Three-dimensional structure of dog Sertoli cells: a computer-aided reconstruction from serial semi-thin sections

The three-dimensional structure of the Sertoli cell in the Korean Jindo dog was investigated by scanning and transmission electron microscopy. Additionally, type-A and type-B Sertoli cells were simulated by three-dimensional computer graphic imaging to clarify the anatomical relationship between Sertoli cell and germ cells. Descriptions in the present study are based on examination of the reconstructed type-A cells at stages IV, V and VI of the spermiogenetic cycle and stages VII, VIII and IX of the reconstructed type-B Sertoli cells. Morphologically, three types of Sertoli cell processes were evident: 1) flat club-like, elliptical processes bifurcating and trifurcating randomly; 2) slender cord-like, tubular processes; and 3) sheet-like processes. The sheet-like processes rested upon more than half the surface of each round spermatid located in the proximity of the Sertoli cell. Curiously, just before spermiation, the apical club-like processes shifted from their initial position at the spermatid head and subsequently covered the disengaged residual body, after which the residual body was no longer evident in the tubule. Though the mechanism for this elimination is not known, the process suggests a reciprocity between the Sertoli and germ cells. An anatomical dissimilarity between type-A and type-B Sertoli cells appeared in the apical region, with the apical club-like processes of the type-B Sertoli cell given off by sheet-like processes as well as by the Sertoli column. At the base of all Sertoli cells, sophisticated sheet-like processes paralleled the basal lamina, tenaciously adhering end-to-end to the sheet-like processes of adjacent Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)