Chronological and structural disorder of the spindle-shaped body during human spermatid differentiation

In a testicular biopsy of an infertile man, most of the spermatids revealed a lack of the middle piece because of a malformed or untimely occurring spindle-shaped body. When during spermatid differentiation the spindle-shaped body appeared, it contained the typical bundles of tubules but was often reduced in size and arranged only unilaterally to the axoneme. After the disappearance of the incomplete spindle-shaped body, the annulus did not descend, the ribs of the fibrous sheath of the principal piece were found far proximally and the mitochondrial sheath of the middle piece could not be formed. In consequence of this faulty development, the spermatozoa were immotile.