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Fig. 1. Temporal and spatial differences in Cre recombinase activity in the
PdxCreearly and PdxCrelate transgenic
lines. Staining for lacZ expression marks cells that have
undergone Cre-mediated recombination in PdxCrelate and
PdxCreearly R26R mice. (A) Control E10.5 embryo.
(B) No ß-galactosidase staining is detectable within the
PdxCrelate R26R embryo at E10.5. (C) Strong
ß-galacotosidase staining is present within the pancreas (arrow) of a
PdxCreearly R26R E10.5 embryo. (D-F) Histological
examination of pancreas sections immunostained for Pdx1 (brown) and
enzymatically stained for ß-galactosidase activity (blue). (F) The
majority of Pdx1+ cells in the PdxCreearly R26R
animal, are also positive for lacZ at E10.5. (G-I)
ß-Galactosidase (blue) and Pdx1 (brown) staining at E12.5.
ß-Galactosidase staining is detectable within a subset of the
Pdx1+ cells in the PdxCrelate R26R animals (H).
(I) Equivalent pancreas sections of a PdxCreearly R26R
animal show robust ß-galactosidase staining in the majority of
Pdx1+ cells. (J-L) Adult animals stained with Eosin (red)
and for ß-galactosidase (blue). Islets are outlined in black. (K) In the
adult PdxCrelate R26R animal, only a subset of islet cells
exhibits ß-galactosidase staining. Cre expression within the exocrine
tissue is also mosaic in these animals. (L) A greater percentage of islet
cells and exocrine cells exhibit strong ß-galactosidase staining in the
adult PdxCreearly R26R pancreas. (M-O) Adult
pancreatic ducts. (O)The majority of pancreatic ducts (stained with an
antibody against mucin 1, red) are also ß-galactosidase +
(green) in the PdxCreearly R26R pancreas (non-specific
staining sometimes encountered within the center of ducts indicated with an
asterisk). (N) ß-Galactosidase+ cells are seldom encountered
within the PdxCrelate R26R pancreas. No
ß-galactosidase staining is observed in control animals (A,D,G,J,M) at
any of the time points characterized. Scale bars: 25 µm.