Breath carbon stable isotope ratios identify changes in energy balance and substrate utilization in humans.

Rapid detection of shifts in substrate utilization and energy balance would provide a compelling biofeedback tool for individuals attempting weight loss. As a proof of concept, we tested whether the natural abundance of exhaled carbon stable isotope ratios (breath δ(13)C) reflects shifts between negative and positive energy balance. Volunteers (n=5) consumed a 40% energy-restricted diet for 6 days followed by 50% excess on day 7. Breath was sampled immediately before and 1 h and 2 h after breakfast, lunch and dinner. Exhaled breath δ(13)C values were measured by cavity ring-down spectroscopy. Using repeated measures analysis of variance (ANOVA) followed by Dunnett's contrasts, pre-breakfast breath values on days 2-6 were compared with day 1, and postprandial day 7 time points were compared with pre-breakfast day 7. Energy restriction diminished pre-breakfast breath δ(13)C by day 3 (P<0.05). On day 7, increased energy intake was first detected immediately before dinner (-23.8±0.6 vs -21.9±0.7‰, P=0.002 (means±s.d.)), and breath δ(13)C remained elevated at least 2 h post dinner. In conclusion, when shifting between negative and positive energy balance, breath δ(13)C showed anticipated isotopic changes. Although additional research is needed to determine specificity and repeatability, this method may provide a biomarker for marked increases in caloric intake.

Outbreak of pathogenic Escherichia coli in an outdoor-housed non-human primate colony.

BACKGROUND: Pathogenic Escherichia coli has been identified as an etiologic agent in humans causing acute diarrhea or even death but has been rarely reported in non-human primates (NHP). An outbreak of diarrhea occurred in an outdoor-housed NHP colony over a period of 2 months with an attack rate of 29%. METHODS: Bacterial culture and PCR were performed on the fecal specimens to identify enteroinvasive E. coli (EIEC) and Enterohemorrhagic E. coli (EHEC) in the NHPs. RESULTS: By random sampling of 10% of fecal samples of diarrheal cases, four cases of EIEC in rhesus macaques and two cases of EHEC in cynomolgus macaques were confirmed. CONCLUSION: This is the first time EIEC and EHEC have been reported in NHPs associated with diarrhea. The primary source of infection could not be determined.

Thermal radiation in metabolic chambers.

Emissivities and ratios of surface areas of metabolic chambers and their contents have been usually ignored in studies of the metabolic rates of animals. Failure to take these factors into account can lead to errors in the interpretation of results.

Fractional factorial analysis of growth and weaning success in Peromyscus maniculatus.

Fractional factorial designs were used to explore simultaneously the effects of eight variables on survival and growth of neonatal deer mice, Peromyscus maniculatus. Two of the variables had significant effects on weaning success. The magnitudes of their effects are illustrated.

Lizard reflectivity change and its effect on light transmission through body wall.

Light transmission through the body wall of living, color-labile desert iguanas (Dipsosaurus dorsalis) was measured by spectrophotometry. In the dark phase, the body wall's absorption of ultraviolet light and visible light was approximately twice that of the body wall in the light phase. The shorter wavelengths of ultraviolet could penetrate the body wall in the light phase but not in the dark phase. The intensity and wavelengths of light which could penetrate the body wall without pigments are potentially mutagenic when judged by bacterial standards.

Toxicant-disease-environment interactions associated with suppression of immune system, growth, and reproduction.

The effects of marginal malnourishment , infections, and environmental chemicals on growth and reproductive success in Swiss-Webster white mice and wild deer mice were studied with fractional factorial designs. Interaction effects were discovered. For example, malnourished mice were more sensitive to virus exposure and environmental chemicals (a plant growth regulator or polychlorinated biphenyls). Since several commercial plant growth regulators also appear to suppress the immune system, these results cast doubt on the adequacy of current toxicity testing procedures in which factors are studied individually and not in combination.

Energyscapes and prey fields shape a North Atlantic seabird wintering hotspot under climate change.

There is an urgent need for a better understanding of animal migratory ecology under the influence of climate change. Most current analyses require long-term monitoring of populations on the move, and shorter-term approaches are needed. Here, we analysed the ecological drivers of seabird migration within the framework of the energyscape concept, which we defined as the variations in the energy requirements of an organism across geographical space as a function of environmental conditions. We compared the winter location of seabirds with their modelled energy requirements and prey fields throughout the North Atlantic. Across six winters, we tracked the migration of 94 little auks (Alle alle), a key sentinel Arctic species, between their East Greenland breeding site and wintering areas off Newfoundland. Winter energyscapes were modelled with Niche Mapper™, a mechanistic tool which takes into account local climate and bird ecophysiology. Subsequently, we used a resource selection function to explain seabird distributions through modelled energyscapes and winter surface distribution of one of their main prey, Calanus finmarchicus. Finally, future energyscapes were calculated according to IPCC climate change scenarios. We found that little auks targeted areas with high prey densities and moderately elevated energyscapes. Predicted energyscapes for 2050 and 2095 showed a decrease in winter energy requirements under the high emission scenario, which may be beneficial if prey availability is maintained. Overall, our study demonstrates the great potential of the energyscape concept for the study of animal spatial ecology, in particular in the context of global change.

Prediction of forced ventilation in animal fur from a measured pressure distribution.

A model and computation scheme are given for predicting forced ventilation in the fur on an animal limb or torso, modelled here as a fur-covered cylinder with the hairs erect. The intra-fur flow is described by an anisotropic Darcy model, and pressure distribution measured previously for flow past a solid cylinder at Reynolds number 1.29 x 10(5) is used for the outer flow. Calculations from the model are presented for five mammalian species.

Behavioral implications of mechanistic ecology : Thermal and behavioral modeling of desert ectotherms and their microenvironment.

Mechanistic principles from engineering, meteorology, and soil physics are integrated with ecology and physiology to develop models for prediction of animal behavior. The Mojave Desert biome and the desert iguana are used to illustrate these principles.A transient energy balance model for animals in an outdoor environment is presented. The concepts and relationships have been tested in a wind tunnel, in a simulated desert, and in the field. The animal model requires anatomical information and knowledge of the thermoregulatory responses of the animal. The micrometeorological model requires only basic meteorological parameters and two soil physical properties as inputs. Tests of the model in the field show agreement between predicted and measured temperatures above and below the surface of about 2 to 3°C.The animal and micrometeorological models are combined to predict daily and seasonal activity patterns, available times for predator-prey interaction, and daily, seasonal and annual requirements for food and water. It is shown that food, water and the thermal environment can limit animal activity, and furthermore, the controlling limit changes with season. Actual observations of activity patterns and our predictions show close agreement, in many cases, and pose intriguing questions in those situations where agreement does not exist. This type of modeling can be used to further study predator-prey interactions, to study how changes in the environment might affect animal behavior, and to answer other important ecological and physiological questions.

The effect of haemolysis on certain canine serum chemistry parameters.

Haemolysis has been known to cause artefacts in certain canine serum chemistry parameters. These parameters are often used by researchers to detect toxicity in certain studies; haemolysis, therefore, can make serum chemistry interpretation very difficult. In order to determine whether a relationship existed between the level of haemolysis and certain canine serum chemistry parameters, haemolysis was artificially induced by adding a haemolysate of known haemoglobin concentration to serum specimens. A routine clinical chemistry profile was performed on each specimen. Statistical analyses were performed on the results to examine the relationship between level of haemolysis and serum chemistry results. Interpretation of serum chemistry results of haemolysed canine sera paralleled, in most cases, human historical data.

A comparison of subcutaneous and intraperitoneal oxytetracycline injection methods for control of infectious disease in the rat.

After receiving once daily intraperitoneal (i.p.) or subcutaneous (s.c.) injections of oxytetracycline (15 mg/100 g bodyweight) for 7 days, laboratory rats had significantly different oxytetracycline serum levels depending on the method of injection. Regardless of injection method, the biological half-life of the antibiotic was 4.25 h and serum antibiotic levels never fell below therapeutic levels for certain rat pathogens during 24 h post-injection. Severe peritonitis and cellulitis were found in rats whether injected s.c. or i.p. and some animals lost bodyweight. It appeared that either injection method would be an effective treatment for certain infectious diseases of laboratory rats but tissue damage, probably from oxytetracycline's acidity, made both methods unattractive.

NMR-based metabolomics and breath studies show lipid and protein catabolism during low dose chronic T(1)AM treatment.

OBJECTIVE: 3-Iodothyronamine (T1 AM), an analog of thyroid hormone, is a recently discovered fast-acting endogenous metabolite. Single high-dose treatments of T1 AM have produced rapid short-term effects, including a reduction of body temperature, bradycardia, and hyperglycemia in mice. DESIGN AND METHODS: The effect of daily low doses of T1 AM (10 mg/kg) for 8 days on weight loss and metabolism in spontaneously overweight mice was monitored. The experiments were repeated twice (n = 4). Nuclear magnetic resonance (NMR) spectroscopy of plasma and real-time analysis of exhaled (13) CO2 in breath by cavity ring down spectroscopy (CRDS) were used to detect T1 AM-induced lipolysis. RESULTS: CRDS detected increased lipolysis in breath shortly after T1 AM administration that was associated with a significant weight loss but independent of food consumption. NMR spectroscopy revealed alterations in key metabolites in serum: valine, glycine, and 3-hydroxybutyrate, suggesting that the subchronic effects of T1 AM include both lipolysis and protein breakdown. After discontinuation of T1 AM treatment, mice regained only 1.8% of the lost weight in the following 2 weeks, indicating lasting effects of T1 AM on weight maintenance. CONCLUSIONS: CRDS in combination with NMR and (13) C-metabolic tracing constitute a powerful method of investigation in obesity studies for identifying in vivo biochemical pathway shifts and unanticipated debilitating side effects.

Modeling animal landscapes.

There is an increasing need to assess the effects of climate and land-use change on habitat quality, ideally from a mechanistic basis. The symposium "Molecules to Migration: Pressures of Life" at the Fourth International Conference in Africa for Comparative Physiology and Biochemistry, Maasai Mara National Reserve, Kenya, 2008, illustrated how the principles of biophysical ecology can capture the mechanistic links between organisms, climate, and other habitat features. These principles provide spatially explicit assessments of habitat quality from a physiological perspective (i.e., "animal landscapes") that can be validated independently of the data used to derive and parameterize them. The contents of this symposium showcased how the modeling of animal landscapes can be used to assess key issues in applied and theoretical ecology. The presentations included applications to amphibians, reptiles, birds, and mammals. The rare Arabian oryx on the Arabian Peninsula is used as an example for energetic calculations and their implications for behavior on the landscape.

Po'ouli landscape bioinformatics models predict energetics, behavior, diets, and distribution on Maui.

This study uses a spatially explicit microclimate/biophysical approach to examine the potential distribution of the Po'ouli on Maui to find either new habitats to search for existence or refine search efforts in previously occupied areas. We used specific physiological and behavioral ecology bird data, and Po'ouli morphological and spectral data obtained from museum specimens to address ecological and conservation-related questions about the Po'ouli that are otherwise very difficult to quantify. Laboratory and field tested microclimate and biophysical-behavioral animal computer models were integrated with remote sensing technologies. To show that the generic microclimate and endotherm models can predict metabolic and water loss requirements of Hawaiian Honeycreepers, we used the 2 species with known physiological properties, the Hawaiian Amakihi, Hemignathus virens, and the Hawaiian Anianiau, Hemignathus parvus. Predictions were within experimental measurement error of the laboratory measurements. Then using field rather than laboratory conditions as input data, we predict the field distribution of the Amakihi on Maui as the first spatial test of the models applied to birds. Results are consistent with Amakihi field distribution data. Fossils show that the Po'ouli once lived on Maui at low elevations in dry/mesic habitats on a likely diet of native tree snails and insects. The arrival of lethal mosquito-borne avian malaria in Hawaii exterminated low elevation Po'ouli forcing a population shift to mountain rainforests and possibly a snail diet instead of insects. To explore the maximum consequences of such a diet shift we assumed exclusive diets of snails versus insects at both low and high elevations. Snail diets require ∼4 times higher foraging rates than do insect diets, making a predominantly snail diet an unlikely prospect for the Po'ouli. Landscape scale simulations suggest that a snail diet would force a Po'ouli distribution inconsistent with observations. A predominantly insect diet is consistent with distribution observations. We show that as local environmental conditions change across the landscape in space and diurnal/seasonal time it is possible to quantify animal physiological and behavioral consequences of those variations in their local environment. This enables quantification of the requisite spatial and temporal distribution and amount or availability of resources that may affect species' potential for survival, growth, reproduction and distribution.

Heat loss regulation: role of appendages and torso in the deer mouse and the white rabbit.

Thermal conductance was subdivided into the component conductances of the appendages and torso using a heat transfer analysis for the deer mouse, Peromyscus maniculatus, and the white rabbit, Oryctolagus cuniculus. Our analysis was based on laboratory measurements of skin temperature and respiratory gas exchange made between air temperatures of 8 and 34 degrees C for the deer mouse, and from published data for the white rabbit. Two series conductances to heat transfer for each appendage and torso were evaluated: internal (hin), for blood flow and tissue conduction to the skin surface, and external (hex), for heat loss from the skin surface to the environment. These two series conductances were represented in a single, total conductance (htot). The limit to htot was set by hex and was reached by the torso htot of both animals. The increase in torso htot observed with air temperature for the mouse suggests that a pilomotor change in fur depth occurred. A control of htot below the limit set by hex was achieved by the hin of each appendage. Elevation of mouse thermal conductance (C) resulted from increases in feet, tail, and torso htot. In contrast, the rabbit showed no change in torso htot between 5 and 30 degrees C and ear htot exclusively increased C over these air temperatures. We suggest that the hyperthermia reported for the rabbit at 35 degrees C resulted from C reaching the physical limit set by torso and near hex. Thus the ear alone adjusted rabbit C, whereas the feet, tail, and the torso contributed to the adjustment of mouse C.

Heat loss from deer mice (Peromyscus): evaluation of seasonal limits to thermoregulation.

This paper investigates the influence of seasonal adaptations to thermoregulatory heat loss for deer mice (Peromyscus) during summer and winter. A general, mechanistic model of heat transfer through fur was evaluated for the structural properties of the fur of deer mice. The model was validated against heat production determined from mice exposed to a range of radiative (wall) temperatures (tr) at air temperatures (ta) of 15, 27 and 34 degrees C. Calculated heat loss from the appendages was subtracted from the measured heat production to yield heat loss from the furred torso. This calculated torso heat loss agreed closely with the predicted fur heat loss for all conditions, as shown by a regression slope near 1 (0.99). Simulations using models of fur and appendage heat loss reveal that the winter increase in thermogenic (heat production) capacity has a greater effect than changes in fur properties in expanding the limits to thermoregulation. Both wind and a clear night sky increase heat loss and can limit thermoregulation to air temperatures above those found in deer mice habitats during winter (-25 degrees C). Thus, despite seasonal adaptations, these simulations indicate that thermoregulation is not possible under certain winter conditions, thereby restricting deer mice to within the protected environment of the leaf litter or snow tunnels.

Temperature, activity, and lizard life histories.

Lizard life-history characteristics vary widely among species and populations. Most authors seek adaptive or phylogenetic explanations for life-history patterns, which are usually presumed to reflect genetic differences. However, lizard life histories are often phenotypically plastic, varying in response to temperature, food availability, and other environmental factors. Despite the importance of temperature to lizard ecology and physiology, its effects on life histories have received relatively little attention. We present a theoretical model predicting the proximate consequences of the thermal environment for lizard life histories. Temperature, by affecting activity times, can cause variation in annual survival rate and fecundity, leading to a negative correlation between survival rate and fecundity among populations in different thermal environments. Thus, physiological and evolutionary models predict the same qualitative pattern of life-history variation in lizards. We tested our model with published life-history data from field studies of the lizard Sceloporus undulatus, using climate and geographical data to reconstruct estimated annual activity seasons. Among populations, annual activity times were negatively correlated with annual survival rate and positively correlated with annual fecundity. Proximate effects of temperature may confound comparative analyses of lizard life-history variation and should be included in future evolutionary models.

Behavioral and neurochemical changes associated with chronic exposure to low-level concentration of pesticide mixtures.

In order to assess behavioral and neurochemical changes resulting from pesticide exposure, food-restricted male weanling rats were exposed for 90 d to low doses (1 ppb-10,000 ppb range) of individual pesticides (aldicarb, metribuzin, or methomyl) or mixtures of them. During exposure, rats were trained to run a T-maze and tested for spatial discrimination reversal learning. At sacrifice, three brain regions (cortex, hippocampus, and neostriatum) were assayed for the neurotransmitters dopamine, acetylcholine, and serotonin. Animals treated with a mixture of two insecticides and one herbicide were found to have slower speeds in maze-running (motor control) and also had altered levels of choline in their neostriatums. Rats treated with one herbicide compound (metribuzin) took longer to learn on two reversals; this group also had a significantly lower acetylcholine/choline ratio in their hippocampus.

Critical radius of endotherms.

The critical radius effect for insulation, well known in the engineering literature, was used by other authors to explain the lack of insulation on newborn endotherms. If that effect existed in small animals, they would lose less heat if nude than if fur or feathers were present. We show 1) that the previous analysis, although incomplete, yields the same result as a solid insulation model with the required sophistication and 2) that a proper model of fur is a porous media model. Neither of two porous media versions yield a critical radius effect. No critical radius effect occurs because simultaneous heat transfer by conduction and radiation makes it impossible to obtain the required logarithmic increase in thermal resistance with increasing insulation radius in a porous medium.