Chronic ethanol feeding modulates inflammatory mediators, activation of nuclear factor-κB, and responsiveness to endotoxin in murine Kupffer cells and circulating leukocytes.

Chronic ethanol abuse is known to increase susceptibility to infections after injury, in part, by modification of macrophage function. Several intracellular signalling mechanisms are involved in the initiation of inflammatory responses, including the nuclear factor-κB (NF-κB) pathway. In this study, we investigated the systemic and hepatic effect of chronic ethanol feeding on in vivo activation of NF-κB in NF-κB(EGFP) reporter gene mice. Specifically, the study focused on Kupffer cell proinflammatory cytokines IL-6 and TNF-α and activation of NF-κB after chronic ethanol feeding followed by in vitro stimulation with lipopolysaccharide (LPS). We found that chronic ethanol upregulated NF-κB activation and increased hepatic and systemic proinflammatory cytokine levels. Similarly, LPS-stimulated IL-1 ß release from whole blood was significantly enhanced in ethanol-fed mice. However, LPS significantly increased IL-6 and TNF-α levels. These results demonstrate that chronic ethanol feeding can improve the responsiveness of macrophage LPS-stimulated IL-6 and TNF-α production and indicate that this effect may result from ethanol-induced alterations in intracellular signalling through NF-κB. Furthermore, LPS and TNF-α stimulated the gene expression of different inflammatory mediators, in part, in a NF-κB-dependent manner.

Basking behaviour in relation to energy use and food availability in one of the smallest marsupials.

Although several mammals have been observed to bask in the sun, little is known about this behaviour or its energetic consequences. We investigated the importance of basking behaviour for one of the smallest marsupials, Planigale gilesi (9g). Metabolic rates of captive planigales (n=6) exposed to simulated natural conditions with access to a radiant heat source were measured. Basking behaviour as a function of food availability was quantified using a video camera installed within the planigales' home cages (n=7). All planigales basked during respirometry measurements, reducing resting energy expenditure by 58% at an ambient temperature of 15 degrees C, which reflects conditions in their nesting sites in the wild during winter. Basking behaviour in home cages was displayed by all but one planigale; food withdrawal either triggered basking or it caused a significant increase in basking duration. Our study demonstrates the effectiveness of basking for reducing energy expenditure in one of the smallest marsupials, supporting recent findings on the importance of behavioural thermoregulation in small mammals in general.

Torpor in birds: taxonomy, energetics, and ecology.

Recent reports on patterns and occurrence of torpor and other natural hypothermic states in birds have prompted a revision of many longstanding opinions. For instance, a larger assortment of birds covering a wider range of body mass than previously recognized uses energy-conserving mechanisms in the face of abundant food supplies. Thus, although acute energetic stress triggers the occurrence of hypometabolic states in many birds, energy deficits can no longer be regarded as the sole stimulus for avian torpor. Additionally, the phenology of this phenomenon (phases, duration, depth) shows more interspecific variation than previously appreciated, and traditional concepts of the phases of torpor are not always adequate. Hence, inclusive definitions of torpor based on physiological and/or behavioral criteria have become more difficult to formulate. However, average nighttime body temperature, which is highly consistent throughout the class Aves (38.54 degrees +/- 0.96 degrees C, n = 202), provides a convenient reference for detecting natural hypothermic states. Of the putative ecological factors associated with avian torpor, food specialization seems a prime candidate as an ultimate factor in the occurrence of this state in birds. With few exceptions, all of these animals capable of torpor are either frugivorous, nectarivorous, or insectivorous, suggesting a correlation between thermoregulatory pattern and predictability of food supply. To date, no clear answer exists as to whether the variety of thermoregulatory patterns evident in birds involves discrete mechanisms or merely steps in a physiological continuum. However, I suggest that the occurrence of differences in torpor patterns among closely related species (e.g., within families) favors the latter interpretation.

Metabolism, body temperature and thermal conductance of fruit-doves (Aves: Columbidae, Treroninae).

Basal metabolic rate (MR), body temperature (T(b)) and wet thermal conductance (C(wet)) of three tropical species of fruit-doves were investigated at ambient temperatures (T(a)) of 11-33 degrees C in activity (alpha) and rest (rho) phases to investigate the possible effect of obligate frugivory on the physiology of columbids. The basal metabolic rates of Ptilinopus melanospila (black-naped fruit-dove, 94 g), Drepanoptila holosericea (cloven-feathered dove, 198 g) and Ducula pinon (Pinon's imperial pigeon, 748 g) are 20-38% lower than predicted for all birds, including granivorous columbid species from temperate and tropical regions. The MR was minimal at a T(a) value of approximately 30 degrees C (=lower critical temperature, T(lc)) for all three species, indicating that these rainforest birds are not able to withstand high ambient temperatures as well as arid-adapted members of the pigeon family. Minimal wet-thermal conductance was, on average, higher than expected, indicating poor insulation in these tropical birds. Body temperatures were as expected; however, below T(lc) the body temperatures decreased to levels of 35-36 degrees C (T(a)=12 degrees C).

Metabolic and thermal physiology of pigeons and doves.

Pigeons and doves (Columbidae) are an interesting group to examine for physiological adaptations to climate and diet because this cosmopolitan family comprises more than 300 species that are mostly granivores, although some are specialized frugivores. We determined allometric and phylogenetic effects on body temperature (T(b)), basal metabolic rate (BMR; J h(-1)), and wet thermal conductance (C(wet); J h(-1) C(-1)), and we examined mass (M) and phylogenetically corrected residuals for further effects of climate, diet, and landmass size (mainland or island). Independent contrasts, correlograms, autoregression, and phylogenetic eigenvector regression (PVR) were used to examine phylogenetically related effects. We found a small but significant phylogenetic pattern for body mass of columbids. For T(b), there was no significant effect of mass or phylogeny. There was a significant effect of climate on T(b) and no significant effects of diet or landmass without mass or phylogenetic correction, but after mass and phylogenetic correction, there were no effects of climate, diet, or landmass. For BMR, there was a strong allometric effect, and residuals were significantly lower for arid and tropical species but not for temperate species, compared to predictions for nonpasserine birds. There was a nearly significant autoregressive phylogenetic relationship for BMR parl0;r=0.44), and the strong allometry of BMR remained for independent contrasts (slope=0.731), autoregressive residuals (0.698), and PVR (0.705). Residuals, from regression of autoregression and PVR residuals of M and BMR, were significantly associated with climate: arid pigeons had a lower BMR residual than tropical and temperate pigeons. PVR residuals were significantly affected by landmass (island columbids had a smaller residual than mainland columbids), but autoregression residuals were not. There was no association of autoregression or PVR residuals with diet. For C(wet), there was a strong allometric effect, and residuals for columbids were significantly higher compared to other birds. There was no significant relationship for C(wet) of columbids to climate, diet, or landmass. There was no significant autoregressive or PVR relationship for C(wet), and the strong allometry remained after phylogenetic analysis by independent contrasts (slope=0.501), autoregression (0.509), and PVR (0.514). Residuals from autoregression and PVR were not significantly correlated with climate, diet, or landmass (mainland/island).

Life in extreme environments: Investigations on the ecophysiology of a desert bird, the Australian Diamond Dove (Geopelia cuneata Latham).

The Diamond Dove, Geopelia cuneata, is the world's second smallest (ca. 35 g) species of the columbid order. The Diamond Dove is endemic in the arid and semiarid Mulga and Spinifex regions of Central and Western Australia. It regularly encounters ambient temperatures (T a ) in its habitat above +40° C, especially when foraging for seeds on bare ground cover, and may be found at up to 40 km from water. This entails extreme thermal stress, with evaporative cooling constrained by limited water supply. Energy metabolism (M), respiration, body temperature (T a ) and water budget were examined with regard to physiological adaptations to these extreme environmental conditions. The zone of thermal neutrality (TNZ) extended from +34° C to at least +45° C. Basal metabolic rate (BMR) was 34.10±4.19 J g-1h-1, corresponding to the values predicted for a typical columbid bird. Thermal conductance (C) was higher than predicted. Geopelia cuneata showed the typical breathing pattern of doves, a combination of normal breathing at a stable frequency (ca. 60 min-1) at low T a and panting followed by gular flutter (up to 960 min-1) at high T a . At T a > +36° C, T a increased to considerably higher levels without increasing metabolic rate, i.e. Q10=1. This enabled the doves not only to store heat but also to save the amout of water that would have been required for evaporative cooling if T a had remained constant. The birds were able to dissipate more than 100% of the metabolic heat by evaporation at T a ≥ +44° C. This was achieved by gular flutter (an extremely effective mechanism for evaporation), and also by a low metabolic rate due to the low Q10 value for metabolism during increased T b . At lower T a , Geopelia cuneata predominantly relied on non-evaporative mechanisms during heat stress, to save water. Total evaporative water loss over the whole T a range was 19-33% lower than expected. In this respect, their small body size proved to be an important advantage for successful survival in hot and arid environments.