Nitromethylenes and their analogues are a novel class of insecticidally active molecules of commercial importance. Here we describe the actions of a novel nitroguanidine analogue, l‐(6‐chloro‐3‐pyridylmethyl)‐N‐nitroimidazolidin‐2‐ylideneamine (imidacloprid; NTN 33893) and a nitromethylene, l‐(3‐pyridylmethyl)‐2‐nitromethylene‐imidazolidine (PMNI) on the cockroach fast coxal depressor motor neurone Df and their effectiveness in displacing [125I]α‐bungarotoxin binding to cockroach nerve cord preparations. When tested on the cell body of this identified neurone both imidacloprid and PMNI induce slow depolarizations, which are sensitive to nicotinic receptor antagonists, such as dihydro‐β‐erythroidine (1.0 × 10−5 M) and mecamylamine (1.0 × 10−4 M). Lower concentrations of imidacloprid (1.0 × 10−8 −1.0 × 10−6 M) and PMNI (1.0 × 10−8 M) show no antagonist action on nicotine‐induced depolarization. At concentrations in the range 1.0 × 10−7 −5.0 × 10−7 M, PMNI partially and reversibly blocks nicotine‐induced depolarization. Both compounds are more effective displacers of specific [125I]α‐bungarotoxin binding than nicotine, with imidacloprid (IC50 = 2.0 × 10−7 M) about tenfold more potent than PMNI (IC50 = 1.3 × 10−6 M).
Extracts of ground seeds from Annona squamosa revealed interesting insecticidal properties. By an activity‐monitored fractionation, different acetogenins, called annonins and annonacin, were determined to be the active components. The investigation of ATP‐levels (at the LT50 value) in Plutella xylostella under treatment with annonin I and antimycin A revealed values of 1.45 and 1.35 μmole g−1 fresh weight respectively, whereas insecticides primarily afecting neurotoxic targets, e.g. cyfluthrin (sodium channels; 2.25 μmole g−1 fresh weight) or parathion (acetylcholinesterase; 2.0 μmole g−1 fresh weight) did not influence the ATP‐levels significantly (control; 1.98 μmole g−1 fresh weight). Further studies on the target site of annonins revealed an inhibitory effect on the NADH‐cytochrome c‐reductase and complex I of insect mitochondria with IC50 values of 4–8 nmole mg−1 protein and 0.8 μM respectively for annonin I. Similar results were observed for the inhibition of complex I from bovine heart muscle (IC50: <0.1 μM) or Neurospora crassa cells (IC50: 0.3 μM), whereas coupling sites II or III were not afected. Furthermore, annonins did not reveal any direct inhibition of oxidative phosphorylation or uncoupling efects.
A GC-MS method capable of completely separating the four pairs of diastereoisomers of cyfluthrin is presented and the method used to show that isomerisation of the cyfluthrin enantiomers occurs in methanol. This methanolinduced isomerisation could also be demonstrated by bioassays using water fleas. The biological activities of the various cyfluthrin isomers contained in the commercial products cyfluthrin and beta-cyfluthrin were assayed using several strains of lepidopteran larvae including Plutella xylostella, Heliothis virescens and Spodoptera frugiperda. With the susceptible strains, the efficiencies of the isomers mixtures of cyfluthrin and beta-cyfluthrin were shown to obey the rules of additivity. However, in tests with a resistant strain of P. xylostella originating from Thailand, the 'inactive' isomer I11 acted synergistically with the active isomer IV.Resistance factors in strains of H. virescens and P. xylostella were found to be higher with cis than with trans isomers. This probably contributes to the superior action of cyfluthrin and beta-cyfluthrin against various pests of agricultural importance since the commercial products contain a high content of trans isomers ('high trans pyrethroids').
Ammonium sulfate fractionation of proteins from extremely halophilic bacteria on Sepharose 4B, carboxymethylcellulose, diethylaminoethylcellulose, and hexamethylenediamine-Agarose is described. Halophilic proteins are absorbed on these gels at 2.5 M ammonium sulfate and eluted by decreasing concentration gradients of this salt. The method has enabled the separation of malate dehydrogenase from glutamate dehydrogenase and aspartate aminotransferase on Sepharose 4B and the additional 15-fold purification of glutamate dehydrogenase on DEAE-cellulose. The technique is simple and convenient, operates at low cost, and possesses great power of resolution. The mechanism of adsorption is discussed and compared to previous instances of "hydrophobic chromatography". It is concluded that the retention of halophilic proteins on the polysaccharide gels at 2.5 M ammonium sulfate is due to hydrophobic interactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.