Epithelium sensitization

In humans, cases of dermatitis have been described after contact with DHBs. Combined exposure to hydroquinone and quinone airborne concentrations causes eye irritation, sensitivity to light, injury of the corneal epithelium, and visual disturbances (126). Cases with an appreciable loss of vision have occurred (127). Long-term exposure causes staining due to irritation or allergy of the conjunctiva and cornea and also opacities. Resorcinol and catechol are also irritants for eyes. 

Odors are perceived via the olfactory system, which is composed of two organs in the nose the olfactory epithelium, a very small area in the nasal system, and the trigeminal nerve endings, which are much more widely distributed in the nasal cavity (11). The olfactory epithelium is extremely sensitive, and humans often sniff to bring more odorant in contact with this area. The trigeminal nerves initiate protective reflexes, such as sneezing or interruption of irrhalation, with exposure to noxious odorants. 

A possible alternative is the microvillous part of the chemosensory epithelium in the Organ of Rodolfo-Masera (Septal Organ), which is VN-like (Taniguchi etal., 1993). This mixed receptor population requires much further study since it could prove to have intermediate odourant sensitivities (Giannetti et al., 1995). Its distribution and function(s) are still incompletely known however it is sufficiently widespread, from Opossums to Rodents, to warrant an intensive survey (Rodolfo-Masera, 1943 Kratzing, 1978 Giannetti et al., 1992 and 1995). 

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. 

Amiloride-sensitive Na+ channels are probably absent from the pigmented rabbit conjunctival epithelium, since the conjunctival Ix is not sensitive to either mucosal or serosal amiloride up to 1 mM. Conjunctival Ix is, however, inhibited... 

Although the ocular absorption of peptide as well as nonpeptide drugs is poor [96,196-198], the ocular route is by far the least studied for the usefulness of penetration enhancers. This is in part due to the perceived sensitivity of ocular tissues to irritation and the fear of corneal and conjunctival damage caused by the enhancers. Whereas the rat nasal epithelium may tolerate up to 5% sodium glycocholate [199], ocular administration of sodium glycocholate at a concentration of 2% and beyond induces reddening of the eye and tear production in rabbits (Kompella and Lee, unpublished observation). 

Intraspecies Because the species used was the most sensitive to monomethylhydrazine toxicity and the most closely related to humans, an uncertainty factor of 3 is justified. A factor of 3 was used. Although the mechanism of toxicity is uncertain and sensitivity among individuals may vary, the exposure-response relationship is steep, suggesting limited variability in the toxic response to methylhydrazine. Furthermore, it is likely that acute toxic responses are, at least initially, a function of the extreme reactivity of methylhydrazine. The interaction of the highly reactive monomethylhydrazine with tissues (e.g., pulmonary epithelium) is not likely to greatly vary among individuals. 

This conclusion is consistent with the observation that responses in mitral cells to odors applied to the epithelium are narrowly tuned and that sensitivity to particular types of odor, determined by either functional group or carbon chain length, is spatially organized in the bulb [20]. Thus, the organization of receptors into broad zones in the epithelium is further refined in the bulb, where receptors find common targets. 

Mammary epithelium is very sensitive to hormonal stimulation. It is where proliferative events take place and where neoplastic transformation begins. 

Different odor substances stimulate different patterns of ORCs in the olfactory epithelium, owing to the different sensitivity spectra of the ORCs (28). The pattern of activity in the epithelium evoked by a particular odor substance constitutes the first molecular image of that stimulus, which represents the determinants of the stimulating molecules (13). Thus, although olfaction is not a spatial sensory modality, in contrast, for example, to vision and somatosensation, the initial representation of an odor stimulus in the olfactory pathway does have spatial structure. 

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