Olfactory epithelium cell types

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. 

Hansen A, Rolen SH, Anderson K, Morita Y, Caprio J, Finger TE (2003) Correlation between olfactory receptor cell type and function in the channel catfish. J Neurosci 23 347-359 Hansen A, Anderson KT, Finger TE (2004) Differential distribution of olfactory receptor neurons in goldfish structural and molecular correlates. J Comp Neurol 477 347-359 Hansen A, Zielinski BS (2005) Diversity in the olfactory epithelium of bony fishes development, lamellar arrangement, sensory neuron cell types and transduction components. J Neurocytol 34 183-208... 

The epithelium covering the nasal cavity. This epithelium contains numerous cell types including the specialized olfactory sensory neurons which detect the chemical stimuli derived from smells by a specific family of G protein-coupled receptors known as olfactory receptors. 

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. 

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]. 

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. 

Experimentally, the macrocyclic trichothecenes satra-toxin G, isosatratoxin F, and roridin A have been shown to cause nasal and pulmonary toxicity when administered intranasally or intratracheally to mice. Intranasal exposure of satratoxin G and roridin A induced apoptosis of olfactory sensory neurons resulting in atrophy of the olfactory epithelium and olfactory nerve layer of the olfactory bulb in the frontal brain (Islam et al, 2006, 2007). Alveolar-type II cells and alveolar macrophages were injured following intratracheal instillation of isosatratoxin F or Stachybotrys spores with marked changes in surfactant synthesis and secretion (Rand et al, 2002). 

The olfactory bulb sits at the base of the brain on the cribriform plate. Humans have two olfactory bulbs, the right bulb that receives signals from the right olfactory epithehum and the left bulb that receives signals from the left olfactory epithelium. In the bulb, centers called glomeruli exist, each of which receives signals from only one type of receptor cell, irrespective of where those receptors are located on the epithehum. Olfactory receptor... 

Fig. 1 (A) Cross-sectional structure of the human nose. NV = nasal vestibule AT = atrium NP = nasopharynx IT = interior turbinate and orifice of the nasolacrimal duct MT = middle turbinate and orifices of frontal sinus, anterior ethmoidal sinuses, and maxillary sinus ST = superior turbinate and orifices of posterior ethmoidal sinuses hatched area, olfactory region. (B) Four major cell types in the nasal epithelium (a) non-ciliated columnar cell with microvilli (b) goblet cell with mucous granules and Golgi apparatus (c) basal cell and (d) ciliated columnar cell with many mitochondria in the apical part. (Reprinted from Ref. with permission from Elsevier.)...

Hansen A, Zielinski BS (2005) Diversity in the olfactory epithelium of bony fishes development, lamellar arrangement, sensory neuron cell types and transduction components. J Neurocytol 34 183-208... 

The olfactory epithelium showing the organization of the olfactory receptor neurons (ORNs) and other cell types... 

The supporting cells of the olfactory epithelium separate and partially wrap the ORNs. Their apical surface, in humans and some other vertebrates, is covered with microvilli, which project along with the olfactory cilia into the mucous layer. A third cell type, the microvillar cells, present at about one-tenth the number of the ORNs in... 

Fig. I. The olfactory epithelium. A. Schematic illustration of the olfactory epithelium showing the major cell types. Inset shows the location of putative 7TM odorant receptors on cilia of ORNs. B. Hypothesized olfactory receptor-transduction mechanisms. Current evidence suggests that odor molecules bind to specific 7 transmembrane receptor (7TMr) proteins located in the cilia of ORNs. These 7 TMrs are thought to be coupled to G-proteins that activate either adenyl cyclase (AC) to generate cyclic AMP (cAMP) or phospholipase C (PLC) to generate phosphatidyl inositol (IP3). These second messengers open channels that admit calcium ( Ca ) or sodium (Na ) into the cilium. These ions lead to membrane depolarization and may modulate intracellular free Ca levels, both of which lead to the generation of action potentials that are conducted along ORN axons to the olfactory bulb.

The peripheral organ for the olfactory system is the olfactory sensory epithelium, located in the dorsal-posterior portion of the nasal cavity. This epithelium, composed of several different types of cells, contains bipolar neurons (also known as olfactory receptor cells) whose axons extend to the brain and terminate in the main olfactory bulb. The VN organ is also situated in the periphery, and similarly contains several different types of cells, the most numerous being bipolar neurons whose axons terminate in the accessory olfactory bulb. The VN organ opens into the roof of the mouth via a very narrow channel, the VN duct. In snakes the tongue delivers odorants to the opening of the VN duct and, by a mechanism at present not understood, these odorants reach the dendritic tips of the bipolar neurons (Halpern and Kubie, 1980). 

What are the specific cytological transformations that occur in the olfactory epithelium during aging Is there a division of labor of the cell types that comprise the neuroepithelium so that some function solely in reproductive system-related phenomena ... 

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