Letteratura scientifica selezionata sul tema "Heat Physiological effect"
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Articoli di riviste sul tema "Heat Physiological effect"
1
Gurney, Shae C., Katherine S. Christison, Tyler Stenersen e Charles L. Dumke. "Effect of uncompensable heat from the wildland firefighter helmet". International Journal of Wildland Fire 30, n. 12 (2021): 990. http://dx.doi.org/10.1071/wf20181.
Testo completoAbstract (sommario):
Heat accumulation from wearing personal protective equipment can result in the development of heat-related illnesses. This study aimed to investigate factors of heat stress with and without a US standard issue wildland firefighter helmet. Ten male subjects finished a 90-min exercise protocol in a heat chamber (35°C and 30% relative humidity), with standard issue meta-aramid shirt and pants and a cotton t-shirt, and either with or without a wildland firefighter helmet. A randomised crossover design was implemented, with a minimum 2-week washout period. Heart rate, physiologic strain index, perceived head heat, head heat and skin blood flow of the head and neck were measured. At the conclusion of the 90-min trial, heart rate, physiological strain index, core temperature, rating of perceived exertion and perceived head heat showed a main effect of time (P < 0.05). Perceived head heat and head heat exhibited a main effect of trial (P < 0.05). The change in physiologic strain was positively correlated with the change in skin blood flow of the head (r = 0.72, P = 0.02). These data suggest that the current wildland firefighter helmet contributes to heat accumulation. The design of the wildland firefighter helmet lacks ventilation, which, from these data, may result in metabolic alterations and perceived discomfort.
2
Jumnake, Aishvarya R., Vishwambhar R.Patodkar, Vikas M.Sardar, Prajwalini V.Mehere, Sameer N.Jadhav e Sachin S. Pawar. "Effect of Heat Stress on Physiological Parameters in Madgyal Sheep". UTTAR PRADESH JOURNAL OF ZOOLOGY 45, n. 14 (27 giugno 2024): 164–69. http://dx.doi.org/10.56557/upjoz/2024/v45i144190.
Testo completoAbstract (sommario):
The current study was carried out to assess the impact of heat stress on physiological parameters in Madgyal Sheep. To investigate this, sheep were exposed to 0,4 and 8 hrs heat of direct sunlight during grazing in 3 different Groups Viz A, B and C. The study was conducted on Day 0, Day 15 and Day 30 of the experiment to observe the effect of different duration of heat exposure on all physiological parameters. The temperature humidity index (THI) values duting the experimental period were found to be (76.28+-0.81) The results of the statistical analysis showed that there was no significant difference group wise and day wise in the Rectal temperature. However, the Respiration Rate, Pulse Rate and Heart Rate in Group wise comparison showed a significant difference (P<0.05) with increasing trend. In Day wise comparison of Respiratory Rate there was no significant difference at different days in Group A & B. However, there was a significance difference (P<0.05) in group C at different days with increasing trend. Pulse Rate and Heart rate Day wise comparison showed no significant difference at different days in Group A and C while there was a significant difference at different days in Group B with higher values at Day 15 and Day 30 as compared to at Day 0.
3
Wojtas, Krzysztof, Przemysław Cwynar e Roman Kołacz. "Effect of thermal stress on physiological and blood parameters in merino sheep". Bulletin of the Veterinary Institute in Pulawy 58, n. 2 (1 giugno 2014): 283–88. http://dx.doi.org/10.2478/bvip-2014-0043.
Testo completoAbstract (sommario):
Abstract Fifteen sheep where placed in climatic chamber and exposed to a high temperature (30°C). Then, the air movement was induced in order to examine its soothing effect on heat stress. The physiological reactions like respiratory and heart rates, as well as the morphologic, biochemical parameters and cortisol levels in blood were examined. It was found that under heat stress conditions, the respiratory rate increased up to 96.43 breaths/min, heart rate up to 107.79 beats/min, and white blood cells count decreased to 9.12 k/μL. The increased level of potassium, chlorine, and calcium was also observed. The increased air movement resulted in thermal stress soothing. A decrease in respiratory rate, heart rate, and cortisol concentration was observed. The study demonstrated that heat stress leads to serious changes in physiological and blood parameters in sheep but this effect can be minimised by air movement.
4
The, Enos, M. Jen Wajo e M. A. Muin. "Respon fisiologis dan hematologis Kambing peranakan Etawah terhadap cekaman panas". Cassowary 1, n. 1 (6 gennaio 2018): 63–74. http://dx.doi.org/10.30862/casssowary.cs.v1.i1.6.
Testo completoAbstract (sommario):
PE goat is a small ruminant crossed between Etawah goat and bean goat, which introduced in Manokwari since 2007. Livestock can well produce depend on environment comfortable temperature in the area of tropical temperature on the day is radiated in high sun light. If the goat is expose to the blazing sun, it supposed experiencing heat stress and caused to the physiological and haematological condition. The aim of this study is to know the physiological and haematological response of PE goat to heat stress. This design of research used is Split Plot (RPT). 8 goats will be a sample which devide in two groups, of unexposed groups and Groups exposed to sunlight. Each group consists of young males, young female, adult male, adult female. The variables observed included physiological aspects (heart rate, rectal temperature, respiratory rate) and haematological aspects (hemoglobin level, hematocrit value, erythrocyte count, leukocyte count). The results showed that interaction between goats and heat stress status did not influence physiological aspect variable (heart rate, rectal temperature, respiratory rate), but very significant effect on some hematological aspect variable such as hemoglobin and erythrocytes. The status of livestock has a very significant effect on some physiological aspect variable such as rectal temperature, respiratory rate) and hematological aspect variable ie hemoglobin, hematocrit and erythrocytesTreatment of heat stress has a very significant effect on the physiological aspects of variables such as heart rate, rectal temperature and respiration whereas on hematologic aspect variable have significant effect on hemoglobin level, very significant effect on hematocrit value and erythrocyte level.
5
Morito, Akihisa, Takayuki Inami, Akihiro Hirata, Satoshi Yamada, Masatsugu Shimomasuda, Keita Kato, Shigeyuki Tahara e Naohiko Kohtake. "Effect of Ice Slurry Ingestion on Post-Exercise Physiological Responses in Rugby Union Players". Physiologia 2, n. 4 (5 novembre 2022): 154–63. http://dx.doi.org/10.3390/physiologia2040013.
Testo completoAbstract (sommario):
Delayed recovery of the core body temperature after exercise adversely affects physiological functions, and the effects of ingesting lower-temperature ice slurry on post-exercise recovery remain unclear. We investigated the effects of ingesting −2 °C ice slurry on physiological recovery after field-based rugby union training. Fifteen university rugby union players participated in our randomized controlled study. The players participated in the training for 60 min in a hot outdoor environment (wet-bulb globe temperature, 30.5 °C). Physiological responses were measured during a physical performance test performed after the players ingested either −2 °C-ice slurry (ICE, N = 7) at 5 g/kg body mass or a 30 °C-fluid (CON, N = 8) during the 15 min recovery period after the training. Tympanic temperatures and heart rates were measured as the physiological indices, as well as heat storage. The ICE group showed significantly decreased tympanic temperatures and heart rates (p < 0.05) during the recovery period and increased heat storage (p < 0.05) but did not show improvement of physiological indices during the performance test compared to the CON group. These results suggest that ingestion of −2 °C ice slurry in even lower amounts than those previously reported is useful for physiological recovery after training in hot outdoor environments.
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Amézaga González, María Fernanda, Jazzely Acosta Bezada, Víctor Gómez Flores, Christian Chapa González, Jose Rurik Farias Mancilla, S. J. Castillo, Carlos Avila Orta e Perla E. García-Casillas. "Effect of Physiological Fluid on the Photothermal Properties of Gold Nanostructured". International Journal of Molecular Sciences 24, n. 9 (6 maggio 2023): 8339. http://dx.doi.org/10.3390/ijms24098339.
Testo completoAbstract (sommario):
Colloidal gold particles have been extensively studied for their potential in hyperthermia treatment due to their ability to become excited in the presence of an external laser. However, their light-to-heat efficiency is affected by the physiologic environment. In this study, we aimed to evaluate the ability of gold sphere, rod, and star-shaped colloids to elevate the temperature of blood plasma and breast cancer-simulated fluid under laser stimulation. Additionally, the dependence of optical properties and colloid stability of gold nanostructures with physiological medium, particle shape, and coating was determined. The light-to-heat efficiency of the gold particle is shape-dependent. The light-to-heat conversion efficiency of a star-shaped colloid is 36% higher than that of sphere-shaped colloids. However, the raised temperature of the surrounding medium is the lowest in the star-shaped colloid. When gold nanostructures are exited with a laser stimulation in a physiological fluid, the ions/cations attach to the surface of the gold particles, resulting in colloidal instability, which limits electron oscillation and diminishes the energy generated by the plasmonic excitation. Fluorescein (Fl) and polyethylene glycol (PEG) attached to gold spheres enhances their colloidal stability and light-to-heat efficiency; post-treatment, they remand their optical properties.
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Bröde, Peter, e Bernhard Kampmann. "Temperature–Humidity-Dependent Wind Effects on Physiological Heat Strain of Moderately Exercising Individuals Reproduced by the Universal Thermal Climate Index (UTCI)". Biology 12, n. 6 (31 maggio 2023): 802. http://dx.doi.org/10.3390/biology12060802.
Testo completoAbstract (sommario):
Increasing wind speed alleviates physiological heat strain; however, health policies have advised against using ventilators or fans under heat wave conditions with air temperatures above the typical skin temperature of 35 °C. Recent research, mostly with sedentary participants, suggests mitigating the effects of wind at even higher temperatures, depending on the humidity level. Our study aimed at exploring and quantifying whether such results are transferable to moderate exercise levels, and whether the Universal Thermal Climate Index (UTCI) reproduces those effects. We measured heart rates, core and skin temperatures, and sweat rates in 198 laboratory experiments completed by five young, semi-nude, heat-acclimated, moderately exercising males walking the treadmill at 4 km/h on the level for three hours under widely varying temperature–humidity combinations and two wind conditions. We quantified the cooling effect of increasing the wind speed from 0.3 to 2 m/s by fitting generalized additive models predicting the physiological heat stress responses depending on ambient temperature, humidity, and wind speed. We then compared the observed wind effects to the assessment performed by the UTCI. Increasing the wind speed lowered the physiological heat strain for air temperatures below 35 °C, but also for higher temperatures with humidity levels above 2 kPa water vapor pressure concerning heart rate and core temperature, and 3 kPa concerning skin temperature and sweat rate, respectively. The UTCI assessment of wind effects correlated positively with the observed changes in physiological responses, showing the closest agreement (r = 0.9) for skin temperature and sweat rate, where wind is known for elevating the relevant convective and evaporative heat transfer. These results demonstrate the potential of the UTCI for adequately assessing sustainable strategies for heat stress mitigation involving fans or ventilators, depending on temperature and humidity, for moderately exercising individuals.
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M.C., Narendra, Chandan Roy, Sudhir Kumar, Parminder Virk e Nitish De. "Effect of terminal heat stress on physiological traits, grain zinc and iron content in wheat (Triticum aestivum L.)". Czech Journal of Genetics and Plant Breeding 57, No. 2 (9 aprile 2021): 43–50. http://dx.doi.org/10.17221/63/2020-cjgpb.
Testo completoAbstract (sommario):
Heat stress is one of the major wheat (Triticum aestivum) production constraints in South Asia (SA), particularly in the Eastern Gangetic Plains (EGP) of India and Bangladesh. Malnutrition is also a severe problem among children and women in SA. Wheat varieties with high grain Zn/Fe are a sustainable, cost-effective solution in the fight against hidden hunger. Thirty wheat genotypes were characterised under the optimum temperature and heat stress conditions in 2016–2017 and 2017–2018 to study the response of the stress on the yield, physiological traits and grain Zn/Fe content. A significant genetic variation was observed for all the traits under the optimum temperature and stress conditions. The yield was reduced by an average of 59.5% under heat stress compared to that of the optimum temperature. A strong positive association of the canopy temperature depression (CTD) with the grain yield (GY) was observed under the heat stress. A negative correlation of the grain Zn/Fe with the yield was observed under the optimum temperature and heat stress conditions, while the association between the grain Zn and Fe was positive. The genotypes BRW 3723, BRW 3759, BRW 3797, BRW 160, HD 2967, HD 2640 were found to be heat-tolerant in both years. Among the tolerant genotypes, BRW 934, BRW 3807 and BRW 3804 showed a high zinc content and BRW 934, BRW 3797, BRW 3788 and BRW 3807 showed a high iron content, respectively. These genotypes can be explored in future breeding programmes to address the problem of nutritional deficiency.
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Ioannou, Leonidas G., Konstantinos Mantzios, Lydia Tsoutsoubi, Zoe Panagiotaki, Areti K. Kapnia, Ursa Ciuha, Lars Nybo, Andreas D. Flouris e Igor B. Mekjavic. "Effect of a Simulated Heat Wave on Physiological Strain and Labour Productivity". International Journal of Environmental Research and Public Health 18, n. 6 (15 marzo 2021): 3011. http://dx.doi.org/10.3390/ijerph18063011.
Testo completoAbstract (sommario):
Background: The aim of the study was to investigate the effect of a simulated heat-wave on the labour productivity and physiological strain experienced by workers. Methods: Seven males were confined for ten days in controlled ambient conditions. A familiarisation day was followed by three (pre, during, and post-heat-wave) 3-day periods. During each day volunteers participated in a simulated work-shift incorporating two physical activity sessions each followed by a session of assembly line task. Conditions were hot (work: 35.4 °C; rest: 26.3 °C) during, and temperate (work: 25.4 °C; rest: 22.3 °C) pre and post the simulated heat-wave. Physiological, biological, behavioural, and subjective data were collected throughout the study. Results: The simulated heat-wave undermined human capacity for work by increasing the number of mistakes committed, time spent on unplanned breaks, and the physiological strain experienced by the participants. Early adaptations were able to mitigate the observed implications on the second and third days of the heat-wave, as well as impacting positively on the post-heat-wave period. Conclusions: Here, we show for first time that a controlled simulated heat-wave increases workers’ physiological strain and reduces labour productivity on the first day, but it promotes adaptations mitigating the observed implications during the subsequent days.
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Qisthon, Arif, e Yusuf Widodo. "PENGARUH PENINGKATAN RASIO KONSENTRAT DALAM RANSUM KAMBING PERANAKAN ETTAWAH DI LINGKUNGAN PANAS ALAMI TERHADAP KONSUMSI RANSUM, RESPONS FISIOLOGIS, DAN PERTUMBUHAN". ZOOTEC 35, n. 2 (18 agosto 2015): 351. http://dx.doi.org/10.35792/zot.35.2.2015.9275.
Testo completoAbstract (sommario):
ABSTRACT EFFECTS OF INCREASING CONCENTRATE RATIO IN THE RATION OF PERANAKAN ETTAWAH GOAT UNDER NATURAL HEAT ENVIRONMENT ON FEED INTAKE, PHYSIOLOGICAL RESPONSES, AND GROWTH. The research was conducted to study the effect of increasing the proportion of concentrate in the ration of Peranakan Ettawah (PE) goats. Animals were maintained in a natural hot environment on feed consumption, physiological responses, and body weight gain. The study used three male goats of PE in Latin Square design. Treatment applied was an increase in the proportion of concentrate in three forage-concentrate ratio (F:C), R1 = 85:15%; R2 = 70:30%; and R3 = 55:45%. The results showed that the treatment ratio of F:C had no effect (P> 0.05) in feed intake, respiration rate, rectal temperature, and body weight gain. In contrast, treatment affected significantly (P <0.05) heart rate, as follows R1 vs. R2 and R1 vs. R3, whereas R2 and R3 were not significantly different (P> 0.05). Keywords: Rations, heat stress, physiological, goat
Tesi sul tema "Heat Physiological effect"
1
Martin, David E. "The effect of heat stress on excess post exercise oxygen consumption". Virtual Press, 1992. http://liblink.bsu.edu/uhtbin/catkey/834623.
Testo completoAbstract (sommario):
While a great deal of research has been directed towards the phenomena of excess post exercise oxygen consumption (EPOC), the effect of thermal stress on EPOC is not well defined. To assess the effect of heat stress on EPOC, seven healthy, active subjects (4 female, 3 male; 23.9 ± 2.0 years of age) performed 4 trials: one control (quiet rest) and one exercise (45 minutes of cycling at 65% VO2max workload) trial in moderate (23° C, 50% humidity) and hot (35° C, 50% humidity) environments. Oxygen consumption (V02), heart rate (HR) and rectal temperature (RT) were assessed pre, during and post control or exercise. Subjects were monitored until post exercise VO2 had returned to within ±2% of baseline. EPOC was determined by subtracting baseline VO2 from total V02 during the post exercise period. During the first 15 minutes (acute) post exercise, a significant EPOC (p = 0.0019) was seen in both exercise conditions over both control conditions. During the slow phase (> 15 minutes post exercise to baseline), there was no significant difference between the hot control (HC), moderate exercise (ME), or hot exercise (HE) EPOC. Total time post exercise until baseline was achieved was 35, 44, and 51 minutes for HC, ME, and HE respectively. HR was significantly elevated in both exercise conditions. During the acute post exercise period, HR in HE was elevated above MC, ME and HC (p < 0.05). RT was elevated in both exercise conditions during and post exercise. The present data indicate that heat stress does not have a significant effect on the magnitude or duration of EPOC.School of Physical Education
2
Houmard, Joseph A. "Rate of heat acclimation : effects of exercise intensity and duration". Virtual Press, 1988. http://liblink.bsu.edu/uhtbin/catkey/533882.
Testo completo
3
Hogan, Kyla B. "The hemostatic responses to exercise in hot and cold temperatures". Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1398717.
Testo completoAbstract (sommario):
Purpose: The impact of temperature on the coagulative response to exercise has not been well described. The purpose of this study was to assess the response of plasma thrombin-antithrombin (TAT) to exercise during exposure to both hot and cold temperatures, and to compare those responses to exercise under normal, temperate conditions. Methods: Fifteen healthy male subjects (25.3 + 4.3 years) volunteered to participate in this study. Subjects completed maximal cycle ergometer exercise tests in three different temperatures (20°C, 5° or 8° C, and 30°C) in an environmental chamber. All tests were conducted in random order and separated by at least seven days. Blood samples were obtained before and immediately after exercise and analyzed by Elisa to determine plasma concentrations of thrombin-antithrombin complex (TAT). Results: Subjects demonstrated significantly elevated plasma levels of TAT in all three temperatures immediately after exercise (normal =1.04 ± 0.44 ng/ml, cold =1.34 ± 0.79 ng/ml, hot =1.18 + 0.95 ng/ml) when compared to baseline measures (normal = 0.45 ± 0.26 ng/ml, cold = 0.88 + 0.57 ng/ml, hot = 0.64 + g/ml). Subjects also showed significant elevations in TAT concentrations both before and after exercise in the cold temperature when compared with the normal temperature. There was no significant difference between the hot and normal temperatures. Conclusion: An individual's coagulation potential is increased following maximal physical exertion and may be further increased by exposure to colder temperature. Key Words: coagulation, physical exertion, temperature, thrombosis.School of Physical Education, Sport, and Exercise Science
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Davis, Jacqueline A. "The hypertensive response to repeated days of heat-exercise exposure". Virtual Press, 1989. http://liblink.bsu.edu/uhtbin/catkey/562777.
Testo completoAbstract (sommario):
The physiological responses of hypertensive subjects to a single bout of exercise in a hot environment have been investigated. It was the purpose of this study to compare the effect of successive days of exercise in the heat on borderline hypertensive and normotensive individuals, with particular interest being paid to the positive relationship that exists between plasma volume and blood pressure. Eight hypertensive subjects (HT) and 8 normotensive controls (NT) performed a standardized work task, (walking for 60 minutes at 3.5 mph on a 5% grade), in dry heat, (40C, 257. RH), on 7 successive days. Working capacity and acclimatization were compared during two, 90 minute heat tolerance tests (HTT), one prior to, and the other following the acclimation period.Both groups demonstrated a similar degree of heat acclimation, as reflected in significantly lower HTT2 core temperatures, (P< 0.05), and heart rates, (p< 0.01). Plasma volume expansion over the 9 days was also equal for both groups (+77.), but appeared to have no effect on their resting or exercising blood pressures. No differences were observed in the ability of either group to complete the work task, although the HT group exercised at a significantly higher percentage of their maximal oxygen uptake, (p< 0.05), than the NTs.These results indicate that no abbreviation in working capacity is experienced by borderline HT'% during exercise in the heat as a consequence of their high blood pressure. The anticipated elevation in blood pressure as a result of an expansion i n plasma volume did not occur. Consequently, these individuals show the same positive acclimation to exercise in the heat as their NT counterparts.School of Physical Education
5
Kerr, Chadwick G. "Hypothermia during Olympic triathlon : influence of body heat storage during the swimming stage". Virtual Press, 1996. http://liblink.bsu.edu/uhtbin/catkey/1014852.
Testo completoAbstract (sommario):
The purpose of this study was to determine if mild heat stress induced by wearing a wet suit while swimming in relatively warm water (25.4 ± 0.1°C) increases the risk of heat injury during the subsequent cycling and running stages. Specificlly, during an Olympic distance triathlon in a hot and humid environment (32°C & 65% RH). Five male triathletes randomly completed two simulated triathlons (Swim=30 min; Bike=40 km; Run=10 km) in the laboratory using a swimming flume, cycle ergometer, and running treadmill. In both trials, all conditions were identical, except for the swimming portion in which a full length, sleeveless neoprene wet suit was worn during one trial (WS) and a competitive brief swimming suit during the other (SS). The swim portion consisted of a 30 min standardized swim in which oxygen consumption (V02) was replicated, regardless of WS or SS. During the cycling and running stages, however, the subjects were asked to complete the distances as fast as possible. Core Temperature (T) was not significantly different between the SS and WS trials at any time point during the triathlon. However, mean skin temperature (TSk) and mean body temperature (Tb) were higher (p<0.05) in the WS at 15 (TSk=+4.1°C, Tb=+1.5°C) and 30 min (TSk=+4°C, Tb=+1.6°C) of the swim. These TSk and Tb differences were eliminated by 15 min of the cycling stage and remained similar (p>0.05) through the end of the triathlon. Moreover, there were no differences (p>0.05) in V02, heart rate (HR), rating of perceived exertion (RPE), or thermal sensation (TS) between the WS and SS. Additionally, no significant differences were found in cycling (SS=1:14:46 ± 2:48 vs. WS=1:14:37 ± 2:54 min), running (SS=55:40 ± 1:49 vs. WS=57:20 ± 4:00 min) or total triathlon times (SS=2:40:26 ± 1:58 vs. WS=2:41:57 ± 1:37 min). Therefore, the primary finding was that wearing a wet suit during the swimming stage of an Olympic distance triathlon in 25.4°C water does not adversely affect the thermal responses or the triathlete's ability to perform on the subsequent cycling and running stages.School of Physical Education
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Arjona, Anibal Augusto. "Molecular responses of neonatally heat stressed broilers exposed to acute heat stress". Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39965.
Testo completoAbstract (sommario):
Exposure of broiler cockerels to between 35.0 to 37.8 C for 24 hr at 5 days of age increases their survival when exposed to a heat challenge at 6 weeks of age (35.0-37.8 C; RH 50% ). This' phenomenon does not resemble acclimation since the physiological changes known to occur in acclimated birds exposed to heat have not been observed in the neonatally stressed birds. A series of experiments were conducted to elucidate the mechanisms of neonatally induced thermotolerance. In Experiment 1, the erythrocyte protein profile of control and 5 days heated birds prior to and during exposure to acute heat were determined. Prior to juvenile heat exposure no differences in the erythrocytic protein profile of neonatally stressed and control birds were observed at any age (10, 17, 24, 31 and 38 days of age) when maintained under control conditions. However, upon exposure to an acute heat challenge (40.5 C; 52 days of age) temporal and differential expressions of proteins similar in molecular weight to heat shock proteins (HSPs) were observed between the neonatally stressed and control birds. In Experiment 2, the effects of neonatal heat stress at various ages (5, 8, 12, 16 days of age) on the protein synthesis profile of heart, brain (telencephalon, diencephalon, brain stem, cerebellum) and liver tissues during exposure to an acute heat challenge were studied. In addition, body temperature during neonatal heat exposure was monitored. A significant increase in body temperature was observed during neonatal heat stress. A steady increase in the magnitude of the temperature change was noticed up to 12 days of age. Body temperature of birds exposed to neonatal heat at 16 days of age was similar to that of birds heated at 5 days of age.Ph. D.
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Heyns, Gerhardus Johannes. "Influence of macro- versus microcooling on the physiological and psychological performance of the human operator". Thesis, Rhodes University, 1995. http://hdl.handle.net/10962/d1016247.
Testo completoAbstract (sommario):
This study evaluated the effect of a macro- versus a microcooling system on the cognitive, psychomotor and physiological performance of human operators. Male subjects (n = 24) were acclimatized for four days and then subjected to three different environmental conditions: hot ambient (40°C; 40% RH), microcooling and macrocooling. Each environmental condition was repeated twice; once under a rest condition and once while simulating a physical workload of 40 W. Four performance tests (reasoning, eye-hand coordination, memory, reaction time) were conducted once every hour for four hours. Five physiological measurements, viz rectal temperature, skin temperature, heart rate, total sweat loss and sweat rate, were taken. A significant difference existed between the physiological responses under the hot ambient condition and both cooling conditions. For all five physiological parameters he human operator benefitted substantially whatever the cooling condition. The psychological performance results indicated a greater benefit under the cooling conditions, though various external factors may have influenced responses. User perception showed that macrocooling was perceived to be the optimal method of cooling. The results showed that there was no difference in the extent to which both rectal temperature and heart rate (for rest and work conditions) decreased over the 4-hour study period with micro- and macrocooling. In the baseline hot environment both increase. Sweat rate was lowest when resting or working in a microcooled environment and at its highest in the hot baseline environment. Mean skin temperature was lowest (for rest and work conditions) with microcooling and highest in the hot baseline environment. Reaction time and memory/attention were the same under all three environmental conditions. Eye-hand coordination was better with cooling than without, but did not differ between the two cooling conditions. Reasoning ability was poorest under the hot baseline condition and best in the macrocooled environment. User perception showed that the subjects found macrocooling highly acceptable. Microcooling was found to be uncomfortable, particularly because cold air (18 - 21°C) entered the jacket at one point which caused numbness of the skin at that point. Jackets did not always fit subjects well and the umbilical cord restricted free movement.
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WIDELITZ, RANDALL BRUCE. "HEAT SHOCK PROTEIN SYNTHESIS AND THERMOTOLERANCE EXPRESSION IN RAT EMBRYONIC FIBROBLASTS (HYPERTHERMIA, GENE REGULATION)". Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183851.
Testo completoAbstract (sommario):
In response to a variety of hyperthermic treatments, rat embryonic fibroblasts synthesize heat shock proteins (hsps), including those with molecular weights of 68,000 (hsp 68), 70,000 (hsp 70) and 89,000 (hsp 89). Hyperthermic stresses, which produce the hsps, also cause expression of thermotolerance. The dependence of thermotolerance expression on hsp synthesis was investigated in this mammalian cell line under different heating conditions. Temperature shift experiments showed that hsp synthesis and thermotolerance expression were dependent not only on the absolute hyperthermic temperature, but also on the difference between the initial incubation temperature and the hyperthermic temperature. Small temperature differences which produced no cell killing did not cause detectable synthesis of hsp 68. Increasing the difference of the initial and hyperthermic temperatures reduced cell survival and increased the synthesis of hsp 68. Thermotolerance could be expressed by surviving cells following an initial heat stress even when both heat shock and general protein synthesis were inhibited. Cells exposed to cycloheximide were heated, incubated at their initial temperature for six hours and reheated in the presence of the drug. The inhibitor was then removed and the cells plated for colony formation. The hsps were expressed during this latter incubation period. The regulation of hsp 70 in rat fibroblasts was investigated next. Hsp 70 synthesis rates correlated with the amount of hsp 70 encoding mRNA. The time course of heat shock synthesis and general protein synthesis recovery were each dependent on the duration of the heat stress. Inhibiting protein synthesis with cycloheximide resulted initially in the accumulation of the RNA encoding hsp 70 but did not effect the normal turnover of this RNA species. The conclusions based on these findings are that thermal survival adaptation can be expressed in the absence of hsp 68 synthesis. Hsp 68 is expressed by cells that will ultimately die (see Chapter 2). The hsps do not appear to protect cells against subsequent heat stress. They may function in a repair capacity (see Chapter 3). Hsp 70 expression is primarily regulated by transcription in Rat-1 cells. Hsp 70 does not act to regulate its own turnover (see Chapter 4).
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Martin, Andrew. "Measurement of heat strain in firefighters". Thesis, Queensland University of Technology, 1990. https://eprints.qut.edu.au/35956/1/35956_Martin_1990.pdf.
Testo completoAbstract (sommario):
A comparative study of six different fire-fighting clothing ensembles to determine the heat stress
imposed on the wearer was conducted. Physiological indicators of heat strain were monitored while
subjects performed set tasks for up to 30 minutes in controlled environments. The differences between
ensembles was considered. For each ensemble, six subjects performed set tasks in two controlled environments for 30 minutes or until one of a set of termination criteria was met. In the first environment subjects stepped at a set rate
in 40°C dry bulb and 60% humidity conditions. A number of weights, pre-determined to work the subject
at a set level of the individual's Heart Rate Increase Capacity, were carried. In the second environment
subjects lifted bricks at a set rate in front of two 1500 W radiators in 30°C and 60% conditions. Dry bulb
temperature, Wet Bulb Globe Temperature, and humidity were monitored to ensure consistency of test
conditions. A control test with light clothing was performed before the suit testing. Subjects were partially acclimatised prior to testing. Physiological indicators of strain (mean skin temperature, heart rate, blood pressure, and body fluid loss) were monitored and differences between ensembles considered. Skin temperature was calculated from a weighted average of measurements at 6 sites (chest, back, cheek, thigh, calf, and upper arm). Thermocouples (#32 gauge T-type) were attached to the skin with Leukoplast adhesive tape and the temperatures were recorded using a Fluke digital thermometer (sensitivity of 0.1°C) after every minute
of work.
Heart rate was stored every 15 seconds with one monitor and a backup monitor stored the rate at
every heart beat. Body fluid loss and amount of fluid absorbed by the clothing were found by weighing
nude subjects and clothing before and after testing. Scales accurate to 1 O g were used. Final systolic
and diastolic blood pressures were compared to resting values using an automatic monitor. Perceived views of the subjects were also obtained using a questionnaire.
Heart rate showed a steady cyclic increase during each test. Skin temperature rose in the hot environment and partially recovered in the moderate environment also producing a cyclic increase. The subjects lost from 600 g to 1200 g of fluid in each test. Systolic B.P. consistently increased and diastolic B.P. on average decreased. The ranks of the suits obtained were similar for all the measured parameters and the questionnaire. Skin temperature and heart rate clearly showed differences between the ensembles.
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Williams, Winifred Elizabeth. "HEAT TRANSFER IN THE MICROCIRCULATION". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275277.
Testo completoLibri sul tema "Heat Physiological effect"
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Suvernev, A. V. Osnovy bezopasnosti pikovoĭ gipertermii. Novosibirsk: Geo, 2007.
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Hui, Zhang, a cura di. Ren yu re huan jing. Beijing: Ke xue chu ban she, 2011.
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Nover, Lutz. Heat shock response. Boca Raton, Fla: CRC Press, 1990.
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M, Krake Ann, McCullough Joel E, King Bradley S e National Institute for Occupational Safety and Health., a cura di. United States Air Force, Seymour Johnson Air Force Base, Goldsboro, North Carolina. [Atlanta, Ga.?]: Dept. of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 2002.
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United States. Environmental Protection Agency. Office of Atmospheric Programs., a cura di. Excessive heat events guidebook. Washington, DC: U.S. Environmental Protection Agency, Office of Atmospheric Programs, 2006.
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Josipovic, Stanislas. Heat stress: Causes, treatment and prevention. Hauppauge, N.Y: Nova Science Publishers, 2012.
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Bhatnagar, A. Heat stress: Its assessment and control measures. Mumbai: University Dept. of Family Resource Management, S.N.D.T. Women's University, 2010.
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Lutz, Nover, a cura di. Heat shock response. Boca Raton, Fla: CRC Press, 1991.
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United States. Congress. Office of Compliance. Heat stress: Don't let the heat get you down. Washington, D.C: Office of Compliance, 2009.
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S, Sharma H., a cura di. The neurobiology of hyperthermia. Amsterdam: Elsevier, 2007.
Cerca il testo completoCapitoli di libri sul tema "Heat Physiological effect"
1
Mensah, Eric Opoku, Philippe Vaast, Richard Asare, Christiana A. Amoatey, Kwadwo Owusu, Bismark Kwesi Asitoakor e Anders Ræbild. "Cocoa Under Heat and Drought Stress". In Agroforestry as Climate Change Adaptation, 35–57. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-45635-0_2.
Testo completoAbstract (sommario):
AbstractCocoa (Theobroma cacao L.) is an important cash crop in many tropical countries, particularly in West Africa. Heat and drought are both known to affect the physiology of cocoa plants through reduced rates of photosynthesis and transpiration, as well as changed physiological processes such as the functions of photosystems, chlorophyll synthesis, stomatal conductance and expression of heat-shock proteins. This in turn leads to decreased yields and increased risks of mortality under severe heat and drought. To help cocoa plants adapt to climate change, the literature suggests agroforestry as a potential farm management practice. It has been argued that the lack of tree cover in cocoa cultivation systems exposes the crop to heat and direct solar radiation, thus increasing evapotranspiration and the risk of drought. Drawing on data generated from two on-field studies, this chapter assesses the shade effect on cocoa’s physiological responses to drought and heat stress to determine whether shade would be beneficial under climate change scenarios. We conclude that shade improves the physiology of cocoa, but that this may not be sufficient to compensate for the negative effects of high temperatures and severe drought exacerbated by climate change in sub-optimal conditions.
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Wang, Pin, Sumei Lu, Xiaowei Wu, Jun Tian e Ning Li. "Periodic Mist Spray's Dynamic Effect on Outdoor Micro-environment and Thermal Perception". In Novel Technology and Whole-Process Management in Prefabricated Building, 529–38. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-5108-2_56.
Testo completoAbstract (sommario):
AbstractMist spraying is an active cooling technology to alleviate heat stress during hot summers. There is no clear conclusion as to when mist spray should be used and its cooling potential in hot-humid regions yet. A periodic mist spraying system was set up, and environmental measurements coupled with questionnaire surveys were conducted, investigating the dynamic effect of spraying on the micro-environment and thermal perception. The results showed that elevated ambient temperatures could lead to a more substantial cooling impact, with a maximum cooling value of 5.68 ℃. The increase in thermal comfort due to the mist outweighed the decrease in thermal sensation. The study indicated that the mist spray system should be activated if the ambient temperature reached 32.5 ℃. Spraying could help local residents maintain a physiological state close to slightly hot and neutral comfort when the ambient temperature exceeded 34℃. The findings provide valuable guidance for the application of mist spray system in practical engineering scenarios in hot-humid areas.
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Lombardi, Giovanni, e Annamaria Colao. "Physiological Effects of Growth Hormone on the Heart". In Growth Hormone And The Heart, 13–22. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4615-1579-1_2.
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Önning, Gunilla, e Nils-Georg Asp. "Analysis, Heat Stability and Physiological Effects of Saponins from Oats". In Advances in Experimental Medicine and Biology, 365–75. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4613-0413-5_31.
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Fallik, Elazar, e Zoran Ilic’. "Positive and Negative Effects of Heat Treatment on the Incidence of Physiological Disorders in Fresh Produce". In Postharvest Physiological Disorders in Fruits and Vegetables, 111–26. Boca Raton : Taylor & Francis, 2018.: CRC Press, 2019. http://dx.doi.org/10.1201/b22001-6.
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Mathur, Sonal, e Anjana Jajoo. "Effects of Heat Stress on Growth and Crop Yield of Wheat (Triticum aestivum)". In Physiological Mechanisms and Adaptation Strategies in Plants Under Changing Environment, 163–91. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8591-9_8.
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DenHartog, Emiel A., Xiaomeng Fang e A. Shawn Deaton. "Effects of Total Heat Loss versus Evaporative Resistance of Firefighter Garments in a Physiological Heat Strain Trial". In Performance of Protective Clothing and Equipment: Innovative Solutions to Evolving Challenges, 204–21. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2020. http://dx.doi.org/10.1520/stp162420190075.
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Hussain, Manzoor, Ljupcho Jankuloski, M. Habib-ur-Rahman, Massoud Malek, Md Kamrul Islam, M. Reza Raheemi, Jawdat Dana et al. "Improving sustainable cotton production through enhanced resilience to climate change using mutation breeding." In Mutation breeding, genetic diversity and crop adaptation to climate change, 145–56. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789249095.0015.
Testo completoAbstract (sommario):
Abstract Cotton, being a leading commercial fibre crop, is grown on 20.5 million hectares in three major cotton-producing countries: China, India and Pakistan. Wide differences in yield per hectare exist among these countries and these are being aggravated by changing climate conditions, i.e. higher temperatures and significant seasonal and regional fluctuation in rainfall. Pakistan is one of the countries most affected by climate change. The disastrous effects of extreme periods of heat stress in cotton were very prominent in Pakistan during the growing seasons 2013-2014 (40-50% fruit abortion) and 2016-2017 (33% shortfall), which posed an alarming threat to the cotton-based economy of Pakistan. Poor resilience of the most commonly grown cotton varieties against extreme periods of heat stress are considered to be major factors for this drastic downfall in cotton production in Pakistan. Using the approach of induced mutation breeding, the Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad, Pakistan, has demonstrated its capabilities in developing cotton mutants that can tolerate the changed climatic conditions and sustain high yields under contrasting environments. The results of studies on the phenological and physiological traits conferring heat tolerance are presented here for thermo-tolerant cotton mutants (NIAB-878, NIAB-545, NIAB-1048, NIAB-444, NIAB-1089, NIAB-1064, NIAB-1042) relative to FH-142 and FH-Lalazar. NIAB-878 excelled in heat tolerance by maintaining the highest anther dehiscence (82%) and minimum cell injury percentage (39%) along with maximum stomatal conductance (27.7 mmol CO2/m2/s), transpiration rate (6.89 μmol H2O/m2/s), net photosynthetic rate (44.6 mmol CO2/m2/s) and physiological water use efficiency (6.81 mmol CO2/μmol H2O) under the prevailing high temperatures.
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Hamli, Sofia, Mostapha Labhilili, Kenza Kadi, Dalila Addad e Hmenna Bouzerzour. "Heat Shock Effects on Physiological Parameters Durum Wheat Seedlings and Relationships with Stress Tolerance Indices". In Recent Advances in Environmental Science from the Euro-Mediterranean and Surrounding Regions, 1333–35. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-70548-4_389.
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Frohns, A., e F. Frohns. "Safety of Water-Filtered Infrared A (wIRA) on the Eye as a Novel Treatment Option for Chlamydial Infections". In Water-filtered Infrared A (wIRA) Irradiation, 259–69. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92880-3_22.
Testo completoAbstract (sommario):
AbstractwIRA has been shown to reduce chlamydial infections in vitro and in vivo and might therefore offer an innovative therapeutic approach for fighting trachoma. However, since the eye is a highly temperature- and radiation-sensitive organ, a safety assessment of the ocular structures affected by wIRA treatment is required to establish wIRA as a potentially successful treatment option for clinical application. A prerequisite for this is to demonstrate that wIRA does not have adverse side-effects such as inducing a non-physiological temperature increase which causes cell stress and damage to ocular tissues and which, in turn, is ultimately associated with impaired vision. Likewise, the potential negative impact of non-thermal photochemical effects of wIRA irradiation needs to be investigated. Data from our ex vivo studies in pig and mouse models, as well as in vivo data in a guinea pig model, provide good evidence for the safe use of wIRA to treat chlamydial infections. These studies have excluded a non-physiological temperature rise as well as the activation of heat and stress-induced proteins after wIRA irradiation with therapy-relevant irradiances. Nevertheless, additional detailed in vitro and in vivo studies are needed to further advance the clinical use of wIRA.
Atti di convegni sul tema "Heat Physiological effect"
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Ley, Obdulia, e Yildiz Bayazitoglu. "Effect of Physiological Parameters on the Temperature Distribution of a Layered Head Model". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32044.
Testo completoAbstract (sommario):
Brain temperature control is important in clinical therapy, because moderate temperature reduction of brain temperature increases the survival rate after head trauma. A factor that affects the brain temperature distribution is the cerebral blood flow, which is controlled by autoregulatory mechanisms. To improve the existing thermal models of brain, we incorporate the effect of the temperature over the metabolic heat generation, and the regulatory processes that control the cerebral blood perfusion and depend on physiological parameters like, the mean arterial blood pressure, the partial pressure of oxygen, the partial pressure of carbon dioxide, and the cerebral metabolic rate of oxygen consumption. The introduction of these parameters in a thermal model gives information about how specific conditions, such as brain edema, hypoxia, hypercapnia, or hypotension, affect the temperature distribution within the brain. Existing biological thermal models of the human brain, assume constant blood perfusion, and neglect metabolic heat generation or consider it constant, which is a valid assumption for healthy tissue. But during sickness, trauma or under the effect of drugs like anesthetics, the metabolic activity and organ blood flow vary considerably, and such variations must be accounted for in order to achieve accurate thermal modeling. Our work, on a layered head model, shows that variations of the physiological parameters have profound effect on the temperature gradients within the head.
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Wang, Haiying, e Songtao Hu. "Effect of Moderate Altitude Exposure on Human Thermal Physiological Parameters and Heat Losses in different activities". In 2016 International Forum on Energy, Environment and Sustainable Development. Paris, France: Atlantis Press, 2016. http://dx.doi.org/10.2991/ifeesd-16.2016.3.
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Takayama, Shuichi, Yi-Chung Tung e Bor-Han Chueh. "Biological Micro/Nanofluidics". In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52087.
Testo completoAbstract (sommario):
Many biological studies, drug screening methods, and cellular therapies require culture and manipulation of living cells outside of their natural environment in the body. The gap between the cellular microenvironment in vivo and in vitro, however, poses challenges for obtaining physiologically relevant responses from cells used in basic biological studies or drug screens and for drawing out the maximum functional potential from cells used therapeutically. One of the reasons for this gap is because the fluidic environment of mammalian cells in vivo is microscale and dynamic whereas typical in vitro cultures are macroscopic and static. This presentation will give an overview of efforts in our laboratory to develop programmable microfluidic systems that enable spatio-temporal control of both the chemical and fluid mechanical environment of cells. The technologies and methods close the physiology gap to provide biological information otherwise unobtainable and to enhance cellular performance in therapeutic applications. Specific biomedical topics that will be discussed include subcellular signalling in normal and cancer cells, in vitro fertilization on a chip, studies of the effect of physiological and pathological fluid mechanical stresses on endothelial and epithelial cells, and microfluidic stem cell engineering. In the nanoscale regime, tunable nanochannels that can manipulate single DNA molecules will be discussed.
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Jiao, Jian, e Zhixiong Guo. "Simulation of Focused Radiation Propagation and Transient Heat Transfer in Turbid Tissues". In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88261.
Testo completoAbstract (sommario):
Thermal analysis of a cylindrical tissue subject to a train of ultrashort pulse irradiations was made by developing a combined time-dependent radiation and conduction bio-heat transfer model. Ultrashort pulsed radiation transport in the cylindrical tissue is simulated using the transient discrete ordinate method. Treatment of focused beam is introduced. The model skin tissue is stratified as three layers with different optical, thermal and physiological properties. Comparisons between the collimated irradiation and focused beam are conducted. The effect of pulse train is investigated.
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Petrović, Miloš, Radojica Đoković, Vladimir Kurćubić, Snežana Bogosavljević-Bošković, Simeon Rakonjac e Milun Petrović. "Intracellular and extracellular Hsp70 in cows: Similarities and differences in physiological and pathophysiology conditions". In Zbornik radova 26. medunarodni kongres Mediteranske federacije za zdravlje i produkciju preživara - FeMeSPRum. Poljoprivredni fakultet Novi Sad, 2024. http://dx.doi.org/10.5937/femesprumns24025p.
Testo completoAbstract (sommario):
Heat shock proteins (Hsp), also called chaperones, are proteins that are indispensable for the proper formation of the polypeptide chain; and have a role in its translocation within the cell. Hsp70 in cells helps to re-establish the native conformation of proteins that have denatured under the influence of various stressogens, by preventing their aggregation, which results in protecting the cell from apoptosis and having an anti-inflammatory effect. These proteins are classified on the basis of molecular mass, and the most significant is heat shock protein 70 (Hsp70) with a molecular mass of about 70 kDa, which is designated as "a master player in protein homeostasis". The concentration of Hsp increases significantly when exposed to a stressor originating from the cell itself or from the external environment. Many chaperones are induced under the influence of high ambient temperatures, when the universal heat shock response (HSR) develops, which is why the name heat shock proteins was defined. Intracellular Hsp70 (iHsp70) shows its protective and anti-inflammatory effects. Induced iHsp70 protects the cell from apoptosis by reducing or blocking the activation of caspases, binding to apoptosis-inducing factor (AIF) and inhibiting AIF-induced chromatin condensation or preventing mitochondrial damage and nuclear fragmentation. It blocks cell morphological changes caused by tumor necrosis factor-induced apoptosis, and has been found to aid in cell repair of damage caused by inflammation. The anti-inflammatory effect of iHsp70 is reflected in the fact that it inhibits the response to lipopolysaccharides and blocks the production of inflammatory mediators such as tumor necrosis factor Alpha (TNF-a), and other mechanisms have been described. he expression of the gene for the production of Hsp70 has been well studied in ruminants or their cell cultures exposed to high ambient temperatures, and the multiple increase of iHsp70 in the cells results in a better adaptation to heat stress. The study of eHsp70 has become relevant due to the availability of diagnostic kits for determining its concentration, and the latest results show that it is a very useful predictor of mortality in patients with septic shock. Hsp70 moves to the extracellular space in several ways: after leaving necrotic cells, under the action of various stress factors and inflammation in undamaged cells, it can be produced in the liver as an acute phase protein, and transport by exosomes and direct contact with the lipid membrane of cells have also been described. The pro-inflammatory effect of eHsp70 is realized by inducing immune cells, which further induces the secretion of inflammatory cytokines (TNF-a, IL-1b, IL-6), inducible nitric oxide synthase (iNOS) expression and nuclear translocation of nuclear factor-cB (NF-cB). According to the chaperone balance theory, the higher the value of eHsp70 compared to iHsp70, the more pronounced its proinflammatory effects. This hypothesis was also confirmed in dairy cows in the periparturient period.
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Čukić, Aleksandar, Marko Cincović, Radojica Đoković, Simeon Rakonjac, Milun Petrović e Miloš Petrović. "Heat stress impact on sheep production". In Zbornik radova 26. medunarodni kongres Mediteranske federacije za zdravlje i produkciju preživara - FeMeSPRum. Poljoprivredni fakultet Novi Sad, 2024. http://dx.doi.org/10.5937/femesprumns24007c.
Testo completoAbstract (sommario):
Research on the impact of heat stress on animals has mainly been related to cattle, while sheep have been neglected and the impact of heat stress on sheep production is still insufficiently researched. There are numerous stressors related to the procedures and methods of breeding sheep in barns and pastures among them ambient temperature is the most important variable because its effect is exacerbated in the presence of high humidity. Thermal indices are useful for assessing the influence of weather parameters in a certain agroecological area, of which the temperature-humidity index proved to be the best thermal index for assessing the harmful effect of heat stress on the productive performance of animals. Sheep have good adaptability and they are resistant to harsh environmental conditions, still in addition to a certain tolerance to heat stress, high temperatures can negatively affect sheep, which most often leads to dehydration, reduced appetite, reduced milk production and increased risk of disease. Mechanisms that help sheep to survive the challenge of heat stress include morphological, behavioural, physiological, blood biochemistry and genetic bases of adaptation. Sheep can combat heat stress by seeking shade, drinking enough water, and properly ventilating the barn. Increasing the productivity of sheep by adapting various management strategies including housing and animal management and climate monitoring may enhance production capacity of the herd. Therefore, heat stress has a negative effect on sheep, temperatures will increase year by year, and therefore it is necessary to investigate the relationship between sheep production and heat stress in time, to improve sheep farming and make life easier in the days ahead.
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Salloum, M., N. Ghaddar e K. Ghali. "A New Transient Bio-Heat Model of the Human Body". In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72303.
Testo completoAbstract (sommario):
A new mathematical multi-segmented model based on an improved Stolwijk model is developed for predicting nude human thermal and regulatory responses within body segments and the environment. The passive model segments the body into the 15 cylindrical parts. Each body part is divided into four nodes of core, skin, artery blood, and vein blood. The body nodes interact with each other through convection, perfusion and conduction. In any body element, the blood exiting the arteries and flowing into the capillaries is divided into blood flowing in the core (exchanges heat by perfusion in the core) and blood flowing into the skin layer (exchanges heat by perfusion in the skin). The model calculates the blood circulation flow rates based on exact physiological data of Avolio [1], real dimensions, and anatomic positions of the arteries in the body. The circulatory system model takes into consideration the pulsatile blood flow in the macro arteries with its effect on the convective heat transport. The inclusion of calculated blood perfusion in both the tissue and the skin, based on the arterial system model and the heart rate is unique for the current model. The bio-heat human model is capable of predicting accurately nude human transient physiological responses such as the body’s skin, tympanic, and core temperatures, sweat rates, and the dry and latent heat losses from each body segment. The nude body model predictions are compared with published theoretical and experimental data at a variety of ambient conditions and activity. The current model agrees well with experimental data during transient hot exposures. The nude human model has an accuracy of less than 8% for the whole-body heat gains or losses and ±0.48°C for skin temperature values.
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Majkić, Mira, Jovan Spasojević, Sandra Nikolić e Marko Cincović. "Monitoring of heat stress in dairy cows: Striving towards better resilience". In Zbornik radova 26. medunarodni kongres Mediteranske federacije za zdravlje i produkciju preživara - FeMeSPRum. Poljoprivredni fakultet Novi Sad, 2024. http://dx.doi.org/10.5937/femesprumns24021m.
Testo completoAbstract (sommario):
Heat stress can be defined as a condition in which there is a changed relationship in the amount of heat produced and heat that is released to the outside environment through physical models of conduction, convection and evaporation. Prolonged exposure to heat stress can negatively affect health-productive traits. The adaptive response of animals to heat stress involves physiological, behavioral and metabolic reactions in order to maintain thermoregulation. The main effect of heat stress is a decrease in milk production, so heat stress has great economic importance. The decrease in milk production can be related to the direct effect of high ambient temperatures, but also related to metabolic, endocrinological and immunological changes, all of which depend on the way of feeding, care and biological predispositions of cows. The aim of this paper is to show how each of the mentioned factors affects milk production in heat stress and what are the biological characteristics of cows and the health and technological measures that we can take in order to increase the resilience of cows to heat stress.
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Smith, Christopher, Zhigang Xu e Jagannathan Sankar. "The Effects of T4 and T6 Heat Treatment on the Corrosion Behavior of MgZnCa Alloys". In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88196.
Testo completoAbstract (sommario):
Some of the most important characteristics of a medical implant biomaterial are its corrosion resistance, cytotoxicity, mechanical property, and overall biological performance. Optimizing these characteristics is therefore vital to the success of creating effective medical biomaterials. It is well known that heat treatment processes affect the microstructure of metallic alloys which consequently can have favorable influences on the mechanical properties. The determination of the effects of heat treatment on the corrosion resistance of metallic alloys is another aspect that must be examined. That is the goal of this investigation. The corrosion characteristics of two MgZnCa alloy systems (MgZnCa-31 and MgZnCa-32) were studied to determine the correlation between T4 and T6 heat treatment and the corrosion rate on the alloys. The alloys were produced by melting and casting at 730°C and then heat treated. The corrosion performances of the alloys were examined by both immersion and electrochemical analysis, which were conduct in 0.9% NaCl physiological saline solution. In terms of the effects of the T4 heat treatment, the corrosion rate of the MgZnCa-31 decreases as the time period of the heat treatment increases, whereas the MgZnCa-32 alloys have an opposite effect meaning that the corrosion rate increases as the time period of the heat treatment increases. There was no significant change in corrosion with the introduction of T6 heat treatment to both alloy systems.
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Sun, Jiaqi, e XinRong Zhang. "Molecular Mechanism of Water Transport Through Cellulose Cell Wall Matrix". In ASME 2019 6th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/mnhmt2019-4031.
Testo completoAbstract (sommario):
Abstract In plant living tissue, water can flow across cells by different paths, through cell membranes (transcellular path) and plasmodesmata (symplastic path), or through the continuous cell walls matrix (apoplastic path). The relative contribution of these three paths in living tissue is currently unclear and could vary according to species, tissue developmental stage or physiological conditions. Experiments suggested that apoplastic water movement predominates during transpiration. The objective of this study was to investigate the hydraulic process of cellulose cell wall pathway. The effective pore diameter for water flow through the primary wall matrix is between 2 and 20nm. Inside the cell wall polymer porous, there exist hydrophilic/hydrophobic crystal surfaces based on structure anisotropic. Besides, hydrogen bonding and electrostatic interaction and van der Waals (vdW) dispersion force play an important role in water transport inside the Nano cellulose porous. Therefore, the molecular dynamics simulation was applied to reveal the molecular mechanism of surface boundary effect together with various driving force during water passing through cellulose cell wall matrix Nano channel.
Rapporti di organizzazioni sul tema "Heat Physiological effect"
1
O'Sullivan, Joseph C. The Effect of Diazoxide Upon Heat Shock Protein and Physiological Response to Hemorrhagic Shock and Cerebral Stroke. Fort Belvoir, VA: Defense Technical Information Center, maggio 2006. http://dx.doi.org/10.21236/ad1014226.
Testo completo
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Bolek, Kevin J., e Michael E. Persia. The Effect of Chick Methionine Status on Broiler Performance and Physiological Response to Acute and Chronic Heat Stress. Ames (Iowa): Iowa State University, gennaio 2013. http://dx.doi.org/10.31274/ans_air-180814-821.
Testo completo
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Yahav, Shlomo, John McMurtry e Isaac Plavnik. Thermotolerance Acquisition in Broiler Chickens by Temperature Conditioning Early in Life. United States Department of Agriculture, 1998. http://dx.doi.org/10.32747/1998.7580676.bard.
Testo completoAbstract (sommario):
The research on thermotolerance acquisition in broiler chickens by temperature conditioning early in life was focused on the following objectives: a. To determine the optimal timing and temperature for inducing the thermotolerance, conditioning processes and to define its duration during the first week of life in the broiler chick. b. To investigate the response of skeletal muscle tissue and the gastrointestinal tract to thermal conditioning. This objective was added during the research, to understand the mechanisms related to compensatory growth. c. To evaluate the effect of early thermo conditioning on thermoregulation (heat production and heat dissipation) during 3 phases: (1) conditioning, (2) compensatory growth, (3) heat challenge. d. To investigate how induction of improved thermotolerance impacts on metabolic fuel and the hormones regulating growth and metabolism. Recent decades have seen significant development in the genetic selection of the meat-type fowl (i.e., broiler chickens); leading to rapid growth and increased feed efficiency, providing the poultry industry with heavy chickens in relatively short growth periods. Such development necessitates parallel increases in the size of visceral systems such as the cardiovascular and the respiratory ones. However, inferior development of such major systems has led to a relatively low capability to balance energy expenditure under extreme conditions. Thus, acute exposure of chickens to extreme conditions (i.e., heat spells) has resulted in major economic losses. Birds are homeotherms, and as such, they are able to maintain their body temperature within a narrow range. To sustain thermal tolerance and avoid the deleterious consequences of thermal stresses, a direct response is elicited: the rapid thermal shock response - thermal conditioning. This technique of temperature conditioning takes advantage of the immaturity of the temperature regulation mechanism in young chicks during their first week of life. Development of this mechanism involves sympathetic neural activity, integration of thermal infom1ation in the hypothalamus, and buildup of the body-to-brain temperature difference, so that the potential for thermotolerance can be incorporated into the developing thermoregulation mechanisms. Thermal conditioning is a unique management tool, which most likely involves hypothalamic them1oregulatory threshold changes that enable chickens, within certain limits, to cope with acute exposure to unexpected hot spells. Short-tem1 exposure to heat stress during the first week of life (37.5+1°C; 70-80% rh; for 24 h at 3 days of age) resulted in growth retardation followed immediately by compensatory growth" which resulted in complete compensation for the loss of weight gain, so that the conditioned chickens achieved higher body weight than that of the controls at 42 days of age. The compensatory growth was partially explained by its dramatic positive effect on the proliferation of muscle satellite cells which are necessary for further muscle hypertrophy. By its significant effect of the morphology and functioning of the gastrointestinal tract during and after using thermal conditioning. The significant effect of thermal conditioning on the chicken thermoregulation was found to be associated with a reduction in heat production and evaporative heat loss, and with an increase in sensible heat loss. It was further accompanied by changes in hormones regulating growth and metabolism These physiological responses may result from possible alterations in PO/AH gene expression patterns (14-3-3e), suggesting a more efficient mechanism to cope with heat stress. Understanding the physiological mechanisms behind thermal conditioning step us forward to elucidate the molecular mechanism behind the PO/AH response, and response of other major organs. The thermal conditioning technique is used now in many countries including Israel, South Korea, Australia, France" Ecuador, China and some places in the USA. The improvement in growth perfom1ance (50-190 g/chicken) and thermotolerance as a result of postnatal thermal conditioning, may initiate a dramatic improvement in the economy of broiler's production.
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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman e Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, aprile 2002. http://dx.doi.org/10.32747/2002.7580685.bard.
Testo completoAbstract (sommario):
Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.
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Yahav, Shlomo, John Brake e Noam Meiri. Development of Strategic Pre-Natal Cycling Thermal Treatments to Improve Livability and Productivity of Heavy Broilers. United States Department of Agriculture, dicembre 2013. http://dx.doi.org/10.32747/2013.7593395.bard.
Testo completoAbstract (sommario):
The necessity to improve broiler thermotolerance and live performance led to the following hypothesis: Appropriate comprehensive incubation treatments that include significant temperature management changes will promote angiogenesis and will improve acquisition of thermotolerance and carcass quality of heavy broilers through epigenetic adaptation. It was based on the following questions: 1. Can TM during embryogenesis of broilers induce a longer-lasting thermoregulatory memory (up to marketing age of 10 wk) that will improve acquisition of thermotolerance as well as increased breast meat yield in heavy broilers? 2. The improved sensible heat loss (SHL) suggests an improved peripheral vasodilation process. Does elevated temperature during incubation affect vasculogenesis and angiogenesis processes in the chick embryo? Will such create subsequent advantages for heavy broilers coping with adverse hot conditions? 3. What are the changes that occur in the PO/AH that induce the changes in the threshold response for heat production/heat loss based on the concept of epigenetic temperature adaptation? The original objectives of this study were as follow: a. to assess the improvement of thermotolerance efficiency and carcass quality of heavy broilers (~4 kg); b. toimproveperipheral vascularization and angiogenesis that improve sensible heat loss (SHL); c. to study the changes in the PO/AH thermoregulatory response for heat production/losscaused by modulating incubation temperature. To reach the goals: a. the effect of TM on performance and thermotolerance of broilers reared to 10 wk of age was studied. b. the effect of preincubation heating with an elevated temperature during the 1ˢᵗ 3 to 5 d of incubation in the presence of modified fresh air flow coupled with changes in turning frequency was elucidated; c.the effect of elevated temperature on vasculogenesis and angiogenesis was determined using in ovo and whole embryo chick culture as well as HIF-1α VEGF-α2 VEGF-R, FGF-2, and Gelatinase A (MMP2) gene expression. The effects on peripheral blood system of post-hatch chicks was determined with an infrared thermal imaging technique; c. the expression of BDNF was determined during the development of the thermal control set-point in the preoptic anterior hypothalamus (PO/AH). Background to the topic: Rapid growth rate has presented broiler chickens with seriousdifficulties when called upon to efficiently thermoregulate in hot environmental conditions. Being homeotherms, birds are able to maintain their body temperature (Tb) within a narrow range. An increase in Tb above the regulated range, as a result of exposure to environmental conditions and/or excessive metabolic heat production that often characterize broiler chickens, may lead to a potentially lethal cascade of irreversible thermoregulatory events. Exposure to temperature fluctuations during the perinatal period has been shown to lead to epigenetic temperature adaptation. The mechanism for this adaptation was based on the assumption that environmental factors, especially ambient temperature, have a strong influence on the determination of the “set-point” for physiological control systems during “critical developmental phases.” Recently, Piestunet al. (2008) demonstrated for the first time that TM (an elevated incubation temperature of 39.5°C for 12 h/d from E7 to E16) during the development/maturation of the hypothalamic-hypophyseal-thyroid axis (thermoregulation) and the hypothalamic-hypophyseal-adrenal axis (stress) significantly improved the thermotolerance and performance of broilers at 35 d of age. These phenomena raised two questions that were addressed in this project: 1. was it possible to detect changes leading to the determination of the “set point”; 2. Did TM have a similar long lasting effect (up to 70 d of age)? 3. Did other TM combinations (pre-heating and heating during the 1ˢᵗ 3 to 5 d of incubation) coupled with changes in turning frequency have any performance effect? The improved thermotolerance resulted mainly from an efficient capacity to reduce heat production and the level of stress that coincided with an increase in SHL (Piestunet al., 2008; 2009). The increase in SHL (Piestunet al., 2009) suggested an additional positive effect of TM on vasculogenesis and angiogensis. 4. In order to sustain or even improve broiler performance, TM during the period of the chorioallantoic membrane development was thought to increase vasculogenesis and angiogenesis providing better vasodilatation and by that SHL post-hatch.
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Yahav, Shlomo, John Brake e Orna Halevy. Pre-natal Epigenetic Adaptation to Improve Thermotolerance Acquisition and Performance of Fast-growing Meat-type Chickens. United States Department of Agriculture, settembre 2009. http://dx.doi.org/10.32747/2009.7592120.bard.
Testo completoAbstract (sommario):
: The necessity to improve broiler thermotolerance and performance led to the following hypothesis: (a) thethermoregulatory-response threshold for heat production can be altered by thermal manipulation (TM) during incubation so as to improve the acquisition of thermotolerance in the post-hatch broiler;and (b) TM during embryogenesis will improve myoblast proliferation during the embryonic and post-hatch periods with subsequent enhanced muscle growth and meat production. The original objectives of this study were as follow: 1. to assess the timing, temperature, duration, and turning frequency required for optimal TM during embryogenesis; 2. to evaluate the effect of TM during embryogenesis on thermoregulation (heat production and heat dissipation) during four phases: (1) embryogenesis, (2) at hatch, (3) during growth, and (4) during heat challenge near marketing age; 3. to investigate the stimulatory effect of thermotolerance on hormones that regulate thermogenesis and stress (T₄, T₃, corticosterone, glucagon); 4. to determine the effect of TM on performance (BW gain, feed intake, feed efficiency, carcass yield, breast muscle yield) of broiler chickens; and 5. to study the effect of TM during embryogenesis on skeletal muscle growth, including myoblast proliferation and fiber development, in the embryo and post-hatch chicks.This study has achieved all the original objectives. Only the plasma glucagon concentration (objective 3) was not measured as a result of technical obstacles. Background to the topic: Rapid growth rate has presented broiler chickens with seriousdifficulties when called upon to efficiently thermoregulate in hot environmental conditions. Being homeotherms, birds are able to maintain their body temperature (Tb) within a narrow range. An increase in Tb above the regulated range, as a result of exposure to environmental conditions and/or excessive metabolic heat production that often characterize broiler chickens, may lead to a potentially lethal cascade of irreversible thermoregulatory events. Exposure to temperature fluctuations during the perinatal period has been shown to lead to epigenetic temperature adaptation. The mechanism for this adaptation was based on the assumption that environmental factors, especially ambient temperature, have a strong influence on the determination of the “set-point” for physiological control systems during “critical developmental phases.” In order to sustain or even improve broiler performance, TM during the period of embryogenesis when satellite cell population normally expand should increase absolute pectoralis muscle weight in broilers post-hatch. Major conclusions: Intermittent TM (39.5°C for 12 h/day) during embryogenesis when the thyroid and adrenal axis was developing and maturing (E7 to E16 inclusive) had a long lasting thermoregulatory effect that improved thermotolerance of broiler chickens exposed to acute thermal stress at market age by lowering their functional Tb set point, thus lowering metabolic rate at hatch, improving sensible heat loss, and significantly decreasing the level of stress. Increased machine ventilation rate was required during TM so as to supply the oxygen required for the periods of increased embryonic development. Enhancing embryonic development was found to be accomplished by a combination of pre-incubation heating of embryos for 12 h at 30°C, followed by increasing incubation temperature to 38°C during the first 3 days of incubation. It was further facilitated by increasing turning frequency of the eggs to 48 or 96 times daily. TM during critical phases of muscle development in the late-term chick embryo (E16 to E18) for 3 or 6 hours (39.5°C) had an immediate stimulatory effect on myoblast proliferation that lasted for up to two weeks post-hatch; this was followed by increased hypertrophy at later ages. The various incubation temperatures and TM durations focused on the fine-tuning of muscle development and growth processes during late-term embryogenesis as well as in post-hatch chickens.
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Meiri, Noam, Michael D. Denbow e Cynthia J. Denbow. Epigenetic Adaptation: The Regulatory Mechanisms of Hypothalamic Plasticity that Determine Stress-Response Set Point. United States Department of Agriculture, novembre 2013. http://dx.doi.org/10.32747/2013.7593396.bard.
Testo completoAbstract (sommario):
Our hypothesis was that postnatal stress exposure or sensory input alters brain activity, which induces acetylation and/or methylation on lysine residues of histone 3 and alters methylation levels in the promoter regions of stress-related genes, ultimately resulting in long-lasting changes in the stress-response set point. Therefore, the objectives of the proposal were: 1. To identify the levels of total histone 3 acetylation and different levels of methylation on lysine 9 and/or 14 during both heat and feed stress and challenge. 2. To evaluate the methylation and acetylation levels of histone 3 lysine 9 and/or 14 at the Bdnfpromoter during both heat and feed stress and challenge. 3. To evaluate the levels of the relevant methyltransferases and transmethylases during infliction of stress. 4. To identify the specific localization of the cells which respond to both specific histone modification and the enzyme involved by applying each of the stressors in the hypothalamus. 5. To evaluate the physiological effects of antisense knockdown of Ezh2 on the stress responses. 6. To measure the level of CpG methylation in the promoter region of BDNF in thermal treatments and free-fed, 12-hour fasted, and re-fed chicks during post-natal day 3, which is the critical period for feed-control establishment, and 10 days later to evaluate longterm effects. 7. The phenotypic effect of antisense “knock down” of the transmethylaseDNMT 3a. Background: The growing demand for improvements in poultry production requires an understanding of the mechanisms governing stress responses. Two of the major stressors affecting animal welfare and hence, the poultry industry in both the U.S. and Israel, are feed intake and thermal responses. Recently, it has been shown that the regulation of energy intake and expenditure, including feed intake and thermal regulation, resides in the hypothalamus and develops during a critical post-hatch period. However, little is known about the regulatory steps involved. The hypothesis to be tested in this proposal is that epigenetic changes in the hypothalamus during post-hatch early development determine the stress-response set point for both feed and thermal stressors. The ambitious goals that were set for this proposal were met. It was established that both stressors i.e. feed and thermal stress, can be manipulated during the critical period of development at day 3 to induce resilience to stress later in life. Specifically it was established that unfavorable nutritional conditions during early developmental periods or heat exposure influences subsequent adaptability to those same stressful conditions. Furthermore it was demonstrated that epigenetic marks on the promoter of genes involved in stress memory are altered both during stress, and as a result, later in life. Specifically it was demonstrated that fasting and heat had an effect on methylation and acetylation of histone 3 at various lysine residues in the hypothalamus during exposure to stress on day 3 and during stress challenge on day 10. Furthermore, the enzymes that perform these modifications are altered both during stress conditioning and challenge. Finally, these modifications are both necessary and sufficient, since antisense "knockdown" of these enzymes affects histone modifications, and as a consequence stress resilience. DNA methylation was also demonstrated at the promoters of genes involved in heat stress regulation and long-term resilience. It should be noted that the only goal that we did not meet because of technical reasons was No. 7. In conclusion: The outcome of this research may provide information for the improvement of stress responses in high yield poultry breeds using epigenetic adaptation approaches during critical periods in the course of early development in order to improve animal welfare even under suboptimum environmental conditions.
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Fromm, Hillel, e Joe Poovaiah. Calcium- and Calmodulin-Mediated Regulation of Plant Responses to Stress. United States Department of Agriculture, settembre 1993. http://dx.doi.org/10.32747/1993.7568096.bard.
Testo completoAbstract (sommario):
We have taken a molecular approach to clone cellular targets of calcium/calmodulin (Ca2+/CaM). A 35S-labeled recombinant CaM was used as a probe to screen various cDNA expression libraries. One of the isolated clones from petunia codes for the enzyme glutamate decarboxylase (GAD) which catalyzes the conversion of glutamate to g-aminobutyric acid (GABA). The activity of plant GAD has been shown to be dramatically enhanced in response to cold and heat shock, anoxia, drought, mechanical manipulations and by exogenous application of the stress phytohormone ABA in wheat roots. We have purified the recombinant GAD by CaM-affinity chromatography and studied its regulation by Ca2+/CaM. At a physiological pH range (7.0-7.5), the purified enzyme was inactive in the absence of Ca2+ and CaM but could be stimulated to high levels of activity by the addition of exogenous CaM (K0.5 = 15 nM) in the presence of Ca2+ (K 0.5 = 0.8 mM). Neither Ca2+ nor CaM alone had any effect on GAD activity. Transgenic tobacco plants expressing a mutant petunia GAD lacking the CaM-binding domain, or transgenic plants expressing the intact GAD were prepared and studied in detail. We have shown that the CaM-binding domain is necessary for the regulation of glutamate and GABA metabolism and for normal plant development. Moreover, we found that CaM is tightly associated with a 500 kDa GAD complex. The tight association of CaM with its target may be important for the rapid modulation of GAD activity by Ca2+ signaling in response to stresses.
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Montain, Scott J., Michael N. Sawka, Bruce S. Cadarette, Mark D. Quigley e James M. McKay. Physiological Tolerance to Uncompensable Heat Stress: Effects of Exercise Intensity, Protective Clothing, and Climate. Fort Belvoir, VA: Defense Technical Information Center, gennaio 1994. http://dx.doi.org/10.21236/ada283851.
Testo completo
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Wideman, Jr., Robert F., Nicholas B. Anthony, Avigdor Cahaner, Alan Shlosberg, Michel Bellaiche e William B. Roush. Integrated Approach to Evaluating Inherited Predictors of Resistance to Pulmonary Hypertension Syndrome (Ascites) in Fast Growing Broiler Chickens. United States Department of Agriculture, dicembre 2000. http://dx.doi.org/10.32747/2000.7575287.bard.
Testo completoAbstract (sommario):
Background PHS (pulmonary hypertension syndrome, ascites syndrome) is a serious cause of loss in the broiler industry, and is a prime example of an undesirable side effect of successful genetic development that may be deleteriously manifested by factors in the environment of growing broilers. Basically, continuous and pinpointed selection for rapid growth in broilers has led to higher oxygen demand and consequently to more frequent manifestation of an inherent potential cardiopulmonary incapability to sufficiently oxygenate the arterial blood. The multifaceted causes and modifiers of PHS make research into finding solutions to the syndrome a complex and multi threaded challenge. This research used several directions to better understand the development of PHS and to probe possible means of achieving a goal of monitoring and increasing resistance to the syndrome. Research Objectives (1) To evaluate the growth dynamics of individuals within breeding stocks and their correlation with individual susceptibility or resistance to PHS; (2) To compile data on diagnostic indices found in this work to be predictive for PHS, during exposure to experimental protocols known to trigger PHS; (3) To conduct detailed physiological evaluations of cardiopulmonary function in broilers; (4) To compile data on growth dynamics and other diagnostic indices in existing lines selected for susceptibility or resistance to PHS; (5) To integrate growth dynamics and other diagnostic data within appropriate statistical procedures to provide geneticists with predictive indices that characterize resistance or susceptibility to PHS. Revisions In the first year, the US team acquired the costly Peckode weigh platform / individual bird I.D. system that was to provide the continuous (several times each day), automated weighing of birds, for a comprehensive monitoring of growth dynamics. However, data generated were found to be inaccurate and irreproducible, so making its use implausible. Henceforth, weighing was manual, this highly labor intensive work precluding some of the original objectives of using such a strategy of growth dynamics in selection procedures involving thousands of birds. Major conclusions, solutions, achievements 1. Healthy broilers were found to have greater oscillations in growth velocity and acceleration than PHS susceptible birds. This proved the scientific validity of our original hypothesis that such differences occur. 2. Growth rate in the first week is higher in PHS-susceptible than in PHS-resistant chicks. Artificial neural network accurately distinguished differences between the two groups based on growth patterns in this period. 3. In the US, the unilateral pulmonary occlusion technique was used in collaboration with a major broiler breeding company to create a commercial broiler line that is highly resistant to PHS induced by fast growth and low ambient temperatures. 4. In Israel, lines were obtained by genetic selection on PHS mortality after cold exposure in a dam-line population comprising of 85 sire families. The wide range of PHS incidence per family (0-50%), high heritability (about 0.6), and the results in cold challenged progeny, suggested a highly effective and relatively easy means for selection for PHS resistance 5. The best minimally-invasive diagnostic indices for prediction of PHS resistance were found to be oximetry, hematocrit values, heart rate and electrocardiographic (ECG) lead II waves. Some differences in results were found between the US and Israeli teams, probably reflecting genetic differences in the broiler strains used in the two countries. For instance the US team found the S wave amplitude to predict PHS susceptibility well, whereas the Israeli team found the P wave amplitude to be a better valid predictor. 6. Comprehensive physiological studies further increased knowledge on the development of PHS cardiopulmonary characteristics of pre-ascitic birds, pulmonary arterial wedge pressures, hypotension/kidney response, pulmonary hemodynamic responses to vasoactive mediators were all examined in depth. Implications, scientific and agricultural Substantial progress has been made in understanding the genetic and environmental factors involved in PHS, and their interaction. The two teams each successfully developed different selection programs, by surgical means and by divergent selection under cold challenge. Monitoring of the progress and success of the programs was done be using the in-depth estimations that this research engendered on the reliability and value of non-invasive predictive parameters. These findings helped corroborate the validity of practical means to improve PHT resistance by research-based programs of selection.