Michael Silbermann

Quantitative and distributional changes in the activity of alkaline phosphatase during the maturation of cartilage.

The quantitative changes in the activity of alkaline phosphatase during the maturation of cartilage cells were evaluated based upon morphometric measurements at the ultrastructural bevel. Undifferentiated chondroprogenitor cells revealed positive reaction products for alkaline phosphatase in their nuclei and along their plasma membrane. With the differentiation of the progenitor cells to chondrobbasts an intensification of enzyme activity took place along the plasma membrane, whereas the cells’ nuclei lost their reactivity to the enzyme. A significant increase in the cellular (plasma membrane) enzyme activity was noted in the mature hypertrophic chondrocytes. Enzyme activity was seen even in fully matured chondrocytes located deep within the mineralization zone. A different pattern of enzyme activity was observed in the pericebbular matrix along the various zones of the maturing cartilage. A significant Since alkaline phosphatase (AlPase) has a very high activity in cartilage undergoing endochondral ossification it has been suggested that this enzyme plays a role in the mineralization process by causing a supersaturation of phosphate ions in the

Reconstruction of the acetabular wall with bone graft in arthroplasty of the hip.

The fate of autologous bone grafts under a layer of methylmethacrylate cement, previously investigated in dogs, was observed in eight patients. The grafts were incorporated into the acetabular bone within six to ten months. Reinforcement of the inadequate acetabulum with autologous bone graft is necessary in order to withstand the long-term repetitive loading in patients with total hip arthroplasties. Reconstruction of the medial acetabular wall (using autologous bone chips), combined with fixation of the socket with methylmethacrylate, was successful in all eight patients with a follow-up period of two to six years.

Corticosteroid-induced enhanced mineralization in neonatal condylar cartilage.

Neonatal mice were treated with triamcinolone hexacetonide and the cartilage of their mandibular condyle was studied biochemically and histochemically. Three days following the hormonal treatment the condylar protein content decreased significantly but a marked increase was noted in the tissues calcium and phosphate. The condylar mineralization front extended up to the chondroblastic and proliferative zones. Triamcinolone arrest cartilage cell proliferation and enhanced an atypical hypertrophy of chondroblasts. One week following the hormonal treatment the condyle revealed clear signs of weight loss and changes in its size and form. Glucocorticoids enhance the mineralization of neonatal cartilage via: a direct effect upon chondrocytic metabolic and control systems (genom) and possibly also through an indirect adverse effect upon other organ systems.

Ultrastructural localization of acid phosphatase in cartilage of young mandibular condyles

SummaryThe fine structural localization of acid phosphatase was studied in cartilage of mandibular condyles of the mouse. Although the final product was found to be deposited within most chondroblasts and chondrocytes, the most abundant precipitate was observed within the hypertrophic chondrocytes in the vicinity of the mineralization front. In these cells, lead phosphate precipitates were noted along the rough endoplasmic reticulum and within lysosome-like bodies. Positive reaction to acid phosphatase was also noticed within vacuoles which were located in the matrix close to the centers of mineralization. It is conceivable that this enzyme is involved in matrix production at one stage of chondrogenesis and in the mineralization process at a later stage.

Dynamic changes in acid mucopolysaccharides during mineralization of the mandibular condylar cartilage

SummarySequential histochemical changes related to acid mucopolysaccharides (AMPS) were studied in the calcifying cartilage of the mandibular condyle. Non-decalcified, 1 μ Eponembedded sections were subjected to a variety of histochemical procedures. The results indicate that AMPS are synthesized and secreted mainly by hypertrophic chondrocytes in the premineralizing zone. Within the matrix at the mineralization front the AMPS complexes are apparently degraded by lysosomal enzymes to yield a highly anionic fraction which is maintained in the matrix. This fraction could function as the site for mineralization and cationic dye reaction which allows for histochemical visualization.

Effect of long-term hyperglucocorticoidism on the neuronal morphology of the trigeminal ganglion of the mouse

Immature mice were treated for up to 12 weeks with daily doses of triamcinolone diacetate. The trigeminal ganglion was studied histologically at regular intervals. By the tenth injection significant morphological changes were noted in the various nerve cells, followed by marked cellular deterioration in the form of lysis or pyknosis. A possible explanation for the above findings is discussed.