Elektronenmikroskopische Untersuchungen an den Ductuli efferentes des Nebenhodens normaler und kastrierter Kaninchen

[Spatial pattern and microvascularization of the ductuli efferentes testis of bulls (Bos taurus)]

The arrangement, origin, course and opening of the ductuli efferents testis of the bull (Bos taurus) were visualized using scanning electron microscopy. The corresponding capillary structure was also described and documented with the help of corrosive microanatomical casts. The number of the ductuli efferents testis of the bull varies narrowly between 12 to 13. Ductuli removed from the surrounding tissue have a length of up to 78 cm. The duct system is composed of linear as well as tortuous parts, permitting division into three distinct segments. Blind ending ductules are very short. We therefore do not see these structures as being associated with spermiostasis. The capillary density as well as the capillary architecture show regional peculiarities. All segments of the ductuli efferents testis are composed of capillaries of the continuous type. The findings indicate that the increased capillary density in the voluminous initial section of the ductuli efferents testis represents the basis for resorptive as well as secretory activities in the bull.

The ductuli efferentes of the goat: a morphological study

The morphology of the ductuli efferentes of the goat was compared with that of other animal species, especially with that of the bull. Both in the goat and in the bull, it forms a slightly brownish, bulbous mass of highly convoluted ductules (18-19 in the goat, 13-16 in the bull) that occupies approximately one third of the first limb of the caput epididymidis. The epithelium consists of two major cell types, ciliated and nonciliated, and a few intraepithelial lymphocytes and macrophages. The nonciliated cells can be further divided into three types: type II cells are characterized by specific granules that are dense, mostly homogeneous, eosinophilic, osmiophilic, and positive to periodic acid-Schiff (PAS) staining; type III cells are characterized by specific vacuoles that appear empty and do not stain with PAS, eosin, or osmium; type I cells lack both granules and vacuoles. These morphological, histochemical, and tinctorial differences observed among nonciliated cell types suggest that they are probably independent cell types rather than functional stages of one cell type. All three cell types are endowed with absorptive features such as microvilli, pinocytotic vesicles, and subapical vacuoles, but a higher differentiation of these features in type III cells suggests their greater role in the absorption of testicular fluid. Whether granules of type II cells and vacuoles of type III cells are absorptive and/or secretory remains unresolved from the available data. However, some circumstantial evidence, as presented in the discussion, supports the latter possibility.

Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat

The nonciliated cells lining the ductuli efferentes presented three distinct cytoplasmic regions. The apical region contained, in addition to cisternae of endoplasmic reticulum and mitochondria, two distinct membranous elements. The tubulovesicular system consisted of dilated tubules connected to the apical plasma membrane and subjacent distended vesicular profiles. The apical tubules, not connected to the cell surface, consisted of numerous densely stained tubules of small size which contain a compact, finely granulated material. The supranuclear region, in addition to a Golgi apparatus and ER cisternae, contained dilated vacuoles, pale and dense multivesicular bodies, as well as numerous dense granules identified cytochemically as lysosomes. The basal region contained the nucleus and many lipid droplets. The endocytic activity of these cells was investigated using cationic ferritin (CF) and concanavalin-A-ferritin (Con-A-ferritin) as markers of adsorptive endocytosis; and native ferritin (NF), concanavalin-A-ferritin in the presence of alpha-methyl mannoside, and horseradish peroxidase or albumin bound to colloidal gold for demonstrating fluid-phase endocytosis. These tracers were injected separately into the rete testis, and animals were sacrificed at various time intervals after injection. At 1 min, CF or Con-A-ferritin were seen bound to the apical plasma membrane, to the membrane of microvilli, and to the membrane delimiting elements of the tubulovesicular system. Between 2 and 5 min, these tracers accumulated in the densely stained apical tubules and at 15 min in the dilated vacuoles. Between 30 min and 1 hr, the tracers appeared in multivesicular bodies of progressively increasing density, whereas at 2 hr and later time intervals, many dense lysosomal elements became labeled. The tracers for fluid-phase endocytosis showed a distribution similar to that for CF or Con-A-ferritin except that they did not bind to the apical plasma membrane, microvilli, or membrane delimiting the tubulovesicular system. At no time interval were any of the tracers observed in the abluminal spaces. Thus, the nonciliated epithelial cells of the ductuli efferentes are actively involved in fluid-phase and adsorptive endocytosis, both of which result in the sequestration of endocytosed material within the lysosomal apparatus of the cell.