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Pyrethroids are insecticides used since the 1970s. They are favored for their low mammalian toxicity, improved environmental stability and insecticidal potency. Voltage-gated sodium channels (VGSCs) are a known target but in vitro evidence indicates that voltage-gated calcium channels (VGCCs) are also targets. Site-directed mutagenesis of CaV2.2 (N-type), altering threonine 422 to glutamate (T422E), produces a mutant channel that acts as if permanently phosphorylated. Deltamethrin increases peak current of T422E CaV2.2 compared to its antagonistic action on wild type CaV2.2 when expressed in Xenopus oocytes. Phosphorylation of wild type CaV2.2 is evoked by the phorbol ester PMA by activating endogenous protein kinase C (PKC) in oocytes. Under steady-state conditions, deltamethrin increases transient peak current and slows deactivation kinetics of the PKC phosphorylated channel thereby increasing Ca2+ influx and neurotransmitter release. Conversely, deltamethrin treatment resulted in no effect on the deactivation kinetics of the unphosphorylated or T422E channels. Under voltage-dependent conditions, deltamethrin enhances peak current, and causes a hyperpolarizing shift in activation midpoint potential of the PKC phosphorylated channel which is consistent with enhanced Ca2+ influx. The hyperpolarizing shift of activation midpoint potential was not observed when deltamethrin was applied to the T422E mutant channels indicating that the other phosphorylation sites on CaV2.2 may be playing a role in the differential effects observed in the action of deltamethrin on the unphosphorylated channel, the T422E mutant and the PMA-activated PKC phosphorylation channel.

Zugl.: Berlin, Freie University, Diss., 2009.

Zugl.: Berlin, Humboldt-Univ., Diss., 2007

Zugl.: Berlin, Freie Univ., Diss., 2008

Zugl.: Berlin, Freie Universiẗat, Diss., 2008. / Auch als Online-Ressource: http://www.diss.fu-berlin.de/diss/receive/FUDISS_thesis_000000010566.

Zugl.: Berlin, Freie Univ., Diss., 2010

Obesity is a growing concern in the world today. As we ponder about the many causes of this global epidemic, we are driven to look at our food and the environmental toxicants that may contribute to obesity. Deltamethrin, being a common synthetic pyrethroid used in agriculture for pest control, is the primary insecticide this study explores to connect with obesity in 3T3-L1 adipocytes. To investigate the relationship between deltamethrin and adipogenesis, various concentrations were tested, 1nM, 10nM, 100nM, 1μM, and 10μM. The result indicated that higher concentration of deltamethrin had a direct impact on fat accumulation. These experiment results indicate that deltamethrin may potentiate adipogenesis in this model. Further in vivo studies will be needed to validate these findings and confirm the effects of deltamethrin on obesity.

Malaria continues to be a significant cause of morbidity and mortality in the developing world with Africa being the most affected. Malaria vector control with chemical insecticides is the primary intervention to curb transmission. However, the success of chemical based interventions is threatened by the escalating development of insecticide resistance in the major anopheline mosquito vectors.

Master of Science / Department of Grain Science and Industry / Subramanyam Bhadriraju / Spinosad, methoprene, deltamethrin, and deltamethrin plus methoprene, are approved in the United States for treating popcorn. The Indian meal moth, Plodia interpunctella (Hübner), and maize weevil, Sitophilus zeamais (Motschulsky) are two stored-product insects found in popcorn. The efficacy of spinosad and methoprene against P. interpunctella in popcorn were determined in laboratory and field studies. In the laboratory study, eggs (to represent first instars), third, and fifth instars of the laboratory strain of P. interpunctella were exposed to 0.7, 1.4, 2.8 ppm methoprene and 1 ppm spinosad treated popcorn, respectively, to assess larval or adult emergence. In the field study, untreated and treated popcorn samples were placed in vinyl mesh pouches with two mesh-opening sizes and were buried 5 cm below popcorn surface. Pouches with large mesh-opening were used to monitor natural insect infestation between May to October, 2017. Pouches with small mesh-opening were used to conduct laboratory bioassays to evaluate adult emergence of P. interpunctella from eggs after exposed to treated popcorn. Probe traps, food- and pheromone-baited traps, and sticky traps were used to monitor insects in storage bins and cleaning processing facility. The laboratory study showed that there was no P. interpunctella adults emerged from eggs, third, and fifth instars in methoprene treated popcorn during 6 month storage. However, methoprene did not reduce egg-to-larval survival. Larval and adult emergence in the spinosad treated popcorn was significantly lower than controls. Field study showed that there was no adult emergence in methoprene treated popcorn in most cases, and significantly lower adult emergence in spinosad treated popcorn compare to control. P. interpunctella larva was the major insect found in large pouches. The red flour beetle, Tribolium castaneum (Herbst), and P. interpunctella were primary insect species captured by probe traps, food- and pheromone-baited traps and sticky traps over the six months’ study. These results suggested that methoprene could reduce P. interpunctella adult emergence. Spinosad also effectively suppressed the infestation of P. interpunctella. The field strain of S. zeamais was exposed to spinosad (1 ppm), methoprene (0.7, 1.4, 2.8 ppm), deltamethrin (0.5, 1.0 ppm), and deltamethrin plus methoprene (0.5+1.25, 1.0+2.5 ppm) treated popcorn, respectively, for 1 to 336 h exposure time. Mortality was assessed at 0, 7, 14, and 21 d after transferring to clean popcorn except for methoprene treatments which only counted mortality at 0 d. Progeny and adult emergence were counted after 42 d incubation in clean or original popcorn, respectively. All insecticides showed no delay toxicity against S. zeamais adults. Spinosad caused 100% mortality of S. zeamais after 336-h exposure. Complete progeny reduction and highest adult emergence reduction at 168 h exposure. The highest mortality of S. zeamais was 67.1 and 70.5% in deltamethrin and deltamethrin plus methoprene treated popcorn, respectively. Methoprene showed limited efficacy against S. zeamais including low mortality, progeny reduction and high adult emergence. These results indicated that spinosad was effective against S. zeamais. It is necessary to combine other insecticides with deltamethrin and methoprene to control field strain of S. zeamais in stored popcorn.