The mechanical behaviour of material bone can be completely described by a group of material properties. The mechanical behaviour of the entire bone organ, however, is much more difficult to predict; it is the result both of the properties of the material of which it is made, and of the geometric spatial architecture in which this is arranged. This review first describes material bone in terms of its complex, graded and hierarchical structure. Basic concepts used in the field of mechanics of materials are defined and explained and then used to describe the mechanical properties of whole bone. Some clinical implications of these properties are provided. Commonly used mechanical testing methods for the study of the mechanical behaviour of whole bone are reviewed and the technical difficulties associated with them are discussed.
OBJECTIVE: Microenvironmental interactions of malignant B cells can modulate various in vitro physiological responses, including proliferation, migration, apoptosis, and drug resistance. Disease manifestations of human malignant B-cell variants, isolated based on their differential interactions with fibronectin, were examined in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. MATERIALS AND METHODS: Disease manifestations were assessed by pathological examinations and skeletal imaging of NOD/SCID mice injected with malignant B-cell variants. Dissemination patterns were analyzed by whole-body real-time imaging of mice injected with fluorescence-labeled malignant cells. RESULTS: Initial dissemination patterns and dynamics of both high (type A) and low (type F)-adherent variants, following intravenous inoculation, were similar. Both cell types reached the spleen and liver within 30 minutes after injection, then increasingly accumulated within the bone marrow. Mice injected with type-A cells developed multiple myeloma-like disease within the bone marrow, with multiple lytic bone lesions. In contrast, type-F cells displayed low tumorigenic capacity in spite of their efficient homing to the bone marrow niche. In addition, type-A cells grew as extramedullary tumors in some of the intravenous-inoculated mice, and formed solid tumors following subcutaneous injection. Both cell variants retained their characteristics surface markers following in vivo outgrowth as tumors, indicating that at least some of their properties are relatively stable. CONCLUSION: Data suggest that the differential tumorigenicity of B-cell adhesive variants is attributable to the capacity of type-A cells to survive and proliferate within the bone marrow, rather than to different initial dissemination of the two cell populations.