Percorrer por autor "Silva, D."
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- Actin cytoskeleton disruption is an early event upon exposure of cerebellar granule neurons to SIN-1-induced oxidative stressPublication . Tiago, Teresa; Silva, D.; Samhan-Arias, A. K.; Aureliano, Manuel; Gutierrez-Merino, CarlosIn this work we have studied the alterations of the actin cytoskeleton in cultured cerebellar granule neurons during exposure to the peroxynitritereleasing agent SIN-1 for less than 2 hours. Actin polymerization state was assessed by fluorescence microscopy ratio images using double labelling for actin filaments (phallacidin) and monomers (DNase-I). In addition, agonists and antagonists of L-type Ca2+ channels and NMDA receptors were used in order to find out whether these compounds were able to attenuate or potentiate the effects of oxidative stress on the perturbation of the actin cytoskeleton. The results reveal that a flux of peroxynitrite as low as 0.5 ;M/min during 1h is sufficient to promote alterations of actin dynamics leading to partial actin cytoskeleton disruption and suggest that this is an early event linked to cytosolic calcium concentration changes.
- Actomyosin modulation by peroxynitritePublication . Tiago, Teresa; Silva, D.; Santos, Ana; Aureliano, M.; Gutiérrez-Merino, CarlosIn the present work we address the oxidative modifications accounting for the structural and functional impairment of the actomyosin complex under the oxidative stress mediated by peroxynitrite (ONOO-). Experiments on purified myosin and actin have shown that submicromolar ONOO- concentrations produce strong inhibition of the F-actin stimulated myosin ATPase activity. The peroxynitrite-induced actomyosin impairment correlated with structural modifications that decrease the thermal stability of both actin and myosin leading to partially unfolded states. The results suggest a major role for the highly reactive cysteines on actin and on myosin and also for some critical methionines on G-actin. 3-nitrotyrosine does not contribute significantly to the observed functional alterations.
- Antimicrobial activity of the essential oils of Dittrichia viscosa subsp viscosa on Helicobacter pyloriPublication . Silva, D.; Denham, E.; Faleiro, Leonor; Miguel, Maria Graça; Cavaleiro, C.; Salgueiro, L. R.Dittrichia viscosa subsp. viscosa (Compositae) is found on edges, wood clearings and in waste places of the Iberian Peninsula. Aerial parts of D. viscosa were collected at flowering phase in September-October 2001 around Lisbon, Portugal and the essential oils isolated by hydro-distillation for 4 h using a Clevenger-type apparatus. The oils were analyzed by gas chromatography and gas chromatography-mass spectrometry. Preliminary examination of the essential oils allowed the identification of 32 components. Only four components reached percentages over 5%: fokienol (11.8%), T-muurorol (7.9%), (E)-nerolidol (5.5%) and delta-cadinene (5.0%). The essential oils were tested against Helicobacterpylori and Listeria monocytogenes. Essential oils did not have antimicrobial activity against L. monocytogenes. The essential oil at 0.88 to 22.22 mu g.ml(-1) did not inhibit the growth of H. pylori, affected the growth slightly at 44.40 mu g.ml(-1), and completely inhibited the growth at 88.80 to 133.20 mu g.ml(-1) Results show that use of D. viscosa essential oil in the treatment of gastric disorders caused by H. pylori can be effective.
- CRUSADE: Is it still a good score to predict bleeding inacute coronary syndrome?Publication . Bento, D.; Marques, N.; Guedes, J.; Azevedo, Pedro; Amado, José; Santos, W.; Bispo. J.; Mimoso, J.; Jesus, I.; Silva, D.Introduction: Major bleeding is a serious complication of acute coronary syndrome (ACS) andis associated with a worse prognosis. The CRUSADE bleeding score is used to stratify the risk ofmajor bleeding in ACS.Objective: To assess the predictive ability of the CRUSADE score in a contemporary ACS popu-lation.Methods: In a single-center retrospective study of 2818 patients admitted with ACS, the CRU-SADE score was calculated for each patient and its discrimination and goodness of fit wereassessed by the area under the receiver operating characteristic curve (AUC) and by the Hosmer-Lemeshow test, respectively. Predictors of in-hospital major bleeding (IHMB) were determined.Results: The IHMB rate was 1.8%, significantly lower than predicted by the CRUSADE score (7.1%,p<0.001). The incidence of IHMB was 0.5% in the very low risk category (rate predicted by thescore 3.1%), 1.5% in the low risk category (5.5%), 1.6% in the moderate risk category (8.6%),5.5% in the high risk category (11.9%), and 4.4% in the very high risk category (19.5%). Thepredictive ability of the CRUSADE score for IHMB was only moderate (AUC 0.73).The in-hospital mortality rate was 4.0%. Advanced age (p=0.027), femoral vascular access(p=0.004), higher heart rate (p=0.047) and ticagrelor use (p=0.027) were independent predictorsof IHMB.Conclusions: The CRUSADE score, although presenting some discriminatory power, significantlyoverestimated the IHMB rate, especially in patients at higher risk. These results questionwhether the CRUSADE score should continue to be used in the stratification of ACS.