FIG. 7.

Electron microscopy analysis of spermatozoa and testis from Neuralized null animals. (A) Cross section of a flagellar midpiece showing normal 9+2 arrangement of axoneme doublets. (B) Cross sections of the principal piece of spermatozoa from Neuralized null animals, showing that although some cross sections appear to be normal with the expected 9+2 configuration (no. 1 to 3), several other cross sections clearly show defects in axonemal organization (no. 4 to 6). (C) Cross section showing a common flagellar defect, i.e., deletion of half the axonemal complex. (D) Cross section of principal piece showing a flagellum where a portion of the fibrous sheath is absent as well as a highly disorganized axonemal complex. (E) Abnormal biflagellate spermatozoa identified in samples from Neuralized null animals. (F and G) Abnormal axonemal complexes occur along the length of the flagellum (arrowheads in panel F), as revealed by various longitudinal and grazing planes of sections. (H) Testicular spermatozoa of Neuralized null animals. Although cross-sections of the principal piece present a normal profile of the axoneme (arrows), it is apparent from grazing planes of sections that in localized regions of the flagellum, the axonemal complex is disorganized (arrowheads). Bars, 0.2 μm.