Vocal Strategies in Confronting Interfering Sounds by a Frog from the Southern Temperate Forest,Batrachyla antartandica

Animals are communicating by sound face interference from biotic and abiotic sources. Contrasting strategies have been reported in different taxa in the presence of prolonged noises, but in particular, interactions among acoustically active species have been studied to a very limited extent. In addition, reactions of a single species to interferences having contrasting structural patterns have not been explored systematically. The vocal responses of 16 male frogs Batrachyla antartandica from the temperate austral forest in Chile were tested with conspecific calls and with the calls of two sympatric species: B. taeniata and B. leptopus, broadcast at amplitudes of 73, 79, 85, 91, and 97 dB peak sound pressure level (SPL). Also, the vocal activity of the subjects during exposure to a 3‐min continuous broadband noise presented at 67 dB root mean square (RMS) SPL was monitored. The subjects gave significantly higher responses to the conspecific relative to the heterospecific calls but increased their vocal output in the presence of continuous noise. The preference of vocal responses for the conspecific relative to heterospecific signals bears a general resemblance to those exhibited by B. taeniata in a previous study and potentially contributes to the typical segregation in conspecific choruses observed in areas where these frogs breed in sympatry. Such lack of vocal responses to heterospecific stimuli contrasts with the increase in vocal activity during exposure to continuous noise lacking a temporal fine structure and points to identify different strategies in confronting interferences of diverse origin.     

Aspidosperma (Apocynaceae) plant cytotoxicity and activity towards malaria parasites. Part I: Aspidosperma nitidum (Benth) used as a remedy to treat fever and malaria in the Amazon

Infusions of Aspidosperma nitidum (Apocynaceae) wood bark are used to treat fever and malaria in the Amazon Region. Several species of this family are known to possess indole alkaloids and other classes of secondary metabolites, whereas terpenoids, an inositol and the indole alkaloids harmane-3 acid and braznitidumine have been described in A. nitidum . In the present study, extracts from the wood bark, leaves and branches of this species were prepared for assays against malaria parasites and cytotoxicity testing using human hepatoma and normal monkey kidney cells. The wood bark extracts were active against Plasmodium falciparum and showed a low cytotoxicity in vitro, whereas the leaf and branch extracts and the pure alkaloid braznitidumine were inactive. A crude methanol extract was subjected to acid-base fractionation aimed at obtaining alkaloid-rich fractions, which were active at low concentrations against P. falciparum and in mice infected with and sensitive Plasmodium berghei parasites. Our data validate the antimalarial usefulness of A. nitidum wood bark, a remedy that can most likely help to control malaria. However, the molecules responsible for this antimalarial activity have not yet been identified. Considering their high selectivity index, the alkaloid-rich fractions from the plant bark might be useful in the development of new antimalarials.     

Physical exercise-induced changes in the core body temperature of mice depend more on ambient temperature than on exercise protocol or intensity

The mechanisms underlying physical exercise-induced hyperthermia may be species specific. Therefore, the present study aimed to investigate the effects of exercise intensity and ambient temperature on the core body temperature (T _core) of running mice, which provide an important experimental model for advancing the understanding of thermal physiology. We evaluated the influence of different protocols (constant- or incremental-speed exercises), treadmill speeds and ambient temperatures (T _a) on the magnitude of exercise-induced hyperthermia. To measure T _core, a telemetric sensor was implanted in the abdominal cavity of male adult Swiss mice under anesthesia. After recovering from the surgery, the animals were familiarized to running on a treadmill and then subjected to the different running protocols and speeds at two T _a: 24 °C or 34 °C. All of the experimental trials resulted in marked increases in T _core. As expected, the higher-temperature environment increased the magnitude of running-induced hyperthermia. For example, during incremental exercise at 34 °C, the maximal T _core achieved was increased by 1.2 °C relative to the value reached at 24 °C. However, at the same T _a, neither treadmill speed nor exercise protocol altered the magnitude of exercise-induced hyperthermia. We conclude that T _core of running mice is influenced greatly by T _a, but not by the exercise protocols or intensities examined in the present report. These findings suggest that the magnitude of hyperthermia in running mice may be regulated centrally, independently of exercise intensity.     

Ab initio simulations of Cu binding sites on the N-terminal region of prion protein

The human prion protein binds Cu²⁺ ions in the octarepeat domain of the N-terminal tail up to full occupancy at pH 7.4. Recent experiments have shown that the HGGG octarepeat subdomain is responsible for holding the metal bound in a square-planar configuration. By using first principle ab initio molecular dynamics simulations of the Car–Parrinello type, the coordination of copper to the binding sites of the prion protein octarepeat region is investigated. Simulations are carried out for a number of structured binding sites. Results for the complexes Cu(HGGGW)(wat), Cu(HGGG), and [Cu(HGGG)]₂ are presented. While the presence of a Trp residue and a water molecule does not seem to affect the nature of the copper coordination, high stability of the bond between copper and the amide nitrogen of deprotonated Gly residues is confirmed in all cases. For the more interesting [Cu(HGGG)]₂ complex, a dynamically entangled arrangement of the two domains with exchange of amide nitrogen bonds between the two copper centers emerges, which is consistent with the short Cu–Cu distance observed in experiments at full copper occupancy.