A histological study of the Harderian gland of Mongolian gerbils, Meriones meridianus

Structural study and expression of the androgen receptors during the reproductive cycle in the Harderian gland of the male Meriones libycus

The goal of this study was to evaluate for the first time the expression of the androgen receptors (AR) in Harderian glands (HG) of the male Meriones lybicus in relation to the reproductive cycle. Six male Harderian glands of the resting period and 6 of the breeding period were collected. The animals were trapped in the desert of Béni Abbès (Algeria). The morphology of the Harderian glands was studied by light microscopy and morphometry, whereas the expression of the androgen receptors was assessed and quantified based on immunohistochemistry techniques. We have shown that the Harderian glands of Meriones libycus are tubuloalveolar glands with wide lumen. The glandular epithelium is composed of two types of cells (types I and II) in the resting season and three types of cells (types I, II and III) in the breeding season. These three types of cells differ in size and shape. Type-I cells have a prismatic shape, an acidophilic cytoplasm, and small lipidic vacuoles, whereas type-II ones are pyramidal in shape, with basophilic cytoplasm. Type-III cells resemble those of type I, and so they are prismatic in shape and have an acidophilic cytoplasm with larger lipidic vacuoles. The immunoreactivity of type-I and type-III cells was mainly cytoplasmic and the intensity of the immunostaining was significantly higher during the breeding season. Among other functions, the Harderian gland seems to be involved in the production of pheromones under the effect of androgens.

Comparative study of phototoxicity of protoporphyrin IX synthetic and extracted from ssp Rattus novergicus albinus rats toward murine melanoma cells

Protoporphyrin IX (PpIX) is a precursor of heme synthesis and is known to be an active photosensitizer and precursor of photosensitizers applied in photodynamic therapy (PDT) and photodynamic diagnostics (PDD). On irradiation with visible light, PpIX undergoes phototransformation, producing photoproducts which may also be phototoxic and increase its efficacy. The mechanism of PpIX phototransformation depends on environmental characteristics and can be different in vitro and in vivo. In this paper, we present a comparative study of the photoactivity of synthetic PpIX and PpIX extracted from the Harderian gland of ssp Rattus novergicus albinus rats, along with their photoproducts toward murine B16F-10 melanoma cells. It was observed that when irradiated with visible light the endogenous PpIX demonstrates photocytotoxicity ten times higher than the synthetic PpIX. The photoproduct of endogenous PpIX also possesses phototoxicity, though slightly lower than that of PpIX itself. The rate of cell internalization for both endogenous PpIX and its photoproduct was eightfold greater than that obtained for the synthetic porphyrin. This difference might result from a complexation of the native PpIX with some amphiphilic compounds during its synthesis within the Harderian glands, which facilitates the cell uptake of PpIX. Fluorescence microscopy images show that both endogenous and synthetic porphyrins are localized after uptake predominantly in the mitochondrial region of cells.

Apocrine secretion: New insights into an old phenomenon

BACKGROUND

While apocrine secretion was among the earliest secretory mechanisms to be identified, its underlying basis remains poorly understood.

SCOPE OF REVIEW

This review reappraises our understanding of apocrine secretion using insights about apocrine secretion from the salivary glands of Drosophila, in which molecular genetic analyses have provided a glimmer of hope for elucidating the mechanistic aspects of this fundamental process.

MAJOR CONCLUSIONS

In contrast to the well-defined process of exocytosis, apocrine secretion is non-vesicular transport and secretory pathway that entails the loss of part of the cytoplasm. It often involves apical protrusions and generates cytoplasmic fragments inside a secretory lumen. In its most intense phase this process is accompanied by the release of large fragments of cellular structures and entire organelles that include mitochondria, Golgi, and portions of the endoplasmic reticulum, among others. Proteomic analyses revealed that the secretion is composed of hundreds to thousands of membranous, cytoskeletal, microsomal, mitochondrial, ribosomal, and even nuclear as well as nucleolar proteins. Strikingly, although many nuclear proteins are released, the nuclear deoxyribonucleic acid itself remains intact. In spite of this complexity, it appears that several protein components of apocrine secretion are identical, regardless of the location of the apocrine gland.

GENERAL SIGNIFICANCE

This type of secretion appears to be common to many, if not all, barrier epithelial tissues including skin derivatives and the epididymis, and is implicated also in lung/bronchi and intestinal epithelium. Apocrine secretion is a mechanism that provides the en masse delivery of a very complex proteinaceous mixture from polarized epithelial tissues to allow for communication at exterior interfaces.

Structure of the secretory cells of male and female adult guinea pigs Harderian gland

The main objective of this study was to investigate the structure of the Harderian gland (HG) in male and female guinea pigs. A total number of sixteen animals of 4 months age were divided according to sex into two groups; eight animals each. Unfixed glands were weighed and their length and width were measured. Specimens from fixed glands were processed and examined using light, transmission electron microscopy and immunohistochemistry for the detection of the presence of chromogranin A (CgA). The gland consisted of a well-developed duct system which included both intra and extra parenchymal ducts and secretory end pieces lined by many types of cells of variable morphological features and modes of secretion. However, the holocrine mode of secretion was rare as mitotic figures were occasionally present. The interstitial cells included fibroblasts and immune cells (mast cells, lymphocyte, plasma cells and macrophages). The secretion produced by the gland included lipid, protein, neutral mucin and CgA which may be a newly identified constituent of biologically potent proteins stored in the cells of the guinea pig HG. Neutral mucin and CgA may function in photoprotection. The gland revealed sexual dimorphism in mast cells and blood capillaries number and chromogranin secretory activity.

Light and electron microscopic studies of the Gerbillus tarabuli (Thomas, 1902) Harderian gland

The purpose of this investigation was to study the morphological aspects of the Harderian gland in Gerbillus tarabuli. Tissues were obtained from both male and female adult Gerbillus tarabuli and processed for light and electron microscopy. The Harderian gland in gerbil is large and well developed, covered by a thin capsule, from which thin septae extend, subdividing the gland into lobes and lobules. The endpieces of the gland are tubuloalveolar, which produce a secretion of lipid character. The glandular epithelium is pseudostratified with two types of secretory cells, the type C cells are columnar in shape with large lipid vacuoles, and type P cells pyramidal and serous, they are basally located with no luminal aspect. The epithelium possesses well-developed myoepithelial cells. The wide lumina are filled with lipid vacuoles, cellular debris, and porphyrins. The Harderian gland of the gerbil has no morphologically distinct duct system; a single extraglandular excretory duct is detected. Electron microscopic examination revealed that type C cells contain large electron-light lipid vacuoles, a well and extensive reticulum endoplasmic and a large number of mitochondria. The pyramidal cells are characterized by a small number of PAS-positive granules at the basal region; these cells exhibit one or two round nuclei, many electron-dense granules, crystalloid bodies, abundant mitochondria and many ribosomes in their cytoplasm. The three mechanism of secretion are seen in the Harderian gland of Gerbillus tarabuli. In its overall characteristics, the Harderian gland of Gerbillus tarabuli conforms to the general pattern observed in rodents. However, further research will be needed to correlate the presence of cytoplasmic slashes, crystalloids bodies and glycoproteins in epithelial cells with the biology of these animals and to their functional significance.

Investigations on the conjunctival goblet cells and the characteristics of the glands associated with the eye in chinchillas (Chinchilla Laniger)

OBJECTIVE

To investigate the density and distribution of conjunctival goblet cells (GC) and study the anatomy and microscopic characteristics of glands associated with the eye in chinchillas (Chinchilla Laniger).

PROCEDURE

12 chinchillas were included in the study. Conjunctiva (divided into four regions), eyelids, and glands were embedded in paraffin wax, sectioned, stained, and analyzed.

RESULTS

Highest GC densities were found in the palpebral region of the nasal and temporal conjunctiva of both eyelids (GC index: 25.1-18.2%), and lowest densities, in the bulbar and marginal region of the nasal and temporal conjunctiva of both eyelids (GC index: 1.5-0.0%). Meibomian glands extend along the entire length of both eyelids, and the whole glandular complex broadens toward the temporal canthus. This is macroscopically visible through the conjunctiva. The openings of the Meibomian glands are macroscopically not discernible. The light pink, smooth, and crescent-shaped lacrimal gland lies next to the aforementioned broadened part of the Meibomian glands in the temporal canthus. The whitish, 0.9-cm-long, smooth Harderian gland is firmly attached to the posterior part of the globe and extends nasally from the optic nerve to the equator. Furthermore, chinchillas possess two lacrimal puncta, situated on the inner conjunctival surface of both eyelids near the medial canthus. A pigmented lacrimal canaliculus originates from each punctum. The vestigial nictitating membrane is supported by a hyaline cartilage and is pigmented at its free margin.

CONCLUSIONS

Chinchillas possess a Harderian gland, a lacrimal gland, and Meibomian glands. The GC density in the nasal and temporal palpebral conjunctiva is higher than in guinea pigs.

Histomorphology of the Harderian gland in the Angora rabbit

This study was aimed to demonstrate the morphological and histochemical properties of the Harderian gland in the Angora rabbit. Ten healthy adult Angora rabbits obtained from private breeders constituted the material of the study. The Harderian gland, which is composed of the pink and white lobes, consists of cells that produce a secretion of lipid character. The pink lobe contained type I cells with large lipid vacuoles. Cells with small lipid vacuoles (type II) were found in the white lobe. Type III cells containing both large and small lipid vacuoles were not observed. While type I cells reacted strongly to staining with Oil red O, type II cells reacted weakly to this stain. The number of plasma cells was greater in the white lobe when compared to the pink lobe. The apical granules within the epithelial cells lining the intralobular and inter-lobular excretory ducts of the gland were positive for periodic acid-Schiff (PAS), periodic acid-Schiff/alcian blue (PAS/AB), alcian blue (AB) and performic acid/alcian blue (PA/AB). Electron microscopic examination revealed that type I cells contain large electron-light lipid vacuoles and an eccentric heterochromatic nucleus, due to the presence of these vacuoles. The cells, which were connected by tight junctions, possessed apically located microfolds. The nucleus of type II cells was situated basally and had an oval shape. Type II cells had apical microvilli-like cytoplasmic protrusions, longer than those of type I cells. Oval shaped myoepithelial cells were observed between the glandular epithelial cells and their basal lamina. The epithelium lining the excretory ducts of the gland contained two types of granules, which were dark and lightly coloured. Histochemical and ultrastructural examinations revealed no difference in the structure of the Harderian gland between female and male Angora rabbits.

Novel function of lipids as a pheromone from the Harderian gland of golden hamster

Sexual diversity of ADG in Harderian gland of golden hamster was demonstrated on TLC. Female ADG contained iso- and anteiso-branched acyl and alkyl components, but male ADG contained only straight chain ones, which suggested the hormonal control of the expression of acyl-CoA dehydrogenases in the catabolism of BCAA. Acyl-CoA dehydrogenases were not expressed in the absence of testosterone, and then isovaleryl-CoA, 2-methylbutyryl-CoA, and isobutyryl-CoA accumulated, and acted as primers for the synthesis of iso- and anteiso-branched fatty acids. The incorporation of [U-(14)C] leucine into lipids was monitored by TLC. The cholesterol fraction was labeled in males but not in female, which means that cholesterol was not produced from BCAA in female gland due to the lack of expression of acyl-CoA dehydrogenases. We monitored the behavior of male hamsters toward female gland lipids, and found slightly greater attractiveness in female ones than that in male ones although the difference was not significant. Considering the lifestyle of golden hamster in nature, we propose a hypothesis that the lipids from the Harderian gland of golden hamster serve as a pheromone to declare their territory and to seek the mate with good congeniality.

Proteome Profiling in the Rat Harderian Gland

The Harderian gland is an orbital gland located behind the ocular bulb in most terrestrial vertebrates probably functioning for production of lipid secretion to protect the eye. We herein present a protein reference database of the rat Harderian gland that may serve as analytical tool for future proteomic work, report lipid and porphyrin handling cascades, address sequence conflicts and report structures that have not been so far described by proteomics methods.

Anatomy, histology, histochemistry and fine structure of the Harderian gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

The anatomical, histological, histochemical and ultrastructural characteristics of the Harderian gland of the armadillo Chaetophractus villosus were described. The gland is the largest structure in the bony orbit. It is situated in the anteroventral region of the orbit. Obvious structural differences are not observed between males and females. The gland is compound-branched tubulo-alveolar, being characterized by a single layer of columnar cells surrounded by myoepithelial cells. It possesses a single excretory duct opened into the inner canthus. All glandular cells show yellow-green autofluorescence and additionally some glandular lumen may contain dense autofluorescent solid accretions. There are two peculiar and outstanding cytoplasmic features. One is represented by the smooth endoplasmic reticulum (SER), forming a closely woven meshwork. The other one is represented by "membranous bodies" apparently derived from the SER, RER and cytoskeleton with a "Star of David" configuration situated in the supranuclear region. Three types of vesicles are detected in the cytoplasm. Histochemical staining methods reveal lipids, proteins, neutral and acidic containing glycoconjugates in secretory vesicles. The mechanism of secretion appears either merocrine or apocrine. The epithelium of the intra- and inter-lobular excretory ducts suggests secretory activity. Tubulo-acinar glands similar to those seen in the lacrimal gland and nictitans glands are found related to the intralobular and main excretory ducts. The capillary network is characterized by fenestrated endothelium. The stroma possesses unmyelinated axons and plasma cells. The normal secretion of the secretory endpieces, particularly lipids, proteins and glycoconjugates, is complemented by mucous and serous secretions released by ductal cells and glands associated to the ducts.

The Harderian gland of the Mexican volcano mouse Neotomodon alstoni alstoni (Merriam 1898): a morphological and biochemical approach

The Harderian glands of rodents are large intraorbital exocrine glands with histologic organization that varies among mammalian species. Here we describe some ultrastructural and biochemical features of the Harderian gland in the Mexican volcano mouse Neotomodon alstoni alstoni, a species of restricted habitat. The Harderian glands from male and female adult mice were dissected, processed and embedded in Epon 812 for light and electron microscopy studies. Porphyrin and total lipids were biochemically determined. The macroscopic appearance of the Harderian gland is similar in the male and female. The gland is a bilobulate structure, situated in the orbit towards the posterior side of the eyeball, of whitish color and is surrounded by a connective tissue capsule. The male gland is slightly heavier (127 mg) than that of the female (113 mg). The Harderian gland shows a tubulo-alveolar organization and is composed exclusively of one type of secretory cells. No branched duct system within the gland was found. Adrenergic nerves endings and mast cell were observed in the interstices of the alveoli. Male and female glands produce similar levels of porphyrins. Triglyceride levels were significantly higher (P < 0.05) in the female compared to the male. Abundance of lipids could induce corneal lubrication of the Harderian gland which may confer a protective and adaptative function to the volcano mouse in its natural habitat during the dry and cold seasons.

The effects of adrenalectomy on the harderian gland of the Wistar albino rats

Harderian glands of the Wistar albino rats normal and adrenalectomized were investigated by light microscopy. In normal, these glands have a tubuloalveolar structure. The gland is located in the medio posterior aspect of the orbit. It is lobulated and appears homogeneous in colour and texture. Harderian gland consist of tubules with wide lumina lined by a single layer of columnar epithelial cells surrounded by myoepithelial cells within their basal lamina. It contains porphyrin pigment which is stored as solid intraluminal deposits. The glandular epithelium possesses two cell types, termed A and B. Type A cells are more numerous. The single excretory duct of the gland is directly continuous with endpieces at the hilus and opens nasally and ventrally to the third eyelid. The excretory duct is accompanied by many acini of small serous glands around it. The tubuloalveoli of the gland is not divided into lobules. There is no branched duct system within the gland. The secretion seems to be associated with porphyrins, is essentially released by exocytosis, but holocrine secretion also occurs. The single excretory duct is lined by a stratified epithelium. The gland is surrounded by a collagenous capsule. The adrenalectomy, caused degenerative changes in the glands. Epithelial height was lower than in normal gland epithelium. Most of the acini were completely disorganised. The acinar lumina were filled with porphyrin debris. The results suggest that rat harderian glands are sensitive to adrenal androgen changes in both male and female rats.

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.

The ultrastructure of periductal connective tissue and distinctive populations of collagen fibrils associated with ductal epithelia of exocrine glands

The ultrastructure of the connective tissue around the intraglandular ducts was observed in rat exocrine glands. Connective tissue with a dense population of collagen fibrils was found either around the ducts and blood vessels (perivasculoductal connective tissue; PVDCT) as in the lacrimal and salivary glands and liver, or solely surrounding the ducts (periductal connective tissue; PDCT) as in the exocrine pancreas, whereas the interlobular and intralobular interstitium of the glands-except for the liver-contained substantially fluid-filled spaces without collagen fibrils. The PVDCT and PDCT of these glands contained two populations of collagen fibrils-fibroblast-associated and epithelium-associated-although the development and density of these fibrils varied considerably in individual glands. Both populations of collagen fibrils were most developed in the lacrimal glands, in which the basal aspects of the ductal epithelium and the basement membrane showed considerable undulation associated with a distinctive peribasement membrane zone with amorphous matter and a small population of the fibrils. In the parotid and submandibular glands, both populations were distinct, though poorly developed. In the exocrine pancreas and hepatic Glisson's sheath, the two populations of collagen fibrils were moderately developed, and the basal aspects of the ductal epithelium were characterized by prominent invaginations in which the multilaminar basement membranes and the epithelium-associated collagen fibrils were frequently engulfed. These observations provide evidence that the two populations of collagen fibrils around the ducts are found universally in exocrine glands, and support the hypothesis of the collagen fibril-synthesizing and -secreting ability of ductal epithelial cells.

Histology, histochemistry and fine structure of the lacrimal and nictitans gland in the South American armadillo Chaetophractus villosus (Xenarthra, Mammalia)

The anatomical, histological, histochemical and ultrastructural characteristics of the lacrimal gland (LG) and nictitans gland (NG) of the armadillo Chaetophractus villosus were described. The histochemical and histological features of both glands in male and female adult animals were compared. The tissues were processed with conventional techniques for light and transmission electron microscopy. Fixed specimens were submitted to a battery of tests for glycans, glycosaminglycans, glycoconjugates, proteins, and lipids. The LG of the armadillo may be considered within the set of glandulae lacrimales superior in which primates, carnivores, perisodactyls and artiodactyls are included. The localization of the NG was similar to that of other mammals. Lacrimal and NG were histologically and histochemically identical. The secretory endpieces consisted of three cell types: (1) Mucous cells (MC) with different types of mucous secretory granules with neutral and sialic acid-containing glycoconjugates (GCs). (2)Seromucous cells (SMC) showing a variety of moderately electron dense secretory granules with flocculent material with carboxylated acidic, neutral, and sialic acid-containing GCs. Intercellular canaliculi with junctional complexes and basolateral intercellular spaces were frequent. (3) Serous cells (SC) with electron dense secretory granules. Histochemically, they showed the strongest reaction for proteins and neutral, weakly acid and carboxylated acidic GCs. The epithelium of the intra- and inter-lobular excretory ducts showed secretory activity, junctional complexes, and wide basolateral intercellular spaces with lateral folds. The endpieces and ducts were surrounded by myoepithelial cells. The stroma was characterized by fenestrated endothelium, unmyelinated axons, and abundant plasma cells. MC, SMC, and the duct system were richly innervated by hypolemmal nerve terminals.

Ocular disorders of pet mice and rats

As mice and rats become more popular as pets, it is expected that they will be seen more often in general veterinary practice. It is hoped that this increase in doctor visits will be associated with an increased number of clinical reports that describe ophthalmic disorders observed in these species. Until then, clinicians must rely on extrapolation and cautious application of data that are generated in laboratory strains.

The Harderian gland of the northern grasshopper mouse, Onychomys leucogaster

The Harderian gland of the northern grasshopper mouse, Onychomys leucogaster, consists of glandular tubuloalveolar endpieces with secretory cells (small- and large-droplet cells) surrounding a wide lumen. Lumina from adjacent endpieces join repeatedly, forming progressively wider channels. Ultimately, a single secretory duct opens at the anterior canthus of the eye. Abundant sudanophilic materials secreted into the lumina of the tubuloalveoli drain into the orbit of the eye. The presence of amber–brown concretions in, and the intense fluorescence of, the Harderian gland suggest that in O. leucogaster the secretory materials also include porphyrins. Fluorescence of these secretions demonstrates that they drain from the orbit into the nasal passages; grooming spreads these materials from the nares onto other parts of the body. Although the Harderian gland of O. leucogaster shows no sexual dimorphism, there are age-related changes. Small-droplet cells are present at 1 week of age and large-droplet cells appear by 2 weeks. By 4 weeks the gland is comparable to that of adults. Glands of a few adults exhibit two features rarely reported in other rodents: (1) clusters of degenerated tubules characterized by a loss of the secretory epithelium and (2) large aggregations of lymphoid cells.

Lipid secretory mechanisms in the mammalian harderian gland

The mammalian Harderian glands are lipid-secreting glands. In an unstimulated condition, the glandular cells frequently exocytose the lipid materials; however, no intracellular calcium ion ([Ca2+]c) changes are detectable. Cholinergic (muscarinic) secretagogues induce secretory activity and increase of [Ca2+]c. A G-protein activator, sodium fluoride, enhances the secretory activity and increase of [Ca2+]c. Removal of extracellular calcium ions inhibits the secretion enhanced by cholinergic stimulation. Under pharmacologic stimulation, glandular cells may show an apocrine-like secretory pattern. Cholinergic stimulation also induces contraction of the myoepithelial cells covering glandular end pieces; however, the reduction in volume of glandular end pieces is not prominent. Catecholamines have no effect on the release of lipid materials. These results indicate the involvement of G-proteins linking with muscarinic receptors and Ca2+ dynamics (increase of [Ca2+]c and Ca2+ influx) in lipid secretion by glandular cells and in contraction of myoepithelial cells of mammalian Harderian glands. However, the increase of [Ca2+]c in Harderian glands was less when compared with other cells--for instance, those which secrete protein.

Invasive processes in the normal Harderian gland of Syrian hamster

In this contribution we will pay special attention to several morphological findings that we can observe, under some circumstances, in the normal Harderian gland of the Syrian hamster. The accumulation of porphyrins in this gland results in mitochondrial damage and extensive cell death. Many damaged cells are secreted into the lumen of the tubule-alveoli, but most of them seem to produce an invasive process that even affects the vascular components of the gland. In this way, many blood vessels are invaded and appear partially filled with the invasive mass, which sometimes totally occludes the lumen of the vessels. We have also observed other surprising features related to a special kind of activity in certain secretory cells. Such activity results in a peculiar "segregation" of a cytoplasmic fragment, containing the nucleus. The affected cells seem to gather up their cytoplasm and nucleus towards the basal zone, while the rest of the cell, including practically the whole amount of lipid droplets, is relegated to the vicinity of the lumen. All these phenomena seem finally to result in the detachment of some clusters, composed of a limited number of cells, which display a basophilic cytoplasm practically free of lipid droplets.

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.

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.

Effect of cholinergic secretagogue substances on the morphology of the harderian gland in the frog, Rana esculenta

The present study using secretagogue substances was undertaken to investigate Harderian gland secretion in the frog, Rana esculenta. Carbamylcholine chloride and bethanechol injections caused enhancement of the secretory activity and hyperemia, while nicotine did not. Morphological examinations showed reduced cellular height and dilated alveolar lumina, containing secretory granule discharge, nuclei and cytoplasmic fragments, indicating an apocrine and holocrine secretion type. The administration of atropine prevented the enhancement of the secretion. Our data suggest that cholinergic stimulation provokes enhancement of the secretory activity on the frog HG, and this mechanism appears to be mediated by the activation of the muscarinic receptors.

Protein kinase C isoenzymes in mouse harderian gland. Differential expression of the alpha- and epsilon-isoforms during pregnancy. Protein kinase C-OC

Protein kinase C (PKC) is known to be involved in the regulation of exocytosis in different cell lines and tissues. Experiments were designed to determine whether the Harderian gland of CD-1 mouse produces PKC isoenzymes and whether the expression of the isoforms changes during pregnancy. The presence of the isoenzymes was assessed by immunoblotting experiments using extract of total Harderian gland and polyclonal antisera specific for nine different PKC isoforms. Antisera giving a positive staining on Western blots were subsequently used for immunohistochemical investigation using a secondary antibody conjugated to alkaline phosphatase. Immunoblotting experiments revealed that the Harderian gland from female mouse expresses PKC isoforms-alpha, -epsilon, -zeta and -eta. These isoforms were also detected in the Harderian gland from 13-day pregnant mouse; however, striking quantitative changes were seen concerning the alpha- and epsilon-isoforms. The 80-kDa native from of PKC-alpha almost doubled in the pregnant mouse in comparison with normal female mouse whereas the amount of 50-kDa catalytic domain did not change. Protein kinase C-epsilon appeared as a 92- to 93-kDa form and a 67-kDa form. While the 92- to 93-kDa protein was expressed to a similar extent in both types of mouse, the 67-kDa form was more abundant in the Harderian gland from normal female mouse. These data were corroborated by immunohistochemical experiments and showing a diffuse and granular staining of the adenomeres. These observations demonstrate for the first time (to our knowledge) that the mouse Harderian gland produces several PKC isoenzymes that could be involved in the regulation of exocytosis and/or other functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Harderian gland ultrastructure of the black sea bottlenose dolphin (Tursiops truncatus ponticus)

Examination of the Harderian gland structure of the Black Sea bottlenose dolphin, Tursiops truncatus ponticus, at macroscopic, microscopic, and electron microscopic levels shows significant sexual dimorphism. The epithelial cells of male and female glands are different cell types, capable of producing chemically different products. Secretory cells in both sexes contain secretion granules that produce a secretion consisting mainly of proteins and carbohydrates, but thought to be sex-specific in composition. The female glands also contain lipid secretion granules. It is suggested that in the bottlenose dolphin the Harderian gland functions to produce sexually distinct pheromones and may have other physiological activities, e.g., participating in local immunological or endocrine-related reactions.

Carbamylcholine-induced morphological changes and spatial dynamics of [Ca2+]c in Harderian glands of guinea pigs: calcium-dependent lipid secretion and contraction of myoepithelial cells

To determine whether lipid-secreting cells have cytosolic Ca2+ concentration ([Ca2+]c)-related secretory mechanisms, morphological changes and intracellular calcium dynamics of Harderian glands of guinea pigs stimulated by secretagogue were studied by electron microscopy and Fura-2/AM digital image analysis. Control glandular cells contained large lipid vacuoles that were bordered by multi-layered membranes. Rough-surfaced endoplasmic reticulum, mitochondria, and smooth-surfaced endoplasmic reticulum may be involved in lipid vacuole formation. Myoepithelial cells surrounded alveoli. After carbamylcholine (CCh, 10(-6), 10(-5), and 10(-3) M) stimulation, lipid materials within the membranous structures were frequently discharged by an exocytotic mechanism. Conspicuous deformation of glandular cells caused by vigorous contraction of myoepithelial cells was observed in isolated alveoli after 10(-6) M CCh stimulation, whereas the deformities of glandular tissues perfused via vessels were small even after 10(-3) M CCh stimulation. Connective tissue between glandular alveoli inhibited unbridled myoepithelial-cell contraction. Fura-2/AM digital imaging analysis revealed that CCh stimulation caused an increase in [Ca2+]c in isolated alveoli. The morphological reactions and changes in [Ca2+]c were prevented by atropine. When extracellular calcium ions were absent, enhanced extrusion of lipid vacuoles, myoepithelial-cell contraction, and a rise in [Ca2+]c after CCh stimulation were not observed. Nicotine and catecholamines had no effect on the secretion or on the dynamics of [Ca2+]c. It can be concluded that acetylcholine elicits exocytosis in glandular cells and contraction of the myoepithelial cells of Harderian glands, accompanied by an increase in [Ca2+]c. The dynamics of [Ca2+]c of the gland alveoli are mostly dependent on extracellular Ca2+.

Mast cells in the Harderian gland of female Syrian hamsters during the estrous cycle and pregnancy: effects of the light/dark cycle

The number of identifiable mast cells and the intraluminal area occupied by porphyrin deposits was studied on semithin sections from female hamster Harderian glands during the estrous cycle and pregnancy. Although the serum levels of estradiol, progesterone, luteinizing hormone and follicle stimulating hormone exhibited significant changes throughout the cycle, no correlation between these changes and the variations in the number of recognizable mast cells was observed. However both during diestrous 1 and proestrous cycles, the number of identifiable mast cells was higher at midnight than at noon (in 14 h light:10 h dark photoperiod with lights on at 07:00 h). A more exhaustive study revealed the presence of 'degranulated mast cells' which were not stained with toluidine blue. Thus, a diurnal cycle in degranulation might occur in the Harderian glands from female hamsters. No significant variations were observed in the area occupied by intraluminal porphyrin deposits during the estrous cycle. However, both the relative number of mast cells and the area occupied by intraluminal porphyrins decreased from day 4 of pregnancy to day 14 showing a strong correlation. The Harderian glands from female Syrian hamsters might provide a useful model for the study of mast cell degranulation during porphyria.

An electron microscopic study of the harderian gland of the Syrian hamster with particular reference to the processes of formation and discharge of the secretory vacuoles

The lipid-secreting cells of the Harderian gland of the Syrian hamster were studied using light, transmission, and scanning electron microscopy. Three morphologically different secretory cell types are identified in the gland: type I and II cells of the male gland and, distinct from either, the female gland cell. In all secretory cell types, lipid droplets in the cytoplasm were surrounded by unit membranes. Ultrastructural evidence of the involvement of the Golgi apparatus in the formation of the secretory vacuoles was obtained. The process of secretion involved the fusion of the boundary unit membrane of the vacuole with the plasma membrane and the release of the vacuolar content alone into the lumen. No evidence of holocrine processes was observed in this study. In addition to lipids, vacuoles contained materials whose solubility properties clearly differed from those of lipids. There appear to be variations in the ultrastructural characteristics of the vacuole content of the different types of secretory cell.

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.

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.

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.

The structure of the kidney of Japanese newts, Triturus (Cynops) pyrrhogaster

The construction of renal lobules in Triturus (Cynops) pyrrhogaster was studied by reconstruction from serial semithin sections, and the structure of nephrons, collecting ducts and ureters was investigated by means of light and electron microscopy. In T. pyrrhogaster the kidney was mesonephros in construction; renal lobules were arranged segmentally and each of them sent one ureter. Male ureters ran caudally and met together before joining the Wolffian duct. In renal lobules, long collecting ducts ran medio-laterally in the dorsal aspect of the kidney and sent several branches ventrally. Each branch duct or short collecting duct received one nephron. Each nephron had five segments; 1) renal corpuscle, 2) ciliated neck segment with or without a naphrostome, 3) proximal tubule, 4) ciliated intermediate segment and 5) distal tubule. Proximal and distal tubules were segregated spacially in renal lobules and occupied the peripheral and central zone respectively. The filtration barrier of the glomerulus consisted of both the basal lamina of podocytes and the subendothelial connective tissue, and was much thicker than the mammalian filtration barrier. Proximal tubule cells had a brush border, apical specialization for reabsorption of organic materials and well-developed smooth endoplasmic reticulum, but few baso-lateral interdigitations. In distal tubule cells, baso-lateral interdigitations and infoldings were well-developed. Collecting duct cells had a sparse cytoplasm. Ureter cells in males contained many secretory granules. On the basis of structural organization of the newt kidney as well as physiological data in literature, we suggest that in land vertebrates proximal tubules were primarily adapted to reabsorption of organic materials and distal tubules to reabsorption of electrolytes and water.