Photoperiodic effects on body mass, energy balance and hypothalamic gene expression in the bank vole.

We examined the effect of increasing photoperiod, at a constant low temperature, on the body mass and energy budget of the bank vole Clethrionomys glareolus. Simultaneously, we determined the hypothalamic gene expression of neuropeptides and receptors known to be involved in short-term energy balance. Despite an increase in body mass (approximately 10% of initial mass), we found no significant changes in any energetic parameters (food intake, energy assimilation rate, resting metabolic rate and total daily energy expenditure by doubly-labelled water).

Resting and daily energy expenditures of free-living field voles are positively correlated but reflect extrinsic rather than intrinsic effects.

Resting metabolic rates at thermoneutral (RMRts) are unexpectedly variable. One explanation is that high RMRts intrinsically potentiate a greater total daily energy expenditure (DEE), but recent work has suggested that DEE is extrinsically defined by the environment, which independently affects RMRt. This extrinsic effect could occur because expenditure is forced upwards in poor habitats or enabled to rise in good habitats.

Limits to sustained energy intake. VIII. Resting metabolic rate and organ morphology of laboratory mice lactating at thermoneutrality.

We have previously shown that the food intake and milk production of MF1 laboratory mice lactating at 30 degrees C, 21 degrees C and 8 degrees C increase as temperature declines. These data suggest that mice are not limited peripherally by the capacity of the mammary glands to produce milk but are limited by the capacity of the animal to dissipate body heat generated as a by-product of food processing and milk production. Here, we measure resting metabolic rate (RMR; prior to breeding and at peak lactation) and organ morphology (at peak lactation) in MF1 mice exposed to 30 degrees C (thermoneutrality) and compare these traits with the same parameters measured previously in mice at 21 degrees C and 8 degrees C.

Limits to sustained energy intake. VII. Milk energy output in laboratory mice at thermoneutrality.

The limits to sustained energy intake at peak lactation could be imposed peripherally, by the capacity of the mammary glands, or centrally, by the capacity of the animal to dissipate body heat generated as a by-product of processing food and producing milk. To distinguish between the two hypotheses, we examined milk energy output at peak lactation in MF1 laboratory mice exposed to 30 degrees C (N=12), 21 degrees C (N=10; published data) and 8 degrees C (N=10; published data). The peripheral limitation hypothesis predicts that milk energy output will remain constant at different temperatures, while the heat dissipation limit hypothesis predicts a decline in milk energy output as temperature increases.

Limits to sustained energy intake. VI. Energetics of lactation in laboratory mice at thermoneutrality.

The limits to sustained energy intake are important because of their implications for reproductive output, foraging behaviour and thermoregulatory capabilities. Recent attempts to elucidate the nature of the limits to sustained energy intake have focused on peak lactation, which is the most energetically demanding period for female mammals. The hypothesis that performance of lactating animals is limited peripherally by the capacity of mammary glands to produce milk has received the most attention.

Age-related changes in the metabolism and body composition of three dog breeds and their relationship to life expectancy.

We measured body composition and resting metabolic rates (RMR) of three dog breeds (Papillons, mean body mass 3.0 kg (n = 35), Labrador retrievers, mean body mass 29.8 kg (n = 35) and Great Danes, mean body mass 62.

Does body mass play a role in the regulation of food intake?

It is widely believed that body fatness (and hence total body mass) is regulated by a lipostatic feedback system. This system is suggested to involve at least one peripheral signalling compound, which signals to the brain the current size of body fat stores. In the brain the level of the signal is compared with a desirable target level, and food intake and energy expenditure are then regulated to effect changes in the size of body fat stores.

Obesity: part one - the greatest health threat facing mankind.

'In the 15 minutes it will take you to read this article nine people in the USA, and one person in the UK, will have died as a direct consequence of obesity related illnesses.'

Long-term divergent selection on fatness in mice indicates a regulation system independent of leptin production and reception.

Divergent selection in mice on fatness over 60 generations produced a fat (F) and a lean (L) line, having about 22% and 4% body fat, respectively. To elucidate the importance of the leptin regulatory feedback loop in the genetic changes produced by this selection, Lep(ob) and Lepr(db) mutations causing leptin production and leptin receptor deficiency, respectively, were introgressed individually into both lines by repeated backcrossing. The fat amount increased significantly in homozygotes for Lep(ob) or Lepr(db) in both lines, for example, in F and L males from 8.

The energetics of lactation in cooperatively breeding meerkats Suricata suricatta.

Species may become obligate cooperative breeders when parents are unable to raise their offspring unassisted. We measured the daily energy expenditure of mothers, helpers and offspring during peak lactation in cooperatively breeding meerkats Suricata suricatta using the doubly labelled water technique. Lactating mothers expended more energy per day than allo-lactating subordinate females, non-lactating females or suckling offspring.

The energetics of autumn mast hoarding in eastern chipmunks.

The timing and basis of the transition from energy reserve accumulation to reserve utilization in autumn may be a key determinant of winter survival in endotherms, but has rarely been examined directly in the field. In the present study we quantify the energetics of autumn mast hoarding in eastern chipmunks (Tamias striatus) to document the degree to which larder hoarding permits capitalizing on brief pulses of resource abundance and to evaluate the basis of the decision to stop hoarding and initiate hibernation. Daily energy expenditure, measured with the doubly labeled water technique, increased significantly with date and decreasing ambient temperature, eventually exceeding 3× resting metabolic rate in late autumn.

Cost of flight in the zebra finch ( Taenopygia guttata): a novel approach based on elimination of (13)C labelled bicarbonate.

On three separate occasions, five zebra finches ( Taenopygia guttata) were injected intraperitoneally with 0.2 ml 0.29 M NaH(13)CO(3)solution and placed immediately into respirometry chambers to explore the link between (13)C elimination and both O(2) consumption (VO(2)) and CO(2) production (VCO(2)).

Climate-mediated energetic constraints on the distribution of hibernating mammals.

To predict the consequences of human-induced global climate change, we need to understand how climate is linked to biogeography. Energetic constraints are commonly invoked to explain animal distributions, and physiological parameters are known to vary along distributional gradients. But the causal nature of the links between climate and animal biogeography remain largely obscure.

The consequences of acute cold exposure on protein oxidation and proteasome activity in short-tailed field voles, microtus agrestis.

During cold exposure, animals upregulate their metabolism and food intake, potentially exposing them to elevated reactive oxygen species (ROS) production and oxidative damage. We investigated whether acute cold (7 +/- 3 degrees C) exposure (1, 10, or 100 h duration) affected protein oxidation and proteasome activity, when compared to warm controls (22 +/- 3 degrees C), in a small mammal model, the short-tailed field vole Microtus agrestis. Protein carbonyls and the chymotrypsin-like proteasome activity were measured in plasma, heart, liver, kidney, small intestine (duodenum), skeletal muscle (gastrocnemius), and brown adipose tissue (BAT).

Antioxidant enzyme activities, lipid peroxidation, and DNA oxidative damage: the effects of short-term voluntary wheel running.

We examined the effect of voluntary exercise on antioxidant enzyme activities (catalase, glutathione peroxidase, superoxide dismutase) in skeletal muscle (hind- and forelimb) and heart of a model small mammal species: short-tailed field vole Microtus agrestis. In addition, DNA oxidation was determined in lymphocytes and hepatocytes using the comet assay and lipid peroxidation estimated in hindlimb muscle by measurement of thiobarbituric-acid-reactive substances. Voles (approximately 6 weeks old), exposed to a 16L:8D photoperiod (lights on 0500 h), ran almost continuously during darkness.

Living fast, dying when? The link between aging and energetics.

The idea that aging should be linked to energy expenditure has a long history that can be traced to the late 1800s and the industrial revolution. Machines that are run fast wear out more quickly, so the notion was born that humans and animals might experience similar fates: the faster they live (expressed as greater energy expenditure), the sooner they die. Evidence supporting the "rate-of-living" theory was gleaned from the scaling of resting metabolism and life span as functions of body mass.

Carbon isotope ratios in exhaled CO(2) can be used to determine not just present, but also past diets in birds.

We show that an animal's past and present diet can be distinguished through the delta(13)C of exhaled CO(2). The exhaled delta(13)C of 12 pigeons fed solely corn (a C(4) plant) for 30 days was -13.63 per thousand (+/-0.

Regional blood flow in sea turtles: implications for heat exchange in an aquatic ectotherm.

Despite substantial knowledge on thermoregulation in reptiles, the mechanisms involved in heat exchange of sea turtles have not been investigated in detail. We studied blood flow in the front flippers of two green turtles, Chelonia mydas, and four loggerhead turtles, Caretta caretta, using Doppler ultrasound to assess the importance of regional blood flow in temperature regulation. Mean blood flow velocity and heart rate were determined for the water temperature at which the turtles were acclimated (19.

The Analysis of 13C/12C Ratios in Exhaled CO2: Its Advantages and Potential Application to Field Research to Infer Diet, Changes in Diet Over Time, and Substrate Metabolism in Birds.

Stable isotopes are becoming an increasingly powerful tool for studying the physiological ecology of animals. The (13)C/(12)C ratios of animal tissues are frequently used to reconstruct the diet of animals. This usually requires killing the subjects.

Variations in respiratory muscle activity during echolocation when stationary in three species of bat (Microchiroptera: Vespertilionidae).

Echolocating bats use respiratory muscles to power the production of biosonar vocalisations. The physical characteristics of these calls vary among species of bat, and variations also exist in the timing and patterns of respiratory muscle recruitment during echolocation. We recorded electromyograms from the respiratory muscles of three species of bat (Family Vespertilionidae) while the animals vocalised from stationary positions.

Thermoregulatory responses of two mouse Mus musculus strains selectively bred for high and low food intake.

We examined the thermoregulatory responses of male and female mice Mus musculus that had been divergently selected on voluntary food intake, corrected for body mass, to produce a high-intake and a low-intake strain. Resting metabolic rate was determined by indirect calorimetry (at 30 degrees C, 25 degrees C, 15 degrees C and 5 degrees C). Body temperature responses were measured in a separate group of mice in a parallel protocol.

Metabolic power, mechanical power and efficiency during wind tunnel flight by the European starling Sturnus vulgaris.

We trained two starlings (Sturnus vulgaris) to fly in a wind tunnel whilst wearing respirometry masks. We measured the metabolic power (P(met)) from the rates of oxygen consumption and carbon dioxide production and calculated the mechanical power (P(mech)) from two aerodynamic models using wingbeat kinematics measured by high-speed cinematography. P(met) increased from 10.

Effect of high-fat diet on body mass and energy balance in the bank vole.

We tested the hypothesis that animals that reduce their body mass in response to decreased photoperiod do not develop diet-induced obesity (DIO) when fed a high-fat diet (HFD). Bank voles (Clethrionomys glareolus) fed a diet with fat content of 13.5% by mass and 28.

Competition between Eurasian red and introduced Eastern grey squirrels: the energetic significance of body-mass differences.

Daily energy expenditure (DEE) was measured in sympatric populations of red and grey squirrels using the doubly labelled water technique. Grey squirrels had significantly higher DEEs than red squirrels. However, the difference between the species was not separable from the effects of body mass on DEE.