?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.relation=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F7984%2F&rft.title=VISCOELASTIC+CHARACTERIZATION+OF+RABBIT+NUCLEUS+PULPOSUS+TISSUE+IN+TORSIONAL+CREEP&rft.creator=Agosti%2C+Christopher+D.&rft.description=Recently%2C+molecular+therapy+approaches+have+been+shown+to+favorably+alter+the+course+of+intervertebral+disc+degeneration+(IDD)+in+a+rabbit+model.+Typical+experimental+outcome+measures+for+the+rabbit+model+of+IDD+include+MRI%2C+x-ray%2C+histology%2C+and+gene+expression.+Biomechanical+function+is+another+desirable+parameter+through+which+to+compare+treatments%2C+although+this+is+difficult+due+to+limited+availability+of+data+for+small+animal+models.+In+the+current+study%2C+nucleus+pulposus+tissue+was+taken+from+the+healthy+rabbit+intervertebral+disc+and+tested+in+torsional+creep+to+establish+a+database+of+healthy+tissue+behavior+for+future+use+in+assessing+the+functional+efficacy+of+molecular+therapy+treatments+of+IDD.+Nucleus+pulposus+tissue+was+excised+from+the+L5-L6+intervertebral+disc%2C+mounted+between+the+cone+and+plate+of+an+AR1000+Rheometer%2C+and+various+torsional+creep+experiments+were+performed.+Several+creep+models+were+fit+to+the+data+and+modeling+analyses+were+conducted.+Of+the+models+compared%2C+the+Andrade+creep+model+provides+the+most+reliable+data+extrapolation.+It+appears+that+the+tissue+is+nonlinearly+viscoelastic+since+it+does+not+adhere+to+the+Boltzmann+superposition+principle.+A+nonlinear+viscoelastic+constitutive+model%2C+derived+for+Andrade+creep+and+used+to+predict+the+strain+behavior+obtained+at+higher+levels+of+stress%2C+provides+consistent+prediction+results.+The+application+of+this+model+to+degenerated+rabbit+NP+tissue+is+expected+to+result+in+altered+model+parameters+-+thus+providing+quantifiable%2C+functional+benchmarks+of+success+for+molecular+therapy+approaches+to+the+treatment+of+IDD.&rft.date=2006-09-27&rft.type=University+of+Pittsburgh+ETD&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.language=en&rft.identifier=http%3A%2F%2Fd-scholarship-dev.library.pitt.edu%2F7984%2F1%2FAgostiCD2006.pdf&rft.identifier=++Agosti%2C+Christopher+D.++(2006)+VISCOELASTIC+CHARACTERIZATION+OF+RABBIT+NUCLEUS+PULPOSUS+TISSUE+IN+TORSIONAL+CREEP.++Master's+Thesis%2C+University+of+Pittsburgh.++++(Unpublished)++