Predictive growth budgets in terns and gulls

Energy budgets for nestling growth are presented for sandwich tern Sterna sandvicensis, common tern S. hirundo, Arctic tern S. paradisaea, and herring gull Larus argentatus. Energy used in the production of body tissue averaged 27% (of which 7% for biosynthesis) while BMR accounted for 45%, the remainder being cost of activity and thermoregulation (28%). Where quantified, cost of temperature regulation accounted for only 10% of the total expenditure under field conditions. A regression made of metabolic energy (ME) intake over the entire nestling period against body mass of the fledgling based on eight studies of gulls and terns resulted in ME=35.14×M1.0105. -from Authors

Fluid intake, hydration, work physiology of wildfire fighters working in the heat over consecutive days

PURPOSE: (i) To evaluate firefighters' pre- and post-shift hydration status across two shifts of wildfire suppression work in hot weather conditions. (ii) To document firefighters' fluid intake during and between two shifts of wildfire suppression work. (iii) To compare firefighters' heart rate, activity, rating of perceived exertion (RPE), and core temperature across the two consecutive shifts of wildfire suppression work. METHOD: Across two consecutive days, 12 salaried firefighters' hydration status was measured immediately pre- and post-shift. Hydration status was also measured 2h post-shift. RPE was also measured immediately post-shift on each day. Work activity, heart rate, and core temperature were logged continuously during each shift. Ten firefighters also manually recorded their food and fluid intake before, during, and after both fireground shifts. RESULTS: Firefighters were not euhydrated at all measurement points on Day one (292±1 mOsm l(-1)) and euhydrated across these same time points on Day two (289±0.5 mOsm l(-1)). Fluid consumption following firefighters' shift on Day one (1792±1134ml) trended (P = 0.08) higher than Day two (1108±1142ml). Daily total fluid intake was not different (P = 0.27), averaging 6443±1941ml across both days. Core temperature and the time spent ≥ 70%HRmax were both elevated on Day one (when firefighters were not euhydrated). Firefighters' work activity profile was not different between both days of work. CONCLUSION: There was no difference in firefighters' pre- to post-shift hydration within each shift, suggesting ad libitum drinking was at least sufficient to maintain pre-shift hydration status, even in hot conditions. Firefighters' relative hypohydration on Day one (despite a slightly lower ambient temperature) may have been associated with elevations in core temperature, more time in the higher heart rate zones, and 'post-shift' RPE.

The double sensor-a non-invasive device to continuously monitor core temperature in humans on earth and in space

The objective of our study was to establish whether rectal temperature recordings in humans could be replaced by a non-invasive skin temperature sensor combined with a heat flux sensor (Double Sensor) located at the forehead to monitor core body temperature changes due to circadian rhythms. Rectal and Double Sensor data were collected continuously for 24h in seven men undertaking strict head-down tilt bed-rest. Individual differences between the two techniques varied between -0.72 and +0.55 degrees C. Nonetheless, when temperature data were approximated by cosinor analysis in order to compare circadian rhythm profiles between methods, it was observed that there were no significant differences between mesor, amplitude, and acrophase (P>0.310). It was therefore concluded that the Double Sensor technology is presently not accurate enough for performing single individual core body temperature measurements under resting conditions at normal ambient room temperature. Yet, it seems to be a valid, non-invasive alternative for monitoring circadian rhythm profiles.

Climate-related spatial and temporal variation in bill morphology over the past century in Australian parrots

Aim: Allen's rule posits that the appendages of endothermic organisms will be larger in warmer climates to allow for dumping of heat loads. Given a link between appendage size and climate, we tested the prediction that climate change has driven the evolution of larger bills in birds, resulting in measurable changes over the recent past. Location: Australia. Methods: We explored geographical and temporal variation in bill surface area of five Australian parrot species to determine whether individuals from warmer climates have larger bills, and whether there have been increases in bill surface area over time, consistent with climatic warming. Measurements were obtained from museum specimens dating from 1871 to 2008. These data were then related to geographical location, collection date and locality-specific climate data, in order to construct and compare models of spatio-temporal and climate-related variation in bill morphology. Results: There have been increases in bill surface area in mulga parrots (Psephotus varius), gang-gang cockatoos (Callocephalon fimbriatum), red-rumped parrots (Psephotus haematonotus) and male crimson rosellas (Platycercus elegans), equating to a c. 4-10% increase in bill surface area since 1871. Average maximum summer temperature in the 5 years prior to specimen collection also positively predicted bill surface area in mulga parrots, red-rumped parrots and crimson rosellas, consistent with Allen's rule. With the exception of red-rumped parrots, however, models with geographical location and year of collection were still better predictors of bill surface area than local climate at the date of collection. Main conclusions: Our analysis provides evidence that four species of parrot have exhibited adaptive change in bills over the past century potentially mitigating the thermal stress caused by climatic warming. Although consistent with the predicted effects of climate change, the temporal patterns we observe may have additional causes, however, such as changes in primary productivity, habitat or food availability.

Short duration heat acclimation in Australian football players

This study examined if five sessions of short duration (27 min), high intensity, interval training (HIIT) in the heat over a nine day period would induce heat acclimation in Australian football (AF) players. Fourteen professional AF players were matched for VO2peak (mL∙kg-1∙min-1) and randomly allocated into either a heat acclimation (Acc) (n = 7) or Control (Con) group (n = 7). The Acc completed five cycle ergometer HIIT sessions within a nine day period on a cycle ergometer in the heat (38.7 ± 0.5 °C; 34.4 ± 1.3 % RH), whereas Con trained in thermo-neutral conditions (22.3 ± 0.2 °C; 35.8 ± 0. % RH). Four days prior and two days post HIIT participants undertook a 30 min constant load cycling test at 60% V̇O2peak in the heat (37.9 ± 0.1 °C; 28.5 ± 0.7 % RH) during which VO2, blood lactate concentration ([Lac-]), heart rate (HR), rating of perceived exertion (RPE), thermal comfort, core and skin temperatures were measured. Heat acclimation resulted in reduced RPE, thermal comfort and [Lac-] (all p < 0.05) during the submaximal exercise test in the heat. Heart rate was lower (p = 0.007) after HIIT, in both groups. Heat acclimation did not influence any other measured variables. In conclusion, five short duration HIIT sessions in hot dry conditions induced limited heat acclimation responses in AF players during the in-season competition phase. In practice, the heat acclimation protocol can be implemented in a professional team environment; however the physiological adaptations result-ing from such a protocol were limited.

Respiratory heat loss in the sheep: a comprehensive model

A model is presented for the respiratory heat loss in sheep, considering both the sensible heat lost by convection (C-R) and the latent heat eliminated by evaporation (E-R). A practical method is described for the estimation of the tidal volume as a function of the respiratory rate. Equations for C-R and E-R are developed and the relative importance of both heat transfer mechanisms is discussed. At air temperatures up to 30 degreesC sheep have the least respiratory heat loss at air vapour pressures above 1.6 kPa. At an ambient temperature of 40 degreesC respiratory loss of sensible heat can be nil; for higher temperatures the transfer by convection is negative and thus heat is gained. Convection is a mechanism of minor importance for the respiratory heat transfer in sheep at environmental temperatures above 30 degreesC. These observations show the importance of respiratory latent heat loss for thermoregulation of sheep in hot climates.

Role of Locus coeruleus noradrenergic neurons in cardiorespiratory and thermal control during hypoxia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Role of preoptic opioid receptors in the body temperature reduction during hypoxia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cold-induced enhancement of avian uncoupling protein expression, heat production, and triiodothyronine concentrations in broiler chicks

The relationships among avian uncoupling protein (avUCP) mRNA expression, heat production, and thyroid hormone metabolism were investigated in 7-14-day-old broiler chicks (Gallus gallus) exposed to a low temperature (cold-exposed chicks, CE) or a thermoneutral temperature (TN). After 7 days of exposure, CE chicks exhibited higher heat production (+83%, P < 0.01), avUCP mRNA expression (+20%, P < 0.01), and circulating triiodothyronine (T-3) levels (+104%, P = 0.07) for non-statistically different body weights and feed intake between 3 and 7 days of exposure as compared to TN chicks. Plasma thyroxine (T-4) concentration was clearly decreased in CE chicks (-33%, P = 0.06). The lower hepatic inner-ring deiodination activity (-47%) and the higher renal outer-ring deiodination activity (+75%) measured in CE compared to TN chicks could partly account for their higher plasma T3 concentrations. This study describes for the first time the induction of avUCP mRNA expression by low temperature in chickens, as it has been previously shown in ducklings, and supports the possible involvement of avUCP in avian thermogenesis. (C) 2003 Elsevier B.V. (USA). All rights reserved.

Latent heat loss of Holstein cows in a tropical environment: a prediction model

Nove vacas Holandesas lactantes com 526 ± 5 kg de peso corporal (cinco predominantemente pretas e quatro predominantemente brancas), criadas em região tropical e manejadas em pastagens, foram observadas com os objetivos de determinar simultaneamente as taxas de evaporação cutânea e respiratória em ambiente tropical e desenvolver modelos de predição. Para a medição da perda de calor latente pela superfície corporal, utilizou-se uma cápsula ventilada e, para a perda por respiração, utilizou-se uma máscara facial. Os resultados mostraram que as vacas que tinham maior peso corporal (classe 2 e 3) apresentaram maiores taxas evaporativas. Quando a temperatura do ar aumentou de 10 para 36ºC e a umidade relativa do ar caiu de 90 para 30%, a eliminação de calor por evaporação respiratória aumentou de aproximadamente 5 para 57 W m-2 e a evaporação na superfície corporal passou de 30 para 350 W m-2. Esses resultados confirmam que a eliminação de calor latente é o principal mecanismo de perda de energia térmica sob altas temperaturas (>30ºC); a evaporação cutânea é a maior via e corresponde a aproximadamente 85% da perda total de calor, enquanto o restante é eliminado pelo sistema respiratório. O modelo para predizer o fluxo de perda de calor latente baseado em variáveis fisiológicas e ambientais pode ser utilizado para estimar a contribuição da evaporação na termorregulação, enquanto o modelo baseado somente na temperatura do ar deve ser usado apenas para a simples caracterização do processo evaporativo.

Latent heat loss of dairy cows in an equatorial semi-arid environment

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de algumas variáveis fisiológicas para avaliação do grau de adaptação de ovinos submetidos ao estresse por calor

Investigaram-se a temperatura retal, a freqüência respiratória e a taxa de evaporação total de ovinos Corriedale sob três temperaturas ambientes, visando uma melhor compreensão dos mecanismos de termorregulação desses animais. Inicialmente, 21 animais adultos foram alojados em câmara climática à temperatura de 45ºC, e pressão parcial de vapor (PV) variável, registrando-se a freqüência respiratória (FR) e a temperatura retal (TR). Baseando-se na FR e TR, foram selecionados 10 animais, cinco com os valores mais baixos, assumindo-os como mais adaptados ao calor (grupo 1) e cinco com valores mais altos, assumindo-os como menos adaptados (grupo 2). Os animais selecionados foram mantidos em câmara climática, onde mediram-se novamente TR, FR e taxa de evaporacão total (TET), sob 20, 30 e 40ºC de temperatura do ar e PV variável. Não houve diferença estatística entre os grupos classificados, para todas as variáveis medidas. Concluiu-se que a utilização das variáveis fisiológicas TR e FR como parâmetros únicos para a seleção destes animais não é suficiente para avaliar o grau de adaptação a temperaturas elevadas.

Variação anual de hormônios tireoideanos e características termorreguladoras de vacas leiteiras em ambiente quente

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preoperative warming combined with intraoperative skin-surface warming does not avoid hypothermia caused by spinal anesthesia in patients with midazolam premedication

CONTEXTO E OBJETIVO: Hipotermia inadvertida no perioperatório é freqüente durante anestesia subaracnóidea e após a administração de midazolam. O objetivo foi avaliar os efeitos do aquecimento da pele no intra-operatório, associado ou não ao aquecimento da pele durante o período de 45 minutos no pré-operatório, na prevenção de hipotermia intra- e pós-operatória determinada pela anestesia subaracnóidea em pacientes com medicação pré-anestésica com midazolam. TIPO DE ETUDO E LOCAL: Estudo prospectivo e aleatório, realizado no Hospital das Clínicas, Universidade Estadual Paulista (Unesp), Botucatu, SP. MÉTODOS: O estudo foi realizado em 30 pacientes com estado físico ASA (da Sociedade Norte-americana de Anestesiologistas) I e II submetidos à cirurgia eletiva do abdômen. Como medicação pré-anestésica, utilizou-se o midazolam, 7,5 mg via intramuscular (IM) e anestesia subaracnóidea padrão. em 10 pacientes (Gcontrole) utilizou-se isolamento térmico passivo; 10 pacientes (Gpré+intra) foram submetidos a aquecimento ativo no pré- e intra-operatório; e 10 pacientes (Gintra) foram aquecidos ativamente somente no intra-operatório. RESULTADOS: Após 45 minutos de aquecimento no pré-operatório, os pacientes do Gpré+intra apresentaram temperatura central mais elevada em relação aos dos grupos não aquecidos antes da anestesia (p < 0,05) mas não no início da cirurgia (p > 0,05). Os pacientes que receberam aquecimento no intra-operatório apresentaram temperatura central mais elevada no final da cirurgia em relação aos de Gcontrole (p < 0,05). Todos os pacientes estavam hipotérmicos na admissão da sala de recuperação pós-anestésica (temperatura central < 36º C). CONCLUSÕES: 45 minutos de aquecimento no pré-operatório combinado com aquecimento no intra- operatório não evita, mas minimiza a ocorrência de hipotermia determinada pela anestesia subaracnóidea em pacientes que receberam midazolam como medicação pré-anestésica.

Estufas climatizadas para experimentos ambientais com rãs, em gaiolas

Foram construídas seis estufas climatizadas, instaladas inicialmente no Ranário Experimental da Universidade Federal de Viçosa (UFV) e, posteriormente, no Ranário Experimental da Fundação Universidade Federal do Rio Grande, com o objetivo de realizar experimentos para avaliar os efeitos do ambiente sobre o desempenho de rãs em gaiolas de fibra de vidro. Ambientes com temperaturas de 25ºC e fotoperíodo de 12/12 horas de luz/horas de escuridão (h L/E) serviram para adaptação das rãs por 15 dias antes de cada experimento. Os tratamentos consistiram em simular ambientes com temperaturas variando de 20 a 35ºC e fotoperíodos de 8/16, 12/12 e 16/8 h L/E. Foram realizados experimentos com rã-touro (Rana catesbeiana Shaw, 1802) e rã-manteiga (Leptodactylus ocellatus Linnaeus, 1758). Nessas estufas foi possível estimar que: a) os maiores ganhos de peso de rã-touro foram obtidos entre 27,6 e 29,7ºC, com melhor crescimento entre 28,2 e 30,1ºC; para rã-manteiga os melhores ganhos e conversão alimentar foram observados a 28,6 e 28ºC, respectivamente; b) a temperatura interage com fotoperíodo sobre o desempenho das rãs e seu desenvolvimento gonadal; c) a 27,7ºC (temperatura de conforto térmico) haverá menos rãs dentro d'água; d) a maior temperatura cloacal de rã-touro, 32,1ºC no seco e 33,8ºC dentro d'água, a 35ºC, evidenciou que as rãs se termorregulam; e) os níveis de tetraiodotironina (T4) no plasma decrescem na temperatura de conforto térmico; f) rã-manteiga condiciona-se ao manejo de rotina, reunindo-se ao redor do cocho na hora da alimentação.