the effect of substratum on responsiveness to these hormones was evaluated by comparing cells cultured for 4 days on tissue culture plastic , on floating type i collagen gels , on rat lung fibroblast feeder layers on floating collagen gels ( floating feeder layers ) , and on engelbreth-holm-swarm ( ehs ) tumor basement membrane gels .
C0041455
type i collagen
C0009325
collagen