Defensive role

Several observations are suggestive of a potential intriguing defensive role of CX3CL1 against the detrimental effects of HIV infection in the nervous system. 

Sudatti DB, Rodrigues SV, Coutinho R, Da Gama BAP, Salgado LT, Amado Filho GM, Pereira RC. Transport and defensive role of elatol at the surface of the red seaweed Laurencia obtusa. J Phycol (in press)... 

Evolution of chemical defenses according to the optimal defense theory presumes, in addition to costly defenses, that there is genetic variation for the defensive metabolites, that herbivory is the major selective agent for such metabolites, and that the chemical trait in question is efficient in reducing herbivory (Stamp 2003). Research on macroalgal chemical defenses has strongly emphasized the last precondition, which has mainly been studied by testing the deterrence effects of secondary metabolites in bioassays. The defensive role for the trait has been assumed on the basis of deterrence it provides. Veiy little research on the first two... 

Kubanek J, Whalen KE, Engel S, Kelly SR, Henkel TP, Fenical W, Pawlik JR (2002) Multiple defensive roles for triterpene glycosides from two Caribbean sponges. Oecologia 131 125-136... 

Proksch P, Defensive roles for secondary metabolites from marine sponges and sponge-feeding nudibranchs, 7 xz co 32 639-655, 1994. 

Adkins, Y., and Lonnerdal, B. (2003). Potential host-defense role of a human milk vitamin B-12-binding protein, haptocorrin, in the gastrointestinal tract of breastfed infants, as assessed with porcine haptocorrin in vitro. Am. ]. Clin. Nutr. 77,1234—1240. 

Brominated compounds widely occur in marine organisms, particularly seaweeds and invertebrates. Many of them play a defensive role against parasites and predators, and are incorporated by opisthobranch mollusks to this scope from the diet. Bromine is uptaken by seaweeds and invertebrates from bromide dissolved at sparingly 1 mM concentration in seawater. The process is catalyzed by haloperoxidases, which have been characterized both as structure and function (Butler 1997). 

Other examples of messengers of biodiversity are shown in Table 12.4. However, observations as to the defensive role of metabolites are often circumstantial. Thus, tetrodotoxin, long thought to be a defensive compound in a tropical fish, Fugu niphobles, has recently been found to play a pheromonal role in the fish (Table 12.4). Similar conclusions have been drawn for prostaglandins in fish (Matsumura 1995). 

Kaempferol can increase seed production in Petunia, whether produced as a result of pollination or by wounding. It has been suggested that the reproductive function of flavonols may have evolved from a defensive role. Allelopathic flavonoids in the stigma may prevent introduction of pathogens into the pistil. 

General purpose anti-personnel grenades are also used by military in both offensive and defensive roles in the hand-mode or launching (from the rifle) mode. The Defence Research and Development Organization, India (DRDO) has recently developed a state-of-the-art multimode grenade named Shivalik which has greatly enhanced the fire power of the infantry soldiers. 

PPO catalyses the dependent oxidation of phenolics to quinones. The secondary reactions of quinones lead to the formation of polymeric brown or black pigments, which are responsible for significant post-harvest losses of fruits and vegetables [72]. Finally, induced PPO activity consists of both systemic and localized components. Systemic induction of PPO in tissues in response to all types of injuries may represent a broad, defensive role for PPO in protection of juvenile tissues from subsequent attack by a broad spectrum of pathogens and pests [71]. 

Many halogenated metabolites are thought to be involved in chemical defense roles to keep predators away from a particular organism. Some of these compounds may also be of pharmacological interest. 

Benkendorff K, Bremner JB, Davis AR (2000) Tyrian Purple Precursors in the Egg Masses of the Australian Muricid, Dicathais orbita A Possible Defensive Role. J Chem Ecol 26 1037... 

The key enzymes of the system are the cytochrome P-450 enzymes, which have active sites that contain an iron atom that cycles between the +2 and +3 oxidation states. These enzymes bind to the substrate and molecular 02as part of the substrate oxidation process. Cytochrome P-450 is found most abundantly in the livers of vertebrates, reflecting the liver s role as the body s primary defender against systemic poisons. Cytochrome P-450 occurs in many other parts of the body, such as the kidney, ovaries, testes, and blood. The presence of this enzyme in the lungs, skin, and gastrointestinal tract may reflect their defensive roles against toxicants. 

Thompson et al. have investigated the ecological role of the brominated isoxazoline alkaloids, aerothionin (Structure 2.84) and homoaerothionin (Structure 2.89), in Californian specimens of A. fistularis.134 139 The alkaloids caused behavioral modification in marine invertebrates, were toxic to dorid nudibranchs other than one specialized feeder, inhibited the settlement and/or metamorphosis of invertebrate larvae, and were strongly antimicrobial and cytotoxic. Sponges exuded significantly more of these two alkaloids when wounded,155 and, consistent with their defensive role, the metabolites were found to be localized in spherulous cells close to the aquiferous exhalant canals.156... 

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