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E B Hunziker

Publications and source records attributed to E B Hunziker.

95 records · Page 6Linked to original sources
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Surface and subsurface morphology of bovine humeral articular cartilage as assessed by atomic force and transmission electron microscopy.

Maintenance of superficial structural integrity is essential for the load-bearing function of articular cartilage. In this study, we used atomic force microscopy (AFM) to image the 3-D surface and subsurface morphology of fresh bovine humeral head articular cartilage maintained in physiological solution. Complementary ultrastructural data were obtained by transmission electron microscopy (TEM) of cryo-processed samples. The surface irregularities observed in previous scanning electron microscopic studies were not apparent with AFM. The most superficial layer, typically 200-500 nm thick, consisted of acellular and nonfibrous tissue. Occasionally, it exhibited local discontinuities through which the underlying network of collagen fibrils, oriented parallel to the surface and displaying the characteristic periodic banding, could been seen. Local variations in force-curve measurements indicate the existence of differences in micromechanical properties along the articular surface. AFM thus furnishes a new method for characterizing the surface structure and properties of freshly excised articular cartilage in physiologically relevant conditions. It confirms the existence of an amorphous, nonfibrous articular surface which may be vital for its normal lubrication and wearing properties in vivo.

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Evidence for a distinct water-rich layer surrounding collagen fibrils in articular cartilage extracellular matrix.

Bovine articular cartilage was vitrified by high-pressure freezing. On the one hand vitrified samples were cryosectioned and investigated by cryoelectron microscopy in an unstained frozen hydrated state. On the other hand, they were freeze substituted in pure acetone, ethanol, or methanol, respectively, and subsequently embedded in Epon. Ultrathin Epon sections were poststained with uranyl acetate and lead citrate. The resulting ultrastructural representation was different for every protocol. The evaluation of the combined results provides evidence for a distinct water-rich layer surrounding collagen fibrils in articular cartilage extracellular matrix, which has not been recognized before. The possible composition and function of this layer is discussed.

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Differential effects of embryonic immobilization on the development of fibrocartilaginous skeletal elements.

The importance of mechanical influences during skeletal development has been well established in both experimental studies and computer models. Under conditions of embryonic immobilization, it has been observed that the early stages of joint formation proceed normally (up to and including interzone formation), but the later stages of joint cavitation and maintenance are impaired, resulting in fusion of the cartilaginous elements across the presumptive joint line. Two structures in particular are noticeably absent from late-stage synovial joints in immobilized chick embryos: the menisci of the tibiofemoral joint and the plantar tarsal sesamoid of the tibiotarsal joint. Both of these fibrocartilaginous structures are known to serve mechanical functions in postnatal animals, helping to distribute loads within the joint and, in the case of sesamoid structures, to provide a mechanical advantage to muscles acting across the joint. We demonstrate in this study that embryonic immobilization differentially affects the developmental fate of these two distinct fibrocartilages. The absence of the plantar tarsal sesamoid in late-stage immobilized embryos is due to a failure in the initial formation of this structure. In contrast, the early stages of meniscus formation proceed normally. Without the normal mechanical stimuli of skeletal muscle contractions, however, the meniscus fails to mature and ultimately degenerates.

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