Figure 9. Confocal fluorescence images showing the subcellular localization of MUPP1 in bull spermatozoa. By following the images from low (C) to high magnification (D), it is obvious that anti-MUPP1 immunoreactivity can be assigned to the acrosomal region of the sperm head with conspicuous labeling of the equatorial segment. (A) Secondary antibody alone. (B) Visualization of the acrosomal region using FITC-conjugated PNA. (C, D) MUPP1 detected by an FITC-conjugated secondary antibody. The insert in (C) indicates a region shown in higher magnification in (D). Confocal photomicrographs were created by the overlay of fluorescence channels with the corresponding transmission channel pictures.