The cell surface during mammalian spermiogenesis

Barriers to diffusion of plasma membrane proteins form early during guinea pig spermiogenesis

The plasma membrane of the mature guinea pig sperm is segregated into at least four domains of different composition. Previous studies have shown that some proteins localized within these domains are free to diffuse laterally, suggesting that barriers to protein diffusion are responsible for maintaining the nonuniform distribution of at least some surface proteins in mature sperm. The different membrane domains appear sequentially during sperm morphogenesis in the testis and during later passage through the epididymis. To determine when diffusion barriers become functional during sperm development, we examined the diffusion of two proteins that are expressed on the cell surface of developing spermatids and become segregated to different plasma membrane domains during the course of spermiogenesis. Both proteins exhibited rapid lateral diffusion throughout spermiogenesis, even after they become localized to specific regions of the surface membrane. These results suggest that barriers to membrane diffusion form concomitantly with membrane domains during spermiogenesis.

Lectin-binding pattern of bull testis and epididymis

Seven rhodamine-conjugated lectins (PNA, RCA I, SBA, Con A, WGA, UEA I, DBA) were used to study the distribution of glycoproteins in the testis and epididymis of immature, juvenile, and adult bulls. A marked change was found in the staining pattern of the lectins in the seminiferous tubules during acrosomal development, and the Sertoli cells seemed to have a cyclic affinity for some of the lectins. The distribution of lectin staining in six regions of the bull epididymis showed some typical differences that were associated with the secretory and absorptive functions of the organ. Region 1 was characterized by strong surface and villous staining and a patchy reaction in the principal cells. Regions 2 and 3 showed a strongly reactive apical Golgi zone and secretory material. In regions 4 and 5, the Golgi zone was subapical but strongly reactive with most lectins, while in region 6 a weakly reactive apical Golgi zone was found. During sexual maturation, an increasing number of basal cells with a strong affinity for some lectins was found at the periphery of the epithelium in regions 2 to 6. These regions also had lectin-stained material along the basal border of the principal cells. These findings suggest that the basal cells may be active in the digestion of absorbed material and that they derive from the principal cells, which may be active in transporting absorbed material to them. The staining pattern of the spermatozoa changed during their transit through the epididymis. The degenerating cells in the testis and epididymal tubules also showed an altered affinity for the lectins.