| |
Figure 1. The experimental paradigm for in vivo heterochronic transplant and an example of
data obtained. At the top fertilized eggs being injected with fluorescein-dextran (one blastomere
injected, one being injected) are shown. These embryos were grown at 17°C and a quadrant of
the optic vesicle was removed. Two cohorts of uninjected embryos were kept to serve as hosts for
the transplant, one was raised at 17°C and therefore developed at the same rate, the other was
raised at 22°C causing it to develop more rapidly and be at a more advanced stage of
development relative to the donor at the time of transplantation. The photomicrographs at the
bottom of the figure show the fluorescent dextran-labeled graft (outlined in white) well integrated
into the host. XAP-1 immunoreactivity (indicated by cross-hatched white area) is at the
outer margin of the retina, where it abuts the retinal pigment epithelium (RPE). At the stage of
initial XAP-1 expression the retina is still relatively immature and has yet to develop laminae. In
the isochronic condition XAP-1 immunoreactivity is uninterrupted by the graft. In contrast, in
the heterochronic condition XAP-1 expression stops abruptly at the borders of the older host
with the younger graft. |
