Are chronic avian haemosporidian infections costly in wild birds?

One group of commonly found parasites in birds, for which fitness consequences and effects on life history traits have been much debated are Haemosporidian blood parasites. In a long term study population of great reed warblers Acrocephalus arundinaceus in Sweden, previous studies have shown that the Haemosporidian blood parasites are in their chronic phase during the breeding season and that the fitness of infected and non‐infected birds are similar. In the present study, we quantified parasite intensity (parasitemia) in 718 adults great reed warblers sampled between 1987 and 1998 for the three most common parasite species; Haemoproteus payevskyi (lineage GRW1), Plasmodium ashfordi (GRW2) and Plasmodium relictum (GRW4). We verified that the q‐PCR method is accurately quantifying Haemoproteus payevskyi (GRW1) as it was highly correlated with the number of parasites seen under microscope. Frequency of mixed infections with two lineages was significantly higher than expected based on the prevalence of each of the three parasite lineages. The mean level of parasitemia was significantly different for the three lineages and individual birds had repeatable parasitemia levels between years. Females tended to have a higher parasitemia than males for all three parasite lineages combined. Females with higher GRW1 parasitemia tended to arrive later in spring to their breeding sites. There was a negative correlation between parasitemia and number of fledged offspring for GRW1, and a tendency for a negative correlation between GRW2 parasitemia and the proportion of recruiting offspring. Overall our results demonstrate that chronic Haemosporidian infections can have slight but significant effects on host life history traits, and therefore may act as important selective agents in wild bird populations.     

Molecular epidemiology of malaria prevalence and parasitaemia in a wild bird population

Avian malaria (Plasmodium spp.) and other blood parasitic infections of birds constitute increasingly popular model systems in ecological and evolutionary host-parasite studies. Field studies of these parasites commonly use two traits in hypothesis testing: infection status (or prevalence at the population level) and parasitaemia, yet the causes of variation in these traits remain poorly understood. Here, we use quantitative PCR to investigate fine-scale environmental and host predictors of malaria infection status and parasitaemia in a large 4-year data set from a well-characterized population of blue tits (Cyanistes caeruleus). We also examine the temporal dynamics of both traits within individuals. Both infection status and parasitaemia showed marked temporal and spatial variation within this population. However, spatiotemporal patterns of prevalence and parasitaemia were non-parallel, suggesting that different biological processes underpin variation in these two traits at this scale. Infection probability and parasitaemia both increased with host age, and parasitaemia was higher in individuals investing more in reproduction (those with larger clutch sizes). Several local environmental characteristics predicted parasitaemia, including food availability, altitude, and distance from the woodland edge. Although infection status and parasitaemia were somewhat repeatable within individuals, infections were clearly dynamic: patent infections frequently disappeared from the bloodstream, with up to 26% being lost between years, and parasitaemia also fluctuated within individuals across years in a pattern that mirrored annual population-level changes. Overall, these findings highlight the ecological complexity of avian malaria infections in natural populations, while providing valuable insight into the fundamental biology of this system that will increase its utility as a model host-parasite system.     

Cardiovascular events in early RA are a result of inflammatory burden and traditional risk factors: a five year prospective study

Introduction  

Co-morbidity and mortality due to cardiovascular disease (CVD) are increased in patients with rheumatoid arthritis (RA). Most published studies in this field are retrospective or cross sectional. We investigated the presence of traditional and disease related risk factors for CVD at the onset of RA and during the first five years following diagnosis. We also evaluated their potential for predicting a new cardiovascular event (CVE) during the five-year follow-up period and the modulatory effect of pharmacological treatment.     

Multilocus genotyping of human Giardia isolates suggests limited zoonotic transmission and association between assemblage B and flatulence in children

Background

Giardia intestinalis is one of the most common diarrhea-related parasites in humans, where infection ranges from asymptomatic to acute or chronic disease. G. intestinalis consists of eight genetically distinct genotypes or assemblages, designated A–H, and assemblages A and B can infect humans. Giardiasis has been classified as a possible zoonotic disease but the role of animals in human disease transmission still needs to be proven. We tried to link different assemblages and sub-assemblages of G. intestinalis isolates from Swedish human patients to clinical symptoms and zoonotic transmission.

Methodology/Principal Findings

Multilocus sequence-based genotyping of 207 human Giardia isolates using three gene loci: ß-giardin, glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) was combined with assemblage-specific tpi PCRs. This analysis identified 73 patients infected with assemblage A, 128 with assemblage B, and six with mixed assemblages A+B. Multilocus genotypes (MLGs) were easily determined for the assemblage A isolates, and most patients with this genotype had apparently been infected through anthroponotic transmission. However, we also found evidence of limited zoonotic transmission of Giardia in Sweden, since a few domestic human infections involved the same assemblage A MLGs previously reported in Swedish cats and ruminants. Assemblage B was detected more frequently than assemblage A and it was also more common in patients with suspected treatment failure. However, a large genetic variability made determination of assemblage B MLGs problematic. Correlation between symptoms and assemblages was found only for flatulence, which was significantly more common in children less than six years of age infected with assemblage B.

Conclusions/Significance

This study shows that certain assemblage A subtypes are potentially zoonotic and that flatulence is connected to assemblage B infections in young children. Determination of MLGs from assemblages A and B can be a valuable tool in outbreak situations and to help identify possible zoonotic transmission.     

Studies on the antibacterial effects of statins--in vitro and in vivo

Background

Statin treatment has been associated with a beneficial outcome on respiratory tract infections. In addition, previous in vitro and in vivo experiments have indicated favorable effects of statins in bacterial infections.

Aim

The aim of the present study was to elucidate possible antibacterial effects of statins against primary pathogens of the respiratory tract.

Methods

MIC-values for simvastatin, fluvastatin and pravastatin against S. pneumoniae, M. catarrhalis and H. influenzae were determined by traditional antibacterial assays. A BioScreen instrument was used to monitor effects of statins on bacterial growth and to assess possible synergistic effects with penicillin. Bacterial growth in whole blood and serum from healthy volunteers before and after a single dose of simvastatin, fluvastatin and penicillin (positive control) was determined using a blood culture system (BactAlert).

Findings

The MIC-value for simvastatin against S pneumoniae and M catarrhalis was 15 µg/mL (36 mmol/L). Fluvastatin and Pravastatin showed no antibacterial effect in concentrations up to 100 µg/mL (230 µmol/L). Statins did not affect growth or viability of H influenzae. Single doses of statins given to healthy volunteers did not affect growth of pneumococci, whereas penicillin efficiently killed all bacteria.

Conclusions

Simvastatin at high concentrations 15 µg/mL (36 µmol/L) rapidly kills S pneumoniae and M catarrhalis. However, these concentrations by far exceed the concentrations detected in human blood during simvastatin therapy (1–15 nmol/L) and single doses of statins given to healthy volunteers did not improve antibacterial effects of whole blood. Thus, a direct bactericidal effect of statins in vivo is probably not the mechanism behind the observed beneficial effect of statins against various infections.     

Resistance of fast- and slow-growing subalpine fir to pheromone-induced attack by western balsam bark beetle (Coleoptera: Scolytinae)

Abstract 1 We investigated the resistance of fast‐ and slow‐growing subalpine fir to pheromone‐induced attack by western balsam bark beetle at two sites in the interior of British Columbia, Canada. 2 Attack success by the beetle and subsequent tree mortality were higher in slow‐growing trees than in fast‐growing trees. 3 Fast‐growing trees were more likely to produce secondary resin, and in greater quantities, than slow‐growing trees after attack. 4 Host vigour (indicated by recent radial growth) was positively related to the induced defense response and resistance of subalpine fir to bark beetle attack. These results are discussed in the context of plant defense and plant–herbivore interaction hypotheses. 5 Given the preference of western balsam bark beetle for weakened trees, as well as the reduced defenses and increased mortality rates in less vigorous trees, effective management tactics for this beetle may include strategies that increase the growth and vigour of its subalpine fir host.     

Transient peaks in the delayed luminescence from Scenedesmus obtusiusculus induced by phosphorus starvation and carbon dioxide deficiency

Cells of the unicellular green alga Scenedesmus obtusiusculus (Chod.) were starved of phosphorus for 24, 48, 72 and 96 h, and the decay kinetics of the delayed luminescence from the differently starved cells was monitored for several minutes. Cells starved for 24 h showed similar delayed luminescence decay kinetics and accumulated output of photons as control cells after excitation with white light. Two transient peaks (with several components) in the decay kinetics of delayed luminescence were observed after 48 h of phosphorus starvation but not after 72 or 96 h. The amplitude of the transient peaks varied depending on the length of the excitation period with white light and on the length of the dark period preceding light excitation. High CO₂ availability induced no transient peak, whereas low CO₂ availability induced a high transient peak. Transient peaks could not be induced by excitation with light of 660 or 680 nm and only a single transient peak developed using 700 nm light. The kinetics of the delayed luminescence was changed, and the accumulated output of photons was decreased when the pH of the medium was changed from 7.2 to 9.5, both in cells starved for phosphorus for 96 h and in controls. The data indicate that a complicated metabolic pattern is involved in the mechanisms giving rise to the observed transient peaks in the delayed luminescence. The main factors may be a reduction in the translocation of trioses from chloroplasts, a concomitant reduction in Calvin cycle activities and changes in the amount of ATP and reducing agents available.     

RNase E cleavage in the 5' leader of a tRNA precursor

In this study, we have used various tRNA(Tyr)Su3 precursor (pSu3) derivatives that are processed less efficiently by RNase P to investigate if the 5' leader is a target for RNase E. We present data that suggest that RNase E cleaves the 5' leader of pSu3 both in vivo and in vitro. The site of cleavage in the 5' leader corresponds to the cleavage site for a previously identified endonuclease activity referred to as RNase P2/O. Thus, our findings suggest that RNase P2/O and RNase E activities are of the same origin. These data are in keeping with the suggestion that the structure of the 5' leader influences tRNA expression by affecting tRNA processing and indicate the involvement of RNase E in the regulation of cellular tRNA levels.     

Odorant-dependent, spatially restricted induction of c-fos in the olfactory epithelium of the mouse

Volatile odorous chemicals are detected by around a thousand different G protein-coupled odorant receptors in the mouse. We demonstrated that exposure of the behaving mouse to odorant for a few minutes led to induction of the immediate early gene c-fos for several hours in a fraction of the olfactory sensory neurones in the nasal cavity. Associated with this odorant-specific induction event was activation of extracellular-regulated kinase (ERK)1/2 that preceded increased c-fos expression. The distribution of odorant-activated neurones mimicked the scattered and spatially limited distribution of neurones expressing a single odorant receptor gene. A small change in odorant chemical structure caused a zonal shift in the spatial distribution of activated neurones, suggesting that the gene expression change resulted from specific receptor interaction. Repeated exposure to odorant or use of different concentrations did not change the pattern of c-fos induction. These results indicate that odorant-induced c-fos expression can be used to visualize odorant representations in the olfactory epithelium that reflect late cellular events regulated by adequate odorant receptor stimulation.