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2.
Int J Biometeorol ; 64(3): 485-499, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32016640

RESUMO

Evaporative cooling is the critical heat dissipation mechanism for working individuals wearing thermal protective clothing in hot environments. However, until now, there is no knowledge on garment size design for evaporative cooling optimization, especially when the human body is in movements. In this study, to understand the dynamic effect of garment size on evaporative cooling, we performed experiments on a sweating thermal manikin with seven garment sizes and three walking speeds. The evaporative cooling of global and local manikin body with this wide range garment sizes was present. Results demonstrated that the effect of garment size on evaporative cooling depended on the walking speed. At lower walking speeds, the global evaporative cooling tended to decrease with greater garment size, while at higher walking speeds, the global evaporative cooling tended to increase with greater garment size. Similarly, according to effects of garment size on local evaporative cooling, body segments could be divided into three categories for evaporative cooling optimization. Further, we analyzed factors which influenced the positive effect of walking speed on the evaporative cooling. Results showed that, for most cases, the increase of evaporative cooling caused by walking showed positive linear relationship with the garment size. Further increase of walking speed led to a greater increase rate of evaporative heat loss for body segments with the small air gap. This study provides insights into clothing local characteristics of evaporative cooling with different garment sizes under dynamic conditions and may help clothing design to optimize the evaporative cooling of working individuals in hot environments.


Assuntos
Manequins , Caminhada , Regulação da Temperatura Corporal , Temperatura Alta , Humanos , Roupa de Proteção , Sudorese
3.
Int J Sports Med ; 41(3): 161-167, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31902130

RESUMO

Aerobic performance is negatively impacted by tropical climate due to impairment of thermoregulatory mechanisms. We tested the hypothesis that a torso application of a 4% menthol solution would have the same effect on a best performance 10-km run as an external use of cold water. Thirteen trained male athletes completed four outdoor 10-km runs (T=29.0±1.3°C, relative humidity 59.0±13.6%) wearing a tee-shirt soaked every 2-km either in a cold (~6°C) or warm/ambient (~28°C) solution, consisting in water or in a 4% menthol solution, (CTL, MENT-Amb, CLD and MENT-CLD). Run performances were improved from 4.8 to 6.1% in CLD (51.4±5.5 min), MENT-Amb (52.2±5.9 min) and MENT-CLD (51.4±5.1 min) conditions (vs. CTL, 55.4±8.4 min, P<0.05), without differences between these three conditions, whereas heart rate (177±13bpm), body temperature (38.7±0.6°C) and drink ingestion (356±170 g) were not modified. Thermal sensation after running was lower in MENT-CLD (vs. CTL, P<0.01) and thermal acceptability was higher in CLD and MENT-Amb (vs. CTL, P<0.05), but thermal comfort, feeling scale and rate of perceived exertion remained unchanged. The use of menthol on skin enhances aerobic performance in a tropical climate, and no differences in performance were observed between menthol and traditional percooling strategies. However, combining both menthol and traditional percooling brought no further improvements.


Assuntos
Desempenho Atlético/fisiologia , Regulação da Temperatura Corporal/efeitos dos fármacos , Umidade , Mentol/administração & dosagem , Corrida/fisiologia , Clima Tropical , Administração Cutânea , Adulto , Ingestão de Líquidos , Marcha/fisiologia , Frequência Cardíaca/fisiologia , Humanos , Masculino , Percepção/fisiologia , Esforço Físico/fisiologia , Perda de Peso/fisiologia , Adulto Jovem
5.
Int J Biometeorol ; 64(1): 39-45, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31473810

RESUMO

We investigated the validity of infrared tympanic temperature (IR-Tty) during exercise in the heat with variations in solar radiation. Eight healthy males completed stationary cycling trials at 70% peak oxygen uptake until exhaustion in an environmental chamber maintained at 30°C with 50% relative humidity. Three solar radiation conditions, 0, 250 and 500 W/m2, were tested using a ceiling-mounted solar simulator (metal-halide lamps) over a 3 × 2 m irradiated area. IR-Tty and rectal temperature (Tre) were similar before and during exercise in each trial (P > 0.05). Spearman's rank correlation coefficient (rs) demonstrated very strong (250 W/m2, rs = 0.87) and strong (0 W/m2, rs = 0.73; 500 W/m2, rs = 0.78) correlations between IR-Tty and Tre in all trials (P < 0.001). A Bland-Altman plot showed that mean differences (SD; 95% limits of agreement; root mean square error) between IR-Tty and Tre were - 0.11°C (0.46; - 1.00 to 0.78°C; 0.43 ± 0.16°C) in 0 W/m2, - 0.13°C (0.32; - 0.77 to 0.50°C; 0.32 ± 0.10°C) in 250 W/m2 and - 0.03°C (0.60; - 1.21 to 1.14°C; 0.46 ± 0.27°C) in 500 W/m2. A positive correlation was found in 500 W/m2 (rs = 0.51; P < 0.001) but not in 250 W/m2 (rs = 0.04; P = 0.762) and 0 W/m2 (rs = 0.04; P = 0.732), indicating a greater elevation in IR-Tty than Tre in 500 W/m2. Percentage of target attainment within ± 0.3°C between IR-Tty and Tre was higher in 250 W/m2 (100 ± 0%) than 0 (93 ± 7%) and 500 (90 ± 10%; P < 0.05) W/m2. IR-Tty is acceptable for core temperature monitoring during exercise in the heat when solar radiation is ≤ 500 W/m2, and its accuracy increases when solar radiation is 250 W/m2 under our study conditions.


Assuntos
Regulação da Temperatura Corporal , Temperatura Alta , Temperatura Corporal , Exercício , Masculino , Temperatura Ambiente
6.
Int J Biometeorol ; 64(1): 105-113, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31485808

RESUMO

The objectives of this study were to determine the main variables which act in the adaptive profile and the dynamic of the thermoregulatory responses of Sindi and Girolando dairy cows in tropical conditions using multivariate analyses as the auxiliary method. Thirty dairy cows were evaluated, in which the data were collected monthly during 12 months. Rectal temperature (RT) and respiratory rate (RR) were measured twice a day (morning and afternoon), along with meteorological variables (air temperature, relative humidity, and wind speed), and later the Black Globe and Humidity Index and Radiant Heat Load were calculated. Blood samples were collected for estimating the levels of triiodothyronine (T3), thyroxine (T4), hemoglobin concentration (HC), red blood cells (RBC), packet cell volume (PCV), mean corpuscular volume (MCV), white blood cells (WBC), glucose (GLU), cholesterol (CHO), triglycerides (TRI), creatinine (CRE), total protein (TP), urea (URE), albumin (ALB), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). The more active variables in the adaptive profile for Sindi cows were T4, PCV, RBC, WBC, TRI, CRE, HC, T3, and URE, while PCV, RBC, ALB, TP, RT, RR, URE, ALT, and AST variables were more active for Girolando cows. All animals were classified according to their corresponding group when considering all variables under study. The classification error percentage was > 40% in the Sindi cows when the physiological responses were considered, whereas an 80% success rate was observed in Girolando cows in the winter and summer seasons. The physiological responses of the dairy cows are similar in winter and distinct in summer in tropical conditions.


Assuntos
Regulação da Temperatura Corporal , Temperatura Alta , Animais , Bovinos , Feminino , Umidade , Lactação , Estações do Ano , Temperatura Ambiente
7.
Diving Hyperb Med ; 49(4): 266-275, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31828745

RESUMO

INTRODUCTION: The purpose of the study was to evaluate the thermal protection provided by a 2-3 mm surfing wet suit during at least two hours of fin diving in shallow water with a temperature of 16-20°C. We examined the effect of wearing the suit while diving in cold water on cognitive performance, muscle strength, and hand motor function. METHODS: Subjects were six male well-trained rebreather divers, 19-23 years old, acclimatised to cold. They attended the laboratory on three separate occasions, when we conducted the experiment at one of three temperatures, 16, 18, and 20°C. Core temperature (gastrointestinal system), skin temperature, oxygen consumption, and cold perception were evaluated during the test. Before and immediately after the dives, subjects performed a series of cognitive, manual dexterity, and muscle strength tests. RESULTS: Core temperature decreased by 0.35-0.81°C over the two hours at all three water temperatures. No subject reached a core temperature below 35°C. The decrease in upper body skin temperature during the two hour dive ranged between 5.97 and 8.41°C (P < 0.05). Two hours diving in 16-20°C water resulted in a significant increase in the time taken to perform the task of unlinking and reassembling four shackles (∼30% longer, P < 0.05). No effect was found on the cognitive or muscle strength tests. CONCLUSIONS: A 2-3 mm wet suit provides adequate thermal protection in trained and cold-acclimatised young males engaged in active diving in shallow water with a temperature of 16°C and above.


Assuntos
Cognição/fisiologia , Temperatura Baixa , Mergulho , Força Muscular/fisiologia , Roupa de Proteção , Regulação da Temperatura Corporal , Mergulho/fisiologia , Mãos/fisiologia , Força da Mão/fisiologia , Humanos , Masculino , Destreza Motora/fisiologia , Consumo de Oxigênio , Temperatura Ambiente , Água
8.
PLoS One ; 14(12): e0226399, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31856183

RESUMO

Alterations in thermal niches have been widely associated with the Anthropocene erosion of reptiles' diversity. They entail potential physiological constraints for organisms' performance, which can lead to activity restrictions and impact fitness and demography. Reptiles are ectotherms which rely on seasonal periodicity to maximize the performance of biological functions. Despite it, the ecological implications of shifts in local temperatures are barely explored at the seasonal scale. This study aims to assess how changes in air temperature and substrate temperature affect the activity, body temperature (Tb) and thermoregulation patterns of the sand lizard, Liolaemus arambarensis (an endangered, microendemic species from southern Brazil), throughout a four-year period. Field surveys were conducted monthly on a restricted population in a sand-dune habitat. The annual fluctuations of the seasonal temperatures led to significant changes in the activity and Tb of L. arambarensis and shaped thermoregulation trends, suggesting biological plasticity as a key factor in the face of such variability. Lizards tended to maintain seasonal Tb in mild and harsh seasons through increased warming/cooling efforts. Anomalous winter conditions seemed especially critical for individual performance due to their apparent high impact favouring/constraining activity. Activity and thermoregulation were inhibited in frigid winters, probably due to a vulnerable physiology to intense cold spells determined by higher preferred body temperatures than Tb. Our results warn of a complex sensitivity in lizards to anomalous seasonal temperatures, which are potentially enhanced by climate change. The current work highlights the importance of multiannual biomonitoring to disentangle long-term responses in the thermal biology of reptiles and, thereby, to integrate conservation needs in the scope of global change.


Assuntos
Regulação da Temperatura Corporal , Lagartos/fisiologia , Estações do Ano , Temperatura Ambiente , Clima Tropical , Animais , Fatores de Tempo
9.
Med. intensiva (Madr., Ed. impr.) ; 43(9): 556-568, dic. 2019. graf
Artigo em Espanhol | IBECS | ID: ibc-185902

RESUMO

La presente revisión narrativa se centra en el diagnóstico, el tratamiento y la gestión de la hipotermia accidental. Si bien todos estos procesos son continuos, en el presente manuscrito las recomendaciones se organizan con fines descriptivos en prehospitalarias y hospitalarias. En el ámbito prehospitalario se recomienda: a) reanimación de alta calidad de toda víctima en parada cardiaca, independientemente de la temperatura corporal; b) instaurar medidas para detener la pérdida de calor; c) iniciar el recalentamiento; d) prevenir el colapso del rescate y el efecto de recaída (afterdrop) y e) elegir adecuadamente el hospital de referencia de acuerdo con la situación clínica y hemodinámica de la víctima. El soporte vital extracorpóreo ha revolucionado, con tasas de supervivencia que han llegado al 100%, el recalentamiento de víctimas con inestabilidad hemodinámica o paro cardiaco. Las nuevas evidencias indican que la gestión de la hipotermia accidental ha evolucionado y ha conseguido mejorar sustancialmente el pronóstico final


A narrative review is presented on the diagnosis, treatment and management of accidental hypothermia. Although all these processes form a continuum, for descriptive purposes in this manuscript the recommendations are organized into the prehospital and in-hospital settings. At prehospital level, it is advised to: a) perform high-quality cardiopulmonary resuscitation for cardiac arrest patients, regardless of body temperature; b) establish measures to minimize further cooling; c) initiate rewarming; d) prevent rescue collapse and continued cooling (afterdrop); and (e) select the appropriate hospital based on the clinical and hemodynamic situation of the patient. Extracorporeal life support has revolutionized rewarming of the hemodynamically unstable victim or patients suffering cardiac arrest, with survival rates of up to 100%. The new evidences indicate that the management of accidental hypothermia has evolved favorably, with substantial improvement of the final outcomes


Assuntos
Humanos , Hipotermia/diagnóstico , Hipotermia/tratamento farmacológico , Medicina Narrativa , Reanimação Cardiopulmonar/métodos , Reaquecimento/métodos , Mortalidade Hospitalar , Temperatura Corporal/fisiologia , Regulação da Temperatura Corporal , Esfriamento , Avalanches , Assistência Pré-Hospitalar/métodos , Hidratação
10.
J Sports Med Phys Fitness ; 59(10): 1601-1607, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31694361

RESUMO

BACKGROUND: Outdoor exercise often proceeds in rainy conditions. However, there are very few studies reporting the physiological effects of cold with rain or wet-cold exposure on humans during exercise. The purpose of this study was to investigate the effects of rain on physiological responses during running exercise at 80% V̇Omax in the cold. METHODS: Twelve healthy men (age: 21.7±3.3 years; height: 1.760±0.085 m; body weight: 68.8±7.1 kg; maximal oxygen consumption: 67.3±5.00 mL/kg/min) exercised on a treadmill at 80% V̇Omax intensity for 60 minutes with rain (RAIN) or not (CON) at 5 °C. RESULTS: Rectal temperature was significantly lower in RAIN than in CON at 10, 40, 50, and 60 minutes (P<0.05). Mean weighted skin temperature was significantly lower in RAIN than in CON during exercise (P<0.05). Oxygen consumption and rating of perceived exertion were significantly higher in RAIN than in CON at 50 and 60 minutes (P<0.05). Plasma lactate was significantly higher in RAIN than in CON at 10 minutes and from 40 to 60 minutes (P<0.05). Plasma norepinephrine levels were significantly higher in RAIN than in CON at 10 minutes and from 40 to 60 minutes (P<0.05). CONCLUSIONS: These results suggest that rain increased heat loss during the early phase of exercise in the cold, then heat production increased and transiently suppressed cold stress. However, with time, body heat loss intensified due to increasing wet area, and then energy expenditure and plasma lactate increased due to cold stress. Therefore, rain may decrease exercise performance and affect sport safety.


Assuntos
Temperatura Baixa/efeitos adversos , Metabolismo Energético/fisiologia , Chuva , Corrida/fisiologia , Adolescente , Adulto , Regulação da Temperatura Corporal/fisiologia , Estudos de Casos e Controles , Teste de Esforço/métodos , Humanos , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio/fisiologia , Temperatura Cutânea , Adulto Jovem
11.
Oecologia ; 191(4): 817-827, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31679039

RESUMO

A classic question in evolutionary biology is whether behavioral flexibility hastens or hinders evolutionary change. The latter idea, that behavior reduces the number of environmental states experienced by an organism and buffers that organism against selection, has been dubbed the "Bogert Effect" after Charles Bogert, the biologist who first popularized the phenomenon using data from lizards. The Bogert Effect is pervasive when traits like body temperature, which tend to be invariant across space in species that behaviorally thermoregulate, are considered. Nevertheless, behavioral thermoregulation decreases or stops when spatial variation in operative temperature is low. We compared environmental temperatures, thermoregulatory behavior, and a suite of physiological and morphological traits between two populations of the southern rock agama (Agama atra) in South Africa that experience different climatic regimes. Individuals from both populations thermoregulated efficiently, maintaining body temperatures within their preferred temperature range throughout most of their activity cycle. Nevertheless, they differed in the thermal sensitivity of resting metabolic rate at cooler body temperatures and in morphology. Our results support the common assertion that thermoregulatory behavior may prevent divergence in traits like field-active body temperature, which are measured during periods of high environmental heterogeneity. Nevertheless, we show that other traits may be free to diverge if they are under selection during times when environments are homogenous. We argue that the importance of the Bogert Effect is critically dependent on the nature of environmental heterogeneity and will therefore be relevant to some traits and irrelevant to others in many populations.


Assuntos
Regulação da Temperatura Corporal , Lagartos , Animais , Evolução Biológica , África do Sul , Temperatura Ambiente
12.
Naturwissenschaften ; 106(9-10): 55, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31612286

RESUMO

Sexual signals serve as an honest indicator of individual quality, reflecting either developmental and/or maintenance costs. A possible underlying physiological mechanism is oxidative stress, which could mediate energy trade-offs between sexual signals and other quality traits. In ectotherms, thermal performance acts as a key indicator of individual quality and influence signal intensity. We investigated how oxidative state is reflected in visual signals of lizards from different thermal habitats. According to our hypothesis, efficient thermoregulation requires different strategies in different thermal environments. In a habitat with predictable temperature changes, animals are less exposed to suboptimal temperature ranges and selection will, therefore, be stronger on the maximum oxidative damage at optimal body temperature. Contrarily, in a habitat with rather stochastic thermal shifts, individuals are often constricted by suboptimal thermal conditions, and oxidative damage can be limiting on a wide temperature range. We used Iberolacerta cyreni and Psammodromus algirus inhabiting stochastic and predictable thermal environments respectively. We examined two aspects of oxidative stress: the level of reactive oxygen metabolites at the preferred temperature (maximal ROM) and the temperature range in which animals produce at least 80% of the maximum level of reactive oxygen metabolites (effective ROM range). In I. cyreni, we found that duller coloration was related to a wider effective ROM range, while expression of coloration in P. algirus was negatively correlated with the maximal ROM. Our results suggest that different thermal constraints affect different aspects of oxidative damage which can indicate individual quality and are, therefore, represented in sexual ornaments.


Assuntos
Ecossistema , Lagartos/fisiologia , Estresse Oxidativo/fisiologia , Pigmentação/fisiologia , Comunicação Animal , Animais , Regulação da Temperatura Corporal , Feminino , Masculino , Espécies Reativas de Oxigênio , Caracteres Sexuais , Temperatura Ambiente
14.
Arq. bras. med. vet. zootec. (Online) ; 71(5): 1750-1758, set.-out. 2019. tab, graf, ilus
Artigo em Português | LILACS, VETINDEX | ID: biblio-1038659

RESUMO

The effects of housing lactating sows at different locations in a shed with evaporative cooling system (ECS) on their thermoregulation and reproductive and productive performance of the sow and the litter in summer were determined. 34 females were used in the three lines of cages at these locations: near the pad cooling; in the middle of the shed and near the exhaust fans. The air temperature and the temperature and humidity index (THI) were lower near the pad cooling (22.38ºC, 71.84) than the middle (24.56ºC, 74.82) and near the exhaust fans (25.00°C, 75.62). Respiratory rate, rectal and surface temperatures were lower in sows near the pad cooling (43.67 breaths.min -1 , 38.40°C; 29.51°C) than in the center (52.04 breaths.min -1 ; 38.48ºC; 32.02ºC) and near the exhaust fans (56.38 breaths.min-1, 38.93ºC; 32.52ºC). The backfat thickness, the weaning-estrus interval and daily average consumption of the sows, number of weaning piglets, corporal mass and daily average gain of the piglets were not influenced by the location of housing in the shed. Lactating sows housed in the middle and near the exhaust fans in the ECS presented increased thermoregulation physiological variables, however, this did not impair the performance.(AU)


Assuntos
Animais , Feminino , Gravidez , Suínos/crescimento & desenvolvimento , Temperatura Ambiente , Regulação da Temperatura Corporal/fisiologia , Bem-Estar do Animal/organização & administração , Transtornos de Estresse por Calor/prevenção & controle , Abrigo para Animais/organização & administração
15.
Nat Commun ; 10(1): 4077, 2019 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-31501432

RESUMO

Climatic conditions changing over time and space shape the evolution of organisms at multiple levels, including temperate lizards in the family Lacertidae. Here we reconstruct a dated phylogenetic tree of 262 lacertid species based on a supermatrix relying on novel phylogenomic datasets and fossil calibrations. Diversification of lacertids was accompanied by an increasing disparity among occupied bioclimatic niches, especially in the last 10 Ma, during a period of progressive global cooling. Temperate species also underwent a genome-wide slowdown in molecular substitution rates compared to tropical and desert-adapted lacertids. Evaporative water loss and preferred temperature are correlated with bioclimatic parameters, indicating physiological adaptations to climate. Tropical, but also some populations of cool-adapted species experience maximum temperatures close to their preferred temperatures. We hypothesize these species-specific physiological preferences may constitute a handicap to prevail under rapid global warming, and contribute to explaining local lizard extinctions in cool and humid climates.


Assuntos
Meio Ambiente , Variação Genética , Genoma , Lagartos/genética , Lagartos/fisiologia , Temperatura Ambiente , Animais , Regulação da Temperatura Corporal/fisiologia , Clima , Evolução Molecular , Filogenia
16.
Biol Lett ; 15(9): 20190530, 2019 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-31506035

RESUMO

Many endothermic animals experience variable limb temperatures, even as they tightly regulate core temperature. The limbs are often cooler than the core at rest, but because the large locomotor muscles of the limbs produce heat during exercise, they are thought to operate at or above core temperature during activity. Bats, small-bodied flying mammals with greatly elongated forelimbs, possess wings with large surfaces lacking any insulating fur. We hypothesized that during flight the relatively small muscles that move the elbow and wrist operate below core body temperature because of elevated heat loss. We measured muscle temperature continuously in the small fruit bat Carollia perspicillata before and during wind tunnel flights, and discretely in diverse bats at rest in Belize. We found that bats maintained high rectal temperatures, but that there was a steep proximal-to-distal gradient in wing muscle temperature. Forearm muscles were 4-6°C cooler than rectal temperature at rest and approximately 12°C cooler during flights at an air temperature of 22°C. These findings invite further study into how bats and other endotherms maintain locomotor performance in variable environments, when some muscles may be operating at low temperatures that are expected to slow contractile properties.


Assuntos
Quirópteros , Animais , Regulação da Temperatura Corporal , Voo Animal , Contração Muscular , Asas de Animais
17.
Undersea Hyperb Med ; 46(4): 429-435, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31509899

RESUMO

Introduction: It is vital to protect divers from the cold, particularly in Arctic conditions. The insulating gas layer within the drysuit is crucial for reducing heat loss. The technical diving community has long claimed the superiority of argon over air as an insulating gas. Although argon is widely used, previous studies have shown no significant differences between the two gases. Owing to its lower heat conductivity, argon should be a better thermal insulating gas than air. Methods: The study aimed to determine whether argon is beneficial for reducing heat loss in divers during development of military drysuit diving equipment in Arctic water temperatures. Four divers completed 14 dives, each lasting 45 minutes: seven dives used air insulation and seven used argon insulation. Rectal and eight skin temperatures were measured from which changes in calculated mean body temperature (MBT) were assessed. Results: There was a significant reduction in area weighted skin temperature over time (0-45 minute) on air dives (ΔTskin = -4.16°C, SE = 0.445, P ⟨ 0.001). On argon dives the reduction was significantly smaller compared to air dives (difference between groups = 2.26°C, SE = 0.358, P ⟨ 0.001). There were no significant changes in rectal temperatures, nor was a significant difference seen between groups. Conclusion: Compared to air, argon may be superior as a drysuit insulating gas in Arctic water temperatures for some divers. Argon used as insulating gas can make diving safer and may diminish the risks of fatal diving accidents and occupational hazard risks in professional diving.


Assuntos
Ar , Argônio , Mergulho , Roupa de Proteção , Temperatura Cutânea , Condutividade Térmica , Adulto , Regiões Árticas , Regulação da Temperatura Corporal , Temperatura Baixa , Desenho de Equipamento/métodos , Finlândia , Humanos , Masculino , Pessoa de Meia-Idade , Militares , Estudos Retrospectivos
18.
Physiol Biochem Zool ; 92(6): 544-553, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31560253

RESUMO

Archaic mammals became exclusively nocturnal by the Late Triassic, and today, the majority of extant mammals remain nocturnal. Although there is ample morphological and physiological evidence supporting Late Mesozoic nocturnalism, a succinct hypothesis for why mammals became nocturnal remains elusive. Here, I propose a hypothesis that, with the onset of body size miniaturization in the Triassic and the concomitant evolution of fur and increased mass-specific metabolic rate and hence body temperature, small mammals became obligatorily nocturnal in order to avoid poor sperm quality, hyperthermia, and high rates of evaporative water loss and to maximize foraging time. The hypothesis hinges heavily on the assumption that, with the absence of externalized testes, the maximum optimum temperature of about 36°C for spermatogenesis was subject to strong stabilizing selection that placed a ceiling on increases in metabolic rate and body temperature. Heat-dissipating capacity during the daytime during the Triassic, Jurassic, and Cretaceous was thereby compromised. The release from the constraint of the optimum temperature of spermatogenesis occurred in placental mammals only with the advent of the externalization of testes in the scrotum in Boreotheria in the Cenozoic or, with the recent claim that the scrotum is plesiomorphic in mammals, as early as the Jurassic with the origin of the marsupials.


Assuntos
Evolução Biológica , Ritmo Circadiano , Mamíferos , Espermatozoides/fisiologia , Animais , Regulação da Temperatura Corporal/fisiologia , Genitália Masculina/fisiologia , Masculino
19.
Zhonghua Wei Zhong Bing Ji Jiu Yi Xue ; 31(8): 1028-1032, 2019 Aug.
Artigo em Chinês | MEDLINE | ID: mdl-31537233

RESUMO

OBJECTIVE: To explore the effects of different fluid replenishment methods on the internal environment, body thermal regulatory response and severe heatstroke of 5-km armed cross-country training soldiers. METHODS: A Special Force officers and soldiers who participated in 5-km armed cross-country training (2-3 times a week, 25-30 minutes each time for 3 weeks) during summer training from June to July in 2018 were enrolled, and they were divided into three groups according to the random number table, with 300 trainees in each group. 200 mL of drinking fluids were given to each group 15 minutes before and after each 5-km armed cross-country training: A group with boiled water, B group with purified water, and C group with beverage prepared by pharmaceutical laboratory of the 990th Hospital of PLA Joint Logistics Support Force (100 mL containing 6 g carbohydrates, 42 mg sodium, and 11 mg potassium). The venous blood was collected before and after the last training or during the onset of severe heatstroke to do the following tests: serum cardiac troponin I (cTnI, chemiluminescence), MB isoenzyme of creatine kinase (CK-MB, immunosuppressive), serum creatinine (SCr, enzymatic method), urea nitrogen (BUN, enzymatic method), alanine aminotransferase (ALT, tryptase), aspartate transaminase (AST, tryptase), and Na+, K+, Cl- (electrode method). The heart rate (HR) and core temperature (Tc, anal temperature) were monitored at the same time. The amount of sweat in training and the occurrence of severe heatstroke were also recorded. RESULTS: There was no significant difference in heart, liver, kidney function, electrolyte and body heat regulation reaction among three groups of 5-km armed cross-country trainees before training. Compared with before training, the levels of serum cTnI, CK-MB, SCr, BUN, ALT, AST, HR and Tc were significantly increased after training or during the onset of severe heatstroke in three groups, while the contents of Na+, K+, Cl- were significantly decreased, but the increase or decrease of group C was relatively smaller compared with group A and group B [cTnI (µg/L): 0.9 (0.6, 1.4) vs. 1.1 (0.7, 2.8), 1.0 (0.6, 3.3); CK-MB (U/L): 7.0 (5.0, 11.0) vs. 9.0 (6.0, 14.5), 8.0 (6.0, 15.0); SCr (µmol/L): 92.09±18.64 vs. 102.78±18.77, 103.64±20.07; BUN (mmol/L): 7 (6, 9) vs. 9 (8, 11), 10 (8, 13); ALT (U/L): 27 (22, 34) vs. 36 (30, 43), 34 (27, 43); AST (U/L): 37 (31, 48) vs. 41 (34, 50), 39 (34, 51); HR (bpm): 87.01±17.07 vs. 95.88±21.06, 96.59±22.04; Tc (centigrade): 37.73±0.81 vs. 38.03±1.05, 38.10±1.04; Na+ (mmol/L): 150.14±3.86 vs. 144.18±8.89, 144.04±9.39; K+ (mmol/L): 4.32±0.57 vs. 4.15±0.62, 4.13±0.51; Cl- (mmol/L): 100.43±3.71 vs. 98.42±4.24, 98.41±4.58; all P < 0.01]. The incidence of severe heatstroke in group C was significantly lower than that in group A and group B [1.67% (5/300) vs. 5.00% (15/300), 5.33% (16/300), χ2 = 6.424, P = 0.040]. There was no significant difference in sweating volume in groups A, B, C (g: 370.47±48.71, 370.85±50.66, 370.17±50.21, F = 0.014, P = 0.986). There was no significant difference in the above indexes between group A and group B (all P > 0.05). Bi-classification Logistic regression analysis showed that the increase of HR, Tc and excessive loss of Na+, K+, Cl- were risk factors for severe heatstroke [odds ratio (OR) was 0.848, 0.138, 1.565, 17.996 and 2.328 respectively, all P < 0.01]. CONCLUSIONS: Timely supplementation of carbohydrate, sodium and potassium ions can effectively change the internal environment and body heat regulation reaction of 5-km armed cross-country trainees, so as to reduce the occurrence of severe heatstroke. The increases of HR, Tc and excessive loss of Na+, K+, Cl- are risk factors for severe heatstroke.


Assuntos
Hidratação/métodos , Golpe de Calor , Militares , Regulação da Temperatura Corporal , Creatina Quinase Forma MB , Eletrólitos , Temperatura Alta , Humanos
20.
J Anim Sci ; 97(10): 4085-4092, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31396618

RESUMO

This experiment compared physiological and productive responses in finishing beef cattle managed under heat stress conditions, and supplemented (SUPP) or not (CON) with an immunomodulatory feed ingredient (Omnigen-AF; Phibro Animal Health, Teaneck, NJ). Crossbred yearling cattle (¾ Bos taurus × » Bos indicus; 64 heifers and 64 steers) were ranked by initial body weight (BW) (440 ± 3 kg) and sex, and allocated to 1 of 16 unshaded drylot pens (8 heifers or steers/pen). Pens within sex were randomly assigned to receive SUPP or CON (n = 8/treatment). Cattle received a total-mixed ration (91% concentrate inclusion and 1.21 Mcal/kg of net energy for gain; dry matter [DM basis]) during the experiment (day 0 to 106). The immunomodulatory feed was offered as a top-dress to SUPP pens (56 g/d per animal; as-fed basis) beginning on day 7. Cattle BW were recorded on day 0, 14, 28, 42, 56, 70, 84, 98, and 106. Feed intake was evaluated from each pen by recording feed offer daily and refusals biweekly. Intravaginal temperature of heifers was recorded hourly from day 1 to 6, 29 to 41, and 85 to 97. Environmental temperature humidity index (THI) was also recorded hourly throughout the experiment, and averaged 79.8 ± 0.6. Concurrently with BW assessment, hair samples from the tail-switch were collected (3 animals/pen) for analysis of hair cortisol concentrations. Blood samples were collected on day 0, 28, 56, 84, and 106 from all animals for plasma extraction. Whole blood was collected on day 0, 56, and 106 (3 animals/pen) for analysis of heat shock protein (HSP) 70 and HSP72 mRNA expression. Cattle were slaughtered on day 107 at a commercial packing facility. Results obtained prior to day 7 served as independent covariate for each respective analysis. Heifers receiving SUPP had less (P ≤ 0.05) vaginal temperature from 1500 to 1900 h across sampling days (treatment × hour, P < 0.01; 39.05 vs. 39.19 °C, respectively; SEM = 0.04), when THI ranged from 85.3 to 90.1. Expression of HSP70 and HSP72 was less (P ≥ 0.03) for SUPP cattle on day 106 (22.6- vs. 51.5-fold effect for HSP70, SEM = 9.7, and 11.0- vs. 32.8-fold effect for HSP72; treatment × day, P ≤ 0.04). No treatment effects were detected (P ≥ 0.22) for performance, carcass traits, plasma concentrations of cortisol and haptoglobin, or hair cortisol concentrations. Results from this study suggest that SUPP ameliorated hyperthermia in finishing cattle exposed to heat stress conditions, but such benefit was not sufficient to improve productive responses.


Assuntos
Ração Animal , Regulação da Temperatura Corporal , Bovinos/fisiologia , Suplementos Nutricionais , Transtornos de Estresse por Calor/veterinária , Imunomodulação/fisiologia , Ração Animal/análise , Animais , Peso Corporal , Dieta/veterinária , Feminino , Haptoglobinas/análise , Transtornos de Estresse por Calor/prevenção & controle , Cavalos , Umidade , Hidrocortisona/sangue , Masculino , Distribuição Aleatória , Carne Vermelha/análise , Temperatura Ambiente
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