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Search Results: 1 - 10 of 223804 matches for " Gattass R. "
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Changes of ongoing activity in Cebus monkey perirhinal cortex correlate with behavioral performance
Lima, B.;Fiorani, M.;Gattass, R.;
Brazilian Journal of Medical and Biological Research , 2005, DOI: 10.1590/S0100-879X2005000100010
Abstract: a cebus apella monkey weighing 4 kg was trained in a saccadic eye movement task and while the animal performed the task we recorded the extracellular activity of perirhinal cortical neurons. although the task was very simple and maintained at a constant level of difficulty, we observed considerable changes in the performance of the monkey within each experimental session. the behavioral states responsible for such variation may be related to arousal, motivation or attention of the animal while engaged in the task. in approximately 20% (16/82) of the units recorded, long-term direct or inverse correlations could be demonstrated between the monkey's behavioral state and the cells' ongoing activity (independent of the visual stimulation or of the specific behavior along a trial). the perirhinal cortex and other medial temporal structures have long been associated with normal memory function. the data presented here were interpreted in terms of recent reports focusing on the subcortical afferents to temporal lobe structures and their possible role in controlling arousal, motivation, or attention.
Changes of ongoing activity in Cebus monkey perirhinal cortex correlate with behavioral performance
Lima B.,Fiorani M.,Gattass R.
Brazilian Journal of Medical and Biological Research , 2005,
Abstract: A Cebus apella monkey weighing 4 kg was trained in a saccadic eye movement task and while the animal performed the task we recorded the extracellular activity of perirhinal cortical neurons. Although the task was very simple and maintained at a constant level of difficulty, we observed considerable changes in the performance of the monkey within each experimental session. The behavioral states responsible for such variation may be related to arousal, motivation or attention of the animal while engaged in the task. In approximately 20% (16/82) of the units recorded, long-term direct or inverse correlations could be demonstrated between the monkey's behavioral state and the cells' ongoing activity (independent of the visual stimulation or of the specific behavior along a trial). The perirhinal cortex and other medial temporal structures have long been associated with normal memory function. The data presented here were interpreted in terms of recent reports focusing on the subcortical afferents to temporal lobe structures and their possible role in controlling arousal, motivation, or attention.
Vacancy diffusion in silicon: analysis of transition state theory
Gattass, R. R.;Koiller, Belita;Capaz, R. B.;
Brazilian Journal of Physics , 1999, DOI: 10.1590/S0103-97331999000400046
Abstract: transition state theory (tst) is the most widely used formalism for theoretical calculations of diffusion coeffcients of defects in solids. in this work, we test its validity for the case of vacancy diffusion in silicon. the diffusion coefficient directly obtained from molecular-dynamics simulations with a classical (stillinger-weber) potential is compared with tst predictions. our results confirm the validity of tst for this system.
Vacancy diffusion in silicon: analysis of transition state theory
Gattass R. R.,Koiller Belita,Capaz R. B.
Brazilian Journal of Physics , 1999,
Abstract: Transition state theory (TST) is the most widely used formalism for theoretical calculations of diffusion coeffcients of defects in solids. In this work, we test its validity for the case of vacancy diffusion in silicon. The diffusion coefficient directly obtained from molecular-dynamics simulations with a classical (Stillinger-Weber) potential is compared with TST predictions. Our results confirm the validity of TST for this system.
The husk fiber of Cocos nucifera L. (Palmae) is a source of anti-neoplastic activity
Koschek, P.R.;Alviano, D.S.;Alviano, C.S.;Gattass, C.R.;
Brazilian Journal of Medical and Biological Research , 2007, DOI: 10.1590/S0100-879X2006005000153
Abstract: in the present study, we investigated the in vitro anti-tumoral activities of fractions from aqueous extracts of the husk fiber of the typical a and common varieties of cocos nucifera (palmae). cytotoxicity against leukemia cells was determined by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (mtt) assay. cells (2 x 104/well) were incubated with 0, 5, 50 or 500 μg/ml high- or low-molecular weight fractions for 48 h, treated with mtt and absorbance was measured with an elisa reader. the results showed that both varieties have almost similar antitumoral activity against the leukemia cell line k562 (60.1 ± 8.5 and 47.5 ± 11.9% for the typical a and common varieties, respectively). separation of the crude extracts with amicon membranes yielded fractions with molecular weights ranging in size from 1-3 kda (fraction a) to 3-10 kda (fraction b) and to more than 10 kda (fraction c). cells were treated with 500 μg/ml of these fractions and cytotoxicity was evaluated by mtt. fractions ranging in molecular weight from 1-10 kda had higher cytotoxicity. interestingly, c. nucifera extracts were also active against lucena 1, a multidrug-resistant leukemia cell line. their cytotoxicity against this cell line was about 50% (51.9 ± 3.2 and 56.3 ± 2.9 for varieties typical a and common, respectively). since the common c. nucifera variety is extensively cultured in brazil and the husk fiber is its industrial by-product, the results obtained in the present study suggest that it might be a very inexpensive source of new antineoplastic and anti-multidrug resistant drugs that warrants further investigation.
The brain decade in debate: VI. Sensory and motor maps: dynamics and plasticity
Das A.,Franca J.G.,Gattass R.,Kaas J.H.
Brazilian Journal of Medical and Biological Research , 2001,
Abstract: This article is an edited transcription of a virtual symposium promoted by the Brazilian Society of Neuroscience and Behavior (SBNeC). Although the dynamics of sensory and motor representations have been one of the most studied features of the central nervous system, the actual mechanisms of brain plasticity that underlie the dynamic nature of sensory and motor maps are not entirely unraveled. Our discussion began with the notion that the processing of sensory information depends on many different cortical areas. Some of them are arranged topographically and others have non-topographic (analytical) properties. Besides a sensory component, every cortical area has an efferent output that can be mapped and can influence motor behavior. Although new behaviors might be related to modifications of the sensory or motor representations in a given cortical area, they can also be the result of the acquired ability to make new associations between specific sensory cues and certain movements, a type of learning known as conditioning motor learning. Many types of learning are directly related to the emotional or cognitive context in which a new behavior is acquired. This has been demonstrated by paradigms in which the receptive field properties of cortical neurons are modified when an animal is engaged in a given discrimination task or when a triggering feature is paired with an aversive stimulus. The role of the cholinergic input from the nucleus basalis to the neocortex was also highlighted as one important component of the circuits responsible for the context-dependent changes that can be induced in cortical maps.
Balanced cytokine-producing pattern in mice immunized with an avirulent Trypanosoma cruzi
Soares, Milena B. P.;Gon?alves, Renata;Pyrrho, Alexandre S.;Costa, Deise A.;Paiva, Claudia N.;Gattass, Cerli R.;
Anais da Academia Brasileira de Ciências , 2003, DOI: 10.1590/S0001-37652003000200005
Abstract: we have previously demonstrated that inoculation of balb/c mice with trypomastigotes of cl-14, an avirulent trypanosoma cruzi clone, prevents the development of parasitemia and mortality after challenge with virulent cl strain. in this report, we investigated the cytokine and antibody profiles induced by inoculation with cl-14 clone. groups of mice were inoculated with trypomastigotes of cl-14 clone and challenged with infective cl strain. challenged cl-14-inoculated mice had lower levels of ifn-g and higher production of igg1 antibodies as compared to cl strain-infected mice. previous inoculation with cl-14 clone partially prevented the suppression of il-2 production caused by cl strain infection. no significant differences were found regarding il-4 production by splenocytes from cl-14-inoculated or control groups after challenge with cl-strain. our results show that protection against acute t. cruzi infection induced by cl-14 inoculation correlates with a balanced t1/t2 cytokine production, a profile likely to be beneficial for the host.
Atividades antinociceptiva e antiinflamatória do óleo essencial de cascas de Duguetia lanceolata St. Hil., Annonaceae
Sousa, O.V.;Soares Júnior, D.T.;Del-Vechio, G.;Mattosinhos, R.G.;Gattass, C.R.;Kaplan, M. A. C.;
Revista Brasileira de Farmacognosia , 2004, DOI: 10.1590/S0102-695X2004000300005
Abstract: the present work evaluated the antinociceptive and anti-inflammatory activities of the essential oil from barks of duguetia lanceolata. for this purpose, acetic acid writhing, formalin and carrageenan tests were performed. the number of writhings (ed50 = 21,79 mg/kg) and the lick of the paw 1st phase (ed50 = 5,27 mg/kg) e 2nd phase (ed50 = 1,43 mg/kg) reduced significantly in a dosedependent form. the doses 50, 100 and 200 mg/kg reduced the paw edema significantly in 20,83; 36,46 and 48,96%, respectively. these results suggest that the essential oil from barks of d. lanceolata has antinociceptive and anti-inflammatory effects and probably the mechanisms(s) involve central and peripheric actions.
Modulation by context of a scene in monkey anterior inferotemporal cortex during a saccadic eye movement task
LIMA, BRUSS;FIORANI, MARIO;GATTASS, RICARDO;
Anais da Academia Brasileira de Ciências , 2003, DOI: 10.1590/S0001-37652003000100008
Abstract: we investigated the effect of a scene on the activity of cells in the anterior inferotemporal (ait) cortex while the monkey performed a saccadic eye movement (sem) task with and without the context of a scene (gray frame). most neurons did not code for the presence of a scene when it appeared alone (monkey free viewing) or when the monkey was fixating. nevertheless, when a peripheral target was turned on and the monkey had to make a sem to it, some cells were capable of differentially coding the presence of the scene before and after the saccade.
Modulation by context of a scene in monkey anterior inferotemporal cortex during a saccadic eye movement task
LIMA BRUSS,FIORANI MARIO,GATTASS RICARDO
Anais da Academia Brasileira de Ciências , 2003,
Abstract: We investigated the effect of a scene on the activity of cells in the anterior inferotemporal (AIT) cortex while the monkey performed a saccadic eye movement (SEM) task with and without the context of a scene (gray frame). Most neurons did not code for the presence of a scene when it appeared alone (monkey free viewing) or when the monkey was fixating. Nevertheless, when a peripheral target was turned on and the monkey had to make a SEM to it, some cells were capable of differentially coding the presence of the scene before and after the saccade.
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