Nanoscale structure of amyloid-β plaques in Alzheimer’s disease

Abstract Soluble amyloid-β (Aβ) is considered to be a critical component in the pathogenesis of Alzheimer’s disease (AD). Evidence suggests that these non-fibrillar Aβ assemblies are implicated in synaptic dysfunction, neurodegeneration and cell death. However, characterization of these species comes mainly from studies in cellular or animal models, and there is little data in intact human samples due to the lack of adequate optical microscopic resolution to study these small structures. Here, to achieve super-resolution in all three dimensions, we applied Array Tomography (AT) and Stimulated Emission Depletion microscopy (STED), to characterize in postmortem human brain tissue non-fibrillar Aβ structures in amyloid plaques of cases with autosomal dominant and sporadic AD. Ultrathin sections scanned with super-resolution STED microscopy allowed the detection of small Aβ structures of the order of 100 nm. We reconstructed a whole human amyloid plaque and established that plaques are formed by a dense core of higher order Aβ species (~0.022 µm3) and a peripheral halo of smaller Aβ structures (~0.003 µm3). This work highlights the potential of AT-STED for human neuropathological studies

Persistence and efficacy of three diatomaceous earth formulations against Sitophilus oryzae (Coleoptera : Curculionidae) on wheat and barley

The insecticidal and residual efficacy of three diatomaceous earth (DE) formulations, Insecto, PyriSec, and SilicoSec, against Sitophilus oryzae (L.) on barley and wheat was assessed. For this purpose, 4-kg lots of barley and wheat were treated with the above-mentioned DE formulations, in three dose rates (0.75, 1, and 1.5 g/kg grain) and stored at 26 degrees C. Samples of these lots were taken at the day of storage, and every 45 d, until the completion of a 450-d period of storage. Bioassays were conducted by exposing S. oryzae adults to these samples, at 26 degrees C and 57% RH. In these bioassays, the DE efficacy was evaluated by recording adult mortality after 24 h, 48 h, 7 d, and 14 d of exposure on the treated grains. After the 14-d count, all adults were removed, and the samples were left at the same conditions for an additional 45 d, to evaluate the capacity for progeny production in the treated grains. Adult mortality after 14 d of exposure was exponentially decreased with time. During the first 270 d of storage, mortality was gt 90%, and progeny production was lt 1 adult per sample, whereas after 270 d a gradual decrease in adult mortality occurred, with a resulting increase in progeny production. Generally, the three DE formulations tested were equally effective against S. oryzae adults. During the first 270 d of storage, the DE formulations were equally effective on both grains tested, but from 315 d of storage and on, S. oryzae mortality was higher on barley than on wheat. At this interval, progeny production was gradually increased, especially on grains treated with the lowest DE dose rate. However, even this rate caused a satisfactory level of mortality ( gt 90% after 14 d of exposure) during the first 270 d of storage

Tomato-aphid-hoverfly: A tritrophic interaction incompatible for pest management

peer reviewedTrichome-based tomato resistance offers the potential to reduce pesticide use, but its compatibility with biological control remains poorly understood. We evaluated Episyrphus balteatus De Geer (Diptera, Syrphidae), an efficient aphidophagous predator, as a potential biological control agent of Myzus persicae Sulzer (Hemiptera, Aphididae) on trichome-bearing tomato cultivars. Episyrphus balteatus’ foraging and oviposition behavior, as well as larval mobility and aphid accessibility, were compared between two tomato cultivars (Lycopersicon esculentum Mill. ‘Moneymaker’ and ‘Roma’) and two other crop plants; broad bean (Vicia faba L.) and potato (Solanum tuberosum L.). Hoverfly adults landed and laid more eggs on broad beans than on three species of Solanaceae. Hoverfly larval movement was drastically reduced on tomato, and a high proportion of hoverfly larvae fell from the plant before reaching aphid prey. After quantifying trichome abundance on each of these four plants, we suggest that proprieties of the plant surface, specifically trichomes, are a key factor contributing to reduced efficacy of E. balteatus as a biological agent for aphid control on tomatoes