Protective mechanism

For most processes, the optimum operating point is determined by a constraint. The constraint might be a product specification (a product stream can contain no more than 2 percent ethane) violation of this constraint causes off-specification product. The constraint might be an equipment hmit (vessel pressure rating is 300 psig) violation of this constraint causes the equipment protection mechanism (pressure relief device) to activate. As the penalties are serious, violation of such constraints must be very infrequent. 

The optimum PVC that provides the best corrosion protection for the substrate is a strong function of the corrosion protecting mechanism. Figs. 8-10 represent primer films based on three different protection mechanisms, and indicate the appropriate formulating windows for each type of primer. 

Skin has several protective mechanisms in addition to its thick epidermis that prevent many chemical compounds from penetrating it. Eccrine (sweat)... 

Even if the receptor by itself has high accuracy, the sensor may be unable to execute the measurement in a defined place. Quality and total accuracy depend on the combination of receptor, the converter for measured values, and mechanical protection. Mechanical protection can take the form of pockets in water and fluid and also assembly boxes which protect against pollution, humidity, and temperature in the surroundings or against electromagnetic transmissions and noise from power-supplied pipes and cables. 

Kaxp channels under investigation resulted in selective rescue of substantia nigra dopaminergic neurons does not prove a deleterious, neurodegeneration-promoting role of Katp channels, but may simply mean that the dopamine neurons, lacking KATP channels, have developed other, undetected self-protection mechanisms. 

EPC is the endogenous cellular protective mechanism in the heart by which brief periods of ischemia induce protection against infarction due to subsequent longer periods of ischemia. 

As a protective mechanism, the corticosteroids are released during periods of stress (eg, injury or surgery). The release of epinephrine or norepinephrine by the adrenal medulla during stress has a synergistic effect along with the corticosteroids. 

Ludlow, M.M. Bjorkman, O. (1984). Paraheliotropic leaf movement in Siratro as a protective mechanism against drought-induced damage to primary photosynthetic rections damage by excessive light and heat. Planta, 161, 505-18. 

Many of the physical changes in membrane structure of cells are reversible and species differences in the degree of disruption of dry membranes may relate to differences in composition, protective mechanisms or to additional damage occurring during desiccation (see below). 

The free radical damage hypothesis of desiccation injury requires that these various protective mechanisms are unable to detoxify reactive species during dehydration and rehydration. There is evidence that free radicals increase with decreasing moisture content of seeds (Priestley et al., 1985), and, in plants subjected to episodic droughting, increased levels of malon-dialdehyde occur (Price Hendry, 1987). 

Silver RB, Mackins CJ, Smith NCE, Koritchneva IL, Lefkowitz K, Lovenberg TW> Levi R Coupling of histamine H3 receptors to neuronal Na+/H+ exchange a novel protective mechanism in myocardial ischemia, Proc Natl Acad Sci USA 2001 98 2855. Silver RB, Poonwasi KS, Seyedi N, Wilson SJ, Lovenberg TW, Levi R Decreased intracellular calcium mediates the histamine H3-receptor-induced attenuation of norepinephrine exocytosis from cardiac sympathetic nerve endings. Proc Natl Acad Sci USA 2002 99 501. 

This interceptor theory does not seem to be the only protective mechanism in operation. Inhibition of cytochrome P450 enzymes related to the bioactivation of mutagens and toxic radical scavenger activities have been proposed to integrate the different modes of action. Other investigations have reported the involvement of chlorophyUin in inducing apoptosis in human colon cells, which may be important in limiting cancer cell invasion and metastasis. ... 

The efficient removal of O2 and H2O2 vvill diminish OH formation and therefore antioxidant defence systems have evolved to limit their accumulation. Enzymic and low molecular weight antioxidants exist to scavenge free radicals as self-protection mechanisms. Some proteins exhibit antioxidant properties because they chelate transition-metal catalysts. The significance of antioxidants in relation to inflammatory joint disease is discussed below. 

O Connell, M.J., Halliwell, B., Moothouse, C.P., Aruoma, O.I., Baum, H. and Peters, T.J. (1986). Formation of hydroxyl radicals in the presence of ferritin and haemosiderin. Is haemosiderin formation a biological protective mechanism Biochem. J. 234, 727-731. 

Prostaglandins, through their effects on mucous cell secretion, basal bicarbonate secretion, and mucosal growth, are important factors in gastric healing and protection. Inhibition of prostaglandin production by NSAIDs compromises these important protective mechanisms. Finally, the antiplatelet effects of NSAIDs may worsen bleeding complications associated with PUD. 

The risk of hospitalization owing to symptomatic pelvic inflammatory disease caused by gonorrheal infection is reduced in oral contraceptive users.14 While the exact protective mechanism is unknown, it is believed that thickening of the cervical mucus and/or reduction in the ability of pathogens to enter the fallopian tubes may contribute.1... 

This system is advantageous for drugs that are highly susceptible to degradation by enzymatic processes, since it offers a protective mechanism by temporarily altering the substrate. This approach to... 

As previous investigations have shown26t37 a study of the "classical" protective mechanisms does not contribute much towards explaining the mode of action of HALS derivatives. An obvious next step therefore seemed to be a closer investigation of the action of these substances on radicals and hydroperoxides. 

One of the more important protective mechanisms is probably the ability of these substances to interact not only with various oxygen-centered radicals but also with hydroperoxides. This ability is supplemented by the formation of associates between the amine light stabilizer and species responsible for polymer degradation. 

---