Engineering Commons^™

Effect Of Applied Uniaxial Stress On Rate And Mechanical Effects Of Cross-Linking In Tissue-Derived Biomaterials, Debbie Chachra, Paul Gratzer, Christopher Pereira, J. Lee

Debbie Chachra

Conformational changes in collagen fibrils, and indeed the triple helix, can be produced by application of mechanical stress or strain. We have demonstrated that the rate of cross-linking in glutaraldehyde and epoxide homobifunctional reagents can be modulated by uniaxial stress (strain). Two poly(glycidyl ether) epoxides were used: Denacol^® EX-810 (a small bifunctional reagent), and Denacol EX-512 (a large polyfunctional reagent). To prevent any possible effect from being masked by saturation of cross-linking sites, bovine pericardium was cross-linked to such an extent that the increase in collagen denaturation temperature, T_d, was one-half of the maximal rise achievable with …

Lumbar Vertebral Density And Mechanical Properties In Aged Ovariectomized Rats Treated With Estrogen And Norethindrone Or Norgestimate, Carla Vanin, Neil Maclusky, Debbie Chachra, Mehran Kasra, Marc Grynpas, Robert Casper

Debbie Chachra

OBJECTIVE: This study was designed to investigate the effects of estrogen alone or combined with two different progestins, norethindrone or norgestimate, on bone density and compressive mechanical properties in an aged rat model.

STUDY DESIGN: Twenty 11-month-old female Sprague-Dawley rats were sham operated (intact control) and 80 wee overiectomized. Three groups of 20 ovariectomized rats were implanted with Silastic silicon rubber (Dow Corning, Midland, Mich.) capsules containing 5% estradiol (wt/wt) in cholesterol. All rats in the intact control (group 1) and the ovariectomized (group 2) and the first of the overiectomized plus estrogen (group 3) groups were injected subcutaneously daily …

The Effect Of Different Hormone Replacement Therapy Regimens On The Mechanical Properties Of Rat Vertebrae, Debbie Chachra, M. Kasra, Carla Vanin, N. Maclusky, R. Casper, Marc Grynpas

Debbie Chachra

The purpose of this study was to examine the effects of estrogen replacement, in concert with three different progestin regimens, on the mechanical properties of rat lumbar vertebrae. Ninety-two Sprague-Dawley rats (11 months old) were divided into six groups for treatment. The first group was an intact control, the second group (OVX) was ovariectomized only, and the third group (estrogen-only) was ovariectomized and received continuous estrogen through a 17-estradiol implant. The remaining groups were ovariectomized and received estrogen and progestin (norethindrone, NET) therapy; 3 g of NET was injected daily (estrogen plus continuous NET), or 6 g of NET was …

A New Tool To Assess The Mechanical Properties Of Bone Due To Collagen Degradation, C. Wynnyckyj, S. Omelon, K. Savage, M. Damani, Debbie Chachra, Marc Grynpas

Debbie Chachra

Current clinical tools for evaluating fracture risk focus only on the mineral phase of bone. However, changes in the collagen matrix may affect bone mechanical properties, increasing fracture risk while remaining undetected by conventional screening methods such as dual energy x-ray absorptiometry (DXA) and quantitative ultrasound (QUS). The mechanical response tissue analyzer (MRTA) is a non-invasive, radiation-free potential clinical tool for evaluating fracture risk. The objectives of this study were two-fold: to investigate the ability of the MRTA to detect changes in mechanical properties of bone as a result of treatment with 1 M potassium hydroxide (KOH) and to evaluate …