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Ultrastructural aspects of the production of extracellular matrix components by the chick embryonic notochord in vitro.

The morphology of extracellular matrix (ECM) components and of the cell organelles, particularly the Golgi complex and its derived structures, implicated in the production of ECM in the chick embryonic notochord have been studied by transmission electron microscopy. Isolated notochordal fragments were cultured in suspension in liquid medium. Native striated collagen fibrils with a period of 540 A were observed in the perinotochordal sheath. Fine granular and filamentous materials suggestive of proteoglycans have been observed in intercellular spaces and under the basal lamina of the notochordal sheath. Golgi mature vesicles with structures resembling the previously described segment-long-spacing (SLS)-like aggregates and secretory vesicles probably containing proteoglycans or condensed collagen precursors have also been observed.