Hungry brains: A meta-analytical review of brain activation imaging studies on food perception and appetite in obese individuals

The dysregulation of food intake in chronic obesity has been explained by different theories. To assess their explanatory power, we meta-analyzed 22 brain-activation imaging studies. We found that obese individuals exhibit hyper-responsivity of the brain regions involved in taste and reward for food-related stimuli. Consistent with a Reward Surfeit Hypothesis, obese individuals exhibit a ventral striatum hyper-responsivity in response to pure tastes, particularly when fasting. Furthermore, we found that obese subjects display more frequent ventral striatal activation for visual food cues when satiated: this continued processing within the reward system, together with the aforementioned evidence, is compatible with the Incentive Sensitization Theory. On the other hand, we did not find univocal evidence in favor of a Reward Deficit Hypothesis nor for a systematic deficit of inhibitory cognitive control. We conclude that the available brain activation data on the dysregulated food intake and food-related behavior in chronic obesity can be best framed within an Incentive Sensitization Theory. Implications of these findings for a brain-based therapy of obesity are briefly discussed

Two-photon polymerized "nichoid" substrates maintain function of pluripotent stem cells when expanded under feeder-free conditions

BACKGROUND: The use of pluripotent cells in stem cell therapy has major limitations, mainly related to the high costs and risks of exogenous conditioning and the use of feeder layers during cell expansion passages. METHODS: We developed an innovative three-dimensional culture substrate made of “nichoid” microstructures, nanoengineered via two-photon laser polymerization. The nichoids limit the dimension of the adhering embryoid bodies during expansion, by counteracting cell migration between adjacent units of the substrate by its microarchitecture. We expanded mouse embryonic stem cells on the nichoid for 2 weeks. We compared the expression of pluripotency and differentiation markers induced in cells with that induced by flat substrates and by a culture layer made of kidney-derived extracellular matrix. RESULTS: The nichoid was found to be the only substrate, among those tested, that maintained the expression of the OCT4 pluripotency marker switched on and, simultaneously, the expression of the differentiation markers GATA4 and α-SMA switched off. The nichoid promotes pluripotency maintenance of embryonic stem cells during expansion, in the absence of a feeder layer and exogenous conditioning factors, such as the leukocyte inhibitory factor. CONCLUSIONS: We hypothesized that the nichoid microstructures induce a genetic reprogramming of cells by controlling their cytoskeletal tension. Further studies are necessary to understand the exact mechanism by which the physical constraint provided by the nichoid architecture is responsible for cell reprogramming. The nichoid may help elucidate mechanisms of pluripotency maintenance, while potentially cutting the costs and risks of both feed-conditioning and exogenous conditioning for industrial-scale expansion of stem cells. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13287-016-0387-z) contains supplementary material, which is available to authorized users

Design and simulation of meshing of a particular internal rotary pump

This paper presents a complete description of a specific geometry applicable to internal rotary pump. A particular design is considered, characterized by superior flow-rate performance and different contact mechanism in respect with the common trochoidal pumps. All the necessary aspects regarding the kinematics and operation of the machine are taken into account, by means of a mathematical formulation. In particular, the kinematic analysis considers the possible presence of transmission errors and assures the absence of interference by a tooth contact analysis. The achieved mathematical model allows the designer to obtain the complete definition of the rotor profiles in parametric form

Introductory Analysis of an Innovative Volumetric Rotary Machine

The study of an innovative volumetric rotary machine is presented in this work. The machine is constituted by a stator and a number of pistons rotating inside the stator and attached to a crank. Due to the particular type of solution, this mechanism realizes for every piston a chamber, that varies its volume during crank rotation, and consequently it can be used to realize a volumetric rotary machine. In the paper the geometrical constraints that characterize the mechanism are analyzed, in order to obtain the equation of the stator profile, using an analytical approach. Once the stator profile is determined and appropriate design parameters settled, the analysis of the motion permits to numerically determine the profile of the rolling pistons. Starting from the geometry, the specific displacement and the maximum compression ratio can be calculated as a function of design parameters. Finally, the analysis is focused on the unbalanced inertia forces generated by the mechanism during its motion. The results obtained permit to choose the design parameters for a particular application, showing that the mechanism can be suitable for pumps, compressors and pneumatic engine

One-Mode Extra Insensitive Input Shapers to Reduce Residual Vibration in Flexible Arms: Experimental Verification

Input shaping is a particular feedforward-control strategy based on the convolution of an input command with a sequence of pulses, whose amplitude and application time are function of the natural frequencies of the system to be controlled. The effect consists in a significant reduction of the residual vibration, compared with the original unshaped command. This paper presents the results of the experimental tests carried out on the master robot arm of the Test-bed for Microgravity Simulation in Robotic Arm Dynamics (TeMSRAD) set up at the Department of Structural Mechanics, Università di Pavia. One-mode extra insensitive shapers were tested experimentally for different vibration limits to determine the sensitivity curve with respect to uncertainties in the system model or environmental noise typical of the operating conditions required by the International Space Station (ISS)

Extra Insensitive Shapers for Flexible Articulated System to Minimize Residual Vibration in Presence of Modeling Errors

Input shaping is an effective method of minimizing vibration in flexible systems. In particular in space robotics the design of light-weight manipulators is motivated by the increasing demand for high-speed performance and low energy consumption assembly and the control of such systems deals with the great flexibility of these structures. Input shaping (IS) is a feedforward-control strategy characterized by simplicity and effectiveness and it can be used in addition to feedback control approaches. One important property of input shapers is the robustness to frequency modeling errors and it can be measured using a sensitivity plot. This paper shows the goal of the input shaping design method to match a minimum time delay of the maneuver with a sufficient insensitivity to system parameters variation. Greater insensitivity can be reached by using robust shapers such as Extra-Insensitive (EI) input shapers which allow a small amount of vibration at the modeled frequency but a considerably wider insensitivity curve. Experimental results carried out on the Test-bed for Microgravity Simulation in Robotic Arm Dynamics (TeMSRAD), set up at the Department of Structural Engineering, Università di Pavia are presented

Complications of videolaparoscopic cholecystectomy: a retrospective analysis of 1037 consecutive cases

The authors describe some of the complications that appear more frequently with laparoscopic cholecystectomy than open cholecystectomy and the mechanisms underlying the occurrence of bile duct injuries, making reference to 0.58% of bile duct injuries in 1037 consecutive laparoscopic cases and the possibility of treatmen

Engineering the vasculature of decellularized rat kidney scaffolds using human induced pluripotent stem cell-derived endothelial cells

Generating new kidneys using tissue engineering technologies is an innovative strategy for overcoming the shortage of donor organs for transplantation. Here we report how to efficiently engineer the kidney vasculature of decellularized rat kidney scaffolds by using human induced pluripotent stem cell (hiPSCs)-derived endothelial cells (hiPSC-ECs). In vitro, hiPSC-ECs responded to flow stress by acquiring an alignment orientation, and attached to and proliferated on the acellular kidney sections, maintaining their phenotype. The hiPSC-ECs were able to self-organize into chimeric kidney organoids to form vessel-like structures. Ex vivo infusion of hiPSC-ECs through the renal artery and vein of acellular kidneys resulted in the uniform distribution of the cells in all the vasculature compartments, from glomerular capillaries to peritubular capillaries and small vessels. Ultrastructural analysis of repopulated scaffolds through transmission and scanning electron microscopy demonstrated the presence of continuously distributed cells along the vessel wall, which was also confirmed by 3D reconstruction of z-stack images showing the continuity of endothelial cell coverage inside the vessels. Notably, the detection of fenestrae in the endothelium of glomerular capillaries but not in the vascular capillaries was clear evidence of site-specific endothelial cell specialisation

Development and application of a computational fluid dynamics methodology to predict fuel-air mixing and sources of soot formation in gasoline direct injection engines

A detailed understanding of the air-fuel mixing process in gasoline direct injection engines is necessary to avoid soot formation that might result from charge inhomogeneities or liquid fuel impingement on the cylinder walls. Within this context, the use of multidimensional models might be helpful to betterunderstand how spray evolution in cylinder charge motions and combustion chamber design affects the mixture quality at spark-timing. In this work, the authors developed and applied a computational fluid dynamics methodology to simulate gas exchange and air-fuel mixture formation in gasoline direct injection engines. To this end, a suitable set of spray submodels was implemented into an open-source code to properly describe the evolution of gasoline jets emerging from multihole atomizers. Furthermore, the complete liquid film dynamics was also considered. For a proper assessment of the approach, a gasoline direct injection engine running at full load was simulated and effects of spray targeting and engine speed were studied. A detailed postprocessing of the computed data of liquid film mass, homogeneity index and equivalence ratio distributions was performed and correlated with experimental data of particulate emissions. Satisfactory results were achieved, proving the effectiveness of the proposed methodology in predicting the effects of injection system and operating conditions on soot formation