| Chicken embryos were incubated with BrdU, embedded in plastic resin, sectioned and screened immunohistochemically to identify proliferating cells in the neural tube and somites. Fixation in 4% paraformaldehyde for 1 h was essential for detecting specific colorimetric signals of BrdU incorporation into cells during the S phase of the cell cycle. Transverse sections of the neural tube showed that the nuclei of proliferating cells (BrdU positive) had a uniform and centralized distribution, whereas unstained nuclei were found only along the extremities of the neural tube. Transverse sections of differentiated somites showed proliferating cells in the scleratome and dermatome. However, no incorporation of BrdU was observed in myotomic cells, which give rise to... |
