CELL FINE STRUCTURE AND BIOSYNTHESIS OF INTERCELLULAR MACROMOLECULES.

Fibroblasts active in collagen production show a rich development of the endoplasmic reticulum (ER) and an enlarged Golgi complex, both characteristic of cells engaged in protein synthesis. The relatively quiescent fibrocyte, on the other hand, is deficient in these same cytoplasmic systems. When fibroblasts (or chondroblasts) are provided with tritiated (H(3)) proline, the label shows, by autoradiography, incorporation first into materials (collagen) in the cisternae of the ER, transfer thence in time to the Golgi, and eventual secretion into the extracellular environment. Sulfur(25) incorporation into chondroitin sulfate appears to involve only structural elements of the Golgi complex. There is increasing evidence of intimate fibroblast (or cell) involvement in the initiation and orientation of unit collagen fibrils. This question is reexamined in relation to the development of the prominent basement lamella of young adult lampreys.