Songbird preen oil odour reflects haemosporidian parasite load.

Investigating the impact of parasitism on host phenotype is key to understanding parasite transmission ecology, host behavioural ecology and host-parasite coevolution. Previous studies have provided evidence that avian odour is one such phenotypic trait, as mosquitoes that vector the haemosporidian blood parasite Plasmodium tend to prefer birds that are already infected. Preen oil is a major source of avian odour, yet studies to date have not identified differences in preen oil odour based on the presence or absence of haemosporidian infection. Because preen oil can vary with physiological dynamics, we predicted that the composition of preen oil odours might vary according to parasite load, rather than solely by the presence or absence of infection. We used gas chromatography-mass spectrometry to characterize the composition of volatile compounds in preen oil taken from female dark-eyed juncos, Junco hyemalis carolinensis, and asked whether their composition varied with relative haemosporidian parasite load, which we assessed using quantitative PCR. We identified a subset of volatile compounds (a 'blend') and two specific compounds that varied with increasing parasite load. Importantly, the quantity of these compounds did not vary based on parasite presence or absence, suggesting that birds with low parasite loads might be phenotypically indistinguishable from uninfected birds. The volatile blend associated with parasite load also varied with sampling date, suggesting a possible seasonal relapse of chronic infections triggered by shifts in junco host reproductive state. Furthermore, we found a positive relationship between parasite load and a volatile blend shown in a previous study to predict reproductive success in juncos. This is the first study to demonstrate quantitative differences in avian host odour based on haemosporidian parasite load. Our findings highlight the importance of focusing on parasite load, rather than solely presence or absence, in investigating host-parasite interactions.

Long-term stability of a coronary stent coating post-implantation.

A coronary stent possessing a phosphorylcholine-based polymer coating was removed from a human patient 6 months after implantation and analyzed for the presence of the coating. An atomic force microscopy (AFM) technique has been employed to scrape away several 10- micro m(2) areas on the struts of the explanted stent. Scanning-electron microscopy (SEM) and tapping-mode AFM confirmed a surface coating had been removed in each case. Cross-sectional analysis and force-of-removal measurements showed that both coating depth and hardness were characteristic of that for the phosphorylcholine- (PC-) based coating prior to implantation. AFM amplitude-phase and distance curves from the explanted stent were comparable to those obtained when an unused stent was analyzed. Furthermore, laser ablation high-resolution inductively coupled-plasma mass spectometery (LA-HR-ICP-MS) was used to detect the low level of silicon present in the PC coating after explantation. The results from these techniques confirm that the stent coating is the original PC polymer and is not of biological origin, and support the long-term stability of the coating in vivo.

Roller mutants of the nematode Caenorhabditis elegans.

The wild type nematode, Caenorhabditis elegans, moves in a sinusoidal wave pattern and leaves sinusoidal paths behind it on a bacterial lawn. The nematode crawls on its side on a special cuticular tread that extends straight down the length of its body. Wild type worms also have rows of musculature and a ventral nerve cord that extend straight down the body. Roller mutants rotate around their long axis as they crawl and move in circular paths. Three roller mutants have been studied. Two mutants are left rollers and one is a right roller. The left rollers have left-handed helical treads, body musculatures, and ventral nerve cords whereas these structures are right-handed helices in the right roller. Double mutants constructed from roller mutants and long mutants indicate that long rollers have helices of the same pitch as normal length rollers. Double mutants constructed from rollers and dumpy mutants that are short and fat indicate dumpy phenotype is epistatic to roller. Double mutants constructed from rollers and blister mutants that have cuticular swelling indicate roller phenotype is epistatic to blister. The results suggest that the roller phenotypes are due to cuticular lesions. Rollers can chemotaxe up a gradient of an attractant by turning off their body muscle movement and continuing their head movements.