Temporal expression of early neural genes and response to Noggin and FGF8a. Semi-quantitative RT-PCR of early neural genes in embryos over time (A, B) or in ectodermal explants (C, D). Explants are from uninjected (UI) embryos or those injected with mRNA coding for Noggin (Nog), FGF8a, or Nog + FGF8a. Embryos in (A) were collected at the times indicated at top (hours post fertilization = hpf) and explants were collected at stage 11.5 (C) or 17 (D). Ef1a expression is a loading control. Samples without MMLV RTase added were used as RT- controls (far right). (E) Immunohistochemistry for phosphorylated Histone H3 of ectodermal explants dissected from embryos injected with mRNA coding for Nog, FGF8a, or Nog+ FGF8a and cultured to stage 17. Explants injected with Nog+ FGF8a are up to 1.7 fold (cm) bigger than those from uninjected embryos. Graph is showing the number of cells marked with pH3 per mm2 expression in n = 10 explants. Nog+ FGF8a caps have 1.8 fold more pH3 per count area than uninjected explants (p=.0001). UI indicates explants that were dissected from uninjected embryos, WE is whole embryo.