Morphological alterations of the parotid gland of rats maintained on a liquid diet

A Possible Novel Protective Effect of Piceatannol against Isoproterenol (ISO)-Induced Histopathological, Histochemical, and Immunohistochemical Changes in Male Wistar Rats

Dry mouth is characterized by lower saliva production and changes in saliva composition. In patients with some salivary gland function remaining, pharmaceutical treatments are not recommended; therefore, new, more effective methods of promoting saliva production are needed. Hence, this study aimed to provide an overview of the histological changes in the salivary gland in the model of isoproterenol (ISO)-induced degenerative changes in male Wistar rats and to evaluate the protective effect of piceatannol. Thirty-two male Wistar rats were randomly divided into four groups: the control group, the ISO group, and the piceatannol (PIC)-1, and -2 groups. After the third day of the experiment, Iso (0.8 mg/100 g) was injected intraperitoneally (IP) twice daily into the animals. PIC was given IP in different daily doses (20 and 40 mg/kg) for three days before ISO and seven days with ISO injection. The salivary glands were rapidly dissected and processed for histological, histochemical, immunohistochemical (Ki-67), and morphometric analysis. Upon seven days of treatment with ISO, marked hypertrophy was observed, along with an increased number of positive Ki-67 cells. Proliferation was increased in some endothelial cells as well as in ducts themselves. Despite the significant decrease in proliferation activity, the control group did not return to the usual activity level after treatment with low-dose PIC. Treatment with a high dose of PIC reduced proliferative activity to the point where it was substantially identical to the results seen in the control group. An ISO-driven xerostomia model showed a novel protective effect of piceatannol. A new era of regenerative medicine is dawning around PIC’s promising role.

Juvenile recurrent parotitis: Soft foods contribute to the delayed development of salivary glands

BACKGROUND

Juvenile recurrent parotitis (JRP) is the second-most common childhood disease of the salivary glands after mumps. Since popularisation of mumps vaccination, children suffered from JRP more often, and the aetiology remains unclear. Chinese children had the habit of soft foods due to the special dietary habit of Asia.

OBJECTIVES

To clarify whether mastication was related to the pathogenesis of JRP and whether the growth of salivary glands was influenced by soft diet.

METHODS

Investigation of dietary habit and masticatory efficiency from 2015 to 2018 of children diagnosed with JRP compared with the normal children by the dentition. Mice had been fed a soft diet beginning in their development phase. The gland weight, amount of saliva, salivary amylase, histological and ultrastructural observation and the expression levels of EGF, FGFr2 and Wnt3a had been tested.

RESULTS

The JRP children preferred soft foods and had a significantly lower masticatory efficiency than do normal children. When normalised by body weight, the gland weight, amount of saliva and amount of salivary amylase in the experimental group were significantly lower. The ultrastructural results showed that the acinar cells in the experimental groups were smaller and contained fewer electron-dense secretory granules than those in the control groups. The expression levels of EGF, FGFr2 and Wnt3a in the salivary glands of mice in the experimental groups were significantly lower than those of mice in the control groups.

CONCLUSION

The soft diet indeed influenced the salivary gland through insufficient mastication, which could be one of the primary factors inducing JRP.

Growth of rat parotid glands is inhibited by liquid diet feeding

This study investigated how liquid diet feeding affects the growth of parotid glands. We weaned 21-day-old rats and thereafter fed them a pellet diet (control group) or a liquid diet (experimental group) for 0, 1, 2, 4, or 8 weeks. Their parotid glands were excised, weighed, examined, and tested for 5-bromo-2'-deoxyuridine (BrdU) and cleaved caspase-3 (Casp-3) as markers of proliferation and apoptosis, respectively. Parotid gland weights were consistently smaller in experimental animals than in controls. Morphometrical analysis showed that control group acinar cells increased in area during the experiment, but experimental group acinar cells were almost unchanged. Labeling indices of BrdU in acinar cells in both groups declined during the experiment, but were consistently lower in the experimental group than in controls. Casp-3-positive acinar cells were rare in both groups, which consistently express significantly similar Casp-3 levels. Ultrastructurally, terminal portions of the experimental parotid glands consisted of a few acinar cells that were smaller than those in controls. Control acinar cells showed mitotic figures within short experimental periods, but not in experimental glands. These observations indicate that liquid diet feeding inhibits growth of parotid glands in growing rats through suppression of growth and proliferation of individual acinar cells, but not through apoptosis.

Low-frequency noise effects on the parotid gland of the Wistar rat

BACKGROUND

Long-term low-frequency noise (LFN) (<or=500 Hz) exposure is known to cause extracellular matrix proliferation by fibrosis in the absence of inflammatory signs.

AIM

We have examined the morphofunctional alterations of the parotid glands of Wistar rats exposed to LFN. The hypothesis is that the parotid glands are a target for LFN-induced lesions.

MATERIALS AND METHODS

Ten rats were exposed to LFN for 2184 consecutive hours while 10 rats were kept under similar conditions but in silence for control purposes. The parotid glands were surgically removed. One gland was sectioned and stained with hematoxylin-eosin and periodic acid Schiff for light microscopy observation. The other was used for functional amylase secretion measurements, basal and nerve-mediated [with electrical field stimulation (EFS)] and secretagogue-evoked secretion [acetylcholine (ACh) 10(-5) m] with established fluorimetric techniques.

RESULTS

All the rats exposed to LFN showed marked morphological lesions including vacuolar degeneration, hyalinization, cell death and blood vessels wall focal thickening. No morphological changes were detected in the control group. The functional results presented significantly diminished basal, EFS and ACh-evoked amylase secretion when compared with the control group.

CONCLUSION

These results suggest that the parotid gland is a target for LFN-induced lesions with an impairment of its function.