Cell olfactory epithelium

Bipolar neurons have tw o processes extending from the cell body (Figure 14.2). Most sensory (or afferent) neurons are this type, carrying messages from the body s sense receptors (eyes, ears, etc.) to the CNS. Sensory neurons account for 0.9% of all the neurons. Examples of sensory neurons are retinal cells, olfactory epithelium cells, and the cochlear and vestibular ganglia. 

Although the nose houses and protects the cells that perceive odor, it does not direcdy participate in odor perception. The primary function of the nose is to direct a stream of air into the respiratory passages. While this function is occurring, a small fraction of the inhaled air passes over the olfactory epithelium, located 5—8 cm inside the nasal passages. This olfactory area occupies about 6.45 cm (one square inch) of surface in each side of the nose. 

Coon H., Curcio F., Sakaguchi K., Brandi M.L. and Swerdlow R.D. (1989). Cell cultures of neuroblasts from rat olfactory epithelium that show odourant responses. Proc Natl Acad Sci 86, 1703-1707. 

Farbman A.I., Buchholz J., Suzuki Y., Coines A. and Speert D. (1999). A molecular basis of cell death in olfactory epithelium. J Comp Neurol 414, 306-314. 

Hansen A., Zeiske E. and Reutter K. (1994). Microvillous and ciliated receptor cells in the olfactory epithelium of the Australian Lungfish, Neoceratodus forsteri. In Advances in Biosciences 93 (Apfelbach R., et al., eds.). Elsevier, Oxford, pp. 43-51. 

Moran D.T., Rowley J.C. and Jafek B.W. (1982). Electron microscopy of human olfactory epithelium reveals a new cell type microvillar cell. Brain Res 253, 39-46. 

Moulton D., Celebi G. and Fink R. (1970). Olfaction in Mammals — two aspects proliferation of cells in the olfactory epithelium and sensitivity to odors. In Taste and Smell in Vertebrates (Wolstenholme G. and Knight J., eds.). Ciba, London, pp. 227-250. 

Ressler K.J., Sullivan S.L. and Buck L. (1993). Zonal organisation of odorant receptor gene expression in the olfactory epithelium. Cell 73, 597-609. 

Suzuki Y., Takeda M. and Obara N. (1998). Colchicine-induced cell death and proliferation in the olfactory epithelium and vomeronasal organ of the mouse. Anat Embryol 198, 43-51. 

Vassar, R., Ngai, ]. and Axel, R. Spatial segregation of odorant receptor expression in the mammalian olfactory epithelium. Cell 74 309-318,1993. 

TOPMINNOW, Poeciliopsis spp. 1 mg BaP/L tor 48 or 90 h Induction of P-4501A proteins in multiple cell types in many organs with some sites of induction (olfactory epithelium) related to exposure route 30... 

After intratracheal instillation of nickel chloride or nickel sulphate in rats, a modest inflammatory response with increased number of macrophages and polynuclear leucocytes was obtained, together with increased activities of lactate dehydrogenase and -glucuronidase in bronchoalveolar fluid [351]. More severe lesions were characterized by type II cell hyperplasia with epithelialization of alveoli, and in some animals, fibroplasia of the pulmonary interstitium. By inhalation in rats, the nickel salts produced chronic inflammation and degeneration of the bronchiolar epithelium [352, 353]. There was also atrophy of the olfactory epithelium and hyperplasia of the bronchial and mediastinal lymph nodes. Nickel sulphate also produced a low incidence of emphysema and fibrosis [353]. 

Hurtt ME, Thomas DA, Working PK, et al. 1988a. Degeneration and regeneration of the olfactory epithelium following inhalation exposure to methyl bromide Pathology, cell kinetics, and olfactory function. Toxicol AppI Pharmacol 94 311-328. 

Although pheromones can be considered as a special form of odorants (scents), their actions, effects and functions have similarities to those of hormones. They bind to a specific receptor which then activates an effector system, which initiates an action potential. They bind to specific sensory cells, the neurones, in the olfactory epithelium, which is located on the roof of the nasal cavities. The epithelium consists of three types of cells, basal, supporting and sensory cells (neurones). The neurones are bipolar, that is they possess a single dendrite, which extends from the cell body to the surface of the olfactory epithelium, and an axon that forms a synapse with a nerve that transfers information to the olfactory centre in the brain. The epithelium is covered with a thick layer of mucus, in which the pheromones dissolve. The mucus contains proteins that bind the pheromone(s) for delivery to the olfactory receptors and then to remove them once they have been detected. 

FIGURE 5.5 Structure of olfactory epithelium in mammals, a schematic view. Only one receptor cell is shown with its entire cilia floating in the olfactory mucus layer. (From Albone, 1984.)... 

The VNO is lined with bipolar receptor cells (Fig. 5.11). The receptor cells possess microvilli, in contrast to the cilia on the receptor cells of the main olfactory epithelium. The VNO of male and female mice have sensory cells with receptors that respond to male urine, and others that respond to female... 

No neoplastic effect was observed in rats exposed to 0, 15, 45, or 135ppm for 6 hours/ day, 5 days/week for 2 years. Dose-related changes, which include atrophy of the neurogenic epithelial cells and hyperplasia of the reserve cells, mainly affected the anterior part of the olfactory epithelium. In the high-dose group there was opacity of the cornea. After a 6-month postexposure period reconstructive effects were observed in both tissues. 

No exposure-related clinical signs or lesions of systemic toxicity and no oncogenic responses were observed in rats exposed by inhalation at concentrations of 0, 15, 45, or 135ppm 6 hours/day, 5 days/week, for 24 consecutive months." Dose-related changes occurred in the anterior portion of the olfactory epithelium and consisted of atrophy of the neurogenic epithelial cells followed by progressive hyperplasia of the reserve cells and ultimately loss of the upper epithelial cell layer. Opacity and neovascularization of the cornea were also observed in methyl acrylate-exposed animals. 

Body weights of female rats were 6-9% lower than controls during the second year. Hematology examinations completed at a 15 month interim sacrifice showed no effects. The only treatment-related changes noted were in the respiratory tract. Minimal to mild chronic active inflammation was observed at all concentrations at the 7 month interim sacrifice, but only at the two higher concentrations at two years. The inflammation was described as multifocal, minimal to mild accumulations of macrophages, neutrophils and cell debris within alveolar spaces. Fibrosis was observed in 2/54, 6/53, 35/53 and 43/53 male rats, and 8/52, 7/53, 45/53, and 49/53 female rats at 0, 0.03, 0.06, and 0.11 mg/m, respectively. Hyperplasia of the bronchial lymph nodes and atrophy of the olfactory epithelium were observed at the high dose. 

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