Asthenozoospermia and the human sperm mid-piece.

This study provides a quantitative comparison between surface and ultrastructural features of motile spermatozoa in asthenozoospermic and fertile men. The study group consisted of 10 individuals with persistent asthenozoospermia and the controls were 10 fertile donors to a sperm bank. Scanning electron microscopy and image analysis were used to objectively measure sperm mid-piece and tail dimensions. Sperm mid-piece length was significantly shorter (P < 0.01) in asthenozoospermic subjects compared with the controls, with mid-piece width and tail length being comparable. Mid-piece ultrastructure was then examined with the transmission electron microscope and the number of mitochondrial gyres and their configuration recorded. At the ultrastructural level the asthenozoospermic subjects demonstrated significantly fewer mitochondrial gyres (P < 0.001) than their fertile counterparts. Energy for sperm movement is provided by mitochondria and a deficit in these organelles in the sub-fertile cohort provides an explanation for poor sperm function in these subjects.