An integrated platform enabling optogenetic illumination of Caenorhabditis elegans neurons and muscular force measurement in microstructured environments

Optogenetics has been recently applied to manipulate the neural circuits of Caenorhabditis elegans (C. elegans) to investigate its mechanosensation and locomotive behavior, which is a fundamental topic in model biology. In most neuron-related research, free C. elegans moves on an open area such as agar surface. However, this simple environment is different from the soil, in which C. elegans naturally dwells. To bridge up the gap, this paper presents integration of optogenetic illumination of C. elegans neural circuits and muscular force measurement in a structured microfluidic chip mimicking the C. elegans soil habitat. The microfluidic chip is essentially a ∼1 × 1 cm² elastomeric polydimethylsiloxane micro-pillar array, configured in either form of lattice (LC) or honeycomb (HC) to mimic the environment in which the worm dwells. The integrated system has four key modules for illumination pattern generation, pattern projection, automatic tracking of the worm, and force measurement. Specifically, two optical pathways co-exist in an inverted microscope, including built-in bright-field illumination for worm tracking and pattern generation, and added-in optogenetic illumination for pattern projection onto the worm body segment. The behavior of a freely moving worm in the chip under optogenetic manipulation can be recorded for off-line force measurements. Using wild-type N2 C. elegans, we demonstrated optical illumination of C. elegans neurons by projecting light onto its head/tail segment at 14 Hz refresh frequency. We also measured the force and observed three representative locomotion patterns of forward movement, reversal, and omega turn for LC and HC configurations. Being capable of stimulating or inhibiting worm neurons and simultaneously measuring the thrust force, this enabling platform would offer new insights into the correlation between neurons and locomotive behaviors of the nematode under a complex environment.     

List of Reviewers 2006

ASCTRACT

This study aims to analyze the potential and constraints of group-based extension approaches as an institutional innovation in the Vietnamese agricultural extension system. Our analysis therefore unfolds around the challenges of how to foster this kind of approach within the hierarchical extension policy setting and how to effectively shape and enable learning groups. The analysis draws on qualitative data from case studies of five newly established extension groups in Son La province, collected between 2007 and 2008. Content analysis was applied as the main analytical tool. The basic principles of group-based learning approaches are still underdeveloped, mainly due to a non-supportive institutional environment and a command-and-follow mentality. Extension groups suffer from an insufficient distinction between social processes and technical procedures. Finding an appropriate balance between enhancing leadership and supporting collective responsibility is identified as key to sustain groups. The research identified room for adjustments in group-organizational issues since the external institutional environment is hard to change. The particular value of this paper lies in addressing how to organize group-extension approaches in the context of reformed extension systems in a transitional socialist setting.     

Total kinetic energy production of body segments is different between racing and training paces in elite Olympic rowers

Total kinetic energy (TKE) was calculated for 28 Canadian national team Olympic rowers during training on water, comparing low-stroke rates (18–22 stroke/min) and high-stroke rates (32–40 stroke/min), using video analysis. Stroke duration was normalized to 100%, beginning and ending at the “catches”, with the drive phase occurring first and recovery second. Two discrete points were identified during the stroke, both occurring when the fingers had the same horizontal position as the ankles (i.e. mid-drive and mid-recovery). The ratios of recovery-to-drive TKE at these points for the entire body at low and high-stroke rates were 0.36 ± 0.34 and 1.26 ± 0.54 respectively. Significant differences were found for the lower leg, upper arm and forearm segments, and within the female groups. Low-stroke rate is a typical training pace and high-stroke rate is analogous to a race pace. This study demonstrates that TKE production during recovery in a race was not replicated during training. While training at low-stroke rates is vital for technique refinement, this study stresses the importance of training appropriately for the energy expenditure during high-stroke rate recovery. This is commonly overlooked by coaches and athletes.     

Gleichgewichtsleistungen im Handlungsbezug

Dynamic balance performance is neither the objective of conscious actions nor the result of unwitting behavior (cf. Groeben & Scheele, 1993). It is more appropriately conceptualized as an affordance extraction and in each mode of coordination is subject to the specific demands of personal, task-related, and environmental conditions (Newell, 1984, 1996; Nitsch, 1995). Skilled balance performance is thus never achieved for its own sake but is rather integrated in the functional interrelationship of activity goals. Unlike the concept of resources, additional tasks as viewed from this perspective do not necessarily decrease balance performance, but can even serve as positive motivation. Therefore, it is justifiable to raise doubts about a paradigm where the test subjects are required to sway as little as possible during measurement. We assume that postural control is not autonomous, but rather functional as an integrated part of a specific system of motion information (Bootsma, 1998). With these theoretical assumptions in mind, some of the research approaches that abound in the literature are presented and our own research strategy that is intended to be more ecological is outlined.