Direct cell seeding on collagen-coated silicone mandrels to generate cell-derived tissue tubes

The large number of patients suffering from cardiovascular diseases has led to a high demand for functional arterial replacements. A variety of approaches to vascular graft tissue engineering have shown promise, including seeding cells onto natural and synthetic scaffolds or by culturing cell sheets which are subsequently rolled into a tube without exogenous scaffolds. The goal of this project is to develop and characterize cell-derived, fully biological small diameter tissue engineered tubes by seeding and culturing cells directly on tubular supports. Rat aortic smooth muscle cells were seeded onto collagen-coated silicone mandrels and cultured for 14 days. Cells proliferated on the mandrels to form tubes (1.19 mm inner diameter, 1.68 +/- 0.1 mm outer diameter and 230 +/- 63 microns thick; n=72). Histological analysis of the developed tissue tubes demonstrated circumferential alignment of smooth muscle cells, abundant glycosaminoglycan production and some amount of collagen production. On inflating at a constant rate, it was observed that the tissue tubes dilated to an average burst pressure of 256 +/- 76 mmHg; (n=11). In order to observe the effects of addition of soluble factors on extracellular matrix synthesis and mechanical properties, tissue tubes were grown in culture medium supplemented with 50 microgram/ml sodium ascorbate. A significant decrease in outer diameter and wall thickness (1.57 +/- 0.02 mm and 189 +/- 10 microns; n=6 respectively) in the treated groups was observed as compared to (1.66 +/- 0.06 mm and 234 +/- 32 microns; n=6; p\u3c0.05) for the untreated control groups. A slight increase in collagen production was observed by visual assessment of histological images of the ascorbate-treated tissue tubes. This suggests that by using a direct cell seeding approach, it is possible to develop completely biologic small diameter cell-derived tissue tubes that can withstand handling, and it may also possible to modulate matrix synthesis by optimizing cell culture conditions

Multiple sclerosis, a treatable disease

This article reviews our current understanding and modern treatment of multiple sclerosis (MS). MS is a disabling condition resulting in devastating social and economic impacts. As MS can affect any part of the central nervous system, the presentation is often diverse; however, there are key features that can be useful in the clinic. We comment on the diagnostic criteria and review the main subtypes of MS, including clinically isolated syndrome, relapsing remitting MS, secondary progressive MS and primary progressive MS. Although the underlying aetiology of MS is still not known, we summarise those with most evidence of association. Finally, we aim to present treatment strategies for managing the acute relapse, disease-modifying therapies and MS symptoms. This review highlights that progressive MS is an area where there is currently a paucity of available disease-modifying treatments and this will be a major focus for future development

Diagnosing faults in autonomous robot plan execution

A major requirement for an autonomous robot is the capability to diagnose faults during plan execution in an uncertain environment. Many diagnostic researches concentrate only on hardware failures within an autonomous robot. Taking a different approach, the implementation of a Telerobot Diagnostic System that addresses, in addition to the hardware failures, failures caused by unexpected event changes in the environment or failures due to plan errors, is described. One feature of the system is the utilization of task-plan knowledge and context information to deduce fault symptoms. This forward deduction provides valuable information on past activities and the current expectations of a robotic event, both of which can guide the plan-execution inference process. The inference process adopts a model-based technique to recreate the plan-execution process and to confirm fault-source hypotheses. This technique allows the system to diagnose multiple faults due to either unexpected plan failures or hardware errors. This research initiates a major effort to investigate relationships between hardware faults and plan errors, relationships which were not addressed in the past. The results of this research will provide a clear understanding of how to generate a better task planner for an autonomous robot and how to recover the robot from faults in a critical environment

A Framework for Sequential Planning in Multi-Agent Settings

This paper extends the framework of partially observable Markov decision processes (POMDPs) to multi-agent settings by incorporating the notion of agent models into the state space. Agents maintain beliefs over physical states of the environment and over models of other agents, and they use Bayesian updates to maintain their beliefs over time. The solutions map belief states to actions. Models of other agents may include their belief states and are related to agent types considered in games of incomplete information. We express the agents autonomy by postulating that their models are not directly manipulable or observable by other agents. We show that important properties of POMDPs, such as convergence of value iteration, the rate of convergence, and piece-wise linearity and convexity of the value functions carry over to our framework. Our approach complements a more traditional approach to interactive settings which uses Nash equilibria as a solution paradigm. We seek to avoid some of the drawbacks of equilibria which may be non-unique and do not capture off-equilibrium behaviors. We do so at the cost of having to represent, process and continuously revise models of other agents. Since the agents beliefs may be arbitrarily nested, the optimal solutions to decision making problems are only asymptotically computable. However, approximate belief updates and approximately optimal plans are computable. We illustrate our framework using a simple application domain, and we show examples of belief updates and value functions

A proposed increase in retinal field-of-view may lead to spatial shifts in images

Visual information determines majority of our spatial behavior. The eye projects a 2-D image of the world on the retina. We demonstrate that when a monocular-like imaging system operates entirely with optically dense fluids, an increase in field-of-view (FOV) is observed compared to an experimental condition, where the ocular medium is optically neutral. Resulting spatial shifts in the retinal image towards the fovea complement the photoreceptor distribution pattern, incidentally revealing a new role for ocular fluids in the image space. Possible effects on the perceived egocentric object location are discussed.Comment: 13 pages, 2 figures, 1 tabl