Resistance animal defenses

Viral infections continue to be significant causes of morbidity and mortality and at the same time continue to be resistant to treatment by small molecules. Avridine (6) is an antiviral compound which has shown some activity in a variety of animal tests apparently based upon its ability to stimulate a number of cells to produce the high molecular weight endogenous antiviral substance interferon. Thus, the compound is believed to operate indirectly by stimulating the body s own natural defenses against viral penetration into host cells. Avridine is synthesized by... 

Potential therapeutic applications of host defense peptides also include the lantibiotic nisin. Indeed, nisin has had an impressive history as a food preservative with FDA approval in 1988 for use in pasteurized, processed cheese spreads. The attractiveness of nisin as a potential therapeutic is also enhanced due to its relative resistance to proteases and broad spectrum Gram-positive antimicrobial activity including multidrug-resistant strains. Biosynexus Inc. has licensed the use of nisin for human clinical applications and Immucell Corp. has licensed the use of Mast Out, an antimastitic nisin-containing product, to Pfizer Animal Health." Indeed, nisin formulations have been used as an active agent in the topical therapies Mast Out and Wipe-Out for bovine mastitis, an inflammatory disorder of the udder that is the most persistent disease in dairy cows." ... 

The practice of incorporating low levels of antibiotics in livestock feeds to promote growth has been particularly controversial. It is feared that this practice will result in development of resistant bacteria in animals, which will in turn be passed on to humans, thus diminishing the effectiveness of antibiotics in treatment of human disease. A petition from the Natural Resources Defense Council to ban such uses of penicillin and tetracyclines recently was denied by the Secretary of Health and Human Services. The controversy therefore is likely to continue. Opinion on the subject is quite polarized, and several points of view are presented in this book. 

In the coevolutionary interactions of plants and animals, lipids play a major role. They function as ecomones (pheromones, allomones and kairomones) and have been classified by their function. Host plant resistance is partially dependent on these chemical constituents. Lipids may be subdivided into two types. Volatile lipids are generally involved in long distance interactions whereas non-volatile lipids are generally involved after the insect has contacted the host plant. Several examples of each are reviewed. Utilization of these compounds to promote increased host plant resistance could be accomplished by selection of plants rich in allomones, lacking kairomones for a particular pest or those with inducible systems of defense. Another approach is to isolate the defensive compounds of one plant and apply them to crop plants. Trap crops could also be used to lure insects away from other crops. 

Some shelled gastropods do produce chemical defenses, although this is far less common. One South African limpet, Siphonaria capensis, occurs at very high densities on rocky shores, apparently protected from predators by chemical feeding deterrents. These animals are rarely consumed relative to Patella granularis (a similar limpet that lacks defensive chemistry) and exude a repellent mucus onto the surface of their shell when attacked. Nonpolar extracts from Siphonaria confer resistance from predation to Patella when they are coated on its shell.20 Because the metabolites responsible for the chemical defense have not been fully isolated and characterized, it is still unclear whether the compounds that confer resistance to predation in Siphonaria are diet derived or synthesized de novo. 

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