Ozone inhibition

Nobel and Wang reported that the permeability of the outer membranes of chloroplasts was increased by exposure to ozone (at 30 ppm for 5 min). They hypothesized that the effect was lipid oxidation. Freebaim showed that ozone inhibited respiratory activities of isolated mitochondria, and Lee found that the effect of ozone on oxidative phosphorylation was greater than on oxygen uptake. Mudd et reported that the metabolism of UDP-galactose by isolated... 

When soybean leaves and pine needles were exposed to ozone, there was an initial decrease in the levels of soluble sugars followed by a subsequent increase. Ozone exposure also caused a decrease in the activity of the glycolytic pathway and the decrease in the activity was reflected in a lowered rate of nitrate reduction. Amino acids and protein also accumulated in soybean leaves following exposure. Ozone increased the activities of enzymes involved in phenol metabolism (phenylalanine ammonia lyase and polyphenoloxidase). There was also an increase in the levels of total phenols. Leachates from fescue leaves exposed to ozone inhibited nodulation. 

The Glow of Phosphorus—Effect of Pressure upon Oxidation of Phosphorus— Velocity of the Reaction—Effect of Temperature—Production of Ozone— Inhibition of the Glow—Nature of the Chemiluminescence—Ionisation by the Glow—The Emission Spectrum. 

As it has been shown the main products of cumene ozonolysis are OZ, DMPC and CHP. In acetic acid, the product composition remains the same, but the amount of the products is decreased by about 1.6 times. The rates of CHP and OZ formation are lower by about 8.8 and 1.6 fold, respectively, and the rate of DMC accumulation grows 1.6 times. The ratio of the products is found to be 2.1 1.9 1 = OZ DMPC CHP. The rate constant (k) characterizing the ozone-acetic interaction at ambient temperature amounts to 1.5x10 M.s that is by about S.SxKH smaller than that found for the ozone reaction with cumene (k = 0.35 M. s ). It is known that AcOH deactivates ozone, inhibits R02 -radicals and protects the benzene ring [9-101], The deactivation of ozone in AcOH is also confirmed by the change of the molar coefficient in the UV-spectmm as compared with that in CCl,. 

These materials are added to plastics to slow the deterioration of the finished product that occurs from exposure to ozone. They typically function by migrating to the surface of the product and then create an ozone-inhibiting barrier layer at the surface. The most eflcctive ozone inhibitors include trimethylquinolines and phenylenediamines. Their functionality is achieved through interference with ozone-induced free radical reactions with the host polymer. 

It is thus anticipated that compressive stress inhibits while tensile stress promotes chemical processes which necessitate a rehybridization of the carbon atom from the sp3 to the sp2 state, regardless of the reaction mechanism. This tendency has been verified for model ring-compounds during the hydrogen abstraction reactions by ozone and methyl radicals the abstraction rate increases from cyclopropane (c3) to cyclononane (c9), then decreases afterwards in the order anticipated from Es [79]. The following relationship was derived for this type of reactions ... 

The kinetics of the various reactions have been explored in detail using large-volume chambers that can be used to simulate reactions in the troposphere. They have frequently used hydroxyl radicals formed by photolysis of methyl (or ethyl) nitrite, with the addition of NO to inhibit photolysis of NO2. This would result in the formation of 0( P) atoms, and subsequent reaction with Oj would produce ozone, and hence NO3 radicals from NOj. Nitrate radicals are produced by the thermal decomposition of NjOj, and in experiments with O3, a scavenger for hydroxyl radicals is added. Details of the different experimental procedures for the measurement of absolute and relative rates have been summarized, and attention drawn to the often considerable spread of values for experiments carried out at room temperature (-298 K) (Atkinson 1986). It should be emphasized that in the real troposphere, both the rates—and possibly the products—of transformation will be determined by seasonal differences both in temperature and the intensity of solar radiation. These are determined both by latitude and altitude. 

Denitrification involves the sequential formation of nitrite, nitric oxide, and nitrous oxide. Two aspects of nitric oxide have attracted attention (a) chemical oxidation of biogenic nitric oxide to Nq, in the context of increased ozone formation (Stohl et al. 1996) and (b) the physiological role in mammalian systems (Feldman et al. 1993 Stuehr et al. 2004), in parasitic infections (James 1995), and in the inhibition of bacterial respiration (Nagata et al. 1998). Nitric oxide may be produced microbiologically in widely different reactions such as... 

Yeadon, M., Wilkinson, D. and Payne, A.N. (1990). Ozone induces bronchial hyperresponsiveness to inhaled substance P through functional inhibition of enkephalinase. Br. J. Pharmacol. 99, 191P. 

It hag been shown that transition of a backbone carbon from the sp to sp state is promoted by tensile stresses and inhibited by compressive strains (10,44). The acceleration of the process of ozone oxidation of the polymers under load is not associated with the changes in supramolecular structure or segmental mobility of the chain. The probably reason of this effect is a decreasing of the activation energy for hydrogen abstraction (44). The mechanism of initial stages of the reaction of ozone with PP can be represented as ... 

Pendino, K J. et al., Inhibition of macrophages with gadolinium chloride abrogates ozone-induced pulmonary injury and inflammatory mediator production, Am. J. Respir. Cell Molec. Biol., 13, 125, 1995. 

GEA-3175 is more stable than GEA-3162 in vitro but still retains its biological activity [95]. The release of NO and NO2 by GEA 3175 was increased 140-fold in the presence of human plasma, as analyzed by ozone chemiluminescence [94]. GEA 3175 inhibited agonist-induced platelet aggregation and induced a more than 4-fold increase in platelet cGMP without affecting cAMP levels [94]. Thrombin-stimulated rises in the cytosolic free Ca2+ concentration and secretion were dose-dependently inhibited by GEA 3175. GEA 3175 showed a reduced capacity to inhibit platelet aggregation of uremic platelets compared to controls [96]. 

As discussed in detail by Dillard et al. and by Mittman et al. the possible relationship of lysosomal proteases to chronic lung disease has been inferred from the finding of an increased incidence of emphysema in subjects deficient in serum ai>antitrypsin factor, an -globulin that can inhibit lysosomal proteases. (No effect of ozone on serum aj-antitrypsin inhibitor was noted in rabbits chronically exposed to ozone. ) Thus, an ozone-induced increase in concentrations of such enzymes in the lung might produce excess proteolysis and result in eventual chronic lung disease. However, the available evidence is inadequate to support the belief that such a process occurs in humans intermittently exposed to ozone. Further studies of this potential hazard would be of value. 

Fetner has also demonstrated chromatid breaks in a human tissue-culture cell line exposed to ozone at 8 ppm for 5 min. Other tissue-culture studies include that of Sachsenmaier et who noted tetraploidy and other chromosomal abnormalities in embryonic chick fibroblasts exposed to ozone and a decrease in transplantability of mouse ascites tumor cells. In addition, Pace et demonstrated an interference by ozone with mitotic activity in two tissue-culture cell lines. More recently, Booher et al. reported that lung cells exposed in culture to ozone concentrations as low as 0.3 ppm demonstrated an inhibition in growth that was proportional to the ozone concentration. 

Fetner, R. H. Mitotic Inhibition Induced in Grasshopper Neuroblasts by Exposure to Ozone. Technical Documentary Report SAM-TDR 63 39. Brodcs Air Force Base, Texas USAF School of Aerospace Medicine, Aerospace Medical Diviskm (AFSa, June 1%3. 

Todd reported that the respiration of pinto bean leaves was stimulated by exposure to ozone (at 4 ppm for 40 min). The first measurements were 4 h after the ozone exposure. The respiration rate later declined to the control value. In all cases, increased respiration correlated well with visible injury. MacdowalP confirmed these results, but made an additional observation during the first hour after ozone exposure (at 0.7 ppm for 1 h), and before visible symptoms appeared, respiration was inhibited. The increase in respiration took place only later, when visible symptoms appeared. Dugger and Palmer" reported an increase in respiration in lemon leaf tissue after 5 days of exposure to ozone at 0.15-0.25 ppm for 8 h/day. They reported no morphologic changes at that time. Anderson and Taylor S found that ozone induced carbon dioxide evolution in tobacco callus tissue. The threshold for evolution was about 0.1 ppm for 2 h in the sensitive Bel W,. The ozone concentration required for maximal carbon dioxide evolution was about twice as much in the more resistant cultivar. Formation of roots decreased sensitivity. 

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