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  • 1
    ISSN: 1573-6903
    Keywords: Spontaneously hypertensive rats (SHR) ; ethanol ; biogenic amines ; catecholamines ; blood pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Spontaneously hypertensive rats (SHR) were administered either 2.4 g/kg ethanol or an isocaloric glucose daily for 4 weeks and the levels of norepinephrine (NE), epinephrine (EP), dopamine (DA), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in different brain regions were determined. Results indicated a 3-fold increase in NE level in brain stem and hypothalamus and more than 2-fold increase in DA in corpus striatum in alcohol-treated rats as compared to controls. There was a significant increase in the level of DA in the corpus striatum but the levels in cerebral cortex, brain stem and hippocampus were decreased instead. Decreases in 5-HT levels were found in hypothalamus, brain stem, cortex and cerebellum of alcohol-treated brain as compared to untreated controls. These results indicate alterations of the biogenic amine contents in different regions of the SHR brain after chronic ethanol ingestion. Since stimulated release of biogenic amines in the SHR brain has been implicated in the regulation of blood pressure, changes due to ethanol ingestion may be a risk factor in hypertensive patients.
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  • 2
    ISSN: 1617-4623
    Keywords: Aromatic metabolism ; Toluene-inducible promoter ; Transcriptional regulation ; Signal transduction ; FadL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 3 kb DNA region upstream of the toluene degradation (tod) genes, todFC1C2BADEGIH, in Pseudomonas putida F1 (PpF1) was sequenced. Two divergently arranged open reading frames, todR and todX, were identified. A toluene-inducible promoter was localized in front of todX, and the transcription start point was mapped. This promoter is probably responsible for the expression of all tod structural genes. TodX was found to be a membrane protein. Its predicted amino acid sequence (453 residues; M r 48265) exhibits considerable similarity with the FadL protein of Escherichia coli, an outer membrane protein required for binding and transport of long-chain fatty acids. An apparent function of TodX is likely to be involved in facilitating the delivery of exogenous toluene inside the PpF1 cells. The sequence of TodR (100 residues) exhibits extensive homology with the DNA-binding domain of transcriptional activators of the LysR family, but todR was found to have a negligible role in tod gene regulation.
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  • 3
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Iron oxide nanoparticles have been synthesized by laser-induced vapor-phase reaction.Mean diameter of the particles varied from approximate 4 nm to 40 nm and the crystalline phase wastransited from γ-Fe2O3 to α-Fe2O3 with increasing operation temperature. The nanometer-sizedα-Fe2O3 powders were used to fabricate a thick film based gas-sensitive sensor. The effects of thedoped noble metals or carbonate and the calcination temperature on sensitivity of the sensor werestudied. The results show that the α-Fe2O3 was doped with 3% noble metal or SrCO3 presents the bestsensitivity to CO
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  • 4
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: In this paper, thixoforging of a magazine plate made of AZ91D magnesium alloy wereinvestigated by means of numerical simulation and experiments. Numerical simulation results showthat with increasing punch displacement, local bending, formation of a concave shell part and bulkplastic deformation occurs in billet continuously. Equivalent strain and stress increase and thetemperature of the semi-solid billet decreases. When the temperature of the semi-solid billet or thedie temperature is elevated, equivalent stain and stress decrease. Optimal technological parameterssuch as a billet temperature of 545°C, die temperature of 450°C and punch velocity of 15 mm/swere obtained by numerical simulation. Experimental results demonstrate that magazine plates withhigh mechanical properties such as tensile strength of 316.8 MPa, yield strength of 228.3 MPa andelongation of 12.6 % can be manufactured successfully when the optimal technological parametersselected according to the results of numerical simulation are applied
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica solida Sinica 4 (1991), S. 449-455 
    ISSN: 0894-9166
    Keywords: out-of-plane ; honeycomb structure ; elastic buckling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A theoretical model and an analytical method, which are suitable for initial elastic buckling analysis of two-dimensional honeycomb structures including hexagonal honeycombs with walls of equal or unequal thickness, rectangular and triangular honeycombs etc., are developed in this paper. The results given in present paper agree well with the experimental data of hexagonal honeycombs with walls of unequal thickness.
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  • 6
    ISSN: 1573-4927
    Keywords: Manis pentadactyla ; protein electrophoresis ; genetic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We examined protein polymorphism of Chinese pangolins (Manis pentadactyla) from Yunnan Province of China, including two forms of three brown and nine dusky Chinese pangolins. Sixty-two genetic loci were screened; 12 loci were found to be polymorphic. The percentage of polymorphic loci (P) is 0.194, the mean individual heterozygosity (H) is 0.078, and the mean number of alleles (A) is 1.258. Furthermore, we calculated the genetic distance (D) between the two forms and found a low level of genetic divergence (D=0.0206) between them, which indicates an almost-indistinguishable divergence at the level of proteins.
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  • 7
    ISSN: 1573-4927
    Keywords: Manis pentadactyla ; protein electrophoresis ; genetic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We examined protein polymorphism of Chinese pangolins (Manis pentadactyla) from Yunnan Province of China, including two forms of three brown and nine dusky Chinese pangolins. Sixty-two genetic loci were screened; 12 loci were found to be polymorphic. The percentage of polymorphic loci (P) is 0.194, the mean individual heterozygosity (H) is 0.078, and the mean number of alleles (A) is 1.258. Furthermore, we calculated the genetic distance (D) between the two forms and found a low level of genetic divergence (D=0.0206) between them, which indicates an almost-indistinguishable divergence at the level of proteins.
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  • 8
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract It is well known that cardiac troponin C (cTnC) regulates the association of force-generating myosin cross-bridges. We report here evidence for an additional role for cTnC. This hypothesis states that Car2+ binds more strongly to cTnC when force-generating myosin cross-bridges are attached to actin and that removal of this bound Ca2+ accelerates the dissociation of force-generating myosin cross-bridges. Intact Fura-2-loaded rat papillary muscles and skinned (permeabilized) ventricular preparations were used. The preparations were mounted in the Guth Muscle Research System which is capable of measuring simultaneously fluorescence and force in response to length perturbations. All mechanical perturbations of muscle length (isotonic shortening, quick stretches and releases, and length vibrations) which cause dissociation of force-generating myosin cross-bridges during a twitch resulted in Ca2+ being released from troponin as judged from changes in the Ca2+ transients (Fura-2 (340/380) fluorescence ratio). Thus dissociation of force-generating myosin cross-bridges cause Ca2+ to be released from cTnC. Conversely, it would be expected that removal of strongly bound Ca2+ from cTnC would result in an increase in the rate of dissociation of force-generating myosin cross-bridges. To test this hypothesis actomyosin ATPase (NADH fluorescence change) and isometric force were measured in skinned cardiac preparations. The ratio of the ATPase/Force is proportional to the rate constant (gapp) for the dissociation of force-generating myosin cross-bridges. The data showed that decreasing the amount of Ca2+ bound to cTnC in skinned cardiac fibers caused an increase in the ratio of ATPase/Force, the rate of dissociation (gapp) of force-generating myosin cross-bridges.
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  • 9
    ISSN: 1573-0743
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A direct comparison of extracellular and intravascular contrast agents for the assessment of myocardial perfusion was carried out in a porcine model (N = 5) with a flow-limiting occluder on the left anterior descending coronary artery. Rapid imaging during the first pass of an extracellular or intravascular contrast agent with a saturation-recovery-prepared TurboFLASH sequence showed comparable peak contrast-to-noise enhancements in myocardial tissue regions with flows averaging 1.1 ± 0.2 at baseline to 4.8 ± 0.6 ml/min/g during hyperemia. The coefficient of variation between the MR estimates of blood flow with Gadomer-17 and the microsphere blood flow measurements was 11 ± 11, while the corresponding coefficient of variation for blood flow estimates with the extracellular CA was 23 ± 11. Blood volume differences between rest and hyperemia observed with the intravascular tracer were significant (V vasc(rest) = 0.078 ± 0.013 ml/g, versus V vasc(hyperemia) = 0.102 ± 0.019 ml/g; p 〈 0.05). The effects of water exchange were minimized through the choice of pulse sequence parameters to provide blood volume estimates consistent with the changes expected between rest and hyperemia. This study represents the first application of multiple indicators in first pass imaging studies for the assessment of myocardial perfusion. The use of an intravascular instead of an extracellular contrast agent allows a reduction of the degrees of freedom for modeling tissue residue curves and results in improved accuracy of blood flow estimates.
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  • 10
    ISSN: 1573-4943
    Keywords: Arginyl-tRNA synthetase ; 4-fluorotryptophan ; 19F NMR ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Escherichia coli 4-fluorotryptophan-substituted arginyl-tRNA synthetase was biosynthetically prepared and purified from a tryptophan auxotroph which could overproduce this enzyme. A method was developed to separate 4-fluorotryptophan from tryptophan and to determine accurately their contents in the 4-fluorotryptophan-containing proteins. It was confirmed that more than 95% of the tryptophan residues in the purified 4-fluorotryptophan-substituted arginyl-tRNA synthetase were replaced by 4-fluorotryptophan. Studies on the effect of the 4-fluorotryptophan replacement on properties of the enzyme showed that, when compared with the native enzyme, both the specific activity and the first-order rate constant of the fluorinated enzyme decreased by approximately 20% with just slightly higher K m values. CD studies, however, did not reveal any difference between the secondary structure of the native and fluorinated enzymes. In addition, thermal unfolding studies showed that the 4-fluorotryptophan replacement did not significantly affect the thermal stability of the enzyme. We may conclude that the substitution of 4-fluorotryptophan in arginyl-tRNA synthetase had no substantial effect on the structure and function of the enzyme. Finally, a preliminary study of 19F nuclear magnetic resonance spectroscopy of the fluorinated enzyme has shown promising prospect for further investigation of its structure and function with NMR.
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