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Query: UMLS:C0085631 (agitation)
 12,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rabbit aortic medial cells were grown on purified elastin membranes, which were then subjected to repeated elongation and relaxation or to agitation without stretching. Cells remained attached to the membranes, and cyclic stretching resulted in a two- to fourfold increase in rates of collagen, hyaluronate, and chondroitin 6-sulfate synthesis over those in agitated or stationary preparations. Synthesis of types I and III collagen was increased to the same degree. Stretching did not increase rates of chondroitin 4-sulfate or dermatan sulfate synthesis. Differences were not attributable to differences in cell number, for DNA synthetic rates were not increased by stretching. The model system devised to demonstrate these effects provides a means for relating various modes of mechanical stimulation to cell metabolism.
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PMID:Cyclic stretching stimulates synthesis of matrix components by arterial smooth muscle cells in vitro. 12 20

The byssal threads of marine mussels are a fiber-reinforced composite material. Fibers are continuous, separated by matrix, and consist of chimeric collagens that encompass within the same primary protein structure domains corresponding to collagen, polyhistidine, and either elastin or dragline spider silk. The elastic modulus (stiffness) of the proximal portion of byssal threads was measured by cyclic stress-strain analysis at 50% extension. Before measurement, the threads were conditioned by various treatments, particularly agitation in aerated or nitrogen-sparged seawater. Stiffness can be permanently increased by more than two times, e.g., from 25 MPa to a maximum of 65 MPa, by simple agitation in aerated seawater. Much but not all of this stiffening can be prevented by agitation under nitrogen. Reversible strain stiffening would seem to be a useful adaptation to lower residual stresses arising from the deformation of two joined materials, i.e., distal and proximal portions with rather different elastic moduli. The permanent strain stiffening that characterizes proximal byssal threads subjected to oxidative stress is probably due to protein cross-linking. In the short term, this results in a stronger thread but at the expense of dynamic interactions between the molecules in the structure.
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PMID:Oxidative stress and the mechanical properties of naturally occurring chimeric collagen-containing fibers. 1172 Oct 19