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  • 1
    ISSN: 1469-8986
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Analysis of baroreceptor sensitivity (BRS) in the time domain through the spontaneous sequence method used a measure of BRS based on the average of all sequences detected, without making any distinction in cardiac cycle length. In this article, we study differentially the functioning of the baroreflex as a function of the length of the cardiac sequences (3, 4, 5, or 6 cardiac cycles). One hundred and four students performed three mental stress tasks: mental arithmetic, memory, and visual attention. The results show that (1) as sequence length decreases, the relationships between BRS and indexes of vagal cardiac control increase, (2) the BRS associated with the more short sequences (3 and 4 beats) is the most vulnerable to mental stress, particularly the mental arithmetic task, and (3) BRS increases progressively as sequence length decreases. These results suggest that the nature and functioning of the baroreflex differ as a function of the length of the cardiac sequences.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect in vivo of salt stress on the activated oxygen metabolism of mitochondria, was studied in leaves from two NaCl-treated cultivars of Pisum sativum L. with different sensitivity to NaCl. In mitochondria from NaCl-sensitive plants, salinity brought about a significant decrease of Mn-SOD (EC 1. 15. 1. 1) Cu, Zn-SOD I (EC 1. 15. 1. 1) and fumarase (EC 4. 2. 1. 2) activities. Conversely, in salt-tolerant plants NaCl treatment produced an increase in the mitochondrial Mn-SOD activity and, to a lesser extent, in fumarase activity. In mitochondria from both salt-treated cultivars, the internal H2O2 concentration remained unchanged. The NADH- and succinate-dependent generation of O2.−radicals by submitochondrial particles and the lipid peroxidation of mitochondrial membranes, increased as a result of salt treatment, and these changes were higher in NaCl-sensitive than in NaCl-tolerant plants. Accordingly, the enhanced rates of superoxide production by mitochondria from salt-sensitive plants were concomitant with a strong decrease in the mitochondrial Mn-SOD activity, whereas NaCl-tolerant plants appear to have a protection mechanism against salt-induced increased O2.− production by means of the induction of the mitochondrial Mn-SOD activity. These results indicate that in the subcellular toxicity of NaCl in pea plants, at the level of mitochondria, an oxidative stress mechanism mediated by superoxide radicals is involved, and also imply a function for mitochondrial Mn-SOD in the molecular mechanisms of plant tolerance to NaCl.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 85 (1981), S. 4139-4141 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: DNA sequence analysis of the Anabaena sp. PCC7120 genome confirmed the presence of three open reading frames (all1691, all2473 and alr0957) containing the histidine-rich region characteristic of the Fur family. The genes coding for the three Fur proteins were cloned and overexpressed in Escherichia coli. The overexpression products, called FurA, FurB and FurC are only distantly related. The ability of the three recombinant proteins to bind iron-boxes identified in the three fur promoter regions was tested by electrophoretical mobility shift assays. FurA binds the three fur promoters with increased affinity in presence of metal. FurB also binds the three fur promoters, and its affinity is increased with DTT. FurC does not bind to furA or furB promoter regions or to its own promoter. However, FurC affects the ability of FurB and FurA to bind their target promoters.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Chicken brain β-N-acetylhexosaminidases from embryos (16 and 21 days old), newborns (1 and 4 days old), and adults (31/2 months and 2 years old) were separated into four different forms by ion exchange chromatography on diethylaminoethyl-cellulose. Three of these forms were “acid” hexosaminidases (I, IIA, and IIB), and the fourth was a “neutral” form. Throughout development of the chicken, forms IIA and III maintained the same activity ratio, whereas that for form I decreased and that for form IIB showed an increase.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 83 (1979), S. 3070-3075 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 82 (1978), S. 2767-2769 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Physiologia plantarum 115 (2002), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In pea (Pisum sativum L.) plants the effect of short-term salt stress and recovery on growth, water relations and the activity of some antioxidant enzymes was studied. Leaf growth was interrupted by salt addition. However, during recovery, growth was restored, although there was a delay in returning to control levels. Salt stress brought about a decrease in osmotic potential and in stomatal conductance, but at 48 h and 24 h post-stress, respectively, both parameters recovered control values. In pea leaves, a linear increase in the Na+ concentration was observed in salt treated plants. In the recovered plants, a slight reduction in the Na+ concentration was observed, probably due to a dilution effect since the plant growth was restored and the total Na+ content was maintined in leaves after the stress period. A significant increase of SOD activity occurred after 48 h of stress and after 8 h of the recovery period (53% and 42%, respectively), and it reached control values at 24 h post-stress. APX activity did not change during the stress period, and after only 8 h post-stress it was increased by 48% with respect to control leaves. GR showed a 71% increase after 24 h of salt stress and also a significant increase was observed in the recovered plants. A strong increase of TBARS was observed after 8 h of stress (180% increase), but then a rapid decrease was observed during the stress period. Surprisingly, TBARS again increased at 8 h post-stress (78% increase), suggesting that plants could perceive the elimination of NaCl from the hydroponic cultures as another stress during the first hours of recovery. These results suggest that short-term NaCl stress produces reversible effects on growth, leaf water relations and on SOD and APX activities. This work also suggests that both during the first hours of imposition of stress and during the first hours of recovery an oxidative stress was produced.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The subcellular localization of superoxide dismutase (SOD; EC. 1.15.1.1) was studied in leaves of two ureide-producing leguminous plants (Phaseolus vulgaris L. cv. Contender and Vigna unguiculata [L.] Walp). In leaves of Vigna and Phaseolus, three superoxide dismutases were found, an Mn-SOD and two Cu, Zn-containing SODs (I and II). Chloroplasts, mitochondria, and peroxisomes were purified by differential and density-gradient centrifugation using either Percoll or sucrose gradients. The yields obtained in intact chloroplasts and peroxisomes from Vigna were considerably higher than those achieved for Phaseolus. Purified chloroplasts only contained the Cu, Zn-SOD II isozyme, but in mitochondria both Mn-SOD and Cu, Zn-SOD I isozymes were present. In purified peroxisomes no SOD activity was detected. The absence of SOD activity in leaf peroxisomes from Vigna contrasts with results reported for the amide-metabolizing legume Pisum sativum L. where the occurrence of Mn-SOD was demonstrated in leaf peroxisomes (del Río et al. 1983. Planta 158: 216–224; Sandalio et al. 1987. Plant Sci. 51: 1–8). This suggests that in leaf peroxisomes from Vigna plants the generation of O2- radicals under normal conditions probably does not take place.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-8922
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The objective of this paper is to present analytical expressions of the basic effective constants (for transducer applications) of fibrous piezoelectric composites with a periodic structure. These expressions were obtained on the basis of the asymptotic averaging method, following the same procedure used in [1] for the purely elastic case. The averaged electromechanical properties for these piezocomposites can be calculated from the above formulas. The results obtained from the theoretical predictions with the use of homogenization method show good agreement with the existing experimental results.
    Type of Medium: Electronic Resource
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