Differential viral RNA methylation contributes to pathogen blocking in Wolbachia-colonized arthropod

Arthropod endosymbiont Wolbachia pipientis is part of a global biocontrol strategy aimed at reducing the spread of mosquito-borne RNA viruses such as alphaviruses. Our prior work examining Wolbachia-mediated pathogen blocking has demonstrated (i) the importance of a host cytosine methyltransferase, DNMT2, in Drosophila, and (ii) viral RNA as a target through which pathogen-blocking is mediated. Here we report on the role of DNMT2 in Wolbachia induced virus inhibition of alphaviruses in Aedes sp.. Mosquito DNMT2 levels were altered in the presence of both viruses and Wolbachia, albeit in opposite directions. Elevated levels of DNMT2 in mosquito salivary glands induced by virus infection were suppressed in Wolbachia colonized animals coincident with a reduction of virus replication, and decreased infectivity of progeny virus. Ectopic expression of DNMT2 in cultured Aedes cells was proviral increasing progeny virus infectivity, and this effect of DNMT2 on virus replication and infectivity was dependent on its methyltransferase activity. Finally, examination of the effects of Wolbachia on modifications of viral RNA by LC-MS showed a decrease in the amount of 5-methylcytosine modification consistent with the down-regulation of DNMT2 in Wolbachia colonized mosquito cells and animals. Collectively, our findings support the conclusion that disruption of 5-methylcytosine modification of viral RNA is an important mechanism operative in pathogen blocking. These data also emphasize the essential role of epitranscriptomic modifications in regulating fundamental processes of virus replication and transmission.

Enhanced Bioactivity of Chemically Oxidization-Modified Titanium Alloys

Anatase-type titanium dioxide oxide layer was formed on the surface of titanium alloy by chemical oxidation. 0.9 um thick anatase was obtained by soaking in a mixed solution of a certain proportion of hydrogen peroxide and hydrochloric acid and then heat treatment. The surface morphology, phase structures and composition of oxide layers were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Thickness of titania coating was measured by the ball pit gauge. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to detect the change of Ca ion and P ion concentration in solution. The results showed that anatase layers deposited apatite within 4 days accompanying the decrease of pH when soaked in simulated human body fluid (SBF). Ion exchange between the negative ions and calcium ions in SBF is proposed as the mechanism operative to favor the deposition on apatite.

Non-uniform distribution of dopant iron ions in TiO2 nanocrystals probed by X-ray diffraction, Raman scattering, photoluminescence and photocatalysis

The phenomenon of ‘self-purification’ is a real mechanism operative in nanocrystals and this should be taken into account while doping semiconductor nanocrystals with external impurities for practical applications.

Strain Measurements on Nitrogen Implanted 4H-SiC

The evolution of the normal strain induced by nitrogen implantation in 4H-SiC was investigated through X-ray diffraction measurements and compared to previous studies on helium implanted SiC. The shape of the normal strain profile in the near surface region shows that the accumulation of point defects is not the only mechanism operative at room temperature. In the highly damaged region, the normal strain profile fits the N concentration.

Complete Avulsion of the Extensor Mechanism of a Finger with Simultaneous Dislocation of the Proximal Interphalangeal Joint

We report a rare case of open dislocation of the proximal interphalangeal (PIP) joint, associated with simultaneous avulsion of the central band and distal insertion of the extensor mechanism, rapture of the proximal volar plate, and rapture of the ulnar collateral ligament of the PIP joint. Although isolated IP joint injuries are common, they rarely occur simultaneously in a single finger. Even more rarely are they accompanied by a complete avulsion of the extensor mechanism. Operative restoration of the injured structures is a necessity in order to achieve a good functional outcome. An initial forceful flexion of the finger resulting to rapture of the extensor apparatus and then followed by finger hyperextension and PIP joint dislocation is our perception of the possible mechanism of this extremely rare injury.

Carbon Catabolite Repression in Bacillus subtilis: Quantitative Analysis of Repression Exerted by Different Carbon Sources

ABSTRACT In many bacteria glucose is the preferred carbon source and represses the utilization of secondary substrates. In Bacillus subtilis, this carbon catabolite repression (CCR) is achieved by the global transcription regulator CcpA, whose activity is triggered by the availability of its phosphorylated cofactors, HPr(Ser46-P) and Crh(Ser46-P). Phosphorylation of these proteins is catalyzed by the metabolite-controlled kinase HPrK/P. Recent studies have focused on glucose as a repressing substrate. Here, we show that many carbohydrates cause CCR. The substrates form a hierarchy in their ability to exert repression via the CcpA-mediated CCR pathway. Of the two cofactors, HPr is sufficient for complete CCR. In contrast, Crh cannot substitute for HPr on substrates that cause a strong repression. Determination of the phosphorylation state of HPr in vivo revealed a correlation between the strength of repression and the degree of phosphorylation of HPr at Ser46. Sugars transported by the phosphotransferase system (PTS) cause the strongest repression. However, the phosphorylation state of HPr at its His15 residue and PTS transport activity have no impact on the global CCR mechanism, which is a major difference compared to the mechanism operative in Escherichia coli. Our data suggest that the hierarchy in CCR exerted by the different substrates is exclusively determined by the activity of HPrK/P.

Social Selection, Agents’ Intentions, and Functional Explanation

Jon Elster and Daniel Little have criticized social scientists for appealing to a mechanism of social selection in functional explanations of social practices. Both believe that there is no such mechanism operative in the social world. I develop and defend an account of functional explanation in which a mechanism of social selection figures centrally. In addition to developing an account of social selection, I clarify what functional hypotheses purport to claim, and re-examine the role of agents’ intentions in functional explanations in an effort to show why a mechanism of social selection is indispensable to adequate functional explanations.