Melatonin ultrastructural localization in mitochondria of human salivary glands

The hormone melatonin was initially believed to be synthesized exclusively by the pineal gland and the enterochromaffin cells, but nowadays its production and distribution were observed in several other tissues and organs. Among others, the ultrastructural localization of melatonin and its receptors has been reported in human salivary glands. In these glands, the fine localization of melatonin in intracellular organelles, above all in mitochondria, remains to be explored comprehensively. Bioptic samples of parotid and submandibular glands were treated to search for melatonin using the immunogold staining method by transmission electron microscopy. Morphometric analysis was applied to micrographs. The results indicated that, both in parotid and submandibular glands mitochondria, a certain melatonin positivity was present. Within glandular cells, melatonin was less retrieved in mitochondria than in secretory granules; however, its presence in this organelle was clearly evident. Inside striated duct cells, melatonin staining in mitochondria was more prominent than in glandular cells. Our data provide an ultrastructural report on the presence of melatonin in mitochondria of human major salivary glands and represent a fundamental prerequisite for a better understanding of the melatonin role in this organelle.     

Overview of Human Salivary Glands: Highlights of Morphology and Developing Processes

Salivary glands are essential organs that produce and secrete saliva to the oral cavity. During gland morphogenesis, many developmental processes involve a series of coordinated movements and reciprocal interactions between the epithelium and mesenchyme that generate the ductal system and the secretory units. Recent studies have shown new findings about salivary gland development, particularly regarding lumen formation and expansion, with the involvement of apoptosis and cell polarization, respectively. Moreover, it has been observed that human minor salivary glands start forming earlier than previously published and that distinct apoptotic mediators can trigger duct lumen opening in humans. This review summarizes updated morphological and cellular features of human salivary glands and also explores new aspects of the human developmental process. Anat Rec, 300:1180–1188, 2017. © 2017 Wiley Periodicals, Inc.     

Estrogen and Insulin Replacement Therapy Modulates the Expression of Insulin‐Like Growth Factor‐I Receptors in the Salivary Glands of Diabetic Mice

Diabetes mellitus results in various complications, also compromising the salivary glands. Hormone levels and interactions with cellular receptors are altered, intensifying the damage caused by this disease. Hormone replacement therapy alone or combined with other treatments may reverse this damage, but doubts still exist regarding the efficacy of this procedure. The objective of this study was to evaluate the effect of estrogen replacement therapy combined with insulin treatment on salivary secretory cells and on the expression of insulin‐like growth factor (IGF)‐I receptors in salivary glands of spontaneously diabetic (NOD) mice. Twenty‐five mice were divided into five groups of five animals each: group I (NOD diabetic), group II (NOD diabetic treated with insulin), group III (NOD diabetic treated with estrogen), group IV (NOD diabetic treated with insulin and estrogen), and group V (control Balb/c mice). Group II received insulin, group III received estrogen, and group IV received insulin plus estrogen administered daily for 20 days. Groups I and V received saline for the same period of time to simulate treatment. Glucose and estrogen levels were monitored during treatment, and salivary gland samples were collected at the end of treatment for stereological analysis and immunofluorescence detection of IGF‐I receptors. Tissue restructuring and regulation of IGF‐I receptors expression were observed in animals submitted to estrogen replacement therapy plus insulin. Estrogen effectively promoted the recovery of salivary secretory cells, demonstrating that this hormone alone, and especially when combined with insulin, might be important for the reversal of hyperglycemia‐induced tissue injury. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.     

Compensatory Increase in Choline Acetyltransferase Activity in Salivary Glands and Diaphragm Muscle of the Rat

When the function of salivary glands was abolished by applying ligatures to their ducts and the function of one half of the diaphragm muscle was abolished by sectioning of its phrenic nerve, the choline acetyltransferase activity was found to be increased in not duct-ligated glands and in the intact hemidiaphragm 4 weeks later. The increase was not seen within the first week. The increase in activity appears to be particularly manifested in the nerve endings, since it was seen in the hemidiaphragm but not in the phrenic nerve. Increased stream of impulses in the efferent nerves is thought to be the cause of this increase in choline acetyltransferase activity.     

电磁场对果蝇唾液腺细胞蛋白质组影响的研究

目的：研究50Hz工频电磁场对果蝇唾液腺细胞蛋白质表达谱的影响。方法：将野生黑腹果蝇置于0．5mT工频电磁场中30min,取唾液腺蛋白质,进行双向凝胶电泳,分析磁场处理组与未经辐射的果蝇唾液腺蛋白质表达差异。结果：对照组3次凝胶的平均蛋白质点数为514。电磁场处理组的3次凝胶的平均蛋白质点数为462。选取所有胶上相互匹配且分辨清楚的蛋白质点进行统计学分析,筛选并鉴定出具有明显差异（Varition〉2．0,P〈0．05）的蛋白质点9个。磁场处理后,果蝇唾液腺组织中的异柠檬酸脱氢酶,VacuolarATPsynthase、果糖二磷酸醛缩酶、肌动蛋白去聚合因子、延伸因子1-α、延伸因子1-β、40S核糖体蛋白、磷酸甘油酸激酶、蛋白质二硫键异构酶表达均升高。结论：电磁场对于果蝇唾液腺作用后,并未产生热休克蛋白。其作用机制区别于热休克反应。电磁场改变果蝇唾液腺细胞膜的通透性与细胞内环境,以此为起点调控细胞内的信号传导,使细胞能量代谢加快,敏感蛋白表达增加,细胞骨架改变。     

Experimental Assessment of Biological Compatibility of Gold Alloys by Functional Indices of Salivary Glands

The effect of implanted gold alloys on composition and rate of excretion of oral fluid was studied on rats. It was found that gold alloy 900 modifies the function of the major salivary glands.     

Electron microscopic immunogold localization of statherin in human minor salivary glands

In this study, which supplements a recent article on the localization of statherin in human major salivary glands, we investigated the intracellular distribution of this peptide in minor salivary glands by immunogold cytochemistry at the electron microscopy level. In the lingual serous glands of von Ebner, gold particles were found in serous granules of all secreting cells, indicating that statherin is released through granule exocytosis. In buccal and labial glands, mostly composed of mucous tubuli, statherin reactivity was detected in the serous element, which represents only a small population of the glandular parenchyma. In these serous cells, however, statherin labeling was absent in secretory granules and restricted to small cytoplasmic vesicles near or partially fused with granules. Vesicle labeling could be related to the occurrence of an alternative secretory pathway for statherin in buccal and labial glands.     

Melatonin release by exocytosis in the rat parotid gland

Several beneficial effects on oral health are ascribed to melatonin. Due to its lipophilic nature, non‐protein‐bound circulating melatonin is usually thought to enter the saliva by passive diffusion through salivary acinar gland cells. Recently, however, using transmission electron microscopy (TEM), melatonin was found in acinar secretory granules of human salivary glands. To test the hypothesis that granular located melatonin is actively discharged into the saliva by exocytosis, i.e. contrary to the general belief, the β‐adrenergic receptor agonist isoprenaline, which causes the degranulation of acinar parotid serous cells, was administered to anaesthetised rats. Sixty minutes after an intravenous bolus injection of isoprenaline (5 mg kg^?1), the right parotid gland was removed; pre‐administration, the left control gland had been removed. Samples were processed to demonstrate melatonin reactivity using the immunogold staining method. Morphometric assessment was made using TEM. Gold particles labelling melatonin appeared to be preferentially associated with secretory granules, occurring in their matrix and at membrane level but, notably, it was also associated with vesicles, mitochondria and nuclei. Twenty‐six per cent of the total granular population (per 100 μm² per cell area) displayed melatonin labelling in the matrix; three‐quarters of this fraction disappeared (P < 0.01) in response to isoprenaline, and melatonin reactivity appeared in dilated lumina. Thus, evidence is provided of an alternative route for melatonin to reach the gland lumen and the oral cavity by active release through exocytosis, a process which is under the influence of parasympathetic and sympathetic nervous activity and is the final event along the so‐called regulated secretory pathway. During its stay in granules, anti‐oxidant melatonin may protect their protein/peptide constituents from damage.     

Morphometric Study of Diabetes Related Alterations in Human Parotid Gland and Comparison with Submandibular Gland

Type 2 diabetes mellitus represents one of the principal diseases that afflict the world population and is often associated with malfunction of salivary glands and consequent oral diseases. We recently described significant ultrastructural alterations in the human submandibular gland in diabetic patients without evident oral pathologies. Herein, an analogs morphometrical investigation was focused on the parotid gland in order to evaluate if one of the two glands is more affected by diabetes. Parotid fragments from diabetic and nondiabetic patients were fixed, dehydrated, and processed for light and electron microscopy. Serous cells were randomly photographed and the density and size of several structures involved in the secretory process were examined by morphometry. Scanning electron microscopy images revealed significant changes in the number of apically docked granules and vesicles, suggesting that the last steps in exocytosis are somehow altered in diabetic cells. Other variables analyzed by light and transmission electron microscopy such as the size of acini and secretory granules did not show significant changes, but comparison with previous data obtained with submandibular gland cells demonstrated that the two glands are affected differently. Anat Rec, 298:1911–1918, 2015. © 2015 Wiley Periodicals, Inc.     

Electron microscopic detection of statherin in secretory granules of human major salivary glands

In order to increase current knowledge regarding statherin secretion into the oral cavity, ultrastructural localization of this peptide was investigated in human salivary glands by using a post-embedding immunogold staining technique. Statherin reactivity was found inside the granules of serous cells of parotid and submandibular glands. In parotid granules immunostaining was preferentially present in the less electron-dense region, whereas in submandibular serous granules the reactivity was uniform and the dense core always stained. By contrast, none or weak reactivity was observed in serous cells of major sublingual glands. These findings reveal for the first time the subcellular localization of statherin by electron transmission microscopy and confirm that of the three major types of salivary glands, the parotid and submandibular glands are the greatest source of salivary statherin. Moreover, they suggest that more than one packaging mechanism may be involved in the storage of statherin within serous granules of salivary glands.     

Modification of Innervation Pattern by Fluoroquinolone Treatment in the Rat Salivary Glands

Fluoroquinolone antibiotics (FQAs) are widely used in dental and medical therapy. Despite their known severe adverse actions on the central and peripheral nervous system, little attention has been directed toward the potential toxic side effects of these compounds on the oral tissues. As the saliva secretion is controlled by the nervous system and neuropeptides, the neurotoxic effect of pefloxacin (PEF), a representative member of FQAs, was studied in rats in the present work. Previously, we demonstrated a significant weight loss of parotid gland tissue, a marked decrease in 3H‐thymidine incorporation, a decreased volume of saliva and amylase activity of the glandular tissue in response to PEF. Animals received intraperitoneal injection of PEF (20 mg/100 g body weight daily) for 3 and 7 days. Normal histology, and neurofilament 200, substance P (SP) and calcitonin gene‐related polypeptide (CGRP) containing nerve fibers were detected with immunohistochemical methods. A marked decrease of the weights in salivary glands and the acinar diameters were measured. Similarly, a strong and significant decrease of the number of SP and CGRP containing nerve fibers were detected. These findings suggest that the impaired morphology and innervation pattern of salivary glands is related to the neurotoxic adverse effect of FQA treatment. Anat Rec, 2010. © 2009 Wiley‐Liss, Inc.     

The Effect of Teeth Amputations on the Choline Aeetyltransferase Activity of Rat Submaxillary Glands

The choline aeetyltransferase activity in parasympathetically decentralized glands was unaffected by repeated teeth amputations over a period of 2 weeks, while after the same period of time the treatment caused the enzyme activity to increase in innervated glands. It appears that the enzyme in the postganglionic nerve is for its activity dependent on an intact connection with the central nervous system. The increase in enzyme activity is attributed to an enhanced reflex stimulation of the glands from pulpal receptors.     

Salivary gland tumours. A review of 2410 cases with particular reference to histological types, site, age and sex distribution

To date the British Salivary Gland Tumour Panel has accumulated 2569 salivary gland tumours. Of these, 2410 were primary epithelial salivary gland tumours and these formed the basis of the present study. The diagnosis of individual tumours was based on the World Health Organisation classification. Tumours were analysed according to histological type, site, age and sex. The principal site was the parotid and the combined minor (oropharyngeal) glands formed the second largest group. Pleomorphic adenomas formed the largest group of tumours in most sites, but were particularly common in the parotid. The frequency of malignant tumours increased with age after the third decade and was maximal in the eighth decade. Malignant tumours were more common in the submandibular and the minor glands than in the parotid. In the sublingual gland six out of seven tumours were malignant.     

三种蚊唾腺蛋白IgE亲和成分的初步分析

从我国分布较广的三种蚊中华按蚊、淡色库蚊和白纹伊蚊中分离出唾液腺 ,制成唾腺蛋白粗提物 ,再应用ELISA、竞争抑制ELISA和免疫印迹试验分析其与IgE结合的组分。结果显示三种蚊唾腺蛋白含能与IgE结合的成分 ,以白纹伊蚊反应所呈现的A值最高 ;免疫印迹在三种蚊均显示 4条阳性带 ,中华按蚊和淡色库蚊相似 ,白纹伊蚊有 3条带差异 ,但其相对分子质量为 30 0 0 0～ 310 0 0组分阳性条带均出现于三种蚊唾腺蛋白     

Histological and Ultrastructural Characterization of Developing Miniature Pig Salivary Glands

Salivary glands are a classic model of organ development and differentiation. Miniature pigs are considered as a unique animal model for salivary gland researchers in the fields of gene transfer, radiation damage, and functional reconstruction. However, there is little information about the development of miniature pig salivary glands. The present article was designed to study the developmental stages of salivary glands in miniature pigs using histological and ultrastructural methods. Sections from E40, E60, E80, E95 embryos, and P0 pups were stained with hematoxylin–eosin, Alcian blue, or periodic acid‐schiff. Selected specimens were also processed for electron microscopy. The development of the miniature pig salivary glands can be divided into five different stages that refer to the stages of the developing mouse submandibular gland. The histological characteristics of the miniature pig salivary glands at different developmental stages were synchronously verified at the ultrastructural level. Interestingly, the development of the miniature pig parotid gland trailed that of the submandibular gland by ～15 days. Our study provides first‐hand data regarding the morphological organogenesis of salivary glands in the miniature pig and provides a foundation for further research on this model. Anat Rec 293:1227–1239, 2010. © 2010 Wiley‐Liss, Inc.     

Cell Death in Salivary Glands of Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae) Females at Semi-engorged Feeding Stage

The ultrastructure of the salivary glands of Rhipicephalus (Boophilus) microplus females is described during feeding. In beginning of feeding, individuals show acini I with many mitochondria and wide basal labyrinth in peripheral cells; glycoprotein granules only in b and c₃ cells (acini II); and epithelial interstitial cells with developed basal labyrinth between f cells (acini III). Semi-engorged females show cells in degeneration, with autophagic vacuoles, lysosomes, myelin figures, and irregular, condensed, and/or fragmented nuclei, in addition to apoptotic bodies. R. B. microplus points to apoptosis in these organs before the detachment from the host, in contrast to others tick species.     

Subcellular distribution of melatonin receptors in human parotid glands

The hormone melatonin influences oral health through a variety of actions, such as anti‐inflammatory, anti‐oxidant, immunomodulatory and antitumour. Many of these melatonin functions are mediated by a family of membrane receptors expressed in the oral epithelium and salivary glands. Using immunoblotting and immunohistochemistry, recent studies have shown that the melatonin membrane receptors, MT1 and MT2, are present in rat and human salivary glands. To date, no investigation has dealt with the ultrastructural distribution of the melatonin receptors. This was the aim of the present study, using the immunogold method applied to the human parotid gland. Reactivity to MT1 and, with less intensity, to MT2 appeared in the secretory granules of acinar cells and in the cytoplasmic vesicles of both acinar and ductal cells. Plasma membranes were also stained, albeit slightly. The peculiar intracytoplasmic distribution of these receptors may indicate that there is an uptake/transport system for melatonin from the circulation into the saliva.     

Serous Cells in the Parotid Glands of Two Species of Tamarins: Polarized Secretory Granules

The parotid glands of two species of tamarins were examined by electron microscopy. Endpiece cells are typical in appearance, with an extensive rough endoplasmic reticulum, prominent Golgi apparatuses, and numerous serous granules. In the saddleback tamarin, the secretory granules contain a dense spherule pressed against the inner aspect of the limiting membrane, leading to a surface bulge. During the course of merocrine secretion (a form of exocytosis), such morphologically polarized granules approach the luminal plasma membranes with the bulge in the vanguard. It is these protuberances that fuse with the plasmalemma. In contrast, although serous granules in the cotton top tamarin contain a spherule, they lack surface bulges and their docking on luminal membranes seems to be a random event with respect to their surface morphology. Moreover, certain other types of cells in a taxonomically wide spectrum of species have granules with a less obvious structural polarity, as well as cells whose granules lack morphological polarity but have a functional polarity that comes into play during exocytosis of such secretory granules. Anat Rec, 291:1254–1261, 2008. © 2008 Wiley‐Liss, Inc.     

Effects of Repeated Administration of Pilocarpine and Isoproterenol on Aquaporin-5 Expression in Rat Salivary Glands

Aquaporins are water channel proteins which enable rapid water movement across the plasma membrane. Aquaporin-5 (AQP5) is the major aquaporin and is expressed on the apical membrane of salivary gland acinar cells. We examined the effects of repeated administration of pilocarpine, a clinically useful stimulant for salivary fluid secretion, and isoproterenol (IPR), a stimulant for salivary protein secretion, on the abundance of AQP5 protein in rat salivary glands by immunofluorescence microscopy and semi-quantitative immunoblotting. Unexpectedly AQP5 was decreased in pilocarpine-administered salivary glands, in which fluid secretion must be highly stimulated, implying that AQP5 might not be required for fluid secretion at least in pilocarpine-administered state. The abundance of AQP5, on the other hand, was found to be significantly increased in IPR-administered submandibular and parotid glands. To address the possible mechanism of the elevation of AQP5 abundance in IPR-administered animals, changes of AQP5 level in fasting animals, in which the exocytotic events are reduced, were examined. AQP5 was found to be decreased in fasting animals as expected. These results suggested that the elevation of cAMP and/or frequent exocytotic events could increase AQP5 protein. AQP5 expression seems to be easily changed by salivary stimulants, although these changes do not always reflect the ability in salivary fluid secretion.