Identification of proliferating cells in chicken embryos using 5-bromo-2 '-deoxyuridine immunohistochemical detection

Chicken embryos were incubated with BrdU, embedded in plastic resin, sectio ned and screened immunohistochemically to identify proliferating cells in t he neural tube and somites. Fixation in 4% paraformaldehyde for 1 h was ess ential for detecting specific colorimetric signals of BrdU incorporation in to cells during the S phase of the cell cycle. Transverse sections of the n eural tube showed that the nuclei of proliferating cells (BrdU positive) ha d a uniform and centralized distribution, whereas unstained nuclei were fou nd only along the extremities of the neural tube, Transverse sections of di fferentiated somites showed proliferating cells in the scleratome and derma tome. However, no incorporation of BrdU was observed in myotomic cells, whi ch give rise to axial skeletal muscle, In spite of their proximity, the der matome and myotome showed marked differences in cell proliferation. The exc ellent preservation of morphological characteristics in the embryonic tissu es facilitated identification of variations in BrdU incorporation.