* Simulating microgravity using a random positioning machine for inducing cellular responses to mechanotransduction in human osteoblasts.
- The mechanotransduction pathways that mediate cellular responses to contact forces are better understood than those that mediate response to distance forces, especially the force of gravity. Removing or reducing gravity for significant periods of time involves either sending samples to space, inducing diamagnetic levitation with high magnetic fields, or continually reorienting samples for a period, all in a manner that supports cell culturing. Undesired secondary effects due to high magnetic fields or shear forces associated with fluid flow while reorienting must be considered in the design of ground-based devices. We have developed a lab-friendly and compact random positioning machine (RPM) that fits in a standard tissue culture incubator. Using a two-axis gimbal, it continually reorients samples in a manner that produces an equal likelihood that all possible orientations are visited. We contribute a new control algorithm by which the distribution of probabilities over all possible orientations is completely uniform. Rather than randomly varying gimbal axis speed and/or direction as in previous algorithms (which produces non-uniform probability distributions of orientation), we use inverse kinematics to follow a trajectory with a probability distribution of orientations that is uniform by construction. Over a time period of 6 h of operation using our RPM, the average gravity is within 0.001 23% of the gravity of Earth. Shear forces are minimized by limiting the angular speed of both gimbal motors to under 42 °/s. We demonstrate the utility of our RPM by investigating the effects of simulated microgravity on adherent human osteoblasts immediately after retrieving samples from our RPM. Cytoskeletal disruption and cell shape changes were observed relative to samples cultured in a 1 g environment. We also found that subjecting human osteoblasts in suspension to simulated microgravity resulted in less filamentous actin and lower cell stiffness.
=>1.超えて, 一面に, 移って, 始めから終わりまで, 終わって, を支配して, の間, しながら, 倒れて, の上に,
を覆って, を越えて, の向こう側に, より多く, 2.もう一度, 繰り返して
Overview of noun over
The noun over has 1 sense (no senses from tagged texts)
1. over -- ((cricket) the division of play during which six balls are bowled at the batsman by one
player from the other team from the same end of the pitch)
Overview of adj over
The adj over has 1 sense (first 1 from tagged texts)
1. (21) complete, concluded, ended, over, all over, terminated -- (having come or been brought to a
conclusion; "the harvesting was complete"; "the affair is over, ended, finished"; "the abruptly
terminated interview")
Overview of adv over
The adv over has 5 senses (first 3 from tagged texts)
1. (23) over -- (at or to a point across intervening space etc.; "come over and see us some time";
"over there")
2. (2) over -- (throughout an area; "he is known the world over")
3. (1) over, o'er -- (throughout a period of time; "stay over the weekend")
4. over -- (beyond the top or upper surface or edge; forward from an upright position; "a roof that
hangs over";)
5. all over, over -- (over the entire area; "the wallpaper was covered all over with flowers"; "she
ached all over"; "everything was dusted over with a fine layer of soot")
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