Cross-resistance interaction phenomena

As in vitro methods for studying cytochrome P-450 in insects became available (11-131, it soon became clear that insects with high cytochrome P-450 activities were resistant to carbamates and most other insecticides. This phenomenon is termed metabolic cross resistance and derives from the characteristic of cytochrome P-450 of accepting a very wide range of molecular structures as substrates the cytochrome binds the substrate very loosely by a lipophilic interaction and rapidly oxidizes it by an oxygen free radical-mediated reaction, a very powerful combination. Moreover, the cytochrome occurs in several or many different isoenzymic forms with broadly overlapping substrate preferences. A normally infrequent form may be selectively induced by allelochemicals in the crop plants (14), and if the induced form has survival value in the presence of an insecticide, it could be selected to dominate in the exposed population (15). 

Although the phenomena of transport of various species to (or from) the interface and the simultaneous reaction can be accounted for by the theories of gas-liquid systems, the third phenomenon crossing of the interface may require a different treatment. Firstly, in cases of heavily contaminated liquid-liquid systems, interfacial resistance may no longer be negligible. Secondly interfacial turbulence, which is produced by the interaction of mass transfer with interfacial tension, is in many cases very important. Indeed, there is very limited information in the role of this and certain other secondary phenomena in extraction with reaction (9). 

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