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Fig. 1. Apoptosis is induced at the graft border in heterografts. Control (24 h
old) homografts of H. oligactis/H. oligactis (A) and H.
vulgaris/H. vulgaris (E), and heterografts H. oligactis/H.
vulgaris (B) and H. vulgaris/H. oligactis (C) vitally stained
with Acridine Orange. (D) H. vulgaris/H. oligactis heterograft
stained by the TUNEL method. (FH) Graft sites indicated by the frames
in BD, respectively, shown at higher magnification. O, H.
oligactis tissue; V, H. vulgaris tissue. Broken lines indicate
the graft border. Arrows show Acridine Orange- or TUNEL-positive cells
undergoing apoptosis. The cells in focus are localized in the ectodermal
epithelium. Note that most of them are apparently restricted to the H.
vulgaris tissue adjacent to the graft border.