170,991 research outputs found
Caracterização dos efeitos biológicos das lectinas de Canavalia brasiliensis (ConBr) e de Canavalia ensiformes (ConA) em preparações do sistema nervoso central e em células tumorais
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciencias Biológicas. Programa de Pós-Graduação em Neurociências.Lectinas são proteínas com especificidade de ligação à resíduos de carboidratos. ConBr e ConA são lectinas com especificidade para D-glicose/D-manose, extraídas de plantas, família Leguminosae, tribo Phaseolae, subtribo Diocleinae. Estas lectinas podem estimular a proliferação de linfócitos e produção de interferon , ativar macrófagos e produzir inflamação, além de induzirem apoptose em vários tipos celulares. Apesar destes efeitos, existem poucos estudos das ações destas lectinas sobre células tumorais e sobre preparações neurais, especialmente sobre os mecanismos de sinalização celular envolvidos na regulação da neurotransmisssão, diferenciação, proliferação e morte celular. O presente trabalho tem como objetivos: a) determinar as possíveis ações de ConBr e ConA sobre a viabilidade e modulação da liberação do neurotransmissor glutamato no terminal sináptico (sinaptossoma); b) determinar possíveis ações destas lectinas sobre a viabilidade celular em fatias hipocampais, em células de linhagens tumorais de glioma C6 e mieloleucêmicas U-937; c) determinar ações dessas lectinas sobre a via de sinalização de proteínas quinases ativadas por mitógenos (MAPKs) nestas preparações. ConBr e ConA (5-100 g/ml) foram incubadas (1-5min) com sinaptossomas ou fatias hipocampais obtidas de ratas adultas (60-70dias). Além disso, estas lectinas (0,5-100 g/ml) foram incubadas por 24-48h com linhagens tumorais de glioma C6 ou mieloleucêmicas U-937. Os testes de viabilidade foram realizados através de medidas da liberação de LDH ou da redução do MTT. A liberação de 3H-glutamato foi medida através de cintilação líquida. A modulação das vias de MAPKs foi avaliada através de Western blotting usando anticorpos contra as formas fosforiladas e totais de ERK1/2, JNK1/2 e p38MAPK. Os resultados mostraram que ConA e ConBr não alteraram a viabilidade e nem a liberação basal de L-[3H]glutamato em sinaptossomas. -Latrotoxina 1nM sozinha aumentou 43% da liberação de L-[3H]-glutamato em relação ao controle e ConBr provocou um incremento significativo de 20% no efeito de -latrotoxina. E em sinaptossomas, a ConBr mas não ConA estimulou ERK1/2. Estas lectinas não alteraram a viabilidade celular e nem a fosforilação de MAPKs em fatias hipocampais. ConA e ConBr diminuiram fortemente a viabilidade celular em linhagens de glioma C6, sendo este efeito acompanhado de redução da fosforilação de ERK1/2. Nas células mieloleucêmicas U-937, ConBr causou uma redução de viabilidade significativa. Apesar da alta homologia estrutural entre ConA e ConBr estas lectinas apresentaram variações em alguns efeitos biológicos. Os resultados descrevem de forma inédita a modulação, por ConBr, da liberação de glutamato e de MAPKs em sinaptossomas. Adicionalmente, demonstram uma ação de ConBr e ConA na morte celular e/ou inibição de proliferação celular em linhagens tumorais. Em conjunto os dados sugerem ConBr como uma possível ferramenta para estudo da transmissão sináptica e ConBr e ConA como potenciais ferramentas para estudo de processos relacionados a morte celular em células tumorais
Tyrosine phosphorylation mediates ConA-induced membrane type 1-matrix metalloproteinase expression and matrix metalloproteinase-2 activation in MDA-MB-231 human breast carcinoma cells
No full textConA-induced cell surface activation of pro-matrix metalloproteinase-2 (pro-MMP-2) by MDA-MB-231 human breast cancer cells is apparently mediated by up-regulation of membrane type 1 MMP (MT1-MMP) through transcriptional and posttranscriptional mechanisms. Here, we have explored the respective roles of cell surface clustering and protein tyrosine phosphorylation in the ConA- induction effects. Treatment with succinyl-ConA, a variant lacking significant clusterability, partially stimulated MT1-MMP mRNA and protein levels but did not induce MMP-2 activation, suggesting that clustering contributes to the transcriptional regulation by ConA but appears to be critical for the nontranscriptional component. We further found that genistein, an inhibitor of tyrosine phosphorylation, blocked ConA-induced pro-MMP-2 activation and ConA-induced MT1-MMP mRNA level in a dose-dependent manner, implicating tyrosine phosphorylation in the transcriptional aspect. This was confirmed by the dose-dependent promotion of pro-MMP-2 activation by sodium orthovanadate in the presence of suboptimal concentrations of ConA (7.5 μg/ml), with optimal effects seen at 25 μg/g orthovanadate. Genistein did not inhibit the ConA potentiation of MMP-2 activation in MCF-7 cells, in which transfected MT1-MMP is driven by a heterologous promoter, supporting the major implication of phosphotyrosine in the transcriptional component of ConA regulation. These data describe a major signaling event upstream of MT1- MMP induction by ConA and set the stage for further analysis of the nontranscriptional component
Heavy metals distribution in pore water of the Cona marsh: a preliminary investigation on surface sediment
No full textThe work describes the results of a preliminary investigation on surface sediment of the Cona marsh (Venice lagoon) ; heavy metal concentration in pore water extracted from sediment samples has been determined by PIXE analysis
Processes of response facilitation and inhibition in the Simon task. A single-pulse transcranial magnetic stimulation (TMS) study
No full textInvestigation on the conA binding properties of klebsiella pneumoniae
No full textKlebsiella pneumoniae is a healthcare-associated bacterial pathogen which causes severe diseases in immunocompromised individuals. Concanavalin A (conA), a lectin which recognizes proteins with mannose or glucose residues, has been reported to agglutinate K. pneumoniae and hence, is postulated to have therapeutical potential for K. pneumoniae-induced liver infection. This study investigated the conA binding properties of a large collection of clinical isolates of K. pneumoniae. ConA agglutination reaction was demonstrated by 94 (51.4%) of 183 K. pneumoniae isolates using a microtiter plate assay. The conA agglutination reactions were inhibited in the presence of 2.5 mg/ml D-mannose and 2.5 mg/ml glucose, and following pretreatment of the bacterial suspension with protease and heating at 80 degrees C. Majority of the positive isolates originated from respiratory specimens. Isolation of conA-binding proteins from K. pneumoniae ATCC 700603 strain was performed using conA affinity column and the conA binding property of the eluted proteins was confirmed by western blotting analysis using conA-HRP conjugates. Proteins with molecular weights ranging from 35 to 60 kDa were eluted from the conA affinity column, of which four were identified as outer membrane protein precursor A (37 kDa), outer membrane protein precursor C (40 kDa), enolase (45 kDa) and chaperonin (60 kDa) using mass spectrometry analysis. Several conA binding proteins (including 45 and 60 kDa) were found to be immunogenic when reacted with rabbit anti-Klebsiella antibody. The function and interplay of the conA binding proteins in bacterium-host cell relationship merits further investigation
Is cognitive control automatic? New insights from transcranial magnetic stimulation
No full textCognitive control has been classically considered as a flexible process engaged to pursue intentional behaviors, as distinct from automatic processes, which are unintentional, inflexible, and triggered by unconscious mechanisms. Our study challenged this view, showing that such a distinction may not be so clear-cut. We analyzed motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation to investigate the neurocognitive mechanisms occurring in a conflict task during trials that either required or did not require a response. We observed a Simon effect on MEPs and sequential modulations of such effects on both kinds of trials. Sequential modulations are usually explained as resulting from the engagement of intentional control mechanisms. Our findings rule against this idea, suggesting that these effects are the result of a mechanism that detects and resolves conflict even when there is no intention to select any response. Accordingly, cognitive control also seems to operate without intention, acting in an automatic fashio
Macroeconomic forecasting using model averaging
No full textPhDRecently, there has been a broadening concern on forecasting techniques that are
applied on large data sets, since economists in business and management want to
deal with the great magnitude of information. In this analysis, the issue of forecasting
a large data set by using different model averaging approaches is addressed.
In particular, Bayesian and frequentist model averaging methods are considered,
including Bayesian model averaging (BMA), information theoretic model averaging
(ITMA) and predictive likelihood model averaging (PLMA). The predictive performance
of each scheme is compared with the most promising existing alternatives,
namely benchmark AR model and the equal weighted model averaging (AV) scheme.
An empirical application on Inflation forecasting for five countries using large
data sets within the model averaging framework is applied. The average ARX model
with weights constructed differently according to each model averaging scheme is
compared with both the benchmark AR and the AV model. For the comparison
of the accuracy of forecasts several performance indicators have been provided such
as the Root Mean Square Error (RMSE), the Mean Absolute Error (MAE), the
U-Theil’s Inequality Coefficient (U), Mean Square Forecast Error (MSFE) and the
Relative Mean Square Forecast Error (RMSFE). Next, within the Granger causality
framework through the Diebold & Mariano (DM) test and the Clark & McCracken
(CM) test, whether the data-rich models represented by the three different model
averaging schemes have made a statistically significant improvement relative to the
benchmark forecasts has been tested. Critical values at 5% and at 10% have been
calculated based on bootstrap approximation of the finite sample distribution of the
DM and CM test statistics.
The main outcome is that although the information theoretic model averaging
scheme is a more powerful approach, the other two model averaging techniques can
be regarded as useful alternatives
Labeling of endosomes with ConA and mCLING.
No full textTrypanosomes were incubated with mCLING-488 and ConA-594 for 15 minutes on ice, then exogenous mCLING was removed. Cells were incubated at 37°C with ConA-594 for 5 or 15 minutes and fixed. DNA in the kinetoplast and nucleus was stained with DAPI. (A) Simplified flow chart of the experimental procedure. (B) Maximum intensity projections of 3D SR-SIM images. 0 min represents the “No uptake” control (kept on ice); 5 min and15 min images include internalized mCLING-positive endosomes. Boxes (in 5 min and 15 min samples) indicate areas of the trypanosome containing endocytosed mCLING and ConA. ConA is observed at the base of the flagellum in the 0 min and 5 min samples. Small image panels below the larger images show the area enclosed by the box, at a higher magnification. K = kinetoplast. N = nucleus. Arrowheads indicate the posterior bases of flagella. Scale bar in large panels = 2 μm. Scale bare in small panels = 1 μm.</p
Cannabidiol (CBD) attenuates ConA-induced hepatitis in mice.
No full text<p>WT mice (n = 6) were injected with PBS (control), or
ConA (12.5 mg/kg bd.wt., <i>i.v.</i>) to induce hepatitis.
ConA injected mice were administered <i>i.p.</i> with vehicle
or CBD at 5, 20 or 50 mg/kg bd.wt. CBD group received CBD alone at 50
mg/kg. A) Blood was collected at 6, 12, 24 and 48 h and serum aspartate
transaminase (AST) was determined by spectrophotometric assay. Data
represent mean ± SEM from 6 individual mice. The changes in AST
levels were analyzed by Student's <i>t</i>-test (#
p<0.01 compared to PBS; *p<0.05, **p<0.01 compared
to ConA+veh). <b>Histological analysis:</b> B. Representative
H&E stained liver sections obtained 24 h post ConA injection in WT
mice (original magnification ×100). a) Vehicle and b) CBD alone,
show normal tissue morphology; c) ConA+veh shows large necrotic
lesion induced by ConA (arrows); d) ConA+CBD (50 mg/kg bd.wt.)
shows less necrosis (arrows) of liver parenchyma. C) Quantification of
necrotic lesions as a percentage of liver parenchyma. Data are mean
± SEM from 4 mice per treatment. At least five fields were
analyzed per section from each liver sample. PBS and CBD controls did
not show any necrotic lesions. Student's <i>t</i>-test,
**p<0.01 compared to ConA.</p
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