Immunoelectron microscopy of amylase in the human parotid gland. Ultrastructural localization by use of both the protein A-gold and the biotin-avidin-gold technique

On approaches to the functional restoration of salivary glands damaged by radiation therapy for head and neck cancer, with a review of related aspects of salivary gland morphology and development

Radiation therapy for cancer of the head and neck can devastate the salivary glands and partially devitalize the mandible and maxilla. As a result, saliva production is drastically reduced and its quality adversely altered. Without diligent home and professional care, the teeth are subject to rapid destruction by caries, necessitating extractions with attendant high risk of necrosis of the supporting bone. Innovative techniques in delivery of radiation therapy and administration of drugs that selectively protect normal tissues can reduce significantly the radiation effects on salivary glands. Nonetheless, many patients still suffer severe oral dryness. I review here the functional morphology and development of salivary glands as these relate to approaches to preventing and restoring radiation-induced loss of salivary function. The acinar cells are responsible for most of the fluid and organic material in saliva, while the larger ducts influence the inorganic content. A central theme of this review is the extent to which the several types of epithelial cells in salivary glands may be pluripotential and the circumstances that may influence their ability to replace cells that have been lost or functionally inactivated due to the effects of radiation. The evidence suggests that the highly differentiated cells of the acini and large ducts of mature glands can replace themselves except when the respective pools of available cells are greatly diminished via apoptosis or necrosis owing to severely stressful events. Under the latter circumstances, relatively undifferentiated cells in the intercalated ducts proliferate and redifferentiate as may be required to replenish the depleted pools. It is likely that some, if not many, acinar cells may de-differentiate into intercalated duct-like cells and thus add to the pool of progenitor cells in such situations. If the stress is heavy doses of radiation, however, the result is not only the death of acinar cells, but also a marked decline in functional differentiation and proliferative capacity of all of the surviving cells, including those with progenitor capability. Restoration of gland function, therefore, seems to require increasing the secretory capacity of the surviving cells, or replacing the acinar cells and their progenitors either in the existing gland remnants or with artificial glands.

Subcellular localization of epidermal growth factor in human parotid gland

The intracellular distribution of epidermal growth factor was investigated in human parotid gland by immunogold cytochemistry at the electron-microscopy level. Epidermal growth factor immunoreactivity was demonstrated in both acini and ducts. In acinar cells, secretory granules appeared moderately stained, clearly indicating that parotid gland contributes to salivary epidermal growth factor through granule exocytosis. In ductal cells, gold particles were found to decorate numerous cytoplasmic vesicles, particularly abundant in striated duct cells. Since epidermal growth factor reactive vesicles were seen not only at the cellular apex, but nearby lateral plasma membranes as well, it leads to the hypothesis that epidermal growth factor may be discharged both apically into the saliva, and basally into the interstitium.

Localization of salivary amylase and epithelial membrane antigen in salivary gland tumours by means of immunoperoxidase and immunogold-silver techniques

A series of 87 salivary glands was examined using an immunogold-silver technique for salivary gland amylase (SGA) and epithelial membrane antigen (EMA) and an indirect immunoperoxidase technique for both antigens. The specimens comprised 21 pleomorphic adenomas, 3 monomorphic adenomas, 25 adenolymphomas, 5 mucoepidermoid carcinomas, 3 acinic cell tumours, 8 adenoid cystic carcinomas, 2 adenocarcinomas and 8 undifferentiated carcinomas. In addition 5 normal salivary glands and 6 salivary glands showing benign lymphoepithelial lesions were included.

Immunohistochemical localization of amylase in sialoadenitis and salivary gland tumors

Immunohistochemical demonstration of alpha-amylase has been made in sialoadenitis-involved tissue and salivary gland tumors, as well as in normal salivary glands. Immunoreactive alpha-amylase with trypsin pretreatment was confined to irregularly staining serous acinar cells in the parotid and submandibular glands, and to demilunes in sublingual glands. In obstructive adenitis, staining was irregular from high to negative in acini in early or intermediate stages. Dilated ductal segments contained cells positive for alpha-amylase in the early stage following obstruction. Pleomorphic adenomas were usually negative for alpha-amylase but in rare cases tumor epithelia stained variably positive; i.e., staining occurred throughout the cytoplasm or at the periphery or apical part of the tumor cells. Luminal cavities of tubular and duct-like structures contained alpha-amylase-positive material. Epithelia in Warthin's tumor were also negative in general; however, scattered single or grouped tumor cells containing alpha-amylase were found. Mucoepidermoid tumors were also negative, though slightly positive cells were found intermingled among the negative squamous and mucous tumor cells. Cystic lesions in mucoepidermoid tumor were sometimes positive in the wall cells together with material secreted into the lumen.