GLP-1 expression in von Ebner's gland of diabetic rats

GLP-1, a peptidergic endocrine hormone, which associate with appetite control, glucose homeostasis and satiety. It might play an important role in the gustatory system. We tried to investigate the expression of GLP-1 in von Ebner's gland of diabetic and control rats, and the ultrastructure changes on von Ebner's gland of diabetes rats. GLP-1 expression in von Ebner's gland was evaluated by immunohistochemistry. The number of GLP-1 positive cells in diabetic rat von Ebner's gland was significantly higher than that in normal controls. Electron micrographs showed that a series of pathologic changes in von Ebner's gland of diabetes rats. The results suggest that GLP-1 have some effects within the gustatory systems, and elevated von Ebner's gland GLP-1 expression may be one cause of diabetic taste impairment.     

Morphologic diversity of the minor salivary glands of the rat: fertile ground for studies in gene function and proteomics

In this article the locations and histologic and ultrastructural features of all of the minor salivary glands of the rat are presented; similarities and differences among them are highlighted. These glands are almost as diverse morphologically as the major salivary glands of the rat. The acini of von Ebner's glands are serous; those of the anterior and posterior buccal glands and minor sublingual glands are mucous; and those of the glossopalatal, palatal, and Weber's glands are mucous with serous demilunes. The anterior buccal, minor sublingual and von Ebner's glands have striated and stratified columnar ducts, while only the minor sublingual and von Ebner's glands have intercalated ducts. The glossopalatal, palatal, posterior buccal and Weber's glands have none of these ducts; the tubulo-acini drain abruptly into short terminal ducts composed of stratified squamous epithelium. All of the mucous acini react with an antibody to a mucin (Muc19) of the rat major sublingual gland, but in some of the glands the reaction varies in intensity among the acinar cells. Ultrastructurally, the mucous secretory granules of the anterior buccal, glossopalatal, palatal and Weber's glands are biphasic, while those of the minor sublingual and posterior buccal glands are monophasic. Although there is a considerable body of literature concerning the development, innervation, physiology and proteomics of von Ebner's glands, investigation of the other minor salivary glands of the rat ranges from modest to nearly nonexistent.     

Postnatal development of von Ebner's glands: accumulation of a protein of the lipocalin superfamily in taste papillae of rat tongue

Summary Antibodies produced against rat von Ebner's gland (VEG) protein, a recently characterized member of a lipophilic ligand carrier protein family, detect this protein immunocytochemically in von Ebner's gland acini and show that it is present at high concentrations in the clefts of circumvallate and foliate papillae. During embryonic development, von Ebner's gland anlagen are innervated (as shown immunocytochemically using neuronal specific antibodies) as early as embryonic day 20, before lateral glandular outgrowth and VEG protein can be observed. Expression of the VEG protein as determined by in sity hybridization and immunocytochemistry begins at postnatal day-2 cells in differentiating and branching off from von Ebner's gland ducts, and sharply increases with further enlargement and maturation of the gland. The close temporal correlation of von Ebner's gland innervation and VEG protein expression with papilla innervation and taste-bud development suggests a functional relationship of both structures. VEG protein might control access of lipophilic sapid molecules, such as bitter substances, to the gustatory receptors.     

Secretions of von Ebner's glands influence responses from taste buds in rat circumvallate papilla

The influence of secretions from von Ebner's lingual salivaryglands on gustatory function was studied in the rat. Neurophysiologicaltaste responses elicited by chemical stimulation of the circumvallatepapilla were recorded from the glossopharyngeal nerve whileinitiating salivary secretion in the same papilla. Salivarysecretion from von Ebner's glands significantly reduced tasteresponses to stimulation of the circumvallate papilla with variouschemicals. However, the magnitude of the reduction in responsediffered depending on the taste stimulus used. The reductionin response due to salivary secretion was blocked by prior administrationof the parasympathetic antagonist, atropine. These results demonstratea direct effect of salivary secretion on taste responses andillustrate the close relationship between taste function andthe secretion of von Ebner's glands.     

Secretion of carbonic anhydrase isoenzyme VI (CA VI) from human and rat lingual serous von Ebner's glands.

Salivary carbonic anhydrase VI (CA VI) appears to contribute to taste function by protecting taste receptor cells (TRCs) from apoptosis. The serous von Ebner's glands locating in the posterior tongue deliver their saliva into the bottom of the trenches surrounding the TRC-rich circumvallate and foliate papillae. Because these glands deliver their saliva directly into the immediate vicinity of TRCs, we investigated whether CA VI is secreted by the von Ebner's glands, using immunochemical techniques. The immunohistochemical results showed that CA VI is present in the serous acinar cells, ductal cells, and ductal content of von Ebner's glands and in the demilune and ductal cells plus ductal content of rat lingual mucous glands. More importantly, CA VI was also detected in taste buds and in the taste pores. Western blotting of saliva collected from the orifices of human von Ebner's glands and CAs purified from rat von Ebner's glands confirmed that CA VI is expressed in these glands and secreted to the bottom of the trenches surrounding the circumvallate and foliate papillae. These findings are consistent with the hypothesis that locally secreted CA VI is implicated in the paracrine modulation of taste function and TRC apoptosis. (J Histochem Cytochem 49:657-662, 2001)     

Neuromodulators of the lingual von Ebner gland: an immunocytochemical study.

The serous lingual glands of von Ebner secrete lingual lipase, an enzyme that begins fat digestion in the stomach. The objective of this study was to characterize the neuromodulators in the rat tongue and von Ebner glands using immunocytochemical techniques. Rat lingual tissues were fixed in formalin, embedded in paraffin and sectioned at 4 microns for light microscopic studies. Immunocytochemical localization of neuromodulators was performed with monospecific anti-rat neuromodulator IgG or control (preimmune) IgG as the primary antibody, using the peroxidase-antiperoxidase (PAP) technique. No staining was seen with control anti-rat IgG. Immunospecific staining for vasoactive intestinal peptide (VIP), tyrosine hydroxylase and choline acetyltransferase (CHAT) was observed in nerves in the tongue, and cells containing immunospecific staining for serotonin (5-hydroxytryptamine) were seen in the stroma between the lingual glands. Selected cells in the serous glands stained positively for the presence of substance P and somatostatin. Adrenergic, VIP-containing and cholinergic nerves appear to innervate the tongue and serous glands. Substance P and somatostatin were identified in cells of the lingual serous glands and may be additional local modulators regulating lingual lipase release.     

Histochemical Phenotypes of Von Ebner's Gland of Ferret and their Functional Implications

Von Ebner's gland of ferret was examined by means of light microscopy, protein, mucosubstance and enzyme histochemistry, and neurohistology. Acinar cells were replete with granules containing neutral mucosubstances and disulphides, and showed strong diffuse acid phosphatase activity and weak granular staining for peroxidase. Staining for cytochrome oxidase, succinate dehydrogenase, and NADH and NAD(P)H dehydrogenases was also seen. Basolateral plasmalemma of acinar cells showed weak, ouabain-sensitive Na⁺,K⁺-ATPase activity. Ductal cells were of a simple appearance, contained thiols and showed variable staining for acid phosphatase, dehydrogenases and cytochrome oxidase. Variable amounts of β-glucuronidase reaction product were localized in the glandular parenchyma, being marked in atrophic areas. Prominent stellate myoepithelial cells embracing acini and also basal ductal cells were demonstrated by alkaline phosphatase. Thiamine pyrophosphatase reaction product was concentrated in blood vessels around parenchyma, with little Golgi-like staining in acinar cells. Acetylcholinesterase activity was associated with an extensive network of nerve fibres embracing parenchyma, whereas catecholamine fluorescence was not seen. The results suggest that the acini of von Ebner's gland of ferret synthesise neutral secretory glycoproteins and peroxidase. Water mobilization is inconspicuous. Lysosomal activities feature in the parenchyma, possibly a consequence of processing secretory products in acini, absorption in ducts and/or adaptation atrophy. The gland receives a rich cholinergic-type innervation, and has extensive myoepithelial and microvascularbreak networks.     

Lipolytic and esterolytic activities in posterior lingual glands of rat: a histochemical study

Catalytic activities of lingual lipase were investigated by enzyme histochemistry in post-mortem tongues from male rats. Sections of fresh-frozen or formalin-calcium fixed tissue were incubated with naphthol-AS-nonanoate and alpha-naphthyl acetate substrate mixtures. The effects of pH level, sodium taurocholate activator and E600 inhibitor were also examined. The use of cryostat sections of tissues fixed in formalin-calcium and of nonanoate substrate within the range of pH 4.4-6.4, were optimal for localizing maximum reaction product, captured by Fast Blue BB, in acini and demilunes of the posterior deep and superficial lingual glands respectively. The reaction product corresponded with the distribution of secretory granules and failed to develop when taurocholate was omitted from the incubation medium. Similarly localized E600-resistant reaction product occurred with the acetate substrate and hexazotized New Fuchsin at pH 7.4, in the absence of taurocholate. Lipase and conventional esterase activities appear to be superimposed in posterior lingual glands of rat. The ability of their acini and demilunes to hydrolyse nonanoate substrate at an acidic pH optimum, when activated by sodium taurocholate, seems attributable to lipase destined for secretion into saliva--hence convenient for routine histochemical identification of the enzyme.     

Neuromodulators of the lingual von Ebner gland: an immunocytochemical study

Summary The serous lingual glands of von Ebner secrete lingual lipase, an enzyme that begins fat digestion in the stomach. The objective of this study was to characterize the neuromodulators in the rat tongue and von Ebner glands using immunocytochemical techniques. Rat lingual tissues were fixed in formalin, embedded in paraffin and sectioned at 4 m for light microscopic studies. Immunocytochemical localization of neuromodulators was performed with monospecific anti-rat neuromodulator IgG or control (preimmune) IgG as the primary antibody, using the peroxidase-antiperoxidase (PAP) technique. No staining was seen with control antirat IgG. Immunospecific staining for vasoactive intestinal peptide (VIP), tyrosine hydroxylase and choline acetyltransferase (CHAT) was observed in nerves in the tongue, and cells containing immunospecific staining for serotonin (5-hydroxytryptamine) were seen in the stroma between the lingual glands. Selected cells in the serous glands stained positively for the presence of substance P and somatostatin. Adrenergic, VIP-containing and cholinergic nerves appear to innervate the tongue and serous glands. Substance P and somatostatin were identified in cells of the lingual serous glands and may be additional local modulators regulating lingual lipase release.     

Lipolytic and Esterolytic Activities in Posterior Lingual Glands of Rat: A Histochemical Study

Catalytic activities of lingual lipase were investigated by enzyme histochemistry in post-mortem tongues from male rats. Sections of fresh-frozen or formalin-calcium fixed tissue were incubated with naphthol-AS-nonanoate and α-naphthyl acetate substrate mixtures. The effects of pH level, sodium taurocholate activator and E600 inhibitor were also examined. The use of cryostat sections of tissues fixed in formalin-calcium and of nonanoate substrate within the range of pH 4.4–6.4, were optimal for localizing maximum reaction product, captured by Fast Blue BB, in acini and demilunes of the posterior deep and superficial lingual glands respectively. The reaction product corresponded with the distribution of secretory granules and failed to develop when taurocholate was omitted from the incubation medium. Similarly localized E600-resistant reaction product occurred with the acetate substrate and hexazotized New Fuchsin at pH 7.4, in the absence of taurocholate. Lipase and conventional esterase activities appear to be superimposed in posterior lingual glands of rat. The ability of their acini and demilunes to hydrolyse nonanoate substrate at an acidic pH optimum, when activated by sodium taurocholate, seems attributable to lipase destined for secretion into saliva – hence convenient for routine histochemical identification of the enzyme.     

Development of secretory activity in serous cells of the rat tongue. Cytological differentiation and accumulation of lingual lipase

The development of the serous cells of the rat tongue was studied by light and electron microscopy and compared with the accumulation of lingual lipase, measured by triglyceride hydrolysis at pH 5.4. The lingual serous (von Ebner's) glands were initiated in 19- to 20-day fetuses as epithelial ingrowths from the vallate and foliate papillae. The cells contained mostly free polyribosomes, few RER cisternae, and a small Golgi apparatus. Branching of the cell cords began shortly after initiation, but formation of acini and production of secretory granules did not begin until 3–4 days postnatally. The acinar cells had abundant basal RER, a supranuclear Golgi apparatus, and apical secretory granules and attained adult appearance by 17–25 days. The serous demilune cells of the lingual mucous glands differentiated more rapidly than the lingual serous acinar cells, attaining functional secretory structure in Day 20 fetuses. Lipase activity was first detected in Day 20 fetuses and increased 14-fold by birth. The activity decreased 50% during the first suckling period, returned to birth levels 1 day later, and increased rapidly thereafter. By 17 days postnatally, lipase activity was 23% of the adult level, although activity per gram body weight was equal to the adult. The results suggest that lingual lipase is produced prenatally by the demilune cells of the lingual mucous glands and postnatally predominately by the lingual serous glands. Lingual lipase may play an important role in lipid digestion in neonates, when levels of pancreatic lipase are low.     

Developmental delay of lingual lipase expression after guanethidine-induced sympathectomy.

Rat lingual lipase increases during postnatal development. To evaluate the role of the sympathetic nervous system in the control of lingual lipase during development, suckling rats were chemically sympathectomized by chronic treatment with guanethidine. This treatment was found to be effective in suppressing the developmental increase of lingual lipase. The effect was age dependent and also related to the dose of guanethidine given (i.e., the higher the dose, the more effective the suppression is, up to 40 micrograms/g body wt). The effect of guanethidine on lingual lipase suppression was not a result of induced stress, since simultaneous treatment with RU-38486, a known glucocorticoid receptor antagonist, did not prevent the decrease in lingual lipase activity. Ephedrine, a known sympathomimetic agent, restored the lingual lipase to a near normal level in guanethidine-treated animals, confirming that guanethidine acts through the sympathetic nerves. Furthermore, histochemical studies showed that guanethidine-treatment resulted in the reduction or elimination of catecholaminergic fibers in the von Ebner's glands. The effect of guanethidine was found to be transient, in that the lingual lipase activity showed complete recovery upon withdrawal of the treatment for 1 week. Together, the results indicated that sympathetic nerves have an important regulatory role in lingual lipase in rat pups during development.     

Porcine VEG Proteins and Tear Prealbumins

Small soluble proteins, belonging to the lipocalin family aresecreted in large amounts by tongue von Ebner's glands and lachrymalglands. In humans, the lingual protein, called VEG, and thelachrymal protein, called tear prealbumin, have shown identicalcDNA sequences. In the pig, we have purified homodimeric proteinswith subunits of 17 kDa, both from von Ebner's glands and fromlachrymal glands. In both cases, the proteins can be resolvedinto two isoforms on a chromatofocusing column. Partial aminoacidsequences and full cDNA sequences have been obtained for themore abundant forms purified from both tissues. The two proteinsappear to be identical, as in humans. The reason why the sameprotein is expressed in different tissues, as well as its physiologicalfunction, still remain to be clarified.     

Antioxidant enzymatic defense in salivary glands of streptozotocin‐induced diabetic rats: a temporal study

Hyperglycemia induces overproduction of superoxide and it is related to diabetic complications. In this study, we analyzed the antioxidant enzymatic defense and the lipid peroxidation of rat salivary glands in six different periods of diabetic condition. Ninety‐six rats were divided into 12 groups: C7/14/21/28/45/60 (non‐diabetic animals) and D7/14/21/28/45/60 (diabetic animals). Diabetes was induced by streptozotocin and the rats were euthanized after 7, 14, 21, 28, 45, or 60 days. Their parotid (PA) and submandibular (SM) glands were removed soon after the sacrifice and the total protein and malondialdehyde (MDA) concentrations, as well as, the superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities were determined. Twenty‐one days after the diabetes induction, the SM glands showed an increase in SOD, CAT, and GPx activities, as well as, MDA concentration. Concerning the PA glands, an increase in the CAT activity and MDA content was observed throughout the observation period. The results suggest that diabetes can cause alterations on the salivary glands and that PA and SM glands react differently when exposed to diabetes condition. However, no impairment of antioxidant system was observed in the group whose diabetic condition had been induced 60 days earlier, herein named 60‐day group. Copyright © 2010 John Wiley & Sons, Ltd.     

Lactose synthetase activities in rat and mouse mammary glands

The activities of lactose synthetase (in the presence and absence of α-lactalbumin), galactosyltransferase and α-lactalbumin levels were determined in rat and mouse mammary glands during pregnancy, lactation and involution. In the rat, essentially none of the above activities were detected prior to parturition. This was followed by a sharp increase with the maximum occurring during late lactation and then by a rapid drop during involution. In the mouse, detectable levels of all the activities occurred at 15 days of pregnancy and these levels increased during pregnancy and reached a maximum level during early lactation and again sharp decreases occurred during involution. The study shows that mammary gland development occurs at an earlier date in the mouse than in the rat.     

The human submandibular gland: immunohistochemical analysis of SNAREs and cytoskeletal proteins

Submandibular acinar glands secrete numerous proteins such as digestive enzymes and defense proteins on the basis of the exocrine secretion mode. Exocytosis is a complex process, including a soluble NSF attachment protein receptor (SNARE)-mediated membrane fusion of vesicles and target membrane and the additional activation of cytoskeletal proteins. Relevant data are available predominantly for animal salivary glands, especially of the rat parotid acinar cells. The authors investigated the secretory molecular machinery of acinar (serous) cells in the human submandibular gland by immunohistochemistry and immunofluorescence and found diverse proteins associated with exocytosis for the first time. SNAP-23, syntaxin-2, syntaxin-4, and VAMP-2 were localized at the luminal plasma membrane; syntaxin-2 and septin-2 were expressed in vesicles in the cytoplasm. Double staining of syntaxin-2 and septin-2 revealed a colocalization on the same vesicles. Lactoferrin and α-amylase served as a marker for secretory vesicles and were labeled positively together with syntaxin-2 and septin-2 in double-staining procedures. Cytoskeletal components such as actin, myosin II, cofilin, and profilin are concentrated at the apical plasma membrane of acinar submandibular glands. These observations complement the understanding of the complex exocytosis mechanisms.     

Histology and ultrastructure of the caudal courtship glands of the red‐backed salamander,Plethodon cinereus (Amphibia: Plethodontidae)

Caudal courtship glands (CCGs) are sexually dimorphic glands described in the skin of the dorsal tail base of some male salamanders in the genera Desmognathus, Eurycea, and Plethodon in the family Plethodontidae. These glands are believed to deliver pheromones to females during courtship, when the female rests her chin on the dorsal tail base during the stereotypic tail straddling walk unique to plethodontids. Although CCGs have been studied histologically, no investigations of their ultrastructure have been made. This article presents the first study on the fine structure and seasonal variation of CCGs, using the plethodontid Plethodon cinereus. The CCGs vary seasonally in height and secretory activity. The mature secretory granules observed in males collected in October and April consist of oval, biphasic granules that are eosinophilic and give positive reactions to periodic acid‐Schiff for neutral carbohydrates but do not stain for acidic mucosusbtances or proteins with alcian blue and bromphenol blue, respectively. Granular glands, some of which contain mucous demilunes, are twice as large as CCGs, are syncytial (unlike CCGs), and stain for proteins. Mucous glands are similar in size to CCGs, but are basophilic, show no seasonal variation in secretory activity, and stain positive for acidic mucosubstances. CCGs do not resemble cytologically the sexually dimorphic mental glands of some plethodontids, which contain round or oval granules filled with an electron‐dense amorphous substance. The CCGs are similar histologically to sexually dimorphic skin glands described in some anurans, but more comparative work is needed. J. Morphol. 276:319–330, 2015. © 2014 Wiley Periodicals, Inc.