An electron microscopical study of cell contacts in the seminiferous tubules of some mammals

Different types of cell contacts in the seminiferous tubules have been studied electron microscopically in some laboratory and domestic mammals. Specialized inter-Sertoli cell contacts are always present. Most of them show a narrow — partly perhaps closed — intercellular space at some distance from the basement membrane, above the spermatogonia but below the spermatocytes. Fibrillar material is present in the cytoplasm near the junction as well as subsurface cisterns of the endoplasmic reticulum. Two main types of narrow junctions and one wide junction are described. These junctions are interpreted as devices for adhesion and perhaps intercommunication between the basal parts of the Sertoli cells. The narrow junctions are also considered to impede the intercellular transport of substances to spermatocytes and spermatides and into the luminal fluid. This interpretation emphasizes the importance of the Sertoli cells as nurse cells for the spermatocytes and spermatids. Numerous fine branches of the Sertoli cells surround spermatocytes, spherical spermatids, and true residual bodies, and others protrude deeply into the postnuclear cytoplasm of elongated spermatids. The plasma membrane of developing spermatids turns thicker and becomes a distinct “unit membrane”. Dense, fibrillar material and long, narrow subsurface cisterns are always present in the Sertoli cells along their border to the acrosomal area of the elongated spermatids. This arrangement is interpreted as an attachment device of hemidesmosomal character. Intercellular bridges are considered to interconnect as many as four primary spermatocytes or sixteen spermatids.