RESUMEN
The possibility of synergized pyrethrin-containing aerosol as a choice for spot-treating C. brevis in Australia was investigated in laboratory tests. Topical toxicity tests, where C. brevis pseudergates were subjected to multiple doses of pyrethrin mist insecticide, showed the concentration-dependent death of termites with a median lethal dose (LD50) of 193.16 µg. Residual toxicity tests, where the termites were exposed to wood surfaces treated with pyrethrin-containing aerosol, showed a rapid mortality in short and continuous exposures. Less than 20% of the termites survived even when the termites were exposed to a treated wood surface for a minute. All the termites died within 1-5 h in continuous exposure tests, depending on the age of the treated surface. In repellency tests, the termites tended to visit treated surfaces, causing an overall lower survival of the termites. The synergized pyrethrin-containing aerosol remained insufficiently volatile to produce the complete mortality of the termites even after 196 h when there was no contact with a treated surface. The number of termites that survived following the application of the synergized aerosol through a simulated wood gallery or silicon tubing with fecal pellets was also negligible, demonstrating the ability of the aerosol to penetrate through pellets and ultimately resulting in a distribution that is ideal for treatment in the termite galleries.
RESUMEN
West Indian drywood termites (Cryptotermes brevis, Blattodea: Kalotermitidae) are an important invasive termite in many countries including Australia where they are spreading across two eastern states. Fumigation is often used to eliminate infestations, but it is costly, has negative environmental effects and does not prevent reinfestation. Heat treatment has been suggested as an alternative. Many insect pest mitigation strategies recommend 30 min exposure at 56 °C, but this may be difficult to achieve in structural applications. The potential for heating at lower temperatures was explored to determine the effect on termite survival and gut fauna. Exposure to 40 °C up to an hour did not kill the termites; however, 1-h exposure at 45 °C was lethal. Exposure for little as 3 min at 50 °C or 2 min at 55 °C was lethal. Protozoa levels were lower in termites that survived shorter exposures, but there appeared to be some recovery over time. The results suggest that short term exposures to 50 or 55 °C could be used to eliminate infestations, creating an opportunity for localized spot heating as a mitigation measure.
Asunto(s)
Cucarachas/fisiología , Isópteros/fisiología , Termotolerancia , Árboles , Animales , Australia , Especies Introducidas , Temperatura , Clima TropicalRESUMEN
Translation initiation is poised between global regulation of cell growth and specific regulation of cell division. The mRNA cap-binding protein (eIF4E) is a critical integrator of cell growth and division because it is rate-limiting for translation initiation and is also rate-limiting for G(1) progression. Translation initiation factor eIF4E is also oncogenic and a candidate target of c-myc. Recently, an activated inhibitory 4E-binding protein (4EBP) that blocks eIF4E was used to study its regulation of Drosophila growth. We adopted this approach in mammalian cells after identifying an autosensing mechanism that protects against increased levels of 4EBP1. Increased 4EBP1 induced a quantitative increase in the inactivated phosphorylated form of 4EBP1 in vitro and in vivo. To overcome this protective mechanism, we introduced alanine substitutions at four phosphorylation/inactivation sites in 4EBP1 to constitutively activate a 4EBP mu to block eIF4E. Overexpression of activated 4EBP mu inhibited cell proliferation and completely blocked transformation by both eIF4E and c-myc, although it did not block all tested oncogenes. Surprisingly, expression of the activated 4EBP mu increased cell size and protein content. Activated 4EBP mu blocked both cell proliferation and c-myc transformation by inhibiting G(1) progression and increasing apoptosis, without decreasing protein synthesis. Our results identify mammalian eIF4E as rate-limiting for cell cycle progression before it regulates cell growth. It further identifies G(1) control by translation initiation factors as an essential genetic target of c-myc that is necessary for its ability to transform cells.