Respiratory tract mechanisms

Chlamydia Humans (Hogan Respiratory tract Mechanism unknown. 

Schlesinger RB. Interaction of gaseous and particulate pollutants in the respiratory tract mechanisms and modulators. Toxicology 1995 105 315 325. 

Acute effects of overexposure are as follows. Exposure to dust may cause mechanical irritation of the eye. PPS is essentially nonirritating to the skin, although freshly molded material may occasionally cause dermatitis. Inhalation of PPS dust may cause mechanical irritation to mucous membranes of nose, throat, and upper respiratory tract. 

Expectorants enhance the production of respiratory tract fluid and thus faciUtate the mobilisation and discharge of bronchial secretions. Historically, expectorants have been divided iato two classes based on specific mechanisms of action. Stimulant expectorants iacrease respiratory tract secretion by a direct effect on the bronchial secretory cells. Sedative expectorants act by gastric reflex stimulation. Many compounds classed as expectorants have been iaadequately studied and the mechanisms of action are not known with certainty. 

Widdicombe, J, G. (1977). Defense mechanisms of the respiratory tract and lungs. In International Review of Physiology Volume 14. Repiratory Physiology U (J. G. Widdicombe, Ed.), pp. 291-316. University Park Press, Baltimore. 

Respiratory tract (nose and throat) problems Increase in bacterial infection. Resistance to throat, nose, and lung infection is increased, due to the breakdown of the proicctive mechanism,s in the body. 

Vitamin C status is supposed to play a role in immune function and to influence the progression of some chronic degenerative diseases like atherosclerosis, cancer, cataracts, and osteoporosis. The role of vitamin C in immune function, especially during common cold and upper respiratory tract infection, is the subject of lively debate. The exact mechanisms of action have not yet been fully elucidated, but the results of several trials point to a reduced duration and intensity of infections in subjects consuming high amounts of vitamin C (200-1000 mg/d). However, the incidence of common cold was not influenced significantly (24). 

Empey, D.W., Laitinen, L.A., Jacobs. L., Gold, W.M. and Nadel, J.A. (1976). Mechanisms of bronchial hyperreactivity in normal subjects after upper respiratory tract infection. Am. Rev. Resp. Dis. 113, 131 - 139. 

Palmer 1989 Robinson et al.1983). However, the ratio was almost certainly affected by initial chelation with Ca-DPTA, followed by daily intravenous therapy with the chelating agent, Zn-DPTA, treatments that would have increased the urinary excretion of americium (Breitenstein and Palmer 1989). The above not withstanding, the observations made on this subject demonstrate that fecal excretion was an important pathway of excretion in this subject long after mechanical clearance of americium from the respiratory tract would have been complete. This is consistent with observations made in nonhuman primates that show that americium is excreted into bile (see Section 3.4.4.4). However, the extent to which the biliary excretion pathway in humans might resemble that of nonhuman primates is not known. 

Acute inhalation exposure to aerosols of certain polyalphaolefin hydraulic fluids produced death in rats associated with respiratory tract irritation, while aerosols of other polyalphaolefin hydraulic fluids produced no apparent respiratory tract irritation or deaths (MacEwen and Vemot 1983 Kinkead et al. 1987b, 1992b). The mechanism by which certain polyalphaolefin fluids may produce respiratory tract irritation is not understood. 

The respiratory tract is protected by a number of defence mechanisms, including ... 

The GI tract plays the most significant role in toxicants entering the body through ingestion. Food or drink is the usual mechanism of exposure. Airborne particles (either solid or liquid) can also lodge in the mucus of the upper respiratory tract and be swallowed. 

A number of cells, including cytotoxic T lymphocytes, NK cells, and mononuclear phagocytic cells, are endowed with cytotoxic abilities and thus mediate important immunosurveillance mechanisms against neoplastic cells and viral infections. In immune-compromised hosts, a correlation has been observed between low NK cell activity and morbidity [22-25] or the incidence and severity of upper respiratory tract infections [24],... 

Mechanisms underlying non-IgE mediated food allergy include immune complex formation and activation of lymphocytes. As with IgE-mediated responses, manifestations can be in the skin, gut, or respiratory tract however, these reactions take several hours to days to develop [65],... 

Respiratory hypersensitivity is an adverse reaction in the respiratory tract driven by immune mechanisms such as IgE antibody mediated allergic responses. Other less well understood mechanisms that have an immune component are also involved in respiratory hypersensitivity. OA is one outcome of respiratory hypersensitivity. Respiratory hypersensitivity and OA to proteins are primarily mediated by IgE antibody with subsequent inflammatory cell infiltrates. This same mechanism is responsible for OA to specific LMW chemicals such as the acid anhydrides and platinum salts. However, the role for IgE mediated responses in OA to other LMW chemicals such as the isocyanates and plicatic acid is poorly defined and other mechanisms may be responsible. 

An increased incidence in mycoplasma infections in rats exposed to 260 ppm hexachloroethane for 6 weeks suggests that hexachloroethane might weaken resistance to infection (Weeks et al. 1979). This could be the result of either a change in the quantity or consistency of the respiratory tract mucus or a systemic weakening of the immune system. The data are inadequate to formulate any hypothesis regarding the mechanism for diminished host resistance or to postulate whether hexachloroethane in the environment might lower the resistance of humans to respiratory infections. 

The available data on retention in the respiratory tract, as summarized by Mitchell (M6) indicate that upwards of 20% of inhaled aerosols are retained in the respiratory tract, approaching 100% for particles over 5 microns in diameter. The order of retention follows reasonably well what would be expected from the physics of the various deposition mechanisms assuming that once deposited a particle is retained by the surface. This would,... 

From a drug delivery perspective, the components of the host defence system comprise barriers that must be overcome to ensure efficient drug deposition as well as retention in and absorption from the respiratory tract. Important non-absorptive clearance mechanisms include mucociliary clearance, alveolar macrophages and metabolism (Figure 6.2). 

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