and embedded in paraffin. Hematoxylin and eosin staining was performed using
standard methods and tissue specimens from experimental animals were reviewed in
a blinded fashion by a clinical pathologist (M. M. I.) For Ki67 staining,
3–4 micron tissue sections were cut from paraffin blocks and baked
overnight in a dry slide incubator, then deparaffinized on a Shandon-Lipshaw
Varistain using a series of incubations in xylene, ethanol, then water. Antigen
retrieval was achieved by incubating slides in Tris-HCL 9.0 AR buffer in a T-FAL
OPTIMA pressure cooker. Slides were rinsed, then endogenous peroxidase was
blocked by immersing slides in 3% hydrogen peroxide for 5 minutes. Following
washes in nanopure water and TBS-20, primary antibody was applied at a dilution
of 1:200 (Ki67, MIB-1 Clone, Dako). Following primary antibody incubation,
slides were washed and then incubated with envision-labelled polymer-HRP
Anti-Mouse (Dako). Slides were washed, then DAB+ solution (DakoCytomation) was
added for a 15-minute incubation, after which slides were rinsed with nanopure
water. Chromogen signal was enhanced using DAB Sparkle Enhancer (Biocare).
Slides were washed, then counterstained with Harris Hematoxylin, dehydrated,
cleared, then mounted using Cytoseal (VWR).