Figure 4. Localization of side population (SP) cells in the lens epithelium. Mouse lenses were incubated in DMEM containing Hoechst 33342 for 90 min and then fixed. A shows Hoechst blue fluorescent image and B shows Hoechst red fluorescent image of the same mouse lens epithelium. The “+” in (A) indicates the center of the lens epithelium. C shows the result of fluorescent intensity analysis using Image Master software. The cells with the lowest levels of fluorescence intensity, shown in the green spot in E, can be seen as green cells highlighted with a green square in C. D shows high magnification images of the cells within the areas marked by black square in C. SP cells localized around the germinative zone of the lens epithelium. The scale bar represents 100 µm. E shows a plot of the cells at the indicated levels of intensity of Hoechst blue (vertical axis) and red fluorescence (horizontal axis).