Frequency of nonspecific staining in wild-type (WT) control C57BL/6N male and female mice. Whole mount (WM), and frozen section (FS) nonspecific staining percentages are indicated in blue and red, respectively. Explanations of differences between WM and FS preparations for nonspecific staining for specific tissues are as follows: (1) bacteria on epithelium of tongue and esophagus in FS preparations; (2) luminal gut bacteria present in intact WM preparations; (3) prostate adjacent to preputial gland and inability to distinguish between preputial gland nonspecific staining and specific prostate gland staining in WM preparations; and (4) likely differences in staining conditions allowing the detection of endogenous galactoside activity in either WM or FS preparations, but not both. Nonspecific staining is particularly problematic in the GI tract and in the male sex organs.
