Tom A. Aire

The testicular capsule and peritubular tissue of birds: morphometry, histology, ultrastructure and immunohistochemistry

The testicular capsule was studied histologically, morphometrically, ultrastructurally and immunohistochemically in the Japanese quail, domestic fowl, turkey and duck (all members of the Galloanserae). The testicular capsule was, relative to mammals, thin, being 81.5 ± 13.7 µm in the quail, 91.7 ± 6.2 µm in the domestic fowl, 104.5 ± 29.8 µm in the turkey and 91.8 ± 18.9 µm in the duck. The orchido‐epididymal border (hilus) of the capsule was much thicker than elsewhere in all birds (from 233.7 ± 50.7 µm in the duck to 550.0 ± 147.3 µm thick in the turkey). The testicular capsule, other than the tunica serosa and tunica vasculosa, comprised, in the main, smooth muscle‐like or myoid cells running mainly in one direction, and disposed in one main mass. Peritubular tissue was similarly composed of smooth muscle‐like cells disposed in several layers. Actin and desmin intermediate filaments were immunolocalized in the inner cellular layers of the capsule in the quail, domestic fowl and duck, but uniformly in the turkey. Vimentin intermediate filament immunoreaction in the capsule was moderately and uniformly positive in the testicular capsule of only the quail. Actin and desmin, but not vimentin (except very faintly in the turkey) or cytokeratin, were immunolocalized in the peritubular tissue of all birds. The results therefore establish, or complement, some previous observations that these birds have contractile cells in their testicular capsule and peritubular tissue, whose function probably includes the transport of testicular fluid into the excurrent duct system.

Aspects of the Functional Morphology of the Ductus Epididymidis in Domestic Anseriform and Galliform Birds

The structure of the ductus epididymidis, and its capacity to take up luminal particulate material (India ink) were studied, using scanning and transmission electron microscopy, in the domestic fowl, turkey and Japanese quail (Order Galliformes) and drake (Order Anseriformes). The epithelium appeared contractile and stable structurally, especially in the drake in which, among other cytoskeletal features, abundant perinuclear intermediate filaments radiated peripherally in the principal, non‐ciliated (Type III) cell. The Golgi complex was well developed, except in the turkey in which it was extremely inconspicuous. Sparsely granulated profiles were the main component of the elaborate endoplasmic reticulum, which was best developed in the drake and least in the turkey. The cell in the turkey was uniquely laden with large aggregates of lipid droplets. Generally, characteristics of a cell active in the synthesis and merocrine secretion of proteinaceous material were evident. There was no evidence of apocrine‐like secretion in well‐fixed tissues. The cell lacked the capacity to take up luminal India ink particles, and displayed very poorly developed endocytic structural features, which are also probably only selectively and minimally absorptive. Ultrastructural features varied between and within the orders studied, necessitating further studies.

The surface features of the epithelial lining of the ducts of the epididymis of the ostrich (Struthio camelus).

The luminal appearance of the various ducts of the epididymis of the ostrich was studied by scanning electron microscopy in tissues fixed by immersion in glutaraldehyde. The ductal types were similar to those previously described for some other species of birds. Numerous short microvilli, as well as a single cilium, projected from the apical surface of the rete testis cell. The ciliated cells of the efferent ductules projected tufts of cilia into the ductal lumen, while the non‐ciliated cells bore short microvilli. The connecting and epididymal ducts were lined by a columnar cell type whose apical surface bore uniformly distributed microvilli and a single, centrally situated cilium. The spermatozoa found in all ducts of the epididymis bore a distal cytoplasmic droplet. This observation has implications for the maturational process in the ostrich spermatozoon in the epididymis. The surface features of the ducts, except for a few noteworthy differences, were generally similar to those previously described for the male domestic fowl, turkey and duck.

The morphological features of the rete testis of the ostrich (Struthio camelus)

The epithelium of the rete testis of the ostrich is simple cuboidal to columnar in nature, unlike the more flattened epithelium encountered in other non-passerine birds. A solitary cilium projects into the ductal lumen. A unique lateral cell membrane modification, similar, in some respects, to a hemi-desmosome, occurs frequently along the length of this membrane. The lateral cell membrane is complexly folded, and the cell contains an abundance of intermediate filaments, particularly in the vicinity of the nucleus and the internal surface of the basal cell membrane. The Golgi complex and endoplasmic reticulum are moderately developed. Another unique feature of the cell is the presence of a solitary, large, heterogeneous lipid body/droplet situated in the immediate supranuclear region of the cell. Overall, the cell structure conveys the impression of a metabolically active cell, which has the capability of transporting material from the duct lumen to the basal part of the cell, and of protein synthesis, apparently much in excess of what is necessary for cellular maintenance and sustenance.

Cyclical Reproductive Changes in the Non-ciliated Epithelia of the Epididymis of Birds

The epididymis of two species of domestic birds, the domestic fowl (Gallus domesticus), duck (Anas platyrhynchos), and of domestic and feral guinea‐fowl (Numida meleagris) was studied during the three main phases of the reproductive cycle (prepuberal, sexually mature and active, and sexually mature but inactive or resting) with a view to identifying major histological and ultrastructural changes associated with and distinctive for each phase. Rete testis cells accumulated numerous variably sized lipid droplets in all birds, as well as large heterogeneous and lipofuscin‐containing dense bodies in the guinea‐fowl, during the resting but not in the other phases. The principal or Type III cells of the connecting and epididymal ducts exhibited profound structural changes, including, but not limited to, rarefied cytoplasm, inconspicuous and general loss of sparsely granular endoplasmic reticulum, loss of secretory vesicles in the drake, and an enhanced and conspicuous presence of lipid droplets in the guinea‐fowl. The rete cells appeared to be less sensitive than the Type III cells to a reduced level or absence of lumenal androgens. These phase‐dependent changes may help to prevent or minimize discrepancies in the interpretation of the normal structure of the epididymis in birds during the sexually active phase, as distinct from the other two phases and their intermediate phases.

The morphology of the efferent ducts of the testis of the ostrich, a primitive bird

The efferent duct of the ostrich consists of two segments, the proximal efferent duct (PED) and the distal efferent duct (DED) that are continuous, as in some other birds. Both segments of the duct possess an epithelium comprising non-ciliated and ciliated cells in varying proportions between the two segments. The non-ciliated cell (type I) of the PED contains a well-developed, subapical endocytic apparatus of apical tubules and endocytic vacuoles, a solitary, large, heterogeneous lipid droplet, and numerous, oval, dense bodies in the supranuclear region of the cell. Mitochondria tend to concentrate in the basal part of the cell. Intercellular spaces between the non-ciliated cells are enlarged, especially in the basal half of the epithelium. Together, these morphological features confer on the PED an efficient fluid absorption capability. The DED epithelium displays the type II non-ciliated cell whose poorly developed subapical endocytic apparatus as well as the absence of dilated basal intercellular spaces indicate its limited fluid absorptive capacity.

Structural and Immunohistochemical Features of the Epididymal Duct Unit of the Ostrich (Struthio camelus)

The epididymal duct unit, comprising the ductus conjugens, ductus epididymidis and ductus deferens, was studied histologically, ultrastructurally and immunohistochemically in five sexually mature and active birds. The main morphological features of the pre‐dominant non‐ciliated (type III) cell of the epithelial lining of this duct unit include, but are not limited to, a moderately abundant smooth or sparsely granulated endoplasmic reticulum, electron‐dense secretory granules and numerous mitochondria in the supranuclear zone of the cytoplasm. A single, large heterogeneous lipid droplet, of unknown function, was characteristically situated immediately proximal to the nucleus. The epithelium is obviously secretory and specifically, of the merocrine, and not apocrine, type of secretion. The epithelium of the epididymal duct unit was only focally and weakly to moderately immunopositive to both actin MF and desmin IF, while the duct unit was immunonegative to cytokeratin and vimentin intermediate filaments. The peritubular muscular layer was moderately to strongly positive to both actin and desmin, and negative to cytokeratins and vimentin.

Macroscopic Features of the Arterial Supply to the Reproductive System of the Male Ostrich (Struthio camelus)

The macroscopic features of the arterial supply to the reproductive system of the male ostrich was studied in 16 pre‐pubertal and eight sexually mature and active birds. The left and right cranial renal arteries arise from the aorta, between the cranial divisions of the kidneys. These vessels supply the cranial divisions of the kidneys, the testes, the epididymides and the cranial segments of the ducti deferentia. Accessory testicular arteries which arise directly from the aorta are present in 45.8% of the specimens. They supply the testes and cranial parts of the ducti deferentia. They are variable in number and origin, and four variants are identified. A cranial ureterodeferential branch originates from the cranial renal artery, supplies the cranial portion of the ductus deferens and ureter, and runs caudally to anastomose with the middle renal artery. The sciatic artery arises laterally from the aorta, just caudal to the acetabulum, and gives rise, ventrally, to a common trunk, the common renal artery, which divides into the middle and caudal renal arteries. The middle renal artery gives rise to the middle ureterodeferential branch which supplies the middle part of the ductus deferens and ureter. A few centimetres caudal to the kidney, the aorta terminates in three branches, namely, the left and right internal iliac arteries and the median caudal artery. The internal iliac artery divides into the lateral caudal artery and the pudendal artery; the latter gives off caudal ureterodeferential branches that supply the caudal segments of the ductus deferens and ureter. In addition, the pudendal artery gives off vessels that supply the cloaca, some of which continue to the base of the phallus, where they form an arterial network. In conclusion, the pattern of the blood supply to the reproductive organs of the male ostrich is, in general, similar to that of the domestic fowl and pigeon, although there are a few highlighted distinctive features.

The ductuli efferentes testis of the greater cane rat (Thryonomys swinderianus)

The structure of the efferent ducts of animals is known to vary from one species to another, it even varies between segments of the ducts in the same species. In the grasscutter or greater cane rat (Thryonomys swinderianus), there are three segments of the efferent duct, based on their content of non-ciliated or principal cell types. Type I non-ciliated cell is present exclusively in the long proximal part of the duct, and exhibits a well-developed subapical endocytic apparatus as well as numerous oval or pleomorphic dense bodies. The type II non-ciliated cell predominates in the middle part of the duct, displays a poorly developed subapical endocytic apparatus but contains large, numerous vacuoles and dense bodies, all of which fill about two-thirds of the cell height. The type III non-ciliated cell, found in the epithelium of the terminal part of the duct, is poorly endowed with a subapical endocytic apparatus and contains no conspicuous endocytic vesicles or vacuoles. Only a few, small, dense bodies are present, if at all. The efferent duct of the cane rat is thus similar to that of man, the bull, goat and dog, in containing three varieties or types of non-ciliated cells. This report is the first to describe multiple non-ciliated cells in the epithelium of the efferent ducts of a rodent and, indeed, of a mammal smaller than the dog.

An immunohistochemical study of the presence and distribution of neuronal and glial markers in simple testicular cysts in the ostrich (Struthio camelus)

Simple testicular cysts are rare in birds and mammals. However, the condition has recently been reported in the ostrich (Struthio camelus), an economically important farmed bird. The innervation of normal and cryptorchid testes, unlike the simple testicular cysts of birds and mammals, has received considerable attention. This study, therefore, immunohistochemically demonstrates the presence and the general distribution pattern of neuronal and glial markers in the simple intratesticular cyst, and its associated structures, of fourteen adult ostriches using antibodies to neurofilament protein, S-100, neuron-specific enolase and protein gene product 9.5. The LSAB+ Kit(DakoCytomation, Denmark) immunostaining protocol was used in this study. The normal seminiferous peritubular tissue showed few or no immunoreactive nerve fibres. A greater density of neurofilament protein, S-100, neuron-specific enolase and protein gene product 9.5 immunopositive nerve fibres were observed in the tunica albuginea adjacent to the cyst, as well as in the peritubular connective tissue of cystic seminiferous tubules. In addition, the tunica adventitia of blood vessels within the interstitial space of the cystic seminiferous tubules displayed neurofilament protein, S-100 and protein gene product 9.5 immunoreactive nerve fibres of varying intensity and pattern. Protein gene product 9.5 immunostaining was also observed in the multinucleated giant cells of both the normal and the cystic seminiferous tubules. The cystic portion of the testis appears to have a richer innervation than the normal portion of the same testis. The richer innervation of simple testicular cysts in the ostrich is similar to that observed in the cryptorchid testis of mammals.