Dimensional changes during specimen preparation are probably associated with changes in shape and in relative relationships between organelles, cells and tissues having different compositions. This should be borne in mind by all those interpreting scanning electron micrographs of dried animal soft tissue specimens.
Octopus vulgaris drills holes in the shells of a variety of molluscs. The walls of the cavities drilled exhibit dissolution of mineral and organic material. The features which characterize the cavities have been described. The composition and structure of the shell itself is important in determining the size, shape and form of the cavity drilled, and not the size of the octopus. Capture, drilling the shell, and eating the occupant may take less than one hour.
The first experimental studies concerning observations of changes in bone cell functional morphology were made using the SEM, and SEM has remained paramount in this field. Bone forming and resorbing cells only exist on surfaces – which are available for study after removal of adjacent tissue layers: The underlying matrix surface can then be studied after removal of the cells, and the mineral front examined after removing the matrix (with an appropriate solvent or by plasma ashing).
In this review, we analyse the main findings which we have made in this laboratory concerning the biological activities of osteoblasts (bone forming cells) and osteoclasts (bone resorbing cells). The technical problems of specimen preparation of cells which shrink more than the substrate to which they are attached have been convered previously (Boyde et al. 1977). Such problems obviously affect the lateral, cell to cell inter‐relationships more than the cell to substrate effects which we cover here.
At present, we can conclude that SEM has made a major contribution to bone biology by permitting observation of normal cells and natural and surrogate substrates. We confidently predict that it will continue to play a pivotal role in the closer observation of cell‐cell‐substrate interactions particularly in respect of local hormonal effects, as well as in bone pathology and implantology.
This study explored the microstructure of human cranial bone at different ages, and the survival, remodelling and modelling of cranial bone grafts. A combination of reflection and fluorescence confocal optical microscopy and scanning electron microscopy in the backscattered electron imaging mode was employed to examine highly polished block faces of plastic-embedded bone fragments as harvested for grafting, or recovered after a period in situ as a graft. The methods enabled remarkably detailed information on bone content, maturation and turnover to be gleaned from tiny scraps of bone. Microfractures in the harvested bone were repaired at the graft site, with welding of old and new bone indicating revascularization. Human cranial bone grafts successfully stimulated bone cell differentiation, supported new bone formation on resorbed and unresorbed surfaces, and underwent bone turnover. The type and organization of new bone reflected the growth rate and maturation of the graft rather than the age of the patient.
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