heat exposure on broiler performance is more noticeable on the selected line.

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The aspects involved in broiler water intake are not well known, despite the importance of water in animal nutrition and physiology. Water intake behavior should be taken into account when deciding on different types of drinkers. Bell and nipple drinkers are the most commonly used in commercial broiler production. Broilers were housed in cages equipped with two different drinker types and raised at two different environmental temperatures (25 and 34 ºC) to evaluate water intake behavior and volume. Broiler water intake behavior was influenced by drinker type. Birds visited bell drinkers less often, but presented higher total water intake per visit to the drinker as compared to those drinking from nipple drinkers. The results of this study suggest that both broilers drinking behavior and water intake volume should be taken into account when deciding on drinker type to equip broiler houses.

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Nutrition for broilers under high temperatures is extremely important for brazilian broiler chicken industry because the amounts of consumed nutrients and environmental temperature have great effects on bird performance and carcass quality. Among diet nutrients, protein has the highest heat increment; thus, during many years, diets with low protein level were recommended in order to reduce heat production in broiler chickens under heat stress. However, reports have shown that low-protein diets have negative effects on broiler performance when environmental temperature is high, because during heat stress, low food intake associated to a low diet protein induce amino acid deficiencies. Other studies have shown that broilers fed low-protein diets increase their energy requirement for maintenance with higher heat production. Thus, with the growth of broiler industry in tropical areas more challenges need to be faced by the farmers. So, both the ambient and nutritional conditions ought to be well managed to avoid negative effects on poultry production once they can affect the metabolism (body heat production under low temperature and body heat dissipation under high temperature) with consequence on poultry performance (meat and eggs).

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In the present study we have investigated the effects of heat acclimation on brain and hepatic Hsp70 protein levels and body temperature of broiler chickens in response to gradual heat stress. Two groups of broilers were raised up to 47 days of age under distinct temperature conditions: thermoneutral (TN, according to bird age) or hot environmental (HS, 31-33°C). At 46 days of age, the birds reared at high ambient temperature were transferred to thermoneutrality conditions. After 18 h, these birds and the birds reared at thermoneutral temperature were submitted to gradual heat stress in a climatic chamber so that environment temperature was increased from 28 to 40ºC at a rate of 2ºC/h. Colonic temperature was measured using a thermometer sensor probe at each two hours, and hepatic and brain tissues were collected immediately after slaughter in order to assess Hsp70 protein level by Western blotting analysis. The colonic temperatures of birds reared at high temperature increased steeply during the first 2 h of heat stress (1.06ºC/h) and more slowly thereafter (0.59ºC/h). Broilers reared at thermoneutral temperature showed a small increase in the first 4 h of heat stress (0.18ºC/h) and then colonic temperature increased sharply (0.72ºC/h). Nevertheless, both groups presented similar final colonic temperature by the end of the stress period. Hsp70 levels (ng Hsp70 µg total protein-1) did not change in the liver or brain of the birds reared at high temperature. on the other hand, both liver and brain Hsp70 levels increased significantly during heat stress in the animals reared at thermoneutrality, with a higher expression of this peptide in brain tissue.

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Heat stress has negative effects on pregnancy rates of lactating dairy cattle. There are genetic differences in tolerance to heat stress; Bos taurus indicus (B. t. indicus) cattle and embryos are more thermotolerant than Bos taurus taurus (B. t. taurus). In the present study, the effects of sire and sire breed on conception and embryonic/fetal loss rates of lactating Holstein cows during the Brazilian summer were determined. In Experiment 1, cows (n = 302) were AI after estrus detection or at a fixed-time with semen from one Gyr (B. t. indicus) or one Holstein sire (B. t. taurus). Pregnancy was diagnosed 80 days after AI. In Experiment 2, cows (n = 811) were AI with semen from three Gyr and two Holstein sires. Pregnancy was diagnosed at 30-40 and at 60-80 days after AI. Cows diagnosed pregnant at the first examination but non-pregnant at the second were considered as having lost their embryo or fetus. Data were analyzed by logistic regression. The model considered the effect of sire within breed, sire breed, days postpartum, period of lactation, and AI type (AI after estrus versus fixed-time). There was no effect of the AI type, days postpartum or milk production on conception or embryonic loss rates. The use of Gyr bulls increased pregnancy rate when compared to Holstein bulls [9.1% (60/657) versus 5.0% (23/456), respectively, P = 0.008; data from Experiments 1 and 2 combined]. Additionally, in Experiment 2, cows inseminated using semen from sire #4 (Gyr) had lower embryonic loss (10%) when compared with other B. t. indicus (35.3% and 40%) or B. t. taurus sires (18.2% and 38.5%, P = 0.03). In conclusion, the use of B. t. indicus sires may result in higher conception rates in lactating Holstein cows during summer heat stress. Moreover, sire can affect embryonic loss and selection of bulls according to this criterion may result in higher parturition rates in lactating Holstein cows. (c) 2006 Elsevier B.V. All rights reserved.