Morphometric Analysis of Paramylon Particles Produced by Euglena gracilis EOD-1 Using FIB/SEM Tomography.

Euglena gracilis EOD-1, a microalgal strain, produces large quantities of paramylon, a class of polymers known as ß-1,3-glucans and has been reported to function as a dietary fiber and to improve the metabolic syndrome including obesity. However, despite its importance, the morphometric analysis of paramylon has not been conducted so far. In this study, we attempted to observe the detailed three-dimensional structure of paramylon by focused ion beam/scanning electron microscopy (FIB/SEM). Paramylon samples were fixed and three-dimensional image reconstruction and segmentation of the image stack were created using computer software (Amira v6.0.1, FEI). The results indicated that the inside of paramylon particles (diameter: 5 µm, thickness: 3 µm) was comprised of a dense structure with no evidence of the presence of large pores and gaps, although a small 100 nm crack was observed. The specific surface area of paramylon particles measured by the Brunauer-Emmet-Teller (BET) method, was not as large as activated charcoal, but similar to those of plant starches, indicating that the cholesterol-lowering effect of paramylon cannot be simply attributed to its adsorption ability. The FIB/SEM method was found to be useful for elucidating the internal structure of small solid particles.

Visual estimation of spatial requirements for locomotion in novice wheelchair users.

Locomotion using a wheelchair requires a wider space than does walking. Two experiments were conducted to test the ability of nonhandicapped adults to estimate the spatial requirements for wheelchair use. Participants judged from a distance whether doorlike apertures of various widths were passable or not passable. Experiment 1 showed that participants underestimated the spatial requirements for wheelchair use but overestimated the spatial requirements for walking. Experiment 2 showed that their underestimation improved but was not completely eliminated after 8 days of practice passing through apertures. Analyses of wheelchair performance in the practice condition showed that the underestimation may have arisen from misperception of the positions of the hands when the participants were grasping the wheelchair hand-rims. The theoretical and practical implications of these findings are discussed.