The role of HLA-G in immunity and hematopoiesis

The non-classical HLA class I molecule HLA-G was initially shown to play a major role in feto–maternal tolerance. Since this discovery, it has been established that HLA-G is a tolerogenic molecule which participates to the control of the immune response. In this review, we summarize the recent advances on (1) the multiple structures of HLA-G, which are closely associated with their role in the inhibition of NK cell cytotoxicity, (2) the factors that regulate the expression of HLA-G and its receptors, (3) the mechanism of action of HLA-G at the immunological synapse and through trogocytosis, and (4) the generation of suppressive cells through HLA-G. Moreover, we also review recent findings on the non-immunological functions of HLA-G in erythropoiesis and angiogenesis.     

Structure of oxidized alpha-haemoglobin bound to AHSP reveals a protective mechanism for haem

The synthesis of haemoglobin A (HbA) is exquisitely coordinated during erythrocyte development to prevent damaging effects from individual alpha- and beta-subunits. The alpha-haemoglobin-stabilizing protein (AHSP) binds alpha-haemoglobin (alphaHb), inhibits the ability of alphaHb to generate reactive oxygen species and prevents its precipitation on exposure to oxidant stress. The structure of AHSP bound to ferrous alphaHb is thought to represent a transitional complex through which alphaHb is converted to a non-reactive, hexacoordinate ferric form. Here we report the crystal structure of this ferric alphaHb-AHSP complex at 2.4 A resolution. Our findings reveal a striking bis-histidyl configuration in which both the proximal and the distal histidines coordinate the haem iron atom. To attain this unusual conformation, segments of alphaHb undergo drastic structural rearrangements, including the repositioning of several alpha-helices. Moreover, conversion to the ferric bis-histidine configuration strongly and specifically inhibits redox chemistry catalysis and haem loss from alphaHb. The observed structural changes, which impair the chemical reactivity of haem iron, explain how AHSP stabilizes alphaHb and prevents its damaging effects in cells.     

Quality in Action Research: Reflections for Second-Order Inquiry

One of the current debates in action research concerns the quality of these practices. Up to now, many contributions have focused on defining specific criteria based on action research epistemology. This article sustains (1) that prior to dealing with these questions, it is necessary to define for what purpose and for whom we are making the evaluation; (2) that this leads us to make a distinction between different evaluation models; and (3) that the quality strategies and criteria will be different for each model. In particular, the article confronts an academic evaluation model as a form of external control over the quality of action research and an internal, participatory evaluation model as a quality strategy aimed at establishing feedback for the process. Final considerations are given about the implications of both models for academia.     

Relative and seasonal abundance of three bark beetle predators (Coleoptera: Trogositidae, Cleridae) across an elevation gradient in ponderosa pine forests of north central Arizona

We examined abundance and flight periodicity of 3 predators of bark beetles (Coleoptera: Curculionidae, Scolytinae), Temnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae), Enoclerus sphegeus (Fabricius) (Coleoptera: Cleridae), and E. lecontei (Wolcott) (Coleoptera: Cleridae), across an elevational gradient of ponderosa pine ( Pinus ponderosa Lawson) forests in north central Arizona. Predator populations were estimated at 10 sites in each of 3 elevation bands (low: 1600–1736 m; mid: 2058–2230 m; high: 2505–2651 m) for 3 years (2004–2006) using pheromone-baited funnel traps targeting 3 primary bark beetle species. We also investigated how predator abundance and flight seasonality related to those of 5 bark beetle species: Ips pini (Say), I. lecontei Swaine, Dendroctonus frontalis Zimmermann, D. brevicomis LeConte, and D. adjunctus Blandford. Temnochila chlorodia was most abundant in the low- and mid-elevation bands, whereas E. sphegeus was most abundant in the high-elevation band. Enoclerus lecontei showed no consistent elevational trend in abundance. Within each elevation band, changes in annual abundance of pooled predator species tracked shifts in abundance of pooled bark beetle species. In general, predator flight initiation coincided with or closely followed bark beetle flight initiation in the spring, but predator flight terminated before flight activity ended for most bark beetle species in the fall. In addition, the ratio of prey to predators was lowest in the summer and highest in the fall. This suggests that all bark beetle species examined may be provided temporal escape from their predators in the fall. For all 3 predator species, the pheromone-baited trap targeting D. brevicomis was less attractive than the pheromone-baited traps targeting I. pini and I. lecontei.     

On the algorithmic complexity of static structures

This paper provides a first indication that this is true for a system comprised of a static structure described by hyperbolic partial differential equations and is subjected to an external random input force. The system deforms the randomness of an input force sequence in proportion to its algorithmic complexity. The authors demonstrate this by numerical analysis of a one-dimensional vibrating elastic solid (the system) on which we apply a maximally-random force sequence (input). The level of complexity of the system is controlled via external parameters. The output response is the field of displacements observed at several positions on the body. The algorithmic complexity and stochasticity of the resulting output displacement sequence is measured and compared against the complexity of the system. The results show that the higher the system complexity, the more random-deficient the output sequence.