Chemical modifications of cartilage matrix during endochondral calcification

Résumé On a étudié la composition chimique de différentes zones fonctionelles de la matrice du cartilage ossifiable scapulaire et costal. On a constaté qu'en s'approchant du front de calcification, le collagène diminue fortement tandis que les mucopolysaccarides et les protéines non collagènes augmentent.

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This investigation was supported by grants from the Italian National Research Council.     

Reinterpretation of the ultrastructure of cartilage matrix

Summary The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.Commonwealth Academic Staff Fellow. Permanent address: Department of Zoology, University of Poona, Poona 411007, India.     

Reinterpretation of the ultrastructure of cartilage matrix.

The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.     

CD44 and integrin matrix receptors participate in cartilage homeostasis

Articular chondrocytes express the matrix receptors CD44 and integrins. Both of these receptors exhibit interactions with adjacent extracellular matrix macromolecules. In addition, both integrins and CD44 have the capacity for signal transduction as well as modulated interactions with the actin cytoskeleton. As such, both receptor families provide the chondrocytes a means to detect changes in matrix composition or to function as mechanotransducers. Disruption of CD44 or integrin-mediated cell-matrix interactions, either experimentally induced or when present in osteoarthritis, have profound effects on cartilage metabolism. Thus, CD44 and integrin receptors play a critical role in maintaining cartilage homeostasis.     

The extracellular matrix during heart development

The embryonic extracellular matrix, which is comprised of glycosaminoglycans, glycoproteins, collagens, and proteoglycans, is believed to play multiple roles during heart morphogenesis. Some of these ECM components appear throughout development, however, certain molecules exhibit an interesting transient spatial and temporal distribution. Due to significant new data that have been gathered predominantly in the past 10 years, a comprehensive review of the literature is needed. The intent of this review is to highlight work that addresses mechanisms by which extracellular matrix influences vertebrate heart development.     

In Vitro calcification of collagen

Zusammenfassung In Collagenfasern kann durch Aufbewahren in einer wässerigen Suspension von gefälltem Kalciumphosphat eine Ablagerung von Hydroxyapatit erhalten werden. Der Niederschlag lässt sich durch Waschen mit Wasser nicht entfernen. Das Röntgenbild der Abscheidung gleicht weitgehend demjenigen des anorganischen Bestandteils der Knochen. Nach Zufügung einer Spur Zitronensäure ist auch die Teilchengrösse von derselben Ordnung wie im Knochen.     

Lipids of epiphyseal cartilage

Riassunto Nella cartilagine metafisaria di maialini neonati omogenata e liofilizzata sono stati determinati, con metodi fisici e chimici, i lipidi totali, il fosforo totale, il fosforo lipidico, il colesterolo totale, il colesterolo libero, l'azoto totale e gli acidi grassi saturi, insaturi e polinsaturi. La determinazione degli acidi grassi è stata effettuata mediante la gas-cromatografia.     

Lysosomal modifications after administration of radioprotective drugs

Résumé L'examen ultrastructural de l'épithélium de la crypte duodénale de souris, effectué à 3 et 24 h après l'injection d'un mélange de radioprotecteurs, a révélé l'existence de nombreuses inclusions vacuolaires. La présence de phosphatase acide les a fait considérer comme des lysosomes dilatés. Cette observation est discutée en fonction du temps d'action des substances radioprotectrices.     

Noncollagenous, nonproteoglycan macromolecules of cartilage

Extracellular matrix comprises approximately 90% of cartilage, with collagens and proteoglycans making up the bulk of the tissue. In recent years, several abundant cartilage proteins that are neither collagens nor proteoglycans have been characterized in detail. The putative roles of these proteins range from involvement in matrix organization or matrix-cell signaling (PRELP, chondroadherin, cartilage oligomeric protein and cartilage matrix protein) through to molecules that are likely to be involved with modulation of the chondrocyte phenotype (CD-RAP, CDMPs, chondromodulin and pleiotrophin). Other molecules, such as the cartilage-derived C-type lectin and cartilage intermediate layer protein have no role as yet. Due to the difficulties associated with experimentally manipulating a tissue that is 90% extracellular matrix in a manner that can be readily transferred to the whole organism, many of these molecules have been focused on by a surprisingly small number of researchers. This review focuses on newly discovered proteins and glycoproteins in cartilage, with a bias towards those that have structural roles or that are unique to cartilage. Received 7 January 1999; accepted 11 March 1999