Explants definition

The most definitive evidence for a role for che-motropism in axon guidance in vertebrates has come from in vitro systems in which neural explants or individual neurons have been shown to send neurites in the direction of the source of a diffusible chemical. For example, the growth cones of chick dorsal-root ganglion neurons orient towards increasing concentrations of nerve growth factor (Letoumeau, 1978 Gunderson and Barrett,... 

The effects of retinoids on differentiation of epithelia in organ culture undoubtedly result from a combination of complex cellular responses and interactions of different cell types in the explant. These systems therefore have definite limitations for analysis of the molecular mechanism of action of the retinoids. The introduction of cell culture methodology to such studies was therefore of great importance and now is allowing molecular investigation of the role of retinoids in proliferation and differentiation. 

---