Warm Body Temperature Facilitates Energy Efficient Cortical Action Potentials

The energy efficiency of neural signal transmission is important not only as a limiting factor in brain architecture, but it also influences the interpretation of functional brain imaging signals. Action potential generation in mammalian, versus invertebrate, axons is remarkably energy efficient. Here we demonstrate that this increase in energy efficiency is due largely to a warmer body temperature. Increases in temperature result in an exponential increase in energy efficiency for single action potentials by increasing the rate of Na+ channel inactivation, resulting in a marked reduction in overlap of the inward Na+, and outward K+, currents and a shortening of action potential duration. This increase in single spike efficiency is, however, counterbalanced by a temperature-dependent decrease in the amplitude and duration of the spike afterhyperpolarization, resulting in a nonlinear increase in the spike firing rate, particularly at temperatures above approximately 35°C. Interestingly, the total energy cost, as measured by the multiplication of total Na+ entry per spike and average firing rate in response to a constant input, reaches a global minimum between 37–42°C. Our results indicate that increases in temperature result in an unexpected increase in energy efficiency, especially near normal body temperature, thus allowing the brain to utilize an energy efficient neural code

Efeitos da reposição hidroeletrolítica sobre parâmetros cardiorrespiratórios em exercício e recuperação

INTRODUÇÃO: a necessidade de reposição ao máximo das perdas hídricas tornou-se estabelecida e difundida nos consensos internacionais. Entretanto, permanece pouco compreendida a influência da reposição quando administrada, igualmente, durante e após o exercício sobre parâmetros cardiorrespiratórios. OBJETIVO: analisar os efeitos da reposição hidroeletrolítica na frequência cardíaca (FC), pressão arterial sistólica (PAS), pressão arterial diastólica (PAD), saturação parcial de oxigênio (SpO2) e frequência respiratória (f) de jovens durante e após um exercício de longa duração. MÉTODOS: 31 jovens (21,55 ± 1,89 anos) realizaram três visitas ao laboratório (intervalo de 48 horas entre elas), sendo na primeira aplicado um teste incremental, para determinação da carga utilizada nas visitas seguintes, e nas duas últimas, denominadas protocolo controle (PC) e protocolo experimental (PE), os sujeitos foram submetidos a 10 min de repouso supino, 90 min de exercício em esteira ergométrica (60% do VO2pico) e 60 min de repouso supino. No PC não houve hidratação e no PE houve ingestão de solução isotônica. Os parâmetros FC, PAS, PAD, SpO2 e f foram mensurados no final do repouso; nos minutos 30, 60 e 90 do exercício, com exceção da f; e nos minutos 1, 3, 5, 7, 10, 20, 30, 40, 50 e 60 pós-exercício. Foi aplicado o teste t de Student ou teste de Mann-Whitney e ANOVA para medidas repetidas ou teste de Friedman seguidos de testes post hoc, com p BACKGROUND: The replacement required of water waste is recognized and established in an international consensus. However, the influence of the replacement in cardiorespiratory parameters, especially when administered during and after physical activity, remains poorly understood. OBJECTIVE: To analyze the effects of fluid replacement in heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), partial oxygen saturation (SpO2) and respiratory rate (f) of the youngsters during and after a long-term exercise. METHODS: 31 individuals (21.55 ± 1.89 years old) performed three visits in the laboratory (48 hours among them), at first an incremental test was applied to determine the load used during subsequent visits. In the last two, called control protocol (CP) and the experimental protocol (EP), the subjects were undergone to a 10 min of supine rest, 90 min of treadmill exercise (60% of VO2peak) and 60 min of supine rest. The difference between the protocols is that in the EP there was the intake isotonic solution and the CP there wasn't hydration. The parameters HR, SBP, DBP, SpO2 and f were measured at the end of the rest, in 30, 60 and 90 minutes of the activity, except the f parameter, and at 1, 3, 5, 7, 10, 20, 30, 40, 50 and 60 minute post-exercise. Student t test or Mann-Whitney, and ANOVA repeated measures or Friedman test followed by post hoc tests, were applied (p < 0.05). RESULTS: the intake isotonic solution provided SBP and DBP maintenance and smaller increment in HR during the exercise; promoted faster return of HR and kept SpO2, SBP (from the 5th minute) and f (from the 30th min) during recovery. CONCLUSION: the hydration protocol influenced the cardiorespiratory parameters for youngsters during and after submaximal physical exercise of constant intensity and long duration

The Aegis orbit determination and impact monitoring system and services of the ESA NEOCC web portal

The NEO Coordination Centre (NEOCC) of the European Space Agency is an operational centre that, among other activities, computes the orbits of near-Earth objects and their probabilities of impact with the Earth. The NEOCC started providing information about near-Earth objects in 2012 on a dedicated web portal, accessible at https://neo.ssa.esa.int/. Since the beginning of the operational phase, many developments and improvements have been implemented regarding the software, the data provided, and the portal. One of the most important upgrades is that the NEOCC is now independently providing data through a newly developed Orbit Determination and Impact Monitoring system, named Aegis. All the data computed by Aegis are publicly available on the NEOCC web portal, and Aegis is also used to maintain all the major services offered. The most important services comprise an orbital catalogue of all known asteroids, a list of possible future impacts with the Earth (also called Risk List), a list of forthcoming close approaches, a set of graphical toolkits, and an on-demand ephemerides service. Many of the services are also available through dedicated APIs, which can be used to automatically retrieve data. Here we give an overview of the algorithms implemented in the Aegis software and provide a summary of the services offered by the NEOCC that are supported by Aegis.European Space AgencyThe work by D. Bracali Cioci, F. Bernardi, A. Bertolucci, L. Dimare, F. Guerra, V. Baldisserotto, A. Chessa, and A. Del Vigna was conducted under European Space Agency contracts: No. AO/1-9075/17/DE/MRP "P3-COM-VI", No. 4000116371/16/D/MRP "P2-NEO-VII" and its CCN, No. 4000123583/18/D/MRP "P3-NEO-XIII" and its CCN, No. 4000133990/21/D/KS "S1-PD-02".Celestial Mechanics and Dynamical Astronom