Level and precision of behavioural thermoregulation in the bearded dragon, Pogona vitticeps : effects of hypoxia and environmental thermal quality /

Most metabolic functions are optimized within a narrow range of body temperatures, which is why thermoregulation is of great importance for the survival and overall fitness of an animal. It has been proposed that lizards will thermoregulate less precisely in low thermal quality environments, where the costs associated with thermoregulation are high; in the case of lizards, whose thermoregulation is mainly behavioural, the primary costs ofthermoregulation are those derived from locomotion. Decreasing thermoregulatory precision in costly situations is a strategy that enhances fitness by allowing lizards to be more flexible to changing environmental conditions. It allows animals to maximize the benefits of maintaining a relatively high body temperature while minimizing energy expenditure. In situations where oxygen concentration is low, the costs of thermoregulation are relatively high (i.e. in relation to the amount of oxygen available for metabolic functions). As a result, it is likely that exposures to hypoxic conditions induce a decrease in the precision of thermoregulation. This study evaluated the effects of hypoxia and low environmental thermal quality, two energetically costly conditions, on the precision and level of thermoregulation in the bearded dragon, Pogona vitticeps, in an electronic temperature-choice shuttle box. Four levels of hypoxia (1O, 7, 5 and 4% 02) were tested. Environmental thermal quality was manipulated by varying the rate of temperature change (oTa) in an electronic temperature-choice shuttle box. Higher oT a's translate into more thermally challenging environments, since under these conditions the animals are forced to move a greater number of times (and hence invest more energy in locomotion) to maintain similar temperatures than at lower oTa's. In addition, lizards were tested in an "extreme temperatures" treatment during which air temperatures of the hot and cold compartments of the shuttle box were maintained at a constant 50 and 15°C respectively. This was considered the most thermally challenging environment. The selected ambient (T a) and internal body temperatures (Tb) of bearded dragons, as well as the thermoregulatory precision (measured by the central 68% ofthe Ta and T b distribution) were evaluated. The thermoregulatory response was similar to both conditions. A significant increase in the size of the Tb range, reflecting a decrease in thermoregulatory precision, and a drop in preferred body temperature of ~2 °C, were observed at both 4% oxygen and at the environment of lowest thermal quality. The present study suggests that in energetically costly situations, such as the ones tested in this study, the bearded dragon reduces energy expenditure by decreasing preferred body temperature and minimizing locomotion, at the expense of precise behavioural thermoregulation. The close similarity of the behavioural thermoregulatory response to two very different stimuli suggests a possible common mechanism and neuronal pathway to the thermoregulatory response.

Characterising Behavioural Thermoregulation in the Bearded Dragon: The Role of TRPM8

Temperature regulation is a necessary part of maintaining life, as most biological processes are influenced by temperature. ThermoTRP channels are considered the primary thermosensors in endotherms, but little is known regarding their function in ectotherms. The goal of this study is to establish TRPM8, a cold sensing channel, as a participant in normal thermoregulation of the bearded dragon (Pogona vitticeps), an ectotherm. Animals were placed inside a ramping temperature shuttle box to assess the common behavioural thermoregulatory strategy of shuttling. Shuttling involves the periodic movement between cold and warm environments to maintain body temperature at moderate levels. The temperatures for cold and warm escapes represent sensory thresholds for inducing the shuttling thermoeffector. Animals were administered with: 1) an injection of the TRM8 antagonist capsazepine, 2) an injection of the TRPM8 agonist menthol, and 3) menthol applied topically. No effect was observed with injected drugs, but topical menthol resulted in a 2-3oC rise in the ambient temperature threshold and 1-2oC rise in skin temperature threshold for escape from the cold compartment. In an additional experiment, gaping behaviour, a warm temperature thermoregulatory strategy, was assessed. No effect was observed in this behaviour when the same dose of menthol was applied topically. These results point to a role for TRPM8 only in thermoregulation as it relates to cold temperature sensation in lizards, since it does not participate in regulating warm temperature behaviours such as gaping.

Control of heart rate during thermoregulation in the heliothermic lizard Pogona barbata: importance of cholinergic and adrenergic mechanisms

During thermo regulation in the bearded dragon Pogona barbata, heart rate when heating is significantly faster than when cooling at any given body temperature (heart rate hysteresis), resulting in faster rates of heating than cooling. However, the mechanisms that control heart rate during heating and cooling are unknown. The aim of this study was to test the hypothesis that changes in cholinergic and adrenergic tone on the heart are responsible for the heart rate hysteresis during heating and cooling in P. barbata. Heating and cooling trials were conducted before and after the administration of atropine, a muscarinic antagonist, and sotalol, a beta-adrenergic antagonist. Cholinergic and beta-adrenergic blockade did not abolish the heart rate hysteresis, as the heart rate during heating was significantly faster than during cooling in all cases. Adrenergic tone was extremely high (92.3%) at the commencement of heating, and decreased to 30.7% at the end of the cooling period. Moreover, in four lizards there was an instantaneous drop in heart rate (up to 15 beats min(-1)) as the heat source was switched off, and this drop in heart rate coincided with either a drop in beta-adrenergic tone or an increase in cholinergic tone. Rates of heating were significantly faster during the cholinergic blockade, and least with a combined cholinergic and beta-adrenergic blockade. The results showed that cholinergic and beta-adrenergic systems are not the only control mechanisms acting on the heart during heating and cooling, but they do have a significant effect on heart rate and on rates of heating and cooling.

Inibidor da ação do etileno na conservação pós-colheita de Chrysanthemum morifolium Ramat cv. Dragon

The durability and postharvest quality of cut flowers are fundamental attributes in value along the production chain and in consumer satisfaction. The objective of this study was to evaluate the effect of chemical inhibitors of ethylene action on maintaining the postharvest quality of chrysanthemum stems (Chrysanthemum morifolium Ramat cv. Dragon). The experiment tested maintenance solutions with silver thiosulfate (STS) under five levels (distilled water, a 0.2 mM STS, the STS 0.2 mM + sucrose at 50 g L-1, STS at 0.4 mM; STS at 0.4 mM + sucrose at 50 g L-1), and date of sampling, for three levels (0, 3, 6 days). Three replications with two flower stems in each treatment were used in the experiment. Physical assessments were made: color, fresh mass and relative water content; chemical evaluations: reducing sugars and pigments, and qualitative assessments: turgidity, flower color, and number of buds, open flowers and partially open flowers. Treatment with 0.2 mM STS resulted in better maintenance of fresh mass of stems. The concentration of pigments and reducing sugar was higher in those treatments in which sucrose was associated. The color and relative water content were favored in treatments STS 0.2 mM and 0.4 mM. The concentration of 0.2 mM STS obtained the best results, prolonging the vase life the stems. The quality of these stems was higher, with the best assessments of water content, color and turgidity.

Soluções de manutenção na pós-colheita de Chrysanthemum morifolium cv. Dragon

The development and use of techniques that extend the life vase of the flowers, maintaining the quality of the product, is essential for reducing postharvest losses. The objective of this work was to evaluate different solutions for maintenance, associated or not to sucrose, in maintaining the postharvest quality of chrysanthemum stems. The treatments used distilled water, 8-HQC to 100 mg L-1, 8-HQC to 100 mg L-1 + sucrose 50 g L-1, 8-HQC to 200 mg L-1, 8-HQC to 200 mg L-1 + sucrose 50 g L-1. Physical assessments were made: color, fresh mass and relative water content; chemical evaluations: reducing sugars and pigments, and qualitative assessments: turgidity, color of the flowers, and number of buttons, open flowers and partially open flowers. The combination of 8-HQC 200 mg L-1 + sucrose 50 g L-1 was the best performance that made for maintaining the quality of flower stems, favoring the opening of buttons and turgidity of petals. Sucrose contributed to better maintenance of the reserve substances in the shaft, which had increased the flower vase life.

A preliminary taxonomic review of the South American bearded saki monkeys genus Chiropotes (Cebidae, Platyrrhini), with the description of a new supspecies / Philip Hershkovitz.

n.s. no.27(1985)

Dragon

Combined media on paper. 85" x 42"

The ‘Dragon’ and the ‘Elephant’ and Global Imbalances

Global financial imbalances receive a great deal of attention in relation to the emerging economies China and India. This chapter analyzes this relation, but argues first that they are actually re-balancing the existing structural inequality in the world economy, in which for so long only the Western economies and Japan dominated economic growth and international trade, moving towards a more multi-polar world economy. China in particular, with its rapid export-led growth, has indeed been part and parcel of the emerging financial imbalances, feeding the ‘over-consumption’ in the US and using its accumulating international reserves in buying US-treasury bonds. Finance therefore is moving to the economy that ‘least needs it’. This imbalance can only be redressed if the US (and some of the other OECD countries) start saving more and consuming less (and become more competitive), with China further stimulating domestic demand (which it already did in response to the crisis). China and to a lesser extend India, as emerging large economies and a more important roles in global markets, also contribute to new imbalances, such as the influence of the insatiable appetite for resources (carbon-hydrates, minerals and bio-mass) of these relatively energy-inefficient economies, while at the same time attracting an increasing share of FDI towards them. The chapter finally raises the issue that these three mentioned imbalances make it more difficult for developing countries (except for those who are resource-rich) to get access to the necessary development finance.

Validation of the DRAGON Score in 12 Stroke Centers in Anterior and Posterior Circulation.

BACKGROUND AND PURPOSE: The DRAGON score predicts functional outcome in the hyperacute phase of intravenous thrombolysis treatment of ischemic stroke patients. We aimed to validate the score in a large multicenter cohort in anterior and posterior circulation. METHODS: Prospectively collected data of consecutive ischemic stroke patients who received intravenous thrombolysis in 12 stroke centers were merged (n=5471). We excluded patients lacking data necessary to calculate the score and patients with missing 3-month modified Rankin scale scores. The final cohort comprised 4519 eligible patients. We assessed the performance of the DRAGON score with area under the receiver operating characteristic curve in the whole cohort for both good (modified Rankin scale score, 0-2) and miserable (modified Rankin scale score, 5-6) outcomes. RESULTS: Area under the receiver operating characteristic curve was 0.84 (0.82-0.85) for miserable outcome and 0.82 (0.80-0.83) for good outcome. Proportions of patients with good outcome were 96%, 93%, 78%, and 0% for 0 to 1, 2, 3, and 8 to 10 score points, respectively. Proportions of patients with miserable outcome were 0%, 2%, 4%, 89%, and 97% for 0 to 1, 2, 3, 8, and 9 to 10 points, respectively. When tested separately for anterior and posterior circulation, there was no difference in performance (P=0.55); areas under the receiver operating characteristic curve were 0.84 (0.83-0.86) and 0.82 (0.78-0.87), respectively. No sex-related difference in performance was observed (P=0.25). CONCLUSIONS: The DRAGON score showed very good performance in the large merged cohort in both anterior and posterior circulation strokes. The DRAGON score provides rapid estimation of patient prognosis and supports clinical decision-making in the hyperacute phase of stroke care (eg, when invasive add-on strategies are considered).