Epithelium damage

Toxicology. The acute oral and dermal toxicity of naphthalene is low with LD q values for rats from 1780—2500 mg/kg orally (41) and greater than 2000 mg/kg dermally. The inhalation of naphthalene vapors may cause headache, nausea, confusion, and profuse perspiration, and if exposure is severe, vomiting, optic neuritis, and hematuria may occur (28). Chronic exposure studies conducted by the NTP ia mice for two years showed that naphthalene caused irritation to the nasal passages, but no other overt toxicity was noted. Rabbits that received 1—2 g/d of naphthalene either orally or hypodermically developed changes ia the lens of the eye after a few days, foUowed by definite opacity of the lens after several days (41). Rare cases of such corneal epithelium damage ia humans have been reported (28). Naphthalene can be irritating to the skin, and hypersensitivity does occur. 

Most studies of respiratory diseases reported for uranium involve noncancerous alveolar epithelium damage in type II cells. These changes are characterized by interstitial inflammahon of the alveolar epithelium leading eventually to emphysema or pulmonary fibrosis in acute exposures or to hyperplasia, hypertrophy, and transdifferentiation (metaplasia) in chronic exposures (Cooper et al. 1982 Dungworth 1989 Stokinger 1981 Wedeen 1992). However, the lack of significant pulmonary injury in most inhalation animal studies indicates that other potentially toxic contaminants such as inhalable dust particles, radium, or radon may contribute to these effects. 

Respiratory Effects. General damage to pulmonary structures, usually noncancerous alveolar epithelium damage of type II cells, can occur upon inhalation of insoluble reactive chemicals such as some uranium... 

Table 24. Bronchial epithelium damage by dust inhalation ...

Mauch F, Bode G, Ditschuneit H, Malfertheiner P (1993) Demonstration of a phospho-lipidrich zone in the human gastric epithelium damaged by Helicobacter pylori Gastroenterology 105 1698-1704... 

Direct eye contact with liquid produces injury, generally transient, to the corneal epithelium. The liquid is mildly imtating to the skin due to the degreasing effect repeated contact may cause dermatitis. Ingestion of substantial quantities of liquid can damage the mucous membranes, and produce acute effects ranging from mild discomfort to profound anaesdiesia. 

Villaschi S, Giovanetti A, Lombardi CC, et al. 1991. Damage and repair of mouse bronchial epithelium following acute inhalation of trichloroethylene. Exp Limg Res 15 601-614. 

Injury (either physical or chemical) to the comeal endothelial cells has a marked efiect on occular function as these cells are responsible for maintaining the thickness and clarity of the cornea, yet they cannot be replaced if damaged. Immunohistochemical studies have revealed that enzymatic antioxidant defences, SOD, CAT and GSHPx, are similarly distributed in the corneal epithelium and endothelium (Rao etal., 1985 Attala et d., 1987, 1988). Other antioxidants include ascorbate, carotenoids and vitamin E (Fleath, 1962). 

GSHPx, CAT and SOD, which normally protect cells from free-radical damage have not been detected in aqueous humour. It has therefore been su ested that damage by free radicals and hydrogen peroxide to the anterior segment is prevented by a non-enzymatic extracellular oxidoreduction system involving a constant supply of reduced glutathione to the aqueous fluid from the ciliary epithelium, cornea and lens (Riley, 1983). 

T. (1985). Damage of the airway epithelium and bronchial reactivity in patients with asthma. Am. Rev. Resp. Dis. 131, 599. 

Ovulation is considered a hostile event to the ovarian epithelium, making it more susceptible to damage and cancer. Interventions or conditions that limit the number of ovulations in a woman s reproductive history will have a protective effect. For instance, multiparity would decrease the number of ovulations. 

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). 

Mucins are also thought to act in cooperation with trefoil proteins in the protection and repair of the epithelium (Kindon et al., 1995). Trefoil factors are expressed along the GI tract and increased levels are noted near sites of inflammation and ulcerative lesions (Babyatsky et al., 1996). Furthermore, it has been demonstrated that mouse intestinal trefoil factor may play a role in the alteration of the physicochemical nature of GC mucins during N. brasiliensis infection (Tomita et al., 1995). Perhaps in GI nematode parasite infection mucins are not aiding in the host s protective expulsion of the parasite, but rather are functioning in the repair of the damaged intestinal epithelium. 

Malabsorption in SIBO is considered the consequence of abnormalities occurring mainly in the intraluminal environment in fact, the excessive number of intraluminal bacteria interfere with the absorption process. However, in some cases, the presence of bacterial species capable of more aggressive adhesion to small bowel epithelium is probably the cause of direct damage to the absorptive surface, in particular in the blind loop syndrome [10,11],... 

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