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Search Results: 1 - 10 of 490100 matches for " Cury-Boaventura M.F. "
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Arachidonic acid triggers an oxidative burst in leukocytes
Pompeia, C.;Cury-Boaventura, M.F.;Curi, R.;
Brazilian Journal of Medical and Biological Research , 2003, DOI: 10.1590/S0100-879X2003001100013
Abstract: the change in cellular reducing potential, most likely reflecting an oxidative burst, was investigated in arachidonic acid- (aa) stimulated leukocytes. the cells studied included the human leukemia cell lines hl-60 (undifferentiated and differentiated into macrophage-like and polymorphonuclear-like cells), jurkat and raji, and thymocytes and macrophages from rat primary cultures. the oxidative burst was assessed by nitroblue tetrazolium reduction. aa increased the oxidative burst until an optimum aa concentration was reached and the burst decreased thereafter. in the leukemia cell lines, optimum concentration ranged from 200 to 400 μm (up to 16-fold), whereas in rat cells it varied from 10 to 20 μm. initial rates of superoxide generation were high, decreasing steadily and ceasing about 2 h post-treatment. the continuous presence of aa was not needed to stimulate superoxide generation. it seems that the nadph oxidase system participates in aa-stimulated superoxide production in these cells since the oxidative burst was stimulated by nadph and inhibited by n-ethylmaleimide, diphenyleneiodonium and superoxide dismutase. some of the effects of aa on the oxidative burst may be due to its detergent action. there apparently was no contribution of other superoxide-generating systems such as xanthine-xanthine oxidase, cytochromes p-450 and mitochondrial electron transport chain, as assessed by the use of inhibitors. eicosanoids and nitric oxide also do not seem to interfere with the aa-stimulated oxidative burst since there was no systematic effect of cyclooxygenase, lipoxygenase or nitric oxide synthase inhibitors, but lipid peroxides may play a role, as indicated by the inhibition of nitroblue tetrazolium reduction promoted by tocopherol.
Arachidonic acid triggers an oxidative burst in leukocytes
Pompeia C.,Cury-Boaventura M.F.,Curi R.
Brazilian Journal of Medical and Biological Research , 2003,
Abstract: The change in cellular reducing potential, most likely reflecting an oxidative burst, was investigated in arachidonic acid- (AA) stimulated leukocytes. The cells studied included the human leukemia cell lines HL-60 (undifferentiated and differentiated into macrophage-like and polymorphonuclear-like cells), Jurkat and Raji, and thymocytes and macrophages from rat primary cultures. The oxidative burst was assessed by nitroblue tetrazolium reduction. AA increased the oxidative burst until an optimum AA concentration was reached and the burst decreased thereafter. In the leukemia cell lines, optimum concentration ranged from 200 to 400 μM (up to 16-fold), whereas in rat cells it varied from 10 to 20 μM. Initial rates of superoxide generation were high, decreasing steadily and ceasing about 2 h post-treatment. The continuous presence of AA was not needed to stimulate superoxide generation. It seems that the NADPH oxidase system participates in AA-stimulated superoxide production in these cells since the oxidative burst was stimulated by NADPH and inhibited by N-ethylmaleimide, diphenyleneiodonium and superoxide dismutase. Some of the effects of AA on the oxidative burst may be due to its detergent action. There apparently was no contribution of other superoxide-generating systems such as xanthine-xanthine oxidase, cytochromes P-450 and mitochondrial electron transport chain, as assessed by the use of inhibitors. Eicosanoids and nitric oxide also do not seem to interfere with the AA-stimulated oxidative burst since there was no systematic effect of cyclooxygenase, lipoxygenase or nitric oxide synthase inhibitors, but lipid peroxides may play a role, as indicated by the inhibition of nitroblue tetrazolium reduction promoted by tocopherol.
Mechanisms underlying skeletal muscle insulin resistance induced by fatty acids: importance of the mitochondrial function
Amanda R Martins, Renato T Nachbar, Renata Gorjao, Marco A Vinolo, William T Festuccia, Rafael H Lambertucci, Maria F Cury-Boaventura, Leonardo R Silveira, Rui Curi, Sandro M Hirabara
Lipids in Health and Disease , 2012, DOI: 10.1186/1476-511x-11-30
Abstract: Insulin resistance is broadly defined as the reduction in insulin ability to stimulate glucose uptake from body peripheral tissues. At physiological conditions, insulin activates glucose uptake by stimulating the canonical IRS-PI3K-Akt pathway and by phosphorylating and inactivating Akt substrate 160 (AS160), a protein that, when activated, prevents glucose transporter (GLUT) 4 translocation to the membrane. Thus, by inhibiting AS160, insulin promotes the GLUT4 translocation from inner vesicules, promoting fusion to the plasma membrane and consequently glucose uptake [1].Although insulin resistance is a key component of several chronic syndromes associated with obesity such as type 2 diabetes mellitus and metabolic syndrome, the involved factors and their underlying mechanisms linking excessive adiposity to insulin resistance were not completely elucidated yet [2-5]. Evidence suggests that fatty acids, whose circulating levels are markedly increased in obesity and associated-diseases, might play a role in the development of skeletal muscle insulin resistance [6,7]. In this sense, prolonged exposure of skeletal muscle and myocytes to high levels of fatty acids leads to severe insulin resistance [8,9]. Among the different types of fatty acids, saturated long-chain fatty acids such as palmitic and stearic acids were demonstrated to be potent inducers of insulin resistance [5,10]. Several mechanisms have been suggested by us [2,5,11,12] and others [6,8,13-16] to explain how saturated fatty acids impair insulin actions such as the Randle cycle, accumulation of intracellular lipid derivatives (diacylglycerol and ceramides), oxidative stress, modulation of gene transcription, inflammation and mitochondrial dysfunction. In the present review, we discuss evidence supporting the involvement of these mechanisms in the regulation of insulin sensitivity by saturated fatty acids and propose the mitochondrial dysfunction found in conditions of elevated fatty acid levels has a cent
Leaching of a gold bearing partially roasted sulphide. Laboratory scale studies
Almeida, M.F.;
Materials Research , 2001, DOI: 10.1590/S1516-14392001000400014
Abstract: this research aimed at defining a route for recovering precious metals from a very heterogeneous gold bearing sulphide and arsenide concentrate that was partially roasted and dumped by the 1960s when santo antónio mine closed. gold occurs in this concentrate as free particles in the range of 10-100 mm, most of them still enclosed in the pyrite and arsenopyrite matrix. its content varies from 20 to 150 g of au/ton, being higher at the dump upper levels and in the finer concentrate fractions. preliminary tests demonstrated the refractoriness of this product, since the leaching with conventional cyanide solutions and with other leaching solutions gave very low recoveries. however, high concentrated cyanide solutions recover more than 60% of au, although with high nacn and lime consumptions and poor settling characteristics. iron was shown to be highly dissolved in these solutions. some prior treatments clearly favoured the cyanidation process, in particular a roasting step. thus, a large number of roasting experiments was carried out to define the most favourable conditions for recovering gold. however, no clear relationship between roasting conditions and gold dissolution was found due to the heterogeneity of the product and high variance of gold experimental recoveries. these recoveries were calculated considering gold contained in both the leaching residues and leachates, and uncertainties of these results are relatively high. roasting the product at 450-700 °c for 1 h guarantees a high probability to dissolve at least 74% au in a highly concentrated nacn solution stirred for 24 h. the 600-700 °c roasting range is clearly preferable for consuming less cyanide and lime. pre-washing the roasted product seems not to reduce the cyanide consumption. regarding the silver recovery, the nacn and lime consumption are higher while using the products roasted at the lowest tested temperatures. products roasted at higher temperatures have better settling performance.
Challenges in using fish communities for assessing the ecological integrity of non-perennial rivers
M.F Avenant
Water SA , 2010,
Abstract: Environmental Water Assessments (EWAs) aim to protect the ecological integrity of rivers amidst increasing anthropogenic pressures on freshwater resources, and fish communities are the ecosystem component most commonly included. The Fish Response Assessment Index (FRAI) was developed to assess the integrity of fish communities in South African rivers and is commonly applied in EWA studies. This paper reports on the suitability of the FRAI for the non-perennial Seekoei River and discusses some of the challenges faced. Our relatively long and thorough study on the Seekoei River confirmed the concerns that earlier, snapshot, fish integrity assessments in the Orange River system raised: that the existing fish indices are not ideally suited for these rivers with their naturally low species richness and hardy, generalist fish communities. Other difficulties with the use of a score-based method include prediction of the expected species, calculation of a frequency of occurrence rating, selection of the right sampling times for comparative purposes, loss of habitats and sampling points under different flow conditions, and problems experienced when using accumulated data to try to correct for a situation of having too few sampling points. At this stage a more generalised approach is suggested for the Seekoei River, and ultimately other similar non-perennial systems. This could include a number of community characteristics, such as abundance, species richness, species diversity and evenness, recruitment, fish health and the presence/absence of exotic species.
A provisional check list of the reptiles and amphibians of Golden Gate Highlands National Park
M.F. Bates
Koedoe : African Protected Area Conservation and Science , 1991, DOI: 10.4102/koedoe.v34i2.431
Abstract: A provisional check list of 26 reptile and amphibian species (8 frog, 8 lizard and 10 snake species) occurring in Golden Gate Highlands National Park is presented. The list does not reflect the results of an intensive survey, but is a record of specimens collected in the park and preserved at the National Museum, Bloemfontein.
Moraliteit, die opdringerige en die voorwaardelike
M.F. Heyns
Koers : Bulletin for Christian Scholarship , 2010, DOI: 10.4102/koers.v75i1.80
Abstract: Morality, the obtrusive and the conditional The secularist (immanentist), historicist and pluralistic nature of current thinking disables the articulation of transcendental conditions for morality. It is ostensibly especially the constancy of a structure for morality, as transcendental condition, for morality that is disputable. However, an aggressive immanentism sees to it that a transcendent origin for morality does not even appear on the agenda of late modern thinkers, which makes the latter probably an equally serious marginalisation of transcendental considerations. In this article the (sometimes unconscious) experience of some philosophers that a constant structure for morality obtrudes itself upon us, is highlighted. A further claim is that a similar obtrusion can be observed about a coherent diversity of moral sources (i.e. sources which find themselves in a transcendental position with regard to each other). The “most daring” argument is for a transcendental transcendent origin for morality.
De/re/centring of subjective power
M.F. Heyns
Koers : Bulletin for Christian Scholarship , 2000, DOI: 10.4102/koers.v65i1.465
Abstract: The centred self is the self in the centre of the universe with an underlying inner centre; that is, with one of the human abilities as the core power of the human being. I apply this distinction to the meta-psychological theories of Kenneth Gergen and Charles Taylor. Gergen liquidates the autonomous individual only to revert to a centring of the social side of the human condition. It is, according to Gergen, the postmodern condition of advanced transport and communication technologies that will be the end of the authentic self. Gergen rejects the possibility of resisting these postmodern technologies. The upshot of Gergen’s socio-technological determinism is totalitarianism as well as agonism between individual and social aspects. Taylor seemingly steers away from centring one aspect. He nevertheless partially centres intention (interpretation). This gives his de/centring also an undecided and agonistic picture; that is a self in a never-ending conflict with itself and surroundings. I suggest that only a re-centring of all human abilities will avert the final failure of the decentring of the centred self.
Akrasia (swakheid van die wil) en die kontemporêre gesprek oor subjektiwiteit
M.F. Heyns
Koers : Bulletin for Christian Scholarship , 1997, DOI: 10.4102/koers.v62i4.580
Abstract: Akrasia (weakness of will) and the contemporary discourse on subjectivity The issue about akrasia (weakness of the will) concerns the question whether the human will is strong enough to choose and realize actions, or whether a conflict, and a certain type of conflict (i.e. the issue of akrasia), will have the potential to paralyse it. My analysis focuses on ideas of thinkers of the last half of the twentieth century - thinkers like Skinner who practically denies the existence and strength of the se lf and Sartre who postulates a transcendental self with godlike capabilities. I conclude that both leave little room for the idea of akrasia. Akrasia needs a more subtle vision of the power and weakness of the self. To arrive at this conclusion I consider views attempting to reconcile the disempowerment of the se lf by the extra-self with the idea of a self in control of its situation. I argue that these views fail because they assume the akratic conflict to be behi’een the self and extra-self instead of an intra-will conflict. I also deny that the dialectic goal of a fusion o f the self and its situation will give an explanation o f the akratic conflict because dialectics still operate with a centred self which assumes a conflict between the centre and a sub-self periphery. Moreover, this kind of dialectics provides the picture of a permanent victimized self rather than an akratic conflict. I conclude by suggesting the existence of a "dense " self with more subjective capacities than is usually assumed. This, I argue, enhances the scope of, and makes the intra-will conflict more credible.
Declared Knowledge of Beginning Writers.
Morin, M.F.
L1 Educational Studies in Language and Literature , 2005,
Abstract: Most studies of the orthographic development of young writers have largely centred their attention on analyses of written productions. However, an increasing number of researchers are now devoting attention to the information provided by spoken comments made by writers during a production activity. Re- ferred to as metagraphic comments, these utterances give researchers access to young writers’ conceptualizations of written language and the various processes mobilized during a writing task. This article presents the results of a Quebec study aimed at grasping the nature of metagraphic comments and establishing their relationship to writing performance. This research was conducted with 67 French-language subjects who were each given an individual word-writing task at two different moments (at mid-year and year end) in grade one. The analysis of the metagraphic comments, using a grid to categorize them, revealed that young writers have many and varied notions about written French, even at the beginning stages of their schooling. This analysis also led to the observation that comments related to what is thought about language – metalinguistic comments – are much more numerous than those revealing thoughts about cognitive processes at work during the writing activity. Lastly, correlation analyses, which enabled an examination of the relationship between the nature of metagraphic comments and writing performance, suggest that the use of spoken aloud comments during a writing activity does not have the same impact on weak and strong writers.
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