Shane K. Maloney

A comparison of subjective estimates of sleep with objective polysomnographic data in healthy men and women

Twenty healthy men and women had their sleep recorded objectively, using polysomnography on 3 nonconsecutive nights. Following each night, the subjects assessed their sleep onset latency and number of awakenings, subjectively. Self-ratings were compared with objective measures of sleep onset latency (SOL), calculated as the time from lights-out to the first continuous minute of stage 2 sleep, and the number of awakenings which lasted 1 minute or longer on the polysomnograms. Apart from the first night, the subjects overestimated the time that it took them to fall asleep, despite sleep onset being scored as the latency to stage 2, rather than stage 1 sleep. On all 3 nights, the subjects underestimated the number of awakenings when compared to objective criteria. Although the subjects were consistent in their errors of estimation of their sleep compared to polysomnographic assessments over the three nights, the between-individual variation was large, so that objective and subjective ratings of SOL and awakenings were not correlated. The young men and women in our study, who were free of medication or sleep complaints, perceived their sleep inaccurately when compared to objective polysomnographic recordings.

Adaptive heterothermy and selective brain cooling in arid-zone mammals.

Adaptive heterothermy and selective brain cooling are regarded as important thermal adaptations of large arid-zone mammals. Adaptive heterothermy, a process which reduces evaporation by storing body heat, ought to be enhanced by ambient heat load and by water deficit, but most mammals studied fail to show at least one of those attributes. Selective brain cooling, the reduction of brain temperature below arterial blood temperature, is most evident in artiodactyls, which possess a carotid rete, and traditionally has been considered to protect the brain during hyperthermia. The development of miniature ambulatory data loggers for recording body temperature allows the temperatures of free-living wild mammals to be measured in their natural habitats. All the African ungulates studied so far, in their natural habitats, do not exhibit adaptive heterothermy. They have low-amplitude nychthemeral rhythms of temperature, with mean body temperature over the night exceeding that over the day. Those with carotid retes (black wildebeest, springbok, eland) employ selective brain cooling but zebra, without a rete, do not. None of the rete ungulates, however, seems to employ selective brain cooling to prevent the brain overheating during exertional hyperthermia. Rather, they use it at rest, under moderate heat load, we believe in order to switch body heat loss from evaporative to non-evaporative routes.

Physiological Mechanisms in Coping with Climate Change

Although many studies have modeled the effects of climate change on future species distributions and extinctions, the theoretical approach most commonly used—climate envelope modeling—typically ignores the potential physiological capacity of animals to respond to climate change. We explore the consequences of the phenotypic plasticity available to animals, by examining physiological responses of free‐living animals in their natural habitats and by applying integrative, mechanistic models of heat exchange in invertebrates and humans. Specifically, we explore how behavioral, autonomic, and morphological modifications such as nocturnal activity, selective brain cooling, and body color may potentially serve as buffers to the consequences of climate change. Although some species may adapt to climate change through phenotypic plasticity, there are significant limits to this strategy. Furthermore, predictions of the response of organisms to changes in climate can be erroneous when modeled at large scales using coarse spatial or temporal data. Environmental heterogeneity can provide habitats suitable for species even though large‐scale changes in the climate might predict a species’ extinction. A detailed understanding of physiology, combined with integrative biophysical modeling and ecological manipulation, provides a powerful tool for predicting future ecological patterns and managing their consequences.

Reappraisal of the comparative cost of human locomotion using gait-specific allometric analyses

SUMMARY The alleged high net energy cost of running and low net energy cost of walking in humans have played an important role in the interpretation of the evolution of human bipedalism and the biomechanical determinants of the metabolic cost of locomotion. This study re-explores how the net metabolic energy cost of running and walking (J kg–1 m–1) in humans compares to that of animals of similar mass using new allometric analyses of previously published data. Firstly, this study shows that the use of the slope of the regression between the rate of energy expenditure and speed to calculate the net energy cost of locomotion overestimates the net cost of human running. Also, the net energy cost of human running is only 17% higher than that predicted based on their mass. This value is not exceptional given that over a quarter of the previously examined mammals and birds have a net energy cost of running that is 17% or more above their allometrically predicted value. Using a new allometric equation for the net energy cost of walking, this study also shows that human walking is 20% less expensive than predicted for their mass. Of the animals used to generate this equation, 25% have a relatively lower net cost of walking compared with their allometrically predicted value. This new walking allometric analysis also indicates that the scaling of the net energy cost of locomotion with body mass is gait dependent. In conclusion, the net costs of running and walking in humans are moderately different from those predicted from allometry and are not remarkable for an animal of its size.

Activity, blood temperature and brain temperature of free-ranging springbok

Abstract We used miniature data loggers to record temperature and activity in free-ranging springbok (Antidorcas marsupialis) naturally exposed to severe nocturnal cold and moderate diurnal heat. The animals were active throughout the day and night, with short rests; the intensity of activity increased during daylight. Arterial blood temperature, averaged over many days, exhibited a circadian rhythm with amplitude <1 °C, but with a wide range which resulted from sporadic rapid deviations of body temperature. Peak blood temperature occurred after sunset. Environmental thermal loads had no detectable effect on blood temperature, even though globe temperature varied by >10 °C from day to day and >20 °C within a day. Brain temperature increased approximately linearly with blood temperature but with a slope <1, so that selective brain cooling tended to be activated at high body temperature, but without a precise threshold for the onset of brain cooling. Low activity attenuated selective brain cooling and high activity abolished it, even at high brain temperature. Our results support the concept that selective brain cooling serves to modulate thermoregulation rather than to protect the brain against heat injury.

Translating Animal Model Research: Does It Matter That Our Rodents Are Cold?

Does it matter that rodents used as preclinical models of human biology are routinely housed below their thermoneutral zone? We compile evidence showing that such rodents are cold-stressed, hypermetabolic, hypertensive, sleep-deprived, obesity-resistant, fever-resistant, aging-resistant, and tumor-prone compared with mice housed at thermoneutrality. The same genotype of mouse has a very different phenotype and response to physiological or pharmacological intervention when raised below or at thermoneutrality.

Body temperature, thermoregulatory behaviour and pelt characteristics of three colour morphs of springbok (Antidorcas marsupialis).

Using intra-abdominal miniature data loggers, we measured core body temperature in female springbok (Antidorcas marsupialis) of three colour morphs (black, normal and white), free-living in the Karoo, South Africa, for one year. During winter, white springbok displayed lower daily minimum body temperatures (37.4+/-0.5 degrees C), than both black (38.1+/-0.3 degrees C) and normal (38.0+/-0.6 degrees C) springbok. During spring, black springbok displayed higher daily maximum body temperatures (40.7+/-0.1 degrees C) than both white (40.2+/-0.2 degrees C) and normal (40.2+/-0.2 degrees C) springbok. These high maximum body temperatures were associated with larger daily amplitudes of nychthemeral rhythm of body temperature (2.0+/-0.2 degrees C), than that of white (1.6+/-0.1 degrees C) and normal (1.7+/-0.2 degrees C) springbok. Biophysical properties of sample springbok pelts were consistent with these patterns, as the black springbok pelt showed lower reflectance in the visible spectral range, and higher heat load from simulated solar radiation, than did the pelts of the other two springbok. Black springbok had lower diurnal activity in winter, consistent with them having to forage less because their metabolic cost of homeothermy was lower, but were disadvantaged in hot periods. White springbok, by contrast, were more protected from solar heat load, but potentially less able to meet the energy cost of homeothermy in winter. Thus energy considerations may underlie the rarity of the springbok colour morphs.

Thermoregulation in the Angolan Free‐Tailed Bat Mops condylurus: A Small Mammal That Uses Hot Roosts

The Angolan free‐tailed bat (Mops condylurus) uses roosts that often exceed 40°C, an ambient temperature (Ta) that is lethal to many microchiropterans. We measured the physiological responses of this species at Tas from 15° to 45°C. Torpor was commonly employed during the day at the lower Ta, but the bats generally remained euthermic at night, with a mean body temperature (Tb) of 35.2°C. Metabolic rate reflected the pattern of Tb, increasing with falling Ta at night but decreasing during the day. Metabolic rate and evaporative losses were lower in torpid than in euthermic bats. Body temperature increased at each Ta >35°C and was 43°C at Ta of 45°C. At Ta of 40°C bats increased dry thermal conductance and evaporative heat loss compared to lower Ta. At 45°C dry thermal conductance was lower than at 40°C and evaporative heat loss was 132% of metabolic heat production. At high Ta there was only a slight increase in metabolic rate despite the employment of evaporative cooling mechanisms and an increase in Tb. Collectively our results suggest that M. condylurus is well suited to tolerate high Ta, and this may enable it to exploit thermally challenging roost sites and to colonise habitats and exploit food sources where less stressful roosts are limiting.

Review of sheep body condition score in relation to production characteristics

Body condition scoring of sheep was first developed as a technique in the 1960s. Unlike live weight, it circumvents the issues of skeletal size, breed and physiological state and is not influenced by gut fill or the length and wetness of the fleece. This review outlines the use of the technique and the relationships between body condition score and other physical measures. In addition, it summarises the literature, across a range of breeds and environments, on the effects of body condition score on reproductive and lactational performance, and the growth and survival of the offspring to weaning. We have proposed that while the relationship between body condition and production traits is positive, it is unlikely to be linear. Where appropriate, the review outlines areas that would benefit from further research. Finally, it outlines what a suitable body condition score profile might be for a ewe over the entire breeding cycle.

CHARACTERISTICS OF THE FEBRILE RESPONSE IN PEKIN DUCKS

Abstract We measured body temperature in Pekin ducks for 22 h after intravenous injection of the lipopolysaccharide (LPS) of gram negative bacteria at doses of 0, 1, 10, and 100 μg · kg body mass−1. The ducks developed monophasic fevers showing increases in peak temperature reached and duration of fever with increases in dose of LPS. Body temperatures of unrestrained telemetered ducks without access to food and water were similar to those of saline-injected controls in the fever experiments, but were lower in the morning than when the same birds had access to food and water. This nocturnal hypothermia may have resulted from energy restriction imposed by lack of food and water. The dose of LPS required to elicit a fever of over 18 h duration (100 μg · kg−1) will elicit a biphasic fever of 5 h duration in rats. Pekin ducks did not exhibit biphasic fever even at the highest LPS dose administered, indicating that while fever is superficially similar in the two homeothermic classes, there may be differences in details of the mechanism. The similarities of the dose/response characteristics to that of mammals lends support to the theory that fever in vertebrates has a common phyletic origin.