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  • 1
    Electronic Resource
    Electronic Resource
    Low temperature deposition of nanocrystalline silicon carbide thin films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2373-2375 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon carbide thin films have been deposited by reactive magnetron sputtering in a pure hydrogen plasma at substrate temperatures, Ts, ranging between 100 and 600 °C. The infrared (IR) absorption spectra and the transmission electron microscopy observations reveal an onset of crystallization at Ts as low as 300 °C. The crystalline fraction increases with Ts and reaches a value of about 60% for Ts=600 °C. Both refractive index n and room temperature dark conductivity σd(RT) show quite consistent behaviors with the structural evolution of the layers. Thus n increases from 1.9 to 2.4 and σd(RT) improves by six orders of magnitude when Ts is raised from 100 to 600 °C. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126350
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  • 2
    Electronic Resource
    Electronic Resource
    Echocardiographic Assessment of the Interventricular Delay of Activation and Correlation to the QRS Width in Dilated Cardiomyopathy (2001)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 24 (2001), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: ROULEAU, F., et al.: Echocardiographic Assessment of the Interventricular Delay of Activation and Correlation to the QRS Width in Dilated Cardiomyopathy. The aim of the study was to define criteria for left ventricular pacing in dilated cardiomyopathy (DCM) using an echocardiographic evaluation of interventricular electromechanical delay (IMD) and a correlation of IMD to QRS duration. Standard 12-lead ECG and echocardiography with pulsed Doppler tissue imaging (DTI) were recorded in 35 DCM patients (mean age 58 ± 11 years) with QRS duration from narrow (80 ms) to broad (222 ms) patterns. The time for left ventricular activation was evaluated from the onset of QRS to the onset of aortic flow (Q-Ao) by standard pulsed Doppler (SP) or to the onset of mitral annulus systolic wave (Q-Mit) (DTI). The time for right ventricular activation was determined from the onset of QRS to the onset of pulmonary flow (Q-Pulm) (SP) or to the onset of tricuspid annulus systolic wave (Q-Tri) (DTI). (Q-Ao)–(Q-Pulm) and (Q-Mit)–(Q-Tri) determined IMD for each method, respectively. QRS width and IMD showed correlation coefficients of r = 0.86 ([Q-Ao]-[Q-Pulm]) and r = 0.82 ([Q-Mit]-[Q-Tri]) (P ≤ 0.001). Mean IMD of 77 ± 15 ms (SP) and 88 ± 26 ms (DTI) were noted for QRS width above 150 ms. Left ventricle delayed activation was positively correlated to QRS widening with both methods, (r = 0.90, [Q-Ao]), (r = 0.83, [Q-Mit]) (P ≤ 0.001). In conclusion, QRS duration is a good marker of an interventricular mechanical asynchrony. According to IMD correction, left ventricular pacing may be mainly proposed to symptomatic DCM patients with QRS duration 〉 150 ms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.01500.x
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of the roles of NikR, a nickel-responsive pleiotropic autoregulator of Helicobacter pylori (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Helicobacter pylori genome contains a gene (hp1338 or nikR) that encodes a nickel-dependent regulator that is homologous to the Escherichia coli nickel-responsive regulator, NikR. The H. pylori nikR product acts as a pleiotropic metal-dependent regulator. We constructed a non-polar isogenic mutant deleted for the nikR gene. NikR was essential for the survival of H. pylori in the presence of high nickel and cobalt ion concentrations in vitro. We screened a DNA macroarray for genes that were differentially expressed in parental and nikR-deficient H. pylori strains grown in the presence of excess nickel. We found that H. pylori NikR mediates the expression of nickel-activated and -repressed genes. In the presence of excess nickel, NikR activated the transcription of ureA-ureB (hp72–73), nixA (hp1077 ), copA2 (hp1072), hpn (hp1427 ) and hpn-like (hp1432) genes and repressed the expression of genes encoding proteins involved in ferric iron uptake and storage [pfr (hp0653), fur (hp1027 ), frpB4 (hp1512), exbB/exbD (hp1339–1340), ceuE (hp1561)], motility [cheV (hp616), flaA (hp0601), flaB (hp0115 )], stress responses [hrcA-grpE-dnaK (hp111–110–109)] and encoding outer-membrane proteins [omp11(hp0472), omp31 (hp1469), omp32 (hp1501)]. Slot blot DNA/RNA hybridization experiments using RNA from three independent bacterial cultures confirmed the transcriptome data for 10 selected genes. The results of gel shift experiments using purified native NikR, β-galactosidase assays with the region between nikR and the exbB/exbD divergent operon, and the study of exbB gene expression using a gentamicin/apramycin reporter gene in H. pylori indicated that NikR is an autorepressor that binds to this intergenic region and also controls the expression of the exbB/exbD/tonB operon, which provides energy for ferric iron uptake. Thus, as previously suggested for Fur in H. pylori, NikR appears to be a global regulator of the metabolism of some divalent cations within a highly complex regulated network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03621.x
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  • 4
    Electronic Resource
    Electronic Resource
    EFFECT OF MAGNESIUM ON MECHANICAL PROPERTIES OF PRESSURIZED MESENTERIC SMALL ARTERIES FROM OLD AND ADULT RATS (2004)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 31 (2004), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The purpose of the present study was to determine the effects of magnesium (Mg) on the mechanical properties of resistance arteries in adult and old rats.2. Studies were performed in adult (17 weeks) and old (104 weeks) male Wistar rats. The vasodilatory response and the passive mechanical properties of the wall of isolated perfused and pressurized arterial segments of mesenteric small arteries were investigated after Mg and verapamil application, both known for their calcium antagonistic properties.3. Mesenteric resistance arteries from old rats exhibited an outward hypertrophic remodelling, with enlargment of the lumen, thickening of the media and enlarged media cross-sectional area.4. The vasodilatory response induced by the application of increasing extracellular concentrations of Mg and verapamil was significantly smaller in preconstricted mesenteric arteries of old rats than in those of adult rats.5. Incremental distensibility in response to increasing intravascular pressures did not change. However, the stress–strain curve was shifted to the left in pressurized mesenteric arteries from old rats, indicating arterial wall stiffness. Verapamil (3 µmol/L) did not modify the stress–strain curves in either adult or aged rats. However, Mg (4.8 mmol/L) significantly shifted the curve to the right in mesenteric arteries from adult rats and, to a greater degree, in those from old rats.6. Although Mg-induced vasodilatation is impaired in aged rats, increased Mg concentration improved the mechanics of pressurized mesenteric resistance arteries. The fact that Mg decreases arterial stiffness in arteries from old rats suggests that Mg has a beneficial effect on age-related changes to the vascular wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.2004.03992.x
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamics and processivity of 40S ribosome scanning on mRNA in yeast (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The eukaryotic 40S ribosomal subunit locates the translation initiation codon on an mRNA via the so-called scanning process that follows 40S binding to the capped 5′ end. This key step in translation is required for the expression of almost all eukaryotic genes, yet the mechanism and dynamics of scanning are unknown. We have performed quantitative studies in vivo and in vitro of the movement of yeast 40S ribosomes along 5′ untranslated regions (UTRs) of different lengths. 40S subunits perform cap-dependent scanning with high processivity for more than 1700 nucleotides in cells of Saccharomyces cerevisiae. Moreover, the observed rates of expression indicate that scanning is performed by an untethered 40S subunit that has been released from the 5′ cap complex. Unexpectedly, the capability to maintain scanning competence on a long 5′ UTR is more dependent on the Ded1/Dbp1 type of helicase than on eIF4A or eIF4B. In a yeast cell-free extract, scanning shows reduced processivity, with an estimated net 5′→3′ rate of approximately 10 nucleotides per second at 26°C. We have developed a biased bidirectional walking model of ribosomal scanning that provides a framework for understanding the above observations as well as other known quantitative and qualitative features of this process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03898.x
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  • 6
    Electronic Resource
    Electronic Resource
    Tetracycline-aptamer-mediated translational regulation in yeast (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We describe post-transcriptional gene regulation in yeast based on direct RNA–ligand interaction. Tetracycline-dependent translational regulation could be imposed via specific aptamers inserted at two different positions in the 5′ untranslated region (5′UTR). Translation in vivo was suppressed up to ninefold upon addition of tetracycline. Repression via an aptamer located near the start codon (cap-distal) in the 5′UTR was more effective than repression via a cap-proximal position. On the other hand, suppression in a cell-free system reached maximally 50-fold and was most effective via a cap-proximal aptamer. Examination of the kinetics of tetracycline-dependent translational inhibition in vitro revealed that preincubation of tetracycline and mRNA before starting translation led not only to the fastest onset of inhibition but also the most effective repression. The differences between the behaviour of the regulatory system in vivo and in vitro are likely to be related to distinct properties of mRNP structure and mRNA accessibility in intact cells as opposed to cell-extracts. Tetracycline-dependent regulation was also observed after insertion of an uORF sequence upstream of the aptamer, indicating that our system also targets reinitiating ribosomes. Polysomal gradient analyses provided insight into the mechanism of regulation. Cap-proximal insertion inhibits binding of the 43S complex to the cap structure whereas start-codon-proximal aptamers interfere with formation of the 80S ribosome, probably by blocking the scanning preinitiation complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03656.x
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  • 7
    Electronic Resource
    Electronic Resource
    A nuclear protein in Schizosaccharomyces pombe with homology to the human tumour suppressor Fhit has decapping activity (2002)
    Oxford, UK : Blackwell Science, Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A number of eukaryotic proteins are already known to orchestrate key steps of mRNA metabolism and translation via interactions with the 5′ m7GpppN cap. We have characterized a new type of histidine triad (HIT) motif protein (Nhm1) that co-purifies with the cap-binding complex eIF4F of Schizosaccharomyces pombe. Nhm1 is an RNA-binding protein that binds to m7GTP-Sepharose, albeit with lower specificity and affinity for methylated GTP than is typical for the cap-binding protein known as eukaryotic initiation factor 4E. Sequence searches have revealed that proteins with strong sequence similarity over all regions of the new protein exist in a wide range of eukaryotes, yet none has been characterized up to now. However, other proteins that share specific motifs with Nhm1 include the human Fhit tumour suppressor protein and the diadenosine 5′, 5′′′-P1, P4-tetraphosphate asymmetrical hydrolase of S. pombe. Our experimental work also reveals that Nhm1 inhibits translation in a cell-free extract prepared from S. pombe, and that it is therefore a putative translational modulator. On the other hand, purified Nhm1 manifests mRNA decapping activity, yet is physically distinct from the Saccharomyces cerevisiae decapping enzyme Dcp1. Moreover, fluorescence and immunofluorescence microscopy show that Nhm1 is predominantly, although not exclusively, nuclear. We conclude that Nhm1 has evolved as a special branch of the HIT motif superfamily that has the potential to influence both the metabolism and the translation of mRNA, and that its presence in S. pombe suggests the utilization of a novel decapping pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03151.x
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  • 8
    Electronic Resource
    Electronic Resource
    Nickel transport systems in microorganisms (2000)
    Springer
    Archives of microbiology 173 (2000), S. 1-9 
    Details
    ISSN: 1432-072X
    Keywords: Key words Metal ion transport ; ABC transporter ; Permease family ; Metalloregulatory protein ; Nickel-containing enzymes ; Metal resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transition metal Ni is an essential cofactor for a number of enzymatic reactions in both prokaryotes and eukaryotes. Molecular analyses have revealed the existence of two major types of high-affinity Ni2+ transporters in bacteria. The Nik system of Escherichia coli is a member of the ABC transporter family and provides Ni2+ ion for the anaerobic biosynthesis of hydrogenases. The periplasmic binding protein of the transporter, NikA, is likely to play a dual role. It acts as the primary binder in the uptake process and is also involved in negative chemotaxis to escape Ni overload. Expression of the nik operon is controlled by the Ni-responsive repressor NikR, which shows functional similarity to the ferric ion uptake regulator Fur. The second type of Ni2+ transporter is represented by HoxN of Ralstonia eutropha, the prototype of a novel family of transition metal permeases. Members of this family have been identified in gram-negative and gram-positive bacteria and recently also in a fission yeast. They transport Ni2+ with very high affinity, but differ with regard to specificity. Site-directed mutagenesis experiments have identified residues that are essential for transport. Besides these uptake systems, different types of metal export systems, which prevent microorganisms from the toxic effects of Ni2+ at elevated intracellular concentrations, have also been described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050001
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  • 9
    Electronic Resource
    Electronic Resource
    Observations on the strength of hydrogen bonding (2000)
    Springer
    Perspectives in drug discovery and design 18 (2000), S. 39-60 
    Details
    ISSN: 1573-9023
    Keywords: basicity scale ; hydrogen bonding strength ; partition coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Both proton transfer and hydrogen bonding play important roles in biological systems. In order to measure hydrogen bond basicity, we are building a new scale that differs significantly from the pKa scale of proton transfer basicity. The strength of hydrogen bond acceptors (HBAs) is measured from the Gibbs energy change ΔGHB for the formation of 1:1 hydrogen bonding complexes between hydrogen bond acceptors (bases) and a reference hydrogen bond donor (4-fluorophenol) in tetrachloromethane at 298 K. The pKHB database (1.364 pKHB =–ΔGHB (kcal mol-1)) comprises ca. 1000 hydrogen bond acceptors. The HBA strength depends on (i) the position of the acceptor atom in the periodic table, (ii) polarizability, field/inductive and resonance effects of substituents around the acceptor atom, and (iii) proximity effects including steric hindrance of the acceptor site, intramolecular hydrogen bonding and lone-pair–lone-pair repulsions. The ranking of oxygen and sp nitrogen bases does not depend very much on the solvent and the reference hydrogen bond donor, but sp2 and sp3 nitrogen bases gain strength in solvents of higher reaction field than CCl4 and lose strength toward CH and weak NH donors. The complete scatter pattern exhibited by the pKa versus pKHB plot demonstrates the non-equivalence of the two scales. The HBA strength scale is applied to the prediction of the hydrogen bonding site in polybasic drugs (e.g strychnine and carbimazole), and to the calculation of octanol–water partition coefficients. A possible relationship between HBA strength and antihistaminic activity is studied for the `push–pull' drugs cimetidine, ranitidine and famotidine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008743229409
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  • 10
    Electronic Resource
    Electronic Resource
    Antioxidant status, lipid peroxidation, mixed function oxidase and UDP-glucuronyl transferase activities in livers from control and DOCA salt-hypertensive male Sprague Dawley rats (2000)
    Springer
    Molecular and cellular biochemistry 203 (2000), S. 33-39 
    Details
    ISSN: 1573-4919
    Keywords: DOCA-salt hypertensive male Sprague Dawley rats ; liver antioxidant enzymes ; glutathione content and glutathione-dependent defense system ; lipid peroxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of DOCA-salt hypertensive treatment on hepatic glutathione-dependent defense system, antioxidant enzymes, lipid peroxidation, mixed function oxidase and UDP-glucuronyl transferase activities were investigated in male Sprague Dawley rats. Compared with controls, DOCA-salt hypertensive rats had lower body weights (linked to liver hypertrophy). Mixed function oxidase and p-nitrophenol-UGT activities were not affected by the treatment but a significant lower rate of the glucuronoconjugation rate of bilirubin (p 〈 0.001) was observed in DOCA-salt hypertensive rats. While cytosolic glutathione contents and glutathione reductase activity were not affected, glutathione peroxidase (p 〈 0.001), glutathione transferase (p 〈 0.001) and catalase (p 〈 0.01) activities were decreased and associated with higher malondialdehyde contents (p 〈 0.001) in treated rats. The imbalance in liver antioxidant status (increasing generation of cellular radical species), associated with increases in lipid peroxidation, suggests that oxidative stress might be directly related to arterial hypertension in DOCA-salt treated male Sprague Dawley rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007041532523
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