The effect of autophagy and mitochondrial fission on Harderian gland is greater than apoptosis in male hamsters during different photoperiods

Photoperiod is an important factor of mammalian seasonal rhythm. Here, we studied morphological differences in the Harderian gland (HG), a vital photosensitive organ, in male striped dwarf hamsters (Cricetulus barabensis) under different photoperiods (short photoperiod, SP; moderate photoperiod, MP; long photoperiod, LP), and investigated the underlying molecular mechanisms related to these morphological differences. Results showed that carcass weight and HG weight were lower under SP and LP conditions. There was an inverse correlation between blood melatonin levels and photoperiod in the order SP > MP > LP. Protein expression of hydroxyindole-O-methyltransferase (HIOMT), a MT synthesis-related enzyme, was highest in the SP group. Protein expression of bax/bcl2 showed no significant differences, indicating that the level of apoptosis remained stable. Protein expression of LC3II/LC3I was higher in the SP group than that in the MP group. Furthermore, comparison of changes in the HG ultrastructure demonstrated autolysosome formation in the LP, suggesting the lowest autophagy level in under MP. Furthermore, the protein expression levels of ATP synthase and mitochondrial fission factor were highest in the MP group, whereas citrate synthase, dynamin-related protein1, and fission1 remained unchanged in the three groups. The change trends of ATP synthase and citrate synthase activity were similar to that of protein expression among the three groups. In summary, the up-regulation of autophagy under SP and LP may be a primary factor leading to loss of HG weight and reduced mitochondrial energy supply capacity.

Ultrasonography of the Harderian gland in the rabbit, guinea pig, and chinchilla

OBJECTIVE

To evaluate the Harderian gland in rabbits, guinea pigs, and chinchillas using B-mode ultrasound and to determine normal size and changes in size and/or location in normal and diseased eyes and orbits by ultrasonographic measurements.

PROCEDURE

Normal Harderian glands were evaluated ultrasonographically in 20 rabbits, 10 guinea pigs, and eight chinchillas. The Harderian gland was measured ultrasonographically in horizontal and vertical planes. Normal Harderian gland sizes were then compared with sizes in 27 rabbits, 13 guinea pigs, and three chinchillas that had exophthalmos.

RESULTS

Harderian glands in normal rabbits were 0.69 ± 0.07 cm (mean value ± SD) horizontally and 1.33 ± 0.14 cm vertically. Harderian glands in normal guinea pigs were 0.58 ± 0.05 cm horizontally and 0.61 ± 0.10 vertically. In normal chinchillas, the Harderian glands were 0.53 ± 0.04 cm horizontally and 0.53 ± 0.03 cm vertically. Harderian glands were significantly larger in the vertical plane in rabbits with exophthalmos (P = 0.001) and in the horizontal plane in guinea pigs with exophthalmos (P = 0.018). Harderian glands of rabbits with exophthalmos were significantly larger in both diseased and healthy glands in both planes compared with those of normal rabbits. Guinea pigs and chinchillas with exophthalmos had larger Harderian glands bilaterally in only the vertical plane.

CONCLUSIONS

Ultrasonography is a valuable diagnostic imaging technique to evaluate the Harderian gland in the rabbit, guinea pig, and chinchilla. Retrobulbar pathologic processes cause enlargement of the Harderian gland, which may be attributable to inflammation or possible obstruction of the excretory ducts.

Analysis of constant tissue remodeling in Syrian hamster Harderian gland: intra-tubular and inter-tubular syncytial masses

The Syrian hamster Harderian gland (HG) has a marked sexual dimorphism and exhibits an extraordinary rate of porphyrinogenesis. The physiological oxidative stress, derived from constant porphyrin production, is so high that the HG needs additional survival autophagic mechanisms to fight against this chronic exposure, provoking the triggering of a holocrine secretion in female glands that forms two types of secretory masses: intra-tubular-syncytial and inter-tubular-syncytial masses. The aim of this work was to study the development of this inter-tubular holocrine secretion. To approach this task, we have considered that the steps developed during the formation of the so-called invasive masses consist of the growth of epithelial cells, cell detachment from the basal lamina and invasion of surrounding tissues. The presence of these masses, particularly in the female HG, are closely linked to sexual dimorphism in redox balance and to alterations in the expression of certain factors such as cytokeratins, P-cadherin, matrix metalloproteinases, cathepsin H, proliferating cell nuclear antigen, p53, CD-31 and vascular endothelial growth factor, which seem to be involved in tissue remodeling. The results document unusual mechanisms of secretion in Syrian hamster HG: an extraordinary system of massive secretion through the conjunctive tissue, disrupting the branched structure of the gland.

"A new lachrymal gland with an excretory duct in red and fallow deer" by Johann jacob Harder (1694): English translation and historical perspective

The Harderian gland is an enigmatic orbital gland that has been described for many tetrapods, although a consistent definition of this structure has remained elusive. In particular, an unambiguous distinction between the Harderian gland and the nictitans gland, which may both occur in the anterior aspect of the orbit of mammals, remains problematic. These glands were first distinguished in 1694 by Johann Jacob Harder, a Swiss physician and anatomist. To facilitate a renewed examination of the anatomical and developmental relationships of the anterior orbital glands, we review the historical context of Harder's discovery, and provide Harder's original Latin text as well as an English translation.

One gland, two lobes: Organogenesis of the “Harderian” and “nictitans” glands of the Chinese muntjac (Muntiacus reevesi) and fallow deer (Dama dama)

The nictitans and Harderian glands are enigmatic glands situated in the anterior aspect of the orbit. Traditionally, the nictitans and Harderian glands of mammals have been considered to be two fundamentally distinct glands. However, a consistent, unambiguous distinction between these two glands has remained elusive due to conflicting anatomical and histochemical definitions. The Harderian gland was originally described, and first distinguished from the nictitans gland, in adult deer. We examined the organogenesis and histochemistry of the anterior orbital glandular mass in two species of deer (Muntiacus reevesi and Dama dama) to determine whether it comprises two distinct glands or one bilobed gland. The anterior orbital regions of 30 fetal specimens of both species, along with some adult material, were examined histologically. Four stages of glandular organogenesis were observed. Most notably, both glandular portions developed from the same inception point, but the deep lobe developed faster than the superficial lobe. The common inception point and the relationship of the collecting ducts clearly shows that this is a single glandular mass that differentiates into two lobes rather than two distinct glands. Moreover, although the histochemical profiles of the two lobes differ slightly, both lobes produce lipids, which is further indication that these are not profoundly different glands but part of a single, heterogeneously developed gland. Thus, it is proposed that the terms nictitans and Harderian glands, as separate entities, be discontinued and that the entire gland be referred to as the anterior orbital gland (glandula orbitalis anterior), with superficial and deep lobes (pars superficialis and pars profundus, respectively).

The Orbital Harderian Gland of the Male Atlantic Bottlenose Dolphin (Tursiops truncatus): A Morphological Study

The ultrastructure of the Atlantic Bottlenose dolphin Harderian gland (HG) has been described but some questions remain unanswered. The purpose of this work was to define the gland's structure, ultrastructure and the differences between cells (types I and II) of the male dolphin using optic, fluorescence and electron transmission microscopy. Three different cells were observed under optic and fluorescence microscopic examination, while only two cell types (types I and II) were distinguished by electron transmission microscopy. Type I (oval nuclear envelope) exhibited three different cell populations and type II (indented nuclear envelope) exhibited two different cell populations. Although, we observed both types of vesicles in both types of cells they differed, principally, in quantity. The glands also possessed prominent duct systems, with three orders of complexity. The dolphin orbital HG appears to function as a mixed heterologous gland with two types of cells that exhibit both types of vesicles and other distinguishable differences.

Breast cancer resistance protein (Bcrp1/Abcg2) is expressed in the harderian gland and mediates transport of conjugated protoporphyrin IX

Proper regulation of intracellular levels of protoporphyrin IX (PPIX), the direct precursor of heme, is important for cell survival. A deficiency in ferrochelatase, which mediates the final step in heme biosynthesis, leads to erythropoietic protoporphyria (EPP), a photosensitivity syndrome caused by the accumulation of PPIX in the skin. We have previously shown that mice with a deficiency in the ABC transporter Bcrp1/Abcg2 display a novel type of protoporphyria. This protoporphyria is mild compared with ferrochelatase-dependent EPP, and in itself not sufficient to cause phototoxicity, but it might exacerbate the consequences of other porphyrias. In this study, we identified the mouse harderian gland as a novel expression site of Bcrp1. Because of its pronounced role in porphyrin secretion, the harderian gland presents a useful tool to study the mechanism of Bcrp1-related protoporphyria and transport of porphyrins. Bcrp1−/− harderian gland displayed a highly increased accumulation of PPIX glycoconjugates, and a similar shift was seen in Bcrp1−/− liver. Tear- and hepatobiliary excretion data suggest that Bcrp1 controls intracellular levels of PPIX by mediating high affinity transport of its glycoconjugates and possibly low-affinity transport of unconjugated PPIX. This mechanism may allow cells to prevent or reduce cytotoxicity of PPIX under excess conditions, without spillage under physiological conditions where PPIX is needed.

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.

Normal anatomical and histochemical characteristics of the lacrimal glands in the American bison and cattle

Dorsal lacrimal glands, superior glands of the third eyelid and Harderian glands (deep gland of the third eyelid) from 19 bison and 18 cattle free of apparent ocular disease were examined to compare the normal anatomical properties of these glands. All glands were characterized and measured (length and width). The gross anatomy of the dorsal lacrimal glands was similar, with the exception of a bipartite gland in cattle. The bison's superior gland of the third eyelid and Harderian gland was longer as compared with cattle. A subset of the bison and cattle samples (five bison and five cattle) was sectioned for histological and histochemical analysis. The histology of the dorsal lacrimal and superior gland of the third eyelid revealed tubuloalveolar cells with basophilic vacuolated cytoplasm in bison and eosinophilic granular cytoplasm in cattle. The Harderian glands consisted of a tubuloalveolar anterior part combined with large lumens acini lined with cuboidal epithelium in the posterior part; the posterior part of the bison Harderian gland was more predominant than in cattle samples. Mucosubstance histochemistry revealed acidic and neutral glycoproteins with similar staining patterns in all glands of both species.

Chemical coding of sympathetic neurons controlling the tarsal muscle of the rat

Sympathetic axons in the upper eyelid and in tissues in the superior retro-orbital space were examined for NPY immunoreactivity. Sympathetic nerve terminals containing co-localised NPY were associated with blood vessels, the conjunctiva and the Meibomian glands. The acini of the Harderian gland completely lacked sympathetic innervation. Sympathetic axons lacking NPY were only found in the tarsal muscle. In addition, a minority of terminals, located in the more proximal part of the tarsal muscle, contained weak immunoreactivity to NPY. Injections of the retrograde tracer, Fast Blue, into the eyelid or retro-orbital space labelled postganglionic somata in the superior cervical ganglion. While many retrogradely labelled somata were immunoreactive for NPY, around half lacked NPY immunoreactivity and so are likely to project to the tarsal muscle. Most of the retrogradely labelled postganglionic somata lacking NPY were surrounded by terminals immunoreactive for met-enkephalin, leu-enkephalin and met-enkephalin arg-gly-leu which were all found to be present in the same nerve terminals. Sectioning the cervico-sympathetic trunk eliminated all enkephalin-immunoreactive pericellular baskets. Many enkephalin-immunoreactive pericellular terminals contained co-localised VAChT, calretinin and calbindin immunoreactivity, but completely lacked nitric oxide synthase immunoreactivity. A second population of nerve terminals that were immunoreactive for nitric oxide synthase also surrounded tarsal muscle-projecting neurons, but these terminals lacked immunoreactivity to enkephalin. Thus, postganglionic neurons projecting to the tarsal muscle are of at least two chemical phenotypes (with or without NPY) and they receive convergent input from at least two populations of preganglionic neurons with distinctive chemical phenotypes.

Microscopic anatomy of the orbital Harderian gland in the common tree shrew (Tupaia glis)

The orbital Harderian gland of the common tree shrew (Tupaia glis) was investigated at the macroscopic and microscopic levels. In the glands of both sexes only one acinar cell type was found. The cell is characterized by the presence of numerous lipid vacuoles of variable size and by a small number of PAS-positive, electron-dense granules distributed throughout the cytoplasm, which are predominant at the basal portion of each acinar cell. The duct system is well developed within the gland. The content of lipid vacuoles within the acinar cells is secreted from the apical portions by exocytosis, indicating the exocrine function of the organ. Apart from the lipid vacuoles, both acinar and ductal luminal contents of the Harderian gland also contain accretion of electron-dense materials. The vascularization within the Harderian gland is unique in that two capillary types (small fenestrated and irregular sinusoidal capillaries) could be demonstrated. The presence of fenestrated capillaries together with other morphological features (such as accumulation of the small electron-dense granules at the basal pole and the presence of basolateral microvilli) near the basal portion of the acinar cells suggest that the Harderian gland in T. glis might also be involved in an endocrine function.

Magnetic resonance imaging of the rat Harderian gland

The intra-orbital lacrimal gland (Harderian gland, or HG) of the female rat was studied by magnetic resonance imaging (MRI) to evaluate whether MRI can be used to visualize the gland in vivo and localized-1H-spectroscopy detect its lipid content. The results were correlated with post-mortem anatomical sections, and with light and electron microscopy. On MRI, HG presented as a mass located between the ocular bulb and the orbit. In strongly T2W sequences the secretory structures had a reduced signal while intraparenchymal connective tissue was visible. T2-quantitative maps values of HG (60.12 +/- 8.15 ms, mean +/- SD) were different from other tissues (i.e. muscular tissue, T2 = 44.79 +/- 3.43 ms and olfactory bulb, T2 = 79.26 +/- 4.25 ms). In contrast-enhanced-MRI, HG had a signal-intensity-drop of 0.074 +/- 0.072 (mean +/- SD), after injection of AMI-25, significantly different from the muscle (0.17 +/- 0.10). Localized MRI spectra gave a large part of the signal originating from fat protons, but with a significant percentage from water protons. At light and electron microscopy the lipid deposition appeared to be composed of low-density material filling a large part of the cytoplasm, and the porphyrin aggregates were easily recognizable. The data demonstrate that an in vivo study of the HG was feasible and that high-field MRI allowed analysis of the gross anatomy detecting the lipid content of the gland.

Different patterns in the histology and autofluorescence of the Harderian glands of the Syrian Hamster, rat, mouse, Mongolian gerbil and guinea pig

The purpose of this study was to compare the natural fluorescence in the Harderian glands of the Syrian hamster, rat, mouse, Mongolian gerbil and guinea pig (both sexes). For each species, 10 animals (five males and five females) were used. Histological autofluorescence studies were performed using a fluorescence microscope (450-490 nm filter). Two different types of fluorescent cells were observed in both hamster (type AFI high intensity and type AFII, low fluorescence) and rat (type AFI, low fluorescence and type AFII, high fluorescence) Harderian glands. The fluorescence was basally located in all mice cells, whereas it was observed near the epithelial cell nuclei in the Mongolian gerbil (occupying two-thirds and one-third of the cells in males and females, respectively). A high intensity of fluorescence was present throughout the acinar cells in the guinea pig. The patterns of fluorescence identified exhibited a sexual dimorphism in all species studied. These results demonstrate that the Harderian glands of the animal species examined exhibit a variety of histological autofluorescence patterns.

The structure of the nasal chemosensory system in squamate reptiles. 2. Lubricatory capacity of the vomeronasal organ

The vomeronasal organ is a poorly understood accessory olfactory organ, present in many tetrapods. In mammals, amphibians and lepidosaurian reptiles, it is an encapsulated structure with a central, fluid-filled lumen. The morphology of the lubricatory system of the vomeronasal organ (the source of this fluid) varies among classes, being either intrinsic (mammalian and caecilian amphibian vomeronasal glands) or extrinsic (anuran and urodele nasal glands). In the few squamate reptiles thus far examined, there are no submucosal vomeronasal glands. In this study, we examined the vomeronasal organs of several species of Australian squamates using histological, histochemical and ultrastructural techniques, with the goal of determining the morphology of the lubricatory system in the vomeronasal organ. Histochemically, the fluid within the vomeronasal organ of all squamates is mucoserous, though it is uncertain whether mucous and serous constituents constitute separate components. The vomeronasal organ produces few secretory granules intrinsically, implying an extrinsic source for the luminal fluid. Of three possible candidates, the Harderian gland is the most likely extrinsic source of this secretion.

Morphology of the Harderian gland of the Gecko, Tarentola mauritanica

The Harderian gland of the gecko, Tarentola mauritanica, was studied at the histological, histochemical, and ultrastructural levels. It is a nonlobate compound acinar gland surrounded by a thin capsule of connective tissue. Numerous connective tissue-type mast cells, ultrastructurally similar to those described in other higher vertebrates, were identified in the interstitial tissue between the acini. Pyramidal or columnar-shaped secretory glandular cells were observed in the acini. In the glandular cells, two types of structures could be distinguished on the basis of their high or low electron density. Lipid droplets were found in the cytoplasm of the Harderian gland of both sexes. Histochemical tests showed that the Harderian gland of the gecko is a seromucous gland. The secretion is essentially merocrine, although an apocrine type of secretion is sometimes observed.

The Harderian gland of the Cheesman's gerbil (Gerbillus cheesmani ) of the Kuwaiti desert

The Harderian gland is a large orbital structure. Several functions have been ascribed to the gland such as lubrication of the eye, a source of pheromones, thermoregulartory lipids and photoprotective secretions and a part of the retinal-pineal axis. In the present study, the Harderian gland of the Cheesman's gerbil, Gerbillus cheesmani, is described for the first time. The gland is located around the posterior portion of the eyeball. The gland is compound tubular, surrounded by a thin connective tissue capsule. Only one secretory epithelial cell type was recognized, characterized by the presence of lipid vacuoles and cytoplasmic slashes in high numbers; the former being more concentrated towards the apical part while the latter being more concentrated towards the central and basal parts. Some of the cytoplasmic slashes contained electron dense filamentous structures. Similar structures were observed in the lipid vacuoles. Thus, a functional relationship between the cytoplasmic slashes and the lipid vacuoles is suggested. A unique structure was observed, termed dome-like cells, located between the epithelial cells and the basement membrane. These cells were characterized by the extensive presence of pleomorphic mitochondria and compact lamellae of granular endoplasmic reticulum (GER) in the form of finger prints. The gland was found to be actively secreting porphyrins as well as lipids. Cellular debris was also seen in the tubular lumina. Myoepithelial cells with their spindle shape and elongated nuclei were evident between the basement membrane and the secretory epithelium. Sparse interstitial tissue was observed in-between the gland tubules of both male and female gerbils. Macrophages, dendritic melanocytes and lymphocytes are the most represented cellular components of the interstitium. Further studies are required to investigate the function of the dome-like cells as well as the role of lymphocytes in the rodents Harderian gland.

The Harderian gland of the Dhub lizard Uromastyx microlepis of the Kuwaiti desert: an ultrastructural approach

Harderian glands exist in the orbits of most terrestrial vertebrates. The basic function of the gland is the lubrication of the eye. The present study was carried out to shed some light on the ultrastructure of the still enigmatic Harderian gland of the lizard Uromastyx microlepis, a common species in Kuwait and other Gulf areas. The Harderian gland of Uromastyx microlepis is well developed, relatively large in size and lingual in shape. The epithelial cells of the anterior part of the gland are characterized by the presence of membrane bound granules of almost homogeneous consistency. These secretory granules are gathered in compartments and separated by membranes and stacks of granular endoplasmic reticulum (GER). Most of the lumina were empty. Moderate amounts of GER, free ribosomes and pleiomorphic mitochondria were observed in the perinuclear area of the epithelial cells. The medial and caudal parts of the gland were rich in special secretory granules, GER, free ribosomes and pleiomorphic mitochondria. The anterior part of the gland could represent the future lacrimal gland of mammals. A network of myoepithelial cells was recognized around the gland tubules. While no melanocytes or lymphocytes were observed in the scarce interstitial tissue, macrophages, that might have an immune function in the gland, were observed.

Squamate Harderian gland: an overview

BACKGROUND

The Harderian gland is an orbital feature found in most terrestrial vertebrates. Although there have been several reports on the structure of the squamate Harderian gland, there has been little recent discussion as to its potential function. This article reviews both the recent morphological observations and their implications on the potential functions of the squamate Harderian gland.

METHODS

Literature on the gross structure, histochemistry, and ultrastructure of the squamate Harderian gland and associated structures was reviewed. These observations were then used to assess morphologically the likelihood of the proposed functions.

RESULTS

A high level of morphological variation was found in the squamate Harderian gland. Three functional hypotheses, including roles in orbital lubrication, digestion, and vomerolfaction, were considered. Both morphology of the squamate Harderian gland and the presence of alternate secretory sources suggest that it is unlikely to function in orbital lubrication. There is little evidence to suggest a function in digestion. Both the presence of the connecting lacrimal apparatus and the reduced intrinsic secretory capacity of the vomeronasal organ suggest that the Harderian gland may function in vomerolfaction.

CONCLUSIONS

The most likely role of the squamate Harderian gland seems to be in vomerolfaction. Morphological variations observed in the Harderian gland may mirror the different degrees and mechanisms of vomerolfaction. Further studies, including comparative morphological, experimental, and microchemical analyses, are required to test this hypothesis.

The harderian gland in autoimmune diabetes of the nonobese diabetic mouse

Infiltration of the nonobese diabetic (NOD) mouse's Harderian gland (HG) was studied in 1-30-week-old animals. A mononuclear cell invasion of this gland is first seen in 8-week-old female mice (i.e., at a slightly later age than that for the onset of infiltration of pancreatic islets). Infiltrating elements are mainly located at the hilus of the gland or at one or two foci (periacinar infiltration) within the parenchyma. In the latter case, a few elements infiltrate the fibrous connective tissue surrounding the acini (one or more) without damaging them. The most severe histopathological lesion was observed in 16-week-old animals; at this time infiltration ranges from a still focal lesion to complete acinar destruction of the gland. Ultrastructural observations confirm that in several cases acinar cells are destroyed and the HG parenchyma is substituted with infiltrating elements, fibroblasts, and connective tissue. HG infiltration is comparable to the pancreatic inflammatory infiltration; the two processes are very similar, though insulitis starts slightly earlier than HG infiltration. Furthermore, as for insulitis and diabetes incidence, HG infiltration affects NOD males less than females. Moreover, immunocytochemistry has shown that T lymphocytes are the prevalent infiltrating element both in pancreatic islets and HGs. Further studies are required to understand the reasons for autoimmune destruction of this gland.

Sexual dimorphism in the harderian gland of the Syrian hamster is controlled and maintained by hormones, despite seasonal fluctuations in hormone levels: functional implications

The Harderian gland of the Syrian hamster (Mesocricetus auratus) is unusual amongst rodents in the degree of dimorphism present. Other types of hamsters have Harderian glands which are apparently identical in male and female animals. Laboratory populations of Syrian hamsters are derived from very limited genetic stock, which makes one concerned lest they not be representative of wild populations; however, until wild stocks of M. auratus become available, we should assume that insights derived from studies of dimorphism in Syrian hamsters represent important considerations for the life of these animals. Two dimorphic features are the histology and the porphyrin content of the Harderian glands. About 95% of the lipid droplets in female glands are small (type 1), whereas only about 65% of those in males in type 1, with the other 35% being type 2 (large droplets). Five weeks of castration of males led to an increase in type 1 droplets to 90%. On the other hand, 2 weeks treatment of females with testosterone led to a reduction in type 1 droplets to about 82%. Short day photoperiods led to a large increase in type 2 droplets in both males and females (to 52% in males, 35% in females after 8 weeks). These results suggest that the lipid contained in type 2 droplets is important to hamsters of both sexes during the winter. Porphyrin concentrations are 100-1,000 times higher in females than males, and this is largely controlled by testosterone as orchidectomy leads to increased male levels and testosterone treatment leads to reduced female levels. However, a number of treatments which also lead to reduced testosterone levels do not lead to increased porphyrins and may, in fact, prevent the rise which would normally follow orchidectomy. One of these antiporphyrinogenic treatments is exposure to short day photoperiods. Thus, the sexual differences in porphyrin, levels in Syrian hamsters are maintained, despite seasonal fluctuations in hormone levels. This suggests that this dimorphism is important for the function of the gland.

The lymphoid substance of the chicken's harderian gland is organized in two histologically distinct compartments

Light and electron microscopical investigations revealed that the lymphoid structure of the chicken Harderian gland is organized in different histological frameworks. In the head the surface epithelium of the central canal can be classified as a lymphoepithelial tissue which covers the dense lymphoid substance. It consists of small and medium-sized lymphocytes, dendritic-like cells, and occasional macrophages. High endothelial venules are associated with intense lymphocyte migration and homing that gives circumstantial evidence for a T-dependent region, as found in a secondary lymphoid organ. The B-dependent germinal centers are also common structural units of the head region's lymphoid substance. The body of the gland is loaded with plasma cells of different maturation stages. They immigrate into the epithelium of the central canal and produce IgM and IgA. Only a few scattered IgG producing plasma cells can be found in the gland of Harder. This plasmocytic region accounts for the immunosurveillance on the conjunctiva and in the upper respiratory tract through antibody production against bacterial or parasitic infections. In both the head and body regions of the gland, anti-B-L (anti-Ia) antibody recognized scattered elongated cells which might represent dendritic cells. The immunological relationship between the two histologically different parts of the Harderian gland is unknown, but we speculate that the dense lymphoid tissue with high endothelial venule receives the blood-borne, immunologically mature, but uncommitted B cells. By the influence of local antigen stimulus, these B cells transform to plasma cells which gradually appear in the body of the gland. The lymphoid structures of the head and the body fulfill the function of secondary and tertiary lymphoid organs, respectively.

Comparative histological and ultrastructural studies of the Harderian gland of rodents

The Harderian glands of six rodents (the Wistar rat, the gerbils Psammomys obesus, Gerbillus gerbillus, Meriones crassus, and Meriones lybicus, and the gundi, Ctenodactylus vali) were investigated by means of light and transmission electron microscopy. In rodents, the Harderian gland consists of branching tubules, lined by a single layer of epithelial cells and possessing myoepithelial cells within their basal lamina. The Harderian gland contains porphyrins, stored as intraluminal masses. The glandular epithelium presents a single cell type (I) in Psammomys obesus, two cell types (I, II) in Ctenodactylus vali and the Wistar rat, and three cells types (I, II, III) in Gerbillus gerbillus, M. crassus, and M. lybicus. The type I and II cells are columnar, characterized by lipid vacuoles and well-developed profiles of the smooth endoplasmic reticulum. In Meriones and Gerbillus, the type I cell can be distinguished from the type II cell by cytoplasmic clefts. In Ctenodactylus vali, the type I cell is characterized by cytoplasmic rod-shaped crystalloid structures. These structures are also present in the sole cell type of Psammomys obesus. In the Wistar rat, the two cell types are distinguished by the number and the size of the lipid vacuoles. The content of the vacuole is released primarily by exocytosis, but holocrine and apocrine secretion was also noted. The type III cell is pyramidal, characterized by numerous mitochondria, and has an extraordinarily well-developed granular endoplasmic reticulum organized in concentric lamellae in Gerbillus gerbillus. The single excretory duct begins at the hilus. Mast cells, plasma cells, macrophages, fenestrated capillaries, and unmyelinated nerve endings with clear or dense-cored vesicles are present in the connective tissue. Melanocytes are predominant in the gland interstices of Psammomys obesus. The gland is surrounded by a thin connective tissue capsule, covered with the endothelium of the orbital venous sinus.

Harderian gland function of Indian tropical palm squirrel, Funambulus pennanti

The Harderian gland (HG) of the Indian palm squirrel, F. pennanti, is composed of acini of a single type of simple columnar cells with uniform-sized lipid droplets and porphyrin (P) in the lumen. Morphologically it presented no sexual dimorphism except for the HG weight which revealed that males are acyclic. Circadian study of Harderian gland porphyrin (HG-P), plasma melatonin, (aMT) and testosterone showed a characteristic two peak cyclicity. In females, HG, HG-P and pineal gland weight, and plasma aMT presented an annual inverse relation. Circadian study in females only exhibited a two peak cyclicity of HG-P, plasma aMT, and estradiol. Pinealectomy (PX) and harderianectomy (HGX) revealed increased HG weight and gonad weight in males. Gonadectomy (GX), on the other hand, had no effect on HG in males. PX in females brought almost a similar effect as noted for males, but HGX had no effect on ovarian weight. GX, interestingly, reduced HG weight and P concentration. Daily evening (4:30-5:00) administration of aMT and 5-methoxytryptamine (5-MT) in males reduced HG weight and HG-P content only in aMT-treated male and female squirrels, thereby suggesting that HG-P is perhaps negatively regulated by pineal gland production and vice versa. Injections of gonadotropin and steroids during the sexually inactive phase showed no effect on HG-P content in both sexes. Short photoperiod (SP) in both sexes stimulated pineal weight without affecting HG weight, while long photoperiod (LP) increased HG-P but reduced the plasma aMT level again without affecting HG-P content. Continuous dark (CD) decreased HG-P, whereas continuous light was ineffective without effecting HG weight in both sexes. In conclusion, HG in this rodent is functionally an important gland having diverse physiological effect in both sexes sometimes with a very clear HG-pineal-gonad relationship.

Quantitative histomorphology of the blind mole rat harderian gland

Anatomical, histological and morphometric studies have been performed on the harderian gland and its surroundings in the blind mole rat (Spalax ehrenbergi). The gland is tubuloalveolar with no true duct system. All ducts within the gland are formed by a single epithelial cell type and drain into a wide secretory duct. This opens into the conjunctival sac which serves as a reservoir for harderian secretions. Drainage from the conjunctival sac follows 2 possible routes: one through the nasolacrimal duct to the external nasal cavity, the other through a unique excretory duct that emerges from the anteromedial part of the conjunctival sac and runs through the dermis to the skin, opening at the base of a hair follicle. The function of this newly described duct is discussed. Morphometric studies revealed that the lumen volume fraction in the female, slightly smaller than that of the male during the summer, becomes significantly greater during the winter breeding season. The dimorphism and seasonal variations found in the gland acini suggests that the gland may be implicated in pheromone production.

Cell biology of the harderian gland

The harderian gland is an orbital gland of the majority of land vertebrates. It is the only orbital gland in anuran amphibians since the lacrimal gland develops later during phylogenesis in some reptilian species. Perhaps because it is not found in man, little interest was paid to this gland until about four decades ago. In recent years, however, the scientific community has shown new interest in analyzing the ontogenetic and morphofunctional aspects of the harderian gland, particularly in rodents, which are the preferred experimental model for physiologists and pathologists. One of the main characteristics of the gland is the extreme variety not only in its morphology, but also in its biochemical properties. This most likely reflects the versatility of functions related to different adaptations of the species considered. The complexity of the harderian gland is further shown in its control by many exogenous and endogenous factors, which vary from species to species. The information gained so far points to the following functions for the gland: (1) lubrication of the eye and nictitating membrane, (2) a site of immune response, particularly in birds, (3) a source of pheromones, (4) a source of saliva in some chelonians, (5) osmoregulation in some reptiles, (6) photoreception in rodents, (7) thermoregulation in some rodents, and (8) a source of growth factors.

Morphological investigations of the glandulae profundae plicae semilunares conjuctivae in the domestic swine (Sus scrofa domesticus) and the wild hog (Sus scrofa ferus)

Samples of glandulae profundae plicae semilunares (Harderian glands) from five domestic swine and five wild hogs were used for this research. The gland samples were fixed in Bouin solution and mounted in paraffin. The paraffin slices were stained with haematoxylin and eosin, according to the periodic-acid-Schiff (PAS) method, with alcian blue (pH 2.5), with toluidine blue (pH 4.0), and applying a combination of staining with alcian blue (pH 2.5) and the PAS method. In domestic swine and wild hogs, these glands are tubular-alveolar with wide glandular lumina. A great deal of acid mucopolysaccharides and PAS-positive substances were noted within swines' glandular cells, while, in wild hogs, PAS-positive substances were not frequent, acid mucopolysaccharides being noted in only a few glandular-acini cells. The appearance of the metachromatic phenomenon was not noted either in domestic swine or in wild hogs. In domestic swine, the level of acid mucopolysaccharides is probably due either to the housing method or to the influence of the alkaline substances that may appear on an eye's mucous conjunctive membrane during intensive breeding, such that the Harderian glands protect the mucous membrane by extracting acid mucopolysaccharides.

The harderian gland: a tercentennial review

The harderian gland was first described in 1694 by Johann Jacob Harder (1656-1711). It occurs in most terrestrial vertebrates and is located within the orbit where, in some species, it is the largest structure. It may be compound tubular or compound tubuloalveolar, and its secretory duct is usually morphologically distinct only after leaving the substance of the gland to open on the surface of the nictitating membrane. The tubules of the gland are formed of a single layer of columnar epithelial cells surrounded by myoepithelial cells. The chief product(s) of the gland varies between different groups of vertebrates, and epithelial cells possess granules or vacuoles whose contents may be mucous, serous or lipid. In rodents, the gland synthesises lipids, porphyrins and indoles. In the case of lipid vacuoles, the gland is unusual in releasing these by an exocytotic mechanism. It is unclear whether the gland can act both as an exocrine and endocrine organ. There is control of gland structure and synthesis through a variety of humoral agents, including gonadal, thyroid and pituitary hormones; in addition there is a rich autonomic innervation and many neuropeptides have been identified. The proposed functions of the gland are remarkably diverse and include the gland being (1) a source of 'saliva', (2) a site of immune response, (3) a photoprotective organ, (4) part of a retinal-pineal axis, (5) a source of pheromones, (6) a source of thermoregulatory lipids, (7) a site of osmoregulation, and (8) a source of growth factors. The gland is discussed in terms of its embryology and phylogeny, and in relation to ecological variables. Several goals of future research are identified.

The harderian gland and its excretory duct in the Wistar rat. A histological and ultrastructural study

The harderian gland in the Wistar rat consists of tubules with wide lumina lined by a single layer of columnar epithelial cells possessing myoepithelial cells within their basal laminae. The gland contains porphyrin pigment which is stored as solid intraluminal deposits. The glandular epithelium possesses 2 cell types, termed A and B. These are characterised by an extraordinarily well-developed tubular smooth endoplasmic reticulum and numerous lipid vacuoles. Type A cells can be distinguished from type B by the number, size and content of the lipid vacuoles. Type A cells are more numerous. They contain large lipid vacuoles with dense ribbon-like material identical in form to the material in the luminal masses of porphyrin pigment, whereas those of type B cells are small with crescentic dense lamellar material. The content of the vacuoles is essentially released by exocytosis, but holocrine secretion also occurs. The lipids and the ribbon-like material represent the bulk of the intraluminal secretory product. The secretion of porphyrins seems to be associated with type A cells. The single excretory duct is lined by a stratified epithelium. The duct epithelium comprises serous cell types, designated C1 and C2 and scarce mucus-secreting cells. Type C1 cells are characterised by numerous dense granules, whereas type C2 cells are distinguished by lysosomal structures. Fibroblasts, macrophages, mast cells, plasma cells, fenestrated capillaries and unmyelinated axons are frequently observed in the connective tissue. The gland is surrounded by a collagenous capsule and an outer layer of endothelial cells of the orbital venous sinus.

Effects of ovariectomy and ageing on the structure and ultrastructure of the female Syrian hamster Harderian gland: a stereological analysis

The effects of ovariectomy and ageing on the structure and ultrastructure of the Syrian hamster Harderian gland were investigated by techniques of quantitative stereology. Tissues were obtained from intact 6-month-old, sham-operated 6-month-old, ovariectomized 6-month-old, intact 18-month-old and ovariectomized 18-month-old female hamsters. Glands from both ovariectomized and aged hamsters showed comparable qualitative and quantitative characteristics. They showed histological alterations that included thinning of the tubule walls, lowering of luminal porphyrins, invasion of lumina by neutrophils and the occurrence of interstitial porphyrins. Glands from both ovariectomized and aged hamsters showed statistically significant differences from control animals in relation to numerical density and cellular size. Finally, quantitative studies with the electron microscope revealed significant decreases in the volume densities of the cytoplasmic organelles concerned with secretion. These results support the hypotheses that the secretory activity of the female hamster Harderian gland is influenced, directly or indirectly, by ovarian hormones, and that many of the age-related modifications of the Harderian gland reflect alterations in ovarian function.

[The mammalian Harderian gland (its structural characteristics)]

The Harderian gland is located in the eye orbit and is part of orbital glands complex. The gland is present in almost all vertebrates, i.e., amphibians (except the completely aquatic ones), reptiles, birds, mammals, but not in fish. Among mammals it was described in the Marsupialia and most Eutheria. This review includes data on the Harderian gland structure and cytology of its secretory epithelium. Location of the gland in the eye orbit, its structure and relative size vary in different mammals. Ultrastructural characteristics of its epithelial cells also vary. There are structural differences not only between protein-, mucus- and lipid-synthesizing cells, but within each of these groups too. The chemical nature of the Harderian gland secretory product is species specific.

The Harderian gland of the Djungarian hamster (Phodopus sungorus): light- and electron-microscopical investigations

The Harderian gland of the Djungarian hamster Phodopus sungorus was investigated by light and electron microscopy in adult animals of both sexes, held under either long or short photoperiods. These glands have a tubulo-alveolar structure. Epithelial cells were seen as small cylindric cells with a large, round nucleus located basally, many small vacuoles distributed throughout the cytoplasm (type I cells) or as rather broad cells with larger vacuoles (type II cells). The ratio of both cell types differed from 1:1 to 2:1 (type I:type II), regardless of the animal's sex. In the electron microscope, abundant smooth endoplasmic reticulum of the vesicular type and rod-like or oval-shaped mitochondria of the crista type were very numerous; while Golgi complexes were rarely seen. 'Membranous bodies' were about nine times higher in amount in type II cells and were further augmented fourfold, in number, in glands of female animals. The few bundles of poly-tubular structures that were observed, were predominantly in type I cells. Myoepithelial cells were linked to the basal part of acinar cells by interdigitations. Many microvilli were observed at the apical portion of cellular membranes. Acinar cells predominantly showed signs of merocrine secretion, although apocrine secretion was seen in some cases. Under epifluorescence, red porphyrin fluorescence was seen predominantly in type I cells, where it is mainly found apically. The comparison of animals held under either long or short photoperiods did not reveal any differences in Harderian gland structure.

The Harderian gland of the rodent Octodon degus: a structural and ultrastructural study

Harderian glands from male and female Octodon degus were examined by light and transmission electron microscopy. Two types of secretory units, designated as type I and type II, were observed. Type I secretory units comprise three types of epithelial cells: Cells packed with numerous lipid droplets (Type a), cells with few lipid droplets (Type b), and cells with numerous mitochondria and a very well developed Golgi complex (Type c). Type II secretory units were found exclusively in female Octodon degus and comprised a type of secretory cells which contained numerous basophilic granules in their apical cytoplasm. In addition, in female Octodon degus, clusters of lymphocyte-like cells and plasmatic cells were also observed. The vascularization of the gland appeared very well developed. The most unique feature of the blood supply was the existence of large sinusoidal vessels extremely variable in shape. In the medullar region, the sinsoidal wall adapts its contour to that of the tubuloalveolar surface. Unmyelinated and myelinated nerve fibers were found in the connective stroma of the gland.

Morphological observations on the harderian gland of the North American opossum (Didelphis virginiana)

The Harderian gland of the North American opossum (Didelphis virginiana) is large and well developed, despite the absence of a nictitating membrane in the adult of this species. The elongate glands are surrounded by a delicate connective tissue capsule from which thin septae extend, subdividing the gland into numerous lobules. The secretory units of the opossum Harderian gland are drained by a well defined but not extensive intralobular and interlobular duct system. Most of the secretory end pieces consist of tubulo-alveolar units with widely dilated lumina filled with secretory product. Numerous intact lipid vesicles suspended within an amorphous material constitute the luminal contents. Cells lining the tubulo-alveolar secretory end-pieces are usually columnar in shape, and characterized by numerous lipid-containing secretory vesicles and aggregations of poly-tubular complexes 40-60 nm in diameter. In addition, these cells contain numerous large irregularly shaped mitochondria, whose matrix is of considerable electron density. Intralobular and interlobular ducts are lined by electron-lucent epithelial cells that lack both the lipid-containing vesicles and the large mitochondria, although typical smaller mitochondria are found scattered within the cytoplasm. Both secretory end-pieces and ductal elements are invested by an abundance of myoepithelial cells. A second, smaller serous type of secretory unit may occur near the centre of some Harderian gland lobules. In these units secretory tubules and acini are compactly arranged surrounding a narrow lumen. Serous cells are pyramidal in shape and the cytoplasm is characterized by numerous electron-dense secretory granules and scattered profiles of rough endoplasmic reticulum.(ABSTRACT TRUNCATED AT 250 WORDS)

The orbital glands of the chelonians Pseudemys scripta and Testudo graeca: comparative histological, histochemical and ultrastructural investigations

The orbital glands of the chelonians Pseudemys scripta and Testudo graeca were investigated at the histological, histochemical and ultrastructural levels. Four acinar cell types were seen in the harderian gland of P. scripta on the basis of histochemical reactions and ultrastructure. Secretory granules were of 2 types, one showing moderate electron density with an electronlucent core, the other being smaller and more osmiophilic with an electron-dense core. In the harderian gland of T. graeca only 2 glandular cell types were found; one type contained secretory granules with a dense core surrounded by a wide zone of lower density. Acinar cells of the anterior lacrimal gland in both species were of 2 types, one being of mucous type. In the harderian gland and in the lacrimal gland of both species, one cell type appeared not to be involved in the secretion of organic material. These cells contained numerous tightly packed mitochondria among which were abundant clumps of glycogen; the cell membrane was specialised at both edges. This cell type was similar ultrastructurally to the 'salt cells' described in the salt-secreting glands of various marine vertebrates, i.e. of the cells involved in transport processes. These combined histological, histochemical and ultrastructural studies have allowed us to distinguish orbital glands. In the past, the harderian and lacrimal glands in chelonians have often been mistaken for one another.

Chronic administration of melatonin induces changes in porphyrins and in the histology of male and female hamster harderian gland: interrelation with the gonadal status

In this paper, we have investigated the influence of melatonin on the histology and porphyrin content of the Syrian hamster Harderian glands. Daily afternoon injections of 25 micrograms of melatonin to female hamsters for 12 weeks resulted in the discontinuity of estrous cyclicity, a marked decrease in the Harderian gland intraluminal area occupied by porphyrins, and in a significant rise in the number of Type II cells. A similar decrease in porphyrins was observed after 8 weeks of ovariectomy. However, if the melatonin injections were given for only 8 weeks (without inducing gonadal atrophy), no changes were observed in the area occupied by intraluminal porphyrins, suggesting that the effects of melatonin in female Syrian hamsters might be associated with the subsequent gonadal atrophy. Castration of male hamsters induced a significant increase in porphyrins and a clear drop in the number of Type II cells. These changes were totally prevented when melatonin was administered daily from the day of castration. Our results suggest that melatonin, at least in male Syrian hamsters, plays a role in Harderian metabolism, acting directly on the Harderian secretory cells or indirectly through pituitary hormones.

Effect of carbamylcholine on Harderian gland morphology in rats

To determine the effect of cholinergic secretagogue on the Harderian gland of rats, several light- and electron-microscopic parameters were morphometrically assessed at different time intervals after carbamylcholine injection. In controls, two types of glandular cells (type A cells having 40-55 large vacuoles per cell profile and type B cells containing 30-38 smaller vacuoles per cell profile) and myoepithelial cells were recognized. At 5 min after injection of carbamylcholine, when rats secreted "bloody tears", many alveoli showing narrower lumina and exocytotic figures in both types of cells were observed. Some vacuoles, which were covered by thin cytoplasmic sheets, protruded into the alveolar lumina. However, there was no evidence of apocrine or holocrine secretion. At 30 min and 120 min after injection, most of the alveolar lumina were dilated, and a pronounced decrease in the number of vacuoles in the glandular cells was observed. At 300 min after injection, the secretory vacuoles in both cell types reaccumulated. Transitional forms between the two cell types were not observed. The two types of Harderian gland cells can therefore be considered independent populations rather than different secretory stages of the same cell. It appears that the secretory process of the Harderian gland of rat is affected by cholinergic stimulation of the two types of glandular cells and of myoepithelial cells.

Further studies on the regulation of the Harderian glands of golden hamsters by the thyroid gland

Long-term increased or decreased circulating levels of thyroid hormones significantly modify porphyrin concentrations and morphology in the Harderian glands of male and female hamsters. Administration of T3 reduced porphyrin concentrations in females; this treatment or decreasing thyroid hormone levels with KClO4 suppressed the post-castration rise of porphyrins in males. Hypophysectomy led to increased porphyrins in the Harderian glands of males; this rise was suppressed in hypophysectomized males by T3 or T4. In females, hypophysectomy reduced porphyrins which were further reduced by daily administration of T3 or T4. These modifications in the normal females were identical in castrated males. Mitotic activity in the Harderian glands of females was stimulated by KClO4 and by hypophysectomy with or without exogenous T3. In males, castration increased mitotic activity which was suppressed by T3 and exacerbated by KClO4. Increased mitotic activity seemingly follows loss of tissue mass. The data show that thyroid hormones act directly on the Harderian glands rather than indirectly through modification of TSH synthesis/release. Female "type" glands in males are a consequence of loss of gonadal androgens by castration, or by suppression or loss of thyroid hormones by hypophysectomy or by treatment with KClO4. However, male "type" glands in females are the result of androgen treatment, and/or increased levels of thyroid hormones via reduced ambient temperatures or of photic input. We conclude that regulation of the Harderian gland appears to be different in the two sexes.

Harderian gland and the lacrimal gland of the lizard Podarcis s. sicula: histology, histochemistry, and ultrastructure

Histology, histochemistry, and ultrastructure of the Harderian gland and lacrimal gland of the lizard Podarcis s. sicula were investigated. The Harderian gland, located at the medial corner of the orbit, can be divided into three zones showing different tinctorial features either with Mallory or hematoxylineosin stains. The glandular cells of the acinar medial zone secrete predominantly acidic sulphated mucosubstances. The acinar cells of the intermediate zone contain secretory granules that show a weak reaction to the histochemical tests for mucosubstances. The lateral zone has a tubulo-acinar type of structure and tests strongly for proteins, whereas Alcian-PAS staining is very weak. The lacrimal gland is smaller than the Harderian gland and lies in the region of the posterior commissure of the eyelids. it shows the same histological and histochemical characteristics of the medial zone of the Harderian gland, i.e., it is mucous secreting. At the ultrastructural level the zonation is well defined, especially when the secretory granules are examined. Granules of the mucoid type are found in the lacrimal gland and the medial zone of the Harderian gland. The secretory granules of the lateral part of the Harderian gland show a composite structure never described before. Therefore, they have been called "special secretory granules." Each of these granules is composed of three sharply separated components. It is not known whether the three components correspond to different secretions. Histochemical tests suggest that they are of the serous type. Both mucous and serous granules are secreted by the same glandular cells of the intermediate zone of the Harderian gland. The two types of granules usually occupy different cell compartments. The mechanism of secretion appears either merocrine or apocrine in both the Harderian gland and the lacrimal gland.

Influence of light and temperature on the secretory activity of the Harderian gland of the green frog, Rana esculenta

1. The secretory activity of the Harderian gland in Rana esculenta varies during the year, reaching its highest activity during the hottest period (July-August). Therefore, secretion may be modulated by temperature and/or photoperiod. 2. Adult males and females were placed under several combinations of light and temperature in two different periods of the year (February and July) in order to elucidate their respective roles, if any, on the stimulation of secretion. 3. Under experimental conditions, high temperature (24 degrees C), irrespective of the photoperiod selected, stimulates secretion shown both at histological and histochemical levels. 4. Low temperature (8 degrees C) impairs secretory activity, again independently of the photoperiod selected. 5. This data suggests that the secretion of the Harderian gland in Rana esculenta is modulated mainly by temperature.

Major ocular glands (harderian gland and lacrimal gland) of the musk shrew (Suncus murinus) with a review on the comparative anatomy and histology of the mammalian lacrimal glands

The Harderian gland of the musk shrew Suncus murinus is elongated anteroposteriorly from in front of the eye to behind the ear. The gland is divided into two portions: an anterior portion (A portion) and a posterior portion (P portion). The single secretory duct of the gland emerges from the anterior end of the P portion, receives several secretory ducts of the A portion during the course along it, runs around the ventral aspect of the eyeball, and finally opens into the anterior corner of conjunctival sacs. The two portions of the gland show a fundamentally similar histological structure, having a poorly developed intraglandular duct system and wide tubular alveoli. The quantity of lipid vacuoles and stromal connective tissue in the A portion is greater than in the P portion. The lipid vacuoles in both portions are surrounded by unit membranes, but their contents appear different. The lacrimal gland of the musk shrew is located along the ventral side of the P portion of the Harderian gland. The lacrimal duct emerges from its anterior end, runs around the ventral and anterior aspects of the ear, crosses the A portion of the Harderian gland, and finally opens at the posterior corner of conjunctival sacs. The lobules of the lacrimal gland comprise a branched duct system and terminal acini with two types of secretory cells: 1) acidic cells positive both for the periodic acid-Schiff reaction (PAS) and for Alcian blue (AB) and 2) neutral cells positive for PAS and negative for AB. Both cell types tend to make separate acini, but when present in the same acinus, the acidic cells occupy relatively peripheral positions in the acinus. Both cell types lack intercellular canaliculi. On the basis of the present study as well as previous descriptions in the literature, the author suggests that the mammalian lacrimal glands can be divided into two sets: 1) a Glandula lacrimalis superior with multiple secretory ducts associated with the upper eyelid and 2) a Glandula lacrimalis inferior with a single secretory duct opening into the lateral corner of the conjunctival sacs. These glands have a fundamentally similar histological structure; but in the rabbit, which possesses both sets of lacrimal glands, they are different. On the other hand, the secretory cells of lacrimal glands generally have no intercellular secretory canaliculi, which are characteristically present between the serous secretory cells of the salivary glands.

Harderian glands of golden hamsters: morphological and biochemical responses to thyroid hormones

Manipulation of circulating levels of thyroid hormones modifies Harderian gland structure and porphyrin concentrations in male and female golden hamsters. Specifically, thyroxine (T4) and triiodothyronine (T3) induce the morphological conversion of the Harderian glands of females to approximate those of the male. Further, porphyrin concentrations are markedly decreased by this treatment. This effect occurs in ovariectomized animals as well, indicating that the gonads are not involved. Suppression of thyroid function by potassium perchlorate (KClO4) drastically reduces Harderian gland weight in both males and females. However, KClO4 decreases porphyrin levels in the Harderian glands of females and increases it in the male. Concurrently, KClO4 also induces a morphological conversion of the Harderian glands of males to the female type. This effect is evident in photoperiods of either 14:10 (h) or 8:16 (h).

The prevention of porphyrin loss from tissues during routine histological processing: quantitative studies on the Harderian gland

The rodent Harderian gland is an important site of porphyrin biosynthesis and storage. Porphyrins are visible at the light and electron microscope level as large intraluminal accretions, as large interstitial accretions surrounded by foreign body giant cells, or as small interstitial deposits within free macrophages. Since porphyrins are soluble in a wide range of solvents, it is important to employ histological routines which minimize porphyrin loss during processing in addition to giving good tissue preservation. In this quantitative investigation, these requirements were optimally achieved with fixation in 3% buffered glutaraldehyde and the use of amyl acetate as a clearing agent.

Quantitative studies on the effects of hormones on structure and porphyrin biosynthesis in the harderian gland of the female golden hamster. II. The time course of changes after ovariectomy

The Harderian gland of the golden hamster is an important model of porphyrin biosynthesis. In the female, ovariectomy leads to changes in porphyrin production and gland structure. The present study demonstrates that these changes are progressive and independent of age and environmental factors which may have similar effects. Porphyrinogenic enzyme activity decreases with time after ovariectomy while tubule wall degeneration and neutrophilic infiltration increase. Tubule degeneration leads in turn to porphyrin stores (normally intraluminal) occurring increasingly in the interstitial tissue of the gland, either as large accretions surrounded by foreign body giant cells or as small deposits inside individual free macrophages. Between 20-30 weeks after ovariectomy, the frequency of mitotic figures begins to increase accompanied by a transient rise in porphyrinogenic enzyme activity. Mast cell numbers (both in the gland and its capsule) increase markedly with time after ovariectomy.

The harderian gland: its tumors and its relevance to humans

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Harderian gland: regulation of sexual "type" by gonads and pineal gland

The sexual dimorphism of the Harderian glands of golden hamsters is regulated by a complex interaction of the gonads and pineal gland. Ovariectomy was shown to prevent the conversion to male-type gland which normally follows blinding. Testosterone administration in combination with blinding and ovariectomy promoted the male type. Ovariectomy after 8 wk of blinding was ineffective in reversing the effects of blinding on the Harderian glands, but ovariectomy and pinealectomy caused complete reconversion to the female type. To our knowledge, this is the first report to demonstrate an influence of the ovaries on the Harderian gland of the hamster. In males, administration of testosterone for 7 days after 8 wk of castration was shown to have little effect on the conversion to the female type which normally attends castration, whereas testosterone injection followed by a period of blinding completely reversed the effects of castration on the Harderian gland. These studies, along with previously published reports, strongly suggest that the male-type Harderian gland is expressed whenever significant androgen levels are present, or when the glands are exposed to androgen priming during or just prior to a period of blinding-induced pineal activation. The probable role of ovarian androgens in mediating conversion to the male-type gland is discussed.

The Harderian gland, its secretory duct and porphyrin content in the mongolian gerbil (Meriones unguiculatus)

The Harderian gland, its secretory duct and porphyrin content were examined in the mongolian gerbil (Meriones unguiculatus). The gland consisted of tubules lined by a single layer of epithelial cells and a myoepithelial network. The tubule cells were often binucleate and possessed lipid vacuoles in the apical half of the cell, a corona of granular endoplasmic reticulum surrounding the nucleus, and cytoplasmic 'slashes'. The latter are probably derived from dense membranous couplets and may be precursors of the lipid vacuoles. Holocrine and merocrine secretion was observed. Interstitial cells included plasma cells, mast cells and (predominantly) melanocytes which render the gland black. The gland was surrounded by a collagen capsule and an outer layer of highly attenuated (possibly endothelioid) cells. Within the gland, the secretory duct was lined by a single layer of normal tubule cells. Outside the gland, the duct enlarged to form an ampulla, from which clefts led off to deep crypts. The ampulla and clefts were lined by cells with small dense apical granules and stubby microvilli; some possessed lipid vacuoles. The crypts were lined by serous cells with active Golgi regions. At the duct opening, ampullary cells became squamous and goblet cells occurred. Geometric crystalloid deposits (with a layered structure of 7.6 nm periodicity) occurred at cleft-crypt junctions. Islets of extra-glandular ductal tissue were occasionally found within the gland. Porphyrins were detectable both by chemical assay and fluorescence microscopy. There was a trend for female glands to have a higher content than males. Solid intraluminal accretions of porphyrin and/or lipid were present.