Protective effect

Apart from antioxidant activity (see Chapter 9), Maillard products have been found to have antimutagenic, antibiotic, and antiallergenic effects. Chemopreventive effects were mentioned at the beginning of this chapter. 

AGEs exhibit a biphasic effect on the proliferation of cells, proliferative at low and antiproliferative at high concentrations, e.g., at 1-10 and 20 fig ml-1 BSA-AGE, respectively.326 Proliferation also depends on the type of AGE, e.g., early-glycation products of BSA reduced the proliferation of pericytes by 40%, whereas AGE-BSA increased it 156%.327 

Yen and Hsieh328 have shown that the mutagenicity of IQ on S. typhimurium TA98 and TA100 was strongly inhibited in the presence of Maillard products from xylose-lysine (1 2 mol, 100 °C, pH 9, 1 h). They demonstrated that the effect was due to the formation of inactive adducts with IQ metabolites and not to the direct inhibition of the hepatic microsomal activation required to transform inactive IQ into a DNA-alkylating agent. 

Scavenging free radicals may also play a role in the antimutagenicity of melanoidins. 

According to Kato et al.,329 nondialysable melanoidins from glucose-glycine degrade nitrite and prevent nitrosamine formation, both maximally at pH 1.2. Treatment with nitrite greatly enhances the antimutagenicity of the melanoidins. 

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Urethane [51-79-6] (ethyl carbamate) occurs as a natural by-product in fermented products such as wine, Hquors, yogurt, beer, bread, oHves, cheeses, and soy sauces. Whereas urethane has a known cancer etiology in experimental animals, no such relationship has yet been proven in humans (108,109). Alcohol may act by blocking the metaboHsm of urethane, and thus exert a protective effect in humans consuming alcohoHc beverages (110). 

Teratogenic effects have been noted with 2- and 4-aminophenol in the hamster, but 3-aminophenol was without effect in the hamster and rat (129,130). 4-Aminophenol is known to inhibit DNA synthesis and alter DNA stmcture in human lymphoblasts (131,132) and is mutagenic in mouse micronuclei tests (133). The aminophenols have been shown to be genotoxic, as evidenced by the induction of sister chromatid exchanges (134,135), but they also exert a protective effect against DNA interaction with other noxious chemicals (136). After assessment of available data a recent report stated that the aminophenols were safe as cosmetic ingredients in their present uses and concentrations (137). 

Diethjidithiocarbamate [20624-25-3] (DDC) is both an inhibitor of SOD and a thiol, and exerts both radiosensitizing and radioprotective properties in mice, depending on factors such as the time of its adniinistration relative to irradiation. For neutrons, DDC shows only protective effects (141). DDC (1 mg/g ip) given 30 min before 15 Gy (1500 rad) also protects mouse jejunal crypt ceUs and reduces the frequency of micronuclei in splenic lymphocytes (134). 

Synergy has been reported between lL-1, lL-3, and SCE, ki enhancing the survival of lethaHy kradiated mice engrafted with 2 x 10 BM cells and immediately given cytokiaes once daily for five days (173). SCE alone does not enhance survival, and lL-1 or lL-3 has limited effect. Pretreatkig mice with thymopentki, a synthetic pentapeptide derivative of thymopoietin, enhances the protective effect of lL-1 a, as kidicated by 30-day survival (174). 

Administration of lL-12 before lethal y-kradiation of mice protects against hemopoietic death and increases the number of BM cells at six days after kradiation, but sensitizes for G1 injury (189). The protective effects are abrogated by anti-lL-1 receptor or anti-SCE antibodies but not by anti-lEN- y antibodies. The sensitizing effect of lL-12 may be due to its abiUty to prime for TNE and lL-6, and can be aboHshed by anti-lEN antibody. 

In contrast to these protective effects, acute high dose (25 mg/kg) INDO injected ip 30 min prior to y-irradiation decreases the LD q of mice from... 

Selenium deficiency has been identified iu humans iu a broad area of China, stretching from the northeast to the southwest. Two syndromes are evident Keshan disease, an endemic cardiomyopathy which affects children, and Kashin-Beck disease, an edemic osteoarthropathy (big-joiat), also mainly involving children, which occurs iu eastern Siberia and parts of China. As a result of these observations, a protective effect for selenium has been proposed, and various selenium-containing preparations have been appHed to preserve animal and human health. 

Several studies have investigated the role of dietary factors in prostate cancer risk, but results appear inconsistent. Significant effects have not been detected for dietary soya products certain vegetables, beans, fruit, rice and seaweed appear to be protective in some studies, while another has shown no protective effect from seaweed or vegetable consumption. In addition, a number of other risk factors have been shown to be associated with an increased risk of this cancer, including meat and dairy products and carotenoids. 

Thus, it is uncertain to what extent the apparent protective effects of fruit and vegetable consumption on risk of stomach cancer can be attributable to their phytoestrogen content. This appears not to have been studied directly, and other constituents such as ascorbic acid (vitamin C), a-tocopherol (vitamin E) and /1-carotene may be potentially protective. 

Electrolytic corrosion occurs in regions I and IV with the formation of soluble iron ions. Solid corrosion products which can have a protective effect are formed in region II. This is the region of surface film passivity. Certain corrosive sub-... 

Production platforms are coated only in exceptional cases or for the purposes of investigation because the life of the structure is greater than the life of the coating. Therefore in the design of the cathodic protection, only the protection potential Us of the steel need be considered. Steels with an ultimate tensile strength of up to 350 N mm are used for these structures, which are weldable even in thick sections, and the hardness of the welded material can be kept to 350 HV (see Section 2.3.4 [2,10]). Aluminum anodes with the same protection effect and life as zinc anodes have much less weight. This is a very important advantage for... 

Since cathodic protection of concrete structures in the United States has been very much advanced, protection criteria have been developed [46]. They correspond to the pragmatic criteria Nos. 3 and 4 in Table 3-3 (see Section 3.3.3.1). It is assumed that the protective effect is adequate if, upon switching off the protection current, the potential becomes more than 0.1 V more positive within 4 hours. The measurements are carried out in various parts of the protected object with built-in Ag-AgCl reference electrodes or with any electrodes on the external surface. 

NB There is also conclusive evidence that these agents have a protective effect against cancers of the ovary and endometrium) Oral contraceptives, sequential (Suppl. 7 1987)... 

A small temperature difference of the supply air relative to the surrounding air will not result in a protection effect since the density difference will be too low to result in the expected vertical air transport. If the temperature of the supply air is too low problems will result due to drafts on the worker, which will increase the risk that he or she will move from the protected zone if possible. 

One of the most important problems in the sphere of industrial activity is that attending high ambient temperature. Therefore, the search is on for substances that can increase the resistance of organisms to dangerous overheating. Experiments on white rats show that substance 103, called azomopine, has a protecting effect in different temperature regimes. 

Pits seldom form in close proximity to one another and it would appear that the area of passivated metal, which acts as the cathode for the local cell, is protected by the anodic dissolution of metal within the pit—a phenomenon that is referred to as the mutually protective effect see Section 1.5). 

Molybdenum tends to be protected by vanadium in aerated 7 1 % hydrochloric acid and it receives a high degree of protection when coupled with copper in this medium. Molybdenum corrodes somewhat faster than normal in 3 1 % nitric acid when coupled with tungsten. It is not affected by contact with titanium in 3-1% nitric acid. It is protected by aluminium and copper in aerated 10% formic acid and by aluminium in air-aerated 9% oxalic acid. In the latter solution, copper had only a slight protective effect when coupled with molybdenum. 

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