Visual obstruction and vigilance: a natural experiment

Visual obstructions can cause an increase in antipredator vigilance in prey animals by making predator detection more difficult. However, visual obstructions can also skew the perception of group size and inter‐individual distances and impair the detection of alarm signals by conspecifics. These changes within the group alone can cause an increase in vigilance. To disentangle the contribution of these various factors to changes in vigilance, I documented vigilance in a gregarious species, the semipalmated sandpiper Calidris pusilla, foraging in a habitat where a naturally‐occurring visual barrier partially prevented predator detection without altering the transfer of information about predation risk within the group. I used a matched sampling design to collect vigilance data for birds using adjacent areas with and without the visual barrier. In the visually‐obstructed area, sandpipers maintained a higher level of vigilance, occurred farther away from cover and in smaller flocks, and preferentially scanned the area of danger with one eye in particular. All these changes suggest that visual obstruction increased perceived predation risk. I conclude that it is the inability to get a good view of any approaching predator, rather than changes in intra‐group communication that caused the increase in vigilance in the visually‐obstructed area.     

Early medication use in new-onset rheumatoid arthritis may delay joint replacement: results of a large population-based study

IntroductionUse of disease-modifying anti-rheumatic drugs (DMARDs) in rheumatoid arthritis (RA) may prevent joint damage and potentially reduce joint replacement surgeries. We assessed the association between RA drug use and joint replacement in Quebec, Canada.MethodsA cohort of new-onset RA patients was identified from Quebec’s physician billing and hospitalization databases from 2002–2011. The outcome was defined using procedure codes submitted by orthopedic surgeons. Medication use was obtained from pharmacy databases. We used alternative Cox regression models with time-dependent variables measuring the cumulative effects of past use during different time windows (one model focussing on the first year after cohort entry) for methotrexate (MTX), and other DMARDs. Models were adjusted for baseline sociodemographics, co-morbidity and prior health service use, time-dependent cumulative use of other drugs (anti-tumor necrosis factor [anti-TNF] agents, other biologics, cyclooxygenase-2 inhibitors [COXIBs], nonselective nonsteroidal antiinflammatory drugs [NSAIDs], and systemic steroids), and markers of disease severity.ResultsDuring follow-up, 608 joint replacements occurred among 11,333 patients (median follow-up: 4.6 years). The best-fitting model relied on the cumulative early use (within the first year after cohort entry) of MTX and of other DMARDs, with an interaction between MTX and other DMARDs. In this model, greater exposure within the first year, to either MTX (adjusted hazard ratio, HR = 0.95 per 1 month, 95 % confidence interval, 95 % CI 0.93-0.97) or other DMARDs (HR = 0.97, 95 % CI 0.95-0.99) was associated with longer time to joint replacement.ConclusionsOur results suggest that longer exposure to either methotrexate (MTX) or other DMARDs within the first year after RA diagnosis is associated with longer time to joint replacement surgery.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0713-3) contains supplementary material, which is available to authorized users.     

Tiludronate treatment improves structural changes and symptoms of osteoarthritis in the canine anterior cruciate ligament model

Introduction

The aim of this prospective, randomized, controlled, double-blind study was to evaluate the effects of tiludronate (TLN), a bisphosphonate, on structural, biochemical and molecular changes and function in an experimental dog model of osteoarthritis (OA).

Methods

Baseline values were established the week preceding surgical transection of the right cranial/anterior cruciate ligament, with eight dogs serving as OA placebo controls and eight others receiving four TLN injections (2 mg/kg subcutaneously) at two-week intervals starting the day of surgery for eight weeks. At baseline, Week 4 and Week 8, the functional outcome was evaluated using kinetic gait analysis, telemetered locomotor actimetry and video-automated behaviour capture. Pain impairment was assessed using a composite numerical rating scale (NRS), a visual analog scale, and electrodermal activity (EDA). At necropsy (Week 8), macroscopic and histomorphological analyses of synovium, cartilage and subchondral bone of the femoral condyles and tibial plateaus were assessed. Immunohistochemistry of cartilage (matrix metalloproteinase (MMP)-1, MMP-13, and a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS5)) and subchondral bone (cathepsin K) was performed. Synovial fluid was analyzed for inflammatory (PGE₂ and nitrite/nitrate levels) biomarkers. Statistical analyses (mixed and generalized linear models) were performed with an α-threshold of 0.05.

Results

A better functional outcome was observed in TLN dogs than OA placebo controls. Hence, TLN dogs had lower gait disability (P = 0.04 at Week 8) and NRS score (P = 0.03, group effect), and demonstrated behaviours of painless condition with the video-capture (P < 0.04). Dogs treated with TLN demonstrated a trend toward improved actimetry and less pain according to EDA. Macroscopically, both groups had similar level of morphometric lesions, TLN-treated dogs having less joint effusion (P = 0.01), reduced synovial fluid levels of PGE₂ (P = 0.02), nitrites/nitrates (P = 0.01), lower synovitis score (P < 0.01) and a greater subchondral bone surface (P < 0.01). Immunohistochemical staining revealed lower levels in TLN-treated dogs of MMP-13 (P = 0.02), ADAMTS5 (P = 0.02) in cartilage and cathepsin K (P = 0.02) in subchondral bone.

Conclusion

Tiludronate treatment demonstrated a positive effect on gait disability and joint symptoms. This is likely related to the positive influence of the treatment at improving some OA structural changes and reducing the synthesis of catabolic and inflammatory mediators.     

Effects of the humic substances of de-inking paper sludge on the antagonism between two compost bacteria and Pythium ultimum

We investigated the in vitro influence of humic substances (HS) extracted from de-inking paper sludge compost on the inhibition of Pythium ultimum by two compost bacteria, Rhizobium radiobacter (Agrobacterium radiobacter) and Pseudomonas aeruginosa. When low concentrations (5 or 50 mg l(-1)) of HS were added to the culture medium, fungal inhibition by R. radiobacter significantly increased (P<0.01) by 2-3%. In contrast, these low levels of HS had no effect on P. ultimum inhibition by P. aeruginosa. The Fe, chelated by HS, was in part responsible for the decrease of P. ultimum inhibition by the bacteria when increasing amounts of HS were added in the culture medium. The addition of 500 mg l(-1) of humic acids isolated from de-inking paper sludge compost or from fossil origin completely eliminated the inhibition of P. ultimum by R. radiobacter. This Fe effect also stimulated growth of R. radiobacter and reduced its siderophore production in a minimal medium supplemented with HS as sole source of Fe. The results showed that HS influence microbial antagonism when added to a culture medium. However, this effect varies with different factors such as the type of bacteria, concentration of HS, molecular weight and Fe content.     

Concordant phylogeography and cryptic speciation in two Western Palaearctic oak gall parasitoid species complexes

Little is known about the evolutionary history of most complex multi‐trophic insect communities. Widespread species from different trophic levels might evolve in parallel, showing similar spatial patterns and either congruent temporal patterns (Contemporary Host‐tracking) or later divergence in higher trophic levels (Delayed Host‐tracking). Alternatively, host shifts by natural enemies among communities centred on different host resources could disrupt any common community phylogeographic pattern. We examined these alternative models using two Megastigmus parasitoid morphospecies associated with oak cynipid galls sampled throughout their Western Palaearctic distributions. Based on existing host cynipid data, a parallel evolution model predicts that eastern regions of the Western Palaearctic should contain ancestral populations with range expansions across Europe about 1.6 million years ago and deeper species‐level divergence at both 8–9 and 4–5 million years ago. Sequence data from mitochondrial cytochrome b and multiple nuclear genes showed similar phylogenetic patterns and revealed cryptic genetic species within both morphospecies, indicating greater diversity in these communities than previously thought. Phylogeographic divergence was apparent in most cryptic species between relatively stable, diverse, putatively ancestral populations in Asia Minor and the Middle East, and genetically depauperate, rapidly expanding populations in Europe, paralleling patterns in host gallwasp species. Mitochondrial and nuclear data also suggested that Europe may have been colonized multiple times from eastern source populations since the late Miocene. Temporal patterns of lineage divergence were congruent within and across trophic levels, supporting the Contemporary Host‐tracking Hypothesis for community evolution.     

Functional Divergence among CD103+ Dendritic Cell Subpopulations following Pulmonary Poxvirus Infection

A large number of dendritic cell (DC) subsets have now been identified based on the expression of a distinct array of surface markers as well as differences in functional capabilities. More recently, the concept of unique subsets has been extended to the lung, although the functional capabilities of these subsets are only beginning to be explored. Of particular interest are respiratory DCs that express CD103. These cells line the airway and act as sentinels for pathogens that enter the lung, migrating to the draining lymph node, where they add to the already complex array of DC subsets present at this site. Here we assessed the contributions of these individual populations to the generation of a CD8⁺ T-cell response following respiratory infection with poxvirus. We found that CD103⁺ DCs were the most effective antigen-presenting cells (APC) for naive CD8⁺ T-cell activation. Surprisingly, we found no evidence that lymph node-resident or parenchymal DCs could prime virus-specific cells. The increased efficacy of CD103⁺ DCs was associated with the increased presence of viral antigen as well as high levels of maturation markers. Within the CD103⁺ DCs, we observed a population that expressed CD8α. Interestingly, cells bearing CD8α were less competent for T-cell activation than their CD8α⁻ counterparts. These data show that lung-migrating CD103⁺ DCs are the major contributors to CD8⁺ T-cell activation following poxvirus infection. However, the functional capabilities of cells within this population differ with the expression of CD8, suggesting that CD103⁺ cells may be divided further into distinct subsets.In order for the body to mount an adaptive immune response to a pathogen, T cells circulating through lymph nodes (LN) must be alerted to the presence of infection in the periphery. This occurs as a result of presentation of pathogen-derived epitopes on professional antigen-presenting cells (APC), primarily dendritic cells (DC). The DC that reside in the tissue continually sample the local environment for the presence of foreign/pathogenic antigens. In a noninfected tissue, DC exist in an immature state, i.e., they are highly phagocytic and have low levels of expression of costimulatory molecules (3). Following an encounter with infection-associated signals, e.g., pathogen-associated molecular patterns (PAMPs) and/or inflammatory cytokines, DC undergo maturation (3). This process results in upregulation of chemokine receptors, which promotes trafficking to the lymph node, as well as increased expression of costimulatory molecules and cytokines, which are necessary accessory signals for the activation of naive T cells (2, 3).Unlike many other tissues, the lung is constantly assaulted with foreign antigens, both environmental and infectious. This includes a large number of viruses which spread via aerosolized droplets. As such, it is critical to understand how the immune system detects these infections and subsequently elicits an efficacious adaptive CD8⁺ T-cell response. While an important role for DC as the activators of naive T cells is clear, the contribution of distinct DC subsets in this process is less understood. Multiple DC subsets are present within the lung draining lymph nodes, and as such, all are potential regulators of T-cell activation (for a review, see references 14 and 32). These subsets are either resident in the lymph node or present at this site as a result of migration from the periphery, in this case, the lung. These DC subsets are defined by the array of molecules expressed at their surface. Among the subsets resident within the lymph nodes are those which express CD8α or CD4 or are double negative (express neither CD4 nor CD8α) (32). These subsets appear to be segregated in their capabilities to elicit T-cell responses. For example, previous studies have suggested that CD8α⁺ DC are the predominant DC subset involved in priming CD8⁺ T cells (4), while CD8α ⁻ CD4⁺ DC are more important in the regulation of CD4⁺ T cells (31). Further, CD8α⁺ DC are efficient at cross-presentation, a property shown to be critical in the generation of CD8⁺ T-cell responses in a number of infectious models (24, 33).In addition to LN-resident populations, lung-resident DC that have migrated to the lymph node following infection make up a significant portion of LN DC. CD103 (an α^E integrin)-expressing DC reside at the airway mucosa and surrounding pulmonary vessels (35). In contrast, CD103⁻ CD11b⁺ DC are restricted to the lung parenchyma. Given the relatively recent identification of these distinct lung-resident DC populations, there is limited information available regarding their role in T-cell activation following infection. However, they have been assessed in several models, including influenza virus, respiratory syncytial virus (RSV), and Bordetella pertussis (1, 5, 15, 19, 23, 26, 37). At present, the relative contributions of migrating versus resident DC populations remain controversial. Earlier studies reported a role for LN-resident CD8α⁺ DC in priming naive CD8⁺ T cells in addition to lung-migrating DC (5). More recently, however, studies have suggested that activating potential is restricted primarily to lung-migrating DC (1, 23). The underlying cause of these discrepancies is currently unknown but may reflect differences in the markers used to identify the DC subsets or in the individual infection models. Regardless, our understanding of the role of these subsets remains incomplete.We have analyzed the migration and maturation of DC following respiratory infection with the orthopoxvirus vaccinia virus (VV). These studies revealed that airway-resident CD103⁺ DC were the most efficient activators of virus-specific CD8⁺ T cells. Further studies determined that this was the result of both increased access to viral antigen and increased maturation within this subset. In our analyses, we found no evidence to support a role for LN-resident CD8α⁺ DC or lung-migrating CD11b⁺ DC in T-cell activation. Further, we found that CD103⁺ DC were heterogeneous with regard to their functional capabilities. Interestingly, this correlated with the expression of CD8α. While more-recent studies have found CD8α expression on CD103⁺ DC (30), none have looked at the functional capabilities of these cells separately from those of CD8α⁻ CD103⁺ DC. Our findings are the first to suggest that CD8α expression within the CD103⁺ population may identify a distinct subset that differs in its functional capabilities.