Multi-year evolutionary dynamics of West Nile virus in suburban Chicago,USA, 2005–2007

West Nile virus has evolved in concert with its expansion across North America, but little is known about the evolutionary dynamics of the virus on local scales. We analysed viral nucleotide sequences from mosquitoes collected in 2005, 2006, and 2007 from a known transmission ‘hot spot’ in suburban Chicago, USA. Within this approximately 11 × 14 km area, the viral envelope gene has increased approximately 0.1% yr⁻¹ in nucleotide-level genetic diversity. In each year, viral diversity was higher in ‘residential’ sites characterized by dense housing than in more open ‘urban green space’ sites such as cemeteries and parks. Phylodynamic analyses showed an increase in incidence around 2005, consistent with a higher-than-average peak in mosquito and human infection rates that year. Analyses of times to most recent common ancestor suggest that WNV in 2005 and 2006 may have arisen predominantly from viruses present during 2004 and 2005, respectively, but that WNV in 2007 had an older common ancestor, perhaps indicating a predominantly mixed or exogenous origin. These results show that the population of WNV in suburban Chicago is an admixture of viruses that are both locally derived and introduced from elsewhere, containing evolutionary information aggregated across a breadth of spatial and temporal scales.     

Activity profile of world-class professional surfers during competition: a case study

The activity profile of men's competitive surfing was investigated during an international contest. Forty-two male surfers were filmed during 42 elimination heats. Surfers' activities were classified into 1 of 4 distinct categories (paddling, wave riding, stationary, and miscellaneous). The surfers were paddling and stationary 51% (25-70%) and 42% (23-72%) of the total time, respectively. Wave riding accounted for 4% (2-7%) of the total time, whereas miscellaneous activity accounted for the remaining 2% (0.1-6%) of the total time. The frequency (average number of motions in a heat) of each activity was 26 for paddling (15-37); 17 for stationary (10-26); 5 for wave riding (2-8); and 6 for miscellaneous activity (1-13). The mean duration lengths of the activities were 30.1 seconds (1-286 seconds), 37.7 seconds (1-413 seconds), 11.6 seconds (1-44 seconds), and 5 seconds (1- 31 seconds) for paddling, stationary, wave riding, and miscellaneous activities, respectively. Most of the paddling bouts ( approximately 60%) were performed at time intervals of between 1 and 20 seconds. Approximately 50% (50.9%) of the rest intervals were between 1 and 20 seconds in duration. The results showed that surfing is an intermittent activity characterized by a large variability and random distribution of each parameter analyzed. This information can be used to assist in the development of fitness training programs and physiological testing for competitive surfers.     

Regional muscle oxygenation differences in vastus lateralis during different modes of incremental exercise

Background

Near infrared spectroscopy (NIRS) is used to assess muscle oxygenation (MO) within skeletal muscle at rest and during aerobic exercise. Previous investigations have used a single probe placement to measure MO during various forms of exercise. However, regional MO differences have been shown to exist within the same muscle which suggests that different areas of the same muscle may have divergent MO. Thus, the aim of this study was to examine whether regional differences in MO exist within the same muscle during different types of incremental (rest, 25, 50, 75, 100 % of maximum) exercise (1 leg knee extension (KE), 2 leg KE, or cycling).

Methods

Nineteen healthy active males (Mean ± SD: Age 27 ± 4 yrs; VO_2max: 55 ± 11 mL/kg/min) performed incremental exercise to fatigue using each mode of exercise. NIRS probes were placed on the distal and proximal portion of right leg vastus lateralis (VL). Results were analyzed with a 3-way mixed model ANOVA (probe × intensity × mode).

Results

Differences in MO exist within the VL for each mode of exercise, however these differences were not consistent for each level of intensity. Comparison of MO revealed that the distal region of VL was significantly lower throughout KE exercise (1 leg KE proximal MO – distal MO = 9.9 %; 2 leg KE proximal MO – distal MO = 13 %). In contrast, the difference in MO between proximal and distal regions of VL was smaller in cycling and was not significantly different at heavy workloads (75 and 100 % of maximum).

Conclusion

MO is different within the same muscle and the pattern of the difference will change depending on the mode and intensity of exercise. Future investigations should limit conclusions on MO to the area under assessment as well as the type and intensity of exercise employed.

     

Association of FCGR2A and FCGR2A-FCGR3A haplotypes with susceptibility to giant cell arteritis

The Fc gamma receptors have been shown to play important roles in the initiation and regulation of many immunological and inflammatory processes and to amplify and refine the immune response to an infection. We have investigated the hypothesis that polymorphism within the FCGR genetic locus is associated with giant cell arteritis (GCA). Biallelic polymorphisms in FCGR2A, FCGR3A, FCGR3B and FCGR2B were examined for association with biopsy-proven GCA (n = 85) and healthy ethnically matched controls (n = 132) in a well-characterised cohort from Lugo, Spain. Haplotype frequencies and linkage disequilibrium (D') were estimated across the FCGR locus and a model-free analysis performed to determine association with GCA. There was a significant association between FCGR2A-131RR homozygosity (odds ratio (OR) 2.10, 95% confidence interval (CI) 1.12 to 3.77, P = 0.02, compared with all others) and carriage of FCGR3A-158F (OR 3.09, 95% CI 1.10 to 8.64, P = 0.03, compared with non-carriers) with susceptibility to GCA. FCGR haplotypes were examined to refine the extent of the association. The haplotype showing the strongest association with GCA susceptibility was the FCGR2A-FCGR3A 131R-158F haplotype (OR 2.84, P = 0.01 for homozygotes compared with all others). There was evidence of a multiplicative joint effect between homozygosity for FCGR2A-131R and HLA-DRB1*04 positivity, consistent with both of these two genetic factors contributing to the risk of disease. The risk of GCA in HLA-DRB1*04 positive individuals homozygous for the FCGR2A-131R allele is increased almost six-fold compared with those with other FCGR2A genotypes who are HLA-DRB1*04 negative. We have demonstrated that FCGR2A may contribute to the 'susceptibility' of GCA in this Spanish population. The increased association observed with a FCGR2A-FCGR3A haplotype suggests the presence of additional genetic polymorphisms in linkage disequilibrium with this haplotype that may contribute to disease susceptibility. These findings may ultimately provide new insights into disease pathogenesis.     

Population structure of the black seabream Spondyliosoma cantharus along the south-west Portuguese coast inferred from otolith chemistry

The chemistry of black seabream Spondyliosoma cantharus otoliths from three main fishery grounds (Olhão, Sagres and Sesimbra) located along c. 400 km of the Portuguese south and west coasts was examined. Element:Ca ratios were determined in whole otoliths and otolith cores of young adult specimens of 2–3 years of age. Using the data from whole otoliths, it was possible to discriminate among S. cantharus from the three fishing grounds with an average accuracy of 91%. Differences among fishing grounds were significant for all element:Ca ratios, and otoliths from Sagres had significantly higher levels of all ratios compared to the other fishing grounds. In contrast, the chemical composition of the otolith core, representative of the larval stage, showed limited variation among the fishing grounds, with an average discrimination accuracy of only 44%, although the Mg:Ca ratio of the otolith cores was also significantly higher for the Sagres samples. The data suggest that larval stages experienced a homogenous environment consistent with an offshore oceanic spawning. Juveniles appeared to display local residency on the inshore fishing grounds, areas probably characterized by greater environmental heterogeneity. Spondyliosoma cantharus population structure is consistent with distinct local population units that share a spawning ground providing recruits to different coastal fishery areas.     

A dileucine signal situated in the C-terminal tail of the lysosomal membrane protein p40 is responsible for its targeting to lysosomes

The suicide inactivation mechanism of tyrosinase acting on its substrates has been studied. The kinetic analysis of the proposed mechanism during the transition phase provides explicit analytical expressions for the concentrations of o-quinone against time. The electronic, steric and hydrophobic effects of the substrates influence the enzymatic reaction, increasing the catalytic speed by three orders of magnitude and the inactivation by one order of magnitude. To explain the suicide inactivation, we propose a mechanism in which the enzymatic form E(ox) (oxy-tyrosinase) is responsible for such inactivation. A key step might be the transfer of the C-1 hydroxyl group proton to the peroxide, which would act as a general base. Another essential step might be the axial attack of the o-diphenol on the copper atom. The rate constant of this reaction would be directly related to the strength of the nucleophilic attack of the C-1 hydroxyl group, which depends on the chemical shift of the carbon C-1 (delta(1)) obtained by (13)C-NMR. Protonation of the peroxide would bring the copper atoms together and encourage the diaxial nucleophilic attack of the C-2 hydroxyl group, facilitating the co-planarity with the ring of the copper atoms and the concerted oxidation/reduction reaction, and giving rise to an o-quinone. The suicide inactivation would occur if the C-2 hydroxyl group transferred the proton to the protonated peroxide, which would again act as a general base. In this case, the co-planarity between the copper atom, the oxygen of the C-1 and the ring would only permit the oxidation/reduction reaction on one copper atom, giving rise to copper(0), hydrogen peroxide and an o-quinone, which would be released, thus inactivating the enzyme.     

Offspring sex ratio in the Common Tern Sterna hirundo, a species with negligible sexual size dimorphism

In many vertebrates, male offspring are affected more than female offspring by adverse conditions during growth, resulting in facultative adjustment of offspring sex ratio by parents in response to social and environmental conditions during breeding. The greater vulnerability of male offspring is generally attributed to their higher energy requirements associated with their larger size, although greater sensitivity to adverse conditions could be related to other factors such as negative effects of androgens on male physiology. To control for sexual differences in body size, we examined variation in offspring sex ratio in the Common Tern Sterna hirundo , a species with negligible sexual size dimorphism. In this species, the last-laid egg (termed the c-egg) is smaller than the first two and hatches last, so that the chick obtains relatively little food and hence has a low probability of survival to fledging. This species thus provides a powerful model for examining sex-linked mortality and sex ratio variation under natural conditions. We found that the sex ratio of c-eggs, but not of earlier laid eggs, was significantly biased in favour of females. Chicks hatched from c-eggs (termed c-chicks) had low survival but female c-chicks had significantly higher survival than male c-chicks. These data provide strong evidence that factors other than sexual size dimorphism are responsible for producing greater vulnerability of male offspring to adverse conditions during growth.