DEVELOPMENT AND REMODELING OF BONE USING EXPERIMENTAL LOADING

该项目的主要目标是检查和 鉴别小鼠股骨的关键结构参数 在不同加载条件下的变化 负责改变材料的极限抗折强度 大腿骨。初步结果表明，发育中的小鼠股骨 当暴露在两种类型的增加的功能负荷下时 Days的回应是通过增加Up的极限断裂强度 通过改变可预测的结构特征提高到74%。然而， 结构特征，即为实现这一增加而改变的 每次实验的断裂强度都不一样。 治疗。这项研究的具体目的是1)将 比结构和矿物质密度随刺激而变化 这引起了人们的反响。2)将结构和 矿物质密度随破碎程度的增加而变化 力量。3)确定小鼠体内的结构变化 暴露在不同的泛函载荷和实验载荷下 在各个年龄段中保持一致和持久，从发展到 成年小鼠。提出了两个有效的假设：1)慢性 中等强度的弯矩引起结构变化 主要增加皮质横截面积的股骨和 转动惯量；2)持续时间短、强度大 弯曲力矩引起骨小梁结构的变化 转动惯量，但皮质交叉处没有变化 截面积。将小鼠分为三种功能 治疗组：正常运动对照组(NE)短疗程 超重力(4G)和慢性穴居(高窝笼)(HL)。 治疗将持续30天，将于第14天开始， 60岁或518岁。实验将从44天持续到548天。一个 第二个实验阶段将使用已知的纯弯矩 压力机发出的震级。施加的应力将 有两种类型：短时间、高强度和较长时间 持续时间短，强度低。未脱钙的股骨将被切开 并在扫描电子显微镜下检查是否有交叉 截面积和转动惯量。串列杂交 未脱钙的股骨切片将用于重建 骨小梁的三维构筑。皮质和 骨小梁d：Ta将在视觉的帮助下被量化 分析系统。安放切片研磨不脱钙股骨 将用于X射线微区分析测定钙 和磷的密度。准备好的股骨将接受测试 Instron材料测试仪的极限断裂强度。 这项研究的结果可能会应用于开发 儿童骨骼结构健全与骨改建的关系 骨质疏松症老人。

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.