Expanding ocean-monitoring capabilities in the Macaronesia with unmanned mobile platforms

The Macaronesia is a vast area playing a key role in the East boundary of the Central North-Atlantic ocean-circulation system. Despite a significant research activity in ocean monitoring for decades using a wide range of observing systems and methodologies, the area is still under-sampled, mainly due access and coverage constrains, as well as the observation sustainability. Ocean gliders offer a new approach in terms of capacity and sustainability, allowing undertake ocean-monitoring in spatiotemporal scales hitherto unavailable. The present work shows preliminary results from the latest mission with buoyancy-driven and surface ocean gliders in the area, whose main goal focuses on to improve and expand ocean observation capabilities strengthening glider endurance lines between archipelagos, as part of the global ocean-observation strategy conducted by the Marine & Maritime Network (R3M), as regional contribution directly aligned with European and international initiatives and strategies in the North Atlantic basin.Peer Reviewe

New dynamics in cerebellar Purkinje cells: torus canards

We describe a transition from bursting to rapid spiking in a reduced mathematical model of a cerebellar Purkinje cell. We perform a slow-fast analysis of the system and find that -- after a saddle node bifurcation of limit cycles -- the full model dynamics follow temporarily a repelling branch of limit cycles. We propose that the system exhibits a dynamical phenomenon new to realistic, biophysical applications: torus canards.Comment: 4 pages; 4 figures (low resolution); updated following peer-review: language and definitions updated, Figures 1 and 4 updated, typos corrected, references added and remove

Transmission of Information in Active Networks

Shannon's Capacity Theorem is the main concept behind the Theory of Communication. It says that if the amount of information contained in a signal is smaller than the channel capacity of a physical media of communication, it can be transmitted with arbitrarily small probability of error. This theorem is usually applicable to ideal channels of communication in which the information to be transmitted does not alter the passive characteristics of the channel that basically tries to reproduce the source of information. For an {\it active channel}, a network formed by elements that are dynamical systems (such as neurons, chaotic or periodic oscillators), it is unclear if such theorem is applicable, once an active channel can adapt to the input of a signal, altering its capacity. To shed light into this matter, we show, among other results, how to calculate the information capacity of an active channel of communication. Then, we show that the {\it channel capacity} depends on whether the active channel is self-excitable or not and that, contrary to a current belief, desynchronization can provide an environment in which large amounts of information can be transmitted in a channel that is self-excitable. An interesting case of a self-excitable active channel is a network of electrically connected Hindmarsh-Rose chaotic neurons.Comment: 15 pages, 5 figures. submitted for publication. to appear in Phys. Rev.

Distribución del sistema del carbonato al sur de las Islas Canarias en la primavera del año 2000

The measurement of the surface molar fraction of CO2 (atmosphere and sea water) and water column pHT, total alkalinity, AT, nutrients and oxygen were carried out in spring 2000 at the European Station for Time Series in the Ocean at the Canary Islands (ESTOC) and in the area located south of the Canary Islands. The significant eddy field strongly affecting the pattern of the chemical and carbonate system variables is presented and discussed. A mixing model based on the thermohaline properties of the water masses was established. The model explained over 97% of the variability found in the distribution of the chemical variables. Intermediate waters to the south of the Canary Islands show a high contribution of Antarctic waters with about 5% of pure Antarctic Intermediate Water. Moreover, the surface structure affected the atmosphere-ocean carbon dioxide exchange, making the area act as a CO2 sink taking up 9.1 mmol m-2 week-1, corresponding to 0.03 Mt of CO2 which were taken up by the area in a week at the end of March 2000.Durante la primavera del año 2000 se realizaron medidas en las aguas superficiales de la fracción molar de CO2 (atmósfera y océano) y en la columna de agua de pHT, alcalinidad total, AT, nutrientes y oxígeno, para la Estación Europea Oceánica de Series Temporales de Canarias (ESTOC) y al sur de las islas Canarias. En este trabajo se presenta y discute el efecto del importante campo de remolinos presente en el área sobre la distribución de las variables químicas y del sistema de carbonato. Se ha establecido un modelo de mezcla, basado en las propiedades termohalinas de las diferentes masas de agua, que explica el 97% de la variabilidad encontrada en la distribución de las variables químicas. Las aguas intermedias al sur de las islas Canarias están caracterizadas por la alta contribución del agua Antártica intermedia diluida, que corresponde con una contribución próxima al 5% de agua Antártica intermedia pura. Por otro lado, las estructuras superficiales afectan al intercambio de CO2 atmósfera-océano, actuando el área como un sumidero de dióxido de carbono incorporando 9.1 mmol m-2 semana-1, que se corresponde con 0.03 MTon de CO2 captadas por el área y en una semana a finales de marzo del 2000

Climbing Fiber Burst Size and Olivary Sub-threshold Oscillations in a Network Setting

The inferior olivary nucleus provides one of the two main inputs to the cerebellum: the so-called climbing fibers. Activation of climbing fibers is generally believed to be related to timing of motor commands and/or motor learning. Climbing fiber spikes lead to large all-or-none action potentials in cerebellar Purkinje cells, overriding any other ongoing activity and silencing these cells for a brief period of time afterwards. Empirical evidence shows that the climbing fiber can transmit a short burst of spikes as a result of an olivary cell somatic spike, potentially increasing the information being transferred to the cerebellum per climbing fiber activation. Previously reported results from in vitro studies suggested that the information encoded in the climbing fiber burst is related to the occurrence of the spike relative to the ongoing sub-threshold membrane potential oscillation of the olivary cell, i.e. that the phase of the oscillation is reflected in the size of the climbing fiber burst. We used a detailed three-compartmental model of an inferior olivary cell to further investigate the possible factors determining the size of the climbing fiber burst. Our findings suggest that the phase-dependency of the burst size is present but limited and that charge flow between soma and dendrite is a major determinant of the climbing fiber burst. From our findings it follows that phenomena such as cell ensemble synchrony can have a big effect on the climbing fiber burst size through dendrodendritic gap-junctional coupling between olivary cells

Blocking Effects of Human Tau on Squid Giant Synapse Transmission and Its Prevention by T-817 MA

Filamentous tau inclusions are hallmarks of Alzheimer’s disease and related neurodegenerative tauopathies, but the molecular mechanisms involved in tau-mediated changes in neuronal function and their possible effects on synaptic transmission are unknown. We have evaluated the effects of human tau protein injected directly into the presynaptic terminal axon of the squid giant synapse, which affords functional, structural, and biochemical analysis of its action on the synaptic release process. Indeed, we have found that at physiological concentration recombinant human tau (h-tau42) becomes phosphorylated, produces a rapid synaptic transmission block, and induces the formation of clusters of aggregated synaptic vesicles in the vicinity of the active zone. Presynaptic voltage clamp recordings demonstrate that h-tau42 does not modify the presynaptic calcium current amplitude or kinetics. Analysis of synaptic noise at the post-synaptic axon following presynaptic h-tau42 microinjection revealed an initial phase of increase spontaneous transmitter release followed by a marked reduction in noise. Finally, systemic administration of T-817MA, a proposed neuro-protective agent, rescued tau-induced synaptic abnormalities. Our results show novel mechanisms of h-tau42 mediated synaptic transmission failure and identify a potential therapeutic agent to treat tau-related neurotoxicityGrant sponsors: NIH AG027476 to Herman Moreno; NS13742/ NS/NINDS/NIH HHS to RLl; FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo, Brasil) projects 2009/01571-6 and CinAPSe 05/56447-7 to Jorge E. Moreira.Peer Reviewe

Blocking Effects of Human Tau on Squid Giant Synapse Transmission and Its Prevention by T-817 MA

Filamentous tau inclusions are hallmarks of Alzheimer's disease and related neurodegenerative tauopathies, but the molecular mechanisms involved in tau-mediated changes in neuronal function and their possible effects on synaptic transmission are unknown. We have evaluated the effects of human tau protein injected directly into the presynaptic terminal axon of the squid giant synapse, which affords functional, structural, and biochemical analysis of its action on the synaptic release process. Indeed, we have found that at physiological concentration recombinant human tau (h-tau42) becomes phosphorylated, produces a rapid synaptic transmission block, and induces the formation of clusters of aggregated synaptic vesicles in the vicinity of the active zone. Presynaptic voltage clamp recordings demonstrate that h-tau42 does not modify the presynaptic calcium current amplitude or kinetics. Analysis of synaptic noise at the post-synaptic axon following presynaptic h-tau42 microinjection revealed an initial phase of increase spontaneous transmitter release followed by a marked reduction in noise. Finally, systemic administration of T-817MA, a proposed neuro-protective agent, rescued tau-induced synaptic abnormalities. Our results show novel mechanisms of h-tau42 mediated synaptic transmission failure and identify a potential therapeutic agent to treat tau-related neurotoxicity

Electrophysiological Characterization of The Cerebellum in the Arterially Perfused Hindbrain and Upper Body of The Rat

In the present study, a non-pulsatile arterially perfused hindbrain and upper body rat preparation is described which is an extension of the brainstem preparation reported by Potts et al., (Brain Res Bull 53(1):59–67), 1. The modified in situ preparation allows study of cerebellar function whilst preserving the integrity of many of its interconnections with the brainstem, upper spinal cord and the peripheral nervous system of the head and forelimbs. Evoked mossy fibre, climbing fibre and parallel fibre field potentials and EMG activity elicited in forelimb biceps muscle by interpositus stimulation provided evidence that both cerebellar inputs and outputs remain operational in this preparation. Similarly, the spontaneous and evoked single unit activity of Purkinje cells, putative Golgi cells, molecular interneurones and cerebellar nuclear neurones was similar to activity patterns reported in vivo. The advantages of the preparation include the ability to record, without the complications of anaesthesia, stabile single unit activity for extended periods (3 h or more), from regions of the rat cerebellum that are difficult to access in vivo. The preparation should therefore be a useful adjunct to in vitro and in vivo studies of neural circuits underlying cerebellar contributions to movement control and motor learning