Ciliated receptors

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. 

Non-ciliated receptors show much variation. Some resemble ciliated receptors in that they have a terminal dendritic bulb with a basal body but no distal cilium (85, 942). Others, as in H. nana (Fig. 2.9), show little structural specialisation and appear to be little more than free nerve endings which may have a single, double or triple structure. Endings which do not penetrate the tegument to the external environment may have a mechanoreceptive or proprioceptive (i.e. receptive to internal stimuli) -rather than chemoreceptive - function (12, 206, 942). 

Morita Y. and Finger T. (1998). Differential projections of ciliated and microvillous olfactory receptor cells in the catfish, Ictalurus punctatus. J Comp Neurol 398, 539-550. 

Nasal epithelium. The nasal cavity superior to the nostrils (vestibule) is covered by skin containing hair follicles and sebaceous and sweat glands. The skin is continuous with the inner nasal mucosa. Posteriorly, the epithelium is a pseudostratified ciliated columnar epithelium that covers the respiratory regions (formed by the maxilloturbinates).45,107,110 The superior turbinate (also called the ethmoturbinate) is lined by a thicker mucosa consisting of olfactory receptors and supporting cells.45,110... 

The biochemistry of odor detection involves at least three types of protein odor receptors (ORs) odorant binding proteins (OBPs) and odor degrading enzymes (ODEs). ORs are expressed by olfactory receptor neurons (ORNs) and localized in the membranes of the ciliated dendrites (Figure 14.1). The result of detection is translated into neuronal electrical activity by transductory proteins. But while transductory proteins are more or less common for all olfactory neurons, differential expression of ORs, OBPs and ODEs allows the neurons to detect specific odor molecules. 

Webb, R. A. Davey, K. G. (1974). Ciliated sensory receptors of the unactivated metacestode of Hymenolepis microstoma. Tissue and Cell, 6 587-98. 

One of the lesser functions of the nose in man is that of olfaction. The olfactory region of the nose, a small patch of tissue containing the smell receptors, is located towards the roof of the nasal cavity and is lined with non-ciliated neuro-epithelium. Approximately 20% of the air flowing through the nasal cavity is directed upwards to the olfactory region. Here, bipolar neurones react to inspired air and initiate impulses in the olfactory nerves. 

Apart from the effects on vision, most of the effects of vitamin A deficiency (Section 2.4) involve derangements of cell proliferation and differentiation (squamous metaplasia and keratinization of epithelia), dedifferentiation, and loss of ciliated epithelia. Retinoic acid has both a general role in growth and a specific morphogenic role in development and tissue differentiation. These functions are the result of genomic actions, modulating gene expression by activation of nuclear receptors. Both deficiency and excess of retinoic acid cause severe developmental abnormalities. 

Acetylcholine is the neurotransmitter at all these sites, acting on a postsynaptic receptor, except on most blood vessels in which the action of cholinergic drugs is unrelated to cholinergic vasodilator nerves. It is also produced in tissues unrelated to nerve endings, e.g. placenta and ciliated epithelial cells, where it acts as a local hormone (autacoid) on local receptors. 

Zabner J, Freimuth P, Puga A, Fabrega A, Welsh MJ. 1997. Lack of high affinity fiber receptor activity explains the resistance of ciliated airway epithelia to adenovirus infection. J. Clin. Invest. 100 1144 19... 

In most mammalian species, two functionally distinct classes of chemicals (odorants and pheromones) are detected and processed through anatomically segregated neural pathways the main olfactory system and the vomeronasal (accessory olfactory) system (Buck 2000 Mombaerts 2004). Volatile odorants are received by a large repertoire of ORs expressed on ciliated OSNs in the OE and the information is transmitted to the main OB. By contrast, pheromones are mostly received by two families of vomeronasal receptors (VIRs and V2Rs) expressed on microvillous sensory neurons in the vomeronasal organ that project their axons to the accessory OB. 

Fig. 4 Odor map in the zebrafish olfactory bulb. Amino acids and nucleotides are received mostly by V2R-type olfactory receptors on microvillous OSNs and are represented in the lateral region of the OB. In contrast, bile acids are received by OR-type olfactory receptors on ciliated OSNs and are represented in the medial region of the OB. LOT lateral olfactory tract, MOT medial olfactory tract...

Mori K, Takahashi YK, Igarashi KM, Yamaguchi M (2006) Maps of odorant molecular features in the mammalian olfactory bulb. Physiol Rev 86 409 133 Morita Y, Finger TE (1998) Differential projections of ciliated and microvillous olfactory receptor cells in the catfish, Ictalurus punctatus. J Comp Neurol 398 539-550 Nasevisius A, Ekker SC (2000) Effective targeted gene knockdown in zebrafish. Nat Genet 26 216-220... 

Lax SF, Pizer ES, Rormett BM, et al. Comparison of estrogen and progesterone receptor, Ki-67, and p53 immunoreactivity in uterine endometrioid carcinoma and endometrioid carcinoma with squamous, mucinous, secretory, and ciliated cell differentiation. Hum Pathol. 1998 29 924-931. 

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