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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We report here the cloning of the arginine repressor gene argR of Bacillus stearothermophilus and the characterization and purification to homogeneity of its product. The deduced amino acid sequence of the 16.8-kDa ArgR subunit shares 72% identity with its mesophilic homologue AhrC of Bacilus subtilis. Sequence analysis of B. stearothermophilus ArgR and comparisons with mesophilic arginine repressors suggest that the thermostable repressor comprises an N-terminal DNA-binding and a C-terminal oligomerization and arginine-binding region. B. stearothermophilus ArgR has been overexpressed in E. coli and purified as a 48.0-kDa trimeric protein. The repressor inhibits the expression of a B. stearothermophilus argC–lacZ fusion in E. coli cells. In the presence of arginine, the purified protein binds tightly and specifically to the argC operator, which largely overlaps the argC promoter. The purified B. stearothermophilus repressor proved to be very thermostable with a half-life of approximately 30 min at 90°C, whereas B. subtilis AhrC was largely inactivated at 65°C. Moreover, ArgR operator complexes were found to be remarkably thermostable and could be formed efficiently at up to 85°C, well above the optimal growth temperature of the moderate thermophile B. stearothermophilus. This pronounced resistance of the repressor–operator complexes to heat treatment suggests that the same type of regulatory mechanism could operate in extreme thermophiles.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 8083-8091 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Doped piezoceramic lead zircanate titanate has been characterized in the frequency range of 20–60 MHz using ultrasonic spectroscopy. Theoretical analyses were performed for the reflection and refraction of acoustic waves at the interface of water-piezoelectric ceramic. The incident directions of the wave were chosen to be appropriate for ultrasonic spectroscopy measurements. Shear wave spectrum was obtained through mode conversion using a pair of longitudinal transducers submerged in water. The phase velocity shows linear dependence on frequency while the attenuation may be described by a second order polynomial of frequency in the frequency range investigated. The Kramers–Kronig relation between ultrasonic phase velocity and attenuation was compared to measured results. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Activated sintering in Bi2O3-doped ZnO has been studied with emphasis on the mechanistic role of intergranular amorphous films. The atomic-level microstructures and bismuth solute distributions in doped powders have been investigated using high-resolution electron microscopy and scanning transmission electron microscopy. Densification is observed to be significant below the bulk eutectic temperature in the presence of Bi2O3 concentrations as low as 0.58 mol%. Transmission electron microscopy of as-calcined and sintered powders shows that significant neck growth and particle coarsening occur in the solid state. Intergranular amorphous films of ∼1 nm thickness, terminating in wetting menisci at sinter-necks, are observed to form concurrently with the onset of activated sintering. In a few instances, amorphous films are also observed at surfaces of the ZnO particles. These films appear to be the free-surface counterpart to equilibrium-thickness intergranular films. Activated sintering in this binary system is attributed to rapid mass transport through subeutectic, equilibrium-thickness intergranular films, with the amorphous phase also providing capillary pressure.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is shown that the solid-state equilibrium configuration of Bi-doped ZnO grain boundaries is a nanometer-thick amorphous film. Polycrystalline Bi-doped ZnO was investigated using high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM). The equilibrium state below the eutectic temperature and at 1 atm total pressure was approached from three different routes: samples were cooled from above the eutectic temperature (Teutectic= 740°C), processed entirely below the eutectic temperature, and desegregated by high applied pressure (1 GPa) followed by annealing at ambient pressure to restore segregation. In all instances, the final state is an amorphous intergranular film 1.0-1.5 nm in thickness. The results show that a thin intergranular film in this system has lower free energy than the crystal-crystal grain boundary. The implications of these results for creation of electrically active grain boundaries in zinc oxide varistors are discussed.
    Type of Medium: Electronic Resource
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  • 5
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    Unknown
    PANGAEA
    In:  Supplement to: Rong, Jiahuan; Su, Wenhao; Guan, Xiaofan; Shi, Wei; Zha, Shanjie; He, Maolong; Wang, Haifeng; Liu, Guangxu (2018): Ocean Acidification Impairs Foraging Behavior by Interfering With Olfactory Neural Signal Transduction in Black Sea Bream, Acanthopagrus schlegelii. Frontiers in Physiology, 9, https://doi.org/10.3389/fphys.2018.01592
    Publication Date: 2024-03-15
    Description: In recent years, ocean acidification (OA) caused by oceanic absorption of anthropogenic carbon dioxide (CO2) has drawn worldwide concern over its physiological and ecological effects on marine organisms. However, the behavioral impacts of OA and especially the underlying physiological mechanisms causing these impacts are still poorly understood in marine species. Therefore, in the present study, the effects of elevated pCO2 on foraging behavior, in vivo contents of two important neurotransmitters, and the expression of genes encoding key modulatory enzymes from the olfactory transduction pathway were investigated in the larval black sea bream. The results showed that larval sea breams (length of 4.71 +- 0.45 cm) reared in pCO2 acidified seawater (pH at 7.8 and 7.4) for 15 days tend to stall longer at their acclimated zone and swim with a significant slower velocity in a more zigzag manner toward food source, thereby taking twice the amount of time than control (pH at 8.1) to reach the food source. These findings indicate that the foraging behavior of the sea bream was significantly impaired by ocean acidification. In addition, compared to a control, significant reductions in the in vivo contents of gama-aminobutyric acid (GABA) and Acetylcholine (ACh) were detected in ocean acidification-treated sea breams. Furthermore, in the acidified experiment groups, the expression of genes encoding positive regulators, the olfaction-specific G protein (Golf) and the G-protein signaling 2 (RGS2) and negative regulators, the G protein-coupled receptor kinase (GRK) and arrestin in the olfactory transduction pathway were found to be significantly suppressed and up-regulated, respectively. Changes in neurotransmitter content and expression of olfactory transduction related genes indicate a significant disruptive effect caused by OA on olfactory neural signal transduction, which might reveal the underlying cause of the hampered foraging behavior.
    Keywords: Acanthopagrus schlegelii; Acetylcholine; Alkalinity, total; Alkalinity, total, standard error; Animalia; Aragonite saturation state; Aragonite saturation state, standard error; Behaviour; Bicarbonate ion; Calcite saturation state; Calcite saturation state, standard error; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chordata; Coast and continental shelf; Containers and aquaria (20-1000 L or 〈 1 m**2); Curvilinear velocity; Experiment duration; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); gamma-Aminobutyric acid; Gene expression; Gene expression (incl. proteomics); Laboratory experiment; Latency time; Linearity index; Nekton; North Pacific; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; Pelagos; pH; pH, standard error; Registration number of species; Response time; Salinity; Salinity, standard error; Single species; Species; Temperate; Temperature, water; Temperature, water, standard error; Type; Uniform resource locator/link to reference; Wobble
    Type: Dataset
    Format: text/tab-separated-values, 4491 data points
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  • 6
    Publication Date: 2015-10-19
    Description: DNA methylation is important for the regulation of gene expression and the silencing of transposons in plants. Here we present genome-wide methylation patterns at single-base pair resolution for cassava (Manihot esculenta, cultivar TME 7), a crop with a substantial impact in the agriculture of subtropical and tropical regions. On average, DNA methylation levels were higher in all three DNA sequence contexts (CG, CHG, and CHH, where H equals A, T, or C) than those of the most well-studied model plant Arabidopsis thaliana. As in other plants, DNA methylation was found both on transposons and in the transcribed regions (bodies) of many genes. Consistent with these patterns, at least one cassava gene copy of all of the known components of Arabidopsis DNA methylation pathways was identified. Methylation of LTR transposons (GYPSY and COPIA) was found to be unusually high compared with other types of transposons, suggesting that the control of the activity of these two types of transposons may be especially important. Analysis of duplicated gene pairs resulting from whole-genome duplication showed that gene body DNA methylation and gene expression levels have coevolved over short evolutionary time scales, reinforcing the positive relationship between gene body methylation and high levels of gene expression. Duplicated genes with the most divergent gene body methylation and expression patterns were found to have distinct biological functions and may have been under natural or human selection for cassava traits.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 7
    Publication Date: 2018-01-16
    Description: Genome-wide characterization by next-generation sequencing has greatly improved our understanding of the landscape of epigenetic modifications. Since 2008, whole-genome bisulfite sequencing (WGBS) has become the gold standard for DNA methylation analysis, and a tremendous amount of WGBS data has been generated by the research community. However, the systematic comparison of DNA methylation profiles to identify regulatory mechanisms has yet to be fully explored. Here we reprocessed the raw data of over 500 publicly available Arabidopsis WGBS libraries from various mutant backgrounds, tissue types, and stress treatments and also filtered them based on sequencing depth and efficiency of bisulfite conversion. This enabled us to identify high-confidence differentially methylated regions (hcDMRs) by comparing each test library to over 50 high-quality wild-type controls. We developed statistical and quantitative measurements to analyze the overlapping of DMRs and to cluster libraries based on their effect on DNA methylation. In addition to confirming existing relationships, we revealed unanticipated connections between well-known genes. For instance, MET1 and CMT3 were found to be required for the maintenance of asymmetric CHH methylation at nonoverlapping regions of CMT2 targeted heterochromatin. Our comparative methylome approach has established a framework for extracting biological insights via large-scale comparison of methylomes and can also be adopted for other genomics datasets.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 8
    Publication Date: 2018-10-10
    Electronic ISSN: 2469-990X
    Topics: Physics
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  • 9
    Publication Date: 2016-11-28
    Description: DNA methylation plays important roles in many biological processes, such as silencing of transposable elements, imprinting, and regulating gene expression. Many studies of DNA methylation have shown its essential roles in angiosperms (flowering plants). However, few studies have examined the roles and patterns of DNA methylation in gymnosperms. Here, we present genome-wide high coverage single-base resolution methylation maps of Norway spruce (Picea abies) from both needles and somatic embryogenesis culture cells via whole genome bisulfite sequencing. On average, DNA methylation levels of CG and CHG of Norway spruce were higher than most other plants studied. CHH methylation was found at a relatively low level; however, at least one copy of most of the RNA-directed DNA methylation pathway genes was found in Norway spruce, and CHH methylation was correlated with levels of siRNAs. In comparison with needles, somatic embryogenesis culture cells that are used for clonally propagating spruce trees showed lower levels of CG and CHG methylation but higher level of CHH methylation, suggesting that like in other species, these culture cells show abnormal methylation patterns.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2017-07-21
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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