Plasma cells in vertebrate paraocular glands

Harderian gland in Canadian ostrich (Struthio camelus): a morphological and histochemical study

Heads of ten healthy adult ostrich obtained from slaughter house were the constituted materials of the study. The Harderian gland (HG) was dissected out, and all of the gross morphometrical parameters including length, width and thickness as well as weight of left and right glands were recorded. Tissue sections were stained, using haematoxylin and eosin, Masson trichrome, periodic acid-Schiff and Alcian blue (pH 2.5) techniques. In ostrich, HG was an orbital organ located ventromedially around the posterior part of the eyeball. It was an oval flatted shape, light pink colour with irregular outline and was pointed in the dorsal end. Its mean length was 35.30 ± 2.84 mm and 35.55 ± 3.58 mm in left and right sides, respectively, and mean width 15.30 ± 1.20 mm and 15.65 ± 1.18 mm in left and right sides, respectively. There was no significant difference between length, thickness, weight and width of left and right glands. Histological results showed that the glandular epithelium was multilobular and compound tubuloalveolar. The gland was surrounded by a connective tissue capsule, and the epithelium was lined by simple columnar epithelial cells of varying height. The secretion of HG was mucous and the secretion type was apocrine. Mucosubstance analysis revealed that secretory units contained acidic and neutral glycoproteins. The granules within the epithelial cells lining the intralobular and inter-lobular excretory ducts of the gland were positive for periodic acid-Schiff and Alcian blue (pH 2.5).

Morphological features of the porcine lacrimal gland and its compatibility for human lacrimal gland xenografting

In this study, we present first data concerning the anatomical structure, blood supply and location of the lacrimal gland of the pig. Our data indicate that the porcine lacrimal gland may serve as a potential xenograft candidate in humans or as an animal model for engineering of a bioartificial lacrimal gland tissue construct for clinical application. For this purpose, we used different macroscopic preparation techniques and digital reconstruction of the histological gland morphology to gain new insights and important information concerning the feasibility of a lacrimal gland transplantation from pig to humans in general. Our results show that the lacrimal gland of the pig reveals a lot of morphological similarities to the analogous human lacrimal gland and thus might be regarded as a xenograft in the future. This is true for a similar anatomical location within the orbit as well as for the feeding artery supply to the organ. Functional differences concerning the composition of the tear fluid, due to a different secretory unit distribution within the gland tissue will, however, be a challenge in future investigations.

The orbitofacial glands of bats: an investigation of the potential correlation of gland structure with social organization

The facial glands of bats are modified skin glands, whereas there are up to three different orbital glands: Harderian, lacrimal, and Meibomian glands. Scattered studies have described the lacrimal and Meibomian glands in a handful of bat species, but there is as yet no description of a Harderian gland in bats. In this study we examined serial sections of orbitofacial glands in eight families of bats. Much variation amongst species was observed, with few phylogenetic patterns emerging. Enlarged facial glands, either sudoriparous (five genera) or sebaceous (vespertilionids only) were observed. Meibomian and lacrimal glands were present in most species examined (except Antrozous), though the relative level of development varied. Two types of anterior orbital glands were distinguished: the Harderian gland (tubulo-acinar: observed in Rousettus, Atribeus, Desmodus and Miniopterus) and caruncular (sebaceous: observed in Eptesicus and Dieamus). The relative development of the nasolacrimal duct and the vomeronasal organ did not appear to be correlated with the development of any of the exocrine glands examined. There does, however, appear to be a correlation between the presence of at least one well developed exocrine gland and the level of communality and known olfactory acuity, best documented in Artibeus, Desmodus, and Miniopterus.

The Harderian gland of two species of skink (Tiliqua rugosa and Hemiergis decresiensis): a discussion of the significance of lymphatic tissue in the squamate Harderian gland

The Harderian gland is an orbital structure ubiquitous in reptiles. Numerous functions have been ascribed to this gland, including osmoregulation, chemoreception, and immunity. The anatomical, histological, histochemical, and ultrastructural characteristics of the Harderian gland of two species of skink, Tiliqua rugosa (Gray, 1825) and Hemiergis decresiensis (Cuvier, 1829), were examined. Mucous and serous secretory cells were observed in both species. In T. rugosa, mucous cells are located in a small anterior region, while serous cells occupy most of the gland. In contrast, the Harderian gland of H. decresiensis contains mainly serous cells, with a few anteriorly located mucous cells. In both species, the serous granules exhibit internal compartmentalization. There is no evidence of either lipid secretions or salt secreting cells. However, there were either a few plasma cells (H. decresiensis) or several lymphatic aggregations (T. rugosa) in the serous portion of the gland. The presence of such lymphatic tissue may suggest a role in either the head-associated lymphatic tissue (HALT) system or the eye-associated lymphatic tissue (EALT). The difference between these two is based upon terminology, the consolidation of which would allow meaningful comparative analyses. The presence of lymphatic tissue implies that the Harderian gland could play a role in ocular immunity.

Alligator tears: a reevaluation of the lacrimal apparatus of the crocodilians

The Harderian gland is a poorly understood anterior ocular gland that occurs in most terrestrial vertebrates. Numerous extraorbital functions have been ascribed to the Harderian gland, principally based on its association with the nasolacrimal duct. Few studies have centered on archosaurs and the majority of those available focused solely on the Harderian gland of birds. Little is known about the lacrimal apparatus of the crocodilians. We examined the lacrimal apparatus of several specimens of Alligator mississippiensis anatomically, histologically, and histochemically and studied the embryogenesis of this system. The nasolacrimal duct possesses a distal secretory area, which is more convoluted than that of typical mammals or lepidosaurs. The alligator Harderian gland possesses a unique combination of characteristics found in lepidosaurs, birds, and mammals. Like that of both mammals and lepidosaurs, it is a large, tuboloacinar gland that appears to secrete both mucoprotein and lipids. However, the presence of blood vessels and immune cells is reminiscent of that of the avian Harderian gland. The immunogenesis of the alligator Harderian gland appears to be tied to the development of the vascular system. The presence of a distinct palpebral gland in the anterior aspect of the ventral eyelid is a feature unique to alligators. Based on position, this gland does not appear to be homologous to the anterior lacrimal gland of lepidosaurs. Lymphatic aggregations were also found in the palpebral gland. The presence of interstitial immune cells in the orbital glands of alligators suggests that the alligator lacrimal apparatus, like that of birds, may play a role in the head-associated lymphatic tissue system.

Plasma cells expressing immunoglobulins M and A but not immunoglobulin G develop an intimate relationship with central canal epithelium in the harderian gland of the chicken

In the Harderian gland of the chicken, the epithelial and plasma cell relationships were studied by light and electron microscopy and immunohistochemical methods. In the wall of the central canal a dark epithelial cell was identified that had long branching cell processes. An anticytokeratin monoclonal antibody demonstrated that the dark cells provided an extremely large contact area for the plasma cells. Although IgM-, IgG-, and IgA-producing plasma cells were present in the Harderian gland, only IgM- and IgA-positive cells were capable of a distinct relationship with dark epithelial cells. The surface of the primary branches contained scattered IgA deposits whereas the epithelial cells of the secondary branches possessed IgA along the lateral cell membrane but not on the surface. Anti-IgA and anti-cytokeratin antibodies produced a similar staining pattern in the acini and secondary branches. Taken together, these observations suggest that IgA secretion is a function of secondary branches and that intracellular transport is influenced by the cytoskeletal system.