ABSTRACT
Unlike other Merkel cell types, the morphology and functions of the Merkel-like basal cells remain unclear. The aim of the present study was to investigate the ultrastructural features of Merkel-like basal cells in the nasal septal island (NSI) of dromedaries (Camelus dromedarius) using transmission electron microscopy and to speculate their potential functions. Ten pairs of nasal septal islands obtained from ten heads of dromedary camels were used for the current study. Interestingly, these cells have been identified in the basal layer of the neuroepithelium of the dromedary nasal septal island near the sensory nerve endings. These cells were ovoid to elliptical in shape and rested on the basal lamina. Their surface had spine like cytoplasmic processes which interwined with the adjacent basal cells. Their nuclei were large lobulated with 2-3 deep notches. Moreover, numerous dense-core granules surrounded by electron-lucent halo were aggregated in the basal portion of the cells close to the nerve ending as well as melanin pigments in the apical portion. The ultrastructural characteristics of the Merkel-like basal cells of NSI were typical to those of Merkel cells, but with some morphological differences, including their location, cellular attachments, and connections to other structures. The potential functions were discussed in the light of the cellular context and architecture. The Merkel-like basal cells of the NSI neuroepithelium might play a role in nociception and magnetoreception in dromedaries.
ABSTRACT
The light microscopic appearance and ultrastructure of the nasopharyngeal tonsil (tonsilla pharyngea), collected from 12 adult buffaloes of local mixed breed, were explored for the distribution of different types of epithelia, lymphoid tissue and high endothelial venules. The tonsillar mucosa was lined by pseudostratified columnar ciliated epithelium having goblet cells. The respiratory epithelium associated with the underlying lymphoid tissue formed the lymphoepithelium. The epithelium was further modified into follicle-associated epithelium (FAE) characterized by reduced epithelial height, presence of a few dome-shaped cuboidal cells equivalent of the M-cells and absence of goblet and ciliated cells. The lymphoid tissue was distributed in the form of isolated lymphoid cells, diffuse lymphoid tissue and lymphoid follicles, mainly distributed within the propria-submucosa along with the sero-mucous glandular tissue. The goblet cells of the respiratory epithelium and the acinar cells contained different mucopolysaccharides. Scanning electron microscopy of the surface mucosa demonstrated a dense mat of cilia, island-like arrangement of microvillus cells, M-cells and a few brush-like cells. The transmission electron microscopy revealed the different cell organelles of the respiratory epithelium and the FAE. Lymphocyte migration via the high endothelial venules in the propria-submucosa was also observed.
