Aberrant distribution of the peri-axonemal structures in the human spermatozoon: possible role of the axoneme in the spatial organization of the flagellar components.

A quantitative ultrastructural study combined with stereology was performed on semen samples from four men selected for apparently isolated anomalies of the peri-axonemal structures. Comparison of the results with those of a control group revealed a decrease: in the mean length of the principal piece; in the mean length of the 9 dense fibres and in the difference in length between the 9 dense fibres, all the fibres being approximately as long as the medium length fibres of the normal spermatozoon. In addition, longitudinal columns were single and/or in abnormal position. However, the extent of the dense fibres (along 60% of the principal piece) and their proportion within the flagellum (35.1% of the principal piece per fibre on average) were normal. Analysis of the results suggests that: A-tubules of the axonemal doublets are involved in the spatial arrangement of the peri-axonemal structures; axonemal microtubule-associated proteins (MAPs) may be responsible for this structural function; and three different types of longitudinal doublet differentiations may exist along the flagellar axoneme.