In osteoblast cells, cells change their intracellular Ca 2+ concentration ([Ca 2+ ]i) as the response to mechanical stimuli. Although it has been reported that osteoblast cells responded to many kinds of mechanical stimuli including stretch of substrate, shear stress in fluid flow, direct indentation of glass microneedle and hydrostatic pressure etc., the detail of the characteristics of intracellular calcium signaling response to substrate stretch still remains unclear because motion artifact during stretch application causes out of focus plane and observation area, and complicates the in situ time lapse observation of change in [Ca 2+ ]i in a single cell level. In this study, we combined our originally developed cell stretching MEMS device with the ratiometric microscopy method with two kinds of visible wavelength calcium indicator dyes. The cell stretching micro device and the ratiometric method reduce the influence of motion artifact during stretch application, and enable us to quantitatively evaluate the characteristics of cellular calcium signaling response to stretch. MC3T3-E1 osteoblastic cells were plated onto the cell stretching micro device and fluorescently labeled by Ca 2+ indicator Fluo 3 and Fura Red. A uniaxial stretch with three magnitudes of strain 5%, 10% and 15% with constant strain rate were applied to the cells, and in situ time lapse observation of cellular calcium signaling response to stretch was conducted with high temporal and spatial resolution. We succeeded in obtaining time lapse fluorescent image sequences during stretch application without excessive out of focus and blank time. The results revealed that MC3T3-E1 cells change the intensity of calcium signaling response to stretch according to the stretch strain magnitude. As stretch strain magnitude was increased, the amount of change in fluorescent ratio value of Ca 2+ indicators in stretched cells also increased. This result suggests the possibility that osteoblastic cells can sense the magnitude of mechanical stimuli at upstream of mechanotransduction pathway such as influx of extracellular Ca 2+ .
The riding comfort of manual wheelchairs is greatly influenced by Tactile Walking Surface Indicators (TWSIs) that are usually set on sidewalks for visually impaired person. The goal of our research is to understand how block patterns and their vertical vibrations influence the ride of manual wheelchairs. This paper also presents a system that easily measures the vibration characteristic of the walking frame. Using various tactile walking surface indicators as a rugged path, this system measured the vibration when using various walking frames. This paper, therefore, considers the vibration influence of TWSIs on wheelchairs with and without suspension equipped wheels and various walking frames.
In recent years, instructional robot materials have often been used in robotics and engineering education. We use LEGO Mindstorms which is an educational robot development kit in its curriculum. In this subject, students are taught basic subjects such as robot mechanisms, robotic control, and programming. To enhance the subject’s educational effects, the students are set the objective of entry into a robot competition. In the subject, the students are grouped into teams comprising two or three members to undertake the aforementioned task, with the objective of improving their communication skills and problem-solving capacities. The effects of participation in the robot competition were observed in the improved performances in the robot competition implemented in a class (hereinafter called “classroom competition”) held after the SMART competition. In the questionnaire survey conducted at the end of the subject, the upper-class students, in particular, conveyed favorable views on the use of LEGO Mindstorms and participation in the robot competition. On comparing the realized educational effects on the first- and third-year students, positive effects were confirmed in both groups.
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