Figure 2

Quantitative parameters of primary rib chondrocytes in micromass culture. Panel A: Cell Proliferation was assessed by BrdU incorporation as detected by immunohistochemistry on sections of micromass cultures harvested after 24 hours of BrdU exposure. At day 15, no positive cells were detected (see also Figure 1, Panel L). The major phase of growth occurs between days 3 and 4, 72 to 96 hours after plating. Panel B: Cell size of chondrocytes was measured by photomicrography on sections, and mean cell size increases over time. Panel C: Alkaline phosphotase activity in protein extracts from micromass cultures was measured as the release of p-nitrophenol from p-nitrophenylphosphate by absorbance at 405 nm. One unit of enzyme activity will produce one μ mole of p-nitrophenol per minute. Panel D: Apoptosis was assessed by TUNEL staining on sections from micromass cultures, and was found to increase over time.