Normal Hyaline Cartilage Research Articles

Ultrastructure of the chondroid regions of benign mixed tumor of salivary gland.

Methods of light and electron microscopy were employed to determine the exact nature of the chondroid portions of the benign mixed tumor of salivary gland. Although these regions could not be distinguished from normal hyaline cartilage when examined with the light microscope, no normal or metaplastic chondrocytes could be identified when the ultrastructure of these regions was examined with the electron microscope. Instead, neoplastic myoepithelial cells embedded in a matrix quite similar to that of immature hyaline cartilage were found to be present. It is concluded that in the benign mixed tumor neoplastic myoepithelial cells undergo partial metaplasia enabling them to produce a typical chondroid matrix. Further, because of the similarity in structure and function between myoepithelial cells and visceral smooth muscle cells, it is suggested that the myoepithelial cell is of mesenchymal origin and, therefore, after metaplasia entirely capable of producing a mesenchymal mucin.

Histochemical Studies on Glycogen in Normal Ossification and Calcification

1. Normal hyaline cartilage contains glycogen in all its cells, with the exception of time peripheral growth zones and the tangential layer of the articular cartilage. 2. In growing epiphyseal cartilage the behavior of glycogen differs according to the rate of growth. The increase of glycogen is constant in hypertrophic cartilage; however, it disappears completely it growth is fast, partially if growth is moderate, or remains if growth is slow. 3. Glycogen is usually scarce in areas of primary bone trabeculae in the subchondral layer of endochondral ossification, except in parts where growth is slow and glycogen is found in moderate quantities. 4. Glycogen is constantly present in direct or membranous ossification; its distribution varies according to the speed of osteogenesis. 5. In areas of active osteogenesis, the hypertrophic osteoblasts contain little or no glycogen, while the adjacent mesenchymal cells (pre-osteoblasts) contain a moderate to abundant quantity of glycogen granules. The flattened atrophic osteoblasts on the surface of slowly growing bone trabecubae contain abundant glycogen. The osteocytes in both of these conditions usually lack glycogen.

Osteoarthritis of the hip: an electron microscope study.

1. A study of normal and osteoarthritic hyaline cartilage has been made with the electron microscope and x-ray diffraction. 2. Normal cartilage consists of a three-dimensional network of collagen fibrils with no preferred orientation, surrounded by a matrix containing polysaccharide. 3. In the osteoarthritic joint the collagen fibrils show definite orientation and a decreased proportion of ground substance. X-ray diffraction confirms this and shows the orientation to be at right angles to the surface of the femoral head. 4. Tensional forces across the joint may explain why osteoarthritic changes first appear in the non-weight-bearing area of the joint.