Rhythmic 24 h Variation of Core Body Temperature and\ud Locomotor Activity in a Subterranean Rodent (Ctenomys\ud aff. knighti), the Tuco-Tuco

The tuco-tuco Ctenomys aff. knighti is a subterranean rodent which inhabits a semi-arid area in Northwestern Argentina. Although they live in underground burrows where environmental cycles are attenuated, they display robust, 24 h locomotor activity rhythms that are synchronized by light/dark cycles, both in laboratory and field conditions. The underground environment also poses energetic challenges (e.g. high-energy demands of digging, hypoxia, high humidity, low food availability) that have motivated thermoregulation studies in several subterranean rodent species. By using chronobiological protocols, the present work aims to contribute towards these studies by exploring day-night variations of thermoregulatory functions in tuco-tucos, starting with body temperature and its temporal relationship to locomotor activity. Animals showed daily, 24 h body temperature rhythms that persisted even in constant darkness and temperature, synchronizing to a daily light/dark cycle, with highest values occurring during darkness hours. The range of oscillation of body temperature was slightly lower than those reported for similar-sized and dark-active rodents. Most rhythmic parameters, such as period and phase, did not change upon removal of the running wheel. Body temperature and locomotor activity rhythms were robustly associated in time. The former persisted even after removal of the acute effects of intense activity on body temperature by a statistical method. Finally, regression gradients between body temperature and activity were higher in the beginning of the night, suggesting day-night variation in thermal conductance and heat production. Consideration of these day-night variations in thermoregulatory processes is beneficial for further studies on thermoregulation and energetics of subterranean rodent

To mine more than gold – an analysis of the brazilian olympic \ud performance

As Olimpíadas são eventos esportivos de relevância mundial. No presente artigo, fazemos uma análise da evolução do quadro geral de medalhas em termos mundiais e do desempenho do Brasil ao longo dos últimos 10 eventos, mostrando que não tem havido melhora de tal desempenho. Procuramos, então, entender e estender as relações entre a colocação no quadro geral e aspectos sociais de desenvolvimento. Discutimos que existe uma base fisiológica envolvida em como despontam atletas de elite, mas que sem o devido investimento social, não há como selecionar, de maneira sistemática e ampla, tais atletas. É neste sentido, do tipo de investimento, que a obtenção do ouro olímpico pode ter um significado muito maior, de cunho social, para o país.The Olympic Games are sportive events of global relevance. Here, we perform an analysis of the medal table from a general perspective and of the Brazilian performance over the last 10 competitions, and we show that there is no real improvement of such a performance at all. We then try to understand the relationships among the place in the medal table and social aspects of development. We discuss that there is a physiological basis involved in how elite athletes emerge, but without the proper social investment it wouldn’t be possible to select, in a systematic and wide way, these athletes. It is in this sense, of the type of the investment, that gold medals can have a much greater social meaning to the country

Phylogenetic analysis of standard metabolic rate of snakes: a new proposal for the understanding of interspecific variation in feeding behavior

The current proposal about the variation of standard metabolic rates (SMR) in snakes predicts that SMR is influenced by the feeding frequency (frequent or infrequent feeders). However, feeding frequency in snakes is poorly studied and hard to quantify under natural conditions. Alternatively, foraging strategy was studied for a large number of species and is usually related to the feeding frequency. In this work, we performed a meta-analysis on the SMR of compiled data from 74 species of snakes obtained from the literature and five more different species of lanceheads (genus Bothrops), after categorization according to the foraging mode (ambush or active foraging) and regarding their phylogenetic history. We tested the hypothesis that foraging mode (FM) is a determinant factor on the interspecific variation of SMR despite the phylogenetic relationship among species. We demonstrated that FM predicted SMR, but there is also a partial phylogenetic structuration of SMR in snakes. We also detected that evolution rates of SMR in active foragers seem to be higher than ambush-hunting snakes. We suggested that foraging mode has a major effect over the evolution of SMR in snakes, which could represent an ecophysiological co-adaptation, since ambush hunters (with low feeding rates) present a lower maintenance energetic cost (SMR) when compared to active foragers. The higher SMR evolution rates for active foraging snakes could be related to a higher heterogeny in the degree of activity during hunting by active foragers when compared to ambush-hunting snakes

Phylogenetic analysis of standard metabolic rate of snakes: a new proposal for the understanding of interspecific variation in feeding behavior

The current proposal about the variation of standard metabolic rates (SMR) in snakes predicts that SMR is influenced by the feeding frequency (frequent or infrequent feeders). However, feeding frequency in snakes is poorly studied and hard to quantify under natural conditions. Alternatively, foraging strategy was studied for a large number of species and is usually related to the feeding frequency. In this work, we performed a meta-analysis on the SMR of compiled data from 74 species of snakes obtained from the literature and five more different species of lanceheads (genus Bothrops), after categorization according to the foraging mode (ambush or active foraging) and regarding their phylogenetic history. We tested the hypothesis that foraging mode (FM) is a determinant factor on the interspecific variation of SMR despite the phylogenetic relationship among species. We demonstrated that FM predicted SMR, but there is also a partial phylogenetic structuration of SMR in snakes. We also detected that evolution rates of SMR in active foragers seem to be higher than ambush-hunting snakes. We suggested that foraging mode has a major effect over the evolution of SMR in snakes, which could represent an ecophysiological co-adaptation, since ambush hunters (with low feeding rates) present a lower maintenance energetic cost (SMR) when compared to active foragers. The higher SMR evolution rates for active foraging snakes could be related to a higher heterogeny in the degree of activity during hunting by active foragers when compared to ambush-hunting snakes.FAPESPINCT Fisiologia Comparada (FAPESP/ CNPq/MCT)PFPMCG/ PRONEX FAPESPNPD-CAPESINCT-ToxInst Butantan, Sao Paulo, BrazilUniv Sao Paulo, Sao Paulo, BrazilUniv Wollongong, Wollongong, NSW, AustraliaUniv Fed Sao Paulo, Campus Diadema, Sao Paulo, BrazilUniv Fed Sao Paulo, Campus Diadema, Sao Paulo, BrazilFAPESP: 09/53202-4, 12/15754-8]INCT Fisiologia Comparada FAPESP/ CNPq/MCT): 08/57712-4]PFPMCG/ PRONEX FAPESP: 08/57687-0]PNPD-CAPESINCT-Tox :08/57898-0Web of Scienc

Comparative physiology investigations support a role for histidine-containing dipeptides in intracellular acid-base regulation of skeletal muscle

Histidine containing dipeptides (HCDs: carnosine, anserine and balenine) have numerous therapeutic and ergogenic properties, but there is a lack of consensus on the mechanistic pathways through which they function. Potential roles include intracellular buffering, neutralisation of reactive species, and calcium regulation. Comparative investigations of the HCD content of various species provide unique insight into their most likely mechanisms of action. This review chronologically describes how the comparative physiology studies, conducted since the beginning of the 20th century, have shaped our understanding of the physiological roles of HCDs. The investigation of a wide range of physiologically distinct species indicates that those species with a strong reliance on non-oxidative forms of energy production are abundant in HCDs. These include: whales who experience long periods of hypoxia while diving; racehorses and greyhound dogs who have highly developed sprint abilities, and chickens and turkeys whose limited capacity for flight is largely fuelled by their white, glycolytic, muscle. Additionally, a higher HCD content in the Type 2 muscle fibres of various species (which have greater capacity for non-oxidative metabolism) was consistently observed. The pKa of the HCDs render them ideally suited to act as intracellular physicochemical buffers within the pH transit range of the skeletal muscle. As such, their abundance in species which show a greater reliance on non-oxidative forms of energy metabolism, and which experience regular challenges to acid-base homeostasis, provides strong evidence that intracellular proton buffering is an important function of the HCDs in skeletal muscle