Figure 1
From: Distal spinal nerve development and divergence of avian groups
Defining the pygostyle to free vertebrae boundary in the chicken. (A) E17 Alcian blue and alizarin red stained wholemount tail. At E17, ossification has not yet commenced, but transverse processes differences are readily observed between pygostyle pre-vertebrae and free caudal vertebrae. (B) TUNEL-stained E5 wholemount, indicating ventral, distal apoptosis in the chick embryo tail (arrow). The segmented pattern of apoptosis in the tail is in ventral lateral dermamyotome. (C) Cross-section of a TUNEL-stained chick embryo tail (E5), showing apoptosis is ventral and excluded from somite domains. (D,E) Phalloidin 488 stained somites in chick embryo tails. Wholemount E4, D and E, E5 cryosection. (F) Hematoxylin-stained oblique coronal cryosection, E6, showing discreet distalmost somites. (G) E11 coronal paraffin section, Alcian blue and picrosirius red stained, on the same plane as the notochord. The pygostyle region encompasses the distalmost four pre-vertebrae, and these elements lack vertebral processes. Abbreviations: HL: hindlimb; Nc: notochord; NT: neural tube; pygo: pygostyle; S, somite; VP, vertebral process.
