y weight 2 h before sacrifice. Tissue sections were deparaffinized with xylene, rehydrated in graded ethanol solutions, and treated with 3% H2O2 methanol for 10 min at room temperature to remove endogenous peroxidase activity. Antigen unmasking was carried out by heating the sections for 10 min in 0.01 M sodium citrate at 100uC. Nonspecific protein binding was blocked using a buffer blocking solution. All sections were incubated using the primary mouse monoclonal antibodies anti-BrdU and the rabbit polyclonal secondary antibodies. Enhanced horseradish peroxidase conjugated streptavidin was subsequently applied at room temperature for 10 min before the sections were visualized with DAB to create an intense brown deposit around the antigenantibodyenzyme complex in the sample. An index of proliferation was determined as the ratio of crypt cells staining positively for BrdU per 10 crypts. Microscopic evaluation Histological sections were prepared from the proximal jejunum and distal ileum in all animals. Segments of small bowel were fixed for 24 h in 10% formalin, washed with absolute alcohol, and then processed into standard paraffin blocks. Fivemicron transverse sections were prepared in a standard fashion and were stained with hematoxylin-eosin. The sections were studied microscopically using a micrometer eyepiece by an observer blinded as to the tissue’s origin. Ten villi and crypts in each section were measured and the mean reading was recorded in microns, using a 1064 magnifying lens. Histological images were loaded on a 7606570 pixels resolution buffer using a computerized image analysis system composed of a trichip RGB videocamera, installed on a light microscope and attached to an IBM-compatible personal computer, equipped with a frame grabber. Images was captured, digitized, and displayed on a high-resolution color 17-inch monitor. The villus height and crypt depth were measured using the Image Pro plus 4 image analysis software. The degree of intestinal tissue injury was evaluated on a grading scale from 0 to 8 as described previously by Park et al: 0-normal mucosa, 1subepithelial space at villus tip, 2-more extended subepithelial space, PAK4-IN-1 3-epithelial lifting along villus sides, 4-denuded villi, 5-loss of villus tissue, 6-rypt layer infarction, 7-transmucosal infarction, 8-transmural infarction. Immunohistochemistry for TGF-b receptor expression along the crypt-villus axis Rat sections 
were fixed in fresh 4% paraformaldehyde for 4 h at 4uC. After deparaffinization, sections were treated with freshly prepared 0.6% H2O2 in methanol for 30 min to quench endogenous peroxidase activity. Sections were then PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22211113 treated with a biotinylated goat anti-rabbit antibody for 45 min and a biotinavidin-peroxidase reagent for 30 min. The primary antibody is an affinity purified rabbit anti-human type II TGF-b receptor polyclonal antibody which is nonreactive with the 53 kDa type I receptor. Incubations with rabbit IgG, as well as primary antibody preincubated for 15 min with synthetic type II TGF-b blocking peptide were used as controls. Color was developed with diaminobenzidine and sections were counterstained with hematoxylin. Western blotting Tissue was homogenized in RIPA lysis buffer containing 50 mM TrisHCl, 150 mM NaCl, 1% NP-40, 2 mM EDTA, supplemented with a cocktail of protease and phosphatase inhibitors. Protein concentrations were determined by Bradford reagent according to the manufacturer’s instructions. Samples Enterocyte apoptosis Immu
