Prion protein cleavage fragments regulate adult neural stem cell quiescence through redox modulation of mitochondrial fission and SOD2 expression

Neurogenesis continues in the post-developmental brain throughout life. The ability to stimulate the production of new neurones requires both quiescent and actively proliferating pools of neural stem cells (NSCs). Actively proliferating NSCs ensure that neurogenic demand can be met, whilst the quiescent pool makes certain NSC reserves do not become depleted. The processes preserving the NSC quiescent pool are only just beginning to be defined. Herein, we identify a switch between NSC proliferation and quiescence through changing intracellular redox signalling. We show that N-terminal post-translational cleavage products of the prion protein (PrP) induce a quiescent state, halting NSC cellular growth, migration, and neurite outgrowth. Quiescence is initiated by the PrP cleavage products through reducing intracellular levels of reactive oxygen species. First, inhibition of redox signalling results in increased mitochondrial fission, which rapidly signals quiescence. Thereafter, quiescence is maintained through downstream increases in the expression and activity of superoxide dismutase-2 that reduces mitochondrial superoxide. We further observe that PrP is predominantly cleaved in quiescent NSCs indicating a homeostatic role for this cascade. Our findings provide new insight into the regulation of NSC quiescence, which potentially could influence brain health throughout adult life.     

Paleodietary changes by penguins and seals in association with Antarctic climate and sea ice extent

Positioned near the top of the food web, the dietary composition of Antarctic penguins and seals can be an excellent indicator of the regional food web and thus the status of the marine ecosystem. The dietary composition of modern penguins and seals has been well investigated; a long-term time series of data on penguin and seal diets, however, are rare. Such data, especially any predating the initiation of human harvesting of fish, whales and seals in Antarctica, are crucial for understanding and predicting responses of regional marine food webs to natural climate changes. Here we review recent progress on research of paleodietary change in Antarctic penguins and seals, specifically the Adelie penguin （Pygoscelis adeliae） and Antarctic fur seal （Arctocephalus gazella）. These studies indicate that the dietary changes of penguins correspond quite well with fluctuations in climate and sea ice extent during the Holocene. The depleted δ15N ratios found in modern Adelie penguins support the ＂krill surplus hypothesis＂ in relation to historic human depletion of krilleating fish, seals and whales.     

Analysts’ Dynamic Decisions: Timeliness versus Accuracy

For analysts there is a tradeoff between the accuracy and the timeliness of their forecasts. Prior literature heavily investigates analyst forecast accuracy. Few papers investigate the importance of timeliness. To our best knowledge, there are no empirical papers to date to investigate the dynamic interplay between these key characteristics. We show that if analysts experience a period of high accuracy relative to their peers, they subsequently focus more on the timeliness of their forecasts in the subsequent period and thus issue their forecasts earlier than they did in the prior period. Copyright © 2016 John Wiley & Sons, Ltd.     

Butterflies (Lepidoptera: Papilionoidea) of Mount Kilimanjaro: Nymphalidae subfamilies Libytheinae,Danainae, Satyrinae and Charaxinae

This paper, which presents an annotated checklist of the ‘lower Nymphalidae’ (Libytheinae, Danainae, Satyrinae, Charaxinae), is the fourth in a series on the butterfly fauna of Mount Kilimanjaro. Four genera of lower Nymphalidae (Danaus, Amauris, Bicyclus, Charaxes), with a total of 11 included species, are known or believed to occur within the main forest zone, from c. 1800 to 2800 m. Of these, only three species of Charaxes (Charaxes berkeleyi, Charaxes ansorgei, Charaxes xiphares) may be restricted locally to this primary forest. The lower slopes fauna, below 1800 m, is considerably richer, with a total of 11 genera and 41 species listed (8 species of which extend into the forest zone). Possible additional species, dubious earlier records, problems with African subspecies of Danaus chrysippus, a need for more work on certain Satyrinae, and classification of the genus Charaxes are discussed. An identification key to the subfamilies of Nymphalidae, and the 19 genera of Libytheinae, Danainae, Satyrinae, Charaxinae that occur in Tanzania, together with a key to the adults of all the species of these four subfamilies considered to occur or have occurred on Kilimanjaro, with 206 colour images, are included as online Supplementary Information.     

Unitary inequivalence as a problem for structural realism

The existence of unitarily inequivalent representations in quantum field theory has been presented as a serious problem for structural realism. In this paper I explore two possible responses. The first involves adopting Wallace's ‘naïve Lagrangian’ interpretation of QFT and dismissing the generation of inequivalent representations as either a mathematical artefact or as non-pathological. The second takes up Ruetsche's ‘Swiss Army Knife’ approach and understands the relevant structure as spanning a range of possibilities. Both options present interesting implications for structural realism and I shall also consider related issues to do with underdetermination, the significance of spontaneous symmetry breaking and how we should understand superselection rules in the context of quantum statistics. Finally, I shall suggest a way in which these options might be combined.     

Empirical factors and structure transference: Returning to the London account

We offer a framework to represent the roles of empirical and theoretical factors in theory construction, and examine a case study to illustrate how the framework can be used to illuminate central features of scientific reasoning. The case study provides an extension of French and Ladyman's (1997) analysis of Fritz and Heinz London's model of superconductivity to accommodate the role of the analogy between superconductivity and diamagnetic phenomena in the development of the model between 1935 and 1937. We focus on this case since it allows us to separate the roles of empirical and theoretical factors, and so provides an example of the utility of the approach that we have adopted. We conclude the paper by drawing on the particular framework here developed to address a range of concerns.     

Early brood-rearing habitat use and productivity of Greater Sage-Grouse in Wyoming

Populations of Greater Sage-Grouse ( Centrocercus urophasianus ) have been declining throughout their range since the 1960s. Productivity, which includes production and survival of young, is often cited as a factor in these declines. We monitored radio-equipped Greater Sage-Grouse at 3 sites in western Wyoming to assess early brood-rearing habitat use (through 14 days post-hatch) and productivity. Logistic and linear regression analyses with Akaike's Information Criterion were used to evaluate early brooding habitat use and to examine relationships between productivity and vegetation, insect size and abundance, and weather parameters. Females with broods were found in areas with greater sagebrush canopy and grass cover, and fewer invertebrates compared to random areas. The number of juveniles per female (estimated from wing barrel collections during fall harvest) was positively related to the abundance of medium-length Hymenoptera and grass cover, and the proportion of females with confirmed chicks 14 days post-hatch was positively related to abundance of medium-length Coleoptera and total herbaceous cover. Although the specific parameters varied slightly, Greater Sage-Grouse productivity in Wyoming appeared to be associated with a combination of insect and herbaceous cover elements. Managing for abundant and diverse insect communities within dense protective sagebrush stands should help ensure high-quality early brood-rearing habitat and increased Greater Sage-Grouse productivity.     

Contributions to the life history of Sacramento perch, Archoplites interruptus, in Pyramid Lake, Nevada

During a two-year period (1976&ndash;1977), 180 Sacramento perch ( Archoplites interruptus ) were sampled from Pyramid Lake, Nevada, on a monthly basis using several capture methods in all lake areas. Age and growth determinations of these fish were inconsistent with previous research on this species. Sacramento perch are entirely carnivorous, adults feeding primarily on tui chub ( Gila bicolor ). Fish accounted for 6 percent of the diet (by volume) of Sacramento perch less than 300 mm fork length, and 98 percent for those exceeding 300 mm. Amphipods, Odonata, and Chironomidae composed 6.3, 5.7, and 1.8 percent, respectively, of the stomach contents by volume for all sizes combined. Females spawned from June to August when water temperatures approached 20 C, and their gonad weight was about 6 percent of the total body weight. A sample of 20 female perch had a mean fecundity of 84,203 eggs. The mean diameter of mature eggs was 0.88 mm. Sacramento perch almost exclusively inhabit the littoral zone of Pyramid Lake. Activity, as indicated by net catches, was greatest during the warm months of May to October. Monthly catches were significantly correlated with temperature (r = 0.577, P < 0.01). No short-term changes in population abundances were observed during 1976&ndash;1977.     

Zoogeographic patterns and faunal change of South Dakota fishes

We summarized historic and recent fish distributions in South Dakota and analyzed fish faunal similarity at 2 spatial scales (geomorphic province and river drainage) for both historic (native) and recent (post-1990) faunas. We quantified zoogeographic patterns between geomorphic provinces and among neighboring river drainages for historic and recent faunas. We also quantified faunal change (species losses and additions) between provinces and among drainages. Ninety-seven fishes were native to South Dakota, but 111 fishes were present in recent collections because 8 native species were missing, and 22 nonnatives were present. There was high β diversity among historic and recent river drainage fish faunas, but there was between 22% and 56% faunal change between periods. Recent faunas were homogenized compared to historic faunas at both provincial and river drainage spatial scales. Patterns of nonnative species establishment were geographically distinct from patterns of native species loss. Most nonnative species additions were in cold-water or human-made habitats of the Great Plains. Most native species declines stemmed from warm water streams of the Central Lowlands and Missouri River valley. Conservation of rare and declining native species and containment of nonnatives are both necessary to preserve historical patterns of fish biodiversity in South Dakota.