title: Growth and proteoglycan metabolism of chick embryonic cartilaginous long bone rudiments and of isolated epiphyses.
abstract: Turnover of extracellular matrix (ECM) proteoglycans was studied in chick cartilaginous femur rudiments grown in organ culture. Femora from six-day-old embryos showed nearly normal growth rates during the first few days in culture. By labeling the rudiment with35S-sulfate or14C-glucosamine, it was demonstrated that the cartilaginous ECM undergoes rapid turnover. It was also found that the metabolic fate of the proteoglycans is to be released as macromolecules into the culture medium. When a rudiment was cut to obtain two epiphyses it was observed that each part grows and synthesizes proteoglycans at nearly normal rates, which indicates that the isolated epiphyses, like the whole rudiment, behave as autonomous systems. We suggest that the turnover of ECM components is part of the continuous remodelling process rudiments undergo during their growth and development. In order to study cell-ECM interaction in morphogenesis, we made an attempt to prepare an intact cell-free ECM. Epiphyses were heated at 45.2° C for 1 h. The treatment caused complete cessation of growth and biosynthesis. When the cut surface of a live epiphysis was brought into apposition to a heat-treated epiphysis and the attached pair placed in organ culture, it was found that the heat-treated epiphysis begins to grow and reaches almost the same size as its live counterpart. We discuss the possible advantage of this new experimental system for studies on the role of ECM in morphogenesis.
authors.affiliation: The Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, Hebrew University - Hadassah Medical School, Jerusalem, Israel.
authors.forename: Yossef
authors.initials: Y
authors.lastname: Markson
authors.affiliation: The Lautenberg Center for General and Tumor Immunology, Hebrew University - Hadassah Medical School, Jerusalem, Israel.
authors.forename: David Walter
authors.initials: DW
authors.lastname: Weiss
authors.affiliation: The Hubert H. Humphrey Center for Experimental Medicine and Cancer Research, Hebrew University - Hadassah Medical School, Jerusalem, Israel.
authors.forename: Fanny
authors.initials: F
authors.lastname: Doljanski
keywords: Cartilage; Extracellular matrix; Femur rudiment; Morphogenesis; Proteoglycan turnover