Ultrastructural investigation of the postnatal development of the hamster Harderian gland. II. Male and female

Lack of adrenal TSPO/PBR expression in hamsters reinforces correlation to triglyceride metabolism

Despite being a highly conserved protein, the precise role of the mitochondrial translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), remains elusive. The void created by studies that overturned a presumptive model that described TSPO/PBR as a mitochondrial cholesterol transporter for steroidogenesis has been filled with evidence that it can affect mitochondrial metabolic functions across different model systems. We previously reported that TSPO/PBR deficient steroidogenic cells upregulate mitochondrial fatty acid oxidation and presented a strong positive correlation between TSPO/PBR expression and tissues active in triglyceride metabolism or lipid storage. Nevertheless, the highlighting of inconsistencies in prior work has provoked reprisals that threaten to stifle progress. One frequent factoid presented as being supportive of a cholesterol import function is that there are no steroid-synthesizing cell types without high TSPO/PBR expression. In this study, we examine the hamster adrenal gland that is devoid of lipid droplets in the cortex and largely relies on de novo cholesterol biosynthesis and uptake for steroidogenesis. We find that Tspo expression in the hamster adrenal is imperceptible compared to the mouse. This observation is consistent with a substantially low expression of Cpt1a in the hamster adrenal, indicating minimal mitochondrial fatty acid oxidation capacity compared to the mouse. These findings provide further reinforcement that the much sought-after mechanism of TSPO/PBR function remains correlated with the extent of cellular triglyceride metabolism. Thus, TSPO/PBR could have a homeostatic function relevant only to steroidogenic systems that manage triglycerides associated with lipid droplets.

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.

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.

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.

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 primate Harderian gland: Does it really exist?

The Harderian gland, an anterior orbital structure, is either absent or vestigial in primates. This is based upon gross anatomical observations of scattered adult specimens. Though largely absent in the adult human, it is present in the fetal and neonatal stages. Thus, histological examination of the orbital region of neonatal material was undertaken in other primates. The orbital region of neonatal specimens of 12 species of strepsirrhines (Lemuriformes and Lorisiformes), and haplorhine (tarsiers and callitrichids) was examined. The Harderian gland is ensconced in either periorbital fat or connective tissue and thus was not readily identifiable gross anatomically. Thus, it may have been missed in the anatomical studies. Tarsal glands are present in all neonatal primate eyelids. The relative size of the neonatal primate Harderian gland can be subdivided into five separate categories, ranging from large to absent (tarsiers), with no apparent phylogenetic trends. Thus, the Harderian gland is present in numerous primates at birth, quite possibly all strepsirrhines. The positive findings on callitrichids question whether any anthropoids lack the Harderian gland postnatally. The enigmatic tarsier appears to possess another apomorphic trait in lacking a Harderian gland. Further study is required to determine the role of this gland and its relationship with the tarsal glands.

Postnatal development of the harderian gland in the rabbit: light and electron microscopic observations

We have investigated the development of the Harderian glands of Japanese white rabbits from birth to 4 months of age. Although two types of secretory cells comprise the glandular epithelium of the pink and white lobes in fully developed glands, the time of neonatal appearance is different between the two. Cells consisting of the pink lobe first appear on the third day of life, while cells of the white appear around seventh day of life. The ultrastructure of the Harderian glands from 1-week-old rabbits resembles that of adult animals. The gland can be divided into three parts on the basis of their epithelial cell composition at the electron microscopic level. The respective parts are composed of: (1) one type of cells with large vacuoles (pink lobe), (2) one type of cells with small vacuoles (white lobe), and (3) two types of cells with large and small vacuoles (pink-white mixed portion). The relative number of plasma cells per 1 mm2 is low in both pink and white lobes during early postnatal life. However, in adult animals, the white lobe has a larger number of plasma cells than the pink lobe. These results suggest the possibility that the white lobe participates in the immune system more than does the pink.

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.

Postnatal development of cell types in the hamster Harderian gland

The morphology, frequency, and distribution of mitotic cells in the epithelium of the Harderian gland was studied in the male and female hamster from birth to the ninetieth day of postnatal life using light and electron microscopic techniques. The results obtained show that there is a gradual decline in the mitotic activity of the Harderian gland as the animals become older which continues until sexual maturity is reached. The study did not find any morphological evidence for the existence of separate precursor cells for the different secretory cell types of the gland. Secretory cells seem to be a homogeneous population in the glands of hamsters younger than 20 days. Cells that could be interpreted as undifferentiated stem cells were not observed. Mitotic cells were observed randomly distributed within tubulo-alveoli, similar to those in interphase. The first sex differences were observed at day 20, when type II cells appeared in male glands. From this point, the percentage of type II cells rapidly increased in male glands. This increase was not accompanied by an increase in the global mitotic activity. However, at this age, male type II cells develop an intense mitotic activity. The observations obtained are in accordance with the hypothesis that the type I and type II cells have the same cell precursor.

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.

Porphyrin accumulation in the harderian glands of female Syrian hamster results in mitochondrial damage and cell death

BACKGROUND

The Harderian glands of female Syrian hamsters contain very high concentrations of protoporphyrin (in the range of micrograms per mg of tissue) which accumulate in the tubulo-alveoli of the gland. We have studied the process of synthesis, accumulation, and secretion of this cyclic compound by the secretory cells of the hamster Harderian glands.

METHODS

The animals used were female Syrian hamster of 15, 35, 75, 180, and 360 days of age. Items first examined were (1) percentage of the "clear cells," (2) area occupied by intraluminal porphyrins, and (3) histological characteristics of "clear cells" by light and transmission electron microscopy (TEM). In a second study the total content of porphyrins was determined. Finally, the levels of mRNA for the enzyme aminolevulinate synthase (ALV-S) were measured.

RESULTS

In the glands of female hamsters, both the tissue concentration and the intraluminal area occupied by protoporphyrin correlate with the appearance of a special type of cell (clear cells) which show signs of cell degeneration. In addition, the expression of the gene for ALV-S, which is the limiting enzyme in porphyrin production, also parallels the relative number of clear cells. Analyzed under TEM, these clear cells display dilated mitochondria and short and swollen endoplasmic reticulum cisternae. In a late phase of necrosis, the nuclear envelope appears disorganized with scarce chromatin. The mitochondria undergo complete destruction, resulting in electron-dense bacillary formations which progressively coalesce in large and dense areas of protoporphyrin. The cell dies after this accumulation, being secreted by a "cytogen" mechanism.

CONCLUSIONS

In view of our results, the Harderian gland of female Syrian hamster may provide a useful model for the study of the mechanism by which the anomalous accumulation of protoporphyrin induces cell damage in human protoporphyria.

Development and androgen regulation of the secretory cell types of the Syrian hamster (Mesocricetus auratus) Harderian gland

The secretory cell types of the hamster Harderian glands were studied in both male and female Syrian hamsters. As previously demonstrated, female hamsters showed a single secretory cell type (type I), while male hamsters displayed two secretory cell types (type I and type II). Type-II cells were observed after the first month of age correlating with the increase in testosterone levels. The administration of testosterone to adult female hamsters resulted in a marked increase in the percentage of type-II cells without a significant increase in the number of mitotic figures. Very low levels of serum testosterone were able to maintain the percentage of type-II cells. Castration of male hamsters produced a decrease in the percentage of type-II cells. This drop correlated with the reduction in serum testosterone levels. The chronic administration of a luteinizing hormone-releasing hormone agonist to male Syrian hamsters induced a significant reduction in both serum luteinizing hormone and testosterone. However, the percentage of type-II cells was similar to that of control hamsters suggesting that very low levels of circulating testosterone are able to maintain the percentage of type-II cells. In a final experiment male Syrian hamsters were treated with the antiandrogen cyproterone acetate. No changes were observed in the percentage of type-II cells, whereas serum luteinizing hormone and testosterone levels were significantly modified. We concluded that (1) type-II cells differentiate from type-I cells; (2) gonadal androgens are the major factor controlling this differentiation; and (3) the disappearance of type-II cells after androgen deprivation occurs through holocrine and apocrine mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Postnatal development of the harderian gland in the Syrian golden hamster (Mesocricetus auratus): a light and electron microscopic study

The main objective of the present investigation was to study the morphological and chronological aspects of the development of the Harderian gland in the Syrian golden hamster. Tissues were obtained from male and female hamsters at days 1,3,5,7,10,12,15,17,20,27,37,46, and 90 after birth and processed for light and transmission electron microscopy. The present observations indicate that a well-defined temporal sequence in microscopic and ultrastructural modification is recognizable in the development of the hamster Harderian gland. Four stages of development were proposed. Between days 1-5 (first stage), the gland shows characteristics of an immature structure. The glandular cells contain many free ribosomes, few and small organelles, and large irregular-shape nuclei. Between days 7-17 (second stage), there is a marked increase of organelles involved in synthesis and secretion. The gland begins the secretion of lipids and porphyrins, but no morphological differences between male and female glands are observed. Between days 20-36 (third stage), the morphological differences between the two sexes appear and progressively develop. In 45-day-old hamsters, the Harderian gland possesses the structural characteristics of adult glands, and further developmental changes are essentially quantitative in nature (fourth stage). At all stages of development, the population of secretory cells has a uniform appearance. The morphological results are discussed as well as the possible relationship of this temporal sequence with hormonal changes.

Effect of castration and testosterone therapy on harderian gland protein patterns of the golden hamster (Mesocricetus auratus)

1. Sodium dodecyl sulphate 7-12% gradient polyacrylamide gel electrophoresis of male and female hamster Harderian gland whole homogenate shows a clear-cut sexual dimorphism, which consists of the presence of two male-specific glycoproteins (168 and 116 kDa) and two specific female proteins (210 and 190 kDa). 2. In the male, castration causes a significant decrease in the concentration of the two glycoprotein fractions. 3. Replacement therapy with testosterone propionate (T) restores the intact male pattern.

Ultrastructural study of lamellar and nucleolus-like bodies in the harderian gland during postnatal development of the hamster (Mesocricetus auratus)

Membranous structures identified as lamellar bodies (LBs) and dense intracytoplasmic bodies referred to as nucleolus-like bodies (NLBs) have been found in the hamster Harderian gland during neonatal stages. Both structures appear between 8 and 12 postnatal days, coinciding with the beginning of secretory activity. LBs in males and NLBs in both sexes gradually decrease in number with further differentiation of the glandular cells. The morphological features of these cytoplasmic structures are described, and their origin as well as their possible functional significance are discussed.

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.

Light affects neonatal rat pineal gland N-acetyltransferase activity by an extra-retinal mechanism

To determine whether extra-retinal mechanisms mediate photoperiodic changes in neonatal rat pineal gland N-acetyltransferase activity, 4-day-old intact or bilateral orbital enucleated rats were killed during the dark phase of the lighting cycle, either in darkness or following 4 hr exposure to fluorescent light. Light suppressed the high nighttime N-acetyltransferase activity equally in intact and enucleated pups. Subsequent studies showed that at least 0.5 hr exposure and nocturnal illuminances of 109 microW/cm2 or greater were required to cause statistically significant reductions in the activity of the enzyme in 4-day-old rats. Taken together, these data indicate that relatively intense environmental light can affect neonatal rat pineal gland biochemistry via extraretinal mechanisms.

Sex differences in haem biosynthesis and porphyrin content in the Harderian gland of the golden hamster

Methods are described for the measurement of seven haem biosynthetic enzymes in Harderian gland tissue from male and female golden hamsters. Sex differences were found in five of the seven enzymes. In each case, female tissue exhibited higher activity than male tissue. These differences in enzyme activity are sufficient to account for the major sex difference in porphyrin content in the Harderian gland of this species.

Sex differences in secretion pattern of neonatal rat Harderian gland under various environmental lighting conditions

1. Secretion pattern of Harderian gland of neonatal rats maintained under (a) diurnal lighting conditions; (b) continuous light or (c) continuous darkness was studied at light microscopy level. 2. All animals were placed in especially designed cages at 13:00 hr on day 1 and studied on day 7 at 13:00 and 23:00 hr, respectively. 3. Acini with intraluminal secretion were counted in glands from each animal and the results were separately grouped for male and female animals. 4. A diurnal rhythm in secretion pattern of rat Harderian gland in neonatal period was demonstrated. 5. A statistically significant difference was observed in the gland secretion pattern between males and females at both, 13:00 and 23:00 hr when the animals were kept under diurnal lighting conditions. 6. Under continuous light or continuous darkness, the diurnal rhythm in secretion pattern was lost and no significant differences were seen when data from males were compared to those from female neonates. 7. Results are discussed in terms of the possible function of Harderian gland as element of an extraretinal photoreceptor system involved in the regulation of pineal function in neonatal rats.

delta-Aminolevulinate synthase activity in the Harderian glands of male and female golden hamsters

1. delta-Aminolevulinate (A1A) synthase activity was determined in the Harderian glands of male and female Golden Hamsters. 2. The enzyme activity was higher in the female gland than in the male gland. 3. The data suggest that the higher enzyme activity is, at least partly, related to the higher porphyrin content in the female gland. 4. This enzyme activity has not been reported in the male gland previously.

Ultrastructure of the harderian gland in male albino rats

Harderian glands of adult male albino rats were examined by light and transmission electron microscopy. The animals were divided into the following experimental groups: (1) castrated only, (2) castrated with testosterone replacement and (3) sham operated controls. Two types of secretory cells, designated as A and B, comprise the glandular epithelium and are distinguished on the basis of morphologic differences in the following cellular components: cytoplasmic secretory vacuoles, mitochondria and smooth endoplasmic reticulum (SER). Cell type A is more numerous and contains larger secretory vacuoles than cell type B which is characterized by the presence of large numbers of mitochondria and packet-like arrangement of SER profiles. The glandular secretion appears to be elaborated via merocrine mechanisms and consists primarily of lipids and a fibrogranular substance. The latter component may consist of porph,yrin compounds. Nerve endings are found in the connective tissue interstices of the gland. Direct synapses were not observed in association with either gland cells or myoepithelial cells. Castration did not produce significant alterations in the morphology of the glandular epithelium. Results of the investigation suggest that the rat Harderian gland may serve as a useful model for the study of cellular mechanisms involved in the production of human porphyrias.