Molecular and Electrophysiological Characterization of GFP-Expressing CA1 Interneurons in GAD65-GFP Mice

The use of transgenic mice in which subtypes of neurons are labeled with a fluorescent protein has greatly facilitated modern neuroscience research. GAD65-GFP mice, which have GABAergic interneurons labeled with GFP, are widely used in many research laboratories, although the properties of the labeled cells have not been studied in detail. Here we investigate these cells in the hippocampal area CA1 and show that they constitute ∼20% of interneurons in this area. The majority of them expresses either reelin (70±2%) or vasoactive intestinal peptide (VIP; 15±2%), while expression of parvalbumin and somatostatin is virtually absent. This strongly suggests they originate from the caudal, and not the medial, ganglionic eminence. GFP-labeled interneurons can be subdivided according to the (partially overlapping) expression of neuropeptide Y (42±3%), cholecystokinin (25±3%), calbindin (20±2%) or calretinin (20±2%). Most of these subtypes (with the exception of calretinin-expressing interneurons) target the dendrites of CA1 pyramidal cells. GFP-labeled interneurons mostly show delayed onset of firing around threshold, and regular firing with moderate frequency adaptation at more depolarized potentials

Altered chloride homeostasis decreases the action potential threshold and increase hyperexcitability in hippocampal neurons

Chloride ions play an important role in controlling excitability of principal neurons in the central nervous system. When neurotransmitter GABA is released from inhibitory interneurons, activated GABA type A (GABAA) receptors on principal neurons become permeable to chloride. Typically, chloride flows through activated GABAA receptors into the neurons causing hyperpolarization or shunting inhibition, and in turn inhibits action potential (AP) generation. However, in situations when intracellular chloride concentration is increased, chloride ions can flow in opposite direction, depolarize neurons, and promote AP generation. It is generally recognized that altered chloride homeostasis per se has no effect on the AP threshold. Here, we demonstrate that chloride overload of mouse principal CA3 pyramidal neurons not only makes these cells more excitable through GABAA receptor activation but also lowers the AP threshold, further aggravating excitability. This phenomenon has not been described in principal neurons and adds to our understanding of mechanisms regulating neuronal and network excitability, particularly in developing brain and during pathological situations with altered chloride homeostasis. This finding further broadens the spectrum of neuronal plasticity regulated by ionic compositions across the cellular membrane

Experimental Analysis of the Vertical Motions of a IACC Yacht with Calm Water Optimized Bulb

Last Louis Vuitton Cup and XXXI America\u2019s Cup revealed that while the hull shapes were strongly similar for all the top teams\u2019 boats, the bulb shapes were quite different, even if boat performances were very close one to each other. XXXII America\u2019s Cup will adopt Version 5 of AC Rule, which is more restrictive than Version 4 as far as the hull shape, leaving the same degree of freedom to the design of appendages, so the bulb shape optimization will become an even more significant task in the development of a winning yacht. Currently CFD gives the way to lower the number of real life trial and error experiments. It is used to study the flow field of different geometries, giving results on the best one. What if we want to get the optimized solutions? In some cases, this is straight to obtain, we only need a few (less than 10) iterations. However, when the system gets more complex, the use of optimization software is required. The use of modern Computational Fluid Dynamics (CFD) codes coupled with automatic process integration and optimization tools allow us to explore the design space by evaluating a large number of design variations in a fast and smart way. It is important to consider not only the drag forces, but also the motions in waves and the related total mean resistance, considering that the location has changed and the weather/sea conditions are different from the Hauraki Gulf. In this work seakeeping tests of an IACC fully appended scale model have been carried out at the towing tank of the University of Trieste. The model has been tested in head waves, with wave lengths that match the encounter frequencies at Valencia site in upwind sailing conditions, calculated with an heading angle of 150 degrees. Three bulb shapes of different length have been designed using an automatic optimization procedure that, for each length chosen, minimizes the drag in calm water of the bulb and gives the lowest VCG. These bulbs have been used during the seakeeping tests to check the influence of their shape, mostly the length and related mass and added inertia, on the performance of the vertical motions of the yacht in waves

Modalit\ue0 sperimentali e ricerche in corso su imbarcazioni a vela

New test methodology and research activity in progress on sailing yachts The experimental tests methodology and the progressing research activity, made at DINMA Department of the University of Trieste, on sailing yachts will be reported. The use of these experimental data for numerical computational codes and for the wave pattern resistance prediction, allows the implementation of new VPP programs, to design new sailing yachts. Optimization processes, made by using the numerical procedures, allow the definition of the optimal geometrical data for an operational condition defined by the designer

EXPERIMENTAL ANALYSIS OF THE VERTICAL MOTIONS IN WAVES OF AN IACC YACHT WITH CALM WATER-OPTIMIZED BULB SHAPES

This paper deals with an experimental investigation of the heave and pitch motions in waves of an IACC yacht. The seakeeping tests of a fully appended scale model have been carried out at the towing tank of the University of Trieste. A single hull has been tested with different bulb configurations to check the influence of the bulb shape on the performance of the yacht in waves. Three bulb shapes of different length have been developed using multi-objective optimization and process integration, in order to obtain three shapes with minimum drag in calm water and with lowest VCG, satisfying length and volume constraints. The results presented are the Response Amplitude Operators for the vertical motion and the total mean resistance in regular waves

Cell-specific switch for epileptiform activity : critical role of interneurons in the mouse subicular network

During epileptic seizures, neuronal network activity is hyper synchronized whereby GABAergic parvalbumin-interneurons may have a key role. Previous studies have mostly utilized 4-aminopyridine to induce epileptiform discharges in brain slices from healthy animals. However, it is not clear if the seizure-triggering ability of parvalbumin-interneurons also holds true without the use of external convulsive agents. Here, we investigate whether synchronized activation of parvalbumin-interneurons or principal cells can elicit epileptiform discharges in subiculum slices of epileptic mice. We found that selective synchronized activation of parvalbumin-interneurons or principal cells with optogenetics do not result in light-induced epileptiform discharges (LIEDs) neither in epileptic nor in normal brain slices. Adding 4-aminopyridine to slices, activation of parvalbumin-interneurons still failed to trigger LIEDs. In contrast, such activation of principal neurons readily generated LIEDs with features resembling afterdischarges. When GABAA receptor blocker was added to the perfusion medium, the LIEDs were abolished. These results demonstrate that in subiculum, selective synchronized activation of principal excitatory neurons can trigger epileptiform discharges by recruiting a large pool of downstream interneurons. This study also suggests region-specific role of principal neurons and interneurons in ictogenesis, opening towards differential targeting of specific brain areas for future treatment strategies tailored for individual patients with epilepsy

Toward the development of a hydrofoil tailored to passively reduce its lift response to fluid load

The objective of this research is to explore the possibility of using Passive Adaptive Composite (PAC) on structures to help control the lift generated by hydrofoils on boats such as the International Moth. Introducing composite fibres oriented at off-principal axis angles, allow a foil to passively control its pitch angle to reduce the lift generated at higher boat speeds helping to achieve a stable flight in a wide range of weather conditions. PAC utilises the inherent flexibility of a composite structure to induce a twist response under bending load which could be used to minimise the use of active control systems, or even improve the dynamic response of foils in waves. However, to design flexible foils requires numerical and experimental tools to assess the complex fluid structure interactions involved. This paper evaluates a simplified hydrofoil geometry designed to reduce its lift coefficient with increased flow speed. A coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) methodology is presented to predict flexible foil performance. Validation of these numerical tools is achieved through the use of wind tunnel experiments including full field deformation measurements. Twist deformations resulted in a reduction in the effective angle of attack by approximately 30% at higher flow speeds reducing the foil lift and drag significantly.</p

Fluid structure interaction design development of passive adaptive composite international moth foil

The International Moth is a single-handed ultra-lightweight foiling development class boat, and it follows open class rules. Therefore, the designer and builder have full liberty to develop and produce the fastest boat [1]. It is possible to adapt the internal structure of the fixed foil to achieve a tailored twist angle for a given load. Exploring the possibility of using Passive Adaptive Composite (PAC) on the moth hydrofoil to control its pitch angle enables the boat to achieve a stable flight in a wide range of weather conditions whilst reducing the induced drag, passively decreasing the angle of attack in increased boat speed. Using PAC in a multi-element foil, such as the International Moth one, will allow the structure to achieve a constant lift force with speeds higher than the design take-off speed with less need to constantly modifying the rear foil section. Toward the development of a PAC moth fixed foil, experimental and numerical results for a single element aerofoil, able to achieve a linear decrease in lift coefficient with increase in wind speed, are presented and discussed. The results present the aero-elastic response of the foil explaining the complexity involved in fluid-structure interaction problems

Lipid mediator n-3 docosapentaenoic acid-derived protectin D1 enhances synaptic inhibition of hippocampal principal neurons by interaction with a G-protein-coupled receptor

Epilepsy is a severe neurological disease manifested by spontaneous recurrent seizures due to abnormal hyper-synchronization of neuronal activity. Epilepsy affects about 1% of the population and up to 40% of patients experience seizures that are resistant to currently available drugs, thus highlighting an urgent need for novel treatments. In this regard, anti-inflammatory drugs emerged as potential therapeutic candidates. In particular, specific molecules apt to resolve the neuroinflammatory response occurring in acquired epilepsies have been proven to counteract seizures in experimental models, and humans. One candidate investigational molecule has been recently identified as the lipid mediator n-3 docosapentaenoic acid-derived protectin D1 (PD1n-3DPA) which significantly reduced seizures, cell loss, and cognitive deficit in a mouse model of acquired epilepsy. However, the mechanisms that mediate the PD1n-3DPA effect remain elusive. We here addressed whether PD1n-3DPA has direct effects on neuronal activity independent of its anti-inflammatory action. We incubated, therefore, hippocampal slices with PD1n-3DPA and investigated its effect on excitatory and inhibitory synaptic inputs to the CA1 pyramidal neurons. We demonstrate that inhibitory drive onto the perisomatic region of the pyramidal neurons is increased by PD1n-3DPA, and this effect is mediated by pertussis toxin-sensitive G-protein coupled receptors. Our data indicate that PD1n-3DPA acts directly on inhibitory transmission, most likely at the presynaptic site of inhibitory synapses as also supported by Xenopus oocytes and immunohistochemical experiments. Thus, in addition to its anti-inflammatory effects, PD1n-3DPA anti-seizure and neuroprotective effects may be mediated by its direct action on neuronal excitability by modulating their synaptic inputs