Dufour’s gland secretion,sterility and foraging behavior: Correlated behavior traits in bumblebee workers

Bombus terrestris colonies go through two major phases: the “pre-competition phase” in which the queen is the sole reproducer and aggression is rare, and the “competition phase” in which workers aggressively compete over reproduction. Conflicts over reproduction are partially regulated by a group of octyl esters that are produced in Dufour’s gland of reproductively subordinate workers and protect them from being aggressed. However, workers possess octyl esters even before overt aggression occurs, raising the question of why produce the ester-signal before it is functionally necessary?In most insect societies, foragers show reduced aggression and low dominance rank. We hypothesize that ester production in B. terrestris is not only correlated with sterility but also with foraging, signaling cooperative behavior by subordinate workers. Such a signal helps to maintain social organization, reduce the cost of fights between reproductives and helpers, and increase colony productivity, enabling subordinates to gain greater inclusive fitness. We demonstrate that foragers produce larger amounts of esters compared to non-foragers, and that their amounts positively correlate with foraging efforts. We further suggest that task performance, potential fecundity, and aggression are interlinked, and that worker–worker interactions are involved in regulating foraging behavior.B. terrestris, being an intermediate phase between primitive and derived eusocial insects, provides an excellent model for understanding the evolution of early phases of eusociality. Our results, combined with those in primitively eusocial wasps, suggest that at early stages of social evolution, reproduction was regulated by a “primordial division of labor”, that comprised foragers and reproducers, which further evolved to a more complex division of labor, a hallmark of eusociality.     

Aggression or ovarian development as determinants of reproductive dominance in Bombus terrestris: interpretation using a simulation model

Insect societies generally manifest reproductive division of labor with one or a few fecund females (queens) and sterile helpers (workers). This is generally mediated by behavioural hierarchy that reduces the cost of within-group aggression. Aggressive behaviour and ovarian development are thus two co-occurring correlates of reproductive skew, but their mutual influence remains unclear. Here we examined the interplay between these factors by constructing a simulation model, based on the biology of Bombus terrestris, to test whether aggression levels are determined by the level of ovarian development or vice versa. We approached this question using virtual groups composed of either equally or unequally matched workers, as well as supplementing the simulation data by experimental data using actual bee groups. The simulation revealed that previous encounter experience (win/lose) rather than mutual assessment of reproductive status determines and maintains hierarchy in B. terrestris. Furthermore, although bumblebee workers largely vary in their aggression tendencies, pre-existing differences between nest-mates were not obligatory for establishment of the hierarchy. The initially formed linear hierarchy became polynomial after 10 days, clearly separating between egg-laying workers and helpers. This was consistent with the results obtained for actual bee groups. We propose that aggressive behaviour and the outcome of previous encounters are major determinants of ovarian development and not vice versa. Workers may gain a head start in the competition due to variation in their innate aggressive tendencies, or by fortuitously winning their first encounters. Small differences in aggressiveness between workers are amplified to initially form a short-term linear hierarchy that subsequently turns to polynomial hierarchy, creating the most basic phenomenon of social groups, reproductive division of labor.     

Nav1.9 channel contributes to mechanical and heat pain hypersensitivity induced by subacute and chronic inflammation

Inflammation is known to be responsible for the sensitization of peripheral sensory neurons, leading to spontaneous pain and invalidating pain hypersensitivity. Given its role in regulating neuronal excitability, the voltage-gated Nav1.9 channel is a potential target for the treatment of pathological pain, but its implication in inflammatory pain is yet not fully described. In the present study, we examined the role of the Nav1.9 channel in acute, subacute and chronic inflammatory pain using Nav1.9-null mice and Nav1.9 knock-down rats. In mice we found that, although the Nav1.9 channel does not contribute to basal pain thresholds, it plays an important role in heat pain hypersensitivity induced by subacute paw inflammation (intraplantar carrageenan) and chronic ankle inflammation (complete Freund's adjuvant-induced monoarthritis). We showed for the first time that Nav1.9 also contributes to mechanical hypersensitivity in both models, as assessed using von Frey and dynamic weight bearing tests. Consistently, antisense-based Nav1.9 gene silencing in rats reduced carrageenan-induced heat and mechanical pain hypersensitivity. While no changes in Nav1.9 mRNA levels were detected in dorsal root ganglia (DRGs) during subacute and chronic inflammation, a significant increase in Nav1.9 immunoreactivity was observed in ipsilateral DRGs 24 hours following carrageenan injection. This was correlated with an increase in Nav1.9 immunolabeling in nerve fibers surrounding the inflamed area. No change in Nav1.9 current density could be detected in the soma of retrolabeled DRG neurons innervating inflamed tissues, suggesting that newly produced channels may be non-functional at this level and rather contribute to the observed increase in axonal transport. Our results provide evidence that Nav1.9 plays a crucial role in the generation of heat and mechanical pain hypersensitivity, both in subacute and chronic inflammatory pain models, and bring new elements for the understanding of its regulation in those models.     

Zn0.35Co0.65O – A Stable and Highly Active Oxygen Evolution Catalyst Formed by Zinc Leaching and Tetrahedral Coordinated Cobalt in Wurtzite Structure

To arrive to sustainable hydrogen‐based energy solutions, the understanding of water‐splitting catalysts plays the most crucial role. Herein, state‐of‐the‐art hypotheses are combined on electrocatalytic active metal sites toward the oxygen evolution reaction (OER) to develop a highly efficient catalyst based on Earth‐abundant cobalt and zinc oxides. The precursor catalyst Zn_0.35Co_0.65O is synthesized via a fast microwave‐assisted approach at low temperatures. Subsequently, it transforms in situ from the wurtzite structure to the layered γ‐Co(O)OH, while most of its zinc leaches out. This material shows outstanding catalytic performance and stability toward the OER in 1 m KOH (overpotential at 10 mA cm^?2 η_initial = 306 mV, η_{98 h} = 318 mV). By comparing the electrochemical results and ex situ analyses to today's literature, clear structure‐activity correlations are able to be identified. The findings suggest that coordinately unsaturated cobalt octahedra on the surface are indeed the active centers for the OER.     

Seasonal variation in spontaneous intracerebral hemorrhage in northern Israel

The incidence of spontaneous intracerebral hemorrhage (sICH) and ischemic stroke vary across seasons. Most studies examining seasonal variation in sICH have been conducted in countries with significant climatic changes across seasons, whereas studies from the Mediterranean region, which has a relatively mild winter, are limited in number and have produced inconsistent results. Further studies from the region are called for, especially from countries where sICH seasonality has not yet been explored. A total of 974 patients with sICH between 1 January 2000 and 31 December 2014 were included in this study. The seasonal, monthly and weekday distribution of hospital admissions, in-hospital mortality, length of hospital stay and functional outcome at discharge were examined. We found that most hospital admissions due to sICH occurred in the winter (n = 286, 29%), whereas the fewest admissions occurred in the summer (n = 205, 21%; p = 0.0011). In terms of monthly distribution, most admissions were in January (n = 107, 11%), and the fewest admissions were in September (n = 60, 6%; p = 0.0004). There were no differences in the distribution of sICH between weekdays and weekends. Also, we found no significant weekday or seasonal variations in in-hospital mortality or functional outcome of sICH. Our results suggest that temporal patterns impact the natural course of sICH in northern Israel. The identification of factors, including biological ones, responsible for seasonal variation in regions with mild seasonal changes requires further research but could aid in the design of strategies for preventing sICH.     

Educational Intervention Increased Referrals to Allopathic Care by Traditional Healers in Three High HIV-Prevalence Rural Districts in Mozambique

Introduction

Delayed uptake of clinical services impedes favorable clinical outcomes in Mozambique. Care is delayed among patients who initiate care with traditional healers; patients with conditions like human immunodeficiency virus (HIV) or tuberculosis are rarely referred to the health system in a timely fashion.

Methods

We conducted a pre-post educational intervention with traditional healers, assessing healer referral rates and HIV knowledge in three rural districts in Zambézia Province.

Results

The median monthly referral rate prior to the intervention was 0.25 patients (interquartile range [IQR]: 0–0.54) compared with a post-intervention rate of 0.34 patients (IQR: 0–0.71), a 35% increase (p = 0.046). A median HIV knowledge score of 67% (IQR: 59–78) was noted 4-months pre-intervention and a median score of 81% (IQR: 74–89) was recorded 2½ months post-intervention (p<0.001). One hundred and eleven healers referred 127 adults, 36 pregnant women, and 188 children to health facilities. Referred patients were most likely to be diagnosed with bronchopneumonia (20% adults; 13% children) and/or malaria (15% adults; 37% children). Of 315 non-pregnant persons referred, 3.5% were tested for HIV and 2.5% were tested for tuberculosis.

Discussion

We engaged traditional healers with some success; referral rates were low, but increased post-intervention. Once seen in the clinics, patients were rarely tested for HIV or tuberculosis, though symptoms suggested screening was indicated. We found increased referral rates through an inexpensive intervention with traditional healers, a viable, cost-effective method of directing patients to health facilities. However, quality improvement within the clinics is necessary before a substantial impact can be expected.     

The effect of group size on the interplay between dominance and reproduction in Bombus terrestris

Social insects provide good model systems for testing trade-offs in decision-making because of their marked reproductive skew and the dilemma workers face when to reproduce. Attaining reproductive skew requires energy investment in aggression or fertility signaling, creating a trade-off between reproduction and dominance. This may be density-dependent because the cost of achieving dominance may be higher in larger groups. We investigated the effect of group-size in B. terrestris queenless workers on two major reproduction-dominance correlates: between-worker aggression, and pheromone production, aiming at mimicking decision-making during the transition of worker behavior from cooperation and sterility to aggressive reproductive competition in whole colonies. Despite the competition, reproductive division of labor in colonies can be maintained even during this phase through the production of a sterility signal by sterile workers that has an appeasement effect on dominant nestmates. Worker-worker aggression, ovary activation, and production of sterility-appeasement signals may therefore constitute components of a trade-off affecting worker reproduction decisions. By constructing queenless groups of different size and measuring how this affected the parameters above, we found that in all groups aggression was not evenly distributed with the α-worker performing most of the aggressive acts. Moreover, aggression by the α-worker increased proportionally with group-size. However, while in small groups the α-worker monopolized reproduction, in larger groups several workers shared reproduction, creating two worker groups: reproductives and helpers. It appears that despite the increase of aggression, this was evidently not sufficient for the α-worker to monopolize reproduction. If we compare the α-worker to the queen in full-sized colonies it can be hypothesized that worker reproduction in B. terrestris colonies starts due to a gradual increase in the worker population and the queen's inability to physically inhibit worker oviposition. This may shift the trade-off between cost and benefit of worker reproduction and trigger the competition phase.     

Drosophila Oocyte Polarity and Cytoskeleton Organization Require Regulation of Ik2 Activity by Spn-F and Javelin-Like

The Drosophila melanogaster Spn-F, Ik2, and Javelin-like (Jvl) proteins interact to regulate oocyte mRNA localization and cytoskeleton organization. However, the mechanism by which these proteins interact remains unclear. Using antibodies to activated Ik2, we showed that this protein is found at the region of oocyte and follicle cell where microtubule minus ends are enriched. We demonstrate that germ line Ik2 activation is diminished both in jvl and in spn-F mutant ovaries. Structure-function analysis of Spn-F revealed that the C-terminal end is critical for protein function, since it alone was able to rescue spn-F sterility. On the other hand, germ line expression of Spn-F lacking its conserved C-terminal region (Spn-FΔC) phenocopied ik2, leading to production of ventralized eggshell and bicaudal embryos. In Spn-FΔC-expressing oocytes, Gurken protein is mislocalized and oskar mRNA and protein localization is disrupted. Expression of Ik2 rescued Spn-FΔC ovarian phenotypes. We found that whereas Spn-F physically interacts with Ik2 and Jvl, Spn-FΔC physically interacts with Ik2 but not with Jvl. Thus, expression of Spn-FΔC, which lacks the Jvl-interacting domain, probably interferes with interaction of Ik2 and Jvl. In summary, our results demonstrate that Spn-F mediates the interaction between Ik2 and Jvl to control Ik2 activity.