No abstract

Cultured rabbit aortic smooth muscle cells produce elastic fibers and elastin in their extracellular matrix. Morphological analyses of elastic fibers indicate that they consist of two distinct components which play a major role in elastic early fiber formation namely, the amorphous component and the "microfibrillar" component. During elastogenesis, the early fiber consists of small bundles of filaments. Later, clearly distinguishable small conglomerates of amorphous material are found distributed among the bundles of filaments. The mature elastic fibers have large conglomerates of amorphous material with the filaments present within the interstices. Long term cultures of these cells in the second passage continue to accumulate elastin. The crosslinking amino acid isomers desmosine and isodesmosine, which are unique to insoluble elastin, increase with time in culture. Twenty-four hour pulses with 14C-proline followed by measurements of 14C-hydroxyproline in the collagenase resistant protein of the cell layer show that the synthesis of insoluble elastin is constant up to the 14 week period studied from the time the amorphous material becomes evident ultrastructurally.

No abstract

No abstract

Cultured rat aortic smooth muscle cells (SMC) were examined by electron microscopy and found to contain polygonal networks of 75 A degrees thin myofilament bundles. The cells also had large bundles of longitudinally aligned thin myofilaments with periodically spaced dense bodies. Abundant plasmalemmal vesicles were present at the cell periphery, and the cells were connected by desmosomes. Intercellular spaces contained sparse amounts of elastic fibers, a material generally present in SMC cultures. Analyses of amino acids by automated column-chromatography showed that isodesmosine and desmosine, two amino acid residues unique for elastin, were present. Accordingly, it was concluded that polygonal networks, previously detected solely in cultured nonmuscle cells, were present in SMC. Other findings suggest 1) a change in myofilament arrangement takes place during cell migration, and 2) rat aortic SMC grown in tissue culture flasks is an important experimental tool in the study of cell motility since such myofilament rearrangements were observed to occur up to fourteen days in first passage.