Environmental drivers of macroinvertebrate communities in high Arctic rivers (Svalbard)

相似文献   

Conflict and death in a late prehistoric community in the American Midwest

Over the past two decades, it has been recognized that the effects of intergroup conflict in prehistoric small-scale societies were greater than previously thought. Osteological evidence provides otherwise unobtainable information on the number of people who were killed, and who was most likely to become a casualty. One such site is Norris Farms #36 in the American Midwest, dating to ca. AD 1300. Skeletal evidence of injuries (blunt force trauma and arrow wounds), body mutilation (scalping, decapitation, and dismemberment), and scavenger damage indicate that one-third of the adults died in a series of ambushes, although children were mostly spared. Both young and old adults were killed, and the age distributions of the male and female victims were similar. Individuals with disabilities that interfered with mobility were more likely to be killed than their healthier counterparts. This level of conflict-related mortality almost certainly had an effect on the community's ability to conduct its affairs and, indeed, to survive as a viable economic and social group.     

Anergic responses characterize a large fraction of human autoreactive naive B cells expressing low levels of surface IgM

B cell anergy represents an important mechanism of peripheral immunological tolerance for mature autoreactive B cells that escape central tolerance enforced by receptor editing and clonal deletion. Although well documented in mice, the extent of its participation in human B cell tolerance remains to be fully established. In this study, we characterize the functional behavior of strictly defined human naive B cells separated on the basis of their surface IgM (sIgM) expression levels. We demonstrate that cells with lower sIgM levels (IgM(lo)) are impaired in their ability to flux calcium in response to either anti-IgM or anti-IgD cross-linking and contain a significantly increased frequency of autoreactive cells compared with naive B cells with higher levels of sIgM. Phenotypically, in healthy subjects, IgM(lo) cells are characterized by the absence of activation markers, reduction of costimulatory molecules (CD19 and CD21), and increased levels of inhibitory CD22. Functionally, IgM(lo) cells display significantly weaker proliferation, impaired differentiation, and poor Ab production. In aggregate, the data indicate that hyporesponsiveness to BCR cross-linking associated with sIgM downregulation is present in a much larger fraction of all human naive B cells than previously reported and is likely to reflect a state of anergy induced by chronic autoantigen stimulation. Finally, our results indicate that in systemic lupus erythematosus patients, naive IgM(lo) cells display increased levels of CD95 and decreased levels of CD22, a phenotype consistent with enhanced activation of autoreactive naive B cells in this autoimmune disease.     

Bridging of anions by hydrogen bonds in nest motifs and its significance for Schellman loops and other larger motifs within proteins

The nest is a protein motif of three consecutive amino acid residues with dihedral angles 1,2‐α_Rα_L (RL nests) or 1,2‐α_Lα_R (LR nests). Many nests form a depression in which an anion or δ‐negative acceptor atom is bound by hydrogen bonds from the main chain NH groups. We have determined the extent and nature of this bridging in a database of protein structures using a computer program written for the purpose. Acceptor anions are bound by a pair of bridging hydrogen bonds in 40% of RL nests and 20% of LR nests. Two thirds of the bridges are between the NH groups at Positions 1 and 3 of the motif (N1N3‐bridging)—which confers a concavity to the nest; one third are of the N2N3 type—which does not. In bridged LR nests N2N3‐bridging predominates (14% N1N3: 75% N2N3), whereas in bridged RL nests the reverse is true (69% N1N3: 25% N2N3). Most bridged nests occur within larger motifs: 45% in (hexapeptide) Schellman loops with an additional 4 → 0 hydrogen bond (N1N3), 11% in Schellman loops with an additional 5 → 1 hydrogen bond (N2N3), 12% in a composite structure including a type 1β‐bulge loop and an asx‐ or ST‐ motif (N1N3)—remarkably homologous to the N1N3‐bridged Schellman loop—and 3% in a composite structure including a type 2β‐bulge loop and an asx‐motif (N2N3). A third hydrogen bond is a previously unrecognized feature of Schellman loops as those lacking bridged nests have an additional 4 → 0 hydrogen bond. Proteins 2014; 82:3023–3031. © 2014 Wiley Periodicals, Inc.     

Rings and ribbons in protein structures: Characterization using helical parameters and Ramachandran plots for repeating dipeptides

Helical parameters displayed on a Ramachandran plot allow peptide structures with successive residues having identical main chain conformations to be studied. We investigate repeating dipeptide main chain conformations and present Ramachandran plots encompassing the range of possible structures. Repeating dipeptides fall into the categories: rings, ribbons, and helices. Partial rings occur in the form of “nests” and “catgrips”; many nests are bridged by an oxygen atom hydrogen bonding to the main chain NH groups of alternate residues, an interaction optimized by the ring structure of the nest. A novel recurring feature is identified that we name unpleated β, often situated at the ends of a β‐sheet strand. Some are partial rings causing the polypeptide to curve gently away from the sheet; some are straight. They lack β‐pleat and almost all incorporate a glycine. An example is the first glycine in the GxxxxGK motif of P‐loop proteins. Ribbons in repeating dipeptides can be either flat, as seen in repeated type II and type II′ β‐turns, or twisted, as in multiple type I and type I′ β‐turns. Hexa‐ and octa‐peptides in such twisted ribbons occur frequently in proteins, predominantly with type I β‐turns, and are the same as the “β‐bend ribbons” hitherto identified only in short peptides. One is seen in the GTPase‐activating protein for Rho in the active, but not the inactive, form of the enzyme. It forms a β‐bend ribbon, which incorporates the catalytic arginine, allowing its side chain guanidino group to approach the active site and enhance enzyme activity. Proteins 2014; 82:230–239. © 2013 Wiley Periodicals, Inc.     

The Role of Gender in Public Perception of Whether Animals Can Experience Grief and Other Emotions

Gender plays a significant role in influencing people's attitudes toward animals, however, little is known about how it influences their attribution of emotions to animals. To investigate the role that gender plays in public attitudes toward animals' experience of emotions and beliefs about whether animals can grieve, a face-to-face survey of 1,000 members of the general public was carried out in Brisbane, Australia. Potential respondents were asked to complete a 10-min “social attitudinal” survey. Males were significantly less likely than females to believe that animals experience complex emotions, including depression (p < 0.05), anxiety (p < 0.05), love (p < 0.01), and grief (p < 0.05), but did not differ in regard to basic emotions including distress, fear, happiness, anger, sadness, and fear. Males were also less likely to believe that animals show some behavioral (eating p < 0.05; vocalizing p < 0.01) changes when they experience grief (p < 0.05) and that animals grieve as a result of separation from a conspecific (p < 0.005). These results demonstrate a greater skepticism in males, compared with females, regarding the attribution of emotions to animals.