A histochemical study of catecholamines and cholinesterases in the autonomic nerves of the human minor salivary glands

Synopsis The cholinergic and adrenergic innervation of human minor sublingual buccal and labial salivary glands has been studied with histochemical techniques for localizing acetylcholinesterase and catecholamines. A rich cholinergic innervation was observed around the acini, blood vessels and some ducts of the three glands.The adrenrgic innervation, however, was virtually absent from the parenchyma although present around the blood vessels, in marked contrast to the dense parenchymal adrenergic innervation observed in the human parotid and submandibular glands. These results suggest that the autonomic nervous mechanism which regulates salivary secretion is more elaborate in the major than in the minor salivary glands.     

Diagnosis of sarcoidosis by lip biopsy of minor salivary glands

In two patients with bilateral parotid gland swelling of unknown etiology the diagnosis of sarcoidosis was established by lip biopsy of the minor salivary glands. This simple, innocuous biopsy procedure may prove useful in tissue documentation of sarcoidosis.     

A freeze-fracture study of adultCalliphora salivary glands

A freeze-fracture study of adult Calliphora salivary glands has revealed a high density (approx. 4500/mu2) of intramembraneous particles (80-110 A) in both the apical and basal membranes. Most of the particles were associated with the A face. The density of the stalked surface particles which coat the cytoplasmic surface of the apical membrane. The possible significance of these particles in ion transport is discussed.     

On the myoepithelium of human salivary glands. An immunocytochemical study

This study investigated the immunocytochemical characteristics of normal myoepithelial cells (MECs) of human major and minor salivary glands using the LSAB method. Other human exocrine glands were used as controls. Immunoreactivity of MECs was observed exclusively with fully differentiated smooth muscle antibodies (a-SMA; SMMS-1; CALP; hCD) and with epithelial markers (cytokeratins) Ck14 and Ck17. This epithelial-muscular immunophenotype was similarly expressed in the MECs of other human exocrine glands used as control. In the salivary MECs, we did not observe evidence for neuroectodermic phenotype (S-100 protein, GFAP, NSE). On the contrary, positivity was observed for S-100 protein in Mecs of control glands (mammary, bronchial and sweat glands). Immunoreaction for extracellular matrix markers (fibronectin, laminin and collagen IV) and vimentin always were negative. Our data show that in normal "non transformed" MECs of the salivary glands the smooth muscle phenotype is in a state of complete differentiation, while the epithelial phenotype expresses only Ck14 and Ck17. This double and simultaneous immunoreactivity represents a differential marker of MECs from the epithelial basal cell (EBCs).     

Defects and rescue of the minor salivary glands in Eda pathway mutants

Despite their importance to oral health, the mechanisms of minor salivary gland (SG) development are largely unexplored. Here we present in vivo and in vitro analyses of developing minor SGs in wild type and mutant mice. Eda, Shh and Fgf signalling pathway genes are expressed in these glands from an early stage of development. Developing minor SGs are absent in Eda pathway mutant embryos, and these mice exhibit a dysplastic circumvallate papilla with disrupted Shh expression. Supplementation of Eda pathway mutant minor SG explants with recombinant EDA rescues minor SG induction. Supplementation with Fgf8 or Shh, previously reported targets of Eda signalling, leads to induction of gland like structures in a few cases, but these fail to develop into minor SGs.     

Distribution of lactoferrin in human salivary glands

Summary An immunoperoxidase technique was used to study the distribution of lactoferrin (LF) in human salivary glands from autopsy tissues fixed in Carnoy's fluid for the optimal preservation of LF antigenicity. Specific LF staining was seen in the intralobular ducts of all salivary glands but never in the interlobular ducts; acinar LF was detected in most serous demilunes of the mixed glands and in some but not all acinar cells of the pure serous glands. No LF was detected in the acinar cells of the pure mucous glands. In the oral tissues studied the only additional cells containing LF were polymorphonuclear leucocytes. Whether LF in the salivary glands is synthesized locally and/or ultrafiltrated from the blood is at present unclear. Present evidence indicates that the biological role of salivary LF is antibacterial.Studies supported by grants from the Sigrid Jusélius Foundation and Finska Läkaresällskapet     

Cyclic AMP-receptor proteins in human salivary glands

In mammalian species, cyclic AMP receptor proteins (cARP) are the regulatory (R) subunits of cyclic AMP-dependent protein kinase (PKA), the cellular effector of cyclic AMP-mediated signal transduction. An isoform of the PKA type II R subunit (RII), cARP, is a polyfunctional protein, present in most tissues and cells. It is expressed in salivary and other glands of rodents, and secreted into the saliva of rats and Man. The aim of the present study was to determine the expression of cARP in human salivary glands using immunoelectron microscopy. Thin sections of normal salivary glands embedded in LR Gold resin were labeled with anti-cARP primary antibody, then with gold-conjugated secondary antibody. Labeling was present in the secretory granules and cytoplasm of parotid, submandibular (SMG) and sublingual gland serous cells. Quantitative analysis showed considerable variability in granule labeling from sample to sample, indicating shifts in expression and cellular location of cARP. Unlike rodent salivary glands, the granules of intercalated and striated duct cells also were labeled. The cytoplasm and granules of mucous cells of the SMG and sublingual glands were unlabeled, while the Golgi complex and filamentous bodies in these cells showed moderate reactivity. Mitochondria and nuclei of both serous and mucous cells were unlabeled. Labeling also was present in the connective tissue adjacent to the epithelial cells. The results indicate that serous cells of the parotid and SMG are the major source of salivary cARP. They also reveal significant species differences in the glandular distribution of RII. RII binds to cytoskeletal and nuclear proteins, and may function to regulate extracellular cyclic AMP levels. Thus, the tissue and cellular distribution of RII may serve as an index of regulation of gene expression and cell differentiation.     

Morphofunctional studies on human labial salivary glands

In this study, the first experimental investigation carried out at the ultrastructural level on mucous cells of human salivary glands, we have examined by light microscopy (LM), transmission electron microscopy (TEM), high resolution scanning electron microscopy (HRSEM), the secretory response of labial glands stimulated in vitro by the beta-adrenergic agent, D,L isoproterenol, and by the muscarinic agent carbachol. For comparison we have used identical methods to study samples of mixed portions of human submandibular glands. Morphological findings obtained here on both submandibular and labial glands mucous cells demonstrate that mucous droplets are released solely by muscarinic stimulation, and that cytological events occurring during secretory discharge are similar to those described by others, using TEM, on stimulated mucous cells of rat sublingual glands. Despite the fact that human labial glands are said to have a prominent cholinergic innervation with scanty adrenergic nerves, the response of seromucous cells in these organs to stimulation with carbachol and with isoproterenol was similar to that observed by us, (using LM, TEM and HRSEM), in serous cells of human major salivary glands.     

Integrin expression in developing human salivary glands

The development and complete differentiation of salivary glands is a complex process that involves a large number of co-ordinated events. Little is known about the molecular basis for salivary gland development. However, we have reported previously that integrins appear to play a role. Integrins are heterodimeric transmembrane receptors consisting of one α and one β subunit that play a pivotal role in the interaction of cells with the extracellular matrix. Such interactions regulate the organisation of cells of tissues and organs during development as well as cell proliferation and differentiation. Using immunohistochemistry and Western and Northern blot analysis, we mapped the localisation and expression of integrins β1, β3 and β4 in human salivary glands obtained from foetuses ranging from weeks 4–24 of gestation and compared it with adult salivary glands. Integrin β1 first appeared during the canalisation stage and during the differentiation stage. A message first appeared at week 6 of development. The expression of β4 integrin protein and message was observed only in the late stage of differentiation. Integrin β3 was not detected in the developing glands; however, integrins β1, β3 and β4 were all expressed in adult salivary gland tissues. The data suggest that integrins, particularly β1, have a role to play in salivary gland development and differentiation.     

Nitric oxide synthase in human salivary glands

The distribution of the three nitric oxide synthase (NOS) isoforms was determined immunohistochemically in the human minor and major salivary glands with comparison to that of rat salivary glands. In contrast to rat glands, which contained a dense plexus of neuronal NOS-immunoreactive nerve fibers, only a minority of the nerve fibers in human glands showed neuronal NOS immunoreactivity. Human labial and submandibular glands contained sparse NOS-immunoreactive fibers, while only occasional nerve fibers in the parotid or sublingual glands were stained. Furthermore, in contrast to the animal glands, most duct epithelial cells in all human salivary glands were immunoreactive for neuronal NOS. No specific immunoreactivity for inducible or endothelial NOS were observed in the nerve fibers or duct epithelium. We provide evidence to suggest that the role of nitric oxide in the regulation of salivary gland function is different in human as compared to experimental animals. Nitricergic innervation in human tissue is very sparse and thus nitric oxide is probably of minor importance as a neural regulator of salivary glands. Instead, NOS localized in duct epithelial cells suggests that nitric oxide might directly regulate saliva secretion and it is a putative source of nitrates previously reportedly secreted into the saliva.     

Ultrastructure of the human submandibular salivary glands]

By means of electron microscopy cells in the human submandibular glands were studied. It was demonstrated that in acini two types of glandular cells were present: mucosal and seromucosal. In the latter, secretory granules are descrete with electron opaque cores in most of them. Mucocytes are filled with an electron transparent secrete; secretory granules often confluent and their membranes rupture. The acini are surrounded with myoepithelial cells. Intercalated ducts consist of cells with moderately electron opaque granules. In some granules there are dense bodies excentrically situated. In these cells there occur lipid inclusions. Striated ducts are composed of basal (electron transparent) and high cylindric (light and dark) cells. The cylindrical cells have a large amount of mitochondria, deep folds in their basal plasmolemma protruding into cytoplasma. Most of the cells in these parts contain small apically accumulated secretory granules with a dense matrix and separate larger ones scattered in the cell. It is possible to suggest that some secretory granules of ductal or, perhaps, acinar origin contain hormonal products.     

Distinct expression of calnexin in major human salivary glands

Calnexin (Cnx) has been characterized as a membrane-bound protein that transiently interacts in a unique chaperone system with newly synthesized glycoproteins in order to allow the establishment of their proper tertiary and, in most cases, quarternary structures. The aim of the study was to identify and to locate the expression of Cnx in the three major salivary glands of humans by different methods. Strong expression of Cnx protein and mRNA were generally found in serous salivary secretory units. With regard to mucous secretory units, expression of Cnx was only detectable at a low level in mucous acinar cells of sublingual glands, but not of submandibular glands. Expression of Cnx was always preserved in the surface epithelium of intralobar and interlobular duct segments. In addition, expression of Cnx was detected in sebaceous glands of parotid tissues, with a distribution pattern resembling that seen in sebaceous glands of the normal skin. In conclusion, production of saliva is associated with the expression of Cnx. Synthesis of molecules in mucous secretory units is not necessarily associated with a strong Cnx expression, whereas synthesis in serous secretory units apparently is. The tissue-specific Cnx expression is also paralleled by the observation that the secretions produced by the major salivary glands differ in their composition and amount.     

Magainin-like immunoreactivity in human submandibular and labial salivary glands

Magainins, antimicrobial peptides secreted by granular glands of frog skin, may be related to the high resistance to infections of this epithelial surface. The oral mucosa of healthy individuals is another tissue in which infection is not frequent, probably owing to the activity of potent salivary and mucosal defense mechanisms. To investigate if magainin-like factors are a component of these oral defense mechanisms, human and animal minor (mucosal) and major salivary glands were examined by immunohistochemistry, using a polyclonal rabbit anti-magainin antibody. Cryostat sections of (para) formaldehyde-fixed tissues were incubated with the antibody and then stained with fluorescein-complexed anti-rabbit IgG. Specific staining was observed in the apical portion of the cytoplasm of ductal epithelial cells of human submandibular and labial salivary glands. Diffuse staining was present in submandibular acinar cells. Bovine, rat, hamster, and mouse tissues were unreactive. The presence of magainin-like substances in human salivary gland duct cells is consistent with reports of the occurrence of other biologically active substances in salivary gland ducts.     

Quantitative histoenzymologic characteristics of the human submandibular salivary glands]

Quantitative activity of oxidative-reductive and hydrolytic enzymes obtained during operation was investigated in different parts of the human submandibular salivary glands. Quantitative estimation of enzymic activity was done by photometry of the negatives prepared on MY-phi-6. Comparative examination of enzymatic activity made it possible to state that according to the peculiarities of metabolic processes, the cells of striated and intralobular secreting ducts are similar to the cells of the secreting terminal parts. A high activity of NADP-diaphorase, G-6-PhDG and acid phosphatase in the epithelium of the secreting ducts, and parallelism, stated between histoenzymatic and morphologic criteria of functional activity proved the participation of these structural-functional units in secret-producing processes. A high activity of NAK-diaphorase, LDG and acid phosphatase in all the parts and in the secreting ducts system, in particular, ensures, besides the processes of protein secret formation, an active transport of natrium and potassium, formation of final saliva and its discharge.     

Immunohistochemical localization of kallikrein in human pancreas and salivary glands

The localization of kallikrein in human exocrine organs was studied with a direct immunofluorescence method. In the submandibular and parotid salivary glands, kallikrein was found apically in the striated duct cells whereas it was absent from the main excretory ducts or present only as a weak luminal rim. Kallikrein was not found in the acinar cells or in cells of the intercalated ducts. In the pancreas, kallikrein-specific fluorescence was seen in the granular portion of the acinar cells, whereas the islets of Langerhans and ductal cells were unstained.