Epithelial hazards

Epithelial hazards. Affect the skin and mucous membranes, causing bums, defatting of tissues, rashes, irritation. Examples acids, phenol, ketones, trichloroethylene (83). 

Enteric bacterial pathogens must maneuver through a lengthy stretch of hazardous terrain before they reach their intended target or infection site within a host. Initially, they must tolerate salivary enzymes having various hydrolytic activities in the mouth, followed by exposure to shedded epithelial cells in the esophagus that may prevent local bacterial adherence (Pearson and Brownlee, 2005). In the stomach, bacteria must endure another severe environment created by the secretion of digestive enzymes and hydrochloric acid (up to 0.1 M concentration and a pH as low as 1.0). Once bacteria reach the intestines, they then encoimter mechanical. 

As indicated earlier in this chapter, these transporter proteins are found in a variety of cell types but especially in those organs exposed to chemicals from the environment (e.g., gastrointestinal tract), excretory organs (e.g., kidney), and sensitive organs (e.g., brain). The proteins are usually found on the luminal side of epithelial cells in organs of exposure, such as the small intestine, which allows the cells to pump out the potentially hazardous chemical. In sensitive organs such as the brain, the transporters are on that side of cells that will allow chemicals to be pumped back into the blood or interstitial fluid. In organs of excretion, such as the kidney, the transporters are located on the apical side of cells such as the proximal convoluted tubular cells. 

Proximal tubule epithelial degeneration is the major renal change observed in humans after inhalation exposure to organotin compounds. Similar changes have been observed in animals following inhalation, oral, and dermal exposure to organotins. As with the hepatic changes, the possibility that tin compounds may cause renal effects at hazardous waste sites must be considered. 

In the respiratory tract, mucus is also involved in the process of mucociliary clearance, which contributes to the epithelial barrier properties by entrapping potentially hazardous substances, such as dust and microorganisms, within a viscoelastic mucus blanket. The mucus is then propelled by the claw-like tips of hair-like cilia towards the throat (movement occurs in a downwards direction from the nasal epithelium, or... 

Biomonitoring for human health hazard surveillance typically involves collection of hair, expired air, bodily fluids (blood, urine, saliva, breast milk, semen), feces, epithelial scrapings, exfoliated cells, or, less frequently, tissue biopsies from people known or suspected of being exposed to potential chemical, physical, or biological hazards. These samples are analyzed for toxic chemicals, their metabolites, or biomarker responses. The most commonly used biomarkers in humans are those relating to DNA and chromosomal damage, because these effects contribute to cancer risk. Besides biomarkers of chemical exposure and effects, there are also human biomarkers of tumor formation and susceptibility to toxic... 

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