Synthetic prions with novel strain-specified properties

Prions are infectious proteins that possess multiple self-propagating structures. The information for strains and structural specific barriers appears to be contained exclusively in the folding of the pathological isoform, PrP^Sc. Many recent studies determined that de novo prion strains could be generated in vitro from the structural conversion of recombinant (rec) prion protein (PrP) into amyloidal structures. Our aim was to elucidate the conformational diversity of pathological recPrP amyloids and their biological activities, as well as to gain novel insights in characterizing molecular events involved in mammalian prion conversion and propagation. To this end we generated infectious materials that possess different conformational structures. Our methodology for the prion conversion of recPrP required only purified rec full-length mouse (Mo) PrP and common chemicals. Neither infected brain extracts nor amplified PrP^Sc were used. Following two different in vitro protocols recMoPrP converted to amyloid fibrils without any seeding factor. Mouse hypothalamic GT1 and neuroblastoma N2a cell lines were infected with these amyloid preparations as fast screening methodology to characterize the infectious materials. Remarkably, a large number of amyloid preparations were able to induce the conformational change of endogenous PrP^C to harbor several distinctive proteinase-resistant PrP forms. One such preparation was characterized in vivo habouring a synthetic prion with novel strain specified neuropathological and biochemical properties.     

Observations on the invading gastropod <Emphasis Type="Italic">Rapana venosa</Emphasis> in Punta del Este,Maldonado Bay,Uruguay

We report on the first sightings of the invasive Rapa Whelk Rapana venosa in Maldonado Bay (Punta del Este Harbor and Gorriti Island) using in vivo, underwater observations and video surveys. The species was first detected in the Río de la Plata (Uruguay and Argentina) in 1999, and by 2004 it had extended its local distribution to Punta del Este at the eastern boundary of the estuary. Observations performed by SCUBA diving showed that R. venosa is preying on native mussels Mytilus edulis and Brachidontes spp., and that formerly abundant mussel beds are being seriously depleted due to a combination of human extraction, habitat deterioration and predation by the Rapa Whelk.     

Relationship between laying dates of black kites Milvus migrans and spring temperatures in Italy: rapid response to climate change?

Many Holarctic bird species have been shown to be laying progressively earlier in response to global warming. Most studies have been conducted on small-bodied species at northern latitudes. In Italy, black kite Milvus migrans populations are concentrated near large pre-Alpine lakes, whose water temperatures have been increasing steadily in recent decades. Annual black kite laying dates have become 10–11 days earlier during the last nine years. This shift was related to temporal variations in spring air temperatures, with earlier laying in warmer springs. The progressive advancement in laying dates was not associated with an increase in population level productivity, despite the fact that productivity declined with laying date at the individual territory level within years. Avian response to climate change may be occurring more rapidly than previously thought, even in relatively long-lived species, and not only at the most northern latitudes or highest elevations. Because this change has occurred so rapidly, and because laying dates match annual variations in spring temperatures, the response must be facultatively driven by prevailing conditions, rather than genetic in response to natural selection.     

Detection of Populations of Amyloid-Like Protofibrils with Different Physical Properties

We used tapping mode atomic force microscopy to study the morphology of the amyloid protofibrils formed at fixed conditions (low pH with high ionic strength) by self-assembly of the N-terminal domain of the hydrogenase maturation factor HypF. Although all protofibrils in the sample share a beaded structure and similar values of height and width, an accurate analysis of contour length and end-to-end distance and the comparison of experimental data with theoretical predictions based on the worm-like chain model show that two different populations of protofibrils are present. These populations are characterized by different physical properties, such as persistence length, bending rigidity and Young's modulus. Fluorescence quenching measurements on earlier globular intermediates provide an independent evidence of the existence of different populations. The finding that differences in mechanical properties exist even within the same sample of protofibrils indicates the presence of different subpopulations of prefibrillar aggregates with potentially diverse tendencies to react with undesired molecular targets. This study describes a strategy to discriminate between such different subpopulations that are otherwise difficult to identify with conventional analyses.     

From individual behaviour to population pattern: weather-dependent foraging and breeding performance in black kites

The links between weather and animal behaviour in population processes have received relatively little attention. I studied the effect of weather conditions on foraging and breeding performance of a medium-sized raptor, the black kite, Milvus migrans. The frequency of prey capture attempts and their likelihood of success increased with temperature and declined with rainfall. Kites used flight styles involving a higher energy expenditure in less favourable weather. Nestling provisioning rates declined during rain spells. More kites hunted during periods of favourable weather and after periods with a high frequency of successful prey capture attempts by conspecifics; this result suggested that individuals may fine-tune their foraging effort to the expected foraging reward. Such compensatory behavioural adjustments may increase species resilience to climate change. The behaviourally mediated effects of weather on prey availability translated into population effects. Yearly weather conditions during the last stage of the prelaying period affected population-level productivity, probably through an effect on female body condition mediated by male provisioning capability and hunting yield. The predicted effects of climate change on kites may already be occurring, with progressively earlier laying and northward range expansion. These results confirm the need to pay greater attention to behaviourally mediated effects of climate on populations, particularly when individuals make compensatory adjustments that may enhance resilience to climate change. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Optimization of 2-piperidin-4-yl-acetamides as melanin-concentrating hormone receptor 1 (MCH-R1) antagonists: Designing out hERG inhibition

Herein, we disclose the discovery and optimization of 2-piperidin-4-yl-acetamide derivatives as MCH-R1 antagonists. Structural investigation of piperidin-4-yl-amide and piperidin-4-yl-ureas identified 2-piperidin-4-yl-acetamide-based MCH-R1 antagonists with outstanding in vivo efficacy but flawed with high affinity towards the hERG potassium channel. While existing hERG SAR information was employed to discover highly potent MCH-R1 antagonists with minimized hERG inhibition, additional hurdles prevented their subsequent clinical exploration.     

Generation of supercoils in nicked and gapped DNA drives DNA unknotting and postreplicative decatenation

Due to the helical structure of DNA the process of DNA replication is topologically complex. Freshly replicated DNA molecules are catenated with each other and are frequently knotted. For proper functioning of DNA it is necessary to remove all of these entanglements. This is done by DNA topoisomerases that pass DNA segments through each other. However, it has been a riddle how DNA topoisomerases select the sites of their action. In highly crowded DNA in living cells random passages between contacting segments would only increase the extent of entanglement. Using molecular dynamics simulations we observed that in actively supercoiled DNA molecules the entanglements resulting from DNA knotting or catenation spontaneously approach sites of nicks and gaps in the DNA. Type I topoisomerases, that preferentially act at sites of nick and gaps, are thus naturally provided with DNA–DNA juxtapositions where a passage results in an error-free DNA unknotting or DNA decatenation.     

Template assisted self-organized chemosensors

The self-organization of fluorescent dyes and receptors on a proper template to form an organized assembly is a new strategy for the realization of fluorescence chemosensors. In the assembly, the two subunits do not interact directly and the communication between the bound substrate and the dye is only determined by their spatial closeness ensured by the template. The method is simple and the main advantages are related to the minimization of the synthetic work, the ease of modification and optimization of the sensor, the possibility to tune its properties by the simple adjustment of the components ratio. Self-organizing methodologies can open new perspectives to fluorescence chemosensors, both by allowing a simplified preparation and by opening the way to new and more complex functions. This article deals with this new approach and discusses its evolution, applications, and limitations.