FIGURE 1.

(A) Scheme of sperm preparation for scanning electron microscopy (SEM) examination–conventional and improved protocols. (B) SEM pictures of a mouse sperm mid-piece with different fixation: glutaraldehyde and tannic acid [(B1) microvesicles are indicated with white arrows]; glutaraldehyde then post-fixation with osmium tetroxide [(B2) plasma membrane damage is indicated with black arrows]; and fixed with glutaraldehyde in PBS [(B3), removal of the plasma membrane revealing the helically arranged mitochondria sheath], scale bar 2 μm. (C) A schematic illustration of the advantage of a conductive substrate (C1) for SEM sample preparation–the conductive coating of the cells can be thinner than it should be for a non-conductive substrate (C2).