Origin of acinar cell regeneration after atrophy of the rat parotid induced by duct obstruction

Acinar cell regeneration in the rat parotid gland after atrophy induced by a one week period of duct obstruction was examined using histology, immunohistochemistry and transmission electron microscopy (TEM). For immunohistochemistry, antibodies to 5-bromo-2'-deoxyuridine (BrdU), injected one hour before tissue collection, and cytokeratin were employed. When clips were removed from the duct, only ductal epithelial cells remained; all acinar cells had been deleted. Some duct cells were BrdU positive. After three days, newly-formed acini comprising immature acinar cells had appeared; many of the cells were BrdU positive and mitotic figures were readily identified. Thereafter progressive acinar cell maturation and proliferation occurred, parotid gland weight returning to control levels by 7 days. Peak BrdU labelling indices for duct and acinar cells were on days 0 and 4, respectively. By TEM, cytoplasmic organelles in epithelial cells of transitional duct-acinar structures seen at 2 days were poorly developed. Immature acinar cells seen on day 3 contained zymogen granules and had increased endoplasmic reticulum and mitochondria. By day 5, maturing acinar cells had abundant endoplasmic reticulum and zymogen granules, resembling acinar cells in control glands. These observations indicated origin of acinar cell precursors from duct cells during regeneration of the acinar cell-free atrophic gland. Subsequent expansion of the acinar cell population was dependent on maturation and proliferation of these newly-formed cells.     

Changing myoepithelial cell distribution during regeneration of rat parotid glands

The distribution of the myoepithelial cells during regeneration of the rat parotid gland after atrophy induced by one week of parotid duct ligation was investigated by immunohistochemistry for actin and transmission electron microscopy (TEM). Immunohistochemically, residual ducts were surrounded by actin-positive cells when clips were removed from the duct. Three days later, most of the newly formed acini originating from the residual ducts were also embraced by actin-positive cells. After 10 days, actin-positivity tended to be seen as dots around acini that decreased in number day by day. On day 21 actin-positive cells mainly surrounded intercalated ducts with only a few positive reactions identified at the acinar periphery. Electron microscopically, residual ducts and newly formed acini were peripherally embraced by myoepithelial cells before day 5. After day 7, shift of myoepithelial cells from the periphery of acini to the duct-acinar junctional region was identified. Then few myoepithelial cells were identified at the periphery of acini. These observations indicate that myoepithelial cells migrate from the acinar periphery to the duct-acinar junctional region during rat parotid regeneration, and that such behaviour is closely related to that seen during rat parotid development.     

Aggressive invasive micropapillary salivary duct carcinoma of the parotid gland

The presence of invasive micropapillary component has been reported to be associated with salivary duct carcinoma and poor outcomes. Herein is described a rare case of invasive micropapillary salivary duct carcinoma of the parotid gland in a 60-year-old man. The micropapillary component was approximately 70% of the area of the tumor. Squamous differentiation was focally seen adjacent to the micropapillary component. On immunohistochemistry the ordinary salivary duct carcinoma component was positive for gross cystic disease fluid protein-15 (GCDFP-15), androgen receptor (AR), and HER2/neu, whereas both micropapillary and squamous components were negative for GCDFP-15 and AR. Immunohistochemical staining for D2-40 highlighted the lymph vessel invasion of tumor cells. This patient developed metastases in the lymph nodes of the neck, and also in the liver, lung, and brain. The lymph nodes and liver metastases had both ordinary salivary duct carcinoma and micropapillary components. The patient died of tumor 11 months after the initial surgical operation. The results support that the presence of micropapillary component is associated with more aggressive behavior of salivary duct carcinoma. It is also important for pathologists to recognize that GCDFP-15 and AR expression can be reduced in micropapillary carcinoma in the differential diagnosis of metastatic tumor.     

Intraoral duct ligation without inclusion of the parasympathetic nerve supply induces rat submandibular gland atrophy

The atrophic effect of ligating the main duct of the right submandibular gland was examined in rat using a novel intraoral approach that did not include the chorda lingual (CL) nerve. Comparison was made with the effect of duct ligation including the attached CL nerve as carried out in previous studies. In all animals, the contralateral, unligated left submandibular gland was used as a control. At different times (1, 2, 7, 14 and 21 days) after ligation, glands were removed and weighed. Tissue was fixed for morphological analysis and homogenized for biochemical assay of secretory proteins. After 21 days, ligated glands showed a significant decrease in wet weight compared with unligated glands. Weight loss was the greatest (P < 0.05) in glands ligated with the CL nerve included. Light microscopy revealed that following ligation, an initial inflammatory reaction was followed by severe atrophy of acini and granular ducts. The atrophy was less severe when the CL nerve was not ligated. Secretory proteins were decreased from day 1 onwards following duct ligation in both groups. It can be concluded that most of the atrophy induced by duct ligation is independent of damage caused to the parasympathetic nerve supply, although the latter causes a greater atrophy presumably due to denervation.     

Intercalated duct cells in the rat parotid gland may behave as tissue stem cells

This study was conducted to determine whether intercalated duct cells in the rat parotid gland have the properties of tissue stem cells. After induction of cellular proliferation by repeated administration of isoproterenol (IPR), a β-adrenergic agonist, proliferation activity in acinar, intralobular, and intercalated ductal cells was quantified using Ki-67 immunohistochemistry. The total number of each type of component cell in a gland was also estimated in the course of IPR treatment. IPR was found to induce proliferation of acinar and intercalated duct cells, but not intralobular duct cells. The total number of acinar cells in a gland on day 5 of IPR treatment was 1.6 times of that at day 0 (baseline). In contrast, the total numbers of intercalated and intralobular duct cells did not change from baseline, indicating a high possibility that the proliferated intercalated duct cells differentiated into acinar cells. On days 2 to 3 of IPR treatment, intercalated duct cells with amylase-positive secretory granules were recognized in a region very close to the acini, and were suspected of being transitional cells from intercalated duct to acinar cells. This quantitative study indicates that intercalated duct cells may have the properties of tissue stem cells upon IPR stimulation.     

Salivary duct carcinoma in situ of the parotid gland

Aims: To describe three cases of purely in situ salivary duct carcinoma, so as better to define the entity. Methods and results: Three primary tumours of the parotid gland are presented, in each case composed of cysts and ducts and lined by high nuclear grade epithelial cells. All parts of each tumour were surrounded by a myoepithelial cell rim and there was no evidence of invasion. The tumour cells expressed immunohistochemical markers seen in invasive salivary duct carcinoma of usual (high‐grade) type. In two cases the androgen receptor (AR) reaction was strong, but there was no immunohistochemical expression of HER2 protein or gene amplification by in situ hybridization. In the remaining case, fewer nuclei stained for AR, but both HER2 protein and gene amplification were demonstrated. Conclusions: Salivary duct carcinoma in situ is morphologically similar to breast ductal carcinoma in situ and, although our cases are few, salivary duct carcinoma in situ can possibly be subdivided into luminal and non‐luminal cell types, as can analogous mammary neoplasms. The present study cannot determine whether low‐grade cribriform cystadenocarcinoma, architecturally similar but immunohistochemically different, is part of the spectrum of salivary duct carcinoma in situ, or whether it represents a separate entity.     

Circahoralian rhythm of cyclic AMP concentration in rat parotid gland slices

The cyclic AMP concentration was measured by a radioimmunoassay method in slices of rat parotid gland after incubation for 12–14 h. In each concrete experiment only one gland was used. Pieces for measurement of cyclic AMP concentration were taken at 10-min intervals for 2 h. Rhythmic changes in the cyclic AMP concentration with a period of 20–50 min were found. The period of the cyclic AMP rhythm is similar to the period of fluctuations in other parameters discovered previously on the same object: the dry weight of the cells, rate of protein synthesis, and ornithine decarboxylase activity.Laboratory of Cytology, N. K. Kol'tsov Institute of Developmental Biology, Academy of Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Chernigovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 12, pp. 711–712, December, 1979.     

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.     

Mode of cell death in the rat metrial gland during peripartum regression

In the rodent uterus, the metrial gland develops during midpregnancy and undergoes regression prior to parturation. The involution of the gland is reported to be accompanied by the loss of gland cells due to their death in situ. Cell death has been classified by using morphological criteria into two types: necrosis and apoptosis. To study the mechanism involved in the peripartum regression of the rat metrial gland, we examined the mode of cell death in the gland during the last week of gestation. We identified apoptotic cells in the regressing metrial gland by using DNA fragmentation, in situ DNA 3'-end labeling, and electron microscopy. Expression of progesterone receptor (PR) and estrogen receptor (ER) was also demonstrated by immunohistochemistry in the gland. The mean weight of metrial gland nodes decreased after day 18 of pregnancy. The apoptotic granulated metrial gland (GMG) cells that were detected by using the in situ DNA 3'-end labeling method were observed on day 16 of pregnancy, and they increased in number after day 20 of pregnancy. Intense fragmentation of DNA was also found from day 20 to day 22 of pregnancy. Electron microscopy demonstrated apoptotic GMG cells in the regressing metrial glands, confirming the results of the labeling studies. Immunohistochemical study revealed that expression of PR and ER, which were localized mainly in fibroblast-like stromal cells but not in GMG cells, was almost unchanged during late pregnancy. Apoptotic cell death is the major mode of rat metrial gland cell death in the peripartum loss of metrial gland cells. Anat. Rec. 252:369–377, 1998. © 1998 Wiley-Liss, Inc.     

Origin and characterization of atrial natriuretic peptide in the rat parotid gland

Summary The heart atria represent the major site of synthesis for atrial natriuretic peptide (ANP) which exerts potent natriuretic, diuretic and vasoactive functions. Recently, ANP-immunoreactivity has been detected in extracardial organs involved in water and electrolyte homeostasis, such as the intestine and certain exocrine glands. The present study investigates ANP in the parotid gland. It was found by immunohistochemical techniques that the peptide is localized in ductal cells of the gland. An analysis of the immunoreactive material by high-pressure liquid chromatography and radioimmunoassay revealed the prohormone of ANP (ANP 1-126) and the biologically active fragment (ANP 99-126). Furthermore, Northern blot hybridization disclosed the presence of mRNA coding for ANP. It is suggested that ANP is synthesized and released from the parotid gland and functions in the control of saliva production.     

Merkel cell carcinoma of the parotid gland associated with Warthin tumour: report of two cases

AIMS: Two cases of Merkel cell carcinoma occurring simultaneously and in close association with a Warthin tumour of the parotid gland are reported. METHODS AND RESULTS: The patients were a 65-year-old man and a 70-year-old man, respectively. The Merkel cell carcinoma component was immunoreactive for chromogranin and keratin 20 and contained neuroendocrine-type granules at the ultrastructural level. CONCLUSIONS: The histogenesis of this heretofore undescribed combination is discussed.     

TIGAR overexpression diminishes radiosensitivity of parotid gland fibroblast cells and inhibits IR-induced cell autophagy

Our previous study proved that TP53-induced glycolysis and apoptosis regulator (TIGAR) abrogation is able to radiosensitize glioma cells. Whether TIGAR over-expression has radio-protective effect in human parotid gland cells is still unknown. In this study human parotid gland fibroblast Hs 917.T cells were transfected with pcDNA3.1-TIGAR, and clonogenic assay was performed to investigate the radiosensitivity of Hs 917.T cells over-expressing pcDNA3.1 or pcDNA3.1-TIGAR. Western blot was carried out to demonstrate the autophagy activity of cells being irradiated, and immunofluorescence assay was used to evaluate the DNA damage repair process of irradiated Hs 917.T cells. It was revealed that TIGAR over-expression could diminish the radiosensitivity of Hs 917.T cells, and the autophagy level induced by ionizing radiation (IR) was also decreased by TIGAR transfection. The mechanism might rely on TIGAR over-expression induced ROS scavenging and NADPH increasing. Using autophagy inhibitor, it was also elaborated that IR-induced autophagy in Hs 917.T cells was protective autophagy but not traumatic autophagy.     

Crystalloids in salivary duct cysts of the human parotid gland

Summary Crystalloids found in salivary duct cysts of the human parotid gland were examined by scanning electron microscopical observations with electron probe X-ray microanalysis. The cystic spaces were filled with numerous crystalloids which had a variety of forms with slight eosinophilic and glassy appearance. Scanning electron microscopically, crystalloids were hexagonal and rhombohedral in shape, and cutting the surface showed a polycyclic structure or regular parallel lamination. By electron probe X-ray microanalysis, sulphur was the only detected element. The present study suggests that crystalloids resulted from deposition from supersaturated saliva containing sulphur containing compounds into the cystic lumen or into epithelial cytoplasm.     

Participation of the Fas and Fas ligand systems in apoptosis during atrophy of the rat submandibular glands

Most acinar cells and some duct cells undergo apoptosis during atrophy of the submandibular gland. The present study was designed to elucidate whether Fas and its receptor ligand (FasL) are involved during apoptotic atrophy of the gland. The excretory duct of the right submandibular gland of rats was doubly ligated with metal clips from 1 to 14 days for induction of gland atrophy. Control rats were untreated. Fas and FasL expression in the atrophied submandibular gland was detected using immunohistochemistry (IHC) and Western immunoblot. Expression of activated caspase 8 and activated caspase 3 was also detected with IHC. Fas-positive acinar and duct cells and FasL-positive duct cells increased in the atrophic glands at 3 and 5 days after duct ligation when apoptotic cells were commonly observed. Thereafter, Fas- and FasL-positive cells declined in number. Patterns of expression of Fas and FasL using Western immunoblots concurred with the IHC results. Activated caspase 8-positive cells were present at every time interval but peaked at 3 and 5 days following duct ligation. The cells showing immunoreaction for activated caspase 3 first appeared on day 3, with the peak in apoptosis, after which they decreased. The results indicate that the Fas/FasL systems likely play an important role in apoptotic pathways during atrophy of the submandibular gland.     

感染HCMV的腮腺导管上皮细胞CK和EMA丢失

目的 研究人类巨细胞病毒(HCMV)感染对腮腺导管上皮细胞表型产生的影响。方法 用免疫组化方法检测腮腺巨细胞包涵体病石蜡包埋组织中巨细胞病毒以及早期抗原、CK、EMA等的表达．结果 腮腺导管上皮细胞感染人巨细胞病毒后，作为上皮性标志物的CK和EMA表达呈阴性。结论 人巨细胞病毒感染腮腺导管上皮细胞使其CK和EMA丢失。单层上皮角蛋白网具有维持上皮细胞机械力学完整性的功能。     

Morphological and functional changes of the rat parotid glandular cells by clipping and reopening the parotid duct, using ham8 antibody

The purpose of this experiment is to examine the proliferative process of rat acinar cells after parotid duct ligation and reopening. Two experimental groups were observed. The first group was killed from 0 to 14 days after the duct ligation. In the second group, the duct was clipped for 14 days, and it was reopened. Following a period of from 2 to 28 days after removal of the clip, the glands were removed to perform a histological analysis, including hematoxylin-eosin (HE), immunofluorescent staining using HAM8 antibody, which recognizes connexin 32, and transmission electron microscopy (TEM). In the experimental gland from the 1st group at 6 days after ligation (I-6D), the acinar cells disappeared. In the tissue from the 2nd group 8 days after reopening (II-8D), newly formed acinar cells were found again. Lobular structure of the parotid glands recovered in the II-21D. HAM8 signals were observed between normal acinar cells, while they declined in the tissue from I-1D, and they were not observed in the I-2D. HAM8 signals were first observed in the II-25D and then subsequently returned to normal levels in the II-28D. These results suggest that the intercellular communication and functional recovery was not complete 25 days after reopening of the duct.In conclusion, the recovery of the acinar structure was recognized during an extended period of duct ligation, however, a time lag between the morphological and functional recovery was found to exist.     

Fine-needle aspiration cytology of basal cell adenoma of the parotid gland: characteristic cytological features and diagnostic pitfalls

We retrospectively studied the cytological features of aspiration cytology in 12 cases of basal cell adenoma (BCA) and 5 cases mistakenly diagnosed as BCA. On macroscopic findings, the 12 cases of BCA included 7 cases of solid type and 5 cases of cystic type. The characteristic cytological features of solid type BCA were three-dimensional clusters in 71%, sharp-angle small clusters in 86%, basement membrane- like material in 71%, and cell crush in 86%. In contrast, 3 of the 5 cystic type BCA cases showed inadequate cellular components or no basaloid tumor cells, and the cytological diagnosis of BCA could not be determined. In the 5 cases misdiagnosed as BCA, there were 2 cases of pleomorphic adenoma, 2 cases of benign lymphoepithelial cyst, and 1 case of basal cell adenocarcinoma. Accurate differential cytological diagnosis of BCA is relatively easy to determine the solid type BCA, but is more difficult for cystic type BCA.