Expression of aquaporin 5 during murine palatine glands development: a light and electron microscopic immunocytochemical study.

Although aquaporin 5 (AQP5) seems to play a role in cytodifferentiation and cell proliferation during the development of salivary glands, its distribution during minor salivary glands development has been scarcely reported. This study examined the temporal-spatial distribution of AQP5 in the developing rat palatine glands using light and electron microscopy. At embryonic (E) age E18, AQP5 labeling was observed on the cell membranes of some terminal bulb cells. After lumenization at E20, AQP5 labeled the apical membrane in acini where a lumen existed, in addition to displaying positive diffuse cytoplasmic and cell membrane staining. At the electron microscopic level, AQP5 labeled the supranuclear cytoplasm and the luminal microvilli along the apical membrane. At birth, AQP5 was also localized to the lateral membranes associated ultrastructurally with the microvilli of intercellular canaliculi. After postnatal (PN) day PN7, mucous acini and serous demilunes showed reactivity. AQP5 reached peak reactivity around PN13 with a similar staining pattern in all acini, but had reduced dramatically by PN21. Thereafter, AQP5 reactivity was mainly associated with serous cells in adults. In conclusion, the transitory expression of AQP5 during palatine glands development may reflect changing physiological functions of the secretory cells and/or AQP5 throughout the maturation of the glands.

Anatomical, histological, and surface ultrastructural evaluation of the palatal mucosa of domestic rabbit (Oryctolagus cuniculus).

The present study investigated the morphology of the palate of rabbit (Oryctolagus cuniculus). Samples from 12 healthy adult rabbits were examined by gross observation, morphometry, scanning electron and light microscopy. The hard palate was elongated and narrowed rostrally. The incisive papilla appeared as a diamond-shaped prominence flanked on both sides by a groove on which a slit-like opening of the nasopalatine duct opened. The palatine raphe was in the form of a groove. On either side of the raphe, 14-16 palatine ridges were present. The direction of these ridges differed according to their position. An incomplete (short) palatine ridge was occasionally present at the caudal part of the hard palate. Several gland openings were scattered on the surface of the palatine ridges. The soft palate extended to about the middle of epiglottis caudally. Its ventral surface had numerous thin transverse mucosal folds separated by furrows, and several openings of glands. Histologically, the incisive papilla, palatine ridges, and soft palate were lined by a parakeratinized stratified squamous epithelium resting on a dense connective layer of lamina propria. The degree of keratinization and the thickness of the lamina propria decreased caudally. Seromucoid glands were present in the rostral and caudal parts of the hard palate, as well as in the soft palate. In conclusion, the palate of rabbit presented characteristic features suggesting functional adaptations for their herbivores diet. Studying the morphological characteristics of the hard and soft palate of rabbits will help veterinary practitioners to investigate pathology malformations and diseases of the oral cavity.

Developmental Morphology of the Palatine Glands in Rats: An Electron Microscope Study.

Although minor salivary glands play a significant functional role in the oral cavity, their developmental morphology and cell differentiation has been scarcely studied. This study aimed to describe the development of rat palatine glands with regard to the ultrastructural morphology of the secretory cells and surrounding myoepithelial cells (MECs). Palatine glands from rats at embryonic ages (E) 18 and 20 days, and postnatal days (PN) 0, 3, 7, 10, 13, 21, 30, 42, and 60 were fixed and prepared for morphological analysis and immunocytochemical labeling of alpha-smooth muscle actin (α-SMA). At E18, epithelial cords were observed extending from the palatal epithelium and showed negative reactivity to α-SMA. After luminization at E20, the cells of immature acini accumulated secretory granules of various densities: electron-dense, electron-lucent and some empty-appearing granules. MECs were poorly differentiated at E20 and exhibited only slight α-SMA expression. At birth, mucous and serous cells were typically located around a common lumen. Thereafter, serous cells began to move to the periphery to form demilunes by PN7. The mucous secretory granules of intermediate electron density became predominant around PN13. At PN21, these granules were dramatically reduced in number and most of the acini in adults contained acinar cells with numerous electron-lucent granules, and a few serous demilune cells with electron-dense granules. After birth, MECs progressively accumulated actin microfilaments until prominent α-SMA expressing MECs invested the acini and the proximal part of the intercalated ducts in the adult. Anat Rec, 301:1820-1833, 2018. © 2018 Wiley Periodicals, Inc.

Distribution of nerve fibers during the development of palatine glands in rats.

BACKGROUND: Salivary gland maturation and function are modulated by the nervous system. Nevertheless, little is known about salivary gland innervation during development, particularly minor salivary glands. This study investigated the development of the innervation of the palatine glands of rat. MATERIALS AND METHODS: Frozen sections of rat palatine glands at different stages were immunohistochemically labeled for detection of the general nerve markers protein gene product 9.5 (PGP 9.5) and growth associated protein 43 (GAP-43), and the autonomic nerve markers calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY). RESULTS: PGP 9.5 and GAP-43-immunoreactive fibers (IRF) were present in the mesenchyme and in association with developing acini, ducts and blood vessels. GAP-43-IRF were more abundant and diffuse than PGP 9.5-IRF at early stages, but showed similar distribution with growth, ramifying out from thick bundles in connective tissues until encircling the secretory units observed around postnatal day 21 (PN21). CGRP-IRF were detected in the mesenchyme at embryonic day 20 (E20) and PN0. CGRP-IRF became numerous around PN7 and PN10. They then decreased to the adult level at PN21, mainly located around ducts and infrequently blood vessels. NPY-IRF were sparsely detected in the mesenchyme at E20, then detected in close proximity to acini in addition to blood vessels at PN3. NPY-IRF increased till reaching the adult stage, and were mainly associated with blood vessels and around mucous cells and some serous demilunes. CONCLUSION: The findings indicated a developmental modification of the sensory and autonomic innervation which may play a role in the functional maturation of the palatine salivary glands.

Lectin histochemistry of palatine glands in the developing rat.

This study examined the binding pattern of lectins, soybean agglutinin (SBA), Dolichos biflorus agglutinin (DBA), Vicia villosa agglutinin (VVA), Ulex europaeus agglutinin-I (UEA-I), peanut agglutinin (PNA), wheat germ agglutinin (WGA), and succinylated WGA (sucWGA) in the developing rat palatine glands. In adult rats, heterogeneous lectin binding patterns were revealed between the anterior and posterior portions of palatine glands, as DBA, VVA, and WGA were bound more intensely and broadly in the posterior portion. SBA, PNA, and sucWGA showed far less reactivity in the anterior than in the posterior portion. At embryonic day 18 (E18), weak labeling was observed with UEA-I and WGA at the basal membrane of terminal buds, UEA-I and PNA labeled the epithelial cord, and there was no apparent binding for SBA, DBA, VVA, and sucWGA. At E20, after acinar lumenization, all lectins were detected at the acinar cell basal membranes. After birth, all lectins detectably labeled at the mucous cell apical membranes and progressively, with maturation, extended from the apical to basal portions of the cytoplasm. Apparent serous cells were observed around postnatal day 10 (PN10) and bound UEA-I. Lectins reached peak reactivity at PN21 and the binding patterns became identical to those of adults around PN28.