Taste-rejection behaviour by predators can promote variability in prey defences

The evolution and maintenance of toxicity in a prey population is a challenge to evolutionary biologists if the investment in toxin does not benefit the individual. Recent experiments suggest that taste-rejection behaviour enables predators to selectively ingest less toxic individuals, which could stabilize investment in defences. However, we currently do not know if taste rejection of defended prey is accurate across different contexts, and that prey always benefit according to their investment. Using avian predators, we show that the rejection probability does not solely depend on the investment in defence by an individual, but also on the investment by other individuals in the same population. Therefore, taste rejection by predators could lead to destabilization in the investment in defences, and allow variability in prey defences to exist.     

A Method for Producing Protein Nanoparticles with Applications in Vaccines

A practical method is described for synthesizing conjugated protein nanoparticles using thioether (thiol-maleimide) cross-linking chemistry. This method fills the need for a reliable and reproducible synthesis of protein conjugate vaccines for preclinical studies, which can be adapted to produce comparable material for clinical studies. The described method appears to be generally applicable to the production of nanoparticles from a variety of soluble proteins having different structural features. Examples presented include single-component particles of the malarial antigens AMA1, CSP and Pfs25, and two component particles comprised of those antigens covalently cross-linked with the immunogenic carrier protein EPA (a detoxified form of exotoxin A from Pseudomonas aeruginosa). The average molar masses (Mw) of particles in the different preparations ranged from 487 kDa to 3,420 kDa, with hydrodynamic radii (Rh) ranging from 12.1 nm to 38.3 nm. The antigenic properties and secondary structures of the proteins within the particles appear to be largely intact, with no significant changes seen in their far UV circular dichroism spectra, or in their ability to bind conformation-dependent monoclonal antibodies. Mice vaccinated with mixed particles of Pfs25 or CSP and EPA generated significantly greater antigen-specific antibody levels compared with mice vaccinated with the respective unmodified monomeric antigens, validating the potential of antigen-EPA nanoparticles as vaccines.     

Detection of mutations in human type I collagen mRNA in osteogenesis imperfecta by indirect RNase protection

A method for detecting a wide variety of mutations within type I collagen has been developed and evaluated on a series of patients with osteogenesis imperfecta. RNA, extracted from the nuclear and cytoplasmic compartment of cultured fibroblasts from affected individuals, is hybridized with antisense single-stranded cDNA to the alpha 1(I) mRNA. The hybrid is digested with RNase A and T1 under varying degrees of stringency. The resistant RNA bands are separated by electrophoresis in agarose, transferred to nitrocellulose, and hybridized with antisense cRNA colinear with the protecting probe. This approach is capable of detecting previously defined mutations such as 252-base pair deletion and a 1-base pair mismatch within the alpha 1(I) mRNA. The method appears to be particularly useful in detecting abnormalities of RNA processing that behave as an insert or deletion within the mature mRNA. The procedure should be generally applicable for the identification and localization of any mutation within an entire gene if the gene is expressed as an RNA and a complete cDNA for the mRNA is available.     

The effect of carbon dioxide on the growth of Yersinia enterocolitica in a simulated milk medium

Carbon dioxide (30 mmol/l) was shown to inhibit the growth of four strains of Yersinia enterocolitica grown separately in a simulated milk medium at 7°C and 60 rev/min for 4 d. This indicates that addition of CO₂ to refrigerated raw milk supplies is likely to be a safe process with respect to that organism.     

A Framework for Identifying Plant Species to Be Used as ‘Ecological Engineers’ for Fixing Soil on Unstable Slopes

Major reforestation programs have been initiated on hillsides prone to erosion and landslides in China, but no framework exists to guide managers in the choice of plant species. We developed such a framework based on the suitability of given plant traits for fixing soil on steep slopes in western Yunnan, China. We examined the utility of 55 native and exotic species with regard to the services they provided. We then chose nine species differing in life form. Plant root system architecture, root mechanical and physiological traits were then measured at two adjacent field sites. One site was highly unstable, with severe soil slippage and erosion. The second site had been replanted 8 years previously and appeared to be physically stable. How root traits differed between sites, season, depth in soil and distance from the plant stem were determined. Root system morphology was analysed by considering architectural traits (root angle, depth, diameter and volume) both up- and downslope. Significant differences between all factors were found, depending on species. We estimated the most useful architectural and mechanical traits for physically fixing soil in place. We then combined these results with those concerning root physiological traits, which were used as a proxy for root metabolic activity. Scores were assigned to each species based on traits. No one species possessed a suite of highly desirable traits, therefore mixtures of species should be used on vulnerable slopes. We also propose a conceptual model describing how to position plants on an unstable site, based on root system traits.