A development of repetitious mechanical stress loading system for cultured cells.

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At the start of project, we obtained the basic dotards for an appropnate strenght and cycle of mechanical stress to load on bone cells using our hand-made stress loading system. During an endurance test of parts, we realized that the solenoid driving system is not durable in CO_2 incubator, and we change the system to waterproof motor driving-cam transmitting system. This change brought some merits besides a durability. An accelerating process in reciprocating movement became controllable with changing a shape of cam, which was impossible for solenoid driving system. A manufacture for trial and reform were repeated for a year and the system was completed as a machine with features,1. A repetitious mechanical stress is loaded for cells embedded in thin layr of collagen gel by stretching a nylon mesh, which is a reinforcement for cllagen gel. Not only a distance of stretch and cycle but also an accelerating process in reciprocating movement is controllable with changing the speed of motor and the shape of cam.2. A collagen gel layr is thin enough (about 1 mm) to neglect the effects of increasing permeability of nutrition into the gel according a repetitious stretch. Moreover, you can set a sample for cyclic control, which moves in the medium reciprocally without any stretch, or a sample for stable control, which standstill in the medium. These features make it possible to distinguish the true effect of mechanical forth.3. A direct microscopic observation of cells in collagen gel layr during the load of stress is possible. This makes it possible to measure the amount of forth loaded on cells as an amount of deformation of cells, and to compare the data obtained from different machines.It was confirmed by an endurance test and two years use for test that this system has a good quality.