Symptoms of SCBI Poisoning in Insects Pseudoparalysis
Pyrazolines and indoxacarb produce identical acute neurotoxic symptoms in the American cockroach Periplaneta americana, progressing through initial incoordination 5-20 min after 1-10 mg injection , then tremors and prostration, and finally a distinctive pseudoparalysis, so named because the apparently paralyzed insects produce violent convulsions when disturbed. This pseudoparalysis was maintained for 3-4 days, after which the ability to move when disturbed waned. By 4-6 days, the insects could...
Intrinsic Activity of Indoxacarb on Na Channels
The initial mode of action studies with indoxacarb indicated that it was a proinsecticide, being metabolized to DCJW, which potently blocked the compound action potential in M. sexta nerve in a voltage-dependent manner Wing et al., 1998 . Indoxacarb itself also had this effect, but was much slower acting while 1 mM DCJW blocked the compound action potential by 50 after 10 min, 40 min were required for indoxacarb to exert this same effect, and in that preparation one cannot be certain that the...
StructureActivity Relationships in Pyrethroids
As described above, pyrethroids form a diverse class of insecticides highly effective against a broad spectrum of insect and acarine pests. The level of activity is determined by penetration, metabolism within the insect, and the requirements at the target site. As an illustration see Figure 2 for structures , pyrethrin I has good activity against houseflies but poor activity against mites, whereas an experimental compound 29 has very high miticidal but poor insecticidal activity. Despite this...
References 1
Abdelaal, Y.A.I., Soderlund, D.M., 1980. Pyrethroid-hydrolyzing esterases in southern armyworm larvae -tissue distribution, kinetic properties, and selective inhibition. Pestici. Biochem. Physiol. 14, 282-289. AbdElghafar, S.F., Knowles, C.O., 1996. Pharmacokinetics of fenvalerate in laboratory and field strains of Helicoverpa zea Lepidoptera Noctuidae . J. Econ. Entomol. 89, 590-593. Ahmad, M., McCaffery, A.R., 1999. Penetration and metabolism of trans-cypermethrin in a susceptible and a...
Indoxacarb and the Sodium Channel Blocker Insecticides Chemistry Physiology and
Chemistry of the Na Channel Blockers 32 6.2.2.1. Chemical Evolution and Structure-Activity of the Na Channel Blocker Insecticides 32 6.2.2.2. Chemistry and Properties of Indoxacarb 32 Metabolism and Bioavailability of Indoxacarb 33 6.2.3.1. Bioactivation of Indoxacarb 33 6.2.3.2. Catabolism of Indoxacarb and Other Na Channel Blocker Insecticides 35 Physiology and Biochemistry of the Na Channel Blockers 35 6.2.4.1. Symptoms of SCBI Poisoning in Insects Pseudoparalysis 35 6.2.4.2. Block of...
Discovery of Ecdysone Agonist Insecticides and Commercial Products
Although attempts to discover insecticides with an insect molting hormone activity were made in the early 1970s Watkinson and Clarke, 1973 , it was not until a decade later that the first bisacylhydra-zine ecdysone agonist 2 in Figure 1 was serendip-itously discovered by Hsu 1991 at Rohm and Haas Company, Springs House, PA, USA. Several years later, after several chemical iterations of this early lead, a simpler, unsubstituted, but slightly more potent analog, RH-5849 3 in Figure 1 , was...
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Figure 7 Schematic diagram showing a yeast cell transformed with plasmids carrying cDNAs encoding ecdysone receptor, RXR-g, co-activator glucocorticoid receptor interaction protein GRIP , and b-galactosidase b-Gal reporter gene fused to 6 heat shock protein 27 hsp27 ecdysone response elements in a reconstituted and ecdysteroid muristerone A inducible high throughput screening system for discovery of new nonsteroidal ecdysone agonists. Figure 7 Schematic diagram showing a yeast cell transformed...
Classification of Pyrethroids
Pyrethroids, which comprise a diverse range of structures, have historically been classified into two broad groups Type I and Type II on the basis of their biological responses Table 3 . Interpretation of most mode of action studies on insects has been predicated on this classification, though this is now considered to be an overly simplistic approach. The two types of symptoms have been associated with the absence Type I or presence Type II of an a-cyano group. For example, permethrin exhibits...
Conclusions
In summary, indoxacarb is the first insecticide product that acts by blocking the voltage-dependent Na channel at site 10. The mode of action of this novel SCBI class was determined by sequential observation of poisoned insect symptoms, electrophysiology starting with intact neuronal preparations and progressing towards more targeted ion channel techniques , and confirmation with Na flux and biochemical radioligand binding techniques. It is believed that this approach is the most direct and...
Resistance Mechanisms
6.1.5.1.1.1. Metabolism of pyrethroids in insects The principal metabolic pathways by which pyre-throids are degraded in insects were mostly evaluated prior to 1985 and are summarized in Roberts and Hutson 1999 . Metabolism is conveniently divided into two phases the initial biotransformation of a pesticide is referred to as Phase I metabolism, comprising mainly oxidative, reductive, and hydrolytic processes Phase II metabolism is biotransformation, in which the pesticide or Phase I metabolite...
Catabolism of Indoxacarb and Other Na Channel Blocker Insecticides
Relatively little is known about the metabolic breakdown of indoxacarb or other SCBIs in insects. On balance, it is clear that bioactivation is occurring much more rapidly than degradation after field application, when satisfactory insect control is observed. However, like any other novel insecticide, resistance management will be a key to maintaining the agricultural utility of this insecticide class. Indeed, several field populations of North American oblique-banded leafroller Choristoneura...
Development of Commercial Pyrethroids
There are several reviews Elliott, 1977, 1995, 1996 Davies, 1985 Henrick, 1995 Pap et al., 1996a Matsuo and Miyamoto, 1997 Pachlatko, 1998 Bryant, 1999 Katsuda, 1999 Khambay, 2002 Soderlund et al., 2002 covering aspects of structure-activity relationships in pyrethroids. To appraise the advances made since 1985, it is useful to recollect the systematic approaches adopted earlier, in particular by Elliott, in the discovery of synthetic pyrethroids see Figure 1 for structures . The key to his...