Figure 1. Hoechst 33342 staining of porcine corneas. Porcine corneas were incubated for one week in N₂ gas (N₂ group), air without freezing (control 1 group [Ctl 1]), or air after freezing (control 2 group [Ctl 2]). Fewer cellular nuclei were present in the porcine cornea incubated in N₂ gas for three days than in the two control groups. After five or seven days, few cellular nuclei were observed in the porcine corneal stroma incubated in N₂ gas while many keratocyte nuclei were observed throughout the corneal stroma in the control groups that were kept in air for five or seven days with or without freezing. Positively stained epithelial cells were observed at day 0. All small figures are at the same magnification, and the bar is 100 µm.