Type IV pili of Geobacter sulfurreducens are composed of PilA monomers and are essential for long-range extracellular electron transfer to insoluble Fe(III) oxides and graphite anodes. A previous ...analysis of pilA expression indicated that transcription was initiated at two positions, with two predicted ribosome-binding sites and translation start codons, potentially producing two PilA preprotein isoforms. The present study supports the existence of two functional translation start codons for pilA and identifies two isoforms (short and long) of the PilA preprotein. The short PilA isoform is found predominantly in an intracellular fraction. It seems to stabilize the long isoform and to influence the secretion of several outer-surface c-type cytochromes. The long PilA isoform is required for secretion of PilA to the outer cell surface, a process that requires coexpression of pilA with nine downstream genes. The long isoform was determined to be essential for biofilm formation on certain surfaces, for optimum current production in microbial fuel cells, and for growth on insoluble Fe(III) oxides.
Antivirals that are currently used to treat influenza virus infections target components of the virus which can mutate rapidly. Consequently, there has been an increase in the number of resistant ...strains to one or many antivirals in recent years. Here we compared the antiviral effects of lysosomotropic alkalinizing agents (LAAs) and calcium modulators (CMs), which interfere with crucial events in the influenza virus replication cycle, against avian, swine, and human viruses of different subtypes in MDCK cells. We observed that treatment with LAAs, CMs, or a combination of both, significantly inhibited viral replication. Moreover, the drugs were effective even when they were administered 8 h after infection. Finally, analysis of the expression of viral acidic polymerase (PA) revealed that both drugs classes interfered with early events in the viral replication cycle. This study demonstrates that targeting broad host cellular pathways can be an efficient strategy to inhibit influenza replication. Furthermore, it provides an interesting avenue for drug development where resistance by the virus might be reduced since the virus is not targeted directly.
Grain growth and abnormal grain growth in tungsten carbide cobalt composites (cemented carbides, hardmetals) are usually discussed with respect to liquid phase sintering (Ostwald ripening). ...Densification and grain growth during solid state sintering are not as thoroughly studied but do play an important role in sintering hardmetals and, particularly tungsten carbide ceramics (binderless hardmetals). In this work the influences of sintering temperature, carbon content, additions of grain growth inhibitors, defects and dislocations (microstrain) introduced by milling on the densification and microstructure of WC ceramics were studied including density, micro structural, thermal and X-ray analysis. Microstrain promotes densification and results in lowering the sintering temperature, whereas free carbon seems to hinder densification at low temperatures and to promote it slightly at higher temperatures. Depending on sintering regime, free carbon and microstrain may drastically boost abnormal grain growth. By adding grain growth inhibitors, densification is shifted to higher temperatures. However, the addition prevents abnormal grain growth regardless of C-content and microstrain. Like in hardmetals grain growth inhibitors also inhibit normal grain growth. The findings are relevant for sintering of WC ceramics and hardmetals alike.
•Grain growth of tungsten carbide ceramics was studied using thermal and other analysis techniques.•Abnormal grain growth occurred with an over stoichmetric carbon content and/or a high microstrain introduced trough milling.•As in Hardmetals grain growth inhibitors VC and Cr3C2 inhibit abnormal grain growth even without any liquid phase.•VC and Cr3C2 inhibit abnormal grain growth regardless of C-content or microstrain.•Milling shifts densification to lower sinter temperatures due to surface activation of the milled powder.
Ultrafine and nanoscaled hardmetals show a significant grain growth already before reaching liquid phase sintering temperature. To limit grain growth during this stage of sintering the known grain ...growth inhibitors, mostly metal carbides like Cr3C2 or VC can be used. To investigate grain growth inhibition and dissolution of these carbides both the solid state sintering without Co (binderless tungsten carbide) and with 10 wt-% Co were investigated in the temperature range between 600°C and 2000°C and 1500°C, respectively. It could be shown that e.g. the Cr3C2 starts to decompose already below 800°C into a Cr-rich and C-rich phase. In both types of material with and without Co this leads to earlier reduction of W-oxides and the formation of Cr-based oxides which alter the chemical processes during sintering and change the grain growth behaviour. By using thermoanalytical methods as well as interrupted sintering experiments and their characterisation by FE-SEM and XRD, the direct influence of Co and grain growth inhibitors regarding the change in the chemical processes happening during sintering was studied.
•Grain growth inhibition in ultrafine/nanoscaled hardmetals was studied.•Interrupted sintering experiments were carried out between 600°C to 2000°C.•Effect of carbide addition (VC, Cr3C2) was investigated by FESEM, XRD, thermoanalytical methods.•Grain growth inhibition hardmetals happens already below liquid phase formation.
Factors from the virus and the host contribute to influenza virus pathogenicity and to the development of immunity. This study thoroughly examined the effects of an initial infectious dose of virus ...and unveiled new findings concerning the antiviral and inflammatory responses, innate and adaptive immunity, memory responses, and protection against secondary heterologous infection. Our results demonstrated that the initial infectious dose significantly affects the gene expression of antiviral (IFN-β) and inflammatory (TNF-α, IL-6, IL-1β) cytokines and of enzymes involved in nitrosative/oxidative stress (iNOS, HO-1, NQO1) early in the response to influenza. This response correlated with significantly increased recruitment of innate immune cells into the lungs of infected mice. We showed that this response also alters the subsequent accumulation of activated IFN-γ(+) CD44(hi) CD62L(lo) influenza-specific CD8(+) T cells into the lungs of infected mice through increased T cell-recruiting chemokine gene expression (CCL3, CCL4, CCL5, CXCL10). Furthermore, we demonstrated that the initial infectious dose determines the generation and the distribution of memory CD8(+) T cell subsets without affecting trafficking mechanisms. This impacted on immune protection against heterologous infection. Lastly, we showed that the effects on innate and adaptive immunity were not dependent on influenza strain or on the genetic background of the host. Collectively, our data show for the first time and in detail that the initial infectious dose of influenza determines the development of several aspects of antiviral immunity. This study provides new insights on virus-host interaction in the generation of the global immune response to influenza.
Raman scattering (RS) spectra and current-voltage characteristics at room temperature were measured in six series of small samples fabricated by means of electron-beam lithography on the surface of a ...large size (5 x 5 mm) industrial monolayer graphene film. Samples were irradiated by different doses of C super(+) ion beam up to 10 super(15) cm super(-2). It was observed that at the utmost degree of disorder, the Raman spectra lines disappear which is accompanied by the exponential increase of resistance and change in the current-voltage characteristics. These effects are explained by suggestion that highly disordered graphene film ceases to be continuous and splits into separate fragments. The relationship between structure (intensity of RS lines) and sample resistance is defined. It is shown that the maximal resistance of the continuous film is of the order of reciprocal value of the minimal graphene conductivity pih/4e super(2) approximately 20 kOhm.
Previous work has pointed to a role for the Wnt canonical pathway in fibrosis formation in aged skeletal muscles. In the present study, we studied the dystrophic mdx mouse, which displays skeletal ...muscle fibrosis. Our results indicated that the muscle resident stromal cell (mrSC) population in the muscles of dystrophic mice is higher than in the muscles of age-matched wild-type mice. Wnt3a promoted the proliferation of and collagen expression by cultured mrSCs but arrested the growth of and collagen expression by cultured myoblasts. Injections of Wnt3A in the tibialis anterior muscles of adult wild-type mice significantly enhanced the mrSC population and collagen deposition compared with the contralateral muscles. Conversely, an injection of the Wnt antagonist Dickkof protein (DKK1) into the skeletal muscles of mdx mice significantly reduced collagen deposition. These results suggested that the Wnt canonical pathway expands the population of mrSCs and stimulates their production of collagen as observed during aging and in various myopathies.
By reducing the metallic binder in cemented carbides, so-called binderless hardmetals or pure tungsten carbide ceramics can ultimately be achieved. Nanoscaled tungsten carbide has a very high ...hardness of above 3000HV1 and still offers quite a good fracture toughness of up to 7.5MPa∗m1/2. Since only solid state sintering can be used, sintering temperatures as high as 2000°C or higher are normally needed to completely densify these materials. At these temperatures abnormal grain growth which leads to a decrease in hardness is an often reported problem. However, using pressure assisted techniques such as SPS, ROC or HIP, WC ceramics can be produced at lower temperatures, although productivity and freedom in size and form are limited.
The aim of this work was to investigate the drivers for densification, grain growth as well as the microstructure and chemical phases occurring during solid state sintering in a conventional SinterHIP furnace. A WC starting powder with DBET=115nm was milled to nanoscaled size (50 to 60nm), sintered at different temperatures (interrupted sintering experiments) and then analysed by using FESEM, XRD, Rietveld analysis, dilatometry and other methods.
It could be shown that three main processes during sintering of slightly under-stoichiometric binderless WC hardmetals occur: first, the reduction of surface oxides at 800°C after which densification starts due to cleaned surfaces and the existence of W in a nascent state; second, the secondary carburisation of WC and W at around 1400°C; and, third, grain growth and pore annealing at around 1600°C when a closed porosity exists. By adding Cr3C2 as grain growth inhibitor the secondary carburisation step was lowered to around 1000°C and a solid solution of (W,Cr)2 instead of pure W2C was formed.
•Interrupted sintering experiments of WC between 800 and 2000°C were carried out.•Thermal analyis and XRD revealed three main processes.•Densification is strongly influenced by the C-content.•The additon of Cr3C2 changes the densfication behaviour and the phases formed.
Summary
Test systems for measuring cell viability in optical microscopy (based on colony formation ability or lysosomal integrity) were established and applied to native cells as well as to cells ...incubated with fluorescence markers or transfected with genes encoding for fluorescent proteins. Human glioblastoma and Chinese hamster ovary cells were irradiated by various light doses, and maximum doses where at least 90% of the cells survived were determined. These tolerable light doses were in the range between 25 J cm−2 and about 300 J cm−2 for native cells (corresponding to about 250−3000 s of solar irradiance and depending on the wavelength as well as on the mode of illumination, e.g. epi‐ or total internal reflection illumination) and decreased to values between 50 J cm−2 and less than 1 J cm−2 upon application of fluorescent markers, fluorescent proteins or photosensitizers. In high‐resolution wide field or laser scanning microscopy of single cells, typically 10−20 individual cell layers needed for reconstruction of a 3D image could be recorded with tolerable dose values. Tolerable light doses were also maintained in fluorescence microscopy of larger 3D samples, e.g. cell spheroids exposed to structured illumination, but may be exceeded in super‐resolution microscopy based on single molecule detection.
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