Knockdown effect

The edible parts of parsnips (Pastimea sativa L.), which have been consumed for centuries by humans without causing any obvious harm, were found to contain a chemical of insecticidal and strong synergistic nature (1). The insecticidal constituent, present at about 200 p.p.m., was isolated and identified as 5-allyl-l-methoxy-2, 3-methylenedioxybenzene or myristicin. Its toxicity to various insects [vinegar flies, houseflies, Mediterranean fruit flies, mosquito larvae, Mexican bean beetles, and pea aphids] was established and compared with pyrethrum and aldrin (Tables I and II). The knockdown effect, although definite, was not as great as that of pyrethrum. In tests... 

The main devices used for mosquito protection in households have been mosquito coils, electric mosquito mats, and liquid vaporizers, all of them methods that vaporize insecticides into the air using heating by means of fire or electricity to control the insects. In recent years, new anti-mosquito products have been commercialized such as fan vaporizers, paper strip type emanators, and resin net type emanators which vaporize insecticides without heating. In all of these products pyrethroid insecticides are used as active ingredients because they are superior in what is called knockdown effect, where noxious insects are rapidly paralyzed and cannot bite, and have a high level of safety for humans. 

Fig. 5 RNAi longevity with exogenously provided synthetic compounds. Depending on cell type and culturing condition, the knockdown of the target transcript is usually sustained up to three to five days using standard, non-modified siRNAs. By chemically modifying the duplexes, it is possible to achieved longer knockdown effects. In this example, the ability of unmodified and chemically modified RNAi compounds to knockdown target transcript was tested side-by-side for one to six days after transfection. (Courtesy of Invitrogen Corporation.)...

Interpretation of results from bioassay techniques where observations are made on the knockdown effect is also questionable. When compounds are sprayed directly onto the insect and a difference in response occurs between the toxicant alone and the mixture of toxicant plus PBO. how quickly should one expect the enhancement effect to be revealed This must depend on the physicochemical properties of the components of the mixture, and on the immediate... 

In space ireaiment ihe insecticide is dispersed as a cloud of fine droplets. This is the main method by which flying insects are controlled, as the chemical is rapidly brought into contact with the insect. As a result of this immediate and intimate contact only small quantities of non-residual active ingredient are necessary. It is important to apply compounds which not only produce a rapid knockdown effect (mainly pyrethrins and some synthetic pyrclhroids, but also provide subsequent mortality,... 

Fig. 12 Evaluation of gene knockdown effect by siRNA complexed with PEG-PAsp(DPT). a GL3 luciferase gene knockdown by siRNA complex with various block copolymers having varying charge ratios, commercially available reagent (RNAiFect), and naked siRNA evaluated in HuH-7 cells ( = 4 SD). GL3 and RL luciferases were pre-transfected by pGL3 and pRL plasmid DNA complexed with LipofectAMlNE. The siRNA complexes (GL3 knockdown) were then applied and evaluated by dual luciferase assay, b Endogenous gene (Lamin A/C) knockdown in the presence or absence of 50% serum evaluated in 293T cells...

Scientists have also measured the extent of RNA knockdown in several genes, and their analysis showed the following parameters affect knockdown effectiveness [10]. 

S)-a-cyano-3-phenoxybenzyl (1R, 3/ )-3-(2,2-dibromovinyl)-2,2-dimethyl-cyclo-propanecarboxylate (decamethrin, 35) represents a further improvement of practical properties such as rapid knockdown effect, low mammalian toxicity and high chemical stability (Elliott et al., 1974). Its insecticidal activity to houseflies is 1700 times that of pyrethrin I and a dose as low as 10 g/ha is sufficient against insects damaging cotton. 

Their insecticidal action is manifested by a rapid knockdown effect, which is characteristic also of pyrethrines. A further property in common with pyrethrines is their pungency, which together with their unsatisfactory stability has prevented their general use in practice, in spite of their strong insecticidal action. 

A non-viral vector PEG-PEI was investigated in the delivery of siRNA to neural stem cells (NSCs). The SEM micrographs showed that PEG-PEI could condense siRNA to form spherical nanoparticles. The gene knockdown effect of PEG-PEI/siRNA nanoparticles was verified at the levels of mRNA and protein, which suggested that PEG-PEI may potentially be used as a siRNA delivery vector for neural regeneration therapy. ... 

Uses Contact insecticide with rapid knockdown effect synergistic with piperonyl butoxide or MGK 264 in pesticide formulations used in aerosols, coils, or sprays indoors against flying and crawling insects... 

Permethrin Is an extremely active insecticide with rapid knockdown effect against a variety of insects (fleas and ticks). Permethrin is marketed in a diversity of formulations such as collar (0.8-1.5%), topical concentrate (spot-on), spray (0.2-1%), shampoo (1%), dip, or cream rinse. Some formulations of permethrin contain furthermore piperonyl butoxide, A-octyl bicycloheptene dicarboximide, di-n-propyl isocinchomeronate, pyrethrins, pyriproxyfen, or butoxypolypropylene glycol (repellent). 

Resmethrin This pyrethroid shows excellent knockdown effect and is marketed for use in sprays and shampoo, fleas and ticks being the target parasites. 

Pyrethroids negatively impact insect systems by binding to the Na-t channel and resulting in rapid depolarization of the nerve axon. This class is well known for characteristic knockdown effects on flying insects, and with sublethal exposures, and excitorepellency. 

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