DEVELOPMENT AND REMODELING OF BONE USING EXPERIMENTAL LOADING

该项目的主要目标是审查和 区分小鼠股骨的关键结构参数， 在差载条件下发生变化， 导致材料的极限断裂强度发生变化， 股骨 初步结果表明，发育中的小鼠股骨 当暴露于两种类型的增加的功能负荷30 天的反应是增加了极限断裂强度， 通过改变可预测的结构特征， 但 为实现这一目标而改变的结构特征增加了 断裂强度是不一样的，为每个实验 治疗 本研究的具体目的是：1）将 特定的结构和矿物密度随刺激而变化 引发了反应 2)将结构和 矿物密度随破碎程度的增加而变化 实力 3)确定在小鼠中观察到的结构变化 暴露于不同的功能和实验负荷， 在各年龄组之间保持一致和持久，从发展到 成年老鼠 提出了两个工作假设：1）慢性 中等强度的弯矩引起结构变化， 股骨主要增加皮质横截面积， 转动惯量，2）短时间高强度 弯矩引起小梁结构的变化， 转动惯量，但皮质交叉没有变化， 截面积 将小鼠分为三个功能组， 治疗组：正常运动控制（NE）短期 超重（4G）和慢性穴居（高窝笼）（HL）。 治疗将持续30天，并将在第14天开始， 60或518岁。 实验将持续44至548天。 一 第二个实验阶段将使用已知的纯弯矩 压力机提供的数值。 施加的应力将 有两种类型：持续时间短，强度高， 持续低强度。 将对未脱钙股骨进行切片 并在扫描电子显微镜下检查交叉- 截面积和转动惯性矩。 系列杂交 将使用未脱钙股骨的部分来重建 松质骨的三维结构。 皮质和 骨小梁d：ta将借助目视 分析系统 不脱钙股骨固定切片和研磨 将用于钙的X射线微量分析测定 和磷密度。 将对准备好的股骨进行测试， 用Instron材料测试仪测试极限断裂强度。 这项研究的结果可能适用于开发 儿童的结构健全的骨骼和骨重建， 狂热的老年人

The broad objectives of this project are to examine and differentiate key structure parameters of the mouse femur that change during conditions of differential loading and are responsible for a change in the ultimate breaking strength of the femur. Preliminary results indicate that developing mouse femora when exposed to two types of increased functional loading for 30 days responded by increasing the ultimate breaking strength by up to 74% by changing predictable structural features. However, the structural feature, that were changed to achieve this increased breaking strength were not the same for each experimental treatment. The specific aims of this study are to 1) Correlate the specific structural and mineral density changes with the stimulus that elicited the response. 2) Correlate the structural and mineral density changes with the related increase in breaking strength. 3) Determine if the structural changes seen in mice exposed to differential functional and experimental loading are consistent and long lasting among age groups, from developing to adult mice. Two working hypotheses are proposed: 1) chronic bending moments of moderate intensity elicit structural changes in the femur that mainly increase cortical cross-sectional area and rotational moment of inertia, and 2) short duration high intensity bending moments elicit changes in trabecular architecture and rotational moment of inertia but no changes in cortical cross- sectional area. Mice will be divided into three functional treatment groups: normal exercise control (NE) short duration hypergravity (4G), and chronic burrowing (high litter cage) (HL). Treatments will last for 30 days and will be initiated on day 14, 60 or 518 of age. Experiments will run from 44 to 548 days. A second experimental phase will use pure bending moments of known magnitudes delivered by a stress machine. Applied stresses will be of two types: short duration high intensity, and longer duration low intensity. Undecalcified femora will be sectioned and examined under the scanning electron microscope for cross- sectional area and rotational moment of inertia. Serial cross sections of undecalcified femora will be used to reconstruct the three dimensional architecture of trabecular bone. Cortical and trabecular bone d:ta will be quantified with the aid of a visual analysis system. Mounted sectioned and ground undecalcified femora will be used for X-ray micro-analysis determinations of calcium and phosphorus densities. Prepared femora will be tested for ultimate breaking strength with an Instron Materials Tester. Results of this study may have application to the development of structurally sound bones in children and the remodeling of bone in the osteoporotic elderly.