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Objective: Intravascular lymphatic valves often occur in proximity to vessel junctions. It is commonly held that disturbed flow at junctions is responsible for accumulation of valve‐forming cells (VFCs) at these locations as the initial step in valve creation, and the one which explains the association with these sites. However, evidence in favor is largely limited to cell culture experiments. Methods: We acquired images of embryonic lymphatic vascular networks from day E16.5, when VFC accumulation has started but the developing valve has not yet altered the local vessel geometry, stained for Prox1, which co‐localizes with Foxc2. Using finite‐element computational fluid mechanics, we simulated the flow through the networks, under conditions appropriate to this early development stage. Then we correlated the Prox1 distributions with the distributions of simulated fluid shear and shear stress gradient. Results: Across a total of 16 image sets, no consistent correlation was found between Prox1 distribution and the local magnitude of fluid shear, or its positive or negative gradient. Conclusions: This, the first direct semi‐empirical test of the localization hypothesis to interrogate the tissue from in vivo at the critical moment of development, does not support the idea that a feature of the local flow determines valve localization. [ABSTRACT FROM AUTHOR]

A team-taught interdisciplinary undergraduate unit in Sustainable Development has been developed and run over the past two years at the University of Bristol. This has been a unique initiative for this university to take. As in most other research-intensive higher education institutions, teaching generally follows rather traditional disciplinary conventions, operating within departmental bounds. The initiative was unusual--and indeed ambitious--enough to gain the Higher Education Environmental Performance Improvement (HEEPI) Green Gown Award in teaching for 2007 (HEEPI is a project supported by the Higher Education Founding Council for England; http://www.heepi.org.uk/green_gown_awards.htm). There are both challenges and pleasures in designing and delivering a team-taught unit in a traditional university setting. This experience is outlined and evaluated here, giving consideration to both the practical and the more fundamentally philosophical issues encountered in the process. (Contains 4 tables.)

We present experimental and computational results that describe the level, distribution, and importance of velocity fluctuations within the venous anastomosis of an arteriovenous graft. The motivation of this work is to understand better the importance of biomechanical forces in the development of intimal hyperplasia within these grafts. Steady-flow in vitro studies (Re=1060 and 1820) were conducted within a graft model that represents the venous anastomosis to measure velocity by means of laser Doppler anemometry. Numerical simulations with the same geometry and flow conditions were conducted by employing the spectral element technique. As flow enters the vein from the graft, the velocity field exhibits flow separation and coherent structures (weak turbulence) that originate from the separation shear layer. We also report results of a porcine animal study in which the distribution and magnitude of vein-wall vibration on the venous anastomosis were measured at the time of graft construction. Preliminary molecular biology studies indicate elevated activity levels of the extracellular regulatory kinase ERK1/2, a mitogen-activated protein kinase involved in mechanotransduction, at regions of increased vein-wall vibration. These findings suggest a potential relationship between the associated turbulence-induced vein-wall vibration and the development of intimal hyperplasia in arteriovenous grafts. Further research is necessary, however, in order to determine if a correlation exists and to differentiate the vibration effect from that of flow related effects.

Pointing to a visual target that disappears prior to movement requires the maintenance of a memory representation about the location of the target. It has been shown that a target can be stored egocentrically, allocentrically, or in both frames of reference simultaneously. The main goal of the present study was to compare the accuracy and kinematics of a pointing movement to a remembered target when egocentric, allocentric, or combined egocentric and allocentric coding was possible. The task was to localize, memorize, and reach to a remembered target. Condition 1 was the ‘no-context’ condition and involved presenting the target in a completely dark environment (egocentric condition). For 2 other conditions, the target was presented within a visual context provided by an illuminated square. Condition 2 was the ‘stationary-context’ condition and involved keeping the context at the same position during the whole trial (egocentric and/or allocentric coding). Condition 3 was a ‘moved-context’ condition that involved shifting the context to a different location during the recall delay (allocentric coding). Movement accuracy and kinematics results were strikingly similar for the moved-context and stationary-context conditions. These results suggest that when both allocentric and egocentric coding are possible, an allocentric strategy is used. [ABSTRACT FROM AUTHOR]

Examines the contributions of gait and trunk movements to prehension. Analysis on three-dimensional movements via world- and body-centered coordinates; Use of task-specific synergies; Variable contributions of synergies to different movement systems.

A pointing task was performed both while subjects stood beside and while subjects walked past targets that involved differing movement amplitudes and differing sizes. The hand kinematics were considered relative both to a fixed frame of reference in the movement environment (end effector kinematics) and to the subject's body (kinematics of the hand alone). From the former view, there were few differences between standing and walking versions of the task, indicating similarity of the kinematics of the hand. However, when the hand was considered alone, marked differences in the kinematics and spatial trajectories between standing and walking were achieved. Furthermore, kinematic analyses of the trunk showed that subjects used differing amounts of both flexion-extension and rotation movements at the waist depending on whether they were standing or walking as well as on the constraints imposed by target width and movement amplitude. The present results demonstrate the existence of motor equivalence in a combined upper and lower extremity task and that this motor equivalence is a control strategy to cope with increasing task demands. Given the complexity involved in controlling the arm, the torso, and the legs (during locomotion), the movements involved in the present tasks appear to be planned and controlled by considering the whole body as a single unit. [ABSTRACT FROM AUTHOR]