Figure 3.

Derivation of primary cultures from mammary outgrowths. (a) Explants isolated from pregnant mammary tissue from transgenic line SV40-2 developed outgrowths after 2 weeks in culture at 37°C on type 1 collagen. The typical cobblestone morphology that is characteristic of epithelial cells was observed in these outgrowths by phase contrast microscopy. (b) After 14 days in culture the explants were removed and the primary cultures maintained for a further 7-14 days. Dome structures formed during this time period. Scale bar 250 μm.