First-principles study of illite-smectite and implications for clay mineral systems

Illite-smectite interstratified clay minerals are ubiquitous in sedimentary basins and they have been linked to the maturation, migration and trapping of hydrocarbons, rock cementation, evolution of porewater chemistry during diagenesis and the development of pore pressure. But, despite the importance of these clays, their structures are controversial. Two competing models exist, each with profoundly different consequences for the understanding of diagenetic processes: model A views such interstratified clays as a stacking of layers identical to endmember illite and smectite layers, implying discrete and independently formed units (fundamental particles), whereas model B views the clays as composed of crystallites with a unique structure that maintains coherency over much greater distances, in line with local charge balance about interlayers. Here we use first-principles density-functional theory to explore the energetics and structures of these two models for an illite-smectite interstratified clay mineral with a ratio of 1:1 and a Reichweite parameter of 1. We find that the total energy of model B is 2.3 kJ atom(-1) mol(-1) lower than that of model A, and that this energy difference can be traced to structural distortions in model A due to local charge imbalance. The greater stability of model B requires re-evaluation of the evolution of the smectite-to-illite sequence of clay minerals, including the nature of coexisting species, stability relations, growth mechanisms and the model of fundamental particles.     

Gene silencing: trans-histone regulatory pathway in chromatin

The fundamental unit of eukaryotic chromatin, the nucleosome, consists of genomic DNA wrapped around the conserved histone proteins H3, H2B, H2A and H4, all of which are variously modified at their amino- and carboxy-terminal tails to influence the dynamics of chromatin structure and function -- for example, conjugation of histone H2B with ubiquitin controls the outcome of methylation at a specific lysine residue (Lys 4) on histone H3, which regulates gene silencing in the yeast Saccharomyces cerevisiae. Here we show that ubiquitination of H2B is also necessary for the methylation of Lys 79 in H3, the only modification known to occur away from the histone tails, but that not all methylated lysines in H3 are regulated by this 'trans-histone' pathway because the methylation of Lys 36 in H3 is unaffected. Given that gene silencing is regulated by the methylation of Lys 4 and Lys 79 in histone H3, we suggest that H2B ubiquitination acts as a master switch that controls the site-selective histone methylation patterns responsible for this silencing.     

Only male fin whales sing loud songs

The low-frequency vocalizations of fin and blue whales are the most powerful and ubiquitous biological sounds in the ocean. Here we combine acoustic localization and molecular techniques to show that, in fin whales, only males produce these vocalizations. This finding indicates that they may function as male breeding displays, and will help to focus concern on the impact of human-generated low-frequency sounds on recovering whale populations.     

Hesperomyces virescens (Fungi,Ascomycota, Laboulbeniales) attacking Harmonia axyridis (Coleoptera,Coccinellidae) in its native range

This study intended to find data on obligate ectoparasitic Laboulbeniales (Fungi, Ascomycota) on Chinese Harmonia axyridis (Coleoptera, Coccinellidae). After having screened over four thousand dried specimens of H. axyridis and close relatives, we present the first (historical) record of Chinese H. axyridis infected with Hesperomyces virescens. We suggest that H. virescens is a historically globally distributed species and hypothesize that (native) infection was lost when H. axyridis was introduced in North America.     

Tbx6-dependent Sox2 regulation determines neural or mesodermal fate in axial stem cells

The classical view of neural plate development held that it arises from the ectoderm, after its separation from the mesodermal and endodermal lineages. However, recent cell-lineage-tracing experiments indicate that the caudal neural plate and paraxial mesoderm are generated from common bipotential axial stem cells originating from the caudal lateral epiblast. Tbx6 null mutant mouse embryos which produce ectopic neural tubes at the expense of paraxial mesoderm must provide a clue to the regulatory mechanism underlying this neural versus mesodermal fate choice. Here we demonstrate that Tbx6-dependent regulation of Sox2 determines the fate of axial stem cells. In wild-type embryos, enhancer N1 of the neural primordial gene Sox2 is activated in the caudal lateral epiblast, and the cells staying in the superficial layer sustain N1 activity and activate Sox2 expression in the neural plate. In contrast, the cells destined to become mesoderm activate Tbx6 and turn off enhancer N1 before migrating into the paraxial mesoderm compartment. In Tbx6 mutant embryos, however, enhancer N1 activity persists in the paraxial mesoderm compartment, eliciting ectopic Sox2 activation and transforming the paraxial mesoderm into neural tubes. An enhancer-N1-specific deletion mutation introduced into Tbx6 mutant embryos prevented this Sox2 activation in the mesodermal compartment and subsequent development of ectopic neural tubes, indicating that Tbx6 regulates Sox2 via enhancer N1. Tbx6-dependent repression of Wnt3a in the paraxial mesodermal compartment is implicated in this regulatory process. Paraxial mesoderm-specific misexpression of a Sox2 transgene in wild-type embryos resulted in ectopic neural tube development. Thus, Tbx6 represses Sox2 by inactivating enhancer N1 to inhibit neural development, and this is an essential step for the specification of paraxial mesoderm from the axial stem cells.     

Feeding interrelations of native fishes in a Sonoran Desert stream

Native fishes in Aravaipa Creek, Arizona, cropped foods proportional to abundance of those foods within the system. Ephemeropteran nymphs and adults comprised the major prey of 5 of 7 fishes ( Gila robusta, Meda fulgida, Rhinichthys osculus, Tiaroga cobitis, and Catostomus insignis ). The omnivorous Agosia chrysogaster ate almost as many nymphal mayflies as did the carnivores. Pantosteus clarki was herbivorous, taking animals only when they were abundant. When ephemeropterans decreased in abundance, a shift by some fish species occurred to other locally or seasonally abundant items. Other fishes continued to feed upon the same foods throughout the year. Abundance of invertebrates in Aravaipa Creek, coupled with marked spatial partitioning of habitat by fishes present, seemingly precluded severe interspecific interactions for food.     

A remarkable new genus and species of Rogadinae (Hymenoptera: Braconidae) of uncertain tribal placement,from Papua New Guinea,resembling Betylobraconini stat. nov.

Cyranorogas gen. nov. (type species C. depardeui sp. nov.) from Papua New Guinea is described and illustrated. The new taxon has a uniquely produced mid-longitudinal facial ridge, which differentiates it from all other genera of Braconidae. The difficulty of distinguishing the Betylobraconinae from the Rogadinae, especially from various members of the Yeliconini, is discussed, and they are formally synonymised here with the Betylobraconini recognised as a tribe of Rogadinae. No clear synapomorphy with either Yeliconini or Betylobraconini could be found for Cyranorogas leaving its tribal placement uncertain, attempts to obtain molecular sequence data having been unsuccessful.

http://zoobank.org/urn:lsid:zoobank.org:pub:62F13CF8-7821-451C-9F14-C40B2D1CC4B5     

MYH9 is a major-effect risk gene for focal segmental glomerulosclerosis

The increased burden of chronic kidney and end-stage kidney diseases (ESKD) in populations of African ancestry has been largely unexplained. To identify genetic variants predisposing to idiopathic and HIV-1-associated focal segmental glomerulosclerosis (FSGS), we carried out an admixture-mapping linkage-disequilibrium genome scan on 190 African American individuals with FSGS and 222 controls. We identified a chromosome 22 region with a genome-wide logarithm of the odds (lod) score of 9.2 and a peak lod of 12.4 centered on MYH9, a functional candidate gene expressed in kidney podocytes. Multiple MYH9 SNPs and haplotypes were recessively associated with FSGS, most strongly a haplotype spanning exons 14 through 23 (OR = 5.0, 95% CI = 3.5-7.1; P = 4 x 10(-23), n = 852). This association extended to hypertensive ESKD (OR = 2.2, 95% CI = 1.5-3.4; n = 433), but not type 2 diabetic ESKD (n = 476). Genetic variation at the MYH9 locus substantially explains the increased burden of FSGS and hypertensive ESKD among African Americans.     

Doing Action Research in One's Own Organization: An Ongoing Conversation Over Time

There are many variants of action research. This article describes a socioecological action research approach done from inside an organization-in-environments. Building on past discussions of action research, an inside-outsider action research model is presented, and using the author's own experience, the paper explores some special relations inherent in such a model. The paper starts with a brief outline of the theory, then discusses some of the structural relations of inside-outsider action research, some practical issues and then reports several vignettes as examples. The paper concludes that action research is still an evolving paradigm.