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Fig. 6. Allocation of the embryonic gut endoderm during gastrulation.
(A) Five separate sites in the endoderm were painted with DiI (red) or
DiO (green) and the movement of these cells tracked at 3 hours and 28 hours
post-labelling. (B) Cells from the distal site (Dist, red) were found
mostly in the prechordal region, whereas those from the posterior-distal site
(PD, green) were distributed to the middle (somitic) region of the embryo.
Dotted circle (red in A, blue in B-E) marks the anterior region of the
primitive streak (APS) (C) Cells from the PD to posterior-middle (PM)
region (red) were distributed to the medial regions from the forebrain to the
posterior (presomitic mesoderm) level (dashed line), whereas the APS cells
(green cells from the yellow region) were found mainly in the middle endoderm.
(D) Cells from the painted (green) region covering the whole primitive
streak from APS to posterior-proximal (PP) region were distributed mostly to
the lateral and intermediate regions of the anterior endoderm and to the most
posterior endoderm and posterior yolk sac. Some labelled cells were present in
the middle medial endoderm. (E) From the posterior endoderm, Dist, PD
and APS cells (red) were distributed to the medial endoderm spanning from the
forebrain to the somitic level. APS, PM and PD cells (green) were distributed
to the lateral endoderm at the forebrain to hindbrain level and to the
posterior endoderm. Overlapping contribution from the APS cells is observed in
the medial middle endoderm (yellow domain). Few labelled cells are found in
the lateral posterior endoderm. (F-I) Histological examination of (F)
E7.0 MS embryo (inset: whole embryo) showing DiIlabelled cells in the endoderm
and (G) labelled embryo after 24 hours of in vitro culture containing labelled
cells in the foregut portal (H) and in the endoderm (I) at the somite
level.
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