The development of the elastic cartilage of the mouse pinna

Abstract

The development of the elastic cartilage in the mouse pinna was studied with the electron microscope. For descriptive purposes, the developmental process was divided into five stages. These begin with the onset of cartilage matrix production by chondroblasts. The second stage is the major mitotic stage although the cells now resemble chondrocytes and cartilage matrix production evidently continues. This is followed by a period during which cartilage matrix production appears to be the major activity of the chondrocytes. In Stage IV, the cells continue to produce cartilage matrix but at the same time they also produce lipid which comes to occupy most of the cell as a large lipid droplet. In the adult, Stage V, matrix production appears to be at an end and each cell contains a lipid droplet which is so large that the cells bear some resemblance to white fat cells and might be designated as lipochondrocytes. The adult cartilage matrix contains elastic plates in a three-dimensional honeycomb pattern. Between the elastic plates and the cells, the matrix contains elements similar to those seen in hyaline cartilage but it does not contain matrix vesicles such as those which have been associated with the calcification of cartilage. Two types of filaments differing in appearance, size, and location are seen within the chondrocytes. They have been designated cytofilaments and cortical filaments. Cytofilaments are dispersed throughout the cell and also contact the substance of the lipid droplet; cortical filaments (sub-plasmalemmal microfilaments) are located directly under the plasma membrane. They are thought to be involved in movement of the plasma membrane as a concomitant to extracellular fibrogenesis.

Submicroscopic Structure of the Human Joint Cartilage

“…The largest of them reach as much as 1.5 flm and are contoured by a distinct smooth membrane. A similar occurrence of lipid droplets is not usual, in literature (Weiss et ale 1968;Zimny and Redler 1969) only a sporadic occurrence of these inclusions in the hyaline cartilage is mentioned, whereas these lipid droplets were found to be very frequent in the elastic cartilage (Sanzone and Reith 1976). Glycogen occurs in larger numbers only in the deepest chondrocytes of this layer (Fig.…”

A distinct regulatory region of the Bmp5 locus activates gene expression following adult bone fracture or soft tissue injury

“…Therefore, well-conserved ECRs that failed to show expression at E14.5 dpc may be driving some of the earliest Bmp5 activity. Bmp5 is also expressed and required in late-developing structures, such as the ear pinna cartilage [29, 65, 66]. Thus some ECRs that are inactive in our tests may function at late embryonic or postnatal stages.…”

Ultrastructure of Bovine Articular Cartilage Between Weeks 8 and 23 of Prenatal Development

“…(1975), Bekoff ,and Klagsbrun (1983, Sat 0 and Uri s t (1984) as well as stating explicit characteristics considering differentiation of chondrocytes with non-differentiated cells (citation Sol u r c h et al 1982; B u c k w a 1 t e rand R 0 sen b erg 1983). Some articles are dealing with only partial problems, as regulatory mechanisms in relation to bone-cartilage (N i j wei d e 1982) or with incidence of ciliae (Wilsman and Flecther 1978;Vidinov and Vas i 1 e v 1985), eventually other types of cartilage (Silbermann and Frommer 1974;Sanzone and Reith 1976). In this area we are left to results of our own study.…”