Other Synergisms

Additions of 1/10 to 2 1/2% of urea to dilute procaine solutions increase materially their potency, to ten times, on direct application to nerve trunks, presumably by favoring penetration. The effect is not due to alkalinization. The action of local anesthetics is reported to be increased by intravenous injection of methylene blue, by the local application of caffeine or theophylline, by morphine, and by the antipyretic analgesics. Cocaine anesthesia is said to be ineffective in tissue impregnated with oxalic acid. Inflamed tissues are less susceptible to local anesthesia, probably because of their difficult penetration. 

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Although aminyl radicals are stable towards oxygen, they can oxidi2e other aromatic amines, phenols and thiols (10), and regenerate the diarylamine. Thus, mixtures of phenols and diarylamines frequendy show better antioxidant activity than either one alone. This is called synergism. 

Competition Predation Commensalism Mutualism Synergism Antibiosis A race for nutrients and space One feeds on another One lives off another with negligible help or barm Each benefits the other Combination has cooperative metabolism One excretes a factor harmful to the other... 

Many groups throughout the world tried to repeat the experiments using similar in vitro assays and other test systems, but without success. Current experimental data suggest additive interactions do occur between EDs, but the issue of interactive effects, and synergism in particular, will undoubtedly remain a topic of intense debate for some time to come. 

Antioxidants are today often used in combination. One reason for this is that certain combinations can exhibit in a polymer an effect sometimes found with other additives, that known as synergism. In these circumstances two antioxidants may exhibit a co-operative effect and be more powerful than either antioxidant used alone, even when the total antioxidant concentration is the same. Certain terms are sometimes encountered here and these are defined in Table 7.6. 

In many of their complexes PF3 and PPI13 (for example) resemble CO (p. 926) and this at one time encouraged the belief that their bonding capabilities were influenced not only by the factors (p. 198) which affect the stability of the a P M interaction which uses the lone-pair of elecU"ons on p and a vacant orbital on M, but also by the possibility of synergic n back-donation from a nonbonding d , pair of electrons on the metal into a vacant 3d , orbital on P. It is, however, not clear to what extent, if any, the a and n bonds reinforce each other, and more recent descriptions are based on an MO approach which uses all (cr and n) orbitals of appropriate symmeU"y on both the phosphine and the metal-containing moiety. To the extent that a and n bonding effects on the stability of metal-phosphorus bonds can be isolated from each otlier and from steric factors (see below) the accepted sequence of effects is as follows ... 

A higher than expected incidence of CHF is also observed in patients treated with DOX and other cytotoxics (e.g., the taxane paclitaxel) or new generation targeted agents (e.g., the humanized anti-ErbB-2/neu monoclonal antibody trastuzumab) [3]. The cardiotoxic synergism of DOX with taxanes or... 

Molybdate is always used in conjunction with other anion inhibitors, not only to reduce the cost of the inhibitor program, but also because, through synergism, much-improved barrier films are produced when coupled with nitrite or silicate. 

Other cases of potentiation will be discussed in later chapters dealing with individual pollutants. These will include the synergism of pyrethroid toxicity to... 

The most common natural antioxidants are tocopherols, ascorbic acid and P-carotene (more often synthetic nature-identical compounds than natural products). Their changes were studied in detail in model systems, fats and oils, but experimental evidence is mainly lacking on more complicated systems, such as natural foods and ready dishes. Still less is known on different antioxidants from spices and from essential oils. These data will probably be obtained gradually. Very little is known about synergism of antioxidants in food products other than edible fats and oils or their regeneration from the respective free radicals and quinones. In mixtures, some antioxidants are preferentially destroyed and others are saved. Some data have already been published, but these complex changes should be studied in more detail. 

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