Detoxification capacity

Harju, A. (1996). Effect of birch (Betula pendula) bark and food protein level on root voles (Microtus oeconomus) II. Detoxification capacity. Journal of Chemical Ecology 22, 719-728. 

In our studies we used model systems to elucidate detoxification capacities of weeds and crops for benzoxazolin-2(3H)-one. Model systems have the advantage of demonstrating biochemical events that may not show under complex natural field conditions. The purpose of these studies is to gain insights in the possible participation of detoxification in the often observed difference of monocots and dicots against allelochemicals. Second, we questioned whether detoxification capacities reflect the membership of species to defined plant communities. 

Several members of the Poaceae were checked for BOA detoxification capacity the results are presented in Table 4.1. All species, with one exception, contained the A/-glucoside, although there were remarkable differences in the accumulated amounts following incubation at 24 h and 48 h. Zea mays exhibited the most effective detoxification capacity, as BOA-6-O-glucoside was synthesized in traces only or was a minor product. The A/-glucosylated compound already... 

We tested a number of dicot species for their ability to detoxify BOA. Most of them were incubated as seedlings but some as adult plants when germination failed under laboratory conditions. Applied BOA concentration was 100 and 500 pM, incubation time was 24 h. The plants were separated into roots and shoots after incubation and the material extracted with 30% methanol. HPLC analyses of the extracts revealed remarkable differences in the detoxification capacities. Major detoxification appeared within the roots, whereas shoots were only involved when roots seemed to be overtaxed. All species tested were able to perform BOA-6-O-glucoside synthesis, but with regard to glucoside carbamate synthesis, differences became obvious (Table 4.2). 

BOA detoxification capacity of several weeds with regard to glucoside carbamate synthesis within 24 h. 

In a further approach, we checked some species belonging to Amarantho-Chenopodion communities (syn. Consolido-Eragrostion poaeoidis) for their detoxification capacities (Table 4.3). 

Detoxification Capacity Species Detoxification Products after 24 h of Incubation Family Vegetation Class... 

Yu, S. J., Age variation in insecticide susceptibility and detoxification capacity of fall armyworm (Lepidoptera Noctuidae) larvae, /. Econ. Entomoi, 76, 219,1983. 

Leopold and Ardrey (1972) have reported that humans have not been plant feeders nearly as long as the other animals, perhaps because they learned early in their evolution that many plants were poisonous. According to these authors, humans learned to detoxify plant toxins by cooking them only about 40,000 years ago. If so, humans have been carnivores throughout most of their evolution and have had less opportunity to evolve biochemical defenses against the plant toxins. This may explain why humans have lower detoxification capacity compared to other mammals (see Figure 9.1). 

Insecticide resistance has been shown to involve three principal mechanisms, i.e., enhanced detoxification, decreased penetration, and target site insensitivity. Usually these factors interact with one another so that the effect of each is magnified. There are two kinds of insects, those that are already tolerant and those that are susceptible at first but become resistant later. The former may be tolerant because of behavior, morphology, or detoxification capacity. The latter become resistant because of selection of individuals that possess higher levels of detoxification enzyme activity and which are thus able to survive and produce progeny. All of these aspects of resistance will be discussed at length in Chapter 10. 

Alkalosis and hypokalaemia (possibly caused by secondary hyperaldosteronism or use of diuretics) shift the dissociation constant towards free, toxic NH3. By contrast, ammonia is considered - in a process resembling a vicious circle - to be a secondary stimulus for aldosterone production. Thiazide diuretics in particular put an overload on the detoxification capacity of the scavenger cells. This is because of an insufficient supply of bicarbonate for carbamoyl phosphate synthetase reaction due to diuretic-induced inhibition of the mitochondrial carboanhydrase. 

In an in vitro study, plasma from HIV-positive patients was less able to detoxify nitrososulfamethoxazole than control plasma, suggesting that a disturbance in redox balance in HIV-positive patients may alter metabolic detoxification capacity, thereby predisposing to sulfamethoxazole hypersensitivity (177). 

Plantago major presents an exception because it is the only dicot tested exhibiting BOA-N-glucosylation comparable with com. As the species colonizes disturbed localities it is possibly under a strong selection pressure. Carduus nutans and Daucus carota are able to co-exsist with Agropyron repens, a very aggressive monocot that contains benzoxazinones as secondary constituents, which are released by root exudation. This association may explain the relatively well developed detoxification capacity. 

Species with good detoxification capacities ( associated with Agropyron repens)... 

Species with moderate detoxification capacities ( extinguished or endangered)... 

Environmental residues of pyrethroids and pyrethr-ins are degraded by hydrolysis, and pyrethrins by photolysis, and so do not accumulate in most ecosystems. The main environmental hazard associated with pyrethroid use is contamination of freshwater by acute run-off after use as an agricultural pesticide or ectoparisitide near to water, which can lead to death of aquatic invertebrates or fish (which have very limited pyrethroid detoxification capacity). 

The biodistribution of CN to various systemic tissues will determine the relative proportions of CN present at detoxification and target tissue or cellular sites. For example, inhaled or percutaneously absorbed CN enters the systemic circulation and only a small proportion of the absorbed dose will be available for first-pass detoxification, particularly in the liver. In contrast, a high proportion of a p.o. dose will pass through the liver and be available for first-pass detoxification. However, hepatic detoxification processes may be complex, since it has been demonstrated that dietary variations that cause alterations in hepatic sulfurtransferase activity do not correlate with CN toxicity (Rutkowski et ah, 1985), and extensive chemical or surgical injury to the liver does not increase the susceptibility of the mouse to CN toxicity (Rutkowski et ah, 1986). The influence of route on toxicity is probably due to the relative effects of plasma transulfuration, sequestration by erythrocytes, intracellular macromolecular binding, and the differential distribution to all tissues with a detoxification capacity. 

Alkenylbenzenes are not directly hepatotoxic or hepatocar-cinogenic. Cytochrome P450 enzymes in the liver oxidize the double bond of alkenylbenzenes to an epoxide, which is mostly conjugated by glutathione for excretion, but at levels exceeding the detoxification capacity, the overflow can... 

If the amount of xenobiotics surpasses the detoxification capacity of the body, the symptoms of poisoning may appear, and damage to the body may follow. In this case, induced or artificial detoxification seems to make sense. The question is do the usually recommended methods help the process Another question is whether it is sufficient to do this aimually or it is better to detoxify continuously. 

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