Evidence for endothermic ancestors of crocodiles at the stem of archosaur evolution

Journal ArticlePhysiological, anatomical, and developmental features of the crocodilian heart support the paleontological evidence that the ancestors of living crocodilians were active and endothermic, but the lineage reverted to ectothermy when it invaded the aquatic, ambush predator niche. In endotherms, there is a functional nexus between high metabolic rates, high blood flow rates, and complete separation of high systemic blood pressure from low pulmonary blood pressure in a four-chambered heart. Ectotherms generally lack all of these characteristics, but crocodilians retain a four-chambered heart

The Effect of Wind on the Rate of Heat Loss from Avian Cup-Shaped Nests

Forced convection can significantly influence the heat loss from birds and their offspring but effects may be reduced by using sheltered micro-sites such as cavities or constructing nests. The structural and thermal properties of the nests of two species, the spiny-cheeked honeyeater (Acanthagenys rufogularis) and yellow-throated miner (Manorina flavigula), were measured in relation to three wind speeds. Nest dimensions differ between the two species, despite the similar body mass of the incubating adults, however nest conductance is comparable. As wind speed increases, so does the rate of heat loss from the nests of both species, and further still during incubation recesses. The significance of forced convection through the nest is a near-doubling in heat production required by the parent, even when incubating at relatively low wind speeds. This provides confirmation that selecting a sheltered nest site is important for avian reproductive success

Measurement of Glutathione as a Tool for Oxidative Stress Studies by High Performance Liquid Chromatography

Background: Maintenance of the ratio of glutathione in the reduced (GSH) and oxidised (GSSG) state in cells is important in redox control, signal transduction and gene regulation, factors that are altered in many diseases. The accurate and reliable determination of GSH and GSSG simultaneously is a useful tool for oxidative stress determination. Measurement is limited primarily to the underestimation of GSH and overestimation GSSG as a result of auto-oxidation of GSH. The aim of this study was to overcome this limitation and develop, optimise and validate a reverse-phase high performance liquid chromatographic (HPLC) assay of GSH and GSSG for the determination of oxidant status in cardiac and chronic kidney diseases. Methods: Fluorescence detection of the derivative, glutathione-O-pthaldialdehyde (OPA) adduct was used. The assay was validated by measuring the stability of glutathione and glutathione-OPA adduct under conditions that could affect the reproducibility including reaction time and temperature. Linearity, concentration range, limit of detection (LOD), limit of quantification (LOQ), recovery and extraction efficiency and selectivity of the method were assessed. Results: There was excellent linearity for GSH (r2 = 0.998) and GSSG (r2 = 0.996) over concentration ranges of 0.1 μM–4 mM and 0.2 μM–0.4 mM respectively. The extraction of GSH from tissues was consistent and precise. The limit of detection for GSH and GSSG were 0.34 μM and 0.26 μM respectively whilst their limits of quantification were 1.14 μM and 0.88 μM respectively. Conclusion: These data validate a method for the simultaneous measurement of GSH and GSSG in samples extracted from biological tissues and offer a simple determination of redox status in clinical samples

Pollination Success of the Corsican Helicodiceros muscivorus (Araceae)

ABSTRACT The pollination success of the dead horse arum, Helicodiceros muscivorus, was studied in one Corsican population. This aroid species is pollinated by deception, attracting blowflies by mimicking the floral volatiles emitted by mammal cadavers. The reproductive individuals were taller and larger than non-reproductive ones, indicating that the plant vigor and thus the available amount of resources is an important factor in the production of an inflorescence. The reproductive success of the dead horse arum increased with the size of the inflorescence, as judged by a positive linear correlation between the appendix length and the total number of flies trapped within the floral chamber. Larger inflorescences had a longer appendix and thus a better probability to attract and dupe pollinating flies. The absence of correlation between floral sex-ratio and the spadix size indicated that there was no expression of the size-advantage model in H. muscivorus apparent in some other Araceae. The most probable explanation is that pollination efficiency is high because of low diversity and high abundance of pollinating insects. KEY WORDS Dead horse arum, deceit pollination, plant vigor, floral trait correlations, Calliphoridae, Diptera

Allometric scaling of mammalian metabolism

© The Company of BiologistsThe importance of size as a determinant of metabolic rate (MR) was first suggested by Sarrus and Rameaux over 160 years ago. Max Rubner's finding of a proportionality between MR and body surface area in dogs (in 1883) was consistent with Sarrus and Rameaux's formulation and suggested a proportionality between MR and body mass (Mb) raised to the power of 2/3. However, interspecific analyses compiled during the first half of the 20th century concluded that mammalian basal MR (BMR, ml O2 h-1) was proportional to Mb3/4, a viewpoint that persisted for seven decades, even leading to its common application to non-mammalian groups. Beginning in 1997, the field was re-invigorated by three new theoretical explanations for 3/4-power BMR scaling. However, the debate over which theory accurately explains 3/4-power scaling may be premature, because some authors maintain that there is insufficient evidence to adopt an exponent of 3/4 over 2/3. If progress toward understanding the non-isometric scaling of BMR is ever to be made, it is first essential to know what the relationship actually is. We re-examine previous investigations of BMR scaling by standardising units and recalculating regression statistics. The proportion of large herbivores in a data set is positively correlated both with the scaling exponent (b, where BMR=aMbb) and the coefficient of variation (CV: the standard deviation of ln-ln residuals) of the relationship. Inclusion of large herbivores therefore both inflates b and increases variation around the calculated trendline. This is related to the long fast duration required to achieve the postabsorptive conditions required for determination of BMR, and because peak post-feeding resting MR (RMRpp) scales with an exponent of 0.75±0.03 (95% CI). Large herbivores are therefore less likely to be postabsorptive when MR is measured, and are likely to have a relatively high MR if not postabsorptive. The 3/4 power scaling of RMRpp is part of a wider trend where, with the notable exception of cold-induced maximum MR (b=0.65±0.05), b is positively correlated with the elevation of the relationship (higher MR values scale more steeply). Thus exercise-induced maximum MR (b=0.87±0.05) scales more steeply than RMRpp, field MR (b=0.73±0.04), thermoneutral resting MR (RMRt, b=0.712±0.013) and BMR. The implication of this observation is that contamination of BMR data with non-basal measurements is likely to increase the BMR scaling exponent even if the contamination is randomly distributed with respect to Mb. Artificially elevated scaling exponents can therefore be accounted for by the inclusion of measurements that fail to satisfy the requirements for basal metabolism, which are strictly defined (adult, non-reproductive, postabsorptive animals resting in a thermoneutral environment during the inactive circadian phase). Similarly, a positive correlation between Mb and body temperature (Tb) and between Tb and mass-independent BMR contributes to elevation of b. While not strictly a defined condition for the measurement of BMR, the normalisation of BMR measurements to a common Tb (36.2°C) to achieve standard metabolic rate (SMR) further reduces the CV of the relationship. Clearly the value of the exponent depends on the conditions under which the data are selected. The exponent for true BMR is 0.686 (±0.014), Tb normalised SMR is 0.675 (±0.013) and RMRt is 0.712 (±0.013).Craig R. White and Roger S. Seymou

The conservation of panel paintings and related objects

Until the early 17th century almost all portable paintings were created on wood supports, including masterpieces by famous painters, ranging from Giotto to Dürer to Rembrandt. The structural conservation of these paintings requires specific knowledge and skills as the supports are susceptible to damage caused by unstable environmental conditions. Unfortunately, past structural interventions often caused significant damage due to insufficient knowledge of the behaviour of the wood panels, glue and paint layers. Over the last fifty years, the field has developed treatment strategies based on interdisciplinary collaboration and on the knowledge of specialist conservators. Most current conservation protocols rely on empirical knowledge of conservators and are not necessarily based on a scientific understanding of the nature and behaviour of wood and paint layers. In order to move the field forward, it is imperative to strengthen scientific research into the production methods, ageing and future behaviour of panel paintings, being an intricate interplay between different materials. A deeper understanding of the processes that adversely affect panel paintings over time will contribute to the improved care and conservation of these artworks. The Netherlands Organisation for Scientific Research (NWO) and the Rijksmuseum Amsterdam brought together a group of experts from different disciplines to recommend specific areas in the field that would benefit from systematic research. The experts concluded that targeted interdisciplinary research projects are key to understanding the behaviour of panel paintings and help conservators make better informed decisions. Research into chemical and physical properties of wood, glue and paint layers should be combined with an evaluation of past and current conservation treatments. Research should also consider the history of the object, studio practice, conservation history and thoughts on long-term impact of treatments

Respiration of thermogenic inflorescences of Philodendron melinonii: natural pattern and responses to experimental temperatures

The patterns of temperature and respiratory changes in the protogynous inflorescences of Philodendron melinonii (Araceae) were studied in the field in French Guiana. These are the first respiratory measurements from a member of the large subgenus Philodendron, a group previously thought to lack thermoregulatory inflorescences, in contrast to thermoregulatory Philodendron species of the subgenus Meconostigma. Heating by the male and sterile male florets was strong on the first evening of anthesis when beetles are attracted and the female florets are receptive. Heat production of the inflorescence peaked at ~0.9 W and spadix temperature reached ~39.5 °C, a level somewhat independent of ambient temperature. Thermogenesis continued throughout the night and the next day, but at a lower level, and floral temperatures fell. On the second evening, when pollen was shed, there was a small elevation in respiration and spadix temperature. Responses of cut spadix sections to experimental step changes in ambient temperature resulted in a prompt response in floral temperature and respiration rate in the direction of the change and then a much slower regulatory adjustment in the opposite direction. These responses are consistent with an immediate van 't Hoff effect, followed by up- or down-regulation of thermogenesis. However, the responses required several hours. It is concluded that the male floret tissues possess the same thermoregulatory mechanism of more precise thermoregulatory species, but a combination of small spadix size (that favours heat loss), moderate thermogenic capacity (that limits heating rate), and slow reaction time (that causes long lags between temperature change and the regulatory response) result in poor thermoregulatory performance during the second day.Roger S. Seymour and Marc Giberna

The conservation of panel paintings and related objects

Until the early 17th century almost all portable paintings were created on wood supports, including masterpieces by famous painters, ranging from Giotto to Dürer to Rembrandt. The structural conservation of these paintings requires specific knowledge and skills as the supports are susceptible to damage caused by unstable environmental conditions. Unfortunately, past structural interventions often caused significant damage due to insufficient knowledge of the behaviour of the wood panels, glue and paint layers. Over the last fifty years, the field has developed treatment strategies based on interdisciplinary collaboration and on the knowledge of specialist conservators. Most current conservation protocols rely on empirical knowledge of conservators and are not necessarily based on a scientific understanding of the nature and behaviour of wood and paint layers. In order to move the field forward, it is imperative to strengthen scientific research into the production methods, ageing and future behaviour of panel paintings, being an intricate interplay between different materials. A deeper understanding of the processes that adversely affect panel paintings over time will contribute to the improved care and conservation of these artworks. The Netherlands Organisation for Scientific Research (NWO) and the Rijksmuseum Amsterdam brought together a group of experts from different disciplines to recommend specific areas in the field that would benefit from systematic research. The experts concluded that targeted interdisciplinary research projects are key to understanding the behaviour of panel paintings and help conservators make better informed decisions. Research into chemical and physical properties of wood, glue and paint layers should be combined with an evaluation of past and current conservation treatments. Research should also consider the history of the object, studio practice, conservation history and thoughts on long-term impact of treatments