Crystal structure of the invertebrate bifunctional purine biosynthesis enzyme PAICS at 2.8 Å resolution

Two important steps of the de novo purine biosynthesis pathway are catalyzed by the 5‐aminoimidazole ribonucleotide carboxylase and the 4‐(N‐succinylcarboxamide)‐5‐aminoimidazole ribonucleotide synthetase enzymes. In most eukaryotic organisms, these two activities are present in the bifunctional enzyme complex known as PAICS. We have determined the 2.8‐Å resolution crystal structure of the 350‐kDa invertebrate PAICS from insect cells (Trichoplusia ni) using single‐wavelength anomalous dispersion methods. Comparison of insect PAICS to human and prokaryotic homologs provides insights into substrate binding and reveals a highly conserved enzymatic framework across divergent species. Proteins 2013; 81:1473–1478. © 2013 Wiley Periodicals, Inc.     

Varied development of trunk segmentation in three related Upper Devonian phacopine trilobites

In many arthropods, the development of the trunk region is a complex part of post-embryonic development. Consideration of fossil ontogeny provides an additional source of data and a broader evolutionary perspective on the evolution of arthropod body patterning. Here, I examine the development of the thoraco-pygidial exoskeleton of three related phacopine trilobites from the Upper Devonian according to the integrated ontogenetic scheme proposed by Hughes et al. Pygidial shields assigned to three ontogenetic series gave us the opportunity to further explore the evolutionary pattern of the trilobite segmentation. The analysis showed a different mode of development in two of three species and thus reveals variability between the related taxa. Comparison of the boundaries of different aspects of ontogenesis ratifies the diversity of the segmentation process among trilobites and even among related phacopine species. Results include (i) in a synarthromeric trunk condition recorded to date, there has consistently been a preceding ‘equilibrium’ phase for the late meraspid pygidium and (ii) two developmental modes, i.e. both hypoprotomeric development and synarthromeric development, occur contemporaneously in closely related taxa. Such developments suggest that aspects of segmental development such as segment accretion and segment articulation were able to vary in a labile manner.     

Dose-response effect of chlorhexidine on a multispecies oral biofilm formed on pure titanium and on a titanium-zirconium alloy

Abstract

This study aimed to test the dose-response effect of chlorhexidine on multispecies biofilms formed on commercially pure titanium (cpTi) and titanium-zirconium (TiZr) alloy. Biofilms were formed on cpTi and TiZr discs and treated two times per day with five different chlorhexidine concentrations (0.12, 0.20, 0.50, 1, 2%). The biofilms were collected for microbiological, biochemical and microscopic analyses. The significance of differences among groups was evaluated by linear regression, ANOVA, Bonferroni and Tukey tests. The mean number of colony-forming units decreased as the chlorhexidine concentration increased for both cpTi and TiZr (p?<?0.05). The maximum effect was observed with the 0.5% concentration. Confocal microscopy images suggested an increase in the number of dead bacterial cells with increased chlorhexidine concentration. The biofilm pH increased after chlorhexidine exposure (p?<?0.05). Chlorhexidine showed an antimicrobial dose-response effect in controlling biofilm on cpTi and TiZr. 0.5% chlorhexidine can be used to achieve the maximum antimicrobial effect on both materials.     

Pyramidal Neurons Derived from Human Pluripotent Stem Cells Integrate Efficiently into Mouse Brain Circuits In Vivo

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The role of fire in structuring trait variability in Neotropical savannas

Intraspecific trait variability plays a fundamental role in community structure and dynamics; however, few studies have evaluated its relative importance to the overall response of communities to environmental pressures. Since fire is considered a key factor in Neotropical savannas, we investigated to what extent the functional effects of fire in a Brazilian savanna occurs via intra- or interspecific trait variability. We sampled 12 traits in communities subjected to three fire regimes in the last 12 years: annual, biennial, and protected. To evaluate fire’s relative effects, we fitted a general linear mixed models with species as random and fire as fixed factors, using: (1) all species in the communities (i.e., considering intra- and interspecific variabilities); (2) 18 species common to all fire regimes (i.e., intraspecific variability only); and (3) all species with their overall average trait values (i.e., interspecific variability only). We assessed the relative role of intra- or interspecific variability by comparing the significance of each trait in the three analyses. We also compared the within and between fire variabilities with a variance component analysis. Five traits presented larger intraspecific than interspecific variability, and the main effect of fire occurred at the intraspecific level. These results confirm that it is important to consider intraspecific variability to fully understand fire-prone communities. Moreover, trait variability was larger within than among fire regimes. Thus, fire may act more as an external filter, preventing some of the species from the regional pool from colonizing the cerrado, than as an internal factor structuring the already filtered cerrado communities.     

New species of Alaus Eschscholtz, 1829 (Coleoptera: Elateridae,Agrypninae, Hemirhipini)

Four new species of Alaus Eschscholtz, 1829 are described: A. cinnamomeus n. sp., A. latlpennls n. sp., A. serlceus n. sp. and A. thoracopunctatus n. sp. Three species removed from Chalcolepldlus Eschscholtz, 1829, are transferred to this genus: A. allcll (Pjatakowa, 1941) n. comb., A. haroldl (Candèze, 1878) n.comb. and A. unlcus (Fleutiaux, 1910) n. comb. The characters of external morphology of these seven species and male and female genitalia, when available, are described and illustrated. An identification key for all species of the genus is included: A. allcll (Pjatakowa, 1941) n. comb., A. calcarlpllosus Casari, 1996, A. cinnamomeus n. sp., A. haroldl (Candèze, 1878) n. comb., A. latlpennls n. sp., A. lusclosus (Hope, 1832), A. melanops Leconte, 1863, A. myops (Fabricius, 1801), A. nobllls Sallé, 1855, A. oculatus (Linnaeus, 1758), A. patrlclus (Candèze, 1857), A. plebejus Candèze, 1874, A. serlceus n. sp., A. thoracopunctatus n. sp., A. tricolor (Olivier, 1790), A. unlcus (Fleutiaux, 1910) n. comb., A. veracruzanus Casari, 1996 and A. zunianus Casey, 1893.     

Macrelmis pubescens (Grouvelle, 1889) – redescription of the species,designation of a lectotype and description of its larva (Coleoptera: Elmidae)

The adult of Macrelmis pubescens (Grouvelle, 1889) is redescribed, illustrated, a lectotype designated, and new locality information provided. The lectotype is housed in the Grouvelle’s collection in the Muséum national d’Histoire naturelle, Paris, France. The larva of M. pubescens is described, illustrated and compared with the known larvae of the genus. A diagnosis for Macrelmis Motschulsky, 1860 larvae is provided.     

Political mobilization of a regional minority: Han Chinese settlers in Xinjiang

The tumultuous events of summer 2009 have brought Uighur protests and minority mobilization in the Xinjiang Uighur Autonomous Region (XUAR) to the forefront. But this focus overlooks similar protests organized by various groups of Han Chinese settlers over the years. This paper contributes to the body of literature on minority mobilization and ethnic relations in Xinjiang by illustrating how the political mobilization of a group that is simultaneously a national majority and a regional minority differs substantially from ‘traditional’ minority mobilization. Reviewing the main instances of Han Chinese political mobilization since the XUAR was created in 1955, I argue that two factors are particularly important in enabling their mobilization: the Han Chinese's subjective perception of discrimination and their close ethnic ties to the state. This paper concludes with a discussion on the presence of a cycle of protests between Han settlers and the Uighurs in Xinjiang.     

The octadecaneuropeptide ODN prevents 6‐hydroxydopamine‐induced apoptosis of cerebellar granule neurons through a PKC‐MAPK‐dependent pathway

Oxidative stress, induced by various neurodegenerative diseases, initiates a cascade of events leading to apoptosis, and thus plays a critical role in neuronal injury. In this study, we have investigated the potential neuroprotective effect of the octadecaneuropeptide (ODN) on 6‐hydroxydopamine (6‐OHDA)‐induced oxidative stress and apoptosis in cerebellar granule neurons (CGN). ODN, which is produced by astrocytes, is an endogenous ligand for both central‐type benzodiazepine receptors (CBR) and a metabotropic receptor. Incubation of neurons with subnanomolar concentrations of ODN (10^?18 to 10^?12 M) inhibited 6‐OHDA‐evoked cell death in a concentration‐dependent manner. The effect of ODN on neuronal survival was abrogated by the metabotropic receptor antagonist, cyclo_1–8[DLeu⁵]OP, but not by a CBR antagonist. ODN stimulated polyphosphoinositide turnover and ERK phosphorylation in CGN. The protective effect of ODN against 6‐OHDA toxicity involved the phospholipase C/ERK MAPK transduction cascade. 6‐OHDA treatment induced an accumulation of reactive oxygen species, an increase of the expression of the pro‐apoptotic gene Bax, a drop of the mitochondrial membrane potential and a stimulation of caspase‐3 activity. Exposure of 6‐OHDA‐treated cells to ODN blocked all the deleterious effects of the toxin. Taken together, these data demonstrate for the first time that ODN is a neuroprotective agent that prevents 6‐OHDA‐induced oxidative stress and apoptotic cell death.     

Extending ecological niche models to the past 120 000 years corroborates the lack of strong phylogeographic structure in the Crested Drongo (Dicrurus forficatus forficatus) on Madagascar

We conduct a phylogeographic study of the Crested Drongo (Dicrurus forficatus forficatus), a broadly distributed bird species on Madagascar. We first determined the demographic and spatial pattern inferred from mitochondrial and nuclear data, and then compared these results with predictions from a present to 0.120‐Myr‐old reconstruction of the spatial dynamics of the range of D. f. forficatus on Madagascar, enabling putative areas of stability (lineage persistence) to be detected. Weak genetic structure along an east–west pattern and comparatively low genetic diversity were recovered, with strong evidence of population expansion found at all ten loci sampled. The palaeoclimatic distribution models over the past 0.120 Myr suggest the presence of extensive areas of suitable climate in the east and west for the species since its colonization of Madagascar, a result in strong concordance with the spatial and genetic signal derived from our multilocus data set. © 2013 The Linnean Society of London