Ultrastructural visualization of intracellular porphyrin in the rat Harderian gland

Fluorescence and UV-visible reflectance in the fur of several Rodentia genera

Mammals are generally brown in colour, but recent publications are showing that they may not be as uniform as once assumed. Monotremes, marsupials, and a handful of eutherians reflect various colours when lit with UV light, mostly purple. Because of these still scarce records, we aimed to explore UV reflectance among rodent genera, the most diverse mammalian group, and the group of eutherians with the most common records of biofluorescence. Here we report structures like nails and quills reflected green, but for most genera, it was faded. However, Hystrix, Erethizon, and Ctenomys showed intense and contrasting green glow, while Chaetomys presented a vivid orange anogenital. The main available explanation of fluorescence in mammals relies on porphyrin. This explanation applies to the cases like Chaetomys, where specimens showed anogenital orange biofluorescence, but does not apply to the green biofluorescence we observed. In our sample, because the structures that reflected green were all keratinized, we have reasons to believe that biofluorescence results from keratinization and is a structurally-based colouration. However, not all spines/quills equally biofluoresced, so we cannot rule out other explanations. Since Rodentia is the most common mammalian group with reports on biofluorescence, this trait likely serves various functions that match the species diversity of this group.

Autophagy facilitates secretion and protects against degeneration of the Harderian gland

The epithelial derived Harderian gland consists of 2 types of secretory cells. The more numerous type A cells are responsible for the secretion of lipid droplets, while type B cells produce dark granules of multilamellar bodies. The process of autophagy is constitutively active in the Harderian gland, as confirmed by our analysis of LC3 processing in GFP-LC3 transgenic mice. This process is compromised by epithelial deletion of Atg7. Morphologically, the Atg7 mutant glands are hypotrophic and degenerated, with highly vacuolated cells and pyknotic nuclei. The mutant glands accumulate lipid droplets coated with PLIN2 (perilipin 2) and contain deposits of cholesterol, ubiquitinated proteins, SQSTM1/p62 (sequestosome 1) positive aggregates and other metabolic products such as porphyrin. Immunofluorescence stainings show that distinct cells strongly aggregate both proteins and lipids. Electron microscopy of the Harderian glands reveals that its organized structure is compromised, and the presence of large intracellular lipid droplets and heterologous aggregates. We attribute the occurrence of large vacuoles to a malfunction in the formation of multilamellar bodies found in the less abundant type B Harderian gland cells. This defect causes the formation of large tertiary lysosomes of heterologous content and is accompanied by the generation of tight lamellar stacks of endoplasmic reticulum in a pseudo-crystalline form. To test the hypothesis that lipid and protein accumulation is the cause for the degeneration in autophagy-deficient Harderian glands, epithelial cells were treated with a combination of the proteasome inhibitor and free fatty acids, to induce aggregation of misfolded proteins and lipid accumulation, respectively. The results show that lipid accumulation indeed enhanced the toxicity of misfolded proteins and that this was even more pronounced in autophagy-deficient cells. Thus, we conclude autophagy controls protein and lipid catabolism and anabolism to facilitate bulk production of secretory vesicles of the Harderian gland.

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.

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.

A physiological role for protoporphyrin IX photodynamic action in the rat Harderian gland?

AIMS

The lipid-secreting exocrine Harderian gland contains a large amount of porphyrins (mainly protoporphyrin IX, PPIX) in the glandular cells, the physiological significance of which is rather poorly understood.

METHODS

In the present study, the possibility of using Fura-2 to measure intracellular calcium ([Ca2+]c) changes in these cells was assessed.

RESULTS

It was found that when Fura-2-loaded cells were excited by light at 340/380 nm, [Ca2+]c increased spontaneously, indicating a photodynamic action powered by light at 340/380 nm. In contrast, with the visible spectrum calcium probe Fluo-3 (lambda(ex) = 475 nm), carbachol at 10 microm induced [Ca2+]c increase; [Ca2+]c did not change without carbachol stimulation. Brief illumination with light at 340/380 nm induced a large [Ca2+]c increase in Fluo-3-loaded cells. Photodynamic stimulation of [Ca2+]c increase was confirmed with an exogenous photosensitizer sulphonated aluminium phthalocyanine (SALPC) and visible light (>580 nm). The wavelength-dependence of the [Ca2+]c increase correlates well with the excitation spectrum of the isolated Harderian glandular cells.

CONCLUSION

These data suggest that PPIX present in rat Harderian glandular cells plays the role of a photosensitizer which upon activation by UVA and blue components of daylight and subsequent singlet oxygen generation, triggers [Ca2+]c increase and secretory response. The PPIX photodynamic action may also play a potential role in photic entrainment of the central circadian clock.

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.

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.

Rat harderian gland porphobilinogen deaminase: characterization studies and regulatory action of protoporphyrin IX

Properties of purified porphobilinogen deaminase (PBG-D; EC 4.3.1.8) from rat harderian gland are here presented. The enzyme behaves as a monomer of Mr 38 +/- 2 kDa and is optimally active at pH 8.0-8.2. Its activation energy, determined by an Arrhenius plot, is 76.1 kJ/mol. Initial velocity studies showed a linear progress curve for uroporphyringen I formation and a hyperbolic dependence of the initial rate on substrate concentration, indicating the existence of a sequential displacement mechanism. Apparent kinetic constants, Km and Vm, calculated at 37 degrees C and pH 8.0 were 1.1 microM and 170 pmol/min mg, respectively. The pH dependence of the apparent kinetic parameters revealed the ionization of residues with pKAES and pKBES of 7.4 +/- 0.1 and 8.6 +/- 0.1, respectively, and a pKE value of 8.0 +/- 0.1. Incubation of PBG-D with 5.0 mM N-ethylmaleimide and 5.0 mM 5,5'-dithiobis(2-nitrobenzoic acid) at pH 8.0 led to inhibitions of 70 and 50%, respectively. The effect of pH, as well as the effect of thiol reagents, on enzyme activity strongly suggests the involvement of cysteine residue(s) in the mechanism of uroporphyrinogen I biosynthesis, in both the catalytic reaction and the substrate binding. Rat harderian gland PBG-D activity decreased with increasing concentrations of protoporphyrin IX, reaching a 40% inhibition at the in vivo concentration of the porphyrin and 7 microM PBG. Even at saturating concentrations of substrate, inhibition by protoporphyrin was not completely reversed. So, accumulated porphyrin may act as an regulator of PBG-D activity in rat harderian gland.

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.

G-protein activation enhances Ca(2+)-dependent lipid secretion of the rat harderian gland

We studied the secretory mechanism of the Harderian gland of rats. After perfusion with HEPES-buffered Ringer's solution containing NaF (10 mM) with AlCl3 (10 microM), a G-protein activator, the glandular cells of the Harderian gland showed massive exocytosis and apocrine-like protrusions on the luminal surface. Some of the secretory vacuoles aggregated within the cytoplasm, and large vacuoles were formed. Contraction of the myoepithelial cells covering the glandular endpieces caused a narrowing of the glandular lumina, which contained cytoplasmic fragments, and deformation of the basal contour of the glandular end-pieces. The basal regions of the glandular cells also bulged between the myoepithelial cells. Secretory vacuoles were also discharged to the lateral cell surface, and the intercellular spaces were dilated. The enhanced secretory activities of the glandular cells and the contraction of the myoepithelial cells were similar to those in rats stimulated with 10 microM carbachol (CCh). However, dilatation of the endoplasmic reticulum in glandular cells (type A cells), which leads to the formation of small vesicles, was observed in those glands stimulated by NaF+AlCl3, but not in those stimulated by CCh. Removal of Ca2+ from the perfusing HR or addition of EDTA (0.5 mM) diminished and inhibited NaF+AlCl3- or CCh-enhanced secretory activity of the glandular cells and also allayed the deformation of glandular cells caused by myoepithelial cell contraction. The present results demonstrate the involvement of G-proteins and Ca(2+)-influx in the lipid secretion of glandular cells and in the contraction of myoepithelial cells of the Harderian gland in rats.

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.

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.

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.

Regulation of the androgen receptors in the harderian gland of the male Syrian hamster: influence of photoperiod, castration, and chronic melatonin treatment

Male Syrian hamsters that were exposed for 8 weeks to short photoperiod (LD 10:14) or treated with melatonin in the late afternoon under long photoperiod conditions (LD 14:10) had a significantly higher content of androgen receptors in the Lipidex-purified soluble fractions isolated from the Harderian glands as compared to the long photoperiod (LD 14:10) exposed controls. Simultaneous computer-assisted analyses of all series of saturation and competition experiments revealed that the numerical value of the apparent Kd, as determined by using the synthetic androgen R-1881 (methyltrienolone), was not different between the experimental groups, and ranged from 0.050 to 0.067 nM. Of the principal natural androgens, testosterone (T) was most potent in inhibiting methyltrienolone binding to the receptor (Ki values from 0.33 to 0.55 nM), and 5 alpha-dihydrotestosterone (DHT) and delta 4-androstenedione (AD) were less effective (Ki values between 1 and 1.9 nM). In the hypothalami and pituitaries of the same animals, used in parallel control assays, DHT was twice as potent as T. Short-term castration (24 hr post-orchidectomy) did not result in significant changes in the receptor binding characteristics. Following 8 weeks exposure to a long photoperiod (LD 14:10) the Bmax values demonstrated a four-fold increase in castrated animals (179 fmoles/mg protein vs. 47 fmoles/mg protein) over intact controls. The relative binding affinity of the major androgens under these conditions remained unchanged, with the exception of AD, where a five-fold increase in the numerical Ki values (decrease in the binding affinity) was recorded (Ki = 9.6 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Harderian gland porphyrin, lysosomal and type II 5'-deiodinase rhythms in Sprague-Dawley and Fischer-344 rats kept under chronic long- or short-photoperiod conditions

1. Harderian gland porphyrin concentrations were 1.5-fold higher in Fischer-344 male rats than in Sprague-Dawley male rats and there were no differences due to exposure to LD 14:10 (LP) or LD 10:14 (SP) lighting conditions for 8 weeks in either strain. 2. 24-hr periodic regression analyses of porphyrin concentration detected a significant rhythm in both lighting conditions in both strains, with no differences in acrophase due to lighting conditions. 3. In both strains, porphyrin levels were highest in the late phase-early dark period and fell during the early part of the dark period. 4. Acid phosphatase activity did not vary with time (circadian rhythm), strain or photoperiodic lighting condition. 5. Circadian rhythms in beta-glucuronidase, alpha-mannosidase and hexosaminidase activity were present in some instances, but, probably due to the low amplitude to these rhythms, a consistent effect of strain or housing condition was not found. When 24-hr rhythms were observed in either strain, the acrophase occurred during the afternoon-early evening daylight period. 6. A significant effect of strain on mean values of type II 5'-deiodinase activity was noted in Fischer-344 rats. 7. Significant rhythms in type II 5'-deiodinase activity were found in both strains exposed to LD 10:14.

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.

Ultrastructure of the blood vessels in the Harderian gland of the hamster (Mesocricetus auratus): existence of sinusoids

The Harderian gland blood supply of female and male hamsters was studied using light and electron microscopy. A profuse vascularization surrounding secretory acini was observed. Among the blood vessels, the existence of large and irregular sinusoidal capillaries was apparent. These sinusoids appeared in close association to the basal aspect of the secretory cells. Typical, small, fenestrated capillaries were also observed within the connective tissue. The existence of this particular vascularization together with other morphological features of the secretory cell basal pole suggest a possible endocrine function of these orbital glands.

Sequential changes in the harderian and exorbital lacrimal glands in Wistar rats infected with sialodacryoadenitis virus

A sequential light and electron microscopic study of the exorbital and Harderian lacrimal glands was done on 2.5- to 15-month-old Wistar rats exposed to sialodacryoadenitis (SDA) virus. Typical coronaviral particles were readily demonstrated in cytoplasmic vesicles of Harderian and exorbital glands examined at 6 days post-inoculation. Lesions were seen in a relatively high percentage of lacrimal glands in infected animals of all ages, with no obvious age-related variations in the incidence and extent of changes. Lesions frequently persisted for a longer interval post-exposure in lacrimal glands than in salivary glands. The persistence of lesions commonly seen in Harderian glands was attributed, at least in part, to the cytotoxic effects of porphyrin-containing secretions released during the acute necrotizing stages of the disease. The persistence of lesions in some lacrimal glands indicates that they are useful tissues for microscopic examination for the retrospective provisional diagnosis of SDA. Persistent lesions also indicate that normal functions of these glands may be compromised for up to several weeks following outbreaks of SDA.