Quantitative ultrastructural analysis of sperm tails reveals flagellar defects associated with persistent asthenozoospermia.

Sperm tail morphology was examined in 10 infertile asthenozoospermic men to determine whether poor sperm motility was caused by ultrastructural defects of the flagellum. In this quantitative analysis, the numbers of outer doublet and central pair microtubules, outer and inner dynein arms and radial spokes were counted in transverse sections of 75 axonemes from each patient and compared with similar data previously collected from 10 men with normal semen characteristics. Four patients had axonemal defects: two had severe microtubule abnormalities and two had more subtle but statistically significant deficiencies of dynein arms. These abnormalities would not have been detected by more commonly used qualitative examination. Three patients had no detectable ultrastructural abnormalities of the sperm tail, possibly indicating a metabolic deficiency. A further three patients had mid-piece abnormalities. Two had few, if any, flagellar mitochondria and the third patient had irregular and disorganized mitochondria. Quantitative ultrastructural analysis has revealed axonemal abnormalities in seven of 10 patients with previously unexplained asthenozoospermia.