To demonstrate by SEM the topography and cytoarchitecture of the different parenchymal components of human salivary glands, we have employed a number of techniques that allow either the exposure of internal and lateral cell surfaces or, following the removal of connective tissue, the visualization of endpieces, ducts, and myoepithelial cells. Serous glands consist of indented acini attached to the ducts in a grape-like fashion, whereas mucous and mixed glands are made up of smooth tubuli. Myoepithelial cells (mecs), which are abundant on the surfaces of acini, tubuli, and intercalated ducts, are sparse on striated ducts. They are star-shaped on acini, striated ducts, and most of the tubuli. Spindle-shaped mecs are seen, instead, on intercalated ducts and, occasionally, on mucous and mixed tubuli as well. Cells of striated ducts split into a number of large basal portions whose surface is covered by long laminated processes responsible for the striations seen with TEM. Excretory ducts are lined by small cup-shaped basal cells and by tall cylindrical cells, which are completely covered by short processes oriented at random. When observed from below, after removal of the basal lamina, the basal surfaces of cells of excretory ducts exhibit polygonal areas delimited by short reliefs. Those of striated ducts show, instead, long laminar processes arranged radially. Results presented here are discussed and put in relationship to the mechanism of saliva production.
Oral Diseases (2011) 17, 217–220 Background and Objectives: Statherin is a salivary protein involved in the formation of enamel pellicle and in regulation of calcium homeostasis. Diabetes and other pathologies affect both salivary flow and protein secretion by salivary glands, causing increased susceptibility to mucosal infections, tooth demineralization, and caries. The purpose of this study was to compare the statherin expression in submandibular glands of healthy and diabetic subjects. Materials and Methods: Fragments of submandibular glands obtained from diabetic and non diabetic patients were fixed, dehydrated, embedded in Epon Resin and processed for the immunogold histochemistry. The results were statistically evaluated. Results: Specific statherin labeling was demonstrated in secretory granules of acinar cells in both diabetic and normal samples. The staining was much more intense in the latter compared to those of diabetics. The labeling density was quantified by evaluating the number and spatial distribution of gold particles within the granules. The number of gold particles was significantly lower in glands from diabetics than in control glands. Conclusions: The results obtained suggest that a reduced statherin secretion by salivary glands might be partly responsible for a less effective protection of the oral tissues, resulting in an higher incidence of caries and oral infections associated with diabetes.
Salivary secretion is principally regulated by autonomic nerves. However, recent evidence from in vivo animal experiments suggests that gastrointestinal peptide hormones can also influence saliva production. The aim of the present study was to define the secretagogue activity of the gastrin-analogue pentagastrin in human salivary glands. For this purpose, parotid tissues were exposed to pentagastrin in vitro. Morphological techniques were used to evaluate modifications to serous acinar cells associated with secretion. Using a variant of the osmium maceration method, high resolution scanning electron microscopy allowed assessment of the morphology of the cytoplasmic aspect of the plasmalemma to demonstrate secretory activity. To quantify responses to pentagastrin, we recorded morphometric data on microvilli, microbuds, and protrusions. Dose-dependent morphological changes were observed, whereas protein concentration increased in the incubate. The use of selective receptor antagonists showed pentagastrin to act principally via cholecystokinin-A receptors. The morphological responses observed following exposure to pentagastrin differed from those elicited following exposure to the pan-muscarinic agonist carbachol. This study provides the first demonstration of a direct secretory action of gastrointestinal peptides on salivary glands in humans.
In all samples, statherin reactivity was specifically localized in secretory granules of acinar cells. The statistical analysis showed that labelling density was significantly lower in diabetic than in non-diabetic parotid glands and that diabetes affects protein expression at identical extent in parotid and submandibular glands. The results strengthen the hypothesis that a reduced statherin secretion may be responsible for the higher incidence of oral disorders in diabetic subjects.
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