Morphofunctional adaptations of the olfactory mucosa in postnatally developing rabbits

Comparative ultrastructure of the olfactory system in the East African root rat (Tachyoryctes splendens) and the naked mole rat (Heterocephalus glaber)

The ultrastructure of the olfactory system of most fossorial rodents remains largely unexplored. This study sought to investigate the functional structure of the olfactory mucosa and olfactory bulb of two species of fossorial rodents that have distinct behaviour and ecology, the East African root rat (RR) and the naked mole rat (NMR). Transmission electron microscopy and scanning electron microscopy were employed. The basic ultrastructural design of the olfactory system of the two species was largely comparable. In both species, the olfactory mucosa comprised an olfactory epithelium and an underlying lamina propria. The olfactory epithelium revealed olfactory knobs, cilia and microvilli apically and sustentancular cells, olfactory receptor neurons and basal cells in the upper, middle and basal zones, respectively. The lamina propria was constituted by Bowman's glands, olfactory nerve bundles and vasculature supported by loose connective tissue. Within the olfactory bulb, intracellular and extracellular structures including cell organelles, axons and dendrites were elucidated. Notable species differences were observed in the basal zone of the olfactory epithelium and on the luminal surface of the olfactory mucosa. The basal zone of the olfactory epithelium of the RR consisted of a single layer of flattened electron-dense horizontal basal cells while the NMR had juxtaposed electron-dense and electron-lucent heterogenous cells, an occurrence seen as being indicative of quiescent and highly proliferative states of the olfactory epithelia in the two species, respectively. The olfactory epithelial surface of the NMR comprised an elaborate cilia network that intertwined extensively forming loop-like structures whereas in the RR, the surface was rugged and consisted of finger-like processes and irregular masses. With gross and histological studies showing significant differences in the olfactory structures of the two species, these findings are a further manifestation that the olfactory system of the RR and the NMR have evolved differently to reflect their varied olfactory functional needs.

Biological aspects of the nasal turbinates of the Anatolian shepherd dog captured from Egypt: Using computed tomography, histological, and scanning electron microscopic observations

The current study was designed to describe the nasal turbinates of 15 heads of Anatolian shepherd dogs using the histology and scanning electron microscope. The caudal part of the nasal cavity is almost occupied by the ethmoidal concha that is related to the high dog's smelling. Keratinized stratified squamous epithelial lining of the rostral part of dorsal and ventral concha were interdigitated with the underlying lamina propria, with numerous sebaceous and sweat glands. The pseudostratified squamous epithelium lining of the middle part of the dorsal and ventral conchae had simple seromucous glands. The caudal third of dorsal, ventral, and ethmoidal conchae covered by olfactory epithelium that had three cell types; basal, supporting, and bipolar cells with mucous glands. SEM of the vestibular region shows that the dorsal conchae had a wrinkled surface with microvilli, little olfactory buds, and small sebaceous and sweat glands openings, while the ventral conchae had a lot of filiform-like microvilli. SEM of the respiratory region shows that the dorsal conchae had a little number of seromucous glands and a rosette-shape cilia, while the ventral conchae had numerous cellular cilia that cover all surface. SEM of the fundus region shows that the dorsal conchae had numerous microvilli of ciliated olfactory cells, while the ventral conchae had numerous long microvilli of ciliated olfactory cells. SEM of the ethmoidal nasal conchae shows a dense network of long microvilli of ciliated olfactory cells. We concluded that the morphological features of the dog's nasal turbinates were correlated with their environmental condition.

Light and scanning electron microscopy of the olfactory mucosa in the rufous sengi (Elephantulus rufescens)

Sengis are eutherian insectivores belonging to superorder Afrotheria, a recently defined clade of mammals that diverged from other placentals over 100 million years ago. In this study, a histological and ultrastructural analysis was carried out on the olfactory mucosa (OM) of the rufous sengi (Elephantulus rufescens) and the data were compared with those reported earlier in the dog (Canis familiaris) and the sheep (Ovis aries), whose dietary lifestyles are carnivorous and herbivorous, respectively. Qualitatively, the microstructure of the sengi's OM was basically similar to that of the other eutherian mammals except for differences in the pattern of cilia projection from the dendritic knobs of the olfactory receptor neurons (ORNs) and distribution of Bowman's glands within the lamina propria of the OM. On morphometry, significant differences (p < .05) were recorded with respect to olfactory epithelial (OE) thickness between the sengi (65.4 ± 2.6 μm) and the other species. ORN packing density and cilia number/ORN knob varied markedly only between the sengi (73.8 ± 5.4 mm^-2  × 10³ and 15 ± 4, respectively) and the sheep. No remarkable differences were noted in regard to ORN bundle diameters between sengis (62.7 ± 12.5 μm) and the other species. The observed differences in OM structural refinement may be attributed to olfactory function demand levels related to feeding lifestyles and ecology. Myrmecophagous insectivory, social monogamy, absentee maternal care and exposed sheltering habits are behavioural features that may warrant substantial OM modification in sengis.

Effects of anticancer drug docetaxel on the structure and function of the rabbit olfactory mucosa

Docetaxel (DCT) is an anticancer drug which acts by disrupting microtubule dynamics in the highly mitotic cancer cells. Thus, this drug has a potential to affect function and organization of tissues exhibiting high cellular turnover. We investigated, in the rabbit, the effects of a single human equivalent dose (6.26 mg/kg, i.v.) of DCT on the olfactory mucosa (OM) through light and electron microscopy, morphometry, Ki-67 immunostaining, TUNEL assay and the buried food test for olfactory sensitivity. On post-exposure days (PED) 5 and 10, there was disarrangement of the normal cell layering in the olfactory epithelium (OE), apoptotic death of cells of the OE, Bowman's glands and axon bundles, and the presence (including on PED 3) of blood vessels in the bundle cores. A decrease in bundle diameters, olfactory cell densities and cilia numbers, which was most significant on PED 10 (49.3%, 63.4% and 50%, respectively), was also evident. Surprisingly by PED 15, the OM regained normal morphology. Furthermore, olfactory sensitivity decreased progressively until PED 10 when olfaction was markedly impaired, and with recovery from the impairment by PED 15. These observations show that DCT transiently alters the structure and function of the OM suggesting a high regenerative potential for this tissue.