Products of cells cultured from @entity11 . VI. Immunofluorescent, morphometric, and ultrastructural characterization of two different cell types growing from explants of @entity1 XXXX .

@entity1 @entity3038 @entity538 @entity11 @entity5588
Explants derived from @entity1 @entity11 have been characterized with respect to their cellular outgrowth pattern after 1-22 weeks in culture. A mat of cells which were fibronectin (FN)-positive and @entity538 ( @entity538 )-negative (hereafter designated FN+ cells) with a polygonal, flat morphology covered the growth substrate in a swirling pattern for a mean diameter of 9.2 mm around FN+ explants. FN+ cells showed ruffled plasmalemma, dilated rough endoplasmic reticulin (RDR), and extracellular filamentous strands. Rare desmosomes were compatible with at most minor leptomeningeal components or differentiation. FN+ cells predominated in six of seven cultures at passage 2, and their features were the same from various high-grade @entity11 and @entity3038 . Around other explants, @entity5588 cells which were @entity538 + and FN- grew in a netlike pattern with little cell-to-cell contact. These @entity538 + cells surrounded explants at a mean diameter of 2 mm, substantially less than FN+ cells (P less than 0.005), and they grew more slowly than FN+ cells around explants. @entity538 + cells had an area/perimeter ratio which was less than that of FN+ cells. @entity538 + cells contained abundant intracellular filaments, rare desmosomes, and narrow RER cisternae. In mixed explants, @entity538 + cells often grew on top of FN+ cells. Individual cells which stained for both @entity538 and FN were evident only from one @entity11 (8% doubly positive). Cells negative for both proteins resembled FN+ cells morphologically. Frozen sections of original @entity11 tissue showed FN+ vessel walls and @entity538 + parenchyma. Results are evidence for very early overgrowth of a preexistent FN+ cell type distinct from the @entity538 + parenchymal cell. The features of this distinct cell type are mesenchymal and resemble the proliferating vascular elements of @entity11 in situ. The tendency for @entity538 + cells to grow on top of these FN+ cells suggests a feeder layer interaction. More knowledge of the origins and interactions of these two cell types may increase our understanding of the mechanism of antigenic changes in @entity11 and may provide clues to improved therapeutic approaches.
